Single-Stage Isolated AC–DC Converter Based on <i>LCL</i> Resonant DAB Converters With Single-Loop Control
Zhiqiang Guo, Weijie Zhan, Zhongyuan Chen
Abstract
This article presents a single-stage AC-DC converter composed of a synchronous rectifier and a dual active bridge (DAB) converter with an LCL resonant tank. The optimum DPS control for the LCL-DAB converter is analyzed to make a tradeoff between the ZVS and conduction loss. Based on the DPS control, the analytical expression of the input current of the single-stage AC-DC converter is revealed. It indicates that the input current is only associated with the phase shift angle and the output voltage rather than the input voltage. Therefore, the control strategy of the LCL-DAB single-stage AC-DC converter is proposed to achieve the output voltage and input current regulation with the single loop control. Without the inner current loop, the converter can still achieve unit power factor and high-quality input current regulation, which eases the implementation and controller design in the digital control. By designing the turns ratio of the transformer and resonant inductor based on the 3-dimensional (3D) loss surface, the efficiency is further improved. A 1kW prototype demonstrates the effectiveness and good performance of the control strategy and the design consideration.