Matching device and method for multi-module solar tandem power generation system

Abstract

The present invention relates to an apparatus for maximizing the power of a multi-module solar string power generation system, comprising an injection circuit (IC) connected to a DC bus and to a string of solar panels, wherein the IC is also connected to at least one separate solar panel of the string. The IC regulates the power generation of the connected string and utilizes excess power to a solar inverter. The IC includes: (i) a first MPPT mechanism for finding the MPP of the string; (ii) a second MPPT mechanism for finding the MPP of the separated panel; (iii) a first DC / DC converter for converting some of the power from the separated panel to regulate the power of the connected string; and (iv) a second DC / DC converter for converting excess power from the separated panel and utilizing the excess power to a solar inverter using the DC bus.

Description

Technical Field

[0001] The present invention relates to a method and apparatus for maximizing the power generated from a multi-module solar string power generation system. Background Art

[0002] Until now, photovoltaic solar power systems, or solar farms, have typically consisted of solar panels containing photovoltaic "cells." Photovoltaic cells are semiconductor devices that convert light into energy. When light shines on the panels, a voltage develops across them, and when connected to a load, a current flows. The voltage and current vary depending on several factors, including the physical size of the panels, their efficiency, the amount of light shining on them, their temperature, and other factors.

[0003] Typically, many solar panels are connected in series, called a "string," to create increased output voltage. Generally speaking, the higher the voltage—the less energy is lost, and therefore the higher the system's efficiency. Therefore, it's desirable to connect as many panels in series as possible in a string. However, due to the dangerous nature of very high voltages, the maximum allowable output voltage of a single string is often limited by standards and national regulations. Therefore, to generate enormous power with minimal losses, photovoltaic power generation systems typically include many "high-voltage" strings connected in parallel. These parallel-connected strings are called an "array."

[0004] Since solar cells generate DC power, whereas the grid is typically AC power, an "inverter" must be connected. An inverter can be connected to an array of many parallel-connected strings to convert their DC power into AC power for feeding the grid or local consumers.

[0005] Many solar inverters include Maximum Power Point Tracking (MPPT) circuitry to maximize the power drawn from the strings. These MPPT circuits, known in the art, adjust the voltage (and current) at which the array operates, measure its output power, and seek the voltage and current values ​​that maximize power output. Therefore, MPPT for the array is typically performed by the inverter.

[0006] An array generates its maximum power when all strings comprising the array are operated at the same maximum power point. However, aging or other defects can cause some cells in the string to fail. Because a damaged panel can have a severe impact on the efficiency of the entire array, it is necessary to replace the damaged panel. However, finding a solar panel with the same initial performance as the damaged panel is difficult and sometimes impossible, especially due to the fact that newer panels are more efficient. In recent years, the efficiency of solar panels has increased by an average of 3% per year.

[0007] When a small portion of the panels in a series string are replaced, the newer panels typically generate more power than the other, older panels. However, the current of each string is determined by the weakest panel in the string, and therefore the robust voltage of the new panels can disturb the balance of the other panels in the string. In addition, the overflow power from the newer panels can cause heating of the rest of the panels, which can be reflected in a drop in power generation and can also accelerate the degradation of these solar panels. In this situation, the performance of the array is lost in three ways, the first is simply that the excess power from the new panels is not utilized, the second is that the excess power is typically converted into heat that can damage the attached panels over time, and the third is that the excess power can disturb the balance of the array.

[0008] It is therefore desirable to introduce cost-effective means to utilise the full power generation from the newer panels of an array by ensuring that excess power is bypassed by the weaker panels and fed directly into the inverter.

[0009] One approach to solving this problem is to equip each panel in the string with an optimizer that adjusts the panel voltage as needed. This approach is expensive because an optimizer is required for each panel in the array.

[0010] US Pat. No. 7,605,498 discloses a high-efficiency photovoltaic DC-DC converter for converting solar power from a high-voltage, highly variable photovoltaic power source. This describes a voltage conversion circuit having a photovoltaic power interruption switch element pair and a photovoltaic power shunt switch element pair to first step up the voltage and then step down the voltage as part of the desired photovoltaic DC-DC power conversion. Thus, the photovoltaic DC-DC converter is able to achieve higher conversion efficiency than conventional methods by utilizing essentially power-homogeneous photovoltaic DC-DC power conversion capabilities. However, this approach has the disadvantage of requiring a specific implementation for each panel.

