东北石油大学秦皇岛分校毕业论文 摘 要
在城市化进程迅速的今天，城市的居住形式主要是生活小区，那么小区供水系统的建设就显得尤为重要。而且随着城市用水量不断增加，对供水系统的建设提出了更高的要求。供水的经济性、可靠性、稳定性直接影响到小区住户的正常生活和工作。本系统是针对居民生活用水而设计的一套由变频器、PLC、水泵机组等设备组成的自动变频恒压供水控制系统。该系统将PLC、变频器、相应的传感器和执行机构有机地结合起来，并发挥各自优势，能够最大程度满足需要，具有运行稳定、操作简单和高效节能等特点。该系统对变频器内置PID模块参数进行预置，通过压力传感器对水压的反馈构成闭环控制系统；PID模块根据用水量的变化调节水泵的输出流量，实现恒压供水，并达到有效节能的目的。本文首先介绍了采取变频调速方式实现恒压供水相对于传统的阀门控制恒压供水方式的节能原理；其次，对水泵机组的各种供水状态及转换的条件、水泵由变频转工频运行方式的切换过程进行分析，着重研究并提出了基于PLC和变频器的恒压供水系统的方案，并给出了硬件设计和PLC控制程序设计以及组态控制界面。
组态软件是实现现场数据采集与过程控制的专用软件，其突出特点是实时多任务 可以实现数据采集与输出、数据处理、图形显示及人机对话、实时数据的存储、检索管理、实时通信等多个任务在同一台计算机上运行。
水厂的控制系统一般采用上位机与下位机相结合的体系结构，体现了“分散控制、集中管理”的现代控制思想。水厂自动监控系统，与所有过程控制计算机系统一样，从硬件上可以分为检测仪表、计算机输入输出接口、计算机以及控制执行机构四大部分。本系统采用现场操作站和控制站两级控制结构。系统操作站主要由以下几部分组成：上位机（工控机），PLC，软启动器等。控制站系统包括主机系统、通讯系统、I/O接口及变送器等组成部分。
本系统具备同时控制多台水泵的功能。水厂自动监控系统主要由中央控制室与各水源站分控制室组成。根据不同需要可以采取多台水泵同时运行、定时换泵等多种工作方式。泵电机采用软启动。
本系统通过力控组态软件编辑的操作界面和PLC控制，实现了远程控制，使其操作更加简便,更加安全。
关键词： 组态软件；PLC; 流量；变频调速；水压；压力传感器；
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东北石油大学秦皇岛分校毕业论文 目录
摘要 ···························································································································· - 1 - 第1章 绪论 ············································································································· - 1 -
1.1课题的意义 ······································································································ - 1 - 1.2方案的拟定 ··········································································································· 2 1.3供水系统的安全性讨论 ························································································ 2 1.4设计思想 ··············································································································· 3 第2章 系统的理论分析 ···························································································· 4 2.1 控制方式的选择 ··································································································· 4 2.2 软件实现 ·············································································································· 5 2.3 程序控制······································································································ 6 2.3.1 安全可靠性程序设计 ·············································································· 6 2.3.2 报警程序设计 ························································································ 7 第3章 供水系统的构成及工作原理 ······································································ 8 3.1 供水系统的构成 ··································································································· 8 3.2 电气控制系统的构成 ··························································································· 8 3.3 组成部分 ·············································································································· 8 3.4 供水系统原理 ····································································································· 10 3.5 工作过程 ············································································································ 10 3.5.1 流量水压控制过程 ······················································································ 11 3.6 硬件系统配置 ···································································································· 12 3.6.1 PLC和计算机的通讯方向 ············································································ 12 3.6.2 PLC的选型 ··································································································· 12 3.6.3 PLC的接线 ··································································································· 14 3.6.4 I/O分配 ········································································································· 15 3.6.5 PID调节 ········································································································ 15 第4章 力控组态软件介绍 ····················································································· 17 4.1 力控组态软件 ····································································································· 17 4.1.1 力控的五大部分 ·························································································· 17 4.2 建立界面 ············································································································ 17 4.2.1 建立窗口 ······································································································ 17 4.2.2 定义数据对象 ······························································································ 18 4.3 界面编辑 ············································································································ 18 4.4 力控与PLC的连接 ····························································································· 19 4.4.1添加PLC设备 ······························································································ 19 4.4.2 PLC设备属性的设置 ···················································································· 20 4.5 总结 ···················································································································· 20
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东北石油大学秦皇岛分校毕业论文 参考文献 ······················································································································ 22 致谢 ······························································································································· 23
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东北石油大学秦皇岛分校毕业论文 第一章 绪论
1.1 课题的意义
随着变频技术的发展和人们对生活饮用水品质要求的不断提高，变频恒压供水系
统以其环保、节能和高品质的供水质量等特点，广泛应用于多层住宅小区及高层建筑的生活、消防供水中。变频恒压供水的调速系统可以实现水泵电机无级调速，依据用水量的变化自动调节系统的运行参数，在用水量发生变化时保持水压恒定以满足用水要求，是当今最先进、合理的节能型供水系统。在实际应用中如何充分利用专用变频器内置的各种功能，对合理设计变频恒压供水设备、降低成本、保证产品质量等有着重要意义。变频恒压供水方式与过去的水塔或高位水箱以及气压供水方式相比，不论是设备的投资，运行的经济性，还是系统的稳定性、可靠性、自动化程度等方面都具有无法比拟的优势，而且具有显著的节能效果。目前变频恒压供水系统正向着高可靠性、全数字化微机控制、多品种系列化的方向发展。追求高度智能化、系列化、标准化，是未来供水设备适应城镇建设中成片开发、智能楼宇、网络供水调度和整体规划要求的必然趋势。
变频恒压供水系统能适用生活水、工业用水以及消防用水等多种场合的供水要求，该系统具有以下特点:
(1)供水系统的控制对象是用户管网的水压，它是一个过程控制量，同其他一些过程控制量(如:温度、流量、浓度等)一样，对控制作用的响应具有滞后性。同时用于水泵转速控制的变频器也存在一定的滞后效应。
(2)变频调速恒压供水系统要具有广泛的通用性，面向各种各样的供水系统，而不同的供水系统管网结构、用水量和扬程等方面存在着较大的差异，因此其控制对象的模型具有很强的多变性。
(3)在变频调速恒压供水系统中，由于有定量泵的加入控制，而定量泵的控制(包括定量泉的停止和运行)是时时发生的，同时定量泵的运行状态直接影响供水系统的模型参数，使其不确定性地发生变化，因此可以认为，变频调速恒压供水系统的控制对象是时时变化的。
(4)当出现意外的情况(如突然停水、断电、泵、变频器或软启动器故障等)时，系统能根据泵及变频器或软启动器的状态，电网状况及水源水位，管网压力等工况点自动进行切换，保证管网内压力恒定。在故障发生时，执行专门的故障程序，保证在紧急情况下的仍能进行供水。
(5)用变频器进行调速，用调节泵和固定泵的组合进行恒压供水，节能效果显著，对每台水泵进行软启动，启动电流可从零到电机额定电流，减少了启动电流对电网的冲击同时减少了启动惯性对设备的大惯量的转速冲击，延长了设备的使用寿命。 利用力控组态软件强大的HMI（人机界面）/ SCADA（监控和数据采集）功能，在上位机上应用组态软件来开发全自动恒压供水系统。在整个控制过程中通过编程实现了供水系统的自调整，设备远程操控，达到恒压、节能的效果，整个系统具有可靠
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