变频恒压供系统的毕业设计.doc

摘要 本论文根据中国城市小区的供水要求，设计了一套基于PLC的变频调速恒压供水系统, 并利用组态软件开发良好的运行管理界面。变频恒压供水系统由可编程控制器、变频器、水泵机组、压力传感器、工控机等构成。 本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，运行切换采用“先启先停”的原则。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电压和频率，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。通过工控机与PLC的连接，采用组态软件完成系统监控，实现了运行状态动态显示及数据、报警的查询。 关键词：变频调速，恒压供水，可编程控制器，组态软件 ABSTRACT According to the requirement of Chinas urban water supply, this paper designs a set of water supply system of frequecey control of constant voltage based on PLC, and have developed good operation management interface using Supervision Control and Data Acquisition.The system is made up of PLC, transducer,units of pumps,pressure sensor and control machine and so on. This system is formed by three pump generators,and they form the circulating run mode of frequency conversion. With general frequency converter realize for three phase pump generator soft start with frequency control,operation switch adopts the principle of”start first stop first”. The detection signal of pressure sensor of hydraulic pressure,via PLC with set value by carry out PID comparison operation,so,control frequency and the export voltage of frequency converter,and then the rotational speed that changes pump generator come to change water supply quantity,eventually,it is nearby to maintain pipe net pressure to stabilize when set value. Through work control machine the connection with PLC,with group form software consummately systematic monitoring,have realized operation state development to show and data,report to the police inquiry. Keywords: variable frequency speed-regulating, constant-pressure water supply, Programmable logic Controller, supervision control and data acquisition 目 录 摘要 I ABSTRACT II 第1章 绪论 1 1.1 课题的提出 1 1.2 PLC概述 1 1.2.1 可编程控制器的定义 1 1.2.2 西门子S7-200PLC简介 2 1.3 本课题的主要研究内容 3 第2章 系统的理论分析及控制方案确定 4 2.1 变频恒压供水系统的理论分析 4 2.1.1 电动机的调速原理 4 2.1.2 变频恒压供水系统的节能原理 4 2.2 变频恒压供水系统控制方案的确定 7 2.2.1 变频恒压供水系统的组成及原理图 7 2.2.2 变频恒压供水系统控制流程 11 2.2.3 水泵切换条件分析 12 第3章 系统的硬件