Motor driving system and control method thereof

Abstract

The invention relates to a motor driving system and a control method thereof. The motor driving system controls the driving mode of the motor, so that the system is switched to one of a first driving mode and a second driving mode. And tracking a second target operation point in the second driving mode when the first target operation point output according to the current demand belongs to a second operation point region corresponding to the second driving mode, and the second target operation point according to the torque derating of the motor belongs to a first operation point region corresponding to the first driving mode.

Description

Technical Field

[0001] This invention relates to a motor drive system and control method with improved drive mode switching logic under torque derating conditions. Background Technology

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

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

[0004] The fuel efficiency (or electrical efficiency) of environmentally friendly vehicles (e.g., electric vehicles) that use torque generated by an electric motor as power is determined by the power conversion efficiency of the inverter-motor. Therefore, in order to improve fuel efficiency, it is essential to maximize the power conversion efficiency of the inverter and the efficiency of the motor.

[0005] The efficiency of an inverter-motor system can be (e.g., primarily) determined by the voltage utilization rate of the inverter. If the vehicle's operating point, which is determined by the relationship between motor speed and torque, is located within a range of high voltage utilization, the vehicle's fuel efficiency can be improved.

[0006] However, when increasing the number of winding turns in the motor to increase its maximum torque, the range with higher voltage utilization becomes further away from the low torque region, which is the vehicle's primary operating point, thus potentially reducing fuel efficiency. Furthermore, if the primary operating point is designed to fall within the range with higher voltage utilization for fuel efficiency, there is a limitation on the motor's maximum torque, which may reduce the vehicle's acceleration and starting performance.

[0007] Because of the need for a motor drive technology that can improve system efficiency while covering both low-power and high-power ranges with a single motor, a technique that uses two inverters and a mode switch to drive a single motor in two different modes has recently been introduced.

[0008] The above background description is intended to enhance understanding of the background of this invention and should not be considered as prior art. Summary of the Invention

[0009] The present invention provides a motor drive system and control method thereof, which can prevent (e.g., or minimize) inverter damage by improving the motor drive mode switching logic under torque derating conditions.

[0010] This invention is not limited to the purposes mentioned herein, and other purposes not mentioned may be understood from the description herein.

[0011] In an exemplary embodiment, a motor drive system is provided, the motor drive system comprising: a motor including a plurality of windings; a first inverter connected to one end (e.g., a first end) of each of the plurality of windings; a second inverter connected to the other end (e.g., a second end) of each of the plurality of windings; and a controller configured to control a drive mode of the motor to switch between a first drive mode using the first inverter and a second drive mode using the first inverter and the second inverter. The second target operating point is tracked in the second drive mode when a first target operating point based on (e.g., according to) the current (e.g., demand) output belongs to a second operating point region corresponding to the second drive mode, and a second target operating point based on the motor's torque derating belongs to a first operating point region corresponding to the first drive mode.

[0012] In an exemplary embodiment, a method for controlling a motor drive system is provided. The motor drive system includes a motor having a plurality of windings, a first inverter connected to one end of each of the plurality of windings, and a second inverter connected to the other end of each of the plurality of windings. The method includes: controlling a drive mode of the motor to switch between a first drive mode using the first inverter and a second drive mode using the first and second inverters; and tracking a second target operating point in the second drive mode when a first target operating point based on current (e.g., demand) torque belongs to a second operating point region corresponding to the second drive mode, and a second target operating point based on torque derating of the motor belongs to a first operating point region corresponding to the first drive mode. Attached Figure Description

[0013] The objects and features of the present invention can be understood from the description herein and the accompanying drawings, wherein:

[0014] Figure 1 This is a circuit diagram of a motor drive system according to an exemplary embodiment of the present invention;

[0015] Figure 2 This is a schematic diagram of the switching of motor drive modes according to an exemplary embodiment of the present invention;

[0016] Figure 3 , Figure 4 and Figure 5 This is a schematic diagram of an operating point tracking method under torque derating according to an exemplary embodiment of the present invention; and

[0017] Figure 6This is a flowchart of a method for controlling a motor drive system according to an exemplary embodiment of the present invention. Detailed Implementation

[0018] The structural and functional descriptions of exemplary embodiments of the invention disclosed herein are illustrative. Exemplary embodiments of the invention may be provided in various forms and should not be construed as limited to the exemplary implementations described herein.

[0019] Since exemplary embodiments of the present invention can be modified in various ways and can have various forms, exemplary embodiments are provided in the accompanying drawings and described herein. The present invention and the accompanying drawings are not intended to limit the exemplary embodiments, and are to be understood to include variations, equivalents, and alternatives that fall within the scope of the invention.

