JPH0480638B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention connects a variable voltage source to the rotor winding of a three-phase winding induction motor, and by manipulating the output voltage of this voltage source, the stator The present invention relates to a device that controls active power and reactive power on the winding side.

[Prior art]

For example, a technique for controlling the active power and reactive power on the stator winding side by connecting a variable voltage source to the rotor winding of a wound induction motor is described in IEEE Transaction on
Industry applications, Vol.IA−10, No.6,
11/12 (1974), P806-813. FIG. 8 is a configuration diagram of the control device shown in this document,
In the figure, 1 is a three-phase AC power supply to which the stator winding of a wound induction motor 2 is connected. The output terminal of a three-phase cycloconverter 3 is connected to the rotor of the induction motor 2 via a slip ring, and a speed detector 4 is connected to the rotor of the induction motor 2.
are mechanically connected. 5 is a frequency detector that detects the frequency of power supply 1, 6 is a subtracter, 7 is an adder, 8 is an integrator, 9 is a subtracter that calculates the difference ΔP between the active power command value P ^* and the actual active power value P , 10 is a subtracter that calculates the difference between the reactive power command value Q ^* and the actual reactive power value Q, and 11 and 12 are these P ^* , Q ^* , P,
A ^current reference generator ¹³ calculates two current command values Iqr ^{* ,} Idr ^* based on A two-phase three-phase converter that outputs Ibr ^* , Icr ^* ; 14a, 14b, and 14c are current detectors that detect the three-phase currents Iar, Ibr, and Icr of the rotor winding;
5a, 15b, 15c are subtractors that obtain the difference between the current command value and the actual current detected by the current detectors 14a, 14b, 14c, and 16a, 16b, 16c are voltage reference values given to the cycloconverter 3 based on this difference. A current controller outputs var ^* , vbr ^* , and vcr ^* , and 17 is a power detector that calculates active power P and reactive power Q from the voltage and current of the system connected to the stator winding of the induction motor 2.

The operation of the control device configured in this way is as follows. That is, the cycloconverter 3 converts the frequency voltage of the input side power supply into another frequency and voltage using the control input and outputs it.Here, the input side power supply is the three-phase AC power supply 1, and the control input is var. Outputs variable frequency, variable voltage voltages var, vbr, and vcr as ^* , vbr ^* , and vcr ^* . The cycloconverter 3 is formed by star-connecting three sets of single-phase cycloconverters, and each single-phase cycloconverter is composed of two groups of cycloconverters. With such a cycloconverter,
A way to get an arbitrary output waveform is, for example, BRPelly
It is described in detail in his book ``Cyclo Converter'' (translated by Saijo, Denki Shoin (1976)).

Now, in the wound induction motor 2, the power supply 1 is connected to the stator winding, and the cycloconverter 3 is connected to the rotor winding. The fundamental frequency of the currents Iar, Ibr, and Icr supplied to the rotor windings is determined by the difference between the angular velocity ωe of the stator and the angular velocity ωr of the rotor, ωs=ωe−ωr, so as to be synchronized with the power supply frequency. The detector of ωe, that is, the frequency detector 5 of the power supply, is a PLL ( P hase L ocked L
oop) circuit F/V (frequency/voltage) converter is used. A pulse generator and an F/V converter providing its output are used as a detector for the rotor angular velocity ωr, that is, a rotor speed detector 4. The transfer of power between the power source 1 and the induction motor 2 is determined by the phase relationship between the stator input voltage and the rotor input current. A third signal ΔP is then input into the fundamental frequency loop to control this power.
ΔP corresponds to the difference between the active power command value P ^* and the actual active power value P, and the rotor current phase with respect to the stator input voltage is controlled so as to make this error zero. The speed difference output from the subtracter 6 is used as a frequency command value for the cycloconverter 3, and after being corrected by ΔP in an adder 7, it is integrated in an integrator 8. This output is the rotor current phase reference value θr
becomes. The two-phase three-phase converter 13 includes a function generator that creates a three-phase sine wave whose phase is shifted by 90 degrees from the phase θr, and the output of this function generator and the current command value Iqr ^* , Idr.
Perform the following calculation from ^* to obtain the three-phase current command value Iar.
^* , Ibr ^* , and Icr ^* and an arithmetic unit that calculates and outputs them.

