基于断续脉宽调制的三电平逆变器中性点电位平衡控制方法

A New Discontinuous PWM Method of Three-Level Inverter for Neutral-Point Voltage Balancing Control

在中压大功率逆变器中,存在开关频率高、开关损耗大等问题。采用断续脉宽调制策略(DPWM)能降低开关频率,同时减小开关损耗。通常,传统的中性点平衡方法是将补偿电压引入到参考电压中,但是当采用DPWM调制方法时,由于开关的通断之间会存在一定的间隔,所以采用传统的平衡方法无法达到中性点平衡控制。本文首先分析了中性点不平衡的原因,其次分析了传统平衡控制方法的局限性,最后采用断续脉宽角调节控制方法。该方法既保证了低的开关频率,同时实现了中性点电压的平衡,并且没有引入额外的硬件电路和复杂的计算方法。最后采用Matlab/Simulink仿真验证了所提出的方法的有效性。

In a medium-voltage high-power inverter, there are problems such as high switching frequency and high switching loss. Discontinuous pulse-width modulation （DPWM） can reduce the switching frequency and the switching loss. Generally, the offset voltage is added to reference voltages in the conventional voltage balancing method. However, when using DPWM, the performance of conventional balancing method is limitary because turn-on and turn-off switching occurs at regular interval. In this paper, the causes of the imbalance of the neutral-point are analyzed at first, and then the limitations of traditional control methods are analyzed, and finally the method of adaptive control of intermittent pulse width angle is proposed. The proposed method maintains low switching losses and achieves the effective voltage balancing, without additional hardware and complex calculation. Finally the results obtained through the Matlab/Simulink simulation verify that the effectiveness of the proposed method.