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In diesem Beitrag wurde gezeigt, wie mit Hilfe von Verfahren zur Analyse von Petri–Netzen ein in der Programmiersprache Kontaktplan erstelltes SPS–Programm analysiert werden kann. Das Ziel des Verfahrens ist dabei nicht eine Verifikation im eigentlichen Sinne sondern das Aufdecken von verbotenen oder unerwünschten Zuständen. Im Beitrag wurden Regeln zur Transformation des im Kontaktplan erstellten Ablaufs in ein Petri–Netz angegeben und anhand der Analyse eines fehlerhaft implementierten Ablaufs die Leistungsfähigkeit des Ansatzes vorgestellt. Das Beispiel zeigt, dass Programmfehler bereits vor einem Test an der realen Anlage erkannt werden können. Bei der weiteren Entwicklung des Verfahrens liegt ein Schwerpunkt auf der Verallgemeinerung auf im Kontaktplan entwickelte Programmorganisationseinheiten, die nicht nur reine
Abläufe implementieren. Ein weiterer wichtiger Entwicklungsschritt ist die graphische Unterstützung der Fehlersuche im Erreichbarkeitsgraphen, so dass insgesamt ein leistungsfähiges Werkzeug zur Unterstützung der Implementierung von Ablaufsteuerungen im Kontaktplan zur Verfügung steht.
In diesem Beitrag wurde gezeigt, wie ein bereits bekanntes Verfahren zur modellprädiktiven Regelung zur Optimierung der Energieeffizienz einer Asynchronmaschine im dynamischen Betrieb eingesetzt werden kann. Dazu wurden zunächst die Beziehungen für die Verlustleistung bei alleiniger Berücksichtigung der Kupferverluste im dynamischen Betrieb hergeleitet. Ausgehend davon wurde das Optimierungsproblem formuliert, der Einfluss von Parametern des modellprädiktiven Verfahrens auf das Optimierungsergebnis untersucht und damit Vorschlagswerte für diese Parameter ermittelt. Der Vergleich mit zwei weiteren Verfahren ohne Optimierung bzw. mit Optimierung allein für stationäre Arbeitspunkte zeigt die Vorteile des modellprädiktiven Verfahrens.
Der vorliegende Beitrag stellte die beiden Verfahrensklassen parameterbasierte Verfahren und Suchverfahren für eine energieeffiziente Betriebsführung von Asynchronmaschinen im stationären Zustand kurz vor und zeigte das Potential zur Reduktion der Verlustleistung in stationären Arbeitspunkten für zwei Motoren unterschiedlicher Baugröße. Dabei wurde deutlich, dass insbesondere im unteren Teillastbereich eine erhebliche Verringerung der Verlustleistung erzielt werden kann.
In this paper a double hogger used in woodworking machines is considered. The machining tools are driven by induction machines operated by standard inverters. During production the load of these motors changes periodically between low load and high load at a given speed. This paper investigates the reduction of power losses in such an application using an appropriate energy efficient control strategy for the induction machines.
In this article feedback linearization for control-affine nonlinear systems is extended to systems where linearization is not feasible in the complete state space by combining state feedback linearization and homotopy numerical continuation in subspaces of the phase space where feedback linearization fails. Starting from the conceptual simplicity of feedback linearization, this new method expands the scope of their applicability to irregular systems with poorly expressed relative degree. The method is illustrated on a simple SISO–system and by controlling the speed and the rotor flux linkage in a three phase induction machine.
The current paper discusses the optimal choice of a filter time constant for filtering the steady state flux reference in an energy efficient control strategy for changing load torques. It is shown that by appropriately choosing the filter time constant as a fraction of the rotor time constant the instantaneous power losses after a load torque step can be significantly reduced compared to the standard case. The analysis for the appropriate choice of the filter time constant is based on a numerical study for three different induction motors with different rated powers.
