Induction motor control device

Abstract

To control torque with high accuracy using a controller for an induction motor to appropriately compensate for any fluctuation in secondary resistance according to the operating state of the induction motor.SOLUTION: A secondary resistance variation compensation processing unit 14 outputs 0 as a sliding frequency correction factor when a motor rotation electric angular frequency ωr is less than a frequency threshold and a q-axis current I1q* or a q-axis current I1q calculated from a torque command value is less than a current threshold, otherwise it outputs a sliding frequency correction factor based on the difference between a primary voltage detection value V1det and a primary voltage theoretical value V1. A sliding calculator unit 10 outputs a sliding angle frequency ωs based on a d-axis current command value I1d*, a q-axis current command value I1q*, and a sliding frequency correction coefficient. This sliding angle frequency is used for drive control of an induction motor IM.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a control device for an induction motor that can appropriately compensate even when the secondary resistance, which is a constant of the induction motor, varies depending on the operating state. [Background technology]

[0002] The problem with Patent Document 1 is that torque accuracy deteriorates due to fluctuations in secondary resistance caused by temperature changes in the induction motor IM. In Patent Document 1, the slip frequency is corrected based on the deviation between the theoretical value and the actual value of the primary voltage, thereby correcting the fluctuations in secondary resistance.

[0003] The problem with Patent Document 2 is that when the motor constants vary depending on the operating state, the secondary magnetic flux cannot be obtained as commanded, resulting in a deterioration in torque control accuracy. Patent Document 2 describes a method for compensating for axis misalignment by calculating a compensation value for the primary frequency from the difference between the detected value and the theoretical value of the induced voltage component of the d-axis. This axis misalignment has the same effect as the method for compensating for fluctuations in secondary resistance due to temperature changes. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 58-51788 [Patent Document 2] JP 2000-333500 A Summary of the Invention [Problem to be solved by the invention]

[0005] Patent Document 1 describes a method for correcting the slip frequency so that the theoretical value of the primary voltage coincides with the actual value of the primary voltage. This method performs correction on the premise that the relationship between equations (1) and (2) has the same polarity.

[0006]

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[0007]

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[0008] However, the polarity is reversed at low speeds and low torques, and for this reason, the method of Patent Document 1 has the problem that compensation cannot be reliably performed.

[0009] In Patent Document 2, since it is necessary to switch the gain depending on whether the motor is powered or regenerated, it is necessary to judge whether the motor is powered or regenerated from the relationship between the rotation speed and the torque. However, there is a delay in the detected value of the rotation speed, and the detection error becomes large at low speeds, making it difficult to detect accurately. Therefore, it is necessary to provide a dead zone at low speeds and stop the secondary resistor operation. In this way, since it is necessary to switch the gain and operate the dead zone, there is a problem that the gain processing becomes complicated.

[0010] In view of the above, a challenge is to provide a control device for an induction motor that can control torque with high precision by appropriately compensating even when the secondary resistance varies depending on the operating state of the induction motor. [Means for solving the problem]

[0011] The present invention has been devised in view of the above-mentioned problems in the related art, and is an induction motor control device that drives and controls an induction motor, the control device comprising: a secondary resistance fluctuation compensation processing unit that outputs 0 as a slip frequency correction coefficient when a motor rotational electrical angular frequency is smaller than a frequency threshold value and a q-axis current calculated from a q-axis current command value or a torque command value is smaller than a current threshold value, and outputs a slip frequency correction coefficient based on a difference between a detected primary voltage value and a theoretical primary voltage value in other cases; and a slip calculation unit that outputs a slip angular frequency based on a d-axis current command value, the q-axis current command value, and the slip frequency correction coefficient, and is characterized in that the slip angular frequency is used for driving and controlling the induction motor.

[0012] As another aspect, a control device for an induction motor that drives and controls an induction motor includes a secondary resistance variation compensation processing unit that varies a torque threshold value according to the motor rotational electrical angle frequency to set a corrected torque threshold value when the motor rotational electrical angle frequency is equal to or higher than a base rotational angular speed, outputs 0 as a slip angle frequency correction coefficient when the motor rotational electrical angle frequency is smaller than the frequency threshold value and a torque command value is smaller than the corrected torque threshold value, and outputs a slip frequency correction coefficient based on a difference between a detected primary voltage value and a theoretical primary voltage value in other cases, and a slip calculation unit that outputs a slip angular frequency based on a d-axis current command value, a q-axis current command value, and the slip frequency correction coefficient, and uses the slip angular frequency for driving and controlling the induction motor.

[0013] As another aspect, a control device for an induction motor that drives and controls an induction motor includes: a secondary resistance variation compensation processing unit that outputs 0 as a slip frequency correction coefficient when a q-axis current command value is smaller than a current threshold value obtained from a table based on a motor rotational electrical angular frequency, and outputs a slip frequency correction coefficient based on a difference between a detected primary voltage value and a theoretical primary voltage value in other cases; and a slip calculation unit that outputs a slip angular frequency based on a d-axis current command value, the q-axis current command value, and the slip frequency correction coefficient, and the slip angular frequency is used for driving and controlling the induction motor.

