METHOD OF PREVENTIVE ELECTRICAL PROTECTION IN AN ELECTRIFIED MOTOR VEHICLE

Abstract

The method is implemented in an electrified motor vehicle (EV), the vehicle comprising an electrical traction network equipped with an electrical storage unit (BAT_HV), a control unit (C_VCU), and at least one circuit breaker (PE). According to the invention, the method comprises the steps of: a) defining a digital model of a virtual fuse carrying an electric current (I_B); b) establishing a current limitation (I_LEE) in the electrical network, determined so as to prevent tripping of the circuit breaker (PE), based on an estimated internal temperature of the virtual fuse and on at least one comparison between at least one calculated current energy limitation value of the virtual fuse and at least one energy limitation activation threshold for derating; and c) regulating (REG) by derating a power supply in the electrical network so as to comply with the current limitation. Figure 1

Description

Title of the invention: METHOD FOR PREVENTIVE ELECTRICAL PROTECTION IN AN ELECTRIFIED MOTOR VEHICLE

[0001] The present invention relates generally to electrical protection in an electrified motor vehicle. More particularly, the invention relates to a method of preventive electrical protection in an electrified motor vehicle. The invention finds a preferred application for the preventive electrical protection of the traction electrical network and its associated electrical storage system in a hybrid, all-electric, or fuel cell electrified vehicle.

[0002] An electrified vehicle comprises an on-board electrical network, referred to as a "low-voltage" network, and a traction electrical network, referred to as a "high-voltage" network. The nominal voltage of the on-board electrical network is typically 12 volts. The traction electrical network typically has a nominal voltage between 48 volts and 800 volts, depending on the vehicle type. 48-volt architectures are generally adopted for mild-hybrid vehicles, which are equipped with a belt-driven starter-generator (BSG) or an integrated starter-generator (ISG), providing torque assistance to the internal combustion engine primarily during starting and acceleration. Architectures with the highest electrical voltages are generally found in all-electric vehicles.In the traction electrical network, the electrical storage device, hereafter referred to as the "traction electrical storage device", is usually of the "Lithium-ion" (Li-ion) or "nickel-metal hydride" (NiMH) type.

[0003] The traction electrical network and its associated electrical storage must be protected against overcurrents which may cause interruptions and subsequent unavailability of the electrical network, or even damage and possible immobilization of the vehicle which would lead to after-sales service costs.

[0004] Various means are known for protecting the traction electric storage system in an electrified vehicle and for the safety of human operators and users. Thus, the traction electric storage system is connected to its electrical network via an electrical contactor. This contactor can be activated, in particular, by a battery management system known as a "BMS" (for "Battery Management System") and allows the storage system to be electrically isolated from the rest of the traction electrical network when necessary. In addition to traditional circuit breakers, calibrated for specific currents, and the pyrotechnic fuse activated in case of impact, inserted in the Circuits for protecting the electrical grid, its components, and ensuring user safety, including temperature-calibrated circuit breakers and thermal fuses, can also be integrated into the electrical storage unit for its thermal protection. Furthermore, it is common practice in electrified vehicles to employ electronic devices for regulating and limiting the charging / discharging currents of the storage unit and the current in the grid, as well as power allocation and current limiting strategies to protect both the storage unit and the electrical grid.

[0005] A traditional circuit breaker fuse is characterized by its rated current, its energy limiting I2t expressed in A2.s (the product of the square of the current and the time), its breaking capacity, its maximum breaking voltage, and its ohmic resistance. The energy limiting I2t represents the maximum energy that the fuse can absorb before it melts. The breaking capacity is the maximum current that a fuse can interrupt while preventing the formation of an electric arc that would dangerously delay the interruption.

[0006] Traditional fuses are not without a number of drawbacks. They are designed to melt and interrupt the current quickly when subjected to a significant overload, but may not react as effectively to slight or moderate overloads. Furthermore, they are single-use and must be replaced manually. They are also relatively expensive and bulky when currents are high, as can be the case in electrified vehicles with a 48-volt architecture.

[0007] The blowing of a circuit breaker fuse and / or the opening of the aforementioned electrical contactor of the traction energy storage system are events likely to significantly impact not only the availability of the electrical network, but also that of the vehicle. These events may require the intervention of a human service technician to restore the vehicle to service.

[0008] Preventive electrical protection is a solution that can be deployed to limit the aforementioned events, as well as the number of traditional fuses in the vehicle's electrical traction network.

