Application of the hottest delta fieldbus products

2022-07-26
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Application of delta fieldbus products in central air conditioning system

Abstract: This paper introduces the application of delta DeviceNet Fieldbus products in central air conditioning system. Delta DeviceNet Fieldbus products are easy to install and debug, and greatly improve the reliability and real-time performance of the control system

key words: dvpnet scanning module dna02 module frequency converter man-machine interface plc

1 introduction

the central air conditioning system used in shopping malls and other large buildings is mainly to provide a comfortable environment for people, but it often consumes a lot of energy while pursuing comfort. How to effectively solve this problem, we need to analyze the impact of the environment on people. The data shows that there is a direct relationship between indoor air conditioning temperature and energy consumption. Therefore, by reasonably setting the operating parameters of indoor air conditioning, we can not only meet the requirements of human body for environmental comfort, but also achieve the purpose of energy saving, reduce the operating time of air conditioning system and save costs

with the increasing maturity of frequency conversion technology, the automatic control system built by using frequency converter, PLC, man-machine interface, temperature sensor and other automatic products can automatically adjust the output flow of the water pump, which not only meets the requirements of human body for environmental comfort, but also achieves the purpose of energy saving. Using delta automation products and DeviceNet Fieldbus products to build the central air conditioning control system not only meets the above requirements, but also facilitates installation and commissioning. Due to the reduction of field wiring, the reliability and real-time performance of the control system are greatly improved

2 characteristics of central air conditioning system

in this project, the central air conditioning system is mainly responsible for the cooling and heating supply of the first to third floors of the store, of which the first floor is mainly for shops and garages, and the second and third floors are for the store area. Because the commodities are placed in different areas and the functions of each area are different, the distribution of people flow density is uneven, resulting in the difference of temperature and CO2 concentration in each area. At the same time, considering that the supermarket air conditioner is installed in suspension, cold (warm) air is supplied in different areas, and local air is returned, the system adopts the control strategy of regional control, local fine adjustment, and centralized management through DeviceNet Fieldbus Network

on the other hand, the passenger flow varies greatly at different times and different periods, and the temperature and CO2 concentration also change with the change of passenger flow. For example, the passenger flow increases at weekends and holidays, but it is relatively small at ordinary times, and the temperature and CO2 concentration are also relatively high at weekends and holidays. This set of automatic control system will automatically adjust the temperature and CO2 concentration according to the site environment

3 control system design of central air conditioning system

3.1 overall structure design

according to the distribution characteristics of air conditioning units, the CO2 concentration and indoor temperature less than 5x104 are called low cycle fatigue test; Area control; Cold (hot) water and fan adopt VWV and VAV mixed control mode, so as to achieve the purpose of comfort and energy saving

the whole building is divided into three floors, three aHUS on the first floor, three aHUS on the second floor, two aHUS and one PAH on the third floor. Each floor is composed of different functional areas. All aHUS and PAHs are under the overall control of a master controller. Each AHU and PAH has one independent control box

the overall architecture of the control system is shown in Figure 1

Figure 1 overall architecture of control system

3.2 structure of general controller

the general controller is mainly composed of touch screen, PLC and dvpdnet scanning module. The master controller communicates with the field controller through the DeviceNet Bus of delta for data exchange

the touch screen communicates with the master controller through the RS485 bus with Modbus protocol to monitor the operation status of each AHU. The temperature and CO2 concentration of the field controller can be set through the touch screen of the general controller, and the set data can be distributed to each field controller through DeviceNet communication

manage the whole network through dvpdnet scanning module, and display the status of each network node through man-machine interface. When the nodes on the network are abnormal, the corresponding indicator lights up. The status of the scanning module is displayed in real time. When an error occurs in the scanning module, the error code of the scanning module is displayed

3.3 field controller

the field controller is mainly composed of dna02 module, PLC, frequency converter, contactor and other components. The field controller receives the temperature and CO2 concentration setting instructions from the master controller. Data sharing can also be realized between field controllers through the general controller, and the collected temperature, CO2 concentration and other signals can be transmitted to other field controllers related to the area. The field controller controls the fan speed, cold (hot) water valve opening and fresh air valve opening of AHU and PAH air conditioners to adjust the indoor temperature and CO2 concentration

3.4 control process of AHU

ahu operation box can select automatic control or manual control. During automatic control, the on-site temperature and CO2 concentration are intelligently controlled within the allowable setting range by Delta PLC; When the operation box fails (such as sensor damage, communication failure, etc.), the frequency converter can be operated at a fixed frequency or power frequency for maintenance

3.5 treatment of CO2 concentration and human flow

in the shopping mall, the location of CO2 sensor is arranged according to the spatial area, and the CO2 concentration value is mainly collected at the densely populated place. The CO2 sensor is connected to the PLC of the field control box nearby. This signal is sent to the controller of the relevant air handling unit in this area through the centralized controller, and then each AHU introduces the fresh air volume by adjusting the opening of the fresh air valve to adjust the indoor CO2 concentration. The opening of the fresh air valve is PID controlled by the target values of CO2 concentration and outdoor temperature according to their weights

3.6 fire alarm interlock

this system is linked with the security system. When a fire alarm occurs, the man-machine alarm screen appears on the main controller, the air conditioner stops working, the water valve and air valve are closed, and the smoke exhaust system is started to exhaust smoke. The system provides a dry contact to connect with the security system

