Prof. Dr. Joachim Holtz
Editor-in-Chief
|
Prof. Dr. Joachim Holtz |
IEEE Transactions on Industrial
Electronics
Volume 44, Number 4, August 1997
Power Electronics
Abstract - This paper reviews recent progress in topology, control and design aspects in three-phase PFC techniques. Different switching rectifier topologies are presented for various applications. Representative soft switching schemes, including zero-voltage and zero-current switched PWM techniques, are investigated. Merits and limitations of these techniques are discussed and illustrated by experimental results obtained on prototype converters. Control and input filter design issues are also discussed.
Abstract - The generation of harmonics and their subsequent
propagation into power line is a topic of increasing concern
to power supply authorities. To prevent obstacles on the power
system, Unity-Power-Factor PWM rectifier is going to apply
to AC-DC power conversion plant. However, PWM rectifier,
especially at single phase circuit, has some serious defects,
that is low frequency ripple current which flows into the DC
line and low frequency ripple voltage which appears on the DC
output. In usual case, it is necessary to connect a very large
capacitor or a passive L-C resonant circuit to the DC line for
the reduction of low frequency ripple voltage. However, in case
of the batteries are connected with the DC output, most of the
DC ripple current flows into the battery even if previous circuits
are used because the impedance of the battery is very low compared
with that of previous circuit. The low frequency ripple current
cause power loss on the battery and the temperature has risen.
It is well known that the life of the battery is deeply influenced
by the temperature. The ripple current, therefore, should be reduced
to as possible as low.
To accomplish the reduction of the low frequency ripple current,
a novel topology of the PWM rectifier is presented in this paper.
The main circuit is constituted by adding only a pair of switching
devices to conventional PWM rectifier circuit. With simple control
technique, the ripple energy on the DC line is converted into the
stored energy on the input AC capacitors though the additional
switches. The theoretical characteristics are obtained on the basis
of statespace-averaging-method. The effect of the ripple reduction
is confirmed by experiments using a bread board set-up.
This rectifier is useful for UPSs and DC power supplies, especially
for cases in which batteries are connected to the DC line.
Abstract - Based on the combination of a three-phase diode bridge and a DC/DC boost converter a new three-phase three-switch three- level PWM rectifier system is developed. It can be characterized by sinusoidal mains current consumption, controlled output voltage and low blocking voltage stress on the power transistors. The application could be, e.g., for feeding the DC link of a telecommunications power supply module. The stationary operational behavior, the control of the mains phase currents and of the output voltage are analyzed. Finally, the stresses on the system components are determined by digital simulation and compared to the stresses in a conventional six- switch two-level PWM rectifier system.
Abstract - This paper develops a real time condition monitoring algorithim for PWM inverter fed induction motor drives. It is designed to detect the intermittent loss of firing of an individual switching device within the inverter. The mathematical model of the induction machine is linearised in the field-torque coordinates and the misfiring of the inverter is represented by pulse functions which have effects in both the field and torque directions. Since the fault considered is of an intermittent nature, the time domain response of the magnetising and torque producing components of the motor stator current are used to form the condition monitoring signal. The method is adaptive to changes in the operating point during variable speed operation. Digital simulation and laboratory experiments are used to illustrate the method and evaluate the computational effort requirred.
Abstract - Current-controlled PWM inverters are widely used in high performance ac drives, because they give high dynamic responses in such systems. This paper presents a comparative study of several current controllers. Particular attention is paid towards the hysteresis controller and the ramp comparator is proposed in which the current error signals are compared to three 120 degree phase shifted triangular waveforms. this eliminates the zero voltage vector applied to the inverter and reduces the inherent amplitude and phase errors. Computer simulations are used to compare the performances. Fast Fourier transform technique is used to show the power spectrum of the current waveforms. Experimental results validate the simulated performances.
