METHOD FOR STARTING AN ENERGY GENERATION NETWORK

Description

[0001] The present invention relates to a method for starting an energy generation network, in particular a wind farm. Furthermore, the present invention relates to a wind turbine and to a wind farm comprising at least one first and one second wind turbine.

[0002] Electrical supply networks are well-known, and they distribute electrical energy between energy producers and consumers. Today, such an electrical supply network operates with alternating current at a predetermined frequency, usually 50 Hz or 60 Hz. Both producers and consumers have adapted to this frequency.

[0003] A key characteristic is that a portion, usually a large portion, of the electrical grid is always operational. When an electrical generating unit is connected to this grid to feed in electrical energy, it can also orient itself to the grid. Specifically, such a generating unit typically receives initial energy from the grid to power any necessary start-up processes. In addition to providing this energy, the electrical grid also provides guidance and control, particularly regarding the grid frequency and voltage.

[0004] Some generation units, such as wind farms with multiple wind turbines, have their own internal electrical grid, which can also be called a power generation grid. Such a power generation grid is typically operational and operates at the same frequency as the main electrical grid, with which it is synchronized. Furthermore, the power generation grid feeds into or draws power from the main electrical grid via a connection point, particularly a grid connection point, and its voltage level at this connection point is matched to that of the main electrical grid. These two voltages are therefore equal at this connection point or are related to each other according to the transformer's transformer ratio.

[0005] When the energy generation network, and in particular the parking network, is started up, for example during initial commissioning or after a situation where it had to be shut down, the energy generation network can receive energy from the electrical supply network and adjust itself to and orient itself to the network frequency and voltage specified by the electrical supply network.

[0006] It has now been recognized that energy generation networks, especially wind farm grids, are playing an increasingly important role in electrical supply networks. It is therefore possible that the electrical supply network may not be able to adequately manage or support such a start-up process of an energy generation network. In particular, it may be expected that the electrical supply network itself will require support. It has also been recognized that an energy generation network, especially a wind farm grid, should therefore be capable of starting independently or even providing support for the electrical supply network, so that the electrical supply network can restart with the help of the energy generation network or at least recover from a situation in which the grid voltage has dropped significantly.

[0007] Especially power plants that were previously planned, which were specifically kept ready for grid restoration or even a black start of an electrical supply network, may now be less frequently available or are to be eliminated, so that an electrical supply network has to manage without such a special power plant for its start or regeneration.

[0008] The German Patent and Trademark Office has searched the following prior art in the priority application for the present application: US 2017 / 0074244 A1, DE 10 2014 214 151 A1, DE 10 2013 102 603 A1, EP 1 665 494 B1 and US 2015 / 0159627 A1.

[0009] US 2015 / 0028593 A1 relates to a method for starting up a wind farm. US 2015 / 380942 A1 relates to a method for starting a park network of a wind farm according to the preamble of claim 1.

[0010] 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 provided that enables an energy generation network, especially a wind farm park network, to start up independently and without the assistance of an electrical supply network, and then, in particular, even to support or assist the electrical supply network during start-up, regeneration, or recovery from a voltage dip.

[0011] At least an alternative solution should be proposed to the methods known so far.

[0012] According to the invention, a method for starting an energy generation network according to claim 1 is proposed. The proposed energy generation network is designed as a wind farm network and accordingly comprises several wind turbines. However, another energy generation network can also be used, comprising several generators that are electrically interconnected via a grid. In principle, several wind farms or wind farm networks are also suitable, which are controlled together and, if necessary, feed into the electrical supply network not only via a common grid connection point, but also via several grid connection points. A network comprising at least one wind farm or wind farm network is also suitable as an energy generation network. In any case, the energy generation network is connected to the electrical supply network at at least one grid connection point.In normal operating mode, the power generation network exchanges electrical power with the electrical supply network via the grid connection point. Usually, the power generation network feeds electrical power into the electrical supply network via the grid connection point. However, in special situations, the power generation network may also draw electrical power from the electrical supply network, particularly for support purposes.

[0013] The procedure for starting the power generation network proposes selecting a setup mode when the electrical supply network experiences a voltage drop. This means that the voltage in the electrical supply network, referred to as the network voltage, has dropped significantly. Such a voltage drop particularly applies to a power outage or blackout of the electrical supply network. In the event of a voltage drop, the setup mode is selected, or the system switches from normal operating mode to setup mode. However, the setup mode can also be selected if the power generation network is disconnected from the electrical supply network. Specifically, it can also be selected if there is a voltage drop in the electrical supply network and, in addition, the power generation network is disconnected from the electrical supply network.This network separation can therefore also occur during a voltage drop in the electrical supply network.

[0014] To start up, the energy generation network is initially operated in this setup mode. This operation of the energy generation network in setup mode includes several characteristics. First, a voltage-forming device (or multiple voltage-forming devices) provides an energy generation network voltage. The voltage-forming device can also be a voltage-forming wind turbine or a switchgear cabinet containing an inverter. The voltage-forming device, the voltage-forming wind turbine, or the voltage-forming switchgear cabinet thus operates by shaping a voltage, i.e., controlling or regulating it. With such a voltage-forming device, the current is not shaped. In any case, the current requirement is subordinate to the voltage requirement. The voltage-forming device provides an energy generation network voltage, i.e., the voltage that prevails in the energy generation network.at least at the output of this voltage-shaping device or at a selected reference point. In the case of a wind farm, this wind power generation grid voltage corresponds to a wind farm grid voltage.

[0015] Furthermore, a primary power supply device is provided, designed as a current-generating wind turbine or as a switchgear cabinet containing an inverter, which initially synchronizes with the power generation grid voltage provided by the voltage-generating device. This primary power supply device is thus oriented to the power generation grid voltage, which is essentially provided by the voltage-generating device. In particular, this power generation grid voltage has a frequency to which the primary power supply device synchronizes. The primary power supply device then specifically delivers a current whose frequency is synchronized with the frequency of the power generation grid voltage.

[0016] The voltage-forming device and the initial supply device now work together, or are coordinated in such a way that they, i.e., the voltage-forming device and the initial supply device, together provide electrical power to the power generation network, namely equal to the network's own demand. This demand particularly concerns the power required to start the power generation network, specifically the power needed to start the wind turbine in the case of a wind farm.

[0017] The power generation network is thus initiated by selecting a setup mode in which at least one voltage-forming device and one primary supply device operate together, each with a specific task. The voltage-forming device initially establishes a voltage, namely the power generation network voltage, and the primary supply device adjusts to this voltage and, in particular, provides current to supply the power generation network. The primary supply device thus assumes the initial supply. The voltage-forming device can also contribute to this, i.e., it can also provide power. However, the main task of the voltage-forming device is to establish the power generation network voltage.

[0018] According to the invention, it is proposed that the at least one voltage-forming device provides the power generation network voltage essentially without power input. In this case, a division is particularly provided such that the primary supply device provides the necessary power to start the power generation network, while one or more voltage-forming devices shape the voltage and provide the primary supply device with a corresponding orientation or reference value.

[0019] Preferably, the at least one voltage-imposing device for providing the power generation grid voltage operates by imposing a voltage. In particular, the voltage-imposing device operates in such a way that it regulates to an output voltage, namely the power generation grid voltage, which it thereby provides. It is also a matter of imposing a frequency, namely the frequency of the voltage. The voltage-imposing device imposes a voltage with a predetermined frequency and phase.

[0020] According to the invention, it is proposed that the at least one primary supply device for providing electrical power in the energy generation network operates in a current-shaping capacity. The primary supply device thus provides or feeds a current into the energy generation network and, in particular, regulates and shapes this current. This allows the voltage-shaping device and the primary supply device to work well together, because each has its own specific function.

[0021] According to thereThe invention proposes that the at least one voltage-forming device is based on at least one first static and the at least one initial supply device is based on at least one second static, wherein each static describes a relationship, in particular a linear relationship, between an electrical voltage of the power generation network and a reactive power to be injected or injected, or between a frequency of the power generation network and an active power to be injected or injected, and the first static has a smaller slope than the second static.

[0022] The stress-correcting device and the initial supply device are thus each characterized by their respective static properties. These static properties can be implemented within the stress-correcting device or the initial supply device. The stress-correcting device and the initial supply device, and there can be multiple devices, therefore exhibit these static properties.

[0023] It is proposed that the first static equation has a smaller slope than the second. This is proposed for both variants of the equations. Specifically, each equation describes a linear relationship. The slope thus relates to the behavior of reactive power with respect to voltage, regardless of whether the reactive power or the voltage constitutes an input in the control engineering sense. The same applies to the relationship between active power and frequency, where the slope relates to the behavior of active power with respect to frequency, also regardless of whether the active power or the frequency constitutes an input in the control engineering sense.

[0024] Operating points can be defined by adjusting the slopes of the static curves. A smaller slope for the static curve of the voltage imprinting device results in less reactive power being fed in at the same voltage compared to the primary power supply, or less active power being fed in at the same frequency compared to the primary power supply.

[0025] It is preferably suggested that where at least one voltage shaping device is based on a first reactive power statics that describes a relationship between an electrical voltage to be provided by the voltage shaping device in the power generation network and a reactive power injected by the voltage shaping device, and where at least one primary supply device is based on a second reactive power statics that describes a relationship between an electrical voltage measured in the power generation network and a reactive power to be injected by the primary supply device, and the first reactive power statics has a smaller slope than the second reactive power statics, and / or where at least one voltage shaping device is based on a first active power statics that describes a relationship between a frequency to be provided in the power generation network by the voltage shaping device and an active power injected by the voltage shaping device, andwhich is based on at least one primary supply device and a second active power statics that describes a relationship between a frequency recorded in the energy generation network and an active power to be fed in by the primary supply device, and where the first active power statics has a smaller slope than the second active power statics.

