Method for testing at least one bypass diode on an installation comprising at least one operating photovoltaic module

Abstract

A method for testing at least one bypass diode (4) on a photovoltaic installation (100) comprising at least one operating photovoltaic module (1), said photovoltaic module (1) comprising at least one string (2) of photovoltaic cells (3) connected to a bypass diode (4) dedicated to said string (2), the method comprising: a. shading a portion of the cells (3) of said string (2) so as to induce a bypass through said diode (4), said bypass causing a temperature increase in the diode (4) if the diode (4) is in a functional state; b. measuring at least one temperature of the diode (4); and c. comparing the measured temperature to a threshold to deduce a state of said diode (4). Abstract figure: Figure 8

Description

Title of the invention: Method for testing at least one bypass diode on an installation comprising at least one operating photovoltaic module technical field

[0001] This disclosure falls within the field of photovoltaic modules or solar panels, and relates in particular to a method for testing at least one bypass diode on an installation comprising at least one operating photovoltaic module and a device for implementing such a method. Previous technique

[0002] Bypass diodes, also known as "bypass" diodes, are electronic components which, placed in parallel with the strings of photovoltaic cells, allow, in the event of a cell failure, to limit the production losses of the photovoltaic module.

[0003] The principle of the use of these bypass diodes is described below.

[0004] In a photovoltaic module comprising a plurality of photovoltaic cells, a partially shaded cell leads to a current loss. For completely opaque objects such as a sheet, the decrease in output current of the cell will be proportional to the surface area of ​​the cell that has been shaded.

[0005] When a series of cells is close to a short circuit, the forward bias voltage of all the cells will reverse bias the shaded cell, which will then operate as a load. A phenomenon known as hot spots occurs when a large number of cells connected in series causes reverse bias through the shaded cell, leading to the dissipation of a large amount of power in the shaded cell. This large power dissipation occurring in a single cell will lead to a localized heating zone that can destroy at least that cell and disrupt the performance of the entire module.

[0006] The destructive effects of a hot spot can be circumvented by using a bypass diode. If a solar cell is reverse biased due to a current imbalance between several cells connected in series, then the bypass diode will become forward-biased, thus allowing current to flow in the external circuit through the bypass diode.

[0007] In practice, placing a bypass diode for each cell is too expensive and not easy to implement. Thus, bypass diodes are generally placed on strings of cells. Each string comprises, for example, between eighteen and twenty-six cells. Each module typically comprises three cell strings and three bypass diodes associated respectively with each cell string.

[0008] Diagnosing the operating status of bypass diodes is important to maximize the production of photovoltaic modules.

[0009] Indeed, there are two failure modes for a bypass diode: short circuit and open circuit. In the first case, a failure of the bypass diode due to a malfunction of one or more photovoltaic cells, caused by shading, a short circuit, among other things, results in a loss of production from the photovoltaic module. In the second case, an open circuit failure can, in the worst-case scenario, lead to a total loss of power from the panel.

[0010] It is known to automatically characterize the operation of bypass diodes. In particular, electrical detection using current / voltage (I / V) curves of the power supplied by the modules is known. Another technique consists of digital detection by machine learning (also known as fuzzy logic). A third known technique is statistical detection implementing a statistical hypothetical test, also called a t-test.

[0011] Such techniques are all based on the analysis of the photovoltaic module's production curves. This analysis is complex to implement on a string of modules where the I / V curves of several photovoltaic modules are combined.

[0012] Moreover, when the bypass diode is defective and remains in conducting mode, the detection of this fault is not certain because electrical type inspections on solar installations are often global.

[0013] Furthermore, when the bypass diode is defective and remains closed during operation, it will not be detected as defective in the absence of an additional fault in the photovoltaic module, as the latter will function normally. However, in the event of a fault or partial or permanent shading, the defective diode will not perform its protective function, and the shaded photovoltaic cells of the module may reach a temperature of several hundred degrees Celsius, potentially compromising the integrity of the photovoltaic module or, in extreme cases, causing a fire.

[0014] Moreover, no technique allows for complete testing of the operation of a bypass diode when the photovoltaic module is operating in a photovoltaic power plant or installation. For example, infrared cameras can be used on drones or airplanes, but diodes that remain stuck in the open position will not be visible.

[0015] There is therefore a need to have a test of at least one bypass diode on An installation comprising at least one functioning photovoltaic module. Summary

[0016] This disclosure improves the situation.

[0017] A method is proposed for testing at least one bypass diode on a photovoltaic installation comprising at least one operating photovoltaic module, said photovoltaic module comprising at least one string of photovoltaic cells connected to a bypass diode dedicated to said string, the method comprising:

[0018] a. shade a part of the cells of said chain so as to cause a parallel connection through said diode, said parallel connection causing a temperature increase of the diode if the diode is in a functional state;

[0019] b. measure at least one diode temperature and

[0020] c. compare the measured temperature to a threshold to deduce a state of said diode.

[0021] The term "diode state" refers at least to whether or not it is functioning. Thus, "diode functional state" can refer, at a minimum, to the fact that the diode is working and can be used in the module. Its operation can be characterized more precisely by accurately recording its temperature or a change in its temperature, for example.

