五电平有源中点钳位型逆变器母线中点电压平衡问题

Neutral-point Potential Balancing Problem of Five-level Active Neutral-point-clamped Inverter

五电平有源中点钳位型拓扑是一种能够克服传统的二极管钳位型和电容钳位型拓扑缺点的多电平变换器。针对五电平有源中点钳位型逆变器的母线中点电压平衡问题展开研究,建立母线中点电压的波动模型,通过计算母线中点电流在一个基波周期内的平均值,证明了母线中点电压在理想和稳态下可自平衡。提出一种基于零序电压注入的中点电压平衡控制方法,通过计算所有关键零序电压对应的中点电流,并从中选择最优的关键零序电压来产生所需的目标中点电流,从而使母线中点电压波动最小。实验结果证明了该控制方法的有效性。

Five-level active neutral-point-clamped（ANPC） converter is a newly emerging topology which can overcome the drawbacks of traditional diode-clamped converters and flying-capacitor converters.The neutral-point potential balancing problem of a five-level ANPC inverter was studied.By calculating the average neutral-point current in a fundamental period,it can be concluded that the neutral-point potential can be balanced by itself under ideal condition and steady state.A neutral-point potential balancing algorithm based on zero-sequence voltage injection was presented.By calculating the neutral-point currents of all key zero-sequence voltages,the most appropriate zero-sequence voltage was selected to generate the required neutral-point current,which can make the neutral-point voltage ripple the lowest.Experimental results were presented to verify the validity of the algorithm.