Method of supplying power to a dc load, energy conversion system and electrolysis system

Abstract

The present application describes a method for powering a DC load (30) by means of an energy conversion system (1) having a first rectifier (2.1), a second rectifier (2.2) and a transformer unit (21), wherein each rectifier (2.1, 2.2) comprises an AC / DC converter (10) and is connected to a common AC voltage (AC) grid (20) by a separate secondary side (24.1, 24.2) of the transformer unit (21), wherein the transformer unit (21) is arranged to provide a first AC voltage having a first voltage amplitude at the first secondary side (24.1) and a second AC voltage having a second voltage amplitude at the second secondary side (24.2), wherein the value of the second voltage amplitude exceeds the corresponding value of the first voltage amplitude. The method comprises the following method steps: i) if the input voltage U DC,Last at the input (32) of the DC load (30) falls below a voltage threshold U TH : operating the first rectifier (2.1) with a first power flow P1 that is non-zero to power the DC load (30), wherein the second power flow P2 through the second rectifier (2.2) is suppressed (P2 = 0), and ii) if the input voltage U DC,Last at the input (32) of the DC load (30) reaches or exceeds the voltage threshold U TH : operating the second rectifier (2.2) with a second power flow P2 that is non-zero to power the DC load. The present application also discloses an energy conversion system for implementing the method and an electrolysis system.

Description

[0001] Technical Field of the Invention

[0002] This invention relates to a method for supplying power from an alternating current (AC) grid to a DC load using an energy conversion system comprising a transformer unit and two rectifiers. The invention also relates to an energy conversion system comprising two rectifiers designed to supply power from an AC grid to a DC load, and an electrolytic system having such an energy conversion system and an electrolytic device as the DC load. Existing technology

[0003] It is known in principle that power is supplied to a DC load with high power consumption through multiple energy sources and / or multiple energy conversion units connected in parallel. For example, an electrolysis unit with a rated power in the range of one to two MW can be powered by an AC power grid through multiple rectifiers. Here, the productivity of the electrolytic products is controlled by the level of the input voltage of the electrolysis unit, thereby controlling the power consumption of the electrolysis unit, where power consumption typically increases with increasing input voltage.

[0004] Traditional electrolysis equipment has an input voltage specific to its operating range, which is limited downward by a minimum input voltage U. min The limitations, and the maximum input voltage U acting upwards. max Limitations. Input voltage U min The minimum value is based on the fact that, in the relevant electrolysis device, only when the input voltage is higher than U min Electrolysis only occurs when the input voltage U... max The maximum value represents the maximum permissible power of the electrolysis device, and this maximum value should not be exceeded, at least not for extended periods. In principle, it is permissible to exceed the input voltage by U... min and U max Any value within the defined operating range. Here, it is desirable to be able to adjust the electrolysis process as steplessly as possible throughout the entire device-specific operating range. However, it must be considered that the initial operating range of the electrolysis unit in its new state may change during its operation (e.g., due to degradation processes). Specifically, for example, the initial operating range may generally shift towards a larger input voltage. Furthermore, it is desirable for the electrolysis process to be as efficient as possible relative to the electrical energy used. Therefore, the corresponding input voltage should be set with the lowest possible conversion losses throughout the entire operating range of the electrolysis unit. Of course, the operation of the electrolysis method and the energy conversion system itself should be as inexpensive as possible.

[0005] Specifically, the single-stage rectifier discussed here can be an actively controllable single-stage rectifier having a bridge circuit including transistors and freewheeling diodes. In the case of such a bridge circuit in the rectifier, the DC voltage U across the freewheeling diode at the output of the bridge circuit in the rectifier... DC It has a lower limit. Specifically, the DC voltage U allocated to the output of the AC / DC converter of the rectifier. DC It must not fall below a specific minimum value. This minimum value depends on the magnitude of the AC voltage at the input of the AC / DC converter. However, on the other hand, the DC voltage U at the output side of the AC / DC converter DC It can always be increased relative to a minimum value, for example, by the appropriate clock of the semiconductor switches in an AC / DC converter. However, when the DC voltage U DC When increasing, the DC voltage U generated on the output side must be taken into account. DC The amplitude relative to the input AC voltage As the ratio increases, the conversion loss also increases.

[0006] If two single-stage rectifiers are connected to the AC grid on the input side via a common transformer, and connected in parallel to each other on the output side to the input of a DC load, then the transformer is designed to ensure that the DC voltage U generated at the output side of the AC / DC converter... DC The minimum value does not exceed the minimum input voltage U of the electrolysis device. min Otherwise, an input voltage range for the DC load that cannot be regulated by a single-stage rectifier will be generated. When the rectifier is connected to a DC load, it can lead to high turn-on current (Einschaltstrom). Problems also arise if the rectifier is disconnected from the DC load, as disconnection is only necessary under high current conditions, increasing the demand for a disconnect unit between the rectifier and the DC load. However, if the DC voltage U at the output of the AC / DC converter supplied to the rectifier... DC The minimum value is less than or equal to the minimum input voltage U of the DC load. min During the operation of an electrolysis unit, non-negligible conversion losses occur, especially when power consumption is high, i.e., the consumption is large and therefore the input voltage of the DC load is high. Furthermore, these conversion losses (e.g., due to degradation processes) increase with the lifespan of the electrolysis unit.

