Solar installation with photovoltaic panels

Abstract

TITLE: Photovoltaic Panel Solar Installation This description concerns a solar installation comprising a photovoltaic panel (10) having first and second terminals (PV1, PV2), intended to be coupled to a load (20), and a first voltage limiting circuit (30) between the first and second terminals comprising a first MOS transistor (M1) coupling the first and second terminals, the first circuit being configured to turn on the first MOS transistor (M1) when the voltage (VPV) exceeds a first voltage threshold (TH1). Figure for the abstract: Figure 3

Description

Title of the invention: Solar installation with photovoltaic panel technical field

[0001] This description generally relates to a solar installation comprising at least one photovoltaic panel. Previous technique

[0002] For certain applications, the use of photovoltaic panels is subject to strict constraints. This is particularly the case for the use of photovoltaic panels in vehicles.

[0003] Fig. 1 schematically represents a vehicle 1 comprising a photovoltaic panel 10 and a load 20 powered by the photovoltaic panel 10, for example a battery of electric accumulators.

[0004] Fig. 2 represents a curve of evolution of the IPV current supplied by the photovoltaic panel 10 as a function of the VPV voltage between the terminals of the photovoltaic panel 10, to which various voltage thresholds from regulations have been added.

[0005] A motor vehicle battery is generally designed to operate within a limited voltage range. For example, a 12 V battery can have a voltage ranging from 0 V to 15 V depending on its state of charge and temperature. A control circuit manages the charging and discharging of the battery's electrical cells. The control circuit requires a minimum supply voltage to function properly. This voltage is generally around 5 V. Therefore, to recharge a battery with a voltage of 15 V, the control circuit must receive at least 20 V to perform the recharge.

[0006] Regulations may require that any voltage supplied to a vehicle be below a certain voltage threshold. For example, Regulation R100 in relation to ISO 6469-3 sets this threshold at 60 V for commonly used vehicles.

[0007] One possibility is to design the structure of the photovoltaic panel 10 intended for automotive applications so that it directly supplies a voltage below 60 V. The maximum voltage that can be supplied by the photovoltaic panel 10 generally corresponds to operating conditions with high irradiance, for example greater than 1000 W / m², and a low temperature, for example -45°C. For ordinary temperatures, the maximum voltage that can be supplied by the photovoltaic panel 10 will be lower, for example on the order of 47 V. Furthermore, it It is generally desirable to operate a photovoltaic panel at an MPP operating point corresponding to the maximum power supply and which corresponds to a voltage of around 80% of the maximum voltage, i.e. around 37 V.

[0008] The available voltage margin for the photovoltaic panel 10 is therefore reduced in practice to 17 V.

[0009] In the context of vehicle applications, the overall shape of a photovoltaic panel is often curved and is subject to irregular and random shading.

[0010] A photovoltaic panel comprises a set of photovoltaic cells connected to each other by a connecting circuit. A photovoltaic cell generally behaves like an open switch when it is not illuminated. Therefore, if all the photovoltaic cells in a photovoltaic panel are connected in series, the absence of illumination of a single photovoltaic cell interrupts the operation of the photovoltaic panel. The connecting circuit can allow one or more groups of photovoltaic cells to be isolated so that the photovoltaic panel can continue to operate even when a photovoltaic cell is not illuminated. However, when a group of photovoltaic cells in the photovoltaic panel 10 is isolated, this results in a decrease in the voltage that can be supplied by the photovoltaic panel.For example, a photovoltaic panel providing an optimal voltage of 37 V and comprising two groups with the same number of photovoltaic cells can only provide an optimal voltage of 18.5 V when one of the groups is isolated, which is insufficient to charge a 12 V battery. One possibility is to use a large number of separately isolable photovoltaic cell groups. However, this increases the manufacturing cost of the photovoltaic panel. Summary of the invention

[0011] An object of an embodiment is to overcome all or part of the disadvantages of solar installations comprising known photovoltaic panels.

[0012] Another object of an embodiment is that the voltage supplied by the photovoltaic panel remains below a voltage threshold.

[0013] One embodiment provides for a solar installation comprising a photovoltaic panel having first and second terminals, intended to be coupled to a load, and a first voltage limiting circuit between the first and second terminals comprising a first MOS transistor coupling the first and second terminals, the first circuit being configured to make the first MOS transistor conduct when the voltage exceeds a first voltage threshold.

