Method for managing the maximum power of an electric battery
The method addresses the challenge of accurately determining electric battery power in aircraft by considering state, temperature, and duration, enabling efficient and timely power management for critical phases, thus enhancing operational reliability and reducing environmental footprint.
Patent Information
- Application Number
- FR2023013900
- Authority / Receiving Office
- FR · FR
- Patent Type
- Patents
- Current Assignee / Owner
- Filing Date
- 2023-12-11
- Publication Date
- 2025-10-31
- Estimated Expiration
- 2043-12-11
AI Technical Summary
Existing methods fail to accurately and instantaneously determine the maximum power of electric batteries in aircraft, which is crucial for efficient battery management during critical phases like takeoff and landing, considering variables such as state of charge, temperature, and condition, and varying application durations.
A method and system for determining the maximum power of electric batteries by accounting for state of charge, temperature, and condition, using equations that incorporate battery voltage and current, with optional adjustments to operating conditions based on determined power, including display, alerts, and system changes.
Enables precise and timely management of battery power to ensure reliable operation during transient phases, optimizing energy efficiency and reducing environmental impact.
Smart Images
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Abstract
Description
Title of the invention: Method for managing the maximum power of an electric battery. TECHNICAL FIELD OF THE INVENTION
[0001] The technical field is that of the management of electric batteries, in particular electric batteries on board a vehicle, especially in an aircraft.
[0002] The present invention relates to a method for managing the maximum power of an electric battery and an associated system. TECHNOLOGICAL BACKGROUND OF THE INVENTION
[0003] Climate change is a major concern for many legislative and regulatory bodies worldwide. Indeed, various restrictions on carbon emissions have been, are being, or will be adopted by various states. In particular, an ambitious standard applies to both new types of aircraft and those currently in operation, requiring the implementation of technological solutions to bring them into compliance with current regulations. Civil aviation has been actively working for several years now to contribute to the fight against climate change.
[0004] Technological research efforts have already led to very significant improvements in the environmental performance of aircraft. The Applicant takes into account the factors impacting all phases of design and development in order to obtain aeronautical components and products that are less energy-intensive, more environmentally friendly, and whose integration and use in civil aviation have moderate environmental impacts, with the aim of improving the energy efficiency of aircraft. The Applicant is constantly working to reduce its climate impact by employing methods and operating virtuous development and manufacturing processes that minimize greenhouse gas emissions to the minimum possible in order to reduce the environmental footprint of its activity.
[0005] This sustained research and development work focuses on new generations of aircraft engines, the weight reduction of aircraft, particularly through the materials used and lighter on-board equipment, the development of the use of electrical technologies to provide propulsion, and finally aviation biofuels.
[0006] In this context, the use and management of electric batteries in aircraft must be optimized. In particular, it is essential to be able to manage the maximum power of an electric battery. The maximum power, also called peak power, Maximum power, and noted here as Pmax, is the maximum power that the battery can provide continuously for a given period.
[0007] It is known that the maximum power Pmax varies according to different battery parameters. In particular, the maximum power Pmax varies according to the battery's state of charge, battery temperature, the current applied to the battery during charging or discharging, and the battery's condition. For example, a battery at "equilibrium," that is, with zero current and stable voltage, has a higher maximum power Pmax than when a non-zero current is applied to the battery during a charging or discharging period. Furthermore, the higher the battery's state of charge, the higher the maximum power Pmax during charging, but the lower it is during discharging. Additionally, a battery at a low temperature has a lower maximum power Pmax. Finally, the more a battery's condition deteriorates, the lower its maximum power Pmax becomes.
[0008] Thus, it is necessary to take into account at least some of these different battery parameters in order to reliably and accurately determine the maximum power Pmax of a battery. The determination of the maximum power Pmax of the battery can be carried out at a present time t, for a future time t+At, with a variable application duration At, for example, between 1 and 60 seconds. Furthermore, this determination must be performed instantaneously, depending on the dynamic state of the battery, particularly to allow for sufficient accuracy in battery management during critical transient phases such as aircraft takeoff or landing. It should be noted that the application duration At, for which the maximum power Pmax of a battery is determined, also influences the determination of the maximum power Pmax.Indeed, as the application duration At increases, the maximum power Pmax of a battery decreases during a discharge period and during a charge period. The application duration At is defined according to the needs of each application. For the same application, it is possible to determine the maximum power Pmax for several application durations At, and therefore, for example, to determine the maximum power PmaxiOs for an application duration At = 10 seconds, the maximum power Pmax30s for an application duration At = 30 seconds, etc. It is therefore possible to determine, at a present time t, the maximum power at the future time t+At with the following equation: [°009] ftWW PTnax(ti + M)=~-------= U(ti + At) xI(ti + M)
[0010] With: • U, the battery voltage, and • I, the current applied to the battery.
