Combination of an electrical network, a power plant and a storage power plant as well as a method for compensating for fluctuating power supply of the power plant

Abstract

A network comprising an electrical network (1) for transmitting and distributing electrical energy and at least one power plant (2), wherein the power plant (2) has a fluctuating power feed into the electrical network (1) and thus a uniform energy output cannot be guaranteed during normal operation of the power plant (2), and at least one storage power plant (3) for compensating for the fluctuating power feed of the power plant (2), wherein the storage power plant (3) has at least one electromechanical converter (4) and the electromechanical converter (4) has a rotating electrical machine (5) and at least one rotational inertia storage device (7) with a rotating flywheel (8), and the electrical machine (5), the rotating flywheel (8) and a further device are connected to one another,wherein the electric machine (5) is a first rotating electric machine (5) and the further device is a component of the electromechanical converter (4), wherein the device is designed as a further, second rotating electric machine (6) or as a magnetic torque coupling with an adjusting device for influencing a mechanical load coupling of the torque coupling, and the rotary flywheel mass (8) of the rotary inertia storage device (7) is arranged between the electric machine (5, 6) and the device and / or the electric machine (5, 6) and the device are connected to one another via the rotary flywheel mass (8), and thus the rotary flywheel mass (8) and a respective rotor (9, 10, 12) of the electric machines (5, 6) form the rotary inertia storage device (7).

Description

The invention relates to a composite comprising an electrical network for transmitting and distributing electrical energy and at least one power plant, wherein the power plant has a fluctuating power feed into the electrical network and therefore a uniform energy output cannot be ensured during the regulating operation of the power plant, and at least one storage power plant for compensating the fluctuating power feed of the power plant, wherein the storage power plant has at least one electromechanical converter and the electromechanical converter has a rotating electrical machine and at least one rotational inertia store having a rotational flywheel mass, and in this case the electrical machine, the rotational flywheel mass and a further device are connected to one another. In this case, the electric machine is a first rotating electric machine and the further device is a component of the electromechanical converter. Further, in one embodiment, the device is configured as a magnetic torque clutch.The invention furthermore relates to a method for compensating a fluctuating provision of electrical power in the electrical network of the combination, which provision is caused by the at least one power plant.The feeding of energy into electrical networks, which has been generated in particular from regenerative energy carriers such as wind and sun, increases steadily. Due to these energy carriers, which usually act only intermittently, and the thus discontinuous feeding of energy, an increased load is present for the electrical networks. The probability of underfeeding or overfeeding an electrical network thus potentially increases, wherein a present energy deficit or a present energy excess has to be compensated via positive or negative control energy or control power.Different methods can be used for the compensation. Thus, in one embodiment, the generic EP 1 485 978 A2 describes an electrical island network which is fed via at least one wind turbine. In addition, connected in parallel with the output of a grid-controlled inverter connected to the wind turbine via a DC voltage intermediate circuit is a synchronous generator functioning as a grid former, which is fed from the island grid in motor operation. In one embodiment, a flywheel is also coupled to the synchronous generator, so that excess energy can be stored during engine operation and fed back into the island grid in the event of an energy deficit during generator operation of the synchronous generator. In addition, an internal combustion engine can also be connected to the synchronous generator via an electromagnetic clutch and the synchronous generator can be operated in the generator mode. In this way, fluctuations in the provision of electrical energy by the wind energy installation can be compensated for at least partially.In addition to the compensation of electrical quantities, such as the electrical energy, devices are known from the prior art, with which it is also possible to compensate for differences in other physical quantities, for example mechanical quantities.In this sense, DE 198 11 966 A1 discloses, for example, an induction coupling and an induction brake. Instead of a sliding ring current collector which supplies energy to an electromagnet arranged on a first shaft, a pole wheel made of permanent magnets and a first short-circuit winding are embodied on a first shaft of the induction coupling. On a second shaft, in turn, only a short-circuit winding is formed, into which a current generating a magnetic field is induced upon rotation of the first shaft. By interaction of the magnetic fields of the first and second shaft, the second shaft is consequently likewise set in rotation. By opening or closing the second short-circuiting winding, the induction clutch can be engaged or disengaged and, in particular, the transmitted torque can be influenced by changing the distance between the shafts.U.S. Pat. No. 7,535,143 B2 discloses a further induction clutch for coupling an input shaft to an output shaft and in this case in particular for coupling an internal combustion engine to the wheels of a motor vehicle. In this case, an electric machine is connected to the input and output shafts. Within the scope of this solution, too, a current consumption via sliding contacts is to be avoided. For this purpose, both electric machines are substantially coaxial to one another, wherein a fixed yoke of the stator, which yoke is arranged radially on the inside and radially on the outside, has the windings which are thus likewise fixed. Thus, the use of sliding contacts can be dispensed with. The coupling of the two electric machines takes place via rotors arranged between the stators, which are arranged consecutively in the radial direction, wherein a first rotor, which is associated with the radially inner electric machine and is connected to the input shaft, consists of soft magnetic material and forms alternating magnetic poles in the circumferential direction during magnetization due to its geometric configuration. A second rotor, which is associated with the radially outer electric machine and is connected to the output shaft, on the other hand, has permanent magnet crowns. Thus, with corresponding magnetization of the first rotor and rotation of the input shaft, a torque can be transmitted to the second rotor and thus to the output shaft. Phase-shifted alternating current excitation of the windings of the radially inner electric machine results in a rotating field excitation, by means of which the slip between the first and second rotor can be positively or negatively influenced. A second rotating field can also be generated via the stator associated with the radially outer electric machine and thus the second rotor can additionally be supplied with a positive or negative torque. Both electric machines can accordingly be operated as a motor or generator.Furthermore, an induction coupling can also be seen in EP 1 524 756 A1. This serves in connection with an engine in particular as a resistance element for sports equipment. For this purpose, a rotatably mounted shaft is formed in the induction coupling, which shaft carries a permanent magnet package, on the circumference of which a plurality of permanent magnets is arranged. The shaft together with the permanent magnet package basically forms a first rotor or rotor of the induction coupling. The permanent magnet package is additionally surrounded at least partially by a cage conductor which is arranged in a sleeve and rotationally fixed with respect to this sleeve. This sleeve and a flange arranged on the end face and rotationally fixedly on the sleeve form, on the one hand, a bearing bush in which the shaft is rotatably mounted at least on one side, and, on the other hand, a housing of the induction clutch. An opposite bearing of the shaft is also provided within a motor clutch connected to the bearing bush in a rotationally fixed manner or a second flange, which in turn belongs to the bearing bush or the housing and is thus likewise connected in a rotationally fixed manner. The bearing bush or the housing is connected to the aforementioned motor via the motor coupling or the second