Grid-connected wind turbines for frequency support of the grid is conducive to improving the grid frequency security level. Grid-following (GFL) converters and grid-forming (GFM) converters are two important types of equipment to support renewable energy integration into the grid. Both GFM and GFL have a variety of different control strategies when performing frequency support. Clarifying the relationship be-tween different strategies of GFM and GFL when performing frequency support will provide guidance for renewable energy frequency support. In this paper, four levels of frequency support uniformity are first established at the generation unit level. (1) The governor and damping branch of the virtual synchronous generator (VSG) control based GFM converter are unified. (2) The VSG based GFM and the droop based GFM are unified. (3) Integrated inertial control based GFL and droop based GFL are unified. (4) The frequency support control link between GFL and GFM is unified. Finally, the theoretical analysis is synthetically verified by MATLAB/Simulink simulation platform.

Grid-following,grid-forming,frequency support,unity,wind turbine,virtual synchronous generator