Systems And Methods For Controlling Maximum Power Point Tracking Controllers

• US 20140103891A1
• Filed: 10/16/2012
• Published: 04/17/2014
• Est. Priority Date: 10/16/2012
• Status: Active Grant

• Current Assignee: Volterra Semiconductor LLC (Analog Devices, Inc.)
• Original Assignee: Volterra Semiconductor Corporation (Analog Devices, Inc.)
• Inventors: Stratakos, Anthony J., McJimsey, Michael D., Jergovic, Ilija, Yao, Kaiwei, Zhang, Xin, Ng, Vincent W.
• Granted Patent: US 9,557,758 B2
• Time in Patent Office: Days
• US Class Current: 323/271
• CPC Class Codes: G05F 1/67 to the maximum power available from a generator, e.g. from solar cell
• CPC Class Codes: H02M 1/0003 Details of control, feedback or regulation circuits
• CPC Class Codes: H02M 3/158 including plural semiconductor devices as final control devices for a single load
• CPC Class Codes: H02S 50/10 Testing of PV devices, e.g. of PV modules or single PV cells testing of semiconductor devices during manufacturing H01L22/00
• CPC Class Codes: Y02E 10/56 Power conversion systems, e.g. maximum power point trackers

Abstract

A method for operating a maximum power point tracking (MPPT) controller including a switching circuit adapted to transfer power between an input port and an output port includes the steps of: (a) in a first operating mode of the MPPT controller, causing a first switching device of the switching circuit to operate at a fixed duty cycle; and (b) in a second operating mode of the MPPT controller, causing a control switching device of the switching circuit to repeatedly switch between its conductive and non-conductive states to maximize an amount of power extracted from a photovoltaic device electrically coupled to the input port.

Claims

1. A method for operating a maximum power point tracking (MPPT) controller including a switching circuit adapted to transfer power between an input port and an output port, comprising the steps of:

in a first operating mode of the MPPT controller, causing a first switching device of the switching circuit to operate at a fixed duty cycle; and

in a second operating mode of the MPPT controller, causing a control switching device of the switching circuit to repeatedly switch between its conductive and non-conductive states to maximize an amount of power extracted from a photovoltaic device electrically coupled to the input port.

2. The method of claim 1, the first switching device including at least one of the control switching device of the switching circuit and a freewheeling switching device of the switching circuit.

3. The method of claim 2, the fixed duty cycle being at least ninety percent duty cycle.

4. The method of claim 3, the fixed duty cycle being one hundred percent duty cycle.

5. The method of claim 2, further comprising operating the MPPT controller in its first operating mode in response to determining that a magnitude of a signal representing voltage across the output port is greater than a threshold value, prior to switching circuit operation at start-up of the MPPT controller.

6. The method of claim 5, further comprising causing the switching circuit to operate in its non-conductive state until a magnitude of a voltage on a power supply rail of the MPPT controller exceeds a predetermined value.

7. The method of claim 6, further comprising powering the power supply rail of the MPPT controller from the output port, in the first operating mode of the MPPT controller.

8. The method of claim 7, the first switching device comprising a first transistor, the method further comprising electrically coupling current to the power supply rail of the MPPT controller using a body diode of the first transistor.

9. The method of claim 2, further comprising operating the MPPT controller in its first operating mode in response to determining that a signal representing current flowing out of the output port is less than or equal to a threshold value.

10. The method of claim 9, the threshold value representing that current is flowing out of the output port in a negative direction.

11. The method of claim 10, further comprising causing the switching circuit to operate in its non-conductive state until a magnitude of a voltage on a power supply rail of the MPPT controller exceeds a predetermined value.

12. The method of claim 11, further comprising powering the power supply rail of the MPPT controller from the output port, in the first operating mode of the MPPT controller.

13. The method of claim 12, the first switching device comprising a first transistor, the method further comprising electrically coupling current to the power supply rail of the MPPT controller using a body diode of the first transistor.

14. The method of claim 10, further comprising continuing to operate the MPPT controller in its first operating mode after a magnitude of current flowing out of the output port falls to zero.

15. The method of claim 2, further comprising operating the MPPT controller in its first operating mode in response to an external signal.

16. The method of claim 2, further comprising operating the MPPT controller in its first operating mode each time the MPPT controller starts up.

17. The method of claim 2, further comprising causing a duty cycle of the first switching device to ramp up to the fixed duty cycle when beginning to operate the MPPT controller in its first operating mode.

