Motor control device

Abstract

The motor control device of the present invention comprises an inverter, a converter, and a control device. The control device comprises: a rotational speed calculation unit for calculating the rotational speed of the motor; an optimal voltage calculation unit for calculating the optimal input voltage at which the total power loss incurred in the inverter, the motor, and the converter is minimized when the motor is operated at a motor operating point defined by the rotational speed and a target value of the torque generated by the motor, i.e., a target set torque; a minimum voltage calculation unit for calculating the minimum input voltage required to operate the motor at the motor operating point; and a target value setting unit for setting either the optimal input voltage or the minimum input voltage as the target input voltage. If the target set torque exceeds a predetermined value, the target value setting unit sets the minimum input voltage, which is lower than the optimal input voltage, as the target input voltage.

Description

Technical Field

[0001] The present invention relates to a motor control device.

[0002] This application claims the benefit of priority based on Japanese Patent Application No. 2020-038669, filed in Japan on March 6, 2020, the contents of which are incorporated herein by reference. Background Art

[0003] Japanese Patent No. 3797361 discloses a motor control device that controls the driving of a motor for traveling that is mounted in a vehicle.

[0004] The motor control device includes a converter that boosts the output voltage from the battery to a predetermined voltage, and an inverter that supplies the voltage boosted by the converter (hereinafter referred to as “input voltage”) to the motor.

[0005] The motor control device calculates a target value of input voltage suitable for efficient motor operation (hereinafter referred to as "target input voltage") based on the target value (hereinafter referred to as "target set torque") of the motor speed and the torque generated in the motor (hereinafter referred to as "motor torque"), and performs PWM (Pulse Width Modulation) control on the switching elements of the converter so that the input voltage reaches the target input voltage. Summary of the Invention

[0006] Problems to be solved by the invention

[0007] The motor control device described in Japanese Patent No. 3797361 requires setting a higher target input voltage to generate higher motor torque. Higher input voltages increase losses in the inverter's switching elements, leading to increased heat generation. Therefore, the motor control device described in Japanese Patent No. 3797361, which performs PWM control on the converter's switching elements to maintain the input voltage at the target input voltage, suffers from increased losses in the switching elements and increased heat generation at high torques.

[0008] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a motor control device that suppresses heat generation of a switching element of an inverter.

[0009] Means for solving problems

[0010] In order to achieve the object of solving the above-mentioned problems, the present invention adopts the following means.

[0011] (1) One embodiment of the present invention is a motor control device for controlling the drive of a motor using DC power output from a DC power supply, comprising: an inverter for converting the DC power into AC power and supplying it to the motor; a converter having a plurality of switching elements for converting the DC voltage from the DC power supply into a voltage input to the inverter, i.e., an input voltage, and supplying it to the inverter; and a control device for controlling the plurality of switching elements so that the input voltage becomes a target value, i.e., a target input voltage, the control device comprising: a speed calculation unit for calculating the speed of the motor; an optimal voltage calculation unit for calculating the optimal voltage when the motor is driven at a speed calculated by the speed calculation unit and a torque generated in the motor. When the motor is operated at the motor operating point specified by the target value, i.e., the target setting torque, the total of the power losses generated in each of the inverter, the motor, and the converter is calculated to be the lowest input voltage, i.e., the optimal input voltage; a minimum voltage calculation unit calculates the minimum value of the input voltage required for the motor to operate at the motor operating point, i.e., the minimum input voltage; and a target value setting unit sets either the optimal input voltage or the minimum input voltage as the target input voltage. When the target setting torque exceeds a specified value, the target value setting unit sets the minimum input voltage lower than the optimal input voltage as the target input voltage.

[0012] (2) In the motor control device described in (1) above, the following structure may also be adopted: when the target setting torque exceeds the prescribed value, the target value setting unit sets the minimum input voltage as the target input voltage; when the target setting torque is below the prescribed value, the higher one of the optimal input voltage and the minimum input voltage is set as the target input voltage.

[0013] (3) In the motor control device described in (1) or (2) above, the following structure may also be adopted: the motor includes a first motor for generating a driving force for the vehicle and a second motor having a power generation function, and when the target setting torque of the first motor is below the prescribed value, the target value setting unit sets the higher voltage between the optimal input voltage and the minimum input voltage as the target input voltage, and when the target setting torque of the first motor exceeds the prescribed value, the minimum input voltage is set as the target input voltage.

[0014] (4) In the motor control device described in any one of the above (1) to (3), the following structure can also be adopted: it also has: a voltage detection unit that detects the DC voltage; a current detection unit that detects the current output from the DC power supply to the converter, that is, the output current; a first storage unit that pre-stores a first loss map in which an operating point loss map is associated with each of the multiple input voltages, the operating point loss map indicating the correspondence between the rotational speed, the target setting torque, the power loss of the motor, and the total value of the power loss of the inverter, that is, the first power loss; a second storage unit that pre-stores a second loss map in which a converter loss map is associated with each of the multiple input voltages, the converter loss map indicating the correspondence between the DC voltage, the output current, and the power loss of the converter, that is, the second power loss; and a minimum voltage acquisition map indicating the correspondence between the rotational speed, the target setting torque, and the minimum input voltage, the optimal voltage calculation unit having: a first acquisition unit that reads a corresponding value from each of the multiple operating point loss maps. a first correspondence between the input voltage and the first power loss obtained by the rotational speed calculation unit and the first power loss corresponding to the target set torque indicated by the torque command value obtained externally; a second acquisition unit that obtains a second correspondence between the input voltage and the second power loss by reading the second power loss corresponding to the DC voltage measured by the voltage detection unit and the output current measured by the current detection unit from each of a plurality of converter loss maps; and a determination unit that, based on the first correspondence and the second correspondence, determines an input voltage at which the sum of the first power loss and the second power loss is minimized, and sends the input voltage to the target value setting unit as the optimal input voltage; and a minimum voltage calculation unit that reads the minimum input voltage corresponding to the target set torque indicated by the rotational speed of the motor calculated by the rotational speed calculation unit and the torque command value from the minimum voltage acquisition map, and sends the read minimum input voltage to the target value setting unit.

[0015] Effects of the Invention

[0016] As described above, according to the above-described aspects of the present invention, heat generation of the switching element of the inverter can be suppressed. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a circuit diagram showing an example of a schematic configuration of a vehicle 1 including a motor control device 4 according to the first embodiment of the present invention.

[0018] Figure 2 It is a schematic configuration diagram of the control device 19 included in the motor control device 4 according to the same embodiment.

[0019] Figure 3A This is a diagram illustrating a first loss graph 100 according to the same embodiment.

[0020] Figure 3B This is a diagram illustrating a first loss graph 100 according to the same embodiment.

[0021] Figure 4A This is a diagram illustrating a second loss graph 200 according to the same embodiment.

[0022] Figure 4B This is a diagram illustrating a second loss graph 200 according to the same embodiment.

[0023] Figure 5 This is a diagram illustrating an example of a minimum voltage acquisition map 300 according to the same embodiment.

[0024] Figure 6 This is a diagram illustrating a method for calculating the optimum input voltage Vref in the same embodiment.

[0025] Figure 7 This is a flowchart showing the flow of converter control operations according to the same embodiment.

[0026] Figure 8 This is a circuit diagram showing an example of a schematic configuration of a vehicle 1B including a motor control device 4B according to a second embodiment of the present invention.

[0027] Figure 9 1 is a schematic configuration diagram of a control device 19B included in a motor control device 4B according to the same embodiment.

[0028] Figure 10A This is a diagram illustrating a third loss graph 400 according to the same embodiment.

[0029] Figure 10B This is a diagram illustrating a third loss graph 400 according to the same embodiment.

[0030] Figure 11A This is a diagram illustrating an example of the first minimum voltage acquisition map 600 according to the same embodiment.