flange for the execution of the resistance element and can thus be set in rotation via the latter, wherein the cage conductor can accordingly also be set in rotation with respect to the permanent magnet package and a second rotor or rotor is thus present. A current generating an opposite magnetic field is induced in the cage conductor by a rotation in the magnetic field of the permanent magnets, on account of which current the permanent magnet package together with the shaft is in turn set in rotation following the rotation of the bearing bush. By acting against the rotation in the case of a sports activity, a resistance is thus produced.EP 0 359 027 A1 discloses an instant standby device for a dynamic, uninterrupted power supply, in this case in particular for voltage and frequency stabilization in critical infrastructure such as hospitals. For this purpose, an electric machine which can be operated in motor or generator operation, or an electric motor and a generator which are embodied separately from one another, is mechanically connected via a transmission to a respective two flywheel systems, wherein the second flywheel system can be coupled to the transmission via an elastic clutch, in this case in particular a controllable induction clutch. In normal operation, a first flywheel system is held at predefined rotational speeds that differ from one another via the electric machine that is in the motor mode and the second flywheel system is held at predefined rotational speeds that differ from one another via at least one further electric motor. In the event of a grid failure or grid malfunction, the electric machine enters into the generator mode, wherein a speed drop across the first flywheel system and thus a frequency and voltage drop of the grid are kept within permissible limits. In addition, the second flywheel system is connected via the induction coupling, wherein an existing rotational speed difference between the second flywheel system and the electric machine in generator operation is compensated by pre-excitation of the induction clutch and, in addition, rotational speed and thus frequency control to a value of 50 hertz plus / minus one percent is made possible.AU 5 840 173 A is moreover known a dual, in this case electromechanical energy transmission and conversion system, which serves in particular as a torque converter between two mechanical systems, in this case a drive such as an internal combustion engine and an output such as the wheels of a motor vehicle, and is furthermore itself provided as a drive. For this purpose, at least two electric machines are used, which are arranged within a housing and are mechanically and / or electrically coupled to one another. At least one of the electric machines is designed as a motor, and a second of the electric machines is designed in particular as an induction clutch, wherein this clutch acts at least partially as a generator and / or motor. For a pure engine or generator operation, a locking element is formed on an input shaft connected to the second electric machine designed as an induction clutch. Thus, in addition to a purely electric operation in which both electric machines are used as a drive, in particular a mixed operation of the motor vehicle by means of the internal combustion engine can also be made possible, wherein a part of the energy transmission takes place mechanically and a part electrically. A high rotational speed difference between the internal combustion engine and the wheels during starting can be compensated for by the energy transmission and conversion system acting as a torque converter, wherein depending on the rotational speed difference, the energy transfer takes place more electrically or more mechanically. In the case of a high rotational speed difference, the induction clutch driven via the internal combustion engine essentially acts as a generator, wherein the generated electrical energy is converted into mechanical energy by the electric motor. If there is a small rotational speed difference, the induction clutch essentially acts as such and the wheels are driven virtually exclusively via the internal combustion engine. In addition to a generator function, the induction clutch can also be used as a motor, as already mentioned. By way of the actual function of driving the wheels via a drive shaft in purely electric operation, there is also the possibility of starting the internal combustion engine or else of setting a flywheel into rotation via the drive shaft.In the methods described for compensating the fluctuating energy supply, it is often difficult to realize a very flexible transmission between an energy store and the electrical grid by means of an in particular compact design.The object of the invention is to configure the aforementioned composite in such a way that a balancing of a fluctuating power provision in the electrical network is made possible via a flexibly configured, compact energy store. It is a further object of the invention to provide a method for compensating the fluctuating power provision in this composite.This object is achieved according to the invention with a composite according to the features of claim 1 and a method according to the features of claim 10. The further embodiment of the invention can be taken from the dependent claims.According to the invention, therefore, a combination of an electrical network or a power network for transmitting and distributing electrical energy, at least one power plant forming a primary power plant and at least one storage power plant which differs in particular from a (primary) power plant is provided. The electrical network could be designed here both as a network or else as an island network. It is also conceivable that the network is constructed from a plurality of, in this case in particular at least two, sub-networks, wherein the sub-networks can be assigned to the same voltage level or to voltage levels which differ from one another accordingly.According to the invention, the power plant has a fluctuating power supply for a fluctuating energy feed into the electrical network, respectively, as a result of which uniform power supply and / or energy feed into the network cannot be ensured during the regulating operation of the power plant. The power plant or the power plants are thus energy generators which do not ensure uniform energy generation during normal operation. This applies in particular to power plants whose power provision and / or energy feeding into the electrical network is based on the conversion of renewable or regenerative energies into electrical energy. Thus, the power plant can be fed, for example, by geothermal energy, water power or else marine energy or solar energy. Preferably, however, the power plant is a wind turbine, wherein in an embodiment of a plurality of power plants, the group can consequently also have a wind farm consisting of a plurality of wind turbines or a plurality of such wind farms.The at least one storage power plant which is additionally present in the combination and is electrically connected to the electrical network serves in this case to compensate for the fluctuating power provision of the power plant, wherein the respective storage power plant in turn has at least one electromechanical converter and / or converter and the electromechanical converter and / or converter has a rotating electrical machine and at least one rotational inertia store having at least one rotational flywheel mass. In this case, the electric machine, the rotational flywheel mass and a further device are connected to one another at least mechanically, in particular in a force- or torque-transmitting manner.Furthermore, according to the invention, the electric machine is a first electric machine and the further device is a component of the converter and / or converter. The device is either designed as a further, second rotating electric machine or as a magnetic torque clutch with an adjusting device for influencing the mechanical load coupling. In the latter case, the magnetic torque coupling would be in particular magnetostatically excited and preferably embodied exclusively as permanent magnet excited. The magnetic torque clutch would therefore not have an electrical excitation or an electrically excited magnet. The load coupling of, for example, two rotors of the torque clutch would be effected in particular by changing an axial overlap of the rotors via the adjustment device.The storage power plant can thus provide positive and negative control power or control energy to the electrical network. At least one covering of the primary control or of the second reserve would be possible here, wherein depending on the configuration of the storage power plant, the number of storage power plants in the electrical network, the number of electromechanical converters and / or converters in a storage power plant and / or