JP2008161027A - Drive unit of synchronous motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To restrain pulsation of motor current for stable speed control by compensating an induced voltage based on axial error Δθ generated between rotational axis of coordinate (d-q axis) and rotational axis of coordinate (dc-qc axis) by means of vector control method. <P>SOLUTION: This synchronous motor drive unit which performs speed control by means of position sensor-less vector control has a motor application voltage computing part 20 which inputs a d-axis current command Id, a q-axis current command Iq, a frequency command f and an induced voltage constant Ke for vector control, and outputs a d-axis voltage command Vd and a q-axis voltage command Vq. It also comprises an induced voltage compensation part 22 for compensating the induced voltage constant Ke based on the axis error Δθ generated between the rotational axis of coordinate (d-q axis) based on a pole position of the synchronous motor and rotational axis of coordinate (dc-qc axis) assumed for control, so that an induced voltage constant Kec compensated by the induced voltage compensation part 22 can be inputted to the motor application voltage computing part 20. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a synchronous motor drive device capable of controlling the speed of a synchronous motor without using a magnetic pole position sensor for detecting the magnetic pole position of the synchronous motor and a current sensor for detecting a current of the synchronous motor.

  The vector control that can rotate the induction synchronous motor and the DC synchronous motor at high speed stably without using the magnetic pole position sensor that detects the magnetic pole position of the synchronous motor and the current sensor that detects the current of the synchronous motor is Conventionally known (for example, see Patent Document 1).

  The basic principle of the magnetic pole position is to estimate and calculate the magnetic pole position based on the electric motor constant of the synchronous motor, the motor voltage, and the motor current, but the position is determined using the induced voltage generated by the rotation of the synchronous motor. Control for estimation is also known (see, for example, Patent Document 2). The magnetic pole position is estimated by estimating and calculating the axis error Δθ between the rotational coordinate axis (dq axis) based on the magnetic pole position of the synchronous motor and the rotational coordinate axis (dc-qc axis) assumed in the control. The position sensorless vector control can be realized by correcting the frequency command of the synchronous motor so that the axis error Δθ obtained by this calculation becomes zero.

  On the other hand, as a method of detecting the current without using the current sensor, the DC current of the inverter that drives the synchronous motor is detected, and the AC of the synchronous motor is detected from the instantaneous value and the ON / OFF signal of the switching element in the inverter bridge circuit. There is known a “method using a shunt resistor arranged on an inverter bus” that reproduces an electric current (see, for example, Non-Patent Document 1). According to this Non-Patent Document 1, the current of the shunt resistor (current detection resistor) is a current that flows / cuts off in synchronization with the on / off of the switching element in the inverter bridge circuit, and the timing of current detection is important. However, when the DC voltage is high, or when the switching element in the inverter bridge circuit is driven at a high frequency, the current flowing through the current detector is reduced when the switching element's on-time is shortened due to various factors of the synchronous motor. The problem arises that the flow time decreases and current detection becomes difficult.

For example, Patent Document 3 proposes a method for solving such a problem. According to this Patent Document 3, the time when the motor current can be reproduced in two phases and the case where only one phase can be reproduced is discriminated for each chopper period of each PWM control, and the time when two phases can be reproduced. Is calculated, and control is performed so as to switch the chopper frequency of PWM control based on this ratio.
Patent No. 3783159 Japanese Patent No. 311878 JP 2004-104977 A 2002 Annual Conference of the Institute of Electrical Engineers of Japan "Sine Wave Drive of PM Motor by Inverter Bus Current Sensing", page 201 (issued March 26, 2002)

  By the way, during the acceleration / deceleration of the synchronous motor, or in a disturbance or high load state, in particular, a state in which the state is switched between high rotation / low rotation during one rotation at a high load at a low rotation speed (a state where there is rotational pulsation during one rotation). ), An axis error Δθ is generated between the rotational coordinate axis (dq axis) based on the magnetic pole position of the synchronous motor and the rotational coordinate axis (dc-qc axis) assumed in the control. Also in the induced voltage generated by the rotation of the synchronous motor, the induced voltage of the synchronous motor (for example, when trying to control the rotational speed of 1000 rpm, in actuality at 950 rpm due to load fluctuations, etc.) There is a difference between the induced voltage actually generated in the stator winding at 950 rpm rotation and the induced voltage assumed in the control (for example, induced voltage due to the rotation speed of 1000 rpm). appear.

