High voltage bypass device, voltage source converter, and method of operation

Abstract

The present disclosure relates to a high voltage bypass device (10) comprising a cavity (13), a trigger element arranged in the cavity (13), a reservoir (17) filled with an electrically conductive flowable material (18), and a gate (19) separating the cavity (13) and the reservoir (17). The trigger element is connected to a first terminal (11) and a second terminal (12) of the high voltage bypass device (10). The shutter (19) is configured to open a channel between the cavity (13) and the reservoir (17) when the trigger element is triggered by an overvoltage condition such that the electrically conductive flowable material (18) at least partially fills the cavity (13) to form an electrically conductive path from the first terminal (11) to the second terminal (12). The present disclosure also relates to a voltage source converter (VSC), in particular a modular multi-cell converter (40), and to a method of operation for a high voltage bypass device (10).

Description

Technical Field

[0001] The present disclosure relates to a high voltage bypass device, its use in a voltage source converter, and an operating method for the high voltage bypass device. Background Art

[0002] High voltage (HV) devices, such as voltage converters operating at voltages exceeding 1 kV or higher, usually include a plurality of switching devices, such as power semiconductor switching devices, which selectively connect or disconnect two different voltage potentials. For example, so-called modular multi-cell converters (MMC) include a plurality of switching cells to generate a desired output voltage from a given input voltage. Such converters are useful, for example, in high voltage direct current (HVDC) transmission systems. Since such devices are part of critical infrastructure, they should operate reliably, even in the event of failure of individual components of the converter.

[0003] It is well known that a mechanical bypass switch (Bypass Switch, BPS) or a circuit breaker is used to bypass a failed switch assembly. However, providing additional electromechanical components increases the complexity and significant cost of the overall device. Alternatively, specific semiconductor protection devices can be used. However, due to the large voltages and currents involved in high-voltage devices, semiconductor-based protection devices generally require active cooling, which also increases the complexity and significant cost of high-voltage devices. If these components are provided redundantly, for example to meet reliability requirements, the increased complexity and cost will double. Summary of the invention

[0004] The present disclosure provides alternative devices, systems, and methods for ensuring reliable operation of high voltage devices.

[0005] According to a first aspect, a high voltage bypass device is disclosed. The device includes a cavity, a trigger element arranged in the cavity, a reservoir filled with a conductive flowable material, and a shutter separating the cavity and the reservoir. The trigger element is connected to a first terminal and a second terminal of the high voltage bypass device. The shutter is configured to open a passage between the cavity and the reservoir when the trigger element is triggered by an overvoltage condition, so that the conductive material at least partially fills the cavity to form a conductive path from the first terminal to the second terminal.

[0006] The device according to the first aspect can bypass another device or part of the high voltage device. In contrast to known bypass devices, the disclosed bypass device does not require any form of active control or forced cooling. Therefore, even in existing devices, such a device is relatively easy to construct and integrate.

[0007] In at least one embodiment, the trigger element includes a first electrode connected to the first terminal and a second electrode connected to the second terminal, the first electrode and the second electrode extending into the cavity and forming a spark gap therein. The spark gap is relatively easy to form and generates a spark under an overvoltage condition, which can be used to release the gate almost immediately. In addition, after the bypass device is triggered, the electrodes forming the spark gap can form part of the conductive path.

[0008] In at least one embodiment, the trigger element includes a varistor connected between a first terminal and a second terminal. Varistors have well-known electrical properties. Among them, they can enter a conductive state above a defined threshold voltage (called a clamping voltage). Due to ohmic losses in the conductive state, the varistor generates heat that can be used to release the gate.

[0009] In at least one embodiment, the conductive flowable material includes at least one of a liquid, a powder, and / or a granular material, such that the material can flow freely from the reservoir to the cavity, for example, under the influence of gravity or other external forces.

[0010] In at least one embodiment, the conductive flowable material includes at least one of a metal or a metal alloy, in particular gallium (Ga), gallium indium tin alloy (Galinstan), mercury (Hg), aluminum (Al), or copper (Cu). Metallic materials have very high electrical conductivity and are therefore suitable for carrying high currents typically found in high voltage devices.

