Modular system for unattended energy generation and storage

• US 7,994,657 B2
• Filed: 12/22/2006
• Issued: 08/09/2011
• Est. Priority Date: 12/22/2006
• Status: Active Grant

• Current Assignee: Enphase Energy Incorporated
• Original Assignee: Solarbridge Technologies Incorporated (Totalenergies Se)
• Inventors: Kimball, Jonathan W., Krein, Philip T., Benavides, Nicholas D.
• Primary Examiner(s): Deberadinis; Robert L.
• Application Number:
  US11/615,074
• Publication Number:
  US 20080150484A1
• Time in Patent Office: 1,691 Days
• Field of Search: 307/82
• US Class Current: 307/82
• CPC Class Codes: H02J 7/34 Parallel operation in networks using both storage and other dc sources, e.g. providing buffering H02J7/14 takes precedence
• CPC Class Codes: H02J 7/345 using capacitors as storage or buffering devices
• CPC Class Codes: H02J 7/35 with light sensitive cells

Abstract

An apparatus and method for supplying energy to a load includes an energy recharge unit, an energy storage unit, an energy converter connected to the energy recharge unit, the energy converter being capable of transferring energy at a power level from the energy recharge unit to an output node, the power level being determined by a power transfer controller, and a bi-directional energy converter connected to the energy storage unit and to the output node. The bi-directional energy converter is capable of converting energy of varying voltages from the energy storage unit to energy of varying current levels to supplement the transferred energy with energy from the energy storage unit so as to maintain a constant voltage on the output node. The bi-directional energy converter is capable of converting the transferred energy to provide charging energy to the energy storage unit when the transferred energy exceeds a demand level of the load while maintaining the constant voltage at the output node.

Claims

1. An apparatus for supplying energy to a load, comprising:

an energy recharge unit;

an energy storage unit;

an energy converter connected to said energy recharge unit, said energy converter being capable of transferring energy at a power level from said energy recharge unit to an output node at a predetermined voltage, said power level being determined by a power transfer controller; and

a bi-directional energy converter connected to said energy storage unit and to said output node;

a sensorless current mode (SCM) controller connected to the energy storage unit to receive an output of the energy storage, to the output node to receive an output of the bi-directional energy converter, and to the bi-directional energy converter, the SCM controller being configured to control the operation of the bi-directional energy converter, based on the output of the energy storage and the output of the bi-directional energy converter, to maintain the voltage of the output node at the predetermined voltage by;

(i) converting energy of varying voltages from said energy storage unit to energy of varying current levels at the predetermined voltage to supplement said transferred energy with energy from said energy storage unit,

(ii) converting said transferred energy to provide charging energy to said energy storage unit when said transferred energy exceeds a demand level of said load, and

(iii) deactivating the bi-directional energy converter in response to the transferred energy falling below the demand level of said load and a charge level of the energy storage unit falling below a predetermined lower charge threshold.

2. The apparatus of claim 1, wherein said bi-directional energy converter interrupts said charging of said energy storage unit when a charge level of said energy storage unit reaches a predetermined upper charge threshold.

3. The apparatus of claim 1, wherein said bi-directional energy converter maintains said constant voltage at said output node under varying input voltages.

4. The apparatus of claim 1, wherein said power transfer controller determines said power level of said transferred energy by optimizing said produced electric energy by adjusting an operating point of said energy recharge unit.

5. The apparatus of claim 1, wherein said energy converter is deactivated when said produced energy falls below a predetermined energy level.

6. The apparatus according to claim 1, further comprising a protection element that serves to disconnect said energy storage unit when a fault is detected at said output node.

7. The apparatus according to claim 6, wherein said protection element reconnects said energy storage unit when said fault has been cleared, and said bi-directional energy converter resumes supplementing said transferred energy with energy from said energy recharge unit.

8. The apparatus according to claim 1, further comprising a unidirectional conducting element provided at an output of said energy recharge unit to prevent current from flowing toward said energy recharge unit.

9. The apparatus according to claim 1, wherein said energy storage unit comprises a plurality of rechargeable elements with a capability of receiving energy from said energy recharge unit.

