Probabilistic Assessment Of Transient Voltage Stability Of Wind Power System

As the world fossil energy reserves continue to decline,more attention has been paid to the use of renewable energy.The wind energy is renewable energy development and utilization in many of the most mature.The wind power generation technology has received extensive attention in various countries around the world.Large scale wind turbine grid will cause the system reactive power fluctuation,directly affects the system voltage stability.Also large-scale wind power integration in power system has many other uncertain factors.It is difficult to give the determinacy conclusion of system voltage stability.Traditional determinacy analysis method is unable to fully describe the voltage stability of the system,so the accurate assessment of the transient voltage stability of wind power system is very necessary.First of all,through the analysis of each wind units under large disturbance transient behavior to determine the transient current in the rotor as the clustering index.The equivalent probabilistic model of wind farm is established using fuzzy C-means clustering algorithm.The model can be used to account for the uncertainties in the wind farm,which can accurately reflect the dynamic characteristics of the wind farm.Secondly,by analyzing the mechanism of the system instability,it is pointed out that the stability of the power system is based on the correct distinction between voltage stability and angle stability.The method of modal series expansion is used to calculate the nonlinear correlation factor to determine whether the equilibrium point is near the voltage stability or the angle stability.Analysis results show that the method can identify the angle instability or voltage instability by determining the nonlinear characteristics near the equilibrium point of the system.Finally,the stability of the system is determined.At the same time in the calculation precision is better than that of the vector field regularization method.Finally,combined with the equivalent probability model of wind farm,fault location,fault type,fault clearing time and wind generator output power of randomness,the probabilistic assessment method for transient voltage stability of wind power system is proposed.Based on the dynamic security region boundary near the controlling unstable equilibrium point of the voltage instability,the probabilistic assessment model of the transient voltage of the wind power grid connected system is obtained by using the Edgeworth series expansion.The accuracy and effectiveness of the proposed method are verified by a numerical example.