JP5958400B2 - Motor drive control device - Google Patents

Description

  The present invention relates to a motor drive control device, and more particularly to a motor drive control device that switches a motor control mode in accordance with a modulation degree.

  Conventionally, drive control is performed by switching the control mode of an AC synchronous motor among a plurality of control modes including a sine wave pulse width modulation control method, an overmodulation control method, and a rectangular wave control method. Since each control mode has a limitation on the modulation degree, the control mode can be switched based on the modulation degree of the motor.

  In a system that generates a motor drive voltage by converting a DC voltage into an AC voltage using an inverter, the ratio of the amplitude of the motor drive voltage to the system voltage input to the inverter corresponds to the degree of modulation of the motor. Therefore, it is possible to switch the motor control mode by adjusting the system voltage according to the degree of modulation of the motor.

  In this case, if a boost converter is provided between the DC power supply and the inverter and the DC voltage from the DC power supply is boosted and supplied to the inverter, the system voltage can be adjusted by controlling the boost degree of the boost converter. It can be performed. In this configuration, the modulation degree changes by controlling the output voltage of the boost converter. Therefore, not only the system voltage is controlled in accordance with the motor output torque, but also the motor control mode can be switched by changing the system voltage.

  For example, in Japanese Patent Application Laid-Open No. 2011-160546 (Patent Document 1), in a control device for an electric vehicle, a system voltage command value that is a command value of a system voltage is determined so that the actual modulation degree matches the target modulation degree. In addition, it is described that the voltage value corresponding to the system voltage command value is output by adjusting the boosting degree of the boost converter.

JP 2011-160546 A

  When performing control to change the boosting degree of the boosting converter according to the modulation degree as described in Patent Document 1, it is possible to switch from the overmodulation control method to the rectangular wave control method by increasing the target modulation degree. When in the operating state, it is desirable to stop the boost operation by the boost converter in order to suppress switching loss and increase the efficiency of the entire system.

  In that case, in order for the modulation degree of the motor to be larger than the threshold value for determining the boost stop and to be less than the threshold value, it may be necessary to increase the system voltage by the converter and lower the modulation degree. In this case, the boosting of the converter is stopped, so that unnecessary boosting that requires further boosting occurs, resulting in a large loss of the entire system and deterioration of fuel consumption when the vehicle is mounted.

  The present invention has been made to solve the above-described problem, and an object of the present invention is to provide a motor drive control device that can reduce loss by executing boost stop by a converter at an appropriate timing.

  A motor drive control device according to the present invention includes a converter capable of boosting a DC voltage supplied from a DC power supply side, and converts a system voltage, which is a DC voltage output from the converter, into an AC voltage and outputs it as a motor drive voltage. And a control unit that controls the operation of the converter and the inverter to drive the motor by switching to a plurality of control modes, wherein the control unit is configured to control the motor with respect to the system voltage. A control mode setting unit that sets the motor control mode to pulse width modulation control or rectangular wave control based on the modulation degree that is the ratio of the amplitude of the drive voltage; and the motor control mode is an excess of the pulse width modulation control. When in modulation control mode and the converter is in the lowest boosting operation state or a low boosting operation state close to this Including a modulation degree deriving unit that derives a prediction modulation when the boosted stopping the said converter, and a boost stop execution unit for executing the step-up stop of the converter on the basis of the predicted modulation depth.

  In the motor drive control device according to the present invention, the control unit includes a loss derivation comparing unit that derives and compares a predicted loss when the rectangular wave control mode is executed with the predicted modulation degree and a current loss during the current operation. In addition, the boost stop unit may execute boost stop of the converter when the predicted loss is smaller than the current loss.

  In the motor drive control device according to the present invention, when the control mode corresponding to the predicted modulation degree is an overmodulation control mode, the boost stop unit may immediately execute the boost stop of the converter.

  In the motor drive control unit according to the present invention, the control unit may be configured such that when the step-up duty ratio of a switching element included in the converter is larger than a predetermined threshold, the converter is in a lowest step-up operation state or a low step-up that is close thereto. You may determine with being in an operating state.

  Further, in the motor drive control device according to the present invention, the loss derivation comparing unit predicts the motor current when the rectangular wave control mode is executed with the predicted modulation degree as a current vector on the dq axis plane, and performs the prediction. The predicted loss corresponding to the current vector may be derived with reference to a loss map stored in advance.

  According to the motor drive control device of the present invention, when the motor control mode is the overmodulation control mode of the pulse width modulation control and the converter is in the lowest boosting operation state or a low boosting operation state close thereto, By deriving the predicted modulation degree when the converter is stopped from boosting and executing the boost stop of the converter based on this predicted modulation degree, without waiting for an instruction to stop boosting the converter by the actual modulation degree The boosting stop of the converter can be executed at an appropriate timing. Therefore, the useless boosting operation of the converter can be reduced and the loss can be reduced, and the fuel efficiency when mounted on the vehicle can be improved.

