Battery Heating System and Method Using an Electric Motor Drive System

Abstract

The present invention relates to a battery heating system and method using an electric motor drive system. By using an electric motor drive system including an inverter and an electric motor provided in a vehicle, alternating current is injected into the battery, and charging and discharging of the battery are repeated to increase the temperature of the battery.

Description

Technical Field

[0001] The present invention relates to a battery heating system and method using an electric motor drive system, and more particularly, to a battery heating system and method using an electric motor drive system in which the temperature of a battery can be increased by injecting alternating current into the battery, so that the charging and discharging of the battery can be repeated using an electric motor drive system including an electric motor and an inverter provided in a vehicle. Background Art

[0002] Generally, an environment-friendly vehicle driven by electric energy may include: a battery for storing electric energy, an inverter for converting the electric energy stored in the battery into alternating current (AC) electricity having a plurality of phases, and an electric motor for generating kinetic energy by rotation using the alternating current converted by the inverter.

[0003] Recently, the batteries of environment-friendly vehicles are mainly made of lithium-ion batteries. Lithium-ion batteries have excellent performance in terms of excellent energy density and charge-discharge cycles at room temperature. However, due to the characteristics of the electrolyte constituting the lithium-ion battery, the lithium-ion battery has disadvantages of reduced capacity, increased resistance, and decreased efficiency at low temperatures. Specifically, when the lithium-ion battery is charged or overcharged at low temperature, a phenomenon occurs in which lithium ions are unevenly deposited on the anode surface, thereby shortening the life of the lithium-ion battery. Due to such problems, the lithium-ion battery requires a heating device that can quickly increase the temperature from a low temperature state to a high temperature state with high efficiency.

[0004] Conventionally, the following method has been applied: directly heating the battery by adding a heater (for example, a positive temperature coefficient (PTC) heater) to the battery or heating the coolant supplied to the battery so that the heated coolant circulates. However, in this conventional battery heating method, a separate heater is required, which leads to additional cost increase and volume increase.

[0005] As another conventional battery heating technology, a method of generating heat inside the battery by an electric method has been studied. This method utilizes the internal resistance of the battery and is a method of flowing a current through the battery and using the loss generated in proportion to the amount of flowing current as heat. This method has the advantage of uniformly increasing the heat in the battery due to the current uniformly conducted through the battery. However, a separate dedicated circuit is required to flow a current through the battery, which also leads to additional volume and cost, and due to the appearance of additional management points for the dedicated circuit for generating and flowing the current for heating the battery, there is a problem of complicating vehicle maintenance.

[0006] The provision of the content described as the related art is only to help understand the background of the present invention and should not be regarded as corresponding to the related art known to those skilled in the art. Summary of the Invention

[0007] An object of the present invention is to provide a battery heating system and method using a motor drive system, wherein, by using the inverter and motor in a vehicle's motor drive system, and injecting alternating current (AC) into the battery, the charging and discharging of the battery can be repeated, and the temperature of the battery can be increased without a separate heating device for increasing the temperature of the battery.

[0008] According to an exemplary embodiment of the present invention, a battery heating system using a motor drive system may include: an inverter having a plurality of branches, each branch including a pair of switching elements connected in series between both ends of the battery and corresponding to a respective one of a plurality of phases; a motor having a plurality of coils, a first end of each coil being connected to a connection terminal between a pair of switching elements included in the plurality of branches, and a second end of each of the plurality of coils being connected to each other; and a controller configured to operate the switching elements such that a first interval and a second interval are alternately repeated, in the first interval, at least some of the switching elements are turned on, and in the second interval, all of the switching elements are turned off.

[0009] The controller may be configured to: in the first interval, operate or drive the switching elements in a first switching drive mode or a second switching drive mode; in the first switching drive mode, the controller drives the switching elements such that the on / off state of the switching elements included in a branch corresponding to a reference phase among the plurality of phases and the on / off state of the switching elements included in the remaining branches are in a complementary relationship; in the second switching drive mode, the controller drives the switching elements such that the on / off state of the switching elements included in the branches corresponding to two phases among the plurality of phases are in a complementary relationship, and drives the switching elements included in the remaining branches to be in an off state.

[0010] The controller may be configured to: when applying the first drive technique, in the first interval, control such that the on / off state of a pair of switching elements included in the plurality of branches and the on / off state of the remaining switching elements are in a complementary relationship; and control such that the on / off state of the switching element among the switching elements included in the branch corresponding to the reference phase and connected to the positive terminal of the battery and the on / off state of the switching elements among the switching elements included in the remaining branches and connected to the positive terminal of the battery are in a complementary relationship.

[0011] In addition, the controller may be configured to: when applying the second driving technique, in the first interval, perform control according to the switching frequency such that the states of a pair of switching elements included in the first branch corresponding to one of the two selected phases are in a complementary relationship, and perform control according to the switching frequency such that the states of a pair of switching elements included in the second branch corresponding to the other of the two selected phases are in a complementary relationship; and may perform control such that the state of the switching element in the first branch that is connected to the positive terminal of the battery is in a complementary relationship with the state of the switching element in the second branch that is connected to the positive terminal of the battery.

[0012] The controller may be further configured to: based on the angle of the rotor of the motor, determine the reference phase applied in the first switching drive mode or the two phases for driving the switching elements in the second switching drive mode. The controller may also be configured to: determine the reference phase of the first switching drive mode or the two phases for driving the switching elements in the second switching drive mode to minimize the difference between the angle of the rotor in the dq stationary coordinate plane and the angle represented by the current supplied to the motor.

[0013] According to another exemplary embodiment of the present invention, a battery heating system of a motor drive system may include: an inverter having an a-phase branch, a b-phase branch, and a c-phase branch, each branch including a pair of switching elements connected in series between both ends of the battery; a motor including an a-phase coil, a b-phase coil, and a c-phase coil, a first end of the a-phase coil being connected to a connection node between a pair of switching elements included in the a-phase branch; a first end of the b-phase coil being connected to a connection node between a pair of switching elements included in the b-phase branch; a first end of the c-phase coil being connected to a connection node between a pair of switching elements included in the c-phase branch, a second end of the a-phase coil, a second end of the b-phase coil, and a second end of the c-phase coil being connected to each other; and a controller configured to: drive or operate the switching elements such that a first interval and a second interval are alternately repeated, in the first interval, at least some of the switching elements are turned on, and in the second interval, all of the switching elements are turned off.

[0014] In addition, the controller may be configured to: in a first interval, drive the switching element in a first switching drive mode or in a second switching drive mode; in the first switching drive mode, the controller drives the switching element such that the on / off states of the switching elements included in a branch corresponding to a reference phase among the a-phase, b-phase, and c-phase and the on / off states of the switching elements included in the branches corresponding to the remaining phases are in a complementary relationship; in the second switching drive mode, the controller drives the switching element such that the on / off states of the switching elements included in the branches corresponding to two of the a-phase, b-phase, and c-phase are in a complementary relationship, and drives the switching elements included in the remaining branches to be in an off state.

