Electrolysis power supply system

Abstract

This invention provides an electrical system having first and second power conversion stages. The first power conversion stage comprises a first transformer having a primary winding and one or more secondary windings. The second power conversion stage comprises a second transformer having a primary winding and a secondary winding, and a rectifier. There may be more than one second power conversion stage. The primary winding of each second transformer is connected in a circuit with the, or one of, the secondary windings of the first transformer so that each second power conversion stage is arranged in parallel with each other second power conversion stage. For each second power conversion stage, the input side of the rectifier is connected to the secondary winding of the second transformer, and the output side of the rectifier is configured to provide electrical power to an electrolyzer. The first transformer comprises a variable voltage transformer.

Description

[0001] S P3205

[0002] Electrolysis Power Supply System

[0003] Field of the Invention

[0004] This invention relates to an electrolysi s power supply system . In particular , this invention relates to an electrical system, to an electrical power supply arrangement , to a method, and to a control system for providing electrical power to one or more electrolyzers .

[0005] Background of the invention

[0006] There is a great deal of interest in hydrogen a s a sustainable fuel . Hydrogen i s generally produced by electrolys is of water in an electrolyzer . Hydrogen production by electrolysis requires a large amount of electrical power . In order to maximise the sustainable characteri stics of the hydrogen fuel , it is des irable to use renewable power sources , such a s electricity generated from wind power , in its production .

[0007] Existing systems for supplying - and controlling the supply of - electrical power to electrolyzers in hydrogen production plants are complex and expensive , consisting of multiple contactors and power electronic switching devices . It is an aim of the current invention to overcome at least some of the disadvantages of the known systems .

[0008] Summary of the Invention

[0009] According to an aspect of the invention , there is provided an electrical system comprising : a f irst power convers ion stage comprising a first trans former having a primary winding and one or more secondary windings , wherein the primary winding of the first transformer is configured to be connected to an electrical power supply in use ; and one or more second power conversion stages , the or each second power conversion stage comprising : a second transformer having a primary winding and a secondary winding ; and a rectifier having an input s ide and an output s ide , wherein : for a single second power convers ion stage , the primary winding of the second trans former of the second power conversion stage is connected in a circuit with the secondary winding of the first transformer ; or for multiple second power convers ion stage s the primary winding of the second transformer of each second power conversion stage is connected in a circuit with one of the secondary windings of the first trans former such that each second power convers ion stage is arranged in parallel with each other second power convers ion stage , wherein , for the or each second power convers ion stage , the input side of the rectifier is connected to the secondary winding of the second trans former , and the output side of the rectifier is configured to provide electrical power to an electrolyzer , wherein the first transformer comprises a variable voltage trans former .

[0010] The present invention is advantageous as the power supplied to the one or more electrolyzers can be controlled without the need for complex and expensive power electronic switching devices .

[0011] Optionally, for the or each second power conversion stage : the second transformer comprises a plurality of secondary windings ; and the input s ide of the rectif ier is connected to each secondary winding of the second trans former . The or each rectifier may be a multi-pulse diode rectifier . At least one second power conversion stage may optionally be configured so that , in use , the electric current in each of the secondary windings of the second trans former is phase shifted with respect to each other secondary winding of the second transformer . This arrangement is advantageous as it allows the phase of the electric current in each of the secondary windings to differ , allowing for reduction of direct current ( DC ) ripple and elimination of harmonics .

[0012] In one example one or more of the second transformers may compri se a variable voltage transformer . This benef icially provides additional power control capability .

[0013] Optionally the first transformer compri se s a tap changing mechanism arranged along the primary winding of the f irst trans former to allow the turns ratio of the first transformer to be modified by operation of a s ingle tap changing mechanism . Alternatively or additionally, the first transformer comprises a tap changing mechanism arranged along one or more of the secondary windings of the f irst trans former . Where there are a plurality of secondary windings , this allows the turns ratio of each secondary winding to be individually tuned to the power requirements of the a s sociated electrolyzer .

