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Extracting Correction Value [%] from CERBO-GX via Modbus TCP


We have Viktron's Cerbo-GX in a PV System, connected to:

- 6 Battery inverters

- 1 Solar Inverter (Fronius)

- 1 Genset

- blueLog XM200 (red below)

Cerbo-GX is purely in charge of power control, being the master of the system, BUT, we are monitoring the system via blueLog-XM200 (Datalogger from Meteocontrol), which is sending the data to VCOM, the monitoring software.

VCOM calculates the system PR (Performance Ratio [%]), which needs to be compensated with the Correction Value [%] from the solar inverter, this is the percentage at which the inverter is operating: 100% if not curtailed, and lower e.g. 50% if operating at half capacity in order to not inject energy in the grid.

blueLog is getting the Cerbo-GX data via the "Mode 2 Register 2700", but the data we are getting does not allow for VCOM to compensate the PR calculation with the Correction Value, basically because we don't get it, but we get a constant Setpoint Value [W] (this is the value given to the grid meter as limit to activate power control preventing to inject PV energy into the grid). We can not compensate PR calculation with this.

Hence my question is:

- Where is the register from which blueLog can get the Correction Value [%] from Cerbo-GX?

This is a value that all controllers send inverters in order to limit their production when needed, to avoid things such as grid fee-din if the site's power demand is too low compared to PV production.

Modbus TCPcommunication protocolTCP IP Networking
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Modbus TCP Basics

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