DE102023202769A1 - Rotating phase shifter with variable ratio - Google Patents

Abstract

An intermediate storage device for temporarily storing energy of an energy network (40), comprising: an asynchronous machine (10) which is designed to draw electrical power from the energy network in a first operating mode of the asynchronous machine and to feed electrical power into the energy network in a second operating mode of the asynchronous machine; and a flywheel (12) which is operatively connected to the asynchronous machine.

Description

The present invention relates to a buffer device for temporarily storing energy of an energy network, a system with the buffer device and a method for operating the buffer device.

In particular, the elimination of thermal or calorific power plants means that the energy grids no longer have any instantaneous reserve.

In order to improve the stability of energy networks, phase shifters are known which can be supplemented by an additional flywheel so that the phase shifter can, due to its inertia, not only extract or feed in reactive power but also active power and thus improve the network stability.

The object of the present invention is to improve the operation of an energy network.

This object is achieved by an intermediate storage device for intermediate storage of energy in an energy network with the features of claim 1. Claims 10, 11 protect a system with an intermediate storage device described here or a method for operating an intermediate storage device described here. The subclaims relate to advantageous further developments.

According to one embodiment of the present invention, a system comprises an energy network and an intermediate storage device which intermediately stores energy of the energy network or is configured or used for this purpose. In the present disclosure, "has an X" generally does not imply an exhaustive list, but is a short form of "has at least one X" and also includes "has two or more Xs" and "has Y in addition to X".

In one embodiment, the energy network is an electrical energy or power network; in a further development, it has a transmission network or electrical energy or power network of network level 1 and/or a supra-regional distribution network or electrical energy or power network of network level 2 and/or 3 and/or a regional distribution network or industrial network or electrical energy or power network of network level 4 and/or 5 and/or a local distribution network or electrical energy or power network of network level 6 and/or 7; in one embodiment, it has one or more decentralized and/or regenerative generation systems or energy sources, in particular photovoltaic system(s) and/or wind turbine(s) or the like. The present invention is particularly suitable for such energy networks, in particular network levels 3-7, due to the associated boundary conditions, in particular network voltages and/or frequency (fluctuations).

According to an embodiment of the present invention, a buffer device for temporarily storing energy of a power grid comprises an electrical asynchronous machine which, preferably temporarily, in a first operating mode of the asynchronous machine, draws electrical power, preferably reactive power and/or active power, from this power grid and, preferably temporarily, in particular alternatively to or alternating with this first operating mode, in a second operating mode of the asynchronous machine, feeds electrical power, preferably reactive power and/or active power, into this power grid or is configured or used for this purpose.

In one embodiment, the asynchronous machine is a rotating electrical machine in which a rotor or runner runs asynchronously with the rotating field of a stator or stand, and/or the asynchronous machine is a three-phase machine or a three-phase asynchronous machine (“three-phase induction machine”). In one embodiment, the asynchronous machine is a squirrel-cage asynchronous machine or is designed as such, or a slip-ring asynchronous machine, in particular not a double-fed asynchronous machine, or is designed as such. In one embodiment, the asynchronous machine is not a double-fed asynchronous machine.

By using an asynchronous machine, in particular a three-phase asynchronous machine, in one embodiment a particularly robust and low-maintenance buffer device can be provided, in particular compared to three-phase machines that are not asynchronous machines or compared to doubly fed asynchronous machines. In one embodiment this makes it possible to provide in particular a buffer device that is simply constructed and/or, at least substantially, does not require any control effort, in particular compared to three-phase machines that are not asynchronous machines or compared to doubly fed asynchronous machines. Furthermore, in one embodiment the acquisition of a buffer device described herein is associated with minimal acquisition costs, in particular compared to buffer devices that have three-phase machines that are designed as synchronous machines or as doubly fed asynchronous machines.

According to one embodiment of the present invention, the intermediate storage device has a flywheel, in particular a rotatably mounted flywheel, in a further development with a vertical or horizontal axis of rotation, wherein the asynchronous machine and the flywheel are mechanically operatively connected to one another, in a further development permanently, in particular clutch-free or clutch-less, or temporarily, in particular via one or more clutches (with closed or closed clutch(es)), are rotationally fixedly coupled or which is set up or used for this purpose, so that in one embodiment the asynchronous machine in the first operating mode increases a kinetic energy of the flywheel, in particular increases its speed (in terms of amount), by, in particular by means of, drawing electrical power, preferably active power, from the energy network, and in the second operating mode can feed electrical power, preferably active power, into the energy network, in particular at least temporarily, by reducing, in particular using, kinetic energy of the flywheel.

