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Journal of Power Electronics
Number of Followers: 8  Hybrid journal (It can contain Open Access articles)ISSN (Print) 1598-2092 - ISSN (Online) 2093-4718 Published by Springer-Verlag  [2468 journals]
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- Bus voltage control of residential PV–HESS–grids using
multimodal simplification-
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Abstract: Abstract This paper presents a residential power system that mainly includes photovoltaic (PV) panels, a hybrid energy storage system (HESS), a grid, and converters. The multimodal operation caused by the large number of states for each of the units increases the complexity of the system operation. It is difficult to adjust the operation state in the face of emergencies. A multimodal simplification method is proposed to simplify multimodal operation into three dominant modes (PV, HESS, and load) according to an energy management flowchart. A novel control strategy is proposed to realize the internal power distribution of the HESS, as well as the power allocation between the HESS and a single-phase full-bridge converter (SFC), while smoothing the double fluctuation of the bus voltage caused by the SFC. The effectiveness of the proposed multimodal simplification and control strategy is verified through the simulation and experimental results from a PV–HESS–grid.
PubDate: 2023-09-23
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- Harmonic compensated individual-phase control of four-leg inverters for
microgrid applications-
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Abstract: Abstract In this paper, harmonic compensated individual-phase voltage control of four-leg inverters is proposed for microgrid applications. Individual-phase control, which is one of the promising voltage control methods of four-leg inverters, ensures robustness for high load unbalance rates. However, the odd harmonics generated by nonlinear loads and dead time deteriorate the quality of load voltages under single-phase control. The proposed method compensates for the odd harmonics included in the load voltages to improve the output power quality. In the proposed method, band-pass and all-pass filters are used to generate the virtual components for the individual-phase control. Additionally, the harmonics are compensated in the synchronous reference frame using a resonant controller, while the fundamental components are controlled by proportional-integral controllers. With the proposed method, the total harmonic distortion of the load voltages is maintained at a low level under unbalanced and nonlinear load conditions. The effectiveness of the proposed method is demonstrated through simulation and experimental results.
PubDate: 2023-09-23
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- Cockcroft–Walton voltage multiplier-based argon vacuum gauge for
high-temperature applications-
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Abstract: Abstract A cost-effective argon atmosphere vacuum gauge based on direct current (DC) excited glow discharge plasma for harsh environmental conditions is presented in this paper. The gauge comprises two copper electrodes separated by a pre-defined gap (1 mm, 5 mm, 10 mm, or 15 mm) excited with a 1.8 kV DC supply using a Cockcroft–Walton (CW) voltage multiplier circuit to measure vacuum pressures from 0.05 to 5 mbar. After gas breakdown has occurred, the voltage across the electrodes (plasma voltage response) is measured with a change in pressure. The proposed gauge with a 5 mm electrode gap showed an average sensitivity of 276 V/mbar with excellent thermal stability from 25 to 400 °C. The hysteresis of the gauge is 11% over the full scale and shows an average plasma voltage response deviation of 0.9 mV/h with time when tested for 10 h under a continuous mode of operation. Overall, the device shows promise in the development of a low-cost vacuum gauge with good sensitivity and excellent immunity to high-temperature environments.
PubDate: 2023-09-19
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- Constant on-time variable frequency control for critical conduction mode
GaN-based totem-pole PFC converters-
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Abstract: Abstract A constant on-time variable frequency control (COTVFC) with feed-forward for a critical conduction mode (CRM) totem-pole power factor correction (PFC) converter is proposed in this paper. This control method only requires a single voltage loop, where the output is taken as the on-time of the main switches of the converter. The off-time of the main switches in different switching cycles is calculated by the voltage-second balance principle, which ensures that the converter always operates in the CRM. Feed-forward is introduced to improve the dynamic response of the converter. The control model is established and the transfer function from the on-time to the output is derived. On this basis, the control parameters of the voltage loop are designed. Then a simulation model is built in PSIM for simulation verification. Finally, a two-phase interleaved parallel GaN-based totem-pole PFC converter prototype is made for experimental verification. Simulation and experimental results verify the feasibility and effectiveness of the control method proposed in this paper.
