METHOD AND DEVICE FOR THE PROTECTION OF AN ELECTRICAL ARCHITECTURE

Description

[0001] The present invention relates to a method for protecting an electrical architecture included in particular in a vehicle and comprising a protective fuse as well as a protective device for the implementation of this method.

[0002] The invention also relates to a computer program and a vehicle, in particular a motor vehicle comprising such a protection device.

[0003] In the prior art, a known vehicle electrical architecture is described in document FR2967823, comprising a protection device and a battery with modules electrically connected by busbars. This protection device is designed to detect overheating at the busbars before it is transmitted to the battery modules, thus preventing damage to the battery. To achieve this, the protection device includes a processing unit connected to thermal fuses arranged at specific points along the busbars.Thus, as soon as one of these areas experiences a temperature rise exceeding a predefined threshold, the corresponding fuse melts and the computer activates a degraded battery usage mode corresponding to a limitation of the charging or discharging current below a certain threshold.

[0004] However, one of the major drawbacks of such a protection device is related to the fact that it is necessary to systematically replace the defective thermal fuse which has melted in order for this protection device to be operational again and for the operation of the battery not to be altered and by extension that of the vehicle in which it is installed.

[0005] In addition, such a protection device also has a high implementation and operating cost related, for example, to the replacement of defective fuses.

[0006] Document EP2393102A2 or document WO2008 / 098532 discloses a process that does not overcome all of these disadvantages, or does so in a non-optimal way.

[0007] The present invention aims to overcome these drawbacks associated with the devices and methods of protection of the prior art.

[0008] To this end, the invention relates to a method for protecting an electrical architecture comprising a protection device equipped with a protective fuse capable of melting in a degraded operating mode during which a breaking current of an intensity greater than a threshold flows in the architecture, the method further comprising, in a nominal operating mode, the following steps: periodic estimation of the temperature of said fuse, and control of the intensity of a useful current flowing through said fuse so that the estimated temperature remains below the melting temperature of said fuse.

[0009] The invention also relates to the following steps: the process includes a step of defining a first setpoint limiting the current intensity to a first maximum intensity flowing in said fuse; the control step includes a step of defining a second setpoint limiting the useful current intensity to a second maximum current intensity if the estimated temperature is greater than a threshold temperature;

[0010] In other embodiments: The periodic estimation step of the fuse temperature includes: a step of measuring the temperature of the fuse, in particular of a fuse element, or a step of measuring the intensity of the current flowing in said fuse, in particular of a fuse element, and a step of calculating the temperature from the measured intensity and a data model relating temperatures to intensities relative to said fuse; the method includes a step of determining a threshold temperature from a difference between the melting temperature of the fuse and a temperature variation relative to an energy that the fuse is likely to dissipate, which energy being less than a melting energy of this fuse;The estimation step includes a step of adjusting a measured or calculated temperature of the fuse from a determined ambient temperature of said fuse, and / or the estimation and control steps are implemented by an algorithm of the PID controller type or similar.

[0011] The invention also relates to a protection device for an electrical architecture implementing such a protection method, the device comprising a protective fuse capable of melting in a degraded operating mode during which a breaking current of an intensity exceeding a threshold flows in the architecture, the device further comprising, in a nominal operating mode: an element for periodically estimating the temperature of said fuse, and an element for controlling the intensity of a useful current flowing in said fuse so that the estimated temperature remains below the melting temperature of said fuse.

[0012] And again: The estimation element includes a processing unit, at least one fuse temperature sensor, a device for determining an ambient temperature of the fuse and / or at least one device for measuring the intensity of the current flowing in said fuse; the control element includes the processing unit and a device for regulating the intensity of the current flowing in the fuse, and / or the processing unit is connected to said at least one temperature sensor, to the devices for measuring and regulating the intensity of the current flowing in the fuse as well as to the device for determining an ambient temperature of the fuse.

[0013] The invention further relates to a vehicle, in particular an electric or hybrid vehicle, comprising an electrical architecture equipped with such a protection device.

