METHOD FOR STABILIZING AN ELECTRIC SUPPLY NETWORK

Description

[0001] The present invention relates to a method and a network control device for stabilizing an electrical supply network.

[0002] Electrical power grids are well-known and typically consist of multiple consumers who draw electrical power from the grid and multiple generators that produce electrical power and feed it into the grid. Such electrical power grids can be large and extensive, transporting power over long distances, sometimes several hundred kilometers or even further.

[0003] In such an energy supply system, stability must always be guaranteed. A balance between generation and load, i.e., consumption, must also be ensured as much as possible at all times. Stability is usually achieved through the design of the equipment and the physical properties of the generators (which can be referred to simply as producers) and the loads (which can also be referred to as consumers). The physical properties of generators can include, for example, their inherent ability to provide an instantaneous reserve, their capacity to impart voltage (i.e., in particular, voltage-imparting feed-in), and their ability to contribute to short-circuit protection.

[0004] In addition to ensuring stability and the desired balance of power output, an energy system should also be economically optimized. This includes operating the power generators and, if applicable, the loads, or some of them, in such a way as to minimize costs while feeding as much power or energy as possible into the electrical grid.

[0005] To operate an electrical supply network stably and as economically as possible, controllers with corresponding tasks can be employed. This may include a power control system designed to manage power balance and / or power flow. This can involve selecting power paths in a meshed electrical supply network or controlling power across different paths to prevent power flow overloads and achieve a more even distribution. The same applies to the injection and consumption of electrical power, which can also be controlled to avoid power peaks.

[0006] Furthermore, an energy control system can be provided for controlling generated energy. Controlling power output pertains to momentary situations and is primarily intended to prevent power surges. Ideally, a smoothing effect is achieved, but this only applies to the immediate moment. An energy control system for controlling generated energy also considers a temporal progression and, in particular, a time period during which the generated energy is controlled. Specifically, an energy control system can be designed to regulate the generated energy in such a way that it meets the energy demand.Energy quantities can be generated and provided, whereby the power control system controls the power, both generated and transported, in such a way that the electrical supply network is loaded as evenly as possible, or at least in such a way that power surges, i.e., power peaks, are avoided or at least remain below specified limits.

[0007] Stability is generally assumed to be an inherent system property, even though different power sources and loads have different influences on stability.

[0008] For example, a conventional power plant, in which an electric synchronous generator is directly coupled to the electrical supply network, can have a different effect in terms of stability than, for example, a wind farm with many modern and therefore large wind turbines, which can potentially feed the same amount of power into the electrical supply network as the aforementioned conventional power plant.

[0009] To achieve a stabilizing effect similar to that of a conventional power plant, solutions exist that require wind farms to have a feed-in behavior similar to that of a conventional power plant with a directly coupled synchronous generator. The same applies to other renewable energy sources, especially photovoltaic systems.

[0010] While some harmonization can be achieved under certain conditions, the physical properties of different generators remain distinct. Not only the physical characteristics of the generator itself can play a role, but also its distribution and / or specific location within the electrical grid. Such unique characteristics cannot be fully addressed, or at least not entirely, simply by partially harmonizing the required behavior of individual generators.

[0011] European patent application EP 2 752 953 A1 concerns a voltage stabilizer or stabilization method in an electrical supply network. This involves an electrical supply network with distributed power sources. These distributed power sources, i.e., feed-in devices, namely PV modules, exhibit fluctuations in their system voltage due to weather-dependent power generation.

[0012] The Chinese disclosure document CN 108281959 A deals fundamentally with the question of how a stable electrical supply network (in China) can be ensured, namely with regard to China's increasing share of renewable energies.

[0013] The German Patent and Trademark Office has searched the following prior art in the priority application for the present application: DE 10 2017 112 944 A1, DE 10 2016 119 422 A1, DE 10 2012 212 364 A1 and DE 10 2017 108 579 A1.

[0014] The present invention is therefore based on the objective of addressing at least one of the aforementioned problems. In particular, a solution is to be proposed that controls the stabilization of an electrical supply network, especially taking into account power control by a power control system and / or taking into account the control of generated energy by an energy control system. At the very least, an alternative to previously known solutions is to be proposed.

[0015] According to the invention, a method according to claim 1 is proposed. Such a method is provided for stabilizing an electrical supply network. Such a supply network has a network voltage and a network frequency. Furthermore, such an electrical supply network comprises several consumers, which can also be referred to as loads, for consuming electrical power from the electrical supply network.

[0016] Furthermore, the electrical supply network comprises several generators for producing electrical power and for feeding electrical power into the electrical supply network. These generators, which can also be referred to as feed-in devices, thus feed in the electrical power that the consumers use.

[0017] The procedure includes a data acquisition step to capture at least one system property that characterizes the stability of the electrical supply network as

[0018] Stability system property of the electrical supply network. This system property is not a system state, specifically neither a frequency nor an electrical voltage of the electrical supply network. A distinction is therefore made here between a system property that fundamentally characterizes the system and can be specifically determined by physical factors, and a system state in the control engineering sense, such as an instantaneous network voltage or frequency. The present method thus captures, in this acquisition step, a system property that characterizes the stability of the electrical supply network and therefore not a system state in the control engineering sense. A system state is also fundamentally unsuitable for characterizing the stability of the electrical supply network.In control engineering terms, a state could at best indicate a current instability, for example, if such a system state were to oscillate. However, this would not be a sign of stability, but rather a suitable indicator of whether the system is currently unstable or not.

[0019] Instead, the stability system property characterizes the system.

[0020] To illustrate this clearly, the eigenvalues ​​of a linear system, by whether and where they lie in the left Laplace plane, indicate the system's stability. To further illustrate, if the system is, for example, a pendulum (assuming linearity for simplicity), two complex conjugate eigenvalues ​​would lie in the left Laplace half-plane. This would be a system property and would indicate stability. The pendulum's current displacement and its current velocity, on the other hand, are each two system states. While such system states, by evaluating their temporal evolution, could be used to identify the system and derive system properties, the system states themselves are not system properties in the control engineering sense.

[0021] To apply this to the electrical supply network, for example, the susceptibility of the electrical supply network to oscillations can be considered a system property, whereas the electrical voltage (i.e., its amplitude) and the network frequency (i.e., the frequency of the electrical voltage in the electrical supply network) are considered system states. While an oscillation tendency could be derived from these through appropriate analysis, the electrical voltage and frequency of the electrical supply network itself are not system properties.

[0022] In this acquisition step, a system property that characterizes the stability of the electrical supply network, such as susceptibility to oscillations, is thus recorded as a stability system property of the electrical supply network.

[0023] Furthermore, a proposal step is provided for suggesting several stabilization measures to modify one of the stability properties at a time. This proposal step is therefore based on the premise that multiple stabilization measures are available to modify one of the stability system properties at a time. These multiple possible stabilization measures are thus identified and proposed in the proposal step.

[0024] For example, to give a simple example, oscillation could result from two directly coupled synchronous generators with the same natural frequency and be recognized as a stability characteristic. Possible stabilization measures, suggested here for illustrative purposes, would be to switch off one synchronous generator, switch off the other synchronous generator, switch off both synchronous generators, disconnect the electrical connection between the two synchronous generators, or implement damping. With damping, various variations would be possible, such as damping the first or the second synchronous generator, and applying different levels of damping to each. Instead of switching them off, which was intended primarily as an illustrative example, reducing the power input would also be an option.

[0025] In any case, such or other stabilization measures will be proposed in this proposal step.

[0026] A selection step is then provided to select one of the proposed stabilization measures. If several stability system properties have been recorded, and several stabilization measures have been proposed in the proposal step, this selection step is considered for each stability system property.

[0027] Finally, the selected stabilization measure is applied or discontinued. Discontinuing a stabilization measure might be considered, for example, if the stabilization measure controls a power flow. While the power flow, or multiple power flows, are always controlled, this control is now being modified. For instance, a higher or lower power flow than before might be controlled. In this case, the corresponding stabilization measure—namely, the modification of the power flow—would be discontinued, or the power flow level would be adjusted.

[0028] Furthermore, it is proposed that the selection, application, and / or adjustment of stabilization measures be dependent on at least one stabilization boundary condition. It was particularly recognized that, due to the existence of multiple possible stabilization measures, at least one additional degree of freedom exists, making it possible to consider a further criterion in addition to stabilization without neglecting the stabilization itself. To facilitate a meaningful selection, stabilization boundary conditions are used as a basis.

[0029] Such stabilization boundary conditions particularly concern criteria for power control and / or criteria for energy control. This allows the selection of the stabilization measure that leads to better or improved power control, for example, to a better power balance and / or power flow.