[0015] The controller may be further configured to: when using a first driving technique, in a first interval, perform control such that the on / off states of a pair of switching elements included in the plurality of branches and the on / off states of the remaining switching elements are in a complementary relationship; and perform control such that the on / off state of the switching element connected to the positive terminal of the battery among the switching elements included in the branch corresponding to the reference phase and the on / off state of the switching element connected to the positive terminal of the battery among the switching elements included in the remaining branches are in a complementary relationship.

[0016] The controller may also be configured to: when applying a second driving technique, in a first interval, perform control according to a switching frequency such that the states of a pair of switching elements in a first branch corresponding to one of two selected phases are in a complementary relationship, and perform control according to the switching frequency such that the states of a pair of switching elements included in a second branch corresponding to the other of the two selected phases are in a complementary relationship; and perform control such that the state of the switching element connected to the positive terminal of the battery among the switching elements in the first branch and the state of the switching element connected to the positive terminal of the battery among the switching elements in the second branch are in a complementary relationship.

[0017] The controller may be configured to: based on the angle of the rotor of the motor, determine the reference phase applied in the first switching drive mode or the two phases for driving the switching element in the second switching drive mode. The controller may be configured to: determine the reference phase of the first switching drive mode or the two phases for driving the switching element in the second switching drive mode so as to minimize the difference between the angle of the rotor in the dq stationary coordinate plane and the angle represented by the current supplied to the motor.

[0018] The controller can be configured such that when the quotient of the value obtained by adding 15° to the angle of the rotor divided by 30° is an even number, the switching element is driven in a first switching drive mode, and when the quotient of the value obtained by adding 15° to the angle of the rotor divided by 30° is an odd number, the switching element is driven in a second switching drive mode. The controller can be configured such that in the first switching drive mode, when the angle of the rotor is from 0° to 30°, from 150° to 210°, and from 330° to 360°, the switching element is driven by determining phase a as the reference phase. The controller can also be configured such that in the first switching drive mode, when the angle of the rotor is from 30° to 90° and from 210° to 270°, the switching element is driven by determining phase c as the reference phase. The controller can be configured such that in the first switching drive mode, when the angle of the rotor is from 90° to 150° and from 270° to 330°, the switching element is driven by determining phase b as the reference phase.

[0019] In the second switching drive mode, the controller can be configured such that when the angle of the rotor is from 0° to 60° and from 180° to 240°, phase c branch and phase a branch are selected, and in a first interval, the on / off states of the switching elements included in phase c branch and phase a branch are driven in a complementary relationship, and the switching elements included in phase b branch are turned off. In the second switching drive mode, the controller can be configured such that when the angle of the rotor is from 60° to 120° and from 240° to 300°, phase b branch and phase c branch are selected, and in a first interval, the on / off states of the switching elements in phase b branch and phase c branch are driven in a complementary relationship, and the switching elements included in phase a branch are turned off. In the second switching drive mode, the controller can be configured such that when the angle of the rotor is from 120° to 180° and from 300° to 360°, phase a branch and phase b branch are selected, and in a first interval, the on / off states of the switching elements included in phase a branch and phase b branch are driven in a complementary relationship, and the switching elements included in phase c branch are turned off.

[0020] According to another exemplary embodiment of the present invention, a battery heating method using the above battery heating system may include: determining, by a controller, an interval of an angle of a rotor of a motor; selecting, by the controller, one of a first switch driving mode and a second switch driving mode based on the interval to which the angle of the rotor belongs; when the first switch driving mode is selected, in a first interval, driving, by the controller, a switching element such that an on / off state of the switching element included in a branch corresponding to a reference phase and an on / off state of the switching element included in a branch corresponding to the remaining phases are in a complementary relationship; and when the second switch driving mode is selected, in the first interval, driving, by the controller, a switching element such that an on / off state of the switching element included in branches corresponding to two phases are in a complementary relationship, and driving, by the controller, a switching element such that the switching element included in the remaining branch is in an off state.

[0021] In selecting one of the first switch driving mode and the second switch driving mode, the controller may be configured to: when a quotient obtained by dividing a value obtained by adding 15° to the angle of the rotor by 30° is an even number, drive the switching element in the first switch driving mode, and when the quotient obtained by dividing the value obtained by adding 15° to the angle of the rotor by 30° is an odd number, drive the switching element in the second switch driving mode. In driving the switching element, when the first switch driving mode is selected, the controller may be configured to: when the angle of the rotor is from 0° to 30°, from 150° to 210°, and from 330° to 360°, drive the switching element by determining the a-phase as the reference phase.

[0022] In driving the switching element, when the first switch driving mode is selected, the controller may be configured to: when the angle of the rotor is from 30° to 90° and from 210° to 270°, drive the switching element by determining the c-phase as the reference phase. In driving the switching element, when the first switch driving mode is selected, the controller may be configured to: when the angle of the rotor is from 90° to 150° and from 270° to 330°, drive the switching element by determining the b-phase as the reference phase. In driving the switching element, when the second switch driving mode is selected, the controller may be configured to: when the angle of the rotor is from 0° to 60° and from 180° to 240°, select the c-phase branch and the a-phase branch, and in the first interval, drive the on / off state of the switching element included in the c-phase branch and the a-phase branch in a complementary relationship, and turn off the switching element included in the b-phase branch.

[0023] In the drive switch element, when the second switch drive mode is selected, the controller can be configured to: select the b-phase branch and the c-phase branch when the angle of the rotor is between 60° and 120° and between 240° and 300°, and in the first interval, drive the on / off states of the switch elements included in the b-phase branch and the c-phase branch in a complementary relationship, and turn off the switch elements included in the a-phase branch. In the drive switch element, when the second switch drive mode is selected, the controller can be configured to: select the a-phase branch and the b-phase branch when the angle of the rotor is between 120° and 180° and between 300° and 360°, and in the first interval, drive the on / off states of the switch elements in the a-phase branch and the b-phase branch in a complementary relationship, and turn off the switch elements included in the c-phase branch. Description of the Drawings

[0024] The objects, features, and advantages of the present invention will be more clearly understood from the following detailed description in conjunction with the accompanying drawings, in which:

[0025] Figure 1 is a circuit diagram of a battery heating system using a motor drive system according to an exemplary embodiment of the present invention.

[0026] Figure 2 is a waveform diagram showing the technique of generating a battery current when applying the first switch drive mode in a motor drive system and method according to an exemplary embodiment of the present invention.

[0027] Figure 3 is a waveform diagram showing the technique of generating a battery current when applying the second switch drive mode in a motor drive system and method according to an exemplary embodiment of the present invention.

[0028] Figure 4 is a vector diagram showing the technique of minimizing torque ripple when applying the first switch drive mode in a motor drive system and method according to an exemplary embodiment of the present invention.

[0029] Figure 5 is a vector diagram showing the technique of minimizing torque ripple when applying the second switch drive mode in a motor drive system and method according to an exemplary embodiment of the present invention.

