Direct power control of three-level NPC grid-connected system combined with fault-tolerant technology.

In this paper, a three-level NPC grid-connected system is studied, and the direct power control strategy based on virtual flux linkage is applied to the grid-connected inverter. When the three-level main circuit fails, if the hardware redundancy method is still used, it will bring a series of problems to the system, such as increasing the volume and cost of the system, resulting in a waste of resources. In view of this situation, the redundant resources of the multilevel converter are used to realize the fault-tolerant control in this paper. Suppose a bridge arm has only one switch short circuit, by re-adjusting the action sequence and action time of the voltage vector, the system can continue to run while ensuring reliability although performance degradation. Simulation and experiment show that the method adopted is correct and feasible.