Journal of Power Supply

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Independent Excitation-response Mechanism of PLL-based Grid-connected Unit and Role Characterization Method for Unit Based on Amplitude-frequency Motion Equation

YUAN Xiaoming, WANG Sicheng, YUN Yangyang

Journal of Power Supply. 2024, 22(5): 1-14. https://doi.org/10.13234/j.issn.2095-2805.2024.5.1

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For evaluating the capacity of wind powers, photovoltaics and other power electronic grid-connected units supporting power systems, the core foundation is to correctly understand the unit’s functional role（i.e., the unit characteristics） that unit adjusts its own internal voltage amplitude/frequency according to the active/reactive power imbalance. However, the mainstream PLL-based grid-connection structure in power electronic units seriously hinders the understanding of the unit’s functional role. In particular, based on a specific PLL-based grid-connection structure, the industry and academia at present form a “grid following” role perception that the internal voltage of unit follows the grid voltage or terminal voltage, and have not recognized the functional role that the unit should take during the system operation. Therefore, through an in-depth understanding of the independent excitation-response mechanism of current control which is hidden under the PLL-based grid-connection structure, i.e., the internal voltage response depends on current excitation alone, the functional role of PLL-based grid-connected units in which the active/reactive power imbalance independently adjusts the internal voltage amplitude/frequency is clarified. Afterwards, a role characterization method for unit is pro-posed based on the relationship between active/reactive power imbalance excitation and internal voltage amplitude/fre-quency response, i.e., the amplitude-frequency motion equation. Finally, the inevitability of characterizing the role of PLL-based grid-connected units through the relationship between power excitation and internal voltage response is elab-orated on, and the existing limitations in the understanding of the role of PLL-based grid-connected units in industry and aca-demia are pointed out.

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Editorial for the Special Issue on Electromagnetic Compatibility in Power Electronic Systems

ZHANG Bo, LI Hong, WANG Shuo, HE Junping

Journal of Power Supply. 2024, 22(5): 15-18. https://doi.org/10.13234/j.issn.2095-2805.2024.5.15

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The new generation of wide bandgap power semiconductors such as SiC and GaN are driving the rapid high-frequency, high-efficiency, and small volume development of power electronic equipment. However, they are also more likely to interfere with sensitive loads, affect wireless communication, and even endanger their own safety and reliable operation, which poses great pressure and challenges to the electromagnetic compatibility（EMC） performance of power electronic equipment. In recent years, the radiated frequency（RF） characteristics of power switches, wideband electromagnetic models of magnetic components, electromagnetic radiation mechanisms of switched mode power supplies, near-field characteristics of wireless power transmission（WPT）, and the new designs of electromagnetic interference（EMI） filters have become current research hotspots and received continuous attention from academia and industry. The Journal of Power Supply has specially released the album "Electromagnetic Compatibility in Power Electronic Systems" to promote the exploration of difficult and hot issues in the field of EMC analysis and design of power electronic systems.

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Analytical RE EMI Model Considering Nonlinear Characteristics of Junction Capacitor and Transconductor

CHEN Wenxia, CHEN Wenjie, CHENG Rui, WANG Hongpeng, HUO Yongqi, WU Huibin

Journal of Power Supply. 2024, 22(5): 19-27. https://doi.org/10.13234/j.issn.2095-2805.2024.5.19

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Nowadays, wide band gap（WBG） semiconductor power electronic devices have caused increasingly serious electromagnetic interference（EMI） problems as noise sources due to their high switching frequency, fast switching speed and large parasitic parameters. However, the conventional study on noise sources mainly focused on the conduction emission frequency range within 30 MHz, and how to evaluate the impact of noise sources within the radiated emission frequency range（30-300 MHz） still remains uncertain. Therefore, an enhanced analytical EMI model for WBG devices is proposed. Compared with the conventional asymmetric trapezoidal wave EMI model, the proposed model takes into account the nonlinear characteristics of junction capacitor and transconductor in WBG devices in detail for the first time. The impact of nonlinear parameters on noises within the radiated emission frequency range is evaluated, and the application of the proposed model to the suppression of noise sources in this frequency range is further put forward. Simulation results demonstrated the accuracy of the proposed calculation method, and the results of hardware tests based on SiC devices were consistent with the theoretical analysis.

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Wide-band Impedance Modeling Method for Common-mode Inductor Considering Frequency-dependent Characteristics

LIAN Zhenzhu, FU Kaining, CHEN Wei

Journal of Power Supply. 2024, 22(5): 28-36. https://doi.org/10.13234/j.issn.2095-2805.2024.5.28

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The common-mode（CM） inductor is composed of windings and a magnetic core. Mn-Zn ferrite can be used as the magnetic core of CM inductor, and the frequency-dependent characteristics of its high-frequency parameters make the CM inductor exhibit non-linearity within a range of 150 kHz-30 MHz. It is difficult to accurately predict the impedance characteristics of the CM inductor in a high-frequency band due to the large deviation between the traditional lumped circuit model of CM inductor and the measured impedance characteristics. The effects of material parameters of the magnetic core and the winding scheme on the high-frequency impedance characteristics of CM inductor are analyzed, and the mechanism of magnetic material parameters and the winding structure affecting the distributed capacitance is described from the perspective of the distributed capacitance characteristics of CM inductor. A wide-band impedance simulation modeling method for CM inductor with the consideration of related frequency-dependent parameters of magnetic core was proposed, and its validity was verified by combining with the impedance test result.

