二极管钳位型多电平逆变器脉宽调制时电容电压均衡方法

Unbalancing Capacitor Voltage for Diode Clamped Multi-Level Inverter

电容电压不均衡是二极管钳位型多电平逆变器中一个关键技术问题。当三电平二极管钳位型逆变器采用SPWM和SVPWM的调制时,直流侧分压电容的电压产生基波频率为三倍输出频率的低频振荡。要使一个采样周期内电容电压不发生不均衡,需要使在该采样周期内向中点电荷注入的电荷总和为零。本文提出了一种新的调制策略,在三电平二极管钳位型调制策略中可以等效为虚拟矢量调制策略,但这种调制策略可以方便地扩展到更多电平二极管钳位型逆变器的调制中。通过向调制波注入零序电压分量,这种调制策略可以等效为基于载波的调制策略。文中以二极管钳位型三电平和五电平逆变器进行了仿真研究,最后建立了二极管三电平逆变器,实验结果验证了算法的有效性。

Unbalance of dc-capacitor-voltage is multi-level inverter. In modulation of tradition SPWM an key technical problem of diode clamped and SVPWM, it produced neutral point current at D＇C ＇part of multi-level inverter, the frequency of the current is treble of AC frequency. For avoiding the unbalance of capacitor voltage, the summation of charge injected in neutral point must be zero. This paper proposes a new modulation strategy, and it can be equivalent to VTSVPWM in diode clamped three-level Inverter and it can be applying in more level inverter. By injecting zero-order-voltage into modulation wave, this strategy can be equivalent to carder modulation. This paper gives the simulation of Three-level Inverter and Five-level Inverter, and constructs the NPC three-level Inverter.