Short-Term Frequency Support Utilizing Inertial Response Of Variable-Speed Wind Plants

In regions with increasing penetration of variable-speed wind generators, grid operators are concerned about frequency security as system inertia is decreasing. The partial replacement of conventional plants with modern wind plants may cause system frequency regulation to fall below acceptable levels, especially in isolated power systems. This study investigates the contribution of variable-speed wind generators to short-term frequency support. This contribution is obtained by transiently releasing part of the stored kinetic energy in the turbine blades, namely the inertial response.;Time-domain simulations were performed to examine the performance of this controller. Based on its impact on system frequency and wind farm operation, the new controller was compared to earlier implementations of wind plant inertial response. The results show that the proposed controller is capable of bringing together the advantages of the different earlier implementations for better grid integration of wind turbine generators. Its effectiveness in reducing the initial frequency fall after a load-generation mismatch promises significant contribution to system inertia. Its controllable, predictable nature is a distinct advantage that enables grid operators to understand, forecast and quantify the impact of incorporating this controller into grid-connected wind generators.;Some inertial response schemes have been researched to be incorporated as auxiliary loops in the controllers of wind generators. First, we compare the performance of these earlier implementations and identify their shortcomings. Then, we quantify the extractable inertial power from a modern wind turbine, given its power characteristic, equivalent inertia, and prevailing wind condition. From this understanding, a new controller, based on the asynchronous release of kinetic energy, is proposed to achieve a superior, more controllable performance. The controller is composed of a 'detection and triggering' scheme that detects the frequency event, a 'power shaping' function that decides the duration and amount of inertial power released, and a 'rotor speed recovery' scheme that brings the turbine back to its optimal speed which corresponds to maximum power tracking.