DC-link Voltage Balancing Converter with Resonant Switched-Capacitor Circuit for Four-Level and Six-Level NPC Inverter

This paper presents research results on a novel concept of switched-capacitor (SC) voltage balancer suitable for DC-link voltage balance in 4-level and 6-level NPC (Neutral Point Clamped) inverters. The balancer enables the transfer the energy between any capacitors in the DC-link with various dynamics in a controlled way, maintaining high efficiency thanks to Zero Current Switching (ZCS) and minimizing application cost using low volume LC components, bootstrap type gate circuitry for transistor switches. This paper presents concepts of operation, switching strategies, simulation results, design issues and finally results of research conducted on experimental setup for various test scenarios.