[0011] It would therefore be desirable to provide a system that does not have these drawbacks. Summary of the Invention

[0012] An object of the present invention is to provide a method for maximizing the power from a multi-module solar string power generation system comprising panels having different power generation capacities.

[0013] Another object of the present invention is to provide a device for utilizing excess voltage and current from newer solar panels connected in a string with older panels, while maximizing the power from the entire string without reducing the power generation of weaker panels and without reducing their useful life.

[0014] Yet another object of the present invention is to provide a method for maximizing power from a string comprising solar panels having different power capacities while accommodating inflexible inverters such as: a central inverter, a single MPPT inverter, or a multi-string multi-MPPT inverter.

[0015] Yet another object of the present invention is to provide a method for using different solar panels together in the same string utilizing different technologies such as: single film, multi-film or thin film that are energy efficient and cost effective.

[0016] Other objects and advantages of the invention will become apparent as the description proceeds.

[0017] The present invention relates to an apparatus for maximizing the power of a multi-module solar string power generation system, comprising: (a) at least one string of solar panels, wherein at least one solar panel of the string is separated from the other panels in the string; (b) a DC bus, the DC bus being connected to the string; (c) a solar inverter, the solar inverter being connected at its input to the DC bus for converting solar DC power from the at least one string into AC power; and (d) an injection circuit (IC), the IC being connected to the DC bus and to the string, wherein the IC is also connected to the at least one separated solar panel, and wherein the IC regulates the power generation of the connected string and and uses a DC bus to utilize excess power from at least one separate panel to a solar inverter, including: (i) a first MPPT mechanism for finding the MPP of at least a portion of the string; (ii) a second MPPT mechanism for finding the MPP of at least one separate panel connected to the IC; (iii) a first DC / DC converter for regulating the power of the connected string by converting some of the power from the at least one separate panel to regulate the power of the connected string; and (iv) a second DC / DC converter for converting excess power from the at least one separate panel and using the DC bus to utilize the excess power to the solar inverter.

[0018] In one embodiment, a string includes panels having different power capabilities, wherein a portion of the panels have a higher power capability than other panels in the string.

[0019] Preferably, the IC includes a third MPPT mechanism for finding the MPP of the higher power panel in the string.

[0020] Preferably, the IC comprises a third DC / DC converter for harnessing excess power from panels with higher power capabilities to the DC bus.

[0021] The present invention also relates to a method for maximizing the power of a multi-module solar string power generation system, comprising: (a) providing at least one string of solar panels; (b) separating at least one solar panel of the string from the other panels in the string; (c) providing a DC bus, the DC bus being connected to the string; (d) providing a solar inverter, the solar inverter being connected at its input to the DC bus for converting solar DC power from the at least one string to AC power; and (e) providing an IC, the IC being connected to the DC bus and to the string, wherein the IC is also connected to at least one separated solar panel; (f) regulating the power of the string by converting some of the power from the at least one separated panel; and (g) using the DC bus to utilize excess power from the at least one separated panel to the solar inverter. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The drawings, and specific references thereto in detail, are used herein to illustratively describe some of the embodiments of the invention by way of example only.

[0023] In the attached figure:

[0024] - Figure 1 FIG. 1 is a graph showing the electrical power generation performance of a solar panel string based on an IV curve according to an embodiment.

[0025] - Figure 2 is a schematic diagram depicting a string of solar panels connected in an array with an injection circuit (IC) according to an example.

[0026] - Figure 3 is a schematic diagram depicting some of the internal parts of an IC according to an embodiment.

[0027] - Figure 4 is a schematic diagram depicting a string of solar panels connected in an array with an injection circuit according to an example.

[0028] - Figure 5 is a schematic diagram of some of the internal parts of an example IC, according to an embodiment.

[0029] - Figure 6 is a schematic diagram depicting some of the internal parts of an IC according to another embodiment.

[0030] - Figure 7 is a schematic diagram of some of the internal parts of an example IC, according to an embodiment.

[0031] - Figure 8 is a schematic diagram of some of the internal parts of an example IC according to yet another embodiment.

[0032] - Figure 9 is a schematic diagram depicting some of the internal parts of an IC according to yet another embodiment.