[0031] Figure 11B This is a diagram illustrating an example of the second minimum voltage acquisition map 700 according to the same embodiment.

[0032] Figure 12 This is a diagram illustrating a method for calculating the optimum input voltage Vref in the same embodiment.

[0033] Figure 13 This is a flowchart showing the flow of converter control operations according to the same embodiment. DETAILED DESCRIPTION

[0034] Hereinafter, a motor control device according to each embodiment of the present invention will be described with reference to the drawings.

[0035] <First embodiment>

[0036] Figure 1 An example of a schematic configuration of a vehicle 1 including the motor control device 4 according to the first embodiment is shown. The vehicle 1 is a vehicle including a motor for traveling, such as a hybrid vehicle or an electric vehicle.

[0037] like Figure 1 As shown, vehicle 1 includes a DC power supply 2 , a motor 3 , and a motor control device 4 .

[0038] The DC power supply 2 is mounted in the vehicle 1. The DC power supply 2 is, for example, a battery, and is a secondary battery such as a nickel-metal hydride battery or a lithium-ion battery. However, the DC power supply 2 is not limited to these, and an electric double layer capacitor (capacitor) may be used instead of a secondary battery.

[0039] The motor 3 is an electric motor whose driving is controlled by the motor control device 4. For example, the motor 3 is a motor for driving the vehicle 1.

[0040] The motor 3 of this first embodiment is a three-phase (U, V, W) brushless motor. Specifically, the motor 3 includes a rotor (not shown) with permanent magnets and a stator (not shown) on which coils Lu, Lv, and Lw corresponding to the three phases (U, V, and W) are wound sequentially in the direction of the rotor's rotation. Each of the coils Lu, Lv, and Lw for each phase is connected to a motor control device 4.

[0041] The motor 3 can also be a motor generator. That is, the motor 3 functions as a generator driven by the engine (not shown) of the vehicle 1, and can also function as a motor for starting the engine. The motor 3 of this first embodiment primarily functions as a motor, driving the wheels (not shown) of the vehicle 1.

[0042] The motor control device 4 converts DC power from the DC power supply 2 into AC power and supplies the AC power to the motor 3 . Alternatively, the motor control device 4 may convert regenerative power generated by the motor 3 into DC power and supply the DC power to the DC power supply 2 .

[0043] Below, use Figure 1 The structure of the motor control device 4 according to the first embodiment will be described. The motor control device 4 according to the first embodiment includes a capacitor 10, a boost converter 11, a capacitor 12, an inverter 13, a first voltage sensor 14, a second voltage sensor 15, a first current sensor 16, a second current sensor 17, a rotation angle sensor 18, and a control device 19.

[0044] Capacitor 10 is a smoothing capacitor provided on the primary side (DC power supply 2 side) of boost converter 11. Specifically, one end of capacitor 10 is connected to the positive terminal of DC power supply 2, and the other end is connected to the negative terminal of DC power supply 2. The negative terminal of DC power supply 2 is grounded.

[0045] The boost converter 11 boosts the DC voltage Vb output from the DC power supply 2 at a predetermined step-up ratio. The voltage boosted by the boost converter 11 is the voltage Vs input to the inverter 13 (hereinafter referred to as the "input voltage"). In this way, the boost converter 11 generates the input voltage Vs by boosting the DC voltage Vb output from the DC power supply 2 at a predetermined step-up ratio, and outputs the input voltage Vs to the inverter 13. Furthermore, the boost converter 11 may also have a function of stepping down the regenerative voltage input from the inverter 13 at a predetermined step-down ratio and outputting it to the DC power supply 2. Furthermore, the boost converter 11 is an example of a "converter" of the present invention. Below, an example of the schematic structure of the boost converter 11 is described.

[0046] Boost converter 11 includes a reactor 20 , and an upper switching element 21 and a lower switching element 22 connected in series with each other.

[0047] One end of the reactor 20 is connected to one end of the capacitor 10 , and the other end is connected to a connection point between the upper switching element 21 and the lower switching element 22 .

[0048] The upper switching element 21 and the lower switching element 22 are described as being IGBTs (Insulated Gate Bipolar Transistors), but the present invention is not limited thereto. For example, they may be FETs (Field Effective Transistors).

[0049] The collector terminal of the upper switching element 21 is connected to one terminal of the capacitor 12. The emitter terminal of the upper switching element 21 is connected to the other end of the reactor 20. The base terminal of the upper switching element 21 is connected to the control device 19.

[0050] The collector terminal of the lower switching element 22 is connected to the other end of the reactor 20. The emitter terminal of the lower switching element 22 is connected to the negative terminal of the DC power supply 2. The base terminal of the lower switching element 22 is connected to the control device 19.

[0051] Furthermore, boost converter 11 includes diodes D connected in antiparallel to upper switching element 21 and lower switching element 22. Diodes D are diode D1 connected in antiparallel to upper switching element 21 and diode D2 connected in antiparallel to lower switching element 22.

[0052] Capacitor 12 is connected to the secondary side (inverter 13 side) of boost converter 11. Capacitor 12 is a smoothing capacitor having one end connected to the collector terminal of upper switching element 21 and the other end connected to the negative terminal of DC power supply 2.

[0053] The inverter 13 converts the DC power output from the DC power supply 2 into AC power and supplies it to the motor 3. Specifically, the input voltage Vs is supplied to the inverter 13 from the boost converter 11. The inverter 13 converts the DC power from the boost converter 11 into AC power and supplies it to the motor 3. The inverter 13 of this first embodiment is a three-phase inverter as shown in the figure, and has three switching legs corresponding to each phase.

[0054] Specifically, inverter 13 includes a plurality of switching elements SW1 to SW6, and diodes D11 to D16 connected in antiparallel to the plurality of switching elements SW1 to SW6. Specifically, diode D11 is connected in antiparallel to switching element SW1. Furthermore, diode D12 is connected in antiparallel to switching element SW2. Furthermore, diode D13 is connected in antiparallel to switching element SW3. Furthermore, diode D14 is connected in antiparallel to switching element SW4. Furthermore, diode D15 is connected in antiparallel to switching element SW5. Furthermore, diode D16 is connected in antiparallel to switching element SW6.

[0055] Switching elements SW1 to SW6 may be IGBTs or FETs. Switching elements SW1 and SW2 are connected in series to form a switching branch. Switching elements SW3 and SW4 are connected in series to form a switching branch. Switching elements SW5 and SW6 are connected in series to form a switching branch.

[0056] The connection point between the switching element SW1 and the switching element SW2 is connected to the coil Lu. The connection point between the switching element SW3 and the switching element SW4 is connected to the coil Lv. The connection point between the switching element SW5 and the switching element SW6 is connected to the coil Lw.

[0057] The first voltage sensor 14 is connected between the terminals of the DC power supply 2 and detects the DC voltage Vb output from the DC power supply 2. In other words, the first voltage sensor 14 is a sensor installed between the terminals of the capacitor 10 to detect the voltage of the capacitor 10. The first voltage sensor 14 outputs the detected DC voltage Vb to the control device 19. The first voltage sensor 14 is an example of the "voltage detection unit" of the present invention.

[0058] The second voltage sensor 15 detects the input voltage Vs supplied from the boost converter 11 to the inverter 13. The second voltage sensor 15 is installed between the terminals of the capacitor 12. The second voltage sensor 15 outputs the detected input voltage Vs to the control device 19.