By using an intermediate storage device that has an asynchronous machine, in one embodiment a phase shifter or an instantaneous reserve or preferably controllable short-circuit power or a control power that is preferably available at short notice can be realized or provided in a particularly advantageous manner. Additionally or alternatively, in one embodiment the use of an asynchronous machine, in particular a three-phase asynchronous machine, can improve the control, in particular make it simpler and/or more reliable, and/or improve the efficiency and/or exert a positive, in particular stabilizing, effect on the energy network, in particular dampen or reduce fluctuations in the network frequency, in particular compared to a synchronous machine or a doubly fed asynchronous machine. Furthermore, in one embodiment this can enable a longer active power feed, in particular compared to a synchronous machine. Advantageously, in one embodiment a high or higher damping, in particular compared to an intermediate storage device with a synchronous machine, can be enabled and in particular thus a positive influence on the system stability.

Advantageously, in one embodiment, a flywheel's flywheel mass can be larger, in particular compared to an intermediate storage device that has a synchronous machine or a doubly fed asynchronous machine, in particular by more than a factor of 5 or more than a factor of 10 or a factor of 10 larger. In particular, in one embodiment, this advantageously enables an extended and/or decaying active power consumption from the grid to be realized. Such "oversizing" of the flywheel mass would not be possible with a synchronous machine.

In one embodiment, the asynchronous machine and the flywheel are operatively connected with a transmission ratio, in particular by means of a gearbox.

In particular, for this purpose, according to an embodiment of the present invention, a transmission ratio i of the transmission is adjusted or is adjustable, which is equal to a quotient |n _FW |/|n _SM | of an amount of a rotational speed n _FW of a flywheel-side first coupling element (of the transmission), which is mechanically connected to the flywheel, in a further development without a clutch or via at least one clutch, divided by an amount of a rotational speed n _SM of an asynchronous machine-side second coupling element (of the transmission), which is mechanically connected to the asynchronous machine, in a further development without a clutch or via at least one clutch (i = |n _FW |/|n _SM |).

In one embodiment, the first and/or the second coupling member has at least one shaft or can be at least one shaft.

In one embodiment, the first operating mode is an engine operating mode and/or the second operating mode is a generator operating mode.

In one embodiment, this makes it possible to use the advantages of an asynchronous machine, in particular a three-phase asynchronous machine compared to a synchronous machine, and at the same time to extract energy variably or specifically from the energy network or to feed it back into it and thus particularly advantageously regulate its network frequency. In one embodiment, this makes it possible to realize or provide instantaneous reserve, short-circuit power or, in particular, control power that is available at short notice.

In one embodiment, the intermediate storage device - in particular in addition to the asynchronous machine - has a starter drive that starts the flywheel or accelerates it, in particular from a standstill, or increases a speed of the flywheel, in one embodiment from zero, (in terms of amount) or is set up or used for this purpose. In a further development, the starter drive has an electric motor, particularly preferably with a VFD ("Variable Frequency Drive") control or a frequency converter, and/or is arranged on a side of the flywheel facing away from the asynchronous machine and/o which is connected to the flywheel clutchlessly or permanently or via a clutch.

In one embodiment, this allows the intermediate storage device to be put into operation in a particularly advantageous manner and/or a disruption to the energy network (as a result) to be reduced or avoided. In one embodiment, the structure can be simplified by a starter drive connected to the flywheel without a clutch, and in one embodiment, the efficiency can be improved by a clutch between the flywheel and the starter drive. In one embodiment, a particularly compact and/or maintenance-friendly structure can be achieved by arranging it on a side of the flywheel facing away from the asynchronous machine.

In one embodiment, the intermediate storage device has a fluid supply device that supplies the asynchronous machine and/or the flywheel with fluid, in a further development coolant and/or lubricant, in one embodiment oil, in particular (for this purpose) supplies and/or removes fluid, or is set up or used for this purpose. In a further development, the fluid supply device has a, preferably controlled, pump and/or a control valve.

