Generalized Turbine Model Based Analysis and Simulation of Ultra-Low Frequency Oscillation of Hydropower Units

Abstract

Abstract The occurrence of ultra-low frequency oscillation (ULFO) events in the power grid has a significant number of hydropower units in recent years. Considering this aspect, relevant studies have shown that the turbine model has an important impact on the ULFO behavior of hydropower units. Based on the study of the generalized turbine model, the flow factor closely related to the inherent parameters of the turbine and the variation of the generating flow is defined in this paper. The ULFO model of the hydropower unit with full consideration of the flow factor is established. Based on the frequency characteristics of the system and the Routh stability criterion, the mechanism of the influence of the flow factor on the ULFO behavior of the hydropower unit is analyzed. The simulation results of single-machine and multi-machine systems show that, compared with the ideal turbine model, the generalized turbine model considering the flow factor can increase the stability margin of the system. It can provide greater damping torque and restrain the ULFO behavior of hydropower units. The flow factor is larger, and the suppression effect of the ULFO is more obvious.