Motor driving device, electrified vehicle, and method for controlling motor driving system

Abstract

Disclosed are a motor driving device, an electrified vehicle, and a method for controlling a motor driving system. The motor driving device comprises: a multi-phase motor having a plurality of windings corresponding to each of a plurality of phases; an inverter controlling a phase current flowing in the multi-phase motor; and a controller which increases the heat generation of the motor through voltage utilization rate restriction.

Description

Control method for motor drive device, electric vehicle and motor drive system

[0001] The present disclosure relates to a motor drive device capable of controlling heat generation of a motor, an electric vehicle, and a control method for a motor drive system.

[0002] The heating and cooling systems of electric vehicles are integrated into the HVAC (Heat, Ventilation, and Air Conditioning) system. During the cold winter months, heating systems utilizing PTC (Positive Temperature Coefficient) heaters are primarily used, and in electric vehicles in particular, PTC heaters are used as the primary heating source.

[0003] When using a PTC heater as a heating source, power consumption increases significantly, it is difficult to secure price competitiveness due to PTC components, and the driving range of electric vehicles may be reduced due to power consumption of high-voltage batteries.

[0004] With the proliferation of electric vehicles, interest in their energy efficiency is growing. In particular, with growing concern over power consumption for winter heating, research is actively underway on ways to improve the efficiency of vehicle thermal management systems using heat pump systems.

[0005] The matters described as background technology above are only intended to enhance understanding of the background of the present disclosure, and should not be taken as an admission that they correspond to prior art already known to a person of ordinary skill in the art.

[0006] The present disclosure provides a method for controlling a motor drive device, an electric vehicle, and a motor drive system that can be used as a heating source by controlling heat generation even without a separate PTC heater.

[0007] The problems to be solved through the embodiments of the present disclosure are not limited to the problems mentioned above, and other problems not mentioned will be clearly understood by those skilled in the art from the description below.

[0008]

[0009] A motor driving device according to the present disclosure for achieving the above object may include a multi-phase motor having a plurality of windings corresponding to each of a plurality of phases, an inverter for controlling phase currents flowing in the multi-phase motor, and a controller for driving the multi-phase motor in a first mode for controlling the inverter with MTPA (Maximum Torque Per Ampere) control based on the speed of the multi-phase motor being lower than a preset base speed, or for driving the multi-phase motor in a second mode for controlling the inverter to have a lower voltage utilization ratio than the first mode to increase the heat generation amount of the multi-phase motor.

[0010] For example, the controller can determine the maximum available voltage of the inverter corresponding to the second mode by multiplying the maximum available voltage of the inverter corresponding to the first mode by a preset limiting factor in the second mode.

[0011] For example, the limiting factor may be set to drive the motor at a point where the power consumption of the motor is maximized under an output torque corresponding to a torque command for the motor.

[0012] For example, the controller can generate a current command based on a map in which the output torque of the multi-phase motor is predefined according to the size of the d-axis current and the size of the q-axis current, and control the inverter based on the current command.

[0013] For example, the limiting factor can be set to change the phase of the voltage output by the inverter by a preset phase angle.

[0014] For example, the phase angle may be set based on the phase at which the power consumption of the motor is maximum, measured for different voltage utilization rates, under an output torque corresponding to a torque command for the motor.

[0015] For example, the multi-phase motor may be an Interior Permanent Magnet Synchronous Motor (IPMSM).

[0016] In order to achieve the above object, an electric vehicle according to the present disclosure may include a multi-phase motor having a plurality of windings corresponding to each of a plurality of phases, an inverter controlling a phase current flowing in the multi-phase motor, and a controller driving the multi-phase motor in a first mode that controls the inverter with MTPA (Maximum Torque Per Ampere) control based on the speed of the multi-phase motor being lower than a preset base speed, or driving the multi-phase motor in a second mode that controls the inverter to have a lower voltage utilization rate than the first mode to increase the heat generation of the multi-phase motor.

[0017] A control method of a motor drive system according to the present disclosure for achieving the above object is a control method of a motor drive system including a multi-phase motor having a plurality of windings corresponding to each of a plurality of phases and an inverter for controlling phase currents flowing in the multi-phase motor, the control method including determining a speed of the multi-phase motor, lowering a voltage utilization ratio of the inverter based on the speed of the multi-phase motor being lower than a preset base speed, generating a current command for the motor based on a torque command and the voltage utilization ratio, controlling the inverter based on the current command, and driving the multi-phase motor to increase heat generation of the multi-phase motor.

