E-communication system> application and implementation of the BAS system in Subway Environment Control

Abstract: With the development of the motherland's modernization, the construction of new urban transportation-underground railway is in the ascendant. With the continuous development of automation technology, the centralized control and management of subway mechanical and electrical equipment, especially the environmental control equipment, provides the possibility for the scientific and efficient operation of subway environmental control equipment, at the same time, it ensures the security and comfort of the underground environment. In this paper, the automatic control scheme and implementation method of the equipment monitoring system (BAS) of the station of Guangzhou Metro Line 1 are described in detail and further discussed.

Keywords: BAS system subway Environmental Control

　1 Overview

Guangzhou Metro Line 1 has 14 underground stations, 2 ground stations, and a subway control center (OCC) building, with a total length of 18.6 kilometers and a Distributed Control System (DCS) centralized Monitoring of all subway ring control equipment and other station mechanical and electrical equipment. Due to the introduction of the concept of building control, the subway station equipment monitoring system is also called the BAS (Building Automation System) system. Guangzhou Metro Line 1 uses the I/net2000 System of CSI to monitor the entire ring control system, and to monitor and trigger alarms for escalators, water supply and drainage equipment, and emergency power supplies at all stations.

　　2. Functions of the BAS system in Subway Environmental Control

2.1. the main role of the subway BAS system in Subway environmental control:

This service controls the safe, efficient, and coordinated operation of all stations and zones and other mechanical and electrical equipment to ensure the good comfort of subway stations and zones and produce the best energy-saving effect, in addition, in case of emergencies (such as fire), the central control equipment is directed to a specific mode to provide security assurance for the subway ride environment.

2.2. Main Functions of the BAS system of Guangzhou Metro Line 1:

(1) monitor and coordinate the operation of ventilation and air conditioning equipment and cold water system equipment at all stations and OCC buildings.

(2) monitor and coordinate the operation of Tunnel Ventilation System equipment across the entire range.

(3) trigger an alarm on the fault of the station's mechanical and electrical equipment, and count the accumulated running time of the equipment.

(4) checks, analyzes, and generates alarms for environmental parameters (temperature and humidity) and operating parameters of the water system.

(5) receive fire alarms from the subway disaster prevention system (FAS) and trigger the disaster operation mode of the BAS system. control the operation of the environmental control equipment in the disaster mode.

(6) receive traffic jam information through the ATS interface, and control the related ring control devices to execute the corresponding commands.

(7) in an emergency, you can use the station Analog Screen to control the environment control device to execute relevant commands.

(8) Monitor the running status of electromechanical equipment, such as water supply and drainage, escalators, and so on, across all stations and tunnel sections.

(9) manage documents and print reports on a regular basis.

(10) interfaces with the main clock to ensure clock synchronization of the BAS system.

　　3. How the BAS system monitors the environmental control devices and its content:

3.1. Composition of the central control system:

Major Systems-ventilation and air-conditioning systems for public stations (stations/stations;

Small System-Ventilation and Air-Conditioning System for station equipment rooms;

Water System-underground station chiller system;

Tunnel Ventilation System-the environmental control subsystem that implements normal tunnel intervals and ventilation and smoke exhaust conditions in emergencies.

3.2. Configure the number of monitoring points for the BAS system:

Taking the chenjiayi station as an example, the total number of environmental control equipment monitored by Bas is about 100 (including wind turbines, air valves, and water system equipment ), the total number of points in the central control monitoring system is about 430 points (including the temperature and humidity parameter detection is about 60 points). The distribution of points in the station monitoring system is as follows:

(1) Tunnel Ventilation System: the BAS system monitors and controls four tunnel fans, linkage air valves, two thrust fans and combination air valves, and monitors fan overload fault alarm signals, detects the temperature and humidity of the tunnels at both ends. The total points are do 20, di 28, and AI 8.

