Method for controlling a power converter, associated device and aircraft

Abstract

A control device (20) for an aircraft power converter, the power converter being connected to a DC voltage source and to the input terminals of an electrical load, is proposed. The control device comprises: - initialization means (39), - first determination means (33), - second determination means (34), - control means (37), - third determination means (35), - comparison means (38), and - fourth determination means (36). Figure for the abstract: Fig 3

Description

Title of the invention: Method for controlling a power converter, associated device and aircraft Technical field

[0001] The invention relates to the control of power converters, and more particularly to a method of controlling a power converter for an aircraft.

[0002] The invention further relates to a control device for a power converter of an aircraft and to an aircraft comprising such a device. Previous techniques

[0003] Climate change is a major concern for many legislative and regulatory bodies around the world. Indeed, various restrictions on carbon emissions have been, are being, or will be adopted by various states. In particular, an ambitious standard applies both to new types of aircraft and those in circulation requiring the implementation of technological solutions in order to make them compliant with current regulations. Civil aviation has been mobilizing for several years now to make a contribution to the fight against climate change.

[0004] Technological research efforts have already made it possible to significantly improve the environmental performance of aircraft. The Applicant takes into consideration the impact factors in all phases of design and development to obtain less energy-intensive, more environmentally friendly aeronautical components and products whose integration and use in civil aviation have moderate environmental consequences with the aim of improving the energy efficiency of aircraft.

[0005] Consequently, the Applicant is constantly working to reduce its negative climate impact by using methods and operating virtuous development and manufacturing processes and minimizing greenhouse gas emissions to the minimum possible in order to reduce the environmental footprint of its activity.

[0006] This ongoing research and development work focuses both on new generations of aircraft engines and the development of the use of electrical technologies to provide propulsion.

[0007] An aircraft may comprise a high voltage HVDC (“high voltage direct current”) network delivering, for example, a voltage greater than 540 V to supply a power converter.

[0008] The power converter, for example of the inverter type, can in particular power an electric motor driving a variable speed fuel pump of the aircraft to supply fuel to a turbomachine of the aircraft.

[0009] The electric motor and fuel pump assembly is generally arranged near fuel tanks located in unpressurized parts of the aircraft, generally in the wings of the aircraft.

[0010] Since said parts do not have sufficient space, are not pressurized and are located close to the fuel tanks, the power converter can be moved to a pressurized part of the aircraft to ensure its proper operation, for example in the fuselage of the aircraft.

[0011] The power converter is connected to the electric motor by a harness comprising cables measuring several meters.

[0012] The power converter comprises transistors switching at high frequency to deliver supply voltages having slots of variable duration to control the rotation speed of the electric motor.

[0013] The rising and falling edges of the slots can create surges at the end of the harness cables connected to the electric motor.

[0014] Overvoltages with steep rising fronts can accelerate the aging of the insulation of the electric motor windings and generate partial discharges within the windings.

[0015] Furthermore, the steeper the rising edges of the power supply voltage pulses, the lower the thermal losses generated by the transistors of the power converter, improving the efficiency of the power converter and decreasing the internal temperature of the power converter to prevent deterioration and destruction of the components of the power converter. Statement of the invention

[0016] The aim of the invention is to overcome all or part of these drawbacks, in particular by finding a compromise between the amplitude of the overvoltages and the value of the thermal losses generated by the power converter.

[0017] To this end, the invention is the result of technological research aimed at very significantly improving the performance of aircraft and, in this sense, contributes to reducing the environmental impact of aircraft. For this purpose, the invention relates to a method for controlling a power converter for an aircraft, the power converter being connected to a DC voltage source and to input terminals of an electrical load.

[0018] The method comprises:

[0019] a) a determination of an interval of admissible rising edge values, each rising edge value being associated with an overvoltage value at the terminals input and a value of an operating parameter representative of the operation of the power converter,

[0020] b) a determination of a maximum admissible current value of overvoltage at the input terminals and of a maximum admissible current value of the operating parameter,

[0021] c) a determination of an initial rising edge setpoint value from characteristics of the power converter and the supply voltage of the power converter,

[0022] d) a control of the power converter from the current value of the rising edge setpoint to supply the electrical load from the DC voltage delivered by the DC voltage source,

[0023] e) when the power converter is controlled from the current value of the rising edge setpoint, a determination of the overvoltage value at the input terminals and a determination of the value of the operating parameter,

[0024] f) a comparison of the overvoltage value to the maximum permissible current overvoltage value and a comparison of the value of the operating parameter to the maximum permissible current value of the operating parameter, and

[0025] g) when the overvoltage value is greater than the maximum permissible current overvoltage value or when the value of the operating parameter is greater than the maximum permissible current value of the operating parameter, determining a new value of the rising edge setpoint different from the current value and repeating steps d) to f) in which the current value is equal to the new value, the new value being included in the range of permissible rising edge values.

