Motor control device

Abstract

The current command value deriving unit (13) of the motor control device (10) of the present invention derives a d-axis current command value and a q-axis current command value based on a torque current map (12map) and a torque command value. The voltage command value deriving unit (14) is capable of executing a first process and a second process, wherein in the first process, a d-axis voltage command value is derived based on the d-axis current command value, and a q-axis voltage command value is derived based on the q-axis current command value, and in the second process, a d-axis voltage command value is derived based on the q-axis current command value, and a q-axis voltage command value is derived based on a limit voltage and the d-axis voltage command value. When the motor (100) is driven by flux weakening control, if it is determined that each voltage command value that satisfies the torque command value can be derived by the first process, the voltage command value deriving unit (14) switches from the second process to the first process.

Description

Technical Field

[0001] The present invention relates to a motor control device for controlling a synchronous motor. Background Art

[0002] Patent Document 1 describes an example of a motor control device that performs vector control when rotating a motor that is a synchronous motor at a low speed and performs field weakening control when rotating the motor at a high speed.

[0003] In vector control, the d-axis current command value and the q-axis current command value are derived based on the torque command value, which is the motor torque command value. The d-axis current command value is the command value for the current of the d-axis component of the rotating coordinate system used for vector control, and the q-axis current command value is the command value for the current of the q-axis component of the rotating coordinate system. In the rotating coordinate system, the d-axis and q-axis axes are orthogonal to each other. Based on the d-axis current command value and the q-axis current command value, the d-axis voltage command value and the q-axis voltage command value are derived. The d-axis voltage command value is the command value for the voltage of the d-axis component, and the q-axis voltage command value is the command value for the voltage of the q-axis component. The motor is then driven by controlling the inverter based on these voltage command values.

[0004] In field-weakening control, a d-axis current command value is derived based on the deviation between the torque command value and the motor's actual torque. A d-axis voltage command value is then derived based on this d-axis current command value. Furthermore, a q-axis voltage command value is derived based on the limit voltage and the d-axis voltage command value. The motor is then driven by controlling the inverter based on these voltage command values.

[0005] In the aforementioned motor control, when a predetermined switching condition is met during field-weakening control, the motor drive control switches from field-weakening control to vector control. Specifically, a d-axis voltage command value and a q-axis voltage command value are derived to achieve the torque command value through vector control. Using the voltage vector represented by these derived d-axis and q-axis voltage command values ​​as a "determination voltage vector," if the length of the determination voltage vector falls below a limit voltage, the predetermined switching condition is determined to be met, and the motor drive control switches from field-weakening control to vector control.

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 2009-171825

[0007] The judgment voltage vector is a point on the equal torque line of the torque command value on the rotating coordinate system. Furthermore, depending on the method for deriving the current command values ​​in vector control, there is a possibility that the judgment voltage vector will continue to cross the intersection of the equal torque line of the torque command value and the voltage limit circle even when the torque command value changes. In this case, since the length of the judgment voltage vector remains equal to the limit voltage, the length of the judgment voltage vector does not fall below the limit voltage, preventing the motor drive control from being switched to vector control. In this case, if field weakening control is continued without switching to vector control, there is a concern that efficiency will be reduced compared to switching to vector control. Summary of the Invention

[0008] The motor control device for solving the above-mentioned problem is a device that derives a first voltage command value and a second voltage command value in the rotating coordinates of vector control, and drives the motor as a synchronous motor based on the above-mentioned first voltage command value and the above-mentioned second voltage command value, wherein the above-mentioned first voltage command value is the command value of the voltage of the first axis component, and the above-mentioned second voltage command value is the command value of the voltage of the second axis component orthogonal to the above-mentioned first axis. The motor control device includes: a current command value deriving unit configured to derive, based on a torque-current map, a first current command value for the first-axis component current corresponding to the torque command value, and a second current command value for the second-axis component current corresponding to the torque command value, the torque-current map indicating the relationship between the torque of the motor and the currents of the first and second-axis components; and a voltage command value deriving unit configured to execute a first process and a second process, wherein the first process derives the first voltage command value based on the first current command value and the second voltage command value based on the second current command value, and the second process derives the first voltage command value based on the second current command value and the second voltage command value based on a limit voltage of the motor control device and the first voltage command value. Furthermore, when the motor is driven based on the voltage command values ​​derived by the second process, if it is determined that the voltage command values ​​satisfying the torque command value can be derived by the first process, the voltage command value deriving unit switches the process of deriving the voltage command values ​​from the second process to the first process.

[0009] Driving the motor based on the voltage command values ​​derived through the first process is called vector control, and driving the motor based on the voltage command values ​​derived through the second process is called field weakening control.

[0010] According to the above structure, when the motor is driven by weak magnetic control, a determination is made as to whether each voltage command value that satisfies the torque command value can be derived by the first process. Then, if it is determined that it can be derived, the process of deriving each voltage command value is switched from the second process to the first process. In this first process, each current command value is derived using a predetermined torque-current map. Then, the motor is driven based on each voltage command value derived by the first process. That is, each voltage command value derived by the first process is a value within a predetermined range, and control switching is performed based on whether the torque command value can be derived within this range. In this way, the drive control of the motor can be switched from weak magnetic control to vector control.

[0011] Furthermore, when the voltage vector represented by the d-axis voltage command value and the q-axis voltage command value is used as the predetermined voltage vector, switching to vector control causes the predetermined voltage vector to point inward of the voltage limit circle on the rotating coordinate system. This results in more efficient motor driving than when the predetermined voltage vector continuously passes through the intersection of the equal torque line and the voltage limit circle. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 This is a block diagram showing the functional configuration of a motor control device according to an embodiment and a motor controlled by the motor control device.

[0013] Figure 2 This is a block diagram showing the functional structure of a voltage command value deriving unit of the motor control device.

[0014] Figure 3 This is a block diagram showing the functional structure of the voltage command value deriving unit.

[0015] Figure 4 This is a flowchart for explaining a processing routine executed by the voltage command value deriving unit.

