JP2020171184A - Converter device, air conditioner, and control method and program of converter device - Google Patents

Abstract

To provide a converter device or the like capable of boosting a DC voltage to a higher voltage in response to a required rotation speed command.SOLUTION: The converter device for outputting a DC voltage to an inverter device for driving a motor includes a rotation speed command acquisition unit for acquiring a required rotation speed command of the motor, a determination unit for determining a magnitude relationship between a required rotation speed command and a predetermined determination threshold value, an on-duty change unit for changing on-duty of a switching signal input to a power factor improvement circuit based on a determination result of the magnitude relationship, and a signal output unit for outputting a switching signal to which the on-duty is applied. The on-duty change unit changes the on-duty so that the DC voltage is boosted when the required rotation speed command exceeds the predetermined determination threshold value.SELECTED DRAWING: Figure 1

Description

The present invention relates to a converter device, an air conditioner, a control method and a program of the converter device.

Conventionally, as a converter device, a device disclosed in Patent Document 1 is known. The converter device disclosed in Patent Document 1 is a device that converts AC power into DC power, and has two switching circuits for the purpose of reducing harmonic components and improving the power factor. Then, when the load is small, only one switching circuit is operated, and when the load is large, both of the two switching circuits are operated.
The converter device is mainly applied to the outdoor unit of an air conditioner and is loaded with a compressor motor.

Further, Patent Document 2 describes changing the on-duty of a signal with respect to the power factor improving circuit.

Japanese Patent No. 6151034 Japanese Unexamined Patent Publication No. 2014-057521

There is a need to boost the DC voltage output by the converter device to a higher voltage in order to be able to respond to the required rotation speed command of a higher motor.

The present invention has been made in view of such circumstances, and is a control method and program for a converter device, an air conditioner, and a converter device capable of boosting a DC voltage to a higher voltage in response to a required rotation speed command. The purpose is to provide.

According to the first aspect of the present invention, the converter device is a converter device that outputs a DC voltage to an inverter device that drives a motor, and is a rotation speed command acquisition unit that acquires a required rotation speed command of the motor. The on-duty of the switching signal input to the power factor improvement circuit is changed based on the determination unit that determines the magnitude relationship between the required rotation speed command and the predetermined determination threshold and the determination result of the magnitude relationship. It includes a duty changing unit and a signal output unit that outputs the switching signal to which the on-duty is applied. The on-duty changing unit changes the on-duty so that the DC voltage is boosted when the required rotation speed command exceeds the predetermined determination threshold value.

Further, according to the second aspect of the present invention, the on-duty changing unit determines the on-duty as a predetermined first on-duty when the required rotation speed command is equal to or less than a predetermined determination threshold value. Then, when the required rotation speed command exceeds the predetermined determination threshold value, the on-duty is determined to be a second on-duty larger than the first on-duty.

Further, according to the third aspect of the present invention, the on-duty changing unit performs the on-duty so as to be proportional to the required rotation speed command when the required rotation speed command exceeds a predetermined determination threshold value. To change.

Further, according to the fourth aspect of the present invention, the signal output unit keeps the switching signal off when the required rotation speed command is equal to or less than a predetermined determination threshold value.

Further, according to a fifth aspect of the present invention, the air conditioner includes the above-mentioned converter device and an inverter device that converts a DC voltage from the converter device into an AC voltage for controlling a motor. ..

Further, according to the sixth aspect of the present invention, the inverter device switches from V / f control to at least one of overmodulation control and field weakening control in response to the required rotation speed command.

Further, according to the seventh aspect of the present invention, the control method of the converter device is a control method of the converter device that outputs a DC voltage to the inverter device that drives the motor, and the required rotation speed command of the motor. The on-duty of the switching signal input to the power factor improvement circuit is determined based on the step of acquiring the above, the step of determining the magnitude relationship between the required rotation speed command and the predetermined determination threshold, and the determination result of the magnitude relationship. It has a step of changing and a step of outputting the switching signal to which the on-duty is applied. In the step of changing the on-duty, when the required rotation speed command exceeds the predetermined determination threshold value, the on-duty is changed so that the DC voltage is boosted.

