JP3487296B2 - Inverter control method and device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inverter control method and an apparatus therefor, and more specifically, it obtains a voltage phase command by performing a speed control calculation based on a difference between an externally applied speed command and an actual speed. The present invention relates to an inverter control method and apparatus for calculating an inverter output voltage based on a voltage phase command to generate an inverter control signal and supplying the inverter control signal to an inverter for driving a motor.

[0002]

2. Description of the Related Art The structure of a general drive system for a brushless DC motor is as shown in FIG.
The microcomputer 82 determines the switching pattern of each switching element of the inverter 83 in accordance with the position signal representing the rotational position (magnetic pole position) of the motor rotor obtained by 1.
The speed control of the brushless DC motor 85 is performed by supplying each of the switching elements.

Further, general characteristics of a brushless DC motor (motor output torque Tm with respect to motor rotation speed ω,
Inverter output voltage Vinv, inverter output current Ii
nv and the inverter output voltage phase δ) are shown in FIG.
As shown in (D), when a certain current is applied to the brushless DC motor, the inverter output voltage increases as the motor speed increases. The torque characteristic is constant until the inverter output voltage is saturated.

After the inverter output voltage is saturated, the torque decreases as the motor speed increases, and the inverter output voltage phase changes. Here, the inverter output voltage phase is the phase of the fundamental wave of the inverter output voltage with respect to the fundamental wave of the motor back electromotive voltage, as shown by δ in FIG. 7.

Therefore, when the brushless DC motor as described above is used in a system in which the maximum value of the inverter output voltage is determined, the motor speed is limited by the load.

FIG. 8 is a block diagram showing the internal configuration of the microcomputer 82 of the brushless DC motor drive system of FIG.

This brushless DC motor drive system comprises an electric angle calculator 91 for calculating the electric angle θe of the rotor of the brushless DC motor 85 by using a position signal as an input, and a current phase for calculating a current phase β by using a position signal as an input. A calculation unit 92; an efficiency control unit 93 which performs efficiency control calculation by inputting the current phase β and outputs a voltage amplitude command Vref;
A speed calculation unit 94 that performs a speed calculation by inputting the electrical angle θe and outputs an actual speed ω, a subtraction unit 95 that calculates a difference between an externally applied speed command ωref and the actual speed, and a difference from the subtraction unit 95. Perform speed control calculation with
Speed control unit 96 that outputs an inverter output voltage phase command
And the inverter output voltage phase command and the actual speed ω as input, the phase limiting process is performed, the inverter output voltage phase is output as it is, or the preset phase limiting value δm
The phase limiting unit 97 that outputs ax, and the inverter output voltage Vref · sin (θe + δ) that receives the inverter voltage phase δ output from the phase limiting unit 97, the electrical angle θe, and the voltage amplitude command Vref as input. Calculation unit 98 and calculated inverter output voltage V
It has a PWM calculation unit 99 that receives ref.sin (θe + δ) as an input, performs a PWM (pulse width modulation) calculation, and outputs a PWM command.

FIG. 9 is a flow chart for explaining the processing of the phase limiting section 97.

In step SP1, the phase limiting section 97
It is determined whether or not the inverter voltage phase δ output from is greater than a preset phase limit value δmax, and δ>
If it is δmax, the phase limit value δmax is set as the inverter voltage phase δ in step SP2.

If the processing in step SP2 is performed or if it is determined in step SP1 that δ ≦ δmax, the processing directly returns to the original processing.

When the brushless DC motor drive system having the above structure is adopted and the load increases in the region where the inverter output voltage is saturated, the following operation is performed. (1) The inverter output voltage phase increases as the load increases {see a → b in FIGS. 10A, 10B, and 10C}. In (2) b, the inverter voltage phase is the phase limit value δm.
It is fixed to ax. (3) Motor speed ω decreases due to insufficient torque {Fig. 1
0 (A) (B) (C) b → c}. (4) When the speed command ωref is not changed, the motor speed is determined by the course of the load, as shown in FIG.
(B) Fluctuates in the vicinity of (C).