[0014] In one aspect, the secondary resistance variation compensation processing unit includes a primary voltage detection value calculation unit that outputs the primary voltage detection value based on a d-axis voltage command value and a q-axis voltage command value, a primary voltage theoretical value calculation unit that outputs the primary voltage theoretical value based on a power source angular frequency, the d-axis current command value, and the q-axis current command value, a third subtractor that outputs a deviation between the primary voltage detection value and the primary voltage theoretical value, and a third subtractor that compares the q-axis current calculated from the q-axis current command value or the torque command value with the current threshold value, and outputs 1 when the q-axis current command value or the q-axis current is smaller than the current threshold value, and outputs 0 otherwise. a first comparator, a second comparator that compares the motor rotational electrical angle frequency with the frequency threshold and outputs 1 when the motor rotational electrical angle frequency is smaller than the frequency threshold and outputs 0 otherwise; a first AND circuit that outputs 1 when outputs of the first comparator and the second comparator are both 1 and outputs 0 otherwise; a first switch that outputs 0 when the output of the first AND circuit is 1 and outputs the output of the third subtractor whose output of the first AND circuit is 0; and a secondary resistance compensator that performs PI control based on the output of the first switch and outputs the slip frequency correction coefficient.

[0015] In another aspect, the secondary resistance variation compensation processing unit includes a primary voltage detection value calculation unit that outputs the primary voltage detection value based on a d-axis voltage command value and a q-axis voltage command value, a primary voltage theoretical value calculation unit that outputs the primary voltage theoretical value based on a power supply angular frequency, the d-axis current command value, and the q-axis current command value, a third subtractor that outputs a deviation between the primary voltage detection value and the primary voltage theoretical value, a second comparator that compares the motor rotational electrical angular frequency with the frequency threshold value and outputs 1 when the motor rotational electrical angular frequency is smaller than the frequency threshold value and outputs 0 otherwise, a second divider that divides the base rotational angular velocity by the motor rotational electrical angular frequency, and a third divider that compares the motor rotational electrical angular frequency with the base rotational angular velocity and outputs 1 when the motor rotational electrical angular frequency is equal to or greater than the base rotational angular velocity and outputs 0 otherwise. a comparator, a second switch which outputs the output of the second divider when the output of the third comparator is 1 and outputs 1 when the output of the third comparator is 0, a fourth multiplier which multiplies a torque threshold value and the output of the second switch to output the correction torque threshold value, a fourth comparator which compares the correction torque threshold value with the torque command value and outputs 1 when the torque command value is smaller than the correction torque threshold value and outputs 0 otherwise, a second AND circuit which outputs 1 when the outputs of the second comparator and the fourth comparator are both 1 and outputs 0 otherwise, a first switch which outputs 0 when the output of the second AND circuit is 1 and outputs the output of the third subtractor when the output of the second AND circuit is 0, and a secondary resistance compensator which performs PI control based on the output of the first switch and outputs the slip frequency correction coefficient.

[0016] In another aspect, the secondary resistance variation compensation processing unit includes: a primary voltage detection value calculation unit that outputs the primary voltage detection value based on a d-axis voltage command value and a q-axis voltage command value; a primary voltage theoretical value calculation unit that outputs the primary voltage theoretical value based on a power supply angular frequency, the d-axis current command value, and the q-axis current command value; a third subtractor that outputs a deviation between the primary voltage detection value and the primary voltage theoretical value; the table that outputs the current threshold value based on the motor rotational electrical angle frequency; a fourth comparator that compares the current threshold value with the q-axis current command value, and outputs 1 when the q-axis current command value is smaller than the current threshold value, and outputs 0 otherwise; a first switch that outputs 0 when the output of the fourth comparator is 1, and outputs the output of the third subtractor when the output of the fourth comparator is 0; and a secondary resistance compensator that performs PI control based on the output of the first switch, and outputs the slip frequency correction coefficient.

[0017] As one aspect of the present invention, there is provided a magnetic flux current command value calculation unit that outputs the d-axis current command value based on a magnetic flux command value, a torque current command value calculation unit that outputs the q-axis current command value based on a torque command value, a current control unit that outputs a d-axis voltage command value and a q-axis voltage command value based on a deviation between the d-axis current command value and the d-axis current detection value and a deviation between the q-axis current command value and the q-axis current detection value, a PWM inverter that outputs a voltage to the induction motor by PWM control based on the d-axis voltage command value, the q-axis voltage command value and a power supply phase, a current detector that detects a current detection value output from the PWM inverter, and the induction motor includes a three-phase to two-phase converter that converts a d-axis current detection value into the q-axis current detection value, a rotational position detection unit that detects a rotational position of the induction motor, a speed detector that outputs the motor rotational electrical angular frequency based on the rotational position, a first adder that adds the motor rotational electrical angular frequency to the slip angular frequency to output a power supply angular frequency, and an integrator that integrates the power supply angular frequency to output the power supply phase, and the secondary resistance variation compensation processing unit outputs the slip frequency correction coefficient based on the d-axis current command value, the q-axis current command value, the d-axis voltage command value, the q-axis voltage command value, the power supply angular frequency, and the motor rotational electrical angular frequency.