the configuration of the rotational inertia store, a covering of the secondary control, the tertiary control and / or even an hour reserve is also conceivable.In principle, within the scope of the invention, there is the possibility that only the first electric machine of the storage power plant is electrically connected and / or connectable to the electrical network. However, it is precisely the embodiment of two electric machines that advantageously has the possibility of being able to react to different load states of the electric network that are established and / or different operating states of the storage power plant and thus of being able to optimally compensate fluctuations in the electric power provided to the electric network.Thus, a preferred embodiment would also be that the first electric machine and the second electric machine are electrically connected and / or connectable to the network. In this case, it can also be provided, on the one hand, that the storage power plant is only connected to a subnetwork of the network. On the other hand, there would also be the possibility of connecting the storage power plant to two sub-networks. These sub-networks could not be directly coupled to one another at all, but rather could be connected only indirectly via the storage power plant-in particular electrically. In one embodiment, it could be provided that the first electric machine is connected to a first subnetwork and the second electric machine is connected to a second subnetwork. In particular within such a configuration, but likewise generally, it is conceivable for the sub-networks of the electrical network to belong to different voltage levels. A storage power plant can thus be designed quasi at the boundary of two such voltage levels.At least one or all of the electric machines should be connected to the electrical network via at least one frequency converter. In a preferred configuration, each of the two electric machines is even connected to the electrical network via a respective-separate-frequency converter. Furthermore, at least one or one power separator each can also be implemented between the electric machines or each of the electric machines of the electromechanical converter and the electric network.In addition, the configuration of the further device of the electromechanical converter and / or converter as a magnetic torque clutch having an adjustment device for influencing the mechanical load coupling advantageously offers the possibility of coupling at least one further consumer, for example in the form of a further energy store, in particular mechanically to the electromechanical converter, wherein the power and / or transmitted energy provided between this consumer and the electromechanical converter could be influenced by the adjustment device, in particular could be controlled and / or regulated.The advantage of being able to couple at least one further load to the electromechanical converter is, however, likewise offered by the configuration of the further device as the second electric machine.Furthermore, it is provided according to the invention that at least one rotational flywheel mass of the rotational inertia storage device, which mass differs in particular from the components of the electric machines, is arranged between the electric machine and the device and / or the electric machine is connected to the device via the rotational flywheel mass to one another-mechanically-and thus the rotational flywheel mass and a rotor of the electric machines in each case form the rotational inertia storage device. The two electric machines are thus mechanically coupled to one another via the rotational flywheel mass and are also configured spaced apart from one another via the latter. In particular within the scope of this embodiment, but also generally, it is considered favorable if the rotational flywheel mass consists of an amagnetic, i.e. nonferromagnetic material or materials. This, in particular in connection with the spacing of the electric machines by way of the rotational flywheel mass, reduces a magnetic flux occurring or exchanged between the electric machines and thus a magnetic coupling of the electric machines. The rotational flywheel mass can be connected here either to external rotors or to internal rotors of the two electric machines and can therefore be embodied accordingly as external rotors or internal rotors in the electromechanical converter and / or converter.A further development of the invention is also found to be highly advantageous if at least one of the electric machines, in this case in particular exclusively one electric machine, has two rotors which are designed to be rotatable with respect to one another, such that this electric machine can be operated in a motor mode, in a generator mode and / or in a clutch mode. This electric machine is preferably the further, second electric machine. Instead of a stator fixed to the rotating frame or frame and a rotor rotatably mounted with respect to this stator, the electric machine thus has two rotors rotatably designed or mounted with respect to one another, of which consequently one rotor is designed lying on the inside and one rotor is designed lying on the outside of the electric machine. In addition to the motor and generator operation, a clutch operation of the second electric machine, in particular, can thus also be realized. In this case, the motor, generator and / or clutch operation takes place as a function of the structural configuration or the structure of the electric machine, in this case in particular of the two rotors, the relative rotational speed of the two rotors with respect to one another and / or the feeding or extraction of electrical energy from the electromagnetic converter and / or converter. In this case, with regard to the structure of the electric machine, it should be noted that both rotors must be magnetically excited or at least magnetically excitable in order to enable, in particular, bidirectional clutch operation of the electric machine. For motor and generator operation, a coil arrangement would also have to be implemented in at least one of the rotors. Thus, on the one hand, only one, in particular a first of the rotors could have a coil arrangement and thus be magnetically energizable via a current flow. In addition to the coil arrangement, the arrangement of at least one laminated core would also be conceivable. The further, in particular second rotor, could consequently not have a coil arrangement, but a permanent magnet arrangement would have to be implemented, as a result of which constant magnetic excitation would be present. Again, an embodiment of at least one laminated core in the further, second rotor would also be possible. A configuration of the electric machine deviating therefrom would furthermore consist in the configuration of a coil arrangement in each case in both rotors, wherein in turn one of the two rotors could have at least one laminated core. In connection with the aforementioned embodiments, an internal and / or external excitation can be implemented.A further particularly promising embodiment of the invention is distinguished in that only one of the electric machines, preferably the first electric machine, has a stator which is in particular fixed to the frame and a rotor which is designed to be rotatable with respect to this stator, with the result that the electric machine can be operated in a motor mode and / or in a generator mode. By constructing one of the electric machines with a stator and a rotor instead of two rotors, the structural outlay of the electromechanical converter remains less complex, as a result of which a higher reliability and a reduced maintenance outlay of the electromechanical converter and / or converter can be ensured. In principle, the stator and / or the rotor can be configured exclusively with at least one laminated core and or at least one squirrel cage and therefore have neither a coil arrangement nor permanent magnets, so that only inductive coupling would be effected via an alternating magnetic field generated by the rotor and / or stator. However, the first electric machine would only be suitable for providing power and / or transmitting energy from the electrical grid into the rotational inertia storage. A preferred embodiment is thus that the stator and / or rotor have at least one permanent magnet. In addition, at least one laminated core can naturally also be designed. The stator or the rotor could be arranged lying on the inside or on the outside and both an internal and / or external excitation of the first electrical machine could be formed by embodying a coil arrangement in the stator and / or rotor.An embodiment of the electrical network according to the invention is also to be classified as advantageous if preferably only one rotor of at least one electrical machine having two rotors is connected