System comprising a photovoltaic panel for supplying electricity to a load

Abstract

System comprising a photovoltaic panel for supplying electricity to a load The present description relates to a system comprising a photovoltaic panel (101), and a power converter (105) adapted to convert an electrical output power of the photovoltaic panel into an electrical power supply to a load (103), the system further comprising a self-activation module (107) configured to, before activating the power converter (105) to supply the load (103), implement the following successive steps: a) measure the maximum electrical power (MPP) that can be produced by the photovoltaic panel (101); b) compare said maximum electrical power (MPP) to a first power threshold (TH2); and c) activate the power converter (105) to supply the load (103) only if said maximum electrical power (MPP) is greater than said first power threshold (TH2). Figure for abstract: Fig. 1.

Description

Title of the invention: System comprising a photovoltaic panel for supplying electricity to a load Technical field

[0001] The present description relates generally to the field of systems or installations based on photovoltaic panels. It relates more particularly to a system comprising a photovoltaic panel for the electrical supply of a load assembly and means for storing electrical energy, requiring precise management of the electrical energy, for example a motor vehicle. Prior art

[0002] An electrically powered motor vehicle has been proposed, equipped with a photovoltaic panel, also called a solar roof, serving as a backup source for recharging an electric battery of the vehicle, in particular with a view to increasing the vehicle's autonomy.

[0003] It would be desirable to at least partially improve certain aspects of such a vehicle.

[0004] More generally, it would be desirable to improve at least in part certain aspects of systems based on photovoltaic panels. Summary of the invention

[0005] One embodiment provides a system comprising a photovoltaic panel, and a power converter adapted to convert an electrical output power of the photovoltaic panel into an electrical power supply to a load, the system further comprising a self-activation module configured to, before activating the power converter to supply the load, implement the following successive steps: a) measure the maximum electrical power that can be produced by the photovoltaic panel; b) comparing said maximum electrical power to a first power threshold; and c) activating the power converter to supply the load only if said maximum electrical power is greater than said first power threshold.

[0006] According to one embodiment, the self-activation module is configured to periodically repeat steps a) and b) as long as said maximum electrical power is lower than said first power threshold.

[0007] According to one embodiment, the first power threshold is greater than or equal to an overconsumption value of the system in the event of activation of the power converter to supply the load.

[0008] According to one embodiment, the self-activation module is configured to measure the voltage across the terminals of the photovoltaic panel and implement steps a) and b) only when said voltage is higher than a predefined voltage threshold

[0009] According to one embodiment, the self-activation module is further configured to, after step c), periodically measure the maximum electrical power that can be produced by the photovoltaic panel, and interrupt the power converter when said maximum electrical power falls below a second power threshold.

[0010] According to one embodiment, the second power threshold is lower than the first power threshold.

[0011] According to one embodiment, the first power threshold can be modified to take one or the other of two predefined values ​​depending on a mode of use of the system.

[0012] According to one embodiment, the load to be supplied is a battery of a vehicle, and the photovoltaic panel is mounted on the vehicle.

[0013] According to one embodiment, the self-activation module comprises a circuit for measuring a current-voltage characteristic of the photovoltaic panel.

[0014] According to one embodiment, the self-activation module further comprises a multiplier providing a signal representative of the product of the current and the voltage of the photovoltaic panel.

[0015] According to one embodiment, the self-activation module further comprises a detector of a maximum value of the signal representative of the product of the current and the voltage of the photovoltaic panel.

[0016] According to one embodiment, the self-activation module further comprises a circuit for comparing said maximum value of the signal representative of the product of the current and the voltage of the photovoltaic panel to a threshold.

[0017] Another embodiment provides a method for controlling a system comprising a photovoltaic panel, and a power converter adapted to convert an electrical output power of the photovoltaic panel into an electrical power supply to a load, comprising the following successive steps: a) measuring the maximum electrical power that can be produced by the photovoltaic panel; b) comparing said maximum electrical power to a first power threshold; and c) activating the power converter to supply the load only if said maximum electrical power is greater than said first power threshold. Brief description of the drawings

[0018] These and other features and advantages will be set forth in detail in the following description of particular embodiments given without limitation in relation with the attached figures among which:

[0019] [Fig.l] schematically represents, in the form of blocks, an example of an embodiment of a system comprising a photovoltaic panel adapted to electrically supply a load;

[0020] [Fig.2] is a diagram schematically illustrating an example of a control method implemented in the system of [Fig.l];

[0021] [Fig.3] shows in more detail, in the form of blocks, an example of the embodiment of a self-activation module of the system of [Fig.l];

[0022] [Fig.4] is a more detailed electrical diagram of an exemplary embodiment of a part of the self-activation module of [Fig.3];

[0023] [Fig.5] is a more detailed electrical diagram of an exemplary embodiment of another part of the self-activation module of [Fig.3]; and

[0024] [Fig.6] is a more detailed electrical diagram of an exemplary embodiment of yet another part of the self-activation module of [Fig.3]. Description of the embodiments

[0025] The same elements have been designated by the same references in the different figures. In particular, the structural and / or functional elements common to the different embodiments may have the same references and may have identical structural, dimensional and material properties.

