JP6766398B2 - Magnet temperature estimation method and magnet temperature estimation device - Google Patents

Description

The present invention relates to a magnet temperature estimation method and a magnet temperature estimation device.

As one of the motors that are synchronous motors, a permanent magnet type motor having a permanent magnet in the rotor is known. In such a permanent magnet type motor, when a voltage is applied to the coil provided in the stator, a rotating magnetic field is generated, and the rotating magnetic field acts on the permanent magnet, so that the rotor is moved in the stator. Rotate.

Generally, as the rotation speed of the motor increases, the temperature of the permanent magnet provided on the rotor rises. On the other hand, when a permanent magnet exceeds a certain upper limit temperature, it is irreversibly degaussed and loses its magnetic force. Therefore, it is necessary to measure the temperature of the permanent magnet and limit the rotation speed of the motor so that the permanent magnet does not reach the upper limit temperature.

When a temperature sensor is used to measure the temperature of a permanent magnet, it is necessary to incorporate the temperature sensor into the rotor, which makes it difficult to miniaturize the motor. Therefore, a method of estimating the temperature of a permanent magnet without using a temperature sensor is being studied. For example, Patent Document 1 discloses a method of estimating the temperature of a permanent magnet by using a current applied to a motor and an induced voltage generated by a stator.

JP-A-2007-6613

The method disclosed in Patent Document 1 has a problem that the estimation accuracy of the temperature of the permanent magnet is deteriorated because the induced voltage becomes small when the rotation speed of the motor is small.

The present invention has been made in view of the above problems, and an object of the present invention is a magnet temperature estimation method and a magnet, which can improve the temperature estimation accuracy of a permanent magnet included in a rotor of a motor. It is to provide a temperature estimation device.

According to one aspect of the magnet temperature estimation method of the present invention, the magnet temperature estimation method controls the rotation of a motor including a stator including a coil and a rotor including a permanent magnet, and estimates the temperature of the permanent magnet. Then, the voltage application step of applying the AC voltage of the fundamental wave frequency for driving the rotor to the stator of the motor and the AC voltage of the superimposed frequency different from the fundamental wave frequency are superimposed on the AC voltage of the fundamental wave frequency. A superimposition step, a superimposition frequency change step in which the superimposition frequency is changed according to the rotation speed of the motor, a superimposition component measurement step for measuring the current corresponding to the superimposition frequency, and an AC voltage of the superimposition frequency superimposed in the superimposition step. It also has a temperature estimation step of calculating the impedance using the current of the superimposition frequency measured in the superimposition component measurement step and estimating the temperature of the permanent magnet according to the impedance.

According to the present invention, a voltage obtained by superimposing a superposed frequency, which is a frequency different from the fundamental wave frequency used for driving the motor, is applied to the motor, and the impedance corresponding to the superposed frequency is measured. Since there is a predetermined correlation between the impedance according to the superimposed frequency and the temperature of the permanent magnet, the temperature of the permanent magnet can be estimated according to the measured impedance.

Here, in order to obtain the current corresponding to the superposed frequency, it is necessary to measure the current at the measurement frequency corresponding to the superposed frequency and the rotation speed of the motor. This measurement frequency becomes a constant frequency by changing the superimposition frequency according to the rotation speed of the motor. When the measurement frequency becomes constant, the current of the measurement frequency can be easily measured, so that the voltage corresponding to the superimposed frequency can be easily obtained. Therefore, the impedance calculation accuracy is improved, and the temperature estimation accuracy of the permanent magnet can be improved.

FIG. 1 is an explanatory diagram of the magnet temperature estimation method of the present invention. FIG. 2 is another explanatory diagram of the magnet temperature estimation method. FIG. 3 is a schematic configuration diagram of a magnet temperature estimation device and a motor. FIG. 4 is an explanatory diagram of frequencies in the magnet temperature estimation method. FIG. 5 is an explanatory diagram of frequencies in other magnet temperature estimation methods.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

First, the principle of estimating the temperature Tm of the permanent magnet included in the rotor of the motor by the magnet temperature estimation method will be described with reference to FIG.

