DESC:TECHNICAL FIELD
[001] The present disclosure pertains to an online current-voltage (I-V) tracer configured for monitoring and maintaining PV panels.

BACKGROUND
[002] Background description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.
[003] Large scale PV installations need to be monitored and maintained to ensure uninterrupted operation at their optimum capacity.
[004] There is therefore a need for a technique for fault detection and localization in large scale PV installations. Such a technique should be low cost, provide ease of deployment, should be able to identify fault(s) and localize to it to a specific string, should work while plant is online (online monitoring).
[005] As existing solutions are not able to satisfy all these conditions, there is a need in the art for a new system/architecture that can fulfill all these parameters and efficiently enable monitoring and maintenance of PV panels.
[006] All publications herein are incorporated by reference to the same extent as if each individual publication or patent application were specifically and individually indicated to be incorporated by reference. Where a definition or use of a term in an incorporated reference is inconsistent or contrary to the definition of that term provided herein, the definition of that term provided herein applies and the definition of that term in the reference does not apply.
[007] In some embodiments, the numbers expressing quantities of ingredients, properties such as concentration, reaction conditions, and so forth, used to describe and claim certain embodiments of the invention are to be understood as being modified in some instances by the term “about.” Accordingly, in some embodiments, the numerical parameters set forth in the written description and attached claims are approximations that can vary depending upon the desired properties sought to be obtained by a particular embodiment. In some embodiments, the numerical parameters should be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. Notwithstanding that the numerical ranges and parameters setting forth the broad scope of some embodiments of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as practicable. The numerical values presented in some embodiments of the invention may contain certain errors necessarily resulting from the standard deviation found in their respective testing measurements.
[008] As used in the description herein and throughout the claims that follow, the meaning of “a,” “an,” and “the” includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein, the meaning of “in” includes “in” and “on” unless the context clearly dictates otherwise.
[009] The recitation of ranges of values herein is merely intended to serve as a shorthand method of referring individually to each separate value falling within the range. Unless otherwise indicated herein, each individual value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g. “such as”) provided with respect to certain embodiments herein is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention otherwise claimed. No language in the specification should be construed as indicating any non-claimed element essential to the practice of the invention.
[0010] Groupings of alternative elements or embodiments of the invention disclosed herein are not to be construed as limitations. Each group member can be referred to and claimed individually or in any combination with other members of the group or other elements found herein. One or more members of a group can be included in, or deleted from, a group for reasons of convenience and/or patentability. When any such inclusion or deletion occurs, the specification is herein deemed to contain the group as modified thus fulfilling the written description of all Markush groups used in the appended claims.

OBJECTS OF THE INVENTION
[0011] It is an object of the present invention to provide for an online current-voltage (I-V) tracer configured for monitoring and maintaining PV panels.
[0012] It is an object of the present invention to provide for an online current-voltage (I-V) tracer that enables fault detection and localization in large scale PV installations.
[0013] It is an object of the present invention to provide for an online current-voltage (I-V) tracer that is low cost, provides ease of deployment, is able to identify fault and localize to specific string, and works while the plant is online (online monitoring).

SUMMARY
[0014] The present disclosure relates to a current-voltage (IV) tracer for monitoring and maintaining PV panels, said tracer comprising: a first capacitor (C1); a second capacitor (C2); a first arm comprising a first switch (SW1) and a second switch (SW2) connected to first capacitor (C1); and a second arm comprising a third switch (SW3) and a fourth switch (SW4) connected to said second capacitor (C2). All switches (SW1 to SW4) are unidirectional. In an exemplary aspect of the present disclosure, in a first state, when switches SW1 and SW4 are ON and switches SW2 and SW3 are OFF, the discharged first capacitor (C1) is brought across a solar Photovoltaic (PV) string, and as the first capacitor (C1) charges, said IV trace is obtained for the solar PV string by sensing PV side DC bus voltage and the first capacitor (C1) current, wherein while the first capacitor (C1) provides an impedance sweep, the charged second capacitor (C2) meets the power requirement of the load; and wherein, after the end of the first state, the first capacitor (C1) is charged while the second capacitor (C2) is discharged such that in a second state, the switches SW3 and SW2 are ON, and the second capacitor (C2) provides IV trace while the first capacitor (C1) meets power requirement of the load.
[0015] In an aspect, the first and second states are be repeated so as to enable energy stored during the IV trace to be delivered to the load during next state.
[0016] In another aspect, the trace from the IV tracer can be recorded without disconnection of the load.
[0017] In another aspect, the IV tracer can be configured at junction box level to provide on demand IV traces on a per string basis. In another aspect, the IV tracer may be bypassed if no trace is needed.
