A power supply device adapted to maintain the inertia of an electrical system

Abstract

The invention relates to a power supply device comprising an electrical energy source (1), an electrical machine (6) including an electric motor (7) and a generator (8), the electrical machine being configured such that the electric motor (7) is adapted to drive the generator (8) in rotation, and a power supply device for supplying the electric motor (7) of the electrical machine (8) with power from the electrical energy source (1). The device also includes an interface (11) adapted for connecting the generator to an electrical network (10) or disconnecting it from this network. The electrical machine (6) exhibits, in operation, a kinetic energy and a maximum power output, when driven by the electrical energy source (1), such that the power supply device has a time constant of between 2 and 6 seconds, preferably on the order of 4 seconds. Figure for the abstract: Fig. 1

Description

Title of the invention: Device for supplying electricity adapted to maintain the inertia of an electrical system

[0001] The present invention relates to the field of electrical systems, and in particular to the problem of their stability.

[0002] The concept of an electrical system includes a physical electricity distribution network, the management of the electrical intensity that can pass through each line of the network, and the processes implemented to ensure the balance of supply and demand (often referred to by the acronym EOD), or "production-consumption balance".

[0003] Electricity production can be achieved using various electrical devices, based on diverse technologies. The distribution, or "mix", between the different types of electricity production devices is currently undergoing significant evolution.

[0004] In a general context of reducing carbon dioxide emissions and decreasing the share of electricity obtained from nuclear power plants, the share of so-called renewable energies in the total electricity produced increases significantly.

[0005] This is the case for large-scale electrical systems, typically continental electrical systems, and it is even more true for smaller electrical systems such as island electrical systems and more generally non-interconnected zones (NIZs), in which the shutdown of a conventional power plant (for example Diesel) in favor of the commissioning of one or more power plants, for example solar or wind, has a strong impact on the mix between the different types of electricity production devices.

[0006] However, this development has consequences for the characteristics that impact the stability and safety of electrical systems.

[0007] In particular, two parameters of the system are important: inertia, which contributes to the stability of the system, and short-circuit power, which notably enables the proper functioning of the protection relays to detect faulty lines or devices and trigger an appropriate action.

[0008] The inertia of an electrical system, which corresponds to the application of Newton's second law to an electrical system, is reflected in its ability to dampen disturbances or instabilities, such as sudden variations in production or consumption, and to maintain the electrical frequency within an acceptable frequency range.

[0009] In an electrical system comprising only electrical sources that employ For rotating machines, i.e., synchronous generators such as turbo-alternator generator sets (for example, with a hydraulic turbine or steam turbine), the equivalent inertia of the system is defined as the ratio between the kinetic energy of rotating masses and the electrical power of the rotating machines, each rotating mass thus contributing to increasing the system's inertia. Hereafter, we will simply refer to the system's inertia to designate its equivalent inertia.

[0010] It should be noted that although inertia is not a "system service," this physical phenomenon contributes to the equilibrium of the electrical system. The frequency of the electrical wave determines the rotational speed of most electric motors powered by the electrical system, as well as the rotational speed of alternators injecting electricity into the system.

[0011] Conventional technologies for the production of electricity using alternators such as those used in thermal power plants (nuclear, fossil fuel, or biomass), or certain so-called renewable energies such as hydroelectricity, thus employ rotating masses whose physical inertia is important for maintaining the frequency of the system.

[0012] In practice, if a power-generating device ceases to function, the resulting frequency drop is delayed by the inertia of the rotating masses. This is important because it generally takes a few seconds before the system's equilibrium can be restored by deploying the necessary additional power reserves.

[0013] Thus, without compensation measures, the substitution in an electrical system of electricity supply devices with turbo-alternator or other rotating machine by devices interfaced to the network by an inverter or more generally by a power electronics device leads to a decrease in the inertia of the system.

[0014] Power supply devices interfaced to the network by power electronics devices are aimed in particular at: solar power plants, certain wind power plants, battery energy storage devices (generally called BESS for "Battery Energy Storage System"), and fuel cells.

[0015] As the load on the electrical system varies constantly, the system frequency fluctuates; however, the system's inertia limits the rate of frequency change, called RoCoF. Therefore, a decrease in inertia (or the inertia constant) results in an increase in the rate of frequency change, which, beyond a given limit for a system, can threaten the system's safety.

