Synchronous motor control device

Abstract

To provide a device for controlling a synchronous motor with a power saving configuration and by high torque to the utmost extent.SOLUTION: A synchronous motor control device includes a synchronous motor having a rotor using a permanent magnet, voltage command value conversion means that converts d-axis current and q-axis current to a three-phase voltage command intermediate value in accordance with a d-axis voltage command value, a q-axis voltage command value, and a motor position, voltage compensation computation means that calculates a three-phase voltage command value by conducting a voltage compensation computation based on the three-phase voltage command intermediate value, and an inverter that outputs voltage to the synchronous motor in accordance with the three-phase voltage command value.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a control device for a synchronous motor that operates by vector control.

Background Art

[0002] A synchronous motor is an electric motor that rotates in synchronization with an input AC voltage, and the rotor follows the magnetic field while being attracted by the rotating magnetic field formed by the input AC current. Generally, it is driven and controlled by a control system using a control device connected thereto.

[0003] An example of a control system in a conventional control device for a synchronous motor is shown in FIG. 4. In this system, the d-axis voltage command value (v dref ), q-axis voltage command value (v qref ) which are vectors rotating in synchronization with the detected or estimated motor position are converted into three-phase voltage command values (v Uref , v Vref , v Wref ), and the switching elements of the inverter are turned on and off to output the three-phase voltage command values to the motor.

[0004] Conventional vector control will be described with reference to FIG. 5. This figure is a vector diagram of the three-phase voltage of the motor and the d-axis voltage and q-axis voltage as seen in the electrical angle. The three-phase voltage is an axis fixed to the stator of the motor and shifted by 120 degrees, while the d-axis and q-axis are axes that follow the motor position (the direction of the rotor). A permanent magnet is attached to the rotor, and the current that generates a magnetic field in the same direction as the magnetic field of this magnet is called the d-axis current, and the current that generates a magnetic field in the orthogonal direction is called the q-axis current. The voltage in the direction in which the d-axis current flows is defined as the d-axis voltage, and the voltage in the direction in which the q-axis current flows is defined as the q-axis voltage. Under conventional vector control, the maximum values of the d-axis voltage and q-axis voltage are determined by the supply voltage of the power source connected to the control device, and the peak value (V MAX ) is the same in any direction of 360 degrees, and the outputtable voltage range draws a circle on the vector.

[0005] On the one hand, in one of the general control methods, for example, in the 120-degree power supply method as shown in Japanese Patent Application Laid-Open No. 1-255494 (Patent Document 1), the peak value of the voltage can exceed the peak value in the conventional vector control and output a voltage (V MAX which is 2 / √3 times that of the conventional vector control), and high torque can be achieved. However, in the 120-degree power supply method, since the vector of the output voltage transitions every 60 degrees, torque ripple occurs, resulting in problems such as the generation of harmonic currents and the deterioration of quietness.

[0006] On the other hand, for example, a motor drive device aimed at reducing torque ripple is known, such as the invention described in Japanese Patent Application Laid-Open No. 3-036986 (Patent Document 2).

[0007] However, in the invention described in Patent Document 2, current detection means and a configuration for flowing reactive current are required, so it requires hardware costs for that purpose.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0009] Therefore, it is an object of the present invention to provide a device that controls a synchronous motor with as few components as possible and high torque.

Means for Solving the Problems

[0010] A control device for a synchronous motor according to the present invention, which has been made to solve the above problems, includes a synchronous motor having a rotor using a permanent magnet, voltage command value conversion means for converting a d-axis current and a q-axis current into an intermediate value of a three-phase voltage command according to a d-axis voltage command value, a q-axis voltage command value, and a motor position, voltage compensation calculation means for performing a voltage compensation calculation based on the intermediate value of the three-phase voltage command and calculating a three-phase voltage command value, and an inverter for outputting a voltage to the synchronous motor based on the three-phase voltage command value. It is characterized by this.

[0011] In the present invention, the maximum values of the d-axis voltage command value and the q-axis voltage command value are equal to the maximum voltage of the three-phase voltage command value at intervals of 60 electrical degrees. When they are larger than the maximum voltage of the three-phase voltage command value at electrical angles other than the 60 electrical degree intervals, while maintaining a vector control that can rotate 360 degrees, the maximum voltage peak value every 60 degrees can output the same voltage as the 120-degree conduction method.

