JP4619712B2 - AC motor control device - Google Patents

Description

  The present invention relates to a control device for a three-phase AC motor.

  Generally, a control device that controls a three-phase AC motor to a desired speed includes a converter device that converts three-phase AC to DC, a smoothing capacitor for the DC output of the converter device, and in parallel with the smoothing capacitor on the converter device output side. The inverter apparatus which is installed and reconverts the direct-current power of a converter apparatus into a three-phase alternating current is provided, and a three-phase alternating current motor is driven by the alternating current output of an inverter apparatus.

  In addition, in order to control the three-phase AC motor, a current detector that detects the currents of the U, V, and W phases of the three-phase AC motor and a position detector that detects the rotor position of the three-phase AC motor are provided. Thus, the rotor speed feedback signal is obtained by time-differentiating the output of the position detector with a differentiator. Then, for the given speed command, the adder calculates the speed deviation between the speed feedback signal from the differentiator and the speed command, and the current command generator calculates the speed deviation from the adder and the current speed signal. From this, a two-phase current command value by vector control is created.

  On the other hand, the current of each phase of the three-phase AC motor detected by the current detector is converted into a digital signal by the A / D converter. In order to perform vector control, the signal of the position detector is converted by the coordinate converter. Three-phase / two-phase conversion is performed on the control coordinate axis. The adder calculates the deviation between the two-phase current command output from the current command generator and the two-phase current feedback signal from the coordinate converter, and this deviation is amplified by the current controller. Is output. The output from the current controller is two-phase / three-phase converted by a coordinate converter to create a three-phase voltage command signal, which is converted to a switching signal by a PWM signal generator. This is input to the gate drive circuit to create a drive signal, and the semiconductor power element in the inverter device is switched at a predetermined duty ratio by this drive signal, thereby outputting the desired three-phase AC power to the three-phase AC motor. Like to do.

  In such a general three-phase AC motor control device, if there is an imbalance in the conversion gain of the current detector and the A / D converter, an imbalance occurs between the phases of the three-phase current flowing through the motor. In some cases, pulsation was caused in the torque of the electric motor.

  As a control device for a three-phase motor for solving the above-mentioned problem, among the detected current values of each phase of the three-phase AC motor, one phase is used as a reference phase, and only this reference phase and the other one-phase winding are used. A predetermined direct current flows, and from each current detection value at this time, a ratio between the current phase detection gain of the reference phase and the current detection gain of the other one phase is obtained, and the reference phase and another one phase lead wire The ratio of the reference phase current detection gain to another one-phase current detection gain is obtained from the current detection value at this time, and the obtained conversion gain ratio is obtained during operation of the motor. Is used to calculate a correction coefficient of the current detection value and multiply this coefficient to correct the imbalance of the current detection gain (see, for example, Patent Document 1).

  By the way, in the control apparatus for the conventional AC motor described above, for example, when obtaining a correction coefficient for the V-phase current conversion gain, a PWM signal is used so that a predetermined direct current flows only through the U-phase and V-phase windings. It is supposed to set the input to the generator. However, if there is a difference in the resistance values of the U-phase and V-phase windings, or if there is an error between the voltage command and the voltage output from the inverter device, the voltage having the same magnitude but the opposite sign Even if is added between the U phase and V phase of the AC motor, the current flowing in the W phase cannot be reduced to 0. To reduce the current flowing in the W phase to 0, PWM is performed while observing the W phase current. There was a problem that the voltage command to the signal generator had to be finely adjusted, and the work was complicated.

  Therefore, in order to cope with such a problem, even when there is a difference in resistance value between windings of the AC motor, or when there is an error between the voltage command and the voltage output from the inverter device, the voltage is reduced. There is a control device for an AC motor that can obtain a correction coefficient of a current conversion gain without adjustment (see, for example, Patent Document 2).

JP-A-5-91780 (first page, FIG. 1) JP 2004-135407 A (first page, FIG. 1)

  However, the prior art has the following problems. In the control apparatus for an AC motor in Patent Document 2, it is assumed that the conversion gain imbalance of the current detector is fixed without depending on the feedback current, and correction of the current conversion gain corresponding to a certain type of current value is performed. Only one coefficient was obtained. However, if the conversion gain imbalance differs depending on the magnitude of the feedback current value, even if correction is performed with a fixed correction coefficient determined as one type, depending on the feedback current value, the correction value and the actual gain Since the unbalance is different, there is a problem that it is difficult to reduce torque pulsation.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to obtain an AC motor control device that can reduce torque pulsation without depending on the magnitude of the feedback current value.