It is a figure which shows schematically the motor drive control apparatus which is embodiment of this invention. It is a block diagram which shows the control part in FIG. It is a figure which shows the structure of the pulse width modulation (PWM) control block of FIG. It is a figure which shows the structure of the rectangular wave control block of FIG. (A) Modulation degree, (b) System voltage after boosting, (c) System voltage before boosting, (d) Actual boosting duty ratio, (e) Loss, and (f) Motor control in the modulation degree boosting control of the comparative example It is a time chart which shows each transition state of a mode. It is a flowchart which shows the control performed in the control part of this embodiment. It is a figure which shows a mode that the motor current after a pressure | voltage rise stop is estimated as a current vector on a dq-axis plane. (A) modulation degree, (b) system voltage after boosting, (c) system voltage before boosting, (d) actual boosting duty ratio, (e) loss, and (f) when the processing shown in FIG. 6 is executed ) It is a time chart showing each transition state of the motor control mode.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments according to the present invention (hereinafter referred to as embodiments) will be described in detail with reference to the accompanying drawings. In this description, specific shapes, materials, numerical values, directions, and the like are examples for facilitating the understanding of the present invention, and can be appropriately changed according to the application, purpose, specification, and the like.

  In addition, when a plurality of embodiments and modifications are included in the following, it is assumed from the beginning that these characteristic portions are used in appropriate combinations. In the following, the same or corresponding parts in the drawings are denoted by the same reference numerals, and the description thereof will not be repeated in principle.

  FIG. 1 is an overall configuration diagram of a motor drive system 100 including a motor drive control device 10 according to an embodiment of the present invention. As shown in FIG. 1, a motor drive system 100 includes a DC power source B, voltage sensors 11 and 17, system relays SR1 and SR2, smoothing capacitors C1 and C2, a current sensor 15, an AC motor M, and a motor. Drive control device 10. The motor drive control device 10 includes a converter 20, an inverter 30, and a control unit 40.

  The AC motor M is, for example, a driving motor for generating torque for driving the driving wheels of a hybrid vehicle or an electric vehicle. Or this AC motor M may be comprised so that it may have the function of the generator driven with an engine, and may be comprised so that it may have the function of an electric motor and a generator together. Further, AC motor M operates as an electric motor for the engine, and may be incorporated in a hybrid vehicle so as to be able to start the engine, for example. Furthermore, a plurality of sets of AC motors M and inverters 30 may be provided and connected in parallel to the common converter 20.

  The DC power source B is composed of a secondary battery such as nickel hydride or lithium ion. Voltage sensor 11 detects DC voltage Vb output from DC power supply B and outputs the detected DC voltage Vb to control unit 40.

  System relay SR1 is connected between the positive terminal of DC power supply B and power line 12, and system relay SR2 is connected between the negative terminal of DC power supply B and ground line 13. System relays SR1 and SR2 are turned on / off by a signal SE from control unit 40. More specifically, system relays SR1 and SR2 are turned on by an H (logic high) level signal SE from control unit 40 and turned off by an L (logic low) level signal SE from control unit 40. Smoothing capacitor C1 is connected between power line 12 and ground line 13.

  Converter 20 includes a reactor L1, power semiconductor switching elements Q1, Q2, and diodes D1, D2. Power switching elements Q 1 and Q 2 are connected in series between power line 14 and ground line 13. On / off of power switching elements Q1 and Q2 is controlled by switching control signals S1 and S2 from control unit 40.

  In the present embodiment, an IGBT (Insulated Gate Bipolar Transistor), a power MOS (Metal Oxide Semiconductor) transistor, a power bipolar transistor, or the like is used as a power semiconductor switching element (hereinafter simply referred to as “switching element”). be able to. Anti-parallel diodes D1, D2 are arranged for switching elements Q1, Q2.

  Reactor L1 is connected between a connection node of switching elements Q1 and Q2 and power line 12. Further, the smoothing capacitor C <b> 2 is connected between the power line 14 and the ground line 13.

  Inverter 30 includes a U-phase arm 32, a V-phase arm 34, and a W-phase arm 36 provided in parallel between power line 14 and ground line 13. Each phase arm is composed of a switching element connected in series between the power line 14 and the ground line 13. For example, the U-phase arm 32 includes switching elements Q3 and Q4, the V-phase arm 34 includes switching elements Q5 and Q6, and the W-phase arm 36 includes switching elements Q7 and Q8. Further, antiparallel diodes D3 to D8 are connected to switching elements Q3 to Q8, respectively. Switching elements Q3 to Q8 are turned on / off by switching control signals S3 to S8 from control unit 40.

  An intermediate point of each phase arm is connected to each phase end of each phase coil of AC motor M. The AC motor M is a three-phase permanent magnet motor, and is configured by commonly connecting one end of three coils of U, V, and W phases to a middle point. Furthermore, the other end of each phase coil is connected to the intermediate point of the switching elements of each phase arm 32 to 36.

  Converter 20 supplies to inverter 30 a DC voltage obtained by boosting the DC voltage supplied from DC power supply B (hereinafter, this DC voltage corresponding to the input voltage to inverter 30 is also referred to as “system voltage”) during boosting operation. To do. More specifically, in response to the switching control signals S1 and S2 from the control unit 40, the ON period of the switching element Q1 of the upper arm and the ON period of the switching element Q2 of the lower arm are alternately provided, and the boost ratio Corresponds to the ratio of these ON periods.

  In the present embodiment, the on-duty ratio of the switching element Q1 within a predetermined constant period is referred to as a boost duty ratio, and as the boost duty ratio increases, the boost degree decreases and the system voltage VH decreases. However, as will be described later, converter 20 has a minimum boosting operation state in which the boosting operation is performed in a state where the boosting duty ratio cannot be further lowered during the boosting operation. In addition, the switching element Q1 of the upper arm of the converter 20 is maintained in the ON state, and the DC voltage Vb supplied from the battery B via the smoothing capacitor C1 is output to the inverter 30 side without being boosted. Is referred to as “upper arm on”, and the step-up duty ratio at this time is 1 (ie, 100%). Accordingly, in the above-described minimum boosting operation state or a low boosting operation state close thereto, the boosting duty ratio is a maximum boosting duty ratio maximum value (for example, 0.98) slightly lower than 1.

