Communication network construction method of compressor in large helium low-temperature system and communication network

Abstract

The invention is suitable for the technical field of long-distance automatic control, provides a communication network construction method for a compressor in a large-scale helium low-temperature system and a communication network, and aims to solve the problem that the transmission rate of PROFIBUS DP communication cannot meet the rate requirement of automatic control of the large-scale helium low-temperature system after the distance exceeds 400 meters. Combining optical fibers with a PROFIBUS DP network is expected to expand the effective transmission range. And through the matching arrangement of the terminal resistors, the situation that the resistance of the whole network terminal is increased due to the addition of the RS485 repeater is reduced, and communication hardware faults are avoided. The effective transmission distance of PROFIBUS DP communication is effectively improved, and the technical effects of automatic control of a large helium low-temperature system and stable operation of a communication network are achieved.

Description

Technical Field

[0001] This application belongs to the field of long-distance automatic control technology, and in particular relates to a method for constructing a communication network for a compressor in a large-scale helium cryogenic system and the communication network itself. Background Technology

[0002] Currently, in large-scale helium cryogenic systems, target temperatures are often as low as 4.2K / -268.95℃ or even 1.8K / -271.35℃. Helium, due to its extremely low boiling point (4.2K at standard atmospheric pressure) and stable chemical properties, has become the core refrigerant, and the compressor is the core power source driving the helium to complete the "refrigeration cycle." Therefore, compressor control is particularly important. Since the complete compressor equipment is provided by the compressor manufacturer, the program is not open source. It only provides key measurement parameters, equipment status and start / stop control, load and frequency control data, etc., to communicate with the large-scale helium cryogenic system, enabling the large-scale helium cryogenic system to monitor the compressor status and perform logical control.

[0003] Existing PROFIBUS DP communication transmission rates range from 9.6 kbps to 12 Mbps, with higher rates resulting in shorter transmission distances. At 12 Mbps, the maximum distance is 100m; at 1.5 Mbps, it's 400m; and at 9.6 kbps, it's 1200m. Large-scale helium cryogenic systems typically use a 1.5 Mbps transmission rate, limiting the PROFIBUS DP communication distance to within 400m. However, in real-world projects, the distance between the compressor workshop and the control cabinet of the large-scale helium cryogenic system can exceed 400m, or even 1000m. PROFIBUS DP communication is ill-suited to the spatial constraints of large-scale helium cryogenic system implementations, highlighting the limitations of current technology. Summary of the Invention

[0004] The purpose of this application is to provide a method for constructing a communication network for a compressor in a large-scale helium cryogenic system and a communication network thereof, aiming to solve the technical problem of compatibility between transmission distance and transmission rate during the automatic control process of a large-scale helium cryogenic system.

[0005] On the one hand, this application provides a method for constructing a communication network for a compressor in a large-scale helium cryogenic system, the method comprising the following steps: s1. After connecting multiple refrigeration unit control cabinets in the cryogenic chamber in a chain structure using PROFIBUS DP communication lines, connect them to the first RS485 repeater and the first DP to fiber optic module in sequence. s2. After connecting the DP communication modules of multiple compressors in the compressor workshop in a chain structure using PROFIBUS DP communication lines, connect them in sequence to the second RS485 repeater and the second DP to fiber optic module. s3. An optical fiber is connected between the first DP to fiber optic module and the second DP to fiber optic module to complete the network closure; s4. Open the DP connector terminal resistor of the refrigeration unit control cabinet at the beginning of the chain structure, and open the DP connector terminal resistor of the DP communication module of the compressor at the end of the chain structure. s5. Shield the terminating resistors of the first RS485 repeater and the second RS485 repeater, and turn on the DP port terminating resistors of the first DP to fiber optic module and the second DP to fiber optic module.