In one embodiment, the intermediate storage device has a control device that controls and/or monitors the asynchronous machine and/or the flywheel and/or the fluid supply device, in particular its at least one pump and/or control valve, or is set up or used for this purpose. Controlling is also understood here to mean regulating. In a further development, the control device communicates with the asynchronous machine, the flywheel and/or the fluid supply device, in particular with one or more sensors for detecting a state, in one embodiment with a rotational speed and/or temperature, of the asynchronous machine, the flywheel and/or the fluid supply device, in particular with its at least one pump and/or fluid delivered by the fluid supply device, and/or with one or more actuators or control elements. As a result, in one embodiment, the energy extraction or feed-in or provision of instantaneous reserve, short-circuit power or control power or regulation of the grid frequency can be carried out particularly precisely and/or adapted to the situation.

In one embodiment, the control device has a programmable logic controller and/or a transmitting/receiving device via which the control device communicates, preferably wirelessly or wired, with a remote control and/or monitoring device or which is set up or used for this purpose. As a result, in one embodiment, the energy extraction or feed-in or provision of instantaneous reserve, short-circuit power or control power or regulation of the grid frequency can be carried out particularly advantageously, in particular quickly, precisely, adapted to the situation and/or, in particular centrally, coordinated with the energy grid.

According to one embodiment of the present invention, the buffer device is configured, in particular in terms of hardware and/or software, in particular in terms of control or programming, to carry out a method described here.

In one embodiment, the asynchronous machine of the intermediate storage device is connected to the energy network via at least one interruption device and/or one or more transformer devices of the system. This allows the intermediate storage device to interact with the energy network in a particularly advantageous, particularly efficient and/or safe manner.

According to one embodiment of the present invention, in or according to a method for operating an intermediate storage device described here, in particular a system described here, the asynchronous machine is operated at least temporarily to extract electrical power, preferably active power, from the energy network in the first operating mode and at least temporarily to feed electrical power, preferably active power, into the energy network in the second operating mode.

In one embodiment, the system has an additional reactive power control, in particular by means of an (additional) converter-based device that is set up or used for reactive power control, in particular a static VAR compensator (SVC). In one embodiment, the converter-based device is connected in parallel to the asynchronous machine, in particular at the same network point, or is included in the buffer device and is set up or used in particular for reactive power control.

In one embodiment, this advantageously makes it possible for the intermediate storage device to be used for reactive power control, in particular compared to synchronous machines and/or a doubly fed asynchronous machine, it is also designed or can be designed or used for reactive power control.

In one embodiment, the kinetic energy, in particular the speed, of the flywheel is increased by appropriately extracting power from the energy network. The resulting increase in the load torque of the asynchronous machine advantageously leads to an active power flow from the energy network to the flywheel. This active power flow has a frequency-reducing effect on the energy network. By adjusting the power extraction from the energy network, in one embodiment the frequency-reducing effect is advantageously controlled or the speed of the flywheel is specified or set depending on a desired frequency-reducing effect on the energy network.

Additionally or alternatively, in one embodiment, the kinetic energy, in particular the speed, of the flywheel is reduced by feeding power or power output into the energy network. In one embodiment, this may reverse the load torque of the asynchronous machine and (then) has a driving effect, which advantageously leads to an active power flow from the flywheel via the asynchronous machine to the energy network. This active power flow has a frequency-raising effect on the energy network. By adjusting the power output, in one embodiment, the frequency-raising effect is advantageously controlled or the speed of the flywheel is specified or set depending on a desired frequency-raising effect on the energy network.

In one embodiment, one or more, in particular all, steps of the method are fully or partially computer-implemented or one or more, in particular all, steps of the method are fully or partially automated, in particular by the system, in particular its control device and/or on the basis of communication with a remote control and/or monitoring via the transmitting/receiving device.

In one embodiment, a power range of the asynchronous machine and/or the gearbox is at least 5 MW and/or at most 80 MW, or the asynchronous machine and/or the gearbox is/are designed in one embodiment for a maximum or nominal power of at least 5 MW and/or at most 80 MW. Additionally or alternatively, in one embodiment, a speed, in particular a nominal speed, of the flywheel is at least temporarily at least 500 rpm, preferably at least 750 rpm, and/or at most 5000 rpm, preferably at most 3600 rpm, or the flywheel is designed in one embodiment for a (nominal) speed of at least 500 rpm, preferably at least 750 rpm, and/or at most 5000 rpm, preferably at most 3600 rpm. Additionally or alternatively, in one embodiment, a grid frequency of the energy network is 50 or 60 Hz, or the asynchronous machine is designed in one embodiment for a grid frequency of the energy network of 50 or 60 Hz. Additionally or alternatively, in one embodiment, a voltage, in particular a nominal voltage, of the asynchronous machine is at least 1 kV and/or at most 25 kV, preferably at most 15 kV, or the asynchronous machine is designed in one embodiment for a (nominal) voltage of at least 1 kV and/or at most 25 kV, preferably at most 15 kV.

