16 results on '"Fuchs, Friedrich Wilhelm"'
Search Results
2. Finite Control Set Model Predictive Current Control for Grid-Connected Voltage-Source Converters With LCL Filters: A Study Based on Different State Feedbacks.
- Author
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Panten, Niklas, Hoffmann, Nils, and Fuchs, Friedrich Wilhelm
- Subjects
PREDICTIVE control systems ,ELECTRIC power distribution grids ,PREDICTION models ,ELECTRIC potential ,CONVERTERS (Electronics) ,HARMONIC suppression filters - Abstract
This paper presents different state feedback approaches of finite control set model predictive control (FCS-MPC) applied to a grid-connected voltage-source converter (VSC) with an LCL filter. Besides converter-side current feedback, two multivariable control approaches and line-side current control are introduced and compared based on theoretical and experimental evaluation. As the LCL filter introduces an additional resonance frequency to the system, the use of different active damping (AD) methods in combination with FCS-MPC is discussed. Furthermore, practical control implementation issues are discussed. The presented methods reveal the great potential, high dynamic performance, and flexibility of FCS-MPC, enabling multivariable control as well as both reduced switching losses and low harmonic current distortion at the same time. Eventually, the feasibility of the theoretical control concepts is shown in a laboratory environment. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
3. General Analysis and Design Guideline for a Battery Buffer System With DC/DC Converter and EDLC for Electric Vehicles and its Influence on Efficiency.
- Author
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Schroeder, Jens Christian and Fuchs, Friedrich Wilhelm
- Subjects
ELECTRIC batteries ,DC-to-DC converters ,ELECTRIC vehicles ,ELECTRIC double layer ,CAPACITORS ,ACCELERATION (Mechanics) - Abstract
In this paper, the general design of a battery buffer system (BBS) consisting of a dc/dc converter and electric double layer capacitors for an electric vehicle is presented. This is intended to save the regenerative braking energy and to support the battery during acceleration. The design of a multiphase converter in interleaved operation with nonideal coupled inductors is stated to minimize volume and power losses while maintaining given current ripple limitations. A reduced sensor current-sharing control method is developed and its correct choice of the sensor position is explained. The peak efficiency of the designed and built converter can be measured to nearly 99%. The corresponding BBS is implemented in a lead-acid battery powered electric lift truck propulsion system. The system operation with and without the BBS is compared to examine the behavior and the overall efficiency. It can be shown that the traction battery stress can be strictly reduced as well as the temperature rise in the battery. Furthermore, the efficiency can be increased in the range of 5-6%. The battery's lifetime improvement is estimated by means of the difference in the temperature rise to approximately 20%. [ABSTRACT FROM AUTHOR]
- Published
- 2015
- Full Text
- View/download PDF
4. Minimal Invasive Equivalent Grid Impedance Estimation in Inductive–Resistive Power Networks Using Extended Kalman Filter.
- Author
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Hoffmann, Nils and Fuchs, Friedrich Wilhelm
- Subjects
ELECTRIC power transmission ,KALMAN filtering ,CONVERTERS (Electronics) ,ELECTRIC waves ,ELECTRIC current rectifiers ,PARAMETER estimation - Abstract
Real-time estimation of the equivalent grid impedance and the equivalent grid voltage seen from a power converter connected to the public electric distribution network by means of extended Kalman filter is addressed. The theoretical background of the extended Kalman filter used for equivalent grid impedance estimation is introduced. Practical aspects like the use of the filter in an environment with highly distorted voltage waveforms, the tuning of the noise covariance matrices, and the implementation on a laboratory system are discussed. The theoretical analysis is verified on a 22-kW test-bench where a grid impedance emulator is used to simulate grid impedance steps in the laboratory environment. The proposed extended Kalman filter is designed to utilize the noise that is already present at the connection point of the power converter to overcome the need of active disturbance injection to estimate the equivalent grid impedance. Thus, electrical equipment connected close to the grid-connected converter is only affected marginally by the equivalent grid impedance estimation technique. [ABSTRACT FROM AUTHOR]
