http://ieeexplore.ieee.org/iel5/5610941/5624686/05624745.pdf

Power electronics

Three DC/DC converter topologies suitable for high-power-density high-power applications are presented. All three circuits operate in a soft-switched manner, making possible a reduction in device switching losses and an increase in switching frequency. The three-phase dual-bridge converter proposed is shown to have the most favorable characteristics. This converter consists of two three-phase inverter stages operating in a high-frequency six-step mode. In contrast to existing single-phase AC-link DC/DC converters, lower turn-off peak currents in the power devices and lower RMS current ratings for both the input and output filter capacitors are obtained. This is in addition to smaller filter element values due to the higher-frequency content of the input and output waveforms. Furthermore, the use of a three-phase symmetrical transformer instead of single-phase transformers and a better utilization of the available apparent power of the transformer (as a consequence of the controlled output inverter) significantly increase the power density attainable. >

A three-phase soft-switched high power density DC/DC converter for high power applications

Solid-state switch-mode rectification converters have reached a matured level for improving power quality in terms of power-factor correction (PFC), reduced total harmonic distortion at input AC mains and precisely regulated DC output in buck, boost, buck-boost and multilevel modes with unidirectional and bidirectional power flow. This paper deals with a comprehensive review of improved power quality converters (IPQCs) configurations, control approaches, design features, selection of components, other related considerations, and their suitability and selection for specific applications. It is targeted to provide a wide spectrum on the status of IPQC technology to researchers, designers and application engineers working on switched-mode AC-DC converters. A classified list of more than 450 research publications on the state of art of IPQC is also given for a quick reference.

/pdf/a-review-of-single-phase-improved-power-quality-ac-dc-2pm6h4zjxq.pdf

A review of single-phase improved power quality AC-DC converters

The performance of a high-power, high-power-density DC-to-DC converter based on the single-phase dual active bridge (DAB) topology is described. The dual active bridge converter has been shown to have very attractive features in terms of low device and component stresses, small filter components, low switching losses, high power density and high efficiency, bidirectional power flow, buck-boost operation, and low sensitivity to system parasitics. For high output voltages, on the order of kilovolts, a cascaded output structure is considered. The effects of snubber capacitance and magnetizing inductance on the soft switching region of control are discussed. Various control schemes are outlined. Coaxial transformer design techniques have been utilized to carefully control leakage inductance. The layout and experimental performance of a prototype 50 kW 50 kHz unit operating with an input voltage of 200 V DC and an output voltage of 1600 V DC are presented. >

Performance characterization of a high-power dual active bridge DC-to-DC converter

A more general averaging procedure that encompasses state-space averaging and that is potentially applicable to a much broader class of circuits and systems is presented. Examples of its application in resonant and PWM power convertors are presented. The technique is shown to be effective on a number of examples. including resonant type converters. The approach offers refinements to the theory of state-space averaging, permitting a framework for analysis and design when small ripple conditions do not hold. The method may find applications in simulation and design since it is considerably easier to simulate an averaged model than a switched model. >

/pdf/generalized-averaging-method-for-power-conversion-circuits-da237et2wc.pdf

Generalized averaging method for power conversion circuits

The paper describes a method of harmonic elimination using a low power auxiliary GTO power converter. The auxiliary power converter handles only harmonic currents with zero fundamental. Such a power converter combination has a lower cost compared to multipulse power converters currently in use.

Harmonic elimination in high power GTO converter using an auxiliary converter with zero fundamental power

Power converters form the main part of any power electronic system. They consist of power semiconductors, energy storage components and microelectronic components. For each application a suitable converter is separately designed increasing the engineering cost. In this paper, the authors present a concept of using a power electronic cell as a basic building block for building power converter systems. The paper shows analysis of cells various converter configurations and studies the effect of communication delay on the voltage output of the combination.

Power electronic systems using versatile power electronic cell: UPEC

Based on a systematic classification of dc source to utility interfacing schemes, this paper presents six major interfacing schemes for connecting fuel cells to a single-phase utility line using high-frequency transformer isolated power converters. The operation, advantages and disadvantages are discussed for each scheme with examples and operating waveforms. Several features e.g., utility line power factor, line current THD, size, ease of connection to utility line and simplicity of control, are compared. Based on their performance and fuel cell characteristics, a suitable scheme is selected. The selected scheme (#4) uses a dc/dc converter followed by a current controlled voltage source inverter. Details of the power conditioning unit (PCU) based on the selected scheme are given with some PSIM simulation results.

Classification and comparison of interfacing schemes for connecting fuel cells to a single-phase utility line

A tri-state boost converter proposed earlier avoids the dynamic response problem of single-switch boost converter operating in continuous-conduction mode by providing an additional inductor-free-wheeling interval. The converter offers an additional degree of control-freedom. Two variations of a multi-variable dual-mode control (DMC) scheme that effectively exploit this control freedom and aim to attain a good compromise between the contradictory multiple-goals of achieving good dynamic performance and high efficiency have also been proposed earlier. The dynamic and steady-state performances of the converter under DMC are closely interrelated and in turn decide the size and rating of power components and also the design of feedback controllers. The aim of this paper is to investigate the trade-offs involved in the design of DMC based tri-state boost converter and to present a systematic design procedure for both variations of the DMC schemes. The relation between dynamic and steady-state performances is investigated and used appropriately in selecting the power and control components. An example design is presented and the design is validated through simulations and experiments.

Design and evaluation of tri-state boost converter

Due to the switching action of the power switches in it, a power converter can be treated as a piecewise linear system. It has been recognised that this nature can be utilised to perform efficient analysis of the converter. In this paper, a general method of performing the large signal simulation by direct solution of each of the switching intervals is discussed. To facilitate the automation of the analysis, a general and standardised way of formulating the threshold conditions, which determine the topological mode transitions is proposed. Based on the large signal model, two different methods of finding the steady state operating point are proposed. The efficiencies of the two methods have also been compared. The algorithms proposed for the large signal and steady state analyses are applicable to all kinds of DC-DC converters, operated under various control methods. >

http://ieeexplore.ieee.org/iel2/3200/9101/00404902.pdf

Ramesh Oruganti

Papers

Harmonic elimination in high power GTO converter using an auxiliary converter with zero fundamental power

Power electronic systems using versatile power electronic cell: UPEC

Classification and comparison of interfacing schemes for connecting fuel cells to a single-phase utility line

Design and evaluation of tri-state boost converter

Large signal and steady state analyses of DC-DC power converters