A Hybrid Modulation Strategy for the Modular Quad-Active Bridge Converters with the Aid of DC Blocking Capacitors

This paper presents a hybrid modulation strategy (HMS) for modular quad-active bridge (QAB) converters to address the efficiency shortcomings of single phase-shift (SPS) modulation methods. The proposed HMS significantly bolsters the efficiency of the converter while maintaining the simplicity inherent to SPS, rendering it highly straightforward to implement in engineering applications. The HMS incorporates a DC bias capacitor to ensure the QAB converter operates under a half-bridge configuration during light load conditions and transitions to a full-bridge configuration under heavy load conditions. Due to the high coupling of the ports of the QAB converter, this paper determines port coefficients using the minimum mode of inductance root-mean-square current. Finally, an experimental prototype of a QAB converter is established and tested.