Abstract:
Various implementations described herein are directed to methods for connecting power devices prior to deployment in a photovoltaic installation, for cost savings and easy deployment. Some embodiments disclosed herein include manufacturing a chain of power devices already coupled by conductors, and providing a mechanical assembly for convenient storage and deployment.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims benefit to U.S. Provisional Patent Application No. 62/318,303 filed Apr. 5, 2016, U.S. Provisional Patent Application No. 62/341,147 filed May 25, 2016, and U.S. Provisional Patent Application No. 62/395,461 filed Sep. 16, 2016, the contents of which are incorporated herein by reference in their entirety. 
     
    
     BACKGROUND 
       [0002]    Power devices may be electrically coupled to photovoltaic (PV) generators and configured the set the operating point of the generators to generate maximum power. They may also be coupled to power production and/or storage units such as batteries, wind or hydroelectric turbines and the like. 
         [0003]    Power devices are often manufactured, packaged and sold as single units, leading to deployment which requires that each device be individually coupled to its power unit and the devices themselves coupled by connecting electric cables between them. 
         [0004]    Accordingly, there is a need for power device systems in which costs, time and complexity in deploying the power devices are reduced. 
       SUMMARY 
       [0005]    The following summary is a short summary of some of the inventive concepts for illustrative purposes only, and is not intended to limit or constrain the inventions and examples in the detailed description. One skilled in the art will recognize other novel combinations and features from the detailed description. 
         [0006]    Embodiments herein may employ a string of photovoltaic power devices (e.g. DC/DC converters, DC/AC inverters, measuring and monitoring devices) which may be deployed in photovoltaic installations. In some embodiments discussed herein, conductors may be used to couple power devices to one another during manufacturing to form a chain of power devices, with the chain packaged and sold as a single unit. The chain may be deployed by coupling the power devices in the chain to photovoltaic (PV) generators (e.g. one or more photovoltaic cells, substrings, PV panels, strings of PV panels and/or PV shingles). The coupling of power devices at the time of manufacturing may reduce costs and enable compact storage of the devices, and the easy deployment may reduce installation time. Connecting power devices at the time of manufacturing may include directly connecting conductors (e.g. by soldering or screwing the conductors into place within a power device enclosure) between adjacent power devices. Furthermore, preconnecting power device may reduce the number of connectors (e.g. MC4™ connectors) featured in each power device from four (two connectors for connecting to a PV generator at the power device input and two connectors for connecting between power devices at the power device output). As connectors may be costly components, substantial savings may be realized. Additionally, preconnecting power devices during manufacturing may increase system safety. For example, if improperly connected, connection points between power devices may be susceptible to overheating, arcing and/or other unsafe event which may result in fire. Preconnecting power devices during manufacturing without use of connectors may increase system safety by reducing the number of connection points from four per power device to two per power device. 
         [0007]    Certain embodiments of illustrative power-circuit chains may be wound around a storage spool similar to spools used for storing electrical cables, and deployed in photovoltaic installations by unrolling the spool and coupling the power devices to photovoltaic generators the power devices unwound from the spool. 
         [0008]    In some embodiments of illustrative power-circuit chains, a distance between adjacent power devices may correspond to an estimated distance between photovoltaic generator junction boxes in a photovoltaic installation, to enable adjacent power devices to be coupled to adjacent photovoltaic generators. In some embodiments, more than one photovoltaic generator may be coupled to each power device. For example, in some solar installations, two PV generators may be coupled in series and the two generators may then be coupled to one power device, in which case the length between adjacent power devices may be about double the distance between adjacent generators. 
         [0009]    The photovoltaic power devices may include, but are not limited to, DC/DC converters, DC/AC inverters, devices configured to measure and monitor photovoltaic parameters, communication devices, safety devices (e.g., fuses, circuit breakers and Residual Current Detectors) and/or Maximum Power Point Tracking (MPPT) devices. The power generation units may include, but are not limited to, photovoltaic modules (e.g. photovoltaic cells, photovoltaic generators), batteries, wind turbines, hydroelectric turbines and fuel cells. 
         [0010]    As noted above, this Summary is merely a summary of some of the features described herein and is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. The Summary is not exhaustive, is not intended to identify key features or essential features of the claimed subject matter and is not to be a limitation on the claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    These and other features, aspects, and advantages of the present disclosure will become better understood with regard to the following description, claims, and drawings. The present disclosure is illustrated by way of example, and not limited by, the accompanying figures. A more complete understanding of the present disclosure and the advantages thereof may be acquired by referring to the following description in consideration of the accompanying drawings, in which like reference numbers indicate like features, and wherein: 
           [0012]      FIGS. 1A-1E  are part schematic, part block diagrams of illustrative photovoltaic systems according to certain embodiments. 