A control device for an AC motor according to the present invention includes a converter device that converts AC power into DC power, an inverter device that converts the DC power of the converter device into AC of variable voltage and variable frequency, and supplies the AC power to the AC motor, and the AC motor The position detector that detects the rotor position of the current, the current detector that detects each phase current output from the inverter device, and the detection value detected by the current detector is multiplied by a correction coefficient to correct the current detection value. Corrected by a correction means, a coefficient calculator for calculating a correction coefficient based on a calculation command from the outside, a PWM signal generator for generating a signal for PWM control of the inverter device based on a voltage command, and a correction means A control unit that outputs a voltage command obtained by converting the detected current value into a three-phase voltage command signal to the PWM signal generator, and the control unit receives an external signal during normal operation. The voltage command based on the degree command and the detection signal of the position detector is output to the PWM signal generator. When the calculation command is input from the outside, the voltage command based on the measurement value of the correction coefficient output from the coefficient calculator The signal calculator switches the signal processing so as to output to the PWM signal generator, and when calculating the correction coefficient of a certain phase, the coefficient calculator, in addition to the current detection values of that phase and the reference phase, In the control apparatus for an AC motor that performs calculation using also the current detection value of the phase, the coefficient calculator has a storage unit that stores the correction coefficient measurement value and the correction coefficient in association with each other. When calculating the correction coefficient, output multiple different values to the control unit as the correction coefficient measurement values, and determine the correction coefficient from each phase current detected by the current detector according to the multiple different values. generating a value table serial in the storage unit Is, during normal operation, to detect a current detection value of the reference phase, it is calculated on the basis of the correction value table stored correction coefficient in the storage unit corresponding to the detected current value, depending on the magnitude of the current detected value The correction coefficient of the correction means is changed by the correction coefficient calculated in the above.

  According to the present invention, by calculating a correction coefficient corresponding to a plurality of different current values in advance by a coefficient calculator for calculating a correction coefficient for correcting the detected current value, the magnitude of the feedback current value is obtained. Accordingly, the current conversion gain correction coefficient is set to correct the gain imbalance, so that it is possible to obtain an AC motor control device that can accurately reduce torque pulsation without depending on the magnitude of the feedback current value.

  Hereinafter, preferred embodiments of an AC motor control device of the present invention will be described with reference to the drawings. The AC motor control device according to the present invention obtains a correction coefficient for correcting the current detection value of the current detector for a plurality of different current values when the inverter is not performing normal operation. When performing normal operation, the gain imbalance is corrected by setting a current conversion gain correction coefficient in accordance with the magnitude of the feedback current value. In addition, as an application of the control apparatus of an AC motor, application to an elevator is described as an example.

Embodiment 1 FIG.
FIG. 1 is a block diagram showing a configuration of a control device for an AC motor according to Embodiment 1 of the present invention. As shown in FIG. 1, the control device that controls the three-phase AC motor to a desired speed includes a converter device 2 that converts the three-phase AC 1 into DC, a smoothing capacitor 3 that smoothes the DC output of the converter device 2, The inverter device 4 is provided in parallel with the smoothing capacitor 3 on the output side of the converter device 2 and reconverts the DC power of the converter device 2 into three-phase AC. The AC output of the inverter device 4 drives a three-phase AC motor 5, for example, a synchronous motor such as a permanent magnet motor.

  In addition, as control devices for controlling the three-phase AC motor 5, current detectors 10a, 10b, and 10c that detect currents of U, V, and W phases of the three-phase AC motor 5, and the three-phase AC motor 5 A position detector 11 for detecting the rotor position is provided. The output of the position detector 11 is time-differentiated by the differentiator 12 to obtain a rotor speed feedback signal. Further, a speed deviation from the speed feedback signal from the differentiator 12 is calculated by the adder 13a with respect to the given motor speed command. Further, the current command generator 14 generates a two-phase current command value by vector control from the speed deviation from the adder 13 a and the speed feedback signal from the differentiator 12.

  On the other hand, the current of each phase of the three-phase AC motor 5 detected by the current detectors 10a, 10b, and 10c is converted into a digital signal by the A / D converters 15a, 15b, and 15c. The outputs of the A / D converters 15b and 15c are multiplied by correction coefficients Kv and Kw by correction calculators 21a and 21b as correction means. In order to perform vector control, the output of the A / D converter 15a and the outputs of the A / D converters 15b and 15c via the correction calculators 21a and 21b are converted into three-phase / two by the coordinate converter 16. Phase converted.

