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Due to their superior material properties, wide bandgap (WBG) semiconductors enable the application of power electronics at higher temperature operation, higher frequencies, and higher efficiencies compared to silicon (Si). However, the commonly-used aluminum wire bonding as topside interconnection technology prevents WBG semiconductors from reaching their full potential, due to inherent parasitic inductances, large size, heat dissipation, and reliability issues of wire bonding technology. Therefore, this article presents a comprehensive review of topside interconnection technologies of WBG semiconductor power devices and modules. First, the challenges and driving factors for the interconnection of WBG semiconductor dies are discussed. Second, for each widely commercially used WBG semiconductor, i.e., silicon carbide and gallium nitride, technical details and innovative features of state-of-the-art interconnection techniques in packages are reviewed. Then, the majority of existing topside interconnection materials for WBG semiconductors are categorized and compared, followed by a discussion of their advantages, challenges, and failure modes. Based on this elaborate discussion, potential future directions of the interconnection technology development are given. It is concluded that the superior performance of WBG semiconductors can be obtained by combining novel materials with innovative designs for the topside interconnections. [ABSTRACT FROM AUTHOR]

Diesel generators in small electricity grids are mostly not used in a very efficient way. The reason for this is twofold. First of all, the efficiency of a diesel generator is dependent on the ratio determined by the average power divided by the peak power of the generator. The smaller this ratio is, the lower the efficiency. Furthermore, some loads can regenerate energy. In small grids, this energy is mostly not needed elsewhere and should be dissipated. A solution solving both problems previously mentioned is using an energy storage device in the system. This storage can be used for peak shaving and storing regenerated energy. This paper focuses on a generator-set with energy storage. Six different power management strategies are discussed. Calculation of the costs shows that adding an energy storage device lowers the cost for all methods. Verification with simulation and experiments has been carried out. Index Terms--Costs, diesel-driven generators, energy conservation, energy storage, lithium-ion battery, power electronics, supercapacitor.

In this paper, the possibility of reaching high power densities in multikilowatt dc-dc converters with galvanic isolation is demonstrated and the main design issues are discussed. The issues related to converter topology, transformer design, and thermal management are addressed, and new conceptual solutions are proposed. Implementing zero-voltage-switching quasi-zero-current-switching topology, optimized transformer design with leakage layer, and thermal management based on conduction enhanced by heat pipes at critical places resulted in very high power density and efficiency. The power density reached by the converter prototype is 11.13 kW/L with water cooling and 6.6 kW/L with air cooling. In the same time, the measured efficiency exceeded 97% in a broad load range. The new design concepts are demonstrated on a 50-kW converter prototype that was successfully tested at full-load conditions. Index Terms--DC-DC converter, galvanic isolation, high-frequency transformer, high power density, thermal management.

Doubly fed induction generator (DFIG) still shares a large part in today's wind power market. It provides the benefits of variable speed operation cost-effectively, and can control its active and reactive power independently. Crowbar protection is often adopted to protect the rotor-side voltage source converter (VSC) from transient overcurrent during grid voltage dip. But under unbalanced grid voltage condition, the severe problems are not the transient overcurrent, but the electric torque pulsation and dc voltage ripple in the back-to-back VSCs. This paper develops dynamic models in MATLAB/Simulink, validates it through experiments, investigates the behavior of DFIG during unbalanced grid voltage condition, and proposes new controllers in separated positive and negative sequence. Methods to separate positive and negative sequence components in real time are also developed, and their responses to unsymmetrical voltage dip are compared. Simulation results prove that the separated positive and negative sequence controllers limit the torque pulsation and dc voltage ripple effectively. Index Terms--Control, doubly fed induction generator (DFIG), operation, unbalanced.

In this paper, a very high power density dc/dc converter module for automotive applications is investigated. The 14-V/42-V converter is specified to operate at a power level of 2.1 kW with a water cooled heat sink at 85[degrees]C. The design and implementation of very high density passive components are discussed. Using the results of the passive component design, a prototype converter is built, achieving a final power density of 170 W/[in.sup.3]. The thermal performance of the passive components and the converter module under different electrical and thermal excitations is investigated and recorded. Results are presented over the full excitation range. Index Terms--Converter module, thermal performance.

