Showing papers on "Induction motor published in 2015"

Modern Power Electronics And Ac Drives

Abstract: (NOTE: Each chapter begins with an Introduction and concludes with a Summary and References.) Preface. List of Principal Symbols. 1. Power Semiconductor Devices. Diodes. Thyristors. Triacs. Gate Turn-Off Thyristors (GTOs). Bipolar Power or Junction Transistors (BPTs or BJTs). Power MOSFETs. Static Induction Transistors (SITs). Insulated Gate Bipolar Transistors (IGBTs). MOS-Controlled Thyristors (MCTs). Integrated Gate-Commutated Thyristors (IGCTs). Large Band-Gap Materials for Devices. Power Integrated Circuits (PICs). 2. AC Machines for Drives. Induction Machines. Synchronous Machines. Variable Reluctance Machine (VRM). 3. Diodes and Phase-Controlled Converters. Diode Rectifiers. Thyristor Converters. Converter Control. EMI and Line Power Quality Problems. 4. Cycloconverters. Phase-Controlled Cycloconverters. Matrix Converters. High-Frequency Cycloconverters. 5. Voltage-Fed Converters. Single-Phase Inverters. Three-Phase Bridge Inverters. Multi-Stepped Inverters. Pulse Width Modulation Techniques. Three-Level Inverters. Hard Switching Effects. Resonant Inverters. Soft-Switched Inverters. Dynamic and Regenerative Drive Braking. PWM Rectifiers. Static VAR Compensators and Active Harmonic Filters. Introduction to Simulation-MATLAB/SIMULINK. 6. Current-Fed Converters. General Operation of a Six-Step Thyristor Inverter. Load-Commutated Inverters. Force-Commutated Inverters. Harmonic Heating and Torque Pulsation. Multi-Stepped Inverters. Inverters with Self-Commutated Devices. Current-Fed vs Voltage-Fed Converters. 7. Induction Motor Slip-Power Recovery Drives. Doubly-Fed Machine Speed Control by Rotor Rheostat. Static Kramer Drive. Static Scherius Drive. 8. Control and Estimation of Induction Motor Drives. Induction Motor Control with Small Signal Model. Scalar Control. Vector or Field-Oriented Control. Sensorless Vector Control. Direct Torque and Flux Control (DTC). Adaptive Control. Self-Commissioning of Drive. 9. Control and Estimation of Synchronous Motor Drives. Sinusoidal SPM Machine Drives. Synchronous Reluctance Machine Drives. Sinusoidal IPM Machine Drives. Trapezoidal SPM Machine Drives. Wound-Field Synchronous Machine Drives. Sensorless Control. Switched Reluctance Motor (SRM) Drives. 10. Expert System Principles and Applications. Expert System Principles. Expert System Shell. Design Methodology. Applications. Glossary. 11. Fuzzy Logic Principles and Applications. Fuzzy Sets. Fuzzy System. Fuzzy Control. General Design Methodology. Applications. Fuzzy Logic Toolbox. Glossary. 12. Neural Network Principles and Applications. The Structure of a Neuron. Artificial Neural Network. Other Networks. Neural Network in Identification and Control. General Design Methodology. Applications. Neuro-Fuzzy Systems. Demo Program with Neural Network Toolbox. Glossary. Index.

Comparative Study of Interior Permanent Magnet, Induction, and Switched Reluctance Motor Drives for EV and HEV Applications

Abstract: With rapid electrification of transportation, it is becoming increasingly important to have a comprehensive understanding of criteria used in motor selection. This paper presents the design and comparative evaluation for an interior permanent magnet synchronous motor (IPMSM) with distributed winding and concentrated winding, induction motor (IM), and switched reluctance motor (SRM) for an electric vehicle (EV) or hybrid electric vehicle (HEV) application. A fast finite element analysis (FEA) modeling approach is addressed for IM design. To account for highly nonlinear motor parameters and achieve high motor efficiency, optimal current trajectories are obtained by extensive mapping for IPMSMs and IM. Optimal turn- on and turn- off angles with current chopping control and angular position control are found for SRM. Additional comparison including noise vibration and harshness (NVH) is also highlighted. Simulation and analytical results show that each motor topology demonstrates its own unique characteristic for EVs/HEVs. Each motor’s highest efficiency region is located at different torque-speed regions for the criteria defined. Stator geometry, pole/slot combination, and control strategy differentiate NVH performance.

