Abstract:
A system for automatically commissioning a solar panel array comprises a plurality of panel monitoring devices, each panel monitoring device connected between a positive and negative terminal of a solar panel. Each panel monitoring device comprises a switching device, the switching device configurable to disconnect an output from the solar panel. The system further comprises logic configured to automatically obtain a relative position of each panel monitoring device in the system by appointing serially a series of masters from among the panel monitoring devices, each master in turn broadcasting a unique identifier and enabling its output. Each panel monitoring device listens to the masters&#39; broadcasts and stores in memory the unique identifier and information indicating whether the panel monitoring device detected the masters&#39; voltage. The panel monitoring devices determine their respective locations by analyzing the information broadcast by, and the voltage detected from, the masters.

Description:
BACKGROUND AND SUMMARY 
       [0001]    Large solar panel fields may comprise many hundreds or many thousands of individual solar panels. Commissioning a solar panel field requires knowing the precise position of each solar panel in the field relative to the other solar panels in the field. The solar panels must be mapped with respect to each other, so that it is known what solar panels share a circuit, are in series, in parallel and the like. Such mapping of the solar panels in a large field can be labor intensive. One way this commissioning is done is by using a bar code reader and scanning individual solar panels and their related panel monitoring devices. Scanning and mapping by hand can take a lot of time and resources. 
         [0002]    A system for automatically commissioning a solar panel array comprises a plurality of panel monitoring devices, each panel monitoring device connected between a positive and negative terminal of a solar panel. Each panel monitoring device comprises a switching device, the switching device configurable to disconnect an output from the solar panel. The system further comprises logic configured to automatically obtain a relative position of each panel monitoring device in the system by appointing serially a series of masters from among the panel monitoring devices, each master in turn broadcasting a unique identifier and enabling its output. Each panel monitoring device listens to the masters&#39; broadcasts and stores in memory the unique identifier and information indicating whether the panel monitoring device detected the masters&#39; voltage. The panel monitoring devices determine their respective locations by analyzing the information broadcast by, and the voltage detected from, the masters. 
         [0003]    A method according to the present disclosure comprises connecting the panel monitoring device to each of the plurality of solar panels; selecting a panel monitoring device to be a master; connecting the output to the solar panel associated with the master and causing the master to broadcast wirelessly a unique identifier, the broadcast receivable by panel monitoring devices in the field; logging in memory, by the panel monitoring devices that are not the master, the unique identifier broadcast by the master; measuring an output voltage of each panel monitoring device and logging in each panel monitoring device&#39;s memory whether the output voltage of that panel monitoring device is greater than a threshold voltage, the panel monitoring devices that detect an output voltage greater than a threshold voltage comprising a first combiner box group; selecting from with the first combiner box group a new master; and repeating these steps until all of the panel monitoring devices in the first combiner box group have logged information sufficient to determine what string each of the panel monitoring devices in the first combiner box group are in. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0004]      FIG. 1  is a block diagram illustrating a system in accordance with an exemplary embodiment of the present disclosure. 
           [0005]      FIG. 2  depicts an exemplary panel monitoring device as depicted in  FIG. 1 . 
           [0006]      FIG. 3  depicts an exemplary gateway as depicted in  FIG. 1 . 
           [0007]      FIG. 4  depicts an exemplary server as depicted in  FIG. 1 . 
           [0008]      FIG. 5  is a flowchart depicting exemplary architecture and functionality of the system logic in accordance with an exemplary embodiment of the disclosure. 
           [0009]      FIGS. 6 a  and 6 b    depict a method utilizing exemplary architecture and functionality of the controller logic of the panel monitoring device of  FIG. 1 , in accordance with an exemplary embodiment of the disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0010]      FIG. 1  illustrates a system  100  in accordance with an exemplary embodiment of the present disclosure. The system comprises a plurality of solar panels  101  coupled in series to form into strings  106 . A plurality of strings  106  coupled in parallel form an array  177 . Although the illustrated embodiment shows four (4) panels  101  in a string  106 , and shows two (2) strings  106  in the array  177 , the illustration is for explanatory purposes and there may be many more panels  101  in a string  106  and many more strings  106  in an array  177 . 
