JP2001078495A - AC motor drive control device - Google Patents

Abstract

(57) [Problem] To provide an AC motor drive control device capable of performing control switching without using a map requiring many experiments and driving an AC motor efficiently. SOLUTION: A switch 28 selectively uses a PWM current control mode and a rectangular wave voltage phase control mode. At this time, when operating in the rectangular wave voltage phase mode, if the absolute value | φi | of the actual current phase supplied to the motor 38 becomes smaller than the absolute value | φ0 | Switch to control mode. For the predetermined switching current phase φ0, for example, a phase at which the torque / current ratio is maximized is set. Conversely, when operating in the PWM current control mode, if the voltage amplitude | V | supplied to the PWM circuit 30 from the current controller 14 becomes equal to or greater than the predetermined switching voltage amplitude V0, the control is performed in the rectangular wave voltage phase control mode. Switch to
For the predetermined switching voltage amplitude V0, for example, a limit voltage that can stably perform PWM current control is set.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drive control device for an AC motor, and more particularly, to a drive control device for an AC motor by selectively using voltage phase control such as rectangular wave voltage phase control and PWM voltage phase control and PWM current control. To a device capable of doing so.

[0002]

2. Description of the Related Art An inverter is used to drive an AC motor using a DC power supply. The switching of such an inverter is controlled by an inverter driving circuit, whereby a pulse width modulation (PWM) waveform voltage is generally applied to the AC motor.

[0003] P which applies a PWM waveform voltage to an AC motor
In the WM current control, although smooth rotation can be obtained even in a low rotation range, there is a problem that the voltage utilization rate of the DC power supply is limited. In response to this, there is a method of obtaining high rotation by giving a weak field current to the AC motor,
This is not appropriate because copper loss increases.

On the other hand, there is a method of controlling the driving of an AC motor by applying a rectangular wave voltage to the AC motor. According to this control method, the voltage utilization rate of the DC power supply can be improved, and as a result, the output in a high rotation range can be improved. Further, since the field weakening current can be reduced, it is possible to suppress the occurrence of copper loss and improve the energy efficiency. Further, since the number of times of switching in the inverter can be reduced, there is an advantage that switching loss can be suppressed.

For this reason, both a PWM waveform voltage and a rectangular wave voltage can be applied to an AC motor, and these can be selectively used depending on the situation to improve the output of the motor particularly in a high rotation range. It is desirable. JP 55
Japanese Patent No. 49996 discloses a technique for selectively applying a PWM waveform voltage and a rectangular wave voltage to an AC motor to improve the output.

[0006]

In such prior art,
When the rotation speed of the AC motor exceeds a predetermined value, the AC motor is driven by the rectangular wave voltage.
The AC motor is driven by the waveform voltage. However, simply switching between the two controls based only on the rotational speed does not always enable efficient driving of the AC motor. The switching timing of the control must be measured in consideration of the voltage. For this purpose, it is necessary to prepare a three-dimensional map that gives an optimum rotation speed for control switching by applying a torque and a DC power supply voltage, but many experiments are required to prepare this map, There is a problem that much time is required.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to perform control switching without using a map requiring many experiments and to drive an AC motor efficiently. An object of the present invention is to provide a drive control device for an AC motor.

[0008]

(1) In order to solve the above problems, the present invention provides a PWM current control means for supplying a sinusoidal current having a predetermined amplitude and a predetermined phase according to a torque command to an AC motor; Voltage phase control means for supplying an alternating current having a phase deviating from the predetermined phase according to the torque command to the AC motor, and when the AC motor is driven by the voltage phase control means, the voltage is supplied to the AC motor. If the relationship between the advance and delay of the current phase of the AC current and the control switching phase corresponding to the predetermined phase is reversed, the drive of the AC motor by the PWM current control means is started instead of the voltage phase control means. And control switching means.

According to the present invention, smooth driving of the AC motor can be obtained by the PWM current control means in the low rotation range, and voltage phase control means such as PWM voltage phase control and rectangular wave voltage phase control in the high rotation range. As a result, the current phase is adjusted with respect to a predetermined phase corresponding to the torque command, field weakening control is performed, and a high output can be obtained. Therefore, efficient driving of the AC motor can be performed. Then, at the time of driving or braking, if the relationship between the advance and delay of the current switching phase and the control switching phase corresponding to the predetermined phase is reversed,
The control switching means switches the control means of the AC motor from the voltage phase control means to the PWM current control means. Although the control switching phase can be changed depending on the torque, the map can be made smaller than the conventional three-dimensional map, and the number of experiments for preparing the map can be reduced.

