一种新的基于混合空间矢量调制的三电平逆变器直流侧电容电压平衡研究

针对二极管中点钳位型(neutral point clamped,NPC)三电平逆变器容易造成直流侧电容电压不平衡问题,提出一种新的中点电位平衡控制方法。在该方法中,采用分扇区精细控制,对不同的小矢量设置不同的时间分配因子,以增加相应正或负小矢量对中点电流的控制能力。对于正负小矢量不能成对出现的扇区,根据相电流的变化情况,使调制在传统算法和基于虚拟矢量的算法之间切换,从而削弱中矢量对中点电流不可控的影响。仿真和实验证实了该方法的正确性和有效性。

A New DC Side Capacitance Voltages Balancing Method for Three-level Inverters Based on Hybrid Space Vector Modulation

Aiming at the DC side capacitance voltage unbalancing problem in the three-level neutral point clamped(NPC) inverters,a new neutral point voltage balancing method was proposed.In this method,each sector of the vector space had a unique control strategy.Different time distribution factors were set for different short vectors,which improved the neutral-point current control effect of the relative positive or negative short vector.In some sectors,the positive and negative vector pair don’t take effect at the same time.Criterion was made according to the sign of three phase currents,which is transited between the traditional nearest three vectors method,and the virtual vector based method.Thus,the influence to the uncontrollable neutral-point current of medium vector was reduced.Simulation and experiment results are given to verify the correctness and validity of the proposed method.