Prof. Dr. Joachim Holtz
Editor-in-Chief
|
Prof. Dr. Joachim Holtz |
IEEE Transactions on Industrial
Electronics
Volume 44, Number 5, October 1997
Power Electronics
Abstract - Distributed power supply systems are an attractive solution to
meet the requirements (redundancy, modularity, battery backup, etc.) for
the next generation of power supply systems. In addition, the
normalization regarding power factor and total harmonic distortion makes
it necessary to include the power factor correction in the input stage
in those architectures.
This paper presents a novel approach of an integrated battery
charger/discharger which offers power factor correction and battery
galvanic isolation in a simple structure. Placing the battery in the
primary side overcomes the need of galvanic isolation integration in
each one of the DC/DC on-board converters when this topology is used as
part of a distributed power supply systems.
Abstract - The paper describes further development of the novel current injection scheme devised by the authors for attenuating line current harmonics in bridge rectifier circuits. The previous passive filters are replaced by controlled filters connected between the bridge rectifiers output and the star point of the transformer secondary. These filters are used to inject controlled third harmonic currents into transformer windings. Variations in bridge working conditions, due to changes in either load or bridge delay angle, lead to corresponding changes in the filter operations if the harmonic attenuation is to remain optimal. The control law for the filters has been derived and the effectivness of the new method confirmed by both simulation and laboratory tests.
Abstract - A series active power filter, working as a sinusoidal current source, in phase with the mains voltage, has been developed and tested. The amplitude of the fundamental current in the series filter, is controlled through the error signal generated between the load voltage and a pre-established reference. The control allows an effective correction of power factor, harmonic distortion, and load voltage regulation. Compared with previous methods of control developed for series active filters, this method is simpler to implement because it is only required to generate a sinusoidal current, in phase with the mains voltage, whose amplitude is controlled through the error in the load voltage. The proposed system has been studied analytically, and tested using computer simulations and experiments. In the experiments, it has been verified that the filter keeps the line current almost sinusoidal, and in phase with the line voltage supply. It also responds very fast under sudden changes in the load conditions, reaching its steady-state in around two cycles of the fundamental.
Abstract - A simple and low cost control strategy for active power filters implemented with PWM voltage-source inverters connected in cascade is presented and analyzed in this paper. The principal component of the control circuit is an INTEL 8031 AH microcontroller, which generates the current reference waveforms and respective switching patterns, for each inverter. The switching pattern is ibtained by usign a vector control technique. The proposed active power filter consists of two PWM voltage-source inverters, connected in cascade, each one operating at different switching frequency. The paper presents the proposed control strategy in terms of principles of operation, circuit design and implementation. Finally, predicted results are verified experimentally on a 10 kVA bread board model.
Abstract - Sepic and Cuk converters working as Power Factor Preregulators (PFP) in Discontinuous Conduction Mode (DCM) present some desirable characteristics for a PFP: the converter works as a voltage follower (no current loop is needed); theoretical power factor is unity; and the input current ripple is defined at the design stage. Besides, input-output galvanic isolation is easily obtained. The paper analyzes the operation of both converters as DCM-PFP. Design equations are derived, as well as a small-signal model to aid the control loop design. Both simulation and experimental results are presented, that are in agreement with the theoretical analysis and complement the work.
Abstract - Off-line applications with single-stage converters (SSCs) are presented in the paper. The approach used in synthesizing the SSCs is first described, and their applications are then introduced. In addition, viable control strategies for the SSCs are addressed. The developed SSCs can fulfill multi-functions, such as input power factor correction, fast output regulation and lamp ballasting, and possess the merits of compact size, simple driver design and high reliability. Prototypes of SSCs applied to an electronic dimming ballast and a dc regulator are built, which show high feasibility in such moderate power applications.
Abstract - The characteristics of Cuk converters in discontinuous- capacitor- voltage mode operation are studied. A Cuk converter in this mode of operation is an inherent power-factor corrector and features soft turn-off switching. Simulation and experimental results are reported to verify the theoretical analysis. In addition, the advantages and disadvantages of power-factor correction circuits using Cuk converters in discontinuous- inductor- current mode operation and Cuk converters in discontinuous- capacitor- voltage mode operation are discussed.
Abstract - A fast controller is presented for single-phase boost type power-factor correction circuits. The twice line frequency ripple component is removed from the measured output voltage with an adaptive estimator. This enables the closed-loop time-constants and overshoots to be reduced by two orders of magnitude compared to traditional designs. The controller copes with considerable uncertainty in input voltage magnitude, line frequency and output capacitance. All sections of the control system are shown to be asymptotically stable. Experimental results are presented to verify the excellent dynamics and robust behaviour of the design.
Abstract - This paper presents an implementation of a fuzzy controller for DC-DC converters using an inexpensive 8-bit microcontroller. An "on-chip" A/D converter and PWM generator eliminate the external components needed to perform these functions. Implementation issues include limited on-chip program memory of 2 kB, unsigned integer arithmetic, and computational delay. The duty cycle for the dc-dc converter can only be updated every eight switching cycles because of the time required for the A/D conversion and the control calculations. However, it is demonstrated here that stable responses can be obtained for both buck and boost converters under these conditions. Another important result is that the same microcontroller code, without any modifications, can control both converters because their behavior can be described by the same set of linguistic rules. The contribution shows that a nonlinear controller such as fuzzy logic can be inexpensively implemented with microcontroller technology.
Abstract - The relationship between Regular-Sampled PWM and Space Vector Modulation is defined and it is shown that under certain circumstances the two approaches are equivalent. The various possibilities of adding a zero sequence component to the Regular-Sampled sinusoidal modulating wave are explored and these effects quantified. It is shown that this leads to "equal null" pulse times which extends the linear modulation range and simplifies the microprocessor implementation.
