JP2003348899A - Control method for motor and control unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a control unit that provides a motor with high efficiency and high-output characteristics by suppressing the degradation of characteristics caused by the copper loss in a high-speed range and the change of the multiplier of a motor apparatus, and enables the expansion of characteristics in the high- speed range, in performing soft field control. <P>SOLUTION: The motor control unit comprises a means for determining a high-output revolution range that determines a revolution range, where even a small current has a high output depending on the combination of the value of a winding current flowing to a stator winding and a lead angle from the q-axis of the winding current, i.e., the value of a current phase; and an output comparison means that compares the motor torques, by combining the value of the winding current and the value of the current phase, i.e., the comparison of the outputs. The output comparison means compares the motor torques calculated by combining the value of the winding current and the value of the current phase, and further compares the number of revolutions, thus selecting the combination of the value of a large-output winding current and the value of the current phase. <P>COPYRIGHT: (C)2004,JPO

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor control method and apparatus for performing field weakening control of a synchronous motor.

[0002]

2. Description of the Related Art As a conventional control method, a field current command value Id in synchronous motor control is described in IEA-92-30 (Document 1) of the Institute of Electrical and Industrial Engineers of Japan.
A control method for calculating * by the following equation (1) and performing field-weakening control is shown.

[0003]

(Equation 1)

Here, ωbase indicates the base rotation speed of the motor, ωmax indicates the maximum rotation speed of the motor, and Idm
Indicates the d-axis current at the maximum rotational speed ωmax. In addition, in the 1991 IEEJ National Conference on Industrial Applications, National Conference on Industrial Applications, No. 74, P310-315 (Reference 2), the field current command value Id * includes the target rotation speed, d-axis winding reactance, and q-axis winding. A control method for performing field-weakening control by calculating using a line reactance, a stator winding resistance, a no-load induced voltage at a unit speed, and the like is shown. Further, Japanese Patent Application Laid-Open No. 57-19689
No. 6 and Japanese Patent Application Laid-Open No. 62-7396 describe a field weakening control method in which a controller detects an error (realization degree) between a motor torque or current actually measured in real time and a command value, and feeds back the error. It is shown. Thus, the field current Id according to the operating state of the motor in real time
Can be given to the motor.

Further, in Japanese Patent Application Laid-Open No. 08-266099, a judgment value of the degree of saturation indicating a ratio at which the winding current can be supplied is set, and when the judgment value is positive, the d-axis current command unit sets the d-axis current command unit to the d-axis. A control method for increasing the current command value is shown. When the increased d-axis current command value exceeds the set maximum value, it is held at the maximum value. If the judgment value is negative, the command value is reduced to the minimum value when the command value decreases beyond the preset d-axis minimum value or when the rotation speed falls below the preset rotation speed setting value. To hold. In this way, the field current Id is obtained by the feedback integration control, and the control is performed by setting the conditions for stably operating the motor, such as the setting of the number of rotations to enter the field weakening.

[0006]

In the conventional control methods described in Documents 1 and 2, in the field-weakening control in the high-speed rotation region of the synchronous motor, the above equation (1) is used according to the target rotation speed ω. The command value Id * of the field current is obtained. However, in an actual motor, each constant of the motor device changes due to a change in the operating state or a change in the winding resistance of the motor with time. Therefore, the field current command value Id * calculated by the above equation (1) is not always the optimum value. Therefore, when it is desired to obtain a high torque by rotating the motor at a high speed, it is necessary to give a relatively large field current Id in anticipation of the variation of each of the constants. As a result, there is a problem that the copper loss increases by the amount of the field current Id which is given more, and the efficiency becomes worse.

In the control methods disclosed in JP-A-57-196896, JP-A-62-7396, and JP-A-08-266099, the current command value is increased in a state where the disturbance of the feedback current value is large. When the current value is large, the error of the current value to be fed back increases in proportion to the magnitude of the current value. Therefore, the efficiency and the characteristics are reduced. Even if the current value to be fed back is a correct value, the error from the command value may become too large and exceed the limit value of the field current Id to be controlled. In such a case, a field current Id that satisfies the characteristics of the motor cannot be realized, which leads to a reduction in efficiency and a reduction in characteristics.

