JPS6028786A - Method and device for controlling asynchronous machine - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of operating an asynchronous machine supplied with power from a converter and an apparatus for carrying out the method.

[Conventional technology]

The rotor rotation of the asynchronous machine supplied with power from the converter is controlled in relation to a predetermined target value t7, and the output current is set to a frequency and amplitude corresponding to a target vector determined by the target value. The method of operating an asynchronous machine is conventional.

The current i supplied to the asynchronous machine has two target values 19. □Bitterness.

i, P2■, if the measured rotor speed n- is still at steady state current frequency ts, then tB=2
3+const @ i, '1/i, □% or when controlled so that -1-const*i input/i ” ψ2 ψl holds in consideration of the dynamic process, the rotor reference of the asynchronous machine The magnetic field is based on the slip frequency %Lh ψL=const*+ψ2/iψ□−(r/x)
Exercise with #. Here, rL represents the rotor resistance of the asynchronous machine, and Xh represents its main magnetic field inductance.

As is known, the stator current, stator voltage and main magnetic field of a rotating field machine are determined by the corresponding stator current vector i, stator voltage vector u''!, or the stator voltage vector u''!, as shown in FIG. It can be expressed by a magnetic flux vector ψ.If a spatially fixed (stator orientirad) reference axis α and a reference axis λ coupled to the rotor (111 rotor orientirad i) are defined in a spatially fixed stator, , the direction of the flux vector ψ is the stator orientirad angle ψS between ψ and α or the flux vector ψ and the frequency, 1s=d(λt9
) /d is given by the rotor orientirad angle ψL between the rotor axis λ rotating with t. The direction of the stator current vector l is correspondingly determined by the stator orientirad current angle εS, while the stator current vector i
and the magnetic flux vector ψ +1 is determined by the angle ε, called the load angle 1', εs−ψL−λS (7), which is the rotational speed between the actual rotational speed value and the rotational speed setpoint value. In this case, the magnitude ψ of the magnetic flux vector is determined by ψ - ing. For the moment of the rotating magnetic field machine) M, the relational expression M-ψ・I (p2 holds true, so at the magnetic flux size ψ kept constant, the magnetic field perpendicular components i, 2 called "effective current 1" directly The rotational moment and therefore the rotational speed can still be influenced linearly.

That is, in the above-mentioned control or adjustment of the asynchronous machine, a constant magnetic flux can be set in advance by applying a constant target value l ≠1 for the magnetizing current, and the target value ! 9.2 can be used as the effective current target value for setting the desired rotational moment or the desired rotational speed. At that time, the effective current target value, , p2-
X-, the shear frequency dψL/d is more directly derived as -ψL.

Such a device is known, for example, from German Patent No. 15 of the Federal Republic of Germany.
63228, in which a slip frequency setpoint value is formed which is proportional to the value (8).

In order to adjust accordingly to the applied effective current, the setpoint value is fed to a function generator with a fixed input function, whereby the magnetizing current setpoint value or the magnetic flux is also set by preloading the function. has been done. In this case, it is additionally provided to control the magnitude of the stator current on the basis of a control deviation between its setpoint value and actual value.

Furthermore, a further function generator forms a corresponding angle ε from the input active current setpoint value and the fixedly set magnetization setpoint value, from which angle the transducer connected after ψ Forms a quantity proportional to the change in load angle. The sum of the slip frequency target value, the measured rotor rotation speed, and the load angle change is the control amount for the frequency 68 of the stator current vector.The electrical structure of a full-length synchronous machine is given by the rotor centrifugal mass of an asynchronous machine. Decoupled from mechanical structure.

At that time, the characteristic formula % formula % Here, the characteristic behavior described by the damping d = cos ε (p = 19., /11 and the time constant τ = 'l' - cos ε, (T is the main magnetic field time constant) remains. This damping decreases with increasing load angle.A typical asynchronous machine is loaded up to a load angle of about 70°, so the damping is d=cos 70°
=034. Therefore, asynchronous machines are still prone to harmful hunting, especially at large load angles.

The problem that the invention seeks to solve is to better attenuate these hunting.

This is especially true when, as in the above-mentioned known technology, a rotational speed regulator or motor is installed above the slip frequency control, that is, the rotational moment is determined by the relational expression M-ψ・I(p2).
Proportional to ε・C03e = i2・sin2g ψ ψ
ψ is there. In FIG. 3, the relationship between the rotational moment and the load angle is shown using the current magnitude i as a parameter. The maximum point occurs for a load angle of 45°, and the change in load angle has a different sign (positive) depending on whether the load angle is larger or smaller than 45°.

