WO2021209650A1

WO2021209650A1 - Power supply circuit, safety device and photovoltaic facility

Info

Publication number: WO2021209650A1
Application number: PCT/ES2020/070240
Authority: WO
Inventors: Joan Marc RIERA PERA
Original assignee: Ridelin S.L.
Priority date: 2020-04-14
Filing date: 2020-04-14
Publication date: 2021-10-21

Abstract

The invention relates to a power supply circuit, a safety device and a photovoltaic facility. The circuit comprises two terminals (2, 3) for the in-line connection thereof to a DC photovoltaic supply line (4), with two branches (5, 6) being connected in parallel: a first branch (5) provided with a diode (51) in series with a capacitor; and a second branch (6) provided with a switch (61), the opening and closing of which are controlled by means of a short-circuit signal generated by a control module (9) from the moment the voltage between the terminals of the capacitor (521, 522) exceeds a second threshold (92) until said voltage falls below a first threshold (91). Said power supply circuit (1) has output power supply terminals (7, 8), electrically connected to the terminals of the capacitor (521, 522) directly or by means of a conditioning module (10).

Description

POWER SUPPLY CIRCUIT, SAFETY DEVICE AND INSTALLATION

PHOTOVOLTAIC

DESCRIPTION

Field of the invention

The invention is in the field of photovoltaic solar installations.

More specifically, the invention refers to a power supply circuit, with a first circuit terminal and a second circuit terminal, configured to be connected in line on a supply line of a photovoltaic direct current source, so that, in said connection, said second circuit terminal is downstream of said first circuit terminal with respect to said source.

The invention also relates to a safety device for a photovoltaic direct current source, and to a photovoltaic installation.

State of the art

In the field of photovoltaic solar installations, it is common for photovoltaic modules to be grouped into what is known as strings, which correspond to a set of photovoltaic modules connected in series with each other, and with a common output power supply line that it carries the energy generated by the modules in the form of electrical current, generally direct current. In other cases, the supply line comes from a single photovoltaic module. Other arrangements are also possible.

The use of complementary devices is often convenient, for example devices intended to monitor the status of solar panels or supply lines. This type of device generally requires electrical power for its operation. However, it is not convenient to cascade a device to the supply line itself so that it can use said electrical energy carried by said supply line. Thus, dedicated power wiring is generally required for such devices. However, and especially in the case of large photovoltaic installations, the installation and maintenance of this supplementary wiring involves a considerable economic cost. Other options such as, for example, the use of batteries for the devices have other drawbacks such as the need to periodically replace or recharge said batteries.

EP2962380 (HOPF, Markus) describes a circuit that is suitable for obtaining an electric potential difference by means of an in-line connection on the supply line, so that it can be used to power an electronic device. The invention is based on having a first diode in line on the supply line, and a second diode connected in parallel to the first, but with the polarity reversed. In this way, the invention takes advantage of the small drop in electrical potential between the ends of the first diode as an on-line power source. The two diodes oriented antiparallel ensure that the potential drop remains small regardless of the direction of current flow.

However, the above solution has the drawback that the electric potential drop is limited and generally low. In particular, depending on the power needs of the device to be powered, it is necessary to use elements such as voltage boosters. This type of element also has some drawbacks, for example, they tend to inject noise and / or harmonics into power lines, which can be difficult to filter in this type of high-power applications.

For all the above, a technical solution is convenient that allows obtaining energy from the supply line itself, but that allows obtaining adequate voltages for the devices to be supplied, while minimizing the appearance of noise and / or harmonics.

Description of the invention

The purpose of the invention is to provide a power supply circuit of the type indicated at the beginning, which makes it possible to solve the problems set out above.

Other objects of the invention are a security device and a photovoltaic installation using said power circuit. This purpose is achieved by a power circuit of the type indicated at the beginning, characterized in that said power circuit comprises a first circuit branch and a second circuit branch, each of said branches connected in parallel between said circuit terminals; wherein said first branch comprises: a diode, having an anode and a cathode, said anode being connected to said first circuit terminal; and a capacitor, having a first capacitor terminal connected to said cathode, and a second capacitor terminal connected to said second circuit terminal; wherein said second branch comprises a switch, controllable by means of a short circuit signal, so that it is configured to: remain closed in the presence of said short circuit signal; and remain open in the absence of said short circuit signal; said supply circuit having: a first supply terminal connected to said first capacitor terminal; and a second supply terminal connected to said second capacitor terminal; wherein said supply circuit further comprises a control module, configured to: generate said short circuit signal from the moment when the voltage between said capacitor terminals is greater than a second threshold; and not generating said short circuit signal when the voltage between said capacitor terminals is less than a first threshold.

In this way, the output voltage of the power circuit is obtained from the terminals of the capacitor of the first circuit branch. The supply terminals are directly connected to the capacitor terminals or they are connected through an intermediate module, for example, configured to suit the voltage and / or current parameters.

This way of obtaining the supply voltage differs from the known state of the art cited above, in which the voltage was obtained in line from the terminals of a pair of diodes arranged antiparallel. The invention replaces said antiparallel diodes by said first branch comprising a diode in series with a capacitor. Furthermore, unlike the cited state of the art, the terminals from which the electric potential difference is obtained are not those of the first branch, but only those of the capacitor. The diode is not used in this case to obtain the potential difference, but its function is to prevent return currents from the capacitor, as will be detailed later.

The circuit also comprises a switch, connected in parallel with the branch formed by the diode and the capacitor, so that one terminal of the switch is connected to the anode of the diode, while the other terminal of the switch is connected to the second terminal of the capacitor. In this way, when the switch is open, the current that passes through the supply line passes through the first branch, that is, through the diode and the capacitor. The diode is arranged in such a way as to allow said current to pass. In contrast, when the switch is closed, the first branch is short-circuited by the second branch, so the current from the supply line flows only through the second branch through the switch. The skilled person will understand that the above explanation corresponds to ideal elements and that, in practice, there may be small deviations from the ideal situation due, for example, to resistance or leakage currents.

