Battery self-heating device and method, and vehicle

A battery self-heating device, comprising a bridge arm converter, an energy storage element, an inductor and a controller,

• a first bus terminal of the bridge arm converter being connected to a positive electrode of a first power battery, and a second bus terminal of the bridge arm converter being connected to a negative electrode of a second power battery;
• a first end of the inductor being connected to a midpoint of the bridge arm converter, and a second end of the inductor being connected to a negative electrode of the first power battery and a positive electrode of the second power battery;
• the energy storage element being connected in parallel between the positive electrode of the first power battery and the negative electrode of the second power battery, a first end of the energy storage element being connected to the first bus terminal of the bridge arm converter, and a second end of the energy storage element being connected to the second bus terminal of the bridge arm converter;
• and
• the controller being configured to control, in a preset state, connection and disconnection of the bridge arm converter to enable the first power battery and the second power battery to be respectively charged/discharged by the inductor, and to respectively form a freewheeling circuit with the energy storage element to realize continuous heating of the first power battery and the second power battery,
• wherein the controller is further configured to control, in the preset state, various elements in the device to be in the following four states cyclically:
• state one:
• the upper bridge arm of the bridge arm converter is connected, the lower bridge arm of the bridge arm converter is disconnected, the first power battery is discharged, the energy storage element is discharged, the second power battery is charged, and the inductor is charged, wherein the device comprises a discharge current and a freewheeling current, the discharge current flows out from the positive electrode of the first power battery, flows through the upper bridge arm of the bridge arm converter and the inductor and flows back to the negative electrode of the first power battery, and the first power battery discharges to the inductor;
• and the freewheeling current flows out from a positive electrode of the energy storage element, flows through the upper bridge arm of the bridge arm converter, the inductor, and the second power battery and flows back to a negative electrode of the energy storage element, and the second power battery is charged by the energy storage element;
• state two:
• the upper bridge arm of the bridge arm converter is disconnected, the lower bridge arm of the bridge arm converter is connected, the first power battery is discharged, the inductor is discharged, the second power battery is charged, and the energy storage element is charged, wherein the device comprises a charge current and a freewheeling current, the charge current flows from the inductor to the positive electrode of the second power battery, flows out from the negative electrode of the second power battery, flows through the lower bridge arm of the bridge arm converter and flows back to the inductor, and the second power battery is charged by the inductor;
• and the freewheeling current flows out from the positive electrode of the first power battery, flows through the energy storage element and flows back to the negative electrode of the second power battery, the first power battery is connected in series with the second power battery, and the first power battery and the second power battery discharge to the energy storage element together;
• state three:
• the upper bridge arm of the bridge arm converter is disconnected, the lower bridge arm of the bridge arm converter is connected, the first power battery is charged, the inductor is charged, the second power battery is discharged, and the energy storage element is discharged, wherein the device comprises a discharge current and a freewheeling current, the discharge current flows out from the positive electrode of the second power battery, flows through the inductor and the lower bridge arm of the bridge arm converter and flows back to the second power battery, and the second power battery discharges to the inductor;
• and the freewheeling current flows out from the positive electrode of the energy storage element, flows through the first power battery, the inductor, and the lower bridge arm of the bridge arm converter and flows back to the negative electrode of the energy storage element, and the first power battery is charged;
• and
• state four:
• the upper bridge arm of the bridge arm converter is connected, the lower bridge arm of the bridge arm converter is disconnected, the first power battery is charged, the energy storage element is charged, the second power battery is discharged, and the inductor is discharged, wherein the device comprises a charge current and a freewheeling current, the charge current flows out from the inductor, flows through the upper bridge arm of the bridge arm converter, flows to the positive electrode of the first power battery, flows out from the negative electrode of the first power battery and flows back to the inductor, and the first power battery is charged by the inductor;
• and the freewheeling current flows out from the positive electrode of the first power battery, flows through the energy storage element and flows back to the negative electrode of the second power battery, the first power battery is connected in series with the second power battery, and the first power battery and the second power battery discharge to the energy storage element together.

A battery self-heating method, comprising:

• controlling, in a preset state, connection and disconnection of a bridge arm converter to enable a first power battery and a second power battery to be respectively charged/discharged by an inductor, and to respectively form a freewheeling circuit by an energy storage element to realize continuous heating of the first power battery and the second power battery,
• wherein a first bus terminal of the bridge arm converter is connected to a positive electrode of the first power battery, and a second bus terminal of the bridge arm converter is connected to a negative electrode of the second power battery;
• a first end of the inductor is connected to a midpoint of the bridge arm converter, and a second end of the inductor is connected to a negative electrode of the first power battery and a positive electrode of the second power battery;
• and the energy storage element is connected in parallel between the positive electrode of the first power battery and the negative electrode of the second power battery, a first end of the energy storage element is connected to the first bus terminal of the bridge arm converter, and a second end of the energy storage element is connected to the second bus terminal of the bridge arm converter,
• wherein the connection and disconnection of the bridge arm converter in the preset state is controlled to have an oscillation current generated by each of the first power battery and the second power battery with the inductor, such that when the first power battery is discharged, the second power battery is charged, and when the second power battery is discharged, the first power battery is charged, keeping a total voltage of the first power battery and the second power battery relatively unchanged so as to reduce battery ripples.