[0030] Furthermore, or alternatively, the stabilization measure can be selected in such a way as to control the generated energy efficiently. For example, a stabilization measure can be selected to generate as much energy as possible. However, it is also conceivable that an energy control system could, depending on the situation, suggest generating a smaller amount of energy, at least temporarily, in order to protect energy producers, particularly wind turbines, during periods of low energy demand.

[0031] According to the invention, it is proposed that each of the detected stability system properties is derived from at least one generator property that constitutes a property of one of the generators. Furthermore, or alternatively, it is proposed that each of the detected stability system properties is derived from a higher-level network property that forms at least one relationship between several network sections and / or is a property distributed across these network sections.

[0032] One characteristic of a generator is, for example, whether it has a directly coupled synchronous generator, as in a conventional power plant, or feeds into the electrical grid via frequency inverters. A stability system characteristic can then be derived from this. To continue with the examples mentioned, the characteristic of a generator having a directly coupled synchronous generator can indicate the potential for oscillation, but it can also indicate that such a synchronous generator exhibits the known stabilizing properties. Of course, this oscillation potential may depend not only on the single directly coupled synchronous generator, but also on whether there are other such directly coupled synchronous generators and what properties they possess.

[0033] The use of generators that feed into the electrical grid via inverters suggests that they do not initially possess the intrinsic grid-stabilizing properties of a directly coupled synchronous generator, nor do they have a similar natural frequency. However, such generators can also contribute to grid stabilization and, for example, especially if they are wind turbines, provide an instantaneous reserve from the kinetic energy of the turbine's rotor and feed it into the grid via the inverter. The magnitude of this instantaneous reserve can also be a characteristic of the generator, from which one of the assessed stability system properties is derived.

[0034] Furthermore, or alternatively, higher-level network properties can be used to derive one of the recorded stability properties. For example, a higher-level network property could be the transmission capacity of network segments, indicating how much power can be transmitted over that segment. A disconnection or interruption of a network segment can also be such a higher-level network property, indicating the interrelationship between multiple network segments. The property of having many, or at least several, generators distributed across a network segment can collectively form a higher-level network property.

[0035] Higher-level network properties can also be properties of the network sections themselves, in particular properties of the transmission lines and / or transformers, which are thus distributed across these network sections. From this, at least one of the recorded stability properties can be derived. For example, network sensitivity can be such a property distributed across these network sections.

[0036] According to the invention, it is proposed that the generators comprise renewable energy sources that feed into the electrical grid via frequency converters. In particular, wind turbines can be provided as renewable energy sources.

[0037] Furthermore, it is proposed that, in addition to renewable energy sources, conventional generators should also be included, specifically those that feed into the electrical grid without the use of frequency converters. This applies particularly to conventional power plants that feed into the grid using at least one synchronous generator directly coupled to the grid. In this respect, the focus is on an electrical grid that includes both renewable and conventional generators. It is specifically proposed that their interaction and / or their respective contributions to the electrical grid be taken into account.

[0038] In principle, the conventional generators, or at least one of them, can each be a diesel generator. The use of one or more diesel generators is particularly advantageous when the electrical supply network is configured as an island grid, where the network is self-contained and relatively small, meaning that changes in power generation and / or consumption have a significant impact on the network's behavior and stability. An island grid can be defined as a self-contained electrical supply network with a maximum load of less than 1 GW. Diesel generators have the advantage of being able to be switched on and off relatively quickly.

[0039] It is proposed that one stability system property be selected from the following list. Therefore, at least one of the following stability system properties should be considered for inclusion in the proposal step.

[0040] One possible stability system characteristic is a generator type ratio for active power, which defines the ratio of the total active power currently fed into the grid by conventional generators to the total active power currently fed into the grid by renewable energy generators. This ratio thus establishes the relationship between conventional and renewable energy generators, based on their current capacity to feed in active power. In this respect, it can go beyond considering nominal values ​​and also take into account, for example, the current wind and / or solar conditions. From this, the dominance of each generator type can be derived, and from this, its stabilization capacity can be deduced.

[0041] Particularly when one of the two generation types—renewable or conventional—is strongly dominant, this can indicate the stability of the electrical grid. Such an indicator doesn't necessarily mean that the stability is high or low; it can also provide information about the potential impact of specific behaviors on the grid and its stability. Specifically, it can reveal the effect of a particular power flow or a change in power flow. Such dominance can also influence the extent to which a power imbalance or imbalance alters, or even jeopardizes, the stability of the electrical grid. The same applies to the control of generated energy.The control of the generated energy can also have an impact on the behavior of the electrical supply network, and this impact can depend on the ratio of renewable generators to conventional generators.

[0042] A stability system property can also be the generator type ratio for reactive power. Such a generator type ratio for reactive power refers to the ratio of the total reactive power potentially feed-in by conventional generators to the total reactive power potentially feed-in by renewable energy generators. Here, too, effects can occur as explained above regarding the generator type ratio for active power.

[0043] The generator type ratio for reactive power can be particularly relevant for voltage stabilization or voltage regulation. It should be noted that the reactive power that can be generated and fed into the grid from renewable energy sources, especially wind turbines, is less dependent on the actual availability of the primary energy source than the potentially generated active power. In other words, the feed-in reactive power from a wind turbine is less dependent on the prevailing wind conditions than the feed-in active power. Therefore, it is suggested that a distinction be made between a generator type ratio for active power and a generator type ratio for reactive power.

[0044] A generator inertia measure is proposed as a stability system property. Such a generator inertia measure indicates the ratio of energy that can be stored as rotational energy in conventional and renewable energy generators to the power that can be fed into the grid. In particular, an instantaneous reserve can be provided from this rotational energy to temporarily meet power and thus energy demands during a frequency drop. To enable short-term grid support, such a ratio—that is, a relative effective and available inertia—is particularly informative for assessing the potential of such grid support through the provision of instantaneous reserves.

[0045] The generator's inertia measure is essentially a ratio of energy to power, with time as its physical unit. This measure is particularly meaningful because it can also be interpreted as the time for which the inertia could provide the available power. While it's not usually required that this power be supplied through rotational energy, the value is still quite informative. For example, the calculated generator's inertia measure can be multiplied by 10 to obtain the time for which the currently available power could be increased by 10%.

[0046] Apart from that, the generator's inertia value can also be normalized if necessary, e.g., to 1 second. Normalization to 1 second is a preferred, and by no means arbitrary, option. If the generator's inertia value is normalized to 1 second, a value of 1 can be interpreted as a generator's inertia value at which the feed-in power can be exceeded by 10% for 10 seconds. While not a very large value, this would be a solid indicator of instantaneous reserve capability for many situations.

[0047] With such a standardization, generator inertia values ​​of 1 or greater would represent a highly stable system characteristic, at least for this application, whereas smaller values ​​would indicate a less stable system characteristic. In the latter case, the electrical supply network would be more susceptible to network situations requiring an instantaneous reserve for support.

[0048] Furthermore, or alternatively, a momentum energy activation measure is proposed as a stability system property. Such a momentum energy activation measure is a measure of the amount of energy extractable from rotational energy within a predetermined activation time. This momentum energy activation measure can thus be expressed, for example, in MW / s. It was particularly recognized here that a high available rotational energy may not be sufficient on its own to provide an instantaneous reserve if this rotational energy cannot be activated quickly enough.

[0049] This momentum energy activation measure can be calculated, for example, by specifying the predetermined activation time, e.g. 10 seconds, and integrating the additional power that can be fed in for that period, or in the simplest case, multiplying it by the period.

[0050] Such a predetermined activation time is preferably selected with values ​​up to 30 seconds. In particular, it is selected with values ​​up to 10 seconds.

[0051] Furthermore, or alternatively, a support energy activation measure is proposed as a stability system property. Such a support energy activation measure is a measure of the amount of energy that can be activated within a predetermined activation time. In this respect, the support energy activation measure is similar to the momentum energy activation measure. However, the support energy activation measure also includes energies that can be activated in other ways. These include, in particular, energies that can be activated, for example, when a wind turbine leaves a throttled operating mode. Thus, in order to provide such support energy, it can be stipulated that a wind turbine be operated at a lower power output than possible, i.e., at only 90% of its potential power.

[0052] Such support energy, which can be activated through reduced operation, may not be activated as quickly as energy from a flywheel, because in the example of a wind turbine, it must first be accelerated from throttled operation to unthrottled operation by the wind.

[0053] It is also proposed that a predetermined activation time of up to 30 seconds, and in particular up to 10 seconds, be used for the support energy activation measure. Such values ​​are particularly suitable for activating a counter-energy to frequency oscillations.