  However, in the prior art disclosed in the above patent document and the above non-patent document, there is a frequency correction unit that corrects the frequency so that the axis error Δθ is zero, but there is no unit that corrects the induced voltage and the synchronous motor is changed. The motor applied voltage remains constant. Therefore, the motor applied voltage to the synchronous motor becomes excessive or insufficient, and the direct current flowing through the shunt resistor (current detection resistor) may pulsate.

  The object of the present invention is to suppress the pulsation of the motor current by correcting the induced voltage based on the axis error Δθ generated between the rotation coordinate axis (dq axis) and the rotation coordinate axis (dc-qc axis) described above. Another object of the present invention is to provide a synchronous motor drive device that enables stable speed control.

In order to solve the above problems, the present invention mainly adopts the following configuration.
In a synchronous motor drive device that performs speed control with a position sensorless vector control method,
A motor applied voltage calculation unit that receives the d-axis current command Id, the q-axis current command Iq, the frequency command f, and the induced voltage constant Ke in vector control and outputs the d-axis voltage command Vd and the q-axis voltage command Vq; The induced voltage constant Ke is based on an axis error Δθ generated between a rotational coordinate axis (dq axis) based on the magnetic pole position of the synchronous motor and a rotational coordinate axis (dc-qc axis) assumed in the control. An induced voltage correction unit for correcting the induced voltage is provided, and the induced voltage constant corrected by the induced voltage correction unit is input to the motor applied voltage calculation unit.

In addition, in a synchronous motor drive device that performs speed control with a position sensorless vector control method,
A motor applied voltage calculation unit that receives the d-axis current command Id, the q-axis current command Iq, the frequency command f, and the induced voltage constant Ke in vector control and outputs the d-axis voltage command Vd and the q-axis voltage command Vq; The d-axis voltage command Vd, the q-axis voltage command Vq, the motor voltage phase instantaneous value θd obtained by adding the shaft error Δθ to the motor voltage phase reference value θ proportional to the frequency command, and the U-phase motor voltage Vu, It has a 2-phase to 3-phase conversion operation section that outputs V-phase motor voltage Vv and W-phase motor voltage Vw, and assumes a rotational coordinate axis (dq axis) based on the magnetic pole position of the synchronous motor and control. An induced voltage correction unit that corrects the induced voltage constant Ke based on an axis error Δθ generated between the rotation coordinate axis (dc-qc axis) and the induced voltage constant corrected by the induced voltage correction unit is provided in the motor. Applied voltage By inputting the calculation unit, a structure to reduce the pulsation of the motor current.

  In the synchronous motor driving apparatus, the induced voltage correction unit multiplies the shaft error Δθ by a correction gain Kp to obtain an induced voltage correction value ΔKe, and the input induced voltage constant Ke is converted to the induced voltage correction Ke. A value ΔKe is added and output as an induced voltage constant after correction.

  According to the present invention, the position of the magnetic pole of the synchronous motor during acceleration / deceleration of the synchronous motor, or in a state of disturbance or high load, particularly in a state where the high / low rotation is switched during one rotation at a high load at a low rotation speed. Motor current pulsation caused by an axial error Δθ between the rotation coordinate axis (dq axis) with reference to the axis and the rotation coordinate axis (dc-qc axis) assumed in control is induced voltage correction It can be mitigated by using means.

  A synchronous motor driving apparatus according to an embodiment of the present invention will be described in detail below with reference to FIGS. FIG. 1 is a diagram showing an overall circuit configuration of a vector control system in a synchronous motor driving apparatus according to an embodiment of the present invention. FIG. 2 is a block diagram constituting a vector control calculation relating to the present embodiment. FIG. 3 is a diagram showing the induced voltage correction means included in the vector control calculation block according to this embodiment. FIG. 4 is a diagram showing a U-phase motor current waveform when the induced voltage correction means according to this embodiment is not applied. FIG. 5 is a diagram showing a U-phase motor current waveform when the induced voltage correction means according to this embodiment is applied.

