三电平PWM整流器双环控制技术及中点电压平衡控制技术的研究

Research on the Technology of the Neutral-point Voltage Balance and Dual-loop Control Scheme for Three-level PWM Rectifier

该文在建立了三电平PWM整流器系统数学模型的基础上,比较了三电平PWM整流器模型与直流电机模型的相似性,基于对控制对象的状态反馈解耦,提出把直流电机的双闭环控制应用于三电平PWM整流器中,使三电平PWM整流器具有良好的动态性能和稳态性能,并且保证输入电流波形正弦性好,实现了单位功率因数。同时,针对三电平PWM整流器所固有的直流侧电容中点电压平衡问题,提出根据每相输入电流方向和中点电压波动方向来优化选取冗余的正小矢量和负小矢量,实现中点电压平衡控制的方法。最后通过实验验证了双环控制器和控制中点电压方法的可行性和有效性。

A mathematical model of the three-level PWM rectifier is set up. Compared with the model of DC motor, some similarities are established. Based on the state feedback decoupling, the dual close-loop control of DC motor is applied to three-level PWM rectifier. As a result, the three-level rectifier has favorable dynamic and steady state performance, sinusoidal input current and unity power factor. Besides, a method is proposed to control the neutral-point voltage charge unbalance, which is an inherent problem of three-level inverter. The redundant positive small vectors and negative small vectors are selected according to the direction information of input current of each phase as well as the ripple of neutral-point voltage. Finally, experimental results verify the feasibility and validity of dual-loop control system and neutral-point voltage control method.