10. The apparatus according to claim 9, further comprising an equalizer that serves to ensure a voltage balance and a charge balance among said plurality of rechargeable elements.

11. The apparatus according to claim 9, wherein said plurality of rechargeable elements comprises batteries.

12. The apparatus according to claim 9, wherein said plurality of rechargeable elements comprises capacitors.

13. The apparatus according to claim 12, wherein said capacitors are ultra-capacitors.

14. The apparatus of claim 1, wherein said energy converter is a dc-dc converter.

15. The apparatus of claim 1, wherein said bi-directional energy converter is a dc-dc bi-directional converter.

16. The apparatus of claim 1, wherein said energy recharge unit is one of a solar power unit, a wind power unit, a flywheel power unit, a geothermal power unit and a generator unit.

17. A method of providing energy to a load from a power supply system, said power supply system comprising an energy recharge unit, an energy converter with an input connected to the energy recharge unit and an output connected to an output node and coupled to a power transfer controller, a rechargeable energy storage unit, a bi-directional energy converter with an input connected to said rechargeable energy storage unit and an output connected to said output node, said output node being connected to an input of said load, and a sensorless current mode (SCM) controller with a first input connected to said rechargeable energy storage unit and a second input connected to the output of the bi-directional energy converter, said method comprising:

exposing said energy recharge unit to a corresponding energy source as to produce electric energy;

determining via said power transfer controller whether a power level of said produced electric energy is above a predetermined power threshold in order to activate said energy converter;

converting said produced electric energy by said energy converter and delivering said converted electric energy to said load at a predetermined voltage in order to meet at least part of a demand level of said load;

monitoring a voltage at said output node; and

controlling the operation of the bi-directional energy converter with the SCM controller, based on an output of the energy storage unit and an output of the bi-directional energy converter, to maintain the voltage of said output node at the predetermined voltage by;

(i) converting energy stored in said energy storage unit by said bi-directional energy converter to supplement said delivery of said converted produced energy to said load, and

(ii) converting said transferred energy to provide charging energy to said energy storage unit when said transferred energy exceeds the demand level of said load, and

(iii) deactivating the bi-directional energy converter in response to the transferred energy falling below the demand level of said load and a charge level of the energy storage unit falling below a predetermined lower charge threshold.

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

deactivating said energy converter when said power level of said produced electric energy falls below said predetermined power threshold.

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

deactivating said energy converter when said demand level of said load falls below a predetermined load threshold and a charge level of said energy storage unit is above a predetermined charge threshold.

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

delivering said produced electric energy to said bi-directional energy converter to charge said energy storage unit when a charge level of said energy storage unit is below a predetermined charge upper threshold.

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

discontinuing charging said energy storage unit when said charge level of said energy storage unit is at or near said predetermined charge upper threshold.

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

preventing delivery of said converted electric energy to said load when a charge level of said energy storage unit is below a predetermined charge lower threshold;

delivering said produced electric energy to said bi-directional energy converter to charge said energy storage unit until said charge level of said energy storage unit is above said predetermined charge lower threshold; and

resuming delivery said converted electric energy to said load.

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

optimizing said produced electric energy by adjusting an operating point of said energy recharge unit via said power transfer controller.

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

disconnecting said energy storage unit when a fault is detected at said output node.

25. The method of claim 17, wherein said energy recharge unit is one of a solar power unit, a wind power unit, a flywheel power unit, a geothermal power unit and a generator.

26. The method of claim 17, wherein said energy converter is a dc-dc converter.

27. The method of claim 17, wherein said energy recharge unit comprises a plurality of rechargeable elements.

28. The method according to claim 27, wherein said plurality of rechargeable elements comprises batteries.

29. The method according to claim 27, wherein said plurality of rechargeable elements comprises capacitors.

30. The method according to claim 29, wherein said capacitors are ultra-capacitors.

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

balancing a voltage balance and a charge balance of said plurality of rechargeable elements via an equalizer.