In this way, when the switch is open, charge is stored in the capacitor, and a potential difference appears between its terminals. When said potential difference equals or exceeds the second threshold, the control module generates a short circuit signal. Upon the appearance of said short-circuit signal, the switch goes to the closed state, and remains in said state until said short-circuit signal disappears. The short circuit signal can take various forms, such as non-limiting examples, a predetermined value of voltage or current, a digital signal, or even an optical or electromagnetic signal. In the closed state, the current from the photovoltaic source no longer passes through the capacitor, so it is discharging. The diode prevents currents back from the capacitor. When the potential difference between the capacitor terminals drops and reaches the first threshold, the control module stops generating the short-circuit signal, so the switch returns to the open state, thus repeating the cycle. As a result, the voltage across the capacitor terminals follows a sawtooth pattern between charge and discharge cycles. The skilled person will understand that this sawtooth description corresponds to a situation in which the capacitor is discharged at constant speed, other power requirements may have different profiles. However, in general the voltage across the capacitor will always cycle up (switch closed) and cycle down (switch open).

By selecting the first threshold and the second threshold, the expert can easily determine the supply voltage and its tolerance range. As an example, if the first threshold is chosen as 11.5V and the second threshold as 12.5V, the voltage between the capacitor terminals will be within 12V ± 0.5V, except in transient stages such as the first charge. .

In this way, the invention makes it possible to easily select the operating parameters of voltage and tolerance, without the need to depend on specific characteristics of some elements, in particular the forward voltage of the diode in the case cited in the state of the art. Given that typically the supply lines of a photovoltaic string usually provide voltages between 1000 and 1500V, the above allows to obtain relatively high voltage values from the start, which can make the use of voltage boosters and their related problems unnecessary. In addition, due to the peculiarities of photovoltaic sources and / or the inductance of the supply line, after a disconnection that leaves the supply line in an open circuit, a voltage increase of between 100 and 200V typically occurs, which can be taken advantage of by the invention.

On the other hand, for the solution based on the direct voltage of a diode, to obtain high voltage values from the beginning it is necessary to use diodes in which said direct voltage is as high as possible, which implies a loss of energy in the line due to the power circuit itself, as well as an increase in heat dissipation. Alternatively, a diode with a low forward voltage and a boost can be used.

Another advantage of the present invention is that it allows the same elements to be used for different power values, that is, different voltages at the capacitor terminals or the power terminals, simply by selecting a first threshold and a second threshold with appropriate values for said values. feeding. In advantageous cases where the control module is programmable or remotely controllable, the same power circuit can provide different power values depending on programming or remote control. In addition, since the elements that support the power step can be the same for a wide range of supply voltages. Thus, the homologation of the circuit elements is facilitated, as well as the manufacturing, stock control and maintenance operations.

Preferably, said control module is electrically powered by at least one of: said power terminals; and said capacitor terminals.

In this way, the power circuit control module can obtain the necessary power to operate from the power terminals, or even directly from the capacitor terminals. As described above, the capacitor terminals provide a voltage profile that exhibits a temporal variation between the first threshold and the second threshold. On the other hand, the power terminals can present a conditioned voltage by means of elements arranged for this purpose. However, depending on the particular implementation of the control module and the selection of the thresholds, such conditioning may be unnecessary. Additionally, the control module can have some elements powered directly by the capacitor terminals and others powered from the power terminals. All of the above allows that the circuit does not require another external power source and minimizes the complexity of the circuit, potentially also reducing its consumption and maintenance.

Preferably, the power circuit further comprises conditioning means arranged between said capacitor terminals and said power terminals, and configured to condition some of the electrical parameters at the output of said power terminals. In this way, the power circuit is capable of offering a conditioned power supply, suitable for the devices that must be powered with it. Preferably said conditioning means comprise a voltage regulator configured to regulate the voltage between said supply terminals, which makes it possible to offer a direct current to the output. Preferably said voltage is 5V or 12V, which represent advantageous options for the power needs of many electronic devices. Preferably, said switch comprises a transistor, so that the switching between the open and closed state can be controlled through the gate of said transistor, even at high switching frequencies, which may be required as a function of the voltage difference between the first threshold and second threshold, and the electrical consumption needs of the device to be powered by the power circuit.

Preferably, said circuit further comprises galvanic isolation means, connected to said supply terminals, and configured to offer a first isolated terminal and a second isolated terminal, such that said isolated terminals are galvanically isolated from said supply terminals. In this way, it is possible to provide different power outputs and there is a protective isolation between them. By way of non-limiting example, the power terminals can be used to power a low power circuit, and the isolated terminals to power a high power circuit, without the latter posing a risk to the low power circuit, thanks to the insulation. galvanic between the two.

Preferably, said galvanic isolation means offer an additional isolated terminal, galvanically isolated from said supply terminals, and having a polarity with respect to said isolated second terminal that is opposite to the polarity between said isolated first terminal and said isolated second terminal, thereby which is particularly advantageous for high power components that may require a positive pole, a negative pole and a neutral pole.

Preferably, said transistor is of the MOSFET type, presenting a drain terminal, a source terminal and a gate terminal, with a transistor threshold voltage, and in which said short-circuit signal comprises a voltage between said gate terminal and said source terminal exceeding said transistor threshold voltage. MOSFET-type transistors allow switching even in high electrical power situations, which makes it an advantageous option to act as a switch for the power circuit described here. In this case, when the potential difference between the gate terminal and the source terminal exceeds the threshold voltage of the MOSFET transistor, the transistor allows current to pass between the drain terminal and the source terminal. For this reason, this potential difference is used as a short-circuit signal. Preferably, the difference between said second threshold and said first threshold is in the range from 0.5V to 13V, which is a suitable range in photovoltaic installations, particularly those that comprise strings with output voltages between 1000-1500V. The expert will understand that, for the same capacitor and the same load connected to the power output of the power circuit, the time required for charging and discharging the capacitor decreases as the difference between the thresholds decreases. Therefore, when this difference is in the lower part of the range, the voltage across the capacitor terminals has a small variation in voltage, but a high switching frequency is required for the switch. On the contrary, when this difference is in the upper part of the range, the variation in voltage is greater but the switching frequency of the switch decreases. Depending on the type of device to be supplied by the power circuit and the rest of the elements of the installation, the expert will have no problems in selecting the value of the capacitor and the area of the range that is most indicated between said second threshold and said first threshold. , based on the considerations outlined here.

