Power conversion system and method of converting power

• US 20050063115A1
• Filed: 09/28/2004
• Published: 03/24/2005
• Est. Priority Date: 03/28/2002
• Status: Active Grant

• Current Assignee: Curtin University of Technology
• Original Assignee: Curtin University of Technology
• Inventors: Malengret, Michel, Nayar, Chemmangot V., Dehbonei, Hooman, Borle, Lawrence J.
• Granted Patent: US 7,072,194 B2
• Time in Patent Office: Days
• US Class Current: 361/82
• CPC Class Codes: H02J 2300/24 of photovoltaic origin
• CPC Class Codes: H02J 2300/26 involving maximum power point tracking control for photovoltaic sources
• CPC Class Codes: H02J 2300/28 The renewable source being wind energy
• CPC Class Codes: H02J 3/381 Dispersed generators
• CPC Class Codes: H02J 3/50 Controlling the sharing of the out-of-phase component
• CPC Class Codes: H02J 7/35 with light sensitive cells
• CPC Class Codes: H02M 1/0074 Plural converter units whose inputs are connected in series
• CPC Class Codes: H02M 7/493 the static converters being arranged for operation in parallel
• CPC Class Codes: Y02E 10/56 Power conversion systems, e.g. maximum power point trackers
• CPC Class Codes: Y02E 10/76 Power conversion electric or electronic aspects

Abstract

A power conversion system includes a first converter having a DC side and an AC side and a second converter having a DC side and an AC side. The DC sides of the converters are connected in series with a battery connected in parallel across the DC side of the first converter. The AC sides of the converters are connected in parallel across an AC voltage grid. A DC generating power source is coupled across the DC sides of both converters. The first converter is bi-directional with the second converter being either an inverter providing DC to AC conversion or alternately a bi-directional inverter.

Claims

1. A power conversion system comprising:

a first converter having a DC side and an AC side;

a second converter having a DC side and an AC side; and

an electrical energy storage device;

wherein the DC sides of said first and second converters are connected together in series, and said electrical energy storage device is connected in parallel to the DC side of said first converter.

2. The system according to claim 1, wherein said second converter is an inverter.

3. The system according to claim 1, wherein said second converter is a bi-directional inverter.

4. The system according to claim 1, wherein said first converter is an inverter.

5. The system according to claim 1, wherein said first converter is a bi-directional inverter.

6. The system according to claim 1, wherein said first converter is a bi-directional inverter and said second converter is an inverter.

7. The system according to claim 1, wherein the AC sides of said first and second converters are connected together in parallel.

8. The system according to claim 1, wherein when said power conversion system is coupled between a DC power source, an AC grid and an AC load;

the AC side of said second converter is connected to said AC grid, and the AC side of said first converter is connected to said AC load, with a coupling inductor placed between said AC grid and said AC load, and said DC power source connected across the DC sides of said first and second converters.

9. The system according to claim 6, wherein each of said first and second converters comprise any one of:

a single phase full bridge converter, a single phase half bridge converter, a three phase converter with three half-bridges, a phase shifted converter, a switch mode converter, and a voltage source inverter.

10. The system according to claim 1, wherein said first converter is a voltage controlled voltage source inverter.

11. The system according to claim 10, wherein said second converter is a current controlled voltage source inverter.

12. An uninterruptible power supply (UPS) comprising:

a power conversion system according to claim 1;

a DC power source coupled across the DC sides of said first and second converters;

an AC grid coupled across the AC side of said first and second converter; and

an AC load coupled across the AC side of said first converter.

13. The UPS according to claim 12, wherein said AC load and AC grid are either tied directly together or with a coupling inductor between them.

14. A method for converting power between a DC power source and an AC system comprising:

(a) providing first and second converters, each having an AC side and a DC side;

(b) providing an electrical energy storage device;

(c) connecting the DC sides of said first and second converters together in series;

(d) connecting the AC sides of said first and second converters together in parallel;

(e) connecting said electrical energy storage device in parallel across the DC side of said first converter;

(f) providing a DC port for connecting said DC power source across the DC sides of said converters; and

(g) providing AC ports for connecting said AC system in parallel across the AC side of said converters;

wherein, when an AC system is coupled to said AC ports and a DC power source is connected to said DC port, power from the DC power source can flow through said converters to said energy storage device and said AC system;

power from said electrical energy storage device can flow through said first converter to said AC system; and

, power from said AC system can flow through said first converter to said electrical energy storage device.

15. The method according to claim 14, wherein (d) includes connecting said AC sides either directly or with a coupling inductor between them.

16. The method according to claim 15, further comprising:

(h) controlling real power flow of said first converter so as to regulate the DC current of said DC power source to thereby provide for maximum power point tracking of said DC power source.

17. The method according to claim 16, further comprising:

(h) controlling real power flow of said second converter to regulate the amount of energy delivered to or from said electrical energy storage device.

18. The method according to claim 17, further comprising:

(h) controlling real power flow of said second converter to regulate the amount of energy delivered from said DC power source.

19. The method according to claim 18, further comprising:

(h) controlling reactive power flow of either or both of said first or second converters to achieve a desired power quality on the AC side.

20. The method according to claim 19, wherein when said AC system includes an AC load and a parallel coupled AC grid, said method further comprises:

(h) controlling reactive power flow of either of said first or second converters to regulate the power factor of said AC grid.

21. The method according to claim 20, further comprising:

(h) controlling real power flow of either of said first or second converters so as to regulate the AC load voltage magnitude or wave form.

22. The method according to claim 21, further comprising:

(h) controlling reacting power flow of either of said first or second converters so as to regulate the AC load voltage magnitude or wave form.

23. The method according to claim 22, further comprising:

(h) controlling harmonic power flow of either of said first or second converters so as to regulate the AC load voltage magnitude or wave form.

24. The method according to claim 23, further comprising:

(h) controlling reactive power flow of either of said first or second converters to provide active VAR compensation for AC grid.

25. The method according to claim 24, further comprising:

(h) controlling harmonic power flow of either of said first or second converters to provide active cancellation of current harmonics of said AC system.