北京航空航天大学毕业设计(论文) 第 I 页 基于plc的中央空调自动控制系统设计

摘要

中央空调系统是现代大型建筑物不可缺少的配套设施之一，电能的消耗非常大，约占建筑物总电能消耗的50%。通常中央空调系统中冷冻主机的负荷能随季节气温变化自动调节负载，而与冷冻主机相匹配的冷冻泵、冷却泵却不能自动调节负载，几乎长期在100%负载下运行，造成了能量的极大浪费，也恶化了中央空调的运行环境和运行质量。本文首先介绍了中央空调的结构和工作原理，然后采用西门子的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，同时又可以节约大量能源。

关键词：PLC；中央空调；控制

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北京航空航天大学毕业设计(论文) 第 II 页 Design of automatic control system for central air conditioning system

based on PLC

Abstract

The central air conditioning system is one of the necessary supporting facilities of modern large-scale buildings. The consumption of electric energy is very large, which accounts for about 50% of the total energy consumption. The frozen host usually in the central air-conditioning system load can automatically according to the change of temperature and load regulation, refrigeration pump and cooling pump matched with the frozen host can automatically adjust the load, almost run 100% under load operation, resulting in a great waste of energy, but also worsen the operation environment and operation quality of Central air conditioning. This paper first introduces the structure and working principle of central air conditioning, then use SIEMENS S7 200PLC as the main control unit, using the traditional PID control algorithm, through the SIEMENS MM440 inverter control pumpspeed ensure system according to the actual situation to adjust load flow, realize constant temperature control, but also can save a lot of energy.

Key words：PLC; central air conditioning; control

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北京航空航天大学毕业设计(论文) 第 III 页

目 录

摘要 ................................................................................................................................ I 1绪论 ............................................................................................................................ 1

1.1课题的研究背景 ............................................................................................. 1 1.2 国内外中央空调控制系统的研究现状 ........................................................ 2 2中央空调控制的原理 ................................................................................................ 4

2.1中央空调系统的结构和原理 ......................................................................... 4 2.2中央空调电机的软启动原理及应用 ............................................................. 4 3中央空调控制系统的硬件设计 ................................................................................ 6

3.1 变频器的原理 ................................................................................................ 6 3.2 西门子MM440变频器性能介绍 ................................................................. 6

3.2.1 主要特征 ............................................................................................. 7 3.2.2 控制性能的特点 ................................................................................. 7 3.3PLC选型 .......................................................................................................... 7 3.4人机界面设计 ................................................................................................. 8 3.5系统硬件设计 ................................................................................................. 9 4控制系统软件设计 .................................................................................................. 12

4.1PLC的初始设定 ............................................................................................ 12 4.2 PLC主程序流程图 ....................................................................................... 14 4.3程序设计 ....................................................................................................... 14

4.3.1中央空调控制系统的I/O分配表 ..................................................... 14 4.3.2 程序中使用的存储器及功能 ........................................................... 16

结论 ............................................................................................................................. 17 参考文献 ..................................................................................................................... 18 致 谢 ......................................................................................................................... 20 附录 PLC软件源程序 ............................................................................................... 22

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