Preferably, said first threshold is a value in the range from 3 to 18V, preferably 16V. It is common for electronic devices to require a power supply of between 3.3 and 12V. The first threshold controls the point of lowest voltage at the output of the capacitor terminals, so the choice of the value of said first threshold must be made accordingly to the type of devices to be powered. Preferably, the first threshold is a value close to the operating voltage of the device to be powered or, if several devices are powered, to the operating voltage of all of them that has the highest value. This makes it possible to avoid the use of voltage boosters that can introduce unwanted noise and harmonics on the line.

Preferably, said second threshold is a value in the range of 6 to 30V, preferably 18V. Similar to the previous case, the second threshold controls the point of highest voltage at the output of the capacitor terminals, so the choice of the value of said second threshold must be made accordingly to the type of devices to be powered. In case the first threshold is selected first, the choice of the second threshold must necessarily take into account the considerations described for the choice of the threshold difference described above. The final value should also take into account the desired effective stress value. This effective voltage is commonly known as the RMS voltage (Root Mean Square, mean square value for its acronym in English) in case of sinusoidal waveforms, or TRMS (True RMS) in other wave types. The value of the RMS or TRMS voltage is relevant since the voltage between the capacitor terminals is not constant, but variable, despite the fact that it does not follow a sinusoidal waveform but rather a sawtooth, as described. previously. In the case of using voltage rectifiers between the capacitor terminals and the power terminals, the rectified voltage will generally be related to the RMS / TRMS voltage value.

The invention also relates to a safety device for a photovoltaic direct current source, comprising:

- a power supply circuit according to one of the preferred forms described above; and

- at least one safety module, electrically powered by said power circuit.

In this way, it is possible to provide the photovoltaic direct current source with a device that is electrically powered by the power circuit described above, without the need to use dedicated power wiring or batteries.

Preferably, each of said at least one security module is electrically powered by at least one of: said capacitor terminals of said power circuit; said supply terminals of said supply circuit; and said terminals isolated from said power circuit.

The power circuit has at least two possible outputs to power other modules: the direct output from the capacitor terminals and the output from the power terminals. Some embodiments also have power terminals galvanically isolated from the rest. In the first option, the offered voltage presents voltage rise and fall cycles due to the capacitor charge and discharge cycles described above. In the case of the second option, the supply circuit can be provided with a matching module, for example a voltage rectifier. In cases where the safety module is tolerant to voltage variations, it is possible to use the direct output of the capacitor terminals. In other cases, the already regulated output from the power terminals will be preferable. Another possible scenario is the use of electrical insulation means, configured to isolate the output of the supply terminals from the output of the capacitor terminals and consequently from the supply line. A combined supply is also possible, for example, that a part of the safety module is supplied via the capacitor terminals and another part is supplied via the supply terminals. All of the above facilitates and provides flexibility in the design of the security device.

Preferably, each of said at least one security module is one of the list consisting of: a warning light, preferably an LED diode; allowing visual identification by an operator; an acoustic alarm; so that a warning arrives even if there is no direct vision; a transmitter of warnings by wireless connection; so that, for example, an alarm can be received at a monitoring console, without the need for wiring; a transmitter of warnings by wired connection; so that the signal can be received, even if environmental conditions make wireless connection difficult; and an overcurrent detector module configured to activate a line break module to cut said supply line.

The foregoing enables the photovoltaic installation to be equipped with warning means to facilitate the detection of anomalous situations or even protection systems to avoid problems derived from said situations, such as the overcurrent detector module. Indeed, this last preferred option makes it possible to cut the supply line in the event that an electrical current of too great intensity is detected. The example safety modules are not exclusive, so that in preferred embodiments the device incorporates a plurality of said modules, for example, a warning LED and an overcurrent detector module.

Preferably, said overcurrent detector module comprises: a shunt resistor, connected in line on said supply line, and which has two terminals between which a shunt voltage is defined that is proportional to the current flowing through said resistor bypass; and a comparison module, configured to generate an overcurrent signal when said bypass voltage is greater than a cutoff threshold voltage; wherein said line break module is configured to cut said supply line upon receiving said overcurrent signal from said comparison module.

In this way, the current flowing through the supply line passes through the shunt resistor, producing a potential difference between its terminals, here called shunt voltage, which is the product of the ohm value of the resistance and the current in amperes of current flowing through it. For reasons that will be clear to a person skilled in the art, it is recommended that the resistance value be low to minimize electrical consumption on the line itself. It will also be necessary to choose a type of resistance that is capable of tolerating the electrical power flowing through the supply line. In the event that the bypass voltage is greater than a threshold, the module interrupts the supply line to avoid any problems derived from downstream overcurrent. The cutoff threshold voltage value is the product of the resistance value and a cutoff threshold current value.

Preferably, in cases where said switch of said supply circuit is a transistor, in particular a MOSFET transistor, said shunt resistance is the conduction resistance of said transistor between its drain and source terminals. In this way, it is possible to obtain the voltage without the use of dedicated resistors that suppose an additional electrical consumption. On the other hand, the precision in the comparison of the shunt voltage value may be affected.

