JP2000278982A - Method for controlling permanent-magnet synchronous motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the increase in the capacity of an inverter and the insulation breakdown voltage of a motor by suppressing a current component in the same direction as the magnetic field of the motor so that the value of a terminal voltage is without a range of the maximum output voltage that can be outputted by the inverter. SOLUTION: When a speed command ω* is outputted from a speed command device 61, a deviation Δω from an output signal ω of a speed detector 53 is inputted as a torque command signal T* of a synchronous motor 51, is inputted to a q-axis current command device 63 to calculate a q-axis current command Iq*, and a d-axis current command device 64 calculates a d-axis current command Id* for inputting to a current control device 65. Then, the output becomes DC voltage commands Vd* and Vq* of d and q axes and is inputted to a modulation wave-generating device 75, a modulation wave signal a* is outputted and is inputted to a PWM pulse-generating device 77 along with a triangular carrier signal Sc, and pulse width modulation is performed, thus controlling the output voltage and output frequency of an inverter 66, and increasing the capacity of the inverter and the insulation breakdown voltage of the motor.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling a permanent magnet type synchronous motor using a small and powerful permanent magnet as a field.

[0002]

2. Description of the Related Art A synchronous motor using a small and powerful permanent magnet for the field can be reduced in size, and the driving device including the motor can be reduced in size and the efficiency is improved.

In order to control the torque of such a motor, a current component (q-axis current component) in a direction perpendicular to the magnetic field direction (d-axis) is controlled according to the magnetic pole position of the motor. This technique is described in Nakano, "Servo Technology and Power Electronics" (published by Kyoritsu Shuppan, September 1994), pp. 94-95. Also, for the same purpose as the DC motor, as the speed of the synchronous motor increases from the specified speed,
There is also a method of controlling the d-axis current to weaken the field. This technique is described in, for example, JP-A-8-182398.

However, the synchronous motor has an armature reaction. Therefore, the voltage increases as the load increases even when operating at a certain rotational speed. This phenomenon occurs in any of the above conventional control methods. In particular, when the load is larger than the rated torque, the voltage rise becomes remarkable. Therefore, when operating near the rated speed, the output voltage of the inverter that controls the motor (maximum output voltage)
Must be large enough to accommodate the voltage increase due to the increased load. As a result, there is a problem that the capacity of the inverter must be increased or the withstand voltage of the motor must be increased.

Furthermore, the inverter input DC voltage related to the output voltage of the inverter is usually generated by a rectifier composed of a diode and a capacitor from an AC power supply, and is thus affected by the voltage fluctuation of the AC power supply. In particular, when the AC power supply voltage decreases, the output voltage of the inverter also decreases as the DC voltage decreases. For this reason, in order to cope with the voltage fluctuation of the AC power supply in addition to the voltage increase due to the increase in the load of the motor described above, a new transformer or the like is provided to increase the receiving voltage in advance, thereby increasing the size of the device. Also occurs. Further, even when the inverter input DC voltage is a battery or the like, a similar measure is required because the voltage fluctuates by continuously applying a load.

[0006]

SUMMARY OF THE INVENTION In view of the above problems, it is an object of the present invention to provide a permanent magnet suitable for reducing an increase in motor output voltage and current and suppressing an increase in inverter capacity and motor withstand voltage. An object of the present invention is to provide a method for controlling a magnet type synchronous motor.

[0007]

SUMMARY OF THE INVENTION The object of the present invention is to provide a permanent magnet type synchronous motor having a terminal voltage in the same direction as a magnetic field of the motor so that the terminal voltage is within a range of a maximum output voltage that can be output from the inverter. The problem can be solved by controlling the component (d-axis current component).

The d-axis current component is calculated by calculating a temporary command value of the d-axis current component based on the relationship between the DC voltage input to the inverter and the torque and rotation speed of the motor. If the value of the provisional d-axis current command is zero or positive, the d-axis current component is set to zero, and if the provisional d-axis current command value obtained by the calculation is negative, the d-axis current component is converted to the provisional d-axis current component. Follow the d-axis current command.

