Suppression method of DC-offset in transformer current for flying capacitor dual active bridge converter at changing operation mode

This paper proposes a modulation method to eliminate the DC-offset in transformer current at changing operation modes, which are square waveform, five-level waveform, and square waveform with half of the DC voltage. In the proposed modulation method, the update of phase-shift angle is divided into two steps. From the experiment, the peak of the transformer current due to the DC-offset current is reduced by up to 28.6% compared with the conventional method. © 2019 The Institute of Electrical Engineers of Japan.