中文摘要：

本文分析了三电平逆变器中点电压不平衡的机理,得出了中点电压不平衡的本质原因是中点电流不为零的结论;进而从载波调制原理出发,介绍了控制中点电压的开环模型和闭环模型.仿真分析证明,开环模型虽然可以消除中点电压的低频震荡但是对于电压偏置无校正作用;闭环模型不仅可以消除中点电压的低频震荡而且可以校正直流电压的偏置,具有很高的工程实用价值;最后通过数字计算的方法,给出了基于载波控制中点电压PWM调制策略的线性工作区,且随着功率因数角的增大,此种调制策略的线性调制区变窄.

英文摘要：

This paper investigates the principle of the imbalance of capacitor voltage of three-level inverter. The essential reason of the imbalance is that the current of the three level inverter＇s neutral point is not zero. In order to balancing the three-level inverter＇s capacitor voltage, an open loop and a closed loop model are introduced, and the simulation proves that low frequency voltage of the neutral point can be eliminated with the open loop model, but basis imbalance of the capacitor voltage can＇t be modified. With the closed loop model the problem of the imbalance of the capacitor voltage can be overcome. At last the linear zone of the PWM modulation is proposed with the help of the numeral calculation.