Current sensor fault diagnosis and tolerant control for VSI-based induction motor drives

Fault-tolerant control is attracting more interests due to its capability of increasing the reliability of voltage source inverters (VSI). Fault detection, localization, and tolerant control schemes of current sensor are presented for high-fault-tolerance induction motor drives. Generally, three-phase current sensors are used in high-power inverters; nevertheless, failure of current sensors degrades the performance and reliability and even leads to the breakdown of the vector control system due to the fact that flux angle cannot be estimated correctly. The proposed scheme integrates three independent observers, taking a-phase current, b-phase current, and c-phase current as inputs, respectively. The observers are capable of online monitoring the state of current sensors under normal operation. Furthermore, after one or even two current sensors getting faulty, the observers can detect and localize the faults and switch the system to tolerant vector control mode even with only one healthy phase current sensor available. Hence, it is very attractive in some safety crucial applications. Stability and convergence of the observer are analytically derived and verified. A dSpace-based 1.1-kW induction motor variable-speed system is set up for the experiment, and experimental results demonstrate the validity of the proposed algorithm.