[0059] The first current sensor 16 detects the current output from the DC power supply 2 to the boost converter 11, that is, the output current Ib. The first current sensor 16 outputs the detected output current Ib to the control device 19. For example, the first current sensor 16 detects the output current Ib by detecting the current flowing in the reactor 20. However, it is not limited to this, and the first current sensor 16 can also be connected to any position if the current output from the DC power supply 2 to the boost converter 11, that is, the output current Ib, can be detected. The first current sensor 16 can also be a current transformer (CT) or a current sensor with a Hall element, or it can have a shunt resistor and detect the output current Ib from the voltage across the shunt resistor. Furthermore, the first current sensor 16 is an example of a "current detection unit" of the present invention.

[0060] Multiple second current sensors 17 detect the currents of each of the three phases (U, V, and W). Specifically, the multiple second current sensors 17 detect the phase current value Iu flowing through the U-phase coil Lu (hereinafter referred to as the "U-phase current value"), the phase current value Iv flowing through the V-phase coil Lv (hereinafter referred to as the "V-phase current value"), and the phase current value Iw flowing through the W-phase coil Lw (hereinafter referred to as the "W-phase current value"), and output these values ​​to the control device 19. For example, the multiple second current sensors 17 can be located between the inverter 13 and the motor 3 or within the inverter 13. As long as the configuration detects the phase current of each phase, the second current sensors 17 are not particularly limited; for example, they can be current transformers (CTs) including transformers or current sensors including Hall elements. Furthermore, the second current sensors 17 can also include shunt resistors and detect the phase current from the voltage across the shunt resistors.

[0061] Rotation angle sensor 18 detects the rotation angle of motor 3. The rotation angle of motor 3 is the electrical angle of the rotor relative to a predetermined reference rotational position. Rotation angle sensor 18 outputs a detection signal indicating the detected rotation angle to control device 19. For example, rotation angle sensor 18 may include a resolver.

[0062] The control device 19 performs inverter control based on the torque command value by performing PWM (Pulse Width Modulation) control on the switching elements SW1 to SW6 of the inverter 13. A known technique can be applied to this inverter control.

[0063] Furthermore, the control device 19 performs converter control based on the torque command value, controlling the upper switching element 21 and the lower switching element 22 to be in the on or off state so that the input voltage Vs reaches a target value (hereinafter referred to as the "target input voltage") Vx. For example, during converter control, the control device 19 performs PWM control on the upper switching element 21 and the lower switching element 22 so that the input voltage Vs reaches the target input voltage Vx.

[0064] Here, the torque command value is a target value (hereinafter referred to as “target setting torque”) Tref of torque (motor torque) to be generated in the motor 3 , and is transmitted to the control device 19 from an external device.

[0065] The control device 19 may also include a processor such as a CPU (Central Processing Unit) or an MPU (Micro Processing Unit), as well as non-volatile or volatile semiconductor memory (e.g., RAM (Random Access Memory), ROM (Read Only Memory), flash memory, EPROM (Erasable Programmable Read Only Memory), or EEPROM (Electrically Erasable Programmable Read Only Memory). For example, the control device 19 may include a microcontroller such as an MCU. Furthermore, the control device 19 may include drive circuits for the boost converter 11 and the inverter 13.

[0066] Below, use Figure 2 A schematic configuration for performing converter control in the control device 19 according to the first embodiment will be described. Figure 2This is a diagram showing an example of a schematic configuration of the control device 19 according to the first embodiment.

[0067] The control device 19 includes a rotation speed calculation unit 30 , a storage unit 31 , an optimum voltage calculation unit 32 , a minimum voltage calculation unit 33 , a torque determination unit 34 , a target value setting unit 35 , and a drive control unit 36 ​​.

[0068] The rotation speed calculation unit 30 calculates the rotation speed Nm of the motor 3 based on the detection signal output from the rotation angle sensor 18. The rotation speed calculation unit 30 calculates the rotation speed Nm using a well-known technique.

[0069] The storage unit 31 includes a first storage unit 40 , a second storage unit 41 , and a third storage unit 42 .

[0070] The first loss map 100 is stored in advance in the first storage unit 40 . Figure 3A and Figure 3B This is a diagram illustrating a first loss map 100 according to the first embodiment.

[0071] In the first loss map 100, an operating point loss map 101 is associated with each of the multiple input voltages Vs. This operating point loss map 101 shows the correspondence between the rotational speed Nm of the motor 3, the target set torque Tref, and the power loss Pk of the motor 3 and the inverter 13. The power loss Pk in this embodiment is an example of the "first power loss" of the present invention. The power loss Pk is the sum of the power loss of the motor 3 and the power loss of the inverter 13. The first loss map 100 is set in advance, for example, experimentally or theoretically.

[0072] The loss map 101 for each operating point is information used to calculate the power loss Pk from the rotational speed Nm and the target set torque Tref. Here, the rotational speed Nm and the target set torque Tref define the operation of the motor 3, that is, the motor operating point. Therefore, the loss map 101 for each operating point is information used to calculate the power loss Pk generated when the motor 3 is operated at the motor operating point defined by the rotational speed Nm and the target set torque Tref.

[0073] exist Figure 3A In the example shown, in the first loss diagram 100, an operating point loss diagram 101 is associated with each of a plurality of input voltages V1 to Vn. Figure 3AIn the example shown, operating point loss map 101-1 defines the correspondence between the target set torque Tref, the rotational speed Nm of the motor 3, and the power loss Pk1 when the input voltage Vs is input voltage V1. Operating point loss map 101-2 defines the correspondence between the target set torque Tref, the rotational speed Nm of the motor 3, and the power loss Pk2 when the input voltage Vs is input voltage V2. Operating point loss map 101-3 defines the correspondence between the target set torque Tref, the rotational speed Nm of the motor 3, and the power loss Pk3 when the input voltage Vs is input voltage V3. Operating point loss map 101-4 defines the correspondence between the target set torque Tref, the rotational speed Nm of the motor 3, and the power loss Pk4 when the input voltage Vs is input voltage V4. Operating point loss map 101-5 defines the correspondence between the target set torque Tref, the rotational speed Nm of the motor 3, and the power loss Pk5 when the input voltage Vs is input voltage V5. In the operating point loss map 101 - n (n is an integer), a correspondence relationship among the target setting torque Tref, the rotation speed Nm of the motor 3 , and the power loss Pkn when the input voltage Vs is the input voltage Vn is defined.

[0074] Therefore, once the motor operating point is set, the correspondence relationship 103 between the input voltage Vs and the power loss Pk (hereinafter referred to as the "first correspondence relationship") is obtained from the first loss map 100 (for example, the dependence of the input voltage Vs on the power loss Pk). Figure 3B As shown, once the motor operating point is set and one of the power loss Pk and input voltage Vs is determined, the correlation between the other is calculated as a first correspondence 103. This first correspondence 103 can be a formula, a lookup table, or a graph.

[0075] The second loss map 200 is stored in advance in the second storage unit 41 . Figure 4A and Figure 4B This is a diagram illustrating the second loss graph 200 according to the first embodiment.

[0076] In the second loss map 200 , a converter loss map 201 showing the correspondence between output current Ib, DC voltage Vb, and power loss Pc of the boost converter 11 is associated with each of the plurality of input voltages Vs. The second loss map 200 is set in advance, for example, experimentally or theoretically.

[0077] The converter loss map 201 is information for calculating the power loss Pc from the output current Ib and the DC voltage Vb. Note that the power loss Pc in this embodiment is an example of the "second power loss" of the present invention.

