JP2023034870A - Motor control device - Google Patents

Abstract

To improve control stability during switching between a PWM control mode and a square wave control mode.SOLUTION: A motor control device includes a current command value calculation unit that calculates a current command value which is a target current value on the basis of a target torque of a motor. The motor control device includes a voltage command value calculation unit that calculates a voltage command value for feedback-controlling a current measurement value to a current command value. The motor control device includes: a first operation unit that operates an inverter in a PWM control mode on the basis of the voltage command value; and a second operation unit that controls the inverter in a square wave control mode. The square wave control mode is a mode that controls a voltage phase of a square wave voltage applied to the motor. The motor control device includes a switching unit that switches an operation unit that operates the inverter between the first operation unit and the second operation unit. The motor control device includes a restriction unit that controls an upper limit of the voltage command value when the PWM control mode is executed by the first operation unit.SELECTED DRAWING: Figure 1

Description

The technology disclosed in this specification relates to a motor control device.

A technique is known for controlling the actual torque of a motor to a target torque by controlling an inverter. In this technique, a current command value, which is a target current value, is calculated based on the target torque of the motor. Then, feedback control is performed so that the measured current value of the current flowing through the motor becomes the current command value. Further, as shown in Patent Document 1, there is known a technique for switching control of an inverter between PWM control and rectangular wave control.

JP 2012-244804 A

The followability to the current command value may differ between the two controls. When there is a difference in follow-up performance, if chattering occurs due to frequent switching between the two controls, feedback control may be performed such that the measured current value deviates from the current command value. In this case, after the chattering ends, the actual torque may suddenly change and the vehicle may vibrate.

A motor control device disclosed in this specification includes a motor. A motor controller includes a current sensor that obtains a current measurement of the current flowing through the motor. The motor control device includes an inverter that drives the motor with AC power converted from DC power. The motor control device includes a current command value calculator that calculates a current command value, which is a target current value, based on a target torque of the motor. The motor control device includes a voltage command value calculator that calculates a voltage command value that is a manipulated variable for feedback-controlling a current measurement value to a current command value. The motor control device includes a first operation unit that operates the inverter in PWM control mode based on the voltage command value. The PWM control mode is a mode in which the motor is driven by PWM control. The motor control device includes a second operation section that controls the inverter in a rectangular wave control mode based on the voltage command value. The rectangular wave control mode is a mode for controlling the voltage phase of the rectangular wave voltage applied to the motor. The motor control device includes a switching section that switches an operating section that operates the inverter between a first operating section and a second operating section. The motor control device includes a limiting section that controls the upper limit of the voltage command value when the PWM control mode is executed by the first operating section.

In general, the PWM control mode has higher followability of feedback control than the rectangular wave control mode. Then, feedback control may be performed such that the measured current value deviates from the current command value due to the unbalance of the manipulated variable between the two control modes. In the technology of the present specification, the upper limit of the voltage command value, which is the manipulated variable of feedback control, is controlled during execution of the PWM control mode. As a result, it is possible to suppress the imbalance of the manipulated variable between the two control modes, so that the feedback control can be performed so that the measured current value does not deviate from the current command value.

Details and further improvements of the technology disclosed in this specification will be described in the embodiments of the invention.

2 is a block diagram of a power system of the motor control device 1; FIG. 7 is a graph showing d-axis and q-axis currents of a comparative example; 7 is a graph showing d-axis and q-axis currents of a comparative example; 4 is a graph for explaining a dq-axis command voltage CV;

(Configuration of motor control device 1)
A motor control device 1 of an embodiment will be described with reference to the drawings. A motor control device 1 according to an embodiment is mounted in a vehicle (for example, an electric vehicle or a hybrid vehicle) having a three-phase motor. FIG. 1 shows a block diagram of the electric power system of the motor control device 1. As shown in FIG. The motor control device 1 includes a control section 10 , an inverter 20 , a motor 30 , a high voltage battery 40 and a voltage detection section 50 . Note that FIG. 1 omits illustration of a boost converter that boosts the output voltage of high-voltage battery 40 and outputs the boosted voltage to inverter 20 . The motor 30 is connected via an inverter 20 to a high voltage battery 40 as a DC power supply. Voltage detection unit 50 detects the output voltage of high voltage battery 40 as power supply voltage PV of inverter 20 .

