for Journals by Title or ISSN
for Articles by Keywords

 A  B  C  D  E  F  G  H  I  J  K  L  M  N  O  P  Q  R  S  T  U  V  W  X  Y  Z  

       | Last   [Sort by number of followers]   [Restore default list]

  Subjects -> ELECTRONICS (Total: 154 journals)
Showing 1 - 200 of 277 Journals sorted alphabetically
Advances in Biosensors and Bioelectronics     Open Access   (Followers: 6)
Advances in Electrical and Electronic Engineering     Open Access   (Followers: 1)
Advances in Magnetic and Optical Resonance     Full-text available via subscription   (Followers: 8)
Advances in Microelectronic Engineering     Open Access   (Followers: 11)
Advances in Power Electronics     Open Access   (Followers: 23)
Aerospace and Electronic Systems, IEEE Transactions on     Hybrid Journal   (Followers: 202)
American Journal of Electrical and Electronic Engineering     Open Access   (Followers: 23)
Annals of Telecommunications     Hybrid Journal   (Followers: 7)
Archives of Electrical Engineering     Open Access   (Followers: 12)
Autonomous Mental Development, IEEE Transactions on     Hybrid Journal   (Followers: 7)
Bell Labs Technical Journal     Hybrid Journal   (Followers: 23)
Biomedical Engineering, IEEE Reviews in     Full-text available via subscription   (Followers: 16)
Biomedical Engineering, IEEE Transactions on     Hybrid Journal   (Followers: 31)
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  
Canadian Journal of Remote Sensing     Full-text available via subscription   (Followers: 40)
China Communications     Full-text available via subscription   (Followers: 7)
Circuits and Systems     Open Access   (Followers: 13)
Consumer Electronics Times     Open Access   (Followers: 6)
Control Systems     Hybrid Journal   (Followers: 160)
Edu Elektrika Journal     Open Access  
Electronic Design     Partially Free   (Followers: 72)
Electronic Markets     Hybrid Journal   (Followers: 8)
Electronic Materials Letters     Hybrid Journal   (Followers: 1)
Electronics     Open Access   (Followers: 56)
Electronics and Communications in Japan     Hybrid Journal   (Followers: 8)
Electronics For You     Partially Free   (Followers: 60)
Electronics Letters     Hybrid Journal   (Followers: 23)
Embedded Systems Letters, IEEE     Hybrid Journal   (Followers: 40)
Energy Harvesting and Systems : Materials, Mechanisms, Circuits and Storage     Hybrid Journal   (Followers: 3)
Energy Storage Materials     Full-text available via subscription   (Followers: 1)
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: 7)
Foundations and Trends® in Signal Processing     Full-text available via subscription   (Followers: 5)
Frequenz     Hybrid Journal   (Followers: 1)
Frontiers of Optoelectronics     Hybrid Journal   (Followers: 1)
Geoscience and Remote Sensing, IEEE Transactions on     Hybrid Journal   (Followers: 126)
Haptics, IEEE Transactions on     Hybrid Journal   (Followers: 3)
IEEE Antennas and Propagation Magazine     Hybrid Journal   (Followers: 54)
IEEE Antennas and Wireless Propagation Letters     Hybrid Journal   (Followers: 44)
IEEE Journal of Emerging and Selected Topics in Power Electronics     Hybrid Journal   (Followers: 31)
IEEE Journal of the Electron Devices Society     Open Access   (Followers: 8)
IEEE Journal on Exploratory Solid-State Computational Devices and Circuits     Hybrid Journal   (Followers: 1)
IEEE Power Electronics Magazine     Full-text available via subscription   (Followers: 48)
IEEE Transactions on Antennas and Propagation     Full-text available via subscription   (Followers: 44)
IEEE Transactions on Automatic Control     Hybrid Journal   (Followers: 48)
IEEE Transactions on Circuits and Systems for Video Technology     Hybrid Journal   (Followers: 15)
IEEE Transactions on Consumer Electronics     Hybrid Journal   (Followers: 31)
IEEE Transactions on Electron Devices     Hybrid Journal   (Followers: 13)
IEEE Transactions on Information Theory     Hybrid Journal   (Followers: 22)
IEEE Transactions on Power Electronics     Hybrid Journal   (Followers: 54)
IEEE Transactions on Signal and Information Processing over Networks     Full-text available via subscription   (Followers: 7)
IEICE - Transactions on Electronics     Full-text available via subscription   (Followers: 13)
IEICE - Transactions on Information and Systems     Full-text available via subscription   (Followers: 7)
IET Microwaves, Antennas & Propagation     Hybrid Journal   (Followers: 15)
IET Power Electronics     Hybrid Journal   (Followers: 29)
IET Wireless Sensor Systems     Hybrid Journal   (Followers: 17)
IETE Journal of Education     Open Access   (Followers: 4)
IETE Journal of Research     Open Access   (Followers: 10)
IETE Technical Review     Open Access   (Followers: 11)
Industrial Electronics, IEEE Transactions on     Hybrid Journal   (Followers: 33)
Industry Applications, IEEE Transactions on     Hybrid Journal   (Followers: 7)
Informatik-Spektrum     Hybrid Journal   (Followers: 1)
Instabilities in Silicon Devices     Full-text available via subscription  
Intelligent Transportation Systems Magazine, IEEE     Full-text available via subscription   (Followers: 8)
International Journal of Advanced Research in Computer Science and Electronics Engineering     Open Access   (Followers: 16)
International Journal of Advances in Telecommunications, Electrotechnics, Signals and Systems     Open Access   (Followers: 7)
International Journal of Antennas and Propagation     Open Access   (Followers: 10)
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: 1)
International Journal of Control     Hybrid Journal   (Followers: 13)
International Journal of Electronics     Hybrid Journal   (Followers: 3)
International Journal of Electronics & Data Communication     Open Access   (Followers: 10)
International Journal of Electronics and Telecommunications     Open Access   (Followers: 12)
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: 9)
International Journal of Nano Devices, Sensors and Systems     Open Access   (Followers: 6)
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: 14)
International Journal of Review in Electronics & Communication Engineering     Open Access   (Followers: 4)
International Journal of Sensors, Wireless Communications and Control     Hybrid Journal   (Followers: 7)
International Journal of Systems, Control and Communications     Hybrid Journal   (Followers: 4)
International Journal of Wireless and Microwave Technologies     Open Access   (Followers: 5)
International Journal on Communication     Full-text available via subscription   (Followers: 12)
International Journal on Electrical and Power Engineering     Full-text available via subscription   (Followers: 8)
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: 8)
Journal of Circuits, Systems, and Computers     Hybrid Journal   (Followers: 2)
Journal of Computational Intelligence and Electronic Systems     Full-text available via subscription   (Followers: 1)
Journal of Electrical and Electronics Engineering Research     Open Access   (Followers: 16)
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: 6)
Journal of Electromagnetic Waves and Applications     Hybrid Journal   (Followers: 5)
Journal of Electronic Design Technology     Full-text available via subscription   (Followers: 5)
Journal of Electronics (China)     Hybrid Journal   (Followers: 4)
Journal of Energy Storage     Full-text available via subscription  
Journal of Field Robotics     Hybrid Journal   (Followers: 2)
Journal of Guidance, Control, and Dynamics     Full-text available via subscription   (Followers: 125)
Journal of Intelligent Procedures in Electrical Technology     Open Access   (Followers: 3)
Journal of Low Power Electronics     Full-text available via subscription   (Followers: 7)
Journal of Low Power Electronics and Applications     Open Access   (Followers: 5)
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: 31)
Journal of Power Electronics & Power Systems     Full-text available via subscription   (Followers: 9)
Journal of Semiconductors     Full-text available via subscription   (Followers: 3)
Journal of Sensors     Open Access   (Followers: 21)
Journal of Signal and Information Processing     Open Access   (Followers: 8)
Jurnal Rekayasa Elektrika     Open Access  
Learning Technologies, IEEE Transactions on     Hybrid Journal   (Followers: 14)
Magnetics Letters, IEEE     Hybrid Journal   (Followers: 7)
Metrology and Measurement Systems     Open Access   (Followers: 4)
Microelectronics and Solid State Electronics     Open Access   (Followers: 14)
Nanotechnology Magazine, IEEE     Full-text available via subscription   (Followers: 32)
Nanotechnology, Science and Applications     Open Access   (Followers: 4)
Networks: an International Journal     Hybrid Journal   (Followers: 5)
Open Journal of Antennas and Propagation     Open Access   (Followers: 5)
Optical Communications and Networking, IEEE/OSA Journal of     Full-text available via subscription   (Followers: 13)
Paladyn, Journal of Behavioral Robotics     Open Access  
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 Patents on Electrical & Electronic Engineering     Full-text available via subscription   (Followers: 9)
Recent Patents on Telecommunications     Full-text available via subscription   (Followers: 2)
Research & Reviews : Journal of Embedded System & Applications     Full-text available via subscription   (Followers: 4)
Security and Communication Networks     Hybrid Journal   (Followers: 3)
Selected Topics in Applied Earth Observations and Remote Sensing, IEEE Journal of     Hybrid Journal   (Followers: 48)
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: 5)
Software Engineering, IEEE Transactions on     Hybrid Journal   (Followers: 57)
Solid-State Circuits Magazine, IEEE     Hybrid Journal   (Followers: 10)
Solid-State Electronics     Hybrid Journal   (Followers: 7)
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  
Telematique     Open Access  
TELKOMNIKA (Telecommunication, Computing, Electronics and Control)     Open Access   (Followers: 6)
Universal Journal of Electrical and Electronic Engineering     Open Access   (Followers: 6)
Visión Electrónica : algo más que un estado sólido     Open Access  
Wireless and Mobile Technologies     Open Access   (Followers: 5)
Women in Engineering Magazine, IEEE     Full-text available via subscription   (Followers: 12)
Електротехніка і Електромеханіка     Open Access  

       | Last   [Sort by number of followers]   [Restore default list]

Journal Cover IEEE Transactions on Power Electronics
  [SJR: 3.005]   [H-I: 160]   [54 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, current staff, committee members, and society editors for this issue of the publication.
      PubDate: Oct. 2017
      Issue No: Vol. 32, No. 10 (2017)
  • IEEE Power Electronics Society
    • Abstract: Presents a listing of the editorial board, current staff, committee members, and society editors for this issue of the publication.
      PubDate: Oct. 2017
      Issue No: Vol. 32, No. 10 (2017)
  • Impedance Analysis of SOGI-FLL-Based Grid Synchronization
    • Authors: Hao Yi;Xiongfei Wang;Frede Blaabjerg;Fang Zhuo;
      Pages: 7409 - 7413
      Abstract: The latest research has pointed out that the phase-locked loop (PLL) plays an important role in shaping the impedance of grid-connected converters, yet most of the works so far merely focus on the synchronous reference-frame PLL. Alternatively, this letter presents the impedance analysis of the second-order generalized integrator frequency-locked loop (SOGI-FLL), which has been introduced for realizing grid synchronization in the stationary reference frame. The influences of the voltage perturbation on the estimated phase and further on the output current are revealed for the grid-connected converter using the SOGI-FLL. The frequency-coupling effect of the SOGI-FLL is also identified and verified in the experimental tests.
      PubDate: Oct. 2017
      Issue No: Vol. 32, No. 10 (2017)
  • An Optimized Three-Phase Multilevel Inverter Topology With Separate Level
           and Phase Sequence Generation Part
    • Authors: Arpan Hota;Sachin Jain;Vivek Agarwal;
      Pages: 7414 - 7418
      Abstract: This paper presents an optimized, 3-φ, multilevel inverter (MLI) topology. The proposed system is derived by cascading the level generation part with the phase sequence generation part. Further, it can be operated at any required level depending upon the configuration of the level generation part. Thus, for higher level operation extra components are required at the level generation part only. Therefore, number of components required for the proposed MLI is lower than the conventional 3-φ MLI topologies for higher level operation. Further, the level generation part is shared by the three phases equally. This eliminates the possibility of phase unbalance. The working principle and the operation of the proposed MLI are supported with the simulation and experimental validations. Further, the proposed optimized MLI is also compared with the conventional 3-φ MLIs to prove its advantage.
