Detector for position of magnetic pole in motor

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Industrial application field]

The present invention relates to a magnetic pole position detecting device for detecting the magnetic pole position of a rotor of an electric motor having an electric salient polarity, for example, a synchronous motor or a reluctance motor without a sensor.

【0002】

[Conventional technology]

When driving a synchronous motor (for example, a brushless motor) or a reluctance motor, it is necessary to supply a current in an appropriate phase corresponding to the magnetic pole position of the rotor in order to generate a desired torque. In the conventional drive device for these electric motors, the magnetic pole position of the rotor is detected by the method shown in FIG. 7 (a). That is, the magnetic pole position sensor 2 is attached to the rotor shaft 1a of the electric motor 1, and when further accuracy is required, the magnetic pole position sensor 2 and the pulse encoder 3 are used together. Note that FIG. 7 (b) is an example of the output signal for each phase of the magnetic pole position sensor 2, and FIG. 7 (c) is an example of the output signal of the pulse encoder 3.

【0003】

[Problems to be Solved by the Invention]

In the above-mentioned prior art, since the magnetic pole position sensor 2 and the pulse encoder 3 are used to detect the magnetic pole position, there is a problem that the cost increases because the sensor itself, the wiring of the output signal thereof, the receiving circuit, etc. are provided. there were. In addition, if the wiring distance for supplying power to the sensor or transmitting the output signal is lengthened, the voltage drop due to the wiring resistance becomes large and the operation of the sensor is hindered. There was a problem that troubles such as incorrect wiring and disconnection occurred in the connection.

【0004】

The present invention has been made to solve the above-mentioned various problems, and an object of the present invention is to eliminate the need for wiring of various sensors for detecting the position of magnetic poles, their power supplies, outputs, etc., and to reduce costs. An object of the present invention is to provide a magnetic pole position detecting device that eliminates inconveniences associated with wiring.

【0005】

[Means for solving problems]

In order to achieve the above object, the first invention is in a system in which a magnetic pole position of an electric motor having an electrical salient pole is detected and the electric motor is driven by a drive device as a variable voltage / variable frequency power source such as an inverter. An alternating voltage applying means for applying an alternating voltage to the motor, a means for detecting the motor current, a vector conversion means for separating the detected motor current into parallel components and orthogonal components with respect to the applied alternating voltage, and the motor current. A magnetic pole position detecting means for detecting a magnetic pole position of an electric motor based on at least one of a parallel component and an orthogonal component is provided.

【0006】

The second invention includes an alternating voltage applying means for applying an alternating voltage in the same direction as the estimated position of the magnetic flux axis of the rotor to the motor, a means for detecting the motor current, and a parallel component and an orthogonal component of the detected motor current. Based on at least one of them, the magnetic flux axis estimated position is changed by an adjuster so as to match the magnetic flux axis estimated position of the rotor with the magnetic flux axis actual position, and the magnetic flux position detecting means for detecting the magnetic flux position with the magnetic flux axis estimated position is provided. ..

【0007】

The third invention is a means for applying an alternating current to an electric motor, a means for detecting an electric motor terminal voltage, and a vector for separating the detected electric motor terminal voltage into a parallel component and an orthogonal component with respect to the applied alternating current. A conversion means and a magnetic pole position detecting means for detecting the magnetic pole position of the motor based on at least one of a parallel component and an orthogonal component of the motor terminal voltage are provided.

【0008】

The fourth invention includes an alternating current applying means for applying an alternating current in the same direction as the estimated position of the magnetic flux axis of the rotor to the motor, a means for detecting the motor terminal voltage, and a parallel component and an orthogonal component of the motor terminal voltage. Based on at least one of them, the magnetic flux axis estimated position is changed by an adjuster so as to match the magnetic flux axis estimated position of the rotor with the magnetic flux axis actual position, and the magnetic flux position detecting means for detecting the magnetic flux position with the magnetic flux axis estimated position is provided. ..

【0009】

The fifth invention includes means for removing the frequency component of the applied alternating voltage or alternating current from the voltage command value or current command value for driving the electric motor in the first to fourth inventions.

【0010】

[Action]

When an alternating voltage vector or alternating current vector is applied to an electric motor, a current or voltage is also generated in the direction orthogonal to the applied vector, except when the applied vector and the rotator magnetic flux axis are parallel or orthogonal to each other. S is a sin function with an angle twice the phase difference angle between the applied vector and the magnetic flux axis. Further, the magnitude of the current or voltage generated in the direction parallel to the applied vector is obtained by giving an offset to the cos function having an angle twice the phase difference angle between the applied vector and the magnetic flux axis.