[0030] Figure 6 is a flowchart showing a battery heating method using a motor drive system according to an exemplary embodiment of the present invention.

[0031] Figure 7 is a flowchart showing in more detail the first switch drive mode in a battery heating method using a motor drive system according to an exemplary embodiment of the present invention.

[0032] Figure 8It is a flowchart showing in more detail a second switch driving mode in a battery heating method using an electric motor drive system according to an exemplary embodiment of the present invention. Detailed Description of the Invention

[0033] It should be understood that the term "vehicle" or "vehicular" or other similar terms used herein generally include motor vehicles, such as passenger cars including sport utility vehicles (SUVs), buses, trucks, various commercial vehicles, vessels including various boats and ships, aircraft, etc., and include hybrid vehicles, electric vehicles, internal combustion engine vehicles, plug-in hybrid electric vehicles, hydrogen-powered vehicles, and other alternative fuel vehicles (e.g., fuels derived from non-fossil energy sources).

[0034] Although the exemplary embodiments are described as using multiple units to perform the exemplary processes, it should be understood that the exemplary processes can also be performed by one or more modules. In addition, it should be understood that the term controller / control unit represents a hardware device including a memory and a processor and specifically programmed to perform the processes described herein. The memory is configured to store modules, and the processor is specifically configured to execute the modules to perform one or more processes further described below.

[0035] The terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the present invention. As used herein, the singular forms "a", "an", and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It should be further understood that when the terms "comprises" and / or "comprising" are used in this specification, it indicates the presence of the stated features, values, steps, operations, elements, and / or components, but does not preclude the presence or addition of one or more other features, values, steps, operations, elements, components, and / or groups thereof. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0036] Unless specifically stated or obvious from the context, the term "about" as used herein is understood to be within the normal tolerances in the art, e.g., within 2 standard deviations of the average. "About" can be understood to be within 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.5%, 0.1%, 0.05%, or 0.01% of the stated value. Unless clear from the context, all numerical values provided herein are modified by the term "about".

[0037] Hereinafter, a battery heating system and method using an electric motor drive system according to each exemplary embodiment will be described in more detail with reference to the accompanying drawings.

[0038] Figure 1is a circuit diagram of a battery heating system using an electric motor drive system according to an exemplary embodiment of the present invention. As Figure 1 shown, a typical system for driving an electric motor 30 may include: a battery 10 and an inverter 20; the battery 10 is an energy storage device configured to store electric power for driving the electric motor 30; the inverter 20 is configured to convert direct current (DC) power stored in the battery 10 into alternating current (AC) having a plurality of phases and supply the AC to the electric motor 30. The inverter 20 has three branches 21, 23, and 25 connected to both ends of the battery 10 in a parallel relationship, two switching elements (two of S1 to S6) are connected in series to each of the branches 21, 23, and 25, and drive power of one phase is supplied to the electric motor 30 from a connection node of the two switching elements. In order to drive such an electric motor, pulse width modulation control of the switching elements S1 to S6 in the inverter 20 may be performed to supply as much current to the electric motor 30 as a current command corresponding to the torque of the electric motor 30 obtained by driving the electric motor 30.

[0039] The battery heating system using an electric motor drive system according to an exemplary embodiment of the present invention controls the states of the switching elements S1 to S6 in the inverter 20 while suppressing the torque generated in the electric motor 30 using such a typical electric motor drive system, so that alternating current (pulsating current) can be injected into the battery 10. Specifically, the battery heating system using an electric motor drive system according to an exemplary embodiment of the present invention may include a battery 10, an inverter 20, an electric motor 30, and a controller 100; the inverter 20 has a plurality of branches 21, 23, and 25, and each branch includes a pair of switching elements S1 to S6 connected in series to both ends of the battery 10; the electric motor 30 has a plurality of coils L1, L2, and L3, and these coils are respectively connected to connection terminals of the switching elements included in the branches 21, 23, and 25 of the inverter 20; the controller 100 is configured to generate alternating current injected into the battery 10 by determining on / off states of the switching elements S1 to S6 included in the plurality of branches included in the inverter 20.

[0040] According to an exemplary embodiment of the present invention, the controller 100 may be configured to drive the switching elements such that a first interval for turning on a part of the switching elements S1 to S6 in the inverter 20 and a second interval for turning off all of the switching elements S1 to S6 are alternately repeated. In the second interval in which all of the switching elements S1 to S6 are turned off, all currents supplied to the electric motor 30 may be zero, and in this state, by switching back to the first interval again and starting to switch the switching elements, zero current switching may be performed so that the switching of the switching elements S1 to S6 is performed in a state where the motor current is zero.

[0041] When this zero-current switching is applied, the switching losses of the switching elements can be reduced, thereby improving the overall system efficiency. Specifically, the controller 100 can be configured to drive the switching elements S1 to S6 in a first switching drive mode and a second switching drive mode according to the phase numbers of the switching elements to be switched in the first interval.

[0042] In the first switching drive mode, the controller 100 can be configured to drive the switching elements S1 to S6 such that the switching elements belonging to the branch corresponding to a reference phase as a reference among multiple phases and the switching elements belonging to the branches corresponding to the remaining phases are in a complementary state in the first interval. In the second switching drive mode, the controller 100 can be configured to drive the switching elements S1 to S6 such that the switching elements belonging to the branches corresponding to two phases among multiple phases are in a complementary state, and all the switching elements of the other phases are in an off state.

[0043] Figure 2 is a waveform diagram showing the technique of generating battery current when applying the first switching drive mode in a motor drive system and method according to an exemplary embodiment of the present invention, Figure 3 is a waveform diagram showing the technique of generating battery current when applying the second switching drive mode in a motor drive system and method according to an exemplary embodiment of the present invention.

[0044] As Figure 2 and Figure 3 shown, the controller 100 can be configured to drive the switching elements S1 to S6 to alternately repeat the first interval D1 and the second interval D2. In the first interval D1, the pole voltages V an 、V bn and V cn appear on at least two phases of each phase of the motor through the on / off drive of the switching elements S1 to S6. On the contrary, in the second interval D2, by turning off all the switching elements S1 to S6, the pole voltages V an 、V bn and V cn are not applied to all phases of the motor.

[0045] More specifically, referring to Figure 2, in the first interval D1 of the first driving mode, the controller 100 can be configured to complementarily operate a pair of switching elements included in each of the branches 21, 23, and 25 in the inverter 20, and complementarily operate the switching element S1 among the switching elements S1 and S2 included in the first branch 21 among the plurality of branches 21, 23, and 25 that is connected to the positive (+) terminal of the battery and the switching elements S3 and S5 among the switching elements included in the remaining two branches 23 and 25 that are connected to the positive (+) terminal of the battery 10. Through this control, the polarity of the phase current I as flowing through the coil L1 corresponding to the a-phase among the plurality of phases included in the motor 30 is opposite to the polarity of the phase currents I bs and I cs flowing through the coils L2 and L3 corresponding to the b-phase and c-phase.

