本科毕业设计基于PLC控制的变频恒压供水系统摘要本文首先调研了国内部分城市的供水系统现状，在此基础上提出了基于PLC控制的变频恒压供水系统。恒压自动供水系统主要组成包括：可编程控制器、控制盒、变频器以及传感器。在恒压供水速度控制系统中，三个水泵使用变频器设置功率频率「，从而实现发动机转速控制N,从而改变水泵的功率曲线。具有恒定水压的变频技术自动控制系统的控制单元主要从三个阶段发展，从继电器到接触器再到单片机，再到目前使用的PLC。同时，还通过速度控制来控制变频器，该速度控制的多个端用于模拟输入控制，然后到达专用变频器。由于调节器和变频器的不断改进，低消耗量的城市供水变得简单高效，对于供水系统的控制过程也实现了自动化使用编程软件创建PID控制器以控制供水系统中的压力，并将PID控制器集成到PLC中。控制器可以通过处理实际测得的压力值以及与设定值的偏差来实时控制变频器的输出频率和电压。目的是改变水泵电机的速度和水泵出口处的流量，以便自动调节整个供水压力，保持压力接近设定值。关键词：PID:PLC:恒压供水：变频器2AbstractThis article combines the basic situation of the water supply system in somecities in our country,and proposes a variable frequency and constant pressurewater supply system based on PLC control.The main components of the constantpressure automatic water supply system include:programmable controller,control box,frequency converter and sensor.In the constant pressure watersupply speed control system,the three water pumps use the frequency converterto set the power frequency f,so as to realize the engine speed control N,therebychanging the power curve of the water pump.The control unit of the variablefrequency technology automatic control system with constant water pressure ismainly developed from three stages,from relay to contactor to single-chipmicrocomputer,and then to the currently used PLC.At the same time,thefrequency converter is also controlled by speed control.Multiple ends of thespeed control are used for analog input control,and then reach the dedicatedfrequency converter.Due to the continuous improvement of regulators andfrequency converters,low-consumption urban water supply has become simpleand efficient,and the control process of the water supply system has also beenautomated.Use programming software to create a PID controller to control the pressurein the water supply system and integrate the PID controller into the PLC.Thecontroller can control the output frequency and voltage of the inverter in realtime by processing the actual measured pressure value and the deviation from theset value.The purpose is to change the speed of the pump motor and the flowrate at the outlet of the pump so as to automatically adjust the entire water supplypressure and keep the pressure close to the set value.Key words:PID;PLC:Constant Pressure Water Supply:Inverter3