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Analysis and Evaluation of Conducted Common-mode Interference of High-frequency Transformer

FU Kaining, TU Jiangtao, CHEN Wei

Journal of Power Supply. 2024, 22(5): 37-43. https://doi.org/10.13234/j.issn.2095-2805.2024.5.37

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An evaluation platform for the CM noise suppression characteristics of high-frequency transformer was established, which was suitable for batch applications in engineering. The conduction mechanism of common-mode（CM） noise in a transformer was analyzed, and the conduction characteristics of CM noise along the coupling path in the transformer was investigated for evaluating the transformer’s capability of suppressing the CM noise. First, a function generator was used to generate a high-frequency voltage pulsation signal, which was assigned on the primary winding of the transformer to simulate the transmission characteristics of CM noise. Then, an oscilloscope was used to capture the voltage drop generated by the CM signal on the sampling resistor to judge the suppression effect of the transformer on the CM noise, so as to analyze the influence of the sampling resistor selection on the evaluation results. The effectiveness of the proposed evaluation method for the CM noise suppression characteristics of transformer was verified by comparing the evaluation results with the test results of conducted electromagnetic interference spectrum.

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Prediction of Far-field Electromagnetic Radiated Emissions from AC/DC Telecommunication Power Supply Module

WANG Weixin, SHU Junhua, SUI Ningning, HE Junping

Journal of Power Supply. 2024, 22(5): 44-51. https://doi.org/10.13234/j.issn.2095-2805.2024.5.44

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The electromagnetic radiation emitted by an AC/DC telecommunication power supply is prone to ex-ceeding the limit standards, so the researches on its electromagnetic radiation mechanism and prediction methods can improve the corresponding electromagnetic compatibility（EMC） design. First, after the analysis of the source and propa-gation path of common-mode（CM） electromagnetic interference in an AC/DC telecommunication power supply module, it is suggested that its far-field electromagnetic radiation can be decomposed into two types, which are driven by input-port and output-port CM voltages, respectively. Then, a novel method of far-field electromagnetic radiation prediction is pro-posed by combining the CM voltage-driven sources with the radiation transfer functions of parasitic radiators. The spec-trum measurement of each CM voltage-driven source is realized by designing a spectrum analyzer and a resistor attenua-tor, and the radiation transfer functions of each parasitic radiator is numerically calculated using an electromagnetic sim-ulation software FEKO. Finally, the radiation prediction of a 4 kW AC/DC telecommunication power supply module was achieved, and the effectiveness of the proposed prediction method was verified by test results.

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Radiated EMI Modeling of Cables Considering Mutual-coupling Effect

JI Junpeng, ZHANG Ning, LIN Shan, LI Zhen, LUO Peng

Journal of Power Supply. 2024, 22(5): 52-59. https://doi.org/10.13234/j.issn.2095-2805.2024.5.52

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The cables of switching power supply which are connected in parallel is an important radiated electromagnetic interference（EMI） source for the switching power supply. Aimed at the problem of inaccurate prediction of radiated EMI of cables connected in parallel due to an unclear mutual-coupling effect, a radiated EMI model of cables of switching power supply is proposed by taking into account the mutual-coupling effect between cables. Through the modeling of mutual-impedance which describes the mutual-coupling effect between cables, the radiated EMI input impedance model describing the radiation characteristics of cables of switching power supply is obtained. Then, the radiated EMI model of cables of switching power supply is obtained considering the mutual-coupling effect. Finally, an experimental platform for measuring the radiated EMI was built, and experimental results show that the proposed radiated EMI model which takes the mutual-coupling effect into account can predict the radiated EMI of cables of switching power supply more accurately.

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Study on Electric-field Distribution Characteristics of Parity-time Symmetric Electric-field Coupled Wireless Power Transfer System

ZHENG Xiaoyao, JIANG Yanwei, SHU Xujian, ZHOU Yang, ZHAO Xiaoguang

Journal of Power Supply. 2024, 22(5): 60-66. https://doi.org/10.13234/j.issn.2095-2805.2024.5.60

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The electric-field coupled wireless power transfer（ECPT） system possesses several advantages, including lightweight coupling pole plates, cross-metal power transmission and negligible eddy current losses. Specifically, the parity-time symmetric ECPT（PT-ECPT） system characterized by its capability to maintain a constant output under variations in the coupling pole plate spacing exhibits promising application prospects. Consequently, the electric-field radiation distribution of the PT-ECPT system was studied. The theoretical analysis, simulations and experimental results indicate that compared with those of the conventional resonant ECPT systems, the electric-field distribution of the PT-ECPT system is more concentrated in the regions of strong coupling while maintaining identical output power. This concentration is particularly pronounced when the coupling coefficient is small, which makes the PT-ECPT system more secure under conditions of reduced coupling coefficients.

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Insertion Loss Prediction of Differential-mode EMI Filter Based on Artificial Neural Networks

CHEN Rongliang, LIANG Haiyan, LIU Yitao

Journal of Power Supply. 2024, 22(5): 67-73. https://doi.org/10.13234/j.issn.2095-2805.2024.5.67

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In power electronic devices, high-speed switching will often lead to serious electromagnetic interference（EMI） problems, which seriously affects the reliability of power electronic systems. To solve these EMI problems, EMI filters are a common solution. The insertion loss is an evaluation index for the noise attenuation capability, and the accuracy of its model directly affects the parameter design accuracy of EMI filters. To improve the prediction accuracy of the EMI filter insertion loss model, accurately describe the system behavior and predict the filtering performance of the EMI filter, and improve the design efficiency of the EMI filter, the insertion loss of a single-stage differential-mode EMI filter is modeled using a back propagation neural network. The proposed neural network model has better practical application value than the ideal model and the behavioral model of a high-frequency circuit, aiming to provide guidance for the design and optimization of EMI filters. This model can quickly evaluate the actual insertion loss of EMI filters to improve their design efficiency.