[0014] The first transformer , and the or each second trans former , is optionally a single phase trans former or a three phase transformer . Use of a three phase transformer is beneficial a s more power may be provided to the or each electrolyzer in a high power requirement hydrogen production plant . According to another aspect of the invention , there is provided an electrical power supply arrangement , compris ing a plurality of electrical systems as described above , wherein the primary winding of the first trans former of each f irst power conversion stage is connected to an electrical power supply . This i s advantageous as the electrical power supplied to the various connected electrical systems may be individually controlled depending on their individual operating requirements and / or the amount of power available from the electrical power supply . Thi s allows loads to be balanced acros s a hydrogen production plant in zones , where each electrical system constitute s a ' zone ' .

[0015] The primary winding of the f irst transformer of each of the first power conversion stage s may be connected to a common electrical power supply or to different electrical power supplies . Optionally the electrical power supply is derived from a renewable power supply source , optionally from a wind power supply source .

[0016] According to a further aspect of the invention, there is provided a method of controlling the electrical system described above or the electrical power supply arrangement described above . The method comprises : receiving one or more control signals indicative of one or more operational parameters of the or each electrolyzer ; and adj usting the voltage change ratio acros s one or more variable voltage trans former of the or each electrical system in dependence on the one or more control s ignals . In this way, the power supplied to each electrolyzer can be controlled in dependence on the operational requirement s of that electrolyzer . According to a still further aspect of the invention , there i s provided a control system for controlling the electrical system des cribed above or the electrical power supply arrangement de scribed above . The control system is configured to : receive one or more control signals indicative of one or more operational parameters of the or each electrolyzer ; and output one or more output control signals in dependence on the one or more input control signals , wherein the one or more output control signals comprise an instruction to adj ust the voltage change ratio acros s one or more variable voltage trans former of the or each electrical system in dependence on the one or more control signals .

[0017] According to yet another aspect of the invention , there i s provided a method of controlling the electrical power supply arrangement des cribed above , the method compris ing : receiving one or more control signals indicative of one or more characteristics of the electrical power supply; and adj usting the voltage change ratio acros s one or more variable voltage trans former of the or each electrical system in dependence on the one or more control signals . In thi s way, the power drawn f rom the electrical power supply and supplied to the one or more electrical systems can be controlled in dependence on the power available f rom the electrical power supply . This may be advantageous when operating a hydrogen production plant f rom a potentially inconsistent electrical power source such as a wind power source .

[0018] Optionally the method compri ses adj usting the voltage change ratio acros s one or more of the variable voltage trans formers of at least two of the electrical systems such that the electrical power drawn by a first one of the plurality of electrical systems dif fers to the electrical power drawn by a second one of the plurality of electrical systems .

[0019] In one example the method of controlling the electrical power supply arrangement comprises receiving one or more control s ignals indicative of one or more operational parameters of the or each electrolyzer ; and adj usting the voltage change ratio acros s one or more variable voltage transformer of the or each electrical system in dependence on said one or more control signal s .

[0020] According to another aspect of the invention , there is provided a control system for controlling the electrical power supply arrangement described above , wherein the control system i s configured to : receive one or more control signals indicative of one or more characteri stics of the common electrical power supply; and output one or more output control s ignals in dependence on the one or more input control signals , wherein the one or more output control s ignals comprise an instruction to adj ust the voltage change ratio acros s one or more of the variable voltage transformers of one or more of the electrical systems in dependence on the one or more control signals .

[0021] Brief Description of the Drawings

[0022] Figure 1 schematically illustrates an electrical system for supplying power to an electrolyzer ;

[0023] Figure 2 schematically illustrates an alternative arrangement of an electrical system to that shown in Figure 1 ; Figure 3 schematically illustrates an alternative variable voltage transformer arrangement to that shown in Figure 2 ;

[0024] Figure 4 schematically illustrates an electrical power supply arrangement for supplying power to a hydrogen production plant ;

[0025] Figure 5 shows a flow chart for controlling an electrical system such as that shown in Figures 1 and 3 ;

[0026] Figure 6 shows a flow chart for controlling an electrical power supply arrangement such as that shown in Figure 4 ;

[0027] Figure 7 shows a simplified electrolyzer power supply control architecture diagram; and

[0028] Figure 8 shows a simplified site system level control architecture diagram.