[0018] In another aspect, the IV tracer can be operatively coupled with an analytics engine that compares recorded IV traces with a reference trace so as to provide any or a combination of cleaning schedules, fault diagnosis, localization of fault, and preemptive maintenance alerts. In another aspect, the IV tracer can be configured to reveal a fault, and wherein the analytics engine maps shape of IV curve to a specific failure mode, said failure mode being selected from any or a combination of partial and/or full shadowing, bypass diode failure. series/shunt interconnect faults, deterioration in anti-reflective coating, and hot-spot failure. In yet another aspect, the IV tracer can be placed at a Junction Box to monitor single string/ combination of strings, and wherein said IV tracer is able to replace string diode in the junction box. In yet another aspect, the IV tracer can be made to multiplex across multiple strings and enable a single IV tracer to provide an online IV trace for multiple strings.
[0019] In another aspect, the IV tracer can be interspersed in series at any position within said solar PV string to allow the IV tracer to monitor all upstream panels in the string. In another aspect, circuit topology of the IV tracer can be scaled to match power rating of the solar PV string. In another aspect, a version of the IV tracer can be made to match specifications of a single panel.
[0020] The present disclosure further relates to a system comprising a load, a solar PV string, and the IV tracer explained above.

BRIEF DESCRIPTION OF THE DRAWINGS
[0021] The accompanying drawings are included to provide a further understanding of the present disclosure, and are incorporated in and constitute a part of this specification. The drawings illustrate exemplary embodiments of the present disclosure and, together with the description, serve to explain the principles of the present disclosure.
[0022] FIG. 1 illustrates an exemplary circuit diagram of the proposed IV tracer in accordance with an embodiment of the present disclosure.
[0023] FIG. 2 illustrates an exemplary photographic representation of the proposed IV tracer in accordance with an embodiment of the present disclosure.
[0024] FIG. 3 illustrates an exemplary IV trace obtained from the proposed IV tracer in accordance with an embodiment of the present disclosure.
[0025] FIG. 4 illustrates an exemplary analytics engine associated with the proposed IV tracer in accordance with an embodiment of the present disclosure.
[0026] FIG. 5 illustrates an exemplary schematic diagram of the proposed online IV tracer in accordance with an aspect of the present invention.

DETAILED DESCRIPTION
[0027] The following is a detailed description of embodiments of the disclosure depicted in the accompanying drawings. The embodiments are in such detail as to clearly communicate the disclosure. However, the amount of detail offered is not intended to limit the anticipated variations of embodiments; on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present disclosure as defined by the appended claims.
[0028] Each of the appended claims defines a separate invention, which for infringement purposes is recognized as including equivalents to the various elements or limitations specified in the claims. Depending on the context, all references below to the "invention" may in some cases refer to certain specific embodiments only. In other cases it will be recognized that references to the "invention" will refer to subject matter recited in one or more, but not necessarily all, of the claims.
[0029] Various terms as used herein are shown below. To the extent a term used in a claim is not defined below, it should be given the broadest definition persons in the pertinent art have given that term as reflected in printed publications and issued patents at the time of filing.
[0030] The present disclosure pertains to an online I-V tracer configured for monitoring and maintaining PV panels. The present disclosure relates to a novel solar Photo-voltaic (PV) plant monitoring system that is configured to detect and identify faults in a large scale solar PV installation. The proposed system can be implemented, in exemplary embodiment, by means of a circuit that can be configured as an online IV tracer that sits at junction box level to provide on demand IV traces on a per string basis. The proposed circuit works online without the need to disconnect load from the panels, wherein, in an aspect, shape of the IV trace can be mapped to a fault. The proposed system can further include or be operatively coupled with an analytics engine that compares recorded IV traces with a reference trace so as to provide cleaning schedules, fault diagnosis, localization of fault, and preemptive maintenance alerts.
[0031] The present disclosure provides for an IV tracer that meets above-mentioned requirements. In an embodiment, the proposed IV tracer can include a capacitor that can be configured as fast, low cost, online IV tracer that is retrofittable at junction box level so as to provide IV traces on a per-string basis. Shape of the IV trace can be configured to reveal the fault, wherein an analytics engine can then map the shape of the IV curve to a specific failure mode. Various possible failure modes can be detected from an IV trace including, but not limited to, partial and/or full shadowing, bypass diode failure. series/shunt interconnect faults, deterioration in anti-reflective coating, and hot-spot failure.