Das Thema Energiewende ist in aller Munde. Sie soll eine sichere, umweltverträgliche und wirtschaftlich erfolgreiche Zukunft ermöglichen. Ein Ansatz dafür ist die dezentrale, also verbrauchernahe Energieversorgung. Der Trend geht weg vom konventionellen Kraftwerk und hin zur Kraft-Wärme-Koppelung und erneuerbaren Energien. Für einen absehbaren Zeitraum geht es auch darum, zentrale und dezentrale Elemente sinnvoll miteinander zu verknüpfen. Mit der Frage, wie Energiesysteme angepasst und kombiniert werden müssen, um den Energiehaushalt – den nationalen wie den von Unternehmen und Privatpersonen – optimieren zu können, beschäftigt sich das Reutlinger Energiezentrum für Dezentrale Energiesysteme und Energieeffizienz in Lehre und Forschung. Es ist die Kombination aus Technik und Betriebswirtschaft, aus einzelwirtschaftlicher Optimierung und aus Gesamtsicht, die das Reutlinger Energiezentrum ausmacht. Im Folgenden werden die Schwerpunkte des Forschungsteams dargestellt.
Methods for increasing the energy efficiency of induction motors by an appropriate control strategy have been a subject of research during the last years. Several methods for loss minimization have been developed for induction motors operated in a steady state. In recent years, some solutions for the dynamic case have been given as well either using an online or offline optimization approach, implying a certain computational burden, which is undesired in practice. This paper shows that the appropriate application of steady state techniques during transients due to a changing motor torque is a suboptimal strategy with an acceptable performance for efficiency optimization given an induction machine where saturation effects of the main inductance must be considered. The optimization problem is simplified such that a simple suboptimal solution is possible and the quality of the suboptimal solution is investigated by simulations and measurements. The proposed solution is simple, easy to implement, and does not require an online optimization. In addition, the influence of magnetizing induction saturation is considered.
This paper presents a laboratory experiment integrating the fields of electronics design, power electronics and drive control. The aim of this experiment is first to illustrate the need for a deep knowledge and the challenges in power electronics and its applications, in this particular case for drive control. The different tasks in this experiment are executed on a complete setup for a brushless dc motor test bench. The tasks assigned to the students are designed such that, in some tasks the knowledge from a particular field, power electronics, electronic design or drive control is deepened, whereas in other tasks the knowledge from more than one of these fields is needed to solve the given problem. Thus, the experiment trains students in the particular domains but illustrates as well the links between power electronics, electronic design and drive control.
One of the challenges in condition monitoring systems is the residual life time prediction. This prediction is done based on statistical methods, based on physical knowledge about the considered process or a combination of these approaches. Physical knowledge of the system is a result of long-term experience of process operators. However, it can be gained as well by analyzing appropriately designed process models. The additional benefit of such models is that particular effects and their impact on the process behavior can be analyzed in detail and without plant operation in a shorter time. The current contribution developed in the framework of the research project Model Based Hierarchic Condition Monitoring presents such models for condition monitoring of roller chains. First, already existing high order dynamic models given by nonlinear differential equations of such chains are extended to incorporate effects that occur due to a deterioration of the chain condition. Then, a simple model is developed and compared to the high order model. Based on the two models the change in the process behavior due to a deterioration of the roller chain condition is analyzed to illustrate that these models can be used in future research in the above mentioned research project to better predict the residual life time of the considered roller chains.
Condition Monitoring for mechanical systems like bearings or transmissions is often done by analysing frequency spectra obtained from accelerometers mounted to the components under observation. Although this approach gives a high amount on information about the system behaviour, the interpretation of the resulting spectra requires expert knowledge, that is, a deep understanding of the effect on condition deterioration on the measured spectra. However, an increasing number of condition monitoring applications demands other representations of the measured signals that can be easily interpreted even by non–experts. Therefore, the objective of this paper is to develop an approach for processing measured process data in order to obtain an easy to interpret measure for assessing the component condition. The main idea is to evaluate the deterioration of a component condition by computing the correlation function of current measurements with past measurements in order to detect a component condition deterioration from a change in these correlation functions. Besides the simplicity of the obtained measure, this approach opens the opportunity for integrating a model based approach as well. The developed method is tested based on a condition monitoring application in a roller chain.
