POWER CONVERTERS WITH AC AND DC OPERATING MODES AND METHODS OF OPERATION THEREOF

• US 20020118556A1
• Filed: 12/10/2001
• Published: 08/29/2002
• Est. Priority Date: 08/13/1999
• Status: Active Grant

• Current Assignee: Eaton Intelligent Power Limited (Eaton Corporation PLC.)
• Original Assignee: Robert W. Johnson Jr
• Inventors: Johnson, Robert W. Jr.
• Granted Patent: US 6,483,730 B2
• Time in Patent Office: Days
• US Class Current: 363/123
• CPC Class Codes: H02J 9/061 for DC powered loads
• CPC Class Codes: H02J 9/062 for AC powered loads
• CPC Class Codes: H02M 1/10 Arrangements incorporating converting means for enabling loads to be operated at will from different kinds of power supplies, e.g. from ac or dc
• CPC Class Codes: H02M 5/4585 having a rectifier with controlled elements
• CPC Class Codes: H02M 7/538 in a push-pull configuration H02M7/5375 takes precedence ; with oscillating arrangements H02M7/53832, H02M7/53846

Abstract

A power converter suitable for use in an uninterruptible power supply (UPS) includes first and second voltage busses, an input port having a first terminal coupled to one of the first and second voltage busses, a neutral bus and an output terminal. A first switching circuit selectively couples a second terminal of the input port to the first and second voltage busses. A second switching circuit selectively couples the first and second voltage busses to the output terminal. A third switching circuit selectively couples the first and second voltage busses to the neutral bus. Preferably, the first, second and third switching circuits are operative to produce an AC output voltage at the output terminal from a DC input voltage at the input port such that alternating ones of the first and second terminals of the first input port are referenced to the neutral bus for successive first and second half cycles of the AC output voltage. According to other embodiments, a DC voltage generating circuit is operative to produce respective first and second DC voltages on first and second voltage busses. A first switching circuit is operative to selectively couple the first and second voltage busses to the output terminal. A storage circuit connected to the output terminal includes a capacitive storage element, a rectifying circuit coupling the capacitive storage element to the output terminal, and a second switching circuit operative to selectively couple the capacitive storage element to the output terminal.

Claims

1. A power converter, comprising:

first and second voltage busses;

a first input port having first and second terminals, the first terminal coupled to one of the first and second voltage busses;

a neutral bus;

an output terminal;

a first switching circuit operative to selectively couple the second terminal of the first input port to the first and second voltage busses;

a second switching circuit operative to selectively couple the first and second voltage busses to the output terminal; and

a third switching circuit operative to selectively couple the first and second voltage busses to the neutral bus.

2. A power converter according to claim 1, wherein the first, second and third switching circuits are operative to produce an AC output voltage at the output terminal from a DC input voltage at the first input port such that alternating ones of the first and second terminals of the first input port are referenced to the neutral bus for successive first and second half cycles of the AC output voltage.

3. A power converter according to claim 2, wherein the first, second and third switching circuits are operative to produce the AC output voltage at the output terminal from a DC input voltage at the first input port such that:

at least one of the second switching circuit and the third switching circuit regulates the AC output voltage for a first portion of a first half cycle of the AC output voltage; and

the first switching circuit regulates the AC output voltage for a second portion of the first half cycle of the AC output voltage.

4. A power converter according to claim 3:

wherein the first portion of the first half cycle of the AC output voltage comprise a portion of the first half cycle of the AC output voltage for which the magnitude of the AC output voltage is less than the magnitude of the DC input voltage; and

wherein the second portion of the first half cycle of the AC output voltage comprises a portion of the first half cycle of the AC output voltage for which the magnitude of the AC output voltage is greater than the magnitude of the DC input voltage.

