JP2000324881A - Control device for permanent magnet synchronous motor - Google Patents

Abstract

(57) [Abstract] [Problem] To use a low-resolution and inexpensive magnetic pole position detector,
A control device capable of preventing loss of synchronism in a PM motor and supplying a sine wave current in a normal state is realized. SOLUTION: First control means for controlling the magnitude of an armature current of a PM motor to coincide with a current command value and controlling the frequency of the armature current to coincide with the frequency command value, and the magnitude of a terminal voltage Is approximately proportional to the frequency command value, and
A second control means for controlling the frequency of the terminal voltage to be equal to the frequency command value; a power converter controlled by an output of the second control means at a high speed, and a power converter controlled by an output of the first control means at a low speed. The present invention relates to a control device that switches a control operation to perform control. Magnetic pole position detecting means 31, 32;
Current angle limiting means for limiting the angle to a predetermined limit value in accordance with the angle of the armature current with respect to the magnetic pole position during the control operation by the first control means, and releasing the limit during the control operation by the second control means 34, 16a.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for a permanent magnet synchronous motor having a permanent magnet in a field.

[0002]

2. Description of the Related Art As a device for driving a permanent magnet type synchronous motor at a variable speed using a power converter such as an inverter, a position detector having an electrical angle of 60 ° resolution is attached to the synchronous motor to detect a magnetic pole position. Therefore, a device called a brushless DC motor that controls a current according to a magnetic pole position has been widely applied. Here, the waveform of the three-phase armature current supplied from the power converter to the synchronous motor is a square wave of 120 ° conduction as shown in FIG. 7 based on the resolution of the position detector. This device will be referred to as a first prior art.

On the other hand, a device for supplying a sinusoidal current without using a position detector is known, and as a simple control method, Japanese Patent Application No. 11-87416 by the present applicant has been proposed. This prior art is characterized in that control is switched between low speed and high speed. That is, at a low speed, the current is controlled to be constant and the frequency is gradually increased to synchronize the permanent magnet synchronous motor. At the time of high speed reaching a predetermined speed, the voltage and the frequency are made substantially proportional to perform so-called V / f constant control. This device will be referred to as a second prior art, and will be described in more detail.

FIG. 6 shows a control block diagram of the second prior art. The rate of change of the first frequency command f ₀ ^* is limited by the ramp function 11, and the second frequency command f ₀ ^*
* Is calculated. The coordinate converter 21 calculates d from the current detection values i _u , i _w of the permanent magnet synchronous motor (PM motor) 24 and the angle θ obtained by integrating the second frequency command f ^* by the frequency integrator 22. The currents i _dc and i _qc on the _c and q _c axes are calculated.

FIG. 8 shows the relationship between various orthogonal coordinate axes and current, and it is assumed that a rotating magnetic field is generated in a counterclockwise direction. The d _c and q _c axes are arbitrary rotating coordinate axes that rotate according to the frequency command f ^* . The d and q axes are coordinate axes on the rotor, and the N pole direction of the permanent magnet is the d axis. The α and β axes are coordinate axes on the stator, and the direction of the magnetic flux generated by the current i _u is the α axis. angle between the α axis and the d _c-axis is θ described above.

In the control block diagram of FIG.
At high speed, the voltage command value is calculated by different means.
You. First, at low speed, the d-axis current controller 14 and the q-axis
The current command value i_dc ^*, I_qc ^*When
Detection value i_dc, I_qcAnd the voltage command value v _dc ^*
(Low speed), v_qc ^*(Low speed), and f /
By the V converter 13, f ^*From d_c, Q_cVoltage finger on axis
Quotation v_dc ^*(High speed), v_qc ^*(High speed) is calculated. these
Is switched by the control switch 12 at f^*of
The control switch signal is output to the switch 16 from the size.
Done. Note that the voltage command value at the time of low speed described above
Convenient control function first control function, voltage at high speed
The command value control function is called the second control function for convenience.
I do.

FIG. 9 shows the relationship between the d _c and q _c axes and the voltage. As can be seen from a comparison between FIG. 8 and FIG. 9, the physical meanings of the angles θ and φ are different between a low speed and a high speed, so that a special shock is not generated when switching control. Although the processing has been performed, it is not shown in the drawing because it has little relevance to the present invention.

