Study On Probabilistic Load Flow With Large-scale Wind Power Integration

The wind power generation technology has become increasingly mature.In China,wind power has shown a large-scale integration situation.Numerous wind turbines are collected and integrated dispersedly into grid.However,in some places where the wind resources is excess,the wind power will be curtailed,so the output of wind farms can not be fully integrated into the grid.It means that the receptivity of wind power is limited by the transmission capacity of tie line.And the output of wind farms in the same region has strong correlation.The large-scale wind power integration will increase the uncertainty of power flow,having a greater impact on the safe operation of power grid.A probabilistic load flow(PLF)calculation method considering wind power correlation and power grid receivability of wind power is proposed and then applied to the Ningxia power grid engineering project and power system static security analysis.(1)A PLF method considering acceptable capacity of wind power is proposed.Based on the wind power model considering the power grid receivability,which is in the form of a piecewise function,a improved Latin hypercube sampling(LHS)method is proposed.The simulation results demonstrate that the proposed method overcomes the shortcoming that traditional LHS is not suitable for the irregular random variable.It can not only reduce the sampling size,but also obtain the similar results with that got by Monte Carlo simulation based on random sampling.The difference of branch power flow when single wind farm integrated is analyzed under different wind power distribution conditions.(2)A PLF calculation method considering wind power correlation and power grid receivability is proposed.The wind power correlation analysis method based on history data and Copula theory is researched and a improved LHS method is proposed to be suitable for wind power random variable whose probability distribution is known or unknown.The proposed PLF calculation method considers power grid receivability and can deal well with the nonlinear correlation between wind farm output variables.The simulation results show that the proposed method has great advantages in accuracy and speed,meanwhile,the correlation is necessarily considered.(3)Combined with Ningxia power grid engineering project,the proposed PLF calculation method is used to analyze operating state.The system operation results verify that the proposed method can efficiently and accurately analyze the PLF distribution characteristics.The PLF calculation visual analysis system for Ningxia power grid is designed by the graphical user interface(GUI)of MATLAB software.(4)The proposed PLF calculation method is applied to the power system static security analysis.A ranking indicator based on the available capacity entropy of branch and sorting method under multi-scenarios for expected contingency are proposed in order to speed up the analysis.The simulation results indicate that the proposed method can evaluate power system static security precisely and find the weakness of power system.