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EP-4259472-B1 - METHOD FOR DISCHARGING A FUEL-CELL STACK FOR SUPPLYING POWER TO A TRACTION ELECTRIC MACHINE OF A MOTOR VEHICLE

EP4259472B1EP 4259472 B1EP4259472 B1EP 4259472B1EP-4259472-B1

Inventors

  • GERARD, DAVID
  • LOUDOT, SERGE

Dates

Publication Date
20260513
Application Date
20211207

Claims (5)

  1. Method for discharging the electrical circuit (10) of a motor vehicle comprising at least one electric traction machine (16) of the vehicle equipped with: - an electrical power supply network (22) comprising: -- a high-voltage battery (24), -- a range extender system (28) comprising a hydrogen fuel cell (30) that is associated with a DC-DC voltage converter (32) itself comprising a filtering inductor (60) traversed by a current (61) of the filtering inductor (60), a primary filtering capacitor (56) that is at the voltage (40) of the hydrogen fuel cell (30), and a secondary filtering capacitor (58) that is at the output voltage (41) of the DC-DC voltage converter (32), - a high-voltage consumption network (12), powered by the electrical power supply network (22), comprising the at least one electric traction machine (16) of the motor vehicle associated with an inverter (14) and ancillary equipment (20), - and a control module (48), the discharging method comprising the successive steps of: - (E0) stopping the motor vehicle, - (E1) electrically disconnecting the high-voltage battery (24) from the high-voltage consumption network (12), - (E2) interrupting the hydrogen supply of the hydrogen fuel cell (30), and - (E3) discharging the energy of the electrical circuit (10) into the stator winding of the electric traction machine (16), wherein the step (E3) of discharging the energy of the electrical circuit (10) is carried out by controlling the DC-DC voltage converter (32) by means of the control module (48), characterized in that the step (E0) of stopping the vehicle corresponds to the voluntary stopping of the motor vehicle, in that the step (E3) of discharging the energy of the electrical circuit (10) comprises the following successive sub-steps: - (E4) discharging the energy produced by consuming the residual hydrogen contained in the hydrogen fuel cell (30) by means of the DC-DC voltage converter (32) by controlling a discharging current (43) by means of the control module (48) until a predetermined voltage threshold value (40) of the hydrogen fuel cell (30) is reached, - (E5) electrically disconnecting the range extender system (28) from the high-voltage consumption network (12), - (E6) discharging the energy from the capacitors of the high-voltage consumption network (12) into the stator of the electric traction machine (16) by means of the inverter (14), and in that the step (E3) of discharging the energy of the electrical circuit (10) comprises a sub-step (E7), which is carried out at the same time as the sub-steps (E5) to (E6), of discharging the energy of the primary (56) and secondary (58) filtering capacitors of the DC-DC voltage converter (32) by controlling the current (61) of the filtering inductor (60) by means of the control module (48).
  2. Method for discharging the electrical circuit (10) of a motor vehicle comprising at least one electric traction machine (16) of the vehicle equipped with: - an electrical power supply network (22) comprising: -- a high-voltage battery (24), -- a range extender system (28) comprising a hydrogen fuel cell (30) that is associated with a DC-DC voltage converter (32) itself comprising a filtering inductor (60) traversed by a current (61) of the filtering inductor (60), a primary filtering capacitor (56) that is at the voltage (40) of the hydrogen fuel cell (30), and a secondary filtering capacitor (58) that is at the output voltage (41) of the DC-DC voltage converter (32), - a high-voltage consumption network (12), powered by the electrical power supply network (22), comprising the at least one electric traction machine (16) of the motor vehicle associated with an inverter (14) and ancillary equipment (20), - and a control module (48), the discharging method comprising the successive steps of: - (E0) stopping the motor vehicle, - (E1) electrically disconnecting the high-voltage battery (24) from the high-voltage consumption network (12), - (E2) interrupting the hydrogen supply of the hydrogen fuel cell (30), and - (E3) discharging the energy of the electrical circuit (10) into the stator winding of the electric traction machine (16), wherein the step (E3) of discharging the energy of the electrical circuit (10) is carried out by controlling the DC-DC voltage converter (32) by means of the control module (48), characterized in that the step (E0) of stopping the vehicle corresponds to an emergency stop of the motor vehicle, in that the method for discharging the electrical circuit (10) comprises a step (E1') of electrically disconnecting the range extender system (28) from the high-voltage network (12) that is carried out simultaneously with the step (E1) of electrically disconnecting the high-voltage battery (24) from the high-voltage consumption network (12), in that step (E3) of discharging the energy of the electrical circuit (10) comprises the following sub-steps: - (E4') discharging the energy of the capacitors of the high-voltage consumption network (12) into the stator of the electric traction machine (16) by means of the inverter (14), - and in that the step (E3) of discharging the energy of the electrical circuit (10) comprises a sub-step (E5'), which is carried out at the same time as the sub-step (E4'), of discharging the residual hydrogen contained in the hydrogen fuel cell (30) and of discharging the energy of the primary (56) and secondary (58) filtering capacitors of the DC-DC voltage converter (32) by controlling the current (61) of the filtering inductor (60) by means of the control module (48).
  3. Method for discharging the electrical circuit (10) of a motor vehicle according to one of Claims 1 and 2, characterized in that the process for controlling the current (61) of the filtering inductor (60) by means of the control module (48) is configured to reach a low value of the voltage (40) of the hydrogen fuel cell (30) by means of a series of n self-discharging cycles (68) of the primary (56) and secondary (58) filtering capacitors of the range extender system (28).
  4. Method for discharging the electrical circuit (10) of a motor vehicle according to Claim 3, characterized in that each self-discharging cycle (68) of the primary (56) and secondary (58) filtering capacitors of the range extender system (28) comprises: - a step (E8) of controlling the DC-DC voltage converter (32) of the range extender system (28) by means of the control module (48) of the DC-DC voltage converter (32) in order to obtain a positive value of the current (61) of the filtering inductor (60), with the positive value of the current (61) of the filtering inductor (60) supplied by the primary filtering capacitor (56) to the secondary filtering capacitor (58) causing (E9): -- a reduction of the value of the voltage (40) of the hydrogen fuel cell (30), and -- an increase of the value of the output voltage (41) of the DC-DC voltage converter (32); and - a step (E10) of controlling the DC-DC voltage converter (32) of the range extender system (28) by means of the control module (48) in order to obtain a negative value of the current (61) of the filtering inductor (60), with the negative value of the current (61) of the filtering inductor (60) supplied by the secondary filtering capacitor (58) to the primary filtering capacitor (56) causing (E11): -- a reduction of the value of the output voltage (41) of the DC-DC voltage converter (32), and -- an increase of the value of the voltage (40) of the primary filtering capacitor (56).
  5. Method for discharging the electrical circuit (10) of a motor vehicle according to Claim 4, characterized in that the process for controlling the current (61) of the filtering inductor (60) by means of the control module (48) is configured so that the value of the voltage (40) of the hydrogen fuel cell (30) at the end of a cycle of n+1 self-discharging cycles (68) is less than the value of the voltage (40) of the hydrogen fuel cell (30) at the end of the cycle of n self-discharging cycles (68).

