I] This application claims priority to and the benefit of U.S. application

1 /837 J I S, which was filed August 27, 201 5 and is entitled POWER PROCESSING. The 18 application is incorporated herein by reference, in Its entirety, into this application. Y MMI T LICENSE RIGHTS

j ^' 0002] This invention was made with government support under DE-AR000021? awarded by The U.S. Department of Energy, The government has certain rights in the invention. ACKGRO!/ND

[0003} Photovoltaic (PV) cells, commonly known as solar ceils, are devices for conversion of solar .radiation into electrical energy. Generally, solar radiation impinging on the surface of, and entering into, the substrate of a solar cell creates electron and hole pairs in the bulk of the substrate. The electron and hole pairs migrate to p-doped and. n-doped regions in the substrate, thereb creating a voltage differential between the doped regions. The doped regions are connected to the conductive regions on the solar cell to direct an electrical current from the cell to an external circuit. When PV cells are combined in an array such, as a PV module, the electrical energy collected from ail of the PV cells can be combined in series and parallel arrangements to provide power with a certain voltage and current.

[0004] Module-level power electronics converters, i.e., MLP.E converters, such as a dc-de optimizer, can conduct maximum power point tracking (MP FT) of individual PV modules, or possibly substrings of PV cells. These MLPEs may include dc-dc optimizers that process 100% of the power being generated and housekeeping circuits that provide power to various circuits. Differential power processing (DPP) may be used in conjunctio with maximum, power point tracking (MPPT) to process power mismatch among PV cells. This power match feature can serve to correct for mismatches in maximu power point (MPP) current that would otherwise occur in series-connected PV ceils.

I (0005 j Figure I illustrates an example block diagram of FY power module having a

PV-to~bus module converter, according to some embodiments,

(000ø ^' ] Figure 2 illustrates a circuit diagram showing a PV-io-bus converter topology, according to some embodiments.

(0007| Figure 3 illustrates a circuit, diagram showing a PV-to-bus converter topology, according to some embodiments.

| ^' 0008] Figures 4 A and 4B illustrate a circuit diagram showing a PV-to-bus converter topology, according to some embodiments.

|00 9] Figure 5A illustrates a circuit diagram showing a PV-to-bus converter topology, according to some embodiments.

(0010J Figure SB illustrates a circuit diagram showing a PV-to-bos converter topology,

(001 If Figure 6 illustrates a circuit diagram showing a PV-to-bus converter topology, according to some embodiments.

(0012} Figure 7 illustrates a circuit diagram showing a P V-to-bus converter topology, according to some embodiments.

(0013| Figure 8 illustrates a flowchart showing a method for convening differential power within a plurality of PV cell substrings, according to some embodiments,

(O0 ^' i | Figure 9 illustrates a flowchart showing a method for supplying power to a housekeeping power supply within, a convener topology, according to some embodiments.

(0015] The following detailed description is merely illustrative in nature and is not intended to limit the embodiments of the subject matter of the application or uses of such embodiments. As used herein, the word "exemplary ^" means se ng as an example, instance, or illustration. ^" Any implementation described herein as exemplary is not necessarily to be construed as preferred or advantageous over other implementations. Furthermore, there is no intention to be bound by any expressed or implied theory presented in the preceding technical field, background, brief summar or the following detailed description. jOO!o] This specification includes references to one embodiment" or " embodiment/ ^' The appearances of the phrases "in. one embodiment^ or "in an embodiment'" do not necessarily refer to the same embodiment Particular features, structures, or characteristics .may be combined in any suitable mariner consistent with this disclosure.

(0017) Terminology, The following paragraphs provide definitions and/or context for terms found in this disclosure (including the appended claims):

fOO!SJ "Comprising " This term is open-ended. As used in the appended claims, this term does not foreclose additional structure or steps.

(0019) "Configured T ^' Various units or components may be described or claimed as "configured to" per.fo.rm. a task or tasks. In such contexts, "configured to" is used to connote structure by indicating that the units/components include structure that performs those task or tasks during operation. As such, the unit/component can. be said to be configured to perform the task even when the specified imi /component is not currently operational (e.g., is not on/aetiveh Reciting that a taiit/circmt/eo ponent is "configured to" perform- one or more tasks is expressly intended not to invoke 35 U.S.C. §1 12, sixth paragraph, -for th unit/component

|0020] "First/ ^" "Second/' etc. As used herein, these terms are used as labels for nouns that they precede, and do not impl any type of ordering (e.g., spatial, temporal logical, etc.), For example, reference to a "first'" solar cell does not necessarily imply thai this solar cell is the first solar cell in a sequence: instead the term "fi st" is used to differentiate this solar cell, f om another solar cell (e.g., a "second" solar cell . Likewise, a first FY module does not necessarily imply that this module is the first one in a sequence, or the top PV module on a panel. Such designations do not have any bearing on the location of the PV module, substrings, and the like,

f002ii "Based On." As used herein, this term, is used to describe one or more factors that affect a determination. This term does not foreclose additional factors that may affect a determination. That is, a determination may be solel based on those factors or based, at least in part, on those factors. Consider the phrase "determine A based on B/ ^* While B may be a factor that affects the determination of A, such a phrase does, not foreclose the determination of A from also being based on. C. in other instances. A may be determined based solely on B. {O022| ^Coupled" ~ The following description refers to elements or nodes or features being "coupled" together. As used herein, unless expressly stated otherwise, "coupled ^' " means that one elementdmde/fcaiure is directly or indirectly joined to (or directly or indirectly communicates with) another elemeni/node/feaiure, and not necessarily mechanically.