[0011] The maximum power Pmax can be defined by reaching predefined limit voltages and predefined limit currents. These predefined limit voltages and predefined limit currents are the maximum limit current Imax for battery charging during the charging phase, the maximum limit current Imax for battery discharging during the discharging phase, the maximum limit voltage Umax during the charging phase, and the minimum limit voltage during the discharging phase. These limit voltages and limit currents can, for example, be defined by the battery supplier or by the constraints of the application in which the battery is used. Thus, four cases can be identified: • During a battery charging phase, the maximum power Pmax corresponds to: • Pmax — IX Umax with I < Imax, load, * Pmax— Jmax X with U Umax • During a battery discharge phase, the maximum power Pmax corresponds to • Pmax = I x < Imax^discharge, or * Pmax — ^max XU with UU min
[0012] Several methods therefore allow us to determine, for a future instant t+At distant from the present instant t by the duration of application At, the maximum power Pmax of a battery.
[0013] A first group of methods uses machine learning to determine the maximum power Pmax of a battery. However, these methods require a large amount of data for training the neural network. This training data is, however, difficult or even sometimes impossible to obtain.
[0014] A second group of methods uses an electrical representation, such as the equivalent electrical circuit illustrated in [Fig. 1], to model the behavior of a battery. These methods determine the maximum power Pmax of a battery as a function of a previously determined internal battery resistance. [Fig. 1] illustrates an example of an equivalent model 1 of an electric battery that can be used by a method from this second group. Model 1 of [Fig. 1] provides a good compromise between simplicity and accuracy in determining the maximum power Pmax of a battery. A current, denoted Iceu, is applied to model 1, and model 1 comprises: • an instantaneous open-circuit voltage (OCV) source, representing the battery voltage when at rest, • a resistance Ro, representing the resistances of connections and those of fast transient phenomena, • preferably, a parallel RC circuit, representing the diffusion phenomenon and comprising a resistance Rdiff and a capacitor Cdiff.
[0015] Some of the methods in this second group are based on Kalman filters and least-squares optimization. The equations of the electrical model are then used iteratively to converge over time towards the maximum battery power Pmax. These methods therefore involve a very significant computational load to determine the maximum battery power Pmax. Consequently, these methods are more difficult to use for embedded applications, for example, in an aircraft.
[0016] Other methods in this second group of methods, based on an electrical representation, perform a direct calculation of the maximum power Pmax of the battery in a manner similar to a simulation of an online electrical model. However, this calculation is simplified to be suitable for an embedded application. To simplify the calculation, it is possible, for example, to not appropriately take into account the state of the battery at the time of the estimation, or to ignore the voltage drop caused by the application of the maximum permissible current, or to ignore the variation of the battery characteristics, such as the parameters of the internal resistance of the equivalent electrical model of the battery during a current pulse, particularly as a function of the battery's state of charge.These methods are therefore imprecise, particularly because they do not adequately consider the battery's state when determining the maximum power (Pmax) of an electric battery. A battery's state at any given moment can be assessed using various parameters such as battery voltage, the current applied to the battery during charging or discharging, the battery's state of charge, the battery temperature, and the battery's overall health.
[0017] There is therefore a need for a method of managing the maximum power of an electric battery which limits, at least in part, the problems associated with the use of the aforementioned prior art methods. Summary of the invention
[0018] The invention provides a solution to the problems mentioned above by enabling the management of a maximum power Pmax of an electric battery in a reliable, precise, and computationally efficient manner. Indeed, the maximum power Pmax of the battery is determined by performing a simplified simulation of an equivalent battery model. The invention preferably comprises updating the parameters of the equivalent battery model as illustrated in [Fig. 1]. The update Updating the parameters can, for example, be done using previously implemented battery tests and characterization studies. These tests and studies allow for the creation of maps, or equations, of these parameters at different battery health states. Finally, determining the battery health state makes it possible to identify the value to use for at least some of the parameters of the equivalent battery model.
