METHOD FOR OPERATING A COMBINED POWER PLANT OR COMBINED POWER PLANT

Description

[0001] Wind turbines can be used as individual systems or as a wind farm consisting of a large number of individual wind turbines. Energy generation facilities such as wind turbines, but also solar power systems, and the like, are increasingly being required to feed an increased amount of power into the grid when the frequency of the electrical grid into which the wind turbine, wind farm, or solar power system feeds its electrical power falls below a certain grid frequency value, which is below the target value, in order to support the grid.

[0002] As is well known, the nominal frequency of an electrical grid in the German and European interconnected grid is 50 Hz, and in the USA it is 60 Hz. Other countries have adopted similar regulations.

[0003] This target frequency can be achieved relatively well if the power consumed by consumers connected to the grid is approximately the same as the electrical power generated by generating units and fed into the electrical grid.

[0004] Therefore, the value of the grid frequency is always a measure of the balance between electrical generation on the one hand and electrical consumption on the other.

[0005] However, if consumption exceeds production, i.e. more electrical power is drawn from the grid than is fed into it, the grid frequency drops.

[0006] For this purpose, the control and network management of the electrical network provides a variety of measures to support the network, in particular to counteract the drop in the network frequency so that the frequency value returns to the target value.

[0007] However, if the grid frequency falls below a predetermined first grid frequency value, e.g., 49 Hz or 48 Hz (this first predetermined grid frequency value can take on a very different specific value, which usually depends on the specific grid topology of the grid), certain measures are taken by the grid management, e.g., even controllable large consumers have their power consumption reduced or are even completely disconnected from the grid and / or certain reserve power plants are put into operation and their output is increased.

[0008] Wind turbines or solar installations that generate electrical power are capable of supporting the grid in a special way when frequencies are too low, but this is often not enough.

[0009] Although it has already been proposed to operate wind turbines below their optimum, i.e. below their power curve, so that a power reserve can be switched on in the event of an underfrequency, such a solution is not very effective because it also means that for the period in which the first predetermined grid frequency is not undercut, the energy or power yield of the wind turbine is only suboptimal and thus a large amount of electrical power that wind energy could supply is not generated at all, which overall significantly reduces the efficiency of the wind turbine.

[0010] It has also been suggested that, in the case of a certain underfrequency, more electrical power could be extracted from the generator of a wind turbine than it is capable of producing from the wind for a short period of time, e.g., a few hundred milliseconds or a few seconds. This is certainly possible due to the inertia of the generator, but it also results in the generator producing significantly less electrical power after the increased power output (inertia operation). A typical example of the active power curve of a wind turbine with inertia emulation is shown in Fig. 1 shown ("Windblatt 03 / 2010", pages 8 and 9).

[0011] A similar solution to that disclosed in the above-mentioned source can also be found in WO 2010 / 108910 or WO 01 / 86143.

[0012] Furthermore, reference is made to the documents DE 10 2009 018126 A1, WO 2010 / 048706A1, CA 2,511,632 A1 and WO 2011 / 060953.

[0013] Therefore, the current approach of ultimately using the momentary reserve from the rotating flywheel of the rotor and generator of the wind turbine can at best lead to an increased power being fed into the grid for a period of 10 to 20 seconds.

[0014] Another problem is that it takes several hundred milliseconds, if not seconds, after the switching event is triggered - e.g., falling below the first predetermined grid frequency value, e.g., 49.7 Hz - and / or exceeding a predetermined frequency gradient (ΔF / Δt) - until the increased power consumption can be made available.

[0015] It is therefore an object of the present invention to improve the previous support of the network in the form of an inertia emulation, in particular to reduce the reaction time when a predetermined network frequency value is undershot and / or when a certain frequency drop gradient is exceeded, and in particular to provide the electrical power increase for a longer period than before in such a case, in order to thus support the network better than before in the event of an underfrequency or a certain frequency drop (frequency gradient), in particular to make a contribution to frequency stability available.

[0016] The object is achieved by a method according to claim 1 or a device according to claim 5. Advantageous further developments are described in the subclaims.

[0017] In the known inertia emulation using a wind turbine, the reaction time, i.e. the time between the triggering event, e.g. falling below a predetermined grid frequency value or exceeding a predetermined grid frequency drop (frequency gradient), is approximately 200 to 500 or even 600 milliseconds.

[0018] With the invention, this reaction time can be drastically reduced, e.g., to values ​​in the range of a few milliseconds, e.g., 5 to 10 milliseconds, less than 20, or less than 100 ms.

[0019] This means that additional power is made available much faster in the event of underfrequency and / or in the event of a predetermined mains frequency drop (frequency gradient) than before.

[0020] The reason for the significantly faster response time is that, as before, the mains frequency as well as the mains frequency gradient are constantly measured. For example, the mains frequency can be recorded every 200 microseconds (µs) and the frequency drop, i.e. the frequency gradient, can be recorded just as quickly, or perhaps somewhat slower.

[0021] If these switching or triggering criteria, i.e. falling below a predetermined grid frequency, e.g. 49.8 Hz, and / or exceeding a predetermined grid frequency drop (frequency gradient), e.g. 20-30 mHz / s, are detected, a control signal is generated in a control and data processing device which records and determines the values ​​presented, and this control signal is used to be forwarded instantly to the control device of a power-to-gas unit, where the power consumption from the grid of the power-to-gas unit can be stopped by blocking and / or opening switches, e.g. IGBT (Insolated Gate Bipolar Transistor), of a rectifier, the consumption of electrical energy from the grid, whereby no galvanic isolation of the power-to-gas unit from the grid is necessary for this.The power-to-gas unit requires, in particular, direct current for electrolysis, which can be provided by a rectifier when connected to the grid. This rectifier features the aforementioned switches, e.g., an IGBT type. When these switches are opened or turned off, the flow of electrical power from the grid is immediately stopped, thus quickly making the electrical power previously consumed by the power-to-gas unit available to the grid.

