Effect of FAlN-PVA Inorganic-Organic Coating Structure on the Insulation Properties of BOPP Film

Dry-type DC film capacitors, as critical components of converter valves in flexible DC transmission systems, primarily utilize biaxially oriented polypropylene (BOPP) film as their internal dielectric medium. The insulation properties of BOPP are key factors ensuring the safe and reliable operation of these capacitors. However, the occurrence of breakdown within the capacitor and flashover in the edge blanking zone are the primary causes leading to reduced capacitor lifespan and even insulation failure. To address this, this paper develops an FAlN-PVA coating to enhance insulation performance. First, an inorganic-organic composite coating is fabricated using AlN and PVA, with the PVA coating designed to modulate the interfacial properties between AlN and the BOPP film, achieving a 4.01% increase in breakdown field strength compared to the BOPP film alone. Simultaneously, AlN is supplemented with fluorinated silane coupling agent liquid-phase grafted to introduce fluorinated groups with strong charge-regulating effects, further modulating the performance of the AlN-PVA composite coating. The breakdown field strength increases by 7.59% compared to BOPP film, further enhancing the interfacial properties of the BOPP film. Subsequently, macro-level testing and micro-level characterization are synergistically employed to analyze the influence of the characteristics and mechanisms of the composite coating's surface application on the insulating properties of BOPP film.