Control method for ripple current reduction and grid current correction in a single phase DC-AC DAB converter

A LLC circuit is developed in this paper to reduce the DC source 100Hz ripple current in a DC-AC dual active bridge (DAB) converter by regulating the duty cycle of the primary side full bridge converter without utilizing additional switches. However, heavy duty cycle changes with relatively small capacitor of LLC circuit will result in the grid current distortion. To address this issue, a repetitive control is proposed to improve the quality of the grid current and related THD. Modulation scheme and ZVS turn-on conditions for both the primary and secondary converters are presented. A control model and a decoupling control strategy in synchronous dq frame for the DC-AC DAB converter are proposed. The proposed methods are examined through simulation tests and the results are presented.