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

Abstract

Accordingto recent grid codes, large-scale wind turbines (WTs) are required to provide fast frequency response (FFR). The 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. These methods have a drawback that they impose severe secondary frequency drops (SFD), or they consider an unrealistic constant wind speed during their inertial control support. This paper proposes a novel Gaussian distribution-based inertial control (GDBIC) scheme that can improve the 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 Gaussian distribution trajectory controlled by a standard deviation parameter, ensuring by this convergence of the rotor speed to a stable equilibrium. The proposed scheme is also capable of responding to a second cascade event. The performance of the GDBIC is tested on the wind-integrated IEEE 9-bus system and the IEEE 39-bus system in DIgSILENT PowerFactory. It is also compared with other methods reported in literature. Furthermore, experimental tests are used to verify the performance of the proposed scheme, using two different hardware-in-the-loop testing facilities. The blade fatigue is studied using Fatigue, Aerodynamics, Structures, and Turbulence (FAST) Code. The simulation and experimental results showed that the release of the kinetic energy in rotors using the proposed GDBIC scheme allows significant improvement of the frequency nadir, with no SFD, as well as contribute to reliable operation during abrupt wind changes.