Combined earth protection device for modular voltage-power converters.

Abstract

The present invention relates to a hybrid ground protection device for a modular voltage power converter for converting a primary AC voltage having one or more phases into a secondary AC voltage. The hybrid ground protection device includes input and output contacts connected to the voltage input and voltage output of a single module of the converter. The input and output contacts connected to the same single module are connected to varistors that are energized when the voltage drop across the varistor exceeds a first threshold. A non-conductive switch bar having a bridging contact can be moved from an operating position to a grounding position. In the grounding position, the bridging contact connects the input and output contacts of the single module to each other and to a ground terminal. In the operating position, the input and output contacts are not connected by the bridging contact and are not connected to the ground terminal (FIG. 2).

Description

[Technical Field]

[0001] The present invention relates to a hybrid earth protection device for a modular voltage power converter for converting a primary AC voltage having one or more phases into a secondary AC voltage. The voltage power converter includes a plurality of individual modules connected in series for respective phases of the primary AC voltage. Each individual module has a voltage input and a voltage output for receiving one phase of the primary AC voltage. [Background technology]

[0002] For example, to convert three-phase high voltage to DC voltage, a modular voltage power converter using a solid-state transformer (SST), also known as a power electronic transformer, replaces the function of a conventional 50 Hz oil-filled transformer or molded transformer in certain applications. For this purpose, the power electronic transformer is composed of multiple single converters. In this case, multiple single converters are connected in series for each phase of the high voltage, and the multiple series-connected single converters are connected in parallel as a whole.

[0003] The single converters, also called cells, are at high potential during normal operation and therefore inaccessible to humans. Nevertheless, if maintenance or other work must be performed on an SST, various safety regulations must be observed. In particular, it must be ensured that there is no voltage, and a grounding device must be installed for each cell of the multiple cells so that each cell is grounded. Therefore, due to the large number of single cells that comprise an SST, preparation work before maintenance is very tedious and time-consuming.

[0004] Furthermore, due to a fault in a cell, the current may no longer be able to pass through one single cell. In this situation, a high voltage, for example, 20 kV, between the conductors drops across the separation point, which may, for example, explosively destroy the cell. Furthermore, the debris of the explosively destroyed cell may destroy other cells located adjacent to it. As a result, the damage is not limited to one single cell. Summary of the Invention [Problem to be solved by the invention]

[0005] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an apparatus with which at least some of the above problems can be solved. [Means for solving the problem]

[0006] The object of the present invention is achieved by a combined earth protection device according to claim 1. Preferred configurations of the combined earth protection device are described in the dependent claims.

[0007] According to a first aspect, a hybrid ground protection device for a modular voltage power converter is provided for converting a primary AC voltage having one or more phases into a secondary AC voltage. The voltage power converter has a plurality of individual modules connected in series with each phase of the primary AC voltage. Each individual module has a voltage input and a voltage output for receiving one phase of the primary AC voltage. The hybrid ground protection device includes a plurality of input contacts and a plurality of output contacts, each configured to electrically connect one input contact to the voltage input of a single module of the voltage power converter and one output contact to the voltage output of a single module of the voltage power converter. To this end, each of the input contacts and output contacts connectable to the voltage input and voltage output of the same single module are connected by a varistor. The varistor is configured to connect the input contact to the output contact when a voltage drop across the varistor exceeds a first threshold. The hybrid ground protection device includes a non-conductive switch bar having a plurality of bridging contacts. The switch bar is configured to be moved from an actuated position to a grounded position. When the switch bar is in the ground position, each of the bridge contacts connectable to the voltage input and voltage output of the same single module conductively connects the input contact to the output contact. Therefore, the input contact and the output contact that are conductively connected by the bridge contact are connected to the ground terminal. When the switch bar is in the actuated position, the input contact and the output contact that are connectable to the voltage input and voltage output of the same single module are not conductively connected by the bridge contact, and the input contact and the output contact are not connected to the ground terminal.

[0008] For this purpose, a device is provided which, due to its preferred configuration, undertakes three functions at once: it connects the output contacts and input contacts of a series-connected series of a plurality of single cells or a plurality of single modules of a modular voltage power converter, i.e. connects these single modules in series, protects each of these single modules individually from overvoltages by means of a varistor, and, when the switch bar is in the ground position, electrically connects the input contacts and the output contacts, thereby making it possible to connect all the single modules connected in series to the ground terminal, i.e. to ground, by moving the switch bar.

[0009] In other words, the device includes a number of input contacts and output contacts, each of which is provided to contact the corresponding voltage input and voltage output of a single module of the hybrid voltage-power converter. Therefore, the number of input contacts and output contacts of the ground protection device corresponds to the number of single cells. One pair of input contacts and one pair of output contacts are provided for each single module and are designed to be connected to the voltage input or voltage output of each single module.

