Asymmetric H-bridge multi-port direct-current circuit breaker

Abstract

The invention, which belongs to the technical field of the power electronic system, discloses an asymmetric H-bridge multi-port direct-current circuit breaker comprising a plurality of direct-current lines and a direct-current fault open-circuit line. The DC line comprises: a current transfer switch; the direct current fault circuit break circuit comprises a common cutoff switch, a follow current thyristor, a capacitor branch thyristor and a capacitor. When any direct-current line has a grounding fault, the common cutoff switch is closed, the current transfer switch on the fault direct-current line is switched off, the fault current on the fault direct-current line is transferred to the branch where the common cutoff switch is located, the follow current thyristor is switched off, the capacitor branch thyristor is closed, and the capacitor branch thyristor is switched off. When a fault occurs, the fault current on the branch where the common cutoff switch is located is transferred to the branch where the capacitor is located, and fault current limiting of the fault direct current line is achieved, so that the problem that direct current circuit breakers need to be installed at the two ends of each direct current line in the prior art can be solved.

Description

Technical Field

[0001] The present invention relates to the technical field of power electronic systems, and in particular to an asymmetric H-bridge multi-port DC circuit breaker. Background Art

[0002] There are two basic DC grid formation methods: The first method uses a modular multilevel converter (MMC) based on half-bridge sub-modules plus a DC circuit breaker. This method is applicable to DC grids with any number of ports. The second method uses an MMC with the ability to self-clear DC faults, such as an MMC based on full-bridge sub-modules, without a DC circuit breaker. This method is applicable to small-scale DC grids with less than 10 ports. When using the formation method of MMC with half-bridge sub-modules plus a DC circuit breaker, during a DC line fault, the converter station is usually required to continue operating and cannot be blocked. The faulty line is quickly cut off by the DC circuit breaker, and its fault handling principle is similar to that of an AC grid. When using the formation method without a DC circuit breaker, during a DC line fault, the relevant converters within the grid are blocked. After about 10 ms, the fault current reaches zero and stabilizes at zero. Then, the faulty line is isolated by a disconnector, and then the relevant converters are unlocked and power supply is restored. The time from the start of the fault to the restoration of power supply is generally about 20 ms, and the impact on the AC grid is usually within an acceptable range.

[0003] When using the method of MMC with half-bridge sub-modules plus a DC circuit breaker to form a DC grid, the DC circuit breaker becomes a key component of the DC grid. Currently, the high-voltage DC circuit breaker construction schemes mainly focus on three types, namely traditional mechanical circuit breakers based on conventional switches, solid-state circuit breakers based on pure power electronic devices, and hybrid circuit breakers based on the combination of the two. Currently, in order to reliably handle various types of faults in DC lines, DC circuit breakers need to be installed at both ends of each DC line. However, a DC grid contains a large number of DC lines, so a large number of DC circuit breakers and fault current limiters need to be installed in the entire DC system, resulting in high costs and large volumes, which poses a huge economic and technical challenge to the further development of DC grids. Summary of the Invention

[0004] The present invention provides an asymmetric H-bridge multi-port DC circuit breaker, which can solve the technical problems in the prior art that in order to reliably handle various types of faults in DC lines, DC circuit breakers need to be installed at both ends of each DC line, and a large number of DC circuit breakers and fault current limiters need to be installed in the entire DC system, resulting in high costs and large volumes.

[0005] To solve the above technical problems, an embodiment of the present invention provides an asymmetric H-bridge multi-port DC circuit breaker, including: a plurality of DC lines and a DC fault breaking line;

[0006] The DC line includes: a current transfer switch;

[0007] The first end of the current transfer switch is connected to the upper DC bus, and the second end of the current transfer switch is connected to the lower DC bus;

[0008] The DC fault interruption line includes: an interruption part and a current limiting part: the interruption part includes: a common current breaking switch; the current limiting part includes: a freewheeling thyristor, a capacitor branch thyristor, and a capacitor;

[0009] The first end of the common current breaking switch is connected to the upper DC bus, and the second end of the common current breaking switch is respectively connected to the first end of the freewheeling thyristor and the first end of the capacitor branch thyristor; the second end of the freewheeling thyristor is connected to the lower DC bus, the second end of the capacitor branch thyristor is connected to the first end of the capacitor, and the second end of the capacitor is connected to the lower DC bus;

[0010] When all DC lines are operating normally, the current transfer switch and the freewheeling thyristor are both in the closed state, and the common current breaking switch and the capacitor branch thyristor are both in the off state;

[0011] When a ground fault occurs in any DC line, the common current breaking switch closes, the current transfer switch on the faulty DC line turns off, the fault current on the faulty DC line is transferred to the branch where the common current breaking switch is located, the freewheeling thyristor turns off, the capacitor branch thyristor closes, and the fault current on the branch where the common current breaking switch is located is transferred to the branch where the capacitor is located, realizing fault current limiting for the faulty DC line.

