JPH11155202A - Electric car control device - Google Patents

Abstract

(57) [Problem] To reduce a decrease in braking torque due to a decrease in maximum torque due to field-weakening control in a high-speed rotation of an electric motor, and to obtain a braking torque of a certain level or more regardless of the rotation of the electric motor. A torque current component command and a field component current command are calculated from a torque command and a motor rotation speed, and a power conversion unit is driven by a current control unit and a drive signal generation unit to generate torque in the motor. The torque current component command and the field component current command are corrected by the voltage correction coefficient calculated by the correction coefficient calculation means based on the voltage detection value of the power supply, and the field weakening is corrected according to the voltage of the power supply to thereby correct the motor voltage. Adjust

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric vehicle control device for controlling an AC motor.

[0002]

2. Description of the Related Art Conventionally, as disclosed in JP-A-3-70402, braking force for braking an electric vehicle generally includes a mechanical braking force by a hydraulic braking device and an electric braking force by regenerative braking. It is well known that this is done. This description is based on the case where the braking force provided by the combined force of the mechanical braking force and the regenerative braking force is insufficient when the vehicle speed of the electric vehicle is high, that is, when the rotation speed of the electric motor is high and the regenerative braking torque is low. It is disclosed that a constant deceleration can always be obtained irrespective of the speed of the electric vehicle by sharing the braking torque with the braking force of the braking device using the electromagnetic brake.

[0003]

In the above prior art, the drive system of an electric vehicle is used to compensate for the lack of braking force that occurs when the electric vehicle is running in a high speed range, that is, when the electric motor is rotating at a high speed. However, this naturally adds an extra device to the electric vehicle, and when the vehicle is running at low speed, that is, when the rotation speed of the electric motor is low, Since no braking force is required by the electromagnetic brake, it is considered that it is not advisable to add this extra device to supplement the braking force.

An object of the present invention is to provide a control device for an electric vehicle that prevents a regenerative braking force from decreasing even when the electric motor is rotating at a high speed during traveling of the electric vehicle, and that can obtain a braking force of a certain level or more. To provide.

[0005]

SUMMARY OF THE INVENTION The present invention provides power conversion means for converting DC power and supplying it to an AC motor, and torque calculation means for calculating a torque command value which is a command for a torque to be generated by the AC motor. A rotation detecting means for detecting the rotation speed of the AC motor; and a vector that separates a torque control component Iq and a field control component Id from a current supplied to the AC motor based on the torque command value and the motor rotation speed. The control calculation, the motor voltage of the AC motor is controlled by the torque control component and the field control component, wherein the torque control component and the field control component are calculated from the torque command value and the motor rotation speed, This is achieved by correcting the torque control component and the field control component based on the voltage of the power supply.

Preferably, when it is determined that the AC motor is performing regenerative braking, the regenerative braking torque is improved based on the voltage of the power supply based on the torque control component and the field control component. Achieved by correcting.

Preferably, the present invention is achieved by adjusting the torque control component and the field control component according to the torque command and the motor rotation speed when it is determined that the AC motor is performing a power running operation. .

Preferably, the torque control component and the field control component are determined by determining a correction adjustment amount of the torque control component and the field control component based on an arbitrary function that receives a voltage of the power supply. Achieved.

Preferably, the present invention is achieved by setting the torque command value during regenerative control to be larger than the torque command value during power running control.

Preferably, in the present invention, the torque command value at the time of the regenerative control is achieved by setting the torque command value on the basis of an arbitrary function which receives the voltage of the power supply.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of an electric vehicle control device according to the present invention will be described with reference to the drawings.

FIG. 1 is a diagram showing a basic configuration of an electric vehicle control device according to the present invention. The control device of the electric vehicle is provided with an accelerator device 1, a brake device 2, and a shift device 3 for converting a driver's intention into an electric signal. Calculation means 5 inside
Is transmitted to The calculating means 5 takes in the signals of the accelerator device 1, the brake device 2, the shift device 3 and the signal of the rotation detection signal 12 which is the signal detected by the rotation detecting means 10 of the rotation of the electric motor 9, and calculates and outputs the drive signal 11. . The drive signal 11 is transmitted to the power conversion element 8 inside the power conversion means 6, converts the power of the power supply 7 and supplies it to the electric motor 9, and the electric motor 9 generates torque to drive and drive the electric vehicle. The current flowing through the motor 9 is detected by the current detecting means 13 and transmitted to the arithmetic means 5 as a current detection signal 14.