[0016] Figure 5 This diagram shows the relationship between the voltage limit circle, the maximum torque curve, and the torque command value iso-torque curve on the rotation coordinates of vector control.

[0017] Figure 6 This is a diagram showing the relationship among the voltage limit circle, the maximum torque curve, and the torque curve of the torque command value on the rotating coordinate system. DETAILED DESCRIPTION

[0018] The following, according to Figures 1 to 6 An embodiment of a motor control device will be described.

[0019] Figure 1The present embodiment shows a motor control device 10 and a motor 100 controlled by the motor control device 10. The motor 100 includes a rotor 101 equipped with permanent magnets. The motor 100 is an embedded magnet synchronous motor with permanent magnets embedded within the rotor 101. The motor 100 includes three-phase coils: U-phase, V-phase, and W-phase. Furthermore, the motor 100 is used, for example, as a power source for a brake fluid discharge pump in a vehicle-mounted brake system.

[0020] The motor control device 10 drives the motor 100 by controlling the drive control of the current of the d-axis component and the current of the q-axis component. The so-called d-axis and q-axis are control axes on the rotating coordinates of the vector control. The d-axis is a control axis extending in the direction of the magnetic flux axis of the permanent magnet. The q-axis is a control axis extending in the direction of the torque and is orthogonal to the d-axis. The motor control device 10 drives the motor 100 by inputting signals based on the command value of the current of the d-axis component and the command value of the current of the q-axis component into the three-phase coil. In addition, in this embodiment, the d-axis is equivalent to the "first axis" and the q-axis is equivalent to the "second axis".

[0021] The motor control device 10 includes a command torque derivation unit 11 , a storage unit 12 , a current command value derivation unit 13 , a voltage command value derivation unit 14 , a two-phase / three-phase conversion unit 15 , an inverter 16 , a three-phase / two-phase conversion unit 17 , a rotation angle acquisition unit 18 , and a rotor position estimation unit 19 .

[0022] The command torque derivation unit 11 derives a torque command value TR*, which is a command value for the torque of the motor 100. Specifically, the command torque derivation unit 11 derives the torque command value TR* based on an estimated value TRLd of the load torque of the motor 100, a speed command value ωm*, which is a command value for the rotor speed of the motor 100, and an estimated speed ωm, which is an estimated value for the rotor speed.

[0023] The storage unit 12 stores a preset torque-current map 12map. The current flowing from the motor power supply 110 to the motor control device 10 is referred to as the power supply current Ibt, and the preset upper limit value of the power supply current is referred to as the power supply current upper limit value Ibtc. The torque-current map 12map represents the relationship between the torque TR of the motor 100 and the d-axis component current and the q-axis component current when a current greater than the power supply current upper limit value Ibtc is allowed to flow from the motor power supply 110 to the motor control device 10. For example, the so-called d-axis component current and q-axis component current corresponding to the first torque are the d-axis component current and q-axis component current used to make the torque of the motor 100 the first torque. In more detail, the current vector represented by the d-axis component current and the q-axis component current derived using the torque-current map 12map points to a point on the maximum torque curve LTRmax on the rotating coordinate.

[0024] The maximum torque curve LTRmax is a line formed by connecting the stored points on the rotation coordinate system, where the maximum torque that can be output from the motor 100 is stored for each constant current circle having different current values.

[0025] Based on the torque command value TR*, the current command value derivation unit 13 derives a d-axis current command value Idc and a q-axis current command value Iqc. The d-axis current command value Idc represents the d-axis current command value, while the q-axis current command value Iqc represents the q-axis current command value. Specifically, the current command value derivation unit 13 obtains the d-axis current command value Idc and the q-axis current command value Iqc based on the torque-current map 12map. The d-axis current command value Idc represents the d-axis current command value corresponding to the torque command value TR*, while the q-axis current command value Iqc represents the q-axis current command value. In this embodiment, the d-axis current command value Idc corresponds to the "first current command value," and the q-axis current command value Iqc corresponds to the "second current command value."

[0026] The voltage command value derivation unit 14 derives a d-axis voltage command value Vdc and a q-axis voltage command value Vqc. The d-axis voltage command value Vdc is the command value for the voltage of the d-axis component, and the q-axis voltage command value Vqc is the command value for the voltage of the q-axis component. Specifically, the voltage command value derivation unit 14 derives the d-axis voltage command value Vdc and the q-axis voltage command value Vqc based on the current command values ​​Idc and Iqc, the d-axis current Id and the q-axis current Iq, the estimated value ωe of the electrical angular velocity of the motor 100, and the power supply current upper limit value Ibtc and the power supply current Ibt. In this embodiment, the d-axis voltage command value Vdc corresponds to the "first voltage command value," and the q-axis voltage command value Vqc corresponds to the "second voltage command value." The specific derivation process for the d-axis voltage command value Vdc and the q-axis voltage command value Vqc will be described later.

[0027] The two-phase / three-phase converter 15 converts the d-axis voltage command value Vdc and the q-axis voltage command value Vqc into a U-phase command voltage VU*, a V-phase command voltage VV*, and a W-phase command voltage VW* based on the estimated rotor rotation angle (electrical angle) θe, which is an estimated value of the rotation angle of the rotor 101. The U-phase command voltage VU* is a command value for the voltage applied to the U-phase coil. The V-phase command voltage VV* is a command value for the voltage applied to the V-phase coil. The W-phase command voltage VW* is a command value for the voltage applied to the W-phase coil.

[0028] The inverter 16 has multiple switching elements that operate with power supplied from the motor power supply 110. The inverter 16 generates a U-phase signal by opening and closing the switching elements based on the U-phase command voltage VU* input from the two-phase / three-phase conversion unit 15. Furthermore, the inverter 16 generates a V-phase signal by opening and closing the switching elements based on the input V-phase command voltage VV*. Furthermore, the inverter 16 generates a W-phase signal by opening and closing the switching elements based on the input W-phase command voltage VW*. Thus, the U-phase signal is input to the U-phase coil of the motor 100, the V-phase signal is input to the V-phase coil, and the W-phase signal is input to the W-phase coil. When the signals generated by the inverter 16 are input to the motor 100, the motor 100 is driven. The signals generated by the inverter 16 are based on the d-axis voltage command value Vdc and the q-axis voltage command value Vqc.

