System and method for controlling parallel power sources

Abstract

This 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 comprises: 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 from 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). Abstract figure: Fig. 4a

Description

Title of the invention: System and method for controlling parallel power sources technical field

[0001] This disclosure relates to the general field of electrical source control systems, and in particular voltage regulation when electrical sources are connected in parallel by a centralized controller. STATE OF THE ART

[0002] 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 various states. In particular, an ambitious standard applies to both new types of aircraft and those currently in operation, 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.

[0003] 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 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.

[0004] 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 the use of electric technologies for propulsion.

[0005] An aircraft generally comprises an electrical network powered by various sources and is propelled by a turbomachine. In order to improve the aircraft's energy efficiency, it is possible to implement internal hybridization of the turbomachine. This involves adding a hybrid electrical system that forms an interface between the rotating mechanical shafts of the turbomachine and the aircraft's electrical network. The hybrid electrical system aims to assist the turbomachine in order to optimize its operation by providing assistance electrical or by drawing power. It must control the sharing of power between the high-pressure and low-pressure mechanical shafts of the turbomachine, and in particular limit the power drawn, ensuring that all sources provide a good supply to the aircraft's electrical network.

[0006] A first proposed solution is an electrical system with a plurality of decentralized or local controllers. In this case, the low-pressure shaft and the high-pressure shaft are controlled independently and are voltage-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. Thus, the bus voltage that one seeks to regulate is strongly affected by local measurement errors.

[0007] 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 present in an aircraft are distributed within it 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 of the communication buses depends on the distance. EXPOSE

[0008] One purpose of the present disclosure is to regulate a voltage of a distribution bus of an electrical system comprising several voltage sources in parallel, without it being necessary for communications to be able to take place rapidly between decentralized controllers and a centralized controller, and / or between the decentralized controllers.

[0009] To this end, a control system is proposed for controlling 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: • 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, • local controllers, each local controller being configured to • receive one of the local instructions, • Implement a drastic control system based on a reference parameter representing the reference voltage and a measured voltage parameter representing a local voltage measured from the power source associated with the received local setpoint, so as to generate a setpoint correction, and • generate, at a local frequency higher than the center frequency, an output setpoint for the power source based on the received local setpoint and the setpoint correction, • control, using the output setpoint, the power source associated with the received local setpoint.

[0010] The central controller allows the power to be drawn to be shared directly by transmitting respective commands to each electrical source at the central frequency, which is lower than the local frequency. The proposed solution thus eliminates the need for rapid communication between the central controller and the local controllers, which may be impossible due not only to the distance between the electrical sources and the central controller, but also to the harsh vibrational and electromagnetic environment in which the electrical system operates. The adjustment of the command 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, more quickly than the central controller could. Thus, the control of the power sources adapts more rapidly to such impacts.The regulation performed by the central controller compensates, at a lower frequency, for the steady-state error due to each respective local controller. Rapid communication between the local controllers and the central controller is not necessary, 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.

[0011] According to certain embodiments:

[0012] - the reference parameter is the reference voltage and the voltage parameter The measured local voltage is the measured voltage, or

[0013] - the reference parameter is the square of the reference voltage and the parameter of The measured voltage is the square of the measured local voltage.

[0014] According to some embodiments, the local controller includes a drastic unit configured to apply a drastic coefficient to a difference between the reference parameter and the measured voltage parameter.

[0015] According to certain embodiments, the local controller comprises, in series: • 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 • a zero-error static controller configured to produce the setpoint correction from: • the difference between the reference parameter and the measured voltage parameter of the power source associated with the received local setpoint, and • of the regulated signal from the static unit.

[0016] 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.

[0017] According to a second aspect, an assembly is proposed comprising an electrical system and a control system as defined previously.

[0018] According to some embodiments, the power sources comprise at least two of the following: • a low-pressure shaft of the turbomachine, • a high-pressure shaft of the turbomachine, and • a source of direct current, in particular a battery.

