Circuit arrangement and method for operating a high-power DC load

Abstract

The invention relates to a method for providing electrical energy to a high-power DC load, in particular to a device for generating hydrogen by electrolysis using the inventive circuit arrangement. Additionally, the invention relates to a circuit arrangement for providing electrical energy to a high-power DC load, in particular to a device for generating hydrogen by electrolysis. Furthermore, a use of the circuit arrangement is proposed. The object of the present invention to provide a method of providing electrical energy to a high-power DC load which allows the use of components with lower dielectric strength is achieved with a circuit arrangement is solved by claim 1.

Description

[0001] December 12, 2025

[0002] Circuit arrangement and method for operating a high-power DC load

[0003] The invention relates to a method for providing electrical energy to a high-power DC load, in particular to a device for generating hydrogen by electrolysis using the inventive circuit arrangement. Additionally, the invention relates to a circuit arrangement for providing electrical energy to a high-power DC load, in particular to a device for generating hydrogen by electrolysis. Furthermore, a use of the circuit arrangement is proposed.

[0004] High-power DC loads are used in a variety of different applications. One application which is getting more important are electrolysis devices for generating hydrogen from water by electrolysis. Electrolysis devices have high demands of DC current when in production. For the operation of electrolysis devices, also known as electrolysis stacks or electrolyser, it is desirable to operate them as energy-efficiently and as safely as possible.

[0005] From the international patent application WO 2019 / 201831 Al a device for operating in parallel connected electrolysis devices is known which comprises a rectifier, which converts an AC voltage from an AC power source into a first DC voltage of a first DC link. The electrolysis devices are connected to the first DC link via a DC / DC step-down converter which converts the first DC voltage into a second DC voltage of at least one DC output. By controlling each DC / DC step-down converter of each electrolysis device a plurality of electrolysis devices can be operated in an efficient manner.

[0006] As rectifier often active front end (AFE) rectifier are used. In an AFE rectifier power switches are usually controlled via a pulse width modulation (PWM). In Fig. 2 the possible voltage vectors of an AFE rectifier with three phases are shown for example for an AFE rectifier based on an 1GBT half-bridge layout. The state vector notion 100, 110 etc. refers to which IGBTs are turned on in the AFE rectifier. 100 means that the top / high side IGBT of phase u is turned on, and bottom switches of phases v and w are turned on. 110 refers to top / high side IGBT switches in both phase u and v are turned on, while the bottom switch of phase w is turned on etc.

[0007] The line voltages at the three-phase AC power source connection of the rectifier to ground vL u, vL v, vL wcan now be calculated depending on the different possible switching states of the AFE rectifier. Table 1 shows the calculated values for all switching states of the AFE rectifier in IGBT half-bridge layout with VDC1 as the DC link voltage of the AFE rectifier. vAC u, vACv,vAC ware the line voltages of the AC power source. Per definition in this document the DC link includes capacitors to smooth VDC1 of the AFE rectifier.

[0008] Table 1

[0009] No Vect VL,v VL.w

[0010] 0 000VAC,uVAC,vVAC,w

[0011] 1 100 VDC1 + vAC,u- 2 / 3 • VDC1 vAC,v+ 1 / 3 • VDC1 + 1 / 3 • VDC1 2 110 VDC1 + vAC,u- 1 / 3 • VDC1 VDC1 + vAC,v- 1 / 3 • VDC1 vAc,w + 2 / 3 • VDC1 3 010 + 1 / 3 • VDC1 VDC1 + vAC,v- 2 / 3 • VDC1 vAc,w + 1 / 3 • VDC1 4 Oil + 2 / 3 • VDC1 VDC1 + vAC,v- 1 / 3 • VDC1 VDC1 + vAC,w- 1 / 3 • VDC1 5 001 + 1 / 3 • VDC1 vAC,v+ 1 / 3 • VDC1 VDC1 + vAC w— 2 / 3 ■ VDC1 6 101 VDC1 + vAC,u- 1 / 3 • VDC1 vAC,v+ 2 / 3 • VDC1 VDC1 + vAC,w- 1 / 3 • VDC1 7 111 VDC1 + vAC,uVDC1 + vAC vVDC1 + vAC AV

[0012]

[0013] In a typical configuration of a circuit arrangement the AFE rectifier is connected to a DC / DC converter whereas the negative pole of the DC link of the AFE rectifier is connected with the negative pole of the DC output of the DC / DC converter connected to the high-power DC load and which is grounded. The line voltages at the three-phase AC power source connection of the rectifier to ground vL u, vL v, vL ware not affected by the

[0014] ZI / ZI 240390WO 12 December 2025 DC / DC converter. Hence, table 1 already provides the line voltages at the three-phase AC power source connection of the rectifier to ground vL u, vL v, vL w.

[0015] From table 1 it can be derived that the highest positive voltage in the connection points VL, U, VL, V and VL, W is provided with voltage vector 111 at maximum AC voltage, where the voltage is VDC1 + vAC. The minimum negative voltage occurs at voltage vector 000 and minimum negative AC voltage. Hence the voltage potential peak values are offset by VDC1, but the minimum values simply results to vAC. For an input AC voltage with a peak voltage on 1060V and a DC link voltage VDC1 of 1200 V the maximum positive voltage becomes 2260V and the minimum negative voltage will be 1060 V.

[0016] As result, the line voltages at the three-phase AC power source connection of the rectifier to ground reaches quite high values. High values of the line voltages to ground makes it necessary to use components with a higher dielectric strength to avoid the risk of spontaneous discharges. As all components of the rectifier needs to comprise higher dielectric strength, this increases the costs of the rectifier significantly.

[0017] A three-phase rectifier circuit with nearly sinusoidal input currents and a regulated DC output voltage using a diode bridge with a neutral point architecture followed by two boost converters and a series-connected output capacitor arrangement is known from DE 4430394 Al.

[0018] The German patent application DE 102023201656 Al discloses a charging device for electric vehicles comprising a rectifier with a DC link comprising a neutral point architecture. A grounded pole at the high-power DC load output is not disclosed.

[0019] In the German patent application DE 4219222 Al a voltage conversion device for supplying a DC load from a single- or multi-phase AC source using a rectifier and an intermediate circuit is disclosed.

[0020] ZI / ZI 240390WO 12 December 2025 The translation of a European patent DE 69508056 T2 describes a voltage-source converter system for high voltage direct current (HVDC) transmission with a DC link capacitor and an equalizing circuit, but the document is totally silent about how to reduce the requirements of the dielectric strength of the components of the voltage source converter.