[0054] Furthermore, or alternatively, it is proposed that a primary control parameter be chosen as a stability system property. Such a primary control parameter refers to a power that can be activated for primary control with respect to a reference power, in particular with respect to a current grid load, which denotes power currently consumed in the electrical supply network, or with respect to the total power that can be fed into the grid by all generators.

[0055] Primary control reserve is a technical term referring to power that must be activated quickly, but which, after activation, must be available for a longer period than the instantaneous reserve. This activatable power, which can thus be called activatable primary control reserve, is therefore set in relation to a reference power, especially in relation to the current grid load. Here, a ratio of activatable primary power to the power consumed is proposed. Alternatively, a ratio to the total power that can be fed into the grid by all consumers can also be used.

[0056] In any case, it was also recognized with regard to the primary control measure that it is particularly meaningful if the activatable primary control power is set in relation to such or other described reference power.

[0057] Alternatively, or in addition, power dynamics can be considered a stability system property. Power dynamics refers to the rate of change of feed-in power relative to the total power that can be fed into the electrical grid. Here, the focus is on how quickly the feed-in power can change, again using a relative value in which this rate of change is related to the total power that can be fed into the electrical grid. Thus, power dynamics is a measure of how quickly the fed-in power can change and therefore a measure of how quickly the system can react to a change in power. This ability to react more or less quickly to changes in power can therefore be a stability system property. In particular, a higher level of stability is generally assumed when the power dynamics is high.

[0058] Furthermore, or alternatively, it is proposed that a control reserve be chosen as a stability system feature. Such a control reserve refers to a power, relative to the total feed-in capacity, that can be additionally fed into the electrical grid within a predetermined activation time. This control reserve can also counteract power fluctuations in the electrical grid, and the effectiveness of this counteracting can be determined from the control reserve itself. A control reserve is a measure of a possible positive power increase that can be sustained, i.e., for a long period such as at least one hour or at least one day, in order to compensate for power plant outages, not just temporary power fluctuations.

[0059] As a further stability system property, an individual settling time is proposed, which defines the time constant of the step response of a generator's frequency tracking system to a frequency step. The individual settling time can thus correspond to a ramp-up time constant. In any case, such an individual settling time can provide information about the inertia of the respective generator. While particularly high inertia can also have a stabilizing effect, it is also desirable for generators to be able to track frequency changes as quickly as possible. The individual settling time could, for example, define the time the generator in question needs to follow the frequency change to within 67%.

[0060] In this respect, the individual settling time, and in particular the consideration of all or many individual settling times together, can constitute a stability system property. It is also possible to consider how much the individual settling times of the generators in the electrical supply network differ from one another; in other words, how large the inertia span of all generators is.

[0061] Furthermore, or alternatively, it is proposed that an overall settling time be chosen as a stability system property, where the overall settling time represents an average of several individual settling times. It is specifically suggested here to record all individual settling times and calculate an average. However, the average can also be obtained from an overall analysis of the system by considering the system response of the entire electrical supply network, or a relevant section thereof.

[0062] To obtain the individual response time and / or the overall response time, it is not absolutely necessary to evaluate a step response by specifying a frequency step. A quasi-excitation can also be achieved by observing the behavior of the electrical supply network in relation to frequency changes over a longer period and evaluating this from a system engineering perspective, for example, through system identification in the context of control engineering.

[0063] One approach proposes selecting or considering available short-circuit power as a stability system property. Available short-circuit power refers to the power that can be fed into the electrical supply network at one or more reference nodes in the event of a short circuit at that node.

[0064] The greater the available short-circuit power, the more stable the electrical grid is considered to be, at least with respect to this reference node. Such a reference node can be, in particular, a grid connection point where a generator, such as a wind farm, feeds into the electrical grid. For example, it may be stipulated that the smaller the available short-circuit power, the more cautiously power control is implemented in that area. This can specifically mean that a stability reserve is chosen to be larger the smaller the available short-circuit power.Such a stability reserve can define an operating point, which may be specifically determined by the active and reactive power supplied to the grid. The stability reserve can also indicate the distance to a critically stable operating point, specifically the nearest critically stable operating point at which stability becomes unstable. Furthermore, the short-circuit power is crucial for the selectivity or tripping behavior of a network protection device. Thus, the short-circuit power is responsible for stable operation after a network fault and its subsequent isolation.

[0065] Furthermore, or alternatively, it is proposed that a voltage stabilization measure be selected or considered as a stability system property. Such a voltage stabilization measure specifies, for all generators, the ratio of power available for voltage stabilization to the total feed-in power. Power available for voltage stabilization is power that can be freely adjusted solely for the purpose of voltage stabilization. In simpler terms, this could also be considered power that can be varied relative to a base load. If this power available for voltage stabilization is small, i.e., if the voltage stabilization measure is small, the electrical supply network may exhibit a stability system property with low stability, and thus be more susceptible to fluctuations. In this case, it can also be proposed to operate the electrical supply network with a high stability reserve.

[0066] According to one embodiment, it is proposed that, in order to detect at least one stability system property, a repeated detection of a total inertia measure is carried out, wherein the total inertia measure indicates a ratio of energy storable as rotational energy in the multiple generators and the multiple consumers to the total power that can be consumed by the multiple consumers.

[0067] Such a total inertial mass measure thus includes all producers and all consumers. If a large amount of energy can be stored as rotational energy, then a large inertial mass is present in the system under consideration, namely the electrical supply network or a section thereof. Such a large inertial mass can therefore have a stabilizing effect.

[0068] It has been recognized that such a stabilizing effect can also be achieved through the inertia of consumers, or rather, that the inertia of consumers can also contribute to this effect. Therefore, it is proposed here to consider this total inertia measure for both producers and consumers together. The focus is less on the absolute values ​​of the inertia; instead, this inertia is related to the total power available for consumption by the consumers. The unit of this total inertia measure is time, and the greater this time, the greater the stabilizing effect can be assumed. This stabilizing effect can then be considered a stability system property.

[0069] Such a total inertia measure essentially characterizes permanent physical properties, particularly the stabilizing physical properties of the electrical supply network, because it relates storable energy to dissipable power, rather than comparing currently stored energy with currently consumed power. Nevertheless, repeated measurement of the total inertia measure is recommended, as such physical properties can also change. In particular, this allows for the detection of changes in the stability of the system that can result from switching generators and / or consumers on and / or off.

[0070] According to one embodiment, it is proposed that each stability system property be derived from a signal behavior of the electrical supply network or a section thereof, where the signal behavior constitutes a transfer behavior between an input variable and a response variable. In particular, power fed into the electrical supply network is proposed as the input variable, and the network frequency or network voltage, dependent on the fed-in power, as the response variable. The resulting network frequency or resulting network voltage is thus the response variable to the power fed into the electrical supply network as the input variable. A change can be considered or specified as the input variable. It is specifically proposed to consider a change in the network frequency or network voltage in response to a change in the fed-in power.The change in the power supplied is then the input variable, and the change in the grid frequency or change in the grid voltage is the response variable.

[0071] It is proposed that particular consideration be given to whether the signal exhibits small-signal, large-signal, or other characteristics. Small-signal behavior is defined as a change in the input variable of less than 10%. Large-signal behavior is defined as a change in the input variable of more than 30%. Other signal characteristics can be assumed for all other ranges.

[0072] It was particularly noted here that the signal behavior is non-linear. To avoid an overall non-linear view of the signal behavior, a differentiated analysis of small-signal and large-signal behavior is proposed. With good approximation and statistical significance, at least according to one embodiment, linear behavior can be assumed for both small-signal and large-signal behavior. The same applies to the remaining signal behavior, which covers the range between 3% and 10% of the change in the input quantity.

[0073] Preferably, however, it is proposed to consider small-signal behavior on the one hand and large-signal behavior on the other and to derive a stability system property from each. While other signal behaviors can also be considered, small-signal behavior and large-signal behavior can each be regarded as characteristic, and a stability system property can be derived from each of these.

[0074] The specific stability system property derived, particularly whether the system is considered stable or unstable, can be determined from empirical data. Such empirical data can be obtained through simulations in which the electrical supply network or the relevant network section is simulated. Alternatively, a correlation with at least one stability system property can be established through long-term network monitoring.

[0075] In particular, the stability of the electrical supply network can be derived from the support behavior of fast-acting generators, especially from the support behavior of wind turbines that feed into the electrical supply network by means of a frequency converter and also carry out support measures via this network.

[0076] If such support behavior is particularly active, with rapid changes in the feed-in being observed, without this being attributable to changes in the prevailing wind in the case of wind turbines, this indicates a rather less stable system.

[0077] If few or no such support measures are observed, a stable state can be assumed, indicating a highly stable system property. This can then be attributed to the small-signal behavior recorded. Such correlations can be recorded and stored multiple times, and conversely, the corresponding stability system property can later be derived from the recorded small-signal or large-signal behavior.

