Apparatus and method for controlling module switching of power converting system

1. An apparatus for converting power comprising:

a central controller that generates a reference AC voltage;

a phase leg including a plurality of power converters; and

a plurality of sub-units,

wherein the central controller allocates respective different phase angles to the respective sub-units, and the respective sub-units individually create local switching carriers based on the allocated phase angles, and controls switching of the power converters corresponding to the respective sub-units according to a result of a comparison of the individually created local switching carriers and the reference AC voltage,

wherein the local switching carriers created by the respective sub-units are sinusoidal waves each having a same frequency and the respective different phase angle from each other allocated by the center controller, and

wherein, when the number of the power converters is M, a difference between any two of the allocated phase angles is a multiple of 2π/M.

2. The apparatus of claim 1 , wherein the power converters included in the phase leg are connected in series with each other.

3. The apparatus of claim 1 , wherein the phase leg is arranged between a DC connection terminal and an AC connection terminal.

4. The apparatus of claim 1 , wherein the respective sub-units control the switching of the power converters corresponding to the respective sub-unit when the local switching carriers intersect with the reference AC voltage.

5. The apparatus of claim 1 , wherein the power converters comprise a plurality of power electronic switches connected in series with each other, and a capacitor connected in parallel with the power electronic switches.

6. A method of converting power, comprising:

allocating different phase angles to a plurality of sub-units, respectively, by a central controller;

individually creating local switching carriers based on the allocated phase angles, by the respective sub-units; and

controlling switching of power converters included in a phase leg and corresponding to the respective sub-units according to a result of a comparison of the individually created local switching carriers and a reference AC voltage, by the respective sub-units,

wherein the local switching carriers created by the respective sub-units are sinusoidal waves each having a same frequency and the respective different phase angle from each other allocated by the center controller, and

wherein, when the number of the power converters is M, a difference between any two of the allocated phase angles is a multiple of 2π/M.

7. The method of claim 6 , wherein the power converters included in the phase leg are connected in series with each other.

8. A non-transitory computer readable recording medium in which a program for executing the method of claim 7 is recorded.

9. The method of claim 6 , wherein the phase leg is arranged between a DC connection terminal and an AC connection terminal.

10. A non-transitory computer readable recording medium in which a program for executing the method of claim 9 is recorded.

11. The method of claim 6 , wherein the controlling of the switching comprises:

controlling the switching of the power converters corresponding to the respective sub-unit when the local switching carriers intersect with the reference AC voltage.

12. A non-transitory computer readable recording medium in which a program for executing the method of claim 11 is recorded.

13. The method of claim 6 , wherein the power converters comprise a plurality of power electronic switches connected in series with each other, and a capacitor connected in parallel with the power electronic switches.

14. A non-transitory computer readable recording medium in which a program for executing the method of claim 13 is recorded.

15. A non-transitory computer readable recording medium in which a program for executing the method of claim 6 is recorded.