Method for diagnosing battery relay disconnection of a hybrid driveline

Abstract

A method for diagnosing a hybrid powertrain (1) of a motor vehicle, the method comprising: - commanding (21) to open a controlled relay (19) to isolate a battery from a DC voltage bus; - commanding (24) an adjustment element to adjust the DC voltage bus to a diagnostic voltage; - diagnosing (26) the opening of the relay according to the following conditions: - diagnosing that the relay is open if, for a predefined duration of a sliding window, the voltage of the DC voltage bus follows the diagnostic voltage with a deviation less than or equal to a defined threshold amplitude; and - diagnosing that the relay is not correctly open if, during the predefined duration, the voltage of the DC voltage bus deviates from the diagnostic voltage with a deviation greater than the defined threshold amplitude.

Description

TECHNICAL FIELD

[0001] The present invention relates to the field of supplying power to a battery from an on-board network of a motor vehicle, and more particularly to diagnosing the operating state of a relay providing the double-pole disconnection and connection of the electrical network and the battery. BACKGROUND

[0002] Some hybrid motor vehicles comprise 2 electric machines, a thermal engine and a high-voltage battery.

[0003] For such vehicles, it is known that the first electric machine, called the main electric machine, is connected to the wheels, while the second electric machine can also be used so that it can be connected to the wheels via a transmission shaft usually linked to a gearbox, or provide electrical power to the first electric machine, the engine or charging assistance. Such an architecture is described for example in document FR3053299. It should however be noted that the main electric machine can be disconnected from the wheels via the gearbox, for example in the event of a malfunction of the main electric machine.

[0004] In such hybrid vehicles, there can be several hybrid modes.

[0005] Hybrid mode is understood to mean a different operating mode of the motor vehicle for providing traction and energy management according to the two electric machines and the internal combustion engine.

[0006] Two main hybrid series are known: parallel hybrid, in which the different energy sources are used in parallel to provide traction, and series hybrid, in which the vehicle is operated using only electrical energy, thermal energy only providing additional support to the electric motor. SUMMARY

[0007] The present invention relates in particular to a specific series hybrid mode, in particular implemented in the event of a malfunction of one of the high-voltage batteries, for example a 400V battery, to avoid a non-mobilisable malfunction. In this mode, the electric machines only provide traction at start-up or at low speed.

[0008] In particular, some battery malfunctions mean that the battery cannot be charged using the energy produced by the available engine or inertia. This leads to very rapid discharge of the battery and to a non-mobilisable malfunction for the driver, since only the electric machines can provide start-up of the motor vehicle.

[0009] In series and parallel hybrid, the internal combustion engine is deactivated below a certain speed, in particular because the type of gearbox used is usually a non-synchronized automatic dog clutch gearbox, which prevents it from running to start the vehicle. Thus, in parallel hybrid mode, a stop of the vehicle will make it impossible to restart the vehicle, while in series hybrid mode, a stop of the vehicle and of the internal combustion engine will make it impossible to restart the vehicle.

[0010] Moreover, in parallel mode, the discharge of the high-voltage bus linked to the high-voltage battery involves stopping the DC-DC conversion supplying the on-board network, called 14V network, and triggering protection measures for the computers on this network. This has the consequence of hindering the proper functioning of the vehicle.

[0011] This particular series mode used in the event of a battery malfunction disconnects the battery of the traction system to avoid damaging it and to prevent a fire from occurring.

[0012] Moreover, this series mode disconnects the internal combustion engine from the wheels, causing it to operate in a speed-regulated manner.

[0013] The voltage of the high-voltage smoothing capacitor connected to the high-voltage bus is then regulated by the secondary electric machine via a known structure called high-voltage starter generator HSG, by converting the energy produced by the internal combustion engine.

[0014] This series mode implemented in the present invention thus makes it possible to continue traction by the main electric machine connected to the wheels and by the DC-DC conversion, in particular by using the energy available on the high-voltage bus, called DC bus, supplied by the secondary electric machine to supply the on-board electrical network.

