Energy converter system with reactive-power-management

• US 7,834,480 B2
• Filed: 06/20/2008
• Issued: 11/16/2010
• Est. Priority Date: 06/20/2007
• Status: Active Grant

• Current Assignee: Mesta Electronics, Inc. (Hammond Power Solutions Incorporated)
• Original Assignee: Mesta Electronics, Inc. (Hammond Power Solutions Incorporated)
• Inventors: Shero, David J., Mandalakas, John N.
• Primary Examiner(s): RUTLAND WALLIS, MICHAEL
• Application Number:
  US12/143,259
• Publication Number:
  US 20080315685A1
• Time in Patent Office: 879 Days
• Field of Search: 307/46
• US Class Current: 307/46
• CPC Class Codes: H02J 3/1842 wherein at least one reactive element is actively controlled by a bridge converter, e.g. active filters
• CPC Class Codes: Y02E 40/20 Active power filtering [APF]

Abstract

A distributed generation system is connected to an AC power line that provides AC electrical power from a source to a load. The distributed generation system includes a DC electrical power source, a capacitor for storing DC electrical power, a converter for converting electrical power stored in the DC electrical power source at a first voltage to a second, greater voltage for storage in the capacitor. The system includes an inverter for inverting the electrical power stored in the capacitor at the second voltage into AC electrical power having a peak voltage less than the second voltage. A controller is provided and operative for controlling the operation of the converter and the inverter to deliver electrical power stored in the DC electrical power source to the capacitor for delivery as AC electrical power to the AC power line.

Claims

1. A distributed generation system connectable to an AC power line that provides AC electrical power from a source to a load, the distributed generation system comprising:

a source of stored DC energy;

a controller operative for;

detecting line voltage and line current of the AC power line and for providing a first set of firing signals related to the AC line voltage and/or the AC line current, and

detecting an amount of energy stored in the source of stored DC energy and for providing a second set of firing signals related thereto;

an inverter connected between the power line and the source of stored DC energy and connected to receive the first set of firing signals from the controller;

a DC power source; and

a converter connected between the DC power source and the source of stored DC energy and connected to receive the second set of firing signals from the controller, wherein;

the controller is operative for controlling the firing of the first and second sets of firing signals to deliver electrical power from the DC power source to the AC power line, or vice versa, via the source of stored DC energy; and

the controller is further operative for controlling the firing of the first and second sets of firing signals to maintain the source of stored DC energy at a voltage greater than a peak AC line voltage and a voltage of the DC power source.

2. The distributed generation system of claim 1, wherein the controller is further operative for causing the inverter to perform at least one of the following:

reducing load induced phase shifts between the line voltage and the line current;

reducing line current harmonics;

or

balancing currents in AC power lines of a polyphase AC electrical distribution system.

3. The distributed generation system of claim 2, further including means for filtering connected between the inverter and the power line for filtering out signals caused by operation of the inverter that are not related to reducing load induced phase shifts between the line voltage and the line current, reducing line current harmonics, and/or balancing currents in the AC power lines of a polyphase AC electrical distribution system.

4. The distributed generation system of claim 1, further including a transformer connected between the inverter and the power line for physically isolating the inverter from the power line while enabling the inverter and the power line to be in electrical communication.

5. The distributed generation system of claim 1, wherein, during delivery of electrical power from the source of DC power source to the AC power line, the controller controls the first and second sets of firing signals to cause the inverter to deliver the electrical power stored on the source of stored DC energy to the AC power line and to cause the converter to deliver electrical power from the DC power source to the source of stored DC energy.

6. The distributed generation system of claim 1, wherein:

the source of stored DC energy includes a capacitor; and

the DC power source includes a battery.

18. The distributed generation system of claim 1, wherein the controller is further operative for causing the inverter to supply either real power, reactive power, or harmonic reactive power to the AC power line up to a limit which is the square root of the sum of the squares of the maximum real power, the maximum reactive power, and the maximum harmonic reactive power that the inverter is capable of simultaneously supplying to the AC power line.