[0016] Rotating machine electricity supply devices correspond in particular to hydroelectric power plants, steam power plants, including coal-fired power plants and nuclear power plants, and gas, fuel oil (or other petroleum derivative) power plants.

[0017] Regarding short-circuit current, the capacity of a synchronous machine to The ability to withstand voltage and inject a short-circuit current is inversely proportional to its subtransient reactance.

[0018] In an electrical system, variations in reactive power demand must be compensated by the reactive power supplied by the electricity generators.

[0019] Also, while replacing rotating machine power generation devices with power electronic devices in an electrical system does not compromise voltage withstand, it does impact the system's ability to inject short-circuit current. In the event of a disturbance in the electrical system, a reduced ability to inject short-circuit current results in deeper voltage dips and a greater influence of these voltage dips on the operation of generators and loads connected to the grid. Short-circuit power also enables the proper functioning of the system's protection relays and thus contributes to the system's electrical protection scheme.

[0020] In summary, increasing the proportion of electrical power sources connected to the grid by a power electronics device leads to an overall decrease in inertia and reduces short-circuit current injection capabilities. The decrease in inertia and short-circuit current injection capacity means that an incident may have worse consequences (e.g., disconnection of more loads, frequency collapse, or even a large-scale power outage commonly referred to as a "blackout") than if the incident had occurred in a system with greater inertia and a greater short-circuit current injection capacity.

[0021] Furthermore, the risk is all the greater when the system is of moderate size, since an electrical system of moderate size has by nature limited inertia.

[0022] Various measures have been considered to address this problem.

[0023] Technologies are progressing rapidly in the field of power electronics, so that fast inverter control can allow for relatively quick adaptation to system load conditions, or even disturbances. Some work also aims to generate "virtual" inertia, as described, for example, in documents CN109586343, CN112018813, and CN110518626. The term "virtual inertia" (also called synthetic inertia) is used to refer to power injections into the system, for example from a set of batteries, carried out under the control of power electronics to emulate the inertia of a synchronous machine or any rotating machine.

[0024] However, these devices are controlled, which by nature implies the existence of a processing time for their control, so that their reaction is not instantaneous. Thus, these solutions are currently insufficient to react to certain situations, and, from the point of view of network managers, it is not possible to guarantee the sufficiency and effectiveness of this type of control.

[0025] In the context described above of the increase in renewable energy sources, it is also possible to add a synchronous compensator, or more generally a centralized device that forms a kinetic energy storage system and is connected to the grid. Document WO2020 / 043306 proposes such a solution.

[0026] However, these solutions are imperfect, particularly for network operators. Specifically, for the operator of a medium-sized electricity network, such as an island network, implementing such a device on their system requires a significant investment, which must be anticipated and planned according to the evolution of the system's energy mix. Furthermore, in the event of a failure or shutdown for maintenance of the synchronous compensator, the system's stability is threatened.

[0027] Based on the idea of ​​storing kinetic energy, EP2696464 discloses a photovoltaic power plant that allows the injection of harmonic- and subharmonic-free current into an electrical system. According to this document, an inverter converts the electricity supplied by a photovoltaic array. An electrical machine comprising a motor and a synchronous generator is driven, which can mitigate power fluctuations in the photovoltaic modules caused, for example, by passing clouds. In summary, this document proposes a device for storing kinetic energy in order to smooth the supply of electricity to the system over time, over periods of a few minutes. However, this document does not directly address the issue of system inertia and the short-circuit current that may be injected into the grid.

[0028] The invention thus aims to provide a solution to all or part of the aforementioned problems. More particularly, it aims to provide an attractive, reliable and demonstrable solution for network operators to the problems of electrical network stability, for example island networks or other medium-sized electrical networks, which are linked to the increasing share of energy sources interfaced to the network by power electronics.

[0029] The invention thus relates to an electricity supply device comprising: - a source of electrical energy, - an electrical machine comprising an electric motor and a generator, the electrical machine being configured so that the electric motor is adapted to drive the generator in rotation, - a power supply system enabling the electric motor of the electric machine to be powered by the electrical energy source, and - an interface suitable for connecting the generator to an electrical network or to the de- connect to this network.

[0030] The electric machine exhibits, in operation, a maximum kinetic energy and power, when driven by the electrical energy source, such that said electricity supply device has a constant of inertia of between 2 seconds and 6 seconds, preferably on the order of 4 seconds.

