Power conservation over frequency transformation in Doubly Fed Asynchronous Generator

With a steep rise in wind farms around the world, Doubly Fed Asynchronous Generator (DFAG) has emerged as a popular machine. Also known as Type 3 wind turbine generator (WTG), this machine employs the well-known principle of injection and control of slip-frequency voltage into the rotor circuit to achieve performance over a large range of speed. Though extensive literature is available related to analysis of this machine, the balance of real and reactive power over frequency transformation has not been clearly addressed. This paper explains how real and reactive powers are preserved over transformation of frequency in the equivalent circuit of DFAG. Theoretical derivations are verified against PSCAD/EMTDC^® simulation of DFAG.