7. A distributed generation system connectable to an AC power line that provides AC electrical power from a source to a load, the distributed generation system comprising:

means for storing DC electrical power at a first voltage;

means for inverting DC electrical power stored by the means for storing DC electrical power into AC electrical power that is delivered to the AC power line and for converting AC electrical power on the AC power line into DC electrical power for storage by the means for storing DC electrical power;

means for generating DC electrical power at a second voltage; and

means for converting the second voltage of the means for generating DC electrical power to the first voltage of the means for storing DC electrical power and vice versa, wherein the first voltage is greater than the second voltage and a peak voltage of the AC electrical power that is delivered to the AC power line.

8. The distributed generation system of claim 7, further including means for controlling the operation of the means for inverting to controllably transfer electrical power to or from the means for storing DC electrical power in a manner to reduce load induced phase shifts between the line voltage and the line current, reduce line current harmonics on the AC power line or balance currents in AC power lines of a polyphase AC electrical distribution system.

9. The distributed generation system of claim 8, further including means for controlling the operation of the means for converting to controllably transfer electrical power to or from the means for storing DC electrical power in a manner to maintain the first voltage within a predetermined limit.

10. The distributed generation system of claim 7, wherein:

the means for storing DC electrical power includes a capacitor; and

the means for generating DC electrical power includes a battery.

11. The distributed generation system of claim 7, further including means for physically isolating the means for inverting from the AC power line while enabling the means for inverting and the AC power line to be in electrical communication.

12. The distributed generation system of claim 8, further including means for filtering signals caused by operation of means for inverting that are not related to reducing load induced phase shifts between the line voltage and the line current, reducing line current harmonics, and/or balancing currents in the AC power lines of a polyphase AC electrical distribution system.

19. The distributed generation system of claim 7, wherein the maximum real power, the maximum reactive power, or the maximum harmonic reactive power that the means for inverting can individually supply to the AC power line by decreasing the supply of one or both said other powers to the AC power line is no more than the square root of the sum of the squares of the maximum real power, the maximum reactive power, and the maximum harmonic reactive power that the means for inverting can simultaneously supply to the AC power line.

13. A distributed generation system connectable to an AC power line that provides AC electrical power from a source to a load, the distributed generation system comprising:

a DC electrical power source;

means for storing DC electrical power;

a converter operative for converting electrical power stored in the DC electrical power source at a first voltage to a second, greater voltage for storage in the means for storing DC electrical power;

an inverter operative for converting electrical power stored in the means for storing DC electrical power at the second voltage into AC electrical power having a peak voltage less than the second voltage; and

a controller operative for controlling the operation of the converter and the inverter to deliver electrical power stored in the DC electrical power source to the means for storing DC electrical power for delivery as AC electrical power to the AC power line.

14. The distributed generation system of claim 13, wherein the controller is further operative for delivering the AC electrical power to the AC power line in a manner that:

reduces load induced phase shifts between the line voltage and the line current;

reduces line current harmonics; and

/or

balances currents in AC power lines of a polyphase AC electrical distribution system.

15. The distributed generation system of claim 13, wherein:

the means for storing DC electrical power includes a capacitor; and

the DC electrical power source includes a battery.

16. The distributed generation system of claim 13, wherein the controller is further operative for controlling the operation of the converter and the inverter to deliver electrical power from the AC power line to the means for storing DC electrical power for delivery to the DC electrical power source.

17. The distributed generation system of claim 13, wherein the DC electrical power source includes one or more of a bank of solar cells or fuel cells, a wind turbine, or batteries.

20. The distributed generation system of claim 13, wherein a maximum value of each of the real power, the reactive power, and the harmonic reactive power that the inverter can individually supply to the AC power line is:

(1) greater than a maximum value of said power that can be supplied to the AC power line when the inverter is simultaneously supplying maximum real power, maximum reactive power, and maximum harmonic reactive power to the AC power line; and

(2) no more than a square root of the sum of the squares of said maximum real power, maximum reactive power, and maximum harmonic reactive power that can be simultaneously supplied to the AC power line.