METHOD AND DEVICE FOR CONTROLLING THE HYBRIDIZATION OF AN AIRCRAFT

Description

Technical Field

[0001] The invention relates to hybrid propulsion systems for aircraft, more particularly for vertical take-off and landing (VTOL) vehicles, and it concerns a system for controlling the distribution of power between electrical sources according to the different operating regimes of the aircraft. Previous technique

[0002] VTOLs tend to constitute an intra-urban and inter-urban mode of transport suitable for the delivery of goods or the transfer of people and for which there is a strong demand for hybrid propulsion systems, preferably integrated, due to the still limited range of current batteries.

[0003] In such a hybrid propulsion system, there are two sources of electrical power: a turbogenerator and a battery bank, supplying one or more electrical loads—in effect, one or more electric motors—via one or more high-voltage direct current (HVDC) buses. The role of the batteries is to supplement the turbogenerator in case of failure and to assist it at operating points where it cannot meet the load demands (transient or continuous) on its own, thus preventing the turbogenerator from being oversized or overstressed.

[0004] The maximum power output of the turbogenerator depends on temperature and altitude, and is limited dynamically. The advantage of batteries lies in the fact that power can be supplied by the battery more rapidly than the power supplied by the turbogenerator in the event of a rapid power demand.

[0005] Typically, such a hybrid propulsion system has several operating modes: a turbogenerator start-up and bus pre-charge regime (where the power supplied to the continuous bus must be limited until the capacities are pre-charged), a hybrid regime where both sources supply power, an electric regime (on setpoint or in case of turbogenerator loss) where only the battery supplies power, and a thermal regime (on setpoint or in case of battery loss) where only the turbogenerator supplies power.

[0006] There figure 4 illustrates more precisely the hybrid operating regime which covers four different situations: in 1), the battery provides the high dynamics (in charge and discharge) which are not covered by the turbogenerator, in 2), the battery provides the surplus power when the turbogenerator is at its power limit, in 3), there is a peak charge on the battery to compensate for the rapid charge drop (the turbogenerator remains at high power since its dynamics are slow, so this power which is no longer used by the electrical loads goes into the battery, until the power of the turbogenerator corresponds to the power demanded by the electrical loads), and in 4) the turbogenerator charges the battery.

[0007] Taking into account the different operating regimes requires control of the hybrid propulsion system to manage the distribution of power between the two electrical sources.

[0008] On current systems, this hybridization control is done via current control of the battery through the DC / DC converter linking this battery to the HVDC bus when the rectifier(s) at the output of the turbogenerator are not controlled, or both through this DC / DC converter and the AC / DC rectifier when the latter is controlled, seeking local optima.

[0009] However, this search for optima proves particularly delicate, and there is therefore a need for an alternative hybridization control system.

[0010] US documents 2015 / 075167 and US 2018 / 022461 describe power distribution control systems in a hybrid propulsion system.

[0011] It is also appropriate to take into account the prior art document EP 3703220 A1, relevant under Article 54(3) EPC, which precedes the preamble of the independent claims. Description of the invention

[0012] The invention aims to provide a less complex, more efficient, more modular, and more scalable control system for hybrid propulsion, while also allowing for optimized integration and installation on the aircraft. Another objective is to enable control modes based on both current and voltage, to adapt to different flight phases and operating conditions. A further objective is to accommodate the various applications of the propulsion system, whether thermal, electric, or hybrid.

[0013] These goals are achieved with a method of controlling the power distribution in a hybrid propulsion system comprising an electrical source delivering an alternating voltage associated with an AC / DC controlled rectifier and a battery, method characterized in that, the AC / DC controlled rectifier and the battery being each directly connected to a continuous HVDC bus supplying at least one electrical load, the control of the power distribution is carried out through the AC / DC controlled rectifier alone by a regulation loop on a power setpoint from a measured power of the battery and a regulation loop on a voltage setpoint from a measured voltage of the HVDC bus, these two regulation loops each delivering a quadratic current setpoint for a regulation loop from a current of the electrical source delivering an alternating voltage.

[0014] With this configuration, the DC / DC converter between the battery and the HVDC bus is eliminated, thus the battery is controlled indirectly.

[0015] Advantageously, the quadratic current setpoint Iqref is selectively delivered by one or the other of the two control loops based on power or voltage setpoints, according to a hybrid operating mode of the hybrid propulsion system for one and one of the thermal or start-up operating modes of the hybrid propulsion system for the other. Similarly, the quadratic current setpoint Idref is delivered by a flow management module.

[0016] Preferably, the quadratic current setpoint Iqref delivered to the control loop is previously summed by a current value corresponding to an estimate of the power consumed by at least one electrical load.

[0017] In addition, the voltage setpoint is delivered by a power manager and defines the voltage to be applied to at least one electrical load.

[0018] The power setpoint is delivered by a hybridization set and defines the desired power distribution between at least one electrical source delivering an alternating voltage and at least one battery.

