Fault current limiters (FCLs) have high impedance during fault conditions. However, it is inevitable to introduce additional impedance to the system, which may increase power losses, cause overvoltage, and degrade system dynamic performance. A voltage-clamping type dc FCL (VC-FCL) with low power losses is proposed in this article. This topology has nearly no on -state loss. Under the demagnetization effect of the coupled inductor, this topology presents a very small inductance during normal operation, which is beneficial to the dynamic response of the system. Therefore, VC-FCL can be installed directly into the system without replacing the dc reactor. In addition, the number of power electronic devices and costs are reduced by using a metal oxide varistor (MOV) for voltage clamping. The parameter design of the coupled inductor and MOV is produced out to ensure both the current limiting capability and low power losses of VC-FCL. The simulation case study and experiment test are implemented to further verify the good performance of the proposed topology.

This study targets insulation challenges in high-frequency power transformers (HFPTs), which are an integral part of the high-voltage, high-capacity isolated DC/DC converter under development for offshore renewable energy systems. We propose a nano-silicon carbide (SiC)-doped polyimide (PI) winding insulation strategy to enhance discharge resistance and thermal stability under high-frequency electric stress. Experimental results show that 10 wt% SiC doping significantly improves insulation performance, extending failure time from 17 to 50 min and reducing maximum discharge amplitude by 76%, owing to enhanced charge trapping and interfacial polarization suppression. Surface and volume resistivity measurements further confirmed the improvement; at 120 °C, the 10 wt% SiC composite maintained high surface resistivity 3.30 × 10¹⁴ Ω and volume resistivity 1.41 × 10¹⁵ Ω·cm, significantly outperforming pure PI. In contrast, 20 wt% SiC, though still resistive, showed reduced stability due to agglomeration and interfacial defects, with a surface resistivity of 2.07 × 10¹⁴ Ω and degraded dielectric performance. Dielectric analysis revealed that 10 wt% SiC suppressed dielectric constant and loss across the frequency range, while 20 wt% SiC exhibited increased values at high frequency. These results highlight 10 wt% SiC as an optimal formulation for HFPT winding insulation.

Since thyristors have better performance than fully controllable devices in terms of on-state resistance and cost, designing thyristor-based solid-state circuit breakers (TSCBs) to protect dc microgrids has become gradually popular. In this article, a new bidirectional TSCB with four significant advantages is proposed. First, it could reliably and actively interrupt both the operating and fault currents with simple operation sequences; thus, ensuring high reliability and controllability. Second, the currents at input and output sides of the proposed TSCB are rapidly suppressed immediately after it starts working, so the source or load sides will not be threatened by large surge currents. Third, both the auxiliary thyristors and capacitors in the proposed TSCB will automatically restore to their initial states after the current breaking processes, which ensures the proposed TSCB has a reclosing protection function. Fourth, it has a low conduction loss, and is therefore effective. All these advantages make the proposed TSCB one great candidate to protect dc microgrids. The detailed topology introduction, circuit modeling analyses, experimental results, and comparative study are presented.

This paper focuses on the Input-Independent Output-Series (IIOS) DC converters within fully DC aggregation systems, which enable independent submodule control and high voltage gain. DC aggregation systems experience output voltage imbalance among submodules due to offshore wind power fluctuations. The proposed isolated DC/DC converter topology incorporates power-balancing capacitors, leveraging intrinsic characteristics to achieve self-power balancing within the system. In addition, this paper proposes an innovative PFMT-PSMN hybrid control strategy that is well-suited for the proposed topology. Firstly, this study performs a time-domain analysis of the intrinsically power-balanced DC series-connected aggregation topology and elucidates the corresponding power-balancing principle. Secondly, based on soft-switching boundary conditions, a hybrid control strategy, PFMT-PSMN, adjusts phase-shift duty cycles to maintain soft-switching conditions while minimizing the system operating frequency. Finally, MATLAB/Simulink simulations validate the power-balancing capability of the intrinsically balanced DC series-connected aggregation system and the effectiveness of the proposed PFMT-PSMN control strategy.