The advent of superior power semiconductor devices and converter topologies
has renewed interest in ac drive systems. Although considerable research efforts have
gone into improving power electronic converter devices and topologies, very little has
been reported on the overall performance optimization of induction machine drive
systems. The report of the research work presented in this thesis is an endeavor in that
direction where enhancement in the system performance is achieved through optimization
of the overall system.
The Brushless Doubly-Fed Machine (BDFM) can reduce the drive system cost
and also retain the robustness of a cage rotor induction machine. Proof-of-concept
prototypes have been used in the laboratory for investigation of BDFM operating modes.
These prototypes, though providing insight into the operation of the BDFM were far
from optimum. Thus, design procedures for optimizing the machine design needed to
be developed. The optimized machine can then be integrated into an optimized system
by using a realistic, application-dependent converter selection scheme.
As mentioned earlier, recent developments in power semiconductor and converter
technologies have led to a proliferation of circuit topologies and their modifications with
sometimes contradictory performance claims. Consequently, for the non-specialist
application engineer designing the BDFM system, this can often lead to uncertainty
which potentially can result in non-optimum converter selection. An extensive and
comprehensive literature review of presently available converter topologies is presented
with a detailed comparative evaluation. Converter selection criteria, as applied to the
BDFM, are also discussed in detail. These provide sufficient guidelines for selecting
an optimum technology for a given application.
Stator design optimization, as discussed in this thesis uses a design parameter
search algorithm and the BDFM steady state d-q model. Projected performance of an
optimized stator BDFM design is compared with simulation results of present and past
laboratory machines. An optimized design with good overall performance is presented.
It is also shown that this optimization scheme lowers the power rating requirement of
the converter.
Thus, for a given rotor structure and its parameters, the converter comparison and
selection scheme for BDFM applications along with the optimization scheme for the
stator design can lead to an overall optimized system with stator losses, reduced power
converter rating and thus lower the initial investment and operational costs
