Power electronic converter cell and modular system comprising a plurality of exchangeable power electronic converter cells

Abstract

The invention relates to a power electronic converter cell (1) comprising a housing (3) having a high-voltage chamber (5) for receiving at least one high-voltage unit (7), a transformer chamber (9) for receiving at least one transformer (11), a low-voltage chamber (13) for receiving at least one low-voltage unit (15), and a cooling system (17), having at least two flow paths (A, B) which run through the housing (3) separately from one another at least in sections, wherein a first of the flow paths (A) extends in such a way that heat can thus be dissipated from the at least one transformer (11), while at least one second of the flow paths (B) extends in such a way that it bypasses the transformer chamber (9) at least in sections. The invention also relates to a modular system (39) comprising a plurality of exchangeable power electronic converter cells (1) described here and a common cooling device (41).

Description

[0001] Power electronic converter cell and modular system with a variety of interchangeable power electronic converter cells

[0002] The present invention relates to a power electronic converter cell and a modular system with a plurality of interchangeable power electronic converter cells.

[0003] Power electronic converter cells are used in solid-state transformers (SSTs) and are used in modern electrical distribution and transmission systems, as well as in the integration of renewable energy sources and in smart grids. In the field of power electronic converter cells for SSTs, cooling systems are known to reduce thermal stress. Cooling systems are used that direct a cooling fluid through the components of the SST's converter cells.

[0004] Cooling systems that utilize water cooling are known from the prior art. The disadvantage of such water cooling systems is that the cooling fluid must be routed through cooling lines and pumped by a pump. Furthermore, the cooling lines must be fluid-tight, as leakage of the cooling fluid can damage the converter cell components and possibly lead to a short circuit. Furthermore, the cooling fluid flowing through the converter cell must always be deionized to prevent any electrical conductivity of the cooling fluid and corrosion of the cooling system.

[0005] Alternatively, cooling systems are known in which the components are cooled via air cooling, in which an air flow is directed through the converter cell. With air cooling, it should be noted that air has a comparatively low cooling effect, making efficient cooling of all components in a converter cell difficult to achieve. A further challenge in this context is that the components of a converter cell can have different temperature levels.

[0006] State-of-the-art converter cells typically feature a stainless steel housing, with the entire housing being designed to be pressure-resistant. On the one hand, a pressure-resistant housing ensures that the converter cell is well protected against external interference. On the other hand, it is intended to limit physical stresses on the converter cell, which occur particularly in the event of a short circuit and a possible pressure release of the converter cell components.

[0007] The purpose of the known converter cells is to prevent pressure within the converter cell from escaping to the outside. A pressure-resistant housing therefore ensures that damage is limited to the converter cell itself. This is intended to prevent a malfunction in one converter cell from damaging neighboring converter cells in the SST. The disadvantage is that such pressure-resistant housings are heavy and require a lot of material. Furthermore, converter cells with such a pressure-resistant housing have high manufacturing and maintenance costs. Due to the high weight and high costs, replacing a faulty converter cell in an SST is only possible with corresponding effort.

[0008] In general, it is desirable for solid-state transformers (SST) and the power electronic converter cells used therein to increase the longevity of the converter cell components through an efficient cooling system, especially with regard to the different temperature levels at which the converter cell components operate.

[0009] Furthermore, it is generally desirable for SSTs to achieve maintenance that is as simple and cost-effective as possible, especially in the event of faults occurring within a converter cell, which can occur in particular in the event of a short circuit and possible depressurization of the converter cell components, without having to replace the entire SST or a large number of converter cells.

[0010] It is therefore an object of the present invention to provide a power electronic converter cell in which advantageously efficient and / or uniform cooling of all components of the converter cell is possible, in particular even when the components have different temperature levels. Furthermore, the aim is to reduce the risk of damage to adjacent converter cells in the event of a fault within a converter cell, in particular in the event of a short circuit and / or a possible pressure release of the components of the converter cell.

[0011] These objects are achieved by the features of the independent patent claims. Further advantageous embodiments of the solution proposed here are specified in the dependent patent claims. It should be noted that the features listed individually in the dependent patent claims can be combined with one another in any technologically expedient manner and can define further embodiments of the invention. Furthermore, the features listed in the patent claims are further specified and explained in the description, where further preferred embodiments of the invention can also be presented.

[0012] According to a first aspect of the invention, the stated object is achieved by a power electronics converter cell having the features of patent claim 1. The power electronics converter cell comprises a housing, a high-voltage chamber for accommodating at least one high-voltage unit, a transformer chamber for accommodating at least one transformer, a low-voltage chamber for accommodating at least one low-voltage unit, and a cooling system. The cooling system comprises at least two flow paths that extend through the housing, at least in sections separated from one another, wherein a first of the flow paths extends in such a way that heat can be dissipated from the at least one transformer, whereas at least a second of the flow paths extends in such a way that it bypasses the transformer chamber, at least in section.

[0013] As already mentioned, the power electronic converter cell has a housing. The housing can be made of a thin-walled sheet metal, preferably a stainless steel sheet. A sheet metal housing can be particularly advantageous because it can increase the stability of the converter cell and / or protect it from external influences, such as electromagnetic interference and radiation, as well as dust, moisture, and mechanical interference. Mechanical interference can occur primarily during transport or during installation and removal of a converter cell.

[0014] The housing can have or consist of several housing parts. For example, the housing can have a first shell and a second shell. The first shell can consist of at least a base and side chamber walls of the converter cell. The second shell can consist of at least a cover and side chamber walls. The advantage of a housing consisting of two shells is that the components of the power electronic converter cell can be accommodated and, if necessary, fastened particularly easily. To close the housing, the shells can be brought together so that the base and cover face each other and form a closed housing. The housing parts can be firmly connected to one another, preferably screwed, so that the housing can be held in a closed state.This has the advantage that the housing can remain closed even if pressure occurs within the converter cell.

[0015] The power electronic converter cell has the high-voltage chamber for accommodating at least one high-voltage unit. A high-voltage unit can be understood as an electrical assembly that enables efficient and reliable high-voltage transformation and regulation. The high-voltage unit can be equipped with active components such as power semiconductor elements, including IGBTs (Insulated Gate Bipolar Transistors), MOSFETs (Metal Oxide Semiconductor Field-Effect Transistors), and advanced materials such as SiCs (Silicon Carbide Semiconductors) and GaN (Gallium Nitride Semiconductors). These semiconductors can offer improved performance characteristics, especially at high voltages and frequencies, and contribute to increasing the efficiency and reliability of the high-voltage unit.

