| EPE 1995 - 37 - Dialogue Session DS4a: Converters (II) |
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 | ANALYSIS OF TRANSIENT PROCESSES IN A SINGLE PHASE CYCLOCONVERTER
By I. Katz; M.A. Slonim | [View]
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Abstract: A new analytical method for the analysis of transient processes in single - phase cycloconverters has been developed. The z-transform is used to derive the equation governing the cycloconverter's current. An analytical solution of the problem is obtained. Physical experiments have been carried out to verify the results obtained. Good agreement between theoretical and experimental results is observed.
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| | AC/DC/AC QUASI-RESONANT TRANSISTOR'S CONVERTER FOR AC DRIVE APPLICATION
By T. Citko; M. Dubowski; A. Sikorski | [View]
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Abstract: In this paper the AC/DC/AC IGBT converter system with quasi-resonant circuit, as common commutation system for all transistors, minimizing the switching losses is presented. The input AC/DC inverter is controlled to keep the input power factor on the level equal to one. The output DC/AC inverter supplies the AC motor, which is controlled by indirectly field oriented method. Behavior of the laboratory model of this drive system in transient and steady state is documented by oscillograms.
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| | A DESIGN OF A NEW SNUBBER CIRCUIT FOR THREE-LEVEL GATE TURN-OFF THYRISTOR INVERTERS
By J.H. Suh; B. S. Suh; D.S. Hyun | [View]
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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 of 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. Experimental results demonstrate that the proposed snubber circuit is very effective for a large capacity three-level GTO inverter.
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| | ASYMMETRICAL TYPE ZERO CURRENT SWITCHING DC-DC CONVERTER WITH CONSTANT FREQUENCY VOLTAGE CONTROL
By Y. Hatanaka; C. Kunitake; J. Tsukamoto | [View]
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Abstract: An asymmetrical type zero current switching (ZCS) DC-DC converter with constant frequency voltage control (CFVC) is developed. Not only the main active switches but also the rectifier diodes are operated with ZCS in CFVC. THe principle of ZCS operation in which an overlapping commutation phenomenon is effectively utilized without additional switch is elucidated. From the results, the design criterion of the asymmetrical type ZCS DC-DC converter is studied. The ZCS characteristics such as output voltage regulation and output voltage ripple are numerically analyzed and verified experimentally. From the results, an improved type asymmetrical ZCS converter is proposed.
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| | DESIGN AND ANALYSIS OF A PWM PARALLEL RESONANT DC-LINK INVERTER
By M. Krogemann; J.C. Clare | [View]
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Abstract: Soft switching inverter topologies offer reduced switching losses and allow higher switching frequencies. Many of the proposed topologies only permit inverter switching at sampled instants in time. There have also been some efforts to combine the benefits of soft switching with the well established pulse-width modulation (PWM) technique. This paper reviews a proposed topology and analyses its operation in terms of device stresses and PWM capability. Effects of load variations and resonant tank layout are considered. Simulation as well as experimental results are given.
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| | SERIES RESONANT CONVERTER WITH SANDWICH-TYPE PIEZOELECTRIC CERAMIC TRANSDUCERS
By P. Fabijanski | [View]
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Abstract: The article presents original results of digital analysis and experimental research on a transistor, resonant converter feeding a group of SANDWICH-type piezoelectric ceramic transducers. The aim of the analysis was to determine the optimum resonance parameters of the converter circuit elements, which allow for the achievement of maximum power output in case of tuning the generator vibration frequency to the mechanical resonance frequency of the transducers. The digital analysis results have been compared with the experimental results obtained with the application of a resonant MOSFET transistor converter feeding the piezoelectric transducers.
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| | DETAILED STUDY OF LIMIT RUNNING MODES OF A QUASI-RESONANT CONVERTER WITH A VIEW TO DOWN-REGULATION
By B. Robert; C. Goeldel | [View]
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Abstract: Most analyses of quasi-resonant DC/DC converter operate adopt some simplifying hypothesis, and ignore the parasitic resistors of the conductors or the active and reactive components. They also assume that there is a free wheeling phase, which limits the validity of the analysis. This raises the problem of running without load or with a low load. We have analysed the operation of a quasi-resonant converter disregarding the free wheeling phase to determine if it will run without load and the effect on its control. Transient cycles are shown to occur and all the limit running modes are determined by exhaustive analysis. Simulations show that there are transient limit running modes during rapid changes in the operating frequency. A 50 W, 100 kHz zero current quasi-resonant converter was built to check the findings.
