Method and device for pre-charging the high-voltage network of an electric vehicle.

Abstract

Method and device for precharging the high-voltage network of an electric vehicle. A reversible DC voltage converter for electric vehicles allows the precharging of capacitors in the vehicle's high-voltage network before a vehicle control unit commands the closing of contactors connecting the high-voltage network to a high-voltage source.A criterion relating to the converter's output voltage is evaluated, representing a future significant oscillation around a target voltage. When the criterion is met: - during at least one decreasing phase of the output voltage, the converter switches are deactivated to obtain a substantially linear decreasing variation of the converter's output voltage; - the slope of this decreasing variation is measured; - a time window for reaching the target voltage is estimated from this slope; - information relating to the time window is sent to the control unit, allowing control of the contactors. (See Figure 6 for the abbreviated version.)

Description

Title of the invention: Method and device for precharging the high voltage network of an electric vehicle. technical field

[0001] This description relates to an electric vehicle and a reversible DC voltage converter device intended to be mounted in an electric vehicle between a low voltage source and a high voltage source of the electric vehicle. Background

[0002] Conventionally, the vehicle's low voltage source (typically 12V) is used to power the vehicle's electronic systems, and the high voltage source (typically 400V or 800V) is used to power the vehicle's high voltage electrical network, which essentially includes one or more traction inverters that convert the direct current from the vehicle's high voltage source into alternating current necessary to power the electric traction motor(s) that drive the vehicle's wheels.

[0003] These two low (LV) and high (HV) voltage sources are interconnected by a direct current voltage converter (DC-DC).

[0004] The high voltage source is connected to the DC voltage converter device and to the vehicle's high voltage electrical network via contactors which are controlled by a vehicle control unit.

[0005] For safety reasons, when the vehicle is not moving, the high voltage source must be switched off. When the vehicle starts, the vehicle control unit sends a command to close the contactors to connect the high voltage source to the high-voltage electrical network and thus to the vehicle's traction inverter.

[0006] When the high-voltage source is about to connect to the other electrical components of the vehicle, if this connection is made abruptly while the voltage at the two connection points is not balanced, the current reaching the contactors is high and can create an electric arc or sparks. This electric arc or these sparks can damage the contactors by accelerating their wear. In extreme cases, the contactors can weld themselves shut, preventing any reopening.

[0007] Before closing the contactors, it is therefore necessary to pre-charge the vehicle's high-voltage network. During pre-charging, the capacitors of the high-voltage network (in particular the capacitors of the traction inverter(s)) are slowly charged from the voltage supplied by the low-voltage source up to reaching a value close to the high voltage source reduces the potential difference between the two connection points. At the end of the pre-charge, the current reaching the contactors is almost zero, minimizing the risk of sparking or arcing.

[0008] The DC voltage converter device converts the voltage from the high-voltage source into a voltage suitable for the low-voltage source, for example, to recharge the low-voltage source from the high-voltage source (buck mode). When this DC voltage converter device is reversible, it also allows precharging the vehicle's high-voltage electrical system (boost mode).

[0009] The reversible DC voltage converter device conventionally comprises power semiconductors based on MOSFET or IGBT switches associated with diodes, and a switch control circuit controlled by the vehicle's control unit. The switch configuration at any given time determines the operating mode of the DC voltage converter device.

[0010] A malfunction of one or more capacitors in the vehicle's high-voltage electrical system can affect the pre-charge. However, even when the vehicle's engine is no longer functional, it is important to be able to continue closing the contactors in order to charge the low-voltage source from the high-voltage source and to operate the vehicle's electronic functions such as the warning lights, windows, air conditioning, etc.

