WO2023006371A1

WO2023006371A1 - Dc bus bar for electrically connecting to a dc link of a power converter, assembly having a dc bus bar and a power converter, and switchgear cabinet

Info

Publication number: WO2023006371A1
Application number: PCT/EP2022/068783
Authority: WO
Inventors: Niels BERGER
Original assignee: Sma Solar Technology Ag
Priority date: 2021-07-27
Filing date: 2022-07-06
Publication date: 2023-02-02
Also published as: DE102021119379A1

Abstract

The application describes a DC bus bar (13) for electrically connecting to a DC link of a power converter, comprising a first and a second positive bar (3) and a first and a second negative bar (4), the positive and negative bars (3, 4) each running parallel to each other, and comprising a first clip (2), which is designed to bring the first and second positive bars (3, 4) to a common first electric potential, and a second clip (2), which is designed to bring the first and second negative bars (3, 4) to a common second electric potential, the first and second positive bars (3) being provided for being electrically connected to a first terminal (8) of a first part of the DC link and to a first terminal (8) of a second part of the DC link, and the first and second negative bars (4) being provided for being electrically connected to a second terminal (8) of the first part of the DC link and to a second terminal (8) of the second part of the DC link. The application also describes an assembly, comprising a DC bus bar (13) and a power converter, and a switchgear cabinet (1).

Description

DC busbar for electrical connection to a DC link of a power converter, arrangement with DC busbar and power converter as well as control cabinet

Technical field of the invention

The application relates to a DC voltage bus bar for connection to a power converter, e.g. B. inverters, as z. B. can be used in implementations in a control cabinet for electrical power in the MW range. In this context, a control cabinet accommodates electrical components in a housing, offers the possibility of electrical connection, mechanical mounting and protects the interior, e.g. B. from dirt. In the field of photovoltaics (PV), power converters can be used as inverters. Other examples of power converters are battery controllers, wind converters, fuel cell inverters. Power converters can e.g. B. can also be used as part of the emergency power supply. Possible operating modes are e.g. B. an island grid operation - independent of a higher-level AC supply network - or mains-parallel operation - parallel to a higher-level AC supply network.

State of the art

Power converters convert one form of electrical power into another, also known as energy converters. Inverters for converting DC electrical power (DC=direct voltage or direct current) to AC power (AC=alternating voltage or alternating current) are an example of power converters. So far, energy converters have been common for one application each, e.g. for feeding PV power into the grid. Various complete converters can be combined to expand to other applications. The coupling can e.g. B. via an AC grid connection or via a common central memory (e.g. battery).

It is known from WO2015165658A1 to couple power converter modules via a common intermediate circuit, which results in a variety of components that can be flexibly combined. A low-inductance connection of two intermediate circuits arranged on different printed circuit boards is known from WO2020030383A1.

Furthermore, DE 102019207 184 A1 discloses a conductor rail arrangement for a submarine with eight partial rails, which are fixed and selectively electrically connected via collector elements in such a way that the submarine has a minimized electromagnetic signature.

Task

The object of the application is to improve the connection of power converters, especially in switch cabinets.

Solution

The object is achieved by a direct current busbar with the features of independent patent claim 1 . The object is further achieved by an arrangement with the features of claim 7 and a switch cabinet with the features of claim 10. Advantageous embodiments are claimed in the dependent claims.

Description of the invention

A DC voltage busbar for electrical connection to a DC voltage intermediate circuit of a power converter has a first and a second positive rail and a first and a second negative rail, the positive and negative rails each running parallel to one another. A first clip is designed to bring the first and the second plus rail to a common first electrical potential and a second clip is designed to bring the first and the second minus rail to a common second electrical potential. The first and the second plus rail are intended to be electrically connected to a first connection of a first part of the DC voltage link and to a first connection of a second part of the DC voltage link and the first and the second minus rails are provided to be electrically connected to a second terminal of the first part of the DC voltage intermediate circuit and to a second terminal of the second part of the DC voltage intermediate circuit.

Such a busbar offers the advantage of being able to implement electrical coupling directly to the DC link of a power converter. Power converter modules can contain part of the intermediate circuit capacity in the form of electrolytic capacitors (Elko) on circuit boards, e.g. B. in the substrate in layers alternately hold the intermediate circuit potentials (e.g. UZWK+ and UZWK-, if necessary, midpoint potential M) as a plate capacitor. In the case of high power and the associated high currents, it is advantageous to connect the intermediate circuit via busbars. A power converter module may also have a control unit, e.g. B. controls the semiconductor switch of the power converter.

