JP2006129698A - Control unit of induction motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide well-conditioned vector control executed, without switching the constitution of control continuously from a low-speed region to a high speed region, where the number of pulses of PWM becomes 1 pulse by means of a simpler control configuration. <P>SOLUTION: The control unit comprises a means which limits the level of a modulation factor (output command) to a prescribed value or larger or by an optional condition after a migration to the control region of a constant voltage variable frequency (1 pulse) from the control of a variable voltage variable frequency, and a means which makes an exciting current component command stop the operation of the feedback control of this current command, hold a predetermined prescribed value, and compute the slip angle frequency by only the corrected torque current component command, during a period that limits the magnitude of the modulation factor to the prescribed value or larger or by arbitrary conditions, when the slip angle frequency of the induction motor is computed by a means for controlling the output frequency of an inverter. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention relates to vector control of an induction motor, and more particularly to an induction motor control device that enables vector control even in a voltage uncontrollable region having a high frequency.

A technique for vector control of an induction motor for driving an electric vehicle for a railway vehicle is disclosed in JP-A-5
-83976. Further, in an electric vehicle for a railway vehicle, generally, in order to reduce the switching loss of the inverter in the high-speed operation region and to make maximum use of the DC power supply voltage, the control in which the PWM pulse mode becomes the 1-pulse mode is used. However, even in the 1-pulse mode where the voltage cannot be controlled, the vector control technology is the 33rd Cybernetics Utilization National Symposium on Railways (November 1996) p.247-250 “Vector Control”. The vehicle drive system to which is applied.
In the vector control described in JP-A-5-83976, two voltage command signals for vector control are based on the deviation between the excitation current command value and the detected excitation current and the deviation between the torque current command value and the detected torque current. In addition to the two current control means for correcting the current, there is a third current control means for correcting the slip frequency, and the control configuration becomes complicated. Therefore, the calculation is performed when the command signal is calculated using a microcomputer. There is a problem that time will become large. Further, in the document “vehicle driving system to which vector control is applied”, it is necessary to add a feedback for performing magnetic flux correction value calculation, that is, field weakening in the 1-pulse mode. In both conventional techniques, it is necessary to switch the control system between the one-pulse mode and the other modes.
In addition to the above prior art, there is JP-A-2-32788. As shown in FIG. 16, the vector control configuration described in the publication is such that the voltage command is calculated in accordance with each component of the excitation current and the torque current, and the primary value is such that the actual value is obtained in the torque current command. It consists of a point having a current control system for commanding the frequency and a point for calculating the voltage command from the obtained primary frequency command. However, in the vector control described in the publication, P
When the WM pulse mode becomes 1 pulse and voltage control becomes impossible, there is a problem that vector control cannot be performed, and no consideration is given to it.

JP-A-5-83976 JP-A-2-32788 Proceedings of the 33rd National Symposium on the Use of Cybernetics in Railways (November 1996) p.247-250

An object of the present invention is to perform PWM control that makes full use of a DC power supply voltage of a PWM inverter from a low speed range with a simpler control configuration when performing vector control of an induction motor.
Without switching the control configuration continuously up to the high speed range where the number of pulses becomes 1 pulse,
An object of the present invention is to provide an induction motor control apparatus capable of performing good vector control.

In order to solve the above-mentioned problems, an inverter that converts a DC voltage into a variable voltage variable frequency AC in a low speed range and a constant voltage variable frequency (one pulse) AC in a high speed range, and excitation in a primary current of an induction motor driven by the inverter Induction motor control device comprising a control device for controlling an output voltage of an inverter based on a modulation factor (output voltage command) obtained from a voltage component command corresponding to each of the components calculated based on a current component command and a torque current component command , The means for detecting the torque current component and the excitation current component from the primary current of the induction motor, and the torque current component command is corrected from the output of the deviation between the detected torque current component value and the command value input to the integral element. And the deviation between the detected excitation current component value and its command value from the output inputted to the integral element from the excitation current Means for correcting the component command, and means for calculating the slip angular frequency of the induction motor from the ratio of the corrected torque current component command and the corrected excitation current component command, and controlling the output frequency of the inverter based thereon After the transition from the variable voltage variable frequency control to the constant voltage variable frequency control region, the control is induced by means for limiting the magnitude of the modulation factor to a predetermined value or more or an arbitrary condition and means for controlling the output frequency of the inverter. When calculating the slip angular frequency of the electric motor, the excitation current component command stops the feedback control operation of the current component during the period when the magnitude of the modulation factor is more than the predetermined value or limited under any condition, Means is provided for holding a predetermined value and calculating a slip angular frequency only by the corrected torque current component command.

