JP2013081321A - Vehicle driven by motor generator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the wasteful increase of a voltage to prevent the wasteful consumption of power, in a vehicle that improves running performance by increasing a battery voltage to apply it to a drive motor generator.SOLUTION: A converter control device serving also as a step-up/step-down function includes a transformation ratio determination device and a transformation ratio substitution device. The transformation ratio determination device determines a transformation ratio that is instructed to the converter on the basis of a driving state of the vehicle. When the transformation ratio determined by the transformation ratio determination device is equal to or less than the lowest transformation ratio, the transformation ratio substitution device substitutes the transformation ratio determined by the transformation ratio determination device for the lowest transformation ratio. This technique adds a condition to a processing for substitution for the lowest transformation ratio, and performs substitution only during regenerative driving. Even when the transformation ratio determined by the transformation ratio determination device is equal to or less than the lowest transformation ratio, if a power running operation is performed, the transformation ratio is not substituted. The wasteful increase of the voltage is prevented to prevent the wasteful consumption of power.

Description

  The present specification discloses an automobile having a function of rotating a motor using battery power and charging the battery using power generated by the motor as a generator. Such vehicles include hybrid vehicles that use an engine together, and also include fuel cell vehicles that generate power with a fuel cell and charge the battery. In this specification, the motor generator is referred to, focusing on the fact that the motor may be a generator. It does not distinguish from what is simply called a motor.

  Some automobiles that run on a motor generator are known to boost the battery voltage and supply it to the motor generator. The type of automobile includes a battery, a converter, an inverter, and a motor generator. A converter is inserted between the battery and the inverter, and a motor generator is connected to the inverter. The battery voltage is boosted by a converter, the boosted direct current is converted to alternating current by an inverter, and the alternating current converted by the inverter is supplied to the motor generator. The motor generator serves as a generator during braking and generates electricity. Therefore, it has a function of converting alternating current generated by the motor generator into direct current using an inverter, stepping down the converted direct current using a converter, and charging the battery with the reduced direct current. Power running operation using the motor generator as a motor and regenerative operation using the motor generator as a generator are possible.

  During power running, the motor output increases as the voltage applied to the motor generator is increased by increasing the boost ratio of the converter, and the running performance is improved. On the other hand, as the step-up ratio of the converter is increased, for example, the amount of heat generated by the switching semiconductor element built in the inverter increases, and the power consumed in vain increases. Therefore, a technique for controlling the boost ratio of the converter based on the driving state of the vehicle has been developed.

  In this specification, a value obtained by dividing the voltage on the inverter side by the voltage on the battery side is referred to as a transformation ratio. In powering operation in which the voltage is boosted by the converter, the transformation ratio is equal to the boost ratio. In the regenerative operation in which the voltage is reduced by the converter, the voltage reduction ratio is a value obtained by dividing the voltage on the battery side by the voltage on the inverter side, so that the transformation ratio is the reciprocal of the voltage reduction ratio. The transformation ratio referred to in this specification is 1 or more for both power running and regenerative operation, and is commonly used for power running and regenerative operation.

An in-vehicle converter includes a coil, and boosts and steps down using the reactance component of the coil. At that time, there exists a minimum transformation ratio at which the converter can operate stably. FIG. 8 shows the prior art described in Patent Document 1.
Step S2: The rotational speed of the motor generator and the torque generated by the motor generator are determined from the running state of the vehicle, the operation amount of the accelerator pedal and the brake pedal, the position of the shift lever, and the like.
Step S4: The converter transformation ratio is determined according to the rotational speed and torque determined in step S2. Since the transformation ratio and the target value of the boosted voltage (voltage on the inverter side) uniquely correspond to each other, step S4 is equivalent to determining the target value of the boosted voltage. In steps S2 and S4, the transformation ratio of the converter is determined based on the driving state of the vehicle.
Step S8: The transformation ratio determined in step S4 is compared with the lowest transformation ratio.
Step S10: If the transformation ratio determined in step S4 <the lowest transformation ratio, the actually used transformation ratio is replaced with the lowest transformation ratio.
Step S12: A control signal having a duty ratio corresponding to the transformation ratio determined through the above process is generated.
Step S14: From the control signal generated in step S12, a gate voltage for switching on / off of the upper transistor included in the converter is generated.
Step S16: Generate a gate voltage for switching on / off the lower transistor included in the converter from the control signal generated in step S12.
According to the technique of Patent Document 1, the converter operates at a transformation ratio that is equal to or higher than the lowest transformation ratio that can be stably operated.

