Device and method for global maximum power point tracking

• US 8,922,185 B2
• Filed: 12/13/2011
• Issued: 12/30/2014
• Est. Priority Date: 07/11/2011
• Status: Active Grant

• Current Assignee: Enphase Energy Incorporated
• Original Assignee: Solarbridge Technologies Incorporated (Totalenergies Se)
• Inventors: Ehlmann, Jonathan, Blair, Daniel, Martina, Eric, Chapman, Patrick, Kuhn, Brian
• Primary Examiner(s): PATEL, RAJNIKANT B
• Application Number:
  US13/324,027
• Publication Number:
  US 20130016536A1
• Time in Patent Office: 1,113 Days
• Field of Search: 323266-268, 323/274, 323280-290, 323/299, 323/906, 323/907, 363 16- 17, 363/34, 363/37, 363/39, 363/40, 363/89, 363/95, 363/97, 363/131, 363/132, 307/23, 307/26, 307/46, 307/64, 307/66, 307/82
• US Class Current: 323/284
• CPC Class Codes: G05F 1/67 to the maximum power available from a generator, e.g. from solar cell
• CPC Class Codes: H02J 2300/26 involving maximum power point tracking control for photovoltaic sources maximum power point systems in particular G05F1/67
• CPC Class Codes: H02J 3/381 Dispersed generators
• CPC Class Codes: H02M 1/007 Plural converter units in cascade push-pull DC/DC converters with pre-regulator H02M3/3374; DC-AC converters following a DC-DC stage including a high frequency transformer H02M7/4807; DC-AC converters following a DC-DC conversion stage generating periodically varying voltages H02M7/4826
• CPC Class Codes: H02M 7/44 by static converters
• CPC Class Codes: H02M 7/48 using discharge tubes with control electrode or semiconductor devices with control electrode
• CPC Class Codes: Y02E 10/56 Power conversion systems, e.g. maximum power point trackers

Abstract

A device, system, and method for global maximum power point tracking comprises monitoring an output power of a DC power source while executing a maximum power point tracking algorithm and adjusting a maximum power point tracking command signal in response to the output power being less than a reference output power. The command signal is adjusted until the output power exceeds a previous output power by a reference amount. The command signal may be a voltage command signal, a current command signal, an impedance command signal, a duty ratio command signal, or the like.

Claims

1. A method for an inverter configured to convert a direct current (DC) received from a DC power source to an alternating current (AC), the method comprising:

executing a maximum power point tracking algorithm to extract a substantially maximum power from the DC power source;

monitoring an output power of the DC power source while executing the maximum power point tracking algorithm; and

in response to the output power of the DC power source being less than a first reference output power, adjusting a command signal to modify a power point of the DC source until the output power of the DC power source is above a second reference output power greater than the first reference output power.

2. The method of claim 1, wherein adjusting the command signal comprises adjusting the command signal by multiple discrete, predetermined amounts.

3. The method of claim 1, wherein adjusting the command signal comprises adjusting the command signal in response to the output power of the DC power source being less than the first reference output power for a first period of time.

4. The method of claim 3, wherein adjusting the command signal comprises adjusting the command signal in response to the output power of the DC power source being less than the first reference output power for a period of time equal to about 10 seconds.

5. The method of claim 3, further comprising returning to execution of the maximum power point algorithm without adjusting the command signal in response to the output power of the DC power source increasing above the second reference output power during the first period of time.

6. The method of claim 1, further comprising:

in response to the output power of the DC power source being less than the first output power, storing (i) a command signal value of the command signal and (ii) an output power value of the DC power source prior to adjusting the command signal.

7. The method of claim 6, wherein adjusting the command signal comprises adjusting the command signal until the output power of the DC power source is above the stored output power value by a reference power amount.

8. The method of claim 7, further comprising returning to the execution of the maximum power point algorithm using the adjusted command signal in response to the output power of the DC power source exceeding the stored output power value by the reference power amount.

9. The method of claim 8, wherein returning to execution of the maximum power point algorithm comprises returning to the execution of the maximum power point algorithm for a second time period, and further comprising:

monitoring the output power of the DC power source during the second time period; and

performing one of;

(i) returning to the execution of the maximum power point algorithm using the adjusted command signal in response to the output power exceeding the second reference output power during the second time period, or

(ii) readjusting the command signal in response to expiration of the second time period.

10. The method of claim 9, wherein the second time period is equal to about 600 seconds.

11. The method of claim 1, further comprising:

comparing the adjusted command signal to a command signal reference; and

returning the command signal back to the stored command signal value in response to the adjusted command signal being less than the command signal reference.

12. The method of claim 11, wherein returning the command signal back to the stored command signal value comprising adjusting the command signal by a discrete predetermined amount until the command signal substantially equals the stored command signal value.

13. The method of claim 1, wherein adjusting the command signal comprises adjusting the command signal in a first direction, and further comprising:

comparing the adjusted command signal to a command signal reference; and

adjusting the command signal in a second direction opposite the first direction in response to the adjusted command signal having a predetermined relationship with the command signal reference.

14. The method of claim 1, wherein the command signal is a voltage command signal and adjusting the command signal comprises decrementing the voltage command signal by a discrete voltage amount.

15. The method of claim 1, wherein the command signal is a current command signal and adjusting the command signal comprises incrementing the current command signal by a discrete current amount.