[0026] Both the reactive power analysis and the active power analysis can each be a single analysis as described above. It is also possible to implement separate reactive power and active power analyses. Each analysis pertains to a single voltage impedance device or primary supply device. If multiple voltage impedance devices or primary supply devices are present, each has its own analysis, which can be identical for all voltage impedance devices and / or for all primary supply devices. Each voltage impedance device or primary supply device considers the reactive power and / or active power it supplies. For this purpose, its active and / or reactive current is preferably measured.

[0027] According to one embodiment, it is proposed that that at least one voltage impedance device provides the electrical voltage to be supplied depending on the reactive power fed in according to the first reactive power characteristic curve, and that at least one primary supply device feeds in the reactive power to be supplied depending on the detected electrical voltage according to the second reactive power statics and / or that at least one voltage impedance device provides the frequency to be supplied depending on the active power fed in according to the first active power statics and that at least one primary supply device feeds in the active power to be supplied depending on the detected frequency according to the second active power statics.

[0028] For the voltage-forming devices on the one hand and the initial supply devices on the other, which are designed to form current, the statics therefore have different significance, at least for the control engineering implementation.

[0029] The voltage measuring device adjusts its output voltage depending on the detected reactive power, or adjusts its frequency, namely the frequency of its output voltage, depending on the detected active power. Reactive power and active power are the input variables.

[0030] The primary power supply adjusts its reactive power depending on the voltage and its active power depending on the frequency. Therefore, voltage and frequency are the input variables. The static values ​​and their slopes, however, always refer to reactive power as a function of voltage and active power as a function of frequency. The voltage used is specifically a voltage deviation, namely a deviation of the electrical voltage from a reference voltage, such as a nominal network voltage.

[0031] Such a dynamic relationship, which describes the connection between voltage and reactive power or between frequency and active power, is also known in the field as a droop. It refers specifically to a voltage deviation between the setpoint and actual voltage, particularly in relation to the power generation grid, and thus fundamentally to the power generation grid voltage. In this respect, this dynamic relationship can also be considered a proportional (P) controller, whereby the primary power supply provides reactive power or additional reactive power proportional to the voltage deviation, or feeds it into the power generation grid.

[0032] Likewise, this static relationship, which describes the connection between frequency and active power, can also be viewed as a P-controller, whereby the primary supply means provides active power or additional active power proportional to the frequency deviation or feeds it into the energy generation network.

[0033] With stress-embossing agents, it's the opposite.

[0034] If the static behavior is not purely linear, a linear component may still be present. This can also be referred to as the proportional (P) component in a controller, or considered as such if other components are present. The proportional (P) component can then describe the slope.

[0035] Preferably, the slope or amplification of the second static, second reactive power, and / or second active power static is at least twice as large, and in particular at least three times as large, as the slope or amplification of the corresponding first static, reactive power, or active power static. It is particularly important that the first slope is significantly larger than the second slope. The statics are thus coordinated in such a way that the at least one primary supply device essentially takes over the reactive and / or active power supply from the voltage imprinting device. The voltage imprinting device provides the initial voltage supply, while the primary supply device provides the initial supply for power and reactive power.

[0036] A voltage-forming device can be, for example, a voltage-forming inverter, and the primary power supply device a current-forming inverter. These are usually housed in separate control cabinets, so for simplicity, they are referred to as voltage-forming control cabinets and current-forming control cabinets, respectively. However, other units are also possible, such as an analog feed-in unit. It is also possible for at least one voltage-forming device and one primary power supply device to be housed together in a single unit, for example, in a wind turbine.

[0037] For illustrative purposes and only as an example, a functional principle is explained below for a voltage-sharing inverter and a current-sharing inverter, without being limited to these.

[0038] Basically, a voltage-sharing inverter works by providing an output voltage with defined amplitude, frequency, and phase. The instantaneous value of the output voltage is fed back via a feedback loop.

[0039] A voltage signal is thus fed back. For example, a tolerance band method can be used, in which the fed-back voltage signal is constantly checked, i.e., at the sampling rate used, to ensure it lies within a tolerance band. As soon as the voltage signal approaches a limit of the tolerance band, the inverter switches to keep the signal within that band.

[0040] The tolerance band is a realization of a target value for the inverter's output voltage. The target value is specified as a target signal, including amplitude, frequency, and phase, and the tolerance band essentially lies close to this target signal, defined by upper and lower limits.

[0041] If a reactive power surge occurs, where the reactive power in the power generation grid changes abruptly or at least rapidly, for example because a capacitive element such as a transmission line has been switched on, then the voltage-regulating inverter also experiences a change in its output and thus its feed-in reactive current. This is because the voltage-regulating inverter, similar to a voltage source, attempts to keep its output voltage constant, so that at approximately the same voltage, the current changes.

[0042] This then leads to a new voltage setpoint being set according to a reactive power statics stored for this voltage-generating inverter. The output voltage then changes accordingly.

[0043] A voltage deviation can occur between the voltage of the power generation grid and a setpoint, referred to here as the grid setpoint voltage. This grid setpoint voltage, and thus this voltage deviation, does not refer to the instantaneous value of the output voltage, but to an RMS value or other characteristic value of the voltage amplitude.

[0044] The current-shaping inverter initially operates very similarly to the voltage-shaping inverter, except that instead of instantaneous values ​​of an output voltage, instantaneous values ​​of an output current are fed back. In other words, an output current signal is fed back. If the reactive power in the power generation grid changes, this initially has no strong, immediate effect on the output current, because the output current is regulated. In this respect, the current-shaping inverter functions like a current source.

[0045] The changed total reactive power therefore initially only affects the voltage-generating inverter.

[0046] The current-shaping inverter detects the voltage deviation caused by the reactive power current it generates. Based on this voltage deviation and its reactive power characteristics, the inverter then determines a reactive power setpoint and, consequently, a target current signal for the output current, which it then feeds into the system.

[0047] This also changes the reactive current of the current-forming inverter, which then takes over a large portion of the reactive current of the voltage-forming inverter. This, in turn, leads to an adjustment of the output voltage of the voltage-forming inverter according to its reactive power characteristics. The two inverters (or more) then adjust to a stable operating point with the same voltage deviation, based on their respective reactive power characteristics. Due to the different slopes of their reactive power characteristics, the current-forming inverter then feeds in more reactive current or reactive power than the voltage-forming inverter.

[0048] In the event of a reactive power surge, the voltage-regulating inverter reacts immediately and adjusts its voltage, which triggers a response from the current-regulating inverter, which then initially feeds in the reactive power. The two, or more, inverters then reach an operating point at which, due to the proposed choice of reactive power stability, the current-regulating inverter essentially takes over the reactive power feed-in, or at least a significant portion of it.

[0049] The system operates in a similar manner during a sudden surge or rapid change in active power. While the total active current changes, initially only the current of the voltage-generating inverter changes. This change in its active current is detected by the voltage-generating inverter and, according to its active power statics, results in a new setpoint for its voltage signal, namely with a changed frequency.

[0050] Next, the current-shaping inverter detects this frequency change and generates corresponding active power setpoints for itself. Due to the greater slope of its active power curve, or amplification thereof, the current-shaping inverter will assume a higher active power value at the same frequency than the voltage-shaping inverter. Both inverters then feed in their respective active power, with the current-shaping inverter feeding in the larger share.

[0051] The described reactions to a reactive power jump and a real power jump can also occur together.

[0052] According to one embodiment, it is proposed that the selection of the setup mode, in particular the switch from normal operating mode to setup mode, occurs, or can occur, when the power generation network also exhibits a voltage drop. Accordingly, it is proposed to consider not only a voltage drop in the electrical supply network but also a voltage drop in the power generation network. Selecting or switching to setup mode can be proposed, especially when the voltage drops, and in particular voltage dips, are already significant in one of the two networks. If the respective voltage drop is small, it is also conceivable that the power generation network must additionally exhibit a voltage drop in order to select or switch to setup mode.

[0053] According to one embodiment, it is proposed that the operation of the power generation network in the setup mode only occurs when the power generation network is de-energized. This allows the setup mode to begin immediately, without having to consider any existing voltage in terms of frequency, phase, and / or amplitude. This ensures that only the at least one voltage imprinting device and the at least one first supply device control the setup mode.

[0054] It is also specifically proposed that the energy generation network be separated from the electrical supply network so that the energy generation network can start up independently and without disturbance.

[0055] According to one embodiment, it is proposed that the at least one primary power supply device, or the subsequent primary power supply devices, for providing electrical power in the energy generation network are cascaded and synchronized. Synchronization thus occurs gradually, with a first primary power supply device being synchronized with the voltage-forming device and simultaneously providing electrical current or feeding it into the energy generation network. The next primary power supply device, if present, then synchronizes with this first minimal system consisting of at least one voltage-forming device and one primary power supply device.

[0056] According to a further embodiment, it is proposed that the electrical power supplied by the at least one primary power source in the power generation network includes at least a reactive power component sufficient to cover the reactive power demand of the power generation network. A power demand in the power generation network can arise particularly from electrical lines within the network, but also from inductive loads. In the configuration mode according to this embodiment, this demand is met by the at least one primary power source. Accordingly, a minimum requirement for the size of the at least one primary power source also results. The at least one primary power source, or the multiple sources if several are used, must be able to provide as much reactive power as the power generation network requires.

[0057] Preferably, the method is characterized in that the electrical power provided by the at least one primary power supply device in the power generation network has at least a reactive power component and an active power component. It is proposed that the reactive power component be larger than the active power component, preferably at least twice as large, and more preferably at least five times as large. It is thus proposed that the reactive power component be significantly higher than the active power component. It was recognized that in this setup mode, the initial focus is on meeting the reactive power demand, and that any consumers requiring active power may not initially be activated in this setup mode. At least at the beginning of the setup mode, reactive power may be the primary focus. Any consumers requiring active power may then need to be switched off or...They should remain switched off. This ensures that as many generators as possible are connected to the grid initially, in order to build up the grid.

