Solar Voltage Rise, a spanner in the FIT works?

graememk wrote: »

Yep bumped into that today too,

Although, more voltage is more power to push more electricity out onto the grid, the inverter has to raise its voltage.

Hits voltage limit and stop, then it slowly ramps the power back up again.

What inverter do you have? Curious to know your setup, distance from transformer, number of other properties on the transformer etc.. What your voltage is when the inverter is off / not supplying any power (from PV or battery).

Fronius have a great video explaining the problem here (video linked at starting time) https://youtu.be/X8tsQhp7hM0?t=1137

I took a peak at the Solis docs and it doesn't look like they have any voltage-based limiting functionality.

Fronius and SolarEdge apparently do and as far as I can tell SolaX also does, but it's not very clear how to configure it properly from any manuals.

Given the prevalence of Solis inverters in Ireland I reckon this is a ticking time bomb.

graememk wrote: »

Does yours just currently cut out when it hits the limit?

Yeah, once the voltage hits the programmed limit (253V) it just dies. See output power:



And voltage:



There are references to reactive power control modes and volt-watt response modes in the manual so I'm working with my installer and SolaX to figure out what's the right setting. This is only really a problem for export, won't affect self consumption.

quentingargan wrote: »

[edit] Sorry - after posting I realised by voltage limiting functionality, you meant power limiting. That is not present on many brands, but you still lose production with it. It is better to see if you caan get permission to adjust the 253v limit up to 255 or 260. In UK, the limit is 264 because their nominal is 240. Ours is meant to be 230]

You can adjust the voltage range on most inverters, including Solis, but you are then in breach of EN5048 (soon to be EN51545). ESB sometimes gives permission to do this but I have never seen them do so in writing.

Your grid connection to the inverter should be on a cable heavy enough to ensure voltage drop <= 1%. I would try reading grid voltage at the consumer unit with a multimeter to check this isn't exacerbating the problem.

This is often a problem on sites close to wind farms. When they roll out solar parks, it will get worse because their output will peak at the same times.

Well there are two methods for limiting voltage as outlined by the Aus/NZ standard in the Fronius video, one is based on limiting exported power back to the grid when approaching the voltage limit. The other is about manipulating the power factor to leverage reactive power to control the voltage (not sure how much this affects the resultant exported power). Again, all this only impacts the power you feed back in, so only a problem if FIT is a big part of your plan. Otherwise, your inverter will keep cycling and you will lose self consumption power as well as exported.

That's interesting to hear anecdotally the ESB might permit a higher voltage limit, I might see what I can do there. I'm not near any other (micro) generators, in a typical rural environment, just single phase.

We've got 16mm2 through and through with the inverters so I think I'm alright cable size wise. I do have a voltage measurement at the consumer unit and down at the inverters and they concur.

ESB are coming out to install a voltage monitor for 10 days and then see what can be done / they're willing to do. Hoping they're flexible given there are no other houses on my transformer and likely never will be.

quentingargan wrote: »

If someone has this issue happening on a Solis inverter, PM me. I may have a setting that can remedy it, but I would need someone on a site with this issue to test it.

What's the setting, out of curiosity?

KCross wrote: »

They can, i think, change the windings in the transformer to lower your voltage which would be the opposite of the usual complaint!

Or they might just swap out your transformer.

Another likely prospect is that they say the voltage is within the spec of the regulator and hence do nothing.... thats what the voltage monitor will tell them. I've had that done on my house for low voltage. They have to do that to gather the stats in case you create an issue with the regulator. There are specific guidelines around what the voltage can/cannot be over a preiod of time.

I wonder if they'll ask me to turn off my solar inverters for the 10 days. I'm inclined not to (which means they'll record the voltage breaching 253V).

It'd be the same if say I had low voltage around 210V and turned on our electric shower (which drops the grid reading by 9-10V last time I checked). They'd record < 207V, and would have to fix it.

KCross wrote: »

Thats the kicker, they dont have to just because you get a few high or low readings.

They are allowed some leeway over a period of time. Its all clearly laid out as to what the criteria for a pass or fail is. If it fails they have to fix it but a few high or low readings over those 10 days wont be enough for a fail.

Yeah that's what I'm worried about. Just gotta wait and see.

