Submodule of power converter

Abstract

The present invention relates to a submodule of a power converter. The submodule according to the present invention comprises: a capacitor; one or more power semiconductor switches connected in parallel to the capacitor; first and second output terminals connected to one of the power semiconductor switches; first and second bypass switches connected in parallel between the first and second output terminals; and a submodule controller for controlling switching of the power semiconductor switches and the first and second bypass switches, wherein the submodule controller simultaneously outputs a switching signal to the first and second bypass switches when a fault occurs in the submodule, and the first bypass switch is switched on faster than the second bypass switch to bypass a fault current therethrough.

Description

Submodule of a power converter

[0001] The present invention relates to a submodule of a power converter, and more particularly to a submodule of a power converter implemented to enable rapid bypass in the event of a failure by providing a redundant bypass switch.

[0002] A High Voltage Direct Current (HVDC) system converts alternating current power produced at a power plant into direct current power and transmits it to a receiving end, where it converts the direct current power back into alternating current power and supplies it to the load.

[0003] HVDC systems enable efficient and economical power transmission through voltage boosting and offer advantages such as interconnection of heterogeneous systems and high-efficiency long-distance transmission.

[0004] Power converters can be integrated into HVDC systems. Modular Multilevel Converters (MMCs) are widely used as power converters.

[0005] The MMC includes multiple sub-modules connected in series and can convert power between direct current and alternating current.

[0006] Each submodule may be equipped with a bypass switch to ensure stable system operation in the event of a failure. Conventional high-voltage power converters use switches to reliably bypass high voltage and high current.

[0007] The technology to quickly bypass fault current in the event of a submodule failure is crucial not only for the submodule itself but also from a system perspective.

[0008] If the switching time of the bypass switch is slow, overvoltage and overcurrent may occur in the faulty submodule, potentially damaging the internal components of the submodule and adversely affecting the reliability of the entire system.

[0009] Technologies for bypassing fault currents through bypass switches in submodules of power converters are widely known. For example, Korean Patent No. 10-1197066 discloses a technology for implementing a bypass switch using a mechanical switch in a power converter. As another example, Korean Patent No. 10-1780265 discloses a submodule bypass device for a modular multilevel converter.

[0010] However, conventional submodules, including the aforementioned prior art, have limitations in solving the problem of adverse effects on the submodule and system because the switching time of the bypass switch is not fast.

[0011] Therefore, in the relevant technology field, there is a demand for a bypass switch capable of rapidly bypassing fault current through fast switching operation in the event of a fault in a submodule of a power converter.

[0012] The present invention provides a submodule of a power converter capable of rapidly bypassing a fault current when a fault occurs in the submodule of the power converter.

[0013] The present invention provides a submodule of a power converter in which a bypass switch is configured in redundancy in the submodule of the power converter.

[0014] The present invention provides a submodule of a power converter equipped with a first bypass switch having relatively fast switching and a second bypass switch connected in parallel with the first bypass switch.

[0015] The present invention provides a submodule of a power converter in which, when a fault occurs in the submodule of the power converter, a first bypass switch is switched first to temporarily and rapidly bypass the fault current, and then a second bypass switch is switched to stably bypass the fault current.

[0016] A submodule of a power converter according to an embodiment of the present invention comprises: a capacitor; at least one power semiconductor switch connected in parallel to the capacitor; first and second output terminals connected to one of the power semiconductor switches; first and second bypass switches connected in parallel to each other between the first and second output terminals; and a submodule controller that controls the switching of the power semiconductor switch and the first and second bypass switches, wherein when a fault occurs in the submodule, the submodule controller outputs a switching signal to the first and second bypass switches simultaneously, and the first bypass switch is turned on faster than the second bypass switch to bypass the fault current through the first bypass switch.

[0017] In the present invention, after the first bypass switch is turned on, the second bypass switch is turned on to bypass the fault current through the second bypass switch.

[0018] In the present invention, when the fault current is bypassed through the second bypass switch, the submodule controller outputs a turn-off switching signal to the first bypass switch, and the first bypass switch is turned off.

[0019] In the present invention, the first bypass switch includes a triggered spark gap switch. The switching time of the spark gap switch is 2 to 8 ns.

[0020] In the present invention, the second bypass switch includes a vacuum circuit breaker or a vacuum interrupter. The switching time of the vacuum circuit breaker or vacuum interrupter is 3 to 5 ms.