Detection of Localized Bearing Faults in Induction Machines by Spectral Kurtosis and Envelope Analysis of Stator Current

Abstract: Early detection of faults in electrical machines, particularly in induction motors, has become necessary and critical in reducing costs by avoiding unexpected and unnecessary maintenance and outages in industrial applications. Additionally, most of these faults are due to problems in bearings. Thus, in this paper, experimental bearing fault detection of a three-phase induction motor is performed by analyzing the squared envelope spectrum of the stator current. Spectral kurtosis-based algorithms, namely, the fast kurtogram and the wavelet kurtogram, are also applied to improve the envelope analysis. Experimental tests are performed, considering outer bearing faults at different stages, and the results are promising.

Induction Machine Bearing Fault Detection by Means of Statistical Processing of the Stray Flux Measurement

Abstract: Rolling bearing faults are generally slowly progressive; therefore, the development of an effective diagnostic technique could be worth detecting such faults in their incipient phase and preventing complete failure of the motor. The methods proposed in the literature for this purpose are mainly based on measuring and analyzing vibration and current. Here, a novel technique based on the stray flux measurement in different positions around the electrical machine is proposed. The main advantages of this method are due to the simplicity and the flexibility of the custom flux probe with its amplification and filtering stage. The flux probe can be easily positioned on the machines and adapted to a wide range of power levels. This paper also reports an extensive survey on the stray-flux-based fault detection methods for induction motors, prior to introducing a novel sensor/diagnostic scheme.

Bearing Currents and Shaft Voltage Reduction in Dual-Inverter-Fed Open-End Winding Induction Motor With Reduced CMV PWM Methods

Abstract: Exploiting the rich switching redundancies of the dual inverter, new hybrid pulsewidth-modulation (PWM) switching methods are proposed in this paper using the degree of freedom of operating the individual inverters independently, in addition to exercising the degree of freedom of controlling the switching action of the individual legs independently. Two voltage entities, namely, common-mode voltage (CMV) and differential-mode voltage are identified in the dual inverter, and all hybrid PWMs are envisaged aimed at reducing and also eliminating the CMV in it. The effects of such attempts on motor shaft voltage and also the motor bearing currents are presented in detail. Furthermore, bearing current profiles of an open-end winding induction motor are also presented with both conventional and hybrid PWMs proposed in this paper. Electric discharge machining discharge currents are completely eliminated with the use of all hybrid PWM methods proposed in this paper. In addition, implications of completely eliminating the CMV are also presented in this paper. All hybrid PWMs proposed in this paper are first simulated using MATLAB and are experimentally verified on a dual two-level inverter feeding a 1.1-kW 415-V 3-φ open-end winding induction motor drive.

Review on model reference adaptive system for sensorless vector control of induction motor drives

Abstract: The most frequently used electrical machine in various modern high-performance drive applications is the induction motor (IM), especially its squirrel cage type rotor counterpart. The high-precision, efficient control of sensorless IM drives throughout its operating range demands an exact knowledge of a few of the IM parameters. The stator resistance, rotor resistances are such important IM parameters whose variations may lead to improper estimation of speed over the whole operating range in sensorless drives. Numerous methods for the estimation of speed of high-performance sensorless IM drives taking into account the effect of parameter variations have been developed. This paper aims at providing a review of the major model reference adaptive system (MRAS) based techniques applied for the estimation of speed of such sensorless drives. This paper is illustrated throughout with relevant mathematical equations, experimental and simulation results, associated to different MRAS-based sensorless vector control of the IM drive.