         [0011]    A combiner box  103  coupled to the plurality of strings  106  combines the current from the strings  106  into a single combined flow of current that represents a cumulative current from each of the strings  106  of combined panels  101 . The combiner box  103  is coupled to an inverter (not shown) that receives the output current, which is DC, and converts the current from DC to alternating current (AC) so that the energy can be applied to a power grid (not shown) for commercial consumption, if desired. 
         [0012]    In the illustrated embodiment, a panel monitoring device  102  monitors each panel  101 . The panel monitoring device  102  is installed between the positive and negative terminals of the panel  101 , so that the panel monitoring device can measure the panel&#39;s voltage and current (not shown). The panel monitoring device  102  obtains power for its operation from the solar panel  101 . 
         [0013]    A combiner box (CB) monitor  107  communicates wirelessly with the panel monitoring devices  102 . In the illustrated embodiment, the CB monitor  107  couples with and generally resides inside the combiner box  103 . In this regard, the CB monitor obtains power for its operation from the combiner box  103 . 
         [0014]    The CB monitor  107  collects data generally wirelessly from the panel monitoring devices  102 . There may be hundreds of panel monitoring devices  102  that are monitored by one CB monitor  107 . In some embodiments, the CB monitor also interfaces electrically with each string  106  so that it can collect voltage and current from the strings  106 . 
         [0015]    A gateway  109  comprises a router or a proxy server (not shown) that routes signals received from the CB monitor  107  to a server  110 . In the illustrated embodiment, neither the CB monitor  107  nor the panel monitoring devices  102  communicate directly with the server  110 . Rather, the CB monitor  107  collects data from the panel monitoring devices  102  and communicates that data to the gateway  109 . In the illustrated embodiment, the server  110  is offsite from the solar array  177 . In other embodiments, the server  110  may be combined with the gateway  109  onsite, or may be onsite and may communicate locally with the gateway  109 . 
         [0016]    The gateway  109  comprises an internet interface and communicates with the server  110  via the internet. In one embodiment, the communication between the gateway  109  and the CB monitor  107  and panel monitoring devices  102  is via a wireless backhaul network (not shown). In other embodiments, the communication may be via a wired network. 
         [0017]    Other embodiments may not include the combiner box  107  and in those embodiments, the panel monitoring devices  102  may communicate directly to the gateway  109 . In still other embodiments, the panel monitoring devices  102  may operate independently and communicate directly to the server  110 . 
         [0018]    During operation, the server  110  further communicates with the access device  111 . The access device  111  may be a computer located at, for example, a customer&#39;s office (not shown). In this regard, the access device is generally not onsite. Upon request from the access device  111  initiated by a user or customer (not shown), the server  110  may transmit data to the access device  111  for display to the user indicative of the performance of solar panels  101  in the customer&#39;s solar array  177 . The customer may access the server  110  via a web-based cloud account, for example. 
         [0019]    From the access device  111 , the user may transmit commands to the server  110  for controlling the panel monitoring devices  102 . Thus, the access device  111  remotely interfaces with and performs operations related to the system  100 . The access device  111  may be any suitable computer known in the art or future-developed. In one embodiment, the access device  111  is a “thin client” device which depends primarily on the server  110  for processing activities, and focuses on conveying input and output between the user and the server  110 . In one embodiment the access device  111  is a personal computer. In other embodiments, the access device  111  is a personal digital assistant (PDA), cellular or mobile phone, radio system, or the like. 
         [0020]    In one embodiment, the server  110  comprises a Web Services application (not shown). The Web Service application provides a plurality of Web application program interfaces (APIs) that allow the data access device  111  to perform operations related to the system  100  through the server  110 . 
