Over the last decade, dc-dc power converters have attracted significant attention due to their increased use in a number of applications from aerospace to renewable energy. The interest in wide bandgap (WBG) power semiconductor devices stems from outstanding features of WBG materials, power device operation at higher temperatures, larger breakdown voltages, and the ability to sustain larger switching transients than silicon (Si) devices. As a result, recent progress and development of converter topologies, based on WBG power devices, are well-established for power conversion applications in which classical Si-based power devices show limited operation. Currently, Si carbide (SiC) and gallium nitride (GaN) are the most promising semiconductor materials that are being considered for the new generation of power devices. The use of new power semiconductor devices, such as GaN high electron mobility transistors (GaN HEMTs), leads to minimization of switching losses, allowing high switching frequencies (from kHz to MHz) for realizing compact power converters. Finally, design recommendations and future research trends are also presented.

For ac electricity grids, the aim has always been at low-cost and disruption-proof solutions. The power grid is inherently vulnerable to environmental disturbances. However, the introduction of power electronics (PEs) and changes in load and generator characteristics have introduced a game changer at an unprecedented pace over the last decade. During this change, load specifications, load characteristics, and control and monitoring requirements for power system security have also dramatically evolved. Efficiency and reliability of system components have progressed in parallel with this evolution. However, high penetration of renewable energy sources has reduced the percentage contribution of conventional electricity based on synchronous generation, which affects grid stability and hence reliability. Furthermore, numerous camouflaged dc generators and dc loads are being embedded in ac and dc microgrids at ever increasing rates. While embedded generation rapidly increases its share in the hybrid power grid (where ac and dc coexist), the current developments in PE switches-based on wide bandgap (WBG) technology-indicate that within the next two decades Max Planck's well-known sentiment that science advances one funeral at a time will repeat itself on the ac grid. This article aims to summarize the technical developments and problems facing the utilization of ac during widescale electrification of the world using numerous distributed energy resources (DERs). Then, it will map out evolutionary changes toward a future dc grid.

On-line impedance measurement is a useful tool to monitor the state, health and characteristics of electrical networks in power systems. This paper proposes a method for on-line, wide-bandwidth, impedance analysis of devices used in power networks. This method uses a signal generator to inject other than mains frequency signals on-line and then measuring current and voltages to determine the impedance at the injected frequencies. Two measurement circuits based on different types of current and voltage measurement methods are discussed. Their experimental results of impedance measurement are shown. This paper also suggested some possible applications of this on-line impedance analysis method in condition monitoring of power distribution transformers and electrical machines.

Negative sequence current analysis is useful for shorted turn detection in induction motors. It can produce fast and reliable monitoring results using a simple measurement technique. However, it is sensitive to disturbances such as sensor calibration, inherent machine asymmetry and supply voltage unbalances. This paper demonstrates an effective phasor compensation technique for these disturbances to allow more accurate shorted turn fault detection. This paper also provides detail investigation of the compensation by demonstrating step-by-step disturbance extraction to obtain the real negative sequence current due to shorted turn faults.