Speed and Current Sensor Fault Detection and Isolation Technique for Induction Motor Drive Using Axes Transformation

Abstract: This paper presents a new technique for fault detection and isolation to make the traditional vector-controlled induction motor (IM) drive fault tolerant against current and speed sensor failure. The proposed current estimation uses d- and q-axes currents and is independent of the switching states of the three-leg inverter. While the technique introduces a new concept of vector rotation to generate potential estimates of the currents, speed is estimated by one of the available model reference adaptive system (MRAS) based formulations. A logic-based decision mechanism selects the right estimate and reconfigures the system (by rejecting the signal from the faulty sensors). Such algorithm is suitable for different drives, including electric vehicles to avoid complete shutdown of the system, in case of sensor failure. The proposed method is extensively simulated in MATLAB/SIMULINK and experimentally validated through a dSPACE-1104-based laboratory prototype.

Advanced Induction Motor Rotor Fault Diagnosis Via Continuous and Discrete Time–Frequency Tools

Abstract: Transient-based fault diagnosis in induction motors has gained increasing attention over the recent years. This is due to its ability to avoid eventual wrong diagnostics of the conventional motor current signature analysis in certain industrial situations (presence of load toque oscillations, light loading conditions, and so on). However, the application of these transient methodologies requires the use of advanced signal processing tools. This paper presents a detailed comparison between the two main groups of transforms that are employed in transient analysis: discrete and continuous. This paper does not focus on trivial fault cases but on difficult real situations where the application of the conventional methods often leads to false diagnostics (outer bar breakages in double-cage motors, motors with rotor axial duct influence, and combined faults). Indeed, it is the first time that continuous tools are applied to some of these controversial situations. The results in this paper prove the special advantages of the continuous transforms, tearing down some false myths about their use.

Automatic Design of Synchronous Reluctance Motors Focusing on Barrier Shape Optimization

Abstract: The automated design of synchronous reluctance (SyR) motors based on multiobjective genetic optimization and finite-element analysis is considered in this paper. Three types of barrier shapes are considered, all described by an effective limited set of input variables. The three solutions are investigated to establish which of the geometries can give the best torque output and also which one represents the best compromise between output performance and computational time. The analysis presented in this paper shows that SyR motors designed automatically can give a good performance and can be designed in a reasonable time, and it is also shown that not all design degrees of freedom are useful in terms of motor performance. Two prototypes of automatically designed machines have been fabricated and experimentally compared with a third prototype designed according to state-of-the-art design principles.

Evaluation of Switching Performance of SiC Devices in PWM Inverter-Fed Induction Motor Drives

Abstract: Double pulse test (DPT) is a widely accepted method to evaluate the switching characteristics of semiconductor switches, including SiC devices However, the observed switching performance of SiC devices in a PWM inverter for induction motor drives is almost always worse than the DPT characterization, with slower switching speed, more switching losses, and more serious parasitic ringing This paper systematically investigates the factors that limit the SiC switching performance from both the motor side and inverter side, including the load characteristics of induction motor and power cable, two more phase legs for the three-phase PWM inverter in comparison with the DPT, and the parasitic capacitive coupling effect between power devices and heat sink Based on a three-phase PWM inverter with 1200 V SiC MOSFETs, test results show that the induction motor, especially with a relatively long power cable, will significantly impact the switching performance, leading to a switching time increase by a factor of 2, switching loss increase up to 30% in comparison with that yielded from DPT, and serious parasitic ringing with 15 μs duration, which is more than 50 times of the corresponding switching time In addition, the interactions among the three phase legs cannot be ignored unless the decoupling capacitors are mounted close to each phase leg to support the dc bus voltage during switching transients Also, the coupling capacitance due to the heat sink equivalently increases the junction capacitance of power devices; however, its influence on the switching behavior in the motor drives is small considering the relatively large capacitance of the motor load

Model-Predictive Flux Control of Induction Motor Drives With Switching Instant Optimization

Abstract: Conventional model-predictive torque control (MPTC) requires tedious and time-consuming tuning work for stator flux weighting factor, and presents relatively high torque ripples. To solve these problems, this paper proposes a model-predictive flux control (MPFC) for two-level inverter-fed induction motor (IM) drives. The references of stator flux magnitude and torque in conventional MPTC are converted into an equivalent reference of stator flux vector in the proposed MPFC. As only the tracking error of stator flux vector is required in the cost function, the use of weighting factor is eliminated. The optimal voltage vector is selected based on the principle of stator flux error minimization and its switching instant is optimized rather than being in the beginning of each control period. The proposed MPFC with and without switching instant optimization are both implemented in a 32-bit floating digital signal processor, and they are compared in detail in terms of torque ripple, current harmonics, and average switching frequency. Both digital simulations and experimental tests were carried out on a two-level inverter-fed IM drive, and the obtained results validate the effectiveness of the proposed method.

