Classifications

• • G—PHYSICS
  • G05—CONTROLLING; REGULATING
  • G05F—SYSTEMS FOR REGULATING ELECTRIC OR MAGNETIC VARIABLES
  • G05F1/00—Automatic systems in which deviations of an electric quantity from one or more predetermined values are detected at the output of the system and fed back to a device within the system to restore the detected quantity to its predetermined value or values, i.e. retroactive systems
  • G05F1/66—Regulating electric power
  • G05F1/67—Regulating electric power to the maximum power available from a generator, e.g. from solar cell

Definitions

• the present invention relates to the field of energy converters and, more particularly, converters equipped with a control circuit in search of the point of maximum power.
• Such converters are generally applied to the conversion of energy supplied by an irregular source.
• the term “irregular energy source” is understood to mean an energy source whose power supplied is liable to undergo sudden variations, in contrast to energy sources whose power supplied is stable and / or varies slowly, as is the case for a battery or for the AC supply network.
• These are, for example, photovoltaic panels whose power supplied varies according to the illumination, wind turbines whose power supplied varies according to the wind speed, elements for exploiting tidal energy whose power supplied varies with the intensity of the waves, etc.
• the present invention will be described later in relation to panels of photovoltaic elements. However, the invention more generally applies to the different energy sources for which a automatic search for the maximum power point to optimize efficiency in the event of energy production.
• An energy converter of the type to which the present invention applies is of the static converter type, the semiconductor components of which work in switching mode (on state - blocked state).
• the input and output voltages can be indifferently continuous, alternating or other (for example, pulse). It can therefore be a DC / DC, DC / AC, AC / DC converter, etc.
• a control technique commonly used for switching the semiconductor component or components of the converter is control by modulation of the width of control pulses at the opening and at the closing of a power transistor (PW).
• PW power transistor
• the width of the control pulses in closing of the power transistor is regulated as a function of the load and the power required by the latter.
• FIG. 1 shows, very schematically and in the form of blocks, a conventional example of an energy converter of the type to which the present invention applies.
• it is a DC step-up converter.
• an energy source 1 made up of photovoltaic elements PV whose voltage V supplied is applied across an inductive element L in series with a power switch 2 controlled by pulse width modulation.
• the power switch 2 consists of a MOS transistor whose gate receives a CTRL signal consisting of a train of pulses of variable width as a function of the control instructions.
• the midpoint 3 between the inductive element L and the switch 2 is connected to the anode of a freewheeling diode D the cathode of which is connected to a first electrode 4 (positive) of a storage capacitor C.
• the capacitor C supplies, between its electrodes 4 and 5, a voltage Vout or a regulated current Iout of direct, alternating or other type depending on the nature of the charge connected between the electrodes 4 and 5.
• the electrode 5 of the capacitor C corresponds to a reference potential, for example the ground, for the voltage V of the panel 1, for the power switch 2 and for the output voltage.
• a control circuit 10 in search of the maximum power point (MPPT) is generally used.
• the role of such a circuit is to modify the width of the closing pulses of the switch 2 as a function of variations in the power supplied by the energy source 1.
• the circuit 10 therefore receives a signal (for example, a voltage) proportional to the power P supplied by the source 1.
• the power P is obtained by means of a multiplier 7 of a measurement of the current I in the photovoltaic elements by a measurement of the voltage V across the terminals of panel 1.
• Circuit 10 provides a two-state signal Q intended to increase, respectively decrease, the width of the control pulses of switch 2.
• the signal CTRL for controlling the switch 2 is supplied by a comparator 11 (COMP) of the converter controlled by the circuit 10.
• This comparator receives, on a first input, a periodic signal from a generator 12, for example, a constant high frequency sawtooth.
• a second input of the comparator 11 receives the output of a ramp generator 13 (RAMP) whose reversal of direction (rising ramp, falling ramp) is conditioned by the state of the signal Q.
• the frequency of the sawtooth conditions the generally constant frequency of the pulse train of the CTRL signal.
• the instantaneous level supplied by the generator 13, consisting for example of an RC circuit fixes the comparison reference, therefore the duty cycle of the pulses.
• the circuit 10 comprises two resistive and capacitive circuits 14, 15 (RCF and RCS) constituting delay lines of the power signal P having different time constants.
• the circuit 14 is, for example, a fast circuit with respect to the circuit 15 whose time constant is longer.
