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Restricted charging (Hybrid EMS)

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Note

The content on this page refers only to the blue'Log XC combined with the Hybrid EMS licence.

About restricted charging

Battery systems can store energy either from the grid or from local generators such as photovoltaic systems:

  • Charging from the grid: Energy is drawn from the grid and stored in the battery

  • Charging from other generators: Energy from PV systems or other local sources is used to charge the battery.

The allowed behavior of a battery system is often determined by regulatory requirements and tariff structures. These constraints define when and how the battery may charge, and under which conditions certain behaviors must be restricted or prioritized.

You can use the feature Restricted battery charging from grid to ensure external charging commands (e.g. from energy traders) comply with battery operation limits.

Note

The feature is only available in the energy management operation mode Default mode.

Configure restricted battery charging from grid

This function limits the charging power of the battery so that the power at the grid connection point does not fall below the configured Threshold for charging.

Prerequisites

  • The PV plant and batteries are both set up under Plant.

Steps

  1. Navigate to Power control > Active power > Energy management.

  2. Ensure that operation mode Default mode is selected.

  3. Activate the toggle Restrict battery charging from grid.

  4. Enter the relevant threshold in kW.

Battery charging from the grid will now be restricted.


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Example

An energy trader controls a plant consisting of a PV and a battery. Due to a tariff restriction, the battery is only allowed to be charged from the PV system and not from the grid. The Threshold for charging is set to 0 kW.

The energy trader uses PV production forecasts to decide when to charge the battery. However, forecast uncertainties, such as sudden cloud cover, can lead to charging commands that exceed current PV production. In this scenario, the blue’Log limits charging to prevent grid power from being used.

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Example restricted charging (threshold for charging = 0 kW)

Before t1

  • The energy trader sends a battery setpoint of -5 MW (charging).

  • Enough PV power (10 MW) is available to charge the battery.

  • Excess PV power is fed into the grid (Power at grid connection point GCP = 5 MW).

After t1

  • Sudden drop of PV power to 1 MW (e.g. due to cloud cover).

  • The energy trader continues to send a setpoint of -5 MW.

  • The energy trader’s setpoint is not implemented, as not enough PV power is available.

  • The blue’Log automatically adapts the charging power to the available PV power (1 MW) so that no power from the grid is used to charge the battery.



Caution

Grid security-related functions (e.g. frequency control) have higher priority and are not affected by this feature.

For example, if a battery is not allowed to charge from the grid (Threshold for charging is set to 0 kW) and an overfrequency event occurs (LFSM-O is activated), the battery may still charge from the grid to ensure grid stability.


Caution

The system may exceed the Threshold for charging for a short amount of time until the controller stabilizes, especially in cases of fast and dynamic changes in operational conditions (e.g. fast change of PV production).