           [0013]      FIGS. 2A-2C  depict photovoltaic power devices according to certain embodiments. 
           [0014]      FIG. 3  is part schematic, part block diagram depicting a photovoltaic power device according to certain embodiments. 
           [0015]      FIGS. 4A-4C  depict illustrative embodiments of strings of photovoltaic power devices coupled by conductors. 
           [0016]      FIGS. 5A-5C  depict illustrative embodiments of portions of photovoltaic strings, with a plurality of photovoltaic power devices coupled to each other by conductors and coupled to photovoltaic generators. 
           [0017]      FIG. 6  depicts an illustrative embodiment of a string of photovoltaic power devices coupled by conductors, stored on a storage device. 
       
    
    
     DETAILED DESCRIPTION 
       [0018]    In the following description of various illustrative embodiments, reference is made to the accompanying drawings, which form a part hereof, and in which is shown, by way of illustration, various embodiments in which aspects of the disclosure may be practiced. It is to be understood that other embodiments may be utilized and structural and functional modifications may be made, without departing from the scope of the present disclosure. 
         [0019]    Since power devices may often be used in bulk (e.g., one power device per photovoltaic generator may be used in a solar installation including multiple photovoltaic strings, each string including ten, twenty or more photovoltaic generators), costs may be reduced and deployment may be easier by packaging power devices in a form which enables multiple devices to be strung out and deployed at one time, along a photovoltaic string. Furthermore, use of a storage device such as a spool to wind multiple cable-connected devices around can make storage and deployment easier and cheaper. 
         [0020]    Referring to  FIG. 1A , illustrative photovoltaic installation  100   a  may include a plurality of photovoltaic (PV) modules  101   a - y . Photovoltaic generators may also be referred to as “photovoltaic modules”. Each PV generator  101   a - y  may be coupled to a photovoltaic power device  102   a - y.    
         [0021]    In some embodiments, one or more PV power device  102   a - y  may comprise a power conversion circuit such as a direct current—direct current (DC/DC) converter such as a buck, boost, buck-boost, flyback and/or forward converter. In some embodiments, one or more PV power device  102   a - y  may comprise a direct current—alternating current (DC/AC) converter, also known as an inverter or a microinverter. In some embodiments, one or more PV power device  102   a - y  may include a Maximum Power Point Tracking (MPPT) and/or Impedance Matching circuit with a controller, configured to extract regulated (e.g. increased) power from the PV generator the power device is coupled to. One or more PV power device  102   a - y  may further comprise a control device such as a microprocessor, Digital Signal Processor (DSP) and/or a field-programmable gate array (FPGA). In some embodiments, one or more PV power device  102   a - y  may comprise circuitry and/or sensors configured to measure parameters on or near the photovoltaic generator, such as the voltage and/or current output by the generator, the power output by the generator, the irradiance received by the generator and/or the temperature on or near the generator. 
         [0022]    In the illustrative embodiment depicted in  FIG. 1A , a plurality of PV power devices  102   a - m  are coupled in series, to form a first photovoltaic string  316   a . One terminal of the resultant photovoltaic string  316   a  may be coupled to a power bus, and the other terminal of the photovoltaic string  316   a  may be coupled to a ground bus. In some embodiments, the power and ground buses may be input to system power device  110 . System power device  110  may comprise a DC/AC converter, and the DC/AC converter may output AC power to the grid, home or other destinations. In some embodiments, the photovoltaic power devices may comprise microinverters, and an additional inverter (e.g. part of system power device  110 ) may not be included. In some embodiments, the power devices may output a time-varying DC signal which emulates a rectified sine wave, in which case system power device  110  may comprise a full-bridge circuit configured to convert the rectified sine wave to a standard, alternating sine wave. In some embodiments, system power device  110  may include a combiner box for combining power from a plurality of photovoltaic strings (e.g.  316   a - 316   n ). In some embodiments, system power device  110  may comprise sensors/sensor interfaces for measuring or receiving measurements of one or more parameters (e.g. current, voltage, power, temperature etc.) associated with PV strings  316   a - 316   n . In some embodiments, system power device  110  may include one or more safety switches for disconnecting and/or short circuiting PV strings  316   a - 316   n  in case of a potentially unsafe condition or in response to a manual trigger (e.g. activating a rapid-shutdown switch or button). 