[0012] As a preferred solution, the DC line further includes: an ultra-fast mechanical switch;

[0013] The first end of the ultra-fast mechanical switch is connected to the second end of the current transfer switch, and the second end of the ultra-fast mechanical switch is connected to the lower DC bus;

[0014] When all DC lines are operating normally, the ultra-fast mechanical switch is in the closed state.

[0015] As a preferred solution, when a ground fault occurs in any DC line, after the common current breaking switch closes, the current transfer switch on the faulty DC line turns off, and the fault current on the faulty DC line is transferred to the branch where the common current breaking switch is located, it further includes:

[0016] The ultra-fast mechanical switch on the faulty DC line turns off, so that the current transfer switch no longer continues to bear pressure.

[0017] As a preferred solution, the DC line further includes: a series reactor;

[0018] The first end of the series reactor is connected to the second end of the ultra-fast mechanical switch, and the second end of the series reactor is connected to the DC line.

[0019] As a preferred solution, the DC line further includes: a disconnector;

[0020] The first end of the disconnector is connected to the second end of the series reactor, and the second end of the disconnector is connected to the DC line;

[0021] When all DC lines are operating normally, the disconnector is in the closed state.

[0022] As a preferred solution, when a ground fault occurs in any DC line, after the freewheeling thyristor is turned off, the capacitor branch thyristor is closed, and the fault current is transferred to the branch where the capacitor is located to achieve fault current limiting of the faulty DC line, the following is further included:

[0023] The disconnector is turned off to achieve fault clearing of the faulty DC line.

[0024] As a preferred solution, the DC line further includes: a diode group;

[0025] The cathode of the diode group is connected to the second end of the ultra-fast mechanical switch, and the anode of the diode group is connected to the lower DC bus.

[0026] As a preferred solution, the breaking part further includes: a lightning arrester;

[0027] The first end of the lightning arrester is connected to the first end of the common current-breaking switch, and the second end of the lightning arrester is connected to the second end of the common current-breaking switch.

[0028] As a preferred solution, the current-limiting part further includes: a reactance branch thyristor and a current-limiting reactor;

[0029] The first end of the reactance branch thyristor is connected to the second end of the common current-breaking switch, the second end of the reactance branch thyristor is connected to the first end of the current-limiting reactor, and the second end of the current-limiting reactor is connected to the lower DC bus;

[0030] When all DC lines are operating normally, the reactance branch thyristor is in the off state.

[0031] As a preferred solution, when a ground fault occurs in any DC line, after the freewheeling thyristor is turned off and the capacitor branch thyristor is closed, and the fault current on the branch where the common current breaking switch is located is transferred to the branch where the capacitor is located, the following steps are further included:

[0032] The reactance branch thyristor is closed to put the current limiting reactor into operation, and the fault current on the branch where the capacitor is located gradually decreases to zero, realizing fault current limiting for the faulty DC line.

[0033] Compared with the prior art, the embodiments of the present invention have the following beneficial effects:

[0034] The present invention provides an asymmetric H-bridge multi-port DC circuit breaker, including: a plurality of DC lines and a DC fault breaking line; the DC lines include: current transfer switches; the first end of the current transfer switch is connected to the upper DC bus, and the second end of the current transfer switch is connected to the lower DC bus; the DC fault breaking line includes: a breaking part and a current limiting part: the breaking part includes: a common current breaking switch; the current limiting part includes: a freewheeling thyristor, a capacitor branch thyristor, and a capacitor; the first end of the common current breaking switch is connected to the upper DC bus, and the second end of the common current breaking switch is respectively connected to the first end of the freewheeling thyristor and the first end of the capacitor branch thyristor; the second end of the freewheeling thyristor is connected to the lower DC bus, the second end of the capacitor branch thyristor is connected to the first end of the capacitor, and the second end of the capacitor is connected to the lower DC bus; when all DC lines are operating normally, the current transfer switch and the freewheeling thyristor are both in the closed state, and the common current breaking switch and the capacitor branch thyristor are both in the off state; when a ground fault occurs in any DC line, the common current breaking switch is closed, the current transfer switch on the faulty DC line is turned off, the fault current on the faulty DC line is transferred to the branch where the common current breaking switch is located, the freewheeling thyristor is turned off, the capacitor branch thyristor is closed, and the fault current on the branch where the common current breaking switch is located is transferred to the branch where the capacitor is located, realizing fault current limiting for the faulty DC line.