|0023| "Inhibit ^" - As used herein, inhibit is used to describe a reducing or minimising effect. When a component or feature is described as inhibiting an action, motion, or condition it may completely prevent the result or outcome or future state completely. Additionally, ^vS mhibif can also refer to & reduction or lessening of the outcome, performance, and/or effect which might otherwise occur. Accordingly, when a component, element, or feature is referred to as inhibiting a result or state, it need not completely prevent or eliminate the result or state,

(0024] In addition, certain terminology may also be used in the following description for the purpose of reference only, and thus are not intended to be limiting. For example, terms such as "upper", "lower ^" , "above ^' , and "below ^* - refer to directions in the drawings to which reference is made. Terms such as "front", "b ck", ""rear"-, "side , Outboard", and. "inboard" describe the orientation and/or location of portions of the com onent within a consistent but arbitrary frame of reference which is made clear by reference to the text and the associated drawings describing the component under discussion. Such terminology may include the words specificall mentioned above, derivatives thereof, and words of similar import.

(0025] In the following description, numerous specific details are set forth, such as specific operations, in order to provide a thorough understanding of embodiments of the present disclosure, li will be apparent to one skilled in the art thai embodiments of the present disclosure may be practiced without these specific details. In other instances, well- known techniques are not described in detail in order to not unnecessarily obscure embodiments of the present disclosure.

10 26] This specification describes exemplary PV-to-bus architectures that can include the disclosed DPP converter implementations, followed by a more detailed explanation of various embodiments of the DPP converter topologies. The specification also includes a description of exemplary methods. Examples of housekeeping power supplies according to embodiments are also provided, i the specification, these housekeeping power supplies have numerous implementations, including the various examples provided throughout, [0027] In embodiments, DPP converters may process the mismatch in power between

PV modules or cells or strings or substrings, rather than the total power of a PV module (or substring or any collection of PV cells that would otherwise be connected according to an arrangement, such as being connected In series), DPP converters can be of benefit because the mismatches may generally be small and because of this relatively small mismatch, sometimes on the order of 1 % - 20% or more, a relatively small correction can be requited. |0828j In embodiments, DPP converters can allow the bulk of current from a FY

.module to pass directl to neighboring rn.odul.es via wires as opposed to flowing the current, through a converter. This process may be considered efficient because in so doing only mismatch current can flow through the DPP converters. For example, if two modules connected in series may have I JVlPP currents of 5 amperes (A) and 6 A, respectively. The mismatch current may be 1 A. If the two modules are connected in series, then the modules are forced to carry the same current, which may not be optimal for either module. In this example, each of the DPP converters preferably provides a path for 0.5 A of the mismatch current. Because the mismatch currents are relatively small, a DPP converter can preferably he capable of low-currentdow-power operation, This low current/low power operation ma be considered an improvement over dc-dc optimizers that, carry full current and full power operation.

Architectures of embodiments may include many configurations. One configuration is the PV-to-PV architecture, which can use a buck-boost topology. Another configuration may he a PV-to-bus architecture. In the PV-to-PV architecture, when the individual conveners have a blocking voltage of two PV modules the DPP converters are connected to neighboring nodes. For PV-to-bus architectures, the DPP converters serve to block the entire string voltage, even though their inductors may carry less current In addition, for PV-to-bus architectures, the DPP converters can be coupled at each source where the output may go to a centralized point or line as opposed to and from one PV string to another. For example, the DPP converters may be connected to a shared, bus as a centralized line. Alternatively, the DPP converters may be connected to a virtual bus. One of ordinary skill in the art would recognize that the PV-to-bus architecture shown in same embodiments is just representative, and that, more generally, the use of a "virtual bus" is known, in. embodiments, the PV-to-bus architectures ma also use a circuit implementation having a flyback differential converter interface with the main bus. 030] Embodiments- can. include a DC power system that includes a PV power converter circuit and a PV module having a plurality of PV cells arranged in strings and substrings. The PV ceils in the substrings- of the PV module may preferably be arranged in series. Other arrangements, however, may be used according to the disclosed embodiments. The PV power system ma include a central converter coupled to the PV module by a shared bus as well as local converters serving individual PV modules. Individual PV modules as well as the PV power system as a whole may include several DPP converter circuits, where the DPP convener circuits are coupled to a shared bus and two or more shared PV cell strings or substrings. The bus may be a virtual bus, in some embodiments. The PV power system may have multiple DPP convener circuits where each DPP converter circuit is coupled to two PV cell substrings of a PV module such that each of the DPP converter circuits processes a difference in power between the coupled PV cell substrings, These DPP converter circuits may further provide the processed power difference to a local or central converter via a shared bus. in embodiments, a DPP converter circuit may include two switches and an inductor where the inductor may be coupled directly to a plurality of PV cell substrings in the absence of a bypass diode. Still further, DPP converter circuits of embodiments may be positioned and configured to shuffle power between strings, substrings, ceils, or other groupings or de power sources depending upon how the DPP converter circuits are tapped to these voltage sources.

