Improvements relating to hydrogen electrolysis systems

Abstract

A hydrogen production system comprising a wind turbine facility comprising a wind turbine generator (18) connected to a hydrogen electrolyser (30) by a power converter system (22). A power converter system (22) includes a generator-side converter (24) and an electrolyzer-side converter (26) electrically coupled together by a DC link (28), and a converter controller (50) including a generator-side control module (50) coupled to the generator-side converter and an electrolyzer-side control module (52) coupled to the electrolyzer-side converter. The converter controller is configured to control the load torque on the wind turbine generator and the electrical power fed to the electrolysis cell to achieve a mechanical damping function associated with the wind turbine facility while maintaining a stable DC link voltage. Accordingly, advantageously, the wind turbine facility can achieve active control of the electromechanical damping system while operating the electrolysis cell at an effective operating point.

Description

Technical Field

[0001] The present invention relates to a system for hydrogen electrolysis and a method for operating an electrolysis system. Background Art

[0002] It is known that hydrogen is an efficient energy carrier that does not cause CO2 emissions when releasing energy. It can be easily stored and transported, making it a viable alternative to fossil fuels such as gasoline and diesel. However, hydrogen production via water electrolysis requires a large amount of electricity, potentially reducing the positive environmental impact of moving to hydrogen fuel.

[0003] Hydrogen produced from renewable energy sources such as wind or solar is environmentally ideal because no fossil fuels are used in its production. Hydrogen produced in this way is called green hydrogen. However, since wind and solar power production depend on changing environmental conditions, it is difficult in practice to efficiently produce hydrogen from these power sources. Despite these challenges, there is great potential in using renewable energy to electrolyze water. A particularly effective arrangement is to directly connect an electrolyzer to the output of a wind turbine. Since the grid transformer and switchgear are omitted, this arrangement can potentially offer many advantages in terms of lower cost and improve electrical efficiency due to the need to use fewer power electronics. However, for the efficient operation of the electrolyzer, it is important to supply a stable voltage to the electrolyzer. This can be challenging in a wind turbine environment when there may be varying power demands due to broader control requirements from the wind turbine facility. For example, powertrain damping and tower damping requirements are typically controlled by the generator torque method, which will have an impact on the available power of the generator and thus affect the stability of the output voltage that can be achieved on the DC bus / DC link.

[0004] It is desirable to be able to integrate a hydrogen electrolyzer into a wind turbine facility with a full mechanical damping function. The present invention has been developed in view of this background. Summary of the Invention

[0005] In a first aspect, an example of the present invention provides a hydrogen production system according to claim 1. In a second aspect, an example of the present invention provides a method according to claim 13.

[0006] Preferred and / or alternative features are set forth in the dependent claims.

[0007] Within the scope of the present application, it is expressly intended that the various aspects, embodiments, examples and alternatives set forth in the foregoing paragraphs, claims and / or the following description and drawings can be understood independently or in any combination, particularly their respective features. That is to say, all embodiments and / or features of any embodiment can be combined in any way and / or combination, unless these features are incompatible. The applicant reserves the right to change any originally filed claim or to file any new claim accordingly, including the right to amend any originally filed claim to make it fall under any other claim and / or incorporate any feature of any other claim, even though originally not claimed in such a manner. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0009] Figure 1 is a schematic view of a wind turbine in which a hydrogen production system according to the present invention can be incorporated;

[0010] Figure 2 is a schematic view of a hydrogen production system according to an embodiment of the present invention;

[0011] Figure 3 and Figure 4 is Figure 2 a schematic view of a first exemplary control structure associated with a converter system of the hydrogen production system in

[0012] Figure 5 and Figure 6 is Figure 2 a schematic view of a second exemplary control structure associated with a converter system of the hydrogen production system in

[0013] Figure 7 illustrates a series of data curves a - d, which illustrate various operating parameters associated with the operation of the hydrogen production system of the present invention. DETAILED DESCRIPTION

[0014] The following detailed description refers to the accompanying drawings, which illustrate, by way of illustration, specific details and embodiments in which the present invention can be practiced. The embodiments are described in sufficient detail to enable those skilled in the art to practice the present invention. Other embodiments can be utilized and structural changes can be made without departing from the scope of the present invention as defined in the appended claims.

