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In this paper, the performance of different continuous-time and discrete-time models of the electrical subsystem of induction machines and permanent-magnet synchronous machines as well as methods based on them for decoupling the direct and quadrature axis components of the stator current are investigated and compared. The focus here is on inverter-fed, pulse width modulated drives when operated with a relatively large product of stator frequency and sampling time, where significant differences between the models and decoupling methods used come to light. Recommendations for a discrete-time model to be used uniformly in the future are made, as well as statements on whether feedforward or feedback decoupling structures are better suited and whether state controllers improve decoupling measures for very steep speed ramps. Simulation studies and measurement results support the statements made above. [ABSTRACT FROM AUTHOR]

The paper describes a novel online identification algorithm for a two-mass drive system. The multi-layer extended Kalman Filter (MKF) is proposed in the paper. The proposed estimator has two layers. In the first one, three single extended Kalman filters (EKF) are placed. In the second layer, based on the incoming signals from the first layer, the final states and parameters of the two-mass system are calculated. In the considered drive system, the stiffness coefficient of the elastic shaft and the time constant of the load machine is estimated. To improve the quality of estimated states, an additional system based on II types of fuzzy sets is proposed. The application of fuzzy MKF allows for a shorter identification time, as well as improves the accuracy of estimated parameters. The identified parameters of the two-mass system are used to calculate the coefficients of the implemented control structure. Theoretical considerations are supported by simulations and experimental tests. [ABSTRACT FROM AUTHOR]

Currently, applications of the algorithms based on artificial intelligence (AI) principles can be observed in various fields. This can be also noticed in the wide area of electrical drives. Consideration has been limited to neural networks; however, the tasks for the models can be defined as follows: control, state variable estimation, and diagnostics. In the subsequent sections of this paper, electrical machines, as well as power electronic devices, are assumed as the main objects. This paper describes the basics, issues, and possibilities related to the used tools and explains the growing popularity of neural network applications in automatic systems with electrical drives. The paper begins with the overall considerations; following that, the content proceeds with the details, and two specific examples are shown. The first example deals with a neural network-based speed controller tested in a structure with a synchronous reluctance motor. Then, the implementation of recurrent neural networks as state variable estimators is analyzed. The achieved results present a precise estimation of the load speed and the shaft torque signals from a two-mass system. All descriptions in the article are considered in the context of the trends and perspectives in modern algorithm applications for electrical drives. [ABSTRACT FROM AUTHOR]

This review paper looks briefly at conventional approaches and examines the intelligent means for fault diagnosis (FD) and condition monitoring (CM) of electrical drives in detail, especially the ones that are common in Industry 4.0. After giving an overview on fault statistics, standard methods for the FD and CM of rotating machines are first visited, and then its orientation towards intelligent approaches is discussed. Major diagnostic procedures are addressed in detail together with their advancements to date. In particular, the emphasis is given to motor current signature analysis (MCSA) and digital signal processing techniques (DSPTs) mostly used for feature engineering. Consequently, the statistical procedures and machine learning techniques (stemming from artificial intelligence—AI) are also visited to describe how FD is carried out in various systems. The effectiveness of the amalgamation of the model, signal, and data-based techniques for the FD and CM of inductions motors (IMs) is also highlighted in this review. It is worth mentioning that a variety of neural- and non-neural-based approaches are discussed concerning major faults in rotating machines. Finally, after a thorough survey of the diagnostic techniques based on specific faults for electrical drives, several open problems are identified and discussed. The paper concludes with important recommendations on where to divert the research focus considering the current advancements in the FD and CM of rotating machines. [ABSTRACT FROM AUTHOR]

The paper discusses problems that occur in robotic arm control. The specific problems arise due to the wear of various types of gears (in the presented case, belt gear and worm gear). It is important to note that such errors need to be diagnosed in time, and the way of their elimination has to be determined, which should be resource-intensive and cost-effective. This article describes the basic types of robotic manipulators (robotic arm, telpher and Cartesian), presenting a review and study of the possibilities of errors in the movement of a robot, adjustment of a mechanical system, and determination of a strategy for solving the emerging problems. A comparison between various types of gear faults is also provided. Different ways of diagnosing faults are discussed, based on the advantages and disadvantages of the methods. The main objective of this study is to provide a complete overview of the mechanical areas where disturbances occur, their diagnosing, and methods of their elimination. [ABSTRACT FROM AUTHOR]

Active disturbance rejection control using extended state observer (ESO) is less dependent on the knowledge of the system. It has proved to be an excellent scheme for speed control of electrical drives. However, for time-varying disturbance, the observation precision of conventional ESO is undesired, which limits the speed tracking accuracy. Accordingly, this article proposes an enhanced speed controller for electrical drives based on adaptive switching high-order ESO (ASHESO). First, the critical parameters affecting the steady-state performance of ASHESO are determined according to frequency analytical results. Then, optimized observer gain is obtained by modifying a part of pole locations, which weakens the influence of noise on estimated state. Finally, an adaptive switching gain mechanism is proposed according to the closed-loop tracking error and the swiftness of dynamic response is maintained. The proposed speed controller has achieved high estimation accuracy for disturbance and strong immunity to measurement noise. The feasibility and effectiveness of the strategy is verified on a laboratory permanent magnet synchronous motor (PMSM) drive system. [ABSTRACT FROM AUTHOR]

