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Power Electronics, IEEE Transactions on

Issue 1 • Date Jan 1992

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Displaying Results 1 - 25 of 26
  • Using AC-fed PWM converters as instantaneous reactive power compensators

    Page(s): 224 - 230
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (516 KB)  

    A general control method that fully utilizes the inherent capability of AC-fed PWM converters to compensate for reactive and harmonic currents adsorbed by other loads is presented. For this purpose, suitable definitions of instantaneous active and reactive current and power terms are introduced. Optimum modulation laws are then derived according to a general control theory valid for PWM multiconverter systems which also results in maximum system efficiency. Simulated results demonstrate the capabilities of the proposed compensation method, which can also be implemented in existing systems as only modifications of the control section are needed View full abstract»

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  • Snubber circuits and losses of voltage-source GTO inverters

    Page(s): 231 - 239
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    The power dissipation of series and parallel snubbers in gate turn-off thyristor (GTO) inverters is investigated. New circuits using optimized snubbers are simulated and compared and solutions that allow the recovery of the energy stored in the snubbers are reported. In particular, an inverter circuit that uses a transformer for the recovery of the energy trapped in the snubbers is investigated, and solutions that avoid saturation of the transformer core are studied View full abstract»

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  • High-performance current control techniques for application to multilevel high-power voltage source inverters

    Page(s): 189 - 204
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    Several high-performance current control techniques are developed for applications to multilevel high-power voltage source inverters (VSIs). The logical sequence of the design choices is described, resulting in a very robust and reliable control system that allows an adequate switching optimization, excellent dynamic responses, and high accuracy in steady-state operation. The advantages of using various accessible DC potentials are fully exploited. The validity of the proposed schemes has been confirmed by digital simulations involving the generation of five-level voltage waveforms; however, the current control strategies developed can easily be extended to any multilevel inverter structure, even in the case of n-level voltage waveforms and three-phase systems View full abstract»

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  • Small-signal circuit modeling in the frequency-domain by computer-aided time-domain simulation

    Page(s): 83 - 88
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    The possibility of obtaining the frequency-domain dynamic model of a circuit from transient analysis data provided by a circuit simulator is shown. The computer-aided design (CAD) program FREDOMSIM, which governs the simulations, processes the output data, and supplies the results in a well suited manner for design optimization, is introduced. Feedback circuits are modeled with all their feedback loops open, so that the designer can optimize systems by proper a posteriori loop closures. The characterization with the loops closed is also given View full abstract»

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  • A circuit model for the class E resonant DC-DC converter regulated at a fixed switching frequency

    Page(s): 99 - 110
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    An averaging circuit model is developed for the class E resonant DC-DC converter regulated at a fixed switching frequency. The regulation is achieved by use of an auxiliary switch. The model is obtained based on the circuit analysis using the Fourier series expansion. Steady-state and small-signal dynamic analysis is presented, which reveals that the DC output is well controlled by the control angle of the auxiliary switch and that there exists a right-half-plane zero in the control-to-output transfer function. The analysis results are verified by the experiments View full abstract»

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  • Adaptive optimal pulse-width modulation for the line-side converter of electric locomotives

    Page(s): 205 - 211
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    Two methods of generating synchronous online optimal PWM sequences for the line-side converter of electrical locomotives are described. The properties of the feeding supply line render the system oscillatory at multiple resonance frequencies, which are time-variable functions of the railway track topography and of the respective locations of traction vehicles. The prevailing topographic conditions define a time-variable virtual model of the overhead line, the harmonic energy of which is the optimum criterion to be minimized. The 176 switching instants of a nine-level PWM converter voltage are optimized using an online algorithm. The necessary computations are performed in the time intervals between two commutations. The performance is illustrated by measurements obtained from a real-time multiprocessing model of an extended railway track topography, including substations and locomotives. The developed hardware structure is designed for the implementation in a railway traction vehicle View full abstract»

