Research On Flexible Control Method Of Complex Time-varying Object

At present,flexibility modification of existing heating units is the main technical measure to solve the following three problems: the first is to break the time and space coupling of electricity and heat for achieve "heat and electrolysis coupling",the second is to improve the comprehensive energy utilization efficiency,and the third is the main technical measure to achieve energy saving and emission reduction.It is more complex that the equipment structure and operation mode of the modified unit.Taking a typical unit as an example,there are many operating conditions,such as conventional pure condensation,deep regulation pure condensation,conventional heating,industrial steam extraction heating,zero output deep regulation heating of low pressure cylinder,deep regulation heating of high and low bypass steam extraction,and so on.Under different working conditions,there are significant changes in the structure and control objectives of the controlled object.It has become the main problem in the design of the control system that improving the adaptability of changing working conditions,changing targets and changing coal quality.This paper studies a flexible control method for this kind of complex,multivariable and time-varying objects,which can automatically and flexibly adjust the working state of the controller according to the above constraints.It can reduce the complexity of the control system,improve the adaptability of the control system,and improve the input rate of automatic control under various operating conditions.The main tasks are as follows:(1)On the basis of the two-in-two-out simplified nonlinear model of the typical subcritical unit,the flexible equipment and system are modeled layer by layer by the mechanism analysis method,and it are obtained that the four-in-four-out,five-in-five-out and six-in-six object models for different operating conditions.According to the flexibility of 300 MW,the heating unit is reformed,the model example is established,and the operating range of each working condition is determined.(2)Based on the analysis of the traditional coordinated control system,it is summarized that the technical improvement measures to improve the adaptability of the coordinated control system in engineering,and the working point linearization and dynamic coupling characteristics are simulated and analyzed with the model.a design scheme of flexible coordinated control system is proposed,which can adapt to the change of complex working conditions.The scheme adopts a two-layer structure,the lower layer is the traditional coordinated control layer,and the upper layer is the flexible optimization layer.The flexible optimization layer determines the working mode of the object according to the setting,feedback and control output state of the coordinated control layer,and constructs the variation interval of the flexibility factor to adjust the dead zone,limit and correction coefficient.Flexibly change the parameters of the coordinated control layer,control output,decoupling between loops,cross restriction,feedforward and other channel parameters to adapt to the changes of objects and control objectives.The effectiveness of the design is verified by simulation.(3)According to the flexibility of a existing power plant to transform the heating unit,the simulation platform under MATLAB environment is established,and the object and control system models of all typical working conditions are established by orthogonal method.On this basis,the working condition adaptability of flexible coordinated control system is analyzed,and the switching process between different operating conditions is simulated to determine the control effect of flexible switching.Finally,this control scheme is implemented when the control system is optimized.The operation of more than one year shows that the flexible coordinated control system can be put into automatic when various operation modes and operation modes are switched,and the performance of AGC(automatic generation control)and primary frequency modulation can meet the requirements of power grid assessment.