Motor drive device

Abstract

The present application relates to a motor drive device that drives a motor having a plurality of windings corresponding to a plurality of phases, respectively, the motor drive device including: a first inverter including a plurality of first switching elements and connected to first ends of the plurality of windings, respectively; a second inverter including a plurality of second switching elements and connected to second ends of the plurality of windings, respectively; and a controller that, when the first inverter and the second inverter are simultaneously operated by a space vector pulse width modulation method and the motor is driven by an open-end winding method, fixes switching states of the second switching elements and switches the first switching elements to synthesize a target voltage vector.

Description

Technical Field

[0001] The present invention relates to an electric motor drive device, and more specifically, to an electric motor drive device that can switch the electric motor drive mode to a Y-connected electric motor drive mode and an open-winding electric motor drive mode according to the required output of the electric motor, so as to improve the efficiency of the inverter used to drive the electric motor. Background Technology

[0002] Typically, one end of each phase winding in an electric motor is connected to an inverter, while the other ends are connected to each other to form a Y-connection.

[0003] When driving a motor, the switching elements in the inverter are switched on / off via pulse width modulation, while 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, which use the torque generated by the electric motor as power as described above, is determined by the power conversion efficiency of the inverter-motor. Therefore, in order to improve fuel efficiency, it is important to maximize the power conversion efficiency of the inverter and the efficiency of the electric motor.

[0005] The efficiency of an inverter-motor system depends primarily on the voltage utilization of the inverter. By establishing a vehicle drive point determined by the relationship between the motor speed and torque in a region of high voltage utilization, the vehicle's fuel efficiency can be improved.

[0006] However, as the number of winding turns in the electric motor is increased to increase its maximum torque, the region of high voltage utilization gradually moves away from the low torque region, which is the main driving point of the vehicle, potentially leading to a decrease in fuel efficiency. Furthermore, considering fuel efficiency, designing the main driving point within the region of high voltage utilization limits the maximum torque of the electric motor, which may result in poorer acceleration and starting performance of the vehicle.

[0007] Therefore, there is a need in this technical field for an electric motor drive technology that can improve system efficiency while using a single electric motor to cover both low-output and high-output regions.

[0008] The above background description is only intended to enhance the understanding of the background of the present invention and should not be regarded as prior art known to those skilled in the art.

[0009] Existing technical documents

[0010] Patent documents

[0011] (Patent Document 1) US 2009-0033253 A1

[0012] (Patent Document 2) JP 6285256 B2 Summary of the Invention

[0013] (a) Technical problems to be solved

[0014] Therefore, the technical problem to be solved by the present invention is to provide a motor drive device that can convert the motor drive mode into a Y-connected motor drive mode and an open winding motor drive mode according to the output required by the motor, so as to improve the efficiency of the inverter used to drive the motor.

[0015] (II) Technical Solution

[0016] As a technical solution to solve the above-mentioned technical problems, the present invention provides a motor drive device that drives a motor having multiple windings corresponding to multiple phases. The motor drive device includes: a first inverter including multiple first switching elements and respectively connected to the first ends of the multiple windings; a second inverter including multiple second switching elements and respectively connected to the second ends of the multiple windings; and a controller that, when simultaneously operating the first inverter and the second inverter through space vector pulse width modulation and driving the motor through an open winding method, fixes the switching state of the second switching elements and switches the first switching elements to synthesize a target voltage vector.

[0017] In one embodiment of the invention, the controller can synthesize a target voltage vector that does not include voltage vectors in the voltage vector synthesized by the first inverter and the second inverter where the difference between the common-mode voltage of the first inverter and the common-mode voltage of the second inverter is not zero.

[0018] In one embodiment of the invention, the controller can fix the on / off state of the second switching element and switch the first switching element for each region of the voltage vector that can be synthesized by the first inverter and the second inverter to synthesize the target voltage vector.

[0019] In one embodiment of the invention, the controller may pre-define the region by connecting points in a vector diagram showing the voltage vector that can be synthesized by the first inverter and the second inverter that have the same switching state as the second inverter.

[0020] In one embodiment of the invention, the controller can synthesize the target voltage vector by fixing the switching state of the second switching element corresponding to the region containing the target voltage vector and switching the first switching element to repeat the switching state of the first switching element in a predetermined mode.

