Automated Detection of Failures in Doubly-Fed Induction Generators for Wind Turbine Applications

Typically open, remote, and windy locations such as mountain tops or off-shore areas are favorable for efficient, continuous wind power generation. However, the hostile environment of these sites and limited accessibility for inspection, testing, and repair makes wind turbine components prone to failure. Therefore, a substantial increase has been seen in the demand for remote and automated condition monitoring of wind generators. In this paper, a new inverter-embedded off-line test method for automated testing of doubly-fed induction generators (DFIGs) is proposed for the detection and classification of defects in the 1) slip ring-brush contact, 2) rotor winding turn insulation, and 3) stator core inter-laminar insulation. The main idea of the proposed method is to utilize the rotor side converter for injecting test signals into the rotor circuit for asymmetry detection in the generator, whenever the DFIG is at standstill. The unique pattern in the equivalent impedance vs pulsating field angle is analyzed for identifying the asymmetry existence and fault type in DFIG at an incipient stage for optimal maintenance scheduling. Experimental results verify that the proposed method can provide a simple means of identifying DFIG faults with high sensitivity and reliability without additional hardware.