[0033] - Figure 10 is a schematic diagram illustrating some of the internal parts of another exemplary IC according to an embodiment. DETAILED DESCRIPTION

[0034] A photovoltaic solar power generation system generates its maximum power when all the strings comprising the array are operated at the same maximum power point (MPP). However, when a small portion of the panels in a string are replaced with newer panels, the newer panels typically generate more power, i.e., more voltage and current, than the other older panels. However, the current of each string is determined by the weakest panel in the string, and therefore the robust power of the newer panels may not be maximally utilized and lost. In addition, the overflow of excess power from the newer panels may interfere with the power balance of the other strings in the array, not to mention the heat from the excess power, which will reduce its power generation and can accelerate the degradation of the connected panels. The term "multi-module solar string" is intended to include hereinafter any string of solar panels having panels with different power generation capacities, such as: strings with newer and older panels or strings with panels that may be randomly or regularly shaded, etc.

[0035] Figure 1 The diagram shows four graphs showing the electrical power generation performance of a solar panel based on its IV curve, i.e., the current and voltage characteristics, according to an embodiment. When many solar panels are connected in series, i.e., in a string, their combined energy output is usually plotted as a curve. Figure 10 When operating in a voltage mode circuit, the current drawn from the string is fairly constant as the voltage increases until a certain point, after which the current rapidly decreases as the voltage increases, as shown by curve 30. Since the power of the string is equal to the current times the voltage (P=I*V), the maximum power point (MPP) of the string is located at MPP 20 on curve 30. Figure 10 As shown, the maximum area of ​​the rectangle bounded by curve 30 is defined by the (X, Y) grid of points 20. When some panels in a string need to be replaced with newer panels, the current and voltage characteristics of the newer panels may differ from those of the older panels. For example, the area representing the power generated by the older panels intended for replacement is drawn in gray and symbolized by S(k). The area representing the power generated by the older panels not intended for replacement is symbolized by S(nk).

[0036] exist Figure 1, graph 11 visually depicts the power generation of a string once some of the older panels have been replaced with newer panels. For example, the area representing the power generated by the newer panels is drawn in gray and symbolized by S(k'), while the area representing the power already generated by the older panels is marked with slashes and symbolized by S(k). As shown in graph 11, the voltage and current of the newer panels are both higher than those of the older panels. Left unchecked, the maximum power point tracking (MPPT) of the inverter will attempt to increase the voltage of the string in order to maximize the power from the string as shown by curve 32 in graph 12. However, if the inverter is connected to many strings, the voltage change can change the power levels of other strings, which will ultimately drag the inverter's MPPT to some average voltage point between the strings that is not the maximum power point of any one of the strings, effectively unbalancing the power generation of the entire array and wasting power.

[0037] In one embodiment, a solution is proposed to utilize excess voltage and current from newer panels and feed them into the inverter. Furthermore, this solution maintains the string's initial MPPT point and maintains a balanced average MPPT for the array. For example, the area representing excess power generated by newer panels is outlined in gray in graph 13. Once the excess voltage and current from the newer panels are properly utilized from outside the string and fed into the inverter, as depicted in graph 13, the string's MPP 23 can be equal to the desired initial balanced MPP 20, which generally corresponds to the MPPs of the other strings.

[0038] Figure 2 is a schematic diagram depicting a matcher for maximizing the power of a multi-module solar string with an injection circuit according to an example. Figure 2An inverter is shown in FIG, however, the proposed system also includes a solar inverter that is connected at its input to the DC bus 500-501 for converting the solar DC power from the string into AC power. The purpose of the injection circuit (IC) is to regulate the power generation of the string to which it is connected and to utilize excess power from the newer panels to the inverter without disrupting the initial balanced MPP of the string. In this example, the array can have many strings, such as string 200, which is a typical string of older solar panels connected in series between the bus lines 500-501. In this example, substring 400 is part of the old string, where substring 400 includes many older panels in working order. Some of the older panels that used to be connected in series to substring 400 have been replaced with newer panels, such as newer panel 401 or newer panel 405. For simplicity, the newer panels have been marked with black triangles in the accompanying drawings. In this example, two substrings 300 and 400 and newer panels 405 together form a multi-module solar string 210. First, the newer panels can be divided according to the following equation:

[0039]

[0040] in:

[0041] Vmp_new(K′) is the total voltage of the newer panel

[0042] Vmp_old(K) is the total voltage of the replaced panel

[0043] Vmp_new is the voltage of a single newer panel

[0044] is the ceiling, that is, the smallest natural number greater than the sum in the equation.