[0010] In the illustrated embodiment, each combined earth protection device is designed to protect all the individual modules of the modular voltage power converter that are provided for converting one phase of the primary AC voltage. Therefore, one separate combined earth protection device must be provided for each of the phases of the primary AC voltage. For example, in the case of a modular voltage power converter in which a three-phase high voltage must be converted to a DC voltage, three groups of individual modules are provided, one group of individual modules for each phase, and three corresponding combined earth protection devices are also provided.

[0011] To protect the individual modules from overvoltages, each of the paired input and output contacts assigned to the individual modules is connected to a varistor. The varistor is designed to electrically connect the input and output contacts to each other, i.e., to bridge the individual module, when the voltage drop across the varistor exceeds a first threshold. The varistor therefore acts as a voltage limiter in the event of a failure of the individual module and the resulting voltage rise between the voltage input and voltage output of the cell or between the associated input and output contacts.

[0012] Furthermore, the hybrid grounding protector includes a number of conductive bridge contacts that are part of a conductive switch bar. The switch bar can be moved between two positions. One of these positions is called an actuated position, and the other position is called a grounded position. For example, the movement of the switch bar between the actuated and grounded positions can be a translational movement in one direction, such that the switch bar is moved from the actuated position to the grounded position or from the grounded position to the actuated position.

[0013] When the switch bar is in the grounding position, each of the bridge contacts connects one input contact to one output contact, where these interconnected contacts are attached to the same single module. Therefore, in the grounding position, the bridge contacts electrically connect the input and output contacts, shorting them out. Therefore, the number of bridge contacts corresponds to the number of single modules on which the combined grounding protection device is installed.

[0014] Furthermore, a ground terminal is provided for grounding the shorted single module, i.e., for connecting it to ground. The ground terminal can be connected to ground. The combined ground protection device is configured such that the input contacts and output contacts shorted by the bridge contacts at the ground position are also connected to the ground terminal, and therefore all the single modules of the combined ground protection device are connected to ground.

[0015] In contrast, when the switch bar is moved to the operating position, or when the switch bar is in the operating position, the bridge contact is moved to a position where the bridge contact does not conductively connect the input contact and the output contact to each other, i.e., these contacts are not short-circuited. There is also no connection between the ground terminal and the input contact or the output contact. As a result, they are not connected to ground, i.e., they are not grounded. Therefore, the hybrid ground protection device advantageously provides the possibility that a single module can be protected from overvoltage and can further be removed, for example, for maintenance.

[0016] In a preferred embodiment of the earth protection device, for connecting a plurality of individual modules of the voltage power converter in series, the output contacts connectable to the voltage output of the preceding individual module connected in series are conductively connected by a current band to the input contacts connectable to the voltage input of the succeeding individual module connected in series. Thus, in a preferred embodiment, the earth protection device serves all the individual modules connected in series that are provided to receive the same phase in the modular voltage power converter.

[0017] In other words, the earth protection device includes a number of current bands, which in a preferred embodiment may be formed, for example, by conductive metal rails. In this case, the number of current bands or current rails is one less than the number of individual modules that must be protected and grounded by the earth protection device. Each of these current bands connects an output contact of the earth protection device to an input contact of the earth protection device. In this case, the output contact is conductively connected to an input contact that is designed to be connected to each of the voltage outputs and voltage inputs of a number of individual modules that are connected in series.

[0018] The bridge contact used to ground a single module, for example, conductively connects two current bands connected to the input and output contacts of the switch bar in the ground position. Therefore, when the modular voltage power converter must be grounded, the input and output contacts are short-circuited by the conductive connection of the current bands. In this case, the current bands are also connected to the ground terminal and thus grounded. For this purpose, for example, an additional current band may be provided that is adapted to be connected to the voltage output of the last single module connected in series, and that additional current band is electrically connected to the ground terminal of the switch bar in the ground position and is isolated from the ground terminal in the operating position.

[0019] In a preferred embodiment, a discharge gap is formed between each input contact and output contact connectable to the voltage input and voltage output of the same single module, such that an arc occurs when the voltage drop across the discharge gap exceeds a second threshold value, which is preferably greater than the first threshold value. In an extreme fault, for example in the event of an arc in the high-voltage insulation of one single module, the voltage of the power grid drops across the few remaining single modules, and when the varistors provided to protect these single modules fail, these single modules are complementarily protected by the discharge gap across which the voltage drops.

[0020] Preferably, each of the plurality of discharge gaps is formed between a second end of the current strip connected to the input contact and a first end of the current strip connected to the output contact. Therefore, no additional components need be provided for the discharge gaps. Rather, the additional components are formed by appropriately configuring and arranging the current strips that are already provided.

