WO2014190300A1

WO2014190300A1 - Systems and methods for power generation

Info

Publication number: WO2014190300A1
Application number: PCT/US2014/039414
Authority: WO
Inventors: Mordechay Golan; Menachem Tipris; Rani Moran; Haim Chayet; Han LOZOVSKY; Ori Kost
Original assignee: Suncore Photovoltaics Incorporated
Priority date: 2013-05-24
Filing date: 2014-05-23
Publication date: 2014-11-27

Abstract

Systems and methods may be configured for providing energy from a photovoltaic array by, e.g., using a plurality of photovoltaic power sources electrically coupled in series and a plurality of converters, each coupled in parallel to the plurality of photovoltaic power sources to receive electricity that exceeds a least amount of current produced by the plurality of photovoltaic power sources.

Description

SYSTEMS AND METHODS FOR

POWER GENERATION

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application Serial No. 61/827,040 filed 24 May 2013, entitled "Voltage Summation for Maximum Power Generation," which is incorporated herein by reference in its entirety.

BACKGROUND

The present disclosure relates to power generation fields, where there are several power sources which are connected in serial in order to generate higher voltage from several low voltage power sources.

An application of the present disclosure may be for use with, or in conjunction with, a photovoltaic (PV) solar energy generation field, where several PV units or panels are connected serially. Another typical application of the present disclosure may be for use with, or in conjunction, with concentrated photovoltaic (CPV) solar energy

generation, where groups of CPV cells are connected serially.

When power sources such as, e.g., PV panels, CPV cells, etc., are connected serially, the electric current that flows through the power sources is equal for each of the power sources. When all the power sources are matched (e.g., generate the same amount of power), all the power sources generate the same current and there may be no power loss effect. However, the power sources may not be exactly matched (e.g., generate different amounts of power). For example, some power sources may be weaker than others and, thus, some power sources may provide less power (e.g., current, voltage, etc.) than other power sources. The difference in strength or power may be caused by component performance variation, partial sun blocking, variation of the sun flux density in CPV systems, etc.

In these situations where the power sources are not exactly matched, the weakest source may determine the current that flows in the system (e.g., power sources connected serially are limited to the lowest current of all the power sources, the weakest source is the "bottle-neck" of the serially connected power sources, etc.). Thus, the overall power generated by the serially-connected power sources) may be smaller than the total available power since the weakest power source cannot accommodate the current drive of the stronger power sources. The present disclosure provides a solution that utilizes the available power of all the power sources without the limiting effect of weaker power sources.

A configuration for the described problem may be to generate power from each power source separately, which eliminates the dependency between power sources but may be a relatively-expensive solution. For example, a separate inverter to translate the direct current (DC) sources to an alternating current (AC) source that can be connected to the electrical grid has to be provided for each source in this configuration. Exemplary technology using this or similar configurations may be described in U.S. Pat App. Pub. No. 2008/0150366 entitled "HIGH RELIABILITY POWER SYSTEMS AND SOLAR POWER CONVERTERS," U.S. Pat App. Pub. No. 2009/0039852 entitled "DIGITAL AVERAGE INPUT CURRENT CONTROL IN POWER CONVERTER," U.S. Pat App. Pub. No. 2009/0140715 entitled "SAFETY MECHANISMS, WAKE UP AND

SHUTDOWN METHODS IN DISTRIBUTED POWER INSTALLATIONS," U.S. Pat App. Pub. No. 2009/0147554 entitled "PARALLEL CONNECTED INVERTERS," and "Cascaded DC-DC Converter Connection of Photovoltaic Modules;" G. R. Walker, P. C. Sernia; School of Information Technology and Electrical Engineering, University of Queensland, each of which is incorporated by reference in its entirety.

Another configuration for the described problem may be to collect power available from each power source by connecting the power sources in a parallel configuration rather than in a serial configuration. The drawback of this configuration may be that, in a parallel configuration, each power source must provide an equal voltage. Once again, the weaker power source, providing the lowest voltage, will determine the total voltage available. Further, another issue with such a configuration is that the available total voltage may be significantly lower, which may make the conversion to the higher AC line voltage more complicated and less effective due to the voltage boost stage it has to include.

