Method for starting electrolytic power supply device having parallel converters and simplified pre-charging units

Abstract

The invention relates to a method for starting up an electrical power supply unit (10) having a first power converter (22), a second power converter (24) and a rectifying unit (26) and provided for supplying electrical energy from an AC network (12) to a DC connection (DCA), at least one DC connection unit (14, 15, 16) being connected at the DC connection (DCA) of the power supply unit (10), and the AC network (12) is connected at an AC connection (ACA) of the power supply unit (10). The method comprises the steps of: pre-charging a first DC intermediate circuit of the first power converter and a second DC intermediate circuit of the second power converter (22 and 24) from an AC grid (12) via an AC pre-charging circuit (18); an AC islanding grid is constructed by means of the second power converter (24), where electrical energy is supplied from the AC islanding grid via the rectification unit (26) to the DC connection (DCA) during construction of the AC islanding grid. The application also relates to an electrical power supply unit (10) and an electrolytic power supply device (40).

Description

Technical Field

[0001] This application relates to a method for starting an electrical power supply unit, an electrical power supply unit, and an electrolytic power supply device. background

[0002] WO2023 / 274776A1 describes a method for starting an electrolysis apparatus. The electrolysis apparatus includes an electrolytic cell and a power supply unit operating as a rectifier. The power supply unit has an AC connection terminal connected to an AC power grid, a DC connection terminal connected to the electrolytic cell, and an AC / DC converter disposed between the AC connection terminal and the DC connection terminal. By operating the electrolytic cell in reverse mode, an output capacitor connected to the DC converter connection terminal of the AC / DC converter is charged as a DC voltage source.

[0003] This type of charging method on the DC side of an AC / DC converter requires hydrogen, which should ideally be produced in an electrolysis unit. Therefore, this type of charging on the DC side is disadvantageous. An improved and resource-efficient alternative needs to be found.

[0004] Alternatively, a pre-charging unit is used in the power supply unit of the electrolysis apparatus, specifically for pre-charging the electrolytic cells. Here, for example, for alkaline electrolytic cells, i.e., those used for alkaline electrolysis (AEL), the cells are pre-charged to their open-circuit voltage of 700 to 800 V, wherein such electrolytic cells have a capacitance characteristic of 2F to 5F. The common practice here is to gradually increase the voltage used for pre-charging the electrolytic cells using the pre-charging unit, so that the pre-charging voltage continuously rises to the open-circuit voltage of the electrolytic cells.

[0005] Furthermore, from an economic perspective, the electrolyzer should be operated for as long as possible to minimize system discharge. Since the need for pre-charging is infrequent, the pre-charging unit is designed to be small, i.e., have low power, to save on pre-charging unit costs. Due to the lower power, the pre-charging duration of the electrolyzer is longer.

[0006] Therefore, in the prior art, there exists a pre-charging unit for electrolyzers, which is dedicated to the pre-charging of the electrolyzers and is rarely used for economic reasons, and has low power consumption. There is also a need to find a cost-effective, time-saving, and efficient alternative. Overview

[0007] The above problems are solved by the subject matter of this invention.

[0008] The electrical power supply unit according to the present invention includes a first power converter, a second power converter, and a rectifier unit. The power supply unit is configured to supply power from an AC mains grid to a DC connection terminal, wherein at least one DC connection unit can be connected to the DC connection terminal of the power supply unit, and the AC mains grid can be connected to the AC connection terminal of the power supply unit. For example, the DC connection unit can be at least one DC source, at least one DC load, and / or at least one additional unit.

[0009] A method for starting an electrical power supply unit, wherein at least one DC connection unit is connected to the DC connection terminal of the power supply unit, and an AC power grid is connected to the AC connection terminal of the power supply unit, the method comprising the following steps: The first DC intermediate circuit of the first power converter and the second DC intermediate circuit of the second power converter are precharged from the AC grid via the AC precharge circuit. An AC islanded grid is constructed using a second power converter, wherein during the construction of the AC islanded grid, electrical energy is supplied from the AC islanded grid to the DC connection via a rectifier unit.

[0010] The electrical power supply unit is configured as follows: The first DC intermediate circuit of the first power converter and the second DC intermediate circuit of the second power converter are precharged from the AC grid via the AC precharge circuit. An AC islanded grid is constructed using a second power converter, wherein during the construction of the AC islanded grid, power can be supplied from the AC islanded grid to the DC connection via a rectifier unit.

[0011] For example, the first and second power converters can be switching inverters, or they can operate as rectifiers. Power converters are specifically designed to transmit large amounts of power, such as in the MW range.