[0022] The invention thus enables a response to an underfrequency event or a predetermined grid frequency drop (frequency gradient), with a response time that is more than ten times faster than before (200-600 ms). This allows immediate counteraction, particularly in the event of a severe frequency drop, e.g., due to the failure of a large 1000 MW power plant, to prevent certain underfrequency values ​​from being reached. If certain underfrequency values ​​are reached, e.g., a frequency value of 49 Hz, the grid control system automatically sheds certain loads, resulting in further instability of the entire electrical grid, requiring further measures to stabilize the entire grid.

[0023] The specific value set for the underfrequency to stop the power-to-gas unit's consumption of electrical power, as proposed, must be determined individually for each project. In an interconnected grid, for example, a preferred underfrequency value would be approximately 49.8 Hz.

[0024] In an island grid, however, this underfrequency value should be set lower, e.g., at 49 or even 48 Hz.

[0025] The value for the frequency drop, i.e., the negative frequency gradient, can also be individually adjusted. It is desirable for this frequency drop, or negative frequency gradient, to be in the range of 20 to 50 mHz per second, or up to 1 to 2 Hz / sec. Higher frequency gradient values ​​are possible, but will often result in this trigger / switching event not being achieved.

[0026] By controlling the power-to-gas unit depending on the presence of a predetermined frequency event in the electrical grid, as described above, a significant contribution can be made to grid support.

[0027] It is particularly advantageous to operate the power-to-gas unit as part of a combined-cycle power plant, whereby the electrical power consumed by the power-to-gas unit is generated within the combined-cycle power plant, and the power generated within the combined-cycle power plant but not consumed by the power-to-gas unit is fed into a connected electrical grid, e.g., also as continuous power.

[0028] It is preferred that the consumption of the power-to-gas unit during normal operation is approximately 2 to 10%, preferably approximately 5%, of the plant output of the electrical generators of the combined cycle power plant.

[0029] For example, if the combined cycle power plant has a wind turbine with a nominal output of 5 MW, the nominal consumption of the power-to-gas unit should be in the range of approximately 300 to 500 kW.

[0030] The power-to-gas unit can be connected to the combined cycle power plant's electrical generator in various ways. For example, it is possible to route the power-to-gas unit's electrical connection to the output terminal of the wind turbine, wind farm, or solar device (photovoltaic). However, if the wind turbine or wind farm has a direct current intermediate circuit, it is also possible to place the power-to-gas unit's electrical connection into this intermediate circuit, which would have the advantage of eliminating the need for reverse current. It is also possible for the power-to-gas unit to be connected to the electrical grid and draw its electrical power from there. Since the combined cycle power plant's electrical generation unit feeds its electrical power into this grid, a certain spatial distance can be maintained between the combined cycle power plant's generation unit, i.e., a wind turbine.a wind farm or a solar facility, and the power-to-gas unit, if the generation unit as well as the power-to-gas unit are connected to the grid and, in addition, the generation unit and the power-to-gas unit are connected to each other via corresponding control, data or communication lines, whether wired (fibre optic light strips) or wireless, in order to increase the power available to the grid in the event of a predetermined underfrequency being undershot or a predetermined grid frequency drop being exceeded, as proposed according to the invention.

[0031] As long as there is no underfrequency or predetermined grid frequency drop (frequency gradient), the power-to-gas unit draws electrical power in a controlled manner and generates a gas from it, be it hydrogen or methane or the like. Such a power-to-gas unit, in which gas is generated from electrical energy, is known, for example, from the company SolarFuel and is also used in Fig. 1 shown in the overview.

[0032] The energy consumption of the power-to-gas unit, i.e. the electrical energy consumption of this power-to-gas unit, can also be adjusted and controlled in such a way that the proportion of energy that fluctuates in a wind turbine over a predetermined period (forecast period), which results from the constant fluctuation of the wind, is consumed in the power-to-gas unit in order to generate gas.

[0033] The power-to-gas unit can be controlled in various ways.

[0034] For example, it is possible for the power-to-gas unit to constantly draw a very specific electrical output, e.g., its rated output. For example, with a power-to-gas unit with a rated output of 1 MW, an electrical output of 1 MW is always drawn, and a corresponding amount of gas is constantly generated from this electrical output.

[0035] However, it is also possible to control the power consumption so that it depends on the electrical power generated by the generating unit in the combined cycle power plant.

[0036] This means that the generation can also be adjusted so that the power-to-gas unit always receives a certain percentage of the generated power from the generation unit, e.g., 10% or 20% or even more of the generated power, provided the generation unit is designed accordingly.

[0037] Therefore, in the case of under-frequency or in the case of exceeding a predetermined frequency gradient, it is possible to make a greater electrical power available to the electrical grid almost instantly, in any case within a few milliseconds, namely 10 or 20 or more percent of the power generated by the generating unit, by stopping the electrolysis or methanation.

