A new combined method to diagnosis loss of excitation from stable power swing in doubly fed induction generator

Loss of excitation (LOE) event is among the most frequent failures in electric generators. However, LOE detection studies heretofore were usually confined to synchronous generators. Common LOE detection methods are based on impedance trajectory what makes the system slow and also prone to misoperation in the case of stable power swing (SPS). This paper presents a new method to detect the LOE based on the measured variables from the DFIG terminal. In this combined method for LOE detecting, rate of change of terminal voltage and output reactive power and for SPS detecting, DC-link voltage of DFIG have been used. The performance of the proposed method has been confirmed by Matlab/Simulink simulations for various power capacities and operating conditions. The results prove the method's velocity, simplicity and security.