• the respective outputs of circuits 14 and 15 are connected to the inputs of a comparator 16 (COMP), the output of which controls a flip-flop 17 (T) supplying the signal Q. Subsequently, the direct output terminal ( non-inverted) of flip-flop 17 or the signal present on this terminal.
• the flip-flop 17 is a flip-flop without clock signal. It is, for example, a JK type rocker mounted on a so-called T type rocker.
• the power P will increase to a maximum then begin to decrease with the increase in the voltage V.
• the output of the comparator 16 switches which causes a switching of the output signal Q of the flip-flop 17. This then goes to the low state which causes the discharge of the RC circuit of the ramp generator 13 and a reduction in the duty cycle.
• the output voltage then starts to increase again.
• the circuit converges to a point of maximum power and oscillates around this point.
• FIG. 2 represents two examples of the shape of the power P as a function of the voltage V for two quantities of illumination received by the panel 1.
• a first curve 21 illustrates, for example, the case of maximum illumination. As has just been described, at constant load, the system will oscillate around the point PMM1 of maximum power.
• This curve also has a maximum power point PMM2.
• a first known solution is to choose very different time constants of the retarders 14 and 15. However, this harms the performance by the large oscillations generated.
• FIG. 3 illustrates an example of the shape of the current I supplied by the photovoltaic panel as a function of time during a change in the power curve of the panel.
• the amplitude of the oscillations around the values Imax and Iomb obviously depends on the time constants of the RC circuits 14 and 15. The greater the difference between the time constants, the greater the oscillations at the output of the comparator 16. The faster we converge towards the maximum power point (duration between times t2 and t3), the greater the amplitude of the oscillations. However, the larger the oscillations, the more it affects the performance of the system. We are therefore forced to make a compromise between efficiency, speed and stability.
• the present invention aims to overcome the drawbacks of known circuits for finding the maximum power point of a static converter of the switching power supply type.
• the invention more particularly aims to optimize the efficiency of the converter without adversely affecting its speed of reaction.
• the invention also aims to allow the control circuit to reconverge to a new point of maximum power in the event of variation of the energy source by means of a simple analog type circuit.
• the invention also aims to preserve the enslavement operated by the circuit in the event of variation of the load connected at the output.
• the invention further aims to propose a solution that can be integrated and is compatible with high-frequency operation of the switching power supply.
• the present invention provides a circuit for finding the point of maximum power of a variable energy source from a comparison of an image of the power supplied by the energy source, the circuit comprising : two elements providing different propagation delays at a magnitude proportional to the image of the power; a comparator of the outputs of the delay elements for controlling a flip-flop supplying a signal with two servo states of a static power converter; means for detecting a transient regime from variations in oscillations of an established regime; and means for modifying the delay provided by the slowest retarding element.
• said means for modifying the delay consist of a switching element suitable for, in transient state, inhibiting the operation of the slowest delay element.
• said detection means compare the duration of an active state on each output signal of the flip-flop with respect to a predetermined threshold.
• the detection means compare, independently of one another, the direct and reverse outputs of the flip-flop and combine the result of these comparisons to provide a control pulse to the means for rendering the variable delay.
• the duration of the transient regime is chosen as a function of the amplitude of oscillation desired around a nominal power setpoint.
• the various elements for measuring voltage, current, and time are analog.
• the circuit includes means for resetting the flip-flop on the appearance of a transient state.
• the circuit comprises means for, on the appearance of a transient regime, reinitializing a ramp generator conditioning the duty cycle of a pulse width modulation control signal of the power converter.
• the invention also provides a method for controlling a circuit for finding the point of maximum power of a variable energy source of the type applying two delays of different value to an image of the power supplied by the energy source, which consists of inhibiting or shortening the shortest delay during a transient regime.
• the existence of a transient regime is determined from a measurement of the frequency of oscillations around a nominal operating point of the maximum power point detector.
• FIG. 2 represents two examples of power shape as a function of the voltage in a photovoltaic panel constituting an energy source of a converter according to the invention
• FIG. 3 represents the variation of the current as a function of time in the event of a change in the illumination of a photovoltaic panel of the converter of FIG. 1
• FIG. 4 very schematically shows in the form of blocks an embodiment of a circuit for finding the point of maximum power according to the present invention
• FIG. 5 represents a functional block diagram of a transient state detector of the circuit of FIG. 4
• FIG. 6 is a more detailed electrical diagram of a control circuit according to the invention
• FIG. 7 represents another example of converter controllable by a circuit according to the invention.