  In addition, a current sensor gain coefficient calculator 22 that measures and calculates the correction coefficients Kv and kw of the correction calculators 21a and 21b according to an external current sensor gain coefficient calculation command is provided. Further, the current sensor gain coefficient calculator 22 receives a predetermined torque current command and a zero command of the reactive current as current command values for measuring the correction coefficient of the current detection gain in response to an external current sensor gain coefficient calculation command. Generate.

  Further, a current command value given to the adders 13b and 13c in response to an external current sensor gain coefficient calculation command is obtained from the two-phase current command value generated by the current command generator 14 by the current sensor gain coefficient calculator 22. A signal switch 23a for switching to the generated two-phase current command value for measurement is provided. In the normal driving operation, since the current sensor gain coefficient calculation command is not given, the signal switch 23a gives the two-phase current command value generated by the current command generator 14 to the adders 13b and 13c.

  The adders 13b and 13c calculate a deviation between the two-phase current command output from the signal switch 23a and the two-phase current feedback signal from the coordinate converter 16. These deviations are amplified and output by current controllers 17a and 17b, respectively. The outputs from the current controllers 17a and 17b are two-phase / three-phase converted by the coordinate converter 18 to generate a three-phase voltage command signal.

  In addition, the coordinate converter 16 and the coordinate converter 18 are configured to generate a current sensor gain coefficient from a rotor electrical angle, which is an output signal of the position detector 11 used during normal operation, according to an external current sensor gain coefficient calculation command. A signal switch 23b for switching to the control electrical angle phase of the inverter generated by the calculator 22 is provided. The control electrical angle phase generated by the current sensor gain coefficient calculator 22 will be described later with reference to FIG.

  The voltage command via the coordinate converter 18 is input to the PWM signal generator 19 and converted into a switching signal. This switching signal is input to the gate drive circuit 20 to generate a drive signal. A desired three-phase AC power is output to the three-phase AC motor 5 by switching the semiconductor power element in the inverter device 4 at a predetermined duty ratio by this drive signal.

  The sheave 24 is driven by the rotational output of the three-phase AC motor 5, and the elevator car 25 and the counter 26 move up and down. The elevator car 25 is required to perform stable speed control with reduced torque pulsation with respect to various load conditions such as a load depending on the number of passengers in the car or a moving speed during ascent and descent.

  In the above configuration, the control device in the portion surrounded by the one-dot chain line shown in FIG. 1 is a digital circuit including a CPU, a memory, a logic circuit, etc. (all not shown), and software installed in the circuit. It is often realized by.

  According to the control device for the three-phase AC motor shown in FIG. 1 configured as described above, one phase (for example, the U phase) among the detected current values of each phase of the three-phase AC motor is used as the reference phase. In addition, a predetermined direct current flows only through the other one-phase (for example, V-phase) winding. From each current detection value at this time, the ratio of the current detection gain of the reference phase and the current detection gain of the other one phase is calculated. Ask. In addition, a predetermined direct current flows only through the reference phase and another one phase (for example, W phase) conductor, and from the current detection value at this time, the current detection gain of the reference phase and another one phase of the other phase Find the ratio of the current detection gain.

  Further, in the present application, a plurality of different current values are set as predetermined DC currents, correction coefficients for the respective current values are obtained and stored, and when the motor is operated, a current detection value of the reference phase is detected, A correction coefficient corresponding to the current detection value is calculated based on the data in the storage unit, and the correction coefficient is multiplied to correct the current detection gain imbalance.

  That is, in the control device shown in FIG. 1, correction arithmetic units 21a and 21b that correct the detected current value by multiplying the outputs of the A / D converters 15b and 15c by the correction coefficients Kv and Kw, and correction of the current detection gain. Current sensor gain coefficient calculator 22 that performs measurement and calculation of correction coefficients Kv and Kw by a current sensor gain coefficient calculation command that instructs measurement of the coefficient, and current that is applied to adders 13b and 13c by current sensor gain coefficient calculation command A signal switch 23 a for switching the command value from the two-phase current command value generated by the current command generator 14 to the two-phase current command value for measurement generated by the current sensor gain coefficient calculator 22, The electrical angle signal given to the coordinate converter 16 and the coordinate converter 18 in accordance with the current sensor gain coefficient calculation command is transmitted from the position detector 11 used during normal operation. From the rotor position is the force signal, the signal switch 23b for switching the control electrical angle phase inverter produced by the current sensor gain factor calculator 22 is added.

