Method for controlling a storage system for storing energy in a battery and associated devices

Abstract

The present invention relates to a method for controlling a storage system for storing energy in a battery delivering active power to an external system, the storage system comprising at least one power-supply assembly comprising a power-conversion system and a battery, the method comprising receiving the requirement in terms of power to be delivered to the external system, and, for each power-supply assembly: - acquiring the maximum active power that the power-supply assembly is able to deliver and the energy remaining in the battery, - calculating the contribution of the power-supply assembly to the delivery of active power by the storage system depending on the acquired remaining energy, - determining the power to be delivered by the power-supply assembly, the method comprising generating a control law for each power-supply assembly depending on the determined power.

Description

[0001] Method for controlling a battery energy storage system and associated devices

[0002] The present invention relates to a method for controlling a battery energy storage system. The present invention also relates to associated devices, namely an associated controller, control device, storage system and installation.

[0003] A battery energy storage system is a system generally comprising a plurality of banks, each bank containing a set of batteries in connection with a respective conversion system.

[0004] Such a storage system is more often referred to as a BESS system, referring to the corresponding English term “Battery Energy Storage System”.

[0005] The battery energy storage system is used to deliver high power to an external system with good stability.

[0006] However, in use, batteries exhibit different states of charge and electrical behaviors that vary from one battery to another.

[0007] There is therefore a need for a method of controlling a battery energy storage system enabling it to deliver the desired power to an external system with good reliability.

[0008] For this purpose, the description describes a method for controlling a battery energy storage system, the storage system being capable of supplying active power to an external system, the storage system comprising at least one power supply assembly, each power supply assembly comprising a power conversion system and one or more batteries, the method being implemented by a control device and comprising a step of receiving the power requirement to be delivered by the storage system to the external system, the method further comprising, for each power supply assembly:

[0009] - a step of acquiring the maximum active power that the power supply unit can provide and the energy remaining in the battery(ies) of the power supply unit,

[0010] - a step of calculating the contribution that the power supply assembly can make to the active power supply of the storage system based on the energy remaining in the battery(ies),

[0011] - a step of determining the power to be supplied by the power supply assembly, the power to be supplied being the minimum in absolute value between the determined contribution and the maximum active power, to obtain a determined power, the method further comprising a step of constituting a control law for each power supply assembly as a function of the power determined for each power supply assembly.

[0012] The maximum active power that a power supply unit can provide is the total active power that can be provided with the power capabilities of each of the elements making up the power supply unit.

[0013] Concrete examples of calculation are given below.

[0014] Taking into account this maximum active power with that of the contribution of the batteries makes it possible to avoid requesting the supply of power that the assembly and / or the battery cannot provide, which results in a better delivery of the desired power to the external system.

[0015] In particular, this consideration makes it possible to manage the case of battery deratings at the end of charge and discharge where the current is limited for protection reasons inducing a different active power.

[0016] More precisely, at the end of charge and at the end of discharge, the battery management systems limit the maximum authorized currents (respectively in charge and discharge) in order to remain within the operating envelope of the chemistry and not to activate protections (respectively voltage too high and voltage too low). Consequently, at the end of charge and discharge, the calculated powers, based on the voltage only, will be higher than the capacity of the battery, capacity limited by the derating of the authorized currents.

[0017] It is also interesting for the case of battery architectures in which the available power of the assembly is less than the available power of the battery.

[0018] For example, if we take an architecture in which the assembly includes two batteries each with a power capacity of 2 MW and a power conversion system with a capacity of 2 MW, the maximum active power is limited by the power conversion system and amounts to 2 MW instead of the 4 MW that the combination of the two batteries could provide.

[0019] Thus, the maximum active power generally corresponds to the minimum between the maximum active power that the power conversion system can deliver and the sum of the maximum active powers that the batteries can provide (for series association).

[0020] This consideration is also relevant for the case of a loss of a set. In addition, the powers to be distributed are calculated based on energy and not voltages. Voltage monitoring instead of power monitoring implies that the voltage allows direct access to the energy, which is not the case for batteries whose state of charge (SOC) variation with voltage shows a plateau (typically LiFePO4-based chemistries).

[0021] The control process therefore also makes it possible to take this issue into account.

