A self-charging and breaking DC circuit breaker and its control method

Abstract

The present invention discloses a self-charging and breaking DC circuit breaker and a control method thereof, comprising a main current loop, a current transfer branch, and an energy absorption branch; the main current loop comprises a first switch S1 and a second switch S2 connected in series, the current transfer branch comprises a first capacitor C1 and a second capacitor C2, an inductor L, and a thyristor Tr, and the energy absorption branch comprises a lightning arrester connected in parallel to both ends of the second switch S2; the main current loop is led out through outlet terminals A1 and A2. The present invention designs a novel loop topology, utilizes arc voltage to charge the capacitor, triggers the thyristor to achieve current transfer, and uses capacitors of two capacitance values to complete breaking for two currents of large and small. The present invention has the function of adapting to various complex operating conditions of circuit breakers, and has a simple structure, low conduction loss, and fast full-current breaking speed.

Description

Technical Field

[0001] The present invention belongs to the technical field of DC circuit breakers, and in particular relates to a self-charging and breaking DC circuit breaker and a control method thereof. Background Art

[0002] With the continuous advancement of urban construction, the development of high-density, large-capacity, and highly reliable DC power distribution systems has become an urgent need for the development of large and medium-sized cities. Certain special power systems operate under complex conditions. Traditional DC circuit breakers, due to their inherent limitations such as long interruption times, limited current-limiting capabilities, and inability to simultaneously accommodate diverse operating conditions, are unable to adapt to the high voltage and high current requirements of DC systems.

[0003] Compared to traditional AC systems, short-circuit faults in DC systems are characterized by a rapid current rise rate, high short-circuit current peaks, and the absence of a natural zero crossing. Furthermore, DC circuit breakers must absorb the energy stored in the system inductance, making DC interruption difficult. Currently, most widely used hybrid circuit breakers achieve DC segmentation by injecting a current opposite to the short-circuit current to create an artificial zero crossing. However, when interrupting low currents, the injected current can reversely break down the contacts of high-speed mechanical switches, making it difficult to extinguish the arc between the contacts during interruption, prolonging the interruption time and adversely affecting the system. Summary of the Invention

[0004] In response to the shortcomings and defects of the aforementioned prior art, the present invention aims to provide a self-charging and disconnecting DC circuit breaker and its control method. By designing a novel circuit topology, the circuit breaker utilizes arc voltage to charge capacitors, triggering thyristors to achieve current transfer, and using two capacitor values to complete the disconnection for both large and small currents. This circuit breaker is adaptable to a variety of complex circuit breaker operating conditions, and features a simple structure, low conduction losses, and fast full-current disconnection speed. This novel DC circuit breaker can simultaneously address both short-circuit and low-current conditions, while eliminating the need for fully controlled power electronic devices. Low-current currents are transferred using smaller capacitors, while high-current currents are transferred and disconnected using two capacitors in parallel, shortening short-circuit troubleshooting time and improving system stability.

[0005] To achieve the above-mentioned object, the technical solution adopted by the present invention is a self-charging and breaking DC circuit breaker, comprising a main current loop, a current transfer branch, and an energy absorption branch; the main current loop comprises a first switch S1 and a second switch S2 connected in series, the current transfer branch comprises a first capacitor C1 and a second capacitor C2, an inductor L, and a thyristor Tr, and the energy absorption branch comprises a lightning arrester connected in parallel to both ends of the second switch S2; the main current loop is led out through output terminals A1 and A2, wherein;

[0006] The circuit breaker outlet terminal A1, the first switch S1, the second switch S2 and the circuit breaker outlet terminal A2 are connected in series in sequence;

[0007] In the current transfer branch, an inductor L is connected in series with a thyristor Tr; a first capacitor C1 is connected in parallel across a first switch S1, with a diode D connected between the first switch S1 and the first capacitor C1; a branch formed by a second capacitor C2 connected in series with a third switch S3 is connected in parallel with the first capacitor C1, and a branch formed by a second capacitor C2 connected in series with the third switch S3 is connected in series with the inductor L; the anode of the diode D is connected to the output terminal A1, and the cathode of the thyristor Tr is connected to the output terminal A2.

[0008] Furthermore, the first switch S1 is an air switch or an SF6 switch, the second switch S2 is a vacuum switch, and the third switch S3 is an air switch.

[0009] Furthermore, it also includes a control system for providing opening control instructions to the switch.

