Motor driving apparatus and control method thereof

Abstract

A motor driving apparatus includes a motor, a first inverter, a second inverter, a mode switching portion including a plurality of mode change-over switches, one end of each mode change-over switch being connected to the other end of each of a plurality of windings, and the other end of each of the plurality of windings being connected to the first inverter, the second inverter, a battery, and a controller. The other end of each of the mode change-over switches is connected with the other end of each of the other mode change-over switches to form a node, and the controller applies a zero-phase current to the motor in a state in which the other end of each of the plurality of windings is electrically separated from the node, thereby increasing the battery temperature.

Description

Technical Field

[0001] This invention relates to a motor drive device and its control method. More specifically, this invention relates to a motor drive device and its control method in an open-end winding configuration where inverters are connected to multiple winding ends on both sides of a motor winding, and a method for increasing battery temperature using zero-phase current. Background Technology

[0002] Typically, one end of the winding of each phase in a motor is connected to an inverter, and the other end is connected to the other end of the winding of other phases, thus forming a Y-type connection.

[0003] When driving the motor, the switching elements in the inverter are turned on and off by pulse width modulation, applying line voltage to the windings of the Y-connected motor to generate alternating current, thereby producing torque.

[0004] The fuel efficiency (or electrical efficiency) of environmentally friendly vehicles, such as electric vehicles powered by the torque generated by such motors, is determined by the power conversion efficiency of the inverter-motor system. Therefore, to improve fuel efficiency, it is important to maximize the power conversion efficiency of the inverter and the efficiency of the motor.

[0005] The efficiency of an inverter-motor system is primarily determined by the inverter's voltage utilization rate. When the vehicle's operating point, determined by the relationship between motor speed and torque, is established within a range with high voltage utilization, the vehicle's fuel efficiency can be improved.

[0006] Meanwhile, to improve fuel efficiency and vehicle starting and acceleration performance, a motor drive technology utilizing open-end winding (OEW) has been proposed in related technical fields. This technology does not short-circuit the other ends of each phase of the motor winding through a Y-connection; instead, it drives two inverters connected to the ends of multiple windings on the relevant sides of the motor winding.

[0007] Compared to the traditional Y-connected motor drive method, the motor drive technology using open end winding (OEW) has the advantage of increasing phase voltage, thereby improving voltage utilization and achieving higher output.

[0008] When a common DC power supply is applied to an inverter that is connected to the ends of multiple windings on the relevant sides of the motor windings, this motor drive technology using open-end windings generates a common-mode current due to the zero-phase voltage.

[0009] The foregoing is intended only to help understand the background of the present invention and is not intended to imply that the present invention falls within the scope of related technologies known to those skilled in the art. Summary of the Invention

[0010] Therefore, the present invention was made in view of the above-mentioned problems in the related art, and the present invention aims to provide a motor drive device and control method thereof, which can improve the battery temperature by means of zero-phase current between the two inverters when driving the motor using an open-end winding method (two inverters are respectively connected to multiple winding ends on the relevant sides of the motor winding).

[0011] The technical aspects to be achieved by this invention are not limited to those described above. Other technical aspects not mentioned will be clearly understood by those skilled in the art through the following description.

[0012] To achieve the above aspects, according to one aspect of the present invention, a motor drive device can be provided, the device comprising: a motor including a plurality of windings; a first inverter including associated terminals connected to one end of each of the plurality of windings; a second inverter including associated terminals connected to the other end of each of the plurality of windings; a mode switching unit including a plurality of mode switching switches, one end of each mode switching switch being connected to the other end of each of the plurality of windings, the other end of each mode switching switch being interconnected with the other end of each of the other mode switching switches to form a node; a battery electrically connected to both the first inverter and the second inverter; and a controller that, in a state where the plurality of mode switching switches are turned off and thus the other end of each of the plurality of windings is electrically disconnected from the node, applies a zero-phase current to the motor, thereby increasing the battery temperature.

[0013] For example, the controller can apply zero-phase current to the motor until the battery temperature reaches a preset target temperature.

[0014] For example, the motor can be thermally connected to the battery through coolant lines through which coolant flows for heat exchange with the battery.

[0015] For example, the controller can apply the zero-phase current based on the characteristics of the battery and the allowable range of zero-phase current.

[0016] For example, battery characteristics may include at least one of the battery's impedance and the maximum current that can pass through the battery.

