To clarify the internal thermal effect of a battery during its charging process, a lithium-ion battery of 27 A·h was taken as the research object. A three-dimensional electrochemical-thermal coupling model of one single battery was established, and the coordinate array mapping method was used to expand the thermal effect of the cell unit to that of the single battery. First, the influence of charging rate on the heat production of the battery was investigated. Then, the detailed heat production in the active layer of negative electrode with different particle radiuses was studied, and the mechanism of influence of particle size on the heat production was analyzed. In addition, the battery temperature distribution with different charging rates under natural convection was also studied. The heating mechanism of lithium-ion battery was elaborated upon, and the overall temperature distribution characteristics of the battery was given, providing a theoretical basis for optimizing the battery structure design and developing the battery thermal management system.

The massive grid connection of renewable energy brings a series of problems to the power grid, such as an insufficient frequency modulation capacity of thermal power units and a poor frequency modulation effect. Aimed at these problems, a combined frequency modulation strategy for thermal power and energy storage based on a battery energy storage system is proposed. First, the frequency modulation signal of area control error (ACE) is decomposed using variational mode decomposition (VMD). Combined with the load forecast data in the future, the number of decomposition modes K and penalty factor α in the VMD algorithm are optimized by the sparrow search algorithm (SSA). The high-frequency signal is assigned to the energy storage system, while the low-frequency signal is assigned to the thermal power units. Second, a double-layer fuzzy controller is designed, in which the fuzzy control in the first layer takes the high-frequency signal of area control error and its changing rate as input to improve the system’s dynamic frequency modulation performance, and the fuzzy control in the second layer takes into account the influence of state-of-charge to prevent the energy storage from encountering problems such as over-charging and over-discharging. Finally, the effectiveness of the proposed control strategy is verified by simulation analysis.

The lithium-ion battery equalizer based on a Buck-Boost converter can only transfer the energy in a step-by-step way, resulting in a long energy transmission path and a low equalization efficiency. On this basis, a lithiumion battery equalizer based on dual active half-bridge is studied. The key parameters affecting the energy flow between cells within a group and between those in different groups in the half-bridge equalizer are analyzed, and a phase-shift control strategy is put forward accordingly. The dual active half-bridge equalizer under phase-shift control can realize a fast energy transfer between cells in the half-bridge group at a high frequency. Since the equalizer operates in a high-frequency state, its volume and weight are greatly reduced. The expressions for the equivalent equalization current between cells within a group and that between cells in different groups were derived in detail, and a simulation model and an experimental prototype were built to perform a verification. Simulation and experimental results show that the proposed dual active half-bridge lithium-ion battery equalizer based on phase-shift control can quickly realize voltage equalization between battery cells.

The loss calculation accuracy of a three-phase full-bridge inverter will be reduced if the parasitic capacitance and parasitic inductance loss of SiC MOSFET in the switching process and the conduction loss caused by changes in the duty cycle in the conduction process are ignored. To solve the problems, a physical model of SiC MOSFET considering parasitic capacitance and parasitic inductance was proposed. The parasitic capacitance and parasitic inductance were obtained by querying a data sheet and using an oscillation method. The losses of parasitic inductance and parasitic capacitance during the switching process were calculated, the average conduction loss equation under space vector pulse width modulation (SVPWM) was deduced, and the three-phase full-bridge loss was obtained. Finally, experiments were carried out on the control system of a permanent magnet synchronous motor based on SiC MOSFET. The influence of PWM frequency on the three-phase full-bridge loss was analyzed, and the accuracy of parameters for the physical model of SiC MOSFET was verified. Moreover, the loss calculation method based on the physical model of SiC MOSFET can improve the loss calculation accuracy of the inverter.

The IGBT module of a motor controller is one of the important components for realizing electric energy conversion and motor control. This module usually works under complex conditions, and its reliability is crucial for the stability of the whole electric drive system. In general, the IGBT loss is directly calculated using the method of manual formulas, which ignores the influence of temperature rise on the IGBT module. Aimed at this problem, a method of thermal coupling analysis is proposed. First, a loss calculation model of IGBT module is established. On the basis, a thermal network model is built for the estimation of junction temperature, and the temperature rise estimation result is further used to correct the loss calculation model. A simulation model of the motor controller is constructed, and the junction temperature and loss of IGBT are simulated. In addition, the effectiveness of the proposed thermal coupling analysis method was verified by the results of a temperature rise experiment conducted on the motor controller.

