System and method for controlling power sources in parallel

Abstract

The present disclosure relates to a control system for controlling an electrical system comprising a plurality of power sources connected in parallel to a distribution bus (30) having a bus voltage (Vdc) to be regulated around a reference voltage (Vref), the control system comprising: a central controller (40) configured to send local setpoints (P) respectively associated with the power sources, and local controllers (311, 321, 331), each local controller being configured to receive one of the local setpoints (P), implement droop control so as to generate a setpoint correction (Pco), generate an output setpoint (Pcs) for the power source on the basis of the received local setpoint (P) and the setpoint correction (Pco), and control, using the output setpoint (Pcs), the power source associated with the received local setpoint (P).

Description

[0001] DESCRIPTION

[0002] TITLE: System and method for controlling parallel power sources

[0003] TECHNICAL FIELD

[0004] This disclosure relates to the general field of power source control systems, and in particular voltage regulation when power sources are connected in parallel by a centralized controller.

[0005] STATE OF THE ART

[0006] 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.

[0007] Technological research efforts have already led to very significant improvements in the environmental performance of aircraft. The Applicant takes into account the factors impacting all phases of design and development in order to obtain less energy-intensive and more environmentally friendly aeronautical components and products whose integration and use in civil aviation have moderate environmental impacts, with the aim of improving the energy efficiency of aircraft.

[0008] Consequently, the Applicant is constantly working to reduce its climate impact by employing sustainable development methods and minimizing greenhouse gas emissions. This sustained research and development work focuses in particular on new generations of aircraft engines and the development of electric propulsion technologies.

[0009] An aircraft typically includes an electrical system powered by various sources and is propelled by a turbomachine. To improve the aircraft's energy efficiency, the turbomachine can be internally hybridized. This involves adding a hybrid electrical system that acts as an interface between the turbomachine's rotating shafts and the aircraft's electrical system. The hybrid electrical system aims to assist the turbomachine to optimize its operation by providing electrical assistance or drawing power from it. It must manage the power distribution between the turbomachine's high-pressure and low-pressure shafts, and in particular, limit the power drawn, while ensuring that all sources contribute to a sufficient supply of power to the aircraft's electrical system.

[0010] One proposed solution is an electrical system with multiple decentralized or local controllers. In this case, the low-pressure and high-pressure shafts are controlled independently and their voltage is regulated by controllers with non-zero steady-state error. However, proper power distribution depends heavily on the accuracy of the voltage measurements and the load level. Therefore, the bus voltage that is being regulated is significantly affected by local measurement errors.

[0011] A second proposed solution is a so-called "centralized" architecture, with a central controller that regulates the voltage of the electrical network and distributes power commands to the local controllers. The various electrical sources within an aircraft are distributed throughout the aircraft at varying distances from the central controller. Such a centralized architecture therefore does not allow for rapid communication between the local controllers, as the information transmission time on the communication buses depends on the distance.

[0012] EXPOSED

[0013] One purpose of this disclosure is to regulate a voltage on a distribution bus of an electrical system comprising multiple voltage sources in parallel, without the need for rapid communication between decentralized controllers and a centralized controller, and / or between decentralized controllers.

[0014] To this end, a control system is proposed to control an electrical system, the electrical system comprising a plurality of power sources connected in parallel to a distribution bus, the distribution bus having a bus voltage to be regulated around a reference voltage, the control system comprising:

[0015] • a central controller configured to send, at a center frequency, local instructions respectively associated with the power sources, and generated from a measured bus voltage and the reference voltage,

[0016] • local controllers, each local controller being configured to o receive one of the local setpoints, o implement droop control from a reference parameter representative of the reference voltage and a measured voltage parameter representative of a local measured voltage of the power source associated with the received local setpoint, so as to generate a setpoint correction, and o generate, at a local frequency higher than the center frequency, an output setpoint for the power source from the received local setpoint and the setpoint correction, o control, using the output setpoint, the power source associated with the received local setpoint.

[0017] The central controller allows for the direct distribution of power to be drawn by transmitting respective commands to each power source at the central frequency, which is lower than the local frequency. This solution eliminates the need for rapid communication between the central controller and local controllers, which can be impossible due not only to the distance between the power sources and the central controller, but also to the harsh vibrational and electromagnetic environment in which the electrical system operates. The command adjustment for each source is implemented locally. Indeed, each local controller can perform efficient high-frequency regulation by attenuating a voltage excursion immediately after a load impact, much faster than the central controller could. Thus, the control of the power sources adapts more quickly to such impacts.The regulation performed by the central controller compensates, at a lower frequency, for the steady-state error due to each individual local controller. Rapid communication between the local controllers and the central controller is unnecessary, since the high-frequency response of each power source to a load impact is handled by the local controllers. This improves the stability of the electrical system.

[0018] According to certain embodiments:

[0019] - the reference parameter is the reference voltage and the measured voltage parameter is the measured local voltage, or

[0020] - The reference parameter is the square of the reference voltage, and the measured voltage parameter is the square of the measured local voltage. In some embodiments, the local controller includes a drastic unit configured to apply a drastic coefficient to the difference between the reference parameter and the measured voltage parameter.

[0021] In some embodiments, the local controller includes, in series:

[0022] • a static unit configured to apply a static coefficient to a reference intensity or to a measured intensity of the power source associated with the local setpoint, so as to produce a regulated signal, and

[0023] • a zero steady-state error controller configured to produce the setpoint correction from: o the difference between the reference parameter and the measured voltage parameter of the power source associated with the received local setpoint, and o the regulated signal from the drowsiness unit.

