WO2022059045A1

WO2022059045A1 - Device for regulating charge of an electrical energy storage device from a photoltaic source

Info

Publication number: WO2022059045A1
Application number: PCT/IT2021/050285
Authority: WO
Inventors: Massimo LESA; Roberto GREGORIC
Original assignee: Era S.R.L.
Priority date: 2020-09-17
Filing date: 2021-09-17
Publication date: 2022-03-24
Also published as: IT202000021976A1

Abstract

A method and a device (10) for regulating charging of an accumulation device (51) from a photovoltaic source (50). The device comprises an intermediate section (12) for selectively connecting/ disconnecting the accumulation device (51) to/from the photovoltaic source (50), and a scanning section (11) configured to apply a variable load to the photovoltaic source (50) when disconnected from the accumulation device (51). The charging device allows to extend a voltage sweep to thereby achieve maximum point power tracking independently of the accumulation device voltage.

Description

DEVICE FOR REGULATING CHARGE OF AN ELECTRICAL ENERGY STORAGE DEVICE FROM A PHOTOLTAIC SOURCE

FIELD OF THE INVENTION

Embodiments described here concern a device for regulating the charge from a photovoltaic source. In particular, the device can be associated with a photovoltaic system configured to charge a battery. Although we have referred to a photovoltaic source, the use of a device according to the present invention to regulate the charge from sources other than photovoltaic ones, for example wind, is not excluded.

BACKGROUND OF THE INVENTION

Devices for regulating the charge from a photovoltaic source are known which, in general, are electrically connected to the photovoltaic source and to the battery to be charged.

Some known devices use MPPT (Maximum Power Point Tracker) type charge regulation algorithms, which allow to charge the battery with the photovoltaic source which always works at the maximum deliverable power point. In fact, it is known that the maximum deliverable power point can vary as a function of the conditions that the photovoltaic source is in, such as for example the degree of solar radiation and the shading to which it is subjected, the state of cleanliness and maintenance, etc.

The functioning principle of MPPT algorithms consists in scanning an I-V curve, or work curve, defined by the current and voltage coordinates of the work points of the photovoltaic source, and in identifying the point of the curve in which the deliverable power is maximum.

Typically, the curve is scanned by means of the same hardware used to regulate the charge of the battery.

One disadvantage of known devices is that this scan is limited by the voltage of the battery connected to the photovoltaic source. In fact, in known devices, the scan starts from a minimum voltage, set by the battery, up to the no-load voltage of the photovoltaic source. In this way, an I-V curve is obtained that only partly describes the work points of the photovoltaic source.

This can be particularly disadvantageous in the event that the photovoltaic source works in non-optimal conditions, for example in the case of total or partial shading of the modules or in the case of damaged electrical connections. In fact, in these cases, a device of the known type is not able, in the scanning phase, to highlight all the inflections of the I-V curve. This may result in an erroneous determination of the maximum deliverable power point with a consequent loss of efficiency of the system.

Another disadvantage of known devices is that they do not allow the user to assess the state of health of the photovoltaic source.

There is therefore the need to perfect a device for regulating the charge from a photovoltaic source that can overcome at least one of the disadvantages of the state of the art.

In particular, one purpose of the present invention is to provide a device that can completely scan the functioning curve of a photovoltaic source, without constraints dictated by the connected battery.

Another purpose of the present invention is to provide a device that can determine the maximum deliverable power point of the photovoltaic source, even in non-optimal functioning conditions.

Another purpose is to provide a device that can supply useful information to a user, for example regarding the state of health or functioning of the photovoltaic source.

The Applicant has devised, tested and embodied the present invention to overcome the shortcomings of the state of the art and to obtain these and other purposes and advantages.

SUMMARY OF THE INVENTION

The present invention is set forth and characterized in the independent claims. The dependent claims describe other characteristics of the present invention or variants to the main inventive idea.

In accordance with the above purposes, a device for regulating the charge from a photovoltaic source is described that overcomes the limits of the state of the art and eliminates the defects present therein.

The device is configured to be electrically connected to a photovoltaic source and to an electrical energy accumulation device, that is, a battery.