[0011] In at least one embodiment, the trigger element is configured to generate heat under an overvoltage condition, and the gate includes a heat-sensitive material, particularly a polymer material, which is at least partially destroyed by melting, evaporation, or combustion. Such a material can be designed to reliably activate the gate mechanism in the event of a spark or other predefined thermal event in the cavity.

[0012] According to various embodiments, the shutter comprises a thermally sensitive membrane separating the cavity from the reservoir or is coupled to a spring-loaded thermally sensitive trigger separating the cavity from the reservoir. Either solution provides a simple mechanical shutter mechanism that can be activated by heat generated under an overvoltage condition.

[0013] In at least one embodiment, the reservoir is arranged above the cavity in the mounted position of the device so that when the trigger element is triggered, the conductive flowable material is released under the action of gravity, thereby opening the gate. The mechanism operated by gravity is particularly reliable and does not rely on any external energy source or control.

[0014] According to at least one embodiment, the trigger element comprises a first electrode connected to the first terminal and a second electrode connected to the second terminal, the first electrode and the second electrode forming a spark gap. The first electrode is arranged at the bottom of the cavity and protrudes upward, and the second electrode is arranged at the top of the cavity near the gate and protrudes downward. Alternatively or in addition, the first electrode is arranged at the first wall of the cavity and protrudes toward the opposite second wall of the cavity, and the second electrode is arranged at the second wall of the cavity and protrudes toward the first wall of the cavity, wherein a direct path between the first and second electrodes is close to the gate. These arrangements ensure that the energy of the spark will reliably trigger the gate mechanism.

[0015] According to at least one embodiment, the trigger element comprises a varistor connected between a first terminal and a second terminal. The varistor is arranged in a central portion of the cavity below the gate. Alternatively or additionally, the varistor is arranged in direct thermal contact with the gate. These arrangements ensure that the heat generated by the varistor will reliably trigger the gate mechanism.

[0016] According to at least one embodiment, before the trigger element is triggered, the cavity is filled with one of a vacuum or a protective gas. This may be advantageous in certain operating environments where accidental discharge or chemical corrosion of the electrode should be avoided.

[0017] In at least one embodiment, the conductive flowable material is configured to form a permanent electrical path between the first and second terminals after the trigger element is triggered. This can be achieved in different ways, for example, by flooding the cavity with a conductive liquid, or by contacting the first and second electrodes extending into the cavity or defining the cavity with a granular conductive medium. The formation of a permanent electrical path enables the high voltage device to remain operational for a relatively long period of time, for example, until a fault in another component is identified and resolved.

[0018] According to a second aspect, a voltage source converter (VSC), in particular a modular multi-cell converter (MMC), is provided. The converter comprises at least one switching unit configured to switch a high voltage and at least one high voltage bypass device according to the first aspect, the high voltage bypass device being configured to bypass at least one switching unit in the event of a fault.

[0019] In the event that a switching cell proves to be faulty, the converter according to the second aspect remains partially or fully operational. In this case, the switching cell may be bypassed by a high voltage bypass device, thereby providing a path for current to bypass the cell.

[0020] In at least one embodiment, the switch unit includes at least one power semiconductor switch device, in particular an IGBT, and the high-voltage bypass device is connected in parallel with the at least one power semiconductor switch device. In this way, the core switch component of the switch unit can be bypassed.

[0021] According to at least one embodiment, the switch unit further comprises at least one mechanical bypass switch connected in parallel with at least one power semiconductor switch device and the high-voltage bypass device. Such a converter combines the advantages of a mechanical bypass switch device with the additional safety of a high-voltage bypass device according to the first aspect. For example, the mechanical bypass switch device may be activated or deactivated by an external control signal and / or multiple times, or may have other advantages. In the event that the mechanical bypass switch cannot be closed, the high-voltage bypass device may be activated without external control. In addition, it meets the requirement of providing a redundant bypass component, thereby avoiding the risks associated with the failure of a single safety component.

[0022] In at least one embodiment, at least one switching unit has a rated voltage exceeding 1 kV, preferably exceeding 3 kV, and / or a rated current exceeding 100 A, preferably exceeding 1000 A.

[0023] In at least one embodiment, at least one high voltage bypass device is triggered by an overvoltage that exceeds a rated voltage of the switching unit by two times or more.

