JP5642306B2 - Electric vehicle drive system, inverter control device, and control method - Google Patents

Description

  The present invention relates to torque control of a power converter such as an inverter that drives a main motor of an electric vehicle.

  FIG. 5A is a block diagram showing a configuration of a conventional electric vehicle control apparatus, and particularly shows a configuration for performing control to turn off an inverter gate command.

  In a variable voltage variable frequency inverter for electric vehicle control (hereinafter referred to as a VVVF inverter), when a VVVF inverter output off command, that is, a notch command 0 is input from the cab during acceleration, the VVVF inverter Generally, a method of gradually decreasing the torque current is employed. This notch command 0 is a command for causing the vehicle to coast by inertia.

  As a method of gradually reducing the torque current of the VVVF inverter, there is a method of narrowing the output current of the VVVF inverter within a certain time regardless of the vehicle speed, that is, the motor rotation speed (hereinafter simply referred to as speed). In the case of this method, when the vehicle speed is relatively low, the acceleration is slowly decreased, and when the vehicle speed is high, the acceleration is decreased relatively abruptly.

  As a second method, there is a method in which the ratio of decreasing the output torque of the VVVF inverter is made constant (the degree of longitudinal vibration acceleration is constant) in order to improve riding comfort. FIG. 5A is a block diagram showing a configuration of a control device for realizing the second method.

  In FIG. 5A, the current calculation unit 11 calculates an inverter output current command value based on the notch command value from the cab and the current speed. The jerk control unit 12 is a current control unit that controls the rise and fall timing and inclination of the current command value. In particular, when the notch command 0 is input, the jerk control unit 12 decreases the current command value at a constant decrease rate (gradient di / dt). The vector control unit 13 performs vector control based on the current command value from the jerk control unit 12 and other information, and generates an inverter gate command. This gate command is provided via the output switch 15 to the VVVF inverter that drives the main motor (induction motor in this example). The off-timer 14 turns off the output switch 15 after a predetermined time from the input of the notch command 0, thereby setting all U, V, and W-phase gate commands of the inverter to 0.

  FIGS. 5B and 5C are time charts showing the operation of the control device shown in FIG.

  First, when a notch command other than 0 is input, an exciting current flows first, a magnetic flux is generated in the motor rotor, and a magnetic flux position is detected. This magnetic flux position is used by the vector control unit 15, and when a gate command corresponding to the command value including the torque current is generated, a torque current flows through the motor and the vehicle starts to accelerate from the stop. Thereafter, when the notch command 0 is input during acceleration, the time measurement of the off-timer 14 is started and the current decreases with a constant slope.

  FIG. 5B shows a case where the time during which the inverter current decreases from the maximum value to the excitation current from when the notch command 0 is input coincides with the constant measurement time Tco of the off timer. FIG. 5C shows a general case where the time during which the inverter current decreases to the exciting current from when the notch command 0 is input is shorter than the constant measurement time Tco of the off timer.

  In the case of FIG. 5C, the operation of the VVVF inverter is continued by the excitation current for a time T1 from when the inverter current decreases to the excitation current until it is turned off. At this time, because of the current feedback control, torque ripples of the inverter frequency component exist minutely due to variations in sensitivity of the current detectors of the inverter output phases. For example, when the sensitivity of the inverter U-phase current detector is lower than that of the other phases, a larger current flows in the U phase than in the other phases, and torque ripple occurs in the motor.

  FIG. 6 shows the structure of the motor drive system.

  The motor (main motor) 20 for driving the vehicle transmits the rotational force to the wheels 22 via the gear box 21 for driving the wheels 22 from the motor drive shaft via the joint. In this structure, when the inverter frequency torque ripple occurs near the output zero due to the excitation current as the VVVF inverter output, the chattering of play between the drive gear 23 and the driven gear 24 occurs, causing noise. It becomes.

  Therefore, an object of the present invention is to suppress noise caused by torque ripple generated at an inverter frequency.