[0022] The notion of "threshold" is general. It can be the measurement of the temperature of the diode at another time (which precedes, for example, the moment of the connection in parallel), or, for example, the temperature measurement of another element, such as the photovoltaic module itself or the temperature of the string of cells to which the diode being tested is attached, or of an area connected to the diode, or even of a fixed temperature such as the ambient temperature (for example, 25°C).

[0023] Activation of the diode, if it is in a functional state, will generate local heating which will be detected by measuring the temperature and characterized by comparing it to said threshold.

[0024] If the diode is not in a functional state, no temperature variation can be observed at its level.

[0025] If the temperature of the diode is measured in the moment preceding the parallel connection, which is the moment when it becomes conducting, and if this temperature constituting said threshold is substantially equal to the ambient temperature and no variation in the temperature of the diode is observed after parallel connection, then it can be concluded that the diode is defective, being blocked in an open circuit.

[0026] If the diode temperature, measured after parallel connection, is compared to the threshold temperature of the diode measured at the moment preceding parallel connection, and if this latter temperature, constituting the threshold, is higher than the ambient temperature and no variation in the temperature of the diode after being put in parallel, then we can conclude that the diode is defective, being blocked in short circuit.

[0027] The diode temperature can be the temperature of the diode itself, of the chain in which it is located, or even of the module.

[0028] Detecting one or more defective diodes can help prevent potential safety risks and / or improve the electrical output of the installation when it includes multiple photovoltaic modules. Furthermore, other related defects, such as one or more defective photovoltaic cells, can be detected using the method according to the invention, particularly by taking temperature measurements.

[0029] Step b is implemented after step a.

[0030] The photovoltaic module advantageously comprises cells that can be chosen from the group consisting of half-cells, full cells, so-called "shingle" cells, cut into five or six, and cells made of thin films such as, for example, cadmium tellurium (CdTe), based on copper, gallium, indium and selenium CIGS, based on Gallium Arsenide GaAs, etc.

[0031] The installation advantageously comprises several photovoltaic modules arranged side by side in pairs and each comprising a plurality of strings each comprising a plurality of cells and each connected to a bypass diode.

[0032] The features described in the following paragraphs may optionally be implemented independently of each other or in combination with each other:

[0033] When the photovoltaic module comprises several strings of cells and several diodes associated with said strings, paralleling can be caused by partial shading for several strings, in which case several diodes are activated simultaneously, and their state can be tested simultaneously using the method according to the invention.

[0034] The method can be implemented on several adjacent photovoltaic modules. Step a can be implemented on several cell strings simultaneously, or even for several photovoltaic modules, depending on the configuration of the assembly, called stand, of photovoltaic modules, which can cause the simultaneous paralleling of several strings within the same photovoltaic module and / or of several strings distributed over different photovoltaic modules, for example arranged side-by-side two by two.

[0035] At least steps a and b are preferably carried out using a robot, in particular a photovoltaic module cleaning robot. To do this, said robot is advantageously configured to shade said portion of the cells. The robot preferably includes a thermal sensor, in particular a thermal camera, to measure said at least one diode temperature. The robot is preferably fixed to the photovoltaic module or installation and moves in translation relative to it in a direction of advancement.

[0036] The process can use, according to this embodiment, the cleaning robot, for example present in fact on the installation comprising the photovoltaic module(s), to shade part of the cells, but another robot or other equipment, or even specific equipment, can be provided, alternatively, in particular other equipment attached to the photovoltaic module or installation and mobile in translation relative to it.

[0037] In the event that the cleaning robot is used, the latter can be moved on the photovoltaic module(s) in order to participate in the functional test of the diode or diodes.

[0038] The advantage of using the cleaning robot is that the cleaning of the module(s) and the functional test of the diode(s) can be combined, the latter not significantly increasing the maintenance cost.

[0039] Step b can be implemented after a time interval after implementation of step a, in particular after bypassing, and / or during a time interval, said time interval being between 10s and 80s.

[0040] The robot can be moved across the photovoltaic installation at a chosen speed to allow temperature measurements of the diode before and after it is connected in parallel, so as to be able to observe a temperature change in the diode if it is in a functional state. In particular, the robot can be moved across the photovoltaic installation at a chosen speed to allow temperature measurements of the diode before (threshold) and after it is connected in parallel, so as to be able to observe a temperature change in the diode between these two points if the diode is in a functional state.

[0041] Such a speed may be uniform throughout the robot's path or vary. In particular, it may be zero for a predetermined duration in one or more predetermined position(s) of the robot.

[0042] The robot's movement can be carried out autonomously or remotely controlled.

[0043] When one or more diodes are connected in parallel, the robot can be ordered to mark a pause time depending on the speed of appearance of the hot spot at the diode(s), for example for a duration between 20 s and 80 s.

[0044] The measurement can be carried out for a period exceeding 10 seconds, in particular exceeding 20 seconds, so as to allow sufficient time for the warming of the diodes so that the heat given off by it or them diffuses to the front of the module, the diode(s) being generally arranged on the rear of the module.

[0045] During the process, a temperature in at least one area, connected to the diode, of the photovoltaic module can be measured in order to have a temperature reference before and / or during the measurement of the diode temperature, after activation thereof, to monitor whether the photovoltaic module itself does not change temperature due to a change in the irradiation received during the measurement.