[0026] For the sake of clarity, only the steps and elements useful for understanding the embodiments described have been shown and are detailed. In particular, only the production of a self-activation module configured to trigger the supply of an electrical load by a photovoltaic panel, conditioned by a maximum instantaneous power producible by the photovoltaic panel, has been detailed. The other elements of the system have not been detailed, the embodiments described being compatible with all or most of the known systems based on photovoltaic panels, subject to possible adaptations within the scope of the person skilled in the art from the indications of the present description.

[0027] Unless otherwise specified, when referring to two elements connected to each other, this means directly connected without intermediate elements other than conductors, and when referring to two elements connected (in English "coupled") to each other, this means that these two elements can be connected or be connected by means of one or more other elements.

[0028] Unless otherwise specified, the expressions "about", "approximately", "substantially", and "of the order of" mean to within 10%, preferably to within 5%.

[0029] [Fig.l] schematically represents, in the form of blocks, an example of an embodiment of a system comprising a photovoltaic panel 101 (PV) adapted to electrically supply a load 103 (L). The system is for example a motor vehicle, for example with an electric motor. The photovoltaic panel 101 is for example installed on the roof of the vehicle. The load 103 is for example an electric battery, for example the traction battery of the vehicle, supplying an electric traction motor of the vehicle, or an auxiliary battery of the vehicle.

[0030] The system of [Fig.l] comprises a power converter 105, for example a switching converter, for example of the direct / direct (DC) type, adapted to convert an electrical output power of the photovoltaic panel 101 into an electrical power supply to the load 103. In the example shown, the converter 105 comprises input terminals e1 and e2 connected, for example connected, respectively to output terminals VH and VL of the photovoltaic panel 101. The terminals VH and VL correspond respectively to the high potential and low potential power supply terminals of the photovoltaic panel. The converter 105 further comprises two output terminals s1 and s2 connected, for example connected, respectively to terminals V+ and V- for supplying the load 103.In the case where the load 103 is an electric battery, the terminals V+ and V- correspond for example respectively to a positive terminal and a negative terminal of the battery. The realization of the power converter 105 has not been detailed, the embodiments described being compatible with all or most of the known architectures of power converters. By way of example, the converter 105 comprises a plurality of power switches (not detailed in the figure) controlled in switching by means of a microcontroller (not detailed in the figure).

[0031] In practice, in a motor vehicle, and in particular when the load 103 corresponds to the traction battery of the vehicle, the activation of the power converter 105 to supply the load 103 from the electrical energy produced by the photovoltaic panel 101 requires the activation of various peripherals of the vehicle, to implement, for example, functions for monitoring the charge levels of the battery cells, functions for monitoring the temperature within the battery, cooling functions, etc. The excess electrical consumption induced due to the activation of these peripherals, that is to say the additional consumption linked to the use of the photovoltaic panel (zero when the panel is not in use), can be significant.For example, if the vehicle is stationary and in standby mode (parking mode), activating the peripherals necessary for the proper functioning of solar charging can induce an overconsumption of between 5 and 50 W, for example in the order of 20 to 30 W. If the vehicle is moving (driving mode), some of the peripherals necessary for the proper functioning of solar charging are already active. Thus, the overconsumption linked to . activation of solar charging is lower. This overconsumption remains, however, not negligible, for example between 2 and 10 W, for example in the order of 5 to 7 W.

[0032] If the electrical power produced by the photovoltaic panel is less than the excess consumption linked to the activation of solar charging, the overall balance of solar charging is negative. It is then preferable to interrupt solar charging. If, on the other hand, the electrical power produced by the photovoltaic panel is greater than the excess consumption linked to the activation of solar charging, the overall balance of solar charging is positive. It is then desirable to continue solar charging.

[0033] The electrical power produced by the photovoltaic panel is likely to vary over time, depending in particular on the sunshine.

[0034] To determine whether the solar charging balance is positive or negative, one possibility is to activate the solar charging, to measure the power supplied to the load 103 at the output of the converter 105, and to compare this power to a predefined overconsumption threshold linked to the activation of the solar charging. If the power supplied at the output of the converter 105 is greater than the overconsumption threshold, the balance is positive and the solar charging can be continued. If, on the other hand, the power supplied at the output of the converter 105 is less than the overconsumption threshold, the balance is negative and the solar charging is interrupted for a predefined time interval, at the end of which a new solar charging attempt is implemented.

[0035] A limitation of this approach is that it involves regularly activating solar charging, without knowing in advance whether the balance will be positive or not, leading to a pumping phenomenon which can prematurely discharge the battery if the vehicle remains for a long period in conditions of low sunlight.

[0036] According to one aspect of the embodiments described, the system of [Fig.l] comprises an auto-activation module 107 (AA) configured to, before activating the power converter 105 to power the load, measure the maximum electrical power that can be produced by the photovoltaic panel 101, compare this power to a predefined overconsumption threshold linked to the activation of the solar recharge, and activate the power converter to power the load only if the maximum electrical power that can be produced by the photovoltaic panel is greater than the overconsumption threshold.

[0037] In other words, solar charging is activated only if the maximum electrical power produced measured by the module 107 is greater than the overconsumption threshold, which makes it possible to avoid the pumping phenomena mentioned above.