[0015] Figure 1FIG. 0 shows a schematic view of a wind turbine 1 that may incorporate the present invention. The wind turbine 1 includes a nacelle 2 supported on a generally vertical tower 4. The nacelle 2 supports a main rotor assembly 6. The main rotor assembly 6 includes a hub 8 and a plurality of wind turbine blades 10 connected to the hub 8. In this example, the wind turbine 1 includes three wind turbine blades 10. Figure 1 The wind turbine 1 in FIG. 0 is a well-known horizontal axis wind turbine, which is the most common form of large-scale wind turbines, but other forms will be acceptable for the present invention.

[0016] The nacelle 2 also houses many functional components of the wind turbine 1. Generally, such a wind turbine 2 will be used to generate electrical energy in the form of AC (alternating current) or DC (direct current) for supply to an associated power distribution network. However, in this embodiment of the present invention, the wind turbine 1 incorporates an integrated hydrogen production system that uses the electrical power generated by a generator housed within the nacelle 2 to store energy in the form of hydrogen through an electrolysis system.

[0017] Although Figure 1 FIG. 0 illustrates a typical wind turbine in which the present invention may be implemented, but Figure 2 FIG. 12 shows a system-level overview of a hydrogen production system 12 according to an embodiment of the present invention.

[0018] Generally speaking, the hydrogen production system 12 includes a power generation system 14 coupled to an electrolysis system 16.

[0019] The power generation system 14 includes a main rotor assembly 6, hereinafter simply referred to as the "rotor", which drives a generator 18 through a gearbox 20. It should be noted that although a gearbox is a typical component in utility-scale wind turbine generators, systems based on so-called direct drive architectures that do not use a gearbox are also known. Embodiments of the present invention are applicable to both types of systems.

[0020] The generator 18 is electrically connected to a power converter system 22. Generally, the generator 18 and the primary power converter system 22 will operate on a three-phase electrical architecture, although this is not necessary.

[0021] The power converter system 22 provides an input power source to the electrolysis system 16 via an electrical coupling or electrolyzer bus 23.

[0022] The power converter system 22 includes a machine-side or generator-side converter 24 and an electrolyzer-side converter 26. The generator-side converter 24 is electrically coupled to the electrolyzer-side converter 26 via a bus or "DC link" 28.

[0023] The generator-side converter 24 is an AC-DC converter and thus converts the AC power generated by the generator 18 into DC power on the DC link 28. Conversely, the electrolyzer-side converter is a DC-AC converter and thus feeds from DC and generates AC power for the electrolysis system 16.

[0024] Those skilled in the art will understand that the power converter system 22 and the DC link 24 actually include what would generally be understood as a full-scale back-to-back power converter system architecture commonly found in utility-scale wind turbines for providing variable-frequency electrical power and associated reactive power support. In such a power scheme, the AC power placed on the electrolyzer bus 23 is decoupled from the AC power generated by the generator 18. Thus, the electrolyzer-side converter 26 can control the voltage delivered to the electrolysis system 16.

[0025] The form of the converter system that can be used for the generator-side converter 24 and the electrolyzer-side converter 26 is well known in the art and within the capabilities of those skilled in the art to specify for a particular power generation application.

[0026] Turning more specifically to the electrolysis system 16, generally speaking, the system includes an electrolysis unit stack or "electrolyzer" 30. An input water stream 32 is supplied to the electrolyzer 30 through a suitable water source 33. This water source 33 can supply fresh water, for example, from a storage tank or from a pipeline. Alternatively, in the case of an offshore-based system, a desalinator can be used to remove salt from seawater and supply fresh water to the electrolyzer 30. Such a desalinator is a known system that those skilled in the art will understand, and thus a complete technical description will not be provided here.

