JP2006074932A - Electric motor controlling device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric motor controlling device that outputs a constant DC link voltage, even if a required output to an electric motor is small. <P>SOLUTION: The electric motor controlling device is provided between a battery 1 and an inverter 3 that drives the electric motor 4. The device raises a voltage when electric power is supplied from a battery f1 to the inverter 3, while it decreases the voltage when the electric power is regenerated from the inverter 3 to the battery 1. When the absolute value of the required output to the electric motor 4 is smaller than a predetermined value in the voltage raising or decreasing operation, the voltage raising operation or the voltage decreasing operation is controlled by switching both of a switching element Q1 and a switching element Q2 inside. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an electric motor control device that drives an electric motor.

  In driving an electric motor of a hybrid vehicle, it is known to provide a buck-boost converter between an inverter and a DC power source (see Patent Document 1). The buck-boost converter controls the DC link voltage of the inverter (inverter input voltage) and controls the voltage applied to the electric motor. In a buck-boost converter, the current flowing in the inductance connected to the midpoint of connection between the lower arm transistor and the upper arm transistor is controlled by switching the lower arm transistor during step-up and the upper arm transistor during step-down. Thus, step-up and step-down operations are realized.

JP 2003-134606 A

  On the other hand, when an IGBT or the like is used for the switching element, the switching time takes about several microseconds. During this switching time, a large loss occurs because the current and voltage intersect. As a result, when the pulse time is shortened, only the switching loss is caused and the efficiency is remarkably lowered. Therefore, when a switching element such as an IGBT is used, the pulse time cannot be made very short. As a result, there is a problem that the energy to be boosted (the current flowing through the inductance) cannot be reduced below a certain value. In order to solve this, for example, it is conceivable to connect a load resistor in parallel with the smoothing capacitor provided in the inverter to consume current. However, in this case, there is a problem that the cost increases due to the addition of the load resistance, and the power consumption due to the load resistance always occurs, and the efficiency of the entire circuit deteriorates.

  The motor control device is provided between the DC power supply and the drive circuit that drives the motor, and performs a step-up operation when supplying power from the DC power supply to the drive circuit, and a step-down operation when supplying power from the drive circuit to the DC power supply. To do. The electric motor control device includes a first switching element having a first terminal and a second terminal, the first terminal being connected to the plus side of the drive circuit, a third terminal, and a fourth terminal. A second switching element having a third terminal connected to the second terminal of the first switching element and a fourth terminal connected to the negative side of the drive circuit and the negative side of the DC power supply; , Having a fifth terminal and a sixth terminal, the fifth terminal being connected to a connection midpoint between the second terminal of the first switching element and the third terminal of the second switching element, The sixth terminal controls the switching of the first switching element and the second switching element based on the inductance connected to the positive side of the DC power supply and the command value corresponding to the magnitude of the average DC current flowing through the inductance. Step-up or step-down operation Control means for controlling, and when the absolute value of the command value is smaller than the first predetermined value, the control means switches the first switching element and the second switching element alternately to increase or decrease the voltage. It is characterized by controlling.

  Since the present invention is configured as described above, the following effects can be obtained. When the absolute value of the command value is smaller than the predetermined value, the first switching element and the second switching element are alternately switched to control the step-up operation or the step-down operation. Can be controlled precisely. That is, even if the required output is small, the DC link voltage can be accurately adjusted.

-First embodiment-
FIG. 1 is a diagram showing an overall configuration diagram of an electric motor control device according to a first embodiment of the present invention. The electric motor control device of the present embodiment is used for controlling an electric motor that drives a hybrid vehicle. In FIG. 1, a voltage is applied to a DC portion of an inverter 3 from a battery 1 capable of regenerative input (charging) via a buck-boost converter 2, and an electric motor (motor) 4 is driven by AC converted by the inverter 3. The DC part of the inverter 3 refers to the side where DC power is input in the inverter 3.

  As shown in FIG. 1, the buck-boost converter 2 connects two switching elements Q1 and Q2 in series so that currents flow in the same direction when turned on. Diodes D1 and D2 are connected in parallel to each switching element Q1 and Q2, and the forward direction of each diode is connected in the opposite direction to the direction in which current flows when the switching element is on. An inductance (reactor) L is connected between the middle point (connection midpoint) of the two switching elements Q1 and Q2 and the battery 1. Switching elements Q1, Q2 are made of, for example, IGBT. The output of the step-up / down converter 2 is input to the DC section of the inverter 3. The switching element Q1 is called an upper arm, and the switching element Q2 is called a lower arm. In FIG. 1, since IGBTs are used for the switching elements Q1 and Q2, the diodes D1 and D2 are provided. However, the present invention is not limited to this. For example, when FETs are used for the switching Q1 and Q2, diodes (parasitic diodes and built-in diodes) are incorporated in the elements, so there is no need to provide the diodes D1 and D2 outside the FETs.

