Stator Inter-Turn Fault Detection of Doubly-Fed Induction Generators Using Rotor Current and Search Coil Voltage Signature Analysis

A novel technique for detecting stator inter-turn faults in a doubly fed induction generator (DFIG) is proposed by analyzing its rotor current and search coil voltage. So far, fault diagnostic techniques proposed for stator inter-turn fault detection in DFIG are based on analysis of stator current or vibration of generator. Results from these methods are ambiguous because either they fail to account for condition when DFIG is operating under unbalanced load or these methods are based on experimental results alone. Our recent observations suggested that harmonics induced in the rotor circuit are very promising in detecting stator inter-turn faults in DFIGs. Hence, in this study, an in-depth investigation was conducted to determine the origin of various harmonic components in the rotor currents and their feasibility to detect inter-turn stator faults unambiguously. Detailed analysis is presented that explains the induction of stator inter-turn fault related harmonics in the rotor circuit. The theory is verified with simulation and extensive experimental results.

I. Introduction

Research in the area of fault-diagnosis and condition monitoring of wind generators has generated keen interest as the clamor for renewable energy [1]–[5] becomes louder and clearer; thanks to the burgeoning oil prices. Wind generators used for high power range (660KW to 2MW) are mainly wound rotor synchronous generators and Doubly-Fed Induction Generators (DFIG) [6]. Low voltage (690V) DFIG are widely used in this power range and relate to major market share [6]. The need for an accurate condition monitoring and fault detection method is highly in demand to reduce the operation and maintenance cost of wind energy systems. In particular with plan of offshore installations, which makes it more inaccessible, it is vital to increase the reliability and simultaneously increase the service interval [1].