• the same elements have been designated by the same references in the different figures. For reasons of clarity, only the elements which are necessary for understanding the invention have been shown in the figures and will be described later. In particular, the constitution of a source of energy used by a converter of the invention has not been detailed and is not the subject of the invention
• a feature of the present invention is to make controllable one of the two delay elements exploiting the power information provided by the energy source.
• the slowest retarding element brings stability to the system while the fastest retarding element accelerates convergence towards the point of maximum power in case of drift. Consequently, by making the slower retarder element faster or, preferably, by inhibiting it during a transient regime corresponding to periods of start-up or disturbance linked to a regime change, the convergence of the system is accelerated towards the maximum power point.
• the slowest retarding element is put back into service or its time constant is extended. Thus, the steady state oscillations are minimized.
• the minimum duration of a transitional regime according to
• the duration range of a transient regime depends on the converter, on the load curve of its input impedance, as well as on the authorized load overshoot, that is to say the oscillation amplitude. that one authorizes oneself under established regime, etc.
• the duration of transient regime provided by the invention essentially depends on the time constant fixed by the equivalent resistance of the panel and by an input capacity of the converter. This input capacity is generally provided at the terminals of the panel to prevent the propagation of switch switching noises.
• the slowest delay element has a time constant of the order of ms while the delay element faster at a time constant of 1 order of about ten ⁇ s
• Another characteristic of the present invention is to provide a detection of the transient regimes, that is to say the need to switch to an operation with accelerated time constant, from the frequency of the oscillations of the established regime. Indeed, a change of state of the system, for example a change of point of maximum power of the energy source, results in a change in the frequency of the oscillations of the established regime, or even in a disappearance of these oscillations.
• a range of oscillation frequencies corresponding to an established regime is defined and the system is switched to a transient operating mode when it is detected that it deviates from this frequency range.
• the minimum and maximum oscillation frequencies are determined from the oscillation rates that one is ready to accept for the system.
• a maximum oscillation rate corresponds to a minimum frequency of these oscillations and corresponds to the maximum power regime supplied by the energy source.
• a minimum oscillation rate corresponds to a maximum frequency and a minimum power regime of the energy source (for example, operation in the shade of a photovoltaic panel).
• the time constant of the ramp generator controlled by the maximum power point search circuit is greater than the maximum time input time of the system.
• This maximum time constant corresponds, for a photovoltaic panel, to the time constant under minimum illumination.
• FIG. 4 represents, by a very schematic view and in the form of blocks, an embodiment of a circuit for searching for a point of maximum power according to the invention.
• the circuit 30 receiving the power information P and supplying a signal Q for controlling a ramp generator of the type illustrated in FIG. 1 has been shown.
• the other elements of the power converter and of the energy source, whether these are the means for obtaining the power information or the exploitation of the control signal Q are conventional and it is possible, by example, use a circuit like the one illustrated in figure 1.
• the control circuit 30 uses a comparator 16 (COMP) for controlling a flip-flop 17 (T) whose direct output Q provides the control signal for the ramp generator (13, FIG. 1). Still conventionally, the two inputs of comparator 16 receive a signal representative of the power information supplied by the energy source with a time offset supplied by two delay elements 14 and 31 respectively.
• the delay element 14 is, as previously relatively fast (RCF).
• the retarder element 31 has a relatively slow nominal speed (RCS) and is controllable, either for a reduction of its time constant during a transient regime, or to be inhibited during this transient regime.
• a signal CT31 for controlling the retarder element 31 is a pulse signal having an inhibition or acceleration pulse each time a transient state is detected.
• This signal CT31 is, for example, supplied by a circuit 32 (TIMER) functionally constituting a generator of isolated pulses, of predetermined durations.
• the circuit 32 is controlled by a signal DEM triggering the appearance of a pulse.
• This signal DEM is supplied by a circuit 33 (OSC-DET) for detecting variation in oscillations in the output signal Q supplied by the flip-flop.
• the circuit 33 takes the signal at the output of the flip-flop 17 to detect a variation in the frequency of the oscillations such that this frequency deviates from a range of predetermined nominal operating values.
• the oscillation detector of the invention may take a signal from any other place on the control circuit 30 having oscillations in steady state, that is to say the signal shape of which indicates the regulation of the regime established. For example, we could take the output signal from comparator 16.
• the detection of a loss of instability can be obtained from images of the current, the voltage, or the power supplied by the energy source, all of these signals having the same frequency.
• a loss or a variation in frequency relative to a predetermined range of the frequency of the oscillations of the steady state is always detected. Reference is made to a loss of instability because it detects a disappearance of oscillations resulting in an unwanted stability of the power converter.