[0010] The control system includes: a human-computer interaction module, a current filtering and processing module, a main circuit current di / dt calculation module, and a communication module; wherein the human-computer interaction module is used to receive user instructions and feedback electrical parameter information; the current filtering and processing module is used to process current detection signals and feedback data to the communication module; the main circuit current di / dt calculation module is used to calculate the main circuit current change rate and feedback data to the communication module; the communication module is used to receive and process the detected current signal and current change rate signal, and issue control commands.

[0011] Furthermore, the capacitance of the first capacitor C1 is smaller than that of the second capacitor C2, and the withstand voltage of the first capacitor C1 and the second capacitor C2 is greater than the turn-on voltage of the lightning arrester in the energy absorption branch.

[0012] Furthermore, the arrester is a metal oxide arrester, a line type metal oxide arrester, a gapless line type metal oxide arrester, a fully insulated composite jacket metal oxide arrester or a detachable arrester.

[0013] Furthermore, a diode is connected in anti-parallel to the diode D;

[0014] A diode D1 is connected in series between a branch formed by the second capacitor C2 connected in series with the third switch S3 and the inductor L, and the inductor L is connected to the cathode of the diode D1. A diode D2 is connected in series between the cathode of the thyristor Tr and the output terminal A2, and the cathode of the thyristor Tr is connected to the anode of the diode D2.

[0015] A diode D3 is connected in series between the output terminal A2 and the inductor L, the output terminal A2 is connected to the anode of the diode D3, and the cathode of the diode D3 is connected to the cathode of the diode D1; a diode D4 is connected in series between the branch formed by the second capacitor C2 connected in series with the third switch S3 and the thyristor Tr, and the cathode of the thyristor Tr is connected to the anode of the diode D4.

[0016] As another object of the present invention, the present invention also discloses a control method for a self-charging and breaking DC circuit breaker. When the system rated current or a current below the rated current needs to be interrupted, the third switch S3 is in the disconnected state; the control system sends a tripping instruction to the first switch S1 and the second switch S2. Both switches start to operate after receiving the tripping action instruction. After the contacts of the switches are pulled apart, an arc begins to burn between the contacts. Due to the arc voltage across the first switch S1, the first capacitor C1 is charged, and the voltage gradually rises to trigger the conduction thyristor Tr, forming a discharge path, the first capacitor C1 starts to discharge, and the current of the second switch S2 passes through zero to extinguish the arc. The first capacitor C1 is reversely charged in this process. When the reverse voltage is greater than the conduction voltage of the lightning arrester, the lightning arrester is turned on. The energy of the short-circuit current is dissipated by the lightning arrester to achieve breaking.

[0017] As another object of the present invention, the present invention also discloses a control method for a self-charging and breaking DC circuit breaker. When a short circuit fault occurs in the system, the system short-circuit current level is high, and the third switch S3 is in the on state. The control system sends a tripping instruction to the first switch S1 and the second switch S2. Both start to operate after receiving the tripping action instruction. After the contacts of the switches are pulled apart, arcing begins between the contacts; due to the arc voltage across the first switch S1, the first capacitor C1 and the second capacitor C2 are charged, and the voltage across the two ends gradually increases. After the capacitor voltage rises to a certain level, the conductive thyristor Tr is triggered, a discharge path is formed, the first capacitor C1 and the second capacitor C2 begin to discharge, and the current of the second switch S2 passes through zero and extinguishes the arc; the first capacitor C1 and the second capacitor C2 are reversely charged in this process, and when the reverse voltage is greater than the arrester conduction voltage, the arrester is turned on; the energy of the short-circuit current is dissipated by the arrester, thereby achieving breaking.

[0018] Compared with the prior art, the present invention has at least the following beneficial effects: the present invention designs two parallel capacitors of different sizes in the current transfer branch, uses arc voltage to charge the capacitors, and then triggers thyristors to transfer current, and uses two methods to disconnect currents of different levels. Small currents use capacitors with smaller capacitance to transfer current, and large currents use a dual-capacitor parallel method to complete current transfer and disconnection, shortening the short-circuit fault troubleshooting time and improving the stability of the system; the present invention realizes the function of quickly disconnecting short-circuit faults under various current conditions in medium-voltage DC systems.

[0019] Furthermore, the present invention adopts a bridge structure to connect the inductor and the thyristor, which can realize bidirectional current transfer and interruption, reduce the size of the circuit breaker, and expand the application scenarios.