[0032] The present disclosure relates to a current-voltage (IV) tracer for monitoring and maintaining PV panels, said tracer comprising: a first capacitor (C1); a second capacitor (C2); a first arm comprising a first switch (SW1) and a second switch (SW2) connected to said first capacitor (C1); and a second arm comprising a third switch (SW3) and a fourth switch (SW4) connected to said second capacitor (C2). All switches (SW1 to SW4) are unidirectional. In an exemplary aspect of the present disclosure, in a first state, when switches SW1 and SW4 are ON and switches SW2 and SW3 are OFF, the discharged first capacitor (C1) is brought across a solar Photovoltaic (PV) string, and as the first capacitor (C1) charges, said IV trace is obtained for the solar PV string by sensing PV side DC bus voltage and the first capacitor (C1) current, wherein while the first capacitor (C1) provides an impedance sweep, the charged second capacitor (C2) meets the power requirement of the load; and wherein, after the end of the first state, the first capacitor (C1) is charged while the second capacitor (C2) is discharged such that in a second state, the switches SW3 and SW2 are ON, and the second capacitor (C2) provides IV trace while the first capacitor (C1) meets power requirement of the load.
[0033] In an aspect, the first and second states are be repeated so as to enable energy stored during the IV trace to be delivered to the load during next state.
[0034] In another aspect, the trace from the IV tracer can be recorded without disconnection of the load.
[0035] In another aspect, the IV tracer can be configured at junction box level to provide on demand IV traces on a per string basis. In another aspect, the IV tracer may be bypassed if no trace is needed.
[0036] In another aspect, the IV tracer can be operatively coupled with an analytics engine that compares recorded IV traces with a reference trace so as to provide any or a combination of cleaning schedules, fault diagnosis, localization of fault, and preemptive maintenance alerts. In another aspect, the IV tracer can be configured to reveal a fault, and wherein the analytics engine maps shape of IV curve to a specific failure mode, said failure mode being selected from any or a combination of partial and/or full shadowing, bypass diode failure. series/shunt interconnect faults, deterioration in anti-reflective coating, and hot-spot failure. In yet another aspect, the IV tracer can be placed at a Junction Box to monitor single string/ combination of strings, and wherein said IV tracer is able to replace string diode in the junction box. In yet another aspect, the IV tracer can be made to multiplex across multiple strings and enable a single IV tracer to be able to provide an online IV trace for multiple strings.
[0037] In another aspect, the IV tracer can be interspersed in series at any position within said solar PV string to allow the IV tracer to monitor all upstream panels in the string. In another aspect, circuit topology of the IV tracer can be scaled to match power rating of the solar PV string. In another aspect, a version of the IV tracer can be made to match specifications of a single panel.
[0038] The present disclosure further relates to a system comprising a load, a solar PV string, and the IV tracer explained above.
[0039] With reference to FIGs. 1-4, as can be appreciated, I-V trace is basically a plot of current (I) versus voltage (V) recorded by sweeping load from short circuit to open circuit condition. IV traces are a signature of PV panels’ health, wherein shape of the IV trace can be mapped to a fault. Existing IV (I-V) tracers require plant to be brought offline (load is to be disconnected) before an IV trace can be recorded.
[0040] The proposed system, on the other hand, provides an online IV tracer topology that allows an IV trace to be recorded without disconnection of the load. The proposed system can implemented by means of a circuit comprising two identical arms, wherein one arm performs a trace and the other arm meets power requirement of the load. In an aspect, energy stored in capacitor during the trace can be configured to provide uninterrupted power to the load. FIG. 1 shows basic block diagram schematic of the proposed online IV tracer, when in a first state when SW1 and SW4 are ON while SW2 and SW3 are OFF, a discharged capacitor 1 is brought across the PV string. As capacitor 1 charges, an IV trace is obtained for the solar PV string by sensing PV side DC bus voltage and capacitor 1 current. While capacitor 1 provides an impedance sweep, charged capacitor 2 meets power requirement of the load. Thus, an IV trace is obtained online without the need to physically disconnect the load. After the end of this state, capacitor 1 is charged while capacitor 2 will be discharged. In the next state, the roles reverse where SW3 and SW2 will now be ON, and capacitor 2 provides IV trace while capacitor 1 meets power requirement of the load. These cycles can be repeated so as to enable energy stored during IV trace to be delivered to the load during next state.
[0041] In an aspect, the proposed system/circuit provides a four-switch (SW1, SW2, SW3, and SW4) power topology that enables state transition flow as described above and practical implementation of a new power topology that is low cost, able to efficiently identify fault and localize to specific string, and works while plant is online (online monitoring).
[0042] The proposed system, as shown in FIG. 4, can further include an analytics engine that can compare recorded trace(s) with one or more reference traces under given temperature and irradiance conditions.
[0043] In another aspect, the proposed IV tracer can be placed at the Junction Box to monitor single string/ combination of strings. The circuit (being unidirectional) can replace string diode in the junction box. The IV tracer sitting in the junction box can be made to multiplex across multiple strings, and therefore, as a result, a single tracer can provide an online IV trace for multiple strings.