- Published
- 2014
- Full Text
- View/download PDF
5. Systematic Design of the Lead-Lag Network Method for Active Damping in LCL-Filter Based Three Phase Converters.
- Author
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Pena-Alzola, Rafael, Liserre, Marco, Blaabjerg, Frede, Sebastian, Rafael, Dannehl, Jorg, and Fuchs, Friedrich Wilhelm
- Abstract
Three-phase active rectifiers guarantee sinusoidal input currents and unity power factor at the price of a high switching frequency ripple. To adopt an LCL-filter, instead of an L-filter, allows using reduced values for the inductances and so preserving dynamics. However, stability problems can arise in the current control loop if the present resonance is not properly damped. Passive damping simply adds resistors in series with the LCL-filter capacitors. This simplicity is at the expense of increased losses and encumbrances. Active damping modifies the control algorithm to attain stability without using dissipative elements but, sometimes, needing additional sensors. This solution has been addressed in many publications. The lead-lag network method is one of the first reported procedures and continues being in use. However, neither there is a direct tuning procedure (without trial and error) nor its rationale has been explained. Thus, in this paper a straightforward procedure is developed to tune the lead-lag network with the help of software tools. The rationale of this procedure, based on the capacitor current feedback, is elucidated. Stability is studied by means of the root locus analysis in z-plane. Selecting the lead-lag network for the maximum damping in the closed-loop poles uses a simple optimization algorithm. The robustness against the grid inductance variation is also analyzed. Simulations and experiments confirm the validity of the proposed design flow. [ABSTRACT FROM PUBLISHER]
- Published
- 2014
- Full Text
- View/download PDF
6. StatCom control at wind farms with fixed-speed induction generators under asymmetrical grid faults.
- Author
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Wessels, Christian, Hoffmann, Nils, Molinas, Marta, and Fuchs, Friedrich Wilhelm
- Subjects
INDUCTION generators ,ELECTRIC generators ,WIND power ,WIND turbines ,WIND power plants - Abstract
The stability of fixed-speed induction generator (FSIG)-based wind turbines can be improved by a StatCom, which is well known and documented in the literature for balanced grid voltage dips. Under unbalanced grid voltage dips, the negative-sequence voltage causes heavy generator torque oscillations that reduce the lifetime of the drive train. In this paper, investigations on an FSIG-based wind farm in combination with a StatCom under unbalanced grid voltage fault are carried out by means of theory, simulations, and measurements. A StatCom control structure with the capability to coordinate the control between the positive and the negative sequence of the grid voltage is proposed. The results clarify the effect of the positive- and the negative-sequence voltage compensation by a StatCom on the operation of the FSIG-based wind farm. With first priority, the StatCom ensures the maximum fault-ride-through enhancement of the wind farm by compensating the positive-sequence voltage. The remaining StatCom current capability of the StatCom is controlled to compensate the negative-sequence voltage, in order to reduce the torque oscillations. The theoretical analyses are verified by simulations and measurement results on a 22-kW laboratory setup. [ABSTRACT FROM PUBLISHER]
