Device for controlling voltage and disconnecting photovoltaic modules for string

Abstract

The present invention relates to a voltage control and disconnection device to reduce the voltage of photovoltaic module strings when the weather conditions are such that the voltage can rise above 1500 VDC. To that end, the device has three inputs and one output, which connects to a photovoltaic module and to the adjacent photovoltaic module, the output leading to the inverter. The device measures the voltage of the photovoltaic module and, when a limit voltage that is internally preset based on the voltage of the module and the number of modules of the string is exceeded, it disconnects this photovoltaic module, reducing the string by one module. The disclosed invention provides the main advantage of better optimising the strings, at a much lower economic cost and with practically zero losses in dissipated power, while increasing the generation of daily energy of the photovoltaic farm, making it possible to always operate at the optimal voltage for the inverter.

Description

[0001] DESCRIPTION

[0002] Voltage control and disconnection device for photovoltaic modules for string

[0003] This specification refers, as its title indicates, to a device for voltage control and disconnection of photovoltaic modules for strings, used to reduce the voltage of the strings when weather conditions cause them to rise above 1500VDC, having for this purpose three inputs and one output, which is connected to a photovoltaic module and its adjacent photovoltaic module, taking the output, which will be positive or negative depending on the connection, to the inverter. The device measures the voltage of the photovoltaic module and, when it detects that it exceeds a limit voltage preprogrammed internally depending on the voltage of the module and the number of modules in the string, it disconnects that photovoltaic module, reducing the string to one less module.

[0004] Field of the invention

[0005] The invention relates to the field of photovoltaic installations, and more specifically to voltage control and disconnection devices for photovoltaic modules for strings.

[0006] Current state of the art

[0007] Photovoltaic parks are typically composed of one or more strings. Strings are groups of several photovoltaic modules connected in series, their voltages summed until the maximum voltage allowed by the site is achieved given its environmental conditions. It is important to ensure that this voltage is as high as possible to minimize wiring losses and increase efficiency by allowing the array to operate with the inverter at its optimal power point. It is also important that this voltage be a maximum of 1500 VDC, as this is the maximum limit of what is considered low voltage in DC. If the voltage exceeds 1500 VDC, the legal regulations applicable to the installation would be different, with different technical requirements and increasing the cost of installation. Therefore, photovoltaic parks are always designed to operate at low voltage.

[0008] However, photovoltaic modules have temperature coefficients that mean that when the ambient temperature drops, the module voltage increases by a percentage. Therefore, the minimum temperature that has occurred at the photovoltaic park site must be taken into account, as well as temperature variations when deciding how many modules will make up the string. This usually requires sizing each string with an appropriate safety margin so that, in the worst-case scenario in terms of weather conditions, the supplied voltage is always less than 1500 VDC. This safety margin means that, under normal weather conditions, which are the most common, the total voltage produced is less than 1500 VDC, resulting in suboptimal performance of the installation and the inverter. This is an oversizing for safety reasons that costs money in both installation and production.

[0009] To solve this problem there are solutions such as those described in WO202104845 “Power system with PV optimizer for the power supply from a photovoltaic installation”, ES2924858 “Photovoltaic power generation control system”, and EP3361631 “Current-voltage curve scan method for photovoltaic module and optimizer”. 1 ' which describe power-optimizing devices that, using DC-DC converters installed in each photovoltaic module, regulate the voltage supplied at all times to obtain the best performance from that module. However, this solution requires a large number of highly complex circuits and high electricity consumption, which must be dissipated as heat through thermal radiators, causing power losses and increasing the cost of the installation. Therefore, it is mainly only applicable to domestic installations.

[0010] Solutions such as those described in WO201008780 “Method for reconfigurably connecting photovoltaic panels in a photovoltaic array', US2012025621 “Device, system and method for sectioning and coupling multiple photovoltaic arrays", and CN112953385A “Photovoltaic system controller, photovoltaic system and control method' are also known, which allow dynamically varying the series-parallel interconnection of solar modules in a centralized manner depending on the production conditions, but this requires complex and expensive non-standard wiring of the photovoltaic modules, also making the installation more expensive.

[0011] There is currently no known device in the state of the art capable of disconnecting a photovoltaic module from the string in the event that the string voltage rises and may exceed the limit of 1500 VDC. Description of the invention

[0012] In order to solve the current problem of reducing the voltage of the strings when weather conditions cause it to rise above 1500VDC, the device for voltage control and disconnection of photovoltaic modules for strings object of the present invention has been devised, which is a device with three inputs and one output, which is connected to a photovoltaic module, preferably the last or the first, and to its adjacent photovoltaic module, taking the output, which will be positive or negative depending on the connection, to the inverter. The device measures the voltage of the photovoltaic module and, when it detects that it exceeds a limit voltage pre-programmed internally depending on the voltage of the module and the number of modules in the string, it switches, disconnecting that photovoltaic module and reducing the string to one less module.