【0011】

Therefore, with respect to the alternating voltage vector or alternating current vector applied to the motor, the current (motor current) vector or voltage (motor terminal voltage) vector of the parallel component and the orthogonal component is detected, and from at least one of the components, The phase difference angle between the applied vector and the magnetic flux axis can be detected. Then, the magnetic pole position can be directly detected from the phase difference angle, or the magnetic pole position can be indirectly detected by adjusting the phase of the applied vector so that the phase difference angle becomes zero. When both components are used, the phase difference angle can be detected based on the angle obtained by taking the inverse function of tan of the size ratio of each component.

【0012】

Furthermore, by detecting only the current vector or voltage vector generated in the direction orthogonal to the applied vector and adjusting the phase of the applied vector so that these current vector or voltage vector become zero, the magnetic pole position is indirectly adjusted. It can also be detected.

【0013】

In addition, by inserting a notch filter in an appropriate place so that the voltage command value or current command value for driving the motor does not include the frequency component of the applied alternating voltage or current, excitation other than the purpose of magnetic pole position detection is performed. Can be removed. On the other hand, on the detection side, an unnecessary signal is removed by using a filter that allows only the applied alternating frequency to pass, or by extracting the applied alternating frequency component by Fourier integration or the like, thereby adjusting the magnetic pole position even while the motor is being driven. It becomes possible to detect.

【0014】

[Example]

Hereinafter, examples of each invention will be described with reference to the drawings. First, the voltage / current equation of an electric motor having electrical salient polarity is expressed by the coordinate axis on the electric motor side as Equation 1.

【0015】

[Number 1]

<img file="JPP3312472B2_D0001.tif" />【0016】

In Equation 1, the subscript d indicates the magnetic flux axis of the motor, q indicates the axis orthogonal to the d axis, and V_d, V_q, I_d, I_q, L_d, L_qIndicates the primary voltage, primary current, leakage inductance d-axis component, and q-axis component of the motor, respectively. R is the winding resistance of the motor, P is the differential operator, and ψ_fIs the field magnetic flux that exists in the case of a synchronous motor and is zero in the case of a reluctance motor.

【0017】

Here, the coordinate axes (d) on the drive device side such as an inverter._c-q_cConsider the voltage / current equations obtained when observing from the axis). Now, the dq axis on the motor side and the d on the drive unit side_c-q_cIt is assumed that the axes are in the relationship shown in FIG. 5 and that there is a phase difference angle θ between them. In this case, the physical quantity on the dq axis and d_c-q_cThe physical quantity on the axis has the relation of the formula 2.

【0018】

[Number 2]

<img file="JPP3312472B2_D0002.tif" />【0019】

Formula 3 can be obtained from Formula 1 and Formula 2.

【0020】

[Number 3]

<img file="JPP3312472B2_D0003.tif" />【0021】

In addition, in formula 3, L₀= (L_d+ L_q) / 2, L₂= (L_d-L_q) / 2. Further, ω is the excitation frequency of the drive device corresponding to the rotation speed of the electric motor, and if ω = 0 is set to simplify the calculation, Equation 4 can be obtained.

【0022】

[Number 4]

<img file="JPP3312472B2_D0004.tif" />【0023】

From Equation 4, d on the drive unit side_cOn axis or q_cWhen the voltage or current is changed on the axis, the PL on the diagonal of the matrix₂sin2θ, -PL₂It can be seen that the term sin2θ affects the current or voltage on the orthogonal axes. Here, in an electric motor with electrical polarity, L₂Is not zero (L_d L_q) Therefore, the dq axis on the motor side and the d on the drive unit side_c-q_cIf the axes do not exactly match and there is a phase difference angle θ, then PL₂sin2θ, -PL₂The term sin2θ appears, which affects the current or voltage. This d_cAxis or q_cSince the axis is taken arbitrarily, the direction of the applied voltage vector or current vector is also arbitrary.

【0024】

Now, when an alternating current is applied to the motor to detect the motor terminal voltage, Equation 4 can be used as it is. As an example, I in Equation 4_dc= I · sin (2πf) t, I_qcEquation 5 can be obtained by setting = 0 and omitting the R term. Note that f is the frequency of the alternating current.