Incidentally, FIG. 10 (A) shows the motor output torque--
Motor rotation speed characteristics are shown in FIG. 10 (B), inverter output current-motor rotation speed characteristics, and FIG. 10 (C), inverter output voltage phase-motor rotation speed characteristics.

When the speed is restored, the following operation is performed. (1) Speed increases as load decreases {Fig. 11
(See d → e in (A) (B) (C)}. (2) After the motor speed reaches the speed command ωref,
The inverter voltage phase decreases as the load decreases {see e → f in FIGS. 11A, 11B, and 11C}.

Incidentally, FIG. 11A shows the motor output torque--
11B shows the motor rotation speed characteristic, FIG. 11B shows the inverter output current-motor rotation speed characteristic, and FIG. 11C shows the inverter output voltage phase-motor rotation speed characteristic.

[0015]

The above-mentioned brushless DC
When operating a compressor for an air conditioner using a motor drive system, the motor speed during speed drooping fluctuates with load, and as a result, there is a disadvantage that the compressor and the air conditioner vibrate.

Further, there is also a disadvantage that the operation noise of the compressor fluctuates due to the speed fluctuation during the speed droop, which is annoying.

Further, there is a disadvantage that the output current of the inverter fluctuates transiently with load fluctuation and speed fluctuation, and the margin for overcurrent protection decreases.

[0018]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and it is an object of the present invention to provide an inverter control method and an apparatus therefor capable of stably controlling the motor speed in a saturation region of an inverter output voltage. Has an aim.

[0019]

According to another aspect of the present invention, there is provided an inverter control method, wherein a voltage control command is obtained by performing a speed control calculation based on a difference between a speed command given from the outside and an actual speed, and based on the voltage phase command. An inverter control method for calculating an inverter output voltage to generate an inverter control signal and supplying the inverter control signal to an inverter for driving a motor, the first reference voltage phase for speed command reduction being smaller than the first reference voltage phase. , The second reference voltage phase for speed command recovery is set in advance, and in response to the voltage phase increasing and reaching the first reference voltage phase, the speed command is decreased by a predetermined value and the voltage phase is decreased. Then, in response to reaching the second reference voltage phase, the speed command is a speed command given from the outside.

In the inverter control method according to the present invention, the first reference voltage phase is a value that is larger than the phase limit value and is within a current range in which the overcurrent protection device does not operate or the motor magnet does not demagnetize. Adopt the second
As the reference voltage phase, a value smaller than the voltage phase that fluctuates due to the steady load fluctuation that occurs during one rotation of the motor in a load state in which the voltage phase fluctuates around the phase limit value is adopted, and the predetermined value Is the value required for the voltage phase that was the first reference voltage phase to decrease to the phase limit value when the speed decreases, or the voltage that was the first reference voltage phase when the speed decreases, for the same load. The value necessary for the phase to become the second reference voltage phase is adopted.

The inverter control method according to a third aspect of the present invention is a method of setting the speed command to the immediately preceding speed command value in response to the voltage phase being equal to or more than the second reference voltage phase and less than the first reference voltage phase. .

An inverter control device according to a fourth aspect of the present invention performs a speed control calculation based on a difference between a speed command given from the outside and an actual speed to obtain a voltage phase command, and calculates an inverter output voltage based on the voltage phase command. A second reference voltage phase for speed command reduction and a second reference voltage phase for speed command reduction, which is supplied to an inverter for driving a motor. Reference voltage phase setting means for presetting the reference voltage phase, and first for decreasing the speed command by a predetermined value in response to the voltage phase increasing and reaching the first reference voltage phase.
It includes speed command control means and second speed command control means for making the speed command an externally applied speed command in response to the voltage phase decreasing and reaching the second reference voltage phase.

According to another aspect of the inverter control device of the present invention, the first reference voltage phase is a value that is larger than the phase limit value and that is a current range in which the overcurrent protection device does not operate or a motor magnet does not demagnetize. Adopt the second
As the reference voltage phase, a value smaller than the voltage phase that fluctuates due to the steady load fluctuation that occurs during one rotation of the motor in a load state in which the voltage phase fluctuates around the phase limit value is adopted, and the predetermined value Is the value required for the voltage phase that was the first reference voltage phase to decrease to the phase limit value when the speed decreases, or the voltage that was the first reference voltage phase when the speed decreases, for the same load. The value necessary for the phase to become the second reference voltage phase is adopted.