  In a normal driving operation, the current sensor gain coefficient calculation command is not given, so the signal switch 23a gives the two-phase current command values generated by the current command generator 14 to the adders 13b and 13c, and the switch 23b The rotor position as an output signal of the position detector 11 is supplied to the coordinate converter 16 and the coordinate converter 18 as an electrical angle signal.

  At this time, in the control device shown in FIG. 1, the outputs of the A / D converters 15b and 15c are multiplied by the correction coefficients Kv and Kw by the correction calculators 21a and 21b, and the V with respect to the U phase which is the reference phase. , W-phase current detection and A / D conversion gain imbalance are corrected, and vector control is performed based on the corrected current value.

  Furthermore, the current sensor gain coefficient calculator 22 in the present invention further includes a correction value table for storing a predetermined current value for measuring a correction coefficient and a correction coefficient in association with each other, and a current sensor gain coefficient calculation command from the outside. , The correction coefficients Kv and Kw corresponding to a plurality of predetermined current values are obtained and stored in the correction value table. In a normal driving operation in which a current sensor gain coefficient calculation command is not given, the current sensor gain coefficient calculator 22 receives a U-phase feedback current as a reference phase via the current detector 10a and the A / D converter 15a. The values are read, correction coefficients Kv and Kw corresponding to the feedback current values are obtained based on the data stored in the correction value table, and the correction coefficients are set in the correction calculators 21a and 21b, respectively.

  In this manner, the control device shown in FIG. 1 can generate a corrected current detection value by employing an appropriate correction coefficient in accordance with the feedback current value of the reference phase in a normal driving operation. By controlling the current using a three-phase two-phase conversion of the corrected current detection value by the coordinate converter 16 as a feedback signal, the current detector value of each phase depends on the feedback current value of the reference phase. The difference in conversion gain is eliminated, current imbalance is eliminated without depending on the magnitude of the feedback current value, and torque pulsation can be reduced.

  Next, the control electrical angle phase generated by the current sensor gain coefficient calculator 22 in order to calculate the correction coefficients Kv and Kw will be described. FIG. 2 is a diagram showing the relationship between the rotor electrical angle and each phase current when the d-axis current 0 control often used in the control of the normal synchronous motor is performed in the first embodiment of the present invention. As shown in FIG. 2, near the timing 1 (electrical angle of 60 °), current flows in the U phase and the V phase, and almost no current flows in the W phase, and near the timing 2 (electrical angle of 120 °) It can be seen that current flows in the U phase and the W phase and almost no current flows in the V phase.

  When the rotor electrical angle is fixed at these timings and a predetermined torque current command is given, a DC current of opposite sign flows in the two phases of the permanent magnet synchronous motor, and almost no current flows in the remaining one phase. It becomes possible to be in a state. In the above description, the timing for detecting each phase current is set to two electrical angles of 60 ° and 120 °. However, the same timing appears at electrical angles of 240 ° and 300 °, and the latter timing is also effective. Is the same. Therefore, the current sensor gain coefficient calculator 22 sets the electrical angle as described above as the control electrical angle phase of the inverter when calculating the correction coefficients Kv and Kw.

Next, the operation when measuring the correction coefficient of the current detection gain will be described. First, the relationship between the digital signal values Xu, Xv, and Xw of the current flowing in each phase of the AC motor 5 at a certain moment and the current conversion gains Kv and Kw will be examined. In a general three-phase AC motor in which the neutral point is not connected to the outside, Expression (1) is established for the currents Iu, Iv, and Iw of each phase.
Iu + Iv + Iw = 0 (1)

When the current value of each phase is digitally converted, an error due to detection / conversion occurs as described above. For example, with reference to the U-phase digital conversion gain, the correction coefficient of the V and W-phase current conversion gain is set to Kv. , Kw, Equation (2) is established between the signal values after digital conversion.
Xu + Kv.Xv + Kw.Xw = 0 (2)

Thus, the following equations (3-1) and (3-2) hold between the digital signal values of each phase current at a certain moment (timing 1) and another moment (timing 2) (subscript 1 is Timing 1 signal, subscript 2 represents timing 2 signal).
Xu1 + Kv.Xv1 + Kw.Xw1 = 0 (3-1)
Xu2 + Kv.Xv2 + Kw.Xw2 = 0 (3-2)

  In the above equations (3-1) and (3-2), there are two unknowns, Kv and Kw. Therefore, Kv and Kw can be obtained by solving the two equations simultaneously. In this case, since it is not necessary to make the current of any phase zero during measurement, it is not necessary to finely adjust the voltage command to the PWM signal generator 19.

