JP2015165757A - Inverter controller and control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To minimize deterioration in the accuracy of inverter control, by providing a switching pause period.SOLUTION: An inverter controller includes a voltage command generation unit 11 for generating a biaxial voltage command by using the speed command of a motor, and obtaining a three-phase voltage command from the biaxial voltage command, a PWM signal generation unit 13 for generating the PWM signal of each phase, by using the three-phase voltage command, and a switching pause unit 12 for stopping the switching of the switching element corresponding to each phase, in a predetermined switching pause period set for each phase. The three-phase/two-phase conversion unit 21 of the voltage command generation unit 11 performs coordinate conversion by using a current coordinate axis θi(θ-(φ+Δφ)), obtained by adding or subtracting a power factor angle set by a power factor angle setting unit 22, and a correction angle Δφ set by a correction angle setting unit 23, to or from the voltage phase θ. The switching pause unit 12 determines whether or not it is the switching pause period, by using a current coordinate axis θi outputted from the voltage command generation unit 11.

Description

  The present invention relates to an inverter control device and a method thereof.

Conventionally, the following control method has been proposed as a control method of a permanent magnet type synchronous motor. For example, Patent Document 1 discloses that in V / f control of a permanent magnet type synchronous motor, a motor current is obtained by adding a phase difference between a coordinate axis for three-phase / two-phase conversion of a motor current and a coordinate axis for two-phase conversion of a voltage command. It is disclosed to reduce.
Patent Document 2 discloses that a brushless DC motor is driven by a rectangular wave current with a conduction angle of 120 [deg] to 160 [deg].
Patent Document 3 discloses that in vector control, switching is suspended in a range of ± δ around a zero cross of current.

JP 2006-197789 A JP 2004-15902 A JP 2013-115955 A

  However, the control method disclosed in Patent Document 1 has a problem that switching loss increases because switching is always performed by PWM control. Further, in the driving by the rectangular wave described in the control method disclosed in Patent Document 2, the rotor position is estimated by detecting the rotor position or using the induced voltage that appears at the motor terminal during a period when no power is supplied. There is a problem that a circuit is required. Further, in the control method described in Patent Document 3, switching is suspended according to the voltage command calculated by the vector control, so that the voltage output from the inverter may deviate from the voltage command.

  This invention is made in view of such a situation, Comprising: It aims at providing the inverter control apparatus which can suppress the precision fall of inverter control by providing a switching idle period, and its method. .

  A first aspect of the present invention is an inverter control device that controls an inverter that converts DC power into three-phase AC power and drives the motor by driving switching elements provided corresponding to the respective phases. A voltage command generating means for generating a two-axis voltage command using the motor speed command and obtaining a three-phase voltage command from the two-axis voltage command; and a PWM for each phase using the three-phase voltage command. PWM signal generating means for generating a signal, and switching pause means for stopping switching of the switching element corresponding to each phase in a predetermined switching pause period set for each phase, the voltage command generating means, A three-phase / 2-phase conversion means for converting a three-phase motor current into an excitation current component and a torque current component; a power factor angle setting means for setting a power factor angle; and a response to the switching pause period. Correction angle setting means for setting a correction angle, and the three-phase / two-phase conversion means performs coordinate conversion using a current coordinate axis obtained by adjusting a voltage phase using the power factor angle and the correction angle. And the switching pause means is an inverter control device that determines whether or not the switching pause period by using the current coordinate axis and the power factor angle.

According to the above inverter control device, the PWM signal is generated using the three-phase voltage command generated by the voltage command generating means, and the predetermined switching pause period set for each phase corresponds to each phase. Switching of the provided switching element is stopped. Thus, since the switching pause period of the switching element is provided, switching loss can be reduced.
In addition, by providing a switching pause period, the motor voltage cannot be controlled according to the motor voltage command. Thereby, if no correction is made, the actual power factor angle will deviate from the power factor angle set by the power factor angle setting means. In this regard, according to the present invention, the correction angle corresponding to the switching pause period is set, and the coordinate transformation of the three-phase / two-phase is performed using the current coordinate axis that is adjusted using this correction angle. Deviation between the power factor angle and the power factor angle set by the power factor angle setting means can be suppressed. Thus, by setting the optimum power factor angle by the power factor angle setting means, the inverter can be operated in an efficient region, and energy saving can be achieved.

