No abstract

This paper proposes an algorithm for fault tolerance of three-phase, inverter-fed, speed-sensor-less control of a three-phase induction motor drive system. The fault tolerance of the inverter when one switch is open or one leg of six-switch inverter is lost is considered. The control of the drive system is based on indirect rotor field-oriented control theory. Also, the speed estimator is based on model reference adaptive system (using stator current and rotor flux as state variables for estimating the speed). The fault-tolerant algorithm is able to adaptively change over from a six-switch inverter to a four-switch inverter topology when a fault occurs; also, it makes a smooth transition of the motor speed, torque, and current when changing over from a faulty condition to a new healthy status, which is four-switch three-phase inverter (FSTPI) topology; thus, the six-switch three-phase inverter (SSTPI) topology (pre-fault status) is almost retained for the medium-power range of induction motor applications. The proposed algorithm is simulated by using the MATLAB/SIMULINK package. Also, the proposed control system is tested experimentally using a digital signal processor (DSP1104). The obtained results from the simulation model and experimental system demonstrate the performance enhancement and good validity of the fault-tolerance control for the speed-sensor-less induction motor drive system. IntorductionThree-phase induction motors have been the workhorse for industrial and manufacturing processes. A high harmonic current content causes torque ripple on the load when variablespeed induction motor drives operate with an open-circuit phase fault. These effects result from the unbalanced nature of the faulted machine. Different diagnosis techniques for transistor opencircuit faults have been developed and analyzed [1][2][3]. A detection method that identifies the power switch in which the fault has occurred based on measurement of motor voltages is presented in Ref. [4]. It also investigates fault compensation via topologies that are able to maintain the system operation for a period. In Ref.[5], a modeling method for induction motor drives is proposed that includes machine saturation and space harmonics effects as well as inverter nonlinearity, which does not require significant computation times. Also, a descriptionon how the model was used to develop a fault ride-through control strategy for a voltage-fed vector-controlled drive is given. In Ref.[6], the effect of measurement failure error due to faulty sensors and power inverter malfunctions was investigated. Both software and hardware redundancies have been investigated during the occurrence of a failure. Software redundancy has been evaluated in the case of a speedsensor failure. In Ref.[7], a fault occurring when open-circuit winding faults appear on the induction motor drive is considered. A feed-forward compensation term is introduced into the a Correspondence to: Z. M. El-Barbary. E-mail: z_elbarbary@yahoo.com * Department of Electrical Engineering, Kafre...

No abstract