FR3079072A1 - MAINTENANCE DEVICE FOR BATTERY BENCHES OF A SOLAR POWER PLANT - Google Patents

Abstract

Maintenance device for performing maintenance loads on the battery banks. (9) a solar power plant (2), the maintenance device comprising a power supply module (20) connected to a power bus (6) connected to both the photovoltaic panel and the battery banks, the first controllable connection means for individually connecting or disconnecting each bank of batteries to the power bus, second controllable connection means for selectively connecting or disconnecting each bank of batteries to an output (S) of the power supply module (20), and an electric control unit (23) arranged to control the first connection means and the second connection means by connecting a particular bank of batteries (9k) to the output of the power supply module (20) and disconnecting said battery bank particular (9k) of the power bus when it is appropriate to carry out a maintenance charge on said particular bank of batteries.

Description

OBJECT OF THE INVENTION

The object of the invention is to make it possible to automatically carry out, without human intervention, the maintenance charges for the battery banks of a “purely” solar power plant.

SUMMARY OF THE INVENTION

In order to achieve this goal, a maintenance device is proposed for carrying out maintenance charges on a plurality of battery banks of a solar electric power station which also comprises at least one photovoltaic panel, the maintenance device comprising a power module having at least one input which can be connected to at least one power bus connected both to the photovoltaic panel and to the battery banks, first controllable connection means for selectively connecting or disconnecting each battery bank individually to the bus power, second controllable connection means for selectively connecting or disconnecting each battery bank individually to an output of the power supply module, and an electric control unit arranged to control the first connection means and the second connection means by connecting a special battery bank at the exit of the m power supply and by disconnecting said particular battery bank from the power bus when it is necessary to carry out a maintenance charge on said particular battery bank, and by disconnecting the particular battery bank from the output of the power module and reconnecting said particular battery bank to the power bus when a maintenance charge is not required.

The maintenance device makes it possible to carry out the maintenance charges for the battery banks of the solar power plant automatically, without human intervention. The electrical energy necessary for these maintenance charges comes, via the power bus, either directly from the photovoltaic panels, or from the banks of batteries which are not in maintenance, so that the maintenance device is compatible with a purely electric power plant. solar.

A solar power plant is also proposed comprising battery banks and a maintenance device such as that which has just been described.

A maintenance method is also proposed using a maintenance device such as that which has just been described and comprising the steps of:

define a date on which a maintenance charge should be carried out on a particular battery bank;

receive information relating to weather forecasts and / or a state of charge of the battery banks and / or a current hour of the current day;

start the maintenance charge on the particular battery bank from this information;

control the first connection means and the second connection means for connecting the particular battery bank to power supply and for disconnecting said particular battery from the bus the output of the power module.

bench of a computer program for processing a work, by a device

In addition, comprising instructions for the electrical maintenance component integrated in a solar power plant, a maintenance method as described above is proposed.

We also propose means characterized in that they store a computer comprising instructions, an electrical component for integrated solar maintenance, a method of de one for storage, program put into treatment of a in a central maintenance such as work, by electrical device that just described.

The invention will be better understood in light of the following description of a particular non-limiting embodiment of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Reference will be made to the appended drawings of the work, among which:

Figure 1 shows a solar power plant in which is integrated a maintenance device according to the invention;

FIG. 2 represents steps of a maintenance method using the maintenance device according to the invention;

FIG. 3 is a graph on which discharge curves are represented as a function of the discharge rate of a battery element of a battery bank, that is to say voltage curves at the terminals of the element of battery as a function of time;

FIG. 4 is a graph on which curves of voltage, current and state of charge readings of two battery banks are represented;

FIGS. 5a to 5g form a table comprising readings of electrical parameters carried out on two banks of EXIDE OPzS 1990 type batteries;

FIG. 6 is a table comprising, capacity values (in Ah) of a battery bank of the OPzS Solar 1990 type as a function of the discharge regime;

FIG. 1 is a table comprising values of capacity and discharge current of a battery bank as a function of the discharge regime.