In accordance with some embodiments, the device comprises an intermediate section configured to electrically connect/separate, in a selective manner, the accumulation device from the photovoltaic source. Furthermore, the device comprises a scanning section electrically connected to the photovoltaic source and to the intermediate section. This scanning section can be configured to apply a variable electrical load to the photovoltaic source when the latter is electrically separated from the accumulation device.

In preferred embodiments, the device can comprise a control and management unit configured to sample voltage and current values of the electrical load applied to the photovoltaic source in order to determine an I-V curve of the photovoltaic source. By I-V curve, we mean a set of work points of the photovoltaic source, and of voltage and current coordinates.

Advantageously, in this way the scanning of the I-V curve is not limited by the voltage of the accumulation device.

The sampled I-V curve can be stored in storage means.

The device can also comprise a regulating section electrically connected to the accumulation device and to the intermediate section.

In some embodiments, the intermediate section is configured to electrically connect/separate the scanning section and the regulating section. The regulating section can be configured to regulate the charge of the accumulation device by means of algorithms of the MPPT type that refer to the I-V curve stored in the storage means.

In addition, the device can analyze the I-V curve to detect possible anomalies, in order to inform a user about the state of health and/or functioning of the photovoltaic source.

The invention also concerns a method for the functioning of a device for regulating the charge from a photovoltaic source which provides to: electrically separate a photovoltaic source from an accumulation device; apply a variable electrical load to the photovoltaic source electrically separated from the accumulation device; periodically detect voltage and current values of the electrical load applied to the photovoltaic source; store detected voltage and current values in order to define an I-V curve of the photovoltaic source. In preferred embodiments, the method also provides to: electrically connect the photovoltaic source to an accumulation device in order to charge it by means of algorithms of the MPPT type which refer to the stored I-V curve.

In other embodiments, the method can provide to: integrate the I-V curve and compare the value resulting from the integration with a comparison value; and/or: establish the trend of the angular coefficient of the I-V curve; in order to determine possible anomalies of the photovoltaic source.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects, characteristics and advantages of the present invention will become apparent from the following description of some embodiments, given as a non-restrictive example with reference to the attached drawings wherein:

- fig. 1 is a schematic representation of an embodiment of a device according to the present invention;

- figs. 2 and 3 are schematic representations of an embodiment of a device according to the present invention in different operating configurations;

- fig. 4 is a schematic representation of an I-V curve, that is, a work curve, of a photovoltaic source in non-optimal conditions.

To facilitate comprehension, the same reference numbers have been used, where possible, to identify identical common elements in the drawings. It is understood that elements and characteristics of one embodiment can conveniently be combined or incorporated into other embodiments without further clarifications.

DETAILED DESCRIPTION OF SOME EMBODIMENTS

We will now refer in detail to the possible embodiments of the invention, of which one or more examples are shown in the attached drawings, by way of a non-limiting illustration. The phraseology and terminology used here is also for the purposes of providing non-limiting examples.

With reference to to fig. 1, number 10 indicates a device for regulating the charge from a photovoltaic source 50 according to embodiments of the present invention. The device 10 can be associated with a photovoltaic source 50 and with an electrical energy accumulation device 51. In particular, the device 10 can be electrically connected to the photovoltaic source 50 and to the accumulation device 51.

The photovoltaic source 50 can be configured as a photovoltaic system that comprises at least one string of photovoltaic modules.

The accumulation device 51 can be configured as any device whatsoever suitable to accumulate electrical energy; preferably, the accumulation device is a battery.

According to some embodiments, the device 10 comprises a scanning section 11, a regulating section 13 and an intermediate section 12.

With reference to the embodiment of fig. 1, the scanning section 11 can be electrically connected to the photovoltaic source 50 and the regulating section 13 can be electrically connected to the accumulation device 51.

In other embodiments, the regulating section 13 can be electrically connected to an electric converter, such as an inverter (not shown).

The intermediate section 12 can be configured to electrically connect/separate, in a selective manner, the photovoltaic source 50 from the accumulation device 51.

