Modeling and parameter identification of multiphase permanent magnet synchronous motors including saturation effects

An extended modeling of a multiphase machine is presented in this paper, under consideration of inductance harmonics. It is shown that an independent control of the phase currents in a multiphase machine can contribute to a higher efficiency by generating constant torque from harmonics in the flux-linkage due to injecting current harmonics into the stator windings. The extended modeling requires the knowledge of differential and absolute inductances and the permanent-magnet rotor flux. Therefore a novel measurement method is demonstrated, which is capable of identifying the inductances and flux-linkages for an arbitrary motor. The measurement method is compared with simulation results from a novel simulation method for a three-phase machine, checked for plausibility and is extended to a five-phase machine. The extended modeling and the knowledge of inductances with respect to the operating point and rotor position enables the design of an improved control system. Simulations of a five-phase motor without a star-point connection show that the torque ripple can be improved significantly, even if measuring errors and noise are considered. The performance and especially the dynamic of the drive system can be increased by adjusting the static gain of the current controller as a function of the operating point.