Electrical generation architecture for a hybridised turbine engine

Abstract

The invention relates to an aircraft series-hybrid electric propulsion assembly, the propulsion assembly comprising: - an electric turbogenerator (110) comprising at least one turbine engine (112) and at least one generator (114) coupled to the turbine engine; - a storage battery (125); - an HVDC bus (130) coupled to the turbogenerator and to the battery (125), the turbogenerator (110) being connected to the HVDC bus (130) via an alternating-current (AC) to direct-current (DC) rectifier (116) connected to phases of the at least one generator (114), the battery (125) being connected directly to the high-voltage direct-current (HVDC) electrical network, the turbogenerator (110) and the battery (125) sharing the power required to supply the HVDC bus (130); - a control system (115) for controlling the rectifier (116), the control system being configured to control the rectifier (116) and to manage electrical power sharing provided on the HVDC bus (130) between the turbogenerator (110) and the battery (125) on the basis of the setpoint control of at least the current (IBAT) delivered by the battery (125), by modulating the output voltage (UBUS) of the rectifier (116) via at least one control signal (CMD), in particular by pulse-width modulation.

Description

[0001] ELECTRICAL GENERATION ARCHITECTURE FOR HYBRID TURBOMACHINE

[0002] DESCRIPTION

[0003] TECHNICAL FIELD AND PRIOR TECHNOLOGY

[0004] This application relates to the field of electric aircraft propulsion and to certain architectures of the type known as "series hybrid electric propulsion" suitable for both fixed-wing and rotary-wing or convertible aircraft.

[0005] Climate change is a major concern for many legislative and regulatory bodies worldwide. Indeed, various restrictions on carbon emissions have been, are being, or will be adopted by different countries. In particular, an ambitious standard applies to both new types of aircraft and those already in service, requiring the implementation of technological solutions to bring them into compliance with current regulations. Civil aviation has been actively working for several years now to contribute to the fight against climate change. Technological research efforts have already led to significant improvements in the environmental performance of aircraft, focusing particularly on hybrid architectures.The Applicant takes into consideration the factors impacting all phases of design and development in order to obtain aeronautical components and products that are less energy-intensive, more environmentally friendly and whose integration and use in civil aviation have moderate environmental impacts with the aim of improving the energy efficiency of aircraft.

[0006] In a series hybrid architecture, the internal combustion engine is not directly involved in propulsion. Instead, the internal combustion engine is used to generate electricity, which then powers an electric motor. This electric motor is responsible for propelling the aircraft and drives propellers, rotors, or propulsion / lift fans. EP 2844556 provides an example of a series hybrid electric propulsion architecture for aircraft.

[0007] There are purely turboelectric architectures that use several turbogenerators as sources of electrical power. As with conventional turbine propulsion systems, the oversizing of the turbomachine for certain specific operating regimes, the high cost, mass, and complexity of the redundancies required to meet flight safety requirements prevent the development of an optimal propulsion architecture.

[0008] A particular series hybrid architecture combines a turbogenerator with a different electrical power source, typically an electrochemical source such as a fuel cell or battery.

[0009] Figure 1 shows an example of such an architecture. A high-voltage DC power grid 30 is supplied by two parallel voltage sources 10, 20 for several identical propulsion units 40, each consisting of an inverter 41 capable of powering a three-phase electric machine 43 designed to drive a propeller 45, possibly via a reduction gearbox. Each propulsion unit is generally equipped with one or more switching elements 42 of the contactor or circuit breaker type, allowing for reconfiguration and / or isolation of a faulty propulsion unit. The voltage inverter 41 of each unit is thus supplied via a grid 30 at a nominal voltage generally on the order of several hundred to several thousand volts, typically in the form of an HVDC (High Voltage Direct Current) bus, itself powered by the parallel-connected sources 10, 20.

[0010] A first source of electrical energy is a turbogenerator 10 consisting of a gas turbine driving an electric generator 14. A rectifier 16 allows a conversion of an alternating AC voltage delivered by the generator 14 into a direct DC voltage for the network 30.

[0011] A second source of electrical energy 20 is here formed by at least one storage battery 25. In the particular embodiment example of Figure 1, the battery 25 is connected to the network via a reversible DC / DC converter Tl of the chopper type provided between the battery 25 and the HVDC bus 30 which allows the charging and discharging of the battery to be managed.

[0012] This architecture offers the advantage of decoupling the HVDC bus voltage 30 from that of the battery 25, allowing the rectifier 16 to operate at a constant voltage. However, adding such a power converter increases the weight and size, primarily due to the inductive components it incorporates, while also reducing overall reliability. US patent 20160176534 describes this type of architecture.

[0013] A lower cost and less bulky power source can be provided by directly connecting battery 25 to HVDC bus 30.

[0014] Document FR 3 056 555 from the applicant provides an example of an implementation without an intermediate energy conversion stage between the battery and the HVDC bus. A drawback of this design is that the battery tends to impose its voltage on the HVDC bus, a voltage that is highly dependent on the battery's state of charge and the current it delivers. This voltage is likely to fluctuate significantly. While such an architecture eliminates the need for the DC / DC converter T1, it typically requires the rectifier control 16 to constantly adapt to the battery voltage and manage its charging and discharging.

[0015] DESCRIPTION OF THE INVENTION

[0016] According to one aspect, the present invention proposes a device for a hybrid electric-series aircraft propulsion system, comprising:

[0017] - an electric turbogenerator comprising at least one turbomachine and at least one generator coupled to said turbomachine,

[0018] - a battery of rechargeable batteries,

[0019] - an HVDC bus coupled to said turbogenerator and to said battery, the turbogenerator being connected to the HVDC bus via an AC to DC rectifier connected to phases of the generator, the battery being connected directly to the HVDC high voltage direct current electrical network, the device further comprising a rectifier control system configured to control the rectifier and achieve a sharing of electrical power supplied on the HVDC bus between the turbogenerator and the battery from the control setpoint of at least the current I BAT delivered by the battery, by modulating the output voltage UBUS of the rectifier via at least one control signal.

[0020] This control signal is typically a pulse width modulation (PWM) signal.

[0021] Typically, the rectifier control system includes:

[0022] - a plurality of correction stages, each correction stage being equipped with a corrector and configured to receive a measurement of a regulation parameter of the rectifier output voltage from among a set of parameters including a rectifier output DC current I, an HVDC bus voltage UBUS, a turbomachine rotation speed N2, a battery output current IBAT, and to establish, from a comparison between this measurement of said regulation parameter and a reference or a limit not to be exceeded: an elementary setpoint, the respective elementary setpoints at the output of said correction stages being all homogeneous to a current or all homogeneous to a voltage,

[0023] - a logic module for selecting elementary setpoints configured to receive said elementary setpoints and to select, based on comparisons between respective values ​​of said elementary setpoints and a predetermined priority order associated with each of said correction stage, an elementary output setpoint from among said elementary setpoints, said selected elementary output setpoint serving as the so-called "general" setpoint from which the rectifier control signal is established.

[0024] The rectifier control system is adapted here to maintain limits on turbomachine output speed, bus voltage, battery output current and turbogenerator output power.

[0025] Thus, among these correction levels, the following are typically included:

[0026] - at least one current correction stage at the battery output,

[0027] - at least one turbomachine speed correction stage (N2)

[0028] - at least one HVDC bus voltage correction stage, - at least one electrical power correction stage at the rectifier output.

[0029] Advantageously, the general control setpoint corresponds to a vector component IQ of phase currents along a first axis of a rotating frame linked to a rotor of the generator.

[0030] Advantageously, the rectifier control system can also be adapted to maintain turbomachine torque limits.

[0031] Thus, among the said correction stages there is typically: at least one torque correction stage of the turbomachine.