[0018]

[0019] According to various embodiments as described above, the role of the PTC heater can be replaced by implementing forced heating through inefficiency control of the electric compressor in the heat pump system of an electric vehicle, thereby reducing cost through elimination of PTC components and solving power consumption problems.

[0020] The effects that can be obtained through the embodiments of the present disclosure are not limited to the effects mentioned above, and other effects not mentioned can be clearly understood by a person having ordinary skill in the art from the description below.

[0021]

[0022] Figure 1 is a configuration diagram of a heat pump system equipped in an electric vehicle.

[0023] Figure 2 is a circuit diagram showing an example of a motor drive system according to one embodiment.

[0024] Figure 3 is a block diagram showing a process in which a controller controls an inverter and a motor according to one embodiment.

[0025] Figure 4 is a diagram showing the MTPA control process of a controller according to one embodiment.

[0026] Figure 5 is a diagram showing an MTPV control process of a controller according to one embodiment.

[0027] FIG. 6 is a diagram showing a control process according to one embodiment of the present invention in which a controller limits voltage utilization.

[0028] FIG. 7 is a diagram showing changes in the output voltage of the inverter and the phase current of the motor as the controller limits the voltage utilization rate according to one embodiment.

[0029] Figure 8 is a flowchart showing a control method of a motor drive system according to one embodiment.

[0030]

[0031] In describing the embodiments disclosed in this specification, if it is determined that a detailed description of related known technology may obscure the gist of the embodiments disclosed in this specification, the detailed description thereof will be omitted. In addition, the attached drawings are only intended to facilitate easy understanding of the embodiments disclosed in this specification, and the technical ideas disclosed in this specification are not limited by the attached drawings, and it should be understood that they include all modifications, equivalents, and substitutes included in the spirit and technical scope of the present disclosure. The following disclosure is not intended to limit the present disclosure to the described form or a specific field, and it is contemplated that various alternative embodiments and modifications of the present disclosure are possible, whether explicitly described or implied herein. A person of ordinary skill in the art to which the present disclosure pertains will recognize that the form and details of the contents of the present disclosure may be changed.

[0032] The present disclosure has been described with reference to specific embodiments. However, as will be appreciated by those skilled in the art, the various embodiments disclosed herein may be modified or implemented in various other ways without departing from the spirit and scope of the present disclosure. Accordingly, the following description is to be considered illustrative and is intended to teach those skilled in the art how to make and use various embodiments. It is to be understood that the forms of the disclosure shown and described herein are to be taken as representative embodiments. Equivalent elements, materials, processes, or steps may be substituted for those exemplified and described herein. The terms "including," "comprising," "incorporating," "consisting of," "have," "is," and the like, used in describing the present disclosure, are to be construed in a non-exclusive manner, that is, to allow for the identification of items, components, or elements that are not explicitly listed. Also, references to the singular should be understood to include references to the plural.

[0033] Furthermore, the various embodiments disclosed herein are to be taken in an illustrative and explanatory sense and should not be construed as limiting the scope of the present disclosure. Any references to joining (e.g., attached, affixed, coupled, connected, etc.) are used solely to aid understanding of the present disclosure and do not limit the location, orientation, or use of any component or method disclosed herein. Accordingly, any references to joining, if any, should be interpreted broadly. Moreover, such references to joining do not imply that two or more elements are directly connected to each other. Additionally, any numeric terms, such as "first," "second," "third," "primary," "secondary," "main," or any other generic or numerical terms, are to be taken only as identifiers to aid in understanding the various components, forms, variations, or modifications of the present disclosure, and do not imply any limitation on any component, form, variation, or modification, or any order or preference therefor. That is, while such expressions may be used to describe various components, the components are not limited by such expressions. Such expressions are used only to distinguish one component from another.

[0034] The suffixes "module" and "part" used for components in the following description are given or used interchangeably only for the convenience of writing specifications, and do not have distinct meanings or roles in themselves.

[0035] When a component is referred to as being "connected" or "connected" to another component, it should be understood that it may be directly connected or connected to that other component, but that there may be other components intervening. Conversely, when a component is referred to as being "directly connected" or "connected" to another component, it should be understood that there are no other components intervening.