[0021] A multi-stage DC power distribution system for large-scale electrolysis, comprising an active rectifier and downstream buck-type DC / DC cell stack regulators is disclosed in US 2021 / 0363651 Al. Details about an advantageous operating method of the AFE to reduce voltage at the AC source voltage connection to the ground are not disclosed.

[0022] The international patent application WO 2019 / 201831 Al discloses a circuit arrangement for the DC power supply of multiple in parallel connected electrolyzers, in which a central rectifier generates a first DC voltage, and each electrolyzer is supplied via its own DC / DC converter. However, also this document is completely silent about voltages to the ground at the line connection of the AC power source.

[0023] From the “Overview of Power Electronic Converter Topologies Enabling Large-Scale Hydrogen Production via Water Electrolysis”, M. Chen et al, Appl. Sci. 2022, 12, 1906 presents various converter topologies for supplying high-power DC loads such as electrolyzers, including AFE rectifiers and DC / DC converters.

[0024] Starting from this prior art, it is an object of the present invention to provide a method of providing energy to a high-power DC load, preferably to a device for generating hydrogen by electrolysis which allows the use of components with reduced dielectric strength to achieve cost reductions. Furthermore, a circuit arrangement for providing electrical energy to a high-power DC load, preferably to a device for generating hydrogen by electrolysis which allows the use of components with lower dielectric strength and an advantageous use of the inventive circuit arrangement shall be provided.

[0025] ZI / ZI 240390WO 12 December 2025 The object is solved by a method according to claim 1, a circuit arrangement according to claim 14 and a use according to claim 15.

[0026] According to the inventive method for providing electrical energy to a high-power DC load, preferably to a device for generating hydrogen by electrolysis using a circuit arrangement, the circuit arrangement comprising

[0027] - at least one Active Front End (AFE) rectifier connected to a three-phase AC power source, preferably a three-phase electrical grid, via a three-phase AC power source connection and,

[0028] - at least one DC / DC converter connected to a DC link provided by the AFE rectifier, wherein the at least one DC / DC converter (6) provides a DC output voltage at a DC output, wherein the high-power DC load is connected to the DC output, and the at least one DC / DC converter is configured to transfer electrical energy from the DC link via the at least one DC output to the high-power DC load and wherein the at least one DC / DC converter is a DC / DC step-down converter comprising

[0029] - at least one power switch,

[0030] - at least one diode,

[0031] - at least one connection point,

[0032] - at least one DC choke and

[0033] - at least one capacitor,

[0034] wherein the at least one power switch is connected to a first pole of the DC link and to the at least one connection point,

[0035] wherein the at least one diode is connected to the second pole of the DC link and to said at least one connection point,

[0036] wherein the at least one connection point is connected via at least one DC choke to a grounded pole of the at least one DC output,

[0037] wherein the other pole of the DC output is connected directly to the second pole of the DC link and,

[0038] wherein the at least one capacitor is connected in parallel to the poles of the at least one DC output, wherein the method includes a production mode in which the at least one DC / DC converter transfers electrical energy from the at least one DC link via the at least

[0039] ZI / ZI 240390WO 12 December 2025 one DC output to the high-power DC load and wherein at least in production mode the at least one DC / DC converter is controlled to reduce an absolute value of the line voltages at the three-phase AC power source connection of the AFE rectifier. In production mode the high-power DC load demands for high voltages at the DC output to allow the transfer of high energy amounts. However, the inventive method reduces absolute values of the line voltages to the ground even in production mode and thus, allows to use of components with a lower dielectric strength reducing significantly the costs of the circuit arrangement.

[0040] According to a first embodiment of the method the grounded pole of the DC output of the DC / DC step-down converter is either the positive pole or the negative pole of the DC output. As outlined later, both configurations allow to provide lower absolute values of the line voltages at the three-phase AC power source connection.

[0041] Minimum absolute values for the line voltage to ground at the three-phase AC power source connection while providing a maximum of electrical energy to the high-power DC load can be achieved according to a next embodiment of the method, in that the DC / DC step-down converter is controlled to provide a ratio of the DC output voltage and the DC link voltage in production mode of 0.5 + / - 20 %, preferably 0.5 + / - 10%, most preferably 0.5 + / - 5 %. If the ratio of the DC output voltage of the DC output and the DC voltage of the DC link is exactly 0.5 the absolute value of the line voltages to ground is minimized as the line voltages to ground at the three-phase AC power source are balanced in production mode to 0 V. This can be derived from table 2 and table 3.

[0042] According to a further embodiment of the method the circuit arrangement comprises a main circuit breaker (MCB) and at least one pre-charge unit, wherein the MCB is configured to connect the three-phase AC power source connection to the AFE rectifier, and the pre-charge unit is configured to connect the AFE rectifier, preferably in parallel to the MCB, with a three-phase AC power source, in particular with the three-phase AC power source connection mentioned before. The embodiment allows to operate the circuit arrangement in a pre-charge mode in which the DC link of the AFE rectifier is pre-

[0043] ZI / ZI 240390WO 12 December 2025 charged without being connected to the grid via the three-phase AC power source connection. This reduces the risks of damages when connecting the AFE rectifier with the three-phase AC source or with the three-phase grid due to high currents flowing when the level of charge of the capacitor of the DC link is very low or zero.

[0044] The method preferably includes a disconnected mode, wherein the connection of the three-phase AC power source to the AFE rectifier is disconnected by the MCB. This allows for example de-energizing the high-power DC load, the accordant rectifier and the DC / DC converter completely with high safety, for example for maintenance purposes.

[0045] Preferably the method includes a pre-charge mode, wherein in pre-charge mode the AFE rectifier is disconnected from the three-phase AC power source by the MCB, the energy transfer from the DC link to the DC output by at least one DC / DC step-down converter is not active and the pre-charge unit is connected to the AFE rectifier to charge the DC link. This allows to smoothly load the capacitors of the DC link without any risk of high currents damaging the AFE rectifier. Furthermore, it is possible to change easily from disconnected mode in pre-charge mode to charge the DC link capacitors by connecting the pre-charge unit to the AFE rectifier.

