Motor control device, vehicle, and motor control method

Abstract

The present invention provides a highly reliable motor control device and motor control method capable of low-noise control (or sensorless control) by superimposing a high-frequency voltage, and capable of compensating for inverter dead time with a minimum required configuration. The present invention is characterized by comprising: a high-frequency voltage superimposing unit that adds a high-frequency voltage command value to a fundamental wave voltage command value and outputs the voltage command value; a high-frequency current estimated value calculation unit that estimates a high-frequency current value based on the high-frequency voltage command value; a dead-time compensation current estimated value calculation unit that adds the high-frequency current estimated by the high-frequency current estimated value calculation unit to the fundamental wave current command value; and a dead-time compensation voltage calculation unit that compensates the inverter output voltage based on the dead-time compensation current estimated value calculated by the dead-time compensation current estimated value calculation unit.

Description

Technical Field

[0001] The present invention relates to a structure of a motor control device and a control method thereof, and in particular to an effective technology suitable for low-noise control of a motor. Background Art

[0002] To improve the quietness of automotive electric motors, research is underway into passive noise reduction technologies, such as adding sound-absorbing and sound-insulating materials to suppress noise transmission, and active noise reduction technologies, such as superimposing a constant voltage from an inverter to distort the reverse voltage generated by the motor into a sine wave, thereby reducing noise.

[0003] Furthermore, in many applications, such as industrial inverters, sensorless control is used, which estimates the motor's rotation angle from the flowing high-frequency current by superimposing a high-frequency voltage that does not directly contribute to the motor torque.

[0004] However, when control in which a high-frequency voltage is superimposed is applied, the dead time of the inverter may not be accurately compensated due to the influence of a high-frequency current flowing due to the superimposed high-frequency voltage.

[0005] As a background technology in this technical field, there is a technology such as Patent Document 1. In Patent Document 1, a high-frequency voltage is superimposed on the current control system in order to estimate the rotation angle.

[0006] Meanwhile, as a technique for compensating for voltage errors caused by inverter dead time, a method has been adopted that calculates a dead time compensation amount based on the motor's three-phase fundamental current command value. For example, in Patent Document 2, to prevent harmonic currents from preventing proper dead time compensation, a reactive current that does not contribute to torque flows during low current conditions.

[0007] Prior art literature

[0008] Patent Literature

[0009] Patent Document 1: Japanese Patent No. 5401500

[0010] Patent Document 2: Japanese Patent Application Laid-Open No. 2015-126641 Summary of the Invention

[0011] Technical problem to be solved by the invention

[0012] According to Patent Document 1, the operation of the motor can be continued even during high-torque operation, and the rotation state of the rotor can be detected with high accuracy without using a sensor for detecting the rotation state of the rotor.

[0013] However, due to the influence of superimposed high frequencies, dead time compensation may not be performed properly, and noise and torque ripple caused by the dead time may be generated.

[0014] Furthermore, according to Patent Document 2, even in a state where a high-frequency voltage is superimposed, dead time compensation can be appropriately performed. However, on the other hand, power loss increases due to reactive current.

[0015] Therefore, the object of the present invention is to provide a highly reliable motor control device and motor control method, which can perform low-noise control (or sensorless control) by superimposing a high-frequency voltage and can compensate for the dead time of the inverter with the minimum required structure.

[0016] Technical solutions to technical problems

[0017] In order to solve the above-mentioned problems, the present invention is characterized in that it includes: a high-frequency voltage superposition unit, which adds a high-frequency voltage command value to a fundamental voltage command value and outputs a voltage command value; a high-frequency current estimation value calculation unit, which estimates a high-frequency current value based on the high-frequency voltage command value; a dead time compensation current estimation value calculation unit, which adds the high-frequency current estimation value estimated by the high-frequency current estimation value calculation unit to the fundamental current command value; and a dead time compensation voltage calculation unit, which compensates the output voltage of the inverter based on the dead time compensation current estimation value calculated by the dead time compensation current estimation value calculation unit.

[0018] In addition, the present invention is characterized in that a high-frequency voltage command value is added to a fundamental voltage command value and a voltage command value is output, a high-frequency current value is estimated based on the high-frequency voltage command value, the estimated high-frequency current estimated value is added to the fundamental current command value, and the output voltage of the inverter is compensated based on the result of the addition.