The motor 30 includes current sensors 31 and 32 and an angle detector 33 . Current sensor 31 detects V-phase current IV of motor 30 . Current sensor 32 detects W-phase current IW of motor 30 . The angle detector 33 detects the electrical angle θe of the motor 30 . As the angle detection unit 33, for example, an analog rotary encoder can be used.

The control unit 10 is mainly composed of a PCU. The control unit 10 is a part that controls the inverter 20 so as to feedback-control the output torque of the motor 30 to the command torque Tr. Note that the command torque Tr is input from, for example, a control device (not shown) provided outside the control unit 10 and above the control unit 10 .

A V-phase current IV, a W-phase current IW, and an electrical angle θe are input to the two-phase converter 11 . Two-phase conversion unit 11 converts U-phase current IU, V-phase current IV, and W-phase current IW in the three-phase fixed coordinate system of motor 30 into d-axis current Idr and q-axis current Idr in a dq coordinate system, which is a two-phase rotating coordinate system. Convert to current Iqr.

The command current calculator 12 calculates a d-axis command current Id and a q-axis command current Iq for realizing the command torque Tr based on the command torque Tr. In the present embodiment, currents for achieving maximum torque per ampere control are calculated as the d-axis command current Id and the q-axis command current Iq.

The d-axis deviation calculator 13 calculates a d-axis current deviation ΔId by subtracting the d-axis current Idr from the d-axis command current Id. A q-axis deviation calculator 14 calculates a q-axis current deviation ΔIq by subtracting the q-axis current Iqr from the q-axis command current Iq.

Based on the d-axis current deviation ΔId, the command voltage calculator 15 calculates the d-axis command voltage Vd, which is the manipulated variable for feedback-controlling the d-axis current Idr to the d-axis command current Id. Also, based on the q-axis current deviation ΔIq, the q-axis command voltage Vq, which is the manipulated variable for feedback-controlling the q-axis current Iqr to the q-axis command current Iq, is calculated. The command voltage calculator 15 also calculates the command voltage amplitude Vn based on the calculated d-axis command voltage Vd and q-axis command voltage Vq. The command voltage amplitude Vn can be calculated as the square root of the sum of the square value of the d-axis command voltage Vd and the square value of the q-axis command voltage Vq.

The limiting unit 16 is a part that performs processing for limiting the upper limits of the d-axis command voltage Vd, the Vq-axis command voltage Vq, and the command voltage amplitude Vn. The limiting unit 16 outputs a limited d-axis command voltage Vd_L, a limited q-axis command voltage Vq_L, and a limited command voltage amplitude Vn_L with a limited upper limit. Note that the processing in the restriction unit 16 will be described in detail later.

The switching determination unit 17 calculates the modulation factor M. Here, the modulation factor M is a value obtained by normalizing the command voltage amplitude Vn with the power supply voltage PV detected by the voltage detection section 50 . That is, the modulation factor M is the ratio of the fundamental wave component (rms value) of the motor applied voltage (line voltage) to the power supply voltage PV.

The operation signal generator 18 is a part that calculates three-phase command voltages VU, VV, and VW whose phases are shifted by an electrical angle of 120 degrees from each other, and outputs them to the inverter 20 . The operation signal generation section 18 includes a first operation section 18a, a second operation section 18b, and a switching section 18c. The first operation unit 18a is a part that operates the inverter 20 in the PWM control mode based on the limited d-axis command voltage Vd_L, the limited q-axis command voltage Vq_L, and the limited command voltage amplitude Vn_L. The second operation part 18b is a part that operates the inverter 20 in the rectangular wave control mode based on the d-axis command voltage Vd, the Vq-axis command voltage Vq, and the command voltage amplitude Vn.

The PWM control mode is a mode in which the duty is controlled so that the fundamental wave component becomes a sine wave. The rectangular wave control mode is a mode in which one pulse of a rectangular wave with a high-level period to low-level period ratio of 1:1 is applied to the motor. In the PWM control mode, the amplitude and phase of the voltage applied to the motor are the manipulated variables, whereas in the rectangular wave control mode, only the phase of the voltage applied to the motor is the manipulated variable. Therefore, when the PWM control mode is applied, control responsiveness is higher than when the rectangular wave control mode is applied. Since the PWM control mode and the rectangular wave control mode are well-known techniques, detailed description thereof will be omitted.