[0038] [Fig.2] is a diagram schematically illustrating an example of a control method implemented by the self-activation module 107 of the system of [Fig.l].

[0039] Initially, the solar recharge is inactive, that is to say that the power converter 105 is inactive and the photovoltaic panel 101 is kept in open circuit.

[0040] During a step 201, the module 107 compares the output voltage VPV of the photovoltaic panel to a threshold TH1 corresponding to a minimum voltage threshold to allow self-powering of the module 107, for example a threshold between 10 and 20 V, for example of the order of 18 V.

[0041] If the voltage VPV is lower than the threshold TH1 (N), a time delay 203 (TMP) is triggered, then step 201 is repeated after a predefined time interval, for example greater than 1 second, for example several seconds. By way of example, steps 201 and 203 can be implemented by means of a microcontroller (not detailed in the figures) powered by a self-powering circuit connected, for example connected, to the output terminals VH and VL of the photovoltaic panel, adapted to operate under a voltage lower than the threshold TH1, for example a voltage of a few volts, for example a voltage of the order of 3.3 V.

[0042] If the voltage VPV is greater than the threshold TH1 (Y), a step 205 of measuring the maximum power MPP producible by the photovoltaic panel is implemented. The power MPP corresponds to the maximum power that can be produced under the irradiation conditions of the panel at the time of the measurement.

[0043] During step 205, the voltage VPV of the photovoltaic panel is varied between a minimum value corresponding to the short-circuit voltage of the panel and a maximum value corresponding to the open-circuit voltage of the panel, by searching for the maximum power point of the panel, i.e. the operating point for which the product VPV*IPV is maximum, IPV designating the current supplied by the photovoltaic panel. The maximum producible power MPP corresponds to the product VPV*I PV at this operating point.

[0044] At the end of step 205, a step 207 of comparing the MPP value measured in step 205, with a predetermined threshold TH2, is implemented. The threshold TH2 corresponds for example to the overconsumption threshold linked to the activation of solar charging, below which it is not advantageous to activate the power converter 105. The threshold TH2 can be modified depending on the mode of use of the vehicle. For example, the threshold TH2 can have a first value, for example between 5 and 50 W, for example of the order of 20 to 30 W, when the vehicle is stationary (parking mode), and a second value lower than the first value, for example between 2 and 10 W, for example of the order of 5 to 7 W, when the vehicle is moving (driving mode).

[0045] If the MPP value is lower than the threshold TH2 (N), a time delay 209 (TMP) is triggered, then steps 205 and 207 are repeated after a time interval predefined, for example greater than 1 ms, for example between 1 millisecond and 5 minutes, for example of the order of 100 milliseconds.

[0046] If the MPP value is greater than the threshold TH2 (Y), the power converter 105 is activated during a step 211 (CHARGE), so as to supply the load 103 from the electrical energy produced by the photovoltaic panel 101. In other words, in this example, the solar charge is activated at step 211.

[0047] After step 211, a monitoring loop 220 can optionally be implemented by the module 107, to interrupt the solar recharge if the maximum electrical power producible by the photovoltaic panel falls below a threshold TH3, for example less than or equal to the threshold TH2, preferably strictly less than the threshold TH2 so as to obtain a hysteresis.

[0048] Loop 220 comprises, after step 211, a new step 221 (MPP) for measuring the maximum MPP power producible by the photovoltaic panel. Step 221 is for example implemented by module 107 in an identical or similar manner to step 205.

[0049] Loop 220 further comprises, after step 221, a step 223 of comparing the MPP value measured in step 221 with threshold TH3, also called deactivation threshold. Like threshold TH2, threshold TH3 can be modified depending on the mode of use of the vehicle.

[0050] If the MPP value is greater than the threshold TH3 (N), a time delay 225 (TMP) is triggered, then steps 221 and 223 are repeated after a predefined time interval, for example greater than 10 ms, for example between 10 ms and 1 minute, for example between 100 milliseconds and 1 second.

[0051] If the MPP value is lower than the threshold TH3 (Y), the solar charging is deactivated, in particular the power converter 105 deactivated, then the timer 203 is triggered and the process resumes at step 201.

[0052] Alternatively, the monitoring loop 220 may be omitted. In this case, other circuits for monitoring the power produced by the photovoltaic panel, distinct from the self-activation module 107, for example circuits based on power measurements at the output of the power converter 105, may be used to decide whether or not to interrupt the solar recharge.

[0053] [Fig. 3] shows in more detail, in the form of blocks, an example of an analog embodiment of the self-activation module 107 of the system of [Fig. 1].

[0054] In this example, the module 107 comprises a circuit 301 for measuring the characteristic Ipv(Vpv) of the photovoltaic panel. In this example, the circuit 301 is connected, for example, to the output terminals VH and VL of the photovoltaic panel 101. During a measurement phase, the circuit 301 is adapted to vary, for example continuously, the value of the voltage VPV between a minimum value, corresponding to the short-circuit voltage of the panel, and a maximum value, corresponding to the open-circuit voltage of the panel. Throughout the measurement, the circuit 301 provides a signal U representative of the voltage VPV at the terminals of the photovoltaic panel 101, for example proportional to the voltage VPV, and a signal I representative of the current IPV supplied by the photovoltaic module 101, for example proportional to the voltage IPV.

