JP5141404B2 - PM motor magnetic pole position estimation method - Google Patents

Description

  The present invention relates to a PM motor control device that controls the speed and torque of a PM motor using a permanent magnet as a field source, and more particularly to a magnetic pole position (phase) estimation method when the PM motor is stopped or at a very low speed.

  In order to drive the PM motor at a variable speed by an inverter, information on the magnetic pole position at the start is required. If the magnetic pole position is not known and control is performed using vector control or the like, the step-out occurs.

  When a phase detector such as an encoder is not attached to the PM motor, or only the A, B, and Z phase signals are If an encoder with only a B-phase signal is installed and the magnetic pole position is unknown when the power is turned on, or if the position / speed detector is not used, the pulse voltage that is switched to the omnidirectional phase is sequentially applied to the PM motor winding. There is a method of estimating the magnetic pole position of the PM motor from the locus of the peak value of the pulse current flowing in the winding of the PM motor for each pulse voltage (see, for example, Patent Document 1).

  FIG. 3 shows a PM motor control device without a position sensor. The figure shows an example in which speed control is performed, and a torque command is obtained in the speed control unit 1 by comparing the speed command with a speed detection value (speed estimation value in the case of sensorless). The current command calculation unit 2 converts the torque command into a current command by using information such as field magnetic flux and inductance. The current control unit 3 obtains a voltage command by comparison with the detected current value, gives a voltage control signal to the power converter (inverter) 5 by coordinate conversion by the reverse rotation coordinate conversion unit 4, and outputs an armature current to the PM motor 6. Supply. The current at this time is detected by the current detector 7, and a detected current signal is given to the current control unit 3 by coordinate conversion by the rotating coordinate conversion unit 8.

  The position estimation calculation unit 9 estimates the magnetic flux from the motor output voltage or voltage command and current detection information, and estimates the phase of the magnetic pole. The coordinate conversion unit 8 converts the alternating current obtained from the current detector 7 into rotational coordinates with reference to the same magnetic pole position as the current command using the estimated position information. Further, the speed detection calculation unit 10 converts the magnetic pole position signal detected by the position estimation calculation unit 9 into a speed detection signal and uses it as a feedback signal to the speed control unit 1.

  As shown in FIG. 4A, the magnetic pole position estimation method disclosed in Patent Document 1 applies a pulse voltage in 12 directions on a fixed coordinate (for example, UVW coordinate system) to the winding of the PM motor at the start of operation. Apply sequentially. Since the PM motor has different inductance depending on the direction of the field by the permanent magnet, the locus of the pulse current vector generated by the applied pulse voltage becomes an ellipse as shown in FIG. Using this fact, the magnetic pole position of the permanent magnet is estimated.

  That is, in the direction of the magnetic pole (N pole), the inductance decreases due to magnetic saturation, and the pulse current value in that direction becomes the largest. In the example of FIG. 4B, since the pulse current with the phase of 15 ° is the largest, the phase of the N pole is estimated to be around 15 °.

  Although FIG. 4B shows a case where 12 pulses are applied at 30 ° intervals, the number of pulses, the pulse interval, and the pulse output method are arbitrary, and the higher the number of pulses, the higher the accuracy. Can detect the magnetic pole position.

  This magnetic pole position estimation method can be applied only when the PM motor is stopped or when the rotational speed is extremely low speed rotation of several revolutions / minute.

FIG. 3 shows a case where the magnetic pole position is estimated. Instead of the position estimation calculation unit 9, an encoder that generates only A, B and Z phase signals is provided in the motor, and control is performed based on the magnetic pole position. Even in the elevator control apparatus, when there is no initial position information (for example, when position information is lost immediately after the inverter is turned on or due to a trouble with the encoder signal), the position information is obtained by estimating the magnetic pole position as described above. Can be used as
JP 2003-180094 A

  FIG. 5 is a graph of the phase versus current value of the omnidirectional pulse current in which the characteristics of FIG. 4 are plotted with the horizontal axis representing the phase and the vertical axis representing the current value. Since this current waveform has an elliptical current vector locus on the UVW axis in FIG. 4, it can be seen that the locus of the peak value of the omnidirectional pulse current has a “two peaks” shape when plotted as shown in FIG. The conventional phase estimation method also uses the characteristic that the peak value of the current with respect to the phase is “two peaks”.

  In this estimation method, the accuracy of the estimated magnetic pole position depends on the accuracy of the measured pulse current rather than the number of applied pulse voltages. That is, it becomes a problem that an error occurs in the estimated phase by detecting a current that is adversely affected by noise or the like in any of the measured 12 pulse currents.

  An object of the present invention is to provide a magnetic pole position estimation method for a PM motor that ensures the estimation of the magnetic pole position from the locus of the peak value of the omnidirectional pulse current.

