Self-charging capacitor commutated dc circuit breaker and breaking method thereof

Abstract

Disclosed are a self-charging capacitor commutation type DC circuit breaker and a breaking method thereof. In the DC circuit breaker, a buffer capacitor C1 is connected in series with a resistor R1 and then connected in parallel across a semiconductor switching device S1; a thyristor T1 has one end connected to one end of the semiconductor switching device S1 and the other end connected in series with one end of a charging capacitor C2; the other end of the charging capacitor C2 is connected to the other end of the semiconductor switching device S1; one end of a thyristor T2 is connected between the thyristor T1 and the charging capacitor C2; the other end of the thyristor T2 is connected in series with one end of a coupling inductor L1; the other end of the coupling inductor L1 is connected to the other end of the semiconductor switching device S1; a coupling inductor L2 is connected in series with a commutation capacitor C3 and then connected in parallel across a fast mechanical switch S2; a metal oxide surge arrester MOV1 is connected in parallel across the semiconductor switching device S1; and a metal oxide surge arrester MOV2 is connected in parallel across the fast mechanical switch S2.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of circuit breakers, in particular to a self-charging capacitor commutation type DC circuit breaker and a breaking method thereof. BACKGROUND

[0002] As an indispensable protection device in power transmission and distribution systems, circuit breakers can achieve rapid removal of fault currents. Compared with AC systems, the low impedance of DC systems results in large expected fault currents and extremely high fault current rise rates, so DC circuit breakers need to have higher breaking speeds. In DC systems, inductive elements store a large amount of energy, and there is no natural zero point for fault currents, making it difficult to break DC fault currents. Currently, the main DC circuit breakers at home and abroad are mechanical DC circuit breakers, all-solid-state DC circuit breakers and hybrid DC circuit breakers. The traditional mechanical DC circuit breaker based on current injection has the advantages of mature technology, stable operation, small on-state loss and low cost, but it still has the following problems: first, the slow establishment of the capacitor voltage of the commutation branch during small current breaking results in unreliable arc extinction and slow breaking speed during small current breaking; second, the mechanical switch must withstand the overvoltage of breaking within a short dielectric recovery time, which is very difficult.

[0003] The above information disclosed in the background section is only intended to enhance the understanding of the background of the present application, and therefore can include information that does not constitute prior art known to those of ordinary skill in the art in the country. SUMMARY

[0004] In view of the deficiencies or defects of the prior art, a self-charging capacitor commutation type DC circuit breaker is provided, which uses power electronic modules to realize self-charging of the commutation capacitor, injects reverse current to the mechanical switch through the magnetic coupling module, realizes the transfer of fault current, and thus realizes the rapid breaking of short-circuit current, while improving the breaking capacity and reliability and reducing the cost of the DC circuit breaker.

[0005] The purpose of the present application is achieved by the following technical solutions.

[0006] The self-charging capacitor commutation type DC circuit breaker comprises a through-flow branch, a self-charging branch, a commutation branch and an energy consumption branch; the through-flow branch comprises a semiconductor switching device S1 and a fast mechanical switch S2 connected in series; the self-charging circuit comprises the semiconductor switching device S1, a buffer capacitor C1, a resistor R1, a thyristor T1 and a charging capacitor C2, wherein the buffer capacitor C1 is connected in parallel to both ends of the semiconductor switching device S1 after being connected in series with the resistor R1, one end of the thyristor T1 is connected to one end of the semiconductor switching device S1, the other end of the thyristor T1 is connected in series with one end of the charging capacitor C2, and the other end of the charging capacitor C2 is connected to the other end of the semiconductor switching device S1; the commutation branch comprises the thyristor T2, a coupling inductor L1 and a coupling inductor L2 and a commutation capacitor C3, wherein one end of the thyristor T2 is connected between the thyristor T1 and the charging capacitor C2, the other end of the thyristor T2 is connected in series with one end of the coupling inductor L1, the other end of the coupling inductor L1 is connected to the other end of the semiconductor switching device S1, the coupling inductor L2 is connected in parallel to both ends of the fast mechanical switch S2 after being connected in series with the commutation capacitor C3, and the energy consumption branch comprises a metal oxide surge arrester MOV1 and a metal oxide surge arrester MOV2, the metal oxide surge arrester MOV1 is connected in parallel to both ends of the semiconductor switching device S1, and the metal oxide surge arrester MOV2 is connected in parallel to both ends of the fast mechanical switch S2.