[0021] A submodule of a power converter according to an embodiment of the present invention has one or more of the following effects.

[0022] According to the present invention, when a failure occurs in a submodule of a power converter, the submodule can bypass the fault current to prevent damage to the submodule and the system.

[0023] According to the present invention, when a fault occurs in a submodule, a first bypass switch with relatively fast switching is switched first to temporarily and rapidly bypass the fault current, and then a second bypass switch is switched to stably bypass the fault current.

[0024] According to the present invention, a submodule of a power converter can rapidly bypass a fault current, thereby enabling the stable maintenance and operation of the system with another submodule.

[0025] FIG. 1 is an exemplary diagram of a power converter according to an embodiment of the present invention.

[0026] FIG. 2 is an exemplary diagram showing the serial connection of submodules for a power converter according to an embodiment of the present invention.

[0027] FIG. 3 is an example diagram of the configuration of a submodule for a power converter according to an embodiment of the present invention.

[0028] FIG. 4 is an example diagram of an arm for explaining the process of voltage conversion through a submodule for a power converter according to an embodiment of the present invention.

[0029] FIG. 5 is an exemplary diagram of a stacked structure in which submodules for a power converter are stacked and arranged according to an embodiment of the present invention.

[0030] FIG. 6 is an example diagram showing how a fault current is bypassed in a submodule of a power converter according to an embodiment of the present invention.

[0031] FIG. 7 is another example of a fault current being bypassed in a submodule of a power converter according to an embodiment of the present invention.

[0032] Hereinafter, some embodiments of the present invention will be described in detail with reference to exemplary drawings. It should be noted that in assigning reference numerals to the components of each drawing, the same components are given the same reference numeral whenever possible, even if they are shown in different drawings. Furthermore, in describing the embodiments of the present invention, if it is determined that a detailed description of related known components or functions would hinder understanding of the embodiments of the present invention, such detailed description is omitted.

[0033] FIG. 1 is an equivalent circuit diagram of a power converter according to an embodiment of the present invention.

[0034] Referring to FIG. 1, the power converter according to the present invention is a device for converting power, and may be, for example, an MMC. The MMC is composed of one or more phase modules (10), and the DC voltage side of the phase module (10) is connected to positive (+) and negative (-) DC voltage buses P0 and N0, respectively.

[0035] There is an unillustrated DC voltage between these DC voltage buses P0 and N0. Each of these phase modules (10) has one intermediate AC voltage terminal and two outer DC voltage terminals as load connection terminals.

[0036] Each phase module (10) is equipped with respective terminals (L1, L2, L3) for connecting to an AC system, and is divided into an upper converter arm (11) and a lower converter arm (12) based on each of these terminals (L1, L2, L3).

[0037] The upper converter arm (11) and the lower converter arm (12) include a plurality of submodules (10) connected in series with each other. Each submodule (100) has two output terminals, namely a first output terminal (X1) and a second output terminal (X2). Current is input and output through the first and second output terminals (X1, X2).

[0038] The second terminal (X2) of the lowest submodule of the upper converter arm (11) and the first terminal (X1) of the uppermost submodule constituting the lower converter arm (12) are connected to any one of the terminals (L1, L2, L3) of the AC system. The AC system can be, for example, a three-phase AC power system.

[0039] A power converter configured in this manner can be incorporated as part of a high-voltage current transmission facility and serves to connect AC voltage power systems to transmit high power between them.

[0040] In addition, such power converters may be part of so-called FACTS facilities that serve to stabilize the system or ensure the desired voltage quality. Furthermore, the power converter shown in Fig. 1 may be used in the driving technology.

[0041] Each submodule (100) may be equipped with a bypass switch to bypass the fault current input between the first and second output terminals (X1, X2) when a fault occurs. In this way, the faulty submodule (100) bypasses the current, and the power converter is made to operate normally by the operation of the other normal submodule (100).

[0042] The bypass switch is switched according to the operation signal of the submodule controller (not shown in FIG. 2 and FIG. 3) to short-circuit the two output terminals (X1, X2), thereby preventing current from being supplied into the submodule and bypassing it. This allows the submodule (100) to be protected from fault current.