[0018] In one aspect, the slip calculation unit includes a first multiplier which multiplies the q-axis current command value by a secondary resistance of a T-type equivalent circuit, a second multiplier which multiplies the d-axis current command value by a mutual inductance of a T-type equivalent circuit, a first divider which divides an output of the first multiplier by an output of the second multiplier, a third multiplier which multiplies the output of the first divider by the slip frequency correction coefficient, and a second adder which adds the output of the first divider and the output of the third multiplier and outputs the slip angular frequency. Effect of the Invention

[0019] According to the present invention, it is possible to provide a control device for an induction motor that controls torque with high precision by appropriately compensating even when the secondary resistance varies depending on the operating state of the induction motor. [Brief description of the drawings]

[0020] [Figure 1] FIG. 2 is a block diagram showing a control device for an induction motor according to the first embodiment. [Diagram 2] FIG. 4 is a block diagram showing a slip calculation unit in the first embodiment. [Diagram 3] FIG. 4 is a block diagram showing a secondary resistance variation compensation processing unit in the first embodiment. [Figure 4] FIG. 11 is a block diagram showing a control device for an induction motor in a second embodiment. [Diagram 5] FIG. 11 is a block diagram showing a secondary resistance variation compensation processing unit in the second embodiment. [Figure 6] FIG. 11 is a block diagram showing a secondary resistance variation compensation processing unit in the third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] First to third embodiments of a control device for an induction motor according to the present invention will now be described in detail with reference to FIGS.

[0022] [Embodiment 1] In the first embodiment, a method is applied in which the variation in secondary resistance is calculated from the deviation between the theoretical value and the actual value of the primary voltage, and the slip frequency is corrected. In order to apply this method, a dead band process is provided to prevent control from becoming unstable, and the variation in secondary resistance cannot be compensated for, resulting in a deterioration in torque accuracy. In addition, by providing an appropriate dead band process, the variation in secondary resistance is appropriately compensated for even in a high-frequency operating state.

[0023] The control device for an induction motor in the present embodiment 1 is shown in Fig. 1. Fig. 1 shows a current control system during induction motor IM control.

[0024] The magnetic flux current command value calculation unit 1 calculates the magnetic flux command value Flux * to d-axis current command value I 1d * The torque current command value calculation unit 2 calculates the torque command value Torque * to the q-axis current command value I 1q * Calculate the following.

[0025] The first subtractor 3 subtracts the d-axis current command value I 1d * to d-axis current detection value I 1d The second subtractor 4 subtracts the q-axis current command value I 1q * to q-axis current detection value I 1q The current controller 5 performs current control on the output of the first subtractor 3, and obtains the d-axis voltage command value V 1d * The current controller 6 performs current control on the output of the second subtractor 4, and outputs the q-axis voltage command value V 1q * Output.

[0026] The PWM inverter 7 outputs the d-axis voltage command value V 1d * ,q-axis voltage command value V 1q * , a voltage is output to the induction motor IM by PWM control based on the power supply phase θ.

[0027] The current detector 8 detects the U-phase current I U ,V-phase current detection value I V ,W-phase current detection value I W The three-phase to two-phase converter 9 detects the U-phase current detection value I U ,V-phase current detection value I V ,W-phase current detection value I W Based on the power supply phase θ, the d-axis current detection value I 1d ,q-axis current detection value I 1q Convert to.

[0028] The rotational position detector pp detects the rotational position of the induction motor IM. The speed detector 11 calculates the motor rotational electrical angular frequency ω r Output.

[0029] The secondary resistance variation compensation processing unit 14 calculates the d-axis voltage command value V 1d * ,q-axis voltage command value V 1q * and the d-axis current command value I 1d * ,q-axis current command value I 1q * , power supply angular frequency ω1, motor rotation electrical angular frequency ω r The slip frequency correction coefficient is output based on the above.

[0030] The slip calculation unit 10 calculates the d-axis current command value I 1d * ,q-axis current command value I 1q * , based on the slip frequency correction coefficient, the slip angular frequency ω s * The first adder 12 calculates the slip angular frequency ω s * Motor rotation electrical angular frequency ω r The integrator 13 integrates the power supply angular frequency ω1 and outputs the power supply phase θ.

[0031] Slip angle frequency ω s * is calculated by the slip calculation unit 10 as the d-axis current command value I 1d* and the q-axis current command value I 1q * and the motor constants, a slip calculation is performed. A secondary resistance variation compensation processing unit 14 performs secondary resistance variation compensation and reflects it in the slip calculation (FIG. 2, equations (3) to (5) described later). With this configuration, the variation in secondary resistance is corrected.

[0032] 2 shows the configuration of the slip calculation unit 10. The slip calculation unit 10 includes a first multiplier 15, a second multiplier 16, a first divider 17, a third multiplier 18, and a second adder 19.