FIG. 1 is an explanatory diagram of the magnet temperature estimation method of the present invention. FIG. 1 (a) shows a schematic configuration of a motor, and FIG. 1 (b) shows a magnetic flux circuit equivalent to that of the motor of FIG. 1 (a). The magnet temperature estimation device (not shown) that performs the magnet temperature estimation method controls the rotation of the motor and estimates the temperature Tm of the permanent magnet included in the rotor of the motor.

As shown in FIG. 1A, the motor 1 is composed of a stator 2 and a rotor 3 that rotates in the stator 2. A coil 5 is wound around the teeth 4 provided on the stator 2. Further, a voltage is applied to the coil 5 from an external magnet temperature estimation device. A permanent magnet 6 is provided in the rotor 3, and when an AC voltage having a fundamental wave frequency is applied to the coil 5 from a magnet temperature estimator, the rotating magnetic field generated in the coil 5 and the magnetic field of the permanent magnet 6 are generated. By attracting or repelling, the rotor 3 rotates in the stator 2.

Here, a method in which the magnet temperature estimation device estimates the temperature Tm of the permanent magnet 6 will be described.

The magnet temperature estimation device superimposes a harmonic voltage having a frequency higher than the fundamental wave frequency on the AC voltage of the fundamental wave frequency used for driving the rotation of the motor 1, and applies the superposed AC voltage to the coil 5. To do. When a voltage having a harmonic component is applied to the coil 5 in this way, a magnetic flux of the harmonic component is generated between the coil 5 and the permanent magnet 6. Then, an eddy current is generated on the surface of the permanent magnet 6 according to the harmonic component of the magnetic field of the coil 5, so that the permanent magnet 6 has an inductance component. In this way, when the motor 1 is rotating, a magnetic flux circuit is formed by the stator 2 and the rotor 3. In the following, the harmonic component to be superposed in this way is referred to as a superimposing component.

FIG. 1B shows a magnetic flux circuit equivalent to that of FIG. 1A. In this figure, a superposed component (superimposed voltage value) Vh of the applied voltage and a superposed component (superimposed current value) Ih of the current flowing through the coil 5 are shown. The resistance of the coil 5 of the stator 2 is shown as Rc and the inductance is shown as Lc, the resistance of the permanent magnet 6 of the rotor 3 is shown as Rx, and the inductance is shown as Lx. Here, the superimposition impedance Zh can be obtained from the superimposition voltage value Vh and the superimposition current value Ih by using the relationship of Zh = Vh / Ih. This superimposed impedance Zh has a correlation with the temperature Tm of the permanent magnet 6.

Therefore, the magnet temperature estimation device superimposes a voltage having a superposed frequency higher than the fundamental wave frequency on the voltage of the fundamental wave frequency, and when the superposed voltage is applied to the motor 1, the voltage corresponding to the superposed component and The superimposed impedance Zh is calculated using the current. Then, the temperature Tm of the permanent magnet 6 is estimated using the calculated superimposed impedance Zh, the relationship between the superimposed impedance Zh stored in advance and the temperature Tm of the permanent magnet 6.

Here, in the magnet temperature estimation device, the voltage of the fundamental wave frequency used for controlling the rotation drive is controlled according to the fundamental wave frequency component of the current flowing through the coil 5 of the motor 1. At the same time, the superimposed voltage value Vh used for estimating the temperature Tm of the permanent magnet 6 is controlled according to the superimposed component of the current. Therefore, the magnet temperature estimation device needs to individually measure the fundamental wave frequency component and the superimposed component for the current flowing through the coil 5.

FIG. 2 is a diagram showing a current flowing through the motor 1. FIG. 2A is a diagram showing the current flowing through the coil 5 of the stator 2 of the motor 1 in a rotating coordinate system. FIG. 2B is a diagram showing the current in a fixed coordinate system. FIG. 2C is a diagram in which the current shown in the fixed coordinate system in FIG. 2B is separated into a fundamental wave frequency component and a superposed component.

