Showing papers in "Iet Electric Power Applications in 2012"

Transformer winding faults classification based on transfer function analysis by support vector machine

Abstract: This study presents an intelligent fault classification method for identification of transformer winding fault through transfer function (TF) analysis. For this analysis support vector machine (SVM) is used. The required data for training and testing of SVM are obtained by measurement on two groups of transformers (one is a classic 20 kV transformer and the other is a model transformer) under intact condition and under different fault conditions (axial displacement, radial deformation, disc space variation and short circuit of winding). Two different features extracted from the measured TFs are then used as the inputs to SVM classifier for fault classification. The accuracy of proposed method is compared with the accuracy of past well-known works. This comparison indicates that the proposed method can be used as a reliable method for transformer winding fault recognition.

Magnetic field and vibration monitoring in permanent magnet synchronous motors under eccentricity fault

Abstract: In this study, a novel frequency pattern is extracted from magnetic field analysis for precise eccentricity fault recognition in permanent magnet synchronous motors (PMSMs). In this analysis, impacts of stator slots, saturation, static and dynamic eccentricities are taken into account. Radial force and unbalanced magnetic pull are evaluated analytically and their spectra are utilised for vibration monitoring in the faulty PMSM. Furthermore, a frequency pattern is presented based on the processing of the radial force in PMSM under eccentricity fault. Since in the finite-element method, geometrical characteristics of all parts of the motor, spatial harmonics because of the stator slots, saturation owing to non-linear characteristics of the ferromagnetic materials in the stator and rotor cores and spatial distribution of stator windings are considered, two-dimensional (2D) and three-dimensional (3D) time-stepping finite-element method (TSFEM) are employed for modelling and analysing PMSM under static and dynamic eccentricities. The results obtained from the analytical approach introduced are validated by 2D and 3D TSFEM solutions. Simulation results are verified by experimental results.

Mechanical vibration reduction control of two-mass permanent magnet synchronous motor using adaptive notch filter with fast Fourier transform analysis

Abstract: A servo drive system with a permanent magnet synchronous motor (PMSM), ball-screw, gear and timing-belt is widely used in industrial applications such as numerical control (NC) machine, machine tool, robot and factory automation. These systems have torsional vibration in the torque transmission from the motor to the mechanical load owing to the mechanical couplings. This vibration reduces the dynamics of the speed responses and may result in damage to the mechanical plant. This study presents an adaptive notch filter with automatic searching of the resonant frequency and bandwidth from the speed error without any mechanical signal feedback to reject the mechanical vibration of the linear feeder system. The proposed control scheme can suppress the torque command signal of a PMSM in the resonant frequency area to reject the mechanical torsional vibration. Since the resonant frequency can be varied by the mechanical configurations and load conditions, the adaptive notch filter is designed to search the vibration frequency automatically and consequently suppress the mechanical resonant vibration. Experimental results show the verification of the proposed adaptive notch filter in a linear feeder system.

Design and evaluation of voltage measurement-based sectoral diagnosis method for inverter open switch faults of permanent magnet synchronous motor drives

Abstract: A sectoral diagnosis method for open switch faults of inverter-fed permanent magnet synchronous motor (PMSM) drives have been described. The proposed diagnosis method defines separate residuals for each of the six switches as a sectoral average of the difference between a reference and measured pole voltage instead of direct use of the instantaneous difference, which has varying AC quantity within one cycle of rotation. How to determine plausible thresholds is described and the effectiveness and limitation of the proposed method are analysed. Several sets of experimental results validate the detection and isolation capability of the proposed method.

Automatic procedure for induction motor parameter estimation at standstill

Abstract: The study presents a self-commissioning procedure for the automatic parameter estimation of three-phase induction motor drives. The procedure consists of a step-by-step approach with different test signals to obtain the parameter values while maintaining the motor at standstill. The actual implementation is capable of mapping both inverter and motor parameters non-linearities, providing accurate data for the tuning of common current regulators and for advanced sensorless drives as well. Theoretical and experimental results are provided, proving the effectiveness of the procedure.