[0058] Preferably, the power generation network voltage is ramped up to the supply network voltage to synchronize the power generation network with the electrical supply network. The supply network voltage is the voltage present in the electrical supply network. In particular, the power generation network can be switched back to the electrical supply network to restore normal operating mode after synchronization.

[0059] According to one embodiment, it is proposed that the energy generation network be connected to the electrical supply network via an energy generation network transformer if the energy generation network has an energy generation network voltage synchronized with the electrical supply network. Such an energy generation network transformer is, in particular, a wind farm transformer if the energy generation network is a park network of a wind farm. The wind farm transformer can also be referred to synonymously as a park transformer or park transformer.

[0060] Alternatively, the energy generation network can also be connected to the electrical supply network even if the electrical supply network is not live. In this case, a grid restoration voltage can be provided at the grid connection point. The electrical supply network can therefore be brought online by the energy generation network.

[0061] According to one embodiment, it is proposed that the at least one voltage-correcting device and the at least one primary supply device are shut down so that the power generation network is de-energized when the electrical supply network exhibits a voltage drop. If the electrical supply network exhibits a voltage drop, i.e., if it was previously operating normally and in normal operating mode, the power generation network can first be shut down to de-energize it. Preferably, the power generation network is only started up when a resolution of the voltage drop in the electrical supply network is expected, or when a fault that caused the voltage drop is expected to be rectified.

[0062] In one embodiment, it is also proposed that the at least one voltage imprinting device only provides a power generation network voltage when the power generation network is de-energized. The power generation network is therefore first shut down, or it is detected that it is shut down, and only then does the first step of the build-up mode begin, namely providing a power generation network voltage via the voltage imprinting device.

[0063] Several definitions are proposed for voltage drop, which refers to the nominal voltage of the electrical supply network. Specifically, it is suggested that the voltage of the electrical supply network is less than 90%, less than 70%, less than 30%, or less than 10% of the nominal voltage. A voltage drop of less than 90% already constitutes a significant voltage drop. To further highlight the voltage drop as a fault, a value of less than 70% of the nominal voltage can be proposed. A value of less than 30% of the nominal voltage is even more clearly recognizable, making it obvious that a fault exists that also necessitates the expansion of the power generation network. Using a value of less than 10% to define this voltage drop is even more explicit.Since the voltage of the electrical supply network is approximately at its nominal voltage during normal operation, it will drop below 90%, 70%, and 30%, and then to 10% if it does not recover beforehand. Defining these different values ​​allows for at least slight time differences in detection if the voltage does not recover. Preferably, a voltage drop includes or is a drop in voltage to zero.

[0064] According to one embodiment, it is proposed that the at least one voltage-forming device for providing the power generation network voltage has a DC link supplied by a capacitor. It is further proposed that the capacitor be configured to supply the DC link with a DC voltage in the event of a voltage drop in the electrical supply network or in the event of a de-energized power generation network, such that the at least one voltage-forming device can provide a stable power generation network voltage. The capacitor, or a corresponding capacitor unit or capacitor bank, thus provides a sufficiently high DC voltage. From this, a voltage can be generated and provided in the power generation network, particularly by an inverter.

[0065] The inverter can be controlled, for example, using a pulse-width modulation (PWM) method. A tolerance band method can also be used. When using the tolerance band method, it is particularly recommended that a voltage at the output of an output inductor connected to the inverter be fed back as the actual voltage for the tolerance band method. In any case, the necessary voltage can be stably provided in the power generation grid by such a method or a similar one. The capacitor bank can be supplied, in particular, by a rectifier connected to a generator, such as a wind turbine.

[0066] According to one embodiment, it is proposed that a voltage drop in the electrical supply network and / or a lack of voltage in the power generation network be detected, whereby voltage detection by the at least one voltage imprinting device is proposed. The voltage imprinting device can thus independently and directly detect the voltage drop or lack of voltage and switch to setup mode, thereby performing a first important step in starting the power generation network.

[0067] According to one embodiment, it is proposed that the energy generation network includes a power control system by means of which the at least one primary supply device feeds electrical power into the electrical supply network depending on a power setpoint. With such a power control system of the energy generation network, which can be designed, for example, as a park control system or central park control system for a wind farm, the fed-in or provided power can thus be coordinated. It is also conceivable that such a power control system receives a setpoint or target value from an external source, such as a network operator of the electrical supply network. Particularly in the case of network restoration, this allows for coordination with the switching on or ramping up of electrical consumers in the electrical supply network.Such coordination could also take place within the energy generation network.

[0068] Preferably, a target power value is specified by an energy generation network operator or an electrical distribution network operator. In particular, the electrical distribution network operator has the ability to influence the energy generation network through such a target value without having to make further control adjustments to the energy generation network itself.

[0069] The electrical power of the primary power supply is then increased accordingly, meaning that it is gradually adjusted to compensate for any deviation between its actual value and the specified setpoint, or another setpoint. Depending on the controller, a certain degree of steady-state deviation may also be accepted. Preferably, however, an integral (I) controller, or at least an integral component within a controller, is proposed to compensate for steady-state deviations and thus achieve steady-state accuracy. Especially with correspondingly high power setpoints, and particularly when additional loads are switched on or ramped up in the meantime, further primary power supplies can be connected and used. Their connection and synchronization can be cascaded. This allows a higher power demand to be met gradually.

[0070] Preferably, it is also proposed that the power generation network includes a frequency control system that reserves a portion of the electrical power from the at least one primary supply device in order to release it, and in particular to feed it into the grid, for frequency control of the electrical supply network when needed. This frequency control system can be implemented as a control mechanism, particularly in a central control unit of the power generation network. In the case of a wind farm, this can be implemented in a central park control system or central park control unit.

[0071] The primary power source can provide electrical power, which describes the power that the primary power source can make available at that moment. In this respect, this electrical power is an upper limit, at least a temporary one. If the primary power source is a wind turbine, it can provide as much electrical power as the prevailing wind provides and any other limitations of the wind turbine allow. Thus, if, for example, rated wind prevails and there are no other limitations on the wind turbine, the electrical power of the primary power source in this case is the rated power of the wind turbine.

[0072] It is proposed to withhold a portion of this power, meaning not to feed it into the grid initially. For example, in the case of the described wind turbine, this could mean reducing its operation by, for instance, partially turning its rotor blades out of the wind. It could also mean that, if an energy storage system is used, the withheld portion of the electrical power is stored in it, or, if the electrical storage system is the power source, only a portion of its available power is used. In the case of the aforementioned wind turbine, it is also conceivable that it generates the full power available from the wind, within its limitations, but temporarily consumes or dissipates the withheld portion, for example, through resistors in which the electrical power is selectively converted into heat. This can be achieved particularly through a chopper process or...a chopper circuit or chopper device is used, whereby a portion of the electrical power is selectively directed into such resistors for conversion into heat by choppers, i.e., by controlling a current through a pulsed control signal.

[0073] If more power is needed for frequency control, this reserved portion of the available power can be used. For example, the rotor blades can be adjusted to extract more power from the wind, to use the first example. Or, less power can be consumed. In particular, the described chopper process can be modified to reduce its power consumption. If necessary, the chopper process can be completely suspended or terminated to use this power for frequency control of the power generation grid.

[0074] Preferably, it is also proposed that the frequency control system draws electrical power from the electrical supply network and preferably consumes it via a chopper device. This allows not only the input power to be reduced or withheld, but even more significantly the power required for frequency support to be reduced, namely into a negative range. This, in turn, allows the control range to be extended.

[0075] Furthermore, such frequency control can be centrally coordinated or implemented independently by each primary supply device. Specifically, it can be stipulated that each primary supply device implements such frequency control, or the described detail, based on a power setpoint or based on a frequency measurement. It is specifically proposed that the withheld portion of the power be made available again, or controlled depending on the frequency of the electrical voltage in the power generation network or the electrical supply network.

[0076] Furthermore, or alternatively, it is proposed that frequency control limit the feed-in of electrical power from at least one primary supply device if the power generation network and / or the electrical supply network has a network frequency that constitutes an overfrequency. Such an overfrequency is, in particular, a frequency that lies above a normal frequency, especially the nominal frequency, by a predetermined permissible frequency overshoot value. In such cases, it is proposed to reduce the fed-in power. Accordingly, a limitation of the fed-in power is proposed.

[0077] According to one embodiment, it is proposed that the power generation network be configured to receive and / or generate a weather forecast, the weather forecast being used to determine a time at which the operation of the power generation network in setup mode can be started. Thus, it is proposed that, based on a weather forecast, particularly if the power generation network is a wind farm or includes wind turbines as voltage-forming devices and / or primary supply devices, the start-up of the power generation network, especially its operation in setup mode, is planned.

[0078] If sufficient wind is expected, the proposed setup mode can be initiated and implemented. If insufficient wind is present, the setup mode may not be able to be initiated. It is also possible that sufficient wind is present, even if the wind speed is relatively low, requiring several wind turbines, for example, as a primary source of power to provide sufficient output. Accordingly, it can be planned that after the voltage regulator, which provides a power generation grid voltage, is started, a corresponding number of wind turbines are started as a primary source of power. Alternatively, it may also be possible to initially use a corresponding number of voltage regulators to provide the power generation grid voltage.