[0045] Thus, B represents the number of newer panels that are separated from the rest of the newer panels in the train. In this example, Figure 2 In the example, B is equal to 1, and therefore, only one panel, panel 405, is separated from the rest of the newer panels in the string. Therefore, at this stage, after separation, the voltage generated by the unseparated newer panel is less than the initial voltage generated by the replaced older panel. In one embodiment, these unseparated panels, i.e., the panels of substring 300, can be connected in series with IC 100 to the older panels of substring 400, as shown in FIG. Figure 2In this example, the two substrings 300 and 400 together produce a voltage at their MPPT that is less than the voltage of other strings in the array, such as string 200 at its initial MPP. At this stage, IC 100 can add the voltage taken from the detached panel 405 to the string to match the voltage of the entire string 210 with the voltage of the other strings at their MPP, such as string 200, in order to balance the array.

[0046] Return to Figure 1 , the power from the unseparated panel is marked by S(k'-b) in graph 12, while the power from the separated panel is marked by S(b). As shown in graph 12, the MPP of the two strings, namely the old panel string and the unseparated newer string, namely S(nk)+S(k'-b), is at a point 22 that is slightly lower in voltage than the initial point 20. In this example, the required power to match the power requirements of the other strings is marked in gray. At this stage, the IC can add power to the strings to achieve the required MPP 23, as depicted in graph 13, and which corresponds to the curve Figure 10 In one embodiment, the IC can add a power consisting of a current equal to the current of the substring 400 and a voltage equal to the voltage required to achieve the desired MPP 23, so that the IC can adjust the power generation of the connected string 210 to match the power of the other strings in the array.

[0047] In one embodiment, the IC may have a first MPPT mechanism for finding the MPP of the substring 400, as described in relation to Figure 2 As described. The IC can then change its internal voltage to find the correct voltage needed to add power to the connected string 400 in order to adjust the power generation of the connected string 400 to maximize and match the voltage of the string 200. For example, since the voltage between the DC bus lines 500-501 is assumed to be stable, the IC 100 can increase its internal voltage and see whether the power of the substring 400 increases or decreases, or the IC 100 can decrease its internal voltage and measure the power of the substring 400. Thus, the IC 100 can fine-tune its internal voltage to maximize the power from the substring 400.

[0048] Figure 3 is a schematic diagram depicting some of the internal parts of an IC according to an embodiment. In this embodiment, IC 100 can be connected to DC busses 500-501 and to string 210, which includes substrings 300 and 400 and panel 405. IC 100 can also be connected at its input to a separate panel 405, or to more than one separate panel, as described above with respect to FIG. Figure 2As described. DC / DC 101 may include a first MPPT mechanism for finding the MPP of substring 400. DC / DC 102 may also include a second MPPT mechanism for finding the MPP of separated panel 405 and its optimized current and voltage. In some cases, DC / DC 103 may also include a third MPPT mechanism for finding the MPP of substring 300. As mentioned above, the current of the entire string 210 is generally determined by string 400, its weakest link. To adjust the voltage of string 210, before replacing the panel, IC 100 is required to supply a voltage that is the difference between the combined voltage of substrings 300 and 400 and the initial voltage of the string. Therefore, when adjusted, the voltage of string 210 should correspond to the MPP voltage of the other corresponding strings in the array. IC 100 may also have a first DC / DC converter 101 for converting a portion of the power from panel 405 into the required voltage and current of string 210.

[0049] In one embodiment, Figure 3 IC 100 is capable of increasing / decreasing its output voltage while measuring the power from substring 400 until substring 400 reaches its MPPT point. Thus, first DC / DC converter 101 can be used to regulate the power of connected string 210 by converting some of the power from separated panel 405 into current and voltage for string 210. IC 100 may also have a second DC / DC converter 102 connected at its input to a separated panel, such as panel 405, and at its output to bus 500-501 via DC / DC 103. DC / DC converter 102 can be used to convert excess power from separated panel 405, i.e., power not used by converter 101 to regulate the power of string 210, and to utilize this excess power on connected DC bus 500-501. Thus, IC 100 is able to regulate the power generation of the connected strings 210 and utilize the DC bus 500-501 to harness excess power from the separated panels 405 to a solar inverter (not shown).

