Guest Editorial: Equipment technology of power transmission and distribution supporting the new-type power system

The new-type power system, with a strong, intelligent and flexible grid as its hub platform, is a key carrier for achieving the goals of carbon peak and carbon neutrality. Among them, AC/DC transmission and distribution equipment is the core for achieving power conversion and transmission. In order to adapt to the high proportion of new energy, large-scale energy storage, and diversified flexible load, and to promote the high-quality construction of the new-type power system, it is urgent to carry out research and development on flexible and intelligent new transmission and distribution equipment.

This Special Issue aims to foster academic exchanges and advance theoretical research in the areas related to the equipment technology of power transmission and distribution, in conjunction with the outstanding papers selected by the 20th IET International Conference on AC and DC Power Transmission. The call for the Special Issue comprises two sections: materials and devices of AC/DC power transmission and distribution systems, and equipment of AC/DC power transmission and distribution systems.

After undergoing a rigorous review by Guest Editors and journal, followed by a stringent external review process, five exceptional articles are ultimately published in this special issue.

Zhanqing Yu et al. from Tsinghua University propose a novel non-current insulation gate drive technology and develop the first current-source gate drivers for Integrated Gate Commutated Thyristor. The innovation represents an advancement towards chip-level integration, fundamentally enhancing gate-drive reliability, compactness and operational efficiency, thus marking a significant leap towards chip-level evolution of next-generation power electronics systems.

Rong Zeng et al. from Tsinghua University propose a hybrid commutation strategy that includes forced commutation control based on active turn-off and natural commutation control. Under this novel control strategy, the hybrid commutated converter (HCC) can completely eliminate the risk of cascading power outages caused by commutation failures inherent in traditional line-commutated converters, marking a significant milestone in equipment in HVDC transmission and promoting the evolution of DC converter from passive commutation to active commutation.

Sungmin Kim and Donguk Kim from Hanyang University propose a medium-voltage single-phase solid-state transformer (SST) tailored specifically for high-speed railway propulsion systems. Their design effectively interfaces a 25 kV AC supply with a 3 kV DC traction inverter. A novel soft-start control method is also introduced to mitigate transformer inrush currents. Experimental validation, including comprehensive thermal testing, further confirms the operational feasibility and practical reliability of the developed SST module, highlighting its promising application prospects in railway power systems.

Lu Qu et al. from Beijing Huairou Laboratory introduce a thermal balancing approach for enhancing the cooling performance of HCC valves. By addressing the persistent issue of uneven heat dissipation due to non-uniform flow distribution across valve layers, their work innovatively adjusts local flow resistances within valve cooling channels, and shifts the coolant distribution from uniform allocation to heat-driven targeted flow, significantly improving thermal uniformity and operational reliability in high-power converter valve applications.

Kaiqi Sun et al. from Shandong University propose an innovative converter station selection methodology for urban VSC-DC interties configured with both grid-following and grid-forming technologies. Their research introduces a comprehensive quantitative index system, providing the first systematic evaluation framework for assessing the influence of converter station, which supports strategic planning and optimised configuration of urban DC interties, substantially enhancing the stability and robustness of urban power systems.

As society advances and the demand for electricity grows, constructing an efficient and dependable power system has become especially critical. The AC/DC transmission and distribution system, being a fundamental element of the modern power system, holds a pivotal position. Consequently, it is imperative to intensify research and development efforts for AC/DC transmission and distribution equipment, to foster the establishment and evolution of innovative power systems, thereby facilitating economic growth and achieving sustainable energy use.