[0046] Subsequently, in the second interval D2, when the controller 100 turns off all the switching elements S1 to S6 in the inverter 20, the current flowing through the motor 30 gradually decreases due to the electrical characteristics of the motor coils L1, L2, and L3, and due to the freewheeling diodes connected across the switching elements S1 to S6, a current in the direction opposite to the direction of the current flowing in the first interval D1 is generated in the battery 10. In the second interval D2, as the phase current of the motor 30 decreases, the magnitude of the current I BAT generated in the battery 10 decreases, and when the phase current becomes zero, the battery current also becomes 0. Therefore, by controlling the switching elements S1 to S6 in the first interval D1 and the second interval D2, phase currents I as 、I bs and I cs that increase and decrease for each phase of the motor can be generated, and accordingly, a pulsating current can be applied to the battery 10.

[0047] In Figure 2 , an example in which the a-phase of the motor is determined as the reference phase has been described, but those skilled in the art can easily perform the same control by determining the b-phase or c-phase of the motor as the reference phase. To increase the temperature of the battery 10, the key points to consider when utilizing the heat generated by the internal resistance of the battery 10 are the amount and efficiency of the generated heat.

[0048] First, the amount of generated heat is proportional to the amount of current flowing through the battery 10. In other words, regardless of the direction, when a large amount of current flows into the internal resistance of the battery 10, a large amount of heat is generated. Therefore, by increasing the charging amount or the discharging amount by charging the battery 10 with a DC current or discharging a DC current from the battery 10, the heat generation amount of the battery 10 can be increased.

[0049] Next, to improve efficiency, the controller can be configured to alternately charge and discharge the battery 10 instead of only performing one of charging or discharging the battery 10. Thus, when the charging and discharging of the battery 10 are alternated, the energy consumed in the battery 10 is minimized, but the amount of current flowing through the battery 10 can be increased. As a result, the energy efficiency can be improved and the heat generation can be significantly increased. In other words, when AC is injected into the battery 10 instead of DC, heat generation of the battery 10 with higher energy efficiency can be induced by repeatedly outputting current from the battery 10 and inputting current into the battery 10.

[0050] At this time, if the frequency of the AC is high enough, heat can be generated in the battery 10 while preventing lithium precipitation inside the battery 10 and aging of the battery due to lithium precipitation. In various exemplary embodiments of the present invention, the switching elements S1 to S6 in the inverter 20 can be operated to inject AC with a higher frequency into the battery.

[0051] To inject AC into the battery 10, operations of receiving and storing energy from the battery 10 and supplying the stored energy to the battery 10 again are required. Specifically, for the required energy storage, in various exemplary embodiments of the present invention, the coils L1 to L3 corresponding to multiple phases provided in the motor 30 can be utilized. In other words, by storing energy in and releasing energy from the coils L1 to L3, AC can be injected into the battery 10.

[0052] Reference Figure 3 , in the first interval D1 of the second driving mode, the controller 100 can be configured to turn on / off the switching elements included in two of the three branches included in the inverter 20 and turn off the switching elements included in the other branch in the first interval D1. Figure 3 An example is shown in which the on / off states of the switching elements S1, S2, S5, and S6 included in the branches 21 and 25 connected to the a-phase coil L1 and the c-phase coil L3 of the motor 30 are operated, and the switching elements S3 and S4 of the branch 23 connected to the b-phase coil L2 are turned off.

[0053] In the first interval D1, the controller 100 can be configured to operate the switching elements S1, S2, S5, and S6 such that the pole voltage V an supplied to the a-phase coil L1 of the motor 30 has a positive value, and the c-phase pole voltage V cn supplied to the c-phase coil L3 has a negative value. In other words, the controller 100 can be configured to turn on the switching element S1 of the branch 21 and turn off its switching element S2, and turn off the switching element S5 of the branch 25 and turn on its switching element S6. In the second switching driving mode, the controller 100 can be configured to turn off all the switching elements S3 and S4 of the branch 23 connected to the b-phase coil L2.

[0054] With such control, in the first interval D1, through the a-phase coil L1 of the motor 30 connected to the positive (+) terminal side of the battery 10, the phase current I flowing through the a-phase coil L1 of the motor 30 as increases, and the phase current I flowing through the c-phase coil L3 cs decreases. Specifically, the phase current I flowing from the inverter 20 to the motor 30 as and I cs can be set in the positive (+) direction. Due to the electrical characteristics of the coils (inductors) storing energy, even if an electrical path is formed by switching the switching elements, the current I flowing through each coil as and I cs may gradually increase or decrease. Therefore, even if the state of the switching elements changes, after the direction of the current flowing in the previous interval remains the same for a predetermined time, the direction of the current will change. Specifically, the coils L1, L2, and L3 corresponding to each phase of the motor 30 can have a first end connected to the node where the pairs of switching elements included in each branch 21, 23, and 25 of the inverter 20 are interconnected, and a second end that is normally connected between the coils L1, L2, and L3 to form a neutral point.

[0055] In the second interval D2, the controller 100 can be configured to turn off all the switching elements S1 to S6 of the inverter 20. As described above, due to the electrical characteristics of the a-phase coil L1 and the c-phase coil L3 of the motor 30, each phase current gradually approaches zero. At this time, as the diodes provided in the switching elements allow the a-phase current and the c-phase current to flow, a negative current (i.e., a charging current input to the battery 10) flows through the battery 10.

[0056] Therefore, by controlling the switching elements S1 to S6 in the first interval D1 and the second interval D2, it is possible to generate phase currents I as 、I bs and I cs that repeatedly increase and decrease for each phase of the motor, and accordingly, a pulsating current can be applied to the battery 10. At the same time, in order to heat the battery 10 by injecting high-frequency alternating current into the battery 10 by using the inverter 20 and the motor 30, in addition to ensuring the battery current as described above, it is also necessary to suppress the torque generated in the motor 30.

[0057] Figure 4 is a vector diagram showing a technique for minimizing torque ripple when applying the first switch drive mode in a motor drive system and method according to an exemplary embodiment of the present invention, Figure 5 is a vector diagram showing a technique for minimizing torque ripple when applying the second switch drive mode in a motor drive system and method according to an exemplary embodiment of the present invention.

[0058] First, the reference Figure 4 will describe the torque suppression technology in the first switch driving mode. In the method of generating current by complementarily determining the phase voltage of the coil corresponding to one phase of the motor and the phase voltages of the coils corresponding to the other two phases of the motor, the current can be generated according to the Figure 4 arrows indicated by the reference numerals "51" to "56" shown in

[0059] When the a-phase voltage and the remaining b-phase and c-phase voltages are complementarily controlled, the motor currents 51 and 54 formed between the center of the hexagon and the vertex corresponding to the

[100] vector and between the center of the hexagon and the vertex corresponding to the

[011] vector can be formed. Additionally, when the b-phase voltage and the remaining a-phase and c-phase voltages are complementarily controlled, the motor currents 53 and 56 formed between the center of the hexagon and the vertex corresponding to the

[010] vector and between the center of the hexagon and the vertex corresponding to the

[101] vector can be formed. When the c-phase voltage and the remaining a-phase and b-phase voltages are complementarily controlled, the motor currents 52 and 55 formed between the center of the hexagon and the vertex corresponding to the

[110] vector and between the center of the hexagon and the vertex corresponding to the

[001] vector can be formed. Specifically, the arrows indicated by the reference numerals "51" and "54" respectively correspond to 0° and 180° based on the a-axis, the arrows indicated by the reference numerals "53" and "56" respectively correspond to 120° and 300° based on the a-axis, and the arrows indicated by the reference numerals "52" and "55" respectively correspond to 60° and 240° based on the a-axis.