[0035] Compared with the prior art method of installing DC circuit breakers at both ends of each DC line, the present invention separately sets a DC fault breaking line, which includes a breaking part and a current limiting part. When a ground fault occurs in any DC line, fault current limiting for the faulty DC line can be realized through the turning off and closing of relevant components in the faulty DC line and the DC fault breaking line. Through the present invention, the DC circuit breakers installed on all DC lines in the prior art can be integrated into a single DC fault breaking line, significantly reducing the number of components of the circuit breaker, reducing the overall volume of the circuit breaker, lowering the project cost, and reducing the investment cost. Brief Description of the Drawings

[0036] Figure 1 FIG. 1 is a schematic structural diagram of an asymmetric H-bridge multi-port DC circuit breaker provided by an embodiment of the present invention;

[0037] Figure 2 FIG. 2 is a schematic diagram of a simulation waveform of the asymmetric H-bridge multi-port DC circuit breaker under DC line fault conditions. Detailed Embodiments

[0038] In order to make the objectives, technical solutions and advantages of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. Apparently, the described embodiments are some but not all of the embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present application without creative efforts shall fall within the protection scope of the present application.

[0039] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the specification and claims of this application and the above description of the drawings are intended to cover non-exclusive inclusion.

[0040] In the description of the embodiments of the present application, technical terms such as "first" and "second" are only used to distinguish different objects and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity, specific order or primary-secondary relationship of the indicated technical features. In the description of the embodiments of the present application, "a plurality of" means more than two unless otherwise specifically defined.

[0041] Reference to "embodiments" herein means that a particular feature, structure or characteristic described in connection with the embodiments can be included in at least one embodiment of the present application. The phrase does not necessarily refer to the same embodiment at every occurrence in the specification, nor is it an independent or alternative embodiment mutually exclusive of other embodiments. Those skilled in the art will explicitly and implicitly understand that the embodiments described herein can be combined with other embodiments.

[0042] In the description of the embodiments of the present application, the term "and / or" is only a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " in this article generally represents an "or" relationship between the associated objects before and after.

[0043] In the description of the embodiments of the present application, the terms "multiple" and "several" refer to two or more (including two). Similarly, "multiple groups" refers to two or more groups (including two groups), and "multiple pieces" refers to two or more pieces (including two pieces).

[0044] In the description of the embodiments of the present application, unless otherwise clearly specified and limited, technical terms such as "installation", "connection", "connection", and "fixation" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or integrated; it can also be a mechanical connection or an electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, and can be the communication inside two components or the interaction relationship between two components. For those of ordinary skill in the art, the specific meanings of the above terms in the embodiments of the present application can be understood according to specific situations.

[0045] Embodiment 1

[0046] Please refer to Figure 1 For solving the technical problem in the prior art that in order to reliably handle various types of faults in DC lines, DC circuit breakers need to be installed at both ends of each DC line, and a large number of DC circuit breakers and fault current limiters need to be installed in the entire DC system, resulting in high costs and large volumes. A structural schematic diagram of an asymmetric H-bridge multi-port DC circuit breaker provided by an embodiment of the present invention includes: several DC lines and a DC fault interruption line;

[0047] The DC line includes: a current transfer switch;

[0048] The first end of the current transfer switch is connected to the upper DC bus, and the second end of the current transfer switch is connected to the lower DC bus;

[0049] The DC fault interruption line includes: an interruption part and a current limiting part: the interruption part includes: a common current interruption switch; the current limiting part includes: a freewheeling thyristor, a capacitive branch thyristor, and a capacitor;