[0013] For this purpose, the voltage control and disconnection device for photovoltaic modules for string comprises

[0014] - a switching module,

[0015] - a control module equipped with internal memory for storing operating parameters, dependent on the voltage of the photovoltaic module and the number of photovoltaic modules in the string,

[0016] - a voltage measurement module,

[0017] - a PLC type communications module (acronym for Power Line Communications - communications over power lines) referring to PLC as any type of communication carried out using different protocols or technologies that use electric power transmission lines to also transmit signals for communication purposes,

[0018] - a DC power supply module (13) for the above modules, obtained from the voltage generated by the photovoltaic module of the string to which the control device is connected, whether or not it is connected to the string, and

[0019] - a plurality of connections comprising at least two input connections to the terminals of the photovoltaic module to which the control device is connected, an input connection to the photovoltaic module of the string adjacent to the photovoltaic module to which the control device is connected, and an output connection to an inverter. It is envisaged that it may also optionally incorporate a short-range wireless communications module, such as RFID, NFC, Bluetooth, or similar, to be able to send information to an external device regarding the device's operation, such as the number of connection-disconnection cycles, times, statistical information, etc.

[0020] Although it will preferably be connected at the end of the string, at the positive output thereof, or at the beginning of the string, at the negative output thereof, it is also planned that alternatively it will be possible to install more than one control device in each string, in several photovoltaic modules of the same string, even combining in the same string devices for positive output and for negative output in the string corresponding to both embodiments, in case a greater regulation margin is needed.

[0021] The switching module has a disabled state, in which

[0022] - the output connection is electrically connected to the input connection connected to the terminal of the photovoltaic module to which the control device is connected,

[0023] - the input connection connected to the other terminal of the photovoltaic module to which the control device is connected is electrically connected to the input connection connected to the terminal of the photovoltaic module adjacent to the photovoltaic module to which the control device is connected, the photovoltaic module to which the control device is connected being connected in series with the adjacent photovoltaic module, and therefore electrically forming part of the string.

[0024] The switching module also has an activated state, in which

[0025] - the output connection is electrically connected to the input connection connected to the terminal of the photovoltaic module adjacent to the photovoltaic module to which the control device is connected,

[0026] - the input connection connected to the terminal of the photovoltaic module to which the control device is connected is electrically disconnected from the input connection connected to the other terminal of the adjacent photovoltaic module, the photovoltaic module to which the control device is connected being electrically disconnected from the adjacent photovoltaic module and therefore electrically disconnected from the string.

[0027] This device for voltage control and disconnection of photovoltaic modules for string, has a characteristic operating procedure that comprises - a preliminary step of programming the operating parameters in the internal memory of the control module, by means of the PLC type communications module, from an external device, not subsequently needing communications for its functionality once installed, and can optionally be used to send information on the operation of the device to an external monitoring device,

[0028] - a measurement step of the voltage supplied by the photovoltaic module to which it is connected, which is communicated to the control module,

[0029] - if the value of the measured voltage is higher than that indicated in the operating parameters programmed in the internal memory, the control module performs a step of putting the switching module into the activated state, electrically disconnecting the photovoltaic module from the string, and therefore reducing the total output voltage of the string of photovoltaic modules,

[0030] - if the value of the measured voltage is lower than that indicated in the operating parameters programmed in the internal memory, the control module performs a step of putting the switching module in the deactivated state, electrically connecting the photovoltaic module of the string, and therefore giving the maximum output voltage of the string of photovoltaic modules, repeating cyclically the voltage measurement step, and the following steps.

[0031] Advantages of the invention

[0032] This voltage control and disconnection device for photovoltaic modules for strings presented offers multiple advantages over currently available systems, the most important of which is that it allows for better optimization of photovoltaic module strings, with much lower economic costs and practically zero losses in dissipated power.

[0033] Another added advantage of using this device is that it increases the daily energy generation of the photovoltaic park since, with higher voltage, the string will reach the inverter's working window much sooner, meaning the inverter will start up earlier in the morning and shut down later.

[0034] It's also important to note that the equipment is powered by the string's own photovoltaic module, which means it can be installed in both existing and new parks, without the need for complicated installation and with virtually no new wiring.

[0035] It's worth noting that many wind farms already in production on the market today have serious problems because they rushed the strings too much in the original design and construction, and they currently exceed 1500VDC at times, jeopardizing the warranties and performance of the products in those projects.