5. A power converter according to claim 3, wherein the first half cycle comprises a positive half-cycle of the AC output voltage, and wherein the first, second and third switching circuits are further operative to produce the AC output voltage at the output terminal from the DC input voltage at the first input port such that:

at least one of the second switching circuit and the third switching circuit regulates the AC output voltage for a first portion of a negative second half cycle of the AC output voltage; and

the first switching circuit regulates the AC output voltage for a second portion of the negative second half cycle of the AC output voltage.

6. A power converter according to claim 5:

wherein the first portion of the negative second half cycle of the AC output voltage comprises a portion of the negative second half cycle of the AC output voltage for which the magnitude of the AC output voltage is less than the magnitude of the DC input voltage; and

wherein the second portion of the negative second half cycle of the AC output voltage comprises a portion of the second half cycle of the AC output voltage for which the magnitude of the AC output voltage is greater than the magnitude of the DC input voltage.

7. A power converter according to claim 1:

wherein the first switching circuit comprises;

a first inductance having first and second terminals, the first terminal of the first inductance coupled to the second terminal of the first input port;

a first switch operative to couple and decouple the second terminal of the first inductance and the first voltage bus; and

a second switch operative to couple and decouple the second terminal of the first inductance and the second voltage bus;

wherein the second switching circuit comprises;

a second inductance having first and second terminals, the first terminal of the second inductance coupled to the output terminal;

a third switch operative to couple and decouple the second terminal of the second inductance and the first voltage bus; and

a fourth switch operative to couple and decouple the second terminal of the second inductance and the second voltage bus; and

wherein the third switching circuit comprises;

a third inductance having first and second terminals, the first terminal of the third inductance connected to the neutral bus;

a fifth switch operative to couple and decouple the second terminal of the third inductance and the first voltage bus; and

a sixth switch operative to couple and decouple the second terminal of the third inductance and the second voltage bus.

8. A power converter according to claim 7, wherein the first and second switches operate in a substantially complementary fashion, wherein the third and fourth switches operate in a substantially complementary fashion, and wherein the fifth and sixth switches operate in a substantially complementary fashion.

9. A power converter according to claim 7, further comprising a seventh switch operative to couple and decouple the first terminal of the first inductance to the second terminal of the first input port.

10. A power converter according to claim 9, further comprising a battery connected to the first and second terminals of the first input port.

11. A power converter according to claim 1, further comprising:

a second input port; and

a fourth switching circuit operative to;

concurrently couple the second terminal of the first input port to the second voltage bus, decouple the second terminal of the first input port from the first switching circuit, and couple the first switching circuit to a first terminal of the second input port, in a first mode; and

concurrently couple the second terminal of the first input port to the first switching circuit, decouple the second terminal of the first input port from the second voltage bus, and decouple the first terminal of the second input port from the first switching circuit, in a second mode.

12. A power converter according to claim 11, wherein the first, second and third switching circuits are operative to generate a DC voltage across the first and second voltage busses from an AC voltage at the second input port.

13. A power converter according to claim 12, wherein the first, second and third switches are operative to generate a DC voltage across the first and second voltage busses in the first mode that is sufficient to cause power to be transferred from the first and second voltage busses to the first input port.

14. A power converter according to claim 1, further comprising a storage circuit coupled to the output terminal, the storage circuit including:

a capacitive storage element;

a rectifying circuit that rectifyingly couples the capacitive storage element to the output terminal to produce a DC voltage across the capacitive storage element from an AC output voltage at the output terminal; and

a fourth switching circuit that selectively couples the capacitive storage element to the output terminal.

15. A power converter according to claim 14:

wherein the storage circuit comprises first and second storage busses;

wherein the capacitive storage element comprises respective first and second capacitors coupling respective ones of the first and second storage busses to the neutral bus; and

wherein the fourth switching circuit comprises;

a first switch operative to couple and decouple the first storage bus and the output terminal; and

a second switch operative to couple and decouple the second storage bus and the output terminal.

18. A power converter according to claim 17, wherein the first and second inductors comprise respective first and second windings wound on a common core.