         [0023]    Since PV power devices of known systems may be generally manufactured, packaged and sold separately, PV installations which include a plurality of PV generators, e.g., installation  100   a  may require unpacking a large number of devices, individually coupling each device to its corresponding photovoltaic generator, and then coupling the power devices to one another using cables which may be sold separately as well. In some embodiments introduced herein, a power device chain is provided. The power device chain may include a plurality of power devices each coupled to at least one other power device using conductors of appropriate length at the time of manufacturing. Accordingly, power device chains as described herein may be packaged and sold as a single unit, and deployed as a single unit when installing installation  100   a . For example, power devices  102   a - m  may comprise a string of power devices or part of a string of power devices, and may be coupled to one another during manufacturing. During installation, the string may simply be strung out alongside photovoltaic modules  101   a - m  and each device may be coupled to its corresponding module quickly and easily, forming photovoltaic string  316   a.    
         [0024]    As shown in  FIG. 1A , installation  100   a  may include a plurality of photovoltaic strings  316   a - n , with a terminal of each photovoltaic string  316   a - n  being coupled to the power bus and the other terminal being coupled to the ground bus. 
         [0025]    Referring now to  FIG. 1B , illustrative system  100   b  may share many of the same characteristics as illustrative installation  100   a  of  FIG. 1A , but the wiring of photovoltaic strings may differ in some respects. For example, in illustrative system  100   b , each photovoltaic power device  103   a - m  may be coupled to two photovoltaic generators. For example, photovoltaic power device  103   a  may be coupled to generators  101   a  and  101   b , power device  103   b  may be coupled to generators  101   b  and  101   c  (not shown), and so on. Wiring each photovoltaic string (e.g.  316   a ) in this manner may save money by requiring thinner and fewer cables to couple the power devices to the generators and to one another. 
         [0026]    In the illustrative embodiment show in  FIG. 1B , the power devices may be pre-coupled to one another during manufacturing, packaged and/or sold together, and deployed easily, similar to as described with reference to installation  100   a  shown in  FIG. 1A . For effective system operation and for easy and fast coupling of the power devices to the photovoltaic generator(s) the power devices are meant to be coupled to, the electrical and/or mechanical design of the power devices used for systems such as  100   a  may differ from the design used for systems such as  100   b . The pre-coupling, packaging and easy deployment described herein may be applied to different kinds of power devices used in different kinds of photovoltaic systems, regardless of mechanical design and electrical topology details which may be specific to certain power devices. 
         [0027]    Reference is now made to  FIG. 1C , which shows an illustrative embodiment of a photovoltaic string  316   a  in which each photovoltaic power device is coupled to two photovoltaic modules. In this embodiment, PV power devices  108   a - m  comprise Buck-Boost DC/DC converters. Additional circuitry may be included in power devices  108   a - m , but is not explicitly depicted in  FIG. 1C . Additional circuitry and/or wiring configurations may be used to couple power devices to photovoltaic generators according to various aspects of the present disclosure. 
         [0028]    Referring to  FIG. 1D , illustrative embodiments may include photovoltaic installation  100   d , comprising a plurality of photovoltaic generators  101   a - m  each coupled to a power device  122   a - m . Each power device may have two outputs, one coupled to a mutual power bus, and one coupled to a mutual ground bus, coupling all the power devices in parallel. In some embodiments, one or more power device  122   a - m  may comprise a DC/DC converter, with each converter&#39;s positive output coupled to the power bus, and the negative terminal coupled to the ground bus. In some embodiments, one or more power device  122   a - m  may comprise a DC/AC converter, with the AC outputs synchronized to allow parallel coupling. In some embodiments including an AC output by the power devices, the AC output may be a single phase coupled to the power and ground buses, and in some embodiments three or more phases may be output to more than two buses. The system may further include the power bus and ground bus being input to grid-coupling device  120 . In embodiments including a DC output by the power devices, grid coupling device  120  may include a DC/AC inverter. In embodiments including an AC output by the power devices, grid coupling device  120  may include a transformer. Grid coupling device  120  may be similar to or the same as system power device  110  of  FIG. 1A , and may comprise safety devices (e.g. sensors, circuit breakers, fuses, etc.) and/or control and/or monitoring devices. 
