變頻技術(shù)應(yīng)用 在工業(yè)現(xiàn)場(chǎng)控制領(lǐng)域，可編程控制器（ PLC）一直起著重要的作用。隨著國(guó)家在供水行業(yè)的投資力度加大，水廠(chǎng)運(yùn)行自動(dòng)化水平不斷提高， PLC 在供水行業(yè)應(yīng)用逐步增多。觸摸屏與 PLC 配套使用，使得 PLC 的應(yīng)用更加靈活，同時(shí)可以設(shè)置參數(shù)、顯示數(shù)據(jù)、以動(dòng)畫(huà)等形勢(shì)描繪自動(dòng)化過(guò)程，使得 PLC 的應(yīng)用可視化。 變頻恒壓供水成為供水行業(yè)的一個(gè)主流，是保證供水管網(wǎng)在恒壓的重要手段?，F(xiàn)代變頻器完善的網(wǎng)絡(luò)通信工程，威電機(jī)的同步運(yùn)行，遠(yuǎn)距離集中控制和在線(xiàn)監(jiān)控等提供了必要的支持。通過(guò)與 PLC 連接的觸摸屏，可以使控制更加 直觀(guān)，操作更加簡(jiǎn)單、方便。組合應(yīng)用 PLC、觸摸屏及變頻器，采用通信方式對(duì)變頻器進(jìn)行控制來(lái)實(shí)現(xiàn)變頻恒壓供水。 變頻恒壓供水系統(tǒng)原理如圖 1；它主要由 PLC、變頻器、觸摸屏、壓力變送器、動(dòng)力及控制線(xiàn)路以及泵組組成。用戶(hù)可以通過(guò)觸摸屏控制系統(tǒng)的運(yùn)行，也可以通過(guò)控制柜面板上的指示燈和按鈕、轉(zhuǎn)換開(kāi)關(guān)來(lái)了解和控制系統(tǒng)的運(yùn)行。通過(guò)安裝在出水管網(wǎng)上的壓力變送器，把出口壓力信號(hào)變成 4 20mA 或 0 10V 標(biāo)準(zhǔn)信號(hào)送入 PLC 內(nèi)置的 PID 調(diào)節(jié)器，經(jīng) PID 運(yùn)算與給定壓力參數(shù)進(jìn)行比較，輸出運(yùn)行頻率到變頻器。控制系統(tǒng)由變頻器控 制水泵的轉(zhuǎn)速以調(diào)節(jié)供水量，根據(jù)用水量的不同， PLC 頻率輸出給定變頻器的運(yùn)行頻率，從而調(diào)節(jié)水泵的轉(zhuǎn)速，達(dá)到恒壓供水。 PLC 設(shè)定的內(nèi)部程序驅(qū)動(dòng) I/O 端口開(kāi)關(guān)量的輸出來(lái)實(shí)現(xiàn)切換交流接觸器組，以此協(xié)調(diào)投入工作的水泵電機(jī)臺(tái)數(shù)，并完成電機(jī)的啟停、變頻與工頻的切換。通過(guò)調(diào)整投入工作的電機(jī)臺(tái)數(shù)和控制電機(jī)組中一臺(tái)電機(jī)的變頻轉(zhuǎn)速，使系統(tǒng)管網(wǎng)的工作壓力始終穩(wěn)定，進(jìn)而達(dá)到恒壓供水的目的。 該系統(tǒng)有手動(dòng)和自動(dòng)兩種運(yùn)行方式。手動(dòng)方式時(shí)，通過(guò)控制柜上的啟動(dòng)和停止按鈕控制水泵運(yùn)行，可根據(jù)需要分別控制 1# 3#泵的啟停，該方式主 要供設(shè)備調(diào)試、自動(dòng)有故障和檢修時(shí)使用。自動(dòng)運(yùn)行時(shí)，首先由 1#水泵變頻運(yùn)行，變頻器輸出頻率從 0HZ 上升，同時(shí) PID 調(diào)節(jié)器把接收的信號(hào)與給定壓力比較運(yùn)算后送給變頻器控制。如壓力不夠，則頻率上升到 50HZ，由 PLC 設(shè)定的程序驅(qū)動(dòng)I/O 端口開(kāi)關(guān)量的輸出來(lái)實(shí)現(xiàn)切換交流接觸器組，使得 1泵變頻迅速切換為工頻， 2泵變頻啟動(dòng)，若壓力仍達(dá)不到設(shè)定壓力，則 2泵由變頻切換成工頻， 3泵變頻啟動(dòng)；如用水量減少， PLC 控制從先起的泵開(kāi)始切除，同時(shí)根據(jù) PID調(diào)節(jié)參數(shù)使系統(tǒng)平穩(wěn)運(yùn)行，始終保持管網(wǎng)壓力。 若有電源瞬時(shí)停電的情 況，則系統(tǒng)停機(jī)，待電源恢復(fù)正常后，人工啟動(dòng)，系統(tǒng)自動(dòng)恢復(fù)到初始狀態(tài)開(kāi)始運(yùn)行。變頻自動(dòng)功能是該系統(tǒng)最基本的功能，系統(tǒng)自動(dòng)完成對(duì)多臺(tái)泵的啟動(dòng)、停止、循環(huán)變頻的全部操作過(guò)程。 在進(jìn)行通信之前必須對(duì) PLC、觸摸屏和變頻器的通訊參數(shù)進(jìn)行正確設(shè)置。本系統(tǒng)定義為 Modbus 協(xié)議，波特率為 9600，數(shù)據(jù)位為 8，無(wú)校驗(yàn)，停止位為 1。變頻器除設(shè)置通信參數(shù)外，還需啟用 “自由停車(chē) ”以保護(hù)電機(jī)。 PLC 通訊參數(shù)設(shè)置 :TWDLCAA24DRF硬件 端口 端口設(shè)置，在端口設(shè)置中進(jìn)行端口參數(shù)設(shè)置；觸摸屏通訊參數(shù) 設(shè)置： IO 管理器ModbusRTU01COM1Modbus Equipment，雙擊 “Modbus Equipment”即可進(jìn)行通訊參數(shù)設(shè)置。 該系統(tǒng)采用施耐德的 TWDLCAA24DRF， I/O 點(diǎn)數(shù)為 24 點(diǎn)，繼電器輸出，PLC 編程采用施耐德 PLC 專(zhuān)用編程軟件 Twidosoft，軟件提供完整的編程環(huán)境，可進(jìn)行離線(xiàn)編程、在線(xiàn)連接和調(diào)試。為了提高整個(gè)系統(tǒng)的性?xún)r(jià)比，該系統(tǒng)采用可編程控制器的開(kāi)關(guān)量輸入輸出來(lái)控制電機(jī)的起停、自動(dòng)投入、定期切換，供水泵的變頻及故障的報(bào)警等，而且通過(guò) PLC 內(nèi)置的 PID 給定電機(jī)的轉(zhuǎn)速、設(shè)定壓力、頻率、電流、電壓等模擬信號(hào)量 。 施耐德 PLC 的編程指令簡(jiǎn)單易懂且程序設(shè)計(jì)靈活，步進(jìn)計(jì)數(shù)器功能模塊（ %SCi）提供了一系列的步，這些步可賦值給動(dòng)作。從一個(gè)步移動(dòng)到另一個(gè)步取決于外部或內(nèi)部事件。通過(guò)模擬輸入和輸出模塊TWAMM3HT以及內(nèi)置的 PID 運(yùn)算器，實(shí)現(xiàn)如圖 2 的順序切泵。 泵組切換示意圖如圖 2，工作條件滿(mǎn)足，開(kāi)始工作時(shí)， 1#泵變頻啟動(dòng)，泵的轉(zhuǎn)速隨變頻器輸出頻率的上升而逐漸升高，如變頻器的頻率達(dá)到 50HZ而此時(shí)水壓還未達(dá)到設(shè)定值， PLC 內(nèi)置的程序控制使得切換到下一個(gè)工作步 ，延時(shí)一段時(shí)間后， 1泵迅速切換至工頻運(yùn)行，同時(shí)解除變頻器運(yùn)行信號(hào)，使變頻器頻率降為 0HZ，然后 2泵變頻啟動(dòng)，若壓力仍未達(dá)到，則 2泵切換至工頻， 3泵變頻啟動(dòng)，在運(yùn)行中始終保持一臺(tái)泵變頻運(yùn)行，當(dāng)壓力達(dá)到設(shè)定值時(shí)變頻輸出將為0HZ，同時(shí) PLC 通過(guò) I/O 端口跳到下一個(gè)工步，由 PLC 決定切除 1工頻泵，此時(shí)由一臺(tái)工頻泵和一臺(tái)變頻泵運(yùn)行，如果此時(shí)壓力達(dá)到設(shè)定值，變頻器的輸出為0HZ，再切換到下一個(gè)工步， PLC 解除 2工頻泵，只由 3泵變頻運(yùn)行來(lái)維持管網(wǎng)壓力。