In DETAILED DESCRIPTION OF THE INVENTION of reference to Figure 1, the device maintenance according to 1 ': invention 1 is integrated into a power plant electric « purely »Solar 2, that is to say fed only by 1 'energy solar. This power plant electric solar 2 is here intended at feed electrically of the amenities of telecommunications 3. The Power plant solar 2 includes a plurality of panels PV 4 which are connected

each to a DC-DC converter 5. The solar power plant 2 further comprises a first power bus 6 and a second power bus 7. The first power bus 6 and the second power bus 7 are connected to the photovoltaic panels 4 via the DCDC converters 5. The photovoltaic panels 4 transform solar energy into electrical energy. The DC-DC converters 5 convert the output voltage of the photovoltaic panels 4 so that the voltage applied to the first power bus 6 is equal to -48V and the voltage applied to the second power bus 7 is equal to 0V. A bus voltage is thus obtained which is normally equal to 48VDC between the first power bus 6 and the second power bus 7 (or, more precisely, between the second power bus 7 and the first power bus 6). The telecommunications equipment 3 are connected to the first power bus 6 and to the second power bus 7 and are electrically supplied by the first power bus 6 and the second power bus 7.

The solar power plant 2 further comprises a plurality of battery banks 9. Each battery bank 9 here comprises 24 2V battery cells. Each battery bank 9 is connected via a first conductor 10 to the first power bus 6 and via a second conductor 11 to the second power bus 7. Each battery bank 9 comprises a temperature probe 13 which measures the temperature of one of the battery elements of said battery bank 9. It is considered that the temperature of the battery bank 9 in question can be estimated by the temperature measured by the temperature probe 13.

The solar power plant 2 also includes a first controller 14. The first controller 14 manages a certain number of functions implemented in the solar power plant 2. In particular, the first controller 14 manages the operation of the DC-DC converters 5 and calculates the state of charge of the batteries (or SoC, for State of Charge).

The solar power plant 2 further comprises a second controller 15. The second controller 15 is a controller. supervision. It is in particular arranged to communicate with the first controller 14 and with a remote supervision server 16, located at a distance from the solar power plant 2.

The supervision server 16 acquires data produced by a weather forecast website 17.

The maintenance device according to the invention 1, for its part, forms individual equipment which is integrated into the solar power plant 2.

The maintenance device 1 comprises a box inside of which are integrated a power supply module 20, first connection means which here comprise first power contactors 21, second connection means which here comprise second power contactors 22, and an electrical control unit 23.

The power supply module 20 produces a maintenance charge current at a maintenance charge voltage, in order to carry out the maintenance charges for each battery bank 9 individually.

The power supply module 20 has a first input El connected to the first power bus 6, a second input E2 connected to the second power bus 7, and an output S. The power module 20 comprises a buck-boost converter and a buck-boost converter control module.

The first power contactors 21 can be controlled to selectively connect or disconnect each battery bank 9 to the first power bus 6 individually. Each first power contactor 21 is associated with a separate battery bank 9, and each second power contactor 22 is associated with a separate battery bank 9.

Each first power contactor 21 is mounted on a first conductor 10 which connects a battery bank 9 to the first power bus 6. Each second contactor 22 is mounted between the output S of the power supply module 20 and an input of a bench of batteries 9.

The electric control unit 23 controls the maintenance device 1. The electric control unit 23 comprises at least one electrical processing component which manages the operation of the electric control unit 23 and therefore of the maintenance device 1. The electrical processing component is for example a processor, a microcontroller, an FPGA, an ASIC, etc. The electrical processing component is adapted to execute instructions of a program to carry out the tasks which are dedicated to the electrical control unit 23.

Note that the maintenance device 1 can be easily integrated into an existing solar power plant without the need to modify said solar power plant. It suffices to connect the maintenance device 1 to the first power bus 6 and to the second power bus 7, on the one hand, and to the battery banks 9, on the other hand.

We will now describe, with reference to FIG. 2, a method of maintaining the battery banks 9, which uses the maintenance device according to the invention 1.

The electrical control unit 23 acquires a calendar (step E1) and a status table (step E2). The calendar defines the planned maintenance dates for each of the battery banks 9. The status table contains the dates of the maintenance charges carried out for each battery bank 9.

The electrical control unit 23 then calculates the forecast date on which the next maintenance charge should be carried out on a particular battery bank 9k (step E3). The forecast date is then compared with the current date (step E4). As long as the current date is earlier than the forecast date, the maintenance method repeats step E4.