DC solid-state circuit breakers (SSCBs) based on SiC MOSFET have attracted much attention owing to their capability of quickly breaking the fault currents. However, the failure mechanism of SiC MOSFET is more complex than those of traditional power semiconductor devices. SiC MOSFET has special gate failure and aging characteristics, but the relevant characteristics and mechanism are not clear, which brings great challenges to the failure and aging discrimination of SSCBs. A 400 V DC SSCB based on SiC MOSFET was taken as the research object, and the single and repetitive hard switching characteristics of the device under this working condition were investigated. It was verified that gate failure may occur in SiC MOSFET during the process of single or repetitive actions, and a new aging characteristic of gate voltage reduction appeared. Based on simulation tools, the temperature and thermal stress distribution inside the device during the process were obtained. It was found that the temperature rise near the gate structure of the device was close to 1 000 K, and a thermal stress of 1.4 GPa would be generated. Through the opening, slicing and SEM scanning of failed devices, the cracks in the gate oxide layer were confirmed, and the mechanism of gate failure and aging caused by gate structure cracking due to thermal stress was verified.

The traditional on-load voltage regulation technology has deficiencies such arc, a slow response speed and a low regulation accuracy, which affect the operation reliability of a transformer. Although the novel power electronic transformers have advantages of no arc and fast response, they have a large loss and a high cost. On the basis, a novel single-phase four-column magnetron transformer structure is proposed, which consists of a magnetron reactor and a transformer connected in series. According to the topological structure of the magnetron reactor, the working principle for the magnetron transformer is analyzed, and the circuit equation and electromagnetic equation are deduced. The right-side yoke in this structure can provide an AC flux loop, which is not interfered by the DC flux. The Maxwell and Simplorer in software Ansys are used to conduct field-circuit coupled multi-physics domain co-simulation to analyze the voltage regulation capability of the model, and the harmonic analysis of output voltage is carried out in Simulink. It is verified that the proposed novel magnetron transformer can adjust the output voltage smoothly without arc and without step, and the harmonic content is low.

The collection of data from high-power power supply output signals (voltage/current) will be unavoidably interfered by electromagnetic noise, which affects the analysis of voltage/current signals. Therefore, the denoising of high-power power supply signals is an essential process. For the analysis of output signal characteristics of high-power power supply, a denoising method is proposed, in which a morphological filter is superimposed on a modified wavelet threshold function. The modified wavelet threshold denoising method can filter random noises by adjusting parameters, which can recover useful signals from noisy signals more effectively and reduce unnecessary distortion while taking into account the advantages of soft/hard threshold functions. In comparison, the morphological filter is mainly used to filter impulse interference. Simulation results show that the proposed algorithm can effectively reduce noise in the high-power power supply signal, which largely preserves the characteristics of the actual signal. From the comparison between the proposed method and other modified wavelet algorithms on which the morphological filter is superimposed, it is found that the signal-to-noise ratio is improved by 17.5%. In addition, the superiority of the proposed method was verified by experimental results.

HIRFL-CSRe is an experimental ring part of the CSR system in the post-accelerated cooling storage ring of HIRFL in Lanzhou heavy-ion accelerator facility, in which the bipolar ferromagnet has higher requirements for the performance of the power supply. To meet the requirements of high-precision indicators for this kind of ferromagnet power supply and solve its technical difficulties, a high-precision DC power supply device is developed. The main circuit of the power supply adopts a multiplex circuit topology, the control part uses a multi-variable coupling digital-analog hybrid control strategy, and the process structure adopts standardized design for the power converter and other key components. Experimental results show that the output current stability of the power supply was less than or equal to 5×10^-6/8 h, and the other performance indicators of the power supply also met the physical design requirements for the accelerator. Finally, the power supply passed the acceptance test.

The electromagnetic interference (EMI) filter is an effective approach to suppressing EMI. However, due to the influence of high-frequency parasitic parameters, EMI filters are difficult to effectively suppress high-frequency EMI noises. In this paper, the characteristics of high-frequency parasitic parameters of EMI filter components including common-mode (CM) inductor and X capacitor are analyzed, and a high-frequency model exhibiting the wide-band impedance characteristics of filter components is established. Moreover, the influence of frequency-varying permeability of ferrite cores on the parasitic parameter cancellation effect is analyzed. The extraction method for the equivalent parallel capacitance of the CM inductor is investigated, the selection of CM inductor cancellation capacitance is optimized, and the wide-band noise filtering of the CM inductor is realized. The wide-band noise filtering characteristics of the whole EMI filter are predicted by finite element simulation. Combined with the simulation and experimental test of insertion loss, the effectiveness of the proposed EMI filter frequency-domain modeling method and the selection basis of CM inductor cancellation capacitance considering the frequency variation of permeability was verified.