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Multi-objective Unified Optimal Control Strategy for DAB Converter with Triple-phase-shift Control

ZENG Jinhui, RAO Yao, LAN Zheng, HE Dong

Journal of Power Supply. 2024, 22(5): 74-85. https://doi.org/10.13234/j.issn.2095-2805.2024.5.74

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To solve the problems of large current stress, difficult soft switching of all switches and slow dynamic response of dual active bridge（DAB） converters, a multi-objective unified optimal control strategy based on triple-phase-shift（TPS） control is proposed. The forward power flow global mode of TPS control is analyzed, and three high-efficiency modes are selected to establish the analytical models of current stress and soft switching. Combined with these models, the optimal phase-shift ratio combination and minimum current stress in different modes are derived using the cost function optimization equation, which makes the switches operate within the zero-voltage-switching power constraint range. At the same time, the virtual power component is introduced in the process of efficiency optimization. A small-signal model is constructed, and the influence of small disturbance of different state variables on output voltage is clarified. Experimental results show that the proposed control strategy can not only reduce the current stress of the DAB converter and make all switches realize zero-voltage-switching, but also improve the dynamic performance of output voltage in the full power range.

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Dynamic Characteristic Optimization Method of Dual Phase Shift Control for Dual Active Bridge Converter

LI Shanshou, WANG Hao, YE Wei

Journal of Power Supply. 2024, 22(5): 86-91. https://doi.org/10.13234/j.issn.2095-2805.2024.5.86

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To improve the dynamic response performance of a dual active bridge（DAB） converter with dual phase shift（DPS） control during load switching and reduce the current stress, a novel dual phase shift（NDPS） control method is studied. By changing the shifting direction of the internal phase shift angle in traditional dual phase shift（TDPS）, the relationship between the transmission power and phase shift ratio is reconstructed, and the adjusting range of phase shift ratio is extended. The solving method for the optimal phase shift ratio of DPS control under the condition of current stress minimization is studied, and the dynamic response characteristics of NDPS and TDPS control under load switching conditions are compared and analyzed. Finally, an experimental platform of DAB converter was built to verify the theoretical analysis, and experimental results show that the optimal phase shift ratio combination based on current stress minimization can effectively reduce the current stress under light load conditions. At the same time, NDPS control has better dynamic response characteristics than TDPS control.

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Minimum Current Stress Control with Varying Switching Frequency for Dual-active-bridge Converter

HE Wei, LIU Xiaofang

Journal of Power Supply. 2024, 22(5): 92-99. https://doi.org/10.13234/j.issn.2095-2805.2024.5.92

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To improve the efficiency of a dual-active-bridge（DAB） converter, a control strategy of minimum current stress with varying switching frequency control is proposed. First, the minimum-current-stress-optimized control method when the voltage changes in a wide range is analyzed, the expressions for the conduction loss and switching loss of the DAB converter under light load conditions are established, and the conduction loss and switching loss at different switching frequencies are further compared. Then, the implementation method for closed-loop control and the power transmission range in each mode are introduced in detail. Under light load conditions, the proposed method can significantly reduce the current stress while improving the efficiency of the DAB converter. Finally, simulation and experimental results verified the advantage of the proposed control method.

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Frequency-controllable Switching Law for Boost Converter Based on Common Quadratic Lyapunov Function

LI Siqi, ZHANG Bo, ZHANG Weiyue

Journal of Power Supply. 2024, 22(5): 100-108. https://doi.org/10.13234/j.issn.2095-2805.2024.5.100

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Aimed at the problem that the switching frequency under the min-type switching law is too high to be applied in engineering practice, a switched system model of Boost converter operating in continuous conduction mode（CCM） is established, and a novel switching law based on common quadratic Lyapunov function is proposed. According to the mathematical expression of the switching law, the steady-state and dynamic performances of the converter are analyzed, and the regulation mechanism of the converter’s switching frequency under the switching law is described. Simulation and experimental results show that under the proposed switching law, the Boost converter’s switching frequency is controllable and the Zeno behavior which is specific to a switched system would not occur. Compared with those under the existing control strategies, the converter under the proposed strategy has a good dynamic performance, with fewer voltage fluctuations and a shorter settling time when suffering external disturbances.

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Expandable Dual-input High Step-up DC-DC Converter

HUANG Yimin, LIN Guoqing, LIN Siqi

Journal of Power Supply. 2024, 22(5): 109-119. https://doi.org/10.13234/j.issn.2095-2805.2024.5.109

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Aimed at new energy combined power supply systems such as photovoltaic and fuel cells, a non-isolated dual-input high step-up DC-DC converter is proposed. This converter is based on a dual-input Boost circuit, and the two input sources and output, as well as each switch tube, share a common ground. A diode capacitor network is introduced at the later stage to achieve high voltage gain and reduce the voltage stress of switching devices. The two input sources can supply power at the same time, and any one of them can supply power independently without adding extra switch tubes. In addition, the voltage gain can be further improved by expanding the booster unit to adapt to different application scenarios. The working principle for the converter and its extended circuit and the corresponding performance such as voltage gain characteristics and voltage stress of switching devices in three power supply modes are analyzed in detail, and its performance is compared with those of the existing similar converters. Finally, an experimental prototype was built to verify its feasibility.

