Optimized harmonic current control strategy for nonlinearities compensation in multiphase AC drives

Low-order odd harmonics are particularly problematic in multiphase drives, due to the small impedance in the no-torque subspaces. The harmonics can be compensated by proportional-integral controllers in multiple synchronous reference frames (SRFs). In three-phase systems, the computational burden of such scheme is often avoided by implementing instead resonant controllers (RCs) tuned at the harmonics that are multiples of six in an SRF rotating with the fundamental frequency. This paper extends that harmonic current control strategy to symmetrical machines of any phase number. The optimum frequencies for the SRFs and for the RCs in each plane, so that the total number of RCs is minimized, are assessed. Simulation results validate the theory.