to an output and / or drive element or has an output and / or drive element, via which a rotational movement of the rotor can be transmitted. Thus, in an advantageously simple configuration, it would be possible to provide a possibility of coupling a further consumer, in particular mechanically, to the electromechanical converter and / or converter via the electric machine having two rotors. The electric machine having two rotors would preferably be the second electric machine, wherein the output and / or drive element would be configured in particular as a shaft, in particular consequently an output and / or drive shaft. The output and / or drive element can in this case in principle be arranged on each of the rotors of the electric machine having two rotors or be connected to each of the rotors. However, it is preferably provided that the output and / or drive element is arranged-exclusively-on the outer rotor of the electric machine or is connected thereto, so that a complicated structural design of the electric machine, in particular under a guidance of the output and / or drive element outwards, piercing the outer rotor, can be avoided.In another embodiment, it can also be provided that the torque clutch with the adjusting device also has an output and / or drive element in the previously described embodiment.In a further development of the invention which additionally has advantages, the rotational inertia store and / or a rotor of at least one electric machine having two rotors can be fixed in a rotationally fixed or frame-fixed manner via a-respective brake device and / or a-respective fixing element. The rotor which can be fixed in a fixed manner in terms of rotation or frame would therefore be the rotor which does not belong to the rotational inertia store and is therefore not fixedly connected to the rotational flywheel mass. A clutch operation of an electric machine having two rotors could thus be prevented at least temporarily by braking until standstill and / or fixing of the rotational inertia store or one of the rotors of the electric machine and an optimum motor and / or generator operation of the first and / or second electric machine could be ensured. In addition, it would be conceivable that a combined clutch and motor operation and / or a combined clutch and generator operation is realized via the electric machine having two rotors by braking the rotational inertia storage and / or the one rotor of the in particular second electric machine, in that only an at least temporary braking of the rotational inertia storage and / or the one rotor, consequently not until a standstill, but for example speed-controlled until a setpoint speed is effected. Thus, a provision of power and / or a transmission of energy, correspondingly a power and / or energy flow between the rotational inertia storage of the electromechanical converter and / or converter, the further energy storage device and the electrical grid, can be controlled or regulated. In order to realize the highest possible efficiency in this case, the brake device would preferably be designed as a regenerative brake or else a recuperation brake or would have at least one such regenerative brake or recuperation brake.In a further embodiment of the electrical network according to the invention which is advantageous in terms of design, the storage power plant has at least one further energy storage device which differs in particular from the electromechanical converter. In this case, this is connected - mechanically - in particular - via the output and / or drive element to the electromechanical converter and / or converter and thus to the rotational inertia storage device, such that - mechanical - energy can be transmitted between the further energy storage device and the rotational inertia storage device. This is particularly advantageous in that, for example, when an amount of energy that can be stored to the maximum in the rotational inertia storage is reached, further excess power provided to the network and / or excess energy fed into the network can be transmitted to the storage power plant. The energy stored in the further energy storage device can, on the one hand, be transferred again into the network and / or the rotational inertia storage device in the presence of a deficit in the network and / or in the rotational inertia storage device.In one embodiment of the invention, it is furthermore provided that the energy storage device has a potential energy reservoir, a hydropneumatic reservoir and / or a pneumatic reservoir. Such an embodiment of the energy store offers an excellent possibility of transmitting mechanical energy and thus represents a very suitable configuration for coupling to the electromechanical converter via the further device of the storage power plant embodied as an electric machine or torque clutch.An advantageous embodiment of the invention furthermore also consists in that the electric machines, in this case in particular the rotors and / or stators of the electric machines, and the rotational inertia store are arranged coaxially with respect to one another. Such a coaxial arrangement permits a more compact configuration and thus a smaller installation space requirement of the storage power plant, in particular in comparison with a series arrangement with axially successive rotational inertia accumulators and electric machines.According to the invention, a method for compensating a fluctuating provision of electrical power and / or feeding of electrical energy into the aforementioned electrical network caused by the at least one power plant is also provided. In this case, in particular different load states of the electrical network and / or, in particular, different operating states of the storage power plant, provision of, in particular electrical, power and / or transmission of, in particular electrical, energy between the electrical network and the storage power plant takes place-exclusively-via the first electrical machine,-exclusively-via the second electrical machine or via both electrical machines of the electromechanical converter and / or converter of the storage power plant. Thus, the method with a high flexibility creates the possibility of providing and / or transmitting power and / or energy between the electrical network and the storage power plant, i.e. of providing positive and / or negative control power and / or control energy to the electrical network.On the one hand, in the case of a load state of the network in which an excess of power is provided continuously or intermittently to the network and thus to the storage power plant by the at least one (primary) power plant, in this case e.g. a wind power plant and / or a wind farm, excess energy can thus be transferred flexibly into the storage power plant and thus negative control power and / or control energy can be made available. For this purpose, the first and / or the second electric machine would be operated in a motor mode. However, the second electric machine could alternatively also be in a combined motor and clutch operation.The energy thus transferred via this power and / or energy consumption into the storage power plant would consequently be stored in the rotational inertia storage and / or the further energy storage device. In this case, energy can be transmitted to the storage power plant or absorbed by the latter both intermittently and continuously, wherein comparatively low powers and in particular also high powers for a short period of time can be provided to the storage power plant on account of the transmission according to the invention via the first, second or first and second electric machines.In this case, it is conceivable that in the case of a continuous but comparatively small excess of electrical power provided by the power station on the network, the excess or at least a part of this excess takes place only via the first electrical machine or the second electrical machine of the electromechanical converter. If, on the other hand, there is a high excess of power provided on the electrical network continuously or intermittently, the transfer of the excess energy could be carried out via both electrical machines of the electromechanical converter; this may be carried out as a function of the operating state of the storage power plant, for example the quantity of energy stored in the rotational inertia storage and / or the further energy storage device.If, on the other hand, the electrical network is in a load state in which there is a deficit of electrical power and / or energy supplied to the network by the power plant, the deficient energy can be transferred flexibly by the storage power plant into the network or fed into the network and thus positive control power and / or control energy can be made available. For this purpose, the first and / or the second electric machine would be operated in generator