Probabilistic approach to voltage stability analysis with load uncertainty considered

This paper proposes a new probabilistic assessment algorithm of voltage stability based on Monte-Carlo simulation and modal analysis considering uncertainty of the load level and load parameters. By Monte-Carlo sampling, the bus load level is determined according to the forecasted bus load curve of a research period. The coefficients of the load polynomials, which include induction motors, are treated as random variables with normal distribution. A technique of normal distribution sampling is utilized to simulate these coefficients uncertainty. Voltage stability is evaluated in the form of indices such as the expected maximum loadability and the statistics of system participations, which are obtained from modal analysis near the point of collapse. A case study of the IEEE 118-node system is given to demonstrate the validity of the proposed algorithm, and the effects of load uncertainty and the proportion of motors on probabilistic assessment of voltage stability are investigated. Copyright © 2007 John Wiley & Sons, Ltd.