PubDate: 2023-09-19
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- PLL method with speed feedforward compensation for extended EMF-based
IPMSM sensorless control-
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Abstract: Abstract This paper proposes a phase-locked loop (PLL) with a low bandwidth and high estimation performance in terms of position and speed through speed feedforward compensation for driving extended back electromotive force (EEMF)-based sensorless control for an interior permanent magnet synchronous motor (IPMSM). In this case, lowering the bandwidth to reduce sensitivity to disturbances of the PI controller, where the position error is controlled to zero, may create a problem of decreased estimation performance. The proposed method calculates speed through mathematical calculations of the EEMF, which is observed using an EEMF-based IPMSM model, and adds it to the output of the PLL. The added speed feedforward compensation reduces the computational burden of the PI controller. Therefore, fast estimation dynamic characteristics can be obtained even at low bandwidths. The improvement of the estimation performance of the proposed method is evaluated by analyzing the equivalent block diagram using the final value theorem theory. Through this, the estimation performance is shown. It can be seen that the position estimation error for various types of speed inputs converges to zero. In addition, validity and implementation of this method are verified by experimental results.
PubDate: 2023-09-19
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- Single-loop order reduction output voltage control with model-free
filtering for DC/DC converters-
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Abstract: Abstract This study devises an advanced single-loop output voltage control method for DC/DC converters incorporating a model-free filter, active damping, and nonlinearly designed feedback terms. The resultant output-feedback controller ensures the order reduction property and reduces both the dependence level of the system model and the number of feedback loops. There are two main features that differentiate this from extant results. First, a model-free first-order pole-zero cancellation (PZC) filter extracts the time derivative component from the output voltage measurement according to the first-order dynamics by the order reduction property without any converter model information. Second, an active damping controller forming a modified proportional-integral-derivative structure tracks the output voltage to its desired trajectory along the first-order low-pass filter dynamics by the order reduction property from the PZC, which is independent of the current feedback. Experimental evidence obtained from an actual feedback system adopting a 3-kW prototype DC/DC converter validates the effectiveness of the proposed technique, which demonstrates the capability of the current sensor fault tolerance.
PubDate: 2023-09-14
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- Hybrid DC circuit breaker with reduced fault isolation time and current
limiting capability-
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Abstract: Abstract DC circuit breakers (DCCBs) are key pieces of equipment to ensure the safe and stable operation of DC grids. However, current DCCB schemes generally have problems such as a slow fault clearing speed and a poor current limiting effect. This paper proposes a current-limited hybrid DC circuit breaker (CLHCB) that limits fault current and has fast fault isolation, which reduces the capacity requirements. The current limiting inductor in the fault current limiter (FCL) provides the current limiting capability. In addition, the energy dissipation circuit (EDC) is in parallel to reduce the energy dissipation in metal oxide arresters (MOAs) and to decrease the fault isolation time (FIT), which can reduce the thermal effects of MOAs and improve their reliability. Simulation results verify the working principle and advantages of the proposed CLHCB. When compared to an ABB HCB under the same simulation parameters, the CLHCB enables fault current limiting and faster fault isolation. Finally, experiments have verified the effectiveness of the proposed CLHCB.
PubDate: 2023-09-11
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- Performance evaluation of carbon nanotube yarn-based inductors for
ISM-frequency band soft-switching converters-
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Abstract: Abstract With the advancement of carbon material science, there have been attempts to apply carbon nanotubes in various engineering fields. In power electronics, application research has been conducted on using carbon nanotube (CNT) yarn in inductors, transformers, and motor windings, because CNT yarns show promising mechanical and electrical characteristics when compared with conventional conduction materials. This paper evaluates the feasibility of CNT yarn-based inductor applications with respect to higher-frequency power converter circuits, especially focusing on the ISM (Industry–Science–Medical) frequency range. Inductors are fabricated using two kinds of CNT yarns with different conductivity values. These inductors are compared with copper and lead coiled inductors, since they have a relatively high conductivity with respect to CNT yarns, and due to their popularity in the industry. The small-signal impedance data of each inductor according to the frequency variation are measured using a network analyzer, and the measurements were compared with a COMSOL simulation. One of the main results of this research is that the CNT yarn-based inductors were shown to have a better normalized AC resistance characteristic than the conventional conductor inductors, which have higher conductivity. It was found that CNT inductors have a similar AC resistance when compared to that of metallic conductors with nearly 1.85 times higher conductivity. A 100 W differential class-E resonant converter is implemented to test the inductors and to verify the small-signal measurement results. Efficiencies and thermal images are obtained at 6.78-MHz and 13.56-MHz ISM frequencies.