[0020] Furthermore, the present invention has the function of adapting to various complex working conditions of circuit breakers, and is a novel DC circuit breaker that does not use fully controlled power electronic devices, has a simple structure, low conduction loss, and a fast full-current breaking speed. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of the circuit breaker circuit structure;

[0022] Figure 2 This is a working principle diagram of the circuit breaker of the present invention for breaking rated current or small current; wherein, Figure 2 (a) is a schematic diagram of normal flow state. Figure 2 (b) is a schematic diagram of the trigger switch opening state. Figure 2 (c) is a schematic diagram of the capacitor discharge transfer current state. Figure 2 (d) is a schematic diagram of the arrester in the conducting state.

[0023] Figure 3 This is a diagram showing the working principle of the circuit breaker for breaking short-circuit current; Figure 3 (a) is a schematic diagram of normal flow state. Figure 3 (b) is a schematic diagram of the trigger switch opening state. Figure 3 (c) is a schematic diagram of the capacitor discharge transfer current state. Figure 3 (d) is a schematic diagram of the arrester in the conducting state.

[0024] Figure 4 This is a deduction of the bidirectional breaking topology of the circuit breaker of the present invention. DETAILED DESCRIPTION

[0025] The specific embodiments of the present invention are described below with reference to the accompanying drawings.

[0026] like Figure 1 As shown, a self-charging and breaking DC circuit breaker includes a main current loop, a current transfer branch, and an energy absorption branch; the main current loop includes a first switch S1 and a second switch S2 connected in series, the current transfer branch includes a first capacitor C1 and a second capacitor C2, an inductor L, and a thyristor Tr, wherein the capacitance of the first capacitor C1 is smaller than that of the second capacitor C2, and the withstand voltage of the first capacitor C1 and the second capacitor C2 are both greater than the conduction voltage of the lightning arrester in the energy absorption branch. The energy absorption branch includes a lightning arrester connected in parallel to both ends of the second switch S2; the main current loop is led out through the output terminals A1 and A2, wherein;

[0027] The circuit breaker outlet terminal A1, the first switch S1, the second switch S2 and the circuit breaker outlet terminal A2 are connected in series in sequence;

[0028] In the current transfer branch, an inductor L is connected in series with a thyristor Tr; a first capacitor C1 is connected in parallel across a first switch S1, with a diode D connected between the first switch S1 and the first capacitor C1; a branch formed by a second capacitor C2 connected in series with a third switch S3 is connected in parallel with the first capacitor C1, and a branch formed by a second capacitor C2 connected in series with the third switch S3 is connected in series with the inductor L; the anode of the diode D is connected to the output terminal A1, and the cathode of the thyristor Tr is connected to the output terminal A2.

[0029] In a specific embodiment of the present invention, the capacitance of the second capacitor C2 is selected according to the breaking current level, usually in the range of several hundred microfarads, and the capacitance of the first capacitor C1 is selected in the range of several tens of microfarads.

[0030] In a specific embodiment of the present invention, the first switch S1 is an air switch or an SF6 switch, the second switch S2 is a vacuum switch, and the third switch S3 is an air switch.

[0031] In one embodiment of the present invention, a control system is further included for providing a trip control instruction to the switch.

[0032] In one embodiment of the present invention, the arrester is a metal oxide arrester, a line type metal oxide arrester, a gapless line type metal oxide arrester, a fully insulated composite jacket metal oxide arrester or a detachable arrester.

[0033] like Figure 2 As shown, the breaking process of the circuit breaker of the present invention under the system rated current working condition or low current working condition is as follows:

[0034] (1) Figure 2 In the normal flow state shown in (a), the system current flows from the main current loop in the direction from the circuit breaker output terminal A1 to the circuit breaker output terminal A2, and the system current flows through the first switch S1 and the second switch S2. The system conduction loss is the current loss in the main current loop; at this time, no current flows through the current transfer branch, the voltage across the lightning arrester of the energy absorption branch is very low, and the lightning arrester is not conducting.

[0035] (2) Figure 2 As shown in (b), when disconnection is required, the third switch S3 is in the open state; the control system issues an opening command to the first switch S1 and the second switch S2. Both switches start to operate upon receiving the opening command, and arcing begins between the contacts after the switches are pulled apart. Due to the arc voltage across the first switch S1, the first capacitor C1 is charged, and the capacitor voltage increases, with the polarity being positive on the left and negative on the right.