[0007] In the self-charging capacitor commutation type DC circuit breaker, the semiconductor switching device S1 is a fully controlled semiconductor switching device.

[0008] In the self-charging capacitor commutation type DC circuit breaker, the thyristor T1 or the thyristor T2 is a unidirectional conduction half-controlled device.

[0009] In the self-charging capacitor commutation type DC circuit breaker, the fast mechanical switch S2 is a vacuum high-speed mechanical switch based on electromagnetic repulsion, a vacuum mechanical switch based on high-speed motor driving or a vacuum high-speed mechanical switch based on explosion driving.

[0010] In the self-charging capacitor commutation type DC circuit breaker, the buffer capacitor C1 comprises any one or a combination of multiple of a film capacitor, an organic dielectric capacitor, an inorganic dielectric capacitor, an electrolytic capacitor, an electrothermal capacitor and an air dielectric capacitor.

[0011] In the self-charging capacitor commutation type DC circuit breaker, the coupling inductor L1 and the coupling inductor L2 are high-low voltage side completely isolated coupling inductors.

[0012] The breaking method of the self-charging capacitor commutation type DC circuit breaker comprises the following steps,

[0013] During normal through flow, the semiconductor switching device S1 is turned on, the fast mechanical switch S2 is closed, the current flows through the semiconductor switching device S1 and the fast mechanical switch S2, and no current flows through the self-charging branch, the commutation branch and the energy consumption branch.

[0014] When a short-circuit fault occurs, the semiconductor switching device S1 is turned off at the initial stage of the fault current rising, and after the semiconductor switching device S1 is turned off, a turn-off overvoltage is generated across the semiconductor switching device S1, and when the turn-off overvoltage reaches the operating voltage of the metal oxide surge arrester MOV1, the metal oxide surge arrester MOV1 is turned on, and the fault current is completely transferred to the branch of the metal oxide surge arrester MOV1; at this time, the thyristor T1 is turned on to charge the charging capacitor C2, and after the charging capacitor C2 is fully charged, the thyristor T1 is turned off;

[0015] When the fast mechanical switch S2 receives a trigger signal and operates, the contacts of the fast mechanical switch S2 are pulled apart, and an arc is generated across the contacts, at this time, the thyristor T2 is turned on, the charging capacitor C2 discharges to the coupling inductor L1, the coupling coil L2 induces a voltage, and the voltage of the coupling coil L2 forms a loop through the mechanical switch to charge the transfer capacitor C3, so that the short-circuit current is quickly transferred from the fast mechanical switch S2 to the commutation branch, and after the current is completely transferred, the commutation capacitor C3 continues to be charged, and when the voltage across the commutation capacitor C3 rises to the operating voltage of the metal oxide surge arrester MOV2, the metal oxide surge arrester MOV2 is turned on, and during this period, the fast mechanical switch S2 reaches a certain opening distance, and the dielectric insulation of the broken gap is restored.

[0016] After the metal oxide surge arrester MOV2 operates, the current is completely transferred to the energy dissipation branch, and with the dissipation of the inductive stored energy, the current continuously decreases, and finally the current decreases to zero to complete the entire breaking process.

[0017] Advantages

[0018] The DC circuit breaker provided by the application utilizes a self-charging capacitor to realize current transfer, the self-charging branch can charge the commutation branch capacitor, the metal oxide surge arrester can limit the fault current rising rate, and the transfer branch realizes the transfer of the fault current through a magnetic coupling module. The DC circuit breaker provided by the application has a power electronic switch in series in the main branch, and the small-current breaking speed is improved. The capacitor is charged by utilizing the turn-off of the power electronic device, and an external charging circuit is omitted, so that the system reliability is improved and the cost of the DC circuit breaker is reduced. Moreover, the coupling inductor can greatly improve the breaking capacity of the DC circuit breaker. The DC circuit breaker can balance the economy and reliability, can break the rated current, can limit the fault current rising rate by utilizing the metal oxide surge arrester, can charge the commutation capacitor by utilizing the self-charging branch, can improve the turn-off capacity of the semiconductor switching device by utilizing the commutation branch, and can break the short-circuit fault, so that the application value and reliability of the DC power transmission and distribution system are further improved.