[0008] In FIG 6 again, the voltage command value after polar coordinate converter 17 switching process v _dc ^*, v from _{q c} ^*, calculates the angle φ from the command V ^* and d _c axis of the magnitude of the terminal voltage I do. The voltage command calculator 18 calculates three-phase voltage commands v _u ^* , v _v ^* , v _w ^* from the sum of θ and φ and V ^* . These three-phase voltage commands are converted by a PWM circuit 19 into a power converter (inverter).
20 to control the terminal voltage of the synchronous motor 24. Reference numeral 23 denotes a three-phase AC power supply. In this prior art, a sine wave voltage can be easily output by setting the three-phase voltage command to a sine wave, and as a result, a sine wave current can be supplied to the synchronous motor 24. Note that a cycloconverter or the like may be used as the power converter 20 instead of the inverter.

[0009]

A synchronous motor cannot output a normal torque unless the rotational speed matches the frequency of the voltage or current. As is well known, this condition is called step-out. In the first prior art, the phase of the current is controlled in accordance with the position of the magnetic pole, so there is no step-out. However, when an inexpensive low-resolution position sensor is used, the current becomes a square wave, and torque ripple and vibration This causes problems such as an increase in noise and a decrease in efficiency due to harmonic current. This problem can be solved by using a high-resolution position sensor, but there is a problem that the device becomes expensive.

On the other hand, in the second prior art, the above problem does not occur because a sine wave current can be supplied. However, when a heavy load exceeding the output limit of a power converter or a synchronous motor is applied,
There is a problem that the rotation speed does not follow the frequency of the voltage or current output from the power converter, and the motor loses synchronism. Further, when a load having a large moment of inertia is accelerated or decelerated, or when the load largely changes suddenly, a large torque exceeding the output limit may be required excessively, and there is a risk of step-out. Therefore, the present invention uses a relatively inexpensive magnetic pole position detecting means to prevent step-out at the time of heavy load or sudden load change, and to supply a normal load with torque ripple by harmonics by supplying a sine wave current. An object of the present invention is to provide a control device for a permanent magnet synchronous motor that can prevent generation of vibration, noise, and the like and a decrease in efficiency.

[0011]

In order to solve the above-mentioned problems, the present invention can use low-resolution magnetic pole position detecting means, and normally supplies a sine wave current to a synchronous motor without using a magnetic pole position detecting signal. The current phase or the voltage phase with respect to the magnetic pole position is limited to a predetermined value only when an excessive torque exceeding the allowable value of the power converter or the synchronous motor is to be output.

That is, according to the first aspect of the present invention, the armature current and the terminal voltage of the permanent magnet type synchronous motor are taken as a vector, the magnitude of the armature current matches the current command value, and First control means for controlling the frequency to match the frequency command value; and controlling the terminal voltage to be substantially proportional to the frequency command value, and controlling the terminal voltage frequency to match the frequency command value. A second control means for controlling the power converter by an output of the second control means when the frequency is high, and a control operation for controlling the power converter by an output of the first control means when the frequency is low; And a magnetic pole position detecting means for detecting a magnetic pole position of the synchronous motor, and a first control unit for controlling the permanent magnet type synchronous motor as shown in FIG. 6 (second prior art). Current angle limiting means for limiting the angle to a predetermined limit value in accordance with the angle of the armature current with respect to the magnetic pole position during the control operation by the step, and releasing the limit during the control operation by the second control means; It is provided with.

According to a second aspect of the present invention, in the first aspect of the invention, the first current command value in the initial state of the flow to the synchronous motor and the second current larger than the first current command value. And a changeover switch for switching between a command value and a current command value switching signal from the current angle limiting means. The changeover switch is operated to select a first current command value in an initial state of flow to the synchronous motor. When the angle of the armature current with respect to the magnetic pole position is limited to the limit value, the second current command value is selected.

According to a third aspect of the present invention, in the control device for a permanent magnet type synchronous motor according to the first aspect, the first current command value and the first current command value in an initial state of the flow to the synchronous motor are set.
And a changeover switch for switching between a second current command value larger than the current command value and the changeover switch in response to a phase deviation signal from the current angle limiting means. Select the current command value of
When the angle of the armature current with respect to the magnetic pole position is limited to the limit value, the second current command value is selected, and when the frequency exceeds a predetermined value, the angle of the armature current with respect to the magnetic pole position becomes less than the limit value. Means for selecting a first current command value if the current value has not been reached.

