JP2007259607A - Electric motor control device - Google Patents

Abstract

An electric motor control apparatus is provided which prevents a voltage saturation phenomenon to suppress a pulsation of electric motor generated torque even when a power supply voltage of an inverter is lowered, thereby preventing a load from being damaged.
The present invention relates to a motor control device (vector control device) that controls the torque and speed of an induction motor using an inverter. Means are provided for controlling the M-axis component of the primary current using the DC voltage of the inverter 13 so as to limit the terminal voltage of the induction motor 17 within the maximum modulation voltage of the inverter 13. Specifically, a magnetic flux limit calculator 30 that calculates the secondary magnetic flux limit value of the induction motor using the DC voltage detection value of the inverter 13, and a limiter 31 that limits the secondary magnetic flux command value by the secondary magnetic flux limit value. And an arithmetic unit 7 for generating an M-axis current command value using the secondary magnetic flux command value limited by the limiter 31.
[Selection] Figure 1

Description

  The present invention relates to a motor control device that controls the torque and speed of an induction motor by vector control.

FIG. 3 is a block diagram showing a conventional technique of this type of electric motor control apparatus, which is described in Patent Document 1 described later.
In the figure, the AC voltage of the AC power supply 12 is converted into an AC voltage of a predetermined magnitude and frequency by an inverter 13 and supplied to the induction motor 17, and the induction motor 17 is operated with a desired torque. Reference numeral 18 denotes a load driven by the induction motor 17, and reference numeral 16 denotes a pulse encoder that detects the rotational speed of the induction motor 17.

The speed setter 1 sets a speed ω _r # at which the induction motor 17 should be operated and outputs it to the speed command calculator 2 in the control device 100A. The speed command calculator 2 calculates and outputs a speed command value ω _r ^* that changes according to a predetermined acceleration and finally matches the speed set value ω _r #.
On the other hand, the feedback signal from the pulse encoder 16 is input to the speed calculator 19, and the rotational speed ω _r of the electric motor 17 is obtained by calculating this.

A deviation between the speed command value ω _r ^* and the detected speed value ω _r is input to the speed regulator 3, and a torque command value τ ^* that makes the input deviation zero by the adjustment operation is calculated, and a magnetic flux command secondary flux command value of the motor 17 phi ₂ ^* is calculated from the speed detection value omega _r by computing unit 4.
From these torque command value τ ^* and secondary magnetic flux command value φ ₂ ^* , a current command value i _M ^* parallel to the secondary magnetic flux φ ₂ of the primary current of the electric motor 17 according to the following formulas 1 and 2 (hereinafter referred to as necessary) Accordingly, an M-axis current command value) and a current command value i _T ^* orthogonal to the secondary magnetic flux (hereinafter referred to as a T-axis current command value if necessary) are calculated. In FIG. 3, 5 is a divider for calculating Formula 2 and 7 is a calculator for calculating Formula 1.

[Equation 1]
i _M ^* = (1 / L _m ) × φ ₂ ^*
(L _m : Excitation inductance of the motor)
[Equation 2]
i _T ^* = τ ^* / φ ₂ ^*

The coordinate converter 11 orthogonally crosses the phase current detected by the current detector 14 with a current i _M parallel to the secondary magnetic flux φ ₂ of the primary current of the electric motor 17 (hereinafter referred to as an M-axis current detection value if necessary). When the angle between the U-phase winding and the secondary magnetic flux φ ₂ of the motor 17 is ψ ₂ , the current i _T is converted into a current i _T (hereinafter referred to as a T-axis current detection value if necessary). , 4 to calculate i _M and i _T.

[Equation 3]
i _T = cos φ ₂ × i _U + cos (φ ₂ −120 °) × i _V + cos (φ ₂ + 120 °) × i _W
[Equation 4]
i _M = sin ψ ₂ × i _U + sin (ψ ₂ −120 °) × i _V + sin (ψ ₂ + 120 °) × i _W

A deviation between the T-axis current command value i _T ^* and the detected T-axis current value i _T is input to the T-axis current regulator 8, and a T-axis voltage command value v _T ^* that makes the input deviation zero by the adjustment operation is obtained. Is output. Also. A deviation between the M-axis current command value i _M ^* and the detected M-axis current value i _M is input to the M-axis current regulator 9, and an M-axis voltage command value v _M ^* that makes the input deviation zero by the adjustment operation is obtained. Is output.
The coordinate converter 10 converts the T-axis voltage command value v _T ^* and the M-axis voltage command v _M ^* using the angle ψ ₂ to convert the three-phase voltage command values V _u ^* , V _v ^* , V _w ^* . V _u ^* , V _v ^* , V _w ^* are calculated according to equations 5, 6 and 7.