[0007] An electrolysis system with multiple electrolysis units is known from document GB 778,989 A. Each electrolysis unit is powered from a single set of secondary windings of a transformer through its own multiphase rectifier. The transformer also has primary windings connected in star and delta configurations. The secondary windings can be three-phase or four-phase, with phase shifts relative to each other.

[0008] Document DE 10 2014 014091 A1 discloses a method for operating an electrolysis apparatus, wherein the electrolysis apparatus is powered by a rectified, particularly three-phase, AC voltage. Here, the voltage applied to the electrolysis apparatus is set by means of a voltage controller that is at least partially decoupled from the rectifier.

[0009] Document GB 2 238 635 B discloses a current source designed to provide a constant DC output voltage, wherein the current source is powered by an AC input voltage within an AC voltage input range. The current source includes a transformer that provides multiple outputs of different voltages, each proportional to the input voltage. Each output is rectified and connected in series to a capacitor-free voltage regulator. The output of each voltage regulator is connected to a common output terminal that provides a constant DC voltage.

[0010] Document EP 2228894 A1 describes a rectifier comprising a rectifier circuit for providing a rectified intermediate voltage from multiple phase voltages of a multiphase system and a DC-DC voltage converter circuit for generating a predetermined output voltage from the intermediate voltage. Here, the DC-DC voltage converter circuit is designed to provide three different converter voltages according to switching states, and to output an output voltage by sequentially selecting at least two of the three converter voltages according to clock operation.

[0011] Document EP 3379679 A1 discloses an energy supply system for grid feeding and grid reverse feeding, comprising a voltage conversion device, an active reverse-feeding rectifier, and a commutating rectifier. The voltage conversion device is electrically connected to an AC voltage grid and to the active reverse-feeding rectifier and / or the commutating rectifier. Here, the active reverse-feeding rectifier is electrically connected to the AC voltage grid on its input side, resulting in a first AC voltage during operation, while the commutating rectifier is electrically connected to the AC voltage grid on its input side, resulting in a second AC voltage during operation. On the output side, the active reverse-feeding rectifier and the commutating rectifier are respectively electrically connected to a DC voltage grid. The voltage conversion device is designed such that the first AC voltage is less than the second AC voltage during operation.

[0012] Invention Task

[0013] The objective of this invention is to describe a method for supplying power to a DC load using an energy conversion system connected to an AC grid at its input side and having at least two rectifiers, particularly single-stage rectifiers, wherein the power consumption of the DC load can be steplessly regulated across the entire operating range of the input voltage allocated to the DC load by means of the input voltage at the DC load. Here, on the one hand, voltage ranges that the input voltage cannot reach should be avoided, but at the same time, high power consumption of the DC load should be achieved with the highest possible efficiency (i.e., the conversion losses of the energy conversion system should be as low as possible). Another objective of this invention is to demonstrate an energy conversion system suitable for implementing this method, and an electrolytic system having such an energy conversion system.

[0014] Solution

[0015] According to the invention, the task of demonstrating a method of the type described at the outset is solved by the features of independent claim 1. According to the invention, the task of demonstrating an energy conversion system for performing the method according to the invention is solved by the features of independent claim 9. The task of demonstrating an electrolysis system having such an energy conversion system is solved by the features of independent claim 16. Advantageous embodiments of the method are described in claims 2 to 8, while advantageous embodiments of the energy conversion system are described in claims 10 to 15.

[0016] Invention Description

[0017] The method according to the invention aims to supply power to a DC load by means of an energy conversion system, wherein the energy conversion system includes a first rectifier, a second rectifier, and a transformer unit. Each rectifier contains an AC / DC converter and is connected to a common AC power grid via a separate secondary side of the transformer unit. The transformer unit is configured to provide a first voltage amplitude on the primary secondary side. The first AC voltage, and a second voltage amplitude is provided on the second stage side. The second AC voltage. Here, the amplitude of the second voltage. The value exceeds the first voltage amplitude The corresponding value. This method includes the following steps:

[0018] i) If the input voltage U at the input terminal of the DC load DC,Last Drops below voltage threshold U TH The first rectifier operates with a non-zero first power flow P1 to supply power to the DC load, wherein the second power flow P2 through the second rectifier is suppressed (P2 = 0), and

[0019] ii) If the input voltage U at the input terminal of the DC load DC,Last Reaching or exceeding the voltage threshold U TH The second rectifier operates with a non-zero second power flow P2 to supply power to the DC load.