      PubDate: Oct. 2017
      Issue No: Vol. 32, No. 10 (2017)
  • An Improved Virtual Space Vector Modulation Scheme for Three-Level Active
           Neutral-Point-Clamped Inverter
    • Authors: Cungang Hu;Xinghuo Yu;Donald Grahame Holmes;Weixiang Shen;Qunjing Wang;Fanglin Luo;Nian Liu;
      Pages: 7419 - 7434
      Abstract: This paper presents an improved virtual space vector modulation (IVSVM) scheme for a three-level active neutral-point-clamped (3L-ANPC) inverter to balance neutral-point potential (NP), reduce switching loss, and suppress common mode voltage (CMV). In the IVSVM scheme, an improved virtual medium vector (VMV) is synthesized by the original medium vector and the adjacent two pairs of the small vectors since there are always two pairs of the small vectors in any regions of the new space vector diagram. The improved VMV provides the flexibility to control the NP balancing under any modulation indexes and power factors in one switching cycle while achieving SL reduction and CMV suppression. This is achieved by the proper selection of two pairs of small vectors in terms of NP charge and the pulse sequence. The experimental platform based on a 3L-ANPC inverter is established and results obtained to verify the effectiveness of the IVSVM control strategy.
      PubDate: Oct. 2017
      Issue No: Vol. 32, No. 10 (2017)
  • A Review of Hybrid Topologies Combining Line-Commutated and Cascaded
           Full-Bridge Converters
    • Authors: Panagiotis Bakas;Lennart Harnefors;Staffan Norrga;Alireza Nami;Kalle Ilves;Frans Dijkhuizen;Hans-Peter Nee;
      Pages: 7435 - 7448
      Abstract: This paper presents a review of concepts for enabling the operation of a line-commutated converter (LCC) at leading power angles. These concepts rely on voltage or current injection at the ac or dc sides of the LCC, which can be achieved in different ways. We focus on the voltage and current injection by full-bridge (FB) arms, which can be connected either at the ac or dc sides of the LCC and can generate voltages that approximate ideal sinusoids. Hybrid configurations of an LCC connected at the ac side in series or in parallel with FB arms are presented. Moreover, a hybrid configuration of an LCC connected in parallel at the ac side and in series at the dc side with an FB modular multilevel converter is outlined. The main contribution of this paper is an analysis and comparison of the mentioned hybrid configurations in terms of the capability to independently control the active (P) and reactive power (Q).
      PubDate: Oct. 2017
      Issue No: Vol. 32, No. 10 (2017)
  • A Boost PFC Stage Utilized as Half-Bridge Converter for High-Efficiency
           DC–DC Stage in Power Supply Unit
    • Authors: Jae-Il Baek;Jae-Kuk Kim;Jae-Bum Lee;Han-Shin Youn;Gun-Woo Moon;
      Pages: 7449 - 7457
      Abstract: The half-bridge (HB) LLC converter is one of the most attractive dc–dc converters for medium power supplies due to its soft switching capability. However, its conversion efficiency is considerably degraded in wide-link-voltage applications because of a small magnetizing inductance and wide switching frequency variation for a high voltage gain. In this paper, a boost power factor correction (PFC) stage, which can also play an important role during the hold-up time, is proposed for a high-efficiency HB LLC converter. In the proposed PFC stage, the boost PFC converter can be effectively utilized as a HB converter by replacing a boost diode and inductor with a synchronous switch and transformer, respectively. After the ac line is lost, the proposed PFC stage can operate as the HB converter and regulate the output voltage instead of the HB LLC converter. Thus, it enables the HB LLC converter to be designed with a large magnetizing inductance and narrow switching frequency variation. As a result, the proposed PFC stage can enhance the overall efficiency of the PSU by improving the efficiency of the HB LLC converter. To confirm the validity of this paper, a prototype with 180–264-Vrms ac line, 250–400-V link voltage, and 48 V/480 W output is tested.
      PubDate: Oct. 2017
      Issue No: Vol. 32, No. 10 (2017)
  • Reduced Active Switch Front-End Multipulse Rectifier With Medium-Frequency
           Transformer Isolation
    • Authors: José Juan Sandoval;Harish Sarma Krishnamoorthy;Prasad N. Enjeti;Sewan Choi;
      Pages: 7458 - 7468
      Abstract: This paper presents a reduced switch count multipulse rectifier with medium-frequency (MF) transformer isolation. The proposed topology consists of a three-phase push–pull based ac to dc rectifier with a MF ac link employing two active switches. A three-phase, five-limb, multiwinding MF transformer is employed for isolation. The secondary side of the transformer is connected in a zig-zag configuration and is fed to two six-pulse diode rectifiers, achieving 12-pulse rectifier operation. The primary advantage of the proposed system is reduction in size/weight/volume compared to the conventional 60 Hz magnetic transformer isolation rectifier system. Operating the transformer at 600 Hz is shown to result in three times reduction in size. Furthermore, the proposed system employs only two active semiconductor switching devices operating under a simple pulse width modulation scheme. Also, the zig-zag transformer connection helps to balance leakage inductance on the secondary side. Detailed analysis, simulation, and experimental results on a 208Vl-l, 3.15 kW laboratory prototype are presented to validate the performance of the proposed approach.
      PubDate: Oct. 2017
      Issue No: Vol. 32, No. 10 (2017)
  • A Hybrid Active Gate Drive for Switching Loss Reduction and Voltage
           Balancing of Series-Connected IGBTs
    • Authors: Fan Zhang;Xu Yang;Yu Ren;Lei Feng;Wenjie Chen;Yunqing Pei;
      Pages: 7469 - 7481
      Abstract: Insulated gate bipolar transistors (IGBTs) are usually connected in series to form high-voltage switches in power electronics applications. However, the series operation of IGBTs is not easy due to the unbalanced voltage sharing between them, especially during the switching transients and the tail-current period. In this paper, a hybrid active gate drive is presented for both switching loss reduction and voltage balancing of the series-connected IGBTs. Compared with the conventional gate drive, the proposed method allows dynamical adjustment of the switching speed of IGBTs; thus the switching loss can be suppressed without increasing the current and voltage stresses of the power device. For series connection, the transient voltage sharing is achieved by using an adaptive control method, while the voltage balancing during the tail-current period is optimized by a low-loss snubber circuit. The performance of the proposed hybrid active gate drive and control method has been validated by experimental results.
      PubDate: Oct. 2017
      Issue No: Vol. 32, No. 10 (2017)
  • Novel Eliminated Common-Mode Voltage PWM Sequences and an Online Algorithm
           to Reduce Current Ripple for a Three-Level Inverter
    • Authors: Tam-Khanh Tu Nguyen;Nho-Van Nguyen;Nadipuram R. Prasad;
      Pages: 7482 - 7493
      Abstract: A novel carrier-based zero common-mode voltage (ZCMV) pulse-width-modulation (PWM) algorithm for a three-level (3L) neutral-point-clamped (NPC) inverter based on a group of modified ZCMV PWM sequences is proposed. In a half-carrier cycle containing four consecutive states, one among the three ZCMV switching states is applied twice. This paper proposes four novel ZCMV PWM sequences in addition to those that are realized from switching state arrangements in PWM techniques for the conventional two-level inverter. The harmonic characteristics due to those sequences are investigated in detail. Then, a simple online algorithm to minimize the root mean square current ripple, which can be advantageously extended for an n-inverter, is proposed. Harmonic performance and switching loss characteristic of the proposed ZCMV PWM have been compared to those of a conventional space-vector PWM and a three-state ZCMV PWM with reduced current ripple. Comparative analytical results verified by experimentation have shown that the proposed PWM scheme reduces the current harmonic distortion considerably in a high modulation index range of a 3L NPC inverter.
      PubDate: Oct. 2017
      Issue No: Vol. 32, No. 10 (2017)
  • A Closed-Loop Time-Domain Analysis Method for Modular Multilevel Converter
    • Authors: Jinyu Wang;Jun Liang;Feng Gao;Xiaoming Dong;Chengfu Wang;Bing Zhao;
      Pages: 7494 - 7508
      Abstract: Time-domain steady-state analysis for modular multilevel converter (MMC) can effectively realize the performance evaluation, circuit parameters design, and semiconductor devices selection. However, the existing/conventional analysis methods could not always ensure the accuracy in the full operation range since they are mostly a kind of open-loop analysis method utilizing approximate switching function. This paper proposes a closed-loop analysis method for MMC utilizing the accurate switching function. This method first constitutes two closed analysis loops inside MMC based on the classical circular interaction. Along with them, two nonlinear key equations are established to solve the accurate switching function and circulating current, and finally to acquire all the other electrical quantities coupled by them. The proposed closed-loop analysis method presents improved analysis accuracy in the full operation range and the accuracy is irrelevant with the operation conditions. Moreover, this method reveals the explicit relationship between the switching function and operation points, and, consequently, can realize accurate ac-side voltage selection for MMC, which is very useful for the transformer design and transformer tap selection in practical applications. The effectiveness and accuracy of the proposed analysis method were verified by both simulation and experimental results.
      PubDate: Oct. 2017
      Issue No: Vol. 32, No. 10 (2017)
  • Cascaded Dual-Buck AC–AC Converter With Reduced Number of Inductors
    • Authors: Ashraf Ali Khan;Honnyong Cha;Ju-Won Baek;Juyong Kim;Jintae Cho;
      Pages: 7509 - 7520
      Abstract: This paper proposes a new type of cascaded ac–ac converter with phase-shift control and reduced number of inductors. It can attain high voltage levels by using standard low-voltage rating semiconductor devices. The proposed converter is resistant to current shoot-through and does not require pulse-width modulation (PWM) dead-time; these lead to greatly enhanced system reliability and effective utilization of PWM voltages. Moreover, it does not require current/voltage polarity sensors, lossy snubbers, or dedicated PWM strategies for commutation. These features make it possible to design the converter with reduced control complexity, and obtain output voltage with less distortion. The cascaded units in the proposed converter share the inductors; therefore, number of inductors, inductors footprints, and magnetic volume can be reduced. The phase-shift PWM control is also presented. It increases the effective frequency of the converter by the number of cascaded units, which decreases the size of the passive components and/or the current and voltage ripples. In order to demonstrate the advantages of the proposed converter, detailed comparative simulations and experimental results of the proposed 2-unit, 3-unit, and 4-unit cascaded converters are provided.
      PubDate: Oct. 2017
      Issue No: Vol. 32, No. 10 (2017)
  • A Modulation Strategy to Operate Multilevel Multiphase Diode-Clamped and
           Active-Clamped DC–AC Converters at Low Frequency Modulation Indices With
           DC-Link Capacitor Voltage Balance
    • Authors: Sergio Busquets-Monge;Alber Filba-Martinez;Salvador Alepuz;Alejandro Calle-Prado;
      Pages: 7521 - 7533
      Abstract: This paper proposes a modulation strategy for multilevel multiphase diode-clamped dc–ac converters (also applicable to other functionally equivalent topologies) able to keep the dc-link capacitor voltages balanced under passive front ends, low frequency modulation indices (i.e., low number of switching transitions per fundamental cycle), any value of the amplitude modulation index, and any ac-side displacement power factor. A suitable phase voltage pattern with minimum number of switching transitions is presented for the n-level three-phase case. Subsequently, it is extended to higher number of switching transitions per fundamental cycle and to higher number of phases. Simulation results with three, four, and five levels; three and five phases; and several frequency-modulation-index values are presented to validate the proposed modulation strategy. Experimental results obtained with a four-level three-phase dc–ac converter prototype are also provided. The proposed modulation strategy enables the use of this type of converters in applications where the ac fundamental frequency may be close to the switching frequency, such as in high-power systems and variable-speed motor drives.
