An Integrated Axial-Flux Magnetic-Geared Double-Rotor Machine Using Harmonic Current Injection Method for HEVs

Enjoying the merits of compact structure, less noise and high specific power, axial-flux magnetic-geared double-rotor machines (AMGDRMs) have been proved a promising candidate for the electrical-continuously variable transmission (e-CVT) in hybrid electric vehicles (HEVs). However, an additional permanent magnet synchronous machine (PMSM) is needed for torque compensation in the e-CVT system. In this paper, a novel integrated scheme which can realize the functional integration of a PMSM is proposed to improve compactness further. By carefully designing pole-pair number combination, the PMSM torque would be produced by the interaction between the armature fifth-harmonic and PM fundamental magnetic fields when injecting harmonic current. However, such combination would cause significant principled torque ripple. Hence, a suppression method based on the phase-shift structure is proposed to cancel the torque fluctuation out, thus the proposed machine can enable both the MGDRM and PMSM operations without significant torque ripple. Compared with existing dual-winding integrated schemes, an integrated winding configuration where only one set of conventional integral-slot winding is placed into one stator is adopted in the proposed machine, simplifying the manufacture process. First, the machine structure and operation principle are investigated. Second, the torque ripple suppression mechanism is analyzed. Finally, 3-D FEA simulations are carried out to validate the proposed machine and evaluate overall performances.