Investigation of sensorless capacitor voltage balancing technique for modular multilevel converters

Abstract

Modular Multilevel converters (MMC) have become one of the most promising topologies for DC-AC conversion in recent years. Capacitor voltage balancing is a vital issue for proper operation of the MMC. Generally, conventional sensor-based balancing techniques require a significant amount of measurements, 2m(N-1) voltage sensors and 2m current sensors are required for a N-level m-phase converter. In this paper, a sensorless voltage balancing technique (self-balancing) is proposed for the MMC. The proposed technique eliminates all measurement boards used for monitoring capacitor voltages and arm currents, which in turn reduces system complexity and cost. Simulation and experimental results support and validate the proposed concept.