Modular power conversion system

1. A method for determining when a connection of a power system to a grid has been disconnected comprising:

the power system supplying a first amount of reactive power to the grid to which the power system is connected; and

the power system determining if there is a frequency change within the grid comprising:

determining a predetermined threshold;

if the frequency change does not exceed the predetermined threshold, the power system supplying a second amount of reactive power to the grid; and

if the frequency exceeds the predetermined threshold, the power system supplying a first amount of reactive power to the grid.

2. The method of claim 1 , wherein the second amount of reactive power is greater than the first amount of reactive power.

3. The method of claim 1 , wherein if the frequency change does not exceed a predetermined threshold, supplying a second amount of reactive power to the grid further comprising:

the power system supplying a third amount of reactive power to the grid.

4. The method of claim 3 , further comprising monitoring the frequency of the grid connected to the power system.

5. The method of claim 4 , further comprising determining if there is a frequency change within the grid.

6. The method of claim 5 , further comprising if a frequency change is detected, the power system determining whether the frequency change exceeds a predetermined threshold.

7. The method of claim 3 , wherein the third amount of reactive power is greater than the second amount of reactive power.

8. The method of claim 6 , further comprising wherein determining whether the frequency change exceeds a predetermined threshold further comprising:

if the frequency change does not exceed a predetermined threshold, the power system supplying a fourth amount of reactive power to the power system.

9. The method of claim 8 , further comprising monitoring the frequency of the grid connected to the power system.

10. The method of claim 9 , further comprising determining if there is a frequency change within the grid.

11. The method of claim 10 , further comprising if a frequency change is detected, the power system determining whether the frequency change exceeds a predetermined threshold.

12. The method of claim 11 , further comprising if the frequency change exceeds the predetermined threshold, determining an island condition.

13. The method of claim 11 , further comprising if the frequency change does not exceed a predetermined threshold, the power system supplying a first amount of reactive power to the grid to which the power system is connected.

14. The method of claim 8 , wherein the fourth amount of reactive power is greater than the third amount of reactive power.

15. A method for determining when a connection of a power system to a grid has been disconnected comprising:

locking the power system to a frequency of the grid using a phase locked loop;

detecting a deviation from the frequency in the power system; and

shutting off the power system,

wherein detecting a deviation from the frequency further comprising:

determining a predetermined deviation threshold; and

determining whether the deviation exceeds the predetermined deviation threshold.

16. The method of claim 15 , wherein shutting off the power system comprising opening a relay.

17. The method of claim 15 , wherein shutting off the power system comprising turning off an inverter.

18. The method of claim 15 , wherein shutting off the power system comprising shutting off at least one component connected to the grid.

19. A method for determining when a connection of a power system to a grid has been disconnected comprising:

detecting a voltage value from a voltage sensor;

applying a transform to the voltage;

if the D-axis voltage value exceeds a predefined threshold;

detecting a fault; and

shutting off the power system.

20. The method of claim 19 , wherein shutting off the power system comprising turning off an inverter.