[0011] There is therefore a need for a pre-charge solution which allows the contactors to be closed safely in the event of a malfunction of the capacitors in the high voltage network. Summary

[0012] One aspect of this description relates to a method for precharging the high-voltage electrical network of an electric vehicle, comprising a vehicle control unit, a low-voltage source, a high-voltage source, and a reversible DC-voltage converter mounted between the low-voltage source and the high-voltage source. The high-voltage source is connected to the reversible DC-voltage converter and to the vehicle's high-voltage electrical network via contactors controlled by the vehicle control unit. The reversible DC-voltage converter includes, on the high-voltage side, a conversion circuit comprising controlled switches associated with diodes.The pre-charge process makes it possible to obtain, from a voltage available at the terminals of the low voltage source, an output voltage at the terminals of the reversible DC voltage converter on the high voltage side, which is substantially equal to a target voltage available at the . terminals of the high voltage source. It includes a first step to evaluate a criterion relating to the output voltage which is representative of a future significant oscillation around the target voltage, and when the criterion is met, a second step to during at least one falling phase of the output voltage, deactivate the switches to obtain a substantially linear falling variation of the output voltage, measure a slope of said falling variation, estimate from said slope a time window for reaching the target value, send to the vehicle control unit information relating to the estimated time window, allowing control of the contactors.

[0013] Another aspect of this description relates to a reversible DC voltage converter device intended to be mounted between a low voltage source and a high voltage source of an electric vehicle comprising a vehicle control unit and a high-voltage electrical network. The vehicle's high voltage source is connected to said reversible DC voltage converter device and to the vehicle's high-voltage electrical network via contactors controlled by the vehicle control unit. The reversible DC voltage converter device comprises, on the high-voltage side, a conversion circuit including controlled switches associated with diodes.The reversible DC voltage converter device includes pre-charge means enabling it to obtain at its high-voltage terminals an output voltage substantially equal to a target voltage available at the terminals of the high-voltage source, from a voltage available at the terminals of the low-voltage source.The reversible DC voltage converter device also includes pre-charge control means configured to, in a first step, evaluate a criterion relating to the output voltage which is representative of a future significant oscillation around the target voltage, and when the criterion is reached in a second step during at least one falling phase of the output voltage, deactivate the switches to obtain a substantially linear falling variation of the output voltage, measure a slope of said linear falling variation, estimate from said slope a time window for reaching the target voltage, send to the vehicle control unit information relating to the estimated time window, enabling control of the contactors.

[0014] The pre-charge method and the reversible DC voltage converter device do not use a dedicated pre-charge circuit, thus avoiding additional costs. They ensure that even if one or more of the capacitors to be pre-charged malfunction, the contactors are still safely closed, that is, at a point when the output voltage of the reversible converter is substantially equal to the target voltage.

[0015] When a capacitor in the vehicle's high-voltage electrical system malfunctions (for example, when its capacitance is significantly lower than the nominal value for which the circuits were designed), the switch control circuit, particularly the PI regulator, no longer functions correctly. This results in a significant oscillation of the reversible converter's output voltage around the target voltage. Various malfunction criteria can be used that are representative of this future oscillation.

[0016] When such a criterion is met, the switches of the reversible DC voltage converter are deactivated. Instead of continuing to oscillate around the target voltage, the output voltage of the reversible DC voltage converter then begins to decrease in a substantially linear fashion. It is thus possible to calculate the slope of a straight line representing this decrease and to deduce a time window within which the output voltage of the reversible DC voltage converter will reach the target voltage. Information regarding this time window is sent to the vehicle control unit, which can use it to close the contactors safely, that is, at a time when the output voltage of the reversible DC voltage converter has a value substantially equal to the target voltage.

[0017] This avoids damaging the contactors and allows the vehicle control unit to close them safely, thus connecting the high voltage source to the reversible DC voltage converter device, which allows the low voltage source to be charged from the high voltage source and the vehicle's electronic functions to be activated despite the malfunction.

[0018] In an embodiment of the pre-charge method and the reversible DC voltage converter device, evaluating a criterion relating to the output voltage that is representative of a future significant oscillation around the target voltage involves determining that the output voltage reaches a level close to the target voltage in less than a predetermined time, and / or evaluating an overshoot of the output voltage relative to the target voltage and determining that the overshoot is greater than a predetermined overshoot.