[0027] The electrolyzer 30 provides a hydrogen output stream 34 to a user 35 of the generated hydrogen. The user 35 can be a direct supply to a distribution network, or it can be a suitable storage capacity, such as a set of tanks. The hydrogen user 35 can also include a suitable compressor / dryer system to compress the hydrogen to a suitable pressure level (e.g., 700 bar) before storage or forward supply to another user. In this embodiment, the electrolyzer 30 can be of the type that provides non-pressurized hydrogen (i.e., hydrogen at substantially atmospheric pressure), such that a compressor is required to pressurize the hydrogen output stream for use and / or storage purposes. However, in an example where the electrolyzer is a high-pressure system, a compressor may not be required, as those skilled in the art will understand. At this point, it should be noted that in principle, any suitable type of electrolyzer 30 can be used, the specifications of which will be within the understanding of those skilled in the art. For example, by way of example, the electrolyzer 30 can be an alkaline electrolyzer, a polymer electrolyte membrane (PEM) electrolyzer, or a solid oxide electrolyzer (SOEC).

[0028] The electrolyzer system 16 also includes a secondary power converter 36 configured to control the incoming AC power delivered by the bus 23 to the DC power supplied to the electrolyzer 30 itself. In the example shown, it is contemplated that the secondary power converter 36 of the electrolyzer system 16 may be implemented as a passive rectifier unit, which is preferably three-phase in utility-scale applications. Such a rectifier can be implemented with suitable semiconductor devices such as diodes and / or thyristors, although it can be implemented in a more complex manner with transistor-based switching devices. The selection of current switching devices such as diodes, thyristors, and semiconductor switches is within the capabilities of those skilled in the art. However, the function of the secondary power converter 36 is to convert the AC power from the bus 23 into DC power for the electrolyzer 30 without any regulation of the delivered power.

[0029] The hydrogen production system 12 also includes a control system 40. For simplicity, the control system 40 is shown here as a single functional block, but it should be noted that this is not intended to infer any physical or logical limitations on the actual implementation of the control system 40. Thus, the control system 40 can be implemented as an independent computing device configured to communicate, under its control, with systems, subsystems, sensing units, etc. via wired or wireless connections. The control system 40 can also be implemented as a distributed control unit, for example, to provide redundancy. The exact physical and logical implementation of the control system 40 is not central to the present invention and is thus outside the scope of this disclosure.

[0030] The control system 40 is coupled to the power converter system 22 via suitable first and second control channels 42, 44 to control the output power delivered to the electrolyzer 30 through the bus 23. The control channels 42, 44 are also configured to return to the control system 40 the sensing information it may need to execute its control objectives. The control system 40 is also configured to receive data inputs 46 from other sources. Such data inputs can include: the pitch angle of one or more blades of the rotor, the rotational speed of the generator, and the wind speed.

[0031] The control system 40 includes a generator-side control module 50 and an electrolyzer-side control module 52. The first control channel 42 couples the generator-side control module 50 to the generator-side converter 24, and the second control channel 44 couples the electrolyzer-side control module 52 to the electrolyzer-side converter 26.

[0032] has been referred to Figure 2 A schematic overview of the hydrogen production system 12 has been described. Now the discussion will turn to the specific functional features of the control system 40 considered in the context of the hydrogen production system 12.

[0033] In Figure 2In the hydrogen production system 12 shown, it should be understood that the busbar 23 represents what can be considered an electrical network. Although in the illustrated embodiment the coupling is connected to a single electrolyzer 30, in principle the busbar 23 can provide more than one connection point to the corresponding electrolyzer. However, as shown, the busbar 23 connects a single generator 18 to a single electrolyzer 30 in a one-to-one connection.

[0034] In such a configuration, it is important that the voltage on the busbar remains stable at a predetermined nominal voltage level for the proper operation of the electrolyzer 30. Generally, the busbar voltage should not vary by more than 5%-10%. Since the control system 40 is able to adjust the operation of the generator-side converter 24 and the electrolyzer-side converter 26 in order to maintain a stable busbar voltage, such a goal can typically be achieved over a wide range of wind conditions.