The DC voltage busbar enables a number of power converters or power converter modules of the power converter to be coupled via their intermediate circuits. The coupled intermediate circuits and the busbar thus serve as a common DC voltage intermediate circuit. A very efficient, low-loss and at the same time flexible coupling of different types of power converters can also be implemented via a common intermediate circuit. A high number of variants can thus be implemented.

In one embodiment, the DC voltage busbar is designed to provide the connectable DC voltage intermediate circuit with an electrical capacitance for use as an intermediate circuit capacitance. With a suitable design, the conductor rail can thereby increase the capacitance of the intermediate circuit and act like 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 make it more expensive.

In one embodiment of the DC current busbar, the plus and minus busbars each have a flat design and are arranged one above the other, with a plus busbar being arranged adjacent to at least one minus busbar. Alternatively or additionally, the first bracket is flat with the first and the second plus rail and the second clip is connected flat to the first and the second minus rail. In this way, particularly when using a plurality of first and second brackets, a low-inductance connection of the intermediate circuit in a control cabinet implementation, e.g. B. between power converters or power converter modules, by means of busbars and z. B. achieved between control cabinets.

The connection of the intermediate circuits of different power converters or power converter modules, e.g. B. in different control cabinets and / or within a control cabinet can be done advantageously with busbars, especially at high power and the associated high currents. The implementation described has the advantage that the connection via the busbar is low-inductive. Inductive (narrow and long) rather than capacitive (wide and short) connections are avoided due to the large dimensions involved. Inductive connections, together with the intermediate circuit capacitances, can lead to unwanted resonances and high-frequency interference current paths. Due to the spatial design of the plus and minus rails as a flat structure and the arrangement parallel to one another, the connection can be designed to be low-inductive, with the busbar then being able to act more as a capacitance.

The inductance per unit length (inductance per unit of 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. The orientation and arrangement of the intermediate circuit elements in the power converter, e.g. B. a circuit board with electrolytic capacitors and plate capacitor, see above, as well as the busbars are selected in such a way that the connections to each other are as short and wide as possible and arranged in alignment with each other without having to twist them or go around corners, for example.

The distances between a plus rail and a minus rail of the power rail can, for. B. be calculated depending on the length and width of the busbars so that desired capacitance and inductance values for the busbar can be reached. It is also possible to arrange an electrically insulating layer between each positive rail and negative rail, the design of which allows the desired capacitance and inductance values to be achieved.

In one embodiment of the direct current busbar, the first and second clamps each have a U-profile, the legs of which are each connected to the plus busbars or the minus busbars over a large area. Such interconnections with rather wide and short elements lead to a low-inductance connection, so that the character of the 'plate capacitor' can be preserved. For example, the low-inductance connections in the form of elements with a wide cross-section are placed on top of each other, like fingers, on positive and negative rails in order to achieve multiple contact and thus a large contact area.

In one embodiment of the DC voltage busbar, the first bracket has an electrically conductive first connector and the second bracket has an electrically conductive second connector for the respective connection to the DC voltage intermediate circuit. The respective connector is z. B. arranged on the base of the U-profile and extends in a direction opposite to the leg. The connectors are designed to make the respective electrical potential of the associated clamp available to the respective connection of the DC voltage intermediate circuit. In this way, the modularity can be further increased since intermediate circuits of power converters or power converter modules can be simply plugged onto the connectors. The connectors are preferably arranged in such a way that they are at the same height for the plus and minus clamps and a power converter or power converter module can be easily plugged on.

In an arrangement with a DC voltage bus bar and with a power converter having a DC voltage link, a first connection of a first part of the DC voltage link and a first connection of a second part of the DC voltage link are electrically connected to the first potential and a second Connection of the first part of the DC link and a second connection of the second part of the DC voltage intermediate circuit electrically connected to the second potential. The first part of the DC voltage intermediate circuit is preferably 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 voltage intermediate circuit is connected to the first potential via a further first connector and to the first potential via a further second connector Connector connected to the second potential.

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 voltage intermediate circuit and the DC voltage busbar connected thereto. The control unit can be provided so that safety functions and monitoring requirements can be met. This can e.g. B. Monitor mains disconnection and/or carry out arc detection. The control unit can e.g. B. be identical to a control unit of the power converter, the z. B. controls the semiconductor switch of the power converter. The control unit can also be designed separately from a control unit which, for. B. controls the semiconductor switch of the power converter.

