Maximum power point matching method

Abstract

A method of matching the power of a photovoltaic system producing electric energy by which a working point at which the system produces maximum power is set by changing the working point in an MPP matching process and by comparing the system power, which changes as a result thereof, is intended to be suited both for stationary characteristic curves and for non stationary generator characteristic curves and to be easy to carry out so that the best working point is always set, even when the system is subjected to external interfering factors. This is achieved in that one or several additional control steps or control cycles are performed in order to track during the matching process a power point changing under external impact for a working point of even higher power to be set.

1. A method of matching the a power of a photovoltaic system producing electric energy by which a working point at which the system produces maximum power is set by changing the working point in an MPP matching process and by comparing the system power, which changes as a result thereof, characterized in that
 at least one additional control step or control cycle is performed for detecting an external meteorological impact on a photovoltaic generator that causes a sudden strong reduction in sun irradiation, whereby the control step or control cycle is performed so that a past working point is set as reference working point to check through the at least one additional control step or control cycle whether an assumed maximum power point indeed corresponds to the an actual maximum power point, so that it can be checked if a non stationary characteristic curve exists, and 
 that said at least one control step or said at least one control cycle is integrated in said MPP matching process, 
 it being checked inwherein the at least one control step or inthe at least one control cycle is configured to check whether the generator characteristic curve has changed under the meteorological impact during one MPP matching cycle and a new working point beingis set in at least one correction step or in at least one correction cycle as a function of the change in position of one reference point so that during the MPP matching process the power point changed under the impact of external meteorological conditions is tracked so as to set a working point at which the system produces more power. 
 
     
     
       2. The method as set forth in  claim 1 , characterized in that wherein the at least one or several additional control portions step or control cycles are cycle is performed at one or several reference pointsor reference portions. 
     
     
       3. The method as set forth in  claim 1 , characterized in that wherein the reference point or the reference points are tracked in cyclical or acyclical intervals to meet the new working point or the new working points or the new working portion. 
     
     
       4. The method as set forth in  claim 1 , characterized in that wherein the matching process is delayed by one or several search steps, one or several of the control steps or of the control cycles being performed during the a delay so that the working point is corrected pursuant to the a direction of a change in power induced by an external impact or is maintained if no power change occurs. 
     
     
       5. The method as set forth in  claim 1 , characterized in that wherein an interruption in the matching process in order to set one or several past working points during one or several control steps or control cycles for a past working point to be set as the reference point, said working point being set pursuant to the a direction of the change in power during a control step or control cycle when the power changes. 
     
     
       6. The method as set forth in  claim 1 , characterized in that wherein two left-side reference points are set during one control step or control cycle, said reference points being closer to a short-circuit point than a previously left previous actual working point. 
     
     
       7. The method as set forth in  claim 1 , characterized in that a wherein the control step or a control cycle is respectively performed by electrically loading or unloading the system for a reference point to change. 
     
     
       8. The method as set forth in  claim 1 , characterized in that, wherein in the matching process, the working point is compulsorily displaced by electrically loading or unloading a current generating generatormatching, a displacement being dependent on a comparative result of two or several consecutive working points. 
     
     
       9. The method as set forth in  claim 1 , characterized in that wherein the matching process is performed in a method based on comprises a slope method, the difference quotients between power and voltage being formed from two successive measurements, and the a sign direction, the a search direction, and the a search width being fixed. 
     
     
       10. The method as set forth in  claim 1 , characterized in that wherein the system includes a photovoltaic generator. 
     
     
       11. The method as set forth in  claim 1 , characterized in that it is wherein the method is carried out by means of an inverter. 
     
     
       12. The method as set forth in claim  1  11, characterized in that wherein the inverter is a photovoltaic inverter. 
     
     
       13. A method comprising:
 performing a maximum power point (MPP) matching process, wherein the MPP matching process comprises moving a working point along a first curve of a power generator, the first curve reflecting a first external condition;   setting a reference point, wherein the reference point is a past working point;   comparing the working point with the reference point in a control cycle or control step;   continuing the MPP matching process if the working point is substantially similar to the reference point; and   changing the MPP matching process from the first curve to a second curve if the working point is substantially different to the reference point, the second curve reflecting a second external condition.   
     