[0020] The energy conversion system has two rectifiers connected to two separate secondary sides of a transformer unit. This should be understood as the energy conversion system comprising at least two rectifiers, each connected to one of at least two secondary sides of the transformer unit. Therefore, according to the invention, the energy conversion system may also include more than two rectifiers and the transformer unit may also include more than two secondary sides, provided that each rectifier is connected to a different secondary side. Each of the two rectifiers can be designed as a so-called single-stage rectifier. Within the scope of the invention, a single-stage rectifier should be understood as one that does not have a DC / DC converter connected downstream of the AC / DC converter. Conversely, a rectifier having a DC / DC converter connected downstream of the AC / DC converter should be understood within the scope of the invention as a multi-stage or two-stage rectifier. Furthermore, each rectifier can be designed as an active controlled rectifier having a bridge circuit including transistors. Here, the transistors can be IGBT (Insulated Gate Bipolar Transistor) or MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) type transistors. In a bridge circuit, each transistor can have a freewheeling diode connected in parallel to the power supply terminal of the corresponding transistor. The freewheeling diode can be an inherent freewheeling diode of the corresponding transistor or a separate diode relative to the corresponding transistor. Unless otherwise stated, in this application, each power flow P1, P2 flowing from the AC grid to the DC load is described or considered a positive power flow. Correspondingly, each power flow P1, P2 flowing from the DC load to the AC grid is described or considered a negative power flow. In this sense, particularly in method step i), the first rectifier for supplying power to the DC load operates with a positive first power flow P1 (P1>0). Furthermore, particularly in method step ii), the second rectifier for supplying power to the DC load operates with a positive second power flow P2 (P2>0).

[0021] This invention utilizes the effect of a transformer unit having at least two separate secondary sides, where each secondary side has a different conversion ratio relative to the primary side of the transformer unit to which it is assigned. The AC voltage from the AC grid is converted into AC voltages of different amplitudes through the two different secondary sides. Specifically, the conversion is performed such that a voltage with a first amplitude is generated on the primary side. The AC voltage, and generates a second amplitude on the second stage side. AC voltage, second amplitude Greater than the first amplitude Each of the two AC voltages is used as the input voltage for one of the two rectifiers. It has a first amplitude. The AC voltage is fed as the input voltage to the first rectifier, while having a second amplitude The AC voltage is fed as the input voltage to the second rectifier. The two different AC voltages result in different minimum DC voltage values ​​at the output of the corresponding AC / DC converters. If the rectifier is designed as a single-stage rectifier, i.e., if no DC / DC converter is connected downstream of the AC / DC converter in each rectifier, then the DC voltage at the output of the AC / DC converter also corresponds to the output voltage of the corresponding rectifier.

[0022] The energy conversion system operates as follows: if the input voltage U at the input terminal of the DC load... DC,Last Drop below threshold U TH Then the DC load is powered only by the first power flow P1 through the first rectifier. Conversely, the second power flow P2 through the second rectifier is suppressed. Only when the input voltage U at the input terminal of the DC load is... DC,Last Corresponding to threshold U TH Or exceeding the threshold U TH Only when the second power flow P2, which is non-zero, is activated through the second rectifier, can it contribute to supplying power to the DC load. Here, when the second power flow P2 through the second rectifier is activated, the first power flow P1 can be either suppressed or enabled. This means that when the voltage at the input of the DC load is greater than or equal to the threshold U... TH At the same time, the DC load can be powered by the second power stream P2 alone, but it can also be powered by a combination of the first power stream P1 and the second power stream P2.

[0023] The entire operating range of the DC load is controlled by the voltage threshold U. TH The system is divided into two ranges, upper and lower. In the lower range, the DC load consumption is typically still very low, and therefore can be covered solely by the first power flow P1 of the first rectifier. Here, the first amplitude of the AC voltage on the first stage side is selected. This allows each voltage value within the lower range of the operating range allocated to the DC load to be achieved by the first rectifier. Therefore, the first rectifier ensures that the DC load is steplessly regulated to the minimum input voltage U allocated to the DC load. min Because the second rectifier has a relative amplitude compared to the first rectifier. Higher second amplitude The AC voltage, therefore, within the upper range of the operating range allocated to the DC load, the input voltage U of the DC load of the second rectifier. DC,Last The ratio is less than the input voltage U of the DC load of the first rectifier. DC,LastTherefore, when there is a second power flow P2, the conversion loss of the second rectifier is also lower than that of the first rectifier, resulting in higher operating efficiency of the second rectifier. Thus, the high power consumption of the DC load can be achieved with the highest possible efficiency overall over the above range by means of the second rectifier, resulting in very low conversion losses. The conversion losses are at least lower when the value of the first amplitude corresponds to the value of the second amplitude. Furthermore, different conversion ratios between the two secondary sides relative to the primary side allocated to the respective secondary sides can be achieved effortlessly and at low cost. Advantageous improvements of the invention are described in detail in the following description and dependent claims, and their features can be used individually and in any combination with each other.

[0024] Rectifiers typically have an AC disconnect unit allocated to the input of the rectifier for disconnecting or connecting the input of the AC / DC converter to the AC power grid. Furthermore, rectifiers usually also have a DC disconnect unit arranged between the output of the AC / DC converter and the output of the rectifier and / or the input of the DC load. Therefore, the open AC disconnect unit between the second stage side of the transformer unit and the AC / DC converter of the second rectifier can easily suppress the second power flow P2 through the second rectifier. Alternatively or supplementarily, suppression can also be achieved by a DC disconnect unit arranged between the AC / DC converter of the second rectifier and the input of the DC load. This similarly applies to the suppression of the first power flow P1 through the first rectifier, in which case suppression is achieved by means of the AC disconnect unit and / or DC disconnect unit allocated to the first rectifier.

