带中点平衡的VIENNA整流器改进SVPWM策略

Improved SVPWM Strategy for VIENNA Rectifier with Midpoint Balance

VIENNA整流器的中点电压不平衡问题使得两均压电容及主开关器件承受的电压应力不均衡,导致交流侧输入电流波形畸变,较大降低系统可靠性。对于此问题,本文研究传统三电平空间矢量调制对VIENNA整流器中点电压的作用原理,在此基础上提出一种改进SVPWM控制策略来抑制中点电位的波动:将传统扇区与输入侧三相电流极性结合,对传统扇区进一步划分,通过新扇区的判断和正负小矢量的调节因子抵消中矢量作用,从而达到中点平衡。最后通过仿真验证所提控制策略与传统SVPWM相比,中点电位和电流的波动由±5 V和±18 A减小为±2.5 V和±7.5V,有效抑制了中点电压不平衡的问题。

The problem of unbalanced mid-point voltage of VIENNA rectifier will lead to unbalanced voltage stress on the two equalizing capacitors and the main switching device,resulting in the distortion of the input current waveform on the AC side,which greatly reduces the reliability of the system.To solve this problem,this paper studies the effect of the traditional three-level space vector modulation on the midpoint voltage of the VIENNA rectifier,so that an improved SVPWM control strategy is proposed to suppress the fluctuation of the midpoint potential.The combination of the three-phase current polarity on the input side further divides the traditional sector,and through the judgment of the new sector and the adjustment factor of the positive and negative small vectors,the effect of the middle vector is cancelled to achieve the midpoint balance.Finally,compared with the traditional SVPWM,it is verified by simulation that the midpoint potential and current fluctuations of the proposed control strategy are reduced from±5 V and±18 A to±2.5 V and±7.5 V respectively,which effectively suppresses the problem of midpoint voltage imbalance.