[0033] The first multiplier 15 multiplies the q-axis current command value I 1q * The second multiplier 16 multiplies the d-axis current command value I 1d * and the mutual inductance M' of the TI type equivalent circuit. The first divider 17 divides the output of the first multiplier 15 by the output of the second multiplier 16. That is, the first and second multipliers 15 and 16 and the first divider 17 calculate the slip angle frequency command ω without compensation processing from the following equation (3). s Calculate the following.

[0034]

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[0035] The third multiplier 18 multiplies the slip frequency correction coefficient K output from the secondary resistance variation compensation processing unit 14 by the uncompensated slip angular frequency command ω s By multiplying this, the compensation term ω s_comp get.

[0036]

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[0037] The second adder 19 receives the output of the first divider 17 (uncompensated slip angle frequency command ω s ) and the output of the third multiplier 18 (compensation term ωs_comp =Kω s ) to obtain the slip angular frequency ω s * get.

[0038]

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[0039] FIG. 3 shows the secondary resistance variation compensation processing unit 14 in the first embodiment.

[0040] The primary voltage detection value calculation unit 20 calculates the d-axis voltage command value V 1d * and the q-axis voltage command value V 1q * Based on this, the calculation of equation (6) is performed to obtain the primary voltage detection value V 1det Calculate the following.

[0041]

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[0042] The primary voltage theoretical value calculation unit 21 calculates the power supply angular frequency ω1 and the d-axis current command value I 1d * and the q-axis current command value I 1q * Based on this, the equations (7), (8), and (9) are calculated to calculate the theoretical primary voltage value V1.

[0043]

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[0044]

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[0045]

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[0046] Where, V1: Primary voltage theoretical value, V 1d : d-axis voltage theoretical value, V 1q : q-axis voltage theoretical value, R1: Primary resistance, L s : Excitation inductance of TI type equivalent circuit, M': Mutual inductance of TI type equivalent circuit.

[0047] The third subtractor 22 subtracts the primary voltage detection value V 1det The first comparator 25 calculates the difference between the q-axis current command value I 1q * and the current threshold, and the q-axis current command value I 1q * is smaller than the current threshold, and outputs 1 otherwise. The second comparator 26 outputs the motor rotation electrical angular frequency ω r and a frequency threshold value, and the motor rotation electrical angular frequency ω r is smaller than the frequency threshold, and outputs 0 otherwise. r and the q-axis current command value I 1q * When both are smaller than the frequency threshold and the current threshold, it outputs 1, and outputs 0 otherwise.

[0048] The first switch 23 is connected to the motor rotation electrical angular frequency ω r and the q-axis current command value I 1q * When is smaller than the frequency threshold and the current threshold, the third subtractor 22 outputs 0, and otherwise outputs the output of the third subtractor 22 to the secondary resistance compensator 24. The secondary resistance compensator 24 performs PI control based on the output of the first switch 23, and outputs a slip frequency correction coefficient.

[0049] The features of the first embodiment are as follows. Motor rotation electrical angular frequency ω r and the q-axis current command value I 1q * is compared with a frequency threshold and a current threshold, and if it is smaller than the frequency threshold and the current threshold, the input to the secondary resistance compensator 24 is set to 0.

[0050] Primary voltage detection value V1det This explains that the value reflects the fluctuation in secondary resistance.

[0051] The current controllers 5 and 6 control the difference between the current command value and the current detection value to be 0. The current detection value of the induction motor IM is controlled to be the same as the current command value, so the voltage command value output from the current controllers 5 and 6 reflects the state change of the induction motor IM. Therefore, the d-axis voltage command value V 1d * and the q-axis voltage command value V 1q * is a voltage command value that reflects the fluctuation of the secondary resistance.

[0052] Therefore, the d-axis voltage command value V 1d * and the q-axis voltage command value V 1q * are expressed as equations (10) and (11), respectively.

[0053]

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[0054]

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[0055]

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[0056]

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[0057] Here, λ 2d :Secondary side d-axis magnetic flux, λ 2q : secondary q-axis magnetic flux, M: mutual inductance of T-type equivalent circuit, R2': secondary resistance of T-type equivalent circuit, R err ': Secondary resistance error of T-type equivalent circuit.

[0058] Primary voltage detection value V 1det As shown in equation (14), the secondary magnetic flux cannot be properly controlled due to the fluctuation of the secondary resistance, so the primary voltage detection value V 1det reflects the variation in secondary resistance.

[0059]

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[0060] Primary voltage detection value V 1det The error voltage component V caused by the variation in the secondary resistance 1diff By extracting this, we obtain equation (15).

[0061]

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[0062] Primary voltage detection value V 1det and the theoretical primary voltage value V1, and the slip frequency correction coefficient output from the secondary resistance compensator 24 is applied to the slip calculation to make the detected value of the primary voltage equal to the theoretical value. This makes it possible to compensate for the fluctuation in the secondary resistance.

[0063] Next, the dead zone processing will be described.