3.7 DeviceNet Network Configuration

3.7.1 module settings

set the nodes on the network according to table 1. Table 1 network node setting parameter table

3.7.2 DeviceNet slave station configuration

(1) open devicenetbuilder software, and the software interface is shown in Figure 2

Figure 2 devicenetbuilder software interface

(2) select the "settings (s)" function point "communication settings", and select the "system channel" command, as shown in Figure 3

Figure 3 system channel settings

(3) set the communication parameters between the computer and the SV host. Such as "communication port", "communication address", "communication rate" and "communication format". After the setting is correct, click "OK" to return to the main interface

(4) select "network (n)" menu point "" to indicate that the speed regulation ratio can reach 1:100000, and the window for selecting communication channel pops up, as shown in Figure 4

Figure 4 select the communication channel

(5) scan the DeviceNet Network according to "OK" in Figure 4, and the scanning progress bar pops up under normal conditions; Press "Cancel" to return to the main screen. If the progress bar of the above dialog box has not acted, it indicates that the communication connection between PC and SV PLC is abnormal or that other programs on PC use serial port. After the scanning is completed, the message "scanning network has been completed" will be prompted. At this time, the icons and device names of all nodes scanned in the network will be displayed on the software interface, as shown in Figure 5. In this example, the node address of dvpdnet is 01

Figure 5 network scanning results

(6) double click the vfd-f drives node with the mouse to pop up the node configuration window, as shown in Figure 6. Here, confirm the identification parameters and IO information of vfd-f frequency converter. After confirming that the configuration is correct, click the "OK" button to return to the main interface.

Figure 6 node configuration

(7) the configuration of other slave stations (such as PLC, etc.) is similar to the operation steps of node 1 and will not be repeated here.

3.7.3 configuration of dvpdnet scanning module (master station)

(1) double click the icon of DNET scanner (node 0) to pop up the "scanning module configuration..." dialog box, The list on the left shows the currently available nodes vfd-f drives 230V 50HP, dvp-ss/sa/eh PLC, vfd-f drives 230V 20HP, dvp-ss/sa/eh PLC, VFD-M drives 230V 5HP, dvp-ss/sa/eh PLC. There is an empty "scan list" on the right, as shown in Figure 7

Figure 7 scan module configuration

(2) move the DeviceNet in the left list in Figure 7 from the station device to the scan list of the scan module. The specific steps are as follows: select the DeviceNet slave node, and then click "" to move the DeviceNet slave node into the scan list of the scan module in turn. Click "OK" after confirmation

(3) select the "network (n)" menu and click the "download" command to download the configuration to the dvpdnet-sl scanning module. When downloading, if the SV host is in the running mode, a "warning" dialog box will pop up, as shown in Figure 8

figure 8 warning dialog box

(4) click the "yes" button to download the configuration to the scanning module and confirm that the PLC is in run mode

3.7.4 IO data mapping of dvpdnet-sl scanning module and slave station

io data mapping from dvpdnet-sl scanning module to DeviceNet slave station is shown in Table 2, and from DeviceNet slave station to dvpdnet-sl scanning module is shown in Table 3. Choose Save from the file menu to save the current network configuration. Table 2 IO data mapping from dvpdnet-sl scanning module to DeviceNet slave station

Table 3 IO data mapping from DeviceNet slave station to dvpdnet-sl scanning module

3.8 DeviceNet Network Monitoring

3.8.1 implementation principle

the scanning module monitors the nodes in the scanning list in real time and maps the status of each node in the scanning list to a bit. The user can obtain the status information of each network node by monitoring the contents of d6032~d6035. The corresponding relationship between PLC device and network node is shown in Table 4. Table 4 correspondence between PLC device and network nodes

when the nodes in the scan list are normal, the corresponding bit is off. When the nodes in the scan list are abnormal, the corresponding bit is on

the user can obtain the status information of the scanning module in real time by monitoring the contents of d6036. When the scanning module works normally, the content of d6036 is 0; When the scanning module is in initialization, the high byte content of d6036 is 1 and the low byte content is 0; When an error occurs in the scanning module, the content of the high byte of d6036 is 2. Refer to the error code of the low byte of d6036 for details of the error, as shown in Table 5

table 5 d6303 error code description

3.8.2 PLC component description (see Table 6) table 6 PLC component description

3.8.3 PLC program (DeviceNet Network monitoring part, see Figure 9)

Figure 9 DeviceNet Network monitoring part PLC program

4 DeviceNet Fieldbus control system advantages

compared with traditional control systems, the air conditioning system based on Fieldbus products has the following advantages:

(1) simple wiring, Save installation cost

devicenet realizes the communication between the nodes of the whole network through a communication line. Compared with the traditional point-to-point control system, it saves a lot of cables, shortens the installation time and reduces the installation cost

(2) high reliability

devicenet controls the whole network through a communication line. The master station module monitors the whole network in real time. By monitoring the master station module, you can quickly know the faulty node equipment, which is convenient for rapid troubleshooting; When a node on the network fails, it will not affect the normal operation of other nodes

5 conclusion

the central air conditioning system adopts DeviceNet Fieldbus Control Technology

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