  In FIG. 1, 1 is a commercial power source, 2 is an inductance (reactor), 3 is a rectifier diode (first rectifier circuit), 4 is a switching relay (switch), 5-7 are smoothing capacitors (5, 6 are voltage dividing capacitors) , 7 is a smoothing capacitor), 8 is a current detection resistor, 9 is an inverter bridge circuit (inverter), 10 is a rectifier diode (second rectifier circuit), 11 is a switching element (IGBT, etc.), 12 is an AD converter, Reference numerals 13 to 15 denote drivers, 16 denotes a central processing unit (CPU), 17 denotes a microcomputer, and 18 denotes a synchronous motor (DC brushless motor).

  The operation of the circuit configuration relating to the present embodiment shown in FIG. 1 will be described. The AC power source from the commercial power source 1 is rectified by the rectifier diode 3 via the inductance 2, smoothed by the smoothing capacitors 5 to 7, and converted into a DC power source. A DC power supply is supplied to the inverter bridge circuit 9, and the synchronous motor 18 is driven by applying a rotating magnetic field to the synchronous motor 18 by the on / off operation of the six switching elements constituting the inverter bridge circuit. When the inverter bridge circuit 9 is turned on and off, the current IDC flows through the current detection resistor 8.

  The microcomputer 17 reads the current IDC digitized from analog by the AD converter 12 and performs arithmetic processing necessary for vector control. A PWM (Pulse Width Modulation) signal is output to the driver 15 so that the amplitude and phase sine wave voltage obtained by the vector control calculation is output to the synchronous motor 18 via the inverter bridge circuit 9. In addition, a switching signal is output to the driver 13 that drives the relay 4 in order to change the level of the DC voltage supplied to the inverter inverter bridge circuit 9. The voltage doubler rectifier circuit is configured by turning on the relay 4 and charging the voltage dividing capacitor 6.

  Furthermore, in order to improve the power factor of the circuit, the level of the DC voltage supplied to the inverter inverter bridge circuit 9 is increased by outputting a drive signal to the driver 14 that drives the switching element 11. As described above, the microcomputer 17 reads the current IDC flowing through the current detection resistor 8 by the AD converter 12 and drives the synchronous motor by vector control.

  Next, the configuration of the vector control calculation will be described with reference to FIG. 20 is a motor applied voltage calculation, 21 is a two-phase to three-phase conversion calculation, 22 is an induced voltage corrector, 23 is a phase corrector, 24 is an axis error calculator, 25 is a first-order lag filter, and 26 is three-phase to two-phase. The conversion calculation, 27 is the phase current reproduction calculation, and 12, 15 and 16 are the same as in FIG. Id * is d-axis current command, Iq * is q-axis current command, f * is frequency command, Vd * is d-axis voltage command, Vq * is q-axis voltage command, Vu is U-phase motor voltage, Vv is V-phase motor Voltage, Vw is W phase motor voltage, Ke is induced voltage constant (power generation constant), Kec is constant after induced voltage correction, θd is voltage phase after axis error correction, Idc is d axis motor current, Iqc is q axis motor Current, Δθ is an axis error between the q-axis current command and the q-axis motor current, Iu is a U-phase motor current, Iw is a W-phase motor current, and IDC is a DC current flowing through the current detection resistor 8.

  The motor applied voltage calculation 20 takes f *, Id *, Iq * and the corrected induced voltage constant Kec as inputs, Vd * and Vq * as outputs, and a relational expression between these inputs and outputs is conventionally known. Incidentally, this is shown by the mathematical formula described in paragraph No. 0126 of Japanese Patent No. 311878 cited in the background art section. Here, Kec is a constant used in this equation, and it is a feature of this embodiment that the constant is changed by the output of the induced voltage corrector 22 shown in FIG. 2 of the present application.

