JP2009177960A - Variable-speed driver for pm motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that, in sensorless control of a PM motor, irreversible demagnetization occurs due to an abnormal temperature rise of a permanent magnet, and consequently, it is highly likely that abnormal behavior of a device, caused by erroneous determination of a magnetic pole, occurs. <P>SOLUTION: A sensorless control system for the PM motor includes a function for detecting a current change component generated when applying a pulse voltage to a PM motor, and an identification function of an initial phase for estimating a phase of a magnetic pole from information of a current change amount. In the sensorless control system for the PM motor, a demagnetization detection means is provided on the output side of the function for detecting the current change component so as to detect a demagnetization fault when a difference between current amplitude of the north pole of the current change component and that of the south pole direction of the current change component becomes smaller than a preset setting value or when an absolute value of a primary component is small. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a variable speed drive device for a PM motor.

When controlling a synchronous motor (PM motor) using a permanent magnet as a field source without a sensor, normally, the magnetic pole is used to determine the N pole side and the S pole side of the magnetic pole. An error occurs due to contamination. Patent Document 1 is known as a method for preventing the influence of this error and estimating the magnetic pole position with high accuracy.
FIG. 3 is a configuration diagram shown in FIG. 1 of Patent Document 1, which is a one-pulse measurement unit (function for detecting a current change component) A having a voltage generation unit and a current measurement unit, and commands and detects the generated voltage. The pulse control / phase estimation unit (initial phase identification function for estimating the phase of the magnetic pole from the information on the current change amount) B is used to estimate the phase of the magnetic pole from the current.

The permeability of the permanent magnet is close to the vacuum value, and is much smaller than the magnetic iron core. For this reason, the PM motor has saliency in which the inductance of the motor's field pole (d-axis) and its orthogonal axis (q-axis) are different. In a motor without a position sensor, in order to check the position of the field at the time of starting, measurement is performed using the difference in inductance, that is, saliency. In Patent Document 1, a voltage is input from a timing control unit 21 in a plurality of directions for a short time with respect to one period of an electrical angle as shown in FIG. Then, the amount of current change when each voltage is input is measured. In this way, when the current component is expressed on the current space vector in consideration of the deviation of the generated phase, the plurality of vectors have a shape close to an ellipse as shown in FIG. FIG. 4A shows the amplitude of the input voltage with the voltage generation phase on the horizontal axis, and FIG. 4B shows the phase difference between the input voltage and the generated current. is there.
Since the current change amount (amplitude component) in FIG. 4A is inversely proportional to the inductance, the direction in which the current change amount is the largest is estimated as the d-axis direction using this characteristic. In the example of FIG. 4, the direction of 45 ° is the generation phase of the maximum current, and a permanent magnet with a small inductance exists near this direction and the magnetic pole axis (d axis) exists.

  Since there are N and S poles in the d-axis component, it is necessary to distinguish between these two poles. Therefore, a method using magnetic saturation of the PM motor is used. In the PM motor, the magnetic flux generated by the permanent magnet and the armature reaction magnetic flux generated by the current when the voltage is input for the d-axis measurement are synthesized. At this time, when a current is generated on the N pole side, the magnetic flux of the permanent magnet and the armature reaction magnetic flux are in the same direction, and the resultant magnetic flux increases and a magnetic saturation phenomenon occurs. When the magnetic saturation phenomenon occurs, the inductance is reduced and a large current amplitude is generated.