[0019] In an embodiment of the pre-charge method and the reversible DC voltage converter device, when the estimated time window is exceeded at the time of sending the information to the vehicle control unit, the information sent includes an indication to prevent the contactors from closing for a sufficient time to allow the output voltage to increase again until a new decay phase and then repeat said second step.

[0020] In one embodiment of the pre-charge method and the reversible DC voltage converter device, the information sent to the vehicle control unit includes a start time indication and an end time or duration indication that depend on the estimated time window.

[0021] In an embodiment of the pre-charge method and the reversible DC voltage converter device, the information sent to the vehicle control unit includes a start time indication and an end time or duration indication that depend on the estimated time window, and when the time window is exceeded at the time of sending the information, the start indication is set so as to be sufficiently far away to fall after the output voltage has risen again to a new decay phase and said second stage has been repeated.

[0022] In one embodiment of the pre-charge process and the reversible DC voltage converter device, the output voltage reaches a level close to the target voltage when it reaches a percentage of approximately 90% of the target voltage.

[0023] Another aspect of this description relates to an electric vehicle comprising a low-voltage source, a high-voltage source, a high-voltage electrical network, and a vehicle control unit. The vehicle also comprises a reversible DC voltage converter as described above, mounted between the low-voltage source and the high-voltage source. The high-voltage source is connected to said reversible DC voltage converter and to the high-voltage electrical network via contactors. The control unit includes means for receiving information from said reversible DC voltage converter regarding a time window during which the output voltage of the reversible DC voltage converter reaches the target value, and means for controlling said contactors based on said information. Brief description of the figures

[0024] Other features and advantages of the invention will become apparent upon reading the detailed description that follows, for an understanding of which reference should be made to the accompanying drawings in which:

[0025] [Fig-1] Figure [Fig.1] is a block diagram of an example of an electric vehicle incorporating a reversible DC-DC voltage converter device.

[0026] [Fig.2] Figure [Fig.2] is a schematic of an example of a converter device reversible DC / DC voltage that can be used in an electric vehicle as shown in figure [Fig.1].

[0027] [Fig.3] Figure [Fig.3] represents a curve of the output voltage of the device reversible voltage converter, during pre-charge, in case of malfunction of one or more capacitors of the high voltage electrical network.

[0028] [Fig.4] Figure [Fig.4] is a diagram illustrating the flow of current in the high voltage half-bridge of the reversible DC voltage converter device, when the output voltage of the device becomes too high relative to the target voltage.

[0029] [Fig.5] Figure [Fig.5] represents the linear variation of the output voltage of the device when the switches of the high-voltage side half-bridge are opened after a certain overshoot has been reached, in case of malfunction of a capacitor in the high-voltage electrical network.

[0030] [Fig.6] Figure [Fig.6] represents an enlarged view of part of the curve of the [Fig.5], on the part corresponding to the linear variation.

[0031] [Fig.7] Figure [Fig.7] is a diagram showing the main steps of a pre-charging process as described here. Detailed description

[0032] Figure 1 shows a diagram of an electric vehicle comprising a reversible DC-DC converter, referenced 10, connected on one side by a two-wire low-voltage bus 11- and 11+ to a low-voltage source 12, and on the other side by a two-wire high-voltage bus 13- and 13+ to a high-voltage source 14 via two contactors 15- and 15+. Wires 11+ and 13+ correspond to high-voltage points, and wires 11- and 13- correspond to low-voltage points. Low-voltage loads 16LV are connected between wires 11- and 11+ of the low-voltage bus. High-voltage loads 16Hv are connected between wires 13- and 13+ of the high-voltage bus. The low-voltage loads 16Lv constitute the vehicle's low-voltage electrical network. They include, for example, a vehicle lighting system, an infotainment system, air conditioning and heating, etc.The 16Hv high-voltage loads constitute the vehicle's high-voltage electrical network. They include one or more traction inverters that convert the direct current from the vehicle's high-voltage source into the alternating current required to power the electric traction motor(s) that drive the vehicle's wheels.

[0033] The device 10 includes power switches (not shown in [Fig.1]) and a referenced control circuit 17 which switches (opens or closes) the power switches in order to control the operation of the device 10.