[0022] According to particular embodiments, the control method has one or more of the following characteristics, taken in isolation or in all technically possible combinations:

[0023] - during the calculation step, the contribution also depends on the power requirement and the remaining energy of the storage system, the remaining energy of the storage system being the sum of the remaining energies of each battery.

[0024] - during the calculation stage, the contribution also depends on the efficiency of the power conversion system.

[0025] - during the constitution step, each control law makes it possible to control each power supply assembly so that the power supply assembly provides the power determined for said power supply assembly.

[0026] - for each power supply unit, the following steps are implemented:

[0027] - a step of calculating the sum of the powers determined for each power supply unit, to obtain a calculated sum, and

[0028] - a step of correction of the powers determined when the calculated sum is strictly less than the power requirement, to obtain corrected powers, the powers determined for which the power to be supplied is in absolute value the maximum active power being unchanged, and for the other powers determined, the calculation and determination steps being implemented again by increasing the power requirement by the difference between the calculated sum and the power requirement, the corrected powers being the powers thus determined.

[0029] - the sum calculation step is implemented again with the corrected powers instead of the determined powers, a new correction step being implemented if the new calculated sum is still strictly lower than the power requirement.

[0030] - the sum calculation and correction steps are implemented iteratively until either the calculated sum becomes equal to the power requirement or each power set provides the maximum active power of the power set's battery.

[0031] - the method further comprises a step of applying the constituted control law to each power supply assembly.

[0032] The description also proposes a controller capable of controlling a battery energy storage system, the storage system being capable of supplying active power to an external system, the storage system comprising at least one power supply assembly, each power supply assembly comprising a power conversion system and one or more batteries, the controller being capable of receiving the power requirement to be delivered by the storage system to the external system, and, for each power supply assembly, of:

[0033] - acquire the maximum active power that the power supply unit can provide and the remaining energy in the battery(ies) of the power supply unit,

[0034] - calculate the contribution that the power supply assembly can make to the active power supply of the storage system based on the energy remaining in the battery(ies), and

[0035] - determine the power to be supplied by the power supply unit, the power to be supplied being the minimum in absolute value between the determined contribution and the maximum active power, to obtain a determined power, the controller being, in addition, capable of constituting a control law for each power supply unit as a function of the power determined for each power supply unit.

[0036] The description also proposes a power control device comprising a controller as previously described and an application module capable of applying the control law constituted by the controller, the controller 30 and the application module preferably being merged.

[0037] The description also describes a battery energy storage system comprising a controller as previously described or a control device as previously described.

[0038] The description also provides an installation comprising a battery energy storage system as previously described.

[0039] In this description, the expression "suitable for" means indifferently "adapted for", "adapted to" or "configured for".

[0040] Characteristics and advantages of the invention will appear on reading the description which follows, given solely by way of non-limiting example, and made with reference to the appended drawings, in which: - figure 1 is a schematic representation of an installation,

[0041] - Figure 2 is a representation of a flowchart of an example of implementation of a method for controlling a battery energy storage system forming part of the installation of Figure 1, and

[0042] - Figure 3 is a representation of a flowchart of an example of implementation of another control method.

[0043] An installation 10 is shown schematically in Figure 1.

[0044] The installation 10 comprises a battery energy storage system 12, an external system 14 and an energy management system 16.

[0045] The storage system 12 is capable of providing active power to the external system 14.

[0046] The outdoor system 14 is a system requiring a power supply.

[0047] Power supply means a high, medium or low voltage power supply, for example the RTE or EDF electricity network, isolated networks (shops, industries or residential blocks for example).

[0048] The energy management system 16 serves as an interface between the storage system 12 and the external system 14.

[0049] In particular, the energy management system 16 is capable of communicating to the storage system 12 information relating to the energy needs of the external system 14, typically the active power and / or the reactive power, and is responsible for valuing these powers.

[0050] Active power corresponds to the average power to be supplied over a predefined period while reactive power is the imaginary part of the complex apparent power and contributes to the stability of the electrical network.

[0051] The energy management system 16 is more often referred to by the acronym EMS, the acronym referring to the corresponding English term “Energy Management System”.

[0052] The storage system 12 comprises several power supply assemblies 18 and a control device 20.

