Veröffentlichungen
- 70.S. Soter, "Windkraftnutzung an der Universität Dortmund", Mundo, vol. 2002, no. 2, 2002.
- 69.J. Holtz and J. Quan, "Sensorless vector control of induction motors at very low speed using a nonlinear inverter model and parameter identification", IEEE Transactions on Industry Applications, vol. 38, no. 4, pp. 1087--1095, 2002.
ISBN: 0197-2618
Abstract:
The performance of vector-controlled induction motor drives without a speed sensor is generally poor at very low speed. The reasons are offset and drift components in the acquired feedback signals, voltage distortions caused by the nonlinear behavior of the switching converter, and the increased sensitivity against model parameter mismatch. New modeling and identification techniques are proposed to overcome these problems. A pure integrator is employed for stator flux estimation which permits high-estimation bandwidth. Compensation of the drift components is done by offset identification. The nonlinear voltage distortions are corrected by a self-adjusting inverter model. A further improvement is a novel method for online adaptation of the stator resistance. Experiments demonstrate smooth steady-state operation and high dynamic performance at extremely low speed. - 68.A. M. Khambadkone and J. Holtz, "Compensated synchronous PI current controller in overmodulation range and six-step operation of space-vector-modulation-based vector-controlled drives", IEEE Transactions on Industrial Electronics, vol. 49, no. 3, pp. 574--580, 2002.
Abstract:
Overmodulation enhances the power utilization of the installed capacity of a voltage-source inverter. A space-vector strategy is used for constant-switching-frequency inverters. In order to achieve the overmodulation, a modified reference signal with nonuniform angular velocity is generated using a preprocessor. Such a reference wave produces low-frequency harmonics in currents. The presence of current harmonics restricts the bandwidth of the synchronous proportional plus integral current controller in the overmodulation range. A compensating current control is presented to allow for high-bandwidth current control in synchronous coordinates during overmodulation and six-step. The proposed scheme allows for an easy upgrade of a conventional vector control scheme to include overmodulation and, thus, reduce the design-to-market time. - 67.R. Roesner, J. Holtz and R. Kennel, "Cellular driver/snubber scheme for series connection of IGCTs" in 2001 IEEE 32nd Annual Power Electronics Specialists Conference (IEEE Cat. No.01CH37230), 2001, pp. 637-641 vol.2.
ISBN: 0275-9306
Abstract:
In high voltage applications of inverters, series connection of power semiconductors is a well known solution. This paper presents a progressive driver/snubber scheme producing its own supply voltage without external power supply. Besides that, voltage distribution and snubber behavior are optimized and snubber energy is regenerated to the DC link of the inverter. Measuring results obtained from a real IGCT-inverter are presented. - 66.S. Soter and S. Buchhold, "Wirkungsgrad- und Kostenvergleich unterschiedlicher Schaltungskonzepte zur Netzeinspeisung von Leistungen bis 10 Kilowatt und kleinen Gleichspannungen (20 bis 80 Volt)" in 15. Symposium Photovoltaische Solarenergie, 2000.
- 65.F. Joswig and S. Soter, "Windenergienutzung - Ein Vergleich von Technik und Kosten" in European Wind Energy Conferences and Exhibitions, 2000.
- 64.J. Holtz, "Sensorless control of induction motors-performance and limitations" in ISIE'2000. Proceedings of the 2000 IEEE International Symposium on Industrial Electronics (Cat. No.00TH8543), 2000, pp. PL12-PL20 vol.1.
Abstract:
Controlled induction motor drives without mechanical sensors for speed or motor shaft position have the attraction of low cost and high reliability. The identification of rotor speed is generally based on measured terminal voltages and currents. Dynamic models are used to estimate the magnitude and spatial orientation of the fundamental magnetic flux waves in the stator or in the rotor. Open loop estimators and closed loop observers differ with respect to accuracy, robustness, and sensitivity against model parameter variations. Dynamic performance and steady-state speed accuracy in the low speed range is achieved by exploiting parasitic effects 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 induction motors. - 63.S. Soter and S. Buchhold, "Increasing Efficiently of a Converter for Feeding the Net with Fuel Cell Power by Using Modern Electronic Components" in PCIM USA, 2000.
- 62.J. Holtz, "Is sensorless position control of standard induction motors a feasible technology?" in Proceedings IPEMC 2000. Third International Power Electronics and Motion Control Conference (IEEE Cat. No.00EX435), 2000, pp. 21-32 vol.1.
Abstract:
Concepts for sensorless position control of induction motor drives rely on anisotropic properties of the machine rotor. The built-in spatial anisotropy is detected by injecting a high-frequency flux wave into the stator. The resulting stator current harmonics contain frequency components that depend on the rotor position. Models of the rotor saliency serve to extract the rotor position signal using phase-locked loop techniques. A different approach makes use of the parasitic effects that originate from the discrete winding structure of a cage rotor. It has the merit of providing high spatial resolution for incremental positioning without a sensor. The practical implementation of sensorless position identification, and of a high-accuracy position control system are reported. - 61.A. M. Khambadkone and J. Holtz, "Current control in overmodulation range for space vector modulation based vector controlled induction motor drives" in 2000 26th Annual Conference of the IEEE Industrial Electronics Society. IECON 2000. 2000 IEEE International Conference on Industrial Electronics, Control and Instrumentation. 21st Century Technologies, 2000, pp. 1334-1339 vol.2.
Abstract:
Overmodulation enhances the power utilization of the installed capacity of a voltage source inverter. A space vector strategy is used for constant switching frequency inverters. In order to achieve the overmodulation a modified reference signal with nonuniform angular velocity is generated using a preprocessor. Such a reference wave produces low frequency harmonics in currents. The presence of current harmonics restricts the bandwidth of the fundamental component current controller in the overmodulation range. On the other hand a high bandwidth current controller is mandatory for vector control. A compensating current control is presented to allow for high bandwidth current control in synchronous coordinates.