[0019] Effects of the Invention

[0020] According to the present invention, in a motor control device and a motor control method that can perform low-noise control (or sensorless control) by superimposing a high-frequency voltage, a highly reliable motor control device and a motor control method that can compensate for the inverter dead time can be implemented with the minimum required structure.

[0021] This can reduce noise during motor driving and improve reliability.

[0022] Technical problems, structures, and effects other than those described above will become more apparent through the following description of the embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a block diagram showing the overall configuration of a motor control device according to the first embodiment of the present invention.

[0024] Figure 2 This is a diagram showing the definition of dead time.

[0025] Figure 3 This is a diagram showing a comparative example of current waveforms depending on whether a high-frequency voltage is superimposed or not.

[0026] Figure 4 This is a diagram showing a comparative example of dead time compensation based on whether or not high-frequency current is considered.

[0027] Figure 5 1 is a diagram showing a modified example of the dead time compensator. (Modification 1)

[0028] Figure 6 Yes Figure 5 The relationship between the estimated U-phase current value for dead time compensation and the dead time compensation value is shown in the figure.

[0029] Figure 7 This figure shows another modified example of the dead time compensator. (Modification 2)

[0030] Figure 8 Yes Figure 7 The relationship between the estimated U-phase current value for dead time compensation and the dead time compensation value is shown in the figure.

[0031] Figure 9 This is a diagram showing a schematic configuration of a vehicle according to a second embodiment of the present invention. DETAILED DESCRIPTION

[0032] Hereinafter, embodiments of the present invention will be described using the accompanying drawings. In the accompanying drawings, identical components are denoted by identical reference numerals, and detailed descriptions of duplicate components are omitted.

[0033] In the following description, a permanent magnet synchronous motor (PMSM) is used as the subject, but the present invention is not limited to this. Similar effects can be achieved with AC motors such as synchronous reluctance motors, permanent magnet synchronous generators, winding-type synchronous motors, induction motors, and induction generators. Furthermore, the semiconductor switching elements of the inverter device are IGBTs (insulated gate bipolar transistors), but the present invention is not limited to this. MOSFETs (metal oxide semiconductor field effect transistors) or other power semiconductor elements can also be used.

[0034] Example 1

[0035] Reference Figures 1 to 8 A motor control device and a motor control method according to a first embodiment of the present invention will be described. Figure 1 This is a block diagram showing the overall configuration of the motor control device in this embodiment.

[0036] The motor control device of this embodiment is as follows Figure 1 As shown, the structure includes: a power converter 2, a phase current detection unit 3, a magnetic pole position detector 4, a frequency calculation unit 5, a DC voltage detection unit 6, a coordinate conversion unit 7, a current controller 10, a high-frequency voltage superposition unit 12, a phase delay compensator 14, a coordinate conversion unit 16, a coordinate conversion unit 18, a high-frequency phase delay compensator 20, a high-frequency current estimation value calculation unit 22, a coordinate conversion unit 24, a current estimation value calculation unit 26 for dead time compensation, a dead time compensation voltage calculation unit (dead time compensator) 28, a dead time compensation unit 30 and a PWM controller 32.

[0037] The power converter 2 converts DC power from a DC voltage source 9 (eg, a battery) into AC power according to a gate signal to be described later, so as to drive a permanent magnet synchronous motor (PMSM) 1 .

[0038] The phase current detection unit 3 is composed of a Hall CT (Current Transformer) and the like, and detects the current waveforms Iuc, Ivc, and Iwc of the three phases U, V, and W flowing from the power converter 2 to the PMSM 1 .

[0039] The magnetic pole position detector 4 is composed of a resolver and the like, detects the magnetic pole position of the PMSM 1 , and outputs magnetic pole position information θ.

[0040] The frequency calculation unit 5 outputs speed information ω1 by, for example, performing a differential calculation based on the magnetic pole position information θ detected by the magnetic pole position detector 4 .

[0041] The coordinate conversion unit 7 performs coordinate conversion on the current waveforms Iuc, Ivc, and Iwc detected by the phase current detection unit 3 using the magnetic pole position information θ detected by the magnetic pole position detector 4 , and outputs dq axis current detection values ​​Idc and Iqc.

[0042] The current controller 10 is constituted by, for example, a PI controller, and outputs dq axis fundamental wave voltage command values ​​Vd*, Vq* so that the dq axis fundamental wave current command values ​​Id*, Iq* match the dq axis current detection values ​​Idc, Iqc.