FIG. 2 is a diagram showing the output characteristics of the electric motor 9 in a control device for an electric vehicle to which the present invention is not applied. The motor 9 generates a torque based on a command value calculated by the calculating means 5 of the control means 4, and its output torque characteristic is represented by the rotation speed Nm of the motor 9 on the horizontal axis and the output torque τm on the vertical axis. As shown in FIG. 2 and FIG. 2, the maximum torque can be output constantly when the rotation speed of the electric motor 9 is in the range A. As the rotation speed Nm of the electric motor 9 in the region B becomes higher, the output torque decreases with respect to the rotation speed Nm of the electric motor 9, and becomes a torque up to τ1 at the time of the maximum rotation speed. This is a general AC motor control,
The voltage that can be applied to the electric motor 9 by the electric power conversion means 6 is determined by the voltage of the power supply 7. Also, when the AC motor is rotated to a high speed, for example, when a permanent magnet synchronous motor is used, the voltage is generated according to the high speed rotation. In order to perform the so-called field-weakening control in which the induced voltage is suppressed and the motor rotates at a high speed, the current flowing through the electric motor 9 includes the current component for the field-weakening at the high-speed rotation. Since the amount of current for generating torque in the current limitation is relatively small, the operation is such that the output torque is reduced in a high-speed range.

The output characteristic of a general motor is such that the operation of constant torque, constant output (constant wattage), and constant voltage (constant motor voltage) is performed by performing the field weakening in this manner.

In the embodiment shown in FIG. 2, by performing the field weakening, the voltage V1 of the motor 9 with respect to the rotation speed Nm of the motor 9 increases in proportion to the rotation speed Nm of the motor 9 in the range A. In the region B, the field weakening control is performed so that the voltage becomes constant regardless of the rotation speed Nm of the electric motor 9. The voltage V1 of the electric motor 9 is equal to the voltage V
The upper limit is determined by B. If a normal PWM inverter is taken as an example, about 70% of the voltage VB is the upper limit of the voltage V1. Further, in the power conversion means 6 such as a PWM inverter, the maximum value of the current that can flow is determined by the capacity of the power conversion element 8, so the maximum torque that the motor 9 can output is determined from the maximum current that can be supplied and the voltage V1. It will be.

In other words, the higher the voltage VB, the higher the voltage V1 of the motor 9 can be. Therefore, if the same motor current is applied, the higher the voltage V1 of the motor 9, the more torque can be generated. This maximum torque characteristic is basically symmetric in the case of power running and in the case of regeneration, and the outputtable torque is the same in any operating state. In other words, the maximum torque during power running at the maximum rotation is τ
1. Assuming that the maximum torque during regeneration is τ2, this torque is τ
1 = τ2.

FIG. 3 is a block diagram showing an example of the processing contents of the arithmetic means 5 inside the control means 4 in the control device for the electric vehicle of the present invention. The signals from the accelerator device 1, the brake device 2 and the shift device 3 are the accelerator signal 1 respectively.
5, the brake signal 16 and the shift signal 17 are input to the torque command calculating means 18. The rotation detection signal 12 is calculated by the rotation speed calculating means 19 and the motor rotation speed 20 is calculated.
Is calculated and transmitted to the torque command calculating means 18. The torque command calculating means 18 calculates the torque to be generated by the electric motor 9 based on the input signal, and outputs it as a torque command 21. The torque command 21 is a torque component current generator 22
And the field component current generator 23, and at the same time, the motor rotation speed 20 is also input to calculate and output a torque component current command 24 and a field component current command 25. The torque component current command 24 and the field component current command 25 are transmitted to the current control means 26. The current detection signal 14 is converted by the current conversion means 27 and outputs a converted current value 28. The current control means 26 includes a torque component current command 24 and a field component current command 2
Current control is performed based on 5 and the converted current value 28, and a voltage command value 29 is output. The drive signal generation means 30 generates a drive signal 11 to be transmitted to the power conversion means 6 based on the value of the voltage command value 29, and operates the power conversion means 6 to drive the electric motor 9.
And a torque is generated.
Here, the field component current command 25 from the field component current generator 23 is a current command for performing the field weakening described above with reference to FIG. 2, and as described with reference to FIG. The operation of flowing a current to the electric motor 9 is performed so that the voltage V1 of the motor 9 becomes constant.

FIG. 4 is a diagram showing a control block diagram in the electric vehicle control device of the present invention.