  During the step-down operation, converter 20 steps down the DC voltage (system voltage) supplied from inverter 30 via smoothing capacitor C2 and charges DC power supply B. More specifically, in response to the switching control signals S1 and S2 from the control unit 40, a period in which only the switching element Q1 is turned on and a period in which both the switching elements Q1 and Q2 are turned off are alternately provided. The step-down ratio is in accordance with the duty ratio during the ON period.

  Smoothing capacitor C <b> 2 smoothes the DC voltage from converter 20, and supplies the smoothed DC voltage to inverter 30. The voltage sensor 17 detects the voltage across the smoothing capacitor C2, that is, the system voltage, and outputs the detected value VH to the control unit 40.

  When the torque command value of AC motor M is positive (Tqcom> 0), inverter 30 responds to switching control signals S3 to S8 from control unit 40 when a DC voltage is supplied from smoothing capacitor C2. The AC motor M is driven so as to convert a DC voltage into an AC voltage and output a positive torque by the switching operation of the elements Q3 to Q8. Further, when the torque command value of AC motor M is zero (Tqcom = 0), inverter 30 converts the DC voltage to the AC voltage by the switching operation in response to switching control signals S3 to S8, and the torque is zero. The AC motor M is driven so that Thereby, AC motor M is driven to generate zero or positive torque designated by torque command value Tqcom.

  Further, during regenerative braking of a hybrid vehicle or electric vehicle equipped with motor drive system 100, torque command value Tqcom of AC motor M is set to be negative (Tqcom <0). In this case, the inverter 30 converts the AC voltage generated by the AC motor M into a DC voltage by a switching operation in response to the switching control signals S3 to S8, and converts the converted DC voltage (system voltage) to the smoothing capacitor C2. To the converter 20 via Although regenerative braking does not operate the foot brake, the driver not only decelerates the vehicle (or stops acceleration) while regenerating power by turning off the accelerator pedal while driving, but also includes a foot brake operation by the driver. Including braking when

  Current sensor 15 detects a motor current flowing through AC motor M, and outputs the detected motor current to control unit 40. Since the sum of instantaneous values of the three-phase currents iu, iv, and iw is zero, the current sensor 15 has two-phase motor currents (for example, a V-phase current iv and a W-phase current iw) as shown in FIG. It is sufficient to arrange it so as to detect.

  The rotation angle sensor (resolver) 16 detects the rotor rotation angle θ of the AC motor M and sends the detected rotation angle θ to the control unit 40. The control unit 40 calculates the rotational speed (rotational speed) of the AC motor M based on the rotational angle θ.

  The control unit 40 includes a torque command value Tqcom input from an electronic control unit (ECU) provided outside, a battery voltage Vb detected by the voltage sensor 11, a system voltage VH detected by the voltage sensor 17, and a current sensor 15. Of the converter 20 and the inverter 30 so that the AC motor M outputs torque according to the torque command value Tqcom by a method described later based on the motor currents iv and iw from the rotation angle sensor 16 and the rotation angle θ from the rotation angle sensor 16. To control. That is, switching control signals S1 to S8 for controlling converter 20 and inverter 30 as described above are generated and output to converter 20 and inverter 30.

  During the boosting operation of converter 20, control unit 40 performs feedback control of output voltage VH of smoothing capacitor C2, and generates switching control signals S1 and S2 such that output voltage VH becomes system voltage command value VH #.

  Further, when receiving a signal RGE indicating that the hybrid vehicle or the electric vehicle has entered the regenerative braking mode from the external ECU, the control unit 40 performs switching control so as to convert the AC voltage generated by the AC motor M into a DC voltage. Signals S3 to S8 are generated and output to inverter 30. Thereby, inverter 30 converts the AC voltage generated by AC motor M into a DC voltage and supplies it to converter 20.

  Further, when receiving a signal RGE indicating that the hybrid vehicle or the electric vehicle has entered the regenerative braking mode from the external ECU, the control unit 40 switches the switching control signals S1, S2 so as to step down the DC voltage supplied from the inverter 30. Is output to the converter 20. As a result, the AC voltage generated by AC motor M is converted into a DC voltage, stepped down, and supplied to DC power supply B.

  Further, control unit 40 generates signal SE for turning on / off system relays SR1, SR2 and outputs the signal SE to system relays SR1, SR2.

  Next, power conversion in the inverter 30 controlled by the control unit 40 will be described in detail.

  In the motor drive control device 10 of the present embodiment, the power conversion in the inverter 30 is switched between three control methods: a sine wave pulse width modulation control method, an overmodulation pulse width modulation control method, and a rectangular wave control method. . Hereinafter, “Pulse Width Modulation control” is abbreviated as PWM control. In addition, the overmodulation PWM control is sometimes simply referred to as overmodulation control.

  The sine wave PWM control method is used as a general PWM control. The switching element in each phase arm is turned on / off by changing the voltage between a sine wave voltage command value and a carrier wave (typically, a triangular wave). Control according to the comparison. As a result, for a set of a high level period corresponding to the on period of the upper arm element and a low level period corresponding to the on period of the lower arm element, the duty is set so that the fundamental wave component becomes a sine wave within a certain period. The ratio is controlled. Thus, as is well known from the inverter 30, in a general sine wave PWM control system, the modulation degree K, which is the ratio of the fundamental component amplitude to the system voltage VH that is the inverter input voltage, can be increased to 0.61. . However, in the case of sinusoidal PWM control by the two-phase modulation method or the third harmonic superposition control, the modulation degree K can be increased to about 0.7.

