Electronics > Power/Renewable Energy/EV's

Power supply issue testing solar generator

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artv:
Hi

I have a solar generator with 35-150V input, max 12A / 700W. I'm try to test this input towards its max - since I don't have enough panels or solar to get the full 700W.

When I plug in my bench supply - and set to its max 60V / 5A it pulses between full 60v 5A and zero - constantly switching between constant voltage and constant current.

If solar panels are connected it can receive well under 5A no problem - but it appears the bench supply is max'ing out current constantly.

I've got 4 bench supplies and none of them work how I was hoping. The best result I get is two 10a 30V supplies in series - that can deliver 7.5A at 60V and I can drop current drop off ok. But if I drop voltage I get no current? Which doesn't make sense to me since the solar generator can support from 35V?

I'm no doubt being an idiot but am I make incorrect assumptions or is it an issue with my power supplies - they're pretty cheap? Ideally I'd have a 100 or 150V 15A supply but can't afford it and not even sure it'd help?

Any help much appreciated!

Thanks.

Faringdon:
So you are putting your bench supply into the solar generator instead of the solar panel in order to test the solar generator?
Well, the solar generator, would be doing MPPT on its input...because it would expect a solar panel to be connected...so i am guessing that this is happening with your bench supply....the bench supply is just too low output impedance
for your solar generator.

trobbins:
Your bench power supply needs to be modified to include some series resistance (to provide voltage droop in the CV region of a PV module), and some shunt resistance (to provide current droop in the CC region of a PV module).  The MPPT solar interface may then be able to move to a stable MPP.  Say the MPPT wants to see voltage droop along a load line from 60V at 0A to 55V at 2.5A, then add a 2 ohm series resistance.  Say the power supply has a 5A CC output, and you want the interface to see 5A droop to 2.5A as voltage increases from 0V to 55V, then add a shunt 22 ohm resistor across the power supply.  The MPPT may then hopefully dither around a 50-55V 2-2.5A MPP.

artv:
Many thanks. I can't say I really understand your reply but it sounds like the issue won't be solved by just buying a bigger better power supply.

In simple terms - if I want to see say 2.5A at 40V going into the solar generator what would I have to do?

I understand that the power station has an MPPT controller - but at 60V 7.5A it does exactly what I'd expect?

Thanks again for your help!

Marco:
Try giving it 45V with a 20W 2 Ohm resistor.

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