Emerging medium-voltage integrated switching power modules for electrified transportation require highly isolated and compact auxiliary power supplies to drive wide-bandgap (WBG) devices in series-stacked architectures. Conventional transformer-based solutions struggle to balance highvoltage isolation requirements with compact packaging. This paper proposes a high-voltage insulated MHz wireless power transfer (WPT) system utilizing a Series-Series (S-S) compensated topology and a compact GaN-based inverter (8.52 W/cm2) to power gate drivers across reinforced insulation gaps. Finite Element Analysis (FEA) validates the insulation design: under a worst-case 23.8 kV accumulated stress, the peak electric field is limited to 0.5 kV/mm across a 40-mm primary baseline gap. To demonstrate system scalability and robustness for practical deployments requiring enhanced thermal and mechanical clearances, extended 80-mm gap prototypes were also evaluated. Experimental results show that the prototype achieves a peak efficiency of 90% at a 40-mm air gap and delivers up to 200 W of power with the optimized 80-mm gap coil design, proving its viability as a safe and robust auxiliary power solution for medium-voltage power modules.

Soft start-up in Dual-Active-Bridge (DAB) converters is a significant challenge due to the need to mitigate initial inrush currents. This challenge is even more pronounced in the Stacked Half-Bridge Full-Bridge (SHB-FB) converter incorporating an additional blocking capacitor and is a derivative of the conventional DAB converter. This paper initially assesses the start-up issues introduced by the dc blocking capacitor in the SHB-FB converter, which has received limited attention in existing literature. Then, a multistage soft start-up technique for the SHB-FB converter is proposed, considering the precharging process of the dc blocking capacitor. The technique is first validated through simulations and further experimentally verified with a Gallium Nitride (GaN)-based SHB-FB converter. The start-up challenges arising from the blocking capacitor are addressed, and experimental results show a 74% decrease in the initial inrush current compared with the hard start-up condition.

10 kV silicon carbide (SiC) MOSFETs have been receiving increasing research attention in medium voltage (MV) applications. Compared with silicon (Si) IGBT counterparts, 10 kV SiC MOSFETs exhibit shorter short-circuit withstand time (SCWT), which requires fast and reliable short-circuit protection (SCP) circuits. The di/dt-based SCP circuit is a promising solution because of its fast response and simple implementation without additional current sensors. However, a major limitation of the di/dt-based method is its inability to detect the dc component of the current, resulting in prolonged detection time during a fault-under-load (FUL) event. This paper proposes a novel di/dt-based SCP circuit with decoupled SCP thresholds for hard-switching-fault (HSF) and FUL of 10 kV SiC MOSFETs. The proposed circuit differentiates HSF and FUL states by monitoring the gate voltage and automatically adjusts the SCP threshold voltage for FUL, thereby accelerating short-circuit (SC) detection for FUL events. In addition, a simple constant-current soft-turn-off (STO) circuit is proposed to minimize the SC turn-off overvoltage. Experimental results with a 10 kV SiC MOSFET module verified the effectiveness of the proposed circuits.

Enabled by the fast switching capability of emerging 10 kV SiC MOSFETs, medium voltage (MV) power converters can achieve significantly reduced power loss. However, high dv/dt of 10 kV SiC MOSFETs also poses challenges for MV converter design. This letter proposes a simple method to reduce turn-on switching loss of 10 kV SiC MOSFET without increasing dv/dt. The proposed circuit employs a widely used desat short-circuit protection circuit to determine the dv/dt stage of the turn-on switching transient and adjust the gate resistance to accelerate current rise period, while maintaining voltage fall period unchanged. The proposed circuit can achieve switching loss reduction under various dc voltages and load currents similar to a closed-loop active gate driver, but the circuit required is quite simple. Experimental results with a 10 kV SiC MOSFET are demonstrated to verify the effectiveness of the proposed circuit.

Crosstalk in voltage source converters (VSCs) occurs when the fast-switching transition of one device induces unwanted gate or drain voltage transients in its complementary device, causing unintended turn-on or turn-off. A similar effect can also exist in solid-state circuit breakers (SSCBs) even without a phase-leg structure, because the high dv/dt produced by the transient voltage suppression (TVS) diode during fault interruption can be coupled into the main switch gate loop and create a negative gate-voltage undershoot. This work analyzes the crosstalk mechanism in TVS-diode-based SSCBs by identifying the dominant parasitic coupling paths and explaining the reason why only the negative gate-voltage transient is critical. Two mitigation methods suitable for SSCBs, i.e. Zener-diode clamping and external drain-source capacitance, are introduced and experimentally verified. Tests on a 1.7 kV, 100 A prototype show that both methods can suppress the gate-voltage undershoot well. These findings provide practical guidance for improving the robustness and reliability of fast SSCBs using SiC MOSFETs with TVS diode clamping.

