Veröffentlichungen
- 60.S. Soter and R. Lach, "Concept of noise minimization of three-phase current machines by variation and modification of control scheme and power electronics" in PCIM Europe, 2000.
- 59.E. P. Wiechmann, R. P. Burgos and J. Holtz, "Sequential connection and phase control of a high-current rectifier optimized for copper electrowinning applications", IEEE Transactions on Industrial Electronics, vol. 47, no. 4, pp. 734--743, 2000.
Abstract:
This paper proposes an optimized sequential control technique for copper electrowinning high-current rectifiers. The converter comprises two series-connected six-pulse double-wye rectifiers, a step-down transformer, and a tuned input filter. The six-pulse rectifiers are fed from delta and polygon primary windings with different turns ratio and phase shifted by 5/spl deg/. Under the proposed control scheme, one rectifier is kept at nominal output voltage, and the other one is phase controlled to control the load's current. The proposed strategy greatly improves the rectifier's performance, reducing its reactive power maximum demand by 62{%} compared to conventional rectifiers and, therefore, reduces the input filters power rating also by 62{%}. This is accomplished while keeping the input power factor above 0.95 throughout the whole operating range. Further, the converter's reactive power consumption presents a low varying characteristic, allowing it to use a fixed filter, even when operating from a power system not capable of withstanding large reactive power variations. Finally, it presents a harmonic current distortion comparable to conventional 12-pulse high-current rectifiers. This paper presents the design and optimization procedure of the rectifying system. A 2.5 kVA laboratory prototype was used to validate the converter model, later employed in evaluating the converter operating in a 10.5 MVA copper electrowinning facility. The results obtained confirm the advantages of the proposed converter and its control strategy. - 58.J. Holtz and M. Stamm, "Gate-assisted reverse and forward recovery of high-power GTOs in series resonant DC-link inverters", IEEE Transactions on Power Electronics, vol. 14, no. 2, pp. 227--232, 1999.
Abstract:
The series resonant DC-link inverter is an attractive circuit topology for interfacing a DC current with a three-phase AC system. It uses gate turn-off thyristors (GTOs) as semiconductor switches. The conventional solution requires an additional series diode to perform the turn off process and to enable forward recovery of the GTO. This paper uses a single GTO along with a special gate drive to provide reverse and forward recovery. A new device testing circuit was designed to create the same electrical and thermal stresses as in a series resonant DC-link inverter. Experimental results using 2000 A GTOs at 26 kHz switching frequency demonstrate that the total device losses are reduced, while the hold-off time is slightly increased. The new single-device solution makes resonant switching attractive for very high-power applications. - 57.J. O. Krah and J. Holtz, "High-performance current regulation and efficient PWM implementation for low-inductance servo motors", IEEE Transactions on Industry Applications, vol. 35, no. 5, pp. 1039--1049, 1999.
Abstract:
This paper reports on a standard microcontroller implementation of a pulsewidth modulator and near-deadbeat current regulator for high switching frequency. The application is in high-performance positioning systems. The control strategy relies on a simplified machine model without incurring performance degradations. Changes between different modulation strategies are programmed depending on the modulation index. The values of switching time durations are obtained exclusively by decision making, thus minimizing computational load. Features like over-modulation (OVM), dynamic OVM, anti-windup, and reduction of switching frequency at thermal overload are included. - 56.E. P. Wiechmann, R. P. Burgos and J. Holtz, "Optimized sequential control for electrowinning high-current phase-controlled rectifiers" in IECON'99. Conference Proceedings. 25th Annual Conference of the IEEE Industrial Electronics Society (Cat. No.99CH37029), 1999, pp. 241-246 vol.1.
