Classifications

• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
  • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
  • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
  • H02J3/381—Dispersed generators
• • G—PHYSICS
  • G05—CONTROLLING; REGULATING
  • G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
  • G05B19/00—Programme-control systems
  • G05B19/02—Programme-control systems electric
  • G05B19/04—Programme control other than numerical control, i.e. in sequence controllers or logic controllers
  • G05B19/042—Programme control other than numerical control, i.e. in sequence controllers or logic controllers using digital processors
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
  • H02J13/00—Circuit arrangements for providing remote indication of network conditions, e.g. an instantaneous record of the open or closed condition of each circuitbreaker in the network; Circuit arrangements for providing remote control of switching means in a power distribution network, e.g. switching in and out of current consumers by using a pulse code signal carried by the network
  • H02J13/00002—Circuit arrangements for providing remote indication of network conditions, e.g. an instantaneous record of the open or closed condition of each circuitbreaker in the network; Circuit arrangements for providing remote control of switching means in a power distribution network, e.g. switching in and out of current consumers by using a pulse code signal carried by the network characterised by monitoring
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
  • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
  • H02J3/18—Arrangements for adjusting, eliminating or compensating reactive power in networks
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
  • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
  • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
  • H02J3/40—Synchronising a generator for connection to a network or to another generator
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
  • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
  • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
  • H02J3/46—Controlling of the sharing of output between the generators, converters, or transformers
  • H02J3/48—Controlling the sharing of the in-phase component
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
  • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
  • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
  • H02J3/46—Controlling of the sharing of output between the generators, converters, or transformers
  • H02J3/50—Controlling the sharing of the out-of-phase component
• • G—PHYSICS
  • G05—CONTROLLING; REGULATING
  • G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
  • G05B2219/00—Program-control systems
  • G05B2219/20—Pc systems
  • G05B2219/26—Pc applications
  • G05B2219/2619—Wind turbines
• • G—PHYSICS
  • G05—CONTROLLING; REGULATING
  • G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
  • G05B2219/00—Program-control systems
  • G05B2219/20—Pc systems
  • G05B2219/26—Pc applications
  • G05B2219/2639—Energy management, use maximum of cheap power, keep peak load low
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
  • H02J2300/00—Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation
  • H02J2300/10—The dispersed energy generation being of fossil origin, e.g. diesel generators
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
  • H02J2300/00—Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation
  • H02J2300/20—The dispersed energy generation being of renewable origin
  • H02J2300/22—The renewable source being solar energy
  • H02J2300/24—The renewable source being solar energy of photovoltaic origin
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
  • H02J2300/00—Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation
  • H02J2300/20—The dispersed energy generation being of renewable origin
  • H02J2300/28—The renewable source being wind energy
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E10/00—Energy generation through renewable energy sources
  • Y02E10/50—Photovoltaic [PV] energy
  • Y02E10/56—Power conversion systems, e.g. maximum power point trackers
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E10/00—Energy generation through renewable energy sources
  • Y02E10/70—Wind energy
  • Y02E10/72—Wind turbines with rotation axis in wind direction
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E10/00—Energy generation through renewable energy sources
  • Y02E10/70—Wind energy
  • Y02E10/76—Power conversion electric or electronic aspects

Definitions

• the present invention relates to a method for exchanging electrical power with an electrical supply network.
• the present invention relates to a method for exchanging electrical power between a wind turbine or a wind park with an electrical supply network.
• the present invention relates to a corresponding wind turbine or a corresponding wind park.
• the exchange of electrical power relates to the feeding of electrical power, but since particularly reactive power can not only be fed in, but also removed, depending on the situation, there is thus also a method or a device for exchanging electrical power. In principle, however, active power can also be taken from the electrical supply network.
• these generators which have a large moment of inertia, can specify a comparatively stable network frequency. But if a voltage dip occurs in the network, namely in the case of a network error, these directly coupled synchronous generators can thereby vibrate, especially by further feedback with the electrical supply network. In particular, such a voltage dip can result in a phase jump. After the voltage dip, the mean pole wheel angle can lead, because the machine, ie the synchronous generator, could not deliver full active power to the grid during the voltage dip. In principle, however, other errors can lead to such or other undesired excitation of the directly coupled synchronous generators.
• Such directly coupled synchronous generators which can also be referred to as synchronous machines, can also be set in vibration by a sudden parallel active power feed, since the operating characteristic of the synchronous generator changes suddenly in accordance with such a sudden parallel active power feed. If such an energy surplus to the synchronous generator is not removed quickly enough, the synchronous generator may not be able to return to its normal operating state or not quickly enough. There is also the danger that the various vibration excitations mentioned overlap so strongly that they cause the synchronous generator to lose their way.
• Such a behavior of a synchronous generator or a plurality of synchronous generators directly coupled to the electrical supply network is also noticeable in the network, for example as frequency oscillations.
• an external stepping device of the synchronous generator can also lead to a collapse of the electrical supply network, if this can not absorb enough other producers in the electrical supply network.
• decentralized producers such as wind turbines.
• Such decentralized generators that feed into the electrical supply network by means of a frequency converter can usually immediately respond to network problems and, for example, at a drop in frequency immediately, at least for a short time in the electrical Ver - Adjust the power supplied to the grid.
• decentralized generators for which wind energy plants are hereinafter referred to as representative, can achieve rapid grid support.
• grid support can be all the more effective, the more wind turbines or other decentralized generators feed into the electrical grid.
• German Patent and Trademark Office has in the priority application for the present PCT application the following state of the art research: DE 10 2016 115 431 A1 and Fu, Y. et al. "Damping control of PMSG-based wind turbines for power system stability enhancement" In: 2nd I ET Renewable Power Generation Conference (RPG 2013), Beijing, 2013.
• the present invention is therefore based on the object, at least one of the o.g. To address problems.
• a solution should be created in which a vibration excitation of a synchronous generator, especially after a network failure, is avoided or even reduced in their occurrence or additionally reduced.
• At least should be proposed to previously known solutions an alternative solution.
• a method according to claim 1 is proposed. This method relates to a method for exchanging electrical power with an electrical supply network having a grid frequency, by means of a converter-controlled generating unit, in particular a wind turbine, at a grid connection point.
