Characteristic Modeling Of Cogeneration Units And Its Application In Operation Analysis And Optimization

Combined heat and power generation(CHP)can not only improve the energy utilization efficiency,but also improve the quality of the environment,which is in line with the principle of using energy according to its quality.It has become a means for large-scale cogeneration units to increase energy efficiency and increase returns.Large-scale cogeneration units are mostly reheat units,and the extraction methods tend to be diversified and complicated,which makes the characteristic modeling complicated.Therefore,it is necessary to study the dynamic characteristic of such units.Realizing the load optimization dispatch of cogeneration units can improve economic efficiency of the unit operation.According to the load demand to reasonably distribute the heat load and electric load between each unit,the characteristic equation of cogeneration units is required,in which the dynamic characteristic equation is the most basic and important characteristic equation.Therefore,the modeling method of dynamic characteristic equations for reheat units and the load optimization dispatch problems are the main research contents of this paper.The main research contents and achievements of this thesis are listed as follows:(1)Modeling method of multi-stage extraction heating for reheat unitsThe characteristic modeling method of the typical extraction heating modes for reheat units is studied.According to the typical desuperheating water source for main steam heating,the compound circulation function equation is established,which extend the application field of the circulation function theory.The correctness of the established characteristic model under each heating mode is verified by examples.(2)Joint modeling method of off-design condition and dynamic characteristic for cogeneration unitsA calculation model for the off-design condition dynamic characteristic equations for cogeneration units is established,including an off-design condition calculation model based on dynamic characteristic equations and the dynamic characteristic equation considering the influence of small turbine extraction steam flow.Combining the off-design condition calculation and dynamic characteristics model,a calculation model of the off-design condition dynamic characteristic equations for cogeneration units is established and the prediction of the off-design condition dynamic characteristic equations is achieved through the rated working conditions.Among them,in the established off-design condition calculation model based on dynamic characteristic equations,a method for calculating the relative internal efficiency of the second-last stage based on pressure ratio and specific volume ratio is proposed.(3)Research on algorithm of load optimization dispatch model based on linear dynamic characteristic equationsBased on the small-micro-increasing distribution principles solving linear optimization problems,a direct load distribution method for single and double extraction units is proposed respectively.The correctness of the proposed method is verified by comparing its optimization results with the Linear Programming results through examples.This method is simple,convenient and universal,and can be realized without the help of computer program.(4)Research on algorithm of load optimization dispatch model based on nonlinear dynamic characteristic equationsAn improved artificial bee colony(GABC)algorithm is proposed to solve the problem of nonlinear load optimization dispatch model.The example shows that compared with the artificial bee colony(ABC)algorithm,the proposed GABC algorithm improves the convergence speed,optimization accuracy and robustness of the algorithm.Under the same load demand,the corresponding steam consumption of the nonlinear load dispatch model is smaller than the linear load dispatch model,which shows that the study of the nonlinear load optimization dispatch model has certain practical significance for guiding the unit economic operation.(5)Research on algorithm of load optimization dispatch model for hybrid type unitsBased on the small-micro-increasing distribution principles,a direct load distribution method for hybrid type units is proposed.The correctness of the proposed method is verified by comparing its optimization results with the Linear Programming results through examples.This method is simple,convenient and universal,and can be realized without the help of computer program.