Cyclic security analysis for security constrained optimal power flow

The security of a power system may be enhanced by supplementing an optimal power flow model with a N-1 security rule (respect of voltage and power flow limits after any single line or generating unit outage). Including a security analysis in the optimal power flow model, a security constraints optimal power flow model is obtained. This paper deals with the application of a new contingency screening model to speed-up the security constrained optimal power flow (SCOPF), which makes possible the on-line applications. The SCOPF resolution process is an iterative one. A cyclic contingency selection model is designed in order to take advantage of the specific characteristics of the optimal power flow problem, such as the lower variations of the control variables between the SCOPF iterations. The cyclic security approach takes the results of a security analysis carried out at time t_k and extracts data for use by another security analysis at time t _k+Δt in order to reduce the computational burden. Tests performed show that the inclusion in the OPF of the proposed cyclic security procedure efficiently produces more secure conditions against critical contingencies and considerably speeds up the security constraint optimal power flow