[0021] In one embodiment of the present invention, the switching loss of the first switching element may be less than the switching loss of the second switching element.

[0022] In one embodiment of the present invention, the first switching element may be a field-effect transistor made of SiC material, and the second switching element may be an insulated-gate bipolar transistor made of Si material.

[0023] As a technical solution to solve the above-mentioned technical problems, the present invention provides a motor drive device that drives a motor having multiple windings corresponding to multiple phases. The motor drive device includes: a first inverter including multiple first switching elements and respectively connected to the first ends of the multiple windings; a second inverter including multiple second switching elements and respectively connected to the second ends of the multiple windings; multiple third switching elements, one end of which is respectively connected to a point that divides the number of turns of the multiple windings into a preset ratio, and the other end of which is connected to each other; and a controller that, when the required output of the motor is above a preset reference value, turns on the third switching elements, fixes the switching state of the second switching elements, and switches the first switching elements to synthesize a target voltage vector, thereby simultaneously operating the first inverter and the second inverter through space vector pulse width modulation.

[0024] (III) Beneficial Effects

[0025] According to the motor drive device, it is possible to determine whether to divide the turns ratio of the motor windings based on the required output of the motor. The turns ratio of the windings is divided in the low output region so that the main driving point of the vehicle is included in the high efficiency region of the motor inverter system, thereby improving the efficiency of the motor inverter system. In the high output region, the overall number of turns of the windings can be used to achieve high torque with low current.

[0026] Therefore, according to the electric motor drive device, compared with the case of a conventional Y-connected electric motor driven by an inverter, the electric motor drive device can improve the efficiency of the entire torque range, thereby helping to improve the fuel efficiency of the vehicle.

[0027] Furthermore, according to the motor drive device, in the open winding mode of driving the motor by simultaneously operating two inverters connected to both ends of the motor winding, when synthesizing the voltage vector for space vector pulse width modulation, the switching of the inverter using switching elements with high switching losses is minimized, and the switching is achieved by using an inverter using switching elements with relatively low switching losses, thereby reducing switching losses and improving the efficiency of the entire system.

[0028] The effects achievable from this invention are not limited to those mentioned above, and other unmentioned effects will be clearly understood by those skilled in the art from the following description. Attached Figure Description

[0029] Figure 1 This is a circuit diagram of an electric motor drive device according to one embodiment of the present invention.

[0030] Figure 2 This is a graph showing the rotational speed (RPM)-torque curves and high-efficiency regions of each motor drive mode of the motor drive device according to an embodiment of the present invention.

[0031] Figure 3 This is a diagram showing the voltage vector synthesized by two inverters applied to an open-winding motor.

[0032] Figure 4 This is a diagram showing the voltage vector synthesized by two inverters when driving an open-winding motor.

[0033] Figure 5 This is a simplified representation of the data from... Figure 4 The vector diagram shown is a vector diagram in which the voltage vector that generates the common-mode voltage difference between the two inverters has been removed.

[0034] Figure 6 It is shown Figure 5 The diagram shows examples of switching between the first and second inverters in each region.

[0035] Figure 7 This is a diagram showing the switching states of the switching elements in the first inverter and the switching states of the switching elements in the second inverter according to an embodiment of the present invention.

[0036] Figure 8 This is a diagram showing the switching states of the switching elements in the first inverter and the switching states of the switching elements in the second inverter when driving a conventional open-winding motor.

[0037] Explanation of reference numerals in the attached figures

[0038] 10: First inverter; 20: Second inverter

[0039] 30: Third switching element; 40: Controller

[0040] 50: Current sensor 100: Motor

[0041] 200: Battery; 300: DC link capacitor

[0042] S11 to S16: First switching element; S21 to S26: Second switching element

[0043] S31 to S33: Third switching elements; C1 to C3: Windings Detailed Implementation

[0044] Hereinafter, electric motor drive devices according to various embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0045] Figure 1 This is a circuit diagram of an electric motor drive device according to one embodiment of the present invention.