[0046] Preferably the method also includes a standby mode. In standby mode the DC voltage level of the DC link of the AFE rectifier is on a nominal value and the DC output voltage level of the at least one DC output is below the production voltage level, preferably below or at a threshold voltage Ui. The nominal value of the DC voltage of the DC link is the DC link voltage necessary to start production mode, in other words which allows the DC / DC converter to provide electrical energy to the high-power DC load. In production mode the production voltage level of the DC output is a DC output voltage which allows to transfer electrical energy to the high-power DC load. The threshold voltage Ui of the DC output voltage is lower than DC output voltage in production mode and ensures that no electrical energy is transferred to the high-power DC load. Ui is preferably chosen in that an unintentional transfer of energy to the high-power DC load is safely avoided. The

[0047] ZI / ZI 240390WO 12 December 2025 standby mode, however, allows to shorten the time to start or to restart transferring energy to the high-power load and to start or to restart production. Thus, preferably, the DC output voltage in standby mode amounts to the threshold voltage Ui. This allows for example to react quickly with the start of an electrolysis device immediately when the price for electrical energy drops below a predefined level.

[0048] Optionally according to a further embodiment of the method, in standby mode the DC output voltage and / or the DC link voltage is kept ata mainly constant voltage level. The voltage level of the DC output voltage may be held constant at an arbitrary level between 0 V and the threshold voltage level Ui, preferably at threshold voltage level Ui.

[0049] To start operation of the high-power DC load smoothly and safely according to a further embodiment the method includes a ramp-up mode, wherein the DC voltage of the DC output is increased to production voltage level of the high-power DC load, wherein the production voltage level allows transferring electrical energy from the DC output to the high-power DC load as outlined before. Preferably, the ramp-up mode is entered from standby mode providing already a DC output voltage level below or at threshold voltage Ui. This allows to shorten the time to reach production mode even more.

[0050] According to a further embodiment of the method in ramp-up mode, in stand-by mode and / or in pre-charge mode the at least one AFE rectifier is operated as passive rectifier. Operating the AFE rectifier as passive rectifier provides an easy way to reduce the line voltages to ground at the three-phase AC power source connection.

[0051] However, with increasing DC output voltages the current harmonic injection into the three-phase AC power source, for example the grid rises. When an increased current harmonic injection cannot be accepted the at least one AFE rectifier is alternatively operated according to a further embodiment to use only one of the two possible zero voltage vectors in production mode, ramp-up mode and / or in standby mode. Operating the AFE rectifier in this mode allows to discard the one zero voltage vector which provides a worse line voltages to ground at the three-phase AC power source

[0052] ZI / ZI 240390WO 12 December 2025 connection. As a result, a further advantageous load point with balanced line voltages to ground at the three-phase AC power source connection can be provided for DC output voltages of VDC2 = 1 / 3 VDC1 in production mode. Moreover, unbalanced line voltages to ground at the three-phase AC power source connection are generally reduced by low DC output voltages by discarding of one zero voltage vectors. Thus, it is advantageous to operate the circuit arrangement in production mode, ramp-up mode and / or standby mode.

[0053] For the embodiment of the method wherein the circuit arrangement comprises a negative pole of the DC output as grounded pole of the DC output of DC / DC step-down converter preferably the AFE rectifier is operated by avoiding zero voltage vector 000 and only zero voltage vector 111 is used in this operation mode. The operation mode of a PWM controlling the power switches of the AFE rectifier is known as DPWMMAX.

[0054] For the embodiment of the method wherein the circuit arrangement comprises a positive pole of the DC output as grounded pole of the DC output of the DC / DC stepdown converter preferably the AFE rectifier is operated by avoiding zero voltage vector 111 and only zero voltage vector 000 is used in this operation mode. The operation mode of the PWM controlling the power switches of the AFE rectifier is known as DPWMM1N.

[0055] According to a further embodiment of the method a transition from the ramp-up mode to the production mode is carried out when the voltage level of the DC output exceeds a predefined threshold voltage Ui and / or when the power provided from the DC output to the high-power DC load exceeds a predefined threshold power Pi. By using a threshold voltage value Ui and / or a predefined threshold power Pi a predefined change from passive mode of the AFE rectifier or actively controlled AFE rectifier with only one zero voltage to the full control mode using all voltage vectors can be provided for example to adapt the harmonic injection on the specific constrains of the three-phase AC power source, in particular the three-phase grid. The threshold voltage Ui depends on the characteristic of the electrolyser.

[0056] ZI / ZI 240390WO 12 December 2025 According to a preferred embodiment of the method a transition from production mode to standby mode is carried out when the DC output voltage level of the DC output is reduced to a predefined threshold voltage Ui or when the power provided from the DC output to the high-power DC load is reduced to a predefined threshold power Pi in order to stop energy transfer to the high power DC load in very short time.

[0057] According to a further embodiment of the method the at least one DC / DC step-down converter comprises at least two power switches, wherein each of the power switches is connected to a first pole of the DC link and to a connection point for each power switch, wherein each connection point for each power switch is connected via a DC choke to a common connection point of the at least two power switches, and the common connection point of the power switches is connected to a grounded pole of the DC output. This embodiment allows to fulfill the demands of electrical energy of high-power DC-loads, preferably of electrolysis devices and reducing an absolute value of the line voltage to ground at the three-phase AC power source connection of the AFE rectifier.

[0058] According to a further embodiment of the method the least one DC / DC step-down converter comprises at least two in parallel connected power switches and the power switches are controlled by a PWM in parallel mode or in shifted timing mode. In parallel mode the switching signals are identical for all power switches of the DC / DC step-down converter, whereas in shifted timing mode the switching signals are different for all power switches, e.g. when using three power switches the switching signals could be shifted by 120° to each other to reduce switching distortions.

[0059] Preferably, an embodiment of the method includes operating a circuit arrangement in at least one of the following modes: disconnected mode, ramp up mode, production mode or stand-by mode allowing a safe and efficient operation of high-power DC loads, in particular electrolysis devices.

[0060] ZI / ZI 240390WO 12 December 2025 The above mentioned object is solved by a circuit arrangement for providing electrical energy to a high-power DC load, in particular to a device for generating hydrogen by electrolysis, operated preferably by a method according to the present invention, which comprises

[0061] - at least one Active Front End (AFE) rectifier connected to a three-phase AC power source, preferably a three-phase electrical grid, via a three-phase AC power source connection and,

[0062] - at least one DC / DC converter connected to a DC link provided by the AFE rectifier, wherein the at least one DC / DC converter provides a DC output voltage at a DC output, wherein the high-power DC load is connected to the DC output, and the at least one DC / DC converter is configured to transfer electrical energy from the DC link via the at least one DC output to the high-power DC load and wherein the at least one DC / DC converter is configured to allow a reduction of an absolute value of the line voltage to ground at the three-phase AC power source connection of the AFE rectifier, wherein the at least one DC / DC converter is a DC / DC step-down converter comprising

[0063] - at least two power switches,

[0064] - at least one diode,

[0065] - at least one connection point for each power switch,

[0066] - at least one DC choke and

[0067] - at least one capacitor,

[0068] wherein each of the power switches is connected to a first pole of the DC link and to a connection point for each power switch, wherein each connection point for each power switch is connected via a DC choke to a common connection point of the at least two power switches, and the common connection point of the power switches is connected to a grounded pole of the DC output and wherein the at least one capacitor is connected in parallel to the poles of the at least one DC output.