According to a fourth aspect of the present invention, there is provided a permanent magnet synchronous motor control apparatus as shown in FIG. 6 (second prior art), wherein a magnetic pole position detecting means for detecting a magnetic pole position of the synchronous motor, Voltage angle limiting means for limiting the angle to a predetermined limit value in accordance with the angle of the armature voltage with respect to the magnetic pole position during the control operation by the control means, and releasing the limit during the control operation by the first control means And with.

According to a fifth aspect of the present invention, in the control apparatus for a permanent magnet type synchronous motor according to any one of the first, second, and third aspects, a magnetic pole position detecting means for detecting a magnetic pole position of the synchronous motor; At the time of the control operation by the second control means, the angle is limited to a predetermined limit value in accordance with the angle of the armature voltage with respect to the magnetic pole position, and the voltage at which the restriction is released during the control operation by the first control means Angle limiting means;
It is provided with.

According to the present invention configured as described above,
By limiting the phase of the current or the phase of the voltage with respect to the magnetic pole position to a predetermined value, it is possible to avoid a step-out at the time of a heavy load or a sudden change of the load. In addition, when the load is within the allowable range of the power converter or the synchronous motor, the sinusoidal current is supplied to the synchronous motor without using the magnetic pole position detection signal. The wave current does not increase.

[0018]

BRIEF DESCRIPTION OF THE DRAWINGS FIG.
Explain the state. First, it corresponds to the invention described in claim 1.
A first embodiment will be described. The control block diagram of FIG.
6, a magnetic pole position of the synchronous motor 24 is detected.
Function within the dashed line with the magnetic pole position sensor 31
To prevent step-out at low speed.
You. Here, the function enclosed by the dashed line is described in claim 1.
Of the magnetic pole position sensor 31.
A magnetic pole position detector 32 to which an output is applied, and a magnetic pole position detection
Value θ_mAnd angle command θ^*Current angle limiter to which is input
(For low speed) 34, the output of this limiter 34 and the original angle
Degree command θ ^*Switch that switches between and outputs as θ
16a (interlocked with the changeover switch 16)
You. Here, the magnetic pole position sensor 31 and the magnetic pole position
2. The magnetic pole position detecting means according to claim 1, wherein the detectors 32 are combined.
It is called Dan.

Here, the current command value i _dc ^* input to the d-axis current controller 14 is set to a constant value I, and the current command value i _qc ^* input to the q-axis current controller 15 is set to zero. Have been. For convenience of explanation, a permanent magnet type synchronous motor 2 will be described below.
It is assumed that there is no saliency in No. 4 and the d-axis inductance is equal to the q-axis inductance. In this case, the synchronous motor 2
4 is expressed by the following equation (1).

[0020]

[Number 1] _{T = P · Φ m · Isin} (θ-θ m)

[0021] In Equation 1, P is the number of pole pairs, the flux linkage [Phi _m is produced by the permanent magnets, theta is 8, the angle of the d _c-axis with respect to α-axis as shown in FIG. 9, for theta _m is α axis This is the angle of the d-axis. From Equation 1, when θ−θ _m > 0, a positive torque T is generated, and as the load increases (θ−θ _m ).
_m ) becomes large, and the torque T becomes maximum when θ−θ _m = 90 °. When the load further increases, (θ−θ _m ) also increases and exceeds 90 °, so that the torque T decreases, and eventually the motor loses synchronism and cannot operate.

Therefore, in the first embodiment, at low speed, the changeover switch 16a is switched to the first control function,
The angle of the d _c-axis with respect to the magnetic pole position (θ-θ _m) as well as monitored by the current angle limiter 34, (θ-θ _m) is 90 °
The angle θ of the armature current with respect to the magnetic pole position is limited and output as follows. Angle theta ^* is a signal before limiting the theta, at light load is equal to the θ θ ^*, (θ ^* -
theta _m) is in the case of more than 90 ° to limit the theta so becomes _{90 ° (θ-θ m)} . That is, θ = θ _m + 90 °
And On the other hand, at the time of high speed, the changeover switch 16a is switched to the second control function to perform the control operation of θ = θ ^* .

