This project uses Mitsubishi PROFIBUS-DP master station module (qj71pb92v) to communicate with 34 Mitsubishi A800 series frequency converters and 15 Weichuang high-power frequency converters. It can control frequency and automatic start and stop.

Problems encountered in debugging:
1. The communication between Mitsubishi PLC master station module and PROFIBUS-DP card of Weichuang inverter is not up.
2. When the master station module of Mitsubishi is connected with 34 Mitsubishi frequency converters and 15 Weichuang frequency converters at the same time, the communication is not up.
3. The operation of high-power Weichuang frequency converter will interfere with the communication, resulting in the instability of communication.
Solution:
1. First of all, the master station and slave station are to be configured in the master station and slave station. Because Weichuang's board card uses the Siemens style, after the configuration is completed, the high and low bytes of the read-out and write data will be misplaced,
Therefore, when writing frequency and reading frequency, the high and low bytes should be processed separately, and then the data processing can be carried out. Finally, the normal communication can be achieved.
2. Because in PROFIBUS-DP communication, the number of allowed connections per segment: master station * 1 + slave station + repeater = 32. There are more than 31 slave stations in the system, so it is necessary to add repeaters to amplify the signals in communication. In addition, the terminal resistance should be turned up at the end. The communication cable of PROFIBUS should use special communication cable to match the impedance of cable and terminal resistance.

3. In the whole system, the power of Weichuang frequency converter is very large, the maximum power is 200kW, so when the high-power inverter is running, there will be strong interference signal, which will cause communication interruption or abnormal communication. First reduce the communication rate, and then separate the Weichuang frequency converter and Mitsubishi frequency converter, and use two PROFIBUS-DP master station modules qj71pb92v to control, keep the power line as far as possible from the communication cable, and do a good job in grounding treatment, which will greatly reduce the interference.