[0031] The invention thus proposes, in a single electricity supply device comprising a single interface for connection to an electrical network, a source of electrical energy and a contribution of inertia and short-circuit current capacity, whereas the energy source is of a technology which generally does not contribute (or only a little) inertia and short-circuit current to the electrical system.

[0032] The configuration and dimensioning of the electricity supply device makes it possible in particular to create an electricity supply device (power plant and / or battery storage device) which, although connected to the electrical network by a power electronics device, reproduces the characteristics of inertia and capacity to supply a short-circuit current of an equivalent turbo-generator power plant in terms of power.

[0033] Throughout this document, the expression "of the order of X" or "approximately X" corresponds to the value X plus or minus 20%.

[0034] More specifically, with an inertia constant on the order of 4 s, the addition of a power supply device according to the invention does not result in a substantial change in the inertia constant of the electrical system, even in a moderately sized system such as an island system. Similarly, the ability of the power supply device according to the invention to inject short-circuit current into the system is analogous to that of a conventional power plant, insofar as the current fed into the grid is generated by a generator, just as in a conventional power plant.

[0035] From the perspective of a network operator, the device proposed in the invention allows for simplified management, in that it enables the addition of a power supply device to their system, or the replacement of an existing rotating-machine power plant with a power electronics device (solar, wind, etc.) without risk of impacting system stability. The solution offered to the network operator is complete, simple, and turnkey.

[0036] Moreover, by the very configuration of the device proposed in the invention, the network manager has the certainty that the electricity supply device helps to bring inertia to the system, unlike in particular devices offering virtual inertia, whose supply could be deactivated invisibly to the manager.

[0037] The electric machine may include a flywheel linked to a rotor.

[0038] Compared to devices combining an electric motor and a generator known in the prior art, the addition of a flywheel, or "flywheel motor", makes it possible to obtain the desired inertia, and therefore the desired inertia constant for the electricity supply device.

[0039] The electric motor and the generator may have a common rotor. The electric motor and the generator may have interlaced stators.

[0040] A common rotor configuration in which the motor stator and the generator stator are intertwined allows for a reduction in size and, consequently, an increase in efficiency compared to a more conventional device in which a motor is coupled to a generator. Efficiency is fundamental to the present invention, since interposing a motor-generator assembly in series between an electrical power source and the network to be supplied certainly guarantees the desired inertia, but necessarily entails losses, which must be limited as much as possible.

[0041] The electrical energy source(s) of the electricity supply device may thus comprise one or more of the following source elements: - a set of photovoltaic panels; - one or more wind turbines; - a BESS; - a fuel cell.

[0042] These are the main sources of electrical energy connected to the networks by a power electronics device, in particular by an inverter or a set of inverters.

[0043] The electrical power source may include a bus, and each power source element of the power supply device may be connected to the bus via a converter. This may be a DC bus or an AC bus. This configuration allows for the connection of several electrical power source elements, each supplying a direct or alternating current of appropriate voltage, and / or the connection of a battery bank to a power plant whose output varies according to environmental conditions (for example, a photovoltaic or wind power plant), in order to smooth the power supply to the electrical system over time.

[0044] Thus, the electricity supply device may include a set of photovoltaic panels and / or one or more wind turbines, the electricity supply device also including an electrical energy storage device connected to the bus.

[0045] Depending on the bus used, and in particular whether it is a DC bus or an AC bus, the source elements are connected to the bus by a suitable converter, namely in particular a suitable transformer or inverter.

[0046] The electric current supplied to the bus by the converters associated with the electrical power source elements can be configured to drive the electric motor of the electric machine, particularly with regard to the current frequency if the bus is an AC bus. Alternatively, the power supply device for the electric machine includes an electrical converter for supplying the electric motor of the electric machine, said converter being adapted to shape the current from the electrical power source according to the desired current characteristics for supplying said electric motor.

[0047] The electric motor of the electric machine is advantageously a synchronous motor. Therefore, the electric machine includes an asynchronous starting motor, adapted to rotate the electric machine from zero rotational speed to a given rotational speed suitable for connecting said electric machine to the electrical network.

[0048] This makes it possible to limit the intensity of the current in the electrical machine during its start-up.

[0049] The electricity supply device may, for example, have a net power output between 180kW and 17MW.

