Battery charging for electric vehicle via a neutral of a polyphase motor with a current command determined by the neutral voltage

An electric vehicle comprising:

• a battery;
• an inverter comprising three arm circuits, wherein each of the three arm circuits comprises an upper switching element connected to a positive electrode of the battery and a lower switching element connected to a negative electrode of the battery, and the upper switching element and the lower switching element are connected in series;
• a motor comprising three coils, wherein in each of the three coils, one end thereof is connected to a neutral point and other end thereof is connected to a midpoint of corresponding one of the three arm circuits;
• a first terminal configured to connect to a positive electrode of an external power supply;
• a second terminal configured to connect to a negative electrode of the external power supply;
• a first wire connecting the first terminal to the neutral point;
• a second wire connecting the second terminal to the negative electrode of the battery,
• a first relay disposed on the first wire,
• a first voltage sensor configured to measure, between the first terminal and the first relay, a potential difference between the first wire and the second wire;
• a second voltage sensor configured to measure, between the first relay and the neutral point, a potential difference between the first wire and the second wire;
• and
• a controller configured to control the inverter to increase a voltage of power supplied from the external power supply and charge the battery,
• wherein
• the controller is configured to:
• calculate permissible power of the battery;
• calculate a first voltage value obtained by adding a first margin to a detected value by the first voltage sensor;
• calculate a second voltage value obtained by adding a second margin to a detected value by the second voltage sensor;
• and
• calculate a current command value to the external power supply based on the permissible power and a smaller value of the first voltage value and the second voltage value.