[0036] (3) Figure 2As shown in (c), the voltage of the first capacitor C1 gradually rises to trigger the thyristor Tr to turn on, forming a discharge path, the first capacitor C1 begins to discharge, the current of the second switch S2 crosses zero and extinguishes the arc, and the first capacitor C1 is reversely charged in this process;

[0037] The thyristor is triggered, capacitor C1 starts to discharge and transfer current, and the current at vacuum switch S2 passes through zero and extinguishes the arc;

[0038] (4) Figure 2 As shown in (d), during the current transfer process, capacitor C1 is reversely charged with a polarity of negative on the left and positive on the right. When the reverse voltage of the first capacitor C1 is greater than the arrester's turn-on voltage, the arrester turns on; the energy of the short-circuit current is dissipated by the arrester, completing the interruption of the small current.

[0039] like Figure 3 FIG. 1 shows the current transfer process of the circuit breaker of the present invention under the system short-circuit condition.

[0040] (1) Figure 3 In the normal flow state shown in (a), the system current flows from the main current loop from the circuit breaker output terminal A1 to the circuit breaker output terminal A2, and the system current flows through the first switch S1 and the second switch S2. The system conduction loss is the current loss in the main current loop. At this time, no current flows through the current transfer branch, the voltage across the lightning arrester in the energy absorption branch is very low, and the lightning arrester is not conducting.

[0041] (2) Figure 3 As shown in Figure (b), when a short-circuit fault occurs in the system, the system short-circuit current level is high, the current in the main current loop rises rapidly, and the third switch S3 is in the on state, triggering the first switch S1 and the second switch S2 to open. After the switch contacts are pulled open, an arc begins between the contacts. Due to the arc voltage across the first switch S1, the first capacitor C1 and the second capacitor C2 are charged, and the voltage across the two terminals gradually increases, with the polarity being positive on the left and negative on the right.

[0042] (3) Figure 3 As shown in (c), when the capacitance voltage of the first capacitor C1 and the second capacitor C2 rises to a certain level, the thyristor Tr is triggered to turn on, a discharge path is formed, the first capacitor C1 and the second capacitor C2 begin to discharge, and the current of the second switch S2 crosses zero and extinguishes the arc;

[0043] (4) Figure 3 As shown in (d), during the current transfer process, the first capacitor C1 and the second capacitor C2 are reversely charged, with the polarity being negative on the left and positive on the right. When the reverse voltage is greater than the arrester's turn-on voltage, the arrester turns on; the energy of the short-circuit current is dissipated by the arrester, completing the interruption of the large current short-circuit fault.

[0044] like Figure 4As shown, a diode is connected in anti-parallel to the diode D; a diode D1 is connected in series between the branch formed by the second capacitor C2 connected in series with the third switch S3 and the inductor L, and the inductor L is connected to the cathode of the diode D1. A diode D2 is connected in series between the cathode of the thyristor Tr and the output terminal A2, and the cathode of the thyristor Tr is connected to the anode of the diode D2; a diode D3 is connected in series between the output terminal A2 and the inductor L, and the output terminal A2 is connected to the anode of the diode D3, and the cathode of the diode D3 is connected to the cathode of the diode D1; a diode D4 is connected in series between the branch formed by the second capacitor C2 connected in series with the third switch S3 and the thyristor Tr, and the cathode of the thyristor Tr is connected to the anode of the diode D4. Figure 4 The middle structure is a bidirectional circuit breaker based on the breaking principle of this invention. A second diode is connected in antiparallel to diode D. When interrupting bidirectional current, the capacitor is charged by the arc voltage. A bridge structure is used to connect the inductor and thyristor, allowing current transfer and interruption in both directions, reducing the size of the circuit breaker.

[0045] The above content is a further detailed description of the present invention in combination with specific preferred embodiments. It cannot be considered that the specific embodiments of the present invention are limited to these. For ordinary technicians in the technical field to which the present invention belongs, they can make several simple deductions or substitutions without departing from the concept of the present invention, which should be regarded as belonging to the scope of protection of the present invention determined by the submitted claims.

Claims

1. A self-charging and breaking DC circuit breaker, characterized in that: It includes a main current loop, a current transfer branch and an energy absorption branch; the main current loop includes a first switch S1 and a second switch S2 connected in series, the current transfer branch includes a first capacitor C1 and a second capacitor C2, an inductor L and a thyristor Tr, and the energy absorption branch includes a lightning arrester connected in parallel to both ends of the second switch S2; the main current loop is led out through the output terminals A1 and A2, wherein; The circuit breaker outlet terminal A1, the first switch S1, the second switch S2 and the circuit breaker outlet terminal A2 are connected in series in sequence; In the current transfer branch, an inductor L is connected in series with a thyristor Tr; a first capacitor C1 is connected in parallel across a first switch S1, and a diode D is connected between the first switch S1 and the first capacitor C1; a branch formed by a second capacitor C2 connected in series with a third switch S3 is connected in parallel with the first capacitor C1; the anode of the diode D is connected to the output terminal A1, and the cathode of the thyristor Tr is connected to the output terminal A2; a branch formed by a diode D connected in series with the first capacitor C1 is connected in parallel with the first switch S1, the anode of the diode D is connected to the first switch S1, and the cathode of the diode D is connected to the first capacitor C1; the cathode of the diode D is connected to the first end of the inductor L, and the second end of the inductor L is connected to the anode of the thyristor Tr; The capacitance of the first capacitor C1 is smaller than that of the second capacitor C2; when it is necessary to interrupt the rated current of the system or a current below the rated current, the third switch S3 is in an off state; When a short circuit fault occurs in the system, the system short circuit current level is high, and the third switch S3 is in the on state.