  In the inverter control device, the correction angle setting means has correction angle information in which the switching pause period and the correction angle are associated, and the correction angle corresponding to the switching pause period is determined from the correction angle information. It is good also as acquiring.

Thereby, it is possible to easily acquire an appropriate correction angle corresponding to the switching pause period.
The correction angle information is obtained by, for example, changing the switching pause period, obtaining the difference between the actual power factor angle at this time and the power factor angle set by the power factor angle setting means as the correction angle, It is created by associating with the switching pause period when the correction angle is obtained.

  In the inverter control device, the switching suspension unit may provide the switching suspension period when the temperature of the inverter is equal to or higher than a predetermined value.

  For example, depending on the motor constant, there may be a relatively large decrease in motor efficiency due to the distortion of the motor current due to the improvement in inverter efficiency. In the case of such a motor, it is possible to suppress a decrease in motor efficiency due to the distortion of the motor current by providing the switching pause period only when the temperature of the inverter is high.

A second aspect of the present invention is a motor drive device including the inverter control device.
A 3rd aspect of this invention is an air conditioner provided with a compressor motor and the said motor drive device which drives the said compressor motor.

  A fourth aspect of the present invention is an inverter control method for controlling an inverter that converts DC power into three-phase AC power and drives the motor by driving switching elements provided corresponding to the respective phases. A voltage command generating step of generating a two-axis voltage command using the motor speed command and obtaining a three-phase voltage command from the two-axis voltage command; and a PWM for each phase using the three-phase voltage command A PWM signal generation step for generating a signal, and a switching pause step for stopping switching of the switching element corresponding to each phase in a predetermined switching pause period set for each phase, the voltage command generation step, A three-phase / 2-phase conversion step for converting a three-phase motor current into an excitation current component and a torque current component, a power factor angle setting step for setting a power factor angle, and a response to the switching pause period. A correction angle setting step for setting a correction angle, wherein the three-phase / two-phase conversion step performs coordinate conversion using a current coordinate axis obtained by adjusting a voltage phase using the power factor angle and the correction angle. And the switching pause process is an inverter control method for determining whether or not the switching pause period using the current coordinate axis and the power factor angle.

  Advantageous Effects of Invention According to the present invention, it is possible to reduce the switching loss and to suppress the decrease in the accuracy of the inverter control due to the provision of the switching pause period.

It is the figure which showed schematically the electric constitution of the motor drive device to which the inverter control apparatus which concerns on one Embodiment of this invention is applied. It is a functional block diagram of the voltage command production | generation part which concerns on one Embodiment of this invention. It is the figure which showed an example of the relationship between a switching rest period and a correction angle. It is the figure which showed the relationship between the current coordinate axis and the U-phase current when no switching pause period is provided. It is the figure which showed the example of the switching waveform in each phase at the time of providing a switching rest period, and a U-phase current waveform.

  Hereinafter, an embodiment in which the inverter control device and the method thereof according to the present invention are applied to a motor drive device that drives a compressor motor of an air conditioner will be described with reference to the drawings.

FIG. 1 is a diagram schematically showing an electrical configuration of a motor drive device according to an embodiment of the present invention. As shown in FIG. 1, the motor drive device 1 converts the DC power into AC power and outputs it to the compressor motor 5, the inverter control device 3 that controls the inverter 2, and the output from the inverter control device 3. And a gate driver 4 for driving the inverter 2 based on the PWM signal.
The compressor motor 5 is, for example, a permanent magnet type synchronous motor.

The inverter 2 includes upper-arm switching elements S _1u , S _1v , S _1w and lower-arm switching elements S _2u , S _2v , S _2w provided corresponding to the respective phases. The element is driven by the gate driver 4 based on the PWM signal from the inverter control device 3, thereby generating a three-phase AC voltage supplied to the compressor motor 5. The switching element is a power semiconductor element such as an IGBT (Insulated Gate Bipolar Transistor), for example.

  A power line that supplies a three-phase voltage from the inverter 2 to the compressor motor 5 is provided with a current detector that detects a three-phase motor current. The three-phase motor currents iu, iv, iw detected by the current detector are output to the inverter control device 3.

  The gate driver 4 gives a drive voltage based on a PWM signal corresponding to each phase supplied from the inverter control device 3 to the conduction control terminals (for example, gate terminals) of the switching elements of the upper arm and the lower arm constituting the inverter 2. .

