System and method for inferring a photovoltaic system configuration specification with the aid of a digital computer

Patent metadata

Field	Value
Publication number	US-10140401-B1
Application number	US-201715588550-A
Country	US
Kind code	B1
Filing date	May 5, 2017
Priority date	Jul 25, 2011
Publication date	Nov 27, 2018
Grant date	Nov 27, 2018

Abstract

A photovoltaic system's configuration specification can be inferred by an evaluative process that searches through a space of candidate values for the variables in the specification. Each variable is selected in a specific ordering that narrows the field of candidate values. A constant horizon is assumed to account for diffuse irradiance insensitive to specific obstruction locations relative to the photovoltaic system's geographic location. Initial values for the azimuth angle, constant horizon obstruction elevation angle, and tilt angle are determined, followed by final values for these variables. The effects of direct obstructions that block direct irradiance in the areas where the actual horizon and the range of sun path values overlap relative to the geographic location are evaluated to find the exact obstruction elevation angle over a range of azimuth bins or directions. The photovoltaic temperature response coefficient and the inverter rating or power curve of the photovoltaic system are determined.

First claim

What is claimed is:

1. A method for inferring a photovoltaic system configuration specification with the aid of a digital computer, comprising the steps of:
obtaining by a computer measured photovoltaic production for a photovoltaic system operating at a known geographic location over a set time period;
obtaining by the computer ambient temperature and solar irradiance data measured for the geographic location over the same set time period;
obtaining by the computer a preexisting configuration for the photovoltaic system;
searching by the computer for optimal values for each variable in a configuration specification for the photovoltaic system by optimizing each variable, one at a time, comprising the steps of:
selecting a candidate value for the variable being optimized;
simulating photovoltaic production for the photovoltaic system using the ambient temperature, the solar irradiance data, and the candidate value;
calculating error between the simulated photovoltaic production and the measured photovoltaic production; and
choosing the candidate value as the optimal value for the variable being optimized upon the error meeting a threshold of error;

modifying with the computer the preexisting configuration used by a production output controller for the photovoltaic system with the optimal values for the variables in the configuration specification; and
operating by the production output controller the photovoltaic system based on the modified preexisting configuration.

2. A method according to claim 1 , further comprising the steps of:
determining the optimal values comprising initial optimal values for the variables in the configuration specification comprising each of an azimuth angle, constant horizon obstruction elevation angle, and tilt angle; and
determining the optimal values comprising final optimal values for the azimuth angle, constant horizon obstruction elevation angle, and tilt angle by using the initial optimal values for the azimuth angle, constant horizon obstruction elevation angle, and tilt angle as candidate values.

3. A method according to claim 2 , further comprising the steps of:
assuming a constant horizon to account for diffuse irradiance insensitive to specific obstruction locations relative to the geographic location;
adjusting the solar irradiance data based upon direct obstructions; and
performing the simulation of the photovoltaic production with the adjusted solar irradiance data.

4. A method according to claim 2 , further comprising the steps of:
determining one of the optimal values for the variable in the configuration specification that comprises an exact obstruction elevation angle.

5. A method according to claim 4 , further comprising the steps of:
assuming direct obstructions to account for obstructions that block direct irradiance in the areas where the actual horizon and the range of sun path values overlap relative to the geographic location;
adjusting the solar irradiance data based upon the direct obstructions; and
performing the simulation of the photovoltaic production with the adjusted solar irradiance data.

6. A method according to claim 4 , further comprising the steps of:
performing the search for one of the optimal values for the exact obstruction elevation angle over a range of azimuth orientations.

7. A method according to claim 6 , further comprising the step of:
determining one of the optimal values for the variable in the configuration specification that comprises a photovoltaic temperature response coefficient.

8. A method according to claim 7 , further comprising the step of:
determining one of the optimal values for the variable in the configuration specification that comprises one of an inverter rating and power curve of the photovoltaic system.

9. A method according to claim 8 , further comprising the steps of:
identifying a constant multiplier to adjust for the difference between the measured photovoltaic production and simulated photovoltaic production; and
incorporating the constant multiplier into the simulation of the photovoltaic production following the determination of the value of the one of the inverter rating and power curve.

10. A method according to claim 1 , further comprising the steps of:
maintaining a lookup table of unique combinations of the candidate values for each variable; and
performing the simulation of the photovoltaic production only for those combinations of the candidate values for each variable that do not appear in the lookup table.

11. A method according to claim 1 , further comprising the step of:
finding each optimal value as the extremum of a strictly unimodal function by successively narrowing the range of values inside which the extremum is known to exist through the search.

12. A method according to claim 11 , wherein the search comprises a Golden-section search, further comprising the steps of:
performing a first iteration of the Golden-section search by performing the simulation of the photovoltaic production using four candidate values for the variable being optimized such that the error calculated for the simulation using the third candidate value x 3 1 is greater than or equal to the error calculated for the simulation using the first candidate value x 1 1 , the second candidate value x 2 1 equals the weight sum of the first and third candidate values determined in accordance with:

x
2
1

=

W
⁡

[

x
1
1

x
3
1

]

=

[

φ

-
1

φ

-
2

]

⁡

[

x
1
1

x
3
1

]

Assignees

• Clean Power Res L L C

Inventors

• Hoff Thomas E

Classifications

• G06F30/13

  Architectural design, e.g. computer-aided architectural design [CAAD] related to design of buildings, bridges, landscapes, production plants or roads · CPC title

• G06F30/20 Primary

  Design optimisation, verification or simulation (optimisation, verification or simulation of circuit designs G06F30/30) · CPC title

• H02S50/00

  Monitoring or testing of PV systems, e.g. load balancing or fault identification · CPC title

• G01W1/12 Primary

  Sunshine duration recorders (measuring intensity of sunshine G01J) · CPC title

• G01J1/42

  using electric radiation detectors (optical or mechanical part G01J1/04; by comparison with a reference light or electric value G01J1/10) · CPC title