JP3395815B2 - Control device for permanent magnet synchronous motor - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a controller for a permanent magnet type synchronous motor used as a motor for driving a vehicle of, for example, an electric vehicle, and more particularly to a controller for a permanent magnet type synchronous motor which performs field weakening control.

[0002]

2. Description of the Related Art FIG. 4 shows a conventional controller for a permanent magnet type synchronous motor. In the figure, 1 is a DC power source, 2
Is a three-phase voltage source inverter, 3 is a current sensor, 4 is a permanent magnet type synchronous motor, 5 is a position sensor for detecting the magnetic pole position attached to the rotor shaft of the motor 4, 6 is a speed sensor,
Reference numeral 7'denotes a control circuit that receives the torque command value τ ^* and generates and outputs a gate pulse signal for the inverter 2. Reference numeral 8 denotes a DC voltage detector.

Next, the structure of the control circuit 7'will be described. First, in a rotating coordinate system that rotates in synchronism with a magnetic flux generated by a permanent magnet on the rotor of the electric motor 4, consider dq coordinates in which the same direction as the magnetic flux is the d axis and the direction orthogonal to this is the q axis. .

The control circuit 7'converts the phase currents I _U and I _W of the motor 4 detected by the current sensor 3 into d-axis and q-axis current detection values I _d and I _q, which is a three-phase / two-phase converter 701. And a q-axis current command calculator 702 that multiplies the torque command value τ ^* by the reciprocal of the torque coefficient K _T to convert it into a q-axis current command value I _q ^* , a rotational angular speed ω detected by the speed sensor 6, and a DC voltage detection. Bowl 8
The d-axis current command calculator 703 that calculates the d-axis current command value I _d ^* from the DC voltage detected by, and the d-axis and q-axis current detection values I _d and I _q for the d-axis and q-axis current command values I A direct current control system 704 that performs an adjusting operation to follow _d ^* , I _q ^* and that compensates a voltage drop due to an armature resistance or a synchronous reactance, and a back electromotive voltage is output from the direct current control system 704. The two-phase voltage command values V _d ^* and V _q ^* on the −q coordinate are amplitude |
V1 |, a polar coordinate converter 705 for converting into a voltage command vector expressed in polar coordinate format at an angle δ1 (first angle command value) with respect to the d axis, and a magnetic pole position detection value output from the position sensor 5. Angle between θ and voltage command vector δ
1 and the inverter 2 that outputs the same voltage as the voltage command vector having the amplitude | V1 | and the angle β.
And a PWM calculator 707 that calculates and outputs a gate pulse signal output by

Next, this operation will be described. Current sensor 3
The phase current detection values I _U and I _{W due to} are converted into d-axis and q-axis current detection values I _d and I _q by the three-phase / two-phase converter 701 using the magnetic pole position detection value θ from the position sensor 5. . On the other hand, the torque command value τ ^* is input to the q-axis current command calculator 702 and converted into the q-axis current command value I _q ^* , and the d-axis current command calculator 703 outputs the d-axis current command value I _d ^*. To be done.

These d-axis and q-axis current command values I _d ^* , I _q ^*
Is input to the DC current control system 704 having the functions of a regulator and a voltage compensator that cause each detected value to follow each detected value, and d
Two-phase voltage command values V _d ^* and V _q ^* on the −q coordinate are output.
These voltage command values V _d ^* and V _q ^* are calculated by the polar coordinate converter 705.
Voltage command vector V1 ^* (amplitude | V1 |, angle δ
It is converted to 1) and input to the PWM calculator 707.

The PWM calculator 707 generates a gate pulse signal having a pulse pattern such that the inverter 2 outputs the same voltage as the voltage command vector V1 ^*, and drives the inverter 2. As a result, the inverter 2 outputs a voltage that matches the voltage command value to drive the electric motor 4.