This paper describes a new method for condition monitoring of a roller chain. In contrast to conventional methods, no additional accelerometers are used to measure and interpret frequency spectra but the chain condition is evaluated using an easy to interpret similarity measure based on correlation functions using the driving motor torque. An additional clustering of current data and reference measurements yields an easy to understand representation of the chain condition.
In this paper we describe the design and development process of an electromagnetic picker for rivets. These rivets are used in a production process of leather or textile design objects like riveted waist belts or purses. The picker is designed such that it replaces conventional mechanical pickers thus avoiding mechanical wear problems and increasing the process quality. The paper illustrates the challenges in the design process of this mechatronic system. The design process was based on both simulation and experiments leading to a prototype that satisfies the requirements.
Ein wesentliches Ziel der unter dem Schlagwort Industrie 4.0 gebündelten neuen Entwicklungen ist die Vernetzung intelligenter Komponenten in industriellen Anlagen, um Prozesse transparenter und effizienter zu gestalten. Ein weiteres Ziel ist das Condition Monitoring, d.h. die Überwachung des Zustands der Komponenten während der Laufzeit und die Abschätzung der Restlebensdauer, damit die gesamte Lebensdauer der Komponente ausgenutzt und Wartungsintervalle besser geplant werden können. Die Bewertung des Komponentenzustands erfolgt anhand von Messgrößen, die entweder durch zusätzlich in den Prozess eingebrachte Sensoren erfasst werden oder durch Prozessdaten, die in den Regel- und Steuereinrichtungen verfügbar sind. Diese Messdaten werden ausgewertet und das Ergebnis wird dem Anwender angezeigt.
Der vorliegende Beitrag gibt einen kurzen Überblick über verwendete Messgrößen sowie verwendete Auswerteverfahren. Darüber hinaus wird ein Verfahren erläutert, das die Schwierigkeiten bei der Beurteilung der üblicherweise verwendeten Frequenzspektren vermeidet.
A simple determination of the error voltage compensation map for motor parameter identification
(2018)
This paper proposes a new method for determining the error voltage compensation map in a parameter identification procedure of three-phase induction motors with an inverter. The compensation curve depending on the motor current is determined using a simple procedure based on given reference voltage steps and the corresponding steady state values of the stator current of the induction motor.
Der vorliegende Beitrag zeigte die Anwendung eines Extended Kalman Filters für die Beurteilung des Verschleißzustandes von Rollenketten. Anders als in den üblicherweise eingesetzten signalbasierten Verfahren wurde damit ein modellbasierter Ansatz gewählt. Der Einsatz des Extended Kalman Filters ermöglicht die Schätzung von Parametern eines reduzierten Kettenmodells, das die Dynamik der einzigen Messgröße, nämlich des Drehmoments des antreibenden Motors näherungsweise nachbildet. Im Beitrag wurde dieses Verfahren auf Messdaten aus vier Dauerversuchen an Rollenketten eingesetzt und gezeigt, dass mit steigendem Verschleiß eine Änderung ausgewählter Modellparameter erfolgt.
Diese Vorgehensweise ist ein erster Ansatz, der durch weitere Forschungsarbeiten noch verbessert werden muss. In zukünftigen Forschungsarbeiten wird zusätzlich zur Parameterschätzung eine Prädiktion durchgeführt, um einen Schätzwert für die Restlebensdauer zu erhalten. Hierzu gibt es Ansätze in der Literatur, die auf das konkrete Problem angepasst werden müssen. Zudem muss die Modellierungssystematik so erweitert werden, dass Wissen über das Prozessverhalten in die Modellierung mit eingebracht wird, um die Aussagekraft der Ergebnisse sowie die Robustheit des Verfahrens bezüglich Betriebsparametern, Umgebungsbedingungen und Exemplarstreuungen zu verbessern.
