Research Of Subsynchronous Resonance Suppression Method Based On SVC

With the development of power system,in the AC transmission system for EHV long distance transmission mode,the transmission method of series capacitor compensation has been used widely and play a better role in improving voltage quality and system stability,but it also can cause serious subsynchronous resonance(SSR)problem.Based on the study of series compensated transmission system,this paper further analyzes the evaluation method and suppression measures of SSR,and lays a foundation for solving the problem of torsional vibration of turbo generator in large power grid.Firstly,this paper introduces the theoretical basis of subsynchronous resonance,by analyzing the mechanism,action form,evaluation method and suppression measures of subsynchronous resonance caused by series compensation,which provides theoretical support for later part of simulation modeling.Secondly,this paper uses the complex torque coefficient method to analyze SSR,by establishing the shaft system model of the turbogenerator,and decoupling the motion equation of the shafting linely,it obtains the damping torque coefficient and the damping torque coefficient of the turbine shaft,which determines whether the SSR occurs.Furtherly analyzing the influence of different series compensation degree on the system oscillation,based on the first standard model of IEEE and combined with the power plant parameters,carrying out the simulation modeling of PSCAD/MATLAB.The simulation results show that the greater the series complement degree,the more serious the system oscillates,which the more it is more harmful to the research of SSR.Under the consideration of mechanical damping,the system occurres the third torsional mode,which is consistent with the result of the complex torque coefficient method.Finally,aiming at the SSR problem of series compensated transmission system,by using static var compensator(SVC),this paper studies the control strategy of suppressing subsynchronous resonance,and analyes the influence of different configuration and different capacity of SVC on the effect of SSR suppression.The suppression of SSR is studied from the voltage control,the additional subsynchronous damping control and the combination of the two methods,and building the simulation in the PSCAD to verify.The simulation results display that when the capacity of SVC is 80 Mvar,the inhibition effect on SSR is better.The inhibitory effect of using Voltage control on SSR was not obvious,and the damping effect is very weak,the additional subsynchronous damping control is better than using voltage control,and the combination of the two methods is more effective than the additional subsynchronous damping control alonly.