[Equation 5]
^{_{V u * = cosψ 2 × v}} M * + sinψ 2 × v T *
[Equation 6]
^{_{V v * = cos (ψ 2}} -120 °) × v M * + sin (ψ 2 -120 °) × v T *
[Equation 7]
V _w ^* = cos (φ ₂ + 120 °) × v _M ^* + sin (φ ₂ + 120 °) × v _T ^*

The three-phase voltage command values V _u ^* , V _v ^* , and V _w ^* are given to the inverter 13, and the inverter 13 converts the three-phase AC voltage of the AC power source 12 into a three-phase AC voltage having a predetermined magnitude and frequency. And supplied to the induction motor 17.
The slip frequency calculator 6 calculates the slip frequency ω _sl by Equation 8, and the rotor frequency converter 20 converts the rotational speed ω _r of the electric motor 17 to the rotor frequency ω ₂ by Equation 9.

[Equation 8]
^{_{ω sl = R 2 × I T}} * / φ 2 *
(R ₂ : secondary time constant of the motor 17)
[Equation 9]
ω ₂ = ωr × P / 120
(P: number of poles of electric motor 17)

Further, by integrating the inverter output frequency ω ₁ obtained by adding the slip frequency ω _sl and the rotor frequency ω ₂ by the integrator 15, the secondary magnetic flux φ ₂ of the U-phase winding and the motor 17 is obtained. the angle [psi ₂ is the calculation of eggplant.
Here, in the magnetic flux command calculator 4 described above, when the rotational speed ω _r of the electric motor 17 is less than the base rotational speed ω _b , a 100% secondary magnetic flux command value φ ₂ ^* is output, and the rotational speed ω _r is the base rotational speed. A secondary magnetic flux command value φ ₂ ^* that decreases in inverse proportion to the speed when ω _b or more is output.

FIG. 4 is a configuration diagram in which the configuration of FIG. 3 is arranged around the inverter 13, and the whole operates as an electric motor control device.
The inverter main circuit 60 includes a diode rectifier 61 connected to the AC power supply 12, an electrolytic capacitor 62 connected to the DC side thereof, and a DC-AC converter 63 formed by connecting semiconductor switching elements in a three-phase bridge. Has been.

The control calculation unit 64A is composed of the speed command calculator 2, the motor control calculator 65A, and the PWM calculator 66. The motor control calculator 65A is a speed command calculator from the components of the control device 100A in FIG. 2 corresponds to a portion excluding the inverter 13 and the current detector 14.
PWM calculator 66, the three-phase voltage command value ^{_V u} _{*, V} v _*, performs PWM operation using a _V ^{w *} and the carrier signal _{f c,} DC - it outputs a switching signal to the AC converting unit 63 is there.

JP 2002-335700 A (paragraphs [0002] to [0016], FIG. 3)

  In the above prior art, the maximum modulation voltage of the inverter 13 is restricted by the power supply voltage (the voltage of the AC power supply 12). When the terminal voltage of the electric motor 17 is high, that is, when the power supply voltage drops for some reason in general during the high-speed operation of the electric motor 17, the inverter 13 falls into a situation where it cannot output a voltage exceeding the electric motor terminal voltage. It becomes difficult to supply the electric current to the electric motor 17 according to the set value.

That is, in this case, the situation in which the detected T-axis current value i _T is lower than the T-axis current command value i _T ^* continues, and the T-axis voltage command value v _T ^* is controlled by the adjustment operation of the T-axis current regulator 8 ^. Is output at a high value (this phenomenon is called voltage saturation phenomenon of the current regulator). The same situation applies to the M-axis current regulator 9.
Since the inverter 13 controlled based on the high voltage command values v _T ^* and v _M ^* as described above tends to operate in an overmodulation state, the output voltage includes a large distortion. This distortion appears as a pulsation different from the motor generated torque intended by the motor control device, causes vibration in the load 18 combined with the motor 17, and in the worst case, the load 18 and the motor 17 are damaged. It will cause a serious accident.

