Flyback converters in consumer and commercial products must adhere to strict regulatory standards for conducted and radiated electromagnetic interference (EMI). Managing EMI has become increasingly complex in modern power electronics, particularly with the integration of high-speed wide bandgap (WBG) devices into compact system layouts. A review of established modeling techniques and mitigation strategies for conducted EMI is presented, focusing on differential mode (DM) and common mode (CM) noise, alongside radiated EMI in flyback converters. The discussion encompasses solutions at both component-level design and converter system optimization.

The power supply system in a data center is its critical infrastructure, which provides stable and reliable power support for all the power-driven equipment therein to ensure itsnormal operation. With the rapid development of technologies such as big data, cloud computing and 5G, the number and scale of data centers in China are increasing rapidly, requiring higher reliability of power supply and increasing the overall power consumption. In addition, the problem of high carbon emissions is even more obvious because the data centers at present mainly use electricity from the traditional energy sources. Therefore, how to achieve a green, energy-saving and low-carbon power supply and distribution mode is the focus of the development of data center power supply systems. The functions and characteristics of typical power supply architectures of data center power supply system are analyzed, and the development and evolution of power supply architectures of data center are introduced. On this basis, “carbon peaking and carbon neutrality” is taken as the background, and a prospect for the power supply architectures of data center in the future is given combined with the problems encountered in the development of power supply system of data center, providing reference for its in-depth research and subsequent development.

Bi-directional DC-DC convertersare usually used in vehicle charging pile application circuits, which have problems such as slow system dynamic response and poor output voltage stability due to load perturbations. On the basis, acapacitor-inductor-inductor-capacitor (CLLC) resonant DC-DC converter is taken as a research object, and a control method for the CLLC resonant converter based on sliding mode active disturbance rejectionis proposed. A model-assisted linear state observer is used to improve the estimation accuracy of perturbation, so as to control the stable operation of the system. Sliding mode control is used to design a linear state error feedback control law to improve the dynamic performance and rapidity of the system. Simulations and experimental verification show that the proposed control strategy can effectively improve the dynamic response of the bi-directional DC-DC converter and enhance the output voltage stability.

To address the issue that the conventional model predictive torque control algorithm for a permanent magnet synchronous motor relies on position sensors, a model predictive torque control approach based on a dual- sliding-mode observer is proposed. First, to accomplish the sensorless control, the real-time speed in the prediction model is substituted by the observed speed by coupling the back electromotive force sliding-mode observer with the optimized quadrature phase-locked loop. Second, the stator flux sliding-mode observer is used to observe the stator flux, and the observed flux introduces prediction error through feedback correction to obtain the prediction torque and flux with higher accuracy, thus improving the prediction speed and accuracy of the model predictive torque control system. By contrasting the MATLAB/Simulink simulation and experimental platform with the conventional model predictive torque control approach incorporating position sensors, the efficacy and feasibility of the proposed method are confirmed.

With the vigorous development of electric vehicles and energy storage industries, the power electronics technology has been applied on an increasing scale. In these applications, power electronic converters not only require wide voltage gain to adapt to different scenarios, but also require a high conversion efficiency to reduce volume. Therefore, bidirectional isolated DC-DC converters with soft switching have been widely studied. On the basis, the principle of isolated DC-DC converters was analyzed, and the conversion efficiency under wide voltage gain was improved by reducing the reactive power current and implementing soft switching. First, a mathematical model was established through fundamental wave analysis to obtain the conditions for controlling the phase shift angle on the primary side, secondary side, and both the primary and secondary sides to achieve reactive power current elimination. Then, the conditions for achieving soft switching of switching devices on the primary and secondary sides were analyzed, and the dead time was designed to adjust the phase shift angle between the primary and secondary sides, so that a modulation strategy for achieving ZVS with minimal reactive power current was obtained. Finally, a 9.6 kW experimental prototype was designed to verify the feasibility of the proposed modulation strategy.

Accurately predicting the remaining useful life (RUL) of lithium-ion batteries is critical to the safe and reliable operation of new energy vehicles. First, the research status of data-driven methods for predicting the RUL of lithium-ion batteries is analyzed in this paper, and the research progress in six commonly used data-driven methods is reviewed. Then, three problems existing in the practical applications of RUL prediction of lithium-ion batteries at present are summarized. At the same time, the issue of battery dataset collection is discussed comprehensively, and the importance of battery datasets to the development of data-driven methods is also elaborated upon. Finally, the development trend in the future is prospected.