Design of novel bearingless switched reluctance motor

Abstract: This study presents a novel bearingless switched reluctance motor (SRM) with decoupled torque and suspending stator poles. Different from the conventional bearingless SRM, the suspending poles of the proposed bearingless SRM are separated from the phase torque poles. Perpendicularly placed suspending poles are designed to produce a continuous radial force for rotor bearing. Owing to independently placed suspending and torque poles, the produced suspending force has excellent linearity according to rotor position and independent characteristics of the torque current. The control of air gap is easier than the conventional one from the linear and independent characteristics. In order to verify the proposed structure, the mathematic model for the suspending force is derived. Finite element analysis is also employed to compare with expressions for the suspending force. A prototype motor is designed and manufactured to verify the proposed bearingless structure.

Analytical method to optimise turn-on angle and turn-off angle for switched reluctance motor drives

Abstract: A new analytical method is proposed to produce optimal turn-on and turn-off angles, based on a non-linear inductance model of low-inductance region for switched reluctance motor (SRM). The optimal turn-on angle is derived from the non-linear model and electrical equation of SRM instead of the linear model while optimal turn-off angle is derived from the turn-on angle and flux-linkage. Considering the back electromotive force, the proposed method has more accuracy than the conventional analytical method and improves the efficiencies both at low speed and high speed. Simulation and experimental results demonstrate the validity and effectiveness of the proposed method, which is suited for low- and high-speed conditions both.

Analytical magnetic field distribution of slotless brushless permanent magnet motors – Part 1. Armature reaction field, inductance and rotor eddy current loss calculations

Abstract: Two-dimensional analytical armature field calculations are presented for slotless permanent magnet brushless motors. The proposed method is applicable to both brushless AC and DC motors with any number of phases. The problem is formulated for eight annular regions: shaft, rotor back-iron, magnets, retaining sleeve, airspace, winding, stator back-iron and exterior. A general armature current density distribution is expressed as a function of spatial angle and time for any number of phases, any current waveform and any winding distribution. The governing partial differential equations of all the regions subject to a set of boundary conditions are represented and solved analytically for both internal and external rotor motors. Self- and mutual-inductance calculations as well as expressions for the calculation of rotor eddy current losses in the magnets, retaining sleeve and rotor back-iron are also represented. In the second part of these two papers, the open-circuit magnetic field is presented for different magnetisation patterns and subsequently the electromagnetic torque is calculated. The effectiveness of the analytical model is validated by comparing the results with those obtained from finite-element analyses as well as an experimental set-up which presented in the second part of the series.

Design and analysis of a brushless DC motor for applications in robotics

Abstract: This study presents the design of a three-phase slotless brushless DC (BLDC) motor for use as an electromagnetic actuator in robotics. To achieve the high torque-to-inertia and torque-to-weight ratios required for fast response in robotic applications, genetic algorithms (GAs) are used to optimise the initial motor design within a reasonable geometry. We examine the machine performance using 3-D finite element analysis (FEA) and validate them by experimental measurement.

Analytical magnetic field distribution of slotless brushless PM motors. Part 2: Open-circuit field and torque calculations

Abstract: This study presents the open-circuit analytical magnetic field distribution of slotless brushless permanent magnet motors equipped with surface-mounted magnets. Although the focus of the study is on open-circuit magnetic field analysis, by augmenting the open-circuit magnetic field distribution with the armature reaction field distribution obtained from the first part of the series of two studies, the electromagnetic torque is calculated. The electromagnetic torque is calculated for both internal and external rotor motors with six different magnetisation patterns and three different armature current waveforms. The analysis domain consists of eight annular concentric regions: motor shaft, rotor back-iron, magnets, retaining sleeve, air-gap, winding, stator back-iron and exterior regions. Based on the open-circuit magnetic field distribution, the induced back-electromotive force (EMF) is also calculated. The validity of the proposed model is confirmed by comparing the analytical results with those obtained from the finite element method and an experimental set-up.

Hybrid excitation synchronous generators for island operation

Abstract: Hybrid excitation synchronous machines (HESMs), which combine the best features of traditional electrically excited synchronous machines (SMs) and permanent magnet synchronous machines (PMSMs), are investigated. Such machines provide energy efficiency benefits over traditional field-winding-excited machines, especially in the lower power region upto a few megawatts. This paper studies the applicability of a hybrid excitation synchronous generator (HESG) to a marine diesel genset. Three HESG structures are proposed, and their performance in island operation are studied by the two-dimensional (2D) finite-element analysis. Comparison of the proposed constructions is performed.