[0026] The control method makes it possible to control the power converter by varying the rising edge in order to find a rising edge value for each operating point of the power converter minimizing the thermal losses dissipated in the power converter and the overvoltages at the input terminals of the load.

[0027] Minimizing the heat losses dissipated in the power converter makes it possible to simplify the design of the power converter, in particular by avoiding the addition of a forced cooling device.

[0028] Preferably, when the overvoltage value is less than or equal to the maximum permissible current overvoltage value and the value of the operating parameter is less than or equal to the maximum permissible current value of the operating parameter, and at least one value among the maximum permissible current overvoltage value at the input terminals and the maximum current value admissible value of an operating parameter determined in step b) is modified, the method comprises repeating steps c) to g) in which the modified maximum admissible current value is equal to the modified value.

[0029] Advantageously, the operating parameter is the temperature at the heart of the power converter.

[0030] Preferably, the determination of the maximum permissible current value of overvoltage and the maximum permissible current value of the temperature at the core of the power converter comprises:

[0031] - the determination of the maximum admissible overvoltage value from the altitude at which the aircraft is flying and a curve associating altitude values ​​with maximum admissible overvoltage values,

[0032] - the determination of the maximum admissible value of the temperature at the heart of the power converter from the altitude, the intensity of the current delivered by the power converter and a curve associating altitude values, current intensity values ​​with maximum admissible values ​​of the temperature at the heart of the power converter.

[0033] Advantageously, the value of the temperature at the core of the power converter is determined in step e) from a temperature sensor located in the power converter.

[0034] Preferably, the power converter comprises a housing, the housing containing at least one electronic card and transistors arranged on the electronic card, step d) comprises controlling the transistors from the current value of the rising edge setpoint to supply the electrical load from the DC voltage delivered by the DC voltage source, the value of the temperature at the core of the power converter being determined in step e) from the switching and conduction losses of the transistors, the temperature of the housing and the junction resistance of the transistors on the card.

[0035] Advantageously, the operating parameter is a global parameter representative of the thermal losses generated by the power converter.

[0036] Preferably, the power converter comprises transistors arranged on at least one electronic card of the power converter, step d) comprises controlling the transistors from the current value of the rising edge setpoint to supply the electrical load from the DC voltage delivered by the DC voltage source, the value of the global parameter being determined in step e) from the switching and conduction losses of the transistors.

[0037] Advantageously, the value of the overvoltage at the input terminals is determined in step e) from a voltage sensor measuring the voltage at the input terminals.

[0038] Preferably, the value of the overvoltage at the input terminals is determined in step e) from the current value of the rising edge setpoint and a curve associating overvoltage values ​​with rising edge setpoint values.

[0039] Also provided is a control device for a power converter of an aircraft, the power converter being connected to a DC voltage source and to input terminals of an electrical load.

[0040] The control device comprises:

[0041] - initialization means configured to determine an interval of values ​​of admissible rising edge, each rising edge value being associated with an overvoltage value at the input terminals and a value of an operating parameter representative of the operation of the power converter,

[0042] - first determining means configured to determine a value maximum permissible overvoltage current at the input terminals and a maximum permissible current value of the operating parameter representative of the operation of the power converter,

[0043] - second determining means configured to determine a value initial rising edge setpoint from power converter characteristics and power converter supply voltage,

[0044] - control means configured to control the converter of power from the current value of the rising edge setpoint so as to supply the electrical load from the DC voltage delivered by the DC voltage source,

[0045] - third determining means configured to determine the value of overvoltage at the input terminals and the value of the operating parameter when the power converter is controlled from the current value of the rising edge setpoint,

[0046] - comparison means configured to compare the overvoltage value to the maximum permissible current value of overvoltage and to compare the value of the operating parameter with the maximum permissible current value of the operating parameter, and

[0047] - fourth determination means configured to determine a new rising edge setpoint value different from the current value when the overvoltage value is greater than the maximum permissible current overvoltage value or when the operating parameter value is greater than the maximum permissible current operating parameter value, the new value being included in the range of permissible rising edge values.

[0048] Also provided is an aircraft comprising a DC voltage source, a power converter connected to said source, an electrical load comprising input terminals connected to the power converter, and a control device such as previously defined connected to the power converter. Brief description of the drawings

[0049] Other aims, characteristics and advantages of the invention will appear on reading the following description, given solely by way of non-limiting example and made with reference to the appended drawings in which:

[0050] - figure [Fig.l] schematically illustrates an example of an aircraft according to the invention,

[0051] - figure [Fig.2] schematically illustrates an example of the embodiment of a power converter according to the invention,

[0052] - figure [Fig.3] schematically illustrates an example of embodiment of a device control according to the invention,

[0053] - figure [Fig.4] schematically illustrates a first abacus according to the invention,

[0054] - figure [Fig.5] schematically illustrates a second abacus according to the invention,

[0055] - figure [Fig.6] schematically illustrates a first example of implementation of the control device according to the invention,

[0056] - figure [Fig.7] schematically illustrates a second example of implementation of the control device according to the invention, and

[0057] - figure [Fig.8] schematically illustrates a third example of implementation of the control device according to the invention. Detailed description

[0058] Reference is made to [Fig.l] which schematically illustrates an example of an aircraft 1 comprising turbomachines 2, a fuel tank 3 containing for example kerosene and a device 4 for supplying fuel to the turbomachines 2.

