Uniformity Analysis of Frequency Regulation for Grid-Following and Grid-Forming Wind Turbines and Distributed Cooperative Frequency Control for Hybrid Wind Farms

Large numbers of grid-connected wind farms challenge frequency stability. Hybrid wind farms (HWFs) with both grid-following (GFL) and grid-forming (GFM) wind turbines (WTs) are better adapted to wide-ranging changes in grid state. However, the frequency support capability of each wind turbine in an HWF depends on factors like wind speed and control type. Current controls do not fully exploit the grid frequency support potential of each WT in different states. Hence, this paper first analyzes the frequency regulation characteristics of GFL WTs and virtual synchronous generator (VSG)-based GFM WTs, revealing the uniformity between them. Furthermore, a distributed cooperative frequency control (DCFC) for HWFs is proposed to improve grid frequency stability. DCFC uses a leaderless consistency algorithm to allocate the output active power of each wind turbine according to the state of the different WTs. Additionally, the adaptive optimisation feature of DCFC adjusts the frequency support coefficients of the wind turbines in real time as their rotor kinetic energy varies, improving the safety of the WTs. Finally, the GFL and GFM frequency regulation uniformity theory and the DCFC are comprehensively verified. The results show that DCFC improves the security of the WTs and enhances the frequency support capability compared to centralised control.