[0019] The simulation of the equivalent model makes it possible to project the maximum power Pmax of the battery over time, for a future instant t+At separated from the present instant t by a time interval At, avoiding iterations requiring significant computing resources. The present instant t is the instant at which the method according to the invention is implemented. The method according to the invention thus defines the characteristics of an overvoltage present A Ut at the present instant t in order to perform said projection. The method according to the invention makes it possible to disregard the battery's usage history, i.e., the current profile that has been applied to the battery and / or is being applied at the present instant t. Indeed, in the method according to the invention, a correspondence is found between the usage history and an equivalent DC resistance DCReq generated under a fixed current Io.The equivalent DC resistance DCReq preferably corresponds to the real part of the impedance of an equivalent model as illustrated in Figure 1. Thus, at the present time t, the cell voltage Vt can be obtained by the following equation: .
[0020] Ut = OCVt+atUt
[0021] With A Ub the overvoltage at the present time t can be obtained by the following equation: A Ut — l*DCRCqt
[0022] With DCReqt, the equivalent DC resistance DCReq at the present instant is generated by a fixed current It during an equivalent current application time, also called equivalent time in this application and denoted teq. The equivalent time corresponds to the time required to reach the voltage Ut of the electric battery by applying the current It constantly to the electric battery. In other words, the equivalent time is the time required to apply the current It to obtain the current voltage Ut of the battery; the current being applied with a constant value and the battery being initially new.
[0023] The method according to the invention therefore comprises determining the equivalent DC resistance DCReq t for the present time t and the equivalent time teq in order to project the battery voltage over time until the future equivalent time teq+At, and to obtain the battery voltage Ut+^ for this future time t+At. Figure 2 shows a diagram illustrating the principle of the equivalent DC resistance DCReq t for the time t and the equivalent time teq. The axis Vertical axis 11 represents the battery voltage, expressed in volts, and horizontal axis 12 represents time, expressed in seconds. The double arrow 13 represents the equivalent time teq for the present instant t, and the double arrow 14 represents the product of the current It applied to the battery at the present instant t and the equivalent DC resistance DCReq t. Curve 15 represents the battery voltage and curve 16 the open-circuit voltage OCV of the battery, both expressed in volts. Rectangle 17 represents the estimated maximum power Pmax of the battery for a future time interval At.
[0024] One aspect of the invention thus relates to a method for managing the maximum power Pmax of an electric battery, comprising computer-implemented steps of: • obtaining, for a given instant t, an open-circuit voltage OCVt of the battery, a battery voltage Utet and a current It applied to the battery, • determination, for the present time t, of an equivalent DC resistance DCReqt as a function of the open-circuit voltage OCVt, the battery voltage Ut, and the current It applied to the battery obtained, • determination of an equivalent time teq as a function of the equivalent DC resistance DCReqt determined, of a simple resistance R^ of the battery for the present moment t, the equivalent time corresponding to the time required to reach the voltage Ut of the electric battery by applying the current It constantly to the electric battery, • determination of a DC resistance DCR teq+At for a future equivalent instant teq+At, separated by an equivalent time teq of a duration of time At, the determination of the DC resistance DCRteq+At being carried out as a function of the simple resistance value ROt+At of the battery for the future instant t+At, • estimation of a battery voltage Ut+At, for a future time t+At distant from the present time t by the same duration of time At, as a function of a future open-circuit voltage OCVt+At for the future time t+At, the DC resistance DCR teq+At for the future time t+At and a predetermined maximum current Imax of the battery, • determination of the maximum power Pmax as a function of . • of the estimated voltage Ut+At of the battery for the future time t+At and of the predetermined maximum current Imax of the battery, when the voltage Ut+At for the future time t+At is within a predetermined range of battery voltage limits, • or the estimated voltage Ut+At of the battery for the future time t +At and an estimated maximum current Imaxestimated of the battery, when the voltage Ut+At of the battery for the future time t+At is not within the predetermined range of battery voltage limits, the estimated maximum current Imaxestimated of the battery being determined from a terminal within the predetermined range of battery voltage limits, the future open-circuit voltage OCVt+At of the battery for the future time t+At and the DC resistance DCRteq +At for the equivalent future time teq+At.
[0025] Thanks to the invention, it is possible to reliably and precisely manage the maximum power Pmax of an electric battery, since the method according to the invention takes into account the battery's state at any given time. Furthermore, the method can be used in an embedded system with limited space and computing resources, since the computing power required to implement the method is limited. Applications of the method according to the invention are therefore possible, particularly in the aeronautical, maritime, and automotive sectors. Finally, the invention eliminates the need for a large amount of training data for a machine learning algorithm, data which can be difficult to obtain.