When the current date reaches the forecast date, the electrical control unit 23 acquires via the second controller 15 information relating to weather forecasts.

Indeed, the energy necessary for the maintenance charge is provided either by photovoltaic production (day), or by the energy stored in the banks of batteries 9 not disconnected (night or cloudy passage). During the maintenance charge, the solar power plant 2 has a reduced battery capacity. This reduced capacity must not lead to a break in service (supply of telecommunications equipment). This implies that solar production must be maximum. We therefore set up a weather forecast reading system to authorize a maintenance charge.

The electrical control unit 23 consequently determines whether a condition linked to this information is verified (step E5). Here, the condition to validate is that the weather forecast is favorable for the coming days. We use a cloudiness criterion. For example, a forecast for the next three days with a cloud cover of less than 10% is considered to be a favorable factor.

If this condition is verified, the electrical control unit 23 acquires, via the second controller 15, information relating to a state of charge of the batteries of the particular battery bank 9k. The electrical control unit 23 then determines whether a condition linked to this information is verified (step E6). The condition to be validated is that the state of charge is greater than a predetermined charge threshold which is here equal to 95%.

If this condition is verified, the electrical control unit 23 acquires, via the second controller 15, information relating to the current time of the current day. The electrical control unit 23 then determines whether a condition linked to this information is verified (step E7). This condition is that the current time corresponds to the end of the current day. The time corresponding to the end of the day is configurable. The configuration can take into account the sunrise and sunset times, for example in tabulated form, possibly acquired from an ephemeris service.

If this condition is satisfied, the maintenance charge starts on the particular 9k battery bank.

The electrical control unit 23 controls the first power contactor 21 and the second power contactor 22 associated with the particular battery bank 9k so as to connect the particular battery bank 9k to the output of the power supply module 20 and so to disconnect said particular battery bank 9k from the first power bus 6. The electrical control unit 23 therefore commands an opening of the first power contactor 21 (step E8) and a closing of the second power contactor 22 (step E9) .

A measurement of the duration of the maintenance charge is then launched. The duration of the maintenance charge must be equal to a configurable time tl. This configurable time tl is provided by the battery manufacturer (periodic equalization charge to be applied in solar use, cycling). generally between intervals of 1 to 3 months.

Then, the particular temperature 9k is measured

This configurable time is

24h and bench thanks to

72h for batteries the associated temperature probe 13 (step Ell).

The electrical control unit 23 then calculates the charging voltage which should be applied at the input of the particular battery bank 9k to carry out the maintenance charge (step E12).

The charging voltage is equal to a total equalization voltage of the particular 9k battery bank. The total equalization voltage is the same for all battery banks 9. The equalization voltage for each battery cell is fixed at 2.4 VDC, or 57.6 VDC for each battery bank 9 with 24 battery cells drums. This equalization voltage is the minimum voltage set by the battery manufacturers for an equalization charge (liquid electrolyte battery). The choice of this equalization voltage of 2.4 VDC makes it possible to preserve the telecommunications equipment (or "load") against an overvoltage during reconnections or in the event of an accidental reconnection.

This charge voltage can be adjusted when using batteries from another technology, for example waterproof batteries (GEL).

The charging voltage which has just been described is actually a nominal charging voltage for a reference temperature T _re f- The reference temperature T _re f is given by the manufacturer of the batteries and is typically 20 ° C or 25 ° C.

The actual charge voltage must therefore be compensated as a function of the temperature of the particular 9k battery bank during maintenance.

A reference voltage U _CO nsigne (V) is thus defined which corresponds to the temperature compensated load voltage.

We have :

Uconsigne (V) - Legalization + (Tref ~ Teatt) * ϋκ, τ _θιη ρ * ^ elements .batteries r with:

Legalization (V) = 2.4 VDC per battery element, or 57.6 VDC for a battery bank 9;

T _re f (° C): reference temperature (typically 20 ° C or 25 ° C), supplied by the battery manufacturer;

Tfiatt (° C): temperature (in real time) of a battery which is representative of the temperature of the particular battery bank n;

U _K .Temp (V): voltage coefficient linked to temperature and supplied by the battery manufacturer. Its value is for example 3mV / ° C / battery cell;

Batteries: number of battery cells in series, here equal to 24).