[0036] It is also important to highlight that new construction projects with this device require approximately 3.5% less string for the same power, which implies an additional saving of at least 3% in structure, 3% in wiring, 3% in civil works, etc.

[0037] Furthermore, the use of PLC communications avoids the need for connectors or additional wiring for programming usage parameters.

[0038] Description of the figures

[0039] To better understand the object of the present invention, the attached drawing shows a preferred practical embodiment of a device for voltage control and disconnection of photovoltaic modules for string.

[0040] In this drawing, figure -1- shows a simplified block diagram of the device, in the preferred embodiment for connection at the end of the string, in its positive output towards the inverter.

[0041] Figure -2- shows an example of a string of photovoltaic modules with the device connected, in the preferred embodiment for connection at the end of the string, at its positive output towards the inverter.

[0042] Figure -3- shows an enlarged detail of the example of a string of photovoltaic modules with the device connected, detailing only the photovoltaic modules directly connected to the device, in the preferred embodiment for connection at the end of the string, with its positive output towards the inverter. Figure -4- shows an example of a string of photovoltaic modules with the device connected, in the preferred embodiment for connection at the beginning of the string, with its negative output towards the inverter.

[0043] Figure -5- shows an enlarged detail of the example of a string of photovoltaic modules with the device connected, detailing only the photovoltaic modules directly connected to the device, in the preferred embodiment for connection at the beginning of the string, in its negative output towards the inverter.

[0044] Preferred embodiment of the invention

[0045] The constitution and characteristics of the invention may be better understood with the following description made with reference to the attached figures. In these figures, a string formed by nine photovoltaic modules has been used, solely as an example, which we have referenced as (2a, 2b, 2c, 2d, 2e, 2f, 2g, 2h and 2¡). When we reference a specific module we will use any of these references depending on its position in the string, and when we reference a photovoltaic module in general we will reference it as (2).

[0046] As can be seen in figures 1, 3 and 5, the voltage control device (1) and disconnection of photovoltaic modules for string (2) comprises

[0047] - a switching module (8), preferably chosen from the group consisting of electromechanical, such as relays, or solid state switches, such as thyristors, triaels, solid state relays,

[0048] - a control module (9) provided with internal memory (10) for storing operating parameters dependent on the voltage of the photovoltaic module (2) and the number of photovoltaic modules (2) in the string,

[0049] - a voltage measurement module (11),

[0050] - a communications module (12) of the PLC type, referring to PLC as any type of communication carried out using different protocols or technologies that use the electric power transmission lines to also transmit signals for communication purposes,

[0051] - a DC power supply module (13) for the above modules, obtained from the voltage generated by the photovoltaic module (2a, 2¡) of the string to which the control device (1) is connected, and

[0052] - a plurality of connections comprising at least two input connections (4,6) for connecting to the terminals of the photovoltaic module (2a, 2¡) to which the control device (1) is connected, an input connection (5) for connecting to the photovoltaic module (2) of the string adjacent to the photovoltaic module (2b, 2h) to which the control device (1) is connected, and an output connection (7) for connecting to an inverter (3).

[0053] It is planned that it can also optionally incorporate a short-range wireless communications module (14), preferably RFID, NFC, Bluetooth or similar, to be able to send information to an external device about the operation of the control device (1), such as the number of connection-disconnection cycles, times, statistical information, etc.

[0054] A preferred embodiment is provided, as illustrated in Figures 2 and 3, in which the connection of the control device (1) with the string is made in the last photovoltaic module (2¡), corresponding to the positive output towards the inverter (3), being connected to the input connection (4) connected to the negative terminal of the last photovoltaic module (2¡) of the string, the input connection (6) connected to the positive terminal of the last photovoltaic module (2¡) of the string, the input connection (5) connected to the positive terminal of the second to last photovoltaic module (2h) of the string, and the output connection (7) being positive and connected to the inverter (3), the last photovoltaic module (2¡) being separated from the series connection of the string and therefore the positive terminal of the second to last photovoltaic module (2h) and the negative terminal of the last photovoltaic module (2¡) of the string not directly connected to each other.

[0055] An alternative embodiment is provided, as illustrated in Figures 4 and 5, in which the connection of the control device (1) with the string is made in the first photovoltaic module (2a), corresponding to the negative output towards the inverter (3), the input connection (4) being connected to the positive terminal of the first photovoltaic module (2a) of the string, the input connection (6) connected to the negative terminal of the first photovoltaic module (2a) of the string, the input connection (5) connected to the negative terminal of the second photovoltaic module (2b) of the string, and the output connection (7) being negative and connected to the inverter (3), the first photovoltaic module (2a) being separated from the series connection of the string and therefore the negative terminal of the second photovoltaic module (2b) and the positive terminal of the first photovoltaic module (2a) of the string not directly connected to each other.