  An electric vehicle drive system according to an embodiment includes an inverter that drives an electric motor and an inverter control device that controls the inverter. The inverter control device outputs a first torque current command value and a first excitation current command value for controlling the inverter based on the received notch command. A second torque current command value that is changed from a torque current command value of 1 at a predetermined reduction rate is output, and when the second torque current command value becomes zero, the gate command for the inverter is turned off.

(A) is a block diagram which shows the structure of the electric vehicle control apparatus which concerns on 1st Embodiment, (b), (c) is a time chart which shows operation | movement of the control apparatus shown to (a). (A) is a block diagram which shows the structure of the electric vehicle control apparatus which concerns on 2nd Embodiment, (b), (c) is a time chart which shows operation | movement of the control apparatus shown to (a). (A) is a block diagram which shows the structure of the electric vehicle control apparatus which concerns on 3rd Embodiment, (b), (c) is a time chart which shows operation | movement of the control apparatus shown to (a). (A) is a block diagram which shows the structure of the electric vehicle control apparatus which concerns on 4th Embodiment, (b), (c) is a time chart which shows operation | movement of the control apparatus shown to (a). (A) shows the structure of the conventional electric vehicle control apparatus which performs control which turns off an inverter gate instruction | command, (b), (c) is a time chart which shows operation | movement of the control apparatus shown to (a). It is. It is a figure which shows the structure of a motor drive system.

  Hereinafter, an electric vehicle control device according to an embodiment will be described with reference to the drawings.

[First Embodiment]
FIG. 1A is a block diagram showing the configuration of the electric vehicle control device according to the first embodiment. The electric vehicle control device receives a notch command from the cab, generates a gate signal to generate torque corresponding to the notch command, and outputs the signal to an inverter that drives the main motor.

  The current calculation unit 11 calculates an inverter output current command value based on the notch command value from the cab and the current speed (vehicle speed or motor rotation speed). Further, as an example, the current calculation unit 11 inputs five levels (notch commands 1 to 5) of notch command values, and as shown in the block of the current calculation unit 11, speed / current characteristics using the notch command values as parameters. The inverter output current command value is calculated according to This speed / current characteristic is a general characteristic when driving by a driver's manual operation. The notch command 0 is a command for turning off all the switching elements constituting the inverter.

  The gate off time calculation unit 16 calculates the gate off time Time by dividing the output current command value of the current calculation unit 11 by a predetermined slope di / dt. Therefore, the larger the current command value, the larger the gate off time Time. Here, the slope di / dt indicates a current (acceleration) reduction rate when the inverter output current is reduced after the notch command 0 is input, and is a constant value determined from riding comfort and the like.

  The off timer 14 starts time measurement when the notch command value falls to 0, and outputs a signal (for example, logic 1) indicating the end of time measurement to the Q terminal when the gate off time Time input to the T terminal elapses. It is a time measurement unit. In response to this signal, the output switch 15 is turned off, and all U, V, and W phase gate commands of the inverter are set to zero.

  The operations of the jerk controller 12 and the vector controller 13 are as described above with reference to FIG.

  FIGS. 1B and 1C are time charts showing the operation of the control device shown in FIG.

  First, when a notch command other than 0 is input, as described above, the exciting current Im first flows to the stator of the motor, a magnetic flux is generated in the rotor, and the magnetic flux position is detected. Based on the magnetic flux position, current command value, speed, and the like, the vector control unit 13 generates a gate command, a torque current flows through the motor, and the vehicle starts.

  Thereafter, when the notch command 0 is input, the off-timer 14 latches the gate-off time provided from the gate-off time calculation unit and counts down the value, for example, and starts time measurement. At this time, the jerk control unit 12 decreases the output current command value with a predetermined slope di / dt from the value immediately before the input of the notch command 0. The vector control unit 13 generates a gate command corresponding to the decreasing current command value and provides it to the VVVF inverter via the output switch 15. As a result, the acceleration of the vehicle is gradually reduced.