[0026] In addition to the characteristics mentioned in the preceding paragraph, the method according to one aspect of the invention may have one or more additional characteristics from among the following, considered individually or in all technically possible combinations: • the step of determining an equivalent time teq further includes the determination of a diffusion resistance Rdifft of the battery for the present time t and a diffusion time constant Tdifff for the present time t, and in which the determination of the DC resistance DCR teq +At for the future equivalent time teq+At is further carried out as a function of the value of diffusion resistance Rdifft+At of the battery for the future time t+At and the diffusion time constant of the battery for the future time t+At. • The future open-circuit voltage OCV t+At for the future time t+At is determined using preliminary steps including: • Determination, for the future time t+At, of a future state of charge SOCt+At of the battery as a function of a state of charge SOCt for the present time t, the future state of charge SOCt+At for the future time t+At being determined for the maximum predetermined current Imax applied to the battery during the time duration At, and • Determination, for the moment futurt+At, of the future open circuit voltage OCVt+At of the battery as a function of the future state of charge SOCt+At of the battery. • the method further comprises an initial step of obtaining a battery temperature Tt and a first map of an open-circuit voltage OCV as a function of a battery state of charge SOC and the battery temperature Tt, and wherein the determination of the equivalent DC resistance DCReqt at the present time t is carried out using the first map obtained, • The initial step of obtaining the first map also includes: • Obtaining a second map of the simple resistance Ro of the battery as a function of the state of charge SOC of the battery, the current I applied to the battery, and the temperature Tt of the battery, and in which: • The simple resistance R^ of the battery at the present time t is determined from the second mapping with the current state of charge SOCt at the present time t, the current It applied to the battery at the present time t and the temperature Tt of the battery at the present time t, • The initial step of obtaining the first map also includes: • Obtaining a third map of the diffusion resistance Rdiffen as a function of the battery's state of charge SOC, the current I applied to the battery, and the battery temperature Tt, and in which: • The diffusion resistance Rdifft of the battery at the present time t is determined from the third mapping with the current state of charge SOCt at the present time t, the current It applied to the battery at the present time t and the temperature Tt of the battery Tt at the present time t, • The initial step of obtaining the first map also includes: • Obtaining a fourth map of the diffusion time constant as a function of the battery's state of charge (SOC), the current (I) applied to the battery, and the battery temperature (Tt) and in which: • The diffusion time constant at the present time t is determined from the fourth mapping with the current state of charge SOCt at the present time t, the current It applied to the battery at the present time t and the temperature Tt of the battery at the present time t, • The initial open-circuit voltage (OCV) mapping is further dependent on the battery's state of health (SOH), and / or • the second simple resistance (Ro) mapping is further dependent on the battery's SOH health status, and / or • the third diffusion resistance mapping Rdiffest further depending on the battery's SOH health status, and / or • The fourth mapping, the diffusion time constant, is further dependent on the battery's SOH health status. and in which the battery's state of health (SOH) is taken into account to determine the maximum power (Pmax) of the battery, • the process further includes a final step of modifying the battery's operating conditions according to the determined maximum power Pmax.
[0027] A second aspect of the invention relates to an electric battery management system comprising an electronic processing and control system configured to execute the steps of the process according to the invention.
[0028] A third aspect of the invention relates to an aircraft comprising an electric battery and a battery management system according to the invention.
[0029] A fourth aspect of the invention relates to a computer program comprising instructions which, when the program is executed by a computer, lead the computer to implement a process according to the invention.
[0030] A fifth aspect of the invention relates to a non-transient, computer-readable data carrier on which the computer program according to the invention is recorded.
[0031] The invention and its various applications will be better understood by reading the following description and examining the accompanying figures. BRIEF DESCRIPTION OF THE FIGURES
[0032] The figures are presented for illustrative purposes only and are in no way limiting of the invention. • Figure 1 shows an example of an equivalent model of an electric battery, • Figure 2 shows a diagram illustrating the principle of modeling the equivalent DC resistance DCReq and the equivalent time teq. • Fig. 3 shows a synoptic diagram illustrating the steps of process 100 according to an example of an embodiment of the invention. DETAILED DESCRIPTION
[0033] Unless otherwise specified, the same element appearing on different figures has a unique reference.
[0034] Figure 3 is a block diagram illustrating the steps of an example of the process according to the invention. The mandatory steps of the example process 100 are indicated by a solid rectangle and the optional steps are indicated by a dashed rectangle.
[0035] Method 100 is a method for managing the maximum power Pmax of one or more electric batteries. It allows for more reliable management of the maximum power Pmax of one or more electric batteries by reliably and precisely determining this maximum power Pmax. Method 100 can be applied during a battery charging or discharging period. For simplicity, the examples below are provided for a battery discharging period, but the method is applied similarly for a battery charging period.
