Multiphase Traction Inverters: State-of-the-Art Review and Future Trends

Abstract

Multiphase inverters (MPIs) continue to increase in popularity owing to their compelling features that include enhanced fault-tolerance capability, improved per-phase power handling, and reduced dc-bus capacitor sizing. This article presents a comprehensive review on MPIs and their application in transportation electrification. More specifically, voltage source inverter (VSI) and nine-switch inverter (NSI) are the two MPI topologies reviewed herein, due to their popularity and potential for employment as traction inverters. The state-of-the-art review covers modeling and control techniques, dc-capacitor sizing, modulation strategies, inverter losses, and cost. Promising future trends of MPIs in terms of topologies, switching devices and integrated design are also investigated.INDEX TERMS Automotive, dc-ac converters, electric vehicles, inverters, power electronics, pulse width modulated power converters, transportation electrification, vector control.

General Online Current-Harmonic Generation for Increased Torque Capability With Minimum Stator Copper Loss in Fault-Tolerant Multiphase Induction Motor Drives

“…The VSD decomposes the machine stator electrical model into subspaces that, in absence of OPFs and non-idealities, are orthogonal to each other [24], [26]. When space harmonics are disregarded, the electromechanical conversion (torque and flux) is only due to the currents in the main VSD subspace, known as α 1 -β 1 or simply α-β plane.…”

“…The currents in the secondary subspaces (x 2 -y 2 , x 3 -y 3 , etc. 2 ) produce just SCL [24], [26], while their impact on the torque [24] and on the rotor and core loss [38] can be neglected. Using this notation, the so-called zero sequences are included in the x-y subspaces [37], [40], [44], [63].…”

“…For instance, they permit reduced current ratings for given power and voltage ratings [6], [21], [23]. Furthermore, they offer superior fault tolerance thanks to their additional stator-current degrees of freedom, associated with secondary subspaces (x-y or zero sequences) of the machine VSD model [21], [24]- [27]. These benefits can be obtained by stator windings arranged in various manners, with the most common being symmetrical (2π/n spatial displacement between phases) and asymmetrical (three-phase sets displaced by π/n, with n being a multiple of three) [26], [28], [29].…”

A Comprehensive Survey on Fault Tolerance in Multiphase AC Drives, Part 1: General Overview Considering Multiple Fault Types

“…Another characteristic that has traditionally been valued is the smaller amount of torque ripple [2]. Furthermore, using more phases makes it possible to reduce the dc-link capacitor volume [3]. Nonetheless, nowadays, the majority of the most appreciated benefits of multiphase machines stem from their extra degrees of freedom (DOFs) with respect to the three-phase alternatives [2,4].…”

“…A few of them tackle the subject of multiphase drives with very ample scope [1,2,[29][30][31][32][33], providing comprehensive summaries of a wide range of aspects related to these systems: advantages, applications, modeling, harmonic mapping, control methods, fault tolerance, space-vector (SV) pulsewidth modulation (PWM), multimotor drives, etc. On the other hand, some of the existing survey papers about multiphase drives are focused on specific aspects, such as six-phase induction machines (IMs) with asymmetrical winding spatial arrangement (WSA) [42], SV PWM for five and six phases [44], integrated on-board battery chargers for electric automotive vehicles [16], traction motor drives [3,48], aircraft applications [52,53], electrical transportation (in general) [49][50][51], drives based on multiple three-phase modules [43], advanced converter topologies (matrix, multilevel, open-end windings) [4,46,52], wind-energy [54], fault tolerance and wind/stand-alone generation [24], fault-tolerant multilevel drives [47], power sharing between multiple three-phase winding sets [37], exploitation of additional DOFs [4,35,36], machine design [34,55], healthy-drive control [34], direct torque control (DTC) [38], model predictive control (MPC) [39][40][41], or fault-tolerant control for five-phase machines using reduced-order transformation matrices [45].…”