[0014] Other advantages and features of the invention will become clearer upon reading the description of a preferred embodiment which follows, with reference to the figures, provided by way of illustrative and non-limiting example: there figure 1 represents a schematic view of a protection device included in an electrical architecture according to the embodiment of the invention; the figure 2 represents a schematic view of a protective fuse according to the embodiment of the invention; the figure 3 is a logic diagram relating to a method for protecting an electrical architecture according to the embodiment of the invention; the figure 4A is a graphical representation of the intensity of a current flowing in the fuse as a function of time, relative to a second variant of a step for controlling this intensity in the protection process according to the embodiment of the invention; the figure 4B is a graphical representation of the fuse temperature as a function of time, relating to the second variant of the piloting step according to the embodiment of the invention; the figure 4C is a graphical representation of the current flowing through the fuse as a function of the fuse temperature relative to the second variant of the piloting step according to the embodiment of the invention; the figure 5A is a graphical representation of the current intensity flowing through the fuse as a function of time, relating to a third variant of the current intensity control step of the protection method according to the embodiment of the invention, and the figure 5B is a graphical representation of the fuse temperature as a function of time relating to the third variant of the piloting step according to the embodiment of the invention.

[0015] In one embodiment shown on the figure 1 The protection device 1 of an electrical architecture 11 includes a protective fuse 2, an estimating element 3 of a temperature Te of the fuse 2 and a control element 4 of an intensity I of a useful current flowing in said fuse 2. Such a protection device 1 is preferably implemented within an electrical architecture 11 of a motor vehicle, in particular an electric or hybrid vehicle.

[0016] Fuse 2 shown on the figures 1 et 2 , is capable of melting into a degraded operating mode during which a break / overload current of an intensity greater than a threshold flows in the architecture 11. This degraded operating mode can be defined as a situation of immobilizing failure.

[0017] This fuse 2 comprises a metallic strip 12, also called the fuse blade 2, for example made of copper, having a sensitive melting zone 13 configured to melt when the upper intensity of the breaking current exceeds a threshold. The strip 12 has two ends, each provided with a connecting tab 15. Such connecting tabs 15 are designed to be connected to an electrical circuit of the electrical architecture 11. In this fuse 2, this tab 12 is contained within a housing 16 forming a closed enclosure containing sand 14, allowing for a clean break of the sensitive zone 13 once it has melted, thus preventing the continued flow of current through an electric arc.

[0018] As we have seen, this device 1 includes in a nominal operating mode a periodic estimation element 3 of a temperature Te of said fuse 2 as well as a control element 4 of the current intensity I which flows in the fuse 2 and therefore in the blade 12 of the latter.

[0019] The periodic estimation element 3 comprises a processing unit 5, a device for measuring the current intensity I flowing through the fuse 2, and at least one temperature sensor 7 for the fuse 2, which may be arranged on the fuse 2's connecting tab. This estimation element 3 also comprises a device 8 for determining the ambient temperature of the fuse 2, which is, for example, an ambient temperature sensor arranged in the immediate vicinity of the fuse 2. The processing unit 5 may be a vehicle on-board computer comprising at least one computing unit equipped with hardware and software resources, specifically at least one processor cooperating with memory elements. This processing unit 5 is capable of executing instructions for the implementation of a computer program.

[0020] The control element 4 includes the processing unit 5 and a regulation device 9 for the intensity I of the current flowing in the fuse 2.

[0021] Under these conditions, the processing unit 5 is connected to the temperature sensor 7 as well as to the measuring and regulating devices 6, 9 of the intensity I of the current flowing in fuse 2 as well as to the device for determining the ambient temperature of fuse 2 8.

[0022] In this protective device 1, the memory elements of the processing unit 5 include a data model relating to the fuse 2, which links the temperatures of the fuse element 12 of the fuse 2 to the currents that can flow through it. This data model is defined according to the characteristics of the fuse 2 in this protective device 1. This data model can be obtained either after experimental measurements of the temperature and current flowing through the fuse 2, for example by varying this current, or after a calculation taking into account the technical characteristics of the fuse 2. In this data model, the temperatures and currents can take into account the ambient temperatures of the fuse 2. Such a data model is predetermined and stored in the memory elements of the processing unit 5.

[0023] The memory elements of the processing unit 5 also include a PID controller-type calculation algorithm (acronym for "Proportional Integral Derivative") or similar for the implementation of, in particular, a process control step described later.