[0038] It is also possible for the power-to-gas unit to obtain so much electrical energy from the generation unit that it constantly makes a predetermined amount of electrical power available to the consumers in the electrical grid for a predetermined time (forecast time), while the electrical power that the generation unit does not make available to the consumers in the electrical grid is consumed in the power-to-gas unit.

[0039] Thus, according to the invention, not only can the grid be supported in the event of an underfrequency, but a constant electrical base load can also be fed into the grid for normal operation of the grid within the target frequency range. Thus, a fluctuating electrical load, which arises, for example, due to constant fluctuations in the wind or, in the case of a photovoltaic system, due to fluctuating brightness, is not made available to the consumers in the grid in the first place. Thus, in particular, a fluctuating portion of the generating unit's electrical output is not made available to the grid or its consumers at all. This means that the combined cycle power plant is also capable of base load beyond the described grid-stabilizing underfrequency case or when a predetermined grid gradient is exceeded, thus increasing its grid feed-in performance.

[0040] The invention proposes operating a power-to-gas unit such that, when a first grid frequency value is undershot, e.g., a value of 49 Hz, the power-to-gas unit reduces or even completely stops its power draw from the grid by disconnecting the power-to-gas unit from the grid. This means that a significantly higher electrical power contribution, which was previously drawn from the grid by the power-to-gas unit, remains available to the grid for a few milliseconds and permanently.

[0041] As mentioned, it is also possible for the wind turbine or the wind farm or the photovoltaic system to be operated in such a way that it always feeds electrical energy into the grid with a certain constant power for a certain intended period, e.g. from 10 to 30 minutes, and the electrical energy generated by the wind turbine or the wind farm or the photovoltaic system in excess of the constant contribution is then taken from the power-to-gas unit, so that from the grid perspective the combined cycle power plant generates a constant electrical power, at least for a predetermined period,This period can be set by the grid operator via a corresponding data line or by the operator of the wind turbine or wind farm or photovoltaic system via a corresponding data line. In the event of the first grid frequency value being undershot or reached and / or a frequency drop being exceeded, the purchase of electrical power by the power-to-gas unit will then be reduced or completely stopped as described above, so that the electrical power previously taken from the power-to-gas unit is always available as the power contribution.

[0042] The advantage of the above solution is not only that a "quasi-inertia contribution" can always be retrieved from the combined cycle power plant, but that it is also possible to stabilize the electrical power fed in at the same time, thus allowing the combined cycle power plant to even supply base load to the grid within certain limits.

[0043] Meteorological data is also used to determine the duration of the constant power to be fed in.

[0044] An example may clarify this: If, for example, the current wind speed is 7 m / sec. and a meteorological forecast indicates that the wind speed will not fall below 5 m / sec. within the next 30 minutes, the value of 5 m / sec., possibly with a safety margin, e.g., 4.5 m / sec., is entered as the measure of the constant electrical power to be delivered. The electrical energy thus obtained from the first 4.5 m / sec. wind speed is constantly fed into the electrical grid for, say, 30 minutes.

[0045] Whenever the wind blows at a speed of more than 4.5 m / sec. within the forecast period of 30 minutes, i.e., the next 30 minutes, the resulting increased wind power will also be "harvested" by a wind turbine as usual, but the energy added to the electrical output above 4.5 m / sec. will be made available directly or indirectly to the power-to-gas unit.

[0046] If the power consumption of the power-to-gas unit is reduced and the resulting increase in electrical power fed into the grid (unused power is equal to the increased feed-in power) and the grid frequency therefore recovers more quickly than before, the power-to-gas unit will not be switched on again immediately or energy consumption will not be increased again immediately if the first grid frequency value is exceeded, but rather it will wait until the grid frequency value returns to a value that corresponds to the setpoint, is close to the setpoint, or is even above the setpoint, i.e. has reached a value of more than 50 Hz.

[0047] The power consumption of the power-to-gas unit will therefore only be increased again once the grid frequency has recovered and a relatively high level of grid stability has been achieved again.

[0048] It is also known that when the grid frequency exceeds a certain value, e.g., 5‰ above its target value, i.e., approximately 50.25 Hz, the electrical feed-in of wind energy is reduced, and as the grid frequency continues to rise, the power fed in by the wind turbine is further reduced.

[0049] In the current state of the art, this is usually done by pitching the blades or by consuming the electrical power provided by the generator in a chopper, i.e. a resistor, so that ultimately a reduced electrical power is fed into the grid.

[0050] Using the combined cycle power plant, it is now also possible to offset the reduction in power output of the wind turbine by ultimately increasing the power consumption of the power-to-gas unit.

[0051] Therefore, when an overfrequency is exceeded, the wind turbine does not reduce its electrical output; instead, the power-to-gas unit consumes more power, so that from a grid perspective, the combined cycle power plant feeds less power into the grid. The combined cycle power plant's power reduction can be adjusted simply by controlling the power consumption of the power-to-gas unit. By then initiating pitching of the wind turbine's rotor blades or by shading a photovoltaic system, the power reduction can be significantly increased, thus making an adequate contribution to frequency and thus grid stability even during overfrequency.

[0052] As described, a power-to-gas unit is capable of generating gas from electrical power, e.g., hydrogen or methane, or similar gases, which is suitable for combustion, but above all also as a fuel for an engine. The installation of large wind farms requires large generators, which have traditionally been powered by diesel, gasoline, or similar fuels. If such generators are converted to burn gas, e.g., CH4 (methane), the gas generated by the power-to-gas unit can also be used to drive the electrical generators used to build a wind farm.