[0050] The first end of the common current interruption switch is connected to the upper DC bus, and the second end of the common current interruption switch is respectively connected to the first end of the freewheeling thyristor and the first end of the capacitive branch thyristor; the second end of the freewheeling thyristor is connected to the lower DC bus, the second end of the capacitive branch thyristor is connected to the first end of the capacitor, and the second end of the capacitor is connected to the lower DC bus;

[0051] When all DC lines are operating normally, the current transfer switch and the freewheeling thyristor are both in the closed state, and the common current interruption switch and the capacitive branch thyristor are both in the off state;

[0052] When a ground fault occurs in any DC line, the common disconnection switch closes, the current transfer switch on the faulty DC line turns off, the fault current on the faulty DC line transfers to the branch where the common disconnection switch is located, the freewheeling thyristor turns off, the capacitor branch thyristor closes, and the fault current on the branch where the common disconnection switch is located transfers to the branch where the capacitor is located, achieving fault current limiting for the faulty DC line.

[0053] Preferably, the DC line further includes: an ultra-fast mechanical switch; the first end of the ultra-fast mechanical switch is connected to the second end of the current transfer switch, and the second end of the ultra-fast mechanical switch is connected to the lower DC bus; when all DC lines are operating normally, the ultra-fast mechanical switch is in the closed state.

[0054] Preferably, when a ground fault occurs in any DC line, after the common disconnection switch closes, the current transfer switch on the faulty DC line turns off, and the fault current on the faulty DC line transfers to the branch where the common disconnection switch is located, it further includes: the ultra-fast mechanical switch on the faulty DC line turns off, so that the current transfer switch no longer bears pressure.

[0055] Preferably, the DC line further includes: a series reactor; the first end of the series reactor is connected to the second end of the ultra-fast mechanical switch, and the second end of the series reactor is connected to the DC line.

[0056] Preferably, the DC line further includes: a disconnector; the first end of the disconnector is connected to the second end of the series reactor, and the second end of the disconnector is connected to the DC line; when all DC lines are operating normally, the disconnector is in the closed state.

[0057] Preferably, when a ground fault occurs in any DC line, after the freewheeling thyristor turns off, the capacitor branch thyristor closes, and the fault current transfers to the branch where the capacitor is located, achieving fault current limiting for the faulty DC line, it further includes: the disconnector turns off, achieving fault clearing for the faulty DC line.

[0058] Preferably, the DC line further includes: a diode group; the cathode of the diode group is connected to the second end of the ultra-fast mechanical switch, and the anode of the diode group is connected to the lower DC bus.

[0059] Preferably, the circuit breaker part further includes: a lightning arrester; the first end of the lightning arrester is connected to the first end of the common disconnection switch, and the second end of the lightning arrester is connected to the second end of the common disconnection switch.

[0060] Preferably, the current limiting part further includes: a thyristor in the reactance branch and a current limiting reactor; a first end of the thyristor in the reactance branch is connected to a second end of the common disconnection switch, a second end of the thyristor in the reactance branch is connected to a first end of the current limiting reactor, and a second end of the current limiting reactor is connected to the lower DC bus; when all DC lines are operating normally, the thyristor in the reactance branch is in the off state.

[0061] Preferably, when a ground fault occurs in any DC line, after the freewheeling thyristor is turned off, the capacitor branch thyristor is closed, and the fault current on the branch where the common disconnection switch is located is transferred to the branch where the capacitor is located, the following steps are further included: the thyristor in the reactance branch is closed to put the current limiting reactor into operation, and the fault current on the branch where the capacitor is located gradually decreases to zero, realizing fault current limiting for the faulty DC line.

[0062] Specifically, according to Figure 1 the structural schematic diagram of the asymmetric H-bridge multi-port DC circuit breaker in, 1 is the first line current transfer switch, 2 is the first line ultra-fast mechanical switch, 3 is the first line disconnector, 4 is the first reactor, 5 is the first line diode group, 6 is the second line current transfer switch, 7 is the second line ultra-fast mechanical switch, 8 is the second line disconnector, 9 is the second reactor, 10 is the second line diode group, 11 is the m-th line current transfer switch, 12 is the m-th line ultra-fast mechanical switch, 13 is the m-th line disconnector, 14 is the m-th reactor, 15 is the m-th line diode group, 16 is the breaking part, 17 is the public disconnection switch, 18 is the lightning arrester, 19 is the current limiting part, 20 is the freewheeling thyristor, 21 is the capacitor branch thyristor, 22 is the capacitor, 23 is the thyristor in the reactance branch, 24 is the current limiting reactor.