[0014] According to one embodiment, the first circuit comprises a first voltage divider a voltage divider coupling the first and second terminals, a second voltage divider coupling the first and second terminals, and an operational amplifier comprising an output coupled to the gate of the first MOS transistor, a non-inverting input coupled to a first midpoint of the first voltage divider, and an inverting input coupled to a second midpoint of the second voltage divider.

[0015] According to one embodiment, the first voltage divider bridge comprises a first resistor in series with a second resistor, and the second voltage divider bridge comprises a third resistor in series with a first Zener diode.

[0016] According to one embodiment, the operational amplifier functions as a comparator.

[0017] According to one embodiment, the installation includes a second voltage limiting circuit between the first and second terminals comprising a thyristor coupling the first and second terminals, the second circuit being configured to make the thyristor conduct when the voltage exceeds a second voltage threshold, strictly greater than the first voltage threshold.

[0018] According to one embodiment, the second circuit comprises a second MOS transistor in series with a capacitor, the assembly comprising the second MOS transistor and the capacitor coupling the first and second terminals, and a voltage step-down circuit coupling one electrode of the capacitor to the gate of the thyristor, the second circuit being configured to conduct the second transistor simultaneously with the first MOS transistor.

[0019] According to one embodiment, the voltage step-down circuit includes at least one second Zener diode.

[0020] According to one embodiment, the second circuit comprises a bipolar transistor in series with a fourth resistor, the assembly comprising the bipolar transistor and the fourth resistor coupling the first and second terminals, the output of the operational amplifier being coupled to the base of the bipolar transistor, and the gate of the second MOS transistor being coupled to a node between the bipolar transistor and the fourth resistor.

[0021] According to one embodiment, the first terminal is intended to be connected to a third terminal of the load. The second terminal is intended to be connected to a fourth terminal of the load, and the first voltage limiting circuit does not include any electronic component coupled between the first terminal and the third terminal or coupled between the second terminal and the fourth terminal.

[0022] One embodiment also provides for a vehicle comprising a solar installation as defined above. Brief description of the drawings

[0023] These features and advantages, as well as others, will be described in detail in the following description of particular embodiments, given by way of non-limiting example, in relation to the accompanying figures, among which:

[0024] the [Fig.1], described above, is a schematic view of a solar vehicle;

[0025] Fig. 2, described above, illustrates tension constraints for a vehicle solar;

[0026] [Fig.3] is an electrical diagram of an embodiment of a solar installation comprising a photovoltaic panel and a voltage limiting circuit;

[0027] [Fig.4] represents a curve of evolution of the current supplied by a photovoltaic panel as a function of the voltage between the terminals of the photovoltaic panel;

[0028] [Fig.5] represents voltage evolution curves during the operation of the solar installation of [Fig.3];

[0029] [Fig.6] is an enlarged view of part of [Fig.5];

[0030] Figure 7 illustrates voltage constraints for the operation of the installation solar of the [Fig.3];

[0031] [Fig.8] is an electrical diagram of another embodiment of the voltage limiting circuit;

[0032] [Fig.9] is an electrical diagram of a more detailed embodiment of the voltage limiting circuit of [Fig.8];

[0033] [Fig. 10] is an electrical diagram of another more detailed embodiment of the voltage limiting circuit of [Fig. 8];

[0034] [Fig.1 1] represents voltage evolution curves during the operation of the solar installation including the voltage limiting circuit of [Fig. 10] during normal operation;

[0035] [Fig. 12] represents voltage evolution curves during the operation of the solar installation including the voltage limiting circuit of [Fig. 10] during a malfunction;

[0036] Figure 13 is an electrical diagram of another embodiment of the voltage limiting circuit; and

[0037] [Fig. 14] represents curves of evolution of voltages and current during the operation of the solar installation including the voltage limiting circuit of [Fig. 13]. Description of the implementation methods

[0038] The same elements have been designated by the same reference numerals in the different figures. In particular, structural and / or functional elements common to the different embodiments may have the same reference numerals and may to have identical structural, dimensional and material properties. For the sake of clarity, only the steps and elements useful for understanding the described embodiments have been represented and detailed.

[0039] Unless otherwise specified, the expressions "approximately," "roughly," "about," and "in the order of" mean within 10%, preferably within 5%. Unless otherwise specified, ordinal numeral adjectives, such as "first," "second," etc., are used only to distinguish elements from one another. In particular, these adjectives do not restrict the described embodiments to a particular order of these elements.

[0040] Unless otherwise specified, when referring to two elements connected together, this means directly connected without intermediate elements other than conductors, and when referring to two elements connected (in English "coupled") together, this means that these two elements can be connected or linked through one or more other elements.

