基于阻抗分析的三相逆变器负载不平衡控制

Control Strategy Based on Impedance Analysis for Three-Phase Inverter with Unbalanced Load

通过逆变器输出阻抗的分析,得出了三相逆变器输出电压不平衡的根本原因,提出通过设计适当的闭环控制来减小逆变器输出阻抗,以减小三相输出电压不平衡度的控制思想。本文根据三相输出电压不平衡时的特点,提出了通过DSC提取出负载电压及电感电流中的正序、负序分量,分别在正序dq坐标系及负序dq坐标系下对正序分量及负序分量采用电压、电流的双环前馈解耦控制的方案,用于对逆变器负载不平衡引起的输出电压不平衡的控制。闭环输出阻抗的分析显示,该控制方案在整体减小闭环系统输出阻抗的同时,能够大幅有效地减小负序分量对应输出阻抗。仿真与实验结果证明,该控制方案对不平衡负载引起的输出电压失衡有较好地控制作用。

The paper researches on the mechanism of the unbalanced output voltage for the three-phase inverter.Based on the analysis of output characteristic of inverter,the method of restraining the unbalanced output voltage according to decrease the output impedance is introduced.Then,on the basis of DSC（Delayed Signal Cancellation）,two synchronous reference frames： a positive-sequence voltage and current regulated by PI controllers in a positive synchronous reference frame,and a negative-sequence voltage and current regulated by PI controllers in a negative synchronous reference frame are used to control the three-phase inverter with unbalanced loads.The comparison of output impedance shows that the proposed control strategy can not only decrease output impedance of all frequency,but also can especially greatly decrease the output impedance of inverter at the frequency of 100Hz in positive-synchronous reference frame.The results of simulation and experiment prove the correctness and availability of control strategy proposed in this paper.