Fault-Tolerant Operation of Six-Phase Energy Conversion Systems With Parallel Machine-Side Converters

Abstract

Abstract The fault tolerance provided by multiphase machines is one of the most attractive features for industry applications where a high degree of reliability is required. Aiming to take advantage of such post-fault operating capability, some newly designed full-power energy conversion systems are selecting machines with more than three phases. Although the use of parallel converters is usual in high-power three-phase electrical drives, the fault tolerance of multiphase machines has been mainly considered with single supply from a multiphase converter. This work addresses the faulttolerant capability of six-phase energy conversion systems supplied with parallel converters, deriving the current references and control strategy that need to be utilized to maximize torque/power production. Experimental results show that it is possible to increase the post-fault rating of the system if some degree of imbalance in the current sharing between the two sets of three-phase windings is permitted.Index Terms Multiphase energy conversion systems, fault tolerance, parallel converters, field oriented control.

Impact of Postfault Flux Adaptation on Six-Phase Induction Motor Drives With Parallel Converters

“…Full-power topologies based on BTB converters have allowed the development of novel and more competitive energy conversion systems [27][28][29]. The decoupling of machine and grid sides through the dc-link provides better low-voltage ride through capability for grid-connected renewable systems, but also offers the possibility to use multiple three-phase windings on the machine-side [12,[27][28][29]. In this scenario the -phase machine is supplied from VSCs ( =3 ) that can be arranged in different manners.…”

“…twelve VSCs are used in [28]). In order to increase the current/power capability of the system and simultaneously enhance the fault-tolerant capability, it has been recently proposed the use of six-phase machines fed by four three-phase two-level voltage source converters (VSCs) [11][12]. Namely, each set of three-phase windings is connected to two three-phase VSCs operating in parallel [11][12] (Fig.…”

“…The machine employed in this work is an asymmetrical dual three-phase ( =2) induction machine with two isolated neutrals and distributed windings. This multiphase machine is a continuous system described by a set of differential equations obtained using the vector space decomposition (VSD) approach [33] and the power-invariant generalized Clarke transformation [12]:…”

“…In such scenario, operating in post-fault situation with pre-fault rated flux may result in low torque/power production and unnecessary losses [7]. Previous works have focused on the determination of the current reference waveforms without optimizing the flux settings in post-fault situation [6,[8][9][10][11][12], but it is advisable to use an efficient fault-tolerant control in order to minimize the drive derating and reduce the system losses.…”

“…This work uses an LMC approach for the post-fault flux optimization considering the specific topology of [12]. The optimum flux is obtained offline from a nonlinear optimization process, and the resulting optimal values are included in the fault-tolerant control scheme, bringing some benefits to the performance of the six-phase induction motor drive:…”