[0079] According to one embodiment, it is proposed that the voltage imprinting device and the initial supply device each form a feed-in unit and operate as a voltage imprinting device and an initial supply device, respectively, by means of a control signal. In particular, the voltage imprinting device can operate as an initial supply device by appropriately changing the control signal, and the initial supply device can operate as a voltage imprinting device by changing the control signal. Specifically, the voltage imprinting device and the initial supply device can be identical except for the control signal. In particular, several feed-in units, especially essentially identical ones, can be provided in the power generation network, operating as voltage imprinting devices or initial supply devices as needed.In particular, it is proposed that the energy generation network is a park network of a wind farm, and that the feed-in units are wind turbines, with each wind turbine capable of operating as a voltage regulator or a primary supply device depending on its control configuration. According to this or any other embodiment, it can also be provided that a wind turbine comprises both a voltage regulator and a primary supply device. For example, a voltage regulator and a primary supply device can each be provided as a power cabinet within the wind turbine, or elsewhere. Preferably, a battery storage container is provided for this purpose, which also includes a battery storage unit for providing electrical power for grid restoration.

[0080] The implementation of a voltage-specifying device or a primary supply device can differ significantly in that, in the case of a voltage-specifying device, an actual voltage value is fed back and compared with a setpoint voltage to regulate the voltage-specifying device to the setpoint voltage. In contrast, the primary supply device can operate primarily as a current-specifying device, feeding back an actual current value and comparing it with a setpoint current to control the primary supply device accordingly. Specifically, the primary supply device is regulated to the setpoint current. This primarily affects instantaneous values ​​and less so the RMS values, which are only indirectly affected.

[0081] It is specifically intended that all feed-in units of the energy generation network can operate as voltage-forming devices or primary supply devices, depending on the control settings. In particular, it is proposed that for a wind farm, all wind turbines in the wind farm can operate as either voltage-forming devices or primary supply devices, depending on the control settings.

[0082] According to the invention, a wind turbine is also proposed, comprising a control unit and a converter configured to operate as a voltage-forming and / or current-forming device. The control unit controls the converter such that the wind turbine is configured to operate as a voltage-forming device or as a primary power supply device, in particular in a method according to at least one embodiment described above.

[0083] The wind turbine is thus prepared, particularly through the appropriate implementation of a control system in its control unit, to execute the control and / or process steps or a part thereof that were described in connection with the voltage-forming device when the wind turbine operates as a voltage-forming device, or that were described for the primary supply device when the wind turbine operates as a primary supply device.

[0084] According to the invention, a wind farm is also proposed comprising at least one first and one second wind turbine, wherein the first wind turbine can operate as a voltage generator and the second wind turbine as a current generator, in particular to function as a primary power source. These at least one first and one second wind turbine are thus equipped to carry out a method according to one of the embodiments described above. Alternatively, at least one first inverter capable of voltage generation and at least one second inverter capable of current generation are provided to carry out a method according to one of the embodiments described above.

[0085] Preferably, at least one first and at least one second wind turbine will each be a wind turbine according to the invention or a wind turbine according to an embodiment.

[0086] According to one embodiment, it is proposed that at least one first inverter capable of voltage generation and at least one second inverter capable of current generation are coupled together with an energy storage unit, in particular a battery storage unit, and together form a black start unit and are prepared to be used for operating the power generation network in the setup mode, in particular such that the energy storage unit provides the energy required to the at least one first and at least one second inverter for operating the setup mode.

[0087] The at least one first inverter serves as the voltage impedance generator, and the at least one second inverter serves as the primary power supply. The energy storage unit provides the power that the inverters require for feeding in or supplying power, as well as the power they need for their own operation, particularly for control and, if applicable, communication equipment. Preferably, this black start unit is designed as a black start container, so that the inverters and the energy storage unit are housed in a single container. By using such a container, a wind farm that was previously not capable of black start can be easily upgraded to one capable of black start operation. The black start container simply needs to be connected to the wind farm's grid, and, if necessary, a communication device or other equipment can be added.A communication interface for communication with a central parking control system or central parking control unit has been installed.

[0088] The invention will now be explained in more detail below with reference to the accompanying figures. Fig. 1 shows a schematic perspective view of a wind turbine. Fig. 2 shows a schematic view of a wind farm. Fig. 3 shows a conventional procedure for a black start and grid restoration after a grid failure. Fig. 4 shows a proposed procedure for a start and restoration after a grid failure. Fig. 5 schematically shows a wind farm in a start-up state. Fig. 6 shows a diagram with different static conditions. Fig. 7 schematically shows a wind farm and some details of the control system for the wind turbine shown. Fig. 8 illustrates the interaction of a voltage impedance generator with a primary supply device.

[0089] Figure 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.

[0090] Figure 2Figure 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. 2This 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 may also be designed differently, for example, by including a transformer at the output of each wind turbine 100, to name just one other example.

[0091] Fig. 3This illustrates a typical sequence from a grid outage through reconstruction back to normal grid operation. This sequence, 300, begins in Unit 302 with a grid outage in which the electrical supply network collapses. This leads, in particular, to safety switches opening, preventing power plants from feeding their output into the grid. Accordingly, Unit 304 explains that after the grid outage, thermal power plants initially attempt to stabilize themselves in a self-sufficiency mode. They try to reduce their power generation as quickly as possible while remaining operational. Ideally, they should achieve a self-sufficiency mode in which they generate only as much energy as they need for their own supply.

[0092] Then, especially after a corresponding fault in the grid has been rectified, or at least after the electrical supply network or a part of it is basically operational, a black-start capable power plant is started. This start-up of black-start capable power plants is illustrated in the next section, Block 306. Black-start capable power plants are specifically those that can start themselves without an external supply of electrical energy and that are also capable of operating at least a small portion of the electrical supply network. "Small portion" in this context can also mean that some consumers in the relevant section are not yet connected.

[0093] Based on the start-up of such black-start capable power plants, a transmission network is also established using these black-start capable power plants, as illustrated by Unit 308. Units 306 and 308 thus describe a black start of the electrical supply network or a part thereof, and this regularly requires two to four black-start capable power plants. These two units, 306 and 308, can be combined as black-start steps 310.

[0094] In Unit 312, the next step involves connecting distribution networks and loads to the transmission network. As a further step, Unit 314 proposes connecting power plants operating for on-site consumption. From Unit 314, the process can return to Unit 312, thus completing a loop in which distribution networks and loads are successively connected to the transmission network, and power plants operating for on-site consumption are connected. This loop 316, which essentially consists of these two units 312 and 314, can also be referred to as network reconstruction. In this network reconstruction, the entire power plant portfolio is rebuilt. This power plant portfolio can be defined as the electrical supply network with all connected power plants.

[0095] If this network reconstruction according to loop 316 has been successfully completed, normal network operation can be resumed in the last step according to block 318.

[0096] One of the processes involved in the Fig. 3 Alternative procedure 400 is in Fig. 4 This process 400 describes the process for a wind farm, i.e., which steps occur in a wind farm, are relevant to it, or need to be considered.

[0097] This sequence 400 starts from a state described in Block 402, in which the wind farm is operating normally. Essentially, power is fed into the electrical grid depending on the wind speed, preferably as much as can be drawn from the wind. A grid collapse then occurs, as described in Block 404. The wind turbines of the wind farm then shut down their operation in a controlled manner and disconnect from the grid. This is illustrated in Block 406. Communication between the wind turbines, especially with a central park control system, is maintained as much as possible. During this shutdown, as described in Block 406, the wind turbines can enter a self-supply mode, in which they generate as much energy as they need for their own operation.The wind farm can also enter a self-supply mode, in which the wind turbines generate as much energy as the entire wind farm needs to maintain its functionality. If a self-supply mode is not used, communication can be maintained, for example, via an energy storage system.

[0098] A central parking control system, especially one powered by an uninterruptible power supply, maintains communication with a grid operator. At the very least, it maintains a means of communication with the operator, as indicated by block 408.

[0099] As a next step, the grid operator, who runs the electrical supply network, reports a total power outage to the park control unit, and block 410 is responsible for this. This makes it clear to the wind farm, and especially to the central park control unit, that a total power outage has occurred, allowing the wind farm and the central park control unit to adjust accordingly.

[0100] Once any faults in the electrical grid have been rectified, or if the grid operator believes for other reasons that a restart of the electrical grid is now possible, the grid operator submits a black start request to the wind farm, specifically to the central park control unit, which is represented by block 412. The wind farm, or rather the central park control unit, then switches to a black start operating mode according to block 414. This can also be referred to as a setup mode. Blocks 406 to 412 can optionally also be considered part of such a setup mode.

[0101] The next step, according to Block 416, is to obtain or prepare a weather forecast. Based on this, the central park control system, according to Block 418, determines a guaranteed minimum output that it can provide shortly based on the prevailing and expected wind speed. This guaranteed minimum output is also reported to the grid operator.

[0102] As a next step, Block 420 proposes that the central park control unit send a black start signal to black start units. Such a black start signal instructs the black start units, which may only need to be a single unit, to perform the necessary steps to execute a black start. Black start units can be wind turbines or battery-powered units. In any case, they include a converter or inverter. A black start unit can function as both a voltage impedance generator and a primary power supply. For example, one wind turbine can act as a voltage impedance generator and another as a primary power supply. Alternatively, one or more power cabinets could act as either voltage impedance generators or primary power supplies. These cabinets can be located together or separately within a wind turbine and receive power from it.However, it is also proposed that dedicated power cabinets be supplied independently of a wind turbine via an energy storage device such as a battery. While such a battery or other energy storage device can be charged within the wind farm using energy from the wind turbines—provided the wind farm and thus the electrical grid are operating normally—otherwise, there need be no direct connection between such a battery or other energy storage device and the wind turbines within the wind farm. Alternatively, it is also conceivable that such a battery or other energy storage device is housed at or within a wind turbine, and that the wind turbine provides its inverters or converters—that is, its power cabinets or a portion thereof—for a black start, along with such a battery or other energy storage device.

