Effect of High-Frequency Square Wave Voltage on Space Charge Characteristics of Epoxy Insulation in Solid-State Transformers

In renewable energy power systems, high-frequency transformers must withstand complex electric fields, which can easily cause discharge or degradation of solid insulation, leading to premature failure of the insulation system. This article focuses on the influence of high-frequency square wave voltage on the space charge characteristics of epoxy resin used in solid-state transformers. The space charge accumulation and dissipation characteristics of epoxy resin were studied by combining high-voltage polarization and short-circuit discharge. The space charge accumulation and dissipation characteristics of epoxy resin were studied by combining high-voltage polarization and short-circuit discharge. The results indicate that the charge accumulation under AC electric field is significantly lower than that under DC. Under high-frequency electric fields, space charges mainly accumulate near the electrode/insulation contact interface, with only a small amount of space charge accumulation inside the dielectric. In addition, as the frequency of the electric field increases, the average charge density decreases. The dynamic characteristics of space charge near the interface under a high-frequency electric field and the influence of frequency on the average charge density were analyzed using the theories of charge mobility and effective carrier migration distance under an AC electric field. The research results are of great significance for the insulation failure of solid-state transformers and the insulation design of high-frequency magnetic components.