一种新的三电平中点电位滞环控制法

该文针对三电平中点电位平衡原理提出了一种中点电位的滞环控制方法，该方法根据当前的PWM组合和各相输出电流方向判断出中点电流方向，通过滞环比较的方式得到中点电压偏向，并由此判断当前PWM对中点电位的作用，将当前的PWM组合中可以实现中点电位平衡的组合重新分配使之有利于中点电位的平衡。该方法独立于具体的PWM调制模式，因此可以胜任各种PWM调制模式下的中点电位调整。而且也可通过调整滞环宽度的方法来调整中点电位的允许波动和开关管开关次数。该文以特定谐波消除PWM方法(SHEPWM)为例，仿真和实验结果显示了很好的中点平衡效果。该方法对三电平中点电位平衡上具有通用性。

A NEW THREE-LEVEL NEUTRAL POINT POTENTIAL HYSTERESIS-BAND CONTROL

A new method for neutral-point balance based on hysteresis-band control for NPC three-level inverters is proposed in this paper. The neutral-point will be balanced by PWM control according to the direction of neutral-point current and the state of neutral-point voltage. The neutral-point current direction is got by output current of each phase and PWM group. The state of neutral point voltage is decided by hysteresis-band control. PWM group will be regrouped when it goes against the neutral point potential balance. Being independent of PWM mode, this scheme can be used in any other PWM mode for neutral-point balance control. The amplitude of neutral point voltage fluctuation and the switch times of IGBT can be adjusted by regulating the width of hysteresis-band. The method is verified by simulation and experiment of three-level converter with SHEPWM control scheme.