Cascade

Method

Each load-dependent loss is computed on the power that reaches its stage after the losses before it. The stages, in the order the power flows, are the AC cables, the copper of the MV transformer, the MV line, the copper of the HV transformer and the HV line; the first takes the inverter output. A stage's coefficient uses its own fraction (1), and its loss acts on the power that leaves the stage before it (2). The AC cables and the MV transformer carry one inverter's power with that inverter's reference; the later stages carry the sum of the inverters with the system's reference.

The math

1. Loss coefficient
2. Loss

$$k_n = \frac{f_n}{P_{ref,n}\,\text{PF}^2} \tag{1}$$ $$L_{n,i} = k_n\,P_{n-1,i}^2 \tag{2}$$

where

Symbol	Meaning	Unit
$k_n$	the loss coefficient of stage $n$	1/W
$f_n$	the loss of stage $n$ at its reference power and unit power factor, as a fraction of that reference power	—
$P_{ref,n}$	the AC power reference of stage $n$: one inverter's for the AC cables and the MV transformer, the system's for the later stages	W
$\text{PF}$	the power factor	—
$L_{n,i}$	the loss of stage $n$ at timestep $i$	W
$P_{n-1,i}$	the power leaving the previous stage at timestep $i$, after all of its losses; $P_{0,i}$ is the inverter output	W

References

1. PVsyst 8 help, AC losses

API

ac_losses.resistive_reference = cascade

Symbols follow the symbol registry.