Method and arrangement in connection with photovoltaic power generator composed of series-connected photovoltaic modules

1. A method for recognizing partial shading conditions of a photovoltaic power generator composed of series-connected photovoltaic modules, the method comprising:

determining a maximum power point of the photovoltaic power generator having a maximum power point voltage and a maximum power point current; the maximum power point being defined as an output power of the photovoltaic modules that increases and decreases, the maximum power point voltage and the maximum power point current being a voltage and a current, respectively, of the photovoltaic modules at the maximum power point;

operating the photovoltaic power generator at the determined maximum power point;

determining the ambient temperature;

calculating an estimated maximum power point voltage by using the maximum power point current and the determined ambient temperature;

calculating a difference between the estimated maximum power point voltage and the determined maximum power point voltage;

comparing the calculated difference to a pre-determined voltage difference value;

determining on the basis of the comparison whether the photovoltaic power generator is operating under uniform conditions or in conditions with two maximum power points;

initiating a search for another maximum power point if it is determined that the generator is operating in conditions with two maximum power points; and

moving the operation point to another maximum power point if it is determined that the other maximum power point is a global maximum power point.

2. A method according to claim 1 , wherein the calculating of the estimated maximum power point voltage comprises using data relating to the used photovoltaic modules.

3. A method as claimed in claim 1 , wherein the method is repeated continuously.

4. A non-transitory computer-readable recording medium having a computer program recorded thereon that causes a processor of a computer processing device to carry out operations for recognizing partial shading conditions of a photovoltaic power generator composed of series-connected photovoltaic modules, the operations comprising:

determining a maximum power point of the photovoltaic power generator having a maximum power point voltage and a maximum power point current; the maximum power point being defined as an output power of the photovoltaic modules that increases and decreases, the maximum power point voltage and the maximum power point current being a voltage and a current, respectively, of the photovoltaic modules at the maximum power point;

operating the photovoltaic power generator at the determined maximum power point;

determining the ambient temperature;

calculating an estimated maximum power point voltage by using maximum power point current and the determined ambient temperature;

calculating a difference between the estimated maximum power point voltage and the determined maximum power point voltage;

comparing the calculated difference to a pre-determined voltage difference value;

determining on the basis of the comparison whether the photovoltaic power generator is operating under uniform conditions or in conditions with two maximum power points;

initiating a search for another maximum power point if it is determined that the generator is operating in conditions with two maximum power points; and

moving the operation point to another maximum power point if it is determined that the other maximum power point is a global maximum power point.

5. The non-transitory computer-readable recording medium according to claim 4 , wherein the calculating of the estimated maximum power point voltage comprises using data relating to the used photovoltaic modules.

6. The non-transitory computer-readable recording medium according to claim 4 , wherein the operations are repeated continuously.

7. An arrangement for recognizing partial shading conditions of a photovoltaic power generator composed of series-connected photovoltaic modules, the arrangement comprising:

means for determining a maximum power point of the photovoltaic power generator having a maximum power point voltage and a maximum power point current; the maximum power point being defined as an output power of the photovoltaic modules that increases and decreases, the maximum power point voltage and the maximum power point current being a voltage and a current, respectively, of the photovoltaic modules at the maximum power point;

means for operating the photovoltaic power generator at the determined maximum power point;

means for determining the ambient temperature;

means for calculating an estimated maximum power point voltage by using the maximum power point current and the determined ambient temperature;

means for calculating a difference between the estimated maximum power point voltage and the determined maximum power point voltage;

means for comparing the calculated difference to a pre-determined voltage difference value;

means for determining on the basis of the comparison whether the photovoltaic power generator is operating under uniform conditions or in conditions with two maximum power points;

means for initiating a search for another maximum power point if the means for determining determine that the generator is operating in conditions with two maximum power points;

means for moving the operation point to another maximum power point if the means for determining determine that the other maximum power point is a global maximum power point.

8. The arrangement according to claim 7 , wherein the means for calculating the estimated maximum power point voltage use data relating to the used photovoltaic modules.