Calculation Of Power System Static Voltage Stability Margin Considering Stochastic Fluctuation Of Wind Farm Output

In recent years,with the rapid development of new energy generation technologies,including photovoltaic power,wind power,etc.,wind power generation technology is relatively mature and the scale of it is large.Due to the uncertain fluctuation of wind speed,the active power output of wind farms has large uncertain fluctuation,and the wind power between different wind farms are obviously related.Therefore,it is necessary to study the uncertainty of SVSM level considering the wind farms access to the power system.Based on the continuous power flow(CPF)and affine-interval algorithm,the SVSM calculation considering the uncertainty of wind power and the correlation of multiple wind farms power are studied.The interval number is used to describe the stochastic fluctuation characteristics of wind farm output,the method of calculating the SVSM interval of power system with wind farm integration is proposed based on the CPF method and affine-interval algorithm.Firstly,the wind power fluctuation interval is segmented according to the different bifurcation types of voltage stability limit points.Then the CPF method is used to calculate SVSM corresponding to each interval central value,and then the first-order sensitivities of SVSM with respect to the wind farms output are calculated according to the corresponding bifurcation point type.Finally,a linear programming model is used to optimize the noise symbols to obtain the interval contraction results,thus the SVSM interval is obtained.Using correlation angles to describe the correlation of different wind farms output intervals.According to the types of bifurcation point are same or not,different methods are used to calculate the SVSM interval.Take the IEEE-39 bus system and a 964-bus actual provincial power grid as examples,the results show that the SVSM interval calculated by the proposed method is more accurate,and the computation time is significantly reduced.For the system with high wind power penetration,based on the improved CPF and improved affine-interval algorithm which considers quadratic terms,a method for calculating the SVSM interval of power system is proposed.Firstly,the improved CPF is used to calculate the SVSM at the central values of the wind farms output intervals and obtain the bifurcation point type,and then the first-order and second-order sensitivities of SVSM with respect to the bus injected power are calculated according to the bifurcation point type,finally,a linear programming model is used to optimize the noise symbols to obtain the interval contraction results,thus the SVSM interval is obtained.The power variation of active load growth and wind power fluctuation are shared by all conventional generators except the swing generator in the improved CPF calculation model.For multiple wind farms,by decorrelation of the related wind farms output intervals to obtain the independent intervals,and the SVSM interval is calculated based on the improved CPF and improved affine-interval algorithm.Take the IEEE-39 bus system and a 964-bus actual provincial power grid as examples,and compared with the Monte-Carlo method,the results show that the SVSM interval calculated by the proposed method is more accurate,and the computation time is significantly reduced.