Drive Control
Abstract - In this paper, a new nonlinear control strategy is proposed for a permanent-
magnet salient-pole synchronous motor. This control strategy simultaneously
achieves accurate torque control and copper losses minimization without recurring
to an internal current loop nor to any feedforward compensation. It takes
advantage of the rotor saliency by allowing the current (id) to have non zero
values. This in turn allows us to increase the power factor of the machine and
to raise the maximum admissible torque. We apply input-output linearization tech-
niques where the inputs are the stator voltages and the outputs are the torque
and a judiciously chosen new output. This new output insures a well defined rela-
tive degree and is linked to the copper losses in such a way that when forced to
zero,it leads to maximum machine efficiency.
The performances of our nonlinear controller is demonstrated by a real-time
implementation using a DSP chip on a permanent-magnet salient-pole synchronous motor
with sinusoidal flux distribution. The results are compared to the ones obtained
with a scheme which forces the id current to zero.
Abstract - The control of an induction motor is a difficult problem since the dynamics of the induction motor are nonlinear, the rotor electrical state variables (i.e., rotor fluxes or currents) are usually unavailable for measurement, and the motor parameters can vary significantly from their nominal values. The main purpose of this paper is to develop a control algorithm that forces the induction motor to track time-varying speed, position and flux trajectories without knowledge of the rotor electrical state variables. To achieve this, a passivity-based method is developed. The key point with this method is the identification of terms, known as workless forces, which appear in the dynamic equations of the induction motor but do not have any effect on the energy balance equation of the induction motor. These terms do not influence the stability properties of the induction motor and hence there is no need to cancel them with feedback control. This leads to a simpler control structure and enhances the robustness of the control system. Experimental results show that the passivity-based method provides close tracking of time-varying speed, position and flux trajectories without knowledge of the rotor electrical state variables.
Robotics and Vision
Signal Processing
Abstract - A new approach to the measurement of three-dimensional position and velocity of moving particle is introduced. A single TV camera with an apparatus to add the circular shift to the image enables us to record the three-dimensional movement of particles as spiral streaks on a single image. Every shape of the spiral streak on the image plane is related to the position and the velocity of the individual particle. The information about three dimensional movement of particles is extracted from the image using an image processing technique. We applied the technique to the measurement of the three-dimensional water flow field suspended with tracer particle in a test tank and obtained satisfactory results.
Abstract - A third-order cumulant based adaptive recursive least-square algorithm (CRLS) for the identification of time-invariant nonminimum phase systems as well as time-variant nonminimum phase systems has been successfully developed. As higher-order cumulants preserve both the magnitude and the phase information of received signals, they have been considered as powerful signal processing tools for nonminimum phase systems. In this paper, the development of the CRLS algorithm is described and examined. A cost function based on the third-order cumulant and the third-order cross cumulant is defined for the development of the CRLS system identification algorithm. The CRLS algorithm is then applied to different MA and ARMA models. In the case of identifying the parameters of a MA model, a direct application of the CRLS algorithm is adequate. When dealing with an ARMA model, the poles and the zeroes are estimated separately. In estimating the zeroes of the ARMA model, the construction of a residual time-series sequence for the MA part is required. Simulation results indicate that the CRLS algorithm is capable of identifying nonminimum phase and time-varying systems. In addition, because of the third-order cumulant properties, the CRLS algorithm can suppress Gaussian noise and is capable of providing an unbiased estimate in a noisy environment.
Abstract - A new algorithm for self-tuning of PID controllers is proposed. A combined least- squares estimation and Newton-Raphson search technique is used to determine the ultimate gain and period of an unknown system for the purpose of automatic tuning of PID controllers based on Ziegler and Nichols (ZN) or Refined Ziegler and Nichols (RZN) formulae. The proposed algorithm can be applied to systems with known time delay as well as those with unknown dead-time. Simulation studies are used to demonstrate the performance of this algorithm. The performance of this PID self-tuner is also compared with a popular commercial auto-tuner for simulated systems and a laboratory-scale real plant.
Emerging Technologies
Abstract - The high demand on computation performance by multimedia information processing such as digital video compression and decompression has made multiprocessor computation more and more popular. In this paper, we present our study on adaptive job assignment for multiprocessor implementation of a MPEG2 video encoding algorithm. Data partitioning technique is used for job assignment to the processors in the multiprocessor environment to exploit the data structure adopted by MPEG standard that divides a frame of picture into macro blocks (MBs) which are processed independently during encoding. An adaptive data partitioning scheme is developed to cope with the inherent non-uniform spatial distribution of motion activities such that the computation load distribution over processors is as uniform as possible, which helps improve the speed-up of the whole multiprocessor system. Simulations with several video sequences have shown that, in comparison to its non-adaptive counterpart, the adaptive scheme can effectively improve the speed-up of the multiprocessor system. In addition, the speed-up scales well with the increase of the number of processors used in the computation.
Letters to the Editor
Abstract - A new technique of reducing torque ripples in inverter fed BDCM drives is proposed. The proposed technique reduces torque ripple components by controlling switching angles of the inverter. The simulation and experimental results indicates that the proposed technique can reduce the torque ripples significantly and improve the performance of the system.
Abstract - This note presents an idea of using the distances along the time-optimal state trajectory as feedback parameters in the computer disk file servo. The method allows smooth switching between saturated control efforts, and can eliminate the common overshoot problem. Due to the nature of the feedback information, the method achieves both track-accessing and track-following within a single stage of control.