Direct power control for Neutral-point-clamped three-level PWM rectifier

This paper proposes a direct power control (DPC) strategy employed for the neutral-point-clamped (NPC) three-level PWM rectifier. Mathematic model of NPC three-level rectifier is conducted firstly as a theoretical base. This topology generates a higher number of output voltage levels, increasing the flexibility for selecting an appropriate voltage vector. The direct instantaneous power control technique for the converter, which has been developed to control the instantaneous active and reactive power directly by selecting the optimum switching state of the converter, is discussed in detail in the paper. The neutral-point potential is controlled according to the direction of the mid-point current and a study of each switching vectorpsilas influence to active and reactive power. Theoretical analysis is presented and the performance of the proposed method is verified by simulation and experiment.