18. The method of claim 2, further comprising switching from the first operating mode to a different operating mode of the MPPT controller after a predetermined amount of time.

19. The method of claim 18, the different operating mode being the second operating mode of the MPPT controller.

20. The method of claim 2, further comprising switching from the first operating mode to a different operating mode of the MPPT controller when a first voltage signal falls below a threshold value.

21. The method of claim 20, the first voltage signal being a function of a voltage across the input port.

22. The method of claim 20, the different operating mode being the second operating mode of the MPPT controller.

23. The method of claim 2, further comprising causing the control switching device to repeatedly switch between its conductive and non-conductive states at a duty cycle which maintains a predetermined output current-voltage characteristic of the MPPT controller, in a third operating mode of the MPPT controller.

24. The method of claim 23, further comprising operating the MPPT controller in its third operating mode in response to determining that a signal representing current flowing out of the output port is less than or equal to a threshold value.

25. The method of claim 24, the threshold value representing that current is flowing out of the output port in a negative direction.

26. The method of claim 23, the predetermined output current-voltage characteristic of the MPPT controller being linear such that magnitude of average voltage across the output port changes linearly in response to a change in magnitude of average current flowing into the input port.

27. The method of claim 23, the predetermined output current-voltage characteristic of the MPPT controller being non-linear such that magnitude of average voltage across the output port changes non-linearly in response to a change in magnitude of average current flowing into the input port.

28. A method for testing a photovoltaic device electrically coupled to an input port of a maximum power point tracking (MPPT) controller, wherein the MPPT controller includes a switching circuit adapted to transfer power between the input port and an output port of the MPPT controller, the method comprising the steps of:

driving a test current into the output port of the MPPT controller;

detecting presence of the test current; and

in response to detecting presence of the test current, causing the switching circuit to provide a path for the test current from the output port to the photovoltaic device.

29. The method of claim 28, the step of causing the switching circuit to provide a path for the test current from the output port to the photovoltaic device comprising causing a switching device of the switching circuit to operate at a fixed duty cycle.

30. The method of claim 29, the fixed duty cycle being at least ninety percent duty cycle.

31. The method of claim 30, the fixed duty cycle being one hundred percent duty cycle.

32. The method of claim 28, the step of causing the switching circuit to provide a path for the test current from the output port to the photovoltaic device comprising causing the MPPT controller to act as a fixed direct current transformer electrically coupling the test current to the photovoltaic device.

33. The method of claim 28, the step of detecting presence of the test current comprising detecting presence of current flowing into the output port from an external source.

34. The method of claim 28, the step of detecting presence of the test current comprising detecting voltage across the output port of the switching circuit.

35. The method of claim 34, the step of detecting voltage across the output port of the switching circuit comprising comparing a signal representing the voltage across the output port to a threshold value.

36. A maximum power point tracking (MPPT) controller, comprising:

an input and an output port;

a switching circuit adapted to transfer power between the input and output ports; and

a control subsystem adapted to;

cause a first switching device of the switching circuit to operate at a fixed duty cycle, in a first operating mode of the MPPT controller, and

cause a control switching device of the switching circuit to repeatedly switch between its conductive and non-conductive states to maximize an amount of electric power extracted from a photovoltaic device electrically coupled to the input port, in a second operating mode of the MPPT controller.

37. The MPPT controller of claim 36, the first switching device including at least one of the control switching device of the switching circuit and a freewheeling switching device of the switching circuit.

38. The MPPT controller of claim 37, the fixed duty cycle being at least ninety percent duty cycle.

39. The MPPT controller of claim 38, the fixed duty cycle being one hundred percent duty cycle.

40. The MPPT controller of claim 37, the control subsystem further adapted to:

compare a magnitude of a signal representing voltage across the output port to a threshold value, prior to switching circuit operation at start-up of the MPPT controller; and

operate the MPPT controller in its first operating mode in response to determining that the magnitude of the signal representing voltage across the output port is greater than the threshold value.

41. The MPPT controller of claim 40, the control subsystem further adapted to cause the switching circuit to operate in its non-conductive state until a magnitude of a voltage on a power supply rail of the MPPT controller exceeds a predetermined value.

42. The MPPT controller of claim 41, wherein the MPPT controller is configured such that the power supply rail of the MPPT controller is powered from the output port, in the first operating mode of the MPPT controller.