(2) station Datong Air Conditioning System: the BAS system monitors and controls air conditioners, new fans, return fans, linkage air valves, adjustment air valves, and other equipment, and monitors fan overload alarm signals, detect new/mixed/air supply and station room/station temperature and humidity, control the opening of the outlet two-way valve of the combination Air Cabinet to adjust the air supply temperature of the air conditioner, total do 44, di 72, 30 o'clock in AI and 4 o'clock in AO

(3) station small ventilation and air conditioning system: the BAS system monitors and controls air conditioners, air blowers, exhaust fans, linkage valves, and regulating valves, and checks the temperature and humidity of equipment and management rooms, controls the opening of the outlet two-way valve of the small air conditioner to adjust the temperature of the relevant equipment room. The total temperature ranges from do, Di, AI, and AO.

(4) station water system: Normally, each underground station is equipped with two centrifuge groups and one Piston Unit (uniformly provided by Kairi ), only the start and stop commands are issued for the BAS system of the centrifuge group. The linkage control of the corresponding pumps, cooling towers, and butterfly valves is completed by the SM module of the Unit. The BAS system only monitors the status and faults. Because the Piston Unit does not have this module, its overall control and linkage control of water pumps, cooling towers and butterfly valves are completed by Bas. Check the necessary water system parameters, such as freezing/cooling water temperature, chilled water return flow, supply/return pressure, and other parameters as the basis for the calculation of water system control. A total of do, di 49, AI and AO 1 are available. The BAS system also provides an advanced data interface for the Kairi chiller dataport to receive operation data from the three chillers.

(5) Others: escalator, water supply and drainage, emergency lighting total di 54, do 2, AI 1.

3.3. Precautions for configuring the monitoring content of Ring Control Devices

In the compilation of monitoring points, a reasonable and comprehensive compilation of monitoring points can improve the system monitoring function and make software programming simpler, more reasonable, and more reliable. Based on the experience of Guangzhou Metro Line 1, pay attention to the following points:

(1) on Guangzhou Metro Line 1, each environmental control device carries the "local/remote" and "Environmental Control/Vehicle Control" Switch switches in the BAS system, which are located at the equipment site and the environmental control and electric control room. Due to the limited number of points (10 hands/automatic signals per station), the BAS system only applies to tunnel fans, the "Local/remote" Switch switch of important equipment such as air conditioners and air blowers of large systems is monitored, and the switch signals of some devices "Local/remote" are combined, for example, the air conditioner's hand/automatic signal is the "local/remote" Parallel Signal of two air conditioners at one end of the station. Because the BAS system cannot know the specific control permissions of the device, the control is blind, therefore, it is necessary for the BAS system to monitor the positions of all the central control devices "Local/remote" and "Central Control/Vehicle Control" Switch switches to ensure the rationality and reliability of the control;

(2) in the control of electric air valves (including butterfly valves), in order to reduce the number of monitoring points, line 1 adopts the open and closed contacts of the intermediate relay at an output point to control the air valves (water valves) and uses only one di point to detect the full open signal of the air valve. This single do and single di monitoring method makes it impossible for BAS to cancel the output Command Based on the action of the device. The long-term existence of the output signal poses a fault risk to the normal operation of the equipment and increases the difficulty of software programming. For example, when the system mode is switched to the working condition, the air valve is switched on and off, the corresponding fan is forced to shut down because it cannot know whether the valve is in the conversion process. Therefore, for the monitoring of this type of equipment, two do points should be used to control the opening and closing, and two Di points should be used to detect the air valve opening and closing signals, to indicate the full on, full off, and intermediate status.

(3) If the chiller has its own automatic control function, such as the centrifuge group, you can consider that the BAS is only responsible for the total Start and Stop commands, and the relevant pumps and other equipment, the BAS system is only responsible for monitoring. The data interface is set to receive the operation data of the chiller and centrally and scientifically manage the unit operation. At the same time, we should minimize the repeated setting of detection parameters (such as Metro Line 1, Bas and piston units are configured with water flow switches at the same time) to simplify control and save investment.

(4) The BAS system has a data interface with the same FAS system at the station level. The FAS system sends the fire partition signal after confirmation to the BAS system for receiving through the data interface, the BAS system starts the corresponding fire mode after receiving the FAS system fire alarm signal. For the subway, because the amount of fire information at the station level is not large (about 30 fire alarms at each station of Guangzhou Metro Line 1), in addition to data interfaces, you can also consider using hard lines (I/O) after the connection is completed, the hard line I/O connection can be used to replace the communication interface. This increases system reliability and reduces interface development costs. However, the input and output modules are added for hard-line I/O connections. Therefore, you can select the connection mode based on the actual situation.

