PLC在無負壓(ya)供(gong)水控制系統中的應用

      無(wu)負壓供(gong)(gong)水(shui)(shui)是在(zai)(zai)變頻恒壓供(gong)(gong)水(shui)(shui)的(de)基礎上發(fa)展起來的(de)，它的(de)先進之處在(zai)(zai)于(yu)將系統(tong)直(zhi)接與(yu)自(zi)來水(shui)(shui)管(guan)(guan)網(wang)串聯對(dui)接，而不(bu)(bu)用建立水(shui)(shui)池和設置水(shui)(shui)箱，供(gong)(gong)給(gei)用戶的(de)水(shui)(shui) 全(quan)在(zai)(zai)一個密封的(de)環境中(zhong)，避免了(le)飲用水(shui)(shui)在(zai)(zai)供(gong)(gong)水(shui)(shui)過(guo)程中(zhong)的(de)二次污(wu)染。這種供(gong)(gong)水(shui)(shui)方(fang)式(shi)實現了(le)無(wu)池供(gong)(gong)水(shui)(shui)與(yu)變頻恒壓供(gong)(gong)水(shui)(shui)的(de)結合，能(neng)夠達到比其(qi)它供(gong)(gong)水(shui)(shui)方(fang)式(shi)更環保節(jie)能(neng)的(de)效果。此(ci)外(wai)在(zai)(zai)供(gong)(gong)水(shui)(shui)過(guo)程中(zhong)，充分(fen)利用自(zi)來水(shui)(shui)原有的(de)壓力(li)，因此(ci)可節(jie)電50%以上。不(bu)(bu)僅如此(ci)，無(wu)負壓供(gong)(gong)水(shui)(shui)系統(tong)結合真空抑(yi)制、穩流補(bu)償(chang)(chang)、預壓平衡補(bu)償(chang)(chang)、能(neng)量儲存(cun)釋放、變頻調速和智(zhi)能(neng)控制等技術，在(zai)(zai)供(gong)(gong)水(shui)(shui)的(de)同時不(bu)(bu)，會(hui)對(dui)市(shi)政管(guan)(guan)網(wang)產生(sheng)壓降，從而保證了(le)市(shi)政管(guan)(guan)網(wang)的(de)正常運行。

2、無(wu)負(fu)壓供水工藝概(gai)述

      無負壓(ya)供水(shui)(shui)控(kong)制(zhi)系統的(de)(de)核心(xin)概念就(jiu)是(shi)通過(guo)變頻器控(kong)制(zhi)水(shui)(shui)泵的(de)(de)運行(xing)頻率，達到節能供水(shui)(shui)的(de)(de)效果，同時(shi)系統還加入了市政管網保護功能、水(shui)(shui)泵保護功能以及故障處理等(deng)功能。為了節約成本，目前人(ren)們(men)大多采用一個變頻器控(kong)制(zhi)多個水(shui)(shui)泵的(de)(de)變頻運行(xing)方式，也就(jiu)是(shi)我們(men)常說(shuo)的(de)(de)一拖二、一拖三(san)或(huo)一拖四等(deng)控(kong)制(zhi)系統。采用這種方式，變頻器輪流控(kong)制(zhi)各個水(shui)(shui)泵變頻運行(xing)。

      水(shui)(shui)泵(beng)的(de)運(yun)行(xing)(xing)(xing)(xing)方(fang)式有兩種，一(yi)(yi)種是變(bian)頻(pin)運(yun)行(xing)(xing)(xing)(xing)，一(yi)(yi)種是工(gong)頻(pin)運(yun)行(xing)(xing)(xing)(xing)。水(shui)(shui)泵(beng)的(de)運(yun)行(xing)(xing)(xing)(xing)方(fang)式由 控制(zhi)器根據用戶(hu)用水(shui)(shui)量的(de)多少(shao)自動控制(zhi)。系統啟動后，水(shui)(shui)泵(beng)首先變(bian)頻(pin)運(yun)行(xing)(xing)(xing)(xing)，當用水(shui)(shui)量增加(jia)時，變(bian)頻(pin)水(shui)(shui)泵(beng)轉換為工(gong)頻(pin)運(yun)行(xing)(xing)(xing)(xing)，并啟動下一(yi)(yi)臺(tai)水(shui)(shui)泵(beng)變(bian)頻(pin)運(yun)行(xing)(xing)(xing)(xing)。用水(shui)(shui)量減少(shao)后，工(gong)頻(pin)水(shui)(shui)泵(beng)退(tui)出運(yun)行(xing)(xing)(xing)(xing)，水(shui)(shui)泵(beng)的(de)投切過程如此循環反復(fu)。