[0050] In the electricity supply device, the electric machine may have a moment of inertia, for example, between 100 kg.m2 and 300 kg.m2, for example on the order of 160 kg.m2 when the inertial device is synchronized with the network.

[0051] The invention also relates to a method for configuring an electricity supply device as described above, comprising the steps of: - determination of the net power of the electricity supply device; - determination of the frequency of the electrical network to which the electricity supply device is intended to be connected; - determination of the kinetic energy that the electrical machine must exhibit so that the electricity supply device has a predefined inertia constant, between 2 seconds and 6 seconds, and preferably on the order of 4 seconds; - determination of the total rotating mass of the electric machine required to obtain the determined kinetic energy, and determination of the mass of a flywheel to be coupled to the electric machine.

[0052] It is thus possible to configure the device proposed in the invention according to the desired target value of inertia constant, and to guarantee to the network manager that the electricity supply device will meet the desired inertia criteria, so that its addition to the system will have totally predictable consequences on the stability of the system (for example, an absence of impact).

[0053] Thus, a network operator can specify a desired minimum inertia constant (for example, 4 seconds) and the proposed device makes it possible to meet this requirement. this specification.

[0054] This greatly simplifies the management of an electrical system, in particular a medium-sized or large system, such as an island system.

[0055] Other features and advantages of the invention will become apparent in the following description.

[0056] To the attached drawings, given by way of non-limiting examples: [Fig.1] represents, according to a schematic diagram, a device conforming to one embodiment of the invention;

[0057] [Fig.2] represents, according to a schematic diagram, a device conforming to another embodiment of the invention;

[0058] Fig. 1 represents, according to a schematic diagram, an electricity supply device conforming to an embodiment of the invention.

[0059] The electricity supply device includes an electrical energy source 1. The electrical energy source may include an electrical energy production means such as a set of photovoltaic panels 2, one or more wind turbines, one or more fuel cells, and / or an energy storage means such as a battery energy storage device (BESS) or a battery 3 adapted to smooth the electricity supply of the aforementioned production means.

[0060] The means of producing electrical energy and the means of storing energy from the electrical energy source are hereinafter referred to as "source elements".

[0061] In the example embodiment shown in [Fig.1], the electrical energy source 1 comprises a set of photovoltaic panels 2 (or "photovoltaic field") and a set of batteries 3 adapted to charge when the electricity production of the photovoltaic field is greater than the contribution required by the system, and to supply electricity to the system when the contribution required is greater than the current production of the photovoltaic panels 3.

[0062] The photovoltaic panel array 2 and the battery array are connected to a direct current bus 4 (referred to as the "DC bus") via a suitable converter 5. The converter 5 is defined here as any device adapted to transform the current supplied by the source element to which it is connected into a direct current at the desired voltage on the DC bus 4. The converter 5 can thus be, in particular, a DC / DC transformer or an AC / DC converter (rectifier), for example, when the source element is a wind turbine. In the example of [Fig. 1], the solar panel array can advantageously be connected to the bus 4 by an MPPT (Maximum Power Point Tracking) controller 5, which regularly checks the electrical voltage produced by the photovoltaic panel array to determine and apply the maximum current output point, i.e., the operating point that maximizes the output power.

[0063] The DC bus 4 supplies power to the electric machine 6. According to the embodiment shown, the electric machine 6 comprises a synchronous electric motor 7 and a generator 8. The synchronous electric motor 7 requires an alternating current supply. An inverter 9 is therefore positioned between the bus 4 and the electric machine in order to convert the current from the bus 4 to supply power to the electric motor 7.

[0064] As regards the electric machine 6, an example of which is illustrated in [Fig.3], it generally comprises an electric motor 7 powered by the electrical energy source, this electric motor being configured to drive the generator 8 in rotation. The generator 8 is adapted to supply a current conforming in voltage and frequency to the specifications of the electrical system 10 intended to be supplied by the electricity supply device (for example 230V at 50hZ).

[0065] The electric machine must have a rotating mass sized to provide the desired kinetic energy during operation, in order to impart to the power supply device the desired inertia and inertia constant. The rotating mass consists of the rotor of the electric motor 71, the rotor of the generator 81, and, if necessary, a flywheel 12, formed in one or more parts, which is connected to a shaft of the generator rotor and / or to the shaft of the electric motor rotor. The rotating mass is determined to provide an inertia equivalent to that of a conventional power plant generator of similar power. Thus, it can be determined so that the inertia constant of the power supply device is on the order of 4 seconds.