• an inverter-controlled generating unit can be synonymously also referred to as a converter-controlled generating unit or converter-controlled feeder.
• the converter-controlled generating unit which can be designed as a wind energy plant, or as a wind park, thus exchanging power with the electrical supply network.
• This exchange initially takes place in such a way that the electrical power is exchanged as a function of a control function, wherein the electrical power can include effective and reactive power.
• the control function controls the power as a function of at least one state variable of the electrical supply network.
• the power is controlled as a function of a mains voltage and / or a mains frequency.
• the mains voltage or the mains frequency thus each form a possible state variable.
• the active power is controlled as a function of a mains frequency and the reactive power as a function of a mains voltage.
• As a control function it is possible to switch between a normal control function and a support control function different from the normal control function. There are thus different control functions available, especially a normal control function and a support control functions.
• the support control function may in turn be variable and / or be selected depending on demand from various potential support control functions.
• the normal control function is used when it has been detected that the electrical supply network is stable. This usually applies to the normal case in which, in particular, there is no network fault or no network fault. Small deviations especially of the mains voltage from a nominal value for the mains voltage as well as the mains frequency from a rated value of the mains frequency can occur without a network fault being assumed.
• the normal function also controls dependent on these values, so that this normal control function also adjusts to at least minor changes. However, if a network error or an end of such a network error has been detected, the backup control function is used.
• this fed-in power controls such that a vibration in the electrical supply network can be counteracted, that is, an oscillation is counteracted.
• a support control function is provided, which can counteract a vibration of a synchronous generator connected in the electrical supply network or an oscillation caused by the synchronous generator.
• the proposed method is based in particular on the idea that a network error or the end of a network error can trigger a vibration in the electrical supply network. This can be caused in particular by one or more synchronous generators connected directly to the electrical supply network.
• the support control function is proposed, already to such a situation, namely adapted to the network error or its end, while at the same time being prepared for a situation in which the said oscillations are to be expected. Namely, by using this backup control function, pre-set parameters and / or characteristics can be selected for such a situation. These preset parameters or characteristics are provided by the proposed support control function and this then only needs to be used in the event of a network error or at the end of the network error.
• Such preset parameters are particularly concerned with slope healing of ramps or partial ramps with which a reactive power and / or an active power can be increased again after the fault. This can also be done gradually.
• this mentioned startup of active power and reactive power can be coordinated with each other.
• this support control function can be used to accelerate one of the two powers of active power and reactive power faster.
• the backup control function may also include a delay with a defined ramp.
• a power return through the wind parks, or a wind park can be performed while the synchronous machine is in a process of re-swinging to a large pole wheel angle, which begins immediately after reaching the lower vertex.
• the machine accelerates not only according to their energy stored in the magnetic field, but is additionally bumped by the return of power of at least one wind parks in this direction.
• the problems of both types explained can be particularly met with a ramp. But it is important to set the ramp in a correct way. In particular, it is proposed that the ramp begins either immediately after the voltage returns, or first waits for a whole oscillation period. It is proposed to perform the power increase only during the swing back to the smaller rotor angle.
• the post-fault behavior here denotes a voltage return at the grid connection point after a significant voltage dip at the grid connection point.
• a significant voltage dip is a break in the grid voltage by at least 50%, based on the rated network voltage and / or based on the mains voltage before the voltage dip.
• the network error as such does not necessarily require the use of a support control function, if necessary to take into account according to their own specifications.
• a so-called. Error sou Kunststoffn stand in the foreground. If the error, that is, this voltage dip, für Kunststofft, it is then particularly important to go back to a stable, then as normal as possible operating point. In particular, in case of using a wind turbine, it is also important to bring it back to an operating point where it stably feeds the power available from the wind.
• the path from the end of the network error to this at least stable operating point can be referred to here as the Nach110 .
• the then used support control function is designed.
• the support control function is designed to counteract an oscillation which is caused by a reaction of at least one synchronous generator coupled directly to the electrical supply network to the network error or the end of the network error.
• This embodiment is particularly focused on that a synchronous generator coupled directly to the electrical supply network responds to the mains fault or the end of the mains fault with a vibration.
• the support control function is designed and it can thereby counteract such oscillation when the support control function is used.
• the support control function is selectable.
• Each stored default function thus forms a support control function and in this sense, any default function can be adapted as a support control function to special circumstances.
• one of the stored default functions is then selected and the selected default function then forms the support control function to be used.
• This selection can also be made before the network fault occurs. It can be selected before the occurrence of a network error thus from several stored default functions one in the moment seems appropriate support control function. If no network error then occurs, the selected support control function will not be used in this respect and it may be that then, before so, at all, a network error a new situation makes a different default function seem advisable as a backup control function. It is then again selected another support control function.
• a support control function selected from a number of default functions is available and can be used immediately in the event of a network error or at the end of the network error. In principle, however, also comes into consideration that when the network error occurs or at the end of the network error in the first selection of the support control function is performed from the default functions. However, it is often advisable to select the backup control function at an early stage so that no time is lost in the event of a network error or its end by selecting the backup control function.
• the selection of the support control function does not take place as a function of specific properties of the network error, but depends on properties of the electrical supply network.
• properties describe the electrical supply network as such and can be distinguished from states such as mains voltage or mains frequency.
• Such properties of the electrical supply network are usually longer term and therefore allow selection of the support control function as a precautionary selection.
• a network sensitivity or short-circuit current ratio at the grid connection point describes the ratio of a voltage change in response to a change in the injected power at the grid connection point.
• a short-circuit current ratio describes the ratio of a short-circuit current available from the electrical supply network at a grid connection point of a feeder to the rated power of the feeder.
• the selection of the support control function takes place as a function of a selection signal received externally.
• an operator of the electrical supply network which is referred to simplifying as a network operator, can thereby influence the selection of the support control function, in particular concretely pretend or demand. This is based in particular on the idea that the network operator knows the concrete situation, ie the specific property of his electrical supply network well and therefore by specifying the desired support control function can also specify a behavior for the error or post-fault case.
