Stability control strategy study of Gaoling BTB HVDC project on PSCAD

The capacity of Gaoling BTB HVDC project reaches 3000MW, while the North China side of the project is weak in structure. It is a typical case of massive DC power feeding into weak AC systems. The study of its stability control strategies is unique. In this paper, a stable operation limit and security control measures after severe faults in the DC and nearby AC system is developed by comparing the simulation results on BPA and PSCAD. The unbalanced DC-AC system results in severe voltage stability problems during the implementation of the strategy. An integrated method of DC power reduction with AC filter fast switching is proposed to inhibit overvoltage and to improve transient stability of the DC-AC system. All the security and stability control strategies has been applied in the Gaoling BTB project.