[0025] DC loads can have a monotonically increasing, especially strictly monotonically increasing, power-voltage (PU) characteristic curve, meaning that the power consumption of a DC load increases as its input voltage increases. To adequately power the load through two rectifiers in this case, the total power flow from the AC grid to the DC load through the two rectifiers increases as the input voltage of the DC load increases. The total power flow from the AC grid to the DC load through the two rectifiers is the sum of the first power flow P1 through the first rectifier and the second power flow P2 through the second rectifier. In the case of a single-stage rectifier connected to the DC load current, the input voltage of the DC load also corresponds to the DC voltage distributed at the output of the AC / DC converter of the corresponding rectifier. If now we want to supply power from below the voltage threshold U... THIf the input voltage of the DC load begins to increase the power consumption of the DC load, then method steps i) and ii) can be executed sequentially, such that method step ii) follows method step i) in time. Conversely, if the power consumption of the DC load is to be reduced over time, method steps i) and ii) can also be executed sequentially in the method, such that method step i) follows method step ii) in time. In one embodiment of this method, method steps i) and ii) can be repeated in time. In this case, by repeatedly checking the input voltage U in time... DC,Last Relative to voltage threshold U TH The relationship can be tracked to track changes in DC load consumption and responded to by means of a control unit. Alternatively or supplementarily, a predetermined consumption-time curve for the DC load can be set or run by means of a control unit by repeatedly performing method steps i) and ii) over time.

[0026] Advantageously, this method can be used as part of a startup process for supplying power to a DC load using an energy conversion system. In this case, in the initial state of the startup process, the first power flow P1 and the second power flow P2 of the energy conversion system are suppressed, for example, by the open DC separation unit of the two rectifiers. Due to the first amplitude Second amplitude Because the values ​​of the two voltages are different, and because current flows through the freewheeling diodes of the AC / DC converters, different DC voltages U will initially be set at the output terminals of the two AC / DC converters. DC,1 U DC,2 During startup, because the DC voltage at the output of the AC / DC converter allocated to the first rectifier does not exceed the minimum input voltage U of the DC load. min Therefore, the first rectifier can now be switched on without load, or at least almost without load, from the DC load by closing the DC disconnection unit of the first rectifier. Alternatively or supplementarily, this method can also be used as part of a shutdown process during power supply to the DC load via the energy conversion system. Here, the power supply system should advantageously be disconnected from the DC load without load. Here, starting from the state where the DC load is powered only by the first power flow P1, the input voltage U of the DC load... DC,Last Minimum input voltage U that drops to the DC load min Therefore, the power consumption of the DC load, and consequently the first power flow P1, is reduced to almost 0W. Thus, at the end of the turn-off process, both the first power flow P1 and the second power flow P2 are suppressed. Here, the first rectifier can be essentially disconnected from the DC load without load and current, which is why DC disconnection units (and possibly AC disconnection units) can be designed relatively simply and at low cost.

[0027] In an implementation of this method, in step ii), to supply power to the DC load, the ratio of the first power flow P1 to the second power flow P2, based on P1 / P2, is minimized as much as possible, and if necessary, is 0, so that the efficiency of the AC / DC conversion is optimized. Here, the ratio of the first power flow P1 to the second power flow P2 can be further reduced as long as the power consumption of the DC load does not exceed the rated power of the second rectifier. By selecting a value for the second power flow P2 that is larger than the value of the first power flow P1 in step ii), the conversion losses of the energy conversion system related to the power supply to the DC load can be further minimized, because the efficiency of the second rectifier is higher than that of the first rectifier when the input voltage of the DC load is large.

[0028] The energy conversion system according to the present invention for supplying power from an alternating current (AC) grid to a DC load comprises:

[0029] - A transformer unit, which can be connected to an AC power grid on its primary side, and is configured to provide a voltage amplitude of a first voltage on the primary side of the transformer unit. The first AC voltage is provided on the second stage side, and a second voltage amplitude is provided on the second stage side. The second AC voltage, wherein the second voltage amplitude The value exceeds the first voltage amplitude The corresponding value,

[0030] - The first and second rectifiers are connected to one of the two secondary sides of the transformer unit on their input sides, respectively, and can be connected in parallel with each other on their output sides to the input of the DC load.

[0031] - A control unit for controlling an energy conversion system. The energy conversion system is characterized in that the control unit, optionally in conjunction with other components of the energy conversion system, is designed and configured to perform the method according to the invention. This achieves the advantages already mentioned in the method.

[0032] According to the implementation of the energy conversion system, the transformer unit may include at least two separate transformers, wherein the first transformer includes a first primary side and a first primary side inductively coupled thereto, and wherein the second transformer includes a second primary side different from the first primary side and a second primary side inductively coupled thereto. Alternatively, the transformer unit may have only one primary side, which is inductively coupled to both the first and second primary sides.

[0033] Advantageously, the transformer unit of the energy conversion system can have multiple taps for changing the amplitude of the first amplitude relative to the AC voltage of the AC grid. and / or second amplitude Specifically, when there is only one primary side that is inductively coupled to both the first and second primary sides of the transformer unit, the taps can preferably be arranged on that primary side. In embodiments where the transformer unit comprises two separate transformers, multiple taps can be arranged on at least one of the first and second primary sides. However, alternatively or additionally, these taps can also be arranged on at least one of the two secondary sides. and / or second amplitude The conversion ratio can be changed manually or automatically by means of a control unit by altering the currently selected tap. Multiple taps allow the conversion ratio and the corresponding AC voltage on the secondary side to be adapted to the drift of the DC load's input voltage over time.

