摘要在热力发电厂中，水汽品质是一项重要指标。好的水汽品质可以提高热力设备的性能，延长设备的使用寿命，节约能源，减少事故发生率。反之水汽品质的失调将会给电厂的热工设备造成不同程度的损伤，给机组的安全和电厂稳经济运行带来隐患。所以水汽采样和化学加药是电厂热工过程的两个重要环节。本文根据水汽采样和化学加药的工艺特点，从硬件和控制算法两方面着手设计热力发电厂化学加药控制系统，采用上位机和下位机相结合的系统。上位机用工业计算机和组态软件构成友好的人机界面，方便了系统的操作；下位机采用西门子S7400HPLC进行数据采集和化学加药控制。用工业以太网构成管理层，负责上位机和下位机之间、本系统和电厂其它系统之间的通信。现场总线构成现场设备的控制层，负责现场设备和PLC间的数据传输。设计上从上位机、下位机、以太网到现场总线均采用了冗余结构，来提高监控系统的可靠性。并把这样的系统作为电厂DCS的子系统。为提高系统的实时性，本文研究了DCS的通信问题，介绍了一些提高通信能力的方法。随着电厂规模的日益扩大，工艺水平的不断提高，要求采用更新颖的控制技术来满足工艺的需要。由于化学加药控制系统的非线性、大时滞、时变的特点，常规的控制方法难以获得满意的控制效果。为了提高系统控制的鲁棒性和自适应能力，本课题将模糊控制引入到热电厂化学加药控制系统中。在算法方面，经过研究决定采用参数自适应模糊PID自动加药控制代替手动控制或是传统PID控制，并用仿真曲线来分析其动态性能和抗扰动能力。仿真结果表明，该策略的控制效果优于常规的PID控制，它能适应对象参数的变化，具有较强的鲁棒性和自适应能力。关键词:现场总线；加药；时滞系统；模糊PID控制；AbstractInthethermalpowerplant,theparametersofwaterandsteamofthermalsystemisaimportancetarget.Thegoodparametersofwaterandsteamofthermalsystemcanimprovetheperformanceofthermalequipment,andprolongtheusefullifeofequipment,theusingofdevices,andsaveenergy,reducetheratiooftheaccidents.Contrarily,itwillcausevaryingdegreesofdamageinthermalequipmentofthePowerPlant,andbringhiddentroublesinthesecureandeconomicrunningofthepowerplant,so,thechemicalvaporsamplingandDosingisanimportantlinkforthermalpowerplant.OnthebasesoftheTechnologicalrequirementsofthewaterandsteamofthermalsystemchemicalandthedosingcontrolsystem,thehardwareandcontrolalgorithmisdesignedinthepaper.Inthehardwaredesign,theupperandthehypogynousarecombinedinthedesign,theupperofthesystemiscomposedofPCandSCADAtobemadeofthefriendlyManandMachineInterface,anditfacilitatestheoperationofthesystem.ThehypogynousofthesystemadoptsSiemensS7400HPLCtocollectdataandtocontroltheprocessofthedosingcontrolsystem.IndustrialEthernetisusedofthemanagement,andseestocommunicationbetweentheupperandthehypogynousorbetweenthesystemandotherplantsystems.FCSisusedoftheControllayer,itseestothedatatransmissionbetweenon-siteequipmentsandPLC.Inthispaper,toincreasethereliabilityoftheMonitoringsystem,theredundantstructureisusedfromthePC、theupper、thehypogynous、theEthernettoFCS.ThesystemislookedonasthesubsystemoftheDCS.Manycommunicationmethodsareintroducedinthispaper,toimprovethereal-timeofthesystem.Withthegrowingscaleofpowerplantsandwiththecontinuousraisingleveloftechnology,itrequirestoupdatethecontrolarithmetic.Sincethechemicaldosingcontrolsystemoffossilpowerplantischaracterizedbynonlinearity,longtimelagandvariationwithtime,satisfyingcontroleffectcannotbeachievedwithtraditionalcontrolmethods.Inordertoincreasetherobustnessandself-adaptabilityofthechemicaldosingcontrolsysteminthesystemofdosingisdesigned.Inthispaper,fuzzycontrolsystemofdosing.Inthealgorithm,Fuzzyself-adaptationPIDcontrolisusedins...
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