[0024] According to some embodiments, the control system further includes a computer configured to generate a power withdrawal allocation setpoint between the power sources from signals representative of the powers generated by the power sources, and the central controller is configured to update the local setpoints from the withdrawal allocation setpoint.

[0025] According to a second aspect, a set is proposed comprising an electrical system and a control system as defined previously.

[0026] According to some embodiments, the power sources comprise at least two of the following:

[0027] • a low-pressure shaft of the turbomachine,

[0028] • a high-pressure shaft of the turbomachine, and

[0029] • a source of direct current, in particular a battery.

[0030] A third aspect is proposed: a method for controlling an electrical system comprising a plurality of power sources connected in parallel to a distribution bus, the distribution bus having a bus voltage to be regulated around a reference voltage, the method being implemented by a central controller and by local controllers, the method comprising steps of: • sending by the central controller, at a central frequency, local setpoints respectively associated with the power sources and generated from a measured bus voltage and the reference voltage,

[0031] • Receipt of one of the local instructions by one of the local controllers,

[0032] • implementation, by the local controller, of a drastic regulation based on a reference parameter representing the reference voltage and a measured voltage parameter representing a local measured voltage of the power source associated with the received local setpoint, so as to generate a setpoint correction,

[0033] • generation, by the local controller and at a local frequency, of an output setpoint for the respective power source from:

[0034] ■ of the local deposit, and

[0035] ■ of the instruction correction

[0036] • control by the local controller of the power source associated with the local setpoint received using the output setpoint.

[0037] According to certain implementations of the process:

[0038] • The reference parameter is the reference voltage and the measured voltage parameter is the measured local voltage, or

[0039] • The reference parameter is the square of the reference voltage and the measured voltage parameter is the square of the measured local voltage.

[0040] According to some implementations of the process, the implementation of a drastic control includes the application, by a drastic unit of the local controller, of a drastic coefficient to a difference between the reference parameter and the measured voltage parameter.

[0041] According to some implementations of the process, the implementation of a static control system includes:

[0042] • the generation, by a static unit of the local controller, of a signal regulated by applying a static coefficient to a reference intensity or to a measured intensity of the power source associated with the local setpoint,

[0043] • the generation, by a zero static error controller of the local controller, of the setpoint correction from: o a difference between the reference parameter and the measured voltage parameter of the power source associated with the received local setpoint, and o the regulated signal.

[0044] DESCRIPTION OF THE FIGURES

[0045] Other features, purposes, and advantages will become apparent from the following description, which is purely illustrative and not exhaustive, and should be read in conjunction with the attached drawings on which:

[0046] [Fig. 1] schematically represents an aircraft.

[0047] [Fig. 2] schematically represents a turbomachine.

[0048] [Fig. 3] represents an aircraft electrical system, according to an embodiment comprising three power sources.

[0049] [Fig. 4a] represents a control system for the electrical system of Figure 3, according to a first embodiment.

[0050] [Fig. 4b] represents a control system for the electrical system of Figure 3, according to a second embodiment.

[0051] [Fig. 5] represents an evolution of a bus voltage for the electrical system of Figure 3 during a load impact.

[0052] [Fig. 6] is a graph illustrating a power-voltage or current-voltage law of local controllers, in steady state and dynamic regime.

[0053] [Fig. 7] schematically illustrates a method of controlling the aircraft's electrical system.

[0054] Across all figures, similar elements bear identical references.

[0055] DETAILED DESCRIPTION OF IMPLEMENTATION METHODS

[0056] In this application, upstream and downstream are defined with respect to the normal flow direction of the gas through the turbomachine. Furthermore, the longitudinal axis X of the turbomachine is the axis of rotation of its rotor parts. The axial direction corresponds to the direction of the longitudinal axis X, and a radial direction is a direction perpendicular to and passing through this axis.

[0057] For illustrative purposes, Figure 1 represents an aircraft 100 comprising at least one propulsion unit 1, in this case two propulsion units 1. The propulsion units 1 are attached and fixed to the aircraft 100, for example each under a wing of the aircraft 100 as illustrated, or alternatively on the wing of the aircraft 100 or at the rear of the fuselage of the aircraft 100. The aircraft 100 is an airplane, but could alternatively be any other type of aircraft 100, for example a helicopter.

[0058] Aircraft electrical system 100

[0059] As is known in itself, aircraft 100 comprises a plurality of electrical loads (or receivers) powered by electrical sources via an electrical network.

[0060] An electrical load is a device powered by electrical energy, usually direct current. It can be configured to transform the electrical energy that powers it into another form of energy, such as heat or mechanical energy.

[0061] Referring to Figure 3, the electrical loads can be divided into two categories. The first category of loads, Ch1, is external to the propulsion system 1. The electrical loads Ch1 specific to the aircraft 100 may include, for example, an electric motor, a heating and / or air conditioning system, or a compressor. These loads enable a number of functionalities, whether the aircraft is in flight or operating on the ground, such as pressurizing and / or illuminating the cabin of the aircraft 100, or operating the cockpit.

[0062] A second category of Ch2 loads is internal to the propulsion unit 1. The propulsion unit 1 generally includes a turbomachine 10, which will be described in detail later. The electrical loads Ch2 of the propulsion unit are loads of the turbomachine 10 (known as the "More Electric Engine" or MEE in English). For example, the electrical loads of the turbomachine Ch2 might include a starter, variable geometry components, or de-icing systems.