  On the other hand, in the rectangular wave control method, an AC motor is applied to one pulse of a rectangular wave whose ratio between the high level period and the low level period is 1: 1 within the predetermined period. Thereby, the modulation degree K is increased to 0.78. In the rectangular wave control, the modulation degree K is constant at 0.78.

  The overmodulation PWM control system performs the same PWM control as the sine wave PWM control system after increasing the amplitude of the fundamental wave component. As a result, the amplitude of the fundamental wave component can be increased, and the modulation degree K can be increased to a range of 0.61 to 0.78.

  Here, it is advantageous to drive the AC motor M by inputting the battery voltage Vb to the inverter 30 without boosting by the converter 20 because the switching loss in the converter 20 can be suppressed. Further, for the inverter 30, rectangular wave control is more advantageous than PWM control in order to suppress switching loss. Therefore, in order to suppress the loss of the entire system and improve fuel efficiency in a vehicle equipped with the motor drive system 100, it is positive to drive the AC motor M by the rectangular wave control method with the converter 20 in the boost stop state. It may be desirable to do so.

  The control method of AC motor M can be selected according to modulation degree K. Specifically, as described above, the sine wave PWM control is selected up to a modulation degree of 0.61 (K ≦ 0.61), and the modulation degree K is set to 0.61 to 0.78 (that is, 0.61 <K < 0.78), overmodulation control can be selected, and rectangular wave control can be selected when the modulation degree is K0.78 or more (K ≧ 0.78).

  The modulation degree K is obtained as a value obtained by dividing the line voltage amplitude (or line voltage command amplitude) of the AC motor M by the system voltage VH. Therefore, since the motor drive system 100 includes the converter 20, the control unit 40 adjusts the switching control signals S1 and S2 to change the boosted system voltage VH, thereby increasing or decreasing the modulation degree K. The motor control method can be set by

  FIG. 2 illustrates the control unit 40 in the present embodiment. FIG. 2 is a block diagram showing the control unit 40 in FIG.

  The control unit 40 includes a control mode setting unit 41, a PWM control block 42, a rectangular wave control block 43, a modulation degree derivation unit 44, a boost duty ratio derivation unit 45, a modulation degree comparison unit 46, a loss derivation comparison unit 47, and an upper arm on execution. (A boost stop execution unit) 48 and a loss map 49. Each of these units 41 to 48 can be realized by software executed by the control unit 40. However, the present invention is not limited to this, and a part thereof may be realized by hardware. The control unit 40 includes a storage device (not shown). In this storage device, a loss map 49 and various tables are stored in advance.

  As described above, the control mode setting unit 41 has a function of selecting and setting the control mode of the AC motor M according to the modulation degree K from any one of sine wave PWM control, overmodulation control, and rectangular wave control.

  The PWM control block 42 has a function of controlling the operation of the inverter 30 so that the AC motor M is driven by the sine wave PWM control method and the overmodulation PWM control method.

  FIG. 3 is a diagram showing a configuration of the PWM control block 42. The PWM control block 42 includes a current command generation unit 421, coordinate conversion units 422 and 425, a rotation speed calculation unit 423, a PI calculation unit 424, and a PWM signal generation unit 426.

  The current command generation unit 421 generates a d-axis current command value Idcom and a q-axis current command value Iqcom according to the torque command value Tqcom of the AC motor M according to a previously stored table or the like.

  The coordinate conversion unit 422 performs the v-phase current iv and the W-phase current detected by the current sensor 15 by coordinate conversion (3 phase → 2 phase) using the rotation angle θ of the AC motor M detected by the rotation angle sensor 16. Based on iv, a d-axis current Id and a q-axis current Iq are calculated. The rotation number calculation unit 423 calculates the rotation number Nmt of the AC motor M based on the output from the rotation angle sensor 16.

  A deviation ΔId (ΔId = Idcom-id) with respect to the command value of the d-axis current and a deviation ΔIq (ΔIq = Iqcom-iq) with respect to the command value of the q-axis current are input to the PI calculation unit 424. PI calculation unit 424 performs a PI calculation with a predetermined gain for each of d-axis current deviation ΔId and q-axis current deviation ΔIq to obtain a control deviation, and d-axis voltage command value Vd # and q-axis corresponding to this control deviation Voltage command value Vq # is generated.

  The coordinate conversion unit 425 converts the d-axis voltage command value Vd # and the q-axis voltage command value Vq # to the U-phase, V-phase, W-phase by coordinate conversion (2 phase → 3 phase) using the rotation angle θ of the AC motor M Each phase voltage command value Vu, Vv, Vw of the phase is converted.

  The PWM signal generation unit 426 generates the switching control signals S3 to S8 shown in FIG. 1 based on the comparison between the voltage command values Vu, Vv, and Vw in each phase and a predetermined carrier wave. The inverter 30 is subjected to switching control according to the switching control signals S3 to S8 generated by the PWM control block 42, whereby an AC voltage for outputting torque according to the torque command value Tqcom is applied to the AC motor M. The As described above, in the overmodulation control method, the carrier wave used in the PWM modulation in the PWM signal generation unit 426 is switched from the general carrier in the sine wave PWM control method.