  In order to solve the above-mentioned problems, the present invention provides a locus of the peak value of the omnidirectional pulse current of “two peaks” depending on whether or not the peak value of the omnidirectional pulse current continuously decreases / increases. It is designed to determine whether it is out of shape or not, and has the following method.

(1) When a PM motor using a permanent magnet as a field source is stopped or at a very low speed, a pulse voltage switched to an omnidirectional phase is sequentially applied to the winding of the PM motor, and the PM motor is applied to each pulse voltage A PM motor magnetic pole position estimation method for estimating the PM motor magnetic pole position from the locus of the peak value of the omnidirectional pulse current flowing in the winding of
It is determined that the locus of the peak value of the omnidirectional pulse current is “two peaks” and that the peak value is not abnormally large, and when these determinations are obtained, the omnidirectional pulse current Phase estimation calculation means for estimating the rotational position (phase) from the peak value locus is provided.

  (2) The phase estimation calculation means monotonously decreases to a current value advanced by + 90 ° from the phase of the largest current among the omnidirectional pulse currents, and further monotonously increases to a current value advanced by + 90 °, When the current value advances by + 90 ° again monotonously decreases, and when the current value further advances by + 90 ° again monotonously increases, it is distinguished from the “two peaks”.

  As described above, according to the present invention, the locus of the peak value of the omnidirectional pulse current is changed from “two peaks” depending on whether or not the peak value of the omnidirectional pulse current continuously decreases / increases. Since it is determined whether or not it has collapsed, the magnetic pole position is reliably estimated.

  Further, it can be determined that an abnormal current value has been measured due to noise or the like, and this determination can prevent the magnetic pole position estimation result from becoming an abnormal value.

  FIG. 1 is a configuration diagram of a position estimation calculation device showing an embodiment of the present invention. In position estimation calculation, pulse voltages in 12 directions on fixed coordinates are sequentially applied to the PM motor winding at the start of operation, and the magnetic pole position is estimated from the locus of the pulse current vector flowing in the PM motor winding by the applied pulse voltage. To do.

  In FIG. 1, a current control unit 3, a reverse rotation coordinate conversion unit 4, a power converter (inverter) 5, a PM motor 6, and a current detector 7 have the same configuration as the PM motor control device shown in FIG. 3.

The timing control unit 11 receives a phase estimation start signal from a higher-level PM motor control device, and instructs the phase estimation calculation using this signal as a reference timing. The pulse generation phase command unit 12 generates pulse voltages V _{1 to} V ₁₂ having phases as shown in FIG. 4A from the reference timing in the order of the numbers, and these pulses are output voltage control signals from the coordinate conversion unit 4. Superimpose on. Accordingly, pulse voltages V _{1 to} V ₁₂ are also applied from the power converter 5 to the PM motor 6, and a pulse current having a phase as shown in FIG. 4B is applied to the PM motor 6 by the pulse voltages V _{1 to} V ₁₂ . Flowing.

The sample and hold circuit 13 sequentially samples and holds the pulse current generated in the PM motor 6 by the pulse voltages V _{1 to} V ₁₂ , and converts the pulse current into a digital value by the A / D converter 14 during this hold period. Current data is temporarily stored in the memory 15 as omnidirectional data. The phase estimation calculation unit 16 determines that the locus of the peak value of the omnidirectional pulse current stored in the memory 15 is “two peaks” and that the peak value is not abnormally large. It is determined that the locus of the peak value of the pulse current is not shifted due to noise or the like, and when this determination is obtained, the rotational position (phase) is estimated from the locus of the peak value of the current. The phase estimation calculation unit 16 obtains a determination output as to whether or not the locus of the peak value of the pulse current is shifted.

2A shows a graph of the phase versus current value of the omnidirectional pulse current when the pulse currents I _{1 to} I ₁₂ are normally detected, and FIG. 2B shows the graph of FIG. A graph is shown when the current value becomes abnormally large due to noise when measuring the middle pulse current I ₅ .

  From these graph examples, the phase estimation calculation unit 16 determines whether or not the phase estimation is performed normally, and the locus of the current peak value is “two peaks” with respect to the phase, and noise is generated. Utilizing the property that the current detection value on the board becomes abnormally large, that is, the trajectory when noise is on any of the current detection values of 12 pulses does not have a “two-crest” shape.

Specifically, it decreases monotonically (from I ₁ to I _{4 in} FIG. 2A) to a current value advanced by + 90 ° from the phase of the largest current, and monotonically increases until a current value advanced by + 90 ° (FIG. 2). 2 (a) from I ₄ to I ₇ ), monotonically decreasing again to the current value further advanced by + 90 ° (from I ₇ to I _{10 in} FIG. 2A), and further to + 90 ° further current value Uses the property of monotonically increasing again (I ₁₁ to I _{1 in} FIG. 2B).