[0056] It is planned that it will alternatively be possible to install more than one control device (1) in each string, in several photovoltaic modules (2) of the same string, even combining in the same string devices for positive output and for negative output in the string corresponding to both embodiments, in case a greater regulation margin is needed.

[0057] The switching module (8) has a disabled state, in which

[0058] - the output connection (7) is electrically connected to the input connection (6) connected to the terminal of the photovoltaic module (2a, 2¡) to which the control device (1) is connected,

[0059] - the input connection (4) connected to the other terminal of the photovoltaic module (2a, 2¡) to which the control device (1) is connected is electrically connected to the input connection (5) connected to the terminal of the photovoltaic module (2b, 2h) adjacent to the photovoltaic module (2a, 2¡) to which the control device (1) is connected, the photovoltaic module (2a, 2¡) to which the control device (1) is connected being connected in series with the adjacent photovoltaic module (2b, 2h), and therefore electrically forming part of the string.

[0060] The switching module (8) also has an activated state, in which

[0061] - the output connection (7) is electrically connected to the input connection (5) connected to the terminal of the photovoltaic module (2b, 2h) adjacent to the photovoltaic module (2a, 2¡) to which the control device (1) is connected,

[0062] - the input connection (4) connected to the terminal of the photovoltaic module (2a, 2¡) to which the control device (1) is connected is electrically disconnected from the input connection (5) connected to the other terminal of the adjacent photovoltaic module (2b, 2h), the photovoltaic module (2a, 2¡) to which the control device (1) is connected being electrically disconnected from the adjacent photovoltaic module (2b, 2h), and therefore electrically disconnected from the string.

[0063] The control device (1) is provided with means of mechanical fixing to the structure of the photovoltaic module (2a, 2¡) to which it is connected, preferably in the form of a support and a stainless steel flange.

[0064] This device (1) for controlling voltage and disconnecting photovoltaic modules for string (2), has a characteristic operating procedure that comprises

[0065] - a preliminary step of programming the operating parameters in the internal memory (10) of the control module (9), by means of the PLC type communications module (12), from an external device, not subsequently needing communications for its functionality once installed, and can optionally be used to send information on the operation of the control device (1) to an external monitoring device,

[0066] - a step for measuring the voltage (11) supplied by the photovoltaic module (2a, 2¡) to which it is connected via the connections (4,6), which is communicated to the control module (9),

[0067] - if the value of the measured voltage is higher than that indicated in the operating parameters programmed in the internal memory (10), the control module (9) performs a step of putting the switching module (8) in the activated state, electrically disconnecting the photovoltaic module (2a, 2¡) from the string, and therefore reducing the total output voltage of the string of photovoltaic modules (2),

[0068] - if the value of the measured voltage is lower than that indicated in the operating parameters programmed in the internal memory (10), the control module (9) performs a step of putting the switching module (8) in the deactivated state, electrically connecting the photovoltaic module (2a, 2¡) to the string, and therefore giving the maximum output voltage of the string of photovoltaic modules (2), repeating cyclically the voltage measurement step, and the following steps.

[0069] A person skilled in the art will readily understand that features of different embodiments can be combined with features of other possible embodiments, provided that such a combination is technically possible. All information relating to examples or embodiments forms part of the description of the invention.