Another configuration for the described problem may use a separate DC-to-DC converter connected to each power source. These converters track the available power of each power source and provide a matching impedance to each power source, thereby extracting the maximum available power from each power source. At its respective output, each converter may provide the same current with different voltages as dictated by the power extracted from the power source. Since the currents available from all the converters are equal, the outputs of the converters can be connected serially while providing the voltage required by the AC converter. A system 10 using DC-to-DC converters for each power source is depicted in FIG. 1.

The system 10 includes a plurality of power sources 100, 101,102, 103 that generate different voltages and currents. Each power source 100, 101, 102, 103 is connected to a separate DC-to-DC converter 110, 111, 112, 113, respectively, which extracts the power source's 100, 101, 102, 103 maximum available power. At their respective outputs, each of the DC-DC converters 110, 111, 112, 113 generates the same current I with different voltages VI, V2, V4, V4, respectively. The voltages VI, V2, V4, V4 are summed to generate the system output voltage of VI + V2 + V3 + V4 with current I.

Assuming lossless DC-DC converters 110, 111, 112, 113, the converter 110 outputs power, VI * I, that is equal to the maximum available power of power source 100. Similarly V2 * I, V3 * I, and V4 * I equal the maximum available power of power sources 101, 102, and 103 respectively. The total output power of the system may be given by summing the voltages of the outputs of each of the DC-to-DC converters 110, 111, 112, 113 and multiplying the sum by the current, I ( (VI + V2 + V3 + V4) * I = VI * I + V2 * I + V3 * I + V4 * I), which is equal to the total available power of the power sources.

Exemplary technology using this configurations or similar configurations may be described in U.S. Pat App. Pub. No.2008/0150366 entitled "METHOD FOR

DISTRIBUTED POWER HARVESTING USING DC POWER SOURCES," U.S. Pat App. Pub. No.2009/0039852 entitled "DIGITAL AVERAGE INPUT CURRENT

CONTROL IN POWER CONVERTER," U.S. Pat App. Pub. No.2009/0140715 entitled "SAFETY MECHANISMS, WAKE UP AND SHUTDOWNMETHODS IN

DISTRIBUTED POWER INSTALLATIONS," U.S. Pat App. Pub. No. 2009/0147554 entitled "PARALLEL CONNECTED INVERTERS," "Cascaded DC-DC Converter

Connection of Photovoltaic Modules;" G. R. Walker, P. C. Sernia; School of Information Technology and Electrical Engineering, University of Queensland, and "PV STRING PER-MODULE MAXIMUM POWER POINT ENABLING CONVERTERS"; G.R. Walker, J. Xue and P. Sernia, School of Information Technology and Electrical

Engineering, The University of Queensland (e.g. this article may describe a scheme of connecting DC-DC converters in parallel to the power sources diverting the extra current available from each individual source around the weaker sources), each of which is incorporated by reference in its entirety.

SUMMARY

One exemplary system for providing electricity from a photovoltaic array may include a plurality of photovoltaic power sources configured to generate electricity from light and electrically coupled in series and a plurality of converters. Each converter may include an input portion and an output portion and may be configured to receive electricity using the input portion, convert electricity to a selected current, and transmit the converted electricity using the output portion. Further, the input portion of each of the plurality of converters may be coupled in parallel with a photovoltaic power source of the plurality of photovoltaic power sources, and the output portions of the plurality of converters may be coupled in series with the plurality of photovoltaic power sources. The exemplary system may further include a controller operatively coupled to the plurality of converters and configured to use the plurality of converters to capture electricity from the plurality of photovoltaic power sources that exceeds the selected current. For example, the controller may monitor the current generated by a photovoltaic power source, subtract the generated current by the lowest current produced by one of the photovoltaic power sources to provide an excess current value, and use a converter to extract, or draw, the excess current from the photovoltaic power source. The converter may convert the excess current to the selected current such that the output of the converter may be electrically coupled in series with the plurality of photovoltaic power sources.