According to the present invention, the induction motor is continuously operated from the low speed range to the high speed range where the magnitude of the voltage command (modulation rate) exceeds the maximum voltage that can be output by the inverter determined by the DC voltage (PWM pulse mode is one pulse range). Good vector control can be performed without switching the control configuration.

Hereinafter, the best mode for carrying out the present invention will be described as an embodiment of the present invention with reference to FIGS.

An embodiment of the present invention will be described with reference to FIG. In the figure, the direct current supplied from the direct current power source 11 is smoothed by a filter capacitor 13 and applied to a pulse width modulation (hereinafter referred to as PWM) inverter 1 which is a power converter.
The PWM inverter 1 converts a DC voltage serving as a power source into a three-phase AC voltage and supplies the AC voltage to the induction motor 2. The electric vehicle travels using this induction motor 2 as a drive source.
The current command generator 3 generates an excitation current command value Id * and a torque current command value Iq *.
The current controller 4 generates a torque current command value Iq ** which is corrected based on a deviation between the torque current command value Iq ** and a torque current detection value Iq which is an output of the coordinate converter 5 which will be described later. Iq ** is input to the voltage command calculator 6 and the slip angular frequency calculator 7.
The slip angular frequency calculator 7 outputs a slip angular frequency command value ωs * from the excitation current command value Id * and the corrected torque current command value Iq **.
The voltage command calculator 6 includes an excitation current command value Id * and a corrected torque current command value Iq *.
* And Vd * and Vq *, which are commands of two voltage components of the rotating magnetic field coordinate system supplied to the induction motor 2 based on a primary angular frequency command value ω1 *, which will be described later, are calculated and output to the polar coordinate converter 8. .
The polar coordinate converter 8 converts the voltage vector represented by Vd * and Vq * into the magnitude V0 and the phase δ of the voltage vector.
On the other hand, the induction motor speed ωr detected by the speed detector 16 is added to the adder 17.
Therefore, it is added to the slip angular frequency command value ωs * which is the output of the slip angular frequency calculator 7,
A primary angular frequency command value ω1 * is generated. This primary angular frequency command value ω1 * is the integrator 1
8 is given to the voltage command calculator 6.
The integrator 18 integrates the primary angular frequency command value ω1 * to calculate the coordinate reference signal θ.
The coordinate converter 5 includes current detectors 15u that detect the output current of the PWM inverter 1.
The inverter output currents iu, iv, iw detected by 15v, 15w are inputted and converted into the excitation current component Id and the torque current component Iq of the rotating magnetic field coordinate system based on the coordinate reference signal θ, and Iq is the current controller 4. Is output.
The adder 19 adds the coordinate reference signal θ output from the integrator 18 and the voltage vector phase δ output from the polar coordinate converter 8 to output θ ′.
The modulation factor calculator 10 outputs the output of the polar coordinate converter 8 so as not to exceed the maximum voltage that the power converter can output based on a signal from the voltage detector 14 that detects the DC voltage VFC serving as the power source of the power converter. The voltage vector magnitude V0 is limited and the modulation factor Vc
Is output.
In the PWM signal calculator 9, on / off pulses Su, Sv, Sw are generated from the output Vc of the modulation factor calculator 10 and the output θ ′ of the adder 19 and supplied to the PWM inverter 1.

Next, the details of each of the above parts will be described.
In the coordinate converter 5, for example, the coordinate reference signal θ and the inverter output currents iu, iv,
The excitation current component Id and the torque current component Iq are calculated from iw by the equation (1).

For example, proportional or integral control is used as the current controller 4. Equation (2) is an example. As a result, the torque current command value Iq ** corrected based on the deviation between the torque current command value Iq * and the torque current detection value Iq is output.

ここに、Ｋ１，Ｋ２はそれぞれ比例係数，積分係数、ｓはラプラス演算子であ
る。
（３）式は、電圧指令演算器６の一例である。

Here, K1 and K2 are a proportional coefficient and an integral coefficient, respectively, and s is a Laplace operator.
Equation (3) is an example of the voltage command calculator 6.

ここに、ｒ１は誘導電動機２の１次抵抗、Ｌｓσは漏れインダクタンス、Ｌ１
は１次インダクタンスを示す。
（４）式は、すべり角周波数演算器７の一例である。

Here, r1 is the primary resistance of the induction motor 2, Lsσ is the leakage inductance, L1
Indicates primary inductance.
Equation (4) is an example of the slip angular frequency calculator 7.