Description

Technical field of the invention The present invention relates to the field of hydrogen fuel cells. The invention relates more particularly to a method of discharging a fuel cell following an interruption, voluntary or emergency, of the hydrogen supply to the fuel cell. Technical background Hydrogen fuel cells are used as a source of electrical power in many applications, particularly in the field of transportation. Some so-called "electric" motor vehicles are equipped with a fuel cell used in combination with a high-voltage battery to power, in particular, the electric drive system of the motor vehicle comprising at least one electric traction machine. More specifically, fuel cell motor vehicles are powered by electricity resulting from an electrochemical reaction between hydrogen, which is for example stored in a tank, and oxygen from the air. In such an architecture, the high-voltage battery constitutes the primary power source, and the hydrogen fuel cell serves as the secondary or auxiliary power source. The fuel cell is therefore part of a so-called "range extender" system, which is designed and engineered to extend the range of the high-voltage battery. This architecture constitutes a multi-energy platform and allows for the integration of a compact high-voltage battery. Indeed, the high-voltage battery is sized to ensure normal vehicle use, while the auxiliary energy source is configured to handle exceptional vehicle uses, such as during very long journeys. This architecture, called multi-energy, is advantageous for utility-type motor vehicles with at least partial electric propulsion because there is a compromise between vehicle range, transportable mass and available volume. There are also motor vehicles whose architecture consists of a high-power hydrogen fuel cell designed to directly power the electric motor vehicle's drivetrain. In general, the interruption of the fuel supply to a hydrogen fuel cell, i.e. hydrogen, can be caused by the stopping of the vehicle's ignition, this is referred to as a voluntary or classic stop, or following any malfunction of the vehicle or during an accident, and this is referred to as an emergency stop. Following the interruption of the fuel cell supply, constituting a voluntary or emergency shutdown, the hydrogen flow rate decreases and then reaches a zero value, the volume of residual hydrogen contained inside the fuel cell being then very low. However, residual hydrogen capable of producing residual energy from the fuel cell is present within the volume of the fuel cell stack, which is formed by a stack of electrochemical cells. This residual energy must be completely consumed to reach zero voltage in the fuel cell and thus ensure the safety of the fuel cell system, and the vehicle in general. In the state of the art, there are systems designed to discharge the residual energy of the fuel cell until a zero value of the fuel cell voltage is obtained. However, the function of discharging residual energy within the fuel cell is generally performed by one or more mechanical or electronic switches associated with one or more dissipative elements such as resistors or varistors. These additional components dedicated to discharge are typically electrically connected in parallel with the fuel cell. For example, the document US5105142 This describes a fuel cell discharge system using multiple switches and resistors connected electrically in parallel. The successive parallel connection of resistors allows for control of the fuel cell's load impedance, thus enabling control of the fuel cell discharge based on the mass and pressure of residual hydrogen. The drawback of this solution is the size required by the numerous resistors and electromechanical relays. Furthermore, this principle is primarily suited to stationary applications. Each of the documents US2019379070 And WO2020020524 proposes a discharge system composed of electromechanical relays associated with a resistor and electrically connected in parallel with the fuel cell. However, these different fuel cell discharge systems have certain drawbacks. First, the components responsible for the discharge function—that is, the combination of switches and dissipative elements—are dedicated solely to this purpose. Any failure of these components can cause a complete failure of the fuel cell system due to their parallel electrical connection to the fuel cell, resulting in high repair costs. The invention proposes in particular to remedy the aforementioned drawbacks and to offer a method of discharging residual energy inside the fuel cell ensured by a reduced number of components and a reduced size. Summary of the invention The invention proposes a method for discharging the electrical circuit of a motor vehicle comprising at least one electric traction machine of the vehicle equipped: of an electrical power supply network comprising: -- a high-voltage battery, -- a range extender system comprising a hydrogen fuel cell which