Preferably, said comparison module comprises a comparison output, said comparison module being configured to offer at said comparison output a predetermined overcurrent voltage when said shunt voltage is greater than a threshold voltage, so that said overcurrent signal is it corresponds to the situation in which the voltage at said comparison output presents the value of said overcurrent voltage. In this way, the comparison module presents at its output a predetermined voltage value when the amplified voltage exceeds a reference voltage. This predetermined output voltage, here called the overcurrent voltage, is used as the overcurrent signal for the line break module, which facilitates the design of the line break module since the type of overcurrent signal is simple to detect. By way of example, said overcurrent voltage may be a predetermined positive value, so that the comparison output offers a voltage of 0V if there is no overcurrent, or this positive value if there is overcurrent. Another illustrative example is in the case that the output voltage in normal operation presents a positive voltage value, while the overcurrent voltage is 0V.

Preferably, said comparison module comprises: a first closed-loop operational amplifier, configured to amplify said shunt voltage; and a comparator, configured to compare said amplified bypass voltage and generate said overcurrent signal in the event that it exceeds a predetermined threshold.

The shunt resistance value should be reduced in order to minimize electrical consumption and associated heat dissipation. Consequently, the bypass voltage will generally be low. However, making a comparison for low voltage levels can be complex as it is necessary to detect small variations in voltage. For this reason, the comparison is carried out in two steps: first an amplification and secondly the comparison itself. Preferably, said comparator is a second open-loop operational amplifier, or an analog comparator. In the first case, the second op amp is arranged in an open loop, so it behaves like a comparator. In this way, high detection precision is obtained using components widely available on the market, which minimizes manufacturing costs and facilitates obtaining spare parts if necessary. In preferred embodiments, the reference voltage is equal to or less than the voltage provided by the supply terminals of the supply circuit. In this way, it is possible to use said supply voltage, for example 12V, as the reference voltage, or to use a voltage divider to obtain the reference voltage from the supply voltage. Thus, the choice of the amplification value of the first operational amplifier can easily be chosen to provide the required voltage. Following these considerations, the skilled person will have no problem in selecting the parameters of the comparison module based on the desired cut-off current value and the value of the shunt resistance.

Preferably, said line cut module comprises: a line cut transistor, arranged in line on said supply line, and configured as a switch of said supply line controlled by its gate voltage, defined as the voltage between the gate and the source of said line cut transistor; and a gate control module, configured to receive said overcurrent signal, and connected to said line cut transistor to control said gate voltage; wherein said line cut transistor has a gate control voltage, defined as the gate voltage above which said line cut transistor allows electrical conduction between its drain and its source, and below the which prevents electrical conduction between said drain and said source; said door control module being configured such that a reception of said overcurrent signal produces a change in said door voltage from a value higher than said door control voltage to a value lower than said door control voltage.

The person skilled in the art will understand that a nomenclature has been used for the line cut transistor corresponding to field effect transistors. In particular, the labels "gate", "drain" and "source" are used. However, such an expert will have no problem identifying equivalent terminals for other types of transistors. By way of example, an insulated gate bipolar transistor, IGBT, has terminals commonly referred to as "gate", "collector" and "emitter", which are equivalent to the "gate", "drain" and "source" terminals. " aforementioned. Likewise, for other types of transistors, the terminal equivalent to the "gate" is called "base".

In the event of an overcurrent, the comparison module detects it and generates the overcurrent signal. When this overcurrent signal is received by the line cut module, in particular the gate control module, it lowers the gate voltage of the line cut transistor until it falls below its gate control voltage. At that moment, the line cut transistor behaves like an open switch, preventing the passage of current between its drain and its source. Consequently, the supply line is cut off. This advantageous form of embodiment involves a high reliability of the system since only the line cut transistor supports the passage of current from the supply line. Since these types of transistors are manufactured for high power applications, the safety device is reliable and the possibility of failure is minimized. Preferably, said line cut transistor is of the insulated gate bipolar transistor, IGBT type, or else a MOSFET type transistor. IGBT transistors are particularly advantageous for use in power circuits, making them a convenient element for use as a cut-off element of the supply line in cases of overcurrent. However, IGBTs tend to get hot, so another advantageous option is the use of a high quality MOSFET transistor, selected to withstand the voltages and, especially, the working currents that are usually around 10-15A for supply lines of a string.

Preferably, said door control module comprises a latching relay, configured as a switch between said door and said first capacitor terminal, said first power supply terminal or said first insulated terminal. In this way, in normal operation, the relay is armed and acts as a closed switch, establishing an electrical connection between a supply terminal among those offered by the supply circuit, and the gate terminal of the line cut transistor, so that the gate voltage is above the gate control voltage and the line cut transistor allows the passage of electrical current between its drain and its source. Upon receipt of the short-circuit signal, the relay goes to the disarmed state and the gate is disconnected from the power supply, so that the gate voltage is then below the gate control voltage and the line cut transistor prevents the passage of electrical current between its drain and its source, thus cutting off the supply line. The interlock relay ensures that the cut-out will be maintained until the interlock relay is reassembled.

In an advantageous embodiment, said source of said line cut transistor is connected to said second insulated terminal; wherein said gate control module comprises an isolated gate driver for said line cut transistor, connected to said comparison output, and configured to keep said gate of said line cut transistor connected to said first isolated terminal, and proceeding to connect said gate with said additional insulated terminal in the event that the voltage at said comparison output is said overcurrent voltage. Isolated gate drivers are commercially available devices that feature an output terminal that is internally switched between two source terminals based on the voltage at the gate driver input. In addition, the output terminal and source terminals are electrically isolated from the gate controller input. This type of insulation It can be achieved through different technologies, although the use of optocouplers is common. In the case of this preferred embodiment, an isolated gate controller and galvanically isolated power terminals are used together, so that the branch of the low-power circuit that performs the comparison is isolated from the branch of the control circuit. high power acting on the supply line. This configuration increases device security and improves reliability. In particular, it minimizes the possibility of damage to some of its components due to the passage of current peaks, especially from high-power circuits to low-power circuits.

In some preferred embodiments, the line cutter module further comprises voltage reduction means arranged between the gate of the cutoff transistor and its source, for example a resistor. The selection of said voltage reduction means and of the output voltage of the capacitor terminals, or of the supply terminals, is carried out as a function of the gate control voltage of the cut-off transistor, so that, in normal operation, the gate voltage value is above the gate control value.

