Hybrid Modulation Strategy for IGBT-Based Isolated Dual-Active-Bridge DC–DC Converter

In the IGBT-based bidirectional isolated dual-active-bridge (DAB) dc-dc converter, it is not necessary that the IGBTs of the secondary-side H-bridge inverter (HB2) retain under on state because in this system, the function of synchronous rectification cannot be realized. This paper firstly analyzes the characteristics of the DAB converter with all of the IGBTs of HB2 keeping under OFF state. Its main drawback is that the flow back current in the primary dc side is caused and the current stress is increased. Furthermore, a hybrid modulation strategy is proposed and the control rule of the two inner phase shifts of the primary and secondary H-bridge inverters is determined to eliminate the flow back currents in the entire power range, enhance the maximum transfer power, and achieve a good inductor current characteristic. The experimental results verify the correctness of the theoretical analysis and the feasibility and practicability of the proposed hybrid modulation strategy.