In a liberalized electricity market, the use of phase shift ing transformers or other power ¿ow controlling devices allows the transmission system operator to utilize the avail able grid infrastructure in a more optimal way. However, each phase shifter adds a degrees of freedom to the control problem, making optimization more dif¿cult. In this paper, the coordination problem is solved by using Particle Swarm Optimization (PSO). The goal is to give an overview of how PSO is used to solve this particular problem, and to demon strate a new area of application for the method.

A tendency to erect ever more wind turbines can be observed in order to reduce the environmental consequences of electric power generation. As a result of this, in the near future wind turbines may start to influence the behavior of electric power systems by interacting with conventional generation and loads. Therefore, wind turbine models that can be integrated into power system simulation software are needed. A model that can be used to represent all types of variable-speed wind turbines in power system dynamics simulations is presented. The modeling approach is commented upon, and models of the subsystems of which a variable speed wind turbine consists are discussed. Some results obtained after incorporation of the model in PSS/E, a widely used power system dynamics simulation software package, are presented and compared with measurements.