[0015] In this way, when the vehicle is operating in this series mode, the battery is disconnected from the system via the opening of the high-voltage relay, called HV relay here, thus preventing a fire from occurring.

[0016] Since the inverter generates a voltage on the high-voltage capacitor of the DC bus, called DC capacitor, there is a risk of supplying the damaged battery if the relay were to close again by mistake.

[0017] However, none of the solutions in the prior art are sufficient to avoid this risk.

[0018] The purpose of the present invention is therefore to find a solution that ensures that no energy can be transmitted to the high-voltage battery.

[0019] More generally, the present invention describes a method applicable to any other situation in which it is necessary to ensure that the high-voltage relay is properly open rather than closed to isolate the battery from the DC bus.

[0020] To this end, a method for diagnosing a hybrid powertrain of a motor vehicle is proposed, the hybrid powertrain comprising a first electric machine for driving the motor vehicle, the first electric machine being connected to a DC voltage bus via a first inverter, the voltage of the voltage bus being smoothed by a passive damping element, for example a capacitor, the hybrid powertrain further comprising: a second electric machine able to receive energy produced by an internal combustion engine and to transmit it to the DC voltage bus; a second inverter regulating the voltage of the DC voltage bus; and a battery connected to the DC voltage bus by a controlled relay for providing a DC voltage to the DC voltage bus; the motor vehicle comprising a control element for controlling the powertrain, the control element being designed to implement the following steps:

[0021] - commanding the disconnection of the controlled relay to isolate the battery from the DC voltage bus;

[0022] - defining a diagnostic voltage function as a function of a setpoint voltage of the DC voltage bus and of a periodic variable component;

[0023] - defining a distance threshold amplitude of the diagnostic voltage;

[0024] - commanding the regulating element to regulate the DC voltage bus to the diagnostic voltage;

[0025] - checking whether the voltage of the DC voltage bus follows the diagnostic voltage with a deviation less than the defined threshold amplitude over a predefined duration of a sliding window;

[0026] - diagnosing the disconnection of the relay according to the following condition:

[0027] if, over the predefined duration of the sliding window,

[0028] the voltage of the DC voltage bus follows the diagnostic voltage with a deviation less than or equal to the defined threshold amplitude, the disconnection of the relay is diagnosed; and

[0029] if, over the predefined duration of the sliding window, the voltage of the voltage bus deviates from the diagnostic voltage with a deviation greater than the defined threshold amplitude, the relay is not correctly disconnected is diagnosed.

[0030] In this way, the invention makes it possible to diagnose the correct disconnection of the relay isolating the battery in a relatively robust manner, without having to measure the voltage of the battery and without having to add sensors or additional hardware.

[0031] Furthermore, this makes it possible to detect the case where the series mode is no longer feasible due to non-functional regulation, for example:

[0032] - when the maximum power that can be provided by the HSG driven by the internal combustion engine is exceeded

[0033] - during any fault affecting the regulation of the HSG current

[0034] Advantageously and in a non-restrictive manner, after the step of opening the relay, a step of waiting for a predefined duration is performed before implementing the step of commanding the regulating element. In this way, the relay has time to open before starting the diagnosis, which makes it possible to ensure that no detection error occurs.

[0035] In particular, the predefined waiting duration corresponds to the maximum opening duration of the relay. Although longer, this makes it possible to start the diagnosis only when the relay should have completed opening.

[0036] Advantageously and in a non-restrictive manner, during this diagnosis step, the relay is diagnosed as not having opened correctly if, within this predefined duration, the voltage of the voltage bus deviates continuously from the diagnosis voltage by a deviation greater than the defined threshold amplitude for a predefined validation duration. Thus, in order to avoid the case where a transient deviation triggers an erroneous diagnosis, a validation duration is defined. If the duration for which the DC voltage is outside the intended limit is less than this validation duration, it is not considered to be a significant deviation, but if the duration for which the DC voltage is outside the intended limit is greater than or equal to this validation duration, it is considered to be a significant deviation and a relay that has opened incorrectly, or a regulation problem NOK.

