System, method, and apparatus for extracting power from a photovoltaic source of electrical energy

Abstract

System, method, and apparatus are provided for harvesting electrical energy from a photovoltaic source of electrical energy. The photovoltaic source has power-generating characteristics defined by a family of voltage-current curves comprising points of maximum electrical power over a respective range of at least one of the following for the photovoltaic source: distinct illumination intensities and distinct temperatures. The apparatus is made up of a switching converter coupled to the photovoltaic source. The converter has an input voltage-current curve having a predefined functional relationship between the input voltage and the input current. The predefined functional relationship of the input voltage-current curve of the converter is configured to provide during operation of the converter an approximation with respect to at least some of the points of maximum electrical power for the photovoltaic source without having to perform current and voltage calculations corresponding to a maximum power from the photovoltaic source.

1 . A photovoltaic system comprising:
 a photovoltaic source of electrical energy, the photovoltaic source comprising power-generating characteristics defined by a family of voltage-current curves comprising points of maximum electrical power over a respective range of at least one of the following for the photovoltaic source: distinct illumination intensities and distinct temperatures;   a switching converter coupled to the photovoltaic source, wherein the converter comprises an input voltage-current curve having a predefined functional relationship between the input voltage and the input current, the predefined functional relationship of the input voltage-current curve of the converter configured to provide during operation of the converter an approximation with respect to at least some of the points of maximum electrical power for the photovoltaic source without having to perform current and voltage calculations corresponding to a maximum power from the photovoltaic source.   
   
   
       2 . The photovoltaic system of  claim 1  wherein the input voltage-current curve of the converter comprises a linear fit approximation with respect to at least some of the points of maximum electrical power for the photovoltaic source. 
   
   
       3 . The photovoltaic system of  claim 1  wherein the input voltage-current curve of the converter comprises a cubic fit approximation with respect to at least some of the points of maximum electrical power. 
   
   
       4 . The photovoltaic system of  claim 2  where the switching converter comprises a type of converter selected from the group consisting of a flyback, a buck-boost, and a buck or boost type of converter. 
   
   
       5 . The photovoltaic system of  claim 2  where the switching converter comprises a buck-boost type of converter comprising further configured to provide a voltage offset along a voltage axis of the input voltage-current curve comprising the linear fit approximation. 
   
   
       6 . The photovoltaic system of  claim 5  where a value for the voltage offset is varied based on a sensed temperature of the photovoltaic source. 
   
   
       7 . The photovoltaic system of  claim 6  wherein a section of the photovoltaic source is masked to avoid a response due to illumination, and wherein an electrical signal from the masked section is used for sensing temperature of the photovoltaic source. 
   
   
       8 . The photovoltaic system of  claim 3  where the converter comprises a flyback type of converter. 
   
   
       9 . The photovoltaic system of  claim 1  comprising a plurality of switching converters each coupled to receive electrical power from a respective photovoltaic source, wherein each individual converter comprises an input voltage-current curve having a predefined functional relationship between the input voltage and the input current configured to provide an approximation with respect to at least some of the points of maximum electrical power for the respective photovoltaic source, and further wherein each individual converter output is connected to one another to form a circuit combination so that a desired scaling of output power is reached. 
   
   
       10 . The photovoltaic system of  claim 9  wherein the circuit combination is selected from a group consisting of a series circuit, a parallel circuit and a combination of the foregoing circuits. 
   
   
       11 . The photovoltaic system of  claim 9  wherein each individual converter comprises a DC-to-DC converter. 
   
   
       12 . The photovoltaic system of  claim 1  wherein the photovoltaic source comprises a first face exposed to illumination and a second face opposite the first face not exposed to illumination and wherein the converter is integrated with the photovoltaic source t the second face thereof. 
   
   
       13 . A method for harvesting electrical power from a photovoltaic system, the method comprising:
 defining power-generating characteristics of a photovoltaic source of electrical energy by a family of voltage-current curves comprising points of maximum electrical power over a respective range of at least one of the following for the photovoltaic source: distinct illumination intensities and distinct temperatures;   coupling a switching converter to the photovoltaic source, wherein the converter comprises an input voltage-current curve having a predefined functional relationship between the input voltage and the input current; and   operating the converter to approximate at least some of the points of maximum electrical power for the photovoltaic based on a configuration of the predefined functional relationship of the input voltage-current curve of the converter without having to perform current and voltage calculations corresponding to a maximum power from the photovoltaic source.   
   
