# Evaluation Of Unit Commitment ( Uc ) Problem

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Introduction Unit Commitment (UC) problem is a procedure for finding economical schedule with respect to generator commitment/de-commitment condition with transmission and voltage constraints. It is a difficult combinatorial optimization mixed integer programming problem that involves a large number of binary (0-1) type variables that denotes up/down status of the units and continuous variables expressing generation output. To solve the Unit Commitment problem various optimization techniques have been applied, such as the dynamic programming(DP) approach, the Lagrangian Relaxation(LR) method, the branch and bound method, the Genetic Algorithm(GA) method, exhaustive enumeration, integer and mixed integer programming. In this paper we…show more content…
This set is passed to OPF again to check for feasibility and if it is impossible to improve the solution with those rules then the process stops. The best candidate is selected as a solution after the process is repeated for a specified number of times. The paper which we are referring [1] indicates that the solution obtained by heuristic method is better than that of LR and GA and the time taken to produce the solution is significantly less than those two method. Voltage, reactive power and transmission constraints are usually not considered while solving the Unit Commitment problem. But, in this paper we have proposed a solution of unit commitment considering all the above mentioned constraints based on heuristic method and optimal power flow (OPF). Mathematical Model Objective Function: Minimization of the total cost making an allowance for all the system constraints is the objective of unit commitment. It is denoted by, min_(P_i^t 〖,U〗_i^t ) C(P_i^t U_i^t ) The objective function thus is, min_(P_i^t 〖,U〗_i^t ) C(P_i^t U_i^t )=min_(P_i^t.U_i^t ) [ ∑_(t=1)^T▒〖∑_(i=1)^N▒〖{FC_i (P_i^t ).(U_i^t)〗+ST_i.U_i^t.(1-U_i^(t-1))〗 Total fuel cost is the function of the generator output. It depends on unit heat rate and fuel price information. For practical purpose quadratic expression is used. 〖FC〗_i (P_i^t) = a_i2 〖〖(P〗_i^t)〗^2 + a_i1 P_i^t + a_i0 The start-up cost is related to the features of the thermal system and