JP4361598B1 - Sensorless AC motor control device - Google Patents

Abstract

An object of the present invention is to provide a sensorless AC motor control device capable of quickly detecting and protecting a control abnormality.
A sensorless control abnormality detection unit 12 including a threshold value calculation unit 13 for calculating a threshold value of a gain value KG from a speed command and a comparison unit 14 is provided. The sensorless control abnormality detection unit 12 compares the gain value KG and the threshold value RV used in the frequency calculation unit 4 with the comparison unit 14, and if the gain value KG exceeds the threshold value RV for a predetermined time, the sensorless control abnormality detection unit 12 determines that a control abnormality has occurred. Output a signal.
[Selection] Figure 1

Description

  The present invention relates to a sensorless AC motor control device that controls an AC motor without using a sensor that detects the speed and magnetic pole position of the AC motor.

  As a conventional control device for a sensorless AC motor of an electric motor, there are an observer method, a method using electric motor parameters, and the like. Recently, Japanese Patent No. 4022630 (Patent Document 1) discloses a sensorless control apparatus that requires few parameters for controlling various AC drive devices including an AC motor. In the control device shown in FIGS. 2-1 and 2-2 of Patent Document 1, a power converter, a current detector, a frequency calculation unit that determines an operating frequency of the power converter, and an output of the frequency calculation unit An integration calculation unit that obtains and outputs a phase angle signal by integration, a quadrature biaxial conversion unit, a biaxial current adjustment unit, a PWM signal generation unit, and a PWM controller that controls the power converter by the PWM signal I have. The orthogonal biaxial conversion unit calculates and outputs the biaxial current of the effective component and the ineffective component by orthogonal biaxial conversion based on the detection signal of the current detector and the phase angle signal of the integration calculation unit. The biaxial current setting unit outputs an effective component command value and an ineffective component command value of the biaxial current. The biaxial current adjustment unit calculates an error amount from the difference between the output of the orthogonal biaxial conversion unit and the output of the biaxial current setting unit, and outputs an amplitude command value corresponding to the error amount for each biaxial component. The PWM signal generation unit generates a PWM signal for controlling the power converter based on the output of the biaxial current adjustment unit and the phase angle signal of the integration calculation unit. In the control device disclosed in Patent Document 1, the frequency calculation unit guides the amplitude command value corresponding to the reactive component current to zero among the amplitude command values that are output from the biaxial current adjustment unit in order to eliminate the sensor. Thus, the operating frequency of the power converter is determined. Specifically, in order to control an AC motor (synchronous motor, induction motor, etc.), an amplitude command value corresponding to an effective component current among the amplitude command values output from the biaxial current adjustment unit is set as an invalid component current. A value obtained by multiplying the gain by the gain value KG, which is the reciprocal of the induced voltage constant obtained from the amplitude command value corresponding to, is determined as the operating frequency of the power converter.

Japanese Patent No. 40222630 FIG.

  In the sensorless AC motor control device disclosed in Patent Document 1, if the magnetic pole position θ output from the integral calculation unit of the control device and the actual magnetic pole position θ of the control device greatly deviate from each other for some reason, the torque will be lost. Stops and the electric motor stops. If it is not detected promptly that the electric motor has stepped out, it may affect the mechanical system in use and damage the mechanical parts. However, the control device disclosed in Patent Document 1 did not have such a protection function.

  An object of the present invention is to provide a sensorless AC motor control device that can quickly detect and protect a control abnormality.

  In the sensorless AC motor control device of the present invention, a power converter, a current detector, a frequency calculation unit, an integration calculation unit, an orthogonal biaxial conversion unit, a biaxial current setting unit, and a biaxial current adjustment unit, And a control signal generator and a PWM controller. The power converter is connected between the DC circuit and the AC motor, and has a switch element to perform DC-AC power conversion. The current detector detects a current output from the power converter. The frequency calculation unit determines an operation frequency of the power converter and outputs an operation frequency signal. The integration calculation unit obtains and outputs a phase angle signal by integration from the output of the frequency calculation unit. The orthogonal biaxial conversion unit calculates and outputs the biaxial current of the effective component and the ineffective component by orthogonal biaxial conversion based on the detection signal of the current detector and the phase angle signal of the integration calculation unit. The biaxial current setting unit outputs the command value of the effective component and the command value of the ineffective component determined based on the speed command and the estimated speed estimated from the operating frequency of the power converter. The biaxial current adjustment unit calculates an error amount from the difference between the output of the orthogonal biaxial conversion unit and the output of the biaxial current setting unit, and outputs an amplitude command value corresponding to the error amount for each biaxial component. The control signal generation unit generates a control signal for controlling the power converter based on the output of the biaxial current adjustment unit and the phase angle signal of the integration calculation unit. The PWM controller performs PWM modulation on the control signal and outputs a drive signal to the power converter. The frequency calculation unit determines the operation frequency of the power converter so as to guide the amplitude command value corresponding to the reactive component current out of the amplitude command value output from the biaxial current adjustment unit to zero. A value obtained by multiplying the amplitude command value corresponding to the active component current by the gain value KG, which is the reciprocal of the induced voltage constant obtained from the amplitude command value corresponding to the reactive component current, of the amplitude command value that is the output of the unit The operating frequency of the power converter.

