Controlling an electrolysis plant to produce hydrogen and oxygen through the electrolysis of water

Abstract

The invention relates to an electrolysis plant (10) with a plurality of electrolysis devices (34, 36) connected to a power supply line (30), wherein the electrolysis devices (34, 36) comprise a power supply unit (38, 40) and an electrolysis module (12, 14, 16, 18, 20, 22, 24, 26) coupled to the power supply unit, wherein the power supply units of the electrolysis devices comprise a transformer (42, 44, 46, 48) and a rectifier unit (50, 52, 54, 56, 58, 60, 62, 64), wherein the transformer comprises a primary winding (66, 68, 70, 72) and a secondary winding (74, 76, 78, 80, 82) connected to an AC voltage side of the rectifier unit. 84, 86, 88).According to the invention, the primary winding of the transformer of at least one of the electrolysis devices (40) is designed to be adjustable in stages, and the rectifier unit of this electrolysis device is designed to be operated uncontrolled, wherein the rectifier unit of the power supply unit of at least one of the second electrolysis devices is designed to be operated in a controlled manner depending on the electrical energy available from the energy source.

Description

The invention relates to an electrolysis system for generating hydrogen and oxygen by electrolysis of water, having a plurality of electrolysis devices which are connected to an electrical energy supply line to which an alternating electrical voltage is applied in order to be supplied with electrical energy via the energy supply line for the intended electrolysis operation, the energy supply line being designed for electrically coupling an electrical energy source, the electrolysis devices each having an energy supply unit and at least one electrolysis module electrically coupled to the energy supply unit, the at least one electrolysis module having a plurality of electrolysis cells which are electrically connected at least partially in series or in parallel, the energy supply unit of the electrolysis devices each having at least one transformer and at least one rectifier unit, wherein the at least one transformer has a primary winding electrically coupled to the power supply line and a secondary winding connected to an AC voltage side of the at least one rectifier unit, wherein a DC voltage side of the at least one rectifier unit is electrically coupled to the at least one electrolysis module. The invention further relates to a method for producing hydrogen and oxygen by electrolysis of water by means of an electrolysis plant which has a plurality of electrolysis devices, wherein the electrolysis devices each have an energy supply unit and at least one electrolysis module electrically coupled to the energy supply unit, wherein the at least one electrolysis module has a plurality of electrolysis cells which are electrically connected at least partially in series or are connected in parallel, wherein the electrolysis devices are supplied with electrical energy via an electrical energy supply line to which an electrical alternating voltage is applied for the intended electrolysis operation, wherein the energy supply line electrically couples an electrical energy source, wherein the energy supply units of the electrolysis devices each have at least one transformer and at least one rectifier unit, wherein the at least one transformer has a primary winding electrically coupled to the energy supply line and a secondary winding connected to an alternating voltage side of the at least one rectifier unit, wherein a DC voltage side of the at least one rectifier unit is electrically coupled to the at least one electrolysis module.Electrolysis systems, electrolysis devices and methods for this of the type in question are widely known in the prior art, so that a separate proof from the publication is not required for this purpose. Electrolysis technologies of the aforementioned type use a cascading demand control philosophy for controlling the power of a respective electrolysis device of the electrolysis plant. For a single or a small number of electrolysis devices, it is necessary to adjust the power according to the available electric energy available for generating hydrogen and oxygen from the electric power source. For large electrolysis systems, for example with more than ten electrolysis devices, this is a great challenge because of the individual controls and the power factor correction that occurs and the filtering of harmonics in order to meet network operator requirements.Due to the high power requirement of electrolysis plants, which is associated with a corresponding current stress, thyristor-based rectifier units are customary in order to achieve the required direct current, for example in a range from about 7 to about 10 kA. Due to the high efficiency and the high reliability in high-current applications, their use is also expected in large electrolysis systems. The high current requirements are currently a major reason why voltage-based converters, for example using transistor-based DC / DC converters, are not currently being used.However, thyristor-based rectifier units have a substantial harmonic disadvantage with respect to current stress of the power source. This generally requires additional components, for example active and / or passive filters, and power factor compensation units, in order to be able to meet the requirements on the power source side, in particular with respect to a reactive power requirement in an AC power grid of the power source. However, this results in correspondingly high additional costs.Furthermore, thyristor-based rectifier units generally require three control units, namely a central control unit for controlling a gradation of the primary winding of the transformer, which can be adjusted in a stepped manner, and an additional control unit for controlling an active power and supplying a corresponding control signal for a DC control unit, which control signal serves for controlling the DC current as a function of the aforementioned control signal by controlling an ignition angle for the thyristors of the thyristor-based rectifier unit and which has a phase-locked loop control (PLL) in order to be able to adjust the ignition angles of the thyristors with respect to the AC voltage present at the AC voltage side of the rectifier unit.These controllers influence the harmonics and the power factor. For each of the electrolysis devices, the central control unit, the additional control unit and the direct current control unit are required. This also results in high outlay.The object of the invention is to reduce the effort with respect to the release of harmonics and an unfavorable power factor for large electrolysis systems.Electrolysis plants and methods according to the independent claims are proposed as a solution with the invention.Advantageous further developments are obtained by features of the dependent claims.With respect to an electrolysis system of the generic type, it is proposed according to a first aspect of the invention in particular that the primary winding of the at least one transformer is designed to be adjustable in stages by at least one first of the electrolysis devices and the at least one rectifier unit of the energy supply unit of this electrolysis device is designed to be operated in an uncontrolled manner, wherein the at least one rectifier unit of the energy supply unit is designed to be operated in a controlled manner by at least one second of the electrolysis devices as a function of the electrical energy that can be provided by the energy source.With respect to an electrolysis system of the generic type, it is proposed in particular according to a second aspect that the electrolysis system has an energy storage unit connected to the energy supply line for reversibly storing electrical energy, wherein the energy storage unit is designed to