Hydro Unit Active Power Controller Minimizing Water Hammer Effect

This paper investigates optimal control of hydro unit active power. The dynamics of hydraulic turbine as control object is characterized as non-minimum phase with transients dominated by the water hammer effect, characterized by alternating pressure waves in conduits leading to active power change in the opposite direction to the control action. The research focuses on design and tests of controller with optimal exponential control law minimizing active power initial negative excursion due to above mentioned water hammer phenomenon. Developed optimal controller incorporates the control action rate calculation and guide vane speed limitation, therefore is suitable for implementation in real control systems, i.e. speed governors and AGCs. The article presents the comparison of proposed control law and linear one. The optimal set points of controller were derived and validated with the help of nonlinear model of hydro unit. Field tests along with simulation proved its better performance than existing active power controllers in terms of overshoot minimization.