Predictive Torque Control Scheme for Three-Phase Four-Switch Inverter-Fed Induction Motor Drives With DC-Link Voltages Offset Suppression

Abstract: The four-switch three-phase (B4) inverter, having a lower number of switches, was first presented for the possibility of reducing the inverter cost, and it became very attractive as it can be utilized in fault-tolerant control to solve the open/short-circuit fault of the six-switch three-phase (B6) inverter. However, the balance among the phase currents collapses due to the fluctuation of the two dc-link capacitor voltages; therefore, its application is limited. This paper proposes a predictive torque control (PTC) scheme for the B4 inverter-fed induction motor (IM) with the dc-link voltage offset suppression. The voltage vectors of the B4 inverter under the fluctuation of the two dc-link capacitor voltages are derived for precise prediction and control of the torque and stator flux. The three-phase currents are forced to stay balance by directly controlling the stator flux. The voltage offset of the two dc-link capacitors is modeled and controlled in the predictive point of view. A lot of simulation and experimental results are presented to validate the proposed control scheme.

High-Torque-Density Control of Multiphase Induction Motor Drives Operating Over a Wide Speed Range

Abstract: The high-order harmonics of the magnetic field can be used in some typologies of multiphase machine to improve the torque density. However, maximizing the torque capability depends on the thermal, voltage, and current constraints of the machine and the inverter. In this paper, a rotor-flux-oriented control scheme, which is capable of exploiting the maximum torque at any speed, is presented for multiphase induction motor drives. Below the base speed, the torque improvement is obtained by adding a third harmonic component to the fundamental component of the air-gap magnetic field. At high speeds, the amplitude of the field harmonics is progressively reduced to ensure the widest possible operating speed range. The validity of the proposed control scheme is confirmed by experimental tests.

A Speed-Sensorless FS-PTC of Induction Motors Using Extended Kalman Filters

Abstract: A sensorless finite-state predictive torque control (FS-PTC) strategy uses stator current, estimated stator and rotor flux, and estimated rotor speed to predict stator flux and torque. Direct application of measured stator currents and using a noisy estimated speed in the prediction model degrade the steady-state performance in terms of higher current total harmonic distortion (THD), torque ripple, and flux ripple, particularly at low speeds. This paper proposes an extended Kalman filter (EKF)-based, which is a promising state observer, improved prediction model of sensorless FS-PTC for induction motor drives. The EKF has been used to estimate rotor speed, rotor/stator flux, and stator currents accurately. The estimated stator currents, instead of measured currents, are fed back to the prediction model, and thus, small stator current THD is confirmed. Depending on the commanded speed, either the rotor current model or the open-loop stator voltage model is proposed for the EKF to achieve better performance in a wide speed range, including the field-weakening region. The proposed control system has been verified experimentally, and excellent torque and flux responses, robustness, and stable operation at lower and higher speeds have been achieved.

Electric Motor Fault Detection and Diagnosis by Kernel Density Estimation and Kullback–Leibler Divergence Based on Stator Current Measurements

Abstract: This paper deals with the problem of fault detection and diagnosis of induction motor based on motor current signature analysis. Principal component analysis is used to reduce the three-phase current space to a 2-D space. Kernel density estimation (KDE) is adopted to evaluate the probability density functions of each healthy and faulty motor, which can be used as features in order to identify each fault. Kullback–Leibler divergence is used as an index to identify the dissimilarity between two probability distributions, and it allows automatic fault identification. The aim is also to improve computational performance in order to apply online a monitoring system. KDE is improved by fast Gaussian transform and a points reduction procedure. Since these techniques achieve a remarkable computational cost reduction with respect to the standard KDE, the algorithm can be used online. Experiments are carried out using two alternate current motors: an asynchronous induction machine and a single-phase motor. The faults considered to test the developed algorithm are cracked rotor, out-of-tolerance geometry rotor, and backlash. Tests are carried out at different load and voltage levels to show the proposed method performance.