Performance analysis of a cylindrical eddy current brake

Abstract: Skin effect and armature reaction are the two major factors that effectively influence the performance of eddy current brake. Although many analytical solutions consider the armature reaction, skin effect has a significant impact on the torque-speed characteristics of the brake as the most important performance factor. This study presents an analytical equation for the torque-speed characteristics of an eddy current brake with cylindrical rotor taking into account both skin effect and armature reaction. This equation is valid over a wide range of speeds, therefore critical speed and maximum torque of the brake can be computed precisely. The presented model is sufficiently fast, accurate and flexible for design of a cylindrical eddy current brake. The predicted results are validated by the experimental results.

Control and operation of fault-tolerant flux-switching permanent-magnet motor drive with second harmonic current injection

Abstract: This study investigates the operations of a recently developed fault-tolerant flux-switching permanent-magnet (FT-FSPM) brushless motor, in which the concentrated coils of each stator phase are wound on alternate teeth and permanent-magnets (PMs) are located in the stator, offering a number of significant advantages over conventional PM brushless machines, such as simpler rotor structure, easier cooling in PMs and independence of phases. The control strategy of the FT-FSPM motor is proposed for torque ripple minimisation, in which the key is to introduce harmonic currents to compensate for non-ideal sinusoidal back-electromotive force (EMF). Both simulation and experimental results confirm that the proposed control algorithms can reduce torque ripple and offer good dynamic performance under normal and fault conditions. Hence, it can be concluded that the developed motor drive system is suitable for applications where reliability, efficiency and power density are of importance in such applications as electric and hybrid electric vehicles.

Modelling and control of a multi-phase permanent magnet synchronous generator and efficient hybrid 3L-converters for large direct-drive wind turbines

Abstract: A novel full-size wind power conversion system based on a multiphase permanent magnet synchronous generator (MPPMSG) and hybrid multi-converter system using 3-level neutral-point-clamp converters (3L-NPC) for high-power direct-drive wind turbines is proposed in this study. Higher efficiency, lower harmonics is achieved by replacing the traditional 2-level converter cells with 3-level cells. Circulating current is eliminated by using hybrid connection for multiphase generator design to replace the commonly used parallel converter structure for 3-phase generator design, the issues for neutral-point voltage imbalance is also eliminated. The mathematical model of MPPMSG and variable-speed control strategy are built and verified in PSCAD/EMTDC. A 3.5 kVA MPPMSG prototype machine and a set of hybrid 3L multi-converter systems are built. The experimental results validate the model and the effectiveness of the control strategies.

Operation and closed-loop control of wind-driven stand-alone doubly fed induction enerators using a single inverter-battery system

Abstract: A simple system has been formulated for the operation of wind-driven stand-alone doubly fed induction generators (DFIGs) supplying isolated loads at stator terminals. The stator voltage magnitude and frequency are maintained constant by closed-loop control. The excitation of the rotor is established using a single inverter which is an sinusoidal pulse width modulation (SPWM) inverter supplied through set of batteries. This allows the proposed system to feed continuous power supply to the isolated load via charging/discharging of the batteries depending on excess/deficit power from the wind. The system operates in various modes depending upon the availability of wind and size of the load. All possible modes of operation have been identified and described in the present study. The magnitude and frequency control strategies proposed in this study have been implemented using TMS320LF2407A digital signal processor (DSP) controller and detailed procedure for such implementation is given. The proposed control strategy is free from machine parameter variation and so the co-ordinate transformations, rotor position detection, measurements of rotor currents are not required. Experimental results obtained on a three-phase DFIG together with the closed-loop controller confirm the usefulness of the proposed system and the validity of its analysis.

Extended Park's vector approach-based differential protection of three-phase power transformers

Abstract: This study presents a new scheme for power transformers protection, which is based on the analysis of the harmonic content of the differential current Park's vector modulus. The proposed method is able to detect turn-to-turn winding insulation failures, and to distinguish them from magnetising inrush current transients. Experimental and simulation results are presented and discussed.