A novel brushless excitation concept for synchronous machines with a rotating power converter is proposed in this paper. The concept does not need an auxiliary winding or any other modification to the machine structure apart from an inverter with a DC link capacitor and a controller on the rotor. The power required for the rotor excitation is provided by injecting harmonics into the stator winding. Thus, a voltage in the field coil is induced. The rotor inverter is controlled such that the alternating current charges the DC link capacitor. At the same time the inverter supplies the DC field current to the field coil. The excitation concept is first developed in theory, then presented using an analytical model and FEA, and lastly investigated with a prelimininary experimental setup.
In this work design rules for a novel brushless excitation system for externally excited synchronous machines are discussed. The concept replaces slip rings with a fullbridge active rectifier and a controller mounted on the rotor. An AC signal induced from the stator is used to charge the rotor DC link. The DC current for the rotor excitation is provided from this DC link source. Finite element analysis of an existing machine is used to analyze the practicability of the excitation system.
This paper discusses the optimal control problem for increasing the energy efficiency of induction machines in dynamic operation including field weakening regime. In an offline procedure optimal current and flux trajectories are determined such that the copper losses are minimized during transient operations. These trajectories are useful for a subsequent online implementation.
This paper presents an approach for the implementation of a modular and scalable power electronics device for controlling electric drives in the field of electric vehicles using wide bandgap semiconductor devices. The main idea is to achieve the required output currents or voltages by connecting adequately designed hardware modules in parallel or in series. This particular design is based on the fact that the single modules generate a continuous and specified output voltage from a given dc voltage, e.g. an intermediate circuit or battery voltage. The main benefit is, that different current or voltage requirements can be satisfied based on a single module thus decreasing development and production costs. The current paper focuses on the connection in parallel of such modules. A control architecture is illustrated and a first proof of concept is given.
Die vorliegende Erfindung betrifft ein Verfahren zum Bestimmen einer Fehlspannung eines Stromrichters, an den eine Last, insbesondere in Form einer Drehfeldmaschine wie Asynchronmaschine, angeschlossen ist, bestimmt und ggf. kompensiert wird, wobei eine Ausgangsspannung an dem Stromrichter stufen- oder schrittweise erhöht und der sich hierbei als Sprungantwort einstellende Strom gemessen wird. Die Erfindung betrifft weiterhin eine Drehfeldmaschine beispielsweise in Form einer Asynchronmaschine, mit einer Leistungselektronik umfassend einen tromrichter sowie einer Kompensationseinrichtung zum Kompensieren der Fehlspannung des Stromrichters, sowie weiterhin ein Verfahren zum Betreiben und/oder Steuern einer solchen Drehfeldmaschine, bei dem die Fehlspannung des Stromrichters bestimmt und kompensiert wird.
Steady state efficiency optimization techniques for induction motors are state of the art and various methods have already been developed. This paper provides new insights in the efficiency optimized operation in dynamic regime. The paper proposes an anticipative flux modification in order to decrease losses during torque and speed transients. These trajectories are analyzed based on a numerical study for different motors. Measurement results for one motor are given as well.
Energy efficient electric control of drives is more and more important for electric mobility and manufacturing industries. Online dynamic optimization of induction machines is challenging due to the computational complexity involved and the variable power losses during dynamic operation of induction machines. This paper proposes a simple technique for sub-optimal online loss optimization using rotor flux linkage templates for energy efficient dynamic operation of induction machines. Such a rotor flux linkage template is given by a rotor flux linkage trajectory which is optimal for a specific scenario. This template is calculated in an offline optimization process. For a specific scenario during real time operation the rotor flux linkage is calculated by appropriately scaling the given template.
In this work, a brushless, harmonic-excited wound-rotor synchronous machine is investigated which utilizes special stator and rotor windings. The windings magnetically decouple the fundamental torque-producing field from the harmonic field required for the inductive power transfer to the field coil. In contrast to conventional harmonic-excited synchronous machines, the whole winding is utilized for both torque production and harmonic excitation such that no additional copper for auxiliary windings is needed. Different rotor topologies using rotating power electronic components are investigated and their efficiencies have been compared based on Finite-Element calculation and circuit analysis.
Purpose. To improve the efficiency of the closed-cycle operation of the field-orientation induction machine in dynamic behavior when load conditions are changing, considering the nonlinearities of the main inductance.