[0078] exist Figure 4AIn the example shown, in the second loss diagram 200 , a converter loss diagram 201 is associated with each of the plurality of input voltages V1 to Vn. Figure 4A In the example shown, converter loss diagram 201-1 defines the correspondence between output current Ib, DC voltage Vb, and power loss Pc1 when input voltage Vs is input voltage V1. Converter loss diagram 201-2 defines the correspondence between output current Ib, DC voltage Vb, and power loss Pc2 when input voltage Vs is input voltage V2. Converter loss diagram 201-3 defines the correspondence between output current Ib, DC voltage Vb, and power loss Pc3 when input voltage Vs is input voltage V3. Converter loss diagram 201-4 defines the correspondence between output current Ib, DC voltage Vb, and power loss Pc4 when input voltage Vs is input voltage V4. Converter loss diagram 201-5 defines the correspondence between output current Ib, DC voltage Vb, and power loss Pc5 when input voltage Vs is input voltage V5. In the converter loss map 201 - n , the correspondence relationship among the output current Ib, the DC voltage Vb, and the power loss Pcn when the input voltage Vs is equal to the input voltage Vn is defined.

[0079] Therefore, once the motor operating point is set, the correspondence relationship between the input voltage Vs and the power loss Pc (hereinafter referred to as the "second correspondence relationship") 203 (for example, the dependence of the input voltage Vs on the power loss Pc) is obtained from the second loss map 200. Figure 4B As shown, once the motor operating point is set and one of the power loss Pc and input voltage Vs is determined, the correlation between the other is calculated as the second correspondence 203. This second correspondence 203 can be a formula, a lookup table, or a graph.

[0080] The third storage unit 42 stores in advance a minimum voltage acquisition map 300 . Figure 5 This is a diagram illustrating an example of the minimum voltage acquisition map 300 according to the first embodiment.

[0081] Minimum voltage acquisition map 300 shows the relationship between the rotational speed Nm of motor 3, the target set torque Tref, and the minimum input voltage Vmin. Minimum input voltage Vmin is the minimum value of input voltage Vs required to operate motor 3 at the motor operating point defined by the rotational speed Nm of motor 3 and the target set torque Tref.

[0082] For example, the minimum voltage acquisition diagram 300 may be a formula, a lookup table, or a graph. The minimum voltage acquisition diagram 300 may be determined experimentally or theoretically so that the minimum input voltage Vmin can be determined based on the speed Nm of the motor 3 and the target set torque Tref. Figure 5 As shown, in the case of using a preset lookup table as the minimum voltage acquisition diagram 300, the minimum voltage acquisition diagram 300 is a lookup table having, for each speed Nm, each target set torque Tref, the minimum input voltage Vmin associated with each combination of the speed Nm and the target set torque Tref.

[0083] When the motor 3 is operated at a motor operating point specified by the speed Nm calculated by the speed calculation unit 30 and the target value of the torque generated in the motor 3, that is, the target set torque Tref, the optimal voltage calculation unit 32 calculates the input voltage Vs at which the total of the power losses generated in each of the motor 3, the inverter 13, and the boost converter 11 is minimized as the optimal input voltage Vref.

[0084] Hereinafter, a schematic configuration of the optimum voltage calculation unit 32 according to the first embodiment will be described.

[0085] The optimum voltage calculation unit 32 includes a first acquisition unit 50 , a second acquisition unit 51 , and a determination unit 52 .

[0086] The first acquisition unit 50 refers to the first loss map 100 stored in the first storage unit 40. The first acquisition unit 50 then reads the power loss Pk corresponding to the motor speed Nm calculated by the speed calculation unit 30 and the target set torque Tref indicated by the externally obtained torque command value from each of the plurality of operating point loss maps 101, thereby acquiring a first correspondence 103 between the input voltage Vs and the power loss Pk.

[0087] The second acquisition unit 51 refers to the second loss map 200 stored in the second storage unit 41. The second acquisition unit 51 then acquires a second correspondence 203 between the input voltage Vs and the power loss Pc by reading the power loss Pc corresponding to the DC voltage Vb detected by the first voltage sensor 14 and the output current Ib detected by the first current sensor 16 from each of the plurality of converter loss maps 201.

[0088] Based on first correspondence relationship 103 and second correspondence relationship 203, decision unit 52 determines input voltage Vs at which the sum of power loss Pk and power loss Pc (hereinafter referred to as "total loss") is the lowest. Determination unit 52 then transmits this input voltage Vs to target value setting unit 35 as optimal input voltage Vref.

[0089] As an example, Figure 6 As shown, the decision unit 52 synthesizes the first correspondence 103 and the second correspondence 203 to obtain the correspondence between the input voltage Vs and the total loss Ps, that is, the third correspondence 303. The third correspondence 303 can be a formula, a lookup table, or a graph. For example, Figure 6 As shown, the first correspondence relationship 103 defines the power loss Pk corresponding to each of the input voltages V1 to V5 (n=5). Furthermore, the second correspondence relationship 203 defines the power loss Pc corresponding to each of the input voltages V1 to V5 (n=5). Therefore, the determination unit 52 can calculate the third correspondence relationship 303 defining the total loss Ps (Ps1 to Ps5) corresponding to each of the input voltages V1 to V5 (n=5) by summing the power loss Pk and the power loss Pc for each input voltage. Furthermore, the determination unit 52 can calculate the total loss Ps between two points in the third correspondence relationship 303 (e.g., between Ps1 and Ps2, between Ps2 and Ps3, between Ps3 and Ps4, or between Ps4 and Ps5) by applying interpolation processing such as linear complementation or polynomial interpolation.

[0090] Then, the decision unit 52 searches the third correspondence 303 for the lowest total loss Ps, or the lowest power Pmin, and determines the input voltage Vs at this lowest power Pmin as the optimal input voltage Vref. Specifically, the decision unit 52 searches the third correspondence 303 for the lowest input voltage Vs, or the lowest total loss Ps, and determines this input voltage Vs as the optimal input voltage Vref.

[0091] The minimum voltage calculation unit 33 reads the minimum input voltage Vmin corresponding to the speed Nm of the motor 3 calculated by the speed calculation unit 30 and the target set torque Tref represented by the torque command value from the minimum voltage acquisition map 300, and sends the read minimum input voltage Vmin to the target value setting unit 35.

[0092] The torque determination unit 34 receives a torque command value from an external device and determines whether the target torque setting Tref indicated by the torque command value exceeds a predetermined value Tth. If the target torque setting Tref indicated by the torque command value exceeds the predetermined value Tth, the torque determination unit 34 outputs a first determination signal indicating this to the target value setting unit 35. If the target torque setting Tref indicated by the torque command value is below the predetermined value Tth, the torque determination unit 34 outputs a second determination signal indicating this to the target value setting unit 35.

[0093] Here, there is a correlation between motor torque and the temperature (loss) of the switching elements SW1 to SW6 and diodes D11 to D16 of inverter 13. Specifically, as motor torque increases, the temperature of the switching elements SW1 to SW6 and diodes D11 to D16 of inverter 13 also increases, increasing the heat generated by the switching elements SW1 to SW6 and diodes D11 to D16 of the inverter. The specified value Tth is a threshold for suppressing heat generation in at least one of the switching elements SW1 to SW6 and diodes D11 to D16 of inverter 13, and is determined through experiments, etc. For example, the specified value Tth is set to the motor torque when the temperature of at least one of the switching elements SW1 to SW6 and diodes D11 to D16 of the inverter exceeds a specified temperature. This specified temperature can be the maximum junction temperature or a temperature slightly lower than the maximum junction temperature by a specified value.

[0094] When the target set torque Tref represented by the torque command value is below the specified value Tth, the target value setting unit 35 sets the optimal input voltage Vref as the target input voltage Vx, provided that the optimal input voltage Vref is greater than the minimum input voltage Vmin. On the other hand, when the target set torque Tref exceeds the specified value Tth, the minimum input voltage Vmin is set as the target input voltage Vx. The target value setting unit 35 then outputs the set target input voltage Vx to the drive control unit 36. Here, the optimal input voltage Vref is generally higher than the minimum input voltage Vmin. However, consider the case where the optimal input voltage Vref is lower than the minimum input voltage Vmin. Therefore, when the target set torque Tref is below (or less than) the specified value Tth, the target value setting unit 35 compares the minimum input voltage Vmin with the optimal input voltage Vref. If the minimum input voltage Vmin is higher than the optimal input voltage Vref, the target value setting unit 35 sets the minimum input voltage Vmin as the target input voltage Vx.

