I installed the DSP board of a good inverter on the faulty one, which remains with the exact same problems.
I see this as a good news! The most complicated part to fix is not the problem.
An important observation of today is that all the inverters works well at low power (200W, low Sun radiation).
What could be an inverter fault that is power related?
@aargee I think that the problem is not related to the PV string because if it was there, I would see the power dip only, while I also see the cosfi going low to 0.2. So I think that the inverter is doing a bad job.
Question:
I would like to be able to test the inverter "at the desk". How can I give it a DC supply of around 300 Vdc, 1-3 kW? (besides waiting for a sunny day
)
Besides specialized test equipments, what about a rectifier bridge, electrolytic capacitors, and 3x500W halogen lamps in parallel?
As the inverter drains more current, the voltage drop on the lamp increases, reducing the input voltage to the inverter.
On top of this, as the filament heats up, the voltage drop increases even more. This gives me an inverse relation between voltage and current, almost linear, that resemble the I-V curve of a Photovoltaic generator.
The inverter should stabilise at a voltage where the product V*I is maximum.
I probably need to isolate the 230V with a 1:1 transformer, because the inverter would stop when detecting a ground fault on the DC side.