Abstract: This study conducts operation stability tests on a large Francis hydropower unit in four start-up modes–large acceleration open loop start of guide vanes, small acceleration open loop start of guide vanes, closed loop start of unit acceleration control, and open-plus-closed-loop start. We analyze and compare the stability of unit operation in these modes comprehensively. The results show that considering start-up time and unit stability, the first mode above is best. This study lays a basis for selecting and optimizing the start-up mode of Francis turbines.

Key words: Francis hydropower unit, start-up mode, optimized control, stability