[0060] Meanwhile, in the case of a permanent magnet synchronous motor with salient poles, the torque generated in the motor according to the motor current can be expressed as Equation 1 below.

[0061] Equation 1

[0062]

[0063] In Equation 1, T e is the torque of the motor, λ f is the electromotive force of the motor, L d and L q are the d-axis and q-axis inductances of the motor, i d and i q are the d-axis and q-axis currents supplied to the motor.

[0064] As shown in Equation 1, when the q-axis current is 0 (i qWhen (θ = 0), the torque generated in the motor is not generated. In other words, when the alternating current generated in the motor is not oriented along the q-axis of the synchronous coordinate system and exists only on the d-axis, no torque is generated in the motor. Therefore, when the d-axis corresponding to the axis connecting the N pole and the S pole of the rotor of the motor 30 coincides with Figure 4 the arrow shown in Figure 4 i.e., when the angle of the rotor corresponds to the angles 0°, 60°, 120°, 180°, 240°, and 300° of the arrow shown in

[0065] The position of the rotor of the motor 30 can be arbitrarily determined. Therefore, in the exemplary embodiment of the present invention, the occurrence of torque can be minimized by selecting the following phases: wherein, the difference between the angle of the rotor detected by the rotor position sensor 40 and the angle of the alternating current generated by the on / off control of the switching elements of the inverter 20 (e.g., Figure 4 the angle formed by the arrows 51 to 56 based on the a-axis in

[0066] Reference Figure 4 , when the angle of the rotor is from 0° to 30°, from 150° to 210°, and from 330° to 360°, preferably, the control is performed based on the a-phase corresponding to the arrows 51 and 54. In other words, preferably, the on / off state of the switching elements in the first interval is controlled such that the a-phase voltage is in a complementary relationship with the remaining b-phase and c-phase voltages. Further, when the angle of the rotor is from 30° to 90° and from 210° to 270°, preferably, the control is performed based on the c-phase corresponding to the arrows 52 and 55. In other words, preferably, the on / off state of the switching elements in the first interval is controlled such that the c-phase voltage is in a complementary relationship with the remaining a-phase and b-phase voltages.

[0067] In addition, when the angle of the rotor is from 90° to 150° and from 270° to 330°, preferably, the control is performed based on the b-phase corresponding to the arrows 53 and 56. In other words, preferably, the on / off state of the switching elements in the first interval is controlled such that the b-phase voltage is in a complementary relationship with the remaining a-phase and c-phase voltages.

[0068] The torque suppression technique in the second switching drive mode will be described with reference to Figure 5 . The torque suppression technique in the second switching drive mode is similar in principle to the torque suppression technique in the first switching drive mode, but is different in terms of the angle of forming the motor current. In the first interval of the second switching drive mode (wherein the current is applied to the coils corresponding to the other two phases and not to the coil corresponding to one phase), the current can be generated as Figure 5The arrows indicated by the reference numerals "61" to "63" shown in the drawings.

[0069] In other words, when all the switching elements of the branch 23 corresponding to the b-phase are turned off so that the coil L2 corresponding to the b-phase is not utilized, and the coils L1 and L3 of the motor 30 corresponding to the a-phase and c-phase are utilized, the current can be represented by the reference numerals "61" or "64" whose b-axis value corresponds to 0 (perpendicular to the b-axis). Similarly, when all the switching elements of the branch 21 corresponding to the a-phase are turned off so that the coil L1 corresponding to the a-phase is not utilized, and the coils L2 and L3 of the motor 30 corresponding to the b-phase and c-phase are utilized, the current can be represented by the reference numerals "62" or "65" whose a-axis value corresponds to 0 (perpendicular to the a-axis).

[0070] Similarly, when all the switching elements of the branch 25 corresponding to the c-phase are turned off so that the coil L3 corresponding to the c-phase is not utilized, and the coils L1 and L2 of the motor 30 corresponding to the a-phase and b-phase are utilized, the current can be represented by the reference numerals "63" or "66" whose c-axis value corresponds to 0 (perpendicular to the c-axis). Specifically, the arrows indicated by the reference numerals "61" and "64" respectively correspond to 30° and 210° based on the a-axis, the arrows indicated by the reference numerals "62" and "65" respectively correspond to 90° and 270° based on the a-axis, and the arrows indicated by the reference numerals "63" and "66" respectively correspond to 150° and 330° based on the a-axis.

[0071] As described above, when the q-axis current is 0 (i q = 0), the torque generated in the motor is not generated. In other words, when the alternating current generated in the motor is not oriented to the q-axis of the synchronous coordinate system and only exists on the d-axis, no torque is generated in the motor. Therefore, when the d-axis corresponding to the axis connecting the n-pole and s-pole of the rotor of the motor 30 is Figure 5 aligned with the arrow shown, that is, when the angle of the rotor corresponds to Figure 5 the angles 30°, 90°, 150°, 210°, 270° and 330° of the arrow shown, the torque of the motor 30 can be 0.

[0072] The position of the rotor of the motor 30 can be determined arbitrarily. Therefore, in the exemplary embodiment of the present invention, the appearance of torque can be minimized by selecting the following two phases: wherein, the difference between the angle of the rotor detected by the rotor position sensor 40 included in the motor 30 and the angle of the alternating current generated by the on / off control of the switching elements in the branch corresponding to the two phases (for example, Figure 4 the angles formed by the arrows 51 to 56 based on the a-axis in ) is minimized to control the switching elements of the branch corresponding to the two phases.

[0073] Reference Figure 5 , when the angle of the rotor is from 0° to 60° and from 180° to 240°, it is desired to generate alternating current by selecting the c-phase branch and the a-phase branch corresponding to arrows 61 and 64, controlling the on / off states of the switching elements included in the c-phase branch and the a-phase branch, and turning off the switching elements included in the b-phase branch. Additionally, when the angle of the rotor is from 60° to 120° and from 240° to 300°, it is desired to generate alternating current by selecting the b-phase branch and the c-phase branch corresponding to arrows 62 and 65, controlling the on / off states of the switching elements included in the b-phase branch and the c-phase branch, and turning off the switching elements included in the a-phase branch. Furthermore, when the angle of the rotor is from 120° to 180° and from 300° to 360°, it is desired to generate alternating current by selecting the a-phase branch and the b-phase branch corresponding to arrows 63 and 66, controlling the on / off states of the switching elements included in the a-phase branch and the b-phase branch, and turning off the switching elements included in the c-phase branch.

