High frequency converters based on silicon carbide (SiC) semiconductors are becoming popular, but due to the integration parameters, they are very likely to generate high voltage overshoot and large oscillation, which increase the voltage stress and cause EMC problems. To suppress the voltage overshoot and oscillation, the mechanism is firstly analyzed. Stray inductance is a culprit in causing these problems. To minimize the inductance of power circuit, this paper proposes optimization method including better design of bus-bar structure and parallel connection of snubber capacitors by means of model analysis and formula derivation. To evaluate the method, an inverter model and a prototype were built, several optimization schemes were compared by co-simulation and experimental tests. Experimental results show that the stray inductance of the new bus-bar is 6.4% of the traditional bus-bar. The loop-inductance can be reduced by 46.4% by connecting the capacitors in parallel, and the switching losses can be reduced by 30.8%. This analysis provides guidelines for a full SiC inverter design.

This study proposes a detuned resonant capacitor selection strategy to eliminate the influence of the changed coupling coefficient on the transferred power and efficiency of a wireless power transfer (WPT) system using the LCC-S resonant topology. The output characteristics of the conventional tuned LCC-S system and the novel detuned system are analyzed and compared in detail, the different effects of the detuned parameters on the system output performance are expounded by simulations, and an optimal detuned parameter design process is presented. By adjusting the compensated capacitors on the transmitting side, the output voltage can be constant under varying coupling conditions without changing the switching frequency. Experiments with a 1.5kW power scale were conducted to verify the proposed theoretical analysis. The results show that the fluctuation of the output voltage is restricted to 8.2% in the optimized system when the coupling coefficient changes from 0.18 to 0.38. Under the rated coupling conditions, the experimental results demonstrate that compared with ZPA (88.29%) and ZVS (90.66%), ZCS (91.52%) operating conditions are more suitable for a WPT system equipped with IGBTs to improve the overall efficiency.

The application of the Three-Level Boost Converter (TLBC) in high-frequency isolated auxiliary inverter system is able to reduce the voltage stress of power switches and diodes in the back-end circuit, reduce the volume and weight of energy storage components, and improve the overall power density of the converter system. However, TLBC topology has its own disadvantage which is the capacitor midpoint potential offset problem. In order to solve this problem, this paper analyzes the limitations of the traditional independent duty control strategy first, and then proposes the pulse phase delay control strategy to balance the midpoint potential of TLBC. After the relevant theoretical analysis based on the AC smallsignal model of the TLBC, which is controlled by the pulse phase delay control strategy, this paper completes its modeling and simulation by using PSIM & Matlab. Finally, this paper presents some experimental results, and combines with the waveforms of the simulation to verify that the proposed control strategy can effectively adjust the bias voltage without changing the TLBC output characteristics.

This paper proposes an active resonant network based on variable resonant capacitances to improve the operating performance of the LCC-S compensated topology in the wireless power transfer (WPT) system for electric vehicles under coil-misaligned conditions. By adjusting the series and parallel compensation capacitances on the transmitting side, the output voltage can be kept constant and the energy transfer efficiency can be improved under different coil offsets. The switch-controlled capacitors (SCCs) are used to change the compensation capacitances continuously. To find the proper compensation capacitances to achieve the excellent performance of the system, the optimization algorithm is applied, and the corresponding digital control strategy is described to regulate the equivalent capacitances of SCCs. Experimental results with a 2.7 kW power scale show that the output voltage is constant, and the operating efficiency is always over 90% in the WPT system with an active resonant network under different misalignment conditions. In addition, the system is delivering an equal amount of energy for all misalignments within the range of 80 mm, which improves the expected value of transferred energy by about 29%.