Performance Diagnosis Of Nuclear Power Secondary Circuit Based On Hybrid Modeling

As a clean,efficient,safe and reliable power source,nuclear power has gradually risen in my country.This paper takes the secondary circuit thermal system of AP1000 nuclear power unit as the research object,and analyzes and diagnoses the thermal performance of the secondary circuit system and its key equipment based on a hybrid modeling method combining mechanism modeling and data modeling.First,the conventional thermal balance method is used to model the general characteristics of the secondary circuit system based on the mass and energy balance equations based on the characteristics of the nuclear power unit’s design structure and working medium that are different from conventional thermal power,and complete the thermal performance file of the system based on the design value.Established,including relative internal efficiency,exergy efficiency,dehumidification efficiency,pressure ratio,characteristic flow area,internal exergy parameters,heater end difference,overall heat transfer coefficient,cylinder efficiency and heat consumption,etc.,and carried out the secondary loop according to the file Thermal performance analysis of systems and equipment.Secondly,a sub-model is established for the steam turbine stage group,regenerative heater and steam-water separator reheater based on the dependence of the parameters,and the actual equipment characteristic model is established through historical operating data,so as to complete the establishment of the mixed model under variable operating conditions regression.Analyze the input and output relationship of each sub-model,establish the connection of the sub-models of the secondary loop sy stem,and complete the state reconstruction of the secondary loop system.Taking the first-stage group HPT1 of the high-pressure cylinder as an example,it is found that the curve value fitted by historical operating data is lower than the design value.It is concluded that as the unit continues to operate,the performance of HPT 1 gradually deteriorates,based on hybrid modeling.The method is more accurate than a single mechanism modeling method for the state reconstruction of nuclear power turbines.The internal exergy parameter is used to diagnose the equipment performance degradation.When the performance of the first stage group HPT1 of the high-pressure cylinder is deteriorated,the absolute value of the internal exergy parameter of HPT1 continues to decrease,but it has no effect on the internal exergy parameter value of the downstream stage group HPT2,which proves The feasibility of using the characteristic index of internal exergy parameter to perform equipment performance diagnosis is discussed.This paper establishes a performance degradation evaluation model for key equipment,and combines the mechanism equations to calculate and analyze the performance of the secondary loop system driven by historical operating data.This is an early fault diagnosis and provides guidance for subsequent operation optimization.