As shown in FIG. 2A, the current flowing through the coil 5 includes a fundamental wave frequency component used for rotational driving and a superposed component used for magnet temperature estimation. The fundamental wave frequency component is composed of a q-axis component so as to affect the torque of the motor 1, and the superimposed component is composed of a d-axis component so as not to affect the torque of the motor 1.

In FIG. 2B, the current flowing through the motor 1 is shown in a fixed coordinate system. In the fixed coordinate system, three-phase currents of U, V, and W are shown. The U-phase current is shown by the solid line, the V-phase current is shown by the alternate long and short dash line, and the W-phase current is indicated by the dashed line. Each of these currents contains a fundamental frequency component with a low frequency and a large amplitude, and a superposed component with a high frequency and a small amplitude.

In FIG. 2C, the current flowing through the motor 1 shown in FIG. 2B is separated into a fundamental wave frequency component shown in the left part of the figure and a superposed component shown in the right part of the figure. ing. Since the superposed component is superposed by the pulsating vector injection method described later, there are two different frequency components in the superposed component. Therefore, in FIG. 2C, two overlapping components are shown by a solid line and a dotted line.

Here, the superimposed component has a smaller amplitude than the fundamental frequency component. Therefore, if the measurement accuracy of the fundamental wave frequency component and the superimposed component is the same, it is difficult to properly measure both the fundamental wave frequency component and the superimposed component. Therefore, in the present embodiment, as will be described later, a current detection unit for measuring the fundamental wave frequency component and the superimposed component is separately provided.

FIG. 3 is a schematic configuration diagram of the magnet temperature estimation device and the motor 1. The two diagonal lines and the three diagonal lines attached to the input / output lines of each configuration indicate that the values input / output in each configuration are two-dimensional and three-dimensional vectors, respectively.

FIG. 3 shows the motor 1 and the magnet temperature estimation device 100. Further, a rotation sensor 1A is provided so that the rotation speed of the motor 1 can be measured.

The outline of the function realized by the magnet temperature estimation device 100 is as follows. By applying the AC power vu, vv, vw of the fundamental wave frequency to the motor 1 according to the fundamental wave current command values idsf ^* and iqsf ^* output from the fundamental wave current command value generator 101, the motor 1 It rotates at a desired rotation speed. At the same time, the power of the superimposition frequency corresponding to the superimposition wave current command values idsc ^* and iqsc ^* output from the superimposition current command value generation unit 111 is superposed on the AC power of the fundamental wave frequency via the adder 104. Therefore, a voltage on which the superimposed component is superimposed is applied to the motor 1. Then, the magnet temperature estimation unit 118 measures the superimposition impedance Zh using the voltage and current of the superimposition component, and estimates the temperature Tm of the permanent magnet 6 included in the rotor 3 of the motor 1 according to the superimposition impedance Zh.

The detailed configuration of the magnet temperature estimation device 100 will be described.

The fundamental wave current command value generation unit 101 outputs the fundamental wave current command values idsf ^* and iqsf ^* to the subtractor 102 so that the motor 1 is driven at a desired rotation speed in response to an input from an operating means (not shown). ..

The subtractor 102 subtracts the fundamental wave current detection values idsf and iqsf from the fundamental wave current command values idsf ^* and iqsf ^* , respectively, and outputs these subtraction results to the current control unit 103. The fundamental wave current detection values idsf and iqsf are detection values of the fundamental wave component of the current flowing through the motor 1.

The current control unit 103 outputs the first voltage command values vd0 ^* and vq0 ^* to the adder 104 so that the subtraction results in the subtractor 102 approach zero, respectively. Specifically, the current control unit 103 performs proportional integration control so that there is no deviation between the fundamental wave current command values idsf ^* and iqsf ^* and the fundamental wave current detection values idsf and iqsf.

The adder 104 adds the superimposed wave voltage command values vdsc ^* and vqsc ^* , which are superimposed components output from the resonance control unit 113, to the first voltage command values vd0 ^* and vq0 ^* output from the current control unit 103. .. Then, the adder 104 outputs the second voltage command values vds ^* and vqs ^* on which the superimposed components are superimposed to the coordinate conversion unit 105.