[0029] The three-phase / two-phase converter 17 receives inputs of U-phase current IU, V-phase current IV, and W-phase current IW, respectively, flowing through the U-phase coil of the motor 100. Based on the estimated rotor rotation angle (electrical angle) θe, the three-phase / two-phase converter 17 converts the U-phase current IU, V-phase current IV, and W-phase current IW into a d-axis current Id and a q-axis current Iq. The d-axis current Id represents the d-axis component of the current, while the q-axis current Iq represents the q-axis component of the current.

[0030] The rotor position estimation unit 19 derives the axial phase deviation Δθ between the actual d-axis direction and the estimated d-axis direction. The d-axis current Id and q-axis current Iq derived by the three-phase / two-phase conversion unit 17 are input to the rotor position estimation unit 19. Furthermore, the d-axis voltage command value Vdc and q-axis voltage command value Vqc derived by the voltage command value derivation unit 14 are input to the rotor position estimation unit 19. The rotor position estimation unit 19 derives the axial phase deviation Δθ using, for example, an extended induced voltage method. In this case, the rotor position estimation unit 19 derives the axial phase deviation Δθ based on the d-axis current Id and q-axis current Iq, as well as the d-axis voltage command values ​​Vdc and q-axis voltage command values ​​Vqc.

[0031] The rotor position estimation unit 19 also derives an estimated value ωe of the electrical angular velocity of the rotor 101. The rotor position estimation unit 19 derives the estimated value ωe of the electrical angular velocity by, for example, performing proportional-integral control to keep the axial phase deviation Δθ at a target value of "0." The rotor position estimation unit 19 divides the estimated value ωe of the electrical angular velocity by the number of pole pairs Pn of the motor 100 to derive the estimated rotational speed ωm, which represents the mechanical angle of the rotor 101.

[0032] The rotation angle acquisition unit 18 acquires the estimated rotor rotation angle θe. The rotation angle acquisition unit 18 derives the estimated rotor rotation angle θe by, for example, integrating the estimated value ωe of the electrical angular velocity derived by the rotor position estimation unit 19.

[0033] Next, refer to Figure 2 , the circuit structure of the voltage command value derivation unit 14 is described in detail.

[0034] The voltage command value deriving unit 14 includes a first d-axis calculator 31 for deriving a d-axis current deviation ΔId, which is a deviation between the d-axis current command value Idc and the d-axis current Id, and a second d-axis calculator 32 for deriving a product of the d-axis current deviation ΔId and the response frequency ωc of the motor 100 .

[0035] The voltage command value derivation unit 14 includes a d-axis accumulator 33 that receives the derived value (=ΔId·ωc) derived by the second d-axis calculator 32. When the value selected by the first d-axis switch unit 34, described later, is used as the d-axis selected value Inpd, the d-axis accumulator 33 derives the sum of the previous value of the d-axis selected value Inpd and the derived value derived by the second d-axis calculator 32 as the latest value of the d-axis current integrated value Id1. The previous value of the d-axis selected value Inpd is the d-axis selected value Inpd selected by the first d-axis switch unit 34 during the previous control cycle.

[0036] The voltage command value derivation unit 14 includes a first d-axis switch unit 34, which selects one of the d-axis current command value Idc and the latest value of the d-axis current integrated value Id1 and outputs the selected value as the d-axis selected value Inpd. The resistance value accumulator 35 derives the product of the d-axis selected value Inpd and the resistance value R of the motor 100 as the d-axis reference voltage Vdb. The voltage command value derivation unit 14 includes a d-axis inductance accumulator 36, which derives the product of the value derived by the second d-axis calculator 32 and the d-axis inductance Ld of the motor 100 as the calculated value Vde. The voltage command value derivation unit 14 includes a high-pass filter 37, which extracts the high-frequency component of the calculated value Vde and outputs it to a third d-axis calculator 39. The voltage command value derivation unit 14 includes a second d-axis switch unit 38 that selects one of the high-frequency component extracted by the high-pass filter 37 and the calculated value Vde, and outputs the selected value to a third d-axis calculator 39. The third d-axis calculator 39 then derives the sum of the value selected by the second d-axis switch unit 38 and the d-axis reference voltage Vdb as a calculated value Vde2.

[0037] The voltage command value deriving unit 14 includes a fourth d-axis calculator 40 that derives the sum of a q-axis F / F value Vffq derived by a q-axis non-interference F / F unit 57 described later and a calculated value Vde2 as a d-axis voltage command value Vdc.

[0038] The voltage command value derivation unit 14 also includes a d-axis non-interference F / F unit 41, which receives as input the d-axis selection value Inpd selected by the first d-axis switch unit 34. The d-axis non-interference F / F unit 41 derives the product of the d-axis selection value Inpd, the estimated value ωe of the motor 100's electrical angular velocity, and the d-axis inductance Ld of the motor 100 as a d-axis F / F value Vffd. The d-axis F / F value Vffd corresponds to the voltage component of the d-axis component that affects the q-axis side. Therefore, the d-axis F / F value Vffd is input to the fifth q-axis calculator 61, described later.

[0039] The voltage command value derivation unit 14 includes a power supply current calculator 51 and an F / B unit 52. The power supply current calculator 51 derives a power supply current deviation ΔIbt, which is the deviation between the power supply current upper limit value Ibtc and the power supply current Ibt. The F / B unit 52 performs feedback control using the power supply current deviation ΔIbt as input to derive a calculated value Iq_comp. The voltage command value derivation unit 14 includes a first q-axis calculator 53 and a second q-axis calculator 54. The first q-axis calculator 53 derives a value obtained by subtracting the calculated value Iq_comp from the q-axis current command value Iqc as a corrected q-axis current command value Iqc1. The second q-axis calculator 54 derives a q-axis current deviation ΔIq, which is the deviation between the corrected q-axis current command value Iqc1 and the q-axis current Iq.

