Neutral Point Balancing for Three-Level Neutral Point Clamped Inverters under Light Load Conditions

摘要

In this paper, a robust fallback method for Neutral Point Balancing of Three-Level Neutral Point Clamped (3L-NPC) inverters under light load conditions is proposed. Measurement errors, non-ideal switching behaviour of semiconductors and minimum pulse width constrains prevent normal balancing methods from controlling the neutral point probably under light load conditions. To overcome these issues, an injected auxiliary current forces the voltage imbalance to zero. Measurement results prove the performance of the concept.