Electrical system and method for diagnosing a faulty electrical connection in an electrical system

Abstract

The present invention discloses a method implemented in an electrical system (1), the electrical system comprising at least one electric power source (10) and at least one electrical component (121 to 123), the at least one electric power source and the at least one electrical component being electrically connected via an electrical transfer switch (11), the method comprising the following steps: a) measuring a first voltage and a second voltage (Ub, Uc1 to Uc3) existing between terminals of the electric power source and between terminals of the electrical component, b) calculating a voltage deviation between the first voltage and the second voltage, c) comparing the voltage deviation with a predetermined voltage threshold, d) diagnosing a faulty electrical connection between the electric power source and the electrical component based on a result of the comparison, and e) controlling the disconnection (CDC) of the electrical transfer switch and / or transmitting an alarm signal when a faulty electrical connection is diagnosed.

Description

Technical Field

[0001] The present application claims priority from French application No. 1905983, filed on June 6, 2019, the content of which (text, drawings and claims) is incorporated herein by reference.

[0002] The present invention generally relates to electrical safety in electrical devices and systems. More specifically, the present invention relates to a method for protecting an electrical system in the presence of a faulty electrical connection. The present invention also relates to an electrical system, in particular an electrical system of a motor vehicle, in which the aforementioned method is implemented. Background Art

[0003] Electrical safety is an important factor in automotive design, especially when higher voltages and higher amperages are present, and this is especially true in electric traction vehicles.

[0004] In electrical systems, faulty electrical connections can lead to safety problems. At high voltages, this can create risks for personnel, for example in the event of a complete disconnection of a connector, as well as risks of thermal runaway due to electrical connections with excessive resistance or due to electric arcs, which can lead to damage to parts of the system or fire.

[0005] In the prior art, connectors are known that are equipped with a device for locking the connector and preventing any movement once the connector has been correctly positioned. Locking the connector can be complex for the operator. This solution relies on human factors and can result in an incomplete or non-locking connection.

[0006] Also known are connectors equipped with a debranching sensor, known as an "interlock line," which allows for the diagnosis of a connector disconnection by detecting the opening of a separate closed circuit integrated into the connector design. The "interlock line" circuit detects the disconnection and emits an alarm signal. Documents TW201608778A and CN105128679A describe this type of circuit for indicating a contact or non-contact state. This prior art solution has the disadvantage of being sensitive to electromagnetic interference, which increases the likelihood of false detections.

[0007] EP 0 829 731 A discloses a testing system for checking the integrity of an electrical connection. The testing system comprises a transformer having a primary winding coupled between a combination of two contact pins and a secondary winding coupled to both an energy source and a testing circuit. An energy source, in the form of a radio frequency oscillator, supplies power to the transformer's secondary winding, which is connected to the testing circuit. A current reference circuit is coupled to the transformer's secondary winding and includes an output coupled to the energy source and the testing circuit. When contact is established, the impedance of the secondary winding assumes a low value detected by the testing circuit. Summary of the Invention

[0008] It is desirable to overcome the shortcomings of the prior art by providing a new method for making electrical systems safe against electrical risks through early and economically advantageous diagnosis of faulty electrical connections.

[0009] According to a first aspect, the present invention relates to a diagnostic method for diagnosing a faulty electrical connection in an electrical system, the electrical system comprising at least one electric power source and at least one electrical component, the at least one electric power source and the at least one electrical component being electrically connected via an electrical conversion switch, the method comprising the following steps: a) measuring a first voltage and a second voltage existing between terminals of the electric power source and between terminals of the electrical component, b) calculating a voltage deviation between the first voltage and the second voltage, c) comparing the voltage deviation with a predetermined voltage threshold, d) diagnosing a faulty electrical connection between the electric power source and the electrical component based on a result of the comparison, and e) controlling the electrical conversion switch to disconnect and / or transmitting an alarm signal when a faulty electrical connection is diagnosed.

[0010] According to a particular feature, said electrical connection is diagnosed as faulty when said voltage deviation exceeds said predetermined voltage threshold value for at least a predetermined time.

[0011] According to another particular feature, the voltage threshold is predetermined to be equal to the maximum normal voltage drop between the electric power source and the electric component when the electrical connection is normal, multiplied by a safety margin factor.

[0012] According to another particular feature, the maximum normal voltage drop is equal to the product of the maximum current that can flow between the electric power source and the electrical component when the electrical connection is normal and the nominal resistance of the electrical circuit between the electric power source and the electrical component.

