This paper proposes a probabilistic model for optimal joint allocation of energy and spinning reserve to determine energy and spinning reserve capacities. The model takes into consideration both the hourly changes of load demands and the probability of generators' contingencies. The objective function aims at minimizing not only fuel costs caused by power generation but also the costs associated with spinning reserve supply.
The proposed model is tackled using the Primal-Dual Interior Point Method (PDIPM), which is capable of solving optimization problems with nonlinear equality and inequality constraints efficiently. This paper reports on the simulation results obtained by using a benchmark IEEE Reliability Test System (IEEE-RTS).The simulation studies also include a comparison between the proposed probabilistic model and the conventional deterministic model, which suggests that the joint allocation of energy and spinning reserve can be optimized by the proposed model for economical and reliable purposes. Consequently, it can be applied to minimize the costs of running the power system with adequate spinning reserve.