Design And Research Of Subsynchronous Oscillation Suppression Controller For HVDC Transmission System

In this paper,the subsynchronous oscillation of power system is taken as the research object,its basic theory and the suppression measures of subsynchronous oscillation are introduced.The mechanism of subsynchronous oscillation in power system caused by high voltage direct current(HVDC)is analyzed,and the relationship between the negative damping of the system and the subsynchronous oscillation mode is presented.By means of eigenvalue analysis and complex torque analysis method,the subsynchronous damping characteristics of the system are analyzed,and the relationship between the modal oscillation and the eigenvalues of the generator shaft system is studied.The state equation of the system is established to study the correlation between the state variables and the vibration of the shaft system.On this basis,the additional damping controller(SSDC)is designed to restrain subsynchronous oscillation,and the input signal,the frequency conversion and phase compensation of SSDC are studied.The chaos optimization algorithm is used to optimize the parameters of the controller,and the model of HVDC subsynchronous oscillation is established on the PSCAD.The simulation results show that the SSDC can suppress the subsynchronous oscillation.Through the establishment of HVDC linear model of subsynchronous oscillation mathematical properties,linear model including the excitation control system of turbine generator and HVDC control system.The linear model of each module system and the transfer function diagram are analyzed,which provides the mathematical model and theoretical basis for the design of the additional damping controller.This paper studies the conversion relation of the subsynchronous electrical components on the AC / DC side,analyzes the characteristics of the sub synchronous frequency response.Furthermore,the inherent relationship between the torsional vibration and the subsynchronous electrical components of the generator shaft is understood.The subsynchronous oscillation additional damping controller is designed by using the generator speed deviation and the instantaneous voltage of three-phase bus as its input signal.To analysis the power system's shaft torque vibration,rotational speed,output voltage changes through the PSCAD simulation under different operation conditions.and then analysis the effect of the SSDC controller.