Reducing torque ripple of switched reluctance machines by relocation of rotor moulding clinches

Abstract: Switched reluctance machines (SRMs) are of great interest because of their simplicity, low-cost, reliability, robustness, fault-tolerance and extended-speed constant-power operation. However, conventional SRMs suffer from high torque ripples. There exist several methods, which have been proposed to reduce torque ripples. One of the proposed methods is to change the geometric structure of the machine. However, analysis of the state-of-the-art designs show that, despite achieving favourable results in applications, the moulding pins of the machines are normally neglected. A motor that gives positive results may get affected negatively by its random moulding during its manufacturing. In this paper, mitigation of torque ripples in short-pitched SRMs (SPSRMs) and fully-pitched SRMs (FPSRMs) are investigated. Three-phase SPSRM and FPSRM are chosen for this study and the effects of the geometric points of moulding pins in the machines are studied comparatively. Maxwell 2D program is used for the analysis and two different models are compared for both SPSRM and FPSRM. The obtained results show that the torque ripples of the two machines are lower when moulding pins are closer to the rotor position. It is reduced by 2.56% at 10 Amps in the proposed SPSRM and 12% at 6 Amps in the proposed FPSRM. It is also observed that the applied method is more effective in reducing torque ripples of FPSRMs than SPSRMs.

Digital signal processor-based probabilistic fuzzy neural network control of in-wheel motor drive for light electric vehicle

Abstract: A digital signal processor (DSP)-based probabilistic fuzzy neural network (PFNN) control is proposed in this study to control an in-wheel motor drive using a six-phase permanent magnet synchronous motor (PMSM) for light electric vehicle (LEV). First, the dynamics of LEV and in-wheel motor drive system with lumped uncertainty are described in detail. Then, a feedback linearisation control is designed to control the in-wheel motor drive system. Moreover, a non-linear disturbance observer (NDO) is applied to estimate the lumped uncertainty for the designed feedback linearisation control. However, the system response is degraded by the existed observer error. In order to achieve the required control performance of LEV, the PFNN control is developed for the control of the in-wheel motor drive system. The network structure and its on-line learning algorithm using delta adaptation law of the PFNN are derived. Moreover, a 32-bit fixed-point DSP, TMS320F2812, is adopted for the implementation of the proposed intelligent controlled drive system. Finally, some experimental results are illustrated to show the validity of the proposed PFNN control for in-wheel motor drive system.

Implicit position and speed estimation algorithm without the flux computation for the rotor side control of doubly fed induction motor drive

Abstract: A simple and implicit sensorless algorithm for estimating the rotor position and speed of the doubly fed induction machine is proposed in this study. Instead of computing the stator magnetic flux directly or indirectly, the stator flux vector components in the stationary reference frame are substituted with analytical equivalents in terms of measurable stator and rotor quantities. Thus, it is an implicit estimation process devoid of computing any flux terms and requires only the measured stator voltage and currents in stator and rotor windings apart from knowledge of the machine parameters. It is an open-loop scheme. However, it does not involve integration, recursive techniques, re-computations or programmable low-pass filters etc. Starting on the fly, accurate estimation near synchronous speed, immunity against variation in stator and rotor resistances or in the magnetising inductance are the principal advantages of the algorithm. Reduced complexity and the computational burden facilitate the easy implementation of the algorithm on a low-cost fixed point processor. Excellent agreement between the simulation and test results on a laboratory doubly fed induction motor validates the proposed estimation algorithm implemented for the vector control of a doubly fed induction motor. On the whole, the estimation algorithm is a new insight that holds promise in the area of sensorless control of the DFIM, whether used as a motor or as a generator.

Analytic modelling and dynamic analysis of pole-changing line-start permanent-magnet motors

Abstract: Pole-changing of line-start permanent magnet motors at start-up has many advantages and improves starting torque, synchronisation capability and steady-state performance. However, some oscillations may occur after switching which may cause dynamic problems. Depending on the speed and torque angle at switching time, the magnitude of oscillations may be large and even may lead to instability and reoccurrence of the sub-synchronous mode. In this study an analytic modelling is implemented to analyse the dynamic performance of motor with pole-changing method and the results have been verified by the 2-D finite-element method. In the analysis the various impacts of parameters such as switching speed, torque angle, inertia and load torque on the synchronisation capability are investigated. Next, two solutions are presented that overcome the stochastic dynamic problems and cause a suitable synchronisation. Finally, the experimental results are presented to verify the validity of the proposed methods and the overcoming of the dynamic problems.

