Design And Optimization Of Coordinated Control System For The Subcritical Cirulating Fluidized Bed Unit

With the rapid development of clean energy and the large-scale grid-connected operation of wind power,thermal power generators are faced with more difficult tasks of peak shaving and frequency modulation.Because the CFB unit has the characteristics of good regulation performance,low pollution,high efficiency,and wide adaptability to combustion,it can operate stably at low load,and has high combustion efficiency.The nitrogen oxide emissions NO_X and SO₂ are small,so the CFB unit can participate in deep peaking.However,due to the particularity and complexity of the CFB boiler combustion,the traditional control strategy has low input rate of automatic control during low load operation.How to establish an accurate CFB unit dynamic model and how to further optimize the control strategy have engineering application value.This article aims at a 330 MW circulating fluidized bed boiler,has an in-depth understanding of its process flow,performs mechanism analysis on the objects involved in the coordinated control system,and establishes a model.For the traditional control strategy is difficult to invest in the automatic operation of the problem,a new control strategy has been designed,and the configuration debugging in the field,obtained a very good control effect.The details are as follows:?1?Based on the analysis of the combustion process of the CFB unit and the characteristics of the coordinated control system,the input and output of the model have been re-qualified and simplified,and three inlets and three outlets of the boiler combustion system and two inlets of the unit coordinated control system have been established.The input of the three-in three-out model is the fuel quantity,primary air volume,secondary air volume,and the output is caloric,bed temperature,and oxygen;the input of the second-in-two model is calorie,gate opening,and the output volume is pre-machine pressure power generation,similar to ordinary pulverized coal furnaces.The two-input and two-out models are load-pressure models,which replace the heat in the original milling system with the amount of fuel.The three-in,three-out model involves three models:thermal model,bed temperature model,and oxygen model.The thermal model and the bed temperature model are all based on the residual carbon model.The oxygen model is calculated from the amount of wind and heat.?2?According to the problems encountered in the traditional bed temperature control strategy when it is invested under low load,the bed temperature control system is optimized based on the operating curve of the site.?3?A feedforward-feedback control system is designed for the problem of slow load response of the conventional coordinated control system.The feedforward system mainly includes the load command feedforward signal and the heat high-order derivative differential signal.The feedback control system uses the direct energy balance method.It combines these three loops together to form a new coordinated control system and set the PID control parameters.The on-site operation verified the effect of the optimized control.The accuracy of the model established by the mechanism analysis in this paper is high.The optimized coordinated control system can increase the load response rate of the CFB unit,exert its advantages,and better participate in deep peak adjustment.