3Ph 90kVA System not accepting Generator

Curious whether anyone's tackled a large 3-phase Quattro setup refusing to accept a generator feed — I've been wrestling with a related (albeit smaller-scale) issue on my static caravan site and it's led me down a rabbit hole of reading about bigger commercial installs.

The scenario I keep seeing discussed involves multiple Quattros per phase (say 2× units paralleled) with a substantial battery bank, trying to hand off cleanly to a 3-phase genset. The inverters apparently just won't accept the AC input — keeps rejecting it or cycling endlessly.

From what I understand, the likely culprits are:

• Generator frequency/voltage drift — cheaper gensets wander outside the Quattro's acceptance window, particularly under light load
• Phase rotation — get this wrong and the Quattros will outright refuse the source
• VE.Bus configuration — parallel and 3-phase assistant settings needing to match exactly across all units, otherwise one phase disagrees and the whole system rejects the feed
• AC input current limits set too conservatively, causing the inverters to never stabilise on the generator before the timeout kicks in

On my own Victron setup (single-phase, much humbler 5kVA), I had similar rejection issues until I extended the AC input detection timeout in VEConfigure and bumped the weak AC threshold. Made a significant difference.

For a 90kVA 3-phase system, I'd want to know what firmware versions are running across all six Quattros — mismatched firmware in a parallel configuration is an absolute nightmare.

Anyone here running multi-unit 3-phase Victron setups professionally? Would love to hear how you've approached generator integration, particularly with units that have iffy governor control.

@MandyRoss the generator acceptance issue on Quattros almost always comes down to UPS function settings or the AC input current limits being set too conservatively — the inverter just rejects the source before it's had chance to stabilise.

On my boat setup (much smaller, single-phase, but same firmware logic) I had this exact battle. Key things to check:

• Generator start/stop settings — minimum run time and detection thresholds
• AC1 input voltage/frequency window — tighten or loosen depending on your genny's output quality
• Dynamic current limiter — sometimes fighting itself on startup surge

The 3-phase element adds complexity because all three legs need to be within tolerance simultaneously before the Quattro array will accept. A cheap generator with wobbly frequency on startup will fail that handshake repeatedly.

What generator are you running? That'll narrow it down considerably.

@MandyRoss worth checking your AC input current limits first — Quattros can be fussy if the generator's frequency wanders even slightly outside tolerance.

On my van setup (much smaller scale, single phase) I had similar rejection behaviour. Turned out the Dynamic Current Limiter in VEConfigure was off. Enabling it let the inverter cope with a soft-start generator that was sagging under load.

For 3-phase you'll also want to confirm all three Quattros have identical firmware and are properly configured as a three-unit system — any mismatch there causes weird acceptance failures.

@CliffGazer's UPS function point is valid too, but I'd rule out the frequency/voltage window settings first. Check AC1 input voltage range is set wide enough for your generator's output characteristics.

@MandyRoss on my motorhome I had a similar head-scratcher with a much smaller Multiplus refusing a generator — turned out the "weak AC input" setting in VEConfig was the culprit. At 90kVA three-phase scale, have you checked that setting on each individual Quattro unit? They each need it configured independently.

Also worth looking at:

• Dynamic current limiter — is it enabled? Helps with wobbly generator output
• Phase rotation — Quattros are particular about L1/L2/L3 sequence
• Ground relay settings if your generator has a floating neutral

What generator are you running? Diesel hire-type machines sometimes have rubbish frequency stability which throws Quattros right off. The "accept wide input frequency range" option in VEConnect can sometimes buy you enough headroom to at least get it syncing whilst you investigate further.

What does the VRM portal show for AC input voltage and frequency at the point it rejects?

@MandyRoss one thing I haven't seen mentioned yet — check your dynamic current limiter settings in VEConnect. If it's enabled and your generator has a soft or wobbly startup (common with older diesel sets), the Quattro can reject the input before the generator's even had chance to stabilise. I had exactly this on a client's site last year with a 3-phase setup. Disabling dynamic current limiting, or at least reducing its sensitivity, sorted it immediately.

Also worth verifying your AC input voltage range thresholds — generators often run slightly high or low compared to mains, and if your acceptable window is set too tight it'll just keep rejecting. A quick look at the VRM portal historical data should show you whether it's frequency or voltage that's causing the dropout.