# Patent

## Title
Solar panel string converter topology

## Abstract

The inventive technology, in certain embodiments, may be generally described as a solar power generation system with a converter, which may potentially include two or more sub-converters, established intermediately of one or more strings of solar panels. Particular embodiments may involve sweet spot operation in order to achieve improvements in efficiency, and bucking of open circuit voltages by the converter in order that more panels may be placed on an individual string or substring, reducing the number of strings required for a given design, and achieving overall system and array manufacture savings.

## Background
CROSS-REFERENCES TO RELATED APPLICATIONS
This application is the United States National Stage of international patent application number PCT/US2010/053253, filed 19 Oct. 2010, published on 28 Apr. 2011 as WO 2011/049985 A1 and claims priority to U.S. Provisional App. No. 61/253,025, filed Oct. 19, 2009, each application hereby incorporated herein in their entirety by reference.


TECHNICAL FIELD
This invention relates to methods and apparatus involving grid- or electrical power network-tied photovoltaic (PV) converters. In one embodiment, it especially relates to multiple panel grid-tied PV converters commonly deployed in either commercial or even residential power installations.
BACKGROUND
Many common PV converters may have challenges to meet cost and reliability challenges. Such challenges need to be viewed from the perspective of generating their electricity savings for payback of initial investment over longer periods. The present invention provides systems that may in some embodiments address cost and reliability goals for many PV systems.
At the current time the use of PV (photovoltaic) panels to generate electricity may be in a period of rapid growth. The cost of solar power may even be decreasing and many factors appear to limit the growth of non-renewable energy sources. Today there are both large scale systems and small scale systems being deployed. In a typical system, many PV panels may be connected to a grid-tied converter or inverter which may take the power from the PV panels, perhaps at or near their maximum power points, and may then transforms it to AC power suitable to back-feeding the grid or other electrical power network.
SUMMARY OF THE INVENTION
This invention solves one fundamental disadvantage of string converters when compared to module level converters. In solar PV installations there are various architectures which address the need for allowing solar PV modules to operate at their Maximum Power Point (MPP). Conventional central inverters (1) operate with their input voltage controlled to find the MPP of an array. This array typically has several (to hundreds or thousands) of strings (2) of individual solar modules (3). But every module has an individual MPP and an array MPP solution leaves energy unharvested. At the other end of the spectrum MPP per module converters allow maximum harvesting from each module. There is a middle ground being considered today whereby each string is equipped with a DC/DC converter (4) operating at the MPP for a series string of PV modules (5).
For certain modules (e.g., thin film modules), the ratio of VOC cold to VMPP hot may be 2:1. Take for example a module having VOC cold=70 volts and hot=35 volts. In this installation the rail voltage on a cold day when the inverter is not connected to the grid will be 70×8=560 volts. This is safely below the US regulatory limit of 600 volts. A conventional string converter could simply be connected to this string. Obviously it would not meet the same regulatory limit with a conventional system if more modules were added to this string.
The normal operating voltage of this string though may be only 35×8=280 volts. This low operating voltage requires a large wire plus the inverter must operate at 280 volts while being able to withstand 560 volts. The circuit of an embodiment of this invention capitalizes on the situation where thin film solar PV modules typically operate with VMPP of, less than, and perhaps only about half of, VOC cold.
One advantage is that string MPP architectures gain much of the energy of individual module MPP architectures while costing a bit less. There are a few limitations of string MPP architectures:

    
    
        The harvesting is less compared to MPP/module as current may vary within a string which cannot be corrected.
        Diagnostic information is only available at the string level instead of module level.
        During periods when the downstream inverter is not able to deliver power, the string voltage moves to the open circuit voltage of each module added together. This limits the number of modules which may be connected in a string for a given regulatory voltage level.
        The string inverter must operate over a wide input voltage range.
    
    


A novel string DC/DC converter with MPP can be used to solve the third limitation while adding several new benefits. Solving this modules-per-string problem allows a solar PV system designer to place more modules per string (perhaps 2× more), resulting in fewer strings and fewer combiner boxes. The final result can be a lowering of Balance Of System (BOS) cost. As will be seen the architecture disclosed also allows a DC/DC converter to operate at its sweet spot improving efficiency. Another aspect of this invention is the suitability of this architecture for thin film photovoltaic modules in that it can address the low fill factor of thin film technologies with a low cost, highly efficient design.
One advantage of the inventive technology may be, in embodiments, the ability to place more modules on a string, thereby lowering the total number of strings that a solar array must have to generate a design power. Such reduction of the total number of strings translates into a cost savings, as strings often require expensive componentry (e.g., combiner boxes). In some embodiments, twice as many solar panels may be placed on a string, relative to conventional technologies.
Additional Exemplary Advantages: Because of the allowed regulatory upper limit voltage (recall that even during an open circuit, during sunlight hours, where no power is output from the DC-AC inverter, there is a voltage output), and because of the fact that typically, an open circuit voltage from a solar panel is greater than a loaded (e.g., operating circuit) voltage from that solar panel (because MPP controls effective during loaded circuit conditions reduce output voltages as compared with open circuit conditions, in order to achieve maximum power), the number of solar panels per string in certain prior art string architecture was limited by the open circuit condition (again, because it produces higher voltages and because compliance with applicable voltage regulations is mandatory), with the inventive technology, the number of modules per string can be increased. This may be due to the bucking of open circuit voltages (which are typically higher than operational voltages); in this way, relative to a conventional apparatus with a maximum number of panels in a string, during open circuit condition, more panels can be added without going over the limit. And during operation, the voltage sum of the loaded panels of a single string can be greater than it otherwise would be (which is beneficial because such means more power per string . . . and the associated cost savings). This may be due to the fact that in embodiments of the inventive technology, the converter, established intermediately within the string, is connected with two portions of the string in which it is established via conductors, and the loaded circuit (e.g., MPP) voltages of such conductors sum to be substantially equal to the output from the converter. Such “sweet spot” operation affords additional efficiency of operation benefits relative to conventional apparatus. As such, not only does the inventive technology, in particular embodiments, offer advantages relative to an increase in the number of modules per string, but it also offers benefits relative to the efficiency of operation (due to “sweet spot” operation). Open circuit voltages may be reduced, or bucked, by the converter, such that they sum to at or below the maximum regulatory voltage. Of course, additional advantages may be as disclosed elsewhere in this patent application.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic diagram of one type of traditional system grid-tied solar power system with an inverter.
FIG. 2 shows a conceptual embodiment of the invention.
FIG. 3 shows one conceptual embodiment of the invention.
FIG. 4 shows a schematic of one embodiment of the invention.
FIG. 5 shows a schematic of one embodiment of the invention, showing loaded circuit voltages (Vcc), or Vmpp (maximum power point), and open circuit voltages (Voc) of various conductors/components. The voltmeter hookups are shown to illustrate where the Voc of 0V, 600V and the Vcc measurements of 300V are taken. Here, a maximum output voltage on rail 62 is 600V.
FIG. 6 shows a schematic of one embodiment of the invention.
FIG. 7 shows a schematic of one embodiment of an inventive DC-DC power converter.
FIG. 8 shows a schematic of one embodiment of an inventive DC-DC power converter.
FIG. 9 shows a schematic of one embodiment of an inventive DC-DC power converter.
FIG. 10 shows a prior art apparatus.