- Published
- 2013
- Full Text
- View/download PDF
7. Analysis of the Passive Damping Losses in LCL-Filter-Based Grid Converters.
- Author
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Peña-Alzola, Rafael, Liserre, Marco, Blaabjerg, Frede, Sebastián, Rafael, Dannehl, Jörg, and Fuchs, Friedrich Wilhelm
- Subjects
ELECTRON tube grids ,PARAMETER estimation ,PHYSICS experiments ,SIMULATION methods & models ,ENERGY dissipation - Abstract
Passive damping is the most adopted method to guarantee the stability of LCL-filter-based grid converters. The method is simple and, if the switching and sampling frequencies are sufficiently high, the damping losses are negligible. This letter proposes the tuning of different passive damping methods and an analytical estimation of the damping losses allowing the choice of the minimum resistor value resulting in a stable current control and not compromising the LCL-filter effectiveness. Stability, including variations in the grid inductance, is studied through root locus analysis in the z-plane. The analysis is validated both with simulation and with experiments. [ABSTRACT FROM AUTHOR]
- Published
- 2013
- Full Text
- View/download PDF
8. PI Control, PI-Based State Space Control, and Model-Based Predictive Control for Drive Systems With Elastically Coupled Loads—A Comparative Study.
- Author
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Thomsen, Sönke, Hoffmann, Nils, and Fuchs, Friedrich Wilhelm
- Subjects
ELECTRIC motors ,PREDICTIVE control systems ,MECHANICAL loads ,FEEDBACK control systems ,DAMPING (Mechanics) ,DYNAMICS ,VIBRATION (Mechanics) ,COMPARATIVE studies - Abstract
Three different control methods for the speed control of drive systems with elastically coupled loads are presented and compared. In drive applications where the load is connected to the driving motor with a drive shaft that has a finite stiffness, unwanted mechanical dynamics can occur. These unwanted dynamics can stress both the mechanical and electrical drive components. Furthermore, the shaft torsion, if neglected in the control synthesis, can dramatically reduce the achievable control performance. To overcome these challenges, the design, analysis, and comparative study of three speed control methods for a drive system with resonant loads are carried out. The considered control methods are the following: a conventional proportional-integral (PI) control, a PI-based state space control, and a model-based predictive control. To ensure a suitable basis for their comparison, the three different speed control methods are designed with equal bandwidths and are verified with the same test setup. Furthermore, all speed control methods presented use only the drive-side speed measurement to control the drive speed. [ABSTRACT FROM PUBLISHER]
- Published
- 2011
- Full Text
- View/download PDF
9. Filter-Based Active Damping of Voltage Source Converters With LCL Filter.
- Author
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Dannehl, Joerg, Liserre, Marco, and Fuchs, Friedrich Wilhelm
- Subjects
DAMPING (Mechanics) ,FILTERS & filtration ,ELECTRIC potential ,CASCADE converters ,RESONANCE ,LEAD ,BANDWIDTHS ,ROBUST control - Abstract
Pulsewidth modulation (PWM) voltage source converters are becoming a popular interface to the power grid for many applications. Hence, issues related to the reduction of PWM harmonics injection in the power grid are becoming more relevant. The use of high-order filters like LCL filters is a standard solution to provide the proper attenuation of PWM carrier and sideband voltage harmonics. However, those grid filters introduce potentially unstable dynamics that should be properly damped either passively or actively. The second solution suffers from control and system complexity (a high number of sensors and a high-order controller), even if it is more attractive due to the absence of losses in the damping resistors and due to its flexibility. An interesting and straightforward active damping solution consists in plugging in, in cascade to the main controller, a filter that should damp the unstable dynamics. No more sensors are needed, but there are open issues such as preserving the bandwidth, robustness, and limited complexity. This paper provides a systematic approach to the design of filter-based active damping methods. The tuning procedures, performance, robustness, and limitations of the different solutions are discussed with theoretical analysis, selected simulation, and experimental results. [ABSTRACT FROM PUBLISHER]