Iar ^* = Iqr ^* cosθr + Idr ^* sinθr Ibr ^* = Iqr ^* cos (θr − 2π/3) + Idr ^* sin (θr − 2π/3) Icr ^* = Iqr ^* cos (θr + 2π/3) + Idr ^* sin (θr + 2π/3) The current command value Iqr ^* is the result of calculating the difference ΔP between the active power reference value P ^* and the actual active power value P using the subtractor 9, and ^{proportionally} integrating this deviation using the current reference generator 11. is determined to be equal to . On the other hand, the current command value Idr ^* is the result of calculating the difference ΔQ between the reactive power reference value Q ^* and the actual reactive power value Q using the subtracter 1, and proportionally integrating this deviation using the current reference generator 12, so that Q ^* is the result of Q is determined to be equal to .

FIG. 9 is a vector diagram explaining the operation of the conventional device, in which the stator input voltage vector is taken as the qs axis, and the ds axis is taken in the direction perpendicular to the qs axis. Therefore, the qs-axis component of the stator current is the active power P
The ds axis component is proportional to the reactive power Q. On the other hand, the qr-dr axis is the reference axis of the rotor current vector, and is determined by the rotor phase reference value θr. In other words, θr=∫(ωs+ΔP)dt, so when ΔP becomes positive as shown in the figure, the rotor phase changes to lead the stator phase, and when A6A4 becomes negative, the rotor phase lags behind the stator phase. . As a result, the qs−ds axis and the qr−
A phase difference Δθ is generated between it and the dr axis. Iqr ^* is output for the purpose of controlling the active power P, and Idr ^* is output for the purpose of controlling the reactive power Q, and the rotor current I·r is determined by these. This rotor current I, when viewed from the qs-ds axis on the stator side, has a qs-axis component IP, a ds-axis component IQ,
Active power proportional to IP and reactive power proportional to IQ are generated on the stator side.

[Problem that the invention seeks to solve]

Since the conventional device is configured as described above, when P ^* is changed to control the active power P, the phase on the rotor side changes by Δθ. Therefore,
The current command values Iqr ^* and Idr ^* on the rotor side do not uniquely correspond to the active power and reactive power on the stator side, respectively. In other words, in order to change the active power, Iqr
^* Not only the IP that changes, but also the IQ,
Reactive power is affected. Conversely, if you try to change the reactive power, the active power will change. the result,
It has been difficult to control active power and reactive power quickly and stably.

The present invention has been made in order to solve the problems of the prior art as described above, and it is possible to control the active power and reactive power on the stator side separately, thereby enabling high-speed and stable power control. An object of the present invention is to provide a power control device for a linear induction motor.

[Means for solving problems]

The power control device for an induction motor according to the present invention detects the phase θe of the voltage applied to the stator winding and the rotational phase θr of the rotor winding, and the phase difference θs=θe.
−θr is calculated to determine the rotor coordinate dr−qr with respect to the stator coordinate axis ds−qs, and the three-phase current of the stator winding is converted into three-phase two-phase using θe to calculate the active power of the stator current. Components iqs and ids proportional to each of the reactive powers are obtained as feedback values, and these are used as the respective command values iqs ^* , ids related to the desired three active reactive power values.
Obtain the two-phase voltage command signal that should match ids ^* ,
This is converted into a three-phase voltage command signal using θs, and is used as a control input for a variable voltage source such as a cycloconverter connected to the rotor winding.

