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Analysis, simulation, implementation and results of a new kiln drive system consisting of two AC motors of 315 kW each, on an existing common tooth gear, as a new contribution for the operational optimisation of rotating kilns, are presented in this study. Two separate inverter units control the two asynchronous motors with a common rectifier. This study also illustrates how backlash problems on tooth gear and maintenance needs are eliminated while reducing operational costs, down-times and energy consumption, by applying contemporary technology, including power electronics and dynamic performance in control systems.

A wind gust can cause severe dynamic conditions that affect the operational behavior of the whole doubly fed induction generator (DFIG) wind energy conversion system and, as a result, the quality of power exchanged with the grid. In addition, it can cause great disturbances to critical system's variables with possible damages to the system's construction—to mechanical or electrical part. The knowledge of DFIG reaction in such conditions is useful for both protection issues and the risk assessment concerning system's tolerance, maintenance costs and revenue losses, because of the disconnection from the grid. In this paper, a quantitative and qualitative behavior analysis of a 2 MW DFIG wind energy conversion system under a wind gust and converter faults, which has been carried out via simulation, is presented. The pitch controller parameters impact to its behavior, when a gust appears, has been investigated. Copyright © 2015 John Wiley & Sons, Ltd.

This paper introduces an improved signal processing technique of zero sequence voltage (ZSV) with the scope of position sensorless commutation of a BLDC motor drive system. Rotor position information is extracted in the proposed technique from ZSV. This signal includes all time intervals where back electromagnetic force (EMF) zero crossings (ZCs) occur, from which the commutation instants are determined. This technique exploits maximally flat group delay of Bessel low-pass filters for switching noise suppression. This attribute leads to a speed-independent time displacement of ZSV. The fundamental frequency of ZSV is determined through a median-filtering algorithm, which is required for a dynamic rate limiter that eliminates erroneous ZCs. In sequence, a pulse train is generated by the detected ZCs of the emerged signal and properly shifted to determine the correct commutation instants. The proposed technique ensures a wide operational speed range for the drive system. A theoretical analysis of the drive system is presented, considering a BLDC motor with nonideal back-EMF. Experimental results presented in this paper validate the effectiveness and robustness of the proposed position sensorless commutation technique under various operational conditions.

The principal objective of this paper is to demonstrate the capability of high speed measurement and acquisition equipment design and build in the laboratory at a very low cost. The presented architecture employees highly integrated market components eliminating thus the complexity of the hardware and software stack. The key element of the proposed system is a Hi-Speed USB to Serial/FIFO development module that is provided with full software and driver support for most popular operating systems. This module takes over every single task needed to get the data from the A/D to the user software gluelessly and transparently, solving this way the most difficult problem in data acquisition systems which is the fast and reliable communication with a host computer. Other ideas tested and included in this document offer Hall Effect measuring solutions using some excellent features and very low cost ICs widely available on the market today.

In this paper, the operation of a wind energy conversion system (WECS) incorporating a Double-Fed Induction Generator (DFIG), under various wind speeds and faulty conditions, is investigated through simulation. In this study the simulation of such a system (DFIG-WECS) was held by using the software Matlab/Simulink.. The simulation results are presented and evaluated for the issues of fault diagnosis and identification. More specifically, a DFIG-WECS has been simulated under various wind speeds and when a short-circuit occurs in the back-to-back converter and in the DC link from the point of view of these issues. In this work, it has been concluded that the investigated faults have caused a specific and unique harmonic content in grid, rotor and stator phase currents, which could be used for fault diagnosis and identification.