[0016] In addition to these active components, the high-voltage unit can also contain passive components. These can include energy storage devices such as capacitors, which serve to smooth voltage fluctuations and provide energy during rapid load changes. Inductors can also be included, which serve to limit the current rise, filter, and transfer energy within the high-voltage unit. These inductors can play a beneficial role in shaping the current and voltage waves and minimizing disturbances in the power grid.

[0017] The components of the high-voltage unit can typically be connected to each other via a printed circuit board, so that the high-voltage unit can be formed by the printed circuit board and the connected components. The high-voltage unit can convert lower voltages to higher voltages (and vice versa). Furthermore, the high-voltage unit can generate different voltage and current waveforms. This allows the high-voltage unit to be used in a wide range of SST applications.

[0018] The power electronics converter cell has a transformer chamber for accommodating at least one transformer. The transformer chamber serves as the physical space for housing the transformer, which is typically responsible for the actual transformation of the voltage levels from high to low voltage or vice versa. The transformer chamber advantageously protects the transformer from external influences such as dust, moisture, and / or mechanical failures. It can also provide an easily accessible space for maintenance and repair work, further increasing the efficiency and longevity of the entire SST system.

[0019] The power electronic converter cell has a low-voltage chamber for accommodating at least one low-voltage unit. A low-voltage unit can be understood as an electrical assembly that enables advantageously efficient and reliable low-voltage transformation and regulation. The low-voltage unit can comprise active components such as power semiconductor elements, for example, IGBTs (Insulated Gate Bipolar Transistors), MOSFETs (Metal Oxide Semiconductor Field-Effect Transistors), or even more advanced materials such as SiCs (Silicon Carbide Semiconductors) and GaN (Gallium Nitride Semiconductors), as well as passive components such as energy storage devices, for example, in the form of capacitors and inductors.The components of the low-voltage unit can typically be interconnected via a printed circuit board, so that the low-voltage unit can be formed by the printed circuit board and the connected components. The low-voltage unit can convert higher voltages to lower voltages (and vice versa). Furthermore, the low-voltage unit can generate different voltage and current waveforms for low-voltage applications, making it particularly suitable for use in distribution grids, for energy distribution in buildings, or for connecting low-voltage energy sources such as photovoltaic systems.

[0020] The high-voltage chamber, the transformer chamber, and the low-voltage chamber can be arranged in a common housing. However, it is also conceivable that the high-voltage chamber, the transformer chamber, and the low-voltage chamber can also be formed as cells. In this case, the power electronic converter cell can have a high-voltage cell, a low-voltage cell, and a transformer cell. The respective cells can be designed, at least in sections, as separate cells and have their own separate housing. To manufacture the power electronic converter cell, the high-voltage cell, the low-voltage cell, and the transformer cell can be mechanically and electrically connected to one another to form the power electronic converter cell. This has the advantage that the high-voltage cell, the transformer cell, and the low-voltage cell have a modular design and can be manufactured separately from one another.The modular design advantageously allows for a higher degree of freedom in the production of the power electronic converter cell, since cells of different dimensions can be connected to one another.

[0021] The components of the high-voltage and low-voltage units can each be connected to one another via a printed circuit board, which in particular makes it possible to achieve an integrated and compact design. This arrangement enables the high-voltage and low-voltage units to be formed by the printed circuit board and the components connected to it, which can contribute to the modularity and scalability of the overall system. The printed circuit boards of the high-voltage and low-voltage units can be equipped such that the active components are mounted in a first area of ​​the printed circuit board and the passive components in a second area of ​​the printed circuit board. As a rule, active components can have a higher temperature level than passive components. It can therefore be particularly advantageous to mount these components in different areas of the printed circuit board in order to achieve more efficient cooling.In addition, passive components can generally require more space, allowing a more uniform design to be achieved.

[0022] The power electronics converter cell is preferably designed such that the high-voltage compartment, the transformer compartment, and the low-voltage compartment are arranged linearly one behind the other. In other words, the transformer compartment can be located between the high-voltage compartment and the low-voltage compartment. The high-voltage and low-voltage compartments can be arranged above, below, or next to the transformer compartment. A linear arrangement has proven particularly advantageous, since the high-voltage or low-voltage unit is usually connected to an input or output of the SST, and the transformer transforms a voltage between the high-voltage and low-voltage units. The linear arrangement can contribute to particularly advantageous space utilization and / or modularity.

[0023] The power electronics converter cell has the cooling system with at least two flow paths that run through the housing, at least in sections separated from one another. The flow paths that are at least in sections separated from one another can serve to cool components of the converter cell that operate at different temperature levels. Furthermore, this can create two flow paths that can run independently of one another within the converter cell. This can make it possible for at least in sections to no heat exchange to take place between two air streams flowing along the two flow paths, such that the two air streams can have different temperature levels. The flow paths can be delimited at least in sections by elements or parts of the housing. Furthermore, one or more of the flow paths can be delimited at least in sections by one or more heat sinks.Elements or parts of the housing can also contribute to ensuring that the flow paths are at least partially separated from one another. The active components of the high-voltage and low-voltage units can generally operate at a higher temperature level than the passive components or the transformer, particularly due to conduction and switching losses. The second flow path can be used to provide an airflow in the low-voltage chamber for cooling the passive components that is not heated by the transformer, thus advantageously achieving more efficient cooling of the passive components of the low-voltage unit.

[0024] The two flow paths can run together, at least in sections, along a common flow path. This can be the case, for example, if the two flow paths are connected to an inlet or outlet at which an air flow is introduced into or discharged from the converter cell. This ensures that an air flow can be supplied to or discharged from the two flow paths via a common supply or discharge unit. Alternatively, a separate supply or discharge unit can be provided for each flow path. This has the advantage that the respective air flows can be guided into the respective flow path independently of one another. It can also ensure that in the event of a fault, for example a possible pressure relief of the components of the converter cell, at least two different paths are provided via which the pressure can be reduced.