store and deliver electrical energy in a continuously controllable manner, wherein the primary winding of the at least one transformer of at least a first of the electrolysis devices can be adjusted in a stepwise manner and the at least one rectifier unit of the energy supply unit of this electrolysis device is designed to be operated in an uncontrolled manner.With respect to a method of the generic type, the invention according to the first aspect proposes in particular that the primary winding of the at least one transformer of at least one first of the electrolysis devices is designed to be adjustable in stages and the at least one rectifier unit of the energy supply unit of this electrolysis device is operated in an uncontrolled manner, wherein the at least one rectifier unit of the energy supply unit of at least one second of the electrolysis devices is operated in a controlled manner as a function of electrical energy which can be provided by the energy source.With respect to a method of the generic type, the invention according to the second aspect proposes in particular that an energy storage unit connected to the energy supply line and configured to reversibly store electrical energy, stores and outputs the electrical energy in a continuously controllable manner, wherein the primary winding of the at least one transformer is configured to be adjustable in stages by at least a first of the electrolysis devices and the at least one rectifier unit of the energy supply unit of this electrolysis device is operated in an uncontrolled manner.The invention is based, inter alia, on the idea that the power of the electrolysis plant can be adapted depending on the available electrical power of the energy source. For this purpose, it is proposed that, in the case of at least one first electrolysis device, the at least one transformer can be adjusted in stages with respect to its primary winding, as a result of which the secondary voltage of the secondary winding can be varied accordingly, with the result that the power can be varied as a function of the alternating voltage adjusted in each case in a respective stage. In this electrolysis device, it is furthermore provided that the at least one rectifier unit is designed to be operated in an uncontrolled manner. That is, in this at least one electrolysis device, the power is varied substantially exclusively by adjusting a respective stage of the primary winding. A power adjustment by means of the at least one rectifier unit does not need to be provided here. This at least one rectifier unit can thereby be configured comparatively cost-effectively. In particular, it does not require any control.At the same time, there is at least one second electrolysis device in which the at least one rectifier unit can be operated in a controlled manner depending on electrical power which can be provided by the energy source. In the at least one first electrolysis device, the adjustment of the stage of the primary winding of the at least one transformer is preferably likewise controlled as a function of the electrical energy which can be provided by the energy source. For this purpose, a superordinate controller or a control device or control unit can provide a corresponding control signal, by means of which the desired control functionalities can be achieved. For the at least one first electrolysis device and for the at least one second electrolysis device, the control signals can be different.This construction makes it possible, on the one hand, to realize the at least one rectifier unit for the at least one first electrolysis device, for example, by means of diodes, so that the uncontrolled rectifier unit can be realized in a simple manner. The rectifier unit can be designed to be adapted to the alternating voltage provided by means of the secondary voltage. The rectifier unit is preferably designed in the manner of a bridge circuit. In addition, the rectifier unit is designed to be adapted to the alternating voltage provided by the energy source. It should be taken into account here that the alternating voltage can be a polyphase alternating voltage, in particular can have three phases. However, the invention is not limited to a particular number of phases. The transformers and the rectifier units are designed to be matched to the number of phases of the AC voltage.For example, the alternating voltage can be provided as a three-phase alternating voltage from the energy source and consequently also from the transformer, whereby the rectifier unit can be configured, for example, as a six-pulse bridge circuit, as a 12-pulse bridge circuit, as a 24-pulse bridge circuit or the like. Therefore, only a comparatively low control effort is required for the at least one first electrolysis device for adjusting the power, namely only insofar as the corresponding stage on the primary winding has to be adjusted by means of an adjusting device of the electrolysis device as a function of the control signal. The adjusting device can have, for example, one or more switching elements to which one or more taps of the primary winding can be selectively coupled in order to be able to adjust the desired stage of the step-adjustable primary winding.In the at least one second electrolysis device, it is instead provided that the at least one rectifier unit is a controlled rectifier unit. This can be formed, for example, similarly to the at least one rectifier unit of the first electrolysis device, wherein, however, the diodes can be replaced by thyristors. A corresponding thyristor control is then provided for the thyristors, which makes it possible to realize a corresponding power control by means of phase gating. At the same time, a stepped primary winding does not necessarily have to be provided here in the case of the at least one transformer. Basically, however, the at least one transformer of the at least one second electrolysis device can be designed and adjustable in the same way as the at least one transformer of the at least one first electrolysis device.This construction results in the overall control effort for the electrolysis plant being able to be significantly reduced. Depending on the alternating voltage and the power consumption and the electrical properties of the electrolysis devices, an alternating current is produced on the energy source side, which alternating current has a very small or even negligible proportion of harmonics with respect to the alternating current in the at least one first electrolysis device. It can likewise be achieved that the power factor of the at least one first electrolysis device is as great as possible, preferably close to 1, so that the outlay for power factor correction and also for the treatment of harmonics can be significantly reduced. The effects on the energy source with respect to the requirements with respect to grid feedback can therefore be very small. Because a corresponding filter or correction measure needs to be provided only for the at least one second electrolysis device, the overall outlay for reducing network interactions can also be kept very low compared to the prior art. The invention therefore makes it possible to reduce the outlay for the electrolysis plant not only overall, but at the same time also a control outlay.Substantially the same effect can also be achieved according to the second aspect in that instead of or in addition to the at least one second electrolysis device an energy storage unit is connected to the energy supply line, which serves for the reversible storage of electrical energy. The energy storage unit is designed to store and output the electrical energy in a continuously controllable manner. This can be achieved, for example, by the energy storage unit having a suitable electrical energy store such as one or more capacitors, one or more inductances and / or the like. The at least one electrical energy store can be