[0046] The photovoltaic module can be connected to an inverter or a micro-inverter. In this case, paralleling can be caused by the inverter or micro-inverter, particularly when the maximum power generated by said string is less than the maximum power generated by an adjacent string of the same module or of an adjacent module connected in series. In this case, the inverter or micro-inverter sets the electrical operating point of the system.

[0047] Indeed, if shading or a defect appears on a cell or group of cells on the same string, the I / V curve will be distorted and the maximum power point, defined by the product of voltage and current according to the equation P=U*I, will change. If the shading or defects are significant, the maximum operating point will be found at the level of the maximum power generated by an adjacent string of the same module or an adjacent module connected in series, and this corresponds to a case where the diode is activated. This is the scenario triggered by the shading to activate the diode in order to test it.

[0048] When a micro-inverter is present, the micro-inverter can perform module-by-module optimization, such that the diode triggers when the maximum power generated by the shaded string or group of strings is less than the maximum power generated by an adjacent string or group of adjacent strings of the same module or of an adjacent module connected in series.

[0049] When the photovoltaic module is connected to an inverter, and a plurality of modules are connected to the inverter, the inverter can optimize the entire array of these modules. In this case, even with low shading, the condition that the maximum power generated by the shaded string is less than the maximum power generated by an adjacent string of the same module or of an adjacent module connected in series is generally met, since all the adjacent modules operate correctly.

[0050] The ambient irradiance is preferably greater than 200 W / m², preferably greater than 500 W / m², during the implementation of steps a and b of the process, and preferably less than 1000 W / m². This condition ensures that the photovoltaic module(s) are in working order. The ambient temperature is preferably less than or equal to 40°C during the implementation of steps a and b. of the process. If the irradiance does not exceed the threshold of 1000W / m2 and the ambient temperature, i.e. outside, is less than 40°C, this ensures that the heat that will be released by the diode(s) being tested is not masked by the heat of the module in operation.

[0051] When the illumination is insufficient, in particular of certain cells, the method may include a step, simultaneous with step a, of artificial illumination of a part of the cells to ensure that the photovoltaic module(s) are in operation, in particular with the help of a lighting system.

[0052] The method may include a step prior to the shading step a, consisting of measuring the temperature of the surface of the photovoltaic module where the diode(s) to be tested are located in order to determine the initial temperature. This measurement may be carried out using a thermal sensor, in particular a thermal camera. This temperature may constitute said threshold.

[0053] Step b can be implemented using a thermal sensor, in particular a thermal camera. The method preferably includes a preliminary step of adjusting the thermal sensor, in particular the thermal camera, for example by performing a test on a bypass diode before implementing steps a and b.

[0054] The threshold indicated in step b of the process may correspond to a temperature measurement of the diode before being put into parallel, in particular just before being put into parallel.

[0055] The photovoltaic module may comprise a plurality of strings of photovoltaic cells connected in series, each string being connected to a dedicated bypass diode. In this case, steps a and b are advantageously implemented on all or part of said plurality of cell strings.

[0056] The cleaning robot's initial function is to clean the photovoltaic module(s). It is capable of being moved across the photovoltaic module(s) while remaining attached to them. Advantageously, for the implementation of the process, the robot is equipped with a shading system and a thermal sensor, in particular a thermal camera. The robot may also be equipped with a processing circuit for implementing step c, for example, implementing a measurement processing algorithm to compare the temperature measurement(s) at the threshold and determine the operating state of the diode(s) being tested. Such a processing circuit may be external to the robot, the latter being capable of exchanging information with said processing circuit.

[0057] Preferably, step a is implemented to shade only a part of the cells for a given chain, another part of the cells of said chain remaining illuminated or being illuminated, by ambient illumination or by an artificial lighting system.

[0058] The method may include, prior to the implementation of step a, a step for optimizing the layout of a shading system designed to implement step a, in order to trigger the activation of the relevant diode(s). This may allow the shading system and its layout to be adapted according to the configuration of the photovoltaic installation and / or the type of cells in the modules.

[0059] Step a may be implemented in such a way as to shade the photovoltaic module(s) symmetrically between strings and / or within the same string. Such an embodiment may consist of shading cells of a string symmetrically using two opaque parts of the shading system, a portion, for example a central portion, of the cells not being shaded, being in particular arranged between these two opaque parts. The unshaded portion of the cells may be covered by a transparent or apertured portion of the shading system, in particular connecting the two opaque parts. Such an embodiment may be particularly suitable for half-cell photovoltaic modules with two strings of cells in series with shared protection diodes.

[0060] The method may include, prior to implementation of step a, a shading calibration step. Such a step may consist of adjusting the shading so that the maximum power of the shaded module coincides with the activation of the diode or diodes. Such a step may be carried out with a shading system adapted to the module(s) and a recording of the I / V curves.

[0061] The temperature measurement in step b can be carried out by an operator. For example, the operator can perform the infrared thermography measurement at the rear of the module stand while the robot moves across the module(s). This may be particularly suitable for small photovoltaic installations.

