A multi-physical time- and frequency-domain fault detection and isolation (FDI) method for power-electronic converters (PECs) of wind turbines is presented in this paper, with focus on open-circuit faults and the doubly-fed induction generator (DFIG) drivetrain topology. In order to reduce the risk of false alarms, the proposed approach combines fault indicators based on time- and frequency-domain analysis of the electrical signals, as well as frequency-domain analysis of vibration signals. The effectiveness of the method is illustrated on test bench data recorded in different healthy and faulty operating modes.