[0095] For example, a flag indicating whether the target torque Tref is below a specified value Tth (hereinafter referred to as a "determination flag") is stored in the target value setting unit 35. For example, if the target torque Tref is below the specified value Tth, the determination flag is "0," and if the target torque Tref exceeds the specified value Tth, the determination flag is "1." That is, if the target value setting unit 35 receives the first determination signal from the torque determination unit 34, the determination flag is "1." On the other hand, if the target value setting unit 35 receives the second determination signal from the torque determination unit 34, the determination flag is "0." Therefore, the target value setting unit 35 checks the value of the determination flag. If the determination flag is "1," the minimum input voltage Vmin is set as the target input voltage Vx. On the other hand, if the determination flag is "0," the target value setting unit 35 sets the optimal input voltage Vref as the target input voltage Vx, except when the optimal input voltage Vref is below (or less than) the minimum input voltage Vmin. Furthermore, if the optimal input voltage Vref and the minimum input voltage Vmin are the same value, either the optimal input voltage Vref or the minimum input voltage Vmin may be set as the target input voltage Vx.

[0096] However, the present invention is not limited to this. In the target value setting unit 35, the determination mark may not be used. When the first determination signal is obtained, the lower voltage between the minimum input voltage Vmin and the optimal input voltage Vref may be set as the target input voltage Vx, and when the second determination signal is obtained, the optimal input voltage Vref may be set as the target input voltage Vx.

[0097] The drive control unit 36 ​​obtains the input voltage Vs detected by the second voltage sensor 15 and performs PWM control on the upper switching element 21 and the lower switching element 22 so that the input voltage Vs reaches the target input voltage Vx. For example, when performing PWM control on the upper switching element 21 and the lower switching element 22, the drive control unit 36 ​​may also obtain the input voltage Vs detected by the second voltage sensor 15 and perform feedback control (PI control or PID control) so that the input voltage Vs reaches the target input voltage Vx.

[0098] use Figure 7 The flow of converter control operations according to the first embodiment will be described. Figure 7 This is a diagram showing the flow of converter control operations according to the first embodiment.

[0099] The control device 19 repeats the process every fixed period. Figure 7 Boost converter 11 is controlled according to the operation shown.

[0100] The optimal voltage calculation unit 32 obtains a torque command value from an external device and a rotational speed Nm from the rotational speed calculation unit 30. Based on the torque command value and the rotational speed Nm, it calculates a first correspondence 103 between the input voltage Vs and the power loss Pk. Furthermore, the optimal voltage calculation unit 32 obtains a DC voltage Vb from the first voltage sensor 14 and an output current Ib from the first current sensor 16. Based on the DC voltage Vb and the output current Ib, it calculates a second correspondence 203 between the input voltage Vs and the power loss Pc. Based on the first correspondence 103 and the second correspondence 203, the optimal voltage calculation unit 32 calculates the input voltage Vs that minimizes the total loss Ps of the power loss Pk and the power loss Pc, and sets this input voltage Vs as the optimal input voltage Vref (step S101).

[0101] The minimum voltage calculation unit 33 obtains the minimum input voltage Vmin by reading the minimum input voltage Vmin corresponding to the rotation speed Nm of the motor 3 calculated by the rotation speed calculation unit 30 and the target setting torque indicated by the torque command value from the minimum voltage acquisition map 300 (step S102 ).

[0102] The torque determination unit 34 determines whether the target setting torque Tref exceeds the predetermined value Tth (step S103 ) and outputs the determination result to the target value setting unit 35 .

[0103] In the above determination result, if the target torque setting Tref is less than or equal to the predetermined value Tth, the target value setting unit 35 determines whether the optimal input voltage Vref is higher than the minimum input voltage Vmin (step S104). If the optimal input voltage Vref is higher than the minimum input voltage Vmin, the target value setting unit 35 sets the optimal input voltage Vref as the target input voltage Vx (step S105). On the other hand, if the optimal input voltage Vref is less than (or less than) the minimum input voltage Vmin in step S104, the target value setting unit 35 sets the minimum input voltage Vmin as the target input voltage Vx (step S106).

[0104] In the case where the target setting torque Tref exceeds the prescribed value Tth in the above-mentioned determination result of step S103 , the target value setting unit 35 sets the minimum input voltage Vmin as the target input voltage Vx (step S106 ).

[0105] Next, the effects of the converter control according to this embodiment will be described.

[0106] There is a correlation between motor torque and the temperature (loss) of the inverter's switching elements SW1-SW6 and diodes D11-D16. Specifically, as motor torque increases, the temperature of the inverter's switching elements SW1-SW6 and diodes D11-D16 also increases, leading to increased heat generation. Here, the control device 19 controls the motor 3 to achieve the target set torque Tref indicated by the torque command value. Therefore, the control device 19 monitors the target set torque Tref indicated by the torque command value and controls the boost converter 11 so that the minimum input voltage Vmin, rather than the optimal input voltage Vref, is input to the inverter 13 when the target set torque Tref exceeds a predetermined value Tth. This reduces power loss in the inverter's switching elements SW1-SW6 and diodes D11-D16, thereby suppressing heat generation in the inverter's switching elements.

[0107] Furthermore, while the optimal input voltage Vref is greater than the minimum input voltage Vmin, under certain conditions the optimal input voltage Vref may be less than the minimum input voltage Vmin. Therefore, when the target set torque Tref is below the predetermined value Tth, the control device 19 may output the higher of the optimal input voltage Vref and the minimum input voltage Vmin. This ensures the required torque while enabling the motor to be driven at the most efficient voltage for the vehicle.

[0108] <Second embodiment>

[0109] A vehicle 1B including a motor control device 4B according to a second embodiment will be described below. Compared to the configuration of the first embodiment described above, the vehicle 1B further includes a motor 60 serving as a motor generator. Figure 8 An example of a schematic configuration of a vehicle 1B including a motor control device 4B according to the second embodiment is shown.

[0110] Vehicle 1B is a vehicle including a motor for traveling, such as a hybrid vehicle or an electric vehicle.

[0111] like Figure 8 As shown, vehicle 1B includes DC power supply 2 , motor 3 , motor 60 , and motor control device 4B.

[0112] The motor 3 is an electric motor for generating driving force for the vehicle 1B through the motor control device 4B. For example, the motor 3 is a motor for driving the vehicle. The motor 3 is an example of the "first motor" of the present invention.

[0113] The motor 60 has a power generation function. The motor 60 is a so-called motor generator that is used as a generator driven by the engine of the vehicle 1B and also as a motor for starting the engine. The motor 60 is an example of the "second motor" of the present invention.

[0114] Motor control device 4B converts DC power from DC power supply 2 into AC power and supplies it to motor 3 and motor 60 . Motor control device 4B also converts regenerative power generated in motor 60 into DC power and supplies it to DC power supply 2 .

[0115] Below, use Figure 8 The configuration of a motor control device 4B according to the second embodiment will be described. The motor control device 4B according to the second embodiment includes a capacitor 10, a boost converter 11, a capacitor 12, an inverter 13, an inverter 61, a first voltage sensor 14, a second voltage sensor 15, a first current sensor 16, a second current sensor 17, a third current sensor 62, a rotation angle sensor 18, a rotation angle sensor 63, and a control device 19B.

[0116] The boost converter 11 of the second embodiment boosts the DC voltage Vb output from the DC power supply 2 at a predetermined boosting ratio. The voltage boosted by the boost converter 11, i.e., the input voltage Vs, is input to each of the inverter 13 and the inverter 61. Thus, the boost converter 11 generates the input voltage Vs by boosting the DC voltage Vb output from the DC power supply 2 at a predetermined boosting ratio, and outputs the input voltage Vs to the inverter 13 and the inverter 61.