[0064] Error voltage component V 1diff is the case of low rotation speed (low output frequency) and the q-axis current I q The polarity is reversed when the error voltage component V 1diff When becomes 0, the motor rotation electrical angular frequency ω r and the q-axis current detection value I 1q Solving for (16) and (17) gives us

[0065]

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[0066]

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[0067] However, A in equation (17) is expressed as equation (18) below. Furthermore, T is a torque command.

[0068]

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[0069] The current threshold and the frequency threshold are set using equations (16) and (17). Motor rotation electrical angular frequency ω r and the q-axis current detection value I 1q are mutually related. Therefore, after setting one of the values, we set the other using equations (16) and (17).

[0070] Motor rotation electrical angular frequency ω r After setting, the q-axis current detection value I 1q When formula (17) is set, the motor rotation electrical angle frequency ω r is set as follows. 1. The range of RPM used. 2. Accuracy of rotation speed detection. For example, the motor rotation electrical angular frequency ω r The frequency threshold is set to the rotation speed at which torque accuracy is required plus the rotation speed detection accuracy.

[0071] Motor rotation electrical angular frequency ω r The frequency threshold of ω in Eq. (17) r The calculated value is the q-axis current detection value I 1q is the current threshold.

[0072] q-axis current detection value I 1q After setting the motor rotation electrical angular frequency ω r When formula (16) is set, the q-axis current detection value I 1q is set as follows. 1. The minimum q-axis current required for the required torque. 2. Current detection accuracy.

[0073] For example, the q-axis current detection value I 1q The current threshold sets the minimum q-axis current + current detection accuracy required for the required torque.

[0074] q-axis current detection value I 1q The current threshold is expressed as I 1q The motor rotation electrical angular frequency ω r The frequency threshold is set to be .

[0075] Here, the q-axis current detection value I 1q The torque command value T(=Torque * ) can be replaced with the q-axis current detection value I 1q and the torque command value T are related by the following equation (19). That is, the q-axis current command value I 1q * should be replaced with the q-axis current I1 obtained by equation (19).

[0076]

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[0077] Here, T is the torque command value, K tiq : Torque command value-q-axis current command conversion coefficient.

[0078] This makes it possible to ensure torque accuracy within a required operating range while implementing stable operation.

[0079] As described above, according to the first embodiment, secondary resistance variation compensation is performed to prevent deterioration of torque accuracy due to variation in secondary resistance. In this secondary resistance variation compensation method, it is necessary to set the point where the gain polarity switches as a dead band, but by appropriately setting the dead band processing, highly accurate torque control can be performed.

[0080] [Embodiment 2] Since the constant output range is not fully taken into consideration in the first embodiment, the second embodiment extends the constant output range and appropriately sets the dead band.

[0081] The configuration of the control device for the induction motor in the second embodiment is shown in FIG. * Input the torque command value Torque * The other parts are the same as those in the first embodiment, so the description thereof will be omitted.

[0082] Fig. 5 shows the secondary resistance variation compensation processing unit 14 in the present embodiment 2. The primary voltage detection value calculation unit 20, the primary voltage theoretical value calculation unit 21, the third subtractor 22, the first switch 23, the secondary resistance compensator 24, and the third comparator 29 are similar to those in Fig. 3 of the first embodiment, and therefore will not be described here.

[0083] The second divider 28 divides the base rotational angular velocity into the motor rotational electrical angular frequency ω r The third comparator 29 divides the motor rotation electrical angular frequency ω r Compare the base rotational angular velocity and the motor rotational electrical angular frequency ω r is greater, it outputs 1, and otherwise outputs 0. The second switch 30 outputs the output of the second divider 28 when the output of the third comparator 29 is 1, and outputs 1 when the output of the third comparator 29 is 0.

[0084] The fourth multiplier 31 multiplies the torque threshold value by the output of the second switch 30 and outputs a correction torque threshold value. The fourth comparator 32 multiplies the correction torque threshold value by the torque command value Torque * and the torque command value Torque * is smaller than the correction torque threshold value, it outputs 1, and otherwise outputs 0. The second AND circuit 33 outputs 1 when the outputs of the fourth and second comparators 32, 26 are both 1.

[0085] As shown in FIG. 5, a fourth multiplier 31 multiplies the torque command value Torque *The torque threshold value is multiplied by the coefficient K1 in equation (20).

[0086]

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[0087] Here, ω rbase is the base rotation angular velocity.

[0088] Motor rotation electrical angular frequency ω r and the torque command value Torque * When is smaller than the frequency threshold and the correction torque threshold, the input to the secondary resistance compensator 24 is set to zero.

[0089] Torque command value * In the case where the dead zone processing is performed at the base rotation angular velocity ω rbase In the above range, the relationship between the q-axis current and the torque command is no longer expressed by equation (19).

[0090] Base rotational angular velocity ω rbase In the above, in order to reduce the secondary magnetic flux, the d-axis current command value is controlled as shown in equation (21).

[0091]

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[0092] Here, I 1dbase : d-axis current command value below the base rotation speed.

[0093] Above the base rotation speed, the q-axis current command value I 1q is controlled as shown in equation (22).