[0069] As outlined before, the circuit arrangement described above allows to fulfill the demands of electrical energy of high power DC-loads, preferably electrolysis devices and allows reducing an absolute value of the line voltage to ground at the three-phase AC power source connection of the AFE rectifier. Furthermore, it allows also different

[0070] ZI / ZI 240390WO 12 December 2025 operation modes of the power switches, for example the power switches are operated in parallel switching mode or time shifted switching mode. The number of power switches depends on the demand of electrical energy. A preferred number of power switches is for example three, six or nine.

[0071] It has been found that the circuit arrangement can be operated so that a reduction of an absolute value of the line voltage to ground at the three-phase AC power source connection of the AFE rectifier is achieved by using the generated DC output voltage provided by a DC / DC converter. As a result, components with reduced dielectric strength can be used and allow a significant cost reduction for the circuit arrangement. This circuit arrangement can be operated by the inventive method of the present invention and allows to affect the line voltage to ground at the three-phase AC power source connection by the DC output voltage of the DC / DC step-down converter. DC / DC step-down converter offsets the voltage values of table 1 by the VDC2 and therefore allows the reduction of the absolute value of the line voltage to ground at the three-phase AC power source connection.

[0072] According to an embodiment of the circuit arrangement the grounded pole of the DC output of the DC / DC step-down converter is the negative pole of the DC output. This results in values of the line voltages at the three-phase AC power source connection of the AFE rectifier according to table 2.

[0073] Whereas in another embodiment of the circuit arrangement the grounded pole of the DC output of the DC / DC step-down converter is the positive pole of the DC output, which results in line voltages at the three-phase AC power source connection of the AFE rectifier according to table 3.

[0074] Both embodiments, however, provide lower absolute values of the line voltages at the three-phase AC power source connection if a DC output voltage VDC2 is provided by the DC / DC step-down converter. Comparing the maximum line voltages at the three-phase AC power source connection it results for example with an DC output voltage VDC2 =

[0075] ZI / ZI 240390WO 12 December 2025 0,5*VDC1, wherein VDC1 is the DC voltage of the DC link of the AFE rectifier a balanced line voltages at the three-phase AC power source connection. Thus, a minimum of an absolute value of the line voltages at the three-phase AC power source connection can be achieved. For example, the value of the voltage vector 111 for 750 VRMS (positive peak voltage = 1060 V) results in + 1660 V line voltages at the three-phase AC power source connection. Voltage vector 000 at minimum peak voltage (- 1060 V) results in - 1660 V line voltages at the three-phase AC power source connection. The absolute value for the line voltage at the three-phase AC power source connection is minimized.

[0076] ZI / ZI 240390WO 12 December 2025 Table 2

[0077] No VectVL, U VL,v VL. W

[0078] 0 000 VDC2 - VDC1 + vAC,uVDC2 - VDC1 + vAC,vVDC2 - VDC1 + vAC w

[0079] 1 100 VDC2 + vAC-u- 2 / 3 • VDC1 VDC2 - VDC1 + vAC,v+ 1 / 3 • VDC1 VDC2 - VDC1 + vAC,w+ 1 / 3 • VDC1 2 110 VDC2 + vAC,u- 1 / 3 • VDC1 VDC2 + vAC,v- 1 / 3 • VDC1 VDC2 - VDC1 + vAC,w+ 2 / 3 • VDC1 3 010 VDC2 - VDC1 + vAC,u+ 1 / 3 • VDC1 VDC2 + vAC,v- 2 / 3 • VDC1 VDC2 - VDC1 + vAC,w+ 1 / 3 • VDC1 4 011 VDC2 - VDC1 + vAC,u+ 2 / 3 • VDC1 VDC2 + vAC,v- 1 / 3 • VDC1 VDC2 + vAC,w- 1 / 3 • VDC1

[0080] 5 001 VDC2 - VDC1 + vAC,u+ 1 / 3 • VDC1 VDC2 - VDC1 + vAC,v+ 1 / 3 • VDC1 VDC2 + vAC,w- 2 / 3 • VDC1

[0081] 6 101 VDC2 + vAC,u- 1 / 3 • VDC1 VDC2 - VDC1 + vAC,v+ 2 / 3 • VDC1 VDC2 + vAC,w- 1 / 3 • VDC1

[0082] 7 111 VDC2 + vAC,uVDC2 + vAC,vVDC2 + vAC,w

[0083]

[0084] 5

[0085] ZI / ZI 240390DE 12 December 2025 Table 3

[0086] No Vect

[0087] VL,uVL,v VL,w

[0088] 0 000 -VDC2 + vAC u-VDC2 + vAC v-VDC2 + vAC w

[0089] 1 100 VDC1 - VDC2 + vAC,u- 2 / 3 • VDC1 -VDC2 + vAC,v+ 1 / 3 • VDC1 -VDC2 + vAC,w+ 1 / 3 • VDC1 2 110 VDC1 - VDC2 + vAC,u- 1 / 3 • VDC1 VDC1 - VDC2 + vAC,v- 1 / 3 • VDC1 -VDC2 + vAC,w+ 2 / 3 • VDC1 3 010 -VDC2 + vAC,u+ 1 / 3 • VDC1 VDC1 - VDC2 + vAC,v- 2 / 3 • VDC1 -VDC2 + vAC,w+ 1 / 3 • VDC1 4 011 -VDC2 + vAC,u+ 2 / 3 • VDC1 VDC1 - VDC2 + vAC,v- 1 / 3 • VDC1 VDC1 - VDC2 + vAC,w- 1 / 3 • VDC1 5 001 -VDC2 + vAC,u+ 1 / 3 • VDC1 -VDC2 + vAC,v+ 1 / 3 • VDC1 VDC1 - VDC2 + vAC,w- 2 / 3 • VDC1 6 101 VDC1 - VDC2 + vAC,u- 1 / 3 • VDC1 -VDC2 + vAC,v+ 2 / 3 • VDC1 VDC1 - VDC2 + vAC,w- 1 / 3 • VDC1 7 111 VDC1 - VDC2 + vAC,uVDC1 - VDC2 + vAC,vVDC1 - VDC2 + vAC,w

[0090]

[0091] ZI / ZI 240390DE 12 December 2025 According to a further embodiment the circuit arrangement comprises a main circuit breaker (MCB) and at least one pre-charge unit, wherein the MCB is configured to connect the three-phase AC power source connection to the AFE rectifier, and the precharge unit is configured to connect the AFE rectifier, preferably in parallel to the MCB, with a three-phase AC power source, in particular with the three-phase AC power source connection mentioned before. The embodiment allows to operate the circuit arrangement in a pre-charge mode in which the DC link of the AFE rectifier is precharged without being connected to the grid via the three-phase AC power source connection. This reduces the risks of damages when connecting the AFE rectifier with the three-phase AC source or with the three-phase grid due to high currents flowing when the level of charge of the capacitor of the DC link is very low or zero.

