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Dynamic modeling, simulation and stability analysis of brushless doubly-fed machines

A brushless doubly-fed machine (BDFM) is a single-frame, self-cascaded
induction machine capable of operating in both the induction
and the synchronous modes. This thesis presents some important
advances concerning dynamic modeling, simulation and analysis of the
Initially, a two-axis model and its associated parameters are developed
and calculated. The development of the model is not subject to the
commonly made assumption that the BDFM is electromagnetically
equivalent to two wound rotor induction motors in cascade connection.
Instead, the model is derived from a rigorous mathematical
transformation of a detailed machine design model. This novel approach
emphasizes not only the analysis of the machine performance in both
dynamic and steady state conditions, but also the design aspects of the
machine by correlating the machine performance with the actual machine
parameters computed from machine geometry.
Using the two-axis model, simulation of the machine dynamic
performance in all conceivable modes of operation is carried out and the
results are compared with test data available with good correlation.
Steady state models, under certain assumptions, are derived based on
the two-axis model. For the synchronous mode, motoring operation, a
solution technique is developed and utilized to perform steady state
performance analysis of the BDFM.
Finally, stability analysis of the machine is examined using the
linearized version of the two-axis model. Since the linearized two-axis
model of the BDFM is time-varying, commonly used eigenvalue analysis
techniques cannot be employed directly to investigate the stability
characteristics of the machine. However, since the system matrix is a
periodic function of time, the theory of Floquet is introduced so that the
original linear time-varying system of equations are transformed into a
set of equivalent system of equations with a constant system matrix.
Eigenvalue analysis is then applied to analyze the stability of the BDFM
system over a wide speed range. Predictions by the eigenvalue analysis
are correlated with test data.
The study concludes that the proposed two-axis model is a good
representation of the BDFM for dynamics, steady state, stability
investigations of the machine and further development of control
strategies for the proposed BDFM system for adjustable speed drive and
variable speed generation applications. / Graduation date: 1991
Date02 May 1991
CreatorsLi, Ruqi
ContributorsWallace, Alan K.
Source SetsOregon State University
Detected LanguageEnglish

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