According to a sixth aspect of the present invention, an inverter control device responds to the voltage phase being equal to or more than the second reference voltage phase and less than the first reference voltage phase by setting the speed command to the immediately preceding speed command value. It further includes command control means.

[0025]

According to the inverter control method of the present invention, the voltage phase command is obtained by performing the speed control calculation based on the difference between the speed command given from the outside and the actual speed, and the inverter output voltage is calculated based on the voltage phase command. When calculating and generating an inverter control signal and supplying it to an inverter for driving a motor, a second reference voltage phase for speed command reduction and a second reference for speed command restoration, which is smaller than the first reference voltage phase. The voltage phase is set in advance, and the speed command is decreased by a predetermined value in response to the voltage phase increasing and reaching the first reference voltage phase, and the voltage phase decreasing and reaching the second reference voltage phase. In response to this, the speed command is set as an externally supplied speed command, and therefore, when the voltage phase increases and reaches the first reference voltage phase, the speed command is decreased by a predetermined value. As a result, it is possible to eliminate the inconvenience that the speed fluctuates according to the course of the load, and positively control the speed. When the voltage phase decreases, the speed command is provided on the condition that the second reference voltage phase is reached. Is a speed command given from the outside, the speed can be positively controlled, and by extension, the motor speed can be stably controlled to suppress the vibration of the system using the motor as a drive source. It is possible to prevent the generation of annoying sound due to irregular fluctuations in the motor speed.

According to the inverter control method of claim 2,
As the first reference voltage phase, a value that is larger than the phase limit value and that is a current range in which the overcurrent protection device does not operate or the motor magnet does not demagnetize is adopted,
As the second reference voltage phase, in a load state in which the voltage phase fluctuates around the phase limit value, a value smaller than the voltage phase fluctuating due to the steady load fluctuation occurring during one rotation of the motor is adopted, As the predetermined value, at the same load, a value necessary for the voltage phase that was the first reference voltage phase to decrease to the phase limit value when the speed decreases, or to the first reference voltage phase when the speed decreases. Since the value necessary for the existing voltage phase to become the second reference voltage phase is adopted, the same operation as in claim 1 can be achieved without causing inconvenience such as stopping of the motor.

According to the inverter control method of claim 3,
Since the speed command is set to the immediately preceding speed command value in response to the voltage phase being equal to or greater than the second reference voltage phase and less than the first reference voltage phase, there is no need to reduce the speed more than necessary. It is possible to achieve the same effect as that of claim 1 or claim 2.

According to the inverter control device of the fourth aspect, the voltage phase command is obtained by performing the speed control calculation based on the difference between the speed command given from the outside and the actual speed, and the inverter output voltage is calculated based on the voltage phase command. In calculating and generating the inverter control signal and supplying it to the inverter for driving the motor, the reference voltage phase setting means causes the first reference voltage phase for speed command reduction and the speed smaller than the first reference voltage phase. A second reference voltage phase for command recovery is set in advance, and the speed command is decreased by a predetermined value by the first speed command control means in response to the voltage phase increasing and reaching the first reference voltage phase. In response to the voltage phase decreasing and reaching the second reference voltage phase, the second speed instruction control means may change the speed instruction to an externally given speed instruction. it can.

Therefore, when the voltage phase increases and reaches the first reference voltage phase, the speed command is reduced by a predetermined value to eliminate the inconvenience that the speed fluctuates according to the load condition and to positively increase the speed. When the voltage phase decreases, the speed command is positively controlled by setting the speed command as a speed command given from the outside on the condition that the second reference voltage phase is reached. And eventually, by controlling the motor speed stably,
It is possible to suppress the vibration of the system using the motor as a drive source and prevent the generation of annoying sound due to irregular fluctuations in the motor speed.

