基于单周期控制的三相VIENNA整流器中点电压平衡控制策略

三相VIENNA整流器作为三电平Boost型中点箝位NPC(neutral point clamped)结构变换器,其具有所需开关器件少、功率因数高、开关管电压应力小和控制环节简单等特点,具有较高的研究价值。而中点电位波动是NPC结构变换器固有的问题,以单周期控制的三相VIENNA整流器作为研究对象。对其直流母线电压利用率较低和中点电压交流波动的问题进行建模分析,提出了在单周期控制基础上加入中点电压平衡控制环,不仅可以基本消除中点电压波动,而且可以提高直流母线电压利用率。最后通过仿真验证了所提控制策略的正确性。

Control Strategy for Neutral-point Voltage Balance of Three-phase VIENNA Rectifier Based on One-cycle Control

As one kind of three-level Boost-type neutral-point-clamped(NPC) converters, a three-phase three-level VIENNA rectifier has many advantages, such as fewer switching devices, high power factor, low voltage stress of switch, and simple control links. Therefore, it has high research values. However, the neutral-point potential fluctuation is inherent to the NPC converters. In this paper, a one-cycle controlled three-phase VIENNA rectifier is taken as a research object. The problems of low voltage utilization rate of DC bus and the fluctuation of neutral-point voltage are modeled and analyzed, and it is suggested that the neutral-point voltage balance control loop should be added on the basis of one-cycle control, which can not only eliminate the neutral-point voltage fluctuation, but also improve the voltage utilization rate of DC bus. Finally, the proposed control strategy is verified by simulations.