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  Subjects -> ELECTRONICS (Total: 161 journals)
Showing 1 - 200 of 277 Journals sorted alphabetically
Advances in Biosensors and Bioelectronics     Open Access   (Followers: 7)
Advances in Electrical and Electronic Engineering     Open Access   (Followers: 5)
Advances in Electronics     Open Access   (Followers: 63)
Advances in Magnetic and Optical Resonance     Full-text available via subscription   (Followers: 9)
Advances in Microelectronic Engineering     Open Access   (Followers: 12)
Advances in Power Electronics     Open Access   (Followers: 29)
Aerospace and Electronic Systems, IEEE Transactions on     Hybrid Journal   (Followers: 262)
American Journal of Electrical and Electronic Engineering     Open Access   (Followers: 24)
Annals of Telecommunications     Hybrid Journal   (Followers: 8)
APSIPA Transactions on Signal and Information Processing     Open Access   (Followers: 8)
Archives of Electrical Engineering     Open Access   (Followers: 12)
Autonomous Mental Development, IEEE Transactions on     Hybrid Journal   (Followers: 9)
Bell Labs Technical Journal     Hybrid Journal   (Followers: 26)
Biomedical Engineering, IEEE Reviews in     Full-text available via subscription   (Followers: 19)
Biomedical Engineering, IEEE Transactions on     Hybrid Journal   (Followers: 35)
Biomedical Instrumentation & Technology     Hybrid Journal   (Followers: 6)
Broadcasting, IEEE Transactions on     Hybrid Journal   (Followers: 10)
BULLETIN of National Technical University of Ukraine. Series RADIOTECHNIQUE. RADIOAPPARATUS BUILDING     Open Access   (Followers: 1)
Bulletin of the Polish Academy of Sciences : Technical Sciences     Open Access   (Followers: 1)
Canadian Journal of Remote Sensing     Full-text available via subscription   (Followers: 42)
China Communications     Full-text available via subscription   (Followers: 7)
Chinese Journal of Electronics     Hybrid Journal  
Circuits and Systems     Open Access   (Followers: 15)
Consumer Electronics Times     Open Access   (Followers: 5)
Control Systems     Hybrid Journal   (Followers: 220)
Edu Elektrika Journal     Open Access  
Electronic Design     Partially Free   (Followers: 93)
Electronic Markets     Hybrid Journal   (Followers: 8)
Electronic Materials Letters     Hybrid Journal   (Followers: 3)
Electronics     Open Access   (Followers: 78)
Electronics and Communications in Japan     Hybrid Journal   (Followers: 9)
Electronics For You     Partially Free   (Followers: 80)
Electronics Letters     Hybrid Journal   (Followers: 27)
Embedded Systems Letters, IEEE     Hybrid Journal   (Followers: 46)
Energy Harvesting and Systems : Materials, Mechanisms, Circuits and Storage     Hybrid Journal   (Followers: 4)
Energy Storage Materials     Full-text available via subscription   (Followers: 2)
EPJ Quantum Technology     Open Access  
EURASIP Journal on Embedded Systems     Open Access   (Followers: 12)
Facta Universitatis, Series : Electronics and Energetics     Open Access  
Foundations and Trends® in Communications and Information Theory     Full-text available via subscription   (Followers: 6)
Foundations and Trends® in Signal Processing     Full-text available via subscription   (Followers: 10)
Frequenz     Hybrid Journal   (Followers: 1)
Frontiers of Optoelectronics     Hybrid Journal   (Followers: 1)
Geoscience and Remote Sensing, IEEE Transactions on     Hybrid Journal   (Followers: 168)
Haptics, IEEE Transactions on     Hybrid Journal   (Followers: 5)
IEEE Antennas and Propagation Magazine     Hybrid Journal   (Followers: 87)
IEEE Antennas and Wireless Propagation Letters     Hybrid Journal   (Followers: 74)
IEEE Journal of Emerging and Selected Topics in Power Electronics     Hybrid Journal   (Followers: 41)
IEEE Journal of the Electron Devices Society     Open Access   (Followers: 9)
IEEE Journal on Exploratory Solid-State Computational Devices and Circuits     Hybrid Journal  
IEEE Power Electronics Magazine     Full-text available via subscription   (Followers: 59)
IEEE Transactions on Antennas and Propagation     Full-text available via subscription   (Followers: 66)
IEEE Transactions on Automatic Control     Hybrid Journal   (Followers: 53)
IEEE Transactions on Circuits and Systems for Video Technology     Hybrid Journal   (Followers: 18)
IEEE Transactions on Consumer Electronics     Hybrid Journal   (Followers: 36)
IEEE Transactions on Electron Devices     Hybrid Journal   (Followers: 18)
IEEE Transactions on Information Theory     Hybrid Journal   (Followers: 26)
IEEE Transactions on Power Electronics     Hybrid Journal   (Followers: 63)
IEEE Transactions on Signal and Information Processing over Networks     Full-text available via subscription   (Followers: 11)
IEICE - Transactions on Electronics     Full-text available via subscription   (Followers: 13)
IEICE - Transactions on Information and Systems     Full-text available via subscription   (Followers: 5)
IET Cyber-Physical Systems : Theory & Applications     Open Access  
IET Microwaves, Antennas & Propagation     Hybrid Journal   (Followers: 31)
IET Power Electronics     Hybrid Journal   (Followers: 40)
IET Wireless Sensor Systems     Hybrid Journal   (Followers: 18)
IETE Journal of Education     Open Access   (Followers: 4)
IETE Journal of Research     Open Access   (Followers: 10)
IETE Technical Review     Open Access   (Followers: 11)
IJEIS (Indonesian Journal of Electronics and Instrumentation Systems)     Open Access   (Followers: 2)
Industrial Electronics, IEEE Transactions on     Hybrid Journal   (Followers: 45)
Industry Applications, IEEE Transactions on     Hybrid Journal   (Followers: 16)
Informatik-Spektrum     Hybrid Journal   (Followers: 2)
Instabilities in Silicon Devices     Full-text available via subscription  
Intelligent Transportation Systems Magazine, IEEE     Full-text available via subscription   (Followers: 10)
International Journal of Advanced Research in Computer Science and Electronics Engineering     Open Access   (Followers: 18)
International Journal of Advances in Telecommunications, Electrotechnics, Signals and Systems     Open Access   (Followers: 8)
International Journal of Antennas and Propagation     Open Access   (Followers: 11)
International Journal of Applied Electronics in Physics & Robotics     Open Access   (Followers: 4)
International Journal of Computational Vision and Robotics     Hybrid Journal   (Followers: 4)
International Journal of Computer & Electronics Research     Full-text available via subscription   (Followers: 3)
International Journal of Control     Hybrid Journal   (Followers: 12)
International Journal of Electronics     Hybrid Journal   (Followers: 6)
International Journal of Electronics & Data Communication     Open Access   (Followers: 11)
International Journal of Electronics and Telecommunications     Open Access   (Followers: 14)
International Journal of Granular Computing, Rough Sets and Intelligent Systems     Hybrid Journal   (Followers: 2)
International Journal of High Speed Electronics and Systems     Hybrid Journal  
International Journal of Image, Graphics and Signal Processing     Open Access   (Followers: 11)
International Journal of Microwave and Wireless Technologies     Hybrid Journal   (Followers: 7)
International Journal of Nano Devices, Sensors and Systems     Open Access   (Followers: 11)
International Journal of Nanoscience     Hybrid Journal   (Followers: 1)
International Journal of Numerical Modelling: Electronic Networks, Devices and Fields     Hybrid Journal   (Followers: 3)
International Journal of Power Electronics     Hybrid Journal   (Followers: 19)
International Journal of Sensors, Wireless Communications and Control     Hybrid Journal   (Followers: 9)
International Journal of Systems, Control and Communications     Hybrid Journal   (Followers: 3)
International Journal of Wireless and Microwave Technologies     Open Access   (Followers: 6)
International Journal on Communication     Full-text available via subscription   (Followers: 12)
International Journal on Electrical and Power Engineering     Full-text available via subscription   (Followers: 9)
International Transaction of Electrical and Computer Engineers System     Open Access   (Followers: 2)
Journal of Biosensors & Bioelectronics     Open Access   (Followers: 3)
Journal of Advanced Dielectrics     Open Access   (Followers: 1)
Journal of Artificial Intelligence     Open Access   (Followers: 10)
Journal of Circuits, Systems, and Computers     Hybrid Journal   (Followers: 4)
Journal of Computational Intelligence and Electronic Systems     Full-text available via subscription   (Followers: 1)
Journal of Electrical and Electronics Engineering Research     Open Access   (Followers: 21)
Journal of Electrical Bioimpedance     Open Access   (Followers: 2)
Journal of Electrical Engineering & Electronic Technology     Hybrid Journal   (Followers: 7)
Journal of Electromagnetic Analysis and Applications     Open Access   (Followers: 7)
Journal of Electromagnetic Waves and Applications     Hybrid Journal   (Followers: 7)
Journal of Electronics (China)     Hybrid Journal   (Followers: 4)
Journal of Energy Storage     Full-text available via subscription   (Followers: 3)
Journal of Field Robotics     Hybrid Journal   (Followers: 2)
Journal of Guidance, Control, and Dynamics     Full-text available via subscription   (Followers: 135)
Journal of Information and Telecommunication     Open Access  
Journal of Intelligent Procedures in Electrical Technology     Open Access   (Followers: 3)
Journal of Low Power Electronics     Full-text available via subscription   (Followers: 6)
Journal of Low Power Electronics and Applications     Open Access   (Followers: 7)
Journal of Microwaves, Optoelectronics and Electromagnetic Applications     Open Access   (Followers: 9)
Journal of Nuclear Cardiology     Hybrid Journal  
Journal of Optoelectronics Engineering     Open Access   (Followers: 2)
Journal of Physics B: Atomic, Molecular and Optical Physics     Hybrid Journal   (Followers: 27)
Journal of Semiconductors     Full-text available via subscription   (Followers: 4)
Journal of Sensors     Open Access   (Followers: 24)
Journal of Signal and Information Processing     Open Access   (Followers: 9)
Jurnal Rekayasa Elektrika     Open Access  
Learning Technologies, IEEE Transactions on     Hybrid Journal   (Followers: 12)
Magnetics Letters, IEEE     Hybrid Journal   (Followers: 7)
Majalah Ilmiah Teknologi Elektro : Journal of Electrical Technology     Open Access   (Followers: 2)
Metrology and Measurement Systems     Open Access   (Followers: 5)
Microelectronics and Solid State Electronics     Open Access   (Followers: 17)
Nanotechnology Magazine, IEEE     Full-text available via subscription   (Followers: 30)
Nanotechnology, Science and Applications     Open Access   (Followers: 6)
Nature Electronics     Hybrid Journal  
Networks: an International Journal     Hybrid Journal   (Followers: 6)
Open Journal of Antennas and Propagation     Open Access   (Followers: 8)
Optical Communications and Networking, IEEE/OSA Journal of     Full-text available via subscription   (Followers: 14)
Paladyn, Journal of Behavioral Robotics     Open Access   (Followers: 1)
Problemy Peredachi Informatsii     Full-text available via subscription  
Progress in Quantum Electronics     Full-text available via subscription   (Followers: 7)
Pulse     Full-text available via subscription   (Followers: 5)
Radiophysics and Quantum Electronics     Hybrid Journal   (Followers: 2)
Recent Advances in Communications and Networking Technology     Hybrid Journal   (Followers: 3)
Recent Advances in Electrical & Electronic Engineering     Hybrid Journal   (Followers: 10)
Security and Communication Networks     Hybrid Journal   (Followers: 2)
Selected Topics in Applied Earth Observations and Remote Sensing, IEEE Journal of     Hybrid Journal   (Followers: 50)
Semiconductors and Semimetals     Full-text available via subscription   (Followers: 1)
Sensing and Imaging : An International Journal     Hybrid Journal   (Followers: 2)
Services Computing, IEEE Transactions on     Hybrid Journal   (Followers: 4)
Software Engineering, IEEE Transactions on     Hybrid Journal   (Followers: 74)
Solid-State Circuits Magazine, IEEE     Hybrid Journal   (Followers: 12)
Solid-State Electronics     Hybrid Journal   (Followers: 8)
Superconductor Science and Technology     Hybrid Journal   (Followers: 2)
Synthesis Lectures on Power Electronics     Full-text available via subscription   (Followers: 3)
Technical Report Electronics and Computer Engineering     Open Access  
TELE     Open Access  
Telematique     Open Access  
TELKOMNIKA (Telecommunication, Computing, Electronics and Control)     Open Access   (Followers: 8)
Universal Journal of Electrical and Electronic Engineering     Open Access   (Followers: 6)
Visión Electrónica : algo más que un estado sólido     Open Access   (Followers: 1)
Wireless and Mobile Technologies     Open Access   (Followers: 5)
Wireless Power Transfer     Full-text available via subscription   (Followers: 4)
Women in Engineering Magazine, IEEE     Full-text available via subscription   (Followers: 11)
Електротехніка і Електромеханіка     Open Access  

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Journal Cover IEEE Transactions on Power Electronics
  [SJR: 3.005]   [H-I: 160]   [63 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 0885-8993
   Published by IEEE Homepage  [191 journals]
  • IEEE Power Electronics Society
    • Abstract: Presents a listing of the editorial board, board of governors, current staff, committee members, and/or society editors for this issue of the publication.
      PubDate: July 2018
      Issue No: Vol. 33, No. 7 (2018)
       
