JP2005192301A - Controller for induction motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem of a device for detecting the rotational direction or the r.p.m. of an induction motor under free run state, wherein since a DC current is conventionally applied stepwise, pulse frequency of the ripple components of current and voltage being generated at that time is measured, such characteristics as that frequency is substantially proportional to the free run rotational speed are detected and the rotational direction is detected from the phase of each of two axial voltage components, variational period of ripple sign is slow in low speed regions and a long time is required for surely grasping it, and to provide a device for quickly detecting r.p.m. and the rotational direction, with high precision. <P>SOLUTION: From a current flowing through an induction motor when a command value is applied from a voltage command output unit, the signal of frequency component lower than the frequency component dependent on the circuit time constant of the induction motor is extracted and then the rotational condition is detected from that signal. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a control device for driving induction motors such as trains, machine tools, fans, pumps, etc., and in particular, free-run rotation speed and rotation direction for the purpose of stable restart of a free-running induction motor. It is related with the control apparatus which detects.

  A conventional induction motor control device detects a free-running rotation state by applying a DC current command value stepwise to a current control loop composed of an induction motor, PWM inverter, current detection means, current control means, etc. Measure the pulsation frequency of the ripple component of the current value and voltage command value generated at that time, detect the rotation speed using the characteristic that this frequency is approximately proportional to the free-run rotation speed, and detect the free-run rotation direction Indicates that the phase relationship of the pulsating component superimposed on each axis component of the voltage command value of the two orthogonal axis components is dependent on the rotation direction (see, for example, Patent Document 1). .

Japanese Patent Laid-Open No. 3-3694 (FIGS. 1, 4, and 5 P630 to P631)

However, in the free-run state detection method disclosed in Patent Document 1, the phase relationship between the pulsating components superimposed on each component of the voltage command value or each axial component of the current value is monitored. Therefore, when the rotational direction is detected in the low speed region, there is a problem that it takes time to reliably grasp the phase relationship because the period of pulsation and sign change is slow.
For example, when the free-run rotation speed is 5 Hz, the time required to detect 7-point sign inversion (3 cycles) is 0.6 seconds. In reality, immediately after the DC current command value is applied stepwise, excessive vibration exists, and a count standby time is provided for the purpose of avoiding false detection of this as a phase change. Becomes even longer. If the number of current pulsation sign inversion detections is reduced, the time required for the final determination in the free-running rotation direction can be shortened. However, in order to maintain the judgment system even if erroneous detection is actually included, multiple sign inversions are required. Detection is desirable. Therefore, there is a problem that there is a limit to reducing the number of detections and shortening the required time.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a control device that can quickly and reliably detect the rotation speed and frequency of an induction motor in a free-run state.

An induction motor control device according to the present invention includes an induction motor, a power conversion device, a voltage command value output device, a current detection device, and a free-run state detection device,
The power conversion device supplies power to the induction motor, the voltage command value output device outputs a voltage command value to the power conversion device, the current detection device detects a current flowing through the induction motor,
The free-run state detection device has a frequency component lower than the frequency determined by the circuit time constant of the induction motor from the current flowing through the induction motor when the voltage command value output from the voltage command value output device is applied to the induction motor. The signal is extracted, and the rotation state of the induction motor in the free-run state is detected from the extracted signal.

Further, the induction motor control device according to the present invention includes an induction motor, a power converter, a voltage command value output device, a current command value output device, a current detection device, first and second free-run state detection devices, and a result. A discrimination device,
The power converter supplies power to the induction motor, the current detection device detects the current flowing through the induction motor, the current command value output device outputs a current command value to the voltage command value output device,
The voltage command value output device outputs the voltage command value calculated based on the current detected by the current detection device and the current command value output by the current command value output device to the power converter,
The first free-run state detection device has a frequency lower than a frequency determined by a circuit time constant of the induction motor from a current flowing through the induction motor when a voltage command value output from the voltage command value output device is applied to the induction motor. The component signal is extracted, the first rotation state of the induction motor in the free-run state is detected from the extracted signal, and output to the result determination device,
The second free-run state detection device extracts the pulsating component from the current flowing through the induction motor and the number of times the pulsating component is inverted when the voltage command value output from the voltage command value output device is applied to the induction motor. And the second rotation state of the induction motor in the free-run state is detected by calculating the pulsation frequency from the time after application of the voltage command value and the number of inversions of the pulsation component, and output to the result determination device And
The result discriminating device rotates the induction motor in the free-run state with the result obtained earlier from the first and second rotation state detection results output from the first and second free-run state detection devices. It is determined as a state.

  The control device for the induction motor according to the present invention detects the component in the free-run state by paying attention to a component that gradually changes according to the circuit time constant of the induction motor among the signals included in the current flowing through the induction motor. A value proportional to the free run rotation frequency including the above information can be obtained, and the free run state (rotation direction, rotation speed) can be detected quickly without relying on frequency measurement of the pulsation signal.

  Furthermore, in addition to the effect obtained by the first free-run state detection device, the control device for the induction motor according to the present invention is configured so that the second free-run state detection device forms a current loop, thereby forming the main circuit of the power converter. It is possible to suppress the influence of the voltage disturbance caused by the dead time, improve the accuracy of the free-run state detection, and further, with the result output first or second by the result discriminator, the free-run state Therefore, the free-run state can be detected accurately and quickly over the entire region from low speed to high speed.