[0034] Typically, a measuring unit is required in a rectifier for regulation during operation, and this measuring unit is used to detect the first DC voltage U at the output of the corresponding AC / DC converter. DC,1 Or the second DC voltage U DC,2 When the DC disconnect unit of the first rectifier is closed, the first DC voltage U distributed at the output terminal of the AC / DC converter of the first rectifier is... DC,1 This corresponds to the input voltage of the DC load. This also applies to the second DC voltage U distributed at the output of the AC / DC converter of the second rectifier when the DC disconnect unit of the second rectifier is closed. DC,2 However, when the DC splitter unit is on, it may be advantageous to detect the main DC voltage on each side of the rectifier's DC splitter unit. Therefore, in an advantageous embodiment, the energy conversion system may alternatively or supplementally have a measuring unit connected to the control unit for detecting the input voltage U at the input terminal of the DC load. DC,Last .

[0035] In principle, an energy conversion system may include two multi-stage rectifiers, with a DC / DC converter positioned between the AC / DC converter and the output of each rectifier. However, according to an advantageous embodiment of the energy conversion system, the first and / or second rectifiers may be designed as single-stage rectifiers. In this case, no DC / DC converter is positioned between the AC / DC converter and the output of the rectifier. Regardless of whether it is designed as a single-stage or multi-stage rectifier, the first and / or second rectifiers can be designed and configured for bidirectional power flow. By designing at least one of the two rectifiers for bidirectional power flow, the energy conversion system can provide grid services beneficial to the AC grid. For example, such grid services may include reactive power compensation for the AC grid.

[0036] The electrolysis system according to the invention comprises an energy conversion system according to the invention and an electrolysis device as a DC load. This combines the advantages already mentioned in the method and energy conversion system. Brief description of the attached diagram

[0038] The present invention will now be described with reference to the accompanying drawings, wherein:

[0039] Figure 1 An implementation of an energy conversion system is shown, which is connected to an AC power grid on the input side and to a DC load on the output side;

[0040] Figure 2 A flowchart of the method according to the present invention is shown in an embodiment.

[0041] Attached Figure Description

[0042] exist Figure 1 The diagram illustrates an embodiment of an energy conversion system 1 according to the present invention, which is connected to an alternating current (AC) power grid 20 at its input side and to the input terminal 32 of a DC load 30 at its output side. Here, the DC load 30 is exemplarily shown as an electrolysis device 31. The energy conversion system 1 includes a transformer unit 21, a first rectifier 2.1, a second rectifier 2.2, a control unit 15 for controlling the first rectifier 2.1 and the second rectifier 2.2, and a measuring unit 13 connected to the control unit 15 for control and data exchange. The measuring unit 13 is designed to measure the input voltage U at the input terminal 32 of the DC load 30. DC,Last Transformer unit 21 includes two separately formed transformers 22.1 and 22.2, each having a primary side 23.1 and 23.2 and a secondary side 24.1 and 24.2, respectively. The primary sides 23.1 and 23.2 of transformers 22.1 and 22.2 are connected in parallel to the AC power grid 20. The primary side 24.1 is connected to the AC input terminal 5 of the first rectifier 2.1, and the secondary side 24.2 is connected to the AC input terminal 5 of the second rectifier 2.2. Transformer unit 21 is designed to transmit voltages with amplitude through the corresponding turns ratio of the primary side 24.1 to the primary side 23.1. The multiphase AC voltage of the AC power grid 20 is converted into a voltage with a first amplitude at the primary stage side 24.1. The first AC voltage with the same number of phases. Accordingly, by adjusting the turns ratio of the second stage side 24.2 to the second primary side 23.2, the voltage with amplitude... The multiphase AC voltage of the AC power grid 20 is converted into a voltage with a second amplitude at the secondary stage side 24.2. And a second AC voltage with the same number of phases. Here, the second amplitude... The value exceeds the first amplitude The corresponding values ​​are specified. Each rectifier 2.1, 2.2 includes an AC disconnect unit 6, a filter unit 9, an AC / DC converter 10, an output capacitor 11 connected to the AC / DC converter on the output side, and a DC disconnect unit 12 between its AC input terminal 5 and its DC output terminal 3. The DC disconnect unit 12 is designed to connect and disconnect the output terminal of the AC / DC converter 10 from the DC output terminal 3 of the rectifiers 2.1, 2.2, thereby connecting and disconnecting from the input terminal 32 of the DC load 30. The AC disconnect unit 6 is designed to disconnect or connect the corresponding secondary sides 24.1, 24.2 of the rectifiers 2.1, 2.2 to the input terminals of the AC / DC converter 10 of the corresponding rectifiers 2.1, 2.2. Optionally, the AC disconnect unit 6 can also be designed to limit the current when the output capacitor 11 of the rectifiers 2.1, 2.2 is pre-charged. For this purpose, the AC separation unit 6 includes two parallel current paths, each with a switch 8, wherein a series resistor 7 is arranged in one of the two current paths to limit the current. For clarity, the reference numerals for the components of rectifiers 2.1 and 2.2 are shown in the figures. Figure 1 Only the first rectifier 2.1 is shown in the diagram.