  In particular, in the present invention, the control device includes a threshold value calculation unit that calculates a threshold value of the gain value KG from the speed command, and a sensorless control abnormality detection unit. The sensorless control abnormality detection unit compares the gain value KG used in the frequency calculation unit with a threshold value. When the gain value KG exceeds the threshold value for a predetermined time, the sensorless control abnormality detection unit determines that the control is abnormal and outputs an alarm signal. The present invention pays attention to the fact that the gain value KG is adjusted (changed) in order to eliminate the sensor. When the gain value KG shows an abnormal value, an alarm signal is output and the PWM controller is stopped. By doing so, the protective function is exhibited.

It is a figure which shows the structure of one Embodiment of the sensorless AC motor control apparatus of this invention which controls the synchronous motor which is a kind of AC motor without a sensor. It is a graph which shows the relationship between a threshold value and a gain value.

  Embodiments of a sensorless AC motor control apparatus according to the present invention will be described below in detail with reference to the drawings. FIG. 1 is a diagram showing a configuration of an embodiment of a sensorless AC motor control device of the present invention that controls a synchronous motor 1 which is a kind of AC motor without a sensor. A synchronous motor (motor) 1 includes a rotor in which a permanent magnet is fixed to the surface of a rotor core to form a rotor magnetic pole (mover magnetic pole), and a three-phase armature winding wound around the stator core. And a stator having a stator magnetic pole configured to be mounted. The position θ of the rotor magnetic pole of the synchronous motor 1 [the relative position of the rotor (moving element) of the synchronous motor 1 with respect to the stator] is determined sensorlessly by the known technique described in Patent Document 1 described above.

  In the control device of the present embodiment, the biaxial current setting unit 2, the biaxial current adjusting unit 3, the frequency calculating unit 4, the integral calculating unit 5, the coordinate converter 6 constituting the control signal generating unit, the current A detection unit 7, a coordinate conversion unit 8 as an orthogonal biaxial conversion unit, a PWM controller 9, a power conversion unit 10, an oscillator 11, and a sensorless control abnormality detection unit 12 are provided. The power converter 10 is connected between a DC circuit (not shown) and the synchronous motor (AC motor) 1 and has a switch element to perform DC-AC power conversion. The current detector 7 detects AC currents IU and IV for two phases from the three-phase AC current output from the power converter 10. The quadrature biaxial conversion unit 8 receives the sine wave signal sin and the cosine wave signal cos having a phase angle based on the detection signals IU and IV of the current detector 7 and the phase angle signal of the integration calculation unit 5 as inputs, The biaxial currents IδF and IγF of the effective component and the ineffective component are calculated and output by conversion. The biaxial current setting unit 2 inputs a difference between a speed command output from a speed command generation unit (not shown) and an estimated frequency (estimated speed) output from the frequency calculation unit 4 to input an effective component command of the biaxial current. A speed controller 21 that generates a value Iδc and a command generator 22 that outputs a command value Iγc of an invalid component of the biaxial current are configured.

  The biaxial current adjustment unit 3 is an orthogonal biaxial conversion unit that outputs the coordinate conversion unit 8 (IδF and IγF) and the biaxial current setting unit 2 (the biaxial current effective component command value Iδc and the biaxial current An error amount is calculated from the difference from the ineffective component command value Iγc), and amplitude command values (Vδc and Vδc) as voltage commands corresponding to the error amount are output for each of the two-axis components through the current controllers 31 and 32. The coordinate converter 6 outputs the sine wave signal sin and the cosine wave signal cos output from the oscillator 11 based on the output (Vδc and Vδc) of the biaxial current adjustment unit 3 and the phase angle signal output from the integration calculation unit 5. The control signal (VUC, VVC, VWC) for three phases is generated by coordinate conversion. In the present embodiment, the coordinate converter 6 constitutes a control signal generator. The PWM controller 9 performs PWM modulation on the control signal for three phases, outputs a drive signal for the power converter 10, and a voltage is applied to the motor 1 by the power converter 10.

  The frequency calculation unit 4 determines the operating frequency ω of the power converter 10 so that the amplitude command value Vγc corresponding to the reactive component current among the amplitude command values output from the biaxial current adjustment unit 3 is led to zero. Specifically, the speed estimation controller 41 outputs a gain value KG that is the reciprocal of the induced voltage constant obtained from the amplitude command value Vγc corresponding to the reactive component current. The frequency calculation unit 4 operates the power converter 10 by multiplying the amplitude command value Vδc corresponding to the effective component current by the gain value KG among the amplitude command values that are output from the biaxial current adjustment unit 3. Output as frequency (estimated speed of motor) ω. Note that the value obtained by multiplying the amplitude command value Vδc corresponding to the active component current by the gain value KG is the operating frequency (estimated speed of the motor) ω of the power converter 10 (that the operating frequency can be estimated without a sensor). Since it is described in detail in Patent Document 1, description thereof is omitted. The integral calculation unit 5 integrates the output ω of the frequency calculation unit 4 to calculate and output a phase angle signal (signal indicating the magnetic pole position) θ. Since the gain (parameter) KG represents the reciprocal of the induced voltage constant, the speed of the motor 1 can be increased by multiplying the amplitude command value Vδc, which is a δ-axis voltage command in which a value proportional to the motor rotation speed appears, by the gain value KG. Presumed.