[0006] On the other hand, this application also provides a communication network for a compressor in a large helium cryogenic system, constructed using the above method; the communication network includes multiple refrigeration unit control cabinets in the cryogenic hall, a first RS485 repeater, a first DP to fiber optic module, a second DP to fiber optic module, a second RS485 repeater, and multiple compressors in the compressor workshop, all connected in sequence. Among them, multiple refrigeration unit control cabinets, the first RS485 repeater and the first DP to fiber optic module are connected in series in a chain structure using PROFIBUS DP communication lines. The second DP to fiber optic module, the second RS485 repeater, and the multiple compressors in the compressor workshop are connected in series in a chain structure using PROFIBUS DP communication lines to connect their DP communication modules. The first DP to fiber optic module and the second DP to fiber optic module are connected by fiber optic cable.

[0007] This application addresses the issue that the PROFIBUS DP communication transmission rate, exceeding 400 meters, is insufficient to meet the speed requirements of automatic control in large-scale helium cryogenic systems. Combining fiber optics with a PROFIBUS DP network aims to extend the effective transmission range. However, due to the large system area and numerous devices, the PROFIBUS DP signal strength is insufficient, hindering normal communication. An RS485 repeater is then added to amplify the PROFIBUS DP signal. Furthermore, by adjusting the terminating resistor settings, the increased overall network terminating resistance caused by the RS485 repeater is reduced, preventing hardware failures in the communication network. This effectively improves the effective transmission distance of PROFIBUS DP communication, achieving the technical effect of stable communication network operation to meet the automatic control requirements of large-scale helium cryogenic systems. Attached Figure Description

[0008] Figure 1This is a schematic diagram of the communication network structure of the compressor in the large helium cryogenic system provided in this application; Figure 2 This is a diagram illustrating a hardware fault after directly combining optical fiber with a PROFIBUS DP network. Figure 3 This is a flowchart illustrating the implementation of a communication network construction method for a compressor in a large-scale helium cryogenic system provided in this application. Detailed Implementation

[0009] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0010] The specific implementation of this application will be described in detail below with reference to specific embodiments: Example 1: Figure 3 The implementation flow of the communication network construction method for the compressor in a large-scale helium cryogenic system provided in Embodiment 1 of this application is illustrated. For ease of explanation, only the parts related to the embodiments of this application are shown, and are described in detail below: On the one hand, this application provides a method for constructing a communication network for a compressor in a large-scale helium cryogenic system, the method comprising the following steps: s1. After connecting multiple refrigeration unit control cabinets in the cryogenic chamber in a chain structure using PROFIBUS DP communication lines, connect them to the first RS485 repeater and the first DP to fiber optic module in sequence. s2. After connecting the DP communication modules of multiple compressors in the compressor workshop in a chain structure using PROFIBUS DP communication lines, connect them in sequence to the second RS485 repeater and the second DP to fiber optic module. s3. An optical fiber is connected between the first DP to fiber optic module and the second DP to fiber optic module to complete the network closure; In steps s1-s3, the hardware construction of the communication network for the compressor in the large helium cryogenic system was completed. However, due to the large working area, an RS485 repeater was added to amplify the DP signal, which introduced an incompatibility issue between the RS485 repeater and the PROFIBUS DP communication network regarding the terminating capacitor. Therefore, subsequent terminating resistor matching settings are required to achieve actual network hardware connectivity.

[0011] s4. Open the DP connector terminal resistor of the refrigeration unit control cabinet at the beginning of the chain structure, and open the DP connector terminal resistor of the DP communication module of the compressor at the end of the chain structure. s5. Shield the terminating resistors of the first RS485 repeater and the second RS485 repeater, and turn on the DP port terminating resistors of the first DP to fiber optic module and the second DP to fiber optic module.

[0012] By configuring the terminating resistors as described above, the impact of adding an RS485 repeater on network resistance can be minimized, while effectively amplifying the DP signal to achieve compatibility with fiber optic cables. This avoids network hardware errors.

[0013] Furthermore, in the refrigeration unit control cabinet, a PROFIBUS DP connector and DP communication line are used to connect the logic controller CPU module and multiple distributed I / O modules.

[0014] Furthermore, the compressor includes: a high-pressure compressor, a low-pressure compressor, and a negative-pressure compressor.

[0015] Furthermore, the length of the optical fiber is set to 1-20 kilometers, and the optical fiber is a single-mode optical fiber.

