JPH07123360B2 - Induction motor vector controller - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to a vector control device for an induction motor.

B. Summary of the Invention The present invention reduces the torque error in a vector controller for an induction motor by making the secondary magnetic flux and the secondary current including the iron loss component current orthogonal to each other.

C. Conventional technology In a vector controller for an induction motor, the primary current of the motor is divided into an exciting current and a secondary current for control, and the secondary magnetic flux and the secondary current vector are always orthogonalized to produce a response equivalent to that of a DC motor. Try to get sex.

Further, in the vector control method, there has been proposed a method of further improving the responsiveness and accuracy by canceling the mutual interference between the secondary magnetic flux component and the secondary current component (for example, Japanese Patent Laid-Open No. 59-59160). -165982 publication).

In such vector control, the basic voltage equation is dq for rotating the induction motor at the electrical angular velocity ω.
When expressed in two axes, it becomes the following formula (1), and the torque T is (2)
It becomes an expression.

T = K (i ₂ d · i ₁ q−i ₂ q · i ₁ d) (2) where V ₁ d, V ₁ q: primary voltage i ₁ d, i ₁ q: d-axis and q-axis primary currents i ₂ d, i ₂ q: d-axis and q-axis secondary currents R ₁ and R ₂ : primary and secondary resistances L ₁ and L ₂ : primary and secondary inductance M: primary And secondary mutual inductance P: d / dt ωs: slip frequency K: constant In the above equation, the q axis is the secondary current, the d axis is the magnetic flux axis, and the non-interference control is the excitation. Mutual interference between the secondary magnetic flux and the secondary current is compensated for obtaining the primary voltages V ₁ d and V ₁ q from the current command i ₀ ^* and the torque current command i _T ^* .

FIG. 2 shows a conventional non-interference vector control device. Voltage type
The PWM inverter 1 controls the output frequency and voltage by the phase voltages ea ^* , eb ^* , ec ^* to drive the induction motor 2, the rotor angular velocity ωr of the motor 2 is detected by the pickup 3, and this angular velocity ωr is the speed command. It is compared with ω ^* and extracted as a torque current command i _T ^* to the speed control amplifier 4. An excitation current command i ₀ ^* and a torque current command i _T ^* are taken into the slip frequency calculation circuit 5, and a slip frequency ωs is obtained from the secondary time constant τ ₂ according to the following equation (3), Further, the slip frequency ωs is added to ωr to obtain the power source angular frequency ω ₀ . Then, in the trigonometric function generating circuit 6, the sine and cosine AC signals SIN ω ₀ t and COS having the power source angular frequency ω ₀
Generate ω ₀ t. The arithmetic circuit 7 obtains the voltage signals V ₁ d and V ₁ q of the dq axes from the excitation current command i ₀ ^* and the torque current command i _T ^* as non-interference calculation, and further, the primary voltage at the fixed biaxial coordinates.
Find V ₁ d and V ₁ q. These primary voltages are converted into two-phase / three-phase by the two-phase / three-phase conversion circuit 8 to obtain three-phase voltages ea ^* , eb ^* , and ec ^* , and this signal and the triangular wave generated by the triangular wave generation circuit 9 are used for PWM by the inverter 1. Control is made.

D. Problems to be Solved by the Invention In the conventional non-interference vector control device, there has been a problem that torque fluctuations and the like occur due to iron loss inherent in the induction motor. This will be described in detail below.

In the configuration of FIG. 2, the relationship of the currents flowing through the electric motor 2 is as shown in FIG. 3 (a), and the exciting current I ₀ and the torque current
Although I _T is made orthogonal, the iron loss component current I ₀ ′ is included in the torque current I _T axis, and the desired primary current i ₁ cannot be obtained. The third diagram the primary current i ₁ in the braking area to the primary current i ₁ in the driving area as shown in (b) 'is reduced. For this reason, the actual torque becomes small in the driving region even if the desired primary current i ₁ is set, and the actual torque becomes large in the braking region.