Further, according to the eighth aspect of the present invention, the program includes a step of acquiring a required rotation speed command of the motor from the computer of the converter device that outputs a DC voltage to the inverter device that drives the motor, and the above. A step of determining the magnitude relationship between the required rotation speed command and a predetermined determination threshold, a step of changing the on-duty of the switching signal input to the power factor improvement circuit based on the determination result of the magnitude relationship, and the on-duty step. The step of outputting the switching signal to which the duty is applied is executed. Further, in the step of changing the on-duty, when the required rotation speed command exceeds the predetermined determination threshold value, the on-duty is changed so that the DC voltage is boosted.

According to each of the above aspects, the DC voltage can be boosted to a higher voltage in response to the required rotation speed command.

It is a figure which showed the schematic structure of the motor drive device which concerns on 1st Embodiment. It is a figure which shows the functional structure of the converter control part which concerns on 1st Embodiment. It is a figure used for demonstrating the process of the converter control part which concerns on 1st Embodiment in detail. It is a figure used for demonstrating the process of the converter control part which concerns on 1st Embodiment in detail. It is a figure used for demonstrating in detail the processing of the converter control part which concerns on 1st modification of 1st Embodiment. It is a figure used for demonstrating in detail the processing of the converter control part which concerns on the 2nd modification of 1st Embodiment.

<First Embodiment>
Hereinafter, the converter device according to the first embodiment will be described in detail with reference to FIGS. 1 to 4. The converter device according to the present embodiment is applied to a motor drive device that drives a compressor motor of an air conditioner.

(Outline configuration)
FIG. 1 is a diagram showing a schematic configuration of a motor drive device according to the first embodiment.
As shown in FIG. 1, the motor drive device 1 converts the AC power from the AC power supply 4 into DC power and outputs the converter device 2, and converts the DC power output from the converter device 2 into three-phase AC power. The inverter device 3 for outputting to the compressor motor (load) 20 is provided as a main configuration.

The converter device 2 includes a rectifier circuit 5 that converts AC power input from the AC power supply 4 into DC power, and a smoothing capacitor (smoothing means) 12 connected in parallel to the rectifier circuit 5 on the DC output side of the rectifier circuit 5. A main configuration is two switching circuits 10a and 10b provided in parallel between the rectifier circuit 5 and the smoothing capacitor 12, and a converter control unit (control means) 15 for controlling the switching circuits 10a and 10b. Prepared as.

The switching circuits 10a and 10b are power factor improving circuits provided for the purpose of improving the power factor and suppressing harmonics to the AC power supply.
The switching circuit 10a includes an inductor (inductive element) 6a provided in series with the positive electrode bus Lp connecting the rectifier circuit 5 and the smoothing capacitor 12, and a diode 7a connected in series with the current output side of the inductor 6a. And a switching element 8a having one end connected between the inductor 6a and the diode 7a and connected in parallel with the rectifier circuit 5.
Similarly, the switching circuit 10b includes an inductor 6b provided in series with the positive electrode bus Lp connecting the rectifier circuit 5 and the smoothing capacitor 12, and a diode 7b connected in series with the current output side of the inductor 6b. It has a switching element 8b having one end connected between the inductor 6b and the diode 7b and connected in parallel with the rectifier circuit 5.
Examples of the switching elements 8a and 8b include field effect transistors (FETs), IGBTs (Insulated Gate Bipolar Transistors), and the like.

The AC power supply 4 is provided with a zero cross detection unit 17 for detecting a zero cross point. The zero-cross signal from the zero-cross detection unit 17 is output to the converter control unit 15.
The inverter device 3 includes a bridge circuit 18 including six switching elements, and an inverter control unit 19 that controls opening and closing of the switching elements in the bridge circuit 18. For example, the inverter control unit 19 generates a gate drive signal Spwm for each switching element based on a required rotation speed command input from a host device (not shown) and gives it to the bridge circuit 18. Specific examples of the inverter control method include vector control, sensorless vector control, V / F control, overmodulation control, field weakening control, etc., but in the present embodiment, in response to the required rotation speed command, V / F control, overmodulation control and field weakening control shall be performed.
In order to realize the above control, the DC voltage detection unit 28 that detects the input DC voltage Vdc of the bridge circuit 18, and the motor current detection unit 29 that detects the phase currents iu, iv, and iwa flowing through the compressor motor 20. Is provided, and these detected values Vdc, iu, iv, and iwa are input to the inverter control unit 19. Here, the motor current detection unit 29 may detect the current flowing through the negative electrode side power line between the bridge circuit 18 and the smoothing capacitor 12, and acquire the phase currents iu, iv, and iwa from this detection signal. Further, in the present embodiment, as shown in FIG. 1, the input DC voltage Vdc detected by the DC voltage detection unit 28 is also input to the converter control unit 15.

