Current Stress Optimization of Dual Active Bridge Converter in Two-Stage Single-Phase Inverter System With Second Harmonic Current Shaping

With consideration of double line-frequency instantaneous power in two-stage single-phase inverter system, a second harmonic current shaping (SHCS) method is proposed in this article to minimize the current stress of front-end dual active bridge (DAB) dc/dc converter. The current stress of DAB is optimized by analytical expressions in time domain so that both the low-frequency fluctuations and inherent high-frequency characteristics of DAB current are considered. As a result, the current stress of DAB can be minimized. The analytical expressions of optimized double line-frequency output current of DAB are derived. An implementation method is presented to combine the traditional single voltage closed-loop (SVC) control method with the feedforward compensation of only double line-frequency output current of DAB. Therefore, the stability and dynamic performance of SVC are not affected by SHCS method. The parameters design of SHCS method is the same as that of SVC method. The minimum current stress and fast dynamic response can be achieved by SHCS method without any compromise. The performance evaluation indicates that SHCS method is superior to traditional methods in terms of optimization effects and implementation method. The experimental results verify the good performance of SHCS method both in steady state and dynamic state.