[0053] For example, if a wind turbine is built in a remote area, the electrical energy generated by this first turbine can be used in a power-to-gas unit to generate the gas. This gas can then be used to build the remaining wind turbines in the wind farm by supplying the gas to the drive units, such as cranes, trucks, vehicles, etc., needed to erect the wind turbines in a wind farm. Thus, the wind farm would largely require no fossil fuels for construction, but could be built using "green gas," such as wind gas as described above, which improves the overall ecological footprint of the wind farm.Especially in remote areas, obtaining fuel is often complicated, often difficult, and therefore the fuel itself is very expensive. By producing fuel on-site, the fuel procurement costs required for the generators needed to build a wind farm can be reduced. If the power-to-gas unit is housed in a container or similar, the container containing the power-to-gas unit can be transported to the nearest construction site after the wind farm is constructed.

[0054] The invention is explained in more detail below using an exemplary embodiment in drawings. Fig. 1a shows a view of a wind turbine, Fig. 1b shows the typical structure and connection of a wind turbine, Fig. 2 shows a view of a combined cycle power plant consisting of a wind turbine and a power-to-gas unit, Fig. 3 shows the typical structure of a power-to-gas unit in the energy system (state of the art; SolarFuel), Fig. 4 shows an example of the power distribution before and after falling below a predetermined underfrequency value, Fig. 5 shows the distribution of the power of the combined cycle power plant before and after exceeding a predetermined frequency drop, Fig. 6 shows a variant according to the invention.

[0055] The same reference numerals may refer to the same but also similar, non-identical elements. For the sake of completeness, a wind turbine with a synchronous generator and gearless design with a full-scale converter is explained below.

[0056] Fig. 1a shows a schematic of a nacelle 1 of a gearless wind turbine. The hub 2 is recognizable due to the partially opened cover (spinner). Three rotor blades 4 are attached to the hub, with the rotor blades 4 only shown in the area near the hub. The hub 2 with the rotor blades 4 forms an aerodynamic rotor 7. The hub 2 is mechanically firmly connected to the rotor 6 of the generator, which can also be referred to as the rotor 6 and is referred to below as the rotor 6. The rotor 6 is rotatably mounted relative to the stator 8.

[0057] The rotor 6 is energized during its rotation relative to the stator 8, typically with a direct current, to generate a magnetic field and build up a generator torque or generator counter-torque, which can be adjusted and varied accordingly by this excitation current. When the rotor 6 is thus electrically excited, its rotation relative to the stator 8 generates an electric field in the stator 8 and thus an alternating electric current.

[0058] The alternating current generated in the generator 10, which is essentially made up of the rotor 6 and stator 8, is generated according to the Fig. 1b The rectified current or voltage is then converted into a three-phase system with the desired frequency using an inverter 14. The resulting three-phase current-voltage system is stepped up in voltage using a transformer 16 in order to be fed into a connected power grid 18. Theoretically, the transformer could be omitted or replaced by a choke. Typically, however, the voltage requirements in the power grid 18 are such that step-up using a transformer is necessary.

[0059] A main controller 20 is used for control, which can also be referred to as the main control unit and forms the highest regulation and control unit of the wind turbine. The main controller 20 receives its information, among other things, about the grid frequency from the subordinate grid measurement unit 22. The main controller controls the inverter 14 and the rectifier 12. In principle, an uncontrolled rectifier could of course also be used. In addition, the main controller 20 controls a DC / DC chopper 24 for feeding the excitation current into the rotor 6, which is part of the generator 10. The main controller 20 modifies, among other things, the feed-in or the operating point of the generator if a predetermined grid frequency limit is undershot. Since the generator is operated at variable speed, the feed-in to the grid is carried out as described using a full-scale converter, which essentially consists of the rectifier 12 and the inverter 14.

[0060] During operation, the mains voltage and frequency are continuously measured in three phases by the mains measuring unit 22. This measurement results in a new value for one of the three phase voltages every 3.3 ms – at least in the case of a mains frequency of 50 Hz. The mains frequency is thus recorded for each voltage half-wave, filtered, and compared with the preset limit values. For a 60 Hz system, a value for one of the three phase voltages would be available approximately every 2.7 ms, namely at every zero crossing.

[0061] In Fig. 2 It is also shown that the wind turbine is electrically connected to a power-to-gas unit 23.

[0062] Such a power-to-gas unit 23 is already known in various forms, for example from WO 2009 / 065577. Such a power-to-gas unit is also known from the company SolarFuel (www.SolarFuel.de) and is also in Fig. 3 shown schematically. In such a power-to-gas unit, hydrogen is first generated by means of electrolysis, for which electrical power is drawn from a wind turbine, a solar source, or a biomass source (with electrical generation). This power-to-gas unit 23 preferably also has a methanation unit, which uses the generated hydrogen with the aid of an additional CO 2 source to produce methane gas (CH 4 ). The generated gas, be it hydrogen or methane, can be fed into a gas storage facility or into a gas pipeline network, e.g., a natural gas network.

[0063] Finally, the power-to-gas unit 23 also has a controller 24, which is connected to the main controller 20 of the wind turbine via a communication line, whether wired (e.g. fiber optic strips LWL) or wireless.

[0064] The power-to-gas unit is a unit in which electrical energy is consumed to ultimately produce a fuel gas.

[0065] For example, the production of hydrogen usually requires electrolysis, so the power-to-gas unit has an electrolyzer that consumes electrical energy and thus produces hydrogen.