[0009] From document EP2393102A2, a power supply device comprising a battery and designed to supply power to a load is known. The device includes a current regulation circuit, a fuse in series with the battery, a first calculation circuit determining a first permissible current based on various battery parameters, and a second calculation circuit determining a second permissible current for the fuse from the time integral of the current. The regulation circuit regulates the current in the device so as to keep it below the permissible currents. The permissible values ​​are determined by the two calculation circuits. The device thus implements a power limitation to prevent the fuse from tripping.

[0010] The present invention provides a new method designed for preventive electrical protection in an electrified vehicle, in particular, that of the traction electrical network and the associated electrical storage integrated into this vehicle.

[0011] According to a first aspect, the invention relates to a preventive electrical protection method in an electrified motor vehicle, the vehicle comprising an electrical traction network equipped with an electrical storage unit, a computer and at least one circuit breaker device which is triggered in the event of an overcurrent of an electrical current in the electrical traction network.According to the invention, the method comprises the steps of: a) defining a digital model of a virtual fuse through which the electric current flows; b) establishing a current limitation in the traction electrical network, determined so as to avoid tripping of the circuit breaker device, based on an estimated internal temperature of the virtual fuse and on at least one energy limitation comparison between at least one calculated current energy limitation value of the virtual fuse and at least one derating activation energy limitation threshold; and c) regulating by derating a power supply in the traction electrical network so as to comply with the current limitation.

[0012] According to a particular feature, the virtual fuse is modeled numerically from features comprising at least a pair consisting of a maximum tripping current and a maximum time before tripping, an ohmic resistance, a thermal capacitance and a thermal resistance, and the internal temperature of the virtual fuse is estimated as a function of the electric current, an ambient temperature, the ohmic resistance, the thermal capacitance and the thermal resistance using a so-called “0D” thermal model of the virtual fuse.

[0013] According to another particular feature, an energy limiting threshold for derating activation is determined from a pair consisting of a derating current and a maximum derating time which is deduced from a pair consisting of a maximum tripping current and a maximum time before tripping, these currents and times being adjusted according to the estimated internal temperature of the virtual fuse, and the derating current being less than or equal to the maximum tripping current and the maximum derating time being less than the maximum time before tripping.

[0014] According to yet another particular feature, the current limitation is established by selecting the most restrictive current limitation between a first current limitation determined from the estimated internal temperature of the fuse virtual and a second current limitation determined from an energy limitation comparison.

[0015] According to yet another particular feature, several energy limiting comparisons are made respectively between several calculated current values ​​of virtual fuse energy limiting and several derating activation energy limiting thresholds, several current limiting values ​​being determined from these energy limiting comparisons, and the most restrictive current limiting value being assigned to the second current limiting.

[0016] According to yet another particular feature, the power supply includes several derating levels, a derating level being selected according to the current limitation.

[0017] The invention also relates to a computer comprising a memory storing program instructions for the implementation of the method as briefly described above, when the program instructions are executed by a processor of the computer.

[0018] The invention also relates to an electrified motor vehicle comprising an electrical traction network equipped with an electrical storage unit, a computer and at least one circuit breaker device which is triggered in the event of an overcurrent of an electrical current in the electrical traction network, in which the computer is a computer as indicated above.

[0019] Depending on a particular feature of the vehicle, the control unit is either a control unit responsible for supervising the general operation of the vehicle or a control unit responsible for managing the electrical storage system. Depending on another feature, the circuit breaker device includes a circuit breaker fuse and / or an electrical contactor.

[0020] Other advantages and features of the present invention will become more apparent upon reading the detailed description below of several particular embodiments of the invention, with reference to the accompanying drawings, in which:

[0021] Fig. 1 is a schematic diagram of an example of the architecture of an electrified vehicle of the "light hybrid" type in which a particular embodiment of the process according to the invention is implemented.

[0022] The [Fig.2] is a block diagram of different functions performed by a processing method according to the invention.

[0023] Figure 3 shows a calculation carried out by the processing method of the process according to the invention to estimate the internal temperature of a virtual fuse.

[0024] Fig. 4 shows tables of illustrative values ​​of currents and durations involved in the process according to the invention.

[0025] The [Fig.5] is a logic diagram of an I2T energy limitation calculation function executed by the processing method of the process according to the invention.

[0026] The [Fig.6] is a logic diagram of a function for determining current limitations based on the energy limitation I2T.

[0027] Fig. 7 shows illustrative curves relating to an example of operation of a particular embodiment of the process according to the invention.