• the default functions are stored, they can be selected by a very simple signal: So if, for example, four default functions deposited from which the support control function can be selected, the network operator, illustratively and exemplary spoken, the selection by a simple 2 Make a bit signal. Accordingly becomes requires a low bandwidth, which also allows regularly to implement a higher security standard.
• the selection of the support control function takes place as a function of topology information or topology properties of the electrical supply network.
• the electrical supply network can be identified to a good degree with respect to its current properties.
• Such topology information may be one or more switch positions in the electrical utility grid.
• switch positions of power disconnectors which are provided for disconnecting or connecting network sections of the electrical supply network.
• switches or their switch positions can be detected, which type of consumers and what kind of producers are connected to the network section, is fed into the.
• an open power disconnect switch mean that a synchronous generator coupled directly to the electrical supply network is not coupled to the network section in which it is fed, because this open power disconnect switch is in between.
• a support control function that is not geared to this directly coupled synchronous generator, because this is not accessible at this moment for this support control function. Accordingly, another support control function can be selected again when said power disconnect switch is closed again. Then it is advisable that the support control function takes into account the now relevant directly coupled synchronous generator in its behavior.
• the topology information may include information about connected generator units.
• information on types of generator units which dominate the electrical supply network namely in particular information about synchronous generators directly coupled to the electrical supply network.
• Especially large power plants are so far dominant types of generator units and these also have correspondingly large coupled directly to the electrical supply grid synchronous generators.
• Especially such large synchronous generators coupled directly to the electrical supply network may be the cause of oscillation following a network fault. Accordingly, it is proposed to consider this information as topology information and to select dependent on the support control function. According to one embodiment, it is alternatively or additionally proposed that the selection of the support control function takes place as a function of an evaluation result of a predetermined evaluation logic.
• Such evaluation logic can take into account, for example, said switch positions. For example. can be excluded depending on the switch position of a first switch, a group of default functions as a support control function and come to another shortlist. Depending on further information, for example on connected generator units, a smaller group or already the concrete predefined function can then be selected from the group that is in the shortlist.
• the support control function is adjustable. This also allows the support control function to be adapted to corresponding conditions.
• the backup control function By setting the backup control function, what has been described above in connection with selecting a backup control function from a plurality of default functions can be achieved. By setting there are basically more options for the settings or more degrees of freedom than when selecting from several default functions.
• this advantage is paid for by the fact that setting in the implementation can also be more complex and, if necessary, a selection from a plurality of predefined functions can be more distinct and better reproducible.
• the support control function can be set externally via a data interface.
• the possibility is created here that a network operator can set the backup control function.
• the backup control function be transmitted externally.
• the selection of the support control function can thus take place in that the support control function to be selected is transmitted externally.
• a support function which in his view is meaningful can be selected and then transmitted for use.
• the use only takes place when a network error or the end of a network error occurs.
• the setting of the support control function preferably takes place in that parameters of the support function are set.
• parameters of the support function are set.
• Such parameters are, in particular, an increase in a reactive power ramp and / or a slope of an active power ramp, which respectively indicates how strongly the active power or reactive power increases after the network fault or the end of the network fault.
• the parameters may also each specify the beginning of a ramp, particularly related to the end of the network error.
• the setting of the backup control function is preferably performed depending on topology information.
• the explanations given in this context for selecting a support control function from a predefined function as a function of topology information are to be applied analogously here as well.
• a converter penetration is determined.
• Inverter penetration is a measure of the fraction of power supplied by converter controlled feeders to power fed through synchronous machines coupled directly to the electrical supply network.
• these two different feeders can also differ significantly in their behavior.
• an increase in regenerative energy producers and thus energy feeders increases the proportion of such feeders which feed into the electrical supply network through converters.
• a controlled by a converter feeder is particularly a wind turbine or even a wind park, wherein the feed is carried out by means of at least one inverter, so a frequency inverter, which feeds the power directly, in particular by specifying a current signal by frequency and phase, or a voltage signal , It is also contemplated that such a converter does not or only partially fed directly into the electrical supply network, but, at least in part, feeds power in that it controls a so-called. Double-fed asynchronous machine.
• converter-controlled feeders of directly coupled to the electrical supply network synchronous machines differ in that they can respond very quickly and very flexible and in particular can be well controlled by a microprocessor and thereby very closely adapt their feed signal to specifications.
• the characteristic of the feeder depends on synchronous generators coupled directly to the electrical supply network also significantly from their physical properties. Directly coupled synchronous generators are more likely to oscillate or are more difficult to influence by a controller than is the case with inverter-controlled feeders. Also initially described and later described reaction characteristics of directly coupled synchronous generators for network faults or their end do not occur in inverter-controlled feeders.
• inverter penetration can be a significant feature of the electrical supply network, which also has an effect on fault behavior or after-fault behavior, and precisely this can be taken into account by means of appropriately adapted auxiliary control functions.
• the converter penetration may refer to the electrical supply network, is fed into, or it may relate to a subsection of the electrical supply network, or it may also refer to a near the network connection point, is fed into the defined short-range.
• the consideration of a converter penetration for example, in a section of the European interconnected network may be useful.
• the European interconnector network to use this example, is very large and a converter-controlled feeder, for example, fed in Denmark, will often have little influence on a behavior in Spain, but at the same time a Umrichter carefullydringung can influence regionally.
• a vibration process which is taken into account here, can also occur in a subsection of the supply network or in a near zone, even without this subsection or this near zone having to be separated from the rest of the electrical supply network, in this example the European interconnected network.
• the inverter penetration can also relate to the entire electrical supply network.
• a situation could, for example, be the case for an electrical supply network the size of the electrical supply network in Ireland or for electrical supply networks which are smaller.
• the support control function is set or selected as a function of the determined converter penetration. Again, all types of setting or selection of the support control function already described come into consideration. It is particularly important in a high inverter penetration is to be expected that on the one hand with a low susceptibility to vibration of the electrical supply network, on the other hand, however, is expected that the other, namely many inverter-controlled feeder at high converter penetration determined even all possibly a vibration can counteract. It must therefore be remembered that there are many more inverter-controlled feeders that try to counteract any vibrations. Accordingly, it is proposed that this be taken into account in such a way that a control overreaction is avoided.