[0029] These drawings depict one or more implementations in accordance with the present teachings , by way of example only, not by way of limitation . In the Figure s , like reference numerals refer to the same or s imilar element s .

[0030] Detailed Description of the Drawings

[0031] Figure 1 schematically illustrates a single pha se repre sentation of an electrical power supply apparatus 5 compris ing an electrical system 10 for providing power to an electrolyzer 12 . The electrical system 10 comprises a first power conversion stage 20 and a second power convers ion stage 30 . The first power conversion stage 20 comprises a first transformer 21 which ha s a primary winding 22 and a secondary winding 23 . The primary winding 22 is connected to an alternating current (AC ) electrical power supply 14 . A tap changing mechanism 24 is arranged on the secondary winding 23 . The tap changing mechanism 24 is conf igured to vary the number of operative turns of the secondary winding 23. The tap changing mechanism 24 may be implemented mechanically or electronically.

[0032] The second power conversion stage 30 comprises a second transformer 31 and a rectifier 35. The second transformer 31 has a primary winding 32 and three secondary windings 33. The primary winding 32 of the second transformer 31 is connected in a circuit with the secondary winding 23 of the first transformer 21. The rectifier 35 has an input side 36 which is connected to each of the secondary windings 33 of the second transformer 31, and an output side 37 which is configured to supply direct current (DC) power to the electrolyzer 12. In this example, the rectifier 35 is a multi-pulse diode rectifier, specifically, a six pulse three phase diode rectifier bridge for AC / DC conversion.

[0033] In use, the power delivered to the electrolyzer 12 may be controlled by altering the voltage drop across the first transformer 21. This is achieved by operating the tap change mechanism 24 to change the number of operative turns on the secondary coil 23 of the first transformer 21 thereby changing the turns ratio across the first transformer 21.

[0034] In one example, the first transformer 21 may be connected to an AC power supply of nominal value 38KV (VI) , which may be stepped down to a nominal voltage of 6.6KV (V2) by the first transformer 21 (depending on the setting of the tap change mechanism 24) . The second voltage V2 may then be stepped down to a nominal voltage of 740V (V3) across each of the three secondary windings 33 of the second transformer 31. The input side 36 of the rectifier 35 is connected to each secondary winding 33 of the second transformer. The second power conversion stage 30 is configured so that the electric current in each of the secondary windings 33 of the second transformer 31 is phase shifted with respect to each other secondary winding 33 of the second transformer 31.

[0035] Although described above in the context of a single phase view of the electrical system 10, it will be understood that the electrical system 10 may be implemented with three phase variable voltage transformers arranged in a Wye-Delta configuration, or in any other suitable configuration such as Delta-Delta, Wye-Wye or Delta-Wye. In examples implemented with three phase transformers, each secondary winding 33 of each phase is connected to a six pulse three phase diode rectifier bridge 35 which are used to form an eighteen pulse diode rectifier circuit. This arrangement reduces DC voltage ripple on the load (electrolyzer 12) and eliminates certain harmonics (e.g. 5th, 7th, 11thand 13th) back into the power supply grid.

[0036] The number of secondary windings 33 of the second transformer 31 may be greater than three or fewer than three depending on the desired system design (this is also true for a single phase implementation) . For example, the total pulse number may be configured as twenty-four pulse or thirty-six pulse to further reduce total DC ripple and harmonics. In one example, the second transformer 31 may comprise only one secondary winding 33.

[0037] In the description above, and in the description that follows, a single phase view of the electrical system 10 is shown and described for the sake of simplicity. It will be understood that each electrical system described herein may be implemented with a three phase transformer and a rectifier 35 for each phase as required.

[0038] Figure 2 schematically illustrates a single phase representation of an electrical power supply apparatus 5 comprising an electrical system 10 for providing power to a pair of electrolyzers 12, 12' . The electrical system 10 shown in Figure 2 is the same in all respects to the system 10 shown in Figure 1 except in that the first transformer 31 of the first power conversion stage 20 comprises two secondary winding 23, 23' such that there are two second power conversion stages 30, 30' , each providing power in parallel to electrolyzers 12, 12' . A tap change mechanism 24, 24' is arranged on each of the secondary windings 23, 23' of the first transformer 21 respectively. All of the variations and options described above in relation to the electrical system 10 shown in Figure 1 are equally applicable to the electrical system 10 shown in Figure 2.