[0043] In the following description, we assume a state where each rectifier 2.1, 2.2 is connected to its assigned secondary side 24.1, 24.2 via its closed AC disconnect unit 6, but the corresponding DC disconnect unit 12 remains open. Therefore, in this state, the first power flow P1 through the first rectifier 2.1 and the second power flow P2 through the second rectifier 2.2 are suppressed. However, in each rectifier 2.1, 2.2, the output capacitor 11 is charged to the corresponding DC voltage U by the current from the AC grid 20 and through the freewheeling diode of the corresponding AC / DC converter 10. DC,1 U DC,2 Here, the first DC voltage U of the first rectifier 2.1 DC,1 The value exceeds the second DC voltage U of the second rectifier 2.2. DC,2 The value is due to the difference in AC voltage at input terminal 5 of rectifiers 2.1 and 2.2, especially their amplitude. different.

[0044] Now, based on the power consumption of DC load 30 and the relevant input voltage U at its input terminal 32... DC,LastThe power flows P1 and P2 through the corresponding rectifiers 2.1 and 2.2 are suppressed or enabled. Specifically, during startup, the first power flow P1 through the first rectifier 2.1 is initially enabled by closing the DC disconnect unit of the first rectifier 2.1, while the second power flow P2 through the second rectifier 2.2 is initially suppressed. This is only when the input voltage U of the DC load 30... DC,Last When the power consumption of the DC load increases, especially when the input voltage U of the DC load 30 increases... DC,Last Reaching or exceeding the voltage threshold U TH Only when the second power flow P2 through the second rectifier 2.2 is activated. This is when the input voltage U of the DC load 30 is... DC,Last Greater than the voltage threshold U TH In this case, based on the power consumption of DC load 30 and the rated power of rectifiers 2.1 and 2.2, DC load 30 can be powered by the second power stream P2 alone or by a combination of the first power stream P1 and the second power stream P2.

[0045] exist Figure 1 In this embodiment, the AC power grid 20 is exemplarily shown as a three-phase AC power grid 20, and therefore rectifiers 2.1 and 2.2 with input terminals 5 designed as three phases are also shown. Similarly, transformer unit 21 is designed to convert the three-phase AC voltage of the AC power grid 20 into a first three-phase AC voltage and a second three-phase AC voltage. However, other numbers of phases are possible within the scope of this invention. For example, the AC power grid can also be designed as a single-phase AC power grid 20, the transformer unit 21 can also be designed as a single-phase transformer unit 21, and / or the input terminals 5 of rectifiers 2.1 and 2.2 can also be designed as single-phase input terminals 5. Alternatively, the input terminals of the AC power grid 20, the transformer unit 21, and / or the rectifiers can also be designed as multi-phase, wherein the number of phases is not three. Furthermore, rectifiers 2.1 and 2.2 can have Figure 1 Other components not explicitly shown, such as a measurement unit for measuring current and / or voltage at the input and / or output of the AC / DC converter 10, or a communication unit.

[0046] exist Figure 2 The diagram shows a flowchart of an embodiment of the method according to the present invention, which can utilize... Figure 1 The energy conversion system 1 performs this operation. The method begins with a first step S1, in which the input voltage U at the input terminal 32 of the DC load 30 is detected by the measuring unit 13. DC,Last And it is transmitted to the control unit 15. However, the first step S1 is only optional and is shown with dashed lines in the flowchart. Therefore, the input voltage U DC,Last It may be known to the control unit 15 for other reasons, such as because the control unit 15 specifies a particular DC voltage U at the output of the AC / DC converter 10.DC,1 U DC,2 And at least one DC separation unit 12 is closed. In this case, the first step S1 is not required. In the second step S2, the control unit 15 will detect the input voltage U DC,Last The value and the predetermined voltage threshold U TH Compare them. If the input voltage U of the DC load is 30... DC,Last The value is lower than the voltage threshold U TH The method then branches to step S5, where the first power flow P1 through the first rectifier 2.1 is enabled, while the second power flow P2 through the second rectifier 2.2 is suppressed. Here, for example, the second power flow P2 is suppressed by turning on the DC separation unit 12 of the second rectifier 2.2. In this case, only the first power flow P1 through the first rectifier 2.1 supplies power to the DC load 30. On the other hand, if the detected input voltage U of the DC load 30... DC,Last Greater than or equal to voltage threshold U TH The method then branches to the third step S3, where the second power flow P2 through the second rectifier 2.2 is enabled, for example, by closing the corresponding DC separation unit 12. In the fourth step S4 following the third step S3, the ratio of the first power flow P1 to the second power flow P2 can be minimized to operate the energy conversion system 1 with the highest possible efficiency and lowest power consumption overall. However, the fourth step S4 is optional and not absolutely necessary, which is shown in dashed lines. In the subsequent sixth step S6, it is checked whether a predefined termination condition is met. If not, the method jumps back to the first step S1. On the other hand, if the termination condition is met, the method ends. The sixth step S6 following the fifth step S5 or the fourth step S4 (depending on the branch executed in response to the query in the second method step S2) is also an optional method step and is therefore shown in dashed lines in the flow. In embodiments where the sixth step S6 is not specified, the method can jump directly back to the first step after the fifth step S5 or the fourth step S4.

