Abstract: The new-type power system is subjected to a sharp increase in its unit regulation frequency under the Automatic Generation Control (AGC) mode, and long-term high-frequency alternating stress in a large-scale axial-flow Kaplan turbine runner causes fatigue damage to its key transmission components such as the operating frame and rocker arm. To meet the system’s operation demand and prevent such damage, this paper presents a systematic study on the fatigue prevention and control method and how to handle the key runner component emergency. We develop a three-dimensional simulation model of the operating frame and the rocker arm in the framework of the ANSYS Workbench finite element code, based on the real crack fault cases of key runner components at the Shawan and Angu hydropower stations on the Dadu River. The fatigue characteristics of core components under the AGC conditions are examined in detail, structural weak areas identified, and targeted optimization schemes suggested. We work out an emergency strategy for fixed-pitch operation of the Kaplan runners under the extreme working conditions that usually cause a failure of the runner transmission mechanism. Specific points for implementing engineering measures are clarified from the aspects of feasibility demonstration, blade angle selection, regulation mode adjustment, blade positioning technology, and operation & maintenance control. We have achieved a full-process technical system of "fatigue analysis–structural optimization–emergency disposal". Our results help the safe and stable operation of axial-flow Kaplan runners under the AGC mode, and would guide designing engineering measures for fatigue damage prevention and emergency handling of similar generating units.

Key words: AGC mode, axial-flow Kaplan runner, key components, fatigue analysis, structural optimization, fixed-pitch emergency operation