WO2004090993A2

WO2004090993A2 - Pholtovoltaic panel which is secure against theft

Info

Publication number: WO2004090993A2
Application number: PCT/FR2004/000820
Authority: WO
Inventors: Jean Alzieu; Guy Schweitz; Laurent Torcheux
Original assignee: Electricite De France
Priority date: 2003-04-02
Filing date: 2004-04-01
Publication date: 2004-10-21
Also published as: WO2004090993A3; FR2853469B1; FR2853469A1

Abstract

A photovoltaic panel (10) provided with means (310, 320, 330) for optimizing the output thereof, means consisting of a converter (310, 320, 330) for displacement of the voltage and/or current operating point of the panel during the operation of said panel in the direction of an increase in the output thereof, said panel also comprising means for detecting a situation of theft (310, 315) whereby the electricity production function of said panel is neutralized in reaction to said theft. The panel is characterized in that the optimization means include digital processing means (310) and in that the means for neutralizing the panel consist at least partially of said digital processing means (310).

Description

"Photovoltaic panel secured against theft"

The invention relates to devices transforming solar energy into electricity, also called photovoltaic devices.

More specifically, the invention relates to such devices, when they include means for optimizing the energy produced, capable of positioning the electrical operating point (voltage, current) of a photovoltaic panel at a location on its curve. behavior (current / voltage characteristic) which corresponds to a maximum produced power. This type of optimization means, conventionally called "MPPT converter" (Maximum Power Point Traking) are direct current / direct current converters, producing a rectified hash, in order to introduce an impedance offset according to the chosen hash ratio.

These systems are capable of self-positioning the chopping ratio by identifying the point of maximum related power of the panel.

It will be noted that this maximum power point and the corresponding impedance modification at the output of the panel depend on several parameters variable over time, in particular the amount of sunshine present, the temperature of the panel and the variable load curve. also, from the connected battery. ι

The means performing this optimization function proposed so far have been mainly analog type means.

However, a total or partial realization of these means by digital type bodies proves advantageous.

Photovoltaic panels with power optimization means are highly coveted products. To compensate for the theft of this type of device, several security methods have been proposed.

In addition to the easily destroyed anti-theft mechanical assemblies, electronic anti-theft modules have been proposed capable of blocking operation in the event of disconnection of the panel. However, the electronic systems proposed so far have proven to be easily circumvented by electrical intervention (shunting, extraction, etc.).

In addition, these known blocking means increase the cost of the photovoltaic panels.

It is therefore desirable, in accordance with the present invention, to propose a photovoltaic panel with optimization of yield, theft of which is rendered fruitless in a more systematic manner, and the cost of production of which remains low.

This object is achieved in the sense given in this preamble to the invention thanks to a photovoltaic panel provided with means for optimizing its performance, means consisting of a converter capable of moving the operating point in voltage during operation of the panel. and / or by current from the panel in the direction of an increase in the efficiency of the latter, the panel further comprising means for detecting a theft situation to produce a neutralization of the electricity production function of the latter in response to this theft, the panel being characterized in that the optimization means include digital processing means and in that the panel neutralization means are constituted at least partially by these same digital processing means.

According to advantageous embodiments of the invention, the following arrangements are recommended:

- The optimization means include a switch and hash control means of this switch, the hash control means being at least partially formed by the digital means.

- The optimization means include a means generating an electrical oscillation of the behavior of the panel and analyzing a power oscillation of the panel corresponding to this electrical oscillation, this module also controlling a shift of the electrical operating point of the panel in the direction of increase in operating power as identified by power oscillations.

- The means generating an oscillation are of analog type.

- The digital processing means produce a scan of the operation of the photovoltaic panel over at least a portion of the operating curve and identify, from electrical readings taken during this scanning, the operating point of this curve where a maximum is found panel power.

- The digital processing means are provided to position the operation of the oscillation means near this maximum.