      PubDate: Oct. 2017
      Issue No: Vol. 32, No. 10 (2017)
  • Design and Experimental Testing of a Resonant DC–DC Converter for
           Solid-State Transformers
    • Authors: Gabriel Ortiz;Michael Georg Leibl;Jonas Emanuel Huber;Johann Walter Kolar;
      Pages: 7534 - 7542
      Abstract: In the solid-state transformer (SST) concept, the key task of voltage adaptation and isolation is performed by a high-power dc–dc converter, which is operated in the medium-frequency range, hence enabling a reduction in size and weight of the converter's reactive components. This dc–dc converter presents the main challenge in the implementation of the SST concept, given its operation at medium frequency together with the direct connection to medium voltage. This combination demands the utilization of dc–dc converter topologies that are able to operate in the soft-switching mode, whereby, given that typically insulated-gate bipolar transistor switches are used as power devices, zero-current switching modulation schemes become highly attractive and often mandatory in order to achieve the targeted efficiency goals. This paper describes in detail the analysis and design of a 166-kW/20-kHz dc–dc converter of the series-resonant type, which results to be particularly interesting for high-power applications, given its tight input-to-output transfer characteristics and its capability to ensure soft-switching transitions of all semiconductor devices. The main focus of this paper is to describe in detail the practical implementation of the aforementioned resonant dc–dc converter, where its main components, i.e., the medium- and low-voltage-side power bridges and the medium-frequency transformer, are described independently. The assembled prototype is presented together with the implemented testing strategy and the final experimental results.
      PubDate: Oct. 2017
      Issue No: Vol. 32, No. 10 (2017)
  • Improved Dual Boost Inverter With Half Cycle Modulation
    • Authors: Yu Tang;Yang Bai;Jiarong Kan;Fei Xu;
      Pages: 7543 - 7552
      Abstract: The output voltage of a traditional full-bridge inverter is lower than the input dc voltage. In applications when the input voltage is low, the front-end step-up converter is usually required, presenting a two-stage power conversion. Dual boost inverter (DBI) can realize single-stage conversion, which has the advantages of a simple structure, less power devices, and buck–boost ability. The traditional modulation strategy of DBI makes all power switches operate in high frequency and sustain high voltage/current stress, which leads to heavy conduction and switching loss. This paper proposed a modulation strategy, namely, half cycle modulation (HCM), which makes power switches work in high frequency just in half cycle, and can greatly reduce the conduction and switching loss of the power devices. Furthermore, to reduce the current circulation loss in DBI, an improved DBI with two clamping switches is proposed based on HCM, which can bypass the inductor current with low stress switches; therefore, the loss caused by circulation current can be greatly reduced. A detailed analysis and comparison between the traditional and HCM strategies are given in this paper. Finally, a 500 VA DBI prototype is designed in the lab. The advantages of the proposed HCM strategy and improved DBI with two clamping switches are verified by experimental results.
      PubDate: Oct. 2017
      Issue No: Vol. 32, No. 10 (2017)
  • Natural Sampling SVM-Based Common-Mode Voltage Reduction in Medium-Voltage
           Current Source Rectifier
    • Authors: Qiang Wei;Bin Wu;Dewei Xu;Navid Reza Zargari;
      Pages: 7553 - 7560
      Abstract: Conventional space vector modulation (SVM)-based common-mode voltage (CMV) reduction in medium-voltage (MV) current source rectifier (CSR) cannot be used in practice. Conventional SVM contains high-magnitude low-order harmonics, particularly the fifth and seventh harmonics, that are lying closely to the resonance frequency (4.5–5.5 p.u.) of the LC filter of the converter, thus, introducing resonance as the grid-side damping is small. Recently, a natural sampling SVM (NS-SVM) with superior low-order harmonics performance has been proposed for MV CSR. On this basis, a NS-SVM-based CMV reduction method is proposed for MV CSR in this paper. The proposed scheme achieves both good CMV reduction and superior low-order harmonics performance simultaneously. Additionally, effort to lower computational burden on calculating dwell times is made. Experiments are finally provided.
      PubDate: Oct. 2017
      Issue No: Vol. 32, No. 10 (2017)
  • Closed-Form Solution for Efficient ZVS Modulation of DAB Converters
    • Authors: Jordi Everts;
      Pages: 7561 - 7576
      Abstract: A directly employable closed-form analytical solution for the calculation of an efficient, full-operating-range zero voltage switching (ZVS) modulation scheme for bidirectional dual active bridge (DAB) dc–dc converters is presented. Contrary to the analytical ZVS modulation schemes previously proposed in literature, the amount of charge that is required to charge the nonlinear parasitic output capacitances of the switches during commutation is incorporated, ensuring complete commutation of the bridge legs and ZVS of the switching devices. Besides quasi-lossless ZVS, the resulting modulation scheme leads to near-minimum high-frequency circulating currents and thus, minimum conduction losses under the condition of ZVS and for given values of the inductances and transformer turns ratio. Although modifiable for other implementations, the method is demonstrated for a full-bridge full-bridge DAB as a core part of a single-phase, single-stage, bidirectional, isolated ac–dc converter. The resulting modulation scheme is compared with a ZVS modulation scheme calculated using a previously published numerical approach, proving its effectiveness. Experimental results obtained from a state-of-the-art, $text{3.7}; text{kW}$ converter prototype which interfaces a $text{400}; text{V}$ battery with the $text{230};text{V}$, $text{50};text{Hz}$ utility grid are given to validate the theoretical analysis and practical feasibility of the proposed strategy.
      PubDate: Oct. 2017
      Issue No: Vol. 32, No. 10 (2017)
  • Adaptive Thyristor-Controlled LC-Hybrid Active Power Filter for Reactive
           Power and Current Harmonics Compensation With Switching Loss Reduction
    • Authors: Chi-Seng Lam;Lei Wang;Sut-Ian Ho;Man-Chung Wong;
      Pages: 7577 - 7590
      Abstract: In this paper, an adaptive dc-link voltage controlled thyristor-controlled LC-coupling hybrid active power filter (TCLC-HAPF) is proposed for reducing switching loss, switching noise, and enhancing the compensating performance. Unfortunately, the TCLC-HAPF has both controllable active TCLC part and active inverter part; thus, the conventional minimum dc-link voltage calculation methods for active power filter (APF) and LC-coupling hybrid APF (LC-HAPF) cannot be directly applied to the TCLC-HAPF. Moreover, the aforementioned dc-link voltage calculation methods were developed based on the fast Fourier transform (FFT), which makes the calculation complex. This paper also presents a simplified minimum dc-link voltage calculation method for TCLC-HAPF reactive power and current harmonics compensation, which can significantly reduce the large amount of the calculation steps by using the FFT method. After that, an adaptive dc-link voltage controller for the TCLC-HAPF is developed to dynamically keep its operating at its minimum dc-link voltage level to reduce its switching loss and switching noise. Finally, representative simulation and experimental results are given to verify the proposed simplified dc-link voltage calculation method and the adaptive dc-link voltage control method of TCLC-HAPF.
      PubDate: Oct. 2017
      Issue No: Vol. 32, No. 10 (2017)
  • Single-Stage Three-Phase Current-Source Photovoltaic Grid-Connected
           Inverter High Voltage Transmission Ratio
    • Authors: Daolian Chen;Jiahui Jiang;Yanhui Qiu;Jie Zhang;Fusong Huang;
      Pages: 7591 - 7601
      Abstract: This paper proposes a circuit topology of a single-stage three-phase current-source photovoltaic (PV) grid-connected inverter with high voltage transmission ratio (VTR). Also, an improved zone sinusoidal pulsewidth modulation (SPWM) control strategy and an active-clamped subcircuit that can suppress the energy storage switch's turn-off voltage spike are introduced. The circuit topology, control strategy, steady principle characteristics, and high-frequency switching process are analyzed profoundly, as well as the VTR's expression and design criterion of the center-tapped energy storage inductor. The improved zone SPWM control strategy consists of two control loops, namely, the outer loop of input dc voltage of PV cells with the maximum power point tracking and the inner loop of the energy storage inductor current. The experimental results of a 3-kW 96VDC/380V50Hz3ϕAC prototype have shown that this kind of a three-phase inverter has the excellent performances such as single-stage power conversion, high VTR and power density, and high conversion efficiency. Nonetheless, it has small energy storage inductor and output CL filter, low output current total harmonic distortion, and flexible voltage configuration of the PV cells. This study provides an effective design method for single-stage three-phase inverting with high VTR.
      PubDate: Oct. 2017
      Issue No: Vol. 32, No. 10 (2017)
  • A PV Power Conditioning System Using Nonregenerative Single-Sourced
           Trinary Asymmetric Multilevel Inverter With Hybrid Control Scheme and
           Reduced Leakage Current
    • Authors: Mohana Sundar Manoharan;Ashraf Ahmed;Joung-Hu Park;
      Pages: 7602 - 7614
      Abstract: A power conditioning system (PCS) using multiple module-integrated converters and a single sourced 27-level asymmetric cascaded H-bridge multilevel inverter (MLI) without regeneration for photovoltaic (PV) applications is proposed. A newly suggested hybrid-switching closed-loop strategy is proposed to enable the use of a 27-level inverter in PV systems. The suggested hybrid-switching strategy implements fundamental line-frequency switching in the main H-bridge to ensure a high efficiency and low leakage current operation. Furthermore, high-frequency switching is used in the auxiliary H-bridge cells to achieve a higher bandwidth control loop. A cost-effective unidirectional single-ended 1-kW dc–dc module based on a boost coupled inductor and charge-pump circuits is proposed to achieve a single PV source per module for a multistring configuration. To couple the unidirectional converters with the central inverter, a jumping element in the hybrid switching strategy is introduced to enable an optimal nonregenerative operation. The proposed PCS with the control scheme is analyzed and verified using hardware results in a grid connected mode of operation.
      PubDate: Oct. 2017
      Issue No: Vol. 32, No. 10 (2017)
  • Single-Phase Inverter With Energy Buffer and DC–DC Conversion
    • Authors: Hirokazu Matsumoto;Yojiro Shibako;Yasuhiko Neba;
      Pages: 7615 - 7625
      Abstract: This paper proposes a new single-phase inverter topology and describes the control method for the proposed inverter. The inverter consists of an energy buffer circuit, a dc–dc conversion circuit and an H-bridge circuit. The energy buffer circuit and H-bridge circuit enable the proposed inverter to output a multilevel voltage according to the proposed pulse width modulation (PWM) technique. The dc–dc conversion circuit can charge the buffer capacitor continuously because the dc–dc conversion control cooperates with the PWM. Simulation results confirm that the proposed inverter can reduce the voltage harmonics in the output and the dc–dc conversion current in comparison to a conventional inverter consisting of a dc–dc conversion circuit and H-bridge circuit. Experiments demonstrate that the proposed inverter can output currents of low total harmonic distortion and have higher efficiency than the conventional inverter. In addition, it is confirmed that these features of the proposed inverter contribute to the suppression of the circuit volume in spite of the increase in the number of devices in the circuit.
      PubDate: Oct. 2017
      Issue No: Vol. 32, No. 10 (2017)
  • SOC Estimation of Lithium-Ion Batteries With AEKF and Wavelet Transform
    • Authors: Zhi-Liang Zhang;Xiang Cheng;Zhou-Yu Lu;Dong-Jie Gu;
      Pages: 7626 - 7634
      Abstract: Due to harsh electromagnetic environment in electric vehicle (EV), the measured current and voltage signals can be seriously polluted, which results in an estimation error of state of charge (SOC). The proposed denoising approach based on wavelet transform matrix (WTM) can analyze and denoise the nonstationary current and voltage signals effectively. This approach reduces the computation burden and is convenient to be programed in microcontroller unit, which is suitable for EV real-time application. The steps of the approach are as follows: 1) decomposition of the current and voltage signals based on WTM; 2) denoising of the wavelet coefficients under the thresholding rule; and 3) reconstruction of the denoised current and voltage signals based on inverse WTM. A battery-management system prototype was built to verify the approach on a Li(NiCoMn)O2 battery module with nominal capacity of 200 Ah and rated voltage of 3.6 V. SOC estimation error with the proposed denoising approach is limited within 1%. Compared to the maximum error of 2.5% using an adaptive extended Kalman filter without denoising, an estimation error reduction of 1.5% is achieved.