[0039] As shown in Figure 2, the primary winding 32, 32' of the second transformer 31, 31' of each second power conversion stage 30, 30' is connected in a circuit with a respective one of the secondary windings 23, 23' of the first transformer 21 such that the second power conversion stage 30 is arranged in parallel with the other second power conversion stage 30' . This allows the power supplied to the electrolyzer 12 to be controlled independently of the power supplied to the other electrolyzer 12' by varying the settings of the tap change mechanisms 24, 24' independently of one another. It will be understood that any suitable number of second power conversion stages 30 may be provided by providing a plurality of secondary windings 23 of the first transformer 21 and a corresponding number of second trans formers 31 . For an example having multiple second power conversion stages 30 , the primary winding 32 of the second transformer 31 of each second power conversion stage 30 i s connected in a circuit with one of the secondary windings 23 of the first transformer 31 such that each second power conversion stage 30 is arranged in parallel with each other second power convers ion stage 30 .

[0040] Figure 3 shows an alternative arrangement for the first transformer 21 . In thi s example there are no tap changing mechanisms arranged on the secondary windings 23 , but rather there is a tap changing mechanism 24 arranged on the primary winding 22 . In this example the power supplied to the electrolyzers 12 , 12 ' is controlled together . In an alternative arrangement , tap changing mechani sms 24 may be arranged on the primary winding 22 and on each of the secondary windings 23 so that the power supplied to each of the electrolyzers 12 , 12 ' may be controlled independently of one another . As above , the trans former 21 of Figure 3 may comprise any suitable number of secondary windings 23 .

[0041] Although not shown in the Figures , the second trans former 31 of the or each second power conversion stage 30 may have a tap changing mechanism arranged on the primary winding 32 , the secondary winding 33 , or both the primary and secondary windings 32 , 33 . The tap change configuration ( if pre sent ) and the turns ratio of each of the second transformers 31 need not match , and the second trans formers 31 may differ f rom one another in configuration and turns ratio .

[0042] Figure 4 schematically illustrates an electrical power supply arrangement 50 for supplying power to a hydrogen production plant . The electrical supply arrangement 50 compri ses a plurality of electrical systems 10 , each corresponding to the electrical system 10 described above in re spect of Figure 2 . Each electrical system 10 illustrated in Figure 4 therefore comprise s a first transformer 21 and two second trans formers 31 , 31 ' configured to supply electrical power to respective electrolyzers 12 , 12 ' . The primary winding 22 of the first trans former 21 of each first power conversion stage 20 is connected to an electrical power supply 14 .

[0043] The electrical power supply 14 may be any suitable electrical power supply such as a national grid or local power generation plant such as a wind power generation plant for example . In the example of Figure 4 , all of the electrical systems 10 are connected to a common electrical power supply 14 . However , it will be understood that one or more of the electrical systems 10 may be connected to a different electrical power source either alone or together with one or more of the other electrical systems 10 .

[0044] The example of Figure 4 ha s been described with reference to the electrical system configuration shown in Figure 2 . It will be understood that any conf iguration of electrical system 10 may be used in the electrical power supply arrangement 50 of Figure 4 . In addition, it will be understood that the electrical power supply arrangement 50 may compri se fewer or more than the three electrical systems illustrated in Figure 4 . Figure 5 schematically illustrates a method 60 of controlling one or more electrical systems 10 , or an electrical power supply arrangement 50 . In a first step 62 the method 60 comprises receiving one or more control signals indicative of one or more operational parameters of the or each electrolyzer 12 . In a second step 64 the method 60 comprises adj usting the voltage change ratio acros s one or more variable voltage trans former 21 , 31 of the or each electrical system 10 in dependence on the one or more control signals . In this way, the power requirements of the one or more electrolyzers 12 can be controlled by changing the turns ratio acros s one or more of the transformers 21 , 31 in dependence on the operational parameters of the or each electrolyzer 12 .