- The digital processing means performing this scanning are also provided to discriminate among several identified power maxima, and to position the oscillation means near the chosen maximum.

- In the latter two cases, the digital processing means capable of scanning and identifying maximum power are also provided to react to a theft detection by commanding a deactivation of the panel.

- In particular, by positioning the oscillation range in a part of the operating curve of the panel where it is not operational.

- More generally, the panel includes theft detection means, associated with the hash switch to control the latter so as to neutralize the production of electricity in the event of theft detection.

Other characteristics, aims and advantages of the invention will appear on reading the description which follows, referring to the appended figures in which:

* Figure 1 is a simplified mounting diagram of a photovoltaic panel with two branches, for illustration of the state of the art.

* Figure 2 is a plot representing two behavior curves of the panel, one in the case of the operation of only one of the two branches, the other in the case of the operation of the two branches. * Figure 3 is a plot representing the evolution, the curves of which respectively represent the evolution of the power of the panel as a function, in the case of operation of the two branches, and the evolution of the power in the event of operation of only one of the two branches.

* Figure 4 is an assembly diagram of a photovoltaic panel according to the invention.

In FIG. 1, the photovoltaic panel shown 10 is made up of two photovoltaic sub-assemblies 20 and 30, each sub-assembly constituting a branch of electricity production.

Each branch is a sub-panel provided each time with a shunt diode (bypass diode) mounted parallel to the latter.

Each of these branches 20 and 30 is, in known manner, subject to a possible failure making it resistive.

In normal operation, that is to say of the two branches, such a photovoltaic panel has a current / voltage curve represented under the reference 100 in FIG. 2.

On such a current / voltage diagram, iso-power lines such as curve 110 are plotted, having a curved curvature towards the normal operating curve 100 of the panel.

Thus, the isopower curve 110 touches the operating curve of the panel at a tangent point 120.

A linear segment 130 representative of the electrical behavior of a load placed at the terminals of the panel 10 has also been drawn in this FIG. 2.

This segment crosses the behavior curve of the panel at a value greater than 12 V, indicating that this ^• load, typically a battery, is designed to operate around a voltage of 12 V when in a situation of electrical source, of which it gradually deviates according to the current flowing through it.

It will be noted that this segment 130 generally crosses the behavior curve 100 of the photovoltaic panel at a point which does not correspond to the maximum power 120 of the latter. In other words, the association of this panel and this battery does not allow, as it is, use of the panel at its maximum efficiency.

This is why, in order to place at the terminals of the electricity-producing part a global load which is situated at an ideal operating point, provision is made for a modification of the output impedance of the panel, that is to say a converter. continuous / continuous which corrects a voltage difference Δu indicated in FIG. 2, and thus allows the panel to be used at its optimum operating point.

In other words, in this corrected operating situation, the battery operates at point 140 of the iso-power curve 110 and the panel at operating point 120, the difference in voltage Δu between these two points being compensated for by the modification of impedance produced by the converter.

In Figure 3, the plot shows the power versus voltage curve for the entire operating range of the panel. The maximum power point 210 corresponds to the operating point 120 in FIG. 2.

This converter, of known type, uses a switch controlled in chopping and rectified for a modification of the average voltage in the chosen direction.

Such an MPPT converter is not described in detail here, and is part of the state of the art, including when this converter selectively produces an increase in voltage or an increase in voltage.

Such MPPT converters are proposed with a chopping command conventionally in the form of an analog circuit, and typically operate by identification of the direction of voltage offset to be produced, by virtue of the production of very small oscillations in the circuit in output of the electricity generation part of the panel.

These circuits detect a possible oscillation of corresponding power at the output of the photovoltaic panel, and detecting the point operating the panel until reaching maximum power at zero tangent (point 210 in Figure 3).

In other words, such a circuit identifies the influence of a voltage change on the power generated and causes a voltage shift in the direction identified as increasing this power.