  The buck-boost converter 2 will be described with different expressions as follows. The switching element Q1 has a terminal T1 and a terminal T2, and the terminal T1 is connected to the plus side of the inverter 3. The switching element Q2 has a terminal T3 and a terminal T4, the terminal T3 is connected to the terminal T2 of the switching element Q1, and the terminal T4 is connected to the negative side of the inverter 3 and the negative side of the battery 1. A diode D1 is connected to the terminals T1 and T2 of the switching element Q1, and a diode D2 is connected to the terminals T3 and T4 of the switching element Q2. The inductance L has a terminal T5 and a terminal T6, the terminal T5 is connected to a point connecting the terminal T2 of the switching element Q1 and the terminal T3 of the switching element Q2, and the terminal T6 is connected to the positive side of the battery 1. The

  A smoothing electrolytic capacitor C is provided in the DC portion of the inverter 3. Three-phase outputs are connected to the motor 4 from the midpoints of the three upper and lower arms of the inverter 3. The inverter 3 drives the motor 4 by a known vector control (power running operation), and regenerates electric power to the direct current portion by a regenerative operation when the motor 4 is braked.

  The vehicle controller 11 controls the entire vehicle, determines a required output for the electric motor 4, a torque command value, and the like, and outputs them to the electric motor controller 12 and the step-up / down controller 14. The electric motor controller 12 controls switching of the switching element of the inverter 3 based on a request output from the vehicle controller 12 to the electric motor 4, a torque command value, a rotational position of the electric motor 4, each phase current, a DC link voltage VD, and the like. The rotational position of the motor 4 is detected by a rotational position sensor 5, each phase current is detected by a current sensor 6, and the DC link voltage VD is detected by a DC link voltage sensor 7.

  The battery controller 13 inputs the battery voltage VB and the battery current IB detected by the sensor 8, performs charge / discharge control of the battery 1, and outputs battery power that can be output to other controllers.

  The step-up / down controller 14 receives a request output from the vehicle controller 11 to the electric motor 4, a torque command value, a DC link voltage VD, and a reactor current IL, and controls switching of the switching elements Q 1 and Q 2 of the step-up / down converter 2. . The reactor current IL flowing through the inductance L is detected by the current sensor 9. Each controller is connected by communication such as CAN, and exchanges command values and the like.

  The vehicle controller 11, the electric motor controller 12, the battery controller 13, and the step-up / down controller 14 are each composed of a microprocessor and a peripheral circuit, and execute respective functions of each controller by executing a predetermined program.

  Next, the operation of the buck-boost converter 2 will be described. The step-up / down converter 2 is constituted by a combination of a so-called step-up chopper and step-down chopper. The inductance L, the switching element Q2, the diode D1, and the capacitor C constitute a so-called step-up chopper, and the switching element Q1, the inductance L, and the diode D2 constitute a so-called step-down chopper.

  The buck-boost converter 2 boosts the DC voltage VB of the battery 1 to a desired DC link voltage VD and supplies power to the DC section of the inverter 3 when the power running output is performed, that is, when the motor 4 is driven. When the regenerative output is performed, that is, when the motor 4 functions as a generator, the DC link voltage VD from the DC part of the inverter 3 is stepped down to the DC voltage VB of the battery 1, and DC power is supplied from the DC part of the inverter 3 to the battery 1. To supply. That is, a desired regenerative (charging) current is supplied to the battery 1.

  The step-up / step-down converter 2 normally turns off the switching element Q1 and switches only the switching element Q2 to obtain a desired DC link voltage VD when powering output. At the time of regenerative output, the switching element Q2 is turned off and only the switching element Q1 is switched to obtain a desired regenerative current. However, the present invention is characterized in that both the switching elements Q1 and Q2 are switched when the power running request output or the regeneration request output is small.

  FIG. 2 is a diagram for explaining the control of the step-up / down controller 14. In the buck-boost converter 2, the side connected to the inverter 3 is an output side, and the side connected to the battery 1 is an input side.

  In FIG. 2, the difference unit 101 takes the difference between the required value VD * with respect to the voltage on the output side of the inverter 3, that is, the measured value of the DC link voltage VD. The control value is output under control. The required value VD * of the DC link voltage is determined by the required output from the vehicle controller 11 to the electric motor 4, the torque command value, and the like. The control value output from the PI control unit 102 and the triangular wave that is the carrier output from the carrier generation unit 103 are compared by the comparator 104 to generate a PWM signal.