Embodiment 1 FIG.
Hereinafter, the present invention will be described with reference to the drawings. FIG. 1 is a configuration diagram showing an induction motor control device 100 according to Embodiment 1, and shows an induction motor 1, a power conversion device 2, a voltage command value output device 3a, a current detection device 4, a free-run state detection device 6a, and a timing. The free-run state detection device 6a includes a low-pass filter 60, an integration unit 61, an inverse number calculation unit 62, a correction unit 63a, and a signal acquisition unit 66.

Next, operations of the induction motor 1, the power conversion device 2, the voltage command value output device 3a, and the current detection device 4 will be described. In this description, the current command value, the voltage command value, and the current value are given by two orthogonal axes (αβ axes) on the stator coordinates.
Voltage command value output device 3 a outputs αβ-axis voltage command values vα_ref and vβ_ref to power conversion device 2. The power converter outputs an actual voltage vector based on the input αβ-axis voltage command values vα_ref and vβ_ref to the induction motor 1. For example, when a voltage-type inverter is used as the main circuit, the αβ-axis voltage command values vα_ref and vβ_ref are converted into a three-phase waveform, and then an arithmetic process for generating a switching pattern of the three-phase inverter is performed. By inputting the switching pattern to the control input, the induction motor 1 is supplied with a pulse width modulated three-phase voltage.
In the current detection device 4, the three-phase values iu, iv, and iw obtained by acquiring the actual current with a current sensor or the like are subjected to coordinate conversion from the following equations 1 and 2 to the values iα and iβ on the αβ axis. Among these, iβ is output to the free-run state detection device 6a.

Next, the behavior of the αβ-axis currents iα and iβ when the voltage command output device 3a outputs DC voltage commands vα_ref = Vo and vβ_ref = 0 when the induction motor 1 is in a free-run state will be described.
FIG. 2 schematically shows the behavior of the αβ-axis currents iα and iβ when the DC voltage commands vα_ref = Vo and vβ_ref = 0 are output stepwise.
As the α-axis current iα, a DC value determined by the voltage command vα_ref = Vo and the α-axis impedance of the induction motor 1 flows.
On the other hand, a transient waveform appears in the β-axis current iβ according to the transfer characteristic G_iβ_vα from the α-axis voltage to the β-axis current in the induction motor 1. G_iβ_vα can be expressed as Equation 3.

  The above expression 3 can be derived based on a widely known induction motor expression. In the general known formula, the stator coordinate axis is described in the form of the following formula 4 where the dq axis is expressed, but the suffix of dq is αβ, the differential operator P and the Laplace operator S are replaced, and the quadratic operator When an equation operation for erasing the current is performed, Equation 3 described above can be derived.

The β-axis current iβ after application of the α-axis voltage step converges to 0 after a sufficient time, but transiently appears a component that pulsates at the free-running rotation frequency wm and other components. Of these, the conventional method uses the characteristic of generating a pulsating component of the frequency wm, but there is a problem that it takes time to measure the frequency of the pulsating component under conditions where the free-running rotation frequency wm is small. Is as described above. In the first embodiment, a free-run state is detected by paying attention to a component that gradually changes in accordance with the circuit time constant of the induction motor among signals included in the β-axis current iβ. The principle will be described below.
Here, a signal x obtained by integrating the β-axis current iβ once is assumed. The transfer characteristic from the α-axis voltage of the induction motor 1 to the signal x is G_iβ_vα / s. Low frequency region of this transfer characteristic G_iβ_vα / s, in particular | s | << | R1 / L1 | (hence obviously | s | << | R1 / σL1 |),
| S | << | R2 / L2 |
The characteristic at is obtained by substituting the above approximate condition into Equation 3 as shown in Equation 5 below.

  In Equation 5, assuming that R2 / L2 is sufficiently small with respect to the range of wm that needs to detect the free-running rotation state (R2 / L2) 2 << wm2, the following Equation 6 holds.

Equation 6 shows that the low frequency gain of G_iβ_vα / s is proportional to the reciprocal of the free-run frequency wm, and the sign of the proportionality coefficient is negative.
Note that G_iβ_vα / s includes information on the rotation direction because the free-run frequency wm takes a positive value when the rotation direction of the induction motor is normal and negative when the rotation direction is reverse.
The free-run state detection device 6a of the induction motor 1 according to the first embodiment detects the free-run rotation frequency including information on the rotation direction by using the characteristic of the equation (6). That is, the integration means 61 that amplifies the DC signal amplifies and extracts the DC component for the β-axis current iβ after the α-axis voltage step is applied as the signal x. Note that it is more desirable to install a low-pass filter 60 in which a cutoff frequency lower than R1 / L1 or R2 / L2 is extracted so as to extract a signal in a low frequency region that is noticed in the derivation of Equations 5 and 6. . 2A to 2D are schematic diagrams of applied voltages and current waveforms, and FIG. 2E is a schematic waveform diagram of the signal x. From Expression 6, the convergence value of the signal x when the α-axis voltage step command vα_ref is V0 is expressed by Expression 7 below.

Thus, the convergence value of x after application of the α-axis voltage step command is extracted as a signal that is proportional to the step width Vo and inversely proportional to the free-run frequency wm.
Accordingly, the reciprocal number calculating means 62 calculates and outputs the reciprocal number 1 / x of x as shown in the following expression 8, and the following expression 9 of the induction motor 1 which is previously obtained and set in the correcting means 63a. If the proportional gain K indicated by is integrated with a 1 / x convergence value and output, a free-run rotation frequency wm including sign information can be obtained.