[0019] According to a third aspect, a method for controlling an electrical system comprising a plurality of power sources connected in parallel to a distribution bus is proposed, 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 the steps of: • transmission by the central controller, at a center frequency, of local instructions respectively associated with the power sources and generated from a measured bus voltage and the reference voltage, • Receipt of one of the local instructions by one of the local controllers, • implementation, by the local controller, of a static regulation based on of 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, • generation, by the local controller and at a local frequency, of an output setpoint for the respective power source from: • of the local deposit system, and • of the instruction correction • control by the local controller of the power source associated with the local setpoint received using the output setpoint.

[0020] According to certain implementations of the process: • The reference parameter is the reference voltage and the measured voltage parameter is the measured local voltage, or • The reference parameter is the square of the reference voltage and the measured voltage parameter is the square of the measured local voltage.

[0021] According to some implementations of the method, 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.

[0022] According to certain implementations of the process, the implementation of a static control system includes: • 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, • the generation, by a zero-error static controller of the local controller, of the setpoint correction from: • a difference between the reference parameter and the measured voltage parameter of the power source associated with the received local setpoint, and • of the regulated signal. DESCRIPTION OF THE FIGURES

[0023] Other features, purposes and advantages will become apparent from the following description, which is purely illustrative and not limiting, and which should be read in conjunction with the accompanying drawings on which:

[0024] [Fig.1] schematically represents an aircraft.

[0025] [Fig. 2] schematically represents a turbomachine.

[0026] [Fig.3] represents an electrical system of the aircraft, according to an embodiment comprising three power sources.

[0027] [Fig.4a] represents a control system for the electrical system of the [Fig.3], according to a first embodiment.

[0028] [Fig.4b] represents a control system for the electrical system of the [Fig.3], according to a second embodiment.

[0029] [Fig.5] represents an evolution of a bus voltage for the electrical system of [Fig.3] during a load impact.

[0030] [Fig.6] is a graph illustrating a power-voltage or current-voltage law of local controllers, in stabilized and dynamic regime.

[0031] [Fig.7] schematically illustrates a method for controlling the electrical system of the aircraft.

[0032] Throughout the figures, similar elements bear identical reference numerals. DETAILED DESCRIPTION OF EMBODIMENTS

[0033] In the present 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.

[0034] By way of illustration, [Fig. 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 even 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.

[0035] Aircraft electrical system 100

[0036] In a manner known per se, the aircraft 100 comprises a plurality of electrical loads (or receivers) powered by electrical sources via an electrical network.

[0037] An electric 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.

[0038] With reference to [Fig. 3], the electrical loads can be divided into two categories. A first category of loads Chl is external to the propulsion system 1. The electrical loads Chl specific to the aircraft 100 may include, by way of example, an electric motor, a heating and / or air conditioning system, or a compressor. They enable, in particular, a number of functionalities, whether the aircraft is in flight or in operation on the ground, such as pressurizing and / or illuminating the cabin of the aircraft 100, or operating the cockpit.

[0039] A second category of Ch2 loads is internal to the propulsion unit 1. The propulsion unit 1 generally comprises 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 Anglo-Saxon terminology). For example, the electrical loads of the turbomachine Ch2 may include a starter, variable geometry, or de-icing systems.

[0040] The plurality of electrical sources makes it possible to supply electrical loads with electrical energy, generally in the form of a continuous signal, typically a direct voltage.

[0041] On the one hand, the turbomachine 10 generally comprises two rotating bodies or shafts providing mechanical energy. Each shaft is associated with a generator motor allowing mechanical energy to be extracted from the associated shaft and converted into electrical energy, in order to supply the electrical network.

[0042] On the other hand, the 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.

[0043] The electrical network typically comprises a set of electrical conductors, typically a set of cables connecting the different electrical loads and the different sources, and bars, for example a high-voltage direct current distribution bus.

[0044] Generally, generator motors that extract mechanical energy from shafts produce alternating current. The alternating current is converted into direct current by an AC / DC converter. The electrical network includes at least a portion of a direct current network, with electrical loads being supplied by direct current.