  In the present embodiment, a sensorless control abnormality detection unit 12 including a threshold value calculation unit 13 that calculates a threshold value of the gain value KG from the speed command and a comparison unit 14 is provided. The sensorless control abnormality detection unit 12 compares the gain value KG and the threshold value RV used in the frequency calculation unit 4 with the comparison unit 14, and if the gain value KG exceeds the threshold value RV for a predetermined time, the sensorless control abnormality detection unit 12 determines that a control abnormality has occurred. Output a signal. Here, the threshold value calculation unit 13 measures the relationship between the speed command and the normal gain value KG in advance by a test, and adds the permissible range to the result and stores it as an arithmetic expression or saves it as data. In addition, each time the speed command changes, a corresponding threshold value is output. The above-mentioned “predetermined time” is also determined by a preliminary test. Incidentally, in the present embodiment, 30 ms is set as a “predetermined time”.

  In the present embodiment, attention is paid to the fact that the gain value KG is adjusted (changes) during frequency calculation, and an alarm signal is issued when the gain value KG shows an abnormal value. As a protection function, for example, the PWM controller 9 stops the control operation when an alarm signal is output. As a result, the synchronous motor stops rotating. Since the speed estimation controller 41 has a gain of a certain amount, when the sensorless control is abnormal, the motor speed decreases and the amplitude command value Vδc that becomes the δ-axis voltage command decreases. Therefore, the speed estimation controller 41 promptly changes the gain value KG to its upper limit side so as to correct this decrease. By detecting that the change width is increased, the comparison unit 14 can quickly detect a sensorless control abnormality.

  According to the present invention, the sensorless control abnormality is detected based on the fact that the gain value KG, which is a parameter of sensorless control, is equal to or longer than a threshold value and longer than a predetermined time. As a result, even when an abnormality occurs in the sensorless control, a sensorless control abnormality can be quickly detected, and a safe sensorless control device that does not affect the mechanical system being used can be realized.

DESCRIPTION OF SYMBOLS 1 Synchronous motor 2 Two-axis current setting part 3 Two-axis current adjustment part 4 Frequency calculation part 5 Integral calculation part 6 Coordinate converter (control signal generation part)
7 Current detector 8 Coordinate converter as orthogonal biaxial converter 9 PWM controller 10 Power converter 11 Oscillator 12 Sensorless control abnormality detector

Claims (2)

A power converter connected between the DC circuit and the AC motor and having a switch element to perform DC-AC power conversion;
A current detector for detecting a current output from the power converter;
A frequency calculator that determines an operating frequency of the power converter and outputs an operating frequency signal;
An integration calculation unit for obtaining and outputting a phase angle signal by integration from the output of the frequency calculation unit;
Based on the detection signal of the current detector and the phase angle signal of the integral calculation unit, an orthogonal biaxial conversion unit that calculates and outputs a biaxial current of an effective component and an ineffective component by orthogonal biaxial conversion, and
A biaxial current setting unit that outputs a command value of an effective component and a command value of an ineffective component determined based on a speed command and an estimated speed estimated from an operating frequency of the power converter;
A biaxial current adjusting unit that calculates an error amount from the difference between the output of the orthogonal biaxial conversion unit and the output of the biaxial current setting unit and outputs an amplitude command value corresponding to the error amount for each biaxial component;
A control signal generator for outputting a control signal for controlling the power converter based on the output of the biaxial current adjuster and the phase angle signal of the integral calculator;
A PWM controller that PWM modulates the control command and outputs a drive signal to the power converter;
In order to determine the operating frequency of the power converter so that the frequency calculation unit leads the amplitude command value corresponding to the reactive component current out of the amplitude command value that is the output of the biaxial current adjustment unit to zero. Among the amplitude command values output from the biaxial current adjuster, the amplitude command value corresponding to the active component current is gained with a gain value that is the inverse of the induced voltage constant obtained from the amplitude command value corresponding to the reactive component current. A sensorless AC motor control device having a multiplied value as an operating frequency of the power converter,
A threshold value calculation unit for calculating a threshold value of the gain value from the speed command;
A sensorless control including a comparison unit that compares the gain value used in the frequency calculation unit with the threshold value, and determines that the control value is abnormal and outputs an alarm signal when the gain value exceeds the threshold value for a predetermined time. A control device for a sensorless AC motor, comprising an abnormality detection unit.   The sensorless AC motor control device according to claim 1, wherein the PWM controller stops a control operation in response to the alarm signal.

Images