Reasons and judgment of the failure of the combiner box to communicate

In the daily operation and maintenance of photovoltaic power plants, the combiner box often fails to communicate normally due to various problems, resulting in the untimely update of the photovoltaic array status, resulting in power generation losses and hidden dangers. Therefore, it is very important to promptly and quickly troubleshoot the communication problems of the combiner box.

Communication line short circuit

The combiner box of a photovoltaic power station is usually 16~20 combiner boxes as a photovoltaic array. When the communication line is short-circuited, all the combiner boxes in the entire array cannot communicate, and the RS485 communication voltage of the combiner box module is zero.

Solution: Disconnect all the communication lines of the combiner boxes in the array and connect them one by one. Voltage measurement is required for each connection. When the measured voltage is zero, it is the short-circuit point.

Damaged monitoring module

The damage of the monitoring module is the most common problem of the photovoltaic power plant, and the manifestation is that one or more combiner boxes of the photovoltaic array cannot communicate. However, this kind of problem is often confused with communication interference, and there is no correct judgment method.

Solution: Release the communication line at the uncommunicated combiner box, and measure the RS485 terminal voltage of the monitoring module. RS485 communication is carried out by voltage fluctuation. If the voltage is displayed as zero and communication cannot be carried out, it can basically be judged that the module is damaged.

Communication Interference

Communication interference may be the most troublesome problem in photovoltaic power plants, and there are many reasons for it, such as too much electrical noise of the inverter, mixed installation of power cables and communication cables, ungrounded communication cables, too long communication distances, and equipment communication terminals are not isolated, etc. Wait. Since it is difficult to determine the problem, we only write remedies here.

solution:

Add a 120 ohm resistor to the access end of the PV array.

Reduce the baud rate of the monitoring module.

The communication cable isolation layer is grounded.

Communication Disconnection

There are not many cases of communication disconnection. Generally, in a photovoltaic array, if the communication cable is disconnected in the middle, all the disconnected combiner boxes cannot communicate. This phenomenon is very obvious.

Solution: just connect the disconnection point