To improve the flexibility of coal-fired units

boilers need to have good controllability and the ability to adapt to rapid load changes. The flexibility of the boiler is closely related to the performance of the control system

which is designed according to the dynamic characteristics of boilers. To study the dynamic characteristics of boilers

a dynamic model of a supercritical 660 MW coal-fired boiler is built in the Dymola platform. The results show that the response time of steam temperature is longer than that of steam flow. When the feedwater temperature

feedwater flow

and fuel quantity are stepped increase by 5%

the main steam temperature changes by 10.2 ℃

–28.5 ℃

and 35.7 ℃

respectively. In the process of adjusting the water-fuel ratio of the boiler

different times of change in feedwater and fuel flow can have different effects on the main steam temperature. The maximum deviation of the main steam temperature during the transient process reduces by 27.4 ℃ when the feedwater flow is delayed by approximately 100 s compared with the fuel flow. When the load change amplitude is the same

the larger the load change rate

the more severe the fluctuation of the main steam parameters

and the longer it takes to stabilize.