An Optimized Design Method of Phase-Shift Angle in DPS Modulation Scheme for LCL-type Resonant DAB DC-DC Converters

Featuring the reduced volume and high efficiency, dual-active-bridge (DAB) DC-DC converters have been widely investigated in energy storage system, DC microgrids, etc. However, special attention should be paid to their backflow power issue, which would reduce the system efficiency and also increase the current stress of the devices. LCL-type resonant DAB (LCL-DAB) DC-DC converters can well suppress the backflow power, and several studies focusing on the circuit analysis have been done. However, the detailed modulation design method has not been presented, which is difficult to realize a better suppression of backflow power. As the harmonic contents in the LCL network current determine the backflow power, the impact of phase-shift angle between arms in one H-bridge on harmonic contents in the LCL network current is first discussed in this paper. It has been found that the harmonic contents in the LCL network current are related to the two phase-shift angles, and an optimized design method of phase-shift angle in dual-phase-shift (DPS) modulation scheme is proposed in this paper. Through the proposed design method, the harmonics in the LCL network current are largely reduced and thus the backflow power can be well suppressed. Finally, the simulation results have been presented for verifying the proposed method.