【0025】

[Number 5]

<img file="JPP3312472B2_D0005.tif" />【0026】

In Equation 5, I, f, L₂If you know, V_qcThe phase difference angle θ can be obtained in the range of ± 45 ° (electrical angle, the same applies hereinafter), and I, f, L₂Even if a part of is unknown, the phase difference angle θ can be obtained for the time being by using an appropriate coefficient, although it includes some error. Furthermore, V as shown in Equation 6 below._dcAnd V_qcFind θ'by taking the inverse function of tan using both and, and V_dcAnd V_qcThe phase difference angle θ can be obtained in the range of ± 90 ° by performing addition and subtraction according to the magnitude of. Based on this phase difference angle θ, it is possible to directly or indirectly detect the magnetic pole position as described later.

【0027】

[Number 6]

θ'= (1/2) tan^-1{-V_qc/ (V_dc-V₀)} θ = θ + 90 ° (V_dc&lt;V₀, V_qc&lt;0), θ = θ (V_dc V₀), θ = θ -90 ° (V_dc&lt;V₀, V_qc≧0) 【0028】

Θ'and θ, V in Equation 6_dc, V_qcThe relationship with is shown in Fig. 6. In addition, in formula 6, V₀= L₀It is ωI · sin (2πf) t.

【0029】

In the above description, the alternating current I to be applied_dcIs a sine wave current, but it is more advantageous to apply a triangular wave current in order to reduce the calculation load on the drive device side.

【0030】

Next, when an alternating voltage is applied to the electric motor to detect the current, the following formula 7 is obtained from the formula 4. In this formula 7, Δ = L₀²-L₂²It is cos4θ.

【0031】

[Number 7]

<img file="JPP3312472B2_D0006.tif" />【0032】

As an example, V_dc= V · sin (2πf) t, V_qcEquation 8 is obtained by setting = 0 and omitting the R term.

【0033】

[Number 8]

<img file="JPP3312472B2_D0007.tif" />【0034】

In Equation 8, V, f, L₀, L₂If you know, I_qcThe phase difference angle θ can be obtained in the range of ± 45 °, and V, f, L₀, L₂However, it is possible to obtain the phase difference angle θ in the same manner as described above even if a part of the above is not known. Further, the phase difference angle θ can be obtained in the range of ± 90 ° in the same manner as in Equation 6. Based on this phase difference angle θ, it is possible to directly or indirectly detect the magnetic pole position as described later. However, in this example, since there is a term of Δ in Equation 8, the accuracy of the phase difference angle θ is slightly lacking.

【0035】

In the above description, the alternating voltage V to be applied_dcIs a sine wave voltage, but it is advantageous to apply a square wave voltage in order to reduce the calculation load on the drive device side. Also, in each example, d_cShaft current I_dcOr voltage V_dcIs changing, but q_cShaft current I_qcOr voltage V_qcThe phase difference angle θ can be detected in the same manner by changing.

【0036】

As a method of detecting the magnetic pole position from the phase difference angle θ, d on the drive device (inverter) side as described in the following embodiment._c-q_cAxial phase angle θ₀In addition to the method of directly obtaining the magnetic pole position by adding the phase difference angle θ to, d so that the phase difference angle θ becomes zero._c-q_cThere is a method of indirectly detecting the phase difference angle θ by rotating the shaft, in other words, changing the estimated magnetic flux axis position so that the estimated magnetic flux axis position of the rotor matches the actual position of the magnetic flux axis.

【0037】

By the way, FIG. 1 is a block diagram showing a first embodiment of the present invention. This embodiment corresponds to the embodiment of the first invention described in claim 1, and an alternating voltage is applied to the electric motor to detect the electric motor current. In the figure, 4a is the sinusoidal voltage V_dc(Command value V_dc^*) And V_qc(Command value V_qc^*) (= 0) and d_c-q_cAxial phase angle θ₀Is an input coordinate converter, and the voltage command value of the three phases (U, V, W phase) that is the output is input to the inverter 8 as a variable voltage / variable frequency power supply, and the output causes an electrical collision. The electric motor 1 having polarity is driven. Here, the coordinate converter 4a and the inverter 8 constitute the alternating voltage applying means in the present invention.