A micro inverter can be directly connected to a photovoltaic board, and it has advantages such as a simple structure, a small size and input output isolation. To expand the power range of the photovoltaic micro inverter, two flyback converters can be interleaved and connected in parallel at the front stage DC-DC section, and an active clamping circuit can be used to improve the efficiency of the micro inverter. In response to the issues of temperature rise in a high-frequency power transformer and low power density in outdoor high-temperature environments, a planar transformer applied to micro inverters is designed. First, the working principle for flyback micro inverters is analyzed. Second, the electrical parameters and winding structure of the planar transformer are designed, and the magnetic density distribution and loss of the planar transformer core are simulated using Maxwell software. Finally, a 220 W interleaved parallel flyback micro inverter prototype was built for experimental testing. Experimental results proved the effectiveness of the design, and the prototype can perform stable work.

The wireless charging technology for electric vehicles has been widely studied and applied owing to its advantages of small footprint, convenience and flexibility, low maintenance cost and strong interaction with power grid. A bidirectional wireless charging system for electric vehicles based on the dual phase shift (DPS) control strategy is proposed. Through the DPS control strategy, the phase shift angle on the primary and secondary sides is changed to change the output power. By changing the phase angle difference between voltages on the primary and secondary sides, the energy flow direction is changed, and the function of “peak shaving and valley filling” is realized eventually. First, the architecture of the bidirectional wireless charging system for electric vehicles based on the DPS control strategy is presented, and its working mode and principle are analyzed. Second, the control strategy for the bidirectional wireless charging system is described in detail, and the output power and direction of the system are adjusted by changing the phase shift angle on the primary and secondary sides, as well as the phase angle difference between voltages on the primary and secondary sides. Third, the working principle for the system and the control method to realize bidirectional charging are analyzed. Finally, a simulation model was built in MATLAB, and experimental verification was carried out. Results show that the designed bidirectional wireless charging system can achieve bidirectional energy transmission, satisfying control performance and good symmetry of positive and negative charging.

The gallium nitride/silicon carbide (GaN/SiC) Cascode device is a composite structure, which employs a low-voltage GaN device as an assistant switch to change the high-voltage depletion-mode SiC device into an enhancement-mode device. A normally-off GaN/SiC Cascode device was constructed by low-voltage enhancement- mode gallium nitride high electron mobility transistor (GaN HEMT) and high-voltage depletion-mode silicon carbide junction field-effect transistor (SiC JFET). The Cascode device combined the advantages of GaN HEMT such as high switching speed and simple gate-driving circuit and the high blocking voltage of SiC JFET. Both the operating principle and the switching process of GaN/SiC Cascode device were analyzed in detail, and its static characteristics were also tested. A double-pulse test platform was constructed, and the switching loss of the GaN/SiC Cascode device was compared with those of the Si/SiC Cascode device and SiC JFET at varying load current. Results show that the turn-off loss of GaN/SiC Cascode device was the lowest. In addition, the three devices were applied in an LLC resonant converter respectively, and the conversion efficiency of the converter was tested, indicating that the LLC resonant converter based on GaN/SiC Cascode device exhibited the highest conversion efficiency.

The overall development statuses and trends of hydrogen-related industries are briefly introduced at first, and different types of electrolytic water hydrogen production technologies are compared in detail. Then, the development statuses of photovoltaic (PV) power hydrogen production, wind power hydrogen generation and wind-PV complementary hydrogen generation technologies are summarized, and the development trends in the future are investigated. Finally, the research framework system of “Green Hydrogen Plant” for a large-scale new energy hydrogen production system is constructed. The research and development ideas for key technologies involved in new energy hydrogen production are provided, the demand analysis for products and solutions required by relevant projects is conducted, and suggestions for the research direction of “wind-PV-hydrogen-storage” energy comprehensive utilization in the future are put forward.

