Connection of the Load to the DC Power Grid

Abstract

The present invention relates to a switching module (M) and a method for connecting a load (L) to a DC power grid (N). The switching module (M) comprises a first module connection (1), a second module connection (2), a third module connection (3), a first electronic switch (T1) and a second electronic switch (T2), wherein the first electronic switch is connected between the first module connection (1) and the second module connection (2), and the second electronic switch is connected between the second module connection (2) and the third module connection (3). The two electronic switches (T1, T2) are anti-series connected between the first module connection (1) and the third module connection (3).

Description

Technical Field

[0001] The present invention relates to a switching module and a method for connecting a load to a DC power grid. Background Art

[0002] In a DC power grid, two types of loads connected to the DC power grid can be distinguished. On the one hand, there is a first type of load, in which the current always flows through the connection line between the DC power grid and the load in the same current direction. Such loads are, for example, pure consumers fed by the DC power grid. On the other hand, there is a second type of load, in which the current can flow through the connection line between the DC power grid and the load in two current directions. Such loads can be supplied with energy by the DC power grid and can output energy to the DC power grid. An example of a second type of load is a rotating electrical machine, which can operate or function both as a motor and as a generator. Protecting the first type of load only requires preventing overcurrent in one current direction, while protecting the second type of load must prevent overcurrent in two current directions. It is generally necessary to be able to very quickly disconnect overcurrents caused, for example, by overload or short circuit in order to avoid or reduce damage. For this purpose, electronic switches are usually used. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a device and a method by which the connection of the two types of loads mentioned above to the DC power grid can be protected against overcurrents appropriately.

[0004] According to the present invention, the above technical problem is solved by a switching module having the features of claim 1, a method having the features of claim 11, and a DC power grid having the features of claim 12.

[0005] Advantageous embodiments of the present invention are the subject matter of the dependent claims.

[0006] A switching module according to the present invention for connecting a load to a DC power grid includes a first module connection, a second module connection, a third module connection, a first electronic switch, and a second electronic switch. The first electronic switch is connected between the first module connection and the second module connection. The second electronic switch is connected between the second module connection and the third module connection. In addition, the two electronic switches are connected in anti-series, that is, in opposite current flow directions, between the first module connection and the third module connection. Here and hereinafter, the term "load" is also understood to mean a load area having a plurality of devices.

[0007] The switching module according to the present invention can be implemented to connect the load to the DC grid in different ways depending on whether bidirectional overcurrent protection is required between the load and the DC grid to prevent overcurrent in both current directions or only unidirectional overcurrent protection is required to prevent overcurrent in one current direction.

[0008] For bidirectional overcurrent protection, the switching module has a first module connection and a third module connection. The anti-series interconnection of two electronic switches between these two module connections can achieve overcurrent protection in both current directions by disconnecting the electronic switch whose conduction direction corresponds to the corresponding flow direction of the overcurrent. Thus, a load to be protected against overcurrent in both directions is connected to the DC grid via the first module connection and the third module connection, where, for example, the first module connection is connected to the DC grid and the third module connection is connected to the load.

[0009] For unidirectional overcurrent protection, the switching module has a second module connection, which is connected to the first module connection via a first electronic switch and to the third module connection via a second electronic switch. This enables a load to be protected against overcurrent only in one direction to be connected to the DC grid, for example, via the second module connection as the load-side connection and via the first or third module connection as the grid-side connection. Thus, the current between the load and the DC grid must only flow through one of the two electronic switches, whereby the losses are advantageously halved compared to the current being conducted through two serially connected switches. In addition, the first module connection and the third module connection can also be connected together and connected to the DC grid, while the second module connection can be connected to the load. Then the two electronic switches are connected in parallel, and the losses are reduced again.

[0010] In one embodiment of the present invention, each electronic switch is an insulated-gate bipolar transistor (IGBT = Insulated-Gate Bipolar Transistor), which has a collector terminal, an emitter terminal, and a gate terminal. Here, for example, the collector terminal of the first electronic switch is connected to the first module terminal, the collector terminal of the second electronic switch is connected to the third module terminal, the emitter terminals of the electronic switches are connected to each other and are respectively connected to the second module terminal. Alternatively, the emitter terminal of the first electronic switch is connected to the first module terminal, the emitter terminal of the second electronic switch is connected to the third module terminal, the collector terminals of the electronic switches are connected to each other and are respectively connected to the second module terminal. In one circuit variant, the emitter terminals of the electronic switches are connected to each other and are respectively connected to the second module terminal. This circuit variant has the advantage that the same control voltage is used for the two gate terminals and thus the gate driver can be omitted. In one circuit variant, the collector terminals of the electronic switches are connected to each other and are respectively connected to the second module terminal. This circuit variant has the advantage of higher stability against grid-commutated electromagnetic interference. Therefore, which advantage prevails and which circuit variant is preferably used depends on the specific application.

[0011] In another embodiment of the present invention, each electronic switch is a metal-oxide-semiconductor field-effect transistor (MOSFET = Metal-Oxide-Semiconductor Field-Effect Transistor) having a drain terminal, a source terminal, and a gate terminal. Here, for example, the drain terminal of the first electronic switch is connected to the first module terminal, the drain terminal of the second electronic switch is connected to the third module terminal, the source terminals of the electronic switches are connected to each other and are respectively connected to the second module terminal. Alternatively, the source terminal of the first electronic switch is connected to the first module terminal, the source terminal of the second electronic switch is connected to the third module terminal, the drain terminals of the electronic switches are connected to each other and are respectively connected to the second module terminal. The above circuit variants correspond to the case where the electronic switch is an IGBT, where the drain terminal of the MOSFET serves as the collector terminal of the corresponding IGBT, and the source terminal of the MOSFET serves as the emitter terminal of the IGBT.

[0012] In another embodiment of the present invention, a diode is anti-parallel connected to each electronic switch. Thereby, for example, in the case of an electronic switch designed as an IGBT, current conduction can be achieved in the cut-off direction of the IGBT through the diode. In the case of an electronic switch designed as a MOSFET, the diode anti-parallel connected to the MOSFET can also be advantageous, for example when the threshold voltage at the reverse diode of the MOSFET becomes too high.

[0013] In another embodiment of the present invention, the switch module has connection markings for the module connections, which identify the first module connection as a unidirectional and bidirectional input connection, the second module connection as a unidirectional output connection, and the third module connection as a unidirectional input connection and a bidirectional output connection. These connection markings advantageously facilitate the wiring of the switch module that matches the desired overcurrent protection (bidirectional or unidirectional) respectively and reduce the risk of incorrect or faulty wiring.

[0014] In another embodiment of the present invention, the first module connection and the third module connection can be connected to each other via a switch. This facilitates the above-mentioned advantageous parallel connection of the two electronic switches in the case of a load where overcurrent is to be prevented only unidirectionally, since this parallel connection can be achieved by closing the switch.

[0015] In a method according to the present invention for connecting a load to a DC grid by means of a switch module according to the present invention, if bidirectional overcurrent protection is required between the load and the DC grid to prevent overcurrent in both current directions, the grid line of the DC grid is connected to the first module connection of the switch module and the load line of the load is connected to the third module connection of the switch module. Conversely, if only unidirectional overcurrent protection is required between the load and the DC grid to prevent overcurrent in one current direction, the grid line of the DC grid is connected to the first module connection and / or the third module connection of the switch module and the load line of the load is connected to the second module connection of the switch module. The advantages of the method according to the present invention correspond to the advantages of the switch module according to the present invention mentioned above. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The features, characteristics and advantages of the present invention described above and the manner of their implementation will be understood more clearly and distinctly in connection with the description of the embodiments detailed below in conjunction with the drawings. Here, in the drawings:

[0017] Figure 1 shows a circuit diagram of a first embodiment of a switch module according to the present invention,

[0018] Figure 2 shows a circuit diagram of a second embodiment of a switch module according to the present invention,

[0019] Figure 3 shows a circuit diagram of a third embodiment of a switch module according to the present invention,

[0020] Figure 4 shows a circuit diagram of a fourth embodiment of a switch module according to the present invention,

[0021] Figure 5 shows a circuit diagram of a fifth embodiment of a switch module according to the present invention,

[0022] Figure 6 Schematically shows a load connected to a DC grid through a switching module for bidirectional overcurrent protection.

[0023] Figure 7 Schematically shows a load connected to a DC grid through a switching module for unidirectional overcurrent protection.

[0024] In the drawings, corresponding parts have the same reference numerals. Detailed implementation

[0025] Figure 1 Shows a circuit diagram of a first embodiment of a switching module M according to the present invention. The switching module M includes a first module terminal 1, a second module terminal 2, a third module terminal 3, a first electronic switch T1, a second electronic switch T2, a first diode D1, and a second diode D2.

[0026] Each electronic switch T1, T2 is an IGBT having a collector terminal C, an emitter terminal E, and a gate terminal G.

