Influence of Power System Stabilizers on HVDC Control Systems in an Asynchronous Interconnection Power Grid

After the implementation of an asynchronous interconnection mode, the Yunnan Province power grid connects to the main network of the China Southern power grid through 7 high-voltage DC (HVDC) transmission systems. Based on results using a electromechanical transient simulation software and a real-time digital simulator, this paper reports that after serious faults such as HVDC monopole or multipole blocking, the remaining HVDC systems in Yunnan may exhibit an obvious power drop. This problem would not only result in a continuous power fluctuation but would also deteriorate the frequency recovery. Additionally, the reason for the problem is analyzed in this paper. Continuous regulation of power system stabilizers, which are affected by the frequency variations after the faults, leads to a voltage change in the Yunnan main stations and HVDC rectifier stations. The HVDC control system switches control modes and eventually results in a power drop. Furthermore, some measures for the functions and parameters of the HVDC control system are proposed.