[0055] The module 107 of [Fig.3] further comprises an analog multiplier receiving at the input the signals U and I and providing at the output a signal PP equal or proportional to the product U*I, representative of the instantaneous power producible by the photovoltaic panel at the operating point (VPV, IPv) considered.

[0056] The module 107 of [Fig.3] further comprises a circuit 305 for detecting the maximum MPP value of the PP signal during the measurement phase. The MPP value is representative of the maximum instantaneous power producible by the photovoltaic panel.

[0057] The module 107 of [Fig. 3] further comprises a circuit 307 for comparing the MPP value to a predetermined threshold, corresponding to the threshold TH2 of the algorithm of [Fig. 2]. The circuit 307 provides an OUT signal, for example a binary signal, representative of the result of the comparison. The OUT signal can be transmitted to a microcontroller, not shown, to activate or not, depending on the result of the comparison, the power converter 105 of the system.

[0058] The module 107 of [Fig. 3] further comprises a control circuit 309 connected, for example connected, to the terminals VH and VL of the photovoltaic panel, adapted to trigger the measurement of the characteristic IPV(VPV) by the circuit 301, in particular when the voltage VPV at the terminals of the photovoltaic panel 101 exceeds a threshold, for example the threshold TH1 of the algorithm of [Fig. 2], then at regular intervals as long as the voltage VPV remains higher than the threshold TH1.

[0059] [Fig.4] is a more detailed electrical diagram of an exemplary embodiment of a part of the self-activation module 107 of [Fig.3].

[0060] [Fig.4] illustrates more particularly an example of embodiment of the circuits 301, 303, 305 and 307 of module 107. [Fig.4] further represents a self-power supply circuit 401 (not visible in [Fig.3]) of module 107.

[0061] The circuit 401 is connected, for example, to the output terminals VH and VL of the photovoltaic panel 101, and is adapted to supply a DC supply voltage to the module 107 when the voltage VPV at the terminals of the photovoltaic panel 101 exceeds a threshold, for example equal to the threshold TH1. By way of example, the circuit 401 is adapted to supply a positive supply voltage +VC, for example of the order of +12V, and a symmetrical negative supply voltage -VC, for example of the order of -12V, when the voltage VPV exceeds a threshold, for example greater than +VC. The DC supply voltages +VC and -VC of the module are for example referenced relative to the same reference terminal GND of the module, for example connected to ground. The circuit 401 comprises for example a DC-DC switching converter.

[0062] In the example of [Fig.4], the circuit 301 comprises a capacitor Cl in series with a resistor RI. During a measurement phase of the IPV(VPV) characteristic, the series association of the capacitor Cl and the resistor RI is connected to the terminals of the photovoltaic panel 101, causing the capacitor CL to charge. At the start of charging (capacitor Cl fully discharged), the current IPV delivered by the photovoltaic panel corresponds to the short-circuit current of the panel. At the end of charging (capacitor Cl fully charged), the current IPV is cancelled and the voltage VPV at the terminals of the photovoltaic panel corresponds to the open-circuit voltage of the panel.In this example, the output signal U of the circuit 301 is a voltage representative of the voltage across the capacitor Cl (and therefore of the voltage VPV of the photovoltaic panel, and the output signal I of the circuit 301 is a voltage representative of the voltage across the resistor RI (and therefore of the current IPV delivered by the photovoltaic panel).

[0063] In this example, the resistor RI has a first end connected, for example connected, to the terminal VL, and a second end connected, for example connected, to a first electrode of the capacitor CL. The second electrode of the capacitor Cl is connected to the terminal VH via a switch M1 for triggering the measurement. The switch M1 is for example a MOS transistor. In the example shown, the switch M1 is a P-channel MOS transistor. The switch M1 has a first conduction node (drain) connected, for example connected, to the second electrode of the capacitor Cl and a second conduction node (source) connected, for example connected, to the terminal VH.

[0064] In the example of [Fig. 4], the circuit 301 further comprises, in parallel with the capacitor C1, a switch M2 for resetting the capacitor C1. The switch M2 is for example a MOS transistor. In the example shown, the switch M2 is an N-channel MOS transistor. The switch M2 has a first conduction node (source or drain) connected, for example connected, to the first electrode of the capacitor C1 and a second conduction node (drain or source) connected, for example connected, to the second electrode of the capacitor C1.

[0065] The switch M1 has a control node (gate node in the example shown) connected to a node for applying a control signal SL. In this example, the control node of the switch M1 is connected to the control node SI via a close control circuit comprising three resistors rl0, rl1 and rl2, and a transistor t1. The resistors rl0 and rl1 and the transistor t1 are connected in series, in this order, between the terminal VH and the reference node. GND. Transistor tl is for example a bipolar transistor of the NPN type whose collector is connected, for example connected, to the end of resistor rl1 opposite resistor rl0, and whose emitter is connected, for example connected, to node GND. Transistor tl has a control node, for example a base node, connected to node SI via resistor rl2. In this example, the midpoint between resistors rl0 and rl1 is connected, for example connected, to the control node of switch ML

[0066] The switch M2 has a control node (gate node in the example shown) connected to a node for applying a control signal S2. In this example, the control node of the switch M2 is connected to the control node S2 via a resistor rl3.

