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1、存档日期：存档日期： 存档编号：存档编号： 江江 苏苏 师师 范范 大大 学学 科科 文文 学学 院院 本科生毕业论文（设计）论论 文文 题题 目：目： 变频恒压供水系统的实现 姓姓 名：名： 刘 凯 歌 系系 别：别： 机电工程系 专专 业业 ： 自 动 化 班班 级级 、 学学 号号： 科 08 自动 088319114 指指 导导 教教 师：师： 刘 丽 俊 江苏师范大学科文学院教务部印制江苏师范大学科文学院教务部印制摘摘 要要随着社会的发展，人们对供水系统的质量和可靠性的要求也在不断提高。使用先进的自动化控制技术和通信技术，设计高性能、高质量、适应能力强的供水系统是适应社会发展的必然要
2、求。本文在总结国内外供水系统的基础上并结合我国中、小城市用水现状，设计了一套以变频调速技术为基础变频恒压供水系统。 本文通过分析变频恒压供水系统的原理及构成，提出了系统的控制方案；水泵机组由三台水泵并联而成，使用变频器或工频电网供电。采用 PLC 实现水泵的切换和控制变频器输出频率的大小。管网水压信号由压力传感器变换成电信号送入PLC，经 PLC 内部的 PID 指令运算处理后获得最佳控制参数，经 D/A 转换后送给变频器的频率控制端子,以此改变变频器的输出频率进而改变水泵电机的转速。当变频器的输出频率达到频率上、下限时，就要依靠 PLC 完成水泵的切换，从而实现系统的恒压供水。水泵切换采用“
3、先启先停”的原则，即当变频运行状态下的水泵工作在50HZ，且管网出水口的水压仍低于额定水压时，就将该水泵切换到工频电网下，同时启动下一台水泵变频运行；当变频运行状态下的水泵工作在频率下限，且管网出水口的水压仍高于给定水压时，就停止最早工作在工频电网下的水泵。在此基础上采用 RS232数据线实现 MCGS 组态软件和 PLC 之间的数据通信，来完成供水系统的远程监控。通过系统调试，所设计的供水系统很好的实现了管网水压的恒定，以及在上位机可以实时监控到整个系统的运行状况。关键词：关键词： 变频器 恒压供水 MCGS 组态软件 PLCAbstractWith the development of s
4、ociety, people pay more attention on the quality and reliability of the water supply systems . The use of advanced automatic control technology and communication technology, The system of water supply which is of high performance,high quality and strong ability is adapted to the requirement of socia
5、l development. Based on both the system of water supply of home and abroad and the use of water in small city,the paper design a set of variable frequency constant pressure water supply system, based on the speed control technology of variable frequency.The paper, through the analysis of principle a
6、nd structure of variable frequency constant pressure water supply system, put forward a own control scheme. Pump unit which is composed by three water pumps can use frequency converter or power frequency to supply power and PLC to achieve the pump switch and control the size of the inverter output f
7、requency. Pipeline water pressure signals from the pressure sensor is transformed into electrical signal into PLC, and then the optimal control parameters is obtained after the processing of PLC inside the PID instruction. The optimal control parameters is transformed into the frequency converter co
8、ntrol terminal by D/A conversion, and the inverters output frequency and the pump motor speed are changed. When the inverters output frequency is to its upper or lower limit, PLC will achieve the pump switch , realizing the constant pressure water supply system. Water pump switch adopts the principl
9、e of first start first stop.When the operation frequency of the water pump is under the pump working frequency of 50HZ, and the network outlet pressure is lower than the rated pressure, the pump is switched to the power frequency, and start the next water pump of frequency conversion operation. When
10、 the operation frequency of the water pump is 20HZ, and the pipe network water outlet pressure is still higher than the rated pressure, stops the earliest pump which is working in the power grid.The data communication between the MCGS configuration software and PLC is realized by Using RS232 data li
11、ne to complete the remote monitoring of the water supply system.Key words: Inverter Constant pressure water supply MCGS PLC目目 录录摘摘 要要. AbstractAbstract.1 绪论绪论.11.1 课题研究的背景与意义.11.2 变频恒压供水系统的现状和发展.11.3 本文研究的主要内容.22 变频恒压供水系统的节能原理变频恒压供水系统的节能原理.42.1 供水系统的几个主要参数.42.2 供水系统的基本特性与工作点.42.2.1 供水系统的基本特性.42.2.2 供水系统的工作点.62.3 水泵变频运行的节能原理.63 变频恒压供水系统的方案论证变频恒压供水系统的方案论证.83.1 传统供水系统与变频恒压供水系统的比较.83.2 变频恒压供水系统控制方案的确定.93.3 系统被控变量的确定.