Another exemplary system for providing electricity from a photovoltaic array may include a plurality of converters, each coupled in parallel with a photovoltaic power source of the plurality of photovoltaic power sources to receive electricity, convert the electricity to a selected current, and transmit the converted electricity. The plurality of converters may be coupled in series with each other and with the plurality of photovoltaic power sources to transmit the converted electricity. The exemplary system may include a controller operatively coupled to the plurality of converters and configured to use the plurality of converters to capture electricity from the plurality of photovoltaic power sources that exceeds the selected current.

In one or more embodiments, each of the plurality of photovoltaic power sources may include a first terminal and a second terminal. The first terminal of each photovoltaic power source of the plurality of photovoltaic power sources may be electrically coupled to the second terminal of another photovoltaic power source of the plurality of photovoltaic power sources to electrically couple the plurality of photovoltaic power sources in series. In one or more embodiments, the output portion of each of the plurality of converters may include a first terminal and a second terminal. The first terminal of each converter of the plurality of converters may be electrically coupled to the second terminal of another converter of the plurality of converters to electrically couple the plurality of converters in series.

In one or more embodiments, the controller may be further configured to monitor an amount of electricity generated by each of the plurality of photovoltaic power sources, determine a least amount of current generated by one of the plurality of photovoltaic power sources, and set the selected current to the least amount of current. In at least one embodiment, the controller may be further configured to set an amount of current to be drawn from a photovoltaic power source of the plurality of photovoltaic power sources using a converter of the plurality of converters to the amount of current generated by the photovoltaic power source minus the least amount of current.

In one or more embodiments, the plurality of converters may be configured to convert the electricity that exceeds the selected current to the selected current (e.g., draw the current that exceeds the selected current from each of the photovoltaic power sources). Further, the controller may be further configured to control the plurality of converters using pulse-width modulation. Still further, the plurality of converters may be direct current-to-direct current converters.

One exemplary method of providing electricity from a photovoltaic array may include monitoring an amount of electricity generated by each of the plurality of photovoltaic power sources, determining a least amount of current generated by one of the plurality of photovoltaic power sources, and capturing electricity that exceeds the least amount of current from the plurality of photovoltaic power sources.

In one or more embodiments, capturing electricity that exceeds the least amount of current from the plurality of photovoltaic power sources may include capturing electricity from each of the plurality of photovoltaic power sources that exceeds the least amount of current, converting electricity from each of the plurality of photovoltaic power sources to the least amount of current, and transmitting the converted electricity from each of the plurality of photovoltaic power sources in series with each other and the plurality of photovoltaic power sources.

In one or more embodiments, determining a least amount of current generated by one of the plurality of photovoltaic power sources may include periodically (e.g., every 1 second, every 2 seconds, every 5 seconds, every 15 seconds, every 20 seconds, every 30 seconds, every 45 seconds, every 1 minute, every 2 minutes, every 5 minutes, etc.) determining the least amount of current generated by one of the plurality of photovoltaic power sources. In one or more embodiments, capturing electricity that exceeds the least amount of current from the plurality of photovoltaic power sources may include providing a plurality of converters including an input portion and an output portion. The input portion of each of the plurality of converters may be coupled in parallel with a photovoltaic power source of the plurality of photovoltaic power sources, and the output portions of the plurality of converters may be coupled in series with the plurality of photovoltaic power sources.

The above summary is not intended to describe each embodiment or every implementation of the present disclosure. A more complete understanding will become apparent and appreciated by referring to the following detailed description and claims taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of a prior art system.

FIG. 2 is a block diagram of an exemplary system for capturing electricity from an array of power sources.

FIG. 3 is a block diagram of a portion of the exemplary system of FIG. 2.

FIG. 4 is flow diagram of an exemplary method for capturing electricity from an array of power sources.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

A drawback of the prior art presented in FIG. 1 is that each of the DC-to-DC converters has to convert the full power available from each of the power sources, which requires converters used in this system to be large and expensive. Additionally, the efficiency of these DC-to- DC converters will affect all of the power generated by the system.

The present disclosure overcomes these drawbacks as will be shown with respect to the illustrative embodiments described herein. In the following detailed description of illustrative embodiments, reference is made to the accompanying figures of the drawing which form a part hereof, and in which are shown, by way of illustration, specific embodiments which may be practiced. It is to be understood that other embodiments may be utilized and structural changes may be made without departing from (e.g., still falling within) the scope of the disclosure presented hereby.