[0008]

According to the present invention, there is provided a motor control apparatus comprising: a current command section for outputting a command value of a winding current of each phase of a stator of a motor; and a dq orthogonal axis of the stator. A d-axis current command unit for giving a command value of the stator d-axis current at
A q-axis current command unit for giving a command value of the q-axis current of the stator in the q orthogonal axis, a rotation speed judgment unit for judging the rotation speed for performing the field weakening control of the motor, and weakening according to the judgment result of the rotation speed judgment unit. When performing field control, a d-axis current control unit that increases or decreases the d-axis current value, a saturation degree determination unit that determines a ratio at which the winding current can be supplied, and a reference value of the q-axis current equal to the maximum q-axis current value of 2 It is assumed that the q-axis current value, which is reduced by advancing the current phase, which is the advance angle of the winding current phase from the q-axis, at a predetermined winding current value, is less than the reference value. High output rotation speed region determination unit for determining
An output comparing unit that changes a winding current and a current phase in each predetermined control cycle, obtains a torque from a winding current value and a current phase value in each cycle, and compares the obtained torque in the control cycle; and A current control unit is provided for controlling the winding current value and the current phase value so that the torque is maximized based on the comparison result of the comparison unit.

A motor control device according to another aspect of the present invention comprises:
A current detection unit that detects a winding current of each phase of the motor stator; a current command unit that outputs a command value of the winding current of each phase; and compares the winding current with a command value of the winding current. An output comparison unit, a command value of the winding current and an output of the output comparison unit are input, a rotation number determination unit that determines whether the rotation number is a rotation number for performing the field weakening control, an output of the rotation number determination unit is input, A command value for a d-axis current, which is a stator current expressed in a dq orthogonal axis coordinate system, based on the determination result of the rotation speed is given by d
An axis current command unit, a command value of the d-axis current is input, a d-axis current control unit that changes the d-axis current in the field weakening control, and a q-axis current that is a stator current expressed in a dq orthogonal axis coordinate system. A q-axis current command unit for giving a command value, an adder for adding the output of the d-axis current control unit and the output of the q-axis current command unit, an addition output of the adder and a detection output of the current detection unit are applied. , Determine the proportion of the winding current that can be supplied,
A saturation determination unit for applying a determination output to the d-axis current control unit, and for a predetermined winding current value input from the adder, a reference value of the q-axis current value is set to a half of a maximum value of the q-axis current. 1
When the current phase, which is the advance angle of the winding current from the q-axis, advances and the q-axis current value falls below the reference value, the predetermined winding current value and the predetermined current phase value The output of the high output rotation speed region determination unit that determines whether the output of the motor is higher at a value lower than the predetermined winding current value, and the output of the high output rotation speed region determination unit is applied to the specific winding current. An output comparing unit that compares the line current value and the motor torque at a specific current phase value for each predetermined control cycle; and a comparison result of the output comparing unit, the winding current value and the current phase value are set so that the torque is maximized. And a current control unit for controlling the current.

According to the present invention, the output comparing section compares the motor torques by the combination of each current and phase. If the conditions are not satisfied, the output comparison is continued until the conditions are satisfied. Do it. When the condition is satisfied, if there is no command change of the winding current and the phase by the time of performing the next output comparison, the state of the winding current and the phase is maintained at the value performed by the normal field weakening control.

The method of controlling a motor according to the present invention includes the steps of: detecting a winding current of each phase of a stator of the motor; outputting a command value of the winding current of each phase; Comparing the current command value with the command value, determining whether the rotation speed is to perform the field-weakening control based on the comparison result of the comparison step, based on the determination result of the rotation speed, in the dq orthogonal axis coordinate system. D is the stator current expressed
A current command step of giving a command value of the axis current, a step of changing the d-axis current based on the command value of the d-axis current when performing field-weakening control, and a stator current expressed in a dq orthogonal axis coordinate system. giving a command value of the q-axis current,
Adding the output of the d-axis current control unit and the q-axis current command value, and applying the added output and the detected value of the winding current to determine a saturation degree indicating a supply ratio of the winding current. Applying the determination output to the d-axis current control unit, setting the reference value of the q-axis current to a value equal to or less than half of the maximum value of the q-axis current, and setting a predetermined winding based on the output of the adder. In the line current value, when the current phase, which is the advance angle of the winding current from the q-axis, advances and the q-axis current value falls below the reference value, the predetermined winding current value and the predetermined current phase value Determining whether the output of the motor increases at a value lower than the predetermined winding current value; and when the output of the motor increases, the motor at the predetermined winding current value and a predetermined current phase value. Output comparison that compares torque at each control cycle Step, and the comparison result of the comparing step comprises the step of controlling the winding current value and its phase so that the torque becomes the maximum.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A motor control method and apparatus according to an embodiment of the present invention will be described with reference to FIGS. << First Embodiment >> A motor control method and a control apparatus according to a first embodiment of the present invention will be described with reference to FIGS. First, the field weakening control of the synchronous motor will be described using equation (2) and FIG. Equation (2) is the basic equation for a synchronous motor well known in the art.