[0094]

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[0095] The q-axis current command value I 1q *In order to obtain the same effect as when using the above, it is necessary to multiply the torque threshold value by the coefficient K1 in the equation (20) to obtain a corrected torque threshold value.

[0096] As a result, even when the torque command value is used for dead-band processing, appropriate compensation for secondary resistance fluctuations is possible at or above the base rotation speed, making it possible to implement highly accurate torque control.

[0097] As described above, according to the second embodiment, the dead-zone processing is performed using the torque command value while achieving the same effect as the first embodiment. In this case, the secondary resistance variation compensation can be performed by appropriately setting the correction torque threshold value even in the constant output range.

[0098] [Embodiment 3] The overall configuration diagram of the control device for an induction motor in the third embodiment is omitted since it is the same as that in the first and second embodiments.

[0099] 6 shows the secondary resistance variation compensation processing unit 14 in the third embodiment. The primary voltage detection value calculation unit 20, the primary voltage theoretical value calculation unit 21, the third subtractor 22, the first switch 23, and the secondary resistance compensator 24 are the same as those in the first and second embodiments, and therefore the description thereof will be omitted. 1q * The current threshold to be compared with is the motor rotation electrical angular frequency ω r The table 34 stores a value calculated in advance according to the motor rotation electrical angle frequency ω r The current threshold value according to the

[0100] The fourth comparator 35 is a comparator that converts the current threshold value output from the table 34 into a q-axis current command value I 1q * The q-axis current command value I 1q * When is smaller than the current threshold, it outputs 1, and otherwise outputs 0.

[0101] q-axis current command value I 1q *Since the formula (17) is complicated, continuous calculation of the motor rotational electrical angular frequency ω requires complicated processing. r If is known, the d-axis current I 1d Also, if the compensation range for secondary resistance fluctuations is estimated according to the operating application, it can be calculated in advance.

[0102] The current threshold is set to multiple motor rotation electrical angular frequencies ω r The motor rotation electrical angular frequency ω is calculated and set as a table. r The number of set points may be set according to the rotation speed and torque accuracy required for the application.

[0103] This makes it possible to set appropriate threshold values ​​for each operating condition with a simple configuration without constantly performing complex calculations.

[0104] As described above, according to the third embodiment, it is possible to perform secondary resistance variation compensation with higher accuracy than the first and second embodiments, although the configuration is simple, without performing complex calculation processing.

[0105] Although the present invention has been described in detail above only with respect to the specific examples, it will be apparent to those skilled in the art that various modifications and variations are possible within the scope of the technical concept of the present invention, and it is natural that such modifications and variations fall within the scope of the claims. [Explanation of symbols]

[0106] 1...Magnetic flux current command value calculation section 2...Torque current command value calculation section 3, 4...1st and 2nd subtractors 5, 6…Current controller 7...PWM inverter 8…Current detector 9...Three-phase to two-phase converter 10...Slip calculation section 11...Speed ​​detector 12...First adder 13...Integrator 14...Secondary resistance fluctuation compensation processing unit IM…Induction motor pp...Rotational position detection section

Claims

1. A control device for an induction motor that drives and controls an induction motor, a magnetic flux current command value calculation unit that outputs a d-axis current command value based on the magnetic flux command value; a torque current command value calculation unit that outputs a q-axis current command value based on the torque command value; a current control unit that outputs a d-axis voltage command value and a q-axis voltage command value based on a deviation between the d-axis current command value and the d-axis current detection value and a deviation between the q-axis current command value and the q-axis current detection value; a PWM inverter that outputs a voltage to the induction motor by PWM control based on the d-axis voltage command value, the q-axis voltage command value, and a power supply phase; a current detector for detecting a current detection value output from the PWM inverter; a three-phase to two-phase converter for converting the current detection value into the d-axis current detection value and the q-axis current detection value based on the power supply phase; A rotational position detection unit that detects a rotational position of the induction motor; a speed detector that outputs a motor rotation electrical angular frequency based on the rotation position; a first adder that adds the motor rotation electrical angular frequency to the slip angular frequency to output a power supply angular frequency; an integrator that integrates the power supply angular frequency and outputs the power supply phase; a secondary resistance variation compensation processing unit that outputs 0 as a slip frequency correction coefficient when the motor rotational electrical angular frequency is smaller than a frequency threshold value and the q-axis current command value or the q-axis current calculated from the torque command value is smaller than a current threshold value, and otherwise outputs a slip frequency correction coefficient based on a difference between a primary voltage detection value and a primary voltage theoretical value; a slip calculation unit that outputs a slip angular frequency based on the d-axis current command value, the q-axis current command value, and the slip frequency correction coefficient; Equipped with The secondary resistance variation compensation processing unit includes: a primary voltage detection value calculation unit that outputs a primary voltage detection value according to the following equation (6) based on the d-axis voltage command value and the q-axis voltage command value; a primary voltage theoretical value calculation unit that outputs the primary voltage theoretical value according to the following equations (7) to (9) on the basis of the power supply angular frequency, the d-axis current command value, and the q-axis current command value; a third subtractor that outputs a deviation between the detected primary voltage value and the theoretical primary voltage value; a first comparator that compares the q-axis current command value or the q-axis current calculated from the torque command value with a current threshold value, and outputs 1 when the q-axis current command value or the q-axis current is smaller than the current threshold value, and outputs 0 otherwise; a second comparator that compares the motor rotational electrical angle frequency with the frequency threshold and outputs 1 when the motor rotational electrical angle frequency is smaller than the frequency threshold, and outputs 0 otherwise; a first AND circuit that outputs 1 when the outputs of the first comparator and the second comparator are both 1, and outputs 0 otherwise; a first switch that outputs 0 when the output of the first AND circuit is 1 and outputs the output of the third subtractor when the output of the first AND circuit is 0; a secondary resistance compensator that performs PI control based on an output of the first switch and outputs the slip frequency correction coefficient; Equipped with The slip calculation unit is a first multiplier that multiplies the q-axis current command value by a secondary resistance of a T-type equivalent circuit; a second multiplier that multiplies the d-axis current command value by a mutual inductance of a T-type equivalent circuit; a first divider for dividing the output of the first multiplier by the output of the second multiplier; a third multiplier that multiplies the output of the first divider by the slip frequency correction coefficient; a second adder that adds an output of the first divider and an output of the third multiplier and outputs the slip angular frequency; Equipped with 13. A control device for an induction motor, comprising: a control circuit for controlling a drive of the induction motor, the control circuit using the slip angular frequency. [006] [0070] [0080] [0090] V1det: Primary voltage detection value V1d*: d-axis voltage command value V1q*: q-axis voltage command value V 1d : d-axis voltage theoretical value V 1q: q-axis voltage theoretical value R1: Primary resistance I1d*: d-axis current command value I1q*: q-axis current command value ω 1: Power source angular frequency L s : Excitation inductance of the T-I type equivalent circuit M': Mutual inductance of the T-I type equivalent circuit V1: Primary voltage theoretical value

