Brushless and Magnetless Synchronous Generator for Standalone DC load with Vienna Rectifier

DC microgrids are becoming popular due to several advantages like easy integration, requirement of less number of power conversion stages, better stability etc.. This paper presents an alternative generating system for dc applications. The Brushless Induction Excited Synchronous Generator (BYNSIG) is used. In BYNSIG the excitation is fed through an induction machine (IM). The main machine and excitation machine are put in the same machine frame and they use the same magnetic core. As both are wound for different number of poles, these are magnetically decoupled. Controlled voltage and frequency fed to the stator of IM will produce controlled current in the IM-rotor. A rotating rectifier in the rotor converts the ac voltage into dc that feeds the field of the synchronous machine. Thus the machine becomes brushless and permanent magnet less as well. A simple diode rectifier can rectify the armature voltage of the Synchronous Generator (SG) and feed the dc load. But this creates huge amount of harmonics in the armature current of SG. A Vienna rectifier is used to overcome this problem. Extensive simulations using MATLAB/Simulink have confirmed the proposed concept.