[0034] The power switch control circuit is connected to a vehicle control unit 18 via a communication network 19 adapted for exchange Data frames, for example, in CAN (Controller Area Network) format. The CAN protocol is well-known and widely used, particularly in the automotive field. Thus, circuit 17, which controls the switches, receives messages from the vehicle control unit 18 to control the switches. It can also transmit information to the vehicle control unit 18, for example, messages relating to the closing of contacts 15- and 15+, as will be seen later in the description.

[0035] In the non-limiting example that will be described, the nominal voltage of the low voltage source is 12V and the nominal voltage of the high voltage source is 400V. The voltage delivered by the high voltage source typically varies between 450V when the high voltage source is fully charged and 250V when it is discharged. The value of the voltage delivered by the high voltage source at any given time is measured by a system integrated into the high voltage source (known as the BMS – Battery Management System). The voltage measurement system of the high voltage source is connected to the communication network 19 so that the measured value can be transmitted to the vehicle control unit 18.

[0036] The reversible DC voltage converter 10 is a bidirectional conversion circuit. Depending on how it is controlled, it can either lower the voltage (buck mode) to obtain a low voltage (typically 12V) from the current of the high voltage source (typically 400V), or raise the voltage (boost mode) to obtain a high voltage (typically 400V) from the current of the low voltage source (typically 12V). The boost mode allows the capacitors of the high-voltage electrical network to be pre-charged before the contactors 15- and 15+ are closed.

[0037] Figure [Fig. 2] shows a classic example of a reversible DC-DC voltage converter device that can be used in an electric vehicle as shown in [Fig. 1]. This example is not limiting. Other variations of bridge or half-bridge structures can be used. For example, it is possible to use several structures of the type described below in series or in parallel.

[0038] The reversible DC voltage converter device shown in [Fig.2] comprises a half-bridge 21 on the high voltage side, mounted between the low voltage point 13- and the high voltage point 13+, a transformer 22 providing galvanic isolation between the low voltage network and the high voltage network, a bridge 23 on the low voltage side, mounted between the low voltage point 11- and a first terminal of a coil 25, in parallel with a passive damper 26 and an active damper 27, the second terminal of the coil 25 being connected to the high voltage point 11+.

[0039] The half-bridge 21 includes a high switch Al in series with a low switch Bl. The switches shown as examples in [Fig. 2] are MOSFET transistors. The source of the high transistor Al is connected to the drain of the low transistor B1 at a midpoint M1, which is connected to the terminal 221 of the high-voltage winding of the transformer 22 that acts as the current input terminal in boost mode. The other terminal 222 of the high-voltage winding of the transformer 22 is connected via a high capacitor CAi to the high voltage point 13+ and via a low capacitor CBi to the low voltage point 13-. The high transistor Al is connected in parallel with a diode DAi oriented so as to block current when the high transistor Al is not conducting, thus preventing any unwanted power transfer from the high-voltage network to the low-voltage network.The low-level transistor Bl is connected in parallel with a diode DBi oriented so as to block current when the low-level transistor B1 is conducting.

[0040] The bridge 23 comprises four transistors arranged in two pairs, each pair forming a half-bridge, similar in structure to the half-bridge 21, mounted between the high voltage point 11+ and the low voltage point 11-. The midpoint M2 between the transistors of pair E1H and FIL is connected to the terminal of the low-voltage winding 223 of the transformer 22 that acts as the current output terminal in boost mode. The midpoint M3 between the transistors of pair F1H and E1L is connected to the other terminal 224 of the high-voltage winding 22.

[0041] The purpose of the pre-charge phase is to bring the output voltage of the high-voltage reversible DC-voltage converter to a value substantially equal to the target voltage available at the terminals of the high-voltage source before closing the contactors 15+ and 15-. As explained above, the value of this target voltage depends on the state of charge of the high-voltage source 14 and is known to the vehicle control unit 18.

