Nonlinear stability and dynamic characteristics of hydropower station under fluctuation of downstream channel water level

Abstract

This paper aims to investigate the hydropower station with downstream channel (HSDC) and reveal the effect of fluctuation from downstream channel on its stability and dynamic characteristics under load disturbance. Firstly, a novel mathematical model of HSDC considering the fluctuation of downstream channel water level is established. Then, the stability and dynamic characteristics of HSDC are analysed by Hopf bifurcation. Finally, it is revealed that the effect of the fluctuation from downstream channel water level on the stability and dynamic characteristics of hydropower station. The results indicate that the HSDC is a supercritical system, and the stable domain is on the lower left to the bifurcation line in K p -K i plane. Considering the fluctuation of downstream water level, the stable domain of HSDC is wider than the reference where downstream channel water level is constant. The fluctuation of downstream water level has two-sided effect on the dynamic characteristics of HSDC, which makes the attenuation rate lager but setting time longer. Moreover, the more obviously the downstream water level changes with flow, the stronger the influence on stability and dynamic characteristics of HSDC are. Therefore, it is safer to design hydropower station and select the parameters of governor according to constant water level in engineering.