[0025] The first of the flow paths extends in such a way that heat can be dissipated from the at least one transformer, whereas the at least one second of the flow paths extends in such a way that it bypasses the transformer chamber at least in part. A plurality of first flow paths can be provided, for each of which the conditions described here for the first flow path apply. A plurality of second flow paths can be provided, for each of which the conditions described here for the second flow path apply. If a plurality of the first or second flow paths are provided, these can run separately from one another at least in part and / or be merged in part. The transformer can have a different temperature level than the high-voltage unit or the low-voltage unit.It has therefore proven advantageous to provide a first flow path, which can be used at least in part to cool the transformer, and a second flow path that bypasses the transformer chamber. The second flow path, which bypasses the transformer chamber and thus the transformer, ensures that an air flow running along the second flow path is not heated by the transformer. As a result, the air flow running along the second flow path can be used particularly advantageously to cool additional components after bypassing the transformer chamber.

[0026] For example, the first flow path can run through the high-voltage chamber, the transformer chamber, and a first region of the low-voltage chamber. The second flow path can run through the high-voltage chamber, bypass the transformer chamber, for example, bypass it, and then run through a second region of the low-voltage chamber. Preferably, the first region and the second region of the low-voltage chamber are separate from one another. This makes it possible to provide an air flow in the low-voltage chamber that is not used to cool the transformer and therefore has not been heated (immediately or directly) by the transformer. The air flow of the second flow path can be used to cool the passive components of the low-voltage unit. This has the advantage that it allows efficient cooling of all components of the converter cell.

[0027] In addition to efficient cooling, the two flow paths that are at least partially separated from one another ensure that any pressure that arises within one of the flow paths can be reduced along one flow path, preferably without the pressure damaging components that run along the other flow path. This makes it possible to provide an efficient pressure reduction concept in which any pressure that arises within the converter cell can be reduced in such a way that the risk of damage to other components can be reduced. This can advantageously prevent a malfunction of one component in one chamber from leading to further malfunctions of components in another chamber. This can reduce the risk of major pressure relief, so that the converter cell and the housing can generally be designed to be less robust.This can lead to a lower weight of the converter cell and to a simpler manufacturing process and lower material usage.

[0028] In summary, it can be stated that the present invention makes it possible to provide a power electronic converter cell that enables the most uniform cooling possible for all components of the converter cell, especially for components with different temperature levels. Furthermore, it is also possible to reduce the risk of damage to adjacent converter cells in the event of a fault, particularly in the event of a short circuit and / or a possible pressure release of the components of the converter cell.

[0029] In one embodiment, the cooling system comprises at least one third flow path that extends only through the high-voltage chamber. A plurality of third flow paths can be provided, for each of which the conditions described here for the third flow path apply. The third flow path preferably runs from a first (lower) side of the high-voltage unit or level of the high-voltage chamber to a second (upper) side of the high-voltage unit or level of the high-voltage chamber. More preferably, the high-voltage unit has an air guide element that guides the third flow path from the first side or level of the high-voltage unit to the second side or level of the high-voltage unit. The air guide element can be formed at least in sections by a circuit board of the high-voltage unit.The air guiding element can be arranged and dimensioned such that the air is guided, in particular, from a lower level into an upper level of the high-voltage chamber, which are at least partially separated from one another by the circuit board. The sides can be opposite sides of the circuit board. For example, the first side can be a bottom side and the second side a top side of the circuit board (or vice versa). Particularly preferably, the air guiding element has an opening or a recess in the high-voltage unit, so that the third flow path leads along the first side, through the opening or recess, and along the second side of the high-voltage unit.The at least one third flow path makes it possible to provide a separate flow path for the high-voltage chamber, which can cool the high-voltage unit, which generally has a higher temperature level than the low-voltage unit or the transformer.

[0030] The first, second, and third flow paths can preferably provide lower-temperature airflows in each chamber of the converter cell, with those components of the converter cell with a higher temperature level being cooled via a dedicated flow path. In particular, the flow paths advantageously ensure that an airflow used to cool one component does not have to be used to cool a component located downstream of it in the flow direction. This enables efficient cooling of the components of the converter cell, which can result in increased longevity and / or reduced maintenance requirements.The amount of heat absorbed by the airflow is proportional to the temperature difference between the component surface and the airflow. The airflow heats up proportionally to the temperature difference, and the components heat up inversely to the temperature difference. This results in an increasing temperature level of the components in series. The different flow paths prevent these components, with their individual power inputs, from being connected in series. Such a series connection would increase the temperature level of the cooling air, and the components located further back would heat up to excessive temperatures.

[0031] In one embodiment, the cooling system has at least one fan with which an active flow through the flow paths can be effected. The fan can have one or more fan blades, also called rotor blades, which are shaped and arranged such that they suck in air as they rotate and direct it in a specific direction to generate an air flow. The air flow generated by the fan can be used to flow through the flow paths. The fan preferably has a PWM (pulse-width modulation) control, allowing precise control of the speed and thus the cooling performance. This has the advantage that the cooling performance can be controlled depending on the power state of the power electronic converter cell. Alternatively, it can be provided that the fan is switched off when the power electronic converter cell is not in operation.The fan can consist of several fan units, which can be mounted side by side or at different locations on the housing. Generally, it is also conceivable for at least one fan unit to be arranged at an inlet of the converter cell and at least one further fan unit to be arranged at an outlet of the flow paths, with the one further fan unit at the outlet being configured to extract air from the flow paths. This allows for more effective airflow through the flow paths.

[0032] In one embodiment, the cooling system has at least one flow-through heat sink, which is arranged and configured to cool any possible flow, in particular of conductive gas, from the high-voltage chamber. In the event of a fault, a conductive gas, for example a plasma, can arise in the high-voltage chamber. The at least one flow-through heat sink can advantageously cool the conductive gas, thereby reducing the risk of the conductive gas entering the transformer and low-voltage chamber. The heat sink can also achieve a shorter insulation distance between the high-voltage chamber and the transformer and low-voltage chamber, since the heat sink cools the conductive gas and can reduce its conductivity, preferably completely. This makes it possible to achieve a more compact design of the converter cell.

[0033] In one embodiment, the cooling system comprises at least one first heat sink, which is arranged at least partially in the high-voltage chamber, wherein the first flow path runs through the first heat sink, the transformer chamber, and the low-voltage chamber. If a plurality of first heat sinks are provided, a corresponding plurality of first flow paths can be provided, each of which runs through one of the first heat sinks. Components of the high-voltage unit, the transformer, and components of the low-voltage unit can be cooled by the first flow path. Preferably, the active components of the high-voltage and low-voltage chambers, which can operate at a higher temperature level, are each cooled by the first flow path.Preferably, the high-voltage chamber is connected to the transformer chamber and has at least one opening to the transformer chamber, wherein the at least one first heat sink is arranged at least partially in front of and / or in the at least one opening. This allows the heat sink to be used as completely as possible to cool the active components of the high-voltage chamber, since these components can have a higher temperature level. This allows for more efficient cooling of the high-voltage unit.