[0012] The pre-charging of the first and second DC intermediate circuits is used for controlled charging of the intermediate circuits to avoid excessive inrush current. This contributes to safety and extends component lifespan. The AC pre-charging circuit is designed, for example, to limit current during charging of the first and second DC intermediate circuits. For this purpose, the AC pre-charging circuit may, for example, have a bypassable resistor.

[0013] The construction of an AC islanded grid involves progressively increasing power transmission through the AC islanded grid in a continuous manner (e.g., in a ramp-like manner). The power converter operates in grid-connected mode. After rectification by the rectifier unit, the electrical power can be provided as DC power via a DC connection terminal. The construction of the islanded grid can be used to precharge DC connection units connected to the DC connection terminal. Therefore, the method and power supply unit can be advantageously used to precharge at least one DC connection unit connected to the DC connection terminal. Here, at least one DC connection unit can be, for example, a DC load that should be precharged, such as an electrolytic cell. Alternatively, it could be a capacitor of at least one other unit connected to the DC connection terminal.

[0014] The described method and power supply unit offer the following advantages: the pre-charging circuit only needs to be configured once at the first power converter, both power converters can be pre-charged, and the DC connection unit can also be pre-charged via the DC connection terminal. The power supply unit can be designed to transmit high power overall, and can also transmit large pre-charge power over an AC islanded grid. However, the pre-charging circuit only needs to be designed to pre-charge the first power converter, and can be designed accordingly to be smaller and cheaper. Furthermore, this method allows for advantageous pre-charging of the DC connection unit at the rated power of the power converter. On the one hand, this accelerates the pre-charging of the DC connection unit because, as mentioned above, the pre-charging unit used in the prior art is designed to have lower power. On the other hand, the pre-charging unit used for the DC connection unit in the prior art can be eliminated, thereby saving costs.

[0015] The described power supply unit may have a control unit having at least one processor, a memory, and at least one input / output interface. The control unit is configured to perform the described method, for example, by controlling the switching of the power supply unit.

[0016] In one embodiment, when the first DC intermediate circuit is pre-charged, the first power converter is connected to the AC connection terminal on the AC side and disconnected from the DC connection terminal on the DC side. Thus, the first power converter is pre-charged in a controlled manner via the AC pre-charge circuit.

[0017] In one embodiment, the DC side of the first power converter is connected to the DC side of the second power converter before pre-charging the first DC intermediate circuit. Thus, for example, by turning on a switch, a connection is established for pre-charging the second power converter via the first power converter. Now, the second power converter can be pre-charged in a controlled manner via the first power converter.

[0018] In one embodiment, when pre-charging the second DC intermediate circuit, the second power converter is disconnected from the AC connection terminal on the AC side and connected to the DC side of the first power converter on the DC side. When pre-charging both the first and second DC intermediate circuits, the DC sides of both power converters are disconnected from their DC connection terminals. Therefore, the electrical power output from the first power converter on the DC side can be used to pre-charge the DC side of the second power converter. Pre-charging can be directly controlled via the electrical power output from the first power converter.

[0019] In one embodiment, after pre-charging the second intermediate circuit, the AC side of the second power converter is connected to the AC side of the rectifier unit. For example, this connection can be established by turning on a switch. The pre-charged second power converter can then deliver electrical power to the rectifier unit from the AC side via this connection.

[0020] In one embodiment, during the construction of the AC islanded grid, the AC voltage is regulated and gradually increased on its AC side by a second power converter. During AC islanded grid construction, the second power converter operates in voltage regulation mode, where the voltage and the electrical power transmitted through the AC islanded grid increase slowly. During AC islanded grid construction, the power transmission via the AC islanded grid increases slowly. The AC voltage of the AC islanded grid is rectified to DC voltage via a rectifier unit. The DC voltage can be provided via a DC connection. As the power and voltage of the AC islanded grid gradually increase, the power and voltage at the DC connection supplied through the rectifier unit also increase in the same manner.

[0021] In one implementation, during the construction of an AC islanded power grid, the second power converter is powered by the first power converter on the DC side. Therefore, the first power converter can be used to supply power to the second power converter, for which the first power converter operates as a rectifier.

[0022] In one embodiment, during the construction of the AC islanded grid, at least one DC connection unit is pre-charged via the DC connection terminal. Therefore, the construction of the AC islanded grid and the associated power boost can be used to pre-charge at least one DC connection unit connected to the DC connection terminal. For this purpose, the AC power of the AC islanded grid is rectified by a rectifier unit.

[0023] In one implementation, after establishing an AC islanded power grid, a first power converter is connected to a DC connection on the DC side to supply electrical energy from the AC grid to the DC connection. For example, this connection can be established by turning on a switch. The first power converter can then be used to supply electrical power from the AC grid to the DC connection.