[0046] Reference Figure 1 According to one embodiment of the present invention, a motor drive device supplies drive power to a motor 100 having multiple windings C1 to C3 corresponding to multiple phases, and the motor drive device may include: a first inverter 10 including multiple first switching elements S11 to S16 and connected to the first end of each winding of the motor 100; a second inverter 20 including multiple second switching elements S21 to S26 and connected to the second end of each winding of the motor 100; third switching elements S31 to S33 selectively interconnecting / disconnecting points that divide the number of turns of each winding of the motor 100 into a predetermined ratio N1:N2; and a controller 40 controlling the on / off states of the first switching elements S11 to S16, the second switching elements S21 to S26 and the third switching elements S31 to S33 based on the output required by the motor 100.

[0047] The first inverter 10 and the second inverter 20 can convert the direct current stored in the battery 200 into three-phase alternating current and supply it to the motor 100, or convert the regenerative braking energy generated by the regenerative braking torque of the motor 100 during regenerative braking into direct current and supply it to the battery 200. The conversion between direct current and alternating current can be performed by pulse width modulation control of a plurality of first switching elements S11 to S16 and a plurality of second switching elements S21 to S26 respectively provided in the first inverter 10 and the second inverter 20.

[0048] The first inverter 10 may include a plurality of pins 11 to 13 to which a DC voltage formed in a DC link capacitor 300 connected between the two ends of the battery 200 is applied. Each pin 11 to 13 may correspond to a plurality of phases of the motor 100 to form an electrical connection. More specifically, the first pin 11 may include two switching elements S11 and S12 connected in series between the two ends of the DC link capacitor 300, and the connection node of the two switching elements S11 and S12 may be connected to one end of the winding C1 of one phase in the motor 100 to input / output AC power corresponding to one of the plurality of phases. Similarly, the second pin 12 may include two switching elements S13 and S14 connected in series between the two ends of the DC link capacitor 300, and the connection node of the two switching elements S13 and S14 may be connected to one end of the winding C2 of one phase in the motor 100 to input / output AC power corresponding to one of the plurality of phases. Additionally, the third leg 13 may include two switching elements S15 and S16 connected in series between the two ends of the DC link capacitor 300, and the connection node of the two switching elements S15 and S16 may be connected to one end of the winding C3 of one phase in the motor 100 to input / output AC power corresponding to one of the multiple phases.

[0049] The second inverter 20 may also have a structure similar to that of the first inverter 10. The second inverter 20 may include multiple pins 21 to 23 to which a DC voltage formed in a DC link capacitor 300 connected between the two ends of the battery 200 is applied. Each pin 21 to 23 may correspond to multiple phases of the motor 100 to form an electrical connection. More specifically, the first pin 21 may include two switching elements S21 and S22 connected in series between the two ends of the DC link capacitor 300, and the connection node of the two switching elements S21 and S22 may be connected to the other end of the winding C1 of one phase in the motor 100 to input / output AC power corresponding to one of the multiple phases. Similarly, the second pin 22 may include two switching elements S23 and S24 connected in series between the two ends of the DC link capacitor 300, and the connection node of the two switching elements S23 and S24 may be connected to the other end of the winding C2 of one phase in the motor 100 to input / output AC power corresponding to one of the multiple phases. Additionally, the third leg 23 may include two switching elements S25 and S26 connected in series between the two ends of the DC link capacitor 300, and the connection node of the two switching elements S25 and S26 may be connected to the other end of the winding C3 of one phase in the motor 100 to input / output AC power corresponding to one of the multiple phases.

[0050] The first inverter 10 is connected to one end of the windings C1 to C3 of the motor 100, and the second inverter 20 is connected to the other end of the windings C1 to C3 of the motor 100. That is, an open winding electrical connection can be formed in which the two ends of the windings C1 to C3 of the motor 100 are respectively connected to the first inverter 10 and the second inverter 20.

[0051] In one embodiment of the invention, the third switching element 30 is configured to selectively interconnect / disconnect points that divide the number of turns of the plurality of windings C1 to C3 included in the motor 100 into a predetermined ratio N1:N2. For example, the third switching element 30 may consist of three switching elements S31 to S33, one end of each switching element S31 to S33 may be connected to the point where the number of turns of the plurality of windings C1 to C3 is divided into a predetermined ratio N1:N2, and the other ends of each switching element S31 to S33 may be interconnected (where N1 and N2 are the actual number of turns).

[0052] In the aforementioned connection structure, when the third switching element 30 is open, the motor 100 can be operated using a winding with N1+N2 turns. When the third switching element 30 is closed, the windings C1 to C3 of the motor 100 form a Y-connection at the location where the third switching element 30 is connected. For example, when the third switching element 30 is closed, and the multiple switching elements S21 to S26 in the second inverter 20 are all open and not in operation, and the first inverter 10 is operated to drive the motor 100, the motor 100 can be driven as a motor with N1 turns.

[0053] As the third switching elements S31 to S33, various switching devices known in the art, such as metal-oxide-semiconductor field-effect transistors (MOSFETs), insulated-gate bipolar transistors (IGBTs), thyristors, and relays, can be employed.

[0054] The controller 40 is essentially a component that performs pulse width modulation control on the switching elements S11 to S16, S21 to S26 included in the first inverter 10 and the second inverter 20, so that the motor 100 can be driven based on the output required by the motor 100. In particular, in various embodiments of the invention, the controller 40 can determine the inverter for driving the motor based on the output required by the motor 100, thereby determining the on / off state of the third switching element 30, and can perform pulse width modulation control on the switching elements of the determined inverter.

[0055] More specifically, when the required output of the motor 100 is less than a preset reference value, the controller 40 can perform pulse width modulation control on the switching elements S11 to S16 of the first inverter 10 and drive the motor 100 without operating the second inverter 20 (referred to as the "first drive mode" for ease of description). At this time, the controller 40 can control the third switching elements S31 to S33 to be in the on state. Therefore, the windings C1 to C3 of the motor 100 are electrically connected to each other from the end connected to the first inverter 10 to the point with N1 turns to form a Y-type connection, and the motor operates as a motor with N1 turns of windings.

[0056] As described above, in the first drive mode, the third switching element 30 is switched on by operating the first inverter 10, thereby controlling the winding with N1 turns to drive the Y-connected motor 100. In the first drive mode, the motor can be driven by the controller 100 receiving the DC voltage from the first inverter 10, the phase current detected and supplied to the motor 100 by the current sensor 50, and the motor angle detected by the motor rotor sensor (not shown) provided in the motor 100, etc., to perform pulse width modulation control on the first switching elements S11 to S16 of the first inverter 10. Since various methods of driving the motor 100 by pulse width modulation control of an inverter are well known in the art, a detailed description of the pulse width modulation control method of the inverter executed in the first drive mode will be omitted.

[0057] On the other hand, when the required output of the motor 100 exceeds a preset reference value, the controller 40 can operate the first inverter 10 and the second inverter 20 to drive the motor 100 (for ease of description, this is referred to as the "second drive mode"). In this case, the controller 40 can control the third switching elements S31 to S33 to be in the open state. Therefore, the number of turns in each winding C1 to C3 of the motor 100 is N1+N2, with one end of winding C1 to C3 connected to the first inverter 10 and the other end connected to the second inverter 20. That is, in the second drive mode, the motor 100 becomes an open-winding motor with both ends of windings C1 to C3 open, and can be driven by pulse width modulation control of the two inverters 10 and 20 respectively connected to the ends of windings C1 to C3.

[0058] In the second drive mode, the motor can be driven by the controller 100 receiving the DC voltage from the first inverter 10 and the second inverter 20, the phase current detected by the current sensor 50 and supplied to the motor 100, and the motor angle detected by the motor rotor sensor (not shown) installed in the motor 100, etc., to perform pulse width modulation control on the first switching elements S11 to S16 of the first inverter 10 and the second switching elements S21 to S26 of the second inverter 20. Since various methods for performing pulse width modulation control on the two inverters connected to the two ends of the windings of the open-wound motor and driving the motor are well known techniques, a detailed description of the pulse width modulation control of the inverters executed in the second drive mode will be omitted.

[0059] Figure 2 This is a graph showing the motor speed (RPM)-motor torque curves and high-efficiency regions for each motor drive mode of the motor drive device according to an embodiment of the present invention.

[0060] As described above, according to one embodiment of the present invention, the motor drive device drives a Y-connected motor with N1 turns by controlling the first inverter 10 in a first drive mode, and drives an open-wound motor with N1+N2 turns by controlling the first inverter 10 and the second inverter 20 in a second drive mode.