[0032] The correction levels may include at least one or more correction levels, or all of the following correction levels:

[0033] - a first correction stage to control a battery current to a reference setpoint developed by the avionics configured to receive a battery current measurement I BAT and to determine an elementary reference battery current setpoint based on the difference between a reference battery current setpoint and the battery current measurement I BAT,

[0034] - a second correction stage to maintain a battery current above a minimum stop, configured to receive a battery current measurement I BAT and to determine an elementary lower battery current limiting setpoint based on the difference between a typically negative minimum battery current stop setpoint I BAT_MIN, equal to the maximum permissible charging current for the battery, and the battery current measurement I BAT,

[0035] - a third correction stage to maintain a battery current below a maximum limit, configured to receive a battery current measurement I BAT and to determine an elementary upper battery current limiting setpoint based on the difference between a maximum battery current limit setpoint I BAT_MAX typically equal to the maximum permissible discharge current for the battery and the battery current measurement I BAT,

[0036] - a fourth correction stage to maintain a turbomachine speed above a minimum stop, configured to receive a turbomachine speed measurement N2 and to determine an elementary lower speed limitation setpoint for the turbomachine based on the difference between a minimum turbomachine speed stop value N2MIN typically equal to the minimum allowable speed of the turbomachine power turbine and the turbomachine speed measurement,

[0037] - a fifth correction stage to maintain a turbomachine speed below a maximum stop, configured to receive a turbomachine speed measurement and to determine an elementary upper speed limitation setpoint for the turbomachine based on the difference between a maximum turbomachine speed stop setpoint N2MAX typically equal to the maximum allowable overspeed of the turbomachine power turbine and generator rotor and the turbomachine speed measurement N2,

[0038] - a sixth correction stage to maintain a turbomachine mechanical torque above a minimum stop, configured to receive a turbomachine mechanical torque measurement TRQ and to determine an elementary lower limit setpoint for turbomachine mechanical torque based on the difference between a typically negative minimum stop setpoint for turbomachine mechanical torque TRQMIN, equal to the maximum permissible transmission torque in engine mode, and the current turbomachine mechanical torque measurement TRQ.

[0039] - a seventh correction stage to maintain a turbomachine mechanical torque below a maximum stop, configured to receive a turbomachine mechanical torque measurement TRQ and to determine an elementary upper limit setpoint for turbomachine mechanical torque based on the difference between a maximum turbomachine mechanical torque stop setpoint TRQMAX typically equal to the maximum allowable transmission torque in generator mode and the current turbomachine mechanical torque measurement TRQ,

[0040] - an eighth correction stage to maintain the HVDC bus voltage above a minimum stop, configured to receive a UBUS bus voltage measurement and to determine an elementary lower bus voltage limiting setpoint based on the difference between a UBUS_MIN minimum bus voltage stop setpoint typically equal to the minimum allowable operating voltage of the various power converters connected to the HVDC bus and the UBUS bus voltage measurement,

[0041] - a ninth correction stage to maintain the HVDC bus voltage below a maximum stop and configured to receive a UBUS bus voltage measurement and to determine an elementary upper bus voltage limiting setpoint based on the difference between the UBUS bus voltage measurement and a maximum bus voltage stop setpoint UBUS_MAX typically equal to the maximum allowable operating voltage of the various power converters connected to the HVDC bus,

[0042] - a tenth correction stage to maintain electrical power at the output of the rectifier below a maximum stop and configured to receive a bus voltage measurement UBUS and a bus current measurement I DC and to evaluate an electrical power measured at the output of the rectifier and to determine an elementary upper power limiting setpoint based on the difference between the measured electrical power and a maximum power stop setpoint PTGENMAX typically equal to the maximum rated electrical power of the turbogenerator.

[0043] According to one possible implementation, the first stage of correction can be associated with a first priority level called "BAS".

[0044] The fourth and fifth correction levels and / or sixth and seventh correction levels can be associated with a second priority level called "INTERMEDIATE" which is higher than the first priority level.

[0045] The tenth correction stage can be associated with a third priority level called "HIGH" which is higher than the second priority level.

[0046] The second and third correction stages and / or eighth and ninth correction stages may be associated with a fourth priority level called "PRIORITY" which is higher than the third priority level.

[0047] Advantageously, the elementary setpoint selection logic module comprises a plurality of selection blocks, each selection block being formed by: - ​​a minimum value selection unit among its inputs arranged in series with a maximum value selection unit among its inputs, or

[0048] - a minimum value selection unit among its inputs, each of the selection blocks being configured to receive, among the elementary instructions, a given elementary instruction or a given pair of elementary instructions emanating from given correction stages among the correction stages receiving the same measurement of the same measurement parameter, the given elementary instruction or the given pair of elementary instructions being different from that received by said other selection blocks, the selection blocks being arranged in a succession of cascaded blocks in an order depending on the order of priority to which the given correction stage(s) is or are associated,

[0049] -a first block in the succession of cascading blocks receiving as input an elementary instruction, called the reference instruction, from among said elementary instructions,

[0050] - a final block in the succession of cascading blocks producing at output a setpoint said elementary output setpoint, each of said other blocks receiving at input an elementary setpoint selected by a previous selection block of the plurality of selection blocks arranged in cascade, and producing, at output, an elementary setpoint selected from its inputs and destined for a following block of said plurality of selection blocks.

[0051] Advantageously, the generator is a three-phase synchronous rotating permanent magnet (PMM) machine.

[0052] According to an advantageous embodiment, the turbomachine has a free turbine.

[0053] According to another aspect, the present invention relates to a series hybrid propulsion aircraft comprising a device for a series hybrid electric propulsion assembly as defined above.

[0054] According to another aspect, the present invention provides a method for controlling the turbogenerator of a device as defined above, wherein the HVDC bus is coupled to at least one set of propulsion loads. In a particular embodiment, the method comprises the following steps:

[0055] - during a first phase following the detection of an increase in electrical power demand from said propulsion load set and as long as the electrical power PTGEN at the output of said rectifier remains below a threshold, control the rectifier so as to maintain its output voltage UBUS at a value such that the battery produces zero output current while increasing the current delivered by the rectifier so that the turbogenerator alone provides electrical power to the HVDC bus in response to said increase, then, following the detection of reaching an electrical power threshold PTGEN_MAX at the rectifier output and a further increase in electrical power demand beyond said threshold from said propulsion load set, during a second phase,to control the rectifier to lower its UBUS output voltage so that the battery discharges while maintaining a constant power output from the rectifier so that the turbogenerator and battery jointly supply electrical power to the HVDC bus in response to said new increase.

[0056] According to another specific aspect, the process may include the following steps:

[0057] - following the detection of an increase, in particular a rapid increase, in the demand for electrical power from said set of loads and the subsequent decrease in the speed N2 of the turbomachine's free turbine below its setpoint, control the rectifier so as to temporarily lower its output voltage UBUS in order to cause a discharge of the battery and thus limit the transient speed drop, then,

[0058] - following the detection of a stabilization of the electrical power demand from said set of loads, control the rectifier to increase its UBUS output voltage in order to cause the battery to charge, then restore a constant UBUS output voltage in order to maintain zero current at the battery output, and / or including the following steps:

[0059] - following the detection of a decrease, in particular a rapid decrease, in the demand for electrical power from said set of loads and the subsequent increase in the speed N2 of the turbomachine's free turbine above its setpoint, control the rectifier to temporarily reduce its output voltage UBUS in order to recharge the battery and thus limit the transient overspeed, then,

[0060] - following detection of a stabilization of the electrical power demand from said set of loads, control the rectifier to increase its UBUS output voltage in order to charge the battery and then restore a constant UBUS output voltage in order to maintain a zero current at the battery output.

[0061] BRIEF DESCRIPTION OF THE DRAWINGS

[0062] The present invention will be better understood and other details, features, and advantages of the present invention will become more apparent upon reading the following description of a non-limiting example, with reference to the accompanying drawings in which:

[0063] Figure 1 serves to illustrate a conventional "series hybrid electric propulsion" architecture with a battery connected to an HVDC bus via a reversible DC / DC converter.

[0064] Figure 2 illustrates an example of a "series hybrid electric propulsion" architecture as implemented according to an embodiment of the present invention and equipped with a turbogenerator and a battery with a direct connection of the battery to an HVDC bus, power sharing between the turbogenerator and the battery being controlled by means of a control system for an active rectifier of the turbogenerator. Figure 3 illustrates a particular embodiment of an active rectifier control system associated with the turbogenerator and designed to generate a control signal for the rectifier based on a vector component setpoint for the phase current of the generator selected from several elementary setpoints;

[0065] Figure 4 serves to illustrate an example of the realization of an elementary setpoint selection logic module integrated into an active rectifier control system and producing the setpoint with a vector component in quadrature of the generator phase current.

[0066] Figures 5A and 5B serve to illustrate, by means of power evolution curves over time and turbine speed evolution curves, a particular operating mode of a propulsion unit as implemented according to the invention in which the power delivered by the battery compensates for a transiently excess or deficit power supply from the turbogenerator following a rapid variation in power demand by the propulsive loads exceeding the acceleration and deceleration performance of the turbomachine.

[0067] Figure 6 serves to illustrate by means of power evolution curves over time a particular operating mode of a propulsion system as implemented according to the invention in which the electrical power delivered by the battery compensates for that of the turbogenerator when a limit of maximum electrical power generated by the latter has been reached.

[0068] Identical, similar or equivalent parts of the different figures carry the same numerical references in order to facilitate the transition from one figure to another.