High-power transient voltage suppression (TVS) diodes serve as the primary energy-absorbing elements in solid-state circuit breakers (SSCBs), providing rapid clamping of overvoltages that threaten main interrupting devices. This article presents a coaxial packaging solution for stacked TVS diodes, which achieves a dramatic reduction in commutation loop inductance from 95to 3.8 nH, resulting in an approximately 96% reduction. Experimental validation, which demonstrates a substantial decrease in turn-off overvoltage from 950 V to 300 V, shows an approximate 68% reduction. A derived modular design is further proposed to achieve higher voltage ratings, enabling scalable deployment across different SSCB applications. The package performance is evaluated through finite-element analysis of inductance and electric field distribution and experimentally confirmed in a 1.7 kV/100 A SSCB. Results verify that the proposed coaxial package effectively mitigates loop inductance and overvoltage, enhancing both reliability and operational safety of high-power SSCBs.

This letter proposes a novel indirect power detection based short-circuit protection (SCP) method for gallium nitride high-electron-mobility transistors (GaN HEMTs). The proposed method requires sensing only v(ds) of a GaN HEMT, similar to the widely used desaturation protection method. However, unlike desaturation protection, the proposed method directly monitors v(ds) after a predefined delay without a diode, enabling faster short-circuit detection and improved noise immunity. Experimental results show that the short-circuit detection time is significantly shorter than that of the desaturation protection. In addition, the proposed method is evaluated over a wide temperature range, from room temperature to cryogenic temperatures, verifying its effectiveness for GaN HEMTs in cryogenic applications.

Emerging 10 kV silicon carbide (SiC) mosfet based medium voltage (MV) converters have attracted increasing research interest due to their significantly improved performance compared with silicon (Si) IGBT based converters. The success of such MV converter design requires an accurate model of 10 kV SiC mosfets, which is proposed in this article. The impact of high voltage on the transconductance and the dynamic gate charge characteristics of the 10 kV SiC mosfet is first characterized. Based on these results, an improved switching model considering high voltage impact is proposed and experimentally verified. The developed model is then applied to aid the design of a five-level MV flying capacitor converter (FCC). A low-cost decoupling capacitor solution for FCC switching cell is proposed. Challenges posed by high switching speed are examined using the developed model, with a gate resistances selection strategy proposed. Finally, a prototype of the 10 kV SiC device based MV 5L-FCC phase-leg is developed. Its reliable operation under high voltage (e.g., 23 kV) and very fast switching speed (e.g., >100 V/ns) is demonstrated, achieving an efficiency of 99.2% at full load.

Paralleling silicon carbide (SiC) MOSFETs is an effective approach to increase the power capacity of medium voltage power electronics converters. However, fast switching transients can excite differential-mode (DM) instability, leading to oscillatory current imbalance among paralleled devices. This paper investigates the underlying mechanism and develops a dynamic model that captures the coupled interaction between the power loop and the gate loop, and further contrasts the DM instability with single-switch self-sustained oscillation. A parametric study is conducted to evaluate stability sensitivities. Based on these insights, a stabilization method is proposed to suppress oscillations while preserving fast switching, thereby imposing minimal penalty on switching loss. Experimental validation is performed on a 1.7 kV/625 A solid-state circuit breaker prototype with six parallel-connected 3.3 kV SiC MOSFETs, demonstrating effective suppression of DM oscillation with negligible impact on switching loss.