(5) for the monitoring of fire-proof valves, because of fire-fighting equipment, Guangzhou Metro Line 1 has included them in the FAS system for monitoring. However, as part of the central control system, for the sake of control system integrity, it should also be included in the BAS system monitoring scope. The following methods can be considered based on actual conditions.

① It is fully integrated into the BAS system and is monitored by the BAS system for fire damper.

② Use the bas/Fas data interface or hard line interface to monitor the fire damper through the FAS System

③ Bas and Fas are used to monitor the fire damper. The switch must be set. (This method is used by the Hong Kong Metro)

　　4 subway station equipment monitoring system (BAS) system composition and Network Configuration

4.1. Main features of the I/net2000 system:

(1) the hierarchical LAN technology can be used to implement control networks from several points to more than 100,000 points, and Ethernet (TCP/IP protocol) communication is used between stations, the station-level Main Network (Controller LAN) uses the Token Bus network communication, and the subnet (sub LAN) uses the round-robin (master/Slaver) communication.

(2) flexible input/output configuration. The PCU and UC input points can be set to AI, Di, PI, and so on in the software. For analog input, the patch cord can be set to receive 0 ~ 20mA, 0 ~ 5 V, 0 ~ 10 V, RTD Temperature and other signals.

(3) The programming configuration adopts the Point concept and completes logic, mathematics, and other control algorithms directly on the control point. The configuration method is simple and flexible.

(4) As a typical building control product, it provides a variety of energy-saving control program modules, such as adaptive optimal start and stop control, self-tuning PID algorithm, and dead zone control algorithm.

4.2. Bas System Network Structure

The Guangzhou metro station equipment monitoring system monitors the environmental control equipment and other mechanical and electrical equipment at the central level, station level, and prefecture level. The system network diagram is as follows:

PCU: Process Control Unit, 8-input and 8-output, which can be expanded to 32-input or 16-in-16 output

UCI: Unit Controller Interface, which can include up to 32 Unit Controllers UC and communicate with each other through master-slave communication. The number of monitoring points can reach 512 points.

MPI: Analog Screen Driver Interface

Hli: Advanced Data Interface

　　

Figure 1 BAS system network structure

Generally, three UCI blocks are placed in the vehicle control room, two of which are responsible for monitoring the ring control devices at both ends of the station and implementing the Analog Screen Control Function of the Ring Control Room, another UCI is responsible for detecting the temperature and humidity of the station/station and some equipment rooms, receiving the FAS fire signal, and monitoring the simulation screen of the vehicle control room and other systems (such as escalators, water supply and drainage systems.

A unit of PCU is set up in the chiller Room to monitor the chiller. A unit of PCU is set for each end of the air conditioning room to check the temperature and humidity of the air room and equipment/Management Room, and to control the opening of the outlet two-way valve of the air conditioner. 2 ~ Four PCU-assisted UCI to monitor the local environmental control system. The BAS system has a data interface hli with FAS and chillers at the station to receive data from third-party devices.

4.3. configuration of central LAN

A set of workstations and backup stations are set up at the central level. The workstations work with backup stations to achieve hot backup over Ethernet. The OCC lan has a data interface and Analog Screen with the signal ATS and the communication master clock. The network configuration is as follows:

　　

Figure 2 Central network configuration of the BAS system

As shown in figure 2, in addition to receiving time synchronization signals from the communication system, OCC also connects hli and Analog Screen devices to the ATS data interface in the occ lan, and uses the central workstation (PC) transmit data to the bas Ethernet to exchange data with other station-level BAS systems. It should be pointed out that, under normal circumstances, all tunnel ventilation modes are calculated and determined by the bas controller connected to the central LAN Based on ATS train blocking signals or manual instructions, the command number is issued to the relevant station through Ethernet, and then the relevant station bas Controller directs the relevant equipment to perform the correct action. When the workstation crashes or fails, the mode cannot be correctly issued, and it can only be controlled by the relevant station through over-relaxation of the on-site Simulation Screen, affecting the reflection speed in the case of accidents. Because tunnel ventilation involves the personal safety of passengers and there are high requirements for correct and timely implementation of tunnel ventilation modes, the central LAN of the BAS system should be connected to Ethernet through a dedicated gateway (switch) or server.