[0037] Advantageously and in a non-restrictive manner, the periodic variable component of the setpoint voltage of the DC voltage bus comprises a triangular or trapezoidal component added to the regulated DC voltage. This triangular or trapezoidal component is particularly effective for performing the diagnosis according to the invention.

[0038] In particular, the trapezoidal component allows faster diagnosis and has less impact on the other consumers of the high-voltage bus.

[0039] The invention also relates to a device for diagnosing a hybrid powertrain of a motor vehicle, the hybrid powertrain comprising a first electric machine for driving the motor vehicle, the first electric machine being connected to a DC voltage bus via a first inverter, the voltage of the voltage bus being regulated by a regulating element,

[0040] the hybrid powertrain further comprising a second electric machine able to receive energy produced by an internal combustion engine and to transmit the energy to the DC voltage bus via a second inverter, and a battery connected to the DC voltage bus by a controlled relay for providing a DC voltage to the DC voltage bus, the device comprising:

[0041] means for commanding the regulating element to regulate the DC voltage bus to said diagnostic voltage;

[0042] means for defining the diagnostic voltage as a function of a setpoint voltage of the DC voltage bus and of a periodic variable component;

[0043] means for defining a distance threshold amplitude of the diagnostic voltage;

[0044] means for commanding the regulating element to regulate the DC voltage bus to said diagnostic voltage;

[0045] means for checking whether the voltage of the DC voltage bus follows the diagnostic voltage with a deviation smaller than the defined threshold amplitude over a predefined duration of a sliding window;

[0046] the diagnostic device is designed so that if, over the predefined duration of said sliding window, the voltage of the DC voltage bus follows the diagnostic voltage with a deviation smaller than or equal to the defined threshold amplitude, it is diagnosed that said relay is open; and if, during the predefined duration, the voltage of the voltage bus deviates from the diagnostic voltage with a deviation greater than the defined threshold amplitude, it is diagnosed that said relay is not properly open.

[0047] The invention also relates to a motor vehicle comprising a hybrid powertrain of the motor vehicle, the hybrid powertrain comprising a first electric machine for driving the motor vehicle, the first electric machine being connected to a DC voltage bus via a first inverter, the voltage of the voltage bus being smoothed by a passive damping element, the hybrid powertrain further comprising: a second electric machine able to receive energy produced by an internal combustion engine and to transmit the energy to said DC voltage bus; a second inverter regulating the voltage of said DC voltage bus; and a battery connected to the DC voltage bus by a controlled relay for providing a DC voltage to said DC voltage bus; and a diagnostic device as described above. BRIEF DESCRIPTION OF DRAWINGS

[0048] Other characteristics and advantages of the invention will become apparent on reading the following description of one specific embodiment of the invention, given by way of indication and not of limitation, and on examining the attached drawings in which:

[0049] [ Figure 1 ] is a schematic view of a hybrid powertrain implemented for the invention;

[0050] [ Figure 2 ] is a schematic flowchart of the main embodiment of the invention, in which the checking phase and the diagnostic phase are performed continuously over a sliding window;

[0051] [ Figure 3 ] is a schematic view of a hybrid powertrain implemented for the invention, in which the checking phase and the diagnostic phase are performed continuously over a sliding window;Figure 2 the graph of the variation over time of the diagnostic voltage and of the DC bus voltage during a correct opening period of the relay diagnosed by the method according to

[0052] [ Figure 4 ] is the graph of the variation over time of the diagnostic voltage and of the DC bus voltage during a false opening period of the relay diagnosed by the method according to Figure 2

[0053] [ Figure 5 ] is the graph of the variation over time of the diagnostic voltage and of the DC bus voltage during another false opening period of the relay diagnosed by the method according to Figure 2 DETAILED DESCRIPTION

[0054] With reference to Figure 1 , the motor vehicle comprises a hybrid powertrain 1.