According to the inverter control device of claim 5,
As the first reference voltage phase, a value that is larger than the phase limit value and that is a current range in which the overcurrent protection device does not operate or the motor magnet does not demagnetize is adopted,
As the second reference voltage phase, in a load state in which the voltage phase fluctuates around the phase limit value, a value smaller than the voltage phase fluctuating due to the steady load fluctuation occurring during one rotation of the motor is adopted, As the predetermined value, at the same load, a value necessary for the voltage phase that was the first reference voltage phase to decrease to the phase limit value when the speed decreases, or to the first reference voltage phase when the speed decreases. Since the value necessary for the existing voltage phase to become the second reference voltage phase is adopted, the same operation as in claim 4 can be achieved without causing inconvenience such as stopping of the motor.

According to the sixth aspect of the inverter control device,
In response to the voltage phase being greater than or equal to the second reference voltage phase and less than the first reference voltage phase, third speed command control means for setting the speed command to the immediately preceding speed command value is further included. Claim 4 without reducing more than necessary.
Alternatively, the same effect as that of claim 5 can be achieved.

[0032]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of an inverter control method and apparatus of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a block diagram showing a main part of an embodiment of an inverter control device of the present invention. In addition, this inverter control device is, for example, a brushless D shown in FIG.
It is applied to a C motor drive system.

This inverter control device calculates the electrical angle θe by inputting a position signal indicating the rotational position (magnetic pole position) of the motor rotor, and the current phase β by inputting the position signal. Current phase calculator 12
An efficiency control unit 13 that calculates a voltage amplitude command Vref by performing an efficiency control calculation with the current phase β as an input, and a speed calculation unit 14 that calculates a speed by performing a speed calculation with the electrical angle θe as an input. Voltage phase δ and actual speed ω described later
And the first speed command ωr given from the outside
ef as an input, a phase speed limiting unit 15 that performs a phase speed limiting process and outputs a second speed command ωref ′, a subtracting unit 16 that calculates a difference between the second speed command ωref ′ and the actual speed ω, and a difference A speed control unit 17 which performs a speed control calculation as an input and outputs a voltage phase δ, and an inverter output voltage which calculates the inverter output voltage by inputting the voltage phase δ, the voltage amplitude command Vref, and the electrical angle θe are input.
An inverter output voltage calculation unit 18 that outputs f · sin (θe + δ) and an inverter output voltage Vref · sin
It has a PWM calculation unit 19 that inputs (θe + δ) and performs PWM (pulse width modulation) calculation and outputs a PWM command.

The phase speed limiter 15 has a preset first reference voltage phase δH for speed command reduction and a second reference voltage phase δL for speed command return, and also has a voltage phase δ and a second reference voltage phase δL. The second speed command ωref ′ is defined with respect to the first speed command ωref according to the magnitude relationship between the first reference voltage phase δH and the second reference voltage phase δL, and the second speed command ωref ′ is held and output. is there.

The actual speed ω is also supplied to the phase speed limiter 15. Based on the actual speed ω, it is judged whether or not the inverter output voltage is in the saturation region. The processing based on the first reference voltage phase δH and the second reference voltage phase δL is performed, and the first speed command ωref is output as it is when it is not in the inverter output voltage saturation region.

FIG. 2 is a flow chart for explaining an example of processing in the phase velocity limiting section 15.

In step SP1, it is determined whether the voltage phase δ is larger than the first reference voltage phase δH, and δ>
When it is determined that δH, the second speed command ωref ′ is decreased by a predetermined value ω1 in step SP2 (ωref ′ = ωref′−ω1 is calculated).

On the contrary, when it is determined in step SP1 that δ ≦ δH, in step SP3
It is determined whether the voltage phase δ is smaller than the second reference voltage phase δL, and when it is determined that δ <δL, the first speed command ωref is changed to the second speed command ωref ′ in step SP4. (Ωref ′ = ωref).

Then, in step SP3, δ ≧ δL
If it is determined, the process of step SP2 is performed, or the process of step SP4 is performed, the series of processes is ended.

The first reference voltage phase δH is the voltage phase limit value δm used in the conventional inverter control.
It is set to a value that is larger than ax and does not operate the overcurrent protection device, or a value that is larger than the voltage phase limit value δmax and that does not demagnetize the motor magnet.

The second reference voltage phase δL is such that the voltage phase δ is less than δL due to a steady load fluctuation occurring during one rotation of the motor in a load state in which the voltage phase fluctuates around the voltage phase limit value δmax. Is set so that the voltage phase δ does not fall below δL due to the periodic load fluctuation of the device in a load state in which the voltage phase fluctuates around the voltage phase limit value δmax.

