Active Disturbance Rejection Control And Its Application In Attenuating Low Frequency Oscillations In Power Systems

Low frequency oscillation is a serious problem that affects the stable operation of power system.At present,most of the projects adopt the method of installing a power system stabilizer,which is used in the generator excitation control system to increase the damping of the system to achieve the purpose of suppressing low-frequency oscillation,but in the large-scale interconnected power system,this method does not fully suppress the low frequency oscillation.Therefore,it is necessary to investigate the problem and design a control scheme that can effectively damp the low-frequency oscillation.Linear active disturbance rejection control(LADRC)has the characteristics of independence of the system model,simple structure and strong disturbance-rejection capability.However,the controller based on the relative order and gain information of the model is not very effective in the complex control systems.Therefore,in this paper,based on the known mathematical model of the system,aiming at the problem of low-frequency oscillation caused by the generator's fast excitation system,we consider utilizing more information of the controlled plant and design an improved LADRC,that is generalized active disturbance rejection control(GADRC),a practical and feasible control scheme to suppress low frequency oscillation of power system is proposed and simulated.The main content of the thesis includes:1)In view of low-frequency oscillation of power system caused by rapid excitation system,a third-order model is adopted in this paper.According to the excitation voltage control of single-machine infinite system,the principle of suppressing low-frequency oscillation by traditional PSS is analyzed,and GADRC is designed and used for additional excitation control.By comparing the GADRC with the traditional PSS,it is proved that the GADRC is better than the Traditional PSS in suppressing the low-frequency oscillation of the power system.2)For the multi-machine power system,this paper firstly analyzes the reason of low-frequency oscillation caused by multi-machine system,and then considers the scheme of decentralized GADRC instead of PSS in multi-machine system.Taking the four-machine and two-area model proposed by Kundur as an example,by comparing decentralized GADRC,conventional PSS and IMC-based PSS,the effectiveness and superiority of GADRC scheme in suppressing low frequency oscillation are proved.Simulation results show that GADRC has good robustness under varying working conditions.