[0078] Preferably, it is proposed to record and store the system states of multiple consumers and / or multiple producers together with stability system properties. Based on this, the corresponding stability system property can then later be derived from the corresponding behavior of the consumers or producers.

[0079] According to one embodiment, it is proposed that a stabilization boundary condition is selected from the following list.

[0080] A stabilization condition can be a measure of power flow, which is a measure of at least one power flow between two or more network sections. It was particularly recognized here that stabilization measures can depend on the magnitude of a power flow between two or more network sections. It was specifically considered that a stabilization measure could involve stopping or changing a power flow, or creating or disconnecting connecting branches that can alter a power flow. Such a stabilization measure is then implemented not only depending on its expected stabilizing effect, but also on whether there are power flows that should be increased or decreased.

[0081] The power flow measure can also indicate power demand and thus be taken into account when selecting stabilization measures. Similarly, loads on network sections can be considered when selecting stabilization measures by taking the power flow measure into account. Any explanations regarding the selection of stabilization measures should also be understood as explanations of how to apply and / or adjust these measures.

[0082] A stabilization boundary condition can also be an equilibrium measure. Such an equilibrium measure is a measure of power equilibrium that describes the ratio between power fed into and consumed in a network section. In particular, a power control system is provided to control the power equilibrium and / or the power flow. This system performs the evaluation of the power equilibrium and outputs the equilibrium measure and / or the power flow measure.

[0083] In particular, a power balance can be assumed when the amount of power generated in a network section equals the amount consumed. Otherwise, power would have to be drawn from or supplied to this network section. Specifically, it is proposed that a stabilization measure be selected, applied, or adjusted in such a way as to achieve the highest possible level of equilibrium, i.e., to minimize the amount of power that needs to be supplied to or withdrawn from a network section.

[0084] Another stabilization boundary condition can be an energy efficiency measure. Such an energy efficiency measure is a measure of generated energy, in particular of generated energy in relation to generateable energy. Preferably, it is proposed here that the generated energy is controlled by means of an energy control system and that the energy control system outputs the energy efficiency measure.

[0085] The less energy is generated relative to the available energy, the lower the energy efficiency rating. This is especially true for renewable energy sources. However, conventional energy sources, particularly conventional power plants, can also operate inefficiently if they only generate a portion of their available energy. This can also be taken into account when selecting stabilization measures. For example, if backup energy is needed, it can be requested from a source that thereby increases its energy efficiency, which can also improve the overall energy efficiency rating.

[0086] According to one embodiment, it is proposed that a stabilization control system be provided for selecting, applying, and / or adjusting at least one of the proposed stabilization measures. Furthermore, it is proposed that a power control system be provided for controlling the power balance and / or the power flow. Likewise, an energy control system is provided for controlling generated energy. Thus, three control systems are proposed here: one for controlling stabilization, one for controlling power, and one for controlling energy. It is proposed that these three control systems operate interdependently, or at least that two of them operate interdependently. In particular, all three operate interdependently.

[0087] It was particularly recognized here that while stabilization measures, which are thus controlled by the proposed stabilization control system, generally take precedence over other control tasks, there are often various possibilities for stabilization. This creates at least one degree of freedom that enables meaningful control of the power balance or power flow and / or meaningful control of the generated energy. To achieve this, these three control systems operate interdependently, and in particular, they preferably work together.

[0088] According to one embodiment, it is proposed that the power control system, and additionally or alternatively the energy control system, determine stabilization boundary conditions. Such stabilization boundary conditions have already been described above and include, in particular, a power flux measure, an equilibrium measure, and an energy efficiency measure.

[0089] The stabilization control system then operates based on this, executing, applying, and / or adjusting stabilization measures according to the stabilization boundary conditions specified by the power control system or the energy control system. In particular, the respective stabilization boundary conditions can be not only individual values ​​but also functions.

[0090] A stabilization measure could, for example, be the disconnection of a connecting line in a delta connection. By disconnecting this line, no more power can flow and no more energy can be transferred through it. In its simplest form, a power flow measure can be expressed as a function, specifying a value when the line is connected and a value when it is connected. The same can apply, for example, to the equilibrium measure.

[0091] The energy efficiency measure can also depend on whether or not this line is disconnected, to continue with this illustrative example. Specifically, the energy efficiency measure can depend on the energy control system recognizing that energy generation must be distributed differently among the existing generators if said line is disconnected. This can change the energy efficiency measure, and these two possibilities for the energy efficiency measure can be represented as a function.

[0092] However, more complex variants are also possible, such as power redistribution between two network sections for stabilization purposes. Such power redistribution can be implemented in a variety of ways within each network section, which can influence the energy efficiency measure. The redistribution can also involve additional network sections, which can then be accounted for using a power flow measure and / or an equilibrium measure. All of this can depend on the extent of the power redistribution. Therefore, power redistribution as a stabilization measure can depend on the boundary conditions, which are also variable, namely the stabilization boundary conditions of the power flow measure, the equilibrium measure, and the energy efficiency measure, as exemplified above.

[0093] As another comprehensive example, the following possible scenario can be assumed:There are two network sections, a first and a second, connected by a dual system with a double line, i.e., by two three-phase AC systems. The first network section carries 10% of the combined load of both systems, and the second carries 90%. Such an uneven distribution can affect stability and was recorded in a data acquisition step as a system property characterizing the stability of the electrical supply network, i.e., as a stability system property. The first network section includes a wind farm and could cover almost the entire network load in both grid areas. The double line would be 100% utilized if the wind farm were feeding in all its power. Two diesel power plants are also present in both the first and second network sections.The energy control system considers the following optimization aspects, which also constitute proposed stabilization boundary conditions, and delivers the following values: • The generation source should be selected with the lowest overall costs, which specifically means avoiding the use of a diesel generator. The energy control system can therefore propose using no diesel generator at all, or using as few diesel generators as possible. Any option in between is also possible. • It is also proposed to supply the most cost-effective source for a specific stabilization measure. Several cost-effective sources can be identified and proposed for this purpose. The power control system attempts to find a suitable generator setup, i.e., to assemble suitable generators, in order to propose possible setpoints for a balanced power supply between generation and consumption.For this purpose, target values ​​can be specified for suitable generators that are capable of achieving at least the necessary power output. Since there will be various generators that can collectively reach this power output, several suggestions can be made. These suggestions can form stabilization measures from which a choice can be made. The stability control system can then select one of the following stabilization measures, taking into account the stabilization boundary conditions mentioned above: • In both network sections, at least a load-dependent level of voltage-impacting feed-in must be specified so that both network sections can compensate if the networks are disconnected. This ensures that a voltage impedance is considered and controlled in both network sections.• The power transfer on the dual system, i.e., the dual line, is set so that it does not exceed 60%, ensuring that in the event of a system failure, the short-term load on the remaining system does not exceed 120%. This measure, or boundary condition, achieves the regulation of power transfer. • In the case of a single fault, it is proposed that the power transfer be quickly reduced to 100%. A measure is proposed to achieve this by reducing the power in the overloaded zone, or network section, and reducing the power in the under-loaded zone. For this to work, the necessary control reserve should be specified for both sections. • It is also proposed to consider a double fault, in which both of the aforementioned lines fail.In this case, the two subsystems are created as island systems, and a control system is proposed that ensures both the oversupplied and undersupplied islands can stabilize. This can be achieved, for example, through load shedding and / or feed-in shedding. It may also be necessary to provide a required control reserve, which can thus also be specified in a so-called emergency operation. Once appropriate settings, especially optimal settings, have been found—that is, once stabilization measures have been selected—a suitable transition path from the current state must be determined or found. This can also be described as a suitable switching path that does not jeopardize stability at any time. For example, the selected stabilization measures could be as follows: In the first network section, the diesel generator is operated at 10% of the network load.▪ In the second grid section, the diesel generator is operated at 30% of the grid load. ▪ The wind farm is operated to supply the remaining 60% of the grid load.

[0094] In particular, it is intended that the stabilization control system provides possible stabilization measures and / or recorded stability system properties, and then the power control system and / or the energy control system determines stabilization boundary conditions for the possible stabilization measures and / or the possible stability system properties.

[0095] The power control system or energy control system can therefore detect potential changes in the electrical supply network based on the proposed stabilization measures or planned stability system characteristics and determine the associated boundary conditions. In particular, it can determine how a power flow measure, an equilibrium measure, an energy efficiency measure, or other stabilization boundary conditions change with regard to these potential changes in the electrical supply network. This can then form the basis for selecting, applying, and / or adjusting stabilization measures. The stabilization control system will therefore select, apply, and / or adjust stabilization measures depending on the determined stabilization boundary conditions.

