Ripple elimination for DC/AC DAB converter with phase shift and duty cycle control

Active ripple current reduction method is proposed for isolated DC/AC dual active bridge (DAB) converter to reduce the double grid frequency ripple in the DC current. Unlike those active methods that require extra switches to construct separate ripple reduction circuit, in this method, one or two branches of LC ripple steering circuits are used along with existing full bridge switches in a multiplexing manner. For the purpose of the ripple elimination, unsymmetrical phase shift modulation and duty cycle regulation methods are proposed and applied to both legs of the converter on the primary side of DAB converter. Also a current sharing (CS) scheme is presented to balance the current on both LC ripple steering circuits.