• FIG. 5 very schematically shows in the form of blocks an embodiment of an instability detection circuit 33 according to the invention.
• the circuit 33 uses the two direct Q and reverse Q outputs of the flip-flop 17 to detect a variation in the two directions of the stability of the system.
• the outputs Q and Q are respectively connected to the inputs of two time comparators 34 and 35 (CPT), the second respective inputs of which receive time thresholds TH1 and TH2.
• CPT time comparators 34 and 35
• each comparator 34 or 35 compares the duration in which the signal Q or Q which is associated with it remains in an active state stable with respect to a predetermined duration. As soon as this time is exceeded, the comparator output switches to trigger a transient pulse thanks to the signal
• Thresholds TH1 and TH2 are chosen according to the longest period of oscillation of the system in steady state. This period is a function, among other things, of the maximum and minimum illuminations that the panel can receive, of the converter and of the load for which the system is intended, and depends on the stability which it is desired to give to the system. For example, the thresholds TH1 and TH2 are adjusted so that they generate a pulse when, for a given time between 2 and 5 times the maximum oscillation period, there has been no oscillation, c ie change of state of outputs Q and Q.
• the two time comparators 34 and 35 make it possible to detect a stable state of the oscillation of the signal supplied by the energy source (for example, the current of FIG. 3), whether this stable state is at the low level or at the level high oscillation allowed.
• the presentation of FIG. 5 corresponds to a functional presentation of the instability detector of the invention. In practice, it will be ensured that the output of the comparators 34 and 35 remains stable for a period corresponding, preferably, to between two and five times the greatest oscillation period that the control can generate, depending on the sensitivity to variations. desired. This avoids inadvertent triggering of the system when it is in steady state.
• An advantage of the present invention is that it allows the detection of a loss of the established speed of the point of maximum power on which the system is stalled without knowing where this loss comes from. In particular, it is not necessary to provide other sensors than the sensors commonly used for determining the point of maximum power.
• FIG. 6 represents a more detailed embodiment of a circuit 30 according to the invention.
• the purpose of the example in FIG. 6 is to illustrate, in particular, the integrable nature of the invention.
• FIG. 6 a classic example of the exploitation of signals I and V (FIG. 1) of the energy source has also been illustrated.
• a measurement of the voltage V, applied to a terminal 41 of the circuit 30, is applied to a first input of the multiplier 7, the output of which supplies the power signal P used by the control circuit.
• On the current detection side I its measurement is applied to a terminal 42 and passes through a scaling circuit 43 before arriving at the second input of the multiplier 7.
• the optional use of a scaling circuit 43 depends on the amplitude of the variations measured at the level of the energy source.
• the scale factor circuit is classic.
• the output of the multiplier 7 supplying the signal P is connected to the respective inputs of the two delay elements 14 and 31.
• these delay elements have the simplest possible form, namely, a resistive and capacitive circuit.
• the output of the multiplier 7 is connected to a first terminal of a resistor R14 of the element 14, a second terminal of which is connected to the inverting input of the comparator 16 and, via a capacitor C14, to ground.
• the output of the multiplier 7 is also connected to a first terminal of a resistor R31 of the delay element 31, the second terminal of the resistor R31 being connected to the positive input of comparator 16 and, by a capacitor C31, to the mass.
• the components of the RC circuits 14 and 31 are of course different in order to introduce the difference in time constant necessary for the operation of the invention.
• resistors of the same value and to differentiate the time constants of the two retarding elements by means of capacitors C14 and C31 of different values.
• the output of comparator 16 passes through an inverter 45, the output of which is connected, in the example shown, to the clock input CLK of flip-flop 17 formed from a flip-flop of type JK.
• the inputs J and K of the flip-flop are connected to a terminal for applying the positive supply potential Vcc, as well as the terminal R for resetting the flip-flop.
• the direct output Q of the flip-flop is connected to the input of a ramp generator 13 'intended to fix the duty cycle of the power supply switching pulses (signal CTRL).
• the output of the generator 13 ' is connected to a first input of the comparator 11, the second input of which receives a periodic signal supplied by the generator 12.
• This signal for example in a sawtooth fashion, is preferably a high frequency signal fixed by an HCLK clock. All that has just been described corresponds approximately to a conventional circuit.
• the non-inverting input of comparator 16 that is to say the output of the delay element 31, is connected to ground by a switch 321 of circuit 32. Functionally, this corresponds to the control signal CT31 exposed in relation to FIG. 4.
