Enhancing the frequency regulation performance of coal-fired power plants under deep peak shaving conditions by coupling external heat into the regenerative systems

With the increasing penetration of intermittent renewable energy sources in the power generation system, coal-fired power plants have to operate in deep peak shaving conditions frequently. Since the frequency regulation capability of coal-fired power plants under low load conditions is limited, increasing the load cycling rate is necessary, and coupling external heat storage to the thermal system to enhance the transient response rate is a good choice. This paper established and validated a dynamic model of a 660 MW ultrasupercritical coal-fired power plant. The transient performance of the power unit during load cycling was simulated and analyzed based on the dynamic model. Therminol VP-1 was used as the thermal source to release heat to the water via an oil-water heater during the power plant loading up from 30% to 50% THA. When the feedwater output temperature remains unchanged, the amount of steam extracted by the high-pressure heater will be reduced, and the output power of the turbine unit can be increased. The simulation results show that the load cycling rate of coal-fired power generation under the peak shaving conditions can be improved from 2.2% to 3.5% Pe min^-1. At a load cycling rate of 2.0% Pe min^-1 and a Therminol VP-1 flow rate of 100 kg s^-1, the coupled thermal storage system reduces the maximum relative deviation of the output power by 11.8% and improved the whole plant thermal efficiency difference by 0.15%.