[0096] According to one embodiment, it is proposed that after a predetermined recalculation time, the power distribution in the electrical supply network is reviewed and, depending on the stability system property, which has been newly determined, the power distribution is replanned and adjusted. This can be achieved, in particular, by having the power control system and / or the energy control system determine stabilization boundary conditions, and then selecting, applying, and / or adjusting the stabilization measures based on these boundary conditions.

[0097] According to this proposal, the power distribution in the electrical supply network will be checked at predetermined intervals, and the stability will be reassessed accordingly. If no changes are found during the power distribution check, the same level of stability can naturally be assumed. However, if changes are found, it is proposed that the power distribution be redesigned and adjusted. The stabilization control system, the power control system, and the energy control system can work together in this process, ensuring that not only is the stability adapted to the newly assessed situation, but that the power and / or energy distribution are also taken into account and adjusted optimally.

[0098] In particular, for the replanning and adjustment of the power distribution, it is proposed that new stabilization boundary conditions be determined and that stabilization measures be selected, implemented, and / or discontinued in light of these stabilization boundary conditions. It is specifically suggested that the stabilization boundary conditions be established first, and then the corresponding stabilization measures selected.

[0099] This makes it particularly important to ensure that regular reassessments are carried out and the electrical supply network can be readjusted. Such stabilization measures can also include structural adjustments, such as disconnecting or connecting network sections, especially connecting lines.

[0100] According to one embodiment, it is proposed that the power control system and / or the energy control system execute planned control changes depending on approval by the stability control system. In this respect, it is proposed here that planned changes in the electrical supply network originate from the power control system and / or the energy control system, and not from the stability control system. In this proposal, the stability control system then assumes the task of verifying whether the planned changes ensure sufficient stability.

[0101] As a precautionary measure, it should be noted that selecting between different stabilization measures depending on stabilization boundary conditions is still a possibility, namely when an additional need for stabilization arises, for example, due to detected changes in the electrical supply network that were not caused by any of the three control systems and that appear to necessitate a stabilization measure. This could include, for example, a large consumer disconnecting from or connecting to the electrical supply network. The same can also apply to a large power plant that, for example, disconnected from or connected to the grid.

[0102] Preferably, the planned control changes originating from the power control system and / or the energy control system are first submitted to the stabilization control system for analysis. Based on these planned control changes, the stabilization control system can then perform at least the detection and selection steps. The planned control change can then be implemented accordingly, if required.

[0103] According to one embodiment, it is proposed that the stabilization control system selects from several stabilization measures one that limits the power flow in the electrical supply network. This can also include limiting the power flow to zero, i.e., interrupting it.

[0104] Depending on the stabilization measure and taking the restriction into account, the power control system then regulates the power flow. In other words, the power control system adapts to the new situation created by the stabilization measure.

[0105] Furthermore, or alternatively, the energy control system regulates the energy flow in the electrical supply network, depending on the stabilization measure and taking the constraints into account. Here too, it is proposed that the energy control system adapts to the new situation created by the stabilization measure.

[0106] According to one embodiment, it is proposed that For a proposed or selected stabilization measure as a new stabilization measure, depending on a previous stabilization measure, a transition process from the previous stabilization measure to the new stabilization measure is determined, whereby the application and / or adjustment of the new stabilization measure is carried out according to the determined transition process, and / or the selection of the new stabilization measure depends on the determined transition process.

[0107] It was recognized here that a particularly strong and / or rapid change in the stabilization measure can jeopardize the system's stability, even if neither the previous nor the new stabilization measure had previously threatened stability. For example, switching a generator and / or consumer on or off can destabilize the system, or at least bring it closer to a stability limit, even if only temporarily. To avoid this, it can be implemented in these examples that generators and / or consumers are not switched on or off abruptly, but rather smoothly, for example, with a predefined edge for increasing or decreasing power. If one generator is switched on and another is switched off, both processes can be coordinated. The same applies to switching consumers on and off. These are examples of transition sequences.

[0108] If it turns out that no suitable transition path can be found, in particular no stable transition path can be found, it is also possible to select another stabilization measure for which a suitable transition path can be found.

[0109] According to the invention, a network control device according to claim 11 is also proposed for stabilizing an electrical supply network having a mains voltage and a mains frequency. The electrical supply network comprises The network control unit comprises several consumers for consuming electrical power from the electrical supply network, and several generators for generating electrical power and feeding the electrical power into the electrical supply network, and the network control unit includes a detection unit for detecting, in a detection step, at least one system property characterizing the stability of the electrical supply network as a stability system property of the electrical supply network, a proposal unit for proposing, in a proposal step, several stabilization measures for changing one of the stability system properties, a selection unit for selecting, in a selection step, at least one of the proposed stabilization measures, each for one of the stability system properties, and applying and / or adjusting the respective selected stabilization measure, wherein the network control unit is prepared tothat the selection, application and / or adjustment of stabilization measures is dependent on at least one stabilization boundary condition.

[0110] The data acquisition device is specifically equipped with one or more communication interfaces to receive and, if necessary, transmit data required to record at least one system characteristic that defines the stability of the electrical supply network. This includes the transmission of data from consumers, producers, and / or control centers of the electrical supply network. Alternatively, or in addition, it can also be used to record measured values ​​from the electrical supply network.

[0111] The suggestion unit and the selection unit can be specifically designed as a process computer or as a corresponding program implemented on a process computer. In this respect, the suggestion unit and the selection unit can also be combined. They can also be integrated with the data acquisition device in a single control unit.

[0112] The network control device is particularly characterized by the fact that it is prepared to execute at least one method according to at least one embodiment described above. In particular, the control unit in which the corresponding method is implemented can be provided for this purpose. The control unit can thus contain the detection device, the suggestion unit, and the selection unit.

[0113] According to one embodiment, it is proposed that at least one of the generators of the electrical supply network is designed as a wind turbine and that this wind turbine is prepared to execute or support at least one stabilization measure. In particular, the wind turbine has an interface for receiving information about the stabilization measure and / or for receiving control commands to execute a stabilization measure or a support measure to assist the stabilization measure. In particular, this wind turbine can be designed as part of the network control system. In particular, it can be connected to the control unit of the network control system via a dedicated communication link, especially a leased line.

[0114] Preferably, the wind turbine or wind farm is designed as a stability control system. In particular, the wind farm can have a wind farm controller that can also function as a stability control system, thus enabling the wind farm to be designed as a stability control system.

[0115] The invention will now be explained in more detail below by way of example embodiments with reference to the accompanying figures. The subject matter of the invention is defined by the independent claims. Fig. 1 shows a wind turbine in a perspective view. Fig. 2 shows a wind farm in a schematic representation. Fig. 3 shows a flowchart of a method according to the invention. Fig. 4 schematically shows a part of an electrical supply network. Fig. 5 shows a simplified network topology to illustrate a further embodiment.

[0116] Figur 1 Figure 1 shows a wind turbine 100 with a tower 102 and a nacelle 104. A rotor 106 with three rotor blades 108 and a spinner 110 is mounted on the nacelle 104. During operation, the wind sets the rotor 106 into rotation, thereby driving a generator in the nacelle 104.

[0117] Figur 2 Figure 112 shows a wind farm with three exemplary wind turbines 100, which can be identical or different. The three wind turbines 100 thus represent, in principle, any number of wind turbines in a wind farm 112. The wind turbines 100 supply their power, namely the generated electricity, via an electrical park grid 114. The currents or power outputs of the individual wind turbines 100 are added together, and a transformer 116 is usually provided to step up the voltage in the park in order to feed it into the supply grid 120 at the feed-in point 118, which is also generally referred to as PCC. Fig. 2 This is only a simplified representation of a wind farm 112, which, for example, does not show a control system, although a control system is of course present. The park network 114 can also be designed differently, for example, by including a transformer at the output of each wind turbine 100, to name just one other example.

[0118] The present invention relates particularly to a method for stabilizing an electrical supply network and a corresponding network control device. In such an electrical supply network, one or more wind turbines, as described in [reference to specific example], are particularly preferably included. Fig. 1 shown and / or one or more wind farms as in Fig. 2 The wind turbines shown are present and feed into the electrical grid. Such wind turbines or wind farms can also contribute to stabilization. In particular, a wind turbine or wind farm can be part of the grid control system or at least connected to one. This allows the wind turbine or wind farm to directly implement or support stabilization measures. The wind turbine or wind farm can also provide information to determine a stability system property. Preferably, it is proposed, especially for any variations, that the grid control system is implemented in a wind turbine and / or in a wind farm, or that the wind turbine or wind farm constitutes the grid control system.

