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This paper proposes a new approach for the detection of stator faults in inverter-fed induction motor under closed-loop control. These faults, generally, start with interturn short circuit and can evolve to phase-to-phase or phase-to-ground faults, leading to stator currents unbalance. In the considered application, the stator windings are supplied by a static converter for the control of the speed and the rotor flux of the motor. The unbalance fault has been artificially created through additional resistance in series with one phase of the stator windings. The proposed diagnosis approach is based on the computation of the symmetrical components of the stator currents. The supply fundamental frequency and the three-phase phasors are estimated based on the maximum likelihood estimator. Then, the generalized likelihood ratio test is applied for unbalance fault detection. Simulation and experimental results on a 1.5-kW induction motor illustrate the effectiveness of the proposed approach, leading to an effective diagnosis procedure for stator faults in inverter-fed induction motor under steady state and closed-loop operation. [ABSTRACT FROM AUTHOR]

This paper investigates a new fault detection method for induction machines diagnosis. The proposed detection method is based on hypothesis testing. The decision is made between two hypotheses: the machine is healthy and the machine is faulty. The generalized likelihood ratio test is used to address this issue with unknown signal and noise parameters. To implement this detector, the unknown parameters are replaced by their estimates. Specifically, four estimations are required, which are model order, frequency, phase, and amplitude estimations. The model order is obtained using the Bayesian information criterion. Total least-squares estimation of signal parameters via rotational invariance techniques is used to estimate frequencies. Then, phases and amplitudes are obtained using the least-squares estimator. The proposed approach performance is assessed using simulation data by plotting the receiver operating characteristic curves. Two faults are considered: bearing and broken rotor bar faults. Experimental tests clearly show the effectiveness of the proposed detector. [ABSTRACT FROM PUBLISHER]

The main objective of this paper is to detect faults in induction machines using a condition monitoring architecture based on stator current measurements. Two types of fault are considered: bearing and broken rotor bars faults. The proposed architecture is based on high-resolution spectral analysis techniques also known as subspace techniques. These frequency estimation techniques allow to separate frequency components including frequencies close to the fundamental one. These frequencies correspond to fault sensitive frequencies. Once frequencies are estimated, their corresponding amplitudes are obtained by using the least squares estimator. Then, a fault severity criterion is derived from the amplitude estimates. The proposed methods were tested using experimental stator current signals issued from two induction motors with the considered faults. The experimental results show that the proposed architecture has the ability to efficiently and cost-effectively detect faults and identify their severity. [ABSTRACT FROM PUBLISHER]

This paper studies the grid-synchronization problem of three-phase system. Second-order adaptive filters are a popular tool for grid-synchronization. In this context, reduced-order generalized integrator has attracted some attention in recent time. However, existing implementations cannot control directly the closed-loop poles (real and imaginary) of reduced-order generalized integrator. To overcome this limitation, this paper proposes a novel reduced-order generalized integrator structure. To make the proposed technique frequency adaptive, an open-loop frequency estimation technique is also used. Comparative performance analysis are provided over two other advanced and recently proposed techniques. Results demonstrate the suitability and effectiveness of the proposed technique. [ABSTRACT FROM AUTHOR]

• Studied the grid synchronization problem for single and three-phase systems. • Novel gain normalized adaptive observer is proposed. • Proposed observer can quickly estimate the phase and frequency. • Detecting the sequences of unbalanced grid is also possible. • Experimental results validated theoretical findings. This paper proposes the estimation of parameters and symmetrical components of unbalanced grid using adaptive observer framework. Recent adaptive observers proposed in the literature doesn't employ any gain normalization in their frequency estimation loop. This can be problematic in the presence of large voltage dip. This paper proposes a solution to overcome this limitation using a novel gain normalized - frequency-locked loop (GN-FLL). Technical details of GN-FLL, stability analysis and tuning are provided in this paper. Comparative experimental results with adaptive Luenberger observer, second-order generalized integrator - phase-locked loop (SOGI-PLL) and enhanced PLL (EPLL) are provided to demonstrate the effectiveness the proposed technique in the single-phase case. Comparative experimental results with double SOGI-FLL (DSOGI-FLL) and adaptive notch filter (ANF) are provided to demonstrate the effectiveness the proposed technique in the three-phase case. [ABSTRACT FROM AUTHOR]

• Studied the grid synchronization problem for single-phase system. • Hybrid grid synchronization technique has been proposed. • Proposed hybrid technique is harmonic robust and provides rapid detection. • Experimental results validated theoretical findings. Harmonic robust grid synchronization technique has been studied in this paper. This implies the estimation of phase and frequency of single-phase grid voltage signal. Motivated by recent developments in linear harmonic oscillator based technique, this paper first propose an adaptive observer based solution that has the potential to speed-up the dynamic performance with respect to other generalized integrator type techniques. However, this may decrease the robustness of the proposed technique in the presence of harmonics and or DC bias. To overcome this issue, a hybrid estimator is proposed. This estimator is comprised of a band-pass type pre-loop filter and the initially proposed adaptive observer. Local stability and tuning of the adaptive observer are provided for the nominal case. In the presence of harmonics, small-signal modeling and tuning of the hybrid estimator are provided as well. Finally, hardware-in-the-loop (HIL) comparative experimental results are provided with similar other recently proposed techniques in the literature. Experimental results demonstrate the suitability of the proposed techniques. [ABSTRACT FROM AUTHOR]