An Active Fault-Tolerant Control Strategy for Current Sensors Failure for Induction Motor Drives Using a Single Observer for Currents Estimation and Axes Transformation

Abstract

This paper proposes a fault-tolerant control technique against current sensors failure in direct torque controlled induction motors drives, based on a new modification of Luenberger observer for currents estimation and axes transformation for vector rotation. Several important aspects are covered in the proposed algorithm, such as the detection of sensors failure, the isolation of faulty sensors, and the reconfiguration of the control system by a correct estimation. A logic circuit ensures fault detection by analyzing the residual signal between the measured and estimated quantities, while a single observer performs the task of estimating the line currents. In addition, a decision logic circuit isolates the erroneous signal and simultaneously selects the appropriate estimated current signal. An axes transformation ensures rotation from (a,b) to (α,β), which keeps a low-cost control using only two current sensors. The proposed scheme is tested on MATLAB/Simulink environment and experimentally validated in a laboratory prototype mainly containing a dS1104 card and 4 kW induction motor.

Fault-Tolerant Control Based on Current Space Vectors against Total Sensor Failures

“…Type Misdiagnosis LO combining axes transformation [6] Yes No Yes Yes Estimated current combining TDO [7] Yes No Yes Yes Dual-torque model [9] Yes No Yes Yes SMO and SEPLL [13] Yes No Yes Yes Current space vector (proposed method) Yes Yes Yes No…”

“…Adaptive observers detect fault conditions and implement solutions to ensure that the system works even when sensor failures occur. The authors in [ 6 ] propose a sensor fault control strategy based on a Luenberger Observer (LO) combining axes transformation methods to detect the current sensor faults. When sensor failure is detected, the missing current information is replaced by the estimated current.…”

Current sensor fault-tolerant control based on modified Luenberger observers for safetycritical vector-controlled induction motor drives

“…In addition, the identification of the observer parameters is highly dependent on the drive operating point, which calls into question the smooth operation of the CS-FTC system under a post-fault situation under different operating conditions. Another model-based method of stator current estimation is the use of the classical Luenberger observer (LO) [37]- [39]. The authors in [37]- [39] presented the possibility of vector control without healthy CS, which means a current sensorless operation.…”

“…Another model-based method of stator current estimation is the use of the classical Luenberger observer (LO) [37]- [39]. The authors in [37]- [39] presented the possibility of vector control without healthy CS, which means a current sensorless operation. However, it should be mentioned that in these works the coefficient value in the LO gain matrix was selected close to 1, resulting in a very small gain factor of the LO and an insignificant influence of the stator current error feedback in the proposed LO.…”

“…The latter will be discussed in details in the main part of the paper. Moreover, it should be noted that the authors of [37]- [39] showed the simulation or experimental result only for CS faults occurring in steady states, for a few operating points, for constant speeds and for constant load torque. The effectiveness of stator current compensation was not shown in the situation when the CS fault occurs in transients or in a regenerating mode of the ASD.…”