• the method is characterized in that a support control functions controls an active power component and a reactive power component, in particular that an active power function and a reactive power function are provided for this purpose.
• the active power function and the reactive power function can be combined in the support control function. In particular, they can together form the backup control function.
• the active power portion is provided for achieving a first support task, in particular for achieving a frequency support.
• the reactive power component is provided for achieving a second supporting task, in particular for achieving a voltage support.
• the first support task and the second support task are prioritized depending on the determined inverter penetration. Depending on the inverter penetration so the first or second support task is taken more into the foreground.
• the active power function or reactive power function accordingly has a correspondingly greater proportion of the backup control function.
• a ratio of the active power component to the reactive power component and / or a ratio of an increase in the active power component to an increase in the reactive power component be selected as a function of the determined converter penetration.
• the active power component and the reactive power component may be the same, so that a ratio of 1. in a balanced case, the increase of the active power component may be the same as the increase in the reactive power component.
• the greater the determined converter penetration the greater the active power component or its increase compared to the reactive power component or its increase.
• the reactive power from a reactive power value during the network fault if power continues to be fed despite network faults, be lowered to a new reactive power value, in particular in the case of a so-called FRT (Fault Ride Through) case.
• FRT fault Ride Through
• the reactive power is controlled by means of a ramp function to the new reactive power value, in particular, that it is lowered to the new reactive power value.
• This new reactive power value may then be considered as a post-fault operating point or form part of it.
• the reactive component or its rise is particularly large. This can also mean that then the active power function is particularly large compared to the reactive power function.
• this is a Nachschreib , in which the active power and reactive power are ramped up after the error especially by ramps, but can also have interruptions.
• the converter penetration is now large, ie if there is a high proportion of converter-controlled feeders in the electrical supply network, it is proposed, in any case according to one embodiment, to increase the active power faster than the reactive power.
• a low converter component that is with a low converter penetration, it can be the other way around.
• Such a comparison can be oriented in particular to nominal values, ie to the nominal effective power or nominal reactive power.
• the proposed prioritization is based in particular on the idea that, in the event of a high level of inrush, following a network fault, few oscillation effects due to directly coupled synchronous generators are to be expected. At the same time, however, even with little supply of the electrical supply network, active power can be expected from such directly coupled synchronous generators. Accordingly, as much as possible or as fast as possible active power should be fed through the converter-controlled feeders, in particular the wind turbine or the wind park. With such a high inverter dominance would not be synonymous with a swing in the electrical Supply network to be calculated, because here, too, the proportion fed by converter-controlled feeders active power is dominant.
• a grid stabilization By feeding in a lot of reactive power, a grid stabilization can be achieved, which tends to prevent a swinging up.
• the active power is correspondingly less or more cautiously fed or started up.
• a converter penetration or a converter component in the electrical supply network refers to the respectively feedable active power. It is therefore not important that the directly coupled synchronous generators of the number of It is preferable to use the real power supplied by both groups as the reference variable.
• the method is characterized in that the support control function specifies or specifies at least one of the following relationships or one of the following properties:
• a chronological progression of the active power to be injected or additionally fed is how the start-up of the active power is controlled in particular, and how this is to take place is indicated by the support control function.
• a time course of a voltage to be impressed As a result, it is possible in particular to achieve stress stamping, which is advantageous not only when there is a high level of converter penetration, and directly coupled synchronous generators can not achieve sufficient voltage support.
• the support control function basically provides a voltage-dependent reactive power supply and this can be adjusted according to the situation, in particular depending on the network topology.
• a connection can be regarded as amplification or amplification factor and this amplification or amplification factor can be selected and set depending on the situation.
• the reactive power or the reactive current in particular its increase after the network error is not set or not only as a function of a mains voltage, but over a time function.
• this can include a reactive power ramp or reactive current ramp, which indicates how the reactive power or the reactive current is increased over time, in order then to reach the most stable operating point possible after the network fault.
• an initial dead time can be considered or adjusted, which must pass before the active power is increased.
• This start dead time can also be part of the predetermined trajectory. This is particularly the startup of the active power controlled by a network error.
• a ramp is used whose pitch can be adjusted. Especially when considering vibration, it may be useful to combine several
• Such a time delay may be in the range of 100 to 500 ms.
• the further course can be marked via the steepness of the respective flank. This is preferably specified for active power and reactive power, but can be specified independently of each other. In both cases, it is a question of active power and reactive power feed-in and start-up of these powers, but in fact this can be done by appropriately controlling the corresponding current, namely the active or reactive current.
• a threshold value can be set via this triggering voltage. Only when the voltage has exceeded this value again, in particular the mains voltage or an equivalent voltage, is the end of the network fault assumed.
• Such a value may be in the range of 50 to 90% of the rated mains voltage or 50 to 90% of the mains voltage before the mains fault.
• a multi-variable function is used as the backup control function.
• a multi-size function is a function that depends on several input variables.
• a reactive power or a reactive current as a function of time and additionally as a function of the mains voltage or a mains voltage change is proposed as a multi-function function for the auxiliary control function. It can thereby be achieved that, over time, the reactive power is boosted after the network fault, but at the same time the voltage is taken into account, so that, for example, depending on the mains voltage or mains voltage change, the reactive power is more or less increased than predetermined solely by the time would.
• a real power or an active current as a function of time and also as a function of the mains voltage or a mains voltage change is proposed as a multivariable function.
• reactive power apply mutatis mutandis.
• it's about a way to power up the active power as a function of time at the same time consider the voltage. It will be especially important pointed out that just the active power is usually changed depending on the grid frequency rather than the grid voltage, but here when restarting after a grid fault, especially the consideration of the mains voltage is useful to achieve a stable operating point.
• a real power or an active current as a function of time and also as a function of the mains frequency or a mains frequency change is proposed as a multivariable function.
• reactive power apply mutatis mutandis.
• the active power which is usually changed as a function of the mains frequency as the mains voltage, is given special consideration here when restarting after a network fault in order to achieve a stable operating point.
