Five-leg inverter PWM technique for reduced switch count two

University of Belgrade
School of Electrical Engineering
Five-leg inverter PWM technique for reduced switch count
two-motor constant power applications
M. Jones, S.N. Vukosavic, D. Dujic, E. Levi, P. Wright
IET ELECTRIC POWER APPLICATIONS, Vol. 2, No. 5, pp. 275-287, Sep, 2008
Industrial applications often require a number of variable speed electric drives. In the majority of
cases, these multi-motor drive systems require independent control of individual motors. Over the
past decade, research efforts have been made to reduce the number of power electronic devices
required in multi-motor drive systems in order to reduce the overall complexity and hence cost of
the drive. It has been shown recently that it is possible to independently control two three-phase
induction machines using a five-leg voltage source inverter (VSI) as the supply, with one inverter
leg being common to both machines. The existing pulse-width modulation (PWM) methods for this
supply topology either limit the amount of DC bus voltage available to each machine or lead to
uneven and increased switching frequency across five legs of the VSI. A new PWM method that
effectively utilises the standard three-phase modulators in conjunction with appropriate
modifications to generate modulation signals for all five legs of the VSI is presented. It enables an
arbitrary distribution of the available DC bus voltage between the two machines. The considered
supply topology, when utilised in conjunction with the developed PWM technique, is well suited to
constant power applications such as centre-driven winders. Verification of the developed
modulation method and its applicabili
induction motor drives, switching convertors, variable speed drives, machine control, PWM