[0021] To connect the current band to the bridge contact, a preferably spring-loaded contact bolt is provided, which is supported on a common support preferably made of a non-conductive material, and when the bridge contact is moved, the spring-loaded contact bolt can be pulled, for example, towards the bridge contact to ensure a secure contact of the bridge contact.

[0022] It is further advantageous if each current band includes two contact bolts, each of which contacts the same bridge contact in the operating position of the switch bar and each of which contacts a different bridge contact in the ground position of the switch bar. Therefore, in a preferred embodiment, it is proposed that during normal operation, the contact surfaces of bridge contacts from the same current band abut or contact the same bridge contact. Therefore, the contact bolts associated with the same current band are conductively connected by both the current band and the bridge contact in the operating position of the switch bar. In the ground position of the switch bar, the contact bolts associated with the same current band are conductively connected only by this current band. Conversely, to short-circuit and thereby ground a single module, a bridge contact is connected to another current band by the bridge contact.

[0023] Preferably, the ground protection device includes an electric drive unit that moves the switch bar from the operating position to the ground position, and the electric drive unit preferably moves the switch bar via a threaded shaft.

[0024] In a preferred embodiment, the ground terminal is formed from a ground rail, and the switch bar is configured so that contact blades conductively connected to the bridge contacts engage with the ground rail when the switch bar is moved from the actuated position to the grounded position. In other words, an electrical connection to ground is established by mechanical engagement between the contact blades conductively connected to or part of the switch bar and the ground rail. This allows a simple visual inspection to confirm whether the contact blades are in contact with the ground rail and whether a single module of the modular voltage-to-power converter is grounded.

[0025] Preferably, when the switch bar is moved from the actuated position to the grounded position, the contact blade locks with the ground rail, thus preventing the connection between the contact blade and the ground rail from being released without external action or operation.

[0026] The earth protection device includes a lever that allows a switch bar to be manually moved from an operating position to a grounding position. In this case, an operator of the earth protection device can preferably recognize whether the switch bar is in the operating position or the grounding position from the position of the lever. Therefore, an operator of the modular voltage-to-power converter can directly confirm whether the device is operating or grounded from the position of the lever.

[0027] According to a second aspect, a modular voltage-power converter for converting a primary AC voltage having one or more phases into a secondary AC voltage using a combined earth protection device according to one of the above-mentioned embodiments is proposed. The voltage-power converter includes a plurality of individual modules connected in series to each phase of the primary AC voltage, each individual module having a voltage input and a voltage output for receiving one phase of the primary AC voltage. Each voltage input is conductively connected to an input contact of the earth protection device, and each voltage output is conductively connected to an output contact of the earth protection device.

[0028] The advantages of the voltage power converter coincide with the advantages of the hybrid earth protection device used in the voltage power converter.

[0029] Each single module includes a transformer and a discharge gap for converting voltage and power between the input side and the output side of the single module. The voltage input and voltage output of the single module are arranged on the input side of the single module. The discharge gap is arranged in parallel with the transformer and is configured to cause an arc discharge when the voltage drop across the discharge gap exceeds a third threshold. In particular, when the varistor and / or discharge gap of the combined earth protection device are insufficient, the discharge gap inside the single module may force the single module to destroy during a fault.

[0030] Preferably, each individual module includes a housing configured such that destruction of an individual module due to an overvoltage does not destroy adjacent individual modules, thereby beneficially limiting damage from destruction of individual individual modules and allowing the voltage power converter to essentially remain operational.

[0031] Preferably, the varistors are arranged so that, in the event of the destruction of one single module due to an overvoltage, the varistors connecting the input and output contacts, which are respectively connected to the voltage input and voltage output of the destroyed single module, are not damaged. This can be ensured in particular by the varistors undertaking the string current until the string current decreases, and at the same time, by using the varistor voltage of the varistors to counter the back electromotive force of the string instead of the cells. Therefore, the varistors bypass the destroyed single module and are not damaged, so the voltage power converter can continue to operate. [Brief explanation of the drawings]