[0024] In at least one embodiment, at least one high voltage bypass device has an activation time of less than 10 ms for bypassing at least one switching unit under an overvoltage condition.

[0025] In at least one embodiment, the at least one high voltage bypass device is configured to bypass at least one switching unit for more than 24 hours, preferably more than 168 hours.

[0026] The above characteristics enable the converter to be used for typical voltages, currents, overvoltage conditions, switching times, and operating times found in high voltage installations.

[0027] According to a third aspect, a method for operating a high voltage bypass device is disclosed. The method comprises:

[0028] triggering a trigger element connected to two terminals of the bypass device under an overvoltage condition, in particular generating heat by spark or ohmic heating;

[0029] In response to triggering the trigger element, at least partially destroying the gate of the bypass device, in particular by melting, evaporating, or burning, thereby releasing the conductive flowable material; and

[0030] The cavity of the bypass device is at least partially filled with a conductive flowable material to form a permanent electrical path between two terminals of the bypass device.

[0031] The steps according to the third aspect achieve a simple mechanism that does not require any external control and thus reliably bypasses parts of the high voltage device.

[0032] The present disclosure includes several aspects of a high voltage device.Each feature described with respect to one aspect is disclosed herein with respect to other aspects, even if the corresponding feature is not explicitly mentioned in the context of a particular aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The accompanying drawings are included to provide further understanding. In the drawings, elements of the same structure and / or function may be represented by the same reference numerals. It should be understood that the embodiments shown in the drawings are illustrative representations and are not necessarily drawn to scale.

[0034] Figures 1A to 1C Schematic cross-sections of a first high voltage bypass device are shown before, during, and after an overvoltage condition occurs.

[0035] Figure 2A , 2B , and 2C show schematic cross-sections of the second high voltage bypass device before, during, and after an overvoltage condition occurs.

[0036] Figure 3 A schematic circuit diagram of a portion of a voltage source converter comprising a single switching cell is shown.

[0037] Figure 4 A schematic circuit diagram of a portion of a modular multi-cell converter comprising a plurality of switching cells is shown.

[0038] Figures 5A to 5C Schematic cross-sections of the third high voltage bypass device are shown before, during, and after an overvoltage condition occurs.

[0039] Figures 6A to 6C Different cross sections of the fourth high voltage bypass device are shown before and after an overvoltage condition occurs.

[0040] Figure 7 A method of operating a high voltage bypass device is shown in schematic form. DETAILED DESCRIPTION

[0041] Figure 1A The functional components of a first bypass device 10 are shown in a schematic manner. The bypass device 10 comprises a first terminal 11 and a second terminal 12 for connecting the bypass device 10 to corresponding electrical connections of a device to be bypassed. For example, the bypass device 10 can be connected in parallel with a switching device (such as an IGBT) and / or a mechanical bypass switch so as to be short-circuited when a corresponding device fails.

[0042] The two terminals 11 and 12 are electrically isolated from each other by multiple parts of an insulating housing or the like, thereby forming a cavity 13. Multiple parts of the first terminal 11 form a first electrode 14 protruding into the cavity 13. Similarly, multiple parts of the second terminal 12 form a second electrode 15 protruding into the cavity 13. The first electrode 14 and the second electrode 15 together form a spark gap 16 therebetween. The spark gap 16 serves as a triggering element of the first bypass device 10 and is triggered in the event of an overvoltage condition occurring between the first terminal 11 and the second terminal 12. The overvoltage value that triggers the bypass device 10 is determined by the shape and distance between the two electrodes 14 and 15 and the potential gas filling the cavity 13. According to one embodiment, a shielding gas or a vacuum may fill the cavity 13. For example, a voltage of 5 kV may trigger an arc across the spark gap 16.

[0043] exist Figure 1A In the bypass device 10 shown, the second terminal 12 forms the outer wall of a reservoir 17 filled with a conductive flowable material 18. In the embodiment shown, the conductive flowable material 18 is arranged in the central portion of the second terminal 12, i.e., directly above the first electrode 14 in the installed position of the bypass device 10. The passage between the reservoir 17 and the cavity 13 below it is sealed by a gate 19. The gate 19 is arranged near the second electrode 15. For example, as shown in the figure, a film formed of a thin polymer material with a low melting point can be used to seal the conductive flowable material 18 in the reservoir 17.