connected to the energy supply line in a controlled manner by means of an energy converter unit or an energy converter unit, so that electrical energy is supplied to the energy supply line or electrical energy can be absorbed by the energy supply line depending on a control signal, which can likewise be provided by the control unit, for example. This makes it possible, for example, to implement power factor correction and / or also to compensate harmonics. The energy converter provided for this purpose can be realized, for example, by means of transistors or also fast-switching thyristors. The energy storage unit can basically be used to achieve a comparable electrical effect with respect to the electrical energy source, as can be achieved with the at least one second electrolysis device. If, namely, electric power is available by the electric energy source to an extent which is greater than a power consumption by the at least one first electrolysis device at a predetermined first stage, but less than the power at a next larger stage of the primary winding of the at least one transformer, this differential power can be absorbed by means of the energy storage unit.The energy storage unit can be used to absorb the electrical power which is in the set stage of the primary winding of the transformer of the at least one first electrolysis device for a predeterminable period of time. As soon as the at least one energy store has absorbed a correspondingly large amount of energy, the next higher stage at the primary winding of the at least one transformer can be set in the at least one first electrolysis device and the storage unit can output the absorbed energy via the energy supply line to the at least one first electrolysis device. By allowing a substantially continuous power transition in this manner, grid feedback to the electrical energy source may be substantially reduced, if not nearly completely avoided. At the same time, a high adjusting speed can be achieved even at high power.Overall, the invention according to the first and the second aspect results in that particularly large electrolysis installations with a plurality of electrolysis devices can be operated very efficiently and with a comparatively low level of network feedback. At the same time, the outlay can be reduced and the possibility of using diode-based rectifier units makes it possible to also improve the efficiency.The at least one transformer of the electrolysis devices is preferably designed to be adapted to the AC voltage provided and to the DC voltage required for electrolysis purposes. If it is a single-phase alternating voltage, the transformer is preferably designed as a single-phase transformer. If, for example, the alternating voltage is a polyphase alternating voltage, in particular a three-phase alternating voltage, the transformer is designed to be correspondingly matched to the number of phases. The at least one transformer can be configured, for example, on the primary side in a delta connection in the case of a three-phase alternating voltage. On the secondary side, it can be provided that the transformer has a delta circuit or a star circuit. However, the invention is not limited to the use of these types of circuits of transformers.An electrolysis device can have an electrical power consumption of, for example, 17 MW. For the gradation of the primary winding of the at least one transformer, it can be provided that two respective successive stages cause a predefined or predefinable power difference. Preferably, the power difference between the successive stages is substantially the same. In alternative embodiments, however, it is also possible to deviate from this.A rated power for the energy supply unit of the at least one second electrolysis device or the energy storage unit preferably corresponds at least to the aforementioned power difference between two successive stages of the primary winding of the transformer of the at least one first electrolysis device.In particular, it is proposed that a rated power of the energy storage unit with respect to the storage and the dispensing of electrical energy is greater than a power difference of two successive stages of the primary winding which can be adjusted in stages during the intended operation of the at least one first electrolysis device. This makes it possible to absorb an available excess power of the electrical energy source at a predetermined set stage of the primary winding of the at least one first electrolysis device or, conversely, to output a corresponding power. Because the energy storage unit can be adjusted substantially continuously with respect to storing electrical energy and delivering electrical energy, an available power of the electrical energy source can thus also be used substantially completely if it does not correspond exactly to the electrical power which the at least one first electrolysis device receives at a specific set level.It is further proposed that the at least one transformer for stepwise adjustment of the primary winding has a tap changer with at least five stages, preferably at least nine stages. The tap changer can of course also have significantly more stages. The larger the number of stages is selected, the finer the adjustment possibility with respect to the at least one first electrolysis device. Under certain circumstances, this makes it possible to choose the rated power for the at least one second electrolysis device or the energy storage unit to be correspondingly smaller. This allows further advantages, in particular with regard to the net feedback. This is advantageous, among other things, in the case of particularly high powers.According to a further development, the electrolysis system has a control unit which is designed to receive an energy availability signal and, depending on the energy availability signal, on the one hand to set the stage of the primary winding of the at least one transformer by the at least one first electrolysis device and, on the other hand, to set at least the electrical power of the at least one second electrolysis device by means of its rectifier unit or at least the electrical power of the energy storage unit. For this purpose, the control unit can be in communication connection with the electrical energy source. If the electrical energy source is an energy supply network, for example a public energy supply network, it can be provided that the control unit is in communication connection with a control center of the energy supply network. The control unit can be designed to provide corresponding control signals for the at least one first and the at least one second electrolysis device and, if appropriate, also for the energy storage unit as a function of the available electrical power, such that the desired electrical power can be absorbed by the electrolysis plant. In this way, it is possible to be able to react particularly easily and quickly also to changing load states with respect to the electrical energy source. Despite the high power of the electrolysis plant, stable operation of the electrical energy source can be achieved, in particular if the electrical energy source is an energy supply network.It is further proposed that a sum of the rated power of the energy storage unit with respect to the storage and output of electrical energy and the rated power of the at least one controlled rectifier unit of the energy supply unit from the at least one second electrolysis device is greater than the power difference of two successive stages of the stage-adjustable primary winding during the intended operation of the at least one first electrolysis device. This development is directed, inter alia, in particular to an embodiment in which the electrolysis plant, in addition to the at least one first electrolysis device, also has at least one second electrolysis device and an energy storage unit. By the joint