[0069] The different parts shown in the figures are not necessarily to a uniform scale, in order to make the figures easier to read. DETAILED DESCRIPTION OF SPECIFIC METHODS OF IMPLEMENTATION

[0070] We now refer to figure 2 which shows a series hybrid propulsion system for an aircraft and as implemented according to an example of an embodiment of the present invention.

[0071] This assembly comprises at least one turbogenerator 110 and at least one battery 125 of accumulators connected to the same high-voltage electrical network, here in the form of an HVDC bus 130, which supplies at least one set of propulsion electrical loads 140 from at least one propulsion chain typically comprising propulsion and / or lift motors and auxiliary converters. The set of loads 140 can be formed from a plurality of propulsion groups such as those referenced 40 and described previously in connection with Figure 1.

[0072] Different types of electrical power generation devices are combined here, and the electrical power is shared between the battery 125 on the one hand, and the turbogenerator 110 on the other, while maintaining certain operating parameters—such as the turbogenerator output current, the battery output current, the bus voltage, the turbogenerator output power, and the turbine rotational speed—within optimal operating ranges. To achieve this, optimized control of at least one rectifier 116 is provided. This rectifier is integrated into the turbogenerator 110 or arranged at its output and is considered "active" because it is made of forced-commutating semiconductors and designed to be controlled by a control system 115.Since the battery 125 is passive, it is the rectifier 116 of the turbogenerator 110 associated with its control system 115 that manages the sharing of power with the battery 125 to supply the HVDC bus 130.

[0073] Such an arrangement can, for example, allow the 110 turbogenerator to be sized only for the power required for cruise flight, with the additional power needed for takeoff and altitude gain then being supplied by the 125 battery. This architecture can also, for example, improve the transient acceleration and deceleration performance of the 110 turbogenerator, particularly in cases where it is equipped with a free-turbine turbomachine, and therefore has low inertia, designed to optimize specific fuel consumption at the expense of transient performance. This arrangement also allows the 125 battery to be used as redundancy for the 110 turbogenerator and to replace it in the event of a failure.

[0074] Such an architecture also lends itself to the implementation of flight phases where the 140 payloads, in particular their propulsion and / or lift components, are powered solely by the 125 battery in order to temporarily benefit from certain advantages such as reduced noise and a smaller thermal signature.

[0075] The 125 battery is connected directly to the HVDC 130 bus. By "connected directly" we mean that there is no intermediate power converter between the battery and the HVDC 130 bus. Thus, an output voltage from the 125 battery corresponds to a voltage on the HVDC 130 bus.

[0076] The battery 125 can be modeled in a simplified manner, as shown in Figure 1, by its open-circuit voltage Eo, which depends in particular on its state of charge (SOC), and by its internal resistance RBAT, which depends in particular on the temperature. Other types of electrical battery models, notably the Randles type where the internal impedance is represented by RC cells, can also be used. The direct connection of the battery to the HVDC bus 130, without an intermediate energy conversion stage, allows for a direct and instantaneous replacement of electrical energy in the event of a failure of the turbogenerator 110. This significantly reduces the availability requirements applicable to the latter, thus simplifying it and lowering its cost.Furthermore, the damping provided by the internal resistance of the battery 125 connected directly to the HVDC bus 130 makes it possible to significantly improve the stability of the UBUS voltage regulation of the HVDC bus 130 via the active rectifier 116 of the turbogenerator 110.

[0077] The battery 125 is associated with, or equipped with, a BMS 126 electronic device that protects it and ensures its proper operation by monitoring the condition of its electrochemical cells. Such a device 126 can provide indicative status data such as the SOC (State of Charge), the SOH (State of Health), and a charging current setting ICHARGE based on various parameters such as the internal temperature of the battery or its SOC.

[0078] The turbogenerator 110 connected to the same HVDC bus 130 consists of a turbomachine 112, in particular a gas turbine which can be of the "linked turbine" type (i.e. with a compressor, one or more expansion turbines and a driven load attached to the same shaft and rotating at the same speed modulo a possible reduction or multiplication ratio) or advantageously of the "free turbine" type, this second type generally having a specific consumption at partial load significantly lower than the first type with a linked turbine.

[0079] The turbomachine 112 is controlled by a turbomachine control module 113. This module 113 includes a digital turbomachine control unit, or EECU (for "Engine Electronic Control Unit"), which is configured, in particular, to regulate the rotational speed of the load driven by the turbomachine—in this case, the electric generator(s)—to its optimal setpoint. To do this, the control unit acquires a speed measurement N2 of the power shaft of the turbomachine 112.

[0080] The turbomachine 112 is designed to drive the mechanical shaft of at least one electric generator 114 having n output phases, for example, n equal to 3, which supplies an AC distribution busbar at the input of the active electrical rectifier 116. The generator 114 is a permanent magnet synchronous generator (PMG). This type of generator has the advantage of a significantly reduced mass compared to a three-stage wound-rotor synchronous generator. It is also suitable for high mechanical drive speeds, for example, between 10,000 and 30,000 rpm, for power outputs on the order of several hundred kW. Direct drive of the generator 114 by a free turbine is possible.

[0081] In the case where the turbogenerator 110 has several generators, these can be driven by the same turbomachine 112, for example, via a gearbox. The rectifier 116 allows the power conversion between an AC distribution busbar at the output of the generator 114 and the HVDC bus 130. The rectifier 116 is an active rectifier controlled by the control system 115, which advantageously implements several feedback loops and consists of one or more logic modules. The rectifier 116 typically uses vector control and PWM (Pulse Width Modulation) to rectify the alternating voltages from the generator and supply electrical energy to an HVDC bus in the form of a controlled, continuous UBUS voltage.

[0082] From the electromotive forces (EMF) of the generator 114 and according to the control command (CMD) of the control system 115, the rectifier 116 thus delivers the direct voltage UBUS whose value is controlled by the control system 115.

[0083] The current I BAT delivered by the battery 125 to the HVDC 130 network can be defined by the following expression: in generator convention with a current I BAT > 0 when the battery 125 supplies energy to the bus and loads, with Eo the open-circuit voltage of the battery 125 and RBAT the internal resistance of the battery 125 for a given state of the latter in other words typically a given state of SOC and / or SOH and / or temperature.

[0084] Thus, in order to allow the battery 125 to be recharged (I BAT < 0), the control system 115 drives the rectifier 116 so that it imposes a voltage UBUS greater than the open-circuit voltage Eo of the battery 125.

[0085] When the battery 125 is required to supply electrical power to the HVDC bus (I BAT > 0), the control system 115 drives the rectifier 116 so that it imposes a UBUS voltage lower than the open-circuit voltage Eo of the battery 125.

[0086] When no contribution from battery 125 is desired to the electrical power delivered to the HVDC bus 130 and battery 125 is to be maintained in the same state of charge (current I BAT = 0), the control system 115 drives the rectifier 116 so that it imposes a constant voltage UBUS, equal to the open-circuit voltage Eo of the battery, so as to maintain a zero current at the output of battery 125.

[0087] Control of the UBUS DC voltage delivered by the rectifier 116 on the HVDC bus 130 thus allows control of the charging or discharging current of the battery 125, and therefore modulation of the respective power contributions of the two generating elements 125, 110 to the propulsion of the aircraft.

[0088] Such control is preferably achieved through closed-loop control of the battery current IBAT, since the open-circuit voltage values ​​Eo and internal resistance RsAide of the battery are difficult to access.

[0089] The 115 control system is typically configured to perform several of the following control functions, and advantageously all of the following functions:

[0090] - contribute to maintaining the rotational speed N2 of the turbomachine 112 within an authorized range between a lower stop N2_MIN and an upper stop N2_MAX;

[0091] - limit the electrical power PTGEN delivered by the turbogenerator 110 at the output of the rectifier 116 to a value lower than a threshold or maximum limit PTGEN_MAX;

[0092] - limit the mechanical torque supplied by the turbomachine TRQ. within a range between a minimum stop TRQMIN and a maximum stop TRQMAX;

[0093] - maintain a UBUS bus voltage of the HVDC 130 bus between a lower stop UBUS_MIN and an upper stop UBUS_MAX;

[0094] - maintain a battery current IBAT between a lower limit IBAT_MIN typically corresponding to a maximum current value during charging and which is strictly negative and IBAT_MAX corresponding to a maximum current value during discharging and which is strictly positive;

[0095] - ensure battery charging according to a current setting IBAT_REF typically developed by the electronic device BMS 126.

