System and method for responding to abrupt load changes on a power system

• US 20070273213A1
• Filed: 05/23/2006
• Published: 11/29/2007
• Est. Priority Date: 05/23/2006
• Status: Active Grant

• Current Assignee: Rhombus Energy Solutions, Inc. (BorgWarner Incorporated)
• Original Assignee: Continental Automotive Systems US Incorporated (Continental AG)
• Inventors: Harmon, Kent M., Wang, Kon-King M., Kowalske, Glenn R.
• Granted Patent: US 7,474,016 B2
• Time in Patent Office: Days
• US Class Current: 307/66
• CPC Class Codes: H02J 3/04 for connecting networks of the same frequency but supplied from different sources
• CPC Class Codes: H02J 3/28 Arrangements for balancing of the load in a network by storage of energy
• CPC Class Codes: H02J 3/38 Arrangements for parallely feeding a single network by two or more generators, converters or transformers
• CPC Class Codes: H02J 4/00 Circuit arrangements for mains or distribution networks not specified as ac or dc

Abstract

A system and method for responding to abrupt load changes on a power system are disclosed. Briefly described, one embodiment transfers an initial amount of power from an external power source to the AC power system through a secondary converter module; senses an abrupt load change occurring on the AC power system; where, in response to sensing the abrupt load change, transfers auxiliary direct current (DC) power to the secondary converter module, wherein the auxiliary DC power corresponds to at least a portion of the abrupt load change; where, in response to sensing the abrupt load change, transfers the initial amount of power from the external power source and the auxiliary DC power through the secondary converter module to the AC power system; and where, in response to sensing the abrupt load change, maintains transfer of the initial amount of power from the external power source through the secondary converter module.

Claims

1. A micro grid system electrically transferring power from at least one external power source to an alternating current (AC) power system, comprising:

a direct current (DC) bus operable at a nominal DC voltage;

a primary converter module electrically coupled between the DC bus and a first external power source, and operable to transfer an initial amount of power received from the first external power source to the DC bus;

a secondary converter module electrically coupled between the DC bus and the AC power system, and operable to transfer power received from the DC bus to the AC power system; and

an auxiliary DC power storage device electrically coupled to the DC bus, and operable to source or sink auxiliary DC power to the DC bus,

where, in response to an abrupt load change, the auxiliary DC power storage device sources or sinks an amount of auxiliary DC power that is equal to at least a portion of the abrupt load change, the primary converter module maintains transfer of the initial amount of power received from the first external power source, and the secondary converter module changes power transferred to the AC power system to at least approximately match a sum of the initial amount of power received from the first external power source and the amount of auxiliary DC power.

2. The micro grid system of claim 1 where, after responding to the abrupt load change, the amount of auxiliary DC power changes from the portion of the abrupt load change to a reduced power amount in accordance with a power change function during a power transfer period, and the primary converter module changes power received from the first external power source by the portion of the abrupt load change in accordance with an inverse of the power change function during the power transfer period.

3. The micro grid system of claim 2 wherein the secondary converter module maintains power transferred to the AC power system to at least approximately match the sum of power received from the first external power source and the amount of auxiliary DC power during the power transfer period.

4. The micro grid system of claim 2 wherein the power change function is a ramp function.

5. The micro grid system of claim 2 wherein the power change function is an exponential function.

6. The micro grid system of claim 2 wherein the reduced amount of power is approximately zero.

7. The micro grid system of claim 1 wherein the auxiliary DC power storage device is operable to source the amount of auxiliary DC power when the abrupt load change causes an increase in power to be drawn by the AC power system from the micro grid system, and wherein the auxiliary DC power storage device is operable to sink the amount of auxiliary DC power when the abrupt load change causes a decrease in power to be drawn by the AC power system from the micro grid system.

8. The micro grid system of claim 1, further comprising:

an auxiliary direct current to direct current (DC/DC) converter coupled between the DC bus and the auxiliary DC power storage device, operable to control transfer of the amount of auxiliary DC power between the DC bus and the auxiliary DC power storage device.