  FIG. 4 is a diagram illustrating a configuration of a rectangular wave control block of the control unit 40. The rectangular wave control block 43 includes a coordinate conversion unit 431, a torque calculation unit 432, a PI calculation unit 433, a rectangular wave generator 434, and a signal generation unit 435.

  Similarly to the coordinate conversion unit 422, the coordinate conversion unit 431 is detected by the current sensor 15 by coordinate conversion (3 phase → 2 phase) using the rotation angle θ of the AC motor M detected by the rotation angle sensor 16. The d-axis current id and the q-axis current iq are calculated based on the v-phase current iv and the W-phase current iv.

  Based on the d-axis current id and the q-axis current iq obtained by the coordinate conversion unit 431, the torque calculation unit 432 derives or calculates the estimated torque value Tq, which is the current torque of the AC motor M, by referring to a map or the like.

  Torque deviation ΔTq (ΔTq = Tqcom−Tq) with respect to torque command value Tqcom is input to PI calculation unit 433. PI calculation unit 433 performs a PI calculation with a predetermined gain on torque deviation ΔTq to obtain a control deviation, and sets phase φv of the rectangular wave voltage according to the obtained control deviation. Specifically, when positive torque is generated (Tqcom> 0), the voltage phase is advanced when the torque is insufficient, while when the torque is excessive, the voltage phase is delayed, and when negative torque is generated (Tqcom <0), the voltage phase is increased when the torque is insufficient. While delaying, the voltage phase is advanced when the torque is excessive.

  The rectangular wave generator 434 generates each phase voltage command value (rectangular wave pulse) Vu, Vv, Vw according to the voltage phase φv set by the PI calculation unit 433. The signal generator 435 generates switching control signals S3 to S8 according to the phase voltage command values Vu, Vv, Vw. When inverter 30 performs a switching operation according to switching control signals S3 to S8, a rectangular wave pulse according to voltage phase φv is applied as each phase voltage of the motor.

  Thus, in the rectangular wave control method, the motor torque control can be performed by the feedback control of the torque (electric power).

  The modulation degree deriving unit 44 (see FIG. 2) of the control unit 40 is based on the effective line voltage effective value Vamp of the AC motor M corresponding to the motor drive voltage and the system voltage VH, and the actual modulation degree Kr and the predicted modulation degree Kp. Has the function of deriving.

Here, the line voltage effective value Vamp is obtained by using the d-axis voltage command value Vd # and the q-axis voltage command value Vq # generated by the PI calculation unit 424 of the PWM control block 42 as follows (1), (2 ).
Vamp = | Vd # · cosφ | + | Vq # · sinφ | (1)
tan φ = Vq # / Vd # (2)

Therefore, the modulation factor deriving unit 44 can derive the actual modulation factor Kr by the following equation (4).
Actual modulation degree Kr = Linear voltage fundamental wave component effective value Vamp / System voltage VH (4)
The derivation of the predicted modulation degree Kp by the modulation degree derivation unit 44 will be described later.

  The PI calculation unit 424 calculates optimum voltage commands Vd # and Vq # according to ΔId and ΔIq supplied from the current command generation unit 421, and accordingly, an optimum system voltage VH is determined at that time. This becomes the target VH #, and the converter 20 is controlled accordingly. Specifically, target system voltage command value VH # is determined so that actual modulation degree Kr becomes target modulation degree Kt. At this time, when the actual modulation degree Km is larger than the target modulation degree Kt, the target system voltage command value VH # is increased, while when the actual modulation degree Km is smaller than the target modulation degree Kt, control for decreasing the target system voltage command value VH # is executed. To do.

  Next, with reference to FIG. 5, the modulation degree boost control so far will be described. 5 shows (a) modulation degree K, (b) post-boosting system voltage VH, (c) pre-boosting system voltage VL (= Vb), (d) actual boosting duty ratio in modulation degree boosting control as a comparative example. It is a time chart which shows each transition state of (e) loss and (f) motor control mode. 5A to 5F, the horizontal axis is shown as a common time axis.

  Referring to FIG. 5A, the actual modulation degree Kr is indicated by a solid line, and a switching line 51 between the sine wave PWM control and the overmodulation control and a switching line 52 between the overmodulation control and the rectangular wave control. This is indicated by two parallel dashed lines. For example, the switching line 51 corresponds to 0.61 which is the maximum modulation degree in the sine wave PWM control, and the switching line 52 corresponds to 0.78 which is the modulation degree in the rectangular wave control. When the actual modulation degree Kr gradually increases and exceeds the switching line 51, the control mode of the AC motor M is switched from sine wave PWM control to overmodulation control as shown in FIG.

  5A, the target modulation degree Kt is indicated by a broken line above the actual modulation degree Kr, and the upper arm-on implementation modulation degree Kuaon is indicated by a broken line below the actual modulation degree Kr. Yes. When it is a preferable operating point that the AC motor M is driven by sinusoidal PWM control in response to a request for vibration suppression control of the AC motor M, the target modulation degree Kt is set to 0.61 (or slightly lower), The system voltage VH after boosting by the converter 20 is controlled so that the actual modulation degree Kr does not exceed the target modulation degree Kt. This is shown in FIG. 5 (b). A difference ΔVH between the boosted voltage VH and the pre-boosting voltage VL corresponding to the battery voltage Vb corresponds to a voltage increased by the boosting operation of the converter 20.

  When the restriction by the vibration suppression control or the like is released and the driving by the rectangular wave control of the AC motor M is permitted, the control unit 40 increases the target modulation degree Kt by a linear function, for example, and is a value corresponding to a rectangular wave. (For example, 0.78 or a value slightly larger than this). The increase in the target modulation degree Kt is not limited to a linear one, and may be increased in a curved line or stepwise.

