Recent advances in power electronic converter control for multiphase drive systems

Multiphase variable speed drives are nowadays serious contenders for various applications. On the other hand, the multilevel (predominantly three-level) voltage source inverters (VSIs) and matrix ac-ac converters have become industrially accepted technologies in three-phase systems. In recent times, attempts have commenced to integrate multilevel VSIs and matrix converters with the multiphase drive technology. This paper provides a review of recent advances in this area. A general configuration of an n-phase to m-phase matrix converter is considered and the differences with regard to the control of standard three-phase to three-phase matrix converters are underlined. Next, two different topologies of the multiphase multilevel supply are discussed and the emphasis is placed on appropriate pulse width modulation (PWM) techniques that can be used in conjunction with the given converter structure. The first topology utilises multilevel (three-level) VSI and the machine's stator multiphase winding is star-connected. In the second topology the winding is open-ended and each side of the winding is connected to a two-level VSI. Carrier-based and space vector based PWM strategies are considered and the performance is illustrated using experimental results.

I. Introduction

THE use of power electronic converters has enabled the number of phases to be considered as an additional design parameter. Multiphase (more than three phases) machines have some advantages over three-phase ones: improved fault tolerance, reduced torque pulsations, lower per phase power handling requirements, enhanced modularity and improved noise characteristics [1]. In spite their notable advantages, wide availability of three-phase machines restricts the application of multiphase ones to specialised applications, for which three-phase drives are either not readily available or do not satisfy the specification.