[0059] The aircraft 1 as shown is an airplane.

[0060] Alternatively, the aircraft is a helicopter.

[0061] The supply device 4 comprises a pump 5 connected to the reservoir 3 and to a turbomachine 2, and an electric machine 6 comprising a rotor shaft connected to the pump 5.

[0062] The electrical machine 6 is intended to drive the pump 5 so that the pump 5 supplies the turbomachine 2 with fuel contained in the tank 3.

[0063] As shown in [Fig.l], the tank 3 and the supply device 4 are arranged in a wing of the aircraft 1.

[0064] It is assumed in the following that the electric machine 6 is a three-phase electric machine.

[0065] Alternatively, the electrical machine 6 may be a single-phase or polyphase machine comprising N phases, N being an integer greater than two.

[0066] The electrical machine 6 forms a three-phase electrical load Z comprising three input terminals 7, 8, 9.

[0067] Alternatively, the load Z may be formed by an electric air conditioning compressor.

[0068] Alternatively, the electrical load Z may be single-phase or polyphase comprising N phases, N being an integer greater than two, the number of input terminals being adapted according to the number of phase(s).

[0069] A voltage sensor 10 is arranged near the input terminals 7, 8, 9 to measure the voltage of the input terminals.

[0070] The aircraft 1 further comprises a control system 11 for the electrical machine 6 and a source 12 of direct voltage located in the fuselage of the aircraft 1.

[0071] The control system 11 comprises a power converter 13 comprising two input terminals 14, 15 connected to the source 12 and output terminals 16, 17, 18 connected to the input terminals 7, 8, 9 of the electrical load Z via a harness 19 comprising beams having a length of several meters.

[0072] The integration of the power converter in the fuselage makes it possible to move the converter away from the fuel tanks, forming an “ATEX” zone in which the explosive risk is significant.

[0073] The control system 11 further comprises a control device 20 of the power converter 13 connected to a control interface 21 of the converter 13.

[0074] The power converter 13 may comprise an inverter intended to supply the electrical machine 6 with a variable current from the source 12 to control the rotation speed of the machine 6.

[0075] Varying the rotation speed of the machine 6 makes it possible to regulate the fuel flow supplied by the pump 5 to the turbomachine 2.

[0076] [Fig.2] schematically illustrates an exemplary embodiment of the power converter 13.

[0077] Since the load Z is three-phase, the power converter 13 comprises three bridges 22, 23, 24.

[0078] Each bridge 22, 23, 24 comprises a first connection 22a, 23a, 24a connected to a first input terminal 14 of the power converter 13, a second connection 22b, 23b, 24b connected to the second input terminal 15 of the power converter 13, a third connection 22c, 23c, 24c and a fourth connection 22d, 23d, 24d.

[0079] The fourth connection 22d of a first bridge 22 is connected to a first output terminal 16 of the power converter 13, the fourth connection 23d of a second bridge 23 is connected to a second output terminal 17 of the power converter 13, and the fourth connection 24d of the third bridge 24 is connected to a third output terminal 18 of the power converter 13.

[0080] Each bridge 22, 23, 24 comprises two switching cells 25, 26 comprising a first connection 25a, 26a, a second connection 25b, 26b, and a third connection 25c, 26c connected to the third connection 22c, 23c, 24c of the bridge 22, 23, 24.

[0081] The first connection 25a of a first switching cell 25 is connected to the first connection 22a, 23a, 24a of the bridge 22, 23, 24, the second connection 25b of the first switching cell 25 is connected to the first connection 26a of the second switching cell 26, and the second connection 26b of the second switching cell 26 is connected to the second connection 22b, 23b, 24b of the bridge 22, 23, 24.

[0082] The fourth connection 22d, 23d, 24d of each bridge 22, 23, 24 is connected to the second connection 25b of the first switching cell 25 of said bridge 22, 23, 24.

[0083] Each switching cell 25, 26 comprises a transistor 27, a diode 28 and a control interface 29 (“gate driver” in English) connected to the gate of the transistor 27 and to the third connection 25c, 26c of the switching cell 25, 26.

[0084] The transistors 27, the diodes 28 and the control interfaces 29 of the bridges 22, 23, 24 are arranged on an electronic PCB (printed circuit board) 30 of the power converter 13.