[0050] In one embodiment, IC 100 may have a third DC / DC converter 103 connected to substring 300 at its input and to bus 500-501 at its output. As described above, a portion of the power of string 300 flows through string 210, primarily a current and a voltage corresponding to the current of string 400. However, excess power from substring 300 may be consumed by third DC / DC converter 103 and utilized to a solar inverter (not shown) using DC bus 500-501. Thus, DC / DC converter 103 may be used to convert a portion of the power from substring 300 and excess power from substring 405 of DC / DC 102, and utilize this excess power to bus 500-501, resulting in excess power to a solar inverter (not shown).

[0051] Figure 4 is a schematic diagram depicting a string of solar panels connected in an array with injection circuits according to an example. In this example, ICs such as ICs 100 and 130 can be connected in series to the panel, or the ICs can be connected in a cascade manner such as depicted. In other words, the excess power utilized by the ICs can be connected directly to bus lines 500-501 or can be connected to each other in a cascade manner before being connected to bus lines 500-501. Cascading can be accomplished in more than one step, with more than two ICs cascaded one after the other. In one embodiment, the ICs can be connected between an older string and a newer string, such as depicted for IC 140. In other embodiments, the ICs can be connected in series to the older string and the newer string and to the positive bus line 500, such as depicted for IC 130.

[0052] Other embodiments are possible. In one embodiment, the separated panels are directly connected to the IC, where the IC uses some of the power from the separated panels to regulate the power of the string. In some cases, this system can be used to cope with some of the panels being shaded.

[0053] Figure 5 Description of the embodiment Figure 3 Schematic diagram of some of the internal parts of IC 100 illustrating possible solutions. As is known in the art, there are many electrical implementations of IC 100, however, for the sake of enabling, an IC using, for example, step-up and step-down modules is depicted as an embodiment of IC 100.

[0054] Figure 6is a schematic diagram depicting some of the internal parts of an IC according to another embodiment. In this embodiment, IC 100 can be connected to DC busses 500-501 and to string 210, which includes substrings 300 and 400 and panel 405. IC 100 can also be connected at its input to a separate panel 405, or to more than one separate panel, as described above with respect to FIG. Figure 3 As described. IC 100 may include a first MPPT mechanism for finding the MPP of substring 400. IC 100 may also include a second MPPT mechanism for finding the MPP of separated panel 405 and its optimized current and voltage. In some cases, IC 100 may also include a third MPPT mechanism for finding the MPP of substring 300. In this embodiment, Figure 6 IC 100 can regulate the voltage on capacitor 610 by draining power from the disconnected panel 405 onto capacitor 610. IC 100 can increase or decrease the voltage on capacitor 610 while measuring the power from string 400 until string 400 reaches its MPPT point. Thus, first DC / DC converter 111 can be used to regulate the power of connected string 210 by converting some of the power from disconnected panel 405 into power on capacitor 610. IC 100 can also have a second DC / DC converter 112, which is connected to a disconnected panel, such as panel 405, at its input and to bus 500-501 at its output. DC / DC converter 112 can be used to convert excess power from disconnected panel 405, i.e., the power remaining after regulating the power of string 210, and apply this excess power to connected DC bus 500-501.

[0055] In one embodiment, Figure 6 IC 100 may have a third DC / DC converter 113 connected at its input to substring 300 and at its output to bus 500-501. As described above, a portion of the power of string 300 flows through string 210, primarily a current and a voltage corresponding to the current of string 400, however, excess power from substring 300 may be drained by third DC / DC converter 113 and utilized to a solar inverter (not shown) using DC bus 500-501.

[0056] Figure 7 Description of the embodiment Figure 6 Schematic diagram of some of the internal parts of IC 100 illustrating possible solutions. As is known in the art, there may be many electrical implementations for IC 100, however, for the sake of enabling, the IC is depicted as an embodiment of IC 100.

[0057] Figure 8 Description of the embodiment Figure 6 Schematic diagram of some of the internal parts of IC 100 illustrating possible solutions. As is known in the art, there may be many electrical implementations for IC 100, however, for the sake of enabling, the IC is depicted as an embodiment of IC 100.