[0034] The cooling system preferably comprises at least two first heat sinks, which are arranged at least partially in the high-voltage chamber. For example, two heat sinks can be arranged spaced apart from one another in the high-voltage chamber. The at least two first heat sinks can be used to cool the active components of the high-voltage unit. Using two heat sinks allows for greater flexibility in the manufacture and assembly of the high-voltage unit, thereby allowing for a greater degree of freedom in the design of the converter cell.

[0035] In one embodiment, the cooling system comprises a second heat sink, which is arranged at least partially in the low-voltage chamber, wherein the first flow path also extends through the second heat sink. In principle, several second heat sinks can also be provided. The second heat sink can be used to cool the active components of the low-voltage chamber. This advantageously provides a flow path that serves to cool the active components and the transformer, thereby enabling efficient cooling of these components.

[0036] Preferably, the second heat sink extends along at least half or the entire length of the low-voltage chamber. This allows the second flow path to pass through a significant portion of the low-voltage chamber, in particular completely through it. This advantageously contributes to keeping the first flow path and the second flow path separate from each other in the low-voltage chamber, which in particular contributes to the efficient cooling of the passive components of the low-voltage chamber, since no air from the first flow path can reach the passive components.

[0037] In one embodiment, the second flow path runs, at least in sections, through at least one duct that is thermally separated, in particular insulated, from the transformer chamber. Several such ducts may also be provided. A thermally separated duct may be understood to mean a duct that either runs outside the transformer chamber or passes through it, wherein the duct may be arranged and designed such that, if possible, no thermal energy from the transformer chamber enters the duct (at least not directly). By thermally separating the duct from the transformer chamber, it is possible to ensure that an air flow running along the second flow path is not (significantly) heated by waste heat from the transformer. This may advantageously be reflected in more efficient cooling of the passive components of the low-voltage chamber.

[0038] In one embodiment, at least a portion of a chamber wall of the high-voltage chamber has at least one first pressure relief element, which releases a predetermined first discharge path from the high-voltage chamber when a limit internal pressure is reached. As already mentioned, a pressure increase can occur in the event of a fault in the high-voltage chamber. Such a fault can be triggered by a local arc or an intermediate circuit short circuit. In order to be able to reduce the pressure in the high-voltage chamber efficiently, the high-voltage chamber can have the first pressure relief element, which releases a first discharge path when a predetermined limit internal pressure is reached. The first discharge path has a shorter distance compared to the first and second flow paths A, B, which is why the pressure can be reduced predominantly via the first discharge path.The first outflow path means that the pressure no longer has to be reduced exclusively along the first and second flow paths, which could lead to further faults in the transformer chamber and the low-voltage chamber. The first outflow path also means that the housing of the converter cell can be designed to be less robust, as the pressure can be reduced via the first outflow path, thus allowing less material to be used and a more compact design. The first pressure relief element is preferably arranged on a chamber wall of the high-voltage chamber facing away from the transformer chamber. Typically, the converter cells in an SST are arranged one above or next to one another, so that no other converter cell is adjacent to the side of the high-voltage chamber opposite the transformer cell.As a result, the first outflow path does not lead to a neighboring converter cell, but to the outside, which can reduce the risk of damage to a neighboring converter cell.

[0039] In one embodiment, at least a portion of a chamber wall of the low-voltage chamber has at least one second pressure relief element, which releases a predetermined second outflow path from the transformer chamber when a limit internal pressure is reached. A fault in the transformer cell, for example due to an arc, can lead to an increase in pressure. In order to be able to reduce the pressure in the transformer chamber efficiently, the transformer chamber or the low-voltage chamber can have the second pressure relief element, which releases the second outflow path from the transformer chamber into the low-voltage chamber when a predetermined limit internal pressure is reached. The second outflow path can then lead through the low-voltage chamber to the outside via an opening in a chamber wall of the low-voltage chamber. The pressure can be reduced via the second outflow path through the low-voltage chamber and via the first and second flow paths.The second exhaust path allows pressure to be released as quickly and effectively as possible, reducing the risk of further failures in the converter cell. The second exhaust path also reduces the need for a less robust converter cell housing, as the pressure can be released via the second exhaust path, allowing for less material usage and a more compact design.

[0040] The low-voltage chamber is preferably connected to the transformer chamber and has at least one opening to the transformer chamber, with the second pressure relief element closing the opening to the transformer chamber. The second pressure relief element can preferably be designed as a unidirectional pressure relief element. This can be understood as meaning that the second pressure relief element only opens the second discharge path in one direction, namely from the transformer chamber into the low-voltage chamber. In the opposite direction, the second pressure relief element can withstand a pressure in the low-voltage chamber, so that no discharge path is opened from the low-voltage chamber into the transformer chamber.This allows pressure within the low-voltage chamber to be released to the outside, while the opening to the transformer chamber remains closed, so that the risk of an arc in the transformer chamber can be minimized.

[0041] The first and / or second pressure relief element can have a predetermined breaking point in the chamber wall or a bursting element in the form of a bursting disc, a bursting wall, or a bursting flap. The pressure relief elements can be formed integrally with the chamber wall. This has the advantage that no additional components need to be attached to the chamber wall. Alternatively, the pressure relief elements can be a separate element arranged on an opening that can be connected to the chamber wall. Preferably, the pressure relief elements can be connected to the converter cell via a magnetic or adhesive connection. This allows for particularly simple production of the converter cell.

[0042] The aspects described here in connection with the first and / or second pressure relief element can also achieve at least one of the above-mentioned objects independently of the previously described cooling system with the flow paths that run at least partially separately. Thus, a power electronic converter cell with the first and / or second pressure relief element can be considered to have an independent inventive content of a power electronic converter cell described here, in this context in particular even without the implementation of the cooling system.

[0043] According to a second aspect of the invention, the stated object is achieved by a modular system having the features of patent claim 10. The modular system has a plurality of replaceable power electronic converter cells described here and a common cooling device. The modular system is characterized in that the replaceable power electronic converter cells can be replaced in a particularly simple manner. For example, this makes it possible for a converter cell of the modular system that has been damaged due to a fault to be replaced with a new, functional converter cell. This provides a system that is particularly easy to maintain and that can continue to operate even if a fault occurs or if a converter cell fails by replacing the defective converter cell.

