International Conference on Renewable Energies and Power Quality (ICREPQ’17) Malaga (Spain), 4 th to 6 th April, 2017 Renewable Energy and Power Quality Journal (RE&PQJ) ISSN 2172-038 X, No.15 April 2017 Analysis of the Power Quality in Six-phase Induction Motor Drives with Arbitrary Winding Spatial Shifting J.J. Aciego 1 , M.J. Duran 1 , I. Gonzalez-Prieto 1 and F. Barrero 2 1 Department of Electrical Engineering E.T.S.I.I., University of Málaga e-mail: mjduran@uma.es 2 Department of Electronic Engineering University pf Seville e-mail: fbarrero@us.es Abstract. Multiphase machines are becoming an alternative to the three-phase standard in high power applications with high reliability requirements. Due to the capability to inherit off-the-shelf three-phase technology, the most popular choice at industry is the use of multiple three- phase windings. The disposition of the different sets of three- phase winding is however varied. In the specific case of six- phase machine, a spatial shifting among the three-phase windings of 0º, 30º and 60º has been used in dual-three-phase, asymmetrical and symmetrical machines, respectively. This spatial displacement has an impact on the power quality of the currents that supply the machine since the same magnetomotive force (MMF) in the airgap can be generated with different harmonic cancellation between phases. This work considers an arbitrary spatial shifting of the three- phase windings in order to explore its impact on the power quality from the machine-side. Extensive simulation results compared the different types of six-phase machine and some conclusions are extracted about the advantages of each choice. Key words. Six-phase drives, induction machines, power quality. 1. Introduction Since the re-emergence of multiphase machines and drives at the beginning of the 21th century, the efforts in the research community have been focused in the analysis of their advantages over the three-phase standard [1-5]. Apart from the well-known fault tolerant capability [6-10], some other innovative uses of the additional degrees of freedom have appeared in recent times [11-13]. Among the different types of multiphase machines, those with multiple three-phase windings have found lower entry barrier at industry because they recycle to a large extent the well-proved three-phase technology [14-17]. Six-phase machines are among this type of 3k-phase systems. Opposite to the case of five- or seven-phase machines where the construction is always symmetrical, in the case of six-phase machines there are different types of configurations according to the spatial shifting of the three-phase windings. When this angle is 0º the two sets of three-phase windings are in phase and the machine is termed double three-phase machine (D3). Nevertheless, the most popular configurations are the symmetrical type (S6) and the asymmetrical type with a spatial displacement of 30º (A6) [18]. In addition the three kind of machines can be configured either with single or two neutrals points [6]. The aim in all cases is to generate a rotating MMF in order to drive the machine smoothly, but the spatial shifting of the windings has an impact on the currents that are needed to create the revolving flux. Certain spatial angles may lead to current harmonic cancellation that results in an improve power quality for the same torque/flux in the machine. Although the THD of specific six-phase machines has been calculated in literature, a comparative analysis of the power quality for the D3, A6 and S6 machines at different operating conditions is still missing. This works aims to fill this gap and provide a comprehensive analysis of the current distortion as a function of the spatial angle between windings. The paper is structured so that the basics about six-phase machines are reviewed in section 2, the field oriented control and power quality indices are described in section 3, the simulation results are presented in section 4 and the main conclusions are lastly summarized. 2. Six-phase induction motor drives. Generalities. The six-phase induction motor drive under consideration consists of a six-phase machine supplied from two three- phase two-level voltage source converters (VSCs) that are connected to a single dc-link. The machine has two sets of three-phase windings and the spatial shifting between the set 1 and 2 of windings is termed  in what follows. When  = 0º, 30º and 60º the double three-phase (D3), asymmetrical six-phase (A6) and symmetrical six- phase (S6) machines are obtained, respectively. https://doi.org/10.24084/repqj15.359 479 RE&PQJ, Vol.1, No.15, April 2017