Abstract
The dynamic processes of the coupled hydro-turbine-governor system and water diversion system are complex. An inappropriate design and regulation may result in poor regulating quality and even unstable operation. This study focused on the stability characteristics of the ultra-low frequency oscillation of hydropower plants caused by the water level oscillation in surge tanks during regulation. The coupled system was divided into the turbine-governor-penstock subsystem (TGPS) and surge tank-headrace tunnel subsystem (STHS) and their magnitude-frequency characteristics were presented respectively. Based on the two subsystems, the stability mechanism of the coupled system was explained by using the oscillation superposition method and a physically based and quantified criteria “superimposed magnitude” was proposed. Then, the influence mechanism of some dominant factors on the regulating stability were analyzed. The results indicated that the stability characteristics depended on the superimposed magnitude of the coupled system. When the superimposed magnitude of the combined TGPS and STHS is greater than 1, the oscillation continuously enlarges and results in instability. Meanwhile, the value of the superimposed magnitude can quantify the regulation quality. Furthermore, increasing the surge tank area or head loss coefficient of the headrace tunnel can reduce the superimposed magnitude, resulting in the improvement of system stability.
Published Version
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