4.4. settings of the station simulation screen:

As an emergency backup operation means in case of emergency or bas workstation failure, Guangzhou Metro Line 1 has set up a map-based Analog Screen in the vehicle control room of each station and the control room of both ends. The operation of the analog screen is mainly based on the interval accident and station fire mode. The settings of the analog screen should follow the following principles:

(1) The simulation screen should highlight the execution in the tunnel interval and station accident operation mode. The execution completion or failure of the mode should provide corresponding feedback.

(2) switch with a key. You can change the operation permissions of workstations, vehicle control room analog screens, and Environment Control Room analog screens to ensure that the control commands are issued by the only place.

(3) The simulation screen is executed in the corresponding mode by pressing a button. As an emergency means, the analog screen should have the ability to relax other control commands. For example, when the operating station software sets the device control mode to single control (point-to-point control) rather than Program (Mode) during control, the mode commands executed by analog screens should be able to relax the single control commands. Therefore, the software algorithm of Analog Screen control mode should be independent of the software algorithm of the operating station mode. In the system software, you must consider the configuration of this part of software resources.

(4) It is best to configure the analog screen controller independent of the master controller to share I/O with the master controller to enhance the reliability of emergency control.

　　5. Implementation of the Environmental Control Process Model

Based on the season, load, and unexpected accidents (fire and train congestion), the environment control professional has developed a large number of environmental control modes to control the operation of the Environment Control Equipment in different conditions. It includes large systems, small systems, water systems, tunnel ventilation, and other ring control technology modes. Taking Chen jiazhi as an example, there are nearly a hundred ring control technology modes.

5.1. hardware configuration

The system mainly uses two types of controllers to complete the control process of the ring control system, namely PCU and UCI. The following lists their main performances:

(1) Process Control Unit PCU: up to 640 point addresses can be freely configured, including internal points (internal points) and indirect points (indirect points) of the software ), A user program memory that can be expanded to a maximum of 96 k is provided, and expansion functions such as boolean logic, time table, and energy-saving algorithm are provided for software programming configuration. Various DDC control algorithm modules are also provided, such: event Sequence, PID, floating, etc;

(2) Unit Controller Interface UCI: A total of 640 address spaces can be freely configured. It provides 24 K user program memory and provides extended functions such as boolean logic, time table, and energy-saving algorithm for software programming configuration.

Due to the complicated subway environment control process and many working conditions, the system configuration should fully consider the configuration of the controller CPU resources and memory resources, leaving sufficient margin. In the BAS system of Guangzhou Metro Line 1, most of the central control devices are controlled and managed by the local UCI, resulting in UCI overload, CPU load up to 95%), reducing the reliability of device operation, and some optimization control algorithms are also subject to resource distribution and difficult to achieve. In addition, this practice of focusing almost all monitoring functions on UCI does not comply with the risk dispersion principle of the DCS system: when a UCI fails, the BAS system will paralyze the Central Control Equipment at one end of the station. It is best to consider the use of independent DDC controllers (UCI) for large and small systems and tunnel ventilation systems).

Application and Implementation of the BAS system in Subway Environment Control: www.shu1000.com

5.2. Implementation of Basic device protection and automatic mode

Take the station system as an example.

　　

Figure 3 schematic diagram

Generally, the low-voltage Secondary Circuit Design of the ring control equipment only takes into account the protection and interlocking requirements of the single device, that is, the interlock between the fan and its associated air valve, therefore, the BAS system needs to consider the protection and optimization of equipment from the system. The main considerations of Guangzhou Metro Line 1 are as follows.

(1) ensure smooth access to the risk Road in the Central Control Mode

(2) When the device fails, the Standby device can be started in time.

(3) The main and standby devices of the central controller should be in balanced operation.