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Research on Hybrid Bridge Dual-LLC Resonant Converter under Fixed-frequency PWM Control

PAN Jian, SONG Haojie, LIU Songlin, XIONG Jiaxin

Journal of Power Supply. 2024, 22(5): 120-132. https://doi.org/10.13234/j.issn.2095-2805.2024.5.120

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Aimed at the problem of wide frequency range and large circulating current with the traditional frequency-controlled LLC resonant converter in wide output voltage applications, a fixed-frequency PWM controlled hybrid bridge dual-LLC resonant converter is studied. According to the difference in the primary-side structure, the converter has three forms of topology, i.e., half-bridge-half-bridge, half-bridge-full-bridge and full-bridge-full-bridge, in which the primary-side structure is in parallel and the two transformers on the secondary-side are in series. Compared with the traditional frequency-controlled LLC converter, the three topologies always work at the resonant frequency, which reduces the switching frequency range. In addition, under the PWM control strategy, the three topologies can achieve 2, 3 and 4 times voltage gain, respectively, thereby adapting to wide voltage scenarios. At the same time, the circuit has a low circulating current loss and a good soft switching performance. Simulink simulation and experimental results verified the feasibility of the proposed scheme.

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DPWM Strategy for T-type Three-level Inverter Considering Common-mode Voltage Reduction and Neutral-point Voltage Balance

YE Shaoxi, ZHANG Xi, ZHU Chong

Journal of Power Supply. 2024, 22(5): 133-142. https://doi.org/10.13234/j.issn.2095-2805.2024.5.133

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To improve the reliability and efficiency of a T-type three-level inverter, a discontinuous pulse width modulation（DPWM） strategy is proposed to reduce the common-mode voltage while reducing the switching loss, which is also named as the RCVDPWM strategy. According to the mechanism of switching sequence in the T-type three-level topology which acts on the common-mode voltage, five DPWM clamping methods for common-mode voltage reduction are summarized. It can be found that there is at least one clamping method for common-mode voltage reduction at any modulation ratio or phase angle. For those phase angle regions where multiple clamping methods exist, the switch tube of the phase with the largest absolute value of current is preferentially selected for clamping to reduce the switching loss. Meanwhile, the proposed strategy can ensure that the DC component of neutral-point voltage is zero, and thus the neutral point shows a self-balancing capability. Experimental results verify the feasibility and effectiveness of the proposed RCVDPWM strategy.

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Active Damping Control Method of Fully Equivalent Shunt Resistor for Grid-connected Inverter

ZHU Jiangge, LI Fei, FENG Qiang, WU Jintao

Journal of Power Supply. 2024, 22(5): 143-149. https://doi.org/10.13234/j.issn.2095-2805.2024.5.143

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Based on the passive damping method of capacitor in parallel with resistor, the active damping method of virtual resistor in parallel with capacitor can complete the virtualization of shunt resistor using the control algorithm and realize the active damping of the resonant peak from the output filter through the capacitor current feedback. However, the existing method of virtual resistor in parallel with capacitor cannot achieve a strict equivalence of shunt resistance, which leads to the problem of poor dynamic performance. To solve this problem, through the transformation of the control block diagram, an active damping control method of fully equivalent shunt resistor based on capacitor voltage and capacitor current feedback is proposed, thus realizing the strict equivalence of passive damping method of capacitor in parallel with resistor. At the same time, the active damping control method of fully equivalent shunt resistor is obtained through the analysis of dominant poles of the system. Compared with the method of virtual resistor in parallel with capacitor based on the current loop, this method can effectively improve the damping ratio and response speed of the system while reducing the overshoot. Finally, simulation and experimental results verified the effectiveness of the proposed method.

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Virtual Torque Impulse Balance Control Strategy for Three-phase Voltage Source PWM Rectifier

ZHANG Chenggao, WANG Yu, ZHANG Yi, HAO Wenjuan, XIA Yuhang

Journal of Power Supply. 2024, 22(5): 150-160. https://doi.org/10.13234/j.issn.2095-2805.2024.5.150

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Owing to its advantages such as simple structure, strong robustness and good dynamic and static performances, model predictive control（MPC） has been widely applied to three-phase voltage source PWM rectifier systems. However, the PI linear regulator adopted in the voltage outer loop of MPC affects the dynamic performance of DC-side voltage. Aimed at this problem, a virtual torque impulse balance control strategy is proposed to achieve a rapid convergence of DC-side voltage through only one time of regulation. To realize this strategy, the expression of virtual torque is derived based on the mathematical model at first. Second, the virtual torque impulse balance control equation under load mutation is analyzed and established according to the fact that the DC-side output voltage will remain unchanged before and after load mutation while combining the principle of power conservation. Afterwards, the acting time of zero and forward vectors can be obtained. Finally, the virtual torque impulse balance control of the three-phase voltage source PWM rectifier system under load mutation is realized through simulations and experiments, which verifies the correctness and effectiveness of the proposed algorithm.

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Research on Generalized State Space Average Model and Control Strategy for Triple Active Bridge DC-DC Converter

SHEN Ke, WANG Wanxing, ZHAO Dan

Journal of Power Supply. 2024, 22(5): 161-169. https://doi.org/10.13234/j.issn.2095-2805.2024.5.161

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The triple active bridge（TAB） DC-DC converter based on the phase-shifting plus duty cycle control strate-gy has advantages such as a high efficiency and an expandable soft switching range. However, its small signal modeling process is complex, and the parameter setting of closed-loop control loop is difficult. To solve these problems, a full-orer continuous generalized state space average modeling and PI controller design method for TAB converter under phase-shifting plus duty cycle control is proposed. First, the operation principle and Y-type equivalent structure of the TAB converter are analyzed. Second, combined with the characteristics of phase-shifting plus duty cycle control and the equivalent method of AC square wave source, the generalized state space average model of the TAB converter is derived. Third, based on the derived model, the transfer function from input to output is obtained, and the parameters of PI con-troller are designed. Finally, the correctness and effectiveness of the proposed method were verified by digital simulations and prototype tests.