The setpoint voltage U _CO nsigne (V) is then transmitted to the control module of the buckboost converter of the power supply module 20.

The control module implements a voltage regulation loop to control the buck-boost converter so as to ensure that the output voltage of the power supply module remains equal to the set voltage (or at least the closest to setpoint voltage possible - step E13).

If the setpoint voltage is greater than the bus voltage present between the first power bus 6 and the second power bus 7 (i.e. 48VDC), the buck-boost converter of the power supply module 20 is controlled as a boost. If the setpoint voltage is lower than the bus voltage, the buckboost converter is ordered in buck.

The control module also implements a current regulation loop arranged to limit a maintenance charge current at the output of the power supply module 20. This current regulation loop makes it possible to ensure that the maintenance charge current remains below a predefined current threshold. The predefined current threshold is here set at:

I (A) = 0.01 * CIO.

CIO represents the capacity in Ah of the batteries for a complete discharge in 10 hours. The capacity of a battery bank depends on the average discharge current (discharge regime). It is expressed as a function of the number of hours of autonomy up to the stop voltage. C10 represents the capacity (in Ah) of the batteries for a complete discharge in 10 hours (10 hour regime). This capacity is provided by the battery manufacturer. Note that, throughout this document, the time t in hours corresponds to the speed index (for example for C10: t = 10 hours).

Then, it is checked that the bus voltage between the first power bus 6 and the second power bus 7 remains greater than or equal to a predefined voltage threshold (step E14).

Indeed, if the bus voltage becomes too low, this indicates that the state of charge of the battery cells of the battery banks 9 which remain connected to the first power bus 6 is abnormally low. This state of charge which is too low may for example be due to a fault or to insufficient daytime charging. If the bus voltage is actually lower than the predefined voltage threshold, the maintenance charge is stopped and the particular 9k battery bank undergoing maintenance (with a state of charge close to 100% SoC) is reconnected to the first bus of power 6 and is used to power telecommunication equipment 3.

An alarm is also generated (step E15). This alarm can indicate to an operator that intervention on the solar power plant 2 is necessary. This alarm can also indicate that an external action is necessary to determine the causes of the anomaly.

The value of the predefined voltage threshold is configurable. By default, the predefined voltage threshold will be configured to correspond to a state of charge equivalent to approximately 25% of SoC (State of Charge).

The value of the predefined voltage threshold is determined using the discharge curves as a function of the discharge regime, supplied by the manufacturer of the batteries.

First calculate the average discharge current in amperes (Discharge average) · θη a Z

Discharge medium (A) = Main.load + System .maintenancer 3V6C Z

Icharge.principale (A): average current consumed by telecommunication equipment 3 (in amperes);

Maintenance system (A) z maximum current consumed by maintenance device 1 (in amperes). This current is equal to 0.01 * C10 from a single bank of batteries 9.

The predefined voltage threshold U _seu n therefore corresponds to a state of charge equivalent to 25% of SoC as a function of the average discharge current in amperes (Imoyen. Of discharge)

The discharge curves of the battery manufacturers have as ordinate the voltage for a battery element and as abscissa the time in hours of discharge. Each discharge curve represents a different discharge regime compared to a reference capacity (Cx).

In order to determine the corresponding curve, it is necessary to calculate the nominal autonomy (Nbhour.discharge.total) in hours of the battery cells of the battery banks 9 which remain connected to the first power bus 6, i.e. batteries from all of the battery banks 9 with the exception of the particular battery bank 9k, the maintenance of which is in progress.

The capacity in discharge mode Cx of the battery cells remaining connected to the first power bus 6 (Cah.total) is calculated by adding the respective capacity (C _Ah ) of all the battery banks 9 (Nb _ban cs) minus the bank of special 9k batteries under maintenance. The capacity is expressed in ampere-hours. It is noted that all the battery banks 9 have here strictly the same capacity.

We have :

C _Ah : unit capacity of a battery bank ^- C Ah. total (Ah) C _AA * - Nbhour. dump. total

· Imoyen.de.décharge

We convert the state of

C _Ah. Total charge in discharge hours

3θΤ1ί1 (Voltage threshold)

SoCseuii (%): Default threshold at 25%;

~ H- _geu j _;] _. of. voltage (hours) - Nbhour. dump . total

SoC _only i) / 100.