[0036] The electric battery to which the method 100 is applied is, for example, a battery installed in an aircraft. The battery is used, for instance, to store and / or deliver electrical energy to equipment in an aircraft turbomachine. The battery is used, for instance, for electric propulsion functions within the turbomachine. Alternatively, the electric battery is a battery for an automotive, railway, marine, etc., embedded system.
[0037] An optional first step 110 of the method 100 includes obtaining a first map of an open-circuit voltage (OCV) as a function of the battery's state of charge (SOC) and battery temperature. The term "obtain" in this application may mean "measure" and / or "receive" and / or "calculate." A map determines the evolution of a first variable, an open-circuit voltage (OCV) for the first map, as a function of one or more other variables, namely the battery's state of charge (SOC) and battery temperature for the first map. In one example, the optional first step 110 of the method 100 also includes obtaining three other maps. The second map is a map of the simple resistance R0 as a function of the battery's state of charge (SOC), the current I applied to the battery, and the battery temperature.The third map is a map of the diffusion resistance Rdiff as a function of the battery's state of charge (SOC), the current I applied to the battery, and the battery temperature. The fourth map is a map of the diffusion time constant as a function of the battery's state of charge (SOC), the current I applied to the battery, and the battery temperature.
[0038] In an example, consistent with the preceding example, the first optional step 110 of the process 100 also includes obtaining a temperature Tt of the Battery. The temperature Ttest is expressed in degrees Celsius. Alternatively, the battery temperature Tt can also be obtained in step 120.
[0039] In an example consistent with the preceding example, one or some maps, or each of the four maps obtained in step 110, is further dependent on the battery's state of health (SOH). Thus, for these maps, the influence of the battery's SOH is taken into account. The first map is therefore an open-circuit voltage (OCV) map as a function of the battery's state of charge (SOC), the battery temperature (Tt), and the battery's SOH. The second map is a simple resistance (Ro) map as a function of the battery's state of charge (SOC), the current (I) applied to the battery, the battery temperature (Tt), and the battery's SOH.The third map is a map of the diffusion resistance Rdiff as a function of the battery's state of charge (SOC), the current I applied to the battery, the battery temperature Tt, and the battery's state of health (SOH). The fourth map is a map of the diffusion time constant Tdiff as a function of the battery's state of charge (SOC), the current I applied to the battery, the battery temperature Tt, and the battery's state of health (SOH). When the four maps obtained in step 110 include the battery's state of health (SOH), process 100 can determine the maximum power Pmax of the battery, taking the battery's SOH into account. In this example, process 100 is therefore even more reliable and accurate in managing the battery's maximum power Pmax.
[0040] A second step 120 of the process 100 comprises obtaining, at the present time t, an open-circuit voltage OCVt of the battery, a battery voltage Ut, a current It applied to the battery, and a battery temperature Tt. The voltages OCVt and Ut are expressed in volts. The current It is expressed in amperes. In an example consistent with the preceding examples, these data can be measured.
[0041] An optional third step 130 of the process 100 comprises determining, for the future time t+At, a future state of charge SOCt+At of the battery as a function of a state of charge SOCt of the battery at the present time t. A state of charge is often expressed as a percentage of the total battery capacity. The future state of charge SOCt+At is determined for a maximum current Imax applied to the battery during the time duration At. In an example, consistent with the preceding examples, the future state of charge SOCt+At of the battery can be obtained for a discharge phase at maximum current Imax with the following equation:
[0042] SOCM,= SOC,+ 100x / ,„„ x;^
[0043] With: • Capacity, the battery capacity expressed in amp-seconds, and • imax, the maximum current applied to the battery.
[0044] The maximum current Imax, also called the limiting current, can be a value predetermined. This maximum current Imax can, for example, be provided by the battery manufacturer and obtained during step 110. The maximum current Imax may differ depending on whether the battery is being charged or discharged.
[0045] An optional fourth step 140 of the process 100 comprises determining, for the future time futuret+At, the future open-circuit voltage OCVt+At of the battery as a function of the future state of charge SOCt+At of the battery. The determination of the future open-circuit voltage OCVt+At can be carried out using the following equation: [00461 ocv,+i, = ocv( soc,J
[0047] In an example, consistent with the preceding examples, the determination of the future open-circuit voltage OCVt+At can be carried out taking into account the temperature Tt at the present time t using the following equation:
[0048] OCVt Af = OCV( SOC, T^ans 'c last example, it is also possible to use the future temperature Tz+A / , instead of the temperature Tt at the present time t, to determine the future open circuit voltage OCVt+At The future temperature Tz+Az can for example be estimated using a thermal model of the electric battery.