[0044] In another aspect, the proposed tracer can be interspersed in series at any position within a string, which can allow IV tracer to monitor all upstream panels in the string. Thus, if the string's power rating exceeds the tracer's power rating, the tracer can still monitor a subset of the string.
[0045] In an aspect, circuit topology of the proposed IV tracer can be scaled to match power rating of string. In another aspect, a version of the IV tracer can be made to match specifications of a single panel. Furthermore, the proposed IV tracer can have high efficiency as energy stored in capacitor during trace can be delivered to load during following cycle.
[0046] FIG. 5 illustrates an exemplary schematic diagram of the proposed online IV tracer in accordance with an aspect of the present invention. As shown, the proposed online IV tracer 502 can be configured/positioned in the junction box 504, said junction box 504 being connected to load 506 on one side and to a PV string on the other side. As also shown, the IV tracer 502 can include a local data storage 552 that receives feedback data from microcontroller 554 and send said data to an analytics engine 556 for further analysis through algorithms such as piece wise linear curve fitting algorithm.
[0047] While the foregoing describes various embodiments of the invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof. The scope of the invention is determined by the claims that follow. The invention is not limited to the described embodiments, versions or examples, which are included to enable a person having ordinary skill in the art to make and use the invention when combined with information and knowledge available to the person having ordinary skill in the art.

ADVANTAGES OF THE INVENTION
[0048] The present disclosure provides for an online current-voltage (I-V) tracer configured for monitoring and maintaining PV panels.
[0049] The present disclosure provides for an online current-voltage (I-V) tracer that enables fault detection and localization in large scale PV installations.
[0050] The present disclosure provides for an online current-voltage (I-V) tracer that is low cost, provides ease of deployment, is able to identify fault and localize to specific string, and works while the plant is online (online monitoring).
,CLAIMS:1. A current-voltage (IV) tracer for monitoring and maintaining PV panels, said tracer comprising:
a first capacitor (C1);
a second capacitor (C2);
a first arm comprising a first unidirectional switch (SW1) and a second unidirectional switch (SW2) connected to said first capacitor (C1); and
a second arm comprising a third unidirectional switch (SW3) and a fourth unidirectional switch (SW4) connected to said second capacitor (C2),
wherein, in a first state, when switches SW1 and SW4 are ON and switches SW2 and SW3 are OFF, the discharged first capacitor (C1) is brought across a solar Photovoltaic (PV) string, and as the first capacitor (C1) charges, said IV trace is obtained for the solar PV string by sensing PV side DC bus voltage and the first capacitor (C1) current, wherein while the first capacitor (C1) provides an impedance sweep, the charged second capacitor (C2) meets the power requirement of the load;
and wherein, after the end of the first state, the first capacitor (C1) is charged while the second capacitor (C2) is discharged such that in a second state, the switches SW3 and SW2 are ON, and the second capacitor (C2) provides IV trace while the first capacitor (C1) meets power requirement of the load.
2. The IV tracer as claimed in claim 1, wherein the first and second states are be repeated so as to enable energy stored during the IV trace to be delivered to the load during next state.
3. The IV tracer as claimed in claim 1, wherein said trace from said IV tracer is recorded without disconnection of the load.
4. The IV tracer as claimed in claim 1, wherein said IV tracer is configured at junction box level to provide on demand IV traces on a per string basis AND wherein the iv tracer can be bypassed when no trace is needed.
5. The IV tracer as claimed in claim 1, wherein said IV tracer is operatively coupled with an analytics engine that compares recorded IV traces with a reference trace so as to provide any or a combination of cleaning schedules, fault diagnosis, localization of fault, and preemptive maintenance alerts.
6. The IV tracer as claimed in claim 5, wherein said IV tracer is configured to reveal a fault, and wherein the analytics engine maps shape of IV curve to a specific failure mode, said failure mode being selected from any or a combination of partial and/or full shadowing, bypass diode failure. series/shunt interconnect faults, deterioration in anti-reflective coating, and hot-spot failure.
7. The IV tracer as claimed in claim 1, wherein the IV tracer is placed at a Junction Box to monitor single string/ combination of strings, and wherein said IV tracer is able to replace string diode in the junction box AND WHEREIN the iv tracer can multiplex across multiple strings and enable a single IV tracer to be able to provide an online IV trace for multiple strings.
8. The IV tracer as claimed in claim 1, wherein the IV tracer is interspersed in series at any position within said solar PV string to allow the IV tracer to monitor all upstream panels in the string.
9. The IV tracer as claimed in claim 1, wherein circuit topology of the IV tracer is scaled to match power rating of the solar PV string or single panel.
10. A system comprising a load, a solar PV string, and the IV tracer as claimed in claims 1-9.