In some embodiments, the device 10 can comprise voltage detection means 15, 16 configured to detect the voltage of the photovoltaic source 50. Furthermore, the device 10 can comprise current detection means 17, 18 configured to detect the intensity of the current of an electrical load passing through the photovoltaic source 50.

According to some embodiments, first voltage detection means 15 and first current detection means 17 are comprised in the scanning section 11. In addition, second voltage detection means 16 and second current detection means 18 are comprised in the regulating section 13.

The current detection means 17, 18 can comprise one or more shunt resistors.

According to some embodiments, the scanning section 11 can comprise conduction/locking means 19 disposed in series with the first current detection means 17. Furthermore, the scanning section 11 can comprise additional conduction/locking means 20 configured to put the scanning section 11 into short-circuit. The conduction/locking means 20 can be disposed upstream of the intermediate section 12.

In accordance with some embodiments, the intermediate section 12 can be configured to electrically connect and/or separate, in a selective manner, the scanning section 11 and the regulating section 13. In particular, the intermediate section 12 can comprise conduction/locking means 21. More in particular, when the conduction/locking means 21 are put into conduction, the intermediate section 12 electrically connects the scanning section 11 and the regulating section 13, and the device 10 is in a regulating operating configuration (fig. 2). When the conduction/locking means 21 are locked, the intermediate section 12 electrically separates the scanning section 11 and the regulating section 13, and the device 10 is in a scanning operating configuration (fig. 3).

In some embodiments, the conduction/locking means 20 of the scanning section 11 are put into conduction in the scanning operating configuration, and are locked in the regulating operating configuration.

According to other embodiments, in the regulating operating configuration, the conduction/locking means 19 can be put into conduction.

According to one aspect of the invention, the device 10 can be configured to detect an I-V curve of the photovoltaic source 50. By I-V curve we mean a set of work points, of the photovoltaic source 50, of voltage and current coordinates. In particular, when the device 10 is in the scanning operating configuration, the scanning section 11 can be configured to apply a variable electrical load to the photovoltaic source 50. In fact, in this operating configuration, the conduction/locking means 20 of the scanning section 11 can be put into conduction (fig. 3), in such a way as to define a closed electrical circuit upstream of the intermediate section 12. The electrical load can be applied in a gradual manner from a zero current value up to a current value close to the value of the short-circuit current I_sc of the photovoltaic source 50. More in particular, the scanning section 11 can comprise conduction/locking means 19, that is, transistors, configured to be driven to perform a pulse-width modulation (PWM) with a gradually increasing duty cycle, until a current close to the short-circuit current I_sc of the photovoltaic source 50 is reached.

Advantageously, in this way it is possible to carry out a scan of the functioning curve of the photovoltaic source 50 from approximately zero voltage values to voltage values close to the no-load voltage V_Oc of the photovoltaic source 50. In this way, the scan of the I-V curve is not limited by the voltage of the accumulation device 51 connected to the photovoltaic source 50.

The device 10 can also comprise a control and management unit 14 configured to command at least the conduction/locking means 19, 20, 21. Furthermore, the control and management unit 14 can be configured to communicate with the first voltage detection means 15 and the first current detection means 17 in order to detect the voltage and current values of the electric field applied to the photovoltaic source 50. In addition, the control and management unit 14 can comprise, or be connected to, storage means 14a on which the current and voltage values detected can be stored. Preferably, n pairs of detected voltage and current values are stored substantially simultaneously, so as to define an I-V, or work curve of the photovoltaic source 50. In particular, the I-V curve of the photovoltaic source 50 can be a set of points, the coordinates of which are voltage and current values (fig. 4).

According to some preferred embodiments, the regulating section 13 can be configured to regulate the charge of the accumulation device 51 by means of algorithms of the MPPT (Maximum Power Point Tracking) type. For purely informative and non-limiting purposes, the algorithms of the MPPT type provide to maximize the power output of a photovoltaic source 50, in any operating situation whatsoever. This result can be achieved by identifying a work point on an I-V curve, characteristic of the photovoltaic source 50, the current and voltage coordinates of which produce the maximum power output.

In preferred embodiments, the control and management unit 14 can be configured to command the regulating section 13 in order to regulate the charge of the accumulation device 51 according to algorithms of the MPPT type which refer to the functioning curve stored in the storage means 14a. This regulation can be carried out when the device 10 is in the regulating operating configuration.

