An Extended Describing Function Model for A Hybrid Frequency/Phase-shift Controlled SiC-Based High-Gain DC-DC Resonant Converter Module

An improved hybrid variable-frequency and phase shift control scheme that is well-suited for extending the soft-switching operation and providing output voltage regulation simultaneously for a DC/DC step-up converter module with a simple passive auxiliary circuit is presented in this paper. The proposed converter incorporates transformer non-idealities (such as the leakage and magnetizing inductances) into a basic operation of the CLL resonant circuit. To eliminate the reverse recovery losses of the diodes, the resonant inductor in the presented converter module is integrated with the high-frequency voltage multiplier to form a current-driven structure. To analyze the presented control algorithm, the small-signal model and the control-to-output transfer functions are obtained using extended describing function (EDF); which can handle multistate variables. Simulation results on a modular 1kVDC/34.2kVDC, 1.2MW are first given to verify with the theoretical analysis of the proposed converter module. The accuracy and validity of the presented small-signal model and the performance of the proposed converter system are further verified using a 1.4kW (two-modules), 140V/1.6kV proof of concept prototype.