JP 2009-296848 A

There is a case where the transformation ratio determined from the driving state of the vehicle is less than the minimum transformation ratio. In the prior art, in that case, the minimum transformation ratio is replaced. As described above, useless power consumption (energy loss) increases as the boost ratio of the converter is increased. When the actually required transformation ratio is less than the minimum transformation ratio, energy loss increases according to the technique of substituting for the lowest transformation ratio.
In the present specification, a technique for reducing the energy loss generated as described above is disclosed.

  The reason why the minimum transformation ratio at which the converter can operate stably is limited is that the lower transistor is turned off in order to prevent the upper transistor and the lower transistor included in the converter from being turned on and short-circuited at the same time. It is necessary to perform control so that the upper transistor is turned on at a timing delayed by a predetermined time and the lower transistor is turned on at a timing delayed by a predetermined time after the upper transistor is turned off. The above delay time is referred to as dead time in this specification. Since it is necessary to provide a dead time, there is a restriction on the minimum transformation ratio.

  The technology disclosed in the present specification uses the knowledge that the influence of the dead time on the transformation ratio is different between the step-up operation and the step-down operation. In other words, there is certainly a minimum transformation ratio during step-down operation, and step-down operation is not possible with a lower transformation ratio, but there is no minimum transformation ratio during step-up operation, and a transformation ratio that is less than the minimum transformation ratio. But use the knowledge that boost operation is possible.

The vehicle disclosed in this specification includes a battery 10, a converter 20, an inverter 50, a motor generator 60, and a control device 70, as schematically shown in FIG. Converter 20 is inserted between battery 10 and inverter 50. A motor generator 60 is connected to the inverter 50. The vehicle can be operated in a power running by boosting the voltage of the battery 10 by the converter 20, converting the boosted direct current to alternating current by the inverter 50, and supplying the converted alternating current to the motor generator 60. Further, a regenerative operation in which the alternating current generated by motor generator 60 is converted into direct current by inverter 50 and the direct current is stepped down by converter 20 to charge battery 10 is possible.
Control device 70 of converter 20 includes a transformation ratio determination device and a transformation ratio substitution device. The transformation ratio determination device determines the transformation ratio of converter 20 based on the driving state of the vehicle. The transformation ratio replacement device replaces the transformation ratio determined by the transformation ratio determination device with the lowest transformation ratio if the transformation ratio determined by the transformation ratio determination device is less than the minimum transformation ratio and the regenerative operation is being performed. During power running, the transformation ratio determined by the transformation ratio determination device is not replaced.

  According to the above apparatus, during the regenerative operation, the converter 20 operates at a transformation ratio that is equal to or higher than the minimum transformation ratio. During powering operation, the transformation ratio instructed to the converter 20 may be less than the minimum transformation ratio. However, during powering operation, the operation of converter 20 does not malfunction even if a transformation ratio less than the minimum transformation ratio is indicated. If the transformation ratio determined from the driving condition of the vehicle during power running is less than the minimum transformation ratio, the conventional technology used the lowest transformation ratio without distinguishing between step-up and step-down. And wasted power. According to the above-described device, the converter is operated at a truly necessary small transformation ratio by utilizing the knowledge that the operation of the converter 20 does not malfunction even when the minimum transformation ratio is not reached during power running. During power running, there is no wasteful pressure boosting and no wasteful power consumption. Generation of energy loss can be avoided.

