Research On The Transient Stability Of Large Scale Wind Farm Connected To Power System

For several decades, people had explored and researched in wind power actively,the installed capacity of wind turbines is expanding day by day, the capacity of stand-alone wind turbine from the initial tens of Kw to Mw in nowadays. Because of wind energy has intermittent and randomness, not man-made features in scheduling, So the output power of wind farm is fluctuant, while more and more large-scale wind farms connect-grid, the proportion of wind power in power system is increasing gradually and make serious impacts to the grid; in the same time, wind farms connect-grid change the original flow distribution of power system and make challenge to the traditional power system analysis. Therefore, it has a practical significance to study wind farm connected to power gridDouble-fed induction wind turbine can achieve active and reactive power decoupling control, variable speed operation for maximum wind tracking; it can improve conversion efficiency, and improve the power factor of wind farms and stability.Stability simulation study of wind farm connected to power system under different interference conditions. First, the wind speed model, aerodynamic model and wind turbine mechanical drive system model are studied; the overall structure model of DFIG based variable speed wind turbine is presented. Second, control system model of DFIG and wind farm model are studied; the integrated control system model of DFIG and rotor side and grid side converters control model are established through analysis of rotor side converter and grid side converter control principle of decoupling; In the meanwhile, equivalent wind farm model to represent large-scale wind farm, the simulation results show that the computational efficiency is greatly improved the equivalent wind farm model than detail model.To improve the transient stability of wind farm in fault state, the control method of rotor side converter controller and fast transient voltage controller of pitch angle are together proposed. Pitch angle control of wind energy captured by changing the fan to enhance the transient voltage stability of doubly fed induction wind generator; the rotor side converter controller with transient voltage support capability provides dynamic reactive power to support the grid voltage, to enhance the transient voltage stability of the DFIG based wind turbines. Stability analysis of wind farm using constant voltage control and constant power factor control in two different ways.Finally, simulation module is developed in MATLAB/SIMULINK software, the dynamic simulation model is feasibility and useful to improve transient stability of wind farm.The research work of this paper has been supported by the important research projects funded by national natural science foundation of China (60534040).