[0117] Inverter 61 converts DC power output from a DC power source into AC power and supplies it to motor 60. Specifically, input voltage Vs is supplied from boost converter 11 to inverter 61. Inverter 61 converts the power from boost converter 11 into AC power and supplies it to motor 60. Inverter 61 is a three-phase inverter as shown in the figure, having three switching arms corresponding to each phase.

[0118] Specifically, inverter 61 includes a plurality of switching elements SW11 to SW16 and diodes D21 to D26 connected in antiparallel to the plurality of switching elements SW11 to SW16. Specifically, diode D21 is connected in antiparallel to switching element SW11. Furthermore, diode D22 is connected in antiparallel to switching element SW12. Furthermore, diode D23 is connected in antiparallel to switching element SW13. Furthermore, diode D24 is connected in antiparallel to switching element SW14. Furthermore, diode D25 is connected in antiparallel to switching element SW15. Furthermore, diode D26 is connected in antiparallel to switching element SW16.

[0119] Switching elements SW11 to SW16 may be IGBTs or FETs. Switching elements SW11 and SW12 are connected in series to form a switching branch. Switching elements SW13 and SW14 are connected in series to form a switching branch. Switching elements SW15 and SW16 are connected in series to form a switching branch.

[0120] The connection point of the switching elements SW11 and SW12 is connected to the coil Lu of the motor 60. The connection point of the switching elements SW13 and SW14 is connected to the coil Lv of the motor 60. The connection point of the switching elements SW15 and SW16 is connected to the coil Lw of the motor 60.

[0121] The plurality of third current sensors 62 have the same configuration as the second current sensor 17 , and detect the current of each of the three phases (U, V, W) of the motor 60 .

[0122] The rotation angle sensor 63 has the same configuration as the rotation angle sensor 18 , detects the rotation angle of the motor 60 , and outputs a second detection signal indicating the detected rotation angle to the control device 19B.

[0123] Based on the first torque command value, the control device 19B performs first inverter control, which performs PWM control on the switching elements SW1 to SW6 of the inverter 13. Furthermore, the control device 19B performs second inverter control, which performs PWM control on the switching elements SW11 to SW16 of the inverter 61. Here, the first torque command value is the target value of the motor torque generated by the motor 3 and is equivalent to the torque command value in the first embodiment described above. Known techniques can be applied to the first and second inverter controls.

[0124] Based on the second torque command value, the control device 19B performs converter control, turning the upper switching element 21 and the lower switching element 22 on or off, so that the input voltage Vs reaches the target input voltage Vx. For example, the control device 19B performs PWM control on the upper switching element 21 and the lower switching element 22 to achieve the target input voltage Vx during converter control. The second torque command value is the target value of the motor torque generated by the motor 60 and is transmitted to the control device 19B by an external device.

[0125] Control device 19B may include a processor such as a CPU or MPU, and non-volatile or volatile semiconductor memory (e.g., RAM, ROM, flash memory, EPROM, EEPROM). For example, control device 19B may include a microcontroller such as an MCU. Control device 19B may also include drive circuits for boost converter 11, inverter 13, and inverter 61.

[0126] Hereinafter, a schematic configuration for performing converter control in control device 19B according to the second embodiment will be described. Figure 9 This is a schematic configuration diagram for performing converter control in a control device 19B according to the second embodiment.

[0127] The control device 19B includes a rotation speed calculation unit 30 , a storage unit 31B, an optimal voltage calculation unit 32B, a minimum voltage calculation unit 33B, a torque determination unit 34B, a target value setting unit 35 , and a drive control unit 36 ​​.

[0128] The rotation speed calculation unit 30 calculates the rotation speed Nm of the motor 3 based on the first detection signal output from the rotation angle sensor 18 . The rotation speed calculation unit 30 also calculates the rotation speed Ng of the motor 60 based on the second detection signal output from the rotation angle sensor 63 .

[0129] The storage unit 31 includes a first storage unit 40B, a second storage unit 41, and a third storage unit 42B.

[0130] The first loss map 100 described in the first embodiment is stored in advance in the first storage unit 40B. Furthermore, the third loss map 400 is stored in advance in the first storage unit 40B. Figure 10A and Figure 10B This is a diagram illustrating a third loss graph 400 according to the second embodiment.

[0131] In the third loss map 400, an operating point loss map 401 showing the correspondence between the rotational speed Ng of the motor 60, the target set torque Tref, and the power loss Pg of the motor 60 and the inverter 61 is associated with each of the plurality of input voltages Vs. The third loss map 400 is set in advance, for example, experimentally or theoretically.

[0132] Furthermore, in this second embodiment, in order to distinguish between the first loss diagram 100 and the third loss diagram 400, the target setting torque Tref specified in the loss diagram 101 of each operating point of the first loss diagram 100 is referred to as "first target setting torque Tref1", and the target setting torque Tref specified in the loss diagram 401 of each operating point of the third loss diagram 400 is referred to as "second target setting torque Tref2".

[0133] The loss map 401 for each operating point is information used to calculate the power loss Pg from the rotational speed Ng and the second target torque Tref2. Here, the rotational speed Ng and the second target torque Tref2 define the operation of the motor 60, that is, the motor operating point. Therefore, the loss map 401 for each operating point is information used to calculate the power loss Pg generated when the motor 60 is operated at the motor operating point defined by the rotational speed Ng and the second target torque Tref2. The power loss Pg in this embodiment is an example of the "second power loss" in the present invention.

[0134] exist Figure 10A In the example shown, in the third loss diagram 400, an operating point loss diagram 401 is associated with each of a plurality of input voltages V1 to Vn. Figure 10A In the example shown, operating point loss map 401-1 defines the correspondence between the second target torque Tref2, the rotational speed Ng of the motor 60, and the power loss Pg1 when the input voltage Vs is input voltage V1. Operating point loss map 401-2 defines the correspondence between the second target torque Tref2, the rotational speed Ng of the motor 60, and the power loss Pg2 when the input voltage Vs is input voltage V2. Operating point loss map 401-3 defines the correspondence between the second target torque Tref2, the rotational speed Ng of the motor 60, and the power loss Pg3 when the input voltage Vs is input voltage V3. Operating point loss map 401-4 defines the correspondence between the second target torque Tref2, the rotational speed Ng of the motor 60, and the power loss Pg4 when the input voltage Vs is input voltage V4. Operating point loss map 401-5 defines the correspondence between the second target set torque Tref2, the rotational speed Ng of the motor 60, and the power loss Pg5 when the input voltage Vs is input voltage V5. Operating point loss map 401-n (n is an integer) defines the correspondence between the second target set torque Tref2, the rotational speed Ng of the motor 60, and the power loss Pgn when the input voltage Vs is input voltage Vn.

[0135] Therefore, once the motor operating point is set, the correspondence relationship (hereinafter referred to as the "fourth correspondence relationship") 403 between the input voltage Vs and the power loss Pg is obtained from the third loss map 400 (for example, the dependence of the input voltage Vs on the power loss Pg). Figure 10B As shown, once the motor operating point is set and one of the power loss Pg and input voltage Vs is determined, the correlation between the other is calculated as a fourth correspondence 403. This fourth correspondence 403 can be a formula, a lookup table, or a graph.

[0136] The first lowest voltage acquisition map 600 and the second lowest voltage acquisition map 700 are stored in advance in the third storage unit 42B. Figure 11A and Figure 11B This is a diagram illustrating an example of the first minimum voltage acquisition map 600 and the second minimum voltage acquisition map 700 according to the second embodiment.

