Control Strategy of Isolated Bi-Directional AC/DC Converter Controlled by Single Phase Shift Control

A single-phase-shift control (SPS) plus variable-frequency control (VF) control strategy for isolated bidirectional AC/DC converters is proposed. The isolated bidirectional AC/DC converter topology consists of a dual active bridge (DAB) and a synchronous rectifier (SR). The proposed strategy converts the non-linear relationship between shift compared to output power in single phase shift control into a linear one by means of frequency control, making the control simple. The transfer function of the control is obtained by modelling the DAB small signal system and the optimal control parameters are obtained after frequency domain analysis. At the same time, the control method can effectively reduce the switching losses and the smaller value of the intermediate capacitor parameter reduces the size of the converter. The control principle of this isolated bi-directional AC/DC converter is described and analyzed in detail, and finally the correctness and effectiveness of the proposed control strategy is verified by simulation.