A novel monitoring system, designed to detect open-circuit (OC) faults that occur in the matrix converter (MC) topology, is proposed in this work. In this monitoring system, a new diagnosis method is implemented which is based on the discrete wavelet transform analysis of the measured output current waveform. In order to ensure the effectiveness of the proposed method and its resistivity to erroneous fault detections, a fuzzy expert system is used in the designed monitoring system. The main advantages of the proposed method are that the implementation cost is minimized because no extra sensors are used and that no information from the control algorithm about the modulation parameters or the applied pulse sequence is required, reducing its implementation complexity and facilitating a more modular design. Additionally, it can be easily adapted to modified matrix topologies. A simple and robust method for the localization of the open-circuited transistor(s) within the identified faulty leg is also proposed. The proposed techniques are validated by simulation and experimental tests. The remedial operation of MC drives after the occurrence of an OC fault by using a redundant leg is also studied. The use of carrier-based modulation methods for this operation is experimentally validated, and related issues are discussed.

Summary A novel model of a variable-speed drive system, consisting of a three-phase induction machine fed by a matrix converter (MC) including its auxiliary circuits, is proposed in this paper. The main novelty of this model lies in the combination of a MC model created in the Matlab/Simulink environment with a finite element method model of an induction machine. The combined operation of these two components as an integrated model allows the detailed simulation of both the MC's and the induction machine's operation. The main advantage of this model is that the introduction of various manufacturing asymmetries and faults, both mechanical and electrical, in the induction machine structure is greatly facilitated. In that way, the created model can be used in order to examine in detail the consequences of these asymmetries or faults to the drive system's operational behavior. Additionally, it can be used for the development and/or evaluation of diagnosis methods for the detection of these faults under different operational conditions using motor current signature analysis, magnetic flux, speed or torque spectrum analysis and other methods. Copyright © 2013 John Wiley & Sons, Ltd.

Fault diagnosis in electromechanical drives has been widely investigated over the last decades, and many diagnostic methods have been proposed based on the reported faults. Additionally to already published works which have dealt with gear faults inside low reduction ratio gearboxes, this paper aims to present a simple and effective method for the early diagnosis of evolving faults in a high reduction ratio gear transmission system used in cement kiln drives. The under study system basically consists of a three-phase induction motor mechanically connected to a gearbox. The output shaft of the gearbox drives a gear pinion which, in turn, rotates a girth gear rim surrounding the cement kiln. The identification of mechanical vibrations due to backlash phenomena appearing between the pinion gear and the girth gear rim of the kiln is realized using the motor current signature analysis and processing the motor electromagnetic torque. The proposed diagnostic method is presented, analyzing the experimental results from an under-scale laboratory simulating system.

In this paper, the behaviour of a wind energy conversion system that uses the structure of Doubly-Fed Induction Generator (DFIG) under faulty conditions is presented. DFIG consists of an asynchronous machine, in which the stator is connected directly to the grid and its rotor is connected to the grid via two electronic power converters (back-to-back converter). In the three-phase rectifier and the inverter with IGBTs the Pulse Width Modulation (PWM) technique is used. DFIG is analysed and simulated under faulty conditions in the environment of Matlab/Simulink. The faults that are investigated in this work take place in the part of the back-to-back converter (either in the rectifier or in the inverter). More specifically, it is investigated how DFIG reacts when an open circuit happens in two IGBTs of the rectifier or of the inverter. Also, the results of Fourier analysis of some important system variables in these faulty conditions are presented and an identification of these faults is done.

In this paper the design and the operation of the drive system in a Fuel Cell Electric Vehicle (FCEV) is presented. The system consists of a Proton Exchange Membrane Fuel Cell (PEMFC) stack, an interleaved boost converter, battery pack connected via a bidirectional buck-boost converter and a brushless DC motor (BLDC) driven by a three phase inverter. A basic analysis of each component of the investigated system is presented. The main objective of this paper is to manage the energy transfer from the PEMFC stack to the DC bus based on wide high efficiency range. A battery pack is used for reducing the size of the stack and thus the cost, with by which regenerative braking is also achieved. In order to testify the nonlinear V-I characteristic curve of the PEMFC system experiments have been carried out. The performance of the overall system in steady state is studied via simulation in MATLAB/SIMULINK software. Two operating scenarios have been investigated. In the first, PEMFC stack and battery pack provide maximum power to the BLDC motor, while in the second, regenerative braking is accomplished via the bidirectional buck-boost converter to the battery pack by changing the control logic of the three phase inverter. Experiments have been carried out to validate the performance of the system at full load at steady state.

