多物理场耦合对金属化膜自愈行为的影响机制OA

The converter valve is the core component of China's flexible direct current transmission and new energy power generation systems,and the dry-type capacitor is referred to as the"heart"of the converter valve.Its performance directly affects the stability and safety of AC-DC conversion.Currently,the capacitors widely used in China mainly include oil-immersed foil-type capacitors and dry-type metallized film capacitors,metallized polypropylene film(MPPF).Compared with oil-immersed foil-type capacitors,metallized film capacitors have unique"self-healing properties",small volume,and no risk of oil leakage,and have been widely applied in the new energy industry.Currently,biaxially oriented polypropylene film(BOPP)is mainly used as the base material for metallized films in industry.However,the mechanism in self-healing dynamic process is still not clear,especially under multiple physical fields which leads to a slow improvement in industrial manufacturing. This paper independently built a multi-physics field coupling test platform for the self-healing property of metallized films,systematically studying the self-healing property and its influencing mechanism under the combined action of electric,thermal,and mechanical fields.The research shows that during the self-healing process,the arc will burn the surface of the polypropylene dielectric layer,forming a large amount of carbon element accumulation in the self-healing evaporation zone.The relationship between temperature and self-healing property shows a"bell-shaped"curve,the knee point is 65℃.below 65℃,the temperature will intensify the damage effect of the self-healing property on the film,but as the temperature continues to rise,the damage caused by self-healing to the film will decrease.At the same time,the high temperature significantly reduces the adhesion between the metal electrode layer and the polypropylene dielectric layer,and the pressure effect will destroy the aggregated structure of the polypropylene dielectric layer,resulting in a decrease in crystallinity. Moreover,this paper constructed a multi-physics field coupled plasma simulation model for the self-healing behavior,theoretically studying the influence mechanism of electric,thermal,and mechanical fields on the dynamic behavior of self-healing.The model calculation results show that when the environmental temperature is below 65℃,the promoting effect of temperature on the self-healing process dominates,causing the self-healing area and self-healing quantity to increase with the increase in temperature.However,when the temperature exceeds 65℃,the promoting effect of temperature on plasma slows down,and at the same time,due to the different thermal expansion coefficients of the metal electrode layer and the polypropylene dielectric layer,the interface bonding condition becomes the main influencing factor.As the adhesion of the metal electrode layer decreases,the plasma energy is difficult to diffuse radially,resulting in a reduction in the single-point self-healing area.Furthermore,the further coupling of pressure will reduce the migration rate of the plasma,causing its movement speed to slow down,and the greater the pressure,the slower the plasma moves,thereby further reducing the single-point self-healing area.The research results of this paper can provide theoretical support for optimizing the manufacturing process of polypropylene metallized films and offer important references for improving the performance and reliability of dry-type film capacitors in high-field environments.