[0061] like Figure 2 As shown, when the electric motor 100 is used to drive the vehicle, the main driving points of the vehicle are driving point Y1 when driving in the city and driving point Y2 when driving on the highway. Preferably, the driving points Y1 and Y2 are contained in the high-efficiency region of the electric motor-inverter system.

[0062] In one embodiment of the present invention, when the motor 100 is applied to a vehicle, preferably, the number of turns N1 is determined such that the high-efficiency region of the motor-inverter system includes the aforementioned main drive points Y1 and Y2 in the first drive mode. Since the efficiency of the motor-inverter system is determined by the voltage utilization rate of the inverter, it is preferable to determine the number of turns N1 of the windings C1 to C3 of the motor 100 in the first drive mode such that the region R1, which is above a preset reference value indicating excellent voltage utilization rate of the inverter, includes the main drive points Y1 and Y2 of the vehicle.

[0063] The second drive mode is for driving open-winding motors. It is well known that, compared to simply driving a motor with a Y-connected winding and the same number of turns using only one inverter, the inverter output can be set to approximately higher in open-winding drive. This means that, when using open-winding drive as the second drive mode, the number of turns of the motor can be increased by a factor of two. Therefore, the current output required for the motor to produce the same output can be reduced by a factor of two. times.

[0064] As mentioned above, in the case of using an open winding drive method, in order to produce the same output, the inverter current can be reduced compared to the drive of a Y-connected motor, thereby improving efficiency, and the material cost is reduced due to the reduction in the amount of power semiconductors used as switching elements.

[0065] On the other hand, such as Figure 2 As shown, when the second drive mode is applied, as the motor output increases, the region R2, which is above a preset reference value indicating excellent voltage utilization of the motor-inverter system, is unlikely to include the main drive points Y1 and Y2. Therefore, as described above, it is preferable to drive the motor 100 in the first drive mode to improve efficiency in the low torque region that includes the main drive points Y1 and Y2, and drive the motor 100 in the second drive mode in the region where high output is required to relatively reduce the inverter output current and reduce the amount of power semiconductors used.

[0066] Furthermore, to further improve the efficiency of the first drive mode, which operates in the low-torque region including the main drive points Y1 and Y2, it is more preferable that the switching elements S11 to S16 applied to the first inverter 10 are MOSFETs made of SiC, a material with relatively low switching losses. On the other hand, it is preferable that the switching elements S21 to S26 applied to the second inverter 20, which operates in the high-output region, are IGBTs made of inexpensive Si.

[0067] As described above, the electric motor drive device according to various embodiments of the present invention can determine whether to divide the turns ratio of the motor windings based on the required output of the motor, divide the turns of the windings in the low output region so that the main driving point of the vehicle is contained in the high efficiency region of the motor-inverter system, thereby improving the efficiency of the system, and utilize the entire number of turns of the windings in the high output region to achieve high torque with low current.

[0068] Therefore, compared to the case where a conventional Y-connected motor is driven by an inverter, the motor drive according to various embodiments of the present invention can improve efficiency throughout the torque range to help improve the vehicle's fuel efficiency.

[0069] On the other hand, in the second drive mode, that is, in the mode of disconnecting all third switching elements and simultaneously operating the first inverter 10 and the second inverter 20 to drive the open-wound motor, the second switching elements S21 to S26 included in the second inverter 20 may be formed of Si or the like with high switching losses, thus reducing the overall drive efficiency of the motor. In order to drive with the same current as the first switching elements S11 to S16 of the first inverter 10 formed of SiC or the like, the size needs to be increased, which may lead to an increase in material costs.

[0070] Therefore, a control method is needed that can reduce the switching losses caused by the second switching elements S21 to S26 to improve efficiency, and can realize the second drive mode without increasing the size of the second switching elements S21 to S26.

[0071] The mode of driving the motor 100 as an open-winding motor by disconnecting all third switching elements N31 to N33 and simultaneously operating the first inverter 10 and the second inverter 20 will be described in further detail below.

[0072] Figure 3 This is a diagram showing the voltage vector synthesized by two inverters applied to an open-winding motor. Figure 4 This is a diagram showing the voltage vector synthesized by two inverters when driving an open-winding motor.