[0028] A particular embodiment of the process of the invention is now described below in the context of an implementation thereof in an electrified vehicle having a 48-volt electrical architecture.

[0029] With reference to [Fig. 1], this example of an embodiment is considered to be an electrified EV of the "mild-hybrid" type comprising in particular an electrified powertrain eGMP, a 48-volt traction electric storage unit BAT_HV, CNV1 and CNV2 electric converters, PE electrical protection means, a C_BMS computer and a C_VCU computer.

[0030] The traction electric storage unit B AT_HV is typically a 48-volt lithium-ion type battery.

[0031] The electrified powertrain (eGMP) comprises a rotating electric machine (IMG), for example of the integrated motor-generator type, which is coupled to an internal combustion engine (ICE). In addition to starting the ICE, the rotating electric machine (IMG) also provides current generation, regenerative braking, and torque assistance functions, and may even provide traction for the vehicle at very low speeds.

[0032] The CNV1 reversible electrical converter is of the "DC-AC" type (hereafter referred to as "AC / DC") and is connected, on one side, to the rotating electric machine IMG via alternating current (AC) and, on the other side, to a 48-volt DC bus BDC of the traction electrical network. When the IMG operates as a generator and in regenerative braking mode, the CNV1 converter supplies DC current that powers 48-volt loads CS and charges the BAT_HV energy storage unit. When the IMG operates as an electric motor, electrical energy is supplied by the BAT_HV energy storage unit, and the conversion of DC current to AC current for the IMG is performed by the CNV1 converter.

[0033] The CNV2 power converter is a DC-DC type converter and is connected, on one side, to the 48-volt DC bus (BDC) and, on the other side, to a 12-volt on-board electrical network (RDB). The CNV2 converter thus acts as a gateway, supplying power from the 48-volt network to the 12-volt network.

[0034] The electrical protection means PE, shown schematically in [Fig. 1], are connected between terminals of the electrical storage unit BAT_HV and electrical conductors of the DC bus BDC and are dedicated to the protection of the storage unit BAT_HV and the traction electrical network. The PE means include, in particular, a series-connected circuit breaker fuse FS and an electrical contactor CE. An electric current I_B flows through the fuse FS and the electrical contactor CE, which charges or discharges the electrical storage unit BAT_HV depending on the operating phase of the traction electrical network.

[0035] The C_BMS control unit houses a battery management system, known as a "BMS," responsible for managing the operation of the BAT_HV electrical storage unit. The C_BMS control unit interfaces with the BAT_HV electrical storage unit and exchanges data, notably with sensors installed on the latter. The C_BMS control unit also interfaces with the CE contactor to control its opening / closing action.

[0036] The C_VCU is a control unit that monitors the overall operation of the EV and, in particular, that of its powertrain. The C_VCU hosts an embedded software system comprising a plurality of software modules that cooperate with each other to implement different control strategies governing the operation of the EV. Via a BCD data communication bus, for example of the "CAN" type, the C_VCU exchanges information and instructions with the C_BMS and other vehicle control units for the implementation of the EV's control strategies.

[0037] The method according to the invention is implemented in the EV by means of an embedded software module SW_PP. In this embodiment, the embedded software module SW_PP is located in the C_VCU control unit, more specifically in a MEM memory of this control unit. Alternatively, the embedded software SW_PP may be hosted in another control unit of the EV, such as the C_BMS control unit. The software module SW_PP cooperates in particular with another embedded software module SW_PL, which implements a current / power limit regulation and electrical protection strategy in the EV.

[0038] The SW_PL software module is responsible in particular for allocating current / power allocations to the various consumers of the traction electrical network, as well as to the charging / discharging of the BAT_HV electrical storage unit, and for controlling the effective power supply on the network.

[0039] The SW_PP software module enables the implementation of the method according to the invention by the execution of program code instructions by a processor (not shown) of the C_VCU computer.

[0040] As shown schematically in [Fig. 1], the SW_PP module here receives as input information representative of the aforementioned current I_B, communicated Typically, the C_BMS calculator provides information representative of the ambient temperature T_A, constants CO used by the process of the invention, current limits I_AL1, I_AL2, a duration D_DB, and a control loop feedback FB. The SW_PP module outputs a current limiting setpoint I_LEE and one or more current / power limiting and protection commands CL.