FIG. 5 shows the space vector of the output voltage of the inverter 2. This voltage vector is V0-V7
(V0 and V7 are zero voltage vectors), there are 8 in total,
For each phase of U, V, and W of the inverter 2, a switching pulse pattern of each phase, for example, the case where the switching element of the upper arm is turned on and the switching element of the lower arm is turned off is, for example, logic "1" and vice versa. It corresponds to. The PWM calculator 707 calculates a pulse pattern such that the inverter 2 outputs the voltage value up to the hexagonal inscribed circle of the voltage vector, which is the maximum output voltage value that does not include the lower harmonics of the fundamental wave. .

Here, when the amplitude of the voltage command vector given to the PWM calculator 707 becomes larger than the hexagonal inscribed circle of FIG. 5, the magnetic flux generated by the permanent magnet is in the opposite direction, that is, the negative d-axis current. Is carried out, so-called field-weakening control is performed to generate a voltage that opposes the induced voltage of the permanent magnet.

On the other hand, as a method of outputting the fundamental wave voltage value larger than the hexagonal inscribed circle of the voltage vector to the inverter 2, there is a method of operating the asynchronous sine wave / triangle wave comparison PWM method by overmodulation. However, in the overmodulation region, the output voltage value becomes non-linear with respect to the modulation rate, and the harmonic component increases. In addition, in the high speed region, the ratio of the fundamental wave frequency to the carrier wave becomes small, causing an obstacle such as a beat.

[0011]

In the above-described conventional control device, the inverter 2 only outputs the voltage value up to the hexagonal inscribed circle of the voltage vector, which is the maximum output voltage value that does not include the lower harmonics of the fundamental wave. When no output is made, the DC voltage cannot be fully utilized, and when the field weakening control is performed to rotate the permanent magnet synchronous motor 4 at high speed, a large amount of negative d-axis current flows, resulting in loss of the inverter 2 and the motor 4. And the current rating of the device increases, the system becomes larger and the cost becomes higher.

Further, when a voltage value equal to or greater than the hexagonal inscribed circle of the voltage vector is output by overmodulation of the asynchronous sine wave / triangular wave comparison PWM method, the output voltage value becomes non-linear with respect to the modulation rate. The calculation of the output voltage command value becomes complicated, and an expensive arithmetic unit capable of executing a complicated calculation is required. Also,
In the high speed region, the ratio of the fundamental wave frequency to the carrier wave becomes small, so that problems such as beats occur and torque control becomes difficult.

[0013]

The present invention has been made to solve the above various problems, and the invention of claim 1 is as follows.
A controller for driving a permanent magnet type synchronous motor having a permanent magnet in a rotor by a three-phase voltage source inverter, and a d-axis in the same direction as the magnetic flux in a coordinate system that rotates in synchronization with the magnetic flux created by the permanent magnet. And the q-axis, which is the direction perpendicular to the d-axis, on the dq coordinates, the d-axis current detection value and the q-axis current detection value obtained by coordinate-converting the stator current detection value of the motor are converted into the d-axis current. A direct current control system that controls so as to follow the command value and the q-axis current command value, and the d-axis voltage command value and the q-axis voltage command value output from this DC current control system, the amplitude of the voltage command vector and the When the voltage that can be output by the polar coordinate converter and the inverter that converts to an angle command value of 1 is represented by a space vector, the voltage value up to the hexagonal inscribed circle created by the six voltage vectors other than the zero voltage vector To output A permanent magnet type synchronization that has a PWM calculator that calculates a PWM pulse, and performs a field weakening control by causing a negative d-axis current in the direction opposite to the magnetic flux to flow to generate a voltage that opposes the induced voltage of the motor by the permanent magnet. In a motor control device, a means for outputting a pulse pattern of one pulse that is turned on and off every 180 degrees in electrical angle and a pulse pattern of this one pulse and a pulse pattern output from the PWM calculator are switched. First switching means, q-axis current command value, d-axis current detection value, electric motor
Based on the rotation speed, DC voltage detection value and motor constant
Angle operation that calculates the second angle command value of the voltage command vector
Switch between the calculator and the angle command value of the voltage command vector
2 switching means, and when the field weakening control, the first
It drives the inverter by using one pulse of the pulse pattern selected by the switching means, one pulse of the pulse
When the pattern is used, the second switching means
The first angle command value is switched to the second angle command value .

