Modeling and Simulation of Multiphase Machines in the Matlab/Simulink Environment

Multiphase machines are AC machines characterized by a stator winding composed of a generic number n of phases. In today’s electric drive and power generation technology, multiphase machines play an important role for the benefits they bring compared to traditional three-phase ones (Levi, 2008; Levi et al., 2007). Such benefits have been widely highlighted by existing literature (Levi et al., 2007) and are mainly related to: an increased fault tolerance; higher power ratings achieved through power segmentation; enhanced performance in terms of efficiency and torque ripple. The use of multiphase machines is spreading both in small-power safety-critical applications as well as in very high-power industrial drives (Tessarolo et al., 2010), in electric-propulsion drives (Castellan et al., 2007) and power generation systems (Sulligoi et al., 2010). Regardless of whether they are used as motors or generators, multiphase electrical machines are almost always connected to power electronics systems (inverters for motors, rectifiers for generators), which interface them to the electric grid (Sulligoi et al., 2010; Castellan et al. 2008). Therefore, if the dynamic behaviour of a multiphase machine is to be predicted through simulations in the design and development stage, it is essential to do this by means of system-level simulations, where not only the electric machine is included, but also the power electronics and control systems that interact with it. Such a system-level simulation approach makes it difficult to use Finite-Element (FE) methods due to the complexity of the domain to be modelled and to the well-known computational heaviness of time-stepping FE simulations. Conversely, lumped-parameter models, to be implemented in the Matlab/Simulink environment, may provide designers with a powerful mean of analysis and investigation, provided that all the system components to be studied are modelled with an adequate level of accuracy and completeness. As concerns power electronics systems usually interfaced to multiphase machines, whether operating as motors or generators, the Matlab/Simulink environment offers wide and complete libraries where the designer can find reliable pre-defined blocks (for electronic switches, snubbers, diodes, etc.) to be used in building the application-related apparatus models. The same pertains to control and regulation blocks, which can be built up directly based on their transfer functions and logics. A possible criticality can be encountered when it comes to build the multiphase machine model. In fact, no predefined blocks are presently available in the Matlab/Simulink environment for this purpose. On the other side, building a dedicated user-defined machine