[0045] A control system for controlling one or more electrical systems 10 , or an electrical power supply arrangement 50 according to the method 60 is envisaged . Where the control system is configured to receive the one or more control signals indicative of one or more operational parameters of the or each electrolyzer 12 , and output one or more output control s ignals in dependence on the one or more input control signals . The one or more output control signal s comprise an instruction to adj ust the voltage change ratio acros s one or more variable voltage transformer 21 , 31 of the or each electrical system 10 in dependence on the one or more control signals .

[0046] Figure 6 schematically illustrates a method 70 of controlling an electrical power supply arrangement 50 . In a first step 72 the method 70 comprises receiving one or more control signals indicative of one or more characteri stics of the electrical power supply 14 . In a second step 74 the method 70 compri ses adj usting the voltage change ratio acros s one or more of the variable voltage transformers 21 , 31 of one or more of the electrical systems 10 in dependence on the one or more control signals . In this way, the power available from the power supply 14 can be distributed between the various loads ( electrolyzers 12 ) by changing the turns ratio acros s one or more of the transformers 21 , 31 in dependence on the characteri stics of the electrical power supply 14 .

[0047] The method 70 may comprise adj usting the voltage change ratio acros s one or more of the variable voltage trans formers of at least two of the electrical systems 10 such that the electrical power drawn by a first one of the plurality of electrical systems 10 differs to the electrical power drawn by a second one of the plurality of electrical systems 10 . This may be beneficial when the electrical power supply 14 comprise s a renewable power supply such as wind power or solar power , which may not be stable depending on the weather conditions . A power supply 14 with such characteristics may be dynamically balanced using a zonal control methodology in which ( referring to Figure 4 ) each electrical system 10 of the electrical power supply arrangement 50 constitutes a separate zone . The zones can be controlled to coordinate power consumption among the different zones to meet the unstable power supply smoothly with small error .

[0048] A control system for controlling an electrical power supply arrangement 50 according to the method 70 is envisaged . Where the control system is configured to receive the one or more control signals indicative of one or more characteristics of the electrical power supply, and output one or more output control signals in dependence on the one or more input control s ignals . The one or more output control s ignals compri se an instruction to adj ust the voltage change ratio acros s one or more of the variable voltage transformers of one or more of the electrical systems , in dependence on the one or more control signals .

[0049] Methods 60 and 70 , and their corresponding implementing control systems , may be combined such that the configuration of the various variable voltage trans formers in the one or more electrical systems 10 may be set in dependence on both the operational parameters of the or each electrolyzer 12 and the characteristics of the or each electrical power supply 14 .

[0050] A simplified electrolyzer power supply control system 100 is shown in Figure 7 . Each electrical system 10 has one or more system controllers 105 , one system controller 105 for each electrolyzer 12 . Each system controller 105 is configured to : collect current and voltage signals 109 from a signal measurement unit 106 ; to send switchgear contactor control signals 108 and variable voltage transformer switch / tap changing control signals 108 to a sub control unit 107 ; and to receive feedback and fault signals 108 from the sub control unit 107 . Each system controller 105 receives measurements from a hydrogen electrolysis control unit 104 , the measurement signals 110 include but are not limited to : electrolysis temperature , pres sure , flow rate and fault flags . An optional site / plant controller 101 ( described below) may communicate with each system controller 105 for operation status monitoring and site level coordination . A simplified system level coordination control architecture is shown in Fig 8 As discus sed above , for an unstable power supply ( for example , wind power) , the power supply and consumption may be dynamically balanced us ing a zone control system 150 . Each zone 151 , 152 , 153 contains one or more power supply control systems 100 . The site / system controller 101 is configured to communicate with each zone 151 , 152 , 153 via a communication channel 111 . As mentioned above , the one or more variable voltage transformers of zone 151 may be set at a higher voltage , therefore higher power level , while the one or more variable voltage transformers of one or more of the other zones 1552 , 153 may be set to a lower voltage , therefore a lower power level . It will be understood that fewer or more than the three zones illustrated in Figure 8 may be used .

[0051] The examples described above with reference to Figures 1 to 8 provide a modular and scalable power supply solution for a hydrogen electrolysi s plant with power demands from several hundred megawatts to several gigawatts . The described solutions are suitable for medium and high voltage grid interconnections up to 150 kilovolts .