operation, the power difference between two successive stages of the at least one first electrolysis device can be correspondingly distributed to the at least one second electrolysis device and the energy storage unit. This makes it possible to distribute the effort for a continuously adjustable power to the at least one second electrolysis device and the electrolysis unit.The advantages and effects indicated for the electrolysis plants according to the invention also apply correspondingly to the processes according to the invention and vice versa. Consequently, method features may also be formulated as corresponding device features and vice versa.For use cases or application situations which can arise in the method and which are not explicitly described here, provision can be made for an error message and / or a request for inputting a user feedback to be output and / or for a default setting and / or a predetermined initial state to be set according to the method.Regardless of the grammatical sex of a certain term, individuals with male, female or other sex identity are included.The exemplary embodiments explained below are preferred embodiments of the invention. The features, feature combinations specified above in the description and also the features and feature combinations specified in the following description of exemplary embodiments and / or shown alone in the figures can be used not only in the respectively specified combination but also in other combinations. Therefore, embodiments are also encompassed by the invention or are to be regarded as disclosed which are not explicitly shown and explained in the figures, but which emerge from the explained embodiments and can be generated by separate combinations of features. The features, functions and / or effects illustrated on the basis of the exemplary embodiments can each represent, per se, individual features, functions and / or effects of the invention, which are to be considered independently of one another and which also develop the invention in each case independently of one another. Therefore, the embodiments are intended to include combinations other than those in the illustrated embodiments. In addition, the described embodiments can also be supplemented by further features, functions and / or effects of the invention already described.In the figures, like reference numerals designate like features and functions. FIG. 1 is a schematic circuit diagram of an electrolysis system with two electrolysis devices and an energy storage unit which are connected to an energy supply line; FIG. 2 shows a schematic diagram illustration of a stepped setting of a primary winding of a transformer of a power supply unit of an electrolysis device according to FIG. 1 ; and FIG. 3 shows a schematic diagram illustration of a power adaptation of the electrolysis system according to FIG. 1 to an available power of an AC voltage source.FIG. 1 shows a schematic circuit diagram representation of an electrolysis plant 10 which serves for generating hydrogen and oxygen by electrolysis of water. For this purpose, the electrolysis plant 10 has two electrolysis devices 34, 36, which are connected to an electrical energy supply line 30, to which a three-phase electrical alternating voltage is applied, in order to be supplied with electrical energy via the energy supply line 30 for the intended electrolysis operation. In the present embodiment, it is provided that the energy supply line 30 serves to couple a three-phase alternating voltage source 32 as an electrical energy source. The three-phase alternating voltage source 32 is in the present case a public energy supply network. In alternative embodiments, an island network or the like can naturally also be provided here. The electrolysis plant 10 can of course also have more than two electrolysis devices 34, 36. As those skilled in the art will appreciate, the number of electrolysis devices is essentially not relevant for explaining the invention. The alternating voltage network 32 is designed in the present case for a three-phase operation.The electrolysis devices 34, 36 each have an energy supply unit 38, 40 and a plurality of electrolysis modules 12, 14, 16, 18, 20, 22, 24, 26 connected in series in the present case, which are connected in series to the respective energy supply unit 38, 40. For example, six electrolysis modules 12 are connected in series to the energy supply unit 38. Similarly, six electrolysis modules 14 connected in series are connected to the energy supply unit 38. Similarly, six electrolysis modules 16 and also six electrolysis modules 18 are each connected to the energy supply unit 38. The same applies to the electrolysis device 36, in which series connections of electrolysis modules 20, 22, 24, 26, which likewise each have six electrolysis modules connected in series, are connected separately to the energy supply unit 40.It is not shown in the FIGS. that each of the electrolysis modules 12, 14, 16, 18, 20, 22, 24, 26 has a predetermined number of electrolysis cells which are electrically connected in a predetermined manner in a matrix circuit. Depending on the design, however, it can also be provided that the electrolysis cells within a respective one of the electrolysis modules 12 to 26 are only connected in parallel or are only connected in series. In the present case, it is provided that the electrolysis cells and also the electrolysis modules 12 to 26 formed therefrom are of substantially identical design. It is likewise not shown in the FIGS. that each of the electrolysis cells or each of the electrolysis modules has a respective connection for water to be electrolysed and respective connections for hydrogen or oxygen produced by the electrolysis. The detailed structure of a respective electrolysis cell or of a respective one of the electrolysis modules 12 to 26 is, however, not relevant for the invention, for which reason further explanations in this respect are omitted here.In the present embodiment according to FIG. 1, it is furthermore provided that the electrolysis system 10 has an energy storage unit 28 connected to the energy supply line 30 for the continuously adjustable reversible storage of electrical energy. The energy storage unit 28 is designed to store and output electrical energy in a substantially continuously controllable manner. For this purpose, the energy storage unit 28 in the present case has electrical energy stores, not shown in any more detail, which can have capacitors, accumulators, inductances and / or the like, for example. The energy stores are electrically coupled to the energy supply line 30 by means of an inverter, likewise not shown in any further detail. The inverter can likewise also serve as a rectifier, in particular as a controlled rectifier. As a result, it is possible to control the energy supply or the energy discharge from the energy storage unit 28 to the energy supply line 30 in a predeterminable manner.The electrolysis system 10 furthermore has a control unit 104, by means of which the functionality of the electrolysis system 10 can be controlled. Among other things, the control unit 104 provides a third control signal to the energy storage unit 28, by means of which the energy flow from and to the energy storage unit 28 can be controlled. In particular, the third control signal can be used to control the inverter, which is not shown, with regard to its functionality and its power in the bidirectional direction.The control unit 104 further provides a first control signal for the power supply unit 40 of the first electrolyser 36 and a second control signal for the power supply unit 38 of the second electrolyser 34. The first and the second control signal can be used, inter alia, to control at least partially the electrical powers of the electrolysis devices 34, 36.It is not shown that the control unit 104 is in communication with a control center of the alternating