Motor Control System

Abstract

To provide a technology capable of suppressing motor vibrations.SOLUTION: A motor control system controls the operation of a motor including a stator having one of an armature winding and a field winding and a rotor having the other of the armature winding and the field winding. The motor control system includes a first inverter that supplies armature current to the armature winding, a second inverter that supplies field current to the field winding, and a control device that controls the operation of the first inverter and the second inverter. The control device is configured to be capable of performing harmonic superposition processing to at least partially cancel harmonics appearing in the motor by superimposing harmonic currents on the field currents on the basis of a motor operation index indicating the operation of the motor.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The technology disclosed in this specification relates to a motor control system. [Background technology]

[0002] Patent Document 1 discloses a motor control system including a motor having a stator with an armature winding and a rotor with a field winding, and a control device that controls the operation of the motor. In the stator, a rotating magnetic field is generated by an armature current (three-phase AC) flowing through the armature winding. In the rotor, a DC magnetic field is generated by a field current (DC) flowing through the field winding. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-40424 Summary of the Invention [Problem to be solved by the invention]

[0004] Typically, slots for accommodating armature windings are provided intermittently along the circumferential direction of the stator (or rotor). As a result, the magnetic flux density of the rotating magnetic field is not uniform along the circumferential direction of the stator (or rotor). Therefore, the rotating magnetic field contains vibration components also known as spatial harmonics. Furthermore, the armature current contains vibration components also known as time harmonics due to the switching operation of the first inverter. Conventional motor control systems are unable to cancel out these harmonics, which can cause the motor to vibrate. This specification provides a technology capable of suppressing motor vibration. [Means for solving the problem]

[0005] The motor control system disclosed in this specification controls the operation of a motor including a stator having one of an armature winding and a field winding, and a rotor having the other of the armature winding and the field winding. The motor control system includes a first inverter that supplies an armature current to the armature winding, a second inverter that supplies a field current to the field winding, and a control device that controls the operation of the first inverter and the second inverter. The control device is configured to perform a harmonic superposition process that at least partially cancels harmonics appearing in the motor by superimposing a harmonic current on the field current based on a motor operation index that indicates the operation of the motor.

[0006] The characteristics (e.g., waveforms) of the spatial harmonics and temporal harmonics are determined from the motor structure and motor operation indices (e.g., rotor rotation speed, torque command value). Since the motor structure is known, once the motor operation indices are known, the harmonic characteristics can be determined. With the above configuration, the motor operation indices can be acquired, and therefore the harmonic characteristics can be determined. Based on the determined harmonic characteristics, harmonic currents capable of at least partially canceling the harmonics can also be determined. Therefore, with the above configuration, harmonics appearing in the motor can be at least partially canceled, thereby suppressing motor vibration.

[0007] In this specification, spatial harmonics and temporal harmonics may be collectively referred to simply as "harmonics." [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a diagram schematically illustrating a motor control system 2 according to an embodiment. [Figure 2] 3 is a diagram showing waveforms of armature currents Iu, Iv, and Iw flowing through an armature winding 18 in a motor control system 2 according to the embodiment. FIG. [Figure 3] 4 is a flowchart showing a harmonic superimposition process executed by a processor 26 in the motor control system 2 according to the embodiment. [Figure 4]4A to 4C are diagrams showing waveforms of the field current If and the output torque To when no harmonic superimposition processing is performed in the motor control system 2 according to the embodiment. [Figure 5] 3A to 3C are diagrams showing waveforms of the field current If and the output torque To when harmonic superposition processing is performed in the motor control system 2 according to the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] In one or more embodiments, the control device may store a waveform table that describes waveforms of the harmonic currents to be superimposed on the field current in association with the motor operation index.

[0010] If the control device were configured to determine the harmonic characteristics one by one from the acquired motor performance indicators, it would take time to determine the harmonic current, which could slow the response speed of the control to the harmonics. With the above configuration, the control device stores a waveform table, so the waveform of the high-frequency current to be superimposed is determined relatively quickly in response to the acquired motor performance indicators. This allows the response speed of the control to the harmonics to be faster.

[0011] In one or more embodiments, the control device may perform the harmonic superposition process when the motor performance indicator is within a predetermined range, and may not perform the harmonic superposition process when the motor performance indicator is not within a predetermined range.