  When the PWM signal is used for controlling the switching element Q1, the phase is used as it is. When the PWM signal is used for controlling the switching element Q2, the NOT circuit 106 uses the phase inverted. The PWM signal and the signal whose phase is inverted drive the switching elements Q1 and Q2 via the dead time control unit 105 and the drive circuit. As described later, the dead time control unit 105 performs dead time control when both the switching elements Q1 and Q2 are driven alternately.

  FIG. 3 is a diagram showing the switching characteristics of the buck-boost converter 2 of the present embodiment. On the horizontal axis, the required output of the motor 4 is taken. In FIG. 3, the power running output has a positive sign and the regenerative output has a negative sign. When the power running output is larger than the predetermined value P1, the switching element Q1 is turned off and the switching element Q2 is switched. When the regenerative output is smaller than the predetermined value P2, the switching element Q2 is turned off and the switching element Q1 is switched. Let When the power running output is P1 or less, both switching elements Q1 and Q2 are switched, and when the regenerative output is P2 or more, both switching elements Q1 and Q2 are switched.

  In other words, if the absolute values of the requested powering output and regenerative output are less than the predetermined values, both switching elements Q1 and Q2 are switched. When the absolute values of the power running output and the regenerative output are larger than predetermined values, positive / negative is discriminated, and only the switching element Q2 is switched in the case of power running and only the switching element Q1 is switched in the case of regeneration. When both switching elements Q1 and Q2 are switched, a dead time is provided between the switching elements Q1 and Q2 to be turned on so that the switching elements Q1 and Q2 are not simultaneously turned on. That is, dead time control is performed.

  FIG. 4 is a diagram for explaining a boosting (powering) operation when the powering request output is equal to or greater than a predetermined value. In this case, the boosting operation is performed by turning off the switching element Q1 and switching the switching element Q2. The switching element Q2 is turned on at t1, and then the current IL flowing through the inductance L increases (t1 to t2). When the switching element Q2 is turned off after a predetermined time (t2), the current accumulated in the inductance L tends to flow, and therefore flows to the DC part of the inverter 3 through the diode D1 connected in parallel to the switching element Q1, The electrolytic capacitor 7 is charged. As a result, the DC link voltage VD obtained by boosting the voltage VB of the battery 1 is supplied to the inverter 3.

  FIG. 5 is a diagram illustrating a step-down (regeneration) operation in which the absolute value of the regeneration request output is a predetermined value or more. The step-down operation in this case is performed by turning off switching element Q2 and switching switching element Q1. Contrary to the step-up operation, when switching element Q1 is turned on for a predetermined time, current flows and reactor current IL increases due to the difference between DC link voltage VD and battery voltage VB. When the switching element Q1 is turned off, the current accumulated in the inductance L continues to flow, and therefore flows to the battery 1 through the diode D2 connected in parallel to the switching element Q2, and the battery 1 is charged.

  FIG. 6 is a diagram for explaining a power running or regenerative operation when the absolute value of the power running request output or the regenerative request output is equal to or less than a predetermined value. In this case, both switching elements Q1 and Q2 are switched. First, the switching element Q2 is turned on at t0. However, since reactor current IL is in the negative direction, that is, current flows through diode D2, current IQ2 does not yet flow through switching element Q2.

  Since the switching element Q2 is turned on at t1, the reactor current IL flows in the positive direction like the operation at the time of boosting. At t2, Q2 is turned off, and this time Q1 is turned on. Since the current accumulated in the inductance L continues to flow, no current flows through the switching element Q1, and a current flows through the diode D1. When the energy of the inductance L is released and the reactor current IL decreases to zero, this time the current is reversed and the current IQ1 begins to flow through the switching element Q1 (t3).

  At t4, the switching element Q1 is turned off and the switching element Q2 is turned on. Similarly, a current flows through the diode D2, but no current flows through the switching element Q2. The current returns to 0 at t5 (= t1). Here, one cycle T occurs from t1 to t5.

  In this way, the direct current between the inverter 3 and the battery 1 can be precisely controlled near positive / negative 0. That is, even if the output of the inverter 3 is small, the DC link voltage VD of the inverter 3 can be precisely controlled. At this time, ripples are generated in the direct current, but the average direct current obtained by averaging the ripples is precisely controlled in the vicinity of zero.

  The switching element Q1 and the switching element Q2 are controlled so as to be turned on according to the duty of one cycle of the PWM signal. That is, the switching element Q1 is turned on when the PWM signal is high within one cycle of the PWM signal, and the switching element Q2 is turned on when the PWM signal is low. The step-up operation or step-down operation is performed depending on the duty of the PWM signal.

