k·P² on the inverter output

Method

The loss is the fraction at the power reference scaled by the square of the inverter output, as the loss in a resistance grows with the square of the current. The current rises as the power factor falls, so the loss is divided by its square. On a timestep the inverter draws its night consumption, there is no cable loss.

The math

$$L_{ac} = f_{ac}\,\frac{P_{out}^2}{P_{ref}\,\cos^2\varphi} \tag{1}$$

where

Symbol	Meaning	Unit
$L_{ac}$	the AC cable loss of one inverter	W
$f_{ac}$	the AC wiring loss at the power reference, a fraction	—
$P_{out}$	the inverter's AC output	W
$P_{ref}$	the power reference of one inverter	W
$\cos\varphi$	the power factor	—

References

1. PVsyst 8 help, AC losses

API

ac_losses.ohmic_model = ohmic_i2r

Symbols follow the symbol registry.