[0085] The drain of transistor 27 is connected to the cathode of diode 28 and to the first connection 25a, 26a of switching cell 25, 26.

[0086] The source of transistor 27 is connected to the anode of diode 28 and to the second connection 25b, 26b of switching cell 25, 26.

[0087] The transistor 27 is for example an insulated-gate bipolar transistor (IGBT) or a metal-oxide-semiconductor field-effect transistor (MOSFET).

[0088] The power converter 13 further comprises a temperature sensor 31 capable of measuring the temperature at the heart of the power converter 13, for example capable of measuring the temperature of the card 30.

[0089] The card 30, the bridges 22, 23, 24 and the temperature sensor 31 are arranged in a housing 13a of the power converter 13.

[0090] [Fig.3] illustrates an exemplary embodiment of the control device 20.

[0091] The control device 20 comprises a memory 32, first means of determination means 33, second determination means 34, third determination means 35, fourth determination means 36, control means 37, comparison means 38 and initialization means 39.

[0092] The first determination means 33 are for example produced by a first circuit, the second determination means 34 are for example produced by a second circuit, the third determination means 35 are for example produced by a third circuit, the fourth determination means 36 are for example produced by a fourth circuit, the control means 37 are for example produced by a control circuit, the comparison means 38 are for example produced by a comparison circuit, and the initialization means 39 are for example produced by an initialization circuit.

[0093] The control device 20 further comprises a processing unit 40 capable of implementing the memory 32 and the means 33, 34, 35, 36, 37, 38, 39.

[0094] [Fig.4] schematically illustrates a first abacus ABQ1 representing a example of the evolution of the overvoltage AV at the input terminals 7, 8, 9 of the electric load Z and of the thermal energy Etot dissipated by the transistors 27 of the power converter 13 as a function of rising edge values ​​FM.

[0095] The thermal energy Etot is equal to the energy losses dissipated by the power converter 13.

[0096] A curve Cl represents the evolution of the overvoltage AV and a curve C2 represents the evolution of the thermal energy Etot.

[0097] The dissipated thermal energy can correspond to the sum of the energy dissipated by the switching losses and the conduction losses of the transistors 27.

[0098] The rising edge represents the slope of the variation of the voltage across the terminals of the transistors 27 during the switching phases of the transistors 27 equal to the time derivative of the voltage across the terminals of the transistors 27.

[0099] AVmax is the value of the maximum overvoltage supported by the load Z and Etotmax is the value of the maximum thermal energy dissipated by the transistors 27 to heat the card 30 to the maximum temperature Tmax equal to the maximum junction temperature of the transistors 27 for an ambient temperature of for example 20°C.

[0100] The value of the maximum overvoltage AVmax is equal to AV4 and the value of the maximum dissipated thermal energy Etotmax is equal to Etot4.

[0101] The value of the maximum overvoltage AVmax is associated with the value FMI of rising edge FM and the value Etotl of dissipated thermal energy.

[0102] The maximum thermal energy Etotmax is associated with the rising edge value FM4 and the overvoltage value AV 1.

[0103] The rising edge values ​​FM2 and FM3 respectively define the lower and upper limits of an IFM interval.

[0104] The rising edge values ​​FM included in the interval IFM are associated with optimal compromises of overvoltage values ​​AV varying between AV2 and AV3, and of dissipated thermal energy values ​​Etot varying between Etot2 and Etot3, allowing optimal operation of the load Z so that the amplitude of the overvoltages at the input terminals 7, 8, 9 of the load Z is not likely to damage the beams of the harness 19 and the load Z, for example the windings of the machine 6, and the thermal energy Etot dissipated is reduced to minimize the thermal losses of the power converter 13.

[0105] [Fig.5] illustrates a second chart ABQ2 representing an example of the evolution of the overvoltage AV at the input terminals 7, 8, 9 of the electrical load Z and of the temperature T at the heart of the converter 13, T being for example the temperature of the electronic card 30 of the power converter 13, as a function of rising edge values ​​FM.

[0106] We find the curve Cl representing the evolution of the overvoltage AV and a curve C3 representing the evolution of the temperature T.

[0107] The value of the maximum overvoltage AVmax is associated with the value FMI of the rising edge FM and the value Tl of the temperature T.

[0108] The maximum temperature Tmax equal to the maximum junction temperature of the transistors 27 is associated with the value FM4 of the rising edge FM and the overvoltage value AVI.

[0109] The FM rising edge values ​​included in the IFM interval are associated with optimal compromises of AV overvoltage values ​​varying between AV2 and AV3, and T temperature values ​​varying between T2 and T3.

[0110] [Fig.6] schematically illustrates a first example of implementation of the control device 20.

[0111] It is assumed that the memory 32 stores the second abacus ABQ2 illustrated in [Fig.5].

[0112] During a step 50, the initialization means 39 determine an interval of admissible rising edge values.