[0040] The voltage command value derivation unit 14 includes a third q-axis calculator 55 that derives the product of the q-axis current deviation ΔIq and the response frequency ωc. The voltage command value derivation unit 14 includes a q-axis integrator 56 that integrates the value derived by the third q-axis calculator 55 (ΔIq·ωc) as the q-axis current integrated value Iq1. When the q-axis integrator 56 uses the q-axis current integrated value Iq1 derived by the q-axis integrator 56 in the previous control cycle as the previous value of the q-axis current integrated value Iq1, the q-axis integrator 56 derives the sum of the previous value of the q-axis current integrated value Iq1 and the value derived by the third q-axis calculator 55 as the latest value of the q-axis current integrated value Iq1.

[0041] The voltage command value derivation unit 14 includes a q-axis non-interference F / F unit 57, which receives as input the latest value of the q-axis current integrated value Iq1. The q-axis non-interference F / F unit 57 derives the product of the q-axis current integrated value Iq1, the estimated value of the electrical angular velocity ωe, and the q-axis inductance Lq of the motor 100 as the q-axis F / F value Vffq. The q-axis F / F value Vffq corresponds to the voltage component of the q-axis component that affects the d-axis side. Therefore, the q-axis F / F value Vffq is input to the fourth d-axis calculator 40.

[0042] The voltage command value derivation unit 14 includes a resistance accumulator 58 and a q-axis inductance accumulator 59. The resistance accumulator 58 derives the product of the latest value of the q-axis current integrated value Iq1 and the resistance value R as the q-axis reference voltage Vqb. The q-axis inductance accumulator 59 derives the product of the value derived by the third q-axis calculator 55 and the q-axis inductance Lq as the calculated value Vqe. The voltage command value derivation unit 14 includes a fourth q-axis calculator 60 and a fifth q-axis calculator 61. The fourth q-axis calculator 60 derives the sum of the q-axis reference voltage Vqb and the calculated value Vqe as the calculated value Vqe2. The fifth q-axis calculator 61 derives the sum of the d-axis F / F value Vffd derived by the d-axis non-interference F / F unit 41 and the calculated value Vqe2.

[0043] The voltage command value derivation unit 14 includes a q-axis switch unit 62. This q-axis switch unit 62 selects one of the values ​​derived by the fifth q-axis calculator 61 and the square root of the difference between the square of the limit voltage Vm of the motor control device 10 and the square of the d-axis voltage command value Vdc. The value selected by the q-axis switch unit 62 is output as the q-axis voltage command value Vqc. The limit voltage Vm is a value based on the voltage of the motor power supply 110 and is a voltage that can be output from the inverter 16. Therefore, the motor 100 cannot output an output exceeding the limit voltage Vm.

[0044] In this embodiment, the drive control of the motor 100 is divided into vector control and field weakening control. Vector control is drive control for low-speed rotation, and field weakening control is drive control for high-speed rotation.

[0045] Next, refer to Figure 2 , vector control is explained.

[0046] When the motor 100 is driven by vector control, the first d-axis switch unit 34 selects the d-axis current integral value Id1. That is, when the motor 100 is driven by vector control, the value obtained by integrating the derived value of the second d-axis operator 32 is used to derive the voltage command values ​​Vdc and Vqc. In addition, the second d-axis switch unit 38 selects the calculated value Vde to be input to the third d-axis operator 39. In addition, the q-axis switch unit 62 selects the value derived by the fifth q-axis operator 61 as the q-axis voltage command value Vqc. Figure 2 The process of deriving the d-axis voltage command value Vdc and the q-axis voltage command value Vqc while the switches 34, 38, and 62 are operated as shown is referred to as the "first process." Specifically, in the first process, the d-axis voltage command value Vdc is derived based on the d-axis current command value Idc, and the q-axis voltage command value Vqc is derived based on the q-axis current command value Iqc.

[0047] Next, refer to Figure 3 , the field weakening control is explained.

[0048] When the motor 100 is driven by the weak magnetic control, the first d-axis switch unit 34 selects the d-axis current command value Idc. In addition, the second d-axis switch unit 38 selects the high-frequency variation component extracted from the calculation value Vde by the high-pass filter 37 to be input to the third d-axis operator 39. That is, when the motor 100 is driven by the weak magnetic control, the high-frequency variation component of the calculation value Vde is used to derive each voltage command value Vdc, Vqc. In addition, the high-frequency variation component extracted by the high-pass filter 37 can also be said to be the high-frequency variation component of the d-axis current Id. In addition, the q-axis switch unit 62 selects the square root of the difference between the square value of the limit voltage Vm and the square value of the d-axis voltage command value Vdc. Also as shown Figure 3 The process of deriving the d-axis voltage command value Vdc and the q-axis voltage command value Vqc while the switches 34, 38, and 62 are operated as shown is referred to as the "second process." Specifically, in the second process, the d-axis voltage command value Vdc is derived based on the d-axis current command value Idc and the q-axis current command value Iqc, and the q-axis voltage command value Vqc is derived based on the limit voltage Vm and the d-axis voltage command value Vdc. More specifically, in the second process, the d-axis voltage command value Vdc is derived based on the high-frequency fluctuation component of the d-axis current Id and the q-axis current command value Iqc.

[0049] Even when executing the second process, that is, even when driving motor 100 using field-weakening control, the fifth q-axis calculator 61 calculates the sum of the d-axis F / F value Vffd calculated by the d-axis non-interference F / F unit 41 and the calculated value Vqe2. This sum is used as the "switching voltage value Vqc'," which is then derived based on the d-axis current command value Idc and the q-axis current deviation ΔIq. While details will be described later, switching voltage value Vqc' serves as a criterion for determining whether to switch from field-weakening control to vector control.