DESCRIPTION OF PREFERRED EMBODIMENTS
As may be understood from the earlier discussions, the present invention includes a variety of aspects, which may be combined in different ways. The following descriptions are provided to list elements and describe some of the embodiments of the present invention. These elements are listed with initial embodiments, however it should be understood that they may be combined in any manner and in any number to create additional embodiments. The variously described examples and preferred embodiments should not be construed to limit the present invention to only the explicitly described systems, techniques, and applications. Further, this description should be understood to support and encompass descriptions and claims of all the various embodiments, systems, techniques, methods, devices, and applications with any number of the disclosed elements, with each element alone, and also with any and all various permutations and combinations of all elements in this or any subsequent application
Consider first the architecture and circuit diagram of one embodiment of the invention shown in FIG. 4. This circuit has two of the former strings 5 combined into a power converter 52 (large blue box) and having a series diode 72, all making up a new string 60. The power converter can have: an intra-string control element 8, a controlled intra-string connector 9, or in a preferred embodiment, two DC/DC converters 55 (the upper box and the lower box; subconverters of a single converter 52) perhaps appearing to operate in a mirror image of each other, among other options. During periods of no load, when the downstream inverter 63 is not connected to the grid, each of the DC/DC subconverters may operate in buck mode and reduce the string input voltage perhaps by about one half. At this time, for example, each DC/DC subconverter 55 may have a VOC input as high as 560 volts but an output of 280 volts. One may see that even though twice as many modules are connected in this string, the output voltage may remain at 560 volts, even when the individual modules are operating at VOC. There is little efficiency penalty for the DC/DC inverter at this time as there is no power being processed.
During power generating periods (loaded circuit condition), when individual module outputs may drop to VMPP. (the series of eight modules making perhaps  ̃280 volts) the DC/DC subconverter 55 may now pass the input voltage relatively unaltered to the output which may remain at 560 volts (conservatively below an upper maximum allowed by regulation of 600V). Importantly at this time when the DC/DC subconverters 55 are operating at significant power, they are also at their sweet spot—neither boosting nor bucking significantly and therefore operate at their highest efficiency!
The DC/DC converters 55 may be simply buck mode converters or may be many differing types of converters. This disclosure does not intend to limit aspects of the actual power converter or other element that may be used. For example, as shown conceptually in FIG. 3, embodiments may include: a circuit which divides voltage 308, a coupled inductor circuit, a simple switch perhaps across one or more DC/DC converters, a circuit having switching capability 309, an intra-string control element 310, a controllable intra-string connection 9, other designs for DC/DC converters, various circuits which may or may not include MPP/string capabilities, or even any circuit which apportions voltages between strings. Various embodiments may result in different operating conditions and/or operational ranges. One preferred embodiment may be dual mode converters perhaps such as shown in FIG. 4. For a detailed circuit operation for an embodiment of a dual mode DC/DC converter one may refer to PCT publication number WO2009051853 and U.S. Pat. No. 7,605,498. These converters may or may not include P & O MPP tracking for the string—even more, this circuit could provide MPP tracking for each half string, extremely high efficiency, and programmable voltage and current limits.
As a result the circuit and architecture of embodiments of the invention may provide the following benefits:

    
    
        Substantially more modules may be included in a string—reducing BOS cost. In the example of FIG. 3, there are twice as many modules in a string.
        This circuit may provide MPP tracking for each half string improving harvesting or conventional string converters.
        This circuit can greatly simplify a downstream inverter by providing constant or a narrow range of operating voltage for the inverter.
        This circuit may operate at the highest possible efficiency by typically operating with input voltage near output voltage for each DC/DC converter.
        This circuit may make use of extremely high efficiency converters, perhaps as described in PCT publication number WO2009051853 and U.S. Pat. No. 7,605,498.
        While individual modules operate at VMPP, the string output and the array may operate at much higher voltage limited only by the regulatory environment.
        This circuit simultaneously operates at a high efficiency while delivering power at the highest allowable string voltage.
        There is no point in the array which exceeds the regulatory voltage limit.
    
    