PubDate: 2023-09-11
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- Design and implementation of 1000 V 20 kW power module for
electric vehicle fast charger-
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Abstract: Abstract This paper presents the design and the implementation of a 20 kW power module (PM) for electric vehicle fast chargers. The proposed PM includes an AC/DC converter using a T-type neutral-point-clamped (TNPC) topology and an isolated DC/DC converter that uses an LLC resonance topology to minimize the switching losses. A cooperative control strategy is proposed to achieve a parallel operation sequence of PMs while considering the actual EV charging sequence. Experimental results validate the effectiveness and the reliability of the proposed PM for various load conditions, and the feasibility of the cooperative control strategy is confirmed through the parallel operation with four PMs. Experimental results show a high-efficiency power conversion of up to 97%.
PubDate: 2023-09-07
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- Novel central-tapped planar transformer structure with natural
current-sharing for LLC resonant converters-
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Abstract: Abstract Planar transformers have been widely used in isolated power supplies. However, with a large current density, the parallel windings usually cannot share the current evenly. This uneven current-sharing may cause additional winding losses, and damage the performance of the power converter. In this paper, a novel central-tapped planar transformer structure is proposed. Regardless of whether it is in the first half cycle or the second half cycle, the proposed twelve-layer transformer can be simplified as four three-layer transformers connected in parallel. Moreover, there is a “shielding layer” between adjacent three-layer transformers. In addition, the proposed transformer structure is optimized with a symmetrical layer arrangement, and the skin effect and proximity effect can be further reduced. Simulation and experimental tests indicate that the optimized planar transformer can stably provide 476.1 W of output power at a frequency of 1.25 MHz. The peak efficiency of the optimized transformer is up to 99.2%, and there is no obvious hot spot on the PCB board. It is noteworthy that the temperature difference in the secondary windings is less than 5 °C, which means the current-sharing in the secondary windings works well.
PubDate: 2023-09-01
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- Asymmetric coaxial three-coil wireless power transmission system
optimization-
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Abstract: Abstract With the rapid development of wireless power transmission (WPT) technology and the demand for a wide range of applications, the common two-coil system is becoming increasingly mature. However, the monotonous structure of two-coil systems limits their development. By incorporating relay coils, the distance of power transmission, efficiency, and electromagnetic field (EMF) leakage can be effectively improved. In this paper, the three-coil system is analyzed, and the relay coil parameters are optimized by an evolutionary algorithm. After that, based on the coil optimization, the compensation capacitance of the relay coil is analyzed and an analytical formula of the compensation capacitance of the optimized relay coil is obtained. The results show that the parameter-optimized system reduces current by 86.9%, increases efficiency by 10%, and suppresses EMF leakage by 18 dB. Meanwhile, the capacitor optimization further improves the transmission efficiency of the system.
PubDate: 2023-09-01
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- Offset voltage injection method for neutral-point AC voltage ripple
suppression in Vienna rectifiers-
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Abstract: Abstract This paper proposes an offset voltage injection method to compensate for AC voltage ripple at the neutral-point of a Vienna rectifier. The proposed method leads to sinusoidal input currents and has a suppression effect on the AC voltage ripple at the neutral-point by injecting three offset voltages to remove both the zero current distortion and voltage unbalance (both DC voltage and AC voltage ripple) at the neutral-point. This can result in an improvement in the Total Harmonic Distortion (THD) of the input current. The offset voltage to realize the suppressing of the AC voltage ripple is defined based on a neutral-point voltage equivalence model of a Vienna rectifier. The priority of the offset voltages is considered to avoid over-modulation. In addition, incompatibility between offset voltages is analyzed to guarantee sinusoidal input currents. By considering both of these characteristics, the proposed method injects the offset voltages in order from the higher priority to the lower priority. The performance and effectiveness of the proposed method are verified with simulation and experimental results.