[0041] Figure 3 is an electrical diagram of an embodiment of a solar installation 5 for supplying a load 20, for example a battery of electrical accumulators. The load 20 includes terminals CH1 and CH2.

[0042] The solar installation 5 comprises: - a photovoltaic panel 10 comprising a coupled PV1 terminal, preferably connected to the CH1 terminal, and a coupled PV2 terminal, preferably connected to the CH2 terminal; and - a voltage limiting circuit 30 coupled between terminals PV1 and PV2.

[0043] In the present embodiment, the voltage limiting circuit 30 corresponds to a first clipping circuit based on a MOS transistor comprising: -a MOS transistor Ml in series with a resistor RI, the assembly including the transistor Ml and the resistor RI being coupled, preferably connected, between the terminals PV1 and PV2; - a comparator AO, preferably an operational amplifier, comprising a first input and a second input and an output; - a coupled resistor R2, preferably connected, between the comparator output and the gate of transistor M1; - a voltage divider bridge comprising two resistors R3 and R4 in series, the assembly comprising resistors R3 and R4 being coupled, preferably connected, between terminals PV1 and PV2, the midpoint NI between resistors R3 and R4 being coupled, preferably connected, to the first input of comparator AO, resistor R3 connecting midpoint N1 to terminal PV1 and resistor R4 connecting midpoint NI to terminal PV2; and - a voltage divider bridge comprising a resistor R5 in series with a diode Zener Zl, the assembly including the resistor R5 and the Zener diode ZI being coupled, preferably connected, between the terminals PV1 and PV2, the midpoint N2 between the resistor R5 and the Zener diode Zl being coupled, preferably connected, to the second input of the comparator AO, the resistor R5 connecting the midpoint N2 to the terminal PV1 and the Zener diode Zl connecting the midpoint N2 to the terminal PV2.

[0044] The voltage limiting circuit 30 may further include a coupled capacitor Cl, preferably connected, between terminals PV1 and PV2. According to one embodiment, the capacitor Cl is not present.

[0045] VPV is the voltage between terminals PV1 and PV2 and IPV is the current exiting the photovoltaic panel through terminal PV1. VAo is further defined as the output voltage of comparator AO.

[0046] In one embodiment, the potential at terminal PV2 is taken as the low reference potential, as schematically represented in [Fig. 3], by the symbol for ground (GND) connected to terminal PV2. The potential at terminal PV2 is hereafter considered to be 0 V, and unless otherwise specified, potentials are referenced to ground (GND). The cathode of the Zener diode Z1 is oriented towards terminal PV1.

[0047] According to one embodiment, the comparator AO is an operational amplifier that operates in comparator mode. The first input of the comparator AO corresponds to the non-inverting input (+) of the operational amplifier and the second input of the comparator AO then corresponds to the inverting input (-) of the operational amplifier.

[0048] According to one embodiment, the operational amplifier AO is a single-voltage type powered by the photovoltaic panel 10 and starts up from a relatively low voltage of the photovoltaic panel 10, for example 12 V. The negative supply terminal of the operational amplifier AO is coupled, preferably connected, to the PV2 terminal. The voltage limiting circuit 30 includes a voltage divider bridge comprising a resistor R6 in series with a Zener diode Z2; the assembly comprising the resistor R6 and the Zener diode Z2 in series is coupled, preferably connected, between the PV1 and PV2 terminals. A capacitor C2 is mounted in parallel with the Zener diode Z2. The cathode of the Zener diode Z2 is oriented towards the PV1 terminal. The midpoint N3 between the resistor R6 and the Zener diode Z2 is coupled, preferably connected, to the positive supply terminal of the operational amplifier AO.The Zener diode Z2 stabilizes the voltage at the midpoint N3, for example, at approximately 12 V. Part of the current diverted by the voltage divider formed by resistor R6, Zener diode Z2, and capacitor C2 is used to power the operational amplifier AO. The operational amplifier AO, used as a comparator, provides an output voltage VAo at a high level, approximately equal to the voltage across its positive supply terminal, or at a low level, approximately equal to the voltage across its terminal. negative supply, i.e. 0 V, depending on the difference between the voltage at its non-inverting input (+) and the voltage at its inverting input (-).

[0049] According to one embodiment, the operational amplifier AO is a fast operational amplifier with a high slew rate, for example greater than 30 V / ps.