(2) In one aspect of the present invention, the predetermined phase according to the torque command is determined so that the torque / current ratio increases. This makes it possible to drive the AC motor with higher efficiency.

(3) In one aspect of the present invention, when the AC motor is driven by the PWM current control means, the switching control means sets the amplitude of the AC voltage applied to the AC motor to a predetermined amplitude. Above the PWM
The drive of the AC motor by the voltage phase control means is started instead of the current control means. With this configuration, for example, by setting the predetermined amplitude to the maximum amplitude that can be stably controlled by the PWM current control, it is possible to realize efficient control switching from the PWM current control unit to the voltage phase control unit.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a diagram showing an overall configuration of a drive control device for an AC motor according to an embodiment of the present invention. The drive control device 10 shown in FIG. 1 is mounted on an electric vehicle, for example, and has two control modes, a PWM current control mode and a rectangular wave voltage phase control mode.

Here, the PWM current control mode is a control mode executed when the switch 28 is switched to the upper side in the figure.
6 is fed back, and the voltage amplitude | V | and the voltage phase ψ are adjusted so that they approach the current amplitude command value | I | and the current phase command value φ.
Is set, and a pseudo sine wave voltage is applied to the motor 38 by the PWM circuit 30 and the inverter 36.

On the other hand, the rectangular wave voltage phase control mode is a control mode executed when the switch 28 is switched to the lower side in the figure. In this mode, a rectangular wave voltage is applied to the motor 38. The voltage amplitude | V | is determined by the power supply voltage Vdc of the DC power supply of the inverter 36 (not shown), and the voltage phase ψ is set according to the torque command value.

In the drive control device 10 shown in FIG.
An electronic control unit (ECU) (not shown) generates a torque command value according to the accelerator opening and the brake depression angle, and the torque command value is input to the current command generation unit 12 and the adder 13 in parallel. Has become. Current command generator 1
2, the current amplitude | I based on the input torque command value.
| And the current phase φ. The current controller 14 performs a proportional-integral control, where a voltage amplitude | V | and a voltage phase ψ are generated. Here, the voltage phase ψ is the angle of the voltage vector with respect to the q axis. These voltage amplitudes | V
| And the voltage phase ψ are supplied to the PWM circuit 30. Although not particularly shown, a current value is fed back from the current sensor 40 to the current controller 14.

The PWM circuit 30 generates a switching command by comparing a sine wave having a voltage amplitude | V | and a voltage phase ψ supplied from the current controller 14 with a previously prepared triangular wave. This switching command is supplied to the inverter 36 via the switch 28. The inverter 36 is a voltage type inverter, and generates a pseudo sine wave voltage based on a switching command supplied from the PWM circuit 30. The pseudo sine wave voltage is supplied to the motor 38.

The motor 38 is a permanent magnet synchronous (PM) motor. A current sensor 40 is mounted on a power supply line from the inverter 36 to the motor 38, and the real-time actual current phase φi detected there is supplied to the current phase determination unit 22. Although not shown, the current sensor 40 also detects a real-time current value, which is fed back to the current controller 14.

Next, as described above, an ECU (not shown)
Are also input to the adder 13. The real-time torque value detected by the torque detector 20 is also input to the adder 13, and a torque deviation ΔT, which is a difference between the two, is generated there. The torque detecting section 20 can be configured using a known torque sensor, but can also be configured to generate a torque by executing an operation represented by the following equation (1).

[0020]

T = Pin / ω = (iu × vu + iv × vv + iw × vw) / ω (1) where Pin represents electric power supplied to the motor 38.
ω represents the angular velocity of the motor 38. iu, iv, iw represent current values of each phase supplied to the motor 38, and vu, v
v and vw represent voltage values of each phase supplied to the motor 38. For vu, vv, and vw, a voltage command value set in the inverter 36 may be used, or an actual value supplied to the motor 38 from the inverter 36 may be detected by a voltage sensor and used.

