LAUSR

Abstract This paper investigates the multi-frequency dynamic performance of hydropower plant (HPP) under coupling effect of power grid and turbine regulating system with surge tank. Firstly, a model of grid-connected HPP with surge tank is established and verified. Dynamic performance of grid-connected HPP with surge tank is evaluated by analyzing stability and dynamic response. Then, the number of frequencies of dynamic response is identified. The generation mechanism of multi-frequency dynamic response is revealed. Finally, the influence of system parameters on multi-frequency dynamic performance is studied. Guidance for actual applications of the obtained law and mechanism is proposed. The results indicate that the dynamic response of grid-connected HPP with surge tank has a feature of multi-frequency. There are three frequencies for the dynamic response corresponding to three subwaves i.e. mass oscillation, water hammer oscillation and grid disturbance oscillation. Low-frequency mass oscillation is induced by water flow and level oscillation in subsystem of headrace tunnel and surge tank. Medium-frequency water hammer oscillation is induced by natural hydraulic oscillation in subsystem of penstock, turbine, governor and generator. High-frequency grid disturbance oscillation is induced by power grid. The coupling effect among penstock, turbine unit and power grid on water hammer oscillation is strong.