The inventive technology, in embodiments, may adjust loaded condition power per string or even per substring (string portion 50) to achieve maximum power point for that string or substring, while bucking open circuit voltages. Indeed, in particular embodiments, the purpose of the converter may be, at least in part, to extract, perhaps using switches (e.g., perhaps one for each string or substring), maximum power from the string or substrings with which it is connected, while bucking open circuit voltages to provide for a greater number of panels for each string (or substring). While the converters disclosed herein may be, at times, presented in the context of solar array power generation, they may have other applications.
In particular embodiments of the inventive technology, a DC-DC converter 52 may be established intermediately within a string of solar panels (which includes but is not limited to directly in the center of). While in certain embodiments a converter so established may be established such that the number of solar panel(s) serially connected between the converter and the lower rail is the same as the number of panels serially connected between the converter and the upper rail, such a symmetric architecture is not a necessary feature.
Particular embodiments may involve operation of the converter at a “sweet spot”, where the sum of the voltages of conductors from string portions to the converter is substantially equal to (e.g., within 20% of) the voltage of the conductor leading to the upper (or positive) rail (voltages measured relative to a lower or negative rail; see FIG. 5). Operational efficiencies inhere in “sweet spot” operation; indeed, as but one example, a converter that takes an input of 300 volts and outputs 600 volts is less efficient than a converter that, operating at its “sweet spot”, takes an input of 600 volts and outputs 600 volts (or substantially 600 volts, wherein 600 volts is the allowable limit, also expressed as the maximum regulatory voltage) (see, e.g., FIG. 5). In particular embodiments, the output from the converter may be at or close to (e.g., slightly below, or conservatively below), a regulatory limit.
Relatedly, the inventive technology, in particular embodiments, may be viewed as power architecture that allows a substantially constant voltage applied to a positive rail during open circuit and loaded circuit conditions (i.e., where the open circuit voltage of the positive rail relative to the negative rail is substantially equal to the loaded circuit voltage of the positive rail relative to the negative rail), and/or that affords the efficiency benefits of sweet spot converter operation while perhaps also outputting a near maximum regulatory voltage (see, e.g., FIG. 5). It should be understood that particular features of certain embodiments of the inventive technology may not be critical to, and may not be found in, all embodiments. For example, “sweet spot” operation might not be found in all types of converters used in the inventive technology.
In particular embodiments, the intermediately connected DC-DC converter may include sub-converters 55. Where two sub-converters are present, a first string portion may be electrically connected with one sub-converter and a second string portion may be electrically connected with the other sub-converter. The subconverters may be connected with an intra-string connector 9. The converter, regardless of whether it includes sub-converters, may be a buck/boost converter (e.g., a dual mode conductor as described in PCT publication number WO2009051853 and U.S. Pat. No. 7,605,498). Indeed the sub-converters themselves may be “dual mode” type as these references describe.
In particular embodiments where an intermediately established converter divides a solar panel string into two portions, the two string portions may operate as if in parallel during an open circuit condition, and operate in as if in series during a closed (operating, e.g., MPP) circuit condition. Further, in particular embodiments, converter circuitry (e.g., switching circuitry), may be able to smoothly transition from series connected substrings (string portions) to parallely connected substrings.
It should be understood that while the exemplary disclosure (e.g., in writing and/or figures) may appear to relate most particularly to unipolar designs, this application is intended to, and in fact does, also disclose bipolar designs (e.g., where the negative, or lower rail has a voltage of zero).
At least one embodiment of the inventive technology may be generally described as a solar power system that includes: at least two solar panels 56 of a first solar power string 60; a first DC-DC converter 52 connected within the first solar power string; a negative rail 64 electrically connected with one of the at least two solar panels and the first DC-DC converter, a positive rail 62 electrically connected with a different one of the at least two solar panels and the first DC-DC converter; and a DC-AC power inverter 63 that acts on power conducted by the negative and positive rails. Often, a rail receives a plurality of inputs from parallely disposed components.
In particular embodiments the first DC-DC converter may operate at a sweet spot during loaded circuit condition of the system. More particularly, the first DC-DC converter connected within the first solar power string may be connected with a first portion 67 of the first solar power string through a first string portion conductor 68 and connected with a second portion 65 of the first solar power string through a second string portion conductor 66, where the second string portion conductor may have a second string portion loaded circuit voltage value (e.g., 600V, including slightly less than 600V) relative to the negative rail, the first string portion conductor may have a first string portion loaded circuit voltage value (e.g., 300V) relative to the negative rail, and a sum of the first string portion loaded circuit voltage value and the second string portion loaded circuit voltage value may be substantially equal to a loaded circuit voltage value 600V of the positive rail relative to the negative rail.
In particular embodiments, the system may further comprise a second solar power string 70 connected in parallel with the first solar power string; and a second DC-DC converter 71 connected may be established within the second solar power string. A diode 72 may be established between the positive rail and the converter.
The positive rail may have an open circuit voltage (e.g., 600V) relative to the negative rail and a loaded circuit voltage relative to the negative rail that are substantially equal. The positive rail may have a loaded circuit voltage relative to the negative rail that is conservatively close (such that expected variations in operating conditions will not cause an excessive voltage) to a regulatory maximum voltage limit (e.g., 560V).
In particular embodiments, the first DC-DC converter may include two sub-converters 55. At least one of the two sub-converters may be a dual mode converter, at least one of the two sub-converters may be a buck converter, and/or at least one of the two sub-converters may be a converter that is neither dual mode, buck, nor boost. Typically, a strictly boost converter would not be applicable, as there may be no need for boosting in converters of certain embodiments of the invention.
It is of note that in certain embodiments, the negative rail (where the rail can have either a negative or zero voltage value), is a lower rail, and the positive rail is an upper rail. Further, the power system can be unipolar or bipolar.
At least one embodiment of the inventive technology may be generally described as a solar power system comprising a string of solar panels 60; a DC-DC converter 52 intermediately connected within the string as a part of the string; a positive rail 62 and a negative rail 64 with which each the string and the DC-DC converter is connected; and at least one DC-AC power inverter 63 that acts on DC power conducted by the positive and negative rails.
In particular embodiments, the first DC-DC converter may operate at a sweet spot during loaded circuit condition of the system. More particularly, the first DC-DC converter connected within the string may be connected with a first portion of the string through a first string portion conductor and connected with a second portion of the string through a second string portion conductor, where the first string portion conductor has a first string portion loaded circuit voltage value relative to the negative rail, the second string portion conductor has a second string portion loaded circuit voltage value relative to the negative rail, and a sum of the first string portion loaded circuit voltage value and the second string portion loaded circuit voltage value is substantially equal to a loaded circuit voltage value of the positive rail relative to the negative rail.
The string may be a first string, and the system may further comprise at least one additional string 70 of solar panels connected in parallel with the first string. The system may further comprise at least one additional DC-DC converter 71, each of which may be connected within one of the at least one additional string of solar panels.
A diode may be established between the DC-DC converter and the positive rail 62. The positive rail may have an open circuit voltage relative to the negative rail 64 and a loaded circuit voltage relative to the negative rail that are substantially equal; further, or instead, the positive rail may have a loaded circuit voltage relative to the negative rail that is equal to or slightly less than a regulatory voltage limit (e.g., a federally imposed limit of 600 V).
In particular embodiments, the DC-DC converter may comprise two sub-converters (e.g., at least one of which is a dual mode converter (see WO2009/051853, and U.S. Pat. No. 7,605,498), at least one of which is a buck converter, and/or at least one of which is neither a dual mode nor buck converter. In particular embodiments, the system may be unipolar or bipolar. Further, the positive rail may be an upper rail and the negative rail may be a lower rail.