(negative) and affects the rotational moment.

For small load angles, the magnetizing current and therefore also the magnetic flux are approximately constant. The notching of the load angle therefore acts primarily on the rotational torque and thus also on the rotational speed change via the active current at such operating points. They can be stabilized through control of the active current.

However, the closer the load angle is to +90°, the less the effective current changes during hunting; on the contrary, the angle changes now primarily affect the magnetizing current and therefore also the magnetic flux. In this case, the angle increase acts to become smaller. The speed regulator responds to this action by increasing the effective current target value I9,2,
This further increases the load angle. That is, the rotation speed regulator acts on the hunting of the load angle in the direction of reducing damping.

For operating points with load angles exceeding 45°, it is therefore necessary to take special damping measures, for example by interfering with the control of the magnetizing current by means of higher-order magnetic flux control. However, this is not always possible, especially at low rotational speeds.

[Means and operations for solving the problem] The starting point of the present invention is that the converter that supplies power to the asynchronous machine provides a target value for the slip frequency in advance and sets a target value for the magnetizing current. This is a method in which the amplitude of the converter output current is controlled or adjusted in accordance with the amplitude of a target current vector defined by a target value. The converter frequency is controlled as a function of the sum of the measured rotor rotational speed and the rotor flux, and thus also the rotational moment or rotational speed (11) (+rL). The present invention
It is based on the idea that load angle hunting should be attenuated by suitable interference with the magnetic flux or the setting of the load angle at load angles exceeding <45°.

Starting from this idea, the problem to be solved by the invention is solved by the method according to claim 1.

Advantageous embodiments of the method and advantageous devices for carrying out the method are listed in the patent claims.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

A given voltage or a given current is input from the converter 2 to the stator winding of the asynchronous machine 1 (FIG. 1) as an input quantity that is not affected by the load state. For this purpose, the power section 3 of the converter is controlled by the control device 4 at a rotational speed of a setpoint current vector with respect to the axis λ such that a given amplitude and a given phase or frequency of the electrical quantity, which is independent of the load state, is obtained. (It automatically settles according to the load condition of 1→.

It is shown in FIG. 1 that by means of one control input each for amplitude and frequency, only these two degrees of freedom can be provided to the converter in each case (
Even if in a specific case the control device has one additional input of the phase control reservoir, one for each output phase of the converter, as for example in the case of a direct frequency converter.
even if two unique sinusoidal reference voltages are input).

In some cases, the above-mentioned Federal Republic of Germany Patent No. 156
As shown in document 3228, a regulator can be connected before the control input of the frequency conversion device 40. This is illustrated in FIG. 1 by an amplitude regulator which compares the amplitude setpoint value with the actual amplitude value taken from the stationary feed line of the asynchronous machine 1.

Furthermore, the rotor rotational speed is taken from the asynchronous machine 1, as indicated by the tachometer generator 5.

The rotation speed control and X-control deviation Δn is formed from the rotor rotation speed and the rotation speed target value, and the effective current target value [,2°
(2) or is applied to the upper rotational speed regulator 6 to form a slip frequency target value ψ1 proportional thereto. Target value for the magnitude of magnetic flux or proportional to it ■ Target value of magnetizing current 1. p□ may be given in advance from the outside, or may be set internally in the control device 7 that supplies the control amount to the control device 4.

Now, the control device 7 has a rotor rotation speed of 18 and an eye of -x-,
+ Reference value I □ , 1 (frequency converter 2 in relation to p2
The control amount for ψ is determined by the vector of the output current of the converter being the target current vector i given in advance by the target value.
It is formed so as to settle to a frequency and amplitude corresponding to . In addition, for example, the control device 7 can internally generate all changes in the load angle setpoint value . = (r"/ψ") ·i, , 2" From the sum of o, a corresponding rotational frequency of current target vector i■: 8■ is formed.

Now, in order to attenuate the load angle hunting of an asynchronous machine, the frequency of the frequency converter is changed to a frequency at which the change in the target value of the slip frequency is temporarily conditioned by the change in the target value of the target vector at a load angle exceeding 45°. 1 causing a change in the frequency of the transducer directed opposite to the change
controlled by sea urchins.