[Effect]

In the device of the present invention, the three-phase current of the stator is coordinate-transformed using the phase θe of the voltage applied to the stator winding, and the three-phase amount of the rotor is determined based on the difference θs between θe and the rotational phase of the rotor. In other words, since the coordinates are converted to the voltage to be applied thereto, it becomes possible to separate the stator current into the active power contribution part iqs and the reactive power contribution part ids and control each part separately.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below based on drawings showing embodiments thereof. FIG. 1 is a block diagram of a control device according to an embodiment of the present invention. In the figure, 2
is a three-phase wound induction motor, a three-phase AC power supply 1 is connected to the stator winding, and a three-phase cycloconverter 3 is connected to the rotor winding as a variable voltage source via a slip ring. ing. The cycloconverter 3 uses the power supply 1 as an input power source, and uses the output of a two-phase three-phase coordinate converter 31, which will be described later, as a control input. A rotor phase detector 21 is mechanically coupled to the rotor of the wound induction motor 2 to detect the position θr of the rotor winding, that is, the rotational phase thereof. A power supply phase detector 20 for detecting the voltage phase θe of the stator winding is provided between the power supply 1 and the induction motor 2.
is input to the subtracter 22, and the phase difference θs=θe−θr is calculated.

θs is input to the coordinate converter 31.

The three-phase currents iu, iv, and iw supplied from the power source 1 to the stator windings of the induction motor 2 are detected by a current detector 25 such as a CT, and these are detected by a three-phase two-phase coordinate converter 2.
6. Power phase detector 2
The 0 output θe is input to the coordinate converter 26 for this conversion.

23 inputs a reference value P ^* of active power on the stator side of the induction motor 2 from an active power setting circuit (not shown), and multiplies it by a predetermined coefficient K to obtain q.
Coefficient unit that generates the axis component current command value Iqs ^* , 2
4 inputs the reference value Q ^* of the reactive power on the stator side of the induction motor 2 from a reactive power setting circuit (not shown), and generates the current command value Ids ^* of the d-axis component by multiplying it by a predetermined coefficient K. It is a coefficient machine,
The respective outputs Iqs ^* , Ids ^* of both coefficient units 23, 24 are input to subtracters 27, 28, where the coordinate converter 26
The difference between the outputs Iqs and Ids is calculated, and this difference is input to the current controllers 29 and 30, respectively.

The coordinate converter 26 calculates Iqs and Ids using the following equation (1).

The current controller 29 (or 30) sets the current command value Iqs
^* (or Ids ^* ) and coordinate transformed detected current value Iqs
(or Ids) is proportionally integrated to calculate the active power P ^*
The two-phase value of the voltage applied to the rotor winding that should achieve
Control signal vqr ^* (or reactive power Q
^* Two-phase value of voltage applied to the rotor winding that should achieve
It calculates and outputs a control signal vdr ^* corresponding to vqr.

The two-phase three-phase coordinate converter 31 converts the phase θs and the two-phase voltage command values vdr ^* , vqr ^* on the rotor coordinate axis dr-qr.
is input, the three-phase voltage command value to be applied to the rotor winding is calculated using the following formula (2), and the control signal vu is used to obtain vu, vv, and vw from the cycloconverter 3.
^* , vv ^* , and vw ^* are output.

vu ^* , vv ^* , vw ^* are given to the three-phase cycloconverter 3, and the cycloconverter of each phase generates voltages vu, vv, vw to the rotor winding of the induction motor 2 according to these command values. Ignition controlled.

Next, the reason why active power and reactive power can be controlled independently by the device of the present invention will be explained.

The active power P and the reactive power Q on the stator side are independently controlled by controlling the stator current Is by dividing it into two orthogonal components. By performing the coordinate transformation of equation (1), two orthogonal components Iqs and Ids of the stator three-phase currents iu, iv, and iw are detected. The phase θe is the phase of the power supply voltage V·s, and for example, the instantaneous value Vus of the U-phase voltage is expressed by equation (3).

