VE and AC coupled PV - Frequency are my settings correct? UK

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h2009 asked Mar 29, '24

VE and AC coupled PV - Frequency are my settings correct? UK

Hi there, I noticed when I updated to v506 on my MP2's I started to see my AC coupled PV being limited. So I did some looking and it was the frequency settings; however I need some help confirm what is the correct settings for my usage. It's worth mentioning that I do have DC PC aswell.

I'm based in the UK, and my system is Off-grid during peak hours 06:00 to 00:00 then the relays switch on and connect to mains grid. I'm running my MP2's at 245v

Looking at the settings of my MP2's:

Under Assistants:
Solar converter start reducing its output power at 50.20hz
Outpower Power will be reduced to minimum when frequency is 52.70hz
Converter will disconnect when frequency higher than 53hz

Under G99 Grid Code
U/V = 184v
OV stage 1 = 262.2v
OV stage 2 = 273.7v
U/F stage 1 = 47hz
U/F stage 2 = 52hz
O/F = 52hz

Solis 5G inverter settings:

U/V Stage 1 = 187v
U/V Stage 2 = 173v
OV Stage 1 = 260v
OV Stage 2 = 265v
OV Freq stage 1 = 52.6hz
OV Freq stage 1 = 53hz
UV Freq Stage 1 = 48hz
UV Freq Stage 2 = 47hz

Basically, I want to limit any AC PV clipping to start as late as possible and shutdown as last resort.
What I have noticed is that my Frequency (regardless of battery level) can be as high as 52.6hz; the frequency does move around a lot.
I'm not sure why the frequency move a lot as it doesn't seem to be to do with load or battery level.

AC PV Coupling frequency

screenshot-2024-03-29-at-172642.png (298.4 KiB)

screenshot-2024-03-29-at-173431.png (507.7 KiB)

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Alexandra ♦ commented · Mar 29 at 07:16 PM

@h2009

The frequency shifting is controlled by the ESS assistant not the grid code. You say under assistants.... What assistant?

It is probably throttled because of the battery control though. Check charge current request there.

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Answer 1 · 2024-03-29T22:22:30Z

h2009 answered · Mar 29 at 10:22 PM

Hi yes it’s controlled by ESS under the inverter settings (when you use the VE tools).

My first thought was the battery which was doing it but how would I see this?

The solis inverter was displaying limited by frequency before I changed it to the above settings on that. Since making the changes to the settings in my post it solved it the issue. But I’m just not sure the settings are correct. Last thing i want to do is cause an issue.

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Alexandra ♦ commented · Mar 31 at 04:18 PM

What batteries do you have?

Under device list if they are can connected you can see the parameters sent such as CCL and CVL etc.

Also in VRM you can load a battery widget for the same information.

Maybe in the ESS assistant change the step frequencies. What do you have set there? Or did you use the default (which are tuned for Fronius).

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Answer 2 · 2024-03-31T09:23:59Z

h2009 answered · Mar 31 at 09:23 AM

This is an example I cannot understand why the frequency is so high at 52.8hz thr batteries should be charging at full rate.

img-5662.jpeg (541.6 KiB)

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Answer 3 · 2024-03-31T13:16:47Z

sharpener answered · Mar 31 at 01:16 PM

You have got the default settings for freq control in ESS Assistant (PV Assistant is same). I think these are not well suited to the Solis, what does the manual for it say? If it does not start to throttle until 52.6 Hz then it is not surprising the MP2 has to run up to 52.8 Hz to control it.

As an example of a working system my 13 y.o. Steca inverters have a shut-down at 51.0 Hz (compliant with the then G83/1 standard) so I have the assistant settings 52.1, 52.2, 52.3 (they can't be the same) which works fine.

In island mode when there is excess generation and the battery is 100% the system freq rises to 52 and the PV shuts down. The battery supplies the houseloads and the freq decays slowly over 5 mins back towards 50 then the PV re-synchronises. This 10 min cycle continues indefinitely.

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h2009 commented · Mar 31 at 01:56 PM

Ok so what I’m understanding, is that the frequency doesn’t really matter what setting it is on as long as there is a match between equipment.

Originally my thinking if the systems were setup for G99 then it should all match. However in this case it doesn’t seem to be the issue.

I believe before v506 Mp2 firmware this didn’t seem to matter or it matched. Since upgrading to v510 that’s when I noticed this issue starting.

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