I. Introduction
The high reliability structure gives the superiority for the brushless doubly-fed induction generator (BDFIG) as a promising machine in the adjustable drive systems. The fixed stator frame of the BDFIG considers two windings separated and isolated with different number of poles. One of the two windings is specified as the main winding of the machine which is denoted as the power winding (PW). The other winding is for control purpose and is known as the control winding (CW) [1]. Furthermore, the rotating frame of the adopted machine coupled the two windings magnetically with different types, including the wound, cage, and reluctance structures [2]. The study presented in [2] has specified the main merits of using the wound-rotor configuration instead of the other types of rotor structure, which assures the highly efficient use of windings, low harmonic effect in the rotor side, and simple arrangement.