[0096] To allow regulation of the aforementioned parameters, various measurement means are provided. Current measurement means 133, typically including a current sensor at the output of the rectifier 116, allow transmission to the control system 115 of the rectifier 116 of a measurement of the DC current I delivered on the HVDC bus 130 at the output of the rectifier 116.

[0097] Voltage measurement means 131, typically including a voltage sensor, are provided to transmit a measurement of the HVDC bus voltage Usus 130 to the control system 115 of the rectifier 116. Current measurement means 129, typically including a current sensor, at the output of the battery 125, transmit a measurement of the battery current IBAT to the control system 115 of the rectifier 116. Such means 129 may optionally be equipped with a current sensor either at the battery 125 itself or at the output of the battery 125 on a portion of the circuit connected to the HVDC distribution network.

[0098] Measurement means 119 for currents to measure the current in each phase of generator 119 are also provided.

[0099] A rotational speed N2 of the turbine can be obtained by means of a speed sensor mounted on or near a power shaft of the turbomachine 112 while a torque measurement TRQ. can be obtained by means of a torque meter installed on the output shaft of the turbomachine and a torque estimator integrated into the turbomachine control module 113.

[0100] A detailed example of the realization of a control system 115 of the active rectifier 116 allowing the aforementioned regulations to be carried out and the turbogenerator 110 and the battery 125 to be maintained within the various operating limits mentioned above is given in Figure 3.

[0101] The control system 115 is equipped with a plurality of correction stages, in this particular embodiment ten stages, 8O1, 8O2, 8O3, 8O4, 80s, 806, 8O7, 80s, 8O9, 8010, each configured to receive a measurement of a parameter and to, from a comparison between this measurement and a setpoint corresponding to a reference or a stop, in other words a threshold not to be exceeded, establish an elementary setpoint, here in particular homogeneous to a current, after passing through a corrector. In this example, the elementary instructions IQREFJBATREF, IQREFJBATMIN, IQREFJBATMAX, IQREF_N2MIN, IQREF_N2MAX, IQREF_TRQMIN, IQREF_TRQMAX, IQREF_UBUSMIN, IQREFJJSBUSMAX, IQREF_PTGENMAX produced at the output of the different stages, 80i, 8O2, 8O3, 8O4, 80s, 80e, 8O7, 80s, 8O9, 8010 are then transmitted to a logic module 85 for selecting the elementary instruction, an example of which is given in Figure 4.

[0102] This module 85 is configured to select a setpoint from among the aforementioned elementary setpoints, with IQREF = (IQREFJBATREF OR IQREFJBATMIN OR IQREFJBATMAX OR IQREF_N2MIN OR IQREF_N2MAX OR IQREF TRQMIN OR IQREF TRQMAX, IQREF_UBUSMIN OR IQREFJJSBUSMAX OR IQREF_PTGENMAX), and to output an output setpoint iQREp corresponding to the selected elementary setpoint. This selection is made based on the respective values ​​of the different elementary setpoints and a predetermined hierarchy that depends on the degree of importance, in other words, the priority, associated with the different control functions implemented through these different elementary setpoints. In this example implementation, the selected elementary setpoint is a homogeneous current setpoint.The selected setpoint IQREF and produced at the output of module 85 then serves as the so-called "general" setpoint transmitted to a control module 99 which generates CMD control signals for switching elements of the rectifier 116 typically in the form of PWM type signals.

[0103] Here, in particular, the generator-rectifier assembly is controlled by means of a current output setpoint IQREF which corresponds to or is homogeneous with a quadrature component IQ of current IA, IB and the in the phases of generator 114, resulting from a Park / Concordia transform ( IA, IB and the) (ID, IQ) in a rotating frame associated with the rotor of generator 114, taking as convention IQ > 0 in generator operation.

[0104] The control module 99, which receives this IQREF setpoint, can be specifically designed to determine an error based on the difference between this vector component IQREF setpoint and a measured value established from phase current measurements IA, IB, and the currents from generator 114, transformed into direct quantities ID and into quadrature quantities IQ by Park transform. It can then use controllers, for example, of the proportional-integral type, to determine voltage setpoints from this error. The control module 99 is designed to determine the CMD switching commands of the rectifier switches from these voltage setpoints, for example, after applying an inverse Park transform. An example of vector control algorithms for a synchronous electric machine to control a torque setpoint using the Park transform is given in document EP2510612.Voltage measurements of bus U BUS and N2 at the input of block 99 in figure 3 serve as control parameters for the inverter-electric motor assembly, with its 3 phase currents IA, IB and le.

[0105] In the example embodiment illustrated in Figure 3, each correction stage 8O1, ... , 8Oio is here equipped with a comparator 82i, 822, 82s, 824, 82s, 82e, 82?, 82s, 82g, 82io to establish a difference between a measured parameter and a reference or stop and a regulator or corrector 82i, 822, 82s, 824, 82s, 82e, 82?, 82s, 82g, 82w for example of the Proportional-Integral-Derivative (PID) type at the output of the comparator.

[0106] The elementary setpoint at the output of the correction stage 8O1 is the reference setpoint. Each elementary setpoint at the output of the different correction stages 8O2, 8O3, 8O4, 8O5, 80e, 8O7, 80s, 80g, 8Oio represents a current value IQ which limits the reference setpoint in order not to exceed a corresponding lower or upper limit.

[0107] A first correction stage 8O1 is configured to receive an iBAT REp current setpoint.

[0108] The first correction stage 8O1 creates a closed loop for controlling the battery current I BAT to a setpoint I BAT_REF, which corresponds to a reference current for charging the battery 125.

[0109] The first correction stage 8O1 is designed to maintain a battery charging current close to a reference value. This stage 8O1 is configured to receive a battery current measurement IBAT, to determine, via comparator 82i, a difference between a reference battery current setpoint IBAT_REF and the measured battery current IBAT, and to determine, at the output of a regulator 84i, an elementary reference battery current setpoint IQREF_BATREF based on this difference. By convention, the charging current and the reference value IBAT_REF are negative. The reference setpoint IBAT_REF is derived from the electronic BMS 126.

[0110] When the turbogenerator 110 is operating within a so-called "stabilized" operating range, far from the limits or operating stops that will be detailed later, and when the battery 125 has been used, for example, during a previous flight phase, the turbogenerator 110 can recharge the battery 125 by controlling, through appropriate control of the rectifier 116, the battery current to a setpoint I BAT_REF derived from and generated by the BMS device 126. This function is typically associated with a "LOW" priority level, and in particular the lowest among the priority levels to which the various correction stages and the different elementary setpoints at the output of these stages correspond.

[0111] A second correction stage 8O2 is provided to maintain the battery current above a minimum limit. This stage 8O2 is configured to receive a battery current measurement IBAT, to determine, via comparator 822, a difference between a minimum limit setpoint IBAT_MIN for battery current and the measured battery current IBAT, and to determine, at the output of a regulator 842, a basic lower limit setpoint for battery current IQREF_BATMIN based on this difference. Since the minimum limit value corresponds to a charging current value, this value is negative. The minimum limit IBAT_MIN acts as a safety stop to prevent excessively rapid battery charging, for example, during overspeed clipping following a rapid decrease in power demand.

[0112] A third correction stage, 8O3, is configured to maintain the battery current below a maximum limit. This stage, 8O3, is configured to receive a battery current measurement, IBAT, and to determine, via comparator 82s, the difference between a maximum battery current limit setpoint, IBAT_MAX, and the measured battery current, IBAT. Based on this difference, the output of a regulator, 842, determines an elementary upper battery current limit setpoint, IQREF_BATMAX. The maximum battery current limit, IBAT_MAX, acts as a safety stop to prevent excessively rapid battery discharge, for example, during the capping of a low-speed load following a rapid increase in power demand.

[0113] The correction stages 8O2 and 8O3 control the current IBAT and maintain it within a range defined by a lower limit IBAT_MIN of battery current and an upper limit IsAT_MAx of battery current. In this example, the respective outputs of the correction stages 802 and 803 are elementary quadrature current setpoints IQREF_BATMIN and IQREF_BATMAX.

[0114] To avoid damaging the 125 battery, the battery current (IBAT) is maintained between the values ​​IBAT_MAX during discharge and IBAT_MIN during charging. These limits are specific operating characteristics of the 125 battery.

[0115] A prolonged exceedance of these thresholds is likely to cause the battery 125 to be isolated from the HVDC bus 130 by the BMS device 126. This current regulation function I BAT is typically associated with a priority level called "PRIORITY," and in particular, with a priority level among the higher levels associated with the different regulation functions provided by the control system 115 of the rectifier 116.