[0035] However, as the production of green hydrogen scales up to larger wind turbine capacities, the wind turbine facility is required to implement various mechanical damping functions by means of controlling the mechanical loads on the wind turbine structure. For example, it is known that damping of tower oscillations can be achieved by adjusting the generator torque such that the adjustment of the electrical load (i.e., torque) on the generator 18 creates a reaction force opposite to the lateral oscillations of the wind turbine nacelle, and similar generator torque control methods are used to damp (suppress) torsional drivetrain vibrations [1],[2].

[0036] The use of such damping functions affects the output power of the generator, which in turn can affect the power that the power converter system 22 can apply to the busbar 23 to drive the electrolyzer 30. In particular, if the electrolyzer-side converter 26 drives the electrolyzer with a constant input power, the variable input power of the generator-side converter 24 may affect the voltage on the DC link 28, and in extreme cases, this may adversely affect the performance of the electrolyzer-side converter 26.

[0037] However, to mitigate this problem, the control system 22 is configured to control the load torque on the wind energy generator 18 and the electrical power fed to the electrolyzer 30 in order to implement the damping functions associated with the wind turbine facility while maintaining a stable DC link voltage. More specifically, the generator-side control module 50 and the electrolyzer-side control module 52 are configured to control the corresponding generator-side converter 24 and electrolyzer-side converter 26 in a complementary manner to balance the load torque on the wind energy generator 18 and the power fed to the electrolyzer 30. Thus, the control method described herein has the advantage of balancing the power flow in both the generator-side converter and the electrolyzer-side converter in order to keep the DC link voltage stable, or at least within a predetermined limit. Note that these limits can be configured to provide a narrower or wider control band as needed.

[0038] Figure 3 andFigure 4 Illustrates the control algorithm, structure, or scheme embodied in the control system 40. The electrolyzer side control module 52 implements the first control structure 100 as shown in Figure 3 and the generator side control module 50 implements the second control structure 200 as shown in Figure 4 .

[0039] First, referring to Figure 3 , the first control structure 100 includes a first controller 102, which is configured to output a power reference P_ref1 to control the electrolyzer side converter 26. In response, the electrolyzer side converter 26 outputs a suitable AC output power to the bus 23. The first controller 102 can be of any suitable controller type, such as a PID controller, or a simpler controller, such as a PI controller. As will be understood by those skilled in the art, more complex controllers, such as model predictive controllers, can also be used.

[0040] The main control objective of the first controller 102 is to control the electrolyzer 30 by outputting power to the bus 23 via the electrolyzer side converter 26 so as to keep the DC link 28 at a stable voltage level. In principle, the first controller 102 will operate to maintain the DC link voltage at a constant level. However, in practice, the DC link voltage is allowed to fluctuate slightly, which can be within 5 - 10% of the nominal DC link voltage level.

[0041] Therefore, for this purpose, a third controller 302 receives a voltage error value V_error associated with the DC link voltage measurement V_dc_link, which is provided by a feedback signal representing the measurement output from the DC link 28.

[0042] The voltage error value V_error is generated from a summing point 104, which also receives a DC link voltage reference signal V_dc_link_ref. The reference signal V_dc_link_ref is a pre - determined signal generated internally, which is set for the correct operation of the electrolyzer 30 and adapts the voltage level of the converter. This can be based on various factors, including the required hydrogen production output of the electrolyzer 30.

[0043] Therefore, the first controller 102 acts on the voltage error V_error and is used to reduce this error value to zero, as in the known function of a closed - loop controller.

[0044] As described above, the first controller 102 outputs a power reference signal P_ref1 that is fed to the electrolyzer-side converter 26. However, the power reference signal P_ref1 is combined at the summing point 106 with a signal derived from additional signal components P_damp and P_aux to generate a second power reference signal P_ref2 that is input to the electrolyzer-side converter 26.

[0045] The purpose of combining the base power reference signal P_ref1 with the additional signal components is to cover the variable power demand that represents the instantaneous power demand of the wind turbine installation. For example, the lateral (left-right) tower damping function may require a sinusoidally varying generator torque demand in order to counteract the swaying motion of the tower 4. Similarly, a variable generator torque demand may be applied in order to counteract torque spikes in the drivetrain due to gusts of wind.