(4) Avoid frequent device movements

(5) optimize switch Sequence

Taking the large-scale air conditioners (Fig. 3) at the-end system of the chenjiayi station as an example, the program logic relationship is as follows:

If S3-1 or S3-2 is not run & (Runtime (S3-1)-Runtime (S3-2)> 0)

Then output (runtime change) = 1

If S3-1 or S3-2 is not run & (Runtime (S3-1)-Runtime (S3-2) <0)

Then output (runtime change) = 0

If S3-1 or S3-2 is run

Then runtime change not change

* Obtain the logical value of runtime change.

If mode (LD <50% )&(~ Runtime change) | mode (LD> 50%)

Then output (S3-1 mode = 1)

If mode (LD <50%) & runtime change | mode (LD> 50%)

Then output (S3-2 mode = 1)

* Device balance run if S3-1 mode | (S3-2 mode & any S3-2 associated equipment in fault) & not any S3-1 associated equipment in fault * failover

Then output (S3-1 call = 1) If S3-2 mode | (S3-1 mode & any S3-1 associated equipment in fault) & not any S3-2 associated equipment in fault * failover

Then output (S3-2 call = 1)

If S3-1 call & all associated damper is open * detect wind paths

Then start S3-1 * enable S3-1

If S3-2 call & all associated damper is open * detect wind paths

Then start S3-2 * enable S3-1

Note: & -- logic and; | -- logic or ;~ -- Non-logical

Mode (LD <50%) indicates all the process modes with a load less than 50%, that is, the billing mode of the air conditioner.

Through the above example, we can see that the Guangzhou Metro mainly considers the basic operation requirements of the equipment from the following aspects in implementing the Program Control of The Ring Control Equipment:

(1) convert the active/standby mode into a single device, and combine the standby mode. This reduces the frequency of mode conversion and improves the efficiency of mode execution.

(2) when the device is not running, you can compare the running time of the master and backup devices to determine which device (including linkage air valve) is enabled when the device is running in the next mode. After the device is enabled, this value remains unchanged to avoid device conversion during operation.

(3) conduct real-time detection of equipment faults. If there is a fault in your own equipment or related equipment, start another backup device. The fault signal is the logic of equipment overload failure and command/Feedback inconsistency and timeout failure.

(4) detect the relevant air valves and equipment on the wind road in this mode. After all the relevant air valves are in place and the air routes are smooth, the command is output to start the on-site equipment.

(5) the air-conditioner should be enabled as much as possible during the startup of the mode, and the fan is then sent. The order of shutdown is the opposite, so as to avoid the possibility of over-flow of the fan during startup and protect the proper operation of the equipment; for the sake of protection equipment, the linkage air valve should be closed after the fan is closed for a period of time as needed.

(6) If there is no standby mode in the process mode itself, when the mode is normal due to a device unable to operate, you can consider transferring to the specified mode or shutting down the mode, to avoid damage to the device caused by Long-term unbalanced operation of the device.

　　6 Determination and execution of the environmental control process mode

Because the Guangzhou Metro Central Control System is designed as a constant air volume system, the focus of BAS system control is not to adjust but to determine the working conditions of the central control process mode. The following uses the normal operation mode of the station system and water system as an example to explain the automatic implementation of the subway Ring Control Process:

6.1. Realization of Automatic judgment of the process mode of the Station System

The automatic determination and execution of the normal process mode of a large system are based on the following conditions: ① air conditioning or non-air conditioning seasonal model is implemented based on the outdoor temperature determination system ② new air or small fresh air mode is determined based on the comparison of the station's internal and external air entropy values ③ the execution load is determined to be greater than 50% mode or mode less than 50% 4) determine the nighttime or daytime mode based on the time. Figure 4 determines the execution process in the automatic mode of normal operation.

(1) The normal operation time is divided into three sections: night time, pre-ventilation time, and normal operation time. The entire line of the bas controller obtains time synchronization through the main clock to ensure that the entire line of time is unified.