  The inverter control device 3 includes, for example, a voltage command generation unit 11, a switching pause unit 12, and a PWM signal generation unit 13. The inverter control device 3 is, for example, an MPU (Micro Processing Unit), and includes a computer-readable recording medium on which a program for executing each process realized by the above-described units is recorded. By reading the program recorded in the recording medium into a main storage device such as a RAM and executing it, the following processes are realized. Examples of the computer-readable recording medium include a magnetic disk, a magneto-optical disk, and a semiconductor memory.

The voltage command generator 11 generates a biaxial voltage command using the speed command of the compressor motor, and obtains a three-phase voltage command from the biaxial voltage command. The details of the voltage command generator 11 will be described later.
The switching pause unit 12 generates a switching pause signal for stopping switching in a predetermined switching pause period θss set across the zero cross points of the motor currents iu, iv, iw, in other words, in a predetermined electrical angle range θss. Output to the PWM signal generator 13. Here, the switching pause unit 12 determines the zero-cross point of each phase current based on the current coordinate axis θi input from the voltage command generation unit 11.

Specifically, the switching pause unit 12 pauses switching of the switching elements S _1u and S _2u of the upper and lower arms of the U phase when the value of the current coordinate axis θi satisfies the condition | θi | <θss. . In addition, for the V phase, the switching of the switching elements S _1v and S _2v of the upper and lower arms of the V phase is suspended in a range in which the switching stop period θss of the U phase is shifted by 120 [deg]. The switching of the switching elements S _1w and S _2w of the upper and lower arms of the W phase is suspended within a range in which the switching stop period θss of the U phase is shifted by 240 [deg].
The switching pause period θss may be a fixed value that is set in advance, or may be variable according to the operating state (for example, the rotational speed) of the compressor motor 5.

  Further, the switching pause period θss may be provided when the temperature of the inverter 2 is higher than a predetermined temperature. For example, depending on the motor constant of the compressor motor 5, there may be a case where the efficiency of the inverter 2 is improved, and thus the motor efficiency is relatively lowered due to the distortion of the motor current. When applied to such a compressor motor 5, the switching pause period θss may be provided only when the temperature of the inverter 2 is high. Thus, only when the temperature of the inverter 2 is high and it is desired to suppress heat generation due to switching loss, it is possible to suppress a decrease in motor efficiency due to distortion of the motor current by providing the switching pause period θss.

The PWM signal generation unit 13 generates a PWM signal S for each phase by comparing the voltage commands vu ^* , vv ^* , vw ^* given from the voltage command generation unit 11 with a carrier wave of a predetermined frequency, and also performs switching. In the period when the switching pause signal is input from the pause unit 12, the PWM signal S of each phase is maintained at a duty of 100% or 0% to stop switching.

  Next, the voltage command generator 11 will be described in detail with reference to FIG. FIG. 2 is a functional block diagram of the voltage command generator 11. As shown in FIG. 2, the voltage command generation unit 11 includes a three-phase / two-phase conversion unit 21, a power factor angle setting unit 22, a correction angle setting unit 23, a voltage command calculation unit 24, and a voltage phase calculation unit. 25 and a two-phase / three-phase converter 26 as main components.

  The three-phase / two-phase converter 21 converts the three-phase currents iu, iv, iw detected by the current detector into current coordinate axes θi (θ determined by a voltage phase θ, a power factor angle φ, and a correction angle Δφ described later. By performing biaxial conversion using − (φ + Δφ)), a δ-axis current iδ that is an exciting current component and a γ-axis current iγ that is a torque current component are obtained. Here, the three-phase current is detected, but only the two-phase current may be detected, and the remaining one phase may be obtained by calculation.

  The power factor angle setting unit 22 sets the power factor angle φ using the γ-axis current iγ. For example, the power factor angle setting unit 22 has power factor angle information in which the γ-axis current iγ and the power factor angle φ are associated, and the power factor corresponding to the γ-axis current iγ using the power factor angle information. Set the angle φ. For the setting of the power factor angle φ, for example, a method disclosed in the above-mentioned Patent Document 1, Japanese Patent Application Laid-Open No. 2009-189106, or the like can be used. For example, if control is to be performed with a power factor of 1, the power factor angle φ may be set to zero, and the power factor angle may be set by using appropriate power factor angle information that also takes into account the reluctance torque of the compressor motor. It becomes possible to drive the compressor motor with a minimum current by actively controlling. As described above, a known method may be appropriately applied as a method for setting the power factor angle.