At a workshop held on the Aeolian Islands in Sicily during May 2004 a group of academic and industry engineers from all over the world discussed the medium- and long-term future of power electronics and its applications in specific areas. The following main issues were identified and discussed. * The demand is not for power electronic solutions but for system integration of electronic power processing. A more multidisciplinary approach is needed. * We will witness a proliferation of energy storage in systems. The technology is in place and the improvement in system performance makes it worthwhile. * A large penetration of power electronics into power systems will happen within the next 25-30 years. The main transmission grid will not be affected. The power electronics development will be in distributed generation and in the loads. * The success of the integrated starter/generator (ISG), hybrid, or electric cars depends on political decisions more than on technological advances. However, the success of a recent Japanese hybrid car and the cost of oil could trigger the critical momentum for large-scale use of power electronics in automotive applications. * We are moving toward standardized power supply building blocks for computers and other applications. The main push is for lower cost, and production technology becomes the important issue. * Demands for improved performance in a diversity of applications will stimulate R&D in power electronics in the future. Intelligent control and energy management will come easily. Thermal and passive component integration is equally important and will require attention.

Passive components, and inductors, in particular, contribute greatly to the overall volume of power electronic converters. These components are normally packaged individually with little concern for the overall system. For high-density switching power supplies it is imperative to minimize the volume to as great an extent as possible which implies that the passive component volume usage needs to be improved. This can be accomplished by applying suitable packaging and cooling techniques to these components. In this paper, two inductor structures finding application in a 2.1-kW synchronous automotive converter are described. The air-gap placement, losses, cooling methods, and thermal profiles are analyzed and verified experimentally with an inductor designed for operation at 85[degrees]C ambient. Index Terms--Direct heat removal, high power density, high temperature, indirect heat removal, packaging, passive component.

This paper covers the experimental investigation and theoretical calculation of losses in a planar inductor under load. Finite-element software is used to perform the loss calculations. Thermally controlled experiments are performed for a range of frequencies to validate the corresponding finite-element method loss calculations. The thermal dependence of the loss mechanisms is also considered. Index Terms--Finite-element method (FEM) calculations, loss analysis, loss measurement, planar inductor, thermal measurement.

The layout of a capacitor bank with clamping diodes is investigated based on an experimental 5.5-kJ energy storage unit for pulsed power applications. While the current sharing between parallel-connected capacitors is good, it is not the case with parallel-connected clamping diodes. Despite a very-low-inductance busbar and attention to symmetrical layout, unequal current sharing results. Good agreement was obtained between measured waveforms and a detailed simulation model. The simulation model indicated that the unequal current sharing is due to small differences between the coupling factors of the parasitic busbar inductances near the capacitors at the ends and at the middle of the bank. It is concluded that the best solution is to place the parallel diodes as close as possible to each other at a position where best averaged coupling is achieved with the individual capacitors of the bank. Index Terms--Current sharing, high-frequency busbar, pulsed power, resonant forced commutation.

The low-pass filter (LPF) is a fundamental component of many power electronic systems, for example, the output filters of dc-to-dc converters. The volume of the two components that constitute the LPF contribute a majority of the final system's volume, thus affecting the overall power density of the system. To be able to reach the high power densities that are required nowadays, the packaging of these components needs to be addressed. A new packaging approach is considered where the main criteria is to increase the packaging density of the LPF. The filter is considered volumetrically, and the minimum possible volume is derived. The construction and losses of such a filter are also discussed. Index Terms--Energy density, high-density packaging, loss distribution, low-pass filter, shield, volumetric optimization.

Design and optimization of high-frequency magnetic components usually involve a number of tradeoffs between performance functions. This paper investigates the relationships between some of these factors by direct implementation of the thermal reference model previously presented by the authors. This unique thermal model provided the foundation for a more flexible approach to design and optimization, forcing uninterrupted coherence between electromagnetic behavior and predefined thermal conditions. Generic scaling of transformer parameters is performed herein, under simultaneous control of the temperature rise. Relationships for performance functions, such as maximum power rating, power density, total losses, efficiency, and leakage impedance are determined, tabulated, and plotted as functions of several different scaling conditions. Index Terms - Design, high-frequency power transformers, magnetic components, optimization, scaling, thermal models.

A new thermal model is introduced which is based on unique references, specifically suited to design and optimization of high-frequency high-power magnetic components. This thermal reference model is independent of shape, size, and orientation, so that a general set of data may be used to optimize transformer structure. The model, its limitations, and applications are described in detail. Unique measurement techniques are used for experimental verification and empirical sets of practical reference data, which are also provided. Index Terms - Design, high-frequency power transformers, magnetic components, optimization, thermal models.

