Dynamic modelling and thermo-mechanical performance evaluation of thermal power plants during the background of enhanced operational flexibility

To integrate the high penetration of renewable energy into the power grid, thermal power plants must expand their load variation range and rate. However, increased these operational flexibility leads to rapid fluctuations in thermal parameters, which induces stress variations that affect the safety of critical components within power plants, particularly steam turbine rotors. Consequently, monitoring rotor stress during dynamic processes is essential for the safe and reliable operation of power plants, which has been underemphasized in previous studies. In this study, a dynamic model of the power plant and an online stress calculation model were developed to assess the thermo-mechanical performance of the steam turbine rotor. The governing stage has been identified as the most critical area during peak shaving processes. The study reveals that as the load variation rate increases from 1.0 % to 4.0 % Pe min−1 during peak shaving processes from 50 % to 75 % THA, the stress amplitude at the governing stage escalates from 1.8 to 22.8 MPa. Furthermore, at a load variation rate of 2.0 % Pe min−1, increasing the peak shaving depth results in a rise in stress amplitude and fatigue damage from 3.7 MPa and 6.6 × 10−11 to 7.8 MPa and 3.0 × 10−9.