A Narrow Pulse Compensation Method for Neutral-Point-Clamped Three-Level Converters Considering Neutral-Point Balance

For medium/high voltage high-power neutral-point-clamped (NPC) three-level converters, narrow pulses appear usually when modulation waves are close to +/- 1 and 0. To ensure reliable switching and the safety, a long narrow pulse limit time needs to be set. Narrow pulse problems will become prominent. Meantime, neutral-point voltage balance problem of three-level NPC converters is a key issue that should be seriously considered. The strong coupling effects between narrow pulse problem and neutral-point voltage balance problem is also worth attention. Ignoring the strong coupling effects, traditional narrow pulse methods realize narrow pulse compensation and neutral-point voltage balance separately. Considering the two problems and the coupling effects, a novel narrow pulse compensation method is proposed. By analyzing the limits of modulation waves caused by narrow pulses, narrow pulses are eliminated completely in this paper. Simulation and experimental results show that it has a good performance for narrow pulse compensation and has few adverse effects on neutral-point voltage balance. The overall performance is better than traditional narrow pulse compensation methods.