[0020] Unless otherwise stated, terms including technical or scientific terms have the same or similar meanings as commonly understood in the field to which this invention pertains. Commonly used terms (such as those defined in dictionaries) may be interpreted in context as having the same meaning as those in the relevant art.

[0021] In this document, exemplary embodiments disclosed herein may be described with reference to the accompanying drawings. Identical or similar reference numerals may be assigned to the same or similar components, and redundant descriptions may be omitted.

[0022] In the following description of the embodiments, the term "preset" means that the value of a parameter is predetermined when it is used in a process or algorithm. According to an exemplary embodiment, the value of a parameter may be set at the beginning of the process or algorithm, or may be set during the execution of the process or algorithm.

[0023] The terms “module” and “unit” or “section” may be used to refer to components in this article to aid in understanding the components, and therefore they are not considered to have a separate meaning or function.

[0024] In the exemplary embodiments disclosed herein, detailed descriptions of functions and configurations may be omitted where such descriptions might obscure the subject matter of the invention. Furthermore, the accompanying drawings are provided to provide an understanding of the exemplary embodiments disclosed herein and are not intended to limit the technical spirit disclosed herein, and may include (e.g., all) modified embodiments, equivalent embodiments, and alternative embodiments provided herein.

[0025] The terms "first" and / or "second" are used to describe various components, but these components are not limited by these terms. The terms are used to distinguish one component from another.

[0026] When a component is "coupled" or "connected" to another component, the component can be (e.g., directly) coupled or connected to the other component, and a third component may also exist between the two components. When a component is "directly coupled" or "directly connected" to another component, there may be no element between the two components.

[0027] Unless the context otherwise indicates, elements described in the singular are intended to include multiple elements.

[0028] In this invention, the terms "comprising" or "including" may indicate the presence of the said feature, value, step, operation, component, part or combination thereof, but do not exclude the presence or addition of one or more other features, values, steps, operations, components or combinations thereof.

[0029] Furthermore, the term "unit" or "control unit" included in the names of components such as motor control unit (MCU) and hybrid power control unit (HCU) refers to a control device used to control (e.g., specific) vehicle functions, and does not imply a general-purpose functional unit.

[0030] The 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 controller's functions. The memory stores the operating system, logic instructions, input / output information, etc. The one or more processors perform determination, calculation, and decision-making for controlling the functions.

[0031] Figure 1 This is a circuit diagram of a motor drive system according to an exemplary embodiment of the present invention.

[0032] refer to Figure 1 The motor drive system according to an exemplary embodiment may include a first inverter 10, a second inverter 20, a motor 30 having a plurality of corresponding windings C1, C2 and C3, a mode switching unit 40, a battery 50, a DC capacitor (e.g., a DC link capacitor) 60 and a controller 70.

[0033] The first inverter 10 may include a plurality of first switching elements S11 to S16 connected to one end of each of the 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 each of the plurality of windings C1, C2, and C3. The mode switching unit 40 may include a plurality of switches S31, S32, and S33 connected between the other end of the plurality of windings C1, C2, and C3 and the neutral terminal of the plurality of windings C1, C2, and C3. 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 switches S31, S32 and S33 based on the motor's (e.g., demand) output power (e.g., motor torque command), the DC link voltage of the inverters 10 and 20 (e.g., battery voltage), the motor's phase current and motor angle.

[0034] The first inverter 10 may include a plurality of branches 11, 12, and 13, which are applied with a DC voltage generated in a DC capacitor 60 connected between the two ends of the battery 50. Branches 11, 12, and 13 may be electrically connected to a plurality of phases of the motor 30.

[0035] In an exemplary embodiment, the first branch 11 includes two switching elements S11 and S12 connected in series between the two ends of the DC capacitor 60, and the connection node of the two switching elements S11 and S12 can be connected to one end of the winding C1 of one phase of the motor 30, thereby inputting and outputting AC power corresponding to one of the multiple phases. Similarly, in an exemplary embodiment, the second branch 12 includes two switching elements S13 and S14 connected in series between the two ends of the DC capacitor 60, and the connection node of the two switching elements S13 and S14 can be connected to one end of the winding C2 of one phase of the motor 30, thereby inputting and outputting AC power corresponding to one of the multiple phases. Furthermore, in an exemplary embodiment, the third branch 13 includes two switching elements S15 and S16 connected in series between the two ends of the DC capacitor 60, and the connection node of the two switching elements S15 and S16 can be connected to one end of the winding C3 of one phase of the motor 30, thereby inputting and outputting AC power corresponding to one of the multiple phases.

