Detection of negative sequence components in diagnosing and tolerating open-gate fault for a voltage-source inverter in an induction motor drive

Power converter faults represent about 12% of electrical system faults. More than 31% of these converter faults are caused by the transistors in the converters. These transistor failures are classified into open-gate and short-gate faults. A fault diagnostic and tolerant control system is proposed in this study for an open-gate fault of a three-phase voltage-source inverter (VSI). The system under study is an induction motor fed by a VSI. The diagnostic technique uses a detection method of positive and negative sequence components, which requires only the measurement of motor currents. The diagnostic signals are derived from the negative sequence components of the motor currents. These signals are then compared using logic functions to trigger the tolerant control. In the case of an open-gate fault, the tolerant system converts the inverter topology from six switches to four switches where the faulty inverter leg is disconnected. The proposed control method was evaluated under steady-state and transient conditions through simulation and experiments. The results confirm an effective and reliable performance of the motor under an open-gate fault.