一种NPC三电平逆变器过调制中点电位控制方法

A neutral-point voltage balancing over-modulation method of three-level NPC inverter

三电平逆变器工作在过调制区域时,中矢量的作用促进了中点电位的波动,然而常规中点电位控制方法不能从根本上解决这个现象。针对该问题提出了一种可以适用于过调制区域的虚拟矢量调制方法,该方法通过虚拟中矢量代替原中矢量参与参考矢量的合成,能够在调制的过程中解决中矢量带来的中点电位波动问题。该方法能够很好的控制了中点电位的波动情况。仿真的实验结果表明了方法的可行性和有效性。

When the three-level neutral point clamped （NPC） inverters work at over-modulation phase, the middle vector leads to the fluctuation of the neutral-point voltage, which cannot be well controlled by common neutral-point voltage balance control techniques. Aimed at solving this issue, a new virtual vector modulation method is proposed to be applied in over-modulation. The characteristic of this method is to use the virtual middle vector instead of the com- bination of the original vector and the reference vector. The new method can effectively mitigate fluctuation of neutral- point voltages in the process of modulation. The simulation experimental results demonstrate the feasibility and effec- tiveness of this method.