  Next, a specific method for obtaining the current conversion gain correction coefficients Kv and Kw from Equations (3-1) and (3-2) will be described.

  If the expressions (3-1) and (3-2) are arranged and expressed in a matrix, they can be expressed as the expression (4).

  Equation (4) is transformed to obtain equation (5).

  If the above equation (5) is used, the current conversion gain correction coefficients Kv, Kw are obtained from the digital signal values (Xu1, Xv1, Xw1) and (Xu2, Xv2, Xw2) of two sets of phase currents at two timings. Can be requested. The inverse matrix on the right side of Equation (5) is specifically expressed by Equation (6).

  Here, if an error with a constant magnitude is mixed in each digital signal value due to measurement noise or the like, if the current flowing in the U phase is the same, paying attention to the calculation accuracy of Kv and Kw obtained by Equation (5) It can be seen that the larger the denominator on the right side of Equation (6), the less the influence of the error. This is because the current flows between the U phase and the V phase and hardly flows in the W phase (timing 1), and the current flows between the U phase and the W phase and hardly flows in the V phase ( This shows that the calculation accuracy of the current conversion gain correction coefficients Kv and Kw is improved when two sets of digital signal values at timing 2) are used.

  Next, correction coefficient calculation processing will be described with reference to the flowchart shown in FIG. FIG. 3 is a flowchart showing the operation of the current sensor gain coefficient calculator 22 when obtaining the correction coefficient of the current conversion gain in the AC motor control apparatus according to Embodiment 1 of the present invention.

  First, in step S301, the current sensor gain coefficient calculator 22 outputs a measurement two-phase current command value to the signal switch 23a to measure the current conversion gain correction coefficient, and controls the control electrical angle phase of the inverter. Is output to the signal switch 23b. In such an output state, by switching the signal switches 23a and 23b based on a current sensor gain coefficient calculation command from the outside, the control electrical angle phase is fixed, and the input to the PWM signal generator 19 is the U phase. In addition, it is possible to give a voltage setting value such that almost a predetermined direct current flows through the V-phase winding and almost no current flows through the W-phase winding. For example, a voltage command having the same magnitude and opposite signs is given to the U phase and the V phase, and a 0 voltage command is given to the W phase. This corresponds to the timing 1 in FIG.

  Next, in step S302, the current sensor gain coefficient calculator 22 converts the current flowing through the U-phase, V-phase, and W-phase windings detected by the current detectors 10a, 10b, and 10c into the A / D converter 15a. , 15b, and 15c are read as digital signal values, and the digital signal values are stored as Xu1 (U phase), Xv1 (V phase), and Xw1 (W phase), respectively.

  Next, in step S303, the current sensor gain coefficient calculator 22 causes a constant direct current to flow through the U-phase and W-phase windings in the same manner as in step S301. This corresponds to the timing 2 in FIG. Next, in step S304, the current sensor gain coefficient calculator 22 reads the currents flowing through the U-phase, V-phase, and W-phase windings as digital signal values in the same manner as in step S302, and each of the digital signal values is Xu2. (U phase), Xv2 (V phase), and Xw2 (W phase) are stored.

  Next, in step S305, the current sensor gain coefficient calculator 22 uses the values of Xu1, Xv1, Xw1 and Xu2, Xv2, Xw2 stored as digital signal values in the reference phase from the above equation (5). V phase and W phase correction coefficients Kv and Kw for a certain U phase are calculated.

  Next, in step S306, the current sensor gain coefficient calculator 22 stores the calculated correction coefficients Kv and Kw in the correction value table in association with the DC current values that are constant for the calculation. Next, in step S307, the current sensor gain coefficient calculator 22 determines whether or not the calculation of the correction coefficients Kv and Kw for the predetermined DC current value has been completed. If it is determined that the calculation has been completed, the process ends. On the other hand, if it is determined that it has not been completed, the process proceeds to step S308.

