Scenario Reduction Method Based On Load Margin Applied In Voltage Stability Problem

With the development of the technology of wind power integration, thepenetration of wind power into power system has been increased drastically. ForChina, the development mode is large-scale and high concentration. And thetransmission of wind power is through the long distance and high voltage network.Because of the forecasting error, the uncertain and random characteristics haveinfluenced the power system. The increasing penetration of wind power will influencethe distribution of power flow and the capacity of transmission, and it will lead to theproblem of voltage stability. For the wind power system, the voltage stability has to beinterpreted as a stochastic problem. In this paper, a method of voltage stabilityanalysis considering the uncertain and random characteristics of wind power has beenproposed.1. Wind power is treated as a stochastic variable which satisfies one probabilitydistribution. Through the scenarios generation method, wind power has beenrepresented by a huge number of scenarios.2. For the scenarios-based stochastic problem, a high effective Problem-dependentscenarios reduction method has been proposed. Compared with the traditionalmethod, the proposed method has taken not only the statistical characteristics ofscenarios but also the problem itself into consideration. Through theproblem-dependent method, the severe scenarios which can lead to voltagecollapse can be found quickly. It is composed of K-means, sensitivity analysis,look-ahead method and continuous power flow method.3. The corresponding load margin of each scenario can be obtained by enhancedlook-ahead method quickly and accurately. Then the probability distribution ofload margin corresponding to the wind power can be obtained. The influence ofwind power on the voltage stability can be got through the distribution.Besides that, the reactive power limit has been taken into considerations. Whenthe system encounters the Q-limit, it may lead to the limit-induced bifurcation whichis more dangerous for the power system.