Dunne is expected to finalise a move to Villa Park before the close of the transfer window after Martin O'Neill's side agreed a fee with Manchester City.
The centre-half has discussed personal terms with Villa, although reports in Sunday's newspapers suggested the deal was being held up due to contractual issues with City.
Petrov expects the deal to go through and the Bulgarian midfielder believes Dunne can help to fill the void created by Martin Laursen's retirement over the summer.
"The deal for Dunne will be great news for Villa," said Petrov. "Richard's an international player, he's been in the Premier League for so many years and is one of the game's big players.
"It's going to be a big signing for Villa. It will give us a strong defender at the back and, of course, he's definitely a true leader. He's the captain of Ireland, he's been the captain of Manchester City, so you love to see players like that coming to this club.
"Laursen was a big player for us, with his presence and his influence. But he, like Gareth Barry, is now gone and we need to get on without him. The arrival of Dunne can help us to do that."