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.

Description

FIELD OF THE INVENTION[0001]The present invention is generally related to harvesting electrical power from a source of electrical energy, and, more particularly, to system and method for extracting, under a wide variety of operational and / or environmental conditions, maximum or near-maximum electrical power from a source of electrical energy, such as a photovoltaic (PV) power source, a fuel cell or a battery.BACKGROUND OF THE INVENTION[0002]For a given level of insolation (illumination intensity), a photovoltaic (PV) energy source may be characterized by a graph of current versus voltage, generally referred to as the current-voltage (I-V) curve. It is known that when the PV source is uniformly illuminated, then such a PV source typically has one unique value of current and voltage at which maximum electrical power can be extracted for a given illumination intensity and / or temperature.[0003]To extract maximum electrical power, an electrical load connected to the PV source must be adj...

AI Technical Summary

Benefits of technology

[0007]Generally, the present invention fulfills the foregoing needs by providing, in one aspect thereof, a photovoltaic system that includes 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. A switching converter is 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 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.

[0008]In another aspect thereof, the present invention further fulfills the foregoing needs by providing a method for harvesting electrical power from a photovoltaic system. The method defines 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. The method allows 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. The converter is operated to approximate at least some of the points of maximum electrical power for the photovoltaic source 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.

[0009]In yet another aspect thereof, the present invention further fulfills the foregoing needs by providing apparatus 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 comprises 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 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.

Problems solved by technology

In practice, however, there are some issues concomitant with maximum power tracking techniques.

First, the implementation of the tracking algorithm in a processor requires an incremental consumption of electrical power for powering such a processor, thus reducing harvesting efficiency of the PV system.

Second, maximum power tracking is generally much more complex than just regulating the switching converter to a reference and the switching operation of the converter can interfere with appropriately determining the maximum power point and, in some cases, is prone to operational instabilities while seeking to solve the maximum power point algorithm.

Third, power tracking algorithms commonly require sensing of both current and voltage of the PV source.

This current sensing often results in additional losses, thus further reducing the overall efficiency of the PV system.

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