[0063] Multiple power sources allow electrical loads to be supplied with electrical energy, generally in the form of a continuous signal, typically a direct current voltage. On the one hand, the turbomachine 10 generally comprises two rotating bodies or shafts that provide mechanical energy. Each shaft is associated with a generator motor that extracts mechanical energy from the associated shaft and converts it into electrical energy to supply the electrical grid.

[0064] On the other hand, aircraft 100 includes a plurality of electrical sources distributed throughout the aircraft 100, for example an auxiliary power unit (APU), an electric battery, or a supercapacitor. These sources allow, in particular, for operation where the two shafts of the turbomachine 10 are assisted, but also for supplying various onboard systems on the ground (electrical voltage, pneumatic and hydraulic pressures, air conditioning) when the turbomachines 2 are stopped in order to save fuel, and during start-up.

[0065] The electrical network typically comprises a set of electrical conductors, typically a set of cables connecting the different electrical loads and sources, and busbars, for example a high-voltage direct current distribution bus.

[0066] Generally, generators that extract mechanical energy from shafts produce alternating current (AC). This AC is converted to direct current (DC) by an AC / DC converter. The electrical grid includes at least a portion of the network that carries direct current, as electrical loads are supplied with direct current.

[0067] Description of the turbomachine

[0068] Figure 2 schematically represents a section of the propulsion unit 1 in a plane containing the longitudinal axis X. The propulsion unit 1 comprises the turbomachine 10 and a nacelle 20 surrounding the turbomachine 10.

[0069] The propulsion unit 1 is intended to be mounted on the aircraft 100. In this regard, the propulsion unit 1 may include a pylon (not shown) intended to connect the propulsion unit 1 to a part of the aircraft 100, transmitting the forces to the aircraft 100.

[0070] This disclosure is not limited to a twin-spool, twin-flow turbofan engine with direct fan drive 11 as illustrated. It extends more generally to various turbofan engine architectures, including unfaired turbofans, and other types of turbomachinery, which may have a different number of cylinders and / or flow paths. This disclosure is also generally situated within the context of the internal hybridization of the turbomachine 10, that is, the presence of an electrical system 3 interfacing with the turbomachine's mechanical shafts and the aircraft's electrical network 100, as detailed below.

[0071] The turbomachine 10 comprises, from upstream to downstream in the direction of the gas flow, a blower 11, a compression section 16 comprising a low pressure compressor 161 and a high pressure compressor 162, a combustion chamber 14, an expansion section 15 comprising a high pressure turbine 152 and a low pressure turbine 151, and an exhaust casing.

[0072] Each of the low-pressure compressor 161, high-pressure compressor 162, high-pressure turbine 152, and low-pressure turbine 151 comprises a rotor portion and a stator portion, the rotor portion being capable of being driven in rotation relative to the stator portion about the longitudinal axis X. The blower 11, the rotor portion of the low-pressure compressor 161, and the rotor portion of the low-pressure turbine 151 are connected to each other by a low-pressure shaft 181 extending along the longitudinal axis X, thus forming a low-pressure body (LP body), which is a first rotating body. The rotor portion of the high-pressure compressor 162 and the rotor portion of the high-pressure turbine 152 are connected to each other by a high-pressure shaft 182 also extending along the longitudinal axis X, around the low-pressure shaft 181, thus forming a high-pressure body (HP body), which is a second rotating body.As can be seen in Figure 2, the compression section 16, the combustion chamber 1 and the expansion section 15 are surrounded by an engine casing 21, to which are connected the stator parts of the low pressure compressor 161, the high pressure compressor 162, the high pressure turbine 152 and the low pressure turbine 151. The engine casing 21 delimits a primary channel 13 allowing the flow of a primary gas stream A.

[0073] As explained previously, the longitudinal axis X defines the axis of rotation for the blower 11, the rotor parts of the compression section 16 and the rotor parts of the expansion section 15, in other words for the LP body and the HP body.

[0074] The nacelle 20 extends radially outside the turbomachine 10, around the longitudinal axis X, so as to surround the engine casing 21, and to define a secondary channel 12 allowing the flow of a secondary gas flow B.

[0075] The turbomachine 10 may also include at least one accessory gear box (AGB), typically housed in a cavity within the nacelle 20. The accessory gear box comprises a set of gears for rotating a plurality of shafts about their own axis, and accessories mounted on the plurality of shafts to derive useful mechanical power from their rotation. The gear set is itself driven by means of a radial drive shaft (RDS) connecting, possibly via a transfer case, the accessory gear box to at least one of the high-pressure (HP) and low-pressure (LP) units. For example, the radial drive shaft (not shown) may extend within a longitudinal cavity within an arm 17.In this way, mechanical power is likely to be taken from at least one of the high pressure body HP and the low pressure body BP to be delivered to at least one of the accessories via the accessory box.

[0076] Figure 3 illustrates an electrical system 3 distributed between the propulsion unit 1 and the aircraft 100 for supplying electrical power to the electrical loads of the aircraft Ch1 and / or the electrical loads of the turbomachine Ch2, typically by means of the direct current network.

