## 2 The TPUMSTSR Under RLV Model
### Operational Characteristics of Thermal Power Units After RLV Retrofit  
To meet the demands of RLVs, thermal power units require equipment, control system, and operational strategy modifications. For example, advanced burner designs and fuel supply systems can be adopted for boiler system retrofitting to improve combustion efficiency and stability during RLVs. According to [13], the ramp rate can be increased to 4% Pe/min when the thermal power high-pressure heater adopts throttling extraction. By optimizing the structure and materials of the boiler and cooling systems, thermal inertia can be reduced, enhancing the boiler's responsiveness to load variations. When the thermal power unit equipment material is upgraded (such as the use of high-temperature alloys), downtime can be reduced by about 15%; however, the initial transformation cost increases by 10-20%. In terms of control system upgrades, advanced control strategies based on artificial intelligence and model predictive control can be introduced to optimize the operational efficiency of the units under RLVs. When the revised control strategy is adopted, the ramp rate can be increased to 7.0% Pe/min, but the maintenance cost can be reduced by 10-15%. These measures enable RLVs, allowing for more timely responses to the variability of stochastic renewable energy generation [30].  
Through these technical modifications, thermal power units have acquired rapid ramping capabilities, significantly enhancing their output variation rates and enabling them to quickly respond to the CS load demands. Additionally, these units now possess a wide load operating range, allowing stable operation from low-load to full-load conditions, thereby accommodating the stochastic nature of wind and PV power generation. The RLV capability of thermal power units effectively compensates for the intermittency, improving the operational stability and regulation capacity of the CS.  
However, under RLVs, mechanical components such as turbine blades and bearings are subjected to greater thermal and mechanical stresses, leading to accelerated wear and increased lifetime degradation [31]. According to [32], the variable load rate is the main factor influencing equipment service life. Compared with the reference value, increasing the variable load rate by 50% reduces the life of the boiler drum and superheater by 31.9% and 52.9%, respectively, while decreasing the variable load rate by 50% compared with the reference value increases the life of the drum and superheater by 16.3% and 35.8%, respectively. Additionally, existing studies [33] indicate that coal consumption under RLVs undergoes significant changes compared with stable operation due to variations in the boiler's heat storage process and resource utilization during the production of main steam and reheat steam. During RLVs, adjusting the condensate water requires additional work from the pumps, and the operating efficiency of the boiler and turbine decreases, resulting in increased coal consumption. Therefore, although the output variation rate improves after RLV technical modifications, enabling them to respond quickly to system demands, coal consumption increases by approximately 5% [34], and the thermal stress shock of thick-walled components increases significantly, resulting in a shortening of the service life by approximately 15-20%.