A Space Vector Modulation based Model Predictive Control for Low Frequency Operation of Nested Piloted NPC

Abstract

Nested neutral point clamped (NNPC) converter is one of the promising topologies in multilevel structures for ac drive application. This topology has a low number of components and can operate with only one DC source. The five-level NNPC can reduce dv/dt higher than the four-level topology. In this topology, however, the voltage balance of flying capacitors is challenging due to a lack of redundancies. New control methods such as finite control-set model predictive control have been evaluated on the 5L-NNPC. But in this method, the variable switching frequency is another challenge in FCS-MPC. In this paper, a modified version of NNPC topology is used which is called nested piloted NPC. The 5L-NPNPC offers more redundancies than conventional NNPC. An optimal switching sequence model predictive control based on space vector modulation is proposed to provide constant switching frequency and voltage balance among flying capacitors. The performance of the proposed OSS-MPC is verified with the simulations in various conditions such as different load power factors and low-frequency operation.