In FIG. 3, whose curve 200 represents the evolution of the power as a function of the voltage, the oscillation thus generated has been represented by double arrows 220, 230, 240.

Such a device, typically known in the form of an analog embodiment, turns out to be able to be easily produced or supplemented by the introduction of digital processing devices, and in particular when digital processing devices perform an analysis of the behavior in power of the photovoltaic panel.

In other words, it turns out that data processing means, ideally controlled by a series of commands in the form of stored instructions, or by a series of commands in the form of logic gates of a structural nature, are all very advantageous both in terms of efficiency and cost, to improve the operation of the converter (for example direct current / direct current) in the context of positioning on a power optimum.

In particular, in the embodiment proposed here, it is recommended to introduce such a digital processing means in the form of a digital chip placed upstream of a conventional MPPT circuit, that is to say an oscillating analog circuit, in order to pre-position the range of oscillation 220, 230, 240 of this conventional means.

The oscillation range is thus prepositioned in a zone corresponding to a maximum 210 of power pre-identified by the digital means.

In accordance with the embodiment shown in FIG. 4, for such an identification of the pre-positioning area, these digital means 310 produce a brief scan in operation of the photovoltaic panel and note during this scan both the voltage and the 'intensity obtained at the output of the latter. The operational scanning of the panel is easily produced by the digital processing means 310, which for this control a variation in the duty cycle (described below), this switch being positioned at the outlet of the panel.

The panel therefore encounters a hash with variable duty cycle, that is to say an impedance with variable value in a corresponding manner.

The panel therefore modifies, in reaction, its electrical behavior. By adapting the piloted chopping duty cycle, the panel describes all of its behavior curve.

As a result of the scanning, these means momentarily memorize the voltage and current data collected and use this data to identify the maximum power over the current and / or voltage interval thus scanned.

Thus in FIG. 3, the digital means described above 310 produce a scan of the operating curve of the panel and identify the maximum 210 corresponding to the desired operating point 120.

The analog means of electric oscillation 320 are thus positioned by the digital means in the sense that they operate immediately near the maximum 210. They in turn carry out a fine adaptation of the operating point for identification and positioning exact on the strict maximum of power 210.

In addition to the embodiment which has just been described where a maximum power is identified, the digital means 310 can also be provided for identifying several maximums over an interval and discriminating these different maximums, in order to establish the one presenting the optimal interest in the yield of the photovoltaic panel.

An advantageous application of such an embodiment is described below, for the simplified panel 10 as shown in FIG. 1, and in the case of a malfunction of one of the two branches 20 and 30.

The malfunction of one of the two branches typically results not only in a loss of photovoltaic power, but also by modifying the shape of the behavior curve of the overall panel.

Thus, in FIG. 2, the behavior curve 150 forms a decreasing wave 160 followed by a lower plateau 170. It therefore has two distinct approximation zones, opposite the isopower curve 180 which is flush this new behavior curve 150.

In FIG. 3 is illustrated, under the reference 250, the corresponding modification of the power curve of the panel. It has two maximums 260 and 270, one of which, 260, is slightly higher than the other and therefore particularly desirable.

With a conventional optimization circuit using only a voltage oscillation to detect the direction of an impedance offset to be introduced at the output of the panel, the identification of the best maximum among the two present is potentially erroneous.

Indeed, as illustrated on the left portion of the figure, an oscillation badly positioned at the start tends to place the operating point on the lowest 270 of the two maximums present.

Thus, the digital processing means 310 able to control an operating scan of the panel, and a reading of the current / voltage data obtained, are advantageously programmed for processing the collected data identifying any maximum, for example by its zero tangent on the curve of voltage / power 250, and comparing, in a second analysis step, the powers obtained for each of the points with zero tangent.

In a third step, these analysis means by digital processing 310 deliver the value of the voltage corresponding to the most advantageous among the different maximums and participate in the positioning of the oscillation means 320 (if the latter are adopted).