  • IEEE Power Electronics Society
    • Abstract: Presents a listing of the editorial board, board of governors, current staff, committee members, and/or society editors for this issue of the publication.
      PubDate: July 2018
      Issue No: Vol. 33, No. 7 (2018)
       
  • Blank page
    • Abstract: This page or pages intentionally left blank.
      PubDate: July 2018
      Issue No: Vol. 33, No. 7 (2018)
       
  • Hill Climbing Power Flow Algorithm for Hybrid DC/AC Microgrids
    • Authors: Omair Khan;Samrat Acharya;Mohamed Al Hosani;Mohamed Shawky El Moursi;
      Pages: 5532 - 5537
      Abstract: Microgrids are becoming popular because of the rise of distributed energy resources (DERs). The quest for efficient utilization of DERs resulted in the development of hybrid dc/ac microgrids, which consist of independent dc and ac subgrids. Controlling the power exchange across hybrid microgrids is an important aspect in maximizing the benefits. There are numerous techniques proposed in the literature to control the power flow; however, most of these techniques use proportional-integral controllers which are difficult to tune and exhibit slow response. To eliminate the drawback of existing control solutions, this letter proposes a novel strategy to exchange active power among dc and ac microgrids. The proposed control strategy is based on the hill climbing algorithm that uses perturbations of power angle δ and observes the corresponding changes in the active power. An average model of the hybrid microgrid is first developed for the evaluation of the proposed algorithm. The proposed algorithm is then applied to verify its effectiveness for achieving sufficient power exchange and enhancing the dynamic response. The model is implemented and tested using MATLAB/Simulink. Moreover, the proposed control strategy is experimentally validated using a real-time simulator, OPAL-RT.
      PubDate: July 2018
      Issue No: Vol. 33, No. 7 (2018)
       
  • A Switched-Capacitor-Based Multilevel Inverter Topology With Reduced
           Components
    • Authors: N. Sandeep;Udaykumar R. Yaragatti;
      Pages: 5538 - 5542
      Abstract: This letter presents an improved sensorless nine-level inverter topology with reduced number of components. It is formed by cascading a three-level T-type neutral clamped point inverter with a floating capacitor (FC) fed two-level converter unit. Additionally, two line-frequency switches are appended across the dc-link. A simple logic-form equations-based pulse width modulator is designed which is in-charge of maintaining the FC voltage at its reference value without any aid of voltage and current sensor. Thus, the complexity in control of the proposed topology is very minimal. The working principle of the proposed inverter and formulation of logic-form equations is deliberated in detail. Furthermore, experimental results obtained from the developed prototype are presented to validate feasibility and operability of the proposed topology. Finally, a comprehensive comparison with some of the recently reported inverter topologies proving the merits of the proposed topology is included.
      PubDate: July 2018
      Issue No: Vol. 33, No. 7 (2018)
       
  • A Novel Seven-Level Hybrid-Clamped (HC) Topology for Medium-Voltage Motor
           Drives
    • Authors: Hao Tian;Yuzhuo Li;Yun Wei Li;
      Pages: 5543 - 5547
      Abstract: This letter proposes a novel seven-level (7L) hybrid-clamped converter, which has competitive performance and lower device count compared to existing topologies. It can easily balance the floating capacitor voltage at the switching frequency, and therefore ensure low capacitor voltage ripples even under very low fundamental frequencies. Both multipulse diode front-end and active front-end structures can be used with the proposed 7L converter, where the 7L active front end has the ability to balance the dc-link capacitors. The proposed 7L converter is very suitable for medium voltage drives (4.16 to 6.6 kV) that feature low costs, high-performance, and low-speed operation capability. Simulation and experiment results are obtained to verify the feasibility of the proposed topology.
      PubDate: July 2018
      Issue No: Vol. 33, No. 7 (2018)
       
  • An Open-Loop Grid Synchronization Approach for Single-Phase Applications
    • Authors: Saeed Golestan;Josep M. Guerrero;Juan. C. Vasquez;
      Pages: 5548 - 5555
      Abstract: From the control point of view, synchronization techniques are divided into two major categories: open-loop and closed-loop methods. Roughly speaking, open-loop synchronization (OLS) approaches are not as popular as closed-loop ones, probably because they suffer from a poor performance in the presence of frequency drifts. This is particularly true in single-phase applications, where the lack of multiple independent input signals makes the implementation of the synchronization technique difficult. The aim of this letter is to develop an effective OLS technique for single-phase power and energy applications. The proposed OLS method benefits from a straightforward implementation, a fast dynamic response (a response time less than two cycles of the nominal frequency), and a complete immunity against the dc component in the grid voltage. In addition, the designed OLS method totally blocks (significantly attenuates) all harmonics up to the aliasing point under a nominal (off-nominal) frequency. The effectiveness of the designed OLS technique is verified using comparative experimental results.
      PubDate: July 2018
      Issue No: Vol. 33, No. 7 (2018)
       
  • Small-Signal Modeling of Three-Phase Synchronous Reference Frame
           Phase-Locked Loops
    • Authors: Florian Hans;Walter Schumacher;Lennart Harnefors;
      Pages: 5556 - 5560
      Abstract: Synchronous reference frame (SRF) phase-locked loops (PLLs) represent a commonly used technique for grid synchronization in distributed generation (DG) systems. Since PLLs affect transient dynamics, they are a crucial component for stability studies. In this letter, it is shown that a commonly used small-signal SRF-PLL model can be used for stability analysis in some preconditioned scenarios with a single grid-connected DG unit, but does necessarily require perturbation quantities that are offset free. Otherwise, an incorrect usage may result in unacceptable errors. To overcome this restriction, an improved small-signal PLL model is proposed, which enables to analyze the effects of grid frequency and phase angle changes as well as variations of the input voltage magnitude. Finally, the model accuracy is validated by means of computer simulations.
      PubDate: July 2018
      Issue No: Vol. 33, No. 7 (2018)
       
  • Active Identification Method for Line Resistance in DC Microgrid Based on
           Single Pulse Injection
    • Authors: Chen Liu;Jinbin Zhao;Shanshan Wang;Wu Lu;Keqing Qu;
      Pages: 5561 - 5564
      Abstract: In dc microgrids, line resistance on the output side of the converters in parallel could lead to nonaccurate results for the traditional droop control method. In this letter, an active identification method for line resistance based on the dc microgrid specific system structure is proposed. By injecting a pulse disturbance actively and detecting the changes of output voltage and current, the line resistance between the paralleled converters and the dc bus could be obtained and used for the compensation of the droop coefficient. Compared with traditional droop control method and other improved methods, this method improves the current sharing accuracy and restores the dc bus voltage without any additional hardware devices to be added into the initial loop. Finally, simulation and experimental results supporting the feasibility and effectiveness of the proposed method are also presented.
      PubDate: July 2018
      Issue No: Vol. 33, No. 7 (2018)
       
  • A New Inductive Power Transfer Topology Using Direct AC–AC Converter
           With Active Source Current Waveshaping
    • Authors: Suvendu Samanta;Akshay Kumar Rathore;
      Pages: 5565 - 5577
      Abstract: Generally, in wireless inductive power transfer (IPT) system, the power is processed through multiple power transfer stages and this leads to lower efficiency and higher cost of the system. Recent research shows that the use of a direct ac–ac converter in an IPT system compensates these limitations significantly. However, one of the major challenges of the IPT circuit with direct ac–ac converter is to achieve multiple control goals through a single converter. These include load power requirement, maintaining high-quality source current and achieving soft switching of inverter switches, etc. In the existing literatures, the research is more focused on meeting load power requirement and soft switching of inverter switches. The major focus of this paper is to propose, analyze, and control a new IPT power converter topology using current-fed direct ac–ac converter. Compare with existing buck derived, i.e., voltage source ac–ac converter topologies, the proposed topology is boost derived; therefore, active source current waveshaping is easily obtained. The complete control is carried out through two loops, where the outer output current loop ensures load requirements and inner loop maintains the high-quality grid current. The detail of steady-state and dynamic analysis and design procedure of the converter is presented. Experimental results obtained from a 1.2-kW lab-build prototype are included to verify the analysis and proposed control.
      PubDate: July 2018
      Issue No: Vol. 33, No. 7 (2018)
       
  • Distributed Control for a Modular Multilevel Converter
    • Authors: Shunfeng Yang;Yi Tang;Peng Wang;
      Pages: 5578 - 5591
      Abstract: Conventional centralized control strategies may reduce the flexibility and expandability of a modular multilevel converter (MMC) system. To tackle this issue, this paper proposes a distributed control architecture that is capable of assigning certain control tasks to distributed local controllers and improves the modularity of an MMC system. A central controller dealing with the output current regulation based on sensed arm currents is adopted. The control of MMC internal dynamics and the pulsewidth modulation (PWM) generation are distributed into local controllers. Unlike the conventional MMC control that needs all submodule capacitor voltages for capacitor voltage averaging, the proposed capacitor voltage control only relies on local submodule voltage measurement. Consequently, communication-intensive capacitor voltage transmission in each control cycle is not required and the communication burden of the control system can be significantly reduced. The control loops and possible control conflicts among submodules are presented and considered for system stability analysis. The effectiveness of the proposed distributed control architecture and capacitor voltage control for an MMC are confirmed by the start-up, steady state, and transient experimental results.
      PubDate: July 2018
      Issue No: Vol. 33, No. 7 (2018)
       
  • Hierarchical Distributed Balancing Control for Large-Scale Reconfigurable
           AC Battery Packs
    • Authors: Efstratios Chatzinikolaou;Daniel J. Rogers;
      Pages: 5592 - 5602
      Abstract: This paper presents a hierarchical balancing algorithm for use in large-scale reconfigurable ac battery packs. Using a decentralized battery management system, the pack is organized in control layers with each layer controller responsible for a small number of slave controllers, thereby significantly reducing communication and centralized processing requirements. The hierarchical balancing algorithm uses all available voltage steps in the pack ensuring a high-quality sinusoidal output voltage while balancing the objects of different layers. Balancing priority can be swapped dynamically between layers according to the maximum state of charge (SoC) variation between the objects of each layer while also ensuring that the output voltage reference is always met even when a cell failure occurs, as long as there are an adequate number of cells available in the pack. An experimental demonstration of the proposed balancing algorithm is presented using an ac battery pack comprising 144 20-Ah lithium–titanate cells. Cell balancing to within 2 mV of the cell open-circuit voltage is achieved between cells with 20% initial SoC variation and 5% capacity difference.
      PubDate: July 2018
      Issue No: Vol. 33, No. 7 (2018)
       
  • Improving the Short-Circuit Reliability in IGBTs: How to Mitigate
           Oscillations
    • Authors: Paula Diaz Reigosa;Francesco Iannuzzo;Munaf Rahimo;Chiara Corvasce;Frede Blaabjerg;
      Pages: 5603 - 5612
      Abstract: In this paper, the oscillation mechanism limiting the ruggedness of insulated gate bipolar transistors (IGBTs) is investigated through both circuit and device analysis. The work presented here is based on a time-domain approach for two different IGBT cell structures (i.e., trench-gate and planar), illustrating the two-dimensional effects during one oscillation cycle. It has been found that the gate capacitance varies according to the strength of the electric field near the emitter, which in turn leads to charge-storage effects associated with low carrier velocity. For the first time, it has been discovered that a parametric oscillation takes place during the short circuit in IGBTs, whose time-varying element is the Miller capacitance, which is involved in the amplification mechanism. This hypothesis has been validated through simulations and its mitigation is possible by increasing the electric field at the emitter of the IGBT with the purpose of counteracting the Kirk effect.
      PubDate: July 2018
      Issue No: Vol. 33, No. 7 (2018)
       
  • Combined Multilevel and Two-Phase Interleaved LLC Converter With Enhanced
           Power Processing Characteristics and Natural Current Sharing
    • Authors: Or Kirshenboim;Mor Mordechai Peretz;
      Pages: 5613 - 5620
      Abstract: This paper introduces a new two-phase interleaved flying-capacitor LLC converter topology with high output current applications. Compared to a conventional two-phase LLC converter, the new converter adds a single capacitor that contributes to lower voltage stress on the primary side's switches, automatically balances the current distribution between the phases, and enhances the power processing capabilities. All the attractive features of LLC converters are preserved, such as zero-voltage switching on the primary side's mosfets, zero-current switching on the secondary side's power devices, narrow switching frequency range, and simple design. Full principle of operation and analysis of the converter are described, as well as the converter's primary characteristics and the impact of nonideal components on the current sharing behavior. A 600 W, 400 V-to-12 V experimental prototype is used as a showcase of the attractive features of the new converter, demonstrating excellent current sharing, simple implementation, and high efficiency of up to 97.3%.
      PubDate: July 2018
      Issue No: Vol. 33, No. 7 (2018)
       
  • Common-Mode Voltage Elimination for Variable-Speed Motor Drive Based on
           Flying-Capacitor Modular Multilevel Converter
    • Authors: Sixing Du;Bin Wu;Navid R. Zargari;
      Pages: 5621 - 5628
      Abstract: The flying-capacitor modular multilevel converter (FC-MMC) overcomes the low/zero-speed operation issues of conventional MMC-based drive. The FC-MMC injects no common-mode voltage (CMV) to the drive system. However, the pulse width modulator (PWM) introduces switching ripples, which appear as CMV on motor stator windings. To completely get rid of the CMV, an elimination method based on a new modulation scheme is proposed in this paper. The modulation algorithm places the switching pulses end to end for upper and lower arms, respectively. The consistent switching positions between upper and lower arms lead to the complete CMV elimination for FC-MMC-based drive system in entire speed range. Although the proposed method slightly increases the switching frequency as compared to conventional phase-shifted PWM, it is still acceptable in medium-voltage applications. The validation of the proposal is proved by simulations and experiments.
      PubDate: July 2018
      Issue No: Vol. 33, No. 7 (2018)
       