The coordinate conversion unit 105 converts the second voltage command values vds ^* and vqs ^* output from the adder 104 from the rotating coordinates (dq axis) to the three-phase coordinates (uvw phase), and the three-phase voltage. Calculate the command values vu ^* , vv ^* , and vw ^* . Then, the coordinate conversion unit 105 outputs the calculated three-phase voltage command values vu ^* , vv ^* , and vw ^* to the power conversion unit 106.

The power conversion unit 106 includes, for example, a power conversion circuit including a converter and an inverter. Further, a DC voltage is supplied to the power conversion unit 106 from a battery (not shown). The power conversion unit 106 converts the DC voltage output from the battery into AC three-phase voltages vu, vv, and vw by controlling the inverter with the three-phase voltage command values vu ^* , vv ^* , and vw ^*. , Output to motor 1.

The current detection units 107 and 114 are configured by using, for example, a Hall element, and detect three-phase currents iu, iv, and iwa flowing from the magnet temperature estimation device 100 to the motor 1. The current detection accuracy of the current detection unit 114 is higher than the current detection accuracy of the current detection unit 107.

The current detection unit 107 outputs the detected analog current values iu, iv, and iwa of the three-phase currents to the A / D conversion unit 108. The A / D conversion unit 108 converts the analog three-phase currents iu, iv, and iwa measured by the current detection unit 107 into digital current values, and outputs them to the coordinate conversion unit 109. The coordinate conversion unit 109 converts the three-phase coordinates into rotating coordinates, and outputs the current value indicated by the rotating coordinates to the band stop filter (BSF) 110. The BSF 110 has a property of not passing through other than the fundamental wave frequency, and outputs the fundamental wave current detection values idsf and iqsf composed of only the fundamental wave frequency components to the subtractor 102.

On the other hand, the current detection unit 114 outputs the detected three-phase currents iu, iv, and iwa to the bandpass filter (BPF) 115.

Here, when the current flowing from the magnet temperature estimation device 100 to the motor 1 is observed in the fixed coordinate system, the superimposed signal of the sum and difference components of the fundamental wave frequency and the superimposed frequency appears in the current. Therefore, the current detection unit 114 measures the current of the component corresponding to the sum and difference frequencies of the fundamental wave frequency and the superposed frequency. Then, the measured current becomes the current of the superimposed component. The frequency measured in this way is referred to as a measurement frequency, and details will be described later with reference to FIG.

Therefore, BPF115 having a property of passing the measurement frequency is used for measuring the current of the measurement frequency component. From the BPF 115, the three-phase currents iu, iv, and iwa of the measurement frequency are output to the A / D converter 116. Then, the A / D conversion unit 116 converts the analog three-phase currents iu, iv, and iw into digital current values and outputs them to the coordinate conversion unit 117. The coordinate conversion unit 117 outputs the current values obtained by converting the three phases into dq-axis coordinates to the subtractor 112 as the superimposed wave current detection values idsc and iqsc of the superimposed component.

The rotation speed of the motor 1 detected by the rotation sensor 1A is input to the superimposed current command value generation unit 111, and the superimposed frequency is determined according to the rotation speed. Then, the superimposed current command value generation unit 111 outputs the superimposed wave current command values idsc ^* and iqsc ^* according to the determined superimposed frequency. The method of determining the superimposition frequency in the superimposition current command value generation unit 111 will be described later with reference to FIG. Further, the superimposed current command value generation unit 111 outputs zero as the superimposed wave current command value iqsc ^* of the q-axis component so that the superimposed component does not affect the rotation of the motor 1.

The superimposed wave current command values idsc ^* and iqsc ^* are input to the subtractor 112, and the superimposed wave current detection values idsc and iqsc from the coordinate conversion unit 117 are input as feedback. The subtractor 112 subtracts the superimposed wave current detection values idsc and iqsc from the superimposed wave current command values idsc ^* and iqsc ^* , respectively, and outputs the subtraction result to the resonance control unit 113.

The resonance control unit 113 generates superposed wave voltage command values vdsc ^* and vqsc ^* so that the output from the subtractor 112 approaches zero. Then, the resonance control unit 113 outputs the superimposed wave voltage command values vdsc ^* and vqsc ^* to the adder 104 and the magnet temperature estimation unit 118.