Abstract - An electronic ballast for High Pressure Sodium (HPS) lamps was designed and evaluated theoretically and experimentally. The ballast is based on the half-bridge topology and includes a high voltage igniter and dimming capability. It was used to drive and examine the high frequency characteristics of a commercial HPS lamp (NAV-T 150W (SON-T), OSRAM). The experimental results reveal that for the frequency range of this study (27kHz to 75kHz), the lamp is free of the acoustic resonance problem. It was also found that for the present experimental conditions, the lamp is purely resistive and that the resistance is practically independent of the power level and operating frequency. The lamp exhibited stable operation over a very large dimming range, down to about 7% of nominal power. The 2.8kV ignition pulse was found to be sufficient for both cold and hot start up under the proposed operating conditions.
Abstract - A new general-oriented time-domain simulation technique for power electronic systems is developed. The algorithm is based on stepwise quadratic extrapolations on the branch voltages across each reactive element together with progressive validation of the switches' operation. The power of this new technique lies in its simplicity in solving purely resistive networks for each topological configuration, generality in requiring no a priori understanding of the switching relationships and sequence of operations, inclusion of the effects of the parasitic elements, effectiveness of using computer memory, and ease of implementation on a desktop computer. Several examples illustrating the generality and computational efficiency of this new approach are presented and verified with experimental measurements and other available literature.
Abstract - Current measurements in Power Electronics or in EMI domains require high- performance probes. These probes must have a very wide bandwidth, be insensitive to electromagnetic interferences and be able to measure large direct and alternating currents (AC-DC) without distortion. This paper will be limited to AC current probes. Various principles will be reviewed, in particular that based on the current transformer; its limitations will be analysed and a solution based on a two-stage transformer will be proposed to extend low- and high- frequency performance. It will be shown that the use of new magnetic materials, such as amorphous or nano- crystalline, can improve the large- current low- frequency operations while preserving the smallest possible probe size. Various solutions will be provided to improve high- frequency operations. Different developments will be depicted; frequency and time domain results will be presented.
Drive Control
Abstract - In this paper, a novel field weakening scheme for the induction machine is presented. The proposed algorithm based on the voltage control strategy ensures the maximum torque operation over the entire field weakening region without using of the machine parameters. Also, by introducing the direct field oriented (DFO) control insensitive to the variation of machine parameters in the field weakening region, the drive system can obtain the robustness to parameter variations. Moreover, the speed sensorless control can be achieved in the very high speed range where the utilization of the speed sensor is limited. Experimental results for the laboratory induction motor drive system confirm the validity of the proposed control algorithm.
Abstract - For drives with very high power and extreme demand on the quality of torque a novel concept of feeding an induction machine with open windings by two GTO three-level inverters is investigated. For optimal operation with the restricted switching frequency of these high power inverters Direct Self Control (DSC) is mostly suited which is well proved with two-level and three-level inverters in traction allowing a highly dynamic control of the induction machine. In comparison with two-level and three-level inverters torque ripple and distortion of motor currents are efficiently reduced, while maintaining the excellent dynamic qualities of DSC.
Abstract - The stator flux orientation concept allows to get very good transient and steady state performances in induction motor drives. However, this control strategy can be conveniently implemented only if the stator flux is correctly observed in all the speed range. The authors have developed a simple flux observer that gives very satisfactory results especially near zero speed and the approach which has been followed allows also a good speed estimation. The observer has been both simulated and implemented on an experimental system that uses a single chip to control the whole drive system. The experimental results show excellent performances despite the low computational load.
Abstract - An investigation of the parameter sensitivities of the d-axis voltage, q-axis voltage and the reactive power models, used in Model Reference Adaptive Control (MRAC) strategy for tuning the Indirect Field Oriented (IFO) controller is presented. These reference models are derived from the dynamic model of the machine under the assumption that the IFO control conditions are valid. In this study, the machine has been considered to operate under variable speed and load conditions. To improve the robustness of the MRAC strategy, a cascade parameter estimation technique has been used to track the variations of the stator resistance and the stator leakage inductance. The experimental results obtained with the proposed estimation technique as well as with the MRAC strategy are presented.