[0050] In one embodiment, the transistor Ml is a power MOS transistor. In another embodiment, the transistor Ml is an N-channel MOS transistor. The source of the transistor Ml is coupled, preferably connected, to the PV2 terminal, and the drain of the transistor Ml is coupled, preferably connected, to one terminal of the resistor RI, the other terminal of the resistor RI being coupled, preferably connected, to the PV1 terminal.

[0051] By way of example, the resistance R2 has a value between 10 ohms and 100 ohms.

[0052] The operating principle of the voltage limiting circuit 30 will now be The voltage limiting circuit 30 detects when the output voltage VPV of the photovoltaic panel 10 exceeds a voltage threshold TH1. When the voltage threshold TH1 is reached, the voltage limiting circuit 30 short-circuits the PV1 and PV2 terminals for a very short duration, on the order of a microsecond, so that the operating point voltage of the photovoltaic panel 10 does not increase. Short-circuiting the PV1 and PV2 terminals causes a decrease in the VPV voltage. Since the short circuit is not maintained, the VPV voltage increases again until it exceeds the voltage threshold TH1, resulting in another short-duration short circuit. As long as the VPV voltage tends to rise above the voltage threshold TH1 again, the series of short-duration short circuits continues.

[0053] The voltage divider bridge, comprising resistor R5 in series with Zener diode ZI, provides a stable voltage reference on the inverting input of operational amplifier AO. This voltage reference is the value of the Zener voltage VZ1 of Zener diode ZI. Resistor R5 serves to bias Zener diode ZI. The voltage divider bridge, comprising resistors R3 and R4 in series, is used to measure the value of the voltage VPV of the photovoltaic panel 10. This bridge is designed so that the midpoint NI is close to the voltage VZ1, which will serve as the switching voltage for the output of operational amplifier AO just as the voltage VPV crosses the voltage threshold TH1. The voltage threshold TH1 is given by the following relationship: [Math 1] TH1=VZ1(^)

[0054] Figure 4 shows a curve of the evolution of the IPV current supplied by the photovoltaic panel 10 as a function of the VPV voltage between the PV1 and PV2 terminals. If the operating point of the photovoltaic panel 10 reaches the TH1 voltage threshold, for example equal to about 60 V, then applying a momentary short circuit to the photovoltaic panel 10 will cause the operating point to be pushed back as indicated by arrow F towards lower voltages, in particular towards 0 V if the short circuit were maintained.

[0055] Simulations were performed. For the simulations, the load 20 is not present and the capacitor Cl is used as the load with a capacitance of 30 pF. For the simulations, the Zener voltage VZ1 of the Zener diode ZI is equal to 6.2 V. The resistance R3 is equal to 47 kΩ and the resistance R4 is equal to 5.4 kΩ. The threshold voltage TH1 is therefore equal to 60.16 V. The resistance R2 is equal to 100 Ω. The resistance RI is equal to 0.1 mΩ.

[0056] Figure 5 shows the evolution curves of the VPV voltage and the VAo voltage as a function of time after the start-up of the solar installation 5 of Figure 3. Figure 6 is a detailed view of Figure 5.

[0057] When the solar installation 5 is started up, the voltage VPV rises from 0 V. The voltage VPV is then below the voltage threshold TH1. The voltage VA0 is therefore approximately 0 V. The transistor M1 is thus in the off state and is essentially equivalent to an open switch. As soon as the voltage VPV reaches the voltage threshold TH1, the voltage VA0 rises. The transistor M1 therefore becomes conducting and is essentially equivalent to a closed switch. This causes the voltage VPV to decrease. As soon as the voltage VPV falls below the voltage threshold TH1, the voltage VA0 drops essentially to 0 V and the transistor M1 becomes off. The voltage VPV then increases again, so that a succession of switching cycles of the transistor M1 is obtained. In this way, it can be seen that the voltage VPV is always limited to a level below the sum of the voltage threshold TH1 and a margin. In [Fig.[6] We have indicated successive times t1, t2, and t3. Time t1 is the instant at which the voltage VPV exceeds the threshold TH1 and the output voltage VA0 of the operational amplifier AO begins to switch. Time t2 is the instant at which transistor M1 becomes conducting, when the gate voltage of transistor M1 deviates above 5.5 V. Time t3 is the instant at which transistor M1 becomes blocking, when the gate voltage of transistor M1 falls below 5.5 V. Between times t2 and t3, transistor M1 is conducting and short-circuits terminals PV1 and PV2, which causes a decrease in the voltage VPV.The time between times t1 and t2 corresponds in particular to the switching time of the output voltage VA0 of the operational amplifier AO and the time for the transistor M1 to turn on, which depends in particular on the time constant due to the resistance R2 and the gate-source capacitance of the transistor M1 and the rise rate at the output of the operational amplifier AO.