The converter control unit 15 and the inverter control unit 19 are, for example, MPUs (Micro Processing Units), and have a computer-readable recording medium in which a program for executing each of the processes described below is recorded. The following processes are realized by the CPU reading the program recorded on the recording medium into a main storage device such as RAM and executing the program. Examples of computer-readable recording media include magnetic disks, magneto-optical disks, semiconductor memories, and the like.
The converter control unit 15 and the inverter control unit 19 may be embodied by one MPU or may be embodied by individual MPUs.

(Functional configuration of converter control unit)
FIG. 2 is a diagram showing a functional configuration of the converter control unit according to the first embodiment.
As shown in FIG. 2, the converter control unit 15 has functions as a rotation speed command acquisition unit 150, a determination unit 151, an on-duty change unit 152, and a signal output unit 153.

The rotation speed command acquisition unit 150 acquires the required rotation speed command input from the host device. The required rotation speed command is a command signal indicating the rotation speed per unit time required for the compressor motor 20, and is determined so that the air conditioner satisfies the required temperature (set temperature) of the user. To. The required rotation speed command acquired by the rotation speed command acquisition unit 150 is the same as the required rotation speed command received by the inverter control unit 19.
The determination unit 151 determines the magnitude relationship between the required rotation speed command acquired by the rotation speed command acquisition unit 150 and a predetermined determination threshold value (determination threshold values R1 to R4 described later).
The on-duty changing unit 152 changes the on-duty of the switching signals Sg1 and Sg2 input to the power factor improving circuit (switching circuits 10a and 10b) based on the determination result of the magnitude relationship by the determination unit 151. More specifically, the on-duty changing unit 152 changes the on-duty of the switching signals Sg1 and Sg2 so that the input DC voltage Vdc is boosted when the required rotation speed command exceeds a predetermined determination threshold value. To do.
The signal output unit 153 outputs switching signals Sg1 and Sg2 for improving the power factor and suppressing harmonics toward the switching circuits 10a and 10b while synchronizing with the zero-cross signal from the zero-cross detection unit 17. Further, the signal output unit 153 applies the on-duty determined (changed) by the on-duty changing unit 152 to the switching signals Sg1 and Sg2 and outputs the signals.

(Detailed explanation of the processing of the converter control unit)
3 and 4 are diagrams used to explain in detail the processing of the converter control unit according to the first embodiment.

First, the processing of the signal output unit 153 of the converter control unit 15 will be described in detail with reference to FIG.

As shown in FIGS. 3A and 3B, the signal output unit 153 compares the reference waveform with the voltage command, and based on the result, switches with the switching signal Sg1 for controlling the switching circuit 10a. A switching signal Sg2 for controlling the circuit 10b is generated.
Specifically, first, the signal output unit 153 generates a reference waveform (for example, a triangular wave) having a predetermined carrier frequency (see (a) in FIG. 3).
Next, the signal output unit 153 synchronizes with the zero cross signal from the zero cross detection unit 17, and generates a voltage command of a sine wave having a predetermined amplitude value. Note that this voltage command is formed as a sine wave having the same frequency as the frequency of the AC voltage input from the AC power supply 4, and the negative half cycle is inverted to the positive side.
As shown in FIG. 3, the signal output unit 153 sets the switching signal Sg1 in which the period in which the reference waveform is larger than the voltage command is “ON” and the period in which the reference waveform is smaller than the voltage command is “OFF”. , Sg2 is output.

Here, the ratio of the amplitude value of the voltage command to the size of the reference waveform (difference between the maximum value and the minimum value) is defined as the "modulation rate" of the voltage command. For example, the size of the reference waveform and the amplitude value of the voltage command are defined. If is equal, the modulation factor is defined as 100%. In this case, the on-duty of the switching signals Sg1 and Sg2 (the ratio of the ON period to the entire ON period and the OFF period) can be controlled by the modulation rate of the voltage command. Specifically, the on-duty of the switching signals Sg1 and Sg2 increases as the modulation rate of the voltage command decreases, and conversely, the on-duty of the switching signals Sg1 and Sg2 decreases as the modulation rate of the voltage command increases.

