Inverter efficiency problem with overpower

[charlesladd]

When inverters are assigned an overpower, this change does not affect the efficiency curve, which automatically drops off to zero starting at the nominal AC power, even if efficiency values are added above the nominal power value. Whether or not this is a bug, it does not reflect inverter operation accurately. In addition to this, inverters with a high difference between nominal power and maximum power seem to have high and unreasonable inverter overpower losses. The system page predicts a 0.1% overload loss and the actual losses are 3.0%.

You can see in this curve that the efficiency drops off at the nominal power of 45 kVA, not at the maximum power of 50 kVA, even though the manufacturer reported a normal efficiency for 50 kVA.

[André Mermoud]

This representation is quite correct.

The efficiency is defined as the Pout / Pin ratio. Now if the Pout is limited to the PNom value, the efficiency Pout/Pin will obviously diminish above Pout, in the way shown on the graph.

Now for the "unreasonable" Overpower loss:

- Please remember that the value in the sizing tool is a rough pre-evaluation, just for helping you to design your system. The reliablel value is the result of the simulation.

See the FAQ Why the overload loss is not the same at designe time as in the simulation ?

- In some conditions (high array voltage), the overpower may significantly increase.

See the FAQ Why sometimes the overload losses increase significantly ?