Research on Auto-Coupling PID Control Method of Firing Rate to Feed Water Ratio System of Supercritical Unit

ObjectivesAiming at the problems of strong coupling, large load, and weak disturbance resistance in the firing rate to feed water ratio (FR/FW) control process of supercritical units, a new type of auto-coupling PI (ACPI) control method is proposed based on the theory of auto-coupling PID control.MethodsThe multivariable FR/FW system is equivalent to multiple single-variable closed-loop systems, and all complex factors such as the coupling, known or unknown internal dynamics, and external disturbances of the FR/FW system are defined as total disturbances. Then, the FR/FW control system is equivalently mapped to a linear disturbance system, and a controlled error system under total disturbance excitation is constructed. Based on this, a speed factor based ACPI controller is designed for each single variable system, and the robust stability and disturbance resistance of the control system are analyzed in the complex frequency domain theory.ResultsCompared with PI and active disturbance rejection control methods, the ACPI control method has fast response speed, dynamic quality without overshoot, and strong steady-state performance with strong disturbance resistance.ConclusionsIt is of great significance to improve the control accuracy and robustness of the FR/FW system in supercritical units.