[0074] The present invention also provides a battery heating method implemented by the battery heating system using the motor drive system as described above. Figure 6 is a flowchart showing a battery heating method using a motor drive system according to an exemplary embodiment of the present invention. The method described below herein can be executed by the above-mentioned controller. Reference Figure 6 , the motor drive system according to an exemplary embodiment of the present invention can first receive the rotor position of the motor 30 and check the quotient and remainder of the value obtained by dividing the position of the rotor of the motor (e.g., the angle of the rotor) by 30° to select the first switch drive mode (S11) and the second switch drive mode (S13), and then perform heating control corresponding to each switch drive mode.

[0075] As described above Figure 4 and Figure 5 shown by the arrows in, the motor current that can suppress the occurrence of torque of the motor 30 during the heating control can be determined in advance. If the arrows as shown in Figure 4 and Figure 5 are combined, the arrows of each mode appear alternately at intervals of 30° in the dq stationary coordinate plane. Among the arrows 51 to 56 shown in Figure 4 , the arrows start from the arrow consistent with the a-axis and appear every 60°. Among the arrows 61 to 66 shown in Figure 5 , the arrows start from the arrow rotated 30° from the a-axis and appear every 60°. Therefore, the case where the quotient of the angle of the rotor of the motor 30 divided by 30 is an even number and the remainder is less than 15 or the case where the quotient of the angle of the rotor of the motor 30 divided by 30 is an odd number and the remainder is greater than 15 corresponds to the angle of the rotor of the motor being closer to as shown in Figure 4For the case of the arrow shown, other cases correspond to the angle of the rotor of the motor being closer to as Figure 5 the case of the arrow shown.

[0076] Therefore, in step S11, the first switch driving mode and the second switch driving mode can be determined based on the quotient and remainder obtained by dividing the angle of the rotor of the motor by 30. In summary, according to the result of dividing the value obtained by adding 15° to the angle of the rotor of the motor by 30, if the quotient is even, the first switch driving mode can be determined, and if the quotient is odd, the second switch driving mode can be determined.

[0077] Figure 7 is a flowchart showing in more detail the first switch driving mode in the battery heating method using a motor drive system according to an exemplary embodiment of the present invention, Figure 8 is a flowchart showing in more detail the second switch driving mode in the battery heating method using a motor drive system according to an exemplary embodiment of the present invention. The methods described below herein can be executed by a controller.

[0078] As Figure 7 shown, in response to determining to execute the first switch driving mode in step S11, the battery heating method can be configured to include step S121 and steps S122, S123, and S124; in step S121, the controller 100 receives the angle of the motor 30 detected by the rotor position sensor 40 and determines the interval to which the angle of the rotor belongs; in steps S122, S123, and S124, the controller 100 determines a reference phase based on the interval to which the angle of the rotor belongs, controls the switching elements to be turned on / off at a predetermined switching frequency, and injects alternating current into the battery 10. The above steps can be repeated until the temperature T of the battery bat increases to a predetermined target temperature (S125).

[0079] In step S121, when the angle of the rotor is between 0° and 30°, 150° and 210°, and 330° and 360°, the controller 100 can be configured to determine the a-phase voltage as a reference (S122). In other words, based on the on / off state of the switching element S1 of the first branch 21 of the inverter 20 in the first interval, by operating the switching element such that the on / off states of the switching elements S3 of the second branch 23 and S5 of the third branch 25 have a complementary relationship with the on / off state of the switching element S1, alternating current can be generated (S122).

[0080] In step S121, when the angle of the rotor is between 30° and 90° and between 210° and 270°, the controller 100 can be configured to determine the c-phase voltage as a reference (S123). In other words, based on the on / off state of the switching element S5 of the third branch 25 of the inverter 20 in the first interval, by operating the switching elements such that the on / off states of the switching element S1 of the first branch 21 and the switching element S3 of the second branch 23 have a complementary relationship with the on / off state of the switching element S5, an alternating current can be generated (S123).

[0081] In step S121, when the angle of the rotor is between 90° and 150° and between 270° and 330°, the controller 100 can be configured to determine the b-phase voltage as a reference (S124). In other words, based on the on / off state of the switching element S3 of the second branch 23 of the inverter 20 in the first interval, by operating the switching elements such that the on / off states of the switching element S1 of the first branch 21 and the switching element S5 of the third branch 25 have a complementary relationship with the on / off state of the switching element S3, an alternating current can be generated (S124).

[0082] Meanwhile, in response to determining to execute the second switching drive mode in step S11, the battery heating method can be configured to include steps S131, S132, S134, and S136, and steps S133, S135, and S137; in step S131, the controller 100 receives the angle of the motor 30 detected by the rotor position sensor 40 and determines the interval to which the angle of the rotor belongs; in steps S132, S134, and S136, the controller 100 determines the branch to be kept in the off state based on the interval to which the angle of the rotor belongs; in steps S133, S135, and S137, the controller 100 controls the on / off states of the switching elements included in the branches other than the branch kept in the off state in the first interval to generate an alternating current. The above steps can be repeated until the temperature T bat of the battery rises to a predetermined target temperature (S138).

[0083] In step S131, when the angle of the rotor is from 0° to 60° and from 180° to 240°, the controller 100 can be configured to turn off the switching elements S3 and S4 included in the b-phase branch 23 (S132), and generate an alternating current by controlling the on / off states of the switching elements S1, S2, S5, and S6 included in the c-phase branch 25 and the a-phase branch 21 in the first interval (S133). In step S133, in the first interval, the controller 100 can be configured to perform control such that the states of the pair of switching elements S5 and S6 included in the c-phase branch 25 are in a complementary relationship, and perform control such that the states of the pair of switching elements S1 and S2 included in the a-phase branch 21 are in a complementary relationship. Additionally, in the first interval, the controller 100 can be configured to: generate an alternating current injected into the battery 10 by performing control such that the state of the switching element S5 connected to the positive (+) terminal of the battery 10 among the switching elements included in the c-phase branch 25 is in a complementary relationship with the state of the switching element S1 connected to the positive terminal of the battery 10 among the switching elements included in the a-phase branch 21.

[0084] In step S131, when the angle of the rotor is from 60° to 120° and from 240° to 300°, the controller 100 can be configured to turn off the switching elements S1 and S2 included in the a-phase branch 21 in the first interval (S134), and generate an alternating current by controlling the on / off states of the switching elements S3, S4, S5, and S6 included in the b-phase branch 23 and the c-phase branch 25 (S135). In step S135, in the first interval, the controller 100 can be configured to perform control such that the states of the pair of switching elements S3 and S4 included in the b-phase branch 23 are in a complementary relationship, and perform control such that the states of the pair of switching elements S5 and S6 included in the c-phase branch 25 are in a complementary relationship. Additionally, the controller 100 can be configured to: in the first interval, generate an alternating current injected into the battery 10 by performing control such that the state of the switching element S3 connected to the positive (+) terminal of the battery 10 among the switching elements included in the b-phase branch 23 is in a complementary relationship with the state of the switching element S5 connected to the positive terminal of the battery 10 among the switching elements included in the c-phase branch 25.