Methodology. The optimal control problem is defined as the minimization of the time integral of the energy losses. The algorithm observed in this paper uses the Matlab/Simulink, dSPACE real-time interface, and C language. Handling real-time applications is made in ControlDesk experiment software for seamless ECU development.
Findings. Adiscrete-time model with an integrated predictive control scheme where the optimization is performed online at every sampling step has been developed. The optimal field-producing current trajectory is determined, so that the copper losses are minimized over a wide operational range. Additionally, the comparison of measurement results with conventional methods is provided, which validates the advantages and performance of the control scheme.
Originality. To solve the given problem, the information vector on the current state of the coordinates of the electromechanical system is used to form a controlling influence in the dynamic mode of operation. For the first time, the formation process of controls has considered the current state and the desired future state of the system in the real-time domain.
Practical value. Apredictive iterative approach for optimal flux level of an induction machine is important to generate the required electromagnetic torque and to reduce power losses simultaneously.
This paper illustrates the implementation of series connected hardware modules as part of a scalable and modular power electronics device, which is ideally suited in the field of electric vehicles using wide bandgap semiconductor devices. The main benefit of the modular concept is that different current or voltage requirements can be satisfied based on the appropriate series or parallel connection of single modules. The particular design is based on the fact that the single modules generate a continuous and specified output voltage from a given dc voltage. The current work focuses on a brief classification of this work in different series connected concepts of power converters and in particular on an active damping approach for the series connected LC output filters based on inductor current feedback.
This contribution presents a three-phase power stage for motor control with continuous output voltages using wide bandgap semiconductors and an asynchronous delta-sigma based switching signal generation. The focus of the paper is on an active damping approach for the LC output filter based on inductor current feedback.
Energy efficiency optimization techniques for steady state operation of induction machines are the state-of-the-art, and many methods have already been developed. However, many real-world industrial and electric vehicle applications cannot be considered to be in steady state operation. The focus of this contribution is on the efficiency optimization of induction machines in dynamic operation. Online dynamic operation is challenging due to the computational complexity and the required low sample times in an inverter. An offline optimization is therefore conducted to gain knowledge. Based on this offline optimal solution, a simple and easy to implement template based solution is developed. This approach aims at replicating the solution found by the offline optimization by resembling the shape and anticipative characteristics of the optimal flux trajectory. The energy efficiency improvement of the template based solution is verified by simulations and measurements on a test bench and using a real-world drive cycle scenario. For comparison, a model predictive numerical online optimization is investigated too.
This paper presents a modular and scalable power electronics concept for motor control with continuous output voltage. In contrast to multilevel concepts, modules with continuous output voltage are connected in series. The continuous output voltage of each module is obtained by using gallium nitride (GaN) high electron motility transistor (HEMT)s as switches inside the modules with a switching frequency in the range between 500 kHz and 1 MHz. Due to this high switching frequency a LC filter is integrated into the module resulting in a continuous output voltage. A main topic of the paper is the active damping of this LC output filter for each module and the analysis of the series connection of the damping behaviour. The results are illustrated with simulations and measurements.
In this work, a comparison between different brushless harmonic-excited wound-rotor synchronous machines is performed. The general idea of all topologies is the elimination of the slip rings and auxiliary windings by using the already existing stator and rotor winding for field excitation. This is achieved by injecting a harmonic airgap field with the help of power electronics. This harmonic field does not interact with the fundamental field, it just transfers the excitation power across the airgap. Alternative methods with varying number of phases, different pole-pair combinations, and winding layouts are covered and compared with a detailed Finite-Element-parameterized model. Parasitic effects due to saturation and coupling between the harmonic and main windings are considered.
Switched reluctance motors are particularly attractive due to their simple structure. The control of this machine type requires the instants, to switch the currents in the motor phases in an appropriate sequence. These switching instants are determined either based on a position sensor, or on signals generated by a sensorless method. A very simple sensorless method uses the switching frequency of the hysteresis controllers used for phase current control. This paper first presents an automatic commissioning method for this sensorless method and second a startup procedure, thus enhancing this approach towards an application in industry.
