Frequency Control Strategy of DFIGs based on Improved Virtual Inertia Method

Abstract

The DFIGs can participate in frequency control by virtual inertia method. After exiting the frequency control, secondary frequency drop will occur inevitably. The current study of the problem mostly focused on the rotor speed recovery strategy and PD control parameter optimization problems, which cannot eliminate the phenomenon of secondary frequency drop in essence. This paper proposes a frequency control strategy based on the improved virtual inertia control method. When the DFIG exits the frequency modulation process, the supplementary control component based on the turbine speed is added to avoid the sudden drop of output power, so as to suppress the secondary frequency drop. Finally, a simulation model is built in Matlab/Simulink, and the feasibility of the proposed strategy is verified in two case studies of power system frequency reduction and load fluctuation.