Power converter for executing anti-islanding procedures upon detecting an islanding condition

1. A power system comprising:

at least one power source providing direct current (DC) power;

a power converter comprising:

an inverter that converts the DC power to alternating current (AC) power;

an AC filter coupled to an output of the inverter;

a voltage sensor coupled to an output of the AC filter;

a current sensor coupled to the output of the AC filter;

an inductive coupler configured to couple the power system to a power grid; and

a switch operable to disconnect the inductive coupler from the power system and retain a connection between the power system and a local load; and,

an inverter controller providing to the inverter, an inverter control signal for modifying an operation of the inverter during an islanding condition, the islanding condition identified by using one or both of the voltage sensor and the current sensor to detect a change from a resistive load to an inductive load, the resistive load corresponding to the local load and the inductive load corresponding to the inductive coupler.

2. The power system of claim 1 , the inverter controller further comprising a feedback loop for generating a component signal that is used to generate the inverter control signal for modifying the operation of the inverter during the islanding condition.

3. The power system of claim 2 , wherein the feedback loop is configured to receive a nominal VAR reference signal from a utility company associated with the power grid.

4. The power system of claim 2 , wherein modifying the operation of the inverter during the islanding condition comprises stopping the inverter from outputting AC power during the islanding condition.

5. The power system of claim 1 , the inverter controller further comprising a phase lock loop (PLL) for generating angular information associated with a portion of an AC voltage measurement provided by the voltage sensor coupled to the output of the AC filter.

6. A power system comprising:

an inductive coupler configured to couple the power system to a power grid;

a switch operable to disconnect the inductive coupler from the power system and retain a connection between the power system and a local load; and

an inverter controller comprising:

a current regulator configured to generate a component signal based in part on a DC voltage measurement at an input of an inverter and a first AC current measurement at an output of the inverter, the component signal provided as feedback in a feedback loop for generating an output signal that is used for generating a command signal; and

a modulator that generates an inverter control signal based in part on the command signal, the inverter control signal provided to the inverter for modifying an operation of the inverter when an islanding condition exists, the islanding condition identified by using at least the first AC current measurement to detect a change from a resistive load to an inductive load, the resistive load corresponding to the local load, and the inductive load corresponding to the inductive coupler.

7. The power system of claim 6 , wherein the inverter control signal controls the inverter to output substantially no output power when the islanding condition exists.

8. The power system of claim 6 , wherein the feedback loop is a positive feedback loop comprising a filter.

9. The power system of claim 6 , further comprising a phase lock loop (PLL) for generating angular information associated with a portion of an AC voltage measurement from the output of an AC filter coupled to the output of the inverter.

10. The power system of claim 9 , further comprising a magnitude calculator for calculating a magnitude of the portion of the AC voltage measurement.

11. A method of controlling an inverter comprising:

determining in an inverter controller, a component signal based on at least a DC voltage measurement at an input of an inverter and a first AC current measurement at an output of the inverter, the component signal indicative of a change from a resistive load to an inductive load in a power converter system;

determining an inverter control signal based at least in part on the component signal; and

using the inverter control signal to stop the inverter from generating AC power during an islanding condition.

12. The method of claim 11 , further comprising controlling power output from the inverter when the islanding condition exists.

13. The method of claim 11 , wherein the component signal is provided in a positive feedback loop.

14. The method of claim 13 , further providing a filter in the positive feedback loop.