9. The micro grid system of claim 8, further comprising:

at least one controller controllably coupled to at least the primary converter module and the secondary converter module, and

where, in response to the abrupt load change, the at least one controller controls the primary converter module to maintain transfer of the initial amount of power received from the first external power source,

where, in response to the abrupt load change, the at least one controller controls the secondary converter module to change the amount of power transferred to the AC power system to at least approximately match the sum of power received from the first external power source and the amount of auxiliary DC power, and

where, in response to the abrupt load change, the at least one controller controls the auxiliary DC/DC converter to transfer the amount of auxiliary DC power between the DC bus and the auxiliary DC power storage device.

10. The micro grid system of claim 9 wherein the at least one controller, after responding to the abrupt load change, is further operable to:

control the secondary converter module to maintain power transferred to the AC power system to at least approximately match the sum of power received from the first external power source and the amount of auxiliary DC power;

control the auxiliary DC/DC converter to change the amount of auxiliary DC power from the portion of the abrupt load change to a reduced power amount in accordance with a power change function during a power transfer period, and

control the primary converter module to change the power received from the first external power source by the portion of the abrupt load change in accordance with an inverse of the power change function during the power transfer period.

11. The micro grid system of claim 1 wherein the first external power source is an external DC power source that generates DC power at a DC source voltage, and wherein the primary converter module comprises:

a direct current to direct current (DC/DC) converter electrically coupled between the DC bus and the external DC power source, wherein the DC/DC converter converts the DC source voltage to the nominal DC voltage, and wherein the DC/DC converter substantially maintains the source DC voltage during at least a power transfer period.

12. The micro grid system of claim 1 wherein the first external power source is an external AC power source that generates AC power at an AC source frequency, and wherein the primary converter module comprises:

an alternating current to direct current (AC/DC) converter electrically coupled between the DC bus and the external AC power source, wherein the AC/DC converter converts the AC power received from the external AC power source into DC power at the nominal DC voltage, and wherein the AC/DC converter substantially maintains the AC source frequency during at least a power transfer period.

13. The micro grid system of claim 1, further comprising:

a second primary converter module electrically coupled between the DC bus and a second external power source, and operable to transfer a second initial amount of power received from the second external power source to the DC bus,

where, in response to the abrupt load change, the secondary converter module changes power transferred to the AC power system to at least approximately match the sum of the initial amount of power received from the first external power source, the second initial amount of power received from the second external power source, and the amount of auxiliary DC power, and

where, in response to the abrupt load change, the second primary converter module maintains transfer of the second initial amount of power received from the second external power source.

14. The micro grid system of claim 13 where, after responding to the abrupt load change,

the auxiliary DC power storage device changes the amount of auxiliary DC power from the portion of the abrupt load change to at least approximately a zero amount of power in accordance with a power change function during a power transfer period,

the primary converter module changes power received from the first external power source by a first portion of the abrupt load change in accordance with an inverse of the power change function during the power transfer period, and

the second primary converter module changes power received from the second external power source by a second portion of the abrupt load change in accordance with the inverse of the power change function during the power transfer period.

15. A method for electrically transferring power from at least one external power source to an alternating current (AC) power system, the method comprising:

transferring an initial amount of power from an external power source to the AC power system through a secondary converter module;

sensing an abrupt load change occurring on the AC power system;

where, in response to sensing the abrupt load change, transferring auxiliary direct current (DC) power to the secondary converter module, wherein the auxiliary DC power corresponds to at least a portion of the abrupt load change;

where, in response to sensing the abrupt load change, transferring the initial amount of power from the external power source and the auxiliary DC power through the secondary converter module to the AC power system; and

where, in response to sensing the abrupt load change, maintaining transfer of the initial amount of power from the external power source through the secondary converter module.

16. The method of claim 15, after responding to the abrupt load change, further comprising:

reducing the auxiliary DC power to a reduced amount in accordance with a power change function; and

increasing power transferred from the external power source by an amount corresponding to the reduced amount of auxiliary DC power in accordance with an inverse of the power change function,

wherein a sum of the reduced amount of auxiliary DC power and the increased power from the external power source remains substantially constant during a power transfer period.

17. The method of claim 16 wherein the power transfer period begins at an initial time and ends at an ending time, and wherein the sum of the reduced amount of auxiliary DC power and the increased power transferred from the external power source is substantially constant at any given time between the initial time and the ending time.