At least one embodiment of the inventive technology may be described as a solar power system comprising a string 60 of solar panels; a DC-DC converter 52 established intermediately within the first string of solar panels, the converter dividing the string into a first portion 67 and a second portion 65, the first portion connected with the DC-DC converter through a first string portion conductor 68 and the second portion connected with the DC-DC converter through a second string portion conductor 66; a negative rail 64 connected with the second string portion and the DC-DC converter, a positive rail 62 connected with the first string portion and the DC-DC converter, and a converter conductor 80 traveling from the converter towards the positive rail 62. In certain embodiments: a loaded circuit voltage of the first string portion conductor relative to a voltage of the negative rail has a first string portion loaded circuit voltage value; a loaded circuit voltage of the second string portion conductor relative to a voltage of the negative rail has a second string portion loaded circuit voltage value; a loaded circuit voltage of the positive rail relative to the negative rail has a positive rail loaded circuit voltage value; an open circuit voltage of the positive rail relative to the negative rail has a positive rail open circuit voltage value; a loaded circuit voltage of the converter conductor relative to the negative rail has a converter conductor loaded circuit voltage value; and a sum of the first string portion loaded circuit voltage value and the second string portion loaded circuit voltage value is substantially equal to the converter conductor loaded circuit voltage value. Such may be sweet spot operation, and operating to achieve such condition is sweet spot operating.
The positive rail loaded circuit voltage value may be substantially equal to the positive rail open circuit voltage value, and/or a sum of the first string portion loaded circuit voltage value and the second string portion loaded circuit voltage value is substantially equal to the positive rail loaded circuit voltage value. This condition may be seen during sweet spot operation.
An open circuit voltage of the first string portion conductor relative to the negative rail may have a first string portion open circuit voltage value, an open circuit voltage of the second string portion conductor relative to the negative rail may have a second string portion open circuit voltage value, and an open circuit voltage of the converter conductor relative to the negative rail may have a converter conductor open circuit voltage value. In certain embodiments, a sum of the first string portion open circuit voltage value and the second string portion open circuit voltage value is substantially equal to the converter conductor open circuit voltage value. In certain embodiments, a sum of the first string portion open circuit voltage value and the second string portion open circuit voltage value is substantially equal to the converter conductor loaded circuit voltage value. In particular embodiments, a sum of the first string portion open circuit voltage value and the second string portion open circuit voltage value is less than or equal to a regulatory maximum voltage limit. Relationships between open circuit voltages as described herein may be the result of bucking of voltages by the converter (or sub-converters that may be established therein).
In particular embodiments, the first string portion loaded circuit voltage value is equal to the second string portion loaded circuit voltage. An open circuit voltage of the positive rail relative to the negative rail may be said to be a positive rail open circuit voltage value, and the positive side of the second string portion open circuit voltage value may be substantially equal to the positive rail open circuit voltage value. The negative side of the first string portion open circuit voltage value may be, in certain embodiments, substantially equal to zero. A sum of the first string portion loaded circuit voltage value and the second string portion loaded circuit voltage value is substantially equal to the positive rail open circuit voltage value. The positive rail open circuit voltage value may be substantially equal to the positive rail loaded circuit voltage value.
In certain embodiments, the converter conductor is a converter output conductor, and the converter conductor loaded circuit voltage value is conservatively less than a regulatory maximum voltage limit. Further, the converter may include two sub-converters, at least one of which is a dual mode converter, at least one of which may include a buck converter; and at least one of which is neither dual mode, buck, nor boost. Additionally, the negative rail may be a lower rail, and the positive rail may be an upper rail. As with other designs, the power system is unipolar or bipolar.
At least one embodiment of the inventive technology may be described as a solar power control method comprising the steps of generating power from at least two solar panel substrings of a solar power string that is connected to negative and positive rails; maximum power point controlling, with a maximum power point controller, a voltage output by each the at least two solar panel substrings; and converting a power at maximum power point to AC. The step of maximum power point controlling may comprise the step of controlling with a maximum power point controller having at least two switches. Such switches may provide shunting functionality. The step of maximum power point controlling, with a maximum power point controller, a voltage output by each the at least two solar panel substrings may comprise the step of maximum power point controlling, with DC-DC converter.
At least one embodiment of the inventive technology may be described as a solar power control method comprising the steps of generating power from two solar panel substrings of a solar panel string that is connected to negative and positive rails; and mirror image controlling the power from two solar panel substrings of a converter established within the solar power string. Mirror image controlling may involve symmetric identical control where inputs are equal. The step of mirror image controlling the power from the two solar panel substrings may comprise the step of maximum power point controlling. It may involve the step of controlling with two sub-converters that each comprise a switch; such sub-converters may be substantially identical, but perhaps oriented in mirror image fashion, perhaps with any diodes changed from a strict mirror image so as to enable proper functionality as intended.
At least one embodiment of the inventive technology is a solar power control method comprising the steps of: bucking open circuit voltage from each of a plurality of solar panel substrings of a solar panel string of a solar power system, with a converter during open circuit condition; and sweet spot processing loaded circuit voltage from each of the plurality of solar panel substrings during loaded circuit condition. The method may further comprise the step of pulling maximum power point power from the each of the plurality of solar panel substrings during loaded circuit condition. A sum of voltages associated with the maximum power point power of each of the plurality of solar panel substrings may be less than or equal to a maximum regulatory voltage. The step of bucking open circuit voltage from each of a plurality of solar panel substrings may comprise the step of bucking so that a sum of bucked voltages is less than or equal to a maximum regulatory voltage; the step of bucking open circuit voltage from each of a plurality of solar panel substrings comprises the step of bucking open circuit voltage to approximately one-half voltage input to the converter by each of the substrings.
At least one embodiment of the inventive technology may be described as a solar power control system comprising: at least two solar panel substrings of a solar panel string of a solar power system; a controller established so as to maintain an open circuit voltage from the controller during an open circuit condition of the solar power system that is substantially equal to a loaded circuit voltage from the controller during a loaded circuit condition of the solar power system. In certain embodiments, an average of the open circuit voltage and the loaded circuit voltage is substantially equal to a maximum regulatory voltage.
At least one additional embodiment of the inventive technology may be described as a solar power control method comprising the steps of: loaded circuit, high efficiency, high power delivering of power generated by a solar panel string; and converting the delivered power to AC. The step of loaded circuit, high efficiency, high power delivering of power generated by a solar panel string comprises the step of loaded circuit, high efficiency, high power delivering of power generated by at least two solar panel substrings of the solar panel string. The step of loaded circuit, high efficiency, high power delivering of power generated by a solar panel string may comprise the step of neither bucking nor boosting (or simply not comprise the step of bucking or boosting, or comprise the step of refraining from bucking or boosting). The step of loaded circuit, high efficiency, high power delivering of power comprises the step of delivering maximum power point power.
It is of note that during “sweet spot” operation, where a converter has sub-converters, the inputs to and the outputs from each of the sub-converters is also substantially the same.