  According to the above-mentioned automobile, it is possible to prevent wasteful power consumption due to wasteful voltage increase when the transformation ratio determined from the driving state of the vehicle is less than the minimum transformation ratio. The battery voltage can be boosted by the converter to improve the running performance of the vehicle, and energy loss can be prevented. Furthermore, since the restrictions on the minimum transformation ratio are observed during regenerative operation, converter operation does not become unsatisfactory.

The figure which shows the structure of the motor vehicle disclosed by the specification. The figure which shows the process sequence which the motor vehicle disclosed by the specification employ | adopts. The figure which shows the structure of the converter of the motor vehicle of an Example. The figure which shows the internal structure of the control apparatus of a converter. The figure explaining the phenomenon which arises from the control duty signal shown to (a). The figure explaining a mode that the transformation ratio at the time of power running is reduced and energy loss is suppressed. The figure which shows the relationship between the duty ratio of a control duty signal, the transformation ratio at the time of power running, and the transformation ratio at the time of regeneration. The figure which shows the process sequence which the conventional converter control apparatus has employ | adopted.

The main features of the embodiments shown below are listed.
(Characteristic 1) The control data signal is inverted, and a signal whose rise timing is delayed by DT (dead time) is added to a transistor that determines a transformation ratio at the time of step-down.
(Characteristic 2) A signal obtained by delaying the rising timing of the control date signal by DT (dead time) is added to a transistor that determines a transformation ratio at the time of boosting.

FIG. 1 shows the configuration of an electric vehicle that runs on a motor generator 60. The electric vehicle includes a battery 10, a converter 20, an inverter 50, a motor generator 60, and a control device 70.
The battery 10 is an assembled battery in which a large number of cells are connected in series, and the battery voltage is about 200 volts. Converter 20 is inserted between battery 10 and inverter 50. The converter 20 is a bidirectional type that can step up the voltage of the battery 10 and apply it to the inverter 50, or step down the voltage on the inverter 50 side and apply it to the battery 10 side. The converter 20 can adjust a value (transformation ratio) obtained by dividing the voltage on the inverter 50 side by the voltage on the battery 10 side during both step-up and step-down. The maximum transformation ratio of the converter 20 is about 3.0. Inverter 50 converts direct current into three-phase alternating current and applies it to motor generator 60. The rotation speed of the motor generator 60 is controlled by the frequency of the three-phase alternating current, and the torque of the motor generator 60 is controlled by the current value of the three-phase alternating current. When the voltage is increased by converter 20, the maximum output of motor generator 60 is increased, and the running performance of the electric vehicle is improved.

  When braking the electric vehicle, the motor generator 60 serves as a generator to generate a three-phase alternating current. In this case, the inverter 50 converts the three-phase alternating current into direct current, and the converter 20 steps down to the battery voltage. Thereby, the battery 10 is charged. In the case of a hybrid vehicle, an engine (not shown) may rotate the motor generator 60 to generate power.

  FIG. 3 shows the internal configuration of the converter 20. The battery 10, the positive electrode line 22, the coil 24, the lower transistor 36, and the ground line 28 constitute a circuit for energizing the coil 24. When the lower transistor 36 is intermittently turned on / off, the energization current of the coil 24 is intermittently turned on / off. When the lower transistor 36 is turned off, the energy accumulated in the coil 24 while the lower transistor 36 is turned on is released, and the potential at the point indicated by Vce in FIG. 3 is boosted to the battery voltage or higher. The boosted voltage is applied to the capacitor 40 via the diode 34 and the high-voltage positive line 30, and the voltage of the capacitor 40 becomes equal to or higher than the voltage of the battery 10. A voltage higher than the battery voltage is applied to the inverter 50.

In the converter 20, a circuit for energizing the coil 24 is configured by the capacitor 40, the high-voltage positive line 30, the upper transistor 32, the coil 24, the positive line 22, the capacitor 26, and the ground line 28. Yes. When the upper transistor 32 is intermittently turned on / off, the energization current of the coil 24 is intermittently turned on / off. When the upper transistor 32 is turned on, a voltage obtained by subtracting the voltage generated in the coil 24 from the voltage Vce is applied to the capacitor 26. The voltage of the capacitor 26 is lower than the voltage Vce. When the upper transistor 32 is off, a current flows through the diode 38.
Vce> battery voltage at both step-up and step-down, and the value (transformation ratio) obtained by dividing Vce by the battery voltage at both step-up and step-down is 1.0 or more.