The resonance controller 113, the superimposed wave voltage command value vdsc ^{*, vqsc *} of and amplitude, superimposed wave voltage command value Vdsc ^*, it is possible to arbitrarily set the output interval vqsc ^*. Here, the superimposed wave voltage command value vqsc ^* of the q-axis component affects the rotational torque of the motor 1. Therefore, the resonance control unit 113 outputs zero as the superimposed wave voltage command value vqsc ^* of the q-axis component so that the superimposed wave component does not affect the rotational torque of the motor 1, and the superimposed wave voltage command of the d-axis component. Only the value vdsc ^* is changed and output.

Further, the resonance control unit 113 outputs the superimposed wave voltage command value vdsc ^* by the pulsating vector injection method. Specifically, the resonance control unit 113 outputs the superimposed wave voltage command value vdsc ^* with positive and negative signs alternately. By doing so, in the second voltage command values vds ^* and vqs ^* output from the adder 104 as the command value to the motor 1, the advance according to the superimposed wave voltage command value vdsc ^* in the d-axis direction. And delay will occur alternately.

The magnet temperature estimating unit 118, the superimposed wave current command value IDSC ^*, with Iqsc ^* is input, superimposed wave voltage command value vdsc from the resonance controller 113 ^*, vqsc ^* is input. As described above, the superimposed wave current command value iqsc ^* and the superimposed wave voltage command value vqsc ^* of the q-axis component are zero. Therefore, the magnet temperature estimation unit 118 calculates the superimposed impedance Zh using the superimposed wave current command value idsc ^* and the superimposed wave voltage command value vdsc ^* .

As described above, the superimposed impedance Zh has a correlation with the temperature Tm of the permanent magnet 6 of the stator 2. Therefore, the magnet temperature estimation unit 118 stores in advance a table showing the correlation between the superimposed impedance Zh and the temperature Tm of the permanent magnet 6, and uses the calculated superimposed impedance Zh and the stored table to make it permanent. The temperature Tm of the magnet 6 is estimated.

Here, the superimposition frequency determined by the superimposition current command value generation unit 111 will be described. The superimposition component alternately superimposes either positive or negative values of the superimposition wave voltage command value vdsc ^{* by} the pulsating vector injection method. Therefore, the superimposed signal appearing in the phase current in the fixed coordinate system can be shown as follows.

However, ω _m is the fundamental wave frequency of the motor 1, ω _hf is the superimposed frequency, I _dhf is the amplitude of the d-axis superimposed signal, and φ _h and φ _l are the initial phases.

As shown in the equation (1), the superimposed signal is an angular frequency of the frequencies of “ω _m + ω _hf ” and “ω _m −ω _hf ”. Therefore, the superimposed current command value generation unit 111 determines the superimposed frequency ω _hf so that the angular frequency of “ω _m + ω _hf ” or “ω _m −ω _hf ” becomes a constant frequency. The details of this operation will be described with reference to FIG.

FIG. 4 is a diagram showing frequencies in a magnet temperature estimation device such as measurement frequencies and superimposed signal components. In this figure, the superimposition frequency ω _hf is determined so that “ω _m + ω _hf ” becomes a constant value. In FIG. 4A, the superimposed frequency ω _hf is shown in the rotating coordinate system. According to this figure, as the rotation speed N [rpm] of the motor 1 increases, that is, as the fundamental wave frequency ω _m increases, the superimposed frequency ω _hf decreases. Specifically, the superimposition frequency ω _hf is changed so that “ω _m + ω _hf ”, which is the sum of the fundamental wave frequency ω _m and the superimposition frequency ω _hf , becomes a constant value.

In FIG. 4B, the fundamental wave frequency component is a solid line, “ω _m + ω _hf ” among the superimposed components appearing in the phase current is a one-dot chain line, and “ω _m −ω _hf ” is a two-dot chain line. Has been done. Since the superposed components are superposed by the pulsating vector injection method, the superposed components are "ω _m + ω _hf " when the superposed components are applied in the positive direction, and when they are applied in the negative direction. The superposed component is "ω _m −ω _hf ".