      PubDate: Oct. 2017
      Issue No: Vol. 32, No. 10 (2017)
  • A Comprehensive Analysis and Control Strategy for Nullifying Negative- and
           Zero-Sequence Currents in an Unbalanced Three-Phase Power System Using
           Electric Springs
    • Authors: Kwan-Tat Mok;Siu-Shing Ho;Siew-Chong Tan;S. Y. (Ron) Hui;
      Pages: 7635 - 7650
      Abstract: This paper presents a general analysis and a control strategy that enables electric springs (ES) to mitigate the negative-sequence and zero-sequence currents in unbalanced three-phase power systems. The analysis indicates that under certain load conditions, power balance can be restored without the need for active power from the ES. Outside such conditions, the theory can pinpoint the precise operating point at which power balance can be achieved with the minimum active power from the ES. Thus, the optimum use of energy usage and battery size for providing/storing active power can be realized. Simulation and experiment results obtained from a 3-kW hardware setup have verified the new theory and the control method.
      PubDate: Oct. 2017
      Issue No: Vol. 32, No. 10 (2017)
  • Active Phase Control for Maximum Power Point Tracking of a Linear Wave
    • Authors: Joon Sung Park;Bon-Gwan Gu;Jeong Rok Kim;Il Hyoung Cho;Ilsu Jeong;Ju Lee;
      Pages: 7651 - 7662
      Abstract: A novel maximum power point tracking (MPPT) method for a wave energy converter is proposed. The output power can be expressed as a product of excitation force and wave speed. Therefore, the condition for maximum extraction of wave energy is ensuring that excitation force is in phase with the velocity of the buoy. However, the phase between excitation force and velocity is determined by the wave period. In the ocean, a wave has an irregular period and amplitude of wave position. In this paper, the wave period was estimated using the velocity and acceleration information. Based on the estimated wave period, the novel MPPT algorithm is proposed. The benefit of the proposed method is that the additional configuration is not required. The proposed MPPT algorithm is presented in detail, in addition to simulation and laboratory test results.
      PubDate: Oct. 2017
      Issue No: Vol. 32, No. 10 (2017)
  • A Novel Self-Power SSHI Circuit for Piezoelectric Energy Harvester
    • Authors: Ali M. Eltamaly;Khaled E. Addoweesh;
      Pages: 7663 - 7673
      Abstract: Piezoelectric energy harvester (PEH) has been used to feed loads in military, health, animal tracking, and many other applications. A considerable amount of energy is dissipated in PEH to flip the output voltage through the internal capacitor and resistor of piezoelectric (PZT) material. One of the most effective techniques to harvest this power loss is called a synchronized switch harvesting on inductor (SSHI) technique. A parallel SSHI technique has been used to flip the terminal voltage of the PEH through external inductor. A new, simple, and effective circuit has been introduced in this paper for this purpose. The new circuit uses two capacitors only to detect the flipping points of terminal voltage replacing two resistors, eight diodes, and two capacitors in the state of the art circuit (SAC). The new proposed circuit (NPC) showed about 26% reduction in losses, 18% increased output power, and 10% increase in efficiency compared to the SAC in normal operating condition. Also, the NPC showed 38% improvement in output power compared to the SAC in different operating conditions. Besides these benefits, the NPC extends the vibration frequency operating range 10 times higher than the circuit without the SSHI and 2.5 times the SAC. The simulation and experimental results showed the superiority of the NPC.
      PubDate: Oct. 2017
      Issue No: Vol. 32, No. 10 (2017)
  • Sequence-Impedance-Based Harmonic Stability Analysis and Controller
           Parameter Design of Three-Phase Inverter-Based Multibus AC Power Systems
    • Authors: Wenchao Cao;Yiwei Ma;Fred Wang;
      Pages: 7674 - 7693
      Abstract: Three-phase inverter-based multibus ac power systems could suffer from the harmonic instability issue. The existing impedance-based stability analysis method using the Nyquist stability criterion once requires the calculation of right-half-plane (RHP) poles of impedance ratios, which would result in a heavy computation burden for complicated systems. In order to analyze the harmonic stability of multibus ac systems consisting of both voltage-controlled and current-controlled inverters without the need for RHP pole calculation, this paper proposes two sequence-impedance-based harmonic stability analysis methods. Based on the summary of all major connection types including mesh, the proposed Method 1 can analyze the harmonic stability of multibus ac systems by adding the components one by one from nodes in the lowest level to areas in the highest system level, and accordingly, applying the stability criteria multiple times in succession. The proposed Method 2 is a generalized extension of the impedance-sum-type criterion to be used for the harmonic stability analysis of any multibus ac systems based on Cauchy's theorem. The inverter controller parameters can be designed in the forms of stability regions in the parameter space, by repetitively applying the proposed harmonic stability analysis methods. Experimental results of inverter-based multibus ac systems validate the effectiveness of the proposed harmonic stability analysis methods and parameter design approach.
      PubDate: Oct. 2017
      Issue No: Vol. 32, No. 10 (2017)
  • A Switched-Coupling-Capacitor Equalizer for Series-Connected Battery
    • Authors: Yunlong Shang;Bing Xia;Fei Lu;Chenghui Zhang;Naxin Cui;Chunting Chris Mi;
      Pages: 7694 - 7706
      Abstract: Due to the low cost, small size, and easy control, the switched-capacitor (SC) equalizer is promising among all types of active cell balancing methods. However, the balancing speed is generally slow and the balancing efficiency is seriously low when the SC equalizer is applied into a long battery string. Therefore, an automatic switched-coupling-capacitor equalizer (SCCE) is proposed, which can realize the any-cells-to-any-cells equalization for a battery string. Only two switches and one capacitor are required for each battery cell. All mosfets are controlled by one pair of complementary pulse width modulation signals, and energy can be automatically and directly delivered from any higher voltage cells to any lower voltage ones without the need of cell monitoring circuits, leading to a high balancing efficiency and speed independent of the cell number and the initial cell voltages. Contrary to the conventional equalizers using additional components for the equalization among modules, the proposed equalizer shares a single converter for the equalization among cells and modules, resulting in smaller size and lower cost. A prototype for four lithium battery cells is implemented, and an experimental comparison between the proposed SCCE and the conventional SC equalizer is presented. Experimental results show the proposed topology exhibits a substantially improved balancing performance, and the measured peak efficiency is 92.7%.
      PubDate: Oct. 2017
      Issue No: Vol. 32, No. 10 (2017)
  • A High-Voltage-Gain DC–DC Converter Based on Modified Dickson Charge
           Pump Voltage Multiplier
    • Authors: Bhanu Prashant Baddipadiga;Mehdi Ferdowsi;
      Pages: 7707 - 7715
      Abstract: A high-voltage-gain dc–dc converter is introduced in this paper. The proposed converter resembles a two-phase interleaved boost converter on its input side while having a Dickson-charge-pump-based voltage multiplier (VM) on its output side. This converter offers continuous input current, which makes it more appealing for the integration of renewable sources like solar panels to a 400-V dc bus. Also, the proposed converter is capable of drawing power from either a single source or two independent sources. Furthermore, the VM used offers low voltage ratings for capacitors that potentially leads to size reduction. The converter design and component selection have been discussed in detail with supporting simulation results. A hardware prototype of the proposed converter with ${V}_{rm{in}}= rm{ 20}$ and ${V}_{rm{out}}= rm{ 400}$ V has been developed to validate the analytical results.
      PubDate: Oct. 2017
      Issue No: Vol. 32, No. 10 (2017)
  • A Soft-Switching Bridgeless AC–DC Power Factor Correction Converter
    • Authors: Muntasir Alam;Wilson Eberle;Deepak S. Gautam;Chris Botting;
      Pages: 7716 - 7726
      Abstract: A new soft-switching, bridgeless power factor correction (PFC) boost converter is proposed for power supply and battery charging applications. The converter operates in both pulse width modulation (PWM) mode and resonant mode each switching cycle, and utilizes standard average current mode control. The converter is bridgeless, therefore eliminating the need for a front-end diode bridge rectifier. It operates in continuous conduction mode and achieves zero voltage switching (ZVS) for all switches. The proposed converter also reduces the turn-off losses of the PWM switches, therefore nearly eliminating switching losses. The output diodes operate with controlled di/dt turn-off, which reduces reverse–recovery losses. The PWM switches of the proposed converter can be driven with the same PWM signal, enabling simplified control. The detailed operation of the proposed converter is presented, including the conditions for ZVS operation and a stress analysis for the circuit components. Experimental results are presented for a 650-W prototype at 150-kHz switching frequency, universal ac input, and 400-V dc output. The proposed converter shows about 1% better efficiency and lower device temperatures at full load and 100-V ac input (maximum loss operating point) compared with the conventional hard switched PFC boost converter.
      PubDate: Oct. 2017
      Issue No: Vol. 32, No. 10 (2017)
  • Performance Evaluation of a Semi-Dual-Bridge Resonant DC/DC Converter With
           Secondary Phase-Shifted Control
    • Authors: Song Hu;Xiaodong Li;
      Pages: 7727 - 7738
      Abstract: In this work, a unidirectional series-resonant dc/dc converter with a semi-dual-bridge structure is evaluated comprehensively. This converter can realize buck–boost conversion by means of the simple secondary phase-shifted control. With the variations of load level and converter gain, the converter may enter into different operation modes. Features of all possible operation modes and the boundary conditions among them are identified explicitly. Despite the differences between the modes, the steady-state solution for all modes with continuous resonant current could be obtained uniformly by using the fundamental harmonics approximation approach. Verifications of each operation modes are exemplified through experimental tests on a 300-W prototype converter. The measured efficiency can be maintained over 90% at low-load level when the input voltage is varied. Through comparison with reported topologies having similar structures, it is shown that this converter has lower circulation energy than a dual-bridge series-resonant converter. And the secondary arrangement of this converter is advantageous in terms of simpler driver circuit, no-risk of shoot-through fault, and low conduction loss.
      PubDate: Oct. 2017
      Issue No: Vol. 32, No. 10 (2017)
  • A High Step-up PWM DC-DC Converter With Coupled-Inductor and Resonant
    • Authors: Yuanmao Ye;K. W. E. Cheng;Sizhe Chen;
      Pages: 7739 - 7749
      Abstract: In this paper, a novel high step-up pulse width modulation dc–dc converter integrating coupled-inductor and switched-capacitor (SC) techniques is presented. The proposed converter consists of a synchronous rectification Boost unit and multiple coupled-inductor-SC units. Its structure can therefore be easily extended for ultrahigh voltage gain. The diodes employed in the proposed converter can operate under soft-switching condition by utilizing leakage inductance of the coupled inductor. Low-voltage-rated transistors can be used to improve the efficiency as the voltage stress on the main switches of the proposed converter is reduced. The feasibility of the proposed converter is experimentally demonstrated by a 200 W prototype converter.
      PubDate: Oct. 2017
      Issue No: Vol. 32, No. 10 (2017)
  • Design of a Highly Efficient (97.7%) and Very Compact (2.2 kW/dm $^3$)
           Isolated AC–DC Telecom Power Supply Module Based on the Multicell ISOP
           Converter Approach
    • Authors: Matthias Kasper;Dominik Bortis;Gerald Deboy;Johann W. Kolar;
      Pages: 7750 - 7769
      Abstract: The rising electricity demand of data centers has initiated a development trend toward highly efficient power supplies. Therefore, a multicell converter approach for a telecom rectifier module breaking through the efficiency and power density barriers of traditional single-cell converter systems is presented in this paper. The potential of the multicell approach for high efficiency is derived from fundamental scaling laws of different system performance aspects in dependence of the number of converter cells and the benefits of the interleaving technique. Based on the available degrees of freedom in the design of such a converter system, a comprehensive multiobjective optimization of the entire system with respect to efficiency and power density is performed with detailed component loss and volume models. In order to verify the analytical models and the design procedure, a hardware demonstrator of a 3.3 kW multicell $text{230},V_text{AC}/text{48}, V_text{DC}$ telecom power supply with $N_{text{cells}}=6$ isolated converter cells in an input-series output-parallel arrangement is presented with measurement results indicating a maximum efficiency of $eta =$ 97.7% and a power density of $rho =$ 2.2 kW/dm3 (= 36 W/in3). Furthermore, different paths for future performance improvements of the multicell arrangement are outlined.
