1. A synchronous motor control device comprising: a synchronous motor having a rotor using a permanent magnet; a voltage command value conversion means configured to convert, according to a d-axis voltage command value, a q-axis voltage command value, and a motor position, a d-axis current and a q-axis current into a three-phase voltage command intermediate value; a voltage compensation calculation means configured to perform a voltage compensation calculation based on the three-phase voltage command intermediate value and to calculate a three-phase voltage command value; and an inverter configured to output a voltage to the synchronous motor based on the three-phase voltage command value.

2. The synchronous motor control device according to claim 1, wherein a maximum value of the d-axis voltage command value and the q-axis voltage command value is equal to a maximum voltage of the three-phase voltage command value at an electrical angle interval of 60 degrees, and the maximum value is greater than a maximum voltage of the three-phase voltage command value at an electrical angle other than the electrical angle interval of 60 degrees.

3. The synchronous motor control device according to claim 1, wherein the voltage compensation calculation is performed according to any one of the following four conditions A, B, C, and D: Condition A: a case in which a U-phase voltage command intermediate value satisfies a V-phase voltage command intermediate value or more, a W-phase voltage command intermediate value or more, and a maximum voltage of the three-phase voltage command value or more; Condition B: a case in which the condition A is not satisfied, and the V-phase voltage command intermediate value satisfies the U-phase voltage command intermediate value or more, the W-phase voltage command intermediate value or more, and the maximum voltage of the three-phase voltage command value or more; Condition C: a case in which the condition B is not satisfied, and the W-phase voltage command intermediate value satisfies the U-phase voltage command intermediate value or more, the V-phase voltage command intermediate value or more, and the maximum voltage of the three-phase voltage command value or more; and Condition D: a case in which none of the conditions A, B, and C is satisfied.

4. The synchronous motor control device according to claim 3, wherein in the voltage compensation calculation, the three-phase voltage command value is calculated by: the following Mathematical Formula (1) when the condition A is satisfied, the following Mathematical Formula (2) when the condition B is satisfied, the following Mathematical Formula (3) when the condition C is satisfied, and the following Mathematical Formula (4) when the condition D is satisfied, wherein •vUref is a U-phase voltage command value, •vVref is a V-phase voltage command value, •vWref is a W-phase voltage command value, •vUref0 is the U-phase voltage command intermediate value, •vVref0 is the V-phase voltage command intermediate value, •vWref0 is the W-phase voltage command intermediate value, and •VMAX is the maximum voltage of the three-phase voltage command value: [Mathematical Formula 1] [Mathematical Formula 2] [Mathematical Formula 3] [Mathematical Formula 4]

Description:TECHNICAL FIELD
[0001]
The present invention relates to a synchronous motor control device 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 a rotor is attracted by a rotating magnetic field formed by an input AC current and rotates following the magnetic field. The synchronous motor is generally driven and controlled by a control system by a control device connected to the synchronous motor.
[0003]
FIG. 4 illustrates an example of a control system in a conventional synchronous motor control device. In this system, a d-axis voltage command value (vdref) and a q-axis voltage command value (vqref), which are vectors rotating in synchronization with a detected or estimated motor position, are converted into a three-phase voltage command value (vUref, vVref, vWref), and the three-phase voltage command value is output to a motor by performing on-off control of a switching element of an inverter.
[0004]
Conventional vector control will be described with reference to FIG. 5. This diagram is a vector diagram of a three-phase voltage, a d-axis voltage, and a q-axis voltage of a motor viewed in terms of electrical angles. The three-phase voltage is an axis that is fixed to a stator of the motor and is shifted by 120 degrees, whereas the d-axis and the q-axis are axes that follow the motor position (the direction of a rotor). A permanent magnet is attached to the rotor, and a current that generates a magnetic field in the same direction as a magnetic field of the magnet is referred to as a d-axis current, and a current that generates a magnetic field in an orthogonal direction is referred to as a q-axis current. A voltage in a direction in which the d-axis current flows is defined as the d-axis voltage, and a voltage in a direction in which the q-axis current flows is defined as the q-axis voltage. Under the conventional vector control, the maximum value of the d-axis voltage and the q-axis voltage is determined by a supply voltage of a power supply connected to a control device, and become the same peak value (VMAX) in any direction of 360 degrees, and a voltage range that can be output draws a circle on the vector.
[0005]
On the other hand, as one of general control methods, for example, in a 120-degree energization method as disclosed in JP H01-255494 A (Patent Literature 1), it is possible to output a voltage (2/√3 times VMAX) in which a peak value of a voltage exceeds a peak value in the conventional vector control, and high torque can be realized. However, in the 120-degree energization method, since the vector of the output voltage transitions every 60 degrees, torque ripple is generated, and there are problems such as generation of harmonic current and deterioration in quietness.
[0006]
In regard to the problems, for example, as in the invention disclosed in JP H03-036986 A (Patent Literature 2), a motor drive device for reducing the torque ripple is known.
[0007]
However, in the invention described in Patent Literature 2, since a current detection means and a configuration for causing a reactive current to flow are required, a hardware cost therefor is required.

