Application Research Of Model Identification In Coordinated System Of Ultra Supercritical Unit Based On Subspace Method

China's energy structure determines coal-fired power generation is still the main way of power generation in the power industry for a long period of time in the future.Ultra Supercritical Unit has become the mainstream of coal-fired power generation with the advantage of the power generation efficiency,pollution control,economy and reliability.Coordinated control system is one of the core of the whole unit control system.On the one hand,steam turbine and boiler are considered as a whole unit to be controlled in quick response to the changes of external load,on the other hand for control of switching between different working conditions,and ensure internal unit operating parameters(especially the main steam pressure)stable.The response differences exist between the turbine and DC furnace make the unit coordinated system has higher control requirements with the structural characteristics of DC furnace.Establishment of mathematical model of the coordinated system has a very important significance to improve the control performance of the whole unit,power efficiency of the unit and ensuresafe and reliable unit operation.Based on the analysis of the process of the whole unit,and combined with the boiler-turbine coordinated control mode,the paper establishes the three-input-three-output multivariable control object.By using different subspace identification algorithm,the step response coefficients can be directly obtained.The model not only can intuitively reflect the dynamic characteristics of the coordinated system,but also can be applied in some advanced control algorithm.The main work of this paper is as follows:1.Based on the analysis of the process of ultra supercritical unit,and combined with the coordinated system dynamic characteristics,establishing a three-input-three-output model identification object.2.Research on closed loop subspace identification algorithm such as SIMPCA,SOPIM,CSOPIM and CSIMPCA.Through theoretical analysis and comparison of these algorithms,a new auxiliary variable is introduced,and combining with SVD decomposition a new closed subspace identification algorithm called SIM_IV_SVD is proposed.By the comparison between the simulation results of the classic example using different algorithms,the proposed algorithm is proved to have a good consistency.3.Research on data-driven Closed loop subspace identification algorithm.By added the constraints on the structure form of the resultmatrix,an improved data-driven closed subspace identification algorithm is proposed,and through a simulation example verifies the algorithm has a better consistency.4.According to the actual needs of the industrial application,completing function demand analysis and the identification software called SYSID is developed.The software developed several modules such as the Modbus and OPC communication protocol,variable configuration module,historical data show module,the test signal module and model identification module.5.Sampling data for the identification experiment from 1000 MW ultra supercritical unit simulation machine.Using data-driven closed subspace identification algorithm and the improved version for the identification experiment respectively,and experimental results are presented to verify the effectiveness of the improved algorithm.