Exemplary systems and methods shall be described with reference to Figures 2-4. It will be apparent to one skilled in the art that elements or processes from one

embodiment may be used in combination with elements or processes of the other embodiments, and that the possible embodiments of such systems and methods using combinations of features set forth herein is not limited to the specific embodiments shown in the Figures and/or described herein. Further, it will be recognized that the

embodiments described herein may include many elements that are not necessarily shown to scale. Still further, it will be recognized that timing of the processes and the size and shape of various elements herein may be modified but still fall within the scope of the present disclosure, although certain timings, one or more shapes and/or sizes, or types of elements, may be advantageous over others.

In one or more exemplary systems and methods described herein, the power sources, such, e.g., photovoltaic panels, concentrated photovoltaic cells, etc. may be connected serially (e.g., in a serial configuration). Due to the serial configuration, the current flowing through all of the power sources is equal to the current available from the weakest power source. Additionally, DC-to-DC converters may be connected to the stronger power sources that are capable of delivering more current than the current flowing through the serial connection. The DC-to-DC converters may be configured to draw any extra available current from each of the stronger power sources enabling them to provide their maximum available power. It is a particular feature of the exemplary systems and methods described herein that these DC-to-DC converters may be relatively small and inexpensive since the converters merely need to convert the extra available current from each of the stronger sources as opposed to the converters used in the prior art configuration that need to convert the entire current provided from each power source. Further, the DC-to-DC converters in the exemplary systems and methods may convert the extra available current of the stronger power sources to a lower voltage current that is equal to the current flowing through the serial connection of the power sources. Since the output current of the DC-to-DC converters is equal to the serial connection current of the power sources, the outputs of the DC-to-DC converters can be connected serially to generate the full output power.

An exemplary system 20 for providing electricity from a photovoltaic array is depicted in FIG. 2. As shown, the exemplary system 20 may include a plurality of power sources 200, 201 , 202, 203, a plurality of converters 210, 211, 212, 213, and a computing apparatus, or controller, 221. Although four power sources 200, 201, 202, 203 are depicted, the exemplary system may include less than four power sources or more than four power sources depending on the configuration.

Each power source 200, 201, 202, 203 may be photovoltaic power source configured to generate electricity from light. A photovoltaic power source may be described as including one photovoltaic cell, more than one photovoltaic cell, or a group of photovoltaic cells grouped in panel. In other words, the particular configuration or arrangement of the photovoltaic elements for each photovoltaic power source is not limiting.

The power sources 200, 201, 202, 203 are serially electrically coupled to each other. More specifically, each of the power sources 200, 201, 202, 203 may include a positive terminal and a negative terminal. The positive terminal of one power source may be connected to the negative terminal of another power source forming the serial connection. For example, as shown, a second terminal of power source 203 is electrically coupled to a first terminal of power source 202, a second terminal of power source 202 is electrically coupled to a first terminal of power source 201, a second terminal of power source 201 is electrically coupled to a first terminal of power source 200, etc. In other words, power sources 200, 201, 202, 203 are connected serially with current I flowing through them.

The plurality of converters 210, 211, 212, 213 may be described as being serially electrically coupled to each other. More specifically, the outputs of the converters 210, 211, 212, 213 may be serially electrically coupled to each other. Further, the plurality of power sources 200, 201, 202, 203 may be serially electrically coupled to the outputs of the plurality of converters 210, 211, 212, 213. In the embodiment shown, the converters are DC-to-DC converters (e.g., convert direct current to another direct current).

Further, the inputs of the converters 210, 211, 212, 213 may be electrically coupled in parallel to the power sources 200, 201, 202, 203, respectively. As shown, each of the converters 210, 211, 212, 213 is electrically coupled in parallel to a different power source 200, 201, 202, 203. In other words, each power source 200, 201, 202, 203 may have its own dedicated converter 210, 211, 212, 213, which may be described as a one-to- one configuration.