[0044] exist Figure 1B In the illustrated situation, an overvoltage condition occurs between the first terminal 11 and the second terminal 12. As a result, a spark 20 is formed between the first terminal 14 and the second electrode 15. Heat associated with the spark 20, such as heated plasma, melts or otherwise damages at least a portion of the gate 19. Figures 1A to 1C In the illustrated embodiment, the membrane separating the reservoir 17 and the cavity 13 is substantially completely broken. In another embodiment, only a portion of the gate 19 may be broken, thereby triggering a mechanical break in the seal between the reservoir 17 and the cavity 13. For example, a fuse formed of a polymer material may be broken by the spark 20 and release a spring-loaded separator (not shown). As a result, the conductive flowable material 18 flows into the cavity 13 under the action of gravity.

[0045] exist Figure 1C In the case shown, the lower part of the cavity 13 is filled with a conductive flowable material 18, such that the conductive flowable material 18 is in contact with both the first electrode 14 and the second electrode 15. Thus, a permanent conductive path 21 is formed between the first terminal 11 and the second terminal 12. In contrast to high power semiconductor switching devices, the conductive path 21 does not require active cooling.

[0046] For example, a metal material that is liquid at normal pressure and room temperature of 20° C. may be used. For example, mercury and certain gallium-based metal alloys, such as gallium, indium, and tin alloys (also called Galistan), have melting points of approximately -39° C. and -19° C., respectively, and have relatively low resistance. Depending on operating conditions, in the case where the high-voltage bypass device 10 is installed in a converter or other portion of a high-voltage electrical device and continuously operates above the melting point of the corresponding metal, a metal or metal alloy with a slightly higher melting point may also be used, for example, gallium having a melting point of approximately 30° C.

[0047] As another example, a powder or granular material may be used as the conductive flowable material 18. For example, relatively small copper particles having a particle size in the micrometer range may be used to form the electrical pathway 21. If a relatively fine powder is used, the high current flowing through the bypass device may in turn melt a portion of the powdered substance filling the gap between the electrodes and form a conductive path 20 having a lower resistance than the original powder.

[0048] Figures 2A to 2C Another embodiment of the second high voltage bypass device 10 is shown. Figures 2A to 2C Most components of the high voltage bypass device 10 correspond to Figures 1A to 1C The corresponding components of the high voltage bypass device 10 are shown. Therefore, only the differences are described here.

[0049] Different from the first embodiment, Figure 2A In the second high voltage bypass device 10 shown, the first and second terminals 11 and 12 form opposite side walls of the bypass device 10. Therefore, the first electrode 14 and the second electrode 15 protrude from the corresponding side walls toward the center of the cavity 13. The bottom of the cavity 13 is formed by the insulating bottom 22. The flowable material 18 is arranged in the reservoir 17 formed as the insulating top 23 of the bypass device 10. Depending on the flowable material 18 used, the reservoir 17 can be open at the top, as shown, and sealed with a lid (not shown).

[0050] As mentioned above, the gate 19 is arranged above and close to the straight line between the two electrodes 13 and 14 forming the spark gap 16. Figure 1B As shown, a spark 20 is formed under an overvoltage condition between the first terminal 11 and the second terminal 12. As a result, the gate 19 will be partially or completely destroyed and the flowable material 18 will partially or completely fill the cavity 13 arranged below the reservoir 17. Figure 2C In the specific embodiment shown in FIG. 1 , the conductive flowable material 18 substantially fills the entire cavity 13 .

[0051] Figure 3A portion of a high voltage arrangement including a bypass device 10 according to the present disclosure is shown. In particular, a single switching cell 30 is depicted which may be used in a voltage source converter such as a modular multi-cell converter (MMC) described later.

[0052] Figure 3 The switching unit 30 shown comprises a half bridge 31. Figure 3 The circuit 100 comprises a voltage source 32 represented by a capacitor in FIG. 1 and two IGBTs 33a and 33b connected in series between the two terminals of the voltage source 32. Each IGBT 33a and 33b also has a respective diode 34a and 34b, respectively, which conducts current in opposite directions. This can take the form of an integrated body diode or an external diode.

