Optimal reactive power control in transmission network with a large wind farm connection

In a weak network where the reactive power capability is not able to satisfy the demand of wind farm based on squirrel-cage induction generator (SCIG), flexible AC transmission system such as static VAR compensator (SVC) is used. Traditionally, the SVC device and other network reactive power facilities are used in optimal way by the network operator, for optimal voltage profile and loss minimization, during different steady-state operations caused by wind resource changes. In this paper, the SVC reactive power reserve (SVC-RPR) is added to the problem as a third objective function to be maximized with the purpose of further compensation usage during dynamic operation. Particle swarm optimization (PSO) is used to optimize the search space of this multi-objective problem. The reactive power optimization scheme is tested in a MATLAB/R2010a based simulation model of Wale & Hale 6-bus system with wind farm integration. It is has been found that the conflict between the three objective functions causes the difficulty of achieving a sufficient SVC-RPR during high wind farm power generation, unless the SVC rating is designed in such away to be higher than the reactive power required by the total number of SCIG at full load.