Search

EP-4740299-A1 - METHOD FOR OPTIMISING THE ELECTRICAL DRIVE CHAIN OF AN AIRCRAFT FUEL PUMP POWERED BY A HIGH-VOLTAGE NETWORK AND ASSOCIATED ELECTRICAL DRIVE CHAIN

EP4740299A1EP 4740299 A1EP4740299 A1EP 4740299A1EP-4740299-A1

Abstract

The invention relates to a method for controlling an electrical drive chain (1) of an aircraft fuel pump, the method comprising receiving (202) a pair of speed and mechanical torque setpoints for the electric motor (2), receiving (204) a maximum voltage setpoint delivered by a DC high-voltage source (3), calculating (206) the minimum voltage required at the input of the electrical inverter (5) for the setpoint torque, calculating (208) the losses in the electrical drive chain (1) for a range of voltages between the minimum voltage and a maximum voltage corresponding to, at most, the maximum voltage setpoint, selecting (210) an optimal voltage to be applied at the input of the electrical inverter (5), the optimal voltage corresponding to the voltage for which the losses in the electrical drive chain (1) are the lowest, and calculating (212) the duty cycle to be applied to the step-down converter (6) on the basis of the selected optimal voltage.

Inventors

  • AMEZIANI, MENOUAR
  • MASSON, BRUNO
  • BOTTAN, Jean-François

Assignees

  • Safran Aerosystems

Dates

Publication Date
20260513
Application Date
20240702

Claims (11)

  1. [Claim 1] A method of controlling an electric drive chain (1) of a fuel pump of an aircraft, the electric drive chain (1) comprising a three-phase electric motor (2), a high DC voltage source (3), and a converter assembly (4) electrically connected between the input of the three-phase electric motor (2) and the high DC voltage source (3) and comprising an electric inverter (5) and a step-down converter (6), the control method comprising: - a reception (202) of a pair of instructions relating to the speed and mechanical torque desired for the operation of the electric motor (2), - a reception (204) of a maximum DC voltage instruction delivered by the DC high voltage source (3) at the input of the converter assembly (4), - a calculation (206) of the minimum voltage required at the input of the electric inverter (5) for the operation of the electric motor (2) at said pair of speed and mechanical torque settings, - a calculation (208) of the losses of the electric drive chain (1) for a voltage range between said calculated minimum voltage and a maximum voltage corresponding at most to said maximum continuous voltage setpoint, - a selection (210) of an optimal voltage to be applied at the input of the electric inverter (5), the optimal voltage being selected in said voltage range and corresponding to the voltage for which the losses of the electric drive chain (1) are the lowest, - a calculation (212) of the duty cycle to be applied to the voltage step-down converter (6) from the ratio between the value of the selected optimum voltage and the value of the high DC voltage delivered by the high DC voltage source (3), and - a control (214) of the voltage step-down converter (6) from the calculated duty cycle.
  2. [Claim 2] A control method according to claim 1, wherein the maximum voltage of the voltage range is less than a voltage threshold at which partial discharges occur, said voltage threshold (V PD ) varying as a function of the altitude of the aircraft.
  3. [Claim 3] Method according to claim 2, in which said voltage threshold (V PD ) from which partial discharges can occur is calculated during operation of the electric drive chain (1) as a function in particular of the altitude at which the aircraft is located, and of an aging factor of the electric drive chain (1).
  4. [Claim 4] Method according to claim 2, in which said voltage threshold (V PD ) from which partial discharges can occur is determined from the signals delivered by a partial discharge sensor mounted on said electric drive chain (1).
  5. [Claim 5] Control method according to one of claims 2 or 3, further comprising a determination (218) of the altitude of the aircraft, a comparison of the measured altitude with a low altitude threshold, and a bypass of the voltage step-down converter (6) when the measured altitude is lower than the low altitude threshold.
  6. [Claim 6] Control method according to claim 4, in which the determination of the altitude of the aircraft is carried out from a pressure measurement of the environment in which the aircraft is located.
  7. [Claim 7] An electric drive chain (1) for a fuel pump of an aircraft, the electric drive chain (1) comprising a three-phase electric motor (2), a high DC voltage source (3), and a converter assembly (4, 40) electrically connected between the input of the electric motor (2) and the high DC voltage source (3), and an electronic control unit (10) controlling the converter assembly (4, 40), the converter assembly (4) comprising an electric inverter (5) and a voltage step-down converter (6), characterized in that the electronic control unit (10) is configured to select the optimum voltage to be applied to the input of the electric inverter (5) and to control the voltage step-down converter (6) with a duty cycle equal to the ratio between the value of the optimum voltage to be applied and the value of the high DC voltage delivered by the high DC voltage source (3), the optimum voltage being selected in a voltage range between a minimum voltage required at the input of the electric inverter for the operation of the electric motor (2) at said pair of speed and mechanical torque setpoints and a maximum voltage corresponding at most to said maximum DC voltage setpoint, and the selected optimum voltage corresponding to the voltage in said voltage range for which the losses of the electric drive chain (1) are the lowest.
  8. [Claim 8] An electric drive chain (1) according to claim 7, wherein the voltage step-down converter (6) is connected between the high DC voltage source (3) and the electric inverter (5).
  9. [Claim 9] An electric drive chain (1) according to claim 8, the converter assembly further comprising a filter (8) electrically connected between the electric inverter (5) and the electric motor (2).
  10. [Claim 10] An electric drive chain (1) according to claim 7, wherein the voltage step-down converter is integrated into the inverter, the converter assembly (40) comprising three electrical branches (41) each coupled to a phase of the electric motor (2), each branch (41) comprising an inductance (44) and a capacitor (45) serving both for voltage step-down and as an output filter.
  11. [Claim 11] An electric drive chain (1) according to one of claims 7 to 10, further comprising a partial discharge sensor (90) configured to detect partial discharges between the converter assembly (4, 40) and the electric motor (3), the electronic control unit (10) being further configured to limit said voltage range so that the maximum voltage is less than a voltage threshold corresponding to the lowest voltage at which partial discharges have been detected by the partial discharge sensor (90). [Claim 12] Electric drive chain (1) according to one of claims 7 to 10, further comprising a pressure sensor (92) configured to measure the pressure of the environment in which the aircraft on which the electric drive chain (1) is mounted is located, the electronic control unit (10) comprising a module for determining the altitude of the aircraft configured to determine the altitude of the aircraft from the pressure measured by the pressure sensor (92).

