Levelling Partial Powers Flowing via the Individual Phases of a Multi-Phase AC Grid

• US 20120280566A1
• Filed: 07/16/2012
• Published: 11/08/2012
• Est. Priority Date: 01/20/2010
• Status: Active Grant

• Current Assignee: SMA Solar Technology AG
• Original Assignee: SMA Solar Technology AG
• Inventors: Umland, Andreas
• Granted Patent: US 9,270,117 B2
• Time in Patent Office: Days
• US Class Current: 307/32
• CPC Class Codes: H02J 3/26 Arrangements for eliminating or reducing asymmetry in polyphase networks
• CPC Class Codes: Y02E 40/50 Arrangements for eliminating or reducing asymmetry in polyphase networks

Abstract

For levelling the partial powers which flow at a grid connection point between a multi-phase AC power grid having a plurality of phase conductors and a unit for feeding electric energy into the AC power grid having a multi-phase inverter as well as electric consumer loads connected to the AC power grid, via the individual phase conductors, differences between the partial powers flowing via the individual phase conductors are determined and are reduced by feeding different partial powers with the inverter into the individual phase conductors.

Claims

1. A method of levelling partial powers at a grid connection point between a multi-phase AC power grid comprising a plurality of phase conductors and a unit including a multi-phase inverter which feeds electric energy into the AC power grid plus consumer loads connected to the AC power grid through the grid connection point, the partial powers flowing via the individual phase conductors, comprising:

determining differences between the partial powers flowing through the individual phase conductors at the grid connection point; and

using the inverter to reduce the determined differences by feeding different partial powers into the individual phase conductors.

2. The method of claim 1, wherein determining differences between the partial powers comprises determining directions of the partial powers flowing through the individual phase conductors and comparing the determined directions with each other to determine the differences between the partial powers to be reduced.

3. The method of claim 1, wherein determining differences between the partial powers comprises determining the partial powers flowing through the individual phase conductors and comparing the partial powers with each other to determine the differences between the partial powers to be reduced.

4. The method of claim 1, wherein determining differences between the partial powers comprises determining currents flowing through the individual phase conductors and comparing the determined currents with each other to determine the differences between the partial powers to be reduced.

5. The method of claim 1, wherein in the case that dominating impedances exist with regard to the AC power grid, determining differences between the partial powers comprises determining differences between the effective voltages present at the individual phase conductors and comparing the effective voltages with each other to determine the differences between the partial powers to be reduced.

6. The method of claim 1, wherein, in the step of reducing, the different partial powers are fed with the inverter out of a common link into the individual phase conductors.

7. The method of claim 6, wherein, in the step of reducing, the different partial powers are fed by feeding different currents with the inverter out of a common link feeding the inverter into the individual phase conductors.

8. An apparatus for leveling partial powers at a grid connection point between a multi-phase AC power grid comprising a plurality of phase conductors and a unit including a multi-phase inverter which feeds electric energy into the AC power grid and consumer loads connected to the AC power grid, the partial powers flowing via the individual phase conductors, the apparatus comprising:

measurement devices configured to determine differences between the partial powers flowing via the individual phase conductors; and

a control device configured to operate the inverter to reduce the differences determined by the measurement devices by feeding different partial powers into the individual phase conductors in response to the determined differences.

9. The apparatus of claim 8, wherein the measurement devices are configured to determine directions of the partial powers flowing through the individual phase conductors, and wherein the control device is configured to level the power flow directions through the individual phase conductors in response thereto.

10. The apparatus of claim 8, wherein the measurement devices are configured to determine the partial powers flowing through the individual phase conductors, and wherein the control device is configured to level the partial powers flowing through the individual phase conductors in response thereto.

11. The apparatus of claim 8, wherein the measurement devices are configured to determine the currents flowing through the individual phase conductors, and wherein the control device is configured to level the currents flowing through the individual phase conductors in response thereto.

12. The apparatus of claim 8, wherein the measurement devices are configured to determine effective voltages present at the individual phase conductors, and wherein the control device is configured to level the effective voltages present at the individual phase conductors in response thereto.

13. A multi-phase inverter for levelling partial powers at a grid connection point between a multi-phase AC power grid comprising a plurality of phase conductors and a unit including a multi-phase inverter which feeds electric energy into the AC power grid and consumer loads connected to the AC power grid, the partial powers flowing via the individual phase conductors, wherein the inverter comprises a controller configured to operate the inverter to feed different partial powers into the individual phase conductors in response to identified differences in partial powers to minimize the identified differences.

14. The inverter of claim 13, wherein the inverter feeds the different partial powers out of a common link into the individual phase conductors.

15. The inverter of claim 14, wherein the inverter feeds the different partial powers by feeding different currents out of the common link into the individual phase conductors.

16. The inverter of claim 14, wherein the inverter comprises a multi-phase inverter circuitry fed out of the common link.

17. The inverter of claim 14, wherein the inverter comprises several single-phase inverters fed out of the common link.

18. The inverter of claim 14, wherein the output partial stages of the inverter, which are attributed to the individual phase conductors, are configured to feed at least 50% of an entire maximum feeding power of the inverter into a single phase conductor of the individual phase conductors.

19. The inverter of claim 18, wherein the output partial stages of the inverter, which are attributed to the individual phase conductors, are configured to feed at least 75% of the entire maximum feeding power of the inverter into a single phase conductor of the individual phase conductors.

20. The inverter of claim 19, wherein the output partial stages of the inverter, which are attributed to the individual phase conductors, are configured to feed 100% of the entire maximum feeding power of the inverter into a single phase conductor of the individual phase conductors.