The paper considers electrical drives control having a hierarchical cascaded structure. This structure has an inner current control loop and outer loops for speed and position control. The design of the control is performed using a discrete-time model of electrical drive. In all the loops, the discrete-time quasi sliding mode control is used for controller design because of its robustness to external and parametric matched disturbances (inherent to electrical drives) and the capability to ensure the desired dynamics. To enhance the robustness to disturbances, a nonlinear disturbance compensator is also implemented. The chattering in sliding mode is eliminated by using a new modified discrete-time super twisting control. The current and the speed controllers are designed for linear discrete-time first-order models, while the position controller is designed for a linear second-order discrete-time model. The axis position is measured by a mechanical sensor (encoder). The speed is estimated from the position measurements using Euler derivative approximation. Alternatively, it can be obtained by an observer. The proposed design is straightforward and results in high-performance, robust control with strong disturbance rejection capability and negligible overshoots. All theoretically obtained claims are demonstrated by experiments on an induction motor drive with a rotor field-oriented control structure. [ABSTRACT FROM AUTHOR]

Reference implementation of Digital Twins for electrical energy conversion systems is an important and open question in the industrial domain. Digital Twins can predict the future performance, behaviour, and maintenance needs of a complex system. Today the concept of Digital Twins is not only an emulation or simulation of the physical object along with its development history but also contains much information from the respective manufacturers and services. This paper presents the current state-of-the-art of Digital Twins in relation to some interesting novel applications from different fields of electrical engineering. The objective of the paper is to give an overview of the successful application of Digital Twins in electrical energy conversion systems, such as industrial robotics and wind turbines; to discuss trends in applications like electric vehicles; and to suggest new applications, such as telescopes. Special attention is paid to the possible application of Digital Twins in faults diagnostics and prognostics of electrical energy conversion systems. Successful implementation of Digital Twins in any electrical energy conversion system diagnostics and prognostics allows for low-cost maintenance, higher utilization of the individual devices and systems, as well as lower usage of material and human resources. A SWOT analysis was performed for Digital Twin applications in electrical energy conversion systems. The latter is a useful analysis technique that explores possibilities for new achievements or solutions to existing problems and makes decisions about the best path. [ABSTRACT FROM AUTHOR]

The performance of the conventional model predictive current control (MPCC) method is not without steady‐state ripples in electrical drives. Although some recently proposed MPCC methods have succeeded to mitigate this drawback, they have led to reductions in the dynamic speed response inherent to the conventional MPCC method. An improved MPCC is proposed here which would enhance the conventional MPCC method without any side effect on its merits. In this proposed method, three control strategies are presented for transient‐ and steady‐state operations. The first two strategies are applied to improve motor performance in the steady state, through calculating the voltage vector (VV) and its optimal duration to minimise ripples in both d–q ‐axis currents. The third strategy is applied in the transient‐state operation, where, instead of two VVs, an allowable non‐zero VV is applied throughout the control cycle to prevent dynamic response reduction caused by zero VV. The experimental results confirm the effectiveness of this proposed method in reducing torque ripples, flux ripples, and the stator current total harmonic distortion in relation to those obtained by the previous MPCC methods. [ABSTRACT FROM AUTHOR]

Two hybrid PWM methods are proposed in this paper for a pump drive based on three-level Neutral-Point Clamped (NPC) inverter. The envisaged PWM methods are aimed at reducing output voltage harmonic distortion. While the first PWM method incorporates suitable voltage injection to the carrier signals, the second PWM method incorporates voltage injection to both carrier and the modulating signals for controlling the NPC drive. Detailed harmonic analysis is presented using Double Fourier Integral Approach (DFIA) for both the hybrid PWM methods by separately identifying their basic unit cells, their boundaries that demarcates different regions of inverter drive. Complete analytical expressions for dc, fundamental, carrier and side-band harmonic components present in the output voltage of the NPC drive are presented for both the hybrid PWM methods. The proposed PWM methods are simulated using Matlab/Simulink and are experimentally validated using an induction motor driven pump load, following V/f control. Superiority of the hybrid PWM methods in comparison to the existing PWM methods are demonstrated with vTHD, weighted THD (vWTHD), iTHD, harmonic loss factor etc., supporting the envisaged PWM methods. [ABSTRACT FROM AUTHOR]

The industrial application of electric machines in variable‐speed drives has recently grown thanks to the development of microprocessors and power converters. Although three‐phase machines constitute the most common case, the interest of the research community is also focused on multiphase machines with more than three phases. The principal reason lies in the exploitation of their advantages such as reliability, better current distribution among phases or lower current harmonic in the converter, to name a few. Nevertheless, multiphase drive applications require the development of complex controllers to regulate the torque (or speed) and flux of the machine. In this regard, predictive current controllers have appeared as a viable alternative due to an easy formulation and high flexibility to incorporate different control objectives. It is found, however, that these controllers face some peculiarities and limitations in their use that require attention. This work attempts to tackle the predictive current control technique as a viable alternative for the regulation of multiphase drives, paying special attention to the development of the control technique and the discussion of the benefits and limitations. Case examples with experimental results using a symmetrical five‐phase induction machine with distributed windings are included to this end. [ABSTRACT FROM AUTHOR]