16. An inverter for converting direct current (DC) power from a DC power source to alternating current (AC) power, the inverter comprising:

an inverter controller configured to;

execute a maximum power point tracking algorithm to extract a substantially maximum power from the DC power source, the maximum power point tracking algorithm to adjust an a power point of the DC power source based on a command signal;

monitor an output power of the DC power source while executing the maximum power point tracking algorithm; and

in response to the output power of the DC power source being less than a first output power for a first period of time;

(i) store a command signal value of the command signal,

(ii) store a power output value of the output power of the DC power source,

(iii) adjust the command signal until the output power of the DC power source is above the stored power output value by a reference power amount, and

(iv) return to the execution of the maximum power point algorithm using the adjusted command signal in response to the DC power source exceeding the stored power output value by the reference power amount.

17. The inverter of claim 16, wherein the inverter controller is further configured to:

compare the adjusted command signal to a command signal reference, and

return the command signal back to the stored command signal value in response to the adjusted command signal having a predetermined relationship with the command signal reference.

18. The inverter of claim 17, wherein to return the command signal back to the stored command signal value comprises to adjust the command signal by a discrete predetermined amount until the command signal substantially equals the stored command signal value.

19. The inverter of claim 16, wherein to return to execution of the maximum power point algorithm comprises to return to the execution of the maximum power point algorithm for a second time period, and wherein the inverter controller is further configured to:

monitor the output power of the DC power source during the second time period; and

perform one of;

(i) return to the execution of the maximum power point algorithm using the adjusted command signal in response to the output power exceeding the second reference output power during the second time period, or

(ii) readjust the command signal to response to expiration of the second time period.

20. The inverter of claim 16, wherein the inverter controller is further configured to return to execution of the maximum power point algorithm without adjusting the command signal in response to the output power of the DC power source increasing above the second reference output power during the first period of time.

21. The inverter of claim 16, wherein to adjust the command signal comprises to adjust the command signal in a first direction, and the inverter controller is further configured to:

compare the adjusted command signal to a command signal reference; and

adjust the command signal in a second direction opposite the first direction in response to the adjusted command signal having a predetermined relationship with the command signal reference.

22. The inverter of claim 16, wherein the command signal is a voltage command signal and to adjust the command signal comprises to decrement the voltage command signal by a discrete voltage amount.

23. The inverter of claim 16, wherein the command signal is a current command signal and to adjust the command signal comprises to increment the current command signal by a discrete current amount.

24. An apparatus comprising:

a solar panel comprising a plurality of solar cells configured to generate a direct current (DC) power output in response to receiving an amount of sunlight; and

an inverter coupled to the solar cell panel and configured to receive the DC power output, the inverter comprising;

a converter circuit to convert the DC power output to the AC power output;

a converter control circuit to control an input converter of the converter circuit based on a voltage command signal;

a maximum power point tracking (MPPT) circuit; and

a memory having stored therein a plurality of instructions, which when executed by the MPPT circuit, result in the MPPT circuit;

executing a maximum power point tracking algorithm to generate the voltage command signal to the input converter to cause the input converter to adjust a power point of the plurality of solar cells to extract a substantially maximum power from the solar panel;

monitoring the DC power output of the solar panel while executing the maximum power point tracking algorithm; and

in response to the DC output power of the solar panel being less than a first output power, adjusting the voltage command signal until the DC output power of the solar panel is above a second reference output power greater than the first reference output power.

25. The apparatus of claim 24, wherein adjusting the voltage command signal comprises adjusting the voltage command signal in response to the DC output power of the solar panel being less than the first reference output power for a first period of time.

26. The apparatus of claim 25, wherein the plurality of instructions further result in the MPPT circuit returning to execution of the maximum power point algorithm without adjusting the voltage command signal in response to the DC output power of the solar panel increasing above the second reference output power during the first period of time.

27. The apparatus of claim 24, wherein the plurality of instructions further result in the MPPT circuit:

in response to the DC output power of the solar panel being less than the first output power, storing (i) a voltage command signal value of the voltage command signal and (ii) an output power value of the solar panel prior to adjusting the command signal.

28. The apparatus of claim 27, wherein adjusting the voltage command signal comprises adjusting the voltage command signal until the DC output power of the solar panel is above the stored output power value by a reference power amount.

29. The apparatus of claim 28, wherein the plurality of instructions further result in the MPPT circuit returning to the execution of the maximum power point algorithm using the adjusted voltage command signal in response to the DC output power of the solar panel exceeding the stored output power value by the reference power amount.

30. The apparatus of claim 29, wherein returning to execution of the maximum power point algorithm comprises returning to the execution of the maximum power point algorithm for a second time period, and wherein the plurality of instructions further result in the MPPT circuit:

monitoring the DC output power of the solar panel during the second time period; and

performing one of;

(i) returning to the execution of the maximum power point algorithm using the adjusted voltage command signal in response to the DC output power exceeding the second reference output power during the second time period, or

(ii) readjusting the voltage command signal to response to expiration of the second time period.

31. The apparatus of claim 24, wherein the plurality of instructions further result in the MPPT circuit:

comparing the adjusted voltage command signal to a voltage command signal reference; and

returning the voltage command signal back to the stored voltage command signal value in response to the adjusted voltage command signal being less than the voltage command signal reference.