To solve the problems related to the safety and stability of regional power grids which are caused by the start-up of large-capacity motors, the mechanism and influencing factors of voltage sag caused by large-capacity motor start-up are studied. First, the dynamic process of large-capacity motor start-up and the mechanism of voltage sag are analyzed in detail, and the quantitative characterization of the severity of voltage sag is conducted using evaluation indexes. Then, the start-up of large-capacity motors in a petrochemical enterprise’s regional power grid is taken as an example, and a time-domain model based on ETAP is established to verify the theoretical analysis of voltage sag caused by large-capacity motor start-up. Finally, the influencing factors of voltage sag caused by large-capacity motor start-up are quantitatively analyzed. The influences of start-up transformer capacity and grid strength on voltage sag are studied, and a comparative analysis of voltage sag indexes for different combinations of multi-motor simultaneous start-up and different start-up modes is conducted. The research results provide a theoretical basis for reducing the risk of voltage sag accidents caused by the start-up of large-capacity motors.

The thermal characteristic modeling of silicon carbide (SiC) power devices is a key aspect in their design and development. The structure function method is crucial for characterizing the devices' thermal characteristics, focusing on acquiring the time-constant spectrum of input data via deconvolution algorithms. However, the environmental noise inevitably affects actual tests, thereby demanding more sophisticated deconvolution algorithms for the structure function. Therefore, a deconvolution structure function algorithm based on improved Wiener filtering is proposed, effectively addressing the noise problem in the measurement data during the transient thermal analysis. First, a structure function model based on Wiener filtering deconvolution is put forward, and the algorithm's effectiveness is validated through analyzing the TDIM-Master benchmark problem. Second, different levels of noise are added to the benchmark problem to explore the signal quality and peak thermal resistance of the time-constant spectrum across various noise conditions. The accuracy and superiority of the improved method when dealing with noises are verified through a comparison with the conventional algorithm. Finally, the transient thermal resistance of two different types of SiC power devices were measured under conditions with or without thermal silicone grease, and the structure function analysis was also performed, thus verifying the stability and applicability of the proposed algorithm under real measurement environment.

A typical configuration of a DC solid-state transformer is formed by connecting standardized power conversion cells in an input-series output-parallel (ISOP) arrangement to achieve DC transformation from medium voltage to low voltage. To provide redundancy for the power conversion cells, a thyristor bypass circuit is typically required. While DC solid-state transformers generally employ SiC MOSFET devices, the high dv/dt characteristic of SiC MOSFETs can readily false triggering in the thyristor bypass circuit. The issue of false triggering in thyristor bypass circuits is focused on, and a co-design methodology involving the thyristor snubber circuit and the gate-parallel resistor is explored. The proposed approach aims to enhance the operational reliability of the thyristor bypass circuit in high dv/dt environments, and experimental validation is provided.

Aimed at the hard-switching issues associated with the traditional zero current switching (ZCS) switched capacitor converters (SCCs), a zero voltage and zero current switching (ZVZCS) DC-DC SCC based on an LC auxiliary network is proposed, which can achieve zero voltage switching (ZVS) for all switches throughout the entire operating range. Under certain conditions, it can also simultaneously achieve both the ZVS and ZCS, significantly reducing the switching losses. On this basis, an in-depth investigation into the impact of dead time on converters is conducted, revealing a quantitative relationship between dead time selection under different load conditions and converter loss distribution. Subsequently, a design methodology for key parameters of auxiliary networks based on dead time is put forward. Finally, based on the proposed ZVZCS SCC, a 24 V DC-12 V DC experimental prototype with 100 W was constructed with a peak efficiency of 99.07%, thus validating the correctness of the theoretical analysis.

Aimed at the problems of a large number of switching devices and complex control strategy for an inverter in the multi-motor drive system of a 800 V high-voltage platform for electric vehicles, a fifteen-switch three-level dual-output inverter is proposed, which simplifies the inverter topology and reduces its cost by device multiplexing. First, a detailed analysis of the proposed inverter topology and working principle is performed, its structural characteristics are summarized, and the effective switching state and maximum voltage stress analysis are given, providing a theoretical basis for the selection of switching devices and system design. Then, a single-leg independent model prediction current control strategy is put forward, and a prediction model of single-leg dual-output port current is established, which effectively reduces the prediction operation under the premise of realizing three-leg independent prediction control and single-leg dual-output current integrated optimal control. Finally, the correctness and effectiveness of the proposed inverter and its control strategy were experimentally verified based on a Typhoon HIL 402 platform.