Each of the converters 210, 211, 212, 213 may be described as including an input portion and an output portion. Further, each of the converters 210, 211, 212, 213 may be configured to receive electricity using the input portion, convert the electricity to a selected current, and transmit the converted electricity using the output portion. The input portion of each of the plurality of converters 210, 211, 212, 213 may be coupled in parallel with a power source of the plurality of power sources 200, 201, 202, 203. For example, each input portion may include a first terminal and a second terminal that are coupled to the first and second terminals of the corresponding power source 200, 201,

202, 203. The output portions of the plurality of converters 210, 211, 212, 213 may be coupled in series with each other and with the plurality of power sources 200, 201, 202,

203. For example, the second terminal of the converter 210 may be electrically coupled to the first terminal of the converter 211, the second terminal of the converter 211 may be electrically coupled to the first terminal of the converter 212, the second terminal of the converter 212 may be electrically coupled to the first terminal of the converter 213, etc. The first terminal of the converter 210 may be electrically coupled to the second terminal of the power source 200 (e.g., to be complete the series electrical connection between the power sources 200, 201, 202, 203 and the outputs of the converters 210, 211, 212, 213).

The converters 210, 211, 212, 213 may be configured to capture excess electricity of the power sources 200, 201, 202, 203. The excess electricity of the power sources 200, 201, 202, 203 may be described as the electricity having a current greater than the maximum current transmitted through the serially connected power sources 200, 201, 202, 203, which as described herein, may be dictated by the power source generating the lowest current (e.g., the lower current sets the maximum current transmitted through the serially-connected power sources 200, 201, 202, 203). In other words, the converters 210, 211, 212, 213 may be connected in parallel to the outputs of power sources 200, 201, 202, 203, respectively, to draw extra available currents dll, dll, dI2, dI3, dI4. The extra available current may be described as being drawn from the power sources 200, 201, 202, 203 at the full voltage levels of the power source output (parallel connection at the output). The converters 210, 211, 212, 213 may be configured to transform the full voltage/low current inputs to low voltage/full current I outputs. These outputs VI -V4 are connected in serial form to the output of the power sources 200, 201, 202, 203, thereby raising the voltage to generate the maximum available power.

The computing apparatus, or controller, 221 may be operatively coupled to the plurality of converters 210, 211, 212, 213 and configured to use the plurality of converters 210, 211, 212, 213 to capture electricity from the plurality of power sources 200, 201, 202, 203 that exceeds a selected current (e.g., the lowest current generated by one of the power sources 200, 201, 202, 203). In other words, the controller 221 may control the amount of current drawn by each of the converters 210, 211, 212, 213 (e.g., DC-to-DC converters). In at least one embodiment, the controller 221 may utilize, or include, a pulse width modulation (PWM) mechanism within each of the converters 210, 211, 212, 213. The controller 221 may be described as being able to execute an algorithm that maximizes the amount of power generated from the plurality of power sources 200, 201, 202, 203 of the system 20. The exemplary system 20 is further depicted in FIG. 3, which may be used to execute the exemplary methods and/or processes described herein, e.g., for providing electricity from a plurality of power sources such as photovoltaic power sources. As shown, the exemplary system 20 includes computing apparatus, or controller, 210. The computing apparatus, or controller, 221 may be configured to receive input from the converters 22. Further, the computing apparatus 221 may include data storage 14. Data storage 14 may allow for access to processing programs or routines 16 (e.g., for controlling current drawn by the converters 22, monitoring electricity generated by the power sources 200, 201, 202, 203, etc.) and one or more other types of data 18 that may be employed to carry out exemplary methods and/or processes (e.g., current values, selected currents, power values, electricity values, electricity metrics, output currents, etc.).

The computing apparatus 221 may be operatively coupled to the converters 22 to, e.g., receive and transmit data to and from the converters 22. For example, the computing apparatus 221 may be electrically coupled to each of the converters 210, 211, 212, 213 using, e.g., analog electrical connections, digital electrical connections, etc.

The processing programs or routines 16 may include programs or routines for providing electricity generation from an array of power sources, current measurement, power measurement, electricity balancing, voltage summation, power

optimization/maximization, computational mathematics, comparison algorithms, or any other processing required to implement one or more exemplary methods and/or processes described herein. Data 18 may include, for example, current values, current outputs, voltage values, voltage outputs, power outputs, power values, results from one or more processing programs or routines employed according to the disclosure herein, or any other data that may be necessary for carrying out the one and/or more processes or methods described herein.