32. The method of claim 17, wherein said bi-directional energy converter is a dc-dc bi-directional converter.

33. A computer readable medium comprising instructions which when executed by a computer system causes the computer to implement a method for providing energy to a load from a power apparatus, said power apparatus comprising an energy recharge unit, an energy converter with an input connected to the energy recharge unit and coupled to a power transfer controller, a rechargeable energy storage unit, a bi-directional energy converter with an input connected to said rechargeable energy storage unit, and a sensorless current mode (SCM) controller connected to said rechargeable energy storage unit and to the bi-directional energy converter, said method comprising:

exposing said energy recharge unit to a corresponding energy source so as to produce electric energy;

determining via said power transfer controller whether a power level of said produced electric energy is above a predetermined power threshold in order to activate said energy converter;

converting said produced electric energy by said energy converter and delivering said converted electric energy to said load at a predetermined voltage in order to meet at least part of a demand level of said load;

monitoring a voltage at said output node; and

controlling the operation of the bi-directional energy converter with the SCM controller, based on an output of the energy storage unit and an output of the bi-directional energy converter, to maintain the voltage of said output node at the predetermined voltage by;

(i) converting energy stored in said energy storage unit by said bi-directional energy converter to supplement said delivery of said converted produced energy to said load,

(ii) converting said transferred energy to provide charging energy to said energy storage unit when said transferred energy exceeds the demand level of said load, and

(iii) deactivating the bi-directional energy converter in response to the transferred energy falling below the demand level of said load and a charge level of the energy storage unit falling below a predetermined lower charge threshold.

34. A system for performing a method for providing energy to a load from a power apparatus, said power apparatus comprising an energy recharge unit, an energy converter with an input connected to the energy recharge unit and coupled to a power transfer controller, a rechargeable energy storage unit, a bi-directional energy converter with an input connected to said rechargeable energy storage unit, said energy recharge unit being exposed to a corresponding energy source so as to produce electric energy, the system comprising:

at least one processor programmed to determine via said power transfer controller whether a power level of said produced electric energy is above a predetermined power threshold in order to activate said energy converter, to activate said energy converter to convert said produced electric energy and to deliver said converted electric energy to said load at a predetermined voltage in order to meet at least part of a demand level of said load; and

a sensorless current mode (SCM) controller connected to the rechargeable energy storage unit to receive an output of the energy storage, to the output node to receive an output of the bi-directional energy converter, and to the bi-directional energy converter, the SCM controller being configured to control the operation of the bi-directional energy converter, based on the output of the energy storage and the output of the bi-directional energy converter, to maintain the voltage of said input at the predetermined voltage by;

(i) converting energy stored in said energy storage unit for supplementing said delivery of said converted produced energy to said load

(ii) converting at least part of said transferred energy to provide charging energy to said energy storage unit when said transferred energy exceeds the demand level of said load, and

(iii) deactivating the bi-directional energy converter in response to the transferred energy falling below the demand level of said load and a charge level of the energy storage unit falling below a predetermined lower charge threshold.

35. The system according to claim 34, further comprising:

at least one processor programmed to deactivate said energy converter when said power level of said produced electric energy falls below said predetermined power threshold.

36. The system according to claim 34, further comprising:

at least one processor programmed to deactivate said energy converter when said demand level of said load falls below a predetermined load threshold and a charge level of said energy storage unit is at or near a predetermined upper charge threshold.

37. The system according to claim 34, further comprising:

at least one processor programmed to discontinue delivery of said produced electric energy to said load when said demand level of said load falls below a predetermined load threshold, and to deliver said produced electric energy to said bi-directional energy converter to charge said energy storage unit when a charge level of said energy storage unit is below a predetermined charge upper threshold.

38. The system according to claim 34, further comprising:

at least one processor programmed to discontinue charging said energy storage unit when said charge level of said energy storage unit is at or above said predetermined charge upper threshold.

39. The system according to claim 34, further comprising:

at least one processor programmed to prevent delivery of said converted electric energy to said load when a charge level of said energy storage unit is below a predetermined charge lower threshold, to deliver said converted electric energy to said bi-directional energy converter to charge said energy storage unit until said charge level of said energy storage unit is above said predetermined charge lower threshold.

40. The system according to claim 34, further comprising:

at least one processor programmed to optimize said produced electric energy by adjusting an operating point of said energy recharge unit via said power transfer controller.

41. The system according to claim 34, further comprising:

at least one processor programmed to disconnect said energy storage unit when a fault is detected at said output node.