[0113] The range of admissible rising edge values ​​is determined from the second chart ABQ2 stored in the memory 32 and includes all the rising edge values ​​FM between the value FMI and the value FM4.

[0114] Each rising edge value FM of the interval of admissible rising edge values ​​is associated with an overvoltage value AV and a value of an operating parameter representative of the operation of the power converter, the operating parameter being in this example the temperature T at the heart of the power converter 13.

[0115] During a step 51, the first determination means 33 determine a maximum admissible current value of overvoltage AVmax_ad at the input terminals 7, 8, 9 and a maximum admissible current value of the temperature T.

[0116] The maximum admissible current value of overvoltage is for example equal to 1.2 times the value of the direct voltage delivered by the voltage source 12 and the maximum admissible current value of the temperature T is determined so that it is less than the maximum temperature Tmax equal to the maximum temperature of junction of transistors 27.

[0117] Alternatively, the maximum admissible current value of overvoltage is for example equal to AV3 and the maximum admissible current value of the temperature T is for example equal to T3 so that the value of the rising edge FM is chosen in the interval IFM.

[0118] During a step 52, the second determination means 34 determine an initial rising edge setpoint value from characteristics of the power converter 13 and the maximum admissible current overvoltage value.

[0119] The initial value of the rising edge CONS setpoint is for example equal to: [° 12 °] CONS =

[0121] where Vaüm is the supply voltage of the power converter 13 applied between the input terminals 14 and 15 of said converter and td is the theoretical switching time of the transistor 27 given for example by the technical data sheet of the transistor 27.

[0122] A current value of the rising edge setpoint is equal to the initial setpoint value CONS.

[0123] During a step 53, the control means 37 control the power converter 13 via the control interface 21 of the converter 13 from the current value of the rising edge setpoint to supply the electrical load from the DC voltage delivered by the DC voltage source 12.

[0124] The power converter 13 cuts the direct voltage delivered by the source 12 at the frequency Fsw to supply the electrical load Z.

[0125] During a step 54, when the power converter 13 is controlled from the current value of the rising edge setpoint, the third determination means 35 determine the overvoltage value at the input terminals 7, 8, 9 of the load Z from the measurements delivered by the voltage sensor 10 and the value of the temperature at the core of the power converter 13 from the measurements delivered by the temperature sensor 31.

[0126] The value of the overvoltage AV is measured in real time by the voltage sensor 10 making it possible to take into account the voltage variations generated by the tolerances of the impedances of the harness beams and the load Z, and by the aging of the harness beams and the load Z.

[0127] Alternatively, the power converter 13 does not include the voltage sensor 10. The third determination means 35 determine the overvoltage value AV at the input terminals 7, 8, 9 of the load Z from a map associating rising edge values ​​with overvoltage values.

[0128] The mapping includes, for example, a curve associating values ​​of overvoltage at rising edge setpoint values.

[0129] The curve is for example determined empirically from tests carried out on a test bench.

[0130] Determining the overvoltage from the mapping makes it possible to eliminate the voltage sensor 10.

[0131] As a variant, the power converter 13 does not include the temperature sensor 31, the value of the temperature T at the heart of the power converter 13 (or junction temperature of the transistors 27) is determined from the losses Pcc in switching and in conduction of the transistors 27, from the temperature Tb of the housing 13a of the power converter 13 and from the junction resistance Rth of the transistors 27 secured to the card 30 according to the following equation:

[0132] T = Tb + Rth-Pcc^

[0133] In a known manner, the switching and conduction losses Pcc of the transistors 27 are determined from the technical data of the transistors 27 (nominal switching losses, threshold voltage, dynamic resistance), the switching frequency Fsw, the intensity of the current delivered by the power converter 13, the voltage delivered by the source 12, the modulation depth and the phase shift between the current and the voltage delivered by the power converter 13.

[0134] During a step 55, the comparison means 38 compare the overvoltage value determined in step 54 with the current maximum admissible overvoltage value AVmax_ad determined in step 51 and compare the value of the temperature T at the heart of the converter 13 determined in step 54 with the current maximum admissible value of the temperature T determined in step 51.

[0135] When the overvoltage value AV is greater than the maximum admissible current overvoltage value AVmax_ad or when the value of the temperature T at the core of the converter 13 is greater than the maximum admissible current value of the temperature T determined in step 51, during a step 56, the fourth determination means 36 determine a new value of the rising edge setpoint CONS included in the interval of admissible rising edge values ​​determined in step 50 and different from the current value. The method continues in step 53.

[0136] When the overvoltage value AV is less than or equal to the maximum admissible current overvoltage value AVmax_ad and the value of the temperature T at the core of the converter 13 is less than or equal to the maximum admissible current value of the temperature T determined in step 51, the control means 37 continue the control of the power converter 13 via the control interface 21 of the converter 13 from the current value of the rising edge setpoint and the method continues in step 54.

