question

marekp avatar image

VRM is not showing energy sent to the grid

Hi,

I moved my PV inverter from AC input to AC output of my 3F MP-II system.

I could see the energy being fed into the grid, but on the VRM there is a 0.0kWh in the "To Grid" box.

Why is that?


Regards,

Marek

screen-shot-2021-04-02-at-65733-pm.pngscreen-shot-2021-04-02-at-72751-pm.png

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VRM
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@Guy Stewart (Victron Community Manager)

Hi,

Is it possible for someone from Victron, involved in VRM, answer my question?

Regards,

Marek

4 Answers
mvader (Victron Energy) avatar image
mvader (Victron Energy) answered ·

Hi Marek,

I confirm: the algorithm calculating the kWhs needs to measure the PV Inverter directly.

Its a limitation, or bug, indeed.


Documented here:

https://www.victronenergy.com/live/vrm_portal:faq#what_are_the_requirements_for_the_solar_yield_and_consumption_tab

specifically, the comment "PV Inverter power and energy needs to be measured. ".

I hope we can at some point fix this. But, even with that fixed in software, the reporting will still be limited: you won't be able to see solar production. Which is the number that everyone is looking for.


The algorithm to calculate all kWhs is quite complex already, and very cumbersome to test when making a change.


All the best, Matthijs


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Hi @mvader (Victron Energy),

Thank you for your answer.

Name "To Grid" implies that the energy shown there, is a difference between PV production (on AC-out side) and house load.

That would be a very useful number for everyone who wants to compare the energy sent to grid, measured by our system, and energy counted by grid supplier meter. In my experience the second one always show higher consumption numbers and lower export numbers. :)

The current name is confusing because one can see energy being fed to grid but this box "To grid" is not reflecting it.

I thing the best way to avoid this confusion in the future, is to rename the box "To Grid" , in dashboard's "Historical data", to "Solar production" or "Local production".

My problem with it comes from the info I got from Victron materials about ESS system.

I asked a question here in the community,

https://community.victronenergy.com/questions/83739/ess-without-power-meter.html

and got the answer from @Daniël Boekel (Victron Energy Staff) that if everything is at AC-out I would not need the PowerMeter to run ESS assistant.

After getting this answer, I rewired my PV inverter from AC-in to AC-out and noticed that energy fed to grid is not registered by a dashboard.

My worry is that the ESS system will do the same.

All those questions, I have been asking to avoid buying not_so_cheep energy meter.

Because the answer, up til now, was not forthcoming, yesterday, I purchased the ET340 meter and USB_to_RS485 cable.

But even with this answer I am not sure where should I place this meter to get the full view of what is happening with energy in my system.

Should I place it to measure PV production only (between PV inverter and AC-out) or the total energy transfer of the system (between grid and AC-in)?

Best Regards,

Marek


"Should I place it to measure PV production only (between PV inverter and AC-out) or the total energy transfer of the system (between grid and AC-in)? "


Place it between the PV inverter and AC-OUT to see your AC-PV production on VRM.


It would make sense to put a meter between grid and AC-IN if you want to measure loads bypassing the ESS (not critical loads) and you want the ESS to compensate for that loads with battery power, if grid is available.

The "kWh to grid" value should work with both installation places, as I can see on my Installations on VRM. I have systems with both configurations, all show this "kWh to grid" value.

BR

marekp avatar image marekp markus ♦♦ ·

Hi @Markus,

Thank you for your suggestions.

I think the more logical is to place this ET340 between PV inverter and AC-out.

This way, the system will be getting exact number of energy produced by PV.

I already know PV production from PV inverter's own controller.

But there is a worry that the CTs in my MP-IIs are not reliable way to measure total energy fed to or taken from the grid.

I would have more confidence in those CTs if dashboard was showing the proper number of energy sent to grid.

Now it is showing ZERO but it may not be, in contrary to its name, the energy sent to grid, but the PV energy generated in the system.

I am still not sure what energy this box named "To grid" is showing. :)

It would make sense to put a meter between grid and AC-IN if you want to
 measure loads bypassing the ESS (not critical loads) and you want the 
ESS to compensate for that loads with battery power, if grid is 
available.

I will not have any loads bypassing MP-II's CTs but, can I rely on those CTs to measure properly energy transfer to and from the grid?

The "kWh to grid" value should work with both installation places, as I 
can see on my Installations on VRM. I have systems with both 
configurations, all show this "kWh to grid" value.

But is it really the true value of kWh sent to grid, when power meter is between PV and AC-out?

Is it really the true value of kWh from PV production, when power meter is between grid and AC-in?

If ET340 is placed between grid and AC-in and there is no ET340 between PV and AC-out, how the system knows size of the PV production, not knowing the house load value? CTs in MP-IIs would have to be relied upon.

If ET340 is placed between PV and AC-out, system knows the PV production and should know the house load, again assuming the CTs inside MP-IIs are measuring energy sent to grid properly.

What I see on the dashboard, does not give mi the confidence that they do that.

What I need from the system is:

1. Maximize my auto-consumption by using battery power when available,

2. Export excess PV energy to the grid for winter use. (in Poland we can store our energy in the grid for a year, with the 20% loss. Over one year is a 100% loss),

3. Have power at home when grid fails with no switch over problems.

Can the ESS assistant do that for me?