[0046] In this regard, the summing point 108 combines at least two power component signals. In the example shown, the summing point 108 combines three power component signals. The first power component signal is a steady-state power level labeled P_gen_ss_ref, which is the base power reference and is an indication of the power obtainable from the current wind conditions. It can be seen that the signal P_gen_ss_ref passes through a high-pass filter 110 in order to filter out the constant (DC) level in the signal and pass through a variable power level that is controlled by the relatively slowly varying power of the wind.

[0047] The second power signal component provides an indication of the power required for one or more mechanical damping systems of the wind turbine 1 and is labeled P_damp. The second power signal component P_damp is shown here as a single input representing one damping power requirement, but those skilled in the art will understand that the signal component P_damp can include multiple signals. Examples of such damping systems that may affect such a signal component are the lateral tower oscillation damping function, the front-back tower damping function in a floating base, and the drivetrain damping function.

[0048] The third power signal component labeled P_aux provides an indication of the power requirements of one or more internal systems such as environmental conditioning systems, oil cooling systems, hydraulic pressurization systems, control systems, and other auxiliary power consumers.

[0049] As those skilled in the art will understand, the output of the summing point 108 provides a time-varying power requirement signal P_ref3, which is input as a feedforward term to the summing point 106 after passing through a gain block 112, and the gain block 112 can provide a configurable gain value to affect the impact of the feedforward power signal component term. Advantageously, the feedforward dynamically varying signal component allows for a rapid response of the converter system to adapt to changes.

[0050] Figure 3 The effect of the first control structure 100 in is the corresponding regulation that balances the power required by the internal wind turbine system with the power supplied to the electrolyzer 30. The first control structure 100 operates synchronously with Figure 4 the second control structure 200 in. It should be noted that, compared with Figure 3 the first control structure 100 in, the second control structure 200 is simplified. The second control structure 200 includes a second controller 202, which provides an input signal P_ref4 to the generator-side converter 24 in response to a power reference signal P_ref3, thereby controlling the torque or current applied to the generator 18. It should be noted that the technical principle for controlling the generator torque through a full-scale power converter is a technique that is well understood by those skilled in the art, and thus further details are not within the scope of this discussion.

[0051] The second controller 202 receives an error signal P_gen_error, which is the sum of the P_ref3 signal and a feedback signal P_gen, and the feedback signal P_gen is the output power from the generator. Note that the P_ref3 signal is the same signal input to the summing point 106 in Figure 3 the control structure 100 of.

[0052] The second controller 202 is used to control the generator-side converter 50 to drive the error signal to zero. As a result, the second control structure 200 is used to ensure that the output power generated by the generator matches the variable power reference P_ref3 generated by the composite power reference signal P_gen_ref, which combines the steady-state power reference P_gen_ss_ref and the internal power demand references (P_damp and P_aux) for the wind turbine.

[0053] Its effect can be understood by looking at the graph shown in Figure 7 . Figure 7 Graph a shows the variable signal P_ref3, which combines the steady-state power reference with the variable internal power demand of the wind turbine 1. For illustrative purposes, the P_ref3 signal varies approximately sinusoidally in Figure 7 graph a. This can represent the power requirement for the oscillation damping function of the wind turbine, because the lateral (left and right) sway of the tower 4 can be corrected by sinusoidally varying generator torque changes, as is known in the art. However, it should be noted that the varying power reference signal may not be a simple sinusoidal signal, and other forms of variation are expected.

[0054] Although Figure 7 graph a shows the time-varying P_ref3 signal, Figure 7b shows the result of the control signal delivered to the generator side converter 24 by illustrating the generator torque following the change of the P_ref3 signal. Figure 7 c shows the resultant power generated by the generator 18, which is Figure 4 A second control structure 200 is shown controlling.