The correction angle setting unit 23 sets a correction angle Δφ corresponding to the switching pause period θss set in the switching pause unit 12. The correction angle setting unit 23 has, for example, correction angle information associating the switching pause period θss and the correction angle Δφ as shown in FIG. 3, and using this correction angle information, the correction corresponding to the switching pause period θss. Obtain the angle Δφ. In FIG. 3, the horizontal axis represents the switching pause period θss, and the vertical axis represents the correction angle Δφ. In FIG. 3, since the switching pause period θss and the correction angle Δφ are in a substantially proportional relationship, this curve may be treated as an approximated proportional function.
The correction angle information is stored as a function including a switching pause period θss as a parameter, a table, or the like, for example.

The reason why such a correction angle setting unit 23 is provided is as follows.
In the present embodiment, as described above, there is a pause period in which switching of the switching element is stopped by the switching pause unit 12. If the correction angle setting unit 23 is not provided, the motor voltage cannot be controlled according to the three-phase voltage command due to the switching pause period. For example, a phase in which switching is suspended is equivalent to a state in which an induced voltage is output, and a voltage having a phase difference of 180 [deg] is applied to phases in which switching is not suspended. As a result, for example, there is a possibility that a deviation occurs between the power factor angle set by the power factor angle setting unit 22 and the actual power factor angle, resulting in deviation from a power factor angle with high inverter efficiency. In order to suppress such a power factor angle shift, a correction angle setting unit 23 is provided to reduce the difference between the power factor angle set by the power factor angle setting unit 22 and the actual power factor angle. .

  The correction angle information is obtained by changing, for example, the switching pause period θss, and acquiring the difference between the actual power factor angle at this time and the power factor angle set by the power factor angle setting unit 22 as a correction angle. It is created by associating the corrected angle Δφ and the switching pause period θss.

The γ-axis current iγ obtained in the three-phase / two-phase converter 21 is multiplied by the gain Kω, and then negatively fed back to the speed command nω ^* to calculate the inverter output frequency ω1. For example, when the load becomes heavy and the rotor position is delayed with respect to the rotating magnetic field, the current increases. Conversely, when the load becomes light and the rotor position advances with respect to the rotating magnetic field, the current decreases. Therefore, by correcting the speed command nω ^{* according} to the γ-axis current iγ, an inverter output frequency ω1 is set such that the compressor motor 5 operates stably. Here, the speed command nω ^* is, for example, a command value given from a host device of the inverter control device, for example, a main microcomputer of a system in which the inverter is mounted or another interface (man machine interface, etc.).

  The inverter output frequency ω1 is output to the voltage command calculation unit 24 and the voltage phase calculation unit 25. The voltage phase calculator 25 calculates the voltage phase θ by integrating the inverter frequency ω1. The voltage phase θ calculated by the voltage phase calculation unit 25 is used for axis conversion in the three-phase / two-phase conversion unit 21 and the two-phase / three-phase conversion unit 26.

The voltage command calculation unit 24 calculates voltage command values vδ ^* and vγ ^* for driving the inverter 2 using the inverter frequency ω1 and the δ-axis current iδ obtained by the three-phase / two-phase conversion unit 21. . For example, the voltage command calculation unit 24 calculates the biaxial voltage commands vδ ^* and vγ ^* using the following equations (1) and (2).

In the above formulas (1) and (2), K _δ and K _v are proportional constants, Λ _d is the d-axis induced voltage coefficient, and Λ _d ω 1 is the induced voltage. As described above, the voltage command calculation unit 24 has a calculation formula using the inverter frequency ω1 and the current iδ as parameters, and calculates the voltage command values vδ ^* and vγ ^* using this calculation formula.

The two-phase / three-phase conversion unit 26 performs axis conversion on the biaxial voltage commands vδ ^* and vγ ^* calculated by the voltage command calculation unit 24 using the voltage phase θ calculated by the voltage phase calculation unit 25. Three-phase voltage command values vu ^* , vv ^* , vw ^* are obtained.

