基于模糊虚拟空间矢量调制的NPC三电平逆变器中点电位平衡的研究

三电平中点钳位型NPC(neutral-point-clamped)逆变器拓扑结构相比于两电平有能承受高电压、效率高和电磁干扰小等优点,但也存在中点电位不平衡这一固有问题。针对此固有问题,提出了一种新的控制中点电位平衡的方法。该方法是在虚拟空间矢量调制策略的基础上,细分扇区,调整输出电压矢量顺序,增加分配时间的模糊控制因子;冗余小矢量对中点电压的影响可以相互抵消,减少了中矢量的作用时间;通过控制因子合理分配冗余小矢量的作用时间,能有效地控制中点电压偏移。仿真结果验证了该方法的正确性和可行性。

Research on Neutral-point Potential of Three-level NPC Inverter Based on Fuzzy Virtual Space Vector Modulation

Compared with two-level topology, this three-level one has obvious advantages: withstand higher voltage of the former; the output waveform is improved, and so on. However, the unbalancing voltage in the DC side capacitors is the inherent problem of the three-level NPC inverter. To solve this inherent problem, a new method of controlling the neutral-point voltage is proposed in this paper. Based on the concept of virtual space vector modulation strategy, this method divides the sector more careful, adjust the sequence of output vector, increase the fuzzy controller to select control factor. The redundant vector pairs have opposite effect on the neutral-point potential,reduce the action time of medium vector,distribution factors are assigned reasonably, the neutral-point potential can be controlled. Simulation results verify the correctness and validity of this method.