[0049] A fifth step 150 of the process 100 comprises determining an equivalent DC resistance DCReq t at the present time t. The equivalent DC resistance DCReq t is determined as a function of the open-circuit voltage OCVt, the battery voltage Ut at the present time t, and the current It applied to the battery at the present time t, obtained in step 120. For example, the equivalent DC resistance DCReq t at the present time t can be obtained with the following equation:
[0051] In an example, consistent with the previous examples, the determination 150 of the equivalent DC resistance DCReqt at the present time t is carried out using the first mapping obtained in step 110.
[0052] A sixth step 160 of the process 100 comprises determining an equivalent time teq at the present instant t as a function of the equivalent DC resistance DCReq t determined in step 150, a simple resistance R^ of the battery at the present instant t, and optionally as a function of a diffusion resistance Rdifft of the battery at the present instant t and a time constant The diffusion resistance TWft for the present time t. The equivalent time teq corresponds to the time it takes to apply the fixed current It at the present time to obtain the equivalent DC resistance DCReq t for the present time t. The equivalent DC resistance DCReq t for the present time t is considered equivalent to the battery's usage history. Thus, regardless of the battery's usage history, the equivalent time teq corresponds to the time it would take to apply the fixed current It that would result in the same voltage as that measured at the present time t if the battery's internal resistance were the equivalent DC resistance DCReqt for the present time. The equivalent time teq can, for example, be determined using the following equation:
[0053] . teq= - ----J
[0054] With the battery diffusion time constant at the present time t being obtained by:
[0055] Tdifft~ Rdifft ^-^difft
[0056] With: • Cdifft, the diffusion capacity of the battery at the present moment t, expressed in Farads.
[0057] In an example, compatible with the previous examples, the simple resistance ROt of the battery at the present time t is determined from the second mapping obtained in step 110 using the state of charge SOCt at the present time t, the current It applied to the battery at the present time t and the temperature of the battery at the present time t,
[0058] In an example, consistent with the preceding examples, the diffusion resistance Rdifft of the battery at the present time t is determined from the third mapping using the current state of charge SOCt at the present time t, the current It applied to the battery at the present time t and the temperature of the battery at the present time t, and
[0059] In an example, compatible with the previous examples, the diffusion time constant at the present time t is determined from the fourth mapping with the current state of charge SOCt at the present time t, the current It applied to the battery at the present time t and the temperature of the battery at the present time t. Alternatively, it is also possible to use a mapping of the diffusion capacity of the battery C^-y ft.
[0060] A seventh step 170 of the process 100 comprises determining a DC resistance DCRteq+At for a future equivalent time teq+At, separated from the present equivalent time teq by the duration of time At. The determination of the resistance in The DC resistance DCRteq+At is calculated based on the simple resistance value ROt+At of the battery at the future time t+At, the diffusion resistance value Rdifft+At of the battery at the future time t+At, and the diffusion time constant Tdifft+At of the battery at the future time t+At. The DC resistance DCRteq+At for the equivalent future time teq+At can, for example, be determined using the following equation:
[0061] TW"'» _ » । ny [ 1 teq+At \ 1 ^teq+At - ^0 t+At+ ^dif f t+At
[0062] The calculations of the simple resistance value Rot+At of the battery for the future time t+At, the diffusion resistance value Rdifft+At of the battery for the future time t+At, and the diffusion time constant of the battery for the future time t+At can be performed as a function of the predetermined maximum current Imax of the battery. Furthermore, these calculations can be performed as a function of the temperature Tt at the present time or as a function of the future temperature T1+A / at the future time T1+A / . The calculation of the simple resistance value ROt+At of the battery for the future time t+At can, for example, be performed using the following equation: 100631 koi+a,= «(1(socw4z, T,)
[0064] An eighth step 180 of the process 100 comprises determining a voltage Ut+At of the battery for the future time t+At. The determination of the battery voltage Ut+At is performed as a function of the open-circuit voltage OCVt+At for the future time t+At, the DC resistance DCR teq+At for the equivalent future time teq+At, and the predetermined maximum current Imax of the battery. In one example, consistent with the preceding examples, this predetermined maximum current Imax was obtained in step 110.
