Mathematical Problems in Engineering
Volume 2010 (2010), Article ID 295645, 15 pages
Research Article

Solving Unit Commitment Problem Using Modified Subgradient Method Combined with Simulated Annealing Algorithm

Department of Electrical and Electronics Engineering, Anadolu University, 26470 Eskisehir, Turkey

Received 13 December 2009; Revised 7 April 2010; Accepted 14 May 2010

Academic Editor: Jyh Horng Chou

Copyright © 2010 Ümmühan Başaran Filik and Mehmet Kurban. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


This paper presents the solving unit commitment (UC) problem using Modified Subgradient Method (MSG) method combined with Simulated Annealing (SA) algorithm. UC problem is one of the important power system engineering hard-solving problems. The Lagrangian relaxation (LR) based methods are commonly used to solve the UC problem. The main disadvantage of this group of methods is the difference between the dual and the primal solution which gives some significant problems on the quality of the feasible solution. In this paper, MSG method which does not require any convexity and differentiability assumptions is used for solving the UC problem. MSG method depending on the initial value reaches zero duality gap. SA algorithm is used in order to assign the appropriate initial value for MSG method. The major advantage of the proposed approach is that it guarantees the zero duality gap independently from the size of the problem. In order to show the advantages of this proposed approach, the four-unit Tuncbilek thermal plant and ten-unit thermal plant which is usually used in literature are chosen as test systems. Penalty function (PF) method is also used to compare with our proposed method in terms of total cost and UC schedule.