To reduce the input current harmonic content of a single-phase PWM rectifier and improve the suppression effect on specific low-frequency harmonics in grid-side current, fuzzy multi-PR control based on PR control is studied, so as to solve the problem of influences due to uncertain factors such as constant parameters under multi-PR control, inability to adapt to variations in parameters in the process of control and system disturbance. Finally, the effectiveness of this method was verified by simulations on MATLAB/Simulink and experiments on an experimental platform. Results show that the proposed control strategy can effectively reduce the total distortion rate of grid-side current, and it can also improve the dynamic and anti-interference performance of the system to a certain extent.

The research on the driving technology for SiC devices has always been a hot issue for scholars both at home and abroad. The existing active drive technology realizes the regulation of switching transient by changing the drive resistance, drive voltage or current. It requires many components, and the drive board is bulky and costly. Therefore, a full-bridge active drive technology based on resonant drive is proposed. By switching on and off the drive switch tube only, different drive circuits are constructed to form different drive currents, thus realizing the switch transient adjustment. First, the 1/4-period full-bridge resonant drive is taken as a reference drive mode for the power tube. Then, a specific design method for active drive switch timing is given by analyzing various stages during the switching on process of the power tube. Finally, through simulations and experimental verification, it is found that the drive mode can reduce 87.0% of current overshoot during the switching on process and 4.2% of voltage overshoot during the switching off process, and it can also achieve flexible speed regulation in a wide range of specific stages.

The calculation of high-frequency transformer winding losses is crucial for optimizing the efficiency of CLLC converters. However, there remains a lack of accurate and efficient methods for calculating the winding losses, particularly the winding losses in Litz wire. A mutual-impedance equivalent circuit-based method for calculating the winding losses in Litz wire high-frequency transformers is proposed. First, the analytical approaches for calculating the Litz wire winding losses based on a one-dimensional Dowell model and a two-dimensional Bessel function method are comparatively analyzed. Then, a mutual-impedance equivalent model is established to simplify the calculation of winding losses. A specific case study is given, and the values calculated using the proposed method are compared with the impedance matrix results derived from two-dimensional finite element simulations. Results demonstrate that the relative error between the equivalent series resistances calculated using the proposed method and the results based on the finite element method does not exceed 6%, validating the effectiveness and accuracy of the proposed method. Finally, a high-frequency transformer prototype for the CLLC converter was constructed, and experimental measurements verified the feasibility of the proposed method.

An enhanced extended phase shift modulation strategy for an LCL-type full-half bridge resonant converter is proposed, which can achieve zero voltage switching (ZVS) for all the switches while eliminating the backflow power on the primary side. Meanwhile, the half-bridge structure on the secondary side enhances the cost-effectiveness of the converter under low-power conditions. The steady-state analysis of the converter is performed by using fundamental harmonic approximation, so as to derive a power model and the corresponding ZVS conditions. In addition, simulations are conducted using the software PSIM. Finally, a 300 W experimental prototype was built, and results verified the feasibility of the theory.

Due to the rank deficiency of identification models, parameter coupling exists in the online identification of a permanent magnet synchronous motor (PMSM). To realize the parameter decoupling identification, an adaptive parameter identification algorithm based on the affine projection algorithm is proposed. By injecting instantaneous flux-weakening current signal on the d axis, the online decoupling identification of parameters such as the stator resistance, inductance and rotor flux linkage of a surface mounted PMSM is realized. Considering the nonlinear voltage drop caused by the dead-zone time of an inverter, turn-on and turn-off delay of switches, freewheeling diode saturated voltage drop, etc., a parameter identification model which is not affected by nonlinear voltage drop is constructed. Experimental results demonstrate that the proposed method can improve the identification accuracy of stator resistance, inductance and rotor flux linkage while speeding up the convergence rate of online identification.

