The NPC Three-Level Inverter Based On SVM Simplified Algorithm

Recently, multi-level inverters are the research focus in medium and/or high voltage high power applications. As a new type of converter, multi-level inverters provide high voltage high power output through changing the circuit topologies, without using voltage-sharing circuit and boost-buck transformer. Compared with the traditional two-level inverter, multi-level converters can output more voltage levels and have such advantages, the voltage across the power device is reduced, the switching frequency is lower, and the output voltage quality is better, so multi-level inverters are founding increased attention in high voltage drives and flexible AC transmission. The common neutral-point-clamped (NPC) three-level inverter is discussed in this paper, and the space vector modulation algorithm and neutral-point potential balancing control method are studied.In this paper, all kinds of multi-level inverter topologies are classified and the topologies are deduced from the parallel-series and series-parallel connections of the power electronics circuits basic cell, which is constituted by power devices. The topology, the operation principle and the switching mathematical model of the NPC three-level inverter are discussed in detail.PWM control strategy is a key technique to multi-level inverters, which can impact the output voltage quality. This paper studies the sector dividing, basic vector calculation, duration computing and vector optimization of three-level space vector modulation. A simplified modulation method is presented based on the previous analysis, and the validity of the proposed method is verified by the theoretical derivation.The neutral-point potential balancing control is the premise of NPC three-level inverter operations. This paper simply introduces the reasons of neutral-point potential unbalancing and the damages brought by the unbalancing in NPC three-level inverter. The effects on neutral-point potential produced by various switching states are analyzed, and a kind of neutral-point potential balancing control method by redistributing the duration of redundant vectors is discussed.The simulation analysis based on MATLAB/SIMULINK and the experiments verify the validity of the simplified modulation method and neutral-point potential balancing control strategy. An experimental setup of NPC three-level inverter including TMS320F2812 and EP1C6Q240C8 is used for the experimental verification.