[0066] In the power-to-gas unit, methane can also be produced by combining hydrogen and carbon dioxide, which is extracted from the air, for example, or provided from a CO 2 tank or from a connected biogas plant, in a methanation unit to produce methane gas (CH 4 ).

[0067] This methane gas can be made available to a connected gas storage facility or fed into a gas network.

[0068] In Fig. 3 The example shown also includes a gas and steam power plant or a combined heat and power plant in which the combustion gas is burned in an internal combustion engine, so that electrical power can be generated in an electrical generator connected to the internal combustion engine, which can then be made available to the electrical grid.

[0069] The wind turbine can be a single turbine, but it can also represent a wind farm consisting of a large number of wind turbines.

[0070] The wind turbine has the main controller 20 with a data processing and control device. This data processing device has, among other things, a data input 25, via which wind forecast data is made available to the data processing device. The data processing device 20 creates a wind forecast from this wind forecast data for a predetermined forecast period, e.g., 20, 30, 40, 50, or 60 minutes or longer. Based on the created wind forecast and by processing the power curve of the wind turbine or wind farm, it can also very reliably determine a forecast power, i.e., a minimum electrical power that can ultimately be reliably and constantly made available to the grid.

[0071] At the same time, the wind turbine or wind farm constantly determines the current electrical output of the wind turbine, which depends on the current wind, for example, at intervals of 5 to 10 seconds.

[0072] The current power of the wind energy, which is above the forecast power (minimum power), is fed as information, data, signal, etc. to the control and data processing device 24 of the power-to-gas unit 23, so that the electrical consumption is specified to the power-to-gas unit 23.

[0073] If, for example, a forecast output of 1 megawatt (MW) has been set for the wind turbine or wind farm, but the wind turbine or wind farm currently generates an output of 1.3 MW, the difference, i.e. 300 kW, is determined as a value and the control and data processing device 24 of the power-to-gas unit 23 receives this value as a control value, so that the power-to-gas unit 23 is then operated with a consumption of 300 kW.

[0074] If the wind drops slightly and the current output subsequently drops to only 1.2 MW, the electrical consumption of the power-to-gas unit also drops accordingly to 200 kW. If the wind increases so that the wind turbine or wind farm generates 1.4 MW, the consumption of the power-to-gas unit increases accordingly to 400 kW, and so on.

[0075] After the forecast period has expired, a new forecast is created and for this new forecast a new constant performance (new forecast performance) is set.

[0076] Through the common data line 26 between the control and data processing device of the wind turbine or wind farm on the one hand and the control and data processing device of the power-to-gas unit on the other hand, current wind data or data on the consumption power of the power-to-gas unit can also be exchanged in order to ensure the constant provision of the constant minimum power fed into the power grid.

[0077] The control and data processing device 20 is also connected to a controller 27 or a central unit for controlling the electrical network of the power grid, so that the values ​​of the constant electrical feed into the electrical network can always be retrieved or are available there.

[0078] If the current wind speed and thus the current electrical power generated by the wind turbine or wind farm falls below the forecast output, the electrical consumption of the power-to-gas unit is reduced to "zero" (or to the lowest possible value). At the same time, a steam and combined cycle power plant or CHP 28 may be started up to provide additional electrical power that cannot be provided by the wind turbine or wind farm. As a result, the forecast electrical power can still be reliably made available to the power grid, and if necessary, even more, by operating the combined cycle power plant / CHP at a higher output than necessary.

[0079] As in Fig. 1b As shown, there is a communication and / or data line between the generating unit of the combined-cycle power plant, e.g., the wind farm on the one hand, and the power-to-gas unit on the other. Via this communication and data line, the following data can be exchanged between the units of the combined-cycle power plant in order to control the wind farm on the one hand and / or the power-to-gas unit on the other.

[0080] For example, if the wind turbine or wind farm continuously records and measures the frequency of the electrical grid and also continuously records the frequency drop, i.e., the negative frequency gradient (derivative of the frequency with respect to time; df / dt), the corresponding values ​​for the grid frequency (absolute value) or for the grid drop (frequency gradient) are transmitted to the control unit of the power-to-gas unit. However, it is also possible to generate a corresponding switching command to stop the power-to-gas unit in the wind farm based on the presence of certain predetermined frequency values ​​or frequency gradient values ​​and then transmit this switching command to the power-to-gas unit.It is also possible for the generating unit, i.e. the wind farm, to transmit the current value for the electrical power currently generated to the power-to-gas unit so that it is always operated in such a way that no more electrical power is consumed than the generating unit produces.

[0081] It is also advantageous if the power-to-gas unit always transmits the value of the current electrical consumption of the entire power-to-gas unit to the generation unit so that it can be controlled accordingly.

[0082] It is also advantageous if the wind farm and / or the power-to-gas unit has a data input so that a control system or the central control unit for a grid can always specify which power the power-to-gas unit should draw, so that this power is reliably available as power for grid support if a predetermined grid frequency value is undershot and / or a predetermined grid frequency drop, i.e. a predetermined frequency gradient, occurs.

