Improved Modulation Strategy for Single-Phase Isolated Quasi-Single-Stage AC–DC Converter to Improve Current Characteristics

In this article, an improved triple-phase-shift (ITPS) modulation for the single-phase isolated quasi-single-stage ac-dc converter is proposed to realize the current decouple between the adjacent switching periods and to reduce the grid current distortion. Moreover, the dead band effect on the proposed ITPS is analyzed for the first time. It reveals that the dead band causes not only the current couple and accordingly the grid current distortion but also the current amplitude loss. A two-step phase-shift compensation scheme is proposed based on the analysis result to solve the problems caused by the dead band. All of the theoretical analysis, the proposed ITPS modulation, and the dead band compensation scheme are validated in detail in the experimental way.