  Switching both the switching element Q1 and the switching element Q2 as described above provides a new switching mode between the conventional power running operation and the regenerative operation. That is, in the switching mode in which the switching element Q1 is turned off and the switching element Q2 is switched, and in the switching mode in which the switching element Q2 is turned off and the switching element Q1 is switched, the switching elements Q1 and Q2 are alternately turned on. Three modes are provided. Thereby, the transition of the control from the power running operation to the regenerative operation or vice versa can be performed smoothly.

  Since switching is not performed by alternately turning on the switching elements Q1 and Q2 in the entire region of power running and regeneration, that is, the switching Q1 and Q2 are alternately switched only when the power running and regeneration power is small. The switching loss does not increase much compared to the case where only one is switched.

  In addition, what is necessary is just to set the predetermined value P1 and the predetermined value P2 with respect to a request | requirement output as follows, for example. In the case of the step-up operation in which the switching element Q1 is turned off and the switching element Q2 is switched, or in the case of the step-down operation in which the switching element Q2 is turned off and the switching element Q1 is switched, as shown in FIG. A ripple occurs in the flowing direct current IL. This ripple current ΔI is | VD−VB | × Ton / L. The width with respect to the average current Iave is | VD−VB | × Ton / 2L. Control is performed to switch both of the switching elements Q1 and Q2 when the lower limit value of the current IL, ie, Iave− (ΔI / 2) is 0 or less and the upper limit value, ie, Iave + (ΔI / 2) is 0 or more. What is necessary is just to set the predetermined value P1 and the predetermined value P2 so that it may carry out. For example, the predetermined value P1 is an output value at which Iave− (ΔI / 2) = 0, and the predetermined value P2 is an output value at which Iave + (ΔI / 2) = 0. That is, the predetermined value P1 and the predetermined value P2 are set such that the current flowing through the inductance L crosses zero (zero crossing). Note that the predetermined value P1 and the predetermined value P2 can be obtained in advance by experiments, calculations, or the like.

  FIG. 7 is a diagram showing a flowchart of control by the step-up / down controller 14. In step S <b> 1, a request output P * for the electric motor 4 is input from the vehicle controller 11. In step S2, the required value VD * of the DC link voltage is calculated and set based on the required output P *. In step S3, it is determined whether the requested output P * satisfies P2 <P2 * <P1. P1 is a predetermined output value for the power running output, and P2 is a predetermined output value for the regenerative output. P1 has a plus sign and P2 has a minus sign.

  If it is determined in step S3 that the above condition is satisfied, the process proceeds to step S5. In step S5, an operation of switching both of the switching elements Q1 and Q2 described above is performed. That is, when the absolute value of the power running request output is smaller than the predetermined value P1, or when the absolute value of the regeneration required output is smaller than the predetermined value P2, an operation of switching both the switching elements Q1 and Q2 is performed.

  On the other hand, if it is determined in step S3 that the condition is not satisfied, the process proceeds to step S4. In step S4, whether the requested output is positive or negative is determined. That is, when the required output is positive, it is determined as power running output, and when it is negative, it is determined as regenerative output. If it is determined in step S4 that the power is output, the process proceeds to step S7. In step S7, the switching element Q1 is turned off and the switching element Q2 is switched to control the power running operation. If it is determined in step S4 that the output is regenerative, the process proceeds to step S6. In step S6, the switching element Q2 is turned off and the switching element Q1 is switched to control the regenerative operation.

  As described above, the required output for the electric motor 4 is determined, and the switching of the switching elements Q1, Q2 is controlled based on the configuration of FIG.

The vehicle electric motor control device of the present invention configured as described above has the following effects.
(1) When the absolute value of the power running request output or the regeneration request output is smaller than a predetermined value, both switching elements Q1 and Q2 are alternately turned on. Can be precisely controlled near positive / negative zero. In other words, the DC link voltage VD can be accurately adjusted to the command value even with a small required output.
(2) Since there is no need to provide a load resistance in parallel with the capacitor C, the DC link voltage VD can be accurately adjusted to the command value even when the required output is small without increasing the cost and reducing the circuit efficiency.
(3) The switching elements Q1 and Q2 are alternately turned on between the switching mode in which the switching element Q1 is turned off and the switching element Q2 is switched, and the switching mode in which the switching element Q2 is turned off and the switching element Q1 is switched. Since the third switching mode is provided, the control transition from the power running operation to the regenerative operation or vice versa can be performed smoothly.

-Second Embodiment-
In the first embodiment, when the required output of the motor 4 is small, by switching both the switching elements Q1 and Q2, even if the required output is small, the loss is not increased due to the load resistance, and is stable. Accurate control was performed.