[0137] When the overvoltage value AV is less than or equal to the current value maximum admissible overvoltage AVmax_ad, the value of the temperature T at the heart of the converter 13 is less than or equal to the maximum admissible current value of the temperature T determined in step 51, and at least one value among the maximum admissible current value AVmax_ad of overvoltage at the input terminals 7, 8, 9 and the maximum admissible current value of the temperature T is modified, the method continues in step 51, the modified maximum admissible current value being equal to the modified value.

[0138] The control device 20 makes it possible to control the power converter 13 by varying the rising edge in order to find a rising edge value for each operating point of the power converter 13 minimizing the thermal losses dissipated in the power converter 13 and the overvoltages AV at the input terminals 7, 8, 9 of the load Z.

[0139] Minimizing the heat losses dissipated in the power converter 13 makes it possible to simplify the design of the power converter, in particular by avoiding the addition of a forced cooling device.

[0140] [Fig.7] schematically illustrates a second example of implementation pre differential of the control device 20.

[0141] It is assumed that the memory 32 stores the second chart ABQ2 illustrated in [Fig.5].

[0142] In this example of implementation, the altitude at which the aircraft 1 is flying is taken into account.

[0143] The effects linked to the temperature and the pressure at the altitude of the aircraft 1 are thus taken into account for the determination by the first determination means 33 of the maximum admissible current value AVmax_ad of overvoltage at the input terminals 7, 8, 9 and the maximum admissible current value of the temperature T.

[0144] We find step 50.

[0145] When the aircraft 1 is operating at low altitude, for example at an altitude below 3300 feet (1006 meters), the ambient temperature of the aircraft 1 may be high, for example 55°C, so that the difference between the ambient temperature and the maximum temperature Tmax equal to the maximum junction temperature of the transistors 27 is reduced.

[0146] It is necessary to reduce the thermal losses generated inside the power converter 13 by reducing the value of the rising edge driving said converter so that the temperature T at the heart of the power converter 13 does not exceed the maximum junction temperature of the transistors 27.

[0147] According to the second chart ABQ2, the choice of the value of the rising edge to reduce the maximum admissible current value of the temperature T in order to reduce thermal losses leads to an increase in the value of overvoltages AV at the input terminals 7, 8, 9 of the load Z. At low altitude, according to the Paschen curve, the increase in the amplitude of the overvoltages is not likely to cause partial discharges damaging the beams of harness 19 and the load Z.

[0148] When the aircraft 1 is operating at high altitude, for example at an altitude above 20,000 feet (6,096 meters), the ambient temperature of the aircraft 1 may be low, for example -40°C, so that the difference between the ambient temperature and the maximum temperature Tmax equal to the maximum junction temperature of the transistors 27 is significant.

[0149] According to the Paschen curve, the partial discharge voltage threshold decreases when the ambient pressure of the harness 19 and the load Z decreases.

[0150] It is necessary to decrease the maximum permissible current value AVmax_ad of overvoltage at the input terminals 7, 8, 9 to prevent the occurrence of partial discharges in the harness 19 and the load Z.

[0151] According to the second chart ABQ2, the choice of the value of the rising edge to reduce the maximum admissible current value AVmax_ad of overvoltage leads to an increase in the temperature inside the power converter 13.

[0152] Since the ambient temperature is low, the temperature increase is not harmful to the transistors 27.

[0153] In order to take into account the effects of the altitude of the aircraft 1, step 50 is followed by a step 60.

[0154] During step 60, the first determination means 33 determine the maximum admissible current value AVmax_ad of overvoltage at the input terminals 7, 8, 9 from the altitude of evolution of the aircraft 1 and from a curve associating altitude values ​​with maximum admissible overvoltage values.

[0155] The altitude of the aircraft 1 is for example provided by an altimeter.

[0156] The first determination means 33 determine the maximum admissible value of the temperature T at the heart of the power converter 13 from the altitude, the intensity of the current delivered by the power converter 13 and a curve associating altitude values, current intensity values ​​with maximum admissible values ​​of the temperature at the heart of the power converter.

[0157] The curve is for example determined empirically during tests.

[0158] The value of the intensity of the current delivered by the power converter 13 is for example measured by a current sensor.

[0159] The method continues in steps 52, 53, 54, 55, 56, as previously described in the first example of implementation of the control device 20 illustrated in [Fig.6].

[0160] The method differs from the first example of implementation of the control device 20 illustrated in [Fig.6] in that the altitude of the aircraft 1 is taken into account to determine the maximum admissible current value AVmax_ad overvoltage at input terminals 7, 8, 9 and the maximum permissible value of temperature T at the heart of the power converter.

[0161] [Fig.8] schematically illustrates a third example of implementation of the control device 20.