[0017] For example, the controller can determine the characteristics of the battery based on at least one of the battery's temperature, voltage, and state of charge (SOC).

[0018] For example, the controller can determine the permissible range of zero-phase current based on the motor's output.

[0019] For example, taking into account the characteristics of the battery within the allowable range of zero-phase current application, the controller can determine the frequency and amplitude of the zero-phase current that maximizes the current through the battery's internal resistance, and apply the zero-phase current based on the determined frequency and amplitude.

[0020] To achieve the above aspects, according to one aspect of the present invention, a control method for a motor drive device can be provided, the method comprising: using a controller to electrically disconnect the other end of each of a plurality of windings from the node by turning off a plurality of mode switching switches; and using the controller to increase the battery temperature by applying a zero-phase current to the motor while the other end of each of the plurality of windings is electrically disconnected from the node.

[0021] For example, increasing battery temperature can include using a controller to apply zero-phase current to the motor until the battery temperature reaches a preset target temperature.

[0022] For example, the motor can be thermally connected to the battery through coolant lines through which coolant flows for heat exchange with the battery.

[0023] For example, increasing battery temperature can further include applying a zero-phase current using a controller based on battery characteristics and the permissible range of zero-phase current application.

[0024] For example, battery characteristics may include at least one of the battery's impedance and the maximum current that can pass through the battery.

[0025] For example, the control method of the motor drive device according to one aspect of the present invention may further include: using a controller to determine the characteristics of the battery based on at least one of the battery's temperature, voltage, and state of charge (SOC).

[0026] For example, the control method of the motor drive device according to one aspect of the present invention may further include: using a controller to determine the allowable range of zero-phase current based on the output of the motor.

[0027] For example, increasing battery temperature may further include: using a controller to determine the frequency and amplitude of the zero-phase current that maximizes the current through the battery's internal resistance by taking into account the characteristics of the battery within the allowable range of zero-phase current application, and then applying the zero-phase current based on the determined frequency and amplitude.

[0028] As described above, according to the motor drive device, the battery temperature is increased by utilizing zero-phase current that does not affect the motor torque, thus increasing the battery temperature not only when the vehicle is stopped but also when the vehicle is in motion.

[0029] In addition, the size and cost associated with separate dedicated circuits used to raise battery temperature can be reduced.

[0030] Furthermore, by increasing the battery temperature, the battery can be managed within a stable temperature range, thereby improving its output performance, charging performance, and lifespan. Attached Figure Description

[0031] The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, wherein:

[0032] Figure 1 This is a circuit diagram of a motor drive device according to one embodiment of the present invention;

[0033] Figure 2 This is a schematic diagram illustrating the switching of motor drive modes according to an embodiment of the present invention;

[0034] Figure 3 This is a block diagram illustrating a detailed configuration of a controller applied to a motor drive device according to an embodiment of the present invention;

[0035] Figure 4 This is a schematic diagram illustrating the heat exchange process of a motor drive device according to an embodiment of the present invention; and

[0036] Figure 5 This is a flowchart illustrating a control method for a motor drive device according to an embodiment of the present invention. Detailed Implementation

[0037] In the following description, embodiments disclosed herein will be described in detail with reference to the accompanying drawings. However, regardless of the reference numerals, the same reference numerals will be assigned to the same or similar components, and repeated descriptions will be omitted. The terms "module" and "part" used for components in the following description are given or used interchangeably for ease of writing only and have no distinguishing meaning or function in themselves. Furthermore, in describing embodiments disclosed herein, detailed descriptions of related known technologies will be omitted where it is determined that such detailed descriptions might obscure the essence of the embodiments disclosed herein. Moreover, the accompanying drawings are provided only to aid in understanding the embodiments disclosed herein. The technical ideas disclosed herein are not limited by the accompanying drawings, and all modifications, including those within the spirit and scope of the invention, should be understood to include equivalent or alternative forms.

[0038] Terms including ordinal numbers such as first, second, etc., may be used to describe various elements, but the elements are not limited by these terms. The terms mentioned above are used only for the purpose of distinguishing one component from another.

[0039] When a component is referred to as "connected" or "linked" to another component, it can be directly connected or linked to another component, but it should be understood that other components may exist in between. On the other hand, when a component is referred to as "directly connected" or "directly linked" to another component, it should be understood that no other components exist in between.