The switching signals Sg1 and Sg2 generated by the signal output unit 153 are given to gate circuits (not shown) that drive the switching elements 8a and 8b, respectively, and switching is performed by driving the gate circuit based on these signals. The opening and closing of the elements 8a and 8b is controlled.

In the graph shown in FIG. 4, the correspondence relationship between the required rotation speed command input from the host device and the input DC voltage Vdc output by the converter device 2 is shown by a solid line. Further, the correspondence relationship between the required rotation speed command and the inverter output voltage output by the inverter device 3 is shown by a broken line.

Next, the control of the converter control unit 15 will be described in detail with reference to the solid line graph shown in FIG.

As shown in FIG. 4, in the range where the required rotation speed command is from “R0” (R0 = 0 [rps]) to “R1” (R1> R0), the converter control unit 15 uses the switching circuits 10a and 10b ( The power factor improvement circuit) is not operated. Specifically, the signal output unit 153 of the converter control unit 15 keeps the switching signals Sg1 and Sg2 off while the required rotation speed command belongs to the above range. This is because it is less necessary to suppress harmonics when the load of the compressor motor 20 is small, and therefore, from the viewpoint of overall operating efficiency, a force is applied when the required rotation speed command is equal to or less than the determination threshold value R1. It is based on not operating the rate improvement circuit.
In this case, the input DC voltage Vdc output from the converter device 2 is exclusively a DC voltage corresponding to the output from the rectifier circuit 5. For example, the DC voltage Vdc1 is √2 times the effective value of the AC voltage supplied from the AC power supply 4.

In the range where the required rotation speed command is from "R1" to "R3" (R3> R1), the converter control unit 15 operates the switching circuits 10a and 10b for the purpose of improving the power factor and suppressing harmonics. Specifically, the signal output unit 153 has a switching signal Sg1 having a predetermined on-duty (first on-duty) when the required rotation number command exceeds the determination threshold value R1 and is equal to or less than the determination threshold value R3. Output Sg2. Here, the first on-duty applied to the switching signals Sg1 and Sg2 is specified exclusively for the purpose of improving the power factor and suppressing harmonics, and is not specified for the purpose of boosting the input DC voltage Vdc. Absent. However, with the operation of the switching circuits 10a and 10b (power factor improving circuit), the input DC voltage Vdc slightly increases (about several V) from the DC voltage Vdc1 to the DC voltage Vdc1'.

In the range where the required rotation speed command exceeds "R3", the converter control unit 15 operates the switching circuits 10a and 10b for the purpose of boosting the input DC voltage Vdc in addition to the purpose of improving the power factor and suppressing harmonics. Let me. Specifically, the signal output unit 153 has a switching signal Sg1 having a predetermined on-duty (second on-duty) when the required rotation number command exceeds the determination threshold value R3 and is equal to or less than the determination threshold value R4. Output Sg2. Here, the second on-duty applied to the switching signals Sg1 and Sg2 is defined for the purpose of boosting the input DC voltage Vdc. More specifically, the second on-duty is set to a value larger than the first on-duty.
That is, the on-duty change unit 152 sets the modulation factor of the voltage command (FIG. 3) applied when the required rotation speed command belongs to the above range, and the required rotation speed command belongs to the range of "R1" to "R3". The value shall be smaller than the modulation rate of the voltage command applied in this case (see FIG. 3). As the modulation factor of the voltage command becomes smaller (that is, the on-duty of the switching signals Sg1 and Sg2 increases), the current flowing through the switching elements 8a and 8b of the switching circuits 10a and 10b increases. As a result, the electric charge stored in the inductors 6a and 6b increases, and the voltage on the downstream side of the diodes 7a and 7b (that is, the input DC voltage Vdc) acts in the direction of being boosted. As a result, the input DC voltage Vdc output from the converter device 2 is boosted to a DC voltage Vdc2 larger than the DC voltage Vdc1'. The DC voltage Vdc2 is defined as a voltage that can satisfy the final rotation speed with respect to the induced voltage of the compressor motor 20.

Next, the control of the inverter control unit 19 will be described in detail with reference to the broken line graph shown in FIG.

In the range where the required rotation speed command is from "R0" to "R2" (R3> R2> R1), the inverter control unit 19 performs V / f control. That is, a gate drive signal Spwm (PWM signal output to the bridge circuit 18) is generated so that the ratio of the amplitude value V of the inverter output voltage and the required rotation speed command (= frequency f of the inverter output voltage) is constant.