[0055] In order to balance the variable power output of the generator 18, Figure 7 d shows the variable power delivered to the electrolyser. It will be apparent to the reader that the power delivered to the electrolyser 30 is balanced by the power generated by the generator 18. Therefore, in principle, the input load on the DC link 28 will be balanced or offset by the output load, which will mean that the voltage on the DC link 28 will remain stable (if not exactly constant).

[0056] Figure 7 e shows the DC link voltage, and it can be seen that, ideally, the DC link voltage would remain constant. However, from a practical point of view, the DC link voltage is allowed to vary by a predetermined amount, which is envisaged to be between 5% and 10%. Therefore, some variation is accepted, as shown by the dashed line V_DC'.

[0057] It will be appreciated in the above discussion that for purposes of illustration, the time-varying output power of the generator 18 and the power delivered to the electrolyser 30 are synchronized. This is based on the assumption that there are no hysteresis effects based on the electrical system dynamics between the generator and the electrolyser. If significant electrical dynamics are present, the control structure can be configured to provide appropriate compensation for the system dynamics. For example, the capacitance of the DC link 28 may mean that a delay may need to be introduced between an increase in the output power of the generator 18 and an increase in the power delivered to the electrolyser 30.

[0058] Therefore, in order to adapt to the capacitance phenomenon, the first control structure 100 can be implemented with a delay function 120, such as Figure 3 The dashed lines in the figure are shown as optional features.

[0059] exist Figure 5 and Figure 6 An alternative example of implementing the present invention is illustrated in Figure 5 A third control structure 300 is shown, and Figure 6 A fourth control structure 400 is shown. It should be noted that Figure 5 The third control structure 300 in Figure 3 The first control structure 100 is equivalent to that in FIG. 1 , although it controls the generator side converter 24, and Figure 6 The fourth control structure 400 in Figure 4 The second control structure 200 in is equivalent, although it controls the electrolyzer side converter 26.

[0060] As in Figure 3 and Figure 4 the previous examples of the present invention shown in Figure 5 and Figure 6 In the examples shown, the control structures 300, 400 act in a complementary manner to balance the load torque on the wind energy generator 18 and the power fed to the electrolyzer 30.

[0061] Referring first to Figure 5 , the third control structure 300 includes a first controller 302 configured to output a power reference P_ref1 to control the generator side converter 24. In response, the generator side converter 24 outputs a suitable power onto the DC link 28. As described above, the third controller 202 can be of any suitable controller type.

[0062] The third control structure 300 controls the generator 18 by outputting power to the DC link 28 via the generator side converter 24 in order to maintain the DC link 28 at a stable voltage level while also providing a variable power demand for the active damping function. In principle, the third controller 302 will operate to maintain the DC link voltage at a constant level, although in practice the DC link voltage is allowed to fluctuate slightly, which can be within 5 - 10% of the nominal DC link voltage level.

[0063] To provide this function, the third controller 302 receives a voltage error value V_error associated with the DC link voltage measurement V_dc_link, which is provided by a feedback signal representing the voltage measured on the DC link by means of the operation of the generator side converter 24.

[0064] The voltage error value V_error is generated from a summing point 304, which also receives a DC link voltage reference signal V_dc_link_ref. The reference signal V_dc_link_ref is a predetermined signal generated internally, which is set for the correct operation of the electrolyzer 30. This can be based on various factors, including the required hydrogen production output of the electrolyzer 30.

[0065] Thus, the third controller 302 acts on the voltage error V_error and is used to reduce this error value to zero, as in the known function of a closed-loop controller.

[0066] As described above, the third controller 302 outputs a power reference signal P_ref1 that is fed to the generator side converter 24. However, the power reference signal P_ref1 is combined at the summing point 306 with a signal derived from additional signal components P_damp and P_aux to generate a second power reference signal P_ref2 that is input to the generator side converter 24. It should be noted that the technical principle for controlling the generator torque through a full-scale power converter is a technique that is well understood by those skilled in the art, and thus further details are not within the scope of this discussion.

[0067] The purpose of combining the base power reference signal P_ref1 with the additional signal components is to cover variable power demands representing the instantaneous power demand of the wind turbine installation, such as electromechanical active damping (such as lateral / torsional tower damping) functions.

