基于零序注入的NPC三电平变流器中点电位反馈控制

摘要

对NPC三电平变流器中点电位不平衡时,输出交流电压的补偿与中点电位的反馈控制问题进行了研究。提出了一种基于零序注入的NPC三电平中点电位反馈控制方法,在保证输出电压无畸变的同时还能实现中点电位的任意调节。调制策略基于SPWM原理,实现十分简单,适用于强化传统的中点电位平衡控制或需要对上下组直流电压进行分别控制的场合。文中给出了本文控制方法的中点电流控制能力,并对中点电位的低频波动问题进行了分析。仿真和实验结果验证了相关理论的正确性。%Output AC voltage compensation and neutral point voltage feedback control under neutral point voltage unbalanced conditions are discussed.A neutral point voltage feedback control strategy based on zero sequence injection is proposed.Using this strategy,not only output voltage can be guaranteed no distortion but also neutral point voltage can be adjusted at will.The modulation strategy is based on SPWM principal,so it's very simple to realize,and suitable for enhancing traditional neutral point balance control or applications where need to control up and down DC link voltage separately.The neutral point current control ability of the strategy is given,and the neutral point voltage low frequency fluctuation problem is also analyzed.Simulation and experimental results verify the correctness of this theory.