Flexibility improvement method of coal-fired thermal power plant based on the multi-scale utilization of steam turbine energy storage

In order to achieve the large-scale grid connection of renewable energy, flexibility of the power generation system operation needs to be improved. The coal-based power supply structure indicates that coal-fired generating units are gradually becoming the main force of power regulation in China. However, the coal-fired power unit load regulation capacity requires significant improvement. Based on the energy storage characteristics of the coal-fired power unit, a load regulation method based on the multi-scale energy storage utilization is proposed. The method is based on the combination of feedwater bypass throttling and feedwater heater extraction steam throttling. The coal-fired power unit mathematical model is established and verified against the field tests, and simulation relative error is approximately 7%. Based on the mechanism mathematical model, the load coordinated controlled model is obtained. Moreover, the load response time of feedwater bypass throttling method is nearly 125 s longer than that of high-pressure heater extraction steam throttling method, the load command is decomposed by multi-scales, and the load regulation method based on the feedwater bypass and extraction steam throttling is proposed. The simulation results indicate that the proposed method is superior to the conventional control method. Furthermore, it can effectively improve the unit load flexibility.