Θ _m is a signal detected by the magnetic pole position detector 32. If the resolution of the magnetic pole position detector 32 is low, the actual (θ−θ _m ) is limited to 90 ° by the first control function. Can not. However, in this case, the upper limit of the torque that can be output is the same as that of the first related art, so that the upper limit of the output torque does not decrease. When the load is a light load within a range that the power converter 20 and the synchronous motor 24 can tolerate, θ = θ at both low speed and high speed.
^* , Which is a circuit configuration substantially equivalent to FIG. That is, a sine-wave current can be supplied to the synchronous motor 24 based on the sine-wave three-phase voltage commands v _u ^* , v _v ^* , v _w ^* without using the detection value of the magnetic pole position detector 32.

Next, a second embodiment corresponding to the invention described in claim 2 will be described. The control block diagram of FIG. 2 is obtained by adding a function indicated by a dashed line to the first embodiment. When the first control function is turned on, a current angle limiter (for low speed) is used.
By switching the changeover switch 35 according to the current command value switching signal output from the current command value i _dc ^*
Was changed. For example, in order to maximize the upper limit of the acceleration torque when starting the permanent magnet type synchronous motor 24, it is necessary to set the current command value i _dc ^* to the maximum value that the power converter 20 or the synchronous motor 24 can tolerate. is there. However, according to this method, there is a disadvantage that a large current flows even when a large acceleration torque is not required, and the second embodiment is an improvement on this point.

In FIG. 2, two current command values i _dc1 ^* and i _dc2 ^* are set to constant values I ₁ and I ₂ , respectively, and I ₁ is I ₂
A smaller value. In the initial state of flow, i _dc1 ^* = I ₁
Is signal value switching current command so as to select the output from the current angle limiter 34, the current command value i _dc ^* becomes I ₁ a. When the current angle limiter 34 detects that (θ ^* −θ _m ) has reached the limit value of 90 °, that is, when a large torque is required, the switching signal changes to change the current command value _idc. ^* is switched from the ^{_{i dc1 * = I 1 i dc2}} * = a I _2. Thus, when a small acceleration torque is sufficient during acceleration, the current is small, and when a large acceleration torque is required, the current can be increased.

Next, a third embodiment corresponding to the third aspect of the present invention will be described. The control block diagram of FIG.
The second embodiment is different from the second embodiment in that a function indicated by a dashed line is added. A current command value switch 36 is separately provided.
The changeover switch 35 is operated by the current command value switching signal from No. 6 to switch the current command value _idc ^* .
The current command value switch 36 has a second frequency command f.
^* And the phase deviation signal from the current angle limiter (for low speed) 34 are input.

The static friction of the moving body is larger than the dynamic friction. Particularly, in the early stage of starting the electric motor, the lubricating oil of the bearing may not function sufficiently, and a large starting torque may be required. The third embodiment has been made in consideration of this point. That is, the current command value switch 36 is
In the initial state where the synchronous motor 24 is started upon receiving the phase deviation signal (θ ^* −θ _m ) from the current angle limiter 34, _idc1 ^* is used as the current command value, and (θ ^* −θ _m ) 90 °
_Is reached, the current command value i _dc ^* is changed from i _dc1 ^* to i
_The changeover switch 35 is operated so as to switch to _dc2 ^* . Further, if the second frequency command f ^* is monitored and (θ ^* −θ _m ) does not reach the limit value of 90 ° when the frequency reaches a predetermined value or more, the current command value is set to i _dc2. ^* To i
An operation to switch to _dc1 ^* is performed.

Here, the values set for the current command values i _dc1 ^* and i _dc2 ^* are constant values I ₁ and I ₂ , respectively, as in the second embodiment, and I ₁ is a value smaller than I _2. is there. For this reason,
(Θ ^* -θ _m) but can be from reaching the limit value of 90 ° to obtain high starting torque, i _{dc 1} predetermined frequency, i.e., the current command value reaches a predetermined speed from the i _dc2 ^{* *}
, The current is reduced and unnecessary current does not flow. However, if (θ ^* -θ _m) reaches the limit of 90 °, and that the current command value is always selected the i _dc2 ^*,
In addition, it is assumed that the state is maintained for a predetermined time or more.