Vus＝VSM cosθe …(3) However, VSM is the peak value of the power supply voltage. If this is expressed as a vector, V・s=1/√2VSM …(4) I・s=1/√2(Iqs−jIds) …( 5) However, I・s is a vector value representing the current in the stator winding. This relationship is illustrated in FIG. 2. The d-q axes are rotating coordinate axes that rotate at the frequency of the power supply, and on this coordinate axis, I·s appears stationary. Therefore, Ids and Iqs are DC amounts. (4), (5)
When P and Q are obtained from the formulas, P=3/2VSMIqs...(6) Q=3/2VSMIds...(7) It can be seen that P and Q are proportional to Iqs and Ids, respectively. Therefore, by controlling the constants K of the coefficient units 23 and 24 to match the detected Iqs and Ids with Iqs ^* and Ids ^* obtained as 2/3 1/VSM, the reference values P ^* and Active power and reactive power can be obtained as shown in Q ^* .

That is, the subtracter 27 calculates Iqs - Iqs ^* , and if this difference is positive, the current controller 29 increases the q-axis voltage command value vqr ^* , and conversely, if this difference is negative,
Decrease vqr ^* . Also for the d-axis, a subtractor 28,
The same thing is done using the current controller 30 to determine vdr ^* .

In the equivalent circuit of the induction motor shown in Fig. 3,
V・s: stator voltage, I・s stator current, V・r:
Rotor voltage (cycloconverter output voltage) I
r: rotor current.

Also, Xs＝XM＋Xsl
is a slip.

Note that Iqr and Idr shown in FIG. 2 are the q-axis and d-axis components of I.r. Note that the amount on the rotor side is shown converted to the amount on the stator side.

The rotational speed of the induction motor is approximately synchronized with the frequency of the power supply, and the induction motor is generally operated within a very small range of slip S. Therefore, the jsXr component on the rotor side and
The jsXM I·s component can be considered negligibly small. As a result, the voltage on the rotor side V・r
Equation (8) holds true between and current I·r.

I・r≒1/rrV・r (8) On the other hand, on the stator side, rs is usually sufficiently smaller than Xs. Therefore, if rs is ignored, the relationship in equation (9) holds true.

I・s≒1/jXs (V・s−jXM I・r) =1/jXsV・s−XM/XsI・r…(9) Equation (10) is obtained from equations (8) and (9).

I·s≒1/jXsV·s−XM/Xs rrV·r (10) When this is decomposed into a d-axis component Ids and a q-axis component Iqs, equations (11) and (12) are obtained.

Iqs≒−XM/Xs rrVqr …(11) Ids≒−XM/Xs rrVdr+1/XsVSM …(12) However, Vqr, Vdr are the q-axis of rotor voltage V・r, r
Each component of the axis.

Since VSM is the peak value of the power supply voltage, assuming that it is constant, increasing Vqr will decrease Iqs, and decreasing Vqr will increase Iqs. On the other hand Vdr
Increasing Vdr will decrease Ids, and decreasing Vdr will decrease Ids
increases. In this way, the voltage of the cycloconverter is set to 2 which is synchronized with the phase θe of the stator power supply voltage V・s.
By decomposing and controlling the component voltages Vqr and Vdr,
Iqs and Ids are controlled independently.

For this purpose, a winding position detector directly connected to the rotor, that is, a rotor phase detector 21, detects the phase θr of the rotor winding, and a subtracter 22 determines the deviation θs from the stator power supply phase θe. Using this phase difference θs, the calculation of equation (2) is performed by the coordinate converter 31, and the actual three-phase voltage command values vu ^* , vv ^* , vw ^* are determined.

The cycloconverter 3 generates voltages vu, vv, and vw in the rotor windings according to the voltage command, but the voltage V・r, which is a vector representation of this voltage, is I・s on the coordinate axis d-q axis rotating at θe. It looks like it is stationary. Orthogonal component of V・r on the d-q axis, vqr,
vdr is the actual three-phase voltage of the rotor vu, vv, vw (13)
The coordinates are transformed to the stator d-q axes as shown in the equation.