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| | NEW CONVERTER WITH PULSE AMPLITUDE MODULATION - AN EXPERIMENTAL STUDY
By G. Blajszczak | [View]
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Abstract: The paper proposes a new configuration for a resonant converter with pulse amplitude modulation. The converter operates with soft switching. The pulse amplitude modulation is an alternative method to the pulse width modulation and allows to construct practically (limitations are discussed in the paper) any shape of current wave form, accordingly to a reference signal. The new converter is investigated by measurements in a 20kVA experimental model.
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| | SPICE MODEL OF THE HF RESONANT DC-AC CONVERTER
By F. Mihalic; M. Milanovic | [View]
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Abstract: Switch-mode operation in almost all Pulse Width Modulated (PWM) DC-to-DC and DC-to-AC converters require from the power semiconductor devices to turn-on and turn-off the entire load current during each switching. In this paper, the converter topology and the switching strategy, which result in zero-current switching's, will be described. Most of these topologies require some form of L-C resonance (serial or parallel), therefore they are broadly classified as "resonant converters". The model of the High Frequency (HF) resonant DC-AC converter for SPICE simulator will be described and simulation results will be presented and discussed in this paper.
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| | MULTIRESONANT TECHNIQUES APPLIED TO A FAMILY OF SINGLE-OUTPUT DC-DC CONVERTERS
By B. Velaerts; J-P. Schauwers; D. Bogaerts; M. Miller; P. Mathys; J-L. Van Eck | [View]
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Abstract: This paper presents a family of prototypes of DC-DC converters, based on the zero-voltage-switching multiresonant converter (ZVS-MRC) topologies developed by F.C.Lee. These 150 W converters, operating in the MHz range, are designed to work on a common DC bus (385V) fed by a power factor controller. Four different output voltages (5 to 48V) are available. The aim of this study is to evaluate the complexity level of the implementation of such converters. Special attention is given to the magnetic components, mainly the resonant inductor, with the perspective to use, as far as possible, technological solutions which are currently applied in the 100-200 KHz range. The paper shows the different options which have been evaluated, with practical results.
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| | ANALYSIS OF A HALF-BRIDGE TYPE SERIES RESONANT DC-DC CONVERTER WITH AUXILIARY SWITCHES
By Mutsuyoshi Asano; Hirofumi Matsuo; Fujio Kurokawa; Haruya Mae | [View]
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Abstract: This paper deals with the analysis of a half-brIdge type series resonant dc-dc converter with auxiliary switches, which are employed to prevent the extremely lowering of the switching frequency caused by the decrease of the load current and/or the increase of the input voltage. This converter has two operation modes; that is, the frequency control and on-time control modes. As a result of analysis, the output characteristics and the regulation mechanism in two modes are clarified, and two appropriate feedback gains in the frequency control and on-time control circuits can be obtained to improve the power efficiency. Also, analytical results are confirmed by experiments.
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| | A 4.5 kW BUCK CONVERTER IMPLEMENTED WITH THREE IGBT'S ASSOCIATED BY MEANS OF A NEW PARALLELING TECHNIQUE
By Henrique A. C. Braga; Ivo Barbi | [View]
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Abstract: This paper outlines a recently introduced new parallel-connection technique and focuses its application to a 4.5 kW buck converter, using three Pulse Width Modulation (PWM) cells. The prototype works at a 20 kHz frequency, with a power source of 240V, delivering 21A to the output load. Three Insulated Gate Bipolar Transistors (IGBT's) are used to constitute the PWM cells, which are associated by means of small inductances. The paper proposes a simplified design procedure based on theoretical analysis and practical considerations. This paper also shows the employed power semiconductor elements, gating requirements and output waveforms, showing the excellent dynamic and steady-state current balance among the switches.
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| | PERFORMANCE OF SVM CONTROLLED MATRIX CONVERTER WITH INPUT AND OUTPUT UNBALANCED CONDITIONS
By D. Casadei; G. Serra; A. Tani; P. Nielsen | [View]
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Abstract: A general approach for the analysis of AC-AC direct converters is presented which allows the performance of three-phase matrix converter to be evaluated even in the case of input and output unbalanced conditions. The control strategy is based on space vector modulation technique and performs in order to keep the input current vector in phase with the input voltage vector. The maximum voltage transfer ratio and the harmonic components of input line currents are determined analytically as function of input and output voltage unbalance degree. It is verified that in the case of input unbalance non-sinusoidal current are obtained having only positive sequence harmonic components, while positive and negative sequence components may be present under input and output unbalance. Simulated results are given to confirm the analytical approach.