[0013] According to another special feature, in an electrical system including an electric power source and a plurality of electrical components, the plurality of electrical components are electrically connected to the electric power source via an electrical conversion switch. The method according to the present invention is designed such that the diagnosis of a faulty electrical connection between the electric power source and at least one of the electrical components causes the control to disconnect the electrical conversion switch for at least the electrical circuit in which the faulty electrical connection is diagnosed and / or causes the emission of at least one alarm signal.

[0014] The present invention also relates to an electrical system comprising at least one electrical power source and at least one electrical component, the at least one electrical power source and the at least one electrical component being electrically coupled via an electrical switch, the electrical switch being controlled and switched by an electronic control unit. According to the present invention, each of the electrical power source and the electrical component comprises a voltage measuring device for measuring the voltage at the terminals of the electrical power source and at the terminals of the electrical component, and the electronic control unit comprises a memory for storing program instructions for implementing the method as briefly described above.

[0015] The invention also relates to a motor vehicle comprising the electrical system mentioned above. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Other advantages and features of the present invention will become more apparent upon reading the following detailed description of several embodiments of the present invention and the accompanying drawings, in which:

[0017] - Figure 1 is a block diagram of a particular embodiment of an electrical system in which the method according to the invention is implemented.

[0018] - Figure 2 is a flow chart illustrating the different functional steps of the method according to the invention. DETAILED DESCRIPTION

[0019] refer to Figure 1 , a specific embodiment 1 of an electrical system is now described as an example, in which the method according to the invention is implemented.

[0020] like Figure 1 As shown, the electrical system 1 includes an electrical energy source 10 , a switch 11 , a plurality of electrical components (here, three electrical components 121 to 123 ), and an electronic control unit 13 .

[0021] The electric power source 10 is, for example, a battery (eg a traction battery in an electric or hybrid vehicle). The electric power source 10 is equipped with a voltage measuring device 100 for measuring the supply voltage Ub at the terminals of the electric power source 10 .

[0022] The switch 11 is arranged between the power source 10 and the electrical components 121 to 123 and is controlled by the electronic control unit 13 via a switching control CDC sent thereto. The switch 11 may be integrated into the power source 10 or separate therefrom.

[0023] The transfer switch 11 allows or prohibits the passage of power currents I1 to I3 between the electric power source 10 and the electrical components 121 to 123, depending on whether the transfer switch 11 is in a closed state or an open state. The transfer switch 11 is thus a disconnection component for disconnecting the electric power transmission between the electric power source 10 and the electrical components 121 to 123.

[0024] Depending on the embodiment, the power currents I1 to I3 can be switched individually or collectively. In the first case, the transfer switch 11 typically includes three electrical contactors or power electronic switches that are individually controlled and switched. In the second case, the transfer switch 11 typically includes one electrical contactor or power electronic switch or multiple parallel electrical contactors or power electronic switches that are simultaneously controlled and switched to switch the current intensity.

[0025] The electrical components 121 to 123 are electrical consumers and / or electrical generators (for example electric motors, alternators or reversible rotary hybrid electric machines in motor vehicles).

[0026] The electrical components 121 to 123 are equipped with voltage measuring devices 1201 to 1203 for measuring the supply voltages Uc1 to Uc3 , respectively, at the terminals of said electrical components.

[0027] The electrical components 121 to 123 are electrically connected to the electric power source 10 via the electric power supply links LP1 to LP3 via the change-over switch 11 , and the currents I1 to I3 flow through the electric power supply links, respectively.

[0028] The electronic control unit 13 comprises a memory MEM in which a software module LOG for implementing the method according to the invention is housed. The method according to the invention is implemented by a processor (not shown) of the unit 13 by executing the program code instructions of said software module.

[0029] The electronic control unit 13 is connected to the voltage measuring devices 100 and 1201 to 1203 via signal links LSb and LS1 to LS3, respectively. Via these signal links LSb and LS1 to LS3, the electronic control unit 13 configures the periodic measurement of the supply voltages Ub and Uc1 to Uc3 by the devices 100 and 1201 to 1203 and receives these measured supply voltages Ub and Uc1 to Uc3, respectively, as input variables.

[0030] The principle of the present invention is based on the detection of an excessive voltage drop (caused by an abnormally increased resistance between an electrical component and an electrical power source) to diagnose a faulty electrical connection between the electrical component and the electrical power source. In fact, as electrical contacts gradually separate in a connector, the resistance between the electrical contacts increases due to the reduced contact surface area of ​​the electrical contacts, and an additional voltage drop is generated in the electrical circuit. Similarly, when an arc occurs between two contact ends in an electrical circuit, an increased voltage drop occurs between the two contact ends.