[0024] With reference to the figure 3 , device 1 is capable of implementing a protection method for this electrical architecture 11 comprising such device 1 equipped with this protective fuse 2.

[0025] In a nominal operating mode, this process includes a periodic estimation step 17 of the temperature Te of fuse 2. During this step 17, the temperature Te can be evaluated in two ways. In the first way, the estimation step 17 includes a measurement step 18 of this temperature Te of fuse 2, specifically of the fuse 2 contact strip 12, from the processing unit 5 which is connected to the temperature sensor 7 located at one of the fuse 2 connection tabs 15. In this first way, the estimation step 17 can include an adjustment step 19 of this measured temperature relative to a determined ambient temperature Ta of said fuse 2.More specifically during this adjustment step 19, the ambient temperature Ta present in the immediate environment of the fuse 2 is measured from the processing unit 5 which is connected to the device for determining this ambient temperature of the fuse 2 8. This ambient temperature Ta is then taken into account by the processing unit 5 in order to make an estimate of the temperature Te of the fuse 2.

[0026] In the second alternative, the estimation step 17 includes a measurement step 20 of the current intensity I flowing through the fuse 2 from the processing unit 5, which is connected to the current intensity I measuring device 6 for the current intensity I flowing through the fuse 2. This measurement step 20 includes a calculation step 21 of the temperature Te from the measured current intensity I and the data model relating the fuse 2, which correlates the temperatures of the fuse 2's contact plate 12 with the currents likely to flow through it. In this second alternative, the estimation step 17 may include an adjustment step 22 of this temperature from a determined ambient temperature Ta of the fuse 2.More specifically, in the data model, the determined temperature of fuse 2 for a given current can be adjusted according to the ambient temperature Ta present in the immediate environment of fuse 2, which ambient temperature Ta is measured from the processing unit 5 which is connected to the device for determining the ambient temperature of fuse 2 8.

[0027] The process then includes a control step 23 of the intensity I of the useful current flowing in the fuse 2 so that the estimated temperature Te of the latter remains below a melting temperature Tf of the fuse 2. This melting temperature Tf corresponds to the temperature at which the plate 12 of the fuse 2 is likely to melt when a breaking / overload current flows in the fuse 2 causing the latter to melt under the effect of a melting energy Ef which melts the plate 12 of this fuse 2. This control step 23 of the intensity I can be implemented according to three variants.As part of this control step 23, the processing unit 5 implements a mechanism for regulating the current I flowing through the fuse 2 using a PID (Proportional, Integral, and Derivative) controller algorithm or a similar one, preferably including a proportional and / or an integral component. More specifically, by executing this algorithm, the processing unit 5 is capable of implementing the different variations of this control step 23.

[0028] In the first variant, this piloting step 23 includes a comparison step 24 of the temperature Te with a threshold temperature Ts. This threshold temperature Ts, which is lower than the melting temperature Tf, corresponds to a temperature for which the characteristics of the fuse 2, and therefore of the blade 12, have been defined for optimal operation of the latter.

[0029] Under these conditions, if the estimated temperature Te is lower than the threshold temperature Ts, i.e., Te < Ts, then the current intensity I flowing through fuse 2 remains unchanged. Therefore, the process then repeats the periodic temperature estimation step 17 for Te.

[0030] Conversely, if the estimated temperature Te is higher than the threshold temperature Ts, i.e., Te > Ts, then the control step 23 includes a step 25 for defining a second setpoint limiting the current intensity I to a second maximum intensity Im2. This maximum current intensity Im2 corresponds to an intensity adapted to the technical characteristics of the fuse 2 and therefore of the strip, in order to ensure optimal operation of this fuse 2. Subsequently, the process again involves performing the periodic temperature estimation step 17 of the temperature Te. In this configuration, the current intensity I flowing through the fuse 2 is then maintained at a value less than or equal to that of the second maximum intensity Im2, which prevents the fuse temperature Te, which is measured periodically, from reaching the melting temperature Tf.

