摘  要:为了满足中国城市小区的供水需求，本文设计了一套基于可编程控制器(PLC)的变频恒压供水系统。变频恒压供水系统由PLC、变频器、水泵机组、压力传感器等构成。系统包含三台水泵电机，它们组成变频循环运行方式，采用变频器实现对三相水泵电机的软启动和变频调速，运行时采用“先启先停”的切换原则。压力传感器检测当前水压信号，送入PLC与设定值比较后进行PID运算，从而控制变频器的输出频率，进而改变水泵电机的转速来改变供水量，最终保持管网压力稳定在设定值附近。系统仿真测试表明该设计操作方便，性能良好，进一步提高了恒压供水控制的安全性、可靠性与实用性。4864
关键词:变频调速；恒压供水；PLC

Design of Various Frequencies Constant Pressure Water Supply System Based on PLC
Abstract: A set of water supply system of frequency control of constant pressure with PLC is designed in this paper which is to satisfy the requirement of china’s urban water supply .The system is made up of PLC, transducer, units of pumps, pressure sensor and so on. This system is formed by three pump generators, and they form the circulating run mode of frequency conversion. The three phase pump generator soft start and frequency control are realized through general frequency converter, and the principle of “start first and stop first” is adopted during the operation switch. The hydraulic pressure signal is detected by the pressure sensor and the PID calculation is carried out after the signal had been compared with set value, so that the export frequency of voltage is controlled .After that, the rotational speed is changed, which results in the change of water supply quantity, and eventually the hydraulic pressure is stabilized nearby the set value. The simulated test of system indicates the design is operated easily and has good quality, which further improves the safety, reliability and practicability of level control.
Key Words: Variable frequency speed-regulating; Constant-pressure water supply; PLC
目    录

摘要    1
引言    2
1.绪论    2
1.1课题目的及意义    2
1.2研究现状    2
1.3本课题的主要研究内容    3
2.系统理论分析及控制方案确定    3
2.1电动机的调速原理    3
2.2控制方案的确定    3
3.系统硬件设计    5
3.1系统主要设备的选型    5
3.2系统控制电路的设计    9
4.系统软件设计    10
4.1主程序设计    10
4.2子程序设计    14
4.3 PID控制器参数整定    16
5.系统仿真    19
6.结束语    22
参考文献    22
致谢    23
基于PLC的变频恒压供水系统设计
引言
随着近几十年的改革开放，我国的经济与城市建设迅猛发展，人民的生活水平不断提高；与此同时，城市的居民及工业用水需求量日益加大，这些都对城市的供水系统提出了更高的要求。我国大部分城市的供水方式主要采用恒速泵加压供水方式或水塔高位水箱供水等方式，恒速泵加压供水不能对供水管网压力做出及时快捷的反应，并且水泵的增减过渡依赖人工操作，而且在用户用水量较少时，电机的硬起动很容易产生水锤效应，破坏性极大。高位水塔水箱供水方式容易引起水源的二次污染，且平常进行设备的检测文修时很不方便。因此，传统的恒压供水方式大都存在自动化程度低、设备使用效率低及不稳定等缺点。目前随着可编程序控制器(PLC)技术的发展及交流异步电动机变频调速技术的改革，将PLC及变频器应用于供水系统，可满足城市供水系统多方面的要求[1]。 基于PLC的变频恒压供水系统设计:http://www.751com.cn/zidonghua/lunwen_1664.html