[0053] Between the two IGBTs, an electrical contact 35 is formed, which can be used, for example, to output the voltage generated by the half bridge 31 to a high voltage device (not shown).

[0054] exist Figure 3 In the case where the lower IGBT 33a of the half bridge 31 shown cannot be activated (i.e. closed), the entire switch unit 30 will permanently open the electrical path between the electrical reference contact 36 and the electrical contact 35. Therefore, the converter or other part of the electrical device including the switch unit 30 will block any current to be transmitted.

[0055] To avoid this, according to Figure 3 , bypass device 10 (as described above with respect to Figures 1A to 2C Detailed description of the bypass device 10) is mounted in parallel with the first IGBT 33a. As described above, in the event that the lower IGBT 33a cannot be activated, i.e. by providing a corresponding gate voltage to its control gate, an overvoltage condition will occur between the electrical contact 35 and the reference contact 36. As a result, a spark 20 will be triggered in the spark gap 16 of the bypass device 10, thereby releasing the conductive flowable material 18 to form a permanent conductive path 21 through the bypass device 10 (see also Figure 7 This effectively shortens the switching unit 30 and maintains the electrical path between the reference contact 36 and the electrical contact 35. Current can flow freely through the unit 30, allowing the entire converter to continue to operate.

[0056] As mentioned above, the gate 19 may be formed of a polymer material that is substantially destroyed under overvoltage conditions. Therefore, the electrical bypass device 10 may be triggered only once. Therefore, it may also be referred to as a sacrificial component, in particular a sacrificial spark shorting device.

[0057] Although the bypass device 10 is relatively simple to arrange and therefore inexpensive to manufacture, it may be desirable to implement additional means of bypassing the first IGBT 33a in a controlled manner. Figure 3 In the embodiment shown, an additional mechanical bypass switch 37 can be connected in parallel to the first IGBT 33a and the bypass device 10. The mechanical bypass switch 37 can be controlled by a corresponding control circuit (not shown). In the event that the control circuit determines that the switch unit 30 should be deactivated or the IGBT 33a cannot be successfully activated, the mechanical bypass switch 37 can be closed to establish an electrical path between the reference contact 36 and the electrical contact 35.

[0058] Preferably, the mechanical bypass switch 37 is activated by the control circuit before the spark 20 is formed in the bypass device 10. In this configuration, the sacrificial bypass device 10 will only be activated when the first IGBT 33a and the mechanical bypass switch 37 fail at the same time. In practice, the switch unit 30 or the IGBT 33a will have a specific rated voltage, such as 1kV or 3kV. In the event of an IGBT failure, the mechanical bypass switch 37 will be triggered by the monitoring circuit. The gap between the first electrode 14 and the second electrode 15 of the bypass device 10 can be configured to be triggered only when the voltage potential between the electrical contact 35 and the reference contact 36 exceeds twice the rated voltage of the IGBT 33a. In operation, this situation may occur within 10ms of the failure of the mechanical bypass switch 37.

[0059] Figure 4 It is shown how to combine multiple switch units 30 to form a modular multi-unit converter 40. In the depicted embodiment, the modular multi-unit converter 40 includes a total of four switch units 30a to 30d connected in series. Among them, the reference contact of each switch unit is connected to the electrical contact of the previous switch unit. The reference contact 36 of the first switch unit 30a is connected to an electrical reference potential, such as an external voltage provided by a high-voltage transmission line. The electrical contact 35 of the last switch unit 30d can be connected to the output of the MMC 40, such as a direct current (DC) network, and the energy from the high-voltage alternating current (HVAC) network will be provided to the direct current (DC) network.

[0060] Each switch unit 30a to 30d of the MMC 40 may include one of the bypass devices 10 as described above. For clarity, only a single bypass device 10 is shown for the second switch unit 30b. If one of the IGBTs 33 of any one of the switch units 30 fails, electrical transmission from the external reference potential to the output line is still possible through the corresponding bypass device 10. Although, for example, the failure of the second switch unit 30b will have a negative impact on the performance of the MMC 40, it can still remain operational, allowing controlled shutdown or repair of the failed portion of the converter.

[0061] Figures 5A to 5CAnother embodiment of the third high voltage bypass device 10 is shown. Figures 2A to 2C Most components of the high voltage bypass device 10 correspond to Figures 1A to 1C and Figures 2A to 2C The corresponding components of the high voltage bypass device 10 are shown. Therefore, only the differences are described here.