[0042] During the pre-charge phase, the device 10 operates in voltage boost mode. The bridge transistors 23 are initially closed. The low voltage (12V) supplied by the low voltage source 12 is then chopped by the bridge 23. When the coil 25 is charged, the bridge transistors 23 are opened. Current then flows through the transformer 22 from the low-voltage network to the high-voltage network. This increases the output voltage of the device, since the vehicle's high-voltage electrical network is not connected to the high voltage source 14, and therefore none of the high-voltage loads 16Hv are consuming power. The control circuit 17 includes a PI (Proportional-Integral) regulator that provides a signal representing the correction required to approach the target voltage. This signal is used by the control circuit 17 to control the switches of the half-bridge 21 and thus control the increase in the output voltage of device 10 and stabilize it around the target voltage. The control circuit 17 then sends a CAN-format message to the vehicle's control unit to inform it and allow it to close the contacts 15+ and 15-.

[0043] The PI controller has fixed parameters that are calibrated to operate in a system whose components have a specific nominal value. In the event of component malfunction, the operation of the PI controller is often disrupted. For example, if a capacitor in the high-voltage power grid is broken or has a value significantly lower than expected, the parameters of the PI controller are no longer suitable, and the PI controller no longer performs its function of stabilizing the output voltage of device 10 around the target voltage. The output voltage of device 10 then tends to exceed the target voltage and subsequently oscillate significantly around the target voltage. For example, for a target voltage of 400V, the oscillation could be ±18V. It is then no longer possible to close the contactors 15+ and 15- safely.

[0044] Figure [Fig. 3] illustrates how such a malfunction can affect the pre-charge. In Figure [Fig. 3], the y-axis indicates the output voltage of device 10 and the x-axis indicates time. It can be observed that the output voltage of device 10 oscillates around the target value HVT along a curve 30 between a maximum value HVmax and a minimum value HVmin.

[0045] It is proposed to control the pre-charge phase differently in the event of a malfunction so as to be able to predict when and for how long the output voltage of device 10 will be sufficiently close to the target voltage. The control circuit 17 can then send the prediction to the vehicle control unit 18, which can use it to close the contactors at the appropriate time and thus allow operation in degraded mode, with access to the vehicle's electronic functions even when the vehicle's engine is no longer running.

[0046] In a first step, the malfunction is detected by evaluating a criterion relating to the output voltage that is representative of the malfunction and thus of a future significant oscillation around the target voltage. For example, it is possible to determine that the output voltage of the device 10 reaches a level close to the target voltage in less than a predetermined time. Alternatively, or in addition, it is also possible to evaluate an overshoot of the output voltage relative to the target voltage and determine that the overshoot is greater than a predetermined overshoot.

[0047] For example, the time required to reach x% of the target voltage (e.g., 90%) is measured. When the measured time is short compared to normal, this indicates that one or more capacities of the high-voltage electrical network are missing or defective components. A second indicator can be used to further confirm whether or not there is a malfunction. For example, the overshoot (i.e., the maximum value HVmax on [Fig. 3]) can be measured and compared to a threshold called the anomaly threshold. Beyond a certain overshoot, the malfunction is confirmed. For example, when the target voltage is 400V, an overshoot of 3V will be considered normal, while an overshoot of 10V will indicate an anomaly.

[0048] The anomaly threshold is compared, for example, and is determined offline during device development. It can be determined by performing different preloads across a full range of target voltage values. For each target voltage value, the maximum measured overshoot is stored in a value map. The anomaly threshold is obtained, for example, by adding a constant offset to the value stored in the value map.

[0049] In a second step, after confirmation of the malfunction, the switches of the half-bridge 21 are deactivated (i.e., opened). The effect of deactivating the transistors of the half-bridge 21 will be explained with reference to [Fig. 4].

