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

Abstract

Multiphase drives offer enhanced fault-tolerant capabilities compared with conventional three-phase ones. Their phase redundancy makes them able to continue running in the event of faults (e.g., open/short-circuits) in certain phases. Moreover, their greater number of degrees of freedom permits improving diagnosis and performance, not only under faults affecting individual phases, but also under those affecting the machine/drive as a whole. That is the case of failures in the dc link, resolver/encoder, control unit, cooling system, etc. Accordingly, multiphase drives are becoming remarkable contenders for applications where high reliability is required, such as electric vehicles and standalone/off-shore generation. Actually, the literature on the subject has grown exponentially in recent years. Various review papers have been published, but none of them currently cover the state-of-the-art in a comprehensive and up-to-date fashion. This two-part paper presents an overview concerning fault tolerance in multiphase drives. Hundreds of citations are classified and critically discussed. Although the emphasis is put on fault tolerance, fault detection/diagnosis is also considered to some extent, because of its importance in fault-tolerant drives. The most important recent advances, emerging trends and open challenges are also identified. Part 1 provides a comprehensive survey considering numerous kinds of faults, whereas Part 2 is focused on phase/switch open-circuit failures.

DC-Signal Injection for Stator-Resistance Estimation in Symmetrical Six-Phase Induction Motors Under Open-Phase Fault

“…In a symmetrical six-phase motor, the stator winding can be considered as two three-phase sets shifted by γ = π/3 [4], [8]. Based on the VSD, a variable u (voltage v, current i or flux linkage λ) of the machine phases can be expressed in six axes that are orthogonal during healthy operation [4], [27]:…”

“…The electromechanical conversion through the main space harmonic only takes place in the α-β plane. The third-order space harmonic is associated with the 0 − axis [4], [27], [29]. In absence of asymmetries, just even harmonics of the winding function are mapped into the x-y and 0 + subspaces, but these components are normally negligible in induction machines, especially if the windings are not chorded [29].…”

“…Some of the typical applications where this property is exploited are those with safety-critical requirements such as aerospace systems [1], [2], as well as those where unscheduled maintenance is highly undesired and difficult such as wind [1] and marine-current turbines [3]. Specifically, the operation of multiphase drives under open-phase faults (OPFs) has received considerable attention [1], [4], [5]. Although a short-circuit fault may also occur, it is commonly transformed into an OPF by applying a remedial action [4]- [8].…”

“…Specifically, the operation of multiphase drives under open-phase faults (OPFs) has received considerable attention [1], [4], [5]. Although a short-circuit fault may also occur, it is commonly transformed into an OPF by applying a remedial action [4]- [8]. Compared with other multiphase machines, six-phase ones are especially convenient due to their modular three-phase structure, which benefits from off-theshelf three-phase solutions [1], [4], [9].…”

“…Although a short-circuit fault may also occur, it is commonly transformed into an OPF by applying a remedial action [4]- [8]. Compared with other multiphase machines, six-phase ones are especially convenient due to their modular three-phase structure, which benefits from off-theshelf three-phase solutions [1], [4], [9]. Among the kinds of six-phase stator arrangements, symmetrical layout offers better postfault performance [8], [10], as well as simpler control and smaller current distortion [11].…”