         [0021]    The network  105  may be of any type network or networks known in the art or future-developed, such as the internet backbone, Ethernet, IEEE 802.15, IEEE 802.11, WiMax, broadband over power line, coaxial cable, and the like. The network  105  may be any combination of hardware, software, or both. 
         [0022]      FIG. 2  depicts a panel monitoring device  102  of the present disclosure. The exemplary panel monitoring device  102  generally comprises a processing unit  204 , a voltmeter  217 , a switching device  209 , and a controller communication device  212 , all communicating over local interface  206 . 
         [0023]    The panel monitoring device  102  further comprises controller logic  214  and controller data  223 . The controller logic  214  and controller data  223  can be software, hardware, or a combination thereof. In the exemplary panel monitoring device  102 , the controller logic  214  and controller data  223  are shown as software stored in memory  202 . The memory  202  may be of any suitable type of computer memory known in the art, such as RAM, ROM, flash-type, and the like. 
         [0024]    As noted herein, the controller logic  214  and the controller data  223  are shown in  FIG. 2  as software stored in memory  202 . When stored in memory  202 , the controller logic  214  and the controller data  223  can be stored and transported on any computer-readable medium for use by or in connection with an instruction execution system, apparatus, or device, such as a computer-based system, processor-containing system, or other system that can fetch the instructions from the instruction execution system, apparatus, or device and execute the instructions. In the context of this document, a “computer-readable medium” can be any means that can contain, store, communicate, propagate, or transport the program for use by or in connection with the instruction execution system, apparatus, or device. The computer readable medium can be, for example but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, device, or propagation medium. 
         [0025]    The processing unit  204  may be a digital processor or other type of circuitry configured to run the controller logic  214  by processing and executing the instructions of the controller logic  214 . The processing unit  204  communicates to and drives the other elements within the panel monitoring device  102  via the local interface  206 , which can include one or more buses. 
         [0026]    The controller communication device  212  is a device through which the panel monitoring device  102  communicates over the network  105 . For example, the communication device  212  may be a Global System for Mobile Communications (GSM) cellular radio port or other type network device, that connects the panel monitoring device  102  with the network  105  for communication with the CB monitor  107  ( FIG. 1 ). The communication device  212  may comprise any number of communications mediums known in the art, for example a wireless solution such as Ethernet, WiMAX, fiber optic, power line carrier (PLC), or the like. 
         [0027]    The switching device  209  interfaces with the solar panel  101  ( FIG. 1 ) output (not shown) and controls the solar panel&#39;s output during data measurement operations. For example, during operation, the controller logic  214  sends commands to the switching device  209 , and in response, the switching device  209  connects and disconnects the solar panel output as needed in the performance of the methods discussed herein. The switching device  209  comprises a plurality of electrical relays, transistors, or other switching devices (not shown). 
         [0028]    The switching device  209  may be hardware or a combination of hardware and software. The operation of the switching device  209  may be controlled automatically (via controller logic  214  ) or remotely through commands sent from the server  110  via the gateway  109  to the CB monitor  107  and to the panel monitoring device  102 . 
         [0029]    The controller logic  214  also downloads controller data  223  to the CB monitor  107  via the communication device  212 . The controller communication device  212  interfaces the panel monitoring device  102  with the network  105  and may comprise software, hardware, or a combination thereof. The controller communication device  212  may consist of, for example, a LAN radio, a WAN radio, an AMPS radio, or other devices suitable for connection to network  105 . 
         [0030]    The controller logic  214  further communicates with the voltmeter  217 . The voltmeter  217  may be hardware, software, firmware, or a combination. The controller logic  214  measures and records the open circuit voltage (not shown) across the solar panel  101  during operation of the system  100 , as further discussed herein. The controller logic  214  is further discussed with respect to  FIGS. 6 a  and 6 b    herein. 
