Bidirectional converter for connecting an electrochemical energy conversion system to an alternating current network and method

Abstract

The invention relates to a bidirectional converter (100) for connecting an electrochemical energy conversion system to an alternating current network (200), comprising at least three converter arms (110), wherein each of the three converter arms (110) - at least one electrochemical conversion element (111) for storing and / or releasing energy via an electrochemical process and - at least one power electronics system (112) connected to the electrochemical conversion element (111), which is designed to establish galvanic isolation between the electrochemical conversion element (111) and the AC network (200), wherein the at least one electrochemical conversion element (111) and the power electronics system (112) form a converter sub-module (120), wherein any number of converter sub-modules (120) can be arranged within the at least three converter arms (110), wherein the converter arms (110) are arranged in a delta shape such that one end of a converter arm (110) is connected to a respective phase (210, 220, 230) of the AC network (200) and to one of the remaining converter arms (110). The invention further relates to a method for bidirectionally converting a voltage.

Description

State of the art

[0001] The invention relates to a bidirectional converter for connecting an electrochemical energy conversion system to an alternating current network and to a method.

[0002] Electrochemical energy conversion systems (such as electrolysis stacks, fuel cell stacks, and lithium-ion batteries) can be connected to the power grid via power electronic converters. For safety and operational reasons, these systems must be galvanically isolated from the grid. Large 50 Hz systems are often used for this purpose. Furthermore, it is desirable to design the conversion bidirectionally. Disclosure of the invention

[0003] A bidirectional converter and a method are proposed. Further features and details of the invention emerge from the dependent claims, the description, and the drawings. Features and details described in connection with the bidirectional converter according to the invention naturally also apply in connection with the method according to the invention, and vice versa, so that with regard to the disclosure of the individual aspects of the invention, reference is always made to each other.

[0004] According to the invention, a bidirectional converter is provided for connecting an electrochemical energy conversion system to an alternating current network, comprising at least three converter arms, each of the three converter arms - at least one electrochemical conversion element for storing and / or releasing energy via an electrochemical process and - at least one power electronics system connected to the electrochemical conversion element, which is designed to establish a galvanic isolation between the electrochemical conversion element and the AC network, wherein the at least one electrochemical conversion element and the power electronics system form a converter sub-module, wherein any number of converter sub-modules can be arranged within the at least three converter arms, wherein the converter arms are arranged in a delta shape such that one end of a converter arm is connected to one phase of the AC network and one of the remaining converter arms.

[0005] In other words, according to the invention, a converter can be provided which can generate alternating voltage and direct voltage in order to connect an alternating voltage network and an energy conversion device to one another, wherein at least three converter arms are provided which are triangularly connected to one another and each to a phase of the alternating voltage network and each contain at least one electrical assembly, wherein each electrical assembly has at least one energy conversion device which is designed to store and / or release electrical energy, and a converter device for converting a voltage, and wherein any number of electrical assemblies can be arranged in each of the at least three converter legs.

[0006] A bidirectional converter can be understood as a device designed to transfer energy both from the input side of the bidirectional converter to an output side of the bidirectional converter and from the output side to the input side. The transfer can be performed as a conversion from direct current to alternating current or from alternating current to direct current.

[0007] DC voltage to AC voltage and vice versa. Alternating current and alternating voltage are used synonymously in this application unless otherwise stated. Furthermore, the bidirectional converter can be designed to convert one or more phases, in particular a three-phase current.

[0008] Electrochemical energy conversion systems can be based on an electrochemical process to convert chemical energy into electrical energy and vice versa. Further details on the electrochemical energy conversion systems are discussed in the dependent claims.

[0009] Within the scope of the invention, a power electronics system can be understood as an assembly of electrical components designed to establish galvanic isolation between the electrochemical conversion element and the alternating current network. Furthermore, the power electronics system can be designed to convert direct current to alternating current or direct voltage to alternating voltage and vice versa. It can be provided that the power electronics system is arranged as a module, in particular on a single or multiple circuit boards. Furthermore, it can be provided that the power electronics system is arranged in a housing. The connection between the power electronics system and the electrochemical conversion element can be designed as an electrical connection, in particular as a cable, conductor track, or busbar.

