Απο το manual του PV-syst.
This feature also allows the use of multi-MPPT inverters: you can define a subsystem for some MPPT input
(s), and a different one for others. In this case the number of MPPT input should be used in place of the
number of inverters.
NB: Some new inverters (namely the Tripower series of SMA) have 2 MPPT inputs with very different
powers. In practice this is very useful as you can define an array without much constraints about the
module number on the main input, and one string with the remaining of your modules to be installed -whatever their number - on the secondary input.
PVsyst is indeed not foreseen for treating such assymmetric MPPT inputs.
Nevertheles you can overcome the problem by modifying the number of MPPT inputs in the inverter definition (an save this as a new inverter). Please set here your total number of strings.
After that, you can define one subfield with the (N-1) virtual MPPT inputs, and a second subfield with one string and the remainder of the modules.
In the reality of your final wiring the (N-1) MPPT inputs will of course be one only MPPT input.