Abstract:
This paper proposes an optimized sequential control technique for electrowinning 12-pulse high-current rectifiers. The converter comprises two series connected 6-pulse double-wye rectifiers, a step-down transformer and a tuned input filter. The 6-pulse rectifiers are fed from delta and polygon primary windings with different turns ratio and phase shifted by 5/spl deg/. Under the proposed control scheme, one rectifier is kept at nominal output voltage and the other one is phase controlled to control the load's current. The proposed strategy greatly improves the rectifier's performance, reducing Its reactive power maximum demand by 62{%} compared to conventional rectifiers. Therefore reduces the input filter's power rating also by 62{%}. All this while maintaining an input power factor above 0.95. Further, the converter's reactive power consumption presents a low varying characteristic, allowing it to use a fixed filter even when operating from a power system not capable of withstanding large reactive power variations. Finally, it presents a harmonic current distortion comparable to conventional 12-pulse rectifiers. This paper presents the design and optimization procedure of the rectifying system. Simulation results are used to evaluate the converter in a 10.5 MVA electrowinning facility, and in conjunction with results obtained with a 2.5 kVA experimental prototype are used to validate the proposed converter and control strategy. - 55.J. Holtz, "Sensorless position control of induction motors. An emerging technology" in AMC'98 - Coimbra. 1998 5th International Workshop on Advanced Motion Control. Proceedings (Cat. No.98TH8354), 1998, pp. 1--14.
Abstract:
Concepts for sensorless position control of induction motor drives rely on anisotropic properties of the machine rotor. Such anisotropies can be incorporated as periodic variations of magnetic saliencies in various ways. 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 sensors. The practical implementation of sensorless position identification, and of a high-accuracy position control system are reported. - 54.J. Holtz, "Sensorless position control of induction motors-an emerging technology" in IECON '98. Proceedings of the 24th Annual Conference of the IEEE Industrial Electronics Society (Cat. No.98CH36200), 1998, pp. I1-12 vol.1.
Abstract:
Concepts for the sensorless position control of induction motor drives rely on anisotropic properties of the machine rotor. Such anisotropies can be incorporated as periodic variations of magnetic saliencies in various ways. 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 sensor. The practical implementation of sensorless position identification, and of a high-accuracy position control system are reported. - 53.S. Soter, "Kosten- und Wirkungsgradoptimierung eines Wechselrichters mit Einzeltransistoren (MOSFET) am Beispiel eines photovoltaisch versorgten Inselsystems" in 13. Symposium Photovoltaische Solarenergie, 1998.
- 52.D. Gebler and J. Holtz, "Identification and compensation of gear backlash without output position sensor in high-precision servo systems" in IECON '98. Proceedings of the 24th Annual Conference of the IEEE Industrial Electronics Society (Cat. No.98CH36200), 1998, pp. 662-666 vol.2.
Abstract:
High-performance position control can be improved by the compensation of gear backlash. This paper presents a compensation method that does not need an output position sensor. In the first section, two different methods of on-system backlash identification are described. One method is based on dynamic reaction to a small torque impulse injected by the motor, while the other analyses the change of torque at the end of the backlash dead zone in a quasi-stationary trajectory. The second section of the paper deals with backlash compensation. Based on the identified value of backlash, the angular error of the output shaft is reduced. A self-learning time-optimal control method is described. Experimental measurements demonstrate the excellent performance and accuracy of the compensated system. - 51.Y. Lou, J. Holtz and T. H. Lee, "Critical implementation issues in compensation for nonlinearities in industrial robot manipulators by adaptive multilayer neural networks" in Proceedings of the 1998 American Control Conference. ACC (IEEE Cat. No.98CH36207), 1998, pp. 2200-2202 vol.4.
ISBN: 0743-1619
Abstract:
To improve the performance of an industrial robot manipulator with linear individual-joint controllers, an adaptive feedforward multilayer neural network (MNN) is proposed as an addition to the existing linear control structure at each joint to compensate the nonlinearity. System stability is guaranteed by three measures: the initialization of the MNN, which ensures that the MNN learning start from a reasonable point; a Lyapunov-based adaptive law in which the MNN is linearized and the residual error is tolerated by a dead-zone or a leakage term; and a contribution function which manipulates the contribution of the MNN to the system. The MNN and the control algorithm are implemented on a TMS320C30 digital signal processor. The realization on a two-link manipulator demonstrates the effectiveness of the proposed scheme.
