What component can I use to measure the frequency of a three phase virtual synchronous inverter in PLECs?

I’m trying to measure the frequency of a 3 phase VSI but i’m not sure of how to do it in PLECs

You can use the PLL components in the PLECS library to track the frequency of three-phase and single-phase AC systems. Some VSI implementations might use an internally defined frequency / angle signal that is part of the control scheme.