[0050] Next, refer to Figure 4 Next, a description will be given of a processing routine executed by the motor control device 10. This processing routine is repeatedly executed in each predetermined control cycle.

[0051] In this processing routine, in step S11, a determination is made as to whether the motor 100 is being driven by field-weakening control. If it is determined that the motor 100 is being driven by field-weakening control (S11: "Yes"), the process proceeds to the next step, S12. In step S12, a determination is made as to whether the first switching condition is satisfied. In this embodiment, the first switching condition is determined to be satisfied if the following conditional expression (Equation 1) is satisfied. On the other hand, if the conditional expression (Equation 1) is not satisfied, the first switching condition is not determined to be satisfied.

[0052] [Formula 1]

[0053] VM 2 ≤Vdc 2 +Vqc' 2 …(Equation 1)

[0054] Here, as Figure 3As shown, the switching voltage value Vqc' can be considered the q-axis voltage command value derived to achieve the torque command value TR* through vector control. Therefore, if the voltage vector with the d-axis component voltage as the d-axis voltage command value Vdc and the q-axis component voltage as the switching voltage value Vqc' is used as the determination voltage vector, and if the determination voltage vector points to a point within the voltage limit circle C1 on the rotating coordinate system, the torque command value TR* can be satisfied even when switching from field-weakening control to vector control. In other words, it can be determined that the voltage command values ​​Vdc and Vqc that satisfy the torque command value TR* can be derived through the first processing. On the other hand, if the determination voltage vector points to a point outside the voltage limit circle C1 on the rotating coordinate system, the torque command value TR* cannot be satisfied when switching from field-weakening control to vector control. Furthermore, if the torque command value TR* changes, the point in the rotating coordinate system where the determination voltage vector points, that is, the direction and length of the determination voltage vector, also change. The so-called voltage limit circle is a circle defined on the rotating coordinate system and varies depending on the characteristics of the motor 100. Motor 100 cannot output d-axis current Id and q-axis current Iq outside the voltage limit circle. As limit voltage Vm increases, the voltage limit circle widens. As the rotor speed of motor 100 increases, the back electromotive force of motor 100 increases, and thus the voltage limit circle narrows. The voltage command values ​​Vdc and Vqc that satisfy torque command value TR* are the d-axis and q-axis voltages that theoretically produce a torque equal to torque command value TR*.

[0055] In step S12, if the difference between the square of limit voltage Vm and the square of d-axis voltage command value Vdc is less than or equal to the square of switching voltage value Vqc' (S12: No), since it is not determined that voltage command values ​​Vdc and Vqc that satisfy torque command value TR* can be derived through the first processing, the first switching condition is not determined to be satisfied, and processing proceeds to the next step S13. In step S13, motor 100 continues to be driven by field-weakening control. This processing routine then temporarily ends.

[0056] On the other hand, in step S12, if the difference between the square of limit voltage Vm and the square of d-axis voltage command value Vdc is greater than the square of switching voltage value Vqc' ("YES"), it is determined that the first processing can derive voltage command values ​​Vdc and Vqc that satisfy torque command value TR*. Therefore, the first switching condition is determined to be met, and processing proceeds to the next step S14. In step S14, the drive control of motor 100 switches from field-weakening control to vector control. That is, the process for deriving voltage command values ​​Vdc and Vqc switches from the second process to the first process. This processing routine then temporarily ends.

[0057] Furthermore, when the derivation process for each voltage command value Vdc and Vqc is switched from the second process to the first process, the first d-axis switch unit 34 selects the d-axis current integrated value Id1. After the first d-axis switch unit 34 switches from selecting the d-axis current command value Idc to selecting the d-axis current integrated value Id1, the previous value of the d-axis current integrated value Id1 becomes the d-axis current command value Idc. Specifically, the d-axis current integrated value Id1 after the switch is the sum of the previous value of the d-axis current command value Idc and the derived value from the second d-axis calculator 32. Furthermore, since the d-axis current deviation ΔId is small after the switch, the derived value from the second d-axis calculator 32 is small after the switch. In other words, the d-axis current integrated value Id1 after the switch is substantially equal to the previous value of the d-axis current command value Idc. Therefore, it can be said that when switching from the second process to the first process, each voltage command value Vdc, Vqc is derived based on the previous value of the d-axis current command value Idc during the initial derivation of each voltage command value Vdc, Vqc in the first process.

[0058] On the other hand, if it is not determined in step S11 that the motor 100 is being driven by field-weakening control ("No"), the process proceeds to the next step S15 because the motor 100 is being driven by vector control. In step S15, a determination is made as to whether the second switching condition is met. In this embodiment, the second switching condition is determined to be met if the following conditional expression (Equation 2) is satisfied. On the other hand, if the conditional expression (Equation 2) is not satisfied, the second switching condition is not determined to be met.

[0059] [Formula 2]

[0060] VM 2 ≤Vdc 2 +Vqc 2 …(Equation 2)

[0061] Specifically, if the difference between the square of limit voltage Vm and the square of d-axis voltage command value Vdc is greater than the square of q-axis voltage command value Vqc ( S15 : NO), the second switching condition is not determined to be satisfied, and the process proceeds to the next step S16. In step S16, drive control of motor 100 is implemented using vector control. This process routine then temporarily terminates.

[0062] On the other hand, in step S15, if the difference between the square value of limit voltage Vm and the square value of d-axis voltage command value Vdc is less than the square value of q-axis voltage command value Vqc ("YES"), it is determined that the second switching condition has been met, and the process proceeds to the next step S17. In step S17, the drive control of motor 100 is switched from vector control to field-weakening control. This process routine then temporarily ends.

[0063] Next, refer to Figure 5 as well as Figure 6 , the function and effect of this embodiment are explained.