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Design and Implementation of Dual-converter for Connecting DFIG to DC Microgrid

MIAO Xiaoyang, LI Bingran, FU Hongquan

Journal of Power Supply. 2024, 22(5): 170-181. https://doi.org/10.13234/j.issn.2095-2805.2024.5.170

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In view of the serious current harmonics in a doubly-fed induction generator（DFIG）-DC connection sys-tem and the large loss of a dual-voltage source inverter（VSI） connection system, a novel dual-converter connection system which connects a three-phase DFIG to DC microgrid is designed. First, the topology, pulse-width modulation（PWM） measurement and DFIG model of the dual-converter connection system are described in detail. Different from the traditional connection systems, the proposed connection system adopts an open-end winding structure and uses a three-bridge arm rectifier on each side of the stator winding. Considering that these arms are usually composed of insulated gate bipolar transistors（IGBTs）, a diode is used instead of the IGBT in the rectifier to decrease the number of control switches and reduce the cost. Second, the control strategies for a stator-side converter（SSC） and a rotor-side convert-er（RSC） under the new topology are given. Third, a comparison with the DFIG-DC connection system and the dual-VSI connection system is performed through simulations, and results show the advantages of the proposed method in terms of current harmonic distortion, torque ripple and semiconductor loss. Finally, experimental verification was carried out on a 0.56 kW DFIG, and results also verified the advantages of this method in terms of loss, harmonics and torque ripple.

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Transient Stability Analysis and Improved Control Strategy for Islanded Microgrid Considering Nonlinear Damping Effect

TANG Yingjie, ZHA Xiaoming, TIAN ZhenLI Yixiang, HU Yufei, WAN Zijing

Journal of Power Supply. 2024, 22(5): 182-192. https://doi.org/10.13234/j.issn.2095-2805.2024.5.182

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With the rapid development of power generation by renewable energy and the grid-connection technology, the microgrid dominated by power electronic converters has attracted more and more attention in recent years. Owing to the low inertia and high nonlinearity of power electronic converters, an islanded microgrid under large disturbances is more likely to lose its transient stability. Considering the interactions between grid-forming and grid-following converters in the microgrid, a transient stability criterion based on the equal area criterion（EAC） and an improved control strategy for transient stability are proposed. First, the simplified second-order dynamic model of the islanded microgrid is established, which contains a nonlinear damping term relying on the power angle. Then, the impact of the nonlinear damping term on the acceleration and deceleration areas is revealed from the energy perspective. Considering the distribution characteristics of nonlinear damping, a transient stability criterion is formulated for the positive damping region. In addition, according to the stable boundary conditions, an improved control strategy for transient stability based on voltage feedforward is also put forward. Finally, simulations are carried out with MATLAB/Simulink to verify the effectiveness of the proposed stability criteria and the improved control strategy. The results show that the microgrid transient stability criterion and the improved control strategy proposed can provide a theoretical basis for the parameter optimization design of power electronic converters and the improvement of the stable operation capability of microgrid.

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Dual-factor Droop Control Strategy for DC Microgrid Based on Adaptive Characteristics

DONG Xu, XU Yonghai, MA Ning, HE Zhixuan

Journal of Power Supply. 2024, 22(5): 193-202. https://doi.org/10.13234/j.issn.2095-2805.2024.5.193

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The inconsistency of line parameters at the outlet of distributed generator（DG） and its random output dis-turbance lead to a decrease in load power distribution accuracy of DC microgrid and grid-side voltage fluctuation. Aimed at these problems, a double-factor droop control strategy based on adaptive characteristics is proposed with the consider-ation of the transient- and steady-state of DG operation. First, the influence of line impedance is taken into account dur-ing the steady-state operation, a voltage regulation coefficient is introduced, and the steady-state component of double-factor droop coefficient is established. The exact distribution of load power can be realized when the impedance value is unknown, and the grid-side voltage can be raised to reduce the difference with the rated voltage. Second, the influence of random disturbance of DG output is considered in the transient process, and the distributed consistency iterative algo-rithm is introduced to establish the double-factor droop coefficient free component, which can quickly suppress the power disturbance and grid-side voltage fluctuation while maintaining the balanced output from DG, thus improving the system stability. Finally, a DC microgrid model is built in PSCAD, and simulation results show the effectiveness of the proposed strategy.

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Passive Enhancement Control of Voltage-controlled Inverters in Grid-connected Microgrids Considering Control Delay and Variation in Grid Impedance

CHEN Li, ZHOU Yongbo, LI Ruiqi, WEI Xiang, YUAN Hao

Journal of Power Supply. 2024, 22(5): 203-212. https://doi.org/10.13234/j.issn.2095-2805.2024.5.203

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With the increasing attention to environmental issues, more and more distributed energy systems represented by microgrids are appearing in the power system, which also poses some challenges to the traditional power systems. For example, the delay in digital control system, variations in grid impedance of weak grid and the interaction between parallel converters in microgrids will cause adverse effects on the stable operation of microgrids. On this basis, a novel type of grid-forming control method for microgrid considering control delay and variation in grid impedance is put forward to enhance the stability of microgrids under uncertainties. First, the above problems are modeled, and a delay compensation method is proposed to improve the robustness of the control system with respect to the variation in grid impedance. Then, a feedforward loop is introduced into the control system to protect it from the interference of parallel inverters in microgrids. Finally, experimental results demonstrate the effectiveness and superiority of the proposed control method.