[0043] The high-frequency voltage superimposing unit 12 adds the dq-axis high-frequency voltage command values ​​Vdh* and Vqh* to the dq-axis fundamental wave voltage command values ​​Vd* and Vq* to output dq-axis voltage command values ​​Vd** and Vq**.

[0044] Phase delay compensator 14 uses speed information ω1 to correct control delay relative to magnetic pole position information θ, and outputs a voltage-based magnetic pole position θv. Control delay is the time from magnetic pole position detection until it is reflected in the three-phase voltage. For example, in a triangular wave comparison PWM, delay compensation is performed for 1.5 control cycles, as shown in equation (1), for control period Δt.

[0045] [Mathematical formula 1]

[0046] θ v =θ+1.5*ω1*Δt…(1)

[0047] The coordinate converter 16 converts the dq-axis voltage command values ​​Vd** and Vq** output from the high-frequency voltage superimposing unit 12 at the voltage magnetic pole position θv calculated by the phase delay compensator 14 and outputs three-phase fundamental wave voltage command values ​​Vu*, Vv*, and Vw*.

[0048] The coordinate conversion unit 18 performs coordinate conversion on the dq-axis fundamental wave current command values ​​Id* and Iq* at the voltage magnetic pole position θv, and outputs three-phase fundamental wave current command values ​​Iu*, Iv*, and Iw*.

[0049] The high-frequency current estimated value calculation unit 22 uses, for example, an inverse model of the motor as shown in equation (2) to calculate the high-frequency current estimated values ​​Idh* and Iqh* based on the dq-axis high-frequency voltage command values ​​Vdh* and Vqh*. Using the inverse model allows for simple calculation.

[0050] [Mathematical formula 2]

[0051]

[0052] The high-frequency phase delay compensator 20 uses speed information ω1 to correct the control delay relative to the magnetic pole position information θ, and outputs the high-frequency magnetic pole position θh. Control delay is the time from when the magnetic pole position is detected until it is reflected in the three-phase voltage. For example, in a triangle wave comparison PWM, delay compensation is performed for 1.5 control cycles. Unlike the phase delay compensator 14, the high-frequency phase delay compensator 20 takes the high-frequency frequency ωh into account when performing delay compensation, as shown in equation (3).

[0053] [Mathematical formula 3]

[0054] θ h =θ+ω h *Δt…(3)

[0055] The coordinate conversion unit 24 performs coordinate conversion on the dq-axis high-frequency current estimation values ​​Idh* and Iqh* calculated by the high-frequency current estimation value calculation unit 22 at the high-frequency magnetic pole position θh calculated by the high-frequency phase delay compensator 20, and outputs the three-phase high-frequency current estimation values ​​Iuh*, Ivh*, and Iwh*.

[0056] Furthermore, it is preferable to use different values ​​for the phase used in the coordinate conversion unit 18 for performing coordinate conversion on the dq-axis fundamental wave current command values ​​Id* and Iq* and the phase used in the coordinate conversion unit 24 for performing coordinate conversion on the dq-axis high-frequency current estimated values ​​Idh* and Iqh*. By using different values, phase delay can be appropriately compensated.

[0057] The dead time compensation current estimated value calculation unit 26 outputs three-phase current command values ​​Iu**, Iv**, and Iw** by adding three-phase fundamental wave current command values ​​Iu*, Iv*, and Iw* to three-phase high-frequency current estimated values ​​Iuh*, Ivh*, and Iwh*.

[0058] As shown in equation (4), the dead time compensation voltage calculation unit (dead time compensator) 28 outputs dead time compensation three-phase voltage command values ​​ΔVu*, ΔVv*, and ΔVw* according to the signs of the three-phase current command values ​​Iu**, Iv**, and Iw**.

[0059] [Formula 4]

[0060]

[0061] Wherein, Vdc represents the inverter DC voltage information, Td represents the dead time, fc represents the PWM carrier frequency, and Sign represents the sign.

[0062] The dead time compensating unit 30 adds the dead time compensated three-phase voltage command values ​​ΔVu*, ΔVv*, ΔVw* to the three-phase fundamental wave voltage command values ​​Vu*, Vv*, ΔVw* to output three-phase voltage command values ​​Vu**, Vv**, Vw**.

[0063] The DC voltage detection unit 6 detects the voltage of the DC voltage source 9 and outputs DC voltage information Vdc.

