Diagnosis and Isolation of Air Gap Eccentricities in Closed-loop Controlled Doubly-Fed Induction Generators
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With the widespread use of doubly-fed induction generators (DFIG) in wind energy conversion systems, condition monitoring is being given importance. Non-intrusive techniques like motor current signature analysis (MCSA), which involves looking for specific frequency components in the current spectrum, are preferred over analysis of magnetic field, temperature, vibrations or acoustic noise which require additional sensors. The major difficulty in MCSA is isolation of the fault, as multiple faults produce similar signatures. Moreover, closed-loop control makes diagnostics more complicated due to inherent compensation by the controller. This thesis presents a method to diagnose static and dynamic air gap eccentricities in doubly-fed induction generators operated for closed-loop stator power control by using a modified control technique to enable detection and isolation of this fault from electrical unbalances in the stator and rotor and load torque oscillations that produce similar effects. The effectiveness of the proposed control is verified using simulations and preliminary experiments performed on a healthy machine.
Subjectdoubly-fed induction generator
air gap eccentricity
Meenakshi Sundaram, Vivek (2011). Diagnosis and Isolation of Air Gap Eccentricities in Closed-loop Controlled Doubly-Fed Induction Generators. Master's thesis, Texas A&M University. Available electronically from