voltage source 32 and is supplied by the latter with data relating to the available power which can be used by the electrolysis system 10.Similarly, the control unit 104 is in signal communication with the energy supply units 38, 40 and the energy storage unit 28 and receives from them, inter alia, signals with respect to the intended operation of the respective electrolysis devices 34, 36, in particular with respect to a respective electrolysis current which flows through the respective electrolysis modules 12 to 26.The second energy supply unit 38 has a transformer unit 92, which in turn has two transformers 42, 44. The transformers 42, 44 are designed identically in the present case for three-phase operation. Each of the transformers 42, 44 has a respective primary winding 66, 68, which is connected in a delta connection in the present case. The primary windings 66, 68 are electrically connected to the power supply line 30 via respective current transformers 114 and a common tap changer 116. By means of the tap changer 116, it is possible to make electrical contact with taps of the primary windings 66, 68 and in this way to undertake a power or voltage adaptation in a stepped manner. The transformers 42, 44 are therefore designed to be adjustable in stages.In addition, the transformer 42 has two secondary windings 74, 76, a first of the secondary windings 74 being connected in a delta connection and a second of the secondary windings 76 being connected in a star connection. A rectifier unit 50 is connected to the secondary winding 74, and a rectifier unit 52 is connected to the secondary winding 76. With respect to the second transformer 44, a corresponding structure applies, wherein a secondary winding 78 is connected to a rectifier unit 54 in a delta connection, whereas a further secondary winding 80 is connected to a rectifier unit 56 in a star connection.In the present case, it is provided that the rectifier units 50 to 56 can be controlled by means of the second control signal depending on electrical energy that can be provided by the energy source 32. For this purpose, it is provided that the rectifier units 50 to 56 each have thyristor-based bridge circuits, by means of which a controlled rectification can be realized according to the phase-gating principle. In the present case, the rectifier units 50 to 56 are controlled as a function of the second control signal of the control unit 76.The rectifier units 50 to 56 are connected with their respective AC voltage sides to the respective secondary windings 74, 76, 78, 80. A respective DC voltage side of the rectifier units 50, 52, 54, 56 is connected to a respective switching unit 106, which in the present case are likewise of substantially identical design. The switching units 106 have a respective current transformer 108 for detecting a direct current of the respective rectifier unit 50, 52, 54, 56. Respective sensor signals of the current transformers 108 are transmitted to the control unit 104. In addition, the switching units 106 have respective switching elements 110, 112, with which electrolysis modules 12, 14, 16, 18 connected to the switching units 106 can be electrically isolated in bipolar fashion. As a result, it is possible with the switching units 106 to electrically disconnect the electrolysis modules 12, 14, 16, 18. The switching elements 110, 112 can likewise be controlled with respect to their switching state by means of the second control signal of the control unit 104. In the present case, it is provided that the switching elements 110, 112 each assume essentially the same switching state as a function of the second control signal.The electrolysis device 34 is thus designed in the present embodiment to be controllable in terms of its power in two different ways, namely on the one hand in that a respective power stage can be set by means of the tap changer 116, whereas the power can be set almost continuously within a preset power stage with the rectifier units 50, 52, 54, 56 which can preferably be operated in a substantially continuously controlled manner.The first electrolysis device 36 is substantially identical to the second electrolysis device 34. The first electrolysis device 36 has a transformer unit 94 which likewise has two transformers 46, 48, the primary windings 70, 72 of which are connected to the power supply line 30 via respective current transformers 114 and a common tap changer 90. Here too, the primary windings 46, 48 are connected in a delta connection, whereas a secondary winding 82 of the transformer 46 is likewise connected in a delta connection and a secondary winding 84 of the transformer 46 is connected in a star connection. In transformer 48, primary winding 72 is also delta connected, whereas secondary winding 86 is delta connected and secondary winding 88 is star connected. In this respect, the construction of the transformer unit 94 corresponds to the transformer unit 92.The energy supply unit 40 further comprises rectifier units 58, 60, 62, 64, wherein the rectifier unit 58 is connected with its AC voltage side to the secondary winding 82, the rectifier unit 60 is connected with its AC voltage side to the secondary winding 84, the rectifier unit 62 is connected with its AC voltage side to the secondary winding 86 and the rectifier unit 64 is connected with its AC voltage side to the secondary winding 88. The respective DC voltage sides are connected to respective switching units 106 which correspond to the switching units 106 already explained above, for which reason further explanations are omitted in this respect. Connected to each of the switching units 106 is a series circuit of six respective electrolysis modules 20, 22, 24, 26. In this respect, this construction also corresponds to that of the electrolysis device 34.The electrosyse device 36 differs from the electrolysis device 34 only by the energy supply unit 40, and in this case by the rectifier units 58, 60, 62, 64, which are designed as uncontrolled bridge rectifier circuits, which in this case are realized by corresponding diodes. The bridge rectifier circuit in uncontrolled form is known to the person skilled in the art, for which reason further explanations are omitted here. In contrast to the electrolysis device 34, therefore, in the electrolysis device 36 the power can be changed only with the tap changer 90. Thus, only a stepped change in the power is possible.Here too, the energy supply unit 40 can be controlled with regard to the adjustment options by means of the first control signal of the control unit 104.The control signals, namely the first, the second and the third control signal of the control unit 104, are correspondingly designed, so that the desired control functionalities for the first and the second electrolysis device 34, 36 and the energy storage unit 28 can be realized. At the same time, corresponding signals are transmitted from the energy supply units 38, 40 and also from the energy storage unit 28 to the control unit 104, so that respective operating states can be determined by the control unit 104.In the present embodiment, provision is made for the tap changer 116, 90 to each allow setting with 10 steps. Even if this is not shown in any more detail in the figures, it is basically possible for the electrolysis plant 10 to additionally have additional electrolysis devices 34 and / or 36.The rated powers of the individual components and of the electrolysis devices 34, 36 are preferably selected to be correspondingly adapted, so that-as explained below-a substantially continuous power setting can be achieved with respect to the AC voltage source 32, specifically with the smallest possible grid feedback. This is explained in more detail below. As a result, it is possible not only to reduce the amount of control of the electrolysis plant 10 compared to the prior art, but it is also possible to reduce the amount of power system