三电平ANPC逆变器中点电压平衡控制策略

Neutral-point potential balancing control strategy in three-level ANPC inverter

针对三电平有源中点箝位型逆变器存在中点电压偏移的问题,提出了一种改进的空间矢量脉宽调制(space vector pulse width modulation,SVPWM)中点电压平衡控制策略。该策略对逆变器的三相桥臂分别进行控制,并根据采样得到的中点电压和三相电流的大小及方向,动态微调每个开关周期内各相开关序列零状态的占空比,从而改变直流侧电容的充放电时间,减小输出电流对中点电位的影响,达到控制中点电压平衡的目的。该控制策略使用和传统的SVPWM一样的矢量分区方法和脉冲开关序列,所以没有额外地增加矢量分区的复杂度和器件的开关损耗。最后搭建了三电平有源中点箝位型逆变器的仿真模型和实验平台对提出的控制策略进行了验证,仿真与实验结果证实了所提控制策略的有效性与可行性。

The imbalance of neutral-point potential（ NP） is an inherent problem for three-level active neutral-pointclamped（ ANPC） inverter. An NP balancing control strategy based on optimized space vector pulse width modulation（ SVPWM） is proposed in this paper. According to the NP offset and three-phase current,this strategy controls three phases＇ legs respectively and adjusts the duration of zero-state during every fundamental period.Therefore,the NP can be controlled by adjusting the charging or discharging time of the capacitors in DC-side. This strategy avoids the extra complexity of vector diagram partition and the extra added switch losses by using the same vector diagram partition method and vectors pulse switch sequences as traditional SVPWM. Finally,the simulation model and experimental platform is built. The simulation and experimental results verify the effectiveness of the proposed control strategy.