[0010] A converter submodule can be understood as a self-contained unit, particularly arranged in a separate housing. According to the invention, any number of converter submodules can be arranged within a converter arm. Since each converter arm has at least one electrochemical conversion element and one power electronics system, each converter arm also has at least one converter submodule. In other words, each converter arm can have two or more converter submodules. However, the converter topology according to the invention results in the advantage that any number of converter submodules can be arranged within a converter arm, whereby the converter arms can even differ from one another.

[0011] Delta-shaped means that the converter arms are arranged in the shape of a delta (Δ). In other words, they form a triangle such that the two ends of each converter arm are connected to one end of the other converter arms. Each converter arm can be connected to a phase of the AC voltage network. If there are more than three converter arms, they can be arranged in a star configuration.

[0012] Overall, the bidirectional converter offers the advantage of ensuring galvanic isolation of the electrochemical elements, whereby upscaling / stacking of a variable number of submodules enables a variety of different types of electrochemical elements and thus applications of the bidirectional converter.

[0013] Within the scope of the invention, it may be advantageous for the power electronics system to have an active double bridge, which is suitable for establishing the galvanic isolation between the electrochemical conversion element and the AC network. In other words, a bridge assembly can be provided which connects two bridges via a transformer. The active double bridge enables control of the current flow and the output voltage. The transformer provides electrical isolation between the bridges. An active double bridge enables efficient and precise bidirectional power transmission. Furthermore, the galvanic isolation via the transformer offers the advantage of preventing the flow of common-mode voltages that generate fault currents.

[0014] Within the scope of the invention, it is conceivable for the power electronics system to have an H-bridge, in particular a cascaded one, which is designed to generate a variable output voltage. An H-bridge can have at least four switching elements arranged in the shape of the letter "H." These switching elements can be designed, in particular, as at least transistors, IGBTs (Insulated Gate Bipolar Transistors), or MOSFETs (Metal Oxide Semiconductor Field Effect Transistors). The switching elements enable the control of the current flow and the output voltage. It can be provided that a diode is connected in parallel with at least one switching element.

[0015] To generate the output voltage, it can be arranged that the diagonally opposite switching elements are switched on and off. For example, the upper left and lower right switching elements are switched on, while the upper right and lower left switching elements are switched off. This causes current to flow from the supply through the load, and the desired output voltage is created. To reverse the output voltage, it can be arranged that the switching elements are activated in a reversed configuration. Then, for example, the upper right and lower left switching elements are switched on, while the upper left and lower right are switched off. This changes the direction of current flow through the load, and the output voltage has the reversed polarity.

[0016] A cascaded H-bridge can comprise multiple H-bridges stacked, or cascaded, in tiers. Each tier can contain a separate H-bridge with an output. The H-bridge outputs are layered to create a multi-level output voltage. This configuration allows for fine grading of the output voltage and can also reduce the effects of voltage spikes compared to a single H-bridge.

[0017] Within the scope of the invention, it can be provided that the H-bridge has at least one energy storage device, which is designed in particular to smooth the output voltage. The energy storage device can be designed as a capacitor, in particular as an electrolytic capacitor.

[0018] It is also conceivable that terminals of the individual H-bridges of the cascaded H-bridge are connected in series such that a predetermined voltage signal is applied. In other words, it can be provided that at least one end of the H-bridge requires a voltage or current that is generated by a specific cascading. For example, a frequency and / or an amplitude and / or a direction of the voltage signal can be predetermined.

[0019] It is also conceivable for the power electronics system, in particular the active double bridge, to have at least one power electronic switch, a leakage inductance, or an ideal transformer. In particular, it can be provided that the active double bridge has exactly eight power electronic switches. The leakage inductance can be arranged, in particular, on the side of the active double bridge that is connected to the electrochemical conversion element.

[0020] Within the scope of the invention, it is optionally possible for at least two of the three converter arms to differ from each other in at least one electrochemical conversion element or one power electronics system. In other words, the converter arms can have different numbers and / or different designs of electrochemical conversion elements and / or power electronics systems.