Alternatively, as shown in the following equation (2), the input power of the inverter 36 is calculated from the DC current and the DC voltage by an operator,
The torque may be calculated and generated.

[0022]

T = Pin / ω = (IB × VB) / ω (2) where IB and VB represent the current and voltage of a DC power supply (not shown) connected to the inverter 36.

The torque deviation ΔT generated by the adder 13 is supplied to a voltage phase controller 18. Voltage phase controller 18
Generates the voltage phase ψ according to the torque deviation ΔT. This voltage phase ψ is the phase of the rectangular wave applied to the motor 38. Specifically, the voltage phase controller 18 controls the voltage phase ψ
Are used as parameters when generating the torque deviation ΔT, the voltage Vdc of a DC power supply (not shown) connected to the inverter 36, and the angular velocity ω of the motor 38, which are substituted into a predetermined arithmetic expression (or equivalent processing). ) To generate the required voltage phase.

In the rectangular wave generator 32, the voltage phase controller 1
A switching command is issued so as to generate a rectangular wave voltage based on the voltage phase ψ output from 8. This switching command is supplied to the inverter 36 via the switch 28. When the switch 28 is switched to the lower side in the figure, the inverter 36 outputs a rectangular wave voltage to the motor 38.
Is applied.

The voltage amplitude judging section 16 and the current phase judging section 22 switch between a PWM current control mode and a rectangular wave voltage phase control mode by switching a switch 28. The voltage amplitude determination unit 16 determines that the drive control device 10
When operating in the WM current control mode, it monitors whether or not the voltage amplitude | V | supplied to the PWM circuit 30 from the current controller 14 is larger than a predetermined switching voltage amplitude V0. If it becomes larger, the switch 28 is switched to the lower side in the figure, and control is switched to the rectangular wave voltage phase control mode. As the predetermined switching voltage amplitude V0, for example, a value obtained by multiplying the voltage of a DC power supply (not shown) connected to the inverter 36 by the modulation factor of the inverter 36 is used.

On the other hand, when the drive control device 10 is operating in the rectangular wave voltage phase control mode, the current phase determination section 22 determines the phase (actual current phase) φi of the AC current supplied from the inverter 36 to the motor 38. Of the predetermined switching current phase φ0 (different between during driving and during braking) is monitored. If the absolute value becomes smaller, the switch 28 is switched to the upper side in FIG. Switch control to control mode. As the predetermined switching current phase φ0, for example, a current phase necessary for realizing the current torque command with the smallest current value, that is, a phase in which the torque / current ratio is the largest is used. A plurality is prepared according to the occasion. The distinction between driving and braking may be made based on, for example, the sign of the torque command.

Next, the operation of the drive control device 10 for an AC motor will be described.

FIG. 2 is a flowchart for explaining control switching of the drive control device 10. As shown in the figure, the drive control device 10 determines whether the current control is being performed in the PWM current control mode or the rectangular wave voltage phase control mode (S101).

In the PWM current control mode, the motor 3
8 is being driven, the voltage amplitude determination unit 16 determines whether the voltage amplitude | V | output from the current controller 14 is equal to or greater than the predetermined switching voltage amplitude V0 (S102). ). Here, when it is determined that the switching voltage amplitude is equal to or greater than the predetermined switching voltage amplitude V0, the voltage amplitude determination unit 16 switches the switch 28 to the lower side in the figure, and shifts the control mode to the rectangular wave voltage phase control mode (S105). On the other hand, when it is determined that the amplitude is less than the predetermined switching voltage amplitude V0, the voltage amplitude determination unit 1
6 maintains the state of the switch 28 and continues the operation in the PWM current control mode as it is (S104).

If it is determined in S101 that the current control mode is the rectangular wave voltage phase control mode, then the current phase determination unit 22 determines that the absolute value | φi | It is determined whether or not the absolute value | φ0 | If it is determined that the current phase is equal to or greater than the absolute value | φ0 | of the predetermined switching current phase, the current phase determining unit 22 maintains the state of the switch 28 and continues the operation in the rectangular wave voltage phase control mode (as it is). S105). When it is determined that the absolute value | φi | of the actual current phase is smaller than the absolute value | φ0 | of the predetermined switching current phase, the current phase determination unit 22 switches the switch 28 to the upper side in the figure and changes the control mode to PWM. The mode is shifted to the current control mode (S104).

