Slim Tnani

Diagnosis by parameter estimation of stator and rotor faults occurring in induction machines

In this paper, the authors give a new model of squirrel-cage induction motors under stator and rotor faults. First, they study an original model that takes into account the effects of interturn faults resulting in the shorting of one or more circuits of stator-phase winding. They introduce, thus, additional parameters to explain the fault in the three stator phases. Then, they propose a new faulty model dedicated to broken rotor bars detection. The corresponding diagnosis procedure based on parameter estimation of the stator and rotor faulty model is proposed. The estimation technique is performed by taking into account prior information available on the safe system operating in nominal conditions. A special three-phase induction machine has been designed and constructed in order to simulate true faulty experiments. Experimental test results show good agreement and demonstrate the possibility of detection and localization of previous failures.

Synchronous Generator Output Voltage Real-Time Feedback Control via

A new approach on synchronous generator (SG) output voltage control is presented. The originality of such a strategy is based on the excitation structure that integrates a permanent-magnet generator combined with a modern control method: the H infin. The main motivation of this paper is the debatable results obtained with the classical excitation structure controlled by a traditional PID controller. The SG model as well as the control strategy will be presented. The implementation in real time domain and a comparison with the classical structure will allow us to prove the efficiency of the proposed structure compared to the classical one as regards the reference tracking and signal quality.

H_\infty

This paper analyses the synchronous machine modeling by taken into account the machine parameters usually used in industry and those used in researcher’s domains. Two models are presented. The first one is developed in the (d, q) natural reference frames and the other one is referred to the (d, q) stator reference frame. To do this, two methods are proposed to compute the reduction factor of the field winding without any input from design information. It is shown that the reduction factors of the (d, q) damper windings do not influence on the terminal behavior of the machine. This means that it is possible to know the terminal behavior of the machine without knowing the real inductances and resistances of the damper windings. The accuracy of these models is validated by experimental tests.

Strategy

In this paper, a technique for estimating the synchronous machine’s parameters using sudden short circuit test, is proposed. Before implementing estimation algorithms, a special method of the machine modelling is given. This last one allows to perform tests such as short-circuit, load impact and shedding test, in an easier way than the models usually developed in the literature. Thanks to the well known electrical equivalent circuit of the generator, the relationships between parameters generally used in the industry (i.e., reactances and time constants) and those used in researcher’s domains will be given. Finally, simulation results of the proposed method, allows to show that the algorithm is capable of providing very good estimated parameters fitting with the actual parameters.

Analysis of synchronous machine modeling for simulation and industrial applications

This paper aims to present three different methods of synchronous generator modelling. The first one is based on electrical scheme and it uses a Parks framework thanks to the Parks matrix. The two others use state space modelling strategy. The difference between these last two models is the load which can be or not be incorporated in the generator model. The comparison results with experiment, presented at the end of this paper allows to choose the one which suits the best to tests generally performed on synchronous generator

Synchronous generator modelling and parameters estimation using least squares method

In this paper, a method for the diagnosis of rotor bar failures for the induction machines has been presented. It based on the analysis of the stator current, using the Fourier transform and discrete wavelet transform (DWT) at the start-up electromagnetic torque. Using the simplified dynamic model of the squirrel cage induction motor taking account the broken rotor bars and the discrete wavelet transform (DWT) in order to extract the different harmonic components of the stator currents. The performance presented by using of the DWT: its ability to provide a local representation of the non stationary current signals for the healthy machine and with fault (two adjacent broken bars). The results are compared with those obtained using the Fourier transform.

Comparative study of three modelling methods of synchronous generator

The authors propose a diagnosis method for on-line interturns short-circuit windings and broken bars detection by parameters estimation. For predictive detection, Kalman filtering algorithm has been adapted to take into account the on-line parameters deviations in faulty case. Experimental rig is used to validate the on-line identification of stator default. Within the framework of the rotor defects diagnosis, it is difficult to conduct experimental tests to validate the on-line identification of such default. For this reason, one propose an on-line technique to detect rotor broken bars. This technique was validated by using a finite element software (Flux2D). Estimation results show a good agreement and demonstrate the possibility of on-line stator and rotor faults detection.

Application of the fourier and the wavelet transform for the fault detection in induction motors at the startup electromagnetic torque

This paper deals with the design and application of eight-linear voltage controllers that provide satisfactory voltage control performance in the presence of unknown load variation. The controller synthesis is based on the synchronous generator (SG) modeling strategy and the feedback control linearization method. Two models are presented. The first one takes into account a fixed load connected to the SG. The second model considers an unknown load. This consideration permits the design of a robust controller as regards the load variation. In addition, the linearization of the feedback control is established using a single-input-single-output controller and a multi-input-single-output (MISO) controller. The MISO solution represents a linearization method without any approximations. To validate the efficiency of each solution, the controllers are developed by using the H∞ method and implementation in a real-time domain is then performed.

On-line detection of stator and rotor faults occurring in induction machine diagnosis by parameters estimation

The paper mainly deals with the synchronous generator output voltage control by using a non linear control strategy: the sliding mode. The originality is not only due to the involved control strategy but also the use of a voltage source for the machinepsilas excitation and thyristors bridge. The favourable arguments to the sliding mode control are decoupling design procedure and easy implementation by power converters. The system stability is ensured by using a Lyapunov function. Thanks to the new excitation system based on voltage source, the systempsilas dynamics is improved in spite of the chattering phenomena induced by the sliding mode control. Simulations are done with Matlab/Simulinktrade and a discussion on the results is exposed at the end of the paper.

Monovariable and Multivariable Voltage Regulator Design for a Synchronous Generator Modeled With Fixed and Variable Loads

A modern strategy is applied to the control of the synchronous generator output voltage: the generalized predictive control. Then a complete discrete-time multi-variable predictive controller is used. Before implementing such a controller a particular method of synchronous generator modelling is presented. This last one is very suitable when tests are to be performed to validate or identify the model. In order to optimize the controller design and to make its implementation in real time domain easier, a reduction of the model order has been achieved. The simulation results presented at the end of the paper illustrate the efficiency and the handiness of the obtained controller in spite of the complexity due to the computation algorithm.