PubDate: 2023-09-01
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- State trend prediction of hydropower units under different working
conditions based on parameter adaptive support vector regression machine
modeling-
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Abstract: Abstract To address the problem where the different operating conditions of hydropower units have a large influence on the parameters of the trend prediction model of the operating condition indicators, a support vector regression machine prediction model based on parameter adaptation is proposed in this paper. First, the Aquila optimizer (AO) is improved, and a sine chaotic map is introduced to influence the population initialization process. An improved adaptive weight factor is used to balance the local search and global search capabilities. Second, according to the power and the head, the operating conditions of the unit are refined into several typical sets of operating conditions. On this basis, an SVR model is established using the improved AO search algorithm proposed in this paper, and the prediction parameters under each of the operating condition are optimized to establish the data of the operating conditions and optimal parameters. Then a neural network is used to fit the working condition and the optimal prediction parameters. In addition, the nonlinear function mapping of the complex relationship between the two is constructed. Finally, the constructed mapping relationship is added to the traditional SVR, and an adaptive SVR prediction model suitable for changes in the working conditions of hydropower units is realized. Simulation results show that when compared to the traditional SVR prediction model, the adaptive SVR prediction model designed in this paper can automatically adjust the prediction parameters according to changes in the working conditions and achieve the goal of maintaining optimal prediction performance under different working conditions. In addition, it has the ability to accurately predict the development trend of the unit operating state index within a certain time scale.
PubDate: 2023-09-01
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- Two-line-same-phase AC standstill measurement method for obtaining
accurate PMSM d–q-axis inductance values-
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Abstract: Abstract With their simple structure, good characteristics, small size, low weight, high starting torque, and high power density, permanent magnet synchronous motors (PMSM) are widely used in industry and national projects. However, accurate PMSM d–q-axis inductance values cannot be obtained after dynamic decoupling of the d–q-axis voltages of a PMSM under vector control. To tackle this challenge, this paper proposes a two-line-same-phase AC standstill measurement (TLSP-ACSM) method. To verify the effectiveness of the proposed method, both the motor synthetic magnetomotive force and theoretical error of inductance measurement based on the TLSP-ACSM method are analyzed, followed by experiments to demonstrate the effectiveness of TLSP-ACSM. By comparing the proposed method with another measurement method, it is demonstrated that the relative error of the d-axis and q-axis inductance measurements is reduced by about 23% and 21%, respectively. When considering magnetic flux leakage, TLSP-ACSM shows better measurement precision and tracking performance.
PubDate: 2023-09-01
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- Small-signal stability of AC/DC capacity and MMC controller voltage loop
dominated systems-
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Abstract: Abstract The stability of an MMC AC/DC hybrid system shows differences with changes in its operating state. However, the time domain analysis method cannot quantitatively evaluate the dynamic characteristics of the system. In this paper, a small-signal model of an MMC AC/DC hybrid system is established to analyze the system stability under continuous changes of the parameters. First, the dynamic characteristics of the small-signal model and the time-domain simulation model are compared to verify the accuracy of the small-signal model. Second, the dynamic stability of the MMC under four typical operating states is analyzed, and the influences of the AC system capacity and impedance angle on the stability domain of the system are evaluated. Then, the modal analysis method is used to solve the dominant mode and participation factor of the critically stable system. In addition, the oscillation characteristics of the system are solved. Finally, the variation trend of the system stability dominated by the controller parameters and DC capacity is obtained. The obtained results show that the controller parameters of the MMC do not contribute to the system oscillation characteristics. The selection of the AC/DC capacity leads to differences in system stability. Under PV control, the MMC AC/DC hybrid system presents stronger stability, and the system is easily affected by low-frequency oscillation.
PubDate: 2023-09-01
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- Energy efficiency characteristic analysis of tri-coil PT symmetric MC-WPT
systems-
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Abstract: Abstract The parity-time (PT) symmetric magnetic coupling wireless power transfer (MC-WPT) system has received a great deal of attention since it was proposed. Its transmission efficiency has been greatly improved when compared with previous research. The operational amplifier (OA) is a typical construction method for PT symmetric MC-WPT systems. On this basis, to achieve a higher transmission efficiency and a longer effective power transmission distance at the same time, this paper constructs an OA-based tri-coil PT symmetric MC-WPT system. The analytical expressions of its singularity, PT symmetric state, and PT symmetric broken state are obtained. Then a complete set of parameter design criteria for the tri-coil PT symmetric system is derived. The transmission efficiency and resonant frequency of two-coil and tri-coil system are simulated on MATLAB software, and the simulation results are consistent with the theoretical analysis results. Finally, an experimental device is constructed to further verify the correctness of the theory. This paper demonstrates that the effective power transmission distance of the tri-coil PT symmetric MC-WPT system is more than twice that of the two-coil PT symmetric MC-WPT system, which can achieve a good balance between transmission efficiency and transmission distance.