[0036] Additionally, the terms “Unit” or “Control Unit” included in the name are terms widely used to name a control device (Controller) that controls a specific function of a vehicle, and do not mean a generic function unit.

[0037] The controller may include a communication device that communicates with other controllers or sensors to control the function in charge, a memory that stores operating system or logic commands and input / output information, and one or more processors that perform judgments, calculations, decisions, etc. necessary for controlling the function in charge.

[0038] Any number of components or a variety of components in any of the configurations described herein may be incorporated into the disclosure described herein. The components may include any combination of the features described herein and may be arranged in any of the various configurations described herein. The concepts relating to the structure and arrangement of the components of the present disclosure, as well as their use and operation, may be applied to any number of embodiments in any combination, as well as to the specific embodiments discussed herein. Embodiments that include those having various features in various arrangements are described below with reference to the drawings.

[0039] Hereinafter, various embodiments disclosed in the present specification will be described in detail with reference to the attached drawings. Regardless of the drawing numbers, identical or similar components are given the same reference numbers and redundant descriptions thereof will be omitted.

[0040] A motor driving device according to the present disclosure may include a multi-phase motor having a plurality of windings corresponding to each of a plurality of phases, an inverter controlling phase currents flowing in the multi-phase motor, and a controller driving the multi-phase motor in a first mode that controls the inverter with MTPA (Maximum Torque Per Ampere) control based on the speed of the multi-phase motor being lower than a preset base speed, or in a second mode that controls the inverter to have a lower voltage utilization ratio than in the first mode to increase the heat generation of the multi-phase motor.

[0041] The multi-phase motor can be implemented as an Interior Permanent Magnet Synchronous Motor (IPMSM), which enables efficient control and heat generation control of the electric compressor. The controller can determine the maximum available voltage of the inverter corresponding to the second mode by multiplying the maximum available voltage of the inverter corresponding to the first mode by a preset limiting factor in the second mode. The limiting factor can be set to drive the motor at a point where the motor's power consumption is maximum under an output torque corresponding to the torque command for the motor, thereby performing heat generation control (or inefficiency control).

[0042] First, the overall configuration of the heat pump system equipped in the electric vehicle of the present disclosure will be described with reference to FIG. 1.

[0043] Fig. 1 is a diagram illustrating a configuration of a heat pump system equipped in an electric vehicle (1). As illustrated in Fig. 1, the heat pump system may include an evaporator (100), a compressor (200), a condenser (300), and an expansion valve (400). The heat pump system illustrated in Fig. 1 is primarily illustrated with respect to a configuration related to an embodiment, and it is apparent to those skilled in the art that the implementation of an actual vehicle heat pump system may include more or fewer components than this.

[0044] Below, each component is described in detail.

[0045] The evaporator (100) can evaporate low-temperature refrigerant and absorb heat from the surroundings. For example, a heat pump system can absorb heat from the outside air that comes into contact with the evaporator (100).

[0046] The compressor (200) can perform the function of compressing low-pressure refrigerant vapor supplied from the evaporator (100) to high pressure, and the temperature of the refrigerant rises during the compression process.

[0047] The condenser (300) can condense and liquefy the high-temperature, high-pressure refrigerant supplied from the compressor (200), and condensation heat can be released during this process. For example, the condenser (300) can release the refrigerant into the interior of an electric vehicle (1) to provide heating.

[0048] The expansion valve (400) can perform the function of expanding the high-pressure liquid refrigerant supplied from the condenser (300) to a low pressure and supplying it back to the evaporator (100).

[0049] In the present disclosure, the compressor (200) can be implemented as an electric compressor and can be utilized as a heat source to replace a PTC heater through heat generation control according to the disclosed embodiment. This can solve the problems of increased power consumption and increased component costs due to PTC heaters in existing electric vehicles.

[0050] Next, a specific circuit configuration of the motor drive system of the present disclosure will be described with reference to FIG. 2.

[0051] Referring to FIG. 2, a motor driving device equipped in an electric vehicle (1) may include a high-voltage battery (210), a direct current capacitor (or DC-Link capacitor, 220), an inverter (230), a motor (240) having a plurality of windings (C1, C2, C3) corresponding to each of a plurality of phases, and a controller (250).