[0024] In one implementation, after establishing an AC islanded power grid, a second power converter is connected to the DC connection terminal on the DC side and to the AC connection terminal on the AC side to supply electrical energy from the AC grid to the DC connection terminal. For example, this connection can be established by turning on a switch. The second power converter can then be used to supply electrical power from the AC grid to the DC connection terminal.

[0025] In one embodiment, a first power converter and / or a second power converter are connected to an AC connection terminal on the AC side and to a DC connection terminal on the DC side for supplying electrical energy from the AC grid to the DC connection terminal. This allows for flexible power supply to the DC connection terminal, where large power can also be transmitted. However, pre-charging the first and second power converters, as well as at least one possible DC connection unit, requires only one AC pre-charging circuit.

[0026] In one embodiment, the rectifier unit has a passive rectifier and / or a switching AC / DC converter. Therefore, the rectifier unit can be designed to be active or passive.

[0027] In one embodiment, after establishing an islanded power grid, the switching AC / DC converter of the rectifier unit is connected to the AC connection terminal on the AC side and to the DC connection terminal on the DC side for supplying electrical energy from the AC grid to the DC connection terminal. For example, this connection can be established by turning on a switch. The switching AC / DC converter of the rectifier unit can then be used to supply electrical power from the AC grid to the DC connection terminal. This further provides transferable electrical power.

[0028] In one embodiment, after establishing an islanded power grid, electrical energy is supplied from the AC grid to at least one DC connection unit and / or at least one additional DC connection unit via a DC connection terminal, wherein the power is supplied via a first power converter, a second power converter, and / or a switching AC / DC converter. This makes the power supply to the DC connection terminal more flexible and allows for the transmission of greater power.

[0029] In one embodiment, after constructing the AC islanded power grid, at least one DC connection unit of the electrical power supply unit is connected in parallel to supply power from the AC grid to the DC connection. For example, at least one DC connection unit is an additional unit comprising a power converter without pre-charging circuitry. Capacitors, such as the DC intermediate circuitry of the power converter in the additional unit, may have already been pre-charged by the power supply unit. The power converter of the additional unit can now be connected in parallel with the power supply unit and can also transfer power from the AC grid to the DC connection, supplying power to the DC connection unit connected there.

[0030] In one embodiment of the power supply unit, at least one DC connection unit is designed as an electrolyzer that can be pre-charged via the DC connection during the construction of the AC islanded power grid. This provides the advantage that an electrolyzer requiring pre-charging and high-power supply during operation after pre-charging can be powered by the described power supply unit, which is started according to the described method. Here, only one AC pre-charging circuit can be designed for use in high-power power supply units.

[0031] In one embodiment, electrical energy can be fed from the DC connection to the AC grid, which can be connected to the AC connection, via an electrical power supply unit. The power supply unit is designed so that electrical power can be transmitted in both directions. For example, this is advantageous for a DC connection unit with a DC source. The DC source can be, for example, a photovoltaic generator, a fuel cell, or the like.

[0032] The electrolysis power supply device according to the invention includes the described electrical power supply unit and an optional transformer. The electrolysis power supply device is used to supply power from an AC power grid (e.g., an AC power supply network) to an electrolysis apparatus having one or more electrolytic cells. List of Attachments

[0033] The embodiments of this application will be further explained and described below with reference to the accompanying drawings. In the drawings: Figure 1 The first embodiment of the electrical power supply unit is schematically shown. Figure 2 A second embodiment of the electrical power supply unit is schematically shown. Figure 3 A third embodiment of the electrical power supply unit is schematically shown. Figure 4 The method for starting the electrical power supply unit is illustrated schematically. Figure 5 The fourth embodiment of the electrical power supply unit is schematically shown. Figure 6 An electrical power supply unit with additional units is schematically shown, and Figure 7 An electrolysis power supply device is schematically shown.

[0034] In the accompanying drawings, the same reference numerals are used for the same or similar elements. The illustrations in the figures are not drawn to scale. Attached Figure Description

[0035] Figure 1A first embodiment of the electrical power supply unit 10 is schematically illustrated. An AC power grid 12, such as an AC power supply grid, is connected to the AC connection terminal ACA of the power supply unit 10. This is illustrated only by way of a high-voltage tower, but this does not represent a limitation on a specific voltage range, and the AC power grid 12 can also be a medium-voltage grid or a low-voltage grid. For example, the AC power grid can be a three-phase, single-phase, or two-phase AC grid. A DC connection unit, such as a DC load 14, is connected to the DC connection terminal DCA of the power supply unit 10. For example, the DC load 14 can include DC-powered equipment, such as an electrolytic cell or a DC motor or the like.

