Efficiency based optimal control of Kaplan hydrogenerators

This paper investigates an optimal strategy for controlling the speed response of Kaplan hydrogenerating systems to decreases in load. Typically, primary control gates restrict and redirect water through the turbine to stabilize and transfer the system to operating point demand. The adjustable turbine blade angle is used to return to maximum operating efficiency at the new load level. The over-speed reduction is limited by the conduit´s ability to withstand the over-pressure caused by the flow restriction at the turbine. A control scheme using gates and blades simultaneously and independently is developed. Simulation results show that the proposed scheme outperforms the traditional gate-dominant control in minimizing turbine over-speed and speed settling time under prescribed load change and conduit pressure limits. However, in its present form, the design is found to be more sensitive to system nonlinearities than its conventional counterpart