Add new `consumption_power` formula to the `LogicalMeter`

[leandro-lucarella-frequenz]

What's needed?

We need to provide a consumption_power metric in the LogicalMeter.

Proposed solution

The LogicalMeter should get a new formula/metric consumption_power would calculate the client/market-side consumption of the microgrid. This should also include consumptions of EV chargers (but of course exclude PVs, batteries, etc.).

Use cases

No response

Alternatives and workarounds

Right now users need to look at the microgrid topology themselves to make this calculation, excluding batteries, PVs, etc.

Additional context

The name is still to be decided, so the issue is blocked until then. In your hands @matthias-wende-frequenz @frequenz-floss/datasci-team

[ela-kotulska-frequenz]

Is this what you need?
https://github.com/frequenz-floss/frequenz-sdk-python/blob/v0.x.x/tests/timeseries/_formula_engine/test_formula_composition.py#L147-L154

[thomas-nicolai-frequenz]

would calculate the client/market-side consumption of the microgrid

Its important to correctly define of what net consumption means. In the past we usually referred to it as market load, however net consumption is the consumption of none-flexible consumers that can't be shut down. EV chargers are obviously a hybrid but we agreed to include them into the net consumption for now, opposite to PVs, CHPs and batteries. The main goal is to:

1. Have one place where net_consumption is being defined
2. Have a common understanding of what net_consumption means (definition)

[cwasicki]

These are the definitions we agreed on:

$P_S$ : Production power
$P_L$ : Consumption power
$P_G$ : Grid power
$P_B$ : Battery power
$P_L+P_S$ : Net Consumption power

Note:

• This uses Passive Sign Convention.
• For now EV is part of consumption only, in future EV will be treated as a battery.