Incipient faults in electrical drives can corrupt overall performance of high-speed trains; however, they are difficult to discover because of their slight fault symptoms. By sufficiently exploiting the distribution information of incipient faults, this paper presents the reason why incipient faults cannot be detected by the existing fault detection and diagnosis (FDD) methods. Under principal component analysis (PCA) framework, we propose a new data-driven FDD method, which is named probability-relevant PCA (PRPCA), for electrical drives in high-speed trains. The salient strengths of the PRPCA-based FDD method are: 1) it can greatly improve the fault detectability; it is suitable for non-Gaussian electrical drives; 2) based on the improved fault detectability, it can achieve accurate fault diagnosis via support vector machine; and 3) it can be easily applied to electrical drives even if neither physical models or parameters nor expert knowledge of drive systems is given; and it is of highly computational efficiency that can meet requirements on the real-time FDD. A set of experiments on a dSPACE platform-based traction system of the CRH2A-type high-speed train are carried out to demonstrate the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

Parameter estimation of the nonlinear electronic schemes, including inductances, capacitances, resistances, and switches represents a nontrivial problem in the "power electronics" and "electrical drives" courses. Difficulties could be observed during solutions of electrical circuits, which describe the behavior of electric motors in drives, and various electronic appliances are being used in power electronics. This situation is a result of complicated analytical approaches aiming to solve nonlinear ordinary differential equations describing the occurring processes. A typical student has a significant problem in attaining the analytical results. Various methods of linearization nonlinear elements permitting to obtain roughly analytical solutions and simplified solution were applied over the past. Nowadays, coarsely obtained results are not acceptable as a rule. As a result, smart simulation based on PSIM, MATLAB Simulink, and WOLFRAM Mathematica giving excellent opportunity for accurate answers are recommended. All software programs represent undoubtedly important and extremely accurate approaches. However, only numerical results are provided and are not capable of solution's generalization. It seems that in the Power Electronics and Electrical Drives courses, a wide submission could obtain methods of numerical nomograms with dimensionless representation of input-output parameters. Dimensionless approach allows significant diminishing of a number of decisive parameters and simplifies calculation, whereas keeping acceptable precision of results, as well as a possibility of outcome's generalization and representation variables trends in a wide range of input parameters. The likely objects of analysis may be, for example, output characteristics of DC motors fed by controllable and uncontrollable n-phase rectifiers, resistive rectifier losses and motor's efficiency, average and root mean square currents or voltages in electronic circuits, total harmonic distortion, and others. Long-time practice of these approaches approved their usefulness, productivity, and helpfulness. [ABSTRACT FROM AUTHOR]

The present paper deals with the concept of a costeffective power-assistant wheelchair. An analysis of the market situation and recent technical achievements is done at the beginning. On its basis, a set of solutions suitable for the development of such wheelchairs has been composed. It is shown that the key features of the considered concept are: segmented electrical motor and drive, sectioned battery pack, modular charger and an ANN matrix that provides easy and intuitive interfacing of sensor networks, pseudo-bionic feedbacks and the decision-making unit. Within the scope of the paper, a 3D model has been developed and 3D modelling has been conducted. As a result, certain drawbacks in the design and placement of elements have been found and a modification of the concept has been proposed. [ABSTRACT FROM AUTHOR]

Electrical drives are more and more used in transportation applications and industrial process because of their effective cost and high efficiency. They have become critical components and therefore any fault or failure affecting them may seriously endanger the users and/or induce huge financial costs. As a consequence, early detection and isolation of these faults is recommended if not mandatory to enhance the safety, the availability, the reliability and improve the maintenance and the operational efficiency. Analytical Redundancy Relations (ARR) are used to compute to structured residuals on which the diagnosis is based. To smooth the residuals and enhance the fault detection capability, a sliding mode observer is developed to compute the derivatives. The analysis of the residuals reveals that they are Gaussian signals with a change in the mean. The comparison between the two-sigma and the two-sided CUSUM methods has shown that the latter is more efficient to compute the thresholds. Therefore with the two-sided CUSUM, the rotor resistance fault is detected with no false alarm. Moreover it is proved that the fault diagnosis is robust to the load torque variations. Beside, thanks to the residual, a load torque estimator is also developed. Extensive simulation results prove the validity of our approach. [ABSTRACT FROM AUTHOR]

The active control of wave energy converters with oil-hydraulic power take-off systems presents important demands on the electrical drives attached to their pumps, in particular on the required drive accelerations and rotational speeds. This work analyzes these demands on the drives and designs reliable control approaches for such drives by simulating a wave-to-wire model in a hardware in-the-loop simulation test rig. The model is based on a point absorber wave energy converter, being the wave, hydrodynamic and oil-hydraulic part simulated in a computer that sends and receives signals from the real embedded components, such as the drive generator, controller and back-to-back converter. Three different control strategies are developed and tested in this test rig and the results revealed that despite the drive limitations to acceleration levels, well above 1 × 10 4 rpm/s, these do not significantly affect the power take-off efficiency, because the required acceleration peaks rarely achieve these values. Moreover this drive is much more economical than an oil-hydraulic and equivalent one that is able to operate at those peaks of acceleration. [ABSTRACT FROM AUTHOR]