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  • Synthesis of zero-impedance converter

    Page(s): 152 - 170
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    A method for synthesizing a system that converts a finite value of an impedance to zero, with an associated finite current and zero voltage, is presented. The synthesis method comprises positive current feedback of an exactly specified nature and value of its transfer function. The stability and dynamics of the system are controlled by an additional voltage loop. The zero-impedance converter is used to synthesize load-independent systems including (switch-mode) power converters and electric motor drive systems incorporating any kind of motor View full abstract»

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  • A new technique to reject DC-link voltage ripple for inverters operating on programmed PWM waveforms

    Page(s): 171 - 180
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (648 KB)  

    A proposal for rejecting DC-link voltage ripple in inverters operating on programmed PWM waveforms is examined in detail. It is demonstrated how continuous elimination of harmonics is achieved at the inverter output while simultaneously rejecting the DC-link voltage ripple. Thus, with the proposed technique, high-quality voltage is guaranteed at the inverter output terminals even with a substantial low-frequency voltage ripple on the DC-link. A thorough modeling of this technique along with the tradeoffs involved in acquiring the immunity to DC-link ripple is illustrated in detail. Potential applications of the technique are in fixed and variable frequency inverters for power supplies and AC motor drives that experience voltage ripple in the DC link such as when fed from a weak AC system that is frequently unbalanced. A design procedure along with the digital implementation of the proposed technique is described. Selected results were verified experimentally on a laboratory inverter View full abstract»

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  • Energy-storage pulsed-power capacitor technology

    Page(s): 251 - 257
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    Fundamentals of dielectric capacitor technology and multifactor stress aging of all classes of insulating media that form elements of this technology are addressed. The goal is the delineation of failure processes in highly stressed compact capacitors. Factors affecting the complex aging processes such as thermal, electromechanical, and partial discharges are discussed. Diagnostic measurement techniques available and those being developed to determine material degradation affecting available life and failure probability of capacitors are presented View full abstract»

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  • Series-resonant single-phase AC-DC power supply with control of reactive power

    Page(s): 111 - 118
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    It is shown that the resolution of the high-frequency input current of the series-resonant converter leads to the possibility of accurately controlling the waveform of the source current. In combination with the accurate positioning of the high-frequency current pulses, it is possible to influence the exchange of power with the source by introducing active filtering. A power factor equal to one would lead to optimal operation. However, the zero crossing of the AC source voltage, introduces the need to store energy. Bulky low-frequency storage elements increase the specific volume and weight of the converter, while the exchange of energy with storage elements decreases the overall efficiency. The energy stored in the resonant circuit is fundamentally too low to solve this problem. The stored energy in the output capacitor necessary to decrease the high-frequency ripple voltage is available for these purposes. To meet the optimal conditions for the power factor at the source, a bipolar flow of energy is required View full abstract»

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  • Topologies for three-element resonant converters

    Page(s): 89 - 98
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    Many of the limitations of two-element resonant topologies can be overcome by adding a third reactive element. However, using three elements greatly increases the number of possible topologies, making it very difficult to explore this class of circuits on a trial-and-error basis. An orderly search procedure that exposes a large number of new topologies, many of which are resonant and have useful properties, is presented View full abstract»

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  • Modeling of chaotic DC-DC converters by iterated nonlinear mappings

    Page(s): 25 - 36
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    In parameter ranges where conventional methods break down, DC-DC converters may be described by iterated mappings, a nonlinear discrete modeling technique. The underlying principles are explained and are applied to the example of a PWM-controlled buck converter. Stable behavior and bifurcations to chaos are predicted by numerical evaluation of the governing mapping and are confirmed by experiment View full abstract»

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  • Coaxially wound transformers for high-power high-frequency applications

    Page(s): 54 - 62
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (840 KB)  