[0045] Description of the turbomachine

[0046] Fig. 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.

[0047] 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.

[0048] This disclosure is not limited to a twin-spool, twin-flow turbojet with direct fan drive 11 as illustrated. It extends more generally to different turbojet architectures, including unfaired turbojets, and other types of turbomachinery, which may have a different number of bodies and / or flows.

[0049] This disclosure falls more generally within the context of the internal hybridization of the turbomachine 10, i.e., having an electrical system 3 in interface with the mechanical shafts of the turbomachine and the electrical network of aircraft 100, as detailed later.

[0050] 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.

[0051] 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 seen in the [Fig.2], the compression section 16, the combustion chamber 14 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 flow A.

[0052] 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.

[0053] 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.

[0054] The turbomachine 10 may also include at least one accessory gearbox (AGB), typically housed in a cavity within the nacelle 20. The accessory gearbox 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, optionally via of a transfer case, the accessory case to at least one of the high-pressure body HP and the low-pressure body BP. For example, the power take-off shaft (not shown) can extend inside a longitudinal cavity formed within an arm 17. In this way, mechanical power can 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 case.

[0055] Fig. 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 Chl and / or the electrical loads of the turbomachine Ch2, typically by means of the direct current network.

[0056] 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 Chl and / or the turbomachine Ch2 by mechanically drawing power from the turbomachine 10, and to assist the starting and / or in-flight operation of the turbomachine 10 using electrical sources from the aircraft 100.

[0057] In the embodiment illustrated in [Fig. 3], the electrical system 3 comprises three electrical sources. The low-pressure body BP is connected to an alternating current generator 31, coupled to the accessory housing of the low-pressure shaft 181. The high-pressure body HP is connected to an alternating current generator 32, coupled to the accessory housing of the low-pressure shaft 182. The electrical system 3 also comprises a direct current source 33, for example, a battery.

[0058] More generally, this disclosure extends to any multi-source electrical system, comprising one or more alternating current electrical sources and / or one or more direct current electrical sources. In particular, electrical system 3 may not include the direct current source 33.

[0059] The alternating current generator 31, 32 and the direct current source 33 can each independently belong to the turbomachine 10, i.e. be controlled at the same time as the turbomachine 10, or even be controlled by the turbomachine 10. Alternatively or complementaryly, the electrical sources 31, 32, 33 can belong to the aircraft 100, i.e. be controlled at the same time as the aircraft 100.

[0060] 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.

[0061] The electrical system 3 includes a distribution bus 30, connected to at least one of the aircraft electrical load Chl and the turbomachine electrical load Ch2, preferably to both loads Chl, Ch2.

[0062] Furthermore, each of the converters 310, 320, 330 is connected to the distribution bus 30.

[0063] The distribution bus 30 is configured to supply electrical power to the electrical load Chl, Ch2 in the form of a continuous signal in order in particular to meet the power requirements of the electrical load Chl, Ch2.

[0064] 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.

[0065] In order for the elements connected to the distribution bus 30, in particular the electrical loads Chl, Ch2 to function correctly, it is necessary to regulate the voltage of the distribution bus 30.

[0066] Bus voltage regulation

[0067] Two examples of a template are illustrated in [Fig. 5]. Even if the Vmax and Vmin limits do not initially define constant electrical voltage values, particularly during the characteristic start-up time of the electrical system 3 or during the steady-state establishment time 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 for 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.

[0068] On the other hand, the voltage regulation of the distribution bus 30 must be able to meet the power demands of the loads Chl, Ch2 connected to the distribution bus 30. Typically, when the amount of power drawn by at least one load Chl, 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, 330, the voltage of the distribution bus 30 decreases significantly. Conversely, when the amount of power injected by at least one converter 310, 320, 330 into the distribution bus 30 is greater than the amount of power drawn from the distribution bus 30 by at least one load Chl, Ch2, the bus voltage The distribution bus voltage 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 Chl, Ch2. In other words, each of the converters 310, 320, 330 is configured to continuously adapt the power it injects into or draws from the distribution bus 30, according to the voltage of the distribution bus 30, so as to precisely meet the power requirements of the loads Chl, Ch2 connected to the distribution bus 30.