The potential benefit of coupling hydraulic and electronic regulation to maximize the energy production of a cross-flow turbine in hydraulic plants is analyzed and computed with reference to a specific case. Design criteria of the cross-flow turbine inside hydraulic plants are first summarized, along with the use of hydraulic regulation in the case of constant water head and variable discharge. Optimal turbine impeller rotational speed is derived, and traditional as well as innovative systems for electrical regulation are presented. A case study is analyzed to evaluate the potential energy production according to the expected monthly mean flow distribution and two possible choices: CFT1 with the hydraulic regulation, and CFT2 with coupled hydraulic and electric regulations. The return time of capital investment (RCI), computed for both the solutions, showed that the CFT2 solution provides an increment of the total produced energy, along with an increment of approximately 30% of the corresponding RCI. The sensitivity of the results to water head variability and to possible different pipe design criteria in future scenarios is finally discussed. [ABSTRACT FROM AUTHOR]

The variable displacement oil-hydraulic pumps for the Power Take-Off (PTO) of wave energy converters must work above 80% of maximum displacement in order to have an overall efficiency of approximately 94.5%. This is achieved by controlling their rotational speed when the oil-hydraulic power fluctuates in time. Three speed control strategies have been presented, the first fixing the maximum possible speed in each sea state, the second by slowly varying the pump speed between speed peak values and average ones, and the third by working with highly variable speed reference values. The worst pump efficiency is achieved with the first strategy while the best one with the third strategy. However, the first has less impact than the third one in the pump lifecycle. On the other hand, the second strategy is used to make a trade-off between pump efficiency and lifecycle. However, this paper presents a fourth speed control strategy, which is a hybrid of the second and third strategies. So, the objectives of this paper were to know if these strategies are implementable in a test rig and also on a new PTO concept and determining what modifications should be introduced in these PTO strategies and hardware. This paper also contributes with the application of new methodologies in this field of research for the modelling of pump efficiency and pressure control, such as Neuro-Fuzzy modelling and Fuzzy Logic control systems. [ABSTRACT FROM AUTHOR]

This paper presents a low cost, simple, and highly accurate resolver-to-digital converter (RDC) for electrical drive applications based on an integrated software approach, thus allowing a significant reduction of hardware components count with significant improvements in terms of reliability, reduction of fault rate, and susceptibility to electromagnetic interference (EMI). Particular attention has been addressed to cost which is 25% off over conventional RDC. Simulations and experimental tests confirm the high quality of the proposed system. [ABSTRACT FROM PUBLISHER]

This study proposes a speed control scheme to improve the speed control performance of the permanent magnet synchronous motor (PMSM) servo system which is equipped with an absolute optical encoder. A two‐degree‐of‐freedom proportional integral speed controller is utilised to make a good compromise between tracking and disturbance rejection performance. Properties of the controller are analysed using the root locus method. As the controller performance is prone to be deteriorated by speed measurement noise and time delay, a novel Kalman filter is used to optimise the speed measurement process. The proposed Kalman filter modifies gain matrix based on the position residue error. By this means it improves dynamic response speed without damaging steady‐state precision. Experimental researches are carried out on a 5.2 kW PMSM drive prototype and the results prove the feasibility and effectiveness of the proposed scheme. [ABSTRACT FROM AUTHOR]

This paper presents a model predictive torque control method for electrical drive systems. A two-step prediction horizon is achieved by considering the reduction of the torque ripples. The electromagnetic torque and the stator flux error between predicted values and the references, and an over-current protection are considered in the cost function design. The best voltage vector is selected by minimising the value of the cost function, which aims to achieve a low torque ripple in two intervals. The study is carried out experimentally. The results show that the proposed method achieves good performance in both steady and transient states. [ABSTRACT FROM AUTHOR]

This paper deals with dynamical modelling and modal identification of a special class of electromechanical systems: the multi-mass electrical drives. The aim of the work is to investigate the usefulness and the performance of the continuous wavelet transform (CWT) for the estimation of modal parameters, such as damping ratios and natural frequencies of these electromechanical systems. For this investigation, two models of elastic drive systems are considered: the two-mass and the three-mass models. The modal analysis identification using CWT is compared to the Hilbert–Huang transform technique and evaluated in terms of accuracy and ability to estimate modal parameters with different inputs, aptitude to distinguish several modes especially in the case of closely spaced modes and resistance to noisy conditions. In view of the results of the study, the advantages and shortcomings of each technique are presented and discussed. [ABSTRACT FROM AUTHOR]