The switching portion 18 c is a portion that selects one of the first operating portion 18 a and the second operating portion 18 b based on the modulation factor M and connects it to the inverter 20 . When the modulation rate M is less than the predetermined threshold modulation rate Mth, the first operation section 18a is selected and operates in the PWM control mode. When the modulation rate M is equal to or greater than the threshold modulation rate Mth, the second operation section 18b is selected and operates in the rectangular wave control mode.

(Issues during chattering)
A problem that occurs when chattering frequently switches between the rectangular wave control mode and the PWM control mode will be described. As a comparative example, a case without the restriction unit 16 of the present specification will be described with reference to FIGS. 2 and 3. FIG.

The horizontal and vertical axes in FIGS. 2 and 3 indicate d-axis and q-axis currents, respectively. The dq-axis command current CI is a command current for performing the aforementioned minimum current maximum torque control. The dq-axis command current CI is a vector determined by the d-axis command current Id and the q-axis command current Iq. The dq-axis command current CI moves on the current command line IL. dq-axis actual current AI is the actual current value measured by current sensors 31 and 32 . The dq-axis actual current AI is a vector determined by the d-axis current Idr and the q-axis current Iqr. The dq-axis actual current AI plotted with squares indicates that the square wave control mode is being executed. The dq-axis actual current AI plotted with circles indicates that the PWM control mode is being executed.

The current command line IL represents the locus of the current vector indicating the current phase that maximizes the torque for the same current on the dq axis plane. The control switching line CL is a line serving as a reference for switching control between the rectangular wave control mode and the PWM control mode. The rectangular wave control mode is mainly executed above the control switching line CL, and the PWM control mode is mainly executed below the control switching line CL. The constant torque line TL is a line connecting points with equal torque on the dq axis plane.

In the motor control device of the comparative example, when chattering occurs, the dq-axis actual current AI may change so as to deviate from the dq-axis command current CI. A specific description will be given below.

The d-axis current Idr and the q-axis current Iqr measured by the current sensors 31 and 32 contain errors. When feedback control is performed using the d-axis current Idr and the q-axis current Iqr having this error, as shown in FIG. It may fluctuate to draw FIG. 2 shows, as an example, how the dq-axis actual current varies from AI1 to AI5. The center of this circular locus is the switching command current CIs.

The switching command current CIs will be described. When the rectangular wave control mode is switched to the PWM control mode, feedback control is performed using switching command currents CIs in place of the dq-axis command currents CI. That is, at the time of switching, the command value used for control is temporarily set to the switching command current CIs. Then, the switching command current CIs is gradually brought closer to the original dq-axis command current CI. This processing is called "current command filtering" in this specification. As a result, even when the rectangular wave control mode is switched to the PWM control mode in a state where the actual dq-axis current AI is greatly deviated from the dq-axis command current CI, the current suddenly follows the dq-axis command current CI. can be prevented. Therefore, sudden changes in torque can be suppressed.

As described above, the PWM control mode has higher responsiveness than the rectangular wave control mode. Therefore, the amount of variation VA1 (the amount of variation from right to left in FIG. 2) during the PWM control mode is greater than the amount of variation VA2 (the amount of variation from left to right in FIG. 2) during the rectangular wave control mode. . During chattering, the next switching from the rectangular wave control mode to the PWM control mode is performed before the switching command current CIs approaches the dq-axis command current CI. Therefore, feedback is repeatedly performed using the switching command current CIs, which is a temporary command value. As a result, as shown in FIG. 3, the entire circular trajectory drawn by the dq-axis actual currents AI11 to AI15 moves away from the dq-axis command current CI (moves to the left). As described above, the switching command current CIs largely deviates from the dq-axis command current CI due to the unbalanced amount of variation in the actual current between the two control modes.

(Operation and effects of the limiting unit 16 of the present embodiment)
The motor control device 1 of the present embodiment can solve the above-described problem during chattering by including the limiting section 16 . Details are given below. The dq-axis command voltage CV will be described with reference to FIG. The horizontal and vertical axes in FIG. 4 indicate the d-axis and q-axis voltages, respectively. The dq-axis command voltage CV is a vector determined by the d-axis command voltage Vd and the q-axis command voltage Vq. By dq-axis command voltage CV, dq-axis actual current AI can be feedback-controlled so as to approach dq-axis command current CI or switching command current CIs.