[0077] The electrical system 3 makes it possible in particular to interface between the rotating bodies BP, HP of the turbomachine 10 and the electrical network of the aircraft 100. The electrical system is in particular configured to meet the electrical power requirements of the loads of the aircraft Ch1 and / or the turbomachine Ch2 by mechanically drawing power from the turbomachine 10, and to assist the start-up and / or the in-flight operation of the turbomachine 10 using electrical sources from the aircraft 100.

[0078] In the embodiment illustrated in Figure 3, the electrical system 3 comprises three electrical sources. The low-pressure body BP is connected to an AC generator 31, coupled to the accessory housing of the low-pressure shaft 181. The high-pressure body HP is connected to an AC generator 32, coupled to the accessory housing of the low-pressure shaft 182. The electrical system 3 also includes a DC power source 33, for example, a battery.

[0079] More generally, this disclosure extends to any multi-source electrical system, comprising one or more alternating current (AC) electrical sources and / or one or more direct current (DC) electrical sources. In particular, the electrical system 3 may not include the DC power source 33. The AC generator 31, 32 and the DC power source 33 may each independently belong to the turbomachine 10, i.e., be controlled simultaneously with the turbomachine 10, or even be controlled by the turbomachine 10. Alternatively or complementaryly, the electrical sources 31, 32, 33 may belong to the aircraft 100, i.e., be controlled simultaneously with the aircraft 100.

[0080] Preferably, each electrical source 31, 32, 33 is associated with a respective converter 310, 320, 330, that is, with an element configured to supply electrical power. For example, the alternating current generator 31, 32 is associated with an AC / DC converter 310, 320 enabling the supply of direct current.

[0081] The electrical system 3 includes a distribution bus 30, connected to at least one of the aircraft electrical load Ch1 and the turbomachine electrical load Ch2, preferably to both loads Ch1, Ch2.

[0082] Furthermore, each of the converters 310, 320, 330 is connected to the distribution bus 30.

[0083] The distribution bus 30 is configured to provide electrical power to the electrical load Ch1, Ch2 in the form of a continuous signal in order to meet the power requirements of the electrical load Ch1, Ch2.

[0084] In fact, at least one, if not each, of the converters 310, 320, 330 is configured to regulate the distribution bus 30 in voltage from an electrical power supplied by the respective electrical source 31, 32, 33. The number and type of converters 310, 320, 330 and of electrical sources 31, 32, 33 is, of course, not limiting.

[0085] In order for the elements connected to the distribution bus 30, in particular the electrical loads Ch1, Ch2, to function correctly, it is necessary to regulate the voltage of the distribution bus 30.

[0086] Bus voltage regulation

[0087] Two examples of templates are illustrated in Figure 5. Even if the limits V ma x and V mIn the event that they do not initially define constant electrical voltage values, particularly during the characteristic time of switching on (or starting up) of the electrical system 3 or during the time of establishing a steady state in the event of a power transient, it is common for these limits to subsequently define constant electrical voltage values, in order to guarantee the operational stability of the distribution bus 30 and the electrical system 3. Such a template can, for example, be defined in a standard relating to the quality of the electrical system 3 and / or the DC network, but also be defined by a specification of the aircraft 100 to which the electrical system 3 is connected, typically specifying the requirements of the manufacturer of the aircraft 100 and / or the turbomachine 1 in which the electrical system 3 is integrated.

[0088] On the other hand, the voltage regulation of the distribution bus 30 must meet the power demands of the loads Ch1 and Ch2 connected to the distribution bus 30. Typically, when the amount of power drawn by at least one load Ch1 or Ch2 from the distribution bus 30 is greater than the amount of power injected into the distribution bus 30 by at least one converter 310, 320, or 330, the voltage of the distribution bus 30 decreases significantly. Conversely, when the amount of power injected by at least one converter 310, 320, or 330 into the distribution bus 30 is greater than the amount of power drawn from the distribution bus 30 by at least one load Ch1 or Ch2, the voltage of the distribution bus 30 increases. Thus, regulating the voltage of the distribution bus 30 not only ensures the safety of the electrical system 3 but also meets the power requirements of the loads Ch1 and Ch2.In other words, each of the converters 310, 320, 330 is configured to continuously adapt the power it injects or takes from the distribution bus 30, according to the voltage of the distribution bus 30, so as to meet exactly the power requirements of the loads Ch1, Ch2 connected to the distribution bus 30.

[0089] This injection or withdrawal of power from the distribution bus 30 by the converters 310, 320, 330 is made possible in particular by their connection to the electrical sources 31, 32, 33. In fact, at least one, if not each, of the alternating current generators 31, 32 is connected to a rotating body BP, HP, of the turbomachine 1 to allow an exchange of mechanical and / or electrical power between the rotating body BP, HP and the alternating current generator 31, 32, preferably to withdraw mechanical power from the rotating body BP, HP and transform it into electrical power, which electrical power is then delivered to the first converter 310 and / or the second converter 320 to be injected into the distribution bus 30. In the embodiment illustrated in Figure 3, the first alternating current generator 310 is connected to the body BP, while the second alternating current generator 320 is connected to the body HP.

[0090] Since the electrical power supplied by the alternating current generators 31, 32 is in the form of an alternating signal, each of the first and second converters 310, 320 is configured to reversibly transform this alternating signal into a direct signal suitable for injection, and then for circulation, on the distribution bus 30. Similarly, the direct current source 33 can deliver power in the form of a direct signal to the third converter 330, which will nevertheless convert it, also reversibly, to shape it according to the constraints specific to the distribution bus 30, and then inject it onto the distribution bus 30.