Best Regards,

Marek


Hi @MarekP

As most PV inverters communicate through ethernet nowadays, a separate meter is less and less needed. for PV inverters without comms, a simple current sensor is enough to do the job:

https://www.victronenergy.com/accessories/ac-current-sensor

marekp avatar image marekp Daniël Boekel (Victron Energy Staff) ♦♦ ·

Hi @Daniël Boekel (Victron Energy Staff),

My PV inverter communicates with its own controller through RS485 cable. This controller is connected to local network and can be accessed by computer running any internet browser. I cannot ask the manufacturer of this inverter for details of this communication because this manufacturer does not exist anymore. :(

This is the price I pay for being a patriot and choosing the local businesses and the service was suppose to be faster.

The problem with CT sensors, you mentioned, is that I need one per phase.

As my system is 3F I would need 3 of them.

The other problem is that I have LFP battery with BMS that uses "2 signal BMS" assistant.

On phase one MP-II Aux 1 and 2 are used by this BMS and Temp sensor input by temp sensor. Nowhere to connect the current sensor.

Price-wise, three current sensors cost as much as one ET340 with USB_RS485 cable. Also installation of three sensors is more complicated that one EF340.

Regards,

Marek


Hi @mvader (Victron Energy),

Following your suggestion, I got ET340 power meter and Victrons RS485 to USB cable.

ET340 is set up to measure PV inverter production.

So now PV production is measured and GX knows about it.

When PV inverter is connected at AC-out of MP-IIs, I can see the energy sent to grid in "historical data" section of dashboard.

When PV inverter (and ET340) is connected at AC-in of MP-IIs, energy sent to grid is not shown in "historical data" section of the dashboard.

The funny part is that dashboard does not show this sun energy as a sent "to grid" but as a "consumption".

I wonder who consumes this energy when there is no load in the system? :)

So the problem/bug still exists and adding ET340 power meter works only when PV inverter is connected on the AC-out of MP-IIs.

I have to connect my PV inverter on the AC-in because it does not react well to frequency shift.

Any suggestions, other than buying another power meter.

Regards,

Marek

pv-at-ac-in.jpg

pv-at-ac-in.jpg (80.7 KiB)
marekp avatar image
marekp answered ·

Hi @Tozz and @stxShadow,

My Inverter is not connected to GX, so GX is not aware of it's existence.

There is nothing to select in "settings/PV inverters/inverters/".

Also this inverter talks only in it's own language with it's own interface to local network.

But my main question is why, when VRM can see grid being fed energy, it does not show the amount of kWh in the box named "To grid"?

Regards,

Marek


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Hi Marek,

I still have VRM access to an installation, I had to support some time ago.

It's the only system in my VRM list, that has a system configuration with unmonitored AC-PV on AC-OUT.

It does show grid export:

1617525443703.png

But the system has an Energy meter installed, to measure the grid.



Do you rely on the Multis only, to measure the grid, or do you also have an energy meter installed?



IF you rely on the Multis to measure the grid, it could help to install a energy meter to measure production of AC-PV on AC-OUT. I have systems in my VRM list configured like that, they also show Export. I just don't have an installation like that without any grid meter to look, if they show export.


I would install an energy meter to begin with... I would never suggest, to have AC-PV on AC-OUT unmonitored, even if it could work like that. It's just not nice ;o)


(Just hints to diagnose, but I have no answer for you, I am sorry)


Best Regards,

Markus

1617525443703.png (153.9 KiB)
marekp avatar image marekp markus ♦♦ ·

Hi @Markus,

Thank you for your input to my problem.

I asked a question, about ESS without a Power Meter to measure the output of PV inverter, and got the answer from Victron energy staff member that if everything is behind the MP-II's it is not needed. The ESS will work without it.

https://community.victronenergy.com/questions/83739/ess-without-power-meter.html

So I moved my PV inverter to the AC-out position and noticed that VRM is showing the energy fed to the grid, but is not counting it in the "Historical data" section in the "To grid" box.

To me it looks like a BUG in the system.

screen-shot-2021-04-03-at-11321-pm.jpg

It should have noting to do with whether I have a Power Meter for my PV inverter or not.

The VRM on one hand is showing the energy fed to the grid, but on the other is ignoring it in the total energy fed to grid.

I am reluctant to buy this Power Meter because, probably sooner than later, I will have to replace my ailing PV inverter and if I buy Fronius I would not need this "not_very_cheep" Power Meter.


Best Regards and Happy Easter,

Marek

P.S.

I do not have any meter (that GX can connect to) in my system.

I agree, kWh to grid should be displayed in your case.

I only have access to similar systems with grid meter, so I cannot confirm if it is a general bug or not.

The VRM portal has to handle lots of different system configurations, your configuration might be used very rarely, so it could be just a bug not reported yet.

Maybe @Teun Lassche (Victron Energy Staff) has a definitive answer for you.

Happy Easter to you too!

Best Regards,

Markus


stxshadow avatar image
stxshadow answered ·

Did you change the position of the pv-inverter to "ac-out" ? -> Settings -> PV Inverters -> Inverters -> select the inverter -> change position to ac-out

Should work then.

Jens

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tozz avatar image
tozz answered ·

I'm not sure if this is the case, but perhaps the system needs to be aware of a PV inverter? Perhaps you can enable sunspec modbus tcp in your inverter, and have your Venus system read that?

Then you'd end up with something like this:

ess.png


ess.png (24.1 KiB)
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