      PubDate: Oct. 2017
      Issue No: Vol. 32, No. 10 (2017)
  • Power Stage and Feedback Loop Design for LLC Resonant Converter in
           High-Switching-Frequency Operation
    • Authors: Hwa-Pyeong Park;Jee-Hoon Jung;
      Pages: 7770 - 7782
      Abstract: As converter switching frequencies are moving toward megahertz frequencies for high power density, secondary leakage parasitics that were previously negligible have to be considered in mathematical modeling for LLC resonant converters. At high-switching-frequency operation, the power stage design must take secondary leakage inductance into account because it can affect the input–output voltage gain. In addition, the feedback loop design should consider the effect of the time delay caused by the performance limitation of a digital controller to improve the small-signal model accuracy of the converter. Using the proposed power stage and feedback control loop design considerations, the LLC resonant converter can achieve high power conversion efficiency and stability enhancement at high switching frequencies. All the proposed methods are experimentally verified using a 240-W prototype LLC resonant converter operating at 1-MHz switching frequency.
      PubDate: Oct. 2017
      Issue No: Vol. 32, No. 10 (2017)
  • Dynamic Response Improvements of Parallel-Connected Bidirectional DC–DC
           Converters for Electrical Drive Powered by Low-Voltage Battery Employing
           Optimized Feedforward Control
    • Authors: Deshang Sha;Jiankun Zhang;Xiao Wang;Wenqi Yuan;
      Pages: 7783 - 7794
      Abstract: Parallel-connected modular current-fed bidirectional dc–dc converters are used for the AC motor drive system powered by batteries with low voltage and wide voltage range. The input current ripple can be reduced significantly by employing interleaving technology not only for individual module but also for all the modules. A current sharing control strategy is applied for the constituent modules. Double pulse width modulation plus double phase shifted control with equal duty cycles for one module can minimize the circulation loss and avoid nonactive power issue. Factors affecting dynamic performance are investigated based on the small-signal modeling. The leakage inductance value is optimized in view of system reliability and better dynamic performance. Besides, to improve the dynamic performance further, feedforward control employing optimized feedforward coefficient based on the small-signal analysis is implemented. A 4-kw prototype composed of two bidirectional dc–dc converters is built to verify the effectiveness for the proposed control strategy in AC motor drive application with fast regenerative braking.
      PubDate: Oct. 2017
      Issue No: Vol. 32, No. 10 (2017)
  • An Asymmetric Half-Bridge Resonant Converter Having a Reduced Conduction
           Loss for DC/DC Power Applications With a Wide Range of Low Input Voltage
    • Authors: Yeonho Jeong;Jae-Kuk Kim;Jae-Bum Lee;Gun-Woo Moon;
      Pages: 7795 - 7804
      Abstract: A new asymmetric half-bridge (HB) resonant converter for dc/dc power system with a wide range of low input voltage is proposed in this paper. The proposed converter is easily derived based on the switch integration technique, merging a buck–boost, which is the same with the active-clamp forward's primary circuit, and the HB LLC resonant converter. By adopting the buck–boost circuit in front of the HB LLC resonant converter, higher input voltage of LLC resonant converter stage can be achieved. As a result, the primary conduction loss can be significantly reduced. In addition, to cover wide input voltage range, an asymmetric pulse width modulation control is applied. It can mitigate the design limitation for a high efficiency. Moreover, the proposed converter can achieve not only the small conduction loss and the optimal design for high efficiency, but also high power density and low cost due to the switch integration technique. The validity of the proposed converter is confirmed by the experimental results of a prototype converter with 36–72 VDC input and 300 W (12 V/25 A) output.
      PubDate: Oct. 2017
      Issue No: Vol. 32, No. 10 (2017)
  • Quasi-Parallel Voltage Regulator Topology for Powering Laptop Processors
    • Authors: Tilak Bala Gangadhar Vangalapudi;Debaprasad Kastha;
      Pages: 7805 - 7815
      Abstract: This paper presents a quasi-parallel voltage regulator topology that is suitable as a laptop processor power supply where the input voltage varies over a wide range. It consists of a phase shift full bridge converter and a buck converter, whose inputs are connected in series to divide the total input voltage and the outputs are connected in parallel to share the load current. The output voltage is regulated with fast dynamics against load change and input voltage variation while the input voltage to the buck converter is also regulated at a relatively low value to improve the overall system efficiency. Different methods to improve the converter efficiency further at both light and high loads are also proposed. The efficiency of the converter at different load currents and input voltages are obtained from a laboratory prototype demonstrating a maximum efficiency of 90.8% at an output voltage of 1.2 V. A small signal model of the converter is then presented and a design methodology for a decoupled controller is discussed. Transient performance of the converter using this controller against 50 A load current change is found to comply with the specifications for a laptop processor power supply.
      PubDate: Oct. 2017
      Issue No: Vol. 32, No. 10 (2017)
  • Effects of Auxiliary-Source Connections in Multichip Power Module
    • Authors: Helong Li;Stig Munk-Nielsen;Xiongfei Wang;Szymon Bęczkowski;Steve R. Jones;Xiaoping Dai;
      Pages: 7816 - 7823
      Abstract: Auxiliary-source bond wires and connections are widely used in power modules with paralleled mosfets or insulated gate bipolar transistor (IGBTs). This paper investigates the operation mechanism of the auxiliary-source connections in multichip power modules. It reveals that the auxiliary-source connections cannot fully decouple the power loop and the gate loop such as the Kelvin-source connection, owing to their involvement in the loop of the power source current. Three effects of the auxiliary-source connections are then analyzed, which are 1) the common source stray inductance reduction, 2) the transient drain–source current imbalance mitigation, and 3) the influence on the steady-state current distribution. Finally, simulations and experimental results validate the theoretical analysis.
      PubDate: Oct. 2017
      Issue No: Vol. 32, No. 10 (2017)
  • A Unified Analysis of the Fault Tolerance Capability in Six-Phase
           Induction Motor Drives
    • Authors: Wan Noraishah Wan Abdul Munim;Mario J. Duran;Hang Seng Che;Mario Bermúdez;Ignacio González-Prieto;Nasrudin Abd Rahim;
      Pages: 7824 - 7836
      Abstract: The fault tolerance of electric drives is highly appreciated at industry for security and economic reasons, and the inherent redundancy of six-phase machines provides the desired fault-tolerant capability with no extra hardware. For this reason some recent research efforts have been focused on the fault-tolerant design, modeling, and control of six-phase machines. Nevertheless, a unified and conclusive analysis of the postfault capability of six-phase machine is still missing. This paper provides a full picture of the postfault derating in generic six-phase machines and a specific analysis of the fault-tolerant capability of the three mainstream six-phase induction machines (asymmetrical, symmetrical, and dual three phase). Experimental results confirm the theoretical post fault current limits and allow concluding, which is the best six-phase machine for each fault scenario and neutral arrangement.
      PubDate: Oct. 2017
      Issue No: Vol. 32, No. 10 (2017)
  • Sizing of Energy System of a Hybrid Lithium Battery RTG Crane
    • Authors: Wangqiang Niu;Xixia Huang;Feng Yuan;Nigel Schofield;Lei Xu;Jianxin Chu;Wei Gu;
      Pages: 7837 - 7844
      Abstract: Rubber tyred gantry (RTG) cranes are an important piece of transport equipment in ship and rail container terminals. They have a diversified power demand, for example, peak powers of 292-kW driving, 178 kW regenerating, and 7-kW idle power. The high peak power demand determines the system prime mover (internal combustion engine) rating, which is highly over-rated for the crane average energy requirements. Such a variation in peak to idle power demand favors a hybrid power solution which, given appropriate design, can yield significant gains in fuel or energy usage and, importantly, reductions in local emissions, thus improving air-quality. In this study, a hybrid energy source for an RTG crane is presented. The hybrid energy source comprises of a lithium battery and a down-sized diesel-generator connected to the dc link through an active front end unit. While other systems have been previously proposed, the system presented here utilizes a smaller diesel-generator, thus reducing plant and fuel consumption. In addition, the battery connects directly to the dc link reducing system power electronics while improving battery response and efficiency. Experimental results from a full-size evaluation system are presented showing a 57% reduction of fuel consumption compared to a conventional RTG crane system.
      PubDate: Oct. 2017
      Issue No: Vol. 32, No. 10 (2017)
  • Modified High-Power Nanosecond Marx Generator Prevents Destructive Current
    • Authors: Guoyong Duan;Sergey N. Vainshtein;Juha T. Kostamovaara;
      Pages: 7845 - 7850
      Abstract: A traditional Marx circuit (TMC) based on avalanche transistors with a shortened emitter and a base was investigated numerically by using a two-dimensional (2-D) physics-based approach and experimentally, and compared with a special Marx circuit (SMC) suggested here, in which an intrinsic base triggering of all the stages protects the transistors, especially the second one, from thermal destruction due to current filamentation. This is because the entire emitter–base perimeter in the SMC participates in switching, whereas in a TMC the switching is initiated across the entire area of the emitter but then changes to current filamentation due to certain 3-D transient effects reported earlier. Very significant difference in local transient overheating in the transistors operating in TMC and SMC determines the difference in reliability of those two pulse generators. The results suggest a new circuit design for improving reliability and explain the difference in the operating mode of different transistors in the chain which makes the second transistor most prone to destructive thermal filamentation. This new understanding points additionally to ways of optimizing the design of the transistors to be used in a Marx circuit.
      PubDate: Oct. 2017
      Issue No: Vol. 32, No. 10 (2017)
  • Smart Electrical Grid Interface Using Floating H-Bridges to Improve the
           Performance of Induction Motors
    • Authors: A. R. N. M. Reaz Ul Haque;Siyu Leng;John Salmon;
      Pages: 7851 - 7861
      Abstract: Three-phase floating H-bridges can be inserted between the utility grid and an induction motor to inject a voltage in series with the grid voltage. The magnitude and phase of this voltage is used to control the motor voltage under steady-state operation so as to lower the motor power losses over its entire load range. This is made possible because the three-phase H-bridge can be used to both increase and decrease the motor voltage relative to the grid voltage as required. This feature affects the performance of the overall system, more specifically, the motor power conversion efficiency is improved, lowering its operating temperature and, hence, improving reliability and lifetime expectancy. A variety of motor voltage control options exist, the controller presented is suitable for applications using loads such as fans and pumps, where variable frequency is not required. Readily available machine nameplate data are used to identify the motor output power associated with its maximum efficiency operating point when operated under rated voltage. This data are then used as the basis to control the motor voltage according to the square root of the measured motor input power. The controller and the performance of the three-phase H-bridge are described. The benefits of the variable voltage control are assessed by comparing the motor performance with the machine operated at its rated voltage. The chosen controller also results in the H-bridge dc voltages being relatively low and constant over a wide load range, hence lowering the power losses and electrical stress in the power electronics. Both experimental results and theoretical predictions are used to illustrate the performance of both the three-phase H-bridge and the motor.
      PubDate: Oct. 2017
      Issue No: Vol. 32, No. 10 (2017)
  • Pole-Phase Modulated Multiphase Induction Motor Drive With Reduced Torque
           Ripple and Improved DC Link Utilization
    • Authors: B. S. Umesh;K. Sivakumar;
      Pages: 7862 - 7869
      Abstract: Wider speed and torque range is one of the major requirements of high-power propulsion and traction applications. Pole-phase modulation (PPM) of multiphase induction motors provide extended speed-torque range without the need of oversizing the motor rating. Particularly, PPM of nine-phase IM gives four-pole and 12-pole mode of operations with wider speed and torque variations. But in three-phase (3-φ) 12-pole mode higher torque ripple degrades the performance of drive system. Further, in nine-phase (9-φ) four-pole mode the extra dc link utilization (DLU) using 9-φ space vector pulse width modulation (SVPWM) is very less compared to the 3-φ SVPWM. Possible techniques to improve DLU by adding third harmonic order offset value to the sine references introduce dominant lower order harmonic currents in to the phase windings. To address these problems, this paper proposes a multilevel voltage generation technique using an auxiliary 3-φ two-level inverter for reducing high torque pulsations during starting. Compared to the conventional multilevel inverters, the proposed multilevel inverter scheme gives the same number of voltage levels with considerably less device count. In addition, this paper also proposes a simple and effective phase grouping method to avoid dominant lower order harmonic currents into the phase windings while improving the DLU of four-pole operation. The proposed performance improvement technique for PPM of 9-φ IM is simulated in ANSYS Maxwell two-dimensional and Simplorer environment. A prototype of 5-hp 9-φ IM drive controlled using SPARTAN 6 FPGA board is developed for validating the proposed performance improvement methods experimentally.