At least one embodiment of the inventive technology may be described as a solar power string control method, comprising the steps of generating power with solar panels of at least two substrings of a solar power string; managing circuit functionality with a DC-DC converter established intermediately of said string, said power controller defining said substrings (e.g., by dividing a larger string connected between rails into two substrings). The step of managing circuit functionality may comprise the steps of bucking open circuit voltages generated by said substrings, and, perhaps also the step of sweet spot operating during loaded circuit condition. Such converter may also achieve MPP control (e.g., with switches of said converter).
While novel converters disclosed herein may be, at times, presented in the context of solar array power generation, they may have other applications. FIGS. 7, 8 and 9 show examples of novel converters that may find application as DC-DC converters for MPP control of panel strings or substrings.
As shown in FIG. 8, a DC-DC power converter 101 may comprise: a switch 102 along a first conductor 103 that is established between two nodes, the two nodes including a first 104 node defined by an intersection of the first conductor, a second conductor 105, a third conductor 106 and a fourth conductor 107, and a second node 108 defined by an intersection of the first conductor with a fifth conductor 109, a sixth conductor 110 and a seventh conductor 111; a first diode 112 established along the second conductor between a third node 113 and the first node, the third node defined by an intersection of the second conductor, the fifth conductor, and a lower voltage conductor 114 that electrically connects the converter, the first diode allowing flow towards the first node; a second diode 115 established along the third conductor between the first node and a fourth node 116, the fourth node defined by an intersection of the third conductor, the sixth conductor, and a higher voltage conductor 117 that electrically connects the converter, the second diode allowing flow towards the fourth node; a third diode 118 established along the fifth conductor between the third node and the second node, the third diode allowing flow towards the second node; a fourth diode 119 established along the sixth conductor between the second node and the fourth node, the fourth diode allowing flow towards the fourth node; a first inductor 120 established along the fourth conductor; and a second inductor 121 established along the seventh conductor.
In particular embodiments, the system may further comprise a first power generator 198 electrically connected with the first inductor. The first power generator may be a first solar panel substring; current from the first solar panel substring may flow away from the first node. The first power generator may be electrically connected with the high voltage conductor. The system may further comprise a second power generator 199 electrically connected with the second inductor, the second power generator may be a second solar panel substring. Current from the second solar panel substring may flow towards the second node. Further, the second power generator may be electrically connected with the low voltage conductor. The system may further comprise at least one additional parallely connected converter 200 and additional power generators 201 associated with (e.g., connected with) each of the at least one additional parallely connected converter. In certain embodiments, the higher voltage conductor connects to a positive rail 62, and the first power generator is connected with the positive rail. In certain embodiments, the lower voltage conductor connects to a negative rail 64 and the second power generator is connected with the negative rail. Further, the DC-DC converter may be established within a solar panel string, the DC-DC converter may be part of a unipolar power generation system; and/or the DC-DC converter may be part of a bipolar power generation system.
As shown in FIG. 9, at least one embodiment of the inventive technology may be a DC-DC converter 130 that comprises: an inductor 131 established along a first conductor 132, between a first 133 and a second node 134, the first node defined by an intersection of the first conductor, a second conductor 135, and a third conductor 136, and the second node defined by an intersection of the first conductor, and a fourth 137 and fifth conductor 138; a first switch 139 established along the second conductor between the first node and a third node 140, the third node defined by an intersection of the second conductor, a sixth conductor 141, and a first power generator connector 142; a diode 143 established along the third conductor between the first node and a fifth node 144 defined by an intersection of the third conductor, the sixth conductor, and a higher voltage conductor 145, the diode allowing flow towards the fifth node; a capacitor 146 established along the sixth conductor between the third node and the fifth node; a second switch 147 established along the fourth conductor between the second node and a fourth node 148, the fourth node defined by an intersection of the fourth conductor, a seventh conductor 149, and a second power generator connector 150; a diode 151 established along the fifth conductor between a sixth node 152 and the second node, the sixth node defined by an intersection of the fifth conductor, the seventh conductor, and a lower voltage conductor 153, the diode allowing flow towards the second node; and a capacitor 154 established along the seventh conductor between the fourth node and the sixth node.
In certain embodiments, the system may include a first power generator 198 connected to the first power generator connector, current may flow from the first power generator away from the DC-DC converter. The system may further comprise a second power generator 199 connected to the second power generator connector, current may from from the second power generator towards the DC-DC converter. The system may further comprise at least one additional parallely connected converter 200 and at least two additional power generators 201 connected with each of the at least one additional parallely connected converter. The converter may be part of a unipolar power generation system or a bipolar power generation system. In certain embodiments, the higher voltage conductor connects to a positive rail 62, as may be the first power generator. The lower voltage conductor may connect to a negative rail 64, as may be second power generator.
As shown in FIG. 7, at least one additional embodiment of the inventive technology may be a DC-DC converter 170 comprising: an inductor 171 established along a first conductor 172 between a first node 173 and a second node 174, the first node defined by an intersection of the first conductor, a second conductor 175, a third conductor 176, and a fourth conductor 177, the second node defined by an intersection of the first conductor, a fifth conductor 178, a sixth conductor 179, and a seventh conductor 180; a first diode 181 established along the third conductor between the first node and a third node, the third node 182 defined by an intersection of the third conductor, the fifth conductor, an eighth conductor 183 and a higher voltage conductor 184, the first diode allowing flow towards the third node; a first switch 185 established along the fifth conductor between the second node and the third node; a second switch 186 established along the fourth conductor between the first node and a fourth node 187, the fourth node defined by an intersection of the fourth conductor, the eighth conductor, and a first power generator connector 188; a first capacitor 189 established along the eighth conductor between the third node and the fourth node; a second diode established along the sixth conductor between the second node and a fifth node 190, the fifth node defined by an intersection of the sixth conductor, a ninth conductor 191, the second conductor, and a lower voltage conductor 192, the second diode allowing flow towards the second node; a third switch 193 established along the second conductor between the first node and the fifth node; a fourth switch 194 established along the seventh conductor between the second node and a sixth node 195, the sixth node defined by an intersection of the seventh conductor, the ninth conductor, and a second power generator connector 196; and a second capacitor 197 established along the ninth conductor between the fifth node and the sixth node. In particular embodiments, the DC-DC converter may be part of a unipolar power generation system or a bipolar power generation system. The first power generator 198 may be connected to the first power generator connector and the higher voltage conductor, current may flow from the first power generator away from the converter. The apparatus may further comprise a second power generator 199 connected to the second power generator connector and the lower voltage conductor. Current may flow from the second power generator towards the converter. The apparatus may further comprise at least one additional parallely connected converter 200 and additional power generators 201.
In the various descriptions provided herein, the following may apply: conductor can be one or more than one wire (it may be whatever conducts). Substantially equal may mean within less than or equal to 20%, 17.5%. 15%. 12.5%. 10%. 7.5%, 5%, or 2.5%. Two components or conductors may be electrically connected even if they are intervening (typically non-converting) devices. Diodes may be optional; indeed some capacitors, particularly in the figures of the various inventive converters, may not even be shown. The term negative rail applies where there is a rail type conductor that is either at negative (e.g., the negative of the positive voltage of the positive rail) or zero volts (negative voltage may be found, e.g., in the case of a bipolar design). It is of note that the inventive converters need not necessarily have power generation connectors as claimed or described, or power generators attached thereto as claimed or described.