Further, based on the relationship between the DC voltage input to the inverter and the torque and rotation speed of the motor, a provisional command value of a current component (d-axis current component) in the same direction as the magnetic field of the motor is calculated. The d-axis current component, which is normally controlled to be zero, is converted to the d-axis current component in response to a predetermined relationship between a modulation wave for generating a PWM pulse input to the inverter and a carrier wave. The component is made to follow the temporary d-axis current command. Further, based on the relationship between the DC voltage input to the inverter and the torque and rotation speed of the motor, a current component (d
A temporary command value of the d-axis current component) is calculated, and the d-axis current component, which is normally controlled to be zero, is calculated by P
The d-axis current component is made to follow the provisional d-axis current command in response to a predetermined relationship between the ON time of the WM pulse and the carrier wave period of the inverter.

[0010]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a method for controlling a permanent magnet type synchronous motor according to an embodiment of the present invention. In FIG. 1, an AC voltage of an AC power supply 70 is converted into DC by a converter 71, and this DC voltage is smoothed by a smoothing capacitor 72, and the smoothed DC is further converted by an inverter 66 into an AC having a variable voltage and a variable frequency. You. The output of the inverter 66 is supplied to the permanent magnet synchronous motor 51, which drives the synchronous motor 51 at a variable speed. The rotating shaft of the permanent magnet synchronous motor 51 is connected to a load (not shown), and further connected to a position detector 52 and a speed detector 53. The position detector 52 uses a resolver, an encoder, or the like, and detects the relative position between the armature of the synchronous motor 51 and the permanent magnet field, that is, the rotation angle. The speed detector 53 is
An encoder or the like is used to detect the rotation speed of the synchronous motor 51. In the illustrated example, the position detector 52 and the speed detector 53 are divided into functions and described separately. However, actually, the position detector 52 and the speed detector 53 may be constituted by the same device such as a resolver and an encoder.

Now, when the speed command ω ^* is output from the speed command device 61, the deviation Δ from the output signal ω of the speed detector 53.
ω is input to the speed control device 62. Speed controller 62
Works according to this deviation, and its output signal becomes the torque command signal T ^* of the synchronous motor 51. The output signal T ^* of the speed control device 62 is input to the q-axis current command device 63,
In the shaft current command device 63, q corresponding to the torque command signal T ^*
A shaft current command I _q ^* is calculated. The q-axis current command I _q ^* is a command of a component orthogonal to the magnetic field direction of the armature current vector of the synchronous motor 51, and is input to the current control device 65.
On the other hand, the d-axis current command device I _d ^* calculates the d-axis current command I _d ^* by a method described later. d-axis current command I _d ^*
Is a command having the same direction component as the magnetic field of the armature current vector of the synchronous motor 51. The main purpose of the command signal is not only the torque of the synchronous motor 51 but also a command signal for suppressing and controlling an increase in the output voltage. To put it out. The d-axis current command signal I _d ^* is also input to the current controller 65.

The current control device 65 controls the actual current detected by the current detector 74 based on the signal from the position detector 52 so as to flow as instructed. And the q-axis DC voltage commands V _d ^* and V _q ^* .
The output signals V _d ^* and V _q ^* of the current control device 65 are input to a modulation wave generation device 75, and the modulation wave generation device 75 uses the DC voltage commands V _d ^* and V _d ^* based on the signal from the phase detector 52. Modulated wave signal a ^* of AC amount according to V _q ^* (In the case of three phases, there are three actual modulated wave signals of U, V, and W phases, but here, these are collectively referred to as a ^* Output). The output signal a modulated wave generator 75 ^* is input to the PWM pulse generator 77 with the carrier signal s _c triangular, which is the output of a carrier generator 76.

[0014] In the PWM pulse generator 77, performs pulse width modulation to create a PWM pulse signal for comparing the modulated wave signal inputted a ^* and carrier signal s _c, to drive the inverter 66, PWM inverter 66 Outputs a pulse signal.

In the inverter 66, PWM control is executed by a PWM pulse signal from a PWM pulse generator 77, and the output voltage and output frequency of the inverter 66 are controlled.

As described above, the current flowing through the synchronous motor 51 is controlled, and the torque and the terminal voltage are controlled.