[0064] The PWM controller 32 performs, for example, triangular wave comparison using the three-phase voltage command values ​​Vu**, Vv**, and Vw** and the DC voltage information Vdc, and outputs a gate signal.

[0065] use Figures 2 to 4 To illustrate the principle and effect of the present invention. Figure 2 This is a diagram showing the definition of dead time. Figure 3 : is a diagram showing a comparative example of current waveforms based on whether a high-frequency voltage is superimposed or not. Figure 4 1 is a diagram showing a comparative example of dead time compensation based on whether or not high-frequency current is considered.

[0066] In the inverter, if the upper arm and the lower arm are turned on at the same time, the DC voltage Vdc is directly applied to the IGBT, which may be damaged. To prevent this from happening, Figure 2 As shown, in order to prevent the upper arm and the lower arm from being turned on at the same time, it is necessary to set a time (dead time) in which the two arms are turned off.

[0067] The voltage during the dead time is determined by the sign of the motor current. When the current sign is positive, the inverter output voltage decreases, while when the current sign is negative, the inverter output voltage increases. The inverter output voltage is compensated based on the signs of the three-phase currents to compensate for the output voltage error caused by the dead time. Generally, when using the sense current, dead time compensation cannot be properly performed due to the harmonics contained in the sense current. Therefore, the current command value is used instead.

[0068] On the other hand, in the low-speed range where the output voltage has a margin, a high-frequency voltage may be superimposed for noise reduction. In this case, a high-frequency current flows due to the superimposed high-frequency voltage. The sign of the current changes due to this high-frequency current, and there is a problem that the dead time compensation cannot be properly performed. Especially when the fundamental current is small, such as Figure 3 and Figure 4 As shown, the original sign of the current changes due to the high-frequency current. If the dead time compensation is performed based on the fundamental current command value, the dead time compensation will be offset.

[0069] Therefore, in the present invention, the high-frequency current value flowing is estimated from the superimposed high-frequency voltage using the inverse model of the motor, and the high-frequency current estimated value is added to the fundamental current command value when determining the sign of the current in dead time compensation.

[0070] This allows high-frequency information to be reflected in the sign of the current used for dead-time compensation. This prevents inappropriate high-frequency current from flowing and preventing noise reduction, especially when the fundamental current is small.

[0071] The present invention uses an inverse model of the motor to perform calculations in estimating the high-frequency current. By using the inverse model of the motor, the high-frequency current can be estimated through simple calculations.

[0072] Alternatively, instead of using an inverse model of the motor, a method that estimates the high-frequency current by referring to a table can also appropriately compensate for dead time. For example, the d-axis and q-axis high-frequency voltage command values ​​Vdh* and Vqh* have a high-frequency component superimposed on the d-axis as shown in equation (5).

[0073] [Formula 5]

[0074]

[0075] At this time, the dq axis high frequency current estimated values ​​Idh* and Iqh* are expressed by equation (6).

[0076] [Formula 6]

[0077]

[0078] Since the amplitude Ih* and phase θih vary according to the frequency ωh of the high-frequency voltage, the amplitude Ih* and phase θih are stored as a map for the frequency ωh of the high-frequency voltage. Even if the map is constructed in the form of a reference table, the same result as the present invention can be obtained.

[0079] Furthermore, as shown in the present invention, when performing coordinate transformation on the high-frequency current estimate, a different coordinate transformation method than that used for the fundamental current command value is used. By performing delay compensation on the magnetic pole position information based on the superimposed frequency ωh, phase delay can be appropriately compensated. This prevents the phase of the dead time compensation from shifting due to the phase delay.

[0080] Furthermore, only when the dq-axis fundamental wave current command values ​​Id* and Iq* are low currents, equal to or lower than a constant value, can the inverter output voltage be compensated based on the three-phase current command values ​​Iu**, Iv**, and Iw** (dead time compensation current estimation values) calculated by the dead time compensation current estimation calculation unit 26. By superimposing a high-frequency voltage in the low-speed range where there is a margin for the output voltage to reduce noise, the inverter dead time can be effectively compensated.

[0081] Modification 1

[0082] Reference Figure 5 and Figure 6 , a modification example of the dead time compensation voltage calculation unit (dead time compensator) 28 will be described. Figure 5 FIG. 1 is a diagram showing a modified example of a dead time compensator. Figure 6 Yes Figure 5 A diagram showing the relationship between the U-phase current estimated value for dead time compensation and the dead time compensation value in the dead time compensator.