[0041] The current limitation information I_AL1,1_AL2, is communicated here by the software module SW_PL. This information I_AL1,1_AL2, indicates current limitations that must be taken into account, such as a maximum current that the electrical cables and connectors can withstand without damage, a maximum charge or discharge current that the electrical storage BAT_HV can accept and / or any other maximum current imposed by an electrical component of the network.

[0042] The CO constant information is explained later in the description.

[0043] The various pieces of information provided as input to the SW_PP module are processed in accordance with the method of the invention, by using a SW_FS functional block and a REG function.

[0044] The SW_FS functional block produces the current limiting setpoint I_LEE from the aforementioned information I_B, T_A, C_O and I_AL1. The setpoint I_LEE is provided as input to the REG function considered here, and can also be used by other functions of the power limit regulation and electrical protection strategy implemented by the aforementioned software module SW_PL.

[0045] The REG function is a controller, for example of the "PID" (Proportional-Integral-Derivative) type, which generates the current / power limiting and protection CL commands based on the setpoint I_LEE, the information I_AL2, the duration D_DB, and the loop feedback information FB of the controller. In this embodiment, the duration D_DB is the time before the CE contactor trips, for example, when a current limit is exceeded during a charge / discharge of the BAT_HV electrical storage device.

[0046] In general, the method of the invention uses a digital model of a virtual fuse whose internal temperature and energy limitation I2T are taken into account to preventively protect the traction electrical network and the associated electrical storage system from overcurrents and ensure their availability. To achieve this result, the method determines a current / power limitation based on the temperature of the virtual fuse, a preventive energy limitation, and other current / power limiting information, and regulates the current / power supply in the network so as to comply with the determined limitation and thus prevent the tripping of a traditional circuit breaker fuse and / or the opening of a contactor.

[0047] With reference to [Fig.2], the processing carried out by the embedded software module SW_PP for the implementation of the method of the invention is now described below.

[0048] The processing of the SW_PP software module essentially comprises functions Fl to F7 included in the aforementioned SW_FS functional block, as well as the REG function.

[0049] In this embodiment example, a virtual fuse is considered to be traversed by the same current I_B as the traditional circuit breaker fuse FS shown in [Fig.1].

[0050] The processing method uses the Fl function to estimate the internal temperature of the virtual fuse, designated T_F. The estimation of the internal temperature of the virtual fuse uses a so-called "0D" thermal model of the fuse.

[0051] As more clearly seen in [Fig. 3], the Fl function receives as input information representing the current I_B, the ambient temperature T_A, and constants Ks, and outputs the internal temperature information T_F. The constants Ks are included in the aforementioned CO constants and comprise characteristics of the virtual fuse, namely, its ohmic resistance R, its thermal capacitance Cth, and its thermal resistance Rth.

[0052] The Fl function uses the following equation EQ1, derived from the "0D" modeling, to estimate the temperature T_F:

[0053] EQ1: d(T_F) / dt = K1.(I_B)2 + K2.((T_A)-(T_F)) where K1 and K2 are constants given by the following equalities:

[0054] Kl = R / Cth,

[0055] K2 = l / (Rth. G*).

[0056] With further reference to [Fig. 2], the processing method uses function F2 to determine a current limit I_LTF based on the estimated internal temperature T_F of the virtual fuse. Function F2 includes a predefined lookup table, stored in memory, which outputs the current limit I_LTF as a function of the internal temperature T_F supplied as input. The current limit I_LTF is used by function F7 to determine the current limit setpoint I_LEE, as will be detailed later in the description.

[0057] The processing method uses functions F3 and F4 to determine current vectors I_M, I_D, and associated duration vectors D_M, D_D. Both functions F3 and F4 access predefined lookup tables stored in memory.

[0058] The function F3 determines the vectors I_M and D_M, which are respectively a maximum tripping current vector and an associated maximum duration vector before tripping. The vectors I_M and D_M are representative of a curve of The virtual fuse trips based on its energy limiting characteristic I2T. The vectors I_M and D_M are given by respective lookup tables as a function of the estimated temperature T_F of the fuse and a reference maximum current vector I_RM. The maximum current vector I_RM is a reference vector at a nominal temperature of 25°C. The lookup tables for the vectors I_M and D_M are constructed from actual characteristic curves of a circuit breaker fuse and known electrical constraints of the traction power network.