FIG. 2 shows the current and voltage showing the principle of the control of FIG.
FIG. In FIG. 2, I: armature current I_d, I_q: D and q axis components of I E_O: No-load induced voltage V_t: Terminal voltage X_d, X_q: Reactance of d and q axes, X_d= X_ad+
X₁, X_q= X_aq+ X_l  X_ad, X_aq, X_l: D, q axis armature reaction reactor
And leakage reactance. From the figure, the output of the synchronous motor
The force P is as shown in equation (1).

[0018]

[Number 1] _{PαV t · I · cosφ = V} t · I · cos (γ + δ) = V t · I · (cosγ · cosδ-sinγ · sinδ) = V t · cosδ · I · cosγ-V t · sinδ · I · sinγ = (E 0 + X d · I d) I q -X q · I q · I d _{= E 0 · I q + (} X d -X q) I d · I q ... (1) i.e., the torque T is expressed by Equation (2).

[0019]

[Number 2] T = P / ω αΦ · I q + (L d -L q) I d · I q ... (2) where, omega: a rotational angular velocity of the motor shaft, ω = ω ₁ / (p / 2) ω ₁ : electric rotation angular frequency p: number of poles of motor Φ: magnetic flux L _d , L _q : inductance of d and q axes,

[0020]

E ₀ = ω ₁ · Φ (3)

[0021]

X _d = ω ₁ · L _d , X _q = ω ₁ · L _q (4) At this time, when the synchronous motor 51 is a cylindrical machine, L
_{Since d} = _Lq = L, the torque T is expressed as in equation (5).

[0022]

T = k · Φ · I _q (k is a constant) (5) As a result, the torque T is proportional to only the q-axis component I _q of the current. Therefore, to control the torque, it is understood that it may be controlled by q-axis component I _q current. Then the terminal voltage V _t of the synchronous motor, from the vector of Figure 2 is expressed as Equation (6).

[0023]

V _t = √ {(E ₀ + X _d · I _d ) ² + (X _q · I _q ) ² ｝ = √ {(ω ₁ · Φ + ω ₁ · L _d · I _d ) ² + (ω ₁ from ^{_{· L q · I q) 2}} } ... (6) equation (6), when the motor is rotating at a constant speed, the terminal voltage V _t can be zero the d-axis current component, the q-axis current component Change. That is, increasing the current component I _q to increase the torque, the terminal voltage V _t It can be seen to increase. At this time, from equation (6), by controlling the d-axis current component I _d in the negative, because the magnitude of the q-axis component of the voltage becomes smaller, apparent that the terminal voltage of the vector sum can be suppressed.

Here, the terminal voltage V of the motor of the equation (6)
by substituting the variable output voltage V _max of the inverter to _t, further,
Solving for I _d gives equation (7).

[0025]

I _d = [√ {(V _max ) ² − (ω ₁ · L _q · I _q ) ² } −ω ₁ · Φ] / ω ₁ · L _d .. (7) From the equation (7), the determination of the field weakening control for suppressing the motor terminal voltage is as follows. If the result of the equation (7) is I _d ≧ 0, the field weakening control is unnecessary (I _d ^* is set to 0). ) results can be expressed by If weakening necessary field control I _d <0 (set the I _d to I _d ^*).

Here, L _q , L _d , and Φ are motor constants, which can be treated as constant, and I _q and ω ₁ change depending on the motor operating state. Therefore, a detected value or a command value in the control device may be used. On the other hand, V _max so varied by the DC voltage V _dc input to the inverter, it may be calculated by the following equation.

[0027]

V _max = (A _max · V _dc ) / (2√2) (8) In the equation (8), A _max is the maximum value of the degree of modulation defined by the amplitude ratio between the carrier and the modulated wave. Normally, A _max = 1 or less is set so as not to exceed the peak of the carrier wave amplitude. In this case, the low-frequency harmonic component is not included in the terminal voltage waveform of the motor. That is, since the terminal voltage waveform is not distorted, torque pulsation generated from the motor can be suppressed, and it can be seen that the terminal voltage waveform is suitable for applications in which vibration of an elevator or the like should be suppressed. Further, in applications that allow some of the torque pulsation is not necessary to set the following A _max = 1, A _max is 1
It can be seen that the value should be set to a value exceeding.