[0103] The next step according to Block 422 involves a voltage-striking device, specifically a voltage-striking power cabinet, energizing an internal busbar. Initially, a low voltage amplitude can be used, allowing the voltage-striking device to provide 10% of the nominal voltage of the power generation grid. This can also mean that the busbar is initially only brought to approximately 10% of its voltage in normal operating mode. Such voltage-striking devices, particularly these voltage-striking power cabinets, thus maintain a voltage that is as constant as possible. However, they feed comparatively little active power and also little reactive power into the wind farm's grid.

[0104] Next, the primary supply equipment, and thus the current-regulating power cabinets, will connect and feed reactive power into the park network to regulate the target voltage. Block 424 is responsible for this. The voltage level to be supported by this reactive power injection is based on the target voltage provided by the voltage-regulating power cabinet according to block 422.

[0105] The voltage-forming devices and current-forming devices, or voltage-forming power cabinets and current-forming power cabinets, are then coordinated according to Block 426, or have correspondingly different regulations, such that the current-forming power cabinets handle the injection of active and reactive power in steady-state conditions. Ideally, the voltage-forming power cabinet injects neither active nor reactive power.

[0106] Block 428, however, signifies that voltage-regulating power cabinets handle transient power surges. They initially compensate for power jumps through these surges. The current-regulating power cabinets then take over the necessary reactive power and, if required, active power feed-in.

[0107] According to Block 430, black start units are gradually connected to the park grid. This applies particularly to voltage-forming and current-forming power cabinets, which can then provide a target voltage in the park grid and, if necessary, increase it further. A black start unit comprises at least one voltage-forming device and one initial power supply device and can, for example, be designed as a black start container that contains such units and, if necessary, also an energy storage device that provides the energy required for starting.

[0108] According to Block 432, further feed-in units will then be gradually connected to the park grid. These feed-in units can also inject reactive power with a particularly high gain to support the target voltage. Such feed-in units can be particularly current-shaping devices, i.e., power cabinets with a high current-shaping capacity. However, Block 432 specifically calls for the connection of further feed-in units that are not necessarily suitable for starting the energy generation grid due to their special characteristics, so that as much of the park as possible can be integrated. Therefore, according to Block 432, essentially the remaining, standard feed-in units will be connected.

[0109] Once a sufficient number, preferably all, of the wind farm's feed-in points are connected to the park grid, the park transformer can be connected in the next step according to section 434. The park transformer, i.e., the transformer through which the park grid feeds into the electrical supply grid or through which energy is exchanged between the electrical supply grid and the wind farm, is connected to the park grid according to this step of section 434. The park transformer is connected to the park grid on one side, but not yet to the electrical supply grid on the other.

[0110] With this parking transformer connected, the next step, according to block 436, is to increase the target voltage in the parking network to its nominal voltage. However, this step of increasing the parking transformer can also be omitted. Once this process is complete, and the parking network is at its nominal voltage, it is proposed that the central parking control unit report its readiness to connect to the network operator, as indicated by block 438.

[0111] If the grid operator agrees, or at least does not prohibit the connection, the wind farm will connect to the blacked-out section of the electrical grid in the next step, as described in Block 440. The wind farm will then be connected to the electrical grid and can feed active and reactive power into it. Specifically, it can feed as much active power into the grid as it has already transferred to the grid operator as guaranteed minimum capacity in Block 418. If necessary, this information regarding the guaranteed minimum capacity can be updated and reported to the grid operator.However, not much time should elapse between the step of reporting the guaranteed minimum output according to Block 418 and the step in which the park connects to the blacked-out section of the grid according to Block 440, ideally only a few minutes, so that the wind forecast and the resulting guaranteed minimum output should still be accurate.

[0112] In any case, the grid operator then expands the electrical supply network at least up to this guaranteed minimum capacity. Block 442 is responsible for this step. The grid operator can connect specific consumers, consumer groups, or consumer clusters for this purpose.

[0113] In accordance with block 444, the network operator then assumes power control of the relevant electrical supply network, at least of the section relevant here.

[0114] Now, an electrical supply network or corresponding network section exists that operates at nominal voltage, and the network operator can now connect further feed-in points to the network in the next step in Block 446. Such feed-in points can be additional wind farms, but also conventional power plants.

[0115] The electrical grid, or rather the section of it under consideration, is now well on its way to normal operation. However, normal operation has not yet been achieved, and depending on the grid situation, it is proposed that in one case the wind turbine, and thus the wind farm, switch to a grid restoration mode, for which block 448 represents. Such a grid restoration mode specifically involves gradually connecting disconnected grid sections and, if necessary, gradually ramping them up.

[0116] Alternatively, each wind turbine, and thus the wind farm, remains in black start mode, also referred to here as start-up mode. In this mode, the wind turbines, or the wind farm as a whole, feed active power into the grid according to a specification provided by the grid operator. Simultaneously, each wind turbine, or the wind farm as a whole, maintains voltage and frequency. In principle, the wind farm can perform this voltage and frequency maintenance, although this can typically be done independently by each individual wind turbine. The task of a central park control unit can then, according to this particular configuration, focus on providing a target value for the active power for each wind turbine, based on an overall target active power value specified by the grid operator for the entire park. The grid operator thus provides this target active power value to the central park control unit.Based on this, the central park control unit sends individual active power setpoints, preferably as percentages, to the wind turbines. The wind turbines feed this active power into the grid according to their setpoint and simultaneously, depending on voltage and frequency measurements or other detection methods, maintain these voltage and frequency values. This maintained black start mode, in which the wind turbines perform voltage and frequency maintenance, is provided as an alternative to Block 448 according to Block 450.

[0117] In any case, this should result in a black start and, if applicable, a grid restoration, allowing the grid operator to assess whether the electrical supply network is functioning normally again. If so, the operator reports normal operation in accordance with block 452.

[0118] In the final step, as described in Block 454, the wind farm, primarily controlled by the central wind farm control unit, will then switch to normal operation. This normal operation means, in particular, that as much active power as possible is generated and fed into the grid—specifically, as much active power as can be generated based on the available wind. Furthermore, each wind turbine will be operated at a speed adapted to the specific situation. At full load, it will therefore operate at its rated speed, and at partial load, it will operate according to a speed-power curve, although other standard operating procedures may also be considered.

[0119] Regarding the described process, it should be noted that some elements specifically concern aspects of communication and are marked with reference 1. This applies particularly to blocks 404-420 and 438-452.

[0120] Aspects relating to special features of the regulation are marked with reference 2 and particularly concern blocks 420 - 436 and 440.

[0121] Fig. 5 Figure 500 illustrates a simplified wind farm in a rebuild mode. In this example, it has at least four power cabinets, 501 to 504. The first power cabinet, 501, is designated as a voltage-specifying power cabinet. It thus acts as a voltage-specifying device. This voltage-specifying power cabinet, 501, is primarily intended to define a voltage. It should also be able to feed in power, particularly reactive power Q, but only to a limited extent. An example value of 0.1 MVA is given here.

[0122] The three remaining power cabinets 502–504 are intended as current-shaping power cabinets, i.e., as current-shaping devices. They can individually or collectively form a primary power supply device. Each of these power cabinets should be able to feed in a greater reactive power Q than the first power cabinet 501. As an example, a reactive power value of 0.3 MVA is specified here for each of the power cabinets 502–504. Together, these four power cabinets 501–504 can feed a reactive power Q of 1 MVA into the exemplary network 506.

[0123] This Windpark 500 may also contain additional feed-in devices, especially additional wind turbines, which can also support a setup mode or which are only switched on during normal operation or later in the setup mode.

[0124] Fig. 5The illustration is intended to clarify the initial configuration, according to which one unit operates in a voltage-generating capacity (here, power cabinet 501) and feeds in little reactive power, whereas other units, or possibly just one further unit, operate in a current-generating capacity (here, power cabinets 502-504) and can also feed in a significant amount of reactive power Q for voltage stabilization. The power cabinets 501-504 shown as examples can also be housed entirely within a black-start container as a black-start unit, which is specifically designed for such a setup mode and can contain a battery or other energy storage device that provides sufficient energy for this setup mode.

[0125] Power cabinets 501-504 can each represent a wind turbine, operating either as a voltage-generating unit (according to power cabinet 501) or as a current-generating unit (according to one of power cabinets 502-504). Each wind turbine can, of course, generate and feed in more power, including more reactive power, and may therefore require multiple power cabinets.

[0126] Fig. 6 This illustrates different static calculations that specify a reactive power Q as a function of a voltage deviation dU. According to the characteristic curves shown, the corresponding power cabinets 501 - 504 of the Fig. 5The power cabinets 501, which operates in a voltage-generating manner, are controlled such that they operate according to curve 601, whereas the current-generating power cabinets 502-504 each operate according to curve 604. Thus, each of the power cabinets 502-504 feeds in three times as much reactive power Q as the voltage-generating power cabinet 501 for the same voltage deviation, i.e., the same dU in the example shown.

[0127] The voltage-regulating power cabinet 501 adjusts the voltage deviation dU via a setpoint voltage according to the resulting reactive power Q, and the current-regulating switchgear cabinets adjust the reactive power Q according to the detected voltage deviation dU. This voltage deviation can be detected at the output terminals of the inverter.

[0128] The graphic of Fig. 6The graph shows a reactive power value of 0 and a differential voltage dU of 0 at its origin, i.e., the center of the coordinate system. The fact that the differential voltage dU has a value of 0 means that the voltage at that point corresponds to the setpoint Usetpoint.