[0116] A fourth correction stage 8O4 is provided to maintain a turbomachine speed N2 above a minimum stop N2MIN. This stage 8O4 is configured to receive a turbomachine speed measurement N2 and, via comparator 824, to determine the difference between a minimum turbomachine speed stop setpoint N2MIN and the measured turbomachine speed N2. It then establishes, via controller 844, an elementary lower turbomachine speed limit setpoint IQREF_N2MIN based on the difference received at the input of this controller 844. The stop N2MIN corresponds to an operating characteristic of the turbomachine to prevent transient underspeed of the power shaft below a certain threshold, particularly during excessively rapid load loading, from damaging it and / or requiring maintenance.

[0117] A fifth correction stage, 80s, is provided to maintain the turbomachine's speed N2 below a maximum limit. This stage 80s is configured to receive a turbomachine speed measurement N2 and, using comparator 82s, to determine the difference between a maximum turbomachine speed limit setpoint N2MAX and the measured turbomachine speed N2. The regulator / corrector 84s then establishes an elementary upper speed limit setpoint for the turbomachine, IQREF_N2MAX, based on the difference received at the input of this regulator 84s. The maximum turbomachine speed limit N2MAX corresponds to an operating characteristic of the turbomachine to prevent transient overspeed of the power shaft above a certain threshold from damaging it and / or requiring maintenance.

[0118] The 8O4 and 80s correction stages create closed feedback loops to protect the turbomachine against excursions below a lower speed stop N2MIN and above an upper speed stop N2MAX, particularly during rapid variations in power demand.

[0119] This N2 speed regulation function is associated with a priority level called "INTERMEDIATE", higher than the priority level "LOW".

[0120] The respective outputs of the correction stages 8O4 and 80s are in this example quadrature current setpoints IQREF_N2MIN and IQREF_N2MAX.

[0121] A sixth correction stage, 80e, is provided to maintain the turbomachine's mechanical torque above a minimum limit. This stage, 80e, receives a measurement of the turbomachine's mechanical torque, TRQ, and determines an elementary lower-limit setpoint for the turbomachine's mechanical torque, IQREF_TRQMIN, based on the difference between a minimum-limit setpoint for the turbomachine's mechanical torque, TRQMIN, and the current measurement of the turbomachine's mechanical torque, TRQ.

[0122] A seventh correction stage, 8O7, is provided to maintain the turbomachine's mechanical torque below a maximum limit. This stage, 8O7, is configured to receive a measurement of the turbomachine's mechanical torque, TRQ, and to determine an elementary upper limit setpoint for the turbomachine's mechanical torque, IQREF_TRQMAX, based on the difference between a maximum limit setpoint for the turbomachine's mechanical torque, TRQMAX, and the measured torque, TRQ. The sixth correction stage, 80e, and the seventh correction stage, 8O7, are the closed-loop control systems whose outputs respectively provide the setpoints IQREF_TRQMIN and IQREF_TRQMAX, which in this example correspond to a quadrature current.

[0123] A limitation of the TRQ torque to keep it below a TRQMAX stop is achieved through the 8O7 correction stage in order not to damage the mechanical transmission.

[0124] Similarly, a limitation of the torque TRQ. to keep it above a minimum stop TR MIN, typically of negative value in order to limit the torque generated in the motor quadrant by the generator on the turbomachine power shaft during operation with electrical power generated on the bus almost zero, is carried out here by means of stage 80e.

[0125] This mechanical torque regulation function TRQ is associated with a priority level called "INTERMEDIATE", in any case higher than the priority level of the battery charging current regulation implemented using the correction stage 8O1, and lower than the priority level of the battery current limiting function during charging and discharging.

[0126] An eighth correction stage, 80 seconds, is provided to maintain the UBUS bus voltage above a minimum limit. This 80-second stage is configured to receive a bus voltage measurement and to determine a basic "lower bus voltage limit" setpoint, IQREF_UBUSMIN, based on the difference between a minimum bus voltage limit value, UBUS_MIN, and the measured UBUS bus voltage. Such a minimum UBUS_MIN limit value typically corresponds to a characteristic of a downstream electrical network and the aircraft equipment connected to it. Below a certain voltage level, the inverters of the electric propulsion motors are likely to shut down.

[0127] A ninth correction stage, 8O9, is provided to maintain the UBUS bus voltage below a maximum limit. This stage, 8O9, is configured to receive a bus voltage measurement and to determine an elementary setpoint, known as the "upper bus voltage limit" (IQREF_UBUSMAX), based on the difference between a maximum bus voltage setpoint (UBUS_MAX) and the measured bus voltage (UBUS_MAX). Such a minimum UBUS_MAX limit value typically corresponds to a characteristic of a downstream electrical network and the aircraft equipment connected to it. Above a certain voltage level, the inverters of the electric propulsion motors are likely to shut down.

[0128] The eighth and ninth correction stages 80s and 8O9 perform closed loops for controlling the minimum voltage limits of bus UBUS_MIN and the maximum voltage limits of bus UBUS_MAX.

[0129] The respective outputs of the eighth and ninth correction stages 80s and 809 correspond in this example respectively to elementary quadrature current setpoints IQREF_UBUSMIN and IQREF_USBUSMAX-

[0130] The HVDC bus voltage 130 is thus maintained above the minimum limit UBUS_MIN to prevent a current increase that could lead to excessive heating of the distribution cables and / or limit the performance of the electric propulsion motors. The HVDC bus voltage 130 is also maintained below the maximum limit UBUS_MAX to prevent potential damage to the insulation of electrical equipment connected to the HVDC bus, particularly propulsion systems, to protect the battery cells 125, or to prevent reaching an overvoltage threshold corresponding to a safety threshold that could cause the turbogenerator 110 to shut down or isolate the battery 125 or the inverters of the propulsion motors integrated into the loads 140.

[0131] This UBUS bus voltage regulation function implemented using stages 80s and 8O9 is associated with a priority level called "PRIORITY", typically among the highest, and advantageously the highest, among the different priority levels of the regulation functions ensured by the control system 115 of the rectifier 116.

[0132] A tenth correction stage 8Oio is provided here to perform maximum power control by the turbogenerator 110. This stage is configured to perform a control loop and maintain the electrical power of the turbogenerator 110 below a maximum limit PTGEN_MAX. The correction stage 8Oio includes a multiplier 81 configured to receive the UBUS voltage from bus 130 and the bus current I DC at the output of the rectifier 116 and to determine a power PTGEN equal to the product UBUS x IDC, this PTGEN power being compared to a limit setpoint PTGEN_MAX by means of the comparator 82w, the difference between PTGEN_MAX and PTGEN being transmitted to the corrector 84w. The 84w controller transmits at output an elementary electrical power limitation command of the turbogenerator IQREF_PTGENMAX homogeneous to a quadrature current to the logic module 85 for elementary command selection.

[0133] This maximum power regulation function provided by the 110 turbogenerator is associated with a "HIGH" priority level.

[0134] Controlling the maximum electrical power PTGEN_MAX delivered by the turbogenerator 110 on the HVDC bus helps to prevent damage to, or even a shutdown of, the turbogenerator 110 due to overheating of the generator 114 or a power module of the rectifier 116.

[0135] Controlling the maximum electrical power of the 110 turbogenerator allows for managing any temporary power supplements provided by the 125 battery during flight phases.

[0136] A particular example of the implementation of the previously mentioned elementary setpoint selection logic module 85 is given in Figure 4.

[0137] Logic module 85 has a chain of selection blocks, some of which use a "MAX" function and output the one among its inputs that has the maximum value, and others use a "MIN" function and output the one among its inputs that has the minimum value.

[0138] Module 85 receives the various elementary setpoints IQREFJBATREF, IQREFJBATMIN, IQREFJBATMAX, IQREF_N2MIN, IQREF_N2MAX, IQREF_TRQMIN, IQREF_TRQMAX, IQREF_UBUSMIN, IQREF_USBUSMAX, and IQREF_PTGENMAX from the outputs of the different correction stages 80i, ..., 80i. Based on comparisons between the respective values ​​of these elementary setpoints and a priority order associated with each of the correction stages 80i, ..., 80i, this module 85 is configured to select and output an elementary setpoint IQREF from among these elementary setpoints. This selected elementary setpoint then serves as the "general" setpoint (IQREF) from which the control block 99 generates the rectifier control signals, typically in the form of PWM signals.

[0139] Module 85 is here formed of several selection blocks 90A, 90B, 90C, 90D, 90E arranged in cascade (from left to right in the figure) successively in increasing order of priority that we wish to give here to the different regulation functions implemented by the different correction stages 80i, 8Oio described previously.