[0053] The 18 power supply assemblies are connected in parallel.

[0054] The number of power supply sets 18 can be very large, typically greater than 200.

[0055] The power supply assembly 18 is often referred to by the corresponding English term “Line-up”. Each power supply assembly 18 comprises a power conversion system 22 and one or more batteries 24.

[0056] More specifically, according to the example of FIG. 1, each power supply assembly 18 is constituted by a conversion system 22 electrically connected to one or more batteries 24.

[0057] The conversion system 22 is often referred to by the abbreviation PCS which corresponds to the corresponding English name of “Power Conversion System”.

[0058] According to the example described, the conversion system 22 comprises an inverter 26 and a transformer 28.

[0059] Inverter 26 and transformer 28 are in series.

[0060] The inverter 26 makes it possible to generate alternating voltages and currents from a direct electrical energy source.

[0061] The transformer 28 makes it possible to adapt the voltage, for example to carry out a transformation between a low voltage and a medium voltage.

[0062] The low voltage domain (also called LV or BT domain) corresponds to a domain in which the electrical voltage values ​​are strictly less than 1000 volts in alternating current.

[0063] The medium voltage domain (also called MV or HTA domain) designates a domain in which the electrical voltage values ​​exceed 1000 volts in alternating current.

[0064] Typically, a battery comprises one or more current accumulators, also called electrochemical generators, cells, or elements. An accumulator is an electricity-generating device in which chemical energy is converted into electrical energy. The chemical energy comes from electrochemically active compounds deposited on at least one face of electrodes arranged in the accumulator. The electrical energy is produced by electrochemical reactions during a discharge of the accumulator. The electrodes, arranged in a container, are electrically connected to current output terminals that ensure electrical continuity between the electrodes and an electrical consumer with which the accumulator is associated.

[0065] In order to increase the delivered electrical power, several sealed accumulators can be combined together to form a battery. Thus, a battery can be divided into modules, each module being composed of one or more accumulators connected together in series and / or in parallel. Thus, a battery can for example comprise one or more parallel branches of accumulators connected in series and / or one or more parallel branches of modules connected in series. Thus, the battery 24 is an arrangement of a plurality of electrochemical elements, each serving to produce electricity by converting chemical energy into electrical energy. Each electrochemical element therefore delivers a current and a voltage between two terminals.

[0066] The control device 20 is a power control device.

[0067] Such a control device 20 is more often designated by the abbreviations PMS or PPC which refer respectively to the corresponding English name of “Power Management System” or “Power Plant Controller”.

[0068] The control device 20 has the role of supplying and regulating the active and reactive powers at a predefined point in accordance with the power setpoint communicated by the energy management system 16.

[0069] The preset point is usually the output of the entire power supply system.

[0070] The predefined point is generally upstream of a medium voltage - high voltage transformer.

[0071] The medium voltage domain (also called HV or HTB domain) designates a domain in which the electrical voltage values ​​exceed 50,000 volts in alternating current.

[0072] This predefined point is subject to specific monitoring by a device for measuring electrical quantities (power, voltage, current, etc.). This device is more often referred to by the acronym PQM, referring to the corresponding English term "Power Quality Meter".

[0073] The control device 20 is also capable of receiving information relating to the state of the storage system 12, in particular the energy and power available.

[0074] The control device 20 also has the role of distributing the active and reactive powers between the different power supply units 18.

[0075] For this, the control device 20 comprises a controller 30 and an application module 32 and is capable of implementing a method for controlling the storage system 12.

[0076] According to an advantageous example, the controller 30 and the application module 32 are merged.

[0077] An example of implementation of such a control method is now described with reference to Figure 2.

[0078] The control method is a method for controlling a battery energy storage system 12 making it possible to ensure that the storage system 12 provides a given power over a period of time with good balancing between the different power supply systems so as to optimize the duration of active power supply.

[0079] The method comprises a reception step E10 during which the controller 30 receives the power requirement to be delivered by the storage system 12 to the external system 14.

[0080] The power requirement is communicated here by the energy management system 16. The method further comprises a set of steps E which are implemented for each power supply assembly 18.

