Stress Impacts on Turbo-generator Shaft in Inverter- Dominated Power System

The large-scale integration of renewable energy (RE) in form of inverter-based resources (IBRs) have posed concerns on required level of rotational inertia in power systems. Gradual decrease of rotational inertia, intermittent nature of renewables and frequency instability issues have raised the occurrence and severity of the rate of change of frequency (RoCoF) events in power system. Design considerations of grid-connected synchronous generators are not adhered to severe RoCoF, thereby leading to mechanical stress on turbine shafts. Impact analysis of this kind is of potential use to generation utility owners and transmission system operators for planning utility activities and reliability. This study investigates the impact of IBRs on a turbo-generator (TG) shaft in modified IEEE-14 bus system. Utilizing a 300 MVA synchronous machine with TGOV4 governing model as a case study, torques induced by varying active power in steps were analyzed and applied to a multi-mass model. The resulting torques were then subjected to structural analysis to identify structural deformations. The findings highlight considerable stress impacts on high-pressure turbine shaft, emphasizing the challenges for turbo-generators in IBR dominated power grids.