  In step S308, the current sensor gain coefficient calculator 22 changes the current value at the time of energization between U-V and U-W, and repeats the processing in steps S301 to S306 again to thereby obtain each predetermined current value. The conversion gain correction coefficient corresponding to is calculated and stored in the correction value table.

  Through the above operation, correction coefficients Kv and Kw corresponding to a plurality of predetermined current values are stored in the correction value table. FIG. 4 is a diagram showing a data structure of the correction value table in the first embodiment of the present invention. The correction value table includes predetermined current values (Iu1, Iu2, Iu3...) And corresponding correction coefficients (Kv (1), Kv (2), Kv) calculated by the current sensor gain coefficient calculator 22. (3) ..., Kw (1), Kw (2), Kw (3) ...).

  FIG. 5 is a graph showing the relationship between the current value and the correction coefficient based on the data stored in the correction value table of FIG. FIG. 5A is a plot of the correction coefficient Kv with respect to three points Iu1 to Iu3 that are predetermined current values, and FIG. 5B is a plot of the correction coefficient Kw. In FIG. 5A, the correction coefficient Kv for the current value equal to or less than the current value Iu1 is constant at Kv (1), and the correction coefficient Kv for the current value equal to or greater than the current value Iu3 is constant at Kv (3). Similarly, in FIG. 5B, the correction coefficient Kw for the current value equal to or lower than the current value Iu1 is constant at Kw (1), and the correction coefficient Kw for the current value equal to or higher than the current value Iu3 is constant at Kw (3). It is said.

  A series of processes as shown in FIG. 3 is performed in a conversion gain ratio calculation mode different from the normal traveling of the elevator based on an external current sensor gain coefficient calculation command. In the elevator normal travel, the current sensor gain coefficient calculator 22 corrects the set values of the correction coefficients Kv and Kw as follows based on the result of the calculated correction value table.

  The current sensor gain coefficient calculator 22 reads the U-phase feedback current value Iu during normal elevator travel as a digital signal value via the current detector 10a and the A / D converter 15a. Then, the current sensor gain coefficient calculator 22 can obtain an optimum correction coefficient corresponding to the feedback current value Iu based on the data stored in the correction value table. For example, as shown in FIG. 5A, when the U-phase feedback current value Iu is a value between a predetermined current value Iu1 and Iu2, the correction coefficient Kv corresponding to Iu is Kv ( 1) and Kv (2) can be obtained by linear interpolation. Similarly, as shown in FIG. 5B, the correction coefficient Kw corresponding to Iu can be obtained by linearly complementing the values of Kw (1) and Kw (2).

  The current sensor gain coefficient calculator 22 updates the correction coefficients set in the correction calculators 21a and 21b using the new correction coefficients Kv and Kw corresponding to the U-phase feedback current value Iu thus obtained. can do. As a result, an A / D conversion gain imbalance can be corrected using a correction coefficient corresponding to the U-phase feedback current value during normal elevator travel, and torque pulsation can be achieved by performing vector control using the corrected current value. Speed control with reduced can be realized.

  In addition, when using the current detector, an AC current that decays in time prior to use is flowed to perform a degaussing operation to remove the hysteresis of the magnetic circuit in the current detector, and further after the degaussing operation. In general, the detection output in the state of current 0 is stored, this value is used as an offset value for current detection, and the value obtained by subtracting the detection value at the time of actual measurement is used as the current detection value. Although these operations are not described in the embodiment of the present invention, the current detection and the current detection are performed also in the present invention by performing these operations before measuring the correction coefficient of the current detection gain. It goes without saying that the accuracy of the gain correction coefficient can be improved. Furthermore, it is a matter of course that the influence of noise can be reduced by processing the current detection value through an appropriate low-pass filter.

  In the above embodiment, when the current conversion gain correction coefficient is obtained, the current mainly flows in two phases of the three phases of the AC motor. However, Equation (5) indicates the magnitude of the current in each phase. Since it is established regardless of the above, it is a matter of course that the correction coefficient of the current conversion gain can be obtained even in any energized state. Further, in the above embodiment, the current detection value is measured by flowing a direct current, and the correction coefficient of the current conversion gain is obtained. However, the flowing current does not need to be a direct current and is low enough not to interfere with the measurement. An alternating current with a frequency may be used. Furthermore, in the above embodiment, the process shown in FIG. 3 is performed once to obtain a current conversion gain correction coefficient for a certain predetermined current value. However, the operation of FIG. 3 is performed a plurality of times. Needless to say, if the average value of the obtained correction coefficients for the plurality of current conversion gains is calculated, a correction coefficient for the current conversion gain with higher accuracy can be obtained.