[0069] This injection or extraction 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 extract 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 onto the distribution bus 30. In the embodiment illustrated in [Fig. 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.

[0070] 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.

[0071] Similarly, the DC power source 33 can deliver power in the form of a continuous 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.

[0072] 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 have the particular advantage of having a lower mass, or such as asynchronous machines (or “Induction machine” in Anglo-Saxon terminology) or variable reluctance machines.

[0073] The DC power source 33 may, for its part, comprise a battery, a supercapacitor, a DC generator, and / or a fuel cell. The DC power source 33 makes it possible, in particular, to relieve the rotating bodies BP, HP, or to take over their operation when, for example, the current draw required to meet the power needs of the loads Chl, Ch2 is too high, but it also makes it possible to absorb certain dynamics, such as sudden variations in the behavior of the loads Chl, Ch2.

[0074] The electrical system 3 includes a control system for controlling the electrical sources 31, 32, 33 connected in parallel on the distribution bus 30.

[0075] During operation, the electrical voltage within the distribution bus 30, or bus voltage Vdc, may vary around a given nominal value, or reference voltage Vref, for example, if an electrical load momentarily requires additional power or if an electrical source disconnects. Therefore, the bus voltage Vdc must be regulated by the control system that controls the power—or current—supplied by each electrical source 31, 32, 33 connected to the distribution bus 30.

[0076] 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 static error, for example PI, PID, integral state feedback LQR, LQF, or Hinf.

[0077] 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 Vmes of the bus voltage Vdc and the reference voltage Vref. 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.

[0078] The central controller 40 has a measurement Vmes of the distribution bus voltage 30, this measurement being transmitted 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 Vdc at the terminals of the distribution bus 30 around the reference voltage Vref. Typically, the reference voltage value Vref is between 500V and 1000V, for example 800V.

[0079] The voltage control unit 41 is for example connected to the voltage sensor 5. The measurement can be received via a physical or wireless link. Sensor 5 can perform a Vmes measurement at the center frequency Fc. The Vmes measurement represents, in particular, the evolution of the power requirements of the loads Chl, Ch2 connected to the distribution bus 30. Typically, when a load Chl, Ch2 suddenly requires a significant amount of power to be drawn from the distribution bus 30, due to the response time of the electrical system 3 in supplying the distribution bus 30 with the power needed to compensate for the power drawn, the voltage of the distribution bus 30 will drop sharply, and this drop will be reported to the control system via the Vmes measurement at the center frequency Fc.Similarly, when a load Chl, Ch2 suddenly sheds a significant 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 load shedding, the voltage of the distribution bus 30 will rise sharply, and this increase will be reported to the control system via the Vmes measurement. Thus, the Vmes measurement is typically a time-domain signal, that is, representing the evolution of the bus voltage Vdc of the distribution bus 30 as a function of time. Many loads Chl, Ch2, particularly 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.

[0080] In addition to the voltage control unit 41, the central controller 40 may include a power sharing unit 42 intended to distribute a power setpoint transmitted by the voltage control unit between the different power sources.

[0081] 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 Vimes, specific to the power source in question. The local voltage measurement Vimes is typically close to the measured bus voltage Vmes, but may not be equal to the bus voltage Vmes measured at the terminals of the distribution bus 30, due to the impedance of the cables connecting the power sources 31, 32, 33 to the distribution bus 30.

[0082] In the embodiment illustrated in [Fig. 3], the control system further comprises a central computer 4. The central computer 4 may, 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 terminology (Anglo-Saxon), 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 Chl, 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).

