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在城市化进程迅速的今天，城市的居住形式主要是生活小区，那么小区供水系统的建设就显得尤为重要。而且随着城市用水量不断增加，对供水系统的建设提出了更高的要求。供水的经济性、可靠性、稳定性直接影响到小区住户的正常生活和工作。本系统是针对居民生活用水而设计的一套由变频器、PLC、水泵机组等设备组成的自动变频恒压供水控制系统。该系统将PLC、变频器、相应的传感器和执行机构有机地结合起来，并发挥各自优势，能够最大程度满足需要，具有运行稳定、操作简单和高效节能等特点。该系统对变频器内置PID模块参数进行预置，通过压力传感器对水压的反馈构成闭环控制系统；PID模块根据用水量的变化调节水泵的输出流量，实现恒压供水，并达到有效节能的目的。本文首先介绍了采取变频调速方式实现恒压供水相对于传统的阀门控制恒压供水方式的节能原理；其次，对水泵机组的各种供水状态及转换的条件、水泵由变频转工频运行方式的切换过程进行分析，着重研究并提出了基于PLC和变频器的恒压供水系统的方案，并给出了硬件设计和PLC控制程序设计。关键词：PLC；变频调速；恒压供水ABSTRACTIntoday'srapidurbanization,urbanlivingismainlylivingquarters,thentheconstructionofresidentialwatersupplysystemisparticularlyimportant.Andwiththegrowingurbanwaterdemand,watersupplysystems,theproposedhigherrequirements.Economicsofwatersupply,reliabilityandstabilitytothedistrictresidentsdirectlyaffectedthenormallifeandwork.Thesystemisdesignedforhouseholdwatersetbythefrequencyconverter,PLC,waterpumpandotherequipmentconsistingofautomaticconstantpressurewatersupplycontrolsystem.SystemPLC,frequencyconverter,thecorrespondingsensorsandactuatorstogetherorganically,andplaytheirrespectiveadvantages,thecontrolsystemeasytooperate,notonlytothegreatestextenttomeettheneedsofstabilityandsecurityofitsoperatingperformance,simpleandconvenientmodeofoperation,andthecompleteandthoughtfulfeatures,willmakewatersavingwater,saving,laborsaving,highefficiencyhigh-qualityfinalrun,reliable,energy-savingpurposes.Thispaperintroducesthewaytoachievefrequencycontrolconstantpressurewatersupplyvalvecontrolcomparedtoconventionalenergy-savingprincipleofconstantpressurewatersupply.Converterbuilt-inPIDmoduleonthepresetparameters,usinghydraulicpressuresensorfeedback,closedloopsystem.Accordingtochangesinwaterconsumption,toPIDregulationmode,byadjustingthepumpoutputflow,constantpressurewatersupplyandefficientenergy.Thenitanalyzesthestateofpumpunitsandconversionofvariouswaterconditions,analysisofthepumpfrequencybythefrequencychangeoperatingmodeoftheswitchprocess.Importantpartsoffunctionalanalysis,focusingonresearchandputforwardbasedonPLCandfrequencyconstantpressurewatersupplysystemprogram,weregivencontrolofthehardwaredesignandPLCprogramming.Keywords:PLC。frequencycontrol。constantpressurewatersupply目录1绪论...........................................................................................................................11.1研究背景.........................................................................................................11.2变频恒压供水系统的国内外研究现状.........................................................21.3供水系统安全性讨论.....................................................................................21.4本文的设计思想.............................................................................................32系统的理论分析及方案的确定...............................................................................42.1调速方式的比较与选择.................................................................................42.2控制系统方案.................................................................................................62.3供水系统的控制流程.....................................................................................92.4变频恒压供水系统中加减水泵的条件分析...............................................113变频恒压供水系统的硬件设计.............................................................................133.1PLC选型及接线...........................................................................................133.1.1PLC选型.............................................................................................133.1.2PLC的接线及I/O分配......................................................................163.2水泵机组选型...............................................................................................183.3变频器选型及接线.......................................................................................193.3.1变频器选型.........................................................................................193.3.2变频器的接线.....................................................................................233.4PID调节器....................................................................................................233.5压力传感器...................................................................................................253.6系统主电路设计...........................................................................................264系统软件设计.........................................................................................................274.1PLC控制.......................................................................................................274.1.1PLC程序流程图.................................................................................274.1.2手动运行.............................................................................................284.1.3自动运行.............................................................................................284.2编程及介绍...................................................................................................294.2.1总程序的顺序功能图.........................................................................294.2.2自动运行顺序功能图...