[0085] In step S131, when the angle of the rotor is between 120° and 180° and between 300° and 360°, the controller 100 can be configured to turn off the switching elements S5 and S6 included in the c-phase branch 25 in the first interval (S136), and generate an alternating current by alternately controlling the on / off states of the switching elements S1, S2, S3, and S4 included in the a-phase branch 21 and the b-phase branch 23 at a predetermined switching frequency (S137). In step S137, in the first interval, the controller 100 can be configured to perform control such that the states of the pair of switching elements S1 and S2 included in the a-phase branch 21 are in a complementary relationship, and perform control such that the states of the pair of switching elements S3 and S4 included in the b-phase branch 23 are in a complementary relationship. Additionally, the controller 100 can be configured to: in the first interval, by performing control, make the state of the switching element S1 connected to the positive (+) terminal of the battery 10 among the switching elements included in the a-phase branch 21 be in a complementary relationship with the state of the switching element S3 connected to the positive terminal of the battery 10 among the switching elements included in the b-phase branch 23, thereby generating an alternating current injected into the battery 10.

[0086] As described above, in the case where an independent heating device is not required, the battery heating system and method according to various exemplary embodiments of the present invention that utilize a motor drive system can effectively heat the battery by injecting an alternating current into the battery by using an inverter and a motor connected to the battery provided to drive an eco-friendly vehicle without incurring additional costs. Specifically, when generating an alternating current by using the inverter and the motor, torque ripple generated in the motor can be suppressed to the maximum extent, thereby improving the stability of the vehicle. Additionally, when operating the switching elements for battery heating, the motor drive system according to various exemplary embodiments of the present invention can further reduce the switching loss by switching the switching elements in a state where the motor current is zero.

[0087] According to the battery heating system and method that utilize a motor drive system, without adding a heating device such as a separate heater, by injecting an alternating current into the battery by using an inverter and a motor necessary for driving an eco-friendly vehicle, the temperature of the battery can be effectively increased without incurring additional costs.

[0088] Specifically, according to the battery heating system and method that utilize a motor drive system, when generating an alternating current by using the inverter and the motor, torque ripple generated in the motor can be suppressed as much as possible, thereby improving the stability of the vehicle. Specifically, according to the battery heating system and method that utilize a motor drive system, the switching loss in the inverter can be further reduced by switching the switching elements in the inverter in a state where the motor current is zero.

[0089] The effects achievable in the present invention are not limited to the above effects, and other effects not mentioned can be clearly understood by those skilled in the art to which the present invention pertains from the following description.

[0090] Although the present invention has been shown and described with reference to specific exemplary embodiments, it will be apparent to those skilled in the art that various modifications and changes can be made to the present invention without departing from the spirit and scope of the present invention as defined by the appended claims.

Claims

1. A battery heating system using an electric motor drive system, comprising: An inverter having a plurality of branches, each branch including a pair of switching elements connected in series between both ends of the battery and corresponding to a respective one of a plurality of phases; An electric motor having a plurality of coils, a first end of each coil being connected to a connection terminal between a pair of switching elements included in the plurality of branches, and a second end of each of the plurality of coils being connected to each other; And A controller configured to drive the switching elements such that a first interval and a second interval are alternately repeated, in the first interval, at least some of the switching elements are turned on, and in the second interval, all of the switching elements are turned off; Wherein the controller is further configured to: In the first interval, drive the switching elements in a first switching drive mode or in a second switching drive mode; In the first switching drive mode, drive the switching elements such that the on / off state of the switching elements included in a branch corresponding to a reference phase among the plurality of phases and the on / off state of the switching elements included in the remaining branches are in a complementary relationship; In the second switching drive mode, drive the switching elements such that the on / off state of the switching elements included in the branches corresponding to two of the plurality of phases are in a complementary relationship, and drive the switching elements included in the remaining branches to be in an off state, When the current supplied to the electric motor in the second interval is zero, the second interval is switched to the first interval.

2. The battery heating system using the motor drive system according to claim 1, wherein, The controller is configured to: When applying the first switching drive mode, in the first interval, perform control such that the on / off state of a pair of switching elements included in the plurality of branches and the on / off state of the remaining switching elements are in a complementary relationship; And Perform control such that the on / off state of the switching element connected to the positive terminal of the battery among the switching elements included in the branch corresponding to the reference phase and the on / off state of the switching elements connected to the positive terminal of the battery among the switching elements included in the remaining branches are in a complementary relationship.

3. The battery heating system using a motor drive system according to claim 1, wherein, The controller is configured to: When applying the second switching drive mode, in the first interval, perform control according to a switching frequency such that the states of a pair of switching elements included in a first branch corresponding to one of two selected phases are in a complementary relationship, and perform control according to the switching frequency such that the states of a pair of switching elements included in a second branch corresponding to the other of the two selected phases are in a complementary relationship; And Perform control such that the state of the switching element connected to the positive terminal of the battery among the switching elements in the first branch and the state of the switching element connected to the positive terminal of the battery among the switching elements in the second branch are in a complementary relationship.

4. The battery heating system using a motor drive system according to claim 1, wherein, The controller is configured to: determine the reference phase applied in the first switching drive mode or the two phases for driving the switching elements in the second switching drive mode based on the angle of the rotor of the electric motor.

5. The battery heating system using a motor drive system according to claim 4, wherein, The controller is configured to: determine a reference phase of the first switching drive mode or two phases for driving the switching elements in the second switching drive mode to minimize a difference between an angle of the rotor in the dq stationary coordinate plane and an angle represented by the current supplied to the motor.

6. A battery heating system using a motor drive system, comprising: An inverter having an a-phase branch, a b-phase branch, and a c-phase branch, each branch including a pair of switching elements connected in series between both ends of the battery; A motor including an a-phase coil, a b-phase coil, and a c-phase coil, a first end of the a-phase coil being connected to a connection node between a pair of switching elements included in the a-phase branch; a first end of the b-phase coil being connected to a connection node between a pair of switching elements included in the b-phase branch; a first end of the c-phase coil being connected to a connection node between a pair of switching elements included in the c-phase branch, and a second end of the a-phase coil, a second end of the b-phase coil, and a second end of the c-phase coil being connected to each other; and A controller configured to: drive the switching elements such that a first interval and a second interval are alternately repeated, in the first interval, at least some of the switching elements are turned on, and in the second interval, all the switching elements are turned off; wherein the controller is configured to: In the first interval, drive the switching elements in a first switching drive mode or in a second switching drive mode; In the first switching drive mode, drive the switching elements such that an on / off state of the switching elements included in the branch corresponding to a reference phase among the a-phase, b-phase, and c-phases and an on / off state of the switching elements included in the branches corresponding to the remaining phases are in a complementary relationship; In the second switching drive mode, drive the switching elements such that an on / off state of the switching elements included in the branches corresponding to two phases among the a-phase, b-phase, and c-phases are in a complementary relationship, and drive the switching elements included in the remaining branch to be in an off state, When the current supplied to the motor in the second interval is zero, the second interval is switched to the first interval.