[0013]

(Equation 2)

Here, V indicates a terminal voltage of a power supply for supplying power to the synchronous motor, ω indicates an angular speed of rotation of the synchronous motor, and R indicates a stator winding resistance per phase. φa
Indicates a no-load armature linkage flux at a unit angular velocity, and Ld,
Lq indicates the phase inductance of the d-axis and the q-axis, respectively.
Id indicates the orthogonal axis stator current (d-axis current), and Iq indicates the orthogonal axis stator current (q-axis current). Ia indicates a winding current. Assuming that Pn is the number of pole pairs, the motor rotation speed N is (6
0 · ω / 2π) / Pn. In (a) to (c) of FIG. 3, dq orthogonal coordinates are rotational coordinates, and show vector diagrams of field weakening control. Id indicates the DC component of the d-axis current, and Iq indicates the DC component of the q-axis current.

In the vector diagram of the field-weakening control shown in FIG. 3A, when the rotational angular velocity ω is increased, the induced voltage ω ·
φa increases. The voltage value V is a winding voltage R · I of the product of the induced voltage ω · φa, the stator winding resistance R and the q-axis current Iq.
q and the vector addition of ω · Lq · Iq of the product of the angular velocity, the q-axis phase inductance Lq, and the q-axis current. When the voltage value V reaches a value corresponding to the radius of the voltage limiting circle C, the synchronous motor cannot increase the rotational speed beyond the rotational angular speed ω at that time. When the power source is a battery, the terminal voltage and the current value of the battery change due to deterioration of the battery, but here, for simplicity, it is assumed that the terminal voltage of the battery corresponding to the voltage limiting circle C is constant. I do.

Next, consider further increasing the rotational speed of the synchronous motor. When the d-axis current Id flows through the synchronous motor, a voltage (ω · Ld · Id) is generated in a direction in which the voltage value V returns to the inside of the voltage limiting circle C as shown in FIG.
As a result, there is a voltage margin that can further increase the rotation speed of the synchronous motor. When the rotation speed is not increased, the torque of the synchronous motor can be increased by passing a torque current by the generated voltage margin. FIG. 3C shows a state in which the voltage value V is increased in order to increase the torque of the synchronous motor. Here, the case where the d-axis current Id is positive is defined as the direction in which the current phase is advanced.
Also, if the advance angle from the q axis is β (current phase value),
The relationship between Ia, Iq, Id, and β is as shown in the following equations (3) and (4).

[0017]

[Equation 3]

[0018]

(Equation 4)

The control for causing the d-axis current Id to flow through the synchronous motor to generate a voltage margin in this manner is called "field weakening control". If an attempt is made to increase the rotation speed in the field-weakening control, the d-axis current will be increased in order to generate a voltage margin as described above. This leads to increasing the current phase value β in equation (4). In field weakening control,
The current phase value β can be said to be a value dependent on the rotation speed of the motor.
D-axis current Id to increase to generate voltage margin
May be the minimum necessary current for returning the terminal voltage applied to the motor to the voltage limit circle C. When the d-axis current Id exceeding the necessary minimum is given to the synchronous motor, copper loss increases and the efficiency of the synchronous motor deteriorates.

FIG. 1 is a block diagram of a motor control device according to the present invention. In FIG. 1, an output of a current command unit 1 for commanding a winding current of a motor is input to a rotation speed determination unit 2. The output of the rotation speed determination unit 2 is input to the d-axis current command unit 3. The output of the d-axis current command unit 3 is a d-axis current control unit 4
Has been entered. The output of the d-axis current controller 4 is the adder 1
5 has been entered. The output of the q-axis current command unit 6 is also input to the adder 15. The addition output of the adder 15 is
It is input to the saturation degree determination unit 5 and the high output rotation speed region determination unit 7. The output of the high output rotation speed region determination unit 7 is input to the output comparison unit 8, and the output of the output comparison unit 8 is input to the rotation speed determination unit 2. The output of the output comparison unit 8 is also applied to the current control unit 12, and the output of the current control unit 12 controls the inverter 13. Power is supplied to the motor 10 from a power supply 14 via an inverter 13. The current of the motor 10 is detected by the current detection unit 9, and a detection signal is input to the saturation determination unit 5.

Next, the operation of this embodiment will be described with reference to FIGS. When a winding current command value corresponding to a desired torque command value is set in the current command unit 1 and started, the synchronous motor starts rotating and the number of revolutions increases to a predetermined value according to the load. The rotation speed determination unit 2 determines whether a predetermined rotation speed for performing the field weakening control has been reached, and the saturation degree determination unit 5 determines the rate at which the winding current value can be increased. When the number of revolutions at which the current phase value β is controlled to perform the field weakening control is reached, the field weakening control is performed.
Next, the reference value Iqh of the q-axis current is set by the high output rotation speed region determination unit 7. The reference value Iqh is a constant value equal to or less than half the maximum value of the q-axis current. If the q-axis current value Iq does not fall below the reference value Iqh during execution of the field weakening control, the normal field weakening control is continued. q-axis current value Iq
Is smaller than the reference value Iqh, it is determined that the motor is in the high output rotation speed region, and the winding current Ia and the current phase value β are determined in a predetermined control cycle.
Is changed, the output comparing unit 8 compares the respective outputs of the previous control cycle and the current control cycle. The motor is driven using the winding current Ia and the current phase value β obtained as a result of the output comparison. Hereinafter, these operations will be described in detail with reference to FIG.