The use of a dual electromechanical drive is a well-established and an efficient solution especially when high-power systems are considered. A very important requirement in such systems is the accomplishment of a load balance between the two drives in order to prevent a potential overloading of the one drive in relation to the other one. Additionally, the appearance of mechanical oscillations must be avoided as it will be catastrophic for the mechanical equipment, particularly in the case of mechanical resonance. In this paper, a general analysis of the existing control strategies already used in dual ac drives is being realized first, and a new hybrid control method is proposed based on the need of equal load and power distribution between the two drives. The efficiency of the proposed method is examined for a cement kiln which is a typical system whose large size and imperative uninterrupted operation enforce the use of such a dual drive. A theoretical analysis is being realized developing a corresponding mathematical model and using Matlab/Simulink. Finally, the proposed method is verified using a low-power laboratory system which has been appropriately designed to experimentally simulate a dual drive cement kiln operation.

This paper presents an investigation of the behavior of a 200-MVA-synchronous hydrogenerator during interturn stator faults, focusing on the affection to the electromagnetic magnitudes, such as the currents and the electromagnetic torque. Two kinds of interturn fault are examined 1) a short circuit between two conductors belonging to the same phase; and 2) a short circuit between two conductors belonging to different phases. These faults have been investigated via simulation using the finite element method. The benefit of this method is that it gives the possibility to calculate, except from the classical electrical magnitudes (e.g., the stator and field currents, the load angle, and the electromagnetic torque), other magnitudes which in general are difficult to compute during transient operation (e.g., the damper currents and the electromagnetic field inside the machine air gap). The main aim of this paper is to highlight quantitative and qualitative the condition in the interior of the machine in the cases of typical faults, which usually can occur during the machine operation. So, it is possible to find out that faults exist in the machine through the measurement of the field and the stator currents.

Broken rotor bar/end-ring and eccentricity are common faults in squirrel-cage induction motors and have been thoroughly investigated in the case of ac grid supply. In this paper, these types of faults are studied in the case of inverter-driven motors. More specifically, a novel investigation in inverter input current spectrum is made in order to reliably detect the fault-indicative frequency components. These harmonics give the ability for fault detection and classification, even under low load and low motor severity fault condition in steady-state or transient operation. The proposed diagnostic method has been particularly designed for open-loop controlled variable frequency induction motor drives, which is a usual case in low-cost industrial drives where precise speed control of the motor is not required. Moreover, an alternative technique is also presented in case the stator current is measured.

This paper investigates the possibility to optimize both the efficiency and the power factor of energy conversion systems which include power electronic converters. The values of these important power quantities depend on different parameters, such as the switching technique and the switching frequency of the power electronic elements. Comparing the already known and used switching techniques with each other we can conclude that the sPWM method offers the highest values of the efficiency and the power factor simultaneously. However, when using this technique the basic current harmonic lags as to the voltage in case of ohmic inductive loads resulting in the decrease in the power factor. In the present work a new sPWM switching technique is suggested in order to achieve higher power factor and efficiency compared to the traditional sPWM method. The aforementioned switching technique is a modified sPWM method based on an appropriate shifting of the input current to the grid voltage. But, the following question is raised: Is there a switching frequency value in a given converter topology by which both the efficiency and the power factor gain optimal value? Thus, the main aim of the present paper is determine this specific switching frequency value. This is achieved by using a simple method based on a criterion suggested in this work. In order to demonstrate how this specific frequency value can be found, a bidirectional AC–DC converter composed of a single phase bridge and two switching elements at the DC side is used. This proposed converter topology excels in that the total number of the switching elements is minimal. The study of this subject is carried out through Matlab/Simulink simulation and experimentation.