[0052] The inverter (230) may include a plurality of switching elements (S1, S2, S3, S4, S5, S6) connected to one end of each of a plurality of windings (C1, C2, C3) of the motor (240). The switching elements (S1, S2, S3, S4, S5, S6) may be implemented as an IGBT (Insulated Gate Bipolar Transistor) or a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor), and may thereby perform a function of converting a direct current voltage into a three-phase alternating current voltage.

[0053] The controller (250) can control the on / off states of a plurality of switching elements (S1, S2, S3, S4, S5, S6) based on the torque command for the motor (240), the DC voltage of the inverter (230) (i.e., the voltage of the battery), the phase current of the motor, and the motor angle. The controller (250) can independently control the torque and magnetic flux of the motor (240) through a vector control method, thereby enabling efficient operation and heat generation control of the motor (240).

[0054] The inverter (230) may include a plurality of legs (31, 32, 33) to which a DC voltage formed in a DC capacitor (220) connected between both ends of a high-voltage battery (210) is applied. Each leg (31, 32, 33) may be electrically connected to a plurality of phases of a motor (240).

[0055] More specifically, the first leg (31) includes two switching elements (S1, S2) that are mutually connected in series between both ends of a DC capacitor (220), and the connection node of the two switching elements (S1, S2) can be connected to one end of a winding (C1) of one phase within the motor (240) so that AC power corresponding to one phase among the plurality of phases is input and output. Similarly, the second leg (32) includes two switching elements (S3, S4) that are mutually connected in series between both ends of a DC capacitor (220), and the connection node of the two switching elements (S3, S4) can be connected to one end of a winding (C2) of one phase within the motor (240) so that AC power corresponding to one phase among the plurality of phases is input and output. In addition, the third leg (33) includes two switching elements (S5, S6) that are connected in series with each other between both ends of a DC capacitor (220), and the connection node of the two switching elements (S5, S6) can be connected to one end of a winding (C3) of one phase in the motor (240) so that AC power corresponding to one phase among the plurality of phases is input and output.

[0056] Through this three-phase inverter structure, direct current voltage can be converted into three-phase alternating current voltage, and the speed and torque of the motor (240) can be precisely controlled through PWM (Pulse Width Modulation) control. In particular, the heat generation amount of the motor (240) can be adjusted through independent control of each leg (31, 32, 33), which can contribute to improving the heating performance of the heat pump system.

[0057] Although not shown in FIG. 2, the motor drive device may further include a so-called Y-capacitor (Y-Cap), which is composed of two capacitors connected in series between the positive (+) DC terminal and the negative (-) DC terminal, and the connection node between the capacitors is grounded. The Y-capacitor can serve to suppress common mode noise, thereby improving the electromagnetic compatibility performance of the system.

[0058] The controller (250) can control the motor (240) to be driven by switching the switching elements (S1, S2, S3, S4, S5, S6) included in the inverter (230) through pulse width modulation control based on a torque command for the motor (240). The controller (250) can perform vector control based on a dq coordinate system, thereby independently controlling the torque and magnetic flux of the motor (240), thereby enabling optimal efficiency or intentional inefficiency operation.

[0059] Next, with reference to Fig. 3, the internal configuration of the controller described above and the specific operation process of the control system will be described.

[0060] Fig. 3 is a block diagram showing a process in which a controller (250) controls an inverter (230) and a motor (240). As shown in Fig. 3, the controller (250) may include a speed control unit (251), a current map (252), a stationary-rotating coordinate system conversion unit (253), a current control unit (254), a rotating-stationary coordinate system conversion unit (255), and a voltage modulation unit (256).

[0061] The speed control unit (251) compensates for the difference between the speed (ω) of the motor (240) and the speed command to obtain the torque command (T * ) can be generated. For example, the speed control unit (251) can be implemented as a PI controller, through which the speed of the motor (240) can be precisely controlled. The generated torque command (T *) can be converted into d-axis and q-axis current commands through current map (252) query.

[0062] The current map (252) may mean a map in which the output torque of the multi-phase motor (240) is predefined according to the size of the d-axis current and the size of the q-axis current, and by referring to this, the current command (i) on the dq-rotational coordinate system r dq * ) can be generated. The optimal current combination for MTPA control and the current combination for MTPV control can be stored in the current map (252), and the controller (250) can select an appropriate current command according to the operating conditions of the motor (240). In addition, in the second mode, an intentionally inefficient current combination can be selected to increase the heat generation of the motor (240).