FIG. 2 is a flowchart showing the operation of this embodiment. In step 21, when a desired torque command value is given, in step 22, a current command value corresponding to the torque command value is given. The number of rotations of the synchronous motor that has started to rotate increases according to the state of the load. In step 23 of the rotation speed determination, a saturation degree indicating a ratio at which a winding current corresponding to the rotation speed can be supplied is determined. Field weakening control is performed according to the degree of saturation. After the field weakening control is performed, the current phase value β changes according to the rotation speed of the motor, and the corresponding q-axis current Iq and d-axis current Id flow. In the determination step 24 of the q-axis current Iq, the q-axis current value Iq and the reference value Iq
Compare the magnitude with qh. The q-axis current value Iq is equal to the reference value Iq
If it is larger than h, the process returns to step 23 to maintain the field weakening control. If the q-axis current value Iq is equal to or less than the reference value Iqh, the process proceeds to step 25 and is controlled as follows. The torque T is calculated from the winding current Ia1 and the current phase value β1 according to equation (5).

[0023]

(Equation 5)

Equation (5) is a well-known equation as a torque equation, where Pn is the number of pole pairs, φa is the armature interlinkage magnetic flux, and Ia is the winding current. In step 24, the q-axis current value Iq
Is the current phase value when it is determined that is equal to or less than the reference value Iqh,
And Further, the winding current value corresponding to the phase value β1 is represented by Ia1
And In step 25, the current phase value β1 is calculated using the following current phase conditional expression (6) to obtain a new phase value β2.

[0025]

(Equation 6)

Equation (6) indicates that the current phase is delayed. The phase value β2 is compared with a constant (40) in the current phase determination step 26. This constant will be described below. In the field weakening control of the synchronous motor, it is known that the current phase that generates the maximum torque is about 40 degrees or more from the torque equation (5). If the value of the current phase becomes smaller than 40 degrees during the field-weakening control, not only a desired torque cannot be obtained but also the efficiency will deteriorate.
Therefore, the lower limit value of the current phase value β2 in step 25 is set to 40. When the current phase value β2 is 40 or more, the process proceeds to step 27. The torque when controlling with the winding current value Ia1 and the current phase value β1 is calculated by the torque equation (5), and the torque is set to T1. In addition, a current command value β1 obtained by delaying the current phase command value β1 using the conditional expression β2 = β1−βk of Expression (6) is set to β2. The torque calculated by the torque equation (5) using the current phase value β2 and the winding current command value Ia1 is represented by T
Let it be 2. Output comparing unit step 27
Are compared as shown in the first conditional expression of the following expression (7).

[0027]

(Equation 7)

If the first conditional expression is not satisfied, the routine proceeds to the current control step 28, and the winding current value Ia is increased or decreased by the second conditional expression of the expression (8).

[0029]

(Equation 8)

Ia2 is a winding current value of the output of the output comparing section 27 obtained by using the second conditional expression. If the first conditional expression is satisfied in step 27, the process proceeds to step 30. In step 30, the winding current value Ia2 and the current phase value β2
Is used to calculate the number of rotations of the motor.

The rotation speed N2 obtained by the calculation in step 30 is compared with the rotation speed N1 in the previous control cycle in a rotation speed comparison step 31. If the rotation speed N2 is higher than the rotation speed N1, the process returns to the rotation speed determination step 23. If the rotation speed N2 is not higher than the rotation speed N1, the process proceeds to the output comparison correction step 32. In step 32, the first conditional expression (7) in the output comparing step 27 is replaced by the following third conditional expression (9).
And the process returns to the rotation speed determination step 23.

[0032]

(Equation 9)

If the current phase β is smaller than 40 in the current phase judging step 26, step 29
The reference value Iqh of the q-axis current Iq is set to 0, and the value of the q-axis phase inductance Lq is obtained by the following equation (10).

[0034]

(Equation 10)

The q-axis phase inductance is set as a new q-axis phase inductance Lq obtained by the equation (10), and the process returns to step S23. Next, proceeding to step 24,
The reference value in the first conditional expression in step 24 is Iq
Since (h) = 0, a comparison is made using the value. When the process proceeds to step 27 via steps 25 and 26, the same output comparison is performed using Lq obtained by equation (10).