  • Capacitor Voltage Balance Control of Five-Level Modular Composited
           Converter With Hybrid Space Vector Modulation
    • Authors: Wuhua Li;Jiawei Hu;Senjun Hu;Heya Yang;Huan Yang;Xiangning He;
      Pages: 5629 - 5640
      Abstract: Multilevel converters are widely employed in the 30-50 kW medium-voltage grid-connected photovoltaic (PV) generation systems due to their higher power quality and lower switching losses compared with the two-level converters. Dual T-type three-level converters and one three-level diode neutral point clamped circuit can be integrated to derive a simplified five-level modular composited converter (5L-MCC) for the medium-voltage PV grid-connected systems. However, realizing the capacitor voltage balance is a challenge to enhance its reliability. First, the model of dc capacitor voltage variation of the 5L-MCC is discussed to expose a limitation once the nearest three-vector synthesis method is employed with conventional space vector modulation (SVM). In order to extend the operational range, a hybrid space vector modulation (HSVM) strategy is proposed, which integrates the optimized SVM switching sequence for the low-modulation (M
      PubDate: July 2018
      Issue No: Vol. 33, No. 7 (2018)
       
  • The Alternate Arm Converter (AAC)—“Short-Overlap” Mode
           Operation—Analysis and Design Parameter Selection
    • Authors: Ewan Mark Farr;Ralph Feldman;Jon C. Clare;Alan J. Watson;Pat W. Wheeler;
      Pages: 5641 - 5659
      Abstract: This paper presents converter operation principles and theoretical analyses for “short-overlap” mode operation of the alternate arm converter (AAC), which is a type of modular multilevel voltage source converter that has been proposed for HVdc transmission applications. Fourier series expressions for the ideal arm current and reference voltage are derived, for the first time, in order to develop an expression for the submodule capacitance required to give a selected peak-peak voltage ripple of the summed submodule capacitor voltages in an arm. The dc converter current contains nonnegligible low-order even harmonics; this is verified by deriving, for the first time, a Fourier series expression for this current. As the dc converter current needs to be filtered to form a smooth dc grid current, a novel dc filter arrangement is proposed, which uses the characteristics of a simplified dc cable model, as well as the capacitance of the dc link and additional dc-link damping resistance, in order to form a passive low-pass filter. Results obtained from a simulation model, which is based on an industrial HVdc demonstrator, are used in order to verify the presented converter operation principles and theoretical analyses.
      PubDate: July 2018
      Issue No: Vol. 33, No. 7 (2018)
       
  • High-Frequency EMI Attenuation at Source With the Auxiliary Commutated
           Pole Inverter
    • Authors: Apollo Charalambous;Xibo Yuan;Neville McNeill;
      Pages: 5660 - 5676
      Abstract: Fast-switching power converters are a key enabling technology for the more electric aircraft (MEA), but the generated electromagnetic interference (EMI) poses significant challenges to the electrification effort. To meet the stringent aerospace EMI standards, passive filters are commonly employed, despite the weight and size constraints imposed by the MEA. Alternatively, the EMI source, i.e., the high $dvtext{/} dt$ and $ditext{/} dt$ slew rates, can be addressed through waveform-shaping techniques. For example, while most soft-switching converters can reduce switching loss, they do so by switching the semiconductor devices in a slower and smoother manner, resulting in the attenuation of high-frequency harmonics. This paper examines the auxiliary commutated pole inverter (ACPI) topology, and its first contribution is the attenuation of the high-frequency content of its EMI source, that is, the output voltage, in a predictable manner, through the active control of the resonant circuit. This is achieved by first, discussing the time-domain characteristics of trapezoidal and S-shaped pulse-trains that lead to attenuated high-frequency harmonic content, and second, by analyzing the equivalent LC circuit of the ACPI. The design of the inverter is then focused on the active control of the resonant parameters, for a predetermined and enhanced output voltage high-frequency response. The second contribution of this paper is the comparison of the EMI performance of hard switching and of three soft-switching modes, fixed-timing control, variable-timing control, and capacitive turn-offs, and how this informs important metrics such as power efficiency, current stress, and implementation complexity. Finally, the third contribution is on the trade-offs that arise when the primary design goal is enhanced EMI pe-formance as opposed to switching loss reduction. A 5-kW, 3-phase ACPI prototype is used for validating the high-frequency content attenuation at source. It is shown that the ACPI can achieve a 37 dB harmonic attenuation of its output voltage at 4 MHz, compared to a hard-switched inverter.
      PubDate: July 2018
      Issue No: Vol. 33, No. 7 (2018)
       
  • An Instantaneously Triggered Short-Circuit Protection Architecture for
           Boost Switching DC/DC Converters
    • Authors: Zhiming Xiao;
      Pages: 5677 - 5685
      Abstract: This paper presents a protection circuit architecture that helps us to reduce the chances of damages in a boost switching converter due to fault conditions of output short-to-ground or power-switch short-circuits. Those two short-circuit faults can cause the inductor current to run away and result in damages. The proposed protection circuit can detect those two fault conditions within a few microseconds and then isolate the converter from its power supply. The fault detection is implemented by sensing the voltage drop across the primary inductor in a 1:1 coupled transformer which replaces the single-winding inductor in a boost converter. If a short-circuit fault happens at either the output load or at the power switch, the secondary inductor will shoot current to turn off a pass PMOSFET, which disconnects the primary inductor from the input supply. The protection circuit was built on the top of a commercial boost converter and was verified under short-circuit faults over a wide load current range. The proposed protection structure effectively reduced the inductor current overshoot during short-circuit event at the expenses of 1.2% drop of the peak efficiency during normal operation.
      PubDate: July 2018
      Issue No: Vol. 33, No. 7 (2018)
       
  • Imbalance Mechanism and Balanced Control of Capacitor Voltage for a Hybrid
           Modular Multilevel Converter
    • Authors: Maozeng Lu;Jiabing Hu;Rong Zeng;Wuhua Li;Lei Lin;
      Pages: 5686 - 5696
      Abstract: Due to different charging and discharging characteristics of full-bridge submodules and half-bridge submodules in hybrid modular multilevel converters (MMC), capacitor voltage imbalance will occur under boosted ac voltage or reduced dc voltage conditions. To address this issue, the mechanism of capacitor voltage imbalance is carefully studied, with three main factors—modulation index, power angle, and hybridization ratio—summarized and their effect on capacitor voltage imbalance analyzed. Further, a control strategy based on fundamental frequency reactive circulating current injection is proposed to keep the capacitor voltage balanced in the hybrid MMC. The amplitude and phase angle of the injected circulating current are calculated and their influence on the energy fluctuation in the submodules’ capacitors and the semiconductors’ current stress is explored. Experimental results under boosted ac voltage and reduced dc voltage conditions demonstrate the feasibility and validity of the proposed scheme.
      PubDate: July 2018
      Issue No: Vol. 33, No. 7 (2018)
       
  • Optimized Control of the Modular Multilevel Converter Based on Space
           Vector Modulation
    • Authors: Yi Deng;Yebin Wang;Koon Hoo Teo;Maryam Saeedifard;Ronald G. Harley;
      Pages: 5697 - 5711
      Abstract: This paper presents a general space vector modulation (SVM) method for the modular multilevel converter (MMC). Compared with earlier modulation methods, the proposed SVM method not only utilizes the maximum level number (i.e., $2n+ 1$, where $n$ is the number of submodules in the upper or lower arm of each phase) of output phase voltages, but also leads to an optimized control performance in terms of capacitor voltage balancing, circulating current suppression, and common-mode voltage reduction. The maximum level number is achieved by introducing a new equivalent circuit of the MMC, and the optimized control is obtained by selecting the optimal redundant switching states. Since the computational burden of the SVM scheme is independent of the voltage level number, the proposed method is well suited to the MMC with any number of submodules. Simulation and experimental results are presented to validate the proposed method.
      PubDate: July 2018
      Issue No: Vol. 33, No. 7 (2018)
       
  • A New Voltage Measure Method for MMC Based on Sample Delay Compensation
    • Authors: Fei Rong;Xichang Gong;Xing Li;Shoudao Huang;
      Pages: 5712 - 5723
      Abstract: The nearest level control is suitable for modular multilevel converter (MMC) with large number of submodules (SM). The voltage measure method for MMC requires to install a voltage sensor for each SM, which increases the system costs and the burden of the data acquisition system. This paper presents a novel voltage measure method to solve this problem. With the proposed method, the SMs are divided into some groups, and each group is configured with only one voltage sensor. The voltage of each SM is obtained by an observer based on the charging and discharging model of the SM. In order to improve measurement accuracy, a compensation method is proposed for the delay of the voltage sensor and the A/D sampling chip. To verify the accuracy of the proposed measure method, the case studies are performed on a 30-level single-phase MMC simulation model under different operating conditions. At last, a nine-level single-phase MMC laboratory prototype is also set up to verify the performance of the proposed method.
      PubDate: July 2018
      Issue No: Vol. 33, No. 7 (2018)
       
  • Design of a 10-kV·A Soft-Switching Solid-State Transformer (S4T)
    • Authors: Hao Chen;Deepak Divan;
      Pages: 5724 - 5738
      Abstract: The soft-switching solid-state transformer (S4T) employs only 12 main active devices and an auxiliary resonant circuit to implement a bidirectional solid-state transformer, with an attractive feature of achieving a full range of zero-voltage-switching conditions for all the main devices. This paper covers detailed design of the power stage, auxiliary resonant circuit, and control of the S4T. The high-frequency transformer is an essential element for the S4T, and it has a unique feature of dc-biased flux. Design of such a high-frequency transformer is also discussed in detail in this paper. Soft startup, shutdown, and fast dynamic response under load transients are also attractive behaviors because of the low inertia of the S4T. Experimental results from a 208-V/10-kV·A S4T unit are presented.
      PubDate: July 2018
      Issue No: Vol. 33, No. 7 (2018)
       
  • Loss Optimization of MMC by Second-Order Harmonic Circulating Current
           Injection
    • Authors: Limin Yang;Yaohua Li;Zixin Li;Ping Wang;Shukai Xu;Ruifeng Gou;
      Pages: 5739 - 5753
      Abstract: For high power voltage source converter based high voltage direct current transmission systems, modular multilevel converter (MMC) is the most popular circuit topology nowadays. It is known that the existence of the second-order harmonic circulating current (SHCC) component in the arm current of MMC increases the loss of the converter. Conventionally, the SHCC component eliminating methods are usually adopted to reduce the loss. The relationship between the loss of MMC and the SHCC component is analyzed first in this paper. The analysis shows that the conventional eliminating methods are not optimal in terms of the minimum loss of MMC. A loss optimization control scheme is also proposed by injecting the optimal SHCC component into the arm current of MMC, rather than eliminating the SHCC component of the arm current. The simulation and experimental results of the ±350 kV/1000 MW MMC and the down-scaled MMC setup verify the correctness and effectiveness of the proposed loss optimization method under different operation conditions.
      PubDate: July 2018
      Issue No: Vol. 33, No. 7 (2018)
       
  • New Modeling Method and Design Optimization for a Soft-Switched
           DC–DC Converter
    • Authors: Liang Jia;Srikanth Lakshmikanthan;Xin Li;Yan-Fei Liu;
      Pages: 5754 - 5772
      Abstract: High-performance cloud computing enables many key future technologies such as artificial intelligence (AI), self-driving vehicle, big data analysis, and the Internet of things (IoT), using clustered CPU and GPU servers in the datacenter. To improve the power efficiency and the infrastructure flexibility, the computing industry is adopting 54 VDC to power the servers in the open compute racks. In this paper, a new modeling technique for a soft-switched dc-dc converter is presented and suitable to guide optimal design in different applications, for example, 54 V to point of load (PoL) for the new open compute rack. To improve the model accuracy and reduce the complexity, this paper proposes a reduced-order linear differential equation (LDE) based modeling technique to discover the following: 1) the tank resonance involving the output inductor; 2) the output current ripple and its impact on power efficiency; 3) the proper on-time control for soft switching; 4) the unique bleeding mode under the heavy load; 5) the output power capability of the converter; and 6) component tolerance analysis and impact on the performance of the converter. With the power loss estimation, design guidelines are provided for a reference design and design improvement based on this new modeling technique. Using the proposed method, great accuracy can be expected in the efficiency estimation. Simulation and experimental results are provided to verify the modeling technique in a 54-1.2 V 25 A dc-dc converter prototype.
      PubDate: July 2018
      Issue No: Vol. 33, No. 7 (2018)
       
  • Custom Power Active Transformer for Flexible Operation of Power Systems
    • Authors: M. A. Elsaharty;Jose Ignacio Candela;Pedro Rodriguez;
      Pages: 5773 - 5783
      Abstract: This paper presents a new transformer, i.e., the custom power active transformer (CPAT) which integrates both series and shunt power conditioning through power electronics into a single transformer. This is achieved through a distinct design of the magnetic circuit and auxiliary windings of the transformer. In this paper, a single-phase CPAT is proposed as well as a preface into its extension to multiphase systems. Through its magnetic equivalent circuit model, several design considerations and control limitations are revealed in the paper. Analysis of the resulting CPAT structure shows some prospects in material saving as well as size and cost reduction when compared to the traditional multitransformer-based configuration. In this paper, the proposed single-phase CPAT is utilized in a distribution system application, where the control architecture is designed to attenuate voltage and current distortions at both the load and the grid side, respectively. Performance and effectiveness of the proposed CPAT are evaluated through simulation and experiments.
      PubDate: July 2018
      Issue No: Vol. 33, No. 7 (2018)
       