[0031] When current circulates in an electrical circuit formed between the electric power source and the electrical component in question, and whose nominal resistance is known by design, Ohm's law makes it possible to calculate the expected normal voltage drop between the electric power source 10 and the electrical component in question 121, 122, or 123. When the voltage drop measured between the electric power source 10 and the electrical component in question 121, 122, or 123 is greater than the expected normal voltage drop, the excess of the detected voltage drop originates from a parasitic resistance that is added to the nominal resistance of the electrical circuit and represents a faulty electrical connection.

[0032] Now also refer to Figure 2 The method according to the invention and the operation of the electrical system 1 are described.

[0033] exist Figure 2 Above, the different functional steps of the method according to the invention are illustrated by blocks E0 to E4.

[0034] Block E0 corresponds to the initial state of the electrical system 1 in a nominal operating mode in which the transfer switch 11 is closed and the electrical elements 121 , 122 and 123 are supplied by the electrical power source 10 with currents I1 , I2 and I3 .

[0035] Block E1 corresponds to the periodic measurement of the supply voltages Ub and Uc1 to Uc3 of the electric power source 10 and the electrical components 121, 122 and 123 by the voltage measuring devices 100, 1201, 1202 and 1203. The measured supply voltages Ub and Uc1 to Uc3 are transmitted to the electronic control unit 13 to be read by the software module LOG.

[0036] In block E2 , the control process of the software module LOG calculates the voltage deviations EV1 to EV3 between the voltage Ub and the voltages Uc1 to Uc3 , ie EV1 =Ub−Uc1 , EV2 =Ub−Uc2 and EV3 =Ub−Uc3 .

[0037] In conditional block E3 , the control process of the software module LOG compares the voltage deviations EV1 to EV3 with predefined voltage thresholds TH1 to TH3 , respectively.

[0038] If the process does not detect (N) any significant exceeding of the voltage thresholds TH1 to TH3 by the voltage deviations EV1 to EV3 , the control process maintains the electrical system 1 in its nominal operating mode and returns to block E0 .

[0039] Block E4 corresponds to the case where it is detected in block E3 that at least one of the (Y) voltage deviations EV1 to EV3 is greater than the corresponding voltage threshold among the voltage thresholds TH1 to TH3. When the voltage threshold is observed to be exceeded for a time D that is greater than a predetermined confirmation time DT, the exceeding of the voltage threshold is confirmed. When the verified threshold is exceeded, the control process thus diagnoses an incorrect electrical connection in the electrical circuit of one or more electrical components involved and may decide to emit an alarm signal AL (AL="1") and / or activate a changeover control CDC (CDC="1") to switch the transfer switch 11 to the open state. The emission of the alarm signal AL alone typically corresponds to a use situation in which there is no immediate electrical danger or risk. In a vehicle, the alarm signal AL is, for example, in the form of an activated indicator light in the instrument panel, which serves to inform the driver that maintenance intervention is required. Switching the transfer switch 11 to the open state typically corresponds to a use situation in which there is an electrical danger or risk and it is necessary to disconnect the electrical power supply.

[0040] Different control strategies for the transfer switch 11 can be implemented by the control process based on the configuration and / or usage of the electrical system 1. Thus, upon detecting an excess of at least one of the voltage thresholds TH1 to TH3, the control process may decide to cut off the electrical power supply to all electrical components, thereby fully rendering the electrical system 1 safe. Alternatively, the control process may decide to cut off the electrical power supply to only one or more electrical components involved in the voltage threshold excess, thereby maintaining the electrical system in a degraded mode by maintaining the maximum number of electrical components in operation. In the latter case, for example, the control process may assess that cutting off the electrical components involved in the voltage threshold excess will not result in adverse effects, while maintaining the electrical power supply to other electrical components without any risk.

[0041] The voltage thresholds TH1 to TH3 are respectively predefined for the electrical components 121 to 123. In this particular embodiment of the electrical system 1, the respective voltage threshold is fixed for each of the electrical components and depends on the maximum current that can flow between the electrical power source and the electrical component and the nominal resistance of the electrical circuit between the electrical component and the electrical power source.