[0140] In this particular implementation, the correction stage 80i, which performs a closed-loop control of the battery current IBAT to the setpoint IBAT_REF generated by the BMS 126 of battery 125, is the stage whose function is associated with the lowest priority. The battery charging current setpoint IBAT_REF is thus transmitted as an input to a first 90A selection block located at one end of the cascaded series of blocks. This first 90A block also receives setpoints IQREF_TRQMIN and IQREF_TRQMAX issued at the outputs of the correction stage 806 and the correction stage 807, respectively, relating to another, higher-priority function: in this example, the control of the mechanical torque TRQ and its maintenance between a lower limit TRQMIN and an upper limit TRQMAX.

[0141] The first 90A selection block comprises a unit 94 performing a MAX function (i.e., a unit selecting the maximum value from among its inputs), one output of which serves as an input to a unit 92 performing a MIN function (i.e., a unit selecting the minimum value from among its inputs). The first 90A block returns as its output the smaller of the two values: on the one hand, the elementary setpoint IQREF_TRQMAX for the upper mechanical torque limitation of the turbomachine, and on the other hand, the larger of the two values: on the one hand, the elementary setpoint IQREF_TRQMIN for the lower mechanical torque limitation of the turbomachine, and on the other hand, the battery charging current setpoint I BAT_REF.

[0142] The output of the first block 90A is transmitted to a second block 90B, located after block 90A in the sequence of selection blocks. The second block 90B receives the elementary commands IQREF_N2MIN and IQREF_N2MAX relating to a third function with a higher priority than the elementary commands issued at the input of the preceding block 90A. This third function concerns the control of transient speed excursions N2 of the turbomachine's power shaft and its maintenance between a lower limit N2MIN and an upper limit N2MAX.The second selection block 90B consists of a unit 92 performing a MIN function, one input of which is connected to an output of the previous block 90A, and which selects the lowest value between this output and the lower speed limitation setpoint of the turbomachine IQREF_N2MiNet, transmits this value to a unit 94 performing a MAX function, which selects from among its inputs the highest one between those connected to the unit 92 and another input receiving the upper speed limitation setpoint of the turbomachine IQREF_N2MAX.

[0143] At the output of the second selection block 90B, a third selection block 90C receives the elementary setpoint IQREF_PTGENMAX related to a fourth function, in this example, the control of the maximum electrical power supplied by the turbogenerator, and its maintenance below a threshold or upper limit PTGEN_MAX. This fourth function thus has, in this example, a higher priority than the first, second, and third functions mentioned above. The third selection block 90C consists of a unit 94 performing a MIN function to select its input with the highest value between an elementary setpoint from the previous block 90B and the elementary setpoint IQREF_PTGENMAX.

[0144] The fourth function, which here concerns the control of limit currents for charging / discharging the battery, has a lower priority than a fifth function and a sixth function associated respectively, with elementary instructions IQREFJBATMAX, IQREFJBATMIN in input to a fourth 90D selection block following the 90C block, and with elementary instructions IQREFJJBUSMAX, IQREFJJBUSMIN in input to a fifth 90E selection block.

[0145] The fourth block 90D includes a unit 92 performing a MIN function between the elementary setpoint IQREFJBATMIN and the input of the previous block and a unit 94 performing a MAX function between the elementary setpoint IQREFJBATMAX, and the output of unit 92.

[0146] The fifth and final 90E block in this sequence receives the elementary commands IQREF_UBUSMIN and IQREF_USBUSMAX, relating to the fifth function, which has the highest priority. In this example, the highest priority function is the one concerning the control of the bus voltage and its maintenance between a lower limit UBUS_MIN and an upper limit UBUS_MAX. The fifth 90E block selects between an elementary command transmitted by the preceding block and the IQREF_UBUSMIN and IQREF_USBUSMAX commands sent as inputs to the latter and relating to the fifth function. A 92 unit performing a MAX function selects the elementary command with the higher value between the IQREF_UBUSMIN elementary command and the command selected in the preceding block.A unit 94 performing a MIN function selects the elementary setpoint with the highest value between the elementary setpoint lciREF_uBusMAxet and the output setpoint of the previous selection unit 92.

[0147] In the example described above, the control system 115 can be implemented, at least in part, by a computer system comprising a processing unit such as a microprocessor and at least one memory in which a computer program is stored, containing computer program instructions designed to be executed by the processing unit. Thus, the modules and stages described above can be implemented through a computer program in the form of software modules.

[0148] Alternatively, all or part of the modules and stages can be implemented in hardware form, i.e. in the form of an electronic circuit, for example micro-wired.

[0149] In an example of an implementation such as described above, the selected setpoint IQREF at the output of the selection module 85 corresponds to a quadrature vector component in the Park frame of the phase current electric generator.

[0150] As an alternative to control via such a current vector component, it is also possible to control the rectifier 116 with a DC voltage setpoint from the rectifier UBUS_REF, developed according to a principle similar to that shown in Figures 3 and 4. The gains of the correction stages 84i, ..., 84w are adapted to generate elementary bus voltage setpoints at the output, allowing compliance with the various limits described, rather than elementary current setpoints IQ. However, control based on a current IQREF has the advantage of faster regulation, in this case less than 2 ms, and is independent of certain system parameters such as the capacitance of the HVDC bus 130, the HVDC bus voltage, and the internal resistance of the battery 125.Furthermore, in the event of a sensor failure or failure of the means of measurement allowing the measurement of the UBUS voltage, the choice of a current control I QREF makes it possible to keep almost all of the aforementioned regulation functions operational, in particular those allowing the regulation of the parameters I BAT, TRQ., N2.

[0151] In the specific embodiment described above, the rectifier control system 115 comprises 10 correction stages 80i,..., 80w. The control system is not necessarily limited to this number of stages. It is therefore possible, for example, to add one or more additional control parameters or limits to be taken into account when developing the overall setpoint IQREF at the output of the selection module 95.

[0152] Thus, for example, the SOC of battery 125 can be taken into account to establish the IQREF setpoint, which regulates the bus voltage U BUS. It is also possible to add a DC current limiting loop I DC at the rectifier output 116.

[0153] A regulation such as the one presented above applies equally to a turbogenerator in which the turbomachine drives an electric generator at the output of which a rectifier is provided, and to a turbogenerator consisting of a turbomachine driving several electric generators in parallel through a gearbox.

[0154] It can also be applied to an electric generator made up of several independent three-phase stator windings, allowing as many active rectifiers and HVDC buses to be powered in parallel.

[0155] Conventionally, in a propulsion system following prior art, the control of the turbine's rotational speed (N2), and the limitation of the turbomachine's accelerations and decelerations to maintain them within its shutdown and pumping limits, is primarily achieved by the EECU control module 113 via fuel metering in the combustion chamber. In certain cases, particularly in rotary-wing aircraft such as helicopters where the inertia of the generator(s) driven by the turbomachine is much lower than that of a rotating assembly, or when the turbomachine has a free turbine, this regulation may prove insufficient.

[0156] Furthermore, power demand variations in an electric propulsion system are significantly faster than in a conventional architecture solely composed of internal combustion engines. The combination of low driven inertia and rapid variations in propulsive power is likely to lead to larger instantaneous variations and excursions in N2 speed with a series electric hybrid propulsion architecture.

[0157] However, to maintain the excursions of the speed N2 within a determined operating range, typically between 90% and 105% of the nominal speed of the turbine power shaft, one can, according to a particular embodiment, use the battery 125 connected to the HVDC bus 130 which serves as a buffer or electrical inertia.For this purpose, the charge and discharge of the battery 125 is controlled via the control system 115 of the rectifier 116 so that it transiently supplies energy to the HVDC bus 130 in order to prevent underspeed of the power shaft following a rapid increase in the demand for propulsive power exceeding the acceleration performance without pumping of the turbomachine, or on the contrary transiently absorb part of a surplus of energy supplied by the turbogenerator 110 in order to prevent overspeed of the power shaft during a rapid decrease in the demand for power exceeding the deceleration performance without shutdown of the turbomachine.

[0158] Rapid increase or decrease typically refers to an increase or decrease of at least 200 kW / s.

[0159] Such a mode of operation is illustrated in figures 5A and 5B which respectively give C_PLOAD, C_PTGEN, C_PBAT curves of time evolution of powers and CSAB, CAAB curves of time evolution of rotation speed N2.

[0160] The power absorbed by the battery being initially zero (assuming it is charged) and the electrical power PTGEN supplied by the turbogenerator therefore equal to the PLOAD power consumed by the propulsive loads, between instants tA and tB (acceleration phase) there occurs a rapid increase in the demand for PLOAD power consumed by the propulsive loads according to a positive gradient exceeding the non-pumping acceleration capacities of the turbomachine.