The time required for x and 1 / x to converge to a steady value is determined by the induction machine constant. However, compared with the time required for pulsation frequency measurement in a low speed region of 5 Hz, for example, shown in the conventional example, 1/2. It can be shortened to about １ ／ time. In addition, the timing management device 7 acquires the sampling timing signal after a predetermined time period in consideration of the time when the signal x converges from the time when the α-axis voltage step command is applied from the voltage command value calculation device 3a. When output to the means 66, the signal acquisition means 66 acquires the signal output from the correction means 63a when the sampling timing signal is input from the timing management device 7, and outputs it as a free-running rotation frequency detection result.
As described above, in the first embodiment, a convergence value of a signal obtained by extracting a DC component and performing integration processing and reciprocal calculation processing on the β-axis current iβ after application of the α-axis voltage step command is acquired. Thus, a value that includes information on the rotation direction and is proportional to the free-running rotation frequency can be obtained, and the free-run state can be detected quickly and accurately without relying on frequency measurement of the pulsation signal.

Embodiment 2. FIG.
Next, the configuration of the second embodiment is shown in FIG. The second embodiment has a configuration in which a resistance value detection device 8 is added to the configuration of the first embodiment shown in FIG. 1 described above, and the details thereof will be described below.
The description of the same components as those in the first embodiment will be omitted, and only new components will be described. The resistance value detection device 8 has a function of detecting the primary resistance value and secondary resistance value of the induction motor 1 that fluctuate due to heat generation during operation, and includes a temperature detection means 81 and a resistance fluctuation correction means 82. It is composed of The temperature detection means 81 detects the temperature of the winding of the induction motor 1 using a temperature sensor or the like and outputs it to the resistance fluctuation correction means 82. The resistance fluctuation correction means 82 stores the temperature data of the primary resistance R1 and the secondary resistance R2 of the induction motor 1, and based on the value of the winding temperature detected by the temperature detection means 81, the resistance fluctuation correction means 82 stores the values of R1 and R2. The actual value is estimated and output to the correction means 63b in the free-run state detection device 6b.
As described in Equation 3 of the first embodiment, the transfer characteristic G_iβ_vα from the α-axis voltage to the β-axis current in the induction motor 1 is influenced by the magnitudes of the primary resistance value R1 and the secondary resistance value R2. R1 and R2 also affect the convergence value of x after the application of the shaft voltage step command and the inverse thereof as shown in Equation 7. That is, when the correction gain K provided in the correction means 63b and calculated in advance is set as a fixed value, if the actual values of the primary resistance R1 and the secondary resistance R2 due to temperature or the like fluctuate, free-run rotation The frequency detection result may also fluctuate and the accuracy may decrease.
Therefore, using the estimated value R1e of the primary resistance value R1, the estimated value R2e of the secondary resistance value R2 obtained by the resistance value detecting device 8, and the following equation 10, the correction gain Ke provided in the correcting means 63b is obtained. Update sequentially. By doing so, it is possible to acquire a free-running rotation frequency detection result without being affected by resistance fluctuation.

In addition, although the structure using a temperature sensor was demonstrated to the example as the resistance value detection means 8, it is not limited to this, For example, it is a method of estimating a primary resistance and a secondary resistance without using a temperature sensor. Also good.
Therefore, it goes without saying that the correction gain Ke in the correction means 63c may be updated using these methods.
In the second embodiment described above, the following effects can be obtained in addition to the first embodiment.
A resistance value detection device is provided to detect the actual primary resistance value R1e and the secondary resistance value R2e that vary during operation, and reflect the actual R1e and R2e in the correction means for the signal x, thereby affecting the effect of resistance variation. It is possible to detect the free-run state that has been abolished, and the detection accuracy is improved.

Embodiment 3 FIG.
The configuration of Embodiment 3 is shown in FIG. The third embodiment has a configuration in which a current control loop is added to the configuration of the first embodiment shown in FIG. 1 described above, and details thereof will be described below.
The description of the same components as those in the above embodiment will be omitted, and only new components will be described. The current command value output means 5 outputs current command values iα_ref and iβ_ref expressed on the αβ axis to the voltage command value output device 3b. 3b is a voltage command value output device, but unlike the voltage command value output device 3a in the first embodiment, the αβ axis currents iα and iβ acquired by the current detection device 4 and the current command output from the command value output device 5 Based on the values iα_ref and iβ_ref, voltage command values vα_ref and vβ_ref are calculated and output to the power converter 2. For example, in the voltage command value output device 3b, proportional integral control calculation and voltage drop compensation calculation are performed as shown in Expressions 11 and 12 below.

By the control calculation, a current control loop including the induction motor 1, the power conversion device 2, the current detection device 4, and the voltage command value output device 3b is configured, and by setting appropriate control gains Kpα, Kiα, Kpβ, Kiβ The followability to the current command values iα_ref and iβ_ref, or disturbance suppression can be adjusted. R1 ^* is a primary resistance setting value set in advance in the voltage command value output means, and voltage drop amounts R1 ^* · iα and R1 ^* · iβ due to primary resistance in each axis of αβ are added to vα_ref and vβ_ref. As a result, the current control is further speeded up.
As described above, in the third embodiment, when the α-axis current command iα_ref is given as iα_ref = Io in a stepwise manner and the β-axis current command iβ_ref is given as 0, the current control step causes the current command step to be in the current command step. A DC step with an amplitude of the voltage value Vo determined by the width Io and the induction motor constant is output, and almost 0 is output to vβ_ref. Almost the same as the state quantity waveforms of FIG. 2 shown in the first embodiment, as the α-axis current iα, a DC value determined by the voltage command vα_ref = Vo and the α-axis impedance of the induction motor 1 flows, and the β-axis current A transient waveform appears in iβ according to the transfer characteristic G_iβ_vα from the α-axis voltage to the β-axis current in the induction motor 1. Strictly speaking, the αβ-axis currents iα and iβ and the αβ-axis voltage command values vα_ref and vβ_ref are superposed with a component that pulsates at the free-running rotation frequency. However, this component is not used as described in the first embodiment. It is the same.

