Methods and apparatus for controlling operation of photovoltaic power plants

1. A method of controlling a photovoltaic power plant, the method comprising:

providing a reactive power setpoint to a photovoltaic inverter that converts direct current generated by a plurality of solar cells to alternating current;

detecting a real power output of the photovoltaic power plant at a point of interconnection (POI) of the photovoltaic power plant to a power grid;

comparing the real power output of the photovoltaic power plant to a minimum real power generation level; and

changing the reactive power setpoint to unity power factor in response to detecting that the real power output of the photovoltaic power plant is below the minimum real power generation level.

2. The method of claim 1 , further comprising:

detecting, using a meter, an output of the photovoltaic power plant at the POI; and

reading the meter to detect the real power output of the photovoltaic power plant.

3. The method of claim 1 , further comprising:

increasing the reactive power setpoint in response to detecting that the real power output of the photovoltaic power plant is above an enabling real power generation level.

4. The method of claim 2 , further comprising: receiving and processing readings from the meter using a compensator.

5. The method of claim 4 , wherein the compensator comprises a proportional-integral (PI) compensator.

6. A method of controlling a photovoltaic power plant, the method comprising:

providing a setpoint variable limit to a photovoltaic inverter that converts direct current generated by a plurality of solar cells to alternating current;

detecting an output of the photovoltaic power plant at a point of interconnection (POI) to a power grid in a first state of operation; and

dynamically adjusting the setpoint variable limit from a first inverter setpoint to a second inverter setpoint to lower a limit on a reactive power output of the photovoltaic inverter when the output of the photovoltaic power plant exceeds a maximum allowable reactive power or power factor of the photovoltaic power plant.

7. The method of claim 6 , wherein the output of the photovoltaic power plant detected at the POI comprises a reactive power output and the setpoint variable limit comprises an inverter reactive power setpoint.

8. The method of claim 6 , wherein the output of the photovoltaic power plant detected at the POI comprises a power factor output and the setpoint variable limit comprises an inverter power factor setpoint.

9. The method of claim 6 , wherein the output of the photovoltaic power plant at the POI is detected using a meter.

10. The method of claim 9 , further comprising:

receiving and processing a reading of the meter in a compensator.

11. The method of claim 10 , further comprising:

after receiving and processing the reading of the meter in the compensator, providing the reading of the meter to a plant controller that adjusts the setpoint variable limit.

12. The method of claim 10 , wherein the compensator comprises a proportional-integral (PI) compensator.

13. The method of claim 6 , wherein the photovoltaic power plant is controlled using automatic voltage regulation (AVR) in the first state of operation.

14. A method of controlling a photovoltaic power plant, the method comprising:

detecting an output of the photovoltaic power plant that is provided to a power grid;

comparing the output of the photovoltaic power plant to a maximum allowable output limit of the photovoltaic power plant, the maximum allowable output limit being a maximum allowable reactive power or power factor of the photovoltaic power plant; and

in response to detecting that the output of the photovoltaic power plant exceeds the maximum allowable output limit, lowering a limit on a reactive power output of a photovoltaic inverter that converts direct current generated by a plurality of solar cells to alternating current.

15. The method of claim 14 , wherein lowering the limit on the reactive power output of the photovoltaic inverter comprises:

lowering a setpoint variable limit of the photovoltaic inverter from a first inverter setpoint limit to a second inverter setpoint limit.

16. The method of claim 15 , wherein the output of the photovoltaic power plant comprises reactive power exported or absorbed by the photovoltaic inverter, the maximum allowable output limit of the photovoltaic power plant comprises a maximum allowable reactive power exported by the photovoltaic power plant, and each of the first and second inverter setpoint limits comprises a reactive power setpoint limit of the photovoltaic inverter.

17. The method of claim 15 , wherein detecting that the output of the photovoltaic power plant exceeds the maximum allowable output limit is performed in a first state of photovoltaic power plant operation and the lowering of the setpoint variable limit of the photovoltaic inverter from the first inverter setpoint limit to the second inverter setpoint limit is performed in a second state of photovoltaic power plant operation.

18. The method of claim 17 , further comprising:

returning to the first state of photovoltaic power plant operation in response to detecting that the output of the photovoltaic power plant no longer exceeds the maximum allowable output limit of the photovoltaic power plant.

19. The method of claim 17 , wherein the photovoltaic power plant is controlled by automatic voltage regulation (AVR) in the first state of photovoltaic power plant operation.

20. The method of claim 15 , wherein the output of the photovoltaic power plant output comprises a power factor output, the maximum allowable output limit comprises a maximum allowable power factor of the photovoltaic power plant, and each of the first and second inverter setpoint limits comprises a power factor setpoint limit of the photovoltaic inverter.