Stability analysis of nonlinear hydroelectric power generating system in the transition of sudden load decrease

This article presents the modeling and the dynamical behavior of a nonlinear hydroelectric power generating system with surge tank effects and its stability in the case of sudden load decrease. A novel seven-dimensional nonlinear model of the complex hydroelectric power generating system with surge tank effects is proposed. Six nonlinear partial derivative coefficients of sudden load decrease are introduced into the generating system. The numerical results are analyzed by the Adams-Bashforth-Moulton algorithm, and the nonlinear dynamic characteristics of the system variables and PID governor parameters are investigated, particularly using characteristic diagrams to discuss the stability of the nonlinear system from the viewpoint of engineering. Involving the surge tank effects, the generating system keeps steady when the range of the governor parameterkdis less than 7.9 s. The increment of the governor parameterkpcan extend stability regions of the governor parameterkd. In addition, the system remains unsteady when the engager relay time constantTyis less than 0.1 s, but when it is more than 0.1 s, the system sustains a steady state. Finally, the analytical results provide principal references for studying and operating hydroelectric power stations during sudden load decrease.