[0040] Unless the context clearly indicates otherwise, singular expressions include plural expressions.

[0041] In this specification, terms such as “comprising” or “having” are intended to indicate the presence of the features, values, steps, operations, components, parts or combinations thereof described in the specification, and it should be understood that this does not preclude the possibility of adding or having one or more other features, values, steps, operations, components, parts or combinations thereof.

[0042] Furthermore, the term "unit" or "controller" in names such as "motor control unit (MCU)" is a widely used term to name control devices (controllers) that control specific functions of a vehicle, and does not imply a general-purpose functional unit. For example, each controller may include a communication device, a memory, and one or more processors. The communication device communicates with other controllers or sensors to control the functions it is responsible for; the memory stores the operating system, or logic instructions, and input / output information; the one or more processors perform the judgments, calculations, decisions, etc., required to control the functions they are responsible for. A controller according to an exemplary embodiment of the invention can be a hardware device implemented through various electronic circuits (e.g., a computer, microprocessor, CPU, ASIC, circuit, logic circuit, etc.). The controller can be implemented using non-volatile memory and a processor that stores, for example, software instructions such as programs and reproducible algorithms, which, when executed, perform the various functions described below. The processor is configured to execute the software instructions such as programs and reproducible algorithms. Here, the memory and processor can be implemented as separate semiconductor circuits. Alternatively, the memory and processor can be implemented as a single integrated semiconductor circuit. The processor can be implemented as one or more processors.

[0043] Figure 1 This is a circuit diagram of a motor drive device according to one embodiment of the present invention.

[0044] refer to Figure 1 According to one embodiment, the motor drive device may include a first inverter 10, a second inverter 20, a motor 30 including a plurality of windings C1, C2 and C3 respectively corresponding to a plurality of windings, a mode switching unit 40, a battery 50, a DC capacitor (or DC link capacitor) 60 and a controller 70.

[0045] The first inverter 10 may include a plurality of first switching elements S11 to S16 connected to one end of a plurality of windings C1, C2, and C3, and the second inverter 20 may include a plurality of second switching elements S21 to S26 connected to the other end of the plurality of windings C1, C2, and C3. The mode switching unit 40 may include a plurality of mode switching switches S31, S32, and S33. One end of each of the mode switching switches S31, S32, and S33 is connected to the other end of the plurality of windings C1, C2, and C3, and the other end of each of the mode switching switches S31, S32, and S33 is interconnected with the other end of each of the other mode switching switches to form a node nd. The controller 70 can control the on / off states of the first switching elements S11, S12, S13, S14, S15 and S16, the second switching elements S21, S22, S23, S24, S25 and S26, and the mode switching switches S31, S32 and S33 based on the motor demand output (i.e., the motor torque command), the DC terminal voltage of the inverters 10 and 20 (i.e., the battery voltage), the motor phase current and the motor angle.

[0046] The first inverter 10 may include a plurality of branches 11, 12, and 13, which are supplied with a DC voltage in a DC capacitor 60 connected between two terminals of the battery 50. Each of branches 11, 12, and 13 may be electrically connected to a corresponding phase of a plurality of phases of the motor 30.

[0047] More specifically, the first branch 11 includes two switching elements S11 and S12 connected in series between the two terminals of the DC capacitor 60, and the two switching elements S11 and S12 are connected to one end of the winding C1 of one phase of the motor 30, thereby enabling input / output of AC power related to one phase of multiple phases. Similarly, the second branch 12 includes two switching elements S13 and S14 connected in series between the two terminals of the DC capacitor 60, and the two switching elements S13 and S14 are connected to one end of the winding C2 of one phase of the motor 30, thereby enabling input / output of AC power related to one phase of multiple phases. Additionally, the third branch 13 includes two switching elements S15 and S16 connected in series between the two terminals of the DC capacitor 60, and the two switching elements S15 and S16 are connected to one end of the winding C3 of one phase of the motor 30, thereby enabling input / output of AC power related to one phase of multiple phases.

[0048] The second inverter 20 may include a plurality of branches 21, 22, and 23, which are supplied with a DC voltage in a DC capacitor 60 connected between two terminals of the battery 50. Each of branches 21, 22, and 23 may be electrically connected to a corresponding phase of a plurality of phases of the motor 30.

