Power frequency single-phase AC traction power supply systems not only serve as the dominant power sources for high-speed and heavy-haul railways but also facilitate the rapid development of urban rail transit systems and suburban railways (Cao in Power supply system for electrified railways. China Railway Press, Beijing, 1983; Li and He in Analysis of traction power supply system. Southwest Jiaotong University Press, 2010; Li in J. China Railw. Soc. 32:119–124, 2010). According to the Statistical Bulletin (Statistical Bulletin 2023 of China State Railway Group Co., Ltd., http://www.china-railway.com.cn/xwzx/zhxw/202403/t20240315_134819.html , 2024), by the end of 2023, the length of operational railways in China reached 159,000 km, including 45,000 km of high-speed railways (HSR), with an electrification rate as high as 73.8%, ranking first in the world. The large-scale construction and operation of electrified railways necessitate higher reliability and safety in their traction power supply systems, guiding China’s future development in traction power supply technologies toward the objectives of “safety, high quality, and efficiency”.