feedback to the AC voltage source 32. This is particularly advantageous because the electrolysis plant 10 is generally equipped for comparatively large power conversions. Although varying power consumption is to be realized by the electrolysis device 10, network feedback can be largely reduced with little effort. This means that, in particular taking account of the high power, costly filter measures for mains feedback, for example in relation to harmonics or the power factor or the like, can be reduced.In order to be able to provide the required direct current for the electrolysis modules 12 to 26, it is necessary for the corresponding rectifier units 50 to 64 to be supplied with a corresponding alternating voltage. Taking into account a variable impedance nature of the electrolysis modules 12 to 26, which can be designed, for example, as PEM modules, this can be achieved by the tap changers 116, 90 in the transformer units 92, 94. However, it should be appreciated that a respective set stage of the tap changer 116, 90 has a significant impact on the power factor that may be detected on the power supply line 30. It is found that the smaller the selected stage at the tap changer, the greater the resulting power factor.Moreover, it should be noted that controlled rectifying units such as rectifying units 50 to 56 also have an influence on the power factor. It is found that the smaller the firing angle for the thyristors, the greater the power factor. In principle, it has been found that when the firing angle is actively adjusted between about 6° to about 20° and an appropriately selected stage of the tap changer 116, 90 is selected, the power factor may be substantially about 0.9. For larger values in relation to the power factor, a corresponding power factor correction unit is required, for example comprising a capacitor bank or the like. This can also be achieved, for example, with the energy storage unit 28. By suitable control measures, the energy storage unit 28 can be used to increase the power factor.With respect to harmonics of the alternating current of the power supply line 30, it can also be stated that these are generally determined essentially by the control of the thyristors. Generally, an AC current total harmonic distortion (THDI) value for a 24-pulse system of a respective rectifier unit 50 to 56 is about 6%. However, it should be appreciated that even with optimum DC control, an improvement in harmonics may be achieved by increasing the active power flux up to about 2% to 3%, which may result in a level of disturbances of about 3% to about 4%. However, with regard to most AC voltage sources which are based on energy supply networks such as the public energy supply network, a disturbance of less than 2% is required, so that corresponding filter measures generally have to be provided.With the electrolysis system according to FIG. 1, it is possible to significantly reduce the outlay for power factor correction and filtering with respect to harmonics.FIG. 2 shows a schematic diagram representation of the actuation of one of the tap changers 116, 90 with a graph 96, wherein an ordinate is assigned to a respective stage of the respective tap changer 116, 90 and an abscissa is assigned to the time in minutes. It can be seen from FIG. 2 that for the exemplary embodiment provided, an elevation of a respective step by 1 is provided at a distance of approximately 0.5 minutes.FIG. 3 now shows, in a further schematic diagram illustration, how a virtually continuous increase in the power consumed by the electrolysis plant 10 can be achieved for such a change in the stages of the tap changer 116 of the energy storage unit 28 and / or of the control of the rectifier units 50 to 56. This is illustrated in FIG. 3 on the basis of the graph 100. An ordinate of the diagram in FIG. 3 is assigned to the electrical power in MW, which is recorded by the electrolysis plant. A graph 98 is associated with the adjusted stage of the tap changer 90 of the electrolyser 36.As already explained above, the rectifier units 58 to 64 of this electrolysis device 36 are not controllable. Therefore, the power consumed by the overall electrolysis system 10 will increase with each stage of the tap changer 90, as is also shown by graph 98. Since the power consumed by the electrolysis plant 10, which must not exceed the power provided by the AC voltage source 32 according to the graph 100, hard power jumps of in each case approximately 1 MW result, as can be seen from the diagram according to FIG. 3. Such power jumps are undesirable on the power supply side, however, and can lead to considerable disturbances. Therefore, it is now provided that energy storage unit 28 is operated according to graph 102. This means that, in order to increase the power according to the graph 100, only a continuous power adaptation according to the graph 102 is required with the energy storage unit 28, which can be operated continuously. That is, only power factor correction and / or harmonic matching need be provided for the power of 0 to 1 MW. The other power steps can be effected in stages, and specifically preferably by means of the electrolysis device 36, in which only a stage power variation is provided.Due to the uncontrolled rectifier units 58 to 64, the influence on harmonics is substantially negligible. That is, power factor matching can be realized by means of the energy storage unit 28 when the power is increased stepwise by means of the tap changer 90, whereas filtering of harmonics substantially only needs to be provided for the energy storage unit 28.In an alternative scenario, the continuous power adaptation is realized by means of electrolysis device 34 and their rectifier units 50 to 56. For this purpose, firing angles of the thyristor-based rectifying units 50 to 56 may be controlled accordingly. Adjustment of the power factor and filtering of harmonics with respect to current therefore need only be provided for the electrolyser 34.According to a further embodiment, it can be provided that both the energy storage unit 28 and the electrolysis device 34 are used for continuous stepwise power adaptation, i.e. in cooperation. Nevertheless, the advantageous effect is maintained, namely that corresponding measures need not be taken with regard to the network feedback for the entire power which the electrolysis plant 10 receives. Therefore, not only is the saved control effort with respect to the electrolysis device 36 to be drawn in comparison with the prior art, but also the reduced effort with respect to grid feedback, because for the electrolysis device 36, this effort can be significantly reduced, if not partly even saved.The invention is of course not limited to using thyristors or the like in rectifier units, but transistors, in particular insulated gate bipolar transistor (IGBT) units and / or the like can also be used at least partially. For the design of the electrolysis system 10, it can also be taken into account that rated powers for the energy storage unit 28 and / or the electrolysis devices 34, 36 can be different.Preferably, these rated powers are selected accordingly-depending on the number of electrolysis devices and / or the energy storage units-so that an energy adaptation according to FIG. 3 as explained above can be achieved. In particular, the power levels as illustrated by graph 98 in FIG. 3 need not be 1 MW. The power can of course be chosen to be different according to requirements.The invention makes it possible to react flexibly to varying power supplies of the AC voltage grid 32 and makes it possible to use available energy as optimally as possible, wherein the outlay for interference suppression or grid feedback and the filtering of harmonics can be comparatively low. This also increases an efficiency of the electrolysis plant 10.The exemplary embodiments serve exclusively to explain the invention and are not restrictive for it.

