Study On Predictive Control Applied To Coordinated Control System In The Units

The predictive control algorithm is a kind of advanced control algorithm, which is gradually developed in the environment of high control requirements about complex and uncertain system, compared with other major advanced control algorithms, its super advantage is:the low dependence on model, capable of advanced, large-scale prediction and it is prone to integrate other intelligent control algorithm. Those advantages can effectively resolve some problem exist in the controlled process of thermal power system, such as coupling, uncertainty, time-varying and nonlinear.In this paper, the application of predictive control in thermal power system is studied and analyzed in detail. Firstly, in the practical process of product, operating condition of the unit plant often change in a wide range of operating circumstances. There will be an obvious feature of nonlinear characteristics in boiler controlled process related with load condition. In this paper, an algorithm of general predictive control (GPC) based on multiple-model is presented. On the basis of each local model of typical operating regimes, with each local GPC controller, appropriate control increment is obtained by weighting of the local controllers according to the change of the real operating condition. Meanwhile, this method is also applied to coordinated control system of unit plant of 500MW coal-fired drum type boiler in direct-fired system, and a good control effect have been collected. Secondly, with the double aims of high require of real-time and pursuit of beneficial result, supervisory predictive control (SPC) based on GPC theory is studied in this paper. In this study, the basic algorithms of SPC have been firstly introduced and certified its economical efficiency and decoupling by 300MW and 500MW unit plant. On the other hand, to simplify the derivation of the algorithm paper uses recursive idea to retrieve predictive model, and to improve its operation optimization time, Off-line approximate computation strategy is introduced in SPC. And then, multivariable fast supervisory predictive control (FSPC) is presented. Furthermore, this improved algorithm is applied to 500MW unit plant of coordinated control system. The simulation results show that the improved algorithm is effective.