|¾03l In embodiments, DPP converter circuits may be configured without discrete inductors, instead, the parasitic/stray inductances, Ls, of a PV module may be relied upon t r converter inductance. While these inductances are ordinarily small (« 1 mi l), they can be adequate for a sufficiently high switching frequency DPP converter circuit switches. Moreover, using diodes for top switches rather than actively switched power MOSFETs may allow the use of discontinuous converter modes. These diodes may be part of MOSFETs turned off for such im lemen ation. While such modes may generate, unwanted current ripple in the sources (the ripple in inductances, Ls, would be high, in other words), this may not be necessaril problematic as the relatively high capacitance of solar ceils may be used to absorb high frequency current ripple, resulting in manageable lost PV power production. A possible advantage of discrete inductor elimination may include cost, space, and weight savings. And, even though efficiency ma not. be as high for the DPP converter circuits without dedicated inductors, DPP converter circuits of embodiments may no need to conduct large amounts of power, therefore reducing die relative importance of their efficiency.

|0 32| Embodiments may also include a PV power converter circuit, that includes a housekeeping "HK" power supply 'TIKPS' ¹ powered at least in part by one or several of the PV cells of a PV module. These housekeeping power supplies may have various output voltages to power components such as op-amps, sensors, and microcontrollers on low voltage outputs, e.g., 3.3 V and gate drivers on higher voltage outputs, e.g.. 8 V. These housekeeping power supplies may be tapped into various points of these PV systems such that the housekeeping power supplies receive supply power from various circuit configurations, including various numbers of PV cells in embodiments and from one or more converters in the same circuit or elsewhere.

[01 ⁾ 33] Multiple PV sources may be employed, in embodiments, tor example, substrings of a PV module may each be considered a PV source. In embodiments, transistor diode pairs, which may be built from power MOSFETS, may be employed as switches and configured with two inductors such thai two bidirectional converter circuits are formed. These bi-directional converter circuits can. exchange power from PV sources to and from a shared bus. m addition, this bidirectional configuration and operation can allow for adjustment of Individual PV substring voltages.

} ^' 0O34] in certain embodiments, inductor, transistor and diode sets may be configured to serve as converter circuits where the diodes may be positioned such that the converter circuits are unidirectional. Such an arrangement can reduce or eliminate the need, to provide a high-side gate drive to a top switch. Such an arrangement may also esult in one of the converter circuits having its output as the input of another converter circuit rather than a shared bus. In so doing, a converter circuit without bus output may not experience as high, of voltage stresses as other convener circuits in the system that are ouipuning to a shared bus. Inherent bypass diode protection may also be provided as PV sources in these embodiments may employ parallel diode for DC currents where related inductors can be treated as short circuits.

[0O35J In embodiments, further electrical isolation may be provided by replacing the inductors with transfo mers. The primary winding of these transformers may provide the main inductance needed for power conversion whereas the secondary winding, may provide a low or different voltage output and may be steadied or rectified through subsequent, treatment by diodes, capacitors or other treatment device. Also, inductive cores may have extra windings and be coupled to housekeeping power supplies or another inductor where either can serve as a power supply for a housekeeping circuit,

[0036J In embodiments, low voltage outputs may be used to power housekeeping circuits. These housekeeping circuits may be positioned near and powered by these low power outputs to promote efficiency and reduce circuit complexity when compared to a housekeeping circuit that was fed by a f ll PV module voltage of other full DC power system voltage. For example, a housekeeping circuit, normally composed of a high~Input~voitage switching power supply may potentiall be replaced by a low-cost linear regulator. Thus, in embodiments, even if switching power supply is still used, it may be fed from a lower voltage and in so doing may have inherently lower cost and be more efficient. Still further, In embodiments, housekeeping power could also be, or alternatively be, fed with full PV panel voltage via a second circuit network as a default so that housekeeping power is continuous, if not efficient. Still .further, the power supplies for the housekeeping power, e.g., low voltage partial circuits, high voltage Ml PV circuits, PV string source lead, etc., could be used only during normal operation or as needed depending on efficiency and avai lability, h preferred embodiments however, housekeeping power can be fed off of a lower voltage supply.

0037{ Other power sources and sequential power adaptations for. a housekeeping power supply are also coveted in embodiments. For example, different PV strings may be used to power the housekeeping power supply to accommodate for certain shading conditions or when voltages from some sources are lo while voltages from other sources are normal or high. Thus, in embodiments, a network of resistors, diodes, and an analog switch may he employed to select available PV sources and to actually connect the available source to the input of the housekeeping supply. The resistors in these circuits may be sized to ensure that if a first PV source reduces in voltage (say below S V), then the sum of other .PV sources is applied to the housekeeping input, enabling the housekeeping supply to remain on and still powered by a relatively low voltage.