KCross wrote: »

Here's the result I got and the regulations, so you have an idea of what they are allowed "get away with"!

https://www.boards.ie/vbulletin/showpost.php?p=106706752&postcount=57

Oh nice, thanks for linking that. How did you resolve things in the end?

Just found out about voltage optimisers: https://energyace.co.uk/voltage-optimisation-residential/

Anyone heard about these before?

air wrote: »

Yes, run, a mile!

Would be great if you could expand on this. Used one before?

air wrote: »

Yes, of course, this is exactly what I said in my previous post.
If you put a transformer between your inverter and the grid, you stand to export to such an extent that you will cause the local grid voltage to exceed that which is allowed.
You could find yourself liable for the consequences of this if it happens as a result of you installing uncertified equipment.

Hence why I'll ask them if this happens. If they say yes, then it's obviously a non-starter. If they claim this doesn't happen, well then either they're lying, don't know or are doing something different to your assumption.

air wrote: »

Well why are you asking questions if you're not interested in taking anyone's word for it.
You obviously know noting about the subject, I know plenty and have invested enough time to explain the issues around them to you.
If you want to disregard my advice, that's well and good and your own prerogative, but you can do your own leg work.
Good luck.

You're right, I don't want people's word. I want concrete verifiable facts. Too much to ask for obviously. Anyone can say "I know plenty".

air wrote: »

I've only just clicked the link you provided and it all but confirms what I've been saying.
It says (3 Tappings of 4%, 6%, 9%) which all but guarantees that it's an auto transformer and will behave exactly as I have described.

That's just the Optivolt one, what about the Energyace one? That specifies "Choice of 4 voltage reduction settings (-10v, -15v, -20v, -25v)" which implies it works differently, i.e. it doesn't just tap down by a percentage, it's an absolute reduction. Same tech?

air wrote: »

How about you ask the supplier to confirm that it is in fact an auto transformer, then go an educate yourself on what an auto transformer is and how it operates and decide whether it will help you or not.

That's the plan.

air wrote: »

I haven't looked into the Fronius solution you'll need to investigate the specifics of EN50438 for voltage lag and lead to see if it will help here, I'm fairly sure it won't but I don't have a copy of the full standard.
That video is referencing a New Zealand grid standard by the looks of it.

Yes I'm trying to find out if there's anything said about it in the standard.

air wrote: »

If you only want to limit export such that your inverter doesn't shut down due to over voltage then you could create a relatively simple voltage sensing circuit that would in turn modulate the DC input to the inverter proportionate to the grid voltage.
I've seen this done before for different reasons and it would likely work on any inverter and not create any risks of non conformance on the AC side.

Now this sounds pretty cool, who did it? How? Links?

air wrote: »

It was some Australian guru with an off grid setup, there was no further details than what I described but it would be fairly simple to replicate with an arduino or similar. I haven't time to go searching for it.

Read the AC voltage X times per second and modulate the gate of a high voltage MOSFET on the DC input to the inverter accordingly.

If you have a look at OpenEnergyMonitor architecture and their PV diverters, a simpler version of the hardware used there could be modified to achieve it.

If I recall correctly he hadn't even added a capacitor on the input, just chopped the PV input and that was it.

Sounds pretty cool but a little out of my own comfort zone.

I think I found at least a copy of EN 50438:2013 here https://shop.gwl.eu/docs/web/2018/EN_50438_2013-BS.pdf and it seems to state in section 4.5 that "In order to avoid disconnection due to the over-voltage protection the micro-generating plant is allowed to reduce active power output as a function of this rising voltage. If this function is activated, the micro-generating plant may reduce active power according to a logic chosen by the manufacturer. Nevertheless, this logic shall not result in steps of output power. " so it sounds like it's allowed.

I finally had the ESB out. They stuck a voltage monitor on at my meter for about 10 days. The engineer shared the data with me, it was well below 250V the entire time, usually around 244V.

He did some live measurements at various sockets for me too (with two different meters) and was getting 244-246V while the two inverters/Zappi would read from 248V-250V. So it appears that they read high, quite high, 4V high! The engineer suggested maybe upping their internal limits to see if that stops them cycling, and maybe getting my own multimeter to read voltage at sockets in the house to be sure. But as far as they're concerned, it's not a problem.

He did say the solution would be to move the transformer further away from me, which would involve doing work on my neighbour's land. So I've a few options.