As mentioned above, at load angles greater than 45°, an increase in the load angle causes a decrease in the magnetic flux and rotational moment, and the rotational speed regulator changes the effective current to the target value! Reacts by increasing 9□. Therefore, the circumference
The frequency of the X- wave number converter is not controlled according to the simple sum (λ8+91), but this sum, at load angles exceeding ψ 45°, is subject to at least a negative change in the frequency target value d12'. Advantageously, a quantity γ approximately proportional to /dt is superimposed.

The superposition of this additional amount γ on the sum of 1 is shown in FIG. 3 by the subtraction circuit 8. This additional amount γ is −X −X
- Quantity 't''=d(arctan+2/iI7.□)
/dt, ψ ψ is taken out from the transmission circuit 9 which is given the target value (15
) obtain.

This configuration is shown in Fig. 4 for the case where the large current -X-° yellowness 1 and the same wave number ε8 of the stator orientirad asynchronous machine current are directly given to the converter 2 as control variables in advance. Shown in detail.

In FIG. 4, a current source conversion mounting is used. The control device of the converter is not shown in detail, but only an integrator 11 which converts the setpoint frequency into a corresponding setpoint phase for the current at the individual outputs of the converter. That is, it is possible to start from the angle itself instead of the frequency, or, if the control device has isolated control inputs for example frequency and phase, it is possible to phase-control the attenuation corresponding to Jrdt. It can also be superimposed on the input end.

In FIG. 4, the inverter 12 on the asynchronous machine side converts the DC current supplied via the current intermediate circuit into L d tb r
rK p −” V r h k + C−h−L(
h m xun V m (16) Distributed to fixed children's supply line. The amplitudes of these stator currents, which are determined by the inverter input current, and thus also the amplitudes of the stator current vectors, can be controlled or adjusted by the supply-side forward converter 13 in accordance with the setpoint value l of the current magnitude.

・■ The transfer circuit 9 receives the magnetizing current target value 'cp 1 e from one input terminal for the magnetic flux target value ψ'' via the transfer circuit 14 which is matched to the respective main magnetic field inductance parameter Xh, and the other is the effective type. ■ The flow target value 19,2 is directly connected to the output end of the rotation speed regulator 6.
It can be extracted easily. In this way, the target current vector 1 is given in advance by the transfer element 9 its orientirad component of the orthogonal coordinate magnetic field, from which the usual rectangular/polar coordinate exchanger 15 determines the magnitude of the stator current, -x=%〒i,
7" OJ: U load angle t"=arCtanψ (! sir %) is formed.

ψ2 ψ1 The rotor resistance parameter r and the set magnetic flux ψ■ are taken out, and the rotor rotational speed λ8 (taken out from the tachometer generator 5) and the coordinate converter 15 (taken out via the differentiation circuit 17) Furthermore, together with the differential of the load angle target value ε■ψ, the additional amount γ is also applied to one superimposed summing point 20.

As an additional quantity, in this case the differentiation of the magnitude I of the stator current is formed by a differentiator circuit 21, which may consist of a simple RC circuit. This differential circuit 2
The output signal 1 is directly negatively superposed on the summing point 20 in motor operation, but the polarity of this additional quantity r can be reversed for generator operation. For this purpose, a changeover switch 22 is used which can be driven in accordance with the sign (positive, negative) of the effective current target value 5° taken out from the limit value circuit 23.

However, within this range, the interference of the effective current setpoint value via the speed regulator 6 is strongly damping. For load angles greater than 45°, the sign of the load angle during hunting is negligible and t≧does not change, so that the additional amount is approximately proportional to the change in the effective current. That is, if the load angle increases as a result of hunting, the magnetic flux and the rotational moment will decrease without any particular interference with the current angle εs, and the rotational speed regulator 6 will have a correspondingly greater effectiveness as shown in FIG. A current setpoint value, ie a load angle setpoint value that increases with time, is given.

Correspondingly to the chain of influence via magnetic flux, torque and rotational speed, an increasing effective current setpoint is recognized as a result of this hunting, and overall the desired frequency required for hunting damping is increased. Superimposed on the angle or frequency control so that a reduction occurs.

Since the proportional gain is when the rotational speed regulator is normally set, the weight of the differential Ig circuit 21 is very small for small load angles (19). Since the additional amount of superposition can be realized through one RC circuit with an unchangeable time constant.