[0059] In the example shown in [Fig.4], the vectors I_M and D_M comprise N = 5 components identified by an index i ranging from 0 to N-1. Thus, in this example, for a given temperature T_F = t_f of the virtual fuse, the maximum current vector I_M comprises the currents 720 A, 670 A, 600 A, 550 A, and 330 A, respectively, for the vector components at levels i = 0, i = 1, i = 2, i = 3, and i = 4. The associated time vector D_M comprises the times 1 s, 2 s, 11 s, 31 s, and 240 s, respectively, for the vector components at levels i = 0, i = 1, i = 2, i = 3, and i = 4. The vectors I_M and D_M define pairs (maximum current, maximum tripping time), namely, (720 A, 1 s), (670 A, 2 s), (600 A, 11 s), (550 A, 31 s), and (330 A, 240 s), each formed from vector components of the same level i. These pairs each correspond to a tripping of the virtual fuse.Thus, for illustrative purposes, with the current pair (720 A, 1 s) in effect, a current I_B of 720 A passing through the virtual fuse will cause the fuse to trip after a period of 1 s.

[0060] The function F4 determines the vectors I_D and D_D, which are respectively a derating current vector and an associated maximum derating time vector. These vectors I_D and D_D represent a derating curve for implementing a preventive energy limitation I2T, in order to prevent tripping of the circuit breaker protection devices and ensure continuity of the power supply on the traction electrical network. The derating current vector I_D is given by a lookup table based on the temperature T_F and the maximum current vector I_M. The maximum derating time vector D_D is given by a lookup table based on the temperature T_F and the maximum tripping time vector D_M.

[0061] In the example shown in [Fig. 4], the vectors I_D and D_D comprise N = 5 components identified by an index i ranging from 0 to N-1. Thus, in this example, for a considered temperature T_F = t_f of the virtual fuse, the derating current vector I_D comprises the intensities 720 A, 670 A, 600 A, 550 A, and 330 A respectively for the vector components at levels i = 0, i = 1, i = 2, and i = 3. and i = 4. The associated maximum derating time vector D_D includes the durations 0.6 s, 1.5 s, 8 s, 28 s, and 220 s respectively for the vector components of level i = 0, i = 1, i = 2, i = 3, and i = 4. The vectors I_D and D_D define derating pairs (derating current, maximum derating time), namely, (720 A, 0.6 s), (670 A, 1.5 s), (600 A, 8 s), (550 A, 28 s), and (330 A, 220 s), each formed by the vector components of the same level i. These derating pairs each correspond to a preventive energy limitation to avoid tripping the virtual fuse. Thus, for illustrative purposes, with the derating torque (720 A, 0.6 s) in force, a current I_B of 720 A passing through the virtual fuse will cause an effective limitation of the current / power supply in the traction electrical network after a period of 0.6 s.

[0062] The lookup tables are established so that the derating currents forming the components of the I_D vectors are always less than or equal to the maximum currents forming the components of the I_M vectors, and the derating durations forming the components of the D_D vectors are always strictly less than the maximum tripping durations forming the components of the D_M vectors.

[0063] The processing method uses the function F5 to determine the energy limitation I2T associated with the current I_B.

[0064] As more clearly seen in [Fig. 5], function F5 receives as input the current I_B, the maximum current vector I_M, constants I_O and DI, and an initialization command INIT, and outputs the energy limiting I2T associated with the current I_B. The constants I_O and DI are included in the aforementioned constants CO. The initialization command INIT originates from a sub-function F60 of function F6 (see [Fig. 2]).

[0065] The function F5 essentially comprises six functional blocks B1 to B6. To calculate the energy limitation I2T corresponding to the current I_B, the processing executes the function F5 considering all the components (see index i in [Fig. 5]) of the maximum current vector I_M. Thus, with the function F5, the processing calculates, for the current I_B, the current value of the energy limitation I2T; of the virtual fuse corresponding to each of the N maximum currents I_M; (i = 0 to i = Nl) forming the vector components of the vector I_M.

[0066] The F5 function initializes its calculation by executing block B1, in which the current value of the energy limitation I2T is initialized to zero. This initialization to zero can also be forced by the INIT initialization command. The processing then proceeds to execute the conditional block B2.

[0067] Conditional block B2 compares the current I_B to the maximum current I_M. If the current IB is greater than or equal to the maximum current I_M, an OK output from block B2 activates the execution of block B3. Otherwise, a NOK output from block B2 activates the execution of conditional block B4.

[0068] Block B3 calculates the energy limitation I2T; for the current I_B by integrating the square of the current I_B and the process then loops back to block B2 for the next processing step.

