Control of a microgrid

Patent metadata

Field	Value
Publication number	US-10199825-B2
Application number	US-201415502716-A
Country	US
Kind code	B2
Filing date	Aug 11, 2014
Priority date	Aug 11, 2014
Publication date	Feb 5, 2019
Grant date	Feb 5, 2019

Abstract

A method performed in an electrical microgrid for facilitating connection of a first and second AC power networks. The method includes, when the power networks are disconnected, from the second power network, controlling the AC frequency of the first power network based on the AC frequency of the second power network for ensuring that when the first and second networks are connected power will flow from the power network of the first and second power networks having a higher frequency to the power network of the first and second power networks having a lower frequency. The method also includes, after the controlling, connecting the first power network to the second power network, whereby power, at the instant of connecting, flows from the power network of the first and second power networks having a higher frequency to the power network of the first and second power networks having a lower frequency.

First claim

The invention claimed is:

1. A method performed in an electrical microgrid for facilitating connection of a first alternating current (AC) power network to a second AC power network, the method comprising:
when the first power network is disconnected from the second power network, controlling the AC frequency of the first power network based on the AC frequency of the second power network for ensuring that when the first and second networks are connected power will flow from the power network of the first and second power networks having a higher frequency to the power network of the first and second power networks having a lower frequency; and
after the controlling, connecting the first power network to the second power network, whereby power, at the instant of connecting, flows from the power network of the first and second power networks having a higher frequency to the power network of the first and second power networks having a lower frequency;
wherein the AC frequency is controlled such that the power, directly after the connecting, flows in the same direction as it would during steady state conditions of the first and second power networks when connected to each other.

2. The method of claim 1 , wherein the AC frequency of the first power network is controlled to a higher frequency than the AC frequency of the second power network, whereby the power flows from the first power network to the second power network after the step of connecting.

3. The method of claim 2 , wherein the method is applied in a cascading manner on different levels of the microgrid.

4. The method of claim 2 , wherein the step of controlling also comprises controlling the AC frequency of the second power network based on the AC frequency of the first power network.

5. The method of claim 2 , wherein the first and second power networks are different segments of the microgrid.

6. The method of claim 1 , wherein the AC frequency of the first power network is controlled to a lower frequency than the AC frequency of the second power network, whereby the power flows from the second power network to the first power network after the step of connecting.

7. The method of claim 1 , wherein the method is applied in a cascading manner on different levels of the microgrid.

8. The method of claim 1 , wherein the step of controlling also comprises controlling the AC frequency of the second power network based on the AC frequency of the first power network.

9. The method of claim 1 , wherein the first and second power networks are different segments of the microgrid.

10. The method of claim 9 , wherein one of the first and second power networks comprises a distributed generator, DG, and the other of the first and second power networks comprises a local load of the DG.

11. The method of claim 1 , wherein the first power network is, or is a segments of, the microgrid, and the second power network is external to the microgrid e.g. a main power grid.

12. The method of claim 1 , wherein the step of connecting comprises connecting the first and second power networks by means of a static switch.

13. The method of claim 1 , wherein the step of controlling also comprises voltage and/or phase angle matching of the first and second power networks.

14. A controller for an electrical microgrid, for facilitating connection of a first alternating current (AC) power network to a second AC power network, the controller comprising:
a processor circuitry; and
a storage unit storing instructions executable by said processor circuitry whereby said controller is operative to:
when the first power network is disconnected from the second power network, control the AC frequency of the first power network based on the AC frequency of the second power network for ensuring that power will flow from the power network of the first and second power networks having a higher frequency to the power network of the first and second power networks having a lower frequency; and
after the controlling, connect the first power network to the second power network, whereby power, at the instant of connecting, flows from the power network of the first and second power networks having a higher frequency to the power network of the first and second power wherein the AC frequency is controlled such that the power, directly after the connecting, flows in the same direction as it would during steady state conditions of the first and second power networks when connected to each other.

15. A microgrid comprising a controller including:
a processor circuitry; and
a storage unit storing instructions executable by said processor circuitry whereby said controller is operative to:
when the first power network is disconnected from the second power network, control the AC frequency of the first power network based on the AC frequency of the second power network for ensuring that power will flow from the power network of the first and second power networks having a higher frequency to the power network of the first and second power networks having a lower frequency; and
after the controlling, connect the first power network to the second power network, whereby power, at the instant of connecting, flows from the power network of the first and second power networks having a higher frequency to the power network of the first and second power wherein the AC frequency is controlled such that the power, directly after the connecting, flows in the same direction as it would during steady state conditions of the first and second power networks when connected to each other.

16. A computer program product comprising computer-executable components for causing a microgrid controller to perform the method including the steps of:
when the first power network is disconnected from the second power network, controlling the AC frequency of the first power network based on the AC frequency of the second power network for ensuring that when the first and second networks are connected power will flow from the power network of the first and second power networks having a higher frequency to the power network of the first and second power networks having a lower frequency;
after the controlling, connecting the first power network to the second power network, whereby power, at the instant of connecting, flows from the power network of the first and second power networks having a higher frequency to the power network of the first and second power networks having a lower frequency;
wherein the AC frequency is controlled such that the power, directly after the connecting, flows in the same direction as it would during steady state conditions of the first and second power networks when connected to each other; and
when the computer-executable components are run on processor circuitry comprised in the controller.

17. A computer program comprising computer program code which is able to, when run on processor circuitry of a microgrid controller, cause the controller to:
when a first power network is disconnected from a second power network, control the AC frequency of the first power network based on the AC frequency of the second power network for ensuring that power will flow from the power network of the first and second power networks having a higher frequency to the power network of the first and second power networks having a lower frequency; and
after the controlling, connect the first power network to the second power network, whereby power, at the instant of connecting, flows from the power network of the first and second power networks having a higher frequency to the power network of

Assignees

• Abb Schweiz Ag

Inventors

• Majumder Ritwik

Classifications

• H02J3/08

  Synchronisation of networks · CPC title

• H02J3/06 Primary

  Controlling the transfer of power between connected networks; Controlling load sharing between connected networks · CPC title

• H02J3/40

  Synchronisation of generators for connection to a network or to another generator · CPC title

• H02J3/42

  with automatic parallel connection when synchronisation is achieved · CPC title