[0091] Each, or at least one, of the alternating current generators 31, 32 can, for example, be a wound-rotor synchronous machine, typically comprising three stages (or "Variable Frequency Generator", VGF in Anglo-Saxon terminology), driven by at least one of the high-pressure shaft 182 and the low-pressure shaft 181 of the turbomachine 1, typically via the accessory gearbox. Other types of electrical machines are conceivable, such as, preferably, permanent-magnet synchronous machines (or "Permanent-Magnet Synchronous Machine Drives", PMSM in Anglo-Saxon terminology), which notably have the advantage of a lower mass, or such as induction machines (or "Induction machines" in Anglo-Saxon terminology) or variable reluctance machines.

[0092] The DC power source 33 may include a battery, a supercapacitor, a DC generator, and / or a fuel cell. The DC power source 33 allows, in particular, for relieving the rotating components BP, HP, or taking over their operation when, for example, the current draw required to meet the power needs of loads Ch1, Ch2 is too high. It also allows for the absorption of certain dynamics, such as sudden variations in the behavior of loads Ch1, Ch2.

[0093] The electrical system 3 includes a control system enabling the control of the electrical sources 31, 32, 33 connected in parallel on the distribution bus 30.

[0094] During operation, the electrical voltage within the distribution bus 30, or bus voltage Vdc, can vary around a given nominal value, or reference voltage V ref, for example, if an electrical load temporarily requires additional power or if an electrical source disconnects. Thus, the bus voltage Vdc must be regulated by the control system which controls the power - or current - supplied by each electrical source 31, 32, 33 connected to the distribution bus 30.

[0095] Figure 4a illustrates a control system architecture for the proposed electrical system. The control system comprises a central controller 40 and a plurality of local controllers 311, 321, 331. Each power converter 310, 320, 330 is connected to or integrated with a respective local controller. The central controller 40 can be of any type with zero steady-state error, for example, PI, PID, integral state feedback LQR, LQF, or Hinf. The central controller 40 is configured to generate, at a center frequency Fc, local setpoints P respectively associated with the electrical sources 31, 32, 33, from a measurement V me s of the bus voltage V <j c and the reference voltage V re f. The center frequency Fc is limited by the bandwidth available in the communication buses linking the central controller 40 to the various local controllers 311, 321, 331.

[0096] The central controller 40 has a V measurementme s of the distribution bus voltage 30, this measurement being able to be transmitted in particular to the central controller 40 by a voltage sensor 5. The central controller 40 may include a voltage control unit 41, which aims to regulate the bus voltage V <j c at the terminals of the distribution bus 30 around the reference voltage V re f. Typically, the reference voltage value V re f is between 500V and 1000V, for example 800V.

[0097] The voltage control unit 41 is, for example, connected to the voltage sensor 5. The measurement can be received via a physical or wireless connection. The sensor 5 can perform a V measurement me s at the center frequency Fc. The measurement V mes represents in particular the evolution of the power requirements of the loads Ch1, Ch2 connected to the distribution bus 30. Typically, when a load Ch1, Ch2 suddenly requires to be able to draw a large amount of power from the distribution bus 30, due to the response time of the electrical system 3 to supply the distribution bus 30 with the power needed to compensate for the power drawn, the voltage of the distribution bus 30 will suddenly drop, and this drop will be reported to the control system via the measurement Vmes, at the center frequency Fc.Similarly, when a load Ch 1, Ch2 suddenly sheds a large amount of power on the distribution bus 30, due to the response time of the electrical system 3 to draw the necessary power from the distribution bus 30 to compensate for this shedding, the voltage of the distribution bus 30 will suddenly increase, and this increase will be reported to the control system via the measurement V. me s. Thus, the measure V me s is typically a time signal, that is, representing the evolution of the bus voltage V <j c of the distribution bus 30 as a function of time. Many Ch1, Ch2 loads, especially so-called "active" loads, typically an air conditioning system, can exhibit this type of dynamic behavior, which can also vary during the different phases of flight.

[0098] In addition to the voltage control unit 41, the central controller 40 may include a power sharing unit 42 for distributing a power setpoint transmitted by the voltage control unit among the different power sources. Preferably, each power source 31, 32, 33 is associated with a local sensor 51, 52, 53 configured to provide the associated local controller 311, 321, 331 with a local voltage measurement Vi,mes, specific to the power source in question. The local voltage measurement Vi, m es is typically close to the measured bus voltage V me s, but may not be equal to the bus voltage V me s measured at the terminals of the distribution bus 30, due to the impedance of the cables connecting the electrical sources 31, 32, 33 to the distribution bus 30.

[0099] In the embodiment illustrated in Figure 3, the control system further includes a central computer 4. The central computer 4 can, for example, be all or part of the system providing the interface between the aircraft cockpit 100 and the turbomachine 10 (or "Full Authority Digital Engine Control," FADEC, in Anglo-Saxon terminology), typically being the control unit of the turbomachine 10 ("Electronic Control Unit" or ECU in Anglo-Saxon terminology), integrated into the FADEC. The central computer 4 is connected to the control system, in this case to the power sharing unit 42. The central computer 4 can determine additional constraints that the electrical system 3 must meet to fulfill the power requirements of the loads Ch1, Ch2. Thus, the central computer 4 can transmit to the power sharing unit 42 a plurality of respective thresholds associated with the electrical sources (called "setpoints" in English).