[0083] In Fig. 4 It is shown that the power-to-gas unit draws a certain electrical power (P PtG ) as long as the grid frequency is above a certain value, e.g. above 49.8 Hz. If the value of 49.8 Hz is reached or undercut, i.e. a predetermined underfrequency value is reached, the power consumption of the power-to-gas unit is stopped by switching off or opening the electrolysis switch of the power-to-gas unit 23 and thus the previously consumed electrical power of the power-to-gas unit is immediately available to the electrical grid because the previously consumed power is no longer being drawn from the grid. The frequency can therefore recover relatively quickly; in any case, for the predetermined underfrequency case described above, the grid is supported by stopping the electrical consumption of the power-to-gas unit.

[0084] If the power-to-gas unit is part of a combined-cycle power plant, where the combined-cycle power plant includes a generation unit, e.g., from a wind farm, the combined-cycle power plant provides power to the electrical grid, which is calculated as the difference between the power generated by the generation unit, e.g., the power of the wind farm, and the power consumed by the power-to-gas unit. As soon as the underfrequency value of 49.8 Hz is reached, the power consumption of the power-to-gas unit drops to zero. Since the wind farm in the example shown always generates electrical power, the electrical power supplied by the combined-cycle power plant when the power-to-gas unit stops consuming electrical power is equal to the electrical power of the entire wind farm, and thus a significantly larger proportion of electrical power is made available to the electrical grid when the underfrequency value is reached.The output of the combined cycle power plant is in . Fig. 4 represented by the dashed line (P combined power plant).

[0085] In Fig. 5 An example is shown in which the triggering event for stopping the power consumption by the power-to-gas unit is not the mains frequency falling below a predetermined value, but rather the triggering event is the presence of a predetermined frequency drop, i.e. a frequency gradient. If this exceeds a value of 10 mHz / sec., for example, i.e. the frequency drops by more than 10 millihertz within one second, this is interpreted as a switching signal and the power consumption by the power-to-gas unit is stopped by opening the switch (of the rectifier) ​​of the power-to-gas unit, or the power consumption is reduced by a predetermined value. Thus, within a very short time, i.e. within a few milliseconds, e.g. 5 to 10 msec., significantly more electrical power is available in the grid because when the power-to-gas unit stops drawing energy, the entire electrical power of the combined cycle power plant can be made available to the grid as electrical power, whereas before the triggering switching event the power-to-gas unit still drew a certain amount of the electrical power generated from the generating unit.

[0086] The dotted line (P without invention) shows in Fig. 5 This shows how the frequency would behave if the power-to-gas unit were not stopped when a certain frequency drop occurred, meaning it no longer consumed energy, but continued to consume electrical energy as before. As can be seen, stopping the power-to-gas unit's energy consumption significantly supports the grid because it prevents the 49 Hz limit from being reached at all, at which point additional consumers would be "dropped" or switched off by the grid control system to support the grid.

[0087] It goes without saying that both the switching criterion according to Fig. 4 than the switching criterion according to Fig. 5 can be designed in one and the same plant (or wind farm) and it is also possible that as long as the power-to-gas unit draws electrical energy, this can be adjusted in such a way that the feed-in of electrical energy from the combined cycle power plant into the electrical grid is stabilized.

[0088] With the described power-to-gas facility, as with any other power-to-gas facility, it is also possible to construct wind turbines with significantly less use of conventional energy sources such as oil, diesel, etc. To do this, a smaller wind turbine is first installed on site, i.e. where the wind turbines, wind farm, or similar facility is to be built. This is then connected to a power-to-gas unit so that gas is continuously generated during its operation. This gas is then supplied to the units located on the construction site, i.e. where the wind turbines, wind farm, or similar facility is to be built, for example,Cranes are made available which are operated with this gas, so that as a result, hardly any fossil fuels need to be used to erect the wind turbines, the wind farm or the like, but these units such as cranes, trucks or the like are operated with the gas, i.e. with the fuel which is generated at the site where the wind turbines are erected by a power-to-gas unit.

[0089] Of course, it is also possible that the necessary fuel, i.e. the gas, is generated by means of a power-to-gas unit connected to a wind turbine installed in the immediate vicinity.

[0090] It is also advantageous if a gas storage facility is built at the site where the wind turbines are erected, which is constantly filled with gas so that energy consumers such as cranes, trucks, etc. can be continuously refueled with gas. Thus, the power-to-gas unit significantly improves the energy balance of a wind turbine project, especially the CO2 balance.

[0091] According to claim 1 of the present application, the power-to-gas unit reduces the electrical power consumption by a predetermined value or does not consume any electrical power at all if the grid frequency of the electrical grid is below the desired target frequency by a predetermined frequency value and / or if the grid frequency falls with a frequency gradient, namely with a change per time (Δf / Δt) whose magnitude exceeds a predetermined change magnitude. As a result, the energy consumption of the power-to-gas unit is controlled depending on how the grid parameter "frequency" develops in the electrical grid.

[0092] Alternatively and going beyond claim 1, it is also possible by means of the invention to control the energy supply and thus the operation of the power-to-gas unit depending on further grid parameters such as overfrequency, grid undervoltage, grid overvoltage, reactive power demand, short circuit, fault-ride-through, zero-ride-through in the grid, etc.

[0093] During such so-called "grid events," i.e., when grid parameters such as frequency, voltage, reactive power, etc., exceed or fall below a certain value, the wind turbine's output is regularly reduced. Now, using the invention, the wind turbine's output can be maintained at its maximum, and the reduction in the power fed into the grid can be achieved by making the power-to-gas unit's energy consumption, and thus the gas production generated by the power-to-gas unit, dependent on the aforementioned grid parameters—i.e., their increase or exceedance of certain grid parameter values—dependent on the exceedance or fall below certain grid voltages, short circuits, or the exceedance of a grid frequency, etc.

