Analysis For The Effect Of Excitation System Reactive Compensation Unit On Low Frequency Oscillation In Power System

With the continuous expansion of power system scale and the wide application of high-gain fast excitation systems,low-frequency oscillation occurs from time to time,which seriously threatens the safe and stable operation of the interconnected power grid.Excitation system adjustment unit access can effectively improve the static voltage adjustment characteristics of the generator,but it also has a certain impact on the dynamic characteristics of the system,so it is significant to study the impact of the excitation system adjustment unit on power system low-frequency oscillation to maintain the stability of the power system Operation.In this paper,through Thevenin's static equivalence method,the influence of the introduction of compensation current in adjustment unit on the low-frequency oscillation is studied.Firstly,the mathematical model and the analysis method of power system low-frequency oscillation are introduced.Secondly,the equivalent circuit of the generator grid connected is established by Thevenin's theorem.Through the equivalent circuit,the static voltage adjustment effect of the automatic excitation regulator and the impact of excitation adjustment on low-frequency oscillation are studied.Besides,the simulation model of generation grid connected under the fixed and automatic excitation control mode are established in Matlab/Simulink simulation environmentto to test and verify the analysis by time-domain simulation.Then,the changing characteristics of the measured voltage of excitation system under the positive and negative adjustment methods are analyzed in detail.It is pointed out that when the low-frequency oscillation occurs between the generator and the system,the compensation current introduced by different adjustment characteristics will have different effects on the oscillation characteristics of the system.Finally,based on Matlab/Simulink simulation platform,the dynamic simulation model of power system low-frequency oscillation with current adjustment unit is established.It analyzes the dynamic change process of power system under different current adjustment units and different conditions by changing the access method of adjustment unit,the polarity of the adjustment current and the size of adjustment coefficient.The simulation results show that when the generator adopted a positive adjustment wiring method,the introduction of the compensation current will suppress the oscillation of the system;when the generator adopted a negative adjustment wiring method,the introduction of the compensation current will further aggravate the oscillation of the system.And the suppressed or aggravated effect of the adjustment unit on low-frequency oscillation of the system is not only related to the size of adjustment coefficient,but also related to the operating conditions of the generator.