The 49-year-old, who has managed 14 clubs since his first in 1998, left his most recent post at FK Istanbul Basaksehir in 2012.
The likes of Sam Allardyce, new Rangers boss Mark Warburton and former Wednesday forward John Sheridan were all linked with the Championship post, but it is believed Carvalhal is now set to take the job.
Carvalhal played for a host of Portuguese teams during a 15-year senior playing career including three spells at Braga, whom he later managed.
He won one Portuguese Cup and Super Cup whilst in charge of Leixoes during the 2001-02 season as well as a Portuguese League Cup with Vitoria Setubal in 2008.
After brief spells with Asteras Tripoli and Maritimo, Carvalhal spent the 2010-11 season in charge of Sporting Lisbon and then the 2011-12 season in charge of Besiktas.