[0137] The first minimum voltage acquisition map 600 is information showing the correspondence relationship between the rotation speed Nm of the motor 3, the first target setting torque Tref1, and the first minimum input voltage Vm ( Figure 11A The first minimum input voltage Vm is the minimum value of the input voltage Vs required to operate the motor 3 at the motor operating point defined by the motor 3's rotational speed Nm and the first target set torque Tref1. The first minimum voltage acquisition chart 600 is set in advance, for example, experimentally or theoretically.

[0138] The second minimum voltage acquisition map 700 is information showing the correspondence relationship between the rotation speed Ng of the motor 60, the second target setting torque Tref2, and the second minimum input voltage Vg ( Figure 11B The second minimum input voltage Vg is the minimum value of the input voltage Vs required to operate the motor 60 at the motor operating point defined by the rotational speed Ng of the motor 60 and the second target set torque Tref2. The second minimum voltage acquisition chart 700 is set in advance, for example, experimentally or theoretically.

[0139] Next, a schematic configuration of the optimal voltage calculation unit 32B according to the second embodiment will be described. The optimal voltage calculation unit 32B includes a first acquisition unit 50B, a second acquisition unit 51, and a determination unit 52B.

[0140] The first acquisition unit 50B refers to the first loss map 100 stored in the first storage unit 40B. The first acquisition unit 50B then reads the power loss Pk corresponding to the motor speed Nm calculated by the speed calculation unit 30 and the first target set torque Tref1 indicated by the externally obtained first torque command value from each of the plurality of operating point loss maps 101, thereby acquiring a first correspondence 103 between the input voltage Vs and the power loss Pk.

[0141] Furthermore, the first acquisition unit 50B refers to the third loss map 400 stored in the first storage unit 40B. The first acquisition unit 50B then reads the power loss Pg corresponding to the motor speed Ng calculated by the speed calculation unit 30 and the second target set torque Tref2 indicated by the externally obtained second torque command value from each of the plurality of operating point loss maps 401, thereby acquiring a fourth correspondence 403 between the input voltage Vs and the power loss Pg.

[0142] Based on first correspondence relationship 103, second correspondence relationship 203, and fourth correspondence relationship 403, decision unit 52B determines input voltage Vs that minimizes total loss Pz (the sum of power loss Pk, power loss Pg, and power loss Pc). Decision unit 52B then transmits this input voltage Vs to target value setting unit 35 as optimal input voltage Vref.

[0143] As an example, Figure 12 As shown, the decision unit 52B synthesizes the first correspondence 103, the second correspondence 203, and the fourth correspondence 403 to obtain the correspondence between the input voltage Vs and the total loss Pz, i.e., the fifth correspondence 503. The fifth correspondence 503 can be a formula, a lookup table, or a graph. For example, Figure 12 As shown, the first correspondence relationship 103 specifies the power loss Pk corresponding to each of the input voltages V1 to V5 (n=5). Furthermore, the second correspondence relationship 203 specifies the power loss Pc corresponding to each of the input voltages V1 to V5 (n=5). Furthermore, the fourth correspondence relationship 403 specifies the power loss Pg corresponding to each of the input voltages V1 to V5 (n=5).

[0144] Therefore, by summing the power loss Pk, power loss Pc, and power loss Pg for the same input voltage for each input voltage, determination unit 52B can determine a fifth correspondence 503 defining total losses Pz (Pz1 to Pz5) corresponding to each of input voltages V1 to V5 (n=5). Furthermore, determination unit 52B can also determine total losses Pz between two points in fifth correspondence 503 (e.g., between Pz1 and Pz2, between Pz2 and Pz3, between Pz3 and Pz4, or between Pz4 and Pz5) through interpolation processing such as linear complementation or polynomial interpolation.

[0145] Then, decision unit 52B searches for the lowest total loss Pz, or the lowest power Pmin, in fifth correspondence 503, and determines the input voltage Vs at this lowest power Pmin as the optimal input voltage Vref. Specifically, decision unit 52B searches for the lowest input voltage Vs at this lowest power Pmin in fifth correspondence 503, and determines this input voltage Vs as the optimal input voltage Vref.

[0146] The minimum voltage calculation unit 33B reads the first minimum input voltage Vm corresponding to the rotational speed Nm of the motor 3 calculated by the rotational speed calculation unit 30 and the first target torque Tref1 indicated by the first torque command value from the first minimum voltage acquisition map 600. Furthermore, the minimum voltage calculation unit 33B reads the second minimum input voltage Vg corresponding to the rotational speed Ng of the motor 60 calculated by the rotational speed calculation unit 30 and the second target torque Tref2 indicated by the second torque command value from the second minimum voltage acquisition map 700. The minimum voltage calculation unit 33B then compares the first minimum input voltage Vm with the second minimum input voltage Vg and sets the higher voltage as the minimum input voltage Vmin. The minimum voltage calculation unit 33B transmits the set minimum input voltage Vmin to the target value setting unit 35.

[0147] The torque determination unit 34 obtains a first torque command value from an external device and determines whether a first target torque setting Tref1 indicated by the first torque command value exceeds a predetermined value Tth. This is because the motor torque of the motor 3 for driving the vehicle significantly affects fuel efficiency.

[0148] When the first target setting torque Tref1 indicated by the first torque command value exceeds the predetermined value Tth, the torque determination unit 34 outputs a first determination signal indicating this to the target value setting unit 35. When the first target setting torque Tref1 indicated by the first torque command value is equal to or less than the predetermined value Tth, the torque determination unit 34 outputs a second determination signal indicating this to the target value setting unit 35.

[0149] In addition, the target value setting unit 35 and the drive control unit 36 ​​of the second embodiment are the same as those of the first embodiment, and therefore their description is omitted.

[0150] use Figure 13 The flow of converter control operations according to the second embodiment will be described. Figure 13 This is a diagram showing the flow of converter control operations according to the second embodiment.

[0151] The control device 19B repeats the process every fixed period. Figure 13 Boost converter 11 is controlled according to the operation shown.

[0152] The optimal voltage calculation unit 32B obtains a first torque command value from an external device and a rotational speed Nm from the rotational speed calculation unit 30. Based on the first torque command value and the rotational speed Nm, the optimal voltage calculation unit 32B calculates a first correspondence 103 between the input voltage Vs and the power loss Pk. The optimal voltage calculation unit 32B obtains a second torque command value from an external device and a rotational speed Ng from the rotational speed calculation unit 30. Based on the second torque command value and the rotational speed Ng, the optimal voltage calculation unit 32B calculates a fourth correspondence 403 between the input voltage Vs and the power loss Pg. Furthermore, the optimal voltage calculation unit 32B obtains a DC voltage Vb from the first voltage sensor 14 and an output current Ib from the first current sensor 16. Based on the DC voltage Vb and the output current Ib, the optimal voltage calculation unit 32B calculates a second correspondence 203 between the input voltage Vs and the power loss Pc. Then, the optimal voltage calculation unit 32B calculates the input voltage Vs at which the total loss Pz of the power loss Pk, power loss Pc and power loss Pg is the lowest based on the first correspondence 103, the second correspondence 203 and the fourth correspondence 403, and sets the input voltage Vs as the optimal input voltage Vref (step S201).

[0153] The minimum voltage calculation unit 33B reads the first minimum input voltage Vm corresponding to the rotational speed Nm of the motor 3 calculated by the rotational speed calculation unit 30 and the first target torque Tref1 indicated by the first torque command value from the first minimum voltage acquisition map 600. Furthermore, the minimum voltage calculation unit 33B reads the second minimum input voltage Vg corresponding to the rotational speed Ng of the motor 60 calculated by the rotational speed calculation unit 30 and the second target torque Tref2 indicated by the second torque command value from the second minimum voltage acquisition map 700. The minimum voltage calculation unit 33B then sets the higher of the first and second minimum input voltages Vm and Vg as the minimum input voltage Vmin (step S202).