[0021] Furthermore, within the scope of the invention, it can be provided that the electrochemical conversion element is at least designed as an electrolysis system or battery. The electrolysis system can be designed as a fuel cell, in particular as a stationary fuel cell. Furthermore, the fuel cell can be designed as at least a solid oxide fuel cell (SOFC), solid oxide electrolyzer cell (SOEC), proton exchange membrane (PEM), or anion exchange membrane (AEM). Furthermore, the electrolysis system can be designed to produce a process gas. The battery can be designed at least as a lithium-ion accumulator or redox flow battery (RFB). Furthermore, it can be provided that the conversion element is designed as an energy generation system. An energy generation system can be designed as a photovoltaic system and / or a wind turbine.Furthermore, a scattering method can be provided which is designed to convert the energy generated by the energy generation plant within the bidirectional converter in a chemical conversion process, which can in particular be designed as a hydrogen generation process.

[0022] It can be provided that the electrochemical conversion element, in particular a stack of the electrochemical conversion element, is grounded. This is made possible by the galvanic isolation.

[0023] With regard to the present invention, it is conceivable that each end of a converter arm is directly connected to a phase of the AC network. In principle, more than three converter arms can also be provided, which are then arranged in a star configuration and each connected to a phase of the AC network.

[0024] Furthermore, it is conceivable that at least one converter arm has a converter arm inductance which is designed to smooth the one voltage of the converter arm.

[0025] Within the scope of the invention, it may be advantageous for at least one of the three converter arms to have at least two converter sub-modules, with the converter sub-modules in particular being connected in series. This allows the converter to be designed and deployed in the field with particular flexibility.

[0026] Within the scope of the invention, it is conceivable to provide a control unit capable of controlling at least one electrical switching element such that a predetermined voltage signal is applied to each end of the three converter arms. The control unit can be embodied as an integrated circuit (IC), in particular at least as a field-programmable gate array (FPGA) or application-specific integrated circuit (ASIC). It can be provided that the control unit controls at least the switching elements of one converter arm, in particular of all converter arms. This can ensure a particularly high voltage quality.

[0027] Furthermore, a method according to the invention for bidirectionally converting a voltage between an alternating current network and electrochemical conversion elements with a bidirectional converter according to one of the preceding claims is proposed.

[0028] The method can be implemented as a computer-implemented method.

[0029] The method steps can be performed at least partially simultaneously and / or sequentially, whereby the sequence of the method steps is not limited by the specified order, so that individual steps can be performed in different orders. Furthermore, individual or all steps can be performed repeatedly.

[0030] This results in the same advantages with regard to a method according to the invention as have already been described with regard to a bidirectional converter according to the invention.

[0031] Further advantages, features, and details of the invention will become apparent from the following description, in which several embodiments of the invention are described in detail with reference to the drawings. The features mentioned in the claims and in the description may be essential to the invention individually or in any combination. These schematically show: Fig. 1 a topology of a converter according to the invention, and Fig. 2 a topology of a converter submodule.

[0032] In the following figures, identical reference numerals are used for the same technical features, even in different embodiments.

[0033] In the Fig. 1 is a bidirectional converter 100 according to the invention for connecting an electrochemical energy conversion system to an alternating current network 200, comprising at least three converter arms 110, wherein each of the three converter arms 110 - at least one electrochemical conversion element 111 for storing and / or releasing energy via an electrochemical process and - at least one power electronics system 112 connected to the electrochemical conversion element 111, which is designed to establish a galvanic isolation between the electrochemical conversion element 111 and the AC network 200, wherein the at least one electrochemical conversion element 111 and the power electronics system 112 form a converter sub-module 120, wherein any number of converter sub-modules 120 can be arranged within the at least three converter arms 110, wherein the converter arms 110 are arranged in a delta shape such that one end of a converter arm 110 is connected to a respective phase 210, 220, 230 of the AC network 200 and to one of the remaining converter arms 110.

[0034] Overall, the bidirectional converter 100 offers the advantage of ensuring galvanic isolation of the electrochemical elements, whereby scaling up / stacking a variable number of submodules enables a variety of different types of electrochemical elements and thus applications of the bidirectional converter 100.

[0035] The ellipsis in the Fig. 1 it is indicated that it can be provided that at least two of the three converter arms 110 differ from each other at least in an electrochemical conversion element 111 or a power electronics system 112.

[0036] Furthermore, the Fig. 1 shows that each end of a converter arm 110 is directly connected to a phase 210, 220, 230 of the AC network 200.

[0037] By way of example, it is also shown that at least one converter arm 110 has a converter arm inductance 119, which is designed to smooth the voltage of the converter arm 110. Alternatively, the converter arm inductance 119 can also be integrated into the converter sub-module 120.