The electric machines are the elements most used at an industry level, and they represent the major power consumption of the productive processes. Particularly speaking, among all electric machines, the motors and their drives play a key role since they literally allow the motion interchange in the industrial processes; it could be said that they are the medullar column for moving the rest of the mechanical parts. Hence, their proper operation must be guaranteed in order to raise, as much as possible, their efficiency, and, as consequence, bring out the economic benefits. This review presents a general overview of the reported works that address the efficiency topic in motors and drives and in the power quality of the electric grid. This study speaks about the relationship existing between the motors and drives that induces electric disturbances into the grid, affecting its power quality, and also how these power disturbances present in the electrical network adversely affect, in turn, the motors and drives. In addition, the reported techniques that tackle the detection, classification, and mitigations of power quality disturbances are discussed. Additionally, several works are reviewed in order to present the panorama that show the evolution and advances in the techniques and tendencies in both senses: motors and drives affecting the power source quality and the power quality disturbances affecting the efficiency of motors and drives. A discussion of trends in techniques and future work about power quality analysis from the motors and drives efficiency viewpoint is provided. Finally, some prompts are made about alternative methods that could help in overcome the gaps until now detected in the reported approaches referring to the detection, classification and mitigation of power disturbances with views toward the improvement of the efficiency of motors and drives. [ABSTRACT FROM AUTHOR]

A new method for flux weakening of either surface permanent magnet or buried permanent magnet machines is proposed in this article. This method, termed the double-bridge winding switching technique, can reliably double the field-weakening speed range of permanent magnet motors. This feature is significant since extending the constant power speed ratio of surface permanent magnet machines is a particularly challenging task due to the presence of low-permeability surface magnets and the resulting low machine inductance. In this method of field weakening, the usual three-phase motor windings are separated into two portions, and each portion is connected to an inverter. The article discusses the stator winding arrangement, which allows the normal and high-speed operation of the machine along with the constant output power and reports simulation results taken from finite-element analysis. [ABSTRACT FROM AUTHOR]

Abstract: Performance optimization of electrical drives implies a lot of degrees of freedom in the variation of design parameters, which in turn makes the process overly complex and sometimes impossible to handle for classical analytical optimization approaches. This, and the fact that multiple non-independent design parameter have to be optimized synchronously, makes a soft computing approach based on multi-objective evolutionary algorithms (MOEAs) a feasible alternative. In this paper, we describe the application of the well known Non-dominated Sorting Genetic Algorithm II (NSGA-II) in order to obtain high-quality Pareto-optimal solutions for three optimization scenarios. The nature of these scenarios requires the usage of fitness evaluation functions that rely on very time-intensive finite element (FE) simulations. The key and novel aspect of our optimization procedure is the on-the-fly automated creation of highly accurate and stable surrogate fitness functions based on artificial neural networks (ANNs). We employ these surrogate fitness functions in the middle and end parts of the NSGA-II run in order to significantly reduce the very high computational effort required by the optimization process. The results show that by using this hybrid optimization procedure, the computation time of a single optimization run can be reduced by 46–72% while achieving Pareto-optimal solution sets with similar, or even slightly better, quality as those obtained when conducting NSGA-II runs that use FE simulations over the whole run-time of the optimization process. [Copyright &y& Elsevier]

The Brushless Doubly Fed Reluctance Machine (BDFRM) is an emerging alternative for variable speed drive systems, providing a significant downsizing of the power electronics converter. This paper proposes a new view on the machine equations, allowing the reuse of the standard control system design for conventional synchronous and asynchronous machines: a cascade control system with an inner current control- and outer speed control loop. The assumptions and simplifications made on the machine model allow for a simple, model-based approach to set the controller gains in a brushless doubly fed machine drive system. The cascade control scheme is combined with an Unscented Kalman Filter as a state observer, capable of estimating the load torque and losses. The performance of the proposed control system design is checked in simulation and tested in real-time on a low power BDFRM prototype. [ABSTRACT FROM AUTHOR]

Space vector modulation (SVM), with its many advantages over classical pulsewidth modulation technique (PWM), is gaining in popularity. However, only deterministic SVM exists. Randomized PWM (RPWM) with its cleaner harmonic spectrum is gaining interest for industrial applications required to meet electromagnetic compatibility standards. Inverter switching losses are optimized and life expectancy can be increased using a suitable discontinuous modulation technique. Here, we present, a discontinuous and randomized-modulation technique based on space vector calculation, intended for electric-drive oriented hybrid electric vehicle, which has the advantages of SVM and clean harmonic-spectrum and the efficiency of RPWM and DPWM, respectively. [ABSTRACT FROM AUTHOR]

Field-oriented control (FOC) has proven effective for controlling ac drives with good dynamic performance. However, operation at low-switching frequencies and the sensitivity of traditional feedforward loops to system parameters pose severe limitations on the achievable performance and require a tedious tuning procedure. In this paper, we present a systematic cascade explicit model predictive control framework for the FOC of electrical drives, resolving the aforementioned issues while being sufficiently simple to be widely implemented on various ac drive systems. The resulting closed-loop system exhibits high dynamic performance for all operating points, even at low-switching frequencies. We present experiments with a permanent-magnet machine and an induction motor, demonstrating the practical feasibility and the merits of the proposed framework over traditional controller designs for electrical drives. [ABSTRACT FROM AUTHOR]

Abstract: This paper deals with direct field oriented control of linear induction motor drives. After elaborating the inductor and induced part space-vector equations of the LIM in several reference frames, some induced part flux models taking into consideration the end effects are presented. In particular, the so called “voltage model” based on the inductor equations in the inductor reference frame and the “current model” based on induced part equations in both the inductor and induced part flux linkage reference frames are deduced and compared to the rotational induction machine counterpart. Afterwards, after a proper tuning of such models based on both FEA (finite element analysis) and experimental measurements, some simulation and experimental tests have been performed. Simulations show that the proposed flux models taking into consideration the LIM end effects permit the drive to achieve better dynamic performance. Moreover, some comparative experimental results, adopting both the current and the voltage flux models, have been performed on a suitably devised test set-up. [Copyright &y& Elsevier]