CITATION LIST
PATENT LITERATURE
[0008]
Patent Literature 1: JP H01-255494 A
Patent Literature 2: JP H03-036986 A

SUMMARY OF INVENTION
TECHNICAL PROBLEM
[0009]
Therefore, an object of the present invention is to provide a device that controls a synchronous motor as possible and with high torque.

SOLUTION TO PROBLEM
[0010]
In order to solve the above-described problems, the present invention provides a synchronous motor control device characterized by including: a synchronous motor having a rotor using a permanent magnet; a voltage command value conversion means configured to convert, according to a d-axis voltage command value, a q-axis voltage command value, and a motor position, a d-axis current and a q-axis current into a three-phase voltage command intermediate value; a voltage compensation calculation means configured to perform a voltage compensation calculation based on the three-phase voltage command intermediate value and to calculate a three-phase voltage command value; and an inverter configured to output a voltage to the synchronous motor based on the three-phase voltage command value.

[0011]
In the present invention, when a maximum value of the d-axis voltage command value and the q-axis voltage command value is equal to a maximum voltage of the three-phase voltage command value at an electrical angle interval of 60 degrees and is greater than a maximum voltage of the three-phase voltage command value at an electrical angle other than the electrical angle interval of 60 degrees, it is possible to output a voltage similar to a voltage of a 120-degree energization method at a maximum voltage peak value every 60 degrees while maintaining vector control rotatable by 360 degrees.
[0012]
In the present invention, the voltage compensation calculation is performed according to any one of the following four conditions A, B, C, and D.
Condition A: a case in which a U-phase voltage command intermediate value satisfies a V-phase voltage command intermediate value or more, a W-phase voltage command intermediate value or more, and the maximum voltage of the three-phase voltage command value or more.
Condition B: a case in which the condition A is not satisfied, and the V-phase voltage command intermediate value satisfies the U-phase voltage command intermediate value or more, the W-phase voltage command intermediate value or more, and the maximum voltage of the three-phase voltage command value or more.
Condition C: a case in which the condition B is not satisfied, and the W-phase voltage command intermediate value satisfies the U-phase voltage command intermediate value or more, the V-phase voltage command intermediate value or more, and the maximum voltage of the three-phase voltage command value or more.
Condition D: a case in which none of the conditions A, B, and C is satisfied.
[0013]
In the voltage compensation calculation of the present invention, the three-phase voltage command value is calculated by:
the following Mathematical Formula (1) when the condition A is satisfied,
the following Mathematical Formula (2) when the condition B is satisfied,
the following Mathematical Formula (3) when the condition C is satisfied, and
the following Mathematical Formula (4) when the condition D is satisfied,
in which
•vUref is a U-phase voltage command value,
•vVref is a V-phase voltage command value,
•vWref is a W-phase voltage command value,
•vUref0 is the U-phase voltage command intermediate value,
•vVref0 is the V-phase voltage command intermediate value,
•vWref0 is the W-phase voltage command intermediate value, and
•VMAX is the maximum voltage of the three-phase voltage command value.
[Mathematical Formula 1]

[Mathematical Formula 2]

[Mathematical Formula 3]

[Mathematical Formula 4]

ADVANTAGEOUS EFFECTS OF INVENTION
[0014]
According to the present invention, it is possible to provide a synchronous motor control device that suppresses generation of torque ripple.