    Design considerations for transformers utilized in high-power high-frequency DC/DC converters are addressed. Major areas of concern are core-material selection, minimization of copper losses due to skin and proximity effects, and the realization of controlled leakage inductances. Coreless characteristics for various high-frequency materials are presented, and the influence of various conventional winding arrangements on the copper losses and leakage field is also demonstrated. Coaxial winding techniques (used commonly in high-frequency transformers) are investigated next as a feasible solution for containing the leakage flux within the interwinding space, thus preventing it from permeating the core and resulting in lower core losses and the avoidance of localized heating. Added benefits of this technique are reduced forces within the transformer, lower copper losses, and robust construction. The performances of two experimental single-phase 50 kW, 50 kHz units are reported. A three-phase version of coaxially wound transformers is also presented View full abstract»

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  • Small-signal analysis of the phase-shifted PWM converter

    Page(s): 128 - 135
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    The specific circuit effects in the phase-shifted PWM (PS-PWM) converter and their impact on the converter dynamics are analyzed. The small-signal model is derived incorporating the effects of phase-shift control and the utilization of transformer leakage inductance and power FET junction capacitances to achieve zero-voltage resonant switching. The differences in the dynamic characteristics of the PS-PWM converter and its PWM counterpart are explained. Model predictions are confirmed by experimental measurements View full abstract»

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  • Analysis of a hybrid series parallel resonant bridge converter

    Page(s): 119 - 127
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    The steady-state operation of a hybrid series parallel resonant bridge is analyzed. Two expressions are derived for the power output as a function of capacitor ratio, switching frequency, and conversion ratio. One power output expression is for conversion ratios less than or equal to one, and the other expression is for conversion ratios greater or equal to one and less than or equal to two. The optimum conversion ratio for maximum power transfer is also derived View full abstract»

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  • Dynamic modeling of a generator/rectifier system

    Page(s): 212 - 223
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    A nonlinear detailed model has been constructed for synchronous generators loaded with a rectifier bridge. This dynamic model is based on the description of the commutation and noncommutation stages. The switching instants depend on the state variables of the system. In order to be able to apply linear system theory for control design, an approximating linear model has been derived, based on application of the Floquet theory. Consequently, asymptotic stability analysis is possible with the linear model. Comparison with the full nonlinear model shows good resemblance View full abstract»

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  • Computer-aided discrete-time large-signal analysis of switching regulators

    Page(s): 75 - 82
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    A computer program based on a general nonlinear discrete formulation procedure for large-signal analysis of switching regulators is introduced. The program provides both time-domain and state-trajectory simulation of converter state variables under different control strategies in either of two conduction modes. As a result, the regulator asymptotic stability can be predicted for large-signal operation. Experimental results verify the theoretical predictions View full abstract»

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  • Input filter design criteria for current-programmed regulators

    Page(s): 143 - 151
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    The design of input filters for switched-mode regulators is discussed, and it is shown that the filter's effect on the power system depends on the control method used in the regulator's DC-DC converter. Design inequalities are reviewed for duty-ratio programmed converters, and specific expressions are presented for current-programmed converters. Examples of application to practical regulator circuits are given where current-programmed criteria, computer-driven measurement tools, and numerical evaluations of analytic expressions are used to design input filters View full abstract»

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  • Canonical modeling of power processing circuits based on the POPI concept

    Page(s): 37 - 43
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    The fundamental power-processing properties of switching converter circuits are modeled using generalized power-conservative (POPI) networks. Depending on the application, it may be most appropriate to model the first-order converter properties as those of an ideal transformer, gyrator, loss-free resistor, or other POPI network. These basic functions can be obtained either through selection of a topology that naturally possesses the desired characteristics or by addition of a suitable control network. Some well-known converter topologies are shown to behave naturally as gyrators, loss-free resistors, and constant power networks. The application of the gyrator to network two voltage sources and the use of the loss-free resistor as a unity power factor rectifier are described View full abstract»

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  • Steady-state analysis of the symmetrical push-pull power converter employing a matrix transformer