(2) Comparison and determination of the external entropy value and the Set entropy value of the air supply during the air conditioning season. When the external entropy value is greater than the set entropy value, it enters the air-conditioning season. To avoid frequent mode conversion caused by frequent switching during the air-conditioning season, the dead zone is used to control the judgment conditions, and time-limited conversion (for example, conversion can be performed once at least 20 minutes ). The new air and small fresh air are determined by comparing the external entropy value with the station hall/station average entropy value, and the time-limit conversion is also adopted, in addition, the unified time-limited timer is used for full/small fresh air and air conditioning/non-air conditioning seasons to ensure synchronous conversion and reduce the operation frequency of the equipment.

(3) The station load is determined by the temperature of the water distributor (chilled water outlet temperature), and the dead zone is 7.5 ℃ ~ 8.5 ℃ Control, non-air conditioning season, the default Implementation of station load> 50% mode of working conditions.

(4) The Environment Control Process mode can be manually selected and automatically determined for execution. Generally, the environmental control process mode is automatically determined and executed by the BAS system based on the calculation results, and the manual mode is set for manual selection in special circumstances. In the case of disasters (such as fire ), the fire mode is prioritized (manual confirmation is required before execution to prevent misoperation ).

　　

Figure 4 flowchart of automatic mode Determination of air conditioning systems

6.2. Implementation of the process mode of station Water System

The BAS system is responsible for group control of three chillers at the station. When the cold water system is automatically controlled by the BAS system, the normal operating process mode of the water system is selected according to the following principles: ① determine the daily or nighttime operation according to the schedule ② determine whether the water system enters the air conditioning season Based on the outdoor entropy value ③ determine the number of power-on instances based on the station cold load. Flow chart for determining the conditions of the station water system:

　　

Figure 5 process flow chart of the Water System

(1) The determination of the air conditioning season is the same as that of the station system.

(2) The normal operation time is divided into three sections: night time, station pre-cooling time, and normal operation time. At night, only the Piston Unit is enabled Based on the temperature of the important equipment room. Before the operation, the station starts the two centrifuge groups for 30 minutes before the station cooling load is determined.

(3) According to the environmental control requirements, the station load is determined by the water system water separation temperature (chilled water outlet temperature) determination, when the temperature of the water separation agent is higher than a certain value to open two centrifuge groups, when the value is lower than this, only one Centrifuge Group is enabled. This value is controlled by the dead zone. The initial value of Guangzhou Metro Line 1 is set to 7 ℃ ~ 9 deg C.

(4) To protect the equipment and avoid frequent movements of chillers, set the minimum running time of the cold water system mode (for example, at least 90 minutes before conversion ).

6.3. Coordinated Operation of wind and water systems

Bas adjusts the air supply temperature of the air conditioner by adjusting the opening of the two-way regulating valve for chilled water outlet of each air conditioner. At the same time, the two-way valve is used as the water system condition conversion valve, control the opening or closing of the two-way valve according to the air conditioner opening and water system running modes to ensure coordinated operation of the air system and water system. The station load and water system load of the large system are determined by the chilled water outlet temperature value. The load of the new large system in Guangzhou Metro is determined to be 7.5 ℃ ~ Set the dead zone control at 8.5 ℃. The water system is 7 ℃ ~ The Dead Zone Control is set at 9 ℃ to avoid the water system running at above 50% (7 ℃ ~ 7.5 ℃), the cold load of the water system is too low, resulting in the chiller jump, the system load judgment to join the cold water system mode execution conditions, 6:

　　

Curve 1: system load determination curve when a single centrifuge group is enabled

Curve 2: Enable the load determination curve of two centrifuge groups for large systems

Figure 6 load determination curve of large systems

To ensure the coordinated operation of the wind and water systems, the water system and the system adopt unified air conditioning season conditions. At the same time, because the working conditions of large systems and water systems vary with time-based timers (20 minutes for large systems and 90 minutes for water systems), there is a possibility of conflict, the operating conditions of the water system must be taken into account when converting the operating conditions of the wind system.

　　7 conclusion

Due to the complexity and particularity of the subway ring control system, the control requirements for the station equipment monitoring system are often different from that of the general building automation system, there are special requirements for hardware configuration and software functions. Therefore, in future subway construction, the system should be reasonably configured and the system functions should be improved according to the actual situation of the subway, to maximize the automation of the subway environment control system.