According to a second aspect of the invention, in the first aspect of the invention, a pulse pattern storage means is provided, and a voltage value for interpolating from the maximum output voltage value of the inverter to the output voltage value at one pulse is output. The pulse pattern is stored and the inverter is driven using the pulse pattern corresponding to the voltage command vector.

According to a third aspect of the present invention, in the second aspect of the present invention, the pulse pattern stored in the storage means is a pulse pattern precalculated so as to minimize low-order harmonics for each voltage value. It is a thing.

[0016]

According to a fourth aspect of the present invention, in the first aspect of the present invention, a voltage command limiter for limiting the amplitude of the voltage command vector is provided, and in the low speed range of the electric motor, the voltage limit value of the limiter is set to the maximum output voltage value of the inverter. Set to P
The pulse pattern by the WM calculator is used, and in the high speed range of the electric motor, the voltage limit value of the limiter is set to the output voltage value for one pulse and the pulse pattern for one pulse is used.

Now, consider a case where the permanent magnet type synchronous motor is subjected to weakening field control. Looking at the space vector display of the output voltage of the inverter shown in FIG. 5, the locus of the output voltage value during the 1-pulse control in which the switching element is turned on and off at every electrical angle 180 degrees moves along the apex of the hexagon,
The locus of the maximum output voltage value based on the pulse pattern calculated by the M calculator moves on the inscribed circle of the hexagon. When the DC intermediate voltage value of the main circuit shown in FIG. 4 is E _D , the line voltage fundamental wave effective value V01 for one pulse is expressed by Equation 1.

[0019]

[Number 1] _{V01 = √6 / π × E D} ≒ 0.7797E D

Further, the line voltage fundamental wave effective value V02 on the hexagonal inscribed circle of the voltage vector is expressed by Equation 2.

[0021]

[Number 2] _{V02 = 1 / √2 × E D} ≒ 0.7071E D

As is clear from the comparison between these equations 1 and 2, the output voltage value for one pulse is about 10% higher than the maximum output voltage value according to the pulse pattern from the PWM calculator. Normally, in the field weakening control, the negative electromotive force of the permanent magnet type synchronous motor that cannot be output by the inverter is compensated by supplying a negative d-axis current. Therefore, the output voltage value of the inverter increases by about 10% during the one-pulse control, so that the speed at which the field weakening control is required increases, and the negative d-axis current can be reduced at the same speed within the field weakening control.

In general, the relation among the current I flowing through the permanent magnet type synchronous motor, the output voltage V _{1 of the} inverter, and the counter electromotive voltage e ₁ is given by the equation (3). In addition, R is a winding resistance and L is a leakage inductance.

[0024]

## EQU3 ## V ₁ = RI ₁ + L (dI ₁ / dt) + e ₁

Current I ₁ ignoring resistance R in equation 3
Equation 4 is solved.

[0026]

[Equation 4] I ₁ = (1 / L) ∫ (V ₁ −e ₁ ) dt

That is, the value obtained by multiplying the difference between V ₁ and e ₁ by the integral gain becomes the current I ₁ . In a permanent magnet type synchronous motor that performs field weakening control, the d-axis inductance L _d is usually increased in order to reduce the field weakening current.
Therefore, when the permanent magnet type synchronous motor is driven in the high-speed range where the field weakening control is performed, the fundamental wave frequency components of V ₁ and e ₁ are high, and the design value of L is large as described above. , The influence of the harmonic voltage such as the 7th harmonic on the current is reduced. Therefore, even if one pulse including the low-order harmonic component of the fundamental wave is output in the high-speed range where the field weakening control is performed, the current waveform is less likely to be distorted by the harmonic voltage component, and no trouble occurs.

In one pulse control, the second angle command value δ2 used in place of the angle command value δ1 in FIG.
Shown in.