[0062] Different from the first and second embodiments, in the third high-voltage bypass device 10, a varistor 50 is used as a trigger element. The varistor 50 is placed in the central part of the cavity 13, below the gate 19 and physically separated from the gate 19. Figure 5A As shown, the terminals of the varistor 50 are electrically connected to the (external) first and second terminals 11 and 12 of the bypass device 10, respectively. In the depicted embodiment, the terminals of the varistor 50 are in direct contact with the first electrode 14 and the second electrode 15, respectively, forming corresponding conductive portions of the sidewall 51 of the cavity 13. The electrodes 14 and 15 are in turn electrically connected to or integrally formed with the first terminal 11 and the second terminal 12.

[0063] As is known to all, the resistance of a varistor changes depending on the voltage across it. A varistor is a ceramic component with nonlinear electrical characteristics. In general, a varistor, also called a surge arrester, remains non-conductive or high-ohmic during normal operation when the voltage across it is well below a threshold voltage (also called clamping voltage). At voltages above this threshold (also called switching voltage), the varistor becomes conductive. In standard applications, such as overvoltage protection, varistors are used to absorb a given maximum energy. However, if the energy is higher than this maximum value, a strong temperature rise or even thermal runaway can occur.

[0064] In the third embodiment, the varistor 50 is deliberately driven into thermal runaway, causing a large amount of heat to be generated in the varistor 50. Thus, when an overvoltage condition occurs between terminals 11 and 12, the varistor 50 heats up and triggers the gate 19 (e.g., by melting or evaporating it, etc.).

[0065] As mentioned above, the gate 19 is arranged above and close to the trigger element formed by the varistor 50. Figure 5B As shown, in the event of an overvoltage condition between the first terminal 11 and the second terminal 12, heat 52 will be generated and dissipated. As a result, the gate 19 will be partially or completely destroyed, and the flowable material 18 will partially or completely fill the cavity 13 arranged below the reservoir 17. Figure 5C In the particular embodiment shown, the electrically conductive flowable material 18 substantially fills the entire cavity 13 .

[0066] exist Figure 5CIn the case shown, the varistor 50 is effectively shunted by the conductive flowable material 18, which is in direct contact with the electrodes 14 and 15, which form respective conductive portions of the side walls 51 of the cavity 13. The varistor 50 itself may be partially or completely destroyed by the thermal runaway condition. However, this is not essential for the conductive flowable material 18 to form an electrical shunting.

[0067] Figures 6A to 6C Another embodiment of the fourth high voltage bypass device 10 is shown. Figures 6A to 6C Most components of the high voltage bypass device 10 correspond to Figures 5A to 5C The corresponding components of the high voltage bypass device 10 are shown. Therefore, only the differences are described here.

[0068] As previously described, the varistor 50 is used as a trigger element in the fourth high-voltage bypass device 10. In contrast to the previous embodiment, the varistor 50 is arranged in direct thermal contact with the gate 19. Therefore, the heat generated by the varistor 50 in response to the overvoltage condition acts directly on the gate material. This generally results in a fast response time. In addition, this configuration may be useful in the case where the cavity is filled with a vacuum or a protective gas with poor thermal properties.

[0069] like Figure 6B As shown in the cross-section of FIG. 1 , the varistor 50 does not extend to the full depth of the cavity 13 , leaving an open area 53 between the varistor 50 and the insulating front wall 54 and / or the insulating rear wall 55 before the gate 19 is released.

[0070] like Figure 6C As shown in the cross-section of FIG. 5 , when the varistor 50 is triggered, the gate 19 is at least partially destroyed and the flowable material 18 passes through the open area 53 to partially or completely fill the cavity 13 .

[0071] Figure 7 The steps occurring during activation of the bypass device 10 are again shown in a schematic manner.

[0072] In a first step S1, an overvoltage occurs across the bypass device 10. Note that the generation of the overvoltage may occur automatically due to a failure of another component, such as a failure of activation of the mechanical bypass switch.