[0162] In this example, unlike the previous examples illustrated in Figures 6 and 7, the operating parameter representative of the operation of the power converter is a global parameter representative of the thermal losses generated by the power converter 13.

[0163] It is assumed that the memory 32 stores the first abacus ABQ1 illustrated in [Fig.4].

[0164] During a step 70, the initialization means 39 determine an interval of admissible rising edge values.

[0165] The range of admissible rising edge values ​​is determined from the first chart ABQ1 stored in the memory 32 and includes all the rising edge values ​​FM between the value FMI and the value FM4.

[0166] Each rising edge value FM of the interval of admissible rising edge values ​​is associated with an overvoltage value AV and a value of an operating parameter representative of the operation of the power converter, the operating parameter being a global parameter representative of the thermal losses generated by the power converter 13.

[0167] During a step 71, the first determination means 33 determine a maximum admissible current value Amax_ad of overvoltage AV at the input terminals 7, 8, 9 and a maximum admissible current value of the global parameter equal to a thermal energy value Etot dissipated by the transistors 27 of the power converter 13.

[0168] The maximum permissible current overvoltage value is for example equal to 1.2 times the value of the direct voltage delivered by the voltage source 12.

[0169] Alternatively, the maximum admissible current overvoltage value is for example equal to AV3 and the value of the thermal energy Etot is for example equal to Etot3 so that the value of the rising edge FM is chosen in the interval IFM.

[0170] The method continues at step 52 and then at step 53.

[0171] During a step 72, when the power converter 13 is controlled from the current value of the rising edge setpoint, the third determination means 35 determine the overvoltage value at the input terminals 7, 8, 9 of the load Z from the measurements delivered by the voltage sensor 10 and the value of the global parameter from the switching and conduction losses of the transistors 27.

[0172] The value of the overvoltage AV is measured in real time by the voltage sensor 10.

[0173] Alternatively, the power converter 13 does not include the voltage sensor 10. The third determination means 35 determine the overvoltage value AV at the input terminals 7, 8, 9 of the load Z from the mapping associating rising edge values ​​with overvoltage values.

[0174] In a known manner, the switching and conduction losses of the transistors 27 are determined from the technical data of the transistors 27 (nominal switching losses, threshold voltage, dynamic resistance), the switching frequency Fsw, the intensity of the current delivered by the power converter 13, the voltage delivered by the source 12, the modulation depth and the phase shift between the current and the voltage delivered by the power converter 13.

[0175] During a step 73, the comparison means 38 compare the overvoltage value determined in step 72 with the current maximum admissible overvoltage value Amax_ad AV determined in step 71 and compare the value of the global parameter determined in step 72 with a current maximum admissible value of the global parameter determined in step 71.

[0176] When the overvoltage value AV is greater than the maximum admissible current value Amax_ad of overvoltage AV or when the value of the global parameter is greater than the maximum admissible current value of the global parameter determined in step 71, during a step 74, the fourth determination means 36 determine a new value of the rising edge setpoint CONS included in the interval of admissible rising edge values ​​determined in step 70 and different from the current value. The method continues in step 53.

[0177] When the overvoltage value AV is less than or equal to the maximum admissible current value Amax_ad of overvoltage AV and the value of the global parameter is less than or equal to the maximum admissible current value of the global parameter determined in step 71, the control means 37 continue the control of the power converter 13 via the control interface 21 of the converter 13 from the current value of the rising edge setpoint and the method continues in step 72.

[0178] When the overvoltage value AV is less than or equal to the maximum admissible current value Amax_ad of overvoltage AV, the value of the global parameter is less than or equal to the maximum admissible current value of the global parameter determined in step 71, and at least one value among the maximum admissible current value Amax_ad of overvoltage AV at the input terminals 7, 8, 9 and the maximum admissible current value of the global parameter is modified, the method continues in step 71, the modified maximum admissible current value being equal to the modified value.

Claims

1. Claims Method for controlling a power converter (13) for an aircraft (1), the power converter being connected to a DC voltage source (12) and to input terminals (7, 8, 9) of an electrical load (Z), characterized in that the method comprises: a) a determination (50, 70) of an interval of admissible rising edge values (FM), each rising edge value being associated with an overvoltage value (AV) at the input terminals and a value of an operating parameter (T, Etot) representative of the operation of the power converter, b) a determination (51, 60, 71) of a maximum admissible current overvoltage value (AV) at the input terminals and a maximum admissible current value of the operating parameter (T, Etot), c) a determination (52) of an initial rising edge setpoint value from characteristics of the power converter (13) and the supply voltage of the power converter (13),d) a control (53) of the power converter from the current value of the rising edge setpoint to supply the electrical load (Z) from the DC voltage delivered by the DC voltage source (12), e) when the power converter (13) is controlled from the current value of the rising edge setpoint (54,72), a determination of the overvoltage value at the input terminals (7, 8, 9) and a determination of the value of the operating parameter, f) a comparison (55,73) of the overvoltage value (AV) with the maximum permissible current overvoltage value and a comparison of the value of the operating parameter (T, Etot) with the maximum permissible current value of the operating parameter, and g) when the overvoltage value (AV) is greater than the maximum permissible current overvoltage value or when the value of the operating parameter (T,Etot) is greater than the maximum permissible current value of the operating parameter, a determination (56,74) of a new value of the rising edge setpoint different from the current value and the reiteration of steps d) to f) in which the current value is equal to the new value, the new value being included in the range of front values of, admissible climbs.