[0066] According to alternative embodiments of the invention, the motor and the generator may be separate machines, coupled to each other permanently or not, for example at the flywheel 12. Alternatively, the rotor of the electric motor 71 and the rotor of the generator 81 may be common, formed as a single unit. In this case, the stator of the electric motor and the stator of the generator may advantageously have an interlaced configuration, that is to say, having interleaved windings of conductors.

[0067] In order to allow the gradual start-up of the electric machine, it also includes an asynchronous starting motor adapted to start the synchronous motor and the generator up to a rotation speed corresponding to a desired frequency.

[0068] In practice, the electric machine is initially (before the power supply device is put into operation) disconnected from the electrical power source by an input contactor 13. The asynchronous starting motor starts and gradually rotates the electric machine 6. The starting motor can be powered by the electrical power source and / or by electricity from the electrical grid 10 (provided the electricity is adapted and regulated to the characteristics of the starting motor). The assembly can, for example, be started until the rotational speed corresponds to 49.5 Hz for a nominal frequency of the electrical grid 10 of 50 Hz. The excitation of the electric machine is then initiated, and the motor voltage increases to reach a nominal value, for example, 400 V.

[0069] When the voltage on the inverter side 9 is synchronous with the voltage of the motor 7, the input contactor 13 of the electric machine 6 closes, so that the synchronous motor operates at 50 Hz. Finally, the power supply to the starting motor is switched off.

[0070] The excitation of the electric machine can be common to the motor 7 and the generator 8. More specifically, the stator voltage of the electric machine is advantageously controlled by a voltage regulator 14, for example an automatic voltage regulator often designated by the acronym "AVR" for "Automated Voltage Regulator". This voltage regulator 14 can be located only at the generator 8.

[0071] Finally, the power supply device includes a connection interface 11, which allows the power supply device to be connected to or isolated from an electrical network 10. The connection interface 11 can thus adopt either a state of connection to the electrical network 10 or a state of disconnection from the electrical network 10. When the starting steps of the electric machine 6 have been carried out, the connection interface 11 is brought to the closed position, so that the generator is coupled to the electrical network 10 and supplies it with electricity, while the electric machine contributes its inertia and its ability to inject short-circuit current to the system.

[0072] Figure 2 represents, according to a schematic diagram, an electricity supply device according to another embodiment of the invention.

[0073] The device of [Fig.2] is essentially identical to that of [Fig.1], and one may therefore refer to the description of [Fig.1] given above, except for the differences explained below.

[0074] Just like the device in [Fig.1], the electricity supply device in [Fig.2] comprises a set of photovoltaic panels 2 and a battery 3.

[0075] The photovoltaic panel assembly 2 and the battery assembly are connected to an alternating current bus 4' (called "AC bus" from the English "alternating current"), via a suitable converter, namely a first inverter 5' which interfaces the photovoltaic panel assembly 2 to the AC bus 4' and a second inverter 5" which interfaces the battery 3 to the AC bus 4'.

[0076] The first 5' inverter and the second 5" inverter can be configured so as to supply bus 4' with electricity having characteristics (voltage and frequency) compatible with the power supply for the electric motor 7 of the electric machine 6. If this is not the case,

[0077] If this is not the case, a suitable converter 15 may be provided between the AC4' bus and the electrical network 10.

[0078] An example of an electrical network in which the invention is particularly advantageous is shown in [Fig.4].

[0079] The electric machine 6 constitutes an important element of the electricity supply device according to the invention.

[0080] Fig. 3 represents, according to a schematic three-dimensional view, an electrical machine 6 that can be used in an embodiment of the invention.

[0081] The electric machine 6 is of the motor-generator type and therefore comprises a synchronous electric motor 7 and a generator 8. These two functions are compactly integrated within the electric machine 6, which has a common rotor 61, arranged on a single shaft, for both functions. The stators, namely the stator of the motor 72 and the stator of the generator 82, are wound and interlaced.

[0082] The electric machine includes a flywheel 12, in the form of a mass attached to the common shaft, this mass being in the form of a single flying element or of several attached masses jointly having the function of a flywheel.