The maintenance of synchronous generators is very significant for the energy production. Being aware of the performance of a synchronous machine during different kinds of faults, such as phase to phase, phase to ground or field shortcircuits, could provide useful information about their protection. A short-circuit in the field excitation is not a common fault, but it is severe enough to create high oscillations to both electrical and mechanical magnitudes (field, stator and damper currents, rotor shaft torque, load angle etc). Such kind of faults is difficult to examine and provide experimental results because of the kinds of generator used for energy production. The size of these machines, either hydrogenerator or turbogenerator, is enormous for experimental laboratory studies. Another important issue that arises is the difficulties in the accurate calculation of the damper currents during transient operation. The Finite Element Method analysis gives solution to this kind of problems, as it can calculate as well the damper, stator and field currents as the electromagnetic field distribution inside the air gap.

This paper introduces a novel approach for the detection of rotor faults in asynchronous machines, based on wavelet analysis of the stator phase current. To be more specific, the measured stator phase current is filtered through a complex wavelet. Theoretical analysis validates that the spectrum of the modulus of the result of the filtering is free from the fundamental supply frequency component, and the fault characteristics can be highlighted. This is advantageous, especially if the induction machine operates at low slip values, where the characteristic frequency components of the rotor fault are very close to the fundamental frequency component. At the same time, by matching the wavelet function to the frequencies of the faulty components, a narrow bandpass filter at the frequency region of the fault characteristic spectral components is obtained. Furthermore, in the context of this paper, features extracted using the proposed technique are used as input to a support vector machine classifier that is employed for the detection of the rotor fault. Simulation and experimental results demonstrate the effectiveness of the proposed technique.

This paper presents a method of calculating in a simple, cheap and computational efficient way the steady-state time variables of three-phase induction or synchronous motors when only the data of the machine and a drawn waveform of its distorted stator input are given. Such waveforms can be considered as converter output voltage or current feeding the machine. According to this method the converter part for simulation can be omitted. The method has been implemented for an induction, as well as a synchronous machine under different cases of distorted voltage waveforms in the stator. Experimental and simulation results are in good agreement. Copyright © 2007 John Wiley & Sons, Ltd.

The effect of the system parameters on the commutation phenomena in a system consisting of a synchronous generator, a controlled rectifier and a DC load is being studied in detail. Furthermore, the behaviour of the system in cases of failure of ignition and short circuit of a controlled semiconducting element, is being investigated. The system under study was simulated by a method appropriate for the simulation of variable topology networks.

In this paper, the influence of the stiffness and damping of real elastic shafts on the behavior of a multidrive system driving a tissue paper machine is investigated. The drive system consists of four DC motors, where two of them drive the Yankee drying cylinder and the other two drive the presses section. Six-pulse thyristor bridge power converters that are connected to the same power transformer supply the motors. The inertias of the motors and the driven machines, in conjunction with the shaft stiffness, form mechanical resonators. Thus, resonance phenomena may occur, which may lead to undesirable results. This particular case results to two three-mass and one five-mass systems. This paper presents an analysis of the resonance frequencies of two sections of the machine during startup and machine production, considering the shaft stiffness (shaft diameter, length, and thickness). The elastic shafts eliminate the ripple of the motor electromagnetic torque, which is transferred to the driven machine. The behavior of elastic shafts with different stiffness in the transmission system is studied. Moreover, the steady state and dynamic behavior of the system considering the influence of the elastic shafts and vibration analysis were investigated using simulation. A model algorithm for system simulation was developed using the MATLAB/SIMULINK software. Characteristic simulation results are presented and are expressed in terms of speed and torque response. Considering the resonance frequency analysis and simulation results, mechanical design guidelines can be given for the most significant drive components in order to avoid torsional oscillation resonance phenomena and minimize torsional oscillations of the drive system.

This paper deals with the operational behavior of the Doubly-Fed Induction Generator Wind Energy Conversion System under power electronic converter and rotor terminals faulty conditions. More specifically, the effect of the short-circuit fault both in one IGBT of the back-to-back power electronic converter and in rotor phases on the overall system behavior has been investigated via simulation using a system of 2 MW. Finally, the consequences of these faults have been evaluated.