operation. However, the second electric machine could alternatively also be in a combined generator and clutch mode. The supply of power by the storage power plant would take place substantially intermittently with delivery of high to very high powers, in particular peak powers, over a comparatively short period of time; this may possibly take place as a function of the operating state of the storage power plant, in this case e.g. the quantity of energy stored in the rotational inertia storage and / or the further energy storage device.In principle, it would be conceivable within the scope of the method for the electric machines to be operated via only one frequency converter connecting the electric machines to the electric grid. However, a promising development of the method according to the invention consists in that each of the electric machines is operated via in each case at least one separate frequency converter connecting the electric machines to the electric grid. It is thus made possible for both electric machines of the electromechanical converter to be controlled or regulated separately from one another. A possible frequency and / or phase offset can be controlled and / or regulated, for example, by means of a control unit connected to the frequency converters.In a gain-producing manner, in one embodiment of the invention, it is furthermore provided that, depending on load states of the electrical network that differ in particular from one another and / or operating states of the storage power plant that differ in particular from one another, provision of in particular mechanical power and / or transmission of in particular mechanical energy between the rotational inertia storage and / or the rotating unit of the electromechanical converter and / or converter and the further energy storage device takes place via the second electrical machine. Thus, in an advantageous manner, in particular depending on the quantity of energy stored in the rotational inertia storage and / or the further energy storage device, energy can be transferred from the rotational inertia storage device into the further energy storage device or from the further energy storage device into the rotational inertia storage device. For this purpose, the second electric machine would in principle be operated in the exclusive clutch mode, so that no energy is transmitted between the storage power plant and the electrical network via the second electric machine. However, a transmission of electrical energy via the first electrical machine and thus between the rotational inertia storage device and the electrical network would be conceivable. In addition to the exclusive clutch operation, however, the second electric machine could likewise be operated in a combined clutch and motor operation or clutch and generator operation, with the result that, in addition to the transmission of energy between the rotational inertia storage unit and the further energy storage device, energy can also be transmitted via the second electric machine between the electrical grid and the storage power plant, in this case in particular the rotational inertia storage unit or the further energy storage device.Furthermore, an embodiment of the invention is to be considered advantageous if, in a first load state of the network in which there is an excess of power provided at the network or of energy fed into the network and / or in a first operating state of the storage power plant in which there is a high deficit of energy stored in the storage power plant, in particular mechanical energy, at least some of the excess power or energy is transmitted into the storage power plant via the first and the second electric machine. Thus, in particular in the case of a high or very high excess on the network of power provided for example for a short time, the high deficit of energy stored in the storage power plant can be advantageously reduced by the transmission simultaneously via both electric machines, in particular in a short period of time. A high deficit of energy stored in the storage power plant is present in particular when no or only a small amount of energy is stored in the storage power plant, thus in the rotational inertia storage and / or the further energy storage device. A small amount can be denoted in this case by the fact that at most 20 percent, preferably at most 10 percent, particularly preferably at most 5 percent of a maximum amount of energy which can be stored overall in the storage power plant or in each case in the rotational inertia storage device and / or the further energy storage device is stored in the storage power plant.In general, but in particular in connection with the above-described embodiment of the invention, a promising embodiment of the method according to the invention is additionally that in the case of a high deficit of mechanical energy stored in the storage power plant-at least partially occurring-in particular in the first operating state-at least partially due to a standstill or a slight rotation of the rotational inertia store, at least a portion of the excess of power provided at the network or energy fed into the network is transmitted via the first electric machine and the second electric machine exclusively into the rotational inertia store. Thus, in the event of an excess of provided power and / or energy, at least a portion of the excess energy can preferably be transferred first of all into the rotational inertia storage serving in particular as a main energy storage of the storage power plant and thus initially stored therein. This is advantageous inter alia because the rotational inertia storage device generally has an more consistent response behavior or shorter response times than embodiments of the further energy storage device, which has, for example, a potentially energetic liquid storage device, a hydropneumatic storage device and / or a pneumatic storage device or is designed as such. The high deficit of energy stored in the rotational inertia storage device manifested via a standstill or a small rotation of the rotational inertia storage device can be advantageously reduced accordingly by the simultaneous transmission of energy via both electric machines, in particular in a short period of time, by the rotational speed of the rotational inertia storage device being increased significantly. A slight rotation of the rotational inertia store is present here in particular when a rotational speed of the rotational inertia store is at most 20 percent, preferably at most 10 percent and particularly preferably at most 5 percent of a permissible maximum rotational speed of the rotational inertia store.In one embodiment of the method according to the invention, it is furthermore advantageously envisaged that-in particular in the first operating state-for the purpose of providing power and / or a transmission of energy between the rotational inertia store of the storage power plant and the electrical network via the second electrical machine, one of the rotors of the second electrical machine is at least temporarily braked and / or established, in this case in particular by means of the brake device assigned to the second electrical machine and / or the assigned locking element. The rotor braked and / or detected in this case would consequently be the rotor of the second electric machine which is not connected to the rotational flywheel mass of the rotational inertia store. As already explained above, a clutch operation of the second electric machine could be prevented and an optimum motor and / or generator operation could be ensured in this way by at least temporary braking until standstill and / or an at least temporary fixing of this rotor of the electric machine, which rotor is not connected to the rotational inertia storage. Thus, a maximum possible provision of power and / or a transmission of energy between the rotational inertia storage and the electrical network could be realized.Furthermore, an advantageous embodiment of the invention is described in that in a - first or second - load state of the network, in which there is an excess of power provided on the network or energy fed into the network, and / or in a - second - operating state of the storage power plant, in which there is a high amount of energy, in particular mechanical energy, stored in the storage power plant, in particular in the rotational inertia storage, via the second electrical machine - mechanical energy is transmitted from the rotational inertia storage and / or - electrical energy is transmitted from the network into the further energy storage device. This has the result that, despite the already high amount of energy stored in the rotational inertia store, further excess energy can be transferred from the electrical network into the storage power plant and any otherwise necessary minimization of the power provided to