• switch 321 When the switch 321 is open, a normal operation corresponding to an established speed and to that of a conventional circuit is reproduced.
• switch 321 When switch 321 is closed, the corresponding input of comparator 16 is, according to the invention, brought to ground which inhibits the operation of the slow retarder element 31.
• the circuit 32 supplying a timed control pulse to the element 31 comprises, for example, a timer circuit 322, for example a monostable circuit (MONOST), the output of which controls the switch 321 (for example, a MOS transistor).
• the control input of circuit 322 is connected to the midpoint of a series association of two resistors R323 and R324 at the terminals of which the supply voltage Vcc is applied.
• the control input of circuit 322 is also connected to ground by means of a capacitor C325.
• the object of circuit 322 is to form a control pulse, the duration of which is fixed by the resistive and capacitive components placed at the input.
• the values of resistors R323 and R324 condition the charging time of the capacitor C325 and, consequently, the duration of the pulse.
• the input of circuit 322 is preferably connected to ground by means of a switch 326 controlled by the signal DEM detecting a transient state. In steady state, the switch 326 is open, the input of the circuit 322 is therefore in the high state (substantially at the potential Vcc while neglecting the voltage drop in the resistor 323 of relatively low value). Switch 321 is therefore open. When the signal DEM causes the closure of the switch 326, this causes the discharge of the capacitor 325 and the switching of the input of the circuit 322 to the low state. This therefore causes a switching of the output of the monostable circuit 322 which closes the switch 321.
• the signal DEM is of impulse shape, the connection to the ground of the input of the circuit 322 quickly disappears by opening the switch 326.
• the capacitor C325 can then be charged again by the resistive divider bridge R323-R324 which conditions the duration of the pulse.
• the signal DEM is also used to reset the ramp generator 13 'consisting, in this example, of an RC cell (resistor R13 and capacitor C13). A first terminal of the resistor R13 is connected to the terminal Q of the flip-flop 17.
• the other terminal of the resistor R13 is connected to a first input of the comparator 11 and, by the capacitor C13 to ground.
• a switch 131 short-circuits the capacitor C13 to force the discharge thereof when the signal DEM is active. This guarantees a restart of the ramp conditioning the duty cycle to a value always identical to each transitional period. In the example shown, this is a restart from zero. Alternatively, a predetermined preload level may be provided for this restart.
• the slow time constant here R31 * C31
• R31 * C31 is chosen to be between 1/20 and 1/2 of the time constant of the ramp generator 13 •, here R13 * C13.
• R14 * C14 is chosen according to the dynamics sought for the system. For example, we could provide a constant R14 * C14 between 1/10 and 1/2 of the slow time constant (R31 * C31).
• the signal DEM is also used according to the invention to reset the flip-flop 17.
• the input S of the flip-flop 17 is connected to a circuit 46 applying a calibrated reset pulse.
• the circuit 46 is, for example, made up of a resistive divider bridge R461, R462 supplied by the voltage Vcc and serving to charge a capacitor C463 connected between the midpoint and the ground.
• the terminal S of the flip-flop 17 is connected to this midpoint.
• a switch 464 controllable by the signal DEM is used to force the discharge of the capacitor C463. In steady state, the switch 464 is open, the capacitor C463 is charged and the input S of the flip-flop 17 is in the high state.
• a closing of the switch 464 by the signal DEM following a detection of a transient regime causes the discharge of the capacitor C463 and the passage of the input S to zero, therefore the reset of the flip-flop 17.
• the switch 464 opens, which allows the progressive charging of the capacitor C463 by the divider bridge R461, R462.
• the role of circuit 46 is to provide a pulse of sufficient duration to reset flip-flop 17.
• the outputs Q and Q of the flip-flop 17 are also sent as input to the two circuits 34 and 35 for detecting loss of instability according to the invention.
• Each circuit 34, 35 is, in the example shown, based on a timing circuit, respectively 341, 351, of the type known under the trade name LM555, mounted as a monostable.
• Each circuit 341 or 351 has its output connected to one of the inputs of gate 36 of the NON-OR-Exclusive type. In the example shown, the output of door 36 passes through a monostable circuit 37 to form the DEM pulse. This circuit is optional.
• the circuits 341 and 351 have their supply terminals Vcc and GND connected respectively to the terminals for applying the supply voltage of the circuit.