[0069] The conditional block B4 compares the current I_B to the maximum current I_M and to a current (I_M - I_O) equal to the maximum current I_M minus an offset (positive value) represented by the constant I_O. If the current I_B is less than the maximum current I_M but greater than or equal to the current (I_M - I_O), an OK output from block B4 triggers the execution of block B5. Otherwise, a NOK output from block B4 triggers the execution of conditional block B6.

[0070] Block B5 determines the energy limitation I2T; for the current I_B as being equal to that I2!) i calculated previously with the maximum current I_M; -1 and the process then loops back to block B2 for the next processing step.

[0071] The conditional block B6 compares the current I_B to the current (I_M; - I_O). If the current I_B remains lower than the current (I_M; - I_O) for at least a time t represented by the constant Dl, block B6 activates an OK output and the process returns to block B1 for a zero initialization of the energy limitation I2T;. Otherwise, block B6 activates an OK output and the process loops back to block B2 for the next processing step.

[0072] At output, the function F5 delivers the current values ​​of the energy limitations I2T i for the current I_B, as determined by the block Bl, B3 or B5.

[0073] With further reference to [Fig. 2] and [Fig. 6], the processing uses function F6 to determine a current limitation IL_I2T based on the energy limitation I2T and applying to the current I_B. Function F6 executes a sub-function F60 which determines current limitations IL associated with the vector components (i = 0 to i = Nl).

[0074] As more clearly seen in [Fig. 6], sub-function F60 receives as input the vectors I_M, D_M, I_D, and D_D, the energy limitations I2T provided by function F5, the current I_B, and constants D2 and D3 included in the aforementioned CO constants. Sub-function F60 outputs the current limitations IL and the aforementioned initialization command INIT.

[0075] The sub-function F60 essentially comprises nine functional blocks Cl to C9.

[0076] The processing method starts the execution of sub-function F60 by block Cl by defining energy limiting thresholds TIM_I2T; and TDM_I2T;. The energy limiting threshold TIM_I2T; is the energy limitation (I_Mi)2.D_M; calculated from the components I_M;, D_M; of the maximum vectors I_M, D_M. The energy limiting threshold TDM_I2T; is the energy limitation (I_Di)2.D_Di calculated from the components I_D;, D_D; of the derating vectors I_D, D_D.

[0077] The conditional block C2 compares the energy limitation I2T; to the threshold TIM_I2T;. If the energy limitation I2T; is greater than or equal to the threshold TIM_IT, an OK output from block C2 activates the execution of block C3. Otherwise, a NOK output from block C2 activates the execution of conditional block C4.

[0078] Block C3 sets the current limit IL; (IL; = 0) to zero, and the processing then proceeds to the execution of functional block C5. In block C5, if the current I_B remains equal to zero for at least a time t represented by the constant D2, block C5 activates an OK output, and the process proceeds to block C6. Otherwise, block C5 activates a NOK output, and the process loops back to block C1 for the next processing step.

[0079] In block C4, activated by the NOK output of block C2, the energy limitation I2T i is compared to the threshold TDM_ I2T;. If the energy limitation I2T; is greater than or equal to the threshold TDM_ I2T;, an OK output of block C4 activates the execution of block C8. Otherwise, a NOK output of block C4 is activated and the process loops back to block C1 for the next processing step.

[0080] Block C8 assigns the value of the previous vector component ID, of the vector I_D to the current limit IL; (IL; = I_D; i) and the processing then proceeds to the execution of functional block C9. In block C9, if the current I_B remains less than or equal to the current limit IL; for at least a time t represented by the constant D3, block C9 activates an OK output and the process proceeds to block C6. Otherwise, block C9 activates a NOK output and the process loops back to block C1 for the next processing step.

[0081] In block C6, activated by the OK output of block C5 or block C9, the processing assigns the value of the vector component I_M to the current limiting IL (IL = I_M), and the processing then proceeds to execute block C7. In block C7, the energy limiting I2T is initialized to zero (I2Ti = 0), and the initialization command INIT is generated. The process passes the initialization command INIT to function F5 and then loops back to block C1 for the next processing step.

[0082] With further reference to [Fig. 2], the current limits IL; obtained with sub-function F60, as described above, are used by a sub-function F61 which performs a minimum (MIN) selection. Sub-function F61 selects the current limit IL; having the lowest current intensity and assigns it to the aforementioned current limit IL_I2T.

[0083] With further reference to [Fig.2], the processing uses function F7 to determine the current limiting setpoint I_LEE from the current limiting IL_I2T delivered by function F6, the current limiting I_LTF delivered by function F2 and the current limiting information I_AL1. Function F7 comprises two sub-functions F70 and F71.

