D-Q modeling and control of a single-phase three-level boost rectifier with power factor correction and neutral-point voltage balancing

This paper deals with the analysis, design and operation of a control system for a single-phase three-level rectifier with a neutral-point-clamped (NPC) topology. Usually the desired operating conditions for this type of converter are: unity displacement factor, output DC voltage regulation and neutral point voltage balancing. A d-q reference frame has been used in this work to model the rectifier behaviour in order to exploit the results obtained in the field of three-phase converters. In this way, a space vector modulation PWM method has been used, with the possibility of using redundant switching states to achieve charge balancing of the capacitors. The time assignment of each redundant switching state is accomplished by utilizing a closed-loop control system. Validity of the modeling and control strategies are confirmed by the transient and steady state simulation and experimental results.