     
       14. The method according to claim 13, wherein the first external condition and the second external condition are or a sun irradiation condition. 
     
     
       15. The method according to claim 13, wherein the first external condition and the second external condition are a meteorological condition. 
     
     
       16. The method according to claim 13, wherein the first external condition is changed to the second external condition in a sudden strong change in an external condition. 
     
     
       17. The method according to claim 13, changing the MPP matching process comprises moving the working point along a second curve of the power generator. 
     
     
       18. The method according to claim 13, wherein the control cycle or control step is repeated in cyclical intervals. 
     
     
       19. The method according to claim 13, wherein moving the working point comprises lowering or increasing a voltage and measuring a respective power. 
     
     
       20. A method of maximizing a power generated by a system, the method comprising:
 determining a first reference power generated at a reference point;   performing a power matching process, wherein the power matching process comprises moving a working point of the system into a matching direction;   subsequently determining a second reference power at the reference point and maintaining or changing the matching direction dependent on a comparison of the second reference power and the first reference power; and   continuing the power matching process by moving the working point into the matching direction.   
     
     
       21. The method according to claim 20, wherein the matching direction is maintained if the second reference power is substantially equal to the first reference power. 
     
     
       22. The method according to claim 21, wherein a meteorological condition or a sun irradiation condition has not substantially changed if the first reference power is substantially equal to the first reference power. 
     
     
       23. The method according to claim 20, wherein the matching direction is changed if the second reference power is substantially different than the first reference power. 
     
     
       24. The method according to claim 23. wherein a meteorological condition or a sun irradiation condition has substantially changed if the first reference power is substantially different to the first reference power. 
     
     
       25. The method according to claim 20, wherein the moving working point comprises lowering or increasing a voltage and measuring a respective power. 
     
     
       26. A method comprising:
 finding a maximum power point (MPP) of a power generator system by applying an algorithm, the algorithm comprises a characteristic curve method;   evaluating an irradiation condition by comparing a reference point to a working point in a first control cycle or control step, wherein the reference point is set in the algorithm; and   adjusting finding the MPP based on the evaluation of the irradiation condition.   
     
     
       27. The method according to claim 26, wherein the reference point is a past working point. 
     
     
       28. The method according to claim 26, further comprising performing a second control cycle or control step after the first control cycle or control step. 
     
     
       29. The method according to claim 28, wherein performing the second control cycle or control step is carried out after continuing finding the MPP or after adjusting finding the MPP. 
     
     
       30. The method according to claim 29, further comprising performing a third control cycle or control step after the second control cycle or control step, wherein intervals between the first, second and third control cycles or control steps are cyclical. 
     
     
       31. The method according to claim 29, further comprising performing a third control cycle or control step after the second control cycle or control step, wherein intervals between the first, second and third control cycles or control step are acyclical. 
     
     
       32. A method of maximizing power generation by a system comprising:
 applying an algorithm comprising a characteristic curve method around a first maximum power point (MPP) of the system;   comparing a first power generation value before applying the algorithm with a second power generation value after applying the algorithm;   determining if there is a change in an irradiation condition based on the comparison of the first power generation value and the second power generation value; and   applying the algorithm around the first MPP or applying the algorithm around a second MPP based on the determination of the irradiation condition.   
     
     
       33. The method according to claim 32, wherein determining if there is a change in an irradiation condition comprises there is no change in the irradiation condition if the first power generation value is substantially the same as the second power generation value; and there is a change in the irradiation condition if the first power generation value is substantially different to the second power generation. 
     
     
       34. The method according to claim 33, wherein applying the algorithm around the first MPP if there is no change in the irradiation condition. 
     
     
       35. The method according to claim 33, wherein applying the algorithm around the second MPP if there is the change in the irradiation condition.