Motor control device

Abstract

The objective is to provide a motor control device that can suppress the effects of ripple. [Solution] The motor control device according to this embodiment includes an inverter having a plurality of switching elements that generates a plurality of phase AC currents supplied to the motor, and a current sensor that detects each phase current among the plurality of phase AC currents generated by the inverter. The inverter has a current control unit that performs feedback control of the plurality of phase AC currents supplied to the motor based on the detection results of the current sensor, and the current control unit excludes the detection results of the current sensor corresponding to the switching timing of the switching elements from the feedback control.

Description

Technical Field

[0001] Embodiments according to the present invention relate to a motor control device.

Background Art

[0002] A three-phase AC synchronous motor may be controlled by an inverter of the PWM (Pulse Width Modulation) method. The control of the three-phase AC synchronous motor is performed, for example, by feeding back the phase current acquired from the current sensor of each phase. Also, a command to the motor is controlled (current control) so that a current according to the command flows by applying a voltage by switching the gates of the upper and lower power modules of each phase at an appropriate duty (PWM). In principle, at the moment when this gate is switched, a ripple occurs in the current. If the timing of detecting the phase current and the timing of this switching match, the ripple current is controlled as feedback, so that this ripple becomes even larger.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] An object is to provide a motor control device capable of suppressing the influence of ripple.

Means for Solving the Problems

[0005] The motor control device according to this embodiment includes an inverter having a plurality of switching elements that generates a plurality of phase alternating currents supplied to the motor, and a current sensor that detects the phase current of each of the plurality of phase alternating currents generated by the inverter. The inverter has a current control unit that performs feedback control of the plurality of phase alternating currents supplied to the motor based on the detection results of the current sensor, and the current control unit excludes the detection results of the current sensor corresponding to the switching timing of the switching elements from the feedback control. [Brief explanation of the drawing]

[0006] [Figure 1] This is a block diagram showing an example of the configuration of a motor control device according to the first embodiment. [Figure 2] This figure shows an example of the decision to adopt or exclude current feedback in the first embodiment. [Modes for carrying out the invention]

[0007] Embodiments of the present invention will be described below with reference to the drawings. These embodiments are not limiting to the present invention. The drawings are schematic or conceptual, and the proportions of each part may not necessarily be the same as those of actual objects. In the specification and drawings, elements similar to those described above with respect to previously shown drawings are denoted by the same reference numerals, and detailed explanations are omitted as appropriate.

[0008] (First Embodiment) Figure 1 is a block diagram showing an example of the configuration of the motor control device 100 according to the first embodiment.

[0009] The motor control device 100 comprises a motor 10, an angle sensor 20, a current sensor 30, a controller 40, and an inverter 50.

[0010] At least a part of the motor control device 100, including the inverter 50, is, for example, for automotive use, but may also be used in industrial machinery, etc.

[0011] Motor 10 is connected to a drive mechanism (not shown) and operates the drive mechanism. Motor 10 is, for example, an EV (Electric Vehicle) motor, but may also be an industrial machinery motor or the like.

[0012] The angle sensor 20 detects the angle (position) of the motor 10. The angle sensor 20 transmits angle feedback of the detected angle to the inverter 50. The angle sensor 20 also transmits speed feedback to the inverter 50. The speed feedback is obtained by differentiating the angle feedback. The angle sensor 20 is, for example, an encoder or a resolver.

[0013] The current sensor 30 detects the current values ​​of U, V, and W supplied to the motor 10. In other words, the current sensor 30 detects the current value of each phase current among the multiple phase AC currents generated by the inverter 50. The current sensor 30 transmits the detected current values ​​to the inverter 50 as current feedback.

[0014] The controller 40 generates a speed command for the motor 10 and transmits the speed command for the motor 10 to the inverter 50. The controller 40 is, for example, an ECU (Electronic Control Unit).

[0015] The inverter 50 has multiple switching elements. The inverter 50 generates alternating current by, for example, generating a PWM (Pulse Width Modulation) signal and applying appropriate voltages to each of the multiple phases of the motor 10.

[0016] The inverter 50 receives speed commands from the controller 40. The inverter 50 receives feedback information from the angle sensor 20 and the current sensor 30. The inverter 50 generates a three-phase alternating current through feedback control and supplies the three-phase alternating current to the motor 10.

[0017] The inverter 50 includes a speed control unit 51 and a current control unit 52.

[0018] The speed control unit 51 receives a speed command from the controller 40 and generates a speed feedback by differentiating the angle feedback received from the angle sensor 20. The speed control unit 51 generates a current command such that the speed feedback becomes equivalent to the speed command by feedback control, and transmits the current command to the current control unit 52.