[0032] [Figure 1] 1 is a schematic diagram of an embodiment of a modular voltage-to-power converter; [Figure 2] 1 is a schematic diagram of an embodiment of a voltage-to-power converter with a ground protection device in an activated position; [Figure 3] 3 is a schematic view of the embodiment according to FIG. 2 in a grounded position. [Figure 4] 1 is a perspective view of an embodiment of a voltage-to-power converter with a ground protection device in a ground position; [Figure 5] 5 is a second perspective view of the embodiment according to FIG. 4 when the ground protection device is in the activated position. [Figure 6] 6 is a cross-sectional view of a portion of an embodiment of the ground protection device according to FIGS. 4 and 5 in an activated position. [Figure 7] 7 is another cross-sectional view of a portion of the embodiment of the ground protection device according to FIGS. 4 to 6 in an activated position. [Figure 8] 8 is a perspective view of a portion of the embodiment of the ground protection device according to FIGS. 4 to 7 in an activated position. [Figure 9] 9 is another perspective view of a part of the embodiment of the ground protection device according to FIGS. 4 to 8 in an activated position. [Figure 10] FIG. 11 is a detailed projection view of another part of the embodiment according to FIGS. [Figure 11] FIG. 11 is another partial cross-sectional view of the embodiment shown in FIGS. [Figure 12] 1 is a schematic diagram of a single module configuration of a modular voltage-to-power converter; DETAILED DESCRIPTION OF THE INVENTION

[0033] Figure 1 illustrates an embodiment of a modular voltage power converter in which a three-phase high voltage is converted to a DC voltage. In Figure 1, a solid-state transformer, also called a power electronics transformer, is shown as an example for the modular voltage power converter 1. For example, the high voltage can be a three-phase AC voltage with a voltage of 20 kV, while the DC voltage is + / - 750 V.

[0034] The voltage power converter 1 has phase wires R, S, and T for each phase of the three-phase high voltage, and two output wires 3 and 4 for the DC voltage. For example, the first output wire 3 outputs a voltage of −750 V, while the second output wire 4 outputs a voltage of +750 V.

[0035] The voltage power converter 1 has six individual modules 5 connected in series for each phase of the primary AC voltage. Therefore, in total, the voltage power converter shown in FIG. 1 has 18 individual modules. Since the individual modules 5, which may also be called cells or individual cells, are connected in series, only a portion of the high voltage drops across each individual module. For clarity of the overall view, only some of the individual modules 5 are labeled in FIG. 1. Each individual module 5 includes a power electronics element. A portion of one phase of the high voltage is converted to a DC voltage by the power electronics element. The configuration of the (identical) individual modules 5 is described in more detail elsewhere with reference to FIG. 12.

[0036] Figures 2 and 3 disclose an embodiment of a combined ground protection device 6 for a modular voltage-to-power converter such as that illustrated in Figure 1. Figure 2 shows the combined ground protection device 6 in an activated position or activated state, and Figure 3 shows the ground protection device 6 in a grounded position.

[0037] 2 and 3 illustrate four individual modules 5 used to convert one phase of the primary voltage of the modular voltage power converter 1. Each individual module 5 has a voltage input section 7 and a voltage output section 8. To connect the individual modules 5 in series, one voltage output section 8 of each individual module 5 connected in series is conductively connected to one voltage input section 7 of the subsequent module 5 to be connected in series. Therefore, the composite earth protection device 6 includes multiple current bands 9. Each current band 9 connects the voltage output section 8 of one individual module 5 to the voltage input section 7 of the subsequent individual module 5.

[0038] Thus, on the one hand, the current bands 9 form input contacts 11, with each of them being directly conductively connected to a voltage input 7 of a single module 5. On the other hand, the current bands 9 also form output contacts 12, with each of them being directly conductively connected to a voltage output 8 of a single module 5. For example, the input contacts 11 and the output contacts 12 can be in direct physical contact with the voltage input 7 or the voltage output 8. In order to avoid overcrowding the notation in Figures 2 and 3, only one input contact 11 and one output contact 12, respectively, are shown by one reference numeral.

[0039] Each of the current bands 9 that are directly conductively connected to the voltage input 7 of a single module 5 and the current bands 9 that are directly conductively connected to the voltage output 8 of the same single module 5 are connected via a varistor 10. These varistors 10 are arranged in such a way that when the voltage drop between the input contacts 11 and output contacts 12 that are attached to the same single module 5 or that are directly connected to the voltage input 7 and voltage output 8 of the same single module 5 exceeds a first limit value or threshold, these varistors 10 conductively connect these current bands 9 that are directly connected in series to each other.

[0040] If a fault occurs in a single module 5 and the current is interrupted within the single module 5 or between the current zone 9 and the single module 5, the voltage between the conductors of the high-voltage network, for example 20 kV, will drop directly across the separation point, causing corresponding damage. In particular, this single module 5 may be completely destroyed, and other single modules 5 may be destroyed as well, resulting in the destruction of the entire modular voltage power converter 1. In this case, a varistor is provided as a protective measure, which limits the maximum voltage drop across the single module 5 to a first threshold value.