Here, the current corresponding to the superposed frequency ω _hf is obtained by measuring the current at the measurement frequency of either “ω _m + ω _hf ” or “ω _m −ω _hf ” using the current detection unit 114 and the BPF 115. .. As described above, since "ω _m + ω _hf " is a constant value, the BPF 115 only needs to have the property of passing the frequency of "ω _m + ω _hf ".

In FIG. 4, an example is used in which "ω _m + ω _hf " has a constant frequency, but the frequency is not limited to this. The superimposition frequency ω _hf may be controlled so that “ω _m −ω _hf ” obtained by subtracting the superimposition frequency ω _hf from the fundamental wave frequency ω _m becomes a constant frequency. In such a case, the current having a frequency of “ω _m −ω _hf ” is measured by using the current detection unit 114 and the BPF 11.

FIG. 5 is a diagram showing a frequency in a magnet temperature estimation device when the value of the superimposed frequency ω _hf is not changed according to the rotation speed N of the motor 1 as in the present embodiment and is a constant value. As shown in FIG. 5A, the superimposed frequency ω _hf is a constant value. In such a case, as shown in FIG. 5 (b), neither of the superimposed components “ω _m + ω _hf ” and “ω _m −ω _hf ” appearing in the phase current becomes a constant value. Therefore, the BPF 115 in FIG. 3 does not have to have the property of passing only a signal having a specific frequency.

Further, it is known that the correlation between the superimposed impedance Zh and the temperature Tm of the permanent magnet 6 differs depending on the superimposed frequency ω _hf . Therefore, the magnet temperature estimation unit 118 stores a plurality of tables showing the correlation between the superimposition impedance Zh and the temperature Tm of the permanent magnet 6 according to the superimposition frequency ω _hf , and uses the table to store the superimposition frequency ω. _The correction amount according to _hf is obtained. Then, by correcting the estimated temperature Tm of the permanent magnet 6 by using the correction amount, the estimation accuracy of the temperature Tm of the permanent magnet 6 can be improved.

Further, the measurement frequency controlled so as to be a constant value by the superimposed current command value generation unit 111 is set to be larger than the fundamental wave frequency ω _m when the rotation speed of the motor 1 is maximum. .. By doing so, no matter how large the rotation speed of the motor 1, the measured frequency in the current flowing through the motor 1 and the fundamental wave frequency ω _m do not become the same. Therefore, the current detection units 107 and 114 can appropriately detect the respective currents.

According to the magnet temperature estimation method of the present embodiment, the following effects can be obtained.

According to the magnet temperature estimation method of the present embodiment, the voltage application step in which the voltage is applied to the motor 1 according to the fundamental wave current command values idsf ^* and iqsf ^* output from the fundamental wave current command value generation unit 101 is executed. Will be done. The resonance control unit 113 and the adder 104 give the superimposed wave voltage command of the superimposed frequency ω _hf output from the superimposed current command value generation unit 111 to the first voltage command values vd0 ^* and vq0 ^* according to the fundamental wave component. A superposition step is performed in which the values vdsc ^* and vqsc ^* are superposed. In the superimposed current command value generation unit 111, a superimposed frequency change step of changing the superimposed frequency ω _hf according to the rotation speed of the motor 1 is performed. The current detection unit 107 executes a superimposition component measurement step of measuring the current according to the superimposition frequency ω _hf . Then, the magnet temperature estimation unit 118 calculates the superimposition impedance Zh from the voltage and current corresponding to the superimposition frequency ω _hf , and estimates the temperature Tm of the permanent magnet 6 included in the rotor of the motor 1 according to the superimposition impedance Zh. The estimation step is performed.

Here, in the superimposition component measurement step, in order to measure the current corresponding to the superimposition frequency ω _hf , the current of the measurement frequency determined by the rotation speed of the motor 1 and the superimposition frequency ω _hf is measured. By changing the superimposition frequency ω _hf according to the rotation speed of the motor 1 in the superimposition frequency change step, the measurement frequency measured in the superimposition component measurement step can be set to a constant value. By doing so, in the superimposed component measurement step, it is only necessary to measure the current at the measurement frequency which is a constant value, so that the measurement accuracy of the current can be improved. Therefore, the impedance measurement accuracy is improved, and the estimation accuracy of the temperature Tm of the permanent magnet 6 can be improved.

