SummaryWith deregulated regime for electricity market, utilities are being operated close to stability boundaries. Therefore, it has become necessary to secure power systems optimally when subjected to transient stability condition. Transient stability constrained optimal power flow (OPF) is a highly nonlinear, high-dimension optimization problem and requires efficient methods to solve it. In this paper, transient stability constrained OPF problem is implemented by using biogeography-based optimization algorithm, a recent evolutionary algorithm that searches for global optimum through migration and mutation of biological species distributed over geographical space and has shown promising results. The OPF model uses economic dispatch as objective function subjected to various constraints. Single machine equivalent, a hybrid method that combines time domain simulations and direct method, has been used to implement transient stability constraint. Tests on Western System Coordinating Council 3 machine, 9 bus system and New England 10 machine, 39 bus system demonstrate the effectiveness of the approach. The simulation results presented by using MATLAB are compared with recent findings that show that the proposed biogeography-based optimization algorithm is capable of obtaining higher quality solutions.KEYWORDS biogeography-based optimization, optimal power flow, SIME, transient stability
| INTRODUCTIONTo establish a secure and optimal state in power system, system operators use optimal power flow (OPF) programs in planning and operating stages. In OPF, the given objective function is optimized subject to operational and physical constraints of the system. Because OPF model can integrate the cost effectiveness and constraints of the power system into a single mathematical formulation, various deterministic approaches have been applied in the past 1 . Deregulation of utilities necessitated transmission of large amounts of electrical energy over long distances with intraday electricity markets. The uncertainty of operating conditions due to distributed generation coupled with complex control hierarchy forced systems to operate at stability boundaries. Against this background, instability has become a major issue, which must be addressed by suitable techniques. This has given rise to a new methodology known as transient stability constrained OPF (TSCOPF) problem, which is a highly nonlinear, nonconvex, and multidimensional optimization problem 2 .Researchers proposed many deterministic approaches of solving TSCOPF problem in the literature. Transient stability constrained optimal power flow problem consists of differential-algebraic equations, which need to be