As can be easily understood from the foregoing, the basic concepts of the present invention may be embodied in a variety of ways. It involves both control techniques as well as devices to accomplish the appropriate controlling. In this application, the control techniques are disclosed as part of the results shown to be achieved by the various devices described and as steps which are inherent to utilization. They are simply the natural result of utilizing the devices as intended and described. In addition, while some devices are disclosed, it should be understood that these not only accomplish certain methods but also can be varied in a number of ways. Importantly, as to all of the foregoing, all of these facets should be understood to be encompassed by this disclosure.
The discussion included in this application is intended to serve as a basic description. The reader should be aware that the specific discussion may not explicitly describe all embodiments possible; many alternatives are implicit. It also may not fully explain the generic nature of the invention and may not explicitly show how each feature or element can actually be representative of a broader function or of a great variety of alternative or equivalent elements. Again, these are implicitly included in this disclosure. Where the invention is described in device-oriented terminology, each element of the device implicitly performs a function. Apparatus claims may not only be included for the device described, but also method or process claims may be included to address the functions the invention and each element performs. Neither the description nor the terminology is intended to limit the scope of the claims that will be included in any subsequent patent application.
It should also be understood that a variety of changes may be made without departing from the essence of the invention. Such changes are also implicitly included in the description. They still fall within the scope of this invention. A broad disclosure encompassing both the explicit embodiment(s) shown, the great variety of implicit alternative embodiments, and the broad methods or processes and the like are encompassed by this disclosure and may be relied upon when drafting the claims for any subsequent patent application. It should be understood that such language changes and broader or more detailed claiming may be accomplished at a later date (such as by any required deadline) or in the event the applicant subsequently seeks a patent filing based on this filing. With this understanding, the reader should be aware that this disclosure is to be understood to support any subsequently filed patent application that may seek examination of as broad a base of claims as deemed within the applicant's right and may be designed to yield a patent covering numerous aspects of the invention both independently and as an overall system.
Further, each of the various elements of the invention and claims may also be achieved in a variety of manners. Additionally, when used or implied, an element is to be understood as encompassing individual as well as plural structures that may or may not be physically connected. This disclosure should be understood to encompass each such variation, be it a variation of an embodiment of any apparatus embodiment, a method or process embodiment, or even merely a variation of any element of these. Particularly, it should be understood that as the disclosure relates to elements of the invention, the words for each element may be expressed by equivalent apparatus terms or method terms—even if only the function or result is the same. Such equivalent, broader, or even more generic terms should be considered to be encompassed in the description of each element or action. Such terms can be substituted where desired to make explicit the implicitly broad coverage to which this invention is entitled. As but one example, it should be understood that all actions may be expressed as a means for taking that action or as an element which causes that action. Similarly, each physical element disclosed should be understood to encompass a disclosure of the action which that physical element facilitates. Regarding this last aspect, as but one example, the disclosure of a “converter” should be understood to encompass disclosure of the act of “converting”—whether explicitly discussed or not—and, conversely, were there effectively disclosure of the act of “converting”, such a disclosure should be understood to encompass disclosure of a “converter” and even a “means for converting”. Such changes and alternative terms are to be understood to be explicitly included in the description.
Any acts of law, statutes, regulations, or rules mentioned in this application for patent; or patents, publications, or other references mentioned in this application for patent are hereby incorporated by reference. Any priority case(s) claimed by this application is hereby appended and hereby incorporated by reference.
Thus, the applicant(s) should be understood to have support to claim and make a statement of invention to at least: i) each of the solar power devices as herein disclosed and described, ii) the related methods disclosed and described, iii) similar, equivalent, and even implicit variations of each of these devices and methods, iv) those alternative designs which accomplish each of the functions shown as are disclosed and described, v) those alternative designs and methods which accomplish each of the functions shown as are implicit to accomplish that which is disclosed and described, vi) each feature, component, and step shown as separate and independent inventions, vii) the applications enhanced by the various systems or components disclosed, viii) the resulting products produced by such systems or components, ix) each system, method, and element shown or described as now applied to any specific field or devices mentioned, x) methods and apparatuses substantially as described hereinbefore and with reference to any of the accompanying examples, xi) the various combinations and permutations of each of the elements disclosed, xii) each potentially dependent claim or concept as a dependency on each and every one of the independent claims or concepts presented, and xiii) all inventions described herein. In addition and as to computer aspects and each aspect amenable to programming or other electronic automation, the applicant(s) should be understood to have support to claim and make a statement of invention to at least: xiv) processes performed with the aid of or on a computer as described throughout the above discussion, xv) a programmable apparatus as described throughout the above discussion, xvi) a computer readable memory encoded with data to direct a computer comprising means or elements which function as described throughout the above discussion, xvii) a computer configured as herein disclosed and described, xviii) individual or combined subroutines and programs as herein disclosed and described, xix) the related methods disclosed and described, xx) similar, equivalent, and even implicit variations of each of these systems and methods, xxi) those alternative designs which accomplish each of the functions shown as are disclosed and described, xxii) those alternative designs and methods which accomplish each of the functions shown as are implicit to accomplish that which is disclosed and described, xxiii) each feature, component, and step shown as separate and independent inventions, and xxiv) the various combinations and permutations of each of the above.
It should be understood that if or when broader claims are presented, such may require that any relevant prior art that may have been considered at any prior time may need to be re-visited since it is possible that to the extent any amendments, claim language, or arguments presented in this or any subsequent application are considered as made to avoid such prior art, such reasons may be eliminated by later presented claims or the like. In drafting any claims at any time whether in this application or in any subsequent application, it should also be understood that the applicant has intended to capture as full and broad a scope of coverage as legally available. To the extent that insubstantial substitutes are made, to the extent that the applicant did not in fact draft any claim so as to literally encompass any particular embodiment, and to the extent otherwise applicable, the applicant should not be understood to have in any way intended to or actually relinquished such coverage as the applicant simply may not have been able to anticipate all eventualities; one skilled in the art, should not be reasonably expected to have drafted a claim that would have literally encompassed such alternative embodiments.
Further, if or when used, the use of the transitional phrase “comprising” is used to maintain the “open-end” claims herein, according to traditional claim interpretation. Thus, unless the context requires otherwise, it should be understood that the term “comprise” or variations such as “comprises” or “comprising”, are intended to imply the inclusion of a stated element or step or group of elements or steps but not the exclusion of any other element or step or group of elements or steps. Such terms should be interpreted in their most expansive form so as to afford the applicant the broadest coverage legally permissible. As one clarifying example, if a claim were dependent “on claim 20 or any other claim” or the like, it could be re-drafted as dependent on claim 1, claim 15, or even claim 715 (if such were to exist) if desired and still fall with the disclosure. It should be understood that this phrase also provides support for any combination of elements in the claims and even incorporates any desired proper antecedent basis for certain claim combinations such as with combinations of method, apparatus, process, and the like claims.

