Faults diagnosis and control in a low-cost fault-tolerant induction motor drive system

•The analysis of the inverter voltages under the drive faulty mode was carried out.•The open-switch fault diagnostic technique was experimentally proved.•The speed sensor fault diagnosis was achieved by model reference adaptive system.•The post-fault drive operation was provided under the unbalanced DC-link voltages.•Both diagnostic techniques were based on a software solution.

The paper deals with faults diagnosis and control methods for a fault-tolerant direct field-oriented controlled by Space Vector Modulation (SVM) two-level voltage-inverter-fed induction motor drive. In order to maintain an uninterrupted motor drive operation even under its faulty condition, two diagnostic algorithms as well as post-fault control techniques are developed. According to the first diagnostic system, that is related to single open-circuit faults in two-level voltage inverter, a failure diagnosis is performed by monitoring a time presence of a reference inverter voltage vector in particular sectors of the α-β coordinate system. After the fault detection, to maintain a high-quality drive performance, a switch-redundant inverter scheme is utilized. In case of the second diagnostic system, for the speed sensor failure detection, a motor speed estimator, that is based on a model reference adaptive system, is utilized. This algorithm is used for the post-fault motor drive operation as well. Both fault monitoring methods are based on a software solution, therefore they do not generate additional implementation costs.To validate the described fault-tolerant control scheme, chosen simulation tests, which were carried out in MATLAB/Simulink, are presented. Additionally, in case of the transistor failure diagnosis, experimental tests were carried out.