辽宁石油化工大学继续教育学院毕业设计（论文）
基于S7-200的楼宇恒压供水控制系统设计
摘 要
随着社会经济的迅速发展，人们对供水质量和供水系统可靠性的要求不断提高;再加上目前能源紧缺，利用先进的自动化技术、控制技术以及通讯技术，设计高性能、高节能、能适应不同领域的恒压供水系统成为必然趋势。本论文结合我国中小城市多层住宅小区的用水现状，设计了一套基于PLC的变频调速恒压自动控制供水系统。
变频调速恒压供水自动控制系统由可编程控制器、内置PID变频器、水泵电机组、压力传感器、及控制柜等构成。系统采用一台变频器拖动2台电动机(30kw)的起动、运行与调速，2台分别采用循环使用的方式运行。
在变频调速恒压供水系统中，单台水泵工况的调节是通过变频器来改变电源的频率f来改变电机的转速n，从而改变水泵性能曲线得以实现的。分析水泵工况的能耗比较图，可以看出利用变频调速实现恒压供水，当转速降低时，流量与转速成正比，功率以转速的三次方下降，与传统供水方式中用阀门节流方式相比，在一定程度上可以减少能量损耗，能够明显节能。
本控制系统中采用了德国SIMENS公司的S7-200可编程控制器，同时选取了一个用于供水系统压力控制的内置PID算法的变频器。该变频器对压力给定值与测量值的偏差进行处理，实时控制变频器的输出电压和频率，进而改变水泵电动机的转速来改变水泵出水口流量，实现管网压力的自动调节，使管网压力稳定在设定值附近。
关键词： PLC；变频调速；恒压供水
- I -
辽宁石油化工大学继续教育学院毕业设计（论文）
Building on the S7-200 Water Supply Control System
Design
Abstract
With the rapid development of social economy, it demands the better of water supply’s quality and reliability of water supply system. Meanwhile energy resources are seriously lack. So it is inevitable tendency to design water supply system which has high function and saves on energy well, with help of advanced technique of automation, control and communication. At the same time this system can adapt different water supply fields. On the basis of analyzing in quo of the waterworks in our country, this designs a suit of constant pressure water supply automatic system paper by using variable frequency speed-regulating technology based on PLC.
The system is made up of PLC, transducer, units of pumps and electromotors, pressure sensor, industrial control computer and console. The system is used a transducer to make four electromotors starting, running and timing. The two electromotors (30Kw) is partly circulated. To connect control computer with PLC and realize supervise, a real time supervise control software of water supply system is developed.
To tune up the frequency of power supply by the transducer in the system, this adjusting make the speed of electromotor and performance curve of pump change. At last, it makes the status of a pump alter. Through analyzing the figure of energy wasting of pump, the quality in pipes is direct proportion of the speed of pump if the speed of
- II -
辽宁石油化工大学继续教育学院毕业设计（论文）
pump is reduced. The power of electromotor fells the cube of the speed of pump. So the energy wasting of constant pressure water supply based on variable frequency speed regulating technology is evidently less than the traditional mode is used throttle to supply water.
Through using S7-200 program software of SIMENS Company in German in the control system. The controller can compare the measure value and the value in advance of pressure. Through real-time controlling the output voltage and frequency of transducer, the output quality of pump is changed along with the changing of pump's speed. It makes the pressure of pipe self-regulating and steady in the scheduled value.
Key Words: PLC；variable frequency speed-regulatingconstant pressure water-supply
- III -
辽宁石油化工大学继续教育学院毕业设计（论文）
目 录
摘要 ............................................................ Ⅰ ABSTRACT ........................................................ Ⅱ 第1章 绪 论 .................................................... 1
1.1 课题来源及其研究意义 ...................................... 1 1.2 多泵恒压供水系统中的关键问题和本文的主要研究内 ............ 1
1.2.1 多泵恒压供水系统中的关键问题 ........................ 1 1.2.2 本文的主要研究内容 .................................. 2
第2章 变频调速恒压供水系统 ...................................... 3
2.1 水泵理论及水泵工况点确定的 ................................ 4
2.1.1 水泵的工作参数 ...................................... 4 2.1.2 水泵基本性能曲线 .................................... 8 2.1.3 水泵理论工况点的确定 ............................... 11 2.2 水泵工况的调节 ........................................... 12 2.3 变频调速恒压供水能耗机理分析 ............................. 13
2.3.1 水泵工况的调节过程 ................................. 13
第3章 可编程控制器PLC .......................................... 14
3.1 PLC的特点与应用领域 ..................................... 14
3.1.1 可编程序控制器的特点 ............................... 14 3.1.2 可编程序控制器与继电器控制系统的比较 ............... 15 3.1.3 PLC的一般结构 ...................................... 16
- IV -
辽宁石油化工大学继续教育学院毕业设计（论文）
3.1.4 PLC基本工作原理 .................................... 18 3.1.5 PLC控制系统设计步骤 ................................ 21 3.1.6 PLC控制系统的硬件设计 .............................. 22 3.2 PLC控制系统的软件设计 ................................... 22
3.2.1 PLC程序设计的常用方法 .............................. 22 3.2.2 PLC程序设计步骤 .................................... 26
第4章 变频调速恒压供水系统设计 ................................. 28
4.1 系统的方案设计及工作过程 ................................. 29
4.1.1 系统的方案设计 ..................................... 29 4.1.2 系统控制方案研究 ................................... 30 4.2 控制系统硬件设计 ......................................... 32
4.2.1 主电路设计 ......................................... 32 4.2.2 控制电路设计 ....................................... 33 4.2.3 PLC配置 ............................................ 34 4.2.4 基于S7-200楼宇恒压供水控制电路 .................... 35 4.3 本系统程序设计 ........................................... 36
4.3.1 PLC程序设计 ........................................ 36 4.3.2 设置切换延时时间 ................................... 38 4.3.3 确保触点互锁 ....................................... 39
第5章 结 论 ................................................... 39 参考文献 ........................................................ 40
- V -