[0049] More specifically, the first branch 21 includes two switching elements S21 and S22 connected in series between the two terminals of the DC capacitor 60, and the two switching elements S21 and S22 are connected to the other end of the winding C1 of one phase of the motor 30, thereby enabling input / output of AC power associated with one of the multiple phases. Similarly, the second branch 22 includes two switching elements S23 and S24 connected in series between the two terminals of the DC capacitor 60, and the two switching elements S23 and S24 are connected to the other end of the winding C2 of one phase of the motor 30, thereby enabling input / output of AC power associated with one of the multiple phases. Additionally, the third branch 23 includes two switching elements S25 and S26 connected in series between the two terminals of the DC capacitor 60, and the two switching elements S25 and S26 are connected to the other end of the winding C3 of one phase of the motor 30, thereby enabling input / output of AC power associated with one of the multiple phases.

[0050] One end of each of the multiple mode switching switches S31, S32, and S33 can be connected to the corresponding other end of multiple windings C1, C2, and C3. The other ends of each of the multiple mode switching switches S31, S32, and S33 are interconnected with the other ends of each of the other mode switching switches to form a node nd. The multiple mode switching switches S31, S32, and S33 can employ various switching devices known in the related art, such as MOSFETs, IGBTs, thyristors, relays, etc.

[0051] although Figure 1 Not shown, but the motor drive may further include a so-called Y capacitor (Y-Cap), which consists of two capacitors connected in series between a positive (+) DC terminal and a negative (-) DC terminal, and grounded between the capacitors.

[0052] The controller 70 can control the motor 30 to drive it by controlling the switching elements S11, S12, S13, S14, S15, S16, S21, S22, S23, S24, S25 and S26 included in the first inverter 10 and the second inverter 20 through pulse width modulation based on the output demand of the motor 30.

[0053] Additionally, the controller 70 can control the on / off state of the mode switching switches S31, S32, and S33 included in the mode switching unit 40 according to the motor drive mode. The motor drive mode may include a first drive mode and a second drive mode. In this case, the first drive mode may be referred to as the "closed end winding (CEW) mode" and the second drive mode may be referred to as the "open end winding (OEW) mode".

[0054] More specifically, when CEW mode is executed, controller 70 can control mode switching switches S31, S32, and S33 to switch to the ON state, and drive motor 30 through the first inverter 10 of the two inverters 10 and 20. When ON, mode switching switches S31, S32, and S33 can electrically connect the other end of each of the multiple windings C1-C3 to node nd. For example, node nd, located at the other end of mode switching switches S31, S32, and S33, becomes the neutral point of motor 30.

[0055] In contrast, when executing OEW mode, controller 70 can control mode switching switches S31, S32, and S33 to switch to the off state, and drive motor 30 through two inverters 10 and 20. Mode switching switches S31, S32, and S33 can electrically disconnect the other end of each of the multiple windings C1-C3 from the node nd of the multiple windings C1-C3 in the off state. For example, the node nd interconnected by the other ends of each of mode switching switches S31, S32, and S33 is not used as the neutral point of motor 30, and motor 30 is connected to both the first inverter 10 and the second inverter 20.

[0056] Figure 2 This is a schematic diagram illustrating the switching of motor drive modes according to an embodiment of the present invention.

[0057] refer to Figure 2 The diagram shows the motor's operating point mapping, which depicts the output limit curve L1 for CEW mode, the output limit curve L2 for OEW mode, and the mode switching baseline L3 based on the efficiency mapping.

[0058] Output limit curves L1 and L2 can represent the motor output torque limit for each motor speed (e.g., RPM) under the corresponding motor drive mode. Within at least a portion of the RPM range, output limit curve L2 has a higher output limit than output limit curve L1, and output limit curves L1 and L2 can be set by taking into account the durability, heat generation, and current controllability of the motor and inverter.

[0059] The mode-switching baseline L3 based on the efficiency map (not shown) can correspond to the boundary between the high-efficiency regions of CEW mode and OEW mode. The efficiency map can contain information about which mode (CEW or OEW) has higher efficiency in various combinations of motor torque and reverse flux, and can be presented in tabular form depending on the implementation. For example, the efficiency map can be derived based on experimental measurements of motor losses according to motor speed and torque under each motor drive mode for each DC terminal voltage of the inverter. In this case, the motor's reverse flux can be inversely proportional to the inverter's DC terminal voltage (i.e., battery voltage) and directly proportional to the motor speed.

