Method and apparatus for synchronizing start-up of grid-forming inverters

1. A method for synchronizing decentralized power conditioner start-up in a distributed resource island system (DRIS), comprising:

determining, by a power conditioner in the DRIS, when a line voltage of the DRIS collapses to zero;

starting, by the power conditioner, when the line voltage collapses to zero, a black-start timer, wherein the black-start timer is set to the same amount of time as a plurality of black-start timers corresponding to a plurality of power conditioners of the DRIS; and

initiating, by the power conditioner, following expiration of the black-start timer, a black-start.

2. The method of claim 1 , further comprising:

initiating, following the expiration of the timer and before initiating the black-start, a time delay.

3. The method of claim 2 , wherein the time delay is a randomized time delay.

4. The method of claim 3 , wherein the randomized time delay is based on a confidence score that indicates a confidence level in generating a particular polarity of current.

5. The method of claim 4 , wherein the confidence score is adjusted based on at least one event observed, by the power conditioner, during ramp-up.

6. The method of claim 5 , wherein the at least one event comprises at least one of a voltage from at least one other power conditioner of the DRIS, an unsuccessful ramp-up attempt, or a successfully completed ramp-up.

7. The method of claim 4 , wherein a delay range for the randomized delay is inversely proportional to the confidence score.

8. The method of claim 7 , wherein the delay range is zero when the confidence score is at its maximum value.

9. An apparatus for synchronizing decentralized power conditioner start-up in a distributed resource island system (DRIS), comprising:

a controller for a power conditioner in the DRIS, wherein the controller comprises at least one processor and:

determines when a line voltage of the DRIS collapses to zero;

starts, when the line voltage collapses to zero, a black-start timer, wherein the black-start timer is set to the same amount of time as a plurality of black-start timers corresponding to a plurality of power conditioners of the DRIS; and

initiates, following expiration of the black-start timer, a black-start.

10. The apparatus of claim 9 , wherein the controller further initiates, following the expiration of the timer and before initiating the black-start, a time delay.

11. The apparatus of claim 10 , wherein the time delay is a randomized time delay.

12. The apparatus of claim 11 , wherein the randomized time delay is based on a confidence score that indicates a confidence level in generating a particular polarity of current.

13. The apparatus of claim 12 , wherein the confidence score is adjusted based on at least one event observed, by the power conditioner, during ramp-up.

14. The apparatus of claim 13 , wherein the at least one event comprises at least one of a voltage from at least one other power conditioner in the DRIS, an unsuccessful ramp-up attempt, or a successfully completed ramp-up.

15. The apparatus of claim 12 , wherein a delay range for the randomized delay is inversely proportional to the confidence score.

16. The apparatus of claim 15 , wherein the delay range is zero when the confidence score is at its maximum value.

17. A non-transitory computer readable medium comprising a program that, when executed by a processor, performs a method for synchronizing decentralized power conditioner start-up in a distributed resource island system (DRIS), the method comprising:

determining when a line voltage of the DRIS collapses to zero;

starting, when the line voltage collapses to zero, a black-start timer, wherein the black-start timer is set to the same amount of time as a plurality of black-start timers corresponding to a plurality of power conditioners of the DRIS; and

initiating, following expiration of the black-start timer, a black-start of a power conditioner of the DRIS.

18. The non-transitory computer readable medium of claim 17 , the method further comprising:

initiating, following the expiration of the timer and before initiating the black-start, a time delay.

19. The non-transitory computer readable medium of claim 18 , wherein the time delay is a randomized time delay.

20. The non-transitory computer readable medium of claim 19 , wherein the randomized time delay is based on a confidence score that indicates a confidence level in generating a particular polarity of current.