As in the block diagram described with reference to FIG. 3, the torque command 21 and the torque component current command 2
4 and the field component current command 25, and the current control means 27 performs current control to generate the drive signal 11. In addition to the processing, the value of the voltage detection value 31 of the power supply 7, the accelerator device 1, and the brake device If the powering / regenerative mode flag 33 indicates the regenerative mode based on the value of the powering / regenerative mode flag 33 generated from the value of the shift gear 2, the shift device 3, and the motor speed 20, the correction coefficient calculating means 32 A voltage correction coefficient 34 for correcting the voltage V1 of the electric motor 9 from the voltage VB of the power supply 7 is calculated and output. The voltage correction coefficient 34 is transmitted to each of the torque component current correction unit 35 and the field component current correction unit 36, and the torque component current correction unit 35 converts the value of the torque component current command 24 into the field component current correction unit 3.
In step 6, the field component current command 25 is corrected by the voltage correction coefficient 34. With this correction, a correction torque component current command 37 and a correction field component current command 38 are calculated, current control is performed by the current control means 26, the drive signal 11 is generated to operate the power conversion means 6, and the electric motor 9 To generate torque.

By performing such processing, the torque command calculating means determines whether the operation of the control device of the electric vehicle is power running or regenerative operation, and in response to the voltage VB of the power supply 7 which increases due to regenerative braking during the regenerative operation. The voltage correction coefficient 34 is generated so that the voltage V1 of the electric motor 9 is increased, that is, the field weakening field is weakened, and the field component current command 25 is corrected by the field component current correction means 36. In the correction of only the field component current command 25, it is assumed that the output torque of the electric motor 9 does not match the torque command 21. Therefore, the torque component current correction means 35 uses the value of the voltage correction coefficient 34 for the correction. The torque component current command 24 is also corrected so that the torque generated by the electric motor 9 with respect to the torque command 21 always matches. The calculation method of the correction coefficient calculating means 32 may generate the voltage correction coefficient 34 in proportion to the voltage VB of the power supply 7, or may calculate a function or a prescribed pattern or table with the input of the voltage VB of the power supply 7. The voltage correction coefficient 34 may be generated based on this. Further, the correction using the voltage correction coefficient 34 may be performed only with the voltage VB of the power supply 7 irrespective of the powering / regeneration operating state.

FIG. 5 shows the relationship between the voltage VB of the power source 7 and the voltage V1 of the electric motor 9 when the field-weakening is corrected by the correction coefficient calculating means 32. The voltage VB of the power supply 7 is
In the case of VB1 or less, the field weakening is performed so that the voltage V1 of the electric motor 9 becomes V1min. When the voltage VB of the power supply 7 increases due to the regenerative braking, the voltage V1 of the electric motor 9 is V1a in VBa, V1b and V1 in VBb according to the voltage VB.
In Bc, the voltage V1 of the electric motor 9 is adjusted to be V1c by weakening and performing field control. When the voltage VB of the power supply 7 reaches VB2, a correction is made so that the voltage V1 of the electric motor 9 does not increase more than V1max. This V1ma
x is determined from the withstand voltage of the power conversion means 6 and the power conversion element 8 and the like. By changing the voltage V1 of the electric motor 9 in accordance with the voltage VB of the power supply 7,
When B is high, the voltage V1 of the motor 9 can be set high.
As the value of 1 is higher, the input to the motor 9 is larger, so that a larger torque can be generated in the motor 9.

FIG. 6 shows the maximum torque characteristics when the voltage V1 of the electric motor 9 is changed in the electric vehicle control device of the present invention. When the horizontal axis represents the rotational speed Nm of the electric motor 9 and the vertical axis represents the output torque τm and the voltage V1 of the electric motor 9, powering can be represented by positive torque and regeneration can be represented by negative torque. Here, in normal power running, the rotation speed N of the electric motor 9
The voltage V1 with respect to m is adjusted so that the voltage V1 becomes constant by a field weakening control from an arbitrary rotational speed Nf as indicated by Vlmin. This voltage Vl is usually set within the operating range of the control device of the electric vehicle, in accordance with the case where the voltage VB of the power supply 7 is the lowest or the lower limit voltage VB which guarantees the power performance. However, when regenerative braking is performed, the voltage VB of the power supply 7 also increases. Therefore, it is not always necessary to determine the voltage V1 of the electric motor 9 in accordance with the case where the voltage VB of the power supply 7 is the lowest. Therefore, during the regenerative braking, the field weakening control is corrected so that the upper limit of the voltage V1 of the electric motor 9 is set to V1a, V1b, V1c stepwise or in proportion to the voltage VB in accordance with the rising voltage VB. By doing so, when the same amount of current is applied to the electric motor 9, the higher the voltage of the electric motor 9, the more torque for regenerative braking can be generated in the electric motor 9. As a result, the regenerative braking torque is τa when the voltage of the electric motor 9 is V1a, τb when V1b, and τc when V1c.