FIGS. 3 to 6 are diagrams for explaining states of the drive control device 10 before and after control switching. In these figures, the voltage amplitude | V | is a predetermined initial voltage amplitude Vini.
t, the state where the absolute value of the current phase | φi | is | φ0 |, the current value is B, and the rotation speed of the motor 38 is zero is X. Further, the state where the voltage amplitude | V | is the predetermined switching voltage amplitude V0, the absolute value of the current phase | φi | is | φ0 |, the current value is B, and the number of revolutions of the motor is N0 is Y. Further, the voltage amplitude | V |
Is the predetermined switching voltage amplitude V0, the state in which the absolute value | φi | of the current phase is larger than the absolute value | φ0 | of the predetermined switching current phase, and the state in which the rotation speed is increased from N0 are Z. In these figures, a solid line connecting the states X to Z indicates a state where the torque is constant.

FIG. 3 shows the rotation speed and voltage amplitude | V | when the operation mode of the drive control device 10 shifts from the PWM current control mode to the rectangular wave voltage phase control mode with a constant torque.
Represents the relationship. In the figure, when the rotation speed gradually increases from the state X, the back electromotive force of the motor 38 increases accordingly. To counter this, the voltage amplitude | V | also gradually increases. At this time, the drive control device 10 is in the PWM current control mode, and the current phase φ is set to a value that maximizes the torque / current ratio (this value corresponds to the predetermined switching current phase φ0).

FIG. 4 is a diagram showing the current-torque characteristics of the PM motor. In FIG.
ＣC (A>B> C) indicates the relationship between the absolute value of the torque and the absolute value | φi | of the current phase. Here, the phase | φi | is shown assuming that the phase angle of the number of permanent magnetic flux intersecting numbers of the windings under no load is 0 °. A curve 51 connecting the tops of the broken lines represents a current phase for achieving a certain motor torque with a minimum current value. Here, since the states X and Y are plotted on the curve 51, in the PWM current control mode until the state changes from X to Y, the motor 38 is driven in the state where the energy efficiency is the best. You can see that.

Returning to FIG. 3, the voltage amplitude |
When V | and the absolute value | φi | of the current phase increase, the voltage amplitude | V | reaches the predetermined switching voltage amplitude V0. At this timing, the drive control device 10 switches the switch 28 to shift the control mode to the rectangular wave voltage phase control mode.
FIG. 5 is a diagram showing the current-voltage characteristics of the PM motor. The horizontal axis represents the absolute value of the current phase | φi |, and the vertical axis represents the voltage constant (motor voltage per rotation of the motor 38). In the same figure, the dashed lines represent the relationship between the absolute value | φi | of the current phase and the voltage constant at the current values A to C, respectively. As shown in FIGS. 5 and 4, after the state has reached state Y from state X, the absolute value of the current phase | while gradually increasing the current value from B to A in order to increase the rotation speed of motor 38. φi | is gradually increased from the absolute value | φ0 | of the predetermined switching current phase. As a result, even if the number of rotations increases, the voltage amplitude can be suppressed to V0. Drive control device 1
The state of 0 reaches Z.

Next, the state Z of the rectangular wave voltage phase control mode
Will be described with reference to FIG. 4 when the state is shifted to the state X in the PWM current control mode while the torque is constant. FIG. 6 shows state Z to state X.
FIG. 11 is a diagram showing a relationship between the rotation speed of the motor 38 and the absolute value | φi | In the figure, state Z is under the rectangular wave voltage phase control mode, and the absolute value | φi | of the current phase is larger than the absolute value | φ0 | of the predetermined switching current phase. When the rotation speed gradually decreases from the state Z toward the state Y, the absolute value | φi | of the current phase decreases, and when it reaches the same value as the absolute value | φ0 | The phase determination unit 22 switches the switch 28 to shift the operation of the drive control device 10 to the PWM current control mode.
Thereafter, as described above, in the PWM current control mode, the current phase φi is maintained at a value at which the torque / current ratio becomes the maximum, that is, the predetermined switching current phase φ0, and the rotation speed falls to zero.