ここに、ｒ２は誘導電動機２の２次抵抗、Ｍは相互インダクタンスである。
極座標変換器８は、（５），（６）式で表される。

Here, r2 is the secondary resistance of the induction motor 2, and M is the mutual inductance.
The polar coordinate converter 8 is expressed by equations (5) and (6).

FIG. 2 shows an example of the modulation factor calculator 10. Polar coordinate converter 8 by divider 201
Output V0 is divided by the filter capacitor voltage VFC, and its output is the coefficient unit 202
And normalized as the modulation factor Vc ′, and the value is input to the limiter 203.
The limiter 203 outputs a modulation rate (voltage command) V to the input modulation rate Vc ′.
This prevents c from exceeding a predetermined value.
The configuration of FIG. 2 is expressed by an equation (7).

ここで、変調率ＶｃはＰＷＭインバータの出力電圧が最大となる１パルスモー
ドのときの電圧が１となるようにスケール変換している。ｍｉｎ( )は最小値を
取る関数で、計算した結果が１を越えた場合にはＶｃを１にリミットする。（７）
式よりＶ０の最大値Ｖ０ｍａｘは（８）式のように書ける。

Here, the modulation factor Vc is scale-converted so that the voltage in the 1-pulse mode in which the output voltage of the PWM inverter is maximum is 1. min () is a function that takes the minimum value, and when the calculated result exceeds 1, Vc is limited to 1. (7)
From the equation, the maximum value V0max of V0 can be written as equation (8).

From the low-speed range, the control configuration according to FIG. 1 and the equations (1) to (7) described above is used.
Good control can be performed up to a high speed range in which the pulse mode of PWM that uses the DC voltage of the WM inverter 1 to the maximum is 1 pulse.

The operation in the above configuration will be described below.
First, the case where the voltage command value is in a low speed range smaller than the maximum voltage that can be output from the power converter determined by the DC voltage of the power supply will be described.
Since the output VO of the polar coordinate converter is smaller than the voltage V0max limited by the modulation factor calculator 10, Vc <1. At this time, there is no error in the voltage output from the PWM inverter 1, and under ideal conditions in which the parameters of the induction motor 2 match the parameters used in the voltage command calculator 6 and the slip angular frequency calculator 7, The PWM inverter 1 outputs a voltage according to the voltage command value. As a result, the outputs Id * and Iq * of the current command generator 3 completely match the outputs Id and Iq of the coordinate converter, and vector control is performed. Actually, there is a discrepancy between Id *, Iq * and Id, Iq due to the output voltage error of the PWM inverter 1 or the fluctuation of the parameters of the induction motor 2, but in that case, the current controller 4 sets the Iq * to Iq *. It is controlled so that Iq matches. For example, considering the case where the secondary resistance r2 of the induction motor is larger than r2 used in the calculation of the slip angular frequency calculator 7, the slip angular frequency command value ωs * output from the slip angular frequency calculator 7 is Since it is smaller than the value that should be originally output, the induction motor current is reduced,
Iq * and Iq do not match. At this time, the current controller 4 works to eliminate this discrepancy and increases the output Iq **. As a result, the slip angular frequency command value ωs * becomes large and the error due to the parameter variation is corrected. Therefore, even if there is a slight parameter error, the current controller 4 can stably perform the vector control. it can.

Next, the case where the voltage output to the induction motor is equal to or higher than the maximum voltage that can be output by the power converter (the PWM pulse mode is 1 pulse) will be described.
Even under ideal conditions without induction motor parameter error, the polar coordinate converter 8
Is larger than the maximum voltage V0max that can be output from the PWM inverter 1, resulting in a mismatch between the voltage command value and the output voltage. As a result, the output Id *, Iq * of the current command generator 3 and the output of the coordinate converter 5
Id and Iq are inconsistent.
A modulation factor calculator 9 is added to solve the problem in this condition.
As shown in FIG. 2, when the calculated voltage command Vc ′ becomes larger than the maximum voltage V0max that can be output, the arithmetic unit 9 limits the value with the value, and the limited value is the modulation factor (output voltage command) of the inverter. ) Output as Vc.
In the conventional vector control, it is necessary to feed back an amount corresponding to the difference between Vc ′ and V0max. For example, in the above-mentioned document “Vehicle Drive System Applying Vector Control”, adjustment is made to reduce the excitation current command value Id *, which is the output of the current command generator 3. (Note that in describing the operation of the present invention,
The excitation current command value when the d * is adjusted and the vector control is performed is the Id
**. )

