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

In designing conventional switching converters, the effort to increase operating frequency in order to reduce weight, size and cost of magnetic and filter elements is constantly hampered by higher switching stresses and switching losses. To overcome these obstacles, the concept of resonant switch was proposed. By incorporating additional Land C elements to shape device current and voltage waveforms, the desired zero-current switching property can be realized which enables converters to operate in the megahertz range.

Resonant switches - Topologies and characteristics

Several techniques to mitigate conducted electromagnetic interference (EMI) in switch-mode power supplies (SMPS) have been reported in literature. Of these, this paper reviews those techniques that are primarily meant for ac-dc and dc-dc power converters. The techniques are broadly classified based on two criteria-1) reduction of the noise after generation and 2) reduction of the noise at the generation stage itself. A detailed classification and review of various noise mitigation techniques currently available in literature are presented. It is believed that the classification and review of the conducted EMI mitigation techniques presented in this paper would be useful to SMPS researchers and designers.

Conducted EMI Mitigation Techniques for Switch-Mode Power Converters: A Survey

In designing switching dc-dc converters, the effort to increase operating frequency to reduce weight, size, and cost of magnetic and filter elements is constantly hampered by higher switching stresses and switching losses. To overcome these obstacles, the concept of the "resonant switch" is proposed. By incorporating additional inductor and capacitor elements to shape the semiconductor switch's current waveform, a "zero-current switching" property can be realized. Based on the resonant switch technique, a new host of quasi-resonant converter circuits have been derived, which can be operated in the megahertz range.

Quasi-Resonant Converters-Topologies and Characteristics

State-plane techniques in conjunction with piecewise-linear analysis is employed to study the steady-state and transient characteristics of a series resonant converter. With the direct viewing of the resonant tank energy and the device switching instant, the state portrayal provides unique insights into the complex behavior of the converter. Operation of the converter under both continuous and discontinuous current modes and at frequencies both below and above resonant frequency are discussed.

Resonant Power Processors, Part I---State Plane Analysis

The unfolding-type flyback inverter operating in discontinuous conduction mode (DCM) is popular as a low-cost solution for a photovoltaic (PV) ac module application. This paper aims to improve the efficiency by using a scheme based on continuous conduction mode (CCM) for this application. Design issues, both for the power scheme and the control scheme, are identified and trade-offs investigated. An open-loop control of the secondary current, based on feedback control of the primary current, is proposed in order to bypass the difficulties posed by the moving right half plane zero in the duty cycle to secondary current transfer function. The results presented show an improvement of 8% in California efficiency compared to the benchmark DCM scheme for a 200-W PV module application. The output power quality at rated power level is capable of meeting IEC61727 requirements. The stability of the flyback inverter in CCM has been verified at selected working conditions.

Ramesh Oruganti

Papers

Resonant switches - Topologies and characteristics

Conducted EMI Mitigation Techniques for Switch-Mode Power Converters: A Survey

Quasi-Resonant Converters-Topologies and Characteristics

Resonant Power Processors, Part I---State Plane Analysis

A Low Cost Flyback CCM Inverter for AC Module Application