Emerging medium-voltage Solid-State Circuit Breakers (SSCBs) utilizing series-connected Silicon Carbide (SiC) devices necessitate efficient, reliable isolated gate driver power supplies. In modular multi-layer stacks, upper submodules experience extreme floating potentials, making conventional transformers unsuitable due to insulation bulk and common-mode noise susceptibility. This paper presents a compact High-Voltage Insulated Gate Driver Supply using a 1 MHz Constant Voltage (CV) LCC-S Wireless Power Transfer (WPT) system. To mitigate high-frequency switching losses, a novel capacitor-detuning strategy is proposed. This method achieves Zero-Voltage Switching (ZVS) by slightly reducing the primary-series capacitance to shape an inductive input impedance, eliminating additional passive components while strictly preserving load-independent CV characteristics. The experimental detuning ratio (7.3%) aligns closely with the simulation design (8.4%), demonstrating the high precision of the proposed analytical model. A prototype with a 50-mm isolation gap was validated to withstand the 23.8 kV worst-case stress of a 14-layer SSCB stack. Operating at 1 MHz, it delivers 209.7 W with a peak efficiency of 81.1% and a surface power density of 3.28 W/cm2, validating its potential as a superior alternative to traditional magnetic isolation for next-generation medium-voltage protection equipment.

This letter proposes a simple and novel gate driver circuit for turn-on overvoltage suppression of emerging 10 kV silicon carbide (SiC) metal-oxide-semiconductor field-effect transistors (MOSFETs). The proposed circuit introduces a predefined delay to temporarily reduce the gate voltage only during the dv/dt stage of the turn-on switching transient, thereby suppressing the turn-on voltage overshoot. The implementation is simple, requiring only a few signal-level components. Experimental results obtained with a 10 kV SiC MOSFET module verify the effectiveness of the proposed circuit.

A four-wire modular multilevel converter (MMC) with the split dc-link capacitor topology is a promising solution for a power conditioning system (PCS) of an asynchronous microgrid (ASMG). In an ASMG, the PCS is applied to connect two distribution-level systems with a transformerless structure, which has numerous challenges in the design and control of the MMC. However, in the existing literature, MMCs have been mainly applied in transmission systems with isolation transformers or serve as static compensators in distribution systems. The design and control methods of MMCs for these applications cannot be directly applied to an ASMG. Therefore, in this article, considering the impacts of the unbalanced load, transformerless structure, and different operation modes on the MMC-based PCS, the corresponding control and hardware design are conducted. The proposed MMC-based PCS solution can limit the microgrid (MG) voltage unbalance caused by the load unbalance, eliminate the harmonic zero-sequence current impacts on the main grid, and compensate for the unbalanced load current of local sources in the M. Moreover, a medium voltage testing setup is developed to verify the analysis and demonstrate the proposed control algorithms on a 10 kV SiC mosfet-based MMC at 13.8 kV ac voltage.

Future electrified aircraft propulsion (EAP) requires solid-state circuit breaker (SSCB) to be: 1) extremely light, efficient, fast and reliable; 2) suitable for both longer-term higher voltage (>10 kV dc) or shorter-term lower voltage (1 to 2 kV dc) systems; 3) suitable for cryogenic cooling enabled by liquified natural gas or liquid hydrogen fuel; and 4) highly flexible, intelligent and easy for protection coordination. This article summarizes the research effort led by the University of Tennessee team of applying gallium nitride (GaN) devices to a cryogenically-cooled SSCB for EAP applications. With the careful device selection, characterization, packaging and system-level integration and control, the developed SSCB reached an extremely high efficiency ( $>99.96$ % in a 40kft altitude chamber with liquid nitrogen cooling), high density (>336 kW/kg for a 750V/100A rating per module), high scalability (able to be configured in the range of 1kV to 10kV and 100A to 1000A), and intelligent and coordinated fault protections, e.g., $10\times $ fault current interruption and i2t protection, polarity-sensitive and voltage-dependent fault detection, and current limiting functions.

The nodal admittance matrix (NAM)-based approach is well-suited for small-signal stability analysis of large-scale power electronics-based power systems (PEPSs), as it preserves the system structure through its admittance matrix. Previous studies have explored partitioning such systems into subareas and interconnections to reduce computational burden; however, they lacked a formal algorithmic procedure for determining feasible partitions. While several grid partitioning methods, such as those based on graph theory or machine learning, exist in the literature, they cannot be directly applied to NAM-based analysis due to differing objectives and constraints. This paper addresses this gap by presenting a systematic, step-by-step procedure for applying a spectral partitioning algorithm that yields a division of the system into subareas suitable for NAM-based analysis. The computational complexity of the proposed method is also derived to demonstrate its efficiency and justify the practicality of the resulting subarea decomposition. The performance of the partitioning method is evaluated by applying the spectral clustering-derived subareas and interconnections to the NAM-based partitioning approach on a 140-bus system. Computational times for the full-system and partitioned NAM analyses are compared using MATLAB. Additionally, PSCAD simulations of the complete system and partitioned subareas are carried out to verify the effectiveness of the proposed method.

