Smith Predictive Decoupling Control Strategy for Combustion Process of Power Boiler

In view of the characteristics of coal-fired boiler, such as multivariable coupling, large lag and nonlinearity, a Smith predictive decoupling control strategy was proposed. Taking the coal injection rate and air supply rate as the input quantity, the main steam pressure and the oxygen content of exhaust gas as the controlled quantity, the two coupling regulating circuits of main steam pressure and oxygen content of exhaust gas in the control system of the coal-fired power generation boiler were decoupled into two independent regulating subsystems. A Smith predictor compensator was designed to compensate and correct the hysteresis in the decoupled subsystem. The simulation results show that compared with the feedforward compensation synthesis method, when the system is operated for 1 000 s and the main steam pressure loop is interfered, the main steam pressure regulating time is reduced by 208.33 s, the overshoot is reduced by 23.83%, the regulating time of exhaust oxygen is reduced by 90.91 s, and the overshoot is reduced by 3.50%. When interference is added in the flue gas oxygen loop, the regulating time of main steam pressure is reduced by 166.66 s, the overshooting amount is reduced by 20.80%, the regulating time of smoke oxygen content is reduced by 166.66 s, and the overshooting amount is reduced by 7.51%. The engineering application shows that the fluctuation range of main steam pressure is set value±0.3 MPa, and the fluctuation range of smoke oxygen discharge is set value±0.5%. Therefore, the proposed control strategy has good control effect and can meet the actual requirements of coal-fired boiler control.