Analysis of Ultra-low Frequency Oscillation Stability of Power Systems

The Low-Frequency Oscillation (LFO), Ultra-Low Frequency Oscillation (ULFO) and other oscillation can endanger the safety and stability operation of the power grid. However current relevant standards only have clear provisions on the critical damping ratio of LFO. Based on the risk of ULFO in high proportion hydropower systems, the principle and key influencing factors of ULFO are derived theoretically. According to the characteristics and hazards of ULFO, a method for determining the critical damping ratio of ULFO is explored, and the effectiveness of the method is tested through the actual response trajectory.