Bidirectional power converter, electric vehicle, and control method for bidirectional power converter

An electric vehicle, comprising:

• an inverter including a bidirectional power converter, the converter including a first terminal, a second terminal, a negative terminal, a main reactor, a plurality of sub-circuits, and a controller that sequentially controls the sub-circuits,
• the first terminal being connected to an input and output end of a first device that allows input and output of electric power,
• the second terminal being connected to an input and output end of a second device that allows input and output of electric power,
• the negative terminal being connected to a negative electrode of the second device,
• the main reactor having a first end connected to the first terminal,
• the plurality of sub-circuits being connected in parallel between a second end of the main reactor and the second terminal, each of the sub-circuits including an upper switching element an upper switching element connected to the second terminal, and a lower switching element connected between the upper switching element and the negative terminal, an upper diode in antiparallel connection with the upper switching element, a lower diode in antiparallel connection with the lower switching element, and a sub-reactor having one end connected to the second end of the main reactor and another end connected to a midpoint of a series connection between the upper switching element and the lower switching element,
• the controller being configured to turn on and turn off the lower switching element of each of the sub-circuits, and then, turn on and turn off the upper switching element of each of the sub-circuits, while a current is flowing from the first terminal toward the second terminal, and
• the controller being configured to turn on and turn off the upper switching element of each of the sub-circuits, and then, turn on and turn off the lower switching element of each of the sub-circuits, while the current is flowing from the second terminal toward the first terminal;
• a battery serving as the second device;
• and
• a traveling motor serving as the first device and including a coil, wherein:
• the second terminal is connected to a positive terminal of the battery, and the negative terminal is connected to a negative terminal of the battery;
• the coil functions as the main reactor;
• the upper switching element of the sub-circuit serves as an upper arm switching element of the inverter and is connected to the second terminal, and the lower switching element of the sub-circuit serves as a lower arm switching element of the inverter and is connected between the second terminal and the negative terminal;
• the sub-reactor is connected between the midpoint of the series connection between the upper switching element and the lower switching element and the coil;
• the sub-reactor includes a conductor connecting the midpoint of the series connection and the main reactor, and a first magnetic ring core and a second magnetic ring core surrounding the conductor;
• and
• a second magnetic saturation current value at which the second magnetic ring core reaches a magnetic saturation is smaller than a first magnetic saturation current value at which the first magnetic ring core reaches a magnetic saturation.

A method for controlling a bidirectional power converter,

• the bidirectional power converter including
• a first terminal connected to an input and output end of a first device that allows input and output of electric power,
• a second terminal connected to an input and output end of a second device that allows input and output of electric power,
• a negative terminal connected to a negative electrode of the second device,
• a main reactor having a first end connected to the first terminal,
• a plurality of sub-circuits connected in parallel between a second end of the main reactor and the second terminal, each of the sub-circuits including
• an upper switching element connected to the second terminal, and a lower switching element connected between the upper switching element and the negative terminal,
• an upper diode in antiparallel connection with the upper switching element,
• a lower diode in antiparallel connection with the lower switching element, and
• a sub-reactor having one end connected to the second end of the main reactor and another end connected to a midpoint of a series connection between the upper switching element and the lower switching element,
• wherein the sub-reactor includes a conductor connecting the midpoint of the series connection and the main reactor, and a first magnetic ring core and a second magnetic ring core surrounding the conductor;
• and
• wherein a second magnetic saturation current value at which the second magnetic ring core reaches a magnetic saturation is smaller than a first magnetic saturation current value at which the first magnetic ring core reaches a magnetic saturation
• the method comprising:
• sequentially controlling, by a controller, the sub-circuits such that the lower switching element is turned on and turned off and then the upper switching element is turned on and turned off in each of the sub-circuits, while a current is flowing from the first terminal toward the second terminal;
• and
• sequentially controlling, by the controller, the sub-circuits such that the upper switching element is turned on and turned off and then the lower switching element is turned on and turned off in each of the sub-circuits, while the current is flowing from the second terminal toward the first terminal.