  FIG. 4 shows the internal configuration of the converter control device 70. A computer device composed of a CPU 72 and a memory 74 is incorporated. The converter control device 70 includes a control duty signal generation circuit 76 controlled by a computer device, an upper gate voltage output circuit 78 that outputs a voltage applied to the gate of the upper transistor 32, and a voltage applied to the gate of the lower transistor 36. A lower gate voltage output circuit 80 for outputting is provided. The upper gate voltage output circuit 78 and the lower gate voltage output circuit 80 incorporate a circuit that delays by the DT time (dead time), and turns on the lower transistor 36 after DT time after the upper transistor 32 is turned off. The upper transistor 32 is turned on DT time after the transistor 36 is turned off. The upper transistor 32 and the lower transistor 36 are not turned on at the same time so that the high positive electrode line 30 and the ground line 28 are not short-circuited.

FIG. 2 shows a processing procedure performed by the converter control device 70.
Step S2: The rotational speed of the motor generator and the torque generated by the motor generator are determined from the running state of the vehicle, the operation amount of the accelerator pedal and the brake pedal, the position of the shift lever, and the like. That is, the number of rotations of the motor generator and the torque generated by the motor generator are determined based on the running state of the vehicle.
Step S4: The converter transformation ratio is determined according to the rotational speed and torque determined in step S2. Since the transformation ratio and the target value of the boosted voltage (voltage on the inverter side) uniquely correspond to each other, step S4 is equivalent to determining the target value of the boosted voltage. In steps S2 and S4, the transformation ratio of the converter is determined based on the driving state of the vehicle.
Step S6: It is determined whether the vehicle is in power running or regenerative operation. That is, it is determined whether the voltage is stepped up or stepped down by the converter 20. If it is during power running, step S10 described later is skipped. That is, during powering operation, the process of replacing the actually used transformation ratio with the lowest transformation ratio is not performed. If it is during power running, the transformation ratio determined in step S4 is set as the transformation ratio that is actually used.
Step S8: This process is performed only during regenerative operation. During the regenerative operation, the transformation ratio determined in step S4 is compared with the lowest transformation ratio.
Step S10: This process is also performed only during the regenerative operation. If regenerative operation is being performed and the transformation ratio determined in step S4 <minimum transformation ratio, the actually used transformation ratio is replaced with the lowest transformation ratio.
Step S12: Transformer ratio determined as described above (if regenerative operation is being performed and if the transform ratio determined in Step S4 is <minimum transform ratio, the minimum transform ratio is used. Otherwise, the transform ratio is determined in Step S4) A control duty signal having a duty ratio determined by using a transformation ratio is generated.
Step S14: A gate voltage for switching on / off of the upper transistor 32 provided in the converter 20 is generated from the control duty signal generated in step S12.
Step S16: From the control duty signal generated in step S12, a gate voltage for switching on / off of the lower transistor 36 included in the converter 20 is generated.

FIG. 5A illustrates the control duty signal generated by the control duty signal generation circuit 76. A control duty signal generation circuit 76 is configured by a computer device that performs the processing from steps S2 to S12 in FIG. The duty ratio (t′on / (t′on + t′off)) of the control duty signal is determined based on the driving state of the automobile.
FIG. 5B illustrates the voltage output by the upper gate voltage output circuit 78, which is generated by inverting (a) and delaying the turn-on timing by DT. The upper gate voltage output circuit 78 is configured by a computer device that performs the process of step S14 of FIG.
FIG. 5C illustrates the voltage output from the lower gate voltage output circuit 80, which is generated by delaying the turn-on timing by DT from FIG. The lower gate voltage output circuit 80 is configured by the computer device that performs the process of step S16 of FIG.

