An Active Power Decoupling Method for Single Phase DC/AC DAB Converters

The existence of the double grid frequency (100 Hz) ripple current in dc/ac dual active bridge (DAB) power converters can degrade their performance and as such these ripples need to be compensated. An active power decoupling method is proposed in this paper to attenuate the 100-Hz current ripple in single phase dc/ac DAB converters. Compared to other current ripple reduction methods for which additional switches are used, the proposed method does not require any additional switching components thus decreasing the system cost. In the proposed method, the existing switching devices of the primary side full bridge converter and an LLC circuit integrated to form a 100-Hz ripple current reduction circuit, which is controlled by regulating the duty cycle of the primary full bridge converter switching legs. The mathematical analysis and the circuit parameter design methods are proposed. In addition, a current sharing method is proposed to keep the currents of the inductors in the LLC circuit are balanced against any possible circuit parameter deviations. The effectiveness of the developed method is evaluated through the simulation and experimental tests.