Optimal scheduling of spinning reserve with ramp constraints

This paper proposes an effective method to schedule spinning reserve optimally. It initially employs Lagrangian relaxation technique to obtain the commitment schedule by relaxing the demand constraint, spinning reserve constraint and every unit ramp rate constraint. Using the forward dispatch, dispatch modification and backward dispatch, a generation schedule which satisfies the spinning reserve requirement and the ramp rate limits is obtained. This schedule is updated by the probabilistic reserve assessment to meet a given risk index. The optimal value of the risk index is selected based on the tradeoff between the total unit commitment schedule cost and the expected cost of energy not served. Finally, a unit decommitment technique is incorporated to solve the problem of reserve over-commitment in Lagrangian relaxation based unit commitment. The algorithm is shown to be efficient and the results are near optimal judging from the simulation runs performed on the extended IEEE reliability test system.