19. A power converter according to claim 17, wherein the first and second switching circuits operate in synchronism.

22. A power converter according to claim 16, wherein the DC voltage generating circuit is operative to produce the first and second DC voltages on the first and second voltage busses from at least one of an AC input voltage and a DC input voltage applied to the DC voltage generating circuit.

23. A power converter according to claim 22, wherein the DC voltage generating circuit comprises a rectifying circuit configured to connect to an AC power source at an AC input port and operative to produce the first and second DC voltages on the first and second voltage busses from an AC input voltage applied to the DC voltage generating circuit, and wherein the rectifying circuit, the first switching circuit and the second switching circuit are operative to produce the AC output voltage at the output terminal while maintaining a substantially unity power factor at the AC input port.

26. A method according to claim 24, comprising the step of alternatingly referencing the first and second terminals of the DC power source to the neutral bus for successive first and second half cycles of the AC output voltage.

27. A method according to claim 24, further comprising the steps of:

selectively coupling the first and second voltage busses to at least one of the second terminal of the load and the neutral bus to regulate the AC output voltage for a first portion of a first half cycle of the AC output voltage for which the magnitude of the AC output voltage is less than the magnitude of the DC input voltage; and

selectively coupling the first and second voltage busses to the second terminal of the DC power source to regulate the AC output voltage for a second portion of the first half cycle of the AC output voltage for which the magnitude of the AC output voltage is greater than the magnitude of the DC input voltage.

28. A method according to claim 25, further comprising the steps of:

selectively coupling the first and second voltage busses to the second terminal of the load through the third and fourth switches or to the neutral bus through the fifth and sixth switches to regulate the AC output voltage for a first portion of a first half cycle of the AC output voltage for which the magnitude of the AC output voltage is less than the magnitude of the DC input voltage; and

selectively coupling the first and second voltage busses to the second terminal of the DC power source through the first and second switches to regulate the AC output voltage for a second portion of the first half cycle of the AC output voltage for which the magnitude of the AC output voltage is greater than the magnitude of the DC input voltage.

29. A method according to claim 27, wherein the first half cycle of the AC output voltage comprises a positive first half-cycle of the AC output voltage, and wherein the method further comprise the steps of:

selectively coupling the first and second voltage busses to at least one of the second terminal of the load and the neutral bus to regulate the AC output voltage for a first portion of a negative second half cycle of the AC output voltage for which the magnitude of the AC output voltage is less than the magnitude of the DC input voltage; and

selectively coupling the first and second voltage busses to the second terminal of the DC power source to regulate the AC output voltage for a second portion of the negative second half cycle of the AC output voltage for which the magnitude of the AC output voltage is greater than the magnitude of the DC input voltage.

30. A method according to claim 28, wherein the first half-cycle of the AC output voltage comprises a positive first half cycle of the AC output voltage, and wherein the method further comprises the steps of:

selectively coupling the first and second voltage busses to the second terminal of the load through the third and fourth switches or to the neutral bus through the fifth and sixth switches to regulate the AC output voltage for a first portion of a negative second half cycle of the AC output voltage for which the magnitude of the AC output voltage is less than the magnitude of the DC input voltage; and

selectively coupling the first and second voltage busses to the second terminal of the DC power source through the first and second switches to regulate the AC output voltage for a second portion of the negative second half cycle of the AC output voltage for which the magnitude of the AC output voltage is greater than the magnitude of the DC input voltage.

31. A method according to claim 24, wherein the DC power source is a battery.

32. A method according to claim 24, further comprising the steps of:

rectifyingly coupling a capacitive storage element to the second terminal of the load to produce a DC voltage across the capacitive storage element from the AC output voltage at the second terminal of the load; and

selectively coupling the capacitive storage element to the second terminal of the load through a switching circuit to transfer power between the capacitive storage element to the load.