[0044] The cooling device can be provided as a central, shared cooling device for the plurality of converter cells and can, for example, comprise a monoblock or a split air conditioning unit. For example, the system with the plurality of converter cells can be accommodated in a system housing, such as a container, in which the converter cells can be arranged above and / or next to one another in a frame. The converter cells can be arranged so that their high-voltage chambers face one side of the frame and their low-voltage chambers face another side of the frame. The cooling device can be arranged on or next to the frame and ensure air circulation within the system housing so that cool air flows to the side of the high-voltage chambers, while heated air can be extracted from the side of the low-voltage chambers. The cooling device can achieve more efficient cooling of all converter cells.

[0045] The cooling unit preferably has an inlet and an outlet, the outlet being connected to the high-voltage chambers via supply lines and being configured to provide a cool air flow to the high-voltage chambers, and the inlet being connected to the low-voltage chambers via discharge lines and being configured to guide a warm air flow out of the low-voltage chamber. The outlet can be understood as the side of the cooling unit at which cool air can be provided. The inlet can be understood as the side of the cooling unit at which air can be drawn in. This has the advantage that more effective circulation of the cooling fluid can be achieved. Further features, advantages, and possible applications of the present invention will become apparent from the following description of the exemplary embodiments and the figures.All described and / or illustrated features, individually and in any combination, constitute the subject matter of the invention, regardless of their composition in the individual claims or their references. In the figures, the same reference numerals continue to represent identical or similar objects.

[0046] Figures 1 a and 1 b show schematic representations of an embodiment of a power electronic converter cell described here,

[0047] Figure 2 shows a schematic representation of the embodiment of the power electronic converter cell from Figures 1 a and 1 b,

[0048] Figures 3 to 5 show further schematic representations of the embodiment of the power electronic converter cell of Figures 1 a to 2,

[0049] Figure 6 shows a schematic representation of an embodiment of a system described here.

[0050] Figures 1a and 1b show schematic representations of an embodiment of a power electronic converter cell 1 described here. The power electronic converter cell 1 has a housing 3. In the present embodiment, the housing 3 has several housing parts, in the form of a first shell and a second shell. The first shell consists of a base and lateral chamber walls of the converter cell 1. The second shell, not shown, consists of at least one cover and can also have lateral chamber walls. The advantage of a housing 3 consisting of two shells is that the components of the power electronic converter cell 1 can be accommodated and fastened particularly easily. To close the housing 3, the shells can be brought together so that the base and the cover lie opposite each other and form a closed housing 3.The housing parts can be firmly connected to one another, preferably screwed, so that the housing 3 can be kept in a closed state. This has the advantage that the housing 3 remains closed even if pressure occurs within the converter cell 1. The converter cell 1 has a high-voltage chamber 5 in which a high-voltage unit 7 is arranged, a transformer chamber 9 in which a transformer 11 is arranged, and a low-voltage chamber 13 in which a low-voltage unit 15 is arranged.

[0051] The power electronic converter cell 1 is constructed such that the high-voltage chamber 5, the transformer chamber 9, and the low-voltage chamber 13 are arranged linearly one behind the other in the longitudinal direction. This means that the transformer chamber 9 is located between the high-voltage chamber 5 and the low-voltage chamber 13. A linear arrangement has proven particularly advantageous, since the high- or low-voltage units 7, 15 are usually connected to an input or output of the SST, and the transformer 11 transforms a voltage between the high- and low-voltage units 7, 15.

[0052] The converter cell 1 has a cooling system 17 with a fan 19, a first heat sink 21, and a second heat sink 23. The cooling system 17 also has a first flow path A, a second flow path B, and a third flow path C. The first flow path A extends such that heat can be dissipated from the transformer 11, whereas the second flow path B extends such that it bypasses the transformer chamber 9, at least in sections. According to the illustration in Fig. 1, it can also be seen that, by way of example, a plurality of first flow paths A can be provided. In a corresponding manner, a plurality of second flow paths B can also be provided.

[0053] Figure 1b shows the first flow path A. The first flow path A runs through the high-voltage chamber 5 and there (parallel) through two first heat sinks 21. In other words, this can also be described in particular as two first flow paths A being provided here, for example, each running through one of the first heat sinks. For example, in the region of the low-voltage chamber 13, the two first flow paths A can be (again) combined to form a common first flow path A. In the present embodiment, the two first heat sinks 21 are each arranged on a chamber wall of the high-voltage chamber 5, viewed or running in the longitudinal direction. This has the advantage that the first flow path A is split (in sections) and leads into the transformer chamber 9 at two points, so that the transformer 11 can be cooled evenly.

[0054] In an alternative embodiment, one or more than two first heat sinks 21 may be provided, so that the first flow path A leads through the one or more first heat sinks 21.

[0055] The two first heat sinks 21 serve as heat sinks for the high-voltage unit 7, in particular for active components (not shown), such as power semiconductor elements, including IGBTs (Insulated Gate Bipolar Transistors), MOSFETs (Metal Oxide Semiconductor Field-Effect Transistors), SiCs (Silicon Carbide Semiconductors), and GaN (Gallium Nitride Semiconductors). The first flow path A extends from the two first heat sinks 21 to the transformer chamber 9, so that an air flow flowing through the first flow path A cools the transformer 11. The first flow path A then leads to a second heat sink 23, which is used to cool active components such as power semiconductor elements, including IGBTs (Insulated Gate Bipolar Transistors), MOSFETs (Metal Oxide Semiconductor Field Effect Transistors), SiCs (Silicon Carbide Semiconductors) and GaN (Gallium Nitride Semiconductors) of the low voltage unit 15.

[0056] Active components can have a higher temperature level during operation than passive components, such as capacitors or inductors, or the transformer. Therefore, it has proven advantageous to use heat sinks to cool the active components and to provide a first flow path A that runs through the heat sinks 21, 23 of the active components. This enables efficient cooling of these components.

