SSO Suppression Priority Analysis of Multi-mode and Multi-condition Units in Large-Scale Direct-Drive Wind Farms

Existing method usually regard the whole direct-drive wind farm as a single turbine or use aggregated equivalent method, which ignored the inside-wind-farm sub-synchronous oscillation (SSO) modes and cannot analyze the stability difference of turbines under different working conditions. Firstly, the eigenvalue method is used to analyze the power system connected with multiple PMSGs, and found the system exist the "wind-farm-grid SSO modes" led by wind turbine and the power grid and the "inside-wind-farm SSO modes" led by DVC links of different wind turbines, Further, based on the root locus, it is judged that the priority of suppressing "wind-farm-grid SSO mode" is higher than that of suppressing "inside-wind-farm SSO modes". Then using eigenvalue method, found the SSO suppression priority of the PMSGs with weak output power or far away from the collecting bus is higher than that of the PMSGs with strong output power or near the collecting bus. It also gives emergency parameter adjustment and order cut-off scheme considering the suppression priority. Time-domain simulation based on PSCAD/EMTDC platform verifies the validity of the above conclusions.