      PubDate: Oct. 2017
      Issue No: Vol. 32, No. 10 (2017)
  • Windowed SHE-PWM of Interleaved Four-Quadrant Converters for Resonance
           Suppression in Traction Power Supply Systems
    • Authors: Kejian Song;Georgios Konstantinou;Wu Mingli;Pablo Acuna;Ricardo P. Aguilera;Vassilios G. Agelidis;
      Pages: 7870 - 7881
      Abstract: AC electric locomotives that use a number of interleaved four-quadrant converters generate high-frequency switching harmonics which may stimulate certain resonances in traction power supply systems (TPSSs). A windowed selective harmonic elimination pulse-width modulation (SHE-PWM) method is proposed to suppress such resonances. Owing to the windowed design and the precalculated solutions, the proposed method covers the wide potential resonant frequency range and addresses the resonant frequency variation while keeping the low switching frequency of the traction converters. The proposed windowed SHE-PWM is fully tested with a closed-loop controller in a simulation model with the TPSS and the ac electric locomotive. Comparative simulation results show that the windowed SHE-PWM is an effective alternative that overcomes the resonance suppression limitations of the conventional phase-shifted PWM (PS-PWM). The performance of proposed windowed SHE-PWM on an experimental equivalent resonant circuit is further evaluated and compared with PS-PWM. Both simulation and experimental results verify the effectiveness and feasibility of the proposed method.
      PubDate: Oct. 2017
      Issue No: Vol. 32, No. 10 (2017)
  • New Passive Filter Design Method for Overvoltage Suppression and Bearing
           Currents Mitigation in a Long Cable Based PWM Inverter-Fed Motor Drive
    • Authors: Yanmin Jiang;Weimin Wu;Yuanbin He;Henry Shu-Hung Chung;Frede Blaabjerg;
      Pages: 7882 - 7893
      Abstract: High-frequency pulse width modulation (PWM) in inverter-fed induction motor drive systems is widely used in industrial applications because of their flexible speed control and energy savings. However, high dv /dt PWM pulses induce overvoltage spikes on the motor via long cable. Such phenomenon would cause serious deterioration of the motor and cable. A passive overvoltage suppression technique of low-loss “RL-plus-C” filter was proposed recently. It has not only some merits of simple structure, low cost, and good robustness, but also a significant merit of low power dissipation. In order to further mitigate the bearing currents, this paper proposes two new power filters and their design method. The theoretical analysis and the design method are introduced in detail. Experimental results are in good agreement with the theoretical analysis.
      PubDate: Oct. 2017
      Issue No: Vol. 32, No. 10 (2017)
  • Fault-Tolerant Control of Six-Phase Induction Motor Drives With Variable
           Current Injection
    • Authors: Ignacio González-Prieto;Mario J. Duran;Federico J. Barrero;
      Pages: 7894 - 7903
      Abstract: Three-phase machines are the industry standard for electrical drives, but the inherent fault tolerance of multiphase machines makes them an attractive alternative in applications requiring high reliability. For this reason, different fault-tolerant control schemes for multiphase drives have been recently suggested, proving their capability to perform a ripple-free operation after an open-circuit fault occurrence. Nevertheless, the postfault strategies proposed so far consider a single mode of operation and do not allow a high-performance braking process in drives with unidirectional power flow where regenerative braking is not possible. This paper first explores the possibility of enhancing the braking process by using a proper injection of circulating currents that prevent the active power to reach the dc-link capacitor. This novel strategy is then combined with minimum losses and maximum torque criteria to obtain a variable current injection method that minimizes the drive derating, reduces the copper losses, and improves the braking transients. Experimental results confirm the successful performance in the different zones for the case of a six-phase induction motor drive.
      PubDate: Oct. 2017
      Issue No: Vol. 32, No. 10 (2017)
  • A Three-Vector Modulation Strategy for Indirect Matrix Converter Fed
           Open-End Load to Reduce Common-Mode Voltage With Improved Output
    • Authors: Quoc-Hoan Tran;Hong-Hee Lee;
      Pages: 7904 - 7915
      Abstract: This paper proposes a three-vector modulation (TVM) strategy for a five-leg indirect matrix converter (IMC) fed three-phase open-end load (OEL) drive to reduce common-mode voltage (CMV) with improved output performance. By utilizing three nearest active voltage vectors to generate desired output voltage, the proposed TVM strategy can eliminate the CMV across the load phase and reduce the peak value of CMV at the load terminal to 42%. Compared to other modulation strategies for the IMC fed OEL drives, the problems associated with simultaneous switching of two legs and zero-sequence current do not occur with the TVM strategy. Also, a constant average dc-link voltage is achieved by using three active current vectors to synthesize reference input current, so that the output performance of the five-leg IMC is improved regarding output current and output voltage harmonic distortions. Simulation and experimental results are provided to verify the performance of the TVM strategy.
      PubDate: Oct. 2017
      Issue No: Vol. 32, No. 10 (2017)
  • Influence of Material Properties and Geometric Shape of Magnetic Cores on
           Acoustic Noise Emission of Medium-Frequency Transformers
    • Authors: Peng Shuai;Juergen Biela;
      Pages: 7916 - 7931
      Abstract: Medium-voltage, medium-frequency transformers (MFTs) are much smaller in size and weight compared to conventional line frequency transformers. MFTs are very attractive for applications where full control of the power flow and high power density are required, such as power electronic interfaces in smart grids and traction converter systems. Because of the switching loss of high-voltage semiconductor switches and the limitation of volume reduction at high frequency due to isolation requirement, MFTs are usually operated in the kHz range, which results in acoustic noise emission. In this paper, the origins of acoustic noise associated with MFTs are investigated based on vibration and acoustic measurements. The work focuses on the influence of material properties and geometric shape of the magnetic core. Based on the measurement results, nanocrystalline uncut cores with oval shape is the best solution for MFT design regarding high efficiency, high power density, and low acoustic noise emission. Finally, the low acoustic noise emission of a prototype transformer built with nanocrystalline uncut cores is verified by measurement. The winding is found to have major contribution to transformer acoustic noise if the low-magnetostrictive uncut core is used.
      PubDate: Oct. 2017
      Issue No: Vol. 32, No. 10 (2017)
  • A Single-Stage Single-Switch Soft-Switching Power-Factor-Correction LED
    • Authors: Behzad Poorali;Ehsan Adib;Hosein Farzanehfard;
      Pages: 7932 - 7940
      Abstract: This paper proposes a new isolated single-stage single-switch soft-switching power-factor-correction (S6-PFC) driver without electrolytic capacitors for supplying light-emitting diodes (LEDs). In the proposed LED driver, all the semiconductor devices are soft-switched without employing any extra active switch. The leakage inductance of transformer acts as a resonant component so that the leakage energy is recycled. Soft-switching operation of the semiconductor devices together with absorption of the leakage energy improve the proposed driver efficiency. Furthermore, input current of the driver has very low harmonics resulting in high power-factor. Operating principles of the proposed S6-PFC LED driver as well as its design guidelines are presented. Also, experimental results of a laboratory prototype for supplying a 21 W/30 V LED module from 220 V/50 Hz ac mains are provided to verify the theoretical analysis. The presented results show that the implemented prototype has an efficiency of 92% under full-load condition and its input current total harmonic distortion is as low as 2.6%.
      PubDate: Oct. 2017
      Issue No: Vol. 32, No. 10 (2017)
  • A Cost-Effective Zero-Voltage Switching Dual-Output LED Driver
    • Authors: U. Ramanjaneya Reddy;B. L Narasimharaju;
      Pages: 7941 - 7953
      Abstract: Coupled-inductor (CI) converters are widely used in the light-emitting diode (LED) lighting applications due to several advantages, such as high step-down conversion, reduced switch/diode stress as compared to conventional buck converters. However, the main drawback of CI buck converter is high-voltage spikes during turn-OFF instant due to the leakage inductance of a CI, which leads to switching device failure. Passive clamp circuits are used to overcome the leakage inductance problem, but these clamp circuit's results in reduced efficiency and increased cost. This paper proposes a high step-down zero-voltage switching dual-output coupled-inductor buck (ZVS-DOCIB) LED driver with dimming control. The proposed LED driver provides various advantages like high step-down conversion, effective recovery of leakage energy, elimination of voltage spikes, reduced switching loss due to ZVS operation of both the switching devices, and less switching device count, particularly for multioutput drivers. Also, ZVS operation provides a significant reduction in switching losses, which results in high efficiency. Furthermore, dimming control is studied to regulate the average output currents. This paper presents design and analysis of the proposed ZVS-DOCIB converter. A prototype of the converter has developed and validated experimentally with simulation counterparts.
      PubDate: Oct. 2017
      Issue No: Vol. 32, No. 10 (2017)
  • An Investigation of Temperature-Sensitive Electrical Parameters for SiC
           Power MOSFETs
    • Authors: Jose Ortiz Gonzalez;Olayiwola Alatise;Ji Hu;Li Ran;Philip A. Mawby;
      Pages: 7954 - 7966
      Abstract: This paper examines dynamic temperature-sensitive electrical parameters (TSEPs) for SiC MOSFETs. It is shown that the switching rate of the output current (dIDS/dt) coupled with the gate current plateau (IGP) during turn-ON could be an effective TSEP under specific operating conditions. Both parameters increase with the junction temperature of the device as a result of the negative temperature coefficient of the threshold voltage. The temperature dependency of dIDS /dt has been shown to increase with the device current rating (due to larger input capacitance) and external gate resistance ($R_{G}^{rm EXT}$). However, as dIDS/dt is increased by using a small $R_{G}^{rm EXT}$, parasitic inductance suppresses the temperature sensitivity of the drain and gate current transients by reducing the “effective gate voltage” on the device. Since the temperature sensitivity of dIDS/dt is at the highest with maximum $R_{G}^{rm EXT}$, there is a penalty from higher switching losses when this method is used in real time for junction temperature sensing. This paper investigates and models the temperature dependency of the gate and drain current transients as potential TSEPs for SiC power MOSFETs.
      PubDate: Oct. 2017
      Issue No: Vol. 32, No. 10 (2017)
  • High-Temperature Electrical and Thermal Aging Performance and Application
           Considerations for SiC Power DMOSFETs
    • Authors: Dean P. Hamilton;Michael R. Jennings;Amador Pérez-Tomás;Stephen A. O. Russell;Steven A. Hindmarsh;Craig A. Fisher;Philip A. Mawby;
      Pages: 7967 - 7979
      Abstract: The temperature dependence and stability of three different commercially-available unpackaged SiC Dmosfets have been measured. On-state resistances increased to 6 or 7 times their room temperature values at 350 °C. Threshold voltages almost doubled after tens of minutes of positive gate voltage stressing at 300 °C, but approached their original values again after only one or two minutes of negative gate bias stressing. Fortunately, the change in drain current due to these threshold instabilities was almost negligible. However, the threshold approaches zero volts at high temperatures after a high temperature negative gate bias stress. The zero gate bias leakage is low until the threshold voltage reduces to approximately 150 mV, where-after the leakage increases exponentially. Thermal aging tests demonstrated a sudden change from linear to nonlinear output characteristics after 24–100 h air storage at 300 °C and after 570–1000 h in N2 atmosphere. We attribute this to nickel oxide growth on the drain contact metallization which forms a heterojunction p-n diode with the SiC substrate. It was determined that these state-of-the-art SiC mosfet devices may be operated in real applications at temperatures far exceeding their rated operating temperatures.