the network by the power plant can be avoided. A transfer of energy into the further energy storage device bypassing the rotational inertia storage would likewise be possible. It should be mentioned that a high amount of energy stored in the storage power plant is present if a maximum amount of energy storable in the rotational inertia storage device or at least 80 percent, preferably at least 90 percent, particularly preferably at least 95 percent of this maximum amount is already stored in the rotational inertia storage device. This maximum amount of energy storable in the rotational inertia storage is achieved in particular when the rotational speed of the rotational inertia storage corresponds to a permissible maximum rotational speed of the rotational inertia storage.A development of the invention also proves to be advantageous if, in a third operating state of the storage power plant, in which there is a high deficit of energy, in particular mechanical energy, stored in the storage power plant via the rotational inertia storage, provision of electrical power and / or transmission of electrical energy between the respective energy via the network and the further energy storage device of the storage power plant takes place exclusively via the second electrical machine. This makes it possible in a gain-saving manner to transfer energy between the further energy storage device and the electrical network, bypassing the rotational inertia storage device. This is advantageous in particular when there is a deficit in the electrical network of power provided by the power plant and / or energy fed into the network, no energy or only a small amount of energy is stored in the rotational inertia store and power must therefore be provided by the storage power plant and / or energy must be fed into the network in order to compensate for the deficit.In particular in connection with the above-mentioned development of the method according to the invention, but also in general, an embodiment of the invention is to be regarded as promising in which-in particular in the third operating state-for the provision of power and / or a transmission of energy between the further energy storage device of the storage power plant and the electrical network via the second electrical machine the rotational inertia storage device is at least temporarily braked and / or established, in particular by means of the brake device assigned to the rotational inertia storage device and / or the assigned locking element. Thus, again by at least temporary braking until standstill and / or by at least temporary fixing of the rotational inertia storage device, a clutch operation of the second electric machine could be prevented and an optimum motor and / or generator operation could be ensured. This advantageously leads to a maximum possible provision of power and / or a maximum possible transmission of energy between the further energy storage device and the electrical network.It should also be mentioned that a transmission of energy between the network and the storage power plant in the above context is to be understood in particular as a transmission of energy between the at least one power plant and the storage power plant and / or the storage power plant and loads of the group connected to the electrical network via the electrical network.The invention allows various embodiments. To further illustrate its basic principle, some of them are illustrated in the drawings and are described below. The drawings show in FIG. 1 shows a simplified overview illustration of a refinement of the inventive combination with a first embodiment of a storage power plant or of an electromechanical converter; FIG. 2 shows a second embodiment of a storage power plant or of an electromechanical converter.FIG. 1 shows a development of a composite according to the invention comprising the electrical network 1 for the transmission and distribution of electrical energy and a plurality of power plants 2, wherein the power plants 2 electrically connected to the electrical network 1 via a transformer unit function here as primary power plants and, in particular, a respective power plant 2 is designed as a wind turbine. Together, these thus form a wind farm. The power plants 2 designed as wind power plants have a correspondingly fluctuating provision of power into the electrical network 1 on account of the conversion of wind energy into electrical energy, with the result that uniform feeding of energy into the electrical network 1 cannot be ensured during the regulating operation of the power plants 2. In addition to the power plants 2, the group additionally has the storage power plant 3 which is likewise electrically connected to the electrical network 1. the storage power plant 3 serves in this case to compensate for the fluctuating provision of power by the power plants 2, this compensation being carried out via an embodiment of the method according to the invention.The storage power plant 3 shown now has the electromechanical converter 4 and the electromechanical converter 4 again the two rotating electric machines 5, 6 and the rotational inertia store 7. Each of the electric machines 5, 6 is operated via a separate frequency converter 17, 18 and is consequently electrically connected via the latter to the electrical network 1. The two frequency converters 17, 18 are in turn controlled or regulated via the control unit 20, so that a frequency and / or phase offset, for example, can be set between the two electric machines 5, 6.As can also be seen from the further development of the electromechanical converter 4 of FIG. 1, only one of the electric machines 5, 6, in this case the first electric machine 5, has an outer stator 11 which is formed fixed to the frame via the holder 21 and the inner rotor 12 which is formed rotatably with respect to this stator 11. The rotor 12 of the first electric machine 5 is designed here to be permanent magnet-excited and has a laminated core with permanent magnets integrated in this laminated core. A coil arrangement of the first electric machine 5 serving for excitation and induction is thus embodied in the stator 11. As a result, the first electric machine 5 is consequently configured as an internal rotor and can be operated both in motor operation and in generator operation.Furthermore, one of the electric machines 5, 6, here the second electric machine 6, has, on the other hand, two rotors 9, 10 which are designed to be rotatable with respect to one another. In order to realize a rotation of the outer rotor 10 relative to the inner rotor 9 of the second electric machine 6, the outer rotor 10 is rotatably mounted via the rotary bearing unit 22. Again, the inner rotor 9 is designed here to be permanent magnet-excited and consequently likewise has a laminated core with permanent magnets integrated in this laminated core. A coil arrangement of the second electric machine 6 serving for excitation and for induction is correspondingly embodied in the rotatably mounted outer rotor 10, whereby the electric machine 5, 6 can be operated in a motor mode, in a generator mode and / or in a clutch mode. In order to enable an electrical contact between the rotatably mounted outer rotor 10 of the second electric machine 6 and the frequency converter 18 or the electrical network 1, the second electric machine 6, in this case in particular the outer rotor 10, has the contact contact 23. In other embodiments, such a contact with the rotors 9, 10 and / or the rotor 12 by grinding is also conceivable via the rotational inertia storage 7.As can also be seen from FIG. 1, the inner rotor 12 of the first electric machine 5 and the inner rotor 9 of the second electric machine 6 together with the rotational flywheel mass 8 form the rotational inertia store 7 of the electric converter 4. In particular, the two inner rotors 9, 12 of the electric machines 5, 6 are in this embodiment even directly connected via the rotational flywheel mass 8.In addition to the rotational inertia store 7 of the electromechanical converter 4, the storage power plant 3 has the further energy storage device 16 for increasing an amount of energy storable in the storage power plant 3, which is connected to the electromechanical converter 4 via the output and / or drive element 13, such that energy can be transferred between the energy storage device 16 and the rotational inertia store 7 of the electromechanical converter 4 by a rotational movement-mechanical-energy, for which purpose the second electric machine 6 would be operated at least partially in a clutch operation. The output and / or drive element 13 is in this case designed specifically on the outer rotor 10 of the second electric machine 6, wherein the further energy storage unit 16 is coupled to the output and / or drive element 13 via the clutch 19.In order to now compensate a fluctuating provision of electrical power in