  Therefore, the problem to be solved by the present invention is to avoid the voltage saturation phenomenon of the current regulator even when the power supply voltage of the inverter is lowered, to suppress the pulsation of the torque generated by the motor, and to prevent the load from being damaged. The object is to provide an electric motor control device.

In order to solve the above-mentioned problem, the invention described in claim 1 divides a primary current of an induction motor driven by an inverter into an M-axis component parallel to a secondary magnetic flux and a T-axis component orthogonal to each of these components. In the motor control device that controls the torque and speed of the induction motor by operating the inverter so that each flows according to the M-axis current command value and the T-axis current command value,
Means are provided for controlling the M-axis component of the primary current of the motor using the DC voltage of the inverter so as to limit the terminal voltage of the induction motor within the maximum modulation voltage of the inverter.

The invention described in claim 2 is the electric motor control device according to claim 1,
The means for controlling the M-axis component is:
Magnetic flux limit calculating means for calculating a secondary magnetic flux limit value of the electric motor using a DC voltage detection value of the inverter;
Limiting means for limiting the secondary magnetic flux command value of the electric motor by the secondary magnetic flux limit value;
Means for generating the M-axis current command value using the secondary magnetic flux command value restricted by the restriction means.

  According to the present invention, even when the power supply voltage is lowered, the motor generated torque is not required by controlling the M-axis current so as to limit the motor terminal voltage below the maximum modulation voltage of the inverter using the DC voltage of the inverter. Thus, it is possible to provide an electric motor control device that can eliminate the pulsation and can continue operation while preventing damage to the load and the electric motor.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
First, FIG. 1 is a block diagram showing a configuration of an electric motor control device according to the embodiment, and FIG. 2 is a configuration diagram in which the configuration of FIG. 1 is arranged around an inverter.
In the following, the same components as those in FIGS. 3 and 4 described as the prior art are denoted by the same reference numerals, description thereof is omitted, and different portions are mainly described.

When the control device 100 shown in FIG. 1 is compared with the control device 100A shown in FIG. 3, a magnetic flux limit calculator 30 and a limiter 31 are added, and the DC voltage detection value V _{dc of the} inverter 13 is input to the magnetic flux limit calculator 30. Has been.
The T-axis current command value i _T ^* and the inverter output frequency ω ₁ are input to the magnetic flux limit calculator 30 together with the DC voltage detection value V _dc , and the secondary magnetic flux limit value φ _2lim is calculated. This secondary magnetic flux limit value φ _2lim is added to a limiter 31 as a limiting means, and is configured to limit the secondary magnetic flux command value φ ₂ ^* output from the magnetic flux command calculator 4.
The DC voltage detection value V _dc of the inverter 13 is obtained by detecting the output side DC voltage of the diode rectifier 61 with a DC voltage detector 67 as shown in FIG.

FIG. 2 corresponds to FIG. 4 of the prior art described above, 64 is a control operation unit, and 65 is an electric motor control operation unit. The electric motor control calculator 65 corresponds to a part obtained by removing the speed command calculator 2, the inverter 13, and the current detector 14 from the components of the control device 100 shown in FIG.
In FIG. 1, the magnetic flux limit calculator 30 performs the calculation of Equation 10.

[Equation 10]
_{φ 2lim = L m × (-Emf} + √ (((V dc / √2) / ω 1) 2 - (L σ × i T *) 2)) / L σ
(Φ _2lim : magnetic flux limit value, Emf: motor counter electromotive voltage coefficient, V _dc : inverter DC voltage detection value, ω ₁ : inverter output frequency, L _m : motor excitation inductance, L _σ : motor leakage inductance)

In Equation 10, Emf, L _m and L _σ are known. The method of deriving Equation 10 is as follows.
First, with respect to the motor induced voltage V ₀ , Formula 11 is established.

[Equation 11]
^{_{V 0 2 = (ω 1 ×}} L σ × i M + Emf × ω 2) 2 + (ω 1 × L σ × i T) 2

Here, considering that the motor terminal voltage limit value V _0m is introduced and the motor induced voltage V ₀ is limited to the limit value V _0m (that is, V ₀ = V _0m ), Equation 12 is obtained. Here, ω ₁ = ω ₂ is set for simplification.

