In PVsyst, the "1990" year is an indicator that the data are not real data fo9r a specified year.
See the FAQ "How to obtain meteo data other than for 1990 ?"
The Meteonorm data represent averages of at least 10 years of measurements. The period is mentioned in the data.
For getting values corresponding to each year of your measured data, you should avail of the corresponding Meteorological data.
You can take the ageing of the plant into account by using "Detailed Losses > Ageing
" in the project's dialog.
You have a tool for simulating the 15-25 operating years in the project's dialog "Advanced simulation > Aging tool
Here you may simulate your operating years with the same Meteo data, or specify a meteo file corresponding to each of your years.
You can import your measured data. And even directly compare them to the simulation, using the "Measured Data
" button on the main page.