Compared with neutral-point-clamped (NPC) inverters, active NPC (ANPC) inverters enable a substantially increased output power and an improved performance at zero speed for high-power electrical drives. This paper analyzes the operation of three-level (3L) ANPC inverters under device failure conditions, and proposes the fault-tolerant strategies to enable continuous operating of the inverters and drive systems under single and multiple device open- and short-failure conditions. Therefore, the reliability and robustness of the electrical drives are greatly improved. Moreover, the proposed solution adds no additional components to standard 3L-ANPC inverters; thus, the cost for robust operation of drives is lower. Simulation and experiment results are provided for verification. Furthermore, a comprehensive comparison for the reliability function of 3L-ANPC and 3L-NPC inverters is presented. The results show that 3L-ANPC inverters have higher reliability than 3L-NPC inverters when a derating is allowed for the drive system under fault-tolerant operation. If a derated operation is not allowed, the two inverters have similar reliability for device open failure, while 3L-NPC inverters have higher reliability than 3L-ANPC inverters for device short failure. [ABSTRACT FROM AUTHOR]

This paper focuses on sensor fault detection and isolation (FDI) for electrical systems. A new, easy and fast FDI algorithm is proposed, keeping system performances unchanged under certain faulty sensor conditions when reconfigurations are available. The proposed FDI algorithm is derived from a parity space approach and is based on temporal redundancies. It is insensitive to parameter variations since no model knowledge is required. Also, it is available for a large class of electrical systems such as single- or three-phase power converters, dc or ac electrical drives, etc. Moreover, the residual threshold used for FDI is accurately defined and is suitable for the whole operating range. Simulations results are presented to illustrate the good functionality of theoretical developments. Numerous experimental results are also shown to validate the effectiveness of the proposed FDI algorithm and to highlight its advantages for the control of electrical systems. [ABSTRACT FROM AUTHOR]

A comprehensive vibration synthesis process for synthesizing the electromagnetically excited acoustic vibrations in electric drives is explored in this paper. The study is performed on a traction drive for a hybrid electric vehicle. The work derives and highlights several key aspects for modeling and assessing the acoustic characteristics of electric drives. The influence of different force excitation shapes on the resulting overall vibration is shown, and the importance of including tangential forces in the synthesis process is highlighted. The resulting operational deflections at selected operating points are analyzed and compared to measurements. The load level dependence of the noise components is investigated. Finally, acoustic maps are introduced as a means to display and compare predicted and measured acoustic characteristics of variable-speed drives. The synthesized acoustic maps are validated by comparison against their measured counterparts. [ABSTRACT FROM AUTHOR]

A position sensorless control method for PM synchronous motors is proposed in this paper. It relies on the magnetic saliencies to estimate the position of the rotor. In usual sensorless methods, a signal is injected in the \alpha\beta or dq components. In the proposed method, the signal is injected in the zero-sequence component. The high-frequency inherent zero-sequence component produced by a space-vector pulsewidth modulator (PWM) is used. In this way, no modification is required in the PWM, even at zero voltage, and the injected signal does not interact with the current controller. The response to the injected signal is obtained by a simple current derivative sensor. With this method, the position can be evaluated with high dynamics and with a high signal-to-noise ratio. The performance of the proposed method is evaluated with an experimental setup, using standard industrial servomotors with surface-mounted magnets. [ABSTRACT FROM AUTHOR]

A key point in simulation and control of the electrical drives is the accuracy of the available dynamic model. Especially for the squirrel-cage induction machines, the exact determination of the rotor's parameters i.e. resistances and inductances is not a straightforward task because these parameters cannot be determined through direct measurements during the drive's operation. Several techniques are used to obtain estimates for the machine's parameters as well as to obtain estimates for the process parameters such as flux-linkages components. Among these techniques, the observer-based methods are widely used in control engineering. The finite elements methods (FEM) are commonly used in design. In this work, the authors implemented both methods to determine the process parameters for a given single/two-phase induction machine. To validate the estimations, the results were compared with the measurements. [ABSTRACT FROM AUTHOR]

Abstract: The aim of this paper is to propose a formal approach to derive direct torque control (DTC). Using the theory of variable structure control (VSC) and in particular the sliding mode approach, a detailed analysis of the possible operating regions for both induction and brushless machines are described. This analysis allows to clarify the consequences of a specific switching table in terms of control stability. In particular, DTC is presented and analysed as a special case of sliding mode strategy. Sliding mode existence conditions are verified and the most critical operating regions are obtained. The proposed formal analysis allows to define more sophisticated switching tables which assure stable operation. [Copyright &y& Elsevier]

