A review of frequency stability services for grid balancing with wind generation

Frequency stability in power systems is achieved by active power control, which aims to balance grid generation with load demand. Historically grid balancing services have been provided by synchronous thermal generating units. As wind penetration levels increase on the power system, it is essential that wind turbine generators (WTGs) provide robust, reliable frequency stability services to grid operators. Like other forms of renewable generation, such as solar photovoltaic generation, modern variable speed wind turbine generators (VSWTGs) are connected to the power system using power electronic convertors. This non-synchronous connection decouples the natural inertia of the WTG from the grid frequency. As system non-synchronous penetration (SNSP) levels increase, non-synchronous generation will be required to participate in frequency stability services, such as automatic generation control (AGC). This paper presents a review of WTG frequency response systems that allow WTGs to participate in frequency stability services by emulating the natural inertia and droop characteristics of conventional synchronous thermal generators. Power system simulations performed in MATLAB/Simulink show that the addition of emulated inertia and droop controllers into WTG’s power/speed control systems can reduce the rate of change of frequency (RoCoF) and increase frequency nadir when the power system is subject to a load/generation imbalance.