         [0029]    Referring to  FIG. 1E , more than one photovoltaic module may be coupled to each photovoltaic power device. System  100   e  includes two photovoltaic modules (e.g. photovoltaic panels or a different type of photovoltaic generator)  111   a ,  111   b  coupled to each other in series, with a photovoltaic power device  112   a  coupled in parallel to the serially coupled modules  111   a ,  111   b . Similar to other embodiments disclosed herein, a plurality of power devices  112   a - x  may be coupled in series to form a photovoltaic string  321   a , with multiple strings  321   a - n  coupled in parallel between the ground and power buses. In some embodiments, inverter  123  may receive a DC input from the ground and power buses and output AC power to the grid or home. In similar embodiments, the power devices may be precoupled to one another at the time of manufacturing, with the conductors coupling the power devices being sized to allow the desired number of photovoltaic generators to be coupled to each power device. For example, if each two PV generators are to be coupled to one another and to a single power device, the length of each conductor between power devices being around double the width or length of each photovoltaic module. 
         [0030]    Referring to  FIG. 2A , photovoltaic power device  102  may be configured in various ways. In one illustrative embodiment, photovoltaic power device  102  may comprise a casing  231  containing circuitry  230 , input terminals  210   c  and  210   d , and output conductors  220   c  and  220   d . In other embodiments, casing  231  may be replaced by a surface on which circuitry  230  is mounted, the surface being snapped to a different part of a photovoltaic apparatus such as a junction box. In some embodiments, there may be more than two input terminals. For example, some embodiments may include four input terminals for coupling the power device to two photovoltaic modules, the power device processing power input from both modules. 
         [0031]    In some embodiments, circuitry  230  may include a power conversion circuit such as a direct current—direct current (DC/DC) converter such as a buck, boost, buck-boost, Cuk, charge pump, flyback and/or forward converter. In some embodiments, circuitry  230  may include a direct current—alternating current (DC/AC) converter, also known as an inverter or a microinverter. In some embodiments, circuitry  230  may include a Maximum Power Point Tracking (MPPT) circuit with a controller, configured to extract increased power from the PV generator the power device is coupled to. Circuitry  230  may further comprise a control device such as a microprocessor, Digital Signal Processor (DSP) and/or an FPGA. In some embodiments, circuitry  230  may include circuitry and/or sensors configured to measure parameters on or near the photovoltaic generator, such as the voltage and/or current output by the generator, the power output by the generator, the irradiance received by the generator and/or the temperature on or near the generator. Input terminals  210   c  and  210   d  may be coupled to outputs of one or more photovoltaic modules, and may also be coupled to circuitry  230  for processing and/or measuring the power output by the corresponding photovoltaic module. Output conductors  220   c  and  220   d  may couple the photovoltaic power device to adjacent devices, to form a serial or parallel photovoltaic string. The input and output terminals may be physically connected to different parts of casing  231 . The input terminals  210   c  and  210   d  may be physically located next to one another along one side of casing  231 , with output conductors  220   c  and  220   d  occupying opposite sides of casing  231 , on either side of input terminals  210   c  and  210   d . In other embodiments, the input terminals and output conductors may be configured differently, as will be shown herein. The location of the input terminals and output conductors may be chosen considering the layout and wiring design of the system at hand. Mechanical considerations, such as enabling optimal storing of the entire chain of power devices, may also factor into designing the location of the input terminals and output conductors. The photovoltaic power device  102  shown in  FIG. 2A  may be particularly suited for coupling to a single photovoltaic generator (in systems such as those shown in  FIGS. 1A and 5A ), since the input terminals are next to each other, though photovoltaic power device  102  may also be deployed in a way that couples it to two generators. 
         [0032]    Referring now to  FIG. 2B , the input terminals and output conductors may be configured such that input terminal  210   a  is adjacent to output conductor  220   a , both connected to a side of casing  231 , and on the opposite side of casing  231  input terminal  210   b  is adjacent to output conductor  220   b . This illustrative embodiment may be particularly suited for coupling photovoltaic power device  103   a  to two photovoltaic generators (in systems such as those shown in  FIGS. 1B and 5B ), since the two input terminals may be coupled to two generators on either side of the power device, though photovoltaic power device  103   a  may also be deployed in a way that couples it to a single generator. 
         [0033]    Referring now to  FIG. 2C , the input terminals and output conductors may be configured such that input terminals  210   e  and  210   f  are located on opposing sides of casing  231 , while output conductors  220   e  and  220   f  are located on the other pair of opposite sides of casing. Thus, four sides of the casing contain either an input terminal or an output conductor. This illustrative embodiment may, in some configurations, enable optimal packaging of the chain of power devices and enable it to be stored in a compact convenient way. The chain according this embodiment can be deployed in a way that couples each power device to either one or two photovoltaic modules. 
