JP3578612B2 - Electric car control device - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a control device for an electric vehicle that controls an AC motor.
[0002]
[Prior art]
Conventionally, as disclosed in JP-A-3-70402, braking force for braking an electric vehicle is generally performed by mechanical braking force by a hydraulic braking device and electric braking force by regenerative braking. well known. 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 regardless of the vehicle speed of the electric vehicle by sharing the braking torque with the braking force of the braking device using the electromagnetic brake.
[0003]
[Problems to be solved by the invention]
In the above prior art, when the electric vehicle is running in a high speed range, that is, when the electric motor is rotating at a high speed, the driving system of the electric vehicle is shared with the braking force by the electromagnetic brake as a supplement to the insufficient braking force. However, this naturally adds extra equipment 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, the braking force by this electromagnetic brake is unnecessary. Therefore, it is considered that it is not advisable to add this extra device to supplement the braking force.
[0004]
SUMMARY OF THE INVENTION It is an object of the present invention to provide a control apparatus for an electric vehicle that prevents a regenerative braking force from decreasing even when an electric motor is rotating at a high speed during traveling of the electric vehicle, and that can obtain a braking force equal to or more than a certain value. It is in.
[0005]
[Means for Solving the Problems]
The electric vehicle control device includes a power conversion unit that converts DC power supplied from a power supply, an AC motor that receives the power converted by the power conversion unit, and a command for a torque to be generated by the AC motor. A torque control component command and a field control component command are calculated based on the torque command and the rotation speed of the AC motor, and a signal for controlling the power conversion means is output based on these commands. Control means for controlling the power conversion means, the regenerative braking torque generated by the AC motor is changed based on the voltage of the power supply when the AC motor is performing regenerative braking, and the voltage of the power supply is increased. Can be achieved by increasing the regenerative braking torque .
[0006]
In the electric vehicle control device, the regenerative braking torque is changed by correcting the torque control component command and the field control component command based on the voltage of the power supply.
[0008]
In the control device for an electric vehicle, the correction amounts of the torque control component command and the field control component command are set based on an arbitrary function that receives a power supply voltage as an input.
[0009]
In the electric vehicle control device, the torque command at the time of regenerative braking of the AC motor is set to be larger than the torque command at the time of power running control of the AC motor.
[0010]
In the above electric vehicle control device, the torque command at the time of regenerative braking of the AC motor is set based on an arbitrary function that receives the voltage of the power supply.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of an electric vehicle control device according to the present invention will be described with reference to the drawings.
[0012]
FIG. 1 is a diagram showing a basic configuration of a control device for an electric vehicle 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. Is transmitted to the calculating means 5 inside the. The calculating means 5 takes in the signals of the accelerator device 1, the brake device 2 and the shift device 3 and the signal of the rotation detecting 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 driving 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 calculating means 5 as a current detection signal 14.
[0013]
FIG. 2 is a diagram showing the output characteristics of the electric motor 9 in the control device of the electric vehicle when 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, when the rotation speed of the electric motor 9 is in the range A, the maximum torque can be output constantly. 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 because in the case of general AC motor control, the voltage that can be applied to the motor 9 by the power conversion means 6 is determined by the voltage of the power supply 7, and when the AC motor is rotated to high speed, for example, a permanent magnet synchronous motor is used. In the case where the motor is used, the induced current generated in response to the high-speed rotation is suppressed and the motor is rotated to a high speed. In order to perform so-called field-weakening control, the current flowing through the electric motor 9 includes a current component for the field-weakening at the high-speed rotation. As a result, the amount of current for generating the torque within the current limit that the power conversion means 6 can supply is relatively small, so that the operation is such that the output torque is reduced in the high-speed range.
[0014]
The output characteristics of a general motor are 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.
[0015]
In the embodiment shown in FIG. 2, by performing the field weakening, the voltage V1 of the electric motor 9 with respect to the rotational speed Nm of the electric motor 9 increases in proportion to the rotational speed Nm of the electric motor 9 in the range of the region 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 upper limit of the voltage V1 of the electric motor 9 is determined by the voltage VB of the power supply 7. In the case of a normal PWM inverter, for 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.
[0016]
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 torque that can be output in any operating state is the same. That is, assuming that the maximum torque during power running at the maximum rotation is τ1 and the maximum torque during regeneration is τ2, this torque has a characteristic of τ1 = τ2.
[0017]
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 input to the torque command calculating means 18 as an accelerator signal 15, a brake signal 16, and a shift signal 17, respectively. The rotation detection signal 12 is calculated by a rotation speed calculation means 19 to calculate a motor rotation speed 20 and to transmit it to a torque command calculation 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 input to a torque component current generator 22 and a field component current generator 23, respectively, and at the same time, the motor 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 performs current control based on the torque component current command 24, the field component current command 25, and the converted current value 28, and outputs a voltage command value 29. 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 flow a current to the electric motor 9 to generate torque. It has a configuration. 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. An operation of flowing a current to the electric motor 9 is performed so that the voltage V1 of the motor 9 becomes constant.
[0018]
FIG. 4 is a diagram showing a control block diagram in the electric vehicle control device of the present invention.
[0019]
As in the block diagram described with reference to FIG. 3, a torque component current command 24 and a field component current command 25 are calculated from the torque command 21 and the motor speed 20, and the current control unit 27 performs current control to generate the drive signal 11. However, in addition to the processing, based on the value of the voltage detection value 31 of the power supply 7 and the value of the powering / regeneration mode flag 33 generated from the values of the accelerator device 1, the brake device 2, the shift device 3, and the motor speed 20. When the powering / regeneration mode flag 33 indicates the regeneration mode, the correction coefficient calculation means 32 calculates and outputs a voltage correction coefficient 34 for correcting the voltage V1 of the electric motor 9 from the voltage VB of the power supply 7. The voltage correction coefficient 34 is transmitted to each of the torque component current correction means 35 and the field component current correction means 36, and the torque component current correction means 35 outputs the value of the torque component current command 24, and the field component current correction means 36 The magnetic component current command 25 is corrected by the voltage correction coefficient 34. By 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, a drive signal 11 is generated to operate the power conversion means 6, and the electric motor 9 To generate torque.
[0020]
By performing such a process, the operation of the control device of the electric vehicle is determined by the torque command calculating unit as to whether the operation is power running or regenerative. A voltage correction coefficient 34 is generated so that the voltage V1 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 calculation 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 specified pattern or table using the voltage VB of the power supply 7 as an input. The voltage correction coefficient 34 may be generated based on this. Further, the correction by the voltage correction coefficient 34 may be performed only by the voltage VB of the power supply 7 irrespective of the powering / regeneration operating state.
[0021]
FIG. 5 shows 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. When the voltage VB of the power source 7 is equal to or lower than VB1, 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 motor 9 is weakened according to the voltage VB such that the voltage V1 of the motor 9 is V1a for VBa, V1b for VBb, and V1c for VBc. To adjust. 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 V1max 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 source 7 as described above, the voltage V1 of the electric motor 9 can be set high when the voltage VB is high. Since the higher the voltage V1 is, the larger the input to the motor 9 is, the larger the torque can be generated in the motor 9.
[0022]
FIG. 6 shows the maximum torque characteristics when the voltage V1 of the electric motor 9 is changed in the control device for an electric vehicle according to the present invention. When the horizontal axis represents the rotation speed Nm of the motor 9 and the vertical axis represents the output torque τm and the voltage V1 of the motor 9, power running can be represented by positive torque and regeneration can be represented by negative torque. Here, in normal power running, the voltage V1 with respect to the rotation speed Nm of the electric motor 9 is adjusted from an arbitrary rotation speed Nf as shown by Vlmin so that the voltage V1 becomes constant by field weakening control. This voltage Vl is usually set within the operating range of the control device of the electric vehicle, when the voltage VB of the power supply 7 is the lowest or at the lower limit voltage VB that 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 stepwise or proportional to the voltage VB with V1a, V1b, V1c in accordance with the rising voltage VB. By doing so, when the same amount of current flows through the motor 9, increasing the voltage of the motor 9 allows the motor 9 to generate more torque for regenerative braking. 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.
[0023]
FIG. 7 shows a maximum torque characteristic when the control device for an electric vehicle of the present invention is applied. As described above, in the conventional control, since the powering and the regenerative torque are the target outputs, the regenerative braking torque is set to a value equal to or greater than the torque at the time of the powering in the high-speed region as shown by the hatched area in the drawing, that is, Even when a braking torque is generated from τ1 = τ2 so that τ1 <τ2 to obtain a deceleration that is not less than a fixed value and does not change the braking force due to the rotation speed, the required regenerative braking torque τrt is braked by τu. Insufficient torque was inevitable. In this case, the regenerative braking torque is reduced in the high-speed region where the regenerative braking torque of the level of τrt is originally required. Therefore, when applied to a battery forklift or the like that requires a strong regenerative braking torque even in the high-speed region, The braking performance was reduced in the high-speed range. However, when the control device for an electric vehicle according to 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 according to the increase in the voltage VB of the power supply 7 due to the regenerative braking. Therefore, a regenerative braking torque having a 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]
【The invention's effect】
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 voltage of the power supply that changes due to the powering operation and the regenerative operation. It is possible to suppress a decrease in the generated regenerative braking torque, and it is possible to obtain a strong braking force of a certain level or more regardless of the rotation of the electric motor.
[0025]
Further, since 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 a 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 a diagram showing a maximum torque characteristic when the voltage V1 of the electric motor 9 is changed in the control device for an electric vehicle according to the present invention.
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 speed calculation means, 20: motor rotation speed, 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 Magnetic component current correction means, 37: corrected torque component current command, 38: corrected field component current command.