2. The self-charging and breaking DC circuit breaker according to claim 1, characterized in that: The first switch S1 is an air switch or an SF6 switch, the second switch S2 is a vacuum switch, and the third switch S3 is an air switch.

3. The self-charging and breaking DC circuit breaker according to claim 1, characterized in that: Also included is a control system for providing an opening control command to the switch.

4. The self-charging and breaking DC circuit breaker according to claim 1, characterized in that: The capacitance of the first capacitor C1 is smaller than that of the second capacitor C2, and the withstand voltage of the first capacitor C1 and the second capacitor C2 is greater than the turn-on voltage of the lightning arrester in the energy absorption branch.

5. The self-charging and breaking DC circuit breaker according to claim 1, characterized in that: The arrester is a line-type metal oxide arrester.

6. The self-charging and breaking DC circuit breaker according to claim 1, characterized in that: A diode is connected in anti-parallel to the diode D; A diode D2 is connected in series between the cathode of the thyristor Tr and the output terminal A2, and the cathode of the thyristor Tr is connected to the anode of the diode D2; a diode D1 is connected between the cathode of the diode D and the first end of the inductor L, the first end of the inductor L is connected to the cathode of the diode D1, and the cathode of the diode D is connected to the anode of the diode D1; a diode D4 is connected between the cathode of the diode D and the cathode of the thyristor Tr; A diode D3 is connected in series between the output terminal A2 and the first end of the inductor L, the output terminal A2 is connected to the anode of the diode D3, and the cathode of the diode D3 is connected to the cathode of the diode D1; a diode D4 is connected in series between the cathode of the diode D and the thyristor Tr, and the cathode of the thyristor Tr is connected to the anode of the diode D4.

7. A control method for a self-charging and breaking DC circuit breaker, characterized in that: Based on the self-charging and disconnecting DC circuit breaker described in claim 1, when it is necessary to disconnect the system rated current or a current below the rated current, the third switch S3 is in the disconnected state; the control system sends a tripping instruction to the first switch S1 and the second switch S2, and both start to act after receiving the tripping action instruction. After the contacts of the switches are pulled apart, arcing begins between the contacts; due to the arc voltage across the first switch S1, the first capacitor C1 is charged, and the voltage gradually rises to trigger the conduction thyristor Tr, a discharge path is formed, the first capacitor C1 starts to discharge, and the current of the second switch S2 passes through zero to extinguish the arc; the first capacitor C1 is reversely charged in this process, and when the reverse voltage is greater than the conduction voltage of the lightning arrester, the lightning arrester is turned on; the energy of the short-circuit current is dissipated by the lightning arrester to achieve disconnection.

8. A control method for a self-charging and breaking DC circuit breaker, characterized in that: Based on the self-charging and disconnecting DC circuit breaker described in claim 1, when a short-circuit fault occurs in the system, the system short-circuit current level is high, the third switch S3 is in the on state, and the control system sends a tripping instruction to the first switch S1 and the second switch S2. Both start to act after receiving the tripping action instruction. After the contacts of the switches are pulled apart, arcing begins between the contacts; due to the arc voltage at both ends of the first switch S1, the first capacitor C1 and the second capacitor C2 are charged, and the voltage at both ends gradually rises. After the capacitor voltage rises to a certain level, the turn-on thyristor Tr is triggered, a discharge path is formed, the first capacitor C1 and the second capacitor C2 start to discharge, and the current of the second switch S2 passes through zero and extinguishes the arc; the first capacitor C1 and the second capacitor C2 are reversely charged in this process, and when the reverse voltage is greater than the turn-on voltage of the lightning arrester, the lightning arrester is turned on; the energy of the short-circuit current is dissipated by the lightning arrester to achieve disconnection.

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