Flexibility and efficiency co-enhancement of thermal power plant by control strategy improvement considering time varying and detailed boiler heat storage characteristics

Flexibility enhancement of coal-fired power plants is extremely urgent to accommodate high-penetrated renewable energy and maintain the stability of power grid. Cycling rate, an important aspect of operational flexibility of coal-fired power plants, is mainly dragged by the large boiler thermal inertia. The idea of this study is to enhance the flexibility of the power plant by clarifying and considering the time varying and detailed boiler heat storage characteristics. The dynamic simulation and control models of a double-reheat power plant are developed and validated. The time varying and detailed boiler heat storage characteristics are represented by the principal parameters obtained by using stepwise regression algorithm. The improved control strategy is proposed and its performances are examined. Results show that the improved control strategy can enhance load cycling rate from 9.9 MW min⁻¹ to 23.1 MW min⁻¹, and the accumulative standard coal consumption rate can be reduced by 0.47%. Moreover, the control parameters, including output power and steam temperature, can reach the target quickly and are accurately controlled. The improved control provides a detailed guidance for the trade-off between the flexibility and high-efficiency in power plants during load cycling processes.