Next, a fourth embodiment corresponding to the invention described in claim 4 will be described. The control block diagram of FIG. 4 prevents the step-out at the high speed by adding the magnetic pole position sensor 31 and the function in the dashed line to the prior art of FIG. First of FIG. 1 for prevention
It is paired with the embodiment. That is, at high speed, the changeover switch 16a is switched to the second control function side, and the voltage angle limiter (for high speed) 37 causes θ =
θ ^* is output, and if heavy load is applied, output is limited to θ = θ _m + 90 °. On the other hand, at the time of low speed, the control operation of θ = θ ^* is performed by switching the changeover switch 16a to the first control function side.

As in the first embodiment, the voltage command value v _dc ^*
Is set to zero and v _qc ^* is set to a constant value V. Since the armature voltage is large at the time of high speed, the torque T is expressed by Equation 2 if the voltage drop due to the armature resistance is ignored.

[0031]

T = (V / ω) · (Φ _m / L _d ) · sin (θ−θ _m )

Here, ω is the angular velocity of the rotor, and L _d is the d-axis inductance. At the time of high speed, V and ω are controlled so as to be approximately proportional, so from Expression 2, the torque T is proportional to sin (θ−θ _m ) as at the time of low speed. From equation 2, (θ
If −θ _m )> 0, a positive torque is generated as in the case of low speed, and as the load increases (θ−θ _m )
Becomes larger, and the torque T becomes maximum when θ−θ _m = 90 °. When the load further increases, (θ−θ _m ) also increases to 9
Since it exceeds 0 °, the torque of the synchronous motor 24 decreases,
Eventually it will lose synchronism and become inoperable.

[0033] Therefore, monitors the angle (theta-theta _m) of d _c-axis with respect to the magnetic pole position by the voltage angle limiter (for high speed) 37, the theta such that (theta-theta _m) is 90 ° or less Restrict. The method of preventing the step-out is the same as that at the time of low speed. However, at the time of low speed, the angle of the armature current with respect to the magnetic pole position is limited by the current angle limiter (for low speed) 34. (High speed) 37 limits the angle of the armature voltage with respect to the magnetic pole position.

FIG. 5 shows a fifth embodiment of the present invention, which is a combination of the third embodiment (FIG. 3) and the fourth embodiment (FIG. 4). The operation is obvious from the operation of each embodiment, and the description is omitted. However, normally, a sine-wave current is supplied to the synchronous motor 24, and when an excessive torque is to be output, the magnetic poles are required at a low speed. Limiters 34 and 37 limit the angle of the armature current with respect to the position and the angle of the armature voltage with respect to the magnetic pole position at high speed, and output a predetermined torque to prevent loss of synchronization in any case. be able to.

[0035]

As described above, according to the present invention, even when a low-resolution and inexpensive magnetic pole position detecting means is used as a magnetic pole position detector, the power converter and the synchronous motor can be used under heavy loads. Step-out can be prevented, and sine-wave current can be supplied to a normal load within the allowable range. Therefore, there is no increase in torque ripple, vibration, noise, and efficiency due to harmonics, and it is inexpensive and has high performance. Control device can be realized.

[Brief description of the drawings]

FIG. 1 is a control block diagram showing a first embodiment of the present invention.

FIG. 2 is a control block diagram showing a second embodiment of the present invention.

FIG. 3 is a control block diagram showing a third embodiment of the present invention.

FIG. 4 is a control block diagram showing a fourth embodiment of the present invention.

FIG. 5 is a control block diagram showing a fifth embodiment of the present invention.

FIG. 6 is a control block diagram of a second prior art.

FIG. 7 is a diagram showing a current waveform at the time of 120 ° conduction (first related art).

FIG. 8 is a diagram showing the relationship between various orthogonal coordinate axes and current.

[9] d _c-axis is a diagram showing the relationship between the d _q-axis voltage.