[0062] According to another aspect, in combination with all or part of the above, a device is proposed for implementing the process as defined above, comprising at least:

[0063] - equipment, in particular autonomous or remote-controlled, preferably attached to the photovoltaic installation and capable of moving, particularly in translation relative to it, the equipment being opaque so as to shade at least partially a portion of the cells of at least one string of at least one photovoltaic module of the installation,

[0064] - a thermal sensor for measuring the temperature of the diode, and

[0065] - a processing circuit for comparing the diode temperature with a threshold and deduce a state of the diode from the comparison.

[0066] According to another aspect, in combination with all or part of the above, it is proposed to equip a device as defined above, comprising a robot, in particular a robot for cleaning the photovoltaic module.

[0067] In this case, the robot may include at least one thermal camera and at least one shading system consisting of at least one flap attached to the robot or of the robot itself.

[0068] The shading system may include a transparent and / or open part to allow light to illuminate part of the photovoltaic cells connected to the diode that one wants to test.

[0069] The shading system may comprise one or more shutters having several, in particular two, opaque parts connected to each other by a transparent part, and, for example, arranged symmetrically. In this case, said transparent part may, in a particular embodiment, have an opening and at least two arms connecting the opaque parts to each other.

[0070] The shading system can be detachable from the robot and / or mobile relative to it.

[0071] The shutter of the shading system may consist of a film or a plate opaque to light. It may be positioned, during the implementation of step a of the process, in front of, behind or on one or more sides of the robot.

[0072] Particularly in cases where the robot itself casts a shadow, the device may include an integrated and controllable lighting system to illuminate a portion of the cells connected to the diode or diodes being tested. This ensures that no chain of cells whose diode is being tested is entirely shaded, but rather that there is an illuminated portion and a shaded portion.

[0073] The robot may include an arm on which the thermal sensor, in particular the thermal camera, is fixed, so as to allow it to access the rear face of the module(s) housing the diode(s), in particular if the ambient temperature is high and the sun is significantly heating the photovoltaic module(s), in which case the heat of the modules could prevent the detection of overheating of the diode(s).

[0074] The robot may include an integrated lighting system to illuminate part of the cells and activate the diode(s), particularly when ambient lighting is insufficient.

[0075] In particular when the photovoltaic cells are thin films, the shading system can be configured according to the arrangement of the cells to guarantee the activation conditions of the diode(s). Brief description of the drawings

[0076] Other features, details and advantages will become apparent upon reading the detailed description below, and upon analysis of the accompanying drawings, on which:

[0077] [Fig. 1] schematically shows an example of a photovoltaic module on which the The method according to the invention can be implemented.

[0078] [Fig.2] is a graph illustrating current curves as a function of voltage measurements taken on a photovoltaic module as a function of the shaded area of ​​the module.

[0079] [Fig.3] schematically shows a photovoltaic module with a string of cells shaded at 25% allowing one of the curves of [Fig.2] to be obtained.

[0080] [Fig.4] schematically shows a photovoltaic module with a string of cells shaded at 50% allowing to obtain another of the curves of [Fig.2].

[0081] [Fig.5] schematically shows a photovoltaic module with a string of cells shaded at 75% allowing to obtain yet another of the curves of [Fig.2],

[0082] [Fig.6] is a graph illustrating the current curve as a function of the voltage measured on the module of [Fig.5].

[0083] [Fig.7] is a graph illustrating the power curve as a function of voltage noted for the module of [Fig.5].

[0084] [Fig. 8] schematically shows in top view a photovoltaic module on which the process is implemented according to an embodiment of the invention.

[0085] [Fig.9] schematically shows the photovoltaic module in cross-section illustrated in [Fig.8] during the implementation of the process.

[0086] [Fig. 10] is a photograph of a photovoltaic installation on which the process according to the invention is implemented.

[0087] [Fig. 11] is a schematic top view of photovoltaic modules on which the process is implemented according to one embodiment.

[0088] [Fig. 12] is a schematic top view of photovoltaic modules on which the process is implemented according to one embodiment.

[0089] [Fig. 13] is a schematic top view of photovoltaic modules on which the process is implemented according to one embodiment.

[0090] [Fig. 14] is a schematic top view of photovoltaic modules on which the process is implemented according to one embodiment.

[0091] [Fig. 15] is a schematic top view of photovoltaic modules on which the process is implemented according to one embodiment.

[0092] [Fig. 16] is a schematic top view of photovoltaic modules on which the process is implemented according to one embodiment.

[0093] [Fig. 17] is a schematic top view of photovoltaic modules on which the process is implemented according to one embodiment.

[0094] [Fig. 18] is a schematic top view of the photovoltaic modules of [Fig. 17] after advancement of the robot.

[0095] [Fig. 19] is a schematic top view of photovoltaic modules on which the process is implemented according to one embodiment.

[0096] [Fig.20] is a schematic top view of the photovoltaic modules of the [Fig. 19] after the robot has advanced.

[0097] [Fig.21] is a schematic top view of photovoltaic modules on which the process is implemented according to a specific embodiment.

[0098] [Fig.22] is a schematic top view of the photovoltaic modules of the [Fig.21] after the robot has advanced.