[0031] In the second variant, the control step includes a step 26 for defining a first maximum intensity Im1 of the useful current intensity I flowing through the fuse 2. More precisely, during this step 26, the current intensity I flowing through the fuse 2 cannot exceed this first maximum intensity Im1; that is, the current intensity I flowing through the contact 12 of this fuse 2 is less than or equal to this first maximum intensity Im1, i.e., I ≤ Im1. In this variant, the control step 23 also includes a step 27 for comparing the estimated temperature Te to the threshold temperature Ts. Under these conditions, if the estimated temperature Te is less than the threshold temperature Ts, i.e., Te < Ts, then the current intensity I flowing through the fuse 2 is not modified. Therefore, the process then again involves performing the periodic temperature estimation step 17 of the temperature Te.

[0032] Conversely, if the estimated temperature Te is greater than the threshold temperature Ts, i.e., Te > Ts, then the control step 23 includes a step 28 for defining the second current limiting setpoint I to the second maximum current Im2. This second maximum current Im2 is less than the first maximum current Im1. The control step 23 then performs the periodic estimation step 17 of the temperature Te of fuse 2 and subsequently includes a further comparison step 29 of the estimated temperature Te with a hysteresis temperature Thys. Under these conditions, if the estimated temperature Te is less than the hysteresis temperature Thys, i.e., Te < Thys, then the control step 23 includes a cancellation step 30 of the second limiting setpoint. Subsequently, the estimation step 17 and the control step 23 are performed again.Conversely, note that if the estimated temperature Te is greater than the hysteresis temperature Thys, i.e., Te > Thys, then the estimation step 17 and the comparison step 29 are performed again. Note, for example, on the... figure 4C , the threshold temperature is 145°C and the hysteresis temperature Thys is 100°C.

[0033] With reference to figures 4A à 4C In an example illustrating this variant of the process in control step 23, between times t0 and t1, the current I flowing through fuse 2 is limited to the first maximum current Im1, which is 350A, following the implementation of step 26, which defines the first setpoint. Between these times t0 and t1, the periodically estimated temperature Te gradually increases until it exceeds the threshold temperature Ts, which is 145°C. Therefore, under these conditions, since the estimated temperature Te at time t1 is greater than the threshold temperature Ts (i.e., Te > Ts), the current I flowing through fuse 2 is then limited to the second maximum current Im2, which is 150A, following the implementation of step 28, which defines the second setpoint. Thus, between times t1 and t2, the current I decreases until it reaches the second maximum current Im2.Such a decrease in intensity I also leads to a drop in temperature Te. In particular, this temperature Te continues to fall until a time t3 where it converges towards a stabilized temperature Tsta, here of 120°C. Then, since the estimated temperature Te is lower than the hysteresis temperature, which is here 100°C, the control step 23 then includes the cancellation step 30 of the second limiting setpoint.

[0034] It should be noted in these first and second variants that the PID regulator preferably includes only the proportional component and can thus be defined by the following equation: Im2 = Kp x (Te - Ts), with Kp corresponding to the proportional gain.

[0035] In the third variant, this process includes a pilot step 23 similar to that described in the first or second variant. Unlike these two variants, in this third variant, the process includes a step 31 for determining a threshold temperature Ts from the difference between the melting temperature Tf of fuse 2 and a temperature variation ΔT related to an energy Ed that fuse 2 is capable of dissipating and which is less than the melting energy Ef of this fuse 2, i.e., Ed < Ef, visible on the figure 5 More precisely, this energy Ed is defined by the following equation: Ed = m Cp ∫ΔT dt, with m the mass of the strip 12 of the fuse 2 and Cp its heat capacity.

[0036] With reference to the figure 5A et 5BIn this third variant, when the estimated temperature Te is greater than the threshold temperature Ts thus determined (i.e., Te > Ts), then at time t1, the control step 23 implements the definition step 24, 27 of the second current limitation setpoint I to the second maximum current intensity Im2, until time t2 when the estimated temperature Te is less than the threshold temperature Ts. Thus, between times t1 and t2, this current intensity I is progressively and continuously reduced as soon as the temperature Te is greater than the threshold temperature Ts without reaching the melting temperature Tf of fuse 2. In other words, the threshold temperature Ts thus determined is very close to the melting temperature Tf. In this third variant, the control step 23 allows for the most precise regulation of the current intensity I and therefore the temperature Te of fuse 2.It should be noted that the threshold temperature Ts thus determined is higher than the experimental / theoretical threshold temperature of fuse 2 used in particular in the first and second variants, but lower than the melting temperature Tf of fuse 2.