[0083] A rotating mass is thus constituted consisting of the common rotor 61 and the flywheel.

[0084] This rotating mass is determined so as to provide the inertia equivalent to the inertia of a conventional power plant generator of similar power, typically on the order of 4 seconds.

[0085] In the example of [Fig.3], the electric machine 6 has a general horizontal arrangement (rotor substantially horizontal in operation), but other arrangements, including a vertical configuration, are conceivable.

[0086] For example, for an electricity supply device capable of providing 500 kW of active power, the rotating mass is adapted to obtain a moment of inertia of 162 kg.m2.

[0087] The electric machine 6 also includes an asynchronous starting motor 16 adapted to start the synchronous motor and the generator up to a rotational speed corresponding to a desired frequency.

[0088] Fig. 4 schematically represents an island electrical network comprising devices conforming to the object of the present invention.

[0089] The island whose electrical network is considered to be of a greater or lesser size dimension. For example, [Fig. 4] represents the island of Réunion, which has an area of ​​approximately 2,500 km² and a population of approximately 850,000. The invention is nevertheless applicable to any electrical system, particularly one smaller than that of [Fig. 4]. The invention is indeed of particular interest when applied to island electrical systems, or more generally to electrical systems that are not interfaced with large continental systems.

[0090] The island shown in [Fig. 4] has an electricity transmission network comprising high-voltage power transmission lines. It should be noted, however, that the device of the present invention can be adapted to interface with a low-voltage (LV) or high-voltage (HV) line of the network.

[0091] On the map in [Fig. 4], hydroelectric (H) and thermal (C) power plants are shown, whether they are coal-fired, gas-fired, or fuel-fired, such as bagasse. These types of power plants, which include a rotating machine generator (turbine or motor), naturally have significant inertia and the capacity to inject short-circuit current into the system. Solar (S) and wind (E) power plants are also shown. These types of power plants, which are connected to the grid by a power electronics device, naturally have low, or even negligible, inertia and little or no capacity to inject short-circuit current.

[0092] On such an island system, energy sources have diversified over time. Once hydroelectric resources were exhausted, the trend shifted towards the development of solar and wind power plants, either to increase the system's electricity generation capacity or to replace some thermal power plants. However, the inertia of each power plant contributes to the overall inertia of the system. Consequently, adding power supply devices with power electronic interfaces impacts the system's inertia (the total power increases while the total kinetic energy of the power supply devices remains unchanged). Replacing a turbine-generator power plant with one (or more) power plant(s) with power electronic devices further impacts the system's inertia (the power remains unchanged while the kinetic energy decreases).

[0093] Let us consider that maintaining a constant of inertia of 4 seconds is desired.

[0094] This value is consistent with the order of magnitude observed in conventional thermal power plants. For example, a power plant may include a turbo-alternator unit of 48MW gross or 44MW net (maximum power Pmax), with a kinetic energy Ec at the nominal speed of the turbo-alternator of 174 MW.s.

[0095] This thermal power plant (C) thus has an inertia constant H of the order of 4 seconds.

[0096] Indeed, H = Ec / Pmax = 174 / 44 ~ 4 seconds.

[0097] If the manager wishes to add a solar power plant (S), this addition may impact the inertia constant of the system, and affect its stability.

[0098] This situation required network operators to assess whether the modification of the inertia and available short-circuit current was permissible and to address it independently of the contract related to the installation and operation of the new solar power plant(s). For example, when the situation no longer allowed for the guarantee of system stability, a synchronous compensator could be installed to provide inertia to the system, to compensate for the loss of inertia, and in anticipation of future system changes.

[0099] The present invention offers a more satisfactory solution for network operators. In particular, it makes it possible to maintain a substantially stable system inertia constant while the share of renewable energy in the system increases. System stability is thus guaranteed during this transitional period towards the use of more renewable energy, and beyond.

[0100] The present invention makes it possible to propose to the network manager the installation of a power plant based on sources of electrical energy which by nature are generally linked to the network by a power electronics device (for example a solar power plant), without affecting the inertia and short-circuit current properties of the system.

[0101] For this purpose, an electrical machine comprising a motor and a generator is interfaced between the electrical energy source and the network, or, more precisely, an electrical machine is interposed between the power electronics device(s) associated with the source elements and the electrical network.