[0099] [Fig. 23 is a schematic top view of photovoltaic modules on which the process is implemented according to one embodiment.

[0100] [Fig.24] is a schematic top view of photovoltaic modules on which the process is implemented according to a specific embodiment.

[0101] [Fig.25] is a schematic top view of photovoltaic modules on which the process is implemented according to a specific embodiment.

[0102] [Fig.26] illustrates schematically and in perspective an example of a device according to an embodiment comprising a cleaning robot for implementing the process according to the invention.

[0103] [Fig.27] illustrates schematically and in perspective the device of the [Fig.26] with the deployment of a shading system. Description of the implementation methods

[0104] Reference is now made to [Fig. 1]. This figure schematically represents, in top view, a photovoltaic module 1 comprising two strings 2, each string containing a plurality of photovoltaic cells 3, eighteen cells 3 for each string 2 in this example. The cells 3 are connected in series. String 2 illustrated in [Fig. 1] has one shaded cell 3a. A bypass diode 4 is associated with each string 2 such that when one or more cells 3 of string 2 are shaded, the current no longer flows through the cells 3 of string 2 but through diode 4. Diode 4 is then activated, becoming forward-biased. A parallel connection has been made.

[0105] In this example, module 1 is connected to a micro-inverter 8. When the strings 2 are not shaded, the micro-inverter 8 selects the maximum power point PI of a string 2 and P2 of an adjacent string, as seen respectively on the curves C0 and Cl illustrated in [Fig.2].

[0106] Conversely, if part of chain 2 is shaded by a shading system 5 as illustrated in Figures 3 to 5, then the power decreases as illustrated in the different curves C2 to C4 of [Fig. 2]. Thus, P2* illustrates the maximum power point obtained when 25% of the surface area of ​​the cells 3 are shaded on a chain 2 as illustrated in [Fig. 3]. P2** illustrates the maximum power point obtained when 50% of the cells 3 are shaded as illustrated in [Fig. 4], while that P2*** illustrates the maximum power point obtained when 75% of cells 3 are shaded as illustrated in [Fig.5].

[0107] The curves illustrated in Figures 6 and 7 represent respectively the I / V curve of the module illustrated in [Fig.5] and the power curve (in watts) as a function of the voltage (in volts) of the same module illustrated in [Fig.5].

[0108] The micro-inverter 8 is programmed to trigger the shunting, i.e. to activate the shunt diode 4 when P1>P2 (P2 being in the form P2, P2*, P2** or P2*** depending on the shading of the chain 2).

[0109] The method according to the invention uses these properties to enable the detection of a defective diode.

[0110] Indeed, the method according to the invention is a method for testing at least one bypass diode 4 on a photovoltaic installation 100 comprising at least one photovoltaic module 1 in operation, the photovoltaic module 1 comprising at least one string 2 of photovoltaic cells 3, in this case three strings 2 of twenty photovoltaic cells 3, each being connected to a dedicated bypass diode 4 for each string 2.

[0111] As shown in [Fig. 8], the method includes the step of shading, using a shading system 5 comprising two opaque shutters 9 in this example, at least a portion of the cells 3 of the chain 2 until a parallel connection is created through the diode 4 dedicated to this chain 2. The parallel connection causes a temperature increase in the diode 4 if the diode 4 is in a functional state. Such a parallel connection can be triggered by the microinverter 8. The method further includes the step of measuring, in particular using a thermal sensor 11, at least one temperature of the diode 4 and a step of comparing, in particular using a processing circuit 20, the measured temperature to a threshold in order to deduce a state of said diode 4, i.e. whether the diode 4 is in a functional state or whether it is defective.

[0112] As can be seen in [Fig.9], the diodes 4 are located in this example on the rear face 7 side of the photovoltaic module 1, the front face 6 being the one that is visible in [Fig.8],

[0113] The micro-inverter 8 performs module-by-module optimization, such that the triggering of diode 4 occurs when the maximum power generated by the shaded chain 2 is less than the maximum power generated by an adjacent chain 2 of the same module 1 or of an adjacent module 1 connected in series.

[0114] In the example of [Fig.8], the installation 100 comprises a single photovoltaic module 1.

[0115] In this example, the ambient illuminance is greater than 200 W / m² during implementation of the process and less than 1000 W / m². Such a condition ensures that the or the photovoltaic modules 1 are in working order. The ambient temperature is preferably less than or equal to 40°C during the implementation of the process.

[0116] Activation of diode 4, if it is in functional state, will generate local heating which will be detected by measuring the temperature and characterized by comparing it to the threshold.

[0117] If the diode is not in a functional state, no temperature variation can be observed at its level.

[0118] If the temperature of diode 4 is measured in the moment preceding the parallel connection, which is the instant when it becomes conducting, and if this temperature constituting the threshold is substantially equal to the ambient temperature and no variation in the temperature of diode 4 is observed after parallel connection, then it can be concluded that diode 4 is defective, being blocked in an open circuit.

[0119] If we compare the temperature of diode 4, measured after paralleling, to the threshold corresponding to the temperature of diode 4 measured in the moment preceding paralleling, and if this temperature constituting the threshold is greater than the ambient temperature and we do not observe any variation in the temperature of the diode after paralleling, then we can conclude that the diode is defective, being blocked in short circuit.