[0067] In the example of [Fig.4], the output signal I of the circuit 301 is directly the voltage across the resistor RL. The output signal U of the circuit 301 is a voltage proportional to the voltage across the capacitor CL. More particularly, in this example, the circuit 301 comprises two resistors rl4 and 15 connected in series across the capacitor Cl and forming a voltage divider bridge. The signal U corresponds to the voltage across the resistor rl5, connected to the bottom electrode of the capacitor Cl, i.e. the electrode of the capacitor Cl connected to the resistor RL.

[0068] In the example of [Fig.4], the circuit 303 is an analog multiplier receiving the voltages U and I as input and providing as output a voltage PP equal to or proportional to the product U*I. The circuit 303 is for example powered by the voltages +VC and -VC provided by the circuit 401. The output voltage PP of the circuit 303 is for example referenced with respect to the reference node GND.

[0069] In this example, the circuit 305 for detecting the maximum value MPP of the signal PP comprises a diode D1, for example a Schottky diode, and a capacitor C2. The anode of the diode D1 is connected, for example connected, to the output node of the multiplier 303, providing the voltage PP as output. The cathode of the diode D1 is connected, for example connected, to a first electrode of the capacitor C2. The second electrode of the capacitor C2 is connected, for example connected, to the reference node GND. The capacitor C2 momentarily retains, thanks to the diode D1, the maximum value of the signal PP at each measurement. Thus, the signal MPP corresponds to the voltage across the capacitor C2 at the end of the measurement. In the example shown, the circuit 305 further comprises a reset switch M3, for example a MOS transistor, connected in parallel with the capacitor C2. The transistor M3 is for example an N-channel MOS transistor.In this example, transistor M3 has a first conduction node (source) connected, for example connected, to the first electrode of capacitor C2 and a second conduction node (drain) connected, for example . connected, to the second electrode of capacitor C2. Switch M3 has a control node (gate node in the example shown) connected, for example connected, to a node for applying a control signal, for example the same control signal S2 as that used to control reset switch M2.

[0070] In the example of [Fig. 4], the comparison circuit 307 comprises an operational amplifier AO1, a non-inverting input (+) of which is connected, for example connected, to the output node of the circuit 305, i.e. to the first electrode of the capacitor C2 (diode side DI in the example shown), and an inverting input (-) of which is connected, for example connected, to a node for applying a DC voltage VTH defining the comparison threshold of the circuit. The output of the operational amplifier AO1 is connected, for example connected, to the output node OUT of the module 107. The output signal of the operational amplifier AO1 is for example a binary signal, for example a voltage having a first state, for example low level, when the voltage MPP is lower than the threshold VTH (corresponding for example to the threshold TH2 of the algorithm of [Fig. 2]), and a second state, for example high level, when the voltage MPP is higher than the threshold VTH.For example, the operational amplifier AO1 is powered by the DC supply voltage +VC provided by the circuit 401.

[0071] [Fig.5] is a more detailed electrical diagram of an exemplary embodiment of another part of the self-activation module 107 of [Fig.3].

[0072] [Fig.5] illustrates more particularly an exemplary embodiment of the control circuit 309 of the self-activation module 107.

[0073] As explained previously, the circuit 309 is adapted to trigger the measurement of the characteristic IPV(VPV) by the circuit 301, that is to say, in the example of [Fig.4], to trigger the charging of the capacitor C1, when the voltage VPV at the terminals of the photovoltaic panel 101 exceeds a threshold, for example the threshold TH1 of the algorithm of [Fig.2], then at regular intervals as long as the voltage VPV remains higher than the threshold TH1.

[0074] The circuit 309 of [Fig. 5] comprises two resistors rl6 and rl7 in series between the terminals VH and VL of the photovoltaic panel 101, forming a voltage divider bridge. More particularly, in this example, the resistor rl6 has a first end connected, for example connected, to the terminal VH, and a second end connected, for example connected, to a first end of the resistor rl7. The second end of the resistor rl7 is connected, for example connected, to the terminal VL.

[0075] The circuit 309 further comprises an operational amplifier AO2 mounted as a voltage comparator, a non-inverting input (+) of which is connected, for example, to the midpoint between the resistors rl6 and rl7. The operational amplifier AO2 further has an inverting input (-) connected, for example, to a node ni applying a reference voltage defining the comparison threshold TH1 of the comparator. In this example, the reference voltage applied to the node ni is generated by means of a Zener diode Zl. The anode of the Zener diode ZI is connected, for example connected, to the node GND, and the cathode of the Zener diode ni is connected to the high potential output terminal VH of the photovoltaic panel 101 via a resistor rl8. More particularly, in this example, the resistor rl8 has a first end connected, for example connected, to the node VH, and a second end connected, for example connected, to the cathode of the Zener diode Zl. In this example, the cathode of the Zener diode Zl is connected, for example connected, to the node ni. Thus, in this example, the threshold TH1 for triggering the measurement of the maximum producible power MPP of the photovoltaic panel is set by the avalanche voltage of the Zener diode Zl.A resistor rH is preferably provided between the non-inverting input (+) and the output of the operational amplifier AO2 to obtain hysteresis operation. In the example shown, the resistor rH has a first end connected, for example connected, to the non-inverting input terminal (+) of the operational amplifier AO2, and a second end connected, for example connected, to the output terminal of the operational amplifier AO2.