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

In one embodiment of the control cabinet, the DC voltage busbar has at least two clamps with connectors for each part of an at least two-part DC voltage intermediate circuit of the at least one power converter, the clamps with the connectors being arranged in such a way that the connections of the respective part of the DC voltage 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 in.

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

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

In one embodiment of the modular system, a control unit is provided which is set up to electrically monitor the electrical safety of the DC voltage link and the DC voltage busbar connected thereto. The control unit can be arranged in one of the power converters or one of the power converter modules, or it can be arranged outside of a power converter in one of the switch cabinets.

It is also possible to implement the monitoring function distributed over several control units of the modular system. So that safety functions and monitoring requirements can be met, 'intelligence' can be installed locally in one or more power converters, e.g. B. in the form of a control unit may be provided. This can e.g. B. Monitor mains disconnection and/or carry out arc detection. Alternatively or additionally, a superordinate 'intelligence', e.g. B. be present in the form of a control unit. This can e.g. B. for hedging, z. B. serve as a global emergency stop. The superior intelligence can also be used for coordination, e.g. B. to determine whether consumers are disconnected, whether batteries should be charged or discharged or the like. The superior intelligence can also be used for synchronization, e.g. B. when determining a common intermediate circuit voltage, which affects all connected power converters or power converter modules, since the common power interface is the intermediate circuit.

The overall result is a modular system with improved interfaces for the flexible assembly of power converters or power converter modules. This means that almost any form of power conversion can be implemented. On the one hand, this flexibility affects performance, i.e. combining several components of the same size or components of different sizes. On the other hand, different energy sources (PV, wind, fuel cell, battery, AC grid, ...) with different energy sinks (fuel cell, battery, AC grid, AC island consumers, ...) can be used flexibly be combined. The common intermediate circuit serves as the central interface. This is particularly suitable for such cases in which the energy demand of consumers is greater than the sources together can supply or, conversely, the sources are capable of supplying more energy than the consumers, e.g. B. without AC mains feed, be removed together.

Mechanically, switch cabinets can be installed next to each other from left to right and vice versa, as well as the possibility of replacing a power converter or power converter module and/or switch cabinet without having to dismantle other modules. The positioning of the switch cabinets side by side should ensure that the required tolerance and the permissible offset from one another are observed. In addition, e.g. two power converters or power converter modules can be arranged one above the other and connected within a control cabinet module.

The DC busbar enables a low-inductance electrical connection of the intermediate circuit of one or more power converters or power converter modules while at the same time realizing the aforementioned mechanical advantages. The safe (device safety and insulation coordination) and tight (climatic and from an EMC point of view) electrical connection can be designed to be (de)mountable and connects at least the two intermediate circuit potentials. Power converters or power converter modules can be mechanically fixed next to and/or on top of one another. This connection via the DC busbar can, for. B. in a control cabinet can also be secured in such a way that only instructed/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 (low inductance) can compensate via the intermediate circuit. This means that otherwise unpredictable, disruptive routes can be avoided. In implementations with several power converter modules, these high-frequency interference currents can e.g. B. arise from the fact that the functionalities can be divided between different power converter modules. It can be the case that transient processes during the switching processes within the power converter modules also affect the other power converter modules and close their switching operations, so that these compensating currents then close via the intermediate circuit and thus the DC voltage busbar. Since these processes are often linked to the fast switching edges, they are high-frequency and can be derived with low inductance via the described direct current busbar and/or the described arrangement.

Brief description of the characters

The invention is explained in more detail below with the aid of figures.

1 schematically shows a modular system with switch cabinets, DC voltage busbar and power converter modules;

2 schematically shows a power converter module with connections and capacitors of the DC link;

3 schematically shows a power converter module with AC connections and FIG. 4 schematically shows a DC bus bar with clamps.

