Huawei EMMA - Support External Meter for cases in which not all loads are connected to EMMA

[mrandt]

Is your feature request related to a problem? Please describe.

For energy measuring point meters: usage: grid I'd like to be able to configure the Huawei EMMA meter integration / template so it uses measurements from an external meter connected to EMMA via Modbus RTU rather than the built-in energy flow sensors.

Huawei EMMA includes energy flow sensors and in many cases will be the only meter required in a Huawei PV setup.

But EMMA also supports connecting an external meter (like a DTSU666 or YDS60-80) via Modbus RTU on the secondary RS485 COMM port.

An external meter might be necessary, if not all loads are connected behind EMMA - either because the loads require too much current in total or the metering concept requires an energy flow measurement at a different location.

I have recently installed the brand new Huawei SmartGuard backup power solution, which always includes EMMA.

In preparation for a cascaded metering solution ("Messkonzept mit Kasakadenmessung zur separaten Messung der Energie für SteuVE in Deutschland") not all loads could be connected behind EMMA but the EV charger and at some point in the future a heatpump are connected in front of the SmartGuard and thus EMMA.

Maybe a picture explains it better than many words:

I hope it is obvious from the picture, that EMMA's internal energy flow sensors (pink) will only capture energy flow from and to household + PV. For surplus charging, this measurement is totally off. It will actually assume the energy goint to the wallbox was exported to grid...

The correct measurement needed is the data from the YDS60-80 (blue) which measures the overall energy flow between household and public grid.

Within EMMA, I could configure the external meter to be used for battery charge / discharge control and statistics in Fusion portal and app.

Describe the solution you'd like

I'd like an optional configuration parameter for meters with template huawei-emma (https://docs.evcc.io/en/docs/devices/meters#emma) which switches to use the external meter rather than the internal one.

I do assume that EMMA provides those values via some Modbus register, even though I don't know which one.

However, if you let me know I can best help analyze, develop and test this, I am absoultely willing to help.

Thank you in advance for considering this!

Describe alternatives you've considered

In theory, we could add a third-party meter (unrelated to Huawei) next to the external meter (directly behind the blue one in my drawing) and use that device's data. But it seems a bit cumbersome to add yet another meter if - in theory - all the data should already be available.

Additional context

Please find a description of how and when to use an external meter in the Huawei Smart Guard manual here:
https://support.huawei.com/enterprise/de/doc/EDOC1100366781/26745df?idPath=258788303|258788489|258789981|21102413|255740899

[mrandt]

@Mungg1818 I saw that you have contributed the huawei-emma template. Could you please have a look at this issue? Thanks!

[mrandt]

After some more searching, I found SmartHEMS Interface Definitions PDF here:
https://photomate.zendesk.com/hc/en-gb/article_attachments/20421983900701

Starting page 16, it lists the modbus registers for external meter data.

It seems the modbus registers 31895 through 31943 contain the desired information.

So my desired feature would probably require reading those instead of the registers for the internal sensor?

[mrandt]

More digging; seems that template huawei-emma reads register 31679 via Modbus for grid energy:

evcc/templates/definition/meter/huawei-emma.yaml

Line 30 in e93e420

address: 31679 # Total negative active energy of built-in electric energy sensor

If I understand correctly, in my scenario the register 31935 would be needed instead - see screenshot from Huawei docs:

So basically an option which switches between 316979 (internal energy meter) and 31935 (external energy meter) would to the trick?!

[Mungg1818]

Hi @mrandt
In my opinion this is correct but i would recommend to change current measurenent aswell. I made the EMMA template on basis of the smartlogger and have no furter insights how to provide such a selection to decide which modbus registers should be read. I'm sorry.

[mrandt]

Thanks for the reply, I appreciate your help.

I think we got a little side-tracked here in duscissing my motiviation and whether this is a valid request or not ;-)

[mrandt]

I had a look at https://github.com/Mungg1818/evcc/blob/0711e562a92343d9c34f8b7f926b32690514da3a/templates/definition/meter/huawei-emma.yaml

I now understand what you meant with the currents. You're probably right, just changing the register for the active power will not suffice but the current for L1 to L3 will also need to be read from the external meter.

[premultiply]

I hope it is obvious from the picture, that EMMA's internal energy flow sensors (pink) will only capture energy flow from and to household + PV. For surplus charging, this measurement is totally off. It will actually assume the energy goint to the wallbox was exported to grid...

The correct measurement needed is the data from the YDS60-80 (blue) which measures the overall energy flow between household and public grid.

The position of "EMMA" and "EnFuRi" needs to be swapped.
Somebody misunderstood the concept.
Z1 is the grid meter. Z2 is only for billing reasons to divide between consumption of the "SteuVE" and all other loads.

[mrandt]

Hello and thanks for the answer.

Yes, switching the two meters would make it work. But physically I cannot do that.

EMMA is part of Huawei SmartGuard hardware in this scenario. It also controls the Smart backup switch. If I removed it, the AR-N certification of the whole backup solution would be void.