PubDate: 2023-09-01
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- Model predictive pulse pattern control of permanent magnet synchronous
motors for medium- and low-speed optimization-
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Abstract: Abstract Taking the permanent magnet synchronous motor (PMSM) as the research object, the model prediction pulse pattern control (MP3C) of a PMSM running in the medium–low-speed zone is adopted to further reduce the torque ripple and phase current total harmonic distortion (THD) of a motor running in the medium–low-speed zone. First, the objective function of the predictive pulse control method is optimized. The objective function is intended to be the difference between the switching voltage vector and the equivalent reference voltage vector. At the same time, the integral of the difference between the d-axis current reference value and the actual value is compensated into the voltage reference vector. Thus, the pulse pattern control selected by the objective function is optimal when the motor is running in the medium–low-speed region. In addition, the PMSM can run stably and reliably. Simulation results show that the torque ripple is reduced by 1.3 Nm and 1.2 Nm, and that the phase current total harmonic distortion is reduced by 0.10% and 0.03% when the motor is running at 5 Nm and 10 Nm and at a speed of 100 rpm, respectively. When the rotation speed is 1000 rpm, the torque ripple is reduced by 0.74 Nm and 0.78 Nm respectively. In addition, the phase current total harmonic distortion is decreased by 0.44% and 0.54%, respectively.
PubDate: 2023-09-01
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- High-efficiency bidirectional low-voltage power converter for fuel-cell
electric vehicles-
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Abstract: Abstract This paper proposes a bidirectional low-voltage DC-to-DC converter for advanced fuel-cell electric vehicles (FCEVs). The proposed converter consists of two parallel-operated power converters driving the low-voltage output stage to reduce the size of the filter. Two power converters are internally connected in series with an isolated LLC resonant converter and a non-isolated buck/boost converter to achieve high efficiency in both directions while ensuring very wide input and output voltage ranges. The LLC resonant converter generates an input from a 12 V low-voltage battery to a non-isolated converter when starting an FCEV. Once the fuel-cell stack is activated, the power flow reverses, and the non-isolated buck/boost converter regulates the input voltage for the LLC resonant converter from the power generated in the fuel-cell stack. To validate the performance of the proposed converter, a prototype converter is designed, built, and tested with 2.0 kW in the forward powering mode, 4.5 kW in the reverse powering mode, a 260–430 VDC input, and a 10–15 VDC output. Experimental results demonstrate that the proposed converter achieves a power conversion efficiency of over 95.5% in both the forward and reverse powering modes, while ensuring stable bidirectional operation and much lower current and voltage ripples.
PubDate: 2023-08-03
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- Correction: Estimation of switching losses considering non-linear
parasitic capacitances of GaN E-HEMT-
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PubDate: 2023-08-01
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- Fault-tolerant capability of MMC with novel structure of middle submodules
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Abstract: Abstract In this paper, an improved modular multilevel converter (MMC) topology has been proposed with fault-tolerant capability and reduced submodule capacitor voltage fluctuation (SMCVF) in a low frequency operating range. In the proposed converter, a novel middle SM, which has salient features, is inserted between the upper and lower arms. For regular operation, the middle SM is applied to mitigate the power fluctuations in both arms by providing distribution of high-frequency power components, which reduces the AC voltage fluctuation on the SM capacitor. When a fault occurs in any SM in the upper or lower arms, a new half-bridge SM can be configured from the middle SM to replace the faulty SM without any interruption, which means the converter is operated in the fault-tolerant mode. Therefore, the performance of the converter is maintained well, and the system reliability is enhanced. Simulation and experimental results have verified the effectiveness of the proposed topology and control strategy.
PubDate: 2023-07-21
DOI: 10.1007/s43236-023-00679-z
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