【0038】

Each phase current of the motor 1 is detected by the current detector 5, and d_c-q_cAxial phase angle θ₀Is input to the coordinate converter 4b with I_dc, I_qcIs converted to. That is, the motor current is separated into a parallel component and an orthogonal component with respect to the applied alternating voltage vector. Here, the coordinate converter 4b constitutes the vector conversion means in the present invention.

【0039】

Each current component I_dc, I_qcIs input to the phase difference detector 6, and the phase difference angle θ with the dq axis is detected by the above equation 8. This phase difference angle θ is d in the adder 7._c-q_cAxial phase angle θ₀By adding with, the magnetic pole position θ_mIs calculated. Here, the phase difference detector 6 and the adder 7 constitute the magnetic pole position detecting means in the present invention.

【0040】

According to this embodiment, the magnetic pole position θ is obtained at the moment when the phase difference angle θ is obtained._mTherefore, there is an advantage that the detection delay is small. However, since the detection of the phase difference angle θ includes not a little calculation error, this is directly the magnetic pole position θ._mThere is a problem that it is reflected in the detection accuracy of.

【0041】

Next, FIG. 2 shows a second embodiment of the present invention. This example corresponds to both the first invention described in claim 1 and the second invention described in claim 2. In this embodiment as well, an alternating voltage is applied to the electric motor to detect the current, and the same components as those in FIG. 1 are numbered the same.

【0042】

In this embodiment, V_dcIs the same as in Fig. 1 until the phase difference angle θ is obtained after changing, but the phase difference angle θ is negatively integrated by the integrator 9 and d._c-q_cAxial phase angle θ_mConvert to. And this phase angle θ_mIs input to the coordinate converters 4a and 4b so that the phase difference angle θ becomes zero._c-q_cRotate the shaft.

【0043】

That is, d so that the phase difference angle θ detected by the phase difference detector 6 is set to zero._c-q_cThe phase difference angle θ is indirectly detected by rotating the shaft to change the estimated position of the magnetic flux axis. With this configuration, d_c-q_cAxial phase angle θ_mWill eventually match the magnetic pole position, so d_c-q_cAxial phase angle θ_mIt itself becomes the magnetic pole position detection value. Here, the phase difference detector 6 and the integrator 9 constitute the magnetic pole position detecting means in the present invention, and the integrator 9 acts as a regulator for changing the estimated position of the magnetic flux axis.

【0044】

According to this embodiment, the detection error included in the phase difference angle θ is irrelevant to the magnetic pole position detection accuracy, which is advantageous in terms of accuracy. Also, with such a configuration, d_cWhen the voltage or current of the shaft is changed, d_c-q_cIf the axis coincides with the magnetic pole axis, the q-axis current becomes zero and torque ripple is not generated, so unnecessary vibration is not generated. In this sense, the axis to which the alternating voltage or current is applied is d_cThe axis is q_cIt can be said that it is more advantageous than the axis.

【0045】

In the examples of FIGS. 1 and 2, a case where the magnetic pole position is directly or indirectly detected by applying an alternating voltage to the motor and detecting the motor current has been described. On the other hand, as in the third invention described in claim 4 and the fourth invention described in claim 5, the magnetic pole position is directly or indirectly determined by detecting the terminal voltage of the motor by applying an alternating current to the motor. The basic principle of the magnetic pole position detecting device for detection has already been clarified by the above-mentioned equations 4 to 6, and the configuration of the embodiment can be easily conceived from FIGS. 1 and 2, respectively.

【0046】

For example, the input of the coordinate converter 4a in FIGS. 1 and 2 is a sine wave I._dc(Command value I_dc^*) And I_qc(Command value I_qc^*) (= 0), replace the current detector 5 with a voltage detector, and V obtained by the coordinate converter 4b._dcAnd V_qcThe phase difference detector 6 may be used to calculate Equation 5 or Equation 6 to obtain the phase difference angle θ.

【0047】

By the way, the above explanation is based on the premise of ω = 0, but in the following, this is extended to ω 0. FIG. 3 is a block diagram showing a third embodiment of the present invention, and corresponds to both examples of the second invention described in claim 2 and the fifth invention described in claim 7. The case where ω 0 will be described with reference to this embodiment.

【0048】

ΔV in Figure 3_dcIs an alternating voltage, which is added to the voltage output of the current control controller 10 by the adder 7a and input to the coordinate converter 4a as a d-axis voltage command value. Current command value i given to the current control controller 10_q^*The alternating frequency component is removed by passing through the notch filter 11a. Therefore, the alternating frequency component included in the voltage command value input to the coordinate converter 4a is ΔV._dcOnly minutes. This voltage command value is applied to the motor 1 as an actual voltage by the inverter 8.

