Modeling Studies Of Time-varying Inductance Load And Its Flexible Compensation

Most of the loads in Chinese industrial production are perceptual loads which are fluctuating strongly.Due to the loads are power customer described as high randomness,strong fluctuations and uncontrollable output,there are a lot of questions such as high line losses,low power factor,insufficient transmission capacity and low voltage at the terminal of power lines.The influence of time variable load to power grid and users becomes more and more prominent,and it propose a higher request of power quality.Reactive power compensation is widely used in power system for improving the power quality of electric system.Because of movement characteristic of beam pumping unit,the loads of it are time variable inductive loads which are fluctuating strongly,and it will consume large amounts of reactive power.Pumping unit models that have existed are mainly built on its movement characteristics,load,speed and so on.Hardly is there a pumping unit model on electrical field,and there isn't accurate reactive compensation design on beam pumping unit' load.Because of the complicated internal structure and the power of pumping unit,it is necessary for pumping unit to compensate reactive power accurately.According to the mechanical,electrical characteristics and movement characteristics of beam pumping unit and taking electricity movement and force into consideration,the actual parameters are used to design the model of beam pumping unit by using Matlab/Simulink simulation software in this paper.Some electrical data such as voltage,current,power and power factor can be observed in this model.The power characteristic curve of the beam pumping unit is simulated and the effect of the fixed compensation on it is verified.Then the necessity of flexible compensation is verified.Based on the load characteristics of the beam pumping unit,a dynamic reactive power compensator which is based on Thyristor Switched Capacitor(TSC)is designed by analyzing the principle of reactive power compensation,TSC triggering method and switching algorithm.This compensator synthesizes fixed compensation and TSC dynamic compensation.Finally,by designing the model of compensation for beam pumping unit,considering the other factors such as harmonics and running speed,the simple filter is designed,algorithm and the operation mode are selected,and the dynamic reactive power compensator is put into the machine.Simulation results show that the compensator of this paper can improve the power factor and voltage and reduce the loss of line better,and verify that the design can improve the quality of power networks and economic benefit.