三电平双PWM变换器电容电压平衡综合控制

Integrated control of capacitance voltage balancing for back-to-back three-level PWM converters

针对三电平双PWM变换器电容中点电压平衡控制问题,提出一种网侧和电机侧电容中点电压平衡综合控制策略。该算法首先在每个开关周期对网侧和电机侧的三相电流和直流侧电容电压进行采样和预测,通过查表得到参考矢量所在扇区的中点平均电流计算式,进而给出一个能够表征电容中点电压预期控制指标的品质函数g。通过递推运算使g函数取最小值,从而获得下一个调制周期最佳中点电压控制的冗余矢量时间分配因子λ。仿真和实验结果表明,相比于常规单独网侧的中点电压控制算法,该算法具有较好的动态响应性能,能够使直流侧电容中点电压波动大大减小。

Aiming at the capacitance voltage balancing control issue of back-to-back three-level PWM converters, an integrated control algorithm for the grid side and motor side was proposed. In this method, three phase currents of both sides and capacitances voltages of DC side were sampled and predicted in each switching period. A quality function g to indicate the control trend of the capacitance voltage was proposed, and the time distribution factor of redundant vectors that minimizes the quality function g was selected to be applied during the next sampling interval. Simulation and experiment results show the pro- posed method has better dynamic response performance in comparison to the conventional grid side alone neutral-point voltage control algorithm.