[0161] Assuming battery assistance (CAAB curve representing a hybrid electric system operating according to the invention), the power shaft speed N2 begins to drop rapidly due to a power supply deficit from the turbogenerator 110. This leads to a decrease in the current setpoint IQREF_N2MIN, linked to the lower speed limit N2 of the power shaft (correction stage 844), and its inclusion in the limitation of the final current setpoint IQREF via the limiting block 90B. Due to the existence of a positive physical gain between the IQREF setpoint and the bus voltage UBUS, limiting the IQREF setpoint by an upper value results in the control system 115 driving the rectifier 116 to temporarily lower its output voltage UBUS, thereby discharging the battery 125. After time tB, the power demand PLOAD stabilizes.As the power supply from the PTGEN turbogenerator gradually increased to the level of the final demand PLOAD and the speed N2 reached its setpoint, the control system 115 controls the rectifier 116 to increase its output voltage UBUS so as to cause a recharge of the battery 125 and then restores the constant output voltage UBUS so as to maintain a zero current at the output of the battery 125.

[0162] Then, between instants te and to (deceleration phase) a rapid decrease in the PLOAD power demand by the propulsive loads according to a negative gradient exceeding the deceleration capacities without extinction of the turbomachine.

[0163] Assuming battery assistance (CAAB curve), the power shaft speed N2 begins to increase rapidly due to the inability of the turbogenerator 110 to reduce its power supply to the loads 140 sufficiently quickly. This leads to an increase in the current setpoint IQREF_N2MAX, linked to the upper speed limit of the power shaft N2 (correction stage 84s), and its inclusion in the limitation of the final current setpoint IQREF via the limiting block 90B. The limitation of the IQREF setpoint by a lower value results in the control system 115 driving the rectifier 116 to temporarily increase its output voltage UBUS in order to recharge the battery 125. After the instant t0, the power demand PLOAD SO stabilizes again.As the power supply from the PTGEN turbogenerator gradually decreased to the level of the final PLOAD demand and the speed N2 reached its setpoint, the control system 115 controls the rectifier 116 to reduce its UBUS output voltage in order to cause a charge of the battery 125 and then restores the constant UBUS output voltage in order to maintain a zero current at the output of the battery 125.

[0164] The power supplied by the PTGEN turbogenerator (C_PTGEN curve) has insufficient dynamics, limited by the laws protecting against pumping and extinction of the turbomachine.

[0165] Assuming no battery assistance (CSAB curve representative of a conventionally operating system), and given the low overall inertia of the system driven by the free turbine, the evolution of the rotational speed N2 is such that it is likely to go below (underspeed) a threshold N2_MIN during acceleration and above (overspeed) a threshold N2_MAX during deceleration of a specified [N2_MIN , N2_MAX] gauge.

[0166] To avoid limiting the performance of the propulsion system, the battery's discharge and charge (C_PBAT curve) are controlled via the control system 115 of the rectifier 116 so that the battery supplies or absorbs the corresponding power deficit or excess, thus limiting speed excursions N2 (CAAB curve). This advantageous operating mode, called "transient assistance," is achieved in particular through the regulation loops implemented by the correction stages 8O4, 80s described previously.

[0167] This operating mode requires only brief use of the battery 125, typically lasting one to two seconds. The instantaneous peak powers involved can range from several tens to several hundred kW, with the energy supplied or absorbed by the battery 125 limited by the typically very brief nature of these operating modes. Another possible operating mode, using a control system 115 for the rectifier 116, is illustrated in Figure 6, to meet the high power demands of propulsion loads.

[0168] Up to a certain point ti, the power demand PLOAD (CPLOAD curve) of the propulsion loads, initially of value Pi, increases but remains below the programmed maximum power limit PTGEN_MAX. The control system 115 drives the rectifier 116 to maintain its output voltage U BUS at a value such that the battery 125 produces zero output current while simultaneously increasing the current delivered by the rectifier 116. The turbogenerator 110 then provides all of the PTGEN power (CPTGEN curve) on its own, and the power supplied by the battery PBAT (CPBAT curve) is zero.

[0169] Then, from a certain instant ti, the demand for propulsive power increases beyond the programmed threshold PTGEN_MAX.

[0170] Crossing this threshold leads to a decrease in the current setpoint IciREF PTGENMAxen linked to the upper limit of electrical power at the output of the rectifier 116 (84w correction stage), and its inclusion in the limitation of the final current setpoint IQREF via the limiting block 90C, provided that no other more restrictive limit applies. The limitation by upper value of the IQREF setpoint results in the control system 115 driving the rectifier 116 to lower its output voltage U BUS so that the battery 125 discharges while maintaining constant, typically by means of a proportional-integral control loop, the electrical power delivered by the rectifier 116. The battery 125, through appropriate control of the rectifier 116 implemented by the system 115, then provides the additional power to the propulsion loads beyond the PTGEN_MAX limit of the turbogenerator 110.

[0171] This advantageous operating mode is obtained in particular thanks to the regulation loop implemented by the 80w correction stage described previously.

Claims

DEMANDS 1. Device for a series-electric hybrid aircraft propulsion system, comprising: - an electric turbogenerator (110) comprising at least one turbomachine (112) and at least one generator (114) coupled to said turbomachine, - a 125 capacitive battery, - an HVDC bus (130) coupled to said turbogenerator and to said battery (125), the turbogenerator (110) being connected to the HVDC bus (130) via an alternating current (AC) to direct current (DC) rectifier (116) connected to phases of said at least one generator (114), said battery (125) being connected directly to the high-voltage direct current (HVDC) electrical network, the device further comprising a control system (115) for the rectifier (116) configured to drive the rectifier (116) and manage a sharing of electrical power supplied on the HVDC bus (130) between said turbogenerator (110) and said battery (125) based on the setpoint control of at least the current (I BAT) delivered by the battery (125), so as to maintain limits on the output speed of the turbomachine, the bus voltage, the current at the battery output and the output power of the turbogenerator,by modulating the output voltage (UBUS) of the rectifier (116) via at least one control signal (CMD), in particular pulse width modulation (PWM), the control system (115) of the rectifier (116) comprising:, - a plurality of correction stages (80i, ..., 80w) each correction stage being equipped with a corrector (84i, ..., 80w) and being configured to receive a measurement of a rectifier output voltage regulation parameter (UBUS) (116) from among a set of parameters including: a rectifier (116) output current (I DC), an HVDC bus voltage (UBUS), a turbomachine power shaft rotation speed (N2), a battery output current (I BAT), and to establish, from a comparison between this measurement of said regulation parameter and a reference or limit not to be exceeded: an elementary setpoint, the elementary setpoints (IQREFJBATREF, IQREFJBATMIN, IQREF IBATMAX, IQREF_N2MIN, IQREF_N2MAX, IQREF_TRQMIN, I QREF_TRQMAX, IQREF_UBUSMIN, IQREF_USBUSMAX, IQREF_PTGENMAX) respective outputs of said correction stages being all homogeneous to a current or all homogeneous to a voltage, - a logic module (85) for selecting elementary setpoints configured to receive said elementary setpoints (IQREFJBATREF, IQREFJBATMIN, IQREFJBATMAX, IQREF_N2MIN, IQREF_N2MAX, IQREF_TRQMIN, IQREF_TRQMAX, IQREF_UBUSMIN, IQREF_USBUSMAX, IQREF_PTGENMAX) and to select, based on comparisons between the respective values ​​of said elementary setpoints and a predetermined priority order associated with each of said correction stages, an elementary output setpoint from among said elementary setpoints, said selected elementary output setpoint serving as the so-called "general" setpoint (IQREF) from which said control signal (CMD) of the rectifier (116) is established, among said correction stages (80i, ..., 80w) figure: - at least one current correction stage (80i, 8O2, 8O3) at the battery output, - at least one turbomachine speed correction stage (804.80s) (N2) - at least one HVDC bus voltage correction stage (80s, 809), - at least one electrical power correction stage (8Oio) at the output of the rectifier.

2. Device according to claim 1, wherein said general control setpoint corresponds to a vector component (IQ) of phase currents (IA, IB, le) along a first axis of a rotating frame linked to a rotor of the generator (114).

