Research On SSO Caused By Grid-integration Of Wind Power Generation Via Series Compensated Lines

With the uneven distribution of energy in China,the construction capacity of wind farms is greatly improved,large-scale wind power construction and grid operation,to solve the energy crisis and eliminate problems to provide solutions.However,the wind power is mainly in series compensation and wind and fire bundled way to send power.The first mode of transmission may be the threat of sub-synchronous oscillation,the second way may be the original synchronous generator system damping characteristics,and thus lead to oscillation phenomenon.In recent years,scholars have divided the sub-synchronous oscillation problem and proposed an interaction phenomenon of energy conversion between the wind farm and the series compensation system in the sub-synchronous frequency range,which is called Sub-synchronous Oscillation,SSO),which includes sub-synchronous resonance(SSR),the sub-synchronous torque(SSTI)caused by the interaction between the wind turbine controller and the shaft system which respond quickly to the secondary synchronous frequency,(SSCI)caused by the shaft system of the wind turbine generator and the fixed series compensation system.In this paper,a DFIG system model for SSO analysis is established based on doubly fed wind turbines,which includes the torque shaft system of the turbine,the doubly fed induction generator,The series compensation transmission line and the converter control system mathematical model,and then through the small signal analysis method to model the model to obtain the linear system equation matrix coefficient matrix and calculate the eigenvalues and eigenvectors,different And the modal analysis method was used to analyze the degree of participation factors of the corresponding state variables in each mode.Then the time domain simulation model is established by MATLAB / Simulink to validate the effectiveness of the system.The influence of the system parameters and the parameters of the converter on the damping ratio of the subsynchronous interaction is analyzed.Then,the damping characteristics of the SSO.The results show that the increase of the series compensation,the capacity of the wind turbine and the wind speed decrease,the increase of the inner ring parameters of the rotor side converter(RSC)controller will make the SSO remarkably enhanced,and prove that the RSC outer ring The effect of parameters on SSO characteristics is not significant.Then the time domain simulation model is established by PSCAD / EMTDC to validate the effectiveness of the system.The influence of the system parameters and the parameters of the converter on the damping ratio of the subsynchronous interaction is analyzed,and then the damping characteristics.The results show that the increase of the series compensation,the capacity of the wind turbine,the decrease of the wind speed and the increase of the inner loop parameters of the rotor side converter(RSC)controller will make the SSO significantly enhanced,and prove that the RSC outer ring The effect of parameters on SSO characteristics is not significant.Finally,the transfer function of the active power-rotational speed and the reactive power-rotational speed is established,and then the phase angle range of each positive damping can be calculated.Then,the objective function is established,and the transfer function parameters of the PID phase compensation are established by genetic algorithm.Optimal Control Strategy of Active-Speed and Reactive-Speed Rings.Time domain simulation shows that the proposed strategy can provide positive damping to the system over the whole frequency band,and the damping control strategy of reactive power and speed loop is better.