五电平有源中点钳位型变换器电容电压平衡控制策略

Capacitor voltage balancing control strategy of a five-level ANPC converter

研究了5L-ANPC母线中点电压及悬浮电容电压的平衡控制策略.为了使5L-ANPC中串联使用的开关管以基波频率动作,而其他开关管工作在恒定的开关频率下,采用了移相载波调制(PS-PWM)的方式.零序电压是基于载波的PWM调制中一个重要的自由度,本文研究了5L-ANPC母线中点平均电流与零序电压之间的关系,得出了最优零序电压的计算方法,通过最优零序电压注入法使母线中点电压保持平衡.悬浮电容电压的充放电与冗余开关状态的选用有关,适当调整每个冗余开关状态在一个开关周期内的作用时间,实现了悬浮电容电压的平衡控制.仿真及实验验证了相关控制策略的正确性与可行性.

This paper presents a capacitor voltage balancing method for the 5L-ANPC converter.In order to ensure that the series connected or high-voltage switches of the 5L-ANPC converter are operated at fundamental frequency and other switches are operated at a constant switching frequency,phase-shifted pulse-width modulation(PS-PWM)is used to control this converter.Zerosequence voltage is an important degree of freedom in the carrier-based PWM.The relationship between the average neutral-point current and zero-sequence voltage is investigated.Furthermore,the algorithm of optimum zero-sequence voltage injection method is presented to regulate the neutral-point potential.Since the charge-discharge of the floating capacitor voltage is related to the redundant switching states.It is regulated by adjusting the operation time of redundant switching states during per switching period.Simulation and experimental results are presented to verify the validity and feasibility of the strategy.