In the figures, identical or similar elements are denoted by the same reference symbols.

fiqure description

Fig. 1 shows a modular system with several switch cabinets 1. A DC voltage busbar 13 extends over the three switch cabinets 1 shown. For this purpose, passages 6 are provided in the walls of the switch cabinet housing 9, so that the DC voltage busbar 13 extends through the three shown Switch cabinets 1 can extend. A housing connection 7 of the DC voltage busbar 13 is provided on a wall of one switch cabinet housing, which isolates the DC voltage busbar 13 from the housing 9 of the switch cabinet. End caps, which seal and ensure reliable insulation, can be used as the housing connection 7 . In the exemplary embodiment shown, the direct current busbar 13 has two plus busbars 3 and two minus busbars 4 . The rails 3, 4 are designed as flat, elongated structures with a rectangular cross section, with a positive rail 3 being formed adjacent to at least one negative rail 4 and vice versa. As a result, the capacitive effect of the direct current busbar 13 is achieved. The positive rails 3 are connected by a first clamp 2 whose legs rest flat on the positive rails 3 . The minus rails 4 are connected by a second clamp 2, the legs of which lie flat on the minus rails 4. The conductor rail can also have more than two positive rails 3 and more than two negative rails 4 . The number of plus rails 3 is preferably equal to the number of minus rails 4. In such an embodiment, the clamps 2 preferably have more than two legs and z. B. exactly as many legs as there are plus rails 3 or minus rails 4. In each case one leg of a clamp 2 then lies flat on a rail 3, 4. This further improves the capacitive effect and allows all plus rails 3 and all minus rails 4 to be brought to the same electrical potential.

Power converter modules 5 of a power converter can be inserted into each of the control cabinets 1 , the DC link circuit of which can be electrically connected to the DC voltage busbar 13 . The switch cabinets 1 also provide mechanical accommodation and protection for the power converter modules 5 and the busbar 13 .

Optionally, the DC voltage busbars 13 running across the switch cabinets 1 can also be enclosed, e.g. B. for shielding, for protection, for isolation. It is then advantageous to connect this housing as well as the DC voltage busbars 13 continuously and also to connect it to the housings of the power converter or the power converter modules 5 in an equally conductive and low-inductance manner.

2 shows a power converter module 5 with electrolytic capacitors 10 in its DC link. The DC voltage intermediate circuit has a first connection 8 and a second connection 8, which and negative terminals of the DC link. The terminals 8 are designed to cooperate with a connector 12 of the bracket 2 to establish a mechanical and electrical connection between the bracket 2 and the terminal 8 . In the exemplary embodiment shown, the connections 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 intermediate circuit, should therefore preferably also be arranged at the same height (cf. FIG. 4). The connector 12 can have openings through which the connector 12 can be screwed to the terminals 8 .

It is possible to supplement the connections 8 with slot combinations (longitudinal/transverse) or with flexible intermediate elements, in particular in order to be able to meet other requirements such as safety or the ability to be assembled or the like.

A power converter module 5 with AC connections 11 is shown in FIG. 3 . This is e.g. B. the case when the power converter is designed as an inverter. The AC connections 11 shown can run vertically through power converter modules 5 lying one above the other. Connectors with openings for fastening can also be provided on the AC terminals 11 . The connectors can be sealed with end caps that ensure safe isolation.

4 shows an embodiment of the direct current busbar 13 with two plus busbars 3 and two minus busbars 4 . A first bracket 2 connects the two plus rails 3 and a second bracket 2 connects the two minus rails 4. Both brackets have a U-profile whose legs lie flat on the rail 3, 4 in question. The first bracket 2 fulfills several functions. It brings the two plus rails 3 and their connector 12 to the same electrical potential. It also supports capacitive properties of the busbar 13 and thus enables a low-inductance connection z. B. the power converter or power converter module 5 via the connector 12 and the DC voltage busbar 13. In the embodiment shown in FIG Power converter module 5 at the same height. One of these connections is intended for connection to the plus rail 3 and the second of these connections is intended for connection to the minus rail 4 . In order to be able to easily connect the power converter module 5 of FIG. 2 to the DC voltage busbar 13 and to be able to establish the electrical and mechanical connection, the clamps 2 are designed so that the connector 12 extends from the base of the clamp 2 in the opposite direction to the legs of the Brackets 2 extends. The position on the base is chosen so that it matches the distance between the plus rails 3 and the minus rails 4 and the two connectors 12 are arranged at the same height.