Initiation of a plasma conduction state requires a relatively large voltage to ionize the gas. A new version of the series resonant converter is proposed that uses the magnetizing inductance of the transformer for resonance. This converter is not suitable for most power supply applications, but the unique load characteristics associated with plasma loads make this type of converter well suited for arc striking, while allowing safe operation during the plasma state. A feature of the resonant converter is that the controller need not be complex, thus making it suitable for application in competitive industrial systems. Possible transformer configurations are investigated, which include an air core and a number of ferrite-cored transformers. The series resonant converter with the best-suited transformer is verified experimentally in a tungsten inert gas welding application. Index Terms - Resonant power conversion, transformers, welding.

This paper investigates a novel uninterruptible power supply (UPS) configuration that features low EMI and draws unity power factor without the addition of a preregulator. A 100-Hz pulsating bus is used in contrast to a smoothed dc bus. The compound converter structure exhibits high efficiency. A 3.3-kW single-phase experimental converter is evaluated. Index Terms - Single-phase uninterruptible power supply, soft-switching converter, unity power factor.

A new family of soft-switching unity power factor converters with high input power factor and isolated output is presented. A feature of the converters is a significant reduction of conducted electromagnetic interference (EMI). Six converter topologies have been identified that share a zero-voltage-switching (ZVS) phase arm on the input boost converter stage. Detailed analysis and experimental results are presented on the double ZVS phase-arm resonant transition converter. Index Terms - AC-DC power conversion, electromagnetic interference, zero-volt switching.

Contactless power delivery systems for mobile loads use transformers comprised of a core with a secondary winding sliding along an extended primary winding. The sliding transformer is identified as the most limiting component in the system and is analyzed by representing it as a special, multiturn power transmission line. Two performance parameters, namely, the transmission line efficiency and system penalty factor, are introduced. It is shown that fundamental restrictions may limit the attainable performance of the system. The inductance of the primary winding is identified as a parameter which can be optimized to improve the system performance. Experimental results for a short- and a long-stroke transformer are presented. Index Terms - Contactless power transfer, linear transformers, medium-frequency inductive power transfer.

A method is introduced for measuring a selected flux threshold below saturation, by means of a pickup winding. The method is illustrated using a block-wave oscillator and involves placing a pickup winding in a square indentation in the center leg of an E-core. Incorporating an air gap, a high-reluctance path is created at the area of the indentation. The remaining area saturates first and forces flux through the high-reluctance path, which induces a voltage on the pickup winding. The method was tested experimentally, and a proposed mathematical model was used to simulate the magnetic behavior of the sensor. Experimental and simulated results are presented and compared to verify the discussed operation. Although similar strategies have been reported previously, the significance of the sensor introduced in this paper is that detection takes place before saturation occurs and the sensor is integrated in the core. Index Terms - Flux balancing, magnetic saturation sensor.

A new high-frequency dc to dc converter, suitable for application in the kilowatt range, is presented. The topology is based on a half bridge series resonant converter, i.e., having only two switches. Resonance occurs only for a part of each switching cycle, and a discrete energy pulse is transferred to the load every half cycle, rendering a variable frequency controller for controlling the output power. The converter features zero-voltage turn-on, and snubbed turn-off at reduced current for the switching devices, and zero current commutation of the rectifier diodes, making it suitable for IGBT switches operating at a switching frequency higher than 20 kHz. The efficiency of the converter is very high under full load and low load conditions, while the dynamic output voltage range is two times larger than that of the conventional half bridge Series Resonant Converter.

The one well-known one-dimensional method for calculating the ac resistance of multilayer windings contains a built-in orthogonality which has not been reported previously. Orthogonality between skin effect and proximity effect makes a more generalized approach for the analytical solution of ac resistance in windings possible. This includes a method to calculate the ac resistance of round conductor windings which is not only convenient to use, but gives more accurate answers than the basic one-dimensional method because the exact analytical equations for round conductors can be used.

An expression for the no-load flux linkage in permanent-magnet (PM) machines is derived. From this expression, a method is proposed to increase the no-load flux linkage generated in a stator winding per volume of PM material. The method is suitable for machines with short pole pitch and is applied to a transverse-flux machine with single-sided surface-mounted PM. The result is an increase of 37% of the no-load flux linkage per volume of PM, compared with the case of rectangular PM covering 100% of the pole pitch. An increase of 15% is also obtained, if compared with the common practice of using PM covering 80% of the pole pitch. Index Terms--Permanent-magnet machines, permanent-magnet shaping, transverse-flux permanent-magnet machines.