Claims

Electrolysis plant (10) for generating hydrogen and oxygen by electrolysis of water, having a plurality of electrolysis devices (34, 36) which are connected to an electrical energy supply line (30) to which an electrical alternating voltage is applied in order to be supplied with electrical energy via the energy supply line (30) for the intended electrolysis operation, wherein the energy supply line (30) is designed for electrically coupling an electrical energy source (32), wherein the electrolysis devices (34, 36) each have an energy supply unit (38, 40) and at least one electrolysis module (12, 14, 16, 18, 20, 22, 24, 26) electrically coupled to the energy supply unit (38, 40), wherein the at least one electrolysis module (12, 14, 16, 18, 20, 22, 24, 26) has a plurality of electrolysis cells which are electrically connected at least partially in series or in parallel, wherein the energy supply units (38, 40) of the electrolysis devices (34, 34, 40), A rectifier unit (58, 60, 62, 62, 62, 36) comprising at least one transformer (42, 44, 46, 48) and at least one rectifier unit (50, 52, 54, 56, 58, 60, 62, 64), the at least one transformer (42, 44, 46, 48) comprising a primary winding (66, 68, 70, 72) electrically coupled to the power supply line (30) and a secondary winding (74, 76, 78, 80, 82, 84, 86, 88) connected to an AC voltage side of the at least one rectifier unit (50, 52, 54, 56, 58, 60, 62, 64), a DC voltage side of the at least one rectifier unit (50, 52, 54, 56, 58, 60, 62, 64) being electrically coupled to the at least one electrolysis module (12, 14, 16, 18, 20, 22, 24, 26), characterized in that the primary winding (66, 68, 70, 72) of the at least one transformer (42, 44, 46, 48) of at least a first of the electrolysis devices (40) is designed to be adjustable in a stepped manner and the at least one rectifier unit (58, 60, 62, 60, 62, 24, 26) is designed to be adjustable in a stepped manner, 64) of the energy supply unit (40) of this electrolysis device (36) is designed to be operated in an uncontrolled manner, wherein the at least one rectifier unit (50, 52, 54, 56) of the energy supply unit (38) is designed to be operated in a controlled manner by at least one second of the electrolysis devices (34) as a function of electrical energy which can be provided by the energy source (32).Electrolysis plant according to Claim 1, characterized by an energy storage unit (28), which is connected to the energy supply line (30), for the reversible storage of electrical energy, wherein the energy storage unit (28) is designed to store and output electrical energy in a continuously controllable manner.Electrolysis plant (10) for generating hydrogen and oxygen by electrolysis of water, having a plurality of electrolysis devices (34, 36) which are connected to an electrical energy supply line (30) to which an electrical alternating voltage is applied in order to be supplied with electrical energy via the energy supply line (30) for the intended electrolysis operation, wherein the energy supply line (30) is designed for electrically coupling an electrical energy source (32), wherein the electrolysis devices (34, 36) each have an energy supply unit (38, 40) and at least one electrolysis module (12, 14, 16, 18, 20, 22, 24, 26) electrically coupled to the energy supply unit (38, 40), wherein the at least one electrolysis module (12, 14, 16, 18, 20, 22, 24, 26) has a plurality of electrolysis cells which are electrically connected at least partially in series or in parallel, wherein the energy supply units (38, 40) of the electrolysis devices (34, 34, 40), A transformer (42, 44, 46, 48) and at least one rectifier unit (50, 52, 54, 56, 58, 60, 62, 64) each, wherein the at least one transformer (42, 44, 46, 48) has a primary winding (66, 68, 70, 72) electrically coupled to the power supply line (30) and a secondary winding (74, 76, 78, 80, 82, 84, 86, 88) connected to an AC voltage side of the at least one rectifier unit (50, 52, 54, 56, 58, 60, 62, 64), wherein a DC voltage side of the at least one rectifier unit (50, 52, 54, 56, 58, 60, 62, 64) is electrically coupled to the at least one electrolysis module (12, 14, 16, 18, 20, 22, 24, 26), characterized by an energy storage unit (28) connected to the power supply line (30) for reversibly storing electrical energy, wherein the energy storage unit (28) is designed to store and output electrical energy in a continuously controllable manner, wherein the primary winding (70, 72) of the at least one transformer (46, 46, 36), 48) of at least a first of the electrolysis devices (36) is designed to be adjustable in stages and the at least one rectifier unit (58, 60, 62, 64) of the energy supply unit (40) of this electrolysis device (36) is designed to be operated in an uncontrolled manner.Electrolysis plant according to Claim 3, characterized in that the at least one rectifier unit (50, 52, 54, 56) of the energy supply unit (38) is designed by the at least one second electrolysis device (34) to be operated in a controlled manner as a function of electrical energy which can be provided by the energy source (32).Electrolysis system according to Claims 2 to 4, characterized in that a rated power of the energy storage unit (28) with respect to the storage and the delivery of electrical energy is greater than a power difference of two successive stages of the primary winding (70, 72), which can be adjusted in stages, during the intended operation of the at least one first electrolysis device (40).Electrolysis plant according to one of the preceding claims, characterized in that the at least one