(D) of FIG. 5 shows the Vce voltage at the time of voltage boosting, and the coil 24 is energized to accumulate energy while the (c) of FIG. 5 is on. The energization period of the coil 24 is shortened by delaying the turn-on timing by the DT time to prevent a short circuit. By providing the dead time DT, the transformation ratio is reduced. (F) of FIG. 5 shows the transformation ratio at the time of step-up. By reducing the turn-on timing by the DT time to prevent a short circuit, the transformation ratio is reduced.
(E) of FIG. 5 shows the Vce voltage at the time of step-down, and the coil 24 is energized during the period in which (b) of FIG. 5 is on. The energization period of the coil 24 is shortened by delaying the turn-on timing by the DT time to prevent a short circuit. By providing the dead time DT, the transformation ratio increases. (G) of FIG. 5 shows the transformation ratio at the time of step-down. By delaying the turn-on timing by the DT time to prevent a short circuit, the transformation ratio is increased.

  As described above, the effect of changing the transformation ratio by delaying the turn-on timing by the dead time DT to prevent a short circuit works oppositely at the time of step-up and step-down. For this reason, there is a minimum transformation ratio at the time of step-down, and the converter 20 cannot operate normally when the step-down operation is performed at a lower transformation ratio, whereas there is no minimum transformation ratio at the time of step-up, and a small transformation ratio (a value close to 1 is small). Value), the converter 20 can operate normally if it is boosted.

The horizontal axis of FIG. 6 shows the transformation ratio (corresponding to the boosted voltage), and the vertical axis shows the energy loss (loss). As described above, the loss increases as the transformation ratio increases. The illustrated P1 indicates a loss that occurs in the case of the minimum transformation ratio (MIN). The loss caused by the prior art is shown.
An arrow A in FIG. 6 shows a phenomenon obtained by utilizing the fact that the converter 20 can operate normally even when the voltage is lower than the minimum transformation ratio in the step-up operation, and releasing the restriction on the minimum transformation ratio in the step-up operation. Yes. At the time of boosting, the loss caused is reduced because the transformation ratio can be lowered below the minimum transformation ratio.
FIG. 7 shows the relationship between the duty ratio of the control duty signal and the transformation ratio. The horizontal axis indicates the duty ratio of the control duty signal, and the vertical axis indicates the actually obtained transformation ratio (corresponding to the boosted voltage). A graph C1 shows the relationship during step-down, and a graph C2 shows the relationship during step-up. Since the restriction on the minimum transformation ratio is removed at the time of boosting (powering), the range indicated by the bold curve D is available. Accordingly, it is possible to prevent wasteful power consumption by boosting pressure.

Specific examples of the present invention have been described in detail above, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above.
The technical elements described in this specification or the drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology illustrated in the present specification or the drawings achieves a plurality of objects at the same time, and has technical utility by achieving one of the objects.

10: battery 20: converter 22: positive line 24: coil 26: capacitor 28: ground line 30: high voltage positive line 32: upper stage transistor 34: diode 36: lower stage transistor 38: diode 40: capacitor 50: inverter 60: motor generator 70 : Control device 72: CPU
74: Memory 76: Control duty signal generation circuit 78: Upper gate voltage output circuit 80: Lower gate voltage output circuit

Claims (1)

Battery, converter, inverter, motor generator and control device,
A converter is inserted between the battery and the inverter, and a motor generator is connected to the inverter.
Power running operation that boosts the battery voltage with a converter, converts it into alternating current with an inverter and supplies it to the motor generator, and regenerative operation that converts the alternating current generated by the motor generator into direct current with the inverter and steps down the voltage with the converter to charge the battery Is possible,
The control device is connected to at least the converter, and includes a transformation ratio determination device and a transformation ratio substitution device,
The transformation ratio determination device determines the transformation ratio of the converter based on the driving state of the vehicle,
The transformation ratio replacement device replaces the transformation ratio determined by the transformation ratio determination device with the lowest transformation ratio if the transformation ratio determined by the transformation ratio determination device is less than the minimum transformation ratio and is in regenerative operation, and during power running operation A motor vehicle driven by a motor generator, characterized in that the transformer ratio determined by the transformer ratio determining device is not replaced.

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