[0052] While many pos sible variations of the hybrid variable voltage transformer have been described above , it will be clear to the s killed person that additional variations and modif ications can be made without departing f rom the scope of the invention as claimed in the appended claims .

Claims

SP3205C L A I M S1. An electrical system comprising: a first power conversion stage comprising a first transformer having a primary winding and one or more secondary windings, wherein the primary winding of the first transformer is configured to be connected to an electrical power supply in use; and one or more second power conversion stages, the or each second power conversion stage comprising: a second transformer having a primary winding and a secondary winding; and a rectifier having an input side and an output side, wherein: for a lone second power conversion stage, the primary winding of the second transformer of the second power conversion stage is connected in a circuit with the secondary winding of the first transformer; or for multiple second power conversion stages, the primary winding of the second transformer of each second power conversion stage is connected in a circuit with one of the secondary windings of the first transformer such that each second power conversion stage is arranged in parallel with each other second power conversion stage, wherein, for the or each second power conversion stage, the input side of the rectifier is connected to the secondary winding of the second transformer, and the output side of the rectifier is configured to provide electrical power to an electrolyzer,wherein the first transformer comprises a variable voltage transformer .

2. The electrical system of claim 1, wherein, for the or each second power conversion stage: the second transformer comprises a plurality of secondary windings; and the input side of the rectifier is connected to each secondary winding of the second transformer.

3. The electrical system of claim 2, wherein at least one second power conversion stage is configured so that, in use, the electric current in each of the secondary windings of the second transformer is phase shifted with respect to each other secondary winding of the second transformer.

4. The electrical system of claim 3, wherein the or each rectifier is a multi-pulse diode rectifier.

5. The electrical system of any preceding claim, wherein one or more of the second transformers comprise a variable voltage transformer .

6. The electrical system of any preceding claim, wherein the first transformer comprises a tap changing mechanism arranged: along the primary winding of the first transformer; or along one or more of the secondary windings of the first transformer .

197. The electrical system of any preceding claim, wherein the first transformer, and the or each second transformer, is a three phase transformer.

8. An electrical power supply arrangement, comprising a plurality of electrical systems according to any preceding claim, wherein the primary winding of the first transformer of each first power conversion stage is connected to an electrical power supply.

9. The electrical power supply arrangement of claim 8, wherein the electrical power supply is derived from a renewable power supply source, optionally from a wind power supply source.

10. A method of controlling the electrical system of claims 1 to 7, or the electrical power supply arrangement of claim 8 or 9, the method comprising: receiving one or more control signals indicative of one or more operational parameters of the or each electrolyzer; and adjusting the voltage change ratio across one or more variable voltage transformer of the or each electrical system in dependence on the one or more control signals.

11. A control system for controlling the electrical system of claims 1 to 7, or the electrical power supply arrangement of claim 8 or 9, wherein the control system is configured to:20 receive one or more control signals indicative of one or more operational parameters of the or each electrolyzer ; and output one or more output control signal s in dependence on the one or more input control signal s , wherein the one or more output control s ignals comprise an instruction to adj ust the voltage change ratio acros s one or more variable voltage transformer of the or each electrical system in dependence on the one or more control signals .12 . A method of controlling the electrical power supply arrangement of claim 8 or 9 , the method compris ing : receiving one or more control signals indicative of one or more characteristics of the electrical power supply; and : adj usting the voltage change ratio acros s one or more of the variable voltage transformers of one or more of the electrical systems in dependence on the one or more control signal s .13 . The method of claim 12 , comprising adj usting the voltage change ratio acros s one or more of the variable voltage transformers of at least two of the electrical systems such that the electrical power drawn by a first one of the plurality of electrical systems dif fers to the electrical power drawn by a second one of the plurality of electrical systems .14 . The method of claim 12 or 13 , compri sing the method of claim 10 .2115. A control system for controlling the electrical power supply arrangement of claim 8 or 9, wherein the control system is configured to: receive one or more control signals indicative of one or more characteristics of the electrical power supply; and output one or more output control signals in dependence on the one or more input control signals, wherein the one or more output control signals comprise an instruction to adjust the voltage change ratio across one or more of the variable voltage transformers of one or more of the electrical systems, in dependence on the one or more control signals.

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