Analysis of Ultra-low Frequency Oscillation in Hydro-Dominant Power System and Turbine Governor Side Suppression Strategy

After asynchronous operation, the Southwest Power Grid has the risk of ultra-low frequency oscillation, which seriously threatens the stable operation of the power grid. Based on the hydropower single-unit with load system, the extend Philips-Heffron model is built considering PSS/GPSS. Then, the damping torque analysis is carried out in the both prime mover and excitation side. The negative damping in the prime mover side is prominent in the ultra-low frequency band, then the effect of damping increase by PSS and GPSS is compared. After that, the small signal analysis of the whole system is conducted and the participation factors of the ULFO mode shows the high participation and controllability of GPSS channel. At last, the proper GPSS parameters configured by small signal analysis are equipped in the hydro unit of asynchronous four-machine two-zone system which reveals an obvious ULFO suppression effect.