Wide-bandgap Switching Devices Research Articles

A new DC-AC Interconnected Cascaded converter (ICC) with sinusoidal output voltage over a wide frequency range

In this paper a new dc to ac Interconnected Cascaded Converter (ICC) is presented. The proposed ICC consists of several modular submodules of two switches and an inductor interconnecting two capacitors. Each submodule is controlled to keep the voltage on each capacitor as a slice of a sinewave. The output voltage of the converter, according to KVL, includes the sum of the voltages on the capacitor that represents a full pure sinewave. The sinusoidal output of the converter can be varied over a wider range. The proposed converter has the following advantages: sinusoidal output voltage with v/f control; absence of dv/dt related issues; compact size/weight/volume due to the use of wide band gap switching devices. The converter is modular in construction, employs high frequency L-C components and semiconductor switches can be stacked for voltage sharing. The proposed converter is a promising candidate for multiple applications such as high performance ac motor drives, microinverters and uninterruptible power supplies, carbon neutral logistics and electric vehicles. The paper details the operating modes, control aspects along with an illustrative design example for a three and eleven module converter. Experimental results on a laboratory prototype converter employing 600 V GaN devices are discussed.

Review on Driving Circuits for Wide-Bandgap Semiconductor Switching Devices for Mid- to High-Power Applications.

Wide-bandgap (WBG) material-based switching devices such as gallium nitride (GaN) high electron mobility transistors (HEMTs) and silicon carbide (SiC) metal-oxide-semiconductor field-effect transistors (MOSFETs) are considered very promising candidates for replacing conventional silicon (Si) MOSFETs for various advanced power conversion applications, mainly because of their capabilities of higher switching frequencies with less switching and conduction losses. However, to make the most of their advantages, it is crucial to understand the intrinsic differences between WBG- and Si-based switching devices and investigate effective means to safely, efficiently, and reliably utilize the WBG devices. This paper aims to provide engineers in the power engineering field a comprehensive understanding of WBG switching devices’ driving requirements, especially for mid- to high-power applications. First, the characteristics and operating principles of WBG switching devices and their commercial products within specific voltage ranges are explored. Next, considerations regarding the design of driving circuits for WBG switching devices are addressed, and commercial drivers designed for WBG switching devices are explored. Lastly, a review on typical papers concerning driving technologies for WBG switching devices in mid- to high-power applications is presented.

A Novel Analysis, Design, and Optimal Methodology of High-Frequency Oscillation for Dual Active Bridge Converters With WBG Switching Devices and Nanocrystalline Transformer Cores

With the fast development of advanced switches and magnetic cores, high-frequency oscillation (HFO) caused by high dv/dt of fast switching devices and stray capacitances of transformer in dual active bridge (DAB) presents a significantly challenge. In this article, a comprehensive analysis, design, and optimal methodology of HFO for DAB with wideband gap (WBG) switching devices and nanocrystalline transformer cores is proposed. The stray parameters equivalent circuit of DAB is built and the key influencing factors to mitigated the HFO are identified by establishing a time-domain analytical model. Based on the theoretical analysis, this article points out for the first time that the traditional method of decreasing the stray capacitance of the transformer to eliminate HFO is not suitable for high dv/dt occasions when using WBG switching devices. Correspondingly, a novel elimination method of HFO by equating the voltage changing time of dv/dt to the oscillation cycle is proposed, through which the minimum voltage spike amplitude (VSA) of HFO can be achieved mathematically. A 6.6-kW DAB prototype with three different transformers is developed and an approximately 95% reduction of the VSA can be achieved when the proposed HFO elimination method is adopted, which verifies the effectiveness of the proposed method.

Analysis and Design of a Charge-Pump-Based Resonant AC–DC Converter With Inherent PFC Capability

This article presents the analysis and design of a resonant power factor correction (PFC) rectifier for the first stage in single-phase front-end offline converters targeting low-power applications (up to 100 W). With the addition of a charge-pump circuit comprised of a capacitor and a diode to a class-DE resonant converter, PFC functionality is achieved inherently. The operation is based on soft switching, allowing for increased switching frequencies with reduced switching losses. A 1-MHz prototype employing wide bandgap switching devices is built and tested to validate the analysis and proposed design method. The prototype achieves up to 50 W of output power with a power factor of 0.99, a total harmonic distortion of 8.6%, and an efficiency of up to 88%; with harmonic magnitudes well-within the IEC 61000-3-2 standard class-C device limits, making it suitable for use as the rectifier stage in light-emitting diode (LED) drivers. Despite the additional circuit stresses from the charge-pump operation, the proposed converter offers simplicity and low component overhead, with the potential for higher frequency operation toward higher power densities.

Multi-Domain Design Optimization of dv/dt Filter for SiC-Based Three-Phase Inverters in High-Frequency Motor-Drive Applications

High slew rate of the line voltage $(\boldsymbol {dv}/\boldsymbol {dt})$ has been a concern for power inverters based on the emerging wide bandgap switching devices, such as silicon carbide (SiC) mosfets . Particularly, for SiC-based power inverters feeding electric machines interconnected with long cables, there could be more severe insulation stress on the stator windings in electric machines, due to the higher d v /d t output from the SiC inverters. Compared to the conventional lower voltage electric transportation applications (e.g., 270 V dc), higher dc bus voltage of 500–600 V can dramatically reduce cable weight and systematic copper losses, hence improve the power density and efficiency of power converters. However, high dc bus voltage further increases the $\boldsymbol {dv}/\boldsymbol {dt}$ level in the converter ac line voltages. Driven by the necessity of developing SiC inverters with 500 V dc bus in electric transportation applications while attenuating the $\boldsymbol {dv}/\boldsymbol {dt}$ stress to a low level, this paper presents a multi-domain design approach for d v /d t filters that comprehensively considers the constraints in electrical, magnetic, and thermal domains. Experimental results based on a 75 kW SiC inverter are provided to verify the efficacy of this design approach.

Wide-Bandgap Solid-State Circuit Breakers for DC Power Systems: Device and Circuit Considerations

DC circuit protection applications provide a unique market opportunity for wide-bandgap (WBG) semiconductors, which are outside the conventional focus on power electronic converters. This paper presents an overview of emerging dc power systems, the needs for dc solid-state circuit breakers (SSCBs), and the benefits and advantages of various WBG SSCB concepts. Furthermore, a new class of self-powered SSCBs based on SiC or GaN normally-ON switching devices is proposed in this paper. One implementation of the SSCB concept based on a 1200 V SiC JFET experimentally demonstrated turn-off of a fault current of 125 A at a dc voltage of 400 V within $1~\mu $ s without requiring any external power supply. The SSCB detects short-circuit faults by sensing its drain–source voltage rise and draws power from the fault condition to turn off the SiC JFET. Various implementations of the SSCB concept for unipolar and bipolar capability using both SiC and GaN are also discussed from both device and circuit perspectives. It is concluded that very low ON-resistance normally-ON WBG switching devices are excellent candidates for the emerging SSCB applications.