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| | BMFET-SWITCHED, CLASS E RESONANT LAMP BALLAST
By G. Busatto; A.M. Luciano; L. Fratelli | [View]
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Abstract: A lamp ballast circuit is proposed, based on a class E topology and using a normally-off BMFET as an active device. Its performances are compared to those obtained by using power MOSFET and IGBT in the same topology. As BMFET sustains the required high voltages with very low conduction losses, it is the best suited device for such circuits and allows to enhance performances of class E converters, which ensure high efficiency, reduction in EMI, low cost.
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| | COMPARISON OF THE LOSSES IN A NEW QUASI-RESONANT INVERTER WITH A HARD-SWITCHED CURRENT-REGULATED VOLTAGE-SOURCE INVERTER
By A. Kotsopoulos; D.G. Holmes | [View]
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Abstract: The six-switch voltage-source inverter is the most common topology used for DC-AC inversion. Performance improves with increasing switching frequencies; however, there is an upper limit on the switching frequency if significant switching losses and electromagnetic interference problems are to be avoided. A variety of soft-switching techniques have been proposed to overcome these limitations, in particular a new topology recently proposed by the authors. This paper presents a comparison between this new, quasi-resonant, soft-switched, inverter, and a current-regulated voltage-source inverter.
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| | THE USE OF THE DUALITY PRINCIPLE IN THE CONCEPTION AND ANALYSIS OF RESONANT DC-DC CONVERTERS
By Luis Garcia de Vicuna; Javier Maixé; Joan Majo | [View]
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Abstract: This paper presents current-source resonant DC-DC converters, obtained from the application of the duality principle to the best known voltage-source resonant conversion structures. The analysis of these converters has been realized by means of the classical AC analysis technique, which enables us to find their most outstanding characteristics and compare these converters with theirs dual converter.
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| | PRACTICAL EVALUATION OF A QUASI-RESONANT CIRCUIT FOR SOFT-SWITCHED INVERTERS WITH MINIMUM VOLTAGE STRESS
By S.Y.R. Hui; E. Gogani; J. Zhang | [View]
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Abstract: This paper presents a practical evaluation of a quasi-resonant circuit which creates zero-voltage switching condition for power inverter with minimum voltage stress. This quasiresonant circuit can pull down the dc link voltage momentarily to zero for zero voltage inverter switching without setting the dc link voltage above the nominal dc link voltage - even under no-load condition. The soft-switching approach has the advantages of lossless, stressless and snubberless inverter switching and can be incorporated into many well-established PWM switching schemes. An experimental prototype circuit has been developed and tested. Experimental results have confirmed the operating principles of the quasi-resonant soft-switched inverter.
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| | IMPROVED OPERATING AREA OF THE ZERO-VOLTAGE-SWITCHING SERIES-RESONANT CONVERTER USING NONLINEAR CAPACITIVE SNUBBERS
By N. Aouda; Y. Cheron; M. Metz; H. Foch | [View]
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Abstract: In the Series-Resonant Converter operating at frequencies above resonance, the capacitive snubbers lead to a commutation failure as the converter approaches no-load oparation. This paper is intended to demonstrate that a significant improvement of this situation is expected by using nonlinear ceramic capacitors as snubbers instead of linear ones. This is done through analytical, simulation and experimental results.
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| | Matrix Converters for Induction Motor Drive
By S. Halasz; I. Schmidt; T. Molnar | [View]
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Abstract: Two control methods of the three-phase induction motor supplied by 3 and 6 phase matrix converters are investigated by Park-vector representation. It is shown that two different control methods can be realized by the relatively simple tools: the first method uses only rotated and zero value voltage vectors, the second one uses only pulsated and zero value vectors. The first method is a very suitable for digital realization and produces low values motor harmonic losses and torque pulsation with the relatively low commutation frequency of the converter, however only for 6 (or more) phase matrix converters. The second method obtains the acceptable motor harmonic losses and torque pulsations for 3-phase matrix converters too, but the realization of this method more sophistical.