The invention also refers to a photovoltaic installation, comprising at least one of: a power circuit according to any of the options described above; and a security device according to any of the options described above.

The invention also encompasses other features of detail illustrated in the detailed description of an embodiment of the invention and in the accompanying figures.

The advantages and characteristics of the invention can be seen from the following description in which, without limiting the scope of the main claim, preferred forms of embodiment of the invention are set forth with reference to the figures.

Fig. 1 shows a simplified electrical diagram of an embodiment of the power circuit of the invention. Fig. 2 shows some graphs of example of the temporal evolution of the voltages and currents at different points of the supply circuit of the example of Fig. 1.

Fig. 3 shows a simplified electrical diagram of an embodiment of the safety device of the invention.

Fig. 4 shows a simplified electrical diagram of an embodiment of the overcurrent detector module.

Fig. 5 shows a simplified electrical diagram of an embodiment of the line break module.

Fig. 6 shows a simplified electrical diagram of another embodiment of the overcurrent detector module.

Fig. 7 shows a simplified electrical diagram of another embodiment of the line cutter module.

Detailed description of some embodiments of the invention

Fig. 1 to Fig. 5 show a first embodiment of a supply circuit 1 according to the invention and of a corresponding safety device 100. It should be noted that all the electrical diagrams in the figures correspond to simplified schematic representations in which common elements have been used in the representation of electrical circuits. Likewise, for the sake of clarity, in the circuits shown in the figures only the components that have been considered necessary to clarify the operation of the invention are represented.

The supply circuit 1 shown in Fig. 1 has a first circuit terminal 2 and a second circuit terminal 3. In Fig. 1 the supply circuit 1 is shown connected on a supply line 4 of a current source continuous photovoltaic. In the figures the supply line 4 has been represented as a solid line. Terminals have been schematically represented at the ends of supply line 4, representing the continuation of the supply line 4. The upper terminal is upstream and would be connected to the output of the photovoltaic direct current source, for example, a string. In this way, the circuit terminals 2 and 3 are connected in line on the supply line 4, so that the second circuit terminal 3 is downstream of the first circuit terminal 2, with respect to the source.

The supply circuit 1 comprises two circuit branches 5 and 6, highlighted in FIG. 1 by boxes in broken lines. Both branches 5 and 6 are connected in parallel between circuit terminals 2 and 3.

A first circuit branch 5 comprises a diode 51 and a capacitor 52 connected in series with each other. Diode 51 has an anode and a cathode. Said anode is connected to the first circuit terminal 2. The capacitor has two capacitor terminals 521 and 522, a first capacitor terminal 521 that is connected to the cathode of diode 51, and a second capacitor terminal 522 that is connected to the second terminal. circuit 3.

A second circuit branch 6 comprises a switch 61, controllable by means of a short-circuit signal, so that it is configured to remain closed in the presence of said short-circuit signal; and remain open in the absence of said short circuit signal. In particular, for the first embodiment, the switch 61 is a MOSFET-type transistor having a drain terminal, a source terminal and a gate terminal, and with a transistor threshold voltage that is the voltage between the gate terminal and source terminal from which transistor 61 allows electrical conduction between drain terminal and source terminal. In this way, the short-circuit signal in this case corresponds to a voltage between the gate terminal and the source terminal that exceeds said transistor threshold voltage.

The supply circuit 1 is additionally provided with supply terminals 7 and 8. In particular a first supply terminal 7 connected to the first capacitor terminal 521, and a second supply terminal 8 connected to the second capacitor terminal 522. As stated As you can see in Fig. 1, the second capacitor terminal 522 and the second power terminal 8 are directly connected to each other, and are used as ground reference. Instead, the first capacitor terminal 521 and the first supply terminal 7 are connected via conditioning means 10 arranged between them. In particular, said conditioning means 100 is a voltage regulator that is configured to regulate the voltage between the supply terminals 7 and 8 to a value of 5V. In the first example, the voltage regulator is the ON Semiconductor® model MC7805, although other equivalent devices may be envisaged. Likewise, other embodiments can be envisaged in which the voltage between the supply terminals 7 and 8 has other values, for example, 12V, using the MC7812 model from ON Semiconductor® or equivalent voltage regulators.

The supply circuit 1 of the first embodiment shown in Fig. 1, is also provided with galvanic isolation means 101, connected to the supply terminals 7 and 8. These galvanic isolation means 101 offer a first isolated terminal 71, a second insulated terminal 81, and a further insulated terminal 71b having a polarity with respect to the second insulated terminal 81 that is opposite to the polarity between the first insulated terminal 71 and the second insulated terminal 81. In particular, the voltage between the The first insulated terminal 71 and the second insulated terminal 81 is 15V, while the voltage between the additional insulated terminal 71b and the second insulated terminal 81 is -15V. All the isolated terminals 71, 71b and 81 are galvanically isolated from the supply terminals 7, 8. In particular, they do not even share the ground reference to which the second capacitor terminal 522 and the second supply terminal 8 are connected. In the case of the example, the second isolated terminal 81 is used as a ground reference for the devices or elements that are powered by said galvanically isolated supply terminals 71, 71b and 81. In this embodiment, the galvanic isolation means 101 is a TRACO POWER® model TMV 0515D isolated DC / DC converter, although other equivalent devices may be envisaged.

In Fig. 1 it is shown how the power circuit 1 also comprises a control module 9, which in the figure has been highlighted by a box in broken line. Said control module 9 is configured to generate the short-circuit signal that causes the closing of the switch 61 from the moment in which the voltage between the capacitor terminals 521, 522 is higher than a second threshold 92, which in the example is of 17.6. The control module 9 is also configured not to generate said short circuit signal when the voltage between the capacitor terminals 521, 522 is less than a first threshold 91, which in the example is 16.4. In the case of the embodiment shown in Fig. 1, the control module 9 is a comparison circuit based on an operational amplifier that is powered by the power terminals 7 and 8. The voltage relative to the reference of ground at the first terminal of capacitor 521 is compared to a reference value, and the output of the amplifier is directed to the gate of the MOSFET transistor that acts as switch 61. In particular, the voltage of capacitor 521 passes through a voltage divider and the output is compared to the 5V voltage from the supply terminal 7. Multiple circuit options may be provided for the control module 9, the one set forth herein by way of example is an illustrative simplified option.

