Modeling and control of a wind turbine as a distributed resource

This paper is a part of a research project to study the dynamics and control of distributed resources (DRs) in the deregulated electric power industry. It reflects the need to look at large wind farms as power plants, as a result of the increased penetration of wind energy in the power systems many places in the world. To obtain an optimal integration of high penetration of wind energy in the system, the wind farms must be able to replace other power plants, i.e. be able to participate in the control and stabilization of the power system. If e.g. a large wind farm trips due to a grid fault, the power system will suffer from a severe loss of supply. The main result of the project is a verified model of a wind farm, which can be used to study and improve the power plant characteristics of the wind farm, and a tentative assessment of the power quality of the wind farm, based on simulations with the developed model and verified by measurements. This research provided a different approach to wind turbine modeling and control design methodology. All the results were in close agreement with results from other studies. The main strategy of the controller was to regulate the rotor angular speed and the power demand to match the required profiles. A simple wind turbine model was linearized about an operating point and it was used to systematically perform trade-off studies between minimization parameters. The robust nature of the PID controller was illustrated and optimal operating conditions were determined. Continued research illustrates that the optimum wind turbine has not yet been build and most of the remaining work lies in how the wind turbine is controlled. Additional design and control strategy improvements can be expected as experience is gained with wind turbine operations.