Research On On-line Adaptive Optimal Dispatch For Thermal System

Optimal dispatch for thermal systems is an applied technology which is produced by combination of thermodynamics and operation research. By this means, the optimal dispatch scheme for a thermal system is determined under the constraint of current power and heat loads according to an analysis of the system so that the total energy consumption can be minimized, thus contributing much to energy saving in an industrial enterprise. The paper concerns thermal systems of a main piping structure used in the petrochemical or electric power industry. In this paper, the conventional optimal dispatch approach is introduced first and its inability in application is pointed out on the basis of an analysis of the corresponding optimal dispatch model. Therefore, on-line adaptive optimal dispatch is put forward with the need of improving the automatization level of power stations, and some major problems involved are discussed in details in this paper.First, as to the problem of modeling a steam turbine's performance, the on-line identification strategy, which is carried out with the help of real-time operation data, is put forward so that the model gained by this strategy can susbtitute the theoretical off-design model of poor accuracy in application. And then, the steps of identifying a steam turbine's performance on line are introduced and various on-line identification methods are summarized. Thereafter, the applicability of these methods and the accuracy of the corresponding models for a steam turbine are compared and analyzed, and the applicable method used in on-line adaptive optimal dispatch is finally determined. The accuracy of modeling a steam turbine's performance in this way is proved through field testing.Second,a computer program used for on-line adaptive optimal dispatch is provided which considers the actual need during the period of carrying out optimal dispatch for thermal systems. In this program, the constraints in the optimal dispatchmodel are extended for the purpose of universalization. On the issue of optimal dispatch algrithms, the Branch-and-Bound & Back-Tracing algorithm is used to solve the 0-1 mixed integer linear programming problem encountered in optimal dispatch for the steam turbine subsystem, and the DSFD algorithm is used to solve the nonlinear problem encountered in optimal dispatch for the boiler subsystem. By comparision and analysis of optimal schemes gained by the conventional optimal dispatch method and the on-line adaptive optimal dispatch method, the conclusion is made that the inacuracy of the theoretical off-design model of a steam turbine is the important factor that results in the ineffectiveness of the conventional optimal dispatch method in application. Finally, on-line adaptive optimal dispatch is used for some thermal systems of a main piping structure in operation. Some optimal dispatch regulations are summerized according to the optimal dispatch scheme, which brings much benefit to operation and design of thermal systems.