[0119] Fig. 3 Figure 300 schematically illustrates the process according to the invention. Flowchart 300 begins with a data acquisition block 302, in which at least one stability system property of the electrical supply network is recorded. For example, a generator type ratio for active power can be recorded there. This block captures the ratio of the sum of the active power currently feed-in by conventional generators to the sum of the active power currently feed-in by renewable energy generators. The sum of the active power currently feed-in by conventional generators can, for example, be the sum of all rated powers of the conventional generators currently feeding into the electrical supply network. This assumes that conventional generators generally have sufficient energy resources available to feed in up to their rated power if necessary.

[0120] Alternatively, a temporal behavior can also be considered, for example, by taking into account the maximum output to which conventional generators could increase their output within a given time period. Such a period could, for instance, be 10 seconds. In this case, it can then be assumed, for simplification, that the power currently fed into the grid by the conventional generators corresponds to the active power that they could potentially feed into the grid, since conventional generators can hardly change their output significantly in 10 seconds.

[0121] The total active power that can currently be fed into the grid by renewable energy producers takes into account, in particular, how much renewable energy is currently available. This means considering how much solar energy is currently available for photovoltaic systems and how much wind energy is currently available for wind turbines. Naturally, it also considers how many renewable energy producers are currently connected to the electrical grid. In the simplest case, all renewable energy producers connected to the grid feed in their full power. In this simple case, the active power currently fed into the grid by renewable energy producers corresponds to the active power that can currently be fed into the grid by renewable energy producers. However, other scenarios are also possible, e.g.,...Due to regulations, renewable energy producers must feed their power into the electrical grid at a reduced rate, for example, by 10% or 20%, or reduced to 60% or 70% of their total capacity. So, if all renewable energy producers feed their power into the grid at a 10% reduced rate, to give another simple example, the total active power that can currently be fed into the grid by renewable energy producers will be 10% higher than their actual power input.

[0122] Of course, other stability system properties can also be recorded in the recording block 302, either additionally or alternatively, such as a generator flywheel mass measure or a flywheel energy activation measure, to name two further examples.

[0123] In query block 304, based on the recorded stability system property, it is then checked whether a stabilization measure is necessary. If this is not the case, at least one stability system property is recorded again in data acquisition block 302, e.g., continuously or after a predetermined waiting period.

[0124] If query block 304 identifies that a stabilization measure appears necessary, several stabilization measures are proposed in proposal block 306. Such a proposal is based on the respective stability system property identified in data collection block 302. To continue with the example of a generator type ratio for active power being recorded as a stability system property, and finding it to be unfavorable (e.g., too low), it may be advisable to activate conventional generators or increase their power feed-in. However, various specific implementations are possible.

[0125] One stabilization measure, in particular, can be to connect a first conventional generator or increase its power generation and feed-in. Similarly, another alternative or supplementary stabilization measure can consist of connecting a second conventional generator or increasing its power feed-in. The same can be considered for a third, fourth, and further conventional generators. Such conventional generators—that is, the first through fourth or further conventional generators mentioned here as examples—can also be located in different sections of the electrical supply network. Thus, there are many different ways to counteract the identified unfavorable stability system characteristic. Each of these options can be considered a stabilization measure.

[0126] To select which of the possible stabilization measures are chosen, stabilization boundary conditions are identified in boundary condition block 308 and provided to the procedure. Such stabilization boundary conditions can be identified, acquired, and / or provided, in particular, by a power control system and / or an energy control system.

[0127] The power control system, which can also be implemented in a higher-level control system, takes power flows into account. To stick with the example above, namely that the generator ratio for active power is to be changed, the proposed increase in conventionally fed-in power also results in a change in power flows.

[0128] For example, the first conventional generator might be located in a first network section, from which a high power flow already flows into a third network section. The second conventional generator might be located in a second network section, from which only a low power flow flows into the third network section, also mentioned as an example. These two exemplary network flows then constitute stabilization boundary conditions. Considering them might, for example, lead to the conclusion that it is more advantageous to connect the second conventional generator or increase its power feed-in, thereby increasing the power flow from the second network section to the third. Since this power flow was previously low in the assumed example, as indicated by the stabilization boundary condition, such an increase is beneficial.Instead, increasing the power input from the first conventional generator in the first network section could lead to an undesirably high power flow from the first network section to the third network section.

[0129] In combination with this, the energy control system, which can also be implemented in a central control unit, can identify, record, and / or provide one or more energy-related stabilization boundary conditions. Such an energy-related stabilization boundary condition can relate to the criterion of whether there is currently a high energy demand or not. If there is no such demand, an increase in output from a conventional generator can also be used to store excess energy.

[0130] In the example given, additional energy generated by the second generator in the second grid section could be stored, or at least a portion of it, in a storage facility in that same section. This would be one of the many stabilization measures in the illustrative example. However, if there is an energy demand, the additionally generated energy could instead be offered to meet that demand. This would be another possible stabilization measure. Furthermore, improved stability would also result if the additionally generated power were essentially stored immediately, as it would still be available for stabilization when needed, since storage could be stopped or at least reduced immediately if required.

[0131] Thus, depending on these or other stabilization boundary conditions, a selection can be made from the possible stabilization measures. This is done in selection block 310, and the result is a stabilization measure, which is symbolically output as M.

[0132] After selecting or outputting this stabilization measure M, the flowchart 300 branches back to the acquisition block 302 in order to acquire at least one more stability system property and thus check the stability of the electrical supply network.

[0133] Fig. 4 Figure 1 schematically shows a section of an electrical supply network 400 with a first, second, and third network section 410, 420, and 430, respectively. Each network section contains a first, second, and third wind farm 411, 421, and 431, respectively, as well as a first, second, and third photovoltaic system 412, 422, and 432, respectively. These wind farms and photovoltaic systems each constitute a renewable energy generator that can feed power into the electrical supply network 400 or their respective network section, as indicated by a power P with a corresponding arrow.

[0134] Each network section 410, 420, and 430 also has a conventional generator 413, 423, and 433, respectively. These conventional generators can also feed power into the electrical supply network or their network section, which is also indicated by a power P with a corresponding arrow.

[0135] Furthermore, for each network section, one industrial consumer (414, 424, or 434) and one city (415, 425, or 435) are shown as additional consumers. Each industrial consumer and each city draws power from the electrical supply network or its respective network section, which is also indicated by a power value P with a corresponding arrow.

[0136] For each wind farm, photovoltaic plant, conventional power plant, industrial consumer, and city, a disconnect switch S is shown to illustrate that disconnection from the electrical grid is possible. All disconnect switches S in Fig. 4 The open position shown is for clarity only. Ideally, all disconnect switches S can be closed, and normally most disconnect switches S should be closed.

[0137] Furthermore, transformers T with a transmission line L between them (shown as a dashed line) are shown for illustrative purposes. The pairs of transformers T with the transmission line L between them are intended to illustrate the separation between the individual network sections, i.e., the first network section 410, the second network section 420, and the third network section 430. The transmission line L is drawn as a dashed line to indicate that it can bridge a large distance.

[0138] The transformers T are also for illustrative purposes only, and it should be noted that a real electrical supply network contains many more transformers. In particular, a city is not usually connected to the same voltage level as a conventional generator. Such transformers are not shown for the sake of clarity. It is also only for illustrative purposes that not all network sections are structured identically; that is, not every network section has the same type and number of generators and consumers. This, too, is for illustrative purposes only.

[0139] Based on the Fig. 4 The proposed procedure will be explained in detail using an example. For illustrative purposes, it could be assumed, for instance, that all wind farms 411, 421, and 431, as well as all photovoltaic systems 412, 422, and 432, are connected to the electrical grid 400 and feed power into it, whereas no conventional generator is connected to the electrical grid 400. In a data acquisition step where a stability system property is recorded, it could thus be determined that the generator type ratio for active power is zero. From this, it could be deduced that at least one conventional generator should be connected. Based on the illustrative representation of the Fig. 4 Therefore, at least one of the conventional generators 413, 423, or 433 would be suitable. If the proposal step determined that activating one of these conventional generators is sufficient as a stabilization measure, then three stabilization measures are available. Further possible stabilization measures could involve activating two conventional generators instead of just one.

[0140] Assuming that of the three industrial consumers shown (414, 424, and 434), only industrial consumer 424 in the second network section (420) is operational and, for example, is a foundry with a correspondingly high power demand, this can be considered a stabilization boundary condition. Assuming that all three cities (415, 425, and 435) are connected and each consumes a similar amount of power, and that the wind farms and photovoltaic systems also generate similar amounts of power, a power flow would result from the first network section (410) to the second network section (420). Furthermore, a power flow would also result from the third network section (430) to the second network section (420). Considering this power flow, it would therefore be advisable to select the stabilization measure that involves connecting the conventional generator (423) in the second network section (420).This would reduce the power flow from the first network section 410 to the second network section 420, as well as the power flow from the third network section 430 to the second network section 420. According to the stabilization constraint of the power flow, the chosen stabilization measure is therefore to activate the conventional generator 423 of the second network section 420.

