Prof. Dr. Joachim Holtz
Editor-in-Chief
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Prof. Dr. Joachim Holtz |
IEEE Transactions on Industrial
Electronics
Volume 44, Number 2, April 1997
Regular Papers
Abstract - A new low loss snubber circuit including overvoltage clamping circuit for three-level GTO inverter is presented. The proposed snubber circuit is effective in restriction of the dv/dt and the overvoltage values across each GTO at turn-off and the snubber loss is less than the half that of the conventional RCD snubber circuit. In addition, there is no blocking voltage balancing problem between the inner and outer GTOs that occurs in the case that conventional RCD snubber circuit is used in three-level inverter topology. Experimental results demonstrate that the proposed snubber circuit is very effective for a large capacitiy three-level GTO inverter.
Abstract - Power electronic burn-in test consumes a huge amount of energy and adds up a significant part to manufacturing cost. To improve this situation, a PWM DC/AC inverter using current-mode control is proposed to feedback burn-in test power to utility system. To achieve the proposed idea, a new control strategy and system design is presented in this paper. Case studies using UPS's and battery chargers are demonstrated by prototype experiments to prove its performance and effectiveness.
Abstract - The description of a novel circuit which utilizes a FET current source and a high voltage diode to realize a simple, inexpensive, single shot, high voltage switch is presented. The switch was specifically designed for use with fast, low impedance pulse power discharge circuits such as those commonly used for plasma physics, and high pressure research. This switch can also be utilized in any application where speed, low cost and small size are important concerns. The design readily lends itself to implementation as a discrete component or hybrid circuit. The circuit has been simulated and the design parameters of the configuration have been numerically investigated utilizing PSPICE. These simulations and experimental data are presented.
Abstract - A novel, randomized control strategy for three-phase voltage source inverters, based on the voltage space vectors, is described. An implicit asymmetrical modulating function results in the switching losses in the inverter reduced by about half in comparison with those when the classic space vector PWM is used. The pulse rate is varied within individual 60° sectors of the vector plane, so that the power spectra of the output voltage are spread over a wide frequency range and acquire a continuous part. The relevant theoretical analysis, computer simulations, and experimental results are presented.
Abstract - Standard PWM techniques assume a ripple free dc-link voltage at the inverter input terminals and ideal switches. Most techniques proposed in the literature to compensate the non-ideal characteristics require additional and complex circuitry. This paper proposes and analyzes a simple method of generating PWM switching patterns which ensures a high quality output voltage and inherently compensates for a non ideal dc bus and switching delays. The method is based on maintaining a sinusoidal volt-second distribution at the inverter output by sensing the output voltage and generating the gating pattern on line. The principles of operation are explained and design procedure is presented. Simulation results illustrating the features of the proposed modulator are verified experimentally on a 3-kVA prototype unit.
Abstract - The dead time necessary to prevent the short circuit of the power supply in pulse width modulated (PWM) voltage inverters results in output voltage errors. Although individually small, when accumulated over an operating cycle, the voltage errors are sufficient to distort the applied PWM signal. This paper presents a method to correct for the dead time errors. The Pulse Based Dead Time Compensator (PBDTC) is less hardware and software intensive than other dead time compensation methods providing a low cost solution. The pulse based technique is developed by analyzing the effects of dead time on a pulse by pulse basis and correcting each pulse accordingly. The technique is evaluated through simulation and experimental results. Other compensation methods are evaluated and the results compared with the pulse based technique. This comparison indicates previous methods can produce magnitude and phase errors in the applied terminal voltage, whereas the proposed method compensates for the dead time without significant magnitude and phase errors in the terminal voltage of PWM voltage source inverters.
Abstract - On-line PWM pattern generators for current source rectifiers and inverters offer a number of control advantages over off-line optimized patterns. However, when implemented using the principles which apply to voltage source inverter PWM pattern generators, the switching frequency is equal to: (a) the carrier frequency in standard carrier-based implementations and (b) a function of the cycle frequency, sequence of space vectors, and selection of the zero space vector in space vector implementations. This paper shows that this frequency can be reduced to 1/2 of the respective frequencies. Two pattern generators are investigated: (a) an analog on-line carrier-based technique, namely the modified dead-band technique; and (b) a digital on-line space vector-based technique, where advantage is taken of the extra zero state available in current source converters. It is shown that the switching frequency reduction is achieved with no penalty in the line current harmonic distortion. Moreover, a significant reduction of ac line current distortion is obtained with the modified dead-band technique for modulation indexes greater than 0.4. The principles of operation of the proposed schemes are explained. Experimental results on a 5 kVA current source rectifier and a 5 kVA current source inverter confirm the feasibility and features of the proposed pattern generators.
Abstract - This paper presents a new emergency ballast for fluorescent lamps. The fundamental block is the microcontroller based control circuit which performs the supervision and control function. High frequency electronics techniques are proposed for the high power factor battery charger and the lamp driver, which provides high luminous efficacy. In this way, size and weight have been minimized for the whole system. With the introduction of the microcontroller the system has the capability of testing itself, checking its functional state and displaying internal faults. Thus, the reliability of the system is improved and concurrently maintenance cost is decreased.