The predetermined value ω1 is a value required for the voltage phase δ, which was the first reference voltage phase δH, to become the voltage phase limit value δmax due to the speed decrease at the same load, or at the same load, As the speed decreases, the voltage phase δ that was the first reference voltage phase δH is set to a value necessary for becoming the second reference voltage phase δL.

The operation of the inverter control device having the above configuration is as follows.

Since the operation when the inverter output voltage is not saturated is the same as that of the conventional inverter control device, its explanation is omitted.

The operating point when the load suddenly increases in the inverter output voltage saturation region changes as follows. (1) The voltage phase δ increases as the load increases {Fig. 3
(See a → b in (A) (B) (C)}. (2) When the voltage phase δ exceeds the first reference voltage phase δH,
The second speed command ωref ′ is decreased by a predetermined value ω1 (see b → c in FIGS. 3A, 3B and 3C). (3) When the voltage phase δ exceeds the first reference voltage phase δH due to the increase of the load, the second speed command ωref ′ is set to the predetermined value ω1.
Decrease only {c → d → in Fig. 3 (A) (B) (C)
See e}. (4) After the increase of the load stops, when the fluctuation of the voltage phase δ due to the load fluctuation is less than the second reference voltage phase δL and the first reference voltage phase δH, the second speed command ωref ′ is maintained as it is. 3 (A) (B) (C) e reference}. (5) The inverter output current fluctuates due to the load fluctuation, but the speed fluctuation does not occur {see e in FIGS. 3 (A) (B) (C)}.

3A shows the motor output torque-motor rotation speed characteristic, FIG. 3B shows the inverter output current-motor rotation speed characteristic, and FIG. 3C shows the inverter output voltage phase-motor rotation speed. The speed characteristics are shown respectively.

The operating point when the speed is restored changes as follows. (1) The voltage phase δ decreases as the load decreases {Fig. 4
(See f → g in (A) (B) (C)}. (2) When the voltage phase δ falls below the second reference voltage phase δL, the first speed command ωref is set to the second speed command ωref ′. (3) After the motor speed reaches the first speed command ωref, the voltage phase δ decreases as the load decreases {FIG.
(See g → h → i in (A) (B) (C)}.

4A shows the motor output torque-motor rotation speed characteristics, FIG. 4B shows the inverter output current-motor rotation speed characteristics, and FIG. 4C shows the inverter output voltage phase-motor rotation characteristics. The speed characteristics are shown respectively.

When the motor is driven by using the inverter control device having the above structure, the motor speed can be stably controlled in the region where the inverter output voltage is saturated, and the vibration of the system using the motor as a drive source is suppressed. In addition, it is possible to eliminate annoying noise due to irregular fluctuations in motor speed.

Further, since the motor speed can be controlled in a stable manner, it is possible to prevent transient fluctuations in the inverter output current, and thus to ensure a sufficient margin for overcurrent protection.

[0052]

According to the first aspect of the present invention, the motor speed can be positively controlled in the region where the inverter output voltage is saturated, and thus the motor speed can be controlled stably.
It is possible to suppress vibration of a system that uses a motor as a drive source, and to prevent the generation of annoying sound due to irregular fluctuations in the motor speed.

The invention of claim 2 has the same effect as that of claim 1 without causing inconvenience such as stopping of the motor.

The invention according to claim 3 has the same effect as that of claim 1 or claim 2 without reducing the speed more than necessary.

According to the fourth aspect of the present invention, the motor speed can be positively controlled even in the region where the inverter output voltage is saturated, and by extension, the motor speed can be controlled stably.
It is possible to suppress vibration of a system that uses a motor as a drive source, and to prevent the generation of annoying sound due to irregular fluctuations in the motor speed.

The invention of claim 5 has the same effect as that of claim 4 without causing inconvenience such as stopping of the motor.

The invention of claim 6 has the same effect as that of claim 4 or claim 5 without reducing the speed more than necessary.

[Brief description of drawings]

FIG. 1 is a block diagram showing a main part of an embodiment of an inverter control device of the present invention.

