Optimal Back Pressure Calculation Of Direct Air Cooling Unit And Control System Optimization

With the development of science and technology and the improvement of people's living standards,China's demand for electricity is increasing.From the data in recent years,thermal power generation is still the most important way of generating electricity.In the actual operation of thermal power plants,not only the consumption of coal is particularly large,but also the waste of water resources is very serious.In view of the special situation that China's “three northern regions” have relatively large coal resources and relatively small water resources,this paper is particularly meaningful for the in-depth study of direct air cooling system.This will not only solve the current situation of the lack of water resources in our country,but also have important significance for the long-term development of our country's electric energy.Based on the research of a 600 MW direct air cooling unit,this paper expounds the operating principle,basic structure and influencing factors of unit back pressure;The mathematical model of the changing working conditions was created by using the ?-NTU method,and the characteristics of the direct air cooling unit back pressure were analyzed.The effects of exhaust steam flow,ambient wind speed,ambient air temperature and fouling thermal resistance inside and outside the finned tube bundle on the back pressure of the unit are obtained,which provides a guarantee for the safe operation of the unit;The relationship between unit back pressure and micro-enhancement power is obtained by equivalent heat drop method,and further case study is carried out.Then according to the theoretical analysis of air-cooled axial flow fan,the power consumption of the unit back pressure and air-cooling fan is obtained.Subsequently,followed by detailed calculations,and based on the definition of the optimal back pressure of the direct air cooling unit,the optimal unit back pressure under local conditions was obtained,which provided great help for the economic reference calculation of the system;Through the introduction of the existing direct air-cooled back pressure control system,it is found that it has certain defects.According to this,two model predictive control methods are proposed,which are dynamic matrix control algorithm(DMC)and generalized predictive control algorithm(GPC).The two methods were introduced theoretically and simulated,and finally found that for the existing PID control methods,both methods can greatly improve the quality of the control system.