The operation of this embodiment will be described in more detail with reference to FIGS. 1, 4 and 5. FIG. 4 shows a rated winding current of 250.
4 is a graph showing output characteristics in which the horizontal axis represents the rotation speed of a motor of ampere (hereinafter, ampere is referred to as A) and the vertical axis represents torque. FIG. 5 shows the q-axis current Iq on the horizontal axis,
It is the graph which took q-axis phase inductance Lq on the vertical axis. In FIG. 4, a dotted line S1 shows output characteristics when the field weakening control is performed when the winding current is 250 A, and a dashed line S2 shows output characteristics when the field weakening control is performed when the winding current is 220 A. , The solid line S3 indicates that the winding current is 1
The output characteristics when the field weakening control is performed at 90 A are shown. The minimum value Iqmin of the q-axis current is set in the high output rotation speed region determination unit 7 in FIG. Maximum value of winding current I
Let amax be 250A. The value of the phase inductance Lq is, as approximately indicated by a straight line 60 in FIG.
It changes according to q. The reference value Iqh of the q-axis current is 125
A. At this time, the reference value is equal to Iqmin.

The characteristic point P1 in FIG. 4 shows the relationship between the rotational speed and the torque when the current value is 250 A and the current phase value β1 is 60 degrees. Q-axis inductance L in step 29
FIG. 5 shows the relationship between the q-axis current Iq and the q-axis inductance Lq in the correction of q. In FIG. 5, the reference value Iqh of the q-axis current value is changed to the q-axis inductance Lq by Lqmi.
If it is set to be the minimum value of Iqh when it becomes n,
It is possible to prevent a calculation error of the torque expression and perform an accurate output comparison. Since the q-axis current Iq in FIG. 5 is the product of the current value 250A and the cosine value cos60, it becomes 125A (25
0 × cos 60 = 125). This current value 125A is the Iqm of the q-axis current set by the high-output rotation speed region determination unit 7.
in. Next, the output comparing section 8 shown in FIG. 1 performs a comparing operation as described below. First, assuming that βk is 4 in the conditional expression of the current phase value: β2 = β1−βk,
β2 = 56 degrees. Current phase value 56 degrees and current value 250
From A, the torque T at that time is calculated by equation (5). The torque value T2 at the characteristic point P2 obtained from the winding current value 250A and the current phase value 56 degrees, and the winding current value 250A
The output comparison unit 8 compares the torque value T1 of the characteristic point P1 obtained with the current phase value of 60 degrees. Next, Ia1 of the second conditional expression (8) is increased or decreased so that the torque value T2 at the characteristic point P2 satisfies the first conditional expression (7). Here, assuming that the current value satisfying the first conditional expression (7) is 220 A, the command value is a current value of 220 A and a current phase value of 56 degrees. The torque and the rotation speed at that time are the values indicated by the characteristic point P3. Next, the relationship between the torque and the number of revolutions
It is assumed that the characteristic A moves on the S2 curve and shifts to the characteristic point P5. Therefore, if it is assumed that the conditional expression is satisfied again in the high-output rotational speed region determination unit 7 as described above, the output comparison by the output comparison unit 8 is performed at the characteristic point P5. In the same manner as described above, the current value Ia1 is increased or decreased until the torque and the rotational speed at the calculated characteristic point P4 satisfy the first conditional expression (7). When the first conditional expression (7) is satisfied, the calculated value Ia2 is used for control. The torque and the number of revolutions are, for example, the value of a characteristic point P6 (current state is state (A)) at a current value of 190A and a current phase value of 52 degrees. As a result, as shown by the points P1, P3, P5, and P6, the relationship between the torque and the rotation speed shifts, and the rotation speed increases. Thereby, the current can be rotated at 190 A at a higher speed than at 250 A. According to the present embodiment, by setting the reference value to the q-axis current value in the high-output rotation speed region determination unit 7, the q-axis current value becomes the q-axis inductance Lq
Can be controlled so as not to enter the area where the value changes. By eliminating the difference between the q-axis phase inductance Lq and the d-axis inductance Ld and the change in the value of Lq-Ld in the torque equation (5) used in the output comparison unit 8, the calculation error in the torque equation is eliminated and accurate control is achieved. It becomes executable. Further, in the normal field-weakening control, the orthogonal axis stator current Id, which tends to increase as the rotation speed increases, can be reduced by utilizing the reduction of the winding current by the output comparison unit. As a result, the copper loss proportional to the magnitude of the current can be reduced, so that the efficiency can be improved, and the efficiency of the high-speed region can be improved by reducing the winding current.

