High-frequency-link (HFL) power conversion systems (PCSs) are attracting more and more attentions in academia and industry for high power density, reduced weight, and low noise without compromising efficiency, cost, and reliability. In HFL PCSs, dual-active-bridge (DAB) isolated bidirectional dc-dc converter (IBDC) serves as the core circuit. This paper gives an overview of DAB-IBDC for HFL PCSs. First, the research necessity and development history are introduced. Second, the research subjects about basic characterization, control strategy, soft-switching solution and variant, as well as hardware design and optimization are reviewed and analyzed. On this basis, several typical application schemes of DAB-IBDC for HPL PCSs are presented in a worldwide scope. Finally, design recommendations and future trends are presented. As the core circuit of HFL PCSs, DAB-IBDC has wide prospects. The large-scale practical application of DAB-IBDC for HFL PCSs is expected with the recent advances in solid-state semiconductors, magnetic and capacitive materials, and microelectronic technologies.

Overview of Dual-Active-Bridge Isolated Bidirectional DC–DC Converter for High-Frequency-Link Power-Conversion System

This paper presents an isolated on-board vehicular battery charger that utilizes silicon carbide (SiC) power devices to achieve high density and high efficiency for application in electric vehicles (EVs) and plug-in hybrid EVs (PHEVs). The proposed level 2 charger has a two-stage architecture where the first stage is a bridgeless boost ac-dc converter and the second stage is a phase-shifted full-bridge isolated dc-dc converter. The operation of both topologies is presented and the specific advantages gained through the use of SiC power devices are discussed. The design of power stage components, the packaging of the multichip power module, and the system-level packaging is presented with a primary focus on system density and a secondary focus on system efficiency. In this work, a hardware prototype is developed and a peak system efficiency of 95% is measured while operating both power stages with a switching frequency of 200 kHz. A maximum output power of 6.1 kW results in a volumetric power density of 5.0 kW/L and a gravimetric power density of 3.8 kW/kg when considering the volume and mass of the system including a case.

A High-Density, High-Efficiency, Isolated On-Board Vehicle Battery Charger Utilizing Silicon Carbide Power Devices

In this paper, a high-temperature, high-frequency, wire-bond-based multichip phase-leg module was designed, fabricated, and fully tested. Using paralleled Silicon Carbide (SiC) MOSFETs, the module was rated at 1200 V and 60 A, and was designed for a 25-kW three-phase inverter operating at a switching frequency of 70 kHz, and in a harsh environment up to 200 °C, for aircraft applications. To this end, the temperature-dependent characteristics of the SiC MOSFET were first evaluated. The results demonstrated the superiority of the SiC MOSFET in both static and switching performances compared to Si devices, but meanwhile did reveal the design tradeoff in terms of the device's gate oxide stability. Various high-temperature packaging materials were then extensively surveyed and carefully selected for the module to sustain the harsh environment. The electrical layout of the module was also optimized using a modeling and simulation approach, in order to minimize the device parasitic ringing during high-speed switching. Finally, the static and switching performances of the fabricated module were tested, and the 200 °C continuous operation of the SiC MOSFETs was verified.

A 1200-V, 60-A SiC MOSFET Multichip Phase-Leg Module for High-Temperature, High-Frequency Applications

The current state of wide bandgap device technology is reviewed and its impact on power electronic system miniaturization for a wide variety of voltage levels is described. A synopsis of recent complementary technological developments in passives, integrated driver, and protection circuitry and electronic packaging are described, followed by an outline of the applications that stand to be impacted. A glimpse into the future based on the current technological trends is offered.

Wide Bandgap Technologies and Their Implications on Miniaturizing Power Electronic Systems

DC microgrids have attracted significant attention over the last decade in both academia and industry. DC microgrids have demonstrated superiority over AC microgrids with respect to reliability, efficiency, control simplicity, integration of renewable energy sources, and connection of dc loads. Despite these numerous advantages, designing and implementing an appropriate protection system for dc microgrids remains a significant challenge. The challenge stems from the rapid rise of dc fault current which must be extinguished in the absence of naturally occurring zero crossings, potentially leading to sustained arcs. In this paper, the challenges of DC microgrid protection are investigated from various aspects including, dc fault current characteristics, ground systems, fault detection methods, protective devices, and fault location methods. In each part, a comprehensive review has been carried out. Finally, future trends in the protection of DC microgrids are briefly discussed.