         [0031]    The controller data  223  may comprise the solar panel  101  location, the recorded voltage data, the information indicating whether a panel monitoring device  102  has detected voltage from a master PMD (as further discussed herein) and other such data. 
         [0032]      FIG. 3  depicts an exemplary CB monitor  107  according to the present disclosure. The CB monitor  107  communicates with the panel monitoring devices  102  ( FIG. 1 ) via the network  105 . In this regard, the CB monitor  107  receives data from the panel monitoring devices  102  and stores the data as CB monitor data  323 . 
         [0033]    The CB monitor  107  further communicates with the gateway  109  via the network  105 . In this regard, the CB monitor sends and receives data to/from the gateway  109  and stores the data as CB monitor data  323 . 
         [0034]    The CB monitor  107  generally comprises a data processing unit  304 , CB monitor logic  314 , CB monitor data  323 , and CB monitor interface logic  313 . The data processing unit  304  may be a digital processor or other type of circuitry configured to run the CB monitor logic  314  by processing and executing the instructions of the CB monitor logic  414 . The data processing unit  304  communicates to and drives the other elements within the CB monitor  107  via a local interface  306 , which can include one or more buses. 
         [0035]    A data input device  308 , for example, a keyboard, a switch, a mouse, and/or other type of interface, can be used to input data from a user (not shown) of the CB monitor. An exemplary data input device  308  may include, but is not limited to, a keyboard device, serial port, scanner, camera, microphone, or local access network connection. An exemplary data output device  324  may include, but is not limited to, a computer display. 
         [0036]    The CB monitor data  323  comprises data obtained from the panel monitoring devices  102  that the CB monitor collects and passes on to the gateway  109 . 
         [0037]    In the exemplary CB monitor  107  of  FIG. 4 , the CB monitor logic  314 , CB monitor data  323 , and CB monitor interface logic  313  are shown as being implemented in software and stored in CB monitor memory  402 . However, the CB monitor logic  314 , CB monitor data  323 , and CB monitor interface logic  313  may be implemented in hardware, software, or a combination of hardware and software in other embodiments. 
         [0038]    In one embodiment of the system  100 , the CB monitor logic  314  manages data flow between the panel monitoring devices  102  and the gateway  109 . Other embodiments of the system  100  may not use a CB monitor  107  at all. 
         [0039]    The CB monitor  107  further comprises CB monitor interface logic  313 . During operation of the system  100  ( FIG. 1 ), the CB monitor logic  314  may receive from a gateway  109  a request for information about the array  177  ( FIG. 1 ). The CB monitor logic  314  stores data in CB monitor data  323  indicative of the information request. When such data is stored in CB monitor data  323 , the CB monitor interface logic  313  transmits a request to the panel monitoring devices  102 . After the CB monitor  107  receives the requested information back from the panel monitoring devices  102 , the CB monitor  107  communicates the data to the CB monitor interface logic  313  via communication device  312 . Communication device  312  may be a modem, T1 line, router, wireless communication device, or the like. Upon receipt of the relay status data, the CB monitor interface logic  313  stores data indicative of the array status in CB monitor data  323 . The CB monitor interface logic  313  translates communications between the gateway  109  and the CB monitor logic  314 . 
         [0040]      FIG. 4  depicts an exemplary server  110  according to the present disclosure. The server  110  communicates with the gateway  109  via the network  105 . In this regard, the server  110  receives data from the gateway  109  and stores the data as server data  423  on the server  110 . 
         [0041]    The server  110  generally comprises a data processing unit  404 , server logic  414 , server data  423 , and interface logic  413 . The data processing unit  404  may be a digital processor or other type of circuitry configured to run the server logic  414  by processing and executing the instructions of the server logic  414 . The data processing unit  404  communicates to and drives the other elements within the server  110  via a local interface  406 , which can include one or more buses. 
         [0042]    A data input device  408 , for example, a keyboard, a switch, a mouse, and/or other type of interface, can be used to input data from a user (not shown) of the server  110 . An exemplary data input device  408  may include, but is not limited to, a keyboard device, serial port, scanner, camera, microphone, or local access network connection. An exemplary data output device  424  may include, but is not limited to, a computer display. 