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| | HIGH POWER FACTOR RECTIFIERS
By J. Rodriguez; E. Wiechmann | [View]
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Abstract: This paper presents an overview of modern rectifiers, which work with a high power factor to increase the efficiency and reliability of power systems. The high power factor is achieved in these converters by means of a high displacement factor and reduced harmonics in the input current, which are obtained by using advanced Pulse Width Modulation (PWM) techniques. The working, control and modulation principles of single-phase and three-phase rectifiers are presented. Some key aspects related with the operation of these converters are discussed. Special attention is dedicated to the distortion levels accepted by standards. As a conclusion, it is observed, for example, that the power factor of a single-phase rectifier with capacitive
filtering can be improved from FP = 0,65 to FP > 0,95, by using a good control strategy. Finally, the most relevant industrial applications of these rectifiers are reviewed, concluding with a discussion of development trends.
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| | AN MCT BASED INDUSTRIAL INDUCTION COOKER CIRCUIT USING ZERO CURRENT SWITCHING
By P.R. Palmer; A.N. Githiari | [View]
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Abstract: In this paper the MCT is compared to the IGBT and conventional fast thyristor with reference to the load resonant application of industrial induction cooker hobs. Such loads may be operated in series or parallel resonance and this provides for a choice of circuit to be made depending on the switching device type. The design of the MCT circuit is considered in detail and SPICE simulations are given. Experimental results for a 6kW (peak), 25kHz prototype circuit are presented. By taking advantage of the MCT ratings, an overall efficiency of over 90% is achieved. The key features of the MCT in ZCS circuits are their low on-state voltage and their high dv/dt rating. The MCT circuit is shown to be more efficient and cost effective than the IGBT circuit for this application.
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| | ANALYSIS AND DESIGN OF A FIXED FREQUENCY BUCK-BOOST ZERO-VOLTAGE SWITCHED QUASI-RESONANT CONVERTER
By G.A. Karvelis; S.N. Manias | [View]
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Abstract: This paper presents the analysis and design of a fixed frequency Buck-Boost Zero Voltage Switched (ZVS) Quasi Resonant Converter (QRC) topology. Although the analysis of a such converter presents some difficulties that do not exist in other converter schemes, the aim of. this paper is to point out and investigate these difficulties and to provide a design example with its experimental results so that to verify the theoretical ones.
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| | A NOVEL METHOD FOR SUPPRESSION OF OVERVOLTAGE IN RESONANT DC LINK INVERTERS
By T. Kataoka; Y. Sato; M. Tobita; P.A. Dahono | [View]
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Abstract: To suppress a high voltage peak which appears on the DC link of a resonant DC link inverter, a novel resonant circuit with partial clamping of resonant capacitor
voltage is proposed. Operation of this resonant circuit is analyzed. Experimental results are shown to confirm the effectiveness of the proposed circuit.
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| | CONTROL OF A THREE-PHASE STEP-DOWN REVERSIBLE AC/DC CONVERTER
By T.C. Green; M.H. Taha; N.A. Rahim; B.W. Williams | [View]
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Abstract: The buck AC/DC converter is not naturally bidirectional unlike the boost converter. A bidirectional buck converter can be derived from anti-parallel bridges but presents control difficulties because it has two distinct modes of operation. The difficulties arise during current reversal transients because the integrity of the current path must be preserved during changes between rectification and inversion. A Simulink model of the proposed converter is developed and used to explore various control options. An arrangement of an inner current-control loop and outer voltage-control loop is found to give good voltage regulation despite load current transients and provides an effective way to change the mode of operation. The system was simulated with step demand changes and transiently regenerative loads.
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| | CYCLOCONVERTER WITH 800 Hz TWO PHASE INPUT VOLTAGE AND PULSE WIDTH MODULATION REFERENCE USED TO TRANSFER ENERGY TO THE 50 Hz SINGLE PHASE MAINS
By J.L. Cocquerelle; J. Cuvillier | [View]
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Abstract: The paper deals with layout and control strategies of a PWM referenced cycloconverter, used to transfer power from the secondary windings of a transformer (800Hz two-phase ac) to the 220V 50Hz ac mains. The goal is to transfer power from a dc source to the 50Hz mains of a laboratory, galvanic insulation being required. The dc source supplies a 800Hz inverter combined with an output filter. The two phase mains ac voltage is obtained by feeding with the inverter, a center-tapped secondary transformer followed by a SCRs bridge acting as a PWM referenced cycloconverter.
