A Study On Predictive Functional Control Technology And Its Applications In Thermodynamics Measurements And Control

The theories and applications of Predictive Functional Control (PFC) are studied in this dissertation.Firstly, the general principles of predictive control method are introduced systematically, and a survey on the development, status and industry application of predictive control method is given. On the basis of the general principles, PFC method based on the state space model is discussed and the algorithm for first-order plus pure delay process is proposed particularly. It is shown from the algorithm that it has less online calculations, and simulation examples illustrate that the PFC method also has the following advantage: high control precision and disturbance attenuation et al.Secondly, according to the characters of the thermal engineering processes in thermal power plant, the static and dynamic characteristics of main superheated steam is introduced and analyzed simply. A typical application of three-stage temperature reducer for superheated steam is presented in detail. Superheated steam temperature control system is a system with large time constant, longtime-delay, slow time-varying and various of disturbance factors, traditional PID cascade control generally can't satisfy the performance requirement. Therefore, PFC-PID cascade control strategy is adopted.Then, PFC-PID cascade control strategy is implemented into a superheated steam temperature control system of a certain boiler unit with 300MW power in thermal power plant. The control algorithm is combining PFC with PID control referred to Smith forecast estimate delay system, its internal loop of the system adopts PID control strategy, and internal loop and superheater constitute generalized control plant of PFC. It is simple because predictive model of PFC is first-order plus pure delay model which is gained by matching generalized plant. The results of simulations show that the advanced control strategy has more favorable dynamic characteristics than PID cascade control strategy, good robustness and disturbance rejection. Furthermore, the system with unmatched model still has favorable quality. And this temperature control system is well adaptive to the alteration of the unit's load and meets the deigned requirements.Finally, the PFC research in this dissertation is summarized and the further research directions about PFC are discussed. So it has hopeful application prospect.