The present invention is particularly advantageous for such areas, in particular here the advantages over, in particular, known asynchronous machines with coupled flywheels are particularly significant.

In one embodiment, the asynchronous machine is connected to the power grid without a frequency converter or not via a frequency converter. In one embodiment, this reduces the effort and allows energy to be temporarily stored in a particularly advantageous manner, particularly in a situation-adapted and/or efficient manner, using the asynchronous machine, in particular via the coupled flywheel.

In one design, the asynchronous machine is not a double-fed asynchronous machine, but a single-phase operated or operable asynchronous machine.

In one embodiment, the buffer device is configured to carry out a method described herein.

In one embodiment, the system has no gearbox, in particular no gearbox between the asynchronous machine and the flywheel.

• 1: ein System mit einer Zwischenspeichereinrichtung nach einer Ausführung der vorliegenden Erfindung;
• 2: ein System mit einer Zwischenspeichereinrichtung nach einer anderen Ausführung der vorliegenden Erfindung;
• 3 ein Verfahren zum Betreiben der Zwischenspeichereinrichtung nach einer Ausführung der vorliegenden Erfindung; und
• 4 ein System mit einer Zwischenspeichereinrichtung nach einer weiteren Ausführung der vorliegenden Erfindung.

Further advantages and features emerge from the subclaims and the embodiments. This shows, partly schematically:

• 1 : a system with a buffer device according to an embodiment of the present invention;
• 2 : a system with a buffer device according to another embodiment of the present invention;
• 3 a method for operating the buffer device according to an embodiment of the present invention; and
• 4 a system with a buffer device according to another embodiment of the present invention.

1 shows a system with a buffer device for temporarily storing energy of an energy network 40 according to an embodiment of the present invention.

The intermediate storage device has an electrical three-phase asynchronous machine 10, which is set up to draw electrical power from the energy network 40 in a first operating mode of the asynchronous machine and to feed electrical power into the energy network 40 in a second operating mode of the asynchronous machine and is connected to the energy network 40 via an interruption device 20 and two transformer devices 21, 22.

The intermediate storage device has a flywheel 12 which is mechanically connected to the asynchronous machine 10 without a clutch.

The intermediate storage device has a fluid supply device 14 for supplying cooling and/or lubricant to the asynchronous machine 10 and/or the flywheel 12.

The intermediate storage device has a control device for controlling and/or monitoring the asynchronous machine 10 and/or the flywheel 12, which has a programmable logic controller 30, in particular for controlling and/or monitoring the asynchronous machine 10 and/or the flywheel 12, and a transmitting/receiving device 31 for communication with a remote control and/or monitoring device 60. The programmable logic controller 30 controls and/or monitors an interruption controller 32, which on the one hand controls and/or monitors the interruption device 20 and in particular on the other hand controls and/or monitors the asynchronous machine 10. In addition, the programmable logic controller 30 controls and/or monitors the fluid supply device 14, preferably at least one pump 14.1 of the fluid supply device.

2 shows a system with an intermediate storage device for temporarily storing energy of an energy network 40 according to an embodiment of the present invention, wherein the system further comprises a, in particular continuously adjustable, transmission 11 which mechanically, in particular clutchlessly, connects the asynchronous machine 10 and the flywheel 12.

The intermediate storage device has an electrical three-phase asynchronous machine 10, which is set up to draw electrical power from the energy network 40 in a first operating mode of the asynchronous machine and to feed electrical power into the energy network 40 in a second operating mode of the asynchronous machine and is connected to the energy network 40 via an interruption device 20 and two transformer devices 21, 22.

The intermediate storage device has a flywheel 12 and a continuously variable transmission 11, which mechanically connects the asynchronous machine 10 and the flywheel 12 without a clutch.

The intermediate storage device additionally has a starter drive 13 for starting the flywheel 12, which is mechanically connected to the flywheel 12 without a clutch.

The intermediate storage device has a fluid supply device 14 for supplying cooling and/or lubricant to the asynchronous machine 10, the transmission 11 and/or the flywheel 12.