It does not make sense to connect the wallbox nor the heatpump to the backup load output. And I cannot connect them to the regular non-backup-load output of SmartGuard either, as the metering concept requires all SteuVE to be connected behind Z1 and in front of Z2.

The metering concept is agreed upon with the distributor (VNB) and is their standard to measure the SteuVE separately.

Huawei recommends connecting the external meter just as we have it here, I had linked to the documentation.

Everything but evcc works fine with this approach. Huawei EMMA and Fusion can be configured to use the external meter data as primary, as it measures all energy flow to and from public grid, as you mentioned.

Only thing I am asking for is a switch in the config for huawei-emma to be able to do the same; use the external meter data over internal meter data from EMMA in scenarios like this one.

I understand that this might an edge-case but I foresee building this more often as dynamic network charges become more attractive.

Many thanks in advance!

[mrandt]

@andig This is IMHO not a question or discussion on electrical installation but still a feature request.
Do you need any additional information? How can I help to get this accepted and implemented?
Many thanks in advance - and also big thank you for the great work you and others are putting in evcc in general!

[mrandt]

Just to add a bit more context / pictues - this is Huawei SmartGuard:

Essentially, SmartGuard is the new backup power solution by Huawei. If case of a power outage on the public grid, it isolates the home (or part of the home) from the grid and instantly provides 3phase backup from the inverter and battery.

Within the SmartGuard box you can see the EMMA in the top right. It is an integral part of the hardware and must not be removed and placed elsewhere as suggested.

In our scenario, we are integrating the backup power solution in a household which has an EV charger and will at some point install a heatpump and maybe a secondary EV charger. And obviously they want to benefit from lower network charges for these devices.

So a cascade metering concept to separately measure the energy for heatpump and EV chargers needed to be implemented, like the following:

When trying to fit the backup power solution into this metering concept, it can only be connected behind Z2.

But then, EMMA only measures the energy flow to and from the household.

Huawei offers a solution, which is connecting an external meter and placing it directly behind Z1 as shown in my initial drawing.

In the Huawei software, you then set the external meter to be used instead of the built-in meter.

For evcc to work in this scenario, it would also need to use the data from the external meter, not the internal one of EMMA.

EMMA apparently provides the values for the external meter in a separate modbus register.

My feature request is a configuration option, to use the other register's data in such scenario.

Thanks.

[premultiply]

As said before:
Z2 is the wrong position.
Move everything to position Z1 and it will just work.

This was discussed many times before in other broken "I do not want the car to drain my battery" setups and long before anybody talked about the german §14a EnWG.

The two meters are just for billing purposes and nothing else.
Z1 remains the electrical grid meter.

[mrandt]

No, this is no such case. I am well aware that I need the measurements taken at Z1 location, this is exactly what I want to achieve.

But as I laid out, I cannot move the EMMA there because it is integrated with the SmartGuard.

You keep suggesting I move "everything" to the Z1 location - so probably connect the SmartGuard unit there - but that is also not possible from a functional perspective.

SmartGuard provides the AC backup load output to which the household is connected. It also directly connects the PV inverter, as this provides the backup power during grid outage. Thus, it needs to be behind Z2 for correct metering and functionality.

But to measure the correct energy it would need to be next to Z1, and then wallbox and heatpump energy would also have to be passed through SmartGuard and EMMA - which again invalidates the metering cascade.

Do you see the conflict?

Instead I have put the additional Huawei meter (YDS60-80) in the correct location - directly behind Z1.

This is what Huawei engineers have recommended. This external meter is a standard option of EMMA. Since I configured EMMA to use the external meter instead of it's internal sensors, the complete Huawei ecosystem has worked as intended.

What I would like is that evcc could (optionally) also read the external meter data from EMMA!

When this option is enabled, huawei-emma should read modbus register 31935 (total negative active energy of external electric energy sensor ) instead of 316979 (total negative active energy of built-in electric energy sensor).

Are there reasons why such an option should harm evcc? It would enable everyone using an external meter with EMMA - whatever the reason might be - to also use evcc.

If you pointed me in the right direction, I could also try to help with this minor extension?!

P.S.: I assume we all speak German?! I only wrote in English because the feature request template was English. If it helps to clarify my situation, I'd happily discuss this im German, too. Instead of writing more posts, we could also have a quick chat on the phone or other voice media if you like. Thanks! :-)

[andig]

Instead I have put the additional Huawei meter (YDS60-80) in the correct location - directly behind Z1.
What I would like is that evcc could (optionally) also read the external meter data from EMMA!

@premultiply if we read the external meter, everything is Z1 afaiu

@mrandt it seems that the template needs a new "use external meter" option to then swap the grid readings? Happy to take a PR.

[premultiply]

It may work this way. Unsure.

[mrandt]

I went ahead and enhanced the template, see here:
2c156a3

While the advanced option works, from my first tests it seems that EMMA does not hold the expected values in those registers.

I will further investigate and keep you updated here.

Thank you!