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Multi-dimensional Control of Power Supply Operation Energy in Cophase Power Supply System Based on RPC

CUI Xiao, XIONG Yu, LIU Guidong, ZENG Gui’e

Journal of Power Supply. 2024, 22(5): 213-219. https://doi.org/10.13234/j.issn.2095-2805.2024.5.213

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To ensure the safe, reliable and economic operation of high-speed railway, a multi-dimensional control method for the power supply operation energy of high-speed railway cophase power supply system is proposed. The composition structure and power supply process of the power supply system are analyzed, and a power flow controller is used to compensate the power of the system, thus ensuring its stable operation. Combined with indicators such as three-phase imbalance degree and distortion of voltage and current waveforms, the optimal load model of operation energy is constructed to minimize the loss of transmission energy. Through the active and reactive power compensation for current in two power supply arms, the negative-sequence current is eliminated. A control strategy for the railway power conditioner is formulated, and the changes in the step-down transformer are obtained to ensure a stable DC-side voltage. Afterwards, a proportional integral controller is used to obtain the ideal value of current and get the control signal, thus realizing the multi-dimensional control of power supply operation energy. Simulation results show that the proposed multi-dimensional control method can improve the three-phase current balance degree and achieve an effect of voltage sharing stability.

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Frequency Regulation Method for Electric Vehicles Cluster Based on Disturbance Observer and Robust Model Prediction

WANG Huinan, WANG Yujin

Journal of Power Supply. 2024, 22(5): 220-229. https://doi.org/10.13234/j.issn.2095-2805.2024.5.220

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A frequency regulation method for a large number of electric vehicles（EVs） in an isolated grid with high permeability renewable energy sources is proposed. First, a disturbance observer is designed for the system’s order reduction model to generate additional frequency control signals for clustered EVs. This order reduction model is obtained by combining the changes in load, wind power, photovoltaic system and clustered EVs, thus generating a lumped disturbance estimated by the disturbance observer. Second, a robust model predictive control method based on the Tube model is proposed to provide effective control signals to improve the responsiveness of clustered EVs. The control signals are generated to obtain the minimum frequency deviation error by means of the minimum control actions while considering various physical constraints on the system operation. Third, the influence of time delay on communication link is studied through the stability analysis, and the time delay margin is obtained. Finally, through simulation analysis, the effectiveness of the proposed method is verified, and the advantages of the proposed method over traditional model predictive control, fuzzy proportional integral control and linear quadratic regulator control are also verified.

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Design and Analysis of Multi-directional WPT Coupling Mechanism

CHANG Yufang, YIN Shuaishuai, YAN Sheng, LI Fei, TANG Yang

Journal of Power Supply. 2024, 22(5): 230-241. https://doi.org/10.13234/j.issn.2095-2805.2024.5.230

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The traditional coupling mechanism of multi-directional wireless power transfer（WPT） often adopts an xyz orthogonal circular coil structure, which requires three power supplies and has a charging area limited by the coil structure. To solve this problem, a novel multi-directional WPT coupling mechanism composed of two groups of 8-shaped coils and one group of circular coils is proposed. It presents five circular rings in different directions as a whole and only needs one single power supply. Based on the S-S type transmitter topology, the magnetic field distribution in the coil is changed by controlling the circuit, thus realizing power transfer inside and outside the coil and broadening the charging area. Based on the coil structure, a mathematical model of the proposed coupling mechanism is established, and the calculation formulas for mutual inductance and efficiency at any spatial position are derived. The best working area of the coupling mechanism is determined according to simulation and experimental results.

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Optimization Strategy for Modular CPC Balanced Charging

ZHANG Jialei, WANG Chaoyu, FAN Guoyu, LI Yue, LÜ Gao

Journal of Power Supply. 2024, 22(5): 242-250. https://doi.org/10.13234/j.issn.2095-2805.2024.5.242

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Along with the widespread applications of lithium batteries in industry and daily life, the efficiency and speed under balanced charging strategies for lithium battery packs have become increasingly important. A modular cell-to-pack-to-cell（CPC） balanced charging system is constructed to solve the problem of fast equalization charging for lithium battery packs. First, the equalization system is modularized, and the equalization circuits within and between modules are established. Then, an optimization strategy for balanced charging is proposed, under which the proposed model is solved hierarchically, i.e., the charging time is calculated using the binary method in the top layer, and the charging current is optimized using the gradient descent method in the bottom layer. Finally, through a comparison with the charging time, equalization time, cell terminal voltage and equalizer voltage under the non-modular balanced charging strategy, the feasibility and effectiveness of the proposed strategy are verified.

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CCM Soft-switching Implementation Algorithm for Battery Equalizer Based on Switched Inductor

GAO Binhuan, HU Yong, LIU Aizhong, LIU Jun, LIU Yuhan, KAN Jiarong

Journal of Power Supply. 2024, 22(5): 251-259. https://doi.org/10.13234/j.issn.2095-2805.2024.5.251

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The lithium-ion battery equalizer based on switched inductor is still of strong practical value in low-power portable electrical equipment. However, the switching devices in the equalizer operate in a hard-switching state under traditional control strategies. A soft-switching implementation algorithm for battery equalizer based on switched inductor in continuous current mode is proposed. The determinants of the inductor current of the equalizer and the charging and discharging current of a battery cell are analyzed. Then, a soft-switching implementation algorithm for the switching devices in the equalizer is proposed, and its control accuracy is analyzed. The equivalent impedance and open-circuit voltage of the battery cell can be obtained in real time by detecting the change rate of battery cell voltage and charging current, which further ensures the accuracy of the algorithm. Experimental results show that the proposed soft-switching control algorithm has a good performance.