3. Device according to claim 1 or 2, wherein said at least one battery output current correction stage (8O1, 8O2, 8O3) comprises: - a first correction stage (8O1) to control a battery current to a reference setpoint, configured to receive the battery current measurement (I BAT) and to determine an elementary reference battery current setpoint (IQREF_BATMIN) depending on the difference between a reference battery current setpoint (I BAT_REF) and the measured battery current (I BAT), - a second correction stage (8O2) to maintain a battery current above a minimum stop, configured to receive the battery current measurement (I BAT) and to determine an elementary lower battery current limiting setpoint (IQREF_BATMIN) as a function of the difference between a minimum battery current stop setpoint (I BAT_MIN) and the battery current measurement (I BAT), - a third correction stage (8O3) to maintain a battery current below a maximum stop, configured to receive the battery current measurement (IBAT) and to determine an elementary upper battery current limiting setpoint (IQREF_BATMAX) as a function of the difference between a maximum battery current stop setpoint (IBAT_MAX) and the battery current measurement (IBAT), and in which said at least one turbomachine speed correction stage (8O4, 80s) (N2) comprises: - a correction stage (8O4) to maintain a turbomachine speed above a minimum stop and called "fourth correction stage (8O4)," the fourth correction stage (8O4) being configured to receive the turbomachine speed measurement (N2) and to determine an elementary lower speed limitation setpoint for the turbomachine (IQREF_N2MIN) as a function of the difference between a minimum turbomachine speed stop value (N2MIN) and the turbomachine speed measurement (N2), - another correction stage (80s) to maintain a turbomachine speed below a maximum limit and called the "fifth correction stage (80s)", the fifth correction stage (80s) being configured to receive a turbomachine speed measurement (N2) and to determine an elementary upper speed limitation setpoint for the turbomachine (I QREF_N2MAX) as a function of the difference between a maximum turbomachine speed limit setpoint (N2MAX) and the turbomachine speed measurement (N2), the device further comprising: - a sixth correction stage (80th) to maintain a turbomachine mechanical torque above a minimum stop, configured to receive a turbomachine mechanical torque measurement (TRQ) and to determine an elementary lower limit setpoint for turbomachine mechanical torque (IQREF_TRQMIN) as a function of the difference between a minimum stop setpoint for turbomachine mechanical torque (TRQMIN) and the current turbomachine mechanical torque measurement (TRQ). - a seventh correction stage (8O7) to maintain a mechanical torque of the turbomachine below a maximum stop configured to receive a measurement of the mechanical torque of the turbomachine (TRQ) and to determine an elementary upper limit setpoint of the mechanical torque of the turbomachine (IQREF_TRQMAX) as a function of the difference between a minimum stop setpoint of the mechanical torque of the turbomachine (TRQMAX) and the current measurement of the mechanical torque of the turbomachine (TRQ), said at least one correction stage (80s) of HVDC bus voltage being formed: - a correction stage (80s) to maintain the HVDC bus voltage above a minimum stop and called the "eighth correction stage (80s)", the eighth correction stage (80s) being configured to receive a bus voltage measurement (UBUS) and to determine an elementary lower bus voltage limiting setpoint (IQREF UBUS MIN) as a function of the difference between a minimum bus voltage stop setpoint (UBUS_MIN) and the bus voltage measurement (UBUS), - a correction stage (8O9) to maintain the HVDC bus voltage below a maximum limit and called the "ninth correction stage (8O9)", the ninth correction stage (8O9) configured to receive a bus voltage measurement (UBUS) and to determine an elementary upper bus voltage limiting setpoint (IQREF_UBUS_MAX) based on the difference between a maximum bus voltage limit setpoint (UBUS_MAX) and the bus voltage measurement (UBUS), said at least one power correction stage (8Oio) being a tenth correction stage (8Oio) to maintain electrical power at the rectifier output below a maximum limit and configured to receive the bus voltage measurement (UBUS) and the bus current measurement (I DC) and to evaluate an electrical power measured at the output of the rectifier and to determine an elementary upper power limiting setpoint (IQREF_PTGENMAX) as a function of the difference between the measured electrical power and a maximum power stop setpoint (PTGENMAX).

4. Device according to claim 3, wherein the first correction stage (80i) is associated with a first priority level, and wherein the fourth and fifth correction stages (8O4, 80s) and / or sixth and seventh correction stages (80e, 8O7) are associated with a second priority level higher than the first priority level, the tenth correction stage (8Oio) being associated with a third priority level higher than the second priority level, the second and third correction stages (8O2, 8O3) and / or eighth and ninth correction stages (80s, 8O9) being associated with a fourth priority level higher than the third priority level.

5. A device according to any one of claims 1 to 4, wherein the elementary setpoint selection logic module (85) (IQREFJBATREF, IQREFJBATMIN, IQREFJBATMAX, IQREF_N2MIN, IQREF_N2MAX, IQREF_TRQMIN, IQREF_TRQMAX, IQREFJJBUSMIN, IQREF_USBUSMAX, IQREF_PTGENMAX) comprises a plurality of selection blocks (90A, 90B, 90C, 90D, 90E), each comprising: - a minimum value selection unit (92) among its inputs arranged in series with a maximum value selection unit (94) among its inputs, or - a minimum value selection unit (92; 94) among its inputs, each of said selection blocks (90A, 90B, 90C, 90D, 90E) being configured to receive, among said elementary setpoints, a given elementary setpoint or a given pair of elementary setpoints emanating from given correction stages among said correction stages receiving the same measurement of the same measurement parameter, said given elementary setpoint or said given pair of elementary setpoints being different from that(s) received by said other selection blocks, the selection blocks being arranged in a succession of cascaded blocks in an order dependent on the priority order to which the given correction stage(s) is / are associated, -a first block (90A) of said succession of cascaded blocks receiving as input an elementary instruction called a reference instruction (IQREFJBATREF) from among said elementary instructions, - a final block (90E) of said succession of cascaded blocks producing at output a setpoint said elementary output setpoint (IQREF) serving as a setpoint said "general" (IQREF), each of said other blocks receiving at input an elementary setpoint selected by a previous selection block of said plurality of selection blocks arranged in cascade, and producing, at output an elementary setpoint selected from its inputs and destined for a following block of said plurality of selection blocks.

6. Device according to any one of the preceding claims, wherein said turbomachine (112) has a free turbine.

7. Series hybrid electric propulsion aircraft comprising a device according to one of the preceding claims.

8. Method for controlling the turbogenerator (110) of a device as defined in claims 1 to 6, the HVDC bus (130) being coupled to at least one set of propulsion loads (140), comprising the following steps: - during a first phase following the detection of an increase in electrical power demand from said propulsion load set (140) and as long as an electrical power (PTGEN) at the output of said rectifier (116) remains below a threshold, control the rectifier (116) so as to maintain its output voltage (UBUS) at a value such that the current delivered by the battery (125) is controlled to a zero setpoint while increasing the current delivered by the rectifier (116) so that the turbogenerator (110) alone provides electrical power to the HVDC bus (130) in response to said increase, then, following the detection of an electrical power threshold (PTGEN_MAX) being reached at the rectifier output (116) and a further increase in electrical power demand beyond said threshold from said propulsion load set (140), during a second phase, the rectifier (116) is driven to lower its output voltage (UBUS) so that the battery (125) discharges while maintaining the power delivered by the rectifier (116) constant and equal to the value of said threshold so that the turbogenerator (110) and the battery (125) jointly provide electrical power to the HVDC bus (130) in response to said new increase.

9. Method for controlling the turbogenerator (110) of a device as defined in any one of claims 1 to 6, the HVDC bus (130) being coupled to at least one set of propulsion loads (140), the method comprising the following steps: - following an increase in the demand for electrical power from said load set (140) exceeding a no-pumping acceleration limit of the turbomachine (112) and resulting in a transient drop in speed (N2) of the power shaft of said turbomachine relative to its setpoint, control the rectifier (116) to temporarily lower its output voltage (UBUS) so as to cause a discharge of the battery (125), then, - following a stabilization of the electrical power demand from said set of loads, an increase in the electrical power delivered by said turbogenerator and a rise in speed (N 2) towards its setpoint, control the rectifier (116) to increase its output voltage (UBUS) so as to cause a charge of the battery (125) then restore a constant output voltage (U BUS) so as to maintain a zero current at the output of the battery (125), and / or comprising the following steps: - as a consequence of a decrease in the demand for electrical power from said set of loads (140) exceeding a deceleration limit without shutdown of the turbomachine (112) and resulting in an increase transient speed (N2) of the power shaft of said turbomachine relative to its setpoint, control the rectifier (116) to temporarily reduce its output voltage (UBUS) so as to recharge the battery (125), then, - following a stabilization of the electrical power demand from said load set, a decrease in the electrical power delivered by said turbogenerator and a return of the speed (N2) towards its setpoint, control the rectifier (116) to increase its output voltage (UBUS) so as to charge the battery (125) then restore a constant output voltage (UBUS) so as to maintain a zero current at the output of the battery (125).

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