[0058] The present invention consists of using an electronic circuit to clip the I(V) characteristic of the photovoltaic panel 10 to a predefined value. The principle The basic configuration deployed is a short circuit of the photovoltaic panel 10 with intermittent voltage control. The proposed solution does not add any series components to the power line connecting the photovoltaic panel 10 to the load 20. This advantageously avoids any energy losses in the line. Furthermore, the energy dissipated during the voltage limitation (i.e., the intermittent short circuit) therefore occurs within the photovoltaic panel 10, specifically within the photovoltaic cells, thus through dissipation over a large surface area, which will limit local self-heating phenomena.

[0059] Fig. 7 represents a curve of evolution of the IPV current supplied by the photovoltaic panel 10 as a function of the VPV voltage between the terminals of the photovoltaic panel 10 of the solar installation 5 of Fig. 3, to which various voltage thresholds from regulations have been added.

[0060] The voltage limiting circuit 30 advantageously allows full exploitation of the voltage range of the photovoltaic panel 10, while also providing the possibility of isolating certain groups of photovoltaic cells of the photovoltaic panel 10 (resulting in a voltage drop) during partial shading of the photovoltaic panel 10, while remaining at an electrical operating point compatible with the vehicle-side charging chain. This is illustrated in [Fig. 7] by the curves CT, Cl, C2, C3, which represent the current / voltage curves of the photovoltaic panel 10 respectively when all groups of photovoltaic cells are active, when one group of photovoltaic cells is isolated, when two groups of photovoltaic cells are isolated, and when three groups of photovoltaic cells are isolated.

[0061] This increase in available voltage range automatically allows finer cutting of the photovoltaic panel 10 in terms of insulation of groups of photovoltaic cells of the photovoltaic panel 10. The photovoltaic panel 10 then becomes more robust against partial shading and exhibits better performance for the intended application.

[0062] According to another embodiment, to make the voltage limiting circuit more reliable and safer in the long term or under heavy stress of any kind, the voltage limiting circuit further includes a second clipping circuit based on a thyristor.

[0063] Figure 8 is an electrical diagram of another embodiment of a voltage limiting circuit 40. The voltage limiting circuit 40 comprises the first clipping circuit 30 of Figure 3 and further comprises a second clipping circuit 45 comprising: - a thyristor Tl whose anode is coupled, preferably connected, to terminal PV1 and whose cathode is coupled, preferably connected, to terminal PV2; and - a trigger circuit 46 for the thyristor Tl connected to the thyristor gate Tl.

[0064] Figure 9 is an electrical diagram of a more detailed embodiment of the voltage limiting circuit 40 in which the tripping circuit 46 of the second clipping circuit 45 comprises: - a voltage divider bridge comprising a resistor R7 and two Zener diodes Z3 and Z4 in series, the assembly including resistor R7 and the two Zener diodes Z3 and Z4 being coupled, preferably connected, between terminals PV1 and PV2; and - a resistor R8 coupling, preferably connecting, the midpoint N4 between the resistor R7 and the two Zener diodes Z3 and Z4 and the gate of the thyristor Tl.

[0065] According to one embodiment, the cathode of Zener diode Z3 is connected to terminal PV1 and the cathode of Zener diode Z4 is connected to the anode of Zener diode Z3.

[0066] The triggering of the thyristor Tl is obtained when the voltage VPV exceeds a voltage threshold TH2, which is strictly greater than the voltage threshold TH1. The voltage threshold TH2 is determined by the value of the Zener diodes Z3 and Z4, which sets the voltage value at the midpoint N4 for which the triggering current on the gate of the thyristor Tl is reached, for example, a few milliamperes.

[0067] For example, the Zener voltage of Zener diode Z3 is equal to 51 V and the Zener voltage of Zener diode Z4 is equal to 12 V, so that the threshold voltage TH2 is equal to approximately 63 V, which is approximately 3 V higher than the threshold voltage TH1.

[0068] In the embodiment illustrated in [Fig. 9], the triggering of thyristor Tl is decoupled from that of transistor Ml, and each triggering of thyristor Tl or transistor Ml is independent of the other. It is simply the selection of the TH2 voltage threshold associated with thyristor Tl, which is higher than the TH1 voltage threshold associated with transistor Ml, that prevents thyristor Tl from triggering before transistor Ml.