  FIG. 1 (b) shows a case where the inverter current decreases from the maximum value to the excitation current from when the notch command 0 is input, and FIG. 1 (c) shows the excitation current from the half current of the maximum value. The case where it decreases to is shown. In any case, when the inverter current decreases to the exciting current, the time measurement of the off timer 14 is completed, the output switch 15 is turned off, and all gate commands are set to off.

  Therefore, as shown in FIG. 5C, after the notch command 0 is input and the current value is reduced, the motor does not operate with the excitation current, so that the inverter frequency component torque ripple does not occur. Motor chatter gear chattering is greatly reduced.

  In this embodiment, the gate-off time Time is calculated based on the current command value, but may be calculated based on the actual current value flowing through the inverter or the average value thereof instead of the current command value.

[Second Embodiment]
FIG. 2A is a block diagram illustrating a configuration of the electric vehicle control device according to the second embodiment.

  The configuration of the second embodiment is different from that of the first embodiment of FIG. 1A in the configurations of the current calculation unit 11 and the gate-off time calculation unit 16. Also in this example, the current calculation unit 11 inputs, as an example, a five-step notch command value, and calculates an inverter output current command value according to the speed / current characteristics shown in FIG. This speed / current characteristic is suitable for automatic constant speed operation, and the output current command value differs for each notch command value in the entire speed range. That is, the output current command value (torque current component) is substantially proportional to the notch command value. When the driver selects automatic constant speed driving while traveling, the speed / current characteristics as shown in FIG. 2A are applied, and the speed is kept constant. This speed / current characteristic is preferably used together with the speed / current characteristic shown in FIG.

  For example, the gate-off time calculation unit 16 always stores a notch command value for a predetermined time, and when the notch command 0 is input, reads the previous notch command value. The gate-off time calculation unit 16 calculates the gate-off time Time by dividing the read notch command value by a predetermined slope di / dt and further multiplying by the coefficient K. Thus, the gate-off time can be suitably calculated using the notch command value itself according to the speed / current characteristic with respect to the notch command value as shown in FIG.

  2 (b) and 2 (c) are time charts showing the operation of the control device shown in FIG. 2 (a), and are the same as those in the first embodiment of FIGS. 1 (b) and 1 (c). Therefore, the detailed explanation is omitted.

[Third Embodiment]
FIG. 3A is a block diagram showing the configuration of the electric vehicle control device according to the third embodiment.

  In the configuration of the third embodiment, a current command correction unit 17a is added between the jerk control unit 12 and the vector control unit 13 as compared with the conventional configuration of FIG.

  When the notch command 0 is input and the current command value decreases with a constant slope di / dt and decreases to a value larger by L than the excitation current value, the current command correction unit 17a holds the value. The output switch 15 is turned off after a predetermined time Tco after the notch command 0 is input based on the time measurement result of the off timer 14.

  3B and 3C are time charts showing the operation of the control device shown in FIG.

  FIG. 3B shows a case where the time during which the inverter current decreases from the maximum value to the excitation current from when the notch command 0 is input matches the constant measurement time Tco of the off timer. Same as b). FIG. 3C shows a general case where the time during which the inverter current decreases from the time when the notch command 0 is input to the exciting current is shorter than the constant measurement time Tco of the off timer.

  In the case of FIG. 3C, when the current of the inverter decreases to the value of the excitation current + L, the value is maintained by the operation of the current command correction unit 17a. By this current command correction control, the motor generates a slight positive torque. This state will be described with reference to the motor drive system configuration diagram of FIG. When the driven gear 24 rotates in the rotation direction A and the vehicle moves forward, the torque in the rotation direction B is slightly generated in the drive gear 23 by the action of the current command correction unit 17a. As a result, the gap C between the gears 23 and 24 disappears and the contact state is always maintained, so that chattering of the gear is greatly suppressed.

[Fourth Embodiment]
FIG. 4A is a block diagram showing the configuration of the electric vehicle control device according to the fourth embodiment.