[0055] The powertrain 1 first comprises an internal combustion engine 18, also called thermal engine 18, and two electric machines 10, 16.

[0056] In the hybrid mode of the powertrain 1 implemented in the present application, the first electric machine 10 is linked to an element 11 for driving the motor vehicle.

[0057] This first electric machine 10 is coupled to a first inverter 15 which receives a DC voltage from a DC voltage bus 12.

[0058] The voltage of this DC voltage bus 12 is regulated by a voltage regulating element 13, here an active component called DC capacitor 13.

[0059] The DC voltage bus 12, also abbreviated to DC bus 12, is also connected to the second electric machine 16 through a second inverter 17.

[0060] This second electric machine 16 is itself connected to the thermal engine 18. In this way, the second electric machine 16 is able to convert the energy produced by the thermal engine 18 into a voltage that can be transmitted by the DC bus 12.

[0061] The DC bus 12 is also connected, via a controlled protection relay 19, to a high-voltage battery 14, generally having a voltage of the order of 400 V.

[0062] In addition, the DC bus 12 is connected, by means of a DC-DC converter 8 (abbreviated to DC / DC 8), to the on-board network 9 of the motor vehicle, also called 14 V network. ​​

[0063] According to the series mode architecture thus described, only the first electric machine 10 can move the motor vehicle.

[0064] This first electric machine is powered by the battery 14, or by the electric energy transmitted by the second electric machine, converted from the energy produced by the thermal engine 18.

[0065] However, there are situations in which it is necessary to disconnect the battery from the DC bus 12. By way of example, when the battery 14 malfunctions, it is necessary to disconnect it from the DC bus 12 to ensure that there are no safety risks.

[0066] Therefore, the battery 14 is disconnected by opening the relay 19. When the relay 19 is open, disconnecting the battery 14, the first electric machine 10 is then powered by the electric power supply from the second electric machine 16, converting the energy provided by the thermal engine 18.

[0067] However, if the relay 19 does not open correctly by chance, there is still a risk of damaging the battery 14 or causing a fire in the event of a defect in the battery.

[0068] Therefore, the present invention implements a diagnosis, implemented during the entire activation phase of the series mode, in the event of opening of the relay, in order to check whether the opening of the relay is performed correctly.

[0069] However, a single measurement of the voltage difference between the voltage across the terminals of the battery 14 and the voltage across the terminals of the capacitor 13 of the DC bus 12 is still not sufficient, since these two voltages can be very close, regardless of whether the relay 19 is open or not.

[0070] Therefore, with reference to Figure 2 , a diagnostic method 20 is implemented, which first comprises a step of implementing a command 21 to open the relay 19.

[0071] Advantageously, a waiting step 22 is then performed, during which the method waits for a duration 35 corresponding substantially to the maximum opening time of the relay 19. Therefore, this delay is determined according to the technical specifications of the relay 19 implemented.

[0072] In parallel with the waiting, or according to an equivalent alternative before or after this waiting step 22, a diagnostic setpoint voltage function Vdiag of the DC voltage bus 12 is also defined 23.

[0073] Such a diagnostic voltage time function Vdiag comprises a setpoint voltage Vcons corresponding to the desired voltage on the DC bus 12 and an added variable component.

[0074] The variable component aims to vary the initial setpoint voltage on the DC bus 12 in order to check whether the voltage effectively provided by the second inverter 17 linked to the second electric machine 16 correctly corresponds to the modified setpoint voltage, called diagnostic voltage.

[0075] The diagnostic according to the method 20 is therefore implemented according to the voltage regulation command of the inverter 17.

