Performance of Brushless Induction Excited Synchronous Generator

This paper reports a brushless induction excited synchronous generator. An induction machine (IM) and a synchronous machine (SM) are embedded in the same machine frame. To avoid the magnetic interaction between these two machines, they are configured for different numbers of poles. However, rotor windings of both machines are electrically coupled using a rotating rectifier. Therefore, field current of the SM can be controlled smoothly from stator side of the IM. Thus, this machine is expected to be more compact and cost effective compared to traditional pilot exciter-based brushless and permanent magnet less synchronous generators. In this paper, SM and IM are configured for four and six poles, respectively. The IM is operated in self-excited or power-zero mode such that it need not draw any active power from the external source at steady state. This is achieved by operating the IM at negative slip through a closed loop controller. A Vector control-based voltage regulation algorithm is proposed and dynamic performance of this controller is examined using PLECS. A 5.5 kVA laboratory prototype has been designed and fabricated to demonstrate the usefulness of the proposed generator and the controller.