Method of controlling photovoltaic power generation system

• US 7,042,195 B2
• Filed: 09/06/2005
• Issued: 05/09/2006
• Est. Priority Date: 09/13/2004
• Status: Active Grant

• Current Assignee: Daihen Corporation
• Original Assignee: Daihen Corporation
• Inventors: Tsunetsugu, Katsuki, Noda, Toshikazu
• Primary Examiner(s): Easthom, Karl
• Assistant Examiner(s): PIGGUSH, AARON C
• Application Number:
  US11/220,109
• Publication Number:
  US 20060055366A1
• Time in Patent Office: 245 Days
• Field of Search: 320/101, 136/243, 700/89, 703/18
• US Class Current: 320/101
• CPC Class Codes: G05F 1/67 to the maximum power available from a generator, e.g. from solar cell
• CPC Class Codes: H01L 31/00 Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof H10K30/00 takes precedence; devices consisting of a plurality of solid state components formed in, or on, a common substrate, other than combinations of radiation-sensitive components with one or more electric light sources, H01L27/00
• CPC Class Codes: H01L 31/02021 for solar cells electrical connection means, e.g. junction boxes, specially adapted for structural association with photovoltaic modules H02S40/34
• CPC Class Codes: H02J 2300/26 involving maximum power point tracking control for photovoltaic sources maximum power point systems in particular G05F1/67
• CPC Class Codes: H02J 3/381 Dispersed generators
• CPC Class Codes: H02S 10/00 PV power plants; Combinations of PV energy systems with other systems for the generation of electric power
• CPC Class Codes: H02S 50/00 Monitoring or testing of PV systems, e.g. load balancing or fault identification
• CPC Class Codes: H02S 50/10 Testing of PV devices, e.g. of PV modules or single PV cells testing of semiconductor devices during manufacturing H01L22/00
• CPC Class Codes: Y02E 10/56 Power conversion systems, e.g. maximum power point trackers

Abstract

A conventional hill climbing method is not capable of tracking a maximum power when a shadow covers a part of a solar cell panel and a plurality of maximal values is thereby developed. The invention provides a photovoltaic power generation system control method that controls a photovoltaic output setting value to be an appropriate value by following up a variation in the solar irradiation, including a genetic algorithm process of employing the photovoltaic output setting value as a gene and the output power as an evaluation value thereof; randomly extracting a plurality of genes and repeating storage, selection and crossover/mutation of the output powers which are the evaluation values of the genes, so as to converge a difference between a maximum and minimum values of the output voltages into a predetermined range; and a hill climbing process of setting the photovoltaic output setting value corresponding to the greatest value of the converged output voltages, and a greater and a lower value than the photovoltaic output setting value by a predetermined amount, so as to select the greatest output power among these values; and repeating such steps to track the maximum output power.

Claims

1. A method of controlling a photovoltaic power generation system including controlling an inverter such that an output voltage or an output current from a solar cell becomes generally equal to a photovoltaic output setting value, so as to deal with a variation in a photovoltaic voltage-power characteristic caused by a change of the solar irradiation, the method for controlling the photovoltaic output setting value to be an appropriate value that makes the output power of the solar cell generally equal to a maximum value, the method comprising:

a genetic algorithm process including employing a GA controller based on a genetic algorithm in which the photovoltaic output setting value serves as a gene and the output power of the solar cell serves as an evaluation value of the gene;

a first step including extracting a plurality of genes randomly or according to a predetermined condition out of a setting range of the photovoltaic output setting value thus to form an initial group of a first generation, sequentially activating the inverter based on each photovoltaic output setting value respectively corresponding to each gene of the initial group and storing the output power from the solar cell under operation as the evaluation value of each of the genes, and inputting the genes of the initial group in the GA controller, so that the GA controller selects the genes and causes the selected genes to crossover/mutate based on the evaluation value thereof, so as to output a predetermined number of genes thus to form a second generation group;