[0064] When motor 100 is driven using field-weakening control, a second process is performed to derive a d-axis voltage command value Vdc and a q-axis voltage command value Vqc. In the second process, d-axis voltage command value Vdc is derived based on d-axis current command value Idc and q-axis current command value Iqc. Furthermore, the square root of the difference between the square of limit voltage Vm and the square of d-axis voltage command value Vdc is derived as q-axis voltage command value Vqc. Inverter 16 is then operated based on the voltage command values ​​Vdc and Vqc thus derived, thereby driving motor 100. When motor 100 is driven using field-weakening control in this manner, a switching voltage value Vqc' is derived.

[0065] Here, when the voltage vector when the d-axis component voltage is set as the d-axis voltage command value Vdc and the q-axis component voltage is set as the switching voltage value Vqc' is used as the determination voltage vector, the determination voltage vector is Figure 5 The rotation coordinates shown point to the intersection P1 of the maximum torque curve LTRmax and the equal torque line L1 of the torque command value TR*. The d-axis current command value Idc is based on the torque command value TR*, and the switching voltage value Vqc' is derived based on the d-axis current command value Idc. That is, if the torque command value TR* is small, the switching voltage value Vqc' is also low. Therefore, according to the torque command value TR*, as Figure 5 As shown, it is determined that the point pointed by the voltage vector, that is, the intersection point P1, is located outside the voltage limit circle C1, or as shown in FIG. Figure 6 As shown, the intersection point P1 is arranged within the voltage limit circle C1. Figure 5 As shown, when the intersection point P1 is outside the voltage limit circle C1, the difference between the square of the limit voltage Vm and the square of the d-axis voltage command value Vdc is less than the square of the switching voltage value Vqc'. Therefore, the drive control of the motor 100 is not switched from field weakening control to vector control.

[0066] However, if the torque command value TR* becomes smaller, then Figure 6 As shown by the dotted arrow in the middle, the equal torque line L1 of the torque command value TR* is displaced on the rotating coordinate. Figure 6 As shown, if intersection point P1 is within voltage limit circle C1, the difference from the square of d-axis voltage command value Vdc is greater than the square of switching voltage value Vqc'. In this case, by driving motor 100 based on the voltage command values ​​Vdc and Vqc derived by the first process, the torque of motor 100 can theoretically be set to torque command value TR*. Consequently, the drive control of motor 100 switches from field-weakening control to vector control.

[0067] Here, let's consider a comparative example in which the q-axis voltage command value Vqc is used instead of the switching voltage value Vqc' in the determination of switching from field-weakening control to vector control. In the second process performed in this comparative example, the first d-axis switch unit 34 selects the d-axis current integrated value Id1. Consequently, the previous value of the d-axis current integrated value Id1 is larger than in the present embodiment, which uses the switching voltage value Vqc' in the switching determination. This is because the d-axis current Id is larger during field-weakening control and deviates from the d-axis current command value Idc. This results in a larger d-axis current deviation ΔId, and a larger value derived by the second d-axis calculator 32. Consequently, the d-axis current integrated value Id1 is larger, and the d-axis current integrated value Id1 is updated based on its previous value. Since the d-axis current integrated value Id1 is larger, the d-axis F / F value Vffd increases. Consequently, the q-axis voltage command value Vqc becomes larger. Similarly, since the d-axis current integrated value Id1 is large, the d-axis reference voltage Vdb increases. Consequently, since the calculated value Vde2 is large, the d-axis voltage command value Vdc also becomes large. As a result, the sum of the squares of the d-axis voltage command value Vdc and the q-axis voltage command value Vqc is always greater than the square of the limit voltage Vm. In this case, the determination in step S12 is not "yes," and field-weakening control continues.

[0068] In contrast, in the second process performed in this embodiment, the first d-axis switch unit 34 selects the d-axis current command value Idc. This allows the switching determination to be made using the switching voltage value Vqc', which is not affected by the d-axis current Id, rather than the q-axis voltage command value Vqc, which is affected by the d-axis current Id. Because the switching voltage value Vqc' is calculated based on the d-axis current command value Idc according to the torque-current map 12map, it does not reach the high value of the q-axis voltage command value Vqc derived in the comparative example. Similarly, in the second process performed in this embodiment, the d-axis voltage command value Vdc is also calculated based on the d-axis current command value Idc, so it does not reach the high value of the d-axis voltage command value Vdc derived in the comparative example. Therefore, as the d-axis current command value Idc decreases, the sum of the squares of the d-axis voltage command value Vdc and the q-axis voltage command value Vqc becomes less than the square of the limit voltage Vm. Consequently, the drive control of the motor 100 can be switched from field-weakening control to vector control.

[0069] When driving motor 100 using vector control, a first process is used to derive a d-axis voltage command value Vdc and a q-axis voltage command value Vqc. In the first process, the d-axis voltage command value Vdc and the q-axis voltage command value Vqc are derived based on the d-axis current deviation ΔId and the q-axis current deviation ΔIq. Inverter 16 is then operated based on the derived voltage command values ​​Vdc and Vqc, thereby driving motor 100.

[0070] When driving motor 100 using vector control, as torque command value TR* increases, the state transitions from a state where the difference between the square of limit voltage Vm and the square of d-axis voltage command value Vdc is greater than the square of q-axis voltage command value Vqc to a state where the difference is less than the square of q-axis voltage command value Vqc. This state transition switches the drive control of motor 100 from vector control to field-weakening control.

[0071] In addition, in this embodiment, the following effects can be further obtained.

[0072] (1) When the motor 100 is driven by magnetic field weakening control, if the rotor speed of the motor 100 increases, there is a concern that the q-axis current Iq may resonate with respect to the corrected q-axis current command value Iqc1. Therefore, in this embodiment, when the motor 100 is driven by magnetic field weakening control, the high-frequency component of the calculated value Vde is used to derive the d-axis voltage command value Vdc. The high-frequency component of the calculated value Vde is the high-frequency vibration component of the d-axis current Id. By driving the motor 100 based on such a d-axis voltage command value Vdc and the q-axis voltage command value Vqc calculated based on the limit voltage Vm, the resonance of the q-axis current Iq with respect to the corrected q-axis current command value Iqc1 can be eliminated. As a result, the controllability when the motor 100 is rotated at high speed by magnetic field weakening control can be improved.

