An Improved Extended Phase Shift Modulation for DAB Converter with the Blocking Capacitor

Based on extended phase shift (EPS) modulation with voltage matching control and the DC blocking capacitor, an improved modulation method for dual-active-bridge (DAB) DC-DC converters with the blocking capacitor is proposed in this paper, which can realize full load range zero voltage switching (ZVS) under wide voltage range with low root-mean-square (RMS) current. In the proposed scheme, the volt-second products of all windings are kept equal to achieve the full load range ZVS, and the secondary side of the converter is switched between the full bridge mode and the half bridge mode to switch the optimal matching point of the voltage and then reduces RMS current and enlarges the ZVS region. The operation principle of the proposed method is analyzed, and ZVS region is illustrated and compared with conventional modulation to demonstrate the performance. A 1kW experimental prototype with 200V input and 100 - 400V output was built to verify the feasibility and effectiveness of the proposed method.