[0100] The central computer 4 can transmit a power distribution instruction between the rotating elements BP, HP and the DC power source 33. This distribution instruction tells the central controller 40 how the total power to be drawn from the turbomachine 10 to meet the load requirements of Ch1, Ch2 should be distributed between the rotating elements BP, HP and the DC power source 33, and typically takes the form of a percentage. In one embodiment, the power distribution instruction is generated by the central computer 4 by taking into account signals representative of the power outputs from the sources, so that the local commands P are updated by the central controller 40 based on the power distribution instruction and thus the output power.

[0101] Figure 4a shows the control system in detail, according to a first embodiment. For clarity, only the local controller 311 associated with the high-pressure shaft is shown in detail; the local controllers 321 and 331 associated with the low-pressure shaft and the battery are represented by blocks. Naturally, the description of the local controller 311 that follows can also be applied to one or both of the local controllers 321 and 331.

[0102] In general, the central controller 40, for example via the power sharing unit 42, transmits to each of the local controllers 311, 321, 331 a local setpoint P. Typically, the local setpoint P corresponds to a power, a torque or a current intensity.

[0103] The control system is configured to compensate for changes in voltage V <j cof the distribution bus 30 by the action of the converters 310, 320, 330, and in particular maintain the voltage of the distribution bus 30 within the limits allowing stable operation of the electrical system 3, between the values ​​V m in and V ma x.

[0104] To achieve this, each local controller 311, 321, 331 is configured to generate, at a local frequency Fl, higher than the center frequency Fc, an output setpoint P cs based on the received local instruction P.

[0105] Preferably, the local frequency Fl is at least ten times greater than the center frequency Fc. Typically, the local frequency Fl is equal to 100Hz, and the center frequency Fc is equal to 10Hz.

[0106] Thus, each of the converters 310, 320, 330 receives the output command P from the respective local controller 311, 321, 331 cswhich is specific to it, and from which the converter 310, 320, 330 regulates the voltage of the distribution bus 30. The combination of the regulations of each converter 310, 320, 330 thus makes it possible to continuously follow the power requirements of the loads Ch1, Ch2.

[0107] Each local controller 311, 321, 331 is configured to control the associated electrical power source by implementing droop control, based on a droop gain associated with that power source. Droop control consists of allowing the measured local voltage Vi, m The voltage of the power source considered may vary slightly relative to the reference voltage V ref, between a minimum and a maximum value. In what follows, the expression "drift control" should be interpreted as including the application to a signal, in particular within a drift unit 7 of the local controller 311, 321, 331, of a drift gain or coefficient, but without excluding the application of other signal processing steps subsequent to the application of the drift gain. The current intensity (or, equivalently, the power) exiting the drift unit 7 is proportional to the voltage drop seen by the power source, for example, following a load impact. The drift gain is notably applied by the central controller 40 to a difference between a measured voltage Vi, m es of the associated power source and the reference voltage V re f. Alternatively, the drastic gain is applied by the central controller 40 to a difference between the squares of these values, namely Vi,m is 2 and V re f 2 More generally, the drastic gain can be applied to any value allowing a comparison between the measured local voltage Vi, m es and the reference voltage V re f. The drowsiness regulation generates a setpoint correction P co that the local controller 311, 321, 331 adds to the local setpoint P sent by the central controller 40, so as to produce the output setpoint P cs The local controller 311, 321, 331 regulates the voltage of its associated electrical power source by means of this output setpoint P cs The instruction correction P co and the output instruction P cs are of the same dimension as the associated local setpoint P: it can be a power, a current intensity or possibly a mechanical torque.

[0108] During a load impact on the distribution bus 30, the static regulation implemented by the local controllers 311, 321, 331 ensures a high-frequency response to the disturbance.

[0109] Figure 5 shows the time evolution of the voltages immediately following a load impact, including the contribution of the central controller 40 (curve I) and the contribution of a local controller 311, 321, 331 (curve II), as well as the time evolution of the bus voltage Vdc (curve III). It can be seen that, despite the distances between the power sources and the central controller 40, despite the highly vibratory and electromagnetic environment, and despite a central controller frequency Fc that is insufficiently fast to directly ensure a rapid response to the load impact, the droop regulation performed by the local controllers 311, 321, 331, which operate at higher frequencies Fl, allows the bus voltage Vdc to be regulated as close as possible to the reference voltage V re f. Due to the voltage variation allowed by the drowsiness regulation, a non-zero error (called "steady-state error") is present in the output setpoint Pcs of the local controller 311, 321, 331, including in stabilized mode following the load impact. The contribution of the local setpoint P sent by the central controller 40 to the output setpoint P cs This effectively cancels out this static error. Thus, the proposed control system allows for an adequate response from the electrical system at both high and low frequencies.

[0110] The proposed control system is suitable for a hybrid electrical system of a turbomachine, particularly an aircraft turbomachine, by satisfying power-sharing criteria between electrical sources. Applying drastic control at each source, due to the voltage variation it allows, prevents instability caused by the simultaneous response of each local controller to a load impact. Indeed, in an electrical system with multiple local controllers that generate a single local voltage setpoint for their respective power sources, a load impact triggers a simultaneous response from each local controller, which can increase or decrease the bus voltage (Vdc) beyond the specified value (V). re f (in English, this is referred to as "overshoot" or "undershoot"), generating an oscillatory behavior of the bus frequency V <j caround the reference value Vref. In addition, thanks to the possibility of providing different values ​​of static gain K for the different local controllers 311, 321, 331, the proposed system advantageously allows great control of the sharing of power between the sources - it is thus possible to take more power from one source than from another, depending on the flight phases of the aircraft in particular.