7. The battery heating system using a motor drive system according to claim 6, wherein, The controller is configured to: When using the first driving technique, in the first interval, perform control such that an on / off state of a pair of switching elements included in a plurality of branches and an on / off state of the remaining switching elements are in a complementary relationship; And Perform control such that an on / off state of the switching element connected to the positive terminal of the battery among the switching elements included in the branch corresponding to the reference phase and an on / off state of the switching element connected to the positive terminal of the battery among the switching elements included in the remaining branches are in a complementary relationship.

8. The battery heating system using the electric motor drive system according to claim 6, wherein, The controller is configured to: When applying the second switching drive mode, in the first interval, perform control according to the switching frequency such that an on / off state of a pair of switching elements included in a first branch corresponding to one of two selected phases is in a complementary relationship, and perform control according to the switching frequency such that an on / off state of a pair of switching elements included in a second branch corresponding to the other of the two selected phases is in a complementary relationship; And Execute control such that the state of the switching element in the first branch that is connected to the positive terminal of the battery is in a complementary relationship with the state of the switching element in the second branch that is connected to the positive terminal of the battery.

9. The battery heating system using the electric machine drive system according to claim 6, wherein, The controller is configured to: determine a reference phase to be applied in the first switching drive mode or two phases for driving the switching elements in the second switching drive mode based on the angle of the rotor of the motor.

10. The battery heating system using a motor drive system according to claim 9, wherein, The controller is configured to: determine a reference phase of the first switching drive mode or two phases of the switching elements driven in the second switching drive mode to minimize the difference between the angle of the rotor in the dq stationary coordinate plane and the angle represented by the current supplied to the motor.

11. The battery heating system using a motor drive system according to claim 9, wherein, The controller is configured to: drive the switching elements in the first switching drive mode when the quotient of the value obtained by adding 15° to the angle of the rotor divided by 30° is an even number, and drive the switching elements in the second switching drive mode when the quotient of the value obtained by adding 15° to the angle of the rotor divided by 30° is an odd number.

12. The battery heating system using a motor drive system according to claim 9, wherein, In the first switching drive mode, the controller is configured to: drive the switching elements by determining the a-phase as the reference phase when the angle of the rotor is from 0° to 30°, from 150° to 210°, and from 330° to 360°.

13. The battery heating system using a motor drive system according to claim 9, wherein, In the first switching drive mode, the controller is configured to: drive the switching elements by determining the c-phase as the reference phase when the angle of the rotor is from 30° to 90° and from 210° to 270°.

14. The battery heating system using a motor drive system according to claim 9, wherein, In the first switching drive mode, the controller is configured to: drive the switching elements by determining the b-phase as the reference phase when the angle of the rotor is from 90° to 150° and from 270° to 330°.

15. The battery heating system using a motor drive system according to claim 9, wherein, In the second switching drive mode, the controller is configured to: select the c-phase branch and the a-phase branch when the angle of the rotor is from 0° to 60° and from 180° to 240°, drive the on / off states of the switching elements included in the c-phase branch and the a-phase branch in a complementary relationship in the first interval, and turn off the switching elements included in the b-phase branch.

16. The battery heating system using an electric motor drive system according to claim 9, wherein, In the second switching drive mode, the controller is configured to: select the b-phase branch and the c-phase branch when the angle of the rotor is from 60° to 120° and from 240° to 300°, drive the on / off states of the switching elements included in the b-phase branch and the c-phase branch in a complementary relationship in the first interval, and turn off the switching elements included in the a-phase branch.

17. The battery heating system using the electric machine drive system according to claim 9, wherein, In the second switching drive mode, the controller is configured to: select the a-phase branch and the b-phase branch when the angle of the rotor is from 120° to 180° and from 300° to 360°, drive the on / off states of the switching elements included in the a-phase branch and the b-phase branch in a complementary relationship in the first interval, and turn off the switching elements included in the c-phase branch.

18. A battery heating method for a battery heating system using a motor drive system according to claim 6, comprising: Determining, by a controller, an interval of the angle of the rotor of the motor; Selecting, by the controller, one of the first switching drive mode and the second switching drive mode based on the interval; When the first switch driving mode is selected, in the first interval, the controller drives the switching element such that the on / off states of the switching elements included in the branch corresponding to the reference phase are in a complementary relationship with the on / off states of the switching elements included in the branches corresponding to the remaining phases; When the second switch driving mode is selected, in the first interval, the controller drives the switching element such that the on / off states of the switching elements included in the branches corresponding to two phases are in a complementary relationship, and the controller drives the switching element such that the switching elements included in the remaining branches are in an off state.

19. The method according to claim 18, wherein Selecting one of the first switch driving mode and the second switch driving mode includes: when the quotient of the value obtained by adding 15° to the angle of the rotor divided by 30° is an even number, driving the switching element in the first switch driving mode, and when the quotient of the value obtained by adding 15° to the angle of the rotor divided by 30° is an odd number, driving the switching element in the second switch driving mode.

20. The method according to claim 18, wherein Driving the switching element includes: when the first switch driving mode is selected, in the case where the angle of the rotor is from 0° to 30°, from 150° to 210°, and from 330° to 360°, driving the switching element by designating the a-phase as the reference phase.

21. The method according to claim 18, wherein Driving the switching element includes: when the first switch driving mode is selected, in the case where the angle of the rotor is from 30° to 90° and from 210° to 270°, driving the switching element by designating the c-phase as the reference phase.

22. The method according to claim 18, wherein Driving the switching element includes: when the first switch driving mode is selected, in the case where the angle of the rotor is from 90° to 150° and from 270° to 330°, driving the switching element by designating the b-phase as the reference phase.

23. The method according to claim 18, wherein, Driving the switching element includes: when the second switch driving mode is selected, in the case where the angle of the rotor is from 0° to 60° and from 180° to 240°, selecting the c-phase branch and the a-phase branch, and in the first interval, driving the on / off states of the switching elements included in the c-phase branch and the a-phase branch in a complementary relationship, and turning off the switching elements included in the b-phase branch.

24. The method according to claim 18, wherein, Driving the switching element includes: when the second switch driving mode is selected, in the case where the angle of the rotor is from 60° to 120° and from 240° to 300°, selecting the b-phase branch and the c-phase branch, and in the first interval, driving the on / off states of the switching elements included in the b-phase branch and the c-phase branch in a complementary relationship, and turning off the switching elements included in the a-phase branch.

25. The method according to claim 18, wherein, Driving the switching element includes: when the second switch driving mode is selected, in the case where the angle of the rotor is from 120° to 180° and from 300° to 360°, selecting the a-phase branch and the b-phase branch, and in the first interval, driving the on / off states of the switching elements included in the a-phase branch and the b-phase branch in a complementary relationship, and turning off the switching elements included in the c-phase branch.

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