Analysis on damping characteristics of subsynchronous oscillation in Hulunbuir power plant

Since Hulunbuir-LiaoNing HVDC transmission project was put into operation, low amplitude subsynchronous oscillation had occurred frequently and exceedingly in Hulunbuir power plant, such problem was of serious concern to power plant and power system operators. This paper calculated the complex torque coefficients of the units in Hulunbuir power plant using complex torque coefficient method based on Complex Frequency Domain Port-equivalence Conductance Matrix (CPCM), analyzed the subsynchronous oscillation damping characteristics, built the simulation model of Hulunbuir AC-DC hybrid power system based on PSCAD/EMTDC, and verified the effectiveness of the analysis results using time-domain simulation method. Theoretical analysis and simulation results showed that the units' subsynchronous damping characteristics in Hulunbuir power plant were weak, therefore subsynchronous oscillation was easily stimulated by system disturbance but the convergence was weak. Analysis results can adequately explain why low amplitude subsynchronous oscillation had occurred frequently and exceedingly in Hulunbuir power plant.