  However, even in the first embodiment, loss due to switching of the switching elements Q1 and Q2 occurs. In the second embodiment, the switching loss of the switching elements Q1 and Q2 is further reduced. For this reason, intermittent oscillation control is performed in the third switching mode in which both the switching elements Q1 and Q2 described in the first embodiment are switched. Hereinafter, this intermittent oscillation control will be described. Since the overall configuration diagram of the motor control device of the second embodiment is the same as that of FIG. 1 of the first embodiment, description thereof is omitted.

  FIG. 8 is a diagram for explaining the operation of the intermittent oscillation according to the second embodiment. As shown in FIG. 8, the intermittent oscillation is to perform switching intermittently by creating a period during which switching is performed and a pause period during which switching is not performed. The period of this intermittent oscillation is Ti which is the sum of the switching time Tion and the switching stop time Tioff. The intermittent oscillation frequency is 1 / Ti, and the intermittent oscillation duty is Tion / Ti. These are distinguished from the switching period and frequency of the switching elements Q1 and Q2. Due to this intermittent oscillation, a time for stopping (stopping) switching is provided, so that switching loss can be reduced.

  FIG. 9 is a diagram for explaining control of intermittent oscillation in the step-up / down controller 14. The same components as those in FIG. 2 of the first embodiment are denoted by the same reference numerals.

  A determination unit 201 that determines whether intermittent oscillation is possible based on the request output P * is provided. Details of the control of the determination unit 201 will be described later. When the determination unit 201 determines that intermittent oscillation occurs, the output signal 202 becomes Hi, and the output of the oscillator 203 that oscillates at the intermittent oscillation frequency is started. The OR of the inverted signal 204 of the output signal 202 of the determination unit 201 and the oscillator output 205 is obtained by the OR circuit 206 and input to the AND circuits 207 and 208. The output of the AND circuit 207 is input to the gate of the switching element Q2, and the output of the AND circuit 208 is input to the gate of the switching element Q1.

  Thereby, when it is determined that intermittent oscillation is to be performed, the logic configuration is such that the oscillator output 205 of the intermittent oscillation oscillator 203 is input to the AND circuits 207 and 208. When the oscillator output 205 of the intermittent oscillator 203 is Hi, a PWM signal generated from the voltage VD and the required value VD * is applied to the gates of the switching elements Q1 and Q2, and a normal switching operation can be performed. However, when the oscillator output 205 of the intermittent oscillator 203 is Lo, the PWM signal is interrupted by the AND circuits 207 and 208, so that the switching elements Q1 and Q2 are not switched.

  When the determination unit 201 determines that intermittent oscillation does not occur, the output signal 202 outputs Lo. The inverted signal 204 of the Lo signal of the output signal 202 is Hi, the output of the OR circuit 206 is always Hi, and the intermittent oscillation output 205 is ignored. As a result, Hi is input to the AND circuits 207 and 208, and the PWM signal is applied to the gates of the switching elements Q1 and Q2 as usual without being intermittent. In this way, it is possible to determine whether or not to perform intermittent oscillation based on the output of the determination unit 201 that determines whether or not intermittent oscillation is possible.

  Further, the oscillator output 205 becomes Hi when the switching time of intermittent oscillation starts. The soft-start triangular wave generator 209 is configured to start the soft-start triangular wave by detecting the edge thereof and to input the output thereof to the input of the comparator 210 for generating the PWM wave. As a result, a soft start operation for slowly increasing the duty at the start of switching is performed. Thereby, generation | occurrence | production of the sound from the reactor iron core of the inductance L by applying a load suddenly at the time of a switching start is prevented.

  The intermittent oscillation frequency is desirably 20 Hz or less as a frequency lower than the audible frequency region.

  Next, a method for determining whether to perform intermittent oscillation will be described. FIG. 10 is a diagram illustrating a flowchart of processing for determining whether or not to perform intermittent oscillation in the step-up / down controller 14. This is an explanation of the portion surrounded by the central dotted line 211 in FIG. Therefore, the description of the characteristics of FIG. 2 described in the first embodiment is also included.

  First, in step S11, it is determined whether or not the requested output P * satisfies P-2 <P2 * <P + 2. If it is determined in step S11 that the condition is not satisfied, the process proceeds to step S12. In step S12, flag 1 is reset to 0, and the timer is also reset. The flag 1 and the timer are used for controlling intermittent oscillation described later. In step S13, whether the requested output is positive or negative is determined. That is, when the required output is positive, it is determined as power running output, and when it is negative, it is determined as regenerative output.

  If it is determined in step S13 that the power is output, the process proceeds to step S14. In step S14, the switching element Q1 is turned off, and the switching element Q2 is switched to control the power running operation. If it is determined in step S13 that the output is regenerative, the process proceeds to step S15. In step S15, the switching element Q2 is turned off and the switching element Q1 is switched to control the regenerative operation.

