摘 要：中央空调已经广泛应用于商用与民用建筑中，用于保持整栋建筑温度恒定。传统的设计中，无论季节、昼夜和用户负荷的怎样变化，各电机都长期固定在工频状态下全速运行，所以会造成极大的能源浪费。本设计采用变频器、PLC、温度传感器等器件的有机结合，构成温差闭环自动控制系统，自动调节水泵的输出流量达到节能目的。该系统采用西门子S7—200PLC作为主控制单元，利用传统PID控制算法，通过西门子MM440变频器控制水泵运转速度，保证系统根据实际负荷的情况调整流量，实现恒温控制，从而最大程度的解决能源浪费问题。本设计通过采用基于USS协议的RS—485总线通讯的网络，通过西门子TD200文本显示器实现人机界面的设计，使用MCGS工控组态软件，对系统进行组态设计。66447

毕业论文关键词：中央空调，PLC，PID，变频器

Abstract: The central air conditioning has been widely used in commercial and civil buildings,which are used to maintain constant temperature of the building.In traditional design,regardless of the season,day and night,and how the user load changes,the motor is fixed to run at full speed for a long time in the condition of power frequency.It will cause great waste of energy.This design is developed based on the combination of frequency converter,PLC,temperature sensor.It makes up a temperature difference closed-loop automatic control system and automatically adjust the output flow of pump to achieve energy saving.The system adopts the Siemens S7-200 PLC as the main control unit,using the traditional PID to control algorithm,using Siemens MM440 frequency converter to control of pump speed,to guarantee system adjust load flow according to actual situation.All of these will bring out constant temperature control,so as to solve the problem of energy waste to a great extent.This design use RS-485 bus communication networks which is based on USS protocol and using the Siemens TD200 to realize the human-computer interface design,and using the software made from MCGS,to carries on the design to the system.   

Keywords: The central air conditioning，PLC，PID，Frequency converter

目   录

1 绪论 4

1.1 中央空调的发展 4

1.2 本设计的意义 4

2 中央空调系统介绍 5

2.1 中央空调结构 5

2.2 中央空调系统工作原理 6

3 中央空调控制系统的硬件设计 8

3.1 变频器 8

3.2 PLC选型 12

3.3 温度传感器 13

3.4 温度变送器 14

3.5人机界面选型方案 14

3.6 总体硬件设计 15

4 软件设计 18

4.1 PID控制 19

4.2 应用软件STEP7 22

4.3 PLC编程 23

4.4设备通讯 25

4.5 监控界面 26

5 结论 26

参考文献 27

致谢 29

附录 30