Abstract: This paper focuses on a distributed computer control system designed for a computer company using the Siemens S600 building automation system.
Keywords: Distributed control building automation
Abstract: The article chiefly introduces a distributed computer control system designed for client service building of computer company, which adopt SIEMENS S600 building automation system
Keyword: the distributed control; the building automation
1. Introduction:
Building intelligence is emerging as a new industry, gaining a status comparable to green environmental protection. The development and application of intelligent technologies have therefore seen significant progress, with their application in Building Automation Systems (BAS) becoming increasingly mature and sophisticated. Building intelligence begins with the intelligentization of electrical equipment within the building. Given the dispersed yet interconnected nature of this equipment, distributed control technology enables comprehensive and real-time monitoring, improving operational quality. It provides building managers with centralized display, operation, control, and powerful data processing capabilities, reducing workload and lowering energy consumption. This technology plays an increasingly important role in buildings. This article introduces a building automation system designed and implemented using Siemens' S600 APOGEE system.
2. Functions of the control system:
The computer company building consists of six floors above ground and one floor below ground, primarily serving as research, office, business, and repair workshops. The subsystems requiring monitoring by this system include: air conditioning system monitoring, cold and heat source and water system monitoring, ventilation equipment monitoring, lighting system monitoring, and water supply and drainage system monitoring.
2.1 Monitoring of the air conditioning system
A good working environment requires suitable indoor temperature, appropriate humidity, and clean air. This necessitates a Building Automation (BA) system to comprehensively manage and monitor the building's numerous HVAC equipment. The main monitoring content is as follows:
2.1.1 Monitoring of fresh air handling units
It can achieve the following functions:
Monitoring functions: Monitors the operation/stop status of the fan motor; monitors the temperature and humidity parameters of the air at the fan outlet; monitors the pressure difference across the fresh air filter to determine if the filter needs replacement; monitors the open/closed status of the fresh air valve;
Control functions: Control the start/stop of the fan; control the water circuit regulating valve of the air-hot water heat exchanger to make the fan outlet temperature reach the set value; control the valve of the dry steam humidifier to make the air humidity at the fan outlet reach the set value in winter; control the opening and closing of the fresh air valve.
Protection function: In winter, when the hot water temperature drops or the hot water supply stops for some reason, the fan should be stopped and the fresh air valve should be closed to prevent the air-water heat exchanger from freezing and cracking due to excessively low temperature inside the unit; when the hot water supply is restored to normal, the fan should be able to be started and the fresh air valve opened to restore the normal operation of the unit.
Centralized management function: The DDC control devices near each unit in the intelligent building are connected to the central management unit through the communication bus, which can display the start/stop status of each unit, supply air temperature, humidity, and valve status values; issue start/stop control signals for any unit, modify supply air parameter settings; and issue alarm signals when any fresh air unit malfunctions.
2.1.2 Monitoring of Air Conditioning Units
Air conditioning units regulate the temperature and humidity of the corresponding area; therefore, the input signals sent to the field controller also include the temperature and humidity signals of the regulated area. For air conditioning units with return air, in addition to ensuring that the processed air parameters meet comfort requirements, energy saving must also be considered. Due to the presence of return air, additional fresh and return air parameter detection points are needed. However, the return air duct has significant inertia, causing the return air state to be not entirely equivalent to the indoor air state; therefore, the indoor air parameter signals must be obtained by sensors located in the air-conditioned area.
2.2 Monitoring of cold and heat sources and their water systems
The building's main heat and cold sources include cooling water, chilled water, and hot water preparation (heat exchanger) systems. The main monitoring components include:
Monitoring of cooling water system, monitoring of chilled water system, and monitoring of hot water preparation system.
2.3 Monitoring of ventilation equipment
The system controls the start and stop of the fans based on the parameters measured by the CO and CO2 detectors in the controlled area. Alternatively, daily start/stop times can be scheduled within a week. The building control system will store the total operating time of each fan, and this data will be displayed to the operator at the workstation as needed.
2.4 Monitoring of the lighting system
The intelligent building is a multi-functional building, and different areas have different lighting requirements. Therefore, the lighting facilities are controlled differently according to their nature and characteristics. This project requires monitoring the lighting distribution boxes on each floor of the building. The main contents include: controlling the lighting equipment in different areas to turn on/off according to seasonal changes and time programs; issuing alarm signals on the host computer when a fault occurs in the normal lighting power supply; and monitoring the switching status of all lighting circuits on each floor.