LLC converters are widely applied in the fields of household energy storage and distributed energy storage owing to their excellent features such as a good soft-switching range and a high power density. In the modulation design of LLC converters, to achieve a high efficiency, it is necessary to meet the conditions for resonant soft-switching based on the design of hardware parameters with a low overall power loss of the converter. The commutation process during the dead-time is analyzed to explore the influences of the parasitic parameters of switching devices on the realization of soft-switching in the converter. By optimizing the switching timing sequence during the dead-time and utilizing the circuit mechanism where the parasitic parameters of switching devices participate in resonance, the realization of soft-switching is facilitated, ensuring a higher operation efficiency. Considering the loss distribution during the dead-time, the impact of not changing the modulation under bidirectional power flow conditions on the efficiency is analyzed. Finally, verification was performed by building a 4 kW LLC prototype to carry out a bidirectional power transmission experiment.

The difference in characteristic parameters of an IGBT module is an important factor leading to the difference in control circuit parameters, which has a significant impact on the dynamic current-sharing characteristics of IGBT parallel applications. When the device parameters cannot be changed, some drive compensation control can make up for the influence of device differences on dynamic current-sharing, and the key to this method is accurately identifying the characteristic parameters of the IGBT module. The influence of parameter (e.g., gate resistance) identification accuracy differences on the dynamic current-sharing characteristics is studied when a synchronous pulse-asynchronous drive method is used. The correlation characteristics of characteristic parameters of IGBT devices are studied, and the characteristic models of each parameter and influencing variables are constructed. The working model of PSpice device parallel switch is established, and the variation curve of IGBT device parameters and influence factors is fitted by combining with the device manual data comparison and multi-working condition test parameter correction. Through the parallel switching characteristic experiments on two groups of modules 1 200 V/200 A and 1 700 V/300 A IGBT, the judgment on the influence of the difference in IGBT characteristic parameters on parallel current-sharing was verified. Finally, the influence of the difference in characteristic parameter identification accuracy on dynamic current-sharing characteristics was summarized.

A novel high-gain DC-DC converter based on switched inductor and switched capacitor units is proposed. By configuring one set of switched inductor units and two sets of switched capacitor units, a high gain is achieved while maintaining the low voltage stress and low current stress on each component in the converter. The operation principle for the novel converter in different current modes is explained, and its voltage gain characteristics are derived. In a continous conduction mode (CCM), the current stress on the main components in the converter decreases as the gain increases, so a high efficiency is maintained at high gains. High gains can also be achieved in a discontinuous conduction mode (DCM). In addition, the boundary between the CCM and DCM modes of the converter is derived according to the gain relationship. A 325 W experimental prototype was built to verify the effectiveness of the topology and theory, and it was found that the measured converter gain can reach 18 times and the highest efficiency can reach 94.9%.

To solve the problem of uncontrollable area of bus neutral-point potential under high modulation depth of conventional virtual space vector pulse-width modulation (VSVPWM), an optimized VSVPWM algorithm was proposed to realize the rapid balance of neutral-point potential in the whole linear modulation area. A virtual medium vector was reconstructed based on the principle of VSVPWM bus neutral-point potential balancing. To ensure the voltage equalization performance of the reconstructed virtual medium vector while improving the adaptability of the algorithm with respect to the perturbation of system parameters, the fuzzy reasoning for the closed-loop control of neutral-point potential was designed to determine the reconstruction factor for optimizing the VSVPWM. Even in the case of asymmetric DC bus capacitance, the optimized VSVPWM can realize rapid voltage equalization control in the full range of the linear modulation region. The algorithm was further simplified in a 60° coordinate system, so that the number of subsector judgment conditions of reference voltage vector and volt-second equilibrium equations can be reduced from 30 to 5. Experimental results show that the proposed control strategy has good performance, the voltage equalization regulation time is significantly reduced, and the steady-state deviation of DC bus neutral-point potential can be controlled within 1.14%. In addition, the total harmonic distortion of grid-connected current is lower compared with that under the conventional VSVPWM.

During the normal utilization of a lithium-ion battery, its capacity will be regenerated in a short term due to factors such as internal chemical reactions and external environment. Aimed at the problems including the inaccurate estimation of state-of-health (SOH) which results from the ignorance of capacity regeneration, an optimal variational mode decomposition (OVMD) strategy based on the number of optimal layers is proposed. The low-frequency stable capacity sequence reflects the overall aging trend, while the high-frequency non-smooth capacity sequence reflects the local capacity regeneration. With the consideration of high- and low-frequency components and by introducing the weighted mean of vectors (INFO) algorithm to improve the support vector regression (SVR), a short-term SOH estimation model for lithium-ion battery is established. With the selection of NASA battery aging data sets, contrast schemes for short-term lithium-ion battery SOH estimation experiment are designed based on BP (back propagation), SVR, INFO-SVR and OVMD-INFO-SVR. Results indicate that in the case of reducing the capacity training sets, the OVMD-INFO-SVR model based on high- and low-frequency compon- ents has higher accuracy when it is used in short-term SOH estimation of lithium-ion batteries.