2. The method of claim 1, wherein when the overvoltage value (AV) is less than or equal to the maximum permissible current overvoltage value and the value of the operating parameter (T, Etot) is less than or equal to the maximum permissible current value of the operating parameter, and at least one of the maximum permissible current overvoltage value at the input terminals and the maximum permissible current value of an operating parameter determined in step b) is modified, the method comprises repeating steps c) to g) in which the modified maximum permissible current value is equal to the modified value.

3. Method according to one of claims 1 and 2, in which the operating parameter is the temperature (T) at the heart of the power converter (13).

4. Method according to claim 3, in which the determination of the maximum admissible current value of overvoltage (AV) and the maximum admissible current value of the temperature (T) at the core of the power converter comprises: - the determination (60) of the maximum admissible value of overvoltage (AV) from the altitude of operation of the aircraft (1) and a curve associating altitude values with maximum admissible values of overvoltage (AV), - the determination of the maximum admissible value of the temperature (T) at the core of the power converter (13) from the altitude, the intensity of the current delivered by the power converter (13) and a curve associating altitude values, current intensity values with maximum admissible values of the temperature (T) at the core of the power converter (13).

5. Method according to claim 3 or 4, in which the value of the temperature (T) at the heart of the power converter is determined in step e) from a temperature sensor (31) located in the power converter (13).

6. Method according to claim 3 or 4, in which the power converter (13) comprises a housing (13a), the housing containing at least one electronic card (30) and transistors (27) arranged on the electronic card, step d) comprises controlling the transistors (27) from the current value of the rising edge setpoint to supply the electrical load (Z) from the DC voltage delivered by the direct voltage source (12), the temperature value (T) at the heart of the power converter being determined in step e) from the switching and conduction losses of the transistors (27), the temperature of the case (13a) and the junction resistance of the transistors (27) on the electronic card (30).

7. Method according to one of claims 1 and 2, in which the operating parameter is a global parameter (Etot) representative of the thermal losses generated by the power converter.

8. Method according to claim 7, in which the power converter (13) comprises transistors (27) arranged on at least one electronic card (30) of the power converter, step d) comprises controlling the transistors (27) from the current value of the rising edge setpoint to supply the electrical load (Z) from the DC voltage delivered by the DC voltage source (12), the value of the global parameter (Etot) being determined in step e) from the switching and conduction losses of the transistors (27).

9. Control device (20) for a power converter (13) of an aircraft (1), the power converter (13) being connected to a DC voltage source (12) and to input terminals (7, 8, 9) of an electrical load (Z), characterized in that the control device comprises: - initialization means (39) configured to determine an interval of admissible rising edge values, each rising edge value being associated with an overvoltage value (AV) at the input terminals (7, 8, 9) and a value of an operating parameter (T, Etot) representative of the operation of the power converter (13), - first determination means (33) configured to determine a maximum admissible current overvoltage value (AV) at the input terminals (7, 8, 9) and a maximum admissible current value of the operating parameter (T, Etot) representative of the operation of the power converter,- second determination means (34) configured to determine an initial rising edge setpoint value from characteristics of the power converter (13) and the supply voltage of the power converter (13)), - control means (37) configured to control the, power converter (13) from the current value of the rising edge setpoint so as to supply the electrical load (Z) from the direct voltage delivered by the direct voltage source (12), - third determination means (35) configured to determine the overvoltage value (AV) at the input terminals (7, 8, 9) and the value of the operating parameter (T, Etot) when the power converter (13) is controlled from the current value of the rising edge setpoint, - comparison means (38) configured to compare the overvoltage value (AV) with the maximum permissible current overvoltage value and to compare the value of the operating parameter (T, Etot) with the maximum permissible current value of the operating parameter, and - fourth determination means (36) configured to determine a new value of the rising edge setpoint different from the current value when the overvoltage value (AV) is greater than the maximum admissible current overvoltage value or when the value of the operating parameter (T, Etot) is greater than the maximum admissible current value of the operating parameter, the new value being included in the interval of admissible rising edge values.

10. Aircraft (1) comprising a direct voltage source (12), a power converter (13) connected to said source, an electrical load (Z) comprising input terminals (7, 8, 9) connected to the power converter (13), and a control device (20) according to claim 9 connected to the power converter (13).

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