Abstract:
The Reduced Asymmetric Neutral Point Clamped converter topology for unipolar driven,
multiphase switched reluctance machines is proposed in this paper. This topology shares similarities
with the conventional NPC and Asymmetric-NPC topologies, however it is unique in that the
components for the capacitor string and outer semiconductor switches are shared among all the
phases for a reduced component count. Some switching state combinations are not possible during
commutation overlap between motor phases, resulting in minor torque transients during regenerative
braking. A custom modulation scheme is implemented with fixed frequency, phase-shifted carrier
waveforms that allow for automatic balancing of the neutral point voltage and interleaved switching
of the semiconductor switches. A simple torque observer control architecture is used with minor
adjustments for arbitrating torque contribution priorities between phases during handover.
