One input per string

Method

When the strings per inverter do not exceed the inverter's MPPT inputs, every string has an input of its own. No strings run in parallel, so the string mismatch loss is not applied. With more than one input, each string's input runs as an inverter of its own. Its AC and DC nominal powers, its night consumption and its temperature-derated maximum are the inverter's divided by the number of inputs (1). Its efficiency curves keep their values in watts, so their part-load fractions are multiplied by the number of inputs (2). Each input keeps the inverter's power threshold. An input without a string adds nothing, its night consumption included. A DC wiring resistance given in ohms for the inverter is multiplied by the strings per inverter, so the wiring loss stays the same. On east-west racking the two faces share one operating point, so only the string mismatch rule applies there.

The math

1. One input's powers
2. One input's efficiency curves

$$P_{ac,in} = \frac{P_{ac,nom}}{n},\qquad P_{dc,in} = \frac{P_{dc,nom}}{n},\qquad P_{night,in} = \frac{P_{night}}{n} \tag{1}$$ $$f_{in} = n\,f \tag{2}$$

where

Symbol	Meaning	Unit
$P_{ac,in},\ P_{dc,in}$	the AC and DC nominal powers of one input	W
$P_{ac,nom},\ P_{dc,nom}$	the inverter's AC and DC nominal powers	W
$P_{night,in},\ P_{night}$	the night consumption of one input and of the inverter	W
$n$	the inverter's number of MPPT inputs	—
$f_{in}$	a part-load fraction of one input's efficiency curve	—
$f$	the same point's part-load fraction on the inverter's curve	—

References

1. PVsyst 8 help, Multi-MPPT inverters
2. Analysis of PVsyst 8.1.5 outputs shows this convention in its results.

API

options.inverter_mppt_inputs = separate

Symbols follow the symbol registry.