[0073] (2) When switching the drive control of motor 100 from flux-weakening control to vector control, if the voltage command values ​​Vdc and Vqc change significantly, there is a concern that the rotation of motor 100 may fluctuate with the switch in drive control. To address this issue, in this embodiment, when switching the voltage command values ​​Vdc and Vqc from the second process to the first process, the previous value of the d-axis current command value Idc is used when deriving the initial d-axis voltage command value Vdc and q-axis voltage command value Vqc. This suppresses sudden changes in the d-axis voltage command value Vdc and q-axis voltage command value Vqc when switching the drive control, and further suppresses fluctuations in the rotation speed of motor 100 associated with the switch in drive control.

[0074] (3) As described above, the torque-current map 12map is a map created to allow a current greater than the power supply current upper limit Ibtc to flow from the motor power supply 110 to the motor control device 10. Meanwhile, the voltage command values ​​Vdc and Vqc are derived based on the calculated value Iq_comp derived through feedback control of the power supply current upper limit Ibtc and the power supply current Ibt. This allows the current command values ​​Idc and Iqc to be derived using the map 12map described above, while also preventing the power supply current Ibt from continuing to exceed the power supply current upper limit Ibtc.

[0075] Furthermore, the power supply current upper limit value Ibtc is a value determined based on the basic performance of the motor 100 as designed. However, due to the manufacturing of the motor 100, it is inevitable that the performance of the motor 100 may vary. In other words, the motor control device 10 may control a motor 100 having performance that differs from the basic performance as designed. In this embodiment, even when controlling such a motor 100, the actual power supply current Ibt can be increased to the power supply current upper limit value Ibtc when the motor 100 is driven. In other words, even if there are variations in the performance of the motor 100 as the control target of the motor control device 10, the motor 100 can be driven by maximizing the power that can be supplied from the motor power supply 110.

[0076] (4) Furthermore, a torque-current map 12map is created so that the current vector represented by the d-axis and q-axis components derived using the torque-current map 12map points to a point on the maximum torque curve LTRmax on the rotating coordinate system. This allows the motor 100 to be driven with maximum efficiency while utilizing electrical energy.

[0077] (5) In this embodiment, the second process performs feedback control using the power supply current deviation ΔIbt, the deviation between the power supply current upper limit value Ibtc and the power supply current Ibt, as input. Feedback control using the power supply current deviation ΔIbt as input is also possible in the first process, but feedback control is performed not only on the q-axis current command value Iqc but also on the d-axis current command value Idc. In contrast, in the second process, the q-axis voltage command value Vqc is derived based on the d-axis voltage command value Vdc and the limit voltage Vm. This d-axis voltage command value Vdc is derived based on the corrected q-axis current command value Iqc1 obtained through feedback control. Therefore, the corrected q-axis current command value Iqc1 is derived to satisfy the power supply current upper limit value Ibtc. Since the d-axis current Id uses the value obtained by subtracting the q-axis current Iq from the power supply current upper limit value Ibtc, the d-axis current Id is independent of the d-axis current command value Idc. Therefore, when feedback control is performed in the second process using the deviation between the power supply current upper limit value Ibtc and the power supply current Ibt as input, it is not necessary to perform feedback control on the d-axis current command value Idc using the deviation between the power supply current upper limit value Ibtc and the power supply current Ibt as input, thereby simplifying the structure accordingly.

[0078] Furthermore, in this embodiment, if the first process generates a command to exceed the power supply current upper limit Ibtc, the determination in step S15 is "Yes," and the process proceeds to the second process. In the second process, feedback control is performed using the deviation between the power supply current upper limit Ibtc and the power supply current Ibt as input, preventing the power supply current Ibt from exceeding the power supply current upper limit Ibtc.

[0079] This embodiment can be modified and implemented as follows. This embodiment and the following modified examples can be combined and implemented within a range that does not technically conflict with each other.

[0080] The torque-current map 12map may be a map that indicates the relationship between the torque TR of the motor 100 and the d-axis and q-axis currents, when a current exceeding the power supply current upper limit Ibtc is permitted not to flow from the motor power supply 110 to the motor control device 10. In this case, the process of correcting the q-axis current command value Iqc using the calculated value Iq_comp derived from feedback control of the power supply current upper limit Ibtc and the power supply current Ibt may be omitted.

[0081] The torque-current map 12map can also be created so that the current vectors represented by the d-axis and q-axis currents derived using the map 12map point to points on a torque curve different from the maximum torque curve LTRmax. For example, in a rotating coordinate system, when the torque curve formed by connecting the points of the constant current circle and the constant torque curve is used as the predetermined torque curve, the torque-current map 12map can also be created so that the current vectors represented by the d-axis and q-axis currents derived using the map 12map point to points on the predetermined torque curve, where the constant current circle represents the value obtained by subtracting the predetermined value from the maximum torque output by the motor 100 at each current.

[0082] If the high-frequency component of the calculated value Vde is used to derive the d-axis voltage command value Vdc in the second process, the torque-current map 12map does not need to be used when deriving the current command values ​​Idc and Iqc.

[0083] When switching from field weakening control to vector control, when initially deriving the voltage command values ​​Vdc and Vqc by the first process, the voltage command values ​​Vdc and Vqc may be derived without using the previous value of the d-axis current command value Idc.

[0084] When deriving the d-axis voltage command value Vdc in the second process, the high-frequency component of the calculated value Vde may not be used. In this case, the d-axis voltage command value Vdc may be obtained using the q-axis current command value Iqc instead of the d-axis current command value Idc.

[0085] In the first process, if the d-axis current command value Idc is used to derive the d-axis voltage command value Vdc, the q-axis current command value Iqc need not be used when deriving the d-axis voltage command value Vdc. For example, the q-axis F / F value Vffq derived by the q-axis non-interference F / F unit 57 need not be used in deriving the d-axis voltage command value Vdc.