  Then, control unit 40 executes by decreasing system voltage command value VH # so that actual modulation degree Kr increases in accordance with target modulation degree Kt. Specifically, control unit 40 increases the step-up duty ratio so that system voltage VH becomes target system voltage command value VH #, and switches on / off switching elements Q1, Q2 of converter 20 based on this step-up duty ratio. Switching control signals S1 and S2 to be turned off are generated, and the actual boost duty ratio Dr is increased in a linear function, for example, as shown in FIG. As system voltage command value VH # decreases in this way, system voltage VH, which is the denominator, decreases in the state where effective line voltage effective value Vamp, which is the numerator in the above equation (3), does not change. The degree Kr will gradually increase.

  When the actual modulation degree Kr increases and reaches the rectangular wave control switching line 52, the control mode is switched from over modulation control to rectangular wave control by the function of the control mode setting unit 41 (see FIG. 2).

  However, as shown in FIG. 5A, before the actual modulation degree Kr reaches the switching line 52, the actual boost duty ratio Dr of the converter 20 may reach the maximum value Drmax. This boosting duty ratio maximum value Drmax is for reasons such as setting the carrier frequency used for boosting control of the converter 20, setting the dead time so that both the upper arm and the lower arm are not turned on, and switching the power running or rotation of the vehicle. Is set.

  When the actual boost duty ratio Dr reaches the maximum value Drmax, the converter 20 enters the lowest boost operation state or a low boost operation state close thereto, and as shown in FIGS. 5B and 5C, the minimum boost is performed over the battery voltage Vb. It will not drop below a value larger by the voltage component ΔVHmin. Then, when the rotation speed / torque is not changed, the actual modulation degree Kr may stagnate as a value immediately before the switching line 52, that is, a value corresponding to overmodulation control.

  On the other hand, if the upper arm-on implementation modulation degree Kuaon is set as a value lower than the target modulation degree Kt by a predetermined value ΔK, and the actual modulation degree Kr becomes equal to or less than the upper arm-on implementation modulation degree Kuaon, the control unit 40 It is possible to execute the upper arm on, which is the 20 boost stop state. However, as described above, when the system voltage VH becomes the minimum boosted voltage and the torque and the rotational speed are constant, the actual modulation degree Kr does not decrease and stagnates at the value corresponding to the overmodulation control. It is possible that the 20 boosting operations are wasted and the overmodulation control continues. As a result, as shown in the region surrounded by the broken line 53 in FIG. 5E, the state in which the switching loss occurs in the converter 20 and the inverter 30 is continued.

  Therefore, in the motor drive control device 10 of the present embodiment, the control unit 40 includes the conventional control mode setting unit 41, the PWM control block 42, the rectangular wave control block 43, the modulation degree deriving unit 44, and the boost duty ratio deriving unit 45. In addition to the above, as a control configuration further including a modulation degree comparison unit 46, a loss derivation comparison unit 47, an upper arm on execution unit 48, and a loss map 49, the following control is executed.

  FIG. 6 is a flowchart showing the upper arm on execution control in the control unit 40 of the present embodiment. This control is repeatedly executed at predetermined time intervals when the motor drive system 100 is operating.

  First, in step S10, the control unit 40 determines whether the upper arm is being released (that is, during the step-up operation). This determination can be made based on switching control signals S1 and S2 for converter 20.

  If a negative determination is made in step S10, the process is terminated as it is. On the other hand, when an affirmative determination is made in step S10, the control unit 40 determines whether or not the actual boost duty ratio Dr is larger than the threshold value Dth and the control mode is overmodulation control in subsequent step S12. The actual boost duty ratio Dr is derived by the function of the boost duty ratio deriving unit 45. The threshold Dth can be set to a value slightly smaller than the maximum boost duty ratio Drmax. In this example, the actual boost duty ratio Dr (t2) at the timing of time t2 when the target modulation degree Kt is equivalent to rectangular wave control. Can be set as the threshold value Dth. Whether or not the control mode is overmodulation control is determined based on whether or not the actual modulation degree Kr derived by the modulation degree deriving unit 44 satisfies 0.61 <Kr <0.78 as described above. it can.

  If a negative determination is made in step S12, the process ends. On the other hand, if an affirmative determination is made in step S12, a predicted modulation degree Kp when the upper arm is turned on is derived in subsequent step S14. The predicted modulation degree Kp is derived by the modulation degree deriving unit 44 of the control unit 40. Specifically, the modulation degree deriving unit 44 calculates the predicted modulation degree Kp by dividing the line voltage effective value Vamp by the pre-boosting voltage VL when the converter 20 is stopped from being boosted. The battery voltage Vb detected by the voltage sensor 11 can be used as the pre-boosting voltage VL.

  Next, in step S16, it is determined whether or not the predicted modulation degree Kp derived in step S14 is 0.78 or more. That is, it is determined whether the control mode after the boost stop by the converter 20 is rectangular wave control.

  If a negative determination is made in step S16, the control unit 40 immediately turns on the upper arm in step S22. If it is not determined that the predicted modulation degree Kp is equivalent to the rectangular wave control, that is, if the overmodulation control is performed even after the boost is stopped, the switching loss in the converter 20 is reduced by immediately executing the boost stop. It is because it is preferable.