We read the minimum SoC, which is fixed * (100 then on the curves supplied battery manufacturer the voltage threshold by the corresponding preset

One at the hours of discharge threshold, provides an example to illustrate what has just been said.

We get solar 2 each one a place in case that has capacity three benches the power plant

The respective average telecommunication current 3 of consumption is predefined corresponds

25% SoC.

therefore equal to one par at 60A.

electric of batteries 9 having 2000Ah in C120 regime. The equipment of the state of charge voltage threshold equivalent to

We have :

AT

I main charge

Maintenance.isystem ^- 0.01 * 2000 = 20 A; Imoyen. of. discharge ⁼ 40 + 20 ⁼ 80 A;

C _Ah. Total = 2000 * (3 - 1) = 4000 Ah;

Total discharge time ~ 4000/80 = 50 hours;

Hseuil. ds. voltage ^- 50 * (100 25) / 100 - 37.5 hours.

With reference to FIG. 3, the manufacturer of the batteries provides the discharge curves for the discharge regimes in 48 hours (curve C1), in 100 hours (curve C2) and in 120 hours (curve C3). Interpolation is necessary to produce the curve C4 corresponding to the discharge regime in 50 hours.

It can be seen that the predefined voltage threshold corresponding to 37.5 hours is equal to U _seu n = 1.94 V per battery cell, ie at 46.56 VDC for battery banks 9 having 24 battery cells.

Referring again to FIG. 2, if the bus voltage is greater than or equal to the predefined voltage threshold, which corresponds to normal operation, it is checked that the temperature of the particular battery bank 9k during maintenance is much lower or equal to a predefined temperature threshold (step E16). The value of the preset temperature threshold is provided by the battery manufacturer.

A temperature above the predefined temperature threshold corresponds to an abnormally high temperature. If the temperature becomes higher than the predefined temperature threshold, the maintenance load is stopped and an alarm is generated (step E15).

We then wait for the end of the configurable time (step E17). If the

1 step E18.

configurable time has elapsed, we go to Otherwise, we return to step EU.

the end of the charge of 9k.

The maintenance stage of the battery bank

E18 corresponds to particular

The maintenance charge required. It is advisable to supply particular batteries 20 and therefore no longer has to disconnect the bench from

9k of the module output to reconnect said particular battery bank 9k to the first power bus 6. For this, the electrical control unit 23 opens the second power contactor 22 disconnect the battery bank output from the power module 20 , power contactor 21, which makes the particular power bank 6.

An order is then sent to recalculate the state of charge of the battery banks, which in particular and closes allows

9k from the first allows reconnecting 9k to the first bus of the first controller (step E20). The maintenance load has indeed disturbed the calculation of the state of charge of all the benches to re-calibrate it.

batteries 9, and it is necessary to note that in the absence of an intelligent charging system (SoC) set in controller 14, is necessary for battery estimation system (SoC).

The stages which of intelligent state estimation restart the force of it

One works in the first first controller to reinitialize from the state of its charge being the banks of described are carried out again successively for each of the battery banks 9.

so others

It is noted that when a battery bank disconnected from the first power bus 6, during the daytime charging phases, all of the current produced consumed by distributes on connected to the east by the the photovoltaic panels 4 and not telecommunications equipment 3 battery banks 9 which have remained the first power bus 6. It is therefore necessary to ensure that this current does not exceed the maximum current authorized for each of the battery banks 9.

by whom

The results of the work carried out to verify the feasibility of the maintenance device according to the invention 1 are now presented.

First of all, periodic readings of a maintenance charge in hybrid mode were carried out. These statements are provided in the tables of Figures 5a to 5g. In this hybrid configuration, the battery banks 9 remain permanently connected to the first power bus 6, and it is a generator which supplies all the energy necessary for the duration of the maintenance charge.

This study makes it possible to evaluate the energy demand for the charge of maintenance of lead-acid batteries in pure solar site.

The statements presented correspond to a maintenance charge of 2 banks of EXIDE OPzS 1990 type batteries (lead-acid with liquid electrolyte) from 1990Ah in C120 regime, connected in parallel. The rectifier is of the hybrid type: solar energy, generator and batteries.