Double frequency tests are used for evaluating stator windings and analyzing the temperature. Likewise, signal injection on induction machines is used on sensorless motor control fields to find out the rotor position. Motor Current Signature Analysis (MCSA), which focuses on the spectral analysis of stator current, is the most widely used method for identifying faults in induction motors. Motor faults such as broken rotor bars, bearing damage and eccentricity of the rotor axis can be detected. However, the method presents some problems at low speed and low torque, mainly due to the proximity between the frequencies to be detected and the small amplitude of the resulting harmonics. This paper proposes the injection of an additional voltage into the machine being tested at a frequency different from the fundamental one, and then studying the resulting harmonics around the new frequencies appearing due to the composition between injected and main frequencies. [ABSTRACT FROM AUTHOR]

This paper deals with a new diagnosis method for detecting bearing faults (BFs) based on frequency response analysis. For non-rigid multi-mass systems with dominant mechanical resonance frequencies, the frequency response has to be calculated during the commissioning of the plant for reasons of safety and controlling. This task can be achieved by measuring two control variables of the drive which are both affected by BFs. This paper proposes that the measurement of the frequency response is a suitable strategy for detecting incipient BFs. In doing so, a two-channel analysis method for bearing damage diagnosis without additional sensors is developed. Deviations from the frequency response of the healthy state serve as indicators for a present BF. As the measurement of the two signals can be carried out during normal operation of the plant, online BF diagnosis is achieved. For the investigated two-inertia system, single-point bearing defects on the inner and outer raceways of rolling bearings and generalized roughness faults are within the scope of this paper. [ABSTRACT FROM AUTHOR]

Motor-current-signature analysis has been successfully used in induction machines for fault diagnosis. The method, however, does not always achieve good results when the speed or the load torque is not constant, because this causes variations on the motor-slip and fast Fourier transform problems appear due to a nonstationary signal. This paper proposes a new method for motor fault detection, which analyzes the spectrogram based on a short-time Fourier transform and a further combination of wavelet and power-spectral-density (PSD) techniques, which consume a smaller amount of processing power. The proposed algorithms have been applied to detect broken rotor bars as well as shorted turns. Besides, a merit factor based on PSD is introduced as a novel approach for condition monitoring, and a further implementation of the algorithm is proposed. Theoretical development and experimental results are provided to support the research. [ABSTRACT FROM AUTHOR]

The use of ac electrical machines in controlled electrical drive applications is reviewed. The major types of electrical machines are briefly summarized to set the context and establish the physical basis for the control techniques used. Machine properties, which are the key to successful control, can be obscured by the necessary mathematics required for machine analysis and control scheme derivations. The main focus of this paper is on control techniques which are being applied to make ac drives a rapidly growing area. Development of the control is discussed, with concentration on recent trends suitable for practical applications in the industry with good dynamic behavior. A particular feature is the increasing importance of speed or position sensorless techniques. [ABSTRACT FROM AUTHOR]

A fully integrated board for resolver-to-digital conversion is proposed in this paper. It is based on a combined analog/digital circuit, which allows one to track the shaft angle of a standard resolver in a digital form. Furthermore, the board also provides the feeding signal for the resolver-rotor circuit. All the tuning and configuration settings, which allow one to adapt different kind of resolvers to the proposed system, can be easily implemented directly on the board. The final assembly is a compact low-cost resolver-to-digital converter. The entire board design and implementation are described in this paper. In addition, several tests at different resolver speeds have been performed for validation. [ABSTRACT FROM AUTHOR]

In the case of long-stator linear drives, unlike rotative drives for which speed or position sensors are a single unit attached to the shaft, these sensors extend along the carriage-way, becoming a costly part of the system. Therefore, sensorless methods are of higher concern in linear motors than in rotative ones. For long carriageways, the stator is usually divided in several independently fed segments in order to reduce the reactive power and to allow more than one vehicle to move on the same carriageway. This arrangement presents additional challenges in the implementation of sensorless methods because the position-dependent variables [as the electromotive force (EMF)] of each segment are nonperiodic signals. Moreover, the acquired speed and position information from one segment must be synchronized with the adjacent one when the mover passes over a segment transition. In this paper, a method to get a continuous estimation of the speed and position, even during the transition between segments, is proposed. This method uses an EMF observer for each active segment (i.e., where the mover is currently located, and the subsequent segment). Then, based on the addition of the observed EMF, a single speed and position observer is implemented for the mover. Using an experimental setup, validation results are attained and presented. [ABSTRACT FROM AUTHOR]

Abstract: This article presents a new speed and flux estimation algorithm for high-performance direct torque control (DTC) induction motor drives based on model reference adaptive systems (MRAS) observers using linear artificial neural networks (ANNs). Two completely new improvements of MRAS speed and flux observers are presented here: the first is a solution to the open-loop integration problem in the reference model, based on the voltage model of the induction machine, by means of a new adaptive neural integrator, the second is the employment of a new adaptation law in the ANN adaptive model, based on the total least-squares (TLS) technique. In particular, the adaptive neural integrator is based on two adaptive noise filters which completely cancel any DC drift present in the voltage or current signals to be integrated. This neural integrator does not need any a priori training of its two only neurons, adapting itself on-line. With regard to the ANN-based adaptive model, since the most suitable least-square technique to be used for training is the TLS technique, here the neuron is trained on-line by means of a TLS EXIN algorithm which is the only neural network able to solve a TLS problem recursively. Also the TLS EXIN algorithm does not require any a priori training, since it adapts itself recursively on-line. Moreover, to improve the dynamical performances of the speed loop of the drive, the adaptive model has been used as predictor, i.e. without any feed-back between its outputs and its inputs. The sensorless algorithm has been verified experimentally both on the classic DTC technique and on the DTC-SVM (space vector modulation), by adopting a proper test set-up. The speed observer has been tested in the most challenging operating conditions. The experimental results show that the dynamical performances of the sensorless drive are comparable or even better than those obtained with the corresponding DTC drives with encoders as for the medium to high-speed ranges. As for low-speed ranges, the presented sensorless DTC algorithm outcomes the performance presented in the literature for MRAS systems, thus permitting to have an accurate estimation equal or better than that obtainable with more complex observers. Finally, experimental results show that the MRAS speed observer is robust to load torque perturbations and permits zero-speed operation at no-load conditions. [Copyright &y& Elsevier]