## Claims

1. A solar power system comprising:
a DC-DC converter connected within and as part of a solar power string;
a first unconverted string portion and a second unconverted string portion of said string, said portions separated by, and in serial connection with, said DC-DC converter;
a first pair of electrical connections connecting said DC-DC converter across said first unconverted string portion;
a second pair of electrical connections connecting said DC-DC converter across said second unconverted string portion;
a positive rail electrically connected with one solar panel of said first unconverted string portion and with said DC-DC converter, and
A negative rail electrically connected with one solar panel of said second unconverted string portion and with said DC-DC converter.

2. A solar power system as described in claim 1 wherein said DC-DC converter is operable at a sweet spot during loaded circuit condition of said system.

3. A solar power system as described in claim 1 wherein said DC-DC converter connected within said solar power string is connected with said first unconverted string portion through a first string portion conductor and connected with said second unconverted string portion through a second string portion conductor, wherein said first string portion conductor has a first string portion loaded circuit voltage value relative to said negative rail, said second string portion conductor has a second string portion loaded circuit voltage value relative to said negative rail, and a sum of said first string portion loaded circuit voltage value and said second string portion loaded circuit voltage value is substantially equal to a loaded circuit voltage value of said positive rail relative to said negative rail.

4. A solar power system as described in claim 3 wherein said string portion loaded circuit voltage values are achieved by bucking by said DC-DC converter.

5. A solar power system as described in claim 1 wherein said solar power string is a first solar power string and further comprising a second solar power string connected in parallel with said first solar power string.

6. A solar power system as described in claim 5 wherein said DC-DC converter is a first DC-DC converter, and further comprising a second DC-DC converter connected within said second solar power string.

7. A solar power system as described in claim 1 further comprising a diode established between said DC-DC converter and said positive rail.

8. A solar power system as described in claim 1 wherein said positive rail is capable of carrying an open circuit voltage relative to said negative rail and a loaded circuit voltage relative to said negative rail that are substantially equal.

9. A solar power system as described in claim 1 wherein said positive rail is capable of carrying a loaded circuit voltage relative to said negative rail that is conservatively close to a regulatory maximum voltage limit.

10. A solar power system as described in claim 1 wherein said DC-DC converter comprises two sub-converters.

11. A solar power system as described in claim 10 wherein at least one of said two sub-converters comprises a dual mode converter.

12. A solar power system as described in claim 10 wherein at least one of said two sub-converters comprises a buck converter.

13. A solar power system as described in claim 10 wherein said two sub-converters share a component selected from the group consisting of inductor and switch.

14. A solar power system as described in claim 1 said negative rail is a lower rail.

15. A solar power system as described in claim 1 said positive rail is an upper rail.

16. A solar power system as described in claim 1 wherein said solar power system is unipolar.

17. A solar power system as described in claim 1 wherein said solar power system is bipolar.

18. A solar power system as described in claim 1 further comprising a DC-AC power inverter that acts on power conducted by said negative and positive rails.

19. A solar power system as described in claim 1 wherein said first unconverted string portion comprises an element selected from the group consisting of: only one solar panel and a plurality of solar panels.