FIG. 3 shows a configuration example of the d-axis current command device 64 to which the above principle is applied. The figure shows the case of a cylindrical machine (L _d = L _q
= L), and the q-axis current command signal I _q ^* is obtained by converting the torque command T ^* from the speed control device 62 by the q-axis current command device 63 based on the principle of Expression (5). The d-axis current calculator 642 receives the signal from the speed detector 53, the signal I _q ^* from the q-axis current command device 63, and the signal V _max from the output voltage setter 643 based on Equation (7). Then, a temporary d-axis current command I _dref is output. Field weakening control determiner 6
At 45, the signal I _dref from the d-axis current calculator 642 is input, and the d-axis current command I _d ^* is determined based on the determination of the field weakening control described above. That is, if I _dref ≧ 0, I
^{_{d * = 0, I dref <}} 0 if I _d ^* = is set to I _dref. Incidentally, the variable output voltage setter 643 based on the equation (8), have set a variable output voltage V _max of the inverter from the voltage detection signal V _dc of the DC voltage detector 73.

By controlling the d-axis current command as described above, the magnitude of the terminal voltage can be suppressed to a predetermined value, so that the withstand voltage of the motor and the control voltage range of the inverter can be reduced. This is effective when the output voltage of the inverter has no margin near the maximum rotation of the motor, and the output capacity of the inverter can be reduced. Furthermore, since the fluctuation of the DC voltage input to the inverter is also taken into consideration, the output voltage of the inverter does not become insufficient even when the receiving voltage decreases, and stable field weakening control is executed.

The current commands I _q ^* and I _d ^* thus obtained are input to the current command device 65. FIG. 4 shows the current control device 65.
The following shows a specific configuration example. The basic configuration of this example is well known,
For example, IEICE Transactions D, 117, 5 (1997)
July), p. 539, FIG. The configuration of FIG. 4 calculates the d- and q-axis voltage components from the vector diagram of FIG. 2, and further calculates ACR-d and ACR-q that act in accordance with the deviation between the d- and q-axis current commands and the actual values. Have. Also,
Figure further consideration of the armature resistance R _a.

The I _d / I _q calculation 651 is based on a sine or cosine signal corresponding to the field pole position (electrical rotation angle) θ from the position detector 52, and the three-phase instantaneous current from the current detector 74. Using the detected values iu, iv, iw, the components I _d ,
_Iq is detected. The outputs of the current controller 65 are d and q axis voltage command signals V _d ^* and V _q ^* , and the modulated wave generator 75
Then, the inverse operation of the I _d / I _q operation 651 is performed, and PW
A modulated wave signal a ^* having a sine wave shape used for generating a PWM pulse in the M pulse generator 77 is generated. This calculation is well known and will not be described.

FIG. 5 is a diagram showing characteristics depending on the presence or absence of such control. (A) is a characteristic example when the control of the present invention is performed, (b) is not performing the control of the present invention, the current for the d-axis is set to zero, and only the current control for the q-axis is performed according to the torque. The example of the characteristic of the conventional control is shown.

In the example of (a), in terms of conditions to become a torque command a field weakening control, and increased in the negative direction in accordance with the d-axis current I _d to the increase in the torque command. The q-axis current is proportional to the torque, as can be seen from equation (5).
When the d-axis current controlling Thus, d, q-axis current armature current I is the vector sum of the components, although slightly increased than I _q, the terminal voltage V _t is hardly increased from no load. Further, also at points b to c when the DC voltage of the inverter decreases, the d-axis current is automatically increased in the negative direction, and the terminal voltage can be suppressed to within the output range of the inverter. For this reason, the variable range of the inverter output voltage can be set to an appropriate minimum required range. As a result, an increase in the capacity of the inverter can be suppressed.

On the other hand, when the zero d-axis component so as in (b), however, the terminal voltage V _t increases with increasing torque command. In addition, when the DC voltage of the inverter decreases, (b)
As described above, the output voltage range of the inverter may be exceeded. As a result, in order to prevent such a phenomenon, a large output voltage of the inverter is required, and as a result, the capacity of the inverter is increased.