• the multi-variable function is a reactive power or a reactive current as a function of time and also as a function of an injected active power and furthermore also the mains voltage or mains voltage change. So here is a multi-size function proposed, which depends on three sizes.
• the injected active power is added here as another input variable.
• aspects such as whether the reactive power is to increase faster or slower than the active power can be considered here.
• the backup control function is composed of several of these multi-size functions.
• the reactive power as a multi-size function u.a. also oriented to the active power as the other multi-size function.
• the active power time- and voltage-dependent controlled namely in particular can be booted and this way of starting the active power then affects not only the time and the mains voltage but also the control of the reactive power and the control of the reactive current.
• information or parameters for selecting a support control function be received externally before the occurrence of the network problem or network error, in particular that the information tions or parameters in predetermined and / or individually changing time intervals and / or after a change in their contents are received by the inverter-controlled generating unit.
• This update may be dictated by time periods or updated due to changes in the situation. If the situation changes, that is, if, for example, a directly coupled synchronous generator is connected or disconnected, the backup control function can be changed. If it is changed, this may be a reason to initiate a transfer of this changed support control function. Likewise, even if the support control function is not transmitted but is changed directly, the example mentioned change in the situation, so the connection or disconnection of the example mentioned directly coupled synchronous generator, as such adjusting, so change, the support control function trigger. The corresponding information is then transmitted. Periods of a few minutes to a few hours are preferably proposed as predetermined time intervals. In particular, it is proposed that the predetermined time intervals be in a range of 10 minutes to 5 hours, in particular in a range of 30 minutes to 2 hours.
• a generating unit in particular a wind energy plant, a wind park, a memory of electrical energy or a combination thereof is also proposed.
• This generating unit is inverter-controlled and prepared for exchanging electrical power with an electrical supply network having a grid frequency. This exchange of electrical power takes place at a grid connection point of the electrical supply network.
• the generating unit comprises a converter for exchanging electrical power in dependence on a control function, wherein the electric power can comprise active and reactive power.
• an inverter is provided, the electric power in a can supply electrical supply network. If necessary, however, it can also remove reactive power from the electrical supply network, if necessary also active power, so that it is prepared for exchanging electrical power.
• a control device for controlling the exchange of electrical power by means of a control function, wherein the control function controls the power as a function of at least one state variable of the electrical supply network.
• the state variable is a mains voltage as well as a mains frequency.
• the power is fed or removed depending on the mains voltage and / or the mains frequency. But there are also other state variables into consideration.
• the control device is also set up so that it is possible to change as a control function between a normal control function and at least one support control function different from the normal control function.
• the normal control function is used when it has been detected that the electrical supply network is working more stable.
• the backup control function is used when a network problem, network failure, or end of network failure has been detected.
• the input power controls so that a vibration in the electrical supply network can be counteracted, especially a vibration of a synchronous generator connected to the electrical supply network or caused by the synchronous generator oscillation. This relates particularly synchronous generators coupled to the electrical supply network.
• a generating unit is proposed, which is prepared to carry out a method according to one of the embodiments described above. Accordingly, for further explanation, reference is made to explanations of at least one embodiment of the method.
• a data interface is provided for the generating unit to receive information or parameters externally for selecting and / or setting a control function.
• the network operator in particular can influence the control function.
• he can select a particular control function, in particular from a plurality of predefined functions, or alternatively, or in addition to this, he can set the control function or change accordingly. This is especially about selecting and / or setting the Support control function.
• the normal control function can be selected or set here.
• Figure 1 shows a wind turbine in a perspective view.
• FIG. 2 shows a wind park in a schematic representation.
• 3 to 5 show diagrams of possible behavior of a synchronous machine in the
• Figure 6 shows a structure of a control device with a feed device schematically.
• FIG. 7 schematically shows a diagram with different strategies of a power increase after a network problem, network error or end of the network error.
• FIG. 8 schematically shows a network structure with a directly coupled synchronous machine and a wind park illustrated as a consumer.
• FIG. 8 a / b show working characteristics for different conditions for the network structure according to FIG. 8.
• FIG. 9 is an illustrative diagram of voltage recovery after a fault along with possible power controls that may be implemented via support functions.
• Fig. 10 shows another illustrative possibility for a backup control function for use after a network failure.
• FIG. 1 shows a wind energy plant 100 with a tower 102 and a nacelle 104.
• the nacelle 104 has a rotor 106 with three rotor blades 108 and a spinner 1 10 arranged.
• the rotor 106 is set in rotation by the wind in rotation and thereby drives a generator in the nacelle 104 at.
• FIG. 2 shows a wind park 112 with, by way of example, three wind turbines 100, which may be the same or different.
• the three wind turbines 100 are thus representative of virtually any number of wind turbines of a wind farm 112.
• the wind turbines 100 provide their power, namely, in particular, the power generated via an electric parking network 114 ready.
• the respectively generated currents or powers of the individual wind turbines 100 are added up and usually a transformer 116 is provided, which transforms the voltage in the park up to then at the feed point 118, which is also generally referred to as PCC, into the supply network 120 feed.
• Fig. 2 is only a simplified representation of a wind farm 112, for example, shows no control, although of course there is a controller.
• the parking network 114 can be designed differently, in which, for example, a transformer at the output of each wind turbine 100 is present, to name just another embodiment.
• FIGS. 3 to 5 illustrate the behavior of a synchronous machine coupled directly to the electrical supply network in the vicinity of a converter-controlled generating unit, in particular in the vicinity of a wind energy plant or a wind farm.
• synchronous generators or synchronous machines which is used here as a synonymous term, in a network error, which leads to a voltage dip, can get into vibration, which can be triggered in particular by a phase jump.
• the mean rotor angle then leads, because the machine could not deliver the full active power to the grid during the voltage dip.
• Synchronous machines can also be vibrated by a sudden parallel active power feed, which is illustrated in FIG. FIG. 3, the same applies to FIGS. 4 and 5, shows working characteristics of a synchronous machine, namely the machine torque ms as a function of the rotor angle 5Q.
• FIG. 3 the behavior of a synchronous machine which is operated in the vicinity of a converter-controlled generating unit is illustrated by a fast connection of a parallel active power feed, specifically by a close-coupled judge-led generating unit.