[0083] Figure 5 The dead time compensator (dead time compensation voltage calculation unit) 28 shown has dividers 41, 51, 61, limiters 43, 53, 63 and dividers 45, 55, 65 corresponding to the input three-phase current command values ​​Iu**, Iv**, Iw**, respectively, and outputs dead time compensated three-phase voltage command values ​​ΔVu*, ΔVv*, ΔVw* having a specified slope relative to the three-phase current command values ​​Iu**, Iv**, Iw**.

[0084] In the above embodiment, the dead time compensation voltage calculation unit (dead time compensator) 28 performs calculations based on the signs of the three-phase current command values ​​Iu**, Iv**, and Iw**. However, in order to prevent the dead time compensation voltage from switching rapidly when crossing zero, Figure 5 and Figure 6 As shown in FIG. 1 , the dead time compensation voltage may be set to have a slope with respect to the three-phase current command values ​​Iu**, Iv**, and Iw**.

[0085] Modification 2

[0086] Reference Figure 7 and Figure 8 , another modification of the dead time compensation voltage calculation unit (dead time compensator) 28 will be described. Figure 7 FIG. 1 is a diagram showing another modified example of the dead time compensator. Figure 8 Yes Figure 7 A diagram showing the relationship between the U-phase current estimated value for dead time compensation and the dead time compensation value in the dead time compensator.

[0087] Figure 7 The dead time compensator (dead time compensation voltage calculation unit) 28 shown has dividers 41, 51, 61, dead zone setting units 47, 57, 67 and dividers 45, 55, 65 corresponding to the input three-phase current command values ​​Iu**, Iv**, Iw**, respectively. When the absolute values ​​of the three-phase current command values ​​Iu**, Iv**, Iw** are less than the specified values, the dead time compensation three-phase voltage command values ​​ΔVu*, ΔVv*, ΔVw* are output so as to have a dead zone set to 0.

[0088] As in Modification 1, in order to prevent the dead time compensation voltage from switching rapidly when crossing zero, Figure 7 and Figure 8 As shown in FIG. 1 , a method may be adopted that includes a dead zone in which the three-phase current command values ​​Iu**, Iv**, and Iw** are set to zero when the absolute values ​​thereof are smaller than a predetermined value.

[0089] Example 2

[0090] Reference Figure 9 , describing a vehicle according to a second embodiment of the present invention. Figure 9 It is a diagram showing a schematic structure of a vehicle in this embodiment.

[0091] like Figure 9As shown, the vehicle structure of this embodiment includes a permanent magnet synchronous motor (PMSM) 1, a power converter (INV) 2, a DC voltage source (BAT) 9, a motor control device 100, a transmission (TM) 101, a differential gear (DEF) 103, a drive shaft 105 and wheels 107. The motor control device 100 is used in the embodiment 1 ( Figure 1 ) described in the motor control device.

[0092] As described in Example 1, motor control device 100 controls the power supplied from power converter (INV) 2 to permanent magnet synchronous motor (PMSM) 1. For example, a DC voltage source (BAT) 9, such as a battery, supplies power to power converter (INV) 2. Permanent magnet synchronous motor (PMSM) 1 is connected to transmission (TM) 101. Transmission (TM) 101 is connected to drive shaft 105 via differential gear (DEF) 103 and supplies power to wheels 107.

[0093] In addition, instead of using the transmission (TM) 101, the permanent magnet synchronous motor (PMSM) 1 may be directly connected to the differential gear (DEF) 103, or the permanent magnet synchronous motor (PMSM) 1 and the power converter (INV) 2 may be applied to the front and rear wheels respectively.

[0094] To reduce electromagnetic noise from the motor in low-speed areas, vehicles sometimes employ a superimposed high-frequency voltage. Furthermore, due to the high carrier frequency, dead time accounts for a relatively large proportion of a PWM cycle, making dead time compensation a particularly important application. By applying this invention, dead time can be prevented from hindering electromagnetic noise reduction control in vehicles, ensuring a more comfortable driving experience for the driver.