• the control voltage terminals CTR of circuits LM555 are left in the air. Their reset terminals RST are brought to the potential Vcc. Their respective trigger terminals TRIG are connected to the outputs Q and Q of the flip-flop 17.
• the outputs Q and Q are also respectively connected to first resistance terminals R342 and R352, the respective second terminals of which are connected to the base of transistors T343 and PN35 type T353.
• the collectors of transistors T343 and T353 are connected to ground.
• Their respective transmitters are connected to the threshold (THR) and discharge (DSCH) terminals of the corresponding circuits 341 and 351.
• each THR terminal is connected to the midpoint of an association in series of a resistor R344, respectively R354, and a capacitor C345, respectively C355.
• the disappearance or reduction of oscillations in the low state can be akin to the case where the system stabilizes in open circuit.
• the disappearance of oscillations in the high state can be akin to the case of a short-circuited system.
• Stage 34 corresponds to the detection of the open circuit while stage 35 corresponds to the detection of the short circuit.
• the THR thresholds of the timer circuits LM555 correspond to a high state (voltage Vcc minus the voltage drop in the resistors R344 and 354, respectively) when the corresponding transistor T343 or T353 is blocked.
• the transistor T343, respectively T353 is on, the corresponding capacitor C345 or C355 is short-circuited and the threshold input THR of the corresponding circuit LM555 is at 1 low state.
• the circuit's TRIG trigger input is also low, its OUT output remains low.
• the transistor T343 or T353 which is associated with it is blocked.
• the corresponding C345 or C355 capacitor is charged via the resistor R344 or R354. It follows that after a predetermined time depending on the dimensions of the resistor R344 (or R354) and of the capacitor C345 (or C354), the threshold THR of the circuit 341 (or 351) becomes approximately equal to the voltage Vcc ( neglecting the voltage drop across resistor R344 or R354).
• the output OUT of circuit 341 (or 351) is likely to switch if the THR threshold goes to the high state before the terminal Q (or Q) switches back down.
• circuit 341 (or 351) will remain low. It can therefore be seen that when one of the outputs of the flip-flop 17 remains in a stable active state, an input of the logic gate 36 is switched to trigger a command pulse of the DEM signal.
• An advantage is that the present invention is particularly suitable for high frequency operation of the switching power supply. In particular, unlike a digital circuit, no computation or processing time is necessary for the implementation of the invention.
• Another advantage of the invention is that the particularly economical solution which it constitutes makes it possible to provide a circuit per panel in the case of a multi-panel system. The problems of inhomogeneity of the illumination (for example, when a shadow appears on the scale of a panel or of a cell) are then resolved at lower cost.
• FIG. 7 shows another embodiment of the present invention to illustrate an assembly on a step-down DC-DC converter.
• a photovoltaic panel 1 is assumed, the two terminals of which are respectively connected to a first terminal of the power switch 2 and, by a resistance R of very low value, to ground 5.
• the other terminal of the switch 2 is connected to a first terminal of an inductive element L, the second terminal of which constitutes terminal 4 supplying the output voltage to an energy storage element, for example, a battery not shown.
• a freewheeling diode D connects the first terminal of the inductor L to ground 5.
• a capacitor Ce connects the positive output terminal of the photovoltaic panel to ground to stabilize the voltage across the terminals of panel 1 and make it insensitive noises ccmutati ⁇ n of 1 switch 2.
• the terminal 41 of voltage measurement is connected to the midpoint of a resistive divider bridge consisting of a resistor R411 in series with a resistor R412 between the positive terminal of the panel 1 and the mass.
• the current measurement applied to terminal 42 (figure 6) is taken on terminal negative of the photovoltaic panel. Resistor R participates in the measurement of the current.
• the invention applies to any type of converter, whether it is a step-down, step-up or step-down converter.
• the energy source can be arbitrary, provided that information relating to its power can be extracted therefrom.
• the present invention is susceptible of various variants and modifications which will appear to those skilled in the art.
• other analog arrangements than that illustrated in FIG. 6 could be envisaged provided that the functionalities described are respected.
• the retarder element 31 may consist of a capacitor, the capacity of which varies as a function of the voltage applied to its terminals, of a network of resistors and of switchable capacitors, etc.
• the dimensioning of the different time constants and resistive and capacitive elements is within the reach of those skilled in the art from the functional indications given above and from the application.
• the above description refers to a measurement of the power as being the product of a voltage by a current
• the image of the power may come from other quantities such as, for example, a measurement of impedance, a quantity proportional to the current assuming constant voltage, a measure proportional to voltage assuming constant current, etc.

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