The modular multilevel matrix converter (M3C) has a cascaded modular structure, which is suitable for scenarios with medium- and high-voltage, high power and wide frequency ranges such as driving high-voltage high-power motors and flexible low-frequency transmission systems. However, due to the large number of system components and the presence of floating capacitors, the difficulty in controlling the M3C is significant, especially in terms of voltage equalization and ripple suppression of numerous floating capacitors in the system. A strategy based on bridge arm energy control is proposed, which is intuitive and simplifies the number of control layers. The goal of directly controlling the energy of each bridge arm in the converter is mainly achieved by setting the energy reference value of the bridge arm and controlling the bridge arm energy at present in real-time in the form of negative feedback. Aimed at each cascaded submodule within the bridge arm, a voltage equalization controller is designed. Finally, the feasibility of the proposed control strategy was verified through simulations.

The state-of-charge (SOC) estimation of batteries generally uses the principle of ampere-hour integration to construct SOC models, which are further combined with filtering algorithms. To address the problems of a slow convergence speed and complex calculation, a predictive static open circuit voltage (PSOCV) method is proposed based on the open circuit voltage principle and second-order RC circuit models. The feasibility of discrete-time forward and backward difference state-space equations was discussed, and the parameter accuracy was also compared between linear interpolation (LI) fitting and least squares (LS) fitting. Experimental results show that LI fitting is generally better than LS fitting. The average absolute error of SOC estimation obtained using the LI-PSOCV algorithm under HPPC and UDDS operating conditions is below 1%. Compared with the cubature Kalman filter (CKF), the LI-PSOCV algorithm can converge instantly when the initial SOC value deviates and run faster.

Due to the lower and significantly fluctuating voltage of micro-source modules (e.g., photovoltaic and fuel cells) in DC microgrids, there is a need for a DC-DC converter with a high gain and a high efficiency to serve as an interface circuit. Therefore, a novel active switched capacitor DC-DC converter based on an isolated Sepic topology is proposed. This converter reduces voltage spikes on the switch tube caused by leakage inductance through a clamp circuit and employs multiple boost units to achieve a high voltage gain. In addition, it also has advantages such as electrical isolation, low stress on the main switch tube and passive clamping. The operation modes and boosting mechanism of the proposed converter are studied, the component stresses are analyzed, and the efficiency of this converter is derived. Finally, a 200 W prototype was constructed in the laboratory to verify its performance.

The grid-forming cascaded H-bridge energy storage system is an optimal solution for mitigating large-scale renewable energy power fluctuations and providing grid support. However, the power control of the system is coupled with line impedance, and the coupling effect intensifies under weak grid, leading to output power inaccuracy and increasing risk of instability. To solve this problem, an adaptive power decoupling control strategy based on reactive voltage compensation is proposed. First, based on the small-signal model of a virtual synchronous generator and through the introduction of power coupling coefficients which take into account closed-loop feedback, a quantitative analysis is conducted on the power coupling effects between line impedance angle and power angle, revealing the mechanism of effect of active power on reactive power control. Second, an adaptive reactive power compensation channel is constructed, and a proportional-integral voltage compensation link in the reactive power control is designed, which dynamically modifies the output voltage references to mitigate the power coupling without the identification of line parameters. As a result, dynamic decoupling control is realized in a wide range of impedance angle with strong adaptability. Finally, validation tests based on a simulation platform and an RT-LAB platform verified the proposed method.