[0019] The above description is only a summary of the technical scheme of the present application. In order to make the technical scheme of the present application more clear and understandable, to the extent that a person skilled in the art can implement the content of the present application, and to make the above and other purposes, features and advantages of the present application more obvious and understandable, the following will be described with specific embodiments of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0020] Various other advantages and benefits of the present application will become apparent to those of ordinary skill in the art, upon reading the following detailed description of the preferred embodiments. The accompanying drawings are included to provide a description of the preferred embodiments, and are not meant to limit the present application. Obviously, the drawings described below are only some embodiments of the present application, and other drawings can be obtained from these drawings by those of ordinary skill in the art without creative labor. Moreover, the same reference numerals are used to represent the same components throughout the drawings.

[0021] In the drawings:

[0022] Figure 1 is a structural schematic diagram of a self-charging capacitor commutation type DC circuit breaker according to an embodiment of the present application;

[0023] Figures 2(a) to 2(e) is a schematic diagram of the breaking process of a self-charging capacitor commutation type DC circuit breaker according to an embodiment of the present application;

[0024] Figure 3 is a structural schematic diagram of a self-charging capacitor commutation type DC circuit breaker according to an embodiment of the present application;

[0025] Figure 4 is a structural schematic diagram of a self-charging capacitor commutation type DC circuit breaker with a freewheeling diode according to an embodiment of the present application.

[0026] In all the drawings, the gray part represents the circuit that is not working in the corresponding state.

[0027] The present application will be further explained in conjunction with the drawings and embodiments. DETAILED DESCRIPTION

[0028] The specific embodiments of the present application will be described in detail below with reference to the accompanying drawings. Figures 1 to 4 Specific embodiments of the present application will be described in more detail. Although specific embodiments of the present application are shown in the drawings, it should be understood that the present application can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided to enable a more thorough understanding of the present application and to fully convey the scope of the present application to those skilled in the art.

[0029] It should be noted that some terms are used in the description and claims herein. Those skilled in the art will understand that one name can be used to refer to a component by different names. The description and claims herein do not distinguish components by the difference in names, but by the difference in functions. As mentioned throughout the description and claims, "including" or "comprising" is an open term, which should be interpreted as "including but not limited to". The subsequent description is a preferred embodiment of implementing the application, which is for the purpose of illustrating the general principles of the application, and is not intended to limit the scope of the application. The scope of protection of the application is defined by the appended claims.

[0030] In order to facilitate the understanding of the embodiments of the application, the following will be further explained and described with several specific examples in conjunction with the accompanying drawings, and each drawing does not constitute a limitation on the embodiments of the application.

[0031] As shown in Figures 1 to 4 A self-charging capacitor commutation type DC circuit breaker includes a current passing branch, a self-charging branch, a commutation branch and an energy consumption branch; the current passing branch includes a semiconductor switching device S1 and a fast mechanical switch S2 in series, the self-charging circuit includes the semiconductor switching device S1, a buffer capacitor C1, a resistor R1, a thyristor T1 and a charging capacitor C2, wherein the buffer capacitor C1 is connected in parallel across the semiconductor switching device S1 after being connected in series with the resistor R1, one end of the thyristor T1 is connected to one end of the semiconductor switching device S1, the other end of the thyristor T1 is connected in series with one end of the charging capacitor C2, and the other end of the charging capacitor C2 is connected to the other end of the semiconductor switching device S1; the commutation branch includes a thyristor T2, a coupling inductor L1, a coupling inductor L2 and a commutation capacitor C3, wherein one end of the thyristor T2 is connected between the thyristor T1 and the charging capacitor C2, the other end of the thyristor T2 is connected in series with one end of the coupling inductor L1, the other end of the coupling inductor L1 is connected to the other end of the semiconductor switching device S1, the coupling inductor L2 is connected in parallel across the fast mechanical switch S2 after being connected in series with the commutation capacitor C3, and the energy consumption branch includes a metal oxide surge arrester MOV1 and a metal oxide surge arrester MOV2, the metal oxide surge arrester MOV1 is connected in parallel across the semiconductor switching device S1, and the metal oxide surge arrester MOV2 is connected in parallel across the fast mechanical switch S2.

[0032] In a preferred embodiment of the self-charging capacitor commutation type DC circuit breaker, the semiconductor switching device S1 is a fully controlled semiconductor switching device.

[0033] In a preferred embodiment of the self-charging capacitor commutation type DC circuit breaker, the thyristor T1 or the thyristor T2 is a unidirectional conduction half-controlled device.

[0034] In the preferred embodiment of the self-charging capacitor commutation type DC circuit breaker, the fast mechanical switch S2 is a vacuum high-speed mechanical switch based on electromagnetic repulsion, a vacuum mechanical switch based on high-speed motor drive, or a vacuum high-speed mechanical switch based on explosion drive.

