In recent years, a variety of high-rise buildings have been built in many cities. Various types of equipment are widely distributed in the building. How to do a good job in the operation and management of these equipment, to provide a comfortable environment for customers, to use energy reasonably, to facilitate management, and to reduce operating costs is the most important concern of the owners. Therefore, many large buildings have designed building intelligent systems to collect the equipment in buildings Management. The essence of building automation control system (BAS) is the application of modern computer distributed control system in modern multi-functional buildings. It makes all kinds of equipment in the building such as power distribution equipment, water supply and drainage equipment, heating and ventilation equipment under the control of their respective field controllers according to the predetermined control strategy, so that each system can coordinate with each other and work in the best state to achieve the effect of energy saving and comfort Fruit. BA system usually has one or two central control master stations. In the central master station, the operation conditions and important operation parameters of each controlled equipment can be monitored, and the historical trend of operation status, the accumulated operation time, alarm type and times of the equipment can be recorded, so as to provide reliable basis for equipment management, analysis and maintenance plan. At present, many famous foreign companies such as Honeywell, johosoh and Siemens have launched some special intelligent building control systems.
Although the functions of these systems are strong, the system investment is large. According to the characteristics of the building control system, we adopt the distributed control system based on Mitsubishi Fieldbus c-clink technology and PLC. It has the characteristics of reliable operation, simple modification of control software and low cost. The central station applies Kingview software developed by yacon Automation Software Technology Co., Ltd., which runs in Windows 95 / nt Configuration software on. With multi task, multi thread and good real-time performance, it has been used in many engineering fields, such as electric power, refrigeration, chemical industry, machinery manufacturing, traffic management and so on. The whole control system has been successfully applied in the new workshop of Zhejiang printing factory. The practice shows that the system is stable and flexible, which is very suitable for some small and medium-sized intelligent building automation system.
2、 System hardware composition:
（1） Introduction to CC link
CC link is the abbreviation of control & communication link. It provides the communication rate from 156kbps to 10Mbps (depending on the communication distance of the system) through a simple three core shielded wire, and the maximum communication distance can reach 1200m (156kbps speed). All kinds of modules (including switch I / O and analog I / O) and sub station controller on CC link network can form various control systems conveniently and simplify the wiring of control system.
（2） Brief introduction of Mitsubishi FX2N series PLC
Mitsubishi FX2N series programmable controller has small volume, fast operation instruction speed (0.08us/basic instruction), built-in 8K step ram and clock, and PID operation instruction. It is the highest performance of FX series, and has various special purpose components for analog control and system communication. It is a set of PLC that can meet various and extensive needs. This series of PLC has strong communication function. It can be directly hung on CC link network through fx2n-ccl communication module to form a distributed control system. Data can be exchanged with master station through CC link network, and the whole system can be managed, monitored and controlled by master station PC.
（3） The block diagram of the whole system is as follows:
3、 System function and control strategy
（1） Power supply and distribution system:
Safe and reliable power supply is the prerequisite for the normal operation of intelligent buildings. According to the need, the system converts the voltage, current, power factor and frequency sensors into 4-20mA signals and sends them to the A / D conversion module of the field controller to read them into the controller to realize energy management. If the distribution system adopts advanced microcomputer to detect air circuit breaker and can provide RS232 or RS485 communication interface and communication protocol, the special module of PLC can replace a / D converter to obtain power data, so as to improve the accuracy and real-time performance and reduce the cost. The system can also detect the switch state of the important circuit and the temperature rise of the transformer, and monitor various abnormal conditions.
（2） Air conditioning subsystem
The energy consumption of the air conditioning system in the building is about 45% of the total energy consumption. According to the climate conditions of Hangzhou, where the time of changing seasons is uncertain and the time is long in the freezing summer, an intelligent console composed of PLC and LCD touch screen is designed in the refrigerator room. The console saves all kinds of instrument panels, makes the panel surface standardized and miniaturized, and saves wiring. The operator can directly monitor the relevant parameters in the building, such as the temperature of each sampling point, the outdoor temperature and humidity, and the water level of each pool through the operation console of the refrigeration room, so as to provide information for the operator. When the climate is not suitable for automatic operation, such as changing seasons or equipment maintenance, the operator can also set the relevant parameters of each equipment through this console to make the equipment Running at its best.
The system consists of three parts: refrigeration unit, heat exchanger and terminal equipment of air conditioning system
Control strategy and function
A. According to the operation requirements of refrigeration unit, the start and stop sequence of cooling water pump, air conditioning water circulating pump, cooling tower fan and refrigeration unit are controlled by automatic, semi-automatic and manual logic control.