Due to multiple operation modes and corresponding mode transitions of microgrids (MGs), the MG grounding design is challenging. An MG may lose its grounding provided by the main distribution grid when it transitions to the islanded operation, resulting in potential hazards to both equipment and personnel. Existing transformer-based grounding schemes are bulky and have low control capability, which leads to poor transition performances and may affect the operation and protection of the whole distribution grid in the grid-connected mode. Power inverters have been applied as interfaces of distributed energy resources (DERs), which can potentially serve as groundings for future MGs. In this article, a novel DER inverter-based MG grounding scheme is proposed to realize flexible grounding in MGs. The detailed grounding structure and control methods are discussed. The proposed grounding scheme is verified on a realistic MG model through simulation. The proposed control strategies are demonstrated on a converter-based hardware testbed.

As the enabler of the direct current (DC) power distribution system, DC solid-state circuit breaker (DC-SSCB) has been extensively studied at the breaker-level (e.g., topology, energy absorption circuit, gate driver, and control) with limited system-level considerations, which is also crucial. This paper provides an all-in-one solution with integrated circuitries as the fault detector, actuator for semiconductor’s operating status regulation, and coordinated control to seamlessly transition from one mode to another (e.g., normal mode, precaution mode, i 2 t mode, and interruption mode). This allows the developed SSCB to limit system fault current not exceeding short-circuit current rating (SCCR) and take different responses under different fault cases. First, two improved fault detection circuits are introduced to better serve the SSCB application. Second, four operation modes are proposed for SSCB to realize system-friendly functions. Third, by leveraging four different operation modes, a control strategy is demonstrated to take different actions based on different fault cases. Finally, the feasibility and the effectiveness of the proposed system-friendly 200V/10A SSCB is validated with experimental results.

This paper presents the design and development of a megawatt (MW) level modular multilevel converter (MMC) based reconfigurable load emulator with wide range of operation voltage and frequency. Through the modification of MMC’s internal configuration with different numbers of submodules (SMs) connected in series and phase legs connected in parallel, the system adapts to various testing requirements, supporting up to 13.8kV in ac voltage and fundamental frequency reaching 3kHz, enhancing its versatility for evaluating power electronics converters. Meanwhile, a distributed control system is designed and implemented that is composed of one central controller, six arm controllers, and local controllers located in SMs. Moreover, a ramping PWM precharging method is utilized that can simultaneously precharge all the SMs using PWM with ramping duty cycle scheme to deal with the imbalanced impedance issue among different SMs caused by self-powered SM auxiliary power supply (APS). Finally, preliminary experimental results are presented to demonstrate the performance of the proposed reconfigurable load emulator.

A microgrid (MG) may lose its grounding provided by the main distribution grid in islanded mode, which could cause equipment insulation damage, hazards to personnel, and protection malfunction. Existing MG grounding schemes include the grounding transformer-based scheme and distributed energy resource (DER) transformer-based scheme. However, the grounding transformer-based scheme will increase MG’s cost, and the DER transformer approach will affect the main grid in the grid-connected mode. Moreover, future MGs may have multiple source locations. In each source location, the source and critical load can potentially operate as a sub-MG, requiring a grounding when it stands alone. In this scenario, the drawbacks of existing grounding schemes will be further magnified. In this paper, a novel controllable DER transformer-based grounding scheme is proposed, where a controllable switch is added to the neutral wire of the transformer. The proposed scheme can disable grounding capability in the grid-connected mode and enable it in the islanded mode by changing the transformer connection. The proposed approach can avoid impacts on the main distribution grid and eliminate the need for additional transformers. The design methodology of the proposed grounding scheme is provided. Simulation verification is conducted on a realistic MG model and experimental verification is conducted.

To dissipate heat effectively, a sufficient cooling system is required for a five-level MMC (Modular Multilevel Converter) based on 10 kV, 100 A power modules. However, achieving efficient heat dissipation necessitates a large cooling system, which in turn reduces the overall power density of the converter. Additionally, ensuring proper insulation between the high voltage switching devices and cooling components poses another challenge. This paper addresses these issues by presenting a detailed numerical design procedure for liquid cooling and selecting appropriate coolant with high dielectric strength. Air cooling with specific clearance and creepage distances is also presented. These two types of cooling methods are compared in terms of thermal performance, size, cost and installation effort. The effectiveness of the design is validated through experimental measurements.