[0111] Another advantage of the proposed system is that, thanks to the local controllers 311, 321, 331, it allows for regulation of the bus voltage V <j c even in the event of loss of the central controller 40.

[0112] Besides the fact that a power sharing between the different sources can advantageously be defined by means of the values ​​of the static coefficients K of each static unit 7, the static coefficients K must be chosen so that each power source can respond sufficiently quickly to the load impact, the response of the local controllers 311, 321, 331 being dominant over the response of the central controller 40 immediately after the load impact.

[0113] Another embodiment of the control system is illustrated in Figure 4b. It is identical to the embodiment illustrated in Figure 4a, except for the architecture of the local controllers 311, 321, 331. In this second embodiment, the drastic unit 7 of the local controller 311, 321, 331 applies a drastic coefficient 1 / K—which has the inverse physical dimension to the dimension of the drastic gain K for the control system according to the embodiment in Figure 4a—to a current intensity i, which can be a reference current i. re f for the power source considered, or a measured current intensity i m is for this power source. The signal thus obtained is added to the difference between the reference voltage V re f and the measured local voltage value Vi, m es, then passed to a zero static error controller

[0114] 6. Thus, at the output of the zero-error static controller 6, we obtain the setpoint correction P co which, added to the local setpoint P issued by the central controller 40 for the power source considered, gives the output setpoint P cs .

[0115] The implementation by local controllers 311, 321, 331 of a static control of the type shown in Figure 4b has the advantage of allowing better adaptability of the control system in the event that it is desired to operate the electrical system in single-source mode: in this case, for the power source that one wishes to control, it is sufficient to disconnect the branch of the local controller 311, 321, 331 which includes the static control unit.

[0116] 7, so that the local controller 311, 321, 331 only applies the regulation performed by the zero-static-error controller 6 to the difference between the reference voltage V re f and the measured local voltage Vi,m es.

[0117] For this embodiment, the local controller can apply a low-pass filter to the intensity signal supplied to the static unit 7.

[0118] According to an alternative not shown, for both the embodiment of Figure 4a and that of Figure 4b, the reference voltage V re f and the measured local voltage Vi, m es can be replaced by the square of these same values, V re f 2 and Vi, m is 2 .

[0119] Figure 6 illustrates the operation of the control system. Curves IV and IVa represent the evolution of the output setpoint P, respectively. cs and the instruction correction P co with the voltage for a first power source, and the curves V and Va represent the evolution of the output setpoint P cs and the instruction correction P cowith the voltage for a second power source. The local setpoint value P provided by the central controller 40 shifts the bus voltage relative to the value that would be obtained without this local setpoint P, taking into account the static coefficient K or 1 / K.

[0120] In the absence of the local setpoint P, as represented by curves IVa and Va, in steady state, the bus voltage V <j c would always be different from the reference voltage V re f, due to the steady-state error permitted by the local controllers 311, 321, 331. The consideration by each local controller 311, 321, 331 of the local setpoint P shifts the curves so that the output setpoint follows curves IV and V, thus canceling the steady-state error. In steady-state operation, the output setpoints take the respective values ​​Pi and P2 for the two sources, and the bus voltage V <j c is equal to the reference voltage V re f. Pœi and PC0 2 are the corresponding values ​​of the setpoint correction.

[0121] In some embodiments, the central computer 4 is configured to send, in addition to local instructions P, instructions relating to the control implemented by the local controllers 311, 321, 331. For example, the central computer can define dead zones: the central controller defines a dead zone for each power source, meaning that the source in question does not supply any power when within a certain bus voltage range V <j c Each local controller applies the dead zone of the source to which it is connected, based on a command provided by the central controller. This allows for source prioritization by the central computer 4.

[0122] This disclosure further relates to a method for controlling an electrical system comprising a plurality of power sources, the power sources being connected in parallel to a distribution bus 30. The method aims to regulate the voltage V <j c of the distribution bus 30. With reference to Figure 7, a central controller 40 sends local commands P on a first central frequency. Each local command P is associated with a given power source and is transmitted by the central controller 40 to a local controller 311, 321, 331, also associated with that power source. The power sources may include, in particular, a low-pressure shaft 180 and a high-pressure shaft 182 of a turbomachine, as well as a DC power source 33 such as a battery.

[0123] Based on the setpoint P received from the central controller 40, the local controller 311, 321, 331 implements a static control based, on the one hand, on a parameter representing a reference voltage V re f for this power source, and on the other hand, a measured local voltage Vi, m es for this power source, so as to generate a setpoint correction P co .

[0124] Representative parameters can be directly the reference voltage V re f and the measured local voltage Vi, m es, or even be the squares of these values. The static regulation includes in particular the application, by a static unit 7, of a static gain K to the difference between these two representative parameters.

[0125] A drastic control unit 7 of the local controller 311, 321, 331 can also apply a drastic gain 1 / K to a current intensity, chosen from a reference intensity i re f for the power source considered and a measured current intensity i m es for this power source. The local controller 311, 321, 331 then adds the signal from the drowsiness unit 7 with a difference between the parameters representing the reference voltage Vi re f and the measured local voltage Vi, m Finally, the signal is transmitted to a zero-dependency controller 6 of the local controller 311, 321, 331 so as to issue a setpoint correction P co . The zero static error controller 6 can notably be of the PI, PID, integral state feedback LQR, LQF or Hinf type.