[0065] A ninth step 190 of the process 100 includes determining the maximum power Pmax of the battery. When the battery voltage Ut+At for the future equivalent time t+At is within a predetermined range of battery voltage limits during battery discharge, the determination is performed based on the battery voltage Ut+At for the future time t+At and the predetermined maximum battery current Imax. When the battery voltage Ut+At for the future time t+At is not within the predetermined range of battery voltage limits, the determination is performed based on the battery voltage Ut+At for the future time t+At and an estimated maximum battery current Imax.The estimated maximum current Imax of the battery is determined from a terminal within the predetermined range of battery limit voltages, the future open-circuit voltage OCVt+At for the future time t+At of the battery, and the DC resistance DCRteq+At for the equivalent future time teq+At. The predetermined range of battery voltage limits can be provided by the battery manufacturer. This range can be obtained during step 110 of process 100. The predetermined range includes a minimum voltage Umin and a maximum voltage Umax. When the battery voltage Ut+At for the future time t+At is within the predetermined range of battery voltage limits, the maximum power Pmax l+Aldc of the battery for the future time t+At can be determined using the following equation:
[0066] P max t + At ~ Ut+ â / ^max
[0067] When the battery voltage Ut+At for the future time t+At is not within the predetermined range of battery voltage limits, the maximum power Pmax t+At of the battery for the future time t+At can be determined with the following equation:
[0068] p A / ]— TT *T 1 max\l~ min imax estimated
[0069] With the estimated value that can be obtained from the following equation:
[0070] j _UmùrOCVr.A, Estimated DCR multiplexer^^
[0071] During a battery discharge phase, the battery voltage Ut+At for the future time t+At is not within the predetermined range of battery voltage limits when the battery voltage Ut+At for the future time t+At is less than the minimum voltage Umin. During a battery charging phase, the battery voltage Ut+At for the future time t+At is not within the predetermined range of battery voltage limits when the battery voltage Ut+At for the future time t+At is greater than the maximum voltage Umax. Thus, in this case, the following equation is used to determine the estimated I>nax:
[0072] T & A / +az *estimated max ~ DCRteq^t
[0073] An optional tenth step 200 of the process 100 includes modifying the battery operating conditions based on the maximum power Pmax determined in step 190. This modification of the battery operating conditions may be automatic, semi-automatic, or manual, i.e., requiring human intervention. In examples, this modification of the battery operating conditions may include at least one of the following actions:
[0074] display of maximum power Pmax,
[0075] generation of an alert message when the maximum power Pmax of the battery is less than a predetermined threshold power,
[0076] decision-making by a user regarding an aircraft maneuver, such as a landing, and implementation of the action resulting from the decision-making,
[0077] charging of a battery whose power setpoint is determined as a function of the maximum power Pmax determined by method 100,
[0078] prediction of a minimum remaining battery charge time as a function of the maximum power Pmax determined by method 100,
[0079] changing a first battery powering a system, such as a system contained in or of an aircraft, and whose maximum power Pmax has been determined by method 100, by a battery whose maximum power Pmax is greater than the maximum power Pmax, and
[0080] implementation of a maintenance operation of a system, such as a system contained in an aircraft or of an aircraft, powered by the battery whose maximum power Pmax is determined.
[0081] The present invention also relates to an electric battery management system comprising means for implementing process 100. For example, the management system according to the invention may include an electronic processing and control system, otherwise called a "computer", comprising at least one processor and one memory, the electronic processing and control system being configured to execute the steps of process 100. In addition, optionally, the electric battery management system may include a means for displaying the maximum power Pmax determined by process 100, at least one means for measuring the temperature of the battery, at least one means for measuring the voltage across the battery terminals, and at least one means for measuring the current flowing between the terminals of said battery.