However, this embodiment has a significant feature in that vector control is performed without the need for feedback as described above. The control principle will be described in detail below.
As described above, the current controller 4 in FIG. 1 is mainly compensated by parameter fluctuations in the low speed range. However, in the high speed range, the controller further reduces the error between Iq * and Iq due to the voltage mismatch described above. It works to match.
For example, when Vc ′ becomes larger than V0max, the current controller 4 is changed according to the difference.
Output Iq ** increases from Iq *. As a result, in an equilibrium state of control, Iq ** / Id *, which is the ratio of the output Iq ** of the current controller 4 and the output Id * of the current command generator 3, is essentially that when vector control is performed. It becomes equal to the ratio Iq / Id. At this time, the slip angular frequency command value ωs *, which is the output of the slip angular frequency calculator 7, is equal to that when the vector control is performed, as is apparent from the equation (4). The coordinate reference signal θ calculated by the integrator 18 is also equal. Similarly, by determining the response time of the current controller 4 so that the speed ωr of the induction motor 2 does not change within the time until the control reaches an equilibrium state, the output Vd *,
The ratio Vq * / Vd * of Vq * does not change from equation (3).
Therefore, from the equation (6), the output δ of the polar coordinate converter 8 is also equal to that when the vector control is originally performed. As a result, since θ ′ calculated by the adder 19 is also equal, the same voltage is applied to the induction motor 2 as when normal vector control is performed, and the coordinate converter 5 ideally outputs the output Id, As Iq, Id * and Iq * equal to the values when normal vector control is performed are output. Since the current controller 4 includes an integral element, even if the inputs Iq * and Iq are equal, Iq ** is in an equilibrium state with a value larger than Iq *.
That is, even when the output V0 of the polar coordinate converter 8 is larger than the maximum value V0max of the voltage output from the PWM inverter 1, according to this embodiment, the current command generator 3 is not adjusted by the action of the current controller 4. However, this is completely equivalent to the case where the vector control with the excitation current command value automatically lowered is performed. In other words, field-weakening control is automatically performed when the output voltage of the PWM inverter is fixed to the maximum output voltage. In addition, this control is automatically corrected by the above-mentioned control system even when the DC voltage of the power supply fluctuates.
Control is performed so that Iq matches the torque current command value Iq *.

FIG. 3 shows a simulation of the operation of the control system of FIG. 1 from the stationary state of the induction motor until the inverter output voltage reaches a maximum value and reaches a constant voltage range.
FIG. 4A shows the speed ωr of the induction motor with respect to time t, and shows that the induction motor is accelerating with time. FIG. 4B shows the time change of Vc ′ obtained by converting the output V0 of the polar coordinate converter 8 to the same scale as the modulation factor Vc and the output Vc of the modulation factor calculator 10. In the vicinity of 18 seconds, Vc ′ is caught by the limiter 203, and thereafter Vc is fixed to 1 (maximum output voltage of the PWM inverter). FIG. 4C shows temporal changes of the outputs Id and Iq of the coordinate converter 5, the output Id * of the current command generator 3, and the output Iq ** of the current controller 4. Here, the outputs Id * and Iq * from the current command generator 3 are always constant. Until the voltage is limited, Id and Id * and Iq and Iq ** match, but after the voltage becomes constant, Iq ** increases the speed of the induction motor due to the action of the current controller 4. It turns out that it becomes large as it becomes. On the other hand, Id after a certain voltage is
It is gradually smaller than Id *. That is, field weakening control is performed.
Although not shown, Iq * commands a constant value with a value that matches Iq by the action of the current controller 4, and the command value of Id * is also given as a constant.
FIG. 4D shows the change over time in the torque of the induction motor. Since the torque current command value Iq * and the excitation current command value Id * are constant until the voltage limit, the torque is also constant. After the voltage limit, the voltage applied to the induction motor is limited even if the command value is constant, so that the torque is automatically reduced by the amount of field weakening.
As described above, the control operation based on the above-described control principle is also confirmed in the simulation, and it can be seen that the vector control can be realized continuously from the low speed to the high speed range.

Next, vector control in this embodiment will be demonstrated from a different point of view. FIG. 4 shows an example of a torque response simulation in a constant voltage region (around 25 seconds in FIG. 3).
In the figure, a slight transient vibration is generated in the response of the torque T of the induction motor to the change of the torque command value Tref. Except for this, T responds quickly to Tref. Thus, it can be seen that vector control is possible according to this embodiment. In addition, the transient vibration which generate | occur | produces above can be reduced by setting the control constant of the current controller 4 with the optimal value according to the constant of the induction motor used as a control object.