Of course, a change in the slip frequency target value itself, which can be taken out directly from the output of the rotational speed regulator 6, can of course be superimposed on the adder circuit 20 as an additional quantity, for example by means of an RC circuit. In this case, the active current target value is applied to the differential RC circuit only at sufficiently large values of the active current target value, so that this superposition becomes effective only at large load angles, that is, at large active current target values. As also explained in , it may be provided through a blocking circuit (eg a Zener diode) that releases the differentiator circuit.

In many cases, for example in pulse control methods, instead of the frequency converter in Figure 2 which is supplied with a load-independent input DC current, an inverter is used which operates with a load-independent input DC voltage. It is advantageous to do so. In principle, the seven centrifugal mass time constants Th of the non-rotating machine are adapted. Next, the setting of the attenuation circuit is T1
．． There is no distinction depending on whether (20) (in this case, the stator voltage vector of the asynchronous machine is given in advance by the control voltage) is used. In this case, simply: ■ Input target value 1 q□ that defines the current target vector.

l may be converted so that an appropriate control amount for one voltage target vector u%, - and T2 - can be obtained from them. The voltage vector is then determined in frequency and amplitude, depending on the given conditions of the asynchronous machine, in such a way that a current vector is settled that corresponds to the current setpoint vector, which is prestressed by the setpoint value.

FIG. 5 shows the magnitude U and the stator orientirad direction for a given magnetic flux ψ (and the electromotive force vector perpendicular to it =! T8) and known values for the stator resistance r and leakage inductance L0. How the voltage vector U given by the angle α8 is related to the freely settling current vector l is determined by the magnetic field orientirad.
This is shown by the vector diagrams ■ and ■. 1 □ , 1 (p2 to convert the magnetic field ψ into the corresponding voltage target vector, simply
It is only necessary to add the corresponding vector r8., -X- of the ohmic voltage drop and the vector L0.9'3.X of the inductive leakage voltage to the electromotive force vector given by the ψ scale. A suitable circuit for carrying out this calculation can be implemented without difficulty by a person skilled in the art and is known as a decoupling network'. Such a circuit network is 1. . Allow only the actual value component to change.

FIG. 6 shows an embodiment in which a direct frequency converter is used as the frequency converter 3. In FIG. Transfer circuit 9
is constructed in accordance with FIG.
.

One decoupling network 9a is used to convert u9,2-X-. One orthogonal coordinate-to-polar coordinate converter 9b provides a control amount u% for the voltage magnitude and a control amount ■ for the magnetic field orientirad voltage angle.

α is formed. Current target value, -X-, -X-ψ
The input of ψ1 ψ2 takes place as in FIG. 4, the proportional element 16 being represented by one voltage divider 16'. At the summing point 20, which can advantageously be realized by an operational amplifier in the manner shown, the measured rotor speed λ8 and the slip frequency setpoint value ``are likewise added together with an additional quantity γ and an angular change. It is synthesized as a frequency control amount.

Instead of the quantity 2'' describing the change in the load angle, in the present case a corresponding change in the physically equivalent magnetic field orientirad voltage angle α■ψ is superimposed.

Of the converter control device 4 (FIG. 1), only the reference voltage generator 4' is shown in FIG. Therein, the frequency setpoint value α8 is converted by an integrator 11' into the corresponding angle setpoint value α-, and then a sine wave generator 25 generates three (23) sine wave generators with a phase shift of 120°. form waves. In this way, the magnitude of the target voltage e
By multiplication with , three control voltages [, RX-, us*■, LIT are obtained, by means of which the direct frequency converter 30 partial converter is controlled in a manner not explained in detail here. The details of the conversion devices and their controls used in each case, as well as of the sub-controls that may be provided, can be realized to any purpose by a person skilled in the art and are not critical to the essence of the invention.

In contrast to FIG. 4, in the embodiment according to FIG. 6, the additional quantity γ is formed by the variant already described, and the effective current setpoint 19,2 consists of two reversely connected Zener diodes 26. It is taken out through two blocking circuits and applied to one gc element 21 which acts as a differential element. A sign reversal of the additional quantity γ upon transition from motor operation to generator operation is not necessary in this case. Because of the effective current! 9,2 already has its sign,
For hunting attenuation (24)

[Brief explanation of drawings]