[0016] Furthermore, the following steps are included before step s1; s0. Configure the WinCC host computer, use the graphical editor and dynamic scripts within the host computer to associate the compressor data, status and IO domain variables, and archive the data.

[0017] Furthermore, step s4 also includes the following steps; Turn off the DP connector termination resistor of the DP communication module of the refrigeration control cabinet and compressor that are not at the beginning or end of the chain structure.

[0018] Example 2 As attached Figure 1 As shown, this application also provides a communication network for a compressor in a large helium cryogenic system, constructed using the above method; the communication network includes multiple refrigeration unit control cabinets in the cryogenic chamber, a first RS485 repeater, a first DP to fiber optic module, a second DP to fiber optic module, a second RS485 repeater, and multiple compressors in the compressor workshop, all connected in sequence. Among them, multiple refrigeration unit control cabinets, the first RS485 repeater and the first DP to fiber optic module are connected in series in a chain structure using PROFIBUS DP communication lines. The second DP to fiber optic module, the second RS485 repeater, and the multiple compressors in the compressor workshop are connected in series in a chain structure using PROFIBUS DP communication lines to connect their DP communication modules. The first DP to fiber optic module and the second DP to fiber optic module are connected by single-mode fiber optic cable.

[0019] Furthermore, in the refrigeration unit control cabinet, a PROFIBUS DP connector and DP communication line are used to connect the logic controller CPU module and multiple distributed I / O modules.

[0020] Furthermore, in the refrigeration control cabinet, the second RS485 repeater and the multiple compressors in the compressor workshop are connected in series via PROFIBUS DP communication lines to form a large-scale helium cryogenic system distributed I / O rack.

[0021] Specifically, the series-connected large-scale helium cryogenic system's distributed I / O rack is used to collect data on cooling water temperature and flow rate, tank pressure in the tank area, and gas analyzer data in the compressor workshop. It also controls the pressure regulating valves at the compressor's inlet and outlet, and collects and controls the valve operating parameters of the cold boxes in the cryogenic chamber.

[0022] In practical implementation, within the cryogenic control cabinet, the logic controller CPU module and multiple distributed I / O modules are connected using PROFIBUS DP connectors and DP communication cables. The ends are connected to the DP ports of the PROFIBUS DP-to-fiber optic modules. Two PROFIBUS DP-to-fiber optic modules are connected using single-mode fiber optic cables, approximately 600m in length. In the compressor workshop, the PROFIBUS DP-to-fiber optic modules connect to eight compressors via DP connections. See the attached network structure reference. Figure 1 .

[0023] DP connector termination resistor setting method: At the start and end of the DP network, the terminating resistors must be switched to the ON position. In this application, the terminating resistors at the DP connectors of the PLC module in the large helium cryogenic system control cabinet and the DP communication module of the high-pressure B-type PLC are set to the ON position. The resistors for other distributed I / O modules and the compressor DP communication module are set to the OFF position.

[0024] Termination resistor configuration for RS485 repeater and DP to fiber optic module: Initially, the PLC CPU module and distributed I / O module were directly connected to the PROFIBUS DP to fiber optic module's DP port via a DP cable. After multiple tests and checks of the network hardware connection, normal communication was still not possible. (See attached reference.) Figure 2The hardware error message indicated the issue. Finally, an RS485 repeater was added to both the end of the DP output line of the PLC module in the large helium cryogenic system control cabinet and the front end of the compressor DP communication module. Normally, according to the DP network structure, the terminating resistors S1 and S2 of the RS485 repeater need to be set to the ON position to comply with operating procedures. However, after testing, normal communication was not possible with the normal setting. Ultimately, the RS485 repeater and DP-to-fiber optic module were configured as follows: the terminating resistors S1 and S2 were set to the OFF position, and the terminating resistors of the DP ports of the pair of PROFIBUS DP-to-fiber optic modules were set to ON. This achieved terminating resistor matching, and DP communication functioned normally.

