A 70-kV Isolated, 100-W Wireless Power Supply with Low Common-Mode Capacitance for Medium-Voltage Applications

Medium-voltage (MV) multilevel systems, such as solid-state transformers (SSTs) and medium-voltage direct current (MVDC) networks, commonly employ input-series output-parallel (ISOP) configurations to reduce voltage and current stresses on power devices. However, these cascaded converters operate at floating potential and require isolated power sources. This paper presents an MV isolated wireless power supply (WPS) system based on inductive power transfer (IPT) technology. Quantitative comparisons of three compensation topologies, each capable of providing load-independent output voltage, were conducted to determine an optimal resonant configuration. A novel MV-class insulation structure, combining silicone elastomer encapsulation, conductive paint coating, electric field edge fillets, and aluminum end plates to achieve 70 kV withstand capability and low 13.3 pF common-mode (CM) capacitance is proposed and validated. This integrated approach ensures reliable high-voltage isolation and electromagnetic interference (EMI) resilience in compact IPT systems. The prototype achieves a maximum efficiency of 83.08% and a power density of 0.84 W/cm³ at an output power of 100 W. Experimental high-voltage testing confirms system reliability through 70 kV over-voltage, 37 kV partial discharge, and CM capacitance measurements.