The energy (Ah) required for this maintenance charge is expressed as follows:

In FIG. 4, the curve C5 corresponds to the maintenance charge voltage, as a function of time, at the terminals of the two banks of batteries under maintenance, the curve C6 corresponds to the maintenance charge current, the area SI to the energy necessary for the maintenance charge, and the curve C7 at the state of charge of the battery banks.

Periodic readings are then used by being reduced to a single battery bank 9: all the values of the readings have been halved. Periodic readings make it possible to break down the following W (Ah) energies by periods.

The total energy consumption over the 48 hour period is:

Wtotal.maintenance 714 / z The consumption ’= 356.5 Ah. energy sure the first period nocturnal 30 is: Wnocturnel .maintenance ⁼ 33 9 / 2 = 169, 5 Ah. The consumption energy sure the first period daytime 31 is: Wdiurnel.maintenance ^- 157 / 2 = 78.5 Ah. The consumption energy sure the second period nocturnal 32 is: Wnocturne2 .maintenance 103 / 2 = 51.5 Ah. The consumption energy sure the second period diurnal 33 is: Wdiurne2.maintenance ~ '114 / 2 = 57 Ah Then we study by simulation a scenario of

maintenance load via the maintenance device according to the invention 1.

The following data are used for the simulation:

current consumed by the load (here, by telecommunication equipment) = 20 A;

bus voltage = 48 VDC;

use of 2 OPzS type battery banks (lead acid with liquid, tubular electrolyte);

capacity = 1990 Ah in C120;

- 24 2V battery cells in series in each battery bank;

the capacities supplied by the battery manufacturer as a function of the discharge regime correspond to the capacities in the table in FIG. 6;

- energy efficiency charge / discharge of the batteries of this technology: around 90% favorable weather forecast for the next 3 days;

start of maintenance charge at sunset, 95% SoC (State of Charge) battery charge status;

daytime = nighttime = 12 hours; site design data:

o photovoltaic panels:

installed power of 10 kWp (kiloWatt-peak);

poly-crystalline technology.

o average energy production potential per day:

worst month = 35.40 kWh;

most favorable month = 44 kWh.

The calculations are focused on the first night period 30 since it is the most energy consuming. If, after this first night period 30, the batteries are able to recover a state of charge greater than or equal to 95% of SoC, this makes it possible to validate the operation of this invention.

The energy required for the first night period 30 is then calculated: W _noctU rnei.necessary (Ah).

We have :

Wnocturnel.necessary (Ah) = ^ discharge.batteries * H _no turnelr âVOC;

~ I discharge.batteries (A) = (^ charge + I system.maintenance) r

Icharge (A): average load current (telecom equipment);

Maintenance.isystem (A): maximum current of the maintenance system (fixed at 0.01 * C10);

~ H _noturne i (hours): duration in hours of the night period.

The following numerical values are obtained:

^- Icharge 20 A ^- .System maintenance. 0,01 * 1411 = 14,11 A /

Hnoturnei: 12 noon;

~ Battery discharge ⁼ 20 + 14.11 = 34.11 A;

~ Wnocturnel .necessary ⁼ 34.11 * 12 = 409.32 Ah.

However, the capacity of a lead-acid battery is not constant. It depends on the discharge current. It is therefore necessary to calculate the capacity of the batteries remaining connected to the first power bus 6 and corresponding to the discharge current of the first night period. To allow this calculation, it is necessary to know the reference capacities which are provided by the battery manufacturer. Then, from these tables, we calculate the real capacity. This calculation is made using Peukert's law.

The Peukert's coefficient k is calculated as a function of two pairs of points. We have :

I _A (A): discharge current for regime A;

t _A (hours): discharge time for a regime

AT ;

I _B (A): discharge current for regime B;

t _B (hours): discharge time for regime B.

We find :

We gets the numerical values who follow. We uses Table of the capacities provided through the maker and correspondent to the table in the figure 7. We calculated all first the currents of landfill

for each diet on the table:

I (A) = C (Ah) / t (hours).

For the calculation of k, we use as a reference for the regime (A) the CIO regime, as well as the regime (B) which limits our discharge current (Idécharge.batteries)

We have :

Idécharge. batteries ⁼ 54.11 A.

The speed (B) = C48 limits the discharge current.

So we have :

The real capacity (C) is calculated via the normalized expression of the capacity as a function of the normalized value of the current.

