Local power tracking for dynamic power management in weather-sensitive power systems

• US 8,295,989 B2
• Filed: 02/12/2009
• Issued: 10/23/2012
• Est. Priority Date: 02/03/2009
• Status: Expired due to Fees

• Current Assignee: ETM Electromatic, Inc.
• Original Assignee: ETM Electromatic, Inc.
• Inventors: Rettger, Philip, Keshner, Marvin, Pligavko, Alexandra Katrina, Moore, Jackson, Littmmann, Bodo W.
• Primary Examiner(s): Masinick, Michael D
• Application Number:
  US12/379,092
• Publication Number:
  US 20100204844A1
• Time in Patent Office: 1,349 Days
• Field of Search: 700/291, 700/295, 706/46
• US Class Current: 700/291
• CPC Class Codes: H02J 2300/22 The renewable source being solar energy
• CPC Class Codes: H02J 2300/24 of photovoltaic origin
• CPC Class Codes: H02J 3/06 Controlling transfer of power between connected networks; Controlling sharing of load between connected networks
• CPC Class Codes: H02J 3/32 using batteries with converting means
• CPC Class Codes: H02J 3/381 Dispersed generators
• CPC Class Codes: Y02E 10/56 Power conversion systems, e.g. maximum power point trackers

Abstract

A power source affected by a geographically propagating condition (e.g. a weather-related condition) is monitored to detect changes in its power output. Characteristics of the monitored changes are analyzed to detect whether the changes are being caused by a geographically-propagating condition that could affect other power sources nearby. The information obtained from the measurements is used to extrapolate impending power-output changes in the same source, in one or more other sources, or in a collection of sources subject to effects of the propagating condition. The extrapolations enable one or more power generating systems associated with the source(s) to maintain the changes in its total power output within operating requirements.

Claims

1. A method for controlling a power generation system, the method comprising:

acquiring a real-time measurement of power output from a first weather-sensitive power source in the power generation system;

identifying any time-dependent variations in the measurement of power output that indicate an influence of a geographically propagating condition;

extrapolating an expected power-output change in a second weather-sensitive power source in the power generation system due to continued propagation of the geographically propagating condition,

comparing the expected power-output change with a predetermined threshold, and

selecting and executing an appropriate response that adjusts the operation of the second weather-sensitive power source or another weather-sensitive power source in the power generation system if the expected power-output change exceeds the predetermined threshold.

2. The method of claim 1, where the extrapolating includes calculating at least one of:

an onset,

an amplitude,

a rate of change, and

a duration of the expected power-output change.

3. The method of claim 1, further comprising combining the expected power-output changes of a plurality of weather-sensitive power sources connected to a supply point to calculate a cumulative expected power-output change for the supply point.

4. The method of claim 1, wherein the geographically propagating condition comprises a weather-related condition capable of affecting power output.

5. The method of claim 4, where the geographically propagating condition comprises one or more of:

a changing solar illumination or solar spectral condition,

a changing temperature condition, and

a changing wind or ambient-pressure condition.

6. The method of claim 4, where the first and second weather-sensitive power sources comprise at least one photovoltaic module and the extrapolating comprises applying modification factors for at least one of:

characteristics of surrounding terrain,

age of the photovoltaic module,

solar illumination angle relative to the photovoltaic module as a function of time, and

historical information on typical local weather.

7. The method of claim 4, further comprising:

correlating the measurement of power output from the first weather-sensitive power source with an independent weather-factor measurement or forecast, and

providing the correlation of the measurement of power output from the first weather-sensitive power source with the independent weather-factor measurement or forecast as an indication of the influence of weather-related conditions .

8. The method of claim 1, where the predetermined threshold represents one or more limits of acceptable power-change aspects, derived from one or more of:

internal or customer specifications,

regulatory requirements,

demand schedules,

limitations of a connected grid, and

production targets of scheduled power &

intermittent energy.

9. The method of claim 1, where:

the expected power-output change comprises a decrease in output power at a rate exceeding the predetermined threshold, and

the appropriate response comprises decreasing the power delivered by the power generating system, beginning in advance of an expected onset of the weather-related decrease, at a rate that does not exceed the predetermined threshold.

10. The method of claim 1, where

the expected power-output change comprises an increase in output power at a rate exceeding the predetermined threshold, and

the appropriate response comprises slowing the increase in power delivered by the power generating system, beginning when the weather-related increase is sensed, at a rate that does not exceed the predetermined threshold.

11. The method of claim 1, where the appropriate response comprises at least one of:

ceasing power generation or delivery from a selected inverter at a selected time,

resuming power generation or delivery from a selected inverter at a selected time,

changing the operating point of a selected inverter at a selected time, and

using an inverter that automatically senses an increase in input power and responds by limiting an upward rate of change in output power.

