Dynamic characteristics for synchronous operation of two-stage cascaded hydropower plants under different water level feedback modes of regulating reservoir

Aiming at the problem of maintaining the water balance of cascaded hydropower plants under the limited regulating reservoir capacity, this paper studies the dynamic characteristics for synchronous operation of two-stage cascaded hydropower plants (TSCHP) under different water level feedback (WLF) modes of regulating reservoir. The main innovation lies in systematically revealing the influence mechanism of different WLF modes on the dynamic characteristics of TSCHP and clarifying the interaction between the first-stage hydropower plant (FSHP) and second-stage hydropower plant (SSHP). Firstly, the mathematical model of the TSCHP under different WLF modes of regulating reservoir is established. Secondly, the regulation of governors and WLF controller on dynamic characteristics is analyzed. Then, based on the original model, three contrastive models are designed. The effect mechanism of different WLF modes on dynamic characteristics is revealed. Finally, the interactions between the FSHP and SSHP on dynamic characteristics are studied from the perspective of hydraulic and mechanical parameters. The results indicate that: when the mode of WLF to the FSHP (SSHP) is adopted, the regulation of governor of the FSHP (SSHP) on dynamic characteristics of the TSCHP is more significant than that of governor of the SSHP (FSHP). The WLF controller plays the regulation effect on dynamic characteristics by regulating the dynamic response of water level. The governors regulate the discharge of the FSHP and SSHP by considering the change of water level. The differences of hydraulic and mechanical parameters between the FSHP and SSHP have a significant effect on the dynamic characteristics of the TSCHP.