• the working characteristic 301 with the operating point A shows the situation before the fast connection. Due to the sudden parallel active power supply, this working characteristic 301 suddenly changes into the new working characteristic 302 and the new operating point B initially results, at least ideally, from the current rotor position.
• the constant drive torque of a power plant can, however, be controlled by the synchronous generator at this operating point are not absorbed, so that there is an excess torque and the flywheel is accelerated according to this torque excess and the inertia of the entire rotor.
• the kinetic energy in the rotor leads to a pass through the pole by the characteristic, namely the new working characteristic 302.
• the rotor is braked by the higher torque again. This excess energy should be removed as soon as possible, so that the synchronous machine returns to a normal operating state.
• a possible return is illustrated by the transition section 303.
• the operating point A is in a swinging and thus oscillating manner to the operating point C on the new working characteristic 302 on.
• an acceleration surface 306 and a braking surface 308 located.
• the acceleration surface 306, ie essentially the triangle ABC is smaller than the possible braking surface 308.
• the movement is thus decelerated more than accelerated, the possible braking energy is thus greater than the acceleration energy.
• FIG. 3 shows the situation for a stable compensation process.
• the working characteristic 402 shows the situation after the rapid connection. If, during the swing back, less active power is fed in by the near-converter-controlled generating unit, this supports the active power recovery of the synchronous machine because it leads to an increase in the operating characteristic 402 to the increased operating characteristic 404.
• the flywheel of the synchronous generator whose vibrations are considered, is further accelerated from the pre-fault condition, ie from the starting point 401 during the fault, to an intermediate point 403, which is further to the right and down.
• Condition for a stable return is now that the area shown to the left of the intermediate point 403 Acceleration surface 406 is not greater than the original braking surface 408, which is located at the top right of the intermediate point 403, namely under the original curve, ie below the working characteristic 402.
• the original braking surface 408 ', which is below the original curve 402, and the likewise plotted modified braking surface 409, which is below the shifted working characteristic 404, are the same size. It turns out, however, that the shifted curve 409 has a larger distance to the tilting point 405, which is formed by the intersection of the curve with the moment m a . Due to this larger distance, the shifted working characteristic 404 has more stability reserves, which can be achieved by the described shifting of the working characteristic.
• the flywheel from the pre-fault condition indicated by the black dot 401 is accelerated further to the right and bottom during the fault (403).
• the condition for a stable return is that the area to the left of the point 403 is not larger than the area in the upper right of the point 403, below the curve.
• the area 408 ', which is below the old working characteristic 402, and the area 408 ", which is below the shifted working characteristic 404, are the same size. It turns out, however, that the surface 408 "has a greater distance to the tipping point, which has the point of intersection of the curve with the moment m a , than the surface 408 'and thus more stability reserves.
• FIG. 8b Another strategy proposed is stabilization through forced reactive power feed-in. This is illustrated in FIG. 8b.
• the working characteristic 830 shows the situation after a quick connection.
• the proposed forced reactive power feed by a near converter-controlled generating unit leads to the shift to the changed second working characteristic 834.
• the ratio of an acceleration surface to a braking surface can be improved.
• the acceleration surface results from the error and it must be basically smaller than the braking surface.
• the effect of the reactive power supply is indeed smaller than that through the active power supply, but specifically by modulating the reactive power, which can be achieved by modulating the Ad mittanz YL, namely by power electronics of the wind park 812 as a function of speed deviation, can improve the Dampening a synchronization process can be achieved, ie a process in which the speed of the synchronous generator is synchronized back to the mains frequency, ideally to the nominal network frequency.
• the converter-controlled feed device in particular the wind farm, is equipped with at least one device for feeding in a transverse voltage.
• This can be achieved by a FACTS device or a cross transformer.
• a stability reserve of a synchronous machine can be achieved by targeted shifting of the rotor angle. This is illustrated in Figure 5, which shows a shift of the working characteristic 502 to a shifted working characteristic 504. In this case, a shift in both directions, depending on the size of the Polradwinkels, stabilizing effect.
• the acceleration surface 506 and the displaced braking surface 508 show that the stability reserve is increased from 502 to 504 by the shift of the operating characteristic.
• the rotor angle of the synchronous machine can also be changed to a small extent by a targeted active and reactive power supply.
• the active power and reactive power have to be changed in such a way that exactly one shift according to Figure 5 occurs.
• Figures 8a and b which will be explained below, superimposed.
• the effect is significantly smaller than by the impression of a transverse stress, which is why even a modulation of the rotor angle can be used again for stabilization, in comparison to the simple increase of the stability reserve.
• FIG. 6 schematically shows a control device 600 with a feed device 602, which feeds into an electrical supply network 604.
• the feed device 602 receives from the control device 600 a power setpoint value S (t).
• generalization refers here to the complex apparent power, ie the apparent power in terms of magnitude and phase.
• the active power P (t) and the reactive power Q (t) are given as separate values.
• the following is simplifying the performance or power specification, which can mean active power and / or reactive power.
• this performance depends on the time t, that is, that no constant is passed, but that a value or several values can or may fluctuate.
• the feed device 602 then receives this power specification and generates therefrom a 3-phase current I, which can also be referred to here as a feed-in current, and which is fed into the electrical supply network 604.
• a 3-phase current I which can also be referred to here as a feed-in current
• a transformer could still be arranged, to which, however, it does not matter.
• a mains choke is provided regularly, which is also not shown here and can be understood as part of the feed device 602.
• the feed device 602 can be constructed from one or more inverters, which derive their power in particular from a generator of a wind energy plant. In order to control the power in accordance with the power specification S (t), it is also often necessary to control the power of said generator or to control this generator.
• a normal control function in the normal control function block 606 In a normal case where the network is stable and, in particular, no network problem or network failure has occurred, a normal control function in the normal control function block 606 generates the power demand S (t). For this purpose, the normal control function block 606 receives the mains voltage U and the network frequency f as input variables.
• the mains voltages U are detected by the voltage measuring means 608. From the network voltage U detected in this way, the frequency f can be detected via the frequency determination block 610 and then entered into the normal control function block 606 as a further input variable.