         [0043]    In the exemplary server  110  of  FIG. 4 , the server logic  414 , server data  423 , and interface logic  413  are shown, as indicated above, as being implemented in software and stored in data server memory  402 . However, server logic  414 , server data  423 , and interface logic  413  may be implemented in hardware, software, or a combination of hardware and software in other embodiments. In one embodiment, server logic  414  is software stored in memory  402 . Notably, server logic  414  can also be a web service application. 
         [0044]    The server logic  414  manages data flow between the gateway  109  and the server  110 . In addition, the server logic  414  manages data flow between the access device  111  and the server  110 . 
         [0045]    The server  110  further comprises interface logic  413 . During operation of the system  100  ( FIG. 1 ), the server logic  414  may receive from an access device  111  a request for information about the array  177  ( FIG. 1 ). The server logic  414  stores data in server data  423  indicative of the request. When such data is stored in server data  423 , the interface logic  413  transmits a request to the gateway  109  ( FIG. 1 ), and the gateway  109  transmits the request to the CB monitor  107 . After the gateway  109  receives the requested information back from the CB monitor, the gateway  109  communicates the information to the interface logic  413  via communication device  412 . Communication device  412  may be a modem, T1 line, router, wireless communication device, or the like. Upon receipt of the status data, the interface logic  413  stores data indicative of the information in server data  423 . Interface logic  413  translates communications between the gateway  109  and the server logic  414 . 
         [0046]      FIG. 5  depicts a method  500  utilizing exemplary architecture and functionality of the system logic (not shown) in accordance with an exemplary embodiment of the disclosure. In step  501  of the method  500 , a coordinator selects a random panel monitoring device (“PMD”)  102  ( FIG. 1 ) to be the “new master” and the new master PMD enables its output. The coordinator may be a processor (not shown) in the gateway, one of the panel monitoring devices itself, the access device  111  ( FIG. 1 ), or some other computer in the system. At step  501 , all of the other panel monitoring devices in the system are in a “listen” mode, with their outputs disconnected. 
         [0047]    In step  502 , the new master PMD announces a unique combiner box identifier and string identifier. The PMD may be provided the combiner box identifier and string identifier by the coordinator, or may generate the identifiers itself. The combiner box identifier is a unique identifier that will indicate which PMDs are on a particular combiner box  103  ( FIG. 1 ), or on a particular circuit, for circuits that may not have combiner boxes. The string number identifier is a unique identifier that will indicate which PMDs are on a particular string  106  ( FIG. 1 ). The new master PMD broadcasts the unique combiner box identifier and string identifier wirelessly, such that all of the PMDs in the field should be able to receive the broadcast. 
         [0048]    In step  503 , all PMDs that have not previously been grouped will log the combiner box identifier and string identifier broadcast by the new master. The PMDs will also in this step measure their output voltage. PMDs that are on the same combiner box as the new master PMD, that are not on the same string as the new master PMD, will be able to detect the voltage of the new master PMD. Each PMD will log in a table whether or not the PMD detects the voltage of the new master PMD, as further discussed herein. 
         [0049]    In step  504 , all ungrouped PMDs compare their present detection status to their previous detection status to determine their grouping status. In this regard, if a PMD detects a voltage above the detection threshold, it knows that it is on the same combiner box as the master at the time of detection. For the PMDs that are on the same combiner box as the master, if the PMD previously did not detect an output voltage (from a previous master), but presently does detect an output voltage (from the new master), the PMD knows that it is on the same string as the previous master. If a PMD previously did detect an output voltage, but presently does not detect an output voltage, then the PMD knows that it is on the same string as the present master. 
         [0050]    In this method, each PMD logs in a table its previous detection status and its present detection. Thus it follows that after an initial broadcast/output enabling by the first new master, each PMD would not have a previous status for comparison purposes, and the first actual grouping of PMDs would after the second new master does its initial broadcast/output enabling. 