[0047] Within the scope of this invention, a specific consumption or consumption-time curve of the DC load can be set and tracked by means of the control unit 15. For example, if the consumption of the DC load 30 is to be increased, the first rectifier 2.1 is controlled by the control unit 15 to increase its first DC voltage U at the output capacitor 11 over time. DC,1 When the DC separation unit 12 of the first rectifier 2.1 is closed, this voltage also serves as the input voltage U at the input terminal 32 of the DC load 30. DC,LastThis also applies to the second rectifier 2.2. Therefore, if the DC load 30 is powered by a combination of a first power flow P1 and a second power flow P2, neither of which is 0W, the second rectifier 2.2 can also be controlled simultaneously with the first rectifier 2.1 by the control unit 15 to increase the second DC voltage U at its output capacitor 11 over time. DC,2 Then, when the DC load 30 is powered by a combination of the first power flow P1 and the second power flow P2, the first DC voltage U DC,1 Second DC voltage U DC,2 and the input voltage U of the DC load 30 DC,Last The values ​​are almost identical. The change in the combined first power flow P1 relative to the second power flow P2 can be caused by the control unit 15, because the control unit accordingly controls the semiconductor switches of the first rectifier 2.1 and the second rectifier 2.2, and in particular the semiconductor switches of the AC / DC converters assigned to them. For example, the DC voltage U at the output capacitor 11 of the respective rectifiers 2.1, 2.2... DC,1 U DC,2 The semiconductor switches can be adjusted slightly relative to each other, and thus changed.

[0048] Reference tag list

[0049] 1. Energy Conversion System

[0050] 2.1, 2.2 Rectifiers

[0051] 3 DC output terminals

[0052] 5 AC input terminals

[0053] 6 AC separation units

[0054] 7 Series resistors

[0055] 8 Circuit Breaker

[0056] 9 Filter Units

[0057] 10 AC / DC converters

[0058] 11 Output capacitor

[0059] 12 DC separation units

[0060] 13 Measurement Units

[0061] 15 Control Unit

[0062] 20 AC voltage power grid

[0063] 21 Transformer Unit

[0064] 22.1, 22.2 Transformers

[0065] 23.1, 23.2 Primary side

[0066] 24.1, 24.2 Secondary side

[0067] 30 DC load

[0068] 31 Electrolysis Unit

[0069] 32 Input Terminals

[0070] S1-S6 Method Steps

[0071] amplitude

[0072] U DC,Last Input voltage

[0073] U DC,1 U DC,2 DC voltage

[0074] U TH Voltage threshold

[0075] P1, P2 power flow.

Claims

1. A method for supplying power to a DC load (30) by means of an energy conversion system (1), the energy conversion system (1) comprising a first rectifier (2.1), a second rectifier (2.2) and a transformer unit (21). in, Each rectifier includes an AC / DC converter (10) and is connected to a common AC voltage (AC) grid (20) via a separate secondary side of the transformer unit (21). Each of the first rectifier (2.1) and the second rectifier (2.2) is designed as an active controlled rectifier having a bridge circuit including transistors, and each of the two rectifiers (2.1, 2.2) is designed as a single-stage rectifier that is not connected to a downstream DC / DC converter of the AC / DC converter (10). The transformer unit (21) is configured to provide a first AC voltage with a first voltage amplitude Û1 on the first stage side (24.1) and a second AC voltage with a second voltage amplitude Û2 on the second stage side (24.2), wherein the value of the second voltage amplitude Û2 exceeds the corresponding value of the first voltage amplitude Û1. The first AC voltage with the first voltage amplitude Û1 is provided as an input voltage to the first rectifier (2.1), and the second AC voltage with the second voltage amplitude Û2 is provided as an input voltage to the second rectifier (2.2). Different values ​​of the minimum DC output voltage at the output terminals of the corresponding rectifiers (2.1, 2.2) are derived from these two different AC voltages. The method includes the following steps: i) If the input voltage U at the input terminal (32) of the DC load (30) DC,Last The minimum DC output voltage drops below the output of the second rectifier (2.2), which is determined by the single-stage second rectifier (2.2) and the second voltage amplitude Û2 applied thereto: the first rectifier (2.1) operates with a non-zero first power flow P1 to supply power to the DC load (30), wherein the second power flow P2 through the second rectifier (2.2) is suppressed, and ii) If the input voltage U at the input terminal (32) of the DC load (30) DC,Last Reaching or exceeding the minimum DC output voltage at the output terminal of the second rectifier (2.2): operating the second rectifier (2.2) with a non-zero second power flow P2 to supply power to the DC load (30).

2. The method according to claim 1, wherein, The second power flow P2 through the second rectifier (2.2) is suppressed by the open AC disconnect unit (6) between the second stage side (24.2) of the transformer unit (21) and the AC / DC converter (10) of the second rectifier (2.2) and / or by the DC disconnect unit (12) between the AC / DC converter (10) of the second rectifier (2.2) and the input terminal (32) of the DC load (30).

3. The method according to claim 1, wherein, The method is used as part of a startup process for supplying power to the DC load (30) through the energy conversion system (1), wherein, in the initial state of the startup process, both the first power flow P1 and the second power flow P2 are suppressed.

4. The method according to claim 2, wherein, The method is used as part of a startup process for supplying power to the DC load (30) through the energy conversion system (1), wherein, in the initial state of the startup process, both the first power flow P1 and the second power flow P2 are suppressed.