As described above, according to the present invention, the variable range of the output voltage of the inverter can be reduced, so that the inverter capacity can be reduced and the withstand voltage of the motor does not increase. Therefore, a compact and economical system can be provided.

FIG. 6 shows another embodiment different from that shown in FIG. In the drawing, those having the same numbers as those in FIG. 3 indicate the same ones. The field-weakening control determiner 641 in FIG. 6 performs the determination at the time of the field-weakening control based on the signal from the modulated wave generator 75 and the signal from the carrier generator 76, and a switching circuit 644.
And outputs the switching signal. Specifically, the modulated wave signal a ^*
When the amplitude has reached the peak value of the carrier signal s _c (peak value), and outputs the d-axis current command I _d ^* to the switching signal for selecting the output signal I _dref of d-axis current calculation unit 642 circuit 644. The switching circuit 644 inputs a 0 signal to the d-axis current command I _d ^* in a state other than the above-described state.

In this case, the determination (start point) of the field-weakening control can be directly determined from the relationship between the carrier wave and the modulation wave that determine the output voltage of the inverter, so that the terminal voltage waveform of the motor does not include the low-time harmonic component. Since torque pulsation generated from the motor can be reliably suppressed and the terminal voltage does not exceed a predetermined value, the margin of the variable range of the output voltage of the inverter can be reduced, and the output capacity of the inverter can be reduced.

[0038] In the above example, it is described that when the amplitude of the modulated wave signal a ^* reaches a peak value of the carrier signal s _c (peak value), the amplitude ratio of the modulated signal a ^* and carrier signal s _c May be defined, and the amplitude ratio may reach a predetermined value set in advance. Furthermore, variable output voltage setter 643 determines it from the voltage detection signal V _dc inverter DC voltage detector 73 has set the variable output voltage V _max of the inverter, the field weakening control as described above (start point) the order is determined directly from the relation between the carrier wave and the modulation wave, without using a detection signal of the direct current voltage may be a fixed value set in advance a variable output voltage V _max. FIG. 7 shows still another embodiment different from those shown in FIGS. In the figures, those having the same numbers as those in FIGS. 3 and 6 indicate the same things. Field weakening control determiner 6 in FIG.
The switch 46 determines the field weakening control based on the PWM pulse signal from the PWM pulse generator 77 and outputs a switching signal to the switching circuit 644. Specifically, PWM
When the ON time of the pulse signal reaches the period of the carrier signal (the carrier period of the inverter), the d-axis current command I _d ^* becomes d.
A signal for selecting the output signal I _dref of the shaft current calculator 642 is output to the switching circuit 644. Also, the d-axis current command I _d ^*
, A 0 signal is input by the switching circuit 644 except in the above-described state.

In this case, the determination (starting point) of the field weakening control can be directly determined from the PWM pulse signal that determines the output voltage of the inverter. Therefore, similarly to the embodiment of FIG. And the output capacity of the inverter can be reduced.

In the above example, the on-time of the PWM pulse signal has reached the carrier cycle of the inverter. However, the time ratio between the on-time of the PWM pulse signal and the carrier cycle is defined. It may be a case where the set predetermined value is reached.

[0041]

As described above, according to the present invention,
To control the current component (d-axis current component) in the same direction as the magnetic field of the motor so that the terminal voltage value of the permanent magnet synchronous motor falls within the range of the maximum output voltage that can be output by the inverter, Since an increase in terminal voltage can be suppressed, an increase in the output voltage and current of the motor can be reduced, and as a result, an increase in the capacity of the inverter and the withstand voltage of the motor can be suppressed. For this reason, the whole control system can be constructed compactly and economically.

[Brief description of the drawings]

FIG. 1 is a diagram showing a control method of a permanent magnet synchronous motor according to one embodiment of the present invention.

FIG. 2 is a vector diagram for explaining a control principle.

FIG. 3 is a diagram showing a configuration example of a d-axis current command device in FIG. 1;

FIG. 4 is a diagram showing a configuration example of a current control device.

FIG. 5 is a diagram showing characteristics according to the present invention.

FIG. 6 is a diagram showing another configuration example of the d-axis current command device.