[00381 Embodiments may also power the housekeeping supply though the use of dedicated PV cel!ts), These dedicated ''housekeeping cell(sf may be brought out of the module lor the express purpose of powering the housekeeping supply. The housekeeping cell, or cells may or may not employ the standard large (5" or (ry typical) PV cell. In embodiments the housekeeping eell.Cs) may be smaller than standard ceils and may be placed among the standard cells expressly tor this purpose, taking, advantage of the lower power demands of the housekeeping supply, When single cells are used a dc-de converter may he used to step up the voltage from 0.5 V to 3.0 V. This dedicated H PS configuration, as with other embodiments, may be synthesized with the DPP approach or other i-box integrated electronics and in so doing providing access to sub-module electrical, nodes. For example, housekeeping power from, another source can be turned on if power from a primary source such as a cell or substring became unavailable. Moreover, this alternative ceil approach may be used to accommodate self shading scenarios where housekeeping cells become shaded during certain periods of the day depending upon their positioning. In these self-shading time periods backup or alternative housekeeping cells may be used to power the housekeeping supply.

]0039j Turning now to Figure I , an example block diagram of PV power module 100 having a PV4o-bus module converter 101 is shown. Module converter 101 may be integrated with PV power module 100. Module converter 101 includes- a central converter 1 2. This component may he a dc-ac microinverter, de-dc convener, dc-dc optimizer, or any other power converter. Central converter 102, and in turn module converter 101 , is coupled to alternating current (AC) power system 104.

β040] Module converter 1 1 also is coupled to PV cell substrings of a PV module

1 10. The PV cell substrings, designated by PV;, PV- and PV¾ supply solar power to central converter 102. Although three PV cell substrings are shown, the number also may be four or five FV cell substrings, or possible other numbers, in some embodiments. Other embodiments may include a different number of PV cell substrings as well. Preferably, each PV cell substring includes .24 PV cells. Thus, a PV module according to the disclosed embodiments may include 72 PV cells. This is one possible configuration. Other configurations may be implemented. For example, a FV module may include 9b cells, with three PV cell substrings of 24, 48 and 24 cells. In other embodiments, the PV cell substrings may have 20 cells. Thus, not all FV cell substrings need to be equal in the number of cells.. As can be appreciated, a variety of configurations of the PV cells and PV cell substrings may be implemented according to the disclosed embodiments. In another example, a PV module with. 1.28 or 256 cells may be used.

[0041} DPP PV-to-bus converters 106 and I OS also are integrated within module convener 101 , In some embodiments, additional DPP converters may be used for a larger number of PV cell substrings. DPP converters 106 and 108 are both coupled to main bus 1 12, which couples PY cell substrings 1 10 to central converter 102. DPP convener 1 6 is coupled to cell substrings PVj and PV? to process the mismatch between these cell substrings of PV module 1 10. DPP converter 108 is coupled to cell, substrings PV2 and PV _: * to process the mismatch between these cell substrings, Mismatches between PV ceil substrings may occur when shading, manufacturing variability or non-uniform, aging characteristics occurs within a PV module. In some embodiments, the number of DPP converters may correspond to the number of PV cell substrings such that one DPP converter is between two PV cell, substrings, In other embodiments, however, the number of DPP conveners may be less or not correspond to the number of P cell substrings. For example, referring to Figure 1 , only the bottom PV cell substring may have a DPP converter and the top two PV cell substrings may just have bypass diodes,

|0042| Module converter 101 also includes a housekeeping power supply 1 14,

Housekeeping power supply .1 .1 is a low power supply thai runs various sensors, controllers, operational amplifiers, ana the like within power module 100. Housekeeping power suppl 1 14 also may run the gate drivers for transistors used in the DPP converters, as disclosed below, in some embodiments, housekeeping power supply 114 may be powered by shared, bus 1 12. In embodiments, as disclosed below, housekeeping power supply .1 .14 may also draw power from various sources within power module 100 or module converter 101 to reduce the requirements for converting a relatively high voltage of main bus 1 12 to a relatively lo voltage.

[00431 Figure 1 also depicts bypass diodes 140. Bypass diodes 140 are optional and as they have little or no impact on the functioning of DPP converters 106 and 108, In fact, bypass diodes may be integrated in DPP converters 106 and 108. Alternatively, bypass diodes .140 may be removed- altogether. Further, -while conventional diodes are depicted, a Schottky diode or any other device that performs like a diode may be implemented. In some embodiments, so-called "smart diodes" may be used in PV applications.

[0044) Module converter 1.01 has central converter 102 and DPP conveners 106 and

108 integrated into a single component. Further, module converter 101 and power module 100 may be- integrated, as disclosed by die topologies discussed below. This integration can save cost by not requiring separate circuits or components and sharing some functions between the module and the converters, -Space and power processing efficiency also may be increased by the various disclosed DPP topologies as the DPP converters are implemented with a central or shared converter.

[004SJ Turning now to Figure 2, a circuit diagram showing a PV-to-bus converter topology 200 is shown according to some embodiments, PV cell substrings 1 10 are shown connected to components of DPP converters 06 and 108. Elements of PV power module 100 are included, though not shown, in Figure 2 where elements of Figure 1 are configured with the supplemental details of topology 200 to convert and provide power in. embodiments. j¾046] Each DPP converter shown in Figure 2 includes two switches and an inductor.