[0036] The power supply unit 10 has a first power converter 22 and a second power converter 24. The first power converter 22 and the second power converter 24 are designed as inverters with a switched bridge circuit, which can also operate as rectifiers. The power supply unit 10 also has a rectifier unit 26. Figure 1 In one embodiment, the rectifier unit 26 has a passive rectifier, such as a diode.

[0037] The first DC intermediate circuit of the first power converter 22 and the second DC intermediate circuit of the second power converter 24 can be precharged from the AC grid 12 via an AC precharge circuit 18, which can be integrated into the first power converter 22 (indicated by dashed lines). During precharging of the first and second DC intermediate circuits, the capacitor of the first DC intermediate circuit is charged, which may alternatively include multiple capacitors. In this process, electrical power is controlled to be transferred from the AC grid 12 to the capacitors via the AC precharge circuit 18. During precharging, current spikes that may occur when voltage is applied to the capacitors are specifically avoided. When the first power converter 22 and the second power converter 24 are precharged, switches S2, S3, S4, and S5 of the power supply unit 10 are disconnected. Precharging via the AC precharge circuit can be controlled, for example, by the control unit 20.

[0038] If the pre-charging of the first intermediate circuit of the first power converter 22 and the second intermediate circuit of the second power converter 24 is completed, the capacitor of the second DC intermediate circuit is charged during pre-charging, which may alternatively include multiple capacitors. During this process, electrical power is controlled to be transferred from the AC grid 12 to the capacitor via the AC pre-charging circuit 18 of the first power converter 22. Pre-charging can be controlled, for example, by the control unit 20.

[0039] If the pre-charging of the second intermediate circuit of the second power converter 24 is complete, the second power converter 24 can be connected to the rectifier unit 26 on the AC side by turning on the switch S2. The second power converter 24 now constructs an AC islanded grid on its AC side. The AC islanded grid is synchronized with the power grid. When constructing the AC islanded grid, the second power converter 24 supplies power on the DC side through the first power converter. During this process, the first power converter 22 obtains power from the AC grid and operates as a rectifier. The second power converter 24 operates as an inverter and operates in a voltage-regulated manner on the AC side, where the AC voltage is slowly increased to construct the AC islanded grid. The AC voltage of the AC islanded grid is rectified by the rectifier unit 26 and supplied via the DC connection terminal DCA. The DC connection terminal DCA may have one or more connection points, at which corresponding voltmeters 28, 30 can be arranged.

[0040] By slowly increasing the voltage of the AC islanded grid, a DC connection unit, such as at least one DC load 14, can be operated at the DC connection point. This DC connection unit should also be pre-charged and / or boosted, for example, with a slowly increasing voltage. This is particularly advantageous when connecting a DC load 14 with one or more electrolytic cells. The DC load 14 with electrolytic cells can be slowly pre-charged and / or boosted by the power supply unit 10.

[0041] If power is no longer transmitted to the DC connection terminal DCA via the AC islanded grid, the pre-charging process is complete, and the power supply unit 10 can switch to the operating mode, in which the power supply unit 10 transmits electrical power between the AC connection terminal ACA and the DC connection terminal DCA.

[0042] Therefore, by disconnecting switch S1 and connecting switches S4 and S5, the first power converter 22 and the second power converter 24 can be connected to the DC connection terminal DCA on the DC side, respectively. By disconnecting switch S2, the rectifier unit 26 can be disconnected from the second power converter 24 on the AC side. By connecting switch S3, the second power converter 24 can be connected to the AC connection terminal ACA on the AC side. The first power converter 22 and the second power converter 24 can now operate as rectifiers respectively and are used to supply electrical power from the AC grid 12 to the DC load 14. The typical rated power of the first power converter 22 and / or the second power converter 24 can be between 2MW and 10MW, for example, 6MW.

[0043] When applied to a three-phase AC power grid, the first and second power converters can be specifically designed as three-phase inverters, and the rectifier unit can be designed, for example, as an uncontrolled three-phase rectifier bridge B6U.

[0044] Figure 1The switches S1, S2, S3, S4, and S5 of the power supply unit 10 can be controlled by the control unit 20. The first power converter 22 and the second power converter 24 can also be controlled by the control unit 20 and / or by their respective additional control units, which can be arranged, for example, in the respective power converters 22 and 24.

[0045] Figure 2 A second embodiment of the electrical power supply unit 10 is schematically shown. (Compared to...) Figure 1 compared to, Figure 2 The DC connection terminal DCA of the power supply unit 10 also has an additional connection point.