- Published
- 2011
- Full Text
- View/download PDF
10. Converter Systems for Fuel Cells in the Medium Power Range--A Comparative Study.
- Author
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Mohr, Malte, Franke, Wulf Toke, Wittig, Bjoern, and Fuchs, Friedrich Wilhelm
- Subjects
ELECTRIC inverters ,FUEL cells ,ELECTRIC current converters ,ELECTRIC power ,BIPOLAR transistors - Abstract
Inverter systems that feed electrical power from fuel cells into the grid must convert the direct current of the fuel cell into the alternating current of the grid. In addition, these inverters have to adapt the different voltages of the fuel-cell system and the grid to each other. In this paper, different topologies of appropriate inverter systems in the medium power range of 20 kW and higher are presented briefly. The inverter operating behavior, power rating, and efficiency are compared. The power rating and efficiency are compared using an analytical calculation of the semiconductor losses. The study includes transformerless inverters as well as two-stage inverter systems with high-frequency transformers (dc/dc converter combined with an inverter). This paper compares converter systems using insulated-gate bipolar transistors (IGBTs), e.g., a boost converter in series with a voltage-source inverter (VSI), current-source inverter, and z-source inverter or converter systems using superjunction MOSFETs, such as voltage- and current-fed full-bridge converters or a boost converter with an autotransformer. The MOSFET-based dc/dc converters must be connected in series to a VSI with IGBTs to feed into the three-phase grid. The presented converters were tested in the laboratory. Some characteristics of their laboratory performance are shown. [ABSTRACT FROM AUTHOR]
- Published
- 2010
- Full Text
- View/download PDF
11. Current Sensor Fault Detection, Isolation, and Reconfiguration for Doubly Fed Induction Generators.
- Author
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Rothenhagen, Kai and Fuchs, Friedrich Wilhelm
- Subjects
FAULT tolerance (Engineering) ,RELIABILITY (Personality trait) ,DETECTORS ,TURBINES ,ELECTRIC potential - Abstract
Fault tolerance is gaining growing interest to in- crease the reliability and availability of distributed energy sources. Current sensor fault detection, isolation, and reconfiguration are presented for a voltage-oriented controlled doubly fed induction generator, which is mainly used in wind turbines. The focus of this analysis is on the isolation of the faulty sensor and the actual reconfiguration. During a short period of open-loop operation, the fault is isolated by looking at residuals calculated from observed and measured signals. Then, replacement signals from observers are used to reconfigure the drive and reenter closed-loop control. Laboratory measurement results are included to prove that the proposed concept leads to good results. [ABSTRACT FROM AUTHOR]
- Published
- 2009
- Full Text
- View/download PDF
12. Doubly Fed Induction Generator Model-Based Sensor Fault Detection and Control Loop Reconfiguration.
- Author
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Rothenhagen, Kai and Fuchs, Friedrich Wilhelm
- Subjects
FAULT tolerance (Engineering) ,RELIABILITY in engineering ,ELECTRIC potential ,ELECTRIC currents ,MEASUREMENT - Abstract
Fault tolerance is gaining interest as a means to in- crease the reliability and availability of distributed energy systems. In this paper, a voltage-oriented doubly fed induction generator, which is often used in wind turbines, is examined. Furthermore, current, voltage, and position sensor fault detection, isolation, and reconfiguration are presented. Machine operation is not interrupted. A bank of observers provides residuals for fault detection and replacement signals for the reconfiguration. Control is temporarily switched from closed loop into open-loop to decouple the drive from faulty sensor readings. During a short period of open-loop operation, the fault is isolated using parity equations. Replacement signals from observers are used to reconfigure the drive and reenter closed-loop control. There are no large transients in the current. Measurement results and stability analysis show good results. [ABSTRACT FROM AUTHOR]
