交交变频轧机系统网侧电流畸变与无功的研究

Current distortion and reactive power on supply network of cycloconverter-fed rolling-mill drive system

为分析交交变频轧机系统对网侧的影响,提出了一种基于瞬时无功理论的仿真分析方法.该仿真分析方法根据交交变频轧机系统的结构、负荷与控制特点,分析了网侧畸变电流的频率、幅值以及相序特征;并推导出网侧畸变电流与瞬时无功功率的关系表达式,从而将畸变无功功率从瞬时无功功率中分离,确定了影响畸变无功功率幅值和波动规律的因素;同时给出了设计无功补偿装置容量的依据.仿真结果表明,电机转速比是影响交交变频轧机系统网侧基波功率因数与电流总畸变率的关键原因.当电机接近其额定转速工作时,可以有效地减少网侧无功功率,降低电流总畸变率.

To analyze the influence of the cycloconverter-fed rolling-mill drive system on the supply network, a simulation method based on instantaneous reactive power theory was presented. According to the configuration, load and control characteristics of the cycloconverter-fed rolling-mill drive system, the frequency, amplitude and phase sequence characteristics of the distortion current were obtained from the method. The relational expressions of the distortion current and the instantaneous reactive power were deduced, and the distortion reactive power was separated from the instantaneous reactive power. The factors influencing the amplitude and frequency of the distortion reactive power were studied. The design criterions of the var compensator capability were given. The simulation results show that the speed ratio of the motor mostly affects the total harmonic distortion of the current and the displacement power factor. The reactive power and the total harmonic distortion of current on the supply network can be effectively reduced when motors work near to their rated speeds.