FIG. 7 is a diagram showing another configuration example of the d-axis current command device.

[Explanation of symbols]

51: Synchronous motor, 52: Position detector, 53: Speed detector, 61: Speed command device, 62: Speed control device, 63:
q-axis current command device, 64: d-axis current command device, 65: current control device, 66: inverter, 70: AC power supply, 71
... Converter, 72 ... Smoothing capacitor, 73 ... DC voltage detector, 74 ... Current detector, 75 ... Modulated wave generator, 7
6 ... Carrier generator, 77 ... PWM pulse generator, 6
41, 645, 646 ... field weakening control determiner, 642 ...
d-axis current calculator, 643 ... output voltage setting device, 644 ...
Switching circuit, 651 ... _Id / _Iq operation.

Continued on the front page (72) Inventor Sadao Hokari 1070 Ma, Hitachinaka-shi, Ibaraki Prefecture, Mito Plant, Hitachi, Ltd. (72) Inventor Hiroshi Nagase 1070 Ma, Hitachinaka-shi, Ibaraki Prefecture, Mito Plant, Hitachi, Ltd. (72) Inventor Takanori Nakata 1070 Ma, Hitachinaka City, Ibaraki Prefecture Inside Mito Plant, Hitachi, Ltd. (72) Inventor Masaya Furuhashi 1070 Ma, Hitachinaka City, Ibaraki Prefecture Mito Plant, Hitachi Ltd. (72) Invention Person Yasutaka Suzuki 1-6-6 Kandanishikicho, Chiyoda-ku, Tokyo F-term in Hitachi Building Systems Co., Ltd. (reference) 3F002 EA05 EA08 5H560 BB12 DA02 DB07 EB01 JJ03 SS07 XA02 XA04 XA12 XA13

Claims (4)

[Claims] 1. A method for controlling a permanent magnet synchronous motor driven by a power converter comprising an inverter for inputting a DC voltage and converting it into an AC having a variable voltage and a variable frequency, comprising: Current component (d-axis current component)
And controlling the motor according to the DC voltage input to the inverter and the torque and rotation speed of the motor to suppress an increase in the terminal voltage of the motor. 2. A method for controlling a permanent magnet synchronous motor driven by a power converter comprising an inverter for inputting a DC voltage and converting the AC voltage into a variable voltage / variable frequency AC, the DC voltage being input to the inverter A temporary command value of a current component (d-axis current component) in the same direction as the magnetic field of the motor is calculated based on the relationship between the torque and the rotation speed of the motor. If the value is zero or positive, the d-axis current component is set to zero, and if the provisional d-axis current command value obtained by the calculation is negative, the d-axis current component is made to follow the provisional d-axis current command. A method for controlling a permanent magnet synchronous motor, characterized in that a rise in terminal voltage of the motor is suppressed. 3. A method for controlling a permanent magnet synchronous motor driven by a power converter comprising an inverter for inputting a DC voltage and converting the AC voltage into a variable voltage / variable frequency AC, the DC voltage being input to the inverter A temporary command value of a current component (d-axis current component) in the same direction as the magnetic field of the motor is calculated based on the relationship between the set value or the detected value of the above and the torque and the rotation speed of the motor, and is usually set to zero. The d-axis current component is controlled by the provisional d-axis current component in response to a modulated wave and a carrier wave for creating a PWM pulse to be input to the inverter. A method of controlling a permanent magnet synchronous motor, characterized by following a current command to suppress a rise in terminal voltage of the motor. 4. A method of controlling a permanent magnet type synchronous motor driven by a power converter comprising an inverter for inputting a DC voltage and converting it into an AC having a variable voltage and a variable frequency, the DC voltage being input to the inverter. A temporary command value of a current component (d-axis current component) in the same direction as the magnetic field of the motor is calculated based on the relationship between the set value or the detected value of the above and the torque and the rotation speed of the motor, and is usually set to zero. The d-axis current component to be controlled is converted to the temporary d-axis component in response to the ON time of the PWM pulse input to the inverter and the carrier cycle of the inverter having a predetermined relationship. A method of controlling a permanent magnet synchronous motor, characterized by following a current command to suppress a rise in terminal voltage of the motor.