[0073] exist Figure 1 In the circuit structure shown, the first inverter 10 and the second inverter 20 may include a pair of switching elements (S11 and S12, S13 and S14, S15 and S16, S21 and S22, S23 and S24, and S25 and S26) on each pin corresponding to the phase of the motor, and the switching elements of each pin may operate complementaryly to each other.

[0074] exist Figure 3 In the vector diagram shown, the vertices and origin of the hexagons represent voltage vectors according to the state of the switching elements of each inverter. For example, the point indicated by index A represents the voltage vector of

[100] of the first inverter 10. Here,

[100] indicates that the upper switching element S11 of the switching elements S11 and S12 included in the pin corresponding to phase a of the first inverter is in the on state, and the upper switching elements S13 and S15 of the switching elements included in the pins corresponding to the other phases are off.

[0075] In addition, the center of the hexagon corresponds to the

[000] or

[111] vector, which means that the upper switches of each pin of the inverter are either in the off state or in the on state.

[0076] like Figure 3As shown, the voltage vector synthesized by each inverter can be totaled into eight voltage vectors through the combination of the on / off states of the six switching elements.

[0077] When the motor 100 is driven in an open-winding configuration after all third switching elements 30 are disconnected, the terminals of the first inverter 10 and the second inverter 20 are connected to the motor coils corresponding to each phase of the motor 100. Therefore, the phase voltage applied to each phase of the motor is the difference between the phase voltages of the first inverter and the second inverter. Furthermore, since the first inverter 10 and the second inverter 20 are controlled independently, therefore, as... Figure 4 As shown, the voltage vector actually applied to the motor can be formed into a total of 64 voltage vectors by combining the eight voltage vectors that can be synthesized by the first inverter 10 and the eight voltage vectors that can be synthesized by the second inverter 20.

[0078] On the other hand, the common-mode voltage in each inverter 10, 20 can be defined as the sum of the phase voltages of each phase divided by 3, and when driving an open-winding motor, preferably, a voltage vector where the difference between the common-mode voltages of the two inverters is not zero is not used when driving the motor. This is because the current flow generated by the difference in the common-mode voltages of the two inverters 10, 20 will cause losses in the motor.

[0079] exist Figure 4 In the figure, the voltage vectors indicated by reference numerals “51” to “56” are voltage vectors where the difference between the common-mode voltages of the two inverters is not zero.

[0080] For example, in Figure 4 In the diagram, the switching state of the first inverter in the OS vector (13' vector) is

[100] , and the switching state of the second inverter is

[010] . Therefore, the common-mode voltage of the first inverter can be calculated as "{(Vdc / 2)+0+0} / 3=Vdc / 6", and the common-mode voltage of the second inverter can be calculated as "{0+(Vdc / 2)+0} / 3=Vdc / 6". Therefore, the difference between the two common-mode voltages is 0.

[0081] On the other hand, due to Figure 4 The switching state of the first inverter in the OG vector (14' vector) is

[100] , and the switching state of the second inverter is

[011] . Therefore, the common-mode voltage of the first inverter can be calculated as "{(Vdc / 2)+0+0} / 3=Vdc / 6", and the common-mode voltage of the second inverter can be calculated as "{0+(Vdc / 2)+(Vdc / 2)} / 3=Vdc / 3". Therefore, the difference between the two common-mode voltages is "-Vdc / 6".

[0082] Vdc can be the DC input voltage of the inverter, i.e., the voltage of battery 200.

[0083] When calculating the difference in common-mode voltage between the two inverters using the method described above, it can be confirmed that... Figure 4 The voltage vectors indicated by reference numerals “51” to “56” in the attached figures are voltage vectors where the difference between the common-mode voltages of the two inverters is not zero.

[0084] Figure 5 It is a simplified representation of... Figure 4 The vector diagram shown is a vector diagram with the voltage vector that generates the difference in common-mode voltage between the two inverters removed.

[0085] like Figure 5 As shown, when the available composite voltage vectors, other than the voltage vector that generates the difference in common-mode voltage between the two inverters, are interconnected, a hexagon is shown, and the six regions divided by the diagonals of each hexagon can control the switching state of the second inverter in the same way.

