Epic: EnWG §14a Dimming - overview of current capabilities and roadmap

[andig]

For a long time, evcc has supported load management and specifically §14a compliance for wall boxes. This epic extends and replaces #23912 with the current state of affairs.

Currently supported scope

1. Loadpoints/ chargers with current control are regulated according to load management limit (i.e. global §14a restrictions are applied via load management). This happens without any specific "dimming" support from the device.
2. Some Loadpoints/ chargers only accept power hints or general "boost" hints. These are currently not controlled according to §14a since load management only puts them into "normal", but not into "dimmed" operations mode.
3. A further exception to 2. is that generic SGReady chargers and any charger supporting dimming via it's setmode implementation is dimmed when mounted into a loadpoint.
4. During dimming, we're also stopping battery grid charging (Battery Control: hold charging when battery is dimmed #24150). Again, this happens without "dimming" support from the device.

How this works

Dimming via DSO is globally applied via eebus, fnn or relay hems which operate an gridcontrol circuit. The gridcontrol circuit wraps the user-defined root circuit and hence applies to all connected devices. For this reason, users must not, atm, define a custom lpc circuit (#24882).
The user configures the individual power limitation via the maxPower property of the relay HEMS (see BK6-22-300 dated 27 November 2023) or the power restriction is communicated dynamically via EEBus HEMS by the grid operator without any further local configuration.

What's not supported (yet)

Limitations we currently have and that we propose to work on cover:

• support dimming for additional meters that are not mounted into a loadpoint (specifically ext/aux). This is proposed in Dim meters via optional api #24074 with a sample implementation for EEBus "meter" devices in EEBus: add dimming #24595). We still need to add actually dimming the meter when grid connection point is dimmed.
• support this Dimmer interface for more meters. We already have an sgready-relay custom charger that extends the older sgready-boost which this capability in SGReady: add dimming via relay (BC) #24704.
• support custom devices chore: add custom dimmer/curtailer #29857
• Dimming is unconditional in that it affects all devices (except for case 1. above). It should be up to the user to determine which devices fall under §14a regime (this was originally covered under SteuVE Improvements #15239).
• Take dimming limits into account. Except for 1. all devices are unconditionally dimmed. This is only necessary when the dimming circuit is actually overloaded.
• Jump prediction: What will happen in extreme cases when dimming or boost mode is activated/deactivated? The device-specific power profile (except for case 1. devices) is unknown. In order to make better use of the available power budget and to be able to respond to changing load situations without exceeding the total power budget, knowledge of the maximum values that actually occur in the dimmed and boosted states is required.

Open points

• Should dimming and boosting (also) be available depending on tariffs?
• Documentation of the current status

[meierchen006]

Hello,
Let's hope that at some point we'll also get control boxes that can pass all this on.