When I use the piwikTracker.trackGoal(1) to register a conversion, it automatically increments the visits as many times the piwikTracker.trackGoal(1) executes.
It increments both visits and conversion even if execute piwikTracker.trackGoal(1)
from console (firebug).
Is there a way to stop the visit increment on conversion?
What do you mean increment visit? It should not create a new visit every time you call it, unless it is indeed a new visit (ie. you call it 30min after previous call)