[0041] The distance d between the second end 13 of the current band 9, which is directly conductively connected to the voltage input 7 of a single module 5, and the first end 14 of the current band 9, which is directly conductively connected to the voltage output 8 of the same single module 5, is selected so that a discharge gap 15 is formed between the first end 14 and the second end 13 of the current band. Due to the selection of the distance d, the voltage across the discharge gap 15 will cause an arc discharge (flashover) when the voltage drop across the discharge gap 15 exceeds a second threshold value, which is greater than the first threshold value. When this first threshold value is exceeded, the varistor 10 connects the input contact 11 and the output contact 12 of the two current bands 9, which are directly connected in series, to each other.

[0042] Thus, in the event of an extreme fault, for example breakdown of the high-voltage insulation of a single module 5, a high voltage of, for example, 20 kV drops across the few remaining single modules 5, and one of the varistors 10 fails, the discharge gap 15 functions as an additional safety device. In this case, a short-circuit current flows through the discharge gap 15, thereby preventing further damage or limiting the occurrence of damage. In Figures 2 and 3, in order to avoid overcrowding, only one of the multiple discharge gaps 15 is indicated by a reference numeral.

[0043] The hybrid ground protection device also includes a non-conductive switch bar having a plurality of bridging contacts 16. The switch bar is not shown in Figures 2 and 3, but will be described in detail in other steps related to other embodiments.

[0044] The number of bridge contacts 16 corresponds to the number of single modules 5. The combined earth protection device 6 in Figures 2 and 3 is provided for each single module 5. That is, one bridge contact 16 is provided for each single module 5 and attached to that single module 5. A switch bar, not shown in Figures 2 and 3, can be reciprocated between an actuated position and a grounded position. The bridge contacts 16 are arranged on the switch bar such that the bridge contacts 16 are reciprocated between the actuated position and the grounded position by the switch bar.

[0045] In this case, the bridge contacts 16 are particularly arranged on the switch bar so that, when the switch bar is in the ground position, each bridge contact 16 conductively connects the input contact 11 to the output contact 12. In other words, each of the plurality of bridge contacts 16 short-circuits the input contact 11 and the output contact 12 that are provided to connect to the same single module 5 when the switch bar is in the ground position. When the switch bar is in the actuated position, the input contact 11 and the output contact 12 that are provided to connect to the same single module 5 are not connected by the bridge contact 16. Therefore, the input contact 11 and the output contact 12 are not short-circuited.

[0046] The hybrid earth protection device shown in Figures 2 and 3 also has a grounding element 17. The short-circuited input contact 11 and output contact 12 can be connected to a ground terminal 18 via the grounding element 17. In the embodiment shown in Figures 2 and 3, the grounding element 17 and the bridge contact 16 are fixed to a switch bar (not shown) and are reciprocated together with the switch bar between an operating position and a grounding position.

[0047] 3 shows the grounding device 6 in a grounded state. In this grounded state, a switch bar (not shown) is in the grounded position. In this position, a grounding element 17 connects the current band 9 to the ground terminal 18. A first end 14 of this current band 9 is connected to the voltage output 8 of the last single module 5 in the series. All current bands 9 are electrically connected or short-circuited to each other via the bridge contact 16. Therefore, all current bands 9 and the single modules 5 are also connected to the ground terminal 18 and thus to ground 19. Therefore, in the grounded state of the combined grounding device 6, the single modules 5 connected to the combined grounding device 6 are not energized.

[0048] The operating state of the earth protection device 6 is shown in Figure 2, where the switch bar (not shown) is in the operating position. As a result, the individual current bands 9 are no longer connected by the bridge contacts 16, and the last current band 9 is no longer connected to the ground terminal 18 by the grounding element 17. Therefore, the single module 5 that must be protected by the earth protection device 6 can be operated and the high-voltage phases can be converted to DC voltage.

[0049] 4 to 11, one embodiment of a modular voltage-power converter 1 will be described with six embodiments of a combined ground protection device 6. In this case, the modular voltage-power converter 1 is shown in external view, while FIGS. 6 to 11 show various details of the voltage-power converter 1 or the combined ground protection device 6.

[0050] Similarly, the voltage power converter 1 shown in Figures 4 and 5 is a solid-state transformer (SST) 2 provided to convert a 20 kV three-phase input AC voltage to a + / - 750 V DC voltage. In Figure 4, the voltage power converter 1 is earthed by a combined earth protection device 6, while the converter 1 in Figure 5 is operational.

[0051] The converter 1 has 28 individual modules 5 connected in series to convert each phase of the input AC voltage or high voltage. For clarity, only one individual module of the plurality of individual modules 5 is labeled in Figures 4 and 5. Each of the individual modules 5 is arranged in a column or cascade in the modular converter 1. In this case, each of the individual modules 5 in two columns 20 is connected in series to convert one of the three phases of the input AC voltage into a DC current or DC voltage.