When the required rotation speed command reaches "R2", the inverter output voltage reaches the upper limit (input DC voltage Vdc) in V / f control. Therefore, the rotation speed cannot be increased any more by V / f control.
Therefore, the inverter control unit 19 switches to overmodulation control under a constant input DC voltage Vdc (DC voltage Vdc1') while the required rotation speed command is from "R2" to "R3". Here, in normal V / f control, the bridge circuit 18 is switched and controlled by the gate drive signal Spwm so that the inverter output voltage is formed into a sine wave. However, in the overmodulation control, the switching frequency of the bridge circuit 18 by the gate drive signal Spwm is reduced, and the inverter output voltage is brought closer to a square wave. By doing so, even when the inverter output voltage reaches the upper limit value, the motor rotation speed can be slightly increased.

In the range where the required rotation speed command is from "R3" to "R4" (R4> R3), the input DC voltage Vdc is boosted from Vdc1 (Vdc1') to Vdc2. Therefore, in this range, the inverter control unit 19 performs V / f control again. That is, a gate drive signal Spwm is generated so that the ratio of the amplitude value V of the inverter output voltage and the required rotation speed command (= frequency f of the inverter output voltage) is constant.

When the required rotation speed command reaches "R4", the inverter output voltage reaches the upper limit (input DC voltage Vdc) again in the V / f control.
Therefore, the inverter control unit 19 switches to field weakening control under a constant input DC voltage Vdc (DC voltage Vdc2) in the range where the required rotation speed command exceeds “R4”. In field weakening control, the phase of the rotor position of the compressor motor 20 and the inverter output voltage is shifted. The induced voltage generated in the compressor motor 20 can be reduced by the field weakening control, and the rotation speed can be increased under a constant input DC voltage Vdc.

In FIG. 4, "overmodulation control" is performed before boosting the input DC voltage Vdc (range of rotation speed command "R2" to "R3"), and after boosting the input DC voltage Vdc (rotation speed command "R4"). Although the description has been made in the mode of performing the “field weakening control” in the range exceeding the above, the mode is not limited to this mode in other embodiments. That is, "overmodulation control" and "weakening field control" can be applied independently, and both "overmodulation control" and "weakening field control" may be performed in their respective ranges.

(Action, effect)
According to the above-mentioned control, when the required rotation speed command exceeds a predetermined determination threshold value (R3), the converter control unit 15 outputs the switching signal Sg1 to the switching circuits 10a and 10b (power factor improving circuit). , Reduces the on-duty of Sg2. In other words, when the required rotation speed command is equal to or less than the determination threshold value R3, the on-duty changing unit 152 determines the on-duty to the first predetermined on-duty, and the required rotation speed command exceeds the determination threshold value R3. In some cases, the on-duty is determined to be a second on-duty larger than the first on-duty.
As a result, the input DC voltage Vdc is further boosted from Vdc1'to Vdc2 while obtaining the effects of power factor improvement and harmonic suppression by the power factor improving circuit (see FIG. 4).

From the above, according to the converter device 2 according to the first embodiment, the DC voltage can be boosted to a higher voltage in response to the required rotation speed command.

(Modification example)
The converter device 2 and the air conditioner provided with the converter device 2 according to the first embodiment have been described in detail above, but the specific embodiment of the converter device 2 is not limited to the above and deviates from the gist. It is possible to make various design changes, etc. within the range not specified.

<First modification>
FIG. 5 is a diagram used to explain in detail the processing of the converter control unit according to the first modification of the first embodiment.
As shown in FIG. 5, the converter control unit 15 according to the first modification of the first embodiment responds to the required rotation speed command when the required rotation speed command exceeds a predetermined determination threshold value (R3). The input DC voltage Vdc is boosted stepwise (divided into a plurality of steps).
By doing so, the power efficiency of the inverter device 3 can be improved.

<Second modification>
FIG. 6 is a diagram used to explain in detail the processing of the converter control unit according to the second modification of the first embodiment.
As shown in FIG. 6, the converter control unit 15 according to the second modification of the first embodiment is proportional to the required rotation speed command when the required rotation speed command exceeds a predetermined determination threshold value (R3). The input DC voltage Vdc may be continuously boosted (in a slope shape) so as to be performed.
In this case, the on-duty changing unit 152 changes the on-duty of the switching signals Sg1 and Sg2 so as to be proportional to the required rotation speed command.
Further, in this case, the inverter control unit 19 may continue the overmodulation control with the input DC voltage Vdc (which changes in a slope shape) as the upper limit in the range from the determination threshold value R2 to the determination threshold value R4.
By doing so, the power efficiency of the inverter device 3 can be further improved.

