Impedance network based isolated three phase AC-AC converter with enhanced voltage gain and safety

Abstract

The matrix converter is designed to achieve three-phase AC-AC direct power conversion, variable frequency, and high power density. The conventional matrix converter has limited voltage gain and requires a large number of switches. The Ultra Sparse Matrix Converter (USMC) was introduced to address this, reducing the number of switches while voltage gain is still significantly low. The lower voltage gain hindered the USMC for versatile applications including renewable energy integration, microgrids, and industrial applications. Researchers also introduced various modified versions of USMC including z-source, quasi z-source, switched inductor, and switched capacitor USMCs. Although these modified USMCs have relative merits and demerits, they are non-isolating, raising safety concerns and voltage gain is still insufficient. This paper focused on achieving higher voltage gain, providing electrical isolation, and reducing the switching voltage stress. In this paper, a novel three-phase isolated duodecuple source (DS) impedance network-based USMC is proposed. The DS impedance network consists of a flyback stage with high-frequency transformer isolation, a boost stage, and a voltage tripler stage. The flyback stage provides electrical isolation, the boost stage enhances voltage gain, and the voltage tripler stage makes it triple. The voltage gain of the proposed DS-USMC converter is 12 at a duty ratio of 0.5. The voltage stress across the DS switches is 30V and 61V, both below the critical threshold. The proposed DS-USMC retains all the merits of their existing USMC, providing a larger range of output voltage with electrical isolation, safety, and reducing switching voltage stress in a cost-effective manner.