Probabilistic steady-state and dynamic security assessment of power transmission system

Abstract

Two-level system model based probabilistic steady-state and dynamic security assessment model is introduced in this paper. Uncertainties of nodal power injection caused by wind power and load demand, steady-state and dynamic security constraints and transitions between system configurations in terms of failure rate and repair rate are considered in the model. Time to insecurity is used as security index. The probability distribution of time to insecurity can be obtained by solving a linear vector differential equation. The coefficients of the differential equation are expressed in terms of configuration transition rates and security transition probabilities. The model is implemented in complex system successfully for the first time by using the following effective measures: firstly, calculating configuration transition rates effectively based on component state transition rate matrix and system configuration array; secondly, calculating the probability of random nodal power injection belonging to security region effectively according to practical parts of critical boundaries of security region represented by hyper-planes; thirdly, locating non-zero elements of coefficient matrix and then implementing sparse storage of coefficient matrix effectively; finally, calculating security region off-line for on-line use. Results of probabilistic security assessment can be used to conduct operators to analyze system security effectively and take preventive control. Test results on New England 10-generators and 39-buses power system verify the reasonableness and effectiveness of the method.