[0035] In the preferred embodiment of the self-charging capacitor commutation type DC circuit breaker, the buffer capacitor C1 includes any one or a combination of thin film capacitor, organic medium capacitor, inorganic medium capacitor, electrolytic capacitor, electrothermal capacitor, and air medium capacitor.

[0036] In the preferred embodiment of the self-charging capacitor commutation type DC circuit breaker, the coupling inductance L1 and the coupling inductance L2 are both high-low voltage side fully isolated coupling inductances.

[0037] In one embodiment, the coupling inductance L1 and the coupling inductance L2 constitute the primary side and the secondary side of the coupling inductance, respectively.

[0038] In one embodiment, Figure 3 is a structure schematic diagram of a self-charging capacitor commutation type hybrid DC circuit breaker according to an embodiment of the present application, and the fault current breaking process is consistent with Figures 2(a) to 2(e) The IGBT device is connected in parallel to the two ends of the fast mechanical switch S2 after replacing the commutation capacitor C3 in series with the coupling inductance L2.

[0039] Figure 4 is a structure schematic diagram of a self-charging capacitor commutation type DC circuit breaker with a freewheeling diode according to an embodiment of the present application. The freewheeling diode is turned on during current transfer, and can provide sufficient dielectric recovery time for the mechanical switch. The freewheeling diode D1 is connected in parallel to the two ends of the fast mechanical switch S2.

[0040] The breaking method of the self-charging capacitor commutation type DC circuit breaker includes the following steps,

[0041] During normal conduction, the semiconductor switching device S1 is turned on, the fast mechanical switch S2 is closed, the current flows through the semiconductor switching device S1 and the fast mechanical switch S2, and no current flows through the self-charging branch, the commutation branch, and the energy consumption branch;

[0042] When a short-circuit fault occurs, the semiconductor switching device S1 is turned off at the initial stage of the fault current rise. After the semiconductor switching device S1 is turned off, a turn-off overvoltage is generated across the two ends. When the turn-off overvoltage reaches the operating voltage of the metal oxide surge arrester MOV1, the metal oxide surge arrester MOV1 is turned on, and the fault current is completely transferred to the metal oxide surge arrester MOV1 branch. At this time, the thyristor T1 is turned on to charge the charging capacitor C2. After the charging capacitor C2 is fully charged, the thyristor T1 is turned off.

[0043] When the fast mechanical switch S2 receives a trigger signal and operates, the fast mechanical switch S2 contacts are pulled apart, and an arc is generated at both ends. At this time, the thyristor T2 is turned on, the charging capacitor C2 is discharged to the coupled inductor L1, the coupled coil L2 induces a voltage, the voltage of the coupled coil L2 is formed into a loop through the mechanical switch to charge the transfer capacitor C3, and the short-circuit current is quickly transferred from the high-speed mechanical switch S2 to the commutation branch. After the current is completely transferred, the commutation capacitor C3 continues to be charged. When the voltage at both ends of the commutation capacitor C3 rises to the operating voltage of the metal oxide surge arrester MOV2, the metal oxide surge arrester MOV2 is turned on. During this period, the fast mechanical switch S2 reaches a certain opening distance, and the break gap insulation is restored.

[0044] After the metal oxide surge arrester MOV2 operates, the current is completely transferred to the energy dissipation branch. With the dissipation of the inductive stored energy, the current continuously decreases, and finally the current decreases to zero to complete the entire breaking process.

[0045] In one embodiment, as shown in Figures 2(a) to 2(e) , the breaking process is described in combination Figures 2(a) to 2(e) Figures 2(a) to 2(e) .

[0046] (1) As shown in FIG. 2(a), in the normal flow state of the system, the current flows through the semiconductor switch device S1 and the fast mechanical switch S2.

[0047] (2) As shown in FIG. 2(b), when a short-circuit fault occurs, the current rapidly rises. The semiconductor switch device S1 is turned off at the initial stage of the rising fault current. After the semiconductor switch device S1 is turned off, a turn-off overvoltage is generated at both ends. When the turn-off overvoltage reaches the operating voltage of the metal oxide surge arrester MOV1, the metal oxide surge arrester MOV1 is turned on, and the fault current is completely transferred to the metal oxide surge arrester MOV1 branch.