In FIG. 4, the chopper therefore consists of a switch 330 and a means of controlling the chopping ratio. The control means hitherto analog and simply exploiting a desirable direction of evolution, here includes the means 310 controlling a scan of the operating range of the panel, and, after processing the data collected, requiring a pre-positioning of the hash ratio. This pre-positioned hash ratio is then refined by the action of analog oscillation means 320 to obtain a precise hash ratio and therefore finely optimized. The means 310 and 320 therefore deliver by their joint action an optimal chopping ratio.

Thus, the replacement or assistance to known means by digital means within the optimization modules of photovoltaic panels has an advantage and should be part of a notable commercial trend since reducing cost and producing technical efficiency, more generally.

Thus, as just described above, digital processing means have a very concrete advantage in the operation of a photovoltaic panel, replacing and / or assisting the optimization means proposed so far.

As will now be described, data processing means 310 thus introduced within optimization means are advantageously used to produce, in addition to their optimization function, a function of securing against theft, by neutralizing the operation of the photovoltaic panel.

Thus, as shown in FIG. 4, the digital processing means 310 advantageously comprises an input 315 for receiving data, on which these means 310 receive a code and analyze the latter to authorize or not the operation of the photovoltaic panel as a function of the recognition or not of this code.

For example, the digital processing means 310 are provided with a memory which includes a code expected upon receipt of a code on the input 315, the means 210 comparing the latter with the stored code.

This code is taken into account, for example, at a fixed time of the day, and initiated by a clock included in the means 310.

The performance of the panel is optimized if the code received complies with the expected code. In the event of non-compliance, the digital processing means 310 command a blocking of the operation of the panel.

The use of these digital optimization processing means 310 for authorizing the operation of the panel proves to be particularly advantageous on several points.

It turns out to be particularly advantageous to confer this double function on these means on the one hand and to adopt on the other hand an intrinsic physical positioning to the panel, of these digital means 310.

The size and ease of positioning of the digital means 310 make it possible to place them as close as possible to the photovoltaic cells, thus making these means 310 inseparable from the cells.

The digital processing means are advantageously placed on the same circuit support as the photovoltaic cells, and / or embedded in the same resin as the latter, so that tearing off of the digital processing means generates irreversible damage to the cells PV. The security means and the photovoltaic cells become inseparably associated.

In other words, security is then also integrated into the photovoltaic panel.

In addition, by physically merging the optimization and security functions, it becomes necessary, to separate the security means from the rest of the circuit, to deprive the panel of the optimization function

In addition, such a device is advantageous in terms of cost, since the additional cost associated with securing turns out to be practically zero and therefore makes the product particularly competitive.

In an embodiment which is also advantageous for similar reasons, the chopping switch controlled in part by these processing means is associated with means specifically provided to control it specifically in neutralizing the system in the event of theft detection. The switch is for example placed in the permanent closed or open position in the event of theft detection, by removing the hash.

In an advantageous embodiment, corresponding to the scanning variant of the operating ranges described above, the positioning of the oscillation point (that is to say of the oscillation range, also called range α), is placed , by the digital means 310 themselves in an area of the behavior curve of the photovoltaic panel where the efficiency of the latter is particularly low, and even not usable.

Thus, as illustrated in FIG. 3, a positioning 280 of the range α close to the origin of the power curve makes the panel inoperative.

The common use of the digital processing means 310 and the chopping switch 330 for the neutralization function is a significant cost reduction compared to a basic system which would consist in introducing a particular switch in the neutralization device.

It should be noted that a common use of the switch alone, controlled by digital means other than those of optimization is also an advantage in itself. Here again, this common use makes it possible to make the security means inseparable from the means for optimizing the photovoltaic panel, since they are intrinsically included within them.

In FIG. 4, the frame 340 surrounding all of the organs present is for example constituted by a sealed envelope of the photovoltaic panel, so that all of the organs described prove to be unreachable.