當(dāng)壓力下降，變頻器頻率升至 50HZ輸出信號(hào)，延時(shí)后 3 泵切換為工頻， 1泵變頻啟動(dòng)，若壓力仍不滿(mǎn)足則 1變切換為 1工， 2泵變頻運(yùn)行，如果壓力仍達(dá)不到， 2變切換為 2工，啟動(dòng) 3變，三臺(tái)泵同時(shí)工作以保證供水要求。 這樣的切換過(guò)程有效地減少泵的頻繁起停，同時(shí)在實(shí)際管網(wǎng)對(duì)水壓波動(dòng)做出反應(yīng)之前，由變頻器迅速調(diào)節(jié)，使水壓平穩(wěn)過(guò)渡，從而有效的避免了高樓用戶(hù)短時(shí)間停水的情況發(fā)生。 以往的變頻恒壓供水系統(tǒng)在水壓高時(shí)，通常采用停變頻泵，再將變頻器以工頻運(yùn)行方式切換到正在以工頻運(yùn)行的泵上進(jìn)行調(diào)節(jié)。這種切換的方式理論上要比直接切換工頻的方式先進(jìn)，但其容易引 起泵組的頻繁起停，從而減少設(shè)備的使用壽命。而在該系統(tǒng)中采用直接停工頻泵的運(yùn)行方式，同時(shí)由變頻器迅速調(diào)節(jié)，只要參數(shù)設(shè)置合適，即可實(shí)現(xiàn)泵組的無(wú)沖擊切換，使水壓過(guò)渡平穩(wěn)，有效的防止了水壓的大范圍波動(dòng)及水壓太低時(shí)的短時(shí)間缺水的現(xiàn)象，提高了供水品質(zhì)。 該系統(tǒng)采用 PLC 和變頻器結(jié)合，系統(tǒng)運(yùn)行平穩(wěn)可靠，實(shí)現(xiàn)了真正意義上的無(wú)人職守的全自動(dòng)循環(huán)切泵、變頻運(yùn)行，保證了各臺(tái)水泵運(yùn)行效率的最優(yōu)和設(shè)備的穩(wěn)定運(yùn)轉(zhuǎn)啟動(dòng)平穩(wěn)，消除了啟動(dòng)大電流沖擊，由于泵的平均轉(zhuǎn)速降低了，從而可延長(zhǎng)泵的使用壽命，可以消除啟動(dòng)和停機(jī)時(shí)的水錘效應(yīng)。通過(guò) 觸摸屏上的人機(jī)界面就可進(jìn)行供水壓力的設(shè)定，監(jiān)視設(shè)備運(yùn)行狀況同時(shí)可以查詢(xún)?cè)O(shè)備故障信息，大大提高恒壓供水系統(tǒng)的自動(dòng)化水平及對(duì)現(xiàn)場(chǎng)設(shè)備的監(jiān)控能力。The application of exchange frequency Introduction in the industry scene control domain, the programmable controller (PLC) has been playing the vital role. Enlarges along with the country in the water supply professions investment efforts, the water works movement automation level enhances unceasingly, PLC increases gradually in the water supply profession application. The touchscreen and the PLC necessary use, causes PLC the applicatio n to be more flexible, simultaneously may establish situation description automation processes and so on parameter, demonstration data, by animation, causes PLC the application visualization. The frequency conversion constant pressure water supply becomes the water supply profession a mainstream, is guarantees the water supply pipe network in the constant pressure important means. The modern frequency changer perfect network service project, the prestige electrical machinerys synchronized movement, the long-distance range common control and the online monitoring and so on have provided the essential support. Through with the PLC connections touchscreen, may cause the control to be more direct-viewing, the operation is simpler conveniently. The combination using PLC, the touchscreen and the frequency changer, uses the mailing address to carry on the control to the frequency changer to realize the frequency conversion constant pressure water supply Frequency conversion constant pressure water supply system principle like chart 1； It mainly by PLC, the frequency changer, the touchscreen, the pressure transmitting instrument, the power and the control wiring as well as the pump group is composed. The user may through the touchscreen control systems movement, may also through the control cubicle kneading boards on indicating lamp and the button, the change-over switch understands and control systems movement. Through installs in the outlet pipe on-line pressure transmitting instrument, turns 420mA or the 010V standard the outlet pressure signal The signal sends in PLC the built-in PID regulator, with assigns the pressure parameter after the PID operation to carry on the comparison, the output movement frequency to the frequency changer. The control system controls water pumps rotational speed by the frequency changer to adjust the volume of diversion, according to the water