In the process of transitioning towards green and low-carbon energy

coal-fired units undertake a large number of peak shaving and frequency regulation tasks to mitigate the fluctuations brought about by the large-scale integration of new energy power into the power grid. This poses significant challenges for the stable control of the drum water level in the in-service subcritical units. An integral time-delayed active disturbance rejection control (ITD-ADRC) strategy is proposed for non-self-regulating process such as drum water level. Firstly

the process is approximated as an integral plus time-delayed nominal model. Then

the delayed link of the manipulated variable is introduced to synchronize the phase of the two input signals of the observer in the extended state. Finally

the stability region of ITD-ADRC parameters is accurately determined using the dual-locus method. Simulation results show that the proposed control method outperforms several other typical control algorithms in terms of set-point tracking

disturbance rejection

and robustness. Furthermore

based on experimental results from the feedwater system of a certain 600 MW subcritical coal-fired unit's simulator

it has been demonstrated that the proposed ITD-ADRC control strategy meets the quality requirements of power industry standards under both constant-load and load-varying conditions of the unit. Moreover

compared with the original cascade three-element proportional-integral-derivative (PID) strategy

the deviation of drum water level is smaller

with deviations of no more than 1.5 mm at constant load and no more than 2.1 mm at varying load. These results also indicate promising prospects of the proposed control strategy in terms of deep peak shaving and performance optimization for power plants.