a second step including sequentially activating the inverter based on the photovoltaic output setting values corresponding to the genes of the second generation group and storing the output power from the solar cell under operation as the evaluation value of each of the genes, and inputting the second generation genes in the GA controller, so that the GA controller selects the genes and causes the selected genes to crossover/mutate based on the evaluation value thereof, so as to output a predetermined number of genes thus to form a third generation group; and

repeating the second step so as to converge the genes thus to update the generation of the gene group, until a difference between a maximum value and a minimum value among the photovoltaic output setting values corresponding to the genes falls within a predetermined range; and

a hill climbing process including selecting a photovoltaic output setting value that has the greatest evaluation value among the converged genes as a reference photovoltaic output setting value;

generating a value greater by a predetermined amount and lower by a predetermined amount than the reference photovoltaic output setting value;

sequentially activating the inverter based on the three photovoltaic output setting values so as to set the photovoltaic output setting value that gives the greatest output power as an updated reference photovoltaic output setting value; and

repeating such steps, so as to return to the genetic algorithm process when a predetermined switching condition for following up the variation in the photovoltaic voltage-power characteristic is satisfied.

2. The control method according to claim 1, further comprising performing, upon starting the control of the photovoltaic power generation system, the hill climbing process utilizing a predetermined photovoltaic output setting value as the reference photovoltaic output setting value, prior to performing the genetic algorithm process.

3. The control method according to claim 1, wherein the hill climbing process includes specifying the switching condition as when the hill climbing process has been performed for a predetermined duration of time.

4. The control method according to claim 2, wherein the hill climbing process includes specifying the switching condition as when the hill climbing process has been performed for a predetermined duration of time.

5. The control method according to claim 1, wherein the hill climbing process includes specifying the switching condition as when the output power has fluctuated by more than a predetermined value with respect to the output power of the preceding step.

6. The control method according to claim 2, wherein the hill climbing process includes specifying the switching condition as when the output power has fluctuated by more than a predetermined value with respect to the output power of the preceding step.

7. The control method according to claim 1, wherein the hill climbing process includes specifying the switching condition as when the output power has fluctuated by more than a predetermined value with respect to the output power of the preceding step, and when the hill climbing process has been performed for a predetermined duration of time.

8. The control method according to claim 2, wherein the hill climbing process includes specifying the switching condition as when the output power has fluctuated by more than a predetermined value with respect to the output power of the preceding step, and when the hill climbing process has been performed for a predetermined duration of time.

9. The control method according to claim 1, further comprising forming the initial group containing the genes corresponding to the reference photovoltaic output setting value of the last step of the hill climbing process, at a transition from the hill climbing process to the genetic algorithm process.

10. The control method according to claim 2, further comprising forming the initial group containing the genes corresponding to the reference photovoltaic output setting value of the last step of the hill climbing process, at a transition from the hill climbing process to the genetic algorithm process.

11. The control method according to claim 3, further comprising forming the initial group containing the genes corresponding to the reference photovoltaic output setting value of the last step of the hill climbing process, at a transition from the hill climbing process to the genetic algorithm process.

12. The control method according to claim 4, further comprising forming the initial group containing the genes corresponding to the reference photovoltaic output setting value of the last step of the hill climbing process, at a transition from the hill climbing process to the genetic algorithm process.

13. The control method according to claim 5, further comprising forming the initial group containing the genes corresponding to the reference photovoltaic output setting value of the last step of the hill climbing process, at a transition from the hill climbing process to the genetic algorithm process.

14. The control method according to claim 6, further comprising forming the initial group containing the genes corresponding to the reference photovoltaic output setting value of the last step of the hill climbing process, at a transition from the hill climbing process to the genetic algorithm process.

15. The control method according to claim 7, further comprising forming the initial group containing the genes corresponding to the reference photovoltaic output setting value of the last step of the hill climbing process, at a transition from the hill climbing process to the genetic algorithm process.

16. The control method according to claim 8, further comprising forming the initial group containing the genes corresponding to the reference photovoltaic output setting value of the last step of the hill climbing process, at a transition from the hill climbing process to the genetic algorithm process.