  In the configuration of the fourth embodiment, a current command correction unit 17b is added between the jerk control unit 12 and the vector control unit 13 as compared to the conventional configuration of FIG.

  When the notch command 0 is input to the current command correction unit 17b and the current command value decreases at a constant slope di / dt and decreases to the excitation current value, a negative correction value is superimposed and held. The output switch 15 is turned off after a predetermined time from the input of the notch command 0 based on the time measurement result of the off timer 14.

  4 (b) and 4 (c) are time charts showing the operation of the control device shown in FIG. 4 (a).

  FIG. 4B shows a case where the time during which the inverter current decreases from the maximum value to the excitation current from when the notch command 0 is input coincides with the constant measurement time Tco of the off timer. Same as b). FIG. 4C shows a general case in which the time during which the inverter current decreases from the time when the notch command 0 is input to the exciting current is shorter than the constant measurement time Tco of the off timer.

  In the case of FIG. 4C, when the inverter current decreases to the exciting current value, a negative correction value (-L) is superimposed on the current by the operation of the current command correction unit 17b. By this current command correction control, a slight negative torque is generated in the motor. This state will be described with reference to the motor drive system configuration diagram of FIG. When the driven gear 24 rotates in the rotation direction A, when the vehicle moves forward, the torque in the direction opposite to the rotation direction B is slightly generated in the drive gear 23 by the action of the current command correction unit 17b. As a result, the gap D between the gears 23 and 24 disappears and the contact state is always maintained, so that chattering of the gear is greatly suppressed.

  As described above, according to the above-described embodiment, it is possible to avoid the occurrence of torque ripple at the inverter frequency near the output zero of the VVVF inverter and to prevent the generation of noise due to chattering of the gear play.

  The above description is an embodiment of the present invention, and does not limit the apparatus and method of the present invention, and various modifications can be easily implemented. For example, various inventions can be configured by appropriately combining a plurality of constituent elements disclosed in the embodiment.

  DESCRIPTION OF SYMBOLS 11 ... Current calculation part, 12 ... Jerk control part, 13 ... Vector control part, 14 ... Off timer, 15 ... Output switch, 16 ... Gate off time calculation part, 17 ... Current command correction part

Claims (9)

An inverter that drives an electric motor;
An inverter control device for controlling the inverter,
The inverter control device
Outputting a first torque current command value and a first excitation current command value for controlling the inverter based on the received notch command;
When there is an input of notch command off, a second torque current command value that changes at a predetermined decrease rate from the first torque current command value is output,
When the second torque current command value becomes zero, the gate command for the inverter is turned off.   2. The electric vehicle drive system according to claim 1, wherein the inverter control device maintains the first excitation current command value after the notch command OFF is input. 3.   3. The electric vehicle drive system according to claim 1, wherein the reduction rate is the same rate regardless of the first torque current command value. 4. In an inverter control device that controls an inverter that drives an electric motor,
Means for outputting a first torque current command value and a first excitation current command value for controlling the inverter based on the received notch command;
Means for outputting a second torque current command value changed at a predetermined decrease rate from the first torque current command value when notch command off is input;
An inverter control apparatus comprising: means for turning off a gate command for the inverter when the second torque current command value becomes zero. Means for maintaining the first excitation current command value after the notch command off is input;
The inverter control device according to claim 4, further comprising:   6. The inverter control device according to claim 4, wherein the decrease rate is the same rate regardless of the first torque current command value. A control method for an inverter that drives an electric motor,
Outputting a first torque current command value and a first excitation current command value for controlling the inverter based on the received notch command;
When there is an input of notch command off, a second torque current command value that changes at a predetermined decrease rate from the first torque current command value is output,
When the second torque current command value becomes zero, the gate command for the inverter is turned off.   The control method according to claim 7, wherein the first excitation current command value is maintained after the notch command off is input.   The control method according to claim 7 or 8, wherein the decrease rate is the same rate regardless of the first torque current command value.

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