In this paper we present a formulation of the unit commitment problem with AC power flow constraints. It is solved by a Benders decomposition in which the unit commitment master problem is formulated as a mixed-integer problem with linearization of the power generation constraints for improved convergence. Semidefinite programming relaxation of the rectangular AC optimal power flow is used in the subproblem, providing somewhat conservative cuts. Numerical case studies, including a 6-bus and the IEEE 118-bus network, are provided to test the effectiveness of our proposal. We show in our numerical experiments that the use of such strategy improves the quality of feasibility and optimality cuts generated by the solution of the convex relaxation of the subproblem, therefore reducing the number of iterations required for algorithm convergence.
A method is described for determining the most economical generating utiit commitment policy and loading schedule for a day's operation of an electric utility system while maintaining a desired level of system reliability. In modern world, every industries including the power industry address technological changes. Therefore, it is necessary to keep track of international experiences and activities taking place in every field. This paper provides an overview of the concept of Unit Commitment (UC) problem with a bibliographical survey of relevant background, the present state and potential methodologies used for solving the concern problem. From the literature, UC problem can be categorized based on the system characteristics and policies applied. This paper reviews not only on regulated and deregulated power systems but also on power systems with renewable energy sources and storage system. In addition, it presents a comprehensive review of the methodologies, which covers a wide span of deterministic, meta-heuristic and hybrid approaches including multi-agent system approach. In terms of contribution, it formulates the problem clearly and describes appropriate approaches to solve the problem. The collected literature of methodologies has been divided into many sections, so that new researchers do not face any difficulty in carrying out research on UC problem under both the regulated and deregulated power industries as well as power system with renewable energy sources and storage system for next generation. With the fast-paced changing technologies in the power industry, new power references addressing new technologies are coming to the market. So there is an urgent need to keep track of international experiences and activities taking place in the field of modern unit-commitment (UC) problem. This paper gives a bibliographical survey, mathematical formulations, and general backgrounds of research and developments in the field of UC problem for past 35 years based on more than 150 published articles. The collected literature has been divided into many sections, so that new researchers do not face any difficulty in carrying out research in the area of next-generation UC problem under both the regulated and deregulated power industry. The paper describes a new method of scheduling thermal generating units to achieve minimum operating costs including both running and start-up costs while at the same time maintaining a desired level of system security.