An energy weak grid consisting of a wind energy conversion system (WECS) which includes an asynchronous generator and a conventional plant consisting of diesel motor - synchronous generator unit, is analyzed. This system has been simulated via a developed general dynamic mathematical model which analytically describes the electric subsystems. Some interesting simulation results are presented in this paper. Specific attention is paid to the investigation of the dynamic analysis of the whole system at the connection and the disconnection of different nominal power WECS to the conventional plant for different wind velocity.

The output characteristics of buck zero-voltage switching quasi-resonant converters (ZVS-QRCs), presented in previously published works, are calculated considering equal input and output energies. Nevertheless, measurements that were taken with breadboarded buck ZVS-QRCs demonstrate an important deviation between the results of the theoretical analysis and the experimental data. This deviation becomes greater when the load current increases. This paper deals with a novel simulation method to approximate the real behavioral characteristics of Buck ZVS-QRCs. Analytical expressions are derived to calculate the power losses in each power converter component as well as the DC-voltage conversion ratio. Computer simulation results are confronted to experimental ones proving the effectiveness of the proposed method.

Field-oriented-controlled induction motor drives have been widely used over the last several years. Conventional direct stator-flux-oriented control schemes have the disadvantage of poor performance in the low-speed operating area when the stator flux is calculated using the voltage model, due to the stator resistance uncertainties and variations. In this paper, a new closed-loop stator-flux estimation method for a stator-flux-oriented vector-controlled induction motor drive is presented in which the stator resistance value is updated during operation. This method is based on a simple algorithm capable of running in a low-cost microcontroller, which is derived from the dynamic model of the induction machine. The effects of stator resistance detuning, especially in the low-speed operating region, are investigated and simulation results are shown. The motor drive system as well as the control logic and the resistance estimator are simulated and characteristic simulation results are derived. In addition, the proposed control scheme is experimentally implemented and some characteristic experimental results are shown. The simulation as well as the experimental results reveal that the proposed method is able to obtain precise flux and torque control, even for very low operating frequencies.

In dieser Arbeit wird die Untersuchung des Betriebsverhaltens eines Synchronmotors sowohl beim Anlauf als auch im stationaren Zustand durchgefuhrt. Dieser wird durch einen Stromrichter bestehend aus einer Thyristogleichrichterbrucke, einem Zwischenkreis mit grosser Induktivitat und einem Stromwechselrichter mit einer einfachen Zwangsloscheinrichtung gespeist. Zunachst wird ein mathematisches Modell fur das ganze System aufgestellt und das Betriebsverhalten durch Simulation mit der Methode der veranderlichen Topologie behandelt. Besonders wird auf das Modell zur Berechnung der Spannungs-belastung der Halbleiterelemente und auf die Simulationslogik geachtet. Aus den Simulationsergebnissen ergeben sich Spannungsraumzeigerdiagramme und Zeitfunktionen der elektrischen Grossen, die zur Erklarung des Systemverhaltens dienen.

[EN] This paper presents an advanced signal processing method applied to the diagnosis of rotor asymmetries in asynchronous machines. The approach is based on the application of complex empirical mode decomposition to the measured start-up current and on the subsequent extraction of a specific complex intrinsic mode function. Unlike other approaches, the method includes a pattern recognition stage that makes possible the automatic identification of the signature caused by the fault. This automatic detection is achieved by using a reliable methodology based on hidden Markov models. Both experimental data and a hybrid simulation experimental approach demonstrate the effectiveness of the proposed methodology., This work was supported in part by the Conselleria d'Educacio, Formacio i Ocupacio of the Generalitat Valenciana, in the framework of the "Ayudas para la Realizacion de Proyectos de I+D para Grupos de Investigacion Emergentes," project reference GV/2012/020.

In this paper an investigation of the Doubly-Fed Induction Generator's start-up procedure, using zero crossing method for the grid voltage's angle's calculation, is carried out in the environment of Matlab/ Simulink. Moreover, the significance of the phase displacement and the amplitude deviation of the stator voltage in the system's synchronization procedure is highlighted via simulation.