Claims

CLAIMS 1 - Control device (1) for voltage and disconnection of photovoltaic modules for string (2) characterized in that it comprises - a switching module (8), - a control module (9) equipped with internal memory (10) for storing operating parameters, - a voltage measurement module (11), - a communications module (12) of the PLC type, - a DC power supply module (13) for the above modules, obtained from the voltage generated by the photovoltaic module (2a, 2¡) of the string to which the control device (1) is connected, - a short-range wireless communications module (14), and - a plurality of connections comprising at least two input connections (4,6) for connecting to the terminals of the photovoltaic module (2a, 2¡) to which the control device (1) is connected, an input connection (5) for connecting to the photovoltaic module (2) of the string adjacent to the photovoltaic module (2b, 2h) to which the control device (1) is connected, and an output connection (7) for connecting to an inverter (3). 2 - Device (1) for voltage control and disconnection of photovoltaic modules for string (2), according to the preceding claim, characterized in that its connection with the string is made in the last photovoltaic module (2), corresponding to the positive output towards the inverter (3), the input connection (4) being connected to the negative terminal of the last photovoltaic module (2¡) of the string, the input connection (6) connected to the positive terminal of the last photovoltaic module (2¡) of the string, the input connection (5) connected to the positive terminal of the penultimate photovoltaic module (2h) of the string, and the output connection (7) being positive and connected to the inverter (3), the last photovoltaic module (2¡) being separated from the series connection of the string and therefore the positive terminal of the penultimate photovoltaic module (2h) and the negative terminal of the last photovoltaic module (2¡) of the string not directly connected to each other. 3 - Voltage control device (1) and disconnection of photovoltaic modules for string (2), according to claim 1, characterized in that its connection with the string is made in the first photovoltaic module (2a), corresponding to the negative output towards the inverter (3), the input connection (4) being connected to the positive terminal of the first photovoltaic module (2a) of the string, the input connection (6) connected to the negative terminal of the first photovoltaic module (2a) of the string, the input connection (5) connected to the negative terminal of the second photovoltaic module (2b) of the string, and the output connection (7) being negative and connected to the inverter (3), the first photovoltaic module (2a) being separated from the series connection of the string and therefore the negative terminal of the second photovoltaic module (2b) and the positive terminal of the first photovoltaic module (2a) of the string not directly connected to each other. 4 - Voltage control device (1) and disconnection of photovoltaic modules for string (2), according to any of the preceding claims, characterized in that the switching module (8) has a deactivated state, in which - the output connection (7) is electrically connected to the input connection (6) connected to the terminal of the photovoltaic module (2a, 2¡) to which the control device (1) is connected, - the input connection (4) connected to the other terminal of the photovoltaic module (2a, 2¡) to which the control device (1) is connected is electrically connected to the input connection (5) connected to the terminal of the photovoltaic module (2b, 2h) adjacent to the photovoltaic module (2a, 2¡) to which the control device (1) is connected, the photovoltaic module (2a, 2¡) to which the control device (1) is connected being connected in series with the adjacent photovoltaic module (2b, 2h), and therefore electrically forming part of the string. 5 - Voltage control device (1) and disconnection of photovoltaic modules for string (2), according to any of the preceding claims, characterized in that the switching module (8) has an activated state, in which - the output connection (7) is electrically connected to the input connection (5) connected to the terminal of the photovoltaic module (2b, 2h) adjacent to the photovoltaic module (2a, 2¡) to which the control device (1) is connected, - the input connection (4) connected to the terminal of the photovoltaic module (2a, 2¡) to which the control device (1) is connected is electrically disconnected from the input connection (5) connected to the other terminal of the adjacent photovoltaic module (2b, 2h), the photovoltaic module (2a, 2¡) to which the control device (1) is connected being electrically disconnected from the adjacent photovoltaic module (2b, 2h), and therefore electrically disconnected from the string. 6 - Voltage control device (1) and disconnection of photovoltaic modules for string (2), according to any of the preceding claims, characterized in that the switching module (8) is chosen from the group consisting of electromechanical or solid state. 7 - Voltage control device (1) and disconnection of photovoltaic modules for string (2), according to any of the preceding claims, characterized in that the control device (1) has mechanical fixing means to the structure of the photovoltaic module (2a, 2¡) to which the control device (1) is connected. 8 - Voltage control device (1) and disconnection of photovoltaic modules for string (2), according to claim 8, characterized in that the mechanical fixing means of the control device (1) to the structure of the photovoltaic module (2a, 2¡) to which the control device (1) is connected consist of a support and a stainless steel flange. 9 - Operating procedure of a voltage control device (1) and disconnection of photovoltaic modules for string (2), according to any of the preceding claims, characterized in that it comprises - a preliminary step of programming the operating parameters in the internal memory (10) of the control module (9), by means of the PLC type communications module (12), from an external device, - a step for measuring the voltage (11) supplied by the photovoltaic module (2a, 2¡) to which it is connected via the connections (4,6), which is communicated to the control module (9), - if the value of the measured voltage is higher than that indicated in the operating parameters programmed in the internal memory (10), the control module (9) performs a step of putting the switching module (8) into the activated state, electrically disconnecting the photovoltaic module (2a, 2¡) from the string, and therefore reducing the total output voltage of the string of photovoltaic modules (2), - if the value of the measured voltage is lower than that indicated in the operating parameters programmed in the internal memory (10), the control module (9) performs a step of putting the switching module (8) in the deactivated state, electrically connecting the photovoltaic module (2a, 2¡) to the string, and therefore giving the maximum output voltage of the string of photovoltaic modules (2), the communications module (12) sending information on the operation of the control device (1) to an external monitoring device and the voltage measurement step and the following steps are repeated cyclically.

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