In the third embodiment, in the step-up control of the α-axis current, the disturbance voltage generated due to the so-called dead time of the upper and lower element short-circuit prevention period of the inverter main circuit in the power converter 2 is represented by the current control loop. Therefore, the voltage command vα_ref can be output with higher accuracy and smoothness. Accordingly, a β-axis current waveform iβ in which the influence of the dead time disturbance voltage is suppressed is obtained, the behavior of the signal x in the free-run state detection device and its inverse 1 / x is stabilized, and the accuracy of the free-run state detection The effect which improves is acquired.
As described above, in order to suppress the dead time disturbance, the current control gain of Equation 10 is set as large as possible, but the low frequency component of the β-axis current used for detecting the free-run state is not suppressed. It is desirable that the β-axis gains Kpβ and Kiβ should not be excessively increased.
The third embodiment described above has the following effects in addition to the first embodiment. That is, by configuring the current loop, the influence of voltage disturbance caused by the dead time of the inverter main circuit can be suppressed, so that a β-axis current waveform iβ in which the influence of the dead time disturbance voltage is suppressed is obtained. The behavior of the signal x inside the free-run state detection device and its inverse 1 / x is stabilized, and the effect of improving the accuracy of free-run state detection is obtained.

Embodiment 4 FIG.
The configuration of the fourth embodiment is shown in FIG. In this configuration, the free-run state detection device 6a in the configuration of the first embodiment shown in FIG. 1 is replaced with a free-run state detection device 6c. Details will be described below.
In the fourth embodiment, the description of the same components as those in the first embodiment will be omitted. The same applies to the behavior of the αβ-axis currents iα and iβ when the step command vα_ref = Vo is output as the α-axis voltage command, and the description thereof is omitted. Then, the β-axis current iβ is output to the free-run state detection device 6c of the fourth embodiment.
The free-run state detection device 6c includes N (N: 1 or more) integrating units 61a to 61n, a correcting unit 63c, and a signal acquiring unit 66. When the step command vα_ref = Vo is output as the α-axis voltage command, attention is paid to the direct current component included in iβ, and the point of using the characteristic of the expression (5) of the induction motor 1 is that of the first to the third embodiments. This is the same as the third embodiment. However, the free-run state detection device 6c of the fourth embodiment performs removal processing of the input iβ pulsation component and DC signal amplification processing by the N integrating means 61a to 61n, and extracts the extracted signals. It outputs to the signal acquisition means 66 as xn.
As in the first embodiment, the timing management device 7 starts after the voltage command value calculation device 3a starts outputting the α-axis voltage step command, after a certain period set in advance in consideration of the time for generating the signal xn. The sampling timing signal is output to the signal acquisition means 66. The signal acquisition unit 66 samples and holds the signal xn output from the integration unit 61n, which is the final stage of the N integration units, when the sampling timing signal is input from the timing management device 7, and sets the value as xn_set. It outputs to the correction means 63c.
The correction means 63c is provided with a table or a calculation formula representing the relationship between xn_set calculated in advance and the free run frequency, and detects and outputs the free run rotation direction and the free run rotation frequency from the input xn_set. Details of the operation principle will be described below.

6A to 6D are schematic diagrams showing the behavior of the applied voltage and each current waveform, and FIG. 6E is a schematic waveform diagram of the signal Xn. The induction motor 1 is in a free-running state. Of the N integrators that input the αβ-axis current iαβ and iβ when the step command is output to the α-axis voltage, the behavior of the signal xn that is the output of the last-stage integrator 61n is shown. is there.
The pulsating component superimposed on the β-axis current iβ is a disturbance in the present invention focusing on the DC component of iβ. However, since a plurality of integrators 61a to 61n connected in series have a strong low-pass characteristic, if iβ is input thereto, a pulsating component can be more efficiently removed than a normal low-pass filter. Therefore, desired signal extraction can be performed stably at high speed.
On the other hand, as shown in Equation 6, the signal x obtained by performing one integration operation on the β-axis current iβ converges to a DC value related to the induction motor constant, the amplitude Vo of the step voltage command, and the free-run frequency wm. To do. Therefore, the signal xn obtained by performing the integral operation twice or more with respect to the β-axis current iβ is, as shown in FIG. 6E, from a certain point in the negative direction when the free-run rotation direction is normal. When the free-running rotation direction is reverse, it decreases or increases in the positive direction. In response to this signal xn, after the step voltage is output, xn_set sampled and held when a certain period T has elapsed is output to the correcting means 63c.
The reciprocal of the convergence value of the signal x obtained by performing one integration operation on the β-axis current iβ shown in the first to third embodiments is proportional to the free-running rotation frequency as shown in Equation 7. That is, the relationship between the free-running rotation frequency wm and the convergence value of 1 / x is proportional as shown in FIG. On the other hand, xn_set obtained by performing n times of integral calculation on the β-axis current iβ according to the fourth embodiment for a certain period is a function of the induction motor constant, the integration time T, and the free-run frequency wm. become that way. The relationship between the free run rotation direction and the sign of 1 / xn_set is the same as the relationship between the free run rotation direction and the sign of the 1 / x convergence value.
The relationship between 1 / xn_set and the free-run frequency wm in FIG. 8 can be calculated in advance by simulation or analysis based on the induction motor constant, the integration time T, and Equation (3). In other words, it can be calculated as a table of xn_set and wm, and this table is mounted on the correction means 63c. The correction unit 63c can detect a free-running rotation frequency including information on the rotation direction by referring to or calculating a table mounted on the value of the input signal xn_set. The fourth embodiment described above has the following effects in addition to the first embodiment.
That is, by performing the integration process a plurality of times, the DC component extraction and pulsation component removal of the β-axis current iβ can be effectively performed, so that the effect of detecting the free-run state more quickly and stably can be obtained.

