From GridLAB-D Wiki
Sync_ctrl
[Comments on 2020-4-7]
I think you may want to be more specific with R3 (or make it a new requirement). Basically state which generation assets it is expected to manipulate.
R4 I would split out into sub-requirements. Basically have R4 be there are bounds, then specify voltage and frequency at R4.1 and R4.2.