[0058] Figure 9 1 is a schematic diagram depicting some of the internal parts of an IC according to yet another embodiment. In this embodiment, IC 120 is similar to that of FIG. Figure 6 Unlike the IC 100 described above, in this embodiment, IC 120 may include another DC / DC converter 114. Since DC / DC converters 112-113 may have to cope with very high voltage variations at their inputs and high voltage variations at their outputs, another DC / DC converter 114 may be added. Thus, DC / DC converters 112-113 may be designed to cope with high variations at their inputs, while their outputs may be designed to be set and known. The set and known output voltage of DC / DC converters 112-113 is also the input voltage of inverter 114. Therefore, inverter 114 only needs to cope with a set and known output variation at its input. Compared to IC 100, this embodiment can simplify the design implementation and improve the overall efficiency of IC 120.

[0059] Figure 10 Description of the embodiment Figure 9 Schematic diagram of some of the internal parts of IC 120 illustrating possible solutions. As is known in the art, there can be many electrical implementations for IC 120, however, for the sake of enabling, the IC is depicted as an embodiment of IC 120.

[0060] In some cases, the proposed IC can be used for solar farms with panels that can be regularly shaded. In some cases, such as when the solar farm is installed on a roof with a chimney, shading can be frequent and known. Panels that may be shaded by the chimney can be classified as "older" panels, while panels that are not shaded by the chimney can be classified as "newer" panels. Therefore, according to the above, ICs can be connected to these panels on the roof. In this case, at least one IC should be connected to each string. When a shadow hits a panel, the IC is able to utilize the excess power from the unshaded panels, thereby improving the overall efficiency of the solar farm. In some embodiments, if there are other shadow obstacles, many ICs can be connected and cascaded.

[0061] In some cases, the proposed IC can be used in a solar farm with panels that may be randomly shaded. In some cases, the shade may be random, for example, clouds passing over the solar farm. The IC can be connected to strings of the solar farm, where each string is connected to the IC. As described above, for each string, at least one panel is separated and its output is connected to the input of the IC, where the rest of the panels can be connected in parallel to the IC, as described with respect to FIG. Figure 3 In this case, the IC can be designed to frequently utilize some of the power of the detached panels to the inverter. Thus, when a shadow strikes one or more panels, the connected IC can compensate for the loss of voltage from the string of shaded panels by increasing the voltage of the string rather than utilizing excess power to the inverter.

[0062] Although the above description discloses many embodiments and specifications of the invention, these are described as illustrations and should not be construed as limiting the scope of the invention. The described invention can be put into practice with many modifications within the scope of the appended claims.

Claims

1. A device for maximizing the power of a multi-module solar tandem power generation system, comprising: at least one multi-module solar array comprising solar panels having different power generation capacities; a DC bus connected to the strings; a solar inverter connected to the DC bus for converting solar DC power from the at least one string into AC power; as well as an injection circuit (IC) connected to the DC bus and to the string, wherein the IC is also connected to at least one solar panel of the string, and wherein the IC regulates power generation of the connected string and utilizes the DC bus to utilize excess power from the at least one solar panel remaining after regulating the power of the string to the solar inverter, comprising: a first maximum power point tracking (MPPT) mechanism for finding a maximum power point (MPP) of at least a portion of the string; a second MPPT mechanism for finding the MPP of the at least one solar panel connected to the IC; a first DC / DC converter for regulating power of the connected string by converting some of the power from the at least one solar panel into current and voltage; and A second DC / DC converter is configured to convert the excess power remaining after regulating the power generation of the string from the at least one solar panel and utilize the excess power to the solar inverter using the DC bus.

2. The device according to claim 1, wherein A portion of the panels in the string has a higher power capability than other panels in the string.

3. The device according to claim 2, wherein The IC includes a third MPPT mechanism for finding the MPP of the higher power panel of the string.

4. The device according to claim 2, wherein The IC includes a third DC / DC converter for utilizing overflow of excess power from newer panels with higher power capabilities to the DC bus.

5. A method for maximizing the power of a multi-module solar string power generation system, comprising: at least one multi-module solar array comprising solar panels having different power generation capacities; providing a DC bus connected to the strings; providing a solar inverter connected to the DC bus for converting solar DC power from the at least one string into AC power; as well as providing an injection circuit (IC), the IC being connected to the DC bus and to the string, wherein the IC is also connected to at least one solar panel; regulating power in the string by converting some of the power from the at least one solar panel into current and voltage; and The DC bus is used to utilize excess power from the at least one solar panel remaining after regulating the power generation of the string to the solar inverter.

6. The method according to claim 5, wherein: A portion of the panels in the string has a higher power capability than other panels in the string.

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