Field programmable gate array-based fault-tolerant hysteresis current control for AC machine drives

Abstract: This study presents a field programmable gate array (FPGA) implementation of a simple fault-tolerant control that ensures continuous operation of hysteresis current controlled AC machine drives under faulty current sensor. The adopted control requires the use of three current sensors and is available for three-phase isolated neutral systems. The third current sensor allows the faulty current sensor detection and isolation based on analytical redundancy that provides residuals with well-defined thresholds. The control is reconfigured in case of faulty current measurement and operation continuity is performed using the remaining two healthy sensors. The main interest of using FPGAs to implement such controllers is the very important reduction of execution time delay in spite of algorithm complexity. As a result, a high sampling frequency can be used and the residual thresholds can be accurately defined even for the experimental set-up. Numerous experimental results are given to illustrate the efficiency of FPGA-based solutions to achieve efficient and reliable fault-tolerant hysteresis current control of AC machine drives.

Discrete-time sliding mode speed observer for sensorless control of induction motor drives

Abstract: This study investigates the rotor speed estimation problem for induction motor drives. The authors propose the design of a scheme based on a discrete-time sliding mode observer which provides the rotor speed estimative. A new algorithm for discrete-time rotor speed estimation is developed and analysed. The conditions for the existence of a discrete-time sliding switching hyperplane are analysed. Moreover, conventional algorithms aiming at the chattering reduction and high-frequency switching on discrete-time implementation are discussed for use with the proposed technique. The stability analysis and parameter convergence of the proposed method are investigated for discrete-time solution. The algorithms developed are tested by experimental results based on fixed-point digital signal processor (DSP) platform (TMS320F2812). Therefore the results demonstrate the good performance of the proposed scheme.

Winding factor calculation for analysis of back EMF waveform in air-core permanent magnet linear synchronous motors

Abstract: This study presents an analytical method for winding factor calculation and back electromotive force (EMF) prediction in air-core permanent magnet linear synchronous motors. In the proposed method, the voltage on each coil of a phase winding is calculated by adding the voltage induced in individual conductors considering a phase shift proportional to the conductor diameter. The proposed method can be used to find back EMF waveform of air-core linear motors with any winding configuration in terms of dimensional specifications of magnet track and winding assembly. Once the back EMF equation is obtained, it can be used to predict the thrust of the motor.The results of the proposed analytical model are compared with finite element analysis results for three different motors to verify the validity of the proposed modelling method. In order to investigate the effect of simplifying assumptions in model derivation, experimental back EMF result on a three-phase eight-pole motor is presented and compared with the proposed analytical model.

Shuffled frog-leaping algorithm for parameter estimation of a double-cage asynchronous machine

Abstract: This study introduces a shuffled frog-leaping algorithm based method for the estimation of induction motor double-cage model parameters from standard manufacturer data: full load torque, full load power factor, full load current, maximum torque, starting torque and starting current. The steady-state equivalent circuit is applied for the simulations. The circuit parameters are found as the result of the error minimisation function between the estimated and maker data. The suggested algorithm solves the parameter estimation problem and surpasses the solutions reached by particle swarm optimisation, genetic algorithms and classical parameter estimation method (a modified Newton method). The algorithm has been tested on three motors.

Position sensorless control of switched reluctance motors based on improved neural network

Abstract: Neural network (NN) has been applied as rotor position estimator in switched reluctance motor (SRM) whose characteristic is highly non-linear. However, conventional two inputs back propagate (BP) NN based rotor position estimator is not appropriate for real-time application in high speed operations because of its considerable computational time consumption in its hidden layer. In this study, an improved BP NN with inductance input pretreatment for the rotor position estimator of SRM is proposed. It achieves 75.44% computational burden reduction while staying at the same accuracy as the conventional one. Moreover, with the pretreatment, the NN can output the angle of full electrical period of the SRM operation. Training data includes rotor position, flux-linage which is acquired by finite element analysis (FEA) and phase current Sensorless control algorithm is also described. Simulations and experiments are performed based on a 12%8 SRM. The results are compared with conventional method. The effectiveness of the proposed sensorless estimator and control strategy are testified under low speed, high speed and sudden loading change operations.

Induction machine current space vector features to effectively discern and quantify rotor faults and external torque ripple

Abstract: Intensive research efforts have been spent with the aim of separating the effects of load torque unbalance from those of rotor faults in induction machines. Recent literature reports that active and reactive components of the current space vector seem to show different features in correspondence of the two fault events. This study shows the angular displacement of the above components is fundamental in order to distinguish external torque ripple from rotor faults. The fault severity and the external torque ripple can also be effectively determined. Moreover, the proposed technique allows to assess the range of validity of the usual motor current signature analysis (MCSA), based on the sum of the amplitude of stator current sidebands, for quantifying rotor bar faults.

