In order to promote the revolution of energy production and consumption, and build a low-carbon, clean, safe and efficient energy system, a new power system with wind power generation, photovoltaic power generation and other new energy sources will be established vigorously in the world (Buttay in Mater. Sci. Eng: B 176:283–288, 2011). The high voltage direct current (HVDC) technology has rapidly developed due to its advantages of high power and long-distance transmission, which could efficiently deliver electricity generated from renewable energy sources to major load centers (Xiao et al. in IEEE Trans. Dielect Elect. Insul. 31:666–673, 2024). In equipment such as ultra-HVDC transmission valve hall and pulse energy storage system, metallized film capacitors assume important roles such as voltage support and energy conversion, whose safety and reliability mainly depend on dielectric insulation performance (Xiao et al. in IEEE Trans. Dielect Elect. Insul. 31:625–632, 2024). However, with the voltage level and capacity of new energy power equipment continuously improving, the deterioration of dielectric performance will occur during actual operation, which seriously threatens the safe and stable operation of the system (Xiao et al. in J. Phys. D: Appl. Phys. 57:5501–5509, 2024). Therefore, the working environment characteristics and structure of HVDC capacitors need to be explored to further improve its dielectric performance has received widespread attention from researchers.