JP2009290929A - Controller for permanent magnet type synchronous motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a controller for a permanent magnet type synchronous motor capable of stabilizing a current control system by preventing a current from becoming zero when a load is light, and preventing a current from being excessive by preventing a torque control error. <P>SOLUTION: The controller controls a d-axis current as a current in a direction parallel to the magnetic pole of a permanent magnet of a rotor of the permanent magnet type synchronous motor 80 and a q-axis current as a current in a direction orthogonal to the magnetic pole, thereby controlling the torque or speed of the motor 80. The controller includes an output limiter 151 for limiting the upper limit value of a first d-axis current command value i<SB>d0</SB><SP>*</SP>calculated by a current command calculator 133 at zero or a negative upper limit value i<SB>dmax</SB>. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a control device for a permanent magnet synchronous motor with improved stability of a current control system at light load.

Permanent magnet synchronous motors (PMSM) take current, terminal voltage, and magnetic flux as vectors and perform current control on the d and q axes, which are rotating coordinate axes that rotate in synchronism with the rotor. Control and speed control can be realized. Here, for the d and q axes, the magnetic pole direction of the permanent magnet of the rotor is defined as the d axis, and the direction advanced 90 degrees from the d axis is defined as the q axis.
Since the torque of the permanent magnet type synchronous motor is an increasing function of the current, the current is normally controlled as an increasing function of the torque command value, and the current is often controlled to be almost zero when there is no load.

  However, if the current is very small, the stability of the current control system decreases due to the effects of offset and noise of the current detector and the decreased stability of the output voltage of the power converter that supplies power to the permanent magnet synchronous motor. There is a problem to do. In order to solve this problem, there has already been provided a technique for preventing the current from becoming zero by actively passing the d-axis current at a light load where the current is very small.

For example, in Patent Document 1, when the q-axis current command value is large, the d-axis current command value is controlled to be zero, and when the q-axis current command value is small, the d-axis current command value is converted to a function of the q-axis current. As a result, a technique for preventing the current from becoming zero is described.
In Patent Document 2, the d-axis current command value is controlled under the condition that the torque / current becomes maximum, and when the torque command value is small, the d-axis current command value is corrected according to the torque command value. Thus, a technique for controlling the current to be equal to or higher than a predetermined lower limit value is described.

Japanese Patent No. 3787757 (paragraphs [0024] to [0026], FIG. 1, FIG. 2, etc.) Japanese Patent No. 3796556 (paragraphs [0015] to [0019], FIG. 1, FIG. 2, etc.)

  The technique described in Patent Document 1 is suitable for current control of a surface magnet structure permanent magnet type synchronous motor (SPMSM) having no saliency in the rotor. However, when this technology is applied to an embedded magnet type synchronous motor (IPMSM) having saliency in the rotor, the d-axis current is controlled to zero under heavy load, so the reluctance torque cannot be used and the torque / current is maximized. In addition, there is a problem that a torque control error occurs due to the influence of the reluctance torque generated by passing the d-axis current at a light load.

  On the other hand, in the case of the technique described in Patent Document 2, the current control can be performed so that the torque / current is maximized using the reluctance torque of the embedded magnet type synchronous motor. be able to. However, the d-axis armature reaction when a d-axis current is passed is used to reduce the interlinkage magnetic flux (hereinafter simply referred to as magnetic flux) of the armature winding, so that the terminal voltage is less than the maximum output voltage of the power converter. When so-called “weakening magnetic flux control” is performed, the current may be excessive.

  Therefore, the problem to be solved by the present invention is to stabilize the current control system so that the current does not become zero at the time of a light load, as in Patent Documents 1 and 2, so that no torque control error occurs, and the d-axis current is It is an object of the present invention to provide a control device for a permanent magnet type synchronous motor that is prevented from becoming excessive.

In order to solve the above problems, the invention according to claim 1 is directed to a d-axis current that is a current parallel to the magnetic pole of the permanent magnet of the rotor of the permanent magnet synchronous motor, and a current that is orthogonal to the magnetic pole. In a control device for controlling the torque or speed of the electric motor by controlling the shaft current,
An upper limit limiting means for limiting the upper limit of the d-axis current command value to zero or a negative value is provided.
According to the present invention, the current can be prevented from becoming zero at a light load with a simple configuration, and the stability of the current control system can be improved.