[0081] According to the example of Figure 2, the set of steps E comprises an acquisition step E30, a calculation step E32 and a determination step E34.

[0082] These steps are now described for an 18 power supply assembly.

[0083] During the acquisition step E30, the controller 30 obtains the maximum active power that the power supply assembly 18 can provide and the remaining energy in the battery 24 of the power supply assembly 18.

[0084] More specifically, via a communication bus, each element of a power supply assembly 18 provides this information to the controller 30.

[0085] This allows the E30 acquisition step to take place in real time.

[0086] During the calculation step E32, the controller 30 calculates the contribution that the power supply assembly 18 can make to the supply of active power to the storage system 12 as a function of the energy remaining in the battery 24.

[0087] Preferably, the controller 30 also takes into account other elements to calculate the contribution as accurately as possible.

[0088] Thus, according to one embodiment, the contribution also depends on the power requirement and the remaining energy of the storage system 12, the remaining energy of the storage system 12 being the sum of the remaining energies of each battery 24.

[0089] Alternatively or additionally, the contribution also depends on the efficiency of the conversion system 22.

[0090] During the determination step E34, the controller 30 obtains the power to be supplied by the power supply assembly 18. The power to be supplied is called the determined power in the following.

[0091] The determined power is the minimum in absolute value between the determined contribution and the maximum active power.

[0092] The calculation and determination steps can be expressed mathematically by mathematical distribution functions which depend on the need, namely charge or discharge.

[0093] In discharge, the distribution function is written:

[0094] Under load, the distribution function is written:

[0095] Or :

[0096] • p is the active power required from the i-th power supply unit 18, the index i being an integer varying between 1 and the number of power supply units 18 of the installation 10 (this power is strictly positive in discharge and strictly negative in charge),

[0097] • Ed, is the remaining energy available for discharge in the battery 24 of the i-th power supply assembly 18,

[0098] • Ea is the energy available to the load in the battery 24 of the i-th power supply assembly 18,

[0099] • Ed tot is the energy available at discharge from the storage system 12,

[0100] • Ec tot is the energy available to the load of the storage system 12,

[0101] • Ldi is the maximum active power that the i-th power supply unit 18 can provide to the discharge,

[0102] • Lci is the maximum active power that the i-th power supply unit 18 can supply to the load,

[0103] • Pref is the power requirement to be delivered by the storage system 12 to the external system 14 (this value is positive when discharging and negative when charging),

[0104] • Jh is the nominal efficiency of the inverter 26, and

[0105] • T2 is the nominal efficiency of transformer 28.

[0106] The method then comprises a step E40 of constituting a control law for each power supply assembly 18 as a function of the power determined for each power supply assembly 18.

[0107] In this example, the constitution consists of converting the determined power into an electrical command of the power supply assembly 18 so that the latter provides the determined power.

[0108] According to the example of Figure 2, the method also comprises an application step E42 during which the application module 32 applies the constituted control law to each power supply assembly 18.

[0109] The method described makes it possible to optimize the performance of the storage system 12 by proposing to distribute the active power within the power supply units 18. The optimization carried out makes it possible to properly take into account the energy available in each battery 24.

[0110] The consideration is thus specific to the installation 10, so that the process allows optimization to be carried out in multiple use cases.

[0111] In particular, the method operates in the presence of an installation 10 having heterogeneities between the supply assemblies 18.

[0112] Heterogeneities may be native or arise during use of the storage system 12.

[0113] Mixed technologies for power supply sets 18 are an illustration of native heterogeneities.

[0114] By way of illustration, it could be envisaged that the batteries 24 of a first plurality of power supply assemblies 18 are produced according to a first technology (chemistry) while the batteries 24 of a second plurality of power supply assemblies 18 are produced according to a second technology (chemistry) different from the first technology.

[0115] Another example of native heterogeneity would be an asymmetric storage system 12 in which the batteries 24 of the power supply sets 18 have different active powers or energies.

[0116] Examples of heterogeneity occurring during use of the storage system 12 include energy variations between the batteries 24 following maintenance, variations in the capacity of the batteries 24, different aging of the batteries 24, variations in line resistance between the power supply assemblies 18 (linked in particular to internal resistance of the batteries 24 or damaged cables) or even a loss of a power supply assembly 18 following a malfunction.