[0063] Specifically, assume that there are m (m is an integer greater than or equal to 3) DC transmission lines connected to the same DC bus. As Figure 1 shown, the asymmetric H-bridge multi-port DC circuit breaker with fault current limiting ability of the present invention includes m DC lines and one DC fault breaking line. The DC lines include: m line current transfer switches, m line ultra-fast mechanical switches, m line diode groups, m line disconnectors, and m line series reactors; the DC fault breaking line includes: 1 current limiting part and 1 breaking part, where the current limiting part is composed of 1 freewheeling thyristor, 1 capacitor branch thyristor, 1 capacitor, 1 thyristor in the reactance branch, and 1 current limiting reactor, and the breaking part is composed of 1 common disconnection switch and 1 lightning arrester.

[0064] Among the above components, the function of the line current transfer switch is to transfer the fault current to the breaking part and the current limiting part; the function of the line ultra-fast mechanical switch is to enable the line current transfer switch not to bear the system-level transient overvoltage; the function of the line diode group is to rectify the current flowing through the breaking part and the current limiting part to the same direction; the function of the line disconnector is to completely isolate the faulty line when the fault current drops to 0; the function of the line series reactor is to provide an initial current limiting function, and its inductance value does not need to be too large to ensure the dynamic performance of the system; the function of the freewheeling thyristor in the current limiting part is to provide a low-impedance conduction branch; the function of the capacitor and the capacitor branch thyristor in the current limiting part is to reliably turn off the freewheeling thyristor through the reverse initial voltage of the capacitor. At the same time, the capacitor can initially suppress the current rise and make the current limiting reactor reliably put into operation after a short delay; the function of the current limiting reactor and the reactor branch thyristor in the current limiting part is to limit the further rise of the fault current. Since it does not need to be put into operation during normal operation, the value of the current limiting reactor can be taken larger considering the current limiting effect; the function of the common current breaking switch in the breaking part is to block the fault current and make the arrester put into operation; after the arrester in the breaking part is put into operation, it can be equivalent to a voltage source connected in series in reverse, so that the fault current drops to 0.

[0065] Among the above components, one end of the breaking part is connected to the upper DC bus, and the other end is connected to one end of the current limiting part. The other end of the current limiting part is connected to the lower DC bus. Let i = 1, 2,..., m. One end of the i-th line current transfer switch is connected to the upper DC bus, the other end of the i-th line current transfer switch is connected to one end of the i-th line ultra-fast mechanical switch, the other end of the i-th line ultra-fast mechanical switch is connected to one end of the i-th line series reactor and the cathode of the diode group, the other end of the i-th line series reactor is connected to one end of the i-th line disconnector, the other end of the i-th line disconnector is connected to the i-th DC line, and the anode of the diode group is connected to the lower DC bus. With this structure, all lines can share 1 breaking part and 1 current limiting part, thus reducing the number of devices used and the investment.

[0066] The breaking part includes 1 common current breaking switch and 1 arrester. The common current breaking switch and the arrester are connected in parallel, and the arrester can protect the overvoltage generated when the common current breaking switch is turned off.

[0067] The current-limiting part includes a freewheeling thyristor, a capacitor-branch thyristor, a capacitor, a reactor-branch thyristor, and a current-limiting reactor. Among them, the anodes of all thyristors are connected to one end of the breaking part. The other end of the freewheeling thyristor is connected to the lower DC bus. The other end of the capacitor-branch thyristor is connected to one end of the capacitor. The other end of the capacitor is connected to the lower DC bus. The other end of the reactor-branch thyristor is connected to one end of the current-limiting reactor. The other end of the current-limiting reactor is connected to the lower DC bus. With this structure, the input of the current-limiting reactance can be achieved only by using thyristors without the need for fully-controlled devices.

[0068] Therefore, the fault current limiter and the DC circuit breaker connected to m DC lines are integrated together to form an asymmetric H-bridge multi-port DC circuit breaker with the ability of fault current limiting. Thus, the DC fault interruption of m DC lines can share some components, reducing the number of components used and improving the economy.

