Preventing Space-Charge-Induced Breakdown in MVDC Systems by Electric Field Cancellation

In medium-voltage direct current (MVDC) systems, charge carriers inject into solid insulators, accumulate, and form space charge that distorts electric fields and reduces the effective thickness of dielectric materials. This study proposes an electric field canceling approach to mitigate space charge injection, accumulation, and space-charge-induced dielectric issues. We use electret films that generate an electric field that counters the system electric field at the metal-dielectric interfaces to prevent charge carriers from flowing into electrical insulators. For numerical analysis, a bipolar charge transport model is used to simulate space charge injection and accumulation behaviors in polyvinylidene fluoride (PVDF) without and with the incorporation of electret films at the interface. Subsequently, instantaneous and delayed breakdown experiments are conducted to validate the results of the numerical analyses. Both the results show that electret films hold the charge injection barrier high, thereby reducing space charge injection and increasing dielectric strength. The results of this work demonstrate that electret films can mitigate space charge accumulation and enhance the dielectric integrity of MVDC power systems.