Thermal management is an important technology for ensuring the normal operation of submarine data centers. Aimed at the special working environment of a submarine data center, the solid oxide fuel cell (SOFC) is used as its emergency power source, and an SOFC thermal management system model with seawater as the only coolant is improved. Then, the total heat dissipation model and dynamic thermal model of SOFC are established, the fuzzy control strategy used for SOFC is optimized by a genetic algorithm, and the implementation effects of non-dominated sorting genetic algorithm-II(NSGA-II) and other algorithms are compared based on MATLAB. Finally, the temperature distribution and average current density of the power stack under different voltages are analyzed in simulation experiments. Experimental results verify that the improved thermal management method can effectively improve the heat dissipation efficiency of the SOFC system in the submarine data center and ensure its safe operation, which is helpful for improving the operation stability of the submarine data center.

A wide-voltage hybrid bridge bidirectional DC-DC converter is proposed. Compared with the CLLC converter, the proposed converter adds linear bridge arms on both sides, so as to improve its gain range and reduce the switching frequency and feedback current. A dynamic control method of pulse-shift modulation is put forward, which can effectively suppress the overvoltage at the inductor terminal in the energy transmission process. In addition, this method also has a function of control initialization. In all of its operating modes, the converter can realize soft switching. A prototype of a bidirectional DC-DC converter with a wide-voltage hybrid bridge was designed, and the correctness and effectiveness of the proposed converter topology and control strategy were verified by experimental results.

A hybrid compensation scheme based on variable output capacitance is proposed to improve the start-up speed and anti-load impact capability of a non-ideal peak current mode (PCM) Buck converter, under which the loop stability and dynamic response performance are ensured while realizing the synchronous switching of output capacitance and loop compensation parameters. A complete small-signal model of the non-ideal PCM Buck converter is established, the open-loop transfer function of the system is analyzed to obtain the influence of different output capacitance parameters on the compensation network, and the design of reasonable loop compensation is carried out. Simulation results show that the compensated system can maintain the crossing frequency around 10 kHz (1/20 fsw) and the phase margin around 70° under a variety of conditions. Moreover, a synchronous switching circuit of output capacitance and compensation parameters is designed. Finally, a 15 W experimental prototype was built, and experimental results further verified the feasibility of the proposed scheme.

The loss and volume of magnetic components in resonant DC-DC converters account for nearly 50%, which seriously restricts the improvement of power density in high-frequency converters. The magnetic integration technology can reduce the loss and volume of magnetic components, so it has been widely studied and applied. However, the traditional magnetic loss measurement methods cannot accurately and conveniently measure and evaluate the magnetic core loss of magnetic components in integrated resonant inductors and transformers, causing difficulties in the optimization of magnetic core loss. In this paper, the magnetic flux distribution in integrated magnetic components is analyzed, and a method is proposed to obtain the magnetic core loss of integrated magnetic components by testing the difference in losses before and after adding auxiliary integrated magnetic components in parallel in a resonant topology. At the same time, a parameter design method for auxiliary magnetic components is also put forward. This method can accurately and conveniently measure the magnetic core loss of integrated magnetic components under actual circuit conditions. Simulation and experimental results verified the effectiveness of the proposed magnetic loss measurement method for integrated magnetic components.

In a modular multilevel converter (MMC) system, there are numerous submodules, and switch faults and voltage sensor faults occur frequently. Some of these faults share similar characteristics, which can affect the system’s operation reliability. A joint diagnosis method for submodule IGBT open-circuit faults and voltage sensor faults based on a sliding mode observer is proposed. First, a fault detection strategy is designed using the actual and measured values of the MMC system’s arm voltage to detect faults in the MMC system and further achieve fault localization at the arm level. On this basis, the sliding mode observer is used to perform online estimation of the capacitor voltage within the faulted arm submodule, and the estimated values are compared with the measured values for submodule-level fault localization. Finally, simulation results verify the effectiveness and robustness of the proposed fault diagnosis algorithm.

Under special conditions such as rapid changes in solar irradiance, local shading or poor solar irradiance, the traditional method will cause a photovoltaic (PV) power generation system to oscillate near the maximum power point (MPP), and the tracking speed will be slow. In serious cases, the PV power generation system will exhibit severe power fluctuations, which will lead to divergence. To solve this problem, a maximum power point tracking (MPPT) control method for PV power generation systems based on reinforcement learning (RL) is proposed in this paper. The RBF neural network weight coefficient in RL is adjusted online and in real time to adapt to the output control signal, so that the active power output from PV power generation can be quickly tracked to the MPP. A PV power generation system was constructed in MATLAB/Simulink, and a comparison with the conventional RBF neural network control method was performed. Results show that the RL control can make the PV power generation system converge to the MPP stably and accurately in a shorter time. At the same time, the PV power generation system can output the maximum active power.