 Here, the structural features of the synchronous motor driving device according to the present embodiment will be outlined first. In the present embodiment, the magnetic pole position of the synchronous motor from the induced voltage generated by the rotation of the synchronous motor with respect to the voltage command calculator (corresponding to the motor applied voltage calculation of FIG. 2) for calculating the applied voltage to the synchronous motor. Between the rotation coordinate axis (dq axis) (actual rotation axis) for which the value is obtained and the rotation coordinate axis (dc-qc axis) assumed on the control (rotation axis assumed to be controlled by the microcomputer) Is provided with a correction means (corresponding to the induced voltage corrector in FIG. 2) for correcting the induced voltage by the axis error Δθ generated in the motor, and the induced voltage correction value ΔKe calculated by the induced voltage corrector is used as a voltage for calculating the motor applied voltage. This is drive control that calculates the optimum motor applied voltage by adding to the induced voltage included in the command calculator and supplies it to the synchronous motor.

To explain qualitatively, the induced voltage generated in the stator winding by the rotation of the synchronous motor is determined by Ke · ω ₁ (2πf ₁ ), but the induced voltage is equal to the induced voltage corresponding to this frequency f _1. If no voltage is generated, it can be said that the axis is displaced. The fact that the generated induced voltage is higher than the induced voltage corresponding to f ₁ indicates that the actual rotational speed is higher than the rotational speed to be controlled and the magnetic pole position is advanced. In this case, since the motor applied voltage is insufficient as the control output to the synchronous motor, the correction value corresponding to the increase of the induced voltage is added and applied to the synchronous motor. In the prior art, the shaft error Δθ is obtained and the rotational speed of the motor is directly controlled by this Δθ. In the present embodiment, a correction value of the induced voltage based on the pulsation of the motor is used. Therefore, since the voltage applied to the motor is controlled, the rotational pulsation of the motor can be reduced.

  Specifically, as will be described in detail with reference to FIGS. 2 and 3, the rotational coordinate axes (dq axes) based on the magnetic pole position of the synchronous motor and the rotational coordinate axes (dc-qc) assumed in the control. The axis error Δθ generated between the axis error and the axis) is calculated by the axis error calculator 24. The induced voltage corrector 22 multiplies the axis error Δθ calculated by the axis error calculator 24 by the correction gain 28 to obtain an induced voltage correction value ΔKe. At this time, the value of the axis error Δθ is that the rotational coordinate axis (dc-qc axis) assumed in the control is advanced with respect to the rotational coordinate axis (d-q axis) based on the magnetic pole position of the synchronous motor. In the state where the synchronous motor is delayed with respect to the frequency command f * on the control side, the induced voltage value of the synchronous motor is smaller than the induced voltage value recognized in the control, and the motor is excessively applied to the synchronous motor. A voltage (20 outputs) is given. Therefore, the induced voltage correction value is set to a negative value.

  Conversely, when the value of the axis error Δθ is behind the rotational coordinate axis (dc-qc axis) assumed in the control with respect to the rotational coordinate axis (dq axis) based on the magnetic pole position of the synchronous motor. In the state where the synchronous motor is advanced with respect to the frequency command f * on the control side, the induced voltage value of the synchronous motor is larger than the induced voltage value recognized in the control, and the motor applied voltage (20 Output) is insufficient. Therefore, the induced voltage correction value ΔKe is a positive value.

  The induced voltage correction value ΔKe calculated by the induced voltage corrector 22 is added to the induced voltage included in the voltage command calculator 20 that calculates the motor applied voltage to calculate the optimum motor applied voltage and supply it to the synchronous motor. That is.

  Subsequently, the contents of the vector control calculation will be described. FIG. 2 shows a general calculation as a vector control operation except for the induced voltage corrector 22 which is a feature of the present embodiment. The calculation formulas for the respective operation blocks are shown on pages 594 to 596 (issued on February 20, 2001) of the electrical engineering handbook, and the description thereof will be omitted. The motor applied voltage calculation 20 is based on the d-axis current command Iq * obtained by smoothing / averaging the d-axis current command Id *, the frequency command f *, and the q-axis motor current Iqc via the primary delay filter 25. The voltage command Vd * and the q-axis voltage command Vq * are calculated.