  When the required output P * is smaller than the lower threshold P-2 for switching both of the switching elements Q1 and Q2, it means that there is a certain amount of regenerative request output. Do. On the other hand, when it is larger than the upper limit threshold P + 2, it means that there is a power running request output of a certain level or more, so that the switching element Q2 is switched to perform the boosting operation.

  If it is determined in step S11 that the condition is satisfied, the process proceeds to step S16. In step S16, it is determined whether or not the required output P * satisfies P-1 <P2 * <P + 1. If it is determined in step S16 that the condition is not satisfied, the process proceeds to step S17. In step S17, flag 1 is reset to 0, and the timer is also reset. In step S18, an operation of switching both switching elements Q1 and Q2 is performed.

  When the requested output P * is P + 2 or less and P-2 or more, it is further determined whether or not the requested output P * is the intermittent oscillation upper limit threshold P + 1 or less and the intermittent oscillation lower limit threshold P-1 or more. When the required output P * is outside the range of the intermittent oscillation threshold, the switching operations of both the switching elements Q1 and Q2 are performed, and the DC link voltage VD is controlled to a predetermined value.

  If it is determined in step S16 that the condition is satisfied, the process proceeds to step S19. In step S19, it is determined whether or not flag 1 = 1. If it is determined in step S19 that the flag 1 is not 1, the process proceeds to step S20. In step S20, 1 is set in flag 1, and the timer is started. The reason for setting the flag 1 and starting the timer is to determine whether or not the requested output is within the range of the intermittent oscillation thresholds P + 1 and P−1 for a certain time or more.

  If it is determined in step S19 that flag 1 = 1, the process proceeds to step S21. In step S21, it is determined whether the timer is equal to or greater than a predetermined value. If it is determined in step S21 that the timer is not yet equal to or greater than the predetermined value, the process proceeds to step S18 to perform an operation for switching both the switching elements Q1 and Q2. On the other hand, if it is determined in step S21 that the timer is equal to or greater than the predetermined value, the process proceeds to step S22. In step S22, intermittent oscillation control for switching both switching elements Q1 and Q2 is performed.

  When the requested output P * is within the range of the intermittent oscillation thresholds P + 1 and P−1 for a certain time or longer, the intermittent oscillation operation is performed, so that the intermittent oscillation operation is performed only when no load continues. This can reduce switching loss. FIG. 11 is a diagram showing the relationship among the required output P *, each threshold value, and the switching operation of the switching elements Q1 and Q2. As shown in FIG. 11, intermittent oscillation is performed near the no-load of the required output for switching both of the switching elements Q1 and Q2.

  In the process of FIG. 10, the example in which both the switching elements Q1 and Q2 are switched by intermittent oscillation has been described. However, depending on whether the requested output is positive or negative, one of the switching elements Q1 and Q2 may be switched to perform an intermittent oscillation operation. FIG. 12 is a diagram showing a modification thereof. Only differences from FIG. 10 will be described below.

  If it is determined in step S21 that the timer is equal to or greater than the predetermined value, the process proceeds to step S25. In step S25, preparation for intermittent oscillation control is performed. In step S26, whether the requested output is positive or negative is determined. That is, when the required output is positive, it is determined as power running output, and when it is negative, it is determined as regenerative output. If it is determined in step S26 that the power is output, the process proceeds to step S27. In step S27, switching of the switching element Q2 is performed by intermittent oscillation control. If it is determined in step S26 that the output is regenerative, the process proceeds to step S28. In step S28, the switching of the switching element Q1 is intermittently controlled.

  When the required output P * is within the range of the intermittent oscillation thresholds P + 1 and P-1 for a certain time or longer, an intermittent oscillation operation is performed, and one of the switching elements Q1 and Q2 is switched depending on whether the required output is positive or negative. And This also makes it possible to reduce the switching loss by performing the intermittent oscillation operation only when the no-load state continues. Further, the above-described soft start control is effective in the control of FIG.

  FIG. 13 is a diagram for explaining a return method from the intermittent oscillation control. When the requested output P * becomes equal to or less than the threshold value P + 1 at time t10, the timer starts. When the timer reaches a predetermined value or more at time t11, intermittent control is started. Switching is stopped from t11 to t12, switching is performed from t12 to t13, switching is stopped again from t13 to t15, and intermittent control is continued.

  When the required output P * exceeds the intermittent oscillation threshold range during such an intermittent oscillation operation, the flag 1 and the timer are reset according to the processing of FIG. 10, and switching is performed according to the value of the required output P *. Switching of both elements Q1 and Q2, or switching element Q1 switching or switching element Q2 switching is performed.