Next, operation | movement of the motor control apparatus 1 provided with the said structure is demonstrated.
First, motor currents iu, iv, iw are detected and input to the inverter control device 3. In the inverter control device 3, the three-phase currents iu, iv, and iw are converted into axes using the current coordinate axis θi (θ− (φ + Δφ)) determined by the power factor angle φ, voltage phase θ, and correction angle Δφ in the previous sampling cycle. The δ-axis current iδ and the γ-axis current iγ are obtained by conversion.
The γ-axis current iγ is multiplied by the gain Kω and negatively fed back to the speed command nω ^* , and the inverter output frequency ω1 is calculated. The inverter output frequency ω1 and the δ-axis current iδ obtained by the three-phase / two-phase converter 21 are input to the voltage command calculator 24, and the δ-axis voltage command vδ ^* is calculated using the above equations (1) and (2) ^. And the γ-axis voltage command vγ ^* are calculated.

Here, for example, in the voltage command calculation by the equations (1) and (2), if the γ-axis voltage command vγ ^* is smaller than the motor voltage, the δ-axis inverter output current iδ becomes negative in order to weaken the field. On the other hand, if the γ-axis voltage command vγ ^* is large, the field strength is increased accordingly, and iδ is positive. Specifically, in the calculation of equation (1), the δ-axis voltage command vδ ^* is negatively proportionally controlled so that the δ-axis current iδ becomes zero. As a result, if there is a positive or negative fluctuation of i _δ , the voltage command v δ * is determined so as to quickly eliminate the fluctuation of i _δ by the gain K _δ .

In addition to setting the γ-axis voltage command vγ ^* to a voltage value that supplements the voltage of Λ _d ω1 corresponding to the induced voltage, iδ is integrated here in order to calculate the δ-axis current iδ to zero. Integration control is performed. That is, in the calculation of equation (2), if the δ-axis current i δ accumulates with either positive or negative value, a voltage value that returns to the original value with a larger value is determined. Although integral control is used here, proportional control, proportional integral control, or the like may be used depending on control responsiveness.

  By doing so, iδ becomes 0, and when iδ becomes 0, vδ also becomes 0. As a result, the motor current and the motor voltage can be only the γ-axis component. At this time, if the power factor angle φ = 0, the phases coincide with each other so that the power factor is 1 control, and the appropriate power factor angle φ is set in consideration of the reluctance torque of the compressor motor 7. The torque range in which V / f control is more appropriate than power factor 1 control is expanded, and it is possible to operate with minimal current, based on simple V / f control from low speed to high speed. It becomes. As a result, the product of voltage and current is minimized, and power-saving control is possible.

The γ-axis voltage command vγ ^* and the δ-axis voltage command vγ ^* calculated by the voltage command calculation unit 24 use coordinate axes based on the voltage phase θ given from the voltage phase calculation unit 25 in the two-phase / three-phase conversion unit 26. Are converted into three-phase voltage commands vu ^* , vv ^* , vw ^* and output to the PWM signal generator 13.

  The power factor angle setting unit 22 sets the power factor angle φ based on the γ-axis current iγ, and the correction angle setting unit 23 sets the correction angle Δφ corresponding to the switching suspension period θss at that time. The rotational coordinate axis θ− (φ−Δφ) obtained by subtracting the power factor angle φ and the correction angle Δφ from the phase θ is output to the three-phase / two-phase conversion unit 21 as the current coordinate axis θi, and the coordinate conversion of the motor current in the next sampling period is performed. Used for.

The current coordinate axis θi is output to the switching pause unit 12. Here, as shown in FIG. 4, the current coordinate axis θi is synchronized with the U-phase current, and the zero cross point and the current coordinate axis θi are synchronized. The V-phase zero-cross point is a position shifted from the U-phase zero-cross point by 120 [deg], and the W-phase zero-cross point is a position shifted from the U-phase zero-cross point by 240 [deg]. As described above, since the current coordinate axis θi is synchronized with the zero-cross point of the U phase, a switching pause signal may be output in a predetermined switching pause period θss sandwiching the zero-cross point using the current coordinate axis θi.
The switching pause unit 12 outputs to the PWM signal generator 13 a switching pause signal that stops U-phase switching when | θi | <θss. Also, a switching pause signal for stopping V-phase switching in an electrical angle range shifted by 120 [deg] from the above range, and a switching pause signal for stopping W-phase switching in an electrical angle range shifted by 240 [deg] from the above range. Is output to the PWM signal generator 13.

As a result, the PWM signal generation unit 13 uses the three-phase voltage command values vu ^* , vv ^* , and vw ^* generated by the voltage command generation unit 11 during a period when the switching suspension signal is not input from the switching suspension unit 12. A PWM signal S based thereon is generated and output to the gate driver 4. As a result, the switching element (see FIG. 1) included in the inverter 2 is on / off controlled based on the PWM signal S. Further, during the period when the switching pause signal is input, the switching of the phase is stopped.

