[Objective] The rapid expansion of grid-connected wind and solar power generation has created an urgent need for enhanced flexibility within power systems. The inherent variability and intermittency of renewable sources demand that traditional thermal power plants provide greater peak regulation capacity

a requirement that often exceeds the inherent operating limits of conventional units. In order to improve the flexibility of thermal power units

an optimization scheme for steam extraction and peak regulation of thermal power units based on phase change material(PCM) heat storage system is proposed. [Methods] The research is grounded in a practical case study

utilizing the detailed operational parameters of a 350 MW supercritical thermal power unit located in western China. A comprehensive simulation model was developed to couple the PCM heat storage system with the thermodynamic cycle of the reference power plant. This model enabled a systematic parametric study to evaluate the influence of two key factor groups: the thermophysical properties of the PCM itself and the structural design parameters of the heat exchanger that facilitates the energy transfer. [Results] The simulation results provide clear and actionable insights. Regarding material selection

erythritol was identified as the most effective PCM among the options studied

delivering a superior heat storage capacity of 18.70 MW

which improves the peak regulation performance of thermal power units. The structural optimization of the heat exchanger proved equally important. By reducing the tube diameter from 0.20 m to 0.05 m and simultaneously increasing the number of tubes from 200 to 3 200

the enthalpy difference of the reheated steam was boosted dramatically from 204.72 kJ/kg to 448.72 kJ/kg. A preliminary techno-economic analysis was conducted to assess the viability of the proposed system. The cost breakdown reveals that the capital investment is predominantly driven by two components: the heat exchanger

which accounts for approximately 58.9% of the total cost

and the PCM material combined with its storage tanks

which represent about 35.2%. [Conclusion] In conclusion

this study demonstrates that integrating a PCM thermal energy storage system is a technically viable and promising strategy for unlocking the flexible operation potential of existing thermal power infrastructure. The findings offer a solid theoretical foundation

detailed technical guidance on parameter optimization for power units

and an initial economic framework

thereby providing essential support for the practical implementation of such retrofits. This work helps reduce the use of fossil fuels and advance the deep integration of renewable energy around the world.