[0050] Figure [Fig. 4] illustrates the current flow in the half-bridge 21 when the output voltage of the reversible DC-current converter 10 becomes too high relative to the target voltage. When the upper transistor Al is closed, the current flows through the upper transistor Al and then into the high-voltage winding of the transformer 22 via the terminal connected to the midpoint M1 (solid arrow in [Fig. 4]). The output voltage of the device 10 on the high-voltage side then drops rapidly. If the upper transistor Al is controlled to be open, the current from the high-voltage source 14 can no longer flow through the upper transistor Al2, nor can it flow through diode DAi (dashed arrows). Due to losses in the circuit, the output voltage of the device 10 on the high-voltage side then drops slowly with a nearly linear variation.

[0051] Thus, by deactivating the switches of the half-bridge 21 during the decay phase of the output voltage, a substantially linear decay of the output voltage can be generated. This result is illustrated in [Fig. 5], which reproduces [Fig. 3], but on which the linear decay 50 of the output voltage of the device 10 from the maximum value HVmax is shown in dashed lines, when the switches of the half-bridge 21 are controlled to be opened following the detection of the malfunction.

[0052] It is then possible to measure a slope of the decreasing variation, to estimate from the slope a time window for reaching the target HVT voltage (for example n = +1V around the target HVT voltage), to send to the vehicle control unit 18 information relating to the estimated time window for closing the contactors. The time window therefore corresponds to a close proximity to the target voltage.

[0053] Such a time window is shown in Figure [Fig. 6]. The information sent to the vehicle's control unit 18 includes, for example, a start time indication Ts and an end time indication Te or duration Td for the estimated time window W. In [Fig. 6], the area Z corresponds to the time interval after the end of the time window W and before the output voltage of the device 10 rises again, under the effect of the regulator PL. During this time interval Z, it is too late to close the contactors.

[0054] For example, the output voltage value HV of device 10 is acquired every 1 ms. The last 20 measured values ​​are stored in a rolling buffer. A gradient G is calculated every 10 ms after the maximum overshoot HVmax is reached. The last 10 gradients are stored to ensure accurate detection of the quasi-linear variation of the output voltage of device 10.

[0055] For example, the gradient G; is calculated as follows:

[0056] G; = (HVi+io-HVi) / 10 with HVi=HVmax. Since the decay is approximately linear, the value of the gradient is approximately constant.

[0057] The time indications of start Ts, end Te, and duration Td can be calculated as follows:

[0058] Ts = (HVmax - HVt + n) / G;

[0059] Te = (HVmax - HVt - n) / Q

[0060] Td = Te - Ts

[0061] where G; is the last value of the gradient available at the time of calculation.

[0062] If, as in the example mentioned above, the value of the output voltage HV of device 10 is acquired every 1 ms, then the first value of the gradient Gi is available 1 ms after the maximum value HVmax has been reached. In one embodiment, the gradient is expected to stabilize before estimating the time window.

[0063] The estimation of the time window W may be late, for example because of gradient instability due to noise impacting the measurements.

[0064] When the time window W is exceeded at the time the information is sent to the vehicle control unit, the information sent includes an indication to prevent the contactors from closing for a sufficient duration to allow the output voltage to rise again until a new decay phase begins. During this phase, new information relating to a new window W' will be sent to the vehicle control unit to enable it to close the contactors in the new window W'. For example, the start time indication Te of window W is set to a high value, for example 10s.

[0065] If the time window is in progress at the time of sending the information to the vehicle control unit, the start time indication Te of the window W is set to zero.

[0066] Fig. 7 is a flowchart that summarizes the steps of a pre-charging process for a high-voltage electrical network of an electric vehicle as described above.