In the above-described embodiment, the processes of various processes of the converter control unit 15 are stored in a computer-readable recording medium in the form of a program, and the various processes are performed by the computer reading and executing this program. It is said. The computer-readable recording medium refers to a magnetic disk, a magneto-optical disk, a CD-ROM, a DVD-ROM, a semiconductor memory, or the like. Further, this computer program may be distributed to a computer via a communication line, and the computer receiving the distribution may execute the program.

The above program may be for realizing a part of the above-mentioned functions. Further, a so-called difference file (difference program) may be used, which can realize the above-mentioned functions in combination with a program already recorded in the computer system.

As described above, some embodiments of the present invention have been described, but all of these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other embodiments, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and variations thereof are included in the scope of the invention described in the claims and the equivalent scope thereof, as are included in the scope and gist of the invention.

1 Motor drive device 2 Converter device 3 Inverter device 4 AC power supply 5 Rectifier circuit 6a, 6b Inductor 7a, 7b Diode 8a, 8b Switching element 10a, 10b Switching circuit (power factor improvement circuit)
12 Smoothing capacitor 15 Converter control unit 150 Rotation speed command acquisition unit 151 Judgment unit 152 On-duty change unit 153 Signal output unit 17 Zero cross detection unit 18 Bridge circuit 19 Inverter control unit

Claims (8)

A converter device that outputs a DC voltage to an inverter device that drives a motor.
A rotation speed command acquisition unit that acquires the required rotation speed command of the motor,
A determination unit that determines the magnitude relationship between the required rotation speed command and a predetermined determination threshold value,
An on-duty change unit that changes the on-duty of the switching signal input to the power factor improvement circuit based on the determination result of the magnitude relationship, and
A signal output unit that outputs the switching signal to which the on-duty is applied, and a signal output unit.
With
The on-duty changing unit is a converter device that changes the on-duty so that the DC voltage is boosted when the required rotation speed command exceeds the predetermined determination threshold value. When the required rotation speed command is equal to or less than a predetermined determination threshold value, the on-duty changing unit determines the on-duty to a predetermined first on-duty, and the required rotation speed command determines the predetermined determination threshold value. The converter device according to claim 1, wherein the on-duty is determined to be a second on-duty larger than the first on-duty. The converter device according to claim 1, wherein the on-duty changing unit changes the on-duty so as to be proportional to the required rotation speed command when the required rotation speed command exceeds a predetermined determination threshold value. The converter device according to any one of claims 1 to 3, wherein the signal output unit keeps the switching signal off when the required rotation speed command is equal to or less than a predetermined determination threshold value. The converter device according to any one of claims 1 to 4.
An inverter device that converts the DC voltage from the converter device into an AC voltage for controlling the motor, and
Air conditioner equipped with. The inverter device is
The air conditioner according to claim 5, wherein the V / f control is switched to at least one of overmodulation control and field weakening control in response to the required rotation speed command. It is a control method of a converter device that outputs a DC voltage to an inverter device that drives a motor.
The step of acquiring the required rotation speed command of the motor and
A step of determining the magnitude relationship between the required rotation speed command and a predetermined determination threshold value,
A step of changing the on-duty of the switching signal input to the power factor improvement circuit based on the determination result of the magnitude relationship, and
The step of outputting the switching signal to which the on-duty is applied, and
Have,
In the step of changing the on-duty, a control method of a converter device that changes the on-duty so that the DC voltage is boosted when the required rotation speed command exceeds the predetermined determination threshold value. To the computer of the converter device that outputs the DC voltage to the inverter device that drives the motor
The step of acquiring the required rotation speed command of the motor and
A step of determining the magnitude relationship between the required rotation speed command and a predetermined determination threshold value,
A step of changing the on-duty of the switching signal input to the power factor improvement circuit based on the determination result of the magnitude relationship, and
The step of outputting the switching signal to which the on-duty is applied, and
Is a program that executes
In the step of changing the on-duty, a program for changing the on-duty so that the DC voltage is boosted when the required rotation speed command exceeds the predetermined determination threshold value.