Study of out-of-step oscillation characteristics for East China grid and applicability analysis of system separation scheme upon the operation of UHV Binjin DC transmission project

Fujian provincial grid was connected into East China grid through two parallel tie lines of 500kV in 2002. Out-of-step oscillation may occur between Fujian Province Grid and East China grid under the critical contingencies. System separation devices have been installed on 500kV tie-lines between Fujian grid and East China grid to maintain system stability. As the newly built UHV Binjin DC transmission system was projected to come in service in 2014, power injected into East China grid through the system was gradually increased to its full capacity in accordance with the implementation of the project by three stages. The characteristics of out-of-step oscillation between Fujian grid and East China grid may be altered due to the significant changes involving tie lines, reinforcement and reconfiguration of local system as well as the scale of power injection. To investigate the characteristics of out-of-step oscillation, extreme contingencies contributing to out-of-step oscillation are identified based on the analysis of the practical grid operation. For each stage of Binjin transmission project, the center of out-of-step oscillation is determined through the simulation analysis of the oscillation characteristics for East China grid. The applicability of the existing system separation devices is evaluated, and system separation strategy is then reviewed for East China grid to accommodate the operation of UHV Binjin DC transmission project.