[0083] The central computer 4 can transmit a power distribution instruction between the rotating bodies BP, HP and the DC power source 33. The distribution instruction tells the central controller 40 how the total power to be drawn from the turbomachine 10 to meet the load requirements of Chl, Ch2 should be distributed between the rotating bodies BP, HP and the DC power source 33, and can typically take 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 instructions P are updated by the central controller 40 taking into account the power distribution instruction and therefore the output power.

[0084] 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 has been shown in detail; the local controllers 321 and 331 associated with the low-pressure shaft and the battery have been represented by blocks. Naturally, the following description of the local controller 311 can also apply to one or both of the local controllers 321 and 331.

[0085] 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.

[0086] The control system is configured to compensate for changes in the voltage Vdc of the distribution bus 30 by the action of the converters 310, 320, 330, and in particular to maintain the voltage of the distribution bus 30 within the limits allowing stable operation of the electrical system 3, between the values ​​Vmin and Vmax.

[0087] To do 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 Pcs from the received local setpoint P.

[0088] 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.

[0089] Thus, each of the converters 310, 320, 330 receives from the respective local controller 311, 321, 331 the output setpoint Pcs which 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 monitor the power requirements of the loads Chl, Ch2.

[0090] 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>mes of the power source in question to vary slightly relative to the reference voltage Vref, between a minimum and a maximum value. In what follows, the expression "droop control" should be interpreted as including the application to a signal, particularly within a droop unit 7 of the local controller 311, 321, 331, of a droop gain or coefficient, but without excluding the application of other signal processing steps subsequent to the application of the droop gain.The current intensity (or, equivalently, the power) output from the droop unit 7 is proportional to the voltage drop seen by the power source, for example, following a load impact. The droop gain is applied by the central controller 40 to the difference between a measured voltage Vi>mes of the associated power source and the reference voltage Vref. Alternatively, the droop gain is applied by the central controller 40 to the difference between the squares of these values, namely Vi>mes² and Vref². More generally, the droop gain can be applied to any value that allows a comparison between the measured local voltage Vi>mes and the reference voltage Vref. The droop control generates a setpoint correction Pco, which the local controllers 311, 321, and 331 add to the local setpoint P sent by the central controller 40, thus producing the output setpoint Pcs.The local controller 311, 321, 331 regulates the voltage of its associated electrical power source by means of this output setpoint Pcs. The setpoint correction Pco and the output setpoint Pcs are of the same dimension as the associated local setpoint P: it can be a power, a current intensity or possibly a mechanical torque.

[0091] 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.

[0092] 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 evolution Time-dependent 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 drastic regulation performed by the local controllers 311, 321, and 331, which operate at higher frequencies Fl, allows the bus voltage Vdc to be regulated as close as possible to the reference voltage Vref. Due to the voltage variation permitted by the drastic regulation, a non-zero error (called "static error") is present in the output setpoint Pcs of the local controllers 311, 321, and 331, even in steady-state operation following the load impact. The contribution of the local setpoint P sent by the central controller 40 to the output setpoint Pcs advantageously cancels this static error.Thus, the proposed control system allows for an appropriate response from the electrical system at both high and low frequencies.

[0093] The proposed control system is suitable for a hybrid electrical system of a turbomachine, particularly an aircraft turbomachine, by allowing it to meet power sharing criteria between the electrical sources. The application of drastic control at the level of each source makes it possible, due to the voltage variation it allows for the source, to avoid instability due to the simultaneous response of each local controller to the load impact - indeed, in the case where an electrical system includes several local controllers that generate a simple local voltage setpoint for their respective power sources, a load impact generates a simultaneous response from each local controller that can increase or decrease the bus voltage Vdc beyond the value Vref (this is referred to in English as "overshoot" or "undershoot"), generating an oscillatory behavior of the bus frequency Vdc around the reference value Vref.Furthermore, thanks to the possibility of specifying different values ​​of static gain K for the different local controllers 311, 321, 331, the proposed system advantageously allows for a high degree of control over power sharing between the sources - it is thus possible to draw more power from one source than from another, depending in particular on the aircraft's flight phases.

