Doubly-fed Induction Research Articles

Open‐circuit faults diagnosis in back‐to‐back converters of DF wind turbine

The open-circuit fault in converters is one of the wind turbine faults, which degrades the power quality and can even cause potential secondary faults in other components. So, an effective fault diagnostic technique for wind turbine converters is needed. This study presents a new open-circuit fault diagnostic approach for back-to-back converters of doubly fed (DF) wind turbines. The proposed fault diagnostic method has fault detection and fault localisation. The fault detection is based on the absolute normalised Park's vector approach; this method can detect multiple open-circuit switch faults and guarantee immunity to false alarms when the DF induction generator operates around the synchronous speed. For fault localisation, this approach applies the normalised current average values, which can be used to identify single and double open-circuit switch faults. The simulation and experimental results indicate that the diagnostic method can not only diagnose multiple open-circuit faults, but that false alarms due to transients can be avoided.

Wind Turbine Gear Fault Diagnosis Experiment Research Based on Sensorless Detection

In the wind turbine gear fault detection, using conventional vibration monitoring exists installation and maintenance inconvenience and numerous other shortcomings, this often leads to the wind turbine vibration detection techniques are not widely promoted. Based on sensorless wind turbine gear fault diagnosis experiment research in this paper, the use of general-purpose inverter and induction motor, built a double-fed asynchronous induction generator simulation test bed, and had a broken tooth gear fault simulation experiments. Through the generator stator current signal and the gear vibration signal contrast and analysis, preliminary validation of the proposed method is effective and feasible.

Effects of machine parameter values on dynamic response and stability regions of doubly-fed cascade induction machines

Doubly-fed cascade-connected induction machines (CCIMs), whether mounted in a single frame or otherwise, are capable of developing useful torque as brushless synchronous machines over a wide speed range. Such machines exhibit instability within certain regions of operation and may be insufficiently damped within others. This paper presents some of the loci of the dominant eigenvalues of the system equations plotted as functions of the values of various design parameters of the machines. It is shown that, by appropriate design, certain areas of instability may be reduced or removed and the response improved, but that it is not possible, by design changes alone, to remove all such unstable areas, nor can the response be improved in all areas simultaneously.

Stability and stabilisation of doubly-fed single-frame cascade induction machines

This paper presents a theoretical and experimental study of the dynamic performance of a doubly-fed single-frame cascade induction machine which can operate synchronously from rest over a wide speed range. The dynamic electromechanical-system equations are developed and theoretical performance boundaries for stable operation are found and compared with experimental results. The nature of its instability and an easily implemented feedback control which stabilises its operation are both described. It is shown that the machine can be operated as a stable variable-speed brushless machine with controllable dynamic response. Its mechanical construction is potentially only a little more complicated than that of a squirrel-cage induction machine.