Claims
1. Demands Method (100) for managing the maximum power Pmax of an electric battery, the method comprising computer-implemented steps of: - obtaining (120), for a present instant t, an open-circuit voltage OCVt of the battery, a battery voltage Ut and a current It applied to the battery, - determination (150), for the present time t, of an equivalent DC resistance DCReq t as a function of the open circuit voltage OCVt, the battery voltage Ut and the current It applied to the battery obtained (120), - determination (160) of an equivalent time teq as a function of the equivalent direct current resistance DCReq t determined (150), of a simple resistance R^ of the battery for the present moment t, the equivalent time corresponding to the time required to reach the voltage Ut of the battery by applying the current It constantly to the battery, - determination (170) of a DC resistance DCR teq+At for a future equivalent instant teq+At, distant by the equivalent time teq of a duration of time At, the determination of the DC resistance DCRteq+At being carried out as a function of the simple resistance value Ro t+At of the battery for the future instant t+At, - estimation (180) of a voltage Ut+At of the battery, for a future instant t+At distant from the present instant t by the same duration of time At, as a function of a future open circuit voltage OCVt+At for the future instant t+At, of the DC resistance DCR teq+At for the future instant t+At and of a predetermined maximum current Imax of the battery, - determination (190) of the maximum power Pmax as a function of: • the estimated battery voltage Ut+At for the future time t+At and the predetermined current maximum Imax of the battery, when the voltage Ut + At for the future time t + At is within a predetermined range of battery voltage limits, or the estimated voltage Ut + At of the battery for the future time t + At and an estimated maximum current Imax of the battery, when the voltage Ut + At of the battery for the future time t + At is not within the predetermined range of battery voltage limits, the estimated maximum current Imax of the battery being determined from a terminal within the predetermined range of battery voltage limits, the future open-circuit voltage OCVt + At of the battery for the future time t + At, and the DC resistance DCRteq + At for the equivalent future time teq
2. +At* Method (100) according to claim 1 wherein the determination step (160) of an equivalent time t^ further comprises the determination of a diffusion resistance Rdifft of the battery for the present time t and a diffusion time constant for the present time t, and wherein the determination (170) of the DC resistance DCR teq+At for the future equivalent time teq+At is further carried out as a function of the value of diffusion resistance Rdifft+At of the battery for the future time t+At and the diffusion time constant of the battery for the future time t+At.
3. A method (100) according to claim 2 wherein the future open-circuit voltage OCV t+At for the future time t+At is determined using preliminary steps comprising: - Determination (130), for the future time t+At, of a future state of charge SOCt+At of the battery as a function of a state of charge SOCt for the present time t, the future state of charge SOCt+At for the future time t+At being determined for the maximum predetermined current Imax applied to the battery during the time duration At, and - Determination (140), for the moment futurt+At, of the future open circuit voltage OCVt+At of the battery as a function of the future state of charge SOCt+At of the battery.
4. A method (100) according to claim 2 or 3 further comprising an initial step (110) of obtaining a temperature Tt of the battery and a first map of an open circuit voltage OCV of the battery as a function of a state of charge SOC of the battery and the temperature Tt of the battery, and wherein the determination (150) of the equivalent DC resistance DCReq t at the present time t is carried out using the first map obtained.
5. A method according to claim 4, wherein the initial step (110) of obtaining the first map further comprises: - Obtaining a second map of the simple resistance Ro of the battery as a function of the state of charge SOC of the battery, the current I applied to the battery and the temperature Tt of the battery, and wherein: - the simple resistance R^ of the battery at the present time t is determined from the second map with the state of charge current SOCt at the present time t, the current It applied to the battery at the present time t and the temperature Tt of the battery at the present time t.
6. A method according to claim 4 or 5, wherein the initial step (110) of obtaining the first map further comprises: - Obtaining a third map of the diffusion resistance Rdiffen as a function of the state of charge SOC of the battery, the current I applied to the battery and the temperature Tt of the battery, and wherein: - the diffusion resistance Rdifft of the battery at the present time t is determined from the third map with the state of charge current SOCt at the present time t, the current It applied to the battery at the present time t and the temperature Tt of the battery at the present time t.
7. A method according to claim 4, 5 or 6, wherein the initial step (110) of obtaining the first map further comprises: - Obtaining a fourth map of the diffusion time constant Tdiff as a function of the state of charge SOC of the battery, the current I applied to the battery and the temperature Tt of the battery and wherein: - the diffusion time constant 'at the present time t is determined from the fourth map with the state of charge current SOCt at the present time t, the current It applied to the battery at the present time t and the temperature of the battery Tt at the present time t.
8. A method (100) according to any one of claims 4 to 7, wherein: - the first mapping of the open circuit voltage OCV is further dependent on a state of health SOH of the battery, and / or - the second mapping of the simple resistance Ro is further dependent on the state of health SOH of the battery, and / or - the third mapping of the diffusion resistance Rdiffest is further dependent on the state of health SOH of the battery, and / or - the fourth mapping of the diffusion time constant Td'ff is further dependent on the state of health SOH of the battery, and wherein the state of health SOH of the battery is taken into account to determine (190) the maximum power Pmax of the battery.
9. Aircraft comprising an electric battery and an electric battery management system comprising an electronic processing and control system configured to perform the steps of the process (100) according to any one of the preceding claims.
10. A computer program comprising instructions which, when the program is executed by a computer, cause the computer to carry out a method according to any one of claims 1 to 8.