The application of the ordered list method and the dynamic programming to the unit commitment

Abstract

The electric energy that our society has been using changes daily, weekly, etc. It is important to have some way to know when to turn ON or OFF the power generation units in order to supply the energy demand with the cheapest cost.Proper commitment of the available generating units results in significant cost saving.The thesis presents a method of committing generating units in a hydro-thermal power system within practical [4,6,7] . To find the solution for the unit commitment, a number of difficulties are encountered because of many constraints that are to be satisfied. The more constraints applied to the system, the more computer resource and time is consumed. The dynamic programming approach has proved to be one of the very effective methods for the unit commitment [1,4]. This method requires significant computer resources in terms of computer memory to store all the data and time to determine the solution.The purpose of this thesis is to find an efficient method that will result in good unit commitment solution within practical computer time and resource.Almost all the electric energy we use is transformed from thermal and hydro energy. Hence, this study will present the combination of dynamic programming and ordered 3 list methods for the commitment of a power system that includes both thermal and hydro units based upon a specified power schedule. The ordered list method is found to be most suitable for the hydro unit commitment and the dynamic programming to be most suitable to the thermal unit commitment. The commitment is such that the total cost is minimum. The total cost includes both the production cost and costs associated with the start-up which consists of hot-start and cold-start cost and shutdown cost of the units. The spinning reserve requirement is also included. In addition, the operation of the individual units must satisfy the specified minimum up-time, minimum shutdown time and maintenance schedule. UNIT COMMITMENTThe unit commitment determines when to start and shut down units such that the load plus spinning reserve requirement within the specified period is always satisfied.A substantial saving is possible by a proper commitment of the available generating units.The difficulty of getting a good solution for unit commitment is that there are many constraints to be satisfied each time we want to commit each unit in a system.The problem becomes more complex because a system may contain both thermal and hydro units that have different type of constraints. Besides the constraints applied to each individual units, another external factor of spinning reserve requirement is applied to the whole system because of system operating requirements. CONSTRAINTS IN UNIT COMMITMENTMany constraints can be placed on the unit commitment problem. The list given below is by no means exhaustive but it is the most usual in the electric power systems. Each individual power system or power pool may impose different restrictions on the scheduling of units, depending on the generation makeup, load curve character...