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DC Microgrid Protection: A Comprehensive Review

Silicon Carbide (SiC) power semiconductors have shown the capability of greatly outperforming Si-based power devices. Faster switching and smaller on-state losses coupled with higher voltage blocking and temperature capabilities make SiC an attractive semiconductor for high-performance, high-power-density power modules. However, the temperature capabilities and increased power density are fully realized only when the gate driver needed to control the SiC devices is placed next to them. This requires the gate driver to successfully operate under extreme conditions with reduced or no heat sinking requirements. In addition, since SiC devices are usually connected in a half- or full-bridge configuration, the gate driver should provide electrical isolation between the high- and low-voltage sections of the driver itself. This paper presents a 225°C operable, silicon-on-insulator (SOI) high-voltage isolated gate driver IC for SiC devices. The IC was designed and fabricated in a 1 μm, partially depleted, CMOS process. The presented gate driver consists of a primary and a secondary side which are electrically isolated by the use of a transformer. The gate driver IC has been tested at a switching frequency of 200 kHz at 225°C while exhibiting a dv/dt noise immunity of at least 45 kV/μs.

High-Temperature Silicon-on-Insulator Gate Driver for SiC-FET Power Modules

This paper presents the challenges and results of fabricating a high temperature silicon carbide based integrated power module. The gate driver for the module was integrated into the power package and is rated for an ambient temperature of 250 °C. The power module was tested up to 300 V bus voltage, 160 A peak current, and 250 °C junction temperature.

High-temperature silicon carbide and silicon on insulator based integrated power modules

This paper presents a bi-directional ac-dc isolated converter designed to be utilized within the US Navy's Integrated Fight Through Power (IFTP) concept. To demonstrate the proposed approach the authors have designed, fabricated, and tested a 20 kW power conversion module (PCM) prototype. The fabricated PCM module was used to demonstrate the proposed overall electrical design approach, high-frequency isolation, bi-directional power flow and soft-switching operation of the quasi-resonant topologies. Moreover, the 20-kW prototype allowed the verification of control methodologies as well as magnetic and thermal designs, and provides a test bed for future, higher power work.

High voltage, high power density bi-directional multi-level converters utilizing silicon and silicon carbide (SiC) switches

Monitoring the health of engine components in-situ and in real-time is critical for reducing life cycle costs of military aircraft, such as F-35. As aircraft complexity and performance requirements increase, inspection-based maintenance at pre-defined intervals becomes costly and insufficient. A more efficient approach is to integrate sensor systems, capable of withstanding harsh operating environments, to provide real-time diagnostics and support condition-based maintenance and failure prognostics.

High temperature telemetry systems for in situ monitoring of gas turbine engine components

This paper addresses the performance of SiC NPN Bipolar Junction Transistors (BJTs) at high and low temperature. A current gain of 50 at room temperature was obtained which decreases to 25 at 275 oC. A maximum current gain (β) of 111 has been reported at -86 oC. At low temperature (below -86 oC), the current gain drops rapidly because of carrier freezout effect. At room temperature, a minimum on-resistance of 7 mΩ-cm2 was obtained. This increases to 28 mΩ-cm2 at 275 oC. The on-resistance of BJTs is approximately unaffected by lowering the temperature down to -86 oC from room temperature. Below -86 oC, the on-resistance jumps up rapidly because of carrier freezeout. Electrical performance of BJTs have been fairly stable during stress measurement at high temperature (120 hours at 100 oC ) at a collector bias of 1000V (with open base) for devices with a breakdown voltage of 1200V.The devices have been stressed further at low (i.e., 6) and high gain (i.e., 15) at room temperature. Initial degradation within first hour of stress test has been reported and then degradation stabilizes out. Packaged devices were tested up to 550 oC and performed admirably well up to that temperature.

Marcelo Schupbach

Papers

High-Temperature Silicon-on-Insulator Gate Driver for SiC-FET Power Modules

High-temperature silicon carbide and silicon on insulator based integrated power modules

High voltage, high power density bi-directional multi-level converters utilizing silicon and silicon carbide (SiC) switches

High temperature telemetry systems for in situ monitoring of gas turbine engine components

Assessment of High and Low Temperature Performance of SiC BJTs