Further, according to the magnet temperature estimation method of the present embodiment, in addition to the superimposed component measurement step performed by the current detection unit 114, the fundamental wave component measurement step of measuring the current of the fundamental wave frequency is executed by the current detection unit 107. Ru. In general, since the superimposed component has a smaller amplitude than the fundamental frequency component, the current of the superimposed component can be appropriately measured by making the measurement accuracy of the current detection unit 114 higher than the measurement accuracy of the current detection unit 107. .. By doing so, the accuracy of calculating the superimposed impedance Zh is improved, so that the accuracy of estimating the temperature Tm of the permanent magnet 6 can be improved.

Further, according to the magnet temperature estimation method of the present embodiment, in the superimposed current command value generation unit 111, the added value “ω _m + ω _hf ” of the fundamental wave frequency ω _m and the superimposed frequency ω _hf according to the rotation speed of the motor 1 , Or the superimposition frequency change step of changing the superimposition frequency ω _hf is executed so that the subtraction value “ω _m −ω _hf ” of the superimposition frequency ω _hf from the fundamental wave frequency ω _m becomes a constant frequency.

The resonance control unit 113 superimposes the superposed component on the fundamental wave component while alternately changing the sign of the superposed component by the pulsating vector injection method. Therefore, the current flowing through the motor 1 includes both the sum or the difference between the fundamental frequency and the superimposed frequency.

Therefore, in the superimposition component detection step, among the currents flowing through the motor 1, the current of the measurement frequency, which is the sum or difference between the fundamental wave frequency and the superimposition frequency according to the rotation speed of the motor 1, is detected. Since the measurement frequency is controlled to be a constant value in the superimposition frequency change step, only the current of the measurement frequency, which is the constant value, needs to be measured in the superimposition component detection step. Therefore, since the measurement accuracy of the current of the superimposed component is improved, the estimation accuracy of the temperature Tm of the permanent magnet 6 can be improved. In addition, the configuration used for current detection can be simplified.

Further, according to the magnet temperature estimation method of the present embodiment, after executing the filter processing step by the bandpass filter (BPF) 115 on the analog current value detected by the current detection unit 114, the A / D conversion unit 116 Converts to a digital current value. Here, the BPF 115 has a property of passing a measurement frequency determined by a fundamental wave frequency and a superposed frequency. As described above, since the measurement frequency is a constant value regardless of the rotation speed of the motor 1, the current of the measurement frequency can be reliably detected. Therefore, the accuracy of detecting the current according to the superimposed frequency is improved, and the accuracy of estimating the temperature Tm of the permanent magnet 6 can be improved. Moreover, the configuration of the BPF 115 can be simplified.

Further, according to the magnet temperature estimation method of the present embodiment, the measurement frequency, which is a constant value, is larger than the fundamental wave frequency when the rotation speed of the motor 1 is maximum. By doing so, no matter how large the rotation speed of the motor 1, the measured frequency and the fundamental wave frequency in the current flowing through the motor 1 will not be the same.

Here, if the measurement frequency and the fundamental wave frequency become the same, it becomes difficult to individually detect the currents of the measurement frequency and the fundamental wave frequency component. Therefore, the measurement system of the current of the superimposed component is lowered. However, by always making the measurement frequency, which is a constant value, higher than the fundamental wave frequency when the rotation speed of the motor 1 is maximum, the measurement frequency and the fundamental wave frequency will not be the same value. The current of the superimposed component can be reliably measured. Therefore, the accuracy of estimating the temperature Tm of the permanent magnet 6 can be improved.