BRIEF DESCRIPTION OF DRAWINGS
[0015]
FIG. 1 is a functional block diagram illustrating an outline of a control system in a synchronous motor control device according to the present invention;
FIG. 2 is a vector diagram of a three-phase voltage, a d-axis voltage, and a q-axis voltage of a motor as viewed in an electrical angle in the control system illustrated in FIG. 1;
FIG. 3 is a flowchart of a voltage compensation calculation in the control system illustrated in FIG. 1;
FIG. 4 is a functional block diagram illustrating an outline of a control system in a synchronous motor control device as a conventional example; and
FIG. 5 is a vector diagram of a three-phase voltage, a d-axis voltage, and a q-axis voltage of a motor as viewed in an electrical angle in the control system illustrated in FIG. 4.
DESCRIPTION OF EMBODIMENTS
[0016]
Embodiments of the present invention will be described below with reference to the drawings.
[0017]
FIG. 1 is a functional block diagram illustrating an outline of a control system in a synchronous motor control device according to an embodiment of the present invention. FIG. 2 is a vector diagram of a three-phase voltage, a d-axis voltage, and a q-axis voltage of a motor as viewed in an electrical angle in the control system illustrated in FIG. 1.
[0018]
As illustrated in FIG. 2, a control method of the embodiment can be output a voltage similar to that of a 120-degree energization method can be output at the maximum voltage peak value for each electrical angle of 60 degrees while maintaining vector control rotatable by 360 degrees.

[0019]
That is, a maximum value of a d-axis voltage command value and a q-axis voltage command value is equal to a maximum voltage (VMAX) of a three-phase voltage command value at an electrical angle interval of 60 degrees, but is greater than a maximum voltage (VMAX) of the three-phase voltage command value at an electrical angle other than the electrical angle interval of 60 degrees (half-tone dot meshing portion illustrated in FIG. 2), and a voltage equivalent to that of the 120-degree energization method can be output.
[0020]
The maximum voltage (VMAX) of the three-phase voltage command value is determined by a supply voltage of a power supply connected to a control device, and has the same peak value in any direction of 360 degrees.
[0021]
In a control system of a conventional example (refer to FIG. 4), a three-phase voltage command value is directly output. However, in the embodiment of the present invention, first, a three-phase voltage command intermediate value (vUref0, vVref0, vWref0) is calculated as an intermediate value according to a d-axis voltage command value (vdref), a q-axis voltage command value (vqref), and a motor position (the magnetic pole position/direction of a rotor). Then, a three-phase voltage command value (vUref, vVref, vWref) obtained by performing a voltage compensation calculation on the three-phase voltage command intermediate value is output to a motor.
[0022]
The d-axis voltage command value (vdref) and the q-axis voltage command value (vqref) can take values exceeding the maximum voltage (VMAX) of the three-phase voltage command value on a virtual axis.
[0023]
In addition, the three-phase voltage command intermediate value (vUref0, vVref0, vWref0) is a virtual three-phase voltage that is calculated as a calculation intermediate value and is not actually output, and can take a value exceeding the maximum voltage (VMAX) of the three-phase voltage command value.

[0024]
FIG. 3 is a flowchart of a voltage compensation calculation in the embodiment of the present invention. In the embodiment of the present invention, first, it calculates a U-phase voltage command intermediate value (vUref0), a V-phase voltage command intermediate value (vVref0), and a W-phase voltage command intermediate value (vWref0), which are the three-phase voltage command intermediate values from the d-axis voltage command value (vdref), the q-axis voltage command value (vqref), and the motor position (magnetic pole position and direction of the rotor). Then, it is determined whether a value having the largest absolute value among the U-phase voltage command intermediate value (vUref0), the V-phase voltage command intermediate value (vVref0), and the W-phase voltage command intermediate value (vWref0) is greater than the maximum voltage (VMAX) of the three-phase voltage command value.
[0025]
When any one of the three-phase voltage command intermediate values (vUref0, vVref0, vWref0) is equal to or more than the maximum voltage (VMAX) of the three-phase voltage command value, the maximum value is calculated to be the maximum voltage (VMAX), and for the other two-phase voltage commands, a voltage calculation is performed so as to maintain three-phase equilibrium while a ratio of the three-phase voltage command intermediate values is maintained.
[0026]
When none of the three-phase voltage command intermediate values exceeds the maximum voltage (VMAX) of the three-phase voltage command values, the three-phase voltage command intermediate value is used as it is as the three-phase voltage command value.
[0027]
That is, conditions are the following four conditions A, B, C, and D.
Condition A: a case in which a U-phase voltage command intermediate value satisfies a V-phase voltage command intermediate value or more, a W-phase voltage command intermediate value or more, and the maximum voltage of the three-phase voltage command value or more.
Condition B: a case in which the condition A is not satisfied, and the V-phase voltage command intermediate value satisfies the U-phase voltage command intermediate value or more, the W-phase voltage command intermediate value or more, and the maximum voltage of the three-phase voltage command value or more.
Condition C: a case in which the condition B is not satisfied, and the W-phase voltage command intermediate value satisfies the U-phase voltage command intermediate value or more, the V-phase voltage command intermediate value or more, and the maximum voltage of the three-phase voltage command value or more.
Condition D: a case in which none of the conditions A, B, and C is satisfied.
[0028]
The three-phase voltage command value is calculated by:
the following Mathematical Formula (1) when the condition A is satisfied,
the following Mathematical Formula (2) when the condition B is satisfied,
the following Mathematical Formula (3) when the condition C is satisfied, and
the following Mathematical Formula (4) when the condition D is satisfied.

