Analysis of Double-Star Permanent-Magnet Synchronous Generators by a General Decoupled $d$ – $q$

This paper proposes a technique to analyze double-star permanent-magnet synchronous generators by transforming the two three-phase winding sets into two couples of windings on the d - and q-axes of the rotor reference frame. The technique introduces improvements with respect to other approaches, as it takes into account the harmonic content of the no-load flux linkages of the armature windings, it applies to a generic angular displacement between the two winding sets, and it greatly simplifies the analysis since the two transformed winding sets are decoupled with respect to each other.