In one or more embodiments, the system 20 may be implemented using one or more computer programs executed on programmable computers, such as computers that include, for example, processing capabilities, data storage (e.g., volatile or non-volatile memory and/or storage elements), input devices, and output devices. Program code and/or logic described herein may be applied to input data to perform functionality described herein and generate desired output information. The output information may be applied as input to one or more other devices and/or methods as described herein or as would be applied in a known fashion. The one or more programs used to implement the methods and/or processes described herein may be provided using any programmable language, e.g., a high level procedural and/or object orientated programming language that is suitable for

communicating with a computer system. Any such programs may, for example, be stored on any suitable device, e.g., a storage media, that is readable by a general or special purpose program running on a computer system (e.g., including processing apparatus) for configuring and operating the computer system when the suitable device is read for performing the procedures described herein. In other words, at least in one embodiment, the system 20 may be implemented using a computer readable storage medium, configured with a computer program, where the storage medium so configured causes the computer to operate in a specific and predefined manner to perform functions described herein. Further, in at least one embodiment, the system 20 may be described as being implemented by logic (e.g., object code) encoded in one or more non-transitory media that includes code for execution and, when executed by a processor, is operable to perform operations such as the methods, processes, and/or functionality described herein.

The computing apparatus 221 may be, e.g., a controller, a microcontroller, etc. The exact configuration of the computing apparatus 221 is not limiting, and any device capable of providing suitable computing capabilities and control capabilities (e.g., DC-to- DC converter control, PWM control, current monitoring, etc.) may be used. As described herein, a digital file may be any medium (e.g., volatile or nonvolatile memory, a CD-ROM, a punch card, magnetic recordable tape, etc.) containing digital bits (e.g., encoded in binary, trinary, etc.) that may be readable and/or writeable by computing apparatus 221 described herein. Also, as described herein, a file in user- readable format may be any representation of data (e.g., ASCII text, binary numbers, hexadecimal numbers, decimal numbers, graphically, etc.) presentable on any medium (e.g., paper, a display, etc.) readable and/or understandable by a user.

In view of the above, it will be readily apparent that the functionality as described in one or more embodiments according to the present disclosure may be implemented in any manner as would be known to one skilled in the art. As such, the computer language, the computer system, or any other software/hardware which is to be used to implement the processes described herein shall not be limiting on the scope of the systems, processes or programs (e.g., the functionality provided by such systems, processes or programs) described herein. The methods and/or logic described in this disclosure, including those attributed to the systems, or various constituent components, may be implemented, at least in part, in hardware, software, firmware, or any combination thereof. For example, various aspects of the techniques may be implemented within one or more processors, including one or more microprocessors, DSPs, ASICs, FPGAs, or any other equivalent integrated or discrete logic circuitry, as well as any combinations of such components, or other devices. The term "processor" or "processing circuitry" may generally refer to any of the foregoing logic circuitry, alone or in combination with other logic circuitry, or any other equivalent circuitry.

Such hardware, software, and/or firmware may be implemented within the same device or within separate devices to support the various operations and functions described in this disclosure. In addition, any of the described components may be implemented together or separately as discrete but interoperable logic devices. Depiction of different features, e.g., using block diagrams, etc., is intended to highlight different functional aspects and does not necessarily imply that such features must be realized by separate hardware or software components. Rather, functionality may be performed by separate hardware or software components, or integrated within common or separate hardware or software components.

When implemented in software, the functionality ascribed to the systems, devices and methods described in this disclosure may be embodied as instructions and/or logic on a computer-readable medium such as RAM, ROM, NVRAM, EEPROM, FLASH memory, magnetic data storage media, optical data storage media, or the like. The instructions and/or logic may be executed by one or more processors to support one or more aspects of the functionality described in this disclosure. An exemplary method 50 for providing electricity generation is depicted in FIG. 4. The exemplary method 50 includes monitoring power (e.g., voltage, current, etc.) from each of the power sources 52. Further, the method 50 may determine the weakest power source 54 out of the plurality of power sources based on the monitoring thereof 52. The weakest power source 54 may determine the maximum current that may be allowed to flow through the serially connected, or coupled, power sources.