The invention according to claim 2 is provided with lower limit limiting means for limiting the lower limit of the vector sum of the d-axis current command value and the q-axis current command value.
Further, the lower limit value limiting means includes means for calculating a d-axis current upper limit value from the q-axis current command value, and calculating an upper limit value of the d-axis current command value by the d-axis current upper limit value. And a d-axis current upper limit value is set to zero or a negative value.
According to these inventions, the current flowing at the time of light load can be minimized, and the stability of the current control system can be improved.

Furthermore, the invention according to claim 4 is the control device according to claims 1 to 3,
Means for calculating the torque from the d-axis current command value and the q-axis current command value, and calculating the d-axis current command value and the q-axis current command value so that the deviation between the torque command value and the torque calculation value is zero. Means for performing.
According to the present invention, it is possible to prevent the current from becoming zero at a light load and to control the torque to a command value.

  According to the present invention, it is possible to stabilize the current control system by preventing the current from becoming zero at a light load with a simple configuration, to prevent a torque control error from occurring, and to prevent the current from becoming excessive.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram according to an embodiment of the invention.
First, the main circuit for driving the permanent magnet type synchronous motor 80 will be described. 50 is a three-phase AC power source, and the rectifier circuit 60 rectifies the three-phase AC voltage of the power source 50 and converts it into a DC voltage. This DC voltage is supplied to a power converter 70 composed of a PWM inverter, and is converted into a predetermined three-phase AC voltage for driving the electric motor 80.

Next, the configuration and operation of a control device for driving the electric motor 80 by the power converter 70 will be described.
In FIG. 1, the voltage detector 12 detects the input voltage E _dc of the power converter 70. The magnetic pole position detector 90 detects the magnetic pole position θ ₁ of the permanent magnet type synchronous motor 80, and the speed detector 91 detects the speed ω ₁ of the motor 80.
The deviation between the speed command value ω ^* and the detected speed value ω ₁ is calculated by the subtractor 16, and this deviation is amplified by the speed regulator 17 to calculate the torque command value τ ^* .

The voltage limit value calculator 22 calculates the voltage limit value V _align substantially in proportion to the input voltage E _dc . The voltage limit value V _align is set to be equal to or lower than the maximum output voltage of the power converter 70 determined from the input voltage E _dc .
From the torque command value τ ^* , the voltage limit value V _alim, and the speed detection value ω ₁ , the current command calculation unit 18 maximizes the torque / current under the condition that the terminal voltage of the motor 80 is less than or equal to the maximum output voltage of the power converter 70. And d and q-axis current command values i _d ^* and i _q ^* for outputting a desired torque are calculated. Details of the current command calculation unit 18 will be described later.

The current coordinate converter 14 detects the phase current detection values i _u and i _w detected by the u-phase current detector 11u and the w-phase current detector 11w, respectively, based on the magnetic pole position detection value θ ₁ and detects the d and q-axis currents. The coordinates are converted into values i _d and i _q .
The deviation between the d-axis current command value i _d ^* and the detected d-axis current value i _d is calculated by the subtractor 19a, and this deviation is amplified by the d-axis current regulator 20a to calculate the d-axis voltage command value v _d ^* . To do. On the other hand, a deviation between the q-axis current command value i _q ^* and the q-axis current detection value i _q is calculated by the subtractor 19b, and this deviation is amplified by the q-axis current regulator 20b to be q-axis voltage command value v _q ^*. Is calculated.
The d and q axis voltage command values v _d ^* and v _q ^* are converted into phase voltage command values v _u ^* , v _v ^* , and v _w ^* by the voltage coordinate converter 15 based on the magnetic pole position detection value θ ₁ .

The PWM circuit 13 generates a gate signal from the phase voltage command values v _u ^* , v _v ^* , v _w ^* and the input voltage E _dc . The power converter 70 controls the internal semiconductor switching element based on the gate signal, thereby controlling the terminal voltage of the permanent magnet type synchronous motor 80 to the phase voltage command values v _u ^* , v _v ^* , v _w ^* . .