[0094] Another advantage of the proposed system is that, thanks to the local controllers 311, 321, 331, it allows regulation of the bus voltage Vdc even in the event of loss of the central controller 40.

[0095] Besides the fact that a power sharing between the different sources can advantageously be defined using 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 quickly enough 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.

[0096] Another embodiment of the control system is illustrated in [Fig.4b]. It is identical to the embodiment illustrated in [Fig. 4a], except with regard to the architecture of the local controllers 311, 321, 331. For 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 of [Fig. 4a]—to a current intensity i, which can be a reference current iref for the power source under consideration, or a measured current intensity imes for this power source. The signal thus obtained is added to the difference between the reference voltage Vref and the measured local voltage value Vi>meSj and then transmitted to a zero-dependency controller 6.Thus, at the output of the zero static error controller 6, we obtain the setpoint correction Pco which, added to the local setpoint P issued by the central controller 40 for the power source considered, gives the output setpoint Pcs. .

[0097] The implementation by the local controllers 311, 321, 331 of a static regulation of the type provided in [Fig.4b] has the advantage of allowing better adaptability of the control system in the case where it is desired to operate the electrical system in single source: in this case, for the power source which it is desired to control, it is sufficient to disconnect the branch of the local controller 311, 321, 331 which includes the static unit 7, so that the local controller 311, 321, 331 applies only the regulation carried out by the zero static error controller 6 to the difference between the reference voltage Vref and the measured local voltage Vi>mes.

[0098] For this embodiment, the local controller can apply a low-pass filter to the intensity signal supplied to the static unit 7.

[0099] According to an unrepresented variant, for the embodiment of [Fig.4a] as for that of [Fig.4b], the reference voltage Vref and the measured local voltage Vi>mes can be replaced by the square of these same values, Vref2 and Vi>mes2.

[0100] Figure 6 illustrates the operation of the control system. Curves IV and IVa respectively represent the evolution of the output setpoint Pcs and the setpoint correction Pco with the voltage for a first power source, and the curves V and Va represent the evolution of the output setpoint Pcs and the setpoint correction Pco with the voltage for a second power source. The local setpoint value P provided by the central controller 40 shifts the bus voltage by relative to the value that would be obtained without this local instruction P, taking into account the static coefficient K or 1 / K.

[0101] In the absence of the local setpoint P, as represented by curves IVa and Va, in steady-state operation, the bus voltage Vdc would always differ from the reference voltage Vref, due to the steady-state error permitted by the local controllers 311, 321, and 331. The inclusion of the local setpoint P by each local controller 311, 321, and 331 shifts the curves so that the output setpoint follows curves IV and V, thus eliminating 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 Vdc is equal to the reference voltage Vref. Pcoi and Pco2 are the corresponding values ​​of the setpoint correction.

[0102] According to certain embodiments, the central computer 4 is configured to be able to send, in addition to the 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 given bus voltage range Vdc. Each local controller applies the dead zone of the source to which it is connected, according to a command provided by the central controller. This allows for prioritization of the sources by the central computer 4.

[0103] 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 Vdc of the distribution bus 30.

[0104] With reference to [Fig. 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.

[0105] From the setpoint P which it receives from the central controller 40, the local controller 311, 321, 331 implements a static regulation based, on the one hand, on a parameter representing a reference voltage Vref for this power source, and on the other hand, on a local measured voltage Vi>mes for this power source, so as to generate a setpoint correction Pco.

[0106] The representative parameters can be directly the reference voltage Vref and the measured local voltage Vi>mes, or they can be the squares of these values. The drastic control notably includes the application, by a drastic unit 7, of a drastic gain K to the difference between these two representative parameters.

