Unit commitment with pumped storage hydro-electric unit

Abstract

A few years ago, Muckstadt et al[29] suggested the idea that the unit commitment problem can be considered for each unit by using the Lagrangian relaxation technique. This idea can be used in the saving of the computer capacity as solving the unit commitment. In this thesis, using the above idea, the formulation will be proposed after considering the unit commitment with the pumped storage hydro-electric units. The unit commitment problem with the pumped storage hydro-electric units can be separated by each unit for the pumped storage hydro-electric units and the thermal units by using the Lagrangian relaxation technique. For each thermal unit, the idea proposed by Muckstadt et al is applied to solve it. For each pumped storage hydro-electric unit, it can be solved by the minimal cost flow problem and the details about it will be explained in this thesis. The advantages in converting the subproblem for each pumped-storage hydro-electric unit to the minimal cost flow problem are as following: - the currently efficient minimal cost flow algorithm can be used directly. - the saving of the computer capacity will be expected. The method for getting the solution to the unit commitment by updating the Lagrange Multipliers is suggested by Merlin et al[28]. Our methodology will be applied to the data in the Korean Electric Company. In this example, we consider the operation of the 39 thermal units and the 1 pumped storage hydro-electric unit for 24 hours. The computation time is 84 seconds on CDC CYBER for obtaining the solution within 6.4\% of the optimum.