12. The method of claim 1, where:

the appropriate response comprises adjusting the power output of the second weather-sensitive power source or another weather-sensitive power source in the power generation system to mitigate an expected power-output change that would otherwise exceed the predetermined threshold, and

the adjusting of the power output comprises delivering less than all available power from the adjusted power source;

and further comprising diverting at least some undelivered available power to energy storage.

13. The method of claim 1, further comprising:

measuring an actual power-output change corresponding to the expected power-output change,

storing the expected power-output change and the corresponding actual power-output change as records,

retrieving a record including a stored expected power-output change similar to a presently extrapolated expected power-output change,

generating a set of correction factors based on the correlation between the expected and actual power-output changes in the retrieved record, and

applying the set of correction factors to the present extrapolation.

14. The method of claim 1, where the second weather-sensitive power source comprises the first weather-sensitive power source.

15. The method of claim 1, further comprising providing an ancillary service to a power grid connected to the power generating system, where the ancillary service comprises power factor correction.

16. A programmed non-transitory storage medium containing instructions and data for controlling a power system, the instructions and data comprising:

instructions for acquiring a measurement related to real-time power output from a first weather-sensitive power source in the power system;

instructions for identifying any time-dependent variations in the measurement that indicate an influence of a geographically propagating condition;

instructions for extrapolating an expected power-output change due to continued propagation of the geographically propagating condition,

instructions for comparing the expected power-output change with a predetermined threshold and

instructions for selecting and executing an appropriate response that adjusts the operation of a second weather-sensitive power source in the power system if the expected power-output change exceeds the predetermined threshold.

17. The programmed non-transitory storage medium of claim 16, further comprising instructions for identifying the influence of a weather-related geographically propagating condition by correlating the acquired measurement with an independent measurement or forecast of a weather-related factor.

18. The programmed non-transitory storage medium of claim 16, further comprising instructions for calculating at least one of an onset, amplitude, rate of change, and duration of the expected power-output change.

19. The programmed non-transitory storage medium of claim 18, further comprising instructions for combining the extrapolations for a plurality of power sources on a common time axis to calculate a net expected power change at a supply point connected to the plurality of power sources.

20. The programmed non-transitory storage medium of claim 16, further comprising data related to at least one of

characteristics of surrounding terrain,

age of a photovoltaic module,

solar illumination angle relative to the photovoltaic module as a function of time, and

historical information on typical local weather.

21. The programmed non-transitory storage medium of claim 16, where the appropriate responses includes adjusting the power output of the second power source to mitigate aspects of an expected power-output change that exceeds the predetermined threshold.

22. The programmed non-transitory storage medium of claim 21, further comprising instructions for adjusting the power output by controlling at least one selected inverter to do at least one of:

ceasing or resuming power generation or delivery, and

changing the inverter operating point to increase or decrease generated power.

23. The programmed non-transitory storage medium of claim 21, further comprising instructions for an inverter to automatically limit a rate of increase in power generation or delivery to a predetermined acceptable ramp-rate when the inverter senses an increase in power input.

24. The programmed non-transitory storage medium of claim 16, further comprising:

instructions for recording an actual power-output change corresponding to the expected power-output change and storing the pair of power-output changes in a record,

instructions for retrieving a record that includes a stored expected power-output change similar to a presently extrapolated expected power-output change,

instructions for generating a set of correction factors based on the correlation between the expected and actual power-output changes in the retrieved record, and

instructions for applying the set of correction factors to the present extrapolation.

25. The programmed non-transitory storage medium of claim 24, where the second weather-sensitive power source comprises the first weather-sensitive power source.

26. The programmed non-transitory storage medium of claim 16, further comprising instructions for providing an ancillary service to a power grid connected to the power generating system, where the ancillary service comprises power factor correction.

27. An apparatus for controlling a power generating system, comprising:

means for acquiring a measurement of power output from a weather-sensitive power source in the power generation system,

means for identifying any time-dependent variations in the measurement that indicate an influence of a geographically propagating condition;

means for extrapolating an expected power-output change due to continued propagation of the geographically propagating condition,

means for comparing the expected power-output change with a predetermined threshold, and

means for selecting and executing an appropriate response that adjusts the operation of a second weather-sensitive power source in the power system if the expected power-output change exceeds the predetermined threshold.

28. The apparatus of claim 27, further comprising:

means for measuring output power from a plurality of geographically separate solar panels in real time,

means for calculating a rate of change of the output power for each of the plurality of geographically separate solar panels,

means for accessing location data for each of the plurality of geographically separate solar panels, and

means for extrapolating a future expected change and a future expected rate of change in output power for solar panels at other locations from results of the measuring, calculating, and accessing operations.