Now, vu, vv, vw are command values vu ^* , vv ^* , vw
Considering that it occurs according to ^* , equations (2) and (13)
From the formula, vqr vdr=vqr ^* vdr ^* , which is the two-phase voltage command vqr ^* , vdr ^* commanded by the current controllers 29 and 30 and the actual d-q axis component voltage.
Vqr and Vdr match. In this way, the coordinate converter 31 makes it possible to control the voltage of the cycloconverter by decomposing it into orthogonal two-component voltages Vqr and Vdr on the coordinate axis synchronized with the stator power supply voltage V.s.

As described above, according to the present invention, since the stator current and rotor voltage are controlled on the coordinate axes synchronized with the stator voltage phase θe, the active power and reactive power can be controlled by the relative deviation between the stator coordinate axis and the rotor coordinate axis. The interference from above is eliminated. Also, the active power,
Since the reactive power is proportional to Iqs ^* and Ids ^* , there is no need to detect and feed back the actual active power P and reactive power Q, and open-loop control of P and Q can be performed using only the coefficient multiplier. , the configuration is simple.

In the above embodiment, the function of the current controllers 29 and 30 was explained as a proportional-integral operation, but it is also possible to perform only a proportional operation. Also, as a method of commanding the orthogonal two-component current reference values Iqs ^* and Ids ^* ,
Although the embodiment has been described using open loop control using the coefficient multipliers 23 and 24, closed loop control is also possible.

That is, as shown in FIG. 4, similarly to the conventional example, the power detector 17 detects the active power value P and the reactive power value Q on the stator side, and the subtracters 9 and 10 detect the active power command value P ^* and the reactive power command. The value Q ^* is subtracted from P and Q, respectively, and the active power controller 11 and the reactive power controller 12 subtract Iqs ^* , Ids ^* so that this deviation becomes zero.
Of course, it is also possible to adopt a configuration that determines .

Furthermore, although the cycloconverter is used as a variable voltage source in the above embodiment, an inverter may also be used.

5, 6, and 7 show other examples of use of the present invention. Focusing on the fact that the reactive power on the stator side of the induction motor can be controlled by Ids ^* as mentioned above, the configuration is such that the terminal voltage on the stator side is maintained at a predetermined value Vs ^* set by the voltage standard setting circuit 41. The example shown in Figure 5 shows this.

The voltage detector 32 detects the stator terminal voltage Vs.
is detected, the subtractor 33 takes the difference between Vs ^* and Vs, and the amplifier 34 amplifies this deviation to obtain Ids ^*
seek. As a result, the terminal voltage Vs becomes the predetermined value Vs ^*
When it becomes smaller, Ids ^* becomes negative, leading reactive power flows, and V·s increases. On the contrary, Vs
When becomes larger than the predetermined value Vs ^* , Ids ^* becomes positive and lagging reactive power is taken, so V・s decreases,
Keep the voltage at a specified value.

In an induction motor, the active power P and the torque T generated by the induction motor are in a proportional relationship.

The circuit shown in FIG. 6 utilizes this, and uses a coefficient unit 35 to calculate a q-axis current command value Iqs ^* that is proportional to a signal corresponding to the desired torque T ^* (set by the torque reference setting circuit 42). By giving
The required active power P is obtained and the torque is controlled thereby.

FIG. 7 shows an extension of the above torque control to speed control. That is, the rotation speed N is detected by a speed detector 36 such as a pulse generator, and compared with the rotation speed N ^* set by the speed reference setting circuit 43 by a subtractor 37, and this deviation is amplified by an amplifier 38. By setting Iqs ^* , speed control is attempted.