A voltage command line VL indicates the trajectory of the voltage command value in the rectangular wave control mode. That is, the voltage command line VL is a trajectory when only the voltage phase φd is changed while the magnitude of the voltage command value is fixed to the magnitude obtained by multiplying the power supply voltage PV by a constant rate. The modulation rate in the PWM control mode is, in principle, less than or equal to the modulation rate in the rectangular wave control mode. Therefore, the voltage command line VL indicates the maximum voltage that can be output in the PWM control mode. That is, the region R1 not exceeding the voltage command line VL (the region on the right side with respect to the voltage command line VL) is originally the region in which output is possible in the PWM control mode. A region R2 beyond the voltage command line VL (region on the left side of the voltage command line VL) is a region in which output cannot be performed in the PWM control mode. Therefore, in the PWM control mode, the dq-axis command voltage CV is preferably within the region R1.

However, during execution of the current command filtering process described above, the switching command current CIs is used as the command value instead of the dq-axis command current CI. This switching command current CIs is a value that is used temporarily, as described above. As described above with reference to FIG. 2, due to the imbalance between the fluctuation amounts VA1 in the PWM control mode is larger than the fluctuation amount VA2 in the rectangular wave control mode, the command current CIs during switching is reduced to the dq-axis command current. The left side of FIG. 2 is commanded to CI. In order to feed back so as to approach the switching command current CIs that deviates to the left, the dq-axis command voltage CV commands a voltage within the region R2 that exceeds the normal voltage range (voltage command line VL) during the PWM control mode. (See FIG. 4). In other words, excessive and unnecessary fluctuations occur in the fluctuation amount VA1 in the PWM control mode. As a result, the dq-axis actual current AI continues to move gradually to the left in FIG. 2 with respect to the dq-axis command current CI.

Therefore, the technique of the present specification includes the limiting unit 16 . After the feedback in the command voltage calculation unit 15, the limit unit 16 sets the voltage command values (d-axis command voltage Vd, q-axis command voltage Vq, voltage amplitude Vn) before outputting the control signal from the operation signal generation unit 18. Limit the upper limit. Specifically, the d-axis command voltage Vd, the q-axis command voltage Vq, and the voltage amplitude Vn are input to the limiter 16 . As shown in FIG. 4, when the input dq-axis command voltage CV is within the region R2 beyond the voltage command line VL, Vd_limit d is set so that the dq-axis command voltage CV_L is within the region R1. Axis command voltage Vd_L, limit q-axis command voltage Vq_L, and limit command voltage amplitude Vn_L are calculated (see arrow Y1). As a result, it is possible to suppress unnecessary operation of the dq-axis actual current AI exceeding the voltage command line VL during the PWM control mode. That is, it is possible to suppress excessive and unnecessary fluctuations that occur in the fluctuation amount VA1 during the PWM control mode. As a result, the unbalanced amount of variation can be suppressed, so that feedback control can be performed so that the dq-axis actual current AI does not deviate from the dq-axis command current CI.

Although specific examples of the present invention have been described in detail above, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above. The technical elements described in this specification or in the drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims as of the filing. In addition, the techniques exemplified in this specification or drawings can simultaneously achieve a plurality of purposes, and achieving one of them has technical utility in itself.

1: Motor control device 10: Control unit 12: Command current calculation unit 15: Command voltage calculation unit 16: Limitation unit 18a: First operation unit 18b: Second operation unit 18c: Switching unit 20: Inverter 30: Motor 31, 32 : Current sensor 40: High voltage battery

Claims (1)

A motor control device,
a motor;
a current sensor for obtaining a current measurement of the current flowing through the motor;
an inverter that drives the motor with AC power converted from DC power;
a current command value calculation unit that calculates a current command value, which is a target current value, based on the target torque of the motor;
a voltage command value calculation unit that calculates a voltage command value that is a manipulated variable for feedback-controlling the current measurement value to the current command value;
A first operation unit for operating the inverter in a PWM control mode based on the voltage command value, wherein the PWM control mode is a mode for driving the motor by performing PWM control. and,
A second operation unit for controlling the inverter in a rectangular wave control mode based on the voltage command value, wherein the rectangular wave control mode is a mode for controlling the voltage phase of the rectangular wave voltage applied to the motor. , the second operation unit;
a switching unit for switching an operation unit for operating the inverter between the first operation unit and the second operation unit;
a limiting unit that controls the upper limit of the voltage command value when the PWM control mode is executed by the first operation unit;
A motor controller.

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