[0092] The pre-charge unit is preferably designed to smoothly load the capacitor of the DC link of the AFE rectifier with adapted currents for charging the capacitors of the DC-link. At a certain load level of the capacitor of the DC link the pre-charge unit can be disconnected and the AC power source is connected via the MCB with the AFE rectifier.

[0093] In parallel switching mode all switches are switched at the same time. In a time shifted switching mode the power switches are controlled to switch at different times, for example with a constant delay between each power switch which results in a smoother DC output voltage at the DC output.

[0094] Preferably, the at least one DC / DC step-down converter of the circuit arrangement can be provided by at least one second AFE rectifier, in particular a second three-phase AFE rectifier, wherein each phase of the second AFE rectifier is connected via a DC choke to a common connection point of all phases of the second AFE rectifier, and the common connection point is connected to a grounded pole of the DC output. Furthermore, the second AFE rectifier is connected to the DC link of the AFE rectifier which is connected with the three-phase AC power source. Thus, both AFE rectifier comprise one common DC link. In this embodiment the DC / DC step-down converter can be provided by

[0095] ZI / ZI 240390DE 12 December 2025 “standard” AFE components having advantages in a reduced assembling effort and assembly space needed of a combination of an AFE connected to the AC power source and an AFE used as DC / DC step-down converter providing the DC output connected to the high-power DC load, preferably at least one electrolysis device.

[0096] Further advantages in the electrical circuit arrangement with respect to reliability and efficiency can be realized by using power switches based on IGBTs or SiC-MosFETs.

[0097] Advantageously, the circuit arrangement is used in a device for providing electrical energy to a high-power DC load, or to a device for generating hydrogen by electrolysis operated with the inventive method 1. Using of the circuit arrangement in a device for generating hydrogen by electrolysis allows the use of AFE components with reduced dielectric strength and leads thus to cost reduction.

[0098] In the following embodiments of the invention will be described in connection with the drawings. The drawings show in

[0099] Fig. 1 a-e, simulation results of the time dependency of the voltage of the DC link, the line side current, the line voltages to ground at the three-phase AC power source connection (vu,vrvw), DC output voltage and the DC load current of an prior art embodiment,

[0100] Fig. 2 the voltage vectors of a common active front end (AFE) rectifier,

[0101] Fig. 3 a schematic diagram of a first embodiment of the inventive circuit arrangement with the ground connection at the negative pole of the DC output,

[0102] Fig.4 a schematic diagram of a second embodiment of the inventive circuit arrangement with the ground connection at the positive pole of the DC output,

[0103] ZI / ZI 240390DE 12 December 2025 Fig. 5 a schematic diagram of a third embodiment with the ground connection at negative pole of the DC link,

[0104] Fig. 6 a schematic diagram of a fourth embodiment with the ground connection at positive pole of the DC link,

[0105] Fig. 7 a-e simulation results of the time dependency of the voltage of the DC link, the line side current, the line voltages to ground at the three-phase AC power source connection (vu,vrvw), DC output voltage and the DC load current of an embodiment of the present invention.

[0106] Fig. 1 a-e displays simulation results of a method to operate a high-power DC load, for example a device for generating hydrogen by electrolysis, with a prior art circuit arrangement. In all diagrams the x-axis is dedicated to the time in seconds. On the bottom of all diagrams four time intervals are marked with A, B, C and D. The physical units of the Y-axis is labeled in each Fig. la to le.

[0107] In the first time interval A the prior art circuit arrangement is not connected to the three-phase AC power source. Thus, time interval A relates to a disconnected mode of the simulated circuit arrangement. The DC voltage in disconnected mode of the DC link of the AFE recitifier is 0 V. It follows time interval B in which the DC link capacitors are pre-charged and the DC link voltage increases in a short time as shown in Fig. la. As can be depicted from Fig. 1c the second time interval B is already characterized by unbalanced line voltages to ground (VLIU, VLI1, VLIW), at three-phase AC power source connection. The lowest voltage is approximately 0 V and the highest voltage is about + 1000 V.

[0108] In the next time interval C the simulated circuit arrangement ramps up the DC output voltage as can be derived from Fig. Id. At the end of time interval C the DC output voltages reaches the production level voltage and production, in other words the energy

[0109] ZI / ZI 240390DE 12 December 2025 consumption of the high-power DC load, starts with time interval D with further increasing DC output voltage. However, as can be derived from Fig. 1c the line voltage to ground at the three-phase AC power source connection is remarkably high due to it unbalanced values. In the production mode D the highest line voltages to ground is around 1860 V whereas the lowest voltage is - 660 V. Due to this unbalanced state, the dielectric strength of all components needs to be adapted to approx. 1860 V line voltage to ground.

[0110] Fig. 3 now shows a schematic diagram of a circuit arrangement according to an embodiment of the invention. The circuit arrangement for providing electrical energy to a high-power DC load, in particular to a device for generating hydrogen by electrolysis, comprises at least one Active Front End (AFE) rectifier 4 connected to a three-phase AC power source, preferably a three-phase electrical grid, via a three-phase AC power source connection 1 and, at least one DC / DC converter 6 connected to a DC link 5 provided by the AFE rectifier 4, wherein the at least one DC / DC converter 6 provides a DC output voltage at the DC output 8, wherein the high-power DC load, not shown in Fig.

[0111] 3, is connected to the DC output 8, and the at least one DC / DC converter 6 is configured to transfer electrical energy from the at least one DC link 5 via the at least one DC output 8 to the high-power DC load and wherein the at least one DC / DC converter 5 is configured to allow a reduction of an absolute value of the line voltage to ground at the three-phase AC power source connection 1 of the AFE rectifier.

