Veröffentlichungen
- 90.R. Lach and S. Soter, "Individual Approach to an Efficient Minimization of Vibration an Noise Stimulation for Inverter-Fed Drives" in PCIM Asia 2004, 2004.
- 89.S. Soter and F. Bertling, "Adjustable converter for injection of fuel cell power as a part of a virtual power plant" in PESC04, Piscataway, N.J: IEEE, 2004, pp. 1988-1990 Vol.3.
ISBN: 0-7803-8399-0
Abstract:
This research project deals with the development of a solid, intelligent converter with a good value. The energy of fuel cells or other low-voltage energy-sources (40 to 80 VDC) is feeded decentral into the public net (230 VAC/50 Hz or 110 VAC/60 Hz). Because of the requirements of the serial product (e.g. low price, reliability, range of use) a prototype of a converter with high frequency transformer was built. The latest electronic devices and a digital signal processor as central controller have been applied to achieve high efficiency and flexible power injection. It is possible to obtain improvements of the local voltage quality and stability by adjusting active and reactive power as well as power factor and current shape. - 88.J. Holtz and H. Pan, "Elimination of saturation effects in sensorless position-controlled induction motors", IEEE Transactions on Industry Applications, vol. 40, no. 2, pp. 623--631, 2004.
Abstract:
Owing to the variable magnetic coupling between the stator windings and the discrete rotor bars of an induction motor, a quasicontinuous rotor position signal can be acquired by instantaneous measurement of the total leakage inductance of the three stator phases. The signals are sampled in synchronism with the regular commutations of the pulsewidth-modulation process, thus making the injection of additional high-frequency carriers obsolete. The acquired position signal exhibits high spatial resolution and high dynamic bandwidth. Magnetic saturation also influences the total leakage inductances and, hence, constitutes a disturbance for position identification. This paper presents a detailed analysis of the saturation effects and proposes methods to eliminate their undesired impact on the position signal. Experimental results of closed-loop sensorless position control at full load and high dynamic performance are presented. - 87.J. Holtz, J. Quan, J. Pontt, J. Rodriguez, P. Newman and H. Miranda, "Design of fast and robust current regulators for high-power drives based on complex state variables", IEEE Transactions on Industry Applications, vol. 40, no. 5, pp. 1388--1397, 2004.
Abstract:
High-power pulsewidth-modulated inverters for medium-voltage applications operate at switching frequencies below 1 kHz to keep the dynamic losses of the power devices at a permitted level. Also, the sampling rate of the digital signal processing system is then low, which introduces considerable signal delays. These have adverse effects on the dynamics of the current control system and introduce undesired cross coupling between the current components i/sub d/ and i/sub q/. To overcome this problem, complex state variables are used to derive more accurate models of the machine and the inverter. From these, a novel current controller structure employing single-complex zeros is synthesized. Experimental results demonstrate that high dynamic performance and zero cross coupling is achieved even at very low switching frequency. - 86.A. Wirsen and S. Soter, "Berührungslose Drehmomenterfassung - Turbosätze altern unter strengeer Beobachtung", SENSOR report, vol. 2004, no. 4, 2004.
- 85.J. Holtz and H. Pan, "Acquisition of rotor anisotropy signals in sensorless position control systems", IEEE Transactions on Industry Applications, vol. 40, no. 5, pp. 1379--1387, 2004.
Abstract:
Sensorless position control of induction motors relies on the detection of rotor anisotropies. The repetitive transient excitation through the switched voltages of the pulsewidth-modulated inverter provides the test signals to identify the spatial orientation of the anisotropies that indicate the rotor position. The position information is contained in the inverter output voltages. These are measured against the neutral point of the star connected stator winding. The signals are heavily corrupted by disturbances. These originate from the propagation of traveling waves on a long motor cable and from the influence of high-frequency common-mode currents. The paper describes how a clean position signal is extracted in the presence of such noise. - 84.E. P. Wiechmann, R. P. Burgos and J. Holtz, "Active front-end converter for medium-voltage current-source drives using sequential-sampling synchronous space-vector modulation", IEEE Transactions on Industrial Electronics, vol. 50, no. 6, pp. 1275--1289, 2003.