18. The method of claim 15, after responding to the abrupt load change, further comprising:

increasing the auxiliary DC power to an increased amount in accordance with a power change function; and

reducing power transferred from the external power source by an amount corresponding to the increased amount of auxiliary DC power in accordance with an inverse of the power change function,

wherein a sum of the increased amount of auxiliary DC power and the reduced power from the external power source remains substantially constant during a power transfer period.

19. The method of claim 15, wherein transferring the auxiliary DC power through the secondary converter comprises:

sinking the auxiliary DC power into an auxiliary DC power storage device.

20. The method of claim 15, wherein transferring the auxiliary DC power through the secondary converter comprises:

sourcing the auxiliary DC power from an auxiliary DC power storage device.

21. The method of claim 15, wherein the external power source is an external DC power source, and further comprising:

substantially maintaining a source DC voltage of the external DC power source.

22. The method of claim 15, wherein the external power source is an external AC power source, and further comprising:

substantially maintaining a source frequency of the external AC power source.

23. A method for electrically transferring power from a plurality of external power sources to an alternating current (AC) power system, the method comprising:

transferring a first initial amount of power from a first external power source through a first input power control (IPC) module to the AC power system;

transferring a second initial amount of power from a second external power source through a second IPC module to the AC power system;

sensing an abrupt load change occurring on the AC power system;

where, in response to sensing the abrupt load change, apportioning a sensed amount of the abrupt load change into at least a first portion of abrupt load change and a second portion of abrupt load change;

where, in response to sensing the abrupt load change, transferring a first amount of auxiliary direct current (DC) power from a first auxiliary DC power storage device in the first IPC module to the AC power system, wherein the first amount of auxiliary DC power corresponds to the first portion of abrupt load change; and

where, in response to sensing the abrupt load change, transferring a second amount of auxiliary DC power from a second auxiliary DC power storage device in the second IPC module to the AC power system, wherein the second amount of auxiliary DC power corresponds to the second portion of abrupt load change.

24. The method of claim 23, after sensing the abrupt load change, further comprising:

maintaining transfer of the first initial amount of power from the first external power source through the first IPC module; and

maintaining transfer of the second initial amount of power from the second external power source through the second IPC module.

25. The method of claim 23, after transferring the first and the second amounts of auxiliary DC power to the AC power system, further comprising:

adjusting the first amount of auxiliary DC power from the first portion of abrupt load change to approximately zero in accordance with a first power change function, the adjusting starting at a first initial time and ending at a first ending time;

adjusting power transferred from the first external power source to the initial first amount of power plus the first portion of abrupt load change in accordance with an inverse of the first power change function, the adjusting starting at the first initial time and ending at the first ending time;

adjusting the second amount of auxiliary DC power from the second portion of abrupt load change to approximately zero in accordance with a second power change function, the adjusting starting at a second initial time and ending at a second ending time; and

adjusting power from the second external power source to the second initial amount of power plus the second portion of abrupt load change in accordance with an inverse of the second power change function, the adjusting starting at the second initial time and ending at the second ending time.

26. The method of claim 23 wherein apportioning the sensed amount of the abrupt load change occurring on the AC power system into the first portion of abrupt load change and the second portion of abrupt load change comprises:

determining the first portion of abrupt load change based upon a first characteristic of the first external power source; and

determining the second portion of abrupt load change based upon a second characteristic of the second external power source.

27. A system for electrically transferring power from at least one external power source to an alternating current (AC) power system, comprising:

means for transferring an initial amount of power from the external power source to the AC power system via an input power control (IPC) module;

means for sensing an abrupt load change occurring on the AC power system;

means for receiving auxiliary direct power (DC) power from an auxiliary DC power storage device residing in the IPC module, wherein the received auxiliary DC power initially corresponds to at least a portion of the abrupt load change;

means for transferring the initial amount of power and the received auxiliary DC power to the AC power system in response to sensing the abrupt load change; and

means for maintaining the initial amount of power from the external power source.

28. The system of claim 27, further comprising:

means for ramping the auxiliary DC power from the portion of the abrupt load change to a reduced amount of power during a power transfer period; and

means for inversely ramping power from the external power source to the initial amount of power plus the reduced amount of power during the power transfer period,

wherein a sum of the ramped auxiliary DC power and the inversely ramped power from the external power source is substantially constant at any given time during the power transfer period.