Joint Optimization Of Steam Turbine Parameters Under Low Load Based On Thermoeconomics

In recent years,with the rapid expansion of hydropower units in Yunnan Province,Yunnan Province has formed a power supply pattern with hydropower as the main source and thermal power as the supplement.This has led to a significant year-on-year decline in the number of hours of use of large coal-fired thermal power units in the Yunnan region,and it has been operating under conditions of low load and low utilization hours(hereinafter referred to as "double low")all year round.In order to improve the operating economy of thermal power units in the “double low” operating conditions,this paper takes the 300 MW coal-fired plant in Yunnan Qujing which has been under low load condition for a long time as the object of study.In this paper,the actual operational data of the power plant is used to develop the consistency model of main steam flow based on data fault tolerance,the establishment of thermal economic structure theoretical evaluation model and the joint optimization of steam turbine parameters under “double low” conditions.The parameter joint optimization referred to in this paper refers to the main steam pressure optimization considering the influence of the ambient temperature.The research results in this paper can provide theoretical basis for the selection of the optimal main steam pressure under different ambient temperatures when the coal-fired units are operating under low-load conditions for a long period of time,which is of theoretical significance for improving the economy under the “double-low” conditions of thermal power units and practically valuable.The main research work and research results as follows:1、An algorithm for the consistency of main steam flow and turbine load is proposed based on data fault tolerance.Firstly,based on the data-driven method,the correction models for the critical parameters of the through-flow section,the regenerative system and the condenser system are established,and the thresholds and methods for parameter calibration were determined.Furthermore,a main steam flow correction model based on power balance equation is established.The model has data fault tolerance and meets the characteristics of power balance equation,so as to ensure the correctness of the performance index measurement results,and provide a basis for subsequent turbine unit parameter optimization.2、The thermo-economic structural model of a 300 MW steam turbine unit is established by using the improved modeling method for thermal system unit cost and unit thermal economics cost.The example shows that this model can be used to calculate the unit product cost,unit thermal economic cost,and unit generation cost of each component of the turbine unit under the “double-low” operating conditions,and realizes the joint evaluation of thermal system economics and energy efficiency levels.3、Joint optimization of the steam turbine operating parameters is conducted based on the theoretical thermal structure of economics.First of all,a steady state determination of a large number of actual operating data of the unit is performed to obtain a steady-state operation data sample for the typical conditions of the joint optimization of parameters.In addition,we screen and check the steady-state operational data samples to determine feasible solutions.Thirdly,cluster the operating data of four different temperatures under different loads of the steam turbine unit,select the center of mind of the data sample custom operating area,and calculate the power generation cost of data samples with a degree of membership greater than 0.9 at the core.Finally,find the best main steam pressure in the custom operating areas under 4 different loads at different ambient temperatures with the objective of minimizing the unit cost of electricity generation.The example shows that the method can be used to find the best main steam pressure under different loads and different ambient temperatures for the steam turbine under the “double low” operating conditions.The variation law of the optimal main steam pressure with the load at the same ambient temperature can provide reference for the economic operation of the steam turbine,and can also provide reference for the joint optimization of other steam turbine parameters.