This paper presents a new model reference adaptive system (MRAS) speed observer for high-performance field-oriented control induction motor drives based on adaptive linear neural networks. It is an evolution and an improvement of an MRAS observer presented in the literature. This new MRAS speed observer uses the current model as an adaptive model discretized with the modified Euler integration method. A linear neural network has been then designed and trained online by means of an ordinary least-squares (OLS) algorithm, differently from that in the literature which employs a nonlinear backpropagation network (BPN) algorithm. Moreover, the neural adaptive model is employed here in prediction mode, and not in simulation mode, as is usually the case in the literature, with a consequent quicker convergence of the speed estimation, no need of filtering the estimated speed, higher bandwidth of the speed loop, lower estimation errors both in transient and steady-state operation, belier behavior in zero-speed operation at no load, and stable behavior in field weakening. A theoretical analysis of some stability issues of the proposed observer has also been developed. The OLS MRAS observer has been verified in numerical simulation and experimentally, and in comparison with the BPN MRAS one presented in the literature. [ABSTRACT FROM AUTHOR]

Controlled dynamometers are normally electrical machines used to provide a loading characteristic to prime mover drive trains, normally for the purpose of testing and validation. This paper describes a new dynamometer control strategy that can practically emulate the linear or non-linear dynamics of modelled mechanical loads. Since the real load dynamics are preserved, it is ideal for the experimental validation of robust or adaptive control strategies. Experimental results showing the effectiveness of the proposed dynamometer control approach are presented. [Copyright &y& Elsevier]

In this paper, a control strategy for speed control of induction motors with field orientation is proposed. The proposed method adjusts the output voltage and frequency of the converter to operate the motor at the desired speed with maximum torque per ampere at all load torques keeping the torque angle equal to 90°. A comparison between the performance characteristics of a 2 hp induction motor using three methods of speed control is presented. These methods are the proposed method, the direct torque control method and the constant V/f method. The comparison showed that better performance characteristics are obtained using the proposed speed control strategy. A computer program, based on this method, is developed. Starting from the motor parameters, the program calculates a data set for the stator voltage and frequency required to obtaining maximum torque per ampere at any motor speed and load torque. This data set can be used by the digital speed control system of induction motors. [Copyright &y& Elsevier]

Power density is one of the most significant issues in designing electromagnetic interference (EMI) filters for power electronic-based applications. Therefore, an effective EMI filter design should consider both its capability to ensure the compliance with the related EMI standard limits and the possibility to build it by suitable components leading to the most compact configuration as well. To fulfill the above requirements, in this paper, an automatic procedure to get an improved design of EMI filters is proposed. Specifically, according to the proposed method, the values of filter parameters for both common mode (CM) and differential mode (DM) sections are selected by a genetic algorithm (GA) exploiting the in-circuit insertion loss, thus obtaining a more effective design. Besides, the components that set up the filter are selected by a rule-based procedure searching through a suitable database of commercial components to identify those allowing for the maximum power density. Experimental tests were performed using an inverter-fed induction motor drive as a case study, and the obtained results have demonstrated the validity of the proposed approach. [ABSTRACT FROM AUTHOR]

The development and the validation of an averaged-value mathematical model of an asymmetrical hybrid multi-level rectifier is presented in this work. Such a rectifier is composed of a three-level T-type unidirectional rectifier and of a two-level inverter connected to an open-end winding electrical machine. The T-type rectifier, which supplies the load, operates at quite a low switching frequency in order to minimize inverter power losses. The two-level inverter is instead driven by a standard sinusoidal pulse width modulation (SPWM) technique to suitably shape the input current. The two-level inverter also plays a key role in actively balancing the voltage across the DC bus capacitors of the T-type rectifier, making unnecessary additional circuits. Such an asymmetrical structure achieves a higher efficiency compared to conventional PWM multilevel rectifiers, even considering extra power losses due to the auxiliary inverter. In spite of its advantageous features, the asymmetrical hybrid multi-level rectifier topology is a quite complex system, which requires suitable mathematical tools for control and optimization purposes. This paper intends to be a step in this direction by deriving an averaged-value mathematical model of the whole system, which is validated through comparison with other modeling approaches and experimental results. The paper is mainly focused on applications in the field of electrical power generation; however, the converter structure can be also exploited in a variety of grid-connected applications by replacing the generator with a transformer featuring an open-end secondary winding arrangement. [ABSTRACT FROM AUTHOR]