E. Means for Solving the Problems The present invention has been made in view of the above problems, and the magnetic flux axis primary current value i ₁ q of the induction motor and the torque axis primary current value i ₁ d and slip that are orthogonal to the magnetic flux axis primary current value i ₁ q The frequency ωs is However, I _0: exciting current setting value I _T: torque current set value I ₀ ': core loss component current R _2: secondary resistance S: Slip _{[= (ω 0 -ωr) /} ω 0] rm: core-loss resistance L ₂ : secondary inductance M: means for controlling the mutual inductance.

F. Action In the above equation (1), the voltage equation with iron loss introduced is as shown in the following equation (5).

When the condition that the secondary magnetic flux and the secondary current are orthogonal to each other is obtained from this voltage equation, the above equation (4) is obtained, and the inverter output current control is performed so that the current i ₁ q and i ₁ d are present and the slip frequency ωs is obtained. Alternatively, the influence of the iron loss is eliminated by controlling the current so that the voltages V ₁ d and V ₁ q are exchanged.

G. Embodiment FIG. 1 is a device configuration diagram showing an embodiment of the present invention, which is a case of primary current control of an electric motor. In the figure,
Those having the same functions as those in FIG. 2 are designated by the same reference numerals. The slip frequency calculation circuit 11 obtains the slip frequency ωs in the equation (4) from the torque current command value I _T ^* , the exciting current command value I ₀ ^* , the power source angular frequency ω ₀ , the rotor angular frequency ωr and the motor constant. . The iron loss current calculation circuit 12 calculates the iron loss component current I ₀ ′ from the iron loss resistance rm by the following equation (6). Ask by. Although the resistance rm is shown as a fixed value,
Since this resistance rm is a function of frequency, it can be calculated more accurately.

The current command calculation circuit 13 includes a torque current command I _T ′ and a torque current command I _T ′ obtained by adding the iron current I ₀ ′ to the torque current command I _T ^*
From I ₀ ^* , slip frequency ωs, and rotor angular frequency ωr The phase current commands ia ^* , ib ^* , ic ^{* are} calculated from these Ask for. These current commands are compared with the output current of the inverter 1 by the current control amplifier 14, and the inverter 1
Output current feedback control is performed.

In addition, although the case where the vector calculation by the current reference | I ₁ |, φ is performed in the above-described embodiment, the present invention is not limited to this, and the vector calculation by the voltages V ₁ d and V ₁ q is performed. By doing so, an equivalent effect can be obtained.

H. Effect of the Invention As described above, according to the present invention, since the non-interference control including the iron loss component current is performed, the non-interference that completely eliminates the interference between the magnetic flux and the torque current due to the iron loss component. To be in control,
There is an effect that high-precision torque control that eliminates the error between the actual torque during driving and regeneration is possible.

[Brief description of drawings]

FIG. 1 is a block diagram of an apparatus showing an embodiment of the present invention, FIG. 2 is a block diagram of a conventional vector control apparatus, and FIG. 3 is a vector diagram showing a conventional current relationship. 1 ... Inverter, 2 ... Induction motor, 4 ... Speed control amplifier, 11 ... Slip frequency calculation circuit, 12 ... Iron loss current calculation circuit, 13 ... Current command calculation circuit, 14 ... Current control amplifier.

Claims (1)

[Claims] 1. A magnetic flux axis primary current value i ₁ q of an induction motor, a torque axis primary current value i ₁ d orthogonal thereto and a slip frequency ω.
s is the following equation i ₁ q = I ₀ (constant) i ₁ d = − (I _T + I ₀ ′) However, I ₀ : Excitation current setting value I _T : Torque current setting value I ₀ ′: Iron loss current R ₂ : Secondary resistance S: Slip rm: Iron loss resistance L ₂ : Secondary inductance M: Mutual inductance A vector control device for an induction motor, comprising: