Arrangement with a power converter and a DC busbar for electrical connection to a DC intermediate circuit of the power converter, as well as a modular system

Abstract

Arrangement comprising a power converter having a DC intermediate circuit, and a DC busbar (13) for electrical connection to the DC intermediate circuit of the power converter, comprising a first and a second positive busbar (3) and a first and a second negative busbar (4), wherein the positive and negative busbars (3, 4) are each parallel to each other, comprising a first clamp (2) which is configured to bring the first and the second positive rails (3) to a common first electrical potential and a second clamp (2) which is configured to bring the first and the second negative rails (4) to a common second electrical potential, wherein the first and the second positive rails (3) are provided to be electrically connected to a first terminal (8) of a first part of the DC intermediate circuit and to a first terminal (8) of a second part of the DC intermediate circuit and wherein the first and the second negative rail (4) are provided to be electrically connected to a second terminal (8) of the first part of the DC intermediate circuit and to a second terminal (8) of the second part of the DC intermediate circuit, wherein a first terminal (8) of a first part of the DC intermediate circuit and a first terminal (8) of a second part of the DC intermediate circuit are electrically connected to the first potential and a second terminal (8) of the first part of the DC intermediate circuit and a second terminal (8) of the second part of the DC intermediate circuit are electrically connected to the second potential.

Description

Technical field of the invention

[0001] The application relates to an arrangement with a power converter and a DC busbar for connection to the power converter, e.g., an inverter, such as can be used in implementations in a switch cabinet for electrical power in the MW range. In this context, a switch cabinet houses electrical components in a housing, provides the possibility for electrical connection, mechanical support, and protects the interior, for example, from dirt. In the field of photovoltaics (PV), power converters can be used as inverters. Other examples of power converters are battery controllers, wind inverters, and fuel cell inverters. Power converters can also be used, for example, in emergency power supplies. Possible operating modes include, for example, island grid operation—independent of a higher-level AC supply grid—or grid-parallel operation—parallel to a higher-level AC supply grid. State of the art

[0002] Power converters convert one form of electrical power into another; they are also known as energy converters. Inverters for converting DC electrical power (DC = direct voltage or direct current) into AC power (AC = alternating voltage or alternating current) are an example of a power converter. Energy converters have traditionally been used for a single application, such as feeding PV power into the grid. To expand the system to other applications, various complete converters can be combined. The coupling can be achieved, for example, via an AC grid connection or via a shared central storage device (e.g., a battery).

[0003] From WO2015165658A1 it is known to couple power converter modules via a common intermediate circuit, which results in a flexibly combinable variety of components.

[0004] From WO2020030383A1, a low-inductance connection of two intermediate circuits arranged on different circuit boards is known. Task

[0005] The purpose of the application is to improve the connection of power converters, especially in control cabinets. Solution

[0006] The object is achieved by an arrangement with a power converter and a DC busbar having the features of independent claim 1 and by a modular system having the features of independent claim 11. Advantageous embodiments are claimed in the dependent claims. Description of the invention

[0007] An arrangement with a power converter and with a DC busbar for electrical connection to a DC intermediate circuit of the power converter comprises a first and a second positive busbar and a first and a second negative busbar, wherein the positive and negative busbars each run parallel to one another. A first clamp is configured to bring the first and the second positive busbar to a common first electrical potential, and a second clamp is configured to bring the first and the second negative busbar to a common second electrical potential.The first and second positive rails are provided to be electrically connected to a first terminal of a first part of the DC intermediate circuit and to a first terminal of a second part of the DC intermediate circuit, and the first and second negative rails are provided to be electrically connected to a second terminal of the first part of the DC intermediate circuit and to a second terminal of the second part of the DC intermediate circuit. A first terminal (8) of a first part of the DC intermediate circuit and a first terminal (8) of a second part of the DC intermediate circuit are electrically connected to the first potential, and a second terminal (8) of the first part of the DC intermediate circuit and a second terminal (8) of the second part of the DC intermediate circuit are electrically connected to the second potential.

[0008] Such a busbar offers the advantage of enabling direct electrical coupling to the DC link of a power converter. Power converter modules can incorporate part of the DC link capacitance in the form of electrolytic capacitors (electrolytic capacitors) on printed circuit boards. These capacitors, for example, hold the DC link potentials (e.g., UZWK+ and UZWK-, possibly center point potential M) in alternating layers in the substrate, like a plate capacitor. Connecting the DC link via busbars is particularly advantageous for high power levels and the associated high currents. A power converter module can also have a control unit that, for example, controls semiconductor switches of the power converter.

[0009] The DC busbar enables the coupling of multiple power converters or power converter modules via their DC links. The coupled DC links and the busbar thus serve as a common DC link. A common DC link also enables a highly efficient, low-loss, and flexible coupling of different types of power converters. This allows for a wide variety of variants.

[0010] In one embodiment, the DC busbar is designed to provide the connectable DC link with an electrical capacitance for use as an intermediate circuit capacitance. With a suitable design, the busbar can thereby increase the capacitance of the intermediate circuit and act as an intermediate circuit with the intermediate circuit of the power converter. The amount of energy that can be stored in the intermediate circuit of the power converter can thus be increased without having to change the design of the power converter itself or increase its cost.

[0011] In one embodiment of the DC busbar, the positive and negative busbars are each flat and arranged one above the other, with a positive busbar being arranged adjacent to at least one negative busbar. Alternatively or additionally, the first clamp is connected flatly to the first and second positive busbars, and the second clamp is connected flatly to the first and second negative busbars. This achieves a low-inductance connection of the intermediate circuit in a switch cabinet implementation, e.g., between power converters or power converter modules, by means of busbars and, for example, between switch cabinets, particularly when using multiple first and second clamps.

[0012] The connection of the intermediate circuits of different power converters or power converter modules, e.g., in different control cabinets and / or within a control cabinet, can be advantageously carried out using busbars, particularly for high power levels and the associated high currents. The implementation described has the advantage that the connection via the busbar is low-inductance. This prevents the large dimensions of the connections from resulting in inductive (narrow and long) rather than capacitive (wide and short) connections. Inductive connections, together with the intermediate circuit capacitance, can lead to unwanted resonances and interference-intensive, high-frequency interference current paths. By spatially designing the positive and negative busbars as flat structures and arranging them parallel to one another, the connection can be designed with low inductance, whereby the busbar can then act more as a capacitance.

[0013] The inductance per unit length (inductance per unit length) of a connection depends on the length of the path of the H-field lines (magnetic field strength) around the current-carrying conductor. The longer this path, the lower the inductance. A wide rectangular cross-section is therefore less inductive than a round one with the same cross-section. It is advantageous to orient and arrange the intermediate circuit elements in the power converter, e.g., a circuit board with electrolytic capacitors and a plate capacitor, and the busbars in such a way that the connections are as short and wide as possible and aligned with one another, without, for example, being twisted or having to go around corners.

[0014] The distances between a positive and a negative busbar can be calculated, for example, depending on the length and width of the busbars, to achieve the desired capacitance and inductance values ​​for the busbar. It is also possible to arrange an electrically insulating layer between each positive and negative busbar, the design of which can achieve the desired capacitance and inductance values.

[0015] In one embodiment of the DC busbar, the first and second clamps each have a U-shaped profile, the legs of which are connected flatly to the positive or negative rails. Such intermediate connections with relatively wide and short elements result in a low-inductance connection, so that the character of the "plate capacitor" can be retained. For example, the low-inductance connections, in the form of wide cross-sectional elements, are arranged multiple times, like fingers, on stacked positive and negative rails to achieve multiple contact and thus a large contact area.

[0016] In one embodiment of the DC busbar, the first clamp has an electrically conductive first connector and the second clamp has an electrically conductive second connector for the respective connection to the DC intermediate circuit. The respective connector is arranged, for example, on the base side of the U-profile and extends in a direction opposite to the legs. The connectors are designed to make the respective electrical potential of the associated clamp available to the respective connection of the DC intermediate circuit. This can further increase modularity, since intermediate circuits of power converters or power converter modules can be easily plugged onto the connectors. The connectors are preferably arranged such that they are at the same height for the positive and negative clamps and a power converter or power converter module can be easily plugged on.

[0017] In the arrangement with a DC busbar and with a power converter having a DC intermediate circuit, a first terminal of a first part of the DC intermediate circuit and a first terminal of a second part of the DC intermediate circuit are electrically connected to the first potential, and a second terminal of the first part of the DC intermediate circuit and a second terminal of the second part of the DC intermediate circuit are electrically connected to the second potential. Preferably, the first part of the DC intermediate circuit is connected to the first potential via the first connector and to the second potential via the second connector, and the second part of the DC intermediate circuit is connected to the first potential via a further first connector and to the second potential via a further second connector.

[0018] In one embodiment of the arrangement, a control unit is provided in the power converter, which is designed to monitor the electrical safety of the DC intermediate circuit and the DC busbar connected to it. The control unit can be provided so that safety functions and monitoring requirements can be met. This can, for example, monitor mains disconnection and / or perform arc detection. The control unit can, for example, be identical to a control unit of the power converter, which, for example, controls semiconductor switches of the power converter. The control unit can also be designed separately from a control unit that, for example, controls semiconductor switches of the power converter.

[0019] A switch cabinet with a DC busbar is designed to accommodate at least one power converter whose DC intermediate circuit can be electrically connected to the DC busbar.

[0020] In one embodiment of the switch cabinet, the DC busbar has at least two clamps with connectors for each part of an at least two-part DC intermediate circuit of the at least one power converter, wherein the clamps with the connectors are arranged such that the terminals of the respective part of the DC intermediate circuit of the at least one power converter can be plugged onto them and can be connected to the first and the second potential by plugging them on.

[0021] In one embodiment of the control cabinet, the DC busbar continues outside the control cabinet housing, with one or more passages being provided for this purpose in a control cabinet wall.

[0022] In a modular system with a plurality of switch cabinets, the DC busbar extends through the plurality of switch cabinet housings and the plurality of switch cabinets are each designed to accommodate at least one power converter or a power converter module, the DC intermediate circuit of which can be electrically connected to the DC busbar.

[0023] In one embodiment of the modular system, a control unit is provided which is configured to electrically monitor the electrical safety of the DC link and the DC busbar connected to it. The control unit can be arranged in one of the power converters or one of the power converter modules, or outside a power converter in one of the control cabinets. It is also possible to implement the monitoring function distributed across several control units of the modular system. In order to ensure compliance with safety functions and monitoring requirements, local "intelligence", e.g. in the form of a control unit, can be provided in one or more power converters. This can, for example, monitor mains disconnection and / or perform arc detection. Alternatively or additionally, higher-level "intelligence", e.g. in the form of a control unit, can be present. This can, for example,for protection, e.g., as a global emergency stop. The higher-level intelligence can also be used for coordination, e.g., to determine whether loads should be disconnected, whether batteries should be charged or discharged, or similar. The higher-level intelligence can also be used for synchronization, e.g., when specifying a common DC link voltage that affects all connected power converters or power converter modules, since the common power interface is the DC link.

[0024] The overall result is a modular system with improved interfaces for the flexible combination of power converters or power converter modules. This allows for virtually any type of power conversion. This flexibility relates to the power, meaning the combination of multiple components of the same size or components of different sizes. However, it also allows for the flexible combination of different energy sources (PV, wind, fuel cells, batteries, AC grid, etc.) with different energy sinks (fuel cells, batteries, AC grid, AC island loads, etc.). The shared intermediate circuit serves as the central interface. This is particularly suitable for cases where the energy demand of loads is greater than the combined supply of the sources or, conversely, where the sources are capable of supplying more energy than the combined supply of the loads, e.g., without AC grid feed-in.

[0025] Mechanically, it is possible to install control cabinets side by side from left to right and vice versa, as well as to replace a power converter or power converter module and / or control cabinet without having to dismantle other modules. Positioning the control cabinets side by side should ensure that the required tolerance and permissible offset are maintained. Furthermore, two power converters or power converter modules can be arranged and connected one above the other within a control cabinet module.

[0026] The DC busbar enables a low-inductance electrical connection of the intermediate circuit of one or more power converters or power converter modules while simultaneously realizing the aforementioned mechanical advantages. The secure (device safety and insulation coordination) and sealed (climatically and from an EMC perspective) electrical connection can be designed to be dismantled and connected at least to the two intermediate circuit potentials. Power converters or power converter modules can be mechanically fixed next to each other and / or one above the other. This connection via the DC busbar can also be secured, for example, in a control cabinet, so that only trained / authorized persons are able to open the connection (e.g., with a special key or a screw).The low inductive components in the DC busbar and the connections reduce resonance problems and problems with high-frequency EMC interference currents, which can be compensated (with low inductance) via the DC link. This can prevent potentially unpredictable interference-intensive paths. These high-frequency interference currents can arise in implementations with multiple power converter modules, for example, because the functionalities may be distributed across different power converter modules. It is possible that compensating processes during the switching operations within the power converter modules also affect the other power converter modules and their switching operations, so that these compensating currents then flow via the DC link and thus the DC busbar.Since these processes are often coupled to the fast switching edges, they are high-frequency and can be dissipated with low inductance via the described DC current rail and / or the described arrangement. Short description of the characters

[0027] In the following, the invention is explained in more detail with the help of figures. Fig. Figure 1 shows a schematic diagram of a modular system with control cabinets, DC busbar and power converter modules; Fig. 2 shows a schematic diagram of a power converter module with terminals and capacitors of the DC link; Fig. 3 shows a schematic diagram of a power converter module with AC connections and Fig. Figure 4 shows a schematic diagram of a DC busbar with clamps.

[0028] In the figures, identical or similar elements are designated by the same reference numerals. Character description

[0029] Fig. 1 shows a modular system with multiple control cabinets 1. A DC busbar 13 extends across the three control cabinets 1 shown. For this purpose, openings 6 are provided in the walls of the control cabinet housings 9, allowing the DC busbar 13 to extend through the three control cabinets 1 shown. A housing connection 7 for the DC busbar 13 is provided on one wall of one of the control cabinet housings, insulating the DC busbar 13 from the housing 9 of the control cabinet. End caps can serve as the housing connection 7, providing a seal and ensuring reliable insulation.

[0030] In the illustrated embodiment, the DC busbar 13 has two positive busbars 3 and two negative busbars 4. The busbars 3, 4 are designed as flat, elongated structures with a rectangular cross-section, with a positive busbar 3 being adjacent to at least one negative busbar 4 and vice versa. This achieves the capacitive effect of the DC busbar 13. The positive busbars 3 are connected by a first clamp 2, the legs of which rest flat on the positive busbars 3. The negative busbars 4 are connected by a second clamp 2, the legs of which rest flat on the negative busbars 4. The busbar can also have more than two positive busbars 3 and more than two negative busbars 4. Preferably, the number of plus rails 3 is equal to the number of minus rails 4. In such an embodiment, the clamps 2 preferably have more than two legs and, for example,exactly as many legs as there are positive rails 3 or negative rails 4. Each leg of a clamp 2 then rests flat on a rail 3, 4. This further improves the capacitive effect and allows all positive rails 3 and all negative rails 4 to be brought to the same electrical potential.

[0031] Power converter modules 5 of a power converter can be inserted into the switch cabinets 1, whose DC link can be electrically connected to the DC busbar 13. The switch cabinets 1 also provide mechanical support and protection for the power converter modules 5 and the busbar 13.

[0032] Optionally, the DC busbars 13 running transversely through the switch cabinets 1 can be additionally enclosed, e.g., for shielding, protection, or insulation. It is then advantageous to connect this enclosure, as well as the DC busbars 13, continuously and to also connect them to the housings of the power converter or power converter modules 5 in a conductive and low-inductance manner.

[0033] In Fig. 2 shows a power converter module 5 with electrolytic capacitors 10 of its DC link. The DC link has a first terminal 8 and a second terminal 8, which correspond to the plus and minus terminals of the DC link. The terminals 8 are designed such that they can interact with a connector 12 of the clamp 2 to establish a mechanical and electrical connection between the clamp 2 and the terminal 8. In the illustrated embodiment, the terminals 8 of the power converter module 5 are arranged at the same height. The connectors 12 of the two clamps 2, which are intended to establish a connection to the DC link, should therefore preferably also be arranged at the same height (cf. Fig. 4). The connector 12 may have openings through which the connector 12 can be screwed to the terminals 8.

[0034] It is possible to supplement the connections 8 with slotted hole combinations (longitudinal / transverse) or with flexible intermediate elements, in particular to meet other requirements such as safety or assembly or similar.

[0035] In Fig. Figure 3 shows a power converter module 5 with AC terminals 11. This is the case, for example, when the power converter is configured as an inverter. The AC terminals 11 shown can run vertically through stacked power converter modules 5. Connectors with openings for fastening can also be provided at the AC terminals 11. The connectors can be sealed with end caps to ensure reliable insulation.

[0036] In Fig. 4 shows an embodiment of the DC busbar 13 with two positive rails 3 and two negative rails 4. A first clamp 2 connects the two positive rails 3 and a second clamp 2 connects the two negative rails 4. Both clamps have a U-profile, the legs of which rest flat on the respective rail 3, 4. The first clamp 2 fulfills several functions. It brings the two positive rails 3 and their connector 12 to the same electrical potential. It also supports the capacitive properties of the busbar 13 and thus enables a low-inductive connection, e.g., of the power converter or power converter module 5 via the connector 12 and via the DC busbar 13. In the Fig. In the embodiment shown in Figure 2, the terminals 8 of the intermediate circuit of the power converter module 5 are located at the same height. One of these terminals is intended for connection to the positive rail 3 and the second of these terminals is intended for connection to the negative rail 4. In order to separate the power converter module 5 from Fig. To easily connect the clamps 2 to the DC busbar 13 and establish the electrical and mechanical connection, the clamps 2 are designed so that the connector 12 extends from the base side of the clamp 2 opposite the direction of the legs of the clamps 2. The position on the base side is selected such that it matches the distance between the positive rails 3 and the negative rails 4 and the two connectors 12 are arranged at the same height.

[0037] In embodiments with, for example, identical power converters or power converter modules 5, which can be arranged and connected one above the other, the connections 8 are suitable for arranging the power converters or power converter modules 5 in such a way that they - depending on the installation sequence, e.g. starting at the bottom - can be inserted one after the other or already connected to each other onto the rails 3, 4 and can be screwed to the rails 3, 4 and to each other, e.g. from the rear. Fig.In the embodiment shown in Figure 1, two power converters or power converter modules 5 can be arranged one above the other in each switch cabinet 1 and connected both to each other and to a corresponding pair of rails 3, 4 of the intermediate circuit. The two pairs of rails 3, 4 are then connected to each other in the respective switch cabinet 1 by means of clamps 2, e.g., on the rear side, in a short and wide manner, i.e., with low inductance. The rear connection can also serve directly as a DC connection to the outside, e.g., to a PV system. This connection can be made via intermediate contactors and fuses. List of reference symbols 1 control cabinet 2 brackets 3 Plus rail 4 Minus rail 5 Power converter module 6 Passage 7 Housing connection 8 Connection 9 housings 10 capacity 11 AC connections 12 connectors 13 DC busbar

Claims

[1] Arrangement with a power converter having a DC intermediate circuit, and with a DC busbar (13) for electrical connection to the DC intermediate circuit of the power converter, with a first and a second plus rail (3) and a first and a second minus rail (4), wherein the plus and minus rails (3, 4) each run parallel to one another, comprising a first clamp (2) which is designed to bring the first and the second positive rail (3) to a common first electrical potential and a second clamp (2) which is designed to bring the first and the second negative rail (4) to a common second electrical potential, wherein the first and the second positive rail (3) are provided to be electrically connected to a first terminal (8) of a first part of the DC voltage intermediate circuit and to a first terminal (8) of a second part of the DC voltage intermediate circuit and wherein the first and second negative rails (4) are provided to be electrically connected to a second terminal (8) of the first part of the DC intermediate circuit and to a second terminal (8) of the second part of the DC intermediate circuit, wherein a first terminal (8) of a first part of the DC intermediate circuit and a first terminal (8) of a second part of the DC intermediate circuit are electrically connected to the first potential and a second terminal (8) of the first part of the DC intermediate circuit and a second terminal (8) of the second part of the DC intermediate circuit are electrically connected to the second potential. [2] Arrangement according to claim 1, wherein the DC busbar (13) is designed to provide the connectable DC intermediate circuit with an electrical capacitance for use as an intermediate circuit capacitance. [3] Arrangement according to claim 1 or 2, wherein the plus and minus rails (3, 4) are each flat and arranged one above the other, wherein a plus rail (3) is arranged adjacent to at least one minus rail (4). [4] Arrangement according to one of the preceding claims, wherein the first clamp (2) has an electrically conductive first connector (12) and the second clamp (2) has an electrically conductive second connector (12) for the respective connection to the DC voltage intermediate circuit and wherein the connectors (12) are designed to make the respective electrical potential of the associated clamp (2) available to the respective connection (8) of the DC voltage intermediate circuit. [5] Arrangement according to one of the preceding claims, wherein the first clamp (2) is connected flatly to the first and second positive rails (3) and the second clamp is connected flatly to the first and second negative rails (4). [6] Arrangement according to claim 5, wherein the first and the second clamp (2) each have a U-profile, the legs of which are each connected flatly to the plus rails (3) or the minus rails (4). [7] Arrangement according to claim 6, insofar as claim 5 is dependent on claim 4, wherein the respective connector (12) is arranged on the base side of the U-profile and extends in a direction opposite to the legs. [8] Arrangement according to one of claims 4 to 7, insofar as claim 5 is dependent on claim 4, wherein the first part of the DC voltage intermediate circuit is connected to the first potential via the first connector (12) and to the second potential (12) via the second connector. [9] Arrangement according to claim 8, wherein the second part of the DC voltage intermediate circuit is connected to the first potential via a further first connector (12) and to the second potential (12) via a further second connector. [10] Arrangement according to one of the preceding claims, wherein a control unit is provided in the power converter, which is designed to monitor the electrical safety of the DC voltage intermediate circuit and the DC voltage busbar (13) connected thereto. [11] Modular system with an arrangement according to one of the preceding claims and a plurality of switch cabinets (1), wherein the DC busbar (13) extends through the plurality of switch cabinets (1) and the plurality of switch cabinets (1) are each designed to accommodate at least one power converter whose DC intermediate circuit can be electrically connected to the DC busbar (13). [12] Modular system according to claim 11, wherein a control unit is provided which is configured to electrically monitor the electrical safety of the DC intermediate circuit and the DC busbar (13) connected thereto.

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