FIG. 7 shows the maximum torque characteristic when the electric vehicle control device of the present invention is applied. As described above, in the conventional control, the output of the power running and the torque of the regeneration are the target outputs. Even when a braking torque is generated from τ1 = τ2 so that τ1 <τ2, and a deceleration that is not less than a certain value and does not change the braking force due to the rotation speed is desired, the required regenerative braking torque τrt is braked by τu. Insufficient torque was inevitable. In this case, the regenerative braking torque decreases in a high-speed region where the regenerative braking torque of the level of τrt is originally required.
When applied to a battery forklift or the like that requires a strong regenerative braking torque even in a high speed range, the braking performance is reduced in a high speed range. However, when the electric vehicle control device of the present invention is applied, the regenerative braking torque can be increased from the level of the a curve to the level of the b curve in accordance with the increase in the voltage VB of the power supply 7 due to the regenerative braking. Therefore, the regenerative braking torque at the level of τrt indicated by oblique lines can be generated at any motor speed. In particular, when the present invention is applied to a vehicle such as a battery forklift that requires a strong braking force even in a high speed range, the traveling performance can be improved.

[0024]

According to the present invention, the motor voltage of the motor can be adjusted according to the voltage of the power supply in accordance with the power supply voltage that changes due to the powering operation and the regenerative operation. , A decrease in regenerative braking torque generated by the field weakening can be suppressed, and a strong braking force of a certain level or more can be obtained regardless of the rotation of the electric motor.

Further, the control device itself can increase only the braking torque while maintaining the conventional size and capacity.
Desired power performance can be secured without increasing the size of the device.

[Brief description of the drawings]

FIG. 1 is a diagram showing a basic configuration of a control device for an electric vehicle according to the present invention.

FIG. 2 is a diagram showing a maximum torque characteristic in a case where the present invention is not applied in a control device for an electric vehicle.

FIG. 3 is a block diagram showing a processing content of a calculation means 5 inside the control means 4 in the control device for an electric vehicle of the present invention.

FIG. 4 is a diagram showing a control block diagram in a control device for an electric vehicle according to the present invention.

FIG. 5 is a diagram showing the relationship between the voltage VB of the power supply 7 and the voltage V1 of the electric motor 9 when the field-weakening is corrected by the correction coefficient calculating means 32.

FIG. 6 is an electric motor 9 in the electric vehicle control device according to the present invention.
FIG. 7 is a diagram showing a maximum torque characteristic when the voltage V1 is changed.

FIG. 7 is a diagram showing power running and regenerative torque characteristics when the electric vehicle control device of the present invention is applied.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Accelerator device, 2 ... Brake device, 3 ... Shift device, 4 ... Control means, 5 ... Calculation means, 6 ... Power conversion means,
7 ... power supply, 9 ... electric motor, 10 ... rotation detection means, 11 ... drive signal, 13 ... current detection means, 18 ... torque command calculation means, 19 ... rotation number calculation means, 20 ... motor rotation number, 21
... torque command, 22 ... torque component current generator, 23 ... field component current generator, 24 ... torque component current command, 25 ...
Field component current command, 26 ... Current control means, 30 ... Drive signal generation means, 32 ... Correction coefficient calculation means, 34 ... Voltage correction coefficient, 35 ... Torque component current correction means, 36 ... Field component current correction means, 37 ... Correction torque component current command, 38 ...
Correction field component current command.

Claims (6)

[Claims] Power conversion means for converting DC power and supplying the AC power to an AC motor; torque calculation means for calculating a torque command value which is a command for a torque to be generated by the AC motor;
Rotation detection means for detecting the rotation speed of the AC motor,
Based on the torque command value and the motor rotation speed, a current to be applied to the AC motor is subjected to vector control calculation by separating a torque control component Iq and a field control component Id, and the motor voltage of the AC motor is determined by the torque control component. Wherein the torque control component and the field control component are calculated from the torque command value and the motor rotation speed, and the torque control component and the field control component are calculated based on the voltage of the power supply. A control device for an electric vehicle, characterized by correcting the following. 2. The regenerative braking torque according to claim 1, wherein when it is determined that the AC motor is performing regenerative braking, the regenerative braking torque is improved by using the torque control component and the field control component based on the voltage of the power supply. A control device for an electric vehicle, wherein the control is performed so as to perform the correction. 3. The method according to claim 1, wherein when it is determined that the AC motor is performing a power running operation, the torque control component and the field control component are adjusted based on the torque command and the motor rotation speed. Characteristic electric vehicle control device. 4. The method according to claim 2, wherein the torque control component and the field control component are used to calculate the correction adjustment amounts of the torque control component and the field control component based on an arbitrary function that receives the voltage of the power supply. A control device for an electric car characterized by the decision. 5. The control device for an electric vehicle according to claim 2, wherein the torque command value during regenerative control is set to be larger than the torque command value during power running control. 6. A control device for an electric vehicle according to claim 5, wherein the torque command value at the time of the regenerative control is set based on an arbitrary function that receives a voltage of a power supply.