Abstract - Properly fabricated polymer gels exhibit an abrupt change in volume in response to a small change in an environmental parameter such as temperature. We have developed gels that change volume in response to an applied alternating magnetic field, and we are working to apply these gels as actuators. This paper describes power electronic circuits suitable for electromagnetic activation of these polymer gels. Issues in the selection of circuit topologies for this application are discussed. Experimental results are presented, which demonstrate magnetic activation of gels using prototype power electronic drives.
Abstract - The work presented here examines the feasibility of using artificial neural networks (ANNs) and evolutionary algorithms (EAs) to develop discrete time dynamic models for fault free and faulted switched reluctance motor (SRM) drive systems. SRMs are capable of functioning despite the presence of faults. Faults impart transient changes to machine inductances that are difficult to model analytically. After this transient period, SRMs are capable of functioning at a reduced level of performance. ANNs are applied for their well known interpolation capabilities for highly nonlinear systems. A dynamical model for the SRM is constructed by feeding values for state variables back to ANN inputs. EAs are employed for their ability to search complex structural and parameter spaces to find good ANN solutions. Furthermore, the ANN structure and training regimen parameters are searched using EAs. Finally, an analysis of the search is performed and the resulting model is presented. The results of using the ANN-EA based model to predict the performance characteristics of prototype SRM drive motion under normal and abnormal operating conditions, are presented and verified by comparison to test data.
Abstract - A new type of mechanism, called "Direct Electrostatic Levitation and Propulsion" (DELP), has been successfully developed. The novel aspect of this mechanism is that an object can be directly levitated and driven via electrostatic forces. In this paper, a brief review of basic principles is presented. This is followed by a description of the structure of a prototype DELP mechanism, including electrode design, position feedback control method for levitation, driving principle and the operational procedure. Experimental results which demonstrate completely contact-less transportation of a 3.5-inch aluminum hard disk media are also presented.
Abstract - Control speed sensorless ac drives have reached a stage of development permitting good dynamic performance above 3% of rated speed. However, the accuracy of the rotor speed estimation under load remains sensitive to parameter errors of the internal machine model. This paper presents an approach that ensures high steady-state speed accuracy in addition to high dynamic performance. To eliminate the speed estimation error, the machine parameters are adapted on-line, based on the evaluation of rotor slot harmonic effects. A stator flux oriented control scheme is implemented in a digital signal processor system to demonstrate the robustness of the speed estimation to parameter variations. Experimental results demonstrate that the control system advantageously combines high dynamic performance with accuracy of speed estimation.
Abstract - The estimation of rotor time constant, or rotor resistance, in a vector controlled induction machine is necessary to achieve high performance torque control. A new method of estimating the rotor resistance on-line, for use in a vector controlled induction machine, is presented. It uses short duration pulses added to the constant flux reference current,and based on the resultant torque command current produced by a proportional-integral compensator adjusts the rotor resistance estimate. This method of self-tuning the vector controller to the rotor time constant, when operating in a closed-loop speed control loop, does not produce torque pulsations when correctly tuned. In comparison to other on-line methods such as the Extended Kalman Filter and the Extended Luenberger Observer, this method does not require voltage sensors and is computationally simpler. The rotor resistance estimation technique is illustrated through simulation and practical implementation of a vector controlled induction machine.
Abstract - We describe two adaptive multistage digital filters for 50/60 Hz line frequency signal processing in zero-crossing detectors and synchronous power systems. These filters combine a median filter with adaptive predictors, either FIR or IIR based, thus making it possible to extract the sinusoidal signals from noise and strong disturbances without phase shifting the primary frequency signal. The median filter is used as a prefilter because it can remove deep commutation notches from the waveform. Adaptation allows the filters to track the exact instantaneous line frequency, and avoids the selectivity problem encountered with a fixed filter.
Letters to the Editor
Abstract - Unity power factor zero-voltage-switched AC-to-DC converters with an active filter are proposed. The line voltage is supplied to AC-to-DC converters through the rectifier circuit with an input filter to reduce high frequency ripple components. The line current is almost synchronized to the line voltage due to the low impedance of the input filter. The forward zero-voltage-switched multi-resonant converters (ZVS_MRCs) are utilized for high frequency operation and lossless switching. An active filter is introduced to minimize the twice line frequency ripple component of the output voltage without large-size passive filters. Experimental results show that the proposed scheme gives good steady-state performances the AC-to-DC converters.
Abstract - The paper describes a novel approach to robotic haptic recognition, which exploits an unsupervised Kohonen self-organizing feature map for performing a match-to-sample classification of 3-D objects. The results obtained, even though currently referring to a simulated environment and to some working assumptions, have emphasized the validity of the approach and its applicability in a variety of dextrous robotic systems.
Abstract - Fuzzy logic based on-line efficiency optimization control has been described in the literature for an indirect vector-controlled induction motor drive. The purpose of this note is to extend the same control to a stator flux oriented electric vehicle induction motor drive, and then implement the fuzzy controller by a dynamic back propagation neural network based controller. The principal advantage of fuzzy control, i.e. fast convergence with adaptive step size of the control variable, is retained. The neural network adds the advantage of fast control implementation either by a dedicated hardware chip or by DSP based software.
Abstract - The discussion on the paper entitled, "Simulation of Power Electronics Circuits Using Sparse Matrix Techniques", points out earlier work and seeks clarification on implementation procedure.Reply from the authors is included.