[0019] The invention also relates to a power distribution control device implementing the aforementioned method, the hybrid propulsion system comprising such a power distribution control device and an aircraft, in particular a VTOL aircraft comprising such a hybrid propulsion system. Brief description of the drawings

[0020] Other features and advantages of the present invention will become apparent from the detailed description given below, with reference to the following figures, which are not exhaustive and in which: [ Fig. 1 ] There figure 1 illustrates a hybridization control architecture in an aircraft for implementing the power distribution method according to the present invention, [ Fig. 2 ] There figure 2 is a flowchart showing the process in a first operating configuration, [ Fig. 3 ] There figure 3 is a flowchart showing the process in a second operating configuration, [ Fig. 4 ] There figure 4 shows the evolution of battery charge, power of the electrical source and total load power in a prior art hybridization control architecture. Description of the implementation methods

[0021] According to the invention, hybridization is controlled by controlling the voltage, power (or output current) of one or more AC / DC controlled rectifiers (i.e., active rectifiers), and not, as is conventional, through a DC / DC converter placed between the battery and the HVDC bus. The battery power is thus controlled indirectly by one or more active rectifiers.

[0022] There figure 1 This illustrates an architecture enabling this hybridization control in a hybrid propulsion system designed to power at least one thruster 10 from at least one HVDC bus 12, to which at least one battery 14 and at least one AC / DC controlled rectifier 16 are connected. The active rectifier(s) 16 are mounted at the output of one or more power sources 18A, 18B delivering an alternating voltage, to which these active rectifiers are connected to convert it into a direct voltage. This power source can be a simple electric generator, a RAT, an APU, or a turbogenerator equipped with a gas turbine 20 (whose control unit or FADEC 20A is shown in dashed lines).

[0023] According to the invention, the control of the power distribution in this hybrid propulsion system is ensured through the AC / DC controlled rectifier 16 by a control including three regulation loops allowing to respond to all the operating regimes of the hybrid propulsion system: a first voltage regulation loop 22 on a voltage setpoint Vref from a measurement of the voltage of the HVDC bus V HVDC, a second power regulation loop 24 on a power setpoint Pref from a measurement of the power of the battery Pbat, and a third close current regulation loop 26 on a quadratic current setpoint Idref, Iqref from a measurement of the current of the alternating electrical source Igen.

[0024] The voltage and power regulation loops are used selectively depending on the operating mode of the hybrid propulsion system. Thus, voltage regulation is used during start-up for pre-charging the HVDC bus 12 and in battery-free mode (thermal mode), while power regulation is used in hybrid mode. The selection of one or the other of these two regulation loops, depending on the desired operating mode, is performed by a power manager 28, which also provides the reference voltage setpoint (Vref).

[0025] It should be noted that the presence of the two regulation loops 22 and 24, the selection of which is made by the power manager 28, makes it possible to manage very simply a loss of battery or a loss of the alternative electrical source (turbogenerator for example) by switching from the power regulation mode activated in hybrid operating mode to the voltage regulation mode activated in thermal or all-electric operating modes.

[0026] The output of the regulation loop (voltage or power) generates part of the quadratic torque current setpoint Iqref, which is sent to the current regulation loop 26. The other part of the quadratic flux current setpoint Idref comes from a flux management module 30. This current loop is unique and is used at the output of both the voltage loop 22 and the power loop 24 to provide vector control of the AC / DC controlled rectifier 16. Since the latter is voltage-controlled, the quadratic current must be converted into a three-phase voltage by a suitable conversion module 32, mirroring the three-phase current Igen from the AC power source, which is converted into quadratic currents Id, Iq by a corresponding conversion module 34. The synchronization of the conversions is performed according to the position of the AC power source supplied by a suitable module 36.Finally, a modulation module 38 applies the requested vector command.

[0027] It should be noted that an adder 40 can be added once the operating mode has been selected by the power manager 28, to sum the current setpoint with a current value corresponding to an estimate of the power consumed by the load(s) 10 before it is sent to the current regulation loop 22. This current value constitutes an optional load compensation which can be deduced from the measurement of the HVDC current I of the HVDC bus 12 in a suitable compensation module 42. This allows the active rectifier 16 to be more responsive, and therefore to relieve the battery 14.

[0028] The power setpoint Pref is derived from a hybridization system 44 whose function is to determine the hybridization ratio, i.e., the power to be supplied by the battery and the power to be supplied by the turbogenerator. This hybridization system knows the battery's state of charge Ebat and the state of the power available for the AC voltage source (turbogenerator or other) Egen and can therefore define, in appropriate modules 46, 48, both a battery power to guarantee the battery's state of charge and the power that the battery must supply based on the power supply capacity of the gas turbine (in the case of a turbogenerator, for example), and thus ensure the desired power distribution between the two.It also defines minimum and maximum battery power thresholds in a threshold module 50, ensuring that the AC power source is properly assisted by the battery, for example, by not demanding too much or too little power from it. In cases where there are multiple HVDC buses on the same AC power source, this hybrid system also assigns each HVDC bus its minimum and maximum power.

[0029] THE figures 2 et 3 show two flowcharts illustrating the process of the invention.