[0019] The current control unit 52 receives a current command from the speed control unit 51, receives an angle feedback from the angle sensor 20, and receives a current feedback from the current sensor 30. The current control unit 52 applies a voltage such that the current feedback becomes equivalent to the current command to the U-phase, V-phase, and W-phase of the motor 10 by vector control and feedback control, thereby supplying currents U, V, W (three-phase alternating current) to the motor 10. That is, the current control unit 52 performs feedback control on the plurality of phases of alternating current supplied to the motor 10 based on the detection result of the current sensor 30. The current control unit 52 controls the plurality of phases of alternating current supplied to the motor 10 by, for example, controlling the PWM signal input to the switching element of the inverter 50.

[0020] Here, at the moment when the switching element of the inverter 50 switches, a ripple occurs in the current. The ripple leads to noise in the current feedback.

[0021] Therefore, the current control unit 52 excludes the detection result of the current sensor 30 corresponding to the switching timing of the switching element from the feedback control. Thereby, it is possible to perform current control feedback by omitting the current feedback affected by the ripple. As a result, the influence of the ripple can be suppressed and the efficiency can be improved. The improvement in efficiency contributes to extending the operation time of the EV device whose input is a battery.

[0022] The current control unit 52 includes a storage unit 521 and a calculation unit 522.

[0023] The memory unit 521 receives current feedback from the current sensor 30. The memory unit 521 accumulates (stores) the received current feedback. The data of the current feedback is accumulated in the memory unit 521, for example, by DMA (Direct Memory Access), suppressing the burden on the arithmetic unit 522.

[0024] The arithmetic unit 522 determines the current feedback to be used for feedback control or the current feedback to be excluded from feedback control by performing analysis (arithmetic processing) on the current feedback accumulated in the memory unit 521. The arithmetic unit 522 is, for example, a CPU (Central Processing Unit).

[0025] Next, the procedure for determining the adoption and exclusion of current feedback will be described.

[0026] The current control unit 52 (arithmetic unit 522) excludes from the feedback control the detection result of the current sensor 30 corresponding to the switching timing of the switching element from the plurality of detection results of the current sensor 30 accumulated during a predetermined period. The predetermined time is, for example, the current control cycle of the current control unit 52.

[0027] First, the arithmetic unit 522 acquires the number of times of phase current AD data sampling by the current sensor 30 in the current control cycle.

[0028] The current control cycle is, for example, 25 μs. The conversion time of AD data is 1 μs per channel. The data of the current feedback of each of the U-phase, V-phase, and W-phase currents enables the sample hold function of the AD controller to ensure synchronization. However, due to hardware reasons, if there is one additional AD data per channel in this sample hold group, it takes 4 μs for one set. Therefore, approximately 6.25 (25 / 4) times of current feedback data is accumulated in the memory unit 521. Note that the above 4 μs varies depending on the performance of the AD.

[0029] Next, the calculation unit 522 loops for the number of AD data sampling times to obtain a total of 6 types (3 x 2) of AD arrays representing the maximum and minimum values ​​of the U-phase current, V-phase current, and W-phase current.

[0030] Furthermore, these six sequence numbers may be identical.

[0031] Next, the arithmetic unit 522 loops for the number of AD data sampling times and obtains the last array index, excluding the six types of maximum and minimum array indexes.

[0032] Furthermore, the calculation unit 522 acquires the sampled and held U-phase current, V-phase current, and W-phase current so that the data is at the same timing.

[0033] Next, the calculation unit 522 acquires the AD data as phase current data to be used for control.

[0034] Figure 2 shows an example of the decision to adopt or exclude current feedback in the first embodiment. Figure 2 shows the current feedback data from the 1st to the 6th time, accumulated every 4 microseconds during the current control period (25 microseconds). Current feedback UN, VN, and WN (N=1~6) are the current feedback for currents U, V, and W at the Nth time, respectively.

[0035] The calculation unit 522 analyzes the current feedback data for each current control cycle. The calculation unit 522 selects the data least affected by switching noise (ripple) for the feedback control of currents U, V, and W.

[0036] The current control unit 52 (calculation unit 522) excludes the detection result of the current sensor 30 corresponding to the timing when any phase current becomes maximum or minimum during a predetermined period from the feedback control.

[0037] In the example shown in Figure 2, the maximum value of the U phase is U1, and the minimum value of the U phase is U6. The maximum value of the V phase is V2, and the minimum value of the V phase is V6. The maximum value of the W phase is W2, and the minimum value of the W phase is W5.

[0038] The current control unit 52 (calculation unit 522) uses the detection results of the current sensor 30 at the same timing for each phase current for feedback control. The calculation unit 522 uses data at the same timing that is unaffected by switching for all three phase currents for feedback control. In other words, the calculation unit 522 does not use current feedback at different timings for each phase (in the example shown in Figure 2, the 5th data for the U and V phases, and the 4th data for the W phase).

[0039] Therefore, the arithmetic unit 522 excludes the 1st, 2nd, 5th, and 6th data points from the feedback control.

[0040] The current control unit 52 (calculation unit 522) adopts the most recent detection result from the current sensor 30, which is not excluded from the feedback control, for the feedback control. By adopting the most recent current data for the feedback control, the control dead time can be reduced and the control performance can be improved.