[0076] In particular, if the regulated voltage V DC There is no convergence towards the setpoint voltage Vcons, which means that the relay 19 is not properly closed. However, as mentioned above, since the setpoint voltage can sometimes be identical to the voltage across the terminals of the battery 14, a single comparison of these two cannot univocally determine whether the relay 19 is closed.

[0077] The variable component of the setpoint voltage therefore aims to vary this setpoint voltage according to several criteria, which are defined in a non-limiting manner in the present embodiment:

[0078] Firstly, the variable component, such as a triangular or trapezoidal component, is defined as having to be compatible with the dynamics of the voltage regulation in order to be able to correctly follow the setpoint and not to cause overshoots / undershoots under nominal conditions. The maximum gradient of the variable component is therefore defined as being less than a threshold value corresponding to the dynamic response capability of the voltage regulation. Furthermore, the minimum gradient of this variable component is defined on the basis of the amplitude distance threshold values 32, 33 and the maximum time allowed for detecting and stopping the series mode before the occurrence of a fire risk.

[0079] Secondly, it is desirable for the period of the variable component to be less than 1 second. This constraint is related to safety requirements, which can vary as a function of the needs. In the example of this implementation, it is desirable to detect an involuntary closure of the relay 19 in less than one second, as a battery safety constraint.

[0080] Furthermore, it is desirable for the variable component to be able to sufficiently deviate in amplitude from the setpoint voltage Vcons in order to encompass the case where the battery voltage is equal to the setpoint voltage. The variable component must therefore be controlled by a determined amplitude value, which is a function of the setpoint value in terms of its definition.

[0081] Finally, it is also necessary for the amplitude of the variable voltage to remain such that the voltage, once added to the setpoint voltage Vcons, is tolerable by the high-voltage equipment connected to the DC bus 12.

[0082] In this respect, in this exemplary embodiment, a triangular curve is defined as Figure 3 shown. However, the application is not limited to a triangular pattern of the periodic variable component. Any type of periodic signal can also be envisaged, such as a sinusoidal signal, a square wave signal or a trapezoidal curve.

[0083] In particular, trapezoidal components are especially suitable because they allow for optimized trade-offs between detection time, ease of implementation, and network outages.

[0084] The procedure also included defining the maximum distance threshold amplitude (ΔVmax) for the diagnostic voltage (Vdiag).

[0085] This distance range is in Figures 3 to 5 The values ​​are shown in the form of amplitude distance threshold functions 32 and 33, corresponding to the same functions as the diagnostic voltage function Vdiag. One is offset by a positive constant, called the positive threshold offset, and the other is offset by a negative constant, called the negative threshold offset, thus forming an envelope around the diagnostic function. The positive and negative threshold offsets here have the same absolute value.

[0086] This invention is not limited to the case where the upper threshold equals the lower threshold. Those skilled in the art can modify this invention so that the positive and negative offsets have different absolute values.

[0087] In other words, these two threshold functions 32 and 33 visually represent the maximum distance amplitude ΔVmax of the diagnostic voltage, constituting the end threshold. Between these end thresholds, the voltage V is adjusted. DC Considered to be following the set point correctly, such as Figure 3 As shown, and beyond the end threshold, as Figure 4 or Figure 5 As shown, the adjusted voltage is considered to no longer follow the diagnostic voltage.

[0088] Once the diagnostic voltage Vdiag is defined and after waiting for step 22 to complete, the command (24) is then executed to adjust the voltage on the DC bus 12 of the second inverter 17 to adjust the voltage on the capacitor 13 of the DC bus 12 to the diagnostic voltage Vdiag.

[0089] Since the diagnostic voltage Vdiag is a variable voltage, the voltage V is adjusted... DC The diagnostic voltage Vdiag curve must be followed throughout the entire diagnostic cycle of 36.

[0090] In this exemplary embodiment, the signal period is less than 1 second. The diagnostics are performed continuously, for example, once every 10 ms.