[0084] Subfunction F70 takes into account the current limitation I_LTF based on the internal temperature T_F of the virtual fuse and the current limitation IL_I2T based on the energy limitation I2T to determine a preventive current limitation of the virtual fuse I_VFL. Subfunction F70 is a minimum (MIN) selection function. Subfunction F70 selects, from among the limitations I_LTF and IL_I2T, the one with the lowest current intensity and assigns this to the current limitation I_VFL.

[0085] Subfunction F71 takes into account the current limitation I_VFL provided by subfunction F70 and the current limitation I_AL1 to determine the current limiting setpoint I_LEE. The current limitation I_AL1 is, for example, a limitation related to electrical cables and connectors. Subfunction F71 is a minimum (MIN) selection function. Subfunction F71 selects, from among the limitations I_VFL and I_AL1, the one with the lowest current intensity and assigns this value to the current limiting setpoint I_LEE.

[0086] A current evolution curve Cbl and three energy limiting curves Ciel, Cle2 and Cle3 are shown in [Fig. 7] by way of illustration. These curves Cbl and Ciel to Cle3 are in no way limiting and are intended solely to illustrate operating principles of the process of the invention.

[0087] The Cbl curve represents a current I comprising first and second phases of evolution, PHI and PH2. Phase PHI is a phase during which the current I is not constrained by a current limitation LEE. No preventive electrical protection derating is activated in this phase PHI on the electrical power supply. Phase PH2 follows phase PHI and is a phase during which the current I is reduced in a stepped fashion by preventive electrical protection deratings that are activated successively on the electrical power supply. During this phase PH2, the current I is constrained by the current limitation LEE. Threshold currents SCI, SC2, and SC3, shown in [Fig. 7], are used for the Preventive electrical protection according to the method of the invention. The threshold currents SCI to SC3 have increasing intensities, SCI being the highest current and SC3 being the lowest.

[0088] The curves Ciel, Cle2, and Cle3 show energy limiting integrals I2T, namely INI, IN2, and IN3, respectively, whose evolutions are represented in time correspondence with that of the current I. Derating activation energy limiting thresholds SD1, SD2, and SD3 are associated with the energy limiting integrals INI, IN2, and IN3, respectively. The aforementioned current thresholds SCI, SC2, and SC3 are associated with the energy limiting integrals INI, IN2, and IN3 and their thresholds SD1, SD2, and SD3, respectively.

[0089] As seen in [Fig.7], the integrals INI to IN3 are calculated from zero. An integral (INI, IN2 or IN3) is initialized to zero when the current I persists below the corresponding threshold current (SCI, SC2 or SC3) for a predefined duration, for example, ten seconds.

[0090] Regarding the integral INI, it remains equal to zero until, during a time interval IT1, the current I first exceeds the threshold SCI. During this interval IT1, the value of the integral INI increases. This value of the integral INI remains constant until, during a subsequent time interval IT2, the current I again exceeds the threshold SCI. The value of the integral INI then reaches the energy limiting threshold SD1, which causes a first derating of the power supply (see arrow Dl), thus reducing the current I to the threshold current SC2, which then provides the current limitation LEE.

[0091] Regarding the integral IN2, it remains equal to zero until, during a time interval IT3, the current I first exceeds the threshold SC2. During this interval IT3, the value of the integral IN2 increases. The value of the integral IN2 increases further during subsequent time intervals IT4 to IT6, during which further exceedances of the threshold SC2 by the current I occur. The time interval IT6 raises the value of the integral IN2 to the energy limiting threshold SD2, which causes a second derating of the power supply (see arrow D2), thus reducing the current I to the threshold current SC3, which then provides the current limitation LEE.

[0092] Regarding the integral IN3, it remains equal to zero until, during a time interval IT7, the current I first exceeds the threshold SC3. During this interval IT7, the value of the integral IN3 increases. The value of the integral IN3 increases further during subsequent time intervals IT8 to IT10, during which further current I exceeds the threshold SC3. The time interval IT10 brings the value of the integral IN3 up to the threshold energy limitation SD3, which causes a third derating on the power supply (see arrow D3), thus reducing the current I to bring it to the current limitation LEE.