[0076] The output of the operational amplifier AO2 is connected, for example, to a node n2. The output signal of the operational amplifier AO2 is, for example, a binary signal, for example, a voltage having a first state, for example low level, when the voltage VPV across the terminals of the photovoltaic panel 101 is lower than the threshold TH1, and a second state, for example high level, when the voltage VPV is higher than the threshold TH1. For example, the operational amplifier AO2 is powered by the DC supply voltage +VC provided by the circuit 401.

[0077] The output node n2 of the operational amplifier AO2 is connected to an input node n3 of a circuit 501 for generating the signal SI for controlling the switch M1 and the signal S2 for controlling the switches M2 and M3. In this example, the node n2 is connected to the node n3 via a circuit 503. The circuit 503 comprises two logic gates NAND1 and NAND2 connected in series, a resistor R26 and a capacitor C8, defining an astable multivibrator.

[0078] The NAND1 gate has a first input node connected, for example connected, to the node n2, and an output node connected, for example connected, to first and second input nodes of the NAND2 gate. The resistor R26 has a first end connected, for example connected, to the output node of the NAND1 gate and a second end connected, for example connected, to a second input node of the NAND1 gate. The capacitor C8 has a first electrode connected, for example connected, at the second end of resistor R26 and a second electrode connected, for example connected, to an output node of gate NAND2. The output node of gate NAND2 is connected, for example connected, to node n3.

[0079] In the example shown, the circuit 503 further comprises two resistors R9 and R15. The resistor R9 has a first connected end, for example connected to the node n2 and a second connected end, for example connected to ground (GND). The resistor RI5 has a first connected end, for example connected to the node n3 and a second connected end, for example connected to ground (GND).

[0080] The circuit 501 comprises, in this example, two monostable circuits MSI and MS2 respectively generating the signals SI and S2.

[0081] In this example, the MSI circuit comprises two NOR logic gates norl and nor2, for example identical or similar, each having two inputs and one output. The MSI circuit further comprises a capacitor C3 and a resistor rl9.

[0082] The logic gate norl has a first input connected, for example, to node n3.

[0083] Capacitor C3 has a first electrode connected, for example connected, to an output node of logic gate nor1, and a second electrode connected, for example connected, to the first and second inputs of logic gate nor2. In other words, in this example, the two inputs of logic gate nor2 are short-circuited and connected to the second electrode of capacitor C3.

[0084] The output of the logic gate nor2 is connected, for example connected, to a node for supplying the control signal SL. The output of the logic gate nor2 is further connected, for example connected, to the second input of the logic gate norl.

[0085] The resistor rl9 has a first end connected, for example connected, to the second electrode of the capacitor C3 (logic gate side nor2), and a second end connected, for example connected, to a node for applying the supply voltage +VC supplied by the supply circuit 401.

[0086] In this example, the circuit MS2 is similar to the circuit MSI, by replacing the NOR logic gates norl and nor2 with NOR logic gates nor3 and nor4, for example identical respectively to the logic gates norl and nor2, and by replacing the capacitor C3 and the resistor rl9 with respectively a capacitor c4 and a resistor r20. The output of the logic gate nor4 is connected, for example, to a node for supplying the control signal S2.

[0087] When the output signal of comparator AO2 (node ​​n2) goes high, the output signal SI of circuit MSI and the output signal S2 of circuit MS2 go high. The signal SI remains in a high state for a duration TS1 fixed by the time constant of the RC circuit formed by resistor rl9 and capacitor C3. The signal S2 remains in a high state for a duration TS2 fixed by the time constant of the RC circuit formed by resistor r20 and capacitor C4. The duration TS2 defines the closing time of the reset switches M2 and M3 at the start of the measurement. The duration TS1, greater than the duration TS2, defines the closing time of the switch ML. The duration TS1-TS2 corresponds to the charging time of the capacitor Cl, at the end of which the MPP value is extracted.

[0088] For example, the duration TS1 is between 5 and 50 times the duration TS2, for example of the order of 20 times the duration TS2. For example, the duration TS2 is a few tens of microseconds, for example of the order of 40 microseconds, and the duration TS1 is a few hundred microseconds, for example of the order of 800 microseconds.

[0089] In the example of [Fig.5], the circuit 503 is configured to periodically retrigger the measurement of the IPV(VPV) characteristic and the extraction of the MPP value, as long as the VPV voltage at the terminals of the photovoltaic panel remains higher than the threshold TH1. The circuit 503 comprises, for this purpose, an astable multivibrator circuit with NAND gates whose operating period determines the recurrence time of the plots of the I(V) curves, for example of the order of 1 second. The time constant of the multivibrator is in the example shown equal to 2.2*R26*C8. This multivibrator is for example formed of 2 NAND gates arranged in series, the second gate of which is wired as an inverting gate and the first has an input node connected to node n2. This arrangement allows the control of the multivibrator in the ON or OFF state depending on the output state of the operational amplifier AO2 at node n2.If the logic state of node n2 is 1 the multivibrator is ON and if the logic state of node n2 is 0 the multivibrator is OFF. Thus the measurement is retriggered as long as the output of the operational amplifier AO2 is at the high logic level.