【0049】

The current of the motor 1 is detected by the current detector 5 and I via the coordinate converter 4b._dc, I_qcIs converted to. These I_dc, I_qcIs input to the current control controller 10 as a feedback signal after the alternating frequency components are removed by the notch filters 11b and 11c, respectively.

【0050】

On the other hand, the outputs of the adders 7b and 7c are the original signals I, respectively._dc, I_qcAnd the output of the notch filters 11b and 11c, so it is equivalent to the output of the bandpass filter. In other words, only the alternating frequency component appears in the outputs of the adders 7b and 7c, and this is ΔI._dc, ΔI_qcThe phase difference angle θ is detected by inputting it to the phase difference detector 6, and if this phase difference angle θ is input to the integrator 9 and negatively integrated, d_c-q_cAxial phase angle θ_mCan be obtained. Here, the notch filters 11a, 11b, and 11c constitute means for removing the frequency components of the applied alternating voltage and current from the voltage command values for driving the electric motor. In addition, Fourier integration may be performed to extract the alternating frequency component on the input side of the phase difference detector 6.

【0051】

With the above configuration, the alternating frequency component of the applied voltage or current can be separated from the voltage command value or current command value for driving the motor. This gives the same result as setting ω = 0 when looking only at the alternating frequency component, and the following equation 9 can be obtained in the same manner as equation 4. Therefore, based on this equation 9, it is possible to directly or indirectly detect the magnetic pole position by obtaining the phase difference angle θ as in the case of ω = 0.

【0052】

[Number 9]

<img file="JPP3312472B2_D0008.tif" />【0053】

Furthermore, as the motor rotation speed increases, θ by the integrator 9 in Fig. 3_mSince the delay of the correction operation of the above causes a steady-state deviation of θ, it becomes a problem. Therefore, a method for eliminating this steady-state deviation will be described with reference to FIG. 4 as a fourth embodiment of the present invention. In addition, this example also corresponds to the example of both the second invention and the fifth invention.

【0054】

In the following, only the differences from FIG. 3 will be described. First, the gain of the negative integral of the integrator 9 in FIG. 3 is divided as the gain (-K) 14 in FIG. Then, θ by the differentiator 12_mThe differential signal of is obtained, the output is input to the adder 7d through the low-pass filter 13, and the addition result is integrated by the integrator 15. With such a configuration, the output of the low-pass filter 13 has an angular velocity ω._mAnd integrate this to d_c-q_cAxial phase angle θ_mBy obtaining, the phase difference angle θ in the steady state can be set to zero.

【0055】

The idea of the fifth invention described with reference to the examples of FIGS. 3 and 4 can be applied not only to the second invention but also to the first, third, and fourth inventions.

【0056】

[Effect of the invention]

As described above, according to the present invention, in a drive system of an electric motor having an electrical salient pole such as a synchronous motor or a reluctance motor, the magnetic pole position is detected from a stopped state to a driven state without using various sensors for detecting the magnetic pole position. Will be possible. This eliminates the need for wiring of the sensor itself, its power supply, output, etc., and can reduce costs. At the same time, the sensor power supply voltage drops due to the voltage drop of the wiring, the output signal is attenuated, miswiring, disconnection, etc. It has the effect of preventing troubles.

[Simple explanation of drawings]

[Figure 1]

It is a block diagram which shows the 1st Example of this invention.

[Figure 2]

It is a block diagram which shows the 2nd Example of this invention.

[Fig. 3]

It is a block diagram which shows the 3rd Example of this invention.

[Fig. 4]

It is a block diagram which shows the 4th Example of this invention.

[Fig. 5]

The dq axis and d in the examples_c-q_cIt is a figure which shows the relationship with the axis.

[Fig. 6]

Θ'and θ, V in the examples_dc, V_qcIt is a figure which shows the relationship with.

[Fig. 7]

It is explanatory drawing which shows the prior art.

[Explanation of symbols]

1 Electric motor 4a, 4b coordinate converter 5 Current detector 6 Phase difference detector 7,7a, 7b, 7c, 7d adder 8 Inverter 9,15 integrator 10 Current control regulator 11a, 11b, 11c notch filter 12 Differentiator 13 Low pass filter 14 gain