Veröffentlichungen
- 100.J. Holtz and J. Juliet, "Sensorless acquisition of the rotor position angle of induction motors with arbitrary stator windings", IEEE Transactions on Industry Applications, vol. 41, no. 6, pp. 1675--1682, 2005.
Abstract:
The anisotropy of a cage rotor is utilized to determine the angular position of the rotor in an induction machine. The switching transients generated by a pulsewidth-controlled inverter serve as test signals. The response of the three-inverter terminal currents is exploited to derive a quasi-instantaneous rotor position signal. The position is sensed at the inverter through the three-phase motor cable by measuring the current derivatives. The method does not require additional wire connections. It is applicable to induction motors having stator windings connected either in wye or in delta. The results are supported by measurements from an experimental setup. - 99.J. Holtz, "Developments in Sensorless AC Drive Technology" in 2005 International Conference on Power Electronics and Drives Systems, 2005, pp. 9--16.
ISBN: 2164-5264
Abstract:
Controlled AC motor drives without mechanical speed sensors at the motor shaft have the attractions of low cost and high reliability. To replace the sensor, the information on the rotor speed is extracted from measured stator currents and from the voltages at the motor terminals. Vector controlled drives require estimating the magnitude and spatial orientation of the fundamental magnetic flux waves in the stator or in the rotor. Open loop estimators or closed loop observers are used for this purpose. They differ with respect to accuracy, robustness, and sensitivity against model parameter variations. Dynamic performance and steady-state speed accuracy around zero speed range is achieved by signal injection, exploiting the anisotropic properties of the machine. The overview in this paper uses signal flow graphs of complex space vector quantities to provide an insightful description of the systems used in sensorless control of AC motors - 98.F. Bertling and S. Soter, "Improving grid voltage quality by decentral injection of current harmonics" in IECON 2005 - 31th Annual Conference of the IEEE Industrial Electronics Society, 2005, pp. 3 pp.
Abstract:
This research project deals with the development of an adjustable converter for injection of fuel cell power. A DC/DC converter stage increasing the voltage level is connected to a DC/AC inverter for grid current injection via a high capacitance DC link. This decouples the momentary power drawn from the energy source from the momentary power being injected into the grid, allowing arbitrary output current waveforms without an increase of input current ripple. Conventionally, pure fundamental frequency currents are considered the optimum waveform regarding the injected currents impact on the grid. This paper demonstrates how grid voltage harmonics caused by nonlinear loads can be minimized by adapting the converters injected current shape. In contrast to harmonics compensation in industrial applications where the compensation current is determined by measuring the local loads current harmonics, the intended decentral application in private houses suggests a different approach to improve overall grid voltage quality. The digital signal processor used for the converters control and monitoring functions calculates the frequency spectrum of the measured grid voltage run by digital Fourier transformation (DFT) and determines the current harmonics necessary to counteract the present voltage harmonics. The resulting current frequency spectrum is modulated into a time dependant current shape that is added to the fundamental frequency current run determined by the requested amounts of active and reactive power. This way, harmonic currents of the local loads are compensated without changes in the house installation for measuring the loads currents. Also current harmonics of neighbouring houses are compensated. - 97.F. Bertling and S. Soter, "Increasing efficiency of an DSP-controlled converter by on-the-fly changing of the gate drive method" in 2005 IEEE 6th International Conference on Power Electronics and Drive Systems (PEDS), 2005, pp. 448--451.
Abstract:
This paper demonstrates how bypassing the MOSFETs body diodes in a full bridge application by freewheeling of the transformer current through the MOSFETs of one input leg decreases the power losses, depending on the operating point. A gate drive control via a modern digital signal processor is described that allows an on-the-fly change of the gate drive method so that freewheeling is activated or deactivated as required to obtain lowest losses in a wide operating range. Unlike other approaches to bypass the MOSFETs body diodes, this technique requires no additional circuit parts (e.g. external freewheeling diodes). The effect of freewheeling on power losses is illustrated by measurements of the current and voltages run, MOSFET temperatures and the characteristic curve of power losses - 96.S. Soter, R. Wegener, J. Dopheide and B. Kiffer, "Low cost vector control for permanent-magnet-synchronmotor with only one DC-link current sensor for pumping application" in IEEE International Conference on Electric Machines and Drives, 2005, 2005, pp. 174--177.
Abstract:
This paper presents a cost-efficient closed loop control of a small permanent magnet machine for pumping application. The special feature of the described solution is only one current probe in the DC-link of the converter. The three phase currents are calculated from this measured current in combination with the state of semiconductors at the time of measurement. Near the sector borders of the space vector modulation the turn-on-time of one semiconductor is too short for measuring the current. A method is developed to compensate these blind areas with the extension of the turn-on-time in half of the PWM-cycles. The measured values are checked by an error detection and exchanged if necessary by an approximation. The position of the rotor is also calculated from the measured current. The paper presents a close loop vector control with less costs than conventional solutions. - 95.R. Lach and S. Soter, "Measuring method for determining the reasons of magnetically caused structure-borne sound on electrical drive systems" in 2005 European Conference on Power Electronics and Applications, 2005, pp. 10 pp--P.10.
Abstract:
A special signal processing method (order analysis) allows well-defined conclusions from accelerometer measurements on electrical drives regarding the reasons of structure-borne and airborne sound. In this paper an analysis of acceleration signals of an 5 kW induction machine is presented. The special feature is that a projection of sound curves is included in this analysis. Thus it is possible to assign an oscillation excitation to harmonics attributed to the machine design or harmonics of the feeding frequency converter. - 94.J. Pontt, J. Rodriguez, P. Newman, A. Liendo and J. Holtz, "Network friendly low-switching frequency high-power three-level PWM rectifier" in 2005 European Conference on Power Electronics and Applications, 2005, pp. 9 pp--P.9.
Abstract:
High-power converters for regenerative drives and distributed generation need a network-friendly operation with low switching frequency for high reliability and performance. This paper presents a multipulse connection of two three-level NPC PWM rectifiers with the selective harmonics elimination technique (SHE) and a novel optimal method for minimal current distortion. - 93.R. Lach, S. Soter and R. Wegener, "Experimental determination of systemeigenfrequencies on electrical drives" in 11th International Power Electronics and Motion Control Conference, Riga: {Riga Technical University}, 2004.
ISBN: 9984320588
- 92.S. Soter and R. Lach, "Von der Sonne zur eigenen Photovaltaik-Anlage: Verbraucher-Informationen im Internet" in 19. Symposium Photovoltaische Solarenergie, 2004.
- 91.R. Lach and S. Soter, "Sound source location measuring system for a systematic design modification of electrical machines" in PCIM Europe, 2004.