[0091] During diagnostic cycle 36, or according to an alternative embodiment, after diagnostic cycle 36, inspection step 25 is performed, during which the voltage V of the DC voltage bus during diagnostic cycle 36 is checked. DC Does it still follow the diagnostic voltage Vdiag with a deviation less than the defined threshold amplitude ΔVmax within a sliding window of a predefined duration?

[0092] In particular, the diagnostic period 36 is a predefined duration of a sliding window.

[0093] In other words, the check voltage V DC is maintained within the limits of the two amplitude distance threshold functions 32, 33 during the diagnostic period 36.

[0094] Therefore, if during the diagnostic period 36 the voltage of the DC voltage bus V DC follows the diagnostic voltage Vdiag with a deviation less than or equal to the defined threshold amplitude, the relay is diagnosed as open; and

[0095] Therefore, if during the predefined duration the voltage of the DC voltage bus V DC follows the diagnostic voltage Vdiag with a deviation less than or equal to the defined threshold amplitude, the relay 19 is diagnosed 26 as correctly open. In this case, the operation in series mode can continue.

[0096] Here, the diagnosis is continuously performed as long as the series mode is activated.

[0097] The same method can also perform the diagnosis of correct opening of the relays as soon as they are open, but also detect their unintentional reclosing during the entire operation in series mode.

[0098] On the contrary, if during the predefined diagnostic duration 36 the voltage of the DC voltage bus V DC deviates from the diagnostic voltage Vdiag with a deviation greater than the defined threshold amplitude, as shown in Figure 4 and Figure 5 the relay 19 is diagnosed as not correctly open. Depending on the safety regulations required, an electrical shutdown or a protection measure aimed at correctly isolating the battery 14 is then performed.

[0099] However, according to a particular embodiment of the application, in order to avoid the case where a transient deviation triggers a false diagnosis, a confirmation duration of the diagnosis is defined, for example 250 ms, or a value comprised between 10 ms and 1 second.

[0100] In this way, if the duration of the DC voltage beyond the established limit is less than this confirmation duration, it is not considered a significant deviation, but if the duration of the DC voltage beyond the established limit is greater than or equal to this confirmation duration, it is considered a significant deviation and a relay that is incorrectly open.

[0101] Therefore, this diagnostic method, which is suitable for powertrain, can be applied to any type of three-phase electrical network used in conditioning modes with DC buses having low capacitance, or smart grid networks that can be disconnected from high voltage systems and whose nominal voltage value can vary within a wide operating range.