[0052] 5 it can be seen that each single module 5 is arranged in its own housing 21. The housing 21 is made, for example, from metal and is manufactured in such a way that even if components of one single module 5 are explosively destroyed by an overvoltage, adjacent single modules 5 are not destroyed, or at least are hardly destroyed at all.

[0053] For each row or column of a plurality of individual modules 5, the modular voltage-to-power converter 1 has a separate composite ground protection device 6. Therefore, for each phase of the high voltage, not only one composite ground protection device 6 is provided, but two composite ground protection devices 6 are provided. Details of the ground protection devices 6 will be described in detail below with reference to Figures 6 to 11. However, it should be noted here that each of the plurality of ground protection devices 6 has a lever 22, and the position of this lever 22 indicates whether the respective ground protection device 6 or the individual module 5 connected to this ground protection device 6 is active (as in Figure 5) or grounded (as in Figure 4).

[0054] To switch between the operating position and the grounding position, a user can reciprocate a lever 22 connected to the switch bar of the respective grounding protection device 6. Alternatively, switching can be performed automatically by an electric servo motor 23 as a spindle drive 23 which also moves the switch bar and lever 22. To avoid overloading the illustration, only some of the spindle servo motors 23 are shown with a single reference number. A user or operator of the device can advantageously directly see whether the converter 1 is de-energized, i.e., grounded, by the position of the lever 22.

[0055] Figures 6 to 9 show part of an embodiment of the combined earth protection device 6 according to Figures 4 and 5. In this case, Figures 6 and 7 show a cross section of part of the earth protection device 6, and Figures 8 and 9 show a projection view in which some components of the device 6 are transparently shown. In Figures 6 and 8, the earth protection device 6 is in the activated position, and in Figures 7 and 9, the earth protection device 6 is in the grounded position. Note that Figures 6 to 9 show slightly different parts of the combined earth protection device 6.

[0056] First, this embodiment of the combined earth protection device 6 includes a support rail 37 on which a number of varistors 10 are arranged. Only one varistor 10 is shown in each of Figures 6 to 9. The combined earth protection device 6 includes a total of 14 varistors, one for each single module 5 that must be protected by the device 6. Other varistors are also arranged in the illustrated portion, as can be inferred by the respective fixing means 24 shown. However, these varistors are not shown so as not to obscure the structure behind the earth protection device 6.

[0057] As already explained with reference to Figures 2 and 3, the varistors 10 are designed to be conductively connected to the voltage inputs 7 and voltage outputs 8 of the individual modules 5. The varistors 10 are configured to conductively connect the voltage inputs 7 to the voltage outputs 8 of the respective individual modules 5 when the voltage drop across the varistors 10 exceeds a first threshold value. In this way, the varistors 10 avoid destruction of the individual modules 5 in the event of overvoltages higher than the first threshold value.

[0058] Furthermore, the earth protection device 6 comprises a number of current bands 9 designed to conductively connect a preceding single module 5 of the series-connected plurality of single modules 5 to the voltage input 7 of a succeeding single module 5 of the series-connected plurality of single modules 5. The input contacts 11 and output contacts 12 of the device 6, which establish contact between the current bands 9 and the voltage input 7 and voltage output 8, are not shown in Figures 6 to 9.

[0059] Additionally, the ground protection device 6 includes a plurality of bridge contacts 16 disposed on a non-conductive switch bar 25. The bridge contacts 16 are disposed on the switch bar 25 such that the bridge contacts 16, together with the switch bar 25, move along an adjustment direction 26 in which the switch bar 25 is moved between a ground position (shown in FIGS. 7 and 9) and an actuated position (shown in FIGS. 6 and 8).

[0060] When the switch bar 25 is in the operating position, each bridge contact 16 is connected to only one of the current bands 9 via two spring-loaded contact bolts 27, 28. Therefore, the bridge contact 16 in the operating position forms a parallel current path for these current bands 9 and thus contributes to the series connection of the multiple single modules 5.

[0061] On the other hand, when the switch bar 25 is placed in the ground position as shown in Figures 7 and 9, each of the bridge contacts 16 connects the spring-loaded contact bolts 27 of the current band 9 preceding the plurality of single modules 5 connected in series to the spring-loaded contact bolts 28 of the current band 9 following the plurality of single modules 5 connected in series, thereby short-circuiting the plurality of current bands 9 and the plurality of single modules 5, and each of the voltage inputs 7 or voltage outputs 8 of the single modules 5 is connected to two current bands 9 conductively connected by the bridge contacts 16, and these single modules 5 are grounded without current flow due to the simultaneous connection of the plurality of bridge contacts 16.