According to other embodiments, the regulating section 13 can comprise accumulation means 25 configured to accumulate electrical energy and to supply it to the accumulation device 51. The accumulation means 25 can comprise one or more capacitors. Advantageously, in this way the regulating section 13 can charge the accumulation device 51 even when the device 10 is in the scanning operating configuration, preventing losses of production.

In other embodiments, the device 10 can be configured to analyze the I-V curve stored in the storage means 14a, in such a way as to identify symptoms of possible anomalies of the photovoltaic source 50. For example, the control and management unit 14 can be configured to integrate the I-V curve of the photovoltaic source 50 in order to compare the value resulting from the integration with a comparison value. The comparison value can, for example, be obtained experimentally and can depend on the value of the short-circuit current Isc, on the value of the no-load voltage V_oc of the photovoltaic source 50. Purely by way of example, if the comparison value is greater than the value resulting from the integration, there could be an anomaly in the photovoltaic source 50.

Furthermore, in other embodiments, the control and management unit 14 can be configured to compare the angular coefficient of the I-V curve of the photovoltaic source 50, at different points thereof. In particular, this comparison can have the purpose of establishing the trend of the angular coefficient, for example if it is increasing or decreasing. Purely by way of example, if the trend of the angular coefficient of the I-V curve is not monotonic increasing, there could be an anomaly in the photovoltaic source 50.

In accordance with some embodiments, the device 10 can also comprise means for interacting with the user 27 which can be commanded by the control and management unit 14. The means for interacting with the user 27 can be configured to communicate information on the status of health and functioning of the photovoltaic source 50 to the user. For example, the means for interacting with the user 27 can graphically represent an I-V curve, for example the last I-V curve stored in the storage means 14a. In addition, the means for interacting with the user 27 can be configured to communicate possible symptoms of anomalies of the photovoltaic source 50 to the user, for example on the basis of the analysis of the I-V curve carried out by means of the control and management unit 14.

According to preferred embodiments, the means for interacting with the user 27 can comprise screens to display images and visual and/or acoustic warning devices. Furthermore, the means for interacting with the user 27 can comprise wireless communication means configured to transmit information on the I-V curve detected to the system operator and/or to other users.

The present invention also concerns a method for the functioning of a device 10 for regulating the charge from a photovoltaic source 50 electrically connected to an accumulation device 51.

According to some embodiments, the method can provide to electrically separate the photovoltaic source 50 from the accumulation device 51.

The method provides to apply a gradual electrical load to the photovoltaic source 50 electrically separated from the accumulation device 51 . Preferably, the electrical load can be applied by means of a pulse length modulation (PWM) with a gradually increasing duty cycle, until a current close to the short-circuit current Isc of the photovoltaic source 50 is reached. The method can also provide to periodically detect voltage and current values of the electrical load applied to the photovoltaic source 50. Preferably, the voltage and current values are detected substantially simultaneously.

The method can also provide to store the detected voltage and current values. Preferably, n pairs of detected voltage and current values are stored substantially simultaneously, in such a way as to define an I-V curve of the photovoltaic source 50. In particular, the I-V curve of the photovoltaic source 50 can be a set of points, the coordinates of which are voltage and current values.

Subsequently, the method can provide to electrically connect the photovoltaic source 50 to an accumulation device 51 in order to charge it by means of algorithms of the MPPT type which refer to the stored I-V curve.

According to other embodiments, the method can provide to analyze the I-V curve of the photovoltaic source 50.

In some embodiments, the analysis can provide to integrate the I-V curve of the photovoltaic source 50 and to compare the value resulting from the integration with a comparison value. In particular, the comparison can consist in determining whether the comparison value is less than the result of the integration of the I-V curve of the photovoltaic source 50. This comparison value can, for example, be obtained experimentally. In particular, the comparison value can depend on the value of the short-circuit current I_sc, on the value of the no- load voltage V_Oc of the photovoltaic source 50. The comparison value can also depend on an arbitrary multiplicative factor K.