We have :

With:

CIO (Ah): capacity of the batteries for a CIO discharge regime (10 hours);

110 (A): battery current for a CIO discharge regime (10 hours);

I (A): actual discharge current of the batteries (Battery discharge);

k: Peukert's coefficient

The following numerical value is obtained:

1411 / 34.113 ^1.148-1

1141.17

1741 Ah.

We then calculate the state of charge SoC (State of

Charging) of the batteries remaining connected to the first power bus 6 after the first night period.

We have :

SoCinitiai (%) = Starting SoC (at the start of the first night period).

So we have :

SoC (»/„) = „ ₁₀₀ ^ _ ₍₁₀₀ _ SoC _irMlal )

The following numerical value is obtained:

/ 1741 -409.32 \ _z

SoC = [---—--- * 100J - (100 - 95) = 71.5%

This level of discharge is correct. The capacity of the battery banks that remain connected to the first power bus 6 is more than 2/3 of their capacity.

The margin with a state of charge SOC of 25% (corresponding to U _seu ii) is sufficient (no confusion for the system).

We calculate the solar energy required W (Wh) during the first daytime period (with favorable weather) for:

recharge the main system batteries to a SoC state of charge of 95% (equal to the state of charge at the start of the 1st night period);

supply the load (telecommunications equipment);

supply the maintenance device.

We have :

^- Recharge .batterie .principales. daytime (Wh): energy required to recharge the batteries during the first daytime period;

Wnocturnei. required (Ah): energy required for the first night period;

U _S ystèitie (V): nominal voltage of the maintenance device;

A: Battery charge / discharge energy efficiency;

E charge, diurnei. (Wh) = energy required to supply the load (telecommunications equipment) during the first daytime phase;

Icharge (A): average current consumed by the load (telecommunications equipment)

Hdiurnei · 12 hours;

Maintenance.isystem (A): maximum current consumed by the maintenance device (set at 0.01 * C10, see above);

- E _S y _S teme .maintenance. daytime (Wh) I energy required to power the maintenance device during the first daytime period;

Etotai. necessary, daytime (Wh): total energy required for the first daytime period (return SoC state of batteries and charge supply + maintenance device);

(Wh)

Wnocturnel.nécessaire

Recharge.batterie.principales.diurne * Usystem / (R / 100);

~ Daytime charge1 (Wh) - I charge * ^- Esysteme.maintenance.diurnel

Usystem * Hdiurnel r ~ Etotal.necessaire.diurnel

Erecharge.batterie.principales.diurnel Esysteme.maintenance.diurnel ·

The following numerical values are obtained: ~ E _rec ti _a rge. main battery. diurnal (Wh) 409.32 * (90/100) = 17,683 Wh;

Eloads. diurnal! (Wh) = 20 * 48 * 12 = 11520 Wh; ~ Egysteme .maintenance. diurnal (Wh) = 14.11 * 48 *

8127 Wh;

^- Etotal .necessaire.diurnel (Wh) ⁼ 17 683 +

37330 Wh = 37.33 kWh.

The energy required for the first provides for 44 kWh (Wh)

37.33 kWh. The daily site design averages 35.40 kWh per month.

We determine the difference between the

Usystem * Hdiurnel r ~ I maintenance system (Wh)

Echarge.diurnel

11520 + 8127 day is of production following the average production of the most unfavorable month necessary for the first day (ΔΕ):

^- Average.day.production (kWh):

and j ournalière

The average daily production energy of the most unfavorable month (design data);

ΔΕ (kWh)

Etotal.necessaire.diurnel ·

We obtain :

^ Production. average day.

ΔΕ (kWh) = 35.40 - 37.33 = - 1.93 kWh.

This difference does not entail a risk for the supply of telecommunications equipment.

Indeed, the capacity of the batteries makes it possible to make up for this deficit without any significant impact on the autonomy of the solar power plant and telecommunications equipment.

The total capacity of the batteries is estimated by the following formula:

Total nominal capacity * system voltage at 1990 Ah * 2 banks * 48VDC = 191 kWh.

In addition, the daily averages given by the design do not take into account the meteorology of the day. The design software is based on databases and estimates the monthly production for the site in question. It is therefore likely that the month with the lowest production estimate is linked to a month with very fluctuating (degraded) weather. By dividing the month by the number of days, we obtain an estimate of day production which ends up with a share of degraded meteorology.