Thus, DPP converter 1.06 includes switches S u and SWH and ^' inductor Li. DPP converter 108 includes switches S¾¾ and 8 ¾ and inductor Ls. The switches ma be transistor-diode pairs, preferably built from power OSFETs. For example, switch SWa may include transistor Switch SWj , also in DPP converter 106, may include tra sistor QK and diode Du. Switches S ¾ and S ¾ of DPP converter .108 are similarly configured. In some embodiments, BJTs, IGBTs, HE Ts and other types of semiconductors may be implemented in the DPP converters. Other embodiments may use various structures using silicon and other semiconductors, including silicon carbide or gallium-nitride technologies. |0047| The switches within each DPP convener along with, the associated inductor form a bidirectional converter that may exchange power from the PV ceil substrings to and from main bus 1 12, represented as the sum of F ^' WPV; cell substrings. The DPP converters also may be connected to a virtual bus. The bidirectional, aspect of DPP converters 1 6 and 108 allows for adjustment of the individual PV cell substring voltages, especially for MPP tracking.

|0048| Housekeeping power supply 1 14 is shown coupled to main bus 1.12.

Housekeeping power supply 1 14 provides an 8 volt and a 3,3 volt output, h other embodiments, housekeeping power supply 1 14 may provide other voltages. These voltages may power an integrated mieroin erier, dc-de optimizer or other central converter within power module 100, Housekeeping power supply 1 1.4 also may power the circuitry of DPP converters 106 and 108. Topology 200 shows housekeeping power supply 1 14 receiving power from main bus 112. Thus, PV cell substrings 1 1 may power IIKPS 1 14 using a relatively high, voltage (up to 80 volts in some instances; such voltage .may increase with a higher number of cells, and the embodiments are not limited to this level). | 49j As taught by Figure 2, DPP converters 1.06 and 1 8 may integrated with

PV cei! substrings 1 10 in power module 100. Inductors within the DPP converters may be attached directly between PV cell substrings withoui the need for capacitors used for non- integrated .module convener, in some embodiments, the inductors may be coupled to each other, though not explicitly shown.

fOOSO Figure 3 illustrates a circuit diagram showing a PV-to-bus converter topology

300, according to some embodiments. Converter topology 300 includes PV cell substrings 1 1 0, DPP converters 1.06 and 108.. main bus 1 1.2 and housekeeping power supply 1 14. Converter topology 300, however, has the output of DPP converter 108 fed into the output node of PV ₂ and the input node of DPP convener 1 6. Elements of PV power module 100 are included, though, not shown, in Figure 3 where elements of Figure 1 are configured with the supplemental details of topology 300 to convert and pro vide power in embodiments.

(0051) Further, the DPP converters include diodes for the top switches m converter topology 300. DPP converter 106 implements diode On for switch SWi?. and ^' DPP converter 108 implements diode D22 for switch SWr>. Although the same reference numerals are used for the top switch diodes as those disclosed in converter topology 200, the diodes are not necessarily identical across the converter topologies.

10052] Use of diodes I½ and D22 as the top switches may make DPP converters 106 and 108 unidirectional, as opposed to the bidirectional feature of converter topology 200. DPP converters 106 and 108 in converter topology 300. however, may be lower in cost to produce because the diodes may cost less than transistors, such as OSFETs. Further, there is no need in this embodiment to provide a. high-side gate drive to the top switches of the DPP converters from housekeeping power supply 1 14.

053| Switch SW24 may also only need a low voltage blocking requirement as DPP converter 108 is not coupled to shared bus 1 12. Thus, switch SW24 may provide a lower cost over switch. SW2.4 in convener topology 200. DPP converter 108, in general, may not experience as high of voltage stresses as DPP converter 106 and may he comprised overall of lower cost components,

10054] Another benefit of converter topology 300 Is that each of PV cell substrings

110 has a diode at a direct current (DC.) implementation. In other words, for DC currents, inductors h\ and hi may be treated as short circuits. This arrangement provides inherent bypass diode protection, especially advantageous if bypass diodes 1 14 are removed, { ^' 8055] Convener topology 300 also is scalable such that any number of DPP converters and PV cell substrings may be implemented. A lower DPP convener may feed into the Input node of a higher DPP conve er. Thus, DPP converter 1 8 may feed its output to an input node of another DPP converter, Each PV cell substring would have a parallel diode to provide die advantages disclosed above.

