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，但供水系统本身却存在着水电供应不足的压力。在传统的供水装置中，往往水泵的选取是由最大供水的容量来确定的，但实际的供水量是时刻变化的，从而导致供水压力不稳、水泵效率低，并导致水资源浪费。这样就要求设计出更好的供水系统，这些系统能利用先进的自动控制技术、计算机技术以及通信技术，具有高性能、低能耗的特点，能适应不同领域的应用。恒压供水系统既是其中之一[1]。
本系统的设计是基于西门子 S7-200 系列 PLC 控制的变频供水系统，本文介绍了该控制系统的节能原理、系统构成和工作原理。通过PLC 进行逻辑控制，由变频器进行压力调节，经PID运算，PLC 进行控制变频和工频切换，从而使闭环自动调节恒压，进行变量供水。本文在系统的设计部分，对硬件系统配置、选型和软件系统的流程设计、程序设计进行了详细的介绍，并指出了系统设计过程中存在的问题，给出相关解决方法。该供水系统对水压实时控制性能良好，硬件模块工作稳定、可靠，变频器的控制方式采用模拟量输入，通信输出控制，通过 PID 指令实现闭环控制正确有效，达到了恒压供水系统的控制要求，满足城区居民工作和生活的日常用水需要。
关键词：PLC 变频 恒压供水
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ABSTRACT
With the rapid social-economic development, people's water quality and water system reliability requirements continue to increase, but the water supply system itself but there is a shortage of water supply pressure. In the traditional water supply device, often pump selection is determined by the maximum capacity of the water supply to determine, but the actual amount of water is constantly changing, resulting in unstable water pressure, water pump, low efficiency, and lead to waste of water resources. This requires design a better water supply systems, these systems can take advantage of advanced automatic control technology, computer technology and communication technology, high performance, low power consumption characteristics, can adapt to different fields of application. Water Supply System is both one of them.
The system design is based on Siemens S7-200 series PLC control frequency of water supply systems, this paper introduces the control system of the energy conservation principle, the system structure and working principle. Through the PLC logic control, pressure control by the inverter, the PID operation, PLC control and frequency switching frequency, allowing constant pressure closed-loop automatic adjustment for variable water supply. This part of the system design, the hardware system configuration, software selection and process design, process design has been described in detail, and points out the problems in the design process, give relevant solutions. The water supply system for real-time control performance is good water pressure, the hardware module is stable, reliable, and inverter control method using analog inputs, communication output control, closed-loop control by the PID instruction correctly and effectively achieve a constant pressure water supply system control requirements
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to meet the urban residents live and work daily water needs.
Key words: PLC inverter constant pressure water supply
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目 录
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第1章 绪论 ............................................................................ 1
1.1 本课题的背景及其意义 .............................................. 1 1.2 供水系统国内外现状 ................................................. 1 1.3 主要设计研究工作及组织结构 ................................... 3 第2章 PLC技术与变频技术概述 ............................................. 5
2.1 可编程控制器（PLC）概述 ........................................ 5
2.1.1 PLC的基本概念 ............................................... 5 2.1.2 PLC的基本结构 ............................................... 5 2.1.3 PLC的工作原理 ............................................... 6 2.1.4 PLC应用介绍 .................................................. 8 2.2 变频器技术 ................................................................ 9
2.2.1 变频技术概念 ................................................. 9 2.2.2 变频器结构分类 ............................................ 10 2.2.3 变频器与PLC使用USS通信 .......................... 11
第3章 系统的总体分析 ........................................................ 13
3.1 供水系统的要求 ....................................................... 13
3.1.1 供水系统电机运行分析 ................................. 13 3.1.2 供水系统的特性分析 ..................................... 14 3.2 供水系统的结构 ....................................................... 15
3.2.1 主要组成部分 ............................................... 15
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3.2.2 电气控制系统 ............................................... 15 3.3 供水系统控制方案的设计与选择 ............................. 16
3.3.1 专用变频器控制 ............................................ 16 3.3.2 可编程序控制器（PLC）控制 ........................ 16 3.4 供水系统的工作原理 ............................................... 17
3.4.1 控制系统总体框图 ........................................ 17 3.4.2 系统运行分析 ............................................... 18
第4章 硬件系统配置 ............................................................ 20
4.1 PLC 的选择 .............................................................. 20
4.1.1 PLC 的具体选型 ............................................ 20 4.1.2 PLC 的 I/O 资源配置 ................................... 21 4.1.3 PLC 控制系统与端口连接 ............................. 22 4.2 变频器的选择 .......................................................... 23
4.2.1 变频器的选型 ............................................... 23 4.2.2 MM430型变频器性能特点及技术指标 ............ 24 4.2.3 MM430型变频器的参数设定和调试 ................ 25 4.3 水泵的选择 .............................................................. 26
4.3.1 选用水泵的原则 ............................................ 27 4.3.2 选择水泵应注意的问题 ................................. 27 4.4 其它相关设备的选择 ............................................... 28
4.4.1 压力传感器的选择 ........................................ 28 4.4.2 接触器 .......................................................... 28 4.4.3 主令电器 ....................................................... 29 4.5 系统硬件连接图 ....................................................... 30 第5章 软件系统的设计 ........................................................ 31
5.1 总体流程设计 .......................................................... 31
5.1.1 手动运行流程设计 ........................................ 32
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