组合开关状态的NPC三电平模型预测不平衡治理策略

Combined switching state of model predictive control for unbalance regulation strategy for three-level NPC inverter

三相四线制中点钳位(NPC)三电平不平衡补偿装置中点电压均衡会导致零序电流补偿不足,影响不平衡治理效果。为解决这一问题,提出组合开关状态的三电平模型预测不平衡治理策略,分析不同类电压矢量开关状态零序电流补偿与中点电压均衡的关系。并根据各类开关状态补偿零序电流能力,组合全零矢量、短矢量和中矢量13种开关状态进行模型预测不平衡治理。仿真对比不同组合开关状态在中点电压均衡前提下零序电流补偿能力,并采用所提出的开关状态进行不平衡治理。结果验证了组合开关状态控制的有效性和准确性。

Neutral point voltage balance of a three-level compensator produces insufficient compensation of zero-sequence current in a three-phase four-wire grid.This will affect the effectiveness of unbalance control.To solve this problem,this paper proposes a combined switching state control strategy after researching the relationship between zero-sequence current and neutral point voltage with regard to different kinds of voltage vectors.According to the ability to compensate zero-sequence current of all switching states,a combined scheme of 13 switching states composed of zero vector,short vector and middle vector is selected to practice model predictive control.The zero-sequence current compensation ability of different combination switching states under the neutral point voltage balance is compared by simulation,and the switching state proposed in this paper is adopted to control the unbalance.The results verify the effectiveness and accuracy of the combined switching state theory and control algorithm.