[0029]

Equation 5] _{^{δ2 = -sin -1 (RI d -ωLI}} q *) / (√6 / π × E D) + π / 2 ( forward _{^{rotation) = sin -1 (RI d -ωLI}} q *) / ( √6 / π × E _D ) + 3π / 2 (during reverse rotation)

Since the second angle command value δ2 takes into consideration the q-axis current command value I _q ^* which is the torque command value, the second angle command value δ2 is set when one-pulse control is performed in the field weakening control. By selecting, it becomes possible to drive the permanent magnet type synchronous motor without impairing the torque accuracy.

[0031]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, claims 1 to 3 will be described with reference to the drawings.
An embodiment of the invention described in Item 4 will be described. FIG. 1 shows the overall configuration of this embodiment, and here, the description will focus on the parts that differ from FIG. In the control circuit 7 of FIG. 1, 711 is a voltage command limiter that limits the amplitude | V1 | of the voltage command vector to a predetermined voltage limit value according to the rotation angle ω, and the amplitude | V |
WM calculator 707, pulse pattern switching judgment circuit 70
8 has been entered in the ROM table 709. The output signal of the pulse pattern changeover judgment circuit 708 is applied to the pulse pattern changeover switch 710 and the angle command changeover switch 713.

Here, the angle command changeover switch 713 is
The angle (first angle command value) δ1 of the voltage command vector,
Second angle command value δ2 output from angle calculator 712
The pulse pattern changeover switch 710 switches between the pulse pattern output from the PWM calculator 707 and the pulse pattern read from the ROM table 709.

The angle calculator 712 calculates the q-axis current command value I _q ^* , the d-axis current detection value I _d , the rotational angular velocity ω of the electric motor 4,
Based on the DC voltage detection value E _D and the motor constant, the second angle command value δ2 is calculated by the above-mentioned formula 5, and is output to the angle command changeover switch 713 side. Further, the ROM table 709 stores a so-called one-pulse pulse pattern that is repeatedly turned on and off for each electrical angle of 180 degrees, and the maximum output of the inverter 2 based on the pulse pattern calculated by the PWM calculator 707. A pulse pattern for outputting a voltage value that interpolates from the voltage value to the output voltage value for one pulse is stored. Then, the output signal of the pulse pattern switching judgment circuit 708 and the adder 7
The pulse pattern selected from the ROM table 709 based on the angle command value output from 06 is output to the pulse pattern changeover switch 710 side.

In this embodiment, when the amplitude | V | of the voltage command vector is larger than the maximum output voltage value of the inverter 2 based on the pulse pattern calculated by the PWM calculator 707, and the field weakening control is required, the pulse The pattern change judgment circuit 708 changes the changeover switch 710 to change the pulse pattern output to the inverter 2 to P
The pulse pattern of the maximum output voltage value of the inverter 2 by the WM calculator 707 is switched to the pulse pattern for one pulse in the ROM table 709. The above action is
According to the embodiment of the invention described in claim 1.

The embodiment of the invention described in claim 2 is a ROM table 7 as a storage device for storing pulse patterns.
09, and a pulse pattern that outputs a voltage value that interpolates from the maximum output voltage value of the inverter 2 to the output voltage value at the time of one pulse is stored in the ROM table 709, and the amplitude | V | Is larger than the maximum output voltage value and smaller than the output voltage value for one pulse, the pulse pattern corresponding to the amplitude | V | is read and output to the changeover switch 710 side. In this case, the changeover switch 710 is changed over to the ROM table 709 side by the output of the pulse pattern changeover judgment circuit 708.

The third embodiment of the present invention will be described. As a pulse pattern for interpolating the above voltage value, the 5th order, 7th order, 11th order and 13th order which are low order harmonics for each voltage value.
The pulse pattern calculated so that the next harmonic component is minimized is used. FIG. 2 shows an example of a pulse pattern that reduces low-order harmonics. This pulse pattern has a symmetrical waveform in units of 1/4 cycle. When this waveform is represented by a Fourier series, it becomes as shown in Expression 6.

[0037]

[Equation 6]

Equation 6 is "semiconductor power conversion circuit"
This is a known calculation formula described on page 135 of the Institute of Electrical Engineers of Japan (5th edition). From Equation 6, the switching angles α1 to α5 in FIG. 2 are calculated and obtained so that the 5th, 7th, 11th, and 13th harmonic components are minimized for each voltage value.