In the above description, as shown in FIG. 6, by utilizing the fact that xn is monotonically increasing or monotonically decreasing and the increase / decrease rate depends on the free-run speed, the α-axis voltage step command The signal xn is sampled and held at the time when a predetermined period T has elapsed in consideration of the time when the signal xn is generated from the time when the output of the signal xn is started, and the free run frequency wm is determined based on this value xn_set. Although the detection method has been described, the free-run frequency wm can also be detected as shown in FIG.
That is, in the signal acquisition unit 66, a limit value ± xn_limit for detecting an increase or decrease in xn is set in advance, and the time value from the step command application input from the timing management unit 7 is monitored. Then, the time T_set required for the signal xn to reach ± xn_limit is measured, and this value T_set is output to the correction means 63c. A conceptual diagram of this T_set measurement method is shown in FIG. Since the required time T_set is a function of the constant of the induction motor, the limit value xn_limit, and the free-run frequency wm, the relationship between T_set and wm is similar to the characteristic of xn_set and wm as shown in FIG. It is possible to obtain. Accordingly, a table or calculation formula indicating the relationship between T_set and wm is mounted in the correction unit 63c in advance, and the free-running rotation frequency can be detected based on the measured T_set and the table or calculation formula of the correction unit 63c. It is.
In the above description of the first to fourth embodiments, the case where the step voltage command value is applied to the α-axis has been described. However, other than the step, for example, a voltage command value that monotonously increases or decreases monotonously, such as a lamp. You may apply.
Basically, if the transfer function notation shown in Equations 5 and 6 is used, the low-frequency signal waveform of iβ can be calculated in advance for any α-axis voltage waveform. That is, the terminal value of the signal waveform xn when a monotonically increasing or monotonically decreasing α-axis voltage is applied for a certain period of time can be acquired in advance as table data as xn_set, just as when applying a step voltage. is there. Therefore, the relationship between xn_set and free run frequency wm when a monotonously increasing command value is applied to the α-axis voltage is set in advance as table data in the correction means 63c, and xn_set and table data actually detected during operation are set. It is also possible to detect the free-run frequency wm using.

Embodiment 5 FIG.
Next, the configuration of the fifth embodiment is shown in FIG. In the fifth embodiment, a current control loop is added to the configuration diagram 5 of the above-described embodiment. The induction motor 1, the power converter 2, the voltage command value output device 3 b, the current detection device 4, and the current command value output device 5 shown in FIG. 10 are current loops configured in the same manner as in Embodiment 3 described above.
On the other hand, in the free-run state detection device 6c, since the operations of the respective constituent devices that are the same as those described in the fourth embodiment are the same as those already described, the description thereof is omitted.
According to the configuration of the fifth embodiment, the following effects can be obtained in addition to the fourth embodiment.
That is, by configuring the current loop, it is possible to suppress the influence of the voltage disturbance caused by the dead time of the inverter main circuit, so that the β-axis current waveform iβ in which the influence of the dead time disturbance voltage is suppressed can be obtained and free. The behavior of the signal x in the run state detection device and its inverse 1 / x is stabilized, and the effect of improving the accuracy of free run state detection is obtained.

Embodiment 6 FIG.
Next, the configuration of the sixth embodiment is shown in FIG. The sixth embodiment has a configuration in which the free-run state detection device 6a shown in FIG. 1 of the first embodiment is replaced with a free-run state detection device 6d. The free-run state detection means 6d does not have a function of detecting the magnitude of the free-run rotation frequency included in the free-run state detection devices 6a, 6b, and 6c in the first to fifth embodiments. It has a function to perform detection at higher speed. Applications that only need to detect the direction of free-running rotation at the time of restart, for example, to improve the free-run restarting function of a device that already has an inexpensive tachometer installed. In the application that can be obtained by the above, the function shown in the sixth embodiment is effective. Details of the operation will be described below.
The induction motor 1, the power conversion device 2, the voltage command value output device 3a, and the current detection device 4 are the same as those in the first embodiment, and a description thereof is omitted. The same applies to the behavior of the αβ-axis currents iα and iβ when the step command vα_ref = Vo is output as the α-axis voltage command, and the description thereof is omitted. Then, the β-axis current iβ is output to the free-run state detection device 6d.
The free-run state detection device 6d includes N (N: 1 or more) integrating means 61a to 61n, a sign calculating means 64, a sign reversing means 65, and a signal acquiring means 66. Similar to Embodiments 1 to 5 above, paying attention to the DC component included in iβ when the step command vα_ref = Vo is output as the α-axis voltage command, and using the characteristic of Formula 5 of the induction motor. .
The free-run state detection device 6d performs removal of the input iβ pulsation component and amplification processing of the DC signal by the N integrating means 61a to 61n. The behavior of the signal xn, which is the output of the integrator 61n at the last stage, is the same as that in FIG. 6 used in the description of the fourth embodiment. The sign calculating means 64 to which the signal xn is inputted obtains the sign sign (xn) of xn and outputs it to the sign reversing means 65. The sign reversing means 65 reverses the sign of sign (xn) and outputs it to the signal acquisition means 66. As shown in FIG. 6E, the signal xn decreases in the negative direction when the free-running rotation direction is normal, and increases in the positive direction when the free-running rotation is normal. Minus, plus is output when reversing. Therefore, the sign reversing means 65 performs an operation of reversing the sign of the output signal of the sign calculating means 64 in order to output the result of determining the free-running rotation direction as a positive signal during forward rotation and as a negative signal during reverse rotation.
The timing management device 7 monitors the time after the step voltage command is applied to the α-axis voltage by the voltage command value output device 3a, and outputs a sampling timing signal when a certain period T has elapsed. The data is output to the acquisition device 66. The signal acquisition means 66 acquires the signal (-sign (xn)) output from the sign reversal means 65 when the sampling timing signal is input from the timing management device 7, and outputs it as a free-running rotation frequency detection result. .

