There nothing particularly special about promos in terms of matchmaking (and indeed, ranks in general are pretty meaningless).
You're matchmade based on your mmr, which goes up when you win and down when you lose, and so in theory every time you win a game, your next game will be ever so slightly harder, and every time you lose one it'll be ever so slightly easier. Since getting into promos implied you just won a match, things are technically harder, but only very slightly. If you've been winning games on your own volition (as opposed to basically feeding but having someone manage to carry the game for you), then just keep doing what you're doing, and promos will probably be a similar experience.
Just have faith that if you belong in silver, you'll get there eventually. Even if you have a string of bad luck in promos, promo helper exists, so next time you reach promos (which shouldn't be that long if you're a silver [or higher!] player) you'll start with a free win, and if you have bad luck again you can even eventually start with 2 free wins. Just a matter of not tilting and keeping at it, and always focusing on yourself and the things you can improve/control rather than fretting over teams which you have no control over.