  • Achieving Multiple Functions of Three-Phase Electric Springs in Unbalanced
           Three-Phase Power Systems Using the Instantaneous Power Theory
    • Authors: Shuo Yan;Ming-Hao Wang;Tian-Bo Yang;Siew-Chong Tan;Balarko Chaudhuri;S. Y. Ron Hui;
      Pages: 5784 - 5795
      Abstract: Three-phase electric spring (3-ph ES) has recently been proposed as a fast demand response technology for applications in unbalanced power systems fed with a mixture of conventional and renewable power generation. Using the instantaneous power theory as the theoretical framework, this paper presents the criteria and conditions for minimizing the average and oscillating power of the 3-ph ES for the first time. A detailed analysis of the use of 3-ph ES is included for providing multiple control objectives of voltage regulation and power balancing of the 3-ph power system, and minimization of the average and oscillating ac power of the ES. A corresponding control scheme implementable in a single controller is included and explained. The control scheme has been practically verified with experiments.
      PubDate: July 2018
      Issue No: Vol. 33, No. 7 (2018)
       
  • A Family of Gradient Descent Grid Frequency Estimators for the SOGI Filter
    • Authors: José Matas;Helena Martín;Jordi de la Hoz;Abdullah Abusorrah;Yusuf A. Al-Turki;Mohammed Al-Hindawi;
      Pages: 5796 - 5810
      Abstract: This paper applies the adaptive gradient descent method to the second-order generalized integrator (SOGI) filter in order to find an online estimation algorithm for the grid frequency, which leads to the proposal of three possible estimators. One of them is identical to the frequency-locked loop algorithm reported in the literature, which proves that it should be understood as a gradient descent estimation algorithm and not as a “frequency locked loop.” The proposed gradient descent estimators are simple and suitable to be implemented into a digital processor with small computational burden. However, due to the SOGI characteristics, the estimators show to be especially sensitive to subharmonic and dc-offset voltage distortion. These problems are removed adopting a cascaded double SOGI approach, which strongly increases the rejection capability to harmonics and enhances the response to voltage sags. Simulation and experimental results are provided to validate the proposed contribution.
      PubDate: July 2018
      Issue No: Vol. 33, No. 7 (2018)
       
  • Active Junction Temperature Control of IGBT Based on Adjusting the
           Turn-off Trajectory
    • Authors: Bo Wang;Luowei Zhou;Yi Zhang;Kaihong Wang;Xiong Du;Pengju Sun;
      Pages: 5811 - 5823
      Abstract: The junction temperature fluctuation of an insulated-gate bipolar transistor (IGBT) is the most important factor of its aging failure, and smoothing the fluctuation is an effective way to improve the life of an IGBT. The existing methods for smoothing the fluctuation by active junction temperature control are not yet ready wide application, and exploring the different approaches to active junction temperature control is a hot topic. This paper presents a method of active junction temperature control that shifts the turn-off trajectory of an IGBT to adjust the IGBT turn-off loss for smoothing the junction temperature. The relationship between parameters of the adjusting circuit and turn-off loss is analyzed. On the basis of this analysis, a method of estimating the smoothing ability for the proposed active junction temperature control is deduced. Using an IGBT installed in a 1.2-MW direct-drive wind power converter as an example, the evaluation result shows that the proposed method can completely smooth the junction temperature fluctuation caused by a 40% rated load fluctuation. Finally, a low-power experiment is carried out.
      PubDate: July 2018
      Issue No: Vol. 33, No. 7 (2018)
       
  • Multiple-Vector Model-Predictive Power Control of Three-Phase Four-Switch
           Rectifiers With Capacitor Voltage Balancing
    • Authors: Dehong Zhou;Xiaoqiang Li;Yi Tang;
      Pages: 5824 - 5835
      Abstract: Model-predictive power control (MPPC) takes the switching nonlinearity of power converters and system constraints into consideration. It is a promising control technique for three-phase four-switch rectifiers (TPFSRs) because capacitor-voltage-balancing control and instantaneous power control can be simultaneously designed for this type of power converters. However, since only one switching vector is allowed in each control interval, conventional MPPC (C-MPPC) may lead to significant output power ripples that can severely degrade system power quality. This is particularly true for TPFSRs due to the limited number of switching states as well as the constraint imposed by the capacitor-voltage-balancing control. To improve the performance of TPFSRs, this paper proposes a multiple-vector MPPC scheme, which can minimize active power and reactive power ripples and achieve capacitor voltage balancing with a constant switching frequency. An equivalent zero-voltage vector model and a capacitor-voltage-balancing model are derived to implement the proposed control scheme. Comparative experimental results are presented to demonstrate the superiority of the proposed control scheme over the C-MPPC.
      PubDate: July 2018
      Issue No: Vol. 33, No. 7 (2018)
       
  • Direct Power Control of Doubly Fed Induction Generator Without
           Phase-Locked Loop Under Harmonically Distorted Voltage Conditions
    • Authors: Heng Nian;Longqi Li;
      Pages: 5836 - 5846
      Abstract: This paper proposes an improved direct power control (DPC) strategy of the doubly fed induction generator without phase-locked loop (PLL) under harmonically distorted voltage conditions. The proposed DPC scheme is implemented in a virtual synchronous reference frame, so that the potential instability problems caused by PLL can be eliminated. A second-order vector integrator is integrated with DPC to suppress the harmonic components directly, so that three different control targets of smooth stator active and reactive powers, sinusoidal stator current and constant electromagnetic torque, can be achieved. The sequential separations and the complex calculations of the power compensating items can also be eliminated. Meanwhile, a simple grid frequency estimation scheme is proposed, which can make the control strategy self-adaptive to the frequency variation in the practical situation. Finally, the experimental results validate the availability of the proposed DPC strategy.
      PubDate: July 2018
      Issue No: Vol. 33, No. 7 (2018)
       
  • Lithium–Sulfur Battery State-of-Charge Observability Analysis and
           Estimation
    • Authors: Abbas Fotouhi;Daniel J. Auger;Karsten Propp;Stefano Longo;
      Pages: 5847 - 5859
      Abstract: Lithium-Sulfur (Li-S) battery technology is considered for an application in an electric-vehicle energy storage system in this study. A new type of Li-S cell is tested by applying load current and measuring cell's terminal voltage in order to parameterize an equivalent circuit network model. Having the cell's model, the possibility of state-of-charge (SOC) estimation is assessed by performing an observability analysis. The results demonstrate that the Li-S cell model is not fully observable because of the particular shape of cell's open-circuit voltage curve. This feature distinguishes Li-S batteries from many other types of battery, e.g., Li-ion and NiMH. As a consequence, a Li-S cell's SOC cannot be estimated using existing methods in the literature and special considerations are needed. To solve this problem, a new framework is proposed consisting of online battery parameter identification in conjunction with an estimator that is trained to use the identified parameters to predict SOC. The identification part is based on the well-known prediction-error minimization algorithm; and the SOC estimator part is an adaptive neuro-fuzzy inference system in combination with coulomb counting. Using the proposed method, a Li-S cell's SOC is estimated with a mean error of 4% and maximum error of 7% in a realistic driving scenario.
      PubDate: July 2018
      Issue No: Vol. 33, No. 7 (2018)
       
  • DC–DC Converter Based Photovoltaic Simulator With a Double Current
           Mode Controller
    • Authors: Weichao Zhang;Jonathan W. Kimball;
      Pages: 5860 - 5868
      Abstract: This paper explores the performance of a dc–dc converter, which emulates the output characteristics of a real photovoltaic (PV) module. The PV simulator uses a double current mode controller to ensure fast and accurate reproduction of a module's current-voltage (IV) characteristics. A portable PV simulator prototype of 85 W is examined in terms of its steady state IV curve matching capacity and the convergence time corresponding to step changes in current source load, voltage source load, and insolation levels. The IV characteristics of the PV module are implemented as a look-up-table, which determines the reference output current from measured output voltage. The Thevenin equivalent circuit of the PV module is used to model its small-signal (linearized) characteristics for stability analysis. Extensive simulation and experimental results, with loads that have current-source, voltage-source, and resistive characteristics, validate the converter's suitability for replacing a PV module in most laboratory situations. Modularity and compatibility with a maximum power point tracker have also been validated.
      PubDate: July 2018
      Issue No: Vol. 33, No. 7 (2018)
       
  • Novel Control Method for Multimodule PV Microinverter With Multiple
           Functions
    • Authors: Hsuang-Chang Chiang;Faa-Jeng Lin;Jin-Kuan Chang;
      Pages: 5869 - 5879
      Abstract: This paper presents a novel control method for multimodule photovoltaic microinverter (MI). The proposed MI employs a two-stage topology with active-clamped current-fed push–pull converter cascaded with a full-bridge inverter. This system can operate in grid-connected mode to feed power to the grid with a programmable power factor. This system can also operate in line-interactive mode, i.e., share load power without feeding power to the grid. In the event of grid power failure, the MI can operate in a standalone mode to supply uninterruptible power to the load. This paper presents a multiloop control scheme with power programmable capability for achieving the above multiple functions. In addition, the proposed control scheme embedded a multimodule parallel capability that multiple MI modules can be paralleled to enlarge the capacity with autonomous control in all operation modes. Finally, three 250-W MI modules are adopted to demonstrate the effectiveness of the proposed control method in simulations as well as experiments.
      PubDate: July 2018
      Issue No: Vol. 33, No. 7 (2018)
       
  • Synthesis and Comparative Analysis of Very High Step-Up DC–DC Converters
           Adopting Coupled-Inductor and Voltage Multiplier Cells
    • Authors: António Manuel Santos Spencer Andrade;Everson Mattos;Luciano Schuch;Hélio Leães Hey;Mario Lúcio da Silva Martins;
      Pages: 5880 - 5897
      Abstract: A synthesis methodology for developing a set of very high step-up dc-dc converters is presented and discussed in this paper. The proposed method makes use of a boost converter as basic topology in which three step-up techniques are combined and incorporated. The studied techniques are the switched capacitors voltage multipliers (VM), the diode VMs, and the coupled-inductors. With the proposed methodology, many well-known converters are identified and two novel converters are proposed. In addition to a detailed analysis of the synthesis of each topology, a comparative analysis among of some important converters is presented. This comparison involves aspects such as voltage gain, voltage stress, component stress factor, component count, and relative cost. By means of these comparisons, the main characteristics and constraints of the analyzed converters are identified. Results from 250 W prototypes, designed according to photovoltaic ac-module specifications, are obtained experimentally to validate the theoretical analyses and point out advantages and limitations of each converter. The results demonstrate that the combination of the three studied techniques provides the best trend off on the comparative analysis carried out in this work.
      PubDate: July 2018
      Issue No: Vol. 33, No. 7 (2018)
       
  • Low Dissipative Snubber Using Flyback-Type Transformer for 10 kV IGCT in 7
           MW Wind Turbine Systems
    • Authors: Siamak Shirmohammadi;Yongsug Suh;
      Pages: 5898 - 5908
      Abstract: 10 kV integrated gate-commutated thyristor (IGCT) has been recently developed and has the potential to push wind turbine systems to higher power and voltage rating. Converters employing IGCTs need snubber and over-voltage protection circuit to limit the rate of current's rising and peak over voltage across IGCT during turn-on and -off state, respectively. The conventional resistor-capacitor-diode (RCD) snubber which is used in such power converter dissipates a significant amount of power. In order to reduce the amount of energy lost by the conventional RCD snubber, this paper proposes flyback-type snubber. Flyback-type snubber not only meets all of the IGCTs characteristics during on- and off-state but also significantly saves the power loss. The proposed flyback-type snubber can save up to 73% of the loss in conventional di/dt snubber circuit according to the PLECS magnetic simulation of three-level neutral point clamped grid side converter. The experiments are performed using IGCT stack. Flyback transformer yields the effectiveness of the proposed snubber in wind turbine systems.
      PubDate: July 2018
      Issue No: Vol. 33, No. 7 (2018)
       
  • Nonlinear Capacitance Evolution of Lithium-Ion Capacitors Based on
           Frequency- and Time-Domain Measurements
    • Authors: Nagham El Ghossein;Ali Sari;Pascal Venet;
      Pages: 5909 - 5916
      Abstract: The integration of energy storage systems (ESSs) in contemporary applications highly depends on the performance of these devices. Supplying high power for a reasonable period of time is one of their main targets in several applications like backup systems and transport technologies. For this purpose, lithium-ion capacitors (LICs) would demonstrate better suitability than conventional ESSs for applications requiring a small installation space and a long lifetime. They are known for their energy density greater than that of supercapacitors and their power density greater than that of lithium-ion batteries. This paper explains the electrochemical processes that interfere in the storage of energy inside an LIC. The analysis of these phenomena was the tool for assessing the nonlinear capacitance evolution of the LIC with respect to its voltage. Several measurement techniques in the frequency and time domains were elaborated and compared in order to assess this nonlinear behavior of the LIC. Some of the measurement protocols contained constant voltage phases that had a significant effect on the variation of the capacitance. The novelty of this study concerns the introduction of a new measurement protocol that takes into account the particular characteristics of LICs. Their unique behavior is explained for the first time based on a physicochemical analysis.
      PubDate: July 2018
      Issue No: Vol. 33, No. 7 (2018)
       
  • Voltage-Lift Technique Based Nonisolated Boost DC–DC Converter:
           Analysis and Design
    • Authors: Farzad Mohammadzadeh Shahir;Ebrahim Babaei;Murtaza Farsadi;
      Pages: 5917 - 5926
      Abstract: In this paper, a new structure of nonisolated boost dc-dc converters based on voltage-lift technique is proposed. In comparison with conventional nonisolated boost dc-dc converters, the proposed converter generates higher voltage gain. In this paper, the relations between voltage and current of all elements in continuous conduction mode and discontinuous conduction mode are calculated as well as voltage gain in each mode. Then, the critical inductance and stress of switch current are extracted. Finally, the validity of given theories is examined by using the experimental results.
      PubDate: July 2018
      Issue No: Vol. 33, No. 7 (2018)
       
  • New Switching Strategy for Single-Mode Operation of a Single-Stage
           Buck–Boost Inverter
    • Authors: Ashok Kumar;Parthasarathi Sensarma;
      Pages: 5927 - 5936
      Abstract: Generally, single-stage buck-boost inverters consist of distinct circuits operating individually in buck/boost or positive/negative modes, the latter definitely leading to crossover distortion in the output current. This paper proposes a switching strategy that changes the bimodal operation of a single-stage buck-boost topology to a single-mode inverter. This is due to the consequent voltage gain that ensures that the output voltage polarity, apart from its magnitude, is an exclusive function of the duty ratio. Operational principle and salient hardware design are explained with the help of equivalent circuits. Details about the dynamic model are presented, based on which controller design is carried out for both stand-alone and grid-connected operation. Experimental results obtained from a 300-W, 110-V laboratory prototype are presented to validate the performance of the proposed switching strategy.
      PubDate: July 2018
      Issue No: Vol. 33, No. 7 (2018)
       
  • Multi-Input Switched-Capacitor Multilevel Inverter for High-Frequency AC
           Power Distribution
    • Authors: S. Raghu Raman;Ka Wai Eric Cheng;Yuanmao Ye;
      Pages: 5937 - 5948
      Abstract: This paper proposes a switched-capacitor multilevel inverter for high-frequency ac power distribution systems. The proposed topology produces a staircase waveform with higher number of output levels employing fewer components compared to several existing switched-capacitor multilevel inverters in the literature. This topology is beneficial where asymmetric dc voltage sources are available, e.g., in case of renewable energy farms based ac microgrids and modern electric vehicles. Utilizing the available dc sources as inputs for a single inverter solves the major problem of connecting several inverters in parallel. Additionally, the need to stack voltage sources, like batteries or supercapacitors, in series which demand charge equalization algorithms, are eliminated as the voltage sources employed share a common ground. The inverter inherently solves the problem of capacitor voltage balancing as each capacitor is charged to the value equal to one of the input voltage every cycle. State analysis, losses, and the selection of capacitance are examined. Simulation and experimental results at different distribution frequencies, power levels, and output harmonic content are provided to demonstrate the feasibility of the proposed multilevel inverter topology.
      PubDate: July 2018
      Issue No: Vol. 33, No. 7 (2018)
       
  • A Dual Active Bridge Converter With an Extended High-Efficiency Range by
           DC Blocking Capacitor Voltage Control
    • Authors: Zian Qin;Yanfeng Shen;Poh Chiang Loh;Huai Wang;Frede Blaabjerg;
      Pages: 5949 - 5966
      Abstract: A Dual active bridge (DAB) converter can achieve a wide high-efficiency range when its input and output voltages are equal, assuming a 1:1 turns ratio for its isolation transformer. If its input or output voltage is doubled, efficiency of the DAB will drop significantly, because of the introduction of the hard switching and high circulating power. Thus, a new modulation scheme has been proposed, whose main idea is to introduce a voltage offset across the dc blocking capacitor connected in series with the transformer. Operational principle of the proposed modulation has been introduced, before analyzing its soft-switching area and circulating power mathematically. The final modulation scheme is not difficult to implement, but can help the DAB achieve soft switching, low circulating power, and thereby high efficiency, even with its input or output voltage doubled. These features have been verified by experimental results obtained with a 1.2-kW prototype.
      PubDate: July 2018
      Issue No: Vol. 33, No. 7 (2018)
       
  • High-Efficiency High Step-Up DC–DC Converter With Dual Coupled Inductors
           for Grid-Connected Photovoltaic Systems
    • Authors: Mojtaba Forouzesh;Yanfeng Shen;Keyvan Yari;Yam P. Siwakoti;Frede Blaabjerg;
      Pages: 5967 - 5982
      Abstract: This paper introduces a non-isolated high step-up dc–dc converter with dual coupled inductors suitable for distributed generation applications. By implementing an input parallel connection, the proposed dc–dc structure inherits shared input current with low ripple, which also requires small capacitive filter at its input. Moreover, this topology can reach high voltage gain by using dual coupled inductors in series connection at the output stage. The proposed converter uses active clamp circuits with a shared clamp capacitor for the main switches. In addition to the active clamp circuit, the leakage energy is recycled to the output by using an integrated regenerative snubber. Indeed, these circuits allow soft-switching conditions, i.e., zero voltage switching and zero current switching for active and passive switching devices, respectively. The mentioned features along with a common ground connection of the input and output make the proposed topology a proper candidate for transformer-less grid-connected photovoltaic systems. The operating performance, analysis and mathematical derivations of the proposed dc–dc converter have been demonstrated in the paper. Moreover, the main features of the proposed converter have been verified through experimental results of a 1-kW laboratory prototype.
      PubDate: July 2018
      Issue No: Vol. 33, No. 7 (2018)
       
  • Voltage-Double Magnetically Coupled Impedance Source Networks
    • Authors: Yuliang Ji;Hongchen Liu;Chengming Zhang;Pat Wheeler;
      Pages: 5983 - 5994
      Abstract: A family of voltage-double magnetically coupled impedance source networks is presented. The scheme of the proposed family is that adding the auxiliary capacitors and diodes to the magnetically coupled transformers to realize the voltage-double function. The proposed impedance networks can produce the higher voltage gain, reduce the voltage stresses across the passive components, have a common ground, realize the continuous input current, and suppress the start-up inrush current. Finally, one of the resulting topologies is verified in the condition of dc–dc converter and dc–ac converter, theoretical analysis and experimental results are offered to verify the topology's validity.
      PubDate: July 2018
      Issue No: Vol. 33, No. 7 (2018)
       
  • Research on a 4000-V-Ultrahigh-Input-Switched-Mode Power Supply Using
           Series-Connected MOSFETs
    • Authors: Xiliang Chen;Wenjie Chen;Xu Yang;Yaqiang Han;Xiang Hao;Tianluan Xiao;
      Pages: 5995 - 6011
      Abstract: A 4000-V-ultrahigh-input voltage-switched-mode power supply (UHV-SMPS) using series-connected MOSFETs is designed in this paper. The main contributions of the proposed scheme include the common-mode interference modeling of the multiswitch structure, voltage balance of the switches and driving method. First, the common-mode interference of UHV-SMPS is evaluated by a high-frequency equivalent model of the proposed scheme. Then, a detailed multiswitch common-mode electromagnetic interference mathematical model is derived and the interference quantity is calculated according to the coupling of series-connected switches. Second, a new mathematical regulation for passive snubber circuit is proposed to realize input voltage balance. Through the regularity of the equivalent parasitic capacitances, the design of compensatory capacitance and voltage balance can realized with ease. Third, a novel driving method based on integrated pulse transformer is proposed. It can achieve both good consistency to the gate signals of MOSFETs and ultrahigh isolation voltage in the wide range input applications. Finally, the experimental results obtained from a 300–4000 V wide range input prototype verified the feasibility of the proposed scheme and accuracy of the theoretical analysis.
      PubDate: July 2018
      Issue No: Vol. 33, No. 7 (2018)
       
  • Zero-Voltage and Zero-Current Switching PWM DC–DC Converter Using
           Controlled Secondary Rectifier With One Active Switch and Nondissipative
           Turn-Off Snubber
    • Authors: Jaroslav Dudrik;Marek Pástor;Milan Lacko;Róbert Žatkovič;
      Pages: 6012 - 6023
      Abstract: Soft switching pulse-width modulation (PWM) dc-dc full-bridge converter with controlled rectifier on the secondary side of the high-frequency power transformer is presented in this paper. An active secondary switch, including new nondissipative passive energy recovery turn-off snubber on the secondary side and modified PWM control algorithm, provide conditions for zero-voltage and zero-current turn-on and zero-current turn-off of IGBT transistors on the primary side of the high-frequency dc-dc converter. The simple passive energy recovery snubber ensures also zero-voltage turn-off of the transistor on the secondary side of the power transformer. The principle of operation is explained and analyzed and consequently verified on a 2 kW, 50 kHz laboratory model of the converter.
      PubDate: July 2018
      Issue No: Vol. 33, No. 7 (2018)
       
  • Resonant Multi-input/Multi-output/Bidirectional ZCS Step-Down DC--DC
           Converter With Systematic Synthesis for Point-to-Point Power Routing
    • Authors: Masoud Jabbari;Mozafar Sharifian Dorcheh;
      Pages: 6024 - 6032
      Abstract: A new resonant zero-current switching (ZCS) multi-input/multi-output (MIMO) converter is presented. The proposed converter routes power from every desired input port to every desired output port independently. Capability of bidirectional operation is also provided. All semiconductor devices operate under the soft-switching conditions independent from operating voltage and output power. Power budgeting for the inputs, individually voltage regulation for the outputs, and internal voltage balancing for the bidirectional ports are attained with few power-element count. The system is synthesized systematically based on a topology belonging to the family of switched-resonator converters (SwRCs). No transformer is utilized, and common ground exists between all ports. The concept of route matrix is developed to determine the power multiplexing paths. This method greatly simplifies the analysis, design, and control of the proposed system. Mathematical formulation based on route matrix is given in detail. Circuit analysis, design procedure, and five different designs along with simulation and experimental results are presented.
      PubDate: July 2018
      Issue No: Vol. 33, No. 7 (2018)
       
  • Voltage Gain Improvement of a High-Step-Down Converter With
           Coupled-Inductor Core Size Reduction Based on Flux Linkage
    • Authors: Kuo-Ing Hwu;Wen-Zhuang Jiang;
      Pages: 6033 - 6047
      Abstract: As compared with the buck converter, the ultrahigh step-down converter can achieve a much higher step-down gain, which can be determined by not only the duty cycle, but also the turns ratio of the coupled inductor. However, this converter suffers from some problems, such as pulsating output current and large dc magnetizing inductance current, which will degrade the core utilization. As compared with the ultrahigh step-down converter, the coupled-inductor-based high step-down converter features a nonpulsating output current and a zero dc magnetizing inductance current. Therefore, the output current ripple is lower and the core utilization can be upgraded. Since the core size is proportional to the square of the applied flux-linkages, an improved coupled-inductor-based high step-down converter is presented herein. By employing an auxiliary circuit, consisting of a small capacitor and a mosfet, the flux linkage of the coupled inductor can be decreased, and hence the required core size can be reduced. In addition, due to the auxiliary circuit, the voltage spike across the tapped switch can be reduced. Above all, the step-down gain can be improved. Finally, detailed theoretical analyses and experimental results are provided to verify the feasibility and effectiveness of the proposed converter.
      PubDate: July 2018
      Issue No: Vol. 33, No. 7 (2018)
       
  • Influence of Temperature on the Pressure Distribution Within Press Pack
           IGBTs
    • Authors: Erping Deng;Zhibin Zhao;Zhongkang Lin;Ronggang Han;Yongzhang Huang;
      Pages: 6048 - 6059
      Abstract: Press pack (PP) packaging technology has been applied to insulated-gate bipolar transistors (IGBTs) for high-voltage and high power density applications in recent years. The pressure distribution within PP IGBTs is very important because it affects both the electrical and thermal contact resistances, thermal cycling capability, and short-circuit current rating. Too much pressure will mechanically damage the chip and too little pressure will increase the thermal contact resistance, which eventually leads to chip thermal damage. In this paper, a finite-element multiphysics model cocoupled with an electrical field, thermal field, and mechanical field is proposed to analyze the collector current distribution, pressure distribution, and junction temperature distribution within PP IGBTs. The most important coupling variables, such as electrical and thermal contact resistances, for this cocoupled multiphysics model are calculated or measured by experiment through a single IGBT/fast-recovery diode chip submodule. Based on this multiphysics model, the influence of the high temperature generated by the chip's power dissipation on the pressure distribution within PP IGBTs (in the heating phase) is discussed, and then, compared with the pressure distribution in the clamping phase. The results show that the pressure distribution within PP IGBTs in the heating phase is extremely uneven and different from the value in the clamping phase. Furthermore, the mechanical model and its boundary conditions are verified through the pressure distribution experimental results in the clamping phase, which is measured based on the Fuji prescale film and the clamping test bench. Based on the simulation and experimental results, an optimization of the collector electrode and pedestal is proposed to improve the pressure distribution within PP IGBTs in the heating phase.
      PubDate: July 2018
      Issue No: Vol. 33, No. 7 (2018)
       