On the contrary, when a current is generated on the S pole side, the magnetic flux of the permanent magnet and the armature reaction magnetic flux are in opposite directions, the resultant magnetic flux cancels and becomes smaller, and no magnetic saturation phenomenon occurs. Therefore, the inductance does not decrease and the current amplitude does not increase. Therefore, the N pole and the S pole can compare two opposite components of the detected current of the d-axis component, and the larger current can be estimated as the N pole. In Patent Document 1, the primary component of the current change is calculated for the electrical angle of 360 °, and the phase of the maximum amplitude is calculated. Further, in the Fourier integral calculation unit, by calculating using the information of both the amplitude component of the generated current diagram 4 (a) and the generated phase diagram 4 (b), a false detection component is present in the current due to noise or the like. Even if it mixes, it has the feature which can reduce an influence.
Japanese Patent No. 3687603

  Current mainstream neodymium iron boron permanent magnets have the characteristic that the residual magnetic flux of the permanent magnets changes as the temperature rises. Normally, if the temperature drops, it will return to the original residual magnetic flux, but if the temperature rise becomes abnormally high or the magnetic field in the demagnetizing direction becomes excessive due to the armature reaction caused by the winding current, the temperature and reaction There is a phenomenon that even if the magnetic field returns to the original value, the residual magnetic flux remains reduced and does not return to the original value. This phenomenon is called irreversible demagnetization (demagnetization).

  When irreversible demagnetization occurs, the magnetic flux of the PM motor decreases, so that an abnormality that the generated torque with respect to the current decreases occurs. As described above, using the phenomenon that the sum of the residual magnetic flux of the magnet and the armature reaction magnetic flux reaches magnetic saturation, when performing magnetic pole determination of the N pole and the S pole, if the residual magnetic flux decreases, the magnetic saturation is reduced. It will not occur, and the N pole and S pole of the magnetic pole cannot be determined. In sensorless control, abnormal behavior occurs due to erroneous discrimination of magnetic poles. For example, when the polarity of the magnetic pole is determined to be opposite to the original polarity, the torque generated to cause a current to flow in the wrong reverse magnetic pole direction is reversed, and as a result, a phenomenon occurs in which the motor runs backward.

  The motor load has the possibility of causing mechanical damage when reverse rotation occurs. Accordingly, when the initial position is estimated, if the influence of magnetic saturation is small, it is necessary to consider the operation abnormal and stop the operation. In order to show that there is a high possibility that an abnormality called irreversible demagnetization of the motor has occurred, it is possible to clearly indicate that there is a demagnetizing factor of the motor using the fault display function of the variable speed drive device. Response is quicker. If there is no abnormality display, a secondary phenomenon such as motor reverse rotation abnormality or overload abnormality occurs, and the operation is finally stopped. In that case, although the true cause is irreversible demagnetization, the secondary cause of abnormality due to abnormal demagnetization of the PM motor is displayed abnormally, and the true cause can be investigated. Therefore, there is a high possibility of taking wrong measures.

  The present invention has been made in view of this point, and an object thereof is to provide a variable speed drive device for a PM motor capable of detecting irreversible demagnetization.

Claim 1 of the present invention has a function of applying a pulse voltage to the PM motor, detecting a current change component generated at that time, and an initial phase identification function of estimating the phase of the magnetic pole from the information of the current change amount In the sensorless control system of PM motor,
A demagnetization detecting means for detecting a demagnetization abnormality when a difference between a current amplitude in the N pole and a current amplitude in the S pole direction of the detected current change component is smaller than a preset value; It is characterized in that it is provided on the output side of the function for detecting the change component.

  According to a second aspect of the present invention, the demagnetization detection unit is configured to detect the absolute value of the amplitude component output by the primary component extraction unit included in the initial phase identification function for estimating the phase of the magnetic pole from the information on the amount of current change. The set value is compared, and when the absolute value of the primary component is small, it is detected as a demagnetization abnormality.

  A third aspect of the present invention is characterized in that the demagnetization detecting means outputs a demagnetization abnormality signal when the detected demagnetization abnormality occurs continuously for a set number of times.

  The fourth aspect of the present invention is characterized in that the detected demagnetization abnormality signal is used as an operation stop signal as an abnormality occurrence signal when starting the PM motor.

  According to a fifth aspect of the present invention, the detected demagnetization abnormality signal is output to a failure display unit of a variable speed drive device, and a failure due to a demagnetization factor is displayed.