Another example of the operation of the output comparing section 8 in the first embodiment of the motor control device of the present invention will be described below.
When executing the processing in the output comparison unit 8, first, the winding current value Ia1 and the phase when rotating at the rotation speed N1 determined as the high output rotation speed region by the high output rotation speed region determination unit 7 are calculated. The value β1 and the value of Lq−Ld are substituted into the torque equation (5) for calculation, and the resulting torque is defined as T1. However, (Lq
The value of -Ld) is a torque value and a winding current value measured when a motor controlled by the control device of the present invention is driven in an area where field weakening control is not performed with an arbitrary winding current value and current phase value. And the current phase value by the inverse calculation of equation (5). Next, the winding current Ia2 and the value β obtained by arbitrarily delaying the phase β1
2 (= β1-k) is similarly substituted into the torque equation (5) for calculation, and this is defined as the torque T2. In the first conditional expression (7), when T2> T1-κ, the current Ia1
Decrease. When T2 <T1-α, the current Ia
Increase one. The winding current satisfying the equation (7) is represented by Ia2
And Therefore, the current Ia2 and the phase β2 are adopted, and the control is executed using the values. Further, by adding a condition for setting a reference value to the torque T2 in the equation (7), it is possible to prevent a sudden torque fluctuation.

Another example of the operation of the output comparing section 8 in the first embodiment of the motor control device of the present invention will be described below. The rotation speed N2 realized by the current Ia2 and the phase β2 obtained as a result of executing the processing in the output comparison unit 8 is the rotation speed N
In the case of 1, in the reference value of the conditional expression of the output comparison unit 8, a constant value K is subtracted from the torque T1 as in the expressions (T1-α-K) and (T1-κ-K). By resetting the rotation speed N2 to a value smaller than the initial reference value in this manner, a state in which the rotation speed N2 becomes smaller than the rotation speed N1 (N2 <N1) is prevented, and smooth operation characteristics can be achieved.

<< Second Embodiment >> A second embodiment of the motor control device according to the present invention relates to another example of the operation of the output comparison section 8 in FIG. In FIG. 5, when the q-axis current Iq is smaller than the minimum value Iqmin (Iq <Iqmi
n), the q-axis phase inductance Lq changes as shown in FIG. 5, and a calculation error occurs in the torque equation (5) used in the output comparison unit 8. In such a case, a calculation error can be prevented by using the Lq change simple expression described below. When Lq changes as shown in FIG. 5, for example, after the state (A), the output comparison unit 8 changes the torque and the rotation speed to the values of the characteristic point P6 with the current value 190A and the current phase value 52 degrees.
Assuming that the winding current value Ia becomes 190 A after executing the processing in step (d), when the phase value β is 49 degrees, the d-axis current value Id
Is as shown in equation (11).

[0041]

(Equation 11)

The processing of the output comparing section 8 is executed according to the equation (11). At that time, the d-axis current value Id is 143.4 A (Id
= 190 · sin (49) = 143.4A). Further, after executing the processing of the output comparing section 8, the winding current value Ia becomes 1
Assuming that the current reaches 70 A, when the phase β is 43 degrees, the winding current value Id becomes as shown in Expression (12).

[0043]

(Equation 12)

When the calculation of the equation (12) is repeatedly executed by the output comparing section 8, the phase β eventually becomes 40 degrees or less. In a synchronous motor that performs field-weakening control, as is well known, the phase value β at which the maximum torque is generated is about 4
However, if the phase value β is 40 degrees or less, the efficiency of the motor may be reduced. Therefore, in the high output rotation speed region, the phase value β is set to 40 degrees or more (β ≧ 40). In this case, even if the winding current Ia is further reduced as in the above-described embodiment, the winding current Ia cannot be reduced, and the characteristics cannot be further improved in the high-speed region. In this embodiment, the expression (1)
The calculation error of the torque equation is eliminated by correcting the value of the q-axis phase inductance Lq using the simple equation for changing Lq shown in 1). Therefore, it is possible to make Iqh smaller than the minimum value Iqmin and perform an optimal output comparison. As a result, the above-described problem is solved, and the efficiency can be further improved and the characteristics in the high-speed range can be improved.