[0046] An additional DC connection unit, designed as a separate unit 16, is connected at the additional connection point. The additional unit 16 may, for example, have a capacitor that can be pre-charged via the DC connection terminal DCA. Alternatively, the additional unit 16 may also be one or more power converters, electrolyzers, or fuel cells, whose respective DC intermediate circuit capacitors can be pre-charged via the DC connection terminal DCA.

[0047] Here, as a reference Figure 1 As described, the pre-charging of the DC connection units 14, 16 connected to the DC connection terminal takes place during the phase of building an AC islanded power grid via the second power converter 24.

[0048] The pre-charging of the first power converter 22 and the second power converter 24 can be referenced as follows. Figure 1 The first embodiment is carried out in the manner described.

[0049] After pre-charging the DC connection unit (in the example shown, the DC load and another unit 16), it can be done as described in the reference. Figure 1 In the manner described, electrical power is supplied from the AC grid 12 to the DC load via the first power converter 22 and the second power converter 24 of the power supply unit 10.

[0050] In the same embodiment, when applied to a three-phase AC grid, the first power converter and the second power converter can be specifically designed as three-phase inverters, and the rectifier unit can be designed, for example, as an uncontrolled three-phase rectifier bridge B6U. Figure 2 The switches S1, S2, S3, S4, and S5 of the power supply unit 10 can also be controlled by the control unit 20. The first power converter 22 and the second power converter 24 can also be controlled by the control unit and / or their respective additional control units, which can be arranged, for example, in the respective power converters 22 and 24.

[0051] Figure 3A third embodiment of the electrical power supply unit 10 is schematically shown in the diagram. (As in...) Figure 2 In this embodiment, an additional unit 16 is connected at the connection point of the DC connection terminal DCA. As described, the additional DC unit 16 may also be, for example, one or more power converters, whose respective DC intermediate circuit capacitors can be pre-charged via the DC connection terminal DCA. The pre-charging of the first power converter 22 and the second power converter 24 can be as described in reference... Figure 1 or Figure 2 The first or second embodiment is carried out in the manner described.

[0052] In this embodiment, during the phase of constructing the AC islanded grid via the second power converter 24, additional units are specifically pre-charged. At least one DC source, such as a photovoltaic generator, is connected to an additional connection point 15. During the phase of constructing the AC islanded grid, the additional unit 16 can be pre-charged via the power supply unit 10. If a DC source requires pre-charging, it can also be pre-charged via the DC connection terminal DCA.

[0053] If power is no longer transmitted to the DC connection terminal DCA via the AC islanded grid, the pre-charging process is complete, and the power supply unit 10 can switch to the operating mode, in which the power supply unit 10 transmits electrical power between the AC connection terminal ACA and the DC connection terminal DCA.

[0054] Therefore, by disconnecting switch S1 and connecting switches S4 and S5, the first power converter 22 and the second power converter 24 can be connected to the DC connection terminal DCA on the DC side, respectively. By disconnecting switch S2, the rectifier unit 26 can be disconnected from the second power converter 24 on the AC side. By connecting switch S3, the second power converter 24 can be connected to the AC connection terminal ACA on the AC side. The first power converter 22 and the second power converter 24 can now operate as inverters, and the DC source can feed electrical power to the AC grid 12 via the first power converter 22 and the second power converter 24 of the power supply unit 10.

[0055] In this embodiment, the first power converter and the second power converter can also be designed for use with an AC power grid, and for example have an uncontrolled three-phase rectifier bridge B6U. Figure 3 The switches S1, S2, S3, S4, and S5 of the power supply unit 10 can also be controlled by the control unit 20. The first power converter 22 and the second power converter 24 can also be controlled by the control unit 20 and / or their respective additional control units, which can be arranged, for example, in the respective power converters 22 and 24.

[0056] A DC connection unit may also exist, which can function as both a DC load 14 and a DC source 15. For example, a rechargeable battery can be mentioned here, which acts as a DC load 14 when charging and as a DC source 15 when discharging, i.e., outputting DC power.

[0057] One or more DC loads 14, one or more DC sources 15, and / or one or more additional units 16 can be connected to the DC connection terminal DCA, respectively. In this case, the power supply unit can pre-charge the corresponding AC connection unit by constructing an AC islanded grid. Depending on the operating mode, power can then be fed to the AC grid 12 via the power supply unit 10, or power can be supplied from the AC grid to the DC connection terminal DCA via the power supply unit 10. Switching between operating modes is possible. Switching between operating modes can be accomplished, for example, by the control unit 20.

[0058] Figure 4 A method for starting the electrical power supply unit 10 is schematically shown.

[0059] In step 200 of the startup method, switches S2, S3, S4, and S5 are disconnected. Switch S1 is connected.