         [0034]    Referring now to  FIG. 3 , the casing  231  may house circuitry  230 . In some embodiments, circuitry  230  may include power converter  240 . Power converter  240  may include a direct current-direct current (DC/DC) converter such as a buck, boost, buck-boost, flyback and/or forward converter. In some embodiments, power converter  240  may include a direct current—alternating current (DC/AC) converter, also known as an inverter or a microinverter. In some embodiments, circuitry  230  may include Maximum Power Point Tracking (MPPT) circuit  295 , configured to extract increased power from the PV generator the power device is coupled to. In some embodiments, power converter  240  may include MPPT functionality, and MPPT circuit  295  may not be included. Circuitry  230  may further comprise control device  270  such as a microprocessor, Digital Signal Processor (DSP) and/or an FPGA. Control device  270  may control and/or communicate with other elements of circuitry  230  over common bus  290 . In some embodiments, circuitry  230  may include circuitry and/or sensors  280  configured to measure parameters on or near the photovoltaic generator, such as the voltage and/or current output by the generator, the power output by the generator, the irradiance received by the generator and/or the temperature on or near the generator. In some embodiments, circuitry  230  may include communication device  250 , configured to transmit and/or receive data and/or commands from other devices. Communication device  250  may communicate using Power Line Communication (PLC) technology, or wireless technologies such as ZigBee, Wi-Fi, cellular communication or other wireless methods. In some embodiments, PLC signals may be transmitted and/or received over output conductors  220   a  and/or  220   b . In some embodiments, a communications link (e.g. an optical fiber) may be integrated with output conductors  220   a  and/or  220   b  and may be communicatively coupled to communication device  250 . In some embodiments, a thermal sensor device (e.g. a thermocouple device or a Linear Heat Detector) may be integrated with output conductors  220   a  and  220   b  and may provide temperature measurements (e.g. measurements obtained at various locations along output conductors  220   a  and  220   b ) to control device  270 . Input terminals  210   a  and  210   b  may be coupled to outputs of one or more photovoltaic modules, and may also be coupled to circuitry  230  for processing and/or measuring the power output by the corresponding photovoltaic module. In some embodiments, circuitry  230  may include safety devices  260  (e.g. fuses, circuit breakers and Residual Current Detectors). The various components of circuitry  230  may communicate and/or share data over common bus  290 . 
         [0035]      FIG. 4A  depicts an illustrative embodiment of chain  410 . Chain  410  may comprise plurality of photovoltaic power devices  411   a - c  coupled by plurality of conductors  412   a - d . In some embodiments, a chain of photovoltaic power devices similar to chain  410  may comprise ten, twenty or even a hundred photovoltaic power devices. In some embodiments, chain  410  may be manufactured and/or sold as a single unit. Photovoltaic power devices  411   a - c  may be similar to or the same as photovoltaic power devices described herein, for example, photovoltaic power device  102  of  FIG. 2A , or photovoltaic power device  103   a  of  FIG. 2B . Conductors  412   a - d  may be directly coupled (e.g. connected) to the output terminals of a DC/DC converter or DC/AC inverter included in a photovoltaic power device (e.g.  411   a - c ). The length of each output conductor  412   a - d  may be appropriate to enable each PV power device to be coupled to photovoltaic generators in a photovoltaic string. Since different PV generators may have different dimensions, and since the PV generators may be oriented differently during deployment, the distance between power devices (i.e., the length of each output conductor) may vary in different chains. However, many PV generators (e.g. PV panels) are of similar dimensions, and PV panels are generally oriented in one of two ways (vertically, aka “portrait”, or horizontally, aka “landscape”), so a chain of photovoltaic power devices (e.g. chain  410 ) featuring a standard distance between power devices may be deployed many photovoltaic systems. For example, photovoltaic panels are generally manufactured in standard sizes, such as around  65  by around  39  inches for residential installations or around  77  by around  39  inches for commercial installations. Therefore, chains of power devices configured to be deployed with panels of dimensions similar to those cited above may include conductors which are around  39 , around  65  or around  77  inches long. While the input terminals and output conductors  412   a - d  of illustrative power devices  411   a - c  denoted in  FIG. 4A  are located similarly to what is shown in  FIG. 2B , this does not rule out embodiments in which the input terminals and output conductors are located similarly to what is shown in  FIG. 2A , or various other configurations without departing from the scope of the present disclosure. 