[0093] Thus, as illustrated by the example in [Fig. 7], the method of the invention makes it possible to maintain maximum power availability on the network under conditions close to an energy overload, by preventing the tripping of circuit breakers (traditional fuse, electrical contactor) through a progressive derating strategy for the power supply that provides appropriate current limitations. In this invention, estimated information, obtained by the numerical modeling of the virtual fuse (temperature, maximum current, maximum time before tripping, energy limitation I2T), makes it possible to anticipate as closely as possible the tripping of the circuit breakers and to avoid them by implementing the progressive derating strategy for the power supply.

[0094] The invention is not limited to the particular embodiments described herein by way of example. In general, a person skilled in the art, depending on the applications of the invention, may make various modifications and variations falling within the scope of protection of the invention.

Claims

Demands

1. A method for preventive electrical protection in an electrified motor vehicle (EV), said vehicle (EV) comprising an electrical traction network equipped with an electrical storage unit (BAT_HV), a computer (C_VCU) and at least one circuit breaker (CE) tripping in the event of an overcurrent of an electric current (I_B) in said electrical traction network, characterized in that it comprises the steps of: a) defining a digital model of a virtual fuse through which said electric current (I_B) flows; b) establishing a current limitation (I_VFL) in said electrical traction network, determined so as to avoid tripping of said circuit breaker (CE), based on an estimated internal temperature (T_F) of said virtual fuse and on at least one energy limitation comparison (F60) between at least one calculated current value of energy limitation (I2T;) said virtual fuse and at least one derating activation energy limitation threshold (TDM_ I2Ti); and c) regulate (REG) by derating a power supply in said traction electrical network so as to comply with said current limitation (I_VFL).;

2. A method according to claim 1, characterized in that said virtual fuse is modeled numerically from features comprising at least a pair consisting of a maximum tripping current (I_M;) and a maximum time before tripping (D_M;), an ohmic resistance (R), a thermal capacitance (C*) and a thermal resistance (R*), and in that said internal temperature (T_F) is estimated as a function of said electric current (I_B), an ambient temperature (T_A), said ohmic resistance (R), said thermal capacitance (C*) and said thermal resistance (Rth) using a thermal modeling called “OD” of said virtual fuse.

3. A method according to claim 1 or 2, characterized in that a said energy limiting threshold for derating activation (TDM_I2Ti) is determined from a pair consisting of a derating current (I_D;) and a maximum derating time (D_Di) which is derived from a pair consisting of a maximum tripping current (I_M;) and a maximum time before a trip (D_M;), said currents (I_M;, I_D;) and said durations (D_M;, D_D;) being adjusted according to said estimated internal temperature (T_F), and said derating current (I_D;) being less than or equal to said maximum tripping current (I_M;) and said maximum derating duration (D_D;) being less than said maximum duration before a trip (D_M;).

4. A method according to any one of claims 1 to 3, characterized in that said current limitation (I_VFL) is established by selecting the most restrictive current limitation (F70) between a first current limitation (I_LTF) determined from said estimated internal temperature (T_F) and a second current limitation (IL_I2T) determined from said energy limitation comparison (F60).

5. Method according to claim 4, characterized in that several said energy limiting comparisons (F60) are performed respectively between several calculated current values ​​of energy limiting (I2T;) of said virtual fuse and several derating activation energy limiting thresholds (TDM_ I2T; ), several limiting current values ​​(IL;) being determined from these energy limiting comparisons, and the most restrictive limiting current value (IL;) (F61) being assigned to said second current limiting (IL_ I2T).

6. Method according to claim 1 to 5, characterized in that said power supply comprises several derating levels (DI to D3), a derating level being selected according to said current limitation (I_VFL).

7. Calculator characterized in that it comprises a memory (MEM) storing program instructions (SW_PP) for the implementation of the method according to any one of claims 1 to 6 when said program instructions (SW_PP) are executed by a processor of said calculator (C_VCU).

8. Electrified motor vehicle (EV) comprising an electrical traction network equipped with an electrical storage unit (BAT_HV), a computer (C_VCU) and at least one circuit breaker device (PE) which trips in the event of overcurrent of an electric current (I_B) in said electrical traction network, characterized in that said computer (C_VCU) is a computer according to claim 7.

9. 18 Vehicle according to claim 8, characterized in that said computer is a computer (C_VCU) responsible for supervising the general operation of said vehicle (VE) or a computer (C_BMS) responsible for managing said electrical storage.

10. Vehicle according to claim 8 or 9, characterized in that said circuit breaker device (PE) comprises a circuit breaker fuse (FS) and / or an electrical contactor (CE).

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