Convergence Analysis of Extended Kalman Filter for Sensorless Control of Induction Motor

Abstract: This paper deals with convergence analysis of the extended Kalman filters (EKFs) for sensorless motion control systems with induction motor (IM). An EKF is tuned according to a six-order discrete-time model of the IM, affected by system and measurement noises, obtained by applying a first-order Euler discretization to a six-order continuous-time model. Some properties of the discrete-time model have been explored. Among these properties, the observability property is relevant, which leads to conditions that can be directly linked with the working conditions of the machine. Starting from these properties, the convergence of the stochastic state estimation process, in mean square sense, has been shown. The convergence is also explored with reference to the difference between the samples of the state of the continuous-time model and that estimated by the EKF. The results theoretically achieved have been also validated by means of experimental tests carried out on an IM prototype.

Integrated Modular Motor Drive Design With GaN Power FETs

Abstract: This paper explores the use of GaN power FETs to realize an integrated modular motor drive (IMMD) with an induction motor. A structure in which inverter modules are connected in series is proposed to reduce the module maximum voltages and to offer an opportunity to utilize low-voltage wide-band-gap GaN devices. With the superb switching performance of GaN power FETs, a reduction in IMMD size is achieved by eliminating inverter heat sink and optimizing dc-link capacitors. Gate signals of the IMMD modules are interleaved to suppress the total voltage ripple of dc-link capacitors and to further reduce the capacitor size. Motor winding configurations and their coupling effect are also investigated as a part of the IMMD design. The proposed structure and design methods are verified by experimental results.

New Optimal Pulsewidth Modulation for Single DC-Link Dual-Inverter Fed Open-End Stator Winding Induction Motor Drive

Abstract: The multilevel topology with dual inverters feeding both ends of an open-end stator winding of an induction motor has been introduced around two decades ago. A common-mode inductor is usually required in series with motor windings to suppress zero-sequence or common-mode currents. In case of medium voltage high-power drives, low device switching frequency operation is preferred to improve the overall system efficiency. However, it increases the harmonic distortion of machine stator currents. Therefore, the goal of our study is to propose new optimal pulse width modulation to achieve: low device switching frequency, minimal harmonic distortion of machine stator currents, and elimination of zero-sequence currents. The main idea is to select the switching angles of two inverters such that zero-sequence components are eliminated and, then, perform optimization to determine switching angles that minimize the harmonic distortion of machine stator currents. The experimental results obtained from dual two-level and dual three-level inverter fed 1.5-kW open-end stator winding IM drive demonstrated the effectiveness of a proposed modulation technique.

Improved Stator Flux Estimator for Speed Sensorless Induction Motor Drives

Abstract: In this paper, an improved induction motor (IM) stator flux estimation method is proposed, based on a novel integrator scheme with a closed-loop dc offset compensation algorithm. When compared with the existing stator flux estimators, the proposed solution represents an improved programmable low-pass filter. Namely, by introducing a novel closed-loop dc offset compensation structure, two major drawbacks of existing stator flux estimators are overcome; their stability and accuracy at low frequencies, and the estimator response time over the whole frequency range, introducing an estimation algorithm much simpler than existing solutions. The performance of the novel stator flux estimator is tested by means of simulation runs and experimental tests, with the proposed algorithm used for the estimation of the stator flux, rotor flux, and rotor speed in a direct field-oriented controlled IM control algorithm. The simulations and experimental results show that the proposed estimator enables accurate and stable operation under all operating conditions, including the critical low stator frequency range.