The production of a photovoltaic panel comprising means 320 for controlling a scanning of the operating range by the photovoltaic panel, and exploiting the data collected to find a maximum, possibly after discrimination of the other maximums identified, turns out to be advantageous in itself regardless of whether the digital processing means 310 fulfill a security function or not. Likewise, the scanning means are capable of fulfilling by themselves the whole of the yield optimization function.

In addition, the operating authorization means are here provided for waiting for a code regularly, and authorizing or blocking operation if the code is not received at the expected time.

Thus, the operation of a photovoltaic panel being in itself periodic since starting daily at the appearance of the sun, the digital processing means are advantageously provided for implementing the taking into account and the analysis of an expected code as the first step of the day.

The appearance of electrical energy at the start of the day is used to authorize or prohibit the production of energy during that day.

In this way, a stolen photovoltaic panel, brought into contact with light with a view to fraudulent use, will wait for the appearance of the code, the absence of which will prevent ab initio any operation of the panel in question.

The functions for authorizing / neutralizing the operation of the panel can be performed by detecting theft using other processes than that described above and relating to waiting for a particular code.

Thus, as an example of theft detection, mention will be made of taking into account a monitored frequency by forming an operating command, and constituting an authorization signal, by wire or over the air, or even entering a code. on keyboard on the photovoltaic panel. These different variants illustrate the principle of analysis of an input by the digital processing means for optimizing the yield.

Claims

1. Photovoltaic panel (10) provided with means for optimizing (310, 320, 330) its performance, means consisting of a converter (310, 320, 330) capable of moving the operating point during operation of the panel in voltage and / or current of the panel in the direction of increasing the efficiency of the latter, the panel further comprising means for detecting a flight situation (310, 315) to produce a neutralization of the function of electricity production of the latter in response to this theft, the panel being characterized in that the optimization means include digital processing means (310) and in that the means for neutralizing the panel are constituted at least partially by these same digital processing means (310).

2. Photovoltaic panel according to claim 1, characterized in that the efficiency optimization means include a switch (330) and control means (310, 320) in chopping of this switch (330), the control means in hashing being at least partially formed by digital means.

3. Photovoltaic panel according to claim 1 or 2, characterized in that the optimization means include a means generating an electrical oscillation of the behavior of the panel and analyzing a power oscillation of the panel corresponding to this electrical oscillation, this module also driving an offset of the electrical operating point of the panel (210, 260) in the direction of an increase in the operating power as identified by the power oscillations.

4. Photovoltaic panel according to claim 3, characterized in that the means generating an oscillation (320) are of analog type.

5. Photovoltaic panel according to any one of the preceding claims, characterized in that the digital processing means (310) produce a scan of the operation of the photovoltaic panel on at least a portion of the operating curve and identify, from a processing of the electrical readings (100, 150) carried out during this scanning, the operating point (120) of this curve where there is a maximum panel power.

6. Photovoltaic panel according to the preceding claim, characterized in that the digital processing means (310) are provided for pre-positioning the operation of the panel near this maximum (210, 260).

7. Photovoltaic panel according to claim 5 or claim 6, characterized in that the digital processing means performing this scanning are also provided to discriminate among several maximums (260, 270) of identified power, and to pre-position the operation of the panel near the maximum chosen (260).

8. Photovoltaic panel according to claim 6 or claim 7 in combination with claim 3, characterized in that the digital processing means (310) are associated with the oscillation means (320), for pre-positioning the range of oscillation near the maximum chosen (210, 260).

9. Photovoltaic panel according to claim 8, characterized in that the digital means are provided to neutralize the operation of the panel, by positioning the range of oscillation of the oscillation means (320) in a part of the operating curve of the panel (280) where it is not operational.

10. Photovoltaic panel according to any one of the preceding claims, characterized in that the panel includes theft detection means (310, 315) associated with the hash switch (330), for controlling the latter so as to neutralize electricity production in the event of theft detection.