         [0036]    Conductors  412   a - 412   d  may be (e.g. during manufacturing or chain  410 ) internally connected to circuitry (e.g. circuitry  230  of  FIG. 3 ) inside photovoltaic power devices  411   a - 411   c  at the time of manufacturing. For example, conductor  412   b  may, at a first end, be soldered or connected via a screw to a power converter or monitoring device in photovoltaic power device  411   a , and at a second end, be soldered or connected via a screw to a power converter or monitoring device in photovoltaic power device  411   b . Preconnecting conductors between power devices may reduce the number of connectors (e.g. MC4™ connectors) featured in each power device from four (two connectors for connecting to a PV generator at the power device input and two connectors for connecting between power devices at the power device output). As connectors may be costly components, substantial savings may be realized. Additionally, preconnecting power devices during manufacturing may increase system safety. For example, if improperly connected, connection points between power devices may be susceptible to overheating, arcing and/or other unsafe event which may result in fire. Preconnecting conductors between power devices during manufacturing without use of connectors may increase system safety by reducing the number of connection points from four per power device to two per power device. 
         [0037]    Referring now to  FIG. 4B , a chain of photovoltaic power devices  104  may comprise output conductors which double as ground and power buses of a parallel-connected photovoltaic installation, similar to the system shown in  FIG. 1D . Input terminals  106  may be coupled to the outputs of a photovoltaic system. Output conductor  105   a  may be coupled to the power bus using a T-connector, and output conductor  105   b  may be coupled to the ground bus using a T-connector. The input terminals  106  and output conductors  105   a ,  105   b  are denoted explicitly in  FIG. 4B  only for power device  104   a , to reduce visual noise. One or more power device  104   a - c  may comprise a DC/DC converter or DC/AC inverter configured to output a DC or AC voltage common to all parallel-connected devices. In some embodiments, one or more power device  104   a - c  may comprise a Maximum Power Point Tracking (MPPT) circuit with a controller, configured to extract maximum power from the PV generator the power device is coupled to. One or more power device  104   a - c  may further comprise a control device such as a microprocessor, Digital Signal Processor (DSP) and/or an FPGA. In some embodiments, one or more power device  104   a - c  may comprise circuitry and/or sensors configured to measure parameters on or near the photovoltaic generator, such as the voltage and/or current output by the generator power output by the generator, the irradiance received by the generator and/or the temperature on or near the generator. The power device chain  104  in the illustrative embodiment shown in  FIG. 4B  may include two long conductors, ground bus  116  and power bus  115 , with PV power devices coupled to the two conductors, with the distance between adjacent power devices enabling them to be coupled to adjacent PV generators in a photovoltaic installation. The power devices may be coupled to the conductors at the time of manufacturing, and may be compactly stored along with the conductors, enabling fast and easy deployment. 
         [0038]    Referring now to  FIG. 4C , illustrative embodiments of photovoltaic power device  107  may feature an open casing or lid  232  instead of a closed casing such as casing  231  depicted in  FIG. 2A . Lid  232  may include circuit-mounting surface  233  which may be used to mount circuitry  230 . Circuitry  230  may comprise any and/or all of the components described herein with reference to other figures. For example, circuitry  230  may comprise a power converter such as a DC/DC or a DC/AC converter. As another example, circuitry  230  may comprise a monitoring device in addition to or instead of a power converter. In some embodiments, power device  107  may be designed to be connectable to a portion of a photovoltaic panel junction box, enabling circuitry  230  to be coupled directly to the electronics located in the panel&#39;s junction box. In some embodiments, PV power device  107  may comprise bypass and/or blocking diodes to prevent and alleviate mismatch effects in the solar arrays comprising the PV panel. In some embodiments, direct coupling of the lid to a photovoltaic generator junction box may render external input terminals unnecessary. Output conductors  234   a - b  may be located on opposite sides of lid  232 , and may be coupled to additional power devices (not depicted explicitly in the figure), forming a chain of serially connected devices. Similar to other illustrative embodiments, the distance (i.e. the length of the coupling conductor) between adjacent power devices  107  may be of appropriate length enabling coupling of adjacent power devices to adjacent photovoltaic modules in a photovoltaic installation. The power devices may be coupled to the conductors at the time of manufacturing, and may be compactly stored along with the conductors, enabling fast and easy deployment. 
