Apparatus and method for controlling inverter for driving motor

1. An apparatus for controlling an inverter for driving a motor, the apparatus comprising:

a current controller configured to generate a d/q-axis voltage reference for allowing a d/q-axis current detection value, which is obtained by measuring a current supplied from the inverter to the motor, to converge on the d/q-axis current reference for driving the motor, and

a voltage modulator configured to control switching of the inverter by selectively applying one among a plurality of predetermined pulse width modulations (PWMs) based on a point at which the d/q-axis voltage reference is located in a hexagonal space voltage diagram,

wherein, when the d/q-axis voltage reference is located on a diagonal line passing through a center of the hexagon in the space voltage vector diagram, the voltage modulator applies a discontinuous PWM (DPWM), and

wherein, when the d/q-axis voltage reference is located inside the hexagon except for the diagonal line passing through the center of the hexagon in the space voltage vector diagram, the voltage modulator applies a space vector PWM (SVPWM).

2. The apparatus of claim 1 , wherein, when the DPWM is applied to the d/q-axis voltage reference located on the diagonal line passing through the center of the hexagon, the number of switching times is ⅓ of the number of switching times when the SVPWM is applied in the space voltage vector diagram.

3. An apparatus for controlling an inverter for driving a motor, the apparatus comprising:

a current controller configured to generate a d/q-axis voltage reference for allowing a d/q-axis current detection value, which is obtained by measuring a current supplied from the inverter to the motor, to converge on the d/q-axis current reference for driving the motor, and

a voltage modulator configured to control switching of the inverter by selectively applying one among a plurality of predetermined pulse width modulations (PWMs) based on a point at which the d/q-axis voltage reference is located in a hexagonal space voltage vector diagram,

wherein, when the d/q-axis voltage reference is located within a predetermined range from a diagonal line passing through a center of the hexagon in the space voltage vector diagram, the voltage modulator applies a DPWM.

4. The apparatus of claim 3 , wherein, when the d/q-axis voltage reference is located within the predetermined range from the diagonal line passing through the center of the hexagon in the space voltage vector diagram, the voltage modulator corrects the d/q-axis voltage reference onto a point on an adjacent diagonal line to apply the DPWM.

5. The apparatus of claim 4 , wherein the voltage modulator determines whether the d/q-axis voltage reference is located in an area within the predetermined range from the diagonal line passing through the center of the hexagon in the space voltage vector diagram by converting the d/q-axis voltage reference into three-phase phase voltage references based on results of comparing differences in magnitude between a first phase voltage reference having a largest magnitude among the converted three-phase voltage references and a second phase voltage reference among the converted three-phase voltage references and differences in magnitude between the second phase voltage reference and a third phase voltage reference having a smallest magnitude among the converted three-phase voltage references.

6. The apparatus of claim 5 , wherein, when the difference in magnitude between the first phase voltage reference and the second phase voltage reference is equal to or less than a predetermined value or when the difference in magnitude between the second phase voltage reference and the third phase voltage reference is equal to or less than the predetermined value, the voltage modulator determines the d/q-axis voltage reference as being present in the area within the predetermined range from the diagonal line passing through the center of the hexagon in the space voltage vector diagram.

7. The apparatus of claim 6 , wherein, when the difference in magnitude between the first phase voltage reference and the second phase voltage reference is equal to or less than the predetermined value, the voltage modulator corrects the magnitude of the second phase voltage reference to the magnitude of the first phase voltage reference to correct the d/q-axis voltage reference onto the point on the adjacent diagonal line.

8. The apparatus of claim 6 , wherein, when the difference in magnitude between the second phase voltage reference and the third phase voltage reference is equal to or less than the predetermined value, the voltage modulator corrects the magnitude of the second phase voltage reference to the magnitude of the third phase voltage reference.

9. The apparatus of claim 3 , wherein, when the d/q-axis voltage reference is located inside the hexagon except for the diagonal line passing through the center of the hexagon in the space voltage vector diagram, a space vector PWM (SVPWM) is applied.

10. A method for controlling an inverter for a motor driving, the method comprising steps of:

generating, by a controller, a d/q-axis voltage reference for allowing a d/q-axis current detection value, which is obtained by measuring a current supplied from the inverter to the motor, to converge on the d/q-axis current reference for driving the motor;

comparing, by the controller, a difference in magnitude between a first phase voltage reference having a largest magnitude among three-phase phase voltage references and a second phase voltage reference having an intermediate magnitude and a difference in magnitude between the second phase voltage reference and a third phase voltage reference having a smallest magnitude;

when the difference in magnitude between the first phase voltage reference and the second phase voltage reference is equal to or less than a predetermined value or when the difference in magnitude between the second phase voltage reference and the third phase voltage reference is equal to or less than the predetermined value, correcting, by the controller, a value on a diagonal line passing through a center of a hexagon of a space voltage vector diagram; and

controlling, by the controller, switching of the inverter by applying a discontinuous pulse width modulation (DPWM) based on the converted three-phase phase voltage references.

11. The method of claim 10 , wherein, when the difference in magnitude between the first phase voltage reference and the second phase voltage reference is equal to or less than the predetermined value, the step of correcting includes a step of converting the magnitude of the second phase voltage reference into the magnitude of the first phase voltage reference.

12. The method of claim 10 , wherein, when the difference in magnitude between the second phase voltage reference and the third phase voltage reference is equal to or less than the predetermined value, the step of correcting includes a step of converting the magnitude of the second phase voltage reference into the magnitude of the third phase voltage reference.

13. The method of claim 10 , further comprising:

as a comparison result of the comparing, when the difference in magnitude between the first phase voltage reference and the second phase voltage reference is greater than the predetermined value or the difference in magnitude between the second phase voltage reference and the third phase voltage reference is greater than the predetermined value, applying a space vector PWM (SVPWM) to control the switching of the inverter based on the three-phase voltage references converted in the step of converting.