[0069] When triggered, the thyristor Tl maintains a short circuit between the PV1 and PV2 terminals of the photovoltaic panel 10 as long as the photovoltaic panel 10 continues to operate, in particular as long as there is sufficient light illuminating the photovoltaic panel 10. Operator intervention is then required to restore the limiting circuit 40 to proper operation. The TH2 voltage threshold is strictly greater than the TH1 voltage threshold, so the triggering of the thyristor Tl only occurs in the event of a malfunction of the transistor ML.

[0070] The thyristor T1 unlocks when the current flowing through it drops to 0 A, which occurs when the photovoltaic panel 10 no longer receives light, particularly at night. Advantageously, if the fault persists the next day on the clipping circuit 30, the thyristor TH1 is re-energized if the voltage VPV reaches the voltage threshold TH2. The second clipping circuit 45 thus acts as a safeguard against a malfunction of the first clipping circuit 30.

[0071] Figure 10 is an electrical diagram of another, more detailed embodiment of the voltage limiting circuit 40 in which the tripping circuit 46 of the second clipping circuit 45 comprises: - a bipolar transistor Q1 and two resistors R9 and RIO in series; - a resistor RI 1 coupling, preferably connecting, the output of the comparator AO to the base of the bipolar transistor Q1; - a MOS transistor M2, a resistor R12 and a capacitor C3 in series with a resistor RI3 mounted in parallel with the capacitor C3; - two Zener diodes Z5 and Z6 and a resistor R14 in series, the assembly comprising the two Zener diodes Z5 and Z6 and the resistor R14 in series coupling, preferably connecting, the midpoint between resistor R12 and capacitor C3 and the gate of thyristor T1; and - a resistor RI5 coupling, preferably connecting, the gate of the thyristor Tl to the PV2 terminal.

[0072] According to one embodiment, the bipolar transistor Q1 is an NPN transistor whose emitter is coupled, preferably connected, to the PV2 terminal, the resistors R9 and RIO in series coupling, preferably connecting, the collector of the bipolar transistor Q1 and the PV1 terminal.

[0073] According to one embodiment, transistor M2 is a P-channel MOS transistor. The source of transistor M2 is coupled, preferably connected, to terminal PV1, and the drain of transistor M2 is coupled, preferably connected, to one terminal of resistor R12, the other terminal of resistor R12 being coupled, preferably connected, to one electrode of capacitor C3, the other electrode of capacitor C3 being coupled, preferably connected, to terminal PV2.

[0074] The operation of the current-limiting circuit 40 shown in [Fig. 10] will now be described. The comparator AO turns its output high when the voltage VPV exceeds the voltage threshold TH1. This turns the transistor M1 on through the gate resistor R2. This corresponds to the operation of the first clipping circuit 30.

[0075] Switching the comparator output AO to a high state also turns on the bipolar transistor Q1 via resistor RI1. This brings the collector potential of the bipolar transistor Q1, previously equal to the potential at terminal PV1, to a potential close to approximately 0 V. More precisely, the collector-emitter voltage of transistor Q1 in saturation is equal to 0.2 V. Turning on transistor Q1 biases the voltage divider formed by resistors R9 and RIO, which then presents a gate voltage VG2 across the gate of transistor M2 given by the following relation: [Math 2] V —V i R1° 3 VG2-VPV\ R9+R10 J

[0076] Resistors R9 and RIO are chosen so that the voltage VG2 is approximately 15 V below the voltage VPV. The gate-source voltage VGs2 of transistor M2 is then approximately -15 V. Transistor M2 is therefore conducting.

[0077] The transistor M2 remains conducting as long as the voltage VPV is greater than the voltage threshold THL. When the transistor M2 is conducting, a charge of the capacitor C3 occurs.

[0078] When the first clipping circuit 30 is operating normally, transistor M2 is in the conducting or blocking state according to the output voltage VAo supplied by comparator AO. This results in the complete charging of capacitor C3. The potential VC3 at the electrode of capacitor C3 located on the side of transistor M2 therefore rises substantially to the voltage VPV.

[0079] The TH2 voltage threshold that controls the triggering of the thyristor T1 corresponds to the voltage at the anode of the Zener diode Z6, which is controlled by the voltage VC3. The TH2 voltage threshold is equal to the sum of the Zener voltage Vz5 of the Zener diode Z5 and the Zener voltage Vz6 of the Zener diode Z6. The Zener voltage Vz5 of the Zener diode Z5 and the Zener voltage Vz6 of the Zener diode Z6 are chosen so that the TH2 voltage threshold is strictly greater than the THL voltage threshold. Resistor R12 allows fine adjustment of the TH2 voltage threshold.