[0086] In the first process, if the q-axis current command value Iqc is used to derive the q-axis voltage command value Vqc, the d-axis current command value Idc need not be used when deriving the q-axis voltage command value Vqc. For example, the d-axis F / F value Vffd derived by the d-axis non-interference F / F unit 41 need not be used in deriving the q-axis voltage command value Vqc.

[0087] The q-axis may be used as the first axis and the d-axis may be used as the second axis to derive the voltage command values ​​Vqc and Vdc, and the inverter 16 may be operated based on the voltage command values ​​Vqc and Vdc to drive the motor 100 .

[0088] The motor control device 10 may have any one of the following configurations (a) to (c).

[0089] (a) The motor control device 10 includes one or more processors that execute various processes according to computer programs. The processors include a CPU and memory such as RAM and ROM. The memory stores program code or instructions that cause the CPU to execute processes. Memory, or computer-readable media, includes any available media that can be accessed by a general-purpose or special-purpose computer.

[0090] (b) The motor control device 10 includes one or more dedicated hardware circuits that execute various processes. Examples of the dedicated hardware circuits include an application-specific integrated circuit (ASIC) or an FPGA.

[0091] (c) The motor control device 10 includes a processor that executes a part of various processes according to a computer program and a dedicated hardware circuit that executes the remaining processes among the various processes.

[0092] Next, technical ideas that can be grasped from the above-mentioned embodiments and modifications will be described.

[0093] (i) A motor control device that derives a first voltage command value and a second voltage command value in a rotating coordinate system for vector control, and drives a motor as a synchronous motor based on the first and second voltage command values, wherein the first voltage command value is a command value for a voltage component of a first axis, and the second voltage command value is a command value for a voltage component of a second axis orthogonal to the first axis, the motor control device comprising:

[0094] a current command value deriving unit that derives a current of the first axis component corresponding to a torque command value as a first current command value, and derives a current of the second axis component corresponding to the torque command value as a second current command value, wherein the torque command value is a command value of the torque of the motor; and

[0095] The voltage command value deriving unit derives the first voltage command value based on the high-frequency fluctuation component of the current of the first axis component and the second current command value, and derives the second voltage command value based on the limit voltage of the motor control device and the first voltage command value.

[0096] When driving a motor using field-weakening control, if the motor's rotational speed increases, the second-axis current component may resonate with the second current command value. In this case, the high-frequency vibration component caused by this resonance is superimposed on the second-axis current component derived for each predetermined control cycle. Therefore, there is room for improvement in the controllability of motors driven using field-weakening control.

[0097] According to the above structure, when the motor is driven by weak magnetic field control, the first voltage command value is derived using the high-frequency variation component of the current of the first-axis component. The high-frequency variation component of the current of the first-axis component is a high-frequency vibration component superimposed on the first current command value. Therefore, by driving the motor based on the first voltage command value derived in this way, the resonance of the current of the second-axis component with respect to the second current command value can be eliminated. This is because the high-frequency vibration component of the current of the second-axis component is offset by the high-frequency vibration of the current of the first-axis component. As a result, the controllability when the motor is driven by weak magnetic field control can be improved.

Claims

1. A motor control device that derives a first voltage command value and a second voltage command value in a rotation coordinate system for vector control, and drives a motor as a synchronous motor based on the first voltage command value and the second voltage command value, wherein: The first voltage command value is a command value of a voltage of a first axis component, and the second voltage command value is a command value of a voltage of a second axis component orthogonal to the first axis. The motor control device includes: a current command value derivation unit that derives, based on a torque-current map, a current of the first axis component corresponding to a torque command value of the motor as a first current command value, and derives a current of the second axis component corresponding to the torque command value as a second current command value, wherein the torque-current map represents a relationship between the torque of the motor and the current of the first axis component and the current of the second axis component; and The voltage command value deriving unit is capable of executing a first process and a second process, wherein, in the first process, the first voltage command value is derived based on the first current command value, and the second voltage command value is derived based on the second current command value; and in the second process, the first voltage command value is derived based on the second current command value, and the second voltage command value is derived based on the limit voltage of the motor control device and the first voltage command value. When the motor is driven based on the voltage command values ​​derived through the second processing, when it is determined that the voltage command values ​​that satisfy the torque command value can be derived through the first processing, the voltage command value derivation unit switches the process of deriving the voltage command values ​​from the second processing to the first processing.

2. The motor control device according to claim 1, wherein: In the second process, the voltage command value deriving unit derives the first voltage command value based on the high-frequency fluctuation component of the current of the first-axis component and the second current command value.

3. The motor control device according to claim 1 or 2, wherein: When the derivation process of each voltage command value is switched from the second process to the first process, when each voltage command value is first derived in the first process, the voltage command value derivation unit derives each voltage command value based on a previous value of the first current command value.

4. The motor control device according to claim 1 or 2, wherein: When the current flowing from the motor power supply to the motor control device is defined as the power supply current and the upper limit of the power supply current is defined as the power supply current upper limit, The torque-current map is a map showing the relationship between the torque of the motor, the current of the first axis component, and the current of the second axis component when a current greater than the upper limit of the power supply current is allowed to flow from the motor power supply to the motor control device. In the second process, the voltage command value deriving unit derives the first voltage command value based on a calculated value derived through feedback control using a deviation between the power supply current upper limit value and the power supply current as input.

5. The motor control device according to claim 3, wherein: When the current flowing from the motor power supply to the motor control device is defined as the power supply current and the upper limit of the power supply current is defined as the power supply current upper limit, The torque-current map is a map showing the relationship between the torque of the motor, the current of the first axis component, and the current of the second axis component when a current greater than the upper limit of the power supply current is allowed to flow from the motor power supply to the motor control device. In the second process, the voltage command value deriving unit derives the first voltage command value based on a calculated value derived through feedback control using a deviation between the power supply current upper limit value and the power supply current as input.

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