Intelligent Control Of Complex Thermodynamic System

With the large-scale development of renewable energy power generation,especially the proposal of the China’s "30-60 dual carbon target",the roadmap and timetable for the transition of coal-fired power plant from the main power generation to capacity support power supply are clarified.Under the highly flexible operation mode,the variation range and frequency of the load instructions received by the coal power unit will increase significantly,and the operation of the unit will become more unstable.At the same time,due to the high price of coal,the coal quality characteristics becomes worse and unstable,which leads to the increase of the equipment load of pulverizing and combustion system,which makes the controlled object show obvious delay and non-minimum phase characteristics.In addition,the power plant units around the city are developing towards the power-heating-steam multi-cogeneration units of the integrated energy system,with complex multivariable and variable structure characteristics.The power station needs more adaptive control system with good control quality to solve the above problems.The research carried out in this paper includes:(1)A five input-five output simplified nonlinear dynamic model in the form of differential equations for typical subcritical power-heating-steam multi-cogeneration units was established,based on all the input variable disturbance simulation experiment and the orthogonal model working point linearization approach on the model characteristics were analyzed,it was found that the main difficulties of the control is the large delay on the boiler side and the multivariate strong coupling on the turbine side,the design idea of control system which divid-and-conquer the above two characteristics was determined.(2)By comparing the boiler following turbine,indirect energy balance and so on the many kinds of furnace coordinated control scheme,it was found that the DEB(Direct Energy Balance)thermal signal was found to be a key signal point for separating the large delay on the boiler side and the multivariate strong coupling characteristics of the turbine side,and the ability to overcome the turbine side closed loop mode furnace side integral feature of the negative impact of the control system design,which were proved by theoretical derivation and simulation experiment.(3)In view of the large delay characteristics of boiler side,Smith predictive control is determined to be convenient for engineering design and site needs by comparing various control schemes;In order to solve the problems of Smith predictive control adaptive modeling error and time-varying difference of object,an open-loop intelligent compensation flexible Smith predictive control scheme was studied,which can flexibly switch between PID(Proportion Integration Differentiation)and Smith predictive control according to the needs of field debugging,and take into account the requirements of adaptability to working conditions and control quality.(4)For several 330 MW pulverized coal furnaces units and 330 MW circulating fluidized bed furnace coal power units,intelligent flexible control was used to optimize the coordinated control system,the DCS(Distributed Control Systems)configuration and debugging.Field experiments and long-term operation data show that this control scheme has the advantages of fast load response,strong adaptability to working conditions and good resistance to coal quality disturbance.