[Explanation of symbols]

 Reference Signs List 11 ramp function 12 control switch 13 f / V converter 14 d-axis current controller 15 q-axis current controller 16, 16a, 35 switch 17 polar coordinate converter 18 voltage command calculator 19 PWM circuit 20 power converter 21 coordinates Converter 22 Frequency integrator 23 Three-phase AC power supply 24 Permanent magnet synchronous motor (PM motor) 31 Magnetic pole position sensor 32 Magnetic pole position detector 34 Current angle limiter (for low speed) 36 Current command value switch 37 Voltage angle limiter (For high speed)

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Naofumi Nomura 1-1, Tanabe-Nitta, Kawasaki-ku, Kawasaki, Kanagawa Prefecture Inside Fuji Electric Co., Ltd. (72) Inventor Nobuo Itoigawa 1, Tanabe-Nitta, Kawasaki-ku, Kawasaki-ku, Kanagawa No. 1 F-term in Fuji Electric Co., Ltd. (Reference) 5H560 BB04 BB12 DA01 DC12 DC13 EB01 EC02 GG04 JJ07 SS06 XA02 XA03 XA05 XA12 XA13 5H576 BB10 DD02 DD05 EE01 EE04 EE11 EE18 FF03 GG01 GG14 LL05 LL05 LL05 LL05

Claims (5)

[Claims] 1. An armature current and a terminal voltage of a permanent magnet type synchronous motor are taken as a vector, the magnitude of the armature current matches the current command value, and the frequency of the armature current matches the frequency command value. Control means for controlling the terminal voltage to be substantially proportional to the frequency command value, and controlling the terminal voltage frequency to match the frequency command value; and Is high, the power converter is controlled by the output of the second control means,
A control unit for switching a control operation to control the power converter based on an output of the first control unit when the frequency is low. Means for limiting the angle to a predetermined limit value in accordance with the angle of the armature current with respect to the magnetic pole position during the control operation by the first control means, and restricting this angle to the control operation by the second control means. A control device for a permanent magnet synchronous motor, comprising: current angle limiting means for canceling. 2. The control device for a permanent magnet synchronous motor according to claim 1, wherein the first current command value in the initial state of the flow to the synchronous motor and a second current command value larger than the first current command value. A changeover switch for switching between a current command value and a current command value, and the changeover switch is operated by a current command value changeover signal from the current angle limiting means, and selects a first current command value in an initial state of the flow to the synchronous motor. And a controller for selecting a second current command value when the angle of the armature current with respect to the magnetic pole position is limited to the limit value. 3. The control device for a permanent magnet type synchronous motor according to claim 1, wherein a first current command value in an initial state of a flow to the synchronous motor and a second current command value larger than the first current command value. A changeover switch for switching between a current command value and a phase deviation signal from the current angle limiting means, operating the changeover switch, and selecting a first current command value in an initial state of current flow to the synchronous motor; When the angle of the armature current with respect to is limited to the limit value, the second current command value is selected, and the angle of the armature current with respect to the magnetic pole position reaches the limit value while the frequency exceeds a predetermined value. Means for selecting a first current command value if not provided, a control device for a permanent magnet type synchronous motor, characterized by comprising: 4. An armature current and a terminal voltage of a permanent magnet type synchronous motor are taken as a vector, the magnitude of the armature current matches the current command value, and the frequency of the armature current matches the frequency command value. Control means for controlling the terminal voltage to be substantially proportional to the frequency command value, and controlling the terminal voltage frequency to match the frequency command value; and Is high, the power converter is controlled by the output of the second control means,
A control unit for switching a control operation to control the power converter based on an output of the first control unit when the frequency is low. Means for restricting the angle to a predetermined limit value in accordance with the angle of the armature voltage with respect to the magnetic pole position during the control operation by the second control means, and restricting this limit to the control operation by the first control means. A control device for a permanent magnet type synchronous motor, comprising: a voltage angle limiting means for canceling. 5. The control device for a permanent magnet synchronous motor according to claim 1, wherein the magnetic pole position detecting means detects a magnetic pole position of the synchronous motor, and the second control means controls the magnetic pole position. Voltage angle limiting means for limiting the angle to a predetermined limit value in accordance with the angle of the armature voltage with respect to the magnetic pole position during the control operation, and releasing the limit during the control operation by the first control means; A control device for a permanent magnet type synchronous motor, comprising: