JP2629196B2 - Vector controller for induction motor - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vector control method for an induction motor, and more particularly, to a control method for suppressing an abnormal phenomenon at the time of re-input after current interruption.

[Conventional technology]

In the inverter drive of an induction motor, when the energization is temporarily interrupted and the energization is restarted after a certain period of time, a phase difference occurs between the residual magnetic flux vector of the motor and the excitation current command vector. Abnormal phenomena, such as flowing, occur.

This will be specifically described by taking the case of the slip frequency control type vector control as an example.

FIG. 4 is a block diagram of the slip frequency control type vector control. The operation of the vector control in FIG. 4 will be described step by step.

Here, the switch 7 is turned on by the current-current cutoff switch 16.
Is closed, that is, the motor is in the energized state, and the vector calculation unit 17 is assumed to be performing the energizing operation described below.

The magnetic flux command Φ ^* output from the magnetic flux command generator 11 is converted by the magnetic flux-excitation current converter 12 into an excitation current command _Im ^* . Exciting current command I _m ^* is a function of the magnetic flux command [Phi ^*, it is expressed by the equation (1).

I _m ^* = f (Φ ^* ) (1) The difference between the speed feedback signal ω _m output from the speed detector 2 and the speed command signal ω _ref ^* is determined by the speed controller 5 having the speed control gain K _N. , And becomes the secondary current command I ₂ ^* . This relationship is represented by equation (2).

I ₂ ^* = K _N (ω _ref ^* −ω _m ) (2) Vector calculation from the excitation current command _Im ^* and the secondary current command I ₂ ^* obtained by the above equations (1) and (2). The generator 8 generates a primary current command vector ₁ ^* on the rotating magnetic field coordinates shown in polar coordinates in FIG. 2 and equations (3) and (4).

θ = tan ⁻¹ (I ₂ ^* / I _m ^* ) (4) Here, the coordinate system on the rotating magnetic field is dq coordinates, the direction of the excitation current command _Im ^* is the d axis, and the secondary current is Command I ₂ ^*
Direction coincides with the q-axis.

On the other hand, in parallel with the calculations of Expressions (3) and (4), a calculation for determining the slip frequency command ω _s ^* is performed. The slip frequency command ω _s ^* is obtained by ^adding the motor secondary resistance constant to the secondary current command I ₂ ^*.
It is obtained by multiplying R ₂ and dividing the result by the magnetic flux command Φ ^* by the divider 14. This is the slip frequency command ω
_This is a basic expression for obtaining _s ^* , and is represented by Expression (5). Reference numeral 15 denotes a secondary resistance constant setting device.

ω _s ^* = (I ₂ ^* / Φ ^* ) R ₂ … (5) Slip frequency command ω _s ^* and speed feedback signal ω
By adding _m , a primary frequency command ω ₁ ^* is calculated. This is shown in equation (6).

ω ₁ ^* = ω _s ^* + ω _m (6) For the following description, let the stator coordinate system be α-β coordinates. Α-axis and excitation current command vector obtained by integrating primary frequency command ω ₁ ^* by integrator 13
Equation (7) shows the relationship between the phase angle θ ₁ ′ with respect to _m ^* and the primary frequency command ω ₁ ^* .

θ ₁ ′ = ∫ω ₁ ^* dt (7) The stator coordinate axis α axis, the primary current command vector ₁ ^*, and the phase angle θ ₁ are, as shown in FIG. It is obtained by adding the phase angle θ between the primary current command vector ₁ ^* and the phase angle θ ₁ ′ between the α axis and the exciting current command vector _m ^* shown in the above equation (7).

Equation (8) shows the relationship among θ, θ ₁ , and θ ₁ ′ of the above-described phase angles.

θ ₁ = θ ₁ ′ + θ = ∫ω ₁ ^* dt + tan ⁻¹ (I ₂ ^* / I _m ^* ) (8) As described above, the primary current command vector on the α-β coordinate calculated is ₁ ^* Are converted by the current command generator 9 into three-phase current commands _IU ^* , _IV ^* , and _IW ^* . Current controller 10
Is the current command ^{_{I U *, I V *,}} I W * and the current detected by the detector 1, three-phase current feedback signal I _fbu, I _fbv, I _fbw
And convert it to an inverter drive signal,
The induction motor 3 is driven via the inverter 4.

[Problems to be solved by the invention]

In such a conventional vector control system shown in FIG. 4, when the control for temporarily stopping the motor current is performed, during the period in which the switch 7 is opened to cut off the motor current, the vector control unit 17 Excitation current command vector
The calculation of the phase angle θ ₁ ′ between _m ^* and the α-axis is continued as it is or is not calculated at all. Therefore, when re-energizing, the residual magnetic flux vector ₀ 'and the exciting current command vector
The phase with _m ^* does not match.

In the conventional vector control method, when re-energization is performed after current interruption, the excitation current command vector _m ^* , the residual magnetic flux vector ₀ ', and the motor magnetic flux vector ₀ during energization are set.
Will be described for the following cases (a) and (b).

(A) The case where the calculation of the phase angle θ ₁ ′ is continued as it is in the current cutoff magnet.

Since the motor current was interrupted, the motor started to decelerate,
The speed feedback signal ω _m shown in FIG. 4 decreases.
At this time, since the speed command signal ω _ref ^* is constant, the secondary current command I ₂ ^* increases from equation (2), and the slip frequency command ω _s ^* also increases from equation (5). From the equation (6), the primary frequency command ω ₁ ^* = ω _m + ω _s ^* and the slip frequency command ω _s ^* ≠ 0, so the primary frequency command ω
₁ ^* is greater than the speed feedback signal ω _m.
At this time, since the angular velocity of the motor residual magnetic flux vector _{0 'is} equal to the speed feedback signal omega _m, is smaller than the excitation current command vector _m ^* of the angular velocity, as shown in FIG. 5 (a), again passing electromagnetic excitation current Command vector
The phases of _m ^* and the residual magnetic flux vector ₀ 'do not match when re-energized.

(B) When the calculation of the phase angle θ ₁ ′ is not performed at all when the current is interrupted.

In this case, the phase angle θ ₁ ′ retains the value before the current interruption as it is, and when the current is re-energized, the retained phase angle is used as an initial value, and the integration of the primary frequency command ω ₁ ^* is started again from the time of the re-energization, Calculate θ ₁ ′.

Therefore, as shown in FIG. 5 (b), the phase of the excitation current command vector _m ^* does not match the phase of the residual magnetic flux vector ₀ 'as in the case of (a).

Here, ₀ α, ₀ in FIGS. 5 (a) and 5 (b)
α ′, _m α ^* are the respective vectors ₀ , ₀ ′, _m
^* Is projected onto the coordinate axis α on the stator, and when the current is interrupted or re-energized, the motor magnetic flux vector ₀ ,
The angular velocity of the residual magnetic flux vector ₀ 'and their absolute values |
It is assumed that there is no significant change in ₀ |, | ₀ ′ |. In FIG. 5 (a) and FIG. 5 (b), it is assumed that the motor flux vector ₀ at the time of energization resumption at the time of energization does not change greatly in absolute value and phase as compared with the current interruption. The excitation current command vector _m when re-energizing
^If the phase between ^* and the residual magnetic flux vector ₀ 'is shifted, the absolute value and phase angle of the motor magnetic flux vector ₀ at the time of energization greatly change, and an abnormal phenomenon such as overcurrent occurs.

The present invention has been made in view of such circumstances, and the excitation current command vector _m ^* is also provided at the time of current interruption and re-energization ^.
The purpose of the present invention is to prevent a phase shift from occurring between the residual magnetic flux vector ₀ 'and the residual magnetic flux vector ₀ ', and to suppress occurrence of an abnormal phenomenon such as an overcurrent.

[Means for solving the problem]

To achieve this object, the present invention provides a speed command ω _ref
^* And the in accordance with the deviation between the speed feedback signal omega _m secondary current command I ₂ speed controller for calculating a ^*, the magnetic flux converts the flux command [Phi ^* to the exciting current command I _m ^* - an excitation current converter,
And the secondary current command I ₂ ^* and the excitation current command I _m ^* from the primary current vector and the vector calculator that calculates a phase angle theta, the flux command [Phi ^*, speed feedback signal omega _m and the secondary current command I ₂ a slip frequency calculator for calculating a primary frequency command omega ₁ ^* based on ^*, the primary frequency command omega
A current command generator for generating a three-phase current command based on the primary current vector and the phase angle θ ₁ obtained by adding the phase angle θ ₁ ′ obtained by integrating ₁ ^* and the phase angle θ; And a current controller for driving the induction motor via an inverter based on a current command.In the vector control device for an induction motor, a switch that is opened when the induction motor is temporarily cut off is output from the speed controller. , And between the current controller and the inverter, respectively.

〔Example〕

Hereinafter, the present invention will be specifically described based on embodiments shown in the drawings. FIG. 1 is a block diagram showing a control system to which vector control according to the present invention is applied.

The operation of the vector control according to the present invention at the time of current interruption will be described with reference to the block diagram shown in FIG. However, the operation during energization is exactly the same as the conventional vector control shown in FIG. In FIG. 1, components having the same functions as those in FIG. 4 are denoted by the same reference numerals, and description thereof is omitted.

This embodiment is different from the conventional example of FIG. 4 in that a switch 6 that is opened and closed by an energization-current cutoff switch 16 is controlled.
Is provided between the output of the speed controller 5 and the vector calculator 8. That is, by opening the switch 7 when the current is cut off by the energization-current cut-off device 16, the motor current is cut off and the switch 6 is opened at the same time, and the secondary frequency input to the slip frequency calculator 18 and the vector calculator 8 are inputted. Set the current command I ₂ ^* to zero, and always set the secondary current command during current interruption.
I ₂ ^* = 0 is maintained, and the operation of the vector operation unit 17 is continued as it is.

By doing so, the phase of the motor residual magnetic flux vector Φ ₀ ′ during the current interruption and the phase of the exciting current command vector _Im ^* can be matched, and no abnormal phenomenon such as overcurrent occurs in the re-transmitted electromagnetic wave, and Transiently stable vector control can be realized.

When the motor current is temporarily interrupted by the energization-current interruption switch 16, the switch 7 is opened and the current controller 10
Is not input to the inverter 4 and the induction motor 3 is not driven. When switch 7 is opened, switch 6
Is opened, the vector calculator 8 and the slip frequency calculator
The secondary current command I ₂ ^* input to 18 becomes zero during current interruption.

Here, during the current interruption, the secondary current command I ₂ ^* = 0, but the functions of the vector operation unit 17 including the slip frequency operation unit 18 continue the operation. Since the secondary current command I ₂ ^* = 0, the following equations (9) to (14) are obtained.

From equation (5), the slip frequency command ω _s ^* is ω _s ^* = 0... (9) From equations (6) and (9), the primary frequency command ω ₁ ^* is ω ₁ ^* = ω _s ^* + ω _m = ω _m (10) From equations (7) and (10), the phase angle θ ₁ ^* is given by θ ₁ ′ = ∫ω ₁ ^* dt = ∫ω _m dt (11) Equation (4), From (9), the phase angle θ is θ = tan ⁻¹ (0 / I _m ^* ) = 0 (12) From the equations (11) and (12), the phase angle θ ₁ is θ ₁ = θ ₁ ′. + Θ = θ ₁ ′ = ∫ω _m dt (13) From equation (3), the absolute value of the primary current command vector | ₁ ^*
| After all, the absolute value of the primary current command vector ₁ ^* from equation (14) is only the excitation current command _m ^*, the phase angle theta ₁ from equation (13) becomes the integral only speed feedback signal omega _m.

Since the residual magnetic flux angular velocity of the vector _{0 'is} equal to the speed feedback signal omega _m, the residual magnetic flux vector and α axis
The phase angle with ₀ 'is equivalently calculated by calculating the phase angle between the α angle and the exciting current command vector _m ^* from equation (13).

Therefore, at the time of re-energization, the phase angle between the residual flux vector ′ and the exciting current command vector _m ^* and the α-axis coincide.

FIG. 6 shows the phase relationship between the motor magnetic flux vector ₀ , the residual magnetic flux vector ₀ ', and the exciting current command vector _m ^* during energization to current interruption in this embodiment. As can be seen from FIG. 6, the residual magnetic flux vector during current interruption
_{0 'and} the excitation current command vector _m ^* phase is consistent, re energized even when energized when the motor is energized vector _0' and the excitation current command vector _m ^* phase can be said to match.

〔The invention's effect〕

As described above, in the present invention, even when the power supply is interrupted, the phase angle of the exciting current command vector is calculated from the speed feedback signal, thereby equivalently calculating the phase angle of the exciting current vector, and At the time of energization, the phase angle between the exciting current vector and the residual magnetic flux vector is matched. As a result, the phase difference between the residual magnetic flux vector and the exciting current vector at the time of re-energization is eliminated, and at the time of current interruption-re-energization, an abnormal phenomenon such as overcurrent does not occur, and transiently stable vector control is realized. be able to.

[Brief description of the drawings]

FIG. 1 is a block diagram of vector control showing an embodiment of the present invention, FIG. 2 is a vector diagram showing a relationship between currents on rotating magnetic field coordinates, FIG. 3 is a vector diagram showing a relationship between angles, and FIG.
The figure is a block diagram of vector control by the conventional control method,
FIG. 5 is a waveform diagram of each signal in the case of energization-interruption-re-energization in the conventional control system, and FIG. 6 is a waveform diagram of each signal in the case of energization-interruption-re-energization in the control system of the present invention. 1: Current detector, 2: Speed detector 3: Induction motor, 4: Inverter 5: Speed controller, 6, 7: Switch 8: Vector calculator, 9: Current command generator 10: Current controller, 11: Magnetic flux command generator 12: Magnetic flux-excitation current converter 13: Integrator, 14: Divider 15: Secondary resistance constant setting device 16: Energization-current cutoff switch 17: Vector operation unit 18: Slip frequency operation unit

 ──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Koujiro Sawamura 12-1, Otemachi, Kokurakita-ku, Kitakyushu-shi, Fukuoka Prefecture Inside the Kokura Plant of Yasukawa Electric Manufacturing Co., Ltd. (56) References JP-A-62-250894 (JP, A )

Claims (1)

(57) [Claims] And 1. A speed command omega _ref ^* and in accordance with the deviation between the speed feedback signal omega _m speed controller for calculating a secondary current command I ₂ ^*, the flux command [Phi ^* to the exciting current command I _m ^* conversion The primary current vector and its phase angle θ from the magnetic flux-exciting current converter and the secondary current command I ₂ ^* and the exciting current command _Im ^*.
, A slip frequency calculator for calculating a primary frequency command ω ₁ ^* based on the magnetic flux command Φ ^* , the speed feedback signal ω _m and the secondary current command I ₂ ^* , and the primary frequency command ω. A current command generator for generating a three-phase current command based on the primary current vector and the phase angle θ ₁ obtained by adding the phase angle θ ₁ ′ obtained by integrating ₁ ^* and the phase angle θ; And a current controller for driving the induction motor via an inverter based on a current command.In the vector control device for an induction motor, a switch that is opened when the induction motor is temporarily cut off is output from the speed controller. A vector control device for an induction motor, wherein the vector control device is provided between the current controller and the inverter, and between the current controller and the inverter.