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Virtual Energy Storage Control Strategy for Virtual DC Motor

TANG Peng, LI Hongwei, LIU Tong, GAN Changkun, ZHANG Lidan

Journal of Power Supply. 2024, 22(5): 260-268. https://doi.org/10.13234/j.issn.2095-2805.2024.5.260

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Virtual DC motor（VDCM） control has been widely applied in suppressing the power fluctuations of DC microgrid and improving the voltage stability of DC bus. Due to the randomness and uncertainty of distributed generations in microgrid, as well as the load switching in microgrid, the DC bus voltage will fluctuate greatly. To improve the regulation capability of bus voltage, a virtual energy storage control strategy based on the coordination of VDCM control and controllable load is proposed by using the regulation capability of controllable load and the virtual motor control of load converter. By adjusting the angular speed of the virtual motor, the power consumption of the controllable load can be adjusted to compensate the fluctuation of bus power and improve the stability of bus voltage. In addition, the relationship between the rotational kinetic energy of VDCM and the charging and discharging energy of the DC capacitor is established. Finally, a simulation model is built on the MATLAB/Simulink platform to verify the effectiveness of the proposed control strategy.

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SOC Prediction for Lithium Battery Based on Fusion Model of Attention Mechanism and CNN-LSTM

ZHANG Shuaitao, JIANG Pinqun, SONG Shuxiang, XIA Haiying

Journal of Power Supply. 2024, 22(5): 269-277. https://doi.org/10.13234/j.issn.2095-2805.2024.5.269

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To improve the state-of-charge（SOC） prediction accuracy of lithium battery, a prediction method based on the fusion model of Attention mechanism and convolution neural network-long short-term memory（CNN-LSTM） is proposed. This model uses one-dimensional CNN and LSTM neural network to learn the nonlinear relationship between SOC and lithium battery discharge data, as well as the long-term dependence existing in SOC sequences. At the same time, it adopts a “many-to-one” structure and establishes a mapping relationship between the SOC at the present moment and the discharge data at multiple historical moments, and pays attention to the historical discharge data which has a greater influence on the SOC at the present moment through the Attention mechanism, thus further improving the SOC prediction accuracy. The SOC prediction experiments under dynamic conditions show that the average prediction error of the proposed method is 0.89% under different temperature conditions, which is 81.2%, 66.7% and 56.5% lower than those of SVM, GRU and XGBoost algorithms, respectively. In addition, this method is also superior to LSTM and CNN-LSTM models that do not combine the Attention mechanism, showing a higher prediction accuracy and higher application values.

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Estimation of Lithium-ion Battery SOH Based on SSA-BPNN

ZHANG Kaifei, ZHANG Jinlong, LÜ Manping

Journal of Power Supply. 2024, 22(5): 278-285. https://doi.org/10.13234/j.issn.2095-2805.2024.5.278

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Since lithium-ion batteries have been widely applied in energy storage systems and electric vehicles, the accurate estimation of their state-of-health（SOH） is a necessary condition for ensuring the reliable and safe operation of the system. SOH is analyzed from the perspective of capacity, with seven health indicators which are extracted from the constant current-constant voltage charging voltage and temperature curves as input. Based on the data-driven method, a sparrow search algorithm-back propagation neural network（SSA-BPNN） SOH estimation method for lithium-ion batteries is proposed, and data enhancement is applied to further improve the model’s robustness. Finally, this method is verified on the NASA Randomized Battery Usage Dataset. Compared with the traditional BP neural network without data enhancement, the SOH estimation accuracy of the proposed method is significantly improved. The maximum absolute error and root mean square error of SOH estimation on the test set are less than 3% and 1.32%, respectively. Experimental results show that this method has advantages of small error, fast convergence, global search capability and adaptation to different characteristics of battery aging.

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Progress in Failure Analysis of Lithium-based Batteries under Harsh Environmental Conditions

SHI Haipeng, DIAO Fengxin, YUAN Hao, DING Yang, WANG Xiufeng, ZHOU Jing

Journal of Power Supply. 2024, 22(5): 286-293. https://doi.org/10.13234/j.issn.2095-2805.2024.5.286

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The adjustment of energy structure is an important issue for China’s energy development in the 21st century, in which the development of renewable new energy is an important means to optimize the energy structure and reduce environmental pollution. Nowadays, lithium-based batteries are still the main devices that can achieve reversible storage of renewable energy, whose electrochemical performance is often affected under harsh environmental conditions such as different temperatures, mechanical stress and humidity. As a result, problems including the damage of battery components, capacity fading, short-circuit explosion, and thermal runaway will occur. The failure mechanism of lithium-based batteries under harsh environmental conditions is systematically analyzed. Then, the main methods for improving their electrochemical and safety performance are reviewed. Finally, the urgent problems to be solved are summarized. This paper provides ideas for the failure mechanism research on lithium-based batteries as well as the development and applications under harsh environmental conditions.

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Research on On-line Measurement Method for MOSFET Junction Temperature Based on Turn-on Delay Time

HUANG Jiaoying, LI Changlin, WANG Qi, GAO Cheng

Journal of Power Supply. 2024, 22(5): 294-299. https://doi.org/10.13234/j.issn.2095-2805.2024.5.294

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With the development of industrial demand, higher requirements are put forward for the reliability of power transistors. The real-time measurement of device junction temperature can ensure the normal operation of the device, so it is very important. Through the research on the on-line measurement method for turn-on delay time, a measurement circuit is designed. By measuring the turn-on delay time at different junction temperatures, the relationship between them is established, the on-line measurement of device junction temperature is realized by measuring the turn-on delay time under actual working conditions, and the device junction temperature is deduced. The results measured using the proposed method are similar to those obtained by an infrared temperature gun. In this way, an on-line measurement method for MOSFET junction temperature based on turn-on delay time is proposed, providing a new idea for the on-line measurement of junction temperature in the future.

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Improved Gate Drive Design to Suppress Crosstalk of SiC MOSFET Bridge Arm

LI Qinghui, PAN Sanbo

Journal of Power Supply. 2024, 22(5): 300-308. https://doi.org/10.13234/j.issn.2095-2805.2024.5.300

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In the case of high switching frequency, the bridge arm crosstalk caused by the parasitic parameters of SiC MOSFET in the traditional drive are more serious. However, most of the existing crosstalk suppression drive circuits suppress the crosstalk at the expense of increasing the switching loss, prolonging the switching delay and adding the control complexity. Therefore, based on the idea of reducing the impedance of the drive loop in the process of crosstalk generation, a novel active Miller clamp gate drive design is proposed by adding PNP triodes connected in series with diodes and capacitors between the gate and source, and its working principle is analyzed. The parallel capacitance parameters of the improved drive circuit are also calculated and designed. Finally, an experimental platform of double-pulse test for a synchronous Buck converter with DC bus voltage of 300 V was built, and the novel crosstalk suppression drive circuit was compared with the traditional and typical crosstalk suppression circuits in terms of the positive and negative crosstalk voltage spike suppression effects and the turn-on and turn-off speeds. Experimental results show that compared with those of the traditional and typical crosstalk suppression circuits, the positive and negative voltage spikes of the proposed crosstalk suppression drive circuit were reduced by 80% and 40%, respectively, and the switching delay of the device was reduced by 32% in the meantime.

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Hybrid Simulation Analysis of Novel Traction Transformer under DC Bias Excitation

YANG Liulin, WANG Taoce, WANG Tao, LI Yongge

Journal of Power Supply. 2024, 22(5): 309-318. https://doi.org/10.13234/j.issn.2095-2805.2024.5.309

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The stability of an urban rail transit traction power supply system is related to the safety of urban power grid and the stable operation of traffic. Due to the large amounts of cables and a series of power electronic devices which have been put into use, problems such as harmonics and reactive power will arise and seriously damage the safety of the traction power supply system. As the core equipment of the traction power supply system, the traction transformer has important functions such as transmitting power supply and filtering nonlinear load harmonics. DC bias is a widespread phenomenon adversely affecting the traction transformer, and it may directly threaten the safe and stable operation of the traction transformer. Based on PSCAD/EMTDC and ANSYS, the UMEC model and finite element model of a novel traction transformer are established, respectively. By means of multi-platform hybrid simulation, the electromagnetic, loss and other excitation characteristics of this traction transformer under DC bias are observed and analyzed. With a comparison with the traditional traction transformer, the excitation situation of the novel traction transformer under DC bias is evaluated.

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Design of Travelling Wave Tube Power Supply under Multi-mode Control

ZHANG Jun, LU Xiaoyue, XIONG Jie, LU Ling, LI Hui, LI Yu

Journal of Power Supply. 2024, 22(5): 319-324. https://doi.org/10.13234/j.issn.2095-2805.2024.5.319

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Since there is only one working mode of continuous wave or pulse after the design of a traditional spaceborne travelling wave tube（TWT） amplifier is finished and the output power at the saturated working point is fixed, a novel design scheme for space TWT power supply is proposed, which is compatible with multiple working modes including continuous wave and pulse. The TWT power supply and multi-mode TWT designed through this scheme are integrated into a multi-mode TWT amplifier, which have functions of continuous wave mode, low repetition rate pulse mode, high repetition rate pulse mode and adjustable on-orbit power. As a result, it can be applied to communication, navigation, data transmission and remote sensing observation satellites, thus making the on-orbit reconfigurable load possible. Through a simulation test, it is found that the power efficiency of the multi-mode space TWT reaches 94%, the repetition frequency range covers the continuous wave up to 10 kHz, and the adjustable output power ranges between 47 and 53 dBm.

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Integration of DM and CM Chokes for 3P4W in the Application of On-board Charger: Integration of DM and CM Chokes with Quasi-cross DM Magnetic Branches

YANG Haijun, LU Zengyi

Journal of Power Supply. 2024, 22(5): 325-330. https://doi.org/10.13234/j.issn.2095-2805.2024.5.325

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In the background of environment protection and power-saving awareness, the requests for new energy electric vehicles and their on-board charger（OBC） keep growing. As one of the important components in the OBC module, magnetics is getting more and more attention accordingly. The magnetics integration of differential mode（DM） and common mode（CM） chokes for a 3-phase 4-wire（3P4W） electromagnetic interference（EMI） filter used in OBC is theoretically analyzed and studied. Based on the analysis and comparison of the background of power supply applications, the integration principle for DM and CM chokes, and the available integration schemes in industry and academia, an integration of DM and CM chokes for 3P4W with quasi-cross DM magnetic branches is proposed. Through the magnetic flux simulation analysis, electrical characteristics under DC-bias and the on-board tested data, the effect of the magnetics integration scheme was proved, i.e., it can obviously decrease the DC-bias on DM magnetic branches in the case of unbalanced 3-phase current and effectively improve the anti-EMI performance of power supply.

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30 September 2024, Volume 22 Issue 5