Device and method for global maximum power point tracking

• US 10,050,446 B2
• Filed: 10/27/2017
• Issued: 08/14/2018
• Est. Priority Date: 07/11/2011
• Status: Active Grant

• Current Assignee: Enphase Energy Incorporated
• Original Assignee: Sunpower Corporation (Totalenergies Se)
• Inventors: Ehlmann, Jonathan, Blair, Daniel, Martina, Eric, Chapman, Patrick, Kuhn, Brian
• Primary Examiner(s): Patel, Rajnikant
• Application Number:
  US15/796,228
• Publication Number:
  US 20180054066A1
• Time in Patent Office: 291 Days
• Field of Search: 323266-268, 323274, 323280-290, 323299, 323906, 323907, 363 16- 17, 363 34, 363 37, 363 39, 363 89, 363 95, 363 97, 363132, 307 26, 307 46, 307 64, 307 82
• 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
• 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. An inverter for converting direct current (DC) power from a DC power source to alternating current (AC) power, the inverter comprising:

an input converter configured for electrically coupling to the DC power source and converting a DC waveform to a bus waveform on a power bus; and

an inverter controller electrically coupled to the input converter and configured to control operation of the input converter based on a global maximum power tracking (“

MPPT”

) method, the inverter controller comprising;

input sense circuitry configured to sense the input power of the DC power source;

an MPPT control module configured to;

execute a global MPPT method to search in a first direction for the global maximum power point; and

generate a command signal based on the input power of the DC power source; and

an input converter control module configured to;

receive the command signal from the MPPT control module;

receive a feedback signal of the input voltage of the DC power source; and

in response to the command and feedback signals, generate a plurality of switch control signals to control a plurality of switches of the input converter to adjust the power point of the DC power source;

whereby a substantially maximum power is extracted from the DC power source.

2. The inverter of claim 1, wherein the global MPPT method comprises:

monitoring the input power of the DC power source;

in response to the input power of the DC power source being less than a threshold, adjusting a value of the command signal and returning to monitoring the input power of the DC power source with the adjusted command signal value; and

in response to the input power of the DC power source not being less than the threshold, returning to monitoring the input power of the DC power source without adjusting the command signal value.

3. The inverter of claim 2, wherein the global MPPT method further comprises:

after adjusting the command signal value, determining if the command signal value has reached a command variable threshold; and

in response to the command signal value not reaching a command variable threshold, performing one of;

returning to monitoring the input power of the DC power source with the adjusted command signal value in response to the input power of the DC power source being greater than the reference input power; and

returning to adjusting the command signal value in response to the input power of the DC power source being not greater than a reference input power.

4. The inverter of claim 3, wherein the global MPPT method further comprises, in response to the command signal value reaching a command variable threshold, performing one of:

executing the global MPPT method in a second direction, opposite the first direction with the adjusted command signal value; and

returning to monitoring the input power of the DC power source with the unadjusted command signal value.

5. The inverter of claim 2, wherein the command signal value is adjusted in response to the input power of the DC power source being less than the threshold for a predetermined period of time.

6. The inverter of claim 5, wherein the command signal value is not adjusted in response to the input power of the DC power source being less than the threshold for less than the predetermined period of time.

7. The inverter of claim 1, wherein:

the inverter further comprises an output converter configured for electrically coupling to an AC grid and converting the bus waveform to the AC power; and

the inverter controller further comprises an output converter control module configured to control operation of the output converter through a pulse width modulation (“

PWM”

) method.

8. The inverter of claim 1, wherein the command signal is a voltage command signal and adjusting the command signal value comprises adjusting the voltage command signal by a discrete voltage amount.

9. The inverter of claim 1, wherein the command signal is a current command signal and adjusting the command signal value comprises adjusting the current command signal by a discrete current amount.

10. The inverter of claim 1, further comprising communication circuitry communicatively coupled to the inverter controller and configured to communicate with remote devices.

11. A system for converting direct current (DC) power from a DC power source to alternating current (AC) power, the system comprising:

an input converter configured for electrically coupling to the DC power source and converting a DC waveform to a bus waveform on a power bus; and

an inverter controller electrically coupled to the input converter and configured to control operation of the input converter based on a global maximum power tracking (“

MPPT”

) method, the inverter controller comprising;

input sense circuitry configured to sense the input power of the DC power source;

an MPPT control module configured to;

execute a global MPPT method to search in a first direction for the global maximum power point; and

generate a command signal based on the input power of the DC power source; and

an input converter control module configured to;

receive the command signal from the MPPT control module;

receive a feedback signal of the input voltage of the DC power source; and

in response to the command and feedback signals, generate a plurality of switch control signals to control a plurality of switches of the input converter to adjust the power point of the DC power source;

whereby a substantially maximum power is extracted from the DC power source.

12. The system of claim 11, wherein the global MPPT method comprises:

monitoring the input power of the DC power source;

in response to the input power of the DC power source being less than a threshold, adjusting a value of the command signal and returning to monitoring the input power of the DC power source with the adjusted command signal value; and

in response to the input power of the DC power source not being less than the threshold, returning to monitoring the input power of the DC power source without adjusting the command signal value.

13. The system of claim 12, wherein the global MPPT method further comprises:

after adjusting the command signal value, determining if the command signal value has reached a command variable threshold; and

in response to the command signal value not reaching a command variable threshold, performing one of;

returning to monitoring the input power of the DC power source with the adjusted command signal value in response to the input power of the DC power source being greater than the reference input power; and

returning to adjusting the command signal value in response to the input power of the DC power source being not greater than a reference input power.

14. The system of claim 13, wherein the global MPPT method further comprises, in response to the command signal value reaching a command variable threshold, performing one of:

executing the global MPPT method in a second direction, opposite the first direction with the adjusted command signal value; and

returning to monitoring the input power of the DC power source with the unadjusted command signal value.

15. The system of claim 12, wherein the command signal value is adjusted in response to the input power of the DC power source being less than the threshold for a predetermined period of time.

16. The system of claim 15, wherein the command signal value is not adjusted in response to the input power of the DC power source being less than the threshold for less than the predetermined period of time.

17. The system of claim 11, wherein:

the inverter further comprises an output converter configured for electrically coupling to an AC grid and converting the bus waveform to the AC power; and

the inverter controller further comprises an output converter control module configured to control operation of the output converter through a pulse width modulation (“

PWM”

) method.

18. The system of claim 11, wherein the command signal is a voltage command signal and adjusting the command signal value comprises adjusting the voltage command signal by a discrete voltage amount.

19. The system of claim 11, wherein the command signal is a current command signal and adjusting the command signal value comprises adjusting the current command signal by a discrete current amount.

20. The system of claim 11, further comprising communication circuitry communicatively coupled to the inverter controller and configured to communicate with remote devices.