[0012] In the present invention, the voltage compensation calculation is performed according to which of the following four conditions A, B, C, and D is applicable. Condition A: When the intermediate value of the U-phase voltage command satisfies that it is greater than or equal to the intermediate value of the V-phase voltage command, greater than or equal to the intermediate value of the W-phase voltage command, and greater than or equal to the maximum voltage of the three-phase voltage command value. Condition B: When the condition A is not satisfied and the intermediate value of the V-phase voltage command satisfies that it is greater than or equal to the intermediate value of the U-phase voltage command, greater than or equal to the intermediate value of the W-phase voltage command, and greater than or equal to the maximum voltage of the three-phase voltage command value. Condition C: When the condition B is not satisfied and the intermediate value of the W-phase voltage command satisfies that it is greater than or equal to the intermediate value of the U-phase voltage command, greater than or equal to the intermediate value of the V-phase voltage command, and greater than or equal to the maximum voltage of the three-phase voltage command value. Condition D: When none of the conditions A, B, and C are satisfied.

[0013] In the present invention, in the voltage compensation calculation, the three-phase voltage command value is In the case of corresponding to the condition A, the following formula (1), In the case of corresponding to the condition B, the following formula (2), In the case of corresponding to the condition C, the following formula (3), When the condition D is satisfied, the following equation (4): is calculated by where ·v Uref is the U-phase voltage command value, ·v Vref is the V-phase voltage command value, ·v Wref is the W-phase voltage command value, ·v Uref0 is the U-phase voltage command intermediate value, ·v Vref0 is the V-phase voltage command intermediate value, ·v Wref0 is the W-phase voltage command intermediate value, ·V MAX is the maximum voltage of the three-phase voltage command value.

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Advantages of the Invention

[0014] According to the present invention, it is possible to provide a control device for a synchronous motor that suppresses the generation of torque ripple without changing the device configuration.

Brief Description of the Drawings

[0015]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Embodiments for Carrying Out the Invention

[0016] Embodiments of the present invention will be described below with reference to the drawings.

[0017] FIG. 1 is a functional block diagram showing the outline of the control system in the control device of a synchronous motor which is the present invention, and FIG. 2 is a vector diagram of the three-phase voltage of the motor and the d-axis voltage and q-axis voltage viewed in electrical angle in the control system shown in FIG. 1.

[0018] As shown in FIG. 2, in the control method of the present invention, while maintaining the vector control that can rotate 360 degrees, a control is realized in which the maximum voltage peak value every 60 degrees of electrical angle can output the same voltage as the 120-degree conduction method.

[0019] That is, the maximum values of the d-axis voltage command value and the q-axis voltage command value are equal to the maximum voltage (V MAX ) of the three-phase voltage command value at intervals of 60 degrees of electrical angle, but at electrical angles other than the 60-degree intervals of the electrical angle, it becomes larger than the maximum voltage (V MAX ) of the three-phase voltage command value (the part shown as the overhang in FIG. 2), and a voltage equivalent to the 120-degree conduction method can be output.

[0020] Here, the maximum voltage (V MAX ) of the three-phase voltage command value is determined by the supply voltage of the power source connected to the control device, and has the same peak value in any direction of 360 degrees.

[0021] In the control system of the conventional example (see FIG. 4), the three-phase voltage command value was directly output, but in the present invention, first, the d-axis voltage command value (v dref ), q-axis voltage command value (v qref) and according to the motor position (the magnetic pole position and orientation of the rotor), as an intermediate value, the three-phase voltage command intermediate value (v Uref0 , v Vref0 , v Wref0 ) is calculated, and then the three-phase voltage command value (v Uref , v Vref v Wref ) obtained by performing voltage compensation calculation on the three-phase voltage command intermediate value is output to the motor.

[0022] Here, the d-axis voltage command value (v dref ) and the q-axis voltage command value (v qref ) can take values exceeding the maximum voltage (V MAX ) of the three-phase voltage command value on the virtual axis.

[0023] Also, the three-phase voltage command intermediate value (v Uref0 , v Vref0 , v Wref0 ) is a virtual three-phase voltage calculated as an intermediate value in calculation and not actually output, and can take values exceeding the maximum voltage (V MAX ) of the three-phase voltage command value.

[0024] FIG. 3 is a flowchart of the voltage compensation calculation in the present invention. In the present invention, for the value with the largest absolute value among the U-phase voltage command intermediate value (v dref ), the V-phase voltage command intermediate value (v qref ), the W-phase voltage command intermediate value (v Uref0 ), the d-axis voltage command value (v Vref0 ), the q-axis voltage command value (v Wref0 ) calculated from the motor position (the magnetic pole position and orientation of the rotor) and the three-phase voltage command intermediate value, it is determined whether it is larger than the maximum voltage (V MAX ) of the three-phase voltage command value.

[0025] If any of the three-phase voltage command intermediate values (v Uref0 , v Vref0 , v Wref0 ) is greater than or equal to the maximum voltage (V MAX ) of the three-phase voltage command value, the largest value is set as the maximum voltage (V MAX) perform calculations so as to achieve this, and for the other two-phase voltage commands, perform voltage calculations such that three-phase balance is maintained while keeping the ratio of the three-phase voltage command intermediate value.