[0120] Detecting one or more defective diodes 4 can help prevent potential safety risks and / or improve the electrical output of an installation comprising a plurality of photovoltaic modules, i.e., a photovoltaic power plant. Furthermore, other related defects, such as one or more defective photovoltaic cells, can be detected using the method according to the invention, particularly by taking temperature measurements.

[0121] The method can be implemented using autonomous or remotely controlled equipment configured to be attached to the photovoltaic installation 100 and to move or be moved relative to the modules 1 thereof. The equipment can be a robot, in this example a robot 10 for cleaning photovoltaic modules 1, an example of which is illustrated in [Fig. 10]. Such a cleaning robot 10, in a manner known per se, is intended to periodically clean the photovoltaic modules 1 of the photovoltaic installation 100 comprising a plurality of photovoltaic modules 1 in this [Fig. 10]. The cleaning robot 10 can advantageously be used to implement the method according to the invention. This avoids significantly increasing maintenance costs, as the cleaning robot 10 is already used for the periodic maintenance of the photovoltaic modules 1.

[0122] In the example illustrated in Figures 11 to 16, the 100 photovoltaic installation The system comprises a plurality of photovoltaic modules 1 arranged side-by-side from bottom to top and laterally. The robot 10 covers the surface from bottom to top of the installation 100. The robot 10 is moved along the direction of travel A illustrated by the arrows in these figures. A shading system 5 is attached to the rear of the cleaning robot 10 to implement the step of shading, using the shading system 5, at least a portion of the cells 3 of one or more strings 2 until a parallel circuit is created through each diode 4 dedicated to this string or these strings 2. The cleaning robot 10 is also equipped with a thermal sensor, in this example consisting of a thermal camera 11, illustrated schematically only in [Fig. 11], but present in all of these embodiments of Figures 11 to 16.

[0123] Such a thermal camera 11 makes it possible to implement at least the step of measuring at least one temperature of the diode 4. The robot 10 is further configured to compare the measured temperature to a threshold in order to deduce the state of the diode(s) 4, i.e., whether the diode 4 is in a functional state or whether it is defective. Alternatively, the robot 10 is connected to a processing circuit that makes it possible to implement this step of comparing the measured temperature to a threshold in order to deduce the state of the diode(s) 4.

[0124] More particularly, in the embodiment illustrated in [Fig. 11], the installation 100 comprises, along a direction transverse to the direction of travel A, three photovoltaic modules 1. Each photovoltaic module 1 comprises three strings 2 of twenty cells 3 each, each also comprising a bypass diode 4. The robot 10 comprises a shading system 5 comprising three shutters 9, each having an opaque part 12 and a transparent part 13, the opaque part 12 being split into two parts on either side of the transparent part 13. The shading formed by the opaque parts 12 is symmetrical in this example, which can allow for more precise control of the diode activation.Each shutter 9 covers a central 2c string of a photovoltaic module 1, shading a portion of this central 2c string with the opaque parts 12 until the parallel connection is triggered, thus activating the diode 4c dedicated to the central 2c string. The speed of the robot 10 is adjusted to allow this parallel connection; the robot 10 is, for example, stopped in the position shown for a duration greater than 10s, for example greater than 20s, and less than 80s. This allows the three diodes 4c of the central 2c strings of the modules 1 to be activated.

[0125] The embodiment of [Fig. 12] differs from that of [Fig. 11] in that the transparent part 13 has an opening 14 formed between two transparent arms 16 connecting the two opaque parts 12. This opening 14 can facilitate the detection of the diode 4c heating up.

[0126] In the example of [Fig. 13], the number of photovoltaic modules 1 in the installation 100 is four, arranged in a direction transverse to the direction of travel A. Furthermore, the shading system 5 comprises two shutters 9, each with an opaque portion 12 and a transparent portion 13. The opaque portion 12 is divided into two parts on either side of the transparent portion 13. Each opaque portion 12 covers two sections of two adjacent strings 2 belonging to two different, adjacent modules 1. Thus, the two shutters 9 allow for the simultaneous activation of four diodes 4 belonging to four different modules 1. The shading formed by the opaque portions 12 is symmetrical in this example, which allows for more precise control of the activation of the diodes 4.

[0127] The embodiment of [Fig. 14] differs from that of [Fig. 13] in that the transparent part 13 has two openings 14 formed between two transparent arms 16 connecting the two opaque parts 12. These openings 14 can facilitate the detection of heating of the diodes 4 concerned.

[0128] In the embodiment of [Fig. 15], illustrating an installation 100 similar to that of [Fig. 13] or 14, the shading system 5 comprises three flaps 9, each partially covering two adjacent strings 2. Two flaps 9 each cover two adjacent strings 2 of the same module 1, causing the paralleling through two diodes 4 of the same module 1, while the central flap 9 covers two adjacent strings 2 of two different modules 1, causing the paralleling through only one of the diodes 4 of each of these modules 1.

