A new multiobjective optimal allocation of multitype FACTS devices for total transfer capability enhancement and improving line congestion using the harmony search algorithm

In this paper, a new approach based on novel heuristic algorithms is used to locate and model multitype flexible alternating current transmission system (FACTS) devices (series and parallel) in order to improve the total transfer capability and decrease the line congestion and total power loss. The multitype FACTS devices, including the static synchronous series compensator, static compensator, and unified power flow controller, have been optimally sized and located simultaneously through the harmony search algorithm (HSA). To achieve this purpose, a program in MATLAB code has been developed in order to extend the conventional Newton-Raphson algorithm for multitype facts applications. Since the optimization is multipurpose, an analytical hierarchy process is used to obtain the priority vector for each alternative. The HSA, with a good convergence property and more accurate results, can satisfy the objective function better. The effectiveness of the proposed method is demonstrated using a modified 30-bus IEEE test system as well as Iranian 230 kV southeast regional grids in normal and contingency conditions. On the other hand, the optimization performance is compared with a genetic algorithm and particle swarm optimization. The simulation results illustrate that the proposed algorithm performs better than the other algorithms. Moreover, it is shown that simultaneous optimizations of multitype FACTS devices have more advantages than the separate optimization of single-type ones.