[0036] The second inverter 20 may include multiple branches 21, 22, and 23, which are applied with a DC voltage generated in a DC capacitor 60 connected between the two ends of the battery 50. Branches 21, 22, and 23 may be electrically connected to multiple phases of the motor 30.

[0037] In an exemplary embodiment, the first branch 21 includes two switching elements S21 and S22 connected in series between the two ends of the DC capacitor 60, and the connection node of the two switching elements S21 and S22 can be connected to the other end of the winding C1 of one phase of the motor 30, thereby inputting and outputting AC power corresponding to one of the multiple phases. Similarly, in an exemplary embodiment, the second branch 22 includes two switching elements S23 and S24 connected in series between the two ends of the DC capacitor 60, and the connection node of the two switching elements S23 and S24 can be connected to the other end of the winding C2 of one phase of the motor 30, thereby enabling the input and output of AC power corresponding to one of the multiple phases. Furthermore, in an exemplary embodiment, the third branch 23 includes two switching elements S25 and S26 connected in series between the two ends of the DC capacitor 60, and the connection node of the two switching elements S25 and S26 can be connected to the other end of the winding C3 of one phase of the motor 30, thereby enabling the input and output of AC power corresponding to one of the multiple phases.

[0038] Each of the multiple switches S31, S32, and S33 can be connected to the other end of each of the multiple windings C1, C2, and C3 included in the motor 30, and the other ends of switches S31, S32, and S33 can be interconnected to form a node. The multiple switches S31, S32, and S33 can be other suitable switches or switching devices, such as MOSFETs, IGBTs, thyristors, relays, etc.

[0039] although Figure 1 Not shown, but the motor drive system may further include a so-called Y capacitor (Y-Cap), which connects two capacitors in series between a positive (+) DC terminal and a negative (-) DC terminal, and grounds the connection node between the capacitors.

[0040] The controller 70 can control the operation of the motor 30 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 power of the motor 30 (e.g., demand).

[0041] Furthermore, the controller 70 can control the on / off states of 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 an exemplary embodiment, the first drive mode may be referred to as a "closed end winding (CEW) mode" and the second drive mode may be referred to as an "open end winding (OEW) mode".

[0042] In an exemplary embodiment, in CEW mode, the controller 70 can control switches S31, S32, and S33 to be turned on, and drive the motor 30 through the first inverter 10 of the two inverters 10 and 20. When the mode switches S31, S32, and S33 are in the turned-on state, they can form the neutral point of the motor through the node connected to their other ends.

[0043] In an exemplary embodiment, in OEW mode, controller 70 can control switches S31, S32, and S33 to be off and drive motor 30 through two inverters 10 and 20. When off, switches S31, S32, and S33 can electrically disconnect the nodes connected to their other ends from the other ends of the plurality of windings C1 to C3. In this case, the nodes connected to the other ends of switches S31, S32, and S33 may not form the neutral point of the motor.

[0044] In this article, reference will be made to Figure 2 Describes the motor drive mode switching according to an exemplary embodiment.

[0045] Figure 2 This is a schematic diagram of the switching of motor drive modes according to an exemplary embodiment of the present invention.

[0046] refer to Figure 2 The first operating point region a1 and the second operating point region a2 are set in the torque and speed curve.

[0047] The first operating point area a1 is the operating point area of ​​the first drive mode. When the current target operating point of the motor 30 belongs to the first operating point area a1 (p1), the controller 70 can perform control to switch the drive mode of the motor 30 to the first drive mode.

[0048] The second operating point area a2 is the operating point area corresponding to the second drive mode. When the current target operating point of the motor 30 belongs to the second operating point area a2 (p2), the controller 70 can perform control to switch the drive mode of the motor 30 to the second drive mode.

[0049] The second operating point region a2 is the region where the torque is greater than that of the first operating point region a1 under the same speed of motor 30. Therefore, the output power of motor 30 can be increased in the second driving mode compared with the first driving mode.

[0050] The controller 70 can switch between a first drive mode and a second drive mode in both directions. When the high output power of the motor 30 may not be needed (e.g., it is not required), the motor 30 can be driven (e.g., effectively driven) in the first drive mode. When the high output power of the motor 30 may be needed (e.g., it is required), the output power of the motor 30 can be provided (e.g., guaranteed) in the second drive mode.