  According to the first embodiment, when the current sensor gain coefficient calculator 22 calculates a correction coefficient of a certain phase, the current detection values of other phases are also used in addition to the current detection values of the phase and the reference phase. Since the calculation is performed, it is not necessary to make the current of any phase zero when measuring the correction coefficient, and it is not necessary to finely adjust the voltage command.

  Further, when the conversion gain imbalance differs from the magnitude of the feedback current value by calculating in advance a plurality of predetermined current values and corresponding correction coefficients based on the current sensor gain coefficient calculation command. However, by updating the correction coefficient according to the feedback current value during normal operation, it is possible to obtain an AC motor control device that can accurately reduce torque pulsation.

  In the above embodiment, the case where the AC motor is vector-controlled using the position detector and the speed control is performed has been described. However, the vector control of the induction motor using the speed detector and the speed control / position detector are used. It goes without saying that the same effect can be obtained in sensorless vector control that is not used, and it is of course effective in control methods other than speed control (position control, torque control, etc.). Furthermore, the scope of the present invention is not limited to vector control for performing current feedback, but can be applied to a control method for calculating a voltage command using a detected current, and has the same effect.

  In the above-described embodiment, linear interpolation is applied when obtaining an optimal correction coefficient based on data stored in the correction value table. However, interpolation between measurement data is not limited to linear interpolation. It is also possible to complement between measured data using a predetermined function.

Embodiment 2. FIG.
FIG. 6 is a flowchart showing the operation of the current sensor gain coefficient calculator 22 when obtaining the correction coefficient of the current conversion gain in the AC motor control apparatus according to Embodiment 2 of the present invention. In the current sensor gain coefficient calculator 22, a plurality of gains necessary for making a correction coefficient measurement DC current variable when energizing between U-V and U-W, recording a plurality of digital conversion values, and forming a table A means for calculating a coefficient is shown.

  In step S601, the current sensor gain coefficient calculator 22 varies the value of the current flowing between U and V in accordance with the current sensor gain coefficient calculation command. Specifically, the U-phase feedback current value is set so as to have a plurality of current values stepwise with time. FIG. 7 is a diagram showing a waveform of the U-phase current that flows between U and V in accordance with the current sensor gain coefficient calculation command in the second embodiment of the present invention. At this time, assuming an electrical angle corresponding to the timing 1 in FIG. 2, the current of the V-phase feedback current value is the same as that of the U-phase feedback current value but has the same sign, and the feedback of the W-phase. As a current value, almost no current flows.

  In step S602, the current sensor gain coefficient calculator 22 detects the current value of each phase at each time, and stores the digital conversion value. Specifically, as shown in FIG. 7, U-phase feedback current values are detected at the timings T1, T2, and T3 in the respective current values Iua, Iub, and Iuc, and the digital conversion values Xu1a, Xu1b, and Xu1c are obtained. Remember. Similarly, the current values of the other phases (V-phase and W-phase) are detected, and the digital conversion values Xv1a, Xv1b, Xv1c and Xw1a, Xw1b, Xw1c are stored. Here, the subscripts a, b, and c represent current values corresponding to times T1, T2, and T3, respectively.

  In step S603, the current sensor gain coefficient calculator 22 changes the value of the current flowing between U and W in the same manner as between U and V in step S601. In S604, the current sensor gain coefficient calculator 22 detects each current value of each phase, and stores the digital conversion values Xu2a, Xu2b, Xu2c, Xv2a, Xv2b, Xv2c and Xw2a, Xw2b, Xw2c. In S605, the current sensor gain coefficient calculator 22 calculates a conversion gain correction coefficient for each current value using the digital conversion value in each current value stored in S602 and S604.

  In step S606, the current sensor gain coefficient calculator 22 calculates the correction coefficients Kv (a), Kw (a) to Kv (c), Kw (c) calculated for the respective current values. Therefore, the current values Iua to Iuc are made constant and stored in the correction value table. By changing the current value continuously by the above operation, the respective correction coefficients Kv and Kw corresponding to the predetermined current value are stored in the correction value table.

  According to the second embodiment, it is possible to reduce the time required for calculating the correction coefficient for a plurality of current values by changing the current flowing between the phases in a plurality of stages as a time function when calculating the correction coefficient. Become.