[0063] Specifically, the current map (252) is the maximum available voltage (or limit voltage, V max ) and the maximum available current (or limit current, I max ) can generate a current command considering the limitations. Here, V max The value may be the limit voltage of the inverter (230), I max The value may be the limit current of the inverter (230). In the second mode, the controller (250) limits the voltage utilization rate to V max The value can be reduced, which allows the motor (240) to be driven out of the MTPA control area and into an inefficient operating point.

[0064] The stationary-rotating coordinate system conversion unit (253) converts the electrical angle of the rotor in the motor (240), i.e., the motor angle (θ) r ) receives information and the phase current (i) flowing in each winding of the motor (240) abc ) can be expressed in the dq-rotation coordinate system (i r dq ) Motor angle (θ r) information may be received from a sensor such as an encoder, resolver, or hall sensor, or may be an estimated value through the back EMF of the motor (240). Through this coordinate transformation, a three-phase AC system can be simplified into a two-axis DC system, which can provide a basis for independently controlling the torque and magnetic flux of the motor (240).

[0065] The current control unit (254) provides a current command (i r dq * ) and the current flowing in the motor winding (i r dq ) based on the current command (i r dq * ) and motor current (i r dq ) voltage reference (v) that compensates for the difference between r dq * ) can be generated. For example, the current control unit (254) may be configured as a PI controller that performs feedback control, but is not limited thereto. In addition, the current control unit (254) may be provided with independent PI controllers for the d-axis and q-axis.

[0066] The rotation-stationary coordinate system conversion unit (255) converts the motor angle (θ r ) based on the voltage reference (v) expressed in the dq-rotational coordinate system r dq * ) is the voltage reference (v) on the dq-stationary coordinate system s dq * ) can be converted to .

[0067] Converted voltage reference (v s dq * ) can be transmitted to the voltage modulation unit (256) and converted into an actual switching signal.

[0068] The voltage modulation unit (256) can generate a control signal for each switching element (S1, S2, S3, S4, S5, S6) of the inverter (230) according to the SVPWM (Space Vector Pulse Width Modulation) technique. Since the control method of the inverter (230) and the motor (240) according to the SVPWM technique is widely known to those skilled in the art, a detailed description thereof will be omitted. The voltage modulation unit (256) can convert the voltage command of the stationary coordinate system into a three-phase PWM signal, through which the switching elements of the inverter (230) can operate at an appropriate duty ratio to supply the desired voltage and current to the motor (240).

[0069] Next, the MTPA control process, which is the first mode of the controller described above, will be described with reference to FIG. 4.

[0070] Fig. 4 illustrates a process by which a controller (250) determines a current command when a motor (240) is driven in a low-speed region. As illustrated in Fig. 4, a current limit source (G401), an MTPA curve (G402), an MTPV curve (G403), and a voltage limit source (G404) in a low-speed region are illustrated in the dq-rotational coordinate system.

[0071] In the low-speed region, since the speed of the motor (240) is lower than the base speed, sufficient voltage margin can be secured in the inverter (230). In this case, the maximum output torque (G405) is determined at the point where the current limit source (G401) of the inverter (230) and the MTPA curve (G402) intersect. The MTPA curve (G402) represents a combination of d-axis and q-axis currents that can generate the maximum torque per unit current, thereby enabling maximum efficiency operation while minimizing copper loss. The operating point of the motor (240) that can be driven in the low-speed region is indicated by the A4 region, and within this region, the motor (240) can be operated at different efficiencies.

[0072] In MTPA control, the current size corresponding to the torque command can be minimized to reduce the I²R loss, thereby maximizing the efficiency of the motor (240). In addition, since the counter electromotive force of the motor (240) is relatively small in the low-speed range, the operating point of the motor (240) is not limited by the voltage limiter (G404).

[0073] Next, the MTPV control process in the high-speed region will be described with reference to Fig. 5.

[0074] Fig. 5 illustrates a current command determination process in a high-speed region. As illustrated in Fig. 5, in a high-speed region, the voltage limit source (G404') of the inverter (230) becomes smaller due to the counter electromotive force of the motor (240). In other words, as the speed of the motor (240) increases, the counter electromotive force increases, reducing the margin of voltage that the inverter (230) can output, which may result in a reduction in the size of the voltage limit source (G404').