20. A solar power system as described in claim 1 wherein said first DC-DC converter comprises at least two inputs.

21. A solar power system comprising:
a string of serially connected electrical components that include solar panels;
a DC-DC converter intermediately electrically connected within said string as a part of said string so as to define a first, solar panel string portion and a second, solar panel string portion;
a positive rail connected with said first, solar panel string portion, and with said DC-DC converter; and
a negative rail connected with said second, solar panel string portion, and connected with said DC-DC converter.

22. A solar power system as described in claim 21 wherein said DC-DC converter is operable at a sweet spot during loaded circuit condition of said system.

23. A solar power system as described in claim 21 wherein said DC-DC converter electrically connected within said string is electrically connected with said first, solar power string portion through a first string portion conductor and electrically connected with said second, solar power string portion through a second string portion conductor, wherein said first string portion conductor has a first string portion loaded circuit voltage value relative to said negative rail, said second string portion conductor has a second string portion loaded circuit voltage value relative to said negative rail, and a sum of said first string portion loaded circuit voltage value and said second string portion loaded circuit voltage value is substantially equal to a loaded circuit voltage value of said positive rail relative to said negative rail.

24. A solar power system as described in claim 23 wherein said string portion open circuit voltage values are achieved by bucking by said DC-DC converter.

25. A solar power system as described in claim 21 wherein said string is a first string, and further comprising at least one additional string that includes additional solar panels, each of said at least one additional string electrically connected in parallel with said first string.

26. A solar power system as described in claim 25 further comprising at least one additional DC-DC converter, each of which is electrically connected within one of said at least one additional string.

27. A solar power system as described in claim 21 further comprising a diode established between said DC-DC converter and said positive rail.

28. A solar power system as described in claim 21 wherein said positive rail is capable of carrying an open circuit voltage relative to said negative rail and a loaded circuit voltage relative to said negative rail that are substantially equal.

29. A solar power system as described in claim 21 wherein said positive rail is capable of carrying a loaded circuit voltage relative to said negative rail that is conservatively close to a regulatory voltage limit.

30. A solar power system as described in claim 21 wherein said DC-DC converter comprises two sub-converters.

31. A solar power system as described in claim 30 wherein at least one of said two sub-converters comprises a dual mode converter.

32. A solar power system as described in claim 30 wherein at least one of said two sub-converters comprises a buck converter.

33. A solar power system as described in claim 30 wherein said two sub-converters share a component selected from the group consisting of inductor and switch.

34. A solar power system as described in claim 21 wherein said system is unipolar.

35. A solar power system as described in claim 21 wherein said system is bipolar.

36. A solar power system as described in claim 21 wherein said positive rail is an upper rail.

37. A solar power system as described in claim 21 wherein said negative rail is a lower rail.

38. A solar power system as described in claim 21 wherein said first string portion comprises an element selected from the group consisting of: only one solar panel and a plurality of solar panels.

39. A solar power system as described in claim 21 wherein said DC-DC converter comprises at least two inputs.

40. A solar power system as described in claim 21 wherein said first string portion is a first unconverted string portion and said second string portion is a second unconverted string portion.

41. A solar power system comprising:
a first solar power generator in serial connection with a DC-DC converter and with a second solar power generator, said DC-DC converter connected between said two solar power generators, and said two solar power generators each having a respective lower voltage end and higher voltage end;
a positive rail electrically connected with said higher voltage end of said first solar power generator and with said DC-DC converter; and
a negative rail electrically connected with said lower voltage end of said second solar power generator and with said DC-DC converter.

42. A solar power system as described in claim 41 wherein said first solar power generator and said second solar power generator each comprise at least one solar panel.

43. A solar power system as described in claim 41 wherein said first solar power generator comprises a first set of series connected solar panels and said second solar power generator comprises a second set of series connected solar panels.

44. A solar power system as described in claim 41 wherein said first solar power generator and said second solar power generator are each unconverted solar power sources.

45. A solar power system as described in claim 41 wherein said DC-DC converter comprises a first capacitor that is connected across said first solar power generator and a second capacitor that is connected across said second solar power generator.

46. A solar power system as described in claim 45 wherein said DC-DC converter further comprises a first pair of two serially connected switch elements connected in parallel with said first capacitor and a second pair of serially connected switch elements connected in parallel with said second capacitor.

47. A solar power system as described in claim 46 wherein said first pair of two serially connected switch elements comprises a first switch and a first diode and said second pair of serially connected switch elements comprises a second switch and a second diode.

48. A solar power system as described in claim 45 wherein said wherein said DC-DC converter further comprises a first pair of two serially connected switch elements that are connected at a connection point, a second pair of serially connected switch elements that are connected at a different connection point, and a single inductor connected between said two connection points.

49. A solar power system as described in claim 45 wherein said DC-DC converter further comprises a first pair of serially connected components connected in parallel with said first capacitor, said first pair of serially connected components comprising at least one switch, said DC-DC converter further comprising a second pair of serially connected components connected in parallel with said second capacitor, said second pair of serially connected components comprising at least one other switch.

50. A solar power system as described in claim 41, wherein said DC-DC converter comprises an inductor connected so as to substantially bisect said converter.

51. A solar power system as described in claim 41 wherein said DC-DC converter comprises two subconverters that share an inductor.

52. A solar power system as described in claim 41 wherein said DC-DC converter comprises two inductors.

53. A solar power system as described in claim 52 wherein said first solar power generator is serially connected with a first of said two inductors, which is serially connected with a switch, which is serially connected with a second of said two inductors, which is serially connected with said second solar power generator.

54. A solar power system as described in claim 52 wherein one of said two inductors is serially connected with said first solar power generator and the other of said two inductors is serially connected with said second solar power generator.

55. A solar power system as described in claim 52 wherein said DC-DC converter further comprises at least one switch between said two inductors.

56. A solar power system as described in claim 55 wherein a connection point for said switch and first inductor is connected to one of said rails through a first diode, and a connection point for said switch and said other inductor is connected to the other of said rails through a second diode.

57. A solar power system as described in claim 55 wherein a connection point for said switch and first inductor is connected with said rails through a first pair of diodes, and a connection point for said switch and said other inductor is connected with said rails through a second pair of diodes.

58. A solar power system as described in claim 41 further comprising a DC-AC power inverter that acts on DC power conducted by said positive and negative rails.