[0067] In step 710, the device 10 receives a pre-charge instruction from the vehicle control unit and starts a pre-charge phase. During pre-charge, a measurement of the current output voltage HVact of the device 10 is taken every 1 ms and stored in the rolling buffer, as shown in 720. In 730, a timer is started. In 740, the current output voltage HVact is compared to a level close to the target voltage HVT, for example, 90%. When the current output voltage HVact reaches 90% of the target voltage HVT, if the time indicated by the timer is short (branch C in [Fig. 7]) compared to a reference value, the system expects the voltage to approach the maximum overshoot HVmax. To this end, in 750, the current voltage HVact is compared to the fault threshold given by the value chart. When the anomaly threshold is reached, in 760 the high-voltage side transistors are switched off.Advantageously, when the 90% level of the target voltage HVT is reached very quickly compared to the reference value (TC branch in [Fig. 7]), step 750 is not implemented: step 760, which opens the switches, is then executed directly. In step 770, concurrently with the opening of the switches, the gradient calculation is initiated. When the gradient stabilizes (S branch in [Fig. 7]), the time window W is estimated in step 780. The gradient calculation continues in step 770 as long as the gradient is not stabilized (NS branch in [Fig. 7]). For example, start time Ts and end time Te are calculated assuming that the decay of the output voltage HVact is quasi-linear.

[0068] If the start and end indications Ts and Te are available before the start of the time window W, in 790 the control circuit 17 sends a CAN frame to the control unit 18 indicating that the contactors must be closed and giving the values ​​obtained for the start and end indications Ts and Te of the time window during which their closure must be commanded.

[0069] If the start and end indications Ts and Te are available during the time window W, in 792 the control circuit 17 sends a CAN frame to the control unit 18 indicating that the contactors must be closed, giving a zero value as the start time indication Te, and giving the calculated value as the end indication Ts of the time window for closing the contactors.

[0070] If the start and end indications Ts and Te are available after the time window W, in 794 the control circuit 17 sends a CAN frame to the unit of control 18 by indicating that the contactors must be closed and by giving a very high value as an indication of the start Te of the time window so that the control unit does not trigger the closing of the contactors before a new window W' has been estimated and the corresponding information has been sent by the control circuit 17.

[0071] Other implementation variants can be used. For example, instead of transmitting a start and end indication of the time window, it is possible to transmit a start indication and a duration indication.

[0072] The functional diagrams presented here represent conceptual views given by way of non-limiting example to illustrate the principles of this disclosure. These principles can be implemented in devices with multiple variations. In particular, the structure of the reversible DC voltage converter device is not necessarily that described by way of example in [Fig. 2]. As will be apparent to a person skilled in the art, many structural variations can be used without impacting the implementation of the method described in this application.

[0073] The terminology used here is solely for the purpose of describing particular embodiments and is not limiting.

[0074] In particular, the terms "includes", "comprising", "includes" and / or "including", specify the presence of given characteristics, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other characteristics, steps, operations, elements, components.

[0075] Furthermore, when an element is described as being "connected", "coupled", or "linked" to another element, it may be directly connected, coupled, or linked to the other element, or intermediate elements may be present. Other terms used to describe the relationship between two elements should be interpreted in the same way.

Claims

1. Demands A method for precharging a high-voltage electrical network of an electric vehicle comprising a vehicle control unit (18), a low-voltage source (12), a high-voltage source (14), and a reversible DC voltage converter (10) mounted between the low-voltage source and the high-voltage source, the high-voltage source being connected to the reversible DC voltage converter and to the vehicle's high-voltage electrical network via contactors (15-, 15+) controlled by the vehicle control unit, said reversible DC voltage converter having, on the high-voltage side, a conversion circuit comprising controlled switches (A1, B1) associated with diodes (DA1, DB1), said high-voltage electrical network comprising at least one capacitor (CA1, CB1), said precharging method enabling the vehicle to obtain, from a voltage available at the terminals of the low-voltage source,an output voltage across the terminals of the reversible DC voltage converter on the high-voltage side, which is substantially equal to a target voltage available across the terminals of the high-voltage source, characterized in that the method comprises a first step for detecting a malfunction of a capacitor (CAi, CBi), said malfunction generating a significant oscillation of the output voltage of the reversible converter around the target voltage, the malfunction is detected by evaluating at least one of the following criteria relating to the output voltage: - determine that the output voltage reaches a predefined percentage of the target voltage in less than a predetermined time (730, 740), and / or - evaluate an overshoot of the output voltage relative to the target voltage and determine that the overshoot is greater than a predetermined overshoot (750), And when a malfunction is detected, the process includes a second step to: - during at least one decreasing phase of the output voltage, deactivate the switches (760) to obtain a substantially linear decreasing variation of the output voltage, - measure a slope of said decreasing variation (770), - estimate from said slope a time window for reaching the target voltage (780), - send to the vehicle control unit information relating to the estimated time window, allowing control of the contactors (790).