As described above, according to the present embodiment, only one current controller that controls torque current and a modulation factor calculator exceed the maximum voltage that can be output from the inverter in which the magnitude of the voltage command is determined by the DC voltage from the low speed range ( It is possible to vector control the induction motor without changing the control configuration continuously until the PWM pulse mode reaches 1 pulse area).
In particular, the torque response can be accelerated even in a high-speed region where the voltage pulse is one pulse.
Further, as shown in FIG. 2, the modulation rate Vc is automatically corrected in accordance with the fluctuation of the DC power supply voltage VFC, so that the output of the inverter according to the command value is not affected by the fluctuation of the DC power supply voltage. Can be controlled.
Furthermore, in the above embodiment, the case where the limit value of the voltage limiter is set to the maximum voltage that can be output from the power converter has been described. However, the limit value of the voltage limiter may be set to any voltage at which field weakening control is to be started. The field weakening control is executed from the arbitrary point. Therefore, the field weakening control can be performed simply by changing this set value.
There is no need to specially prepare a field weakening pattern of the excitation current command Id * as in the prior art, and the control configuration can be simplified.

In this embodiment, the current controller is provided only for the torque current. However, in the low speed range where the voltage command value is smaller than the maximum voltage that can be output by the power converter determined by the DC voltage of the power source, the excitation current and the torque current Both may be provided with current controllers.
However, when the output V0 of the polar coordinate calculator 8 becomes larger than the maximum output possible voltage V0max, it is necessary to switch the control so that the current controller for the excitation current does not operate. In this case, as can be seen from FIG. 3, the current command generator 3
Excitation current command value Id * which is the output of the current and the excitation current detection value I which is the output of the coordinate converter 5
This is because d does not always match, and therefore, if a current controller having an integral element that makes the steady deviation zero based on the deviation between Id * and Id is inserted, the control of this embodiment does not hold.

The present invention continuously controls the induction motor from a low speed range to a high speed range where the magnitude of the voltage command (modulation factor) exceeds the maximum voltage that can be output by the inverter determined by the DC voltage (PWM pulse mode is 1 pulse range). This makes it possible to perform good vector control without switching the motor, so it is suitable for use in electric vehicles traveling on roads as well as in railway electric vehicles that require torque response characteristics. .

The block diagram of the control apparatus of the induction motor which shows one Embodiment of this invention Detailed configuration diagram of the modulation factor calculator in FIG. Simulation example of control of the present invention Example of torque response simulation of control of the present invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Pulse width modulation inverter, 2 ... Induction motor, 3 ... Current command generator, 4 ... Current controller, 5 ... Coordinate converter, 6 ... Voltage command calculator, 7 ... Slip angular frequency calculator, 8
... Polar coordinate converter, 9 ... PWM signal calculator, 10 ... Modulation factor calculator, 11 ... DC power supply,
DESCRIPTION OF SYMBOLS 13 ... Filter capacitor, 14 ... Voltage detector, 15 ... Current detector, 16 ... Speed detector, 17 ... Adder, 18 ... Integrator, 19 ... Adder

Claims (1)

Inverter for converting DC voltage into AC of variable voltage variable frequency and constant voltage variable frequency (1 pulse) in high speed range in low speed range, excitation current component command and torque current component command in primary current of induction motor driven by the inverter In the induction motor control device comprising a control device for controlling the output voltage of the inverter by a modulation factor (output voltage command) obtained by a voltage component command corresponding to each of the components calculated based on
Means for detecting a torque current component and an excitation current component from the induction motor primary current;
Means for correcting the torque current component command from the output obtained by inputting the deviation between the detected torque current component value and the command value to an integration element, and integrating the deviation between the detected excitation current component value and the command value A means for correcting the excitation current component command from its output input to the element, and calculating a slip angular frequency of the induction motor from a ratio of the corrected torque current component command and the corrected excitation current component command; Based on this, the means for controlling the output frequency of the inverter, and after shifting from the control of the variable voltage variable frequency to the control region of the constant voltage variable frequency, the magnitude of the modulation factor is greater than a predetermined value or under an arbitrary condition In calculating the slip angular frequency of the induction motor by means for limiting and means for controlling the output frequency of the inverter, the magnitude of the modulation factor is The excitation current component command stops the feedback control operation of the current component, holds a predetermined value in advance, and the slip angular frequency is corrected as long as the excitation current component command is longer than a fixed value or limited by an arbitrary condition. A control device for an induction motor comprising means for calculating only with a torque current component command.

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