Multilevel Inverter DC-Link Active Voltage Regulation System

This paper presents an active voltage regulation system for regulating dc-link capacitor voltages in multilevel inverter topologies. These voltage levels typically originate from a single dc source and multiple capacitors. Effective regulation is essential for maintaining ac waveform quality and minimizing harmonic distortion. The work includes the analysis, design, and experimental validation of a closed-loop active voltage regulation system based on a buck-boost voltage balancer for a two-capacitor dc link. The system is integrated into an asymmetric T-type multilevel inverter, suitable for photovoltaic applications. A closed-loop stability analysis is conducted for general load conditions, and the inverter dc-link current demands are evaluated for compatibility with the active voltage regulator. Experimental results demonstrate accurate ac waveform reconstruction, reduced harmonic distortion, elimination of dc offsets, and fast, robust dynamic response, highlighting the system suitability for high-efficiency multilevel inverters.