Reactive Power Control Strategy for Isolated Single-Stage AC–DC Converter Based on Dual Active Bridge

This article presents a reactive power control strategy for the isolated single-stage dual active bridge (DAB) ac–dc converter. Triple phase shift (TPS) control is employed to achieve zero-voltage switching and reduce conduction losses, ensuring globally optimal working modes. The impact of the phase difference between the grid voltage and current on the input current direction of the DAB dc–dc converter is analyzed. Under TPS control, the input current direction is regulated by adjusting the polarity of the phase shift angle (i.e., positive or negative values). A control algorithm for the DAB ac–dc converter is proposed to enable reactive power control on the grid side and output regulation on the load side, thereby improving the power quality of the system. The variations in working modes concerning load power and line-frequency angle under the reactive power control strategy are investigated. Based on the control strategy for optimal working modes, the proposed method ensures that the DAB ac–dc converter operates efficiently across a wide range of load power. In addition, the design methodology of the series inductor is analyzed to achieve reactive power control while meeting target load power requirements. Finally, the proposed control strategy is applied to a 1-kW DAB ac–dc converter with a 220 V/50 Hz input voltage and a 200-V output voltage. The experimental results validate the feasibility and effectiveness of the reactive power control strategy.