[0075] In this case, the maximum output torque (G405') is determined at the point where the voltage limit source (G404') of the inverter (230) and the MTPV curve (G403) intersect. The MTPV curve (G403) represents the current combination that can produce the maximum torque per unit voltage, which is implemented through flux reduction control that reduces the field flux. The area where operation is possible through flux reduction control is indicated by A5, and in this area, MTPA control is difficult due to voltage limitations.

[0076] MTPV control reduces counter electromotive force by increasing the d-axis current in the negative direction, thereby weakening the field flux. This ensures sufficient voltage margin to continue driving the motor (240) even at high speeds. However, MTPV control requires more current to output the same torque, resulting in reduced efficiency compared to MTPA control.

[0077] Next, with reference to FIG. 6, the inefficiency control process according to the second mode, which is the core of the present disclosure, will be described.

[0078] FIG. 6 illustrates an example of control according to the disclosed embodiment, that is, the second mode, i.e., inefficient control. As illustrated in FIG. 6, although in the low-speed region (lower than the base speed), the voltage utilization rate is limited, so the size of the voltage limit source (G404") can be reduced. In this case, the motor (240) is driven with lower efficiency than when driven in the MTPA region, i.e., the first mode, and additional heat generation of the motor (240) may be induced.

[0079] In the second mode, the voltage limiter (G404") can be reduced by intentionally limiting the voltage utilization. This changes the intersection of the MTPA curve (G402) and the voltage limiter (G404"), moving to the inefficient operating point. The maximum torque (G405") can be formed at the intersection of the current limiter (G401) and the voltage limiter (G404"), and the possible operating point can be limited to the A6 area.

[0080] This inefficient control requires more d-axis current to output the same torque, which may lead to increased copper loss (I²R loss) and thus increased heat generation of the motor (240). The increased heat generation can heat the refrigerant inside the compressor (200), thereby improving the heating performance of the heat pump system, thereby replacing the existing PTC heater.

[0081] Next, with reference to Fig. 7, the changes in voltage and current waveforms according to the first and second modes will be described.

[0082] Figure 7 compares driving in the first mode (i.e., MTPA control) with driving in the second mode (i.e., inefficiency control). As illustrated in Figure 7, when driving in the second mode, the phase voltage of the inverter (230) decreases and the phase current increases compared to when driving in the first mode.

[0083] Specifically, G701 represents the output phase voltage of the inverter (230) according to MTPA control, and G701' represents the output phase voltage of the inverter (230) according to voltage utilization rate limitation. For convenience of explanation, only one phase among multiple phases is illustrated in Fig. 7.

[0084] The amplitude of the G701' waveform may become smaller than the amplitude of the G701 waveform because the controller (250) limits the voltage utilization of the inverter (230). This is because the maximum available voltage of the inverter (230) is limited in the second mode.

[0085] G702 represents the phase current of the motor (240) according to MTPA control, and G702' represents the phase current of the motor (240) according to the voltage utilization limit. Since more current is required to output the same torque due to the voltage utilization limit, the amplitude of the G702' waveform may be larger than the amplitude of the G702 waveform. G703 represents the counter electromotive force of the motor (240), which may be an electromotive force generated in proportion to the speed of the motor (240).

[0086] This combination of voltage reduction and current increase increases the copper loss of the motor (240), which means that the heat generation increases in proportion to the square of the current according to the relationship P = I²R. The increased heat generation can increase the refrigerant temperature inside the compressor (200), thereby improving the heating efficiency of the heat pump system.

[0087] Finally, a control method of the motor drive system of the present disclosure will be described with reference to FIG. 8.

[0088] Figure 8 is a flowchart showing a situation in which the controller (250) enters inefficiency control (second mode) when receiving an inefficiency control request.

[0089] Referring to FIG. 8, the controller (250) can first determine whether an inefficiency control request is received from an external source (S801). For example, the controller (250) can receive an inefficiency control request from a higher-level controller (not shown) of an electric vehicle.

[0090] If there is no inefficiency control request (No in S801), the controller (250) determines the driving mode as the first mode (S802) and can perform maximum efficiency control through MTPA control (S803).

[0091] In contrast, when there is a request for inefficiency control (Yes in S801), the controller (250) can determine the driving mode as the second mode (S804) and perform inefficiency control by limiting the voltage utilization rate of the inverter (230) (S805).

[0092] More specifically, the controller (250) can limit the voltage utilization by multiplying the voltage utilization according to the MTPA control by a limiting factor. For example, the voltage utilization of the inverter (230) can be additionally limited by multiplying the limited voltage of the inverter (230) according to the MTPA control by a limiting factor having a value less than 1. The limiting factor can be set to drive the motor (240) at a point where the power consumption of the motor (240) is maximum under an output torque corresponding to a torque command for the motor (240).

[0093] In addition, the phase of the voltage output by the inverter (230) may be changed as the controller (250) limits the voltage utilization of the inverter (230) so that the motor (240) is driven in an inefficient region. In other words, the controller (250) can not only adjust the voltage utilization of the inverter (230) by determining the limiting factor, but also adjust the phase of the output voltage of the inverter (230).

[0094] The phase of the output voltage of the inverter (230) can be set based on the phase at which the power consumption of the motor (240) measured for different voltage utilization rates is maximum under the output torque corresponding to the torque command for the motor (240).

[0095] The controller (250) can check the voltage utilization rate of the inverter (230) currently in use and reduce the voltage utilization rate by adjusting the limiting factor (S805). At this time, the controller (250) can monitor the output power of the motor (240) while reducing the voltage utilization rate or the limiting factor by a small unit value (S805) (S806).

[0096] When the output of the motor (240) reaches the maximum (Yes in S806), the controller (250) determines the voltage phase value when the output power according to the inefficiency control reaches the maximum (S807) and can perform inefficiency control with the phase with the highest power consumption (S808). When the power consumption of the motor (240) does not reach the maximum value (No in S806), the controller (250) can readjust the voltage utilization rate or the limiting factor (S805).

[0097] The heat generation amount of the motor (240) can be maximized through inefficiency control in the second mode described above, which leads to an increase in the temperature of the refrigerant inside the compressor (200), thereby improving the heating performance of the heat pump system.

[0098] Inefficiency control through voltage utilization rate limitation according to the embodiments described so far can be implemented to intentionally limit the maximum voltage utilization rate that can be used by the inverter (230) so as to enable early entry into the weak magnetic flux region. The direction of the current flowing to the motor (240) changes depending on the voltage difference between the motor (240) and the inverter (230), and when the inverter voltage is greater than the motor voltage, a positive current in the same direction as the motor voltage is applied to the motor (240).

[0099] As the phase of the voltage changes, it is possible to secure a voltage margin output from the inverter (230) to the motor (240), and in order to output the same torque, the d-axis current can operate in the direction of increasing and the q-axis current decreasing according to the torque curve. In this way, the controller (250) can increase the copper loss of the motor (240), and as a result, the heat generation of the motor (240) can increase, thereby heating the refrigerant inside the compressor (200).

[0100] The multi-phase motor (240) may include a motor provided in the compressor (200) of the heat pump system, and the heat generated by the multi-phase motor (240) may be used to increase the temperature of the refrigerant of the heat pump system. This configuration may be utilized as a main heating system to replace existing PTC heaters, and may reduce costs and resolve power consumption issues by eliminating PTC components.

[0101] The technical benefits of the present disclosure are as follows. First, in the heat pump system of an electric vehicle, the role of a PTC heater can be replaced by implementing forced heating through inefficiency control of the electric compressor. Second, cost reduction and power consumption issues can be resolved by eliminating PTC components. Third, heating functionality can be added to existing motor drive systems through software modifications alone, ensuring heating performance without increasing system complexity. Fourth, heat transfer efficiency can be improved by directly heating the refrigerant through the heat generation of the compressor motor.

[0102] Although the present disclosure has been illustrated and described with respect to specific embodiments thereof, it will be apparent to those skilled in the art that the present disclosure may be variously improved and modified without departing from the technical spirit of the present disclosure as defined by the following claims.

Claims

1. A multi-phase motor having multiple windings corresponding to each of the multiple phases; An inverter that controls the phase current flowing in the multi-phase motor; and Based on the speed of the multi-phase motor being lower than the preset base speed, the multi-phase motor is driven in a first mode that controls the inverter with MTPA (Maximum Torque Per Ampere) control, or A motor drive device including a controller that drives the multi-phase motor in a second mode that increases the heat generation of the multi-phase motor by controlling the inverter to have a lower voltage utilization rate than the first mode.