         [0039]    Reference is now made to  FIG. 5A , which depicts a portion of a chain of power devices coupled to photovoltaic generators, according to illustrative embodiments. PV generator  101   e  may include junction box  601   e , featuring two outputs which may be coupled to input terminals  210   q  and  210   r  of power device  102   e . Power generated by the PV generator may be transferred via the junction box to the power device via the input terminals  210   q  and  210   r , which may be coupled directly to the junction box. Power device  102   e  may further include circuitry  230  (not explicitly depicted in the figure) which may comprise various elements as described herein. Output conductor  220   e  may couple power device  102   e  to an adjacent power device on one side (not shown explicitly), while output conductor  220   f  may couple power device  102   e  to an adjacent power device  102   f  on the other side, with output conductor  220   f  coupling power device  102   f  to power device  102   g . To reduce visual noise, the input terminals and output conductors of power devices  102   f ,  102   g  are not labeled explicitly in the figure. Conductors  220   e ,  220   f  and  220   g  may be of appropriate length to enable fast and easy coupling of each of the power devices to their respective generators, without overuse of conductive cables. For example, if PV modules  101   e ,  101   f  and  101   g  are of standard width of 39 inches and are placed next to one another while oriented vertically, each output conductor may be about 40-45 inches long. 
         [0040]    Reference is now made to  FIG. 5B , which depicts a portion of a chain of power devices coupled to photovoltaic generators, according to illustrative embodiments. PV generator  101   a  may include junction box  601   a , to which generator cables  501   a  and  501   b  are coupled. Power generated by the PV generator is transferred via the junction box to the generator cables, with cable  501   a  coupled to input terminal  210   b  of power device  102   a , and cable  501   b  coupled to input terminal  210   c  of power device  102   b . Power devices  102   a  and  102   b  may be coupled to one another by output conductor  220   b . Power device  102   a  may include circuitry  230  (not explicitly depicted in the figure) which may comprise various elements as described herein. Output conductor  220   a  may couple power device  102   a  to an adjacent power device on one side (not shown explicitly), with input terminal  210   a  being coupled to an adjacent power cable (also not shown explicitly). To reduce visual noise, the input terminals and output conductors of power devices  102   b ,  102   c  are not labeled explicitly in the figure. Conductors  220   a , 220   b  and  220   c  may be of appropriate length to enable fast and easy coupling of each of the power devices to two adjacent photovoltaic modules, without overuse of conductive cables. For example, if PV generators  101   a    101   b  and  101   c  are of standard width of 39 inches and are placed next to one another while oriented vertically, each output conductor may be about 40-45 inches long. 
         [0041]    Referring to  FIG. 5C , illustrative embodiments may include a plurality of PV power devices  104   a - c , each featuring two input terminals  106  (only labeled explicitly for power device  104   a ) coupled to a photovoltaic generator&#39;s junction box (e.g.,  601   a ). The photovoltaic power may flow via the junction box and input terminals to the PV power device. The power device may include output conductor  105   a , which is coupled via a T-connector to a ground bus, and output conductor  105   b , which is coupled via a T-connector to a power bus. The ground bus and power bus may be coupled to the output conductors of each power device in the chain, thus coupling all the photovoltaic modules in the string in parallel. The distance between adjacent PV power devices may enable them to be coupled to adjacent PV generators in a photovoltaic installation. The power devices may be coupled to the two conductors (the ground and power buses) at the time of manufacturing, and may be compactly stored along with the conductors, enabling fast and easy deployment. 
         [0042]    Referring now to  FIG. 6 , some illustrative embodiments include a storage device used to store a chain of power devices in a way that enables convenient storing and fast and easy deployment of the chain of power devices. A chain of photovoltaic power devices may comprise PV power devices  102  coupled to one another by output conductors  220 . The chain may be stored by being wound around storage device  400 . In the illustrative embodiment depicted in  FIG. 6 , storage device  400  is a cylindrical reel, though other shapes may be using for winding. A cylindrical shape may make deployment easier, as a cylindrical reel may be rolled along the ground in a photovoltaic installation, much like cabling reels. The storage device may be designed to allow the chain of power devices to be packaged efficiently. For example, if the storage device is similar to the cylindrical reel depicted in  FIG. 4 , the diameter of the reel may be chosen considering the length of the conductors coupling the power devices, so that when the chain is wound around the reel, the power devices may be located next to one another on the reel, pressed tightly together for compact storing. 