[0112] A three-phase AC power source, for example an electrical grid, is connected to the three-phase AC power source connection 1. Preferably, a Main Circuit Breaker (MCB) 2 connects the three-phase AC power source connection 1 with an AFE rectifier 4. The AFE rectifier in Fig. 3 is shown as three phase half-bridge rectifier with 1GBT power switches. The use of other high power semiconductor switches is possible. Optionally, a precharge unit 3 is connected in parallel to the MCB 2 with the AFE rectifier 4. The precharge unit 2 allows pre-charging of the capacitors of the DC link 5 when the AFE rectifier is disconnected by the MCB 2 from the three-phase AC power source. The pre-

[0113] ZI / ZI 240390DE 12 December 2025 charge unit charges the DC link capacitors smoothly and without any risks of high current damages.

[0114] In the embodiment of Fig. 3 the at least one DC / DC converter 6 is a DC / DC step-down converter comprising at least one power switch 9, at least one diode 10, at least one connection point 9a, at least one DC choke 12 and at least one capacitor 11, wherein the at least one power switch 9 is connected to a first, in this embodiment the negative pole of the DC link and to the at least one connection point 9a, wherein the at least one diodelO is connected to the second pole, in this embodiment the positive pole of the DC link and to said at least one connection point 9a, wherein the at least one connection point 9a is connected via at least one DC choke 12 to a grounded pole 8a of the at least one DC output 8, wherein the other pole 8b of the DC output 8 is connected directly to the second pole of the DC link 5 and, wherein the at least one capacitor 11 is connected in parallel to the poles 8a, 8b of the at least one DC output 8. Grounding is provided by grounding device 7.

[0115] According to Fig. 3 the positive pole 8b of the DC output 8 is directly connected to the positive pole of the first DC link 5, whereas the negative pole 8a of the DC output 8 is grounded and connected via the choke 12 with the power switch 9. In the embodiment shown in Fig. 3 the DC output voltage at the DC output 8 affects the DC link voltage of the first DC link and thus, influence the line voltage to ground at the three-phase AC power source connection. The shown embodiment provides line voltages to ground at the three-phase AC power source connection depending on the voltage vectors of the AFE rectifier 4 according to table 2 for the different switching states of the AFE rectifier 4 described above.

[0116] Fig.4 shows another schematic diagram of an embodiment of the invention which provides line voltages to ground at the three-phase AC power source connection depending on the voltage vectors of the AFE rectifier 4 according to table 3. In difference to embodiment of Fig. 3 the positive pole 8b of the DC output is grounded and connected via a DC choke 12 and the connection point 9a with the power switch 9, whereas the

[0117] ZI / ZI 240390DE 12 December 2025 power switch is connected to the positive pole of the DC link 5. The negative pole 8a of the DC output 8 is connected directly to the negative pole of the first DC link 5.

[0118] Grounding is provided by ground connection 7a.

[0119] The inventive embodiment of Fig. 5 comprises a first AFE rectifier 4 connected to the grid 1 similar to the embodiments in Fig. 3 and Fig.4, whereby for simplicity a MCB and a pre-charge unit are merely not shown in Fig. 5. The same applies to Fig. 6.

[0120] The AFE rectifier 4 is connected to a first DC link 5. However, in Fig. 5 the DC / DC stepdown converter 6b comprises a three-phase half bridge with 1GBT based power switches connected to the DC link of AFE rectifier 4 and is provided as a second AFE rectifier. Thus, DC / DC step-down converter 6b comprises at least two in parallel connected power switches, the bottom power switches 9.1, 9.2, 9.3. The diode is provided by the 1GBT base top power switches 10.1, 10.2, 10.3. Each of the power switches 9.1, 9.2, 9.3 is connected to a first pole, in the present embodiment the negative pole of the DC link and to a connection point 9a.l, 9a.2, 9a.3 for each power switch 9.1, 9.2, 9.3, wherein each connection point 9a.l, 9a.2, 9a.3 for each power switch is connected via DC chokes 12, 13, 14 to a common connection point 15. The common connection point 15 of the power switches is connected to a grounded pole 8a of the DC output 8. The in parallel connected power switches 9.1, 9.2, 9.3 of the AFE rectifier 6b allow to switch in parallel connected power switches in different timing modes, like in parallel mode or shifted timing mode. In parallel mode all power switches are controlled to switch at the same time, whereas in shifted timing mode the three power switches 9.1, 9.2, 9.3 can be controlled to switch at different time points, with preferably identical time difference. For parallel switching mode of the power switches merely a single switching signal needs to be provided to all power switches. However, switching the power switches of the DC / DC converter in shifted timing mode allows to reduce parasitic effects caused by switching the power switches.

[0121] Providing the DC / DC step-down converter 6b by a three-phase half bridge layout enables to use standard AFE components to provide the DC / DC step-down converter 6b

[0122] ZI / ZI 240390DE 12 December 2025 which reduces expenses and assembly efforts. On the other hand the at least two in parallel connected power switches 9.1, 9.2, 9.3 allow to transfer more energy to the DC high-power load.

[0123] The embodiment in Fig. 5 shows the ground connection 7b located at the negative pole of the DC output 8, whereas the positive pole 8b of the DC output 8 is directly connected with the positive pole of the DC link 5. The positive pole of the DC output 8 is directly connected to the positive pole of the first DC link 5 which allows reduced absolute values of the line voltage to ground at the three-phase AC power source connection due to the voltage vectors of the AFE connected with the AC power source, the grid 1 as shown in Table 2.

[0124] Line voltages to ground at the three-phase AC power connection according to Table 3 provides the embodiment of Fig 6 depending on the voltage vectors of the AFE rectifier 4. Also the embodiment of Fig. 6 includes a DC / DC step-down converter 6c provided in three-phase half bridge layout based on 1GBT power switches. The ground connection 7c is connected to the positive pole 8b of the DC link 8 and the negative pole 8a of the DC output 8 is directly connected to the negative pole of the first DC link 5. Deviant from embodiment of Fig. 5 the power switches 9.1, 9.2, 9.3 are now top power switches and the diodes 10.1, 10.2, 10.3 are provided by bottom power switches in

[0125] 1GBT layout. The different use of top and bottom switches can be preferably provided simply by the control software of the DC / DC step-down converter in three-phase half bridge layout.

[0126] A simulation of operating a high-power DC load with the circuit arrangements of the embodiment of Fig. 6 is shown in Fig. 7a. to 7e. Similar to Fig. la to le in all diagrams the x-axis is dedicated to the time in seconds. On the bottom of all diagrams 4 time intervals are marked with A, B, C and D. The physical units of the Y-axis is labeled in each Fig. 7a to 7e.