Next, a first embodiment of the current command calculation unit 18 in FIG. 1 will be described with reference to FIG.
In FIG. 2, a magnetic flux command calculator 111 calculates a first magnetic flux command value Ψ ₀ ^* from a torque command value τ ^* . The first magnetic flux command value Ψ ₀ ^* is calculated under the condition that the torque / current is maximized, but it is difficult to execute this calculation online. Therefore, as the magnetic flux command calculator 111, a table of magnetic flux command values at which torque / current is maximized is prepared in advance, and during operation, this table is used to obtain the first magnetic flux command from the torque command value τ ^* . The value Ψ ₀ ^* is calculated.
The magnetic flux limit value calculator 141 limits the terminal voltage of the electric motor 80 to be equal to or lower than the maximum output voltage of the power converter 70, and _uses the voltage limit value V _alim and the speed detection value ω ₁ to calculate the magnetic flux limit value Ψ _lim as shown in Equation 1. It calculates by.

The second magnetic flux command value Ψ ^* is calculated by limiting the upper limit value of the first magnetic flux command value Ψ ₀ ^* to the magnetic flux limit value Ψ _lim by the output limiter 142.
The load angle command calculator 112 calculates a feedforward compensation value δ ₀ ^* of the load angle command value based on the torque command value τ ^* . Further, the load angle adjuster 132 amplifies the deviation between the torque command value τ ^* calculated by the subtractor 131 and the torque calculation value τ _calc to calculate the correction value δ _PI ^* of the load angle command value. Here, the load angle adjuster 132 is configured by a proportional integration amplifier.
The adder 135 calculates the load angle command value δ ^* by adding the feedforward compensation value δ ₀ ^* and the correction value δ _PI ^* .

The torque calculation value τ _calc is calculated by the torque calculator 134 from the second d, q-axis current command values i _d ^* , i _q ^{* according} to Equation 2.

The current command calculator 133 calculates d and q-axis magnetic flux command values Ψ _d ^* and Ψ _q ^* from the second magnetic flux command value ψ ^* and the load angle command value δ ^*, and these d and q-axis magnetic flux commands. First current command values i _d0 ^* and i _q0 ^* are calculated from the values Ψ _d ^* and Ψ _q ^* . The arithmetic expressions are as shown in Expression 3 and Expression 4, respectively.

Next, by limiting the upper limit value of the first d-axis current command value i _d0 ^{* to} the d-axis current upper limit value i _dmax by the output limiter 151 as the upper limit value limiting means in claim 1, the second d The shaft current command value i _d ^* is calculated. Here, the d-axis current upper limit value i _dmax is a value equal to or less than zero (zero or negative value).
On the other hand, as the second q-axis current command value i _q ^* , the first q-axis current command value i _q0 ^* is set as it is.

Next, FIG. 3 shows a vector diagram of the second current command values i _d ^* and i _q ^* calculated by the configuration of FIG.
When the speed is low (generally, below the base speed), the first current command values i _d0 ^* and i _q0 ^* are controlled on the curve that is the torque / current maximum condition in FIG. On the other hand, when the speed is high (generally, above the base speed), the first current command values i _d0 ^* and i _q0 ^* control the magnetic flux to the magnetic flux limit value Ψ _lim, and therefore (b) constant magnetic flux condition in FIG. The so-called flux-weakening control is performed on the ellipse. In any case, when the torque command value is zero, the first current command values i _d0 ^* and i _q0 ^* are controlled on the d-axis where the q-axis current is zero, and the q-axis increases as the torque command value increases. The current increases and is controlled in the direction of the arrow.

Here, by the upper limit value of the first current command value _{i d0} ^* to limit the d-axis current upper limit value _{i dmax,} the second current command value _i ^d _{*, i} ^{q *} is the d-axis current _{i d} It is limited to the left side region of the straight line 151L in Fig. 3 showing the conditions equivalent to the d-axis current upper limit value _{i dmax.} As a result, the second current command values i _d ^* and i _q ^* are limited when the d-axis current is low and the load is low, and the second current command values i _d ^* and i _q ^* are not limited. .

As described above, according to the present embodiment, it is possible to prevent the current from becoming zero at a light load with a simple configuration. In addition, the present embodiment can be easily adapted to the case where the d-axis current is actively passed at the time of light load as in the magnetic flux weakening control, and the d-axis current does not increase more than necessary.
Furthermore, the second current command value i d *, the calculated torque tau calc computed from the fact that feedback control from i q *, the second current command value i d *, i q * is the desired torque The output value is automatically controlled, and there is no torque control error caused by limiting the current command value.

Next, a second embodiment of the current command calculation unit 18 in FIG. 1 will be described with reference to FIG.
In the second embodiment, the lower limit value of the vector sum of the second current command values i _d ^* and i _q ^* is limited so that the current does not become minute even at a light load. Specifically, the d-axis current upper limit value i _dmax in the first embodiment is used as the vector sum of the second current command values i _d ^* and i _q ^* using the first q-axis current command value i _q0 ^*. Calculation is performed so as to be larger than a predetermined lower limit value.