Further , in the embodiment of the invention described in claim 1 , in FIG. 1, the angle calculator 712 controls the q-axis current command value I _q ^* , the d-axis current detection value I _d , the rotational angular velocity ω of the electric motor 4, Based on the DC voltage detection value E _D and the motor constant, the second angle command value δ2 is calculated by the above equation 5, and when the pulse pattern switching determination circuit 708 selects the pulse pattern of 1 pulse, the changeover switch 713 is changed to the first value. The angle command value δ1 of 1 is switched to the second angle command value δ2, and the angle command value δ is input to the adder 706 as δ2.

Further, in the embodiment of the invention described in claim 4 , the voltage command limiter 711 is arranged so as not to output one pulse in the low speed region of the electric motor 4 detected by the speed sensor 6.
The voltage limit value is set to the maximum output voltage value of the inverter 2, and the voltage limit value is set to the output voltage value for one pulse so that one pulse can be output in the high speed range.

FIG. 3 shows an example of the voltage limit value of the voltage command limiter 711. If the speed is less than n1 in FIG.
The voltage limit value is set to V _lim1 which is the maximum output voltage value of the inverter 2 so that no pulse is output. Further, at a speed of n2 or more, the voltage limit value is set to V _lim2 which is the output voltage value at the time of one pulse so that one pulse can be output. Furthermore, the speed n
In the range of 1 to n2, the voltage limit value is proportional to the speed. In addition to this example, the effect of the present invention can be obtained even if the voltage limit value has a hysteresis due to the speed.

[0042]

As described above, according to the invention of claim 1,
When operating a permanent magnet type synchronous motor at high speed using field weakening control, by controlling the inverter with one pulse, the negative d-axis current, which is the field weakening current, is reduced and the use of equipment with a small current rating is possible. This makes it possible to realize downsizing of equipment and cost reduction.

According to a second aspect of the invention, in the first aspect of the invention, by using a pulse pattern for interpolating a voltage value between the maximum output voltage value of the inverter and the output voltage value at one pulse, the output voltage is It is possible to prevent the disturbance of the current waveform due to the abrupt change of, and to continuously change the output voltage value up to the output voltage value of one pulse according to the voltage command value.

According to the third aspect of the present invention, the pulse pattern for interpolating the voltage value in the second aspect uses a pulse pattern that minimizes low-order harmonics, thereby minimizing distortion of the current waveform and torque ripple. can do.

Further, in the first aspect of the present invention, when performing the 1-pulse control, by using the second angle command value in consideration of the q-axis current command value and the torque command value, the current due to the distortion of the current waveform It is possible to realize the field weakening control that compensates the torque accuracy without being affected by the detection error.

According to the invention of claim 4, in the invention of claim 1, by using the voltage command limiter, in the low speed range where the influence of the distortion of the current waveform due to the low order harmonic voltage is large, Distortion of the current waveform is eliminated by outputting only the pulse pattern of the PWM calculator that does not include the low-order harmonics without outputting the pulse pattern of one pulse that contains the harmonics, and the distortion of the current waveform due to the low-order harmonic voltage In the high-speed range where the influence of is small and a large amount of field weakening current is required,
By making it possible to output a pulse pattern of one pulse, it is possible to make maximum use of the DC voltage and reduce the field weakening current.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram showing an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a pulse pattern in the embodiment of the invention described in claim 3;

FIG. 3 is an explanatory diagram of a voltage limit value in the embodiment of the invention described in claim 4 ;

FIG. 4 is an overall configuration diagram showing a conventional technique.

FIG. 5 is a diagram showing a space vector of an output voltage of an inverter.