[0057] As indicated in Figure 1b, the first flow path A runs from the high-voltage chamber 5 into the transformer chamber 9 and further into the low-voltage chamber 13. For this purpose, the converter cell 1 has openings between the high-voltage chamber 5 and the transformer chamber 9 and between the transformer chamber 9 and the low-voltage chamber 13. In the present exemplary embodiment, the second flow path B runs through the high-voltage chamber 5, past the transformer chamber 9 through a channel 25 and through the low-voltage chamber 13. In the high-voltage chamber 5, the second flow path B leads through an area in which passive components of the high-voltage unit 7 are arranged, so that an air flow running along the second flow path B can cool the passive components of the high-voltage unit 7.The converter cell 1 has a first opening 27 in the high-voltage chamber 5, which connects the high-voltage chamber 5 to the channel 25, such that the second flow path B leads through the first opening 27 along the channel 25. In the present embodiment, the first opening 27 is arranged in a floor of the high-voltage chamber 5 and the channel 25 is arranged below the transformer chamber 9. In an alternative embodiment, the channel 25 can be arranged on a side or above the transformer chamber 9, wherein the first opening 27 is also arranged on a chamber wall or a ceiling of the high-voltage chamber 5 in order to connect the high-voltage chamber 5 to the channel 25 and to form the second flow path B. In principle, a plurality of channels 5, in particular running parallel, can also be provided.

[0058] As shown in Figure 1b, converter cell 1 has a second opening 29 in the low-voltage chamber 13, which connects the channel 25 to the low-voltage chamber 13. The second opening 29 is arranged in a floor of the low-voltage chamber 13, analogous to the first opening 27, so that the second flow path B leads through the channel 25 into the low-voltage chamber 13. In the low-voltage chamber 13, an air flow leading along the second flow path B can be used to cool the low-voltage unit 15.As can be seen from Figure 1b, the second flow path B in the low-voltage chamber 13 can be divided so that a lower part of the second flow path B runs through a region of the low-voltage chamber 13 in which passive components of the low-voltage unit 15 are arranged, and an upper part of the second flow path B runs through a region of the low-voltage chamber 13 in which a circuit board of the low-voltage unit 15, on which further electronic components can be arranged, is arranged. This ensures that the low-voltage unit 15 is cooled as evenly and effectively as possible. The channel 25 provides an air flow for cooling the passive components and the circuit board of the low-voltage unit 15, which air flow has not been heated by the transformer 11, so that more efficient cooling of the low-voltage unit 15 is achieved.

[0059] The low-voltage unit 15 has an air guide element that directs the second flow path B from a first (bottom) side of the low-voltage unit 15 to a second (top) side of the low-voltage unit 15. The air guide element can be arranged and dimensioned to direct the air. In the present embodiment, the air guide element has an opening or a recess in the low-voltage unit 15, for example, the circuit board, so that the second flow path B leads along the first side, through the opening or recess, and along the second side of the low-voltage unit 15.In other words, this can also be described in particular in such a way that here (at least in sections) two second flow paths B are provided, which run essentially parallel to one another along the low-voltage unit 15, in particular one of the flow paths B along an upper side of the low-voltage unit 15 and the other of the flow paths B along an underside of the low-voltage unit 15.

[0060] As shown in Figure 1a, the third flow path C leads exclusively through the high-voltage chamber 5, wherein the third flow path C initially leads along a first (lower) side of the high-voltage unit 7 and is used to cool passive components of the high-voltage unit 7 and then leads along a second (upper) side of the high-voltage unit 7 and is used to cool a circuit board of the high-voltage unit 7, on which further components can be arranged. For this purpose, the high-voltage unit 7 has an air guide element that guides the third flow path C from the first side of the high-voltage unit 7 to the second side of the high-voltage unit 7. The air guide element can be arranged and dimensioned such that the air is guided.The air guide element has an opening or a recess in the high-voltage unit 7, for example the circuit board, so that the third flow path C leads along the first side, through the opening or recess, and along the second side of the high-voltage unit 7. The at least one third flow path C ensures that a separate flow path is provided for the high-voltage chamber 5, which can cool the high-voltage unit 7, which generally has a higher temperature level than the low-voltage unit 15 or the transformer 11. Figure 2 shows a schematic representation of the embodiment of the power electronic converter cell 1 from Figures 1a and 1b.The converter cell 1 has a first pressure relief element 31 and a second pressure relief element 33, wherein the first pressure relief element 31 releases a predetermined first outflow path D from the high-voltage chamber 5 when a limit internal pressure is reached and the second pressure relief element 33 releases a predetermined second outflow path E from the transformer chamber 9 when a limit internal pressure is reached.

[0061] As already mentioned, in the event of a fault, a pressure increase can occur in the high-voltage chamber 5. Such a fault can be triggered by a local arc or a DC link short circuit. In order to be able to reduce the pressure in the high-voltage chamber 5 efficiently, the high-voltage chamber 5 has the first pressure relief element 31, which opens the first discharge path D when a predetermined limit internal pressure is reached. The first discharge path D has a shorter distance compared to the first and second flow paths A, B, which is why the pressure is predominantly reduced via the first discharge path D. The first discharge path D ensures that the pressure is no longer reduced exclusively along the first and second flow paths A, B, which could lead to further faults in the transformer chamber 9 and the low-voltage chamber 13.The first outflow path D also means that the housing 3 of the converter cell 1 can be designed to be less robust, since the pressure can be reduced via the first outflow path D, so that less material is used and a more compact design is achieved.

[0062] In the present embodiment, two first pressure relief elements 31 are arranged on a chamber wall of the high-voltage chamber 5 facing away from the transformer chamber 9. Typically, converter cells in an SST are arranged one above or next to one another, so that no other converter cell 1 is adjacent to the side of the high-voltage chamber 5 opposite the transformer cell 9. As a result, the first outflow path D does not lead to an adjacent converter cell 1, but rather to the outside, thereby reducing the risk of damage to an adjacent converter cell 1. Figure 2 shows a second pressure relief element 33 on at least a partial region of a chamber wall of the transformer chamber 9 or the low-voltage chamber 13, which opens a predetermined second outflow path E from the transformer chamber 9 when a limit internal pressure is reached.A fault in the transformer chamber 9, for example due to an arc, can lead to an increase in pressure. In order to be able to reduce the pressure in the transformer chamber 9 efficiently, the transformer chamber 9 or the low-voltage chamber 13 can have the second pressure relief element 33, which, when a predetermined limit internal pressure is reached, opens the second outflow path E from the transformer chamber 9 into the low-voltage chamber 13. The second outflow path E then leads through the low-voltage chamber 13 via an opening in a chamber wall of the low-voltage chamber 13 to the outside. The pressure can be reduced via the second outflow path E through the low-voltage chamber 13 and via the first and second flow paths A, B. The second outflow path E ensures that the pressure is reduced as quickly and effectively as possible, thereby reducing the risk of further faults in the converter cell 1.