[0043] FIG. 2 is a configuration diagram according to one example of a submodule of a power converter according to an embodiment of the present invention, and FIG. 3 is a configuration diagram according to another example of a submodule of a power converter according to an embodiment of the present invention.

[0044] Referring to FIG. 2, a submodule (100) according to one embodiment may be configured in a half-bridge form with two power semiconductor switches (101) connected in series and a capacitor (102) connected in parallel thereto.

[0045] Referring to FIG. 3, a submodule (100) according to another embodiment may be configured in a full-bridge form with a pair of two power semiconductor switches (101) connected in series and a capacitor (102) connected in parallel to the pair.

[0046] Referring to FIGS. 2 and 3, the power semiconductor switch (101) can be turned on / turn off according to a control signal of the submodule controller (105).

[0047] When current is supplied to the submodule (100) through the first output terminal (X1), current is supplied to the capacitor (102) by the switching operation of the internal power semiconductor switch (101) of the submodule (100), and the DC voltage is charged to the capacitor (102), and the current continues to flow to the first output terminal of another submodule (100) through the second output terminal (X2).

[0048] A redundant first bypass switch (103) and a second bypass switch (104) can be connected in parallel between the first output terminal (X1) and the second output terminal (X2) of the submodule (100).

[0049] The first and second bypass switches (103, 104) can be switched by the submodule controller (105). The first and second bypass switches (103, 104) are switched by a specific signal output from the submodule controller (105) to form a current conduction path, and can bypass current directly from the first output terminal (X1) to the second output terminal (X2).

[0050] That is, when the first and second bypass switches (103, 104) are switched, the first and second output terminals (X1, X2) are short-circuited, so that the current supplied to the first output terminal (X1) is not supplied to the submodule (100) but is output directly to the second output terminal (X2).

[0051] In this embodiment, the first bypass switch (103) includes a triggered spark gap (SG) switch that is switched by a trigger voltage output from a submodule controller (105), and the second bypass switch (104) includes a vacuum circuit breaker (VCB) or a vacuum interrupter (VI).

[0052] The spark gap (SG) can be switched to form a current conduction path when the trigger voltage applied from the submodule controller (105) is greater than or equal to a preset reference value.

[0053] Spark gap switches have a much faster switching time (switching speed) than vacuum circuit breakers (VCB) or vacuum interrupters (VI). For example, the switching time of a spark gap switch is several nanoseconds, while the switching time of a vacuum circuit breaker (VCB) or vacuum interrupter (VI) is several milliseconds.

[0054] In this embodiment, the switching time of the spark gap switch is 2 to 8 ns, and the switching time of the vacuum circuit breaker or vacuum interrupter is 3 to 5 ms.

[0055] Spark gap switches, vacuum circuit breakers, and vacuum interrupters are air devices, so detailed descriptions will be omitted here.

[0056] In this way, the present invention connects a first bypass switch (103) having a switching time much faster than the switching time (switching speed) of the second bypass switch (104) for stably bypassing high voltage and high current to the submodule (100) in parallel with the second bypass switch (104).

[0057] Since the first and second bypass switches (103, 104) are connected in parallel, the current supplied to the first output terminal (X1) can be output to the second output terminal (X2) through either of the first and second bypass switches (103, 104) that are turned on.

[0058] When a fault occurs in the submodule (105), the submodule controller (105) can simultaneously output a switching signal to the first bypass switch (103) and the second bypass switch (104) to bypass the fault current.

[0059] In this case, since the first bypass switch (103) has a much faster switching time (switching speed) than the second bypass switch (104), even if the switching signals are output simultaneously, the first bypass switch (103) is turned on much faster than the second bypass switch (104).

[0060] Accordingly, the fault current is first bypassed through the first bypass switch (103), and then can be bypassed through the second bypass switch (104) when the second bypass switch (104) is turned on.

[0061] At this time, after the second bypass switch (104) is turned on, the submodule controller (105) can optionally control the first bypass switch (103) to be turned off.

[0062] The following describes in detail the operation process of the submodule of the power converter of the present invention configured as described above.

[0063] FIG. 4 is an operation diagram of a submodule of a power converter according to an embodiment of the present invention when it is normal, FIG. 5 is an operation diagram of a submodule of a power converter according to an embodiment of the present invention when a fault occurs, FIG. 6 is an example diagram of a fault current being bypassed in a submodule of a power converter according to an embodiment of the present invention, and FIG. 7 is another example diagram of a fault current being bypassed in a submodule of a power converter according to an embodiment of the present invention.

