The unflavoured whey protein has a lot less carbs than the flavoured ones - see https://www.bulk.com/uk/pure-whey-protein.html
I'm unsure to what extent carbs are actually required to do a proper workout (because carbs give you the energy), and to what extent carbs in such powders would in any case be burned off during a work out. There are some people here who are bodybuilders, and I hope they join the thread and give an expert answer.