All the "get_ " return internal lists that are understood by other commands. So you can do:
set_clock_groups -asynchronous -group {[get_clocks {*pll1* inclk}]} -group {[get_clocks {*pll2* inclk2}]}
or something like that. Note that set_clock_groups can only use clocks for its arguments, so it will basically do a get_clocks on whatever you type anyway. I personally never type get_clocks in that command, and just do:
set_clock_groups -asynchronous -group {*pll1* inclk} -group {*pll2* inclk2}
(Actually, I always set up my input clocks with create_clock statements, add derive_pll_clocks, and then run TQ. I run the command "Report Clocks", which gives me the name of every clock created. I highlight all the names and paste them into my .sdc, and then format set_clock_groups around it.)