Fig. 1 is a block diagram of a device for implementing the method of the present invention, Fig. 2 is a vector diagram of stator current and magnetic flux, Fig. 3 is a diagram showing the relationship between rotational moment and load angle, Fig. 4 is a block diagram of a device operating according to the method of the present invention having a current source wave number converter for asynchronous machine power supply, and Fig. 5 shows the relationship between the voltage applied to the converter and the output current of the converter. The vector diagram shown in FIG. 6 is a block diagram of a device operating with the method of the invention having a voltage source converter for powering an asynchronous machine. DESCRIPTION OF SYMBOLS 1... Asynchronous machine, 2... Conversion device, 3... Power unit, 4... Control device for conversion device, 5... Tachometer generator, 6... Rotation speed regulator, 7 ...control device, 8...
Subtraction circuit, 913... Forward conversion device, 14... Transfer circuit, 15... Coordinate converter, 16... Proportional circuit, 17
...Differentiating circuit, 2゜... Addition point, 21... Differentiating circuit, 22... Changeover switch, 23... Limit value circuit,
25... Sine wave generator, 26... Zener diode (27) U1. esl / / /I') / O 1

Claims (1)

[Claims] 1) Measure the rotor rotation speed of the asynchronous machine (1) supplied with power from the converter, and convert the frequency converter (2) to the rotor rotation speed (
λS) and the set target value for the magnetizing current (i-X-
□) and a pre-given target value (i bar) for the slip frequency (εS), the output current (i) will be at a frequency (i) corresponding to the target vector determined by the target value.
λS) and amplitude (i), the frequency of the load angle (ε) exceeds 45° due to the attenuation of the load angle (ε) of the asynchronous machine.
At , the change in the slip frequency ψ ° -≠ L ≠ target value (ψL-1q, 2 ・r/ψ ) is temporarily directed opposite to the frequency change in the target vector conditioned by the change in the target value. A control method for an asynchronous machine, characterized in that the asynchronous machine is controlled. 2. In the method according to claim 1, the frequency converter frequency is greater than 45 degrees from the change in angle between the measured rotor rotational speed, the frequency target value, and the target vector with respect to the rotor axis. At the load angle, an additional amount (γ=
di 2sho/dt) (2s+=pL+i ”)ψ
1. A control method for an asynchronous machine, characterized in that the control is performed in accordance with a target frequency CtB%) given by ψ. 3) In the method according to claim 2, 45°
A method for controlling an asynchronous machine, characterized in that a change in a slip frequency target value is formed as an additional amount for a load angle exceeding . 4) A method for controlling an asynchronous machine according to claim 2, characterized in that the additional amount is a load of the magnitude of the target vector. 5) In the method according to any one of claims 1 to 4, the magnetizing current target value is a magnetic field parallel component proportional to the magnetic flux target value of the target stator current vector,
A control method for an asynchronous machine, characterized in that an output amount of the rotation speed regulator that determines the magnetic flux perpendicular component of the target stator current vector is input as a slip frequency target value. 6) A device for controlling or adjusting an asynchronous machine (1) supplied with power from a converter to attenuate hunting, in which the control amount (amplitude, frequency) of the frequency converter (2) is
A device consisting of a control device (7) in which setpoint values defining one stator current setpoint vector for the magnetizing current and the active current are given in advance, in which the frequency of the converter device is such that the measured rotor speed <; B), the sum of the slip frequency target value (?L≠) proportional to the angle target value, and the change in the load angle. (3) 9) In the apparatus according to claim 8, At least at load angles exceeding , the output amount CtB of the adder circuit (20) is negatively superimposed with an additional amount (γ) that is approximately proportional to the change in the target slip frequency value
A control device for an asynchronous machine, characterized in that it can be controlled in proportion to. 7) In the device according to claim 6, the target is taken out via the differentiating circuit (21) from the transmission circuit (21) to which the target value is given as the additional amount (r) to the adding circuit (20). A control device for an asynchronous machine, characterized in that the magnitude of the current vector is superimposed via a changeover switch (22) that reverses the polarity of the additional amount during power generation operation. 8) The device according to claim 7, characterized in that a slip frequency target value taken out via a differentiating circuit (21) is superimposed on the adding device (20) as an additional amount. Machine control device. (4) A control device for an asynchronous machine, characterized in that it is provided with a blocking circuit (26) that releases the differential circuit only at sufficiently large values of the set target value for the switching current and the target value of the slip frequency active current. . 10) In the device according to any one of claims 6 to 9, the transmission circuit is a rectangular coordinate-to-polar coordinate converter (15) in a current source converter, and a subtractor (15) in a voltage source converter. A control device for an asynchronous machine, characterized in that it includes a coupling circuit.