      PubDate: Oct. 2017
      Issue No: Vol. 32, No. 10 (2017)
  • Multifault Tolerance Strategy for Three-Phase Multilevel Converters Based
           on a Half-Wave Symmetrical Selective Harmonic Elimination Technique
    • Authors: Mohsen Aleenejad;Hamid Mahmoudi;Reza Ahmadi;
      Pages: 7980 - 7989
      Abstract: This paper presents a generalized fault-tolerant strategy to improve the performance of the three-phase cascaded H-bridge converters with faulty cells. The proposed fault-tolerant strategy combines the fundamental phase-shift compensation (FPSC) method with half-wave symmetrical selective harmonic elimination (SHE) to rebalance the inverter voltages and limit the total harmonic distortion (THD) of the waveforms. In this paper, first, the FPSC method is explained and the formulation for a new half-wave symmetric SHE technique is provided. Then, the main idea of the paper is presented as to adjust the phase angles of the fundamental harmonic of the line-ground voltages while equalizing the amplitudes and phase shifts of the third-order harmonics and eliminating some higher order harmonics. The proposed fault-tolerant strategy uses the increased degree of freedom provided by half-wave symmetrical SHE to adjust phase angles and eliminate a wide range of lower order harmonics for limiting the THD of the converter voltages under the faulty conditions. Finally, several experimental results are provided to validate the operation of the proposed strategy.
      PubDate: Oct. 2017
      Issue No: Vol. 32, No. 10 (2017)
  • Reliability Improvement of Power Converters by Means of Condition
           Monitoring of IGBT Modules
    • Authors: Ui-Min Choi;Frede Blaabjerg;Søren Jørgensen;Stig Munk-Nielsen;Bjørn Rannestad;
      Pages: 7990 - 7997
      Abstract: Power electronic systems have gradually gained an important status in a wide range of industrial applications such as renewable generation, motor drives, automotive, and railway transportation. Accordingly, recent research makes an effort to improve the reliability of power electronic systems to comply with more stringent constraints on safety, cost, and availability. The power devices are one of the most reliability-critical components in power electronic systems. Therefore, its condition monitoring plays an important role to improve the reliability of power electronic systems. This paper proposes a condition monitoring method of insulated-gate bipolar transistor (IGBT) modules. In the first section of this paper, a structure of a conventional IGBT module and a related parameter for the condition monitoring are explained. Then, a proposed real-time on-state collector–emitter voltage measurement circuit and condition monitoring strategies under different operating conditions are described. Finally, experimental results confirm the feasibility and effectiveness of the proposed method.
      PubDate: Oct. 2017
      Issue No: Vol. 32, No. 10 (2017)
  • Synchronization of the Carrier Wave of Parallel Three-Phase Inverters With
           Virtual Oscillator Control
    • Authors: Jian Hu;Hao Ma;
      Pages: 7998 - 8007
      Abstract: In this paper, a method to synchronize the carrier wave of parallel three-phase inverters without communication is proposed. This method is based on the digital-based virtual dead-zone oscillators coupled with each other through electrical connections between parallel inverters. These oscillators are synchronized based on the phenomenon of synchronization in networks of coupled oscillators. Thus, the carrier waves of different inverters are confirmed to be synchronized since they are generated by the oscillators. The model of the circulating current and the sufficient condition of global synchronization of oscillators are derived in this paper. The methodology for controller design is outlined based on the aforementioned analysis. Experimental results for a system with three inverters are given to illustrate the effectiveness of the proposed control.
      PubDate: Oct. 2017
      Issue No: Vol. 32, No. 10 (2017)
  • Digital Implementation of Soft Start-Up and Short-Circuit Protection for
           High-Frequency LLC Converters With Optimal Trajectory Control (OTC)
    • Authors: Chao Fei;Fred C. Lee;Qiang Li;
      Pages: 8008 - 8017
      Abstract: Achieving soft start-up and short-circuit protection have always been challenging for resonant converters due to severe stresses in the resonant tank. Optimal trajectory control (OTC) has been proven to be the most effective control method to optimize energy delivery with given stresses. This paper proposes a method to implement soft start-up and short-circuit protection for LLC converters by using low-cost microcontrollers (MCUs) with minimum stresses and optimal energy delivery. Our current understanding of the relationship between the switching frequency and the output voltage is based on the state-plane analysis, and the requirement for the controllers is significantly reduced when using the lookup table. Further improvement enables the application of the proposed control method to high-frequency LLC converters without increasing the cost for the controllers. This paper proposes a method to protect the LLC converter from abrupt short-circuit with low-cost MCUs, which improves transient response to short-circuit significantly, and investigates limitations when operating the high-frequency LLC converter under short-circuit conditions. The proposed methods minimize the CPU resource requirement and can be further integrated with other state-trajectory control functions within one MCU. Experimental results are demonstrated on a 500-kHz 1-kW 400-V/12-V LLC converter with 60-MHz MCU TMS320F28027.
      PubDate: Oct. 2017
      Issue No: Vol. 32, No. 10 (2017)
  • Computationally Efficient DMPC for Three-Level NPC Back-to-Back Converters
           in Wind Turbine Systems With PMSG
    • Authors: Zhenbin Zhang;Christoph M. Hackl;Ralph Kennel;
      Pages: 8018 - 8034
      Abstract: Direct model predictive control (DMPC) is an attractive control method, in particular, for multilevel converters. However, the computation time for classical DMPC schemes increases exponentially with the number of switching states and, compared to modulation-based controllers, real-time implementation may not be feasible. In this paper, two computationally efficient DMPC schemes with hexagon candidate region (HCR) and triangle candidate region (TCR) for torque and power control of three-level neutral-point clamped back-to-back converters in wind turbine systems with permanent-magnet synchronous generator are proposed. By an appropriate selection of the candidate regions, the number of reasonable switching states is drastically reduced which saves computation time up to 55% for HCR and up to 83% for TCR, respectively. The computational efficiency improvements and the control performances of the proposed DMPC schemes are compared and validated by real-time implementations on an field programmable gate array (FPGA) system and by measurement results at a lab-constructed test bench. The achieved control performance of the proposed methods is comparable with that of the classical DMPC, while the computation times are drastically reduced.
      PubDate: Oct. 2017
      Issue No: Vol. 32, No. 10 (2017)
  • Triple Phase Shift Control of an LLL Tank Based Bidirectional Dual Active
           Bridge Converter
    • Authors: Shiva S. Muthuraj;V. K. Kanakesh;Pritam Das;Sanjib Kumar Panda;
      Pages: 8035 - 8053
      Abstract: Isolated bidirectional dc–dc converters (IBDCs) with high efficiency and high power density demand for complete zero voltage switching (ZVS) of all active devices for its entire operating range. This paper presents a comprehensive analysis and optimization problem formulation of a triple phase shift (TPS)-controlled inductive link based voltage fed-dual active bridge (VF-DAB) converter. Limitation on natural ZVS range for the TPS-controlled inductive link based VF-DAB is presented. To extend the ZVS range in a TPS-controlled VF-DAB converter, passive auxiliary inductors are connected in parallel (LLL tank) to the primary and secondary sides of the high-frequency transformer. Analysis and subsequent numerical solutions for the TPS-controlled VF-DAB with auxiliary inductors show complete ZVS of all the mosfets for the entire operating range. Experimental results confirm complete ZVS of all mosfets under various voltage gains and load conditions. A comparative loss breakdown for the TPS-controlled LLL tank VF-DAB and the conventional inductive link VF-DAB at various operating conditions show the necessity of the additional auxiliary inductors in the conventional design for increasing optimal switching frequency of the IBDC.
      PubDate: Oct. 2017
      Issue No: Vol. 32, No. 10 (2017)
  • Wide-Range Adaptive IPT Using Dipole-Coils With a Reflector by Variable
           Switched Capacitance
    • Authors: Eun S. Lee;Byeong G. Choi;Jin S. Choi;Duy T. Nguyen;Chun T. Rim;
      Pages: 8054 - 8070
      Abstract: A dipole-coil-based inductive power transfer (IPT) with a reflector, which first adopts the variable switched capacitance for load power regulation under very wide-range distance variation between transmitter (Tx) and receiver (Rx) coils, is newly proposed. The resonant frequency of the LC tank of the proposed IPT can be appropriately modulated by the variable switched capacitance with reliable zero-voltage-switching (ZVS) operations. Therefore, even though the distance changes very widely, load power can be regulated solely by the variable switched capacitance in the Rx circuit without complicated communication links between the Tx and Rx coils. A detailed static analysis based on a recent imaginary gyrator model and design procedure for the proposed IPT are presented to build a simplified LC resonant tank of the proposed IPT and ZVS condition and to identify applicable distance variation range for constant load power. A prototype of the Tx and Rx coils for 100 W of load power, considering average power consumptions of home appliances, was fabricated and verified by simulations and experiments, which showed that load power was completely regulated to 100 W for 23–70 cm of very wide-range distance variation at a fixed switching frequency of 140 kHz.
      PubDate: Oct. 2017
      Issue No: Vol. 32, No. 10 (2017)
  • Hot-Swapping Analysis and Implementation of Series-Stacked Server Power
           Delivery Architectures
    • Authors: Enver Candan;Derek Heeger;Pradeep S. Shenoy;Robert C. N. Pilawa-Podgurski;
      Pages: 8071 - 8088
      Abstract: Current data center power delivery architectures consist of many cascaded power conversion stages, where the system-level power conversion efficiency is reduced each time the power is processed through the individual stages. Recently, series-stacked power delivery architectures have shown how the overall power conversion can be reduced through architectural changes, reporting above 99% system-level power conversion efficiencies for data centers. In this paper, we contribute to the development of the series-stacked power delivery architectures by addressing the important hot-swapping challenge, without sacrificing the high power conversion efficiency. We analyze the hot-swapped operation of the series-stacked architecture, and experimentally validate it on a testbed that includes four series-connected 12 V, 120 W servers and four custom-designed differential converters with associated circuitry for hot-swapping. The results show that continuous operation of the series-stacked servers can be maintained while a server is hot-swapped without a significant reduction in the high power conversion efficiency.
      PubDate: Oct. 2017
      Issue No: Vol. 32, No. 10 (2017)
  • Synchronverter-Enabled DC Power Sharing Approach for LVDC Microgrids
    • Authors: Saeed Peyghami;Pooya Davari;Hossein Mokhtari;Poh Chiang Loh;Frede Blaabjerg;
      Pages: 8089 - 8099
      Abstract: In a classical ac microgrid (MG), a common frequency exists for coordinating active power sharing among droop-controlled sources. Like the frequency-droop method, a voltage-based droop approach has been employed to control the converters in low voltage direct current (LVDC) MGs. However, voltage variation due to the droop gains and line resistances causes poor power sharing and voltage regulation in dc MG, which in most cases are solved by a secondary controller by using a communication network. To avoid such an infrastructure and its accompanied complications, this paper proposes a new droop scheme to control dc sources by introducing a small ac voltage superimposed onto the output dc voltage of converters. Therefore, dc sources can be coordinated together with the frequency of the ac voltage, without any communication network like synchronous generators (SGs) in conventional power systems. Small signal stability analysis, as well as mathematical calculations, is presented to demonstrate the analogy between the proposed strategy and frequency-based droop approach of the SGs. The effectiveness of the proposed control system is evaluated by simulations and verified by experiments.
      PubDate: Oct. 2017
      Issue No: Vol. 32, No. 10 (2017)
  • Discrete-Time Domain Modeling of Voltage Source Inverters in Standalone
           Applications: Enhancement of Regulators Performance by Means of Smith
    • Authors: Federico de Bosio;Luiz A. de S. Ribeiro;Francisco D. Freijedo;Michele Pastorelli;Josep M. Guerrero;
      Pages: 8100 - 8114
      Abstract: The decoupling of the capacitor voltage and inductor current has been shown to improve significantly the dynamic performance of voltage source inverters in standalone applications. However, the computation and pulse width modulation delays still limit the achievable bandwidth. In this paper, a discrete-time domain modeling of an LC plant with consideration of delay and sample-and-hold effects on the state feedback cross-coupling decoupling is derived. From this plant formulation, current controllers with wide bandwidth and good relative stability properties are developed. Two controllers based on lead compensation and Smith predictor design, respectively, are obtained. Subsequently, the voltage regulator is also designed for a wide bandwidth, which permits the inclusion of resonant filters for the steady-state mitigation of odd harmonics at nonlinear unbalance load terminals. Discrete-time domain implementation issues of an antiwind up scheme are discussed as well, highlighting the limitations of some discretization methods. Extensive experimental results, including a short-circuit test, verify the theoretical analysis.