[0129] Figure 6 The diagram shows static analyses for reactive power as a function of voltage deviation. Similarly, static analyses for active power as a function of frequency deviation are also proposed. This could be particularly useful in... Figure 6On the abscissa, the voltage deviation dU is exchanged for a frequency deviation df, and on the ordinate, the resulting reactive power Q is exchanged for a resulting active power P. This then yields a representation for static analyses of active power as a function of frequency deviation. It is also proposed that the primary supply device, i.e., in this case the current-generating power cabinets 502-504, each supply more active power at the same frequency deviation than the primary supply device, i.e., in this case the voltage-generating power cabinet 501.

[0130] In essence, the voltage-generating power cabinet 501 also feeds in a voltage with the frequency f corresponding to the resulting active power, and the current-generating switch cabinets feed in the active power according to the detected frequency or frequency deviation.

[0131] Fig. 7schematically shows a wind farm 700 with a central park control unit 702 with three exemplary wind turbines 704, two of which are only indicated by a symbol and one of which also schematically shows a control device 706.

[0132] The control device 706 shown comprises a rectifier unit 708 with an attached DC link 710 and a downstream inverter 712. The rectifier unit 708 with the DC link 710 and the inverter 712 can also be referred to together as a converter.

[0133] The rectifier unit 708 is powered by a generator of the wind turbine, which in Fig. 7The energy or power thus obtained is rectified by the rectifier unit 708 and made available on the DC link 710. The inverter 712 generates a three-phase AC voltage or AC current from this. For this purpose, an inductor 714 is connected to the inverter, to which the inverter is tuned. A voltage u(t) and a current i(t) can therefore be measured at the output of this inductor 714, and a voltage measuring device 716 and a current measuring device 718 are also provided for this purpose. The voltage and current thus measured are fed back to an inverter controller 720, and this inverter controller 720 controls the inverter 712 based on these readings.

[0134] The central park control unit 702 can transmit a target power value P to each wind turbine 704. If the wind turbines 704 are all the same size, it is also possible that these values ​​are the same. In fact, these target power values ​​P are only intended to be representative of possible target power values, which can also have different values, or can be transmitted as relative values, e.g., percentages.

[0135] The control unit 706 of the wind turbine 704 shown illustrates that this power setpoint P is to be transmitted to the inverter control unit 720. However, other control or evaluation architectures are also possible in the wind turbine 704.

[0136] The in Fig. 7The control unit 706 shown can operate as a current-forming unit or as a voltage-forming unit. When operating as a voltage-forming unit, the feedback voltage u(t) is used to control the inverter 712. The inverter can then generate and output a voltage signal that corresponds to a predefined voltage profile. The inverter thus operates in a voltage-forming mode.

[0137] It can also operate in a current-shaping manner by essentially orienting itself to the detected and fed-back current i(t) and generating a corresponding current signal, i.e., by operating in such a way that its output is specifically adjusted to the current according to a current setpoint.

[0138] This current and voltage shaping is particularly important because it specifies the exact sine wave signal that the inverter generates or attempts to generate. Accordingly, in the Fig. 7The instantaneous values ​​u(t) and i(t) for voltage and current are displayed for feedback. Naturally, the 720 inverter controller can also evaluate and use the amplitude of the respective signals as an RMS value, if necessary. This feedback of instantaneous values ​​is also to be understood as phase-wise; thus, three current values ​​and three voltage values ​​are fed back at a time.

[0139] Thus, the inverter 712 can operate in different ways, generating power and feeding it into the grid 724 via a park transformer 722, which can also be referred to simply as a park transformer. The other wind turbines can feed power into the electrical supply grid 724 via the same park transformer 722.

[0140] Furthermore, a disconnect switch 726 or 728 is provided both on the park side and on the side leading to the electrical supply network 724. A connecting line to the other wind turbines 704 is indicated upstream of disconnect switch 726, which here represents a park network 730.

[0141] For a black start, particularly for operating the control unit 706 in a setup mode, an additional battery may be provided, which is not shown here. Such a battery can, for example, supply the DC link 710. A DC voltage from such a battery can thus be provided in a simple manner and, if necessary, converted into an AC voltage or AC current by the inverter 712.

[0142] Figure 8 Figure 800 illustrates an energy generation network 800 which can be connected to an electrical supply network 806 via a disconnect switch 802 and a parking transformer 804.

[0143] For illustrative purposes, a voltage imprinting device 808 and a primary supply device 810 are shown, which are themselves also part of the power generation network 800.

[0144] The voltage-forming device 808 includes a voltage-forming inverter 812, which generates a voltage u(t) at its output and is measured specifically at the output of the indicated first output filter 814. The voltage u(t) is continuously measured and fed back to the first microcontroller 816. The first microcontroller 816 evaluates the instantaneous values ​​of this measured voltage u(t). These measured values, like the output voltage, are three-phase. To explain the Figure 8 However, it is not necessary to discuss this three-phase structure. This also applies to the first-aid remedy 810.

[0145] The first microcontroller 816 also receives a voltage signal u soll,w , which specifies the voltage u(t) to be set in terms of magnitude, frequency and phase.

[0146] This setpoint u soll,w is generated in the first inverter control unit 818. It depends on a setpoint voltage U soll,N and the measured values ​​U, I, f, φ, which are measured at the output of the first line choke 820.

[0147] The primary power supply unit 810, which operates in a current-specifying manner, has a current-specifying inverter 822, which operates similarly to the voltage-specifying inverter 812, but regulates to an output current i(t). This output current i(t) is detected at the output of the indicated second output filter 824 and evaluated in the second microcontroller 826. The second microcontroller 826 thus receives a current setpoint i setpoint, w, which specifies the current i(t) to be generated in terms of magnitude, frequency, and phase. The second microcontroller 826 accordingly controls the switching operations in the current-specifying inverter 822, which is indicated by the reference symbol S. Incidentally, the first microcontroller 816 controls switching operations in the inverter 812.

[0148] The setpoint current isollen, w_ is determined in the second inverter control unit 828. It depends on the voltage U, the current I, the frequency f, and the phase angle φ, and these quantities are measured at the output of the second line choke 830. The second inverter control unit 828 also receives a setpoint voltage Usollen,N as an input.

[0149] The voltage-forming device 808 thus generates a first current I1, and the primary supply device 810 generates a second current I2. These two currents I1 and I2 add up to the combined current IG. This combined current flows, for illustrative purposes, into the symbolic power generation network 800. This is meant to be illustrative because the voltage-forming device 808 and the primary supply device 810 are also part of the power generation network 800. Therefore, the combined current IG flows into the remaining part of the power generation network.

[0150] During operation, for example, if a reactive power surge occurs in the energy generation network 800, this is reflected in the total current IG. Because the output current I2 of the first supply device 810 is regulated by it, a change in the common current IG initially only leads to a change in the first current I1 of the voltage shaping device 808.

[0151] The change in the common current IG initially led to a change in the first current I1, which was detected by the first inverter control unit 818. The first inverter control unit 818 then uses this change, based on a reactive power or active power static value, to determine a new value for a voltage amplitude and / or a frequency. Accordingly, the target voltage signal u_target_w is adjusted and transmitted to the first microcontroller 816. This microcontroller then controls the voltage-generating inverter 812 accordingly. This results in a change in the voltage amplitude and / or frequency, which is measured by the primary power supply unit 810 at the output of the second line choke 830 and evaluated by the second inverter control unit 828.Depending on this, a new reactive power value and / or a new active power value is calculated, specifically based on the underlying reactive power or active power statics. Accordingly, a target current signal itarget,w is specified and transmitted to the second microcontroller 826. This then controls the current-generating inverter 822 accordingly. The result is that the second current I2 changes, which in turn changes the first current I1, leading to a further adjustment by the first inverter controller 818, again based on the respective statics, i.e., the reactive power statics and / or the active power statics.

[0152] As a result, the voltage imprinting device 808 and the initial supply device 810 will adjust to each other in such a way that they feed in a corresponding active or reactive power according to the statics relevant to them at the same voltage deviation or the same frequency.

[0153] A solution for starting an energy generation network is therefore proposed, especially for starting a parking network. The following general points are also noted.

[0154] A crucial aspect of starting up a power generation network, and consequently also of starting and restoring an electrical supply network or a section thereof, is suitable communication. It is proposed that an uninterruptible power supply (UPS) be provided for a central park control unit. This UPS includes a battery to ensure sufficient power for operating the central park control unit even during a power outage. Alternatively, or in addition, the wind turbine can operate in a self-supply mode, i.e., a self-maintenance mode for the wind turbine or wind farm. This can be achieved via a direct DC cable connection to the wind turbine, for example, to a DC link. Alternatively, or in addition, an AC connection to an AC output of an inverter on the wind turbine can be provided.Ultimately, it is also conceivable that the central park control unit is located locally in a wind turbine and preferably uses energy from the wind turbine that it generates in a self-maintenance mode, i.e., a self-supply mode.

[0155] Communication modules in the wind turbines and, if necessary, black start units are also proposed. For this purpose, communication via a Power over Ethernet (PoE) system is particularly suitable, where power is supplied via an existing Ethernet cable. It is specifically proposed that energy from the central park control unit, which may be equipped with an uninterruptible power supply (UPS), be supplied to the wind turbines via the Ethernet cable.

[0156] Alternatively, it can be suggested that each wind turbine should have its own battery, or at least several separate batteries for some wind turbines.

[0157] It is also possible that the wind turbine will power itself in a self-sustaining mode once it has recovered after the power outage.

[0158] Furthermore, communication with the network operator is proposed, namely that a communication interface is provided for this purpose.

[0159] This communication interface is intended to facilitate communication, particularly during network outages and when normal operation resumes. This information is specifically meant to be transmitted from network operators to the central parking control unit.

[0160] A black start request can also be submitted by the network operator to the central parking control unit, and conversely, the central parking control unit can indicate its readiness to perform such a black start.