[0051] In the case of torque derating of motor 30, it is useful (e.g., necessary) to include (e.g., reflect) the torque fluctuations caused by derating in the drive mode switching logic. In an exemplary embodiment, torque derating can be (e.g., intentionally) a control that limits or reduces torque, and controller 70 can perform torque derating when the temperature of at least one of the first inverter 10 and the second inverter 20 meets (e.g., satisfies) a preset temperature condition. For example, torque derating can be performed when the temperature of at least one of the first inverter 10 and the second inverter 20 exceeds a preset temperature and is (e.g., becomes) overheated. Reference will be made herein to... Figure 3 and Figure 4 Provides drive mode switching in case of torque derating.

[0052] Figure 3 , Figure 4 and Figure 5 This is a schematic diagram of an operating point tracking method under torque derating conditions according to an exemplary embodiment of the present invention.

[0053] First, refer to Figure 3 In the case of torque derating, when the first target operating point t1 output according to the current (e.g., demand) belongs to the second operating point region a2 corresponding to the second drive mode, and the second target operating point t2 according to the torque derating of the motor 30 belongs to the first operating point region a1 corresponding to the first drive mode, the controller 70 can track the second target operating point t2 in the second drive mode.

[0054] and Figure 2 In comparison, Figure 3 In the case of torque derating, the controller 70 performs control such that even if the second target operating point t2 (which is the current target operating point) belongs to the first region a1, the drive mode is switched to the second drive mode and the second target operating point t2 is tracked in the second drive mode.

[0055] In an exemplary implementation, after the target operating point changes due to torque derating, when the torque derating is lifted due to the satisfaction of the torque derating removal condition (e.g., overheating relief of inverters 10 and 20), the target operating point recovers from the second target operating point t2 to (e.g., the original) target operating point (first target operating point t1). In an exemplary implementation where the drive mode switches to a first drive mode due to derating based on the operating point region to which the current target operating point belongs, if the derating is lifted, the first target operating point t1, included in the second operating point region a2, is tracked in the first drive mode (e.g., temporarily) until the drive mode switches again. In this case, current exceeding the specifications of switches S31 to S33 may be applied to inverters 10 and 20, which could lead to damage.

[0056] Therefore, in an exemplary embodiment, when the first target operating point t1 belongs to the second operating point region a2, the controller 70 tracks the first target operating point t1 in a second drive mode, and when the target operating point changes to the second target operating point t2 due to torque derating and belongs to the first operating point region a1, the controller 70 tracks the second target operating point t2 while maintaining the second drive mode, without switching the drive mode to the first drive mode. Thus, the situation described herein, where the controller tracks operating points included in the second operating point region a2 in the first drive mode, can be prevented.

[0057] refer to Figure 4 When both the first target operation point t1 and the second target operation point t2 belong to the second operation point region a2, the controller 70 can track the second target operation point t2 in the second drive mode.

[0058] In an exemplary implementation, if both the target operating point before torque derating and the target operating point after torque derating belong to the second operating point region a2, then as follows: Figure 2 As shown, the drive mode is controlled according to the operation point region to which the current target operation point belongs.

[0059] Similarly, refer to Figure 5 When both the first target operation point t1 and the second target operation point t2 belong to the first operation point region a1, the second target operation point t2 can be tracked in the first driving mode.

[0060] In an exemplary implementation, when both the target operating point before torque derating and the target operating point after torque derating belong to the first operating point region a1, it can be as follows: Figure 2 As shown, the control drive mode is based on the operation point region to which the current target operation point belongs.

[0061] Reference Figure 6 A method for controlling a motor drive system according to an exemplary embodiment is described.

[0062] refer to Figure 6 First, a torque command based on the output power of the motor 30 (e.g., demand) is applied to the controller 70 (step S610), and the controller 70 determines the operating point region to which the first target operating point belongs based on the torque command (step S620).

[0063] If the first target operation point belongs to the second operation point area (step S620), the controller 70 performs control to switch the drive mode of the motor 30 to the second drive mode (step S630).

[0064] Meanwhile, during the operation of motor 30, when the temperature of inverters 10 and 20 exceeds the preset temperature, controller 70 changes the first target operating point to the second target operating point through torque derating (step S650).

[0065] In this case, if the first target operation point belongs to the second operation point region (step S660 is "Yes") and the second target operation point belongs to the first operation point region (step S670 is "Yes"), then the controller 70 can (e.g., forcibly) maintain the second operation mode without switching the drive mode, and can track the second target operation point (step S680).

[0066] When the first target operation point belongs to the first operation point area (when step S620 is "No" and step S660 is "No"), the control drive mode is switched to the first operation mode (S690).