    Page(s): 44 - 53
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    Data published for the symmetrical push-pull power converter (SPPPC) show that the matrix transformer and the cross-coupling capacitors in this buck-type topology introduce unusual waveforms and properties. Circuit operation is examined in order to seek a simplified explanation of the published observations. Steady-state performance is analyzed and design equations are developed using state-space averaging. It is found that the SPPPC is equivalent to the conventional push-pull converter with an input filter as far as steady-state behavior and voltage/current ripple are concerned. Despite the presence of the cross-coupling capacitors, the currents in the primary windings in series with the same switch are identical. The RMS current in the primary windings of the SPPPC is lower than that in the conventional push-pull converter View full abstract»

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  • Comparison of performance of single-loop and current-injection control for PWM converters that operate in both continuous and discontinuous modes of operation

    Page(s): 136 - 142
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    An analysis of current-injection-controlled (CIC) power converters operating in both the continuous and discontinuous modes is performed using the PWM switch model and a new, continuous-time model of CIC. The stability, output impedance, audio susceptibility, and transient response are compared with single-loop control. The control of an example buck converter is designed with CIC and single-loop control. It is shown how single-loop controlled power converters exhibit a large change in the dynamic performance when crossing the boundary between continuous mode and discontinuous mode. This is especially true for the output impedance and transient response. The dynamic performance of CIC power converters remains relatively fixed when crossing this boundary. A significant performance improvement can be realized when CIC is employed in converters that operate over a wide load range View full abstract»

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  • A two-dimensional FFT algorithm for three-phase inverter-fed systems

    Page(s): 181 - 188
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    A spectrum analyzer for three-phase inverter-fed balanced systems which is capable of calculating up to 24 harmonic components of the line currents every 130 μs is presented. The method is based on a synchronized sampling technique and on a highly efficient fast Fourier transform (FFT) for three-phase systems. The latter consists of a two-dimensional six-point discrete Fourier transform (DFT) followed by a two-dimensional four-point DFT. The total FFT algorithm has been successfully implemented on a TMS32010 digital signal processor View full abstract»

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  • The relationship between size and power dissipation in a 1-10 MHz transformer

    Page(s): 63 - 74
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    The trade-off between size and power dissipation in the design of low-profile 1-10 MHz transformers with planar spiral windings is considered. For a fixed power loss and number of conductor layers, the transformer with the smallest possible footprint can be designed by a trade-off of core and copper loss. The relationship between the marginal reduction of the transformer footprint and the associated marginal increase in power dissipation and/or number of conductor layers for the design of the smallest possible transformer is discussed View full abstract»

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  • Lyapunov-based control for switched power converters

    Page(s): 17 - 24
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    Beginning with fundamental properties such as passivity or incremental passivity of the network elements comprised by a switched power converter, the nominal open-loop operation of a broad class of such converters is shown to be stable in the large via a Lyapunov argument. The obtained Lyapunov function is then shown to be useful for designing globally stabilizing controls that include adaptive schemes for handling uncertain nominal parameters. Numerical simulations illustrate the application of this control approach in DC-DC converters View full abstract»

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  • Implementation of a controlled rectifier using AC-AC matrix converter theory

    Page(s): 240 - 250
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    It is well known that a PWM-controlled rectifier can offer advantages of reduced low-order harmonics and unity input power factor when compared to a conventional thyristor converter. However, theoretically optimum PWM strategies are often difficult to implement physically or are not easily extended to regenerative operation. The authors propose an alternative PWM strategy based on AC-AC matrix converter theory, which generates only high-order switching harmonics, presents a unity power factor load to the supply, implicitly extends to regeneration (and operation with a center tapped DC output), and is feasible to physically implement for real-time output voltage control. Both the theory and physical simulation results are presented View full abstract»

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Aims & Scope

IEEE Transactions on Power Electronics covers fundamental technologies used in the control and conversion of electric power.

Full Aims & Scope