Drive control device 1 for AC motor described above
According to 0, the time for preparing a map for determining the switching timing can be reduced. Further, in the PWM current control mode, the motor 38 is operated with the motor current being minimum, and in the rectangular wave voltage phase control mode, the motor voltage is maximized, so that the output can be improved and the output efficiency can be maintained. Then, since the optimum control method is automatically selected according to the operation state of the motor 38, the motor 38 can always be operated efficiently and a high output can be obtained.

The AC motor drive control device 10 described above can be implemented in various modifications. For example, although rectangular wave voltage phase control is employed as voltage phase control in the above description, PWM voltage phase control may be employed.

FIG. 7 is a diagram showing the overall configuration of a drive control device 50 for an AC motor operable in both the PWM current control mode and the PWM voltage phase control mode. In the figure, the same components as those of the drive control device 10 shown in FIG. 1 are denoted by the same reference numerals, and the detailed description is omitted here.

The main difference from the drive controller 10 shown in FIG. 1 is that the voltage amplitude | V | and the voltage phase ψ supplied to the PWM circuit 30 are supplied from the current controller 14 and the voltage amplitude controller 15 And the state supplied from the voltage phase controller 18 is switched by the switch 35. Here, the voltage amplitude controller 1
5 shifts from the PWM current control mode to the PWM voltage phase control mode, at the start of the operation, continuously outputs the voltage amplitude | V | Increase or decrease the value,
The voltage amplitude | V | is supplied to the switch 35.

Even if the drive control device 50 according to this modified example is used, the most suitable control method is automatically selected according to the operation state of the motor 38, and the motor 38 can be operated efficiently.

In the above description, the predetermined switching voltage amplitude V0 and the predetermined switching current phase φ0, which define the control switching timing, are set to the optimum values in consideration of the operation efficiency of the motor 38, but in order to prevent frequent control switching. There is no practical problem even if it deviates to some extent from the optimum value.

[Brief description of the drawings]

FIG. 1 is a diagram showing an overall configuration of a drive control device for an AC motor according to an embodiment of the present invention.

FIG. 2 is a flowchart illustrating control switching in the drive control device for the AC motor according to the embodiment of the present invention.

FIG. 3 is a diagram illustrating states of the drive control device before and after control switching.

FIG. 4 is a diagram illustrating states of a drive control device before and after control switching.

FIG. 5 is a diagram illustrating states of the drive control device before and after control switching.

FIG. 6 is a diagram illustrating states of the drive control device before and after control switching.

FIG. 7 is a diagram showing an overall configuration of a drive control device for an AC motor according to a modification.

[Description of Signs] 10, 50 Drive control device, 12 Current command generation unit, 1
3 adder, 14 current controller, 15 voltage amplitude controller, 16 voltage amplitude determination unit, 18 voltage phase controller, 2
0 torque detector, 22 current phase determiner, 28, 35
Switch, 30 PWM circuit, 36 inverter, 38
Motor, 40 current sensor, 51 (optimal phase) curve.

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Hiroki Otani 41-cho, Yokomichi, Nagakute-cho, Aichi-gun, Aichi Prefecture F-term in Toyota Central Research Laboratory Co., Ltd. 5H576 AA15 BB02 DD02 DD07 EE11 EE25 EE30 GG04 GG07 HB02 LL22 LL28 LL39 LL60

Claims (3)

[Claims] 1. A PWM current control means for supplying a sinusoidal current having a predetermined amplitude and a predetermined phase according to a torque command to an AC motor, and applying an AC current having a phase deviating from the predetermined phase according to a torque command to the AC motor. Voltage phase control means for supplying the electric motor; and when the AC motor is driven by the voltage phase control means, the advance of the current phase of the AC current supplied to the AC motor and the control switching phase corresponding to the predetermined phase And a control switching means for starting the driving of the AC motor by the PWM current control means in place of the voltage phase control means if the relationship of the delay and the delay is reversed. 2. The drive control device for an AC motor according to claim 1, wherein the predetermined phase according to a torque command is determined so that a torque / current ratio increases. 3. The drive control device for an AC motor according to claim 1, wherein the switching control unit is configured to control the AC applied to the AC motor when the AC motor is driven by the PWM current control unit. When the amplitude of the voltage exceeds a predetermined amplitude, the drive control of the AC motor is started by the voltage phase control means instead of the PWM current control means.