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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.

There exist two well-known types of power transfer ac or dc. Power transfer at multiple frequencies has not yet gained much attention. This article aims at bringing out such topologies, which are capable of integrating different electrical power sources (ac or dc) irrespective of its frequency of generation, form a multifrequency (MF) bus, transmit power over a single line, and extract/convert them at the load side. This leads to the definition of unified utility/grid concept. For this, this article presents more insight into three possible MF converter topologies with renewable energy sources (RESs)/battery integration. The proposed topologies work on the principle of orthogonal power transfer. Furthermore, power transfer at multiple frequencies shows an effective way of decoupling the individual sources of the system. Finally, the feasibility of transferring power at multiple frequencies is validated experimentally and the results are discussed herein along with its potential benefits.

The power electronic converter, especially the power semiconductor, is a major contributor to the failure rates of the wind turbine drivetrain. As the temperature is a major driving factor behind the failure mechanisms of these power semiconductors, the choice of topology and switching strategy can have a significant effect on the reliability of the converter. This paper presents a detailed comparison of several three-level converter topologies and switching strategies on the basis of loss distribution, thermal, and lifetime performance. This investigation is done through simulations on a 10-MW direct drive permanent magnet drivetrain. The study shows that overrating in the form of using overrated topologies, or the use of overrated components can result in large gains in lifetime expectancy and quantifies these gains. It concludes that the improvements offered by overrated topologies and overrated components are comparable and this use of the overrated topologies do not offer a significant advantage over the use of topologies with overrated components.

This paper presents an investigation on modulation modes for dual active bridge modules stacked in a 10-kV input parallel output series converter for energy extraction in dielectric electroactive polymer (DEAP) wave energy converters. The converter requirements for energy harvesting with DEAPs are derived, and the operating areas and limitations of each modulation mode are compared. A hybrid modulation strategy consisting of several variable frequency modulation modes is proposed, which is capable of operating over a wide voltage and current range at high-efficiency levels as required by the DEAP harvesting cycles. Through loss calculations using an experimentally validated loss model and by including both material and converter losses in the harvesting cycle, it is shown that the hybrid modulation method increases the energy output of low-strain cycles by 25%.

Recently, flux-switching permanent magnet (FSPM) machines have been increasingly investigated due to its torque density and fault tolerance. Because of this, they are attractive for aerospace applications where weight, installation spaces, and safety play a critical role. Recent research has investigated a variation of the conventional FSPM machine called the C-core FSPM machine, which offers 40% greater electromagnetic torque, while using half of the magnet mass. This paper proposes a new topology called Halbach-FSPM capable of achieving an electromagnetic torque 20% higher than the C-core FSPM machine, while maintaining machine volume and phase current constant and using no more magnet material than a conventional FSPM machine. First, a physical explanation of the advantages are developed for use in all FSPM machines using Halbach arrays. An analysis and comparison of torque, power and efficiency are made. Further, magnet losses and segmentation applicable to all FSPM topologies are discussed, plus an analysis on magnet usage is given.

This paper reviews the trends in wind turbine generator systems. After discussing some important requirements and basic relations, it describes the currently used systems: the constant speed system with squirrel-cage induction generator, and the three variable speed systems with doubly fed induction generator (DFIG), with gearbox and fully rated converter, and direct drive (DD). Then, possible future generator systems are reviewed. Hydraulic transmissions are significantly lighter than gearboxes and enable continuously variable transmission, but their efficiency is lower. A brushless DFIG is a medium speed generator without brushes and with improved low-voltage ride-through characteristics compared with the DFIG. Magnetic pseudo DDs are smaller and lighter than DD generators, but need a sufficiently low and stable magnet price to be successful. In addition, superconducting generators can be smaller and lighter than normal DD generators, but both cost and reliability need experimental demonstration. In power electronics, there is a trend toward reliable modular multilevel topologies.

Different aspects of the design of inverters for industrial applications including static power supplies, light welding equipment, and high-speed motor control at input voltages from 30 to 300 V are described. High frequencies (5-30 kHz) are used at power levels between 1 and 50 kW, and emphasis is placed on minimization of losses in order to obtain efficient and compact systems. Attention is given to optimization of snubber technology for low switching losses and feedback of the snubbing power to the supply at the larger powers, design aspects of large ferrite transformers, as well as protection of the equipment. The on-voltage of the Darlington switches is reduced by adding a compensation voltage source to the base of the main transistor, thus lowering on-losses drastically. Experimental results obtained from 1-kVA, 6-kVA, and 50-kVA single-phase units are used to highlight certain aspects of the inverter design principles.