High-Conversion Ratio Modular Series-Capacitor Boost for PV Systems with MPPT Control

This study presents a high-gain multi-phase non-isolated DC-DC topology constructed around universal series-capacitor step-up building blocks, employing universal LC structure. The resulting topology features high modularity of the converters and facilitates high gain. The interaction between L and C elements contributes to a soft charging of the capacitors, which in turn significantly reduces converter losses and increases efficiency. The basic building block was used to implement a multi-phase boosting DC-DC converter running a maximum power point tracking (MPPT) control and applied as a pre-regulation stage for microinverters. The multi-phase boosting DC-DC converter reduces the stress of the MOSFETs, significantly extends the effective duty cycle, and exhibits natural current sharing that assists in load balancing between the phases. Experimental prototype was built in the laboratory and evaluated against numerical simulations and theoretical premises. The results were found to agree well with the theory presented in this paper.