一种降低三电平逆变器中性点电压交流纹波的新方法

针对三电平中点箝位(NPC)逆变器的中点电位平衡问题,基于载波脉宽调制的中点电压的交流不平衡分析,提出了一种降低中性点电压交流纹波的精确补偿方法。该方法通过向相电压占空比注入一个最佳补偿值来消除中性点电压的交流不平衡,对所需注入的最佳补偿值进行了准确的数学计算。并根据计算结果分析了完全消除中点电压交流纹波所受的限制,及由此决定的中性点交流纹波电压降低法的适用范围。利用Matlab/Simulink搭建了三电平逆变器的仿真模型,并对该方法进行了仿真验证。仿真结果表明了所提方法是正确且有效的。

A new method for neutral-point AC ripple voltage reduction in a three-level inverter

For the neutral point potential balancing problem of three level Neutral Point Clamped (NPC) inverter, this paper analyzes the AC unbalance of neutral point voltage based on carrier pulse width modulation, and proposes an accurate compensation method to reduce the AC ripple of neutral point voltage. The method eliminates the AC unbalance of the neutral point voltage by injecting an optimum compensation value to the phase voltage duty cycle, and the accurate mathematical calculation of the optimum compensation value is given. According to the calculation results, the limitation of completely eliminating the AC ripple of neutral point voltage and the applicable range of the neutral point AC ripple voltage reduction method are analyzed. A three level neutral point clamped inverter model is built using Matlab/Simulink. The proposed method is simulated and the simulation results show its correctness and effectiveness. This work is supported by National Key Research and Development Program of China (No. 2017YFB0903100) and National High-tech R & D Program of China (863 Program) (No. 2015AA050104).