Evaluation of frequency response of variable speed wind farms for reducing stability problems in weak grids

Maintaining the frequency within certain limits in a power system is a basic operational requirement as many loads may be very sensitive to frequency deviations. Increasing wind penetration in the power grid may lead to stability problems in isolated systems, or systems with weak interconnections with surrounding areas. Modern wind farms are based on variable speed wind turbines where the rotor speed and the electrical frequency are not coupled, thus, these farms do not add inertia to the system. At certain levels of wind penetration, the system inertia may become critically small, and the system may get unstable. In this work, some frequency response capabilities are incorporated into a wind farm. A validated wind model, developed by the authors, is used to obtain the wind series which is used for the simulations. Typical models of conventional generation power plants are used to fulfill the system operation requirements.