- Published
- 2009
- Full Text
- View/download PDF
13. Limitations of Voltage-Oriented PT Current Control of Grid-Connected PWM Rectifiers With LCL Filters.
- Author
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Dannehi, Joerg, Wessels, Christian, and Fuchs, Friedrich Wilhelm
- Subjects
PULSE width modulation ,ELECTRIC filters ,ELECTRIC controllers ,VOLTAGE regulators ,DETECTORS ,ALGORITHMS ,FREQUENCY response ,ELECTRONIC modulation ,ELECTRIC circuits - Abstract
Voltage-oriented PI control of three-phase grid- connected pulsewidth-modulation rectifiers with LCL filters is addressed. LCL filters require resonance damping. Active resonance damping is state of the art to face the problem, but it is still under investigation because of the manifold solutions. It is often realized using many sensors and/or complex control algorithms. In contrast, pure PI control requires only one set of current sensors, and its implementation and design are rather simple and well known from the L filter control. PI control has already been shown to be a suitable solution also for LCL filters, but there are limitations. These are investigated in this paper. System stability is analyzed with respect to different ratios of LCL filter resonance and control frequencies. The latter are important parameters for system design and control. Both line and converter current control are analyzed. For a certain range of frequency ratios, the voltage.oriented PI control gives stable performance without additional feedback, but for ratios outside this range, stable operation is impossible. Experimental tests validate the theoretical results. In addition, an experimentally determined LCL filter transfer function is shown in this paper, which shows a lower resonance peak as expected from commonly used filter models. [ABSTRACT FROM AUTHOR]
- Published
- 2009
- Full Text
- View/download PDF
14. Active Damping for Three-Phase PWM Rectifiers With High-Order Line-Side Filters.
- Author
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Bierhoff, Michael H. and Fuchs, Friedrich Wilhelm
- Subjects
ELECTRIC current rectifiers ,ELECTRIC filters ,ELECTRIC controllers ,REACTIVE power ,ELECTRIC power factor ,ALTERNATING currents ,ELECTRIC current regulators ,VOLTAGE-frequency converters ,VOLTAGE regulators - Abstract
Active rectifiers interfacing the grid have gained much attention in recent years due to their current control capability that enables the application to exchange a certain range of power at the benefit of low harmonic distortion compared to line commutated converters. Moreover, the amount of active and reactive powers can be arbitrarily chosen within certain limits. These limits as well as the degree of harmonic attenuation is determined by the line-side filter. This paper basically focuses on the current control of active rectifiers incorporating a line-side filter of first-up to third-order degree. Thus, it treats both the current-source converter (CSC) as well as the voltage-source converter (VSC). The basic models of the plant are derived for each case, and important dualities are pointed out. As a conclusion, a recipe for the controller design of particularly CSCs with LC filters and VSCs with LCL filters is proposed. [ABSTRACT FROM AUTHOR]
- Published
- 2009
- Full Text
- View/download PDF
15. DC-Link Harmonics of Three-Phase Voltage-Source Converters Influenced by the Pulsewidth-Modulation Strategy An Analysis.
- Author
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Bierhoff, Michael H. and Fuchs, Friedrich Wilhelm
- Subjects
CASCADE converters ,PULSE width modulation ,ELECTRONIC pulse techniques ,CAPACITORS ,FOURIER series ,ELECTRIC currents ,SPECTRUM analysis ,INDUSTRIAL electronics - Abstract
DC-link current harmonics are the predominant factor to be considered for dimensioning dc capacitors in three-phase pulsewidth-modulation (PWM) voltage-source converters. In this paper, an analysis of the dc-link current harmonics applying a double Fourier series is derived. The analytical results for the dc-link current spectra of continuous and discontinuous PWMs are presented and compared with measurement results taken from a converter test setup. A good match between theoretically expected and actually obtained experimental results can be stated. Moreover, characteristic differences between the investigated modulation strategies regarding their dc-link current spectra become evident. [ABSTRACT FROM AUTHOR]
- Published
- 2008
- Full Text
- View/download PDF
16. Switched Link PWM Current Source Converters with Harmonic Elimination at the Mains.
- Author
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Sharon, Daniel and Fuchs, Friedrich Wilhelm
- Subjects
CASCADE converters ,ELECTRIC switchgear ,PULSE width modulation - Abstract
Presents a novel switched link pulse-width-modulated current source converters. Limitations and constraints in three-phase current source converters; Topologies for harmonic elimination; Simulation results.
- Published
- 2000
- Full Text
- View/download PDF
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