[0161] Furthermore, a weather forecast is to be received or transmitted from the central parking control unit. As a result, the central parking control unit is to transmit a guaranteed minimum power output to the grid operator so that the operator can plan based on this guaranteed minimum output. The aforementioned black start request can also depend on such a guaranteed minimum output being provided.

[0162] Furthermore, it is proposed to use such a communication point with the grid operator for power control. This particularly concerns the grid operator specifying active power setpoints to the central park control unit. This can also be used for grid restoration, which may be part of starting up the energy generation grid. Preferably, the grid operator can also intervene in a controlling capacity, in particular switching between control modes, especially between normal operating mode and restoration mode.

[0163] Finally, a mode can also be transmitted that indicates this station in the electrical supply network after connecting further units. Information about the status of a network restoration or other voltage and frequency controls can be transmitted here. Both a completed and a desired network restoration can be communicated. Similarly, a functioning or desired voltage and frequency control can be communicated in this way.

[0164] In a black start mode that includes or corresponds to the described setup mode, the wind turbines and possibly a central park control unit are particularly affected in a wind farm.

[0165] Initially, it is proposed to transmit a signal to disconnect all circuit breakers on the low, medium and high voltage sides, insofar as these voltage levels exist.

[0166] It is further proposed to transmit a black start signal to black start units. These could be wind turbines that are appropriately equipped, especially those that can function as voltage impedance devices and / or as first-response power supplies.

[0167] These black start units then build an internal network.

[0168] It is specifically proposed that a voltage-generating wind turbine, and / or a voltage-generating power cabinet (which may be part of the wind turbine, but could also be, for example, a UPS), bring a DC busbar online with a reduced voltage. This ensures that a busbar, i.e., a DC link of a converter or inverter, has a voltage that is at least lower than in a normal operating mode.

[0169] The power supply from a DC link can operate in a so-called self-supply mode, also known as self-maintenance mode, in which the wind turbine generates as much electricity as it needs for its own operation. Alternatively, or in addition, a power supply from a battery or other energy storage device is also possible. For example, a battery might be used to start the wind turbine in the first place.

[0170] Connection to a DC link of a UPS is also an option.

[0171] For wind turbines, it is particularly suggested that power is initially supplied from a battery or similar storage device, such as a capacitor, and then from the DC link of the wind turbine once it has started up in its self-supply mode.

[0172] As a further step, it is proposed that power-generating wind turbines, or at least power-generating power cabinets, could be connected and feed power in together.

[0173] It is then proposed that operating points of the energy generation network, especially the park network, be adjusted so that voltage-sharing power cabinets or voltage-sharing wind turbines generate as little active and / or reactive power as possible.

[0174] Then, transformers for the wind turbines or other units in the power generation grid are connected. A park network is activated within the wind farm for the units involved in the wind farm's start-up, particularly wind turbines, and these units, especially wind turbines, are then interconnected and can work together.

[0175] Additional black start units, if available, can synchronize and support each other.

[0176] In a further step, the remaining units are connected, especially the remaining wind turbines, if the energy generation network is a wind farm.

[0177] Furthermore, a transformer can then be connected at the grid connection point, which in the case of a wind farm can be referred to as a park transformer.

[0178] The next step in the setup involves increasing the target voltage. This can be done using a control signal from a central parking control unit.

[0179] Voltage and frequency control can then be performed as part of the black start mode.

[0180] The wind farm regulates the voltage and frequency of the wind farm, i.e., the energy generation grid, and / or the electrical supply grid. The latter is particularly relevant when the electrical supply grid has already been reconnected to the energy generation grid for power exchange.

[0181] Active and reactive power surges can be provided by voltage-generating wind turbines or power distribution units within a short initial timeframe, particularly in the first milliseconds. In this respect, these voltage-generating units briefly handle these power surges. The power feed-in should then be handled by fast-acting current-generating units, especially wind turbines or power distribution units. These current-generating units are designed to quickly provide or feed in power. This can be achieved through current control, in which the actual current is fed back and compared with a setpoint current for regulation.

[0182] A synchronization mode and / or a frequency stabilization mode can then be used. In frequency stabilization mode, the primary focus is on ensuring that the frequency in the power generation grid and / or the electrical supply grid does not change, or changes only minimally, while stabilization to an absolute frequency value is not the primary focus and can be suspended.

[0183] According to one embodiment, it is proposed to use different control gains for voltage support in the voltage-forming units and the current-forming units. Such control gains for voltage support, in which reactive power is injected depending on a voltage deviation, are also referred to as static or droop. Due to the different control gains, i.e., different statics or different droop slopes, voltage-forming units, especially voltage-forming converters, only handle a very small portion of the reactive power injected for voltage support during steady-state operation. Reactive power surges are initially handled by voltage-forming devices, such as the voltage-forming converter, but are then quickly taken over by primary power supplies, especially current-forming converters.

[0184] Frequency-dependent active power control systems, also known as active power droops, should be set so that the operating point of the voltage-regulating inverter is just above zero with respect to its input active power. This means that in the event of a frequency deviation, the change in active power is relatively small compared to the current-regulating power cabinets. When positive active power is demanded, the voltage-regulating inverter initially takes over, and the current-regulating inverters then quickly adjust. Similarly, when negative active power is demanded, i.e., when a power reduction is necessary, the voltage-regulating inverter initially takes over and consumes active power. A fast-acting load, especially a chopper controller, can then dissipate this power.In the case of chopper control, chopping, i.e. pulsed control, controls a current into a resistance unit or resistance bank with ohmic resistors in order to convert the electrical power to be dissipated into heat.

[0185] It was particularly recognized that while system services from wind turbines are well known, they have so far been essentially adapted to the physical properties of the previously dominant feed-in technology, namely large power plants with synchronous machines.

[0186] It was recognized that, in the short and medium term, depending on the grid operating point, the feed-in technology that dominates at that moment should assume system responsibility. This would then be either a conventional feed-in technology with directly coupled synchronous machines or a converter-based feed-in technology. It was also recognized that simply replicating conventional, and therefore slow-responding, generators using converters is not necessarily effective. This finding is also relevant for black starts and intelligent grid restoration after a blackout.

[0187] Control and regulation strategies for wind farms were therefore proposed to carry out the black start in a black start situation and to support the grid restoration, in particular to provide intelligent support or even to accelerate it compared to a black start and grid restoration with regard to conventional feed-in systems.

[0188] The primary goal is to increase the share of inverter-based generation in electrical supply networks, especially interconnected networks. To this end, a control concept has been developed for networks that can be operated almost entirely by inverter-coupled or inverter-controlled feed-in of renewable energies at certain times, without compromising system security.

[0189] In particular, one or more of the following goals can be achieved, namely: Possible black start with renewable power plant capacities; accelerated grid restoration with renewable power plant capacities; grid integration of a temporarily very high proportion of renewable energies in the grid; secure grid operation even in grids that are temporarily almost entirely supplied by inverters; assumption of system responsibility in the electrical energy supply by wind turbines; avoidance of an allegedly technically determined upper limit for renewable energies, especially wind turbines in an electrical supply network; substitution of conventional power plants; increased acceptance of renewable energy producers by grid operators.

[0190] The proposed solution is based in particular on the idea of ​​dividing the steps for a black start into two functional groups.

[0191] These are the two functional groups: 1. Communication during power outages 2. Black start mode for units, especially wind turbines in wind farms and for a central park control unit

[0192] One possible sequence of events, especially considering these two functional groups, is in the Fig. 4 explained. There, these two functional groups are also labelled with the corresponding numbers 1 and 2.

[0193] An important aspect is the power distribution between voltage-generating and current-generating units, especially converters and power cabinets. This has the following purpose and background: Due to the varying steepness of the droops, i.e., the statics, which in Fig. 6As shown, a voltage-regulating converter handles only a very small portion of the reactive power, thus contributing only a very small part of the total reactive power fed into the grid. Reactive power surges are initially handled by the voltage-regulating converter and then quickly compensated for by the current-regulating converters. Similarly, for active power droops—that is, active power feed-in that is frequency-dependent or dependent on frequency deviations—the system is preferably configured so that the operating point of the voltage-regulating converter is only slightly above zero, meaning it is selected to feed in very little active power.When positive active power is requested, i.e., when active power is to be fed into the electrical grid, the voltage-regulating converter initially handles the excess power, and the current-regulating converters then quickly adjust accordingly, so that the voltage-regulating converter does not have to perform this task, or only for a very short time. The voltage-regulating converter can react to voltage changes much faster than the current-regulating converters and thus immediately takes over such a request for positive active power. It should be noted that active power demands are primarily noticeable in the voltage, i.e., in voltage changes in the electrical grid. This can also involve a phase shift or a frequency change in the voltage. The injected current then changes only in response to these changes.Therefore, the voltage-regulating converters initially handle such active power demands or reactive power surges, while the current-regulating converters then quickly take over and adjust accordingly. Even in the case of a negative active power surge, i.e., when the active power is reduced, the voltage-regulating converter takes over and absorbs active power. It is proposed that a chopper or a chopper circuit with appropriate ohmic resistors then convert this reduced power into heat until the current-regulating converters have adjusted accordingly.

