Multivariable Control Systems Optimization For Thermal Power Process

Thermal power plants are essentially complicated multivariable systemsand have strong coupling among variables. It is clear that the parametersoptimization becomes the key difficulty in operation. So the study on a kindof general and effective optimization method for multivariable controlsystems has great significance for improving the economic and safe runninglevel of thermal power processes. Under the general framework provided bygenetic algorithm, this paper deals with the control system optimization ofsingle variable system and multivariable system. The main contributions ofthe paper are as follows:1. Improve the optimization and evaluation method of single variablecontrol system. By combining the information of stable parameteric regionand robust stable space with genetic algorithm, the search effiency of geneticalgorithm optimization on single variable control system is greatly improved.The robust performance of resulted uncertainty system is evaluated throughMento-Carlo method, and this evaluation criteria is comfortably extended toother control methods.2. Based on integrity analysis, a kind of optimization method formulti-loop control systems is proposed. To achieve the optimized performanceon the multi-loop control system, the genetic algorithm and integrity theoryare used simultaneously in parameter optimization. Simulation results showthat the performance of the optimized system has been improved notably. Itonly requires that the objective function can be calculated numerically, andwith the increase of system dimention, the workload of the optimization hasnot obviously increased.3. A kind of optimization method is proposed for multivariable controlsystem with multi-objective, multi-disturbance and multi-model. For thestructure-specified multivariable system, by defining the objective function,which contains the multi-objective, multi-disturbance and multi-model, theoptimization problem is formulated and solved using genetic algorithm. Theproposed method is generally suitable for parameter design of complicatedthermal process control system, which has hybrid control requirements andconstraints.4. The proposed method is applied to several typical multivariablethermal processes: turbine-generator sets control system, boiler-turbinecoordinated control system and gasifier benchmark problem. The controlstructure adopted is easy to realize in practice, and the objective functions aredefined to refect the integrated demands respectively according tocharacteristics of each system. The simulation results show that the proposedmethod is quite suitable for the optimization of multivariable thermalprocesses, owing to good control performance and the feature of feasibilityand generolity.And in the last part, a comparison between the identification accuracy ofsaturation relay and standard relay feedback idenfication method isquantitively drawn on four kind of typical thermal objects. Then it is clearwhen and how much the saturation relay feedback method can make animprovement on the identification accuracy.