[0080] When the voltage VPV exceeds the voltage threshold TH2, a current supplies the gate of the thyristor Tl, causing it to trigger. As described previously, when triggered, the thyristor Tl maintains a short circuit between the PV1 and PV2 terminals of the photovoltaic panel 10 as long as the photovoltaic panel 10 continues to operate, in particular as long as there is sufficient light illuminating the photovoltaic panel 10. Operator intervention is then required to make the limiting circuit 40 function correctly again. The voltage threshold TH2 is strictly greater than the voltage threshold TH1, so the triggering of the thyristor Tl only occurs in the event of a malfunction of the transistor ML. The thyristor Tl unlocks when the current flowing through it drops to 0 A, which occurs when the photovoltaic panel 10 no longer receives light, particularly at night.Advantageously, if the fault persists on the clipping circuit 30 the following day, the thyristor TH1 is reactivated if the voltage VPV reaches the voltage threshold TH2. The second clipping circuit 45 therefore acts as a safeguard against a malfunction of the first clipping circuit 30.

[0081] The embodiment of the voltage limiting circuit 40 of [Fig. 10] advantageously prevents the untimely triggering of the second clipping circuit 45 since it makes the start-up of the second clipping circuit 45 dependent on the start-up of the first clipping circuit formed by the comparator AO and its two divider bridges.

[0082] In the embodiments of the voltage limiting circuit 40 described above, the short-circuiting of the photovoltaic panel 10 by the second clipping circuit 45 in a lasting manner facilitates fault detection, for example in the case of an application in a solar vehicle by the vehicle electronics.

[0083] Simulations were performed. The simulation parameters are the same as those described previously for obtaining the curves in [Fig. 5]. In addition, the resistance R9 is equal to 4.7 kΩ, the resistance R10 is equal to 15 kΩ, the resistance RI1 is equal to 2.2 kΩ, the capacitance of capacitor C3 is equal to 470 nF, the resistance R12 is equal to 10 Ω, and the resistance R13 is equal to 15 kΩ. The Zener voltage Vz5 is equal to 51 V and the Zener voltage Vz6 is equal to 12 V. The threshold voltage TH2 is therefore equal to 63 V. The resistance R12 is equal to 10 Ω.

[0084] Figure 11 shows the evolution curves of the voltage VPV, the voltage VAo and the voltage VC3 as a function of time after the start-up of the solar installation including the current limiting circuit 40 of Figure 10 during normal operation of the first clipping circuit 30. Since the transistor M2 is conducting whenever the output voltage VAo supplied by the comparator AO is in the high state, it can be clearly seen that the potential VC3 at the electrode of the capacitor C3 located on the side of the transistor M2 rises substantially up to the voltage VPV.

[0085] Fig. 12 represents curves of evolution of the voltage VPV, the voltage VAO and the voltage VC3 as a function of time after the start-up of the solar installation including the current limiting circuit 40 of Fig. 10 during an abnormal operation of the first clipping circuit 30, the transistor M1 being replaced by an open circuit.

[0086] The VAOs voltage rises as soon as the VPV voltage exceeds the TH1 voltage threshold, which is approximately 60 V. Since transistor M1 is not functional, the VPV voltage continues to rise until it reaches the TH2 voltage threshold, which is 63 V. This triggers thyristor T1 and essentially short-circuits the photovoltaic panel 10. This results in a decrease in the VPV voltage.

[0087] Figure 13 is an electrical diagram of a voltage limiting circuit 50 comprising another embodiment of the first MOS transistor clipping circuit. The first MOS transistor clipping circuit comprises all the elements of the first clipping circuit 30 shown in Figure 3 and further comprises a capacitor C4 and a resistor R16 in series, the assembly comprising capacitor C4 and resistor R16 in series coupling, preferably connecting, the inverting input (-) of the operational amplifier AO to the output of the operational amplifier AO. The first clipping circuit further comprises a resistor R17 coupling, preferably connecting, node N2 to the inverting input (-) of the operational amplifier AO.

[0088] The operational amplifier AO is used with a feedback loop of the type RC from the output to the inverting input (-) formed by capacitor C4 and resistor R16 in series. The non-inverting input (+) of the operational amplifier AO is subjected to a voltage fraction of the voltage VPV. This results in a Proportional-Integral voltage regulator, where the voltage at the midpoint N2 is the regulator's setpoint and the voltage at the midpoint NI is the measured voltage feedback to be controlled.

