Enhanced Frequency Control for DFIG WTs to Improve Transient Power Sharing with SGs

Abstract

This paper proposes an enhanced frequency control strategy for coordinating DFIG wind turbines (WTs) and synchronous generators (SGs) to serve for frequency regulation. The proposed control employs a correcting unit to make the frequency response of DFIG WTs collaborate with that of SGs. This enhances the adequacy of transient power sharing between them and meanwhile optimizes the frequency performance. This paper first clarifies the differences in frequency response characteristics of SGs and DFIG WTs which produce undesired mismatch in their power sharing. To mitigate such mismatch, the active power-frequency (P-ω) relationships of SGs and DFIG WTs are both established and then a frequency-coordinating droop control is proposed to reshape the frequency response of DFIG WTs. This improves the transient power allocation between SGs and DFIG WTs in terms of the power availability and responding duration. Finally, the validation regarding the effectiveness of the proposed control is conducted through time-domain simulations on a four-machine two-area system.