[0086] For example, Figure 5 The switching state of the second inverter in the first region can be achieved by 4', i.e.,

[011] , and the switching state of the second inverter in the second region can be achieved by 5', i.e.,

[001] . Furthermore, the switching state of the second inverter in the third region can be achieved by 6', i.e.,

[101] , and the switching state of the second inverter in the fourth region can be achieved by 1', i.e.,

[100] . Additionally, the switching state of the second inverter in the fifth region can be achieved by 2', i.e.,

[110] , and the switching state of the second inverter in the sixth region can be achieved by 3', i.e.,

[010] . The first to sixth regions correspond to electrical angles of 60°, and all of the first to sixth regions can correspond to electrical angles of 360°.

[0087] With this in mind, one embodiment of the present invention involves controlling the switching elements of the second inverter 20, which uses switching elements made of Si with high switching losses, to continuously maintain the switching state corresponding to the relevant region, and switching the switching elements of the first inverter 10 to synthesize the desired voltage vector. Thus, one embodiment of the present invention maximally suppresses the switching of switching elements with high switching losses, thereby minimizing switching losses and improving system efficiency.

[0088] Figure 6 It is shown Figure 5 The diagram shows examples of the switching of the first and second inverters in each region.

[0089] refer to Figure 6 When using space vector pulse width modulation to drive motor 100, it is necessary to... Figure 5In the case of synthesizing a voltage vector in the first region, the switching elements in the second inverter INV2 switch to maintain the

[011] state corresponding to the switching state of 4', and the switching elements in the first inverter INV1 switch to output the switching states corresponding to 2, 4, and 6, thereby synthesizing the desired voltage vector. The duty cycle of each phase in the first inverter can be appropriately adjusted according to the location of the voltage to be synthesized.

[0090] Similarly, in space vector pulse width modulation used to drive motor 100, it is necessary to... Figure 5 In the case of synthesizing a voltage vector in the second region, the switching elements in the second inverter INV2 switch to maintain the

[001] state as the switching state corresponding to 5', and the switching elements in the first inverter INV1 switch to output the switching states corresponding to 1, 3 and 5, so that the desired voltage vector can be synthesized.

[0091] Similarly, when using space vector pulse width modulation to drive the motor 100, it is necessary to... Figure 5 In the case of synthesizing a voltage vector in the third region, the switching elements in the second inverter INV2 are switched to maintain the

[101] state as the switching state corresponding to 6', and the switching elements in the first inverter INV1 are switched to output the switching states corresponding to 2, 4 and 6, so that the desired voltage vector can be synthesized.

[0092] When using space vector pulse width modulation for driving motor 100, it is necessary to... Figure 5 In the case of synthesizing a voltage vector in the fourth region, the switching elements in the second inverter INV2 switch to maintain the

[100] state as the switching state corresponding to 1', and the switching elements in the first inverter INV1 switch to output the switching states corresponding to 1, 3 and 5, so that the desired voltage vector can be synthesized.

[0093] When using space vector pulse width modulation for driving motor 100, it is necessary to... Figure 5 In the case of synthesizing a voltage vector in the fifth region, the switching elements in the second inverter INV2 are switched to maintain the

[110] state corresponding to the switching state of 2', and the switching elements in the first inverter INV1 are switched to output the switching states corresponding to 2, 4 and 6, so that the desired voltage vector can be synthesized.

[0094] When using space vector pulse width modulation for driving motor 100, it is necessary to... Figure 5In the case of synthesizing a voltage vector in the sixth region, the switching elements in the second inverter INV2 switch to maintain the

[010] state as the switching state corresponding to 3', and the switching elements in the first inverter INV1 switch to output the switching states corresponding to 1, 3 and 5, so that the desired voltage vector can be synthesized.

[0095] Figure 7 This is a diagram showing the switching states of the switching elements in a first inverter and the switching states of the switching elements in a second inverter according to an embodiment of the present invention. Figure 8 This is a diagram showing the switching states of the switching elements in the first inverter and the switching states of the switching elements in the second inverter when driving a conventional open-winding motor.

[0096] like Figure 7 As shown, it can be confirmed that in one embodiment of the present invention, the switching of the second inverter is significantly reduced. From Figure 8 This can be more clearly observed when the switching state is used to drive a motor with a traditional open winding method.

[0097] like Figure 8 As shown, when driving a conventional open-winding motor, the switching elements in the second inverter also have a high-speed switching region b2. When the second inverter is implemented with switching elements that have high switching losses, such as those made of Si material, the switching losses caused by the switching of the second inverter increase significantly, which may lead to a reduction in the efficiency of the entire system.

