Direct power control strategies of a grid-connected three-level voltage source converter VSI-NPC

In this paper, a new switching table for direct power control (DPC) strategy is proposed for three-level NPC rectifier. The strategy is developed by analyzing active and reactive power and introducing convenient controllers to optimize the voltage selection which is the fundamental task in that control method. The dc-link voltages are maintained at the required level using hysteresis controller for the NP current exploiting the redundancy states of the rectifier. With a simple switching table, the excellent dynamic and transient performances are achieved under unity power factor operation. Simulation results verify the validity and feasibility of the proposed strategies.