Based on the maximum current, the method 50 may determine how much power (e.g., current) may be drawn from each of the power sources 54 that are generating more electricity than the weakest power source. For example, the method 50 may set the current to be drawn from the each of the power sources using the converters 56 to be the current exceeding the maximum current that is allowed to flow through the serially connected, or coupled, power sources. In other words, the current to be drawn from each power source by a converter may be set to the current generated by the power source subtracted by least amount of current generated by one of the power sources (i.e., the weakest power source).

For example, another exemplary method may also be described as (1) ramping through the current drawn by the DC-to-DC converter 210, monitoring the total power generated by the system, and (3) setting the current drawn by DC-to-DC converter 210 to the one that generates the maximum total power in step 1 and monitoring the change in current drawn by the DC-to-DC converter 210 relative to the previous setting of the DC- to-DC converter. Further, (4) steps 1 to 3 may be repeated for the rest of the DC\ DC converters, and (5) steps 1 to 4 may be repeated until the correction in the of all DC-to-DC converters is below a preset threshold.

Steps 1 to 3 of the exemplary method, or algorithm, may determine a local maximum of the generated total power based on configuring one of the DC-to-DC converters. Since there is a dependency between the power drawn by one converter and the setting of the other converters, the algorithm cycles repeatedly through the converters until convergence to the optimal settings is reached. EXAMPLE

The following example demonstrates the operation of one exemplary embodiment of the present disclosure.

Assume the following power sources are available:

1^st Power Source: 50 Volts (V) - 24 Amps (A)

2^nd Power Source: 51 V - 25 A

3^rd Power Source: 51 V - 26 A

4^th Power Source: 52 V - 27 A

If one were to connecting the powers sources serially, the following performance will be provided:

Voltage output = 204 V

Current output = 24 A, which is determined by the weakest power source Power output = 4896 Watts (W)

Using the prior art configuration presented in FIG. 1, the DC-to-DC converters may be assumed to be arranged to generate 30 A outputs. Further, the DC-to-DC converters are assumed to have an efficiency of 95%.

The outputs of the DC-to-DC converters under the prior art configuration of FIG. 1 are as follows:

1^st Converter. Voltage = 50 V* 24 A* .95 / 30 A = 38 V; Current = 30 A; Power = 1140 W

2^nd Converter. Voltage = 51 V* 25 A* .95 / 30 A = 40.375 V; Current = 30 A; Power = 1211.25 W

3^rd Converter. Voltage = 51 V * 26 A*.95 / 30 A = 41.99 V; Current = 30 A;

Power = 1259.7 W 4^m Converter. Voltage = 52 V * 27 A * .95 / 30 A = 44.46 V; Current = 30 A; Power = 1333.8 W

The total output generated voltage will be

38 V + 40.375 V + 41.99 V + 44.46 V = 164.825 V and the total power will be:

1140 W + 1211.25 W + 1259.7 W + 1333.8 W = 4944.75 W.

As such, close to 50 W are gained by using 4 DC-DC converters each with more than 1 KW output when compared to the serially connected power sources.

Using the exemplary systems and methods as shown in FIGS. 2-4, the serial current may be established at 24 A, which is the current of 1^st source, while extracting the extra available currents from the stronger three power sources with the DC-to-DC converters. The converters output will also be set to 24 A. Assuming again 95% efficiency the following voltages will be generated:

1^st Converter. VI = 0; (which is electrically coupled in parallel to the weakest power source, 1^st Power Source)

2^nd Converter. V2 = 51 V * (25 A - 24 A) * .95 / 24 A = 2.02 V; Power = 48.45

W

3^rd Converter. V3 = 51 V * (26 A- 24 A) * .95 / 24 A = 4.04 V; Power = 96.9 W 4^th Converter. V4 = 52 V * (27 A- 24 A) * .95 / 24 A = 6.175 V; Power = 148.2 W

The total generated output voltage will be

50 V + 51 V +51 V +52 V + 2.02 V +4.04 V + 6.175 V = 216.235 V And the total generated power produced will be

216.235 V * 24 I = 5189.6 W. As such, the exemplary systems and methods show significant improvement over previous schemes by using relatively-small, inexpensive DC-to-DC converters.

