Highly Efficient Single-Stage DAB Microinverter Using a Novel Modulation Strategy to Minimize Reactive Power

This article proposes a highly efficient single-stage dual-active-bridge (DAB) microinverter with a novel modulation strategy to minimize the reactive power flow of DAB converter. Using the proposed modulation, the DAB microinverter achieves good controllability and high efficiency with the following features. First, the variable-frequency control algorithm linearizes the nonlinear function of the phase shift angle, enabling a simple closed-loop control for the sinusoidal trajectory tracking. Second, the proposed modulation strategy minimizes the reactive power flow during the switching period while guaranteeing the zero-voltage-switching (ZVS) turn-on of all switches. With minimized reactive power, current stress and power losses are significantly reduced. Thus, the DAB microinverter achieves a maximum efficiency of 96.87%. Third, the proposed phase shift angles and switching frequency are obtained in an analytic form, thereby that they are computationally simple and easy to implement. The operation principle of the proposed modulation strategy is theoretically analyzed and verified. Experimental results based on a 330-W prototype module are conducted to evaluate the performance of the proposed inverter and to verify the analysis.