An RMS Current Minimization Method for Three-Level ANPC-DAB-Based Distributed Energy Storage System With Full Operation ZVS

Distributed energy storage system has been developed rapidly with the rising employment of sustainable energy sources. In order to withstand higher voltage, achieve larger capacity, and increase control flexibility, a three-level active neutral-point-clamped dual active bridge (ANPC-DAB) converter is employed for the interface between energy sources and energy storage ports. In order to achieve efficient power transmission inside the ANPC-DAB converter, both root-mean-square (rms) current and zero-voltage-switching (ZVS) range are taken into consideration for further optimization. On the one hand, using fmincon function in MATLAB with multiple nonlinear restrictions, optimal rms current can be obtained to realize minimum conduction loss. On the other hand, to reduce switching loss, several typical modes are chosen to realize the ZVS of all switches inside the entire power range. Compared with existing modulations in a three-level DAB converter, the efficiency promotion strategy proposed in this article can achieve the lowest rms current and widest ZVS range. Eventually, an ANPC-DAB prototype is established and the effectiveness and correctness of the proposed method can be proved.