         [0051]    In steps  505  and  506 , the new master PMD queries all PMDs and asks for a response from any PMDs who have not previously been grouped, but who now measure voltage above the detection threshold. In step  508 , any PMDs who respond to this query are on the same combiner box as the new master. 
         [0052]    In steps  507  and  509 , the new master PMD queries all PMDs which of them have not been grouped yet. In step  512 , if any PMDs respond, all of the PMD tables are cleared, and in step  511 , a new combiner box identifier is generated. Step  501  is then repeated for a new master chosen randomly from the PMDs who have not yet been grouped. Steps  501  through  509  are repeated until all PMDs have been grouped. 
         [0053]    In step  510 , if no PMDs respond to the query of steps  507  and  509 , then all PMDs now know their string identifiers and combiner box identifiers, as further discussed herein. 
         [0054]      FIGS. 6 a  and 6 b    depict a method  600  utilizing exemplary architecture and functionality of the controller logic  214  ( FIG. 2 ) of the panel monitoring device  102  ( FIG. 1 ) in accordance with an exemplary embodiment of the disclosure. The method  600  depicted in  FIGS. 6 a    and  6   b  is described from the point of view of a single PMD, and in this regard differs from the method  500  of  FIG. 5 , which depicts a system-level method. 
         [0055]    Referring to  FIG. 6 a   , in step  601  of the method  600 , the panel monitoring device  102  disables its output. In this regard, the controller logic  214  causes the switching device  209  ( FIG. 2 ) to disconnect the solar panel  101  ( FIG. 1 ) from any external load. 
         [0056]    In step  602 , the PMD  102  sets its status to “ungrouped.” A PMD with a status of “ungrouped” does not know yet which combiner box  103  ( FIG. 1 ) it is on, or what string  106  ( FIG. 1 ) it is on. 
         [0057]    In step  603 , the PMD  102  “listens” for a broadcast from the present master PMD to see if the PMD has been selected new master. If the PMD  102  has not been selected new master, the method proceeds to step  615  ( FIG. 6 b   ). If the PMD  102  has been selected new master, in step  604  the PMD  102  generates (or is provided) a unique combiner box identifier and a string identifier. In step  605 , the new master enables its output. In this regard, the controller logic  214  ( FIG. 2 ) causes the switching device  209  to connect the solar panel&#39;s external output. The new master then broadcasts the string identifier and combiner box identifier wirelessly. Other PMDs in the field who are on the same combiner box (but not in the same string as the new master) will then be able to detect some portion of the new master PMD&#39; s output voltage. 
         [0058]    In step  606 , the new master PMD then asks if any PMDs who have not been previously grouped detected the new master PMD&#39; s voltage. If any PMDs respond that they do detect the voltage, in step  607  the new master will select a random respondee as the new master, and then in step  608 , the former new master will disable its output. 
         [0059]    Referring back to step  606 , if no PMDs respond that they are ungrouped and detected the voltage, then in step  609  the new master sends a broadcast asking if any ungrouped PMDs did not detect the voltage. In step  610 , any PMDs who respond in the affirmative are not on the same combiner box as the master and need to be grouped. The master will then select a new master from among these respondees, in step  611 , and then disables its output in step  608 . If no respondees respond in step  610 , that means all of the PMDs have been grouped, and the master disables its output in step  608 , and the process has been completed. 
         [0060]    In  FIG. 6 b   , step  615 , if the PMD has not been selected master (per step  603 ,  FIG. 6 a   ), the PMD waits for a broadcast from the master PMD. In step  616 , after the PMD receives a broadcast from the master PMD, the “non-master” PMD stores the string identifier broadcasted by the master PMD. The non-master PMD also measures its output voltage to see if it detects the master PMD. 
         [0061]    In step  617 , if the output voltage measured by the PMD is over a predetermined threshold, then in step  618 , the PMD sets a “voltage detected” flag in a table and stores the combiner box ID broadcasted in the table The predetermined threshold will be chosen based on the voltage of the master panel and the number of panels in a string. In one embodiment, the threshold is two (2) volts. If the output voltage measured by the PMD is not over a predetermined threshold, that means the PMD does not detect the master PMD&#39; s voltage. 
         [0062]    In step  619 , the PMD determines if the broadcast received by the master PMD is the first broadcast the PMD has received. If it is the first broadcast, in step  620 , the PMD stores the detection status (yes/no) along with the combiner box identifier and string identifier in the table. 
         [0000]    
       