[0102] By adopting appropriate technologies and sizing of the electrical machine, it is possible to guarantee the electricity supply device a constant of inertia similar to that generally desired in the electrical system, for example of the order of 4s, so that the addition of the electricity supply device to the system has no impact on its stability.

[0103] It is noteworthy that the invention does not involve storing large quantities of kinetic energy to compensate for production drops lasting several minutes, such as those caused by clouds passing over a field of photovoltaic panels (this function can be performed by adding a set of batteries to the electrical power supply of the electricity generation device). The sizing of the rotating mass, and in particular the flywheel of the electric machine, is determined with the sole objective of providing the desired inertia constant. This results in very little energy loss.

[0104] The proposed solution is based on a mechanical device (as opposed to power electronic devices), which can, where appropriate, provide inertia (virtual), it exhibits no reaction time. By providing inertia and the capacity to inject short-circuit current into the system, similar to that of a generator-type power plant, the invention offers a simple, complete, and effective solution. This solution, whose efficiency can be demonstrated by the very implementation of a rotating mass, is a turnkey solution for network operators to add a power plant or to replace a power electronics device with a power plant, thereby replacing a rotary-machine generator-type power plant (such as a turbo-generator), without risk to system stability. In particular, it allows for the provision of additional electricity to the system without degrading its overall inertia constant.

Claims

Claims

1. Electricity supply device comprising: - an electrical energy source (1), - an electrical machine (6) comprising an electric motor (7) and a generator (8), the electrical machine (6) being configured so that the electric motor (7) is adapted to drive the generator (8) in rotation, - a power supply device allowing the electric motor (7) of the electric machine (6) to be powered by the electrical energy source (1), - an interface adapted to connect the generator (8) to an electrical network (10) or to disconnect it from this electrical network (10), characterized in that the electric motor (7) and the generator (8) comprise a common rotor and the electric motor (7) and the generator (8) comprise interlaced stators, and in that the electric machine (6) has, in operation, a kinetic energy and a maximum power, when it is driven by the electrical energy source,such that said electricity supply device has an inertia constant of between 2 seconds and 6 seconds, preferably of the order of 4 seconds.,

2. An electricity supply device according to claim 1, wherein the electrical machine (6) comprises a flywheel linked to a rotor.

3. Electricity supply device according to one of the preceding claims, in which the electrical energy source (1) comprises one or more of the following source elements: - a set of photovoltaic panels (2); - one or more wind turbines; - a BESS; - a fuel cell.

4. An electricity supply device according to claim 3, wherein the electrical energy source comprises a bus (4, 4'), and, for each of the source elements of the electricity supply device, a suitable electrical converter connecting the source element to said bus.

5. An electricity supply device according to claim 4, comprising a set of photovoltaic panels (2) and / or one or more wind turbines, the electricity supply device comprising furthermore an electrical energy storage device connected to the bus (4.4').

6. Electricity supply device according to one of the preceding claims, in which the power supply device comprises an electrical converter for supplying the electric motor (7) of the electric machine (6), said converter being adapted to conform the current from the electrical energy source according to the desired current characteristics for supplying said electric motor (7).

7. An electricity supply device according to one of the preceding claims, wherein the electric motor (7) of the electric machine (6) is a synchronous motor.

8. An electricity supply device according to claim 7, wherein the electrical machine (6) comprises an asynchronous starting motor, adapted to set the electrical machine (6) rotating from a zero rotation speed to a given rotation speed adapted to the connection of said electrical machine (6) to the electrical network (10).

9. An electricity supply device according to one of the preceding claims, said electricity supply device having a net power of between 180kW and 17MW.

10. Electricity supply device according to one of the preceding claims, in which the electrical machine (6) has a moment of inertia of between 100 kg.m2 and 300 kg.m2, for example of the order of 160 kg.m2, when it is synchronized with the electrical network (10).

11. Method for configuring an electricity supply device according to one of claims 1 to 10, comprising the steps of: - determining the net power of the electricity supply device; - determining the frequency of the electrical network (10) to which the electricity supply device is intended to be connected; - determining the kinetic energy that the electrical machine (6) must have so that the electricity supply device has a predefined inertia constant, between 2 seconds and 6 seconds, and preferably of the order of 4 seconds; - determining the total rotating mass of the electrical machine (6) required to obtain the determined kinetic energy, and determining the mass of a flywheel (12) to be coupled to the electrical machine (6).

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