16. A power converter, comprising:

first and second voltage busses;

a neutral bus;

an output terminal;

a DC voltage generating circuit operative to produce respective first and second DC voltages on respective ones of the first and second voltage busses;

a first switching circuit operative to selectively couple the first and second voltage busses to the output terminal; and

a storage circuit connected to the output terminal, the storage circuit including;

a capacitive storage element;

a rectifying circuit coupling the capacitive storage element to the output terminal and operative to produce a DC voltage across the capacitive storage element from an AC output voltage at the output terminal; and

a second switching circuit operative to selectively couple the capacitive storage element to the output terminal.

17. A power converter according to claim 16:

wherein the first switching circuit comprises;

a first inductor having first and second terminals, the first terminal coupled to the output terminal; and

respective first and second switches operative to selectively couple the second terminal of the inductor to the first and second voltage busses;

wherein the power converter further comprises a second inductor that electrically couples the storage circuit to the output terminal and that is inductively coupled to the first inductor.

20. A power converter according to claim 17:

wherein the storage circuit comprises first and second storage busses;

wherein the capacitive storage element comprises respective first and second capacitors coupling respective ones of the first and second storage busses to the neutral bus; and

wherein the second switching circuit comprises;

a third switch operative to couple and decouple the first storage bus and the output terminal; and

a fourth switch operative to couple and decouple the second storage bus and the output terminal.

21. A power converter according to claim 20, wherein the first and third switches open and close in synchronism, and wherein the second and fourth switches open and close in synchronism.

24. A method of generating an AC output voltage at a load from a DC input voltage produced by a DC power source, the method comprising the steps of:

coupling a first terminal of the DC power source to one of a first voltage bus and a second voltage bus;

selectively coupling a second terminal of the DC power source to the first voltage bus and a second voltage bus;

coupling a first terminal of a load to a neutral bus;

selectively coupling the first and second voltage busses to a second terminal of the load; and

selectively coupling the first and second voltage busses to the neutral bus.

25. A method according to claim 24:

wherein said step of selectively coupling a second terminal of the DC power source to the first voltage bus and a second voltage bus comprises the step of selectively coupling respective ones of the first and second voltage busses to the DC power source through respective first and second switches;

wherein said step of selectively coupling the first and second voltage busses to a second terminal of the load comprises the step of selectively coupling respective ones of the first and second voltage busses to the second terminal of the load through respective third and fourth switches; and

wherein said step of selectively coupling the first and second voltage busses to the neutral bus comprises the step of selectively coupling respective ones of the first and second voltage busses to the neutral bus through respective fifth and sixth switches.

33. A method of producing an AC output voltage at a load, the method comprising the steps of:

generating respective first and second DC voltages on the first and second voltage busses;

selectively coupling the first and second voltage busses to the load through respective first and second switches to generate an AC output voltage at the load;

rectifyingly coupling first and second capacitors to the load to produce respective first and second DC voltages across respective ones of the first and second capacitors from an AC output voltage at the load; and

selectively coupling the first and second capacitors to the load through respective third and fourth switches to transfer power between the first and second capacitors and the load.

34. A power converter according to claim 33:

wherein the step of selectively coupling the first and second voltage busses to the load comprises the step of selectively coupling the first and second voltage busses to the load through a first inductor;

wherein the step of rectifyingly coupling comprises the step of rectifyingly coupling the first and second capacitors to the load through a second inductor; and

wherein the step of selectively coupling the first and second capacitors to the load comprises the step of selectively coupling the first and second capacitors to the load through the second inductor; and

wherein the method further comprises the step of inductively coupling the first and second inductors.

35. A method according to claim 34, wherein the first and second inductors comprise respective first and second windings wound on a common core.

36. A method according to claim 34, comprising the steps of:

operating the first and third switches in synchronism; and

operating the second and fourth switches in synchronism.

37. A method according to claim 33, wherein the step of generating respective first and second DC voltages comprises the step of rectifying an AC input voltage applied at an input port to produce the first and second DC voltages while maintaining a substantially unity power factor at the input port, and wherein the method comprises the step of operating the first, second, third and fourth switches to produce the AC output voltage at the load.