The intermediate storage device has a control device for controlling and/or monitoring the asynchronous machine 10, the transmission 11, the flywheel 12 and/or the starter drive 13, which has a programmable logic controller 30, in particular for controlling and/or monitoring the asynchronous machine 10, the transmission 11 and/or the flywheel 12, and a transmitting/receiving device 31 for communication with a remote control and/or monitoring device 60. The programmable logic controller 30 controls and/or monitors an interruption controller 32, which on the one hand controls and/or monitors the interruption device 20 and on the other hand in particular controls and/or monitors the asynchronous machine 10. In addition, the programmable logic controller 30 controls and/or monitors the fluid supply device 14, preferably at least one pump 14.1 of the fluid supply device, and/or a frequency converter or a VFD (“Variable Frequency Drive”) controller 15 for controlling the starter drive 13, which is connected to an electrical power network 41. Furthermore, in 2 schematically shows a first coupling element 11.1 and a second coupling element 11.2, which couple the transmission with the flywheel 12 and the asynchronous machine 10, respectively.

3 shows a method for operating the buffer device according to an embodiment of the present invention.

In a step S10, in a first or engine operating mode, taking electrical power from the energy network 40 increases a kinetic energy of the flywheel 12.

In a step S30, in a second or generator operation (mode) while reducing the kinetic energy of the flywheel 12, electrical power is fed into the energy network 40.

In particular, if the intermediate storage device has a transmission 11, a transmission ratio of the transmission 11, which is equal to a quotient of an amount of a rotational speed of a flywheel-side first coupling element 11.1, which mechanically connects the transmission 11 and the flywheel 12, divided by an amount of a rotational speed of a synchronous machine-side second coupling element 11.2, which mechanically connects the transmission 11 and the asynchronous machine 10, is adjusted ( 3 : step S20 or S40).

In this case, the transmission ratio of the transmission 11 is adjusted as a function of a grid frequency of the energy grid 40 and/or with a predetermined rate of change and/or increased to extract, in particular increase a withdrawal, electrical power from the energy grid 40 (step S40) and/or reduced to feed, in particular increase a feed, electrical power into the energy grid 40 (step S20).

This is shown schematically by arrows in 2 indicated, with an upper line showing an increase (“↑”) in a speed n of the flywheel 12 and a lower line, in contrast, a reduction (“↓”) in the speed n of the flywheel 12. If the intermediate storage device has a gearbox 11, the increase in a speed can be achieved by increasing the gear ratio i and a corresponding active power flow P as well as a corresponding frequency-reducing effect in the energy network 40 (“↓f”) is indicated accordingly. Accordingly, if the intermediate storage device has a gearbox 11, in contrast, a reduction (“↓”) in the speed n of the flywheel 12 by reducing the gear ratio i and a corresponding active power flow P as well as a corresponding frequency-raising effect in the energy network 40 (“↑f”) are schematically shown in a lower line.

This advantageously makes it possible to realize a quickly retrievable active power exchange with the grid 40 for a limited period of time, while the instantaneous reserve or instantaneous active power provision or consumption is advantageously maintained.

If the buffer device does not have a gear 11, steps S20 and S40 in particular are omitted. 3 or a change in the gear ratio i as in 2 shown.

4 shows a system with a buffer device for temporarily storing energy of an energy network 40 according to an embodiment of the present invention.

The intermediate storage device has an electrical three-phase asynchronous machine 10, which is set up to draw electrical power from the energy network 40 in a first operating mode of the three-phase machine and to feed electrical power into the energy network 40 in a second operating mode of the three-phase machine and is connected to the energy network 40 via an interruption device 20 and two transformer devices 21, 22.

The intermediate storage device has a flywheel 12 and a continuously variable transmission 11, which mechanically connects the three-phase machine 10 and the flywheel 12 without a clutch.

The intermediate storage device additionally has a starter drive 13 for starting the flywheel 12, which is mechanically connected to the flywheel 12 without a clutch.

In a modification, a clutch 50, 51 or 52 for temporary mechanical coupling can be arranged between the starter drive 13 and flywheel 12 and/or between the flywheel 12 and the gearbox 11 and/or between the gearbox 11 and the three-phase machine 10. As described, one or more, in particular all, clutches 50-52 can also be omitted or the starter drive 13 and flywheel 12 and/or flywheel 12 and the gearbox 11 and/or the gearbox 11 and the three-phase machine 10 can also be mechanically connected to one another without a clutch. This advantageously enables a more robust and/or more compact structure.

The intermediate storage device has a fluid supply device 14 for supplying cooling and/or lubricant to the asynchronous machine 10, the transmission 11 and/or the flywheel 12 and, if applicable, the clutch(es) 50, 51 and 52.