[0064] FIGS. 4 to 7 illustrate an exemplary description of the half-bridge type submodule shown in FIG. 2, but this is merely for convenience of explanation and will, of course, also apply to the full-bridge type submodule shown in FIG. 3.

[0065] As shown in FIG. 4, when the submodule (100) is operating normally, the submodule controller (105) can control the switching of the power semiconductor switch (101) by outputting a switching signal to the power semiconductor switch (101).

[0066] As shown in FIG. 5, when a fault is detected in the submodule (100), the submodule controller (105) can simultaneously output a switching signal to the first bypass switch (103) and the second bypass switch (104) to immediately bypass the fault current.

[0067] In this case, even if the switching signal is transmitted simultaneously to the first and second bypass switches (103, 104), the first bypass switch (103) is switched first because the switching speed of the first bypass switch (103) is faster than the switching speed of the second bypass switch (104).

[0068] As shown in FIG. 6, the first bypass switch (103) is switched so that the first output terminal (X1) and the second output terminal (X2) are short-circuited by the first bypass switch (103), and a current conduction path can be formed between the first and second output terminals (X1, X2).

[0069] Accordingly, the fault current flowing into the first output terminal (X1) is bypassed to the second output terminal (X2) through the first bypass switch (103), thereby protecting the submodule (100) from the fault current.

[0070] As shown in FIG. 7, the second bypass switch (104), which has a relatively slower switching speed compared to the first bypass switch (103), is also switched, so that the first output terminal (X1) and the second output terminal (X2) can also be short-circuited by the second bypass switch (103). Thus, the fault current can be temporarily bypassed through the first and second bypass switches (103, 104).

[0071] Subsequently, the first bypass switch (103) is turned off by a control signal from the submodule controller (105), so that the first and second output terminals (X1, X2) can be opened. As a result, the fault current is bypassed only to the second bypass switch (104).

[0072] As described above, the second bypass switch (104) may include, for example, a vacuum circuit breaker (VCB) or a vacuum interrupter (VI) to reliably interrupt high-voltage, high-current fault currents.

[0073] In this way, the submodule (100) of the power converter according to the present invention implements a bypass switch in a redundant manner so that when a fault occurs, the fault current is first bypassed through a first bypass switch (103) with a relatively fast switching speed, such as a spark gap switch, and subsequently, the fault current is bypassed through a second bypass switch (104) which can stably bypass the high-voltage, high-current fault current even if the switching speed is slow, such as a vacuum circuit breaker or a vacuum interrupter.

[0074] Although embodiments of the present invention have been described above with reference to the attached drawings, the present invention is not limited to the above embodiments and can be manufactured in various different forms, and those skilled in the art will understand that the present invention can be implemented in other specific forms without changing the technical concept or essential features of the present invention. Therefore, the embodiments described above should be understood as illustrative in all respects and not restrictive.

Claims

1. Capacitor; At least one power semiconductor switch connected in parallel to the above capacitor; First and second output terminals connected to one of the above power semiconductor switches; First and second bypass switches connected in parallel between the first and second output terminals; and It includes a submodule controller that controls the switching of the power semiconductor switch and the first and second bypass switches, and A submodule of a power converter in which the above submodule controller outputs a switching signal to the first and second bypass switches simultaneously when a fault occurs in the submodule, and the first bypass switch is turned on faster than the second bypass switch to bypass the fault current through the first bypass switch.

2. In Claim 1, A submodule of a power converter that bypasses the fault current through the second bypass switch after the first bypass switch is turned on.

3. In Claim 2, When the fault current is bypassed through the second bypass switch, the submodule controller outputs a turn-off switching signal to the first bypass switch, and the first bypass switch is a submodule of a power converter that is turned off.

4. In Claim 1, The first bypass switch is a submodule of a power converter including a triggered spark gap switch.

5. In Claim 4, A submodule of a power converter in which the switching time of the spark gap switch is 2 to 8 ns.

6. In Claim 1, The above second bypass switch is a submodule of a power converter including a vacuum circuit breaker or a vacuum interrupter.

7. In Claim 6, A submodule of a power converter in which the switching time of the above vacuum circuit breaker or vacuum interrupter is 3 to 5 ms.

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