[0095] Furthermore, the present invention is not limited to the above-described embodiments but also includes various variations. For example, the above-described embodiments are described in detail to facilitate understanding of the present invention and are not necessarily limited to embodiments including all of the structures described. Furthermore, a portion of the structure of a particular embodiment can be replaced with a structure of another embodiment, and a structure of another embodiment can be added to a structure of a particular embodiment. Furthermore, with respect to a portion of the structure of each embodiment, other structures can be added, deleted, or replaced.

[0096] Description of labels

[0097] 1: Permanent magnet synchronous motor (PMSM), 2: Power converter (INV), 3: Phase current detection unit, 4: Magnetic pole position detector, 5: Frequency calculation unit, 6: DC voltage detection unit, 7, 16, 18, 24: Coordinate conversion unit, 9: DC voltage source (BAT), 10: Current controller, 12: High-frequency voltage superposition unit, 14: Phase delay compensator, 20: High-frequency phase delay compensator, 22: High-frequency current estimated value calculation unit, 26: Dead time compensation Current estimation value calculation unit, 28: Dead time compensation voltage calculation unit (dead time compensator), 30: Dead time compensation unit, 32: PWM controller, 39: Gain, 41, 51, 61: Divider, 43, 53, 63: Limiter, 45, 55, 65: Multiplier 47, 57, 67: Dead zone setting unit, 100: Motor control device, 101: Transmission (TM), 103: Differential gear (DEF), 105: Drive shaft, 107: Wheel.

Claims

1. A motor control device, characterized in that: include: a high-frequency voltage superimposing unit that adds the high-frequency voltage command value to the fundamental wave voltage command value and outputs the voltage command value; a high-frequency current estimated value calculation unit that estimates a high-frequency current value based on the high-frequency voltage command value; a dead time compensation current estimated value calculation unit that adds the high-frequency current estimated value estimated by the high-frequency current estimated value calculation unit to the fundamental wave current command value; as well as a dead time compensation voltage calculation unit that compensates the output voltage of the inverter based on the dead time compensation current estimation value calculated by the dead time compensation current estimation value calculation unit; 2. The motor control device according to claim 1, wherein The high-frequency current estimated value calculation unit calculates a high-frequency current estimated value from the high-frequency voltage command value using an inverse model of the electric motor to be controlled.

3. The motor control device according to claim 1, wherein The phase used for coordinate conversion uses different values ​​for the fundamental wave current command value and the high-frequency current estimated value.

4. The motor control device according to claim 1, wherein The dead time compensation voltage calculation unit has a limiter for each phase corresponding to the input three-phase current command value. A dead time compensation voltage having a predetermined slope with respect to the three-phase current command value is output.

5. The motor control device according to claim 1, wherein The dead time compensation voltage calculation unit includes a dead time setting unit for each phase corresponding to the input three-phase current command value. When the absolute value of the three-phase current command value is smaller than a prescribed value, a dead time compensation voltage having a dead band set to 0 is output.

6. The motor control device according to claim 1, wherein Only when the fundamental wave current is a low current equal to or lower than a constant value, the output voltage of the inverter is compensated based on the dead time compensating current estimated value calculated by the dead time compensating current estimated value calculation unit.

7. A vehicle equipped with a motor control device for driving a motor, characterized in that: Use the motor control device according to any one of claims 1 to 6.

8. A motor control method, characterized in that: Add the high-frequency voltage command value to the fundamental voltage command value and output the voltage command value. The high-frequency current value is estimated based on the high-frequency voltage command value. The estimated high-frequency current value is added to the fundamental current command value. The output voltage of the inverter is compensated according to the addition result.

9. The motor control method according to claim 8, wherein: A high-frequency current estimate value is calculated from the high-frequency voltage command value using an inverse model of the electric motor to be controlled.

10. The motor control method according to claim 8 or 9, characterized in that: The phase used for coordinate conversion uses different values ​​for the fundamental wave current command value and the high-frequency current estimated value.

11. The motor control method according to claim 8, wherein: A dead time compensation voltage having a predetermined slope with respect to the three-phase current command value is output, and the dead time compensation voltage is added to the fundamental wave voltage command value.

12. The motor control method according to claim 8, wherein: When the absolute value of the three-phase current command value is smaller than a prescribed value, a dead time compensation voltage having a dead band set to 0 is output, and the dead time compensation voltage is added to the fundamental wave voltage command value.

13. The motor control method according to claim 8, wherein: Only when the fundamental wave current is a low current equal to or lower than a constant value, the output voltage of the inverter is compensated based on the result of the addition.

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