A least squares solution for optimal power flow sensitivity calculation

Sensitivities of an optimal power flow (OPF) solution to small changes in bus loads, flow limits, bus voltage limits, and other OPF constraints are becoming increasingly important to the electric utility industry. Many of these sensitivities are not produced by most existing OPF algorithms. A least-squares-based algorithm that is suitable for post-OPF sensitivity calculations is proposed. The algorithm provides acceptable sensitivities of optimal solutions under the consideration of all important operational and security constraints. The optimal solutions need not be exact. This is especially important for real-time applications where only approximate, but close to the true optimum, solutions are available. The proposed algorithm has been implemented in a production grade computer software and is sufficiently general to be used by other electric power utilities. It is intended to be used as part of the OPF calculations in the new energy management system (EMS) of the Pacific Gas and Electric Company. Test results on a 1700-bus system are presented