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.

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.

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.

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.

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.

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.

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 com-mon 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 inte-gration 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 simula-tion analysis, electrical characteristics under DC-bias and the on-board tested data, the effect of the magnetics integra-tion 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.

The inconsistency of line parameters at the outlet of distributed generator(DG) and its random output disturbance 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 consideration of the transient-and steady-state of DG operation. First, the influence of line impedance is taken into account during 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 algorithm 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.

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.

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.