CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to and the benefit of Korean Patent Application No. 10-2019-0107408, filed Aug. 30, 2019, which is incorporated herein by reference in its entirety.

FIELD

The present disclosure relates to a system and method for increasing a temperature of a battery used in a motor driving system of a vehicle.

BACKGROUND

The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.

In general, an eco-friendly vehicle driven by electrical energy includes a battery for storing electrical energy, an inverter for converting the electrical energy stored in the battery into alternating current (AC) having a plurality of phases, and a motor for generating kinetic energy for rotation using the AC converted by the inverter.

Recently, a lithium ion battery has been mainly used for an eco-friendly vehicle. The lithium ion battery has excellent performance by virtue of excellent energy density, and charge and discharge cycle at room temperature. However, due to the properties of electrolyte included in the lithium ion battery, it is disadvantageous in terms of reduced capacity, increased resistance, and reduced efficiency at low temperatures. In particular, when the lithium ion battery is charged or overcharged at a low temperature, lithium ions are irregularly deposited on a surface of a negative electrode, thereby reducing the lifespan of the battery. Due to this issue, the lithium ion battery desires a temperature-increasing device for rapidly increasing the temperature thereof from a low-temperature state to a high-temperature state with high efficiency.

Conventionally, there is a method of additionally installing a heater (e.g., a positive temperature coefficient (PTC) heater) in a battery and directly heating the battery or heating and circulating coolant supplied to the battery. However, in a conventional battery temperature-increasing method, we have discovered that a separate heater needs to be additionally installed in the battery and the added separate heater in the battery increases the additional costs and volume of the battery.

As another conventional battery temperature-increasing method, research has been conducted into a method of generating heat in a battery in an electrical manner. In this method, the internal resistance of a battery is used to enable current to flow in the battery, and loss generated in proportion to the amount of flowing current is used as heat. This method has advantages in that current uniformly flows in the battery to uniformly generate heat in the battery, but we have discovered that this method needs to use a separate dedicated circuit for enabling current to flow in the battery, so that the volume and costs of the battery additionally increase and an additional management point is created with respect to the dedicated circuit for generating current for increasing a temperature of the battery and enabling the current to flow in the battery, thereby complicating the maintenance of a vehicle.

The above information disclosed in this Background section is only for enhancement of understanding of the background of the present disclosure, and therefore it may contain information that does not form the prior art that is already known to a person of ordinary skill in the art.

SUMMARY

The present disclosure provides a system for increasing a temperature of a battery used in a motor driving system. The system includes an inverter including a plurality of legs each including one pair of switching devices connected in series to each other between opposite ends of the battery and corresponding to a plurality of phases, respectively, a motor including a plurality of coils corresponding to the plurality of phases, respectively, one end of each of the plurality of coils being connected to a connection node between the pair of switching devices included in a corresponding leg and other ends of the coils being connected to each other, and a controller configured to select two phases of the plurality of phases, and to generate alternating current (AC) supplied to the battery by alternately controlling an on/off state of the pair of switching devices included in each of two legs in the inverter, corresponding to the two selected phases, at a preset switching frequency.

The controller may control the on/off state of a first pair of switching devices included in a first leg corresponding to one phase of the two selected phases to have a complementary relationship at the switching frequency and control the on/off state of a second pair of switching devices included in a second leg corresponding to a remaining phase of the two selected phases to have the complementary relationship at the switching frequency, and the controller may control the on/off state of one of the first pair of switching devices connected to a positive terminal of the battery in the first leg and the on/off state of one of the second pair of switching devices connected to the positive terminal of the battery in the second leg to have the complementary relationship.

The controller may turn off a third pair of switching devices included in a third leg corresponding to a phase other than the two selected phases.

The system may further include a rotor position sensor configured to detect a rotor angle of the motor, wherein the controller may select two phases of the plurality of phases based on the rotor angle.

The controller may select two phases for reducing a difference between the rotor angle and an angle of AC generated by control of the pair of switching devices included in each of the legs corresponding to two phases among the plurality of phases, and the angle of the AC is indicated on a dq rest frame.

In accordance with another aspect of the present disclosure, a system for increasing a temperature of a battery used in a motor driving system includes an inverter including an a-phase leg, a b-phase leg, and a c-phase leg each including one pair of switching devices connected in series to each other between opposite ends of the battery, a motor including an a-phase coil having one end connected to a connection node between a first pair of switching devices included in the a-phase leg, a b-phase coil having one end connected to a connection node between a second pair of switching devices included in the b-phase leg, and a c-phase coil having one end connected to a connection node between a third pair of switching devices included in the c-phase leg, another end of the a-phase coil, another end of the b-phase coil, and another end of the c-phase coil being connected to each other, and a controller configured to select two legs among the a-phase leg, the b-phase leg, and the c-phase leg, and to generate AC supplied to the battery by alternately controlling an on/off state of the pair of switching devices included in the selected legs at a preset switching frequency.