[0030] On the figure 2 The battery is connected to the HVDC bus first, then the AC power source is connected to the HVDC bus, which has already been pre-charged by the battery. More specifically, in a first step 60, the battery 14 is pre-charged and connected to the HVDC bus 12. The hybrid propulsion system is then, in a subsequent step 62, ready to operate in load-supply mode. Next, in a step 64, the gas turbine 20 is started. Then, in a subsequent step 66, the voltage of the AC / DC controlled rectifier 16 is pre-charged in voltage regulation mode, and in a subsequent step 68, still in voltage regulation mode, the voltage of the AC / DC controlled rectifier 16 is regulated to a value identical to that of the battery 14.Once the AC / DC controlled rectifier 16 is connected to the HVDC bus 12 in a subsequent step 70, operation in hybrid mode in power regulation mode is then possible in a final step 72.

[0031] On the figure 3The alternating current (AC) power source is connected to the HVDC bus first, and then the battery is connected to the HVDC bus, which has already been pre-charged by this AC power source. More specifically, in a first step 80, the gas turbine 20 is started, and the AC / DC controlled rectifier 16 is connected to the HVDC bus 12 in a step 82. Then, in a subsequent step 84, the HVDC bus voltage is pre-charged in voltage regulation mode, and in a step 86, still in voltage regulation mode, the voltage of the AC / DC controlled rectifier 16 is regulated to a value identical to that of the battery 14. The hybrid propulsion system is then, in a subsequent step 88, ready to operate in thermal mode. Once the battery is connected to the HVDC bus in a step 90, hybrid operation in power regulation mode is then possible in a final step 92.

[0032] Thus, with the present invention, it is possible: to manage power distribution by defining what power comes from the AC voltage electrical source (for example, a turbogenerator) and what power comes from the batteries, and to control the electrical sources by verifying that the power setpoint defined by this distribution is correctly applied, to adapt to the different operating regimes of the hybrid propulsion system (thermal, all-electric, hybrid), to adapt to the power and energy supply capacities of the two sources and to the power requirements of the electrical loads (thrusters), to offer a scalable hybridization solution that can meet different needs (series hybrid, parallel hybrid, complete or partial system, centralized or segregated systems, etc.).) and to the evolution of battery capacities, to offer a mass-optimized hybridization solution, to offer the least complex hybridization solution possible (in number of modules, logics, etc...), to optimize reliability.

Claims

1. A method for controlling the power distribution in a hybrid propulsion system including at least one electrical power source delivering an AC voltage (18A, 18B) associated with a controlled AC / DC rectifier (16) and at least one battery (14), the controlled AC / DC rectifier and the battery being each directly connected to an HVDC DC bus (12) powering at least one electrical load, the control of the power distribution is performed through the controlled AC / DC rectifier (16) on its own by a regulation loop on a power setpoint (Pref) based on a measured power of the battery (Pbat) and a regulation loop on a voltage setpoint (Vref) based on a measured voltage of the HVDC bus (VHVDC), one or the other of these two regulation loops each delivering a quadratic current setpoint Idref and Iqref for a regulation loop based on a current (Igen) of the electrical power source delivering an AC voltage, characterized in that the quadratic current setpoint Iqref is selectively delivered by one or the other of the two regulation loops on the power or voltage setpoints, according to a hybrid rating of the hybrid propulsion system for one of them and one of the thermal or start-up ratings of the hybrid propulsion system for the other.

2. The method as claimed in claim 1, characterized in that the quadratic current setpoint Iqref delivered to the regulation loop is previously summed by a current value equivalent to an estimate of the power consumed by said at least one electrical load.

3. The method as claimed in claim 1, characterized in that the quadratic current setpoint Idref is delivered by a flux management module (30).

4. The method as claimed in any of claims 1 to 3, characterized in that the voltage setpoint (Vref) is delivered by a power manager (28) and defines the voltage to be applied to the at least one electrical load.

5. The method as claimed in any of claims 1 to 4, characterized in that the power setpoint (Pref) is delivered by a hybridization assembly (44) and defines the desired power distribution between the at least one electrical power source delivering an AC voltage and the at least one battery.

6. A device for controlling the power distribution between an electrical power source delivering an AC voltage associated with a controlled AC / DC rectifier and a battery, the controlled AC / DC rectifier and the battery each being directly connected to an HVDC DC bus powering at least one electrical load, the device being configured to perform the control of the power distribution through the controlled AC / DC rectifier (16) by a regulation loop on a power setpoint (Pref) based on a measured power of the battery (Pbat) and a regulation loop on a voltage setpoint (Vref) based on a measured voltage of the HVDC bus (VHVDC), one or the other of these two regulation loops each delivering a quadratic current setpoint Idref and Iqref for a regulation loop based on a current (Igen) of the electrical power source delivering an AC voltage, characterized in that the quadratic current setpoint Iqref is selectively delivered by one or the other of the two regulation loops on the power or voltage setpoints, according to a hybrid rating of the hybrid propulsion system for one of them and one of the thermal or start-up ratings of the hybrid propulsion system for the other.

7. A hybrid propulsion system comprising a device for controlling power distribution as claimed in claim 6.

8. An aircraft of VTOL Vertical Take-Off and Landing type comprising a hybrid propulsion system as claimed in claim 7.