[0025] The reason for the normal communication is that the terminating resistor of the PROFIBUS DP to fiber optic module must be set to ON when working normally. If the terminating resistors of the input and output sections of the RS485 repeater are also set to ON as described in the manual, this will result in a high terminating resistance for the entire network, leading to communication failure. In this invention, due to the large number of devices in the PROFIBUS DP communication network (including an S7-319 CPU, 9 ET 200M distributed I / Os, 8 compressors, 10 Lakeshore 240 cryogenic data acquisition modules, and 1 PAC32 ammeter), the large amount of data collected, and the long transmission distance, the DP signal cannot be directly converted to an optical signal. Therefore, configuring the terminating resistor and adding an RS485 repeater is necessary to achieve compatibility between the DP network and fiber optics, thus meeting the speed requirements of automatic control in large-scale helium cryogenic systems.

[0026] In summary, the communication network construction method for compressors in large-scale helium cryogenic systems proposed in this application enables the DP network to adapt to high-rate signal transmission within a range of 20 kilometers, providing the necessary network communication foundation for the stable automatic control of compressors in large-scale helium cryogenic systems.

[0027] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for constructing a communication network for a compressor in a large-scale helium cryogenic system, characterized in that, The method includes the following steps: s1. After connecting multiple refrigeration unit control cabinets in the low-temperature hall in a chain structure using PROFIBUS DP communication lines, connect them to the first RS485 repeater and the first DP to fiber optic module in sequence. s2. After connecting the DP communication modules of multiple compressors in the compressor workshop in a chain structure using PROFIBUS DP communication lines, connect them in sequence to the second RS485 repeater and the second DP to fiber optic module. s3. An optical fiber is connected between the first DP to fiber optic module and the second DP to fiber optic module to complete the network closure; s4. Open the DP connector terminal resistor of the refrigeration unit control cabinet at the beginning of the chain structure, and open the DP connector terminal resistor of the DP communication module of the compressor at the end of the chain structure. s5. Shield the terminating resistors of the first RS485 repeater and the second RS485 repeater, and turn on the DP port terminating resistors of the first DP to fiber optic module and the second DP to fiber optic module.

2. The method as described in claim 1, characterized in that, In the refrigeration unit control cabinet, a PROFIBUS DP connector and DP communication lines are used to connect the logic controller CPU module and multiple distributed I / O modules.

3. The method as described in claim 2, characterized in that, The compressor includes: a high-pressure compressor, a low-pressure compressor, and a negative-pressure compressor.

4. The method as described in claim 1, characterized in that, The fiber length is set to 1-20 kilometers, and the fiber is a single-mode fiber.

5. The method as described in claim 1, characterized in that, The following steps are included before step s1; s0. Configure the WinCC host computer, use the graphical editor and dynamic scripts within the host computer to associate the compressor data, status and IO domain variables, and archive the data.

6. The method as described in claim 2, characterized in that, Step s4 also includes the following steps; Turn off the DP connector termination resistor of the DP communication module of the refrigeration control cabinet and compressor that are not at the beginning or end of the chain structure.

7. A communication network for a compressor in a large-scale helium cryogenic system, characterized in that, The communication network is constructed using the method described in any one of claims 1-6; the communication network includes multiple refrigeration unit control cabinets in the low-temperature hall, a first RS485 repeater, a first DP to fiber optic module, a second DP to fiber optic module, a second RS485 repeater, and multiple compressors in the compressor workshop, which are connected in sequence. Among them, multiple refrigeration unit control cabinets, the first RS485 repeater and the first DP to fiber optic module are connected in series in a chain structure using PROFIBUS DP communication lines. The second DP to fiber optic module, the second RS485 repeater, and the multiple compressors in the compressor workshop are connected in series in a chain structure using PROFIBUS DP communication lines to connect their DP communication modules. The first DP to fiber optic module and the second DP to fiber optic module are connected by single-mode fiber optic cable.

8. The communication network as described in claim 7, characterized in that, In the refrigeration unit control cabinet, a PROFIBUS DP connector and DP communication lines are used to connect the logic controller CPU module and multiple distributed I / O modules.

9. The communication network as described in claim 7, characterized in that, In the refrigeration control cabinet, the second RS485 repeater and the multiple compressors in the compressor workshop are connected in series via PROFIBUS DP communication lines to form a large helium cryogenic system distributed I / O rack.

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