Export Limit with HW in addition to SW possible?

[bt77]

Hi,
I have a behind-the-meter Huawei SUN2000 3 kW system with a 5 kWh battery which I use for self consumption only. So no export to grid as I don't have a feed-in contract anyway.
I am implementing the export limitation using the smart meter and the Huawei Fusion Solar software. It works well but a few days ago my meter was broken, I am currently waiting for the replacement.
My question is:
Would it be possible to implement zero export with a hardware (in addition to software)? Something like a breaker which would only open if there is a flow of current into the grid? When my meter was broken, until I realized it I must have exported energy to the grid. Would it be possible to avoid that with a hardware basically, which would make it impossible to export to the grid? I am thinking such an overcurrent breaker can't really exist as they sense the overcurrent regardless of the direction of the current but is there any other special hardware to realize what I am asking?
Thanks

 

[SeaGal]

Can you clarify what you are trying to achieve?

A grid-tied inverter needs the grid to work, otherwise it will shut down - so a breaker would not be helpful.

There will always be small amounts of short duration exports when a large load is turned off - it takes the inverter time to detect this and reduce its output to match the house load. Similarly, when a load is turned on there will be a brief import, until the inverter detects the load and increases its output.

Normally this is achieve via a CT clamp on the grid feed connected to the inverter.

 

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[bt77]

Can you clarify what you are trying to achieve?

A grid-tied inverter needs the grid to work, otherwise it will shut down - so a breaker would not be helpful.

There will always be small amounts of short duration exports when a large load is turned off - it takes the inverter time to detect this and reduce its output to match the house load. Similarly, when a load is turned on there will be a brief import, until the inverter detects the load and increases its output.

Normally this is achieve via a CT clamp on the grid feed connected to the inverter.

Yes I am aware of this. And yes I have a CT clamp on the grid feed. I am doing all this, no problem here.

My question was, if there is a software issue, or as in my case my measurement sensor (connected to the CT) is broken for a reason, and say I was away for 3 days (which was exactly the case), the export limitation was no longer effective and I was exporting a lot of excess generation to the grid (given I wasn't home, no load other than fridge, and battery was already fully charged). Since I am not supposed to export to grid (I am not talking about the small imports/exports you mention, those are fine, would there be a way to disconnect or disable the system when something like this happened? Of course I could send someone to my home and have them open the inverter breaker and that's it but I mean something which would do this automatically when a large amount of energy export is detected.

 

[wpns]

large amount of energy export is detected.

You have that but it broke. Adding another one would also be prone to failure.

What’s this measurement sensor?

 

[SeaGal]

My question was, if there is a software issue, or as in my case my measurement sensor (connected to the CT) is broken for a reason, and say I was away for 3 days (which was exactly the case), the export limitation was no longer effective and I was exporting a lot of excess generation to the grid (given I wasn't home, no load other than fridge, and battery was already fully charged). Since I am not supposed to export to grid (I am not talking about the small imports/exports you mention, those are fine, would there be a way to disconnect or disable the system when something like this happened? Of course I could send someone to my home and have them open the inverter breaker and that's it but I mean something which would do this automatically when a large amount of energy export is detected.

In the UK inverters with export limit control come under G100 regulations. Not sure about the Huawei, but my Solis and most other inverters I have come across have an option (which in the UK is mandatory to enable if you are compliant with G100) is that, in the case of a failure of meter readings from the CT, then the inverter will shut down. It's the 'Failsafe' option here...



So, when that is enabled, if the comms or CT clamp fail the inverter will turn off an no power will be exported.

I would guess your inverter would have a similar option if it is sold in the UK and other countries where control of export power may be needed.

 

[bt77]

In the UK inverters with export limit control come under G100 regulations. Not sure about the Huawei, but my Solis and most other inverters I have come across have an option (which in the UK is mandatory to enable if you are compliant with G100) is that, in the case of a failure of meter readings from the CT, then the inverter will shut down. It's the 'Failsafe' option here...

View attachment 202201

So, when that is enabled, if the comms or CT clamp fail the inverter will turn off an no power will be exported.

I would guess your inverter would have a similar option if it is sold in the UK and other countries where control of export power may be needed.

OK, this makes sense. Let me go through all the settings of the Huawei SUN2000 to see if there is such a failsafe option. Thanks.

 

[bt77]

You have that but it broke. Adding another one would also be prone to failure.

What’s this measurement sensor?

Huawei DDSU666-H

Actually I think it broke as a result of a nearby lightning strike, possibly in my premises. There is all kinds of protection (SPDs etc.) in place so other components (panels, inverter) are fine but I think as these smart meters are very sensitive electronic devices, it couldn't withstand it?

I am hoping it will be replaced it under warranty. I already bought a new one as I didn't want to wait for the replacement process but if they do replace, that will be my spare.

 

[wpns]

Huawei DDSU666-H

Actually I think it broke as a result of a nearby lightning strike, possibly in my premises. There is all kinds of protection (SPDs etc.) in place so other components (panels, inverter) are fine but I think as these smart meters are very sensitive electronic devices, it couldn't withstand it?

I am hoping it will be replaced it under warranty. I already bought a new one as I didn't want to wait for the replacement process but if they do replace, that will be my spare.

Now I get it, never seen a separate CT interface for a CT that talks Modbus to the inverter, but now I have. Yeah, I’d think the inverter should shut down if it stopped seeing data from the sensor, but maybe it just blew out the front end and was sending zeroes? (And yeah, it should notice all zeroes all the time but that’s an inverter firmware issue you should take up with Huawei).

 

[bt77]

Now I get it, never seen a separate CT interface for a CT that talks Modbus to the inverter, but now I have. Yeah, I’d think the inverter should shut down if it stopped seeing data from the sensor, but maybe it just blew out the front end and was sending zeroes? (And yeah, it should notice all zeroes all the time but that’s an inverter firmware issue you should take up with Huawei).

Problem is it never stopped sending data to the inverter. It kept working but was sending incorrect current values (frequency and voltage was still correct). I mean they were impossible high current values like tens of amps, 20A, 25A, 30A and more (I have a 3 kW inverter and 3 kW grid connection, my currents are rarely higher than 5-6A), so I realized it was broken.

 

[bt77]

OK, this makes sense. Let me go through all the settings of the Huawei SUN2000 to see if there is such a failsafe option. Thanks.

In the UK inverters with export limit control come under G100 regulations. Not sure about the Huawei, but my Solis and most other inverters I have come across have an option (which in the UK is mandatory to enable if you are compliant with G100) is that, in the case of a failure of meter readings from the CT, then the inverter will shut down. It's the 'Failsafe' option here...

View attachment 202201

So, when that is enabled, if the comms or CT clamp fail the inverter will turn off an no power will be exported.

I would guess your inverter would have a similar option if it is sold in the UK and other countries where control of export power may be needed.

OK I think I found it. There is these parameters in the config which is certainly what I was talking about. Thanks again.

Shutdown at high feed-in power >> Enable/Disable
Upper feed-in power threshold for inverter shutdown (kW)
High feed-in power duration threshold for triggering inverter shutdown (s)