FIG. 6 shows the relationship between the number of revolutions of the motor and the torque when the motor control device of this embodiment is applied to a motor mounted on an electric vehicle or a hybrid electric vehicle (hereinafter abbreviated as a vehicle). FIG. In the drawing, ω0 is the required maximum rotation speed, ω1 is the maximum rotation speed achievable by the conventional control method, and ω2 is the maximum rotation speed achievable by the motor control device and method according to each of the above embodiments of the present invention. is there. ωk is the rotation speed determined by the high-output rotation speed region determination unit 7. When the driver intends to run the vehicle at the highest speed, the driver normally keeps the accelerator fully depressed. In the conventional motor control method, even if the accelerator is depressed to the maximum, the rotation speed of the motor increases only to the maximum rotation speed ω1 in FIG.
In a vehicle equipped with the motor control device of the present embodiment,
When the driver attempts to run the vehicle at the highest speed, the accelerator is depressed to the maximum and the motor is rotated at the rotation speed ωk or more, the rotation speed gradually increases, and finally increases to the maximum rotation speed ω2. This is because the high-speed range characteristic of the motor is improved and the rotation speed is increased by the control of the high-output rotation speed region determination unit 7 and the output comparison unit 8. That is, the ability of the motor can be maximized in accordance with the driver's accelerator operation. FIG. 7 is a plan view illustrating a configuration example of a hybrid vehicle having a synchronous motor controlled by the motor control device according to the present embodiment. The vehicle 45 is provided with a synchronous motor 41, a control device 42, an engine 43, and an inverter 44 for driving the synchronous motor 41. The synchronous motor 41 is rotated by a battery (not shown) to drive the wheels. 46 is driven. By using the motor control device and method of the present embodiment, it is also possible to perform speed control from a low speed to a high speed without using a transmission, so that cost reduction and weight reduction are realized, and the load on the motor can be reduced. it can.

[0046]

As described in the above embodiments, according to the present invention, when performing the field-weakening control on the synchronous motor, the winding current and the winding current are controlled so as not to cause the characteristic deterioration mainly in a high speed range. The current phase is controlled in association with the current phase to reduce the winding current and delay the current phase. As a result, copper loss is reduced, errors due to disturbances in the current waveform are minimized, and efficiency and high-speed performance can be improved without being greatly affected by changes in motor device constants.

[Brief description of the drawings]

FIG. 1 is a block diagram of a motor control device according to a first embodiment of the present invention.

FIG. 2 is a flowchart showing the operation of the first embodiment of the present invention.

FIGS. 3A to 3C are vector diagrams of voltages indicated by dq orthogonal coordinates when performing the field weakening control of the first embodiment.

FIG. 4 is a graph showing a relationship between torque and rotation speed when the motor is rotated at high speed in the first embodiment of the present invention.

FIG. 5 shows q-axis currents Iq and q in the second embodiment of the present invention.
It is a graph which shows the relationship of phase inductance Lq of a shaft.

FIG. 6 is a graph showing an operation at the time of high-speed rotation of a motor according to a second embodiment of the present invention.

FIG. 7 is a plan view of a vehicle to which the motor control device of each embodiment of the present invention is applied.

[Explanation of symbols]

1 Current command section 2 Rotational speed judgment unit 3 d-axis current command section 4 d-axis current controller 5 Saturation judgment section 6 q-axis current command section 7 High output rotation speed region judgment section 8 Output comparison section 9 Current detector 10 Motor 11 Operation part 12 Current control unit 13 Inverter 14 Power supply 41 Synchronous motor 42 transmission 43 Engine 44 Inverter 45 Vehicle body 46 drive wheels

   ────────────────────────────────────────────────── ─── Continuation of front page    (72) Inventor Yasuhiro Kondo             Matsushita Electric, 1006 Kadoma, Kazuma, Osaka             Sangyo Co., Ltd. F term (reference) 5H560 DA14 DB14 DC01 DC03 DC12                       EB01 SS01 XA02 XA13 XA17                 5H576 BB02 BB09 CC01 DD05 EE01                       EE02 FF08 GG04 HB01 JJ02                       LL14 LL22 LL38 LL39

Claims (7)