FIG. 2 is a flowchart illustrating an example of processing in a phase velocity limiting unit.

FIG. 3 is a diagram illustrating a change in operating point when a load suddenly increases in an inverter output voltage saturation region.

FIG. 4 is a diagram illustrating a change in operating point when the speed returns.

FIG. 5 is a schematic diagram showing an example of the configuration of a brushless DC motor drive system.

FIG. 6 is a diagram showing changes in motor output torque, inverter output voltage, inverter output current, and inverter output voltage phase with respect to motor rotation speed.

FIG. 7 is a diagram illustrating an inverter output voltage phase.

FIG. 8 is a block diagram showing a conventional inverter control device.

FIG. 9 is a flowchart illustrating a conventional phase limiting process.

FIG. 10 is a diagram illustrating an operation when a load suddenly increases in an inverter output voltage saturation region.

FIG. 11 is a diagram illustrating a speed return operation.

[Explanation of symbols]

15 Phase speed limiter

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-10-14276 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H02P 6/06

Claims (6)

(57) [Claims] 1. A voltage phase command is obtained by performing a speed control calculation based on a difference between a speed command given from the outside and an actual speed,
An inverter control method for calculating an inverter output voltage based on a voltage phase command to generate an inverter control signal and supplying the inverter control signal to an inverter for driving a motor, the method comprising: a first reference voltage phase for speed command reduction; A second reference voltage phase for speed command recovery, which is smaller than the reference voltage phase, is set in advance, and the speed command is decreased by a predetermined value in response to the voltage phase increasing and reaching the first reference voltage phase. The inverter control method is characterized in that the speed command is an externally applied speed command in response to the voltage phase decreasing and reaching the second reference voltage phase. 2. The first reference voltage phase is a value that is larger than the phase limit value and is a current range in which the overcurrent protection device does not operate or a current range in which the motor magnet does not demagnetize. The voltage phase is a value smaller than the voltage phase that fluctuates due to a steady load fluctuation that occurs during one rotation of the motor in a load state in which the voltage phase fluctuates around the phase limit value, and the predetermined value is At the same load, the value required for the voltage phase that was the first reference voltage phase to reach the phase limit value when the speed decreased or the voltage phase that was the first reference voltage phase when the speed decreased The inverter control method according to claim 1, wherein the inverter control method has a value required to reach the second reference voltage phase. 3. The speed command is set to the immediately preceding speed command value in response to the voltage phase being equal to or more than the second reference voltage phase and less than the first reference voltage phase. Inverter control method. 4. A voltage phase command is obtained by performing a speed control calculation based on a difference between a speed command given from the outside and an actual speed, and an inverter output voltage is calculated based on the voltage phase command to generate an inverter control signal. , An inverter control device for supplying to an inverter for driving a motor, wherein a first reference voltage phase for speed command reduction and a second reference voltage phase for speed command restoration smaller than the first reference voltage phase are previously set. Reference voltage phase setting means (15) to be set and first speed command control means (15) for decreasing the speed command by a predetermined value in response to the voltage phase increasing and reaching the first reference voltage phase. And a second speed command control means (15) for making the speed command an externally applied speed command in response to the voltage phase decreasing and reaching the second reference voltage phase. Inverter control device. 5. The first reference voltage phase is a value that is larger than the phase limit value and is a current range in which the overcurrent protection device does not operate, or a current range in which the motor magnet does not demagnetize, and the second reference voltage phase. The voltage phase is a value smaller than the voltage phase that fluctuates due to a steady load fluctuation that occurs during one rotation of the motor in a load state in which the voltage phase fluctuates around the phase limit value, and the predetermined value is At the same load, the value required for the voltage phase that was the first reference voltage phase to reach the phase limit value when the speed decreased or the voltage phase that was the first reference voltage phase when the speed decreased The inverter control device according to claim 4, wherein the inverter control device has a value required to reach the second reference voltage phase. 6. A third speed command control means (1) for setting a speed command to a immediately preceding speed command value in response to the voltage phase being equal to or more than the second reference voltage phase and less than the first reference voltage phase.
The inverter control device according to claim 4 or 5, further comprising 5).