Apparatus and method for maximizing power delivered by a photovoltaic array
AssigneeMidwest Research Institute
InventorsEduard Muljadi, Roger W. Taylor
Life of this patent
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Abstract
A method and apparatus for maximizing the electric power output of a photovoltaic array connected to a battery where the voltage across the photovoltaic array is adjusted through a range of voltages to find the voltage across the photovoltaic array that maximizes the electric power generated by the photovoltaic array and then is held constant for a period of time. After the period of time has elapsed, the electric voltage across the photovoltaic array is again adjusted through a range of voltages and the process is repeated. The electric energy and the electric power generated by the photovoltaic array is delivered to the battery which stores the electric energy and the electric power for later delivery to a load.
Claims48
Apparatus for controlling electric power that is generated by a photovoltaic cell and delivered to a battery that has positive and negative terminals, wherein the photovoltaic cell also has positive and negative terminals and the photovoltaic cell generates an electric voltage between its positive and negative terminals and a corresponding electric current flowing out of its positive terminal when radiation is incident on the photovoltaic cell, and wherein the battery has an electric voltage between its positive and negative terminals that is approximately constant during a predetermined time period, comprising:
- converter means electrically connected to the photovoltaic cell and to the battery for electrically connecting and disconnecting the photovoltaic cell to and from the battery, for controlling and varying the electric voltage generated between the positive and negative terminals of the photovoltaic cell, and for generating and controlling an electric current that flows through the battery such that the electric power generated by the photovoltaic cell is at a maximum during the time period when the electric current flowing through the battery is at a maximum during the time period, said converter means including a switch means for controlling when said converter means electrically connects the photovoltaic cell to the battery and when said converter means electrically disconnects the photovoltaic cell from the battery, wherein said switch means has a first state of operation and a second state of operation such that when said switch means is operating in its first state of operation the photovoltaic cell is electrically connected to the battery and when said switch means is operating in its second state of operation the photovoltaic cell is electrically disconnected from the battery;
- peak current determining means coupled to the battery for determining when the electric current flowing through the battery is at a maximum and for generating an electric signal when the electric current flowing through the battery is at a maximum;
- and
- switch control means electrically connected to said switch means and to said peak current determining means for controlling when said switch means is operating in said first state of operation and when said switch means is operating in said second state of operation, wherein said switch control means is responsive to said electric signal generated by said peak current determining means.
Method of controlling electric power generated by a photovoltaic cell and delivered to a battery that has positive and negative terminals, wherein the photovoltaic cell also has positive and negative terminals and the photovoltaic cell generates an electric voltage between its positive and negative terminals and a corresponding electric current flowing out of its positive terminal when radiation is incident on the photovoltaic cell, and wherein the battery has an electric voltage between its positive and negative terminals that is approximately constant during a predetermined time period, comprising the steps of:
- electrically coupling the photovoltaic cell and the battery such that an electric current flows through the battery, varying the electric voltage generated between the positive and negative terminals of the photovoltaic cell will result in varying of the electric current flowing through the battery, and such that the electric power generated by the photovoltaic cell during the time period is at a maximum when the electric current flowing through the battery during the time period is at a maximum;
- varying the electric voltage between the positive and negative terminals of the photovoltaic cell during a first portion of the time period;
- determining when the electric current flowing through the battery is at a maximum during said first portion of the time period;
- and
- maintaining the electric voltage between the positive and negative terminals of the photovoltaic cell for a second portion of the time period such that said determined maximum electric current flowing through the battery is maintained during said second portion of the time period.
Apparatus for optimizing electrical power production by a photovoltaic power source that is electrically connected by an electric circuit to a battery, comprising:
- a voltage converter positioned in the electric circuit between the photovoltaic power source and the battery with the capability of varying voltage across the photovoltaic power source in response to a firing signal;
- and
- a peak current detector connected to the electric circuit and a firing circuit, said peak current detector having a capability to detect when a varying electric current flowing through the battery is at a maximum and to produce a peak current signal when said electric current flowing through the battery is at the maximum, wherein said firing circuit is also connected to said voltage converter and has a capability of producing said firing signal in a variable manner that causes said voltage converter to vary voltage across the photovoltaic power source until said peak current detector produces a peak current signal and, in response to said peak current signal, producing said firing signal in a nonvariable manner.
A method of optimizing power production by a photovoltaic power source that is being used to charge a battery, comprising the steps of:
- using a boost converter with a variable duty cycle to vary voltage across the photovoltaic power source while monitoring current flow through the battery until maximum current flow through the battery is detected and then maintaining for a period of time whatever duty cycle that existed to produce the maximum current flow.
A method of optimizing power production by a photovoltaic power source that is being used to charge a battery, comprising the steps of:
- varying the voltage across the photovoltaic power source while monitoring current flow through the battery until maximum current flow through the battery is detected and then maintaining for a period of time whatever voltage existed across the photovoltaic power source to produce the maximum current flow through the battery.
Apparatus for controlling electric power that is generated by a photovoltaic cell and delivered to a battery that has positive and negative terminals, wherein the photovoltaic cell also has positive and negative terminals and the photovoltaic cell generates an electric voltage between its positive and negative terminals and a corresponding electric current flowing out of its positive terminal when radiation is incident on the photovoltaic cell, and wherein the battery has an electric voltage between its positive and negative terminals that is approximately constant during a time period, comprising:
- converter means electrically connected to the photovoltaic cell and to the battery for electrically connecting and disconnecting the photovoltaic cell to and from the battery, for controlling and varying the electric voltage generated between the positive and negative terminals of the photovoltaic cell, and for controlling an electric current that flows through the battery such that the electric power generated by the photovoltaic cell is at a maximum during the time period when the electric current flowing through the battery is at a maximum during the time period, said converter means including a switch means for controlling when said converter means electrically connects the photovoltaic cell to the battery and when said converter means electrically disconnects the photovoltaic cell from the battery, wherein said switch means has a first state of operation and a second state of operation such that when said switch means is operating in its first state of operation the photovoltaic cell is electrically connected to the battery and when said switch means is operating in its second state of operation the photovoltaic cell is electrically disconnected from the battery;
- peak current determining means coupled to the battery for determining when the electric current flowing through the battery is at a maximum and for generating an electric signal when the electric current flowing through the battery is at a maximum;
- and
- switch control means electrically connected to said switch means and to said peak current determining means for controlling when said switch means is operating in said first state of operation and when said switch means is operating in said second state of operation, wherein said switch control means is responsive to said electric signal generated by said peak current determining means.
Dependencies are inferred from the claim text.