[0098] Conversely, in one embodiment of the invention, such as Figure 8 As shown in region "b1" corresponding to "b2", the efficiency of the entire system can be improved by minimizing the switching of the second inverter, which uses switching elements with high switching losses, and driving the first inverter, which has switching elements made of materials such as SiC with relatively low switching losses.

[0099] The above have shown and described specific embodiments of the present invention, but it will be apparent to those skilled in the art that various modifications and alterations can be made to the present invention within the scope of the claims.

Claims

1. An electric motor drive device for driving an electric motor having multiple windings corresponding to multiple phases, wherein, The electric motor drive device includes: The first inverter includes a plurality of first switching elements and is respectively connected to the first ends of the plurality of windings; A second inverter, comprising a plurality of second switching elements respectively connected to the second ends of the plurality of said windings; and When the controller operates the first inverter and the second inverter simultaneously via space vector pulse width modulation and drives the motor via open winding, it fixes the switching state of the second switching element whose switching loss is greater than that of the first switching element, and switches the first switching element to synthesize the target voltage vector.

2. The electric motor drive device according to claim 1, characterized in that, The controller synthesizes the target voltage vector, which does not include voltage vectors in the voltage vector synthesized by the first inverter and the second inverter where the difference between the common-mode voltage of the first inverter and the common-mode voltage of the second inverter is not 0.

3. The electric motor drive device according to claim 1, characterized in that, The controller fixes the on / off state of the second switching element for each region of the voltage vector synthesized by the first inverter and the second inverter, and switches the first switching element to synthesize the target voltage vector.

4. The electric motor drive device according to claim 3, characterized in that, The controller connects points in a vector diagram showing the voltage vector synthesized by the first inverter and the second inverter that have the same switching state as the second inverter, in order to pre-define the area.

5. The electric motor drive device according to claim 3, characterized in that, The controller synthesizes the target voltage vector by fixing the switching state of the second switching element corresponding to the region containing the target voltage vector and switching the first switching element to repeat the switching state of the first switching element in a predetermined mode.

6. The electric motor drive device according to claim 1, characterized in that, The first switching element is a field-effect transistor made of SiC material, and the second switching element is an insulated-gate bipolar transistor made of Si material.

7. An electric motor drive device for driving an electric motor having multiple windings corresponding to multiple phases, wherein, The electric motor drive device includes: The first inverter includes a plurality of first switching elements and is respectively connected to the first ends of the plurality of windings; The second inverter includes a plurality of second switching elements and is respectively connected to the second ends of the plurality of windings; Multiple third switching elements, one end of which is connected to a point that divides the number of turns of the multiple windings into a predetermined ratio, and the other ends of which are connected to each other; and When the required output of the motor is above a preset reference value, the controller disconnects the third switching element, fixes the switching state of the second switching element whose switching loss is greater than that of the first switching element, and switches the first switching element to synthesize the target voltage vector, thereby operating the first inverter and the second inverter simultaneously through space vector pulse width modulation.

8. The electric motor drive device according to claim 7, characterized in that, The controller synthesizes the target voltage vector, which does not include voltage vectors in the voltage vector synthesized by the first inverter and the second inverter where the difference between the common-mode voltage of the first inverter and the common-mode voltage of the second inverter is not 0.

9. The electric motor drive device according to claim 7, characterized in that, The controller fixes the on / off state of the second switching element for each region of the voltage vector synthesized by the first inverter and the second inverter, and switches the first switching element to synthesize the target voltage vector.

10. The electric motor drive device according to claim 9, characterized in that, The controller connects points in a vector diagram showing the voltage vector synthesized by the first inverter and the second inverter that have the same switching state as the second inverter, in order to pre-define the area.

11. The electric motor drive device according to claim 9, characterized in that, The controller synthesizes the target voltage vector by fixing the switching state of the second switching element corresponding to the region containing the target voltage vector and switching the first switching element to repeat the switching state of the first switching element in a predetermined mode.

12. The electric motor drive device according to claim 7, characterized in that, The first switching element is a field-effect transistor made of SiC material, and the second switching element is an insulated-gate bipolar transistor made of Si material.

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