  • Investigation of Spatial Harmonic Magnetic Field Coupling Effect on Torque
           Ripple for Multiphase Induction Motor Under Open Fault Condition
    • Authors: Wubin Kong;Min Kang;Dawei Li;Ronghai Qu;Dong Jiang;Chun Gan;
      Pages: 6060 - 6071
      Abstract: This paper investigates spatial harmonic magnetic field coupling effect on torque ripple for multiphase induction motor under open fault condition. The coupling results in severe torque ripple generated by ellipse asynchronous magnetomotive force, and the current space vectors are utilized for coupling phenomenon analysis in the multiple planes. The optimal current space vector is proposed to achieve the minimum torque ripple, and the traditional method is used for comparison. Both fundamental and harmonic current space vectors are derived, when single-phase and two-phase open fault conditions are analyzed, respectively. Furthermore, the proportional integral resonant controller is used to realize zero-error tracking, and proper values of parameters in the transfer function are derived. Finally, a five-phase variable speed drive system is constructed and the proposed method is validated by experiments.
      PubDate: July 2018
      Issue No: Vol. 33, No. 7 (2018)
       
  • An Ultralow Loss Inductorless $dv/dt$ Filter Concept for
           Medium-Power Voltage Source Motor Drive Converters With SiC Devices
    • Authors: Erik Velander;Georg Bohlin;Åsa Sandberg;Thomas Wiik;Fredrik Botling;Martin Lindahl;Giovanni Zanuso;Hans-Peter Nee;
      Pages: 6072 - 6081
      Abstract: In this paper, a novel $dv/dt$ filter is presented targeted for 100-kW to 1-MW voltage source converters using silicon carbide (SiC) power devices. This concept uses the stray inductance between the power device and the converter output as a filter component in combination with an additional small RC-link. Hence, a lossy, bulky, and costly filter inductor is avoided and the resulting output $dv/dt$ is limited to 5–10 kV/$mu$s independent of the output current and switching speed of the SiC devices. As a consequence, loads with $dv/dt$ constraints, e.g., motor drives can be fed from SiC devices enabling full utilization of their high switching speed. Moreover, a filter-model is proposed for the selection of filter component values for a certain $dv/dt$ requirement. Finally, results are shown using a 300-A 1700-V SiC metal–oxide–semiconductor field-effect transistor (mosfet). These results show that the converter output $dv/dt$ can be limited to 7.5 kV/ $mu$s even though values up to 47 kV/ $mu$s were measured across the SiC mosfet module. Hence, the total switching losses, including the filter losses, are verified to be three times lower compared to when the mosfet $dv/dt$ was slowed down by adjusting the gate driver.
      PubDate: July 2018
      Issue No: Vol. 33, No. 7 (2018)
       
  • A Prediction-Based Current Sampling Scheme Using Three Resistors for
           Induction Motor Drives
    • Authors: Ziyi Li;Qiang Gao;
      Pages: 6082 - 6092
      Abstract: In the traditional three-resistor-based current sampling scheme, the sampled currents will become inaccurate when the duration of zero-voltage vectors of an inverter is too short, which leads to a limited modulation index (MI). To overcome this problem, an improved three-resistor sampling method is proposed by establishing a predictive current model of an inverter load, which is that of an induction motor on the synchronous rotating frame for the demonstration purpose in this paper. The principle of this method is detailed in the paper. Then a simulation model of a vector-controlled induction motor drive that utilizes the proposed current sampling scheme is built in the Simulink environment. Finally, the experiment on the new sampling scheme is performed in both steady-state and dynamic conditions. The results verify that the existing current sampling problems can be solved effectively and the motor can perform well with higher MI under the new scheme. As a result, the loading capacity of the system can be enhanced notably.
      PubDate: July 2018
      Issue No: Vol. 33, No. 7 (2018)
       
  • Comparison of Tripolar and Circular Pads for IPT Charging Systems
    • Authors: Seho Kim;Grant A. Covic;John T. Boys;
      Pages: 6093 - 6103
      Abstract: Recently, a magnetic pad called the tripolar pad (TPP) has been introduced for inductive power transfer (IPT) systems. This paper evaluates the effective coupling factor and leakage magnetic field of a 20-kW IPT system that uses a combination of TPP and circular pad (CP) topologies over a range of lateral displacements. The results show that the effective coupling factor and the leakage magnetic field of the TPP-TPP system are substantially better when the secondary is displaced away from ideal alignment. Leakage magnetic field is reduced up to 43% compared to the CP-CP system at the worst-case misalignment, which is due to the ability of the TPP-TPP system to generate and capture different types of magnetic field shapes. Simulation methods for both the TPP and CP are validated in the laboratory using a 2-kW system operating at 85 kHz.
      PubDate: July 2018
      Issue No: Vol. 33, No. 7 (2018)
       
  • A Combining FPE and Additional Test Vectors Hybrid Strategy for IPMSM
           Sensorless Control
    • Authors: Xin Luo;Qipeng Tang;Anwen Shen;Hanlin Shen;Jinbang Xu;
      Pages: 6104 - 6113
      Abstract: This paper proposes a hybrid strategy by combining fundamental pulsewidth modulation excitation (FPE) and additional test vectors, which is used in interior permanent-magnet synchronous motor (IPMSM) sensorless control. In contrast to the typical indirect flux detection by on-line reactance measurement-based methodology where the rotor position is calculated and updated in every three successive pulsewidth modulation (PWM) cycles, the proposed hybrid strategy can achieve the one-cycle acquisition of the rotor position by utilizing both response currents of FPE and additional test vectors, which makes the proposed strategy more robust and suitable in higher speed or load sudden change conditions. Meanwhile, a new PWM scheme for four-space-vector PWM (FSVPWM) is presented, which sharply simplifies the implementation process. Furthermore, for the case that the amplitude of the object fundamental voltage is so small that it cannot satisfy minimum time demand for the slopes of response currents sampling, a compensation technique is presented. In addition, the multiple-point current sampling (MPCS) technology and linear least square fitting method are used to decrease the current sampling disturbance, which improves obviously the accuracy of position estimation. Finally, the experimental results confirm that the proposed strategy can obtain the rotor position accurately and simply.
      PubDate: July 2018
      Issue No: Vol. 33, No. 7 (2018)
       
  • Development of a Prime Mover Emulator Using a Permanent-Magnet Synchronous
           Motor Drive
    • Authors: Po-Yen Chen;Kai-Wei Hu;Yi-Guang Lin;Chang-Ming Liaw;
      Pages: 6114 - 6125
      Abstract: This paper presents the development of a surface-mounted permanent-magnet synchronous motor (SPMSM) drive for constructing the prime mover emulators. It draws power from the mains via a single-phase boost type switch mode rectifier (SMR) with good line drawn power quality and well-regulated dc-link voltage. The SPMSM drive control scheme can be arranged to drive the tested generator in a conventional speed control mode or a specific wind turbine torque-speed control mode. For performing the prime mover loading test, an interior permanent-magnet synchronous generator (IPMSG) followed by a three-phase Vienna SMR is established. It receives the mechanical driven power from the prime mover and establishes a 400 V dc-link for a dc microgrid. Various wind turbine torque-speed characteristic curves under different wind speeds can be faithfully emulated by the developed prime mover. And the maximum power point tracking function for the IPMSG followed by Vienna SMR is achieved using the perturb and observation method. The established whole prime mover emulator driven IPMSG system is evaluated experimentally under autonomous and microgrid interconnected operation.
      PubDate: July 2018
      Issue No: Vol. 33, No. 7 (2018)
       
  • An Improved IGBT Short-Circuit Protection Method With Self-Adaptive
           Blanking Circuit Based on V CE Measurement
    • Authors: Min Chen;Dehong Xu;Xingyao Zhang;Nan Zhu;Junxiong Wu;Kaushik Rajashekara;
      Pages: 6126 - 6136
      Abstract: IGBT short-circuit protection is the key factor to improve the reliability of the power electronics system. The conventional short-circuit protection method based on $V_{CE}$ measurement detects the collector–emitter voltage of an IGBT to determine whether the IGBT short-circuit fault occurs. The blanking circuit is needed in this kind of protection method to avoid the false triggering of the short-circuit protection during IGBT turn-on transient. However, this blanking circuit should be carefully designed for different types of IGBT modules. In order to make the IGBT short-circuit protection circuit suitable for the tolerance of IGBT modules, a self-adaptive blanking circuit combined with the aforementioned short-circuit protection method based on $V_{CE}$ measurement is proposed. The proposed method is achieved by feeding back the required minimum blanking time interval which is decided by comparing the desaturation reference voltage with the collector–emitter voltage. The short-circuit protection delay time for the conventional circuit and the proposed circuit are compared. Experimental results are included to prove the effectiveness of the proposed circuit.
      PubDate: July 2018
      Issue No: Vol. 33, No. 7 (2018)
       
  • Communication Functions for a Gate Driver Under High Voltage and High
           dv/dt
    • Authors: Christophe Bouguet;Nicolas Ginot;Christophe Batard;
      Pages: 6137 - 6146
      Abstract: The control of mosfet or IGBT transistors is carried out by a dedicated circuit called « driver », which is located as close as possible to the power module. It transmits switch-on and switch-off orders coming from the control unit and ensures the integrity of the component through safety functions. It also provides a galvanic isolation essential to guarantee the effective functioning of the system and the users’ safety. Switching times of SiC mosfet are faster than Si IGBT, and SiC mosfet can also work under a greater dc voltage than Si mosfet. This involves the presence of higher dv/dt in the converter. In this paper, a communication function is studied to be integrated into the new generations of drivers for SiC mosfet . The interest of the implementation of a communication system in a driver is presented. Currently available solutions on the market to provide isolation to communication channels are debated. The theoretical development of a solution called « CAN-ISO » is detailed and experimental results under a high peak voltage of 2 kV and a high dv/dt equal to ${text{125}};{text{kV}}/{mu}{text{s}}$ are presented.
      PubDate: July 2018
      Issue No: Vol. 33, No. 7 (2018)
       
  • Analytical Technique for Evaluating Stray Capacitances in Multiconductor
           Systems: Single-Layer Air-Core Inductors
    • Authors: Luiz Fernando de Freitas Gutierres;Ghendy Cardoso;
      Pages: 6147 - 6158
      Abstract: This paper presents a procedure for evaluating self-capacitances and parasitic capacitors between physically adjacent turns in multiconductor systems—with a special focus on single-layer air-core inductors. To this end, the paper proposes the use of standard cells, which correspond to a minimal and basic turn, layer, or macrolevel arrangement of a winding in reference to its patterns of stored electrostatic energy. A standard cell embraces mathematical rules derived by means of a curve fitting approach through a set of finite element analysis (FEA) simulations. Besides, it is applied in a matching routine wherein self- and stray capacitances are evaluated according to the relative position of each turn, layer, or macrolevel arrangement along the length of the winding. Finally, the analytical technique is validated by comparing frequency-domain results obtained from an implemented SPICE model and laboratory measurements.
      PubDate: July 2018
      Issue No: Vol. 33, No. 7 (2018)
       
  • Single-Phase LED Drivers With Minimal Power Processing, Constant Output
           Current, Input Power Factor Correction, and Without Electrolytic Capacitor
           
    • Authors: Hao Wu;Siu-Chung Wong;Chi K. Tse;S. Y. Ron Hui;Qianhong Chen;
      Pages: 6159 - 6170
      Abstract: High-power light-emitting diodes (LEDs) having properties of high luminous efficacy and long life span are becoming a major light source for general illumination. To fully utilize the advantages of LED in lighting applications, the offline power supply that drives the LED should possess the following features: high efficiency, long life span, high input power factor, and (COC). In this paper, high efficiency is achieved by using a minimal power processing (MPP) configuration. Near perfect power factor correction (PFC) is achieved by a simple dual-output disc-ontinuous-conduction-mode (DCM) pulse-width-modulated (PWM) front-end converter. One output of the front-end converter is connected to the LED load using a control switch. The other output is connected directly to a dc storage capacitor cascaded with a downstream DCM PWM converter driving the same LED load to achieve COC driving. The power flow is controlled to achieve the required MPP that can also reduce the storage capacitance by balancing only the ac input ripple power and the dc output power without power recycling. Thus, the design requires no electrolytic capacitor, hence extending the system life span. The achievement of input PFC, MPP, and COC requires design tradeoff among design freedom, ease of control and component count. LED drivers having all these properties are developed, designed, and tested.
      PubDate: July 2018
      Issue No: Vol. 33, No. 7 (2018)
       
  • Switched-Capacitor-Based Current Compensator for Mitigating the Effect of
           Long Cable Between PWM Driver and LED Light Source
    • Authors: Rui Zhou;Ryan Shun-cheung Yeung;John Yau-chung Chan;Norman Chung-fai Tse;Henry Shu-hung Chung;
      Pages: 6171 - 6186
      Abstract: It is sometimes unavoidable to have light-emitting-diode (LED) light sources and their pulsewidth modulation (PWM) drivers connected by long cables in large-scale illuminations. However, long-cable inductance delays the rate of rise of the driving current pulses and thus leads to the reduction of luminous flux output. It also causes the off-state voltage across the light sources negative, which would deteriorate the life expectancy of the LEDs. A switched-capacitor-based current compensator for correcting the wave shape of the driving current pulses is presented. The methodology is based on transferring the energy stored in the cable to a capacitor at the end of the current pulse and then momentarily boosting the voltage with the capacitor applying to the cable at the beginning of the next current pulse. Thus, the rise time of the current pulses can be shortened. The topological states and operations of the compensator will be described. A simplified design procedure will be given. A prototype for a 12-V, 3-A PWM driver has been built and evaluated. Performance comparisons between the proposed current compensator and prior art and between the systems with and without the compensators will be conducted.
      PubDate: July 2018
      Issue No: Vol. 33, No. 7 (2018)
       