[Claims] 1. A current command unit that outputs a command value of a winding current of each phase of a stator of a motor, a d-axis current that gives a command value of a d-axis current of the stator in a dq orthogonal axis of the stator. A command section, a q-axis current command section for giving a command value of the q-axis current of the stator in the dq orthogonal axes, a rotation number determination section for determining a rotation number for performing field weakening control of the motor, the rotation number determination section When performing field-weakening control based on the determination result, a d-axis current control unit that increases and decreases the d-axis current value, a saturation determination unit that determines the ratio of the winding current that can be supplied, and sets the reference value of the q-axis current to q The value of the q-axis current is set to a value equal to or less than half of the shaft current value, and at a predetermined winding current value, the q-axis current value that decreases as the current phase, which is the advance angle of the winding current phase from the q-axis, advances. High-output rotation speed region An output comparing unit that changes a current and a current phase in each predetermined control cycle, obtains a torque from the winding current value and the current phase value in each cycle, and compares the obtained torque in each of the control cycles; and A motor control device including a current control unit for controlling the winding current value and the current phase value so that the torque is maximized based on the comparison result of the above. 2. A current detection unit for detecting a winding current of each phase of a stator of a motor, a current command unit for outputting a command value of the winding current of each phase, a command for the winding current and a command for the winding current. An output comparison unit that compares the value with the command value of the winding current and an output of the output comparison unit,
A rotation number determination unit that determines whether the rotation number is a rotation number at which the field weakening control is performed, an output of the rotation number determination unit being input, and a stator expressed in a dq orthogonal axis coordinate system based on a determination result of the rotation number. A d-axis current command unit that supplies a command value of a d-axis current that is a current; a d-axis current control unit that receives the command value of the d-axis current and changes the d-axis current in field-weakening control; A q-axis current command unit that gives a command value of a q-axis current that is a stator current represented by: an adder that adds the output of the d-axis current control unit and the output of the q-axis current command unit; An output and a detection output of the current detection unit are applied, the supply ratio of the winding current is determined, and a saturation determination unit that applies the determination output to the d-axis current control unit is input from the adder. At a given winding current value,
The reference value of the q-axis current value is set to a predetermined value which is equal to or less than half of the maximum value of the q-axis current, and the current phase, which is the advance angle of the winding current from the q-axis, advances, and the q-axis current value decreases. If the output value is less than the predetermined winding current value and the predetermined current phase value, a high output rotation speed region determination unit that determines whether the output of the motor has increased at a value lower than the predetermined winding current value. The output of the high output rotation speed region determination unit is applied, an output comparison unit that compares the motor torque at the specific winding current value and a specific current phase value for each predetermined control cycle, and an output comparison unit. A motor control device including a current control unit that controls a winding current value and a current phase value so that torque is maximized based on a comparison result. 3. The motor control device according to claim 1, wherein the motor is a synchronous motor. Detecting a winding current of each phase of the stator of the motor; outputting a command value of the winding current of each phase; comparing the winding current with a command value of the winding current. A step of determining whether or not the number of revolutions is to perform field-weakening control based on the comparison result of the comparison step; and a stator current expressed in a dq orthogonal axis coordinate system based on the result of the determination of the number of revolutions. a current command step for giving a command value of the d-axis current, a step of changing the d-axis current based on the command value of the d-axis current when performing the field weakening control, and a stator current expressed in a dq orthogonal axis coordinate system. Providing a command value of a certain q-axis current; adding the output of the d-axis current control unit to the q-axis current command value; applying the added output and the detected value of the winding current to the winding current; Supply ratio Determining the saturation degree and applying a determination output to the d-axis current control unit; setting the reference value of the q-axis current to a value equal to or less than half of the maximum value of the q-axis current; In a predetermined winding current value based on the above, if the current phase, which is the advance angle of the winding current from the q-axis, advances and the q-axis current value falls below the reference value, the predetermined winding current value and the predetermined Determining whether the output of the motor increases at a value lower than the predetermined winding current value at the current phase value.When the output of the motor increases, the predetermined winding current value and a predetermined A motor control comprising: an output comparison step of comparing the motor torque in the current phase value for each control cycle; and a step of controlling the winding current value and the phase thereof so as to maximize the torque based on the comparison result of the comparison step. Method. 5. The output comparing step of comparing motor torques by a combination of a winding current value and a current phase value of each phase, wherein the output current value is calculated from the winding current command value Ia1 and the phase command value β1 in the current command step. A torque T1 calculated using a predetermined torque formula, a phase command value β2 obtained by delaying the phase command value β1 using the following formula, β2 = β1-k (k is a positive value), and a winding current The torque T2 calculated using the command value Ia1 is compared in the output comparing unit step, and each of the torques T1 and T2 is determined by a first conditional expression, T1-α <T2 <T1-κ (α and κ are positive values, α
The motor control method according to claim 4, wherein the winding current command value Ia1 is increased or decreased until the following condition is satisfied. 6. In the output comparing step, the phase command value β2 and a current command value Ia2 obtained by increasing / decreasing the winding current command value Id are used for control, and the resulting rotational speed N2 is a torque When the rotational speed N1 is lower than the rotational speed N1 at the time of T1, a conditional expression formed by subtracting a predetermined constant K from each term in the first conditional expression, T1-α-K <T
6. The motor control method according to claim 4, wherein 2 <T1-.kappa.-K (K is a positive value) is used instead of the first conditional expression. 7. The maximum value of the q-axis inductance Lq, which is a constant of the motor device, is Lqmax, and the minimum value is Lqmi.
When n is used, the q-axis inductance Lq is used as the maximum value Iqmax of the q-axis current that saturates the torque when the current phase is 0 degree, and q when the q-axis current Iq falls below a predetermined reference value. A simple equation showing the change in the shaft inductance Lq, Lq = Lqmax + 2Iq · (Lqmin−Lqm
ax) / Iqmax, and correcting the constant of the motor device by using the obtained value in the calculation of the torque in the output comparison step. Control method.