A Single-Stage Photovoltaic System for a Dual-Inverter-Fed Open-End Winding Induction Motor Drive for Pumping Applications

Abstract: This paper presents an integrated solution for a photovoltaic (PV)-fed water-pump drive system, which uses an open-end winding induction motor (OEWIM). The dual-inverter-fed OEWIM drive achieves the functionality of a three-level inverter and requires low value dc-bus voltage. This helps in an optimal arrangement of PV modules, which could avoid large strings and helps in improving the PV performance with wide bandwidth of operating voltage. It also reduces the voltage rating of the dc-link capacitors and switching devices used in the system. The proposed control strategy achieves an integration of both maximum power point tracking and V/f control for the efficient utilization of the PV panels and the motor. The proposed control scheme requires the sensing of PV voltage and current only. Thus, the system requires less number of sensors. All the analytical, simulation, and experimental results of this work under different environmental conditions are presented in this paper.

A New Formulation of Reactive-Power-Based Model Reference Adaptive System for Sensorless Induction Motor Drive

Abstract: Various functional candidates such as flux, back electromotive force, and reactive power are used to form a model reference adaptive system (MRAS) to estimate the speed of an induction motor drive. Of these, reactive power ( $Q$ ) based controllers perform well at low speeds and are inherently independent of stator resistance. However, such configuration fails to provide stability in the regenerative mode. This paper proposes a new formulation of reactive-power-based MRAS that is stable in all the four quadrants of operation. A detailed MATLAB/Simulink based simulation study is presented. Superior performance of the proposed controller is confirmed by prototype experimentation using a field-programmable-gate-array based controller in the laboratory.

Maximum Efficiency per Torque Direct Flux Vector Control of Induction Motor Drives

Abstract: In this paper, a loss-minimizing strategy is proposed for induction motor drives to ensure maximum efficiency operation for a given torque demand. The proposed strategy directly regulates the machine stator flux, according to the desired torque, using an optimal stator flux reference. Therefore, the proposed strategy is suitable for motor control schemes that are based on direct flux regulation, such as direct torque control or direct flux vector control. The maximum efficiency per torque (MEPT) stator flux map is computed offline using the traditional no-load and short-circuit test data. An iron loss model based on the stator flux and frequency is also proposed for the calibration of the machine loss model and also for online monitoring of the iron losses during motor operation. The proposed MEPT strategy has been validated on a 2.2-kW induction machine, and the motor efficiency has been measured for different speed values and variable load conditions. The experimental results confirm the effectiveness of the proposed solution.

Empirical Mode Decomposition Analysis for Broken-Bar Detection on Squirrel Cage Induction Motors

Abstract: Induction motor is a ubiquitous machine. In industrial settings, online monitoring of motors’ health status in order to schedule maintenance operations with the goal of damage prevention has become an essential necessity. Broken rotor bar is one of the most common failures in the rotor of a squirrel cage motor. Motor current signature analysis (MCSA) has become a popular method for the detection of this failure because of its high reliability. Recent works have performed the MCSA with a combination of different signal processing techniques to identify the presence of broken bars. In this paper, the MCSA is done with empirical mode decomposition from which a set of intrinsic mode functions (IMFs) is obtained. The extracted features from two of the obtained IMFs form the basis of the proposed classification criterion; these are the samples between zero crossings (SBZCs) and the time between successive zero crossings (TSZCs). The standard deviation from the SBZCs and the TSZCs is used as a classification feature. Experimental results using our method show high accuracy in the detection of a broken and a half-broken rotor bar.

A technology review paper for drives used in electrical vehicle (EV) & hybrid electrical vehicles (HEV)

Abstract: The pollution of environment is increasing due a very large numbers of conventional vehicles present today To reduce pollution the electric and hybrid electric vehicle are very beneficial As the decade of low cost fuel is coming to an end the electric vehicle or hybrid electric vehicle is a good alternative to the conventional vehicles These electric vehicles are driven by an electric motor may be AC or DC fed by battery through electric converter The various drives used for the EVs & HEVs are discussed in this paper The main two types of drive based on the supply are used DC or AC drive The AC drives consisting of three phase permanent magnet synchronous motor (PMSM) is most popular amongst them The other widely used drives are three phase Induction motor (IM), Switched reluctance motor (SRM), Brushless DC motor (BLDC) These motor are fed by different power electronic converters such as DC-DC converter, DC- AC converters per the supply requirements