2. A control device for an induction motor that drives and controls an induction motor, a magnetic flux current command value calculation unit that outputs a d-axis current command value based on the magnetic flux command value; a torque current command value calculation unit that outputs a q-axis current command value based on the torque command value; a current control unit that outputs a d-axis voltage command value and a q-axis voltage command value based on a deviation between the d-axis current command value and the d-axis current detection value and a deviation between the q-axis current command value and the q-axis current detection value; a PWM inverter that outputs a voltage to the induction motor by PWM control based on the d-axis voltage command value, the q-axis voltage command value, and a power supply phase; a current detector for detecting a current detection value output from the PWM inverter; a three-phase to two-phase converter for converting the current detection value into the d-axis current detection value and the q-axis current detection value based on the power supply phase; A rotational position detection unit that detects a rotational position of the induction motor; a speed detector that outputs a motor rotation electrical angular frequency based on the rotation position; a first adder that adds the motor rotation electrical angular frequency to the slip angular frequency to output a power supply angular frequency; an integrator that integrates the power supply angular frequency and outputs the power supply phase; a secondary resistance variation compensation processing unit that varies a torque threshold value according to the motor rotational electrical angle frequency to set a correction torque threshold value when the motor rotational electrical angle frequency is equal to or higher than a base rotational angular velocity, outputs 0 as a slip frequency correction coefficient when the motor rotational electrical angle frequency is smaller than the frequency threshold value and the torque command value is smaller than the correction torque threshold value, and otherwise outputs a slip frequency correction coefficient based on a difference between a primary voltage detection value and a primary voltage theoretical value; a slip calculation unit that outputs a slip angular frequency based on the d-axis current command value, the q-axis current command value, and the slip frequency correction coefficient; Equipped with The secondary resistance variation compensation processing unit includes: a primary voltage detection value calculation unit that outputs a primary voltage detection value according to the following equation (6) based on the d-axis voltage command value and the q-axis voltage command value; a primary voltage theoretical value calculation unit that outputs the primary voltage theoretical value according to the following equations (7) to (9) on the basis of the power supply angular frequency, the d-axis current command value, and the q-axis current command value; a third subtractor that outputs a deviation between the detected primary voltage value and the theoretical primary voltage value; a second comparator that compares the motor rotational electrical angle frequency with the frequency threshold and outputs 1 when the motor rotational electrical angle frequency is smaller than the frequency threshold, and outputs 0 otherwise; a second divider that divides the base rotational angular velocity by the motor rotational electrical angular frequency; a third comparator that compares the motor rotational electrical angular frequency with the base rotational angular velocity, and outputs 1 if the motor rotational electrical angular frequency is equal to or greater than the base rotational angular velocity, and outputs 0 otherwise; a second switch that outputs the output of the second divider when the output of the third comparator is 1 and outputs 1 when the output of the third comparator is 0; a fourth multiplier that multiplies a torque threshold value and an output of the second switch to output the corrected torque threshold value; a fourth comparator that compares the correction torque threshold value with the torque command value, and outputs 1 when the torque command value is smaller than the correction torque threshold value, and outputs 0 otherwise; a second AND circuit that outputs 1 when the outputs of the second comparator and the fourth comparator are both 1, and outputs 0 otherwise; a first switch that outputs 0 when the output of the second AND circuit is 1, and outputs the output of the third subtractor when the output of the second AND circuit is 0; a secondary resistance compensator that performs PI control based on an output of the first switch and outputs the slip frequency correction coefficient; Equipped with The slip calculation unit is a first multiplier that multiplies the q-axis current command value by a secondary resistance of a T-type equivalent circuit; a second multiplier that multiplies the d-axis current command value by a mutual inductance of a T-type equivalent circuit; a first divider for dividing the output of the first multiplier by the output of the second multiplier; a third multiplier that multiplies the output of the first divider by the slip frequency correction coefficient; a second adder that adds an output of the first divider and an output of the third multiplier and outputs the slip angular frequency; Equipped with 13. A control device for an induction motor, comprising: a control circuit for controlling a drive of the induction motor, the control circuit using the slip angular frequency. [006] [0070] [0080] [0090] V1det: Primary voltage detection value V1d*: d-axis voltage command value V1q*: q-axis voltage command value V 1d : d-axis voltage theoretical value V 1q: q-axis voltage theoretical value R1: Primary resistance I1d*: d-axis current command value I1q*: q-axis current command value ω 1: Power source angular frequency L s : Excitation inductance of the T-I type equivalent circuit M': Mutual inductance of the T-I type equivalent circuit V1: Primary voltage theoretical value