Abstract:
This paper presents an active front-end converter for medium-voltage current-source drives. It comprises two series-connected pulsewidth-modulation (PWM) rectifiers fed from a delta-wye isolation transformer. These employ sequential-sampling synchronous space-vector modulation (SVM), and operate at a switching frequency of 100 Hz, thus reducing the switching losses by 66{%} compared to previous PWM approaches. Digital processing requirements of this technique are minimized by using decision-making SVM. This online modulation technique ensures full harmonic current cancellation through the magnetic interface, and minimizes the sampling/control-action delay. Therefore it enables the use of advanced control strategies notwithstanding the low sampling frequency of the control system. Exploiting this fact, the proposed converter is controlled using a nonlinear strategy in the synchronous frame. The strategy employs input-output and feedback linearization, and is derived from the complex-signal flow diagram of the converter. The proposed strategy linearizes and partially decouples the converter d-q-axes dynamics, ensuring a dynamic response totally independent from the operating point, even under regeneration. This is a highly desirable feature for high-performance drives presenting continuous transitions from motoring to regeneration. Moreover, the converter presents an independent active and reactive power flow, which enables it to operate as a reactive power compensator if desired. Computer analysis and experimental work with a TMS320C32 digital-signal-processor-based 5-kVA laboratory prototype validate the excellent results attained by the proposed converter. - 83.D. Hansen, J. Holtz and R. Kennel, "Close contact [cross cutters, knives]", IEEE Industry Applications Magazine, vol. 9, no. 5, pp. 33--39, 2003.
Abstract:
This article presents a cutter knife for synchronous and asynchronous cutters with scissors-cutting technique. A well-known design is using mechanically coupled cutters to provide synchronous motion of cutter cylinders, The cutting cylinders are braced by torsional force. The contact force between the knives has to be adjusted by a couple of adjusting devices (e.g., screws). It is necessary to readjust the equipment rather often for maintenance reasons. An improvement of this situation would be appreciated by the printing and foil production industries. A cutter distance sensor with good performance is required to introduce separately controlled servo drives in cutter knives. The test results obtained by test samples of the proposed sensor show that all information necessary for adapting the control structure and control parameters can be obtained by the proposed sensor concept. This type of sensor enables further progress in industrial drive applications, which leads to more replacement of mechanical designs by servo drives with flexible control. - 82.J. Holtz and J. Quan, "Drift- and parameter-compensated flux estimator for persistent zero-stator-frequency operation of sensorless-controlled induction motors", IEEE Transactions on Industry Applications, vol. 39, no. 4, pp. 1052--1060, 2003.
Abstract:
The performance of sensorless-controlled induction motors is poor at very low speed. The reasons are the limited accuracy of stator voltage acquisition and the presence of offset and drift components in the acquired signals. To overcome these problems, a pure integrator is employed for stator flux estimation. The time-variable DC offset voltage is estimated from the flux drift in a parallel stator model and used to eliminate the offset by feedforward control. Residual high-frequency disturbances are compensated by feedback flux amplitude control. A linearization of the pulsewidth-modulation inverter transfer function and an improved stator resistance estimation scheme further enhance the system performance. Experiments demonstrate high dynamic performance of sensorless control at extreme low speed and zero stator frequency. - 81.J. Holtz, J. Quan, G. Schmittt, J. Pontt, J. Rodriguez, P. Newman and H. Miranda, "Design of fast and robust current regulators for high power drives based on complex state variables" in 38th IAS Annual Meeting on Conference Record of the Industry Applications Conference, 2003, 2003, pp. 1997-2004 vol.3.
Abstract:
High-power PWM inverters for medium voltage applications operate at switching frequencies below 1 kHz to keep the dynamic losses of the power devices at permitted level. Also the sampling rate of the digital signal processing system is then low, which introduces considerable signal delays. These have adverse effects on the dynamics of the current control system and introduce undesired cross-coupling between the current components i/sub d/ and i/sub q/. To overcome this problem, complex state variables are used to derive more accurate models of the machine and the inverter. From these, a novel current controller structure employing single-complex zeroes is synthesized. Experimental results demonstrate that high dynamic performance and zero cross-coupling is achieved even at very low switching frequency.
