一种N相解耦的三相四桥臂逆变器控制策略

A Control Strategy of Three-phase Four Leg Inverter With N-phase Decoupling

三相四桥臂逆变器具有N相桥臂,可以给三相不平衡负载提供零序电流回路,解决了三相输出电压中性点偏移问题。但该拓扑中,三相输出电压与N相电压存在耦合关系,系统控制输出时须考虑耦合影响。目前,有些控制方案将三相四桥臂逆变器各桥臂看作整体,采用三维空间矢量脉宽调制(3D-SVPWM)方法进行调制控制,也有些方法将N相调制电压与其他三相输出电压解耦进行控制。对于有N相电感的三相四桥臂逆变器,上述方法无法对耦合项进行全部解耦,控制性能存在一定不足。提出一种N相解耦的控制策略,采取全通滤波器构造N相电感电压观测器,最终实现对三相四桥臂逆变器耦合项的全部解耦。仿真及实验表明,所提出的策略降低了N相电压及电感压降带来的耦合影响,可改善系统三相电压的不平衡度等性能。

The three-phase four leg inverter has N-phase bridge arm,which can provide zero sequence current circuit for three-phase imbalance load,and solve the problem of neutral point offset of three-phase output voltage.However,in this topology,there is a coupling relationship between three-phase output voltage and N-phase voltage,and the coupling effect must be considered when the system controls the output.At present,some control schemes regard each bridge arm of the three-phase four leg inverter as a whole and adopt the three-dimensional space vector pulse width modulation(3D-SVPWM) method for modulation control,while others decouple the N-phase modulation voltage from other three-phase output voltages.For the three-phase four leg inverter with N-phase inductance,the above method can not decouple all the coupling terms,and the control performance is insufficient.An N-phase decoupling control strategy is proposed.An all pass filter is used to construct an N-phase inductive voltage observer,and finally all the coupling terms of the three-phase four leg inverter are decoupled.Simulation and experiments show that the proposed strategy can reduce the coupling effect caused by the N-phase voltage drop and improve the imbalance of the threephase voltage of the system.