Current control system

Abstract

Provided is a current control system capable of reducing vibration at a lower cost than when changing the rigidity of a magnetic circuit or a motor. 【Solution means】The control device 20 has a current table 25 in which d-axis current commands and q-axis current commands corresponding to torque and rotational speed are stored. In the current table 25, the phase of the current when the torque is within the first range and the rotational speed is within the second range is delayed from the phase of the current when the torque is within the first range and the rotational speed is outside the second range, and the magnitude of the current when the torque is within the first range and the rotational speed is within the second range is made larger than the magnitude of the current when the torque is within the first range and the rotational speed is outside the second range. The d-axis current command and q-axis current command are stored. The control device 20 refers to the current table 25 to derive d-axis current commands and q-axis current commands based on torque and rotational speed, and outputs an output command based on the derived d-axis current commands and q-axis current commands to the power converter 40.

Description

Technical Field

[0001] The present invention relates to a current control system for reducing the vibration of an electric motor.

Background Art

[0002] In recent years, miniaturization of electric motors mounted on electric vehicles (hereinafter referred to as EVs) has been demanded. However, when a miniaturized electric motor is used at high torque, the vibration increases. Regarding the vibration of an EV motor, it is important to reduce the vibration at the 24th and 48th rotations.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] As a method for reducing the vibration of a permanent magnet synchronous motor for EVs, a method of changing the magnetic circuit and a method of changing the rigidity of the motor are known. However, when reducing the vibration by the above-described methods, it is necessary to change many components such as the rotor, stator, and motor frame, which incurs costs such as time and expenses.

[0005] From the above, it is an object to provide a current control system that can reduce vibration at a lower cost than when changing the magnetic circuit or the rigidity of the motor by changing the current supplied to the motor.

Means for Solving the Problems

[0006] The present invention has been devised in view of the above-described conventional problems. In one aspect, the present invention includes: an electric motor that is driven with torque and a rotational speed corresponding to a supplied current; a power converter that controls the current supplied to the electric motor based on an output command; a current table in which a d-axis current command and a q-axis current command corresponding to the torque and the rotational speed are stored, the d-axis current command and the q-axis current command being derived based on the torque and the rotational speed by referring to the current table, and a control device that outputs an output command based on the derived d-axis current command and q-axis current command to the power converter. In the current table, when the torque is within a first range and the rotational speed is within a second range, the phase of the current supplied to the electric motor is delayed compared to the phase of the current supplied to the electric motor when the torque is within the first range and the rotational speed is outside the second range, and the magnitude of the current supplied to the electric motor when the torque is within the first range and the rotational speed is within the second range is made larger than the magnitude of the current supplied to the electric motor when the torque is within the first range and the rotational speed is outside the second range. The d-axis current command and the q-axis current command are stored as described above.

[0007] Also, in one aspect, the current table sets the d-axis current command when the torque is within the first range and the rotational speed is within the second range to a value smaller than the d-axis current command when the torque is within the first range and the rotational speed is outside the second range, and sets the q-axis current command when the torque is within the first range and the rotational speed is within the second range to a value larger than the q-axis current command when the torque is within the first range and the rotational speed is outside the second range.

[0008] Also, in one aspect, the electric motor is an embedded magnet type synchronous motor.

Advantages of the Invention

[0009] According to the present invention, by changing the current supplied to the motor, it becomes possible to provide a current control system that can reduce vibration at a lower cost than changing the rigidity of the magnetic circuit or the motor.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Embodiments for Carrying Out the Invention

[0011] Hereinafter, embodiments of the current control system in the present invention will be described in detail with reference to FIGS. 1 to 5.

[0012] [Embodiment] [Overall Configuration] First, the configuration of the current control system 1 according to the embodiment will be described. FIG. 1 is a block diagram showing the configuration of the current control system 1 of the present embodiment.

[0013] As shown in FIG. 1, the current control system 1 includes a motor (rotating machine) 10, a control device 20, a torque command unit 30, a power converter (for example, an inverter, hereinafter referred to as an inverter) 40, and a DC power supply 50.

[0014] The motor 10 is, for example, a permanent magnet synchronous motor (PMSM). More specifically, the motor 10 is an interior permanent magnet synchronous motor (IPMSM) in which permanent magnets are embedded in the rotor.

[0015] The electric motor 10 is connected to the inverter 40 and is driven by a torque corresponding to the magnitude of the current supplied from the inverter 40 and a rotational speed corresponding to the frequency of the current. The electric motor 10 has a speed detector 11 that detects the rotational phase and rotational speed. The speed detector 11 is, for example, an encoder such as a resolver.

[0016] The control device 20 includes a current command calculation unit 21, a current controller 22, coordinate conversion units 23, 24, and a current table 25.