Claims (5)

A power converter for converting DC power supplied from a power supply, an AC motor receiving the power converted by the power converter, and a torque command which is a command for torque to be generated by the AC motor. Calculating a torque control component command and a field control component command based on the torque command and the rotational speed of the AC motor, and outputting a signal for controlling the power conversion means based on these commands to output the power conversion means. Controlling the electric vehicle having control means for controlling, when the AC motor is performing regenerative braking, changes the regenerative braking torque generated by the AC motor based on the voltage of the power supply, the voltage of the power supply is A control device for an electric vehicle, wherein the regenerative braking torque is increased when it rises . 2. The electric vehicle control device according to claim 1, wherein the regenerative braking torque is changed by correcting the torque control component command and the field control component command based on a voltage of the power supply. . 3. The control device for an electric vehicle according to claim 2, wherein the correction amounts of the torque control component command and the field control component command are set based on an arbitrary function that receives the voltage of the power supply. Electric car control device. 3. The control device for an electric vehicle according to claim 2, wherein the torque command during regenerative braking of the AC motor is set to be larger than the torque command during power running control of the AC motor. 4. Electric vehicle control device. 5. The electric vehicle according to claim 4, wherein the torque command at the time of regenerative braking of the AC motor is set based on an arbitrary function that receives a voltage of the power supply. 6. Control device.

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