[0094] If a power-to-gas unit is connected and operated according to the invention at approximately 90% (± 5%) of its rated power, the power consumption of the power-to-gas facility can be increased again depending on the grid parameters described above, so that less electrical power from the wind turbines is fed into the grid, while at the same time gas production is increased. This prevents the wind turbines' output from being reduced as before, thus resulting in a portion of the potentially generated electrical energy not being used and fed into the grid. Thus, by means of the invention, the controlling intervention in the wind turbine can be reduced, and solely through the operation of the power-to-gas facility and its higher electrical power consumption and thus higher gas production, a reduction in the electrical power of the wind turbine fed into the grid is achieved.The main consequence of this is that the wind turbine (or a wind farm) can continue to operate without control intervention, and the entire system does not generate energy losses if certain grid parameters are outside their target range, requiring a reduction in the electrical power fed into the grid. In the event of a short circuit, the wind turbine must normally drastically reduce its output immediately, possibly even to zero. Such an intervention represents a tremendous control intervention for the wind turbine, which is difficult to manage. If a power-to-gas facility is connected to the wind turbine, the electrical power of the wind turbine can be largely diverted to the power-to-gas facility in the event of a grid short circuit, allowing the wind turbine to continue operating for the time being.

[0095] If, for example, a power-to-gas facility is operated and, even during normal operation, draws its power not only from a wind turbine but also directly from the grid, the electrical energy drawn from the grid is lost in the event of a short circuit, so that there is sufficient potential for the power-to-gas unit to continue operating optimally at its best possible output and the entire output of the power-to-gas unit is then provided by the wind turbine.

[0096] This example also clearly shows that a very complex control intervention in the wind turbine in the event of a grid short circuit can be omitted or can be made much milder. This ultimately increases the reliability of the wind turbine and also prevents the electrical output of the wind turbine from being throttled down unnecessarily.

[0097] If the grid short circuit or a similar event then clears, the wind turbine can immediately feed electrical power back into the grid and thus support the grid. During the transition, it is also quite possible that the wind turbine will initially support the grid and provide less electrical power to the power-to-gas unit. This is ultimately not significant, as stabilizing the electrical grid is always the priority, and as soon as the stability of the electrical grid is restored, both the power-to-gas unit and the wind turbine can resume regular operation.

[0098] The invention therefore also allows a method for operating a power-to-gas device, i.e. a device which generates a gas, e.g. hydrogen and / or methane or the like, from electrical energy, wherein the power-to-gas unit draws electrical energy from an electrical network to which the power-to-gas unit is connected in order to generate the gas, wherein the network has a predetermined target frequency orhas a target frequency range, whereby in the event of a grid short circuit the power-to-gas unit draws electrical power from a wind turbine or wind farm connected to the power-to-gas unit, i.e. a collection of wind turbines, and in the event that the grid short circuit is lifted, the wind turbines then feed electrical energy into the grid to support the grid and, if necessary, the power-to-gas unit temporarily draws less electrical power than is necessary for its nominal power operation in order to ultimately also make a contribution to grid support.

[0099] The above description of the invention applies not only to a grid short circuit, but also to cases (grid events) such as "fault ride-through," "zero ride-through," etc. Finally, the invention allows a power-to-gas facility to be operated in such a way that a wind farm ultimately only continuously offers a certain minimum power, thus allowing the entire wind farm to be considered a reliable grid size for electrical power production. Any additional electrical energy generated by the wind farm above the minimum power is then fed to the power-to-gas unit.

[0100] The above alternatives to the invention according to claim 1 can be readily implemented if a controller exists to which the grid parameters, i.e., the parameters for frequency, voltage, current, etc., are fed in the grid (these grid parameters are usually already continuously measured anyway), and which then takes over the control and energy distribution of the wind turbines (or a wind farm) and that of a power-to-gas unit. Another, entirely independent alternative or even a supplement to the invention described above can also consist in controlling the gas production of the power-to-gas unit with a STATCOM system. Such a STATCOM is usually a static synchronous compensator, i.e., a power converter pulse mode that generates a three-phase voltage system with a variable voltage amplitude, the voltage of which is phase-shifted by 90° relative to the corresponding line currents.This allows inductive or capacitive reactive power to be exchanged between the STATCOM and the grid. In the field of power electronics, the STATCOM is one of the flexible three-phase transmission systems (FATS) and offers advantages over the functionally similar static reactive power compensation in stabilizing AC grids, as its reactive power is independent of the AC grid voltage level.

[0101] If the operation of the power-to-gas unit, and thus its gas production, is controlled by a STATCOM system, the power-to-gas facility initially draws its electrical energy from the STATCOM system, which can also be connected to the grid at the same time. This allows a decision to be made, depending on the current tariffs—namely, the tariff for electrical power fed into the grid on the one hand, and the current tariff for methane gas on the other—as to how much electrical power from the wind farm (which feeds its power into the grid via the STATCOM system) is fed into the grid and how much of the wind farm's electrical power is fed into CH4 production.Such a solution therefore enables a method for operating a power-to-gas facility that is connected to a STATCOM system, which in turn is connected to a wind farm and a grid and has a control system that processes current tariffs, e.g. the remuneration tariff for electrical power fed into the grid on the one hand and the current tariff for methane gas on the other, and uses this to control the feed-in of electrical energy to the grid or the production of gas in the power-to-gas unit, depending on which tariff is currently better, namely either for the electrical power fed into the grid or for methane gas production, so that the ratio of how much electrical power from the wind farm is fed into the grid and how much electrical power from the wind farm is fed into the power-to-gas unit and thus into CH4 production is possible and set depending on the most current tariffs.The STATCOM system is therefore an ideal tool for adjusting the power distribution (energy distribution) between grid feed-in and power-to-gas unit operation, and thus the supply of electrical power to the power-to-gas unit, at any time, without having to intervene in the power production of the wind turbine itself. It is also possible for the STATCOM system to be connected to an electrical storage device, e.g., an accumulator battery, etc., thus providing another option for temporarily storing electrical energy for later retrieval from the electrical storage device and feeding it into the grid or feeding it into the power-to-gas unit for CH4 production.