  When an affirmative determination is made in step S16, that is, when it is determined that the predicted modulation degree Kp is equivalent to rectangular wave control, the current vector Ip of the current that flows to the AC motor M after the boost stop by the converter 20 is determined in a subsequent step S18. Predict. This prediction can be performed using a table or the like referred to by the current command generation unit 421 included in the PWM control block 42 (see FIG. 3) of the control unit 40.

  Here, prediction of a current vector will be described with reference to FIG. FIG. 7 is a diagram illustrating a state in which the motor current after the boost stop is predicted as a current vector I on the dq axis plane.

  As shown in FIG. 7, the storage device of the control unit 40 includes a sine wave PWM control and a graph in which a d-axis current Id is taken on the horizontal axis and a q-axis current Iq is taken on the vertical axis perpendicular thereto. An optimum advance line 60 formed by connecting a d-axis current value Id and a q-axis current value Iq that minimizes motor loss by PWM control including overmodulation control is stored in advance in the form of a table or the like. Here, the “advance angle” is the phase of the current belt on the dq axis plane, and is specifically expressed as an angle from the q axis.

  The current d-axis current Id and q-axis current Iq flowing through the AC motor M under overmodulation control are obtained as the intersection 61 between the equal torque line TE of the current torque Tqn and the optimum advance line 60, and the current at that time It can be derived as a vector I (Id, Iq). Here, the current torque Tq can be derived by the function of the torque calculator 432 of the rectangular wave control block 43. Note that the current d-axis current Id and q-axis current Iq flowing through the AC motor M may be calculated from values detected by the current sensor 15.

  As described above, the loss map 49 (see FIG. 2) is stored in advance in the storage device of the control unit 40. Therefore, the current loss Ploss1 can be derived by referring to the loss map 49 based on the phases Id and Iq of the current current vector I.

  On the other hand, the current vector Ip when the upper arm is turned on and the system voltage VH becomes the pre-boosting voltage VL is predicted on the current command map. The predicted current vector Ip moves to the advance side (that is, the phase becomes larger) along the equal torque line TE of the current torque Tqn. A predicted d-axis current Idp and a predicted q-axis current Iqp of the predicted current vector Ip at that time are derived. The loss Ploss2 when the upper arm is on can be predicted by referring to the loss map 49 based on the predicted d-axis current Idp and the predicted q-axis current Iqp.

  Such derivation of the current loss Ploss1 and the predicted loss Ploss2 is executed as a function of the loss derivation comparison unit 47 of the control unit 40.

  Referring to FIG. 6 again, the control unit 40 determines whether or not the current loss Ploss1 is larger than the predicted loss Ploss2 in step S20. This loss comparison is also executed as a function of the loss derivation comparing unit 47 of the control unit 40.

  When an affirmative determination is made in step S20, that is, when it is confirmed that the predicted loss Ploss2 when the upper arm is turned on is smaller than the current loss Ploss1, the upper arm is turned on in the subsequent step S22. Specifically, control unit 40 maintains switching control signal S1 corresponding to the switching element of the upper arm of converter 20 at a high level, while switching control signal S2 corresponding to switching element Q2 of the lower arm is set to a low level. maintain. As a result, the switching element Q1 of the upper arm is held in the on state, and the pre-boosting voltage VL equal to the battery voltage Vb is supplied to the inverter 30.

  On the other hand, when a negative determination is made in step S20, that is, when the loss Ploss2 when the upper arm is on is equal to or greater than the current loss Ploss1, the process is terminated without executing the upper arm on.

  8 shows (a) modulation degree, (b) post-boosting system voltage, (c) pre-boosting system voltage, (d) actual boosting duty ratio when the upper arm is turned on by the processing shown in FIG. It is a time chart which shows each transition state of a loss and (f) motor control mode. FIG. 8 is substantially the same as FIG. 5, except that the upper arm is turned on at time t3. Therefore, only the difference will be described.

  When the upper arm is turned on at time t3, the system voltage VH becomes the pre-boosting voltage VL (= Vb) as shown in FIG. 8B. As a result, as shown in FIG. 8A, the actual modulation degree Kr is increased to be equivalent to rectangular wave control (ie, 0.78 or more). As a result, the control mode setting unit 41 of the control unit 40 adjusts the switching control signals S3 to S8 to the inverter 30 so as to be in the rectangular wave control mode. Therefore, as shown in FIG. 8F, the control mode of AC motor M is switched from overmodulation control to rectangular wave control.

  When switching to the rectangular wave control in this way, as shown in FIG. 8E, the loss decreases as shown by the solid line 54 as compared to the broken line 53 indicating the case where the overmodulation control is continued.

  As described above, according to the motor drive control device 10 of the present embodiment, the control mode of the AC motor M is the overmodulation control mode of the pulse width modulation control, and the converter 20 is in the lowest boosting operation state or the same. When the converter 20 is in a near low boosting operation state, the predicted modulation degree Kp when the converter 20 is stopped from being boosted is derived, and the boosting stop of the converter is executed based on the predicted modulation degree Kp (steps S12 and S14 described above). , S16, S22). Thereby, the boost stop of the converter can be executed in a timely manner without waiting for the instruction to stop the boost of the converter 20 by the actual modulation degree Kr. Therefore, the useless boosting operation of converter 20 can be reduced and the loss can be reduced, and the fuel efficiency when mounted on the vehicle can be improved.