  The induced voltage corrector 22 obtains a correction value based on the axis error Δθ calculated by the axis error calculator 24 to the induced voltage constant Ke, and adds the correction value to calculate the constant Kec after the induced voltage correction. The phase corrector 23 obtains the motor voltage phase reference value θ in proportion to the frequency command f *, and adds the axis error Δθ calculated by the axis error calculator 24 to obtain the instantaneous value θd of the motor voltage phase. The voltage phase θd after the axial error correction is applied to the 2-phase → 3-phase conversion calculation 21. The two-phase → three-phase conversion calculation 21 calculates the U-phase motor voltage Vu, the V-phase motor voltage Vv, and the W-phase motor voltage Vw from the voltage phase θd, the d-axis voltage command Vd *, and the q-axis voltage command Vq *.

  The axis error calculator 24 calculates an axis error Δθ generated between the rotation coordinate axis (dq axis) for which the magnetic pole position of the synchronous motor is obtained and the rotation coordinate axis (dc-qc axis) assumed in the control. To do. The phase current reproduction calculation 27 reads the DC current IDC flowing through the current detection resistor 8 by the AD converter 12 and calculates the U-phase motor current Iu and the W-phase motor current Iw. The three-phase → two-phase conversion calculation 26 calculates a q-axis motor current Iqc and a d-axis motor current Idc from the W-phase motor current Iw of the U-phase motor current Iu.

  Also, if the DC current IDC cannot be read, Iu and Iw cannot be reproduced. Therefore, based on the q-axis motor current Iqc and d-axis motor current Idc obtained from the previously effective Iu and Iw, the values of Iu and Iw are obtained, and the phase current can be reproduced by the phase current reproduction calculation 27. If not, the values of Iu and Iw are substituted. The first-order lag filter 25 is for calculating the q-axis current command Iq *, and the first-order lag filter process is performed on the q-axis motor current Iqc to obtain a q-axis current command Iq *.

  Next, the induced voltage corrector 22, which is a structural feature of the present embodiment, will be described with reference to FIG. 28 is a correction gain Kp, 29 is an adder, and 22 is the same as in FIG. Δθ is an axis error generated between the rotation coordinate axis (dq axis) obtained for the magnetic pole position of the synchronous motor and the rotation coordinate axis (dc-qc axis) assumed in the control, and Ke is the rotation of the synchronous motor. The constant of the induced voltage generated by this, ΔKe, is a value obtained by multiplying the axis error Δθ by the correction gain Kp.

  The correction gain Kp28 multiplies the axis error Δθ by the correction gain Kp and outputs an induced voltage correction value ΔKe. The adder 29 adds the induced voltage correction value ΔKe and the reference induced voltage constant (reference power generation constant) Ke to obtain an induced voltage constant (power generation constant) Kec after correcting the induced voltage.

  Next, the current waveforms shown in FIGS. 4 and 5 will be described. FIG. 4 shows a U-phase motor current waveform when a synchronous motor is driven at a low rotational speed and a high load state in a conventional drive device without induced voltage correction means (the same applies to any phase, not limited to the U phase). Waveform). As can be seen from the figure, the motor current pulsates at a certain cycle.

  FIG. 5 shows waveforms when the synchronous motor is driven by the drive device using the induced voltage correction means employed in the present embodiment under exactly the same conditions as FIG. As can be seen from the figure, the pulsation of the motor current is reduced by using the induced voltage correction means. Furthermore, the pulsation of the motor current can be further suppressed by adjusting the correction gain Kp in the induced voltage corrector 24 shown in FIG. As a result, the shaft error Δθ approaches nearly zero, and the pulsation of the motor rotation speed is reduced, so that stable drive control can be performed.

It is a figure which shows the whole circuit structure of the vector control system in the synchronous motor drive device which concerns on embodiment of this invention. It is a block diagram which comprises the vector control calculation regarding this embodiment. It is a figure which shows the induced voltage correction | amendment means contained in the vector control calculation block regarding this embodiment. It is a figure which shows the motor current waveform of the U phase in the case where the induced voltage correction | amendment means regarding this embodiment is not applied. It is a figure which shows the U-phase motor current waveform at the time of applying the induced voltage correction | amendment means regarding this embodiment.

