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Modbus Power Control interface

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About the Modbus power control interface

The Modbus Power Control interface is an open Modbus TCP interface. It facilitates the real-time process data exchange with the grid operator. If telecontrol protocols (IEC 60870-5-101/-104, IEC 61850, or DNP3) are used, the interface serves as the ideal connection between a protocol converter (such as a programmable logic controller - PLC) and the telecontrol system of the grid operator.

For technical details and the complete read and write registers, see the Modbus power control license data sheet.

You can activate a variety of features via Modbus and customize many different values, for example:

  • Active power limitation of the battery and PV system. See Grid operator commands.

  • Reactive power control setpoint.

  • Switching between different reactive power control methods:

    • Without Hybrid EMS: Both active and reactive power: Method switch.

    • Hybrid EMS: Available for reactive power only.

  • Sending reference values, such as a voltage reference for a parallel shift of the characteristic curves.

  • Setting simulated frequency and voltage for testing purposes.

Configuration

The configuration in the blue’Log web interface differs depending on whether the Hybrid EMS license is installed or not.

Note
The register list contains two separate sections:

  • Registers for the blue’Log XC without the Hybrid EMS licence.

  • Registers for the blue’Log XC with the Hybrid EMS licence.

Prerequisites

  • blue’Log XC with firmware ≥ 10.0.8

  • For plants with both PV and battery: Hybrid EMS license

  • Modbus power control license

Configuration example: Mobus power control interface (without Hybrid EMS)

The configuration described below is an example. For the full range of options, refer to the register list.

  1. To configure active power (P), navigate to Power control > Active power.

  2. Under Setpoint command method, select Variable fixed value Pvar Modbus.

  3. A window appears with further configurations.

  4. To configure reactive power (Q), navigate to Power Control > Reactive power.

  5. Select the relevant Setpoint method command, e.g. Variable fixed value Qvar Modbus or Variable fixed value cos φvar Modbus.

  6. Depending on the method, additional configurations may be required.

Modbus power control is now configured.

Configuration example: Mobus power control interface (Hybrid EMS)

The configuration described below is an example. For the full range of options, refer to the register list.

  1. To configure active power (P), navigate to Power Control > Active power.

  2. Under Grid operator commands, select the check box for the Power limitation you want to configure. See also Grid operator commands.

  3. Under Interface, select Modbus.

  4. Select the unit, error behavior, and fallback value.

  5. To configure reactive power (Q), navigate to Power Control > Reactive power.

  6. Select the relevant Setpoint method command, typically Variable fixed value Qvar Modbus or Variable fixed value cos φvar Modbus.

Modbus power control is now configured.

Test the Modbus power control interface

You can use Modpoll to test the Modbus power control interface. For modpoll commands, refer to the example on the page SCADA interface.

To find the relevant Modbus IP address on the blue’Log web interface, follow these steps:

  • Without Hybrid EMS

    • For e.g. active power, select the image-20251204-151711.png Gear icon next to the setpoint command method you selected.

    • A window will appear. Select Transmission parameters Modbus TCP server.

  • Hybrid EMS

    • For e.g. active power, go to Grid operator commands.

    • Select Transmission parameters Modbus TCP server.