Loss Optimized Modulation of Three-Phase DAB for Cascaded Battery Energy Storage System

Three-phase DAB (3P-DAB) is a potential topology for cascaded battery energy storage system with lower current stress, smaller volt-second curve area and smaller filter capacitance requirement. The open circuit voltage (OCV) of battery module changes with different state of charge (SOC), which causes 3P-DAB to operate in the wide gain range with large reactive power and switching current stress. Thus, it is worth studying to improve the efficiency under the condition of wide gain range. This paper analyzes the loss distribution including conduction loss and switching loss with wide bandgap device, which draws the conclusion that switching loss can’t be ignored in the optimization process. With Fourier transform, the loss model of 3P-DAB is established. Using interior point method, optimal control parameters with the total loss as the optimization objective is determined, which improves the efficiency especially at low loads. Finally, a 250kW/20kHz experimental platform is built to verify the performance of the optimization result.