An integrated control method for three-level NPC based PWM rectifier-inverter

This paper presents a novel integrated control scheme for three-level neutral point clamped (NPC) based PWM rectifier-inverter. Two measures are taken to minimize the size of dc-bus capacitors which are expensive, bulky and have a lifetime limit. Firstly, the direct power control (DPC) for front-end three-level PWM rectifier is applied, which will provide better dynamic performance for the dc-link. Secondly, a power feed-forward control loop from inverter to rectifier side is introduced to reduce the response delay. Some experiments have been performed on an IGBT-based three-level PWM rectifier-inverter, and the results show that with the proposed scheme, the three-level NPC based rectifier-inverter exhibits excellent dynamic performance, and can minimize dc-bus voltage fluctuations remarkably.