基于零序电压注入的三电平中点箝位整流器中点电位控制方法的研究

三电平NPC PWM整流技术中一个重要的问题是中点电位的波动问题。该文首先建立了 坐标系下中点电位波动的数学模型，揭示了控制输入的 轴分量(即零序电压分量)，作为一个控制自由度，对中点电位的影响。并提出了一种完全消除中点电位波动的控制方法，通过理论分析，所需零序电压的准确解析计算方法，以及中点电位平衡控制的内在规律被给出。另外，为了得到三相调制电压的符号，文中提出了一种符号滞后判断方法，证明了上述控制方法的实时性。最后，通过系统的仿真，验证了理论分析的正确性，以及该控制方法的优异性能。

Study on Neutral-point Potential Control Method for Three-level NPC Rectifiers by Injecting Zero-sequence Voltage

A significant problem with neutral-point- clamped (NPC) three-level rectifiers is the fluctuation in the neutral-point-potential (NPP). In this paper, the mathematical model of neutral point potential in coordinates was founded firstly, the function of the -axis component (zero-sequence component) of the control input, as a degree of freedom for the balancing of the capacitors voltages, was revealed. A new control method by which the fluctuation of NPP can be completely eliminated is presented, the analytical method to calculate the zero sequence voltage accurately and the inherent relationship for NPP balancing control are given by theoretical calculation. In order to obtain the signs of modulation voltages, the paper also proposes a hysteretic sign calculation algorithm and proves the real-time property of the control method. Simulations validate the proposed model, theoretical analysis and good performance of the proposed control strategy.