[0073] In step S2, a trigger element connected to the two terminals 11 and 12 carrying the overvoltage is triggered. For example, the trigger element may generate heat in response to the overvoltage condition. For example, if the voltage potential between the first terminal 11 and the second terminal 12 exceeds a predetermined voltage, a spark 20 will be generated between the two electrodes 14 and 15. Alternatively, a thermal runaway condition in the varistor 50 or similar electrical component can be used to generate heat, for example by ohmic heating.

[0074] In step S3, in response to the triggering event of step S2, the gate 19 is released to separate the flowable material 18 from the corresponding cavity 13. For example, the gate 19 including the heat-sensitive material can be released by the heat generated by the arc (i.e., spark 20) ​​or the thermal runaway conduction of the trigger element. For example, the generation of the spark 20 may cause the local generation of hot plasma, which in turn melts, vaporizes, or burns the polymer material to release the gate 19. Similarly, the thermal runaway condition of the varistor 50 also releases heat sufficient to melt, vaporize, or burn the polymer material.

[0075] In the absence of the gate 19, in step S4, the conductive flowable material 18 will fill the cavity 13 arranged on the other side of the destroyed gate 19. This may occur naturally due to the force of gravity acting on the flowable material 18, or it may be assisted or performed by an external force (such as a spring loaded mechanism).

[0076] Once the conductive flowable material 18 fills the space between the first terminal 11 and the second terminal 12 to a sufficient extent, such as by contacting the first electrode 14 and the second electrode 15 , a solid or liquid conductive path 21 is formed.

[0077] Although the present disclosure may be modified and substituted in various forms, details thereof have been shown by way of example in the accompanying drawings and will be described in detail. However, it should be understood that it is not intended to limit the present disclosure to the specific embodiments described. On the contrary, it is intended to cover all modifications, equivalents, and substitutions that fall within the scope of the disclosure defined by the appended claims.

[0078] For example, although the present invention has been described with respect to a half-bridge 31 and an MMC converter 40, it may also be applied to a full-bridge and / or other types of power converters.

[0079] Reference numerals

[0080] 10 Bypass Devices

[0081] 11 First terminal

[0082] 12 Second terminal

[0083] 13 Cavity

[0084] 14. First electrode

[0085] 15. Second electrode

[0086] 16 Spark gap

[0087] 17 Reservoir

[0088] 18 Flowable Materials

[0089] 19 Gate

[0090] 20 Spark

[0091] 21 Conductive Path

[0092] 22 Insulation bottom

[0093] 23 Insulation Top

[0094] 30 Switching unit

[0095] 31 Half Bridge

[0096] 32 Voltage Source

[0097] 33a / b IGBT

[0098] 34a / b body diode

[0099] 35 electrical contacts

[0100] 36 Reference contact

[0101] 37 Mechanical bypass switch

[0102] 40 Modular Multi-Unit Converter

[0103] 50 Varistor

[0104] 51 Conductive portion of the side wall

[0105] 52 calories

[0106] 53 open areas

[0107] 54 Isolation of the front wall

[0108] 55 Isolation back wall

Claims

1. A high voltage bypass device (10), comprising: Cavity (13); a trigger element, arranged in the cavity (13) and connected to a first terminal (11) and a second terminal (12) of the high-voltage bypass device (10); a reservoir (17) filled with a conductive flowable material (18); and A gate (19) is provided to separate the cavity (13) and the reservoir (17), wherein the gate (19) is configured to open a passage between the cavity (13) and the reservoir when the trigger element is triggered by an overvoltage condition, so that the conductive flowable material (18) at least partially fills the cavity (13) to form a conductive path (21) from the first terminal (11) to the second terminal (12).

2. The device (10) according to claim 1, wherein The trigger element includes at least one of the following: a first electrode (14) connected to the first terminal (11) and a second electrode (15) connected to the second terminal (12), the first electrode (14) and the second electrode (15) extending into the cavity (13) and forming a spark gap (16) therein; and / or A varistor (50) is connected between the first terminal (11) and the second terminal (12).

3. The device (10) according to claim 1 or 2, wherein: The conductive flowable material (18) comprises at least one of the following: Liquids, powders, and granular materials; and / or Metal or metal alloy, in particular gallium, gallium-indium-tin alloy, mercury, aluminum, or copper.