      在用水(shui)(shui)量很少，或沒有(you)用水(shui)(shui)時(shi)(shi)，為了節能(neng)與延長水(shui)(shui)泵(beng)(beng)(beng)的(de)使用壽命(ming)，水(shui)(shui)泵(beng)(beng)(beng)還可以進入休眠(mian)狀態(tai)。當用水(shui)(shui)量增加時(shi)(shi)，水(shui)(shui)泵(beng)(beng)(beng)會(hui)自(zi)動從休眠(mian)狀態(tai)中(zhong)被喚(huan)醒。當一臺水(shui)(shui)泵(beng)(beng)(beng)長時(shi)(shi)間運行(xing)時(shi)(shi)，為了使各個水(shui)(shui)泵(beng)(beng)(beng)均衡運行(xing)，系統(tong)會(hui)自(zi)動選擇運行(xing)時(shi)(shi)間 短的(de)水(shui)(shui)泵(beng)(beng)(beng)運行(xing)。當有(you)水(shui)(shui)泵(beng)(beng)(beng)出現故障(zhang)時(shi)(shi)，系統(tong)會(hui)自(zi)動跳過(guo)該水(shui)(shui)泵(beng)(beng)(beng)，不會(hui)影響其他水(shui)(shui)泵(beng)(beng)(beng)的(de)投切過(guo)程(cheng)。

3、無負壓供水控(kong)制系統(tong)結(jie)構設(she)計

      在傳統的(de)無負壓(ya)供水設備(bei)中，控(kong)制(zhi)器(qi)(qi)大多采用(yong)單片(pian)機設計，這種控(kong)制(zhi)器(qi)(qi)一(yi)般都(dou)不允許(xu)用(yong)戶(hu)對其內(nei)部的(de)程序進行修改。如果想增加一(yi)些功能(neng)，則(ze) 須找(zhao)控(kong)制(zhi)器(qi)(qi)的(de)供應商幫助完(wan)成。這就(jiu)導致(zhi)了系統的(de)靈活性(xing)較差(cha)，而且這種控(kong)制(zhi)器(qi)(qi)一(yi)般都(dou)沒有經過可靠性(xing)測試，在可靠性(xing)方面可能(neng)存在或多或少的(de)問題。

      采用(yong)PLC作為(wei)(wei)核心控(kong)制(zhi)單(dan)元，在可(ke)靠性上得(de)到了(le)保證，其開放的(de)(de)(de)編程(cheng)(cheng)環境(jing)也使系統(tong)開發和維(wei)護更加方便。不僅如此，和利時還為(wei)(wei)無(wu)負(fu)壓(ya)供(gong)水設備(bei)提(ti)供(gong)了(le)標準的(de)(de)(de)例(li)程(cheng)(cheng)，用(yong)戶可(ke)以直接使用(yong)這個例(li)程(cheng)(cheng)搭建無(wu)負(fu)壓(ya)供(gong)水控(kong)制(zhi)系統(tong)，或者可(ke)以根據需要對例(li)程(cheng)(cheng)進行簡單(dan)的(de)(de)(de)修改，這樣大(da)大(da)提(ti)高了(le)系統(tong)的(de)(de)(de)建立效(xiao)率(lv)以及系統(tong)的(de)(de)(de)開放性。