A current source pulse width modulation (PWM) rectifier has advantages of continuously adjustable current and strong capability to limit the short-circuit current, which is suitable for DC ice-melting application. However, it still has problems of a low switching frequency and a low filter cut-off frequency, possibly causing the problem of harmonic amplification. The active and reactive characteristics of the current source PWM converter are studied under constant-current load and constant-resistance load conditions, which is helpful in designing an LC filter to realize the high power factor of the rectifier. On the basis of stability analysis, a controller based on active damping and decoupling control is designed. Simulation results show that compared with the traditional non-decoupling control, the proposed method has better DC transient characteristics, so that it can effectively suppress lower-order harmonic current to eliminate the possible problem of harmonic amplification.

With the massive growth of the electric vehicle (EV) market, the applications of EV charging equipment have also increased. Aimed at the disadvantages of traditional EV charging converters such as a small voltage-gain range, a low efficiency in low voltage output mode and a high voltage stress in rectifier diodes on the secondary side, the topology of a three-level LLC resonant converter with integrated flying-capacitor cell is improved, and a Burst control strategy with variable pulse width is proposed to enhance the efficiency in low voltage output mode. Through the hybrid control composed of pulse frequency modulation and the proposed Burst control strategy with variable pulse width, a wide output voltage is achieved, and the voltage-gain range under the Burst control strategy with variable pulse width is analyzed using first harmonic approximation. Finally, an experimental prototype with maximum power of 2 000 W was built, and results verified the feasibility of the novel topology of the improved three-level LLC resonant converter with integrated flying-capacitor cell and its Burst control strategy with variable pulse width.

A low-ripple DC-DC converter with quasi-Z-source coupled inductance is proposed, which integrates a quasi-Z-source network, a coupled inductor and voltage doubler cells. The quasi-Z-source network has functions of Boost voltage and passive clamp. While the converter achieves a high gain, the switching tube realizes passive clamp and recovers leakage energy from the coupled inductors. When the duty cycle is in the range of 0-0.5, the high gain, high efficiency and low ripple of input current required by new energy power generation can be achieved, avoiding the influence of an extreme duty cycle. The steady-state analysis, efficiency analysis and experimental verification for the converter were carried out, and its performance was compared with those of similar converters. A 200 W prototype was fabricated in a laboratory, and experimental results were basically consistent with the theoretical analysis.

To solve the problem of a small output voltage range in single-inductor dual-output Buck-Boost converters, a quadratic unit structure is introduced in this paper, which is the voltage gain by D_i/(1-D_i) times and significantly expand the voltage range.According to the working state of the power supply inductor, the power supply modes of the converter can be divided into four types, i.e., complete inductor supply mode, incomplete inductor supply mode, dual-branch supply mode and single-branch supply mode. The voltage gain, ripple voltage and critical inductance values between each mode of the four power supply modes are calculated. The converter has four output states, i.e., Boost, Buck, Boost-Buck and constant-voltage, and the duty cycle conditions in each output state are derived. Finally, experiments were conducted in four power supply modes and four output states of the converter, proving that the theoretical analysis is correct and the performance of the converter is reliable.

Since the inverter-interfaced distributed generations (IIDGs) in microgrids exhibit special output characteristics, traditional protection schemes are no longer suitable for microgrids. Simultaneously, the idea of “Signal-injected active protection” introduces a novel perspective on microgrid protection. However, the shunt problem of non-injection source results in a poor protection performance. Under this background, in light of the idea of control-protection coordination, an active protection method for microgrids based on harmonic component injection is proposed. First, the frequency response characteristics of IIDG are analyzed. Then, the controllers of injection source and non-injection source are designed, and the corresponding start-up criteria are established. When a fault occurs, the injection source injects the characteristic signal of harmonic component with constant amplitude into the microgrid, while the non-injection source limits the shunt of the characteristic signal, so that the characteristic frequency equivalent network of the microgrid exhibits a single-source structure. Simulation results show that the proposed strategy can reliably start the harmonic component injection and solve the shunt problem of the characteristic signal, providing a solution for signal-injected microgrid protection.