Abstract
A novel single carrier pulse-width modulation
(PWM) for a new quad-inverter configuration for multilevel sixphase
asymmetrical open-winding ac converter is proposed in this
article. Modularity of the circuit consist of four standard twolevel
voltage source inverters (VSIs) with slight modifications, i.e.
one additional bi-direction switch (MOSFET/IGBT) in each
phase and a link to neutral with two capacitors to generate
increased output levels. Furthermore, original optimal single
carrier zero-shifted five-level modulation (SCZSFM) algorithm is
developed for each VSI to behave as equivalent to ones, a classical
five-level multilevel inverter. Moreover, feasibility of the topology
allows the VSIs to provide multilevel output voltage regardless of
the open-winding electrical machine configuration. Also, the
developed single carrier based PWM presents a straightforward
solution compared to space vector modulation approaches for
real time implementation. The total electric power shared among
the four dc buses and quadruples the power capability of VSIs.
Complete ac drive modules are developed numerically using
simulation in MATLAB/PLECS software. Observed set of results
are depicted in this paper under balanced conditions to show the
effectiveness of the proposal in good agreement with theoretical
background. This proposal suits the need of low-voltage/highcurrent
applications to ac tractions, electrical vehicles and ‘More-
Electric Aircraft’ propulsion systems.