The controller may control the on/off state of one pair of switching devices included in one leg of the selected legs to have a complementary relationship at the switching frequency and controls the on/off state of one pair of switching devices included in a remaining leg of the selected legs to have a complementary relationship at the switching frequency, and the controller may control the on/off state of one of the pair of switching devices connected to a positive terminal of the battery in each of the two selected legs to have a complementary relationship.

The controller may turn off one pair of switching devices included in one leg that is not selected.

The system may further include a rotor position sensor configured to detect a rotor angle of the motor, wherein the controller may select two legs based on the rotor angle.

The controller may select two of the phase legs for reducing a difference between the rotor angle and an angle of AC generated by control of the first and second pair of switching devices included in each of the a-phase leg and the b-phase leg, AC generated by control of the second and third pair of switching devices included in each of the b-phase leg and the c-phase leg, and AC generated by control of the third and first pair of switching devices included in each of the c-phase leg and the a-phase leg, and the angle of the AC is indicated on a dq rest frame.

When the rotor angle is 0° to 60° and 180° to 240°, the controller may select the c-phase leg and the a-phase leg, may alternately control the on/off state of the third and first pair of switching devices included in each of the c-phase leg and the a-phase leg at the preset switching frequency, and may turn off the second pair of switching devices included in the b-phase leg to generate the AC.

When the rotor angle is 60° to 120° and 240° to 300°, the controller may select the b-phase leg and the c-phase leg, may alternately control the on/off state of the second and third pair of switching devices included in each of the b-phase leg and the c-phase leg at the preset switching frequency, and may turn off the first pair of switching devices included in the a-phase leg to generate the AC.

When the rotor angle is 120° to 180° and 300° to 360°, the controller may select the a-phase leg and the b-phase leg, may alternately control the on/off state of the first and second pair of switching devices included in each of the a-phase leg and the b-phase leg at the preset switching frequency, and may turn off the third pair of switching devices included in the c-phase leg to generate the AC.

In accordance with another aspect of the present disclosure, a method of increasing a temperature of a battery using the system above includes the steps of determining a section to which the rotor angle belongs, determining one of the legs maintained in an off state based on the section to which the rotor angle belongs, and generating the AC by alternately controlling an on/off state of the pair of switching devices included in two legs other than the leg maintained in the off state at the switching frequency.

The step of determining may be performed when the rotor angle is 0° to 60° and 180° to 240°. The step of determining may include the step of turning off the second pair of switching devices included in the b-phase leg, and the step of generating may include the step of generating the AC by alternately controlling the on/off state of the third and first pair of switching devices included in each of the c-phase leg and the a-phase leg at the preset switching frequency.

The step of generating may include the step of controlling the on/off state of the third pair of switching devices included in the c-phase leg to have a complementary relationship at the switching frequency, and controlling the on/off state of the first pair of switching devices included in the a-phase leg to have a complementary relationship at the switching frequency, and controlling the on/off state of one of the third pair of switching devices connected to the positive terminal of the battery in the c-phase leg and the on/off state of one of the first pair switching devices connected to the positive terminal of the battery in the a-phase leg to have a complementary relationship at the switching frequency.

The step of determining may be performed when the rotor angle is 60° to 120° and 240° to 300°. The step of determining may include the step of turning off the first pair of switching devices included in the a-phase leg, and the step of generating may include the step of generating the AC by alternately controlling the on/off state of the second and third pair of switching devices included in each of the b-phase leg and the c-phase leg at the preset switching frequency.

The step of generating may include the steps of controlling the on/off state of the second pair of switching devices included in the b-phase leg to have a complementary relationship at the switching frequency, controlling the on/off state of the third pair of switching devices included in the c-phase leg to have a complementary relationship at the switching frequency, and controlling the on/off state of one of the second pair of switching devices connected to a positive terminal of the battery in the b-phase leg and the on/off state of one of the third pair of switching devices connected to the positive terminal of the battery in the c-phase leg to have a complementary relationship at the switching frequency.

The step of determining may be performed when the rotor angle is 120° to 180° and 300° to 360°. The step of determining may include the step of turning off the third pair of switching devices included in the c-phase leg, and the step of generating may include the step of generating the AC by alternately controlling the on/off state of the first and second pair of switching devices included in each of the a-phase leg and the b-phase leg at the preset switching frequency.

The step of generating may include the steps of controlling the on/off state of the first pair of switching devices included in the a-phase leg to have a complementary relationship at the switching frequency, controlling the on/off state of the second pair of switching devices included in the b-phase leg to have a complementary relationship at the switching frequency, and controlling on/off state of one of the first pair of switching devices connected to a positive terminal of the battery in the a-phase leg and the on/off state of one of the second pair of switching devices connected to the positive terminal of the battery in the b-phase leg to have a complementary relationship at the switching frequency.

Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.