      PubDate: Oct. 2017
      Issue No: Vol. 32, No. 10 (2017)
  • Capacitor Voltages Measurement and Balancing in Flying Capacitor
           Multilevel Converters Utilizing a Single Voltage Sensor
    • Authors: Glen Farivar;Amer M. Y. M. Ghias;Branislav Hredzak;Josep Pou;Vassilios G. Agelidis;
      Pages: 8115 - 8123
      Abstract: This paper proposes a new method for measuring capacitor voltages in multilevel flying capacitor (FC) converters that requires only one voltage sensor per phase leg. Multiple dc voltage sensors traditionally used to measure the capacitor voltages are replaced with a single voltage sensor at the ac side of the phase leg. The proposed method is subsequently used to balance the capacitor voltages using only the measured ac voltage. The operation of the proposed measurement and balancing method is independent of the number of the converter levels. Experimental results presented for a five-level FC converter verify effective operation of the proposed method.
      PubDate: Oct. 2017
      Issue No: Vol. 32, No. 10 (2017)
  • A Novel Adaptive Quasi-Constant On-Time Current-Mode Buck Converter
    • Authors: Chin-Fu Nien;Dan Chen;Sheng-Fu Hsiao;Le Kong;Ching-Jan Chen;Wei-Hao Chan;Yen-Liang Lin;
      Pages: 8124 - 8133
      Abstract: There have been a variety of constant on-time (COT) controllers for dc power converter applications reported in recent years [1]–[5] . In this paper, a novel adaptive quasi-constant on-time current-mode control scheme is proposed and implemented in buck converters. While preserving the advantages of the conventional COT current-mode converters, this scheme allows fast transient response to step-load that is a critical requirement of a computer load with smart management. A small-signal model of the proposed circuit is also developed. Experimental results are also provided. This scheme is well suited for the next-generation dc converters for power management central-processor-unit devices.
      PubDate: Oct. 2017
      Issue No: Vol. 32, No. 10 (2017)
  • Analysis and Dynamic Performance Improvement of Grid-Connected
           Voltage–Source Converters Under Unbalanced Network Conditions
    • Authors: Shamed Mortazavian;Masoud M. Shabestary;Yasser Abdel-Rady I. Mohamed;
      Pages: 8134 - 8149
      Abstract: The energy sector is moving toward an extensive utilization of distributed and renewable energy resources. Such resources are usually interfaced to power grids via voltage–source converters (VSCs). Due to the increased penetration level of VSC-interfaced resources, the utilization of interfacing VSCs to support host grids under unbalanced conditions (e.g., due to grid voltage unbalance, unbalanced load conditions and unsymmetrical faults) becomes essential. However, detailed dynamic analysis and systematic design procedure to enhance the dynamic performance of grid-connected VSCs equipped with grid-support controllers are not reported in the literature. To fill in this gap, this paper presents a detailed small-signal model and analysis of the dynamics of a grid-connected VSC equipped with the recently developed balanced positive-sequence control and positive/negative-sequence control methods to support the grid under unbalanced conditions. The effects of the short-circuit ratio, angle of the ac system impedance, and phase-locked-loop parameters on the transient behavior of the VSC are thoroughly studied and characterized. Furthermore, to improve the dynamic performance of grid-connected VSCs, a simple yet effective current-control-based compensator is developed to mitigate possible instabilities associated with the low-voltage operation. Comparative simulation and experimental results validate the theoretical analysis and the effectiveness of the proposed compensation scheme.
      PubDate: Oct. 2017
      Issue No: Vol. 32, No. 10 (2017)
  • Reducing the Inductors of Rectifiers Having Two Outputs to Improve Power
    • Authors: Qing-Chang Zhong;Wen-Long Ming;
      Pages: 8150 - 8162
      Abstract: In this paper, a recently reported single-phase rectifier with two outputs (RECTO) is improved to reduce the neutral inductor and the grid inductor, by moving the neutral inductor away from the path of the grid current. The neutral inductor does not carry the grid current any more so the current stress of the neutral inductor can be significantly reduced, and the size of the inductor becomes much smaller. In theory, the current stress can be reduced by at least three times and the size of the inductor can be reduced by nine times. At the same time, the grid inductor can be reduced to achieve the same level of grid-current switching ripples because of the changed operation modes and modulation strategy. Together, the reduced neutral and grid inductors help improve the system power density. It is worth noting that the voltage and current stresses of the switches and the other features of the RECTO, e.g., two dc outputs and unity power factor, are not affected. Comparative experimental results are presented to demonstrate the reduction. If the two load currents are the same then the neutral inductor is only required to handle the switching ripples. This improved RECTO is particularly suitable for applications with two balanced loads without increasing the cost much.
      PubDate: Oct. 2017
      Issue No: Vol. 32, No. 10 (2017)
  • Modified Cascaded Boundary-Deadbeat Control for a Virtually-Grounded
           Three-Phase Grid-Connected Inverter With LCL Filter
    • Authors: Yuanbin He;Henry Shu-Hung Chung;Carl Ngai-Man Ho;Weimin Wu;
      Pages: 8163 - 8180
      Abstract: Cascaded boundary-deadbeat controller has been proven to be effective in controlling single-phase grid-connected inverter with LCL output filter. Such architecture mitigates filter resonance and offers good stability under stiff- and weak-grid conditions. However, its merits are offset by requiring many sensors, dedicated control loop to regulate the operating frequency, and high-precision intracycle information of the circuit variables to dictate the states of the switches. A modified cascaded boundary-deadbeat control law with reduced number of current sensors, the use of current band to regulate the operating frequency, and intracycle information recovery mechanism of the filter capacitor voltage for a virtually-grounded three-phase grid-connected inverter with LCL filter is presented. It inherits the merits of allowing the inverter to exhibit fast dynamic response and mitigating filter resonance. The contaminated intracycle information of the filter capacitor voltage is recovered so as to estimate and predict state trajectories accurately. Furthermore, a dc bus voltage feedforward injection scheme with reduced number of voltage sensor is proposed. It utilizes the duty cycle information of the gate signals to compensate the effect of the unbalanced dc bus capacitor voltages on causing modulation saturation and current distortion. The system characteristics under parametric variations will be studied. A 3-kW prototype has been built and evaluated under stiff- and weak-grid conditions.
      PubDate: Oct. 2017
      Issue No: Vol. 32, No. 10 (2017)
  • A Novel Source Current Control Strategy and Its Stability Analysis for an
           Indirect Matrix Converter
    • Authors: Na Han;Bo Zhou;Jiang Yu;Xianhui Qin;Jiaxing Lei;Yang Yang;
      Pages: 8181 - 8192
      Abstract: Indirect matrix converter (IMC)'s source current may contain low-order harmonics caused by asymmetric modulation in a variable-speed-constant frequency generation system. However, without capacitor/inductor decoupling effect, IMC's source current depends on loads and cannot be controlled independently. In this paper, the expressions of source current harmonics in the synchronous rotating reference frame are analyzed first. It leads to the conclusions that the only uncontrollable part of the source current is its d-axis dc component, and the quality of the source current can be improved by suppressing the harmonics. On the basis of above analysis, a novel source current control strategy is proposed for an IMC with asymmetric modulation, which can improve the source current quality and correct the input power factor. Self-tuning resonant controllers and a proportional integral controller are employed to achieve above goals. The stability of the system is also analyzed considering the change of input impendence after adding the source current control, which can be used as the guidance for the selection of control parameters. Finally, the validity and the feasibility of the control strategy are verified via experiments.
      PubDate: Oct. 2017
      Issue No: Vol. 32, No. 10 (2017)
  • Transient Control of the Reactive Current for the Line-Side Converter of
           the Brushless Doubly-Fed Induction Generator in Stand-Alone Operation
    • Authors: Xingwei Wang;Hua Lin;Zhe Wang;
      Pages: 8193 - 8203
      Abstract: In this paper, the transient control algorithm of the reactive current by the line-side converter (LSC) control is proposed when the inductive load is suddenly connected or disconnected from the stator power winding (PW) of the brushless doubly-fed induction generator. In stand-alone operation, the quality of the voltage waveform at the point-of-common coupling (PCC) will be strongly affected due to the reactive power change of load. Moreover, when the amplitude of the PCC voltage is higher than the dc-link voltage, the LSC cannot work normally. To tackle this problem, many control strategies, such as predictive current control, direct voltage control, etc., are usually developed in the machine-side converter to supply the reactive power, but the LSC can also assist in stabilizing the PCC voltage fluctuation by supplying or absorbing reactive current. This paper analyzes the transient state of the load current and the PCC voltage when the load is suddenly connected to the stator PW, and proposes a compensation algorithm which has a good transient-state performance. Then, the controllability of the LSC during the PCC voltage swell is analyzed when the load is disconnected from the stator PW. A high-voltage ride-through control strategy is proposed by using the reactive current of the LSC. The correctness of the proposed method is demonstrated by simulations and experiments.
      PubDate: Oct. 2017
      Issue No: Vol. 32, No. 10 (2017)
  • Impact of Power Flow Direction on the Stability of VSC-HVDC Seen From the
           Impedance Nyquist Plot
    • Authors: Mohammad Amin;Marta Molinas;Jing Lyu;Xu Cai;
      Pages: 8204 - 8217
      Abstract: The high-voltage dc (HVDC) systems are appearing more and more, and it is becoming a requirement that the HVDC voltage-source converters (VSCs) operate both as an inverter and a rectifier without changing the controls to provide the flexibility of having power flows in both directions. It is observed that the HVDC system operates stably when the power flow direction is from the power-controlled converter to the dc-voltage-controlled converter, and it becomes unstable when the power flow direction has been altered. In order to analyze such an instability problem and to design the local control, an impedance-based method is proposed. Identifying the source and the load impedance are prerequisite to apply the impedance-based method. The existing method of determining the source and the load impedance cannot predict the stability when the power flow direction is altered; therefore, a method based on the power flow direction has been presented to determine the source and the load impedance. The converter that injects power to the dc system is the current source represented with its Norton equivalent parallel impedance, while the other converter impedance is considered as the load impedance. The stability of the system is determined by the ratio of the load impedance to the current-source impedance. Once the source and the load impedance are analytically obtained, the impedance-based Generalized Nyquist stability criterion is applied to determine the stability. The system stability for the two power flow directions is well predicted from the Nyquist plot of impedance ratio. A two-terminal HVDC system has been developed in MATLAB/Simulink to demonstrate the application of this method, and the results are compared with the experimental results.
      PubDate: Oct. 2017
      Issue No: Vol. 32, No. 10 (2017)
  • A Root-Locus Design Methodology Derived From the Impedance/Admittance
           Stability Formulation and Its Application for LCL Grid-Connected
           Converters in Wind Turbines
    • Authors: Francisco D. Freijedo;Enrique Rodriguez-Diaz;Mohammad S. Golsorkhi;Juan C. Vasquez;Josep M. Guerrero;
      Pages: 8218 - 8228
      Abstract: This paper presents a systematic methodology for the design and the tuning of the current controller in LCL grid-connected converters for wind turbine applications. The design target is formulated as a minimization of the current loop dominant time constant, which is in accordance with standard design guidelines for wind turbine controllers (fast time response and high stability margins). The proposed approach is derived from the impedance/admittance stability formulation, which, on one hand, has been proved to be suitable for the controller design when the active damping is implemented and, on the other hand, has also been proved to be very suitable for system-level studies in applications with a high penetration of renewable energy resources. The tuning methodology is as follows: first, the physical system is modeled in terms of the converter admittance and its equivalent grid impedance; then, a sensitivity transfer function is derived, from which the closed-loop eigenvalues can be calculated; finally, the set of control gains that minimize the dominant time constant are obtained by direct search optimization. A case study that models the target system in a low-power scale is provided, and experimental verification validates the theoretical analysis. More specifically, it has been found that the solution that solves the minimization of the current controller time constant (wind turbine controller target) also corresponds to a highly damped electrical response (robustness provided by the active damping).
      PubDate: Oct. 2017
      Issue No: Vol. 32, No. 10 (2017)
School of Mathematical and Computer Sciences
Heriot-Watt University
Edinburgh, EH14 4AS, UK
Tel: +00 44 (0)131 4513762
Fax: +00 44 (0)131 4513327
Home (Search)
Subjects A-Z
Publishers A-Z
Your IP address:
About JournalTOCs
News (blog, publications)
JournalTOCs on Twitter   JournalTOCs on Facebook

JournalTOCs © 2009-2016