[0027] The collector terminal C of the first electronic switch T1 is connected to the first module terminal 1. The collector terminal C of the second electronic switch T2 is connected to the third module terminal 3. The emitter terminals E of the electronic switches T1, T2 are connected to each other and are respectively connected to the second module terminal 2. Thus, the first electronic switch T1 is connected between the first module terminal 1 and the second module terminal 2, the second electronic switch T2 is connected between the second module terminal 2 and the third module terminal 3, and the two electronic switches T1, T2 are anti - series connected between the first module terminal 1 and the third module terminal 3.

[0028] The cathode of the first diode D1 is connected to the collector terminal C of the first electronic switch T1. The anode of the first diode D1 is connected to the emitter terminal E of the first electronic switch T1. Thus, the first diode D1 is anti - parallel connected to the first electronic switch T1.

[0029] The cathode of the second diode D2 is connected to the collector terminal C of the second electronic switch T2. The anode of the second diode D2 is connected to the emitter terminal E of the second electronic switch T2. Thus, the second diode D2 is anti - parallel connected to the second electronic switch T2.

[0030] Figure 2 Shows a circuit diagram of a second embodiment of the switching module M according to the present invention. This embodiment is the same as Figure 1The difference of the first embodiment shown is only that the interconnection of the collector terminals C and emitter terminals E of the electronic switches T1 and T2 is swapped compared to the first embodiment: the emitter terminal E of the first electronic switch T1 is connected to the first module terminal 1, the emitter terminal E of the second electronic switch T2 is connected to the third module terminal 3, and the collector terminals C of the electronic switches T1 and T2 are connected to each other and are respectively connected to the second module terminal 2. Again, the first diode D1 is anti-parallel connected to the first electronic switch T1 and the second diode D2 is anti-parallel connected to the second electronic switch T2.

[0031] Figure 3 The circuit diagram of the third embodiment of the switching module M according to the present invention is shown. The difference of this embodiment from Figure 1 the first embodiment shown is only the additional switch 4, which is connected between the first module terminal 1 and the third module terminal 3, so that the first module terminal 1 and the third module terminal 3 can be connected to each other by closing the switch 4. Thus, by closing the switch 4, the two electronic switches T1 and T2 can be connected in parallel with each other between the first module terminal 1 or the third module terminal 3 and the second module terminal 2.

[0032] Figure 4 The circuit diagram of the fourth embodiment of the switching module M according to the present invention is shown. The difference of this embodiment from Figure 2 the second embodiment shown is only the additional switch 4, which is connected between the first module terminal 1 and the third module terminal 3, so that similar to Figure 3 , the first module terminal 1 and the third module terminal 3 can be connected to each other by closing the switch 4.

[0033] Figure 5 The circuit diagram of the fifth embodiment of the switching module M according to the present invention is shown. The main difference of this embodiment from Figure 1 the first embodiment shown is that each of the electronic switches T1 and T2 is a MOSFET having a drain terminal D, a source terminal S and a gate terminal G, where the drain terminal D assumes the role of the collector terminal C of the corresponding IGBT in Figure 1 and the source terminal S assumes the role of the emitter terminal E of the IGBT. In addition, Figure 5 the switching module M shown in Figure 5 does not have the diodes D1 and D2, or rather, in the embodiment shown in Figure 1 , the functions of the diodes D1 and D2 shown in Figure 5 are assumed by the (intrinsic) reverse diodes of the electronic switches T1 and T2 designed as MOSFETs. However, if necessary, especially if the threshold voltage at the reverse diode becomes too high, Figure 1The embodiment shown is changed in such a way that the diodes D1, D2 are anti-parallel connected to each electronic switch T1, T2.

[0034] Similar to changing the embodiment shown in Figure 1 to the embodiment shown in Figure 5 the embodiment shown in Figures 2 to 4 can also be changed in such a way that each electronic switch T1, T2 designed as an IGBT is replaced by an electronic switch T1, T2 designed as a MOSFET, with or without a diode D1, D2 anti-parallel connected thereto, where the drain terminal D of the MOSFET is connected as the collector terminal C of the IGBT, and the source terminal S of the MOSFET is connected as the emitter terminal E of the IGBT.

[0035] Figures 1 to 4 The embodiment shown in

[0036] Figure 1 and Figure 5 The switch module M shown therein and the changes described above are designed to connect the load L to the DC grid N and protect the connection against overcurrent in such a way that, in the case of overcurrent, the respective electronic switches T1, T2 through which the overcurrent flows are disconnected. For this purpose, module terminals 1, 2, 3 are led out from the switch module M respectively.

[0037] Figure 6 Schematically shows the case where bidirectional overcurrent protection is required between the load L and the DC grid N to prevent overcurrent in both current directions. In this case, in all embodiments of the switch module M, the grid line 5 of the DC grid N is connected to the first module terminal 1 of the switch module M, and the load line 6 of the load L is connected to the third module terminal 3 of the switch module M.

[0038] Figure 7 Schematically shows the case where only unidirectional overcurrent protection is required between the load L and the DC grid N to prevent overcurrent in one current direction. In this case, the load line 6 of the load L is connected to the second module terminal 2 of the switch module M, and the grid line 5 of the DC grid N is connected to the first module terminal 1 and the third module terminal 3. Alternatively, in this case, the grid line 5 of the DC grid N can also be connected only to the first module terminal 1 or the third module terminal 3. In the case of the embodiment shown in Figure 3 and Figure 4 the switch 4 can be switched on here.

[0039] Preferably, the switch module M has connector markings for the module connectors 1, 2, 3 respectively, which identify the first module connector 1 as a unidirectional and bidirectional input connector, the second module connector 2 as a unidirectional output connector, and the third module connector 3 as a unidirectional input connector and a bidirectional output connector.

[0040] Although the present invention has been described in detail by way of preferred embodiments in terms of details, the present invention is not limited to the disclosed examples and other variations can be derived therefrom by those skilled in the art without departing from the scope of the present invention.

Claims

1. A method for connecting a load (L) to a DC power grid (N) by means of a switching module (M), the switching module (M) comprising a first module connection (1), a second module connection (2) and a third module connection (3), and - a first electronic switch (T1), which is connected between the first module connection (1) and the second module connection (2), and - a second electronic switch (T2), which is connected between the second module connection (2) and the third module connection (3), wherein - the two electronic switches (T1, T2) are connected in inverse series between the first module connection (1) and the third module connection (3), wherein - if bidirectional overcurrent protection is required between the load (L) and the DC power grid (N) to prevent overcurrents in both current directions, the grid line (5) of the DC power grid (N) is connected to the first module connection (1) of the switching module (M), and the load line (6) of the load (L) is connected to the third module connection (3) of the switching module (M), and the second module connection (2) is kept unconnected, and - if only unidirectional overcurrent protection is required between the load (L) and the DC power grid (N) to prevent overcurrents in one current direction, the grid line (5) of the DC power grid (N) is connected to the first module connection (1), and the load line (6) of the load (L) is connected to the second module connection (2) of the switching module (M), and the third module connection (3) is kept unconnected or connected to the grid line (5) of the DC power grid (N).

2. The method according to claim 1, wherein each electronic switch (T1, T2) is an insulated gate bipolar transistor having a collector connection (C), an emitter connection (E) and a gate connection (G).

3. The method according to claim 2, wherein the collector connection (C) of the first electronic switch (T1) is connected to the first module connection (1), the collector connection (C) of the second electronic switch (T2) is connected to the third module connection (3), and the emitter connections (E) of the electronic switches (T1, T2) are connected to each other and respectively connected to the second module connection (2).

4. The method according to claim 2, wherein the emitter connection (E) of the first electronic switch (T1) is connected to the first module connection (1), the emitter connection (E) of the second electronic switch (T2) is connected to the third module connection (3), and the collector connections (C) of the electronic switches (T1, T2) are connected to each other and respectively connected to the second module connection (2).

5. The method according to claim 1, wherein each electronic switch (T1, T2) is a metal oxide semiconductor field effect transistor having a drain connection (D), a source connection (S) and a gate connection (G).

6. The method according to claim 5, wherein The drain terminal (D) of the first electronic switch (T1) is connected to the first module terminal (1), the drain terminal (D) of the second electronic switch (T2) is connected to the third module terminal (3), and the source terminals (S) of the electronic switches (T1, T2) are connected to each other and are respectively connected to the second module terminal (2).

7. The method according to claim 5, wherein, the source terminal (S) of the first electronic switch (T1) is connected to the first module terminal (1), the source terminal (S) of the second electronic switch (T2) is connected to the third module terminal (3), and the drain terminals (D) of the electronic switches (T1, T2) are connected to each other and are respectively connected to the second module terminal (2).

8. The method according to any one of claims 1 to 7, wherein, diodes (D1, D2) are anti-parallel connected to each electronic switch (T1, T2).

9. The method according to any one of claims 1 to 7, wherein, the first module terminal (1) and the third module terminal (3) can be connected to each other through a switch (4).

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