This article illustrates a method for sensorless control of a switched reluctance motor. The detection of the time instants for switching between the working phases is determined based on the evaluation of the switching frequency of the hysteresis current controllers for appropriately selected sensing phases. This enables a simple and cost efficient implementation. The method is compared with a pulse injection method in terms of efficiency and resolution.
The current paper proposes a design method for an active damping approach for LC output filters in a power stage for motor control with continuous output voltage. The power stage uses GaN-HEMTs and operates at switching frequencies in a range between 500 kHz and 1MHz. The active damping of the output filter is achieved here by a feedback of the filter inductor current using a high-pass structure. The paper discusses the impact of this feedback on the system behavior and proposes a design method.
Class Phi2 amplifier using GaN HEMTs at 13.56MHz with tuned transformer for wireless power transfer
(2022)
This paper discusses a design procedure of a wireless power transfer system at a RF switching frequency of 13.56MHz. The wireless power transfer amplifier uses GaN HEMTs in aClass phi2 topology and is designed in order to achieve high efficiency and high power density. A design method for the load over a certain bandwidth is presented for a transformer with its tuning network.
In this work, a brushless, harmonic-excited wound-rotor synchronous machine without any auxiliary windings which can provide full torque at startup is investigated experimentally. The excitation power is transferred inductively by superimposing an additional harmonic field of different pole-pair number on top of the airgap field. This is achieved by feeding the parallel paths of the stator and rotor winding separately. A prototype for the harmonic-excited synchronous machine has been constructed and experimental results are presented to verify the concept. The main loss contributors are identified and the importance of considering core losses under harmonic excitation is discussed. A general analytical model for harmonic excited synchronous machines is proposed which enables a quick estimation of the iron core flux densities and the core losses generated by the additional harmonic currents.
The efficient production and utilization of green hydrogen is vital to succeed in the global strive for a sustainable future. To provide the necessary amount of green hydrogen a high number of electrolyzers will be connected as decentralized power consumers to the grid. A large amount of decentralized renewable power sources will provide the energy. In such a system a control method is necessary to dispatch the available power most efficiently. In particular, the shutdown of renewable energy sources due to temporary overproduction must be avoided. This paper presents a decentralized tertiary control algorithm that provides a new decentralized control approach, thus creating a flexible, robust and easily scalable system. The operation of each grid participant within this grid connected microgrid is optimized for maximum financial profit, while minimizing the exchange of power with the mains grid and reducing the shutdown of renewable power sources.
Simulation eines dezentralen Regelungssystems zur netzdienlichen Erzeugung von grünem Wasserstoff
(2023)
Wasserstoff wird einen bedeutenden Beitrag zum Wandel von Industrie und Gesellschaft in eine klimaneutrale Zukunft leisten. Der Aufbau und die ökologisch und ökonomisch sinnvolle Nutzung einer Wasserstoffinfrastruktur sind hierbei die zentralen Herausforderungen. Ein notwendiger Baustein ist die effiziente Bereitstellung von grünem Strom und dem daraus produzierten grünen Wasserstoff. Der vorliegende Beitrag stellt ein dezentrales Regel- und Kommunikationssystem vor, mit dem Angebot und Nachfrage von grünem Strom und Wasserstoff in einem System aus dezentralen Akteuren in Einklang gebracht werden. In einer hierzu entwickelten Simulationsumgebung wird die Funktion und der Nutzen dieses dezentralen Ansatzes verdeutlicht.
Modern wide bandgap power devices promise higher power conversion performance if the device can be operated reliably. As switching speed increases, the effects of parasitic ringing become more prominent, causing potentially damaging overvoltages during device turn-off. Estimating the expected additional voltage caused by such ringing enables more reliable designs. In this paper, we present an analytical expression to calculate the expected overvoltage caused by parasitic ringing based on parasitic element values and operating point parameters. Simulations and measurements confirm that the expression can be used to find the smallest rise time of the switches’ drain-source voltage for minimum overvoltage. The given expression also allows the prediction of the trade off overvoltage amplitude in case of faster required rise times.