Fig. 2 shows a simulation of a temporal evolution of the currents and voltages in some points of the supply circuit 1 corresponding to Fig. 1. The horizontal axis of the graphs corresponds to time and, in the example, it is a window of about 90 microseconds. For the simulation, an element equivalent to a resistance connected to capacitor terminals 521 and 522 has been used, and another resistance between terminals 7 and 8. The third graph corresponds to the current flowing through the second branch 6 of circuit 1 a across transistor 61, measured in amps. It can be seen that it remains substantially constant except for brief dips to zero. These drops correspond to the situation in which the switch 61 is open, and the electric charge is directed to the capacitor 52. The third graph also shows current peaks that are due to the fact that the simulation has been carried out with mathematical models of real components. , in which the diode passes a peak of reverse current before completely cutting off the capacitor current. The first graph of Fig. 2 shows the voltage in volts between capacitor terminals 521, 522. As can be seen, if switch 61 is open, capacitor 52 charges rapidly and when switch 61 closes, capacitor 52 discharges as the elements supplied by the power circuit use the charge stored in the capacitor. The charge and discharge cycles of the capacitor 52 have a sawtooth profile in Fig. 2 since it is a simulation with a constant discharge (equivalent to a resistance). For the example of Fig. 2, the first threshold 91 has a value of around 16.4, while the second threshold 92 has a value of around 17.6. In this way, the difference between the two is about 1.2V, so the potential difference between the terminals of capacitor 521, 522 varies between 17V ± 0.6V. Other examples can be envisaged in which the difference between thresholds 92 and 91 is in the range of 0.5V to 13V, the first threshold 91 has a value between 3 and 18V and the second threshold has a value in the range of 6 to 30V. The second graph shown in Fig. 2 represents the voltage in gate volts of the MOSFET transistor used as switch 61 that is controlled by the control module 9. In the example, the transistor threshold voltage is around 3 V. When the gate voltage exceeds said threshold, switch 61 is closed and allows current to flow. On the other hand, when the gate voltage is below the transistor threshold voltage, the switch 61 opens and prevents the passage of current, which corresponds to the drops to zero in the third graph. The fourth graph shows the voltage in millivolts between circuit terminals 2 and 3. In the case of the example, supply circuit 1 produces a drop of about 300mV between its circuit terminals 2 and 3, which is constant, despite the commutations shown in the rest of the graphs.

Fig. 3 shows the first embodiment of a safety device 100 for a photovoltaic direct current source according to the invention. In this embodiment, the safety device 100 has a power circuit 1 as described above and represented in Fig. 1. In Fig. 3 the representation of said power circuit 1 has been simplified, replacing it with a block marked with the corresponding reference.

The security device 100 of Fig. 3 comprises two security modules 200. Each of said security modules 200 is electrically powered by said power circuit 1. In particular, the security device 100 has a first security module 200 which comprises an LED and is powered by capacitor terminals 521 and 522. Likewise, the safety device 100 has a second safety module 200, which comprises an overcurrent detector module 210 configured to activate a line cut-off module 250 to cut said supply line 4. The overcurrent detector module 210 is powered by the power terminals 7 and 8, while the line cut module 250 is powered by both the power terminals 7 and 8, as well as the terminals isolated 71, 71b and 81.

In Fig. 3 it is shown how the overcurrent detector module 210 comprises a shunt resistor 211 that is connected in line on the supply line 4, so that it has two terminals between which a shunt voltage is defined that is proportional to the intensity of current flowing through said shunt resistor 211. The overcurrent detector module 210 further comprises a comparison module 220 that is configured to generate an overcurrent signal when the shunt voltage is greater than a cutoff threshold voltage. In particular, the comparison module 220 has a comparison output 223, in which a predetermined overcurrent voltage is offered when the bypass voltage across bypass resistor 211 is greater than a predetermined threshold voltage. In this way, for the case of the first embodiment, the overcurrent signal corresponds to the situation in which the voltage at said comparison output 223 presents the value of said overcurrent voltage. For its part, the line cutting module 250 is configured to cut the supply line 4 when it receives the overcurrent signal from the comparison module 220, that is, when the voltage at the comparison output 223 presents the value of the default overcurrent voltage.

Fig. 4 shows the detail of the overcurrent detector module 210 and its comparison module 220. The circuit uses a Texas Instruments® model INA300 comparison device. The references marked in the entries have been maintained with respect to the documentation of the device so that they are easily identifiable by an expert. The IN + and IN- references correspond to the input terminals of the shunt resistor, GND connects to the ground reference, and ALERT to the comparison output. The upper line in the ALERT label indicates that the signal is inverted, that is, the comparison output 223 displays a value of 0V when overcurrent is detected, and a constant positive value of 5V when no overcurrent is detected. Thus, the default overcurrent voltage value is 0V. The comparison device is powered by power supply terminals 7 and 8 of power circuit 1. It is not an objective of this document to provide an exhaustive description of the operation of the INA300 comparison device, however, in order to improve general understanding, they are included brief indications of the use of the rest of the labels. LIMIT, is used to select the comparison threshold based on the connected resistance. In some embodiments not shown in the figures, the overcurrent detector module comprises a potentiometer connected to the LIMIT label that allows the comparison threshold to be adjusted. VS, corresponds to the power supply, in this case, it is connected to the first power terminal 7 that offers 5V. ENABLE, is used to activate / deactivate the overcurrent detection, which is useful to avoid generating the overcurrent signal under transient conditions. LATCH, is used to latch the overcurrent signal once it has been detected. DELAY, in this case is not used. HYS, is used to perform a hysteresis effect in the event that interlocking is not used.