[0067] According to various exemplary embodiments of the present invention described herein, by improving the drive mode switching logic under torque derating conditions, it is possible to prevent or minimize the deviation of the motor's operating point from the operating point range of the current drive mode during torque derating and torque derating relief, thereby preventing or minimizing inverter damage.

[0068] This invention is not limited to the effects mentioned herein, and other effects not mentioned may be understood from the disclosure herein.

[0069] Although the invention has been provided and described with respect to exemplary embodiments, it will be apparent that modifications and changes may be made to the invention without departing from the invention and the claims provided herein.

Claims

1. A motor drive system, comprising: An electric motor, which includes multiple windings; The first inverter is connected to the first end of each of the plurality of windings; The second inverter is connected to the second end of each of the multiple windings; as well as A controller configured to control the motor drive mode to one of a first drive mode using a first inverter to drive the motor and a second drive mode using a first inverter and a second inverter, the controller being further configured to track the second target operation point in the second drive mode when a first target operation point output according to current demand belongs to the second operation point region corresponding to the second drive mode, and a second target operation point according to the torque derating of the motor belongs to the first operation point region corresponding to the first drive mode.

2. The motor drive system according to claim 1, wherein, When the temperature of at least one of the first inverter and the second inverter meets a preset temperature condition, the controller performs torque derating.

3. The motor drive system according to claim 1, wherein, When torque derating is not performed, if the first target operating point is within the first operating point region, the controller will control the drive mode to the first drive mode.

4. The motor drive system according to claim 3, wherein, When torque derating is not performed, if the first target operating point belongs to the second operating point region, the controller will control the drive mode to the second drive mode.

5. The motor drive system according to claim 1, wherein, The second operating point region includes the region where the torque is greater than that of the first operating point region under the condition that the motor speed is the same.

6. The motor drive system according to claim 1, wherein, When both the first target operation point and the second target operation point belong to the second operation point region, the controller tracks the second target operation point in a second drive mode.

7. The motor drive system according to claim 1, wherein, When both the first target operation point and the second target operation point belong to the first operation point area, the controller tracks the second target operation point in a first drive mode.

8. The motor drive system according to claim 1, further comprising a plurality of switches, wherein a first end of each of the plurality of switches is connected to a second end of each of the plurality of windings.

9. The motor drive system according to claim 8, wherein, Each of the plurality of switches has a second end, and the second ends of the plurality of switches are connected to each other to form a node.

10. The motor drive system according to claim 8, wherein, The controller controls the motor's drive mode by turning the plurality of switches on or off.

11. A method for controlling a motor drive system, the motor drive system comprising a motor having a plurality of windings, a first inverter connected to a first end of each of the plurality of windings, and a second inverter connected to a second end of each of the plurality of windings, the method comprising: The motor's drive mode is controlled to be one of a first drive mode that uses the first inverter to drive the motor and a second drive mode that uses the first inverter and the second inverter to drive the motor. When the first target operating point based on the current required torque belongs to the second operating point region corresponding to the second drive mode, and the second target operating point based on the torque derating of the motor belongs to the first operating point region corresponding to the first drive mode, the second target operating point is tracked in the second drive mode.

12. The method of claim 11, further comprising: When the temperature of at least one of the first inverter and the second inverter meets the preset temperature condition, torque derating is performed.

13. The method according to claim 11, wherein, The drive mode for controlling the motor includes: when torque derating is not performed, if the first target operating point is within the first operating point region, the drive mode is controlled to the first drive mode.

14. The method of claim 13, further comprising: When torque derating is not performed, if the first target operating point is within the second operating point region, the drive mode will be controlled to the second drive mode.

15. The method according to claim 11, wherein, The second operating point region includes the region where the torque is greater than that of the first operating point region under the condition that the motor speed is the same.

16. The method of claim 11, further comprising: When both the first target operation point and the second target operation point belong to the second operation point region, the second target operation point is tracked in the second drive mode.

17. The method of claim 11, further comprising: When both the first target operation point and the second target operation point belong to the first operation point area, the second target operation point is tracked in the first drive mode.

18. The method according to claim 11, wherein, The motor drive system further includes a plurality of switches, each of which has a first end connected to a second end of a plurality of windings.

19. The method according to claim 18, wherein, Each of the plurality of switches has a second end, and the second ends of the plurality of switches are connected to each other to form a node.

20. The method according to claim 18, wherein, The drive mode for controlling the motor includes turning the plurality of switches on or off.

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