[0129] The embodiment of [Fig. 16] differs from that of [Fig. 15] in that it comprises a shading system 5 covering the entire width, transverse to the direction of travel A, of the robot 10 and therefore of the installation 100. The shading system 5 comprises a single flap 9 having an opaque portion 12 in two parts symmetrically surrounding a central transparent portion 13. All the diodes 4 of all the modules 1 arranged from bottom to top of the installation 100 are thus activated simultaneously and can therefore be tested simultaneously.

[0130] In the embodiments illustrated in Figures 17 to 22, the installation 100 comprises a series of photovoltaic modules 1 arranged side-by-side in the direction of travel A of the robot 10. Each module 1 comprises three strings 2 of twenty cells 3 each. In the embodiments of Figures 11 to 16, the strings 2 extend parallel to the direction of travel A. In the embodiments of Figures 17 to 22, the strings 2 extend transversely, perpendicularly, to this direction of travel A.

[0131] Still in these examples in Figures 17 to 22, the robot 10 itself is the shading system 5, the latter not being deployed outside the robot 10 but being constituted by a part of the robot. In addition, the cleaning robot 10 includes a lighting system 15 in order to illuminate part of the shaded cells and contribute to triggering the diodes 4. This lighting system 15 can be used to compensate for a lack of illumination. In this case, it is used to compensate for the shading cast by part of the robot 10 in an area of ​​the chain 2 that we do not want to shade in order to activate the diodes 4.

[0132] In the example illustrated in [Fig. 17], the shading system 5 comprises two opaque shutters 9 arranged symmetrically around the diode 4 of a string 2 of a module 1. The part of the string 2 which is not intended to be shaded is illuminated by the lighting system 15 in order to ensure that the diode 4 dedicated to this string 2 is activated.

[0133] Fig. 18 illustrates the movement of robot 10 from Fig. 17 to the next chain 2 of the adjacent module 1 to cause the connection through diode 4 dedicated to this next chain 2, in order to check its state.

[0134] In the embodiment of figures 19 and 20, two adjacent chains 2 of a module 1 are involved in the implementation of the method according to the invention, the robot 10 forming a shading system 5 covering symmetrically two parts of the two chains 2 on either side of a central part thereof, said central part being illuminated by the lighting system 15. Thus, two diodes 4 dedicated to said chains 2 concerned can be tested.

[0135] Fig. 20 illustrates the movement of the cleaning robot 10 from Fig. 19 to the next two chains 2 of the adjacent module 1 to cause the shunting through the diodes 4 dedicated to these next two chains 2, in order to check their state.

[0136] In the embodiment of figures 21 and 22, the three chains 2 of the same module 1 are involved in the implementation of the method according to the invention, the robot 10 forming a shading system 5 covering symmetrically two parts of the three chains 2 on either side of a central part thereof, said central part being lit by the lighting system 15. Thus, the three diodes 4 of the module 1, dedicated to said chains 2 of the module 1 are tested.

[0137] Fig. 22 illustrates the movement of the robot 10 from Fig. 21 to the next three chains 2 of the adjacent module 1 to cause the paralleling through the diodes 4 of the adjacent module 1, dedicated to these three chains 2, in order to check their state.

[0138] In the embodiments illustrated in Figures 23, 24, and 25, the robot 10 does not extend over the entire width, transverse to the direction of travel A, of the modules 1 of the installation 100. Furthermore, the installation 100, as in that of Figures 17 to 22, comprises only one module 1 in this width. In addition, the shading system 5 comprises two flaps 9, each having only an opaque portion 12, which deploys at the rear of the robot 10 to shade a portion of the cells 3.

[0139] In the embodiment of [Fig. 23], a part, in particular half, of the cells 3 of a chain 2 is shaded in such a way as to cause the paralleling and therefore the activation of diode 4 dedicated to this chain 2.

[0140] In the embodiment of [Fig.24], a part, in particular half, of the cells 3 of two adjacent chains 2 is shaded so as to cause the paralleling and therefore the activation of the two diodes 4 associated with these chains 2.

[0141] Finally, in the embodiment of [Fig.25], a part, in particular half, of the cells 3 of the three chains 2, i.e. of all the chains 2 of module 1 in this example, is shaded so as to cause the three diodes 4 of module 1 to be put into parallel and thus activated.

[0142] Activating diode(s) 4 is the first step before measuring the temperature of diode(s) 4 in order to compare it or them to a threshold and deduce whether diode(s) 4 are in a functional state or not.

[0143] The temperature measurement step is advantageously carried out by the robot 10, which is equipped with at least one thermal sensor, in particular a thermal camera 11. Such a thermal camera 11 is capable of measuring the temperature of the diode 4 or of several diodes 4, for example before and after paralleling, and / or of the surface of the module, of an ambient temperature, etc.

[0144] The step of comparing the measured temperature to a threshold and deducing the state of the diode 4 can be carried out by the robot 10 itself if it is equipped with a processing circuit or by an external processing circuit with which the robot 10 can communicate to exchange information.

[0145] In the embodiment illustrated in Figures 26 and 27, the cleaning robot 10 includes a shading system 5 consisting of a movable flap 9 that rotates relative to the body 18 of the robot 10 in order to move from a folded position illustrated in [Fig. 26] to a deployed position illustrated in [Fig. 27]. In the folded position, the shading system 5 is not able to shade part of the cells 3, whereas the deployed position allows it to cover part of the cells 3 when the robot 10 is attached to a photovoltaic installation 100 and / or to at least one photovoltaic module 1.

