Aris,
As far as i have used energy modelling, i have not came across this as i relate energy generation directly to demand.
If i get you right, i guess you mean generation form solar, which are usually at lower voltage and converted to higher for distribution purpose. Even other mechanical generators' output voltage are low and are stepped up for distribution. As long as you take account of generation and demand in terms of energy, voltage won't matter. You can include the effect of voltage drop into loss/efficiency.
However, if you intend to include the technologies with different voltage and make them show up, you have the flexibility in LEAP to add User Variables where you can put your own functions and formulas and finally link them to energy modules. You also could add Dummy Branch and Fuel type to show the flow of energy.
I hope this helps you
Best,
Utsav