Dynamic Modelling of Multiphase Machines Based on the VSD Transformation

• Published in: SAE International journal of advances and current practices in mobility 2021-04, Vol.3 (4), p.1620-1631, Article 2021-01-0774
• Main Authors: Taylor, Joshua, Valencia Garcia, Diego Fernando, Taha, Wesam, Mohamadian, Mustafa, Luedtke, Daniel, Nahid-Mobarakeh, Babak, Bilgin, Berker, Emadi, Ali
• Format: Article
• Language: English
• ISSN: 2641-9645; 2641-9645
• DOI: 10.4271/2021-01-0774

Multiphase machines continue to increase in popularity in high power applications due to their proven benefits compared to their three-phase counterparts. However, with the increased phase number and, therefore, the increased number of degrees of freedom, the complexity of both modelling and control strategies significantly increases. This paper proposes a dynamic modelling method for six-phase interior permanent magnet machines using the vector space decomposition transformation, which can be extended to machines with any number of phases. The proposed technique considers the nonlinear characteristics of the machine, such as spatial harmonics, magnetic saturation, and cross-coupling, which are based on flux linkage look-up tables from finite element analysis. The main contribution of this paper is the consideration of the effect of harmonic components and asymmetries within the machine windings on losses. These effects are mapped into a subspace orthogonal to the conventional dq subspace, which calls for additional transformations based on the field-oriented control structure. The proposed modelling strategy also allows for the inclusion of the high-frequency components generated from the switching instances from an inverter. The accuracy of the proposed model is validated through a comparison of the finite element analysis and Simulink torque waveforms and a comparison of Simulink and experimental current waveforms at low load operating conditions.