[0127] ZI / ZI 240390DE 12 December 2025 Although, the values of the DC link voltage (Fig. 7a) and the line side current (Fig. 7b) are more or less similar with Fig la and Fig. lb the differences of the present invention with prior art circuit arrangements are shown in the line voltage to ground at the three-phase AC power connection diagram of Fig. 7c. In time interval A in the disconnected mode, of course the line voltage to ground at the three-phase AC power connection are identical to Fig. 1c.

[0128] In pre-charge mode in time interval B the line voltage to ground at the three-phase AC power connection drops in an unbalanced state when connecting the AFE rectifier with the three-phase AC power source. This results from the fact that in the simulated embodiment the power switches of the DC / DC stepdown converter are connected via DC chokes to the positive pole of the DC output which is grounded in this embodiment as shown in Fig. 6 contrary to the prior art embodiment.

[0129] The ramp-up mode starts with time interval C at around 0,6 s. The DC output voltage is increased by the DC / DC step-down converter from around 0 V up to below 400 V before entering production mode in time interval D.

[0130] A transition from production mode to standby mode can be achieved by reducing the DC output voltage to values between 0 V and threshold voltage Ui. In standby mode it is in principle not necessary to keep the DC output voltage at a constant level as long as the threshold voltage Ui is not exceeded. However, in order to achieve a better control, it is advantageous to keep the DC output voltage at a fixed level, for example at threshold voltage Ui. Additionally, a transition from standby mode in ramp up mode allows to start or restart production mode smoothly and safely.

[0131] In production mode in time interval D the DC output voltage is further increased to for example about 600 V so that VDC2 = 0,5 VDC1 applies, with VDC2 as DC output voltage and VDC1 as DC link voltage. As can be derived from Fig. 7c the line voltages to ground at the three-phase AC power connection in production mode, in particular at nominal DC output voltage, are symmetrical distributed around 0 V which leads to a minimum of

[0132] ZI / ZI 240390DE 12 December 2025 absolute value of the line voltage to ground at the three-phase AC power connection in production mode to approx. 1050 V instead of 1660 V in Fig 1c.

[0133] As the simulation of the DC Load Current shows, the inventive embodiment allows a similar smooth increase of the energy consumption of the high-power DC load, Fig. 7d and Fig. 7e as the known circuit arrangements. However, at the same time the inventive circuit arrangement allows a reduction of the absolute value of the line voltage to ground at the three-phase AC power connection at least in production mode. In production mode the highest line voltage to ground at the three-phase AC power connection occur. Thus, the dielectric strength of all components in the AFE rectifier can be reduced, which reduces the expenses for providing the inventive circuit arrangement.

[0134] Not shown in Fig. 7a to 7e is that the AFE rectifier of the circuit arrangement can be operated in ramp-up mode, in standby mode and / or in pre-charge mode the at least one AFE rectifier as passive rectifier. However, the increasing amount of harmonic currents injected into the three-phase AC power source, into the grid, set constraints with respect to this easy way to eliminate unbalanced line voltages to ground at the three-phase AC power connection.

[0135] To avoid increasing injection of harmonic currents in production mode, ramp-up mode and / or in standby mode the at least one AFE rectifier is controlled to use only one of two possible zero voltage vectors for controlling the power switches of the AFE rectifier, for example using the PWM operation modes DPMWMAX or DPMWM1N. This allows to provide at VDC2 = 1 / 3 VDC1, in the present embodiment, at around 200 V already a balanced state in ramp-up mode for example.

[0136] As can be derived from Fig. 7d and 7e a transition from the ramp-up mode in time interval C to the production mode in time interval D is carried out when the voltage level of the DC output reaches a predefined threshold voltage U1 which is approximately 400 V in the present embodiment. In the alternative the transition from ramp-up to

[0137] ZI / ZI 240390DE 12 December 2025 production mode can be carried out when the power provided from the DC output to the high-power DC load reaches a predefined threshold power Pl, not shown in Fig. 7e.

[0138] For example with changing from ramp-up mode to production mode also the mode of operation of the power switches of the AFE rectifier 4 of the circuit arrangement may be altered from DPMWMAX or DPMWM1N to using full PWM control in production mode.

[0139] ZI / ZI 240390DE 12 December 2025

Claims

Zl / Zl 240390DEDecember 12, 2025C l a i m s1. Method for providing electrical energy to a high-power DC load, preferably to a device for generating hydrogen by electrolysis using a circuit arrangement, the circuit arrangement comprising- at least one Active Front End (AFE) rectifier (4) connected to a three-phase AC power source, preferably a three-phase electrical grid, via a three-phase AC power source connection (1) and,- at least one DC / DC converter (6) connected to a DC link (5) provided by the AFE rectifier (4),wherein the at least one DC / DC converter (6) provides a DC output voltage at a DC output (8), wherein the high-power DC load is connected to the DC output (8), and the at least one DC / DC converter (6) is configured to transfer electrical energy from the DC link (5) via the at least one DC output (8) to the high-power DC load and wherein the at least one DC / DC converter (6, 6a, 6b, 6c) is a DC / DC step-down converter comprising- at least one power switch (9, 9.1, 9.2, 9.3),- at least one diode (10, 10,1. 10.2, 10.3),- at least one connection point (9a),- at least one DC choke (12, 13, 14) and- at least one capacitor (11),wherein the at least one power switch (9, 9.1, 9.2, 9.3) is connected to a first pole of the DC link (5) and to the at least one connection point (9a),wherein the at least one diode (10, 10.1, 10.2, 10.3) is connected to the second pole of the DC link (5) and to said at least one connection point (9a), wherein the at least one connection point (9a) is connected via at least one DC choke (12, 13, 14) to a grounded pole (8a, 8b) of the at least one DC output (8), wherein the other pole (8a, 8b) of the DC output (8) is connected directly to the second pole of the DC link (5) and,wherein the at least one capacitor (11) is connected in parallel to the poles (8a,8b) of the at least one DC output (8), wherein the method includes a production mode (D) in which the at least one DC / DC converter (6, 6a, 6b, 6c, 6d) transfers electrical energy from the at least one DC link (5) via the DC output (8) to the high-power DC load and wherein at least in production mode (D) the at least one DC / DC converter (6, 6a, 6b, 6c, 6d) is controlled to reduce an absolute value of the line voltage to ground at the AC power source connection (1) of the AFE rectifier [4).

