嵌套式中点可控型五电平变换器新型空间电压矢量调制策略

A Novel Space Vector Pulse Width Modulation for Five-level Nested Neutral Point Piloted Converter

针对嵌套式中点可控型（nested neutral point piloted,NNPP）五电平变换器电容电压平衡问题,提出一种基于gh坐标系的五电平NNPP变换器新型空间电压矢量脉宽调制（space vector pulse width modulation,SVPWM）算法。同时,给出悬浮电容电压平衡和直流侧中点电压平衡控制策略。通过选取各相输出电平对应的冗余开关组合,实现悬浮电容电压平衡。根据中点电压波动模型,提出一种基于开关序列优化（switching sequence optimization,SSO）的中点电压平衡控制策略。采用五段式开关序列设计,建立目标函数,根据中点电压偏差,对开关序列进行动态选择,选取最优开关序列。最后搭建了五电平NNPP变换器实验样机,稳态和动态实验结果验证了所提新型SVPWM算法和电容电压平衡控制策略的有效性。

In order to solve the capacitor voltage balance problems for five-level nested neutral point piloted （NNPP） converter, a novel space vector pulse width modulation （SVPWM） algorithm based on gh coordinate for five-level NNPP converter was presented. Meanwhile, the floating-capacitor voltage balance control strategy and neutral-point voltage balance control strategy were proposed. Floating-capacitor voltages were balanced by selecting the appropriate switch combinations corresponding to the output voltage level for each phase. Moreover, according to the fluctuation model of neutral-point voltage, the neutral-point voltage balance control based on switching sequence optimization （SSO） was proposed. The five-segment switching sequence design was used and the cost function was established. The optimal switching sequence was dynamically selected according to the neutral-point voltage deviation. Finally, the five-level NNPP converter experimental prototype was built. The steady-state and dynamic experimental results verify the correctness of the proposed SVPWM algorithm with the capacitor voltage balance control strategies.