[0063] In the present embodiment, the second pressure relief element 33 is arranged above an opening to the low-voltage chamber 13, so that the second pressure relief element 33 closes the opening. The second pressure relief element 33 is unidirectional, meaning that the second pressure relief element 33 only opens the second outflow path E in one direction, namely from the transformer chamber 9 into the low-voltage chamber 13. This ensures that pressure within the low-voltage chamber 13 can be released to the outside, while the opening to the transformer chamber 9 remains closed by the second pressure relief element 33, thus minimizing the risk of an arc in the transformer chamber 9.

[0064] The first and / or second pressure relief elements 31, 33 can have a predetermined breaking point in the chamber wall or a bursting element in the form of a bursting disk, a bursting wall, or a bursting flap. The pressure relief elements 31, 33 can be formed integrally with the chamber wall. This has the advantage that no additional components need to be attached to the chamber wall. Alternatively, the pressure relief elements 31, 33 can be a separate element arranged on an opening that is connected to the chamber wall. Preferably, the pressure relief elements 31, 33 can be connected to the converter cell 1 via a magnetic or adhesive connection. This results in particularly simple production of the converter cell 1.

[0065] The function of the first and second pressure relief elements 31, 33 and the release of the first and second outflow paths D, E are described below with reference to Figures 3 to 5, wherein Figures 3 to 5 each show a scenario in which a pressure increase occurs in the high-voltage chamber 5, the transformer chamber 9 and the low-voltage chamber 13.

[0066] Figure 3 shows a schematic representation of the embodiment of the power electronic converter cell 1 of Figures 1 a to 2. In Figure 3, several passive components of the high-voltage unit 7 in the form of capacitors 35 are shown.

[0067] A fault in the high-voltage chamber 5 can lead to a pressure increase, whereby the pressure must be reduced to prevent an explosion of the converter cell 1 or further damage. Such a fault can be triggered by a local arc or a DC link short circuit. In order to be able to reduce the pressure in the high-voltage chamber 5 efficiently, the high-voltage chamber 5 has the first pressure relief element 31, which opens the first discharge path D when a predetermined limit internal pressure is reached. As indicated in Figure 3, the pressure can also be reduced via the fan 19, since the fan 19 is at least partially permeable. As can be seen in Figure 3, the high-voltage chamber 5 has an opening in the form of a grid element in the region of the first pressure relief element 31.In this embodiment, the first pressure relief element 31 is arranged on the outside of the grid element, so that the grid element is closed by the first pressure relief element 31. When a predetermined limit pressure is reached in the high-voltage chamber 5, the first pressure relief element 31 is pushed outward and detached, so that the first discharge path D is opened through the grid element.

[0068] In an alternative embodiment, the first pressure relief element 31 can be designed integrally in the high-voltage chamber 31 in the form of a bursting wall or a bursting element, wherein the bursting wall or the bursting element is destroyed when a predetermined limit pressure is reached and releases the first outflow path D.

[0069] In the event of a fault, a local arc fed by the AC grid, also in conjunction with the discharge of one or more of the capacitors 35, can create a conductive gas, for example a plasma. The majority of the conductive gas can be conducted outward via the first outflow path D. It can also happen that some of the conductive gas flows along the first flow path A. If conductive gas enters the insulation gap between the high-voltage unit 7 and the transformer 11, a short circuit can occur, discharging all of the energy and potentially leading to major damage. The risk of conductive gas entering the insulation gap to the transformer 11 can be reduced by the first heat sink 21, because the first heat sink 21 can extract thermal energy from the conductive gas, causing the conductive gas to cool and reduce its conductivity.

[0070] Figure 4 shows a schematic representation of the embodiment of the power electronic converter cell 1 of Figures 1a to 2. A fault in the transformer chamber 9 can lead to a pressure increase, whereby the pressure must be reduced in order to prevent an explosion of the converter cell 1 or further damage. Such a fault can be triggered by an arc in the transformer chamber 9. In order to be able to reduce the pressure in the transformer chamber 9 efficiently, the second pressure relief element 33 is arranged in a chamber wall between the transformer chamber 9 and the low-voltage chamber 13. The second pressure relief element 33 opens the second outflow path E when a predetermined limit internal pressure is reached in the transformer chamber 9. As can be seen in Figure 4, the transformer chamber 9 has an opening to the low-voltage chamber 13 in the region of the second pressure relief element 33.The opening is designed in the form of a grid element. In this embodiment, the second pressure relief element 33 is arranged on the grid element from the side of the low-voltage chamber 13, so that the grid element is closed by the second pressure relief element 33. When a predetermined limit pressure is reached in the transformer chamber 9, the second pressure relief element 33 is pressed into the low-voltage chamber 13 and released, so that the second discharge path E is opened through the grid element. Because the second pressure relief element 33 is arranged on the grid element, the second pressure relief element 33 acts unidirectionally.This ensures that the second pressure relief element 33 only releases the second discharge path E when a limit internal pressure is reached in the transformer chamber 9, but not when a pressure increase occurs in the low-voltage chamber 13, since the second pressure relief element 33 is held by the grid element. The scenario of the pressure increase in the low-voltage chamber 13 is shown in Figure 5.

[0071] As indicated in Figure 4, the pressure from the transformer chamber 9 can also be reduced along the first flow path A, along the first outflow path D and through the fan 19.

[0072] Figure 5 shows a schematic representation of the embodiment of the power electronic converter cell 1 of Figures 1 a to 2. In Figure 5, several passive components of the low-voltage unit 15 in the form of capacitors 35 are shown.

[0073] A fault in the low-voltage chamber 13 can cause a pressure increase, which must be relieved to prevent an explosion in the transformer cell 1 or further damage. Such a fault can be triggered by a local arc fed by the DC grid, also in conjunction with a DC link short circuit. The pressure in the low-voltage chamber 13 can be efficiently relieved to the outside via the second flow path B. The second pressure relief element 33 prevents conductive gas or metal particles from entering the transformer cell 9 and the high-voltage cell 5.

[0074] Because the second pressure relief element 33 is arranged on the grid element, the second pressure relief element 33 can only be pressed in the direction of the low-voltage chamber 13. A pressure increase in the low-voltage chamber 13 does not cause the second pressure relief element 33 to open the second outflow path E, since the second pressure relief element 33 is pressed against the grid element and withstands the pressure. In an alternative embodiment, the second pressure relief element 33 can be designed as a unidirectional flap. The advantage of a flap is that the second pressure relief element 33 is not destroyed, thereby reducing maintenance of the converter cell 1.