It is a block diagram which shows the structure of the control apparatus of the alternating current motor in Embodiment 1 of this invention. In Embodiment 1 of this invention, it is a figure which shows the relationship between a rotor electrical angle and each phase electric current in the case of performing d-axis current 0 control often used by control of a normal synchronous motor. 6 is a flowchart showing the operation of a current sensor gain coefficient calculator 22 when obtaining a correction coefficient for a current conversion gain in the control apparatus for an AC motor according to Embodiment 1 of the present invention. It is a figure which shows the data structure of the correction value table in Embodiment 1 of this invention. 5 is a graph showing a relationship between a current value and a correction coefficient based on data stored in the correction value table of FIG. 6 is a flowchart showing an operation of a current sensor gain coefficient calculator 22 when obtaining a correction coefficient of a current conversion gain in the control apparatus for an AC motor according to the second embodiment of the present invention. It is a figure which shows the waveform of the U-phase electric current sent between U-V by the current sensor gain coefficient calculation command in Embodiment 2 of this invention.

Explanation of symbols

  1 three-phase AC, 2 converter device, 3 smoothing capacitor, 4 inverter device, 5 three-phase AC motor, 10a, 10b, 10c current detector, 11 position detector, 12 differentiator, 13a, 13b, 13c adder, 14 Current command generator, 15a, 15b, 15c A / D converter, 16 coordinate converter, 17a, 17b Current controller, 18 coordinate converter, 19 PWM signal generator, 20 gate drive circuit, 21a, 21b correction calculator (Correction means), 22 Current sensor gain coefficient calculator (coefficient calculator), 23a, 23b Signal switch (signal switch section).

Claims (3)

A converter device for converting AC power into DC power;
An inverter device that converts the DC power of the converter device into AC of variable voltage and variable frequency and supplies the AC power to the AC motor;
A position detector for detecting a rotor position of the AC motor;
A current detector for detecting each phase current output from the inverter device;
Correction means for correcting the detected current value by multiplying the detected value detected by the current detector by a correction coefficient;
A coefficient calculator for calculating the correction coefficient based on an external calculation command;
A PWM signal generator for generating a signal for PWM controlling the inverter device based on a voltage command;
A control unit that outputs a voltage command obtained by converting the detected current value corrected by the correction unit into a three-phase voltage command signal to the PWM signal generator, and
The control unit outputs a voltage command based on a speed command from the outside and a detection signal of the position detector to the PWM signal generator during normal operation, and the coefficient when the calculation command is input from the outside. A signal switch unit that switches signal processing so that a voltage command based on a measurement value of a correction coefficient output from a calculator is output to the PWM signal generator;
In the control device for an AC motor that performs calculation using current detection values of other phases in addition to the current detection values of the phase and the reference phase when obtaining the correction coefficient of a certain phase,
The coefficient calculator has a storage unit that stores a correction coefficient measurement value and a correction coefficient in association with each other, and a plurality of different correction coefficient measurement values are obtained when obtaining a correction coefficient of a certain phase. A value is output to the control unit, a correction coefficient is obtained from each phase current detected by the current detector according to the plurality of different values, a correction value table is generated, and stored in the storage unit. During operation, the current detection value of the reference phase is detected, a correction coefficient corresponding to the current detection value is calculated based on the correction value table stored in the storage unit, and the current detection value is determined according to the magnitude of the current detection value. The AC motor control apparatus is characterized in that the correction coefficient of the correction means is changed by the correction coefficient calculated in the above. In the control apparatus for an AC motor according to claim 1,
The controller is
A differentiator for time-differentiating the output of the position detector and outputting a speed feedback signal;
A current command generator that outputs a current command value based on a deviation between the speed feedback signal output from the differentiator and an external speed command;
The signal switch unit is
During normal operation, the signal from the current command generator is used as a current command value, and when a calculation command is input from the outside, the current command value is switched to the current command value for measuring the correction coefficient output from the coefficient calculator. 1 signal switch;
The timing signal for generating the voltage command is the rotor position signal from the position detector during normal operation, and the measurement of the correction coefficient output from the coefficient calculator when a calculation command is input from the outside. And a second signal switch for switching to a signal for use in an AC motor. In the control apparatus of the alternating current motor according to claim 1 or 2,
2. The AC motor control apparatus according to claim 1, wherein the coefficient calculator obtains correction coefficients for a plurality of different values by changing the correction coefficient measurement values in multiple stages at predetermined time intervals.

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