  • A Constant-on-Time Control DC–DC Buck Converter With the Pseudowave
           
    • Authors: Wen-Hau Yang;Chao-Jen Huang;Han-Hsiang Huang;Wei-Ting Lin;Ke-Horng Chen;Ying-Hsi Lin;Shian-Ru Lin;Tsung-Yen Tsai;
      Pages: 6187 - 6198
      Abstract: Constant-on-time (COT) control with an additional current feedback path in conventional buck converters can remove the need of large equivalent series resistance (ESR) at the output capacitor but it induces degraded output voltage regulation accuracy and slow transient response owing to opposite reaction between the output voltage and the additional current feedback information. Therefore, this paper proposes the pseudowave tracking (PWT) technique to reduce the load-dependent dc offset voltage of output load regulation while keeping the fast transient response similar to conventional COT buck converter with large ESR. The PWT technique further improves the transient response instantly by extending on-time and off-time periods during light-to-heavy and heavy-to-light load changes, respectively. The test chip fabricated in 28 nm CMOS process has demonstrated the improvement of offset voltage from 42 to 4 mV, while the transient response can be improved to 4 and 5 μs with load changes from 0.3 to 1.7 A and vice versa, respectively.
      PubDate: July 2018
      Issue No: Vol. 33, No. 7 (2018)
       
  • A High-Bandwidth Integrated Current Measurement for Detecting Switching
           Current of Fast GaN Devices
    • Authors: Kangping Wang;Xu Yang;Hongchang Li;Laili Wang;Praveen Jain;
      Pages: 6199 - 6210
      Abstract: Gallium nitride (GaN) devices are suitable for high-frequency power converters due to their excellent switching performance. To maximize the performance of GaN devices, it is necessary to study the switching characteristics, which requires measuring the switching current. However, GaN devices have a fast switching speed and are sensitive to parasitic parameters, so the current measurement should have a high bandwidth and should not introduce excessive parasitic inductance into the power converters. Traditional current measurements are difficult to meet these requirements, especially for fast GaN devices. This paper presents a high-bandwidth integrated current measurement for detecting the switching current of fast GaN devices. By effectively utilizing the parasitic inductance in the circuit, a single-turn coil is embedded in the printed circuit board. This coil could pick up a sufficiently strong voltage signal, which is then processed to reconstruct the switching current. Moreover, corrections are carried out to further improve the accuracy. The current measurement has a small insertion impedance and a high bandwidth with a small influence on the parasitic inductance of the converter. The accuracy of the current measurement is experimentally verified by a 40 V GaN-based double pulse test circuit with a load current up to 25 A.
      PubDate: July 2018
      Issue No: Vol. 33, No. 7 (2018)
       
  • Thermal Impedance Meter for Power mosfet and IGBT Transistors
    • Authors: Vitaliy Ivanovich Smirnov;Viacheslav Andreevich Sergeev;Andrey Anatolievich Gavrikov;Anton Mihailovich Shorin;
      Pages: 6211 - 6216
      Abstract: Modulation method and the device for thermal impedance measuring of power mosfets and IGBT transistors, and measurement results are described. The measurements were performed by generic modulation method that implies heating a device under test by power varying harmonically. A pulse sequence of heating current, with the pulse length varying harmonically, is passed through the device under test. The p-n junction temperature is determined by measuring a temperature-sensitive parameter, which is forward voltage drop on the p-n junction between heating pulses at low measuring current. Analysis of the dependence of thermal impedance on modulation frequency allows us to determine thermal impedance components corresponding to the structural elements of the object under test. The method allows us to significantly reduce the effect of heating the device's case during the measurement, and thereby increase the accuracy of thermal resistance measurement.
      PubDate: July 2018
      Issue No: Vol. 33, No. 7 (2018)
       
  • Separation of Wear-Out Failure Modes of IGBT Modules in Grid-Connected
           Inverter Systems
    • Authors: Ui-Min Choi;Frede Blaabjerg;
      Pages: 6217 - 6223
      Abstract: Wear-out condition monitoring of IGBT modules with failure mode separation gives some benefits. First, it allows proactive maintenance plans. Further, depending on the failure mode, different proactive control strategies can be applied to inverters in order to improve the reliability and availability of power electronic systems. This paper proposes a new method for the separation of two representative wear-out failure modes of wire-bonded IGBT modules in a grid-connected inverter in real time. The proposed method requires just two preliminary I- V characterizations of IGBT modules. Further, only one monitoring parameter is used, and thus, it is cost-effective compared with using one more monitoring parameter in order to separate failure modes. Experimental results verify the validity and feasibility of the proposed method.
      PubDate: July 2018
      Issue No: Vol. 33, No. 7 (2018)
       
  • An Isolated Quasi-Resonant Multiphase Single-Stage Topology for 48-V VRM
           Applications
    • Authors: Stefano Saggini;Osvaldo Zambetti;Roberto Rizzolatti;Massimiliano Picca;Paolo Mattavelli;
      Pages: 6224 - 6237
      Abstract: In order to increase the efficiency of modern microprocessors power supplies used in data centers, the 48-V dc distribution bus is gaining growing attention. For such applications, voltage regulation modules (VRMs) are currently obtained using two-stage conversion systems with an intermediate 12-V dc bus. This paper presents an innovative single-stage approach for the 48-V VRM based on a quasi-resonant constant on-time (COT) operation. The proposed topology inherently integrates the multiphase approach, providing fast phase shedding and flat high-efficiency curves even at light load conditions. This is a unique advantage, usually not available in the two-stage approach, that is very important in server architectures, where high efficiency is required even at light load conditions. The paper analyses the circuit topology, and proposes a control architecture for fast transient response, including the current sharing capabilities, and a solution for implementing the integrated magnetics. The digital controller has been implemented in 0.16-$mu$ m lithography together with a digital pulse-width-modulation with a 195 ps resolution, and a 40 MS/s, 7-bit ADC. Experimental results show an efficiency of 93.1% for a 250 A, 1.8 V VRM, and of 93.2% for a 102 A, 1.2-V double data rate (DDR) power supply.
      PubDate: July 2018
      Issue No: Vol. 33, No. 7 (2018)
       
  • Optimized Switching Repetitive Control of CVCF PWM Inverters
    • Authors: Yongqiang Ye;Guofeng Xu;Yuheng Wu;Qiangsong Zhao;
      Pages: 6238 - 6247
      Abstract: In this paper, a novel optimized switching repetitive control (OSRC) scheme is developed and applied to a constant-voltage constant-frequency pulse width modulation inverter to enhance the stability and tracking performance with low sampling frequency. In OSRC, a switching integral phase lead compensator is applied to enlarge the stability margin, which is impaired by the phase lag of the inverter system. With the optimized switching strategy, the stable region can be much wider, which means that a larger robust filter Q can be applied to reduce the tracking error. The stability analysis and optimized design procedure are also given. Comparative experiments in different load situations are performed to demonstrate the validity of the proposed scheme.
      PubDate: July 2018
      Issue No: Vol. 33, No. 7 (2018)
       
  • Mitigation of Grid-Current Distortion for LCL-Filtered Voltage-Source
           Inverter With Inverter-Current Feedback Control
    • Authors: Zhen Xin;Paolo Mattavelli;Wenli Yao;Yongheng Yang;Frede Blaabjerg;Poh Chiang Loh;
      Pages: 6248 - 6261
      Abstract: LCL filters feature low inductance; thus, the injected grid current from an LCL -filtered voltage-source inverter can be easily distorted by grid-voltage harmonics. This problem is especially tough for the control system with inverter-side current feedback (ICF), since the grid-current harmonics can freely flow into the filter capacitor. In this case, because of the loss of harmonic information, traditional harmonic controllers fail to mitigate the grid-current distortion. Although this problem may be avoided using the grid-voltage feedforward scheme, the required differentiators may cause the noise amplification. In light of the above issue, this paper develops a simple method for the ICF control system to mitigate the grid-current harmonics without extra sensors. In the proposed method, resonant harmonic controllers and an additional compensation loop are adopted at the same time. The potential instability introduced by the compensation loop can be avoided through a special design of the compensation position. Finally, the effectiveness of the proposed method for harmonic rejection is verified by detailed experimental results.
      PubDate: July 2018
      Issue No: Vol. 33, No. 7 (2018)
       
  • An Integral Droop for Transient Power Allocation and Output Impedance
           Shaping of Hybrid Energy Storage System in DC Microgrid
    • Authors: Pengfeng Lin;Peng Wang;Jianfang Xiao;Junjun Wang;Chi Jin;Yi Tang;
      Pages: 6262 - 6277
      Abstract: Power allocation in hybrid energy storage systems (HESSs) is an important issue for dc microgrids. In this paper, an integral droop (ID), inspired by the electrical characteristics of capacitor charging/discharging process, is proposed and applied to a cluster of energy storages (ESs) with high ramp rates. Through the coordination of the ID and conventional V-P droop, the transient power allocation in HESSs can be intrinsically realized in a decentralized manner. The high-frequency components of power demand can be compensated by the ESs with ID, whereas the ESs with V-P droop respond to the smooth change of load power. Additionally, the ID coefficient can be designed according to the nominal ramp rate of the ESs with slow response, which helps to extend the lifespan of the HESS. On the other hand, to easily assess the stability of the system feeding constant power loads, a minimum relative impedance criterion (MRIC) is developed. Based on MRIC, it is revealed that the proposed ID can shape the output impedance of the HESS and stabilize the entire system. The feasibility and effectiveness of ID are verified by both simulations and experimental results.
      PubDate: July 2018
      Issue No: Vol. 33, No. 7 (2018)
       
  • Buck–Boost Dual-Leg-Integrated Step-Up Inverter With Low THD and Single
           Variable Control for Single-Phase High-Frequency AC Microgrids
    • Authors: Ling Qin;Mao Hu;Dylan Dah-Chuan Lu;Zhiqiang Feng;Yafang Wang;Jiarong Kan;
      Pages: 6278 - 6291
      Abstract: To support the development of high-frequency ac microgrids in terms of compact design, high-voltage gain and low total harmonic distortion (THD), a buck–boost dual-leg-integrated step-up inverter is proposed in this paper. The inverter is formed by integrating a buck–boost converter into a conventional single-phase full-bridge inverter by sharing the upper switch and the body diode of the lower switch in both bridge-legs. Consequently, the component count is significantly reduced over the step-up inverter counterparts. In addition, to address the drawbacks of hybrid modulation methods adopted by existing dual-leg-integrated inverters, such as double-variable control, and high THD of output voltage/current at high input voltage and heavy load conditions, unipolar frequency doubling sinusoidal pulse width modulation scheme is adopted in this inverter. As a result, the modulation ratio M becomes the only control variable to regulate the output voltage/current and the control is simplified. The THD of the proposed inverter output can remain low throughout the entire input voltage range and load power range. This paper presents the topology derivation procedure, operation principle, and steady-state characteristics of the proposed inverter. To validate the effectiveness of theory, experimental results of a 400 W hardware prototype, where the output voltage frequency is at 500 Hz, are reported.
      PubDate: July 2018
      Issue No: Vol. 33, No. 7 (2018)
       
  • Limitations and Accuracy of a Continuous Reduced-Order Model for Modular
           Multilevel Converters
    • Authors: Andres M. Lopez;Daniel E. Quevedo;Ricardo P. Aguilera;Tobias Geyer;Nikolaos Oikonomou;
      Pages: 6292 - 6303
      Abstract: This paper analyzes the limitations of a reduced-order model for modular multilevel converters (MMCs) by elucidating the relation between its accuracy, operating frequency, and converter parameters. A reduced-order simplifies the analysis of the MMC and thereby may provide additional information about the converter behavior. However, the accuracy of such model depends on several factors. In this paper, the effect of approximating the converter as a continuous system by neglecting quantization issues associated with having a finite number of modules is studied in detail. The analysis is done based on Fourier-series approximations with which it is possible to elucidate the relationship between the resonant frequencies of the MMC and the error of the reduced-order model. With the Fourier approximation, it is also possible to characterize resonant frequencies of the converter, both numerically and analytically, in terms of the converter parameters. The results can serve as a tool to identify situations when the reduced-order model produces good and also less accurate approximations especially when a low number of modules is available.
      PubDate: July 2018
      Issue No: Vol. 33, No. 7 (2018)
       
  • Model Predictive Control of Power Converters for Robust and Fast Operation
           of AC Microgrids
    • Authors: Tomislav Dragičević;
      Pages: 6304 - 6317
      Abstract: This paper proposes the application of a finite control set model predictive control (FCS-MPC) strategy in standalone ac microgrids (MGs). AC MGs are usually built from two or more voltage source converters (VSCs) which have the capability of regulating the voltage at the point of common coupling, while sharing the load power at the same time. Those functionalities are conventionally achieved by hierarchical linear control loops. However, they present severe limitations in terms of slow transient response and high sensitivity to parameter variations. This paper aims to mitigate these problems by first introducing an improvement of the FCS-MPC strategy for a single VSC that is based on explicit tracking of derivative of the voltage reference trajectory. Using only a single step prediction horizon, the proposed strategy exhibits very low computational expense, but provides steady-state performance comparable to carrier-based sinusoidal PWM, while its transient response and robustness to parameter variation is far superior to hierarchical linear control. These benefits are exploited in a general ac MG setting where a methodology for paralleling multiple FCS-MPC regulated VSCs is described. Such an MG is characterized by rapid transient response, inherent stability in all operating conditions, and fully decentralized operation of individual VSCs. These findings have been validated through comprehensive simulation and experimental verification.
      PubDate: July 2018
      Issue No: Vol. 33, No. 7 (2018)
       