[0107] A drastic control unit 7 of the local controller 311, 321, 331 can also apply a drastic control gain of 1 / K to a current intensity, selected from a reference current iref for the power source under consideration and a measured current intensity imes for that power source. The local controller 311, 321, 331 then adds the signal from the drastic control unit 7 to the difference between the parameters representing the reference voltage Viref and the measured local voltage Vi>mes. Finally, the signal is transmitted to a zero-dependency controller 6 of the local controller 311, 321, 331 so as to output a setpoint correction Pco. The zero-dependency controller 6 can, in particular, be of the PI, PID, integral feedback LQR, LQF, or Hinf type.

[0108] Based on the setpoint correction Pco and the local setpoint P transmitted to it by the central controller 40, the local controller 311, 321, 331 issues an output setpoint Pcs, which it uses to control its associated power source. The output setpoint Pcs is issued by the local controller 311, 321, 331 at a local frequency Fl higher than the central frequency Fc. Thus, in the immediate aftermath of a load impact, the local controller regulates the voltage Vdc of the distribution bus 30 to bring this voltage Vdc close to a reference voltage Vref, even though the central controller 40 can only intervene after a longer delay, 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 (Vdc) to be regulated around a reference voltage (Vref), the control system comprising: • a central controller (40) configured to send, at a center frequency (Fc), local commands (P) respectively associated with the power sources, and generated from a measured bus voltage (Vmes) and the reference voltage (Vref), • local controllers (311, 321, 331), each local controller being configured to • receive one of the local commands (P),• Implement drastic control based on a reference parameter representing the reference voltage (Vref) and a measured voltage parameter representing a local measured voltage (Vi>mes) of the power source associated with the received local setpoint (P), so as to generate a setpoint correction (Pco), and • generate, at a local frequency (Fl) higher than the center frequency (Fc), an output setpoint (Pcs) for the power source based on the received local setpoint (P) and the setpoint correction (Pco), • control, using the output setpoint (Pcs), the power source associated with the received local setpoint (P).

2. A control system according to claim 1, wherein: - the reference parameter is the reference voltage (Vref) and the measured voltage parameter is the measured local voltage (Vi.mes), 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,mes).

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 drastic unit (7) configured to apply a drastic coefficient (1 / K) to a reference current (iref) or to a measured current (imes) of the power source associated with the local setpoint (P), so as to produce a regulated signal, and • a zero-static error controller (6) configured to produce the setpoint correction (Pco) from: • the difference between the reference parameter and the measured voltage parameter of the power source associated with the local setpoint (P) received, and • the regulated signal from the drastic 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 allocation setpoint between the power sources from signals representative of powers generated by the power sources, and wherein the central controller (40) is configured to update the local setpoints (P) from the draw allocation 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 sources from: • 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. 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 (Vref), the method being implemented by a central controller (40) and by local controllers (311, 321, 331), the method comprising the steps of: • sending by the central controller (40), at a center frequency (Fc), local setpoints (P) respectively associated with the power sources and generated from a measured bus voltage (Vmes) and the reference voltage (Vref), • receiving one of the local setpoints (P) by one of the local controllers (311, 321, 331), • implementation, by the local controller (311, 321, 331),of a drastic control based on a reference parameter representing the reference voltage (Vref) and a measured voltage parameter representing a local measured voltage (Vi>mes) of the power source associated with the received local setpoint (P), so as to generate a setpoint correction (Pco), • generation, by the local controller (311, 321, 331) and at a local frequency (Fl), of an output setpoint of the respective power source from: • the local setpoint (P), and • the setpoint correction (Pco) • control by the local controller (311, 321, 331) of the power source associated with the received local setpoint (P) using the output setpoint (Pcs).

9. A method according to claim 8, wherein: • the reference parameter is the reference voltage (Vref) and the measured voltage parameter is the measured local voltage (Vi.mes), or

10.

11. • the reference parameter is the square of the reference voltage (Vref) and the measured voltage parameter is the square of the measured local voltage (Vi,mes). 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. 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 (iref) or to a measured intensity (imes) 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 (Pco) from: • a difference between the reference parameter and the measured voltage parameter of the power source associated with the received local setpoint (P), and • of the regulated signal.