Claims

1. A method for starting an energy generation grid, in particular a farm grid (114, 730) of a wind farm (112), wherein the energy generation grid has at least one grid connection point connected to an electrical supply grid (120, 724, 806), and wherein the energy generation grid, in a normal operating mode, exchanges electrical power with the electrical supply grid (120, 724, 806) via the grid connection point, comprising the steps of: - selecting an establishment mode, which is different than the normal operating mode, if the electrical supply grid (120, 724, 806) has a voltage drop, and / or the energy generation grid is isolated from the electrical supply grid (120, 724, 806), and - operating the energy generation grid in the establishment mode, wherein in the establishment mode - at least one voltage influencing means (808), in particular a voltage influencing wind power installation (100, 704), an energy generation grid voltage, in particular a wind farm grid voltage, is provided, wherein the at least one voltage influencing means (808) operates in a voltage influencing manner to provide the energy generation grid voltage and - at least one initial supply means (810), namely a current influencing wind power installation (100, 704), synchronizes to the energy generation grid voltage provided via the voltage influencing means, wherein the at least one initial supply means (808) operates in a current influencing manner to provide an electrical power in the energy generation grid and - the voltage influencing means (808) and the initial supply means (810) in total provide an electrical power in the energy generation grid at the level of an inherent need of the energy generation grid, wherein - the at least one voltage influencing means (808) provides the energy generation grid voltage substantially without power, or supplies a power having a distinctly lower absolute value than the at least one initial supply means (810), preferably provides no more than 20%, in particular no more than 10%, of the power of the at least one initial supply means (810). - the at least one voltage influencing means (808) is based on at least one first droop and the at least one initial supply means (810) is based on at least one second droop, wherein each droop describes a respective relationship, particularly a linear relationship, between a voltage (u(t)) of the energy generation grid and a reactive power (Q) that is to be supplied or that has been supplied or between a frequency (f) of the energy generation grid and a real power that is to be supplied or has been supplied, and charactertized in that, that the first droop has a smaller gradient than the second droop.

2. The method as claimed in one of the preceding claims, characterized in that - the at least one voltage influencing means (808) is based on a first reactive power droop describing a relationship between a voltage to be provided by the voltage influencing means in the energy generation grid and a reactive power (Q) supplied by the voltage influencing means (808), and - the at least one initial supply means (810) is based on a second reactive power droop describing a relationship between a voltage (u(t)) recorded in the energy generation grid and a reactive power (Q) to be supplied by the initial supply means (10), and - the first reactive power droop has a smaller gradient than the second reactive power droop, and / or in that - the at least one voltage influencing means (808) is based on a first real power droop describing a relationship between a frequency (f) to be provided in the energy generation grid by the voltage influencing means (808) and a real power supplied by the voltage influencing means (808), and - the at least one initial supply means (808) is based on a second real power droop describing a relationship between a frequency (f) recorded in the energy generation grid and a real power to be supplied by the initial supply means (810), and - the first real power droop has a smaller gradient than the second real power droop.

3. The method as claimed in claim 2, characterized in that - the at least one voltage influencing means (808) provides the voltage (u(t)) that is to be provided on the basis of the supplied reactive power (Q) in each case according to the first reactive power droop, and - the at least one initial supply means supplies (810) the reactive power (Q) that is to be supplied on the basis of the recorded voltage (u(t)) in each case according to the second reactive power droop and / or - the at least one voltage influencing means (808) provides the frequency (f) that is to be provided on the basis of the supplied real power in each case according to the first real power droop, and - the at least one initial supply means (810) supplies the real power that is to be supplied on the basis of the recorded frequency (f) in each case according to the second real power droop.

4. The method as claimed in one of preceding claims 1 to 3, characterized in that the gradient or gain of the second droop, second reactive power droop and / or second real power droop is at least twice as great, in particular at least three times as great, as the gradient or gain of the corresponding first droop, reactive power droop and real power droop respectively.

5. The method as claimed in one of the preceding claims, characterized in that - the selecting of the establishment mode, in particular changing from the normal operating mode to the establishment mode, is effected if alternatively or additionally the energy generation grid has a voltage drop.

6. The method as claimed in one of the preceding claims, characterized in that - the operating of the energy generation grid in the establishment mode is effected only when the energy generation grid is de-energized.

7. The method as claimed in one of the preceding claims, characterized in that - the at least one initial supply means (810) and the further initial supply means (810) are synchronized in cascaded fashion to provide the electrical power in the energy generation grid.

8. The method as claimed in one of the preceding claims, characterized in that - the electrical power provided by the at least one initial supply means (810) in the energy generation grid has at least one reactive power component that is sufficiently large to cover the reactive power requirement of the energy generation grid.

9. The method as claimed in one of the preceding claims, characterized in that - the electrical power provided by the at least one initial supply means (810) in the energy generation grid has at least one reactive power component and one real power component, wherein the reactive power component is greater than the real power component, preferably at least twice as great, particularly preferably at least five times as great.

10. The method as claimed in one of the preceding claims, characterized in that - the electrical supply grid (120, 724, 806) has a supply voltage and the energy generation grid voltage is ramped up to the supply grid voltage in order to synchronize the energy generation grid to the electrical supply grid (120, 724, 806).

11. The method as claimed in one of the preceding claims, further comprising the step of: - connecting the energy generation grid to the electrical supply grid (120, 724, 806) via an energy generation grid transformer, in particular a wind farm transformer (722), if the energy generation grid has an energy generation grid voltage synchronized to the electrical supply grid (120, 724, 806) or in order to provide a grid reestablishment voltage at the grid connection point if the electrical supply grid (120, 724, 806) has no voltage (u(t)).

12. The method as claimed in one of the preceding claims, further comprising the step of: - ramping down the at least one voltage influencing means (808) and the at least one initial supply means (810) such that the energy generation grid is de-energized if the electrical supply grid (120, 724, 806) has a voltage drop.

13. The method as claimed in one of the preceding claims, characterized in that - the at least one voltage influencing means (808) provides an energy generation grid voltage only when the energy generation grid is de-energized.

14. The method as claimed in one of the preceding claims, characterized in that - the voltage drop is defined in relation to a rated voltage of the electrical supply grid (120, 724, 806) as: - a voltage (u(t)) less than 90 percent of the rated voltage or - a voltage (u(t)) less than 70 percent of the rated voltage or - a voltage (u(t)) less than 30 percent of the rated voltage or - a voltage (u(t)) less than 10 percent of the rated voltage.

15. The method as claimed in one of the preceding claims, characterized in that - the at least one voltage influencing means (808) has a DC link circuit fed from a capacitance to provide the energy generation grid voltage (710), wherein the capacitance is configured to supply the DC link circuit (710) with a DC voltage in the event of a voltage drop in the electrical supply grid(120, 724, 806) and / or in the event of a de-energized energy generation grid such that the at least one voltage influencing means (808) can provide a stable energy generation grid voltage.

16. The method as claimed in one of the preceding claims, further comprising the step of: - recording a voltage drop in the electrical supply grid (120, 724, 806) and / or detecting a loss of voltage in the energy generation grid by means of a voltage recording of the at least one voltage influencing means (808).

17. The method as claimed in one of the preceding claims, characterized in that - the energy generation grid comprises a power controller by means of which the at least one initial supply means supplies (810) an electrical power to the electrical supply grid (120, 724, 806) on the basis of a power setpoint value (Psoll) wherein preferably a power setpoint value (Psoll) is prescribed by an energy generation grid operator or by a grid operator of the electrical supply grid (120, 724, 806), and / or the electrical power is increased such that in the event of a system deviation it is slowly corrected, in particular by means of an I controller.

18. The method as claimed in one of the preceding claims, characterized in that - the energy generation grid has a frequency stability - that holds back a portion of the available electrical power of the at least one initial supply means (810) in order to release it, in particular supply it, for the frequency stability of the electrical supply grid (120, 724, 806) when required and / or - that limits a supply of electrical power of the at least one initial supply means (810) if the energy generation grid and / or the electrical supply grid (120, 724, 806) has a grid frequency that is an overfrequency, and / or - that draws electrical power from the electrical supply grid (120, 724, 806) and preferably consumes it by means of a chopper apparatus.

19. The method as claimed in one of the preceding claims, characterized in that - the energy generation grid is configured to receive a weather forecast and / or to produce a weather forecast, wherein the weather forecast is used to stipulate a time at which operation of the energy generation grid in the establishment mode can be started.

20. The method as claimed in one of the preceding claims, characterized in that the voltage influencing means (808) and the initial supply means (810) each form a supply unit and operate as voltage influencing means (808) or initial supply means (810) by means of actuation, wherein in particular the voltage influencing means (808) can operate as initial supply means (810) by virtue of an appropriate change of actuation and the initial supply means (810) can operate as voltage influencing means (808) by virtue of a change of actuation.

21. A wind power installation (100, 704) comprising a control unit and a converter configured to operate in voltage-influencing and / or current-influencing fashion, wherein the control unit actuates the converter such that the wind power installation (100, 704) is configured to be used as voltage influencing means or as initial supply means in a method as claimed in one of claims 1 to 20.

22. The wind power installation (100, 704) as claimed in claim 21, characterized by a chopper apparatus for consuming electrical power from the energy generation grid to support frequency backup control.

23. A wind farm (112, 500, 700) comprising at least one first and one second wind power installation (100, 704), wherein the first wind power installation (100, 704) can operate in voltage-influencing fashion and the second wind power installation can operate in current-influencing fashion, or wherein there is provision for at least one first inverter (812), which can operate in voltage-influencing fashion, and there is provision for at least one second inverter (822), which can operate in current-influencing fashion, in order to carry out a method as claimed in one of claims 1 to 20 in both cases.

24. The wind farm (112, 500, 700) as claimed in claim 23, characterized in that the first and / or the second wind power installation (100, 704) is a wind power installation (100, 704) as claimed in claim 22.

25. The wind farm (112, 500, 700) as claimed in claim 23 or 24, characterized in that at least one first or the at least one first inverter (812), which can operate in voltage-influencing fashion, and at least one second or the at least one second inverter (822), which can operate in current-influencing fashion, are together coupled to an energy storage unit, in particular a battery store, and together form a black starting unit and are prepared to be used to operate the energy generation grid in the establishment mode, in particular such that the energy storage unit provides the at least one first and the at least one second inverter with energy needed to operate the establishment mode.