2.5 Monitoring of water supply and drainage systems
The water supply and drainage monitoring system is a crucial component of intelligent buildings. Its main function is to adjust the number of operating pumps in the system in real time through computer control to achieve a balance between water supply and demand, and between incoming and outgoing water, thus realizing optimal operation of the pump room and achieving high-efficiency, low-energy-consumption optimized control. Its main monitoring functions include: detecting the water level in underground and rooftop water tanks and issuing alarms when the high/low levels exceed limits; controlling the start/stop of water pumps based on the high/low water levels in the tanks (reservoirs); detecting the operating status and faults of domestic water supply pumps; automatically activating backup pumps when a pump malfunctions; detecting the water level in sewage and wastewater collection wells and issuing alarms for exceeding limits; detecting the operating status of drainage pumps and issuing alarms when malfunctions occur; starting/stopping hot water circulation pumps according to a timed program; and detecting the status and issuing alarms for hot water circulation pumps (automatically activating the corresponding backup pump when a malfunction occurs).
3. System Design:
S600 APOGEE is a mature building automation system based on distributed control theory. It features flexible structure, strong adaptability, convenient expansion, software-optimized equipment operation, and simple operation. Based on the Windows NT platform, S600 APOGEE's system software package can directly integrate into the building's computer network system, exchanging information with other subsystems within the integrated system. It is a crucial link in the integrated system, fully demonstrating its openness. S600 employs a multi-layered network structure and world-leading technology, making the S600 distributed system a world leader in both reliability and technology. The network structure and functions are as follows:
The high-rise network reports various alarm information and forms, improving management level and efficiency. In this project, the central graphics workstation is located in the central control room on the first floor of Building 2. The S600 central graphics workstation (using an IBM PC) can connect to Ethernet for data management, and simultaneously operate and manage the entire building control system from this workstation. It also connects to a printer for real-time printing.
Mid-level network: PCs can connect to up to 100 building controllers (such as MBCs, MECs, etc.) via a Peer-to-Peer Network (a shared bus system on the same floor without master-slave functionality). This project uses two MBCs, i.e., modular building controllers, for monitoring the heating and cooling sources and water supply and drainage systems.
Local Area Network (LAN): Each MBC's LAN (with up to 3 LAN cables) can connect to up to 96 independent unit controllers (UC, DPU, etc.). This facilitates system expansion and the completion of larger distributed systems. This project uses 18 UCs and 20 DPUs, located in the fresh air handling room, air conditioning room, or near related equipment, for monitoring the fresh air handling units, air conditioning units, ventilation systems, and lighting systems. A schematic diagram of the overall system structure is shown in Figure 1.
Figure 1 Schematic diagram of the overall system structure
4. Software system functions:
4.1 Control Software
It can achieve proportional control, proportional-integral control, and proportional-calculus-integral control. When the power is restored to normal after an outage, the control software will issue start/stop commands to the device according to the individual start/stop schedule of each device.
4.2 Energy-saving software
The main functions include daily scheduled schedules, annual scheduled schedules, holiday schedules, temporary control schedules, optimal start/stop functions, automatic adjustment control of nighttime setpoints, enthalpy switching functions, restrictions on peak electricity consumption periods, temperature setpoint reset, and control of the combination and sequence of refrigeration units.
4.3 Alarm Management:
All alarms display detailed information about the monitored point, including the time and date of occurrence. Alarms are categorized into at least three severity levels for more effective and rapid handling of serious alarms. Users can customize the severity level for different alarms.
4.4 Historical and Trend Records of Monitoring Points
The historical data of all monitoring points within the building automation system is automatically stored in the relevant network controller. Analog input monitoring points are sampled every half hour, and records from the past 24 hours can be retrieved and analyzed by the user at any time. Users can utilize trend analysis software at any monitoring point within the system, with sampling intervals ranging from once per minute to once every two hours, selectable by the user as needed.
4.5 Cumulative Records
Each network controller maintains the following cumulative records; if the user-defined limits are exceeded, the system will issue a warning: Cumulative operation records—such as the cumulative operating time of water pumps; and cumulative analog and pulse records—such as the cumulative electricity consumption records.
5. Conclusion:
The building control system described in this article has been successfully applied in the design of a computer company's customer service building. The system operates reliably and has achieved considerable economic benefits.
References:
1. Hou Chaozhen, ed. Distributed Computer Control Systems, Beijing Institute of Technology Press, 1997.
2. S600 Peak System Technical Manual
3. PPCL Language Programming Technology Manual
