Gaussian Distribution-Based Inertial Control of Wind Turbine Generators for Fast Frequency Response in Low Inertia Systems

Decline of rotating inertia due to the high share of renewable sources cause challenges in controlling grid frequency. With recent grid codes, large-scale wind turbines (WTs) are required to provide frequency support. Existing stepwise inertial control methods suggest immediate incremental power injection by WTs, followed by the abrupt over-production termination to avoid over-deceleration of the rotor speed. Unfortunately, these methods are not practically desirable as they impose severe secondary-frequency-drops (SFD) or considering unrealistic constant wind speed for tens of seconds. This paper proposes a novel inertial control scheme that can improve frequency nadir without rotor speed over-deceleration. Upon detecting a power imbalance, WT increases the output power with an incremental power and declines it following a Gaussian distribution trajectory controlled by a standard deviation parameter, to ensure convergence to an equilibrium point. The proposed scheme can be practically implemented for fast frequency response. This scheme is tested on the wind-integrated IEEE 9-bus system and IEEE 39-bus system and compared with other methods reported in literature. Furthermore, experimental tests are conducted to verify the performance of the proposed scheme in practice. Blade fatigue is studied using FAST Code. Results show reliable operation during abrupt wind speed changes or cascade events