The intermediate storage device has a control device for controlling and/or monitoring the asynchronous machine 10, the transmission 11, the flywheel 12 and/or the starter drive 13 and/or, if applicable, the clutch 50, 51 and/or 52, which has a programmable logic controller 30, in particular for controlling and/or monitoring the asynchronous machine 10, the transmission 11 and/or the flywheel 12 and/or optionally the clutch 50, 51 and/or 52, and a transmitting/receiving device 31 for communication with a remote control and/or monitoring device 60. The programmable logic controller 30 controls and/or monitors an interruption controller 32, which on the one hand controls and/or monitors the interruption device 20 and on the other hand in particular controls and/or monitors the asynchronous machine 10. In addition, the programmable logic controller 30 controls and/or monitors the fluid supply device 14, preferably at least one pump 14.1 of the fluid supply device, and/or a frequency converter or a VFD (“Variable Frequency Drive”) controller 15 for controlling the starter drive 13, which is connected to an electrical power network 41. Furthermore, in 4 schematically shows a first coupling element 11.1 and a second coupling element 11.2, which couple the transmission to the clutches 51 and 52, respectively.

Although exemplary embodiments have been explained in the preceding description, it should be noted that a large number of modifications are possible. It should also be noted that the exemplary embodiments are merely examples that are not intended to limit the scope of protection, applications and structure in any way. Rather, the preceding description provides the person skilled in the art with a guide for implementing at least one exemplary embodiment, whereby various changes, in particular with regard to the function and arrangement of the components described, can be made without departing from the scope of protection as it results from the claims and combinations of features equivalent to these.

List of reference symbols

10

three-phase asynchronous machine

11

transmission

11.1

first coupling link

11.2

second coupling link

12

flywheel

13

starter drive

14

fluid supply device

14.1

pump

15

frequency converter or VFD control

20

interruption device

21, 22

transformer device

30

programmable logic controller

31

transmitting/receiving device

32

interrupt control

40

energy network

41

power grid

50-52

coupling

60

remote control and/or monitoring

Claims (11)

Intermediate storage device for temporarily storing energy of an energy network (40), comprising: - an asynchronous machine (10) which is designed to draw electrical power from the energy network in a first operating mode of the asynchronous machine (10) and to feed electrical power into the energy network in a second operating mode of the asynchronous machine (10); and - a flywheel (12) which is operatively connected to the asynchronous machine (10). Intermediate storage device according to the preceding claim, wherein the asynchronous machine (10) and the flywheel are operatively connected to a transmission ratio and/or wherein the asynchronous machine (10) and the flywheel are operatively connected to a transmission. Intermediate storage device according to one of the preceding claims, characterized in that the asynchronous machine (10) and the flywheel are connected without a clutch and/or that the transmission is connected to the asynchronous machine (10) and/or the flywheel without a clutch. Intermediate storage device according to one of the preceding claims, characterized in that the asynchronous machine (10) and the flywheel are mechanically connected via at least one clutch and/or that the transmission is mechanically connected via at least one clutch (50, 51, 52) to the asynchronous machine (10) and/or via at least one clutch to the flywheel. Intermediate storage device according to one of the preceding claims, characterized in that the transmission ratio of the gear is continuously adjustable. Intermediate storage device according to one of the preceding claims, characterized in that the intermediate storage device has, in addition to the asynchronous machine (10), a starter drive (13) for starting the flywheel and/or the asynchronous machine (10). Buffer device according to one of the preceding claims, characterized in that the buffer device has a static reactive power compensator. Intermediate storage device according to one of the preceding claims, characterized by a fluid supply device (14) for supplying fluid to the asynchronous machine, the transmission and/or the flywheel and/or a control device (30, 31, 32, 15) for controlling and/or monitoring the asynchronous machine, the transmission, the flywheel and/or the fluid supply device, wherein the control device in particular has a programmable logic controller (30) and/or a transmitting/receiving device (31) for communication with a remote control and/or monitoring device (60). System comprising an energy network and an intermediate storage device according to one of the preceding claims for intermediate storage of energy from the energy network. System according to the preceding claim, characterized in that the asynchronous machine (10) of the intermediate storage device is connected to the energy network via at least one interruption device of the system and/or at least one transformer device of the system. Method for operating a buffer device according to one of the preceding Claims 1 until 8 , characterized in that the asynchronous machine (10) is operated at least temporarily to draw electrical power from the energy network in the first operating mode (S10) and at least temporarily to feed electrical power into the energy network in the second operating mode (S30).

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