[0017] The current command calculation unit 21 is connected to the torque command unit 30, the speed detector 11, the current controller 22, and the current table 25. The current command calculation unit 21 refers to the current table 25, derives a d-axis current command and a q-axis current command based on the rotational speed detected by the speed detector 11 and the torque command output from the torque command unit 30, and outputs the d-axis current command and the q-axis current command to the current controller 22.

[0018] The current table 25 stores a d-axis current command and a q-axis current command corresponding to each torque and each rotational speed. The d-axis current command and the q-axis current command stored in the current table 25 are values calculated in advance through experiments or the like, and are values capable of reducing the vibration of the electric motor 10. Details of the current table 25 will be described later in the description of FIG. 2.

[0019] The current controller 22 is connected to the current command calculation unit 21 and the coordinate conversion units 23, 24. The current controller 22 compares the d-axis current command and the q-axis current command output from the current command calculation unit 21 with the d-axis current detection information and the q-axis current detection information output from the coordinate conversion unit 24, and outputs a d-axis q-axis output command (for example, a d-axis q-axis output current command or a d-axis q-axis output voltage command) for adjusting the current to the coordinate conversion unit 23 based on the comparison result.

[0020] The coordinate conversion unit 23 is connected to the current controller 22, the speed detector 11, and the inverter 40. The coordinate conversion unit 23 converts the d-axis and q-axis output commands output from the current controller 22 into three-phase (u-phase, v-phase, w-phase) output commands (for example, output current commands or output voltage commands) based on the rotation phase of the motor 10, and outputs them to the inverter 40. Note that the phase of the current supplied to the motor 10 is determined based on the d-axis current command and the q-axis current command.

[0021] The coordinate conversion unit 24 converts the information on the current (three-phase current detection information) supplied from the inverter 40 to the motor 10 into d-axis current detection information and q-axis current detection information based on the rotation phase of the motor 10, and outputs them to the current controller 22.

[0022] The DC power supply 50 supplies current to the inverter 40. The inverter 40 converts the DC current supplied from the DC power supply 50 into an AC current based on the three-phase output command output from the coordinate conversion unit 23, and controls the current supplied to the motor 10 to a desired phase and magnitude.

[0023] <Configuration of the current table 25> Next, the details of the current table 25 will be described. FIG. 2 is a diagram showing an example of the current table 25. In FIG. 2, the torque (Nm) is shown on the vertical axis and the rotational speed (rpm) is shown on the horizontal axis. As shown in FIG. 2, the current table 25 stores the d-axis current command Id and the q-axis current command Iq corresponding to the torque (Nm) and the rotational speed (rpm).

[0024] The d-axis current command Id will be described. When the torque is within a predetermined first range A1 and the rotational speed is within a predetermined second range A2, the d-axis current command Id is smaller than the d-axis current command Id when the torque is within the first range A1 and the rotational speed is outside the second range A2. When the above characteristics are represented by a graph, it becomes as shown in FIG. 3.

[0025] Therefore, for example, the d-axis current command Id in FIG. 2 174 ~Id 178 is the d-axis current command Id 169 ~Id 173 ,Id 179~Id 180 is smaller than.

[0026] The q-axis current command Iq will be described. When the torque is within the first range A1 and the rotational speed is within the second range A2, the q-axis current command Iq is larger than the q-axis current command Iq when the torque is within the first range A1 and the rotational speed is outside the second range A2. When the above characteristics are represented by a graph, it becomes as shown in FIG. 4.

[0027] Therefore, for example, the q-axis current command Iq in FIG. 2 174 ~Iq 178 is the q-axis current command Iq 169 ~Iq 173 , Iq 179 ~Iq 180 is larger than.

[0028] Here, the method for determining the first range A1 of torque and the second range A2 of rotational speed will be described. Generally, as the torque increases, the vibration of the motor 10 increases. Also, when the torque is small, the d-axis current command Id is originally small and the range in which the d-axis current command Id can be decreased is small. Therefore, it is desirable that the first range A1 be a range where the torque is larger than a predetermined value. In the example of FIG. 2, the first range A1 of torque is set to 140 to 190 Nm.

[0029] The second range A2 of rotational speed is desirably the rotational speed with high usage frequency. Also, when performing field weakening control, since the phase adjustment is difficult in that rotational speed range, it is desirable that the second range A2 be a rotational speed not affected by the field weakening control. In the example shown in FIG. 2, it is set to 2500 to 4500 rpm.

[0030] Here, assuming that the phase of the current output from the inverter 40 to the motor 10 is θ, when the torque is within the first range A1 and the rotational speed is within the second range A2, the phase θ of the current is delayed compared to the case where the torque is within the first range A1 and the rotational speed is outside the second range A2. In other words, since the phase θ of the current is determined based on the d-axis current command Id and the q-axis current command Iq, the d-axis current command Id and the q-axis current command Iq are set so that the phase θ of the current is delayed when the torque is within the first range A1 and the rotational speed is within the second range A2 compared to the case where the torque is within the first range A1 and the rotational speed is outside the second range A2.