  • Analysis and Control of Direct Voltage Regulated Active DC-Link
           Capacitance Reduction Circuit
    • Authors: Martin Mellincovsky;Vladimir Yuhimenko;Mor Mordechai Peretz;Alon Kuperman;
      Pages: 6318 - 6332
      Abstract: The paper focuses on control analysis and operational issues of a recently proposed direct voltage regulated active capacitance reduction circuit, consisting of a small auxiliary capacitance interfaced to dc link by bidirectional dc-dc converter. The aim of such a system is replacing the bulk dc bus capacitor without escalating the ripple. While the hardware of the system under study is similar to some of the proposed active capacitance reduction solutions, the control structure is quite different. The primary goal of the controller is direct regulation of dc-link voltage rather than dc-link current, performed by most of existing solutions, thus avoiding the use of invasive dc-link current measurement/s. It is revealed that such an active capacitance reduction circuitry may be perceived as output-voltage regulated wide-input-range converter feeding a bidirectional power load. Such an arrangement was neither mentioned nor analyzed in the literature by far, requiring nontrivial and challenging control design. A dual-loop voltage-current arrangement widely used in typical power supplies is proposed to control the active capacitance reduction circuitry. It is shown that the control structure is sufficient to yield satisfactory performance even though the system possesses a slow unstable mode when absorbing power from the dc link. The revealed findings are fully supported by simulations and experimental results.
      PubDate: July 2018
      Issue No: Vol. 33, No. 7 (2018)
       
  • Stability Analysis of Digital-Controlled Single-Phase Inverter With
           Synchronous Reference Frame Voltage Control
    • Authors: Yang Han;Xu Fang;Ping Yang;Congling Wang;Lin Xu;Josep M. Guerrero;
      Pages: 6333 - 6350
      Abstract: Stability analysis of single-phase power converters controlled in stationary reference frame is now mature and well developed, by using either linear or nonlinear methods. However, for the single-phase converters with synchronous reference frame (SRF) control loops, little work has been done on the evaluation of the nonlinear approaches for stability analysis. In this paper, the stability of a digital-controlled single-phase voltage-source inverter (VSI) with SRF voltage control loop is investigated from the perspective of nonlinear system. The analysis is based on the discrete-time model defined by the stroboscopic map, which is derived using the state-space averaging (SSA) technique. Furthermore, two different nonlinear analysis methods, the Jacobian matrix method and the Lyapunov exponent method, are adopted to analyze the fast-scale stability and the slow-scale stability of the pulsewidth-modulated (PWM) inverter under variations of control parameters; hence, the stability regions can be obtained. The theoretical results indicate that, for the established stroboscopic models, the Jacobian matrix method and the Lyapunov exponent method are mathematically equivalent, which means that the fast-scale stability and the slow-scale stability of the studied single-phase VSI are consistent, especially under linear load conditions. Experimental results under resistive load, inductive-resistive load, and diode rectifier load conditions are presented to support the theoretical results, which also proves that the discrete-time model plus the Jacobian matrix method or the Lyapunov exponent method is capable to investigate the stability of a converter with SRF control loops accurately.
      PubDate: July 2018
      Issue No: Vol. 33, No. 7 (2018)
       
  • Dynamic Improvement of Series–Series Compensated Wireless Power Transfer
           Systems Using Discrete Sliding Mode Control
    • Authors: Yun Yang;Wenxing Zhong;Sitthisak Kiratipongvoot;Siew-Chong Tan;Shu Yuen Ron Hui;
      Pages: 6351 - 6360
      Abstract: This paper presents a discrete sliding mode control (DSMC) scheme for a series-series compensated wireless power transfer (WPT) system to achieve fast maximum energy efficiency (MEE) tracking and output voltage regulation. The power transmitter of the adopted WPT system comprises a dc/ac converter, which incorporates the hill-climbing-search-based phase angle control in achieving minimum input current injection from its dc source, thereby attaining minimum input power operation. The power receiver comprises a buck-boost converter that emulates an optimal load value, following the MEE point determined by the DSMC scheme. With this WPT system, no direct communication means is required between the transmitter and the receiver. Therefore, the implementation cost of this system is potentially lower and annoying communication delays, which deteriorate control performance, are absent. Both the simulation and experiment results show that this WPT system displays better dynamic regulation of the output voltage during MEE tracking when it is controlled by DSMC, as compared to that controlled by the conventional discrete proportional-integral (PI) control. Such an improvement prevents the load from sustaining undesirable overshoot/undershoot during transient states.
      PubDate: July 2018
      Issue No: Vol. 33, No. 7 (2018)
       
  • Second-Harmonic Current Reduction for Two-Stage Inverter With
           Boost-Derived Front-End Converter: Control Schemes and Design
           Considerations
    • Authors: Li Zhang;Xinbo Ruan;Xiaoyong Ren;
      Pages: 6361 - 6378
      Abstract: The instantaneous output power of the two-stage single-phase inverter pulsates at twice the output frequency $(2f_{{rm{o}}})$, generating notorious second-harmonic current (SHC) in the front-end dc–dc converter and the input dc voltage source. This paper focuses on the SHC reduction for a two-stage single-phase inverter with boost-derived front-end converter. To reduce the SHC, a virtual series impedance, which has high impedance at $2f_{{rm{o}}}$ while low impedance at other frequencies, is introduced in series with the boost diode or the boost inductor to increase the impedance of the boost-diode branch or boost-inductor branch at $2f_{{rm{o}}}$. Meanwhile, for achieving good dynamic performance, a virtual parallel impedance, which exhibits infinite impedance at $2f_{{rm{o}}}$ while low impedance at other frequencies, is introduced in parallel with the dc-bus capacitor to reduce the output impedance of the boost-derived converter at the frequencies except for $2f_{{rm{o}}}$. The virtual series impedance is realized by the feedback of the boost-diode current or the boost-inductor current, while the virtual parallel impedance is implemented by the feedback of the dc-bus voltage. Based on the virtual-impedance approach, a variety of SHC reduction control schemes are derived. A step-by-step closed-loop parameters design approach with considerations of reducing the SHC and improving the dynamic performance is also proposed for the derived SHC reduction control schemes. Finally, a 1-kW prototype is built and tested, and experimental results are presented to verify the effectiveness of the propos-d SHC reduction control schemes.
      PubDate: July 2018
      Issue No: Vol. 33, No. 7 (2018)
       
  • Reconfigurable Wireless Power Transfer Systems With High Energy Efficiency
           Over Wide Load Range
    • Authors: Wenxing Zhong;S. Y. Hui;
      Pages: 6379 - 6390
      Abstract: Optimum energy efficiency in a wireless power transfer (WPT) system usually occurs only at a specific load value while the load such as a battery is normally not constant. A major challenge in WPT is, therefore, to achieve high energy efficiency over a wide load range. Previously, impedance transformation methods such as dc-dc converters and use of a relay coil have been used to transform the practical load resistance to the optimum (or near-optimum) value. In this paper, a new approach based on reconfigurable magnetic resonant structures is proposed to achieve high energy efficiency and low volt-amp ratings. This basic principle is to create more than one efficiency-load curve. The WPT system is controlled to be operated within the top regions of the energy efficiency curves of the reconfigurable circuits so that high energy efficiency can be achieved over a very wide load range. The principle of this new approach is explained with an analysis and verified with practical measurements.
      PubDate: July 2018
      Issue No: Vol. 33, No. 7 (2018)
       
  • A Dual-Coupled LCC-Compensated IPT System With a Compact Magnetic Coupler
    • Authors: Fei Lu;Hua Zhang;Heath Hofmann;Wencong Su;Chunting Chris Mi;
      Pages: 6391 - 6402
      Abstract: This paper proposes a dual-coupled LCC-compen-sated inductive power transfer system with a compact magnetic coupler to improve misalignment performance. In the magnetic coupler, the main coils form the first coupling, and compensation inductors are integrated with the main coils to form a second coupling. In the design presented in this paper, the main coils are unipolar and the compensation inductors are in a Double D structure. The fundamental harmonics approximation method is used to analyze the circuit, and the couplings between the main coils and compensation inductors are considered to determine the net power flow. In misalignment cases, it is shown that the coupling between the compensation inductors, and the cross couplings between the compensation inductors and main coils, contribute to increasing the system power. A 3.5 kW prototype is designed and implemented to validate the proposed dual-coupled system. The primary coil size is ${text{450 mm}times text{450 mm}}$, and the secondary coil size is ${text{300 mm}times text{300 mm}}$. Experimental results show that the proposed dual-coupled system can significantly improve the misalignment performance, and retains at least 56.8% and 82.6% of the well-aligned power at 150 mm misalignment in the x- and y-directions, respectively.
      PubDate: July 2018
      Issue No: Vol. 33, No. 7 (2018)
       
  • Current-Sensorless VSC-PFC Rectifier Control With Enhance Response to
           Dynamic and Sag Conditions Using a Single PI Loop
    • Authors: Mario A. Santoyo-Anaya;Juan Ramón Rodríguez-Rodríguez;Edgar L. Moreno-Goytia;Vicente Venegas-Rebollar;N. M. Salgado-Herrera;
      Pages: 6403 - 6415
      Abstract: This paper presents the design, modeling, implementation, and experimental results of an advanced current-sensorless control scheme for voltage source converter-power factor correction rectifiers. This proposal is aimed to reduce the complexity of the control while maintaining desirable features for ac/dc conversion, such as unity power factor, low total harmonic distortion in input current, continuous regulation of the dc voltage even facing ac voltage sags and dynamic load changes. Unlike other proposals, this scheme has a single feedback proportional-integral loop, uses few mathematical operations, and the dq0 reference frame is not included in the control scheme. These characteristics simplify the implementation of the proposed control thus improving its efficiency. The theoretical analysis and simulation validate the technical feasibility of the proposed control, and finally, various cases of study and experimental results obtained with a laboratory scale-down prototype are presented to confirm the viability and performance of the control.
      PubDate: July 2018
      Issue No: Vol. 33, No. 7 (2018)
       
  • Distributed Nonlinear Control With Event-Triggered Communication to
           Achieve Current-Sharing and Voltage Regulation in DC Microgrids
    • Authors: Renke Han;Lexuan Meng;Josep M. Guerrero;Juan C. Vasquez;
      Pages: 6416 - 6433
      Abstract: A distributed nonlinear controller is presented to achieve both accurate current-sharing and voltage regulation simultaneously in dc microgrids (MGs) considering different line impedances effects among converters. Then, an improved event-triggered principle for the controller is introduced through combining the state-dependent tolerance with a nonnegative offset. In order to design the event-triggered principle and guarantee the global stability, a generalized dc MG model is proposed and proven to be positive definite, based on which Lyapunov-based approach is applied. Furthermore, considering the effects from constant power loads, the damping performance of proposed controller is further improved which is comparative with the traditional V-I droop controller. The proposed event-triggered-based communication strategy can considerably reduce the communication traffic and significantly relax the requirement for precise real-time information transmission, without sacrificing system performance. Experimental results obtained from a dc MG setup show the robustness of the new proposal under normal, communication failure and communication delay operation conditions. Finally, communication traffic under different communication strategies is compared, showing a drastic traffic reduction when using the proposed approach.
      PubDate: July 2018
      Issue No: Vol. 33, No. 7 (2018)
       
  • Smooth Reference Modulation to Improve Dynamic Response in Electric Drive
           Systems
    • Authors: Mehrdad Yazdanian;Ali Mehrizi-Sani;Roland R. Seebacher;Klaus Krischan;Annette Muetze;
      Pages: 6434 - 6443
      Abstract: Response overshoot is an undesired behavior that can be experienced by a dynamic system. Reduction of overshoot, without compromising the speed of the system response, increases the permissible operational range by enabling the system to operate closer to its limits. Previous work related to set point modulation proposed an effective strategy to improve set point tracking by temporarily modifying the set point based on the trend of the response and its proximity to the set point. However, this strategy is designed for solid-state units with no inertia and is not directly applicable to applications such as electric drive systems, in which frequent step changes in the set point may cause mechanical stress. This paper addresses this issue and proposes an alternate strategy based on continuous, rather than step, changes in the set point. The proposed approach is implemented for an electric drive system. Simulation and experimental results confirm the desirable performance of the proposed approach.
      PubDate: July 2018
      Issue No: Vol. 33, No. 7 (2018)
       
  • Virtual Variable Sampling Discrete Fourier Transform Based Selective
           Odd-Order Harmonic Repetitive Control of DC/AC Converters
    • Authors: Zhichao Liu;Bin Zhang;Keliang Zhou;Jingcheng Wang;
      Pages: 6444 - 6452
      Abstract: This paper proposes a frequency adaptive discrete Fourier transform (DFT) based repetitive control (RC) scheme for dc/ac converters. By generating infinite magnitude on the interested harmonics, the DFT-based RC offers a selective harmonic scheme to eliminate waveform distortion. The traditional DFT-based selective harmonic RC, however, is sensitive to frequency fluctuation since even very small frequency fluctuation leads to a severe magnitude decrease. To address the problem, the virtual variable sampling (VVS) method, which creates an adjustable virtual delay unit to closely approximate a variable sampling delay, is proposed to enable the DFT-based selective harmonic RC to be frequency adaptive. Moreover, a selective odd-order harmonic DFT filter is developed to deal with the dominant odd order harmonic. Because it halves the number of sampling delays in the DFT filter, the system transient response gets nearly a 50% improvement. A comprehensive series of experiments of the proposed VVS DFT-based selective odd-order harmonic RC controlled programmable ac power source under frequency variations are presented to verify the effectiveness of the proposed method.
      PubDate: July 2018
      Issue No: Vol. 33, No. 7 (2018)
       
 
 
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