  However, if the required output P * exceeding the threshold is still within the upper limit threshold P + 2 and the lower limit threshold P-2 for switching both of the switching elements Q1 and Q2, the intermittent output is intermittent when Wait until the next switching time of oscillation before returning. In the example of FIG. 13, even if the required output P * falls below the threshold value P-1 at time t14 as indicated by a dotted line, it is assumed that the request output P * returns after waiting until the next switching time t15 of intermittent oscillation.

  On the other hand, when the required output P * changes greatly and is smaller than the lower limit threshold P-2 or larger than the upper limit threshold P + 2, the required output is large, so immediately before the next switching time of intermittent oscillation comes, The switching element Q1 or the switching element Q2 is switched to control to perform step-down or step-up operation. As a result, even when the required output P * fluctuates, it is possible to respond appropriately.

  FIG. 14 is a flowchart illustrating a modified example of the process for determining whether to perform intermittent oscillation in the step-up / down controller 14. The same steps as those in FIG. 10 are denoted by the same step numbers and description thereof is omitted. The difference from the process of FIG. 10 is that steps S31 and S32 are added between steps S16 and S19 of the process of FIG. Hereinafter, this point will be described.

  If it is determined in step S16 that the condition is satisfied, the process proceeds to step S31. In step S31, an absolute value ΔP obtained by subtracting the previous request output (P * −1) from the current request output P * is calculated. After the calculation, the current request output P * is stored in the previous request output (P * -1) memory. In step S32, it is determined whether or not ΔP is smaller than a predetermined value. If it is determined in step S32 that ΔP is not smaller than the predetermined value, the process proceeds to step S18. If it is determined in step S32 that ΔP is smaller than the predetermined value, the process proceeds to step S19.

  Thus, the intermittent oscillation operation can be performed when the required output P * is equal to or longer than the threshold value for a certain time and less fluctuates.

The vehicular motor control apparatus according to the second embodiment configured as described above has the following effects in addition to the effects of the vehicular motor control apparatus according to the first embodiment.
(1) Since switching is performed by intermittent control when the absolute value of the required output is small, the switching loss can be further reduced.
(2) Since the intermittent control is performed when the request output is kept small for a predetermined time or longer by the timer, the control with small switching loss can be performed more accurately. The fact that the request output remains low for a predetermined time or more means that there is a high possibility that the request output will remain low in the future. Therefore, there is a low possibility that the required output changes when the intermittent control switching is stopped.
(3) Since the intermittent oscillation frequency is lower than the audible frequency region, it is possible to prevent the generation of sound due to intermittent oscillation.
(4) When intermittent oscillation is on, switching is soft-started. Thereby, generation | occurrence | production of the sound from the reactor iron core of the inductance L by applying a load rapidly at the time of a switching start can be prevented.
(5) When the required output changes during the intermittent oscillation control and is within the upper limit threshold value P + 2 and the lower limit threshold value P-2 described above, it waits until the next switching time of the intermittent oscillation, and then returns. When the requested output changes outside the upper limit threshold P + 2 and the lower limit threshold P-2, the switching element Q1 or the switching element Q2 is immediately switched to perform step-down or step-up operation. As a result, it is possible to appropriately cope with the change in the required output.

  Although the said embodiment demonstrated in the example which uses the request | requirement output of the electric motor 4 as a command value, it does not necessarily need to be limited to this content. It may be a torque command value. Any command value may be used as long as it can be determined that the load on the buck-boost converter 2 is small, that is, that the average direct current flowing through the buck-boost converter 2 is small.

  Although the said embodiment demonstrated the example which drives the one electric motor 4, it does not necessarily need to be limited to this content. The present invention can also be applied to driving a plurality of electric motors.

  Although the said embodiment demonstrated the example of the electric motor control apparatus used with a hybrid vehicle, it does not necessarily need to be limited to this content. It may be applied to an electric vehicle. Moreover, the case of the other vehicle driven with an electric motor may be sufficient. Furthermore, driving with an electric motor need not be limited to a vehicle. That is, the present invention can be applied to all cases in which an electric motor is driven based on DC power from a DC power source.

  Although various embodiments and modifications have been described above, the present invention is not limited to these contents. Other embodiments conceivable within the scope of the technical idea of the present invention are also included in the scope of the present invention.

