A power supply system for isolating charging power prior to being supplied to a vehicle charging system within battery operated vehicle, which system comprises - an isolation transformer allowing electric isolation between a primary power source and the vehicle charging system, which transformer comprises ∘ a primary side, wherein one or more terminals of the primary side are electrically connectable to the primary power source and ∘ a secondary side, wherein one or more terminals of the secondary side are electrically connectable to the vehicle charging system, - an EVSE control device electrically connectable to the vehicle charging system, - a data communication line connected to the EVSE control device and connectable to the vehicle charging system, which data communication line allows, when connected to the vehicle charging system, ∘ transmission of control signals to the vehicle charging system, ∘ monitoring coupling between secondary side and the vehicle charging system and ∘ monitoring at least one parameter related to the charging status of the vehicle charging system during charging, characterized in that the isolation transformer is an AC-to-AC solid state transformer and further that the isolation transformer and the EVSE control device constitutes an integrated mobile unit, the AC-to-AC solid state transformer being a three-phase solid state transformer configured to allow one or more of the following power conversions: - converting a single-phase alternating voltage to a galvanic isolated three-phase alternating voltage, - converting a three-phase alternating voltage to a galvanic isolated single-phase alternating voltage and - converting a three-phase alternating voltage to a galvanic isolated three-phase alternating voltage. - an isolation transformer allowing electric isolation between a primary power source and the vehicle charging system, which transformer comprises ∘ a primary side, wherein one or more terminals of the primary side are electrically connectable to the primary power source and ∘ a secondary side, wherein one or more terminals of the secondary side are electrically connectable to the vehicle charging system, electric isolation ∘ a primary side, wherein one or more terminals of the primary side are electrically connectable to the primary power source and ∘ a secondary side, wherein one or more terminals of the secondary side are electrically connectable to the vehicle charging system, - an EVSE control device electrically connectable to the vehicle charging system, - a data communication line connected to the EVSE control device and connectable to the vehicle charging system, which data communication line allows, when connected to the vehicle charging system, ∘ transmission of control signals to the vehicle charging system, ∘ monitoring coupling between secondary side and the vehicle charging system and ∘ monitoring at least one parameter related to the charging status of the vehicle charging system during charging, ∘ transmission of control signals to the vehicle charging system, ∘ monitoring coupling between secondary side and the vehicle charging system and ∘ monitoring at least one parameter related to the charging status of the vehicle charging system during charging, - converting a single-phase alternating voltage to a galvanic isolated three-phase alternating voltage, - converting a three-phase alternating voltage to a galvanic isolated single-phase alternating voltage and - converting a three-phase alternating voltage to a galvanic isolated three-phase alternating voltage.