A novel fault diagnosis scheme for FOC induction motor drives by using variable structure observers

In this paper, a new fault detection and isolation (FDI) strategy is proposed for FOC induction motor drives. Actuator faults are addressed, and specifically, open-circuit faults are considered in this study. The residual signals are synthesized by taking the resulting closed-loop dynamics when a FOC strategy is applied, i.e., the residuals are referenced to the synchronously reference frame (dq^e - coordinates), which are generated by using a bank of variable structure observers to obtain a robust FDI scheme. Thus, subsystems sensitive to a specific fault, but decoupled from other faults and disturbances are obtained in a natural way, and only two stator currents are required for fault isolation purposes. Residual evaluation is carried out in the stator reference frame (dq - coordinates) for the induction motor model, where the residual direction (angle) is employed to isolate a fault in each one of the 6 IGBT´s in a PWM voltage source inverter (VSI). In addition, the observer FDI scheme is combined with a fault re-configuration strategy in order to improve the reliability of the motor drive. Simulation results are illustrated for a three-phase 1 HP induction motor drive application that verify the ideas presented in this work.