[0154] The torque determination unit 34 determines whether the first target setting torque Tref1 indicated by the first torque command value exceeds a predetermined value Tth (step S203 ) and outputs the determination result to the target value setting unit 35 .

[0155] In the above determination, if the first target torque setting Tref1 is less than or equal to the predetermined value Tth, the target value setting unit 35 determines whether the optimal input voltage Vref is greater than the minimum input voltage Vmin (step S204). If the optimal input voltage Vref is greater than the minimum input voltage Vmin, the target value setting unit 35 sets the optimal input voltage Vref as the target input voltage Vx (step S205). On the other hand, if the optimal input voltage Vref is less than (or less than) the minimum input voltage Vmin in step S204, the target value setting unit 35 sets the minimum input voltage Vmin as the target input voltage Vx (step S206).

[0156] In step S203 , when the first target setting torque Tref1 exceeds the predetermined value Tth, the target value setting unit 35 sets the minimum input voltage Vmin as the target input voltage Vx (step S206 ).

[0157] While the embodiments of the present invention have been described in detail above with reference to the accompanying drawings, the specific configuration is not limited to these embodiments and encompasses designs within the scope of the present invention.

[0158] (Variation 1)

[0159] For example, the method for obtaining the optimal input voltage Vref and the method for obtaining the minimum input voltage Vmin of the control devices 19 and 19B are not particularly limited, and they may be calculated using methods other than those described in the first and second embodiments. For example, the control devices 19 and 19B may calculate the optimal input voltage Vref and the minimum input voltage Vmin using known techniques.

[0160] (Variation 2)

[0161] The boost converter 11 of the first embodiment and the second embodiment may be a multiphase converter having two or more phases. Furthermore, the boost converter 11 includes a plurality of reactors 20, and the plurality of reactors 20 may be magnetically coupled to each other.

[0162] As described above, when the target setting torque indicated by the torque command value exceeds the predetermined value Tth, the motor control device 4 in each of the above embodiments sets the minimum input voltage Vmin lower than the optimal input voltage Vref as the target input voltage Vx.

[0163] With such a configuration, heat generation of the switching elements SW1 to SW6 of the inverter 13 can be suppressed.

[0164] Furthermore, all or part of the control device 19 and control device 19B may be implemented by a computer. In this case, the computer may include a processor such as a CPU or GPU and a computer-readable recording medium. Furthermore, a program for implementing all or part of the functions of the control device 19 and control device 19B by a computer may be recorded on the computer-readable recording medium, and implemented by causing the processor to read and execute the program recorded on the recording medium. Here, "computer-readable recording medium" refers to removable media such as floppy disks, magneto-optical disks, ROMs, CD-ROMs, and storage devices such as hard disks built into the computer system. Furthermore, "computer-readable recording medium" may also include recording media that dynamically retain programs for a short period of time, such as when transmitting programs via a network such as the Internet or a communication line such as a telephone line, or recording media that retain programs for a certain period of time, such as volatile memory within a computer system that serves as a server or client in this case. In addition, the above-mentioned program can be a program for realizing part of the aforementioned functions, and can be a program for realizing the aforementioned functions by combining with a program already recorded in a computer system, or can be a program realized using a programmable logic device such as FPGA.

[0165] Description of labels

[0166] 1, 1B vehicle

[0167] 2 DC power supply

[0168] 3,60 motor

[0169] 4 Motor control device

[0170] 11 Boost Converter

[0171] 13,61 Inverter

[0172] 19, 19B Control Device

[0173] 30 Speed ​​calculation unit

[0174] 32 Optimal voltage calculation unit

[0175] 33 Minimum voltage calculation unit

[0176] 34 Torque determination unit

[0177] 35 Target value setting unit

[0178] 36 Drive control unit

[0179] 40 1st storage unit

[0180] 41 2nd storage unit

[0181] 42 3rd storage unit

Claims

1. A motor control device, characterized in that: This is a motor control device that uses DC power output from a DC power supply to control the drive of a motor. It has: an inverter that converts the DC power into AC power and supplies the AC power to the motor; a converter having a plurality of switching elements, configured to convert a DC voltage from the DC power supply into an input voltage to the inverter, i.e., an input voltage, and supply the converted voltage to the inverter; as well as a control device that controls the plurality of switching elements so that the input voltage becomes a target value, that is, a target input voltage; The control device has: A speed calculation unit, for calculating the speed of the motor; an optimal voltage calculation unit for calculating an optimal input voltage at which the sum of power losses generated in each of the inverter, the motor, and the converter is minimized when the motor is operated at a motor operating point defined by the rotational speed calculated by the rotational speed calculation unit and a target set torque, which is a target value of torque generated in the motor; a minimum voltage calculation unit for calculating a minimum value of the input voltage required for the motor to operate at the motor operating point, that is, a minimum input voltage; as well as a target value setting unit that sets either the optimal input voltage or the minimum input voltage as the target input voltage, When the target setting torque exceeds a predetermined value, the target value setting unit sets the lowest input voltage lower than the optimal input voltage as the target input voltage. The predetermined value is a threshold value for suppressing heat generation of at least any one of semiconductor elements including a switching element of the inverter.

2. The motor control device according to claim 1, wherein: The target value setting unit: When the target setting torque exceeds the predetermined value, the minimum input voltage is set to the target input voltage. When the target setting torque is equal to or less than the predetermined value, a higher voltage between the optimal input voltage and the minimum input voltage is set as the target input voltage.

3. The motor control device according to claim 1, wherein: The motor includes a first motor for generating driving force for the vehicle and a second motor having a power generation function; The target value setting unit: When the target setting torque of the first motor is equal to or less than the predetermined value, the higher one of the optimal input voltage and the minimum input voltage is set as the target input voltage. When the target setting torque of the first motor exceeds the predetermined value, the minimum input voltage is set as the target input voltage.

4. The motor control device according to any one of claims 1 to 3, wherein: Also features: a voltage detection unit, configured to detect the DC voltage; a current detection unit for detecting a current output from the DC power supply to the converter, ie, an output current; a first storage unit pre-stored with a first loss map, wherein an operating point loss map in the first loss map is associated with each of the plurality of input voltages, the operating point loss map indicating a correspondence relationship between the rotational speed, the target set torque, the power loss of the motor, and the power loss of the inverter, i.e., a total value of the first power loss; a second storage unit pre-stored with a second loss map, wherein a converter loss map in the second loss map is associated with each of the plurality of input voltages, the converter loss map indicating a correspondence between the DC voltage, the output current, and a power loss of the converter, i.e., a second power loss; as well as A minimum voltage acquisition diagram showing the corresponding relationship between the rotational speed, the target set torque and the minimum input voltage, The optimal voltage calculation unit has: a first acquiring unit for acquiring a first correspondence between the input voltage and the first power loss by reading, from each of the plurality of operating point loss maps, the first power loss corresponding to the rotational speed of the motor calculated by the rotational speed calculating unit and the target set torque represented by a torque command value obtained externally; a second acquiring unit configured to acquire a second correspondence between the input voltage and the second power loss by reading the second power loss corresponding to the DC voltage measured by the voltage detecting unit and the output current measured by the current detecting unit from each of a plurality of converter loss maps; as well as a determination unit that, based on the first correspondence relationship and the second correspondence relationship, determines an input voltage at which the sum of the first power loss and the second power loss is minimized, and sends the input voltage to the target value setting unit as the optimal input voltage; The minimum voltage calculation unit reads the minimum input voltage corresponding to the motor speed calculated by the speed calculation unit and the target setting torque represented by the torque command value from the minimum voltage acquisition map, and sends the read minimum input voltage to the target value setting unit.

Images