[ MI56) Figures 4 A and 4.8 illustrate a circui diagram showing a P to-bus converter topology 400, according to some embodiments. Converter topology 400 may resemble convener topology 300 except that inductors Li of DPP converter 106 and LJ of DPP convener 108 have been replaced, by transformer arrangements, shown as transformers T> and Ti. DPP converter 106 includes switches SWsa and SWi*. as disclosed above, and transformer primary winding Tjp of transformer Ύ-., Transformer primary winding Tu> provides the main inductance for power conversion within DPP convener 1 06. DPP converter 1 8 includes a similar arrangement with transformer primar winding ¾» of transformer T?. In some embodiments, transformer primary windings Tj» and >x> may be referred to as an inductance element. Switches SW22 and SW24 may act as disclosed in. previous converter topologies. For the purposes of converter topology 400, the switches may be any of the switch configurations disclosed above. For example, switches SW;2 and S 22 may be diodes to provide the unidirectional converters of converter topology 300 or may be the transistor-diodes pairs of converter topology 200 to provide bidirectional converters.

|IH)57| The transformers of DPP converters 106 and 108 may include secondary windings matched to the primary windings. Referring to Figure 4B _? transformer secondary winding Tss is matched to transformer primary winding Tjp of DPP converter 106 and transformer secondary winding T s is matched 10 transformer primary winding I n of DPP converter 108 in the secondary portion of converter topology 400. A current in the primary windings of the transformers may generate a magnetic field that impinges on the secondary windings. The magnetic field induces a voltage within the secondary windings,

[00S8] Thus, as differential power is detected in the PV cell substrings Π 0, the current flowing through transformer primary windings T;p and ¾ may cause a voltage and resulting current (shown by arrows A) to flow, Transformer secondary windings Ts$ and Tis may be designed to generate a higher or lower current than that flowing in the primary windings. A lower current generates a lower voltage output within the secondary portion of converter topology 400, Transformer secondary windings TVs and T.¾ may be coupled through diodes 402 or another ra ification device to a capacitor 404. or other means to generate a st ady DC voltage. Element 406 in Figure 4B refers to ground.

|0059| The DC voltage generated through the transformer secondary windings may he fed to housekeeping power supply 1 14. Alternatively, the voltage generated by the transformer secondary windings may be stored by other components within the secondary portion of converter topology 400. Housekeeping power supply 114 is disclosed as receiving the lower power from the transformer secondary windings because this configuration may alleviate the need to reduce the large voltage from shared bus 1 12,

{096β| The voltage reduction provided by the transformers Τ and ^' may facilitate a capacitor voltage of capacitor 404 that may be similar in value to the desired housekeeping voltage. Preferably, the housekeeping voltage for housekeeping power supply 1 14 may be lower than the voltage for the full PV module of FY cell substrings 1 10, It is more efficient to feed housekeeping power supply .1 14 off of a lower voltage. Thus, the housekeeping circuit of converter topology 400 may be more efficient or simpler than previous topologies. (0061 for example, the housekeeping circuit for housekeeping power supply 1 14 may replace the high-mput-voitage switching power supply with a low-cost linear regulator Even if a switching power supply is still used, housekeeping power supply 114 of converter topology 400 is fed from a lower voltage source in the transformer secondary windings T ;* and ¾, which is lower in cost and more efficient.

19062} Switch S ^' Wj. or W¾ -switches frequently enough to provide a steady supply of current to transformers T; and lb. Otherwise, housekeeping power may be lost if no current is generated within transformer secondary windings Tts and lbs. For example, if PV-j is shaded, then no power ma be generated in the PV cell substring to flow to transformer primary winding lb . Alternatively, housekeeping power supply 1 14 may be fed with the full panel voltage of PV cell substrings 1 10 via another circuit network as a default so that power is not lost. The housekeeping power supply configuration shown in converter topology 400 may be used only during normal operation or as needed depending on efficiency and availability.

|β0ί*3{ mplementation of a lower voltage to feed housekeeping power supply 1 14 is desirable to improve efficiency and lower costs. PV cell substrings 1. 10 may have voltages of 30 volts or higher, with 96 cells generating voltages of 50 volts or higher during normal operation. To power 8 volt and 3.3 volt outputs from housekeeping power supply 1 14, for example, a large step-down conversion may be needed. Conve er topology 400 may help provide the lower voltage preferably without the: need for the step-down conversion,

[0064| Further, additional topologies may be implemented according to the disclosed embodiments. Figures 5A and SB illustrate a circuit diagram showing PV-to-bus converter topologies 500 and 502, according to some embodiments. Converter topology 500 includes PV cell substrings 110 and DPP converters 1 6 and 108. The exact configuration of DPP converters 106 and 08 are not shown, ^' but may correspond to the embodiments disclosed above. For example, DPP converter 108 ma couple to shared bus 1 12 instead of the input node of DPP converter 1 6. Converters 106 and 108 may implement the transistor-diode pair switches of converter topology 200, or the circuits disclosed by converter topologies 300 and 400,

|0065] Housekeeping power supply 1 14 may be powered off a single FV eel! substring and provides the desired outputs of S volts and 3.3 volts. The disclosed embodiments, however, are not limited to these outputs. In some embodiments, other voltages may be output for gate drive, communications, and logic. Figure SA shows the PV cell substring as PV;, but PV?. or PV * may be used, A PV cell substring may generate an output of about 10-15 volts, which is less than the 30-50 volts output from the entire PV cell substrings 110. Housekeeping power supply 1 14 may be connected to the top or bottom FV ceil, substring, or an PV cell substring,

[0 66| If PV s is shaded or otherwise unavailable, then housekeeping power supply

1 14 may not receive enough power to supply the output voltages. This condition may cause DPP converters 106 and 108 and central converter 1.02 to shut down. An alternative to converter topology 500 that prevents this condition may be converter topology 502 shown in Figure 5B.