         [0043]    In some embodiments, an apparatus includes a plurality of power devices and a plurality of photovoltaic generators connected to the power devices. The power devices may include an input terminal, a common terminal and first and second output terminals. An input terminal of a first power device may be connected to a first power source terminal of one of the plurality of photovoltaic generators, a first output terminal of a second power device may be connected to a second power source terminal of one of the plurality of photovoltaic generators, and a second output terminal of the second power device may be connected to a common terminal of the first power device. The first and second output terminals may output a common output voltage, with a total output current flowing through the power device (e.g. a photovoltaic string current where the power device is part of a photovoltaic string) being divided between a first output current flowing through the first output terminal and a second output current flowing through the second output terminal. The first output current may further flow through a connected photovoltaic generator, and in some embodiments, the power device may be operated to provide a first output current corresponding to a Maximum Power Point current of the photovoltaic generator. The power device may be operated to provide a second output current corresponding to a differential current between the total output current and the first output current. 
         [0044]    In some embodiments, the first output terminal may comprise a connector designed to be connected to a photovoltaic generator terminal, for example, using an MC4™ connector. In some embodiment, the second output terminal and the common terminal may comprise conductors preconnected to the power device and other power devices (e.g. conductors  220   c  and  220   d  of  FIG. 2A , or conductors  220   a  and  220   b  of  FIG. 2B ). Dividing the current of a power device into two or more portions may create smaller current portions that allow for cables which may be thinner and cheaper than those which would otherwise be needed. 
         [0045]    At least one of the power devices may include a combiner box configured to couple to a plurality of photovoltaic strings and to combine power from the plurality of photovoltaic strings. One or more power devices may include one or more sensors or sensor interfaces configured to measure or to receive measurements of one or more parameters associated with the plurality of photovoltaic generators. One or more power devices may include one or more safety switches configured to disconnect and/or short circuit the photovoltaic generators upon detection of a predefined potentially unsafe condition or in response to a manual trigger. The manual trigger may include activation of a rapid-shutdown switch or button. 
         [0046]    In some embodiments, the power device may include output conductors configured to transmit and/or receive PLC signals. A communications link (e.g. may be integrated with output conductors and may be communicatively coupled to a communication device. A thermal sensor device may be integrated with output conductors and may provide temperature measurements to a control device associated with the apparatus. The thermal sensor device may include a thermocouple device and/or a linear heat detector. Temperature measurements by the thermal sensor device may be obtained at one or more locations along the output conductors. 
         [0047]    In some embodiments, an apparatus includes a plurality of power devices and a plurality of conductors connecting, each connecting one power device to at least one other power device. A first conductor may be connected between an input of a first power device and a first output of a first power generator. A second conductor may be connected between an output of the first power device and a second output of first power generator. A third conductor may be connected between an output of a second power device and the common terminal of the first power device. The conductors may be internally connected to circuitry inside a respective power device. At least one of the plurality of conductors may, at a first end, be soldered or connected via a screw to the power device. A second end of the conductor may be soldered or connected via a screw to another power device. Specifically, the first end and second end may each be connected to a power converter or monitoring device in a respective power device. 
         [0048]    Other embodiments may consider alternative storage techniques, such as packing power device chains into boxes, winding the chain around multiple poles, and the like. 
         [0049]    Although selected embodiments of the present invention have been shown and described, it is to be understood the present invention is not limited to the described embodiments. Instead, it is to be appreciated that changes may be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and the equivalents thereof. Further, elements of one embodiment may be combined with elements from other embodiments in appropriate combinations or subcombinations. For example, conductors  234   a - b  of  FIG. 4C  may be located at a same side of lid  232 , similarly to as shown with regard to terminals  210   c  and  210   d  of  FIG. 2A . As another example, a chain of power devices may connect a plurality of photovoltaic generators in parallel, as shown in  FIG. 5C , wherein each of the plurality of photovoltaic generators comprises a plurality of serially connected photovoltaic panels (as shown in  FIG. 1E ) or photovoltaic cells. 
         [0050]    In illustrative embodiments disclosed herein, photovoltaic generators are used as examples of power sources which may make use of the novel features disclosed. Each PV generator may comprise one or more solar cells, one or more solar cell strings, one or more solar panels, one or more solar shingles, or combinations thereof. In some embodiments, the power sources may include batteries, flywheels, wind or hydroelectric turbines, fuel cells or other energy sources in addition to or instead of photovoltaic panels. Systems, apparatuses and methods disclosed herein which use PV generators may be equally applicable to alternative systems using additional power sources, and these alternative systems are included in embodiments disclosed herein.