Veröffentlichungen
- 14.J. Holtz and E. Bube, "Field-oriented asynchronous pulse-width modulation for high-performance AC machine drives operating at low switching frequency", IEEE Transactions on Industry Applications, vol. 27, no. 3, pp. 574--581, 1991.
Abstract:
A novel pulse-width modulation (PWM) technique is based on the prediction of the trajectory patterns that the stator current vector describes in a field-oriented coordinate system. The method of field-oriented PWM control minimizes the switching frequency at given torque ripple. The harmonics of the field producing current are left to develop freely, permitting operation at values of switching frequency that are lower than those of the optimal schemes known so far. The optimal switching times are computed off line and are called from a memory during operation. Signal processing is performed in a simple hardware structure.{\textless}{\textgreater} - 13.D. Antic and J. Holtz, "High-efficiency dual transistor base drive circuit based on the Cuk converter topology", IEEE Transactions on Industrial Electronics, vol. 38, no. 3, pp. 161--165, 1991.
Abstract:
A dual transistor base drive circuit that unifies all important functions (on-state base current power supply for two power transistors, off-state negative U/sub be/ =-5 V base-emitter voltage, overcurrent and short-circuit protection scheme based on saturation voltage, and on- and off-state monitoring circuits) is described. The unit provides two base drive outputs using a single switching converter. It can be used to control two individual power transistors in different inverter configurations, e.g. common emitter or bridge configuration. The concept of a dual transistor base drive circuit using the Cuk switching regulator topology enables the low volume construction of a high-efficiency base drive unit for a high-power transistor inverter bridge leg. The circuit is powered from a common DC rail. The base current waveforms are characterized by steep slopes and an overcurrent peak at turn on.{\textless}{\textgreater} - 12.J. Holtz and T. Thimm, "Identification of the machine parameters in a vector-controlled induction motor drive", IEEE Transactions on Industry Applications, vol. 27, no. 6, pp. 1111--1118, 1991.
Abstract:
High dynamic performance of pulse-width-modulated (PWM) inverter-fed induction motor drives was achieved by using the method of field-oriented control. This method requires the actual value of the rotor time constant as essential system information, based on how the magnitude and the position of the rotor flux are calculated. An online identification technique for the rotor time constant and for other machine parameters is described. The identification is based on an evaluation of the stator current trajectory, which is the dynamic response of the induction motor to the PWM-switching sequence. An analytical machine model is operated in parallel to the actual machine, having the stator voltages and the mechanical speed of the induction motor as input signals. The coincidence of the two stator current trajectories of the model and the machine serves as an error indicator for the parameter identification scheme, permitting repetitive updates of the model parameters.{\textless}{\textgreater} - 11.A. M. Khambadkone and J. Holtz, "Vector controlled induction motor drive with a self-commissioning scheme" in [Proceedings] IECON '90: 16th Annual Conference of IEEE Industrial Electronics Society, 1990, pp. 927-932 vol.2.
Abstract:
Different vector controlled structures are discussed, and their suitability for an economical and reliable industrial drive system is explored. The design of compact control hardware, comprising an 80196 microcontroller and an application-specific IC (ASIC) for generating pulse-width-modulation (PWM) signals is derived. The drive system can be configured from a host computer or a hand-held servicing unit through a serial data link. Monitoring and diagnostic functions are included. A self-commissioning scheme permits the setting of the parameters for optimum dynamic performance of the induction motor. Various oscillograms demonstrate the behaviour of the vector controller operating a 25 kVA PWM inverter.{\textless}{\textgreater} - 10.J. Holtz, S. Salama and K. H. Werner, "A nondissipative snubber circuit for high-power GTO inverters", IEEE Transactions on Industry Applications, vol. 25, no. 4, pp. 620--626, 1989.
Abstract:
A novel snubber circuit for high-power GTO inverters is composed of only passive components which, idealized, produce no losses. The stored energy in the turn-on and turn-off snubbers is completely recovered during a switching cycle. In the absence of a permanent circulating current in the recovery transformer, the minimum on-time duration of one half-bridge is very low. The nondissipative operation of the snubber circuit permits a liberal design of the snubber components by which the switching losses in the power semiconductors are greatly reduced.{\textless}{\textgreater} - 9.J. Holtz and H. -. Kelin, "The propagation of harmonic currents generated by inverter-fed locomotives in the distributed overhead supply system", IEEE Transactions on Power Electronics, vol. 4, no. 2, pp. 168--174, 1989.
