The Dual-Voltage Match Modulation and Control Method for Inductor RMS Current Optimization in the Three-Port MMDC DAB Converter

Lowering the inductor root-mean-square (rms) current is crucial for enhancing the performance of the three-port dual active bridge (DAB) converter. In this article, a dual-voltage match (DVM) modulation and control method is put forward for the three-port modular multilevel dc (MMdc) DAB converter. This asymmetric modulation and control method enables simultaneous adjustments of the optimal voltage level VP2 and its pulse width in the primary voltage vP for the first time. By rapidly reversing the inductor current’s polarity, its rms value and the reactive power can be significantly reduced at a given transmission power. Moreover, the discontinuous analytical expression for the optimal value of VP2 is derived, fully utilizing the high degree of control freedom in the primary submodules (SMs). Based on the 3 kW MMdc DAB converter with two output ports, the proposed DVM method is compared with three typical MMdc modulation schemes in experiments. The experimental comparison results under asymmetric and symmetric load conditions are presented. According to the experimental results, it is validated that the DVM method proposed in this article has good performance in optimizing both the inductor rms current and efficiency under various operation conditions.