A Probabilistic Load Flow Method with Consideration of Random Branch Outages and Its Application

An AC probabilistic load flow analysis considering the fluctuation of loads, the unscheduled unit outages and random branch outages is proposed. Then it is applied to analyze the power system´s static state security. By using the sensitivity matrix and taking the random branch outages as the 0-1 distribution of incremental power injections at each end of the branch, the probabilistic distribution of nodal voltages and line flows is obtained by a combined Cumulants and Gram-Charlier Series expansion method, instead of complex convolution calculation. It adopts the technology of contingency sequencing to analyze the random outages of each branch according to the severity order of contingency, which reduces amount of calculation in consequence. Then apply this method into probabilistic load flow analysis and static state security analysis through the IEEE118 test system. The comparison results with Monte Carlo simulation show the accuracy and higher speed of the proposed method.