Here, from the viewpoint of the time required for detecting the free-run state, the first to fifth embodiments are compared with the sixth embodiment. In the free-run state detection devices 6a and 6b of the first to third embodiments, a period during which the signal x converges is necessary, and a lower limit is necessary for the time necessary for detection. Also in the free-run state detection device 6c of the fourth and fifth embodiments, since it is necessary to secure the S / N ratio of xn as a signal including the information of the magnitude of the free-run rotation frequency, a certain period required for detection There is a lower limit on the size of T. However, in the free-run state detection device 6d of the sixth embodiment specializing in the function of detecting the free-running rotation direction, it is sufficient to ensure the S / N ratio considering only the code discrimination of the signal xn. It is possible to shorten the predetermined period T required for the above.
As described above, the following effects can be obtained by the configuration of the sixth embodiment.
By performing integration on the β-axis current iβ after application of the α-axis voltage step command, information on the free-running rotation direction included in the DC component of iβ can be obtained. In other words, there is an effect that the direction of free run rotation can be detected at high speed regardless of the size of the free run frequency.
In addition, since the integration process is performed a plurality of times, the DC component extraction and pulsation component removal of the β-axis current iβ can be effectively performed, so that the effect of detecting the free-running rotation direction can be detected more quickly and stably. It is done.

Embodiment 7 FIG.
Next, the configuration of the seventh embodiment is shown in FIG. In the seventh embodiment, a current control loop is added to the configuration diagram 11 of the sixth embodiment described above.
The induction motor 1, the power converter 2, the voltage command value output device 3b, the current detection device 4, and the current command value output device 5 shown in FIG. 12 are current loops configured in the same manner as in the third embodiment described above. On the other hand, the free-run state detection device 6d is the same as that described in the sixth embodiment.
With the configuration of the seventh embodiment, the following effects can be obtained in addition to the sixth embodiment. That is, by configuring the current loop, the influence of voltage disturbance caused by the dead time of the inverter main circuit can be suppressed, so that a β-axis current waveform iβ in which the influence of the dead time disturbance voltage is suppressed is obtained. The behavior of the signal xn inside the free-run state detection device is stabilized, and the effect of improving the accuracy of detecting the free-run rotation direction is obtained.

Embodiment 8 FIG.
Next, FIG. 13 shows the configuration of the eighth embodiment. The eighth embodiment differs from the configuration diagram 10 of the fifth embodiment in the following points. That is, the device for detecting the free-run state of the eighth embodiment having the same configuration as that of the free-run state detecting device 6c shown in FIG. Description of the operation is omitted. Then, the outputs of the second free-run state detection device 9 provided in parallel with the first free-run state detection device 6e and the outputs of the first and second free-run state detection devices 6e and 9 are input. A result discriminating apparatus 10 for discriminating the result is provided. The second free-run state detection device 9 includes, for example, a pulsation extraction unit 91, a sign inversion number counter 92, a pulsation frequency measurement unit 93, and a correction unit 94. The pulsation extracting means 91 is composed of a filter having a high-pass characteristic, extracts a pulsation component of the β-axis current generated when a step command is applied as the α-axis current command, and extracts it to the sign inversion counter 92. The sign inversion counter 92 counts the number of times the sign of the pulsating component of the β-axis current is inverted, and outputs the count value to the pulsation frequency measuring means 93. The pulsation frequency measuring means 93 calculates the pulsation frequency of the β-axis current from the time from the application of the step voltage command monitored by the timing management means 7 and the number of sign inversions of the pulsation component of the β-axis current. For example, if the time elapsed between N sign inversions is T_count, the β-axis current pulsation frequency fβ is

Can be calculated as
fβ is substantially proportional to the free run frequency wm, and this is output to the detection result final discrimination means 10. When T_count is calculated backward as the time required for measuring fβ,

If the minimum N required to maintain the measurement accuracy is 7 (3 pulsation cycles), T_count = 3 / fβ [sec]. Assuming that N is fixed, T_count becomes longer as the free run frequency is lower, that is, fβ is lower. However, when the free run frequency is high, that is, when fβ is high, the measurement can be completed with a short T_count.

On the other hand, the first free-run state detection device 6e detects the free-run frequency based on the magnitude of the low-frequency component of the β-axis current as described in the first and third embodiments. There is an advantage that the required time T required for frequency detection can be reduced even in a low speed region.
The result discriminating device 10 provided in the eighth embodiment receives both the output of the first free-run state detecting device 6c and the output of the second free-run state detecting device 9, and the first, Of the second rotation state detection results, the result input earlier is selected and output as the free run rotation frequency detection result of the induction motor 1 in the free run state. With this configuration, it is possible to detect the free-run state at a higher speed in all speed ranges.
In the eighth embodiment, in addition to the effects shown in the fifth embodiment, the following effects can be obtained. In other words, since the first and second free-run state detection devices are arranged in parallel and the result determination device is provided for determining the input by inputting both of the first and second free-run state detection devices. By selecting and outputting as the final free-running rotation frequency detection result based on the result input to, the effect of being able to detect the free-run state at a higher speed in all speed ranges can be obtained.

