Unit commitment based on modified unit decommitment method

A modified unit decommitment method is proposed for unit commitment. The algorithm starts with the initial solution where all the available units are on stream. One and only one unit schedule optimization is made in each iteration to minimize the power production (or purchasing) cost in conventional (or market) environment. The iteration continues till two consecutive iterations give the identical solution or the value of the objective function cannot be further improved. A noticeable advantage of the new method is that all the intermediate solutions during the iterations retain the feasibility. In the single-unit optimization process, minimum up and down time constraints are considered through a novel approach so that the number of feasible solutions can be reduced significantly. The mathematical models for UC under both traditional and market environments are presented together with the suggested algorithm and solution procedure. The constraints of power balance, spinning-reserve request, minimum up and down time, generation capacity and the ramp rate are all considered. Computer test results for a 20-unit system and a 110-unit system are presented to show the effectiveness of the proposed approach.