The operational flexibility of coal-fired power plant is very important for the integration of large-scale renewable energy to the grid. In order to increase the operational flexibility of coal-fired power plant, a 600 MW subcritical coal-fired power plant was selected as research example to analyze the influence of steam extraction parameters and operation load by simulation. A novel main steam extraction system was proposed to adjust the power output under the low load period. The sensible and latent heat of the extracted steam was stored in molten salts and phase change materials, respectively, during the load reduction process. While the stored heat was reused again to heat the feed water and condensate water during the load raising process. The 50% rated load (300.03 MW) of the unit was used as the research benchmark to further adjust the load. The results show that the proposed steam extraction system can improve the operational flexibility of coal-fired power plant. The power output can be reduced to 204.51 MW from 300.03 MW when the main steam extraction mass flow rate is 250 t/h during the load reduction process. The sensible heat storage power factor and the operation load of the unit can affect the power output increment of coal-fired power plant during the load raising process. Under the condition of the maximal sensible heat storage power factor is 0.2462, the power output can be increased to 325.47 MW from 300.03 MW when the bypassed feed water mass flow rate of 251 t/h was heated by the stored heat during the load raising process. Using such operation model, the coal-fired power plant can achieve the maximum deep peak shaving time of 8.4 h/d, and its equivalent thermal efficiency is increased by 2.28%. With the same stored thermal energy to heat the bypassed feed water of 308.65 t/h, the power output can be increased to 394.2 MW from 360.07 MW (60% rated load) at the same sensible heat storage power factor of 0.2462 during the load raising process, and the coal-fired power plant can achieve the maximum deep peak shaving time of 9.86 h/d with its equivalent thermal efficiency increase of 2.55%. The results show that the proposed steam extraction method can make the unit operate in the lowest stable load and provide a wider renewable energy access space below the minimum stable load. The research provides a theoretical guidance for the flexibility design of coal-fired power plant, especially suitable for the large-scale renewable energy access to the grid in China.

燃煤电厂的运行灵活性对于大规模可再生能源并网非常重要。为提高燃煤电厂的运行灵活性，以600 MW亚临界燃煤电厂为研究实例，通过仿真分析了抽汽参数和运行负荷的影响。提出了一种新的主​​抽汽系统来调整低负荷时期的功率输出。在减载过程中，提取的蒸汽的显热和潜热分别储存在熔盐和相变材料中。而在负荷提升过程中，储存的热量再次被重新用于加热给水和冷凝水。50% 额定负载 (300. 以机组03 MW)为研究基准，进一步调整负荷。结果表明，所提出的抽汽系统可以提高燃煤电厂的运行灵活性。在减载过程中，当主抽汽质量流量为250 t/h时，功率输出可从300.03 MW降低到204.51 MW。显热蓄热功率因数和机组运行负荷会影响燃煤电厂在负荷提升过程中的出力增量。在最大显热蓄热功率因数为0.2462的条件下，当旁通给水质量流量为251 t/h的旁路给水质量流量为251 t/h时，在提升负荷过程中通过蓄热加热，功率输出可从300.03 MW提高到325.47 MW . 使用这样的运营模式，燃煤电厂最大深度调峰时间可达8.4 h/d，等效热效率提高2.28%。以相同的储存热能加热旁通给水308.65 t/h，在相同显热蓄热功率因数0.2462的情况下，功率输出可以从360.07 MW（60%额定负载）增加到394.2 MW。燃煤电厂最大深度调峰时间为9.86 h/d，等效热效率提高2.55%。结果表明，所提出的抽汽方法可以使机组在最低稳定负荷下运行，并在最低稳定负荷以下提供更广阔的可再生能源接入空间。该研究为燃煤电厂的柔性设计提供了理论指导，