[0067] In converter topology 502, housekeeping power supply 1 14 preferably is not connected to one of the PV cell substrings in converter topology 502. Instead, housekeeping PV cell 504 is configured to supply power to housekeeping power supply 1 14. Additional PV ceils or even a PV cell substrings may be used to power housekeeping power supply 1 14, and the embodiments are not limited to one PV cell. For simplicity, the PV cell or plurality of PV cells will be referred to as PV cell 504.

| ^' «068| PV cell 504 preferably does not need to be large. More preferably, PV cell

504 may be a 5 or 6 inch cell or other size. PV ceil 504 may be placed among the standard cells in a PV cell substring and dedicated to providing power to housekeeping power supply 1.14. This condition is possible because the power output of PV ceil 504 need not be particularly high. In some embodiments, the output power of PV ceil 504 may be approximately 0.5 volts.

\i)iW)} Alternatively, PV cell 504 ma be decoupled from the PV ceil substrings, and is its own cell placed on the solar panel array where it will most likely to receive continuous sunlight. As the sun moves during the daylight hours, the upper panels of a solar panel may shade the lower substrings. PV cell 504 may be placed at. the top of the panels so that it preferably is not shaded or blocked by the physical construction of the solar panel Incorporating PV power module 100. hi other embodiments, PV cell 504 may be used when housekeeping power supply 1 14 does not receive enough power from other means, such as PV cell substrings 1.10, an. individual P cell substring, or .main bus 1 12.

[8070] Figure 6 illustrates a circuit diagram showing PV-to-bus converter topology

600, according to some embodiments. Although not shown, DPP converters 106 and 108 are coupled to PV cell substrings 1.10 as disclosed above. Converter topology 600 may select the appropriate power source .for housekeeping power supply 1.1.4. Though not shown, PV ceil 504 may be included as a selection source tor housekeeping power.

[0071 ] Converter topology 600 uses a network of resistors, diodes and a analog switch to select which of two PV sources connects to the input of housekeeping power supply 1 14, Resistors I½> t and 1¼ may have resistances to ensure that if PV cell substring PV* reduces in voltage, such as below S volts, then the sum of the power from PV cell substrings PV'2 and PV is applied to the input of housekeeping power supply 1 14. This feature enables housekeeping power supply 1 14 to stay powered even when PV ceil, substring or PV cell 504 is shaded or may not be operating efficiently.

[00721 Diode Dm allows PV cell substring PV-, to supply power during normal conditions. Diode D provides power when the state (open or closed) of analog switch. S\%> determines that not enough power is being provided to housekeeping power supply 114. Preferably, analog switch S oo is a transistor. In other embodiments, analog switch SWso may be coupled to PV cell 504, which provides a reliable low power source during shading conditions.

[0873| Thus, the disclosed embodiments provide alternate power sources f housekeeping power supply 1 14. These alternate sources may mitigate the need tor converting high voltage from shared bus 1 12 to the low voltage provided by housekeeping power supply 1 14, Further, costs may be reduced by integrating housekeeping power supply 1 14 into module converter 101 or P V power module 00.

(0074) Figure 7 is a circuit diagram showing PV-lo-bus converter topology 700, according to some embodiments. Converter topology 700 includes PV cell substrings 1 10, DPP converters 106 and 108 and housekeeping power supply 1.1.4. The configuration of the circuit may incorporate any of the topologies disclosed above wiih regard ιο the placement of the DPP converters and the housekeeping power supply.

[ )075] Converter topology 700. however, preferably does not use discrete inductors to connect DPP converters 106 and 108 directly to PV cell substrings 1 10. Instead, the parasitic or stray inductances, shown as inductance elements Ls in figure 7, of the PV ceil substrings may provide the convener inductance. These inductances may be small, such as less than 1. microhenry, but can be adequate for a sufficiently high switching frequency of switches SW: and SW^.

|0 76| Moreover, discontinuous converter modes for DPP converters 1 6 ^' and 108 may be implemented by using diodes for switches SW^ and SW _; ¾ as opposed to actively switched power MOSFETS, such, as those shown in converter topology 200. m some embodiments, the diode used as a switch may he part of a MOSFET (the body diode of the MOSFET). The MOSFET is turned off so that the diode may conduct In other embodiments, the MOSFET may be turned on. Thus, though not shown, the DPP converters in topology 200 (and the other topologies) ma include a MOSFET for this feature though a diode is shown. Such modes may generate a lot of current ripple in the sources. In other words, the ripple in inductance elements L¾ would be high. Yet this may ot be a problem as solar cells have a relatively high capacitance, such as tens of microfarads. This capacitance may absorb substantially ail of high frequency current ripple, which results in very little lost PV power production,

[00??| Converter topology 700 may have reduced costs due not using inductors as the inductance elements for the DPP converters, inductors may be the largest and most expensive component in a DPP converter. By using the parasitic inductances in the PV cell substrings, this cost may be removed. Efficiency, however, also may not be as high as other converter topologies but the DPP converters normally conduct little power compared to the PV cell substrings so that efficiency is not as important. |8078| The converter topologies disclosed above are shown as hard-switched boost converters. The disclosed, configurations also work using other converter circuits, particularly if the converters are fed via an inductor. Thus, the disclosed embodiments may be adapted, to incorporate other known power converter topologies.