In embodiments with z. B. the same power converters or power converter modules 5, which can be arranged one above the other and connected, the connections 8 are suitable for arranging the power converters or power converter modules 5 so that they - depending on the installation order, for example starting at the bottom - one after the other or already connected to each other the rails 3, 4 can be inserted and screwed, for example, from the rear to the rails 3, 4 and to one another. In the exemplary embodiment shown in FIG. 1, two power converters or power converter modules 5 can be arranged one above the other for each control cabinet 1 and connected both to one another and to an associated pair of rails 3, 4 of the intermediate circuit. The two pairs of rails 3, 4 are then in the respective cabinet 1 by brackets 2, z. B. on the back with each other short and wide, so low inductance connected. The rear connection can also be used directly as a DC connection to the outside, eg to a PV system. This connection can be made via intermediate contactors and fuses. Reference character list

switch cabinet

bracket

plus rail

minus rail

power converter module

passage

housing connection

Connection

Housing

capacity

AC connections

Interconnects

DC power rail

Claims

patent claims

1. DC busbar (13) for electrical connection to a DC link of a power converter, with a first and a second plus busbar (3) and a first and a second minus busbar (4), the plus and minus - Rails (3, 4) each running parallel to one another, having a first clamp (2) which is designed to bring the first and the second positive rail (3, 4) to a common first electrical potential and a second clamp ( 2), which is designed to bring the first and the second minus rail (3, 4) to a common second electrical potential, the first and the second plus rail (3) being provided with a first connection (8 ) of a first part of the DC voltage intermediate circuit and to be electrically connected to a first connection (8) of a second part of the DC voltage intermediate circuit and wherein the first and the second negative rail (4) are provided, with a zw to be electrically connected to a second connection (8) of the second part of the DC voltage intermediate circuit.

2. DC busbar (13) according to claim 1, wherein the

DC voltage busbar (13) is formed, the connectable DC voltage intermediate circuit, an electrical capacity for use as

to provide intermediate circuit capacity.

3. DC busbar (13) according to claim 1 or 2, wherein the plus and minus busbars (3, 4) are each flat and arranged one above the other, with a plus busbar (3) adjacent to at least one minus Rail (4) is arranged.

4. DC busbar (13) according to any one of the preceding

Claims, wherein the first clip (2) has an electrically conductive first connector (12) and the second clip (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 , the to provide the respective electrical potential of the associated clamp (2) to the respective connection (8) of the DC voltage intermediate circuit.

5. DC busbar (13) according to any one of the preceding claims, wherein the first clamp (2) is connected over an area to the first and the second positive rail (3) and the second clamp is connected over an area to the first and the second negative rail (4) is connected.

6. DC busbar (13) according to claim 5, wherein the first and the second bracket (2) each have a U-profile, the legs of which are each connected to the plus rails (3) or the minus rails (4). are.

7. DC busbar (13) according to claim 6, when 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 with a DC voltage busbar (13) according to one of the preceding claims and with a power converter having a DC voltage intermediate circuit, wherein a first connection (8) of a first part of the DC voltage intermediate circuit and a first connection (8) of a second part of the DC voltage intermediate circuit are electrically connected to the first potential and a second terminal (8) of the first part of the DC voltage intermediate circuit and a second terminal (8) of the second part of the DC voltage intermediate circuit are electrically connected to the second potential.

9. Arrangement according to claim 8, when dependent on claim 4 or 7, wherein the first part of the DC voltage intermediate circuit is connected to the first potential (12) via the first connector (12) and to the second potential (12) via the second connector.

10. Arrangement according to claim 9, 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.

11. Arrangement according to one of claims 7 to 10, 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.

12. Control cabinet (1) with a DC voltage busbar (13) according to one of claims 1 to 7, wherein the control cabinet (1) is designed to accommodate at least one power converter whose DC voltage intermediate circuit can be electrically connected to the DC voltage busbar (13). is.

13. Control cabinet (1) according to claim 12, wherein the DC voltage busbar (13) has at least two brackets (2) with connectors (12) for each part of an at least two-part DC voltage intermediate circuit of the at least one power converter, the brackets (2) are arranged with the connectors (12) in such a way that the connections (8) of the respective part of the DC voltage 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 in.

14. Control cabinet (1) according to claim 12 or 13, wherein the DC voltage busbar (13) continues outside of the control cabinet housing (9), one or more openings (6) being provided for this purpose in a wall of the control cabinet housing (9).

15. Modular system with multiple switch cabinets (1) according to one of claims 12 to 14, in which the DC voltage busbar (13) extends through the multiple switch cabinets (1) and the multiple switch cabinets (1) are each formed with at least one power converter record, the DC voltage intermediate circuit to the DC voltage busbar (13) can be electrically connected.

16. Modular system according to claim 15, wherein a control unit is provided, which is set up to electrically monitor the electrical safety of the DC voltage intermediate circuit and the DC voltage busbar (13) connected thereto.