  Here, the phase is advanced in the + direction from the largest current, but there is no problem even if the direction in which the phase is advanced is set to the − direction.

  In the following, the phase determination processing procedure using the “two peaks” shape will be described.

Procedure 1: The largest current value (current I _{1 in} FIG. 2A) is obtained from the pulse currents I _{1 to} I ₁₂ .

Procedure 2: Check whether the current value is continuously decreased from the largest current value obtained in Procedure 1 to the third current value. In FIG. 2A, it is confirmed whether the relationship of I ₁ > I ₁ > I ₃ > I ₄ is established.

Procedure 3: Following the procedure 2, it is confirmed whether the current value is continuously increased up to the third current value. In FIG. 2A, it is confirmed whether the relationship of I ₄ <I ₅ <I ₆ <I ₇ is established.

Procedure 4: Following the procedure 3, it is confirmed whether the current value is continuously decreased to the third current value. In FIG. 2, it is confirmed whether the relationship of I ₇ > I ₈ > I ₉ > I ₁₀ is established.

Procedure 5: Check whether the current value is increasing continuously from Procedure 4 to Procedure 1. In FIG. 2A, it is confirmed whether the relationship of I ₁₀ <I ₁₁ <I ₁₂ <I ₁ is established.

  Step 6: If there is no abnormal state from Step 1 to Step 5, it is determined as normal and a phase estimation calculation is performed. If there is an abnormality, it is determined that the pulse current could not be normally measured due to some influence such as noise.

In the example of FIG. 2B, the largest current value is I ₅ . According to the above procedure, since it does not decrease from the first current I ₆ to the second I ₇ in the procedure 3, it can be determined as abnormal.

  In this abnormality determination, the PM motor is prevented from being operated in a state where the estimated phase is wrong by taking the following means.

  ・ Stop the inverter by failure and output an abnormal alarm signal.

  ・ Retry the magnetic pole position estimation process.

  In the present embodiment, the case where the pulse voltage is simply superimposed on the voltage command and the magnetic pole position is estimated from the locus of the pulse current value (sampling value) at that time is shown. As in Reference 1, a current control period for setting the current of current control to a set value is provided before applying the pulse voltage, and the final voltage value of current control is set immediately before and after applying the pulse voltage. A configuration in which a fixed output period is provided, one or more current samples are obtained during the fixed voltage period, an averaging process is performed, and a current change amount is detected from the average processed current before and after the pulse current; can do.

  Furthermore, the difference between the detected current before and after the pulse generation is calculated, the primary and secondary components of the Fourier coefficient are calculated from the phase and amplitude components of the current difference vector, and statistical processing is performed from these primary and secondary components. The magnetic pole position is estimated by the above, and when applying the approximation formula of the numerical calculation to the integration of the discrete data for the calculation of the primary and secondary components, the calculation of the discrete data is performed with the phase difference of the current difference vector as a reference, and can do.

The block diagram of the position estimation calculating apparatus which shows embodiment of this invention. Graph of phase versus current value of omnidirectional pulse current. The block diagram of the control apparatus of PM motor by a position sensorless. The vector diagram of the pulse voltage phase and the generated phase versus current value. Graph of phase versus current value of omnidirectional pulse current.

Explanation of symbols

5 Power converter (inverter)
6 PM motor 7 Current detector 11 Timing control unit 12 Pulse generation phase command unit 13 Sample hold circuit 15 Omni-directional data memory 16 Phase estimation calculation unit

Claims (2)

When a PM motor using a permanent magnet as a field source is stopped or at a very low speed, a pulse voltage switched to a phase in all directions is sequentially applied to the PM motor winding, and the PM motor winding is applied to each pulse voltage. A PM motor magnetic pole position estimation method for estimating the PM motor magnetic pole position from the locus of the peak value of the omnidirectional pulse current flowing through
It is determined that the locus of the peak value of the omnidirectional pulse current is “two peaks” and that the peak value is not abnormally large, and when these determinations are obtained, the omnidirectional pulse current A magnetic pole position estimation method for a PM motor, comprising phase estimation calculation means for estimating a rotational position (phase) from a locus of peak values.   The phase estimation calculation means monotonically decreases to a current value advanced by + 90 ° from the phase of the largest current in the omnidirectional pulse current, further monotonously increases to a current value advanced by + 90 °, and further advances by + 90 °. 2. The magnetic pole of the PM motor according to claim 1, wherein when the current value monotonously decreases to a current value and further monotonously increases again to a current value advanced by + 90 °, the magnetic pole of the PM motor according to claim 1 is identified. Position estimation method.

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