Power System Risk Assessment Considering Wind Farm Intermittency

With a large number of wind power energy put into operation, the capacity and scale of wind power installed in China are more and more bigger. Due to the character of intermittent, the threat to traditional power grid are serious.It will be significance to study the impact of large scale wind power to grid and we can make reasonable use of wind power.This paper is mainly focused on the influence on node voltage and branch power flow considering wind farm and provide a comprehensive analysis on wind power grid. Probabilistic load flow (PLF) method is used in this paper considering the character of intermittent in voltage and branch power flow analysis.Combined Cumulants and Gram-Charlier expansion are introduced to study the intermittent of wind power. According to the probabilistic analysis, the probability of voltage and branch power flokv violation.can be attained from the probability distribution of wind power input power.using the stochastic theory.Meanwhile the probability density function (PDF) and cumulant distribution function(CDF) are obtained from the probability distribution of wind power input power.At the same time, an improved probabilistic load flow method considering the intermittence of wind power is proposed in this paper to increase the compute accuracy and practical reference value. The simplified steady state equivalent circuit iteration of IG in wind farm is considered to compute the base load flow, avoiding the inaccuracy that wind farm is only treated as PQ or PV model.First,the modles of wind speed and wind farm are built as well as the linear model of power flow compute.Second, the probability of voltage and line flow can be got by according to the wind power input power as well as CDF and PDF. Last, the theory of risk assessment is applied to the power system with wind power to make a quantitative evaluation of voltage and line flow risk. The indexes of node voltage and line flow violation are built considering the economic factors. The paper also provides theory reference to the wind power security penetration.