[0090] Resistors R9 and R15 have, for example, a high value, for example of the order of 100 kohms. These resistors make it possible not to leave floating electrical states at any time on the logic control input of the NAND gate multivibrator and on the logic inputs of the two NOR gate monostables, these inputs being of high impedance, for example in the case of a CMOS technology implementation.

[0091] For example, the NAND gate circuit may be a circuit suitable for being powered by a voltage of between 3 volts and 18 volts, for example a circuit of the type marketed by the company Texas Instrument under the reference CD4011. This circuit is for example powered by the direct supply voltage +VC provided by the circuit 401.

[0092] As previously indicated, when the output signal of comparator AO2 (node ​​n2) goes high, the output signal SI of circuit MSI and the output signal S2 of circuit MS2 go high. The signal SI remains in a high state for a duration TS1 fixed by the time constant of the RC circuit formed by the resistor rl9 and the capacitor C3. The signal S2 remains in a high state for a duration TS2 fixed by the time constant of the RC circuit formed by the resistor r20 and the capacitor C4.

[0093] Throughout the duration TS1 of the measurement, the logic state of node n3 is at 1, the time constant of the multivibrator formed by circuit 503 being much greater than the duration TS1 and the duty cycle of the multivibrator of circuit 503 being approximately 50%. After a time fixed by the choice of the values ​​of resistor R26 and capacitor C8, the multivibrator resumes a new cycle and again presents a rising edge to nodes MSI and MS2. This leads to retriggering the monostable circuits MSI and MS2 to generate the high level pulses of respective durations TS1 and TS2 of the control signals SI and S2.

[0094] [Fig.6] is a more detailed electrical diagram of an exemplary embodiment of yet another part of the self-activation module 107 of [Fig.3].

[0095] [Fig.6] illustrates more particularly an exemplary embodiment of a circuit 601 adapted to generate the comparison threshold of the comparison circuit 307, that is to say, in the example of [Fig.4], the voltage VTH applied to the inverting input (-) of the operational amplifier AO1 of the comparison circuit 307.

[0096] In the example of [Fig.6], the circuit 601 makes it possible to adapt the threshold VTH, for example so as to adjust the threshold TH2 or TH3 according to the operating mode of the vehicle as described above in relation to [Fig.2].

[0097] In this example, the circuit 601 comprises an analog switch or multiplexer 611, comprising two input nodes EA and EB, two output nodes SA and SB, and two control nodes cA and cB. The switch 611 is for example powered by the direct supply voltage +VC provided by the circuit 401.

[0098] A voltage divider bridge consisting of a series association of two resistors r22 and r23 makes it possible to generate a first DC voltage VI applied to the input EA of the switch 611. In this example, the resistor r22 has a first end connected, for example connected, to a node for applying the DC supply voltage +VC provided by the supply circuit 401, and a second end connected, for example connected, to the input node EA of the switch 611. The resistor r23 has a first end connected, for example connected, to the node EA, and a second end connected, for example connected, to the reference node GND.

[0099] In the example of [Fig.6], the circuit 601 further comprises a digital-to-analog converter 613 (DAC), adapted to convert a digital reference signal CN supplied by a microcontroller (not shown), into a continuous analog voltage V2 applied to the input EB of the switch 611.

[0100] The output nodes SA and SB are both connected, for example connected, to a VTH signal supply node (connected, for example connected, to the inverting input (-) of the operational amplifier AO1 in the example of [Fig.4]).

[0101] The operation of the analog switch 611 is as follows. When a high level control signal is applied to the control node cA of the switch, the voltage VI applied to the input EA of the switch is transferred to its output SA. Thus, the voltage VTH takes the value VL When a high level control signal is applied to the control node cB of the switch, the voltage V2 applied to the input EB of the switch is transferred to its output SB. Thus, the voltage VTH takes the value V2.

[0102] In this example, the circuit 601 comprises a circuit for generating the control signals cA and cB comprising a NAND logic gate NAND3 connected as an inverting gate for the control cA, the direct signal being applied to the control cB. More particularly, in this example, the gate NAND3 has first and second input nodes connected, for example connected, to the node cB, and an output node connected, for example connected, to the node cA.

[0103] In this example, the input nodes of the NAND3 gate are connected, for example, to the output node of the operational amplifier AO1 of the comparison circuit 307 (providing the signal OUT). Thus, when the signal OUT is in the low state (logic 0), the NAND3 gate sets its output to the high state (logic 1) allowing the circuit 611 to present the level VI to the input VTH of the operational amplifier AOL. The control signals applied to the control nodes cA and cB of the switch 611 are then respectively in the high state and in the low state. The threshold VTH then corresponds to the voltage value VI, generated by the voltage divider point formed by the resistors r22 and r23. When the OUT signal goes high, the NAND3 gate sets its output low (0) on the ac input, the direct signal on the cB input being high (1).The control signals applied to the control nodes cA and cB of the switch 611 are then respectively in the low state and in the high state. The threshold VTH then corresponds to the voltage value V2, defined by the microcontroller (not shown). The value V2 is for example lower than the value VI, which makes it possible to obtain a hysteresis. The circuit 611 can also be adapted to define several power comparison thresholds for respectively several different operating modes of the vehicle.