[0042] Thus, for example, for the considered electrical component 12 (which has a nominal resistance R=5 mOhm and a maximum current Imax=100 A for an electrical circuit with an electrical power source 10), the maximum voltage drop Umax between the electrical power source 10 and the electrical component 12 will be equal to Umax=R.Imax=500 mV. By adopting a safety margin factor M (for example, M=2), the voltage threshold TH assigned to the electrical component 12 will be predefined as TH=M.Umax=1 V. By taking into account the confirmation time DT (which is fixed to DT=5 s, for example), if the supply voltage Uc at the terminals of the electrical component 12 is less than the supply voltage Ub of the electrical power source 10 by at least TH (TH=1 V) for a time greater than DT (DT=5 s), the changeover control CDC is activated (CDC="1") to change the changeover switch 11 to the open state.

[0043] In other embodiments, in order to obtain a more accurate diagnosis, for the same electrical component, multiple voltage thresholds may be defined according to the current intensity or current intensity range consumed or generated by the electrical component.

[0044] It is noted that the method of the invention allows to easily determine the location of the resistance fault and thus facilitates after-sales repair operations.

[0045] Thus, in case an exceeding of the voltage threshold is detected for all electrical components, the resistance fault will thereby be considered to be in the electric power source common mode position.

[0046] In the event that only one exceeding of the voltage thresholds is detected, the resistive fault is located in the electrical circuit between the electrical component in question and the electrical power source.

[0047] In the event that more than one exceeding of the voltage threshold is detected, the resistive fault is located in a common electrical circuit section of the electrical components involved.

[0048] The present invention is not limited to the specific embodiments described herein as examples. A person skilled in the art may provide various modifications and variations that fall within the scope of protection of the present invention based on the application of the present invention.

Claims

1. A diagnostic method for diagnosing a faulty electrical connection in an electrical system (1), the electrical system comprising at least one electrical power source (10) and at least one electrical component (121 to 123), the at least one electrical power source and the at least one electrical component being electrically connected via an electrical transfer switch (11), the diagnostic method comprising the following steps: a) measuring a first voltage Ub existing between the terminals of the electric power source (10) and a second voltage Uc1 to Uc3 between the terminals of the electrical components (121 to 123), b) calculating a voltage deviation EV1 to EV3 between the first voltage Ub and the second voltage Uc1 to Uc3, c) comparing the voltage deviation EV1 to EV3 with a predetermined voltage threshold TH1 to TH3, d) diagnosing a faulty electrical connection between the electric power source (10) and the electrical components (121 to 123) based on the result of the comparison, and e) controlling the disconnection (CDC) of the electrical transfer switch (11) and / or emitting an alarm signal (AL) when a faulty electrical connection is diagnosed, the voltage threshold TH1 to TH3 being predetermined to be equal to the maximum normal voltage drop Umax between the electric power source (10) and the electrical components (121 to 123) when the electrical connection is normal multiplied by a safety margin factor M.

2. The diagnostic method according to claim 1, wherein When the voltage deviations EV1 to EV3 exceed the predetermined voltage threshold values ​​TH1 to TH3 for at least a predetermined time period DT, it is diagnosed that the electrical connection is faulty.

3. The diagnostic method according to claim 1 or 2, characterized in that The maximum normal voltage drop Umax is equal to the product of the maximum current Imax that can flow between the electric power source (10) and the electrical components (121 to 123) when the electrical connection is normal and the nominal resistance R of the electrical circuit between the electric power source (10) and the electrical components (121 to 123).

4. The diagnostic method according to claim 1 or 2, wherein in an electrical system (1) comprising an electrical power source (10) and a plurality of electrical components (121 to 123), the plurality of electrical components being electrically connected to the electrical power source (10) via an electrical conversion switch (11), characterized in that: Diagnosis of a faulty electrical connection between the electrical power source (10) and at least one of the electrical components (121 to 123) causes controlled disconnection (CDC) of at least the electrical transfer switch (11) for the electrical circuit in which the faulty electrical connection was diagnosed and / or causes emission of at least one alarm signal (AL).

5. An electrical system comprising at least one electric power source (10) and at least one electrical component (121 to 123), wherein the at least one electric power source and the at least one electrical component are electrically connected via an electrical conversion switch (11), wherein the electrical conversion switch (11) is controlled and converted by an electronic control unit (13), wherein: Each of the electric power source (10) and the electric components (121 to 123) comprises a voltage measuring device (100; 1201 to 1203) for measuring the voltage at the terminals of the electric power source and at the terminals of the electric components, and the electronic control unit (13) comprises a memory (MEM) for storing program instructions (LOG) for implementing the diagnostic method according to any one of claims 1 to 4.

6. A motor vehicle comprising an electrical system (1) according to claim 5.

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