[0060] According to the implementation scheme, and based on the specifications of the motor drive unit, the mode switching reference line L3 can have a shape such as L3'. However, Figure 2 The mode switching baselines L3 and L3' shown are exemplary and not necessarily limited to them.

[0061] The controller 70 can refer to an efficiency map and bidirectionally switch between CEW and OEW modes based on the motor's torque command value and reverse flux to change the motor drive mode according to the mode switching reference line L3. At this time, the reverse flux value can be calculated based on the motor's torque command, the inverter's DC terminal voltage, and the motor's required speed. According to the implementation scheme, the controller 70 can correct the mode switching reference line by considering the output limitations or hysteresis of the motor drive mode. For example, the motor drive mode can be switched based on the corrected mode switching reference line, according to the motor's torque command value and reverse flux value.

[0062] Figure 3 This is a block diagram illustrating the detailed configuration of a controller applied to a motor drive device according to an embodiment of the present invention.

[0063] The controller 70 may include a zero-phase current command map 41 and a current controller 42, wherein the current controller 42 may be configured to include a first current controller 421, a second current controller 422, a first data map 423, a second data map 424, a third harmonic calculator 425, and an adder 426.

[0064] The first current controller 421 can transmit the dq-axis current command I determined by the current command mapping 41. dq * The dq axis current I flowing through motor 100 dq The comparison is performed, and the dq-axis voltage command V for the motor is generated to reduce errors. dq * .

[0065] The dq axis current I flowing through motor 30dq This can be achieved by converting the motor's rotation angle θ into dq coordinates, and by converting the values ​​of the currents flowing through each phase winding of the motor, detected by current sensors, into the form of dq-axis currents. The techniques for converting the abc coordinates (including the a-axis, b-axis, and c-axis corresponding to each phase of the motor) to d-axis and q-axis coordinates (Clarke / Park transformation) and their reverse conversion (inverse Clarke / Park transformation) are well-known in related technologies, and therefore will not be explained separately.

[0066] The first current controller 421 can be implemented in various forms such as a proportional-integral (PI) controller, a proportional (P) controller, an integral (I) controller, etc., and can be implemented as a PI controller.

[0067] The second current controller 422 can transmit the zero-phase current command I of the motor. n * The zero-phase current I flowing through motor 30 n The comparison is performed, and a voltage value Vn0 is generated to reduce the error. * .

[0068] The zero-phase current I flowing through motor 30 n The value can be obtained by converting the current detected by current sensors or the like from the current flowing through each phase winding of the motor using a rotational transformation.

[0069] The second current controller 422 can be implemented in various forms such as a proportional-integral (PI) controller, a proportional (P) controller, an integral (I) controller, etc.

[0070] The third harmonic calculator 425 can be based on the motor's rotation angle θ and speed ω. r Zero-phase magnetic flux amplitude λ n,amp Phase λ of zero-phase magnetic flux n,phase To calculate the third harmonic component in the zero-phase voltage of the motor.

[0071] The third harmonic component calculated by the third harmonic calculator 425 is added to the output value V of the second current controller 422 by the adder 426. n0 * The values ​​are added together to perform feedforward compensation. That is, the output value V of the second current controller 422, calculated by the adder 426, is... n0 * With the output value V from the third harmonic calculator 425 n,FF The sum of these values ​​can be used as the zero-phase voltage command value V for pulse width modulation control of the motor. n .

[0072] Meanwhile, the amplitude λ of the zero-phase magnetic flux of the motorn,amp and phase λ n,phase This can be determined through data mapping 423 and 424.

[0073] In addition, zero-phase current command I n * The output of motor 30 (demanded torque and speed), battery 50 voltage, temperature, and SOC can be used as input values, and a zero-phase current command I corresponding to the input values ​​can be generated. n * The zero-phase current command mapping is determined.

[0074] Simultaneously, when multiple mode switching switches S31, S32, and S33 are turned off and the other end of each of the multiple windings C1, C2, and C3 is electrically disconnected from the node (i.e., in OEW mode), the motor drive device according to one embodiment of the invention applies a zero-phase current to the motor 30 that does not affect the torque, thereby increasing the temperature of the battery 50. Thus, even during driving, the battery can be managed within a suitable temperature range, while reducing the volume and cost associated with increasing battery temperature.

[0075] For example, the controller 70 can apply zero-phase current to the motor 30 until the temperature of the battery 50 reaches a preset target temperature.