[Equation 12]
(V _0m / ω ₁ ) ² = (L _σ × i _M + Emf) ² + (L _σ × i _T ) ²
(V _0m : Motor terminal voltage limit value)

When Formula 12 is converted and solved for M-axis current detection value i _M and i _T is replaced with T-axis current command value i _T ^* , Formula 13 is obtained.

[Equation 13]
i _M = (− Emf + √ ((V _0m / ω ₁ ) ² − (L _σ × i _T ^* ) ² )) / L _σ

When the M-axis current i _M of Formula 13 is passed, the motor induced voltage V ₀ can be limited to the motor terminal voltage limit value V _0m, and the secondary magnetic flux command value (secondary magnetic flux limit) corresponding to this M-axis current i _M The value φ _2lim ) is _expressed by Equation 14 based on Equation 1.

[Formula 14]
φ _2lim = L _m × i _{M
= L m × (-Emf + √} ((V 0m / ω 1) 2 - (L σ × i T *) 2)) / L σ

When the motor terminal voltage is limited within the maximum modulation voltage of the inverter 13, the motor terminal voltage limit value V _0m in Expression 14 may be replaced with Expression 15 using the DC voltage detection value V _dc of the inverter 13. .

[Equation 15]
V _0m = V _dc / √2

By substituting Equation 15 into Equation 14, Equation 10 described above can be obtained.
Therefore, by limiting the secondary magnetic flux command value φ ₂ ^* using the secondary magnetic flux limit value φ _2lim obtained by calculating Formula 10 by the magnetic flux limit calculator 30, for example, a state in which the motor 17 is operating at high speed. Even if the power supply voltage decreases, the terminal voltage of the electric motor 17 can be limited within the maximum modulation voltage of the inverter 13, and the voltage saturation phenomenon of the M-axis current regulator 9 as in the prior art can be avoided.
Thereby, distortion is not included in the output voltage of the inverter 13, and unnecessary pulsation does not occur in the torque generated by the electric motor 17, so that the load 18 is not adversely affected.

In addition, when it is desired to set the motor terminal voltage limit value V _0m individually for each motor using Formula 14, the voltage limit value V _0m may be assigned to the inverter setting parameter.

It is a block diagram which shows embodiment of this invention. It is the block diagram which arranged the structure of FIG. 1 focusing on the inverter. It is a block diagram which shows the prior art of the motor control apparatus by vector control. It is the block diagram which arranged the structure of FIG. 3 centering on the inverter.

Explanation of symbols

1: Speed setter 2: Speed command calculator 3: Speed controller 4: Magnetic flux command calculator 5: Divider 6: Slip frequency calculator 7: Calculator 8: T-axis current controller 9: M-axis current controller 10, 11: Coordinate converter 12: AC power supply 13: Inverter 14: Current detector 15: Integrator 16: Pulse encoder 17: Induction motor 18: Load 20: Rotor frequency converter 30: Magnetic flux limit calculator 31: Limiter 60 : Inverter main circuit 61: Diode rectifier 62: Electrolytic capacitor 63: DC-AC converter 64: Control calculator 65: Motor control calculator 66: PWM calculator 67: DC voltage detector

Claims (2)

The primary current of the induction motor driven by the inverter is separated into a T-axis component orthogonal to the M-axis component parallel to the secondary magnetic flux, and these components flow in accordance with the M-axis current command value and the T-axis current command value, respectively. In the motor control device that controls the torque and speed of the induction motor by operating the inverter as described above,
An electric motor control apparatus comprising: means for controlling an M-axis component of a primary current of the electric motor using a DC voltage of the inverter so as to limit a terminal voltage of the induction motor within a maximum modulation voltage of the inverter. In the motor control device according to claim 1,
The means for controlling the M-axis component is:
Magnetic flux limit calculating means for calculating a secondary magnetic flux limit value of the electric motor using a DC voltage detection value of the inverter;
Limiting means for limiting the secondary magnetic flux command value of the electric motor by the secondary magnetic flux limit value;
Means for generating the M-axis current command value using the secondary magnetic flux command value restricted by the restriction means;
An electric motor control device comprising:

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