It is a figure which shows the whole block diagram of the electric motor control apparatus of the 1st Embodiment of this invention. It is a figure explaining control of a buck-boost controller. It is a figure which shows the switching characteristic of the buck-boost converter of this Embodiment. It is a figure explaining pressure | voltage rise (power running) operation | movement when a power running request output is more than predetermined value. It is a figure explaining pressure | voltage fall (regeneration) operation | movement with the absolute value of a regeneration request | requirement output being more than predetermined value. It is a figure explaining power running or regeneration operation in case an absolute value of power running demand output or regeneration demand output is below a predetermined value. It is a figure which shows the flowchart of control by a buck-boost controller. It is a figure explaining the operation | movement of the intermittent oscillation of 2nd Embodiment. It is a figure explaining control of intermittent oscillation in a buck-boost controller. It is a figure which shows the flowchart of the process of judgment whether the intermittent oscillation in a buck-boost controller is performed. It is a figure which shows the relationship of the request | requirement output P *, each threshold value, and the switching operation of a switching element. It is a figure which shows the flowchart of the modification of the process of the judgment of whether to perform intermittent oscillation in a buck-boost controller. It is a figure explaining the return method from intermittent oscillation control. It is a figure which shows the flowchart of the modification of the process of the judgment of whether to perform intermittent oscillation in a buck-boost controller.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Battery 2 Buck-boost converter 3 Inverter 4 Electric motor 5 Rotation position sensor 6 Current sensor 7 Voltage sensor 8 Sensor 9 Current sensor 11 Vehicle controller 12 Electric motor controller 13 Battery controller 14 Buck-boost controller

Claims (11)

Provided between a DC power supply and a drive circuit that drives an electric motor, and performs a step-up operation when power is supplied from the DC power supply to the drive circuit, and a step-down operation when power is supplied from the drive circuit to the DC power supply. An electric motor control device to perform,
A first switching element having a first terminal and a second terminal, wherein the first terminal is connected to the positive side of the drive circuit;
A third terminal connected to the second terminal of the first switching element; the fourth terminal connected to the negative side of the drive circuit; and the direct current A second switching element connected to the negative side of the power supply;
A fifth terminal and a sixth terminal, wherein the fifth terminal is connected to a connection midpoint between the second terminal of the first switching element and the third terminal of the second switching element; And an inductance in which the sixth terminal is connected to the positive side of the DC power supply,
Control means for controlling the step-up operation or the step-down operation by controlling switching of the first switching element and the second switching element based on a command value corresponding to the magnitude of the average DC current flowing through the inductance; With
The control means controls the step-up operation or the step-down operation by alternately switching the first switching element and the second switching element when the absolute value of the command value is smaller than a first predetermined value. An electric motor control device. In the electric motor control device according to claim 1,
The motor control apparatus according to claim 1, wherein the command value is at least one of a required output and a required torque for the electric motor. In the electric motor control device according to any one of claims 1 to 2,
The control means provides a dead time between pulses for turning on the first switching element and the second switching element when alternately switching the first switching element and the second switching element. An electric motor control device characterized by controlling. In the electric motor control device according to any one of claims 1 to 3,
The command value instructs the step-up operation with a positive value, instructs the step-down operation with a negative value,
The control means turns off the first switching element and switches the second switching element to switch the second switching element when the command value is equal to or greater than a predetermined value on the plus side of the first predetermined value. When the command value is equal to or less than a predetermined value on the minus side of the first predetermined value, the second switching element is turned off and the first switching element is switched to control the step-down operation. An electric motor control device characterized in that In the motor control device according to any one of claims 1 to 4,
The control means performs switching of at least one of the first switching element and the second switching element when the absolute value of the command value is smaller than a second predetermined value that is smaller than the first predetermined value. An electric motor control device which is intermittently performed. In the motor control device according to claim 5,
The motor control device, wherein the control means starts control for performing the switching intermittently when a state where the absolute value of the command value is smaller than the second predetermined value continues for a predetermined time or more. In the electric motor control device according to any one of claims 5 to 6,
The motor control device, wherein the control means sets an intermittent frequency of control for intermittently performing the switching to be lower than an audible frequency. In the electric motor control device according to any one of claims 5 to 7,
When the control means intermittently starts switching of at least one of the first switching element and the second switching element, an ON pulse width of the first switching element or the second switching element The motor control device is characterized in that the motor is controlled to gradually increase. In the motor control device according to any one of claims 5 to 8,
The control means is in a dormant state until the next switching start time when the absolute value of the command value is larger than a second predetermined value during the control for performing the switching intermittently and in the dormant state of the switching. The electric motor control device characterized by continuing. In the motor control device according to claim 9,
When the absolute value of the command value is larger than a second predetermined value during the control in which the switching is intermittently performed and when the switching is in a dormant state, the control means immediately An electric motor control device that starts switching of one switching element or the second switching element. In the electric motor control device according to any one of claims 1 to 10,
The DC power source is a battery means that can be charged,
The drive circuit is an inverter circuit;
The electric motor control apparatus according to claim 1, wherein the electric motor is an electric motor that drives driving wheels of a vehicle.

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