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 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 par-ity-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 sys-tem 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.

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.

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.

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.

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.

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.

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.

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.

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.