[0068] In this regard, the summing point 308 combines at least two power component signals. In the example shown, the summing point 308 combines three power component signals. The first power component signal is a steady-state power level labeled P_gen_ss_ref, which is the base power reference and is an indication of the power obtainable from the current wind conditions. It can be seen that the signal P_gen_ss_ref passes through a high-pass filter 310 to filter out the constant level in the signal and pass the variable power level governed by the relatively slowly changing power of the wind.

[0069] The second power signal component provides an indication of the power required for one or more electromechanical damping systems of the wind turbine and is labeled P_damp. The second power signal component P_damp is shown here as a single input representing one damping power requirement, but those skilled in the art will understand that the signal component P_damp can include multiple signals. As described above, examples of such damping systems that may affect this signal component are the lateral tower oscillation damping function and the drivetrain damping function.

[0070] The third power signal component, labeled P_aux, provides an indication of the power requirements for one or more internal systems such as environmental conditioning systems, oil cooling systems, and hydraulic pressurization systems.

[0071] The output of the summing point 308 provides a variable power demand signal P_ref3, which is input as a feedforward term to the summing point 306 after passing through a gain block 312, which can provide a configurable gain value to affect the impact of the feedforward power signal component term.

[0072] Figure 5The effect of the third control structure 300 therein is to balance the power required by the internal wind turbine system with the corresponding regulation of the generator torque control applied to the generator 18. The third control structure 300 operates synchronously with Figure 6 the fourth control structure 400 therein. It should be noted that, compared with the third control structure 300 in Figure 5 , the fourth control structure 400 is simplified and structurally closely corresponds to Figure 4 the second control structure 200 shown in

[0073] The fourth control structure 400 includes a fourth controller 402 which provides an input signal P_ref4 to the electrolyzer side converter 26 in response to a power reference signal P_ref3, thereby controlling the power supplied to the electrolyzer 30. The output of the electrolyzer side converter 26 (labeled P_ely) is measured by a feedback signal indicating the power supplied to the electrolyzer 30.

[0074] The fourth controller 402 receives an error signal P_ely_error which is the sum of the P_ref3 signal and the feedback signal P_ely. Note that the P_ref3 signal is the same signal input to the summing point 306 in the control structure 300 of Figure 5 .

[0075] The fourth controller 402 is used to control the electrolyzer side converter 26 to drive the error signal P_ely_error to zero. As a result, the fourth control structure 400 is used to ensure that the power delivered to the electrolyzer 30 matches the variable power reference P_ref3 generated by the composite power reference signal P_gen_ref which combines the steady-state power reference P_gen_ss_ref and the internal power demand references (P_damp and P_aux) for the wind turbine.

[0076] As in the previous examples of the present invention, the control structures 300, 400 can be configured to compensate for electrical system dynamics, such as the capacitance of the DC link 28. This is illustrated in Figure 5 by the delay function 320 which acts on the time-varying parameter P_ref3 and is input to the summing point 306.

[0077] The resulting functions of the third and fourth control structures 300, 400 are equivalent to the functions of the first and second control structures 100, 200 and have been described above with reference to Figure 7 a-e.

[0078] Those skilled in the art will understand that various modifications and adaptations can be made to the examples shown and described without departing from the inventive concept defined by the claims.

[0079] For example, the illustrated example has been described with reference to a system architecture having a generator-side converter 24 as an AC-DC converter, an electrolyzer-side converter 26 as a DC-AC converter, and a secondary converter system 36 characterized as an AC-DC converter. In principle, the present invention is applicable to other system architectures. For example, in the illustrated example, the electrolyzer-side converter 26 and the secondary converter system 36 may replace a DC-DC power converter coupled between the DC link 28 and the electrolyzer 30. In such a configuration, Figure 3 the first control structure 100 in Figure 6 and the fourth control structure 400 in

[0080] would be suitable for controlling such a DC-DC power converter system.

[0081] [1]Active damping (suppression) of torsional vibrations in the drivetrain of a DFIG wind turbine, Chen, Xu, and Wenske.