[0062] A discharge gap 15 is formed between the first end 13 and the second end 14 of the current band 9 such that when the voltage between the first end 13 and the second end 14 exceeds a second threshold value greater than the first threshold value, the voltage from the second end 14 of the preceding current band 9 connected in series to the first end 13 of the succeeding current band 9 connected in series will cause an arc discharge. The second threshold value can be adjusted over the distance d between the first end 13 and the second end 14. The discharge gap 15 is therefore arranged in parallel with the varistor 10, protecting the single module 5 from damage due to overvoltage when the varistor 10 fails.

[0063] FIG. 10 shows the configuration of the lever mechanism 29 in detail. The switch bar 25 can be moved back and forth between an actuated position and a grounded position. Typically, the switch bar 25 is moved by a servo motor 23 powered by an external power source (not shown). The servo motor 23 has a non-self-retaining threaded shaft and is equipped with a brake. In the event of a motor failure, the switch bar 25 can be moved manually using the lever 22.

[0064] Therefore, the contact blade 30, which connects the current band 9 to the ground terminal 18, is moved by the movement of the switch bar 25. The contact blade 30 locks onto the ground terminal 18. Therefore, additional force is required to disengage the contact blade 30 from the ground terminal 18 again.

[0065] 11 shows the configuration of the lever mechanism 29 in more detail. In particular, the bolt 31 connecting the contact blade 30, the (long) current band 9, the switch bar 25 and the adjusting element 32 is shown. The servo motor 23 can change the position of the switch bar 25 by means of the adjusting element 23. The contact blade 30 and the long current band 9 are electrically conductively connected to each other, while a disc spring 33 prevents electrically conductive contact between the contact blade 30 and the adjusting element 32. The bolt 31 is likewise made non-conductive.

[0066] Finally, FIG. 12 shows an equivalent circuit of one single module 5. The single module 5 includes a voltage input 7 and a voltage output 8, to which the high voltage to be transformed is applied. Therefore, the single module 5 has two DC voltage outputs 34. The main component of this single module is a compact transformer 35, preferably a medium-frequency transformer with a frequency of 10 kHz to 100 kHz, because this allows for a simple, compact design. In case the transformer 35 fails due to an overvoltage, another discharge gap 36 is also provided. The discharge gap 36 inside the single module 5 is configured to generate an arc when a third threshold is exceeded. In this case, the third threshold is greater than the second threshold. In the event of an extreme fault, in which the high voltage drops across almost the entire single module 5, the discharge gap 36 prevents or limits destruction of the single module. [Explanation of symbols]

[0067] 1. Combined voltage-to-power converter 2. Solid-state transformers, power electronic transformers R, S, T phase wire 3, 4 Output wires for DC 5 Single module, single cell, cell 6. Composite earth protection device 7 Voltage input section 8 Voltage output section 9 Current Zones 10. Barista 11 Input contact 12 Output Contact 13 Second end of current band 9 14 First end of current band 9 15 Discharge gap d distance between the second end of the current band 9 and the first end of the subsequent current band 9 16 Bridge Contact 17 Grounding Elements 18 Ground terminal 19 Grand 20 Rows or columns of multiple single modules 21 Single module housing 22 Lever 23 Servo motors, spindle motors 24 Fixing means 25 Switch Bar 26 Adjustment direction 27 Contact bolt 28 Contact Bolt 29 Lever mechanism 30 contact blades 31 volts 32 Adjustment Factors 33 Disc spring 34 DC current output section 35 Transformer 36 Discharge gap 37 Support Rail

Claims

1. A combined earth protection device (6) for a modular voltage power converter (1) for converting a primary AC voltage having one or more phases into a secondary AC voltage, comprising: The voltage power converter (1) comprises a plurality of single modules (5) connected in series for each phase of a primary AC voltage; Each single module (5) has a voltage input (7) and a voltage output (8) for receiving one phase of the primary AC voltage; The composite earth protection device (6) comprises a plurality of input contacts (11) and a plurality of output contacts (12), each configured so that one input contact (11) can be electrically connected to a voltage input section (7) of a single module (5) of the voltage power converter (1) and one output contact (12) can be connected to a voltage output section (8) of a single module (5) of the voltage power converter (1), wherein each of the input contacts (11) and the output contacts (12), which can be connected to the voltage input section (7) and the voltage output section (8) of the same single module (5), are connected by a varistor (10); The varistor (10) is configured to conductively connect the input contact (11) to the output contact (12) when the voltage drop across the varistor (10) exceeds a first threshold value; The hybrid ground protection device (6) includes a non-conductive switch bar (25) having a plurality of bridging contacts (16); The switch bar (25) is configured to be moved from an actuated position to a grounded position; When the switch bar (25) is in a ground position, each of the bridge contacts (16) connectable to the voltage input section (7) and the voltage output section (8) of the same single module (5) conductively connects the input contact (11) to the output contact (12), and the input contact (11) and the output contact (12) conductively connected by the bridge contact (16) are connected to a ground terminal (18); When the switch bar (25) is in the operating position, the input contact (11) and the output contact (12), which can be connected to the voltage input (7) and the voltage output (8) of the same single module (5), are not conductively connected by the bridge contact (16), and the input contact (11) and the output contact (12) are not connected to the ground terminal (18).