Fig. 5 shows the detail of the line cut-off module 250. Said module comprises a line cut-off transistor 251 which is arranged in line on the line of supply 4, and configured as a switch for said supply line 4. In the example, the line cut transistor 251 is a MOSFET-type transistor that is controlled by its gate voltage, defined as the voltage between its input terminals. gate 2511 and source 2512. Furthermore, said transistor has a gate control voltage, defined as the gate voltage above which said line cut transistor 251 allows electrical conduction between its drain 2513 and its source 2512, and below which it prevents electrical conduction between said drain 2513 and said source 2512.

The line cut module 250 further comprises a gate control module 252, which is configured to receive the overcurrent signal, and which is connected to said line cut transistor 251 to control said gate voltage. In particular, the overcurrent signal is a voltage of 0V at the comparison output 223 which is connected to an input of the door control module 252. The door control module 252 is configured such that, upon receiving said signal from Overcurrent causes a change in the gate voltage of the line cutoff transistor 251 from a value higher than its gate control voltage to a value lower than said gate control voltage. Consequently, the switch goes from being closed to being open and the passage of electric current through the supply line 4 is interrupted. For the case of the first embodiment shown in Fig. 5, the interruption is supplied by the insulated terminals 71, 71b and 81. In particular, the source 2512 of the line cutoff transistor 251 is connected to the second isolated terminal 81, while the gate 2511 is connected to the first isolated terminal 71 or to the additional isolated terminal 71b, depending on the overcurrent signal. Thus, the gate voltage goes from + 15V when no overcurrent is detected, to -15V when overcurrent is detected. The switching between both values as a function of the input voltage from the comparison output 223 is carried out by means of an isolated gate controller 2521, in particular, the UCC23511 model from Texas Instruments®, although other equivalent devices may be envisaged. By way of clarifying reference, in Fig. 5 the main internal components of the isolated door controller 2521 are represented in a blurred way, although they are not the object of the invention. In this way, the gate control module 252 keeps the gate 2511 of the line cut transistor 251 connected with the first isolated terminal 71 and proceeds to connect said gate 2511 with the additional isolated terminal 71b in the event that the voltage at the comparison output 223 is the overcurrent voltage of 0V. Next, other embodiments of the safety device 100 and of the corresponding power circuit 1 are described that share a large part of the characteristics of the first embodiment described above. Therefore, only the differentiating elements will be described hereinafter. In the figures, the same reference numerals as in the first embodiment have been used to designate equivalent elements.

In a second embodiment not shown in the figures, the supply circuit 1 is additionally provided with a low-pass RC filter connected to the capacitor terminals 521 and 522, in such a way that it offers a filtered voltage that presents a more temporal variation. gentle. This type of voltage profile can be used to power various electronic components, avoiding overloads on the voltage regulator 10.

In a third embodiment not shown in the figures, the control module 9 of the power circuit comprises an analog comparator to compare the voltage at the capacitor terminals 521 and 522, and a gate controller to control the switch 61 in function of the output of said analog comparator.

In a fourth embodiment not shown in the figures, the security device 100 of the invention incorporates an acoustic alarm. In other embodiments, it incorporates a wired or wireless alarm transmitter. Still in other forms, security devices 100 can be provided that incorporate a combination of the security modules 200 described above.

In a fifth embodiment shown in Fig. 6 and Fig. 7, the comparison module 220 comprises a first closed-loop operational amplifier 221, which amplifies the bypass voltage of the bypass resistor 211; and a comparator 222, in particular a second open-loop operational amplifier, which compares said amplified bypass voltage and generates the overcurrent signal in the event that it exceeds a predetermined threshold. In the case of the example in Fig. 6, the overcurrent signal corresponds to a predetermined overcurrent voltage, coming from the first power supply terminal 7. In this way, the comparison output is 0V when no overcurrent is detected and 5V when overcurrent is detected. Other embodiments can be envisaged in which the voltage offered by the supply terminals 7 and 8 is different, for example 12V. Likewise, Fig. 7 shows how the line cut transistor 251 in this case is an IGBT, although other transistors of equivalent functionality can be envisaged, for example, of the MOSFET type. For its part, the gate control module 252 comprises an interlocking relay 2522, configured as a switch between the gate 2511 of the line cut transistor 251 and the first capacitor terminal 521. Thus, in the case of In this embodiment, the supply circuit 1 is not provided with galvanic isolation means 101. In the case of this embodiment, electrical isolation is achieved by physically separating the relay contacts in the event of an interruption. In any case, other embodiments can be envisaged in which said relay 2522 is used and in which the supply circuit 1 is provided with galvanic isolation means 101.

Although not represented in the figures, any of the safety devices 100 described above are used in the strings of a photovoltaic installation, so that each string is provided with a safety device 100.

Claims

1- Power supply circuit (1), with a first circuit terminal (2) and a second circuit terminal (3), configured for online connection on a supply line (4) of a photovoltaic direct current source, of so that, in said connection, said second circuit terminal (3) is downstream of said first circuit terminal (2) with respect to said source; characterized in that said supply circuit (1) comprises a first circuit branch (5) and a second circuit branch (6), each of said branches connected in parallel between said circuit terminals (2, 3); wherein said first branch (5) comprises: a diode (51), having an anode and a cathode, said anode being connected to said first circuit terminal (2); and a capacitor (52), having a first capacitor terminal (521) connected to said cathode, and a second capacitor terminal (522) connected to said second circuit terminal (3); wherein said second branch (6) comprises a switch (61), controllable by means of a short-circuit signal, so that it is configured to: remain closed in the presence of said short-circuit signal; and remain open in the absence of said short circuit signal; said supply circuit (1) having: a first supply terminal (7) connected to said first capacitor terminal (521); and a second supply terminal (8) connected to said second capacitor terminal (522); wherein said power circuit (1) further comprises a control module (9), configured to: generate said short-circuit signal from the moment in which the voltage between said capacitor terminals (521, 522) is greater than a second threshold (92); and not generating said short circuit signal when the voltage between said capacitor terminals (521, 522) is less than a first threshold (91).