[0069] In another specific embodiment, based on the above-mentioned asymmetric H-bridge multi-port DC circuit breaker with the ability of fault current limiting, the present invention proposes a DC fault handling strategy applicable to the asymmetric H-bridge multi-port DC circuit breaker with the ability of fault current limiting to cope with the grounding fault of the i-th DC transmission line. The fault current is transferred by controlling the line current transfer switch and the line ultra-fast mechanical switch. Subsequently, the current-limiting part and the breaking part are controlled in sequence to limit and interrupt the fault current, including the following steps:

[0070] During normal operation, m line current transfer switches, m line ultra-fast mechanical switches, m line disconnectors, and the freewheeling thyristors are all closed, and the common current-breaking switch and the capacitor and reactor-branch thyristors are in the off state;

[0071] When a grounding fault occurs in the $i$-th DC transmission line, the system detects the DC fault and sends a fault signal to the asymmetric H-bridge multi-port DC circuit breaker with fault current limiting ability. After receiving the fault signal, it first applies an opening signal to the common disconnector switch; then applies a closing signal to the $i$-th line current transfer switch to transfer the fault current to the branch where the common disconnector switch is located; then applies a closing signal to the $i$-th line ultra-fast mechanical switch so that the line current transfer switch no longer needs to bear voltage; then applies a closing signal to the freewheeling thyristor and an opening signal to the thyristors in the capacitor and reactance branches. Under the action of the reverse voltage of the capacitor, the freewheeling thyristor is turned off, and the fault current gradually transfers to the branch where the capacitor is located. Then, with the charging effect of the DC grid on the capacitor, the positive capacitor voltage will gradually turn on the current limiting reactor to achieve fault current limiting for the $i$-th DC transmission line; when the current flowing through the branch where the capacitor is located drops to 0, the current limiting inductor is fully turned on. At this time, an opening signal is applied to the common disconnector switch to block the fault current path; finally, the $i$-th line disconnector is disconnected to achieve fault clearing for the $i$-th DC transmission line.

[0072] In another specific embodiment, the following uses a single-pole 320 kV test system for simulation verification. There are a total of three DC transmission lines connected at the same location, and the DC circuit breaker is as shown in Figure 1 the circuit breaker shown.

[0073] It is assumed that the test system has entered steady-state operation before the simulation starts. At $t = 1.0$ s, a single-pole ground short circuit occurs in DC line 1. When the fault current exceeds 5.0 kA, the DC circuit breaker starts to operate. Please refer to Figure 2 , which is a schematic diagram of the simulation waveform of the asymmetric H-bridge multi-port DC circuit breaker under DC line fault conditions. Figure 2 In (a), (b), (c), and (d) in Figure 2 are the current change curve of the current transfer switch, the current change curve of the common disconnector switch, the current change curve of the arrester, and the voltage change curve across the common disconnector switch, respectively. It can be seen from Figure 2 that after the fault occurs, the DC current rises rapidly. When the DC current reaches 5.0 kA, line current transfer switch 1 turns off, causing the current to transfer to the common disconnector switch; after the common disconnector switch conducts current for 2 ms, it turns off, and the current further transfers to the arrester branch. At the same time, the common disconnector switch generates an overvoltage of about 480 kV; the DC circuit breaker can clear the DC line fault within a short time of several milliseconds, indicating that the circuit breaker has good current breaking characteristics.

[0074] As can be seen, the present invention provides an asymmetric H-bridge multi-port DC circuit breaker. Compared with the prior art in which DC circuit breakers are installed at both ends of each DC line, the present invention separately sets up a DC fault interruption line, which includes an interruption part and a current-limiting part. When a ground fault occurs in any DC line, the fault current limiting of the faulty DC line can be achieved by controlling the turning off and on of the relevant components in the faulty DC line and the DC fault interruption line. Through the present invention, the DC circuit breakers installed on all DC lines in the prior art can be integrated into a DC fault interruption line, so as to significantly reduce the number of components of the circuit breaker, reduce the overall volume of the circuit breaker, reduce the project cost, and reduce the investment cost.

[0075] The above is the preferred embodiment of the present invention. It should be noted that for those of ordinary skill in the art of the present technology, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements are also regarded as the protection scope of the present invention.