[0089] In this embodiment, the transistor Ml is controlled in linear mode and no longer in saturated blocked mode as in the embodiment described previously in relation to [Fig.3].

[0090] Simulations were carried out. The simulation parameters are the same as those described previously for obtaining the curves in [Fig. 5]. In addition, the resistance R16 is equal to 3.3 kΩ, the capacitance of capacitor C4 is equal to 220 pF, and the resistance R17 is equal to 3.3 kΩ.

[0091] Fig. 14 represents curves of evolution of the voltage VPV, the voltage VAO and the current IM1 flowing in the transistor Ml as a function of time after the start-up of the solar installation including the voltage limiting circuit 50 of Fig. 13.

[0092] The voltage limiting circuit 30, 40, or 50 described above can be integrated into the input of the electronics on the load side 20, but also within the photovoltaic panel 10 to obtain a self-contained photovoltaic panel in terms of voltage limiting. The operation of the voltage limiting circuit is completely transparent to the control of the photovoltaic panel 10, which can implement a maximum power point tracking (MPPT) algorithm.

[0093] Various embodiments and variants have been described. Those skilled in the art will understand that certain features of these various embodiments and variants could be combined, and other variants will become apparent to those skilled in the art. In particular, the embodiment of the first clipping circuit shown in [Fig. 13] can be used in combination with each of the embodiments of the second clipping circuit shown in Figures 8, 9, and 10.

[0094] Finally, the practical implementation of the embodiments and variants described is within the reach of a person skilled in the art, based on the functional indications given above.

Claims

Demands

1. Solar installation comprising a photovoltaic panel (10) having first and second terminals (PV1, PV2), intended to be coupled to a load (20), a first voltage limiting circuit (30) between the first and second terminals comprising a first MOS transistor (Ml) coupling the first and second terminals, the first circuit being configured to turn on the first MOS transistor (Ml) when the voltage (VPV) exceeds a first voltage threshold (TH1), and a second voltage limiting circuit (45) between the first and second terminals comprising a thyristor (Tl) coupling the first and second terminals (PV1, PV2), the second circuit being configured to turn on the thyristor when the voltage (VPV) exceeds a second voltage threshold (TH2), strictly greater than the first voltage threshold (TH1).

2. Solar installation according to claim 1, wherein the first circuit (30) comprises a first voltage divider bridge coupling the first and second terminals (PV1, PV2), a second voltage divider bridge coupling the first and second terminals, and an operational amplifier (OA) comprising an output coupled to the gate of the first MOS transistor (M1), a non-inverting input coupled to a first midpoint (NI) of the first voltage divider bridge, and an inverting input coupled to a second midpoint (N2) of the second voltage divider bridge.

3. Solar installation according to claim 2, wherein the first voltage divider bridge comprises a first resistor (R3) in series with a second resistor (R4), and wherein the second voltage divider bridge comprises a third resistor (R5) in series with a first Zener diode.

4. Solar installation according to claim 2 or 3, wherein the operational amplifier (OA) operates as a comparator.

5. A solar installation according to claim 1, wherein the second circuit comprises a second MOS transistor (M2) in series with a capacitor (C3), the assembly comprising the second MOS transistor (M2) and the capacitor (C3) coupling the first and second terminals (PV1, PV2), and a step-down circuit coupling one electrode of the capacitor to the gate of the thyristor (T1), the second circuit being configured to conduct the second transistor simultaneously with first MOS transistor (Ml).

6. Solar installation according to claim 5, wherein the voltage step-down circuit comprises at least one second Zener diode (Z5, Z6).

7. Solar installation according to claim 5 in its connection with claim 2, wherein the second circuit comprises a bipolar transistor (Ql) in series with a fourth resistor (R9), the assembly comprising the bipolar transistor (Ql) and the fourth resistor (R9) coupling the first and second terminals (PV1, PV2), the output of the operational amplifier (AO) being coupled to the base of the bipolar transistor (Ql), and the gate of the second MOS transistor (M2) being coupled to a node between the bipolar transistor (Ql) and the fourth resistor (R9).

8. Solar installation according to any one of claims 1 to 7, wherein the first terminal (PV1) is intended to be connected to a third terminal (CH1) of the load (20), wherein the second terminal (PV2) is intended to be connected to a fourth terminal (CH2) of the load, and wherein the first voltage limiting circuit (30; 40; 50) (VPV) does not include any electronic component coupled between the first terminal and the third terminal or coupled between the second terminal and the fourth terminal.

9. Vehicle (1) comprising a solar installation according to any one of claims 1 to 8.

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