[0012] For example, when the motor's output torque (an example of a motor operation index) is large, the device or mechanism receiving the output torque is expected to operate vigorously. In this case, the device or mechanism may experience relatively large vibrations regardless of the motor's vibration. Since the main purpose of suppressing motor vibration is to suppress the vibration of the device or mechanism that operates in response to the output torque, suppressing motor vibration is not very meaningful when the output torque is large. In other words, performing harmonic superposition processing is not very meaningful. Considering the energy loss associated with the superposition of harmonic currents, performing harmonic superposition processing in this case is actually ineffective. With the above configuration, it is possible to distinguish between cases where harmonic superposition processing is not performed when the output torque is large and where it is performed when the output torque is small. Therefore, harmonic superposition processing can be performed only when it is effective.

[0013] In one or more embodiments, the stator may include the armature winding, the rotor may include the field winding, and the armature winding may be a three-phase winding.

[0014] In one or more embodiments, the motor operation indicators may include at least one of a rotational speed of the rotor and a torque command value for the motor.

[0015] (Example) 1 is mounted on a vehicle (not shown). The motor control system 2 includes a power supply device 4, a motor 6, a first inverter 8, a second inverter 10, a rotation detection unit 12, an accelerator pedal 14, and a control device 16.

[0016] The power supply device 4 is, for example, a battery mounted on a vehicle, and can also be considered a DC power supply. The motor 6 includes a stator 20 having an armature winding 18 and a rotor 24 having a field winding 22. The armature winding 18 includes a U-phase winding 18u, a V-phase winding 18v, and a W-phase winding 18w. The first inverter 8 electrically connects the power supply device 4 to the armature winding 18. The second inverter 10 electrically connects the power supply device 4 to the field winding 22. Although not shown, the first inverter 8 and the second inverter 10 each include a switching element. By operating the switching element, the first inverter 8 and the second inverter 10 can convert the DC current supplied from the power supply device 4 into AC current. The rotation detection unit 12 is a sensor (e.g., a resolver) that detects the rotation of the rotor 24. The rotation detection unit 12 inputs a pulse signal Ps indicating the magnetic pole position of the rotor 24 to the control device 16. For example, the rotation speed Rv of the rotor 24 can be determined from the pulse signal Ps. The accelerator pedal 14 is a part for accepting an operation by a user. The depression amount As of the accelerator pedal 14 is input to the control device 16.

[0017] The control device 16 includes a processor 26 and a memory 28. The memory 28 stores various information including a waveform table 30 (described in detail below) and a torque table 32. The torque table 32 describes a torque command value Tc to be obtained in association with any combination of the rotation speed Rv of the rotor 24 and the depression amount As of the accelerator pedal 14.

[0018] The processor 26 controls the operation of each part of the motor control system 2 in accordance with a predetermined program stored in the memory 28.

[0019] (Basic processing performed by processor 26) The processor 26 performs switching control for the first inverter 8, thereby supplying armature currents (three-phase AC) Iu, Iv, and Iw as shown in FIG. 2 to the armature winding 18. The processor 26 also supplies the field current If to the field winding 22 by conducting current between the power supply device 4 and the field winding 22 without performing switching control for the second inverter 10. At this time, the rotor 24 rotates due to the interaction between the rotating magnetic field generated by the armature currents Iu, Iv, and Iw and the magnetic field generated by the field current If. In other words, the motor 6 is driven. The processor 26 also performs PWM control on the first inverter 8, for example, to cause the output torque To of the motor 6 to follow the torque command value Tc obtained from the torque table 32.

[0020] However, the armature currents Iu, Iv, and Iw contain time harmonics due to the switching operation of the first inverter 8. The rotating magnetic field contains spatial harmonics due to the structure of the motor 6. In the conventional motor control system 2, these harmonics are applied to the output torque To of the motor 6, which can result in the motor 6 vibrating. To suppress these phenomena, the processor 26 of this embodiment executes a harmonic superposition process, which will be described later.

[0021] (Harmonic superposition processing; Figure 3) In step S2, the processor 26 acquires the rotation speed Rv and the torque command value Tc. After step S2, the process proceeds to step S4.

[0022] In step S4, processor 26 determines whether or not a harmonic superposition condition is satisfied. The harmonic superposition condition includes, for example, a condition that the rotation speed Rv acquired in step S2 exceeds a predetermined value and / or a condition that the torque command value Tc acquired in step S2 exceeds a predetermined value. If it is determined that the harmonic superposition condition is not satisfied (NO), the processing shown in Fig. 3 ends. If it is determined that the harmonic superposition condition is satisfied (YES), the processing proceeds to step S6.

[0023] In step S6, processor 26 refers to waveform table 30 to obtain the waveform of the harmonic current to be superimposed on field current If. Waveform table 30 describes the waveform of the harmonic current to be superimposed on field current If in association with any combination of rotational speed Rv and torque command value Tc. Therefore, in step S6, the waveform of the harmonic current associated with the combination of rotational speed Rv and torque command value Tc obtained in step S2 is obtained. After step S6, the process proceeds to step S8.