  As described above, according to the present invention, when the difference between the current amplitude of the N pole phase and the current amplitude in the S pole direction of the change component of the measured pulse current becomes smaller than a predetermined set value, or The absolute value of the amplitude component output from the primary component extraction unit is compared with the set value, and when the absolute value of the primary component is small, it is detected as a demagnetization abnormality of the motor. Therefore, by using this detection signal, it is possible to determine that there is a high possibility of stopping operation and irreversible demagnetization by determining an abnormality at the time of starting the motor by using the failure display function of the variable speed drive device, The cause investigation is simplified, and it is possible to quickly cope with the demagnetization abnormality of the PM motor without causing a secondary phenomenon due to the abnormal demagnetization of the PM motor.

FIG. 1 is a block diagram showing a first embodiment of the present invention. The same reference numerals are given to the same parts as those shown in FIG. That is, the present invention is provided with the demagnetization detection means C, and the data stored in the omnidirectional data storage unit 29 of the one-pulse measurement unit A is input to the demagnetization detection means C. The data stored in the omnidirectional data storage unit 29 is shown in FIG.
The amplitude data of the change component of the pulse current as in (a) is input to the maximum amplitude data selection unit 41 and the opposite phase data selection unit 42 of the maximum amplitude of the demagnetization detection means C. The maximum amplitude data selection unit 41 selects the maximum amplitude data (N pole), and the opposite phase data selection unit 42 of the maximum amplitude has an electrical angle 180 ° opposite to the maximum data selected in 41 (S pole). ) Is selected, and the subtractor 45 calculates the difference amount between the N pole and S pole directions, and then outputs the difference to the determination unit 43.

  44 is a determination reference setting unit in which a reference value is set in advance, and measures the amount of difference caused by magnetic saturation at the time of normal test or trial operation adjustment. To do. Therefore, when starting as a normal operation, the difference amount calculated by the subtraction unit 45 and the set value from the determination reference setting unit 44 are compared by the determination unit 43 based on the result of the estimated measurement of the magnetic pole position. If it is smaller than the set value, an abnormality is detected as insufficient magnetic saturation (irreversible demagnetization). When there is a concern about the influence of noise or the like when detecting an abnormality, the accuracy is improved by performing re-measurement or the like. In that case, when an abnormal signal is generated continuously for the set number of times or more, an irreversible demagnetization failure display is generated and the apparatus is abnormally stopped.

In addition, although the function of each part of 1 pulse measurement part A and pulse control and phase estimation part B is explained in full detail in patent document 1, it is as follows.
The timing control unit 21 generates a timing signal for controlling the generation phase of the measurement pulse based on a measurement start command from the control device, and outputs the timing signal to each unit. The pulse generation phase command unit 22 outputs a control signal to the current controller 23 and the voltage generator 24 from the start timing for one pulse and the generation phase of the pulse voltage. The current controller 23 performs control to bring the output current closer to the set value before applying the pulse voltage by current control, and the voltage generator 24 executes control to generate a voltage command. A variable speed drive 5 controls the PM motor 6 based on the input voltage control signal.

Reference numeral 7 denotes a current detector that detects a motor current, and the detected current is input to the L level current sampler 25 and the H level current sampler 27, respectively. The L level current sample unit 25 detects the I _L current in a predetermined period T _C before applying the pulse voltage, and the output is averaged by the average processing unit 26. The H level current sample unit 27 detects the I _H current in a predetermined period T _E after application of the pulse voltage, and the output is averaged by the average processing unit 28. The omnidirectional data storage unit 29 temporarily accumulates the sample data from the average processing units 26 and 28 for the entire circumference.

  The primary component extraction unit 30 inputs the measurement data accumulated in the omnidirectional data storage unit 29 and performs Fourier integration, and outputs the maximum phase of the current amplitude to the phase estimation calculation unit 32. The secondary component extraction unit 31 performs second order Fourier integration from the measurement data accumulated in the omnidirectional data storage unit 29 and outputs the maximum phase of the current amplitude to the phase estimation calculation unit 32. The phase estimation calculation unit 32 executes phase estimation calculation based on the signals from 30 and 31, and outputs an estimated phase.