the electrical network 1 of the group caused by the power plants 2, it is provided that in load states of the electrical network 1 that differ from one another in particular and / or operating states of the storage power plant 3 that differ from one another in particular, a provision of power or a transmission of energy between the electrical network 1 and the storage power plant 3 takes place via the first electrical machine 5, the second electrical machine 6 or both electrical machines 5, 6 of the electromechanical converter 4 of the storage power plant 3. In this context, it is likewise provided that, depending on these load states of the electrical network 1 and / or these operating states of the storage power plant 3, power is provided or energy is transmitted between the rotational inertia storage 7 of the electromechanical converter 4 and the further energy storage device 16 via the second electrical machine 6.Within the scope of the fluctuating provision of power by the power plants 2, on the one hand, a load state of the network 1 can exist in which there is a deficiency of power in the network and thus positive control power basically has to be provided. On the other hand, there may also be a load state of the network 1, in which state the network 1 is provided with an excess of power by the power plants 2. In this case, particularly in the case of low or moderate deficits or excesses, there is the possibility that power is provided only via one of the electric machines 5, 6 between the network and the storage power plant 3. Thus, the electrical energy from the power plants 2 is converted either via the first electrical machine 5 or the second electrical machine 6 of the electromechanical converter 4 into mechanical energy of the storage power plant 3, in this case in particular into kinetic energy of the rotational inertia storage device 7 and / or kinetic and / or potential energy of the further energy storage device 16 and / or vice versa.However, if there is a load state of the network 1, in which there is an excess of power or energy fed in at the network 1 by the power plants 2, and an operating state of the storage power plant 3, in which there is a high deficit of energy stored in the storage power plant 3, such excess energy is transferred into the storage power plant 3 via the first electric machine 5 and the second electric machine 6 within the scope of this refinement of the method, in order to minimize the deficit as quickly as possible. Furthermore, in the case of a standstill present in this context or a-currently-low rotation of the rotational inertia storage device 7, for example in a startup phase of the rotational inertia storage device 7, the excess energy is exclusively transferred into the rotational inertia storage device 7, since this serves as the main energy storage device of the storage power plant 3. During the transmission of the energy from the electrical network 1 into the rotational inertia storage 7 of the storage power plant 3 via the second electrical machine 6 that takes place in this operating state, the outer rotor 10 of the second electrical machine 6, should there still be a residual rotation, is braked temporarily if necessary and is then fixed fixed in a temporarily rotationally fixed or fixed frame-fixed manner. For this purpose, the storage power plant 3, precisely the electromechanical converter 4, has the braking device 14 assigned to the outer rotor 10 and acting on the output and / or drive element 13 in the development of FIG. 1, which also has the locking element 15. The further energy storage device 16 would in this case be released from the output and / or drive element 13 via the clutch 19.In addition to the braking device 14 assigned to the outer rotor 10, the storage power plant 3, in this case again the electromechanical converter 4, has the further braking device 14 assigned to the rotational inertia storage 7. In this case, this also has the fixing element 15, wherein the rotational inertia store 7 is optionally temporarily braked via the brake device 14 in a second operating state of the storage power plant 3 and is subsequently temporarily fixed in a rotationally fixed or frame-fixed manner; this is done via the second electric machine 6 against the background that, in this second operating state of the storage power plant 3, in contrast to the first operating state explained above, when there is a again high deficit of energy stored in the storage power plant 3 via the rotational inertia store 7, power is provided between the electric network 1 and the further energy storage device 16 of the storage power plant 3. In this case, on account of the braking and / or fixing of the rotational inertia storage device 7, a virtually optimum transmission of energy between the electrical network 1 and the further energy storage device 16 can be ensured. The second electric machine 6 is operated in motor or generator operation.If, in the context of the development of the method, there is also a third operating state of the storage power plant 3, which is determined in that there is a high amount of energy stored in the rotational inertia storage 7 of the storage power plant 3, then, in the case of a load state of the network 1, in which there is again an excess of power provided on the network 1 or of energy fed into the network 1, energy is transmitted from the rotational inertia storage 7 and / or energy from the network 1 to the further energy storage device 16 via the second electric machine 6. In this case, the energy can be transmitted, on the one hand, exclusively from the rotational inertia storage device 7 into the further energy storage device 16, for which purpose the second electric machine 6 is operated in the clutch-only mode. Due to the permanent magnet excitation and the rotation of the inner rotor 9 of the second electric machine 6, a current, which in turn generates a magnetic field, is induced in the coil arrangement of the outer rotor 10 of the second electric machine 6, so that the outer rotor 10 follows the inner rotor and the rotational movement caused thereby is transmitted via the output and / or drive element 13 to the further energy storage device 16. This is coupled to the output and / or drive element 13 via the clutch 19. In this case, the rotational speed of the outer rotor 10 approaches the rotational speed of the inner rotor 9, but slip is always formed between the rotors 9, 10. The energy stored in the rotational inertia storage 7 is minimized by the transmission of energy from the rotational inertia storage 7, wherein the rotational speed of the rotational inertia storage 7 consequently decreases. For example, energy can be transferred again from the electrical network 1 into the rotational inertia storage 7 via the first electrical machine 5.Instead of a transmission of energy from the rotational inertia storage device 7, however, the excess energy can also be transmitted-directly-via the second electric machine 6 into the further energy storage device 16. For this purpose, the coil arrangement of the outer rotor 10 of the second electric machine 6 would be excited with a current which has at least one frequency corresponding to the rotational speed of the rotational inertia storage device 7. A higher frequency is also correspondingly conceivable. In order to prevent a further transmission of energy into the rotational inertia storage 7 and an exceedance of the permissible maximum rotational speed of the rotational inertia storage 7 which may be connected therewith, the rotational inertia storage can be braked on the one hand by means of the brake device 14 assigned to the rotational inertia storage 7. In order to avoid a reduction in efficiency, the brake device 14 would be configured as a recuperation brake. Alternatively or additionally, the rotational inertia storage device 7 could also be braked by transferring energy from it into the electrical grid 1 via the first electrical machine 5, so that the first electrical machine 5 likewise acts as a braking device 14.FIG. 2 also shows a second refinement of the storage power plant 3 and, in this case, specifically of the electromechanical converter 4. The electromechanical converter 4 in this case in turn has the output and / or drive element 13 and the two electric machines 5, 6, of which the first electric machine 5 has a stator 11 lying on the inside in this case and an outer rotor 12 designed to be rotatable with respect to this stator 11. The second electric machine 6, on the other hand, again has two rotors 9, 10 designed to be rotatable with respect to one another. In this case, the inner rotor 9 of the second electric machine 6 forms the rotational inertia store 7 together with the outer rotor 12 of the first electric machine 5 and the rotational flywheel mass 8 arranged radially between the electric machines 5, 6. The rotors 9, 10, 12 and the rotational flywheel mass 8 are supported here via the stator 11 fixed to the frame on the holder 21 of the stator 11. The rotors 9, 10, 12 are substantially pot-shaped. The outer rotor 12 of the first electric machine 5 and the outer rotor 10 of the second electric machine 6 can furthermore be fixed in a rotationally fixed or fixed manner by means of the brake devices 14 assigned to the rotors 10, 12. The brake devices 14 also have the locking elements 15. In order, moreover, to avoid cross-talk of a magnetic flux between the electric machines 5, 6 in turn, the rotational flywheel mass 8 is again made of an amagnetic material. In addition, to further minimize the crosstalk, spacer 24 is arranged axially between outer rotor 12 of first electric machine 5 and inner rotor 9 of second electric machine 6.LIST OF REFERENCE CHARACTERS1 Electrical network 2 Power plant 3 Storage power plant 4 Electromechanical converter 5 First electrical machine 6 Second electrical machine 7 Rotational inertia store 8 Rotational flywheel mass 9 Rotor 10 Rotor 11 Stator 12 Rotor 13 Output and / or drive element 14 Braking device 15 Fixing element 16 Energy storage device 17 Frequency converter 18 Frequency converter 19 Clutch 20 Control unit 21 Holder 22 Rotary bearing unit 23 Contact contact 24 Spacer