Robust Speed Control of Induction Motor Drives Using First-Order Auto-Disturbance Rejection Controllers

Abstract: A novel robust control scheme employing three first-order auto-disturbance rejection controllers (ADRCs) is presented for the speed control of induction motor drives. Compared with the existing high-order ADRC-based speed control structures, the proposed method does not need to estimate the rotor flux. As a result, the implementation of the proposed scheme on a digital signal processor (DSP) is easier, and the runtime of the proposed ADRC control algorithm is shorter. The simulation results show that the proposed control scheme can cope with the internal disturbance and external disturbance, such as the motor's parameter variations, the load disturbances, etc. A TMS320F2812 DSP-based prototype using the proposed control scheme was developed. The comparative experimental results show that the robustness of the proposed ADRC system is obviously better than the conventional proportional–integral system when various disturbances occur, and the scheme is feasible and effective.

Model predictive torque control of induction motor drives with reduced torque ripple

Abstract: Model predictive torque control (MPTC) is emerging as a high-performance control strategy for induction motor (IM) drives, due to its intuitive nature, flexibility to incorporate constraints and quick dynamic response. However, the implementation of MPTC requires high computational ability and the use of single voltage vector during one control period fails to reduce the torque ripple to the minimal value. This study proposes an improved MPTC for IM drives with reduced torque ripple and low complexity. On the basis of the relationship between stator current and stator flux, the complicated current prediction for each voltage vector is eliminated, reducing the control complexity significantly. Torque ripple reduction is achieved by allocating only a fraction of control period to the active vector selected from conventional MPTC, whereas the rest of time is allocated for a null vector. Two kinds of methods for optimising the duty ratio of the active vector are proposed and evaluated in detail. Presented experimental results prove that, compared with conventional MPTC, the proposed MPTC achieves better steady-state performance by reducing the torque ripple significantly. Meanwhile, the quick dynamic response of conventional MPTC is reserved.

Nonlinear H-infinity Feedback Control for Asynchronous Motors of Electric Trains

Abstract: A new method for feedback control of asynchronous electrical machines is introduced, with application example the problem of the traction system of electric trains. The control method consists of a repetitive solution of an H-infinity control problem for the asynchronous motor, that makes use of a locally linearized model of the motor and takes place at each iteration of the control algorithm. The asynchronous motor’s model is locally linearized round its current operating point through the computation of the associated Jacobian matrices. Using the linearized model of the electrical machine an H-infinity feedback control law is computed. The known robustness features of H-infinity control enable to compensate for the errors of the approximative linearization, as well as to eliminate the effects of external perturbations. The efficiency of the proposed control scheme is shown analytically and is confirmed through simulation experiments.

Multi-class fault diagnosis of induction motor using Hilbert and Wavelet Transform

Abstract: Two powerful signal processing tools CWT and HT used for feature extraction.A novel approach to find the important fault frequencies using GA.Seven important fault frequencies found to exist in frequency range 50-300Hz. A new method of selecting CWT scales according to the fault frequencies found.Only vertical frame vibration found sufficient for multi-class fault diagnosis.Six induction motor faults considered and successfully detected. The information extraction capability of two widely used signal processing tools, Hilbert Transform (HT) and Wavelet Transform (WT), is investigated to develop a multi-class fault diagnosis scheme for induction motor using radial vibration signals. The vibration signals are associated with unique predominant frequency components and instantaneous amplitudes depending on the motor condition. Using good systematic and analytical approach this fault frequencies can be identified. However, some faults either electrical or mechanical in nature are associated with same or similar vibration frequencies leading to erroneous conclusions. Genetic Algorithm (GA) is proposed and used successfully to find the most relevant fault frequencies in radial (vertical) frame vibration signal which can be used to diagnose the induction motor faults very effectively even in the presence of noise. The information obtained by Continuous Wavelet Transform (CWT) was found to be highly redundant compared to HT and thus by selecting the most relevant features using GA, the fault classification accuracy has considerably improved especially for CWT. Almost similar fault frequencies were found using CWT+GA and HT+GA for radial vibration signal.