2. In claim 1, The above controller, In the above second mode, A motor driving device that determines the maximum available voltage of the inverter corresponding to the second mode by multiplying the maximum available voltage of the inverter corresponding to the first mode by a preset limiting factor, 3. In claim 2, The above limiting factors are, A motor driving device configured to drive the motor at a point where the power consumption of the motor is maximum under an output torque corresponding to a torque command for the motor.

4. In claim 1, The above controller, The output torque of the multi-phase motor generates a current command based on a predefined map according to the size of the d-axis current and the size of the q-axis current, A motor driving device that controls the inverter based on the above current command.

5. In claim 2, The above limiting factors are, A motor driving device set to change the phase of the voltage output by the inverter by a preset phase angle.

6. In claim 5, The above phase angle is, A motor drive device set based on the phase at which the power consumption of the motor is maximum, measured for different voltage utilization rates, under an output torque corresponding to a torque command for the motor.

7. A compressor for a heat pump system comprising a multi-phase motor as described in claim 1.

8. In claim 1, The above multi-phase motor is a motor drive device that is an IPMSM (Interior Permanent Magnet Synchronous Motor).

9. A multi-phase motor having multiple windings corresponding to each of the multiple phases; An inverter that controls the phase current flowing in the multi-phase motor; and Based on the speed of the multi-phase motor being lower than the preset base speed, the multi-phase motor is driven in a first mode that controls the inverter with MTPA (Maximum Torque Per Ampere) control, or An electric vehicle comprising a controller for driving the multi-phase motor in a second mode that increases the heat generation of the multi-phase motor by controlling the inverter to have a lower voltage utilization rate than the first mode.

10. In claim 9, The above controller, In the above second mode, An electric vehicle that determines the maximum available voltage of the inverter corresponding to the second mode by multiplying the maximum available voltage of the inverter corresponding to the first mode by a preset limiting factor.

11. In claim 10, The above limiting factors are, An electric vehicle configured to drive the motor at a point where the power consumption of the motor is maximum under an output torque corresponding to a torque command for the motor.

12. In claim 9, The above controller, The output torque of the multi-phase motor generates a current command based on a predefined map according to the size of the d-axis current and the size of the q-axis current, An electric vehicle that controls the inverter based on the above current command.

13. In claim 10, The above limiting factors are, An electric vehicle configured to change the phase of the voltage output by the inverter by a preset phase angle.

14. In claim 13, The above phase angle is, An electric vehicle set based on a phase in which the power consumption of the motor is maximum, measured for different voltage utilization rates, under an output torque corresponding to a torque command for the motor.

15. In claim 9, The above multi-phase motor is an IPMSM (Interior Permanent Magnet Synchronous Motor) for an electric vehicle.

16. A control method for a motor drive system including a multi-phase motor having multiple windings corresponding to each of multiple phases and an inverter that controls phase current flowing in the multi-phase motor, Determine the speed of the above multi-phase motor, Based on the speed of the above multi-phase motor being lower than the preset base speed, the voltage utilization factor of the inverter is lowered, Generate a current command for the motor based on the torque command and the voltage utilization ratio, A control method for a motor drive system, comprising controlling the inverter based on the current command and driving the multi-phase motor to increase heat generation of the multi-phase motor.

17. In claim 16, Lowering the above voltage utilization rate is A control method for a motor drive system, comprising lowering the voltage utilization factor by adjusting the maximum available voltage of the inverter by multiplying the maximum available voltage of the inverter by a preset limiting factor.

18. In claim 17, The above limiting factors are, A control method of a motor drive system set to drive the motor at a point where the power consumption of the motor is maximum under an output torque corresponding to a torque command for the motor.

19. In claim 17, The above limiting factor is set to change the phase of the voltage output by the inverter by a preset phase angle, The above phase angle is a control method of a motor drive system, wherein the phase angle is set based on the phase at which the power consumption of the motor is maximum, measured for different voltage utilization rates, under an output torque corresponding to a torque command for the motor.

20. In claim 16, The above multi-phase motor includes a motor equipped with a compressor of a heat pump system, A control method of a motor drive system further comprising increasing the temperature of the refrigerant of the heat pump system through heat generation of the multi-phase motor.

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