      本次設(she)計針(zhen)對(dui)1拖3無負壓供水(shui)控(kong)制系統(tong)。系(xi)統(tong)(tong)(tong)主要由PLC、變(bian)頻(pin)(pin)器(qi)(qi)、離(li)心(xin)泵、壓力(li)傳感器(qi)(qi)、水位(wei)傳感器(qi)(qi)、缺相保護器(qi)(qi)、故障(zhang)報(bao)警(jing)(jing)燈(deng)等組成。PLC負責三個(ge)水泵的(de)(de)投(tou)切控(kong)(kong)制算法，根據(ju)管網出(chu)(chu)(chu)口(kou)(kou)的(de)(de)設(she)(she)定壓力(li)動態調節(jie)變(bian)頻(pin)(pin)器(qi)(qi)的(de)(de)輸出(chu)(chu)(chu)頻(pin)(pin)率，以(yi)及實現(xian)(xian)倒泵、休眠、故障(zhang)處理、無負壓補(bu)償等功(gong)能(neng)。本系(xi)統(tong)(tong)(tong)采用和(he)利(li)時LM系(xi)列(lie)PLC作為系(xi)統(tong)(tong)(tong)控(kong)(kong)制器(qi)(qi)，并且通(tong)過(guo)LM系(xi)列(lie)PLC自帶(dai)的(de)(de)RS232接(jie)(jie)口(kou)(kou)連(lian)接(jie)(jie)現(xian)(xian)場的(de)(de)觸(chu)摸屏(ping)HT6720T，觸(chu)摸屏(ping)程序具有系(xi)統(tong)(tong)(tong)參(can)數設(she)(she)置(zhi)、顯(xian)示(shi)系(xi)統(tong)(tong)(tong)運(yun)行(xing)狀(zhuang)(zhuang)態、查詢(xun)系(xi)統(tong)(tong)(tong)報(bao)警(jing)(jing)記錄等功(gong)能(neng)。為了便(bian)于用戶查詢(xun)控(kong)(kong)制系(xi)統(tong)(tong)(tong)的(de)(de)運(yun)行(xing)狀(zhuang)(zhuang)況以(yi)及設(she)(she)置(zhi)出(chu)(chu)(chu)口(kou)(kou)壓力(li)等參(can)數，這里還用LM系(xi)列(lie)PLC自帶(dai)的(de)(de)RS485接(jie)(jie)口(kou)(kou)連(lian)接(jie)(jie)了一個(ge)短信數傳模(mo)塊(kuai)，用戶可以(yi)通(tong)過(guo)手(shou)機隨(sui)時查詢(xun)水泵的(de)(de)運(yun)行(xing)狀(zhuang)(zhuang)況以(yi)及設(she)(she)定管網的(de)(de)出(chu)(chu)(chu)口(kou)(kou)壓力(li)。無負壓供水控(kong)(kong)制系(xi)統(tong)(tong)(tong)結構如圖1所示(shi)。

      無(wu)(wu)負(fu)壓(ya)供水(shui)控制系(xi)統操(cao)(cao)作(zuo)界面由觸摸(mo)屏HT6720T制作(zuo)。操(cao)(cao)作(zuo)界面主要可以(yi)完成無(wu)(wu)負(fu)壓(ya)供水(shui)控制系(xi)統運(yun)(yun)行(xing)工況的監視、系(xi)統運(yun)(yun)行(xing)參(can)數設置、實(shi)時報(bao)警(jing)顯示(shi)(shi)、歷史報(bao)警(jing)顯示(shi)(shi)等(deng)(deng)功能。觸摸(mo)屏工況界面如圖3所(suo)示(shi)(shi)，可以(yi)查看各個水(shui)泵的運(yun)(yun)行(xing)狀(zhuang)態(tai)以(yi)及進水(shui)壓(ya)力、目標壓(ya)力和出水(shui)壓(ya)力等(deng)(deng)幾個重(zhong)要的輸出參(can)數。