         
               
               
               
             
               
               
               
               
             
           
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                 Master Broadcast 
                 Voltage Detected? 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 Present 
                 CB ID # 
                 Yes 
               
               
                   
                   
                 String # 
               
               
                   
                   
               
             
          
         
       
     
         [0063]    Table 1 illustrates a PMD detection table for a PMD that has heard only one broadcast from one master PMD. A “Yes” in the “Voltage Detected?” means that the PMD detected the master PMD&#39; s voltage, and that means the PMD is on the same combiner box as the master and on a different string from the master, parallel to the string that the master is in. But the PMD does not know what specific string it is in. 
         [0064]    Note that Table 1 shows that the PMD stores both a combiner box ID # and a string ID #. However, in the illustrated method, the combiner box ID# does not necessarily have to be stored, if the location detection is done for one combiner box (for all PMDs on that combiner box) before moving to the PMDs on another combiner box. 
         [0065]    Referring back to  619 , if the broadcast was not the first broadcast received by the PMD, in step  622 , the PMD determines whether the present detection status is different from the previous status. Table 2 below is an exemplary table of a PMD that is not the master PMD, after more than one broadcast has been received by the PMD: 
         [0000]    
       
         
               
               
               
             
               
               
               
               
             
           
               
                   
                 TABLE 2 
               
               
                   
                   
               
               
                   
                 Master Broadcast 
                 Voltage Detected? 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 Previous 
                 CB ID # 
                 No 
               
               
                   
                   
                 String # 
               
               
                   
                 Present 
                 CB ID # 
                 Yes 
               
               
                   
                   
                 String # 
               
               
                   
                   
               
             
          
         
       
     
         [0066]    Referring to Table 2, the PMD table keeps up with the PMD&#39;s reception of the present broadcast and immediately-previous broadcast of the master PMD. In the Table 2 example, the present detection status (a “yes” in the “Voltage Detected?” column) is different from the previous detection status (a “no” in the “Voltage Detected?” column). If the PMD previously did not detect the previous master&#39;s voltage, but now does detect present master&#39;s voltage, that means the PMD is on the same combiner box and in the same string as the previous master. That PMD has thus been grouped by combiner box and by string. 
         [0067]    If, however, there is a “yes” in both the present and previous rows, then the PMD knows it is on the same combiner box as both the present and previous master, in parallel with both, but does not know which string it is in. It is not until the table has a previous “no” followed by a present “yes,” or a previous “yes” followed by a present “no,” from two units on the same combiner box that the PMD will know its specific string, because then it knows it is in the same string as the previous master. 
         [0068]    Referring back to  FIG. 6 b   , in step  622 , if the present detection status is different from the previous, then in step  623 , the PMD&#39;s string is known. In this regard, if the previous status was “no” and the present status is different from previous (i.e. is “yes”), then the PMD is in the same string as the previous master. Similarly, if the previous status was “yes” and the present status is “no,” then the PMD is in the same string as the current master. 
         [0069]    If, however, both the “previous” and “present” status was the same, then in step  620 , the PMD stores its detection status, along with the string ID. Then, in step  624 , the PMD determines if the present detection flag is set (i.e., whether the PMD presently detects the master&#39;s voltage). If the PMD detects the present master&#39;s voltage, then the PMD proceeds to step  621  and the PMD broadcasts that it detected the voltage from the master, and proceeds to step  615  to await another broadcast. 
         [0070]    Referring back to step  624 , if the present detection flag is not set (i.e., the PMD does not detect the present master&#39;s voltage), then the PMD does not broadcast anything, and proceeds to step  615  to await another broadcast. 
         [0071]    This disclosure may be provided in other specific forms and embodiments without departing from the essential characteristics as described herein. The embodiments described are to be considered in all aspects as illustrative only and not restrictive in any manner.