[0026] If any of the three-phase voltage command intermediate values do not exceed the maximum voltage (V MAX ) of the three-phase voltage command values, use the three-phase voltage command intermediate value as the three-phase voltage command value as it is.

[0027] That is, the conditions are the following four conditions A, B, C, and D. Condition A: When the intermediate value of the U-phase voltage command is greater than or equal to the intermediate value of the V-phase voltage command, and greater than or equal to the intermediate value of the W-phase voltage command, and greater than or equal to the maximum voltage of the three-phase voltage command values. Condition B: When the above Condition A is not satisfied, and the intermediate value of the V-phase voltage command is greater than or equal to the intermediate value of the U-phase voltage command, and greater than or equal to the intermediate value of the W-phase voltage command, and greater than or equal to the maximum voltage of the three-phase voltage command values. Condition C: When the above Condition B is not satisfied, and the intermediate value of the W-phase voltage command is greater than or equal to the intermediate value of the U-phase voltage command, and greater than or equal to the intermediate value of the V-phase voltage command, and greater than or equal to the maximum voltage of the three-phase voltage command values. Condition D: When none of the above Conditions A, B, and C are satisfied.

[0028] And the three-phase voltage command value is In the case corresponding to the above Condition A, the following formula (1), In the case corresponding to the above Condition B, the following formula (2), In the case corresponding to the above Condition C, the following formula (3), In the case corresponding to the above Condition D, the following formula (4), is calculated by.

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[0029] As a result, while maintaining the output direction of the voltage vector, it becomes possible to output up to the maximum voltage equivalent to the 120-degree conduction method.

[0030] According to the present invention, it becomes possible to output higher torque than the maximum voltage (V MAX ) of the three-phase voltage command value, and torque ripple can be suppressed even compared with the 120-degree conduction method.

Claims

1. A synchronous motor having a rotor using a permanent magnet, voltage command value conversion means for converting a d-axis current and a q-axis current into an intermediate value of a three-phase voltage command according to a d-axis voltage command value, a q-axis voltage command value, and a motor position, voltage compensation calculation means for performing a voltage compensation calculation based on the intermediate value of the three-phase voltage command and calculating a three-phase voltage command value, and an inverter that outputs a voltage to the synchronous motor based on the three-phase voltage command value. A control device for a synchronous motor, characterized in that.

2. The maximum values of the d-axis voltage command value and the q-axis voltage command value are equal to the maximum voltage of the three-phase voltage command value at intervals of 60 electrical degrees, and are larger than the maximum voltage of the three-phase voltage command value at electrical angles other than the 60 electrical degree intervals. The control device for a synchronous motor according to claim 1, characterized in that.

3. The voltage compensation calculation is performed according to which of the following four conditions A, B, C, and D is satisfied: Condition A: When the intermediate value of the U-phase voltage command satisfies that it is greater than or equal to the intermediate value of the V-phase voltage command, greater than or equal to the intermediate value of the W-phase voltage command, and greater than or equal to the maximum voltage of the three-phase voltage command value. Condition B: When condition A is not satisfied and the intermediate value of the V-phase voltage command satisfies that it is greater than or equal to the intermediate value of the U-phase voltage command, greater than or equal to the intermediate value of the W-phase voltage command, and greater than or equal to the maximum voltage of the three-phase voltage command value. Condition C: When condition B is not satisfied and the intermediate value of the W-phase voltage command satisfies that it is greater than or equal to the intermediate value of the U-phase voltage command, greater than or equal to the intermediate value of the V-phase voltage command, and greater than or equal to the maximum voltage of the three-phase voltage command value. Condition D: When none of conditions A, B, and C are satisfied. The control device for a synchronous motor according to claim 1, characterized in that.

4. In the voltage compensation calculation, the three-phase voltage command value is in the case of corresponding to condition A, the following formula (1), in the case of corresponding to condition B, the following formula (2), in the case of corresponding to condition C, the following formula (3), in the case of corresponding to condition D, the following formula (4), is calculated by Here, ・v Uref is the U-phase voltage command value, ・v Vref is the V-phase voltage command value, ・v Wref is the W-phase voltage command value, ・v Uref0 is the intermediate value of the U-phase voltage command, ・v Vref0 is the intermediate value of the V-phase voltage command, ・v Wref0 is the intermediate value of the W-phase voltage command, ・V MAX is the maximum voltage of the three-phase voltage command value The control device for a synchronous motor according to claim 3, characterized in that. 【Number 1】 【Number 2】 【Number 3】 [Number 4]

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