In one embodiment, with reference to fig. 4, the comparison can consist in establishing whether the following quantity is positive or negative, that is:

.

According to some embodiments, the method can provide to signal anomalies of the photovoltaic source 50, on the basis of the result of the comparison. Purely by way of example, if the quantity above is positive, there could be an anomaly in the photovoltaic source 50.

In other embodiments, the analysis can also provide to compare the angular coefficient of the I-V curve at different points thereof. In particular, this comparison can have the purpose of establishing the trend of the angular coefficient, for example if it is increasing or decreasing. More in particular, with reference to fig. 4, the comparison above can provide to establish whether the following condition is met:

'

In some embodiments, the method can also provide to report anomalies on the basis of the comparison of the angular coefficient. Purely by way of example, if the condition above is not met, there could be an anomaly in the photovoltaic source 50.

It is clear that modifications and/or additions of parts or steps may be made to the device 10 and to the method as described heretofore, without departing from the field and scope of the present invention as defined by the claims.

In the following claims, the sole purpose of the references in brackets is to facilitate reading: they must not be considered as restrictive factors with regard to the field of protection claimed in the specific claims.

Claims

1. Device (10) for regulating the charge from a photovoltaic source configured to be electrically connected to a photovoltaic source (50) and to an electrical energy accumulation device (51), characterized in that it comprises an intermediate section (12) configured to electrically connect/separate, in a selective manner, said accumulation device (51) to/from said photovoltaic source (50), and in that it comprises a scanning section (11), electrically connected to said photovoltaic source (50) and to said intermediate section (12), configured to apply a variable electrical load to said photovoltaic source (50) when said photovoltaic source (50) is electrically separated from said accumulation device (51).

2. Device (10) as in claim 1 and comprising a regulating section (13), characterized in that said intermediate section (12) is configured to electrically connect/separate, in a selective manner, said scanning section (11) and said regulating section (13).

3. Device (10) as in claim 1 or 2, characterized in that said scanning section (11) comprises current detection means (17), and voltage detection means (15) configured to detect voltage and current values of said electrical load applied to said photovoltaic source (50).

4. Device (10) as in claim 3, characterized in that it comprises a control and management unit (14) configured to cooperate with said current detection means (17) and said voltage detection means (15) in order to sample voltage and current values of said electrical load applied to said photovoltaic source (50), in order to define an I-V curve of said photovoltaic source (50).

5. Device (10) as in claim 4, characterized in that it comprises storage means (14a) on which an I-V curve of said photovoltaic source (50) can be stored and in that said regulating section (13) is configured to regulate the charge of said accumulation device (51) by means of algorithms of the MPPT type.

6. Device (10) as in any claim from 2 to 5, characterized in that said regulating section (13) comprises accumulation means (25) configured to accumulate electrical energy in order to allow to charge the accumulation device (51) even when said intermediate section (12) electrically separates said photovoltaic source (50) from said accumulation device (51).

7. Device (10) as in any claim from 4 to 6 and comprising means for interacting with the user (27), characterized in that said control and management unit (14) is configured to analyze said I-V curve in order to detect possible anomalies of said photovoltaic source (50) and in that said control and management unit (14) is configured to alert a user, by means of said user interaction means (27), of the presence of said anomalies.

8. Method for the functioning of a device (10) for regulating the charge from a photovoltaic source (50), as defined in any claim hereinbefore, characterized in that it provides to: electrically separate a photovoltaic source (50) from an accumulation device (51); gradually apply an electrical load to said photovoltaic source (50) electrically separated from said accumulation device (51); periodically detect voltage and current values of said electrical load applied to said photovoltaic source (50); store detected voltage and current values so as to define an I-V curve of said photovoltaic source (50).

9. Method as in claim 8, characterized in that it provides to: electrically connect said photovoltaic source (50) to an accumulation device (51) in order to charge it by means of algorithms of the MPPT type which refer to the stored I-V curve.

10. Method as in claim 8 or 9, characterized in that it provides to: integrate said I-V curve and compare the value resulting from the integration with a comparison value; and/or: establish the trend of the angular coefficient of said I-V curve; in order to determine possible anomalies of said photovoltaic source (50).