Veröffentlichungen
- 80.M. Linke, R. Kennel and J. Holtz, "Sensorless speed and position control of synchronous machines using alternating carrier injection" in IEEE International Electric Machines and Drives Conference, 2003. IEMDC'03, 2003, pp. 1211-1217 vol.2.
Abstract:
High frequency carrier injection is a promising approach solving high performance sensorless drive demands. Position control at low and zero speed is only possible using anisotropic effects considered in high-frequency models. The usually open loop carrier signal injection is impacted by nonlinear inverter properties like the dead-time effect. This paper discusses the influence of the dead time effect on the carrier signal excitation comparing alternating and revolving injection principles. To overcome disturbing effects an alternating injection procedure is proposed using a predefined injection angle. The approach reduces the effects of the inverter distortion voltages. As a result it is possible to track even small saliencies typical for surface mounted permanent magnet synchronous machines. For processing the high frequency current for position estimation, there is no additional hardware necessary within a standard drives with field oriented control. The paper presents theoretical analysis and experimental results. - 79.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. - 78.J. Holtz, "Sensorless control of induction motor drives", Proceedings of the IEEE, vol. 90, no. 8, pp. 1359--1394, 2002.
Abstract:
Controlled induction 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 voltages and currents 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 in the low-speed range can be 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. - 77.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. - 76.S. Soter, "Windkraftnutzung an der Universität Dortmund", Mundo, vol. 2002, no. 2, 2002.
- 75.S. Soter and S. Buchhold, "Adaptable inverter for injection of fuel cell and photovoltaic power" in Proceedings of the Power Conversion Conference-Osaka 2002 (Cat. No.02TH8579), 2002, pp. 1453-1455 vol.3.
Abstract:
Due to environmental conditions it is becoming more and more important to apply renewable energies and efficient technologies. For power injection of photovoltaic and fuel cell energy an inverter is needed. The presented modular and flexible prototype works with different energy sources such as photovoltaic, fuel cell and battery. It is possible to adjust active and reactive power as well as current shape separately within limits to improve power quality. The power electronics works very well and is able to convert 20 to 80 VDC into 110 VAC/60 Hz or 230 VAC/50 Hz with a high flexibility and efficiency. - 74.R. P. Burgos, E. P. Wiechmann and J. Holtz, "Complex state variables modeling and nonlinear control of PWM voltage- and current-source rectifiers" in IEEE 2002 28th Annual Conference of the Industrial Electronics Society. IECON 02, 2002, pp. 187-192 vol.1.
Abstract:
This paper proposes the use of complex state variables to model and control PWM voltage- and current-source rectifiers, a technique originally developed for AC machines based on space vector theory. This technique employs complex signal flow graphs to model systems of differential equations, hence rendering them intelligible by visual inspection. Moreover, it allows nonlinear control laws to be directly obtained from converter models, further simplifying the control system design. Feedback linearization is herein used, a nonlinear strategy of great simplicity and intuitiveness. Under the proposed control schemes both rectifiers attained fully decoupled d-q axes dynamics, thus enabling them as VAr compensators, and also achieved a constant dynamic response totally independent from the drive operating point. The latter is highly desirable for high-performance drives featuring continual accelerations and decelerations. The paper includes a detailed modeling and nonlinear control law design-procedure for both PWM rectifiers, together with experimental results from 10 kVA TMS320C32 DSP-based laboratory prototypes used for evaluation purposes. - 73.S. Soter and S. Buchhold, "Converter for Mains Supply - Low-Priced and Intelligent" in 10th International Power Electronics and Motion Control Conference, Dubrovnik, 2002.
- 72.D. Hansen, J. Holtz and R. Kennel, "Cutter distance sensor for an adaptive position-/torque control in cross cutters" in Conference Record of the 2002 Annual Pulp and Paper Industry Technical Conference (Cat. No.02CH37352), 2002, pp. 54--61.
Abstract:
Cross cutters are important equipment in the paper industry. A well-known design is to use mechanically coupled cutters providing synchronous motion. To improve dynamic behavior of cross cutters and to reduce maintenance effort it would be advantageous to operate the cutters by separately controlled servo drives. This idea requires very exact knowledge concerning cutter positions to ensure proper operation and to avoid any crash. This paper presents a progressive sensor measuring the distance between the cutter knives and distinguishing between knives approaching or touching each other directly on the one hand and normal cutting operation with material between the knives on the other hand. Measuring results obtained by a test example of the sensor are presented. - 71.S. Soter and S. Buchhold, "Low Voltage Converter for Feeding the Net with Fuel Cell Power" in PCIM Asia 2002, 2002.