[0076] Specifically, the controller 70 can apply a zero-phase current to the motor 30 based on the characteristics of the battery and the allowable range of zero-phase current. For this purpose, the zero-phase current command mapping 41 can be referenced.

[0077] More specifically, the characteristics of battery 50 may include at least one of the impedance of battery 50 and the maximum current that can flow through the battery. These characteristics may be determined based on at least one of battery temperature, voltage, and state of charge (SOC). Such characteristics can be determined by experimental values ​​of the temperature, voltage, and SOC behavior of battery 50, which may be reflected in the zero-phase current command map 41.

[0078] Furthermore, the permissible range of zero-phase current application can be determined based on the output (demanded torque and speed) of motor 30. It is necessary to ensure the d-axis and q-axis currents that generate torque. Consequently, the range of zero-phase current that can be used to increase the temperature of battery 50 becomes limited.

[0079] Furthermore, the controller 70 can integrate the above information and determine the frequency and amplitude of the zero-phase current by considering the battery characteristics within the allowable range of the zero-phase current. This ensures that the current through the battery's internal resistance is maximized. The controller can then generate a zero-phase current command I. n * A zero-phase current is applied based on the determined frequency and amplitude.

[0080] For example, by applying a zero-phase current while taking into account the impedance of battery 50, the frequency at which the amplitude of the zero-phase current is maximized under current battery conditions can be determined. As the amplitude of the applied zero-phase current increases, the current through the internal resistance of the battery increases, thereby generating more heat within battery 50.

[0081] Meanwhile, in one embodiment, the temperature of the battery 50 may increase not only due to its own heat generation, but also due to the heat generated by the motor 30 which is thermally connected to the battery 50.

[0082] This will refer to Figure 4 To explain.

[0083] Figure 4 This is a schematic diagram illustrating the heat exchange process of a motor drive device according to an embodiment of the present invention.

[0084] refer to Figure 4 The motor 30 can be thermally connected to the battery 50 via a coolant line (CL) through which coolant flows for heat exchange with the battery 50. In other words, the motor 30 and the battery 50 can share the coolant line (CL). Figure 4 As shown, when the motor 30 is positioned in front of the battery 50 in the coolant flow of the coolant line (CL), the heat generated in the motor 30 can be transferred to the battery 50 through the coolant, resulting in an increase in the temperature of the battery 50. In particular, since the motor 30 generates heat when a zero-phase current is applied, the temperature of the battery 50 can increase as the generated heat is transferred through the cooling water line (CL).

[0085] at the same time, Figure 4 The main components required to illustrate one implementation are shown. Other components may be present between the motor 30 and the battery 50, as well as at their front and rear ends. In this case, these components may also serve as heat sources.

[0086] In the following text, reference will be made to Figure 5 A control method for a motor drive device according to one embodiment of the present invention is described.

[0087] refer to Figure 5 First, in step S510, the controller 70 can acquire information about the temperature, voltage, and state of charge (SOC) of the battery 50, which can be provided by the battery management system (BMS) equipped in the vehicle. In step S520, based on the acquired information, the controller 70 can determine battery characteristics, such as the impedance of the battery 50 and the maximum current that can flow through the battery 50.

[0088] Furthermore, in step S530, the controller 70 can acquire information about the output of the motor 30, such as the required torque and speed. This information can be provided by a controller installed in the vehicle to control the motor or a higher-level controller that manages it. Then, in step S540, based on the acquired information, the controller 70 can determine the permissible range for the zero-phase current.

[0089] Subsequently, in step S550, based on the currently determined battery characteristics and the allowable range of the zero-phase current, the controller 70 can determine the frequency and amplitude of the zero-phase current. For example, the frequency and amplitude of the zero-phase current can be determined to maximize the current through the internal resistance of the battery 50.

[0090] In step S560, the controller 70 can generate a zero-phase current command based on the determined frequency and amplitude of the zero-phase current, and apply the zero-phase current. When the temperature of the battery 50 reaches the target temperature due to the application of the zero-phase current (if the condition in step S570 is met), one cycle of increasing the battery temperature is completed. When the temperature of the battery 50 does not reach the target temperature (when the condition in step S570 is not met), the entire process is repeated.

[0091] In motor drive systems, zero-phase current, which does not affect motor torque, can be used to increase battery temperature, thereby raising the battery temperature both when the vehicle is stopped and when it is in motion.

