LLC circuit based ripple current suppression method for single phase bidirectional DC-AC DAB converter

A new ripple current reduction method utilizing a LLC type ripple current steering circuit is proposed in this paper to significantly reduce 100Hz ripple current in an isolated DC-AC dual active bridge (DAB) converter. Unlike some of the proposed ripple reduction methods for which auxiliary circuit consists of additional switches is applied, this new method benefits from less switching components and cost while providing effective ripple current reduction performance. In this method, the existing full bridge switches on primary side are used and symmetrical phase shift modulation and duty cycle regulation for both legs are adopted. Control-oriented mathematical analysis and parameter design method for LLC circuit are presented. Due to possible variations in parameters of hardware circuit, current sharing (CS) control method is also provided in this paper to balance the current of the two inductors. Simulation and results are provided to validate the proposed method.