Claims

CLAIMS What is claimed is:

1. A system for providing electricity from a photovoltaic array, the system

comprising:

a plurality of photovoltaic power sources configured to generate electricity from light and electrically coupled in series;

a plurality of converters comprising an input portion and an output portion and configured to receive electricity using the input portion, convert electricity to a selected current, and transmit the converted electricity using the output portion, wherein the input portion of each of the plurality of converters is coupled in parallel with a photovoltaic power source of the plurality of photovoltaic power sources, wherein the output portions of the plurality of converters is coupled in series with the plurality of photovoltaic power sources; and

a controller operatively coupled to the plurality of converters and configured to use the plurality of converters to capture electricity from the plurality of photovoltaic power sources that exceeds the selected current.

2. A system for providing electricity from a photovoltaic array comprising a plurality of photovoltaic power sources configured to generate electricity from light and electrically coupled in series, the system comprising:

a plurality of converters, each coupled in parallel with a photovoltaic power source of the plurality of photovoltaic power sources to receive electricity, convert the electricity to a selected current, and transmit the converted electricity, wherein the plurality of converters are coupled in series with each other and with the plurality of photovoltaic power sources to transmit the converted electricity; and

3. The system of claim 1, wherein each of the plurality of photovoltaic power sources comprises a first terminal and a second terminal, wherein the first terminal of each photovoltaic power source of the plurality of photovoltaic power sources is electrically coupled to the second terminal of another photovoltaic power source of the plurality of photovoltaic power sources to electrically couple the plurality of photovoltaic power sources in series.

4. The systems of any one of claims 1 and 3, wherein the output portion of each of the plurality of converters comprises a first terminal and a second terminal, wherein the first terminal of each converter of the plurality of converters is electrically coupled to the second terminal of another converter of the plurality of converters to electrically couple the plurality of converters in series.

5. The systems of any one of claims 1-4, wherein the controller is further configured to:

monitor an amount of electricity generated by each of the plurality of photovoltaic power sources;

determine a least amount of current generated by one of the plurality of photovoltaic power sources; and

set the selected current to the least amount of current.

6. The systems of any one of claims 1-5, wherein the controller is further configured to set an amount of current to be drawn from a photovoltaic power source of the plurality of photovoltaic power sources using a converter of the plurality of converters to the amount of current generated by the photovoltaic power source minus the least amount of current.

7. The systems of any one of claims 1-6, wherein the plurality of converters are configured to convert the electricity that exceeds the selected current to the selected current.

8. The systems of any one of claims 1-7, wherein the controller is further configured to control the plurality of converters using pulse-width modulation.

9. The systems of any one of claims 1-8, wherein the plurality of converters are direct current-to-direct current converters.

10. A method of providing electricity from a photovoltaic array, wherein the photovoltaic array comprises a plurality of photovoltaic power sources configured to generate electricity from light and electrically coupled in series, the method comprising: monitoring an amount of electricity generated by each of the plurality of photovoltaic power sources;

determining a least amount of current generated by one of the plurality of photovoltaic power sources; and

capturing electricity that exceeds the least amount of current from the plurality of photovoltaic power sources.

11. The method of claim 10, wherein capturing electricity that exceeds the least amount of current from the plurality of photovoltaic power sources comprises:

capturing electricity from each of the plurality of photovoltaic power sources that exceeds the least amount of current;

converting electricity from each of the plurality of photovoltaic power sources to the least amount of current; and

transmitting the converted electricity from each of the plurality of photovoltaic power sources in series with each other and the plurality of photovoltaic power sources.

12. The method of any of claims 10-11, wherein determining a least amount of current generated by one of the plurality of photovoltaic power sources comprises periodically determining the least amount of current generated by one of the plurality of photovoltaic power sources.

13. The method of any one of claims 10-12, wherein capturing electricity that exceeds the least amount of current from the plurality of photovoltaic power sources comprises providing a plurality of converters comprising an input portion and an output portion, wherein the input portion of each of the plurality of converters is coupled in parallel with a photovoltaic power source of the plurality of photovoltaic power sources, wherein the output portions of the plurality of converters is coupled in series with the plurality of photovoltaic power sources.