5. The method according to any one of claims 1-4, wherein, The method is used as part of a shutdown process during power supply to the DC load (30) via the energy conversion system (1), wherein, in the final state of the shutdown process, both the first power flow P1 and the second power flow P2 are suppressed.

6. The method according to any one of claims 1-4, wherein, In the method, method steps i) and ii) are executed sequentially, such that method step ii) follows method step i).

7. The method according to claim 5, wherein, In the method, method steps i) and ii) are executed sequentially, such that method step ii) follows method step i).

8. The method according to any one of claims 1-4 and 7, wherein, In the method, method steps i) and ii) are executed sequentially, such that method step i) follows method step ii).

9. The method according to claim 5, wherein, In the method, method steps i) and ii) are executed sequentially, such that method step i) follows method step ii).

10. The method according to claim 6, wherein, In the method, method steps i) and ii) are executed sequentially, such that method step i) follows method step ii).

11. The method according to any one of claims 1-4, 7, and 9-10, wherein, In step ii) of the method, in order to supply power to the DC load (30), the ratio of the first power flow P1 to the second power flow P2 according to P1 / P2 is minimized.

12. The method according to claim 11, wherein, The ratio of the first power flow P1 to the second power flow P2, based on P1 / P2, is minimized to 0.

13. The method according to any one of claims 1-4, 7, 9-10 and 12, wherein, The method steps i) and ii) are repeated over time in order to track changes in the consumption of the DC load (30) or to set the consumption-time curve of the DC load (30) by means of the control unit (15).

14. An energy conversion system (1) for supplying power from an alternating current (AC) grid (20) to a DC load (30), comprising: A transformer unit (21) is connected to the AC power grid (20) on its primary side and is configured to provide a first AC voltage with a first voltage amplitude Û1 on the primary stage side (24.1) and a second AC voltage with a second voltage amplitude Û2 on the secondary stage side (24.2), wherein the value of the second voltage amplitude Û2 exceeds the corresponding value of the first voltage amplitude Û1. A first rectifier (2.1) connected to the first stage side (24.1) on the input side and a second rectifier (2.2) connected to the second stage side (24.2) on the input side, the first rectifier and the second rectifier are connected in parallel to each other on the output side to the input terminal (32) of the DC load (30), wherein each of the first rectifier (2.1) and the second rectifier (2.2) is designed as an active controlled rectifier having a bridge circuit including transistors, and wherein each of the two rectifiers (2.1, 2.2) is designed as a single-stage rectifier not connected to a DC / DC converter downstream of the AC / DC converter (10), wherein different values ​​of the minimum DC output voltage at the output terminal of the respective rectifier (2.1, 2.2) are derived from the two different AC voltages. Control unit (15) for controlling the energy conversion system (1). Its features are, The control unit (15) is designed and configured to perform the method according to any one of claims 1-13.

15. The energy conversion system (1) according to claim 14, characterized in that, The transformer unit (21) includes at least two separate transformers, wherein the first transformer (22.1) includes a first primary side (23.1) and a first primary side (24.1) inductively coupled to the first primary side (23.1), and the second transformer (22.2) includes a second primary side (23.2) different from the first primary side (23.1) and a second primary side (24.2) inductively coupled to the second primary side (23.2).

16. The energy conversion system (1) according to claim 14, characterized in that, The transformer unit (21) has a primary side (23) that is inductively coupled to both the first stage side (24.1) and the second stage side (24.2).

17. The energy conversion system (1) according to any one of claims 14-16, characterized in that, The first rectifier (2.1) and / or the second rectifier (2.2) are designed and configured for bidirectional power flow.

18. The energy conversion system (1) according to any one of claims 14-16, characterized in that, The energy conversion system (1) has a measuring unit (13) connected to the control unit (15), the measuring unit (13) being used to detect the input voltage U at the input terminal (32) of the DC load (30). DC,Last .

19. The energy conversion system (1) according to claim 17, characterized in that, The energy conversion system (1) has a measuring unit (13) connected to the control unit (15), the measuring unit (13) being used to detect the input voltage U at the input terminal (32) of the DC load (30). DC,Last .

20. The energy conversion system (1) according to any one of claims 14-16 and 19, characterized in that, The transformer unit (21) has multiple taps for adjusting the amplitude of the AC voltage relative to the AC power grid (20). AC Change the first voltage amplitude Û1 and / or the second voltage amplitude Û2.

21. The energy conversion system (1) according to claim 17, characterized in that, The transformer unit (21) has multiple taps for adjusting the amplitude of the AC voltage relative to the AC power grid (20). AC Change the first voltage amplitude Û1 and / or the second voltage amplitude Û2.

22. The energy conversion system (1) according to claim 18, characterized in that, The transformer unit (21) has multiple taps for adjusting the amplitude of the AC voltage relative to the AC power grid (20). AC Change the first voltage amplitude Û1 and / or the second voltage amplitude Û2.

23. The energy conversion system (1) according to any one of claims 14-16, 19 and 21-22, characterized in that, The control unit (15) is designed and configured to perform the method according to any one of claims 1-13 in conjunction with other components of the energy conversion system (1).

24. An electrolysis system comprising an energy conversion system (1) according to any one of claims 14-23 and an electrolysis device (31) as a DC load (30).

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