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.

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.

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.

The cables of switching power supply which are connected in parallel is an important radiated electromag-netic 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 switch-ing 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 de-scribing 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-cou-pling effect into account can predict the radiated EMI of cables of switching power supply more accurately.

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.

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.

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.

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.

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.