Effect of the coupling between hydraulic turbine set and power grid on power grid dynamic stability

With the proportion of hydroelectric power station in power grid and the single-turbine capacity larger and larger, the effect of hydraulic turbine set on power system dynamic stability will be more significant. The power oscillation phenomenon, which affects the safe and stable operation of power system, occurred many times in China. For example, on October 29th, 2005, low frequency oscillation occurred in Central China Power Grid. The most of researches on the hydraulic turbine system and power system were carried out independently in the past. First, according to the physical characteristics of the draft tube hydraulic system, the hydraulic turbine set model considering the draft tube hydraulic pressure dynamic was established in this paper. Secondly, based on the single machine infinite bus system, the effect of draft tube hydraulic pressure pulsation on the power grid dynamic security and stability was studied and the coupling between the hydraulic turbine set and power grid was investigated. Thirdly, taking Zhelin Hydropower Plant in Jiangxi Power Grid as an example, the influence of the draft tube hydraulic pressure pulsation to power grid stability was illustrated in this paper. The loads of unit 5, 6 at Zhelin hydropower station have a wide range of vortex operating conditions, about 20~100 MW. In this case, the vortex frequency will enhance as the loads of vortex operation conditions increase.