3. A control device for an induction motor that drives and controls an induction motor, a magnetic flux current command value calculation unit that outputs a d-axis current command value based on the magnetic flux command value; a torque current command value calculation unit that outputs a q-axis current command value based on the torque command value; a current control unit that outputs a d-axis voltage command value and a q-axis voltage command value based on a deviation between the d-axis current command value and the d-axis current detection value and a deviation between the q-axis current command value and the q-axis current detection value; a PWM inverter that outputs a voltage to the induction motor by PWM control based on the d-axis voltage command value, the q-axis voltage command value, and a power supply phase; a current detector for detecting a current detection value output from the PWM inverter; a three-phase to two-phase converter for converting the current detection value into the d-axis current detection value and the q-axis current detection value based on the power supply phase; A rotational position detection unit that detects a rotational position of the induction motor; a speed detector that outputs a motor rotation electrical angular frequency based on the rotation position; a first adder that adds the motor rotation electrical angular frequency to the slip angular frequency to output a power supply angular frequency; an integrator that integrates the power supply angular frequency and outputs the power supply phase; a secondary resistance variation compensation processing unit that outputs 0 as a slip frequency correction coefficient when the q-axis current command value is smaller than a current threshold value obtained from a table based on the motor rotational electrical angular frequency, and otherwise outputs a slip frequency correction coefficient based on a difference between a primary voltage detection value and a primary voltage theoretical value; a slip calculation unit that outputs a slip angular frequency based on the d-axis current command value, the q-axis current command value, and the slip frequency correction coefficient; Equipped with The secondary resistance variation compensation processing unit includes: a primary voltage detection value calculation unit that outputs a primary voltage detection value according to the following equation (6) based on the d-axis voltage command value and the q-axis voltage command value; a primary voltage theoretical value calculation unit that outputs the primary voltage theoretical value according to the following equations (7) to (9) on the basis of the power supply angular frequency, the d-axis current command value, and the q-axis current command value; a third subtractor that outputs a deviation between the detected primary voltage value and the theoretical primary voltage value; the table for outputting the current threshold value based on the motor rotational electrical angular frequency; a fourth comparator that compares the current threshold value with the q-axis current command value, and outputs 1 when the q-axis current command value is smaller than the current threshold value, and outputs 0 otherwise; a first switch that outputs 0 when the output of the fourth comparator is 1 and outputs the output of the third subtractor when the output of the fourth comparator is 0; a secondary resistance compensator that performs PI control based on an output of the first switch and outputs the slip frequency correction coefficient; Equipped with The slip calculation unit is a first multiplier that multiplies the q-axis current command value by a secondary resistance of a T-type equivalent circuit; a second multiplier that multiplies the d-axis current command value by a mutual inductance of a T-type equivalent circuit; a first divider for dividing the output of the first multiplier by the output of the second multiplier; a third multiplier that multiplies the output of the first divider by the slip frequency correction coefficient; a second adder that adds an output of the first divider and an output of the third multiplier and outputs the slip angular frequency; Equipped with 13. A control device for an induction motor, comprising: a control circuit for controlling a drive of the induction motor, the control circuit using the slip angular frequency. [006] [0070] [0080] [0090] V1det: Primary voltage detection value V1d*: d-axis voltage command value V1q*: q-axis voltage command value V 1d : d-axis voltage theoretical value V 1q: q-axis voltage theoretical value R1: Primary resistance I1d*: d-axis current command value I1q*: q-axis current command value ω 1: Power source angular frequency L s : Excitation inductance of the T-I type equivalent circuit M': Mutual inductance of the T-I type equivalent circuit V1: Primary voltage theoretical value

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