  Embodiments 1 to 8 of the present invention as described above can be applied to induction motor control devices that require restart from a free-run state such as driving induction motors for trains, machine tools, fans, pumps, and the like. .

It is a block diagram which shows the control apparatus of the induction motor of Embodiment 1 of this invention. It is a schematic diagram which shows the behavior of the applied voltage and each current waveform of Embodiment 1 of this invention. It is a block diagram which shows the control apparatus of the induction motor of Embodiment 2 of this invention. It is a block diagram which shows the control apparatus of the induction motor of Embodiment 3 of this invention. It is a block diagram which shows the control apparatus of the induction motor of Embodiment 4 of this invention. It is a schematic diagram which shows the behavior of the applied voltage and each current waveform of Embodiment 4 of this invention. It is a figure which shows the relationship between the free run rotation frequency and convergence value of Embodiment 1-3 of this invention. It is a figure which shows the relationship between the free run rotation frequency and convergence value of Embodiment 4 of this invention. It is a figure which shows the relationship between the signal of Embodiment 4 of this invention, and required time. It is a figure which shows the control apparatus of the induction motor of Embodiment 5 of this invention. It is a figure which shows the control apparatus of the induction motor of Embodiment 6 of this invention. It is a figure which shows the control apparatus of the induction motor of Embodiment 7 of this invention. It is a figure which shows the control apparatus of the induction motor of Embodiment 8 of this invention.

Explanation of symbols

1 induction motor, 2 power converter, 3a, 3b voltage command value output device,
4 current detection device, 5 current command value output device,
6a, 6b, 6c, 6d Free-run state detection device,
6e 1st free-run state detection device, 7 timing management device,
8 resistance value detection device, 9 second free-run state detection device, 10 result discrimination device,
61, 61a to 61n integration means, 62 reciprocal calculation means, 66 signal acquisition means,
94 Correction means, 100 Induction motor control device.

Claims (10)