Explanation of symbols

  1: commercial power supply, 2: inductance (reactor), 3: rectifier diode (first rectifier circuit), 4: switching relay (switch), 5-6: voltage dividing capacitor, 7: smoothing capacitor, 8: current detection Resistance: 9: inverter bridge circuit (inverter), 10: rectifier diode (second rectifier circuit), 11: switching element (IGBT, etc.), 12: AD converter, 13-15: driver, 16: central processing Device: 17: Microcomputer, 18: Synchronous motor (DC brushless motor), 20: Motor applied voltage calculation, 21: Two-phase to three-phase conversion calculation, 22: Induced voltage corrector, 23: Phase corrector, 24: Axis error Arithmetic unit, 25: primary delay filter, 26: three-phase to two-phase conversion calculation, 27: phase current reproduction calculation, Id *: d-axis current command, Iq *: q-axis current command, f *: frequency command Vd *: d-axis voltage command, Vq *: q-axis voltage command, Vu: U-phase motor voltage, Vv: V-phase motor voltage, Vw: W-phase motor voltage, Ke: induced voltage constant, Kec: after induced voltage correction Constant, θd: Voltage phase after axis error correction, Idc: d-axis motor current, Iqc: q-axis motor current, Δθ: Axis error between synchronous motor magnetic pole position and control magnetic pole position, Iu: U-phase motor current , Iw: W-phase motor current, IDC: DC current flowing through the current detection resistor 8, 22: induced voltage corrector, 28: correction gain, 29: adder, Δθ: synchronous motor magnetic pole position and control magnetic pole position Error, Ke: constant of induced voltage, ΔKe: induced voltage correction value, Kec: constant after induced voltage correction

Claims (4)

In a synchronous motor drive device that performs speed control with a position sensorless vector control method,
A motor applied voltage calculation unit that receives the d-axis current command Id, the q-axis current command Iq, the frequency command f, and the induced voltage constant Ke in vector control and outputs the d-axis voltage command Vd and the q-axis voltage command Vq;
The induced voltage constant Ke is based on an axis error Δθ generated between a rotational coordinate axis (dq axis) based on the magnetic pole position of the synchronous motor and a rotational coordinate axis (dc-qc axis) assumed in the control. An induced voltage correction unit for correcting
An apparatus for driving a synchronous motor, wherein the induced voltage constant corrected by the induced voltage correction unit is input to the motor applied voltage calculation unit. In a synchronous motor drive device that performs speed control with a position sensorless vector control method,
A motor applied voltage calculation unit that receives the d-axis current command Id, the q-axis current command Iq, the frequency command f, and the induced voltage constant Ke in vector control and outputs the d-axis voltage command Vd and the q-axis voltage command Vq;
The d-axis voltage command Vd, the q-axis voltage command Vq, the motor voltage phase instantaneous value θd obtained by adding the shaft error Δθ to the motor voltage phase reference value θ proportional to the frequency command, and the U-phase motor voltage Vu, It has a two-phase to three-phase conversion operation unit that outputs a V-phase motor voltage Vv and a W-phase motor voltage Vw,
The induced voltage constant Ke is based on an axis error Δθ generated between a rotational coordinate axis (dq axis) based on the magnetic pole position of the synchronous motor and a rotational coordinate axis (dc-qc axis) assumed in the control. An induced voltage correction unit for correcting
A synchronous motor drive device characterized by reducing the pulsation of the motor current by inputting the induced voltage constant corrected by the induced voltage correction unit to the motor applied voltage calculation unit. In claim 1 or 2,
The induced voltage correction unit multiplies the axis error Δθ by a correction gain Kp to obtain an induced voltage correction value ΔKe, and adds the induced voltage correction value ΔKe to the input reference induced voltage constant Ke to obtain a corrected value. A synchronous motor driving device characterized in that it outputs as an induced voltage constant. In claim 3,
A synchronous motor driving device, wherein the motor current pulsation reduction is finely adjusted by adjusting the value of the correction gain Kp.

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