question

ian@solarplants avatar image

Generator - variable output frequency issue

I have an issue with the AC output on an off grid system - 10 Kva quattro / 2 x 13.8 Kwh BYD / 6 Kwp DC coupled PV with a Stephill geni (approx 12 Kva). There seems to be a "wobble" in the frequency of the AC out when the transfere switch operates. This seems to be most prevalent on generator shut-down and causes issues with electronic equipment on the AC side of the installation. I have tried the usual "tweeks", any advice as to how I can clean up the output to prevent this .. nic equipment installed.

Generatorfrequency
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1 Answer
Daniël Boekel (Victron Energy Staff) avatar image
Daniël Boekel (Victron Energy Staff) answered ·

Hi @ian@solarplants

the trick is probably to set the minimum AC-voltage higer, as described in the manual:

https://www.victronenergy.com/live/multiplus_faq#minimum_voltage_levels

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Hi Daniel, thanks for your response.

I have disallowed except wide range of frequency (45-65 Hz)

and set the minimum AC voltage from 180V to 210V but the output is still pretty wobbly (please see below VRM graphs:

Any ideas ?

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Hi Ian. Likely more questions from me than useful help, so please pardon..

I note 'Ext Control' bobs up in your Solar Charger screen. What's that from, ESS? Why? Maybe not related though..

In that period between ~0900 to 1600 on Input Hz, is that the genny running continuously, and the input cutting out without continual genny restarting? If so, see here: https://www.victronenergy.com/live/multiplus_faq

There's a procedure to run through there, and amongst other things the Dynamic Current Limiter may be worth a look at, also Weak AC Input, which may fool with the power factor and reduce input capacity, but maybe necessary to give acceptance stability.

Bad Hz is hard to deal with, but stability will help reduce the spikes. Just prodding at the edges here..

And oh, maybe reduce your VRM logging to 1 min til you sort this. Might help with reading the graphs..



Its just a very standard off grid 10 Kva quattro / 26.7 Kwh BYD no assistants , tried all the usual tweaks for geni's .. I just need to stabilise the output frequency more to protect equipment on the AC output. The problem seems worst on geni shutdown, and unfortunately loads are high during the Winter causing the geni to kick in to "power assist" frequently ...

It's a tricky one, as the geni input is not ideal (there probably wouldn't be issues with another geni), however this can be difficult to prove to the client when there were no issues when the site ran on geni only.