4. The device (10) according to any one of claims 1 to 3, wherein: The trigger element is configured to generate heat (52) under an overvoltage condition, and the gate (19) comprises a heat-sensitive material, in particular a polymer material, which is at least partially destroyed by one of melting, evaporating, or burning.

5. The device (10) according to claim 4, wherein The gate (19) includes one of: a thermally sensitive membrane separating the cavity (13) and the reservoir (17), or a thermally sensitive trigger coupled to a spring-loaded partition separating the cavity (13) and the reservoir (17).

6. The device (10) according to any one of claims 1 to 5, wherein: The reservoir (17) is arranged above the cavity (13) in the mounted position of the device (10) so that when the trigger element is triggered, the electrically conductive flowable material (18) is released by gravity.

7. The device (10) according to any one of claims 1 to 6, in, The trigger element comprises a first electrode (14) connected to the first terminal (11) and a second electrode (15) connected to the second terminal (12), the first electrode (14) and the second electrode (15) forming a spark gap (16) and being arranged as follows: The first electrode (14) is arranged at the bottom of the cavity (13) and protrudes upward, and the second electrode (15) is arranged at the top of the cavity near the gate (19) and protrudes downward; and / or The first electrode (14) is arranged at a first wall of the cavity (13) and protrudes toward an opposite second wall of the cavity (13), and the second electrode (15) is arranged at a second wall of the cavity (13) and protrudes toward the first wall of the cavity (13), wherein a direct path between the first and second electrodes (14, 15) is close to the gate (19); Or wherein the trigger element comprises a varistor (50) connected between the first terminal (11) and the second terminal (12) and arranged as follows: The varistor (50) is arranged in the central part of the cavity (13) below the gate (19), and / or The varistor (50) is arranged in direct thermal contact with the shutter (19).

8. The device (10) according to any one of claims 1 to 7, wherein: Before the triggering element is triggered, the cavity (13) is filled with one of a vacuum and a protective gas.

9. The device (10) according to any one of claims 1 to 8, wherein: The conductive flowable material (18) is configured to form a permanent electrical path between the first terminal (11) and the second terminal (12) after the trigger element is triggered, in particular by one of the following means: flooding the cavity (13) with a conductive liquid; or by contacting the first electrode (14) and the second electrode (15) extending into or defining the cavity (13) with a granular conductive medium.

10. A voltage source converter VSC, in particular a modular multi-cell converter MMC, comprising: at least one switching unit (30) configured to switch a high voltage; and At least one high voltage bypass device (10) according to any one of claims 1 to 9, configured to bypass the at least one switching unit (30) in case of a fault.

11. The VSC of claim 10, wherein: The switch unit (30) comprises at least one power semiconductor switch device, in particular an IGBT (33a), and the high-voltage bypass device (10) is connected in parallel with the at least one power semiconductor switch device.

12. The VSC according to claim 10 or 11, wherein: The switch unit (30) further comprises at least one mechanical bypass switch (37) connected in parallel with the at least one power semiconductor switch device and the high voltage bypass device (10).

13. The VSC according to any one of claims 10 to 12, wherein: The at least one switching unit (30) has a rated voltage exceeding 1 kV, preferably exceeding 3 kV, and / or a rated current exceeding 100 A, preferably exceeding 1000 A.

14. A VSC according to any one of claims 10 to 13, wherein: The at least one high-voltage bypass device (10) is triggered by an overvoltage that exceeds twice or more the rated voltage of the switch unit (30); The at least one high voltage bypass device (10) has an activation time of less than 10 ms and is used to bypass the at least one switching unit (30) under an overvoltage condition; and / or The at least one high voltage bypass device (10) is configured to bypass the at least one switching unit (30) for a period of time exceeding 24 hours, preferably exceeding 168 hours.

15. A method for operating a high voltage bypass device (10), comprising: In an overvoltage condition, heat (52) is generated, in particular by sparking or ohmic heating, to trigger a trigger element connected to two terminals (11, 12) of the bypass device (10); In response to triggering the trigger element, at least partially destroying, in particular by melting, evaporating, or burning, the gate (19) of the bypass device (10), thereby releasing the conductive flowable material (18); and The cavity (13) of the bypass device is at least partially filled with the conductive flowable material (18) to form a permanent electrical path between the two terminals (11, 12) of the bypass device (10).

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