transformer (46, 48) for the stepped adjustment of the primary winding (70, 72) has a tap changer with at least 5 steps, preferably at least 9 steps.Electrolysis plant according to one of the preceding claims, characterized bya control unit (76) which is designed to receive an energy availability signal and, on the one hand, to set the stage of the primary winding (70, 72) of the at least one transformer (46, 48) by the at least one first electrolysis device (40) as a function of the energy availability signal and, on the other hand, to set at least the electrical power of the at least one second electrolysis device (38) by means of its rectifier unit (50, 52, 54, 56) or at least the electrical power of the energy storage unit (28).Electrolysis plant according to one of the preceding claims, characterized in that a sum of the rated power of the energy storage unit (28) with respect to the storage and the output of electrical energy and the rated power of the at least one controlled rectifier unit (50, 52, 54, 56) of the energy supply unit (38) from the at least one second electrolysis device (34) is greater than the power difference of two successive stages of the stage-adjustable primary winding (70, 72) during the intended operation of the at least one first electrolysis device (36).Method for generating hydrogen and oxygen by electrolysis of water by means of an electrolysis plant (10) which has a plurality of electrolysis devices (34, 36), wherein the electrolysis devices (34, 36) each have an energy supply unit (38, 40) and at least one electrolysis module (12, 14, 16, 18, 20, 22, 24, 26) electrically coupled to the energy supply unit (38, 40), wherein the at least one electrolysis module (12, 14, 16, 18, 20, 22, 24, 26) has a plurality of electrolysis cells which are electrically connected at least partially in series or in parallel, wherein the electrolysis devices (34, 36) are supplied with electrical energy via an electrical energy supply line (30) to which an electrical alternating voltage is applied for the intended electrolysis operation, wherein the energy supply line (30) electrically couples an electrical energy source (32), wherein the energy supply units (38, 40) of the electrolysis devices (34, 36) each have at least one transformer (42, 44, 46, 48) and at least one rectifier unit (50, 52, 54, 56, 58, 60, 62, 64), wherein the at least one transformer (42, 44, 46, 48) has a primary winding (66, 68, 70, 72) electrically coupled to the power supply line (30) and a secondary winding (74, 76, 78, 80, 82, 84, 86, 88) connected to an AC voltage side of the at least one rectifier unit (50, 52, 54, 56, 58, 60, 62, 64), wherein a DC voltage side of the at least one rectifier unit (50, 52, 54, 56, 58, 60, 62, 64) is electrically coupled to the at least one electrolysis module, characterized in that the primary winding (70, 72) of the at least one transformer (46, 48) is designed to be adjustable in stages by at least one first of the electrolysis devices (34), and the at least one rectifier unit (58, 60, 62, 64) of the power supply unit (38) of this electrolysis device (34) is operated in an uncontrolled manner, wherein the at least one rectifier unit (50, 52, 54, 54, 64) is operated in an uncontrolled manner, 56) of the energy supply unit (40) of at least a second of the electrolysis devices (36) is operated in a controlled manner as a function of electrical energy which can be provided by the energy source (32).Method for generating hydrogen and oxygen by electrolysis of water by means of an electrolysis plant (10) which has a plurality of electrolysis devices (34, 36), wherein the electrolysis devices (34, 36) each have an energy supply unit (38, 40) and at least one electrolysis module (12, 14, 16, 18, 20, 22, 24, 26) electrically coupled to the energy supply unit (38, 40), wherein the at least one electrolysis module (12, 14, 16, 18, 20, 22, 24, 26) has a plurality of electrolysis cells which are electrically connected at least partially in series or in parallel, wherein the electrolysis devices (34, 36) are supplied with electrical energy via an electrical energy supply line (30) to which an electrical alternating voltage is applied for the intended electrolysis operation, wherein the energy supply line (30) electrically couples an electrical energy source (32), wherein the energy supply units (38, 40) of the electrolysis devices (34, 36) each have at least one transformer (42, 44, 46, 48) and at least one rectifier unit (50, 52, 54, 56, 58, 60, 62, 64), wherein the at least one transformer (42, 44, 46, 48) has a primary winding (66, 68, 70, 72) electrically coupled to the power supply line (30) and a secondary winding (74, 76, 78, 80, 82, 84, 86, 88) connected to an AC voltage side of the at least one rectifier unit (50, 52, 54, 56, 58, 60, 62, 64), wherein a DC voltage side of the at least one rectifier unit (50, 52, 54, 56, 58, 60, 62, 64) is electrically coupled to the at least one electrolysis module, characterized in that an energy storage unit (28) connected to the power supply line (30) and configured to reversibly store electrical energy, stores and outputs the electrical energy in a continuously controllable manner, wherein the primary winding (70, 72) of the at least one transformer (46, 48) is configured in a stepwise adjustable manner by at least a first of the electrolysis devices (34), and the at least one rectifier unit (58, 60, 60, 58, 60, 48), 62, 64) of the energy supply unit (38) of this electrolysis device (34) is operated in an uncontrolled manner.

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