Improved Current Dynamics of Proportional-Integral-Resonant Controller for a Dual Three-Phase FSPM Machine

Resonant controllers are commonly used in parallel with proportional-integral controllers in the current control of multiphase machines and other three-phase drives where current harmonics need elimination. However, additional oscillatory and slow poles arise with the resonant controllers, resulting in a degradation in both reference tracking and disturbance rejection. In this article, an improved current control scheme with a discrete-time PI-resonant controller is proposed for a dual three-phase flux switching permanent magnet (FSPM) machine to eliminate the current unbalance and harmonics. First, a partial prefilter is used in the resonant controller path, yielding a pole-zero cancelation for the resonant poles in the closed-loop system; thus, the oscillation in command response becomes negligible. Then, the active resistance method is employed to improve the low-frequency disturbance rejection, and the resonant poles are damped with a pole-placement strategy. Finally, the experimental results on a dual three-phase FSPM machine validate the effectiveness of the proposed method, which can be extended to other ac drives for harmonic suppression.