基于LM系列PLC的(de)無負壓供水系統具(ju)有(you)如下特點：

可靠性

      可(ke)靠性是無(wu)負壓(ya)供(gong)水系(xi)統(tong)的(de)(de)關鍵(jian)。與(yu)傳統(tong)的(de)(de)單片機控制器相比，LM系(xi)列PLC在(zai)(zai)穩(wen)定(ding)(ding)性、抗干擾性以(yi)及惡劣條件下的(de)(de)工作(zuo)性能(neng)都要更(geng)勝一(yi)籌。LM系(xi)列PLC的(de)(de)輸(shu)入和輸(shu)出點都是與(yu)現場隔離的(de)(de)，這為(wei)系(xi)統(tong)的(de)(de)可(ke)靠性提(ti)供(gong)了硬(ying)件基礎(chu)。系(xi)統(tong)所提(ti)供(gong)的(de)(de)增量(liang)PID運算功(gong)能(neng)塊使(shi)系(xi)統(tong)能(neng)夠根據用戶的(de)(de)用水量(liang)迅速調節給水泵的(de)(de)工作(zuo)頻(pin)率，使(shi)給水壓(ya)力以(yi)較快的(de)(de)速度穩(wen)定(ding)(ding)在(zai)(zai)設定(ding)(ding)值，這也在(zai)(zai)功(gong)能(neng)上保證了系(xi)統(tong)的(de)(de)穩(wen)定(ding)(ding)運行。

易用性

      LM系(xi)列(lie)PLC體積小、集成(cheng)化程度高(gao)、運(yun)算速度快、邏輯控(kong)制(zhi)容量(liang)大(da)，還(huan)可(ke)(ke)以進行(xing)在線調(diao)試(shi)(shi)(shi)和離線調(diao)試(shi)(shi)(shi)，有(you)強大(da)的(de)(de)視圖功能，可(ke)(ke)以大(da)大(da)降(jiang)低編程調(diao)試(shi)(shi)(shi)的(de)(de)工作量(liang)，縮短調(diao)試(shi)(shi)(shi)的(de)(de)周期。靈活的(de)(de)編程功能，可(ke)(ke)以給未來(lai)(lai)的(de)(de)系(xi)統(tong)升級帶來(lai)(lai) 方便(bian)。系(xi)統(tong)采用(yong)7英寸(cun)TFT觸摸屏，整個(ge)系(xi)統(tong)的(de)(de)運(yun)行(xing)狀況一目了然，各項(xiang)控(kong)制(zhi)參數(shu)(shu)也(ye)可(ke)(ke)以根據不同工況進行(xing)調(diao)整，并(bing)可(ke)(ke)以生成(cheng)實時(shi)報警(jing)與歷史報警(jing)列(lie)表。同時(shi)，還(huan)利用(yong)LM系(xi)列(lie)PLC自帶的(de)(de)RS485接口連接短信(xin)數(shu)(shu)傳模塊，用(yong)戶可(ke)(ke)以直(zhi)接通(tong)過手機(ji)隨時(shi)查(cha)詢系(xi)統(tong)的(de)(de)運(yun)行(xing)工況，并(bing)可(ke)(ke)以進行(xing)管(guan)網出口壓力(li)等參數(shu)(shu)的(de)(de)設置。

功能性

      本系統(tong)是在(zai)LM系列PLC的無(wu)負壓(ya)供水(shui)標(biao)準(zhun)程(cheng)序的基礎上(shang)建立(li)的，實現(xian)的功(gong)(gong)(gong)(gong)能包括了水(shui)泵(beng)的自動投切功(gong)(gong)(gong)(gong)能、休眠(mian)倒泵(beng)功(gong)(gong)(gong)(gong)能、水(shui)泵(beng)優(you)先級判(pan)斷功(gong)(gong)(gong)(gong)能、優(you)化的故障處(chu)理功(gong)(gong)(gong)(gong)能、多時段設(she)定(ding)功(gong)(gong)(gong)(gong)能、低水(shui)位自動保護功(gong)(gong)(gong)(gong)能、無(wu)負壓(ya)功(gong)(gong)(gong)(gong)能、短信通訊(xun)功(gong)(gong)(gong)(gong)能以(yi)及PLC鎖定(ding)功(gong)(gong)(gong)(gong)能等(deng)。整(zheng)個系統(tong)的搭建過(guo)程(cheng)幾(ji)乎沒(mei)有對標(biao)準(zhun)程(cheng)序進行修改，在(zai)實現(xian)了強大功(gong)(gong)(gong)(gong)能的基礎上(shang)，方便快速地完(wan)成了控制系統(tong)的搭建。