Abstract:
Pulse-width-modulated converter-fed locomotives generate current harmonics that give rise to traveling waves in the overhead supply system. The waves are partially reflected at the feeding substances, causing parallel and series resonances at various discrete frequencies. An investigation based on the wave propagation approach demonstrates the influence of the track topography and the varying position of locomotives within the track. The distribution of harmonic currents in the overhead supply system is evaluated and discussed. These currents are shown to be much higher in certain locations of the railway track than the harmonic current injected by a locomotive. They may also appear at distant tract locations. The natural resonances in the overhead supply system determine the intensity of electromagnetic interference with the track-side communication lines.{\textless}{\textgreater} - 8.J. Holtz and K. -. Werner, "Multi-inverter UPS system with redundant load sharing control" in 15th Annual Conference of IEEE Industrial Electronics Society, 1989, pp. 159-164 vol.1.
Abstract:
The concept of a redundant multi-inverter UPS (uninterruptible power supply) system includes extended monitoring of the status and the operating conditions of all power electronic equipment. Each block of the UPS system is monitored by two independent microcomputers that process the same data. The microcomputers are part of a redundant distributed monitoring system, being separately interlinked by two serial data buses through which they communicate. They establish a hierarchy among the participating blocks, defining one of the healthy inverter blocks as the master. The actual master runs the central synchronizing unit for the entire system, while the slave units perform the control of equal active and reactive load sharing. Operation and fault detection are experimentally exemplified in a dual inverter system having a rating of 10 kVA of redundant power.{\textless}{\textgreater} - 7.J. Holtz and T. Thimm, "Identification of the machine parameters in a vector controlled induction motor drive" in Conference Record of the IEEE Industry Applications Society Annual Meeting, 1989, pp. 601-606 vol.1.
Abstract:
A method for the online identification of the parameters of an induction machine is described. This method requires the actual value of the rotor time constant as essential system information, on the basis of which the magnitude and the position of the rotor flux is calculated. An online identification technique for the rotor time constant and other machine parameters is described. The identification is based on an evaluation of the stator current trajectory as the dynamic response of the induction motor to the pulse-width modulation (PWM) switching sequence. An analytical machine model is operated in parallel with the stator voltages and the mechanical speed of the induction motor as input signals. The coincidence of the two stator current trajectories of the model and the machine serves as an error indicator for the parameter identification scheme, permitting repetitive updates of the model parameters.{\textless}{\textgreater} - 6.J. Holtz and U. Boelkens, "Direct frequency convertor with sinusoidal line currents for speed-variable AC motors", IEEE Transactions on Industrial Electronics, vol. 36, no. 4, pp. 475--479, 1989.
Abstract:
A novel concept for a static three-phase to three-phase power converter for an AC drive with a unity power factor and reduced harmonics on the line side is presented. The power circuit comprises two back-to-back connected six-pulse bridges having no energy storage elements in the DC link. This permits pulse-width modulation (PWM) control in both bridges while requiring active turn-off semiconductor switches in only one bridge. The line-side harmonics are suppressed by a three-phase second-order filter. The method of predictive optimization is used for the control of the power converter. The complex control structure of the system is based on an online prediction of space vector trajectories. The steady-state operation of the system is exemplified by simulation results.{\textless}{\textgreater} - 5.J. Holtz and E. Bube, "Field-oriented asynchronous pulsewidth modulation for high performance AC machine drives operating at low switching frequency" in Conference Record of the 1988 IEEE Industry Applications Society Annual Meeting, 1988, pp. 412-417 vol.1.
Abstract:
A novel pulsewidth-modulation technique is reported that is based on the prediction of the trajectory patterns which the stator current vector describes in a field-oriented coordinate system. The method limits only the error of the torque-producing current component while exerting no constraint on the harmonics of the field-producing current. High dynamic performance and minimum switching frequency is achieved with the help of precalculated memory data, permitting implementation in low-cost hardware.{\textless}{\textgreater}