[Mathematical Formula 5]

[Mathematical Formula 6]

[Mathematical Formula 7]

[Mathematical Formula 8]

[0029]
As a result, it is possible to output up to the maximum voltage equivalent to that of the 120-degree energization method while maintaining the output direction of the voltage vector.
[0030]
In accordance with the embodiment of the present invention, torque higher than the maximum voltage (VMAX) of the three-phase voltage command value can be output, and torque ripple can be suppressed even compared with the 120-degree energization method. In addition, it can be applied without changing the configuration of an existing synchronous motor control device.
, Claims:1. A synchronous motor control device comprising:
a synchronous motor having a rotor using a permanent magnet;
a voltage command value conversion means configured to convert, according to a d-axis voltage command value, a q-axis voltage command value, and a motor position, a d-axis current and a q-axis current into a three-phase voltage command intermediate value;
a voltage compensation calculation means configured to perform a voltage compensation calculation based on the three-phase voltage command intermediate value and to calculate a three-phase voltage command value; and
an inverter configured to output a voltage to the synchronous motor based on the three-phase voltage command value.

2. The synchronous motor control device according to claim 1, wherein
a maximum value of the d-axis voltage command value and the q-axis voltage command value is equal to a maximum voltage of the three-phase voltage command value at an electrical angle interval of 60 degrees, and the maximum value is greater than a maximum voltage of the three-phase voltage command value at an electrical angle other than the electrical angle interval of 60 degrees.

3. The synchronous motor control device according to claim 1, wherein
the voltage compensation calculation is performed according to any one of the following four conditions A, B, C, and D:
Condition A: a case in which a U-phase voltage command intermediate value satisfies a V-phase voltage command intermediate value or more, a W-phase voltage command intermediate value or more, and a maximum voltage of the three-phase voltage command value or more;
Condition B: a case in which the condition A is not satisfied, and the V-phase voltage command intermediate value satisfies the U-phase voltage command intermediate value or more, the W-phase voltage command intermediate value or more, and the maximum voltage of the three-phase voltage command value or more;
Condition C: a case in which the condition B is not satisfied, and the W-phase voltage command intermediate value satisfies the U-phase voltage command intermediate value or more, the V-phase voltage command intermediate value or more, and the maximum voltage of the three-phase voltage command value or more; and
Condition D: a case in which none of the conditions A, B, and C is satisfied.

4. The synchronous motor control device according to claim 3, wherein
in the voltage compensation calculation, the three-phase voltage command value is calculated by:
the following Mathematical Formula (1) when the condition A is satisfied,
the following Mathematical Formula (2) when the condition B is satisfied,
the following Mathematical Formula (3) when the condition C is satisfied, and
the following Mathematical Formula (4) when the condition D is satisfied,
wherein
•vUref is a U-phase voltage command value,
•vVref is a V-phase voltage command value,
•vWref is a W-phase voltage command value,
•vUref0 is the U-phase voltage command intermediate value,
•vVref0 is the V-phase voltage command intermediate value,
•vWref0 is the W-phase voltage command intermediate value, and
•VMAX is the maximum voltage of the three-phase voltage command value:
[Mathematical Formula 1]

[Mathematical Formula 2]

[Mathematical Formula 3]

[Mathematical Formula 4]