To accommodate grid-connected large-scale renewable power

coal-fired power plants need to undertake more peak shaving and frequency regulation tasks

so it will engage in the processes of deep peak shaving and load cycling for a long time. In this situation

the performance of wet flue gas desulfurization system(WFGD) will degradation and the auxiliary power consumption will increase significantly. To solve this problem

the dynamic model of an ultra-supercritical 660 MW coal-fired power unit and the dynamic model of the WFGD system based on the double-membrane theory are established. The performance of the desulfurization system is simulated when the slurry circulation pumps are switched under different operating conditions during the load cycling processes. It is found that the precise matching of slurry and flue gas during load cycling processes can achieve the minimum power consumption of the desulfurization system while meeting the SO_2 emission standard.Furthermore

when the slurry circulation flowrate changes stepwise during load cycling processes

the prediction model of changes in SO_2 mass concentration at the WFGD system outlet is obtained. An optimization control strategy for the slurry circulation pumps in fixed-frequency mode is proposed

which can achieve the best match between the slurry and flue gas during load cycling processes. Finally

the energy saving potential for the proposed control strategy is analyzed. When the load cycling rates are 1.0%

1.5% and 2.0% Pe/min

the energy saving potential is 20.12%

21.52% and 22.82% during loading down processes from 75% THA to 50% THA conditions

and that value will be 10.04%

9.90% and 8.66% during loading up processes

respectively. The difference in flue gas flowrate during load cycling processes is found as a key factor causing the disparate of energy saving potential during loading down and loading up processes.