Claims

1. A hydrogen production system, comprising: A wind turbine installation, the wind turbine installation comprising a wind energy generator (18) connected to a hydrogen electrolyzer (30) via a power converter system (22), wherein the power converter system (22) comprises a generator-side converter (24) and an electrolyzer-side converter (26) electrically coupled together via a DC link (28); a converter controller (50), which comprises a generator-side control module (50) coupled to the generator-side converter and an electrolyzer-side control module (52) coupled to the electrolyzer-side converter; wherein the converter controller is configured to control the load torque on the wind energy generator and the electrical power fed to the electrolyzer to achieve a mechanical damping function associated with the wind turbine installation while maintaining a stable DC link voltage.

2. The system according to claim 1, wherein, The generator-side control module (50) and the electrolyzer-side control module (52) are configured to control the respective generator-side converter (24) and electrolyzer-side converter (26) in a complementary manner to balance the load torque on the wind energy generator and the power fed to the electrolyzer.

3. The system according to claim 1, wherein, The electrolyzer-side control module obtains a time-varying power reference (P_ref3) comprising a reference component (P_damp) from at least one mechanical damping function, and obtains a voltage reference (V_dc_link_ref) indicative of a desired voltage on the DC link, and wherein, in response, the electrolyzer-side control module is configured to control the power delivered from the electrolyzer-side converter to the electrolyzer to maintain a stable DC link voltage.

4. The system according to claim 3, wherein, The generator-side control module obtains the time-varying power reference (P_ref3), and in response, the generator-side control module is configured to control the load torque exerted by the wind energy generator to meet the time-varying power reference (P_ref3).

5. The system according to claim 1, wherein, The generator-side control module (50) obtains a time-varying power reference (P_ref3) comprising a reference component (P_damp) from at least one mechanical damping function, and obtains a voltage reference (V_dc_link_ref) indicative of a desired voltage on the DC link, wherein, in response, the generator-side control module (50) is configured to control the load torque exerted by the wind energy generator (18) to maintain a stable DC link voltage.

6. The system according to claim 5, wherein, The electrolyzer-side control module (52) obtains the time-varying power reference (P_ref3), and in response, the electrolyzer-side control module (52) is configured to control the power delivered from the electrolyzer-side converter (26) to the electrolyzer (30) to meet the time-varying power reference (P_ref3).

7. The system according to claim 2, wherein, The electrolyzer-side control module (52) is configured to control the power delivered from the electrolyzer-side converter (26) to the electrolyzer (30) while compensating for system dynamics.

8. The system according to claim 7, wherein, Compensating for system dynamics includes accounting for a time delay to account for the capacitance of the DC link.

9. The system according to claim 8, wherein, The electrolyzer side control module is configured to account for the time delay by implementing a time delay function on the obtained time-varying power reference (P_ref3).

10. The system according to claim 5, wherein, The generator side control module is configured to control the load torque applied by the wind energy generator while compensating for system dynamics.

11. The system according to claim 10, wherein, Compensating for system dynamics includes accounting for the time delay to account for the capacitance of the DC link.

12. The system according to claim 11, wherein, The generator side control module is configured to account for the time delay by implementing a time delay function on the obtained time-varying power reference (P_ref3).

13. The system according to any one of the preceding claims, wherein, The converter controller (50) is configured to maintain the stable DC link voltage within + / - 10% and preferably within + / - 5% of the nominal voltage level.

14. A method of operating a hydrogen production system including a wind turbine facility, the wind turbine facility including a wind energy generator (18) connected to a hydrogen electrolyzer (30) via a power converter system (22), wherein, The power converter system (22) includes a generator side converter (24) and an electrolyzer side converter (26) electrically coupled together through a DC link (28); and a converter controller (50) including a generator side control module (50) coupled to the generator side converter and an electrolyzer side control module (52) coupled to the electrolyzer side converter, wherein the method includes controlling the load torque on the wind energy generator and the electrical power fed to the electrolyzer to achieve a mechanical damping function associated with the wind turbine facility while maintaining a stable DC link voltage.

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