43. The MPPT controller of claim 41, wherein:

the control switching device is electrically coupled between a first terminal of the input port and a first terminal of the output port;

the switching circuit further comprises a freewheeling device electrically coupled between the first terminal of the output port and a second terminal of the output port, the freewheeling device adapted to provide a path for current flowing between the first and second terminals of the output port when the control switching device is in its non-conductive state;

the first switching device is the control switching device; and

the first terminal of the output port is electrically coupled to a switching node.

44. The MPPT controller of claim 43, the control switching device comprising a control transistor, the control transistor including a body diode having an anode electrically coupled to the switching node and a cathode electrically coupled to the first terminal of the input port.

45. The MPPT controller of claim 37, the control subsystem further adapted to:

compare a signal representing current flowing out of the output port to a threshold value; and

operate the MPPT controller in its first operating mode in response to determining that the signal representing current flowing out of the output port is less than or equal to the threshold value.

46. The MPPT controller of claim 45, the threshold value representing that current is flowing out of the output port in a negative direction.

47. The MPPT controller of claim 46, the control subsystem further adapted to cause the switching circuit to operate in its non-conductive state until a magnitude of a voltage on a power supply rail of the MPPT controller exceeds a predetermined value.

48. The MPPT controller of claim 47, wherein the MPPT controller is configured such that the power supply rail of the MPPT controller is powered from the output port, in the first operating mode of the MPPT controller.

49. The MPPT controller of claim 47, wherein:

the control switching device is electrically coupled between a first terminal of the input port and a first terminal of the output port;

the switching circuit further comprises a freewheeling device electrically coupled between the first terminal of the output port and a second terminal of the output port, the freewheeling device adapted to provide a path for current flowing between the first and second terminals of the output port when the control switching device is in its non-conductive state; and

the first switching device is the control switching device.

50. The MPPT controller of claim 49, the control switching device comprising a control transistor, the control transistor including a body diode having an anode electrically coupled to the first terminal of the output port and a cathode electrically coupled to the first terminal of the input port.

51. The MPPT controller of claim 46, the control subsystem further adapted to continue to operate the MPPT controller in its first operating mode after a magnitude of current flowing out of the output port falls to zero.

52. The MPPT controller of claim 37, the control subsystem further adapted to operate the MPPT controller in its first operating mode in response to an external signal.

53. The MPPT controller of claim 37, the control subsystem further adapted to operate the MPPT controller in its first operating mode each time the MPPT controller starts up.

54. The MPPT controller of claim 37, the control subsystem further adapted to cause a duty cycle of the first switching device to ramp up to the fixed duty cycle when beginning to operate the MPPT controller in its first operating mode.

55. The MPPT controller of claim 37, the control subsystem further adapted to cause to the MPPT controller to switch from its first operating mode to a different operating mode after a predetermined amount of time.

56. MPPT controller of claim 55, the different operating mode being the second operating mode of the MPPT controller.

57. The MPPT controller of claim 37, the control subsystem further adapted to:

compare a first voltage signal to a threshold value, the first voltage signal being a function of a voltage across the input port; and

cause the MPPT controller to switch from its first operating mode to a different operating mode of the MPPT controller, when the first voltage signal falls below the threshold value.

58. The MPPT controller of claim 57, the different operating mode being the second operating mode of the MPPT controller.

59. The MPPT controller of claim 37, the control subsystem further adapted to cause the control switching device to repeatedly switch between its conductive and non-conductive states at a duty cycle which maintains a predetermined output current-voltage characteristic of the MPPT controller, in a third operating mode of the MPPT controller.

60. The MPPT controller of claim 59, the control subsystem further adapted to:

compare a signal representing current flowing out of the output port to a threshold value; and

operate the MPPT controller in its third operating mode in response to determining that the signal representing current flowing out of the output port is less than or equal to the threshold value.

61. The MPPT controller of claim 60, the threshold value representing that current is flowing out of the output port in a negative direction.

62. The MPPT controller of claim 59, the predetermined output current-voltage characteristic of the MPPT controller being linear such that magnitude of average voltage across the output port changes linearly in response to a change in magnitude of average current flowing into the input port.

63. The MPPT controller of claim 59, the predetermined output current-voltage characteristic of the MPPT controller being non-linear such that magnitude of average voltage across the output port changes non-linearly in response to a change in magnitude of average current flowing into the input port.