Hereinafter, a description will be given centering on the points different from the first embodiment, based on FIG.
In FIG. 4, the d-axis current upper limit calculator 152 calculates a d-axis current upper limit value i _dmax by Equation 5 to obtain a negative value or zero.

FIG. 5 shows a vector diagram of the second d and q-axis current command values i _d ^* and i _q ^* calculated by the configuration of FIG.
The d-axis current upper limit value i _dmax is calculated by Equation 5, and the upper limit value of the first current command value i _d0 ^* is limited by the output limiter 151 using the d-axis current upper limit value i _dmax . Current command values i _d ^* and i _q ^* are limited to a circle whose distance from the origin is equal to the current vector sum lower limit value i _amin and a region on the left side of the q axis, as shown in FIG. As a result, as in the first embodiment, the second current command values i _d ^* and i _q ^* are limited when the d-axis current is small and the load is low, and the second current command values i _d ^* and i _q ^* are limited. There is no limit.
In the above configuration, the d-axis current upper limit calculator 152 and the output limiter 151 constitute the lower limit limiting means in claims 2 and 3.
In the second embodiment, the same effect as that of the first embodiment can be obtained, and in particular, the current at the time of light load can be reduced as compared with the first embodiment.

  In the above description, an example in which the magnetic pole position and speed of the permanent magnet type synchronous motor 80 are respectively detected by the detector has been shown. However, the present invention estimates the magnetic pole position and speed from the electric current and terminal voltage of the motor. The present invention can also be applied when performing control.

It is a block diagram which shows embodiment of this invention. It is a block diagram which shows the 1st Example of the current command calculating part in FIG. It is a vector diagram for demonstrating operation | movement of the electric current command calculating part shown in FIG. It is a block diagram which shows the 2nd Example of the current command calculating part in FIG. It is a vector diagram for demonstrating operation | movement of the electric current command calculating part shown in FIG.

Explanation of symbols

11u u-phase current detection circuit 11w w-phase current detection circuit 12 input voltage detection circuit 13 PWM circuit 14 current coordinate converter 15 voltage coordinate converter 16 subtractor 17 speed regulator 18 current command calculation unit 19a subtractor 19b subtractor 20a d Axis current regulator 20b q-axis current regulator 22 Voltage limit value calculator 50 Three-phase AC power supply 60 Rectifier circuit 70 Power converter 80 Permanent magnet synchronous motor 90 Magnetic pole position detector 91 Speed detector 111 Magnetic flux command calculator 112 Load Angle command calculator 131 Subtractor 132 Load angle controller 133 Current command calculator 134 Torque calculator 135 Adder 141 Magnetic flux limit value calculator 142 Output limiter 151 Output limiter 152 d-axis current upper limit value calculator

Claims (4)

By controlling a d-axis current that is a current parallel to the magnetic pole of the permanent magnet of the rotor of the permanent magnet type synchronous motor and a q-axis current that is a current orthogonal to the magnetic pole, the torque or speed of the motor is controlled. In a control device for controlling
A control device for a permanent magnet type synchronous motor, comprising upper limit value limiting means for limiting an upper limit value of a d-axis current command value to zero or a negative value. By controlling a d-axis current that is a current parallel to the magnetic pole of the permanent magnet of the rotor of the permanent magnet type synchronous motor and a q-axis current that is a current orthogonal to the magnetic pole, the torque or speed of the motor is controlled. In a control device for controlling
A control device for a permanent magnet type synchronous motor, comprising lower limit value limiting means for limiting a lower limit value of a vector sum of a d-axis current command value and a q-axis current command value. The control device according to claim 2,
The lower limit limiting means is
Means for calculating a d-axis current upper limit value from the q-axis current command value;
Means for limiting the upper limit value of the d-axis current command value by the d-axis current upper limit value,
A control device for a permanent magnet type synchronous motor, wherein the d-axis current upper limit value is set to zero or a negative value. In the control device according to any one of claims 1 to 3,
Means for calculating torque from the d-axis current command value and the q-axis current command value;
Means for calculating the d-axis current command value and the q-axis current command value so that a deviation between the torque command value and the torque calculation value becomes zero;
A control device for a permanent magnet type synchronous motor.

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