Multivariable constrained predictive control method based on MHE of circulating fluidized bed boiler unit

To improve the load-following capability of a circulating fluidized bed boiler (CFBB) unit, a new multivariable constrained predictive control method based on MHE is proposed in this paper. This method takes the primary air as another new control variable into the AGC control of CFBB unit, which can take advantage of the unburned carbon in bed to improve its load-following capability. With the theory of zone control introduced to the control of bed temperature, the engineering requirements are met. Simultaneously, a multivariable predictive control method based on augmented state space model is designed which introduces moving horizon estimation (MHE) to increase the estimation accuracy of system unmeasurable state. Finally, to improve the performance of predictive control algorithm, linear-parameter-varying model is proposed to describe prediction model of control algorithm which can deal with the non-linear characteristics of the plant preferably. The simulation results for a 330MW CFBB unit shows that the method proposed in this paper can significantly improve the load-following capability and have great anti - perturbation performance and robustness. Meanwhile, the zone control of bed temperature presents satisfactory control effect which can reduce the frequent movement of the controller.