[0048] (3) As shown in FIG. 2(c), the thyristor T1 is turned on, and the charging capacitor C2 is charged. After the charging capacitor C2 is fully charged, the thyristor T1 is turned off.

[0049] (4) As shown in FIG. 2(d), the fast mechanical switch S2 is controlled to open, and an arc is generated at both ends. At this time, the thyristor T2 is turned on, the charging capacitor C2 is discharged to the coupled inductor primary side, the coupled coil secondary side induces a voltage, and the secondary side voltage is formed into a loop through the mechanical switch to charge the transfer capacitor C3, and the short-circuit current is quickly transferred from the high-speed mechanical switch to the commutation branch.

[0050] (5) As shown in Fig. 2 (e), after the fault current is completely transferred, the capacitor C3 continues to charge, and when the voltage across the commutating capacitor C3 rises to the operating voltage of the metal oxide surge arrester MOV2, the metal oxide surge arrester MOV2 is turned on, and during this period, the fast mechanical switch has a certain opening distance, and the broken gap medium insulation is restored. After the metal oxide surge arrester MOV2 is operated, the current is completely transferred to the energy dissipation branch. With the dissipation of the energy stored in the system inductance, the current continuously decreases, and finally the current decreases to zero to complete the entire breaking process.

[0051] The circuit breaker can break the rated current, the metal oxide surge arrester MOV1 can limit the short-circuit fault current rise rate, the self-charging branch can charge the charging capacitor, the commutation branch can improve the breaking capacity of the semiconductor switching device, and the short-circuit fault breaking can be performed.

[0052] Although the embodiments of the present application are described above in combination with the drawings, the present application is not limited to the above specific embodiments and application fields, and the above specific embodiments are only illustrative and guiding, but not limiting. Those skilled in the art can make many forms under the guidance of the present application and without departing from the scope protected by the claims of the present application, which all belong to the protection of the present application.

Claims

1. A self-charging capacitor-commutated DC circuit breaker, characterized in that: It includes a current-carrying branch, a self-charging branch, a commutation branch, and an energy-dissipating branch; the current-carrying branch includes a semiconductor switching device S1 and a fast mechanical switch S2 connected in series; the self-charging branch includes the semiconductor switching device S1, a buffer capacitor C1, a resistor R1, a thyristor T1, and a charging capacitor C2, wherein the buffer capacitor C1 is connected in series with the resistor R1 and then in parallel across the semiconductor switching device S1; one end of the thyristor T1 is connected to one end of the semiconductor switching device S1, and the other end of the thyristor T1 is connected in series with one end of the charging capacitor C2; the other end of the charging capacitor C2 is connected to the other end of the semiconductor switching device S1; the commutation branch includes the thyristor T2, ... The circuit includes coupling inductors L1 and L2, and commutation capacitor C3. One end of thyristor T2 is connected between thyristor T1 and charging capacitor C2. The other end of thyristor T2 is connected in series with one end of coupling inductor L1. The other end of coupling inductor L1 is connected to the other end of semiconductor switching device S1. Coupling inductor L2 is connected in series with commutation capacitor C3 and then connected in parallel across fast mechanical switch S2. The energy dissipation branch includes metal oxide surge arrester MOV1 and metal oxide surge arrester MOV2. Metal oxide surge arrester MOV1 is connected in parallel across semiconductor switching device S1, and metal oxide surge arrester MOV2 is connected in parallel across fast mechanical switch S2.

2. The self-charging capacitor-commutated DC circuit breaker according to claim 1, characterized in that: The semiconductor switching device S1 is a fully controllable semiconductor switching device.

3. The self-charging capacitor-commutated DC circuit breaker according to claim 1, characterized in that: The thyristor T1 or thyristor T2 is a unidirectional semi-controlled device.

4. The self-charging capacitor-commutated DC circuit breaker according to claim 1, characterized in that: The fast mechanical switch S2 is a vacuum high-speed mechanical switch based on electromagnetic repulsion, a vacuum mechanical switch driven by a high-speed motor, or a vacuum high-speed mechanical switch driven by explosion.

5. The self-charging capacitor-commutated DC circuit breaker according to claim 1, characterized in that: The buffer capacitor C1 includes any one or a combination of organic dielectric capacitors, inorganic dielectric capacitors, and air dielectric capacitors.

6. The self-charging capacitor-commutated DC circuit breaker according to claim 1, characterized in that: Both coupled inductors L1 and L2 are coupled inductors that are completely isolated between the high and low voltage sides.

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