consumption difference, the PLC frequency output assigns frequency changers movement frequency, thus adjusts water pumps rotational speed, achieves the constant pressure water supply. The PLC hypothesiss internal procedure actuates the I/O port switch quantity to lose realizes the cut exchange to meet Touches the group, puts into the work coordinated by the water pump electricity radio station number, and completes the electrical machinery to open stops, the frequency conversion and the power frequency cut. Through in the adjustment investment works electricity radio station number and the control electrical machinery an electrical machinerys frequency conversion rotational speed, causes the system pipe networks working pressure to stabilize throughout, then achieves the constant pressure water supply the goal. This system has manual and the automatic two movement way. When manual way, through control cubicles on start and the pause button control water pump movement, may according to need to control the 1#3# pump to open separately stops, this way mainly for the equipment debugging, automatically has time the breakdown and the overhaul uses. When automatic movement, first by the 1# water pump frequency conversion movement, the frequency changer output frequency from the 0HZ rise, simultaneously the PID regulator after assigning the pressure comparison operation gives the receive signal the frequency changer control. If the pressure is insufficient, then the frequency rises 50HZ, actuates the I/O port switch quantity by the PLC hypothesiss procedure to lose realizes the cut exchange contact device group, causes the 1# pump frequency conversion rapid cut is the power frequency, the 2# pump frequency conversion starts, if the pressure still could not achieve the hypothesis pressure, then 2# The pump cuts the power frequency by the frequency conversion, 3# the pump frequency conversion start； If the water consumption reduces, the PLC control gets up formerly the pump starts to excise, simultaneously causes the system according to the PID adjustment parameter to move steadily, maintains the pipe network pressure throughout. If has the power source instant power cut situation, then the system engine off, after treating the power source restores normally, manually actuated, the system self-recovery to the original state starts to move. The frequency conversion automatic function is this system most basic function, the system completes automatically to many pumps starts, the stop, the circulation frequency conversion complete operating process。 Plant parameters establishment before carrying on the correspondence must to PLC, the touchscreen and frequency changers communication parameter carries on the correct establishment. This system definition is the Modbus agreement, the baudrate is 9600, the data position is 8, does not have the verification, stops the position is 1. Frequency changer besides establishment correspondence parameter, but must begin using “the free parking” to protect the electrical machinery. PLC communication parameter establishment: The TWDLCAA24DRF- hardware - - port - - port establishment, carries on the port parameter establishment in the port establishment； Touchscreen communication parameter establishment: IO supervisor - - ModbusRTU01COM1-Modbus Equipment, the double click “Modbus Equipment” then carries on the communication parameter establishment This system uses Shinaide TWDLCAA24DRF, I/O points is 24 spots, the relay