A Three-phase MVAC to Multi-port LVDC Converter with High Frequency Isolation for Fast DC Charging Station for EVs

A DC fast charging station for electric vehicles (EV) comprising multiple high-power EV chargers consumes a significant amount of power in the range of 1MW from the AC side. Today a 50Hz transformer is used to step down Medium Voltage (MV) AC (11kV) to Low Voltage (LV) AC (400V), after which several AC-DC converters followed by isolated DC-DC converters are used to create isolated DC ports for charging EV batteries and to integrate local storage and solar PV. This solution has a large and expensive 50Hz transformer and multiple conversion stages, resulting in poor efficiency, power density, and high cost. This paper presents a novel MVAC to multi-port LVDC converter with high-frequency isolation. The proposed modulation strategy ensures bidirectional power flow at all ports and equal sharing of active power in all three MVAC phases, while unequal power is transferred between different LVDC ports. Power factor correction or reactive power support is also possible for the proposed configuration. The operation is verified using simulation tools along with experimental verification.