[0037] In this third variant the PID regulator can include the proportional and integral components, and correspond to the following equation: Im2 = Kp x (Te - Ts) + KI x ∫ ΔTdt, with Kp being the proportional gain and KI the integral gain.

[0038] Furthermore, this process may include a step of alerting a vehicle user with such an electrical architecture 11, when, in variants of the control step 23, the second instruction definition step 24, 27 is carried out. This alert step may then include a step of transmission by the processing unit 5 of a message to the vehicle's dashboard or even an audible signal.

[0039] Advantageously, this device 1 and this method make it possible to protect the fuse 2 against its own thermal drift and to maintain its temperature within a range in which its operation is optimal. Furthermore, they also allow for consideration of the dynamics and thermal response time of the fuse 2.

Claims

1. Method for protecting an electrical architecture (11) comprising a protective device (1) provided with a protective fuse (2) that is able to melt in an impaired mode of operation during which a break current, with a magnitude higher than a threshold, flows in the architecture (11), the method furthermore including, in a nominal mode of operation, the following steps: - periodically estimating (17) a temperature (Te) of said fuse (2), and - controlling (23) a magnitude (I) of a useful current flowing in said fuse (2) such that the estimated temperature (Te) remains lower than a melting temperature (Tf) of said fuse (2), the method being characterized in that it comprises a step (26) of defining a first limit setpoint for the magnitude (I) of the current at a first maximum magnitude (Im1) flowing in said fuse (2) and in that the control step (23) comprises, if the estimated temperature (Te) is higher than a threshold temperature (Ts), a step (25, 28) of defining a second limit setpoint for the useful current magnitude (I) at a second maximum magnitude (Im2) of the current, the second setpoint being lower than the first.

2. Method according to the preceding claim, characterized in that the step (17) of periodically estimating the temperature (Te) of the fuse (2) comprises: - a step (18) of measuring the temperature (Te) of the fuse (2), in particular of a strip (12) of the fuse (2), or - a step (20) of measuring the magnitude (I) of the current flowing in said fuse (2), in particular of a strip (12) of the fuse (2), and - a step (21) of calculating the temperature (Te) on the basis of the measured magnitude (I) and of a data model linking temperatures with magnitudes relating to said fuse (2).

3. Method according to any one of the preceding claims, characterized in that it comprises a step (31) of determining a threshold temperature (Ts) on the basis of a difference between the melting temperature (Tf) of the fuse (2) and a temperature variation (ΔT) relating to a power (Ed) that the fuse (2) is liable to dissipate, this power (Ed) being lower than a melting power (Ef) of this fuse (2).

4. Method according to any one of the preceding claims, characterized in that - the estimation step (17) comprises a step (19, 22) of adjusting a measured or calculated temperature of the fuse (2) on the basis of a determined ambient temperature (Ta) of said fuse (2), and / or - the estimation (17) and control (23) steps are implemented by an analogue or PID controller algorithm.

5. Device (1) for protecting an electrical architecture (11) implementing a protection method according to any one of the preceding claims, the device (1) including a protective fuse (2) able to melt in an impaired mode of operation during which a break current, with a magnitude higher than a threshold, flows in the architecture (11), the device being characterized in that it furthermore includes, in a nominal mode of operation: - an element (3) for periodically estimating a temperature (Te) of said fuse (2), the estimation element (3) comprising a processing unit (5), at least one sensor (7) for sensing the temperature of the fuse (2), a device (8) for determining an ambient temperature of the fuse (2) and / or at least one device (6) for measuring the magnitude (I) of the current flowing in said fuse (2), and - an element (4) for controlling a magnitude (I) of a useful current flowing in said fuse (2) such that the estimated temperature (Te) remains lower than a melting temperature (Tf) of said fuse (2), the control element (4) comprising the processing unit (5) and a device (9) for controlling the magnitude (I) of the current flowing in the fuse (2), - the processing unit (5) being connected to said at least one temperature sensor (7), to the devices (6, 9) for measuring and controlling the magnitude (I) of the current flowing in the fuse (2), and to the device (8) for determining an ambient temperature of the fuse (2).

6. Vehicle, in particular an electric or hybrid vehicle, comprising an electrical architecture provided with a protective device (1) according to Claim 5.