Dynamic Stability Analysis of the Interconnected Power System with Mengxi UHVDC Integration

Due to the mismatch between power supply and demand, in addition with the increasingly prominent problem of environmental pollution, UHV AC/DC power transmission over long distance obtains rapid development in our country. With the expansion of the power grid, regional low frequency oscillation has become one of the major problems that endanger safe and stable operation of power system. In this paper, taking a large area interconnected system integrated with Mengxi UHVDC transmission line as the background, dynamic stability of the system is analyzed using small signal analysis method and time domain simulation based on PSASP under different load and UHVDC operating conditions. The results show that when DC out of running, weak damping will appear in the interconnected power grid. PSS is the most economical and effective equipment for damping low frequency oscillation, which can perform well to both the local mode and the inter-area one. In view of the existing weak damping mode, PSS parameters are optimized which effectively improve the system damping, thus insuring the safe and stable operation of the system after the UHVDC line access.