  As a result, as shown in FIG. 5, switching of each phase is stopped in a period of 2θss set across the zero cross point. In FIG. 5, SWU + represents a switching element for the upper arm of the U phase, SWU− represents a switching element for the lower arm of the U phase, and the V-phase and W-phase are similarly labeled. Here, although the motor current is distorted from the sine wave, the influence is relatively small because the current is originally near zero.

As described above, according to the inverter control device and method therefor according to the present embodiment, switching is stopped near the zero-cross point of each phase, so switching loss does not occur during the idle period, and switching loss is reduced. It becomes possible to make it.
In addition, since the period for stopping the switching is generated, the motor voltage is not in accordance with the voltage command, but the rotation coordinate axis in the three-phase / two-phase converter 21 includes the monotonically increasing phase difference Δφ corresponding to the pause period θss. The influence of the phase difference during the switching pause period can be eliminated, and the power factor angle φ set in the power factor angle setting unit 22 can be maintained. Thereby, by setting the power factor angle to an efficient phase angle, inverter efficiency can be improved and energy saving can be achieved.

  As mentioned above, although embodiment of this invention was explained in full detail with reference to drawings, the specific structure is not restricted to this embodiment, The design change etc. of the range which does not deviate from the summary of this invention are included.

DESCRIPTION OF SYMBOLS 1 Motor drive device 2 Inverter 3 Inverter control device 4 Gate driver 5 Compressor motor 11 Voltage command generation part 12 Switching pause part 13 PWM signal generation part 21 3 phase / 2 phase conversion part 22 Power factor angle setting part 23 Correction angle setting part 24 Voltage command calculation unit 25 Voltage phase calculation unit 26 2-phase / 3-phase conversion unit

Claims (6)

By driving a switching element provided corresponding to each phase, it is an inverter control device that converts DC power into three-phase AC power and controls an inverter that outputs to the motor,
A voltage command generating means for generating a biaxial voltage command using the speed command of the motor and obtaining a three-phase voltage command from the biaxial voltage command;
PWM signal generating means for generating a PWM signal for each phase using the three-phase voltage command;
A switching pause means for stopping switching of the switching element corresponding to each phase in a predetermined switching pause period set for each phase;
The voltage command generating means is
Three-phase / two-phase conversion means for converting a three-phase motor current into an excitation current component and a torque current component;
Power factor angle setting means for setting the power factor angle;
Correction angle setting means for setting a correction angle according to the switching pause period,
The three-phase / two-phase conversion means performs coordinate conversion using a current coordinate axis obtained by adjusting a voltage phase using the power factor angle and the correction angle,
The switching pause means is an inverter control device that determines whether or not the switching pause period by using the current coordinate axis and the power factor angle.   The correction angle setting means has correction angle information in which the switching pause period and the correction angle are associated, and acquires a correction angle corresponding to the switching pause period from the correction angle information. The inverter control device described.   The inverter control device according to claim 1, wherein the switching suspension unit provides the switching suspension period when the temperature of the inverter is equal to or higher than a predetermined value.   A motor drive apparatus provided with the inverter control apparatus in any one of Claims 1-3. A compressor motor;
An air conditioner comprising: the motor drive device according to claim 4 that drives the compressor motor. By driving a switching element provided corresponding to each phase, DC power is converted into three-phase AC power, and an inverter control method for controlling an inverter output to a motor,
A voltage command generating step of generating a two-axis voltage command using the motor speed command and obtaining a three-phase voltage command from the two-axis voltage command;
A PWM signal generating step for generating a PWM signal for each phase using the three-phase voltage command;
A switching pause process for stopping switching of the switching element corresponding to each phase in a predetermined switching pause period set for each phase;
The voltage command generation step includes
A three-phase / two-phase conversion step of converting a three-phase motor current into an excitation current component and a torque current component;
A power factor angle setting step for setting a power factor angle;
A correction angle setting step of setting a correction angle according to the switching pause period,
The three-phase / two-phase conversion step performs coordinate conversion using a current coordinate axis in which a voltage phase is adjusted using the power factor angle and the correction angle,
The switching control step is an inverter control method for determining whether or not it is the switching stop period by using the current coordinate axis and the power factor angle.

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