Claims

A composite comprising an electrical network (1) for transmitting and distributing electrical energy and at least one power plant (2), wherein the power plant (2) has a fluctuating power feed into the electrical network (1) and therefore a uniform energy output cannot be ensured during the regulating operation of the power plant (2), and at least one storage power plant (3) for compensating the fluctuating power feed of the power plant (2), wherein the storage power plant (3) has at least one electromechanical converter (4) and the electromechanical converter (4) has a rotating electrical machine (5) and at least one rotational inertia store (7) with a rotational flywheel mass (8), and in this case the electrical machine (5), the rotational flywheel mass (8) and a further device are connected to one another, the electric machine (5) here is a first rotating electric machine (5) and the further device is a component of the electromechanical converter (4), wherein the device is designed as a further, second rotating electric machine (6) or as a magnetic torque clutch having an adjusting device for influencing a mechanical load coupling of the torque clutch, and the rotational flywheel mass (8) of the rotational inertia accumulator (7) is arranged between the electric machine (5, 6) and the device, and / or the electric machine (5, 6) and the device are connected to one another via the rotational flywheel mass (8) and thus the rotational flywheel mass (8) and in each case one rotor (9, 10, 12) of the electric machines (5, 6) form the rotational inertia accumulator (7).The combination according to claim 1, characterized in that at least one of the electric machines (5, 6) has two rotors (9, 10) designed to be rotatable with respect to one another, so that the electric machine (5, 6) can be operated in a motor mode, in a generator mode and / or in a clutch mode.The composite according to claim 1 or 2, characterized in that only one of the electric machines (5, 6) has a stator (11) and a rotor (12) configured to be rotatable with respect to this stator (11), so that the electric machine (5, 6) can be operated in a motor mode and / or in a generator mode.The combination according to at least one of the preceding claims, characterized in that a rotor (9, 10) of at least one electric machine (5, 6) having two rotors (9, 10) is connected to an output and / or drive element (13) or has an output and / or drive element (13), via which a rotational movement of the rotor (9, 10) can be transmitted.The composite according to at least one of the preceding claims, characterized in that the rotational inertia storage device (7) and / or a rotor (9, 10) of at least one electric machine (5, 6) having two rotors (9, 10) can be fixed in a rotationally fixed manner via a brake device (14) and / or a fixing element (15).The combination according to at least one of the preceding claims, characterized in that the storage power plant (3) has at least one further energy storage device (16), which is connected to the electromechanical converter (4), such that energy can be transmitted between the energy storage device (16) and the rotational inertia storage device (7) of the electromechanical converter (4).The composite according to at least one of the preceding claims, characterized in that the energy storage device (16) has a potentially energetic liquid storage, a hydropneumatic storage and / or a pneumatic storage.Composite according to at least one of the preceding claims, characterized in that the electric machines (5, 6) and the rotational flywheel mass (8) are arranged coaxially with respect to one another.Method for compensating a fluctuating provision of electrical power in the electrical network (1) of the combination, which is caused by the at least one power plant (2), according to at least one of the preceding claims, characterized in that, in load states of the electrical network (1) and / or operating states of the storage power plant (3), a provision of power between the electrical network (1) and the storage power plant (3) takes place via the first electrical machine (5), the second electrical machine (6) or both electrical machines (5, 6) of the electromechanical converter (4) of the storage power plant (3).Method according to Claim 9, characterized in that each of the electric machines (5, 6) is operated via a separate frequency converter (17, 18) in each case connecting the electric machines (5, 6) to the electric network (1).Method according to Claim 9 or 10, characterized in that, as a function of load states of the electrical network (1) and / or operating states of the storage power plant (3), power is provided between the rotational inertia storage device (7) of the electromechanical converter (4) and the further energy storage device (16) via the second electrical machine (6).Method according to at least one of the preceding claims 9 to 11, characterized in that in a load state of the network (1) in which there is an excess of power provided on the network (1) and / or in an operating state of the storage power plant (3) in which there is a high deficiency of energy stored in the storage power plant (3), at least some of the excess energy is transmitted via the first electric machine (5) and the second electric machine (6) into the storage power plant (3).Method according to at least one of the preceding claims 9 to 12, characterised in that in the case of a high deficiency of energy stored in the storage power plant (3) which exists at least partly on account of a standstill or a small rotation of the rotational inertia store (7), at least part of the excess of the power provided to the network (1) or of the energy fed into the network (1) is transmitted exclusively into the rotational inertia store (7) via the first electric machine (5) and the second electric machine (6).Method according to at least one of the preceding claims 9 to 13, characterized in that, in order to provide power between the rotational inertia store (7) of the storage power plant (3) and the electrical network (1), one of the rotors (9, 10) of the second electrical machine (6) is at least temporarily braked and / or established via the second electrical machine (6).Method according to at least one of the preceding claims 9 to 14, characterized in that in a load state of the network (1) in which there is an excess of power provided on the network (1) or of energy fed into the network (1), respectively, and / or in an operating state of the storage power plant (3) in which there is a high amount of energy stored in the storage power plant (3), energy is transmitted from the rotational inertia storage device (7) and / or energy from the network (1) into the further energy storage device (16) via the second electric machine (6).Method according to at least one of the preceding claims 9 to 15, characterized in that in an operating state of the storage power plant (3) in which there is a high deficit of energy stored in the storage power plant (3) via the rotational inertia storage device (7), power is provided between the electrical network (1) and the further energy storage device (16) of the storage power plant (3) via the second electrical machine (6).Method according to at least one of the preceding claims 9 to 16, characterized in that, in order to provide power between the further energy storage device (16) of the storage power plant (3) and the electrical network (1) via the second electrical machine (6), the rotational inertia storage device (7) is at least temporarily braked and / or established.

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