【正文】 Generally speaking, when performed by a frequency converter to control a motor, just make the inverter motor capacity and the actual capacity of the motor can be. When one inverter control two motors, principle of inverter motor capacity should be equal to the capacity of the two motors. But if the peak load of water more than two pumps at full supply a lot of difference, Shanghai arts and science and technology engineers suggested, may be considered appropriate to reduce the capacity of the frequency converter, but attention should be paid to leave enough capacity.Although the pump at low speed, small working current of the motor. However, when the user with the water volume changes frequently, the motor will be in frequent ascending, descen。2, because the average rotational speed of pump is reduced, thereby prolonging the service life of pump and valve etc.。 and each water pump with a frequency converter. After a method based on pressure feedback signal, operated by PID automatically adjusts the output frequency of the inverter, change the speed of the motor, eventually reaching the purpose of network voltage, a closed loop, is relatively simple, but the cost is high. The previous method of low cost, less than kind of poor performance, but the control program is plex, is the future direction of development, such as the Shanghai arts and science and technology of constant pressure water supply control system can realize a inverter control any number of motor function. The principle mentioned below are multiple motor inverter drive system.三．The PID control principleAccording to the feedback principle: to maintain a physical quantity unchanged or essentially unchanged, it should bring the physical quantity and the constant parison, to form a closed loop system. We want to keep the pressure constant, so we must introduce the hydraulic feedback value with a given value, thereby forming a closed loop system. But the control system is characterized by nonlinear, inertial system, now the control method bined with PID in the large pressure fluctuation, using fuzzy control, in order to accelerate the response speed in the pressure range。 because the average rotational speed of pump is reduced, which can extend the pumps and valves and other things of life。( 6) pump unit and circuit protection detection alarm, signal display.The actual pressure of the pipe network feedback and a given pressure were pared, when the pressure of a pipe network is low, increase the output of frequency converter, pump speed faster, water supply quantity increases, forcing the pipe network pressure rise. Vice pump speed slow down, reduce the water supply pipe network pressure drop, to keep the constant pressure water supply.System hardware structureSystem uses a pressure sensor, PLC and inverter as a central control device, to achieve a desired function. Source: network transmission and distribution equipment installation in pipe line pressure sensor, for detecting the water pressure of the pipe network, converting pressure is 4 ~ 20 mA current or voltage signal is 0 ~ 10V, supplied to the inverter.Converter pump motor control device, in accordance with the constant water pressure needs to be 0 ~ 50 Hz