This paper presents a simplified strategy in neutral-point (NP) potential balance of the neutral-point-clamped (NPC) three-level three-wire active power filter (APF). By introducing a simplified carrier-based pulse width modulation (CB-PWM) strategy and analysing the occurrence mechanism of NP potential unbalance, we proposed a NP potential balancing control strategy based on the simplified strategy. With this strategy, the NP current in a sampling period can be calculated through the detection of compensating current of APF. The three phase’s duration time of reference voltage can also be computed through detecting the voltage fluctuation of upper and lower capacitors accurately, according to the law of charge conservation. Experiment results show that this proposed approach with simplified computation can effectively achieve NP potential balance.

中文翻译：

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三电平有源电力滤波器中点电位平衡控制策略

本文提出了一种简化中性点钳位 (NPC) 三电平三线有源滤波器 (APF) 中性点 (NP) 电位平衡的策略。通过引入一种简化的基于载波的脉宽调制（CB-PWM）策略，分析NP电位不平衡的发生机制，提出了一种基于简化策略的NP电位平衡控制策略。通过该策略，可以通过检测APF的补偿电流来计算采样周期内的NP电流。根据电荷守恒定律，通过准确检测上下电容的电压波动，也可以计算出三相参考电压的持续时间。实验结果表明，所提出的这种简化计算的方法可以有效地实现 NP 电位平衡。