[0024] In step S8, processor 26 superimposes the harmonic current having the waveform acquired in step S4 on field current If. Specifically, processor 26 superimposes the harmonic current on field current If by performing switching control for second inverter 10. After step S8, the process shown in FIG. 3 ends.

[0025] (Effect of harmonic superposition processing) With the rotation speed Rv and torque command value Tc held constant, the operation of the motor 6 when harmonic superposition processing is not performed is compared with the operation of the motor 6 when harmonic superposition processing is performed. Based on the comparison results, the effect of harmonic superposition processing will be explained.

[0026] As can be seen from Figure 4, when harmonic superposition processing is not performed, the field current If becomes DC. In this case, the field current If does not contain any vibration components that cancel out the harmonics. However, vibration components caused by the harmonics are applied to the output torque To of the motor 6.

[0027] As can be seen from Figure 5, when harmonic superposition processing is performed, harmonic currents are superimposed on the field current If. The waveform of the field current If after the harmonic currents are superimposed has a shape that is an inversion of the waveform of the harmonics generated at that time (see the lower part of Figure 4). Because the harmonics are canceled out by this field current If, vibration components caused by the harmonics are not applied to the output torque To of the motor 6. Therefore, by performing harmonic superposition processing, vibration of the motor 6 is suppressed.

[0028] (Variation) The motor control system 2 may be mounted on a device or mechanism other than a vehicle (for example, a work machine).

[0029] The stator 20 may include a field winding 22. The rotor 24 may include the armature winding 18.

[0030] The armature winding 18 may be a two-phase winding or a multi-phase winding having four or more phases.

[0031] The torque command value Tc may be determined independently of the rotation speed Rv of the rotor 24. For example, instead of the accelerator pedal 14, a device (such as a remote control) that can directly input the torque command value Tc may be provided.

[0032] In the harmonic superposition process, after step S2, processor 26 may execute the process of step S6 without executing the process of step S4.

[0033] The waveform table 30 may contain information indicating the waveform of the harmonic current to be superimposed on the field current If, and a switching pattern for superimposing the waveform on the field current If. The processor 26 may perform switching control of the second inverter 10 based on the switching pattern.

[0034] The waveform table 30 may describe the waveform of the harmonic current to be superimposed on the field current If in association with either the rotational speed Rv or the torque command value Tc. That is, the processor 26 may obtain the waveform of the harmonic current to be superimposed on the field current If based on either the rotational speed Rv or the torque command value Tc.

[0035] Although specific examples of the technology disclosed in this specification 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 variations of the specific examples exemplified above. The technical elements described in this specification or in the drawings exhibit technical utility alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. The technology exemplified in this specification or in the drawings can achieve multiple objectives simultaneously, and achieving one of these objectives itself has technical utility. [Explanation of symbols]

[0036] 2: Motor control system, 4: Power supply unit, 6: Motor, 8: First inverter, 10: Second inverter, 12: Rotation detection unit, 14: Accelerator pedal, 16: Control device, 18: Armature winding, 18u: U-phase winding, 18v: V-phase winding, 18w: W-phase winding, 20: Stator, 22: Field winding, 24: Rotor, 26: Processor, 28: Memory, 30: Waveform table, 32: Torque table

Claims

1. A motor control system for controlling the operation of a motor, comprising: The motor a stator having one of an armature winding and a field winding; a rotor having the other of the armature winding and the field winding, the armature winding is a three-phase winding, The motor control system includes: a first inverter for supplying a three-phase AC armature current to the armature winding; a second inverter for supplying a field current to the field winding; a control device that controls operations of the first inverter and the second inverter, the control device is configured to supply the armature current to the armature winding by performing switching control for the first inverter based on the rotational speed of the rotor and a torque command value for the motor, the control device stores a waveform table describing waveforms of harmonic currents to be superimposed on the field current in association with the rotational speed and the torque command value; the control device is configured to acquire the waveform of the harmonic current described in the waveform table, and perform switching control for the second inverter so as to superimpose the harmonic current of the acquired waveform on the field current, thereby executing harmonic superposition processing to cancel the amplitude of the harmonics appearing in the motor. Motor control system.

2. 2. The motor control system of claim 1, wherein the control device executes the harmonic superposition process when at least one of the rotational speed and the torque command value is within a predetermined range, and does not execute the harmonic superposition process when the at least one of the rotational speed and the torque command value is not within the predetermined range.

3. the stator has the armature winding, The motor control system of claim 1 , wherein the rotor includes the field winding.

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