The design of the maintenance device according to the invention 1 is therefore probably based on unfavorable weather forecasts. Production per day will therefore actually be higher than the daily average for the month planned by the design.

The energy required for the second day is less than the first day because the maintenance load requires less current (see Figure 4). We can therefore consider that the energy consumed is less than or equal to the energy produced.

The surveys and simulations carried out therefore make it possible to conclude that the maintenance device according to the invention is perfectly achievable without degrading the performance of the solar power plant 2.

Of course, the invention is not limited to the embodiment described but encompasses any variant coming within the scope of the invention as defined by the claims.

Claims (13)

1. Maintenance device intended to carry out maintenance charges on a plurality of battery banks (9) of a solar electric power station (2) which also comprises at least one photovoltaic panel (4), the maintenance device comprising a module power supply (20) having at least one input which can be connected to at least one power bus (6) connected both to the photovoltaic panel and to the battery banks, first controllable connection means for selectively connecting or disconnecting each battery bank to the power bus, second controllable connection means for selectively connecting or disconnecting each battery bank individually to an output (S) of the power supply module (20), and an electrical control unit (23) arranged to control the first connection means and the second connection means by connecting a specific battery bank (9k) to the output of the module power supply (20) and by disconnecting said particular battery bank (9k) from the power bus when it is necessary to carry out a maintenance charge on said particular battery bank, and by disconnecting the particular battery bank from the output of the power supply module and reconnecting said power bank when one of the batteries specific to the maintenance charge bus is not required. 2. Maintenance device according to claim 1, in which the electrical control unit (23) is arranged to receive information relating to weather forecasts and / or to a state of charge of the battery banks and / or to an hour. during a current day, and to start a maintenance load from this information. 3. Maintenance device according to one of the preceding claims, in which the power supply module (20) comprises a buck-boost converter and a control module for the buck-boost converter. 4. Maintenance device according to claim 3, in which the control module is arranged to implement a voltage regulation loop intended to ensure that a maintenance charge voltage produced by the power supply module remains equal to one setpoint voltage which is defined as a function of a temperature of the particular battery bank. 5. Maintenance device according to claim 3, wherein the control module is also arranged to implement a current regulation loop intended to limit a current of maintenance charge at the output of the power supply module (20). 6. Maintenance device according to one of the preceding claims, in which the first connection means comprise a plurality of first power contactors (21) each associated with a battery bank (9), and in which the second connection means comprise a plurality of second power contactors (22) each associated with a battery bank (9). 7. Solar power plant (2) comprising battery banks maintenance (1) according to previous. 8. Method of previous maintenance device and comprising; (9) and one of the maintenance according to one of the stages of: claims device using a claims define a date on which a maintenance charge should be carried out on a particular battery bank (9k); receive information relating to weather forecasts and / or a state of charge of the battery banks and / or a current hour of the current day; start the maintenance charge on the particular battery bank (9k) from this information; control the first connection means and the second connection means for connecting the particular battery bank (9k) to the output of the power supply module (20) and for disconnecting said particular battery bank from the power bus. 9. Maintenance method according to claim 8, in which the maintenance charge starts only if the weather forecast is favorable for the coming days and if the state of charge of the battery banks is above a predetermined charge threshold and if the current time corresponds to the end of the current day. 10. The maintenance method as claimed in claim 8, further comprising the steps, following the piloting step, of measuring a temperature of the particular battery bank (9k), of calculating a reference voltage as a function of the temperature, and to control the power supply module for maintenance equal to 11. Process that generates a charging voltage from the setpoint voltage. of 10, maintenance according to one of, further comprising the step of bus on the bus of power equal to a voltage threshold of claims 8 to verify that a voltage remains higher or predefined, and to produce an alarm if the voltage of bus becomes lower than the predefined voltage threshold. 12. Computer program comprising instructions for implementing, by an electrical processing component of a maintenance device integrated in a solar electric power plant, a maintenance method according to one of claims 8 to 11. 5 13. Storage means, characterized in that they store a computer program comprising instructions for implementing, by an electrical processing component of a maintenance device integrated in a solar power plant, a maintenance process according to one of claims 8 to 11.