[0038] It is also indicated that a control unit 130 is provided which is suitable for controlling at least one electrical switching element in such a way that a predetermined voltage signal is present at each end of the three converter arms 110.

[0039] The Fig. Figure 2 shows a topology of a converter submodule 120. It can be provided, in particular, that the converter submodule 120 is configured and, in particular, interconnected as shown. Not every connection is described individually below, but only functional units. Nevertheless, the circuit shown as an example can also be part of the invention.

[0040] As in the Fig. 2, it can be provided that the power electronics system 112 has an active double bridge 113, which is suitable for establishing the galvanic isolation between the electrochemical conversion element 111 and the AC network 200.

[0041] Furthermore, the power electronics system 112 can have an H-bridge 114, in particular cascaded as shown, which is designed to generate a variable output voltage. The H-bridge 114 can have at least one energy storage device 115, which is designed in particular to smooth the output voltage.

[0042] It is further shown that the active double bridge 113 has at least one power electronic switch 116, a stray inductance 117 and an ideal transformer 118.

[0043] The above explanation of the embodiments describes the present invention exclusively by way of examples. Of course, individual features of the embodiments can be freely combined with one another, provided they are technically feasible, without departing from the scope of the present invention.

Claims

[1] Bidirectional converter (100) for connecting an electrochemical energy conversion system to an alternating current network (200), comprising at least three converter arms (110), each of the three converter arms (110) - at least one electrochemical conversion element (111) for storing and / or releasing energy via an electrochemical process and - at least one power electronics system (112) connected to the electrochemical conversion element (111), which is designed to establish a galvanic isolation between the electrochemical conversion element (111) and the AC network (200), wherein the at least one electrochemical conversion element (111) and the power electronics system (112) form a converter sub-module (120), wherein any number of converter sub-modules (120) can be arranged within the at least three converter arms (110), wherein the converter arms (110) are arranged in a delta shape such that one end of a converter arm (110) is connected to a respective phase (210, 220, 230) of the AC network (200) and to one of the remaining converter arms (110). [2] Bidirectional converter (100) according to claim 1, characterized bythat the power electronics system (112) has an active double bridge (113) which is suitable for establishing the galvanic isolation between the electrochemical conversion element (111) and the AC network (200). [3] Bidirectional converter (100) according to claim 1 or 2, characterized by that the power electronics system (112) has an H-bridge (114), in particular a cascaded one, which is designed to generate a variable output voltage. [4] Bidirectional converter (100) according to claim 3, characterized by that the H-bridge (114) has at least one energy storage device (115), which is designed in particular to smooth the output voltage. [5] Bidirectional converter (100) according to one of claims 3 or 4, characterized by that terminals of the individual H-bridges of the cascaded H-bridge (114) are connected in series in such a way that a predetermined voltage signal is present. [6] Bidirectional converter (100) according to one of the preceding claims, characterized by that the power electronics system (112), in particular the active double bridge (113), has at least one power electronic switch (116), a leakage inductance (117) or an ideal transformer (118). [7] Bidirectional converter (100) according to one of the preceding claims, characterized by that at least two of the three converter arms (110) differ from each other at least in an electrochemical conversion element (111) or a power electronics system (112). [8] Bidirectional converter (100) according to one of the preceding claims, characterized by that the electrochemical conversion element (111) is at least designed as an electrolysis system or battery. [9] Bidirectional converter (100) according to one of the preceding claims, characterized bythat each end of a converter arm (110) is directly connected to a phase (210, 220, 230) of the alternating current network (200). [10] Bidirectional converter (100) according to one of the preceding claims, characterized by that at least one converter arm (110) has a converter arm inductance (119) which is designed to smooth the one voltage of the converter arm (110). [11] Bidirectional converter (100) according to one of the preceding claims, characterized by that at least one of the three converter arms (110) has at least two converter sub-modules (120), wherein in particular the converter sub-modules (120) are connected in series. [12] Bidirectional converter (100) according to one of the preceding claims, characterized bythat a control unit (130) is provided which is suitable for controlling at least one electrical switching element in such a way that a predetermined voltage signal is present at each end of the three converter arms (110). [13] Method for bidirectionally converting a voltage between an alternating current network (200) and electrochemical conversion elements (111) with a bidirectional converter (100) according to one of the preceding claims.

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