[0060] In step 201, if the DC-side output voltage of the first power converter 22 is zero, meaning the first DC intermediate circuit and the second DC intermediate circuit have been discharged, then pre-charging of the first power converter 22 and the second power converter 24 is initiated via the AC pre-charging circuit 18. After pre-charging is completed, the DC-side output voltages of the first power converter 22 and the second power converter 24 correspond to the DC voltage of the first DC intermediate circuit.

[0061] In step 203, when the DC voltage of the second rectifier 24 corresponds to the rated voltage, the pre-charging of the first power converter 22 and the second power converter 24 is terminated.

[0062] In step 204, after the pre-charging is completed in step 203, switch S2 is turned on, and the second power converter 24 begins to operate as an inverter, building an AC islanded grid on its AC side. During the construction of the islanded grid, electrical power can be transferred to the DC connection terminal via rectifier unit 26. This electrical power can be used to pre-charge the DC connection unit connected to the DC connection terminal.

[0063] In step 205, it is checked whether the power transfer from the AC islanded grid and rectifier unit 26 to the DC connection terminal DCA has ended.

[0064] If so, then disconnect switch S2 in step 206.

[0065] In step 207, it is checked whether the second power converter 24 needs to transmit power through the power supply unit 10.

[0066] If the result of the check in step 207 is "yes", then in step 208, switch S1 is disconnected and the second power converter 24 is synchronized on the DC side to the voltage measured using voltmeter 30.

[0067] In step 209, it is checked whether the DC voltage at the second power converter 24 corresponds to the voltage measured using voltmeter 30.

[0068] If so, in step 210, switch S4 is turned on and the operation of the second power converter 24 is stopped.

[0069] In step 211, it is checked whether the second power converter 24 has stopped.

[0070] If so, switch S3 is turned on in step 212, and the second power converter 24 is started in the desired power converter mode.

[0071] If the result of the check in step 207 is "no", then in step 213, the operation of the second power converter 24 is stopped and the switch S1 is turned off.

[0072] After step 212 or after step 213, in step 214 it is checked whether the first power converter 22 needs to transmit power via the power supply unit 10.

[0073] If the result of the check in step 214 is "yes", then in step 215, the first power converter 22 is synchronized on the DC side to the voltage measured using voltmeter 28.

[0074] In step 216, it is checked whether the DC voltage at the first power converter 22 corresponds to the voltage measured using voltmeter 28.

[0075] If so, switch S5 is turned on in step 217, and the first power converter 22 is started in the desired power converter mode.

[0076] If the result of the check in step 216 is "no", then the operation of the first power converter 22 is stopped in step 218.

[0077] In step 219, the power supply unit 10 is used to transmit electrical power between the DC connection terminal DCA and the AC connection terminal ACA.

[0078] In step 220, it is checked whether there is a command to stop the power supply unit 10.

[0079] If so, then in step 221, the operation of the first power converter 22 and the second power converter 24 is stopped.

[0080] Figure 5 A fourth embodiment of the electrical power supply unit 10 is schematically shown. At least one DC load 14, such as at least one electrolytic cell, is connected to the DC connection terminal DCA. In this embodiment, the rectifier unit 26 has an active rectifier with a switched bridge circuit. In this embodiment, the rectifier unit 26 may also optionally operate as an inverter.

[0081] The pre-charging of the first power converter 22 and the second power converter 24 can be referenced as follows. Figure 1 , Figure 2 or Figure 3 The first, second, or third embodiment is carried out in the manner described, or according to the reference. Figure 4 The method described is used.

[0082] During the phase in which the DC load 14 connected to the DC connection terminal DCA is pre-charged by the AC islanded power grid constructed by the second power converter 24, the switching rectifier of the rectifier unit 26 is used as a rectifier to rectify the AC power for the DC connection terminal DCA.

[0083] Then, if power is no longer transmitted to the DC connection terminal DCA via the AC islanded grid, the pre-charging process is complete, and the power supply unit 10 can switch to the operating mode, in which the power supply unit 10 transmits electrical power between the AC connection terminal ACA and the DC connection terminal DCA. In the fourth embodiment shown, in addition to the first power converter 22 and the second power converter 24, this power transmission can also optionally be performed via the switching rectifier of the rectifier unit 26.