• the mains voltage U and the mains frequency f are not represented as a quantity dependent on the time. In fact, both depend on time From and to this dependence on time, so their temporal change, it is also often here.
• the normal control function determines the normal control function block 606, the power S (t) and this is the selector 612 in the normal case, so if there are no network problem or error or short term templates and otherwise no loss of stability of the electrical supply network 604 is expected, passed to the feeder 602 .
• the normal control function which is stored or implemented in the normal control function block 606, can in particular determine an active power specification P as a function of the network frequency and determine a reactive power specification Q as a function of the system voltage U. The result can then be summarized in the power specification S (t). In principle, however, it is also considered that no reactive power component Q or no active power component P is determined.
• the selector 612 switches over and forwards a power setting S (t) from the backup control function block 614 to the feeder 602.
• Such a switch can be triggered by the detection of a network problem, network error or end of such a network error.
• This is shown in FIG. 6 as an event E for simplicity.
• This event E is detected in an event detection unit 616.
• both the event detection unit 616 and the selection device 612 and also the other elements shown can also be implemented differently.
• the structure shown overall for the control device 600 can also be implemented as software in a control device, to name just one further example.
• the event detection unit 616 illustrates that the event E can be detected as a function of the mains voltage U and the mains frequency f. This may, for example, be such that a voltage dip leads to the detection of an event E.
• the support control function in the support control function block 614 receives as inputs, as does the normal control function block 606, the grid voltage LJ and the grid frequency f.
• the support control function, and hence the support control function block 614 receives as a further input from the line frequency f a time derivative.
• This derived network frequency / is generated in the diverter 618.
• an active power P depending on such
• Frequency derivative f are generated or take this into account additionally.
• a frequency analysis or via a DFT in the frequency analysis device 620 is provided.
• the result is in particular a frequency spectrum f (f) of the network frequency f.
• a frequency analysis that is, for example, a corresponding Fourier transformation
• a characteristic oscillation of a synchronous generator 622 of a large-scale power plant 624, shown schematically in FIG. 6 can be detected.
• This frequency-dependent frequency spectrum f (f) can thus also be evaluated in the event detection unit 616, which is not shown here for the sake of simplicity.
• the event detection unit 616 which is not shown here for the sake of simplicity.
• Event detection unit 616 from the frequency spectrum f (f) of the network frequency f that has generated the frequency analyzer 620 know the characteristic oscillation frequency of the synchronous generator 622 and then determine when monitoring the network frequency f, if the mains frequency f just oscillates with this characteristic frequency of the synchronous generator 622 , If this happens with a correspondingly high amplitude, this can lead to an event E being detected. Accordingly, this event E can also form an input variable for the backup control function and thus the backup control function block 614.
• Such an identified event E can be used for the support function in the support control function block 614 as temporal, namely temporally precise, trigger, which is also referred to in the jargon as a trigger.
• a dynamic, in particular an eigenvalue, of the backup control function may depend on a detected characteristic oscillation frequency of the synchronous generator 622.
• the selector 612 toggles such that the power preset S (t) is given by the support control function in the support control function block 614, and the support control function block 614 receives as inputs the utility voltage U, the grid frequency f and its derivative.
• the frequency spectrum f (f) and the triggering or recognized event E can additionally be taken into account.
• FIG. 7 schematically shows a diagram with different strategies of a power increase after a network problem, network error or end of the network error.
• a frequency gradient 710 which can also be referred to mathematically as df / dt, is shown with decaying amplitude.
• the lower diagram shows various performance increases as performance curves 701 to 704. Both diagrams use the same time axis.
• FIG. 7 shows a power dip in which the power drops, for example, from an initial value Po to zero.
• the actual viewing or illustration does not start until the time to, at which time a power feed-in, namely active power feed-in, is to be resumed.
• the oscillating behavior of the frequency or the vibration of the frequency gradient 710 shown in the upper diagram is only considered from this point in time to. In particular, the two diagrams in the area before time to are not matched.
• the course of the frequency gradient 710 is also approximately equal sinusoidal and decaying.
• a curve of a peak value S fG (t) of the frequency gradient 710 is shown, which can also be referred to as the peak value function 712.
• the peak value function 712 thus indicates at each instant a maximum value of the frequency gradient 710 and thus forms approximately an upper curve of two enveloping curves of the oscillating frequency gradient.
• the first power curve 701 forms a simple ramp that does not depend on the frequency gradient 710. Such a ramp may constitute the state of the art, but it may also serve as a basis for superposition with a frequency function 710-dependent power function.
• the second power curve 702 shows such a superimposition. It is composed of the ramp of the first power curve 701 or a similar ramp, and a power function directly dependent on the frequency gradient, which superimposed forms the second power curve 702 with the ramp.
• the directly dependent on the frequency gradient power function may, for example, be a proportional to the frequency gradient function. It thus results in an increase in power, but can specifically counteract vibrations, which can be achieved by the superimposed dependent of the frequency gradient performance function. The power thus increases, without thereby stimulating the oscillation, which is reflected in the frequency gradient 710. Instead, such a vibration is damped.
• the third power curve 703 is only dependent on the peak value function, ie does not consider the oscillation of the frequency gradient 710, but only the course of the amplitude. Thus, the third power curve 703 has no oscillation. At the beginning of the desired power increase, it only weakens the power. When the vibration stops, the power can be increased more. As a result, the third performance curve 703 has a gradient increasing with time, which is also proposed as a general feature.
• a further proposal is to superimpose a performance function 703 on a power function which depends on the frequency gradient 710. Instead of superimposing this power function on the ramp-shaped power curve 701, it is therefore proposed here to superimpose this power function on the third power curve 703.
• the result is the fourth performance curve 704.
• the initially weak increase in the third power curve prevents an excessive power increase in the event of a swinging condition and the power function, which is directly dependent on the frequency gradient, specifically controls the vibrations.
• the slight increase in the third power curve there also allows a stronger countersteering by the directly dependent on the frequency gradient power function.
