MPP Solar MPPT charging issues - Parasitic oscillations in Switching supply

[Sparktastic]

Hi guys, I have a new(ish) 3 months old PIP3024GEW AIO.

For the first few months, I was relatively happy with the performance (basically just using the inverter function). At that point, I was not using the inbuilt MPPT charger because my small PV array couldn't produce the minimum voltage for the MPPT to fire up.

Recently, I installed 2kw worth of new panels, connected up in series, and hooked up the 3024 as the charger.
The arrays MPP voltage/current is around 135-144v @ 10A-12A MPP.

I've recently noticed that when this inverter generates 30-50A into the battery, it starts to intermittently squeal like an injured baby pig and the the output current drops by 30%.

It sounds like the MPPT switching circuit is producing parasitic oscillations, which then absolutely kills charge efficiency

I've msged MPP but I doubt I'll get a satisfactory response.

At this point, I'm going to have to order an external MPPT charger and just use the AIO as an inverter - Not happy.

Has anyone else noticed this on the cheaper AIO's?

 

[Sparktastic]

Further to this..

Below is an audio spectrum plot (taken from a phone) near the AIO. When the MPPT switching goes parasitic/spurious,
You can see well defined audio peaks across the audio spectrum and increased noise above 20Khz. Unfortunately, my phone mic only detects up to about 25Khz, but I wouldn't be surprised if the parasitic oscillations exceed that.

When 'squealing' the AIO charge efficiency drops by at least 30% or 10-15Amps @ 27v.

 

[OffGridForGood]

Recently, I installed 2kw worth of new panels, connected up in series, and hooked up the 3024 as the charger.
The arrays MPP voltage/current is around 135-144v @ 10A-12A MPP.

Better check on the MPP input voltages supported by your inverter,
I didn't look up your exact model, however am familar with MPP (I have five MPP inverters running) - the input DC from the PV is typically limited to MAX 145v DC and the manual will typically list 60-115v target operating range (for a 48v battery system) for your 24 volt I would expect the MPP operating range to be 30-115v.

When I first got PV panels for my own MPP 6048 I connected them 3s - and although the voltage was under the 145v limit they didn't work reliably, changing to 2s the PV voltage was in the operating range and the Inverter could vary the voltage up and down to find the MPPT point.

 

[Sparktastic]

Shouldn't be a PV voltage issue.
The MPPT on these units is rated at 60-450v DC.

I've got an Epever 100A 200v MPPT charge controller coming (I've had great experience with the lower power Epever controllers in the past), but I'm a bit annoyed that it has come to this.

 

[v_green57]

Got any ferrite cores lying about? Loop the array wiring through them and see what happens.

 

[OffGridForGood]

While you are waiting on the SCC, can you reconfigure the PV and test what happens?
Since you have yours in one series string, I would test using a few number of panels, and see what you get, if all good, add one panel to the string at a time and see what happens.
I wonder if one bad panel in a string would cause what you are seeing.
Is there any shading on part of the array while the rest is in full sun?