[0117] The modification of installation 10 could also lead to the generation of new heterogeneities.

[0118] Furthermore, the present method can be implemented in real time, so that the adaptation is done in real time, thus allowing the storage system 12 to deliver the desired power to an external system 14 with good stability and good reliability.

[0119] Other embodiments of the method benefiting from these advantages which have just been described are conceivable.

[0120] In particular, with reference to FIG. 3, the set of steps E implemented for each power supply set 18 is more complex, the other steps remaining similar. In this example, a calculation step E36 of a sum and a correction step E38 are implemented.

[0121] During the step of calculating a sum E36, the control device 20 calculates the sum of the powers determined for each power supply assembly 18, to obtain a calculated sum.

[0122] Ideally, the calculated sum corresponds to the power requirement.

[0123] When this is not the case, that is to say when the calculated sum is strictly less than the power requirement, the control device 20 implements a correction step E38 of the powers determined to obtain corrected powers.

[0124] The corrected powers thus obtained aim to replace the determined powers, which leads to a control law making it possible to control each power supply assembly 18 so that the power supply assembly 18 provides the corrected power for said power supply assembly 18 (and not the determined power).

[0125] For some power supply sets 18, however, the determined power may be equal to the corrected power.

[0126] These are the powers determined for which the power to be supplied is in absolute value the maximum active power.

[0127] In such a case, the determined powers remain unchanged, so that the corrected power is equal to the power determined for the power supply sets 18 verifying the equality in absolute value between the power to be supplied and the maximum active power.

[0128] For the other determined powers, that is to say those whose power to be supplied is in absolute value strictly lower than the maximum active power, the corrected powers are determined as follows.

[0129] The steps of determining the contribution and determining the power to be supplied are again implemented by increasing the power requirement by the difference between the calculated sum and the power requirement.

[0130] This leads to obtaining new power values ​​for the power supply assembly(s) 18 associated with a non-maximum power to be supplied.

[0131] These new power values ​​are the corrected powers.

[0132] By construction, the corrected powers are greater than or equal to the powers determined previously.

[0133] Most often the corrected powers are strictly higher than these powers, the idea being to benefit from the power reserve of certain power supply assemblies 18 by requesting them more. Indeed, for the power supply assemblies 18 which have a power to supply which is not the maximum active power, there is a power reserve which can be used.

[0134] This amounts to asking for a little more power from 18 power supplies that have the capability to deliver higher power.

[0135] This makes it possible to better meet the power requirement without changing the storage system 12. It is only the control law that changes and becomes more adapted to the specific case.

[0136] To improve this adaptation, it is also possible to consider an iterative implementation of the calculation operation.

[0137] In a first example, a new iteration takes place so that the calculation operation is again implemented with the corrected powers instead of the determined powers.

[0138] The new correction operation is implemented if the new calculated sum is still strictly less than the power requirement.

[0139] This allows for a finer adjustment than the previous adjustment.

[0140] In a second example, the calculation and correction operations are implemented iteratively until a criterion is met.

[0141] The criterion here depends on the capacity of the storage system 12 to meet the power requirement.

[0142] If the storage system 12 is capable of providing the power requirement, the criterion will be that the calculated sum becomes equal to the power requirement.

[0143] In fact, by distributing the excess power over the power supply units 18 which can still provide more power, a configuration can be achieved in which the power requirement is met.

[0144] Alternatively, it may also be that the storage system 12 is unable to meet the power requirement.

[0145] In such a case, the iteration will be stopped when each power supply assembly 18 provides the maximum active power of the battery 24 of the power supply assembly 18, i.e. the correction operation no longer provides any correction, all the determined powers remaining identical.

[0146] In each of these hypotheses, the control law of the storage system 12 makes it possible to best respond to the need to be supplied within the limits of the electrical capacities of the storage system 12.

[0147] Mathematically, this amounts to new distribution formulas that always depend on the need, namely charging or discharging. For discharging, the distribution function is written:

[0148] Under load, the distribution function is written: Or:

[0149] • p act is the active power to be distributed at each iteration of the steps,

[0150] • Fd totc is the energy available for discharging the storage system 12, this energy being updated at each iteration of the steps, and

[0151] • Ec totc is the energy available to the load of the storage system 12, this energy being updated at each iteration of the steps.