\Wf9] Turning now to Figure 8. a flowchart illustrating a method for converting differential power within a plurality of PV cell substrings is shown, according to some embodiments. In various embodiments, the .method of Figure 8 can include additional {or fewer) blocks, or steps, than Illustrated. Further, where applicable, reference is .made to elements shown. In the previous figures showing converter topologies. The disclosed topologies, however, are not limited to the steps shown in Figure 8.

{0080] Step 802 executes by detecting differential power between two PV ceil substrings. Differential power refers to a mismatch between the power levels found in two PV cell substrings. Preferably, the differential power may be detected by mismatched current or voltage within the PV cell substrings. Referring to Figure 3. mismatched current or voltage may be detected between PV cell substring PV ₂ and PV cell substring PVj. For example. PV cell substring ; may produce a current of 5 amps while PV cell, substring PV ¾ produces a current of 6 amps. The difference may be detected in di ferent spots. Depending on the switching state of the converters, the current, voltage or power mismatch may be i nferred instead of directly measured.

[ 81] Step 804 executes by inputting the detected differential power directly to an. inductance element of a DPP converter. Staying with the above example, the difference in current may flow to inductor l . Alternatively, the differential current may flow through an inductance element, disclosed above. The differential current may flow directly to DPP converter 1GS. in some embodiments, the detected difference in. voltage is used.

[0082] Step 806 executes by ©inputting the converted differential power to an. input of another DPP converter. Thus,, the output of DPP converter 108 may go to inductor L ¾ of DPP converter 106 in. some embodiments. In other embodiments, the converted differential power may be output to main bu 1 12 directly to central converter 102. Again, DPP converters are coupled directly to each other,

{O083J This configuration may continue for any number of DPP converters. Thus, the output of DPP converter 106 may be applied to an input node of another DPP converter. Eventually, step 80S executes by outputting the sum, or a part thereof, of the converted

I S differential power to central converter 102 via main bus 1 12. Some of the converted differential power .may be divert back to the PV cel ls or substrings,

10084) Figure 9 illustrates a flowchart illustrating a method for supplying power to a housekeeping power supply within a converter topology, according to some embodiments. In various embodiments, the method of Figure 9 can include additional (or fewer) blocks, or steps, than illustrated. Further, where applicable, reference is made to elements shown in the previous figures showing converter topologies. The disclosed topologies, however, are not limited to the steps shown in Figure 9.

{0085J Step 902 executes by receiving power at housekeeping power supply 1 1.4 horn a subset of PV cell substrings 1 10. Preferably, as shown, in Figures 5A, 5B and 6, the subset may be a single PV cell substrings, a pluralit of PV cell substrings, or a dedicated PV cell. The subset indicates that housekeeping power supply 1 1.4 preferably is not receiving its power from main bus 1 12, Thus, the voltage provided to housekeeping power supply 1 14 may be reduced using the subset

I ^' OO ] Step 904 executes by detecting that power preferably is not available from the subset of PV ceil substrings. Power may not be available for a variety of reasons, including shading of the solar cells or a malfunction, in this condition, housekeeping power supply 1 14 may not receive enough power to perform its function to power the converters.

[0087] Step 906 executes by switching to another subset of the PV cell substrings.

For example, as shown in Figure 6, power input may be switched to another PV cell substring. Power input is switched to cells that preferably are not shaded or imderper.fb.mung. Optionally, step 908 may be executed to switch power input to a PV cell dedicated to providing power to housekeeping power supply, as disclosed by converter topolog 502, PV cell 504 may be kept in the event that no suitable subset can be found to power housekeeping power supply 1.14.

0088| Step 91.0 executes by receiving the voltage at the input of housekeeping power supply 1 14. As disclosed above, preferably, the voltage is lower in value than using voltage from the main bus. Step 912 executes by outputting the voltage f om, housekeeping power supply 1:1.4 to the DPP converters and the central converter.

[0089) Although specific embodiment have been described above, these embodiments are not intended to limit the scope of the present disclosure, even where onl a single embodiment is described with respect to a particular feature. Examples of features provided in the disclosure are intended to be illustrative rather than restrictive unless stated otherwise, The above description is intended to cover such alternatives, modifications, and equivalents as would he apparent to a person skilled in the art having the benefit of this disclosure. For example, the DPP converters of embodiments are often shown as hard- switched boost converters. The configurations can work as well using other converter circuits, particularly if they are led via an. inductor (the SEFIC converter, for example). Engineers familiar with power topologies should recognize how to adapt the concepts to other well-known power converter topologies,

|0098} The scope of the present disclosure includes any feature or combination of features disclosed herein (either explicitly or implicitly), or any generalization thereof, whether or not it mitigates any or all of the problems addressed herein. Accordingly, new claims may be formulated during prosecution of this application (or an application claiming priority thereto) to any such combination of features, in particular, with reference to the appended claims, features from dependent claims may be combined with those of the independent claims and features from respective independent claims may he combined in any appropriate manner and not merely in the specific combinations enumerated in the -appended, claims.