Cost/benefits analysis of an optimal power flow: the PG&E experience

This paper documents the results of a study to analyze the potential costs and benefits that may be realized from the future on-line use of an optimal power flow (OPF) application in PG&E´s new energy management system (EMS). This application minimizes production cost while eliminating thermal overloads using active power controls. The methodology of the study was to simulate as closely as possible the operation of the PG&E power system under the currently used method based on a modified economic dispatch algorithm and the optimal dispatch provided by the OPF. The modified economic dispatch method is based on an economic dispatch with some manual redispatching to eliminate thermal overloads consistent with existing operating procedures. The results of the study showed that the use of this OPF application resulted in a substantial increase of the MW transfer capability of a constrained transmission corridor in the PG&E system. This increase can potentially result in substantial annual savings due to reduced operating costs. Furthermore, the study showed that this application can minimize load shedding, if the other control options have been exhausted, to eliminate thermal overloads, can produce realistic solutions for infeasible problems and could conceivably validate/improve current operating procedures under a wide range of operating conditions