Multiphase permanent-magnet synchronous machines (PMSMs) with nonsinusoidal back-electromotive force (back-EMF) offer high fault tolerance and torque density for electric vehicles. Most current-reference generation methods either minimize stator copper loss (SCL) or maximize achievable torque. Optimization of both goals is accomplished by full-torque-range minimum-loss (FRML) strategies, but so far just for sinusoidal back-EMF. Thus, FRML for nonsinusoidal back-EMF should be sought. Moreover, many methods are only suitable for healthy conditions or specific machines, harmonics, or open-phase-fault (OPF) scenarios. Additionally, the torque range may be extended by permitting torque ripple or (transiently) greater rms current, but this approach is not general nor FRML yet. This paper proposes online FRML current-reference generation for multiphase PMSMs with nonsinusoidal back-EMF: nonsinusoidal-back-EMF FRML (NSBE-FRML). When the torque reference is feasible, minimum SCL is attained while maximizing the achievable torque (i.e., FRML). For higher torque references, the instantaneous torque deviation is minimized, and the torque reference is saturated in consecutive samples limiting the torque ripple to a pre-specified threshold. Furthermore, the rms current is limited after transient overload by automatically decreasing the torque reference. The NSBE-FRML is suitable for any harmonics, healthy/OPF conditions, and multiphase PMSMs with negligible saliency ratio. Experiments are performed with a six-phase PMSM.

This paper proposes a current-reference generation method including current harmonic injection (CHI) for enhancing the torque capability of multiphase induction machines (IMs) with negligible space-harmonic effects, which is useful, e.g., during transient overload in electric vehicles. The admissible torque is increased because the harmonics reduce the phase-current peaks, so that the instantaneous peak-current constraint of the drive, usually associated with the converter ratings, is respected. The harmonics are injected in the so-called x-y subspaces of the IM, which do not produce torque, so that no torque ripple is introduced. The optimum harmonics are found online for each load, making it possible to minimize the stator copper loss (SCL) per torque in the entire torque range, ensuring full-range minimum loss (FRML). The method is suitable for healthy operation or open-phase faults, and for multiphase machines of any phase number and with either symmetrical or asymmetrical windings. Compared with FRML methods without CHI, higher torque is achieved. Although some techniques were available for increasing the torque capability by CHI, FRML was not attained, laborious offline optimization was needed, or they were only suitable for specific drives or for healthy conditions, unlike the proposal. Experimental results with a symmetrical six-phase IM are provided.

Multiphase drives exhibit remarkable advantages (e.g., fault tolerance) over three-phase ones. Six-phase drives are particularly attractive, given their moderate complexity and suitability for off-the-shelf three-phase converters. Regarding the stator winding arrangement, the symmetrical one offers superior postfault capabilities in most scenarios. On the other hand, resistance asymmetry in the stator phases or connections may arise due to different causes. The conventional full-range minimum-loss strategy (FRMLS) generates stator-current references under open-phase (infinite resistance) faults so that torque ripple is prevented while minimizing the losses for each torque ( $\boldsymbol{d}$ - $\boldsymbol{q}$ current) value and maximizing the torque range; however, this method is unsuitable for unequal resistances of finite value. This article proposes an FRMLS for setting the current references to reach these goals in symmetrical six-phase drives with any resistance asymmetry. The optimum references are found online depending on the resistances, without lookup tables. The phase currents are individually limited by an iterative algorithm, so that minimum stator copper loss (SCL) is achieved over the maximum admissible torque range. In this manner, unlike the conventional FRMLS, minimum SCL and maximum torque range are attained even for finite resistance imbalance. The currents in phases affected by high resistances are suitably reduced. Experimental results are provided.

Integrated On-Board Battery Chargers (IOBCs) have shown promise as an elegant charging solution for electric vehicles in recent literature. Although the three-phase charging technique of IOBCs has extensively been discussed in the literature, single-phase charging is still a challenging research topic. The Predictive Current Control (PCC) approach has shown many benefits, including a straightforward algorithm, simple implementation, comparatively quick response, and appropriate performance, when compared to conventional control techniques. This paper investigates the impact of single-phase charging of a six-phase-based IOBC system with different winding configurations using PCC, which, up to the best authors’ knowledge, has not been conceived thus far. Under single-phase charging, the zero-sequence current component is utilized to ensure zero torque production during charging mode. Since the impedance of the zero subspace is highly affected by the employed winding design, the performance of PCC with different winding layouts of either induction machine (IM) or permanent magnet synchronous machine (PMSM) is investigated and compared. The proposed method is experimentally validated using a 1.1kW six-phase IM and a 2 kW 12-slot/10-pole PMSM. Finite Element analysis is also carried out to investigate the effect of single-phase charging mode on the induced radial forces and vibration level when PM machine is employed.

Recently, finite-control-set model predictive control (FCS-MPC) has become ubiquitous in multiphase drives (MPDs), whose decomposed subspaces should be regulated through the control actions of a zero xy -voltage projection to alleviate disruptive xy currents. Among multiphase traction inverters, the lower switch count of nine-switch inverters (NSIs) has made them a popular choice for six-phase induction motor (6PIM) drives. However, when the structure of the inverter changes, such as in the case of a NSI, it becomes necessary to redevelop finite control actions in order to attain the same objectives. Hence, this paper introduces a predictive current control (PCC) for NSI-fed 6PIM drives with a new control set selected to nullify xy voltage and maximize αβ voltage as much as possible for six-phase winding configurations. Furthermore, the post-fault operation of NSI-fed 6PIM drives is also introduced under a complete open converter leg (OCL), where two phases, sharing the same faulty leg, are disconnected. The concept of phase transposition under OCL is found effective to achieve the same torque operating range of the conventional voltage source inverter (VSI)-fed 6PIM drive at the expense of additional hardware for winding reconfiguration. Experiments on 6PIMs with different winding arrangements showcase the significance of the proposal.

Electric propulsion based on six-phase machines in marine propulsion and automotive traction applications are undergoing rapid development due to its high capacity, fault tolerance, reduced size, and reduced torque pulsations. Among different control techniques of six-phase machines, direct controllers, such as finite control set model predictive control (FCS-MPC), have extensively been studied in recent literature. One of the main problems of this controller type is the relatively poor current quality due to circulating xy current components. This problem has been tackled in literature through enhanced control techniques and/or winding design. Following both approaches, this paper extends a previous study to deeply investigate the effect of winding design on the performance of the model predictive control applied to a six-phase induction machine (SPIM). Three six-phase winding layouts have been compared, namely, dual-three phase (D3P), asymmetrical (A6P) and symmetrical (S6P) configurations. The main objective of this study is to investigate the effect of winding chording when standard three-phase stator frames are employed on the current quality of different winding configurations under classical predictive current control (PCC). A 1.5Hp prototype system has been used for this experimental comparative study.