  Further, according to the motor drive control device 10 of the present embodiment, the loss when the upper arm is turned on is predicted, and the upper arm is turned on when the predicted loss is smaller than the current loss (step S18 described above). , S20, S22). As a result, it is possible to avoid a situation in which the loss (for example, copper loss or iron loss) increases beyond the switching loss reduction due to the motor current increasing when the upper arm is on, and the loss can be reliably reduced by executing the upper arm. .

  Therefore, the fuel efficiency can be improved in the vehicle equipped with the motor drive system 100 including the motor drive control device 10 of the present embodiment.

  In addition, this invention is not limited to embodiment mentioned above and its deformation | transformation, A various change is possible in the matter described in the claim, and its equivalent range.

  For example, in the above description, it is determined by comparing the actual boost duty ratio Dr with the threshold value that the converter 20 is in the lowest boost operation state or a low boost operation state close thereto, but the present invention is not limited to this. The determination may be made based on system voltage VH detected by sensor 17 or system voltage command value VH # generated in control unit 40 and battery voltage Vb detected by voltage sensor 11. In this case, it can be determined that converter 20 is in the lowest boost state when the difference between VH or VH # and Vb becomes a predetermined value (for example, 20 V) or less.

  Further, as shown in FIG. 7, an upper arm on release line 62 is set on the advance side (left side in the figure) of the optimum advance line 60, and the current vector Ip predicted in step S18 in FIG. The release line 62 may be controlled so as not to cross the left side. In this way, it is possible to prevent the hunting phenomenon in which the upper arm is released immediately after the upper arm is executed in the converter 20 and this is repeated.

  DESCRIPTION OF SYMBOLS 10 Motor drive control apparatus, 11, 17 Voltage sensor, 12, 14 Power line, 13 Ground line, 15 Current sensor, 16 Rotation angle sensor, 20 Converter, 30 Inverter, 32 U-phase arm, 34 V-phase arm, 36 W-phase arm , 40 control unit, 41 control mode setting unit, 42 PWM control block, 43 rectangular wave control block, 44 modulation degree derivation unit, 45 step-up duty ratio derivation unit, 46 modulation degree comparison unit, 47 loss derivation comparison unit, 48 upper arm on Execution unit, 49 Loss map, 51, 52 switching line, 53 broken line (loss due to conventional method), 54 solid line (loss due to this method), 60 optimum advance line, 61 (equal torque line and optimum advance line) Intersection, 62 upper arm on release line, 100 motor drive system, B battery or DC power supply, C1, C2 smoothing capacitor, D1-D8 anti-parallel diode, Dr actual boost duty ratio, Drmax actual boost duty ratio maximum value, Dth threshold, I current vector, Id d-axis current, Id, Iq current vector phase, Idcom d current Command value, Idp predicted d-axis current, Ip predicted current vector, Iq q-axis current, Iqcom q-axis current command value, Iqp predicted q-axis current, iu, iv, iw Three-phase current or motor current, K modulation factor, Kp prediction Modulation degree, Kr actual modulation degree, Kt target modulation degree, Kuaon upper arm-on implementation modulation degree, L1 reactor, M AC motor, Nmt rotation speed, Ploss1 current loss, Ploss2 prediction loss, Q1-Q8 switching element, S1-S8 switching control Signal, SR1, SR2 System relay, t1, t2, t3 , TE equal torque line, Tq torque or estimated torque value, Tqn current torque, Tqcom torque command value, Vamp line voltage effective value, Vb battery voltage or DC voltage, Vdd d-axis voltage command value, VH system voltage or after boost Voltage, VH # system voltage command value, VL pre-boosting voltage, Vq q-axis voltage command value, Vu, Vv, Vw phase voltage command value, θ rotor rotation angle, φ, φv voltage phase, ω angular velocity.

Claims (5)

A converter capable of boosting a DC voltage supplied from a DC power supply side, an inverter that converts a system voltage, which is a DC voltage output from the converter, into an AC voltage and outputs it as a motor drive voltage, and the converter and the inverter A motor drive control device comprising: a control unit that controls operation and switches the motor to a plurality of control modes and drives the motor;
The controller is
A control mode setting unit for setting the motor control mode to pulse width modulation control or rectangular wave control based on the modulation degree which is the ratio of the amplitude of the motor drive voltage to the system voltage;
When the motor control mode is an over-modulation control mode of the pulse width modulation control, and the converter is in a minimum boosting operation state or a low boosting operation state close to this, when the converter is boosted and stopped A modulation degree deriving unit for deriving a predicted modulation degree;
A boost stop execution unit that executes boost stop of the converter based on the predicted modulation degree;
Including a motor drive control device. The motor drive control device according to claim 1,
The control unit further includes a loss derivation comparing unit that derives and compares a predicted loss when the rectangular wave control mode is executed with the predicted modulation degree and a current loss at the current operation,
The boost stop unit performs a boost stop of the converter when the predicted loss is smaller than the current loss. In the motor drive control device according to claim 1 or 2,
The motor drive control device, wherein when the control mode corresponding to the predicted modulation degree is an overmodulation control mode, the boost stop unit immediately executes boost stop of the converter. In the motor drive control device according to any one of claims 1 to 3,
The control unit determines that the converter is in the lowest boosting operation state or a low boosting operation state close thereto when a boosting duty ratio of a switching element included in the converter is larger than a predetermined threshold value. . In the motor drive control device according to any one of claims 2 to 4,
The loss derivation comparing unit predicts a motor current when the rectangular wave control mode is executed with the predicted modulation degree as a current vector on the dq axis plane, and stores a predicted loss corresponding to the predicted current vector in advance. A motor drive control device that is derived with reference to the loss map.

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