[0152] In each case, the control method allows the storage system 12 to deliver the desired power to an external system 14 with good reliability.

Claims

CLAIMS 1. Method for controlling a battery energy storage system (12), the storage system (12) being capable of supplying active power to an external system (14), the storage system (12) comprising at least one power supply assembly (18), each power supply assembly (18) comprising a power conversion system (22) and one or more batteries (24), the method being implemented by a control device (20) and comprising a step of receiving the power requirement to be delivered by the storage system (12) to the external system (14), the method further comprising, for each power supply assembly (18): - a step of acquiring the maximum active power that the power supply assembly (18) can provide and the energy remaining in the battery(ies) (24) of the power supply assembly (18), - a step of calculating the contribution that the power supply assembly (18) can make to the supply of active power to the storage system (12) as a function of the energy remaining in the battery(ies) (24), - a step of determining the power to be supplied by the power supply assembly (18), the power to be supplied being the minimum in absolute value between the determined contribution and the maximum active power, to obtain a determined power, the method further comprising a step of constituting a control law for each power supply assembly (18) as a function of the power determined for each power supply assembly (18).

2. Method according to claim 1, wherein, during the calculation step, the contribution also depends on the power requirement and the remaining energy of the storage system (12), the remaining energy of the storage system (12) being the sum of the remaining energies of each battery (24).

3. Method according to claim 1 or 2, wherein, during the calculation step, the contribution also depends on the efficiency of the power conversion system (22).

4. Method according to any one of claims 1 to 3, in which, during the constitution step, each control law makes it possible to control each set power supply (18) so that the power supply assembly (18) provides the power determined for said power supply assembly (18).

5. Method according to any one of claims 1 to 3, in which, for each power supply assembly (18), the following steps are implemented: - a step of calculating the sum of the powers determined for each power supply assembly (18), to obtain a calculated sum, and - a step of correction of the powers determined when the calculated sum is strictly less than the power requirement, to obtain corrected powers, the powers determined for which the power to be supplied is in absolute value the maximum active power being unchanged, and for the other powers determined, the calculation and determination steps being implemented again by increasing the power requirement by the difference between the calculated sum and the power requirement, the corrected powers being the powers thus determined.

6. Method according to claim 5, in which the step of calculating the sum is again implemented with the corrected powers instead of the determined powers, a new correction step being implemented if the new calculated sum is still strictly less than the power requirement.

7. The method of claim 6, wherein the steps of calculating the sum and correcting are implemented iteratively until either the calculated sum becomes equal to the power requirement or each power supply assembly (18) provides the maximum active power of the battery(ies) (24) of the power supply assembly (18).

8. Method according to any one of claims 1 to 7, in which the method further comprises a step of applying the constituted control law to each power supply assembly.

9. Controller (30) capable of controlling a battery energy storage system (12), the storage system (12) being capable of supplying active power to an external system (14), the storage system (12) comprising at least one power supply assembly (18), each power supply assembly (18) comprising a power conversion system (22) and one or more batteries (24), the controller being capable of receiving the power requirement to be delivered by the storage system (12) to the external system (14), and, for each power supply assembly (18), of: - acquiring the maximum active power that the power supply assembly (18) can provide and the remaining energy in the battery(ies) (24) of the power supply assembly (18), - calculate the contribution that the power supply assembly (18) can make to the active power supply of the storage system (12) as a function of the energy remaining in the battery(ies) (24), and - determining the power to be supplied by the power supply assembly (18), the power to be supplied being the minimum in absolute value between the determined contribution and the maximum active power, to obtain a determined power, the controller (30) being, in addition, capable of constituting a control law for each power supply assembly (18) as a function of the power determined for each power supply assembly (18).

10. Power control device (20) comprising a controller (30) according to claim 9 and an application module (32) capable of applying the control law constituted by the controller (30), the controller (30) and the application module (32) preferably being merged.

11. Battery energy storage system (12) comprising a controller (30) according to claim 9 or a control device (20) according to claim 10.

12. Installation (10) comprising a battery energy storage system (12) according to claim 11.

Images