Application of PROFIBUS Bus Bridge in Polysilicon Production Line

PROFIBUS is an open digital communication system with a wide range of applications, especially suitable for factory automation and process automation. PROFIBUS is suitable for fast, time-critical applications and complex communication tasks. The main control network of a well-known domestic polysilicon production line uses PROFIBUS fieldbus. Polysilicon is the most important functional raw material for the electronic information industry and solar photovoltaic power generation industry, and it is extremely important for the development of my country's electronic information industry and solar energy industry.

When designing a 10KV electric control system for a polysilicon reduction furnace, the designer needs to read the parameters of the relay protection device produced by Schneider into the S7-400 PLC and Yokogawa DCS of Siemens, and integrate it into the SCADA (Supervisory Control And Data Acquisition) monitoring system to participate in the actual interlocking control. The relay protection device provides an RS-485 communication interface, and its communication protocol is the Modbus RTU (Remote Terminal Unit) protocol. In order to realize the conversion from Modbus RTU protocol to PROFIBUS protocol, the design uses the Profibus-Modbus bridge (PB-B-MODBUS) produced by Beijing Dingshi Company to realize the communication between the PROFIBUS master station and the Modbus device, and then connects to the enterprise SCADA system through the industrial Ethernet module and fieldbus module in the PLC, so that the two are perfectly combined.

1. System Overview

The main equipment of the electrical system of the polysilicon reduction furnace is a high-power voltage regulator. The load carried by the voltage regulator is a pure resistance load formed by polysilicon rods connected in series. The function of the voltage regulator is actually to electrically heat the load resistance and keep the surface temperature of the silicon rod constant (generally 1080℃). The resistance formed by the silicon rods in series is a variable resistance: first, the silicon rod temperature rises from room temperature to 1000℃, and the Φ8 diameter silicon core resistance drops from hundreds of kΩ to tens of Ω; second, to keep the silicon rod surface temperature at 1080℃, the silicon rod diameter increases from Φ8 to Φ150, and the silicon rod resistance drops from tens of Ω to tens of mΩ. It can be seen that the wide range of changes in silicon rod resistance causes the voltage regulator to have a large adjustment range of output voltage and current, which is the design feature of this voltage regulator. According to the nature of the actual work, the voltage regulator is divided into a preheating voltage regulator in which the silicon rod temperature is heated from room temperature to 1000℃ and a reduction voltage regulator in which the silicon rod diameter increases from Φ8 to the final diameter and the silicon rod surface temperature is always maintained at 1080℃.

The main functions of the electrical system of the polysilicon reduction furnace are:

1. Carry out digital communication for all reduction furnace electrical equipment (voltage regulator, transformer, switch cabinet) under jurisdiction.

2. Display the electrical data of all reduction furnace electrical equipment under its jurisdiction on the screen and record the curves, and provide screen prompts and records of the faults of all reduction furnace electrical equipment.

PB-B-MODBUS bus bridge is mainly used for communication between reduction furnace switch cabinet and PROFIBUS master control system. The system adopts dual redundant PROFIBUS and optical fiber communication, with high reliability and strong anti-interference ability.

Figure 1 Reduction furnace electrical control principle

2. System network structure

The polysilicon (controlling 10KV polysilicon reduction furnace) production line was built in two phases, and both phases used PROFIBUS DP as the main control network. The first phase used Siemens S7 400H redundant PLC, and the configuration software used STEP 7.

Figure 2 Control system based on Siemens S7 400

The main control system of the second phase project adopts Yokogawa DCS, and the configuration software is SYCON.

Figure 3 Control system based on Yokogawa DCS CS3000

3. PB-B-MODBUS bus bridge reads Schneider MODBUS comprehensive protection instrument point table

Table 1 PB-B-MODBUS and comprehensive protection instrument data correspondence table

4. Configuration method of PB-B-MODBUS bus bridge

Since the product manual of Dingshi Technology PB-B-MODBUS has already explained the configuration method based on Siemens STEP 7 in detail, this article will not repeat it. This article will focus on the configuration method based on the configuration software SYCON of Henghe DCS.

1. After importing the GSD file, add a slave station and try to use the V33 version (V33 is an improved version of V32 with some new functions)

Figure 4

2. Select Slave configuration in the right-click menu

Figure 5

3. The first two modules "status" and "control" must be configured, and the others can be added according to your needs. Now read the slave station with MODBUS address 2 and read the Schneider comprehensive protection instrument data according to Table 1. Pull down the Module menu and select the read 3 Words (4xxxx) module and read 1 Words (4xxxx).

Figure 6

4. Click the third "Parameter Data" in the upper right corner

Figure 7

5. Click "Common" to set the communication interface, which must be consistent with the MODBUS device communication interface below.

Figure 8

Double-click the value under the "Value" menu to make corresponding changes. The following figure shows how to modify the baud rate.

Fig. 9

6. Click "Module" to modify the MODBUS slave address and register start address of the configured module (set according to Table 1).

Fig.10

5. Conclusion

Since the operation of this communication system, the communication between PLC and Modbus RTU has been normal, and there has never been any software or hardware failure or other interference, which effectively ensures the normal operation of the automatic control system. It can be seen that the communication between PLC and Modbus RTU through the PB-B-MODBUS bus bridge is an effective method. From this point of view, using the PB-B-MODBUS bridge to solve the communication between the PROFIBUS master station (SIEMENSE S7300/400, ABB AC800, Yokogawa DCS, AB PLC) and the third-party intelligent control instrument is a method worth promoting, and it will definitely achieve more successful applications in the electrical control system of polysilicon.