2. 2. Pre-charge method according to the preceding claim, characterized in that when the estimated time window is exceeded at the time of sending the information to the vehicle control unit (794), the information sent includes an indication allowing the contactors to not close for a sufficient time to allow the output voltage to rise again until a new decay phase and then repeat said second step.

3. 3. A pre-charge method according to claim 1, characterized in that the information sent to the vehicle control unit includes a start time indication and an end time or duration indication which depend on the estimated time window, and when the time window is exceeded at the time of sending the information (794), the start indication is fixed so as to be sufficiently far away to fail after the output voltage has risen again to a new decay phase and said second stage has been repeated.

4. 4. A pre-charge method according to any one of claims 1 to 3, characterized in that the output voltage reaches a predefined percentage of the target voltage when it reaches a percentage of the order of 90% of the target voltage.

5. 5. A reversible DC voltage converter device for mounting between a low voltage source (12) and a high voltage source (14) of an electric vehicle comprising a vehicle control unit (18) and a high-voltage electrical network, said high-voltage electrical network comprising at least one capacitor (CAb CB i), the high voltage source being connected to said device and to the vehicle's high-voltage electrical network via contactors (15-, 15+) controlled by the vehicle control unit (18), said device comprising, on the high-voltage side, a conversion circuit (10) comprising controlled switches (A1, B1) associated with diodes (DAi, DBi), said device comprising pre-charge means for obtaining at its high-voltage terminals, an output voltage substantially equal to a target voltage available at the terminals of the high-voltage source, from a voltage available at the terminals of the low-voltage source, characterized in that it comprises pre-charge control means configured to, in a first stage, detect a malfunction of a capacitor (CAi, CBi), said malfunction generating a significant oscillation of the output voltage of the reversible converter around the target voltage, the malfunction is detected by evaluating at least one of the following criteria relating to the output voltage: - determining that the output voltage reaches a predefined percentage of the target voltage in less than a predetermined time, and / or - evaluating an overshoot of the output voltage relative to the target voltage and determining that the overshoot is greater than a predetermined overshoot, and when a malfunction is detected,The method includes a second step to: - during at least one decreasing phase of the output voltage, deactivate the switches to obtain a substantially linear decreasing variation of the output voltage, - measure a slope of said linear decreasing variation, - estimate from said slope a time window for reaching the target voltage, - send to the vehicle control unit information relating to the estimated time window, allowing control of the contactors.

6. 6. Device according to the preceding claim, characterized in that when the time window is exceeded at the time of sending the information to the vehicle control unit, the information includes an indication allowing the contactors to be prevented from closing for a sufficient time to allow the output voltage to rise again until a new decay phase and then repeat said second step.

7. 7. Device according to claim 5, characterized in that the information sent to the vehicle control unit includes a start time indication and an end time or duration indication which depend on the estimated time window.

8. 8. Device according to claim 7, characterized in that when the time window is exceeded at the time of sending the command, the start indication is set so as to be sufficiently far away to fail after the output voltage has risen again to a new decay phase and said second stage has been repeated.

9. 9. Device according to any one of claims 5 to 8, characterized in that the output voltage reaches a predefined percentage of the target voltage when it reaches a percentage of the order of 90% of the target voltage.

10. 10. Electric vehicle comprising a low voltage source (12), a high voltage source (14), a high voltage electrical network, and a vehicle control unit (18), characterized in that it comprises a reversible voltage converter device (10) according to any one of claims 5 to 9, mounted between the low voltage source and the high voltage source, the high voltage source being connected to said device and to the high voltage electrical network via contactors (15-, 15+), the control unit (18) comprising means for receiving said device information relating to a time window during which the output voltage of the reversible voltage converter device reaches the target value, and means for controlling said contactors as a function of said information.

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