An induction motor control device comprising an induction motor, a power converter, a voltage command value output device, a current detection device, and a free-run state detection device,
The power conversion device supplies power to the induction motor, the voltage command value output device outputs a voltage command value to the power conversion device, and the current detection device includes the induction motor. Is to detect the current flowing through
The free-running state detection device has a frequency determined by a circuit time constant of the induction motor from a current flowing through the induction motor when a voltage command value output from the voltage command value output device is applied to the induction motor. A control device for an induction motor, wherein a signal having a lower frequency component is extracted, and a rotation state of the induction motor in a free-run state is detected from the extracted signal. An induction motor control device comprising an induction motor, a power converter, a voltage command value output device, a current command value output device, a current detection device, and a free-run state detection device,
The power conversion device supplies power to the induction motor, the current detection device detects a current flowing through the induction motor, and the current command value output device outputs the voltage command value output. The current command value is output to the device.
The voltage command value output device outputs a voltage command value calculated based on a current detected by the current detection device and a current command value output by the current command value output device to the power conversion device. ,
The free-running state detection device has a frequency determined by a circuit time constant of the induction motor from a current flowing through the induction motor when a voltage command value output from the voltage command value output device is applied to the induction motor. A control device for an induction motor, wherein a signal having a lower frequency component is extracted, and a rotation state of the induction motor in a free-run state is detected from the extracted signal. The voltage command value output device outputs a command value of a voltage to be applied to the α axis among the α and β axes orthogonal to each other on the stator of the induction motor to the power converter,
The current detection device calculates a β-axis current value by detecting a current flowing through the induction motor,
The free-run state detection device includes an integration unit, an inverse number calculation unit, and a correction unit, and the integration unit integrates the β-axis current value after voltage application to the α-axis, A signal x having a frequency component lower than a frequency determined by a circuit time constant is extracted, the reciprocal computing means calculates and outputs a reciprocal 1 / x of the signal x, and the correcting means sets the reciprocal 1 / x in advance. 3. The induction motor according to claim 1, wherein the rotation state of the induction motor is detected based on a signal wm obtained by integrating the proportional gain K of the induction motor that has been added. Control device. In addition to the control device for the induction motor, a timing management device is provided,
The timing management device acquires a sampling timing signal provided in the free-run state detection device from a time point when a voltage is applied to the α-axis to a predetermined time when the signal x converges. 4. The induction motor according to claim 3, wherein the signal acquisition unit acquires a signal wm output from the correction unit when the sampling timing signal is input. 5. Control device. In addition to the control device for the induction motor, a resistance value detection device is provided,
The resistance value detection device detects the temperature of the primary and secondary windings of the induction motor, estimates the resistance value of the winding at that time, and outputs the estimated resistance value to the correction means. 5. The induction motor control device according to claim 3, wherein the proportional gain K is sequentially updated by inputting a value. 6. An induction motor control device comprising an induction motor, a power converter, a voltage command value output device, a current detection device, a timing management device, and a free-run state detection device,
Furthermore, the free-run state detection device is provided with a plurality of integration means, signal acquisition means and correction means,
The power converter is configured to supply power to the induction motor, and the voltage command value output device is configured to determine a voltage applied to the α axis among α and β axes orthogonal to each other on a stator of the induction motor. A command value is output to the power converter,
The current detection device detects a current flowing through the induction motor and calculates a β-axis current value, and the timing management device performs sampling after a predetermined time has elapsed since the voltage was applied to the α-axis. The plurality of integrating means integrates the β-axis current value after voltage application to the α-axis twice or more times, and is lower than a frequency determined by a circuit time constant of the induction motor. Extracting the frequency component signal Xn,
The signal acquisition means outputs the signal Xn to the correction means when the sampling timing signal is input,
The correction means is provided with a table indicating a relationship between a free run frequency and the signal Xn, and detects a rotation state of the induction motor in a free run state from the input signal Xn. Induction motor controller. An induction motor control device comprising an induction motor, a power converter, a voltage command value output device, a current detection device, a timing management device, and a free-run state detection device,
Further, the free-run state detection device is provided with a plurality of integration means, sign calculation means, sign reverse means, and signal acquisition means, and the power converter supplies power to the induction motor. Yes,
The voltage command value output device outputs a command value of a voltage applied to α among α and β axes orthogonal to each other on the stator of the induction motor to the power conversion device, and the current detection device Detecting a current flowing through the induction motor to calculate a β-axis current value, and the timing management device outputs a sampling timing signal after a predetermined time has elapsed since the voltage was applied to the α-axis. The plurality of integrating means integrates the β-axis current value after voltage application to the α-axis at least twice, and a signal having a frequency component lower than a frequency determined by a circuit time constant of the induction motor. Xn is extracted,
The sign calculating means inputs the signal Xn and calculates and outputs a sign Sign (Xn), and the sign reversing means reverses the sign of the Sign (Xn) and outputs it. The signal acquisition means outputs the sign [-sign (Xn)] output by the sign reverse means at the time when the sampling timing signal is input, thereby determining the rotation direction of the induction motor in the free-run state. An induction motor control device characterized by detecting. In addition to the control device for the induction motor, a current command value output device is provided, and the current detection device detects a current flowing through the induction motor to obtain an α-axis current value and a β-axis current value. The voltage command value output device calculates the voltage calculated based on the α-axis current value and β-axis current value calculated by the current detection device and the current command value output by the current command value output device. 8. The induction motor control device according to claim 6, wherein a command value is output to the voltage converter. 9. An induction motor control device comprising: an induction motor, a power converter, a voltage command value output device, a current command value output device, a current detection device, first and second free-run state detection devices, and a result determination device. Prepared,
The power conversion device supplies power to the induction motor, the current detection device detects a current flowing through the induction motor, and the current command value output device outputs the voltage command value output. The current command value is output to the device.
The voltage command value output device outputs a voltage command value calculated based on a current detected by the current detection device and a current command value output by the current command value output device to the power conversion device. ,
The first free-run state detection device is configured to apply a voltage command value output from the voltage command value output device to the induction motor, so that a current flowing through the induction motor is detected by a circuit time constant of the induction motor. A signal having a frequency component lower than a determined frequency is extracted, a first rotation state of the induction motor in a free-run state is detected from the extracted signal, and the result is output to the result determination device,
The second free-run state detection device extracts a pulsation component from a current flowing through the induction motor by applying a voltage command value output from the voltage command value output device to the induction motor, and the pulsation The second rotation state of the induction motor in the free-run state is detected by counting the number of times the component is reversed and calculating the pulsation frequency from the time after the voltage command value is applied and the number of times the pulsation component is reversed. And outputting to the result discriminating device,
The result discriminating device is in the free-run state with the result obtained earlier among the first and second rotation state detection results output from the first and second free-run state detection devices. A control device for an induction motor, wherein the control device determines a rotation state of the induction motor. Induction motor control apparatus, including induction motor, power converter, voltage command value output device, current command value output device, current detection device, timing management device, first and second free-run state detection devices, and results A discrimination device,
Further, the first free-run state detection device is provided with a plurality of integration means, a signal acquisition means, and a correction means, and the second free-run state detection device includes a pulsation extraction means and a sign. An inversion counter and a pulsation frequency measuring means are provided, and the power converter supplies power to the induction motor,
The current detection device detects a current flowing through the induction motor to calculate an α-axis current value and a β-axis current value, and the current command value output device is connected to the voltage command output device of the induction motor. A current command value is output to the α axis among α and β axes on the stator, and the voltage command value output device includes the α-axis current value and the β-axis current value calculated by the current detection device, An α-axis voltage command value and a β-axis voltage command value are calculated based on the current command value output by the current command value output device, and output to the power converter,
The timing management device outputs a sampling timing signal after elapse of a predetermined time from the time when the α-axis current command value is applied, and a plurality of integration means provided in the first free-run state detection device Is to integrate the β-axis current value after application of the α-axis current command value twice or more to extract a signal Xn having a frequency component lower than the frequency determined by the circuit time constant of the induction motor. Yes,
The correction means is provided with a table indicating a relationship between a free run frequency and the signal Xn, and detects a first rotation state of the induction motor in a free run state from the input signal Xn, and Output to the result discriminator,
The pulsation extraction means provided in the second free-run state detection device extracts a pulsation component of the β-axis current and outputs the pulsation component to the sign inversion number counter. The sign inversion number counter The number of times the sign of the pulsating component of the shaft pulsating current is inverted is counted, and the value is output to the pulsating frequency measuring means. The second rotation state of the induction motor in the free-run state is detected by calculating the pulsation frequency from the time from the time point of the occurrence and the sign inversion number of the β-axis current pulsation component, and output to the result determination device Is what
The result discriminating device is in the free-run state with the result obtained earlier among the first and second rotation state detection results output from the first and second free-run state detection devices. A control device for an induction motor, characterized in that it is determined as a rotation state of the induction motor.

Images