Comparison of Performance of Phase-Shift and Asymmetrical Pulsewidth Modulation Techniques for the Novel Galvanically Isolated Buck–Boost DC–DC Converter for Photovoltaic Applications

Abstract

This paper discusses realization possibilities of the buck mode in the novel magnetically integrated quasi-Z-source series resonant converter (qZSSRC) with secondary resonance. Our aim was to achieve higher power conversion efficiency at different power levels and dc voltage gains of the converter. The phase-shift modulation (PSM) was comprehensively compared with the asymmetrical pulsewidth modulation (PWM). Both control techniques were evaluated for the case of the discontinuous current through the resonant network, which made their realization more challenging. The operating principle of the qZSSRC in the buck mode with two compared control techniques was explained by means of steady-state analysis. To verify the theoretical assumptions, a 250-W prototype of the photovoltaic module integrated converter was assembled and tested. It was experimentally confirmed that in contrast to the PSM, the asymmetrical PWM for the buck mode control of the qZSSRC will lead to higher power conversion efficiency at different power levels and dc voltage gains of the converter, except the operating points close to the boundary with the normal mode of the converter.