[0041] Therefore, the calculation unit 522 uses the most recent fourth data point from the third and fourth data points that were not excluded for feedback control.

[0042] Furthermore, at any given timing, if any phase current is at its maximum or minimum, the calculation unit 522 adopts the most recent current feedback data. In other words, if the current control unit 52 (calculation unit 522) excludes all detection results other than the most recent detection result of the current sensor 30 from the feedback control, it adopts the detection result of the most recent current sensor 30 into the feedback control without excluding it. By adopting the most recent current data into the feedback control, control dead time can be reduced and control performance can be improved.

[0043] As described above, according to the first embodiment, the current control unit 52 excludes the detection result of the current sensor 30 corresponding to the switching timing of the switching element from the feedback control. This suppresses the effects of ripple and improves efficiency. This improved efficiency contributes to extending the operating time of EV equipment whose input is a battery.

[0044] Current control may be performed by hardware such as an ASIC (Application Specific Integrated Circuit) rather than a CPU like the arithmetic unit 522. The ASIC performs current control each time it acquires the detection result from the current sensor 30. This current control period corresponds to the AD conversion time of the current sensor 30 and is short, approximately 4 microseconds. In this case, current data affected by switching will be used for control, but because it is short compared to half a switching period (50 microseconds for a PWM frequency of 10 kHz), it is less susceptible to the effects of switching.

[0045] In contrast, the first embodiment uses a CPU such as the arithmetic unit 522. Since current control is not performed for each current sample as in an ASIC, the impact on the CPU load is small. Furthermore, even if an ASIC is not used, or if it is not possible to use an ASIC, current control can be performed while suppressing the effects of ripple using a CPU such as the arithmetic unit 522.

[0046] Furthermore, in the switching generation logic, there is a period of non-switching every half-cycle of the PWM frequency. It is conceivable to acquire current data at this time. However, in this case, changing the PWM frequency would change the period. Current control requires not only current data but also magnetic pole position information acquired from the angle sensor, and since this must be coordinated with the detection period of the angle sensor, it is undesirable for the current control period to change depending on the PWM frequency setting.

[0047] In contrast, in the first embodiment, the effect of ripple can be suppressed without changing the current control period.

[0048] At least a portion of the data processing method in the motor control device according to this embodiment may be implemented in hardware or in software. If implemented in software, a program that implements at least a portion of the functions of the data processing method may be stored on a recording medium such as a flexible disk or CD-ROM, loaded into a computer, and executed. The recording medium is not limited to removable ones such as magnetic disks or optical disks, but may also be a fixed recording medium such as a hard disk drive or memory. Furthermore, the program that implements at least a portion of the functions of the data processing method may be distributed via a communication line such as the Internet (including wireless communication). In addition, the program may be encrypted, modulated, or compressed, and then distributed via a wired or wireless line such as the Internet, or stored on a recording medium.

[0049] While several embodiments of the present invention have been described, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These embodiments can be carried out in a variety of other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims and their equivalents. [Explanation of Symbols]

[0050] 100 Motor control device, 10 Motor, 20 Angle sensor, 30 Current sensor, 40 Controller, 50 Inverter, 51 Speed ​​control unit, 52 Current control unit, 521 Memory unit, 522 Calculation unit

Claims

1. An inverter having multiple switching elements that generates multi-phase alternating current supplied to a motor, A current sensor detects the current value of each phase current among the multiple phase AC currents generated by the inverter, Equipped with, The aforementioned inverter is The motor has a current control unit that provides feedback control of the multi-phase AC current supplied to the motor based on the detection results of the current sensor. The current control unit is a motor control device that excludes the detection result of the current sensor corresponding to the switching timing of the switching element from the feedback control.

2. The motor control device according to claim 1, wherein the current control unit excludes from the feedback control the detection result of the current sensor that corresponds to the switching timing of the switching element from a plurality of detection results of the current sensor accumulated during a predetermined period.

3. The motor control device according to claim 2, wherein the current control unit excludes from the feedback control the detection result of the current sensor corresponding to the timing in which any phase current becomes maximum or minimum during the predetermined period.

4. The motor control device according to claim 2, wherein the current control unit adopts the most recent detection result of the current sensor from among the detection results of the current sensor that are not excluded from the feedback control for the feedback control.

5. The motor control device according to claim 2, wherein, when the current control unit excludes all detection results other than the most recent detection result of the current sensor from the feedback control, the most recent detection result of the current sensor is adopted into the feedback control without being excluded from the feedback control.

6. The motor control device according to claim 2, wherein the current control unit employs the detection results of the current sensor at the same timing for each phase current in feedback control.

7. The motor control device according to claim 2, wherein the predetermined period is the current control period of the current control unit.

8. The motor control device according to claim 1, wherein the current control unit controls the multi-phase AC current supplied to the motor by controlling the PWM signal input to the switching element.

9. The motor control device according to claim 1, further comprising the motor.

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