frequency signal supply pump motor, adjust its speed SAJ converter is powerful, . preprogrammed set parameter set, will use the required in the process of setting the number of parameters is reduced to a minimum, default value according to the application parameter of the macro choice and different. The system adopts the PID control application macro, closed loop control. Inverter based on a constant pressure corresponding to the voltage setting value and from the pressure sensor to obtain the feedback current signal, the use of PID control macro automatically adjust, change the frequency output value to adjust the control the speed of the pump motor, to ensure that the pipe network pressure constant requirements.The application of inverter in the constant pressure water supply一．The characteristic and analysis of variable frequency speed regulationThe water users in general is dynamic, so the water supply is insufficient or excess water supply situation has occurred. The water supply and the imbalance between the concentrated reflection in water supply pressure, namely water and water supply is less, the low pressure。( 4) system of sleep and wake, when people stop when water, the system is in a sleep state, until the water demand automatically wake。( 2) the control system can be manual or automatic operation。另外，在整個(gè)設(shè)計(jì)的過程中，還得到了同組其他同學(xué)的真誠(chéng)幫助，在此一并表示感謝！回顧這四年的學(xué)習(xí)和生活，還有許多的朋友和同學(xué)在各個(gè)方面給予了我很多的幫助和支持，讓我堅(jiān)持到了最后。在此，我將感謝各位代課老師，是他們教會(huì)我做人的道理。所以我要感謝所有的任課老師，是您們的教育和培養(yǎng)，才使我學(xué)有所獲。在今后，我還要更加努力學(xué)習(xí)，跟上時(shí)代的步伐。雖然設(shè)計(jì)可能還有瑕疵，并且還有很多不盡人意的地方。分析水泵工況點(diǎn)節(jié)流調(diào)節(jié)和變速調(diào)節(jié)能耗比較圖，可以看出利用變頻調(diào)速實(shí)現(xiàn)恒壓供水，當(dāng)轉(zhuǎn)速降低時(shí)，流量與轉(zhuǎn)速成正比，功率以轉(zhuǎn)速的三次方下降，與恒速泵供水方式中用閘閥增加阻力的節(jié)流方式相比，在一定程度上可以減少能量損耗，能夠明顯節(jié)能。電加熱器可能不是最經(jīng)濟(jì)的加熱方式但采用電加熱的方式是最簡(jiǎn)單也是最容易控制的一種加熱方式是最適合本設(shè)計(jì)的加熱方式。在本設(shè)計(jì)中，本人對(duì)設(shè)計(jì)思路進(jìn)行了詳細(xì)的概括，主體分為3部分，溫度控制部分、壓力控制部分，液位控制部分以及三個(gè)控制對(duì)象的銜接。以此來保證壓力的相對(duì)恒定達(dá)到恒壓供水的目的。判斷模塊是否正常初始化 NY溫度設(shè)定A測(cè)混合水箱溫度B與A比較即（BA）啟動(dòng)加熱器PID調(diào)節(jié)SCR溫度設(shè)定A測(cè)混合水箱溫度 壓力控制系統(tǒng)流程圖PLC投入運(yùn)行，程序初始化。并且測(cè)量供水箱的水溫溫度并計(jì)入PLC，測(cè)量溫度B與設(shè)定溫度A進(jìn)行比較得到差值即BA。自動(dòng)運(yùn)行方式判斷水位的高低，如果水位低于下限水位驚醒報(bào)警，如果低于設(shè)定水位打開電動(dòng)調(diào)節(jié)閥對(duì)水箱進(jìn)行補(bǔ)水，當(dāng)水位高于上限水位進(jìn)行報(bào)警，此功能圖保證水位在上限與下限之間。 程序流程設(shè)計(jì) 液位控制系統(tǒng)流程圖PLC投入運(yùn)行進(jìn)行程序的初始化。不同的指令用不同的圖形符號(hào)表，它包括三種基本形式。閉合的觸點(diǎn)允許能量通過它們流到下一個(gè)元素，而打開的觸點(diǎn)阻止能量的流動(dòng)。梯形圖程序允許程序仿真來自電源的電流通過一系列的邏輯輸入條件，決定是否使能邏輯輸出。在這里我們使用的是梯形圖（LAD）。STEP 7Micro/WIN提供三種編輯器來創(chuàng)建您的程序：梯形圖（LAD）、語句表（STL）和功能塊圖（FBD）。在程序編輯器的底部有子程序和中斷服務(wù)程序的標(biāo)簽。程序編輯器中包括程序邏輯和局部變量表。指令樹顯示了所有的項(xiàng)目對(duì)象和創(chuàng)建的控制程序所需要的指令。您可以顯示或者隱藏任意工具欄。STEP 7Micro/WIN項(xiàng)目窗口為創(chuàng)建的控制程序提供了一個(gè)便利的工作環(huán)境。 可以利用PC/PPI 電纜和自由口通訊功能把 S7200 CPU 連接到許多和RS232標(biāo)準(zhǔn)兼容的設(shè)備。如果使用STEP 7Micro/WIN32 ，則也可以通過SIMATIC CP 5511或CP 5611編程。STEP 7Micro/WIN32 221/222/224/224XP/226功能進(jìn)行編程。利用該軟件的監(jiān)控功能還可以實(shí)現(xiàn)用戶程序的調(diào)試及監(jiān)控。STEP7Micro/Win32的基本功能是協(xié)助用戶開發(fā)應(yīng)用軟件，在該環(huán)境下可創(chuàng)建用戶程序，修改和編輯原有的用戶程序，實(shí)現(xiàn)用戶所編輯程序的管理?？勺魅缦驴傮w調(diào)整： P增益，在不發(fā)生振蕩條件下增大其值； I積分時(shí)間，在不發(fā)生主振蕩條件下減小其值