[0126] Based on the correction of instruction P coand the local setpoint P transmitted to it by the central controller 40, the local controller 311, 321, 331 issues an output setpoint P cs by which it controls the associated power source. The output setpoint P cs is emitted by the local controller 311, 321, 331 at a local frequency Fl higher than the center frequency Fc. Thus, in the time immediately following a load impact, the local controller allows the voltage V to be regulated <j c of the distribution bus 30 so as to approach this voltage V <j c of a reference voltage V re f, despite the fact that the central controller 40 can only intervene over a longer period of time, particularly due to its distance from the power source.

Claims

DEMANDS 1. Control system for controlling an electrical system, the electrical system comprising a plurality of power sources connected in parallel to a distribution bus (30), the distribution bus (30) having a bus voltage (V <j c ) to be regulated around a reference voltage (V re f) the control system comprising: • a central controller (40) configured to send, at a center frequency (Fc), local instructions (P) respectively associated with the power sources, and generated from a measured bus voltage (V me s) and the reference voltage (V re f), • local controllers (311, 321, 331), each local controller being configured to: o receive one of the local setpoints (P), o implement droop control based on a reference parameter representative of the reference voltage (V ref) and a measured voltage parameter representative of a measured local voltage (Vi, m es) of the power source associated with the received local setpoint (P), so as to generate a setpoint correction (P co ), and to generate, at a local frequency (Fl) higher than the center frequency (Fc), an output setpoint (P cs ) for the power source from the received local setpoint (P) and the setpoint correction (Pco), or to control, using the output setpoint (P cs ), the power source associated with the received local setpoint (P).

2. Control system according to claim 1, wherein: - the reference parameter is the reference voltage (V re f) and the measured voltage parameter is the measured local voltage (Vi, m es), or - the reference parameter is the square of the reference voltage (V ref) and the measured voltage parameter is the square of the measured local voltage (Vi, m es).

3. Control system according to claim 2, wherein the local controller (311, 321, 331) includes a drastic unit (7) configured to apply a drastic coefficient (K) to a difference between the reference parameter and the measured voltage parameter.

4. Control system according to claim 2, wherein the local controller (311, 321, 331) comprises, in series: • a static unit (7) configured to apply a static coefficient (1 / K) to a reference intensity (i re f) or at a measured intensity (i mes ) of the power source associated with the local setpoint (P), so as to produce a regulated signal, and • a zero steady-state error controller (6) configured to produce the setpoint correction (Pco) from: o the difference between the reference parameter and the measured voltage parameter of the power source associated with the received local setpoint (P), and o the regulated signal from the drowsiness unit (7).

5. Control system according to any one of claims 1 to 4, further comprising a computer (4) configured to generate a power draw distribution setpoint between the power sources from signals representative of powers generated by the power sources, and in which the central controller (40) is configured to update the local setpoints (P) from the draw distribution setpoint.

6. Assembly comprising an electrical system and a control system according to any one of claims 1 to 5.

7. Assembly according to claim 6, wherein the power sources comprise at least two of the following: • a low-pressure shaft (181) of the turbomachine, • a high-pressure shaft (182) of the turbomachine, and • a direct current source (33), in particular a battery.

8. Method for controlling an electrical system comprising a plurality of power sources connected in parallel to a distribution bus, the distribution bus having a bus voltage to be regulated around a reference voltage (V re (f) the process being implemented by a central controller (40) and by local controllers (311, 321, 331), the process comprising steps of: • transmission by the central controller (40), at a center frequency (Fc), of local instructions (P) respectively associated with the power sources and generated from a measured bus voltage (V mes) and the reference voltage (V re f), • receipt of one of the local instructions (P) by one of the local controllers (311, 321, • implementation, by the local controller (311, 321, 331), of a static regulation based on a reference parameter representative of the reference voltage (V re f) and a measured voltage parameter representative of a measured local voltage (Vi,mes) of the power source associated with the received local setpoint (P), so as to generate a setpoint correction (P co ), • generation, by the local controller (311, 321, 331) and at a local frequency (Fl), of an output setpoint of the respective power source from: ■ of the local setpoint (P), and ■ of the instruction correction (P co ) • control by the local controller (311, 321, 331) of the power source associated with the local setpoint (P) received using the output setpoint (P cs ).

9. A method according to claim 8, wherein: • The reference parameter is the reference voltage (V re f) and the measured voltage parameter is the measured local voltage (Vi, m es), or • The reference parameter is the square of the reference voltage (V re f) and the measured voltage parameter is the square of the measured local voltage (Vi, m es).

10. Method according to claim 9, wherein the implementation of a drastic control includes the application, by a drastic unit (7) of the local controller (311, 321, 331), of a drastic coefficient (K) to a difference between the reference parameter and the measured voltage parameter.

11. A method according to claim 10, wherein the implementation of a static control system comprises: • the generation, by a static unit (7) of the local controller (311, 321, 331), of a signal regulated by applying a static coefficient (1 / K) to a reference intensity (i re f) or at a measured intensity (i mes ) of the power source associated with the local setpoint (P), • the generation, by a zero-error static controller (6) of the local controller (311, 321, 331), of the setpoint correction (P co ) from: o a difference between the reference parameter and the measured voltage parameter of the power source associated with the received local setpoint (P), and o the regulated signal.

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