Stability of speed regulating system of hydropower station with surge tank considering nonlinear turbine characteristics

The paper investigates the stability of speed regulating system (SRS) of hydropower station with surge tank (HSST) considering nonlinear turbine characteristics. Firstly, the model of HSST considering nonlinear turbine characteristics is established. Then, both the theoretical analysis and example analysis are carried out to comprehensively explain the rule and essence of SRS stability of HSST. Finally, the effect mechanism of nonlinear turbine characteristics on stability of the SRS of HSST is revealed by using contrastive analysis. The results indicate that the nonlinear turbine characteristics are composed of nonlinear head characteristics and nonlinear speed characteristics. The emerged Hopf bifurcation of SRS of HSST is supercritical. The nonlinear speed characteristics of turbine almost have no effect on the stability and dynamic response of SRS. The effect of nonlinear turbine characteristics on stability and dynamic response of SRS is mainly realized by the nonlinear head characteristics of turbine. For the stability of the SRS of HSST, the nonlinear head characteristics of turbine is favorable under negative load disturbance and unfavorable under positive load disturbance. The rules for dynamic response of comprehensive characteristics coefficient of turbine reveal the effect mechanism of nonlinear turbine characteristics on stability of SRS of HSST. (c) 2020 Elsevier Ltd. All rights reserved.