[0092] In addition, the size and cost associated with separate dedicated circuits used to raise battery temperature can be reduced.

[0093] Although various embodiments of the invention have been described for illustrative purposes, those skilled in the art will understand that various modifications, additions, and substitutions may be made without departing from the scope and spirit of the invention as disclosed in the appended claims.

Claims

1. An electric motor drive apparatus, the apparatus comprising: an electric motor including a plurality of windings; a first inverter connected to one end of each winding of the plurality of windings; a second inverter connected to the other end of each winding of the plurality of windings; a mode switching section including a plurality of mode switching switches, one end of each mode switching switch being connected to the other end of each winding of the plurality of windings, the other end of each mode switching switch being connected to each other to form a node; a battery electrically connected to both the first inverter and the second inverter; and a controller configured to apply a zero-phase current to the electric motor to increase a temperature of the battery in a state where the plurality of mode switching switches are turned off so that the other end of each winding of the plurality of windings is electrically separated from the node. The controller is configured to apply the zero-phase current to the electric motor until the temperature of the battery reaches a preset target temperature.

2. The motor drive apparatus according to claim 1, wherein The electric motor is thermally connected to the battery through a coolant line in which a coolant for heat exchange with the battery flows inside.

3. The motor drive apparatus according to claim 1, wherein The controller is configured to apply the zero-phase current based on characteristics of the battery and an allowable application range of the zero-phase current.

4. The motor drive apparatus according to claim 1, wherein The characteristics of the battery include:

5. The motor drive apparatus according to claim 4, wherein one or more of an impedance of the battery and a maximum current that can pass through the battery. The controller is configured to determine the characteristics of the battery based on one or more of a temperature, a voltage, and a state of charge of the battery.

6. The motor drive apparatus according to claim 5, wherein The controller is configured to determine the allowable application range of the zero-phase current based on an output of the electric motor.

7. The motor drive apparatus according to claim 4, wherein The controller is configured to determine a frequency and a magnitude of the zero-phase current that maximizes a current passing through an internal resistance of the battery based on the characteristics of the battery within the allowable application range of the zero-phase current, and to apply the zero-phase current based on the determined frequency and magnitude.

8. The motor drive apparatus according to claim 4, wherein 9. A method for controlling an electric motor drive apparatus, the electric motor drive apparatus including an electric motor, a first inverter, a second inverter, a mode switching section, and a battery, the electric motor including a plurality of windings, the first inverter being connected to one end of each winding of the plurality of windings, the second inverter being connected to the other end of each winding of the plurality of windings, the mode switching section including a plurality of mode switching switches, one end of each mode switching switch being connected to the other end of each winding of the plurality of windings, the other end of each mode switching switch being connected to each other to form a node, the battery being electrically connected to both the first inverter and the second inverter, the method comprising: electrically separating, by a controller, the other end of each winding of the plurality of windings from the node by turning off the plurality of mode switching switches; increasing, by the controller, a temperature of the battery by applying a zero-phase current to the electric motor in a state where the other end of each winding of the plurality of windings is electrically separated from the node. Increasing the temperature of the battery includes:

10. The method of claim 9, wherein, applying the zero-phase current to the electric motor until the temperature of the battery reaches a preset target temperature. The electric motor is thermally connected to the battery through a coolant line in which a coolant for heat exchange with the battery flows inside.

11. The method of claim 9, wherein, Increasing the temperature of the battery further includes:

12. The method of claim 9, wherein, applying the zero-phase current based on characteristics of the battery and an allowable application range of the zero-phase current. The characteristics of the battery include:

13. The method of claim 12, wherein, one or more of an impedance of the battery and a maximum current that can pass through the battery. one or more of an impedance of the battery and a maximum current capable of passing through the battery.

14. The method of claim 13, further comprising: determining, by the controller, a characteristic of the battery based on one or more of a temperature, a voltage, and a state of charge of the battery.

15. The method of claim 12, further comprising: determining, by the controller, an allowable application range of the zero-phase current based on the output of the motor.

16. The method of claim 12, wherein, increasing the temperature of the battery further comprises determining, based on the characteristic of the battery, a frequency and a magnitude of the zero-phase current that maximizes a current passing through an internal resistance of the battery within the allowable application range of the zero-phase current, applying the zero-phase current based on the determined frequency and magnitude.

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