[0075] In the present embodiment, the low-voltage chamber 13 has a partition wall 37 that separates an area in which the capacitors 35 are arranged from the second heat sink 23. The partition wall 37 serves, on the one hand, to separate the first flow path A from the passive components of the low-voltage unit 15 and, on the other hand, to prevent conductive gas from entering the transformer chamber 9 along the first flow path A if a fault occurs within the low-voltage chamber 13. This prevents the conductive gas or metal particles from entering the insulation gap, thereby reducing the risk of a short circuit.

[0076] Figure 6 shows a schematic representation of an embodiment of a modular system 39 described here. The modular system 39 has a cooling device 41 and a plurality of replaceable power electronic converter cells 1. The converter cells 1 are removably arranged one above the other in a frame 43 so that they can be replaced. It can also be provided that additional converter cells 1 are arranged side by side in the frame 43.

[0077] The cooling device 41 is provided as a central, common cooling device 41 for the plurality of converter cells 1 and can, for example, comprise a monoblock or a split air conditioning unit.

[0078] The converter cells 1 are arranged such that their high-voltage chambers 5 face one side of the frame 43 and their low-voltage chambers 13 face another side of the frame 43. In this embodiment, the cooling device 41 is arranged on or above the frame. Alternatively, the cooling device 41 can be arranged next to the frame.

[0079] The cooling device 41 is connected to the converter cells 1 via a supply line 45.

[0080] The supply line 45 carries a cooling medium, for example air, to the converter cells 1, which can be used to flow through the flow paths A, B, C. The cooling medium can be conducted through the converter cells 1 by the cooling system 17 of the converter cells 1 and conveyed back to the cooling device 41 via a discharge line 47. As the cooling medium is conducted through the converter cells 1, it is heated and fed to the cooling device 41 via the discharge line 47. The cooling device 41 can cool the heated cooling medium from the discharge line 47 and make it available to the supply line 45.

[0081] In an alternative embodiment, the system 39 is arranged in a closed system housing, for example a container, wherein the cooling device 41 is not connected to the converter cells 1 via supply and discharge lines 45, 47. The cooling device 41 ensures air circulation within the system housing, so that cool air can also be provided on the side of the high-voltage chambers 5. The cool air provided on the side of the high-voltage chambers 5 can then be used via the cooling device, for example by the fan 19 of each converter cell, to ensure flow through the flow paths A, B, C. The air heated as it flows through the converter cell 1 and exits on the side of the low-voltage chamber 13 can be extracted by the cooling device 41 and cooled.

[0082] Additionally, it should be noted that "comprising" does not exclude other elements or steps, and "a" or "an" does not exclude a plurality. Furthermore, it should be noted that features described with reference to one of the above embodiments can also be used in combination with other features of other embodiments described above. Reference signs in the claims are not to be considered as limitations.

[0083] List of reference symbols

[0084] 1 converter cell

[0085] 3 housings

[0086] 5 High-voltage chamber

[0087] 7 High voltage unit

[0088] 9 Transformer chamber

[0089] 11 Transformer

[0090] 13 Low-voltage chamber

[0091] 15 Low voltage unit

[0092] 17 Cooling system

[0093] 19 fans

[0094] 21 first heat sink

[0095] 23 second heat sink

[0096] 25 channel

[0097] 27 first opening

[0098] 29 second opening

[0099] 31 first pressure relief element

[0100] 33 second pressure relief element

[0101] 35 Capacitor

[0102] 37 Partition wall

[0103] 39 Systems

[0104] 41 Cooling device

[0105] 43 frame

[0106] 45 supply line

[0107] 47 Derivation

[0108] A first flow path

[0109] B second flow path

[0110] C third flow path

[0111] D first outflow path

[0112] E second outflow path

Claims

Patent claims 1. Power electronic converter cell (1) with a housing (3) comprising: a high-voltage chamber (5) for accommodating at least one high-voltage unit (7), a transformer chamber (9) for accommodating at least one transformer (11), a low-voltage chamber (13) for accommodating at least one low-voltage unit (15), and a cooling system (17), comprising at least two flow paths (A, B) running through the housing (3) at least partially separated from one another, wherein a first of the flow paths (A) extends in such a way that heat can be dissipated from the at least one transformer (11), whereas at least a second of the flow paths (B) extends in such a way that it bypasses the transformer chamber (9) at least partially.

2. Power electronic converter cell (1) according to claim 1, wherein the cooling system (17) comprises at least one third flow path (C) extending only through the high-voltage chamber (5).

3. Power electronic converter cell (1) according to claim 1 or 2, wherein the cooling system (17) has at least one fan (19) with which an active flow through the flow paths (A, B, C) can be effected.

4. Power electronic converter cell (1) according to one of the preceding claims, wherein the cooling system (17) has at least one flow-through heat sink (21, 23) which is arranged and configured to cool a possible flow, in particular of conductive gas, from the high-voltage chamber.

5. Power electronic converter cell (1) according to one of the preceding claims, wherein the cooling system (17) comprises at least one first heat sink (21) which is arranged at least in sections in the high-voltage chamber (5), wherein the first flow path (A) runs through the first heat sink (21), the transformer chamber (9) and through the low-voltage chamber (13).

6. Power electronic converter cell (1) according to claim 5, wherein the cooling system (17) has a second heat sink (23) which is arranged at least in sections in the low-voltage chamber (13), wherein the first flow path (A) also extends through the second heat sink (23).

7. Power electronic converter cell (1) according to one of the preceding claims, wherein the second flow path (B) runs at least in sections through at least one channel (25) which is thermally separated, in particular insulated, from the transformer chamber (9).

8. Power electronic converter cell (1) according to one of the preceding claims, wherein at least a partial region of a chamber wall of the high-voltage chamber (5) has at least one first pressure relief element (31) which, when a limit internal pressure is reached, releases a predetermined first outflow path (D) from the high-voltage chamber (5).

9. Power electronic converter cell (1) according to one of the preceding claims, wherein at least a partial region of a chamber wall of the low-voltage chamber (13) has at least one second pressure relief element (33) which, when a limit internal pressure is reached, releases a predetermined second outflow path (E) from the transformer chamber (9).

10. Modular system (39) with a plurality of interchangeable power electronic converter cells (1) according to one of the preceding claims and a common cooling device (41).

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