Prediction of the oil flow distribution in oil-immersed transformer windings by network modelling and computational fluid dynamics

Abstract: In the context of thermal performance and thermal design, it is of significance to predict the magnitude and the location of the `hot-spot` temperature inside a power transformer. In an attempt to accurately predict this hot-spot in an oil-immersed transformer, various numerical modelling approaches have been developed for calculating the cooling oil flow distribution, which are generally categorised as either `network models` or the methods that incorporate forms of computational fluid dynamics (CFD). In network modelling, the complex pattern of oil ducts and passes in a winding is approximated with a matrix of simple hydraulic channels, where analytical expressions are then applied to describe oil flow and heat transfer phenomena. On the other hand, CFD models often adopt discretisations of much higher fineness, which can be expected to offer a higher order of accuracy but also comes with a large increase in the required computational resources. In order to compare both modelling approaches, the network model implementation TEFLOW and a commercial CFD package, ANSYS-CFX, were applied on a typical `zigzag` oil channel arrangement of a disc-type winding to predict oil flow distribution and disc temperatures; experiments on hydraulic models have also been performed to validate the models. The principle work of this study is then comparing the results and concluding recommendations to industrial practices.

Performance of the brushless doubly-fed machine under normal and fault conditions

Abstract: In this study, the steady-state operation of the brushless doubly-fed machine (BDFM) in various modes is physically elaborated and the active power flow and torque analysis are presented for each operating mode alongside confirmatory experimental results on a 4/8 pole D160 size machine. The machine behaviour in asynchronous operating modes is described similar to the conventional induction machines with corresponding pole numbers. Moreover, its performance in synchronous mode is shown to be similar to synchronous machines. On the basis of the above, the BDFM performance is further analysed under two possible fault conditions: first, a controller or converter fault leading to loss of synchronism is considered, where the asynchronous, double-cascade mode must be introduced to describe the machine performance. Second, a voltage dip at the mains terminal is considered. The simplistic behaviour of the BDFM during this fault, including the operation of a converter protective crowbar, is investigated using steady-state torque-speed curves to obtain a general view of the machine performance.

Adaptive fuzzy cerebellar model articulation control for switched reluctance motor drive

Abstract: This work presents a novel adaptive fuzzy cerebellar model articulation controller (AFCMAC) to regulate the speed of a switched reluctance motor (SRM). The proposed controller comprises two parts – a fuzzy cerebellar model articulation controller (CMAC) and a compensating controller. The fuzzy CMAC learns and approximates system dynamics; the compensating controller compensates the approximation error of the fuzzy CMAC. The parameters of the AFCMAC are adjusted online according to adaptive rules, which are derived from Lyapunov stability theory, so that both the stability of the control system and error convergence can be guaranteed. The effectiveness and robustness of the proposed AFCMAC are investigated by numerical simulation and experimental studies. Three control strategies, AFCMAC, ACMAC and proportional–integral (PI) control, are experimentally investigated and the performance index, root mean square error (RMSE) of each scheme is evaluated. The experimental results indicate that AFCMAC provides a much better system performance than the other compared schemes. The proposed AFCMAC performs well in tracking ability, parameter variation capacity and load disturbance rejection capability. The effectiveness and practicability of the proposed control scheme in a practical SRM drive are experimentally verified.

Design and tuning of fixed-switching-frequency second-order sliding-mode controller for doubly fed induction generator power control

Abstract: A pulse-width modulation-based second-order sliding-mode control (2-SMC) scheme for the rotor-side converter feeding a doubly fed induction generator (DFIG) is presented. It is aimed at achieving both high robustness to DFIG parameter variations and close tracking of a predefined rotor speed-dependent optimum power curve, while preserving a fixed switching frequency. In addition, it eludes the appearance of chatter. Tuning equations are also derived to adjust all its gains and constants. The proposed 2-SMC algorithm is evaluated as part of a sensorless scheme on the mathematical model of a 660-kW DFIG via numerical simulation. Its operation in terms of robustness and dynamic performance is then compared with that of a classical PI-based vector control (VC) strategy. The validity of the suggested 2-SMC scheme, as well as its superior performance in comparison with its PI-based VC counterpart, are corroborated through experimentation carried out on a 7-kW DFIG test bench.