Claims

1. An asymmetrical H-bridge multi-port DC circuit breaker, characterized in that, Including: A plurality of DC lines and a DC fault interrupting line; The DC line includes: a current transfer switch; The first end of the current transfer switch is connected to the upper DC bus, and the second end of the current transfer switch is connected to the lower DC bus; The DC fault interrupting line includes: an interrupting part and a current limiting part: the interrupting part includes: a common disconnection switch; the current limiting part includes: a freewheeling thyristor, a capacitor branch thyristor, and a capacitor; The first end of the common disconnection switch is connected to the upper DC bus, and the second end of the common disconnection switch is respectively connected to the first end of the freewheeling thyristor and the first end of the capacitor branch thyristor; the second end of the freewheeling thyristor is connected to the lower DC bus, the second end of the capacitor branch thyristor is connected to the first end of the capacitor, and the second end of the capacitor is connected to the lower DC bus; When all DC lines are operating normally, the current transfer switch and the freewheeling thyristor are both in the closed state, and the common disconnection switch and the capacitor branch thyristor are both in the off state; When a ground fault occurs in any DC line, the common disconnection switch closes, the current transfer switch on the faulty DC line turns off, the fault current on the faulty DC line is transferred to the branch where the common disconnection switch is located, the freewheeling thyristor turns off, the capacitor branch thyristor closes, and the fault current on the branch where the common disconnection switch is located is transferred to the branch where the capacitor is located, realizing fault current limiting of the faulty DC line.

2. The asymmetrical H-bridge multi-port DC circuit breaker according to claim 1, characterized in that, The DC line further includes: an ultra-fast mechanical switch; The first end of the ultra-fast mechanical switch is connected to the second end of the current transfer switch, and the second end of the ultra-fast mechanical switch is connected to the lower DC bus; When all DC lines are operating normally, the ultra-fast mechanical switch is in the closed state.

3. The asymmetric H-bridge multi-port DC circuit breaker according to claim 2, wherein When a ground fault occurs in any DC line, after the common disconnection switch closes, the current transfer switch on the faulty DC line turns off, and the fault current on the faulty DC line is transferred to the branch where the common disconnection switch is located, it further includes: The ultra-fast mechanical switch on the faulty DC line turns off, so that the current transfer switch no longer continues to bear pressure.

4. The asymmetrical H-bridge multi-port DC circuit breaker according to claim 3, wherein The DC line further includes: a series reactor; The first end of the series reactor is connected to the second end of the ultra-fast mechanical switch, and the second end of the series reactor is connected to the DC line.

5. The asymmetrical H-bridge multi-port DC circuit breaker according to claim 4, characterized in that, The DC line further includes: a disconnector; The first end of the disconnector is connected to the second end of the series reactor, and the second end of the disconnector is connected to the DC line; When all DC lines are operating normally, the disconnector is in the closed state.

6. The asymmetric H-bridge multi-port DC circuit breaker according to claim 5, characterized in that, When a ground fault occurs in any DC line, after the freewheeling thyristor turns off, the capacitor branch thyristor closes, and the fault current is transferred to the branch where the capacitor is located, realizing fault current limiting of the faulty DC line, it further includes: The disconnector turns off to achieve fault clearing of the faulty DC line.

7. The asymmetric H-bridge multi-port DC circuit breaker according to claim 6, wherein The DC line further includes: a diode group; The cathode of the diode group is connected to the second end of the ultra-fast mechanical switch, and the anode of the diode group is connected to the lower DC bus.

8. The asymmetrical H-bridge multi-port DC circuit breaker according to claim 7, wherein The breaking part further includes: a lightning arrester; The first end of the lightning arrester is connected to the first end of the common current-breaking switch, and the second end of the lightning arrester is connected to the second end of the common current-breaking switch.

9. The asymmetrical H-bridge multi-port DC circuit breaker according to claim 8, wherein The current-limiting part further includes: a thyristor of the reactance branch and a current-limiting reactor; The first end of the thyristor of the reactance branch is connected to the second end of the common current-breaking switch, the second end of the thyristor of the reactance branch is connected to the first end of the current-limiting reactor, and the second end of the current-limiting reactor is connected to the lower DC bus; When all DC lines are operating normally, the thyristor of the reactance branch is in the off state.

10. The asymmetric H-bridge multi-port DC circuit breaker according to claim 9, wherein, When a ground fault occurs in any DC line, after the freewheeling thyristor is turned off, the capacitor branch thyristor is closed, and the fault current on the branch where the common current-breaking switch is located is transferred to the branch where the capacitor is located, further including: The thyristor of the reactance branch is closed so that the current-limiting reactor is put into operation, and the fault current on the branch where the capacitor is located gradually decreases to zero, realizing fault current limiting for the faulty DC line.

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