Further, the magnet temperature estimation unit 118 corrects the estimated temperature Tm of the permanent magnet 6 by using the correction amount obtained by using the correlation between the impedance and the temperature Tm of the permanent magnet 6 according to the superimposed frequency ω _hf. Perform the temperature compensation step. The correlation between the impedance and the temperature Tm of the permanent magnet 6 differs depending on the superimposed frequency ω _hf . Therefore, by executing such a temperature correction step, the temperature Tm of the permanent magnet 6 estimated by using a more appropriate correlation is corrected, so that the estimation accuracy of the temperature Tm of the permanent magnet 6 can be improved. Can be done.

Although the embodiments of the present invention have been described above, the above embodiments are only a part of the application examples of the present invention, and the technical scope of the present invention is limited to the specific configurations of the above embodiments. Absent.

1 Motor 1A Rotation sensor 5 Coil 6 Permanent magnet 100 Magnet temperature estimator 101 Fundamental wave current command value generator 107, 114 Current detector 110 Band stop filter (BSF)
111 Superimposed current command value generator 113 Resonance control unit 115 Bandpass filter (BPF)
118 Magnet temperature estimation unit

Claims (7)

A magnet temperature estimation method that controls the rotation of a motor including a stator equipped with a coil and a rotor provided with a permanent magnet, and estimates the temperature of the permanent magnet.
A voltage application step of applying an AC voltage having a fundamental wave frequency for rotationally driving the rotor to the stator of the motor, and
A superimposition step of superimposing an AC voltage having a superimposition frequency different from the fundamental wave frequency on the AC voltage of the fundamental wave frequency,
A superimposition frequency change step that changes the superimposition frequency according to the rotation speed of the motor, and
A superimposition component measurement step for measuring the current corresponding to the superimposition frequency, and
Impedance is calculated using the AC voltage of the superimposition frequency superimposed in the superimposition step and the current of the superimposition frequency measured in the superimposition component measurement step, and the temperature of the permanent magnet is calculated according to the impedance. Has a temperature estimation step, which estimates
A magnet temperature estimation method characterized by this. The magnet temperature estimation method according to claim 1.
Further having a fundamental wave component measuring step for measuring a current corresponding to the fundamental wave frequency with a measurement accuracy lower than that of the superimposed component measuring step.
In the voltage application step, the current of the fundamental wave frequency is used to control the AC voltage of the fundamental wave frequency.
A magnet temperature estimation method characterized by this. The magnet temperature estimation method according to claim 1 or 2.
In the superimposition frequency change step, the superimposition frequency is changed so that the addition value of the fundamental wave frequency and the superimposition frequency or the subtraction value of the superimposition frequency from the fundamental wave frequency becomes a constant frequency.
A magnet temperature estimation method characterized by this. The magnet temperature estimation method according to claim 3.
Further comprising a filter processing step of performing a bandpass filter process for passing the constant frequency with respect to the current of the superimposed frequency measured in the superimposed component measurement step.
A magnet temperature estimation method characterized by this. The magnet temperature estimation method according to claim 3 or 4.
The constant frequency is larger than the fundamental frequency when the rotation speed of the motor is maximized.
A magnet temperature estimation method characterized by this. The magnet temperature estimation method according to any one of claims 1 to 5.
Further, it has a temperature correction step of correcting the estimated temperature of the permanent magnet by using the relationship between the impedance corresponding to the superimposed frequency and the temperature of the permanent magnet.
A magnet temperature estimation method characterized by this. A magnet temperature estimation device that controls a motor including a stator equipped with a coil and a rotor provided with a permanent magnet and estimates the temperature of the permanent magnet.
A voltage application unit that applies an AC voltage of the fundamental wave frequency that rotationally drives the rotor to the stator of the motor, and
A superimposing unit that superimposes an AC voltage having a superposed frequency different from the fundamental wave frequency on the AC voltage having a fundamental wave frequency.
A superposed frequency changing unit that changes the superposed frequency according to the rotation speed of the motor,
A superimposition component measuring unit that measures the current corresponding to the superimposition frequency,
Impedance is calculated using the AC voltage of the superimposition frequency superimposed by the superimposition unit and the current of the superimposition frequency measured by the superimposition component measuring unit, and the temperature of the permanent magnet is estimated according to the impedance. Has a temperature estimation unit and
A magnet temperature estimator characterized by this.

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