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| | PWM STRATEGIES TO CONTROL THREE-LEVEL INVERTERS - APPLICATION TO THE INDUCTION MOTORS DRIVE
By M. Berkouk; Y. Ben Romdhane; G. Manesse | [View]
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Abstract: The object of this paper is to present some control strategies of two and three phases three-level voltage inverters and their application in the drive of the single phase induction motor without capacitor and three phases one. We present in the first time a global model of three-level voltage inverters using Petri nets. Then we expose five control strategies of these converters. Some of these strategies are novel and are presented for the first time. The common points of these different strategies are feeble harmonics rate of the output voltage current and then the torque of the machine. In the last part of this paper, we present the performances of a direct field oriented control of a three phases induction motor fed by two synchronous PWM rectifters- three phases three-level voltage inverter. This drive system find applications in great power and high speed drive fields as the electrical traction.
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| | MULTlRESONANT ZERO VOLTAGE SWITCHING INVERTER DESIGNED FOR A CAPACITOR TESTING BENCH
By François Pezet; Gerard Rojat; Guy Clerc | [View]
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Abstract: This paper presents a testing bench for capacitor reliability. The goal is to verify the quality of those devices when supplied by large and high frequency currents. A multi resonant ZVS inverter is used for this purpose. Expected behavior is validated through experimental results.
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| | SNUBBERS FOR GATE TURN-OFF THYRISTOR INVERTERS
By B.W. Williams; X. He; S.J. Finney; Z. Qian | [View]
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Abstract: The paper considers three common snubber circuits used on gate turn-off thyristor inverters. Each circuit incorporates both tum-on and turn-off snubbering action. The first snubber, which has resistive losses, is converted into an active recovery snubber with the addition of a switch. The remaining two snubbers to be considered are passive lossless circuits, and improvements and modifications to these are considered. The comparative features and operation of the three improved recovery snubbers are considered and supported by PSpice simulations and experimental results.
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| | CIRCUIT FOR THE ACTIVE CONTROL OF CURRENT EQUALISATION IN PARALLELED INVERTERS
By Philip P. Waite; Robert V. Fulcher | [View]
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Abstract: A problem with paralleling inverters, is that they do not inherently supply equal proportions of the current. This paper describes a circuit which actively controls the current sharing between paralleled inverters. The circuit is used on a commercially available, 700kW, IGBT based ac drive, comprising three paralleled inverter bridges.
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| | AN IMPROVED ZERO-VOLTAGE AND ZERO-CURRENT SWITCHING FULL BRIDGE CONVERTER
By Karl-Heinz Rinne; Klaus Theml; Oliver McCarthy | [View]
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Abstract: A new topological variation of a Zero-Voltage and Zero-Current-Switching (ZVZCS) Phase-Shifted (PS) Full Bridge Converter (FBC) is introduced. By adding three saturable inductors to the ZVZCS FBC presented in (1) most of its problems, namely thermal stress of the saturable inductor, secondary side parasitic oscillations, and high reverse recovery losses of the rectifiers, can be alleviated. IGBTs rather than mosfets can be readily used for all primary side switches, leading to considerable cost savings. Due to the missing secondary side clamp circuit, the improvements can be obtained without additional costs compared to (1). A DC analysis together with design considerations are presented and backed up with experimental results taken from a 1.2kW IGBT-based power stage operated at a conversion frequency of 160kHz.
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| | COMPARISON BETWEEN THEORETICAL AND REAL CHARACTERISTICS OF ZERO-VOLTAGE SWITCHING QUASI-RESONANT CONVERTERS
By N. Polyzos; E. Tatakis; A. Safacas | [View]
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Abstract: This paper presents a comparison between the ideal and the real characteristics of Zero-Voltage Switching Quasi-Resonant Converters (ZVS-QRCs). The theoretical characteristics (already presented in the literature) have been calcuIated by considering an efficiency equal to one that means ideal semiconductor and passive devices. In this paper the real characteristics are reproduced qualitatively by computer simulation, taking into account the losses in each converter element. For this purpose approximation formulas are used. The simulation results are confronted to measurements that were taken with different breadboards ZVS-QRCs. These experimental results are also discussed.
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