How to model equations, considering equality constraints in which decision vectors are included, like Generator voltage magnitude, Transformer tap ratios, shunt compensators are to be modelled in GAMS HOW ?
To my knowledge there may be no work done on the optimization of reactive power distribution using GAMS, however there is plenty of work based on metaheuristics such PSO, GA, TS...
For more information about this subject, I suggest you see the links on the topic.