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Abstract
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In view of its special features, the brushless doubly
fed induction generator (BDFIG) shows high potentials to be
employed as a variable-speed drive or wind generator. However,
the machine suffers from low efficiency and power factor and
also high level of noise and vibration due to spatial harmonics.
These harmonics arise mainly from rotor winding configuration,
slotting effects, and saturation. In this paper, analytical equations
are derived for spatial harmonics and their effects on leakage flux,
additional loss, noise, and vibration. Using the derived equations
and an electromagnetic-thermal model, a simple design procedure
is presented, while the design variables are selected based on
sensitivity analyses. A multiobjective optimization method using
an imperialist competitive algorithm as the solver is established
to maximize efficiency, power factor, and power-to-weight ratio,
as well as to reduce rotor spatial harmonic distortion and voltage
regulation simultaneously. Several constraints on dimensions,
magnetic flux densities, temperatures, vibration level, and converter
voltage and rating are imposed to ensure feasibility of the
designed machine. The results show a significant improvement
in the objective function. Finally, the analytical results of the
optimized structure are validated using finite-element method and
are compared to the experimental results of the D180 frame size
prototype BDFIG.
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