Abstract - A new concept is proposed for an elevator group control system which can change control settings according to individual floor utilization situations. The floor attribute based control method uses a combination of floor attribute based evaluation and car attribute based evaluation. Computer simulations show it can improve multiple preferential floor settings at the same time. Additionally, an on-line parameter tuning method using genetic algorithms is proposed. The floor attribute control method needs several dozen control parameters be tuned according to each building's traffic, and the proposed method can do it. The elitist preserving strategy is an effective way to keep control stability. A diversity recovering operation, which initializes population, excluding the elitist individual, when traffic flow data have changed, improves the following ability for transitions of utilized conditions.
Abstract - Controller area network (CAN) was originally developed to support cheap and rather simple
automotive applications. However, because of its performance and low-cost it is also being considered
in automated manufacturing and process control environments to interconnect intelligent devices such
as modern sensors and actuators. Unfortunately CAN, in its current form, is not able either to share
out the system bandwidth among the different devices fairly or to grant an upper bound on the
transmission times experienced by the nodes connected to the communication medium as it happens,
for instance, in the token-based networks.
In this paper two slight modifications of the basic CAN protocol are presented that satisfy the above-
mentioned requirements at the expenses of a very small degradation of the system's performance. Both
these solutions exhibit a high degree of compatibility with those devices which have already been
designed for the conventional CAN fieldbus.
Besides introducing the new mechanisms the paper also presents some performance figures obtained
using a specially developed software simulator, while the behaviour of the new mechanisms is
compared to the traditional CAN systems in order to see how effective they are.
Signal Processing
Abstract - A class of analog continuous-time filters is introduced, having predictive properties for specified narrow-band signal models, such as low-order polynomials or sinusoids. Such filters are designed by using model transfer functions designed in the discrete-time domain. Z- to s- domain mapping is done using the inverse bilinear transformation. The analog filters are implemented with active-RC structures, using the state-variable structure for biquads, and a single-op-amp structure for real poles and zeros. The application examples include a filter for zero-crossing detectors, polynomial predictors for sensor signal smoothing, and an optimized sixth-order ramp-tracking filter for anti-aliasing and anti-imaging in DSP systems where high selectivity is required.
Abstract - We propose a new type of highly accurate multi-viewpoint stereo measurement using the maximum likelihood method. This method is used for measuring positions of facilities such as telegraph poles on a road. In this method, a normal distribution is assumed for a measurement error on stereo image planes. First, the probability density functions of the measurement errors at the multi-viewpoints are combined. Next, the combined function is expressed using both real space coordinates and coordinate transformation parameters which give relative viewpoint positions, and the most probable coordinates are estimated from a condition that minimizes the function. Then, the best viewpoint positions which minimize the area of the combined error ellipse are investigated by analyzing the variance included in the estimated coordinates, and the relationship between the number of viewpoints and the variance of the best viewpoint positions is obtained. Finally, these theoretical results are confirmed experimentally by measuring outdoor facilities.
Abstract - The purpose of this paper is to present a state variable model for the drying section of a paper making machine. This model is baationships give a set of six non-linear partial derivative equations. The form of these equations changes somewhat from one cylinemperature while obtaining good paper drying. Boundary conditions are specified by a stochastic generator and initial conditions he state variable model for the paper drying as well as comparing the obtained results with dynamic model results. Solving the se which represents the dynamic version of the model used for process control.
Letters to the Editor
Abstract - The note describes a zero speed start-up method of a speed sensorless stator flux oriented direct vector controlled induction motor drive with the help of machine current model that does not use any speed signal. The machine starts smoothly with vector control at finite developed torque, and then transitions to the standard direct vector control mode with the voltage model signals as the speed begins to develop. The direct vector control mode with voltage model uses programmable cascaded low pass filters for flux vector synthesis [2] and enables the drive to operate from zero speed to field-weakening mode. As the drive speed falls to zero, the drive again transitions to start-up mode so that it can be smoothly started again. The performance of the start-up scheme has been verified on a 100 kW electric vehicle drive.
Abstract - A novel overmodulation strategy for space-vector PWM inverters is proposed. The method, which increases the range of linear control of the output voltage by 10%, is based on Fourier series representation of the reference voltage.
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