Description

Description Title of the invention: Method for optimizing the electric drive chain of an aircraft fuel pump supplied by a high-voltage network and associated electric drive chain Technical Domain The invention relates to the optimization of an electric drive chain and more particularly to a method for controlling an electric drive chain of an aircraft fuel pump supplied by a high voltage network. Previous technique The present invention is used on high voltage avionics networks typically for voltages of 540V or more. More specifically, it is a converter assembly equipped with a "buck" type voltage reducer, an electric inverter and an electric motor for the variable speed drive of a fuel pump of an aircraft. High voltage operation of a system such as a drive chain causes problems with the insulation of cables and electrical components, and can lead to “partial discharges” or even insulation breakdown. Two solutions for the design of electrical equipment can then be considered to resolve this problem. A first solution consists of developing new solutions capable of operating directly at high voltages (540 V) in a safe and reliable manner over time. A second solution is to reduce the operating voltage at the electrical equipment to voltages below the voltage threshold at which partial discharges appear by inserting a step-down converter (buck converter) between the high-voltage avionics network (540 V) and the electrical inverter supplying the three-phase electric motor. The main disadvantage of the second solution is the addition of a potentially bulky converter with an impact on cost. The first solution seems more interesting but may require more complex architectures (multilevel) or hardened components which are therefore more expensive. The general problem is therefore to find a solution for optimal and reliable operation of a fuel pump on a high voltage network (typically 400 V to 900 V) while guaranteeing operational safety, reduced cost and sufficient efficiency. Disclosure of the invention The invention aims to overcome the drawbacks mentioned above and to provide an electrical drive chain for a fuel pump of an aircraft making it possible to reduce the losses of the inverter and the motor and therefore to improve the energy efficiency of the overall chain. This aim is achieved first of all by means of a method for controlling an electric drive chain of a fuel pump of an aircraft, the electric drive chain comprising a three-phase electric motor, a high DC voltage source, and a converter assembly electrically connected between the input of the three-phase electric motor and the high voltage source and comprising an electric inverter and a voltage step-down converter. According to a general characteristic of the invention, the control method comprises the following steps: - reception of a pair of instructions relating to the speed and mechanical torque desired for the operation of the motor, - reception of a maximum continuous voltage instruction delivered by the high voltage source at the input of the converter assembly, - a calculation of the minimum voltage required at the input of the electrical inverter for the operation of the motor at the said set speed and mechanical torque torque, - a calculation of the losses of the electric drive chain for a voltage range between said calculated minimum voltage and a maximum voltage corresponding at most to said maximum continuous voltage setpoint, - a selection of an optimal voltage to be applied at the input of the electrical inverter, the optimal voltage being selected in said voltage range and corresponding to the voltage for which the losses of the electric drive chain are the lowest, - a calculation of the duty cycle to be applied to the voltage step-down converter from the ratio between the value of the selected optimum voltage and the value of the continuous high voltage delivered by the high voltage source, and - a control of the voltage step-down converter from the calculated duty cycle. At low speed and/or low torque of the electric motor, an electric inverter has a better efficiency at low voltage than at high voltage. The switching losses in the inverter increase if its input voltage increases. For the buck converter, the losses come from conduction and switching losses in the semiconductors (MOSFET or IGBT) and from copper losses and iron losses in the inductor. The larger the voltage difference between the output and the input, the larger the current ripple in the inductor, and consequently, the larger the losses in the magnetic circuit and in the copper of the inductor. For the motor, we consider the copper losses in the three-phase winding as well as the iron losses in the magnetic circuit. To reduce these losses, it is necessary to reduce the excess current consumed by adopting the voltage at a level sufficient to reduce the current and the excess current consumption due to the defluxing mode. However, the voltage delivered by the electric i