[0104] An advantage of the embodiments described above is that the power converter 105 coupled to the photovoltaic panel 101 is activated only when the self-activation module 107 detects that the maximum power producible by the photovoltaic panel is greater than a threshold corresponding to the overconsumption of the system linked to the activation of the solar power supply.

[0105] It will be noted that advantageously, the maximum producible power measurement circuits of the self-activation module 107 can replace peripheral circuits power measuring spheres placed downstream of the converter 105.

[0106] Furthermore, the repetition frequency of the extraction of the maximum producible power MPP can be adapted to the mode of use of the vehicle, for example adapted according to the speed of the vehicle.

[0107] The IPv(VPV) characteristic plotting function implemented by the self-activation module 107 can also advantageously be used to implement diagnostic functions of the photovoltaic panel (detection of soiling, failures, aging, etc.), or detection of partial shading.

[0108] 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 occur to those skilled in the art. In particular, the described embodiments are not limited to the particular example described in relation to Figures 3, 4, 5 and 6, of embodiment of the self-activation module 107. Other implementations of a circuit 107 adapted to implement the operation described in relation to Figures 1 and 2 may be provided. In particular, although an example of an analog implementation has been described in relation to Figures 4, 5 and 6, other implementations, analog and / or digital, may be provided.

[0109] Furthermore, the described embodiments are not limited to the aforementioned example of application to an electrically powered motor vehicle equipped with a solar roof. More generally, the described embodiments can be applied to any system comprising one or more photovoltaic panels for the electrical supply of a load, for example an electric battery. By way of example, the described embodiments can be applied to other types of vehicles, for example boats, or to autonomous robots, or to autonomous installations of the automotive radar type or autonomous radio wave transmission-reception installations.

[0110] Finally, the practical implementation of the embodiments and variants described is within the reach of those skilled in the art from the functional indications given above.

Claims

Claims

1. System comprising a photovoltaic panel (101), and a power converter (105) adapted to convert an electrical output power of the photovoltaic panel into an electrical power supplying a load (103), the system further comprising a self-activation module (107) configured to, before activating the power converter (105), implement the following successive steps: a) measure the maximum electrical power (MPP) that can be produced by the photovoltaic panel (101); b) compare said maximum electrical power (MPP) with a first power threshold (TH2); and c) activate the power converter (105) to supply the load (103) only if said maximum electrical power (MPP) is greater than said first power threshold (TH2).

2. System according to claim 1, wherein the self-activation module (107) is configured to periodically repeat steps a) and b) as long as said maximum electrical power (MPP) is lower than said first power threshold (TH2).

3. System according to claim 1 or 2, in which the first power threshold (TH2) is greater than or equal to an overconsumption value of the system in the event of activation of the power converter (105) to supply the load (103).

4. System according to any one of claims 1 to 3, in which the self-activation module (107) is configured to measure the voltage (V pv) at the terminals of the photovoltaic panel (101) and implement steps a) and b) only when said voltage (VPV) is greater than a predefined voltage threshold (TH1).

5. System according to any one of claims 1 to 4, wherein the self-activation module (107) is further configured to, after step c), periodically measure the maximum electrical power (MPP) that can be produced by the photovoltaic panel (101), and interrupt the power converter (105) when said maximum electrical power (MPP) falls below a second power threshold (TH3).

6. The system of claim 5, wherein the second power threshold (TH3) is lower than the first power threshold (TH2).

7. System according to any one of claims 1 to 6, in which the first power threshold (TH2) is modifiable to take one or the other of two predefined values ​​depending on a mode of use of the system.

8. System according to any one of claims 1 to 7, wherein the load (103) to be supplied is a battery of a vehicle, and wherein the photovoltaic panel (101) is mounted on the vehicle.

9. System according to any one of claims 1 to 8, in which the self-activation module (107) comprises a circuit (301) for measuring a current-voltage characteristic (IPV(VPV)) of the photovoltaic panel (101).

10. System according to claim 9, wherein the self-activation module (107) further comprises a multiplier (303) providing a signal (PP) representative of the product of the current (IPV) and the voltage (VPV) of the photovoltaic panel (101).

11. System according to claim 10, wherein the self-activation module (107) further comprises a detector (305) of a maximum value (MPP) of said signal (PP) representative of the product of the current (IPV) and the voltage (VPV) of the photovoltaic panel (101).

12. System according to claim 11, in which the self-activation module (107) further comprises a circuit (307) for comparing said maximum value (MPP) of said signal (PP) representative of the product of the current (IPV) and the voltage (VPV) of the photovoltaic panel (101) to a threshold (VTH).

13. Method for controlling a system comprising a photovoltaic panel (101), and a power converter (105) adapted to convert an electrical output power of the photovoltaic panel into an electrical power supplying a load (103), comprising, before activating the power converter (105), the following successive steps: a) measuring the maximum electrical power (MPP) that can be produced by the photovoltaic panel (101); b) comparing said maximum electrical power (MPP) with a first power threshold (TH2); and c) activating the power converter (105) to supply the load (103) only if said maximum electrical power (MPP) is greater than said first power threshold (TH2).

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