[0084] Therefore, by disconnecting switch S1 and connecting switches S4, S5, and S6, the first power converter 22, the second power converter 24, and the rectifier unit 26 can be connected to the DC connection terminal DCA on the DC side. By disconnecting switch S2, the rectifier unit 26 can be disconnected from the second power converter 24 on the AC side. By connecting switch S8, the first power converter 22 can be connected to the AC connection terminal ACA on the AC side. By connecting switch S3, the second power converter 24 can be connected to the AC connection terminal ACA on the AC side. By connecting switch S7, the rectifier unit 26 can be connected to the AC connection terminal ACA on the AC side. The first power converter 22, the second power converter 24, and the rectifier unit 26 can now operate as rectifiers, and can supply electrical power from the AC grid 12 to the DC load via the first power converter 22, the second power converter 24, and the rectifier unit 26 of the power supply unit 10. Here, the power supply unit 10 can flexibly use the first power converter 22, the second power converter 24, and / or the rectifier unit 26 for power transmission.

[0085] Figure 6 An electrical power supply unit 10 with an additional unit 16 is schematically shown. The power supply unit 10 shown is similar to... Figure 5 The power supply unit shown is similar.

[0086] The additional unit 16 is connected to another connection point of the DC connection terminal DCA. In this example, the additional unit 16 is configured for power transfer between the AC and DC sides. For this purpose, the additional unit 16 has three power converters with switching bridge circuitry, which are configured for this power transfer. These power converters have their own DC intermediate circuitry, which can be pre-charged via the AC islanded grid of the power supply unit.

[0087] If switches S6, S4, S5, S9, and S10 are closed, the DC load 14 at the DC connection terminal DCA and / or the DC intermediate circuit of the other unit 16 can be pre-charged. If switch S11 is closed, the other DC load 14 connected at this switch can also be pre-charged through the AC islanded grid constructed by the second inverter 24 of the power supply unit 10.

[0088] Figure 7 An electrolytic power supply device 40 is schematically shown. The electrolytic power supply device 40 has one of the described power supply units 10, another unit 16, and a transformer 32. The AC connection terminal of the electrical power supply unit 10 is connected to an AC power grid 12 via the transformer 32. The AC power grid 12 is, for example, a three-phase AC power grid.

[0089] The electrolysis power supply unit 40 is configured to supply power to one or more DC loads 14 (e.g., electrolytic cells).

[0090] Power supply unit 10 can be started as described, wherein by turning on switches S10, S11, S12, and S13, an AC islanded power grid can be constructed, allowing power supply unit 10 to precharge the other unit 16 and DC load 14 via the DC connection terminal DCA of power supply unit 10. After precharging, both power supply unit 10 and the other unit 16 can supply DC power to DC load 14 from the AC power grid. For this purpose, switches S13, S10, and S11 are turned on and switch S12 is turned off.

[0091] The described electrolytic power supply device 40 can transmit electrical power in the MW range. Meanwhile, to precharge the power supply unit 10 and the DC load 14, the described AC precharge circuit 18 is sufficient. This makes an economical solution possible, as the component parameters of the AC precharge circuit 18 only need to be designed according to the first power converter 22 and the second power converter 24.

[0092] Reference tag list 10 Power Supply Units 12 AC power grid 14 DC loads 15 DC source 16 Other Units 18 AC pre-charge circuit 20 Control Units 22 Power Converter 24 Power Converter 26 Rectifier Units 28. Voltmeter 30 Voltmeter 32 Transformers S1-S13 switches ACA AC connection terminal DCA DC connection terminal Steps 200-221.

Claims

1. A method for starting an electrical power supply unit (10), the electrical power supply unit having a first power converter (22), a second power converter (24), and a rectifier unit (26), and configured to supply electrical energy from an AC power grid (12) to a DC connection terminal (DCA), wherein, At least one DC connection unit (14, 15, 16) is connected to the DC connection terminal (DCA) of the power supply unit (10), and the AC power grid (12) is connected to the AC connection terminal (ACA) of the power supply unit (10), wherein the method includes: The first DC intermediate circuit of the first power converter (22) and the second DC intermediate circuit of the second power converter (24) are precharged from the AC grid (12) via the AC precharge circuit (18). An AC islanded grid is constructed via the second power converter (24), wherein, during the construction of the AC islanded grid, electrical energy is supplied from the AC islanded grid to the DC connection terminal (DCA) via the rectifier unit (26).

2. The method according to claim 1, wherein, Before precharging the first DC intermediate circuit, the DC side of the first power converter (22) is connected to the DC side of the second power converter (24).

3. The method according to claim 1 or 2, wherein, After precharging the second intermediate circuit, the AC side of the second power converter (24) is connected to the AC side of the rectifier unit (26).

4. The method according to any one of the preceding claims, wherein, During the construction of the AC islanded power grid, the AC voltage is regulated and gradually increased by the second power converter (24) on its AC side.

5. The method according to any one of the preceding claims, wherein, During the construction of the AC islanded power grid, the second power converter (24) is supplied with electrical energy on the DC side by the first power converter (22).