2. Method according to claim 1,wherein the grounded pole (8a, 8b) of the DC output of the DC / DC step-down converter (6, 6a, 6b, 6c) is either the positive pole (8b) or the negative pole (8a) of the DC output (8).

3. Method according to claim 1 or 2,wherein the DC / DC step-down converter is controlled to provide a ratio of the DC voltage of the DC output (8) and the DC voltage at the DC link (5) in production mode of 0.5 + / - 20 %, preferably 0.5 + / - 10%, most preferably 0.5 + / - 5 %.

4. Method according to one of claims 1 to 3,wherein the circuit arrangement comprises a main circuit breaker (MCB) (2) and at least one pre-charge unit (3), wherein the MCB (2) is configured to connect the three-phase AC power source connection (1) to the AFE rectifier (4), and the precharge unit (3) is configured to connect the AFE rectifier (4) via the pre-charge unit, preferably in parallel to the MCB (2), with a three-phase AC power source, preferably with the three-phase AC power source connection (1), wherein optionally or in the alternative the method includes a disconnected mode (A), wherein the AFE rectifier (4) is disconnected from the AC power source connection (1) via the MCB (2).

5. Method according to one of the claims 1 to 4,wherein the method includes a pre-charge mode (B), wherein in pre-chargeZI / ZI 240390DE 12 December 2025mode the AFE rectifier (4) is disconnected from the AC power source by the MCB (2), the energy transfer from the DC link (5) to the DC output (8) by at least one DC / DC step-down converter (6, 6a, 6b, 6c, 6d] is not active and the pre-charge unit (3) is connected to the AFE rectifier (4) to charge the DC link (5).

6. Method according to one of claims 1 to 5,wherein the method includes a standby mode, wherein in standby mode the DC voltage level of the DC link (5) of the at least one AFE rectifier (4) is on its nominal value and the DC output voltage level of the at least one DC output (8) is below the production voltage level, preferably below or at a threshold voltage Ui.

7. Method according to one of claims 1 to 6,wherein the method includes a ramp-up mode (C), wherein in ramp-up mode (C) the DC output voltage of the DC output (8) is increased at least to a production voltage level of the high-power DC load, wherein the production voltage level allows transferring electrical energy from the DC output (8) to the high-power DC load.

8. Method according to one of claims 5 to 7,wherein in ramp-up mode (C), in standby mode and / or in pre-charge mode (B) the at least one AFE rectifier is operated as passive rectifier.

9. Method according to one of claims 1 to 8,wherein in production mode (D), ramp-up mode (C) and / or in standby mode the at least one AFE rectifier (4) is controlled to use only one of two possible zero voltage vectors for controlling the power switches of the AFE rectifier (4).

10. Method according to one of claims 1 to 9,wherein a transition from ramp-up mode (C) or standby mode to production mode (D) is carried out when the DC output voltage level of the DC output (8) exceeds a predefined threshold voltage (Ui) or when the power provided fromZI / ZI 240390DE 12 December 2025the DC output to the high-power DC load exceeds a predefined threshold power [Pi).

11. Method according to one of claims 1 to 10,wherein a transition from production mode[D) to standby mode is carried out when the DC output voltage level of the DC output [8) is reduced to a predefined threshold voltage [Ui) or when the power provided from the DC output to the high-power DC load is reduced to a predefined threshold power [Pi).

12. Method according to one of claims 1 to 11, wherein the at least one DC / DC stepdown converter [6, 6a, 6b, 6c) comprises at least two power switches [9.1, 9.2, 9.3), wherein each of the power switches [9.1, 9.2, 9.3) is connected to a first pole of the DC link [5) and to a connection point [9a.l, 9a.2, 9a.3) for each power switch, wherein each connection point [9a.l, 9a.2, 9a.3) for each power switch [9.1, 9.2, 9.3) is connected via a DC choke [12, 13, 14) to a common connection point [15) of the at least two power switches [9.1, 9.2, 9.3), and the common connection point [15) of the power switches [9.1, 9.2, 9.3) is connected to a grounded pole [8a, 8b) of the DC output [8).

13. Method according to one of claims 1 to 12,wherein the at least two in parallel connected power switches [9.1, 9.2, 9.3) of the at least one DC / DC step-down converter [6b, 6c) are controlled by a pulse width modulation [PWM) in parallel mode or in shifted timing mode.

14. Circuit arrangement for providing electrical energy to a high-power DC load, in particular to a device for generating hydrogen by electrolysis, optionally operated by a method according to claim 1 to 13 comprising- at least one Active Front End [AFE) rectifier [4) connected to a three-phase AC power source, preferably a three-phase electrical grid, via a three-phase AC power source connection [1) and,ZI / ZI 240390DE 12 December 2025- at least one DC / DC converter (6) connected to a DC link (5) provided by the AFE rectifier (4),wherein the at least one DC / DC converter (6) provides a DC output voltage at a DC output (8), wherein the high-power DC load is connected to the DC output (8), and the at least one DC / DC converter (6) is configured to transfer electrical energy from the DC link (5) via the at least one DC output (8) to the high-power DC load and wherein the at least one DC / DC converter (6) is configured to allow a reduction of an absolute value of the line voltage to ground at the three-phase AC power source connection (1) of the AFE rectifier (4), wherein the at least one DC / DC converter (6, 6a, 6b, 6c) is a DC / DC step-down converter comprising - at least two power switches (9, 9.1, 9.2, 9.3),- at least one diode (10, 10,1. 10.2, 10.3),- at least one connection point for each power switch (9a.l, 9a.2, 9a.3),- at least one DC choke (12, 13, 14) and- at least one capacitor (11),wherein each of the power switches (9.1, 9.2, 9.3) is connected to a first pole of the DC link (5) and to a connection point (9a.l, 9a.2, 9a.3) for each power switch, wherein each connection point (9a.1, 9a.2, 9a.3) for each power switch (9.1, 9.2, 9.3) is connected via a DC choke (12, 13, 14) to a common connection point (15) of the at least two power switches (9.1, 9.2, 9.3), and the common connection point (15) of the power switches (9.1, 9.2, 9.3) is connected to a grounded pole (8a, 8b) of the DC output (8) and wherein the at least one capacitor (11) is connected in parallel to the poles (8a, 8b) of the at least one DC output (8).

15. Use of a circuit arrangement of claim 14 in a device for providing electrical energy to a high-power DC load, or to a device for generating hydrogen by electrolysis, operated by a method according to claim 1 to 13.ZI / ZI 240390DE 12 December 2025

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