[0141] However, alternatively or additionally, energy consumption can also be considered. For example, a situation could arise where the industrial consumer 434 of the third network section 430 is operated at a reduced capacity because, for example, it is a large cooling system that can be temporarily throttled due to its thermal capacity without jeopardizing its cooling target.

[0142] However, such a throttled system still requires more energy when energy is available. This, too, can be a stabilization boundary condition. The consequence of this stabilization boundary condition could be that the conventional generator 433 of the third network section 430 is activated as a stabilization measure. To nevertheless avoid a large power flow from the third network section 430 to the second network section 420, the stabilization measure could be chosen such that both the conventional generator 423 of the second network section 420 and the aforementioned conventional generator 433 of the third network section 430 are activated. Increasing the energy consumption of the industrial consumer 434 of the third network section 430, namely the large cooling system, can also be controlled as a stabilization measure or as part of a stabilization measure.In this way, several stabilization boundary conditions could be taken into account simultaneously, namely both the described power flow as a stabilization boundary condition and the described energy demand as another stabilization boundary condition.

[0143] To carry out this procedure, in particular to determine the stability system properties, to propose several stabilization measures, and to select at least one of the stabilization measures taking into account at least one stabilization boundary condition, a schematically represented network control device 440 is provided. This network control device 440 can be connected via communication links to all wind farms 411, 421, and 431, all photovoltaic plants 412, 422, and 432, all conventional generators 413, 423, and 433, all industrial consumers 414, 424, and 434, and to all cities 415, 425, and 435.

[0144] The network control device may, in particular, include a stability control system 441, which may also be referred to as a stability management system (SMS). The stability control system 441 may, in particular, be designed to record a stability system property, propose several stabilization measures, and / or select at least one stabilization measure depending on stabilization boundary conditions.

[0145] The network control unit 440 can also include a power control system 442, which can also be referred to as a power management system (PMS). Such a power control system 442 is specifically designed to control a power balance and / or a power flow.

[0146] The network control unit 440 can also include an energy control system 443, which can also be referred to as an energy management system (EMS). Such an energy control system 443 is specifically designed for controlling generated energy. It can control generators, particularly in response to demand, to provide energy in order to meet a corresponding demand or to reduce energy generation when the corresponding energy demand has decreased.

[0147] The network control unit 440 also includes a detection unit 445, a suggestion unit 446 and a selection unit 447, which are functionally connected and interact with the stability control system 441, the power control system 442 and the energy control system 443.

[0148] Fig. 5Figure 500 shows a simplified network topology to illustrate another embodiment. It includes a wind farm 502, a photovoltaic system 504, and a consumer 506. The wind farm 502, the photovoltaic system 504, and the consumer 506 also represent other corresponding elements, namely producers and consumers.

[0149] Wind farm 502, photovoltaic plant 504, and consumer 506 are connected to each other via a first, second, and third transmission line 511, 512, and 513. Each of these transmission lines 511, 512, and 513 can be disconnected at two ends by one of six disconnect switches, namely a first to sixth disconnect switch 521 to 526.

[0150] Such a disconnection can be triggered by a current flowing through the corresponding disconnect switch, specifically a short-circuit current, which the switch then trips. If necessary, a correspondingly high short-circuit current can be generated, either by a generator such as wind farm 502 or photovoltaic system 504, or by a consumer such as consumer 506. This allows transmission lines to be selectively disconnected and thus faults on these transmission lines to be isolated.

[0151] As an example, a network fault 530 is indicated on the first transmission line 511. The transmission line 511 can now be disconnected by tripping the first and second disconnect switches 521 and 522, thereby isolating the network fault 530.

[0152] It is now proposed that a network stability characteristic be recorded first. One such characteristic would be whether such a disconnection of transmission line 511 is even possible in the simplified network topology 500. Ensuring this can be considered a stabilization measure. Being able to provide a corresponding short-circuit current, or ensuring a sufficient level of such a short-circuit current, can also be referred to as a short-circuit current measure.

[0153] To trigger the disconnection, short circuits can be generated from different sources and / or different short-circuit currents can be absorbed by different consumers. To illustrate the example of different sources, a short-circuit current, or a portion thereof, can be supplied to the second disconnect switch 522 by the wind farm 502. A portion of the short circuit can also be supplied via the second transmission line 512 by the photovoltaic system 504.

[0154] There are therefore various ways to compose the required short-circuit current, and each of these possibilities can be seen as a stabilization measure from which a choice can be made.

[0155] The selection of how the short-circuit current is composed depends on stabilization boundary conditions. One stabilization boundary condition is that wind farm 502 is not overloaded, which is a generation characteristic in this respect, and can then continue to feed power into the grid stably. Another stabilization boundary condition is to transmit as little power as possible, or at least not too much, via the second transmission line 512, which can be a higher-level grid characteristic, at least if wind farm 502, photovoltaic plant 504, and consumer 506 each represent a grid section, each connected by one of the three transmission lines 511, 512, and 513.

[0156] To control all of this, the stabilization controller 532 is provided, which can be connected to the wind farm 502, the photovoltaic system 504, and the consumer 506. However, it is also possible, for example, that the stabilization controller 532 is part of the wind farm 502, specifically part of a suggested central park control system 534 of the wind farm 502.

Claims

1. Method for stabilizing an electrical supply network (400) having a network voltage and a network frequency, and the electrical supply network (400) comprises - multiple consumers (414, 415) for consuming electrical power from the electrical supply network (400), and - multiple generators (411, 412, 413) for generating electrical power and for feeding the electrical power into the electrical supply network (400), and the method comprises the steps of - detecting, in a detection step (302), at least one system property characterizing a stability of the electrical supply network as the stability system property of the electric supply network (400), - proposing, in a proposal step (306), multiple stabilization measures for changing one of the stability system properties in each case, - selecting, in a selection step (310), at least one of the proposed stabilization measures, in each case for one of the stability system properties, and applying and / or setting the respectively selected stabilization measure, wherein - the stabilization measures are selected, applied and / or set on the basis of at least one stabilization boundary condition (308), wherein one of the detected stability system properties is derived in each case - from at least one generator property that forms a property of one of the generators (411, 412, 413), and / or - from a superordinate network property that forms at least one connection between multiple network sections (410, 420, 430) and / or a property distributed over these network sections, wherein the generators (411, 412, 413) - include regenerative generators (411, 412), which feed into the electrical supply network (400) by way of frequency converters, in particular wind power installations or wind farms (411), and - conventional generators (413), which feed into the electrical supply network (400) without using frequency converters, and a respective stability system property is selected from the list comprising: - a generator type ratio for active power (P), which refers to a ratio of the sum of the active power currently able to be fed in by conventional generators (413) to the sum of the active power (P) currently able to be fed in by the regenerative generators (411, 412), - a generator type ratio for reactive power (Q), which refers to a ratio of the sum of the reactive power (Q) potentially able to be fed in by the conventional generators (413) to the sum of the reactive power (Q) potentially able to be fed in by the regenerative generators (411, 412), - a generator flywheel mass measure, which indicates a ratio of energy (E) able to be stored as rotational energy in the conventional generators (413) and regenerative generators (411, 412) to power (P) able to be fed in, - a flywheel energy activation measure, which refers to a measure of an amount of energy (E) able to be drawn from rotational energy in a predetermined activation time, - a support energy activation measure, which refers to a measure of an amount of energy (E) able to be activated in a predetermined activation time (T), - a primary control measure, which refers to a power (P) able to be activated for primary control in relation to a reference power (P), in particular in relation to a current network load, which refers to power (P) currently consumed in the electrical supply network (400), or in relation to the total power able to be fed in by all generators (411, 412, 413), - a power dynamic, which refers to a rate of change of power (P) able to be fed in in relation to the total power (P) able to be fed into the electrical supply network (400), - a control reserve, which refers to a power (P) related to the total power (P) able to be fed in and is additionally able to be fed into the electrical supply network (400) within a predetermined activation time, - an individual rise time, which refers to a time constant of a jump response of a frequency tracking system of a generator (411, 412, 413) to a frequency jump, - a total rise time, which refers to an average of multiple individual rise times, - an available short-circuit power, which refers to a power (P) able to be fed into the electrical supply network (120, 400) at a reference network node (118), or at multiple reference network nodes (118), in the event of a short-circuit at that one reference network node (118) or multiple reference network nodes (118), and - a voltage stabilization measure, which, for all generators (411, 412, 413), indicates a ratio of power available for voltage stabilization to the total power able to be fed in.

