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.

70.

S. Soter, S. Buchhold and R. Lach, "Niederspannungswechselrichter mit hohem Wirkungsgrad" in 17. Symposium Photovoltaische Solarenergie, 2002.

69.

S. Soter and R. Lach, "Noise minimization of three-phase current machines by variation and modification of control scheme and power electronics" in PCIM Europe, 2002.

68.

M. Linke, R. Kennel and J. Holtz, "Sensorless position control of permanent magnet synchronous machines without limitation at zero speed" in IEEE 2002 28th Annual Conference of the Industrial Electronics Society. IECON 02, 2002, pp. 674-679 vol.1.

Abstract:
Sensorless position control of surface mounted permanent magnet synchronous machines (SMPMSM) still is a challenge. High performance position control at low and zero speed is only possible using anisotropic effects being considered not in the fundamental-frequency machine models, but in extended high-frequency models. This paper presents a new high-frequency injection method estimating the rotor position, which overcomes the small signal to noise ratio inherent to methods of this type published so far. This enables to track even small saliencies typical for SMPM synchronous machines. A small high-frequency voltage signal is injected into the rotor d-axis with no influence on the torque producing q-current. The demodulation of the responding high-frequency current signal is independent on machine parameters. Therefore the proposed method is independent on machine parameters and simply adaptable to different machines. As only the high frequency current has to be processed for position estimation, there is no additional hardware necessary besides that for standard drives with field oriented control.

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.

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.

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.

65.

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.