Modular Wireless Power Transfer Systems Based on Relay Coils With Self-Voltage Balancing Capabilities for Charging Stations

In charging stations, connecting the charging systems to an medium-voltage (MV) dc bus in series has become an attractive solution, which can reduce the power loss and number of devices. However, this kind of topology will face the challenge of voltage imbalance. This letter proposes a modular arrangement of wireless power transfer (WPT) systems with self-voltage balancing for charging stations. The dc voltages of the inverters are connected in series to the MV dc bus. The input voltages of the charging ports can be balanced through the proposed simple voltage balancing coils. Relay coils are added to each WPT system. They are connected in series to pick up power from the transmitting coils and then deliver to each receiving coil. In this way, the power of each inverter can be balanced whenever in loading or unloading conditions. Constant-voltage output can be achieved at each charging port. An experimental protype is built to verify the effectiveness of the proposed system.