2. 2. The earth protection device (6) according to claim 1, wherein, for connecting a plurality of individual modules (5) of a voltage power converter (1) in series, an output contact (12) connectable to the voltage output (8) of a preceding individual module (5) connected in series is conductively connected by a current band (9) to an input contact (11) connectable to the voltage input (7) of a succeeding individual module (5) connected in series.

3. Between each of the input contacts (11) and output contacts (12) connectable to the voltage input (7) and voltage output (8) of the same single module (5), a discharge gap (15) is formed, which is configured so that an arc discharge occurs when the voltage drop across the discharge gap (15) exceeds a second threshold value; 3. The earth protection device (6) according to claim 1 or 2, wherein the second threshold value is preferably greater than the first threshold value.

4. 4. The earth protection device (6) according to claim 2 or 3, wherein each of the plurality of discharge gaps (15) is formed between a second end (13) of the current band (9) connected to the input contact (11) and a first end (14) of the current band (9) connected to the output contact (12).

5. 5. The earth protection device (6) according to claim 1, wherein spring-loaded contact bolts (27, 28) are provided for connecting the current band (9) to the bridge contact (16), the contact bolts being supported on a common support, preferably made of a non-conductive material.

6. 6. The earth protection device (6) according to claim 5, wherein each current band (9) includes two contact bolts (27, 28), each of which contacts the same bridge contact (16) in the operating position of the switch bar (25), and each of which contacts a different bridge contact (16) in the earth position of the switch bar (25).

7. The ground protection device (6) includes an electric drive (23) that moves the switch bar (25) from an operating position to a ground position; The earth protection device (6) according to any one of claims 1 to 6, wherein the electric drive (23) moves the switch bar (25), preferably via a threaded shaft.

8. The ground terminal (18) is formed from a ground rail, The ground protection device (6) according to any one of claims 1 to 7, wherein the switch bar (25) is configured to engage a contact blade (30) conductively connected to the bridge contact (16) with the ground rail (18) when the switch bar (25) is moved from the operating position to the ground position.

9. 9. The ground protection device (6) according to claim 8, wherein the contact blade (30) engages with the ground rail (18) when the switch bar (25) is moved from the operating position to the ground position.

10. The ground protection device (6) includes a lever (22) by which a switch bar (25) can be manually moved from an operating position to a ground position; 10. The ground protection device (6) according to claim 9, wherein an operator of the ground protection device (6) can recognize whether the switch bar (25) is in the operating position or the ground position, preferably from the position of the lever (22).

11. A modular voltage-to-power converter (1) for converting a primary AC voltage having one or more phases into a secondary AC voltage using one or more combined earth protection devices (6) according to any one of claims 1 to 10, comprising: The voltage power converter (1) comprises a plurality of single modules (5) connected in series for each phase of a primary AC voltage; Each single module (5) has a voltage input (7) and a voltage output (8) for receiving one phase of the primary AC voltage; The voltage power converter (1) has one voltage input section (7) conductively connected to an input contact (11) of a ground protection device (6), and each voltage output section (8) conductively connected to an output contact (12) of the ground protection device (6).

12. Each single module (5) includes a transformer (35) and a discharge gap (36) for converting voltage and power between the input side of the single module (5) and the output side of the single module (5); The voltage input (7) and the voltage output (8) of the single module (5) are arranged on the input side of the single module (5), 12. The voltage-to-power converter (1) according to claim 11, wherein the discharge gap (36) is arranged in parallel with the transformer (35) and is configured to cause an arc discharge when a voltage drop across the discharge gap (36) exceeds a third threshold value.

13. 13. A voltage-to-power converter (1) as claimed in claim 11 or 12, wherein each individual module (5) includes a housing (21) formed so that in the event of destruction of a single module (5) due to an overvoltage, a single module (5) arranged adjacent to the destroyed single module (5) is not destroyed.

14. 14. A voltage power converter (1) according to claim 11, 12 or 13, wherein the plurality of varistors (10) are arranged so that, in the event of destruction of one single module (5) due to an overvoltage, the varistors (10) connecting the input contacts (11) and output contacts (12) connected to the voltage input section (7) and voltage output section (8) of the destroyed single module (5) are not damaged.

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