• the network structure of Figure 8 illustrates a network section 800 formed essentially by first and second reactances 801 and 802, which for simplicity are assumed to be equal in size.
• This network section 800 is connected to the rest of the network 804, which for simplicity is assumed to be a rigid network.
• a synchronous machine 806 is present, which can also be referred to as a synchronous generator, and which is coupled directly, so without the interposition of an inverter, to the electrical supply network, namely here with the network section 800 at the first reactance 801.
• the synchronous machine 806 can via a Turbine 808 with drive shaft 810, which is only hinted here, driven and these three elements are also representative of a power plant 816.
• the synchronous machine 806 is connected via this network section 800 with the rest of the network 804.
• the network section 800 particularly the two reactances 801 and 802 form a load flow path.
• a wind farm 812 is represented here by an ad mittance YL as a consumer and connected between the first and second reactance 801, 802.
• a switch 814 illustrates that the wind farm 812 may also be disconnected from the grid section 800.
• FIG. 8a shows a working characteristic curve 830 which assures a torque / rotor angle dependence of the synchronous machine 806 in normal operation a parallel feed through the synchronous machine 806 and the wind park 812 represents.
• FIGS. 8a and 8b use the same representation as FIGS. 3 and 4.
• FIG. 8 a shows how a working characteristic, which in principle can also be called synonymous as an operating characteristic, changes when a
• FIG. 8a shows how the operating characteristic 830 of the synchronous generator 806 moves to the upper left to the changed first operating characteristic 832 by the reduction of the
• FIG. 8b shows the influence of an additional reactive current feed-in on the torque / rotor angle dependence by the wind park 812.
• the operating characteristic 830 which is assumed to correspond to the operating characteristic 830 of FIG. 8a.
• the working characteristic 830 in FIG. 8b again forms an output characteristic curve in the case of a parallel supply by the synchronous generator 806, that is to say the power plant 816 and the wind farm 812.
• the stability reserve (the possible braking surfaces) of the synchronous machine 806 increases by the shift of the torque Polradwinkelkennline, ie the working characteristic 830 up to an altered second working characteristic 834th This shift namely achieves an increase or increase in the braking surfaces, as explained in Figures 3 and 4.
• FIG. 8b also shows a reaction to an injection of an inductive reactive current through the wind park 812. This results in the changed third working characteristic 836, which is shifted downwards. It shows that this feeding of an inductive reactive current degrades the stability of the synchronous machine 806 corresponding to the lower operating characteristic 836.
• the pole wheel angle of the synchronous generator 806 of the power plant 816 alone can be changed.
• the effects according to the changed first and second working characteristic 832, 834 can overlap.
• the shift in the other direction can be done accordingly by an increase in active power with simultaneous capacitive power supply.
• a behavior of a synchronous machine is emulated for the control of the power supply by the converter-controlled generating unit and for this purpose a virtual synchronous machine with a virtual moment of inertia can be used as the basis.
• This behavior and / or an increase in the virtual mass moment of inertia is preferably activated after a voltage recovery. Activation is also considered in the passage of the oscillating frequency through the Vorêtnetzfrequenz, ie by the frequency that existed before the error. That would correspond to a passage through an equilibrium point.
• the proposed measures relate to a hybrid supply structure, in which conventional and converter-fed input are used simultaneously.
• it is also proposed to take into account the inverter penetration and depending on the proposed measures to take.
• a very high proportion of a converter-fed feed in particular> 95%
• a tendency to instability of the synchronous machine is accepted, since in networks with a very high regenerative penetration, the restoration of the power balance must be prioritized. This is particularly based on the recognition that in such a system, the flywheel low, and the frequency sensitivity is high.
• a system stability and stability of electrically adjacent synchronous generators should be achieved with a locally and globally high penetration with converter-controlled generation units. It is also to be achieved that more inverter-controlled generation units may be set up and connected to the grid in the future, even if only a few directly coupled synchronous generators are still operating on the grid.
• Fig. 9 shows two diagrams indicating the same time axis. The lower diagram shows a voltage curve of the mains voltage U over the time t before, during and after a network fault. The network error occurs approximately at time to and is considered to be finished at time ti. Before the grid fault, the grid voltage LJ has approximately nominal voltage UN and then drops to a low value, which may be 5% of the rated voltage UN, for example.
• a possible power curve of the injected active power P is shown in the upper diagram. Accordingly, an active power is, for example, fed before the network error until the time to with the amplitude Pp, which then drops to zero in the network error. After or after the end of the network fault at time L, the injected active power P is then increased.
• This increase is carried out by a backup control function which, for example, can specify a slope m of this increase in active power. The slope may depend on various criteria, as described above for embodiments of the method according to the invention.
• the slope may depend on an inverter component in the electrical supply network. This is illustrated in FIG. 9 by three different time-related slopes mi, it ⁇ 2 and rrn.
• the support control function can thus be selected, for example, from a plurality of default functions, each having one of the slopes.
• the slopes mentioned as examples rrn, rri 2 or rm are set as parameters.
• the support control function is selected or adjusted so that a, caused by the synchronous generator, oscillation is counteracted. This is done here by the appropriate slope.
• FIG. 10 starts from the same initial situation as FIG. 9 and also uses the same time axis.
• the support control function has different slopes mi and m2. This is illustrated in FIG. 10, according to which, starting from or after the end of the network fault at the time t 1, the active power is first of all with the first slope mi is increased, so it is increased by a ramp with the slope mi.
• the fed-in power P be kept constant for a predetermined period of time, namely until time t3.
• the injected power P is then increased with a second slope m2, which in the example shown is smaller than the first slope m2.
• This can be counteracted a swing, especially a swinging of a vibration in the electrical supply network, with appropriate parameterization and worked towards a stable operating point.
• the initial fast increase in active power can achieve a first operating point with much injected active power, whereas the second slower increase can achieve or promote vibration calming.
• FIGS. 9 and 10 may be different despite the same designation (irn and ITI2). However, in both examples, ie FIGS. 9 and 10, it is fundamentally provided that the power then again reaches the power Pp which was fed in before the network fault, unless further boundary conditions, such as, for example, a temporary weakening of the wind, are opposed.

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• 2018
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