[0102] Fig. 6shows a block diagram of such a STATCOM application with a wind turbine 1, an electrical storage system, a controller, a power-to-gas unit, and a grid. It can be seen that the STATCOM system is connected to the electrical storage system and / or the power-to-gas unit, the wind turbine 1, and the grid, and has a controller that meets the aforementioned criteria.

Claims

1. Method for operating a power-to-gas unit, i.e. a unit which generates a gas, e.g. hydrogen and / or methane and / or the like, from electrical energy, wherein the power-to-gas unit draws electrical energy from an electrical grid to which the power-to-gas unit is connected to generate the gas, wherein the power-to-gas unit (23) is coupled to a wind turbine (1) or a wind farm and the power-to-gas unit (23) and the wind turbine (1) and / or the wind farm form a combined cycle power plant and are operated as such, so that the electrical energy drawn by the power-to-gas unit (23) is generated by the wind turbine (1) and / or the wind farm, and wherein further the wind turbine (1) and / or the wind farm being connected to an electrical grid into which the wind turbine (1) and also the wind farm feed electrical energy, and wherein the wind turbine (1) and / or the wind farm reliably feeds a certain minimum power into the electrical grid for a predetermined duration and any further electrical energy generated by the wind turbine (1) and / or the wind farm in excess of the minimum power is fed to the power-to-gas unit (23), and wherein a controller is formed to which a measured value of the grid frequency is fed and which takes over the control of the energy distribution of the energy generated by the wind turbine (1) or the wind farm between the grid on the one hand and the power-to-gas unit (23) on the other hand, and wherein the certain minimum power is determined from a wind forecast, wherein a reliable forecast power is determined as the certain minimum power for a predetermined forecast period, which can be provided to the grid reliably and constantly for the forecast period.

2. Method according to claim 1, characterized in that the power-to-gas unit draws only a minimum power or no power at all from the electrical grid when the electrical grid frequency reaches or is below a certain first grid frequency value.

3. Method according to claim 2, characterized in that the predetermined frequency value is 1 ‰, preferably 2 ‰, particularly preferably 3 ‰ or more below the nominal grid frequency, e.g. 50 Hz, and / or in that the predetermined amount of change is greater than 0.1 Hz / sec, particularly in the range from 0.2 to 7 Hz / sec, preferably in the range from 0.5 to 2 Hz / sec.

4. Method according to one of the preceding claims, characterized in that the power-to-gas unit is coupled to a wind turbine or a wind farm, consisting for example of wind turbines, and the power-to-gas unit and the wind turbine and / or the wind farm form a combined cycle power plant and are preferably operated as such, so that the electrical energy drawn by the power-to-gas unit is generated by the wind turbine and / or the wind farm.

5. Combined cycle power plant comprising a wind turbine and / or a wind farm comprising a plurality of wind turbines on the one hand and a power-to-gas unit (23) on the other hand, wherein the wind turbine and / or the wind farm generates electrical energy under given wind conditions and feeds it into a connected electrical grid and the power-to-gas unit takes a certain predetermined proportion of the electrical energy generated by the wind turbine and / or wind farm and uses it to produce a fuel, e.g. hydrogen, methane or the like, and wherein the wind turbine (1) and / or the wind farm reliably feeds a certain minimum power into the electrical grid for a predetermined duration and any further electrical energy generated by the wind turbine (1) and / or the wind farm in excess of the minimum power is fed to the power-to-gas unit (23), and wherein a controller is formed to which a measured value of the grid frequency is fed and which takes over the control of the energy distribution of the energy generated by the wind turbine (1) or the wind farm between the grid on the one hand and the power-to-gas unit (23) on the other hand, and wherein the certain minimum power is determined from a wind forecast, wherein a reliable forecast power is determined as the certain minimum power for a predetermined forecast period, which can be provided to the grid reliably and constantly for the forecast period.

6. Combined cycle power plant according to claim 5, characterized in that the power-to-gas unit is electrically coupled to the wind turbine and / or the wind farm, for example by a power line, and the electrical energy which the power-to-gas unit requires for its operation is either drawn directly from the wind turbine or the wind farm or its output, or the power-to-gas unit draws the electrical energy for operating the power-to-gas unit from the electrical grid to which it is connected and into which the wind turbine or the wind farm feeds the generated electrical energy.

7. Combined cycle power plant according to one of the preceding claims, wherein the power-to-gas unit reduces the supply of electrical power by a predetermined value or does not draw any electrical power if the grid frequency of the electrical grid is below the desired nominal frequency of the grid by a predetermined frequency value and / or if the grid frequency falls with a frequency gradient, namely with a change per time (Δf / Δt), the amount of which exceeds a predetermined amount of change.