6. The method according to any one of the preceding claims, wherein, During the construction of the AC islanded power grid, the at least one DC connection unit (14, 16) is precharged via the DC connection terminal (DCA).

7. The method according to any one of the preceding claims, wherein, After the AC islanded grid is constructed, the first power converter (22) is connected to the DC connection terminal (DCA) on the DC side to supply power from the AC grid (12) to the DC connection terminal (DCA).

8. The method according to any one of the preceding claims, wherein, After the AC islanded grid is constructed, the second power converter (24) is connected to the DC connection terminal (DCA) on the DC side and to the AC connection terminal (ACA) on the AC side for supplying electrical energy from the AC grid (12) to the DC connection terminal (DCA).

9. The method according to any one of the preceding claims, wherein, The rectifier unit (26) includes a passive rectifier and / or a switching AC / DC converter.

10. The method according to claim 9, wherein, After the islanded power grid is constructed, the switching AC / DC converter of the rectifier unit (26) is connected to the AC connection terminal (ACA) on the AC side and to the DC connection terminal (DCA) on the DC side for supplying power from the AC power grid (12) to the DC connection terminal (DCA).

11. The method according to any one of claims 7 to 10, wherein, After the islanded power grid is constructed, electrical energy is supplied from the AC grid (12) to the at least one DC connection unit (14) and / or at least one additional DC connection unit (14) via the DC connection terminal (DCA), wherein the electrical energy is supplied via the first power converter (22), the second power converter (24) and / or the switching AC / DC converter.

12. The method according to any one of the preceding claims, wherein, The at least one DC connection unit (14) is designed as an electrolyzer that is precharged via the DC connection terminal (DCA) during the construction of the AC islanded power grid.

13. The method according to any one of the preceding claims, wherein, After the AC islanded power grid is constructed, at least one DC connection unit (16) of the electrical power supply unit (10) is connected in parallel to supply power from the AC power grid (12) to the DC connection terminal (DCA).

14. An electrical power supply unit (10) having a first power converter (22), a second power converter (24), and a rectifier unit (26), and configured to supply electrical energy from an AC power grid (12) to a DC connection terminal (DCA), wherein, At least one DC connection unit (14, 15, 16) is capable of being connected to the DC connection terminal (DCA) of the electrical power supply unit (10), and the AC power grid (12) is capable of being connected to the AC connection terminal (ACA) of the electrical power supply unit (10), wherein the power supply unit (10) is configured as follows: The first DC intermediate circuit of the first power converter (22) and the second DC intermediate circuit of the second power converter (24) are precharged from the AC grid (12) via the AC precharge circuit (18). An AC islanded grid is constructed using the second power converter (24), wherein, during the construction of the AC islanded grid, electrical energy can be supplied from the AC islanded grid to the DC connection terminal (DCA) via the rectifier unit (26).

15. The electrical power supply unit according to claim 14, wherein, During the pre-charging process of the first DC intermediate circuit and the second DC intermediate circuit, the first power converter (22) is connected to the AC connection terminal (ACA) on the AC side and disconnected from the DC connection terminal (DCA) on the DC side.

16. The electrical power supply unit according to claim 14 or 15, wherein, During the pre-charging process of the first DC intermediate circuit and the second DC intermediate circuit, the second power converter (24) is separated from the AC connection terminal (ACA) on the AC side and connected to the DC side of the first power converter (22) on the DC side, wherein the DC side of the first power converter (22) and the second power converter (24) is separated from the DC connection terminal (DCA) during the pre-charging process of the first DC intermediate circuit and the second DC intermediate circuit.

17. The electrical power supply unit according to any one of claims 14 to 16, wherein, The first power converter (22) and / or the second power converter (24) are connected to the AC connection terminal (ACA) on the AC side and to the DC connection terminal (DCA) on the DC side for supplying electrical energy from the AC grid (12) to the DC connection terminal (DCA).

18. The electrical power supply unit according to any one of claims 14 to 17, wherein, The rectifier unit (26) includes a passive rectifier and / or a switching AC / DC converter.

19. The electrical power supply unit according to any one of claims 14 to 18, wherein, The at least one DC connection unit (14) is designed as an electrolyzer that can be pre-charged via the DC connection terminal (DCA) during the construction of the AC islanded power grid.

20. The electrical power supply unit according to any one of claims 14 to 19, wherein, Electrical energy can be fed from the DC connection terminal to the AC power grid (12) that can be connected to the AC connection terminal via the electrical power supply unit.

21. An electrolytic power supply device (40) having an electrical power supply unit (10) according to any one of claims 14 to 20.

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