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The article proposes and investigates an alternative coupled inductor configuration in a three-level interleaved dc–dc converter. The new common-leg coupled inductor structure is introduced, and possible modulation methods are studied and theoretically analyzed, focusing on the impact on current ripples, power losses, and common-mode noise. The concept is validated using an MV-rated, SiC-based bidirectional converter dedicated to battery storage application in a bipolar EV charging station, tested up to 1 kV and 10 kW. Furthermore, the comparative study shows that the suggested method exhibits a smaller volume when compared to the conventional approach with several single inductors, comparable performance but with a more straightforward inductor design than the tapped inductor solution, and full section current controllability, unlike the single-inductor option. Finally, using the proposed technique, common-mode noise can be entirely limited, allowing the minimization of excess filtering. Overall, the proposed inductor configuration can be effectively and competitively used in modern SiC-based three-level dc–dc converters.

This article investigates the soft-switching quasi-square-wave (QSW) technique in dc/dc SiC-based flying capacitor converter with quasi-two-level (Q2L) control establishing design guidelines for constructing high-efficiency soft-switched bidirectional converters with low-voltage power transistors. The general idea behind the soft-switching in the proposed system is based on near critical conduction mode operation using TCM (triangular current mode) and Q2L control with the addition of auxiliary transistor capacitances. The soft-switching process is based on a resonance between the capacitances in parallel to each transistor, and the main inductor—ZVS at turn on is ensured through proper modulation pattern according to TCM-Q2L control, and the turn-off soft-switching mechanism is assured through the novelty in the form of adding auxiliary capacitance in parallel to each of the SiC power mosfets according to the QSW operation. Thus, the converter can reach very high efficiency (peak at 99.5%), maintaining soft-switching for a wide operating range, using only small auxiliary SMD capacitors and a low-volume flying capacitor, leading to high power density. The presented study is based on experimental tests using a 1.5 kV model at up to 15 kW and includes the impact of various auxiliary capacitance values and optimal capacitor value selection for maximizing the converter efficiency.

This article presents a novel method for the dynamic measurement of $C_{\mathrm {OSS}}$ – $V_{\mathbf {DS}}$ characteristic of SiC MOSFET power modules based on the process of charging the output capacitance of the transistors. This technique has been used to determine the $C_{\mathrm {OSS}}$ – $V_{\mathrm {DS}}$ characteristics of medium voltage SiC MOSFET modules, which allows for the extraction of the capacitive current while switching off the transistor. Based on this measurement method, the influence of the turn-off gate voltage $V_{\mathrm {GS-OFF}}$ on the $C_{\mathrm {OSS}}$ – $V_{\mathrm {DS}}$ characteristics has been studied, exhibiting an impact on the output capacitance at low drain–source voltages. However, it is shown that the effect of $V_{\mathrm {GS-OFF}}$ on the capacitive current and power loss is limited in this area. Finally, the channel current and the capacitive current distribution within the drain current were determined based on the determined $C_{\mathrm {OSS}}$ – $V_{\mathrm {DS}}$ in the experimental test at various switched currents and switching speeds. According to the capacitive charge calculations for several cases, the method’s accuracy is high enough to perform switching power loss estimations for medium voltage power modules to be employed in the design of the state-of-the-art power converters. Furthermore, the method is very simple, based on basic capacitance equations, and the required experimental setup is very similar to one used in double-pulse tests.