[0031] Furthermore, the magnitudes of the three-phase currents after converting the d-axis current command Id and the q-axis current command Iq described in the current table 25 into three phases are larger when the torque is within the first range A1 and the rotational speed is within the second range A2 than when the torque is within the first range A1 and the rotational speed is outside the second range A2. In other words, when the torque is within the first range A1 and the rotational speed is within the second range A2, the d-axis current command Id and the q-axis current command Iq are set so that the magnitude of the current can compensate for the reduction in torque caused by the delay in the phase θ.

[0032] <Control Procedure> FIG. 5 is a flowchart showing the procedure of the process performed by the control device 20.

[0033] As shown in FIG. 5, the control device 20 (current command calculation unit 21) acquires the torque command from the torque command unit 30 and the rotational speed from the speed detector 11 (S1, S2). Note that the method of acquiring the rotational speed is not limited to the method of acquiring it from the speed detector 11, and it may be specified from the frequency of the inverter 40.

[0034] Next, the control device 20 (current command calculation unit 21) refers to the current table 25 (S3), and derives the d-axis current command Id and the q-axis current command Iq based on the torque command and the rotational speed (S4). Subsequently, the control device 20 outputs the d-axis current command Id and the q-axis current command Iq to the current controller 22 (S5).

[0035] <Effect> When the phase of the current supplied to the motor 10 is delayed, the magnetic force acting on the rotor decreases and the vibration decreases. Then, when the current is increased to compensate for the torque shortage due to the phase delay, the magnetic force acting on the rotor increases and the vibration increases. At this time, the effect of vibration reduction due to the phase delay is higher than the effect of vibration increase due to the current increase.

[0036] In the control device 20 in the present embodiment, in the current table 25, when the torque is within the first range A1 and the rotational speed is within the second range A2, the d-axis current command Id and the q-axis current command Iq that delay the phase of the current and increase the current are stored. Since the control device 20 controls the current supplied to the motor 10 based on this current table 25, vibration can be reduced without changing the mechanical configuration (magnetic circuit and motor rigidity) of the motor 10. Therefore, it is possible to reduce the cost of time and expenses when suppressing the vibration of the motor.

[0037] Also, generally, the larger the d-axis current, the larger the vibration of the motor. In the present embodiment, when the torque is within the first range A1 and the rotational speed is within the second range A2, the d-axis current command is made small and the q-axis current command is made large, so that the vibration of the motor can be reduced. More specifically, it is possible to reduce the vibration at the 24th and 48th rotations.

[0038] Furthermore, the method of reducing vibration by reducing the d-axis current as in the present embodiment is more effective when applied to an interior permanent magnet synchronous motor (IPMSM).

[0039] As described above, in the present invention, although detailed description has been made only for the specific examples described, it is obvious to those skilled in the art that various modifications and corrections are possible within the scope of the technical idea of the present invention, and it is natural that such modifications and corrections belong to the scope of the claims.

Explanation of Signs

[0040] 1... Current control system 10... Motor (rotating machine) 20... Control device 30…Torque command unit 40…Power converter (inverter) 50…DC power supply 11…Speed detector 21…Current command calculation unit 22…Current controller 23, 24…Coordinate conversion unit 25…Current table

Claims

1. an electric motor that operates at a torque and a rotational speed according to a current supplied thereto; a power converter that controls the current supplied to the electric motor based on an output command; a control device having a current table in which a d-axis current command and a q-axis current command corresponding to the torque and the rotation speed are stored, the control device derives the d-axis current command and the q-axis current command based on the torque and the rotation speed by referring to the current table, and outputs the output command based on the derived d-axis current command and q-axis current command to the power converter; Equipped with The current table includes: a d-axis current command and a q-axis current command are stored such that the phase of the current supplied to the motor when the torque is within a first range and the rotational speed is within a second range is delayed relative to the phase of the current supplied to the motor when the torque is within the first range and the rotational speed is outside the second range, and the magnitude of the current supplied to the motor when the torque is within the first range and the rotational speed is within the second range is greater than the magnitude of the current supplied to the motor when the torque is within the first range and the rotational speed is outside the second range.

2. The current table is the d-axis current command when the torque is within the first range and the rotation speed is within the second range is set to a value smaller than the d-axis current command when the torque is within the first range and the rotation speed is outside the second range; 2. The current control system according to claim 1, wherein the q-axis current command when the torque is within the first range and the rotational speed is within the second range is set to a value larger than the q-axis current command when the torque is within the first range and the rotational speed is outside the second range.

3. 2. The current control system according to claim 1, wherein the electric motor is an interior magnet type synchronous motor.

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