〔effect〕

As described above, the device of the present invention detects the phase θe of the stator voltage and the phase θr of the rotor winding, and decomposes the stator current into a component related only to active power P and a component related only to reactive power Q. By converting the three-phase and two-phase coordinates using θe and also converting the rotor voltage command value using the phase difference θs = θe − θr, two orthogonal coordinates synchronized with the phase θe of the stator voltage can be obtained. Since it can be broken down into components and operated, it is possible to control active power and reactive power independently, and there is no interference with each other, allowing stable and high-speed active and reactive power control. I can do it.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention;
Fig. 2 is a vector relationship diagram explaining the operating principle of the device of the present invention, Fig. 3 is an equivalent circuit diagram of a wound induction motor, Fig. 4 is a block diagram showing another embodiment of the invention, Fig. 5, 6 and 7 are block diagrams showing examples of diversion of the invention to other applications, FIG. 8 is a configuration block diagram of a conventional power control device for an induction motor, and FIG. 9 is an operation vector relationship diagram of the conventional device. . DESCRIPTION OF SYMBOLS 1... Power supply, 2... Wound induction motor, 3... Variable voltage source (cycloconverter), 20... Power supply phase detector, 21... Rotor phase detector, 22, 27, 2
8, 33, 37... Subtractor, 23, 24, 35... Coefficient unit, 25... Current detector, 26, 31... Coordinate converter, 29, 30... Current controller, 32... Voltage detector, 34, 38... Amplifier, 36...speed detector.

Claims (1)

[Scope of Claims] 1. A device for applying voltage to a rotor winding of a three-phase wound induction motor to control power on the stator winding side, comprising: a variable voltage source connected to the rotor winding; and the stator winding. A power supply phase detector detects the phase θe of the voltage applied to the rotor, a rotor phase detector detects the rotational phase θr of the rotor winding, and θe detected by the power supply phase detector and θr detected by the rotor phase detector. a phase difference calculator that calculates the difference θs=θe−θr, and a first current command value iqs related to the desired active power value.
A first reference generator that generates ^* , and a second current command value ids related to a desired reactive power value.
^* ; a current detector that detects three-phase currents iu, iv, and iw of the stator winding; and iu, iv, and iw detected by the current detector and the phase θe. A first coordinate converter that calculates the first and second current feedback values iqs, ids based on the following equation (1), and the first and second current command values iqs ^* , ids ^* and the first ，
a current controller that calculates first and second voltage command values vqr ^* , vdr ^* based on the deviation from second current feedback values iqs, ids; and a current controller that calculates first and second voltage command values vqr ^* , vdr*. ^* and the phase difference θs as input, and based on the following equation (2),
a second coordinate converter that calculates voltages vu, vv, and vw to be applied to the rotor windings, and is configured to control the voltages vu, vv, and vw to be the output voltages of the variable voltage source. A power control device for an induction motor, characterized by: 2. The power control device for an induction motor according to claim 1, wherein the variable voltage source is a cycloconverter. 3. The power control device for an induction motor according to claim 1, wherein the first reference generator includes an arithmetic unit that multiplies the set value of the active power reference by a predetermined coefficient. 4. The power control device for an induction motor according to claim 1, wherein the second reference generator includes an arithmetic unit that multiplies a set value of the reactive power reference by a predetermined coefficient. 5. The second reference generator detects the difference between the outputs of the voltage reference setting circuit that generates the voltage reference signal, the voltage detector that detects the voltage of the stator winding of the induction motor, and the voltage reference setting circuit and the voltage detector. 2. A power control device for an induction motor according to claim 1, comprising a computing unit for calculating the calculation, and a computing unit for multiplying the output of the computing unit by a predetermined coefficient. 6. The power control device for an induction motor according to claim 1, wherein the first reference generator includes a torque reference setting circuit that generates a torque reference signal, and an arithmetic unit that multiplies the torque reference signal by a predetermined coefficient. 7. A patent comprising a speed reference setting circuit in which the first reference generator emits a speed reference signal, a rotation speed detector of an induction motor, and an arithmetic unit that calculates the difference between the outputs of the speed reference setting circuit and the rotation speed detector. A power control device for an induction motor according to claim 1.