【正文】 This paper discusses the reasonability of water supply scheme with much pump parallel connection, and analyses the conversion condition and the various states of water supply of the much pump way of water supply as well as the switch process and the problem of a generator from variable frequency operation mode to work frequency operation mode. In addition，the bination of the system and the puter is achieved，which improved the overall function of the system．Key words：PLC。并與計算機實現(xiàn)了有機的結(jié)合，提升了系統(tǒng)的總體性能。給出了實現(xiàn)有效狀態(tài)循環(huán)轉(zhuǎn)換控制的電氣設(shè)計方案和 PLC 控制程序設(shè)計方案。通過對變頻器內(nèi)置 PID 模塊參數(shù)的預(yù)置，利用遠傳壓力表的水壓反饋量，構(gòu)成閉環(huán)系統(tǒng)，根據(jù)用水量的變化，采取 PID 調(diào)節(jié)方式，在全流量范圍內(nèi)利用變頻泵的連續(xù)調(diào)節(jié)和工頻泵的分級調(diào)節(jié)相結(jié)合，實現(xiàn)恒壓供水且有效節(jié)能。本文根據(jù)城區(qū)供水管網(wǎng)改造工程設(shè)計了一套由 PLC、變頻器、遠傳壓力表、多臺水泵機組、計算機等主要設(shè)備構(gòu)成的全自動變頻恒壓供水及其遠程監(jiān)控系統(tǒng)，具有自動工頻/變頻恒壓運行、可實現(xiàn)遠程自動控制和現(xiàn)場手動控制等功能。I摘 要隨著改革開放的不斷深入，我國中小城市的城市建設(shè)及其經(jīng)濟迅猛發(fā)展，人民的生活水平不斷提高；同時，城市需水量日益加大，對城市供水系統(tǒng)提出了更高的要求。供水的可靠性、穩(wěn)定性、經(jīng)濟節(jié)能性直接影響到城區(qū)的建設(shè)和經(jīng)濟的發(fā)展，也影響到城區(qū)居民的正常工作和生活。論文分析了采取變頻調(diào)速方式實現(xiàn)恒壓供水相對于傳統(tǒng)的閥門控制恒壓供水方式的節(jié)能機理。 論文論述了采用多泵并聯(lián)供水方案的合理性，分析了多泵供水方式的各種供水狀態(tài)及轉(zhuǎn)換條件，分析了電機由變頻轉(zhuǎn)工頻運行方式的切換過程及存在的問題。系統(tǒng)有效地解決了傳統(tǒng)供水方式中存在的問題，增強了系統(tǒng)的可靠性。關(guān)鍵詞：PLC ；變頻調(diào)速；恒壓供水；變頻工頻切換Abstract With the continuous deepening of reforming and opening up, the construction and economy of small and mediumsized cities in China have developed rapidly. People39。 Variable Velocity Variab le frequency。 variable frequency to working frequency目錄摘 要 ........................................................................................................................IABSTRACT .............................................................................................................II1 緒 論 .....................................................................................................................1 課題背景及意義 ................................................................................................1 變頻恒壓供水的現(xiàn)況 ........................................................................................1 變頻恒壓供水系統(tǒng)的特點 ................................................................................32 變頻恒壓供水系統(tǒng)理論分析 ...............................................................................4 供水系統(tǒng)的基本特性 ........................................................................................4 不同控制方式下的能耗分析與比較 ................................................................5 變頻恒壓控制的理論模型 ................................................................................6 供水系統(tǒng)中的水錘效應(yīng)及消除方法 ................................................................73 供水系統(tǒng)恒壓控制與硬件設(shè)計 ...........................................................................8 異步電動機調(diào)速方法及選型 ............................................................................8 變極調(diào)速 .........................................................................................................8 變頻調(diào)速 .........................................................................................................9 供水系統(tǒng)的方案確定 ......................................................................................10 供水系統(tǒng)的流量類型 ...................................................................................10 總體設(shè)計方案確定 ........................................................................................10 恒壓供水電控系統(tǒng)組成 ................................................................................12 控制系統(tǒng)的硬件設(shè)計與選型 ...........................................................................13 主電路設(shè)計 ....................................................................................................13 電氣控制電路設(shè)計 ........................................................................................14 系統(tǒng)主要配置的選型 ....................................................................................16 PLC 的選型 .......................................................................................................19 系統(tǒng)可靠性措施 ..............................................................................................204 PLC 控制系統(tǒng)的設(shè)計 .......................................................................................22 水泵工頻/變頻運行狀態(tài)及轉(zhuǎn)換過程分析 .....................................................22 供水狀態(tài)及其轉(zhuǎn)換 ........................................................................................22 狀態(tài)轉(zhuǎn)換關(guān)系 ...............................................................................................22 狀態(tài)轉(zhuǎn)換條件 ...............................................................................................24 PLC 程序設(shè)計 .................................................................................................25 PLC 編程語言 .............................................................................................25 梯形圖語言編程的一般規(guī)則 .....................................................................25 供水系統(tǒng)控制模塊的設(shè)計 ..............................................................................26 系統(tǒng)初始化模塊 ............................................................................................26 水泵運行與狀態(tài)轉(zhuǎn)換模塊 ............................................................................265 恒壓供水系統(tǒng)的 PID 調(diào)節(jié) .................................................................................28 PID 控制及其控制算法 ...............................................................................