Claims

1. A method for diagnosing a hybrid powertrain (1) of a motor vehicle, the hybrid powertrain comprising a first electric machine (10) for driving the motor vehicle, connected to a DC voltage bus (12) via a first inverter (15), the voltage of the DC voltage bus being smoothed by a passive damping element, a second electric machine (16) capable of receiving and transmitting to the DC voltage bus (12) the energy produced by an internal combustion engine (18), a second inverter (17) connected between the second electric machine (16) and the DC voltage bus (12) for regulating the voltage of the DC voltage bus (12), and a battery (14) connected to the DC voltage bus (12) by a controlled relay (19) for providing the DC voltage bus (12) with a DC voltage; the motor vehicle comprising a control element for controlling the powertrain (1), the control element being designed to implement the following steps: - commanding (21) the opening of the controlled relay (19) to isolate the battery (14) from the DC voltage bus; - defining a function of a diagnostic voltage Vdiag as a function of a setpoint voltage of the DC voltage bus (12) and of a periodic variable component; - defining (23) a threshold amplitude AVmax of deviation from the diagnostic voltage Vdiag; - commanding (24) the second inverter (17) to regulate the DC voltage bus (12) to the diagnostic voltage Vdiag; - checking (25) whether the voltage of the DC voltage bus follows the diagnostic voltage Vdiag with a deviation less than the defined threshold amplitude AVmax over a predefined duration of a sliding window; - diagnosing (26) the opening of the controlled relay according to the following conditions: o diagnosing the opening of the controlled relay (19) if the voltage of the DC voltage bus follows the diagnostic voltage Vdiag with a deviation less than or equal to the defined threshold amplitude AVmax over the predefined duration of the sliding window; and o diagnosing the incorrect opening of the controlled relay (19) if the voltage of the voltage bus deviates from the diagnostic voltage Vdiag with a deviation greater than the defined threshold amplitude AVmax during the predefined duration of the sliding window. The hybrid powertrain (1) further comprises: After the step of commanding (21) the opening of the controlled relay (19), the step of waiting for a predetermined duration (35) is performed before implementing the step of commanding the second inverter. During the diagnostic step, the incorrect opening of the controlled relay (19) is diagnosed if, over the predefined duration, the voltage of the voltage bus deviates from the diagnostic voltage Vdiag with a deviation greater than the defined threshold amplitude AVmax continuously over a predetermined confirmation duration. The periodic variable component of the diagnostic voltage Vdiag comprises a triangular or trapezoidal component added to the setpoint voltage. ​ ​ ​ ​ ​ ​ ​ ​ 2. The method of claim 1, wherein, ​ 3. The method of claim 1 or 2, wherein, ​ 4. The method of claim 1 or 2, wherein, ​ 5. A device for diagnosing a hybrid powertrain (1) of a motor vehicle, the hybrid powertrain comprising a first electric machine (10) for driving the motor vehicle, the first electric machine being connected to a DC voltage bus (12) via a first inverter (15), the voltage of the voltage bus being smoothed by a passive damping element, The hybrid powertrain (1) further comprises: a second electric machine (16) capable of receiving energy produced by an internal combustion engine (18) and of transmitting the energy to the DC voltage bus (12); a second inverter (17) connected between the second electric machine (16) and the DC voltage bus (12) for regulating the voltage of the DC voltage bus (12); and a battery (14) connected to the DC voltage bus (12) by a controlled relay (19) for providing a DC voltage to the DC voltage bus (12); the device comprising: - means for commanding the opening of the controlled relay (19) to isolate the battery (14) from the DC voltage bus; - means for defining a diagnostic voltage Vdiag as a function of a setpoint voltage of the DC voltage bus (12) and of a periodic variable component; - means for defining a threshold amplitude AVmax of deviation from the diagnostic voltage Vdiag; - means for commanding the second inverter (17) to regulate the DC voltage bus (12) to the diagnostic voltage Vdiag; - means for checking whether the voltage of the DC voltage bus follows the diagnostic voltage Vdiag with a deviation less than the defined threshold amplitude AVmax over a predefined duration of a sliding window; - diagnostic means designed to diagnose the opening of the controlled relay (19) according to the following condition: if, over the predefined duration of the sliding window, the voltage of the DC voltage bus follows the diagnostic voltage Vdiag with a deviation less than or equal to the defined threshold amplitude AVmax, the controlled relay (19) is diagnosed as open; and if, during the predefined duration, the voltage of the voltage bus deviates from the diagnostic voltage Vdiag with a deviation greater than the defined threshold amplitude AVmax, the controlled relay (19) is diagnosed as not properly open.

6. Motor vehicle comprising a hybrid powertrain (1) of the motor vehicle, the hybrid powertrain comprising a first electric machine (10) for driving the motor vehicle, the first electric machine being connected to a DC voltage bus (12) via a first inverter (15), the voltage of the voltage bus being smoothed by a passive damping element (13), the hybrid powertrain (1) further comprising: a second electric machine (16) capable of receiving energy produced by an internal combustion engine (18) and of transmitting the energy to the DC voltage bus (12); a second inverter (17) connected between the second electric machine (16) and the DC voltage bus (12) for regulating the voltage of the DC voltage bus (12); and a battery (14) connected to the DC voltage bus (12) by a controlled relay (19) for providing a DC voltage to the DC voltage bus (12); and the diagnostic device of claim 5.

Images