outputs, the PLC programming uses Shinaide PLC special-purpose programming software Twidosoft, the software provides the complete programming environment, may carry on the off-line programming, the online connection and the debugging. In order to enhance the overall system The performance-to-price ratio, this system uses the programmable controllers switch quantity input to lose controls the electrical machinery to stop, the automatic investment, the regular cut, water supply pumps frequency conversion and the breakdown warning and so on, moreover assigns simulated signal quantities and so on electrical machinerys rotational speed, hypothesis pressure, frequency, electric current, voltage through PLC built-in PID. The pump group cuts the schematic drawing like chart 2, the working condition satisfies, starts when works, the 1# pump frequency conversion starts, pumps rotational speed elevates gradually along with the frequency changer output frequencys rise, if frequency changers frequency achieves 50HZ, but this time hydraulic pressure has not achieved the setting value, the PLC built-in programmed control causes to cut the next work step, after time delay period of time, the 1# pump rapid cut to the power frequency movement, simultaneously relieves the frequency changer movement signal, causes the frequency changer frequency to reduce to 0HZ, then the 2# pump frequency conversion starts, if the pressure had still not achieved, then the 2# pump cut to the power frequency, the 3# pump frequency conversion starts, maintains a pump frequency conversion movement throughout in the movement, when the pressure achieves the setting value the frequency conversion output will be 0HZ, simultaneously PLC jumps through the I/O port to the next labor step, by PLC decided that excises the 1# power frequency pump, this time by a power frequency pump and a frequency conversion pump movement, if this time pressure achieves the setting value, frequency changers losing Leaves is 0HZ, cuts the next labor again step, PLC relieves the 2# power frequency pump, only maintains the pipe network pressure by the 3# pump frequency conversion movement. When the drop of pressure, the frequency changer frequency climbs to the 50HZ output signal, after the time delay, the 3# pump cut is the power frequency, the 1# pump frequency conversion starts, if the pressure still did not satisfy, then 1# changes the cut is the 1# labor, 2# pump frequency conversion movement, if the pressure still could not achieve, 2# changes the cut is the 2# labor, starts 3# changes, three pumps simultaneously work guarantee the water supply request. Such cut process reduces the pump to be frequent effectively stops, simultaneously in the actual pipe network makes the response before the hydraulic pressure fluctuation, adjusts rapidly by the frequency changer, causes the hydraulic pressure stable transition, thus effective has avoided the situation occurrence which the tall building user short time cuts off the water supply. Former frequency conversion constant pressure water supply system when height of water, usually uses stops the frequency conversion pump, cuts again the frequency changer by the power frequency movement way is carrying on by on the power frequency movement pump the adjustment. This cuts way must be more advanced than theoretically the direct cut power frequency way, but it easy to cause the pump group to be frequent stops, thus reduces equipments service life. But uses in this system stops