Disturbance-adaptive Short Term Frequency Support Method of Wind Turbine Generators

For short term frequency support (STFS) methods of wind turbine generators (WTGs) adopting extra inertia loop and droop loop, the tuning of the inertia gain for inertia loop and the droop gain for droop loop is crucial for these methods. In this paper, a disturbance-adaptive STFS method of WTGs is proposed, which tunes the inertia gain and droop gain based on the stages of a frequency disturbance, with considering both active frequency support and rotor speed recovery. The inertia gain changes based on the dynamic relation between the rotor speed and the system frequency, and it will remain zero after the frequency nadir (FN). The droop gain includes two variable components, one varies with the stages of a frequency disturbance considering the disturbance severity and the system composition. The other is related to the releasable kinetic energy of WTGs to ensure a safe operation. Besides, in order to restore the rotor speed and prevent an aggravated quasi-steady-state frequency deviation, the droop gain will decrease to zero before primary control finishes. Finally, to validate the performance of the proposed method, the simulations based on EMTP-RV simulator are carried out by considering different wind speeds, disturbance severities, and wind power penetration levels. The results verify that the proposed method can adapt to different scenarios, and is superior to conventional methods in terms of the FN, the second frequency dip and the quasi-steady-state frequency deviation.