[Explanation of symbols]

1 DC power supply 2 Three-phase voltage source inverter 3 Current sensor 4 Permanent magnet type synchronous motor 5 Position sensor 6 Speed sensor 7 control circuit 701 Three-phase / two-phase converter 702 q-axis current command calculator 703 d-axis current command calculator 704 DC current control system 705 Polar coordinate converter 706 adder 707 PWM calculator 708 pulse pattern switching judgment circuit 709 ROM table 710,713 changeover switch 711 Voltage command limiter 712 Angle calculator

Front page continuation (72) Inventor Masahiko Hanazawa 1-1 Tanabe Shinden, Kawasaki-ku, Kawasaki-shi, Kanagawa Fuji Electric Co., Ltd. (72) Inventor Go Aso, Takara-cho, Kanagawa-ku, Yokohama-shi, Kanagawa Nissan Motor Co. (72) Inventor Toshio Kikuchi 2 Takaracho, Kanagawa-ku, Yokohama, Kanagawa Nissan Motor Co., Ltd. (72) Inventor Shinichiro Kitada 2 Takaracho, Kanagawa-ku, Yokohama, Kanagawa Nissan Motor Co., Ltd. (56) References Unexamined Japanese Patent Publication No. 7-194200 (JP, A) Actual development No. 6-21394 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) H02P 5/408-5/412 H02P 7/628 -7/632 H02P 21/00 H02P 6/00-6/24 H02M 7/42-7/98

Claims (4)

(57) [Claims] 1. A control device for driving a permanent magnet type synchronous motor having a permanent magnet in a rotor by a three-phase voltage type inverter, wherein a magnetic flux is generated in a coordinate system that rotates in synchronization with the magnetic flux generated by the permanent magnet. The d-axis current detection value and the q-axis current detection value obtained by coordinate-converting the stator current detection value of the electric motor on the dq coordinates consisting of the d-axis in the same direction and the q-axis orthogonal to the d-axis. To a d-axis current command value and a q-axis current command value, respectively, and a direct current control system for controlling the d-axis current command value and the q-axis current command value. A polar coordinate converter that converts the vector amplitude and the first angle command value, and a hexagonal inscribed line created by six voltage vectors other than the zero voltage vector when the voltage that can be output by the inverter is expressed as a space vector. Voltage value up to the circle P such as to force
A permanent magnet type synchronization that has a PWM calculator that calculates a WM pulse, and performs a field weakening control by causing a negative d-axis current in the opposite direction of the magnetic flux to generate a voltage that opposes the induced voltage of the motor by the permanent magnet. In a motor control device, means for outputting a pulse pattern of one pulse that is turned on and off every 180 degrees in electrical angle and a pulse pattern of this one pulse and a pulse pattern output from the PWM calculator are switched. First switching means, q-axis current command value, d-axis current detection value, motor rotation speed,
Based on the DC voltage detection value and the motor constant, the voltage command
Angle calculator for calculating the second angle command value of the torque and second switching for switching the angle command value of the voltage command vector
And means, and at the time of field-weakening control, to drive the inverter with a 1 pulse of the pulse pattern selected by said first switching means, when using the one pulse of the pulse pattern, said second switching
The first angle command value is transferred to the second angle finger by the conversion means.
A controller for a permanent magnet type synchronous motor, which is characterized by switching to a command value . 2. The control device for a permanent magnet type synchronous motor according to claim 1, further comprising a pulse pattern storage means for outputting a voltage value for interpolating from a maximum output voltage value of the inverter to an output voltage value at one pulse. Memorize the pulse pattern that
A controller for a permanent magnet type synchronous motor, which drives an inverter using a pulse pattern corresponding to a voltage command vector. 3. A controller for a permanent magnet synchronous motor according to claim 2, wherein the pulse pattern stored in said storage means is a pulse calculated in advance so as to minimize low-order harmonics for each voltage value. A controller for a permanent magnet type synchronous motor, which is a pattern. 4. A controller for a permanent magnet synchronous motor according to claim 1, further comprising a voltage command limiter for limiting the amplitude of the voltage command vector.
In the low speed range of the motor, the voltage limit value of the limiter is
Set the maximum output voltage value of the burner to the PWM calculator
The pulse pattern according to
Set the limiter voltage limit value to the output voltage value for one pulse
The controller for a permanent magnet synchronous motor is characterized by using a pulse pattern for one pulse .