2. Method according to Claim 1, characterized in that to detect the at least one stability system property a total flywheel mass measure is repeatedly detected, wherein the total flywheel mass measure indicates a ratio of energy (E) able to be stored as rotational energy in the multiple generators (411, 412, 413) and the multiple consumers (414, 415) to total power (P) able to be consumed by the multiple consumers (414, 415).

3. Method according to either of Claims 1 and 2, characterized in that a stability system property is derived in each case - from a signal behaviour of the electrical supply network (400) or a subsection (410, 420, 430) thereof, wherein the signal behaviour forms a transmission behaviour between - an input variable, in particular power (P) fed into the electrical supply network, and - a response variable, in particular the network frequency (f) or network voltage (U) dependent on the power (P) fed in, taking into account in particular whether - a small-signal behaviour, a large-signal behaviour or another signal behaviour is present, wherein - the signal behaviour is referred to as small-signal behaviour when the input variable changes by less than 3%, and - the signal behaviour is referred to as large-signal behaviour when the input variable changes by more than 10%.

4. Method according to any one of the preceding claims, characterized in that a respective stabilization boundary condition is selected from the list comprising: - a power flow measure, which is a measure of at least one power flow flowing between two or more network sections (410, 420, 430), - a balance measure, which is a measure of a power balance describing a ratio between the power fed in and the power consumed in a network section (410, 420, 430), and wherein in particular - a power control system (442) is provided for controlling the power balance and / or the power flow and the power control system (442) evaluates the power balance and outputs the balance measure and / or the power flow measure, - an energy efficiency measure, which is a measure of generated energy, in particular generated energy in relation to energy that can be generated, in particular the generated energy being controlled by means of an energy control system (443) and the energy control system (443) outputting the energy efficiency measure.

5. Method according to any one of the preceding claims, characterized in that - a stabilization control system (441, SMS) is provided to select, apply and / or set in each case at least one of the proposed stabilization measures, - a power control system (442, PMS) is provided to control a or the power balance and / or a or the power flow, and - an energy control system (443, EMS) is provided to control generated energy, wherein - the stabilization control system (441), the power control system (442) and / or the energy control system (443) operate in a manner dependent on one another.

6. Method according to Claim 5, characterized in that - the power control system (442, PMS) and / or the energy control system (443, EMS) determine stabilization boundary conditions and - the stabilization control system (441, SMS) selects, applies and / or sets the stabilization measures depending on the stabilization boundary conditions specified by the power control system (442) or the energy control system (443), in particular in that - the stabilization control system (441, SMS) provides possible stabilization measures and / or detected stability system properties and - the power control system (442, PMS) and / or the energy control system (443, EMS)determine stabilization boundary conditions for the possible stabilization measures and / or the possible stability system properties and - the stabilization control system (441, SMS) selects, applies and / or sets stabilization measures depending on the stabilization boundary conditions determined.

7. Method according to any one of the preceding claims, characterized in that, after a predeterminable recalculation time, - a power distribution in the electrical supply network (400) is checked and, - depending on the stability system property, which has been redetected in particular, - the power distribution is replanned and set, in particular in such a way that - a or the power control system (442, PMS) and / or a or the energy control system (443, EMS) determine stabilization boundary conditions and - a or the stabilization control system (441, SMS) selects, applies and / or sets the stabilization measures depending on the stabilization boundary conditions specified by the power control system (442) or the energy control system (443).

8. Method according to any one of the preceding claims, characterized in that - a or the power control system (442, PMS) and / or a or the energy control system (443, EMS) carry out planned control changes depending on a release by the stability control system (441, SMS), wherein provision is made in particular that - such planned control changes are given to the stabilization control system (441, SMS) for analysis, and - the stabilization control system (441, SMS), if necessary, performs at least the detection step (302) and the selection step (310) based on the planned control changes.

9. Method according to any one of the preceding claims, characterized in that - a or the stabilization control system (441, SMS) selects one stabilization measure from multiple stabilization measures that restricts a power flow (P) in the electrical supply network (400), - a or the power control system (442, PMS) controls the power flow (P) depending on the stabilization measure, taking into account the restriction and / or - a or the energy control system (443, EMS) controls an energy flow in the electrical supply network (400) depending on the stabilization measure, taking into account the restriction.

10. Method according to any one of the preceding claims, characterized in that - a transition curve from the previous stabilization measure to the new stabilization measure is determined for a proposed or selected stabilization measure as the new stabilization measure depending on a previous stabilization measure, wherein - the new stabilization measure is applied and / or set according to the determined transition curve, and / or - the selection of the new stabilization measure depends on the determined transition curve.

11. Network control device (440) for stabilizing an electrical supply network (400) having a network voltage (U) and a network frequency (f), and the electrical supply network (400) comprises - multiple consumers (414, 415) for consuming electrical power (P) from the electrical supply network (400), and - multiple generators (411, 412, 413) for generating electrical power (P) and for feeding the electrical power (P) into the electrical supply network (400), and the network control device (440) comprises - a detection device (445) for detecting, in a detection step (302), at least one system property characterizing a stability of the electrical supply network (400) as the stability system property of the electric supply network, - a proposal unit (446) for proposing, in a proposal step (306), multiple stabilization measures for changing one of the stability system properties in each case, - a selection unit (447) for selecting, in a selection step (310), at least one of the proposed stabilization measures, in each case for one of the stability system properties, and applying and / or setting the respectively selected stabilization measure, wherein - the network control device (440) is prepared to select, apply and / or set the stabilization measures on the basis of at least one stabilization boundary condition, wherein one of the detected stability system properties is derived in each case - from at least one generator property that forms a property of one of the generators (411, 412, 413), and / or - from a superordinate network property that forms at least one connection between multiple network sections (410, 420, 430) and / or a property distributed over these network sections, and wherein the generators (411, 412, 413) - include regenerative generators (411, 412), which feed into the electrical supply network (400) by way of frequency converters, in particular wind power installations or wind farms (411), and - conventional generators (413), which feed into the electrical supply network (400) without using frequency converters, and a respective stability system property is selected from the list comprising: - a generator type ratio for active power (P), which refers to a ratio of the sum of the active power currently able to be fed in by conventional generators (413) to the sum of the active power (P) currently able to be fed in by the regenerative generators (411, 412), - a generator type ratio for reactive power (Q), which refers to a ratio of the sum of the reactive power (Q) potentially able to be fed in by the conventional generators (413) to the sum of the reactive power (Q) potentially able to be fed in by the regenerative generators (411, 412), - a generator flywheel mass measure, which indicates a ratio of energy (E) able to be stored as rotational energy in the conventional generators (413) and regenerative generators (411, 412) to power (P) able to be fed in, - a flywheel energy activation measure, which refers to a measure of an amount of energy (E) able to be drawn from rotational energy in a predetermined activation time, - a support energy activation measure, which refers to a measure of an amount of energy (E) able to be activated in a predetermined activation time (T), - a primary control measure, which refers to a power (P) able to be activated for primary control in relation to a reference power (P), in particular in relation to a current network load, which refers to power (P) currently consumed in the electrical supply network (400), or in relation to the total power able to be fed in by all generators (411, 412, 413), - a power dynamic, which refers to a rate of change of power (P) able to be fed in in relation to the total power (P) able to be fed into the electrical supply network (400), - a control reserve, which refers to a power (P) related to the total power (P) able to be fed in and is additionally able to be fed into the electrical supply network (400) within a predetermined activation time, - an individual rise time, which refers to a time constant of a jump response of a frequency tracking system of a generator (411, 412, 413) to a frequency jump, - a total rise time, which refers to an average of multiple individual rise times, - an available short-circuit power, which refers to a power (P) able to be fed into the electrical supply network (120, 400) at a reference network node (118), or at multiple reference network nodes (118), in the event of a short-circuit at that one reference network node (118) or multiple reference network nodes (118), and - a voltage stabilization measure, which, for all generators (411, 412, 413), indicates a ratio of power available for voltage stabilization to the total power able to be fed in.

12. Network control device (440) according to Claim 11, characterized in that the network control device (440) is prepared to carry out a method according to any one of Claims 1 to 10, in particular in that a control unit (440) is provided for this purpose, wherein the detection device (445), the proposal unit (446) and the selection unit (447) are preferably included in the control unit (440).

13. Network control device (440) according to Claim 11 or 12, characterized in that - at least one of the generators (411, 412, 413) is in the form of a wind power installation or wind farm (411), and - the wind power installation or wind farm (411) is prepared to carry out or support at least one stabilization measure, wherein in particular - the wind power installation or wind farm (411) is formed as part of the network control device (440), and / or - the wind power installation or wind farm is in the form of a stability control system.