[0146] Of course, the invention is not limited to the examples just described.

[0147] The robot can be autonomous or remotely controlled.

[0148] When there are several photovoltaic modules, their management can be carried out by an inverter instead of a micro-inverter. A plurality of modules is then connected to the inverter. The inverter can optimize all of these modules. In this case, even with low shading, the condition that the maximum power generated by the shaded string is less than the maximum power generated by an adjacent string of the same module or of an adjacent module connected in series is generally satisfied, since all the adjacent modules operate correctly. directly.

[0149] Any other robot or equipment, of the autonomous or remote-controlled type, than the cleaning robot 10, dedicated or not to the implementation of the process, may be used in the invention.

[0150] The method may include a step prior to the shading step consisting of measuring the temperature of the surface 6 of the photovoltaic module 1 where the diode(s) 4 to be tested are located in order to determine the initial temperature, this measurement being able to be carried out using a thermal sensor, in particular a thermal camera 11. This temperature may constitute said threshold.

[0151] The method may include, prior to shading, a shading calibration step. Such a step may consist of adapting the shading so that the maximum power of the shaded module 1 coincides with the activation of the diode(s) 4. Such a step may be carried out with a shading system 5 adapted to the module 1 and a recording of the I / V curves.

[0152] During the process, a temperature in at least one area connected to diode 4 of the photovoltaic module 1 can be measured, for example as a threshold, in order to have a temperature reference before and / or during the measurement of the temperature of diode 4, after activation thereof, to monitor whether the photovoltaic module 1 itself changes temperature due to a change in the irradiation received during the measurement.

[0153] The step of measuring the temperature of diode 4, after shading, can be carried out using a thermal sensor, in particular a thermal imaging camera. The method preferably includes a preliminary step of adjusting the thermal sensor, in particular the thermal imaging camera, for example by performing a test on a bypass diode 4 before carrying out the shading and temperature measurement steps of diode 4.

Claims

Demands

1. A method for testing at least one bypass diode (4) on a photovoltaic installation (100) comprising at least one operating photovoltaic module (1), said photovoltaic module (1) comprising at least one string (2) of photovoltaic cells (3) connected to a bypass diode (4) dedicated to said string (2), the method comprising: a. shading a portion of the cells (3) of said string (2) so as to cause a bypass through said diode (4), said bypass causing a temperature increase of the diode (4) if the diode (4) is in a functional state; b. measuring at least one temperature of the diode (4) and c. comparing the measured temperature to a threshold to deduce a state of said diode (4).

2. A method according to claim 1, wherein at least steps a and b are carried out using a robot (10), in particular a photovoltaic module cleaning robot, said robot (10) being configured to shade said part of the cells (3) and comprising a thermal sensor, in particular a thermal camera (11), to measure said at least one temperature of the diode (4).

3. A method according to claim 2, wherein the robot (10) is moved over the photovoltaic installation (100) at a speed chosen to allow a temperature measurement of said diode (4) before and after being put in parallel so as to be able to observe a temperature variation of said diode (4) if it is in a functional state.

4. A method according to any one of the preceding claims, wherein said photovoltaic module (1) is connected to an inverter or micro-inverter (8) and wherein the shunting is caused by the inverter or micro-inverter (8), in particular when the maximum power generated by said string (2) is less than the maximum power generated by an adjacent string (2) of the same module (1) or of an adjacent module (1) connected in series.

5. A method according to any one of the preceding claims, wherein the ambient illuminance is greater than 200 W / m², and preferably less than 1000 W / m², during the implementation of steps a and b of the method, and wherein the ambient temperature is preferably in- less than or equal to 40°C during the implementation of steps a and b of the process.

6. A method according to any one of the preceding claims, step b being carried out using a thermal sensor, in particular a thermal camera (11), the method comprising a preliminary step of adjusting the thermal sensor, in particular the thermal camera (11), in particular by performing a test on a bypass diode (4) before carrying out steps a and b.

7. A method according to any one of the preceding claims, wherein said threshold corresponds to a temperature measurement of the diode (4) before it is put in parallel.

8. A method according to any one of the preceding claims, said photovoltaic module (1) comprising a plurality of strings (2) of photovoltaic cells (3) connected in series, each string (2) being connected to a dedicated bypass diode (4), wherein steps a and b are carried out on all or part of said plurality of strings (2) of cells (3).

9. Device for implementing the method according to any one of the preceding claims, comprising at least: - opaque equipment for shading at least partially a portion of the cells (3) of at least one string (2) of at least one photovoltaic module (1) of the photovoltaic installation (100), - a thermal sensor for measuring a temperature of the diode (4), and - a processing circuit for comparing the temperature of the diode (4) with a threshold and deducing from the comparison a state of the diode (4).

10. Equipment of a device according to claim 9, comprising a robot (10), in particular a robot for cleaning the photovoltaic module (1).

11. Equipment according to claim 10, wherein the robot (10) comprises at least one thermal camera (11) and at least one shading system (5) consisting of at least one flap (9) attached to the robot (10) or by the robot (10) itself.

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