  FIG. 2 shows a second embodiment. In this embodiment, a signal is extracted from the primary component extraction unit 30 of the pulse control / phase estimation unit B to the demagnetization detection means C ′. The primary component extraction unit 30 calculates biaxial components of a1 and b1 which are primary components using the equation (1).

However, | ΔI (θ _V ) | is the absolute value of the amplitude component of the measured current difference vector.

The a1 and b1 components calculated by the primary component extraction unit 30 are input to the absolute value calculation unit 46 of the demagnetization detection means C ′ to obtain | I ₁ | = √ (a12 + b12). The primary component obtained using the absolute value of the amplitude component is output to the determination unit 43 and compared with the set value of the determination criterion setting unit 44. When the absolute value of the primary component is smaller than the set value, an abnormality is detected as insufficient magnetic saturation (irreversible demagnetization).
If there is a concern about the influence of noise or the like when this abnormality is detected, the accuracy is improved by performing re-measurement or the like. In that case, when an abnormal signal is generated continuously for the set number of times or more, an irreversible demagnetization failure display is generated and the apparatus is abnormally stopped.

  As described above, according to each embodiment of the present invention, the difference between the current amplitude in the N-pole phase and the current amplitude in the S-pole direction of the change component of the measured pulse current is smaller than a predetermined set value. Or by comparing the absolute value of the amplitude component obtained by Fourier integration or the like in the primary component extraction unit with the set value, and detecting the demagnetization abnormality of the PM motor when the absolute value of the primary component is small. is there. Therefore, using this detected demagnetization abnormality signal, it is possible to stop the operation by determining an abnormality at the time of starting the motor, and to indicate that there is a high possibility of irreversible demagnetization. This makes it easy to investigate the cause and promptly deal with PM motor demagnetization anomalies without causing secondary phenomena due to PM motor demagnetization anomalies. Is.

The block diagram which shows the Example of this invention. The block diagram which shows the 2nd Example of this invention. The block diagram which shows the magnetic pole position estimation apparatus of PM motor. FIG. 4 is a combination diagram of current difference vector phase and amplitude, where (a) is an amplitude diagram of current change, and (b) is a deviation angle diagram of voltage generation phase and current change phase. Vector diagram of pulse voltage and current difference.

Explanation of symbols

A ... 1 pulse measurement unit B ... Pulse control / phase estimation unit C ... Demagnetization detection means 41 ... Maximum amplitude data selection unit 42 ... Opposite phase data selection unit for maximum amplitude 43 ... Judgment unit 44 ... Judgment criterion setting unit 45 ... Subtraction Unit 46 ... Absolute value calculation unit

Claims (5)

In a sensorless control system for a PM motor that has a function of applying a pulse voltage to a PM motor and detecting a current change component generated at that time, and an initial phase identification function for estimating the phase of a magnetic pole from information on the amount of current change.
A demagnetization detecting means for detecting a demagnetization abnormality when a difference between a current amplitude in the N pole and a current amplitude in the S pole direction of the detected current change component is smaller than a preset value; A variable speed drive device for a PM motor, which is provided on the output side of a function for detecting a change component. The demagnetization detection means compares the set value with the absolute value of the amplitude component output from the primary component extraction unit included in the initial phase identification function for estimating the phase of the magnetic pole from the information on the amount of current change. 2. The variable speed drive device for a PM motor according to claim 1, wherein the demagnetization abnormality is detected when the absolute value of the component is small. 3. The variable speed of the PM motor according to claim 1, wherein the demagnetization detection means outputs a demagnetization abnormality signal when the detected demagnetization abnormality occurs continuously for a set number of times or more. Drive device. 4. The variable speed drive device for a PM motor according to claim 1, wherein the detected demagnetization abnormality signal is used as an operation stop signal as an abnormality occurrence signal when starting the PM motor. 5. The PM motor according to claim 1, wherein the detected demagnetization abnormality signal is output to a failure display unit of a variable speed drive device to display a failure due to a demagnetization factor. Variable speed drive.

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