2- Power supply circuit (1) according to claim 1, characterized in that said control module is electrically powered by at least one of: said power terminals (7, 8); and said capacitor terminals (521, 522).

3- Power circuit (1) according to any of claims 1 or 2, characterized in that it also comprises conditioning means (10) arranged between said capacitor terminals (521, 522) and said power terminals (7, 8) , in which said conditioning means (10) preferably comprise a voltage regulator configured to regulate the voltage between said supply terminals (7, 8), preferably at 5V or at 12V.

4- Power circuit (1) according to claim 3, characterized in that it also comprises galvanic isolation means (101), connected to said power terminals (7, 8), and configured to offer a first isolated terminal (71) and a second insulated terminal (81), such that said insulated terminals (71, 81) are galvanically isolated from said supply terminals (7, 8).

5- Power circuit according to claim 4, characterized in that said galvanic isolation means (101) offer an additional isolated terminal (71b), galvanically isolated from said supply terminals (7, 8), and which has a polarity with respect to said second insulated terminal (81) which is opposite the polarity between said first insulated terminal (71) and said second insulated terminal (81).

6- Power supply circuit (1) according to any of claims 1 to 5, characterized in that said switch (61) comprises a transistor, preferably a MOSFET-type transistor, presenting a drain terminal, a source terminal and a terminal gate, with a transistor threshold voltage, and wherein said short circuit signal comprises a voltage between said gate terminal and said source terminal that exceeds said transistor threshold voltage.

7- Power supply circuit (1) according to any of claims 1 to 6, characterized in that the difference between said second threshold (92) and said first threshold (91) is in the range from 0.5V to 13V. 8. Power circuit (1) according to any of claims 1 to 7, characterized in that said first threshold (91) is a value in the range of 3 to 18V, preferably 16V.

9. Power circuit (1) according to any of claims 1 to 8, characterized in that said second threshold (92) is a value in the range of 6 to 30V, preferably 18V.

10- Safety device (100) for a photovoltaic direct current source, characterized in that it comprises:

- a power circuit (1) according to any of claims 1 to 9; and

- at least one security module (200), electrically powered by said power circuit (1).

11. Security device (100) according to claim 10, characterized in that each of said at least one security module (200) is electrically powered by at least one of: said capacitor terminals (521, 522) of said power circuit

OR); said power terminals (7, 8) of said power circuit (1); and said insulated terminals (71, 81, 71b) of said power circuit (1).

12- Security device (100) according to any of claims 10 or 11, characterized in that each of said at least one security module (200) is one of the list consisting of: a warning light, preferably a diode LED; an acoustic alarm; a transmitter of warnings by wireless connection; a transmitter of warnings by wired connection; and an overcurrent detector module (210) configured to activate a line break module (250) to cut said supply line (4).

13. Safety device (100) according to claim 12, characterized in that said overcurrent detector module (210) comprises: a shunt resistor (211), connected in line on said supply line (4), and having two terminals between which a shunt voltage that is proportional to the intensity of current flowing through said shunt resistor (211); and a comparison module (220), configured to generate an overcurrent signal when said bypass voltage is greater than a cutoff threshold voltage; wherein said line break module (250) is configured to cut said supply line (4) upon receiving said overcurrent signal from said comparison module (220).

14. Security device (100) according to claim 13, characterized in that said comparison module (220) comprises a comparison output (223), said comparison module (220) being configured to offer in said comparison output (223 ) a predetermined overcurrent voltage when said shunt voltage is greater than a threshold voltage, so that said overcurrent signal corresponds to the situation in which the voltage at said comparison output (223) presents the value of said voltage of overcurrent.

15. Safety device (100) according to claim 14, characterized in that said comparison module (220) comprises: a first closed-loop operational amplifier (221), configured to amplify said bypass voltage; and a comparator (222), preferably a second open-loop operational amplifier or an analog comparator, configured to compare said amplified bypass voltage and generate said overcurrent signal in the event that it exceeds a predetermined threshold.

16. Safety device (100) according to any of claims 14 or 15, characterized in that said line cut module (250) comprises: a line cut transistor (251), arranged in line on said supply line ( 4), and configured as a switch of said supply line (4) controlled by its gate voltage, defined as the voltage between the gate (2511) and the source (2512) of said line cut transistor (251) ; and a gate control module (252), configured to receive said overcurrent signal, and connected to said line cut transistor (251) to control said gate voltage; wherein said line cut transistor (251) presents a gate control voltage, defined as the gate voltage above which said line cut transistor (251) allows electrical conduction between its drain (2513) and its source (2512), and below which it prevents electrical conduction between said drain (2513) and said source (2512); said door control module (252) being configured such that a reception of said overcurrent signal produces a change in said door voltage from a value higher than said door control voltage to a value lower than said control voltage of door.

17. Safety device (100) according to claim 16, characterized in that said line cut transistor (251) is of the insulated gate bipolar transistor, IGBT, or a MOSFET type transistor.

18. Security device (100) according to any of claims 16 or 17, characterized in that said door control module (252) comprises an interlocking relay (2522), configured as a switch between said door (2511) and said first capacitor terminal (521), said first power terminal (7) or said first insulated terminal (71).

19. Safety device (100) according to any of claims 16 or 17, characterized in that said source (2512) of said line cut transistor (251) is connected to said second insulated terminal (81); wherein said gate control module (252) comprises an isolated gate driver (2521) for said line cut transistor (251), connected to said comparison output (223), and configured to keep said gate ( 2511) of said line cut transistor (251) with said first insulated terminal (71), and proceed to connect said gate (2511) with said additional insulated terminal (71b) in the event that the voltage at said comparison output (223) is said overcurrent voltage.

20- Photovoltaic installation, characterized in that it comprises at least one of: a power circuit (1) according to any of claims 1 to 9; and a security device (100) according to any of claims 10 to 19.