   
       14 . The method of  claim 13  wherein the input voltage-current curve of the converter comprises a linear fit approximation with respect to at least some of the points of maximum electrical power. 
   
   
       15 . The method of  claim 13  wherein the input voltage-current curve of the converter comprises a cubic fit approximation with respect to at least some of the points of maximum electrical power. 
   
   
       16 . The method of  claim 13  wherein the input voltage-current curve of the converter is configured to provide a linear fit approximation and is further configured to provide a voltage offset along a voltage axis of the input voltage-current curve. 
   
   
       17 . The method of  claim 16  further comprising sensing a parameter indicative of temperature of the photovoltaic source, and using the sensed parameter to determine a value for the voltage offset. 
   
   
       18 . The method of  claim 13  further comprising coupling a plurality of switching converters to receive electrical power from a respective photovoltaic source, wherein each individual converter comprises an input voltage-current curve having a predefined functional relationship between the input voltage and the input current configured to provide an approximation with respect to at least some of the points of maximum electrical power for the respective photovoltaic source, and further wherein each individual converter output is connected to one another to form a circuit combination so that a desired scaling of output power is reached. 
   
   
       19 . The method of  claim 18  further comprising selecting the circuit combination from a group consisting of a series circuit, a parallel circuit and a combination of the foregoing circuits. 
   
   
       20 . Apparatus for harvesting electrical energy from a photovoltaic source of electrical energy, the photovoltaic source comprising power-generating characteristics defined by a family of voltage-current curves comprising points of maximum electrical power over a respective range of at least one of the following for the photovoltaic source: distinct illumination intensities and distinct temperatures, the apparatus comprising;
 a switching converter coupled to the photovoltaic source, wherein the converter comprises an input voltage-current curve having a predefined functional relationship between the input voltage and the input current, the predefined functional relationship of the input voltage-current curve of the converter configured to provide during operation of the converter an approximation with respect to at least some of the points of maximum electrical power for the photovoltaic source without having to perform current and voltage calculations corresponding to a maximum power from the photovoltaic source.   
   
   
       21 . The apparatus of  claim 20  wherein the input voltage-current curve of the converter comprises a linear fit approximation with respect to at least some of the points of maximum electrical power for the photovoltaic source. 
   
   
       22 . The apparatus of  claim 20  wherein the input voltage-current curve of the converter comprises a cubic fit approximation with respect to at least some of the points of maximum electrical power. 
   
   
       23 . The apparatus of  claim 21  where the switching converter comprises a type of converter selected from the group consisting of a flyback, a buck-boost, and a buck or boost type of converter. 
   
   
       24 . The apparatus of  claim 21  where the switching converter comprises a buck-boost type of converter comprising further configured to provide a voltage offset along a voltage axis of the input voltage-current curve comprising the linear fit approximation. 
   
   
       25 . The apparatus of  claim 24  where a value for the voltage offset is varied based on a sensed temperature of the photovoltaic source. 
   
   
       26 . The apparatus of  claim 22  where the converter comprises a flyback type of converter. 
   
   
       27 . The apparatus of  claim 20  comprising a plurality of switching converters each coupled to receive electrical power from a respective photovoltaic source, wherein each individual converter comprises an input voltage-current curve having a predefined functional relationship between the input voltage and the input current configured to provide an approximation with respect to at least some of the points of maximum electrical power for the the respective photovoltaic source, and further wherein each individual converter output is connected to one another to form a circuit combination so that a desired scaling of output power is reached. 
   
   
       28 . The apparatus of  claim 27  wherein the circuit combination is selected from a group consisting of a series circuit, a parallel circuit and a combination of the foregoing circuits. 
   
   
       29 . The apparatus of  claim 27  wherein each individual converter comprises a DC-to-DC converter.