Mechanical DC Circuit Breaker with Adaptive Oscillating Capacitor Voltage and Its Control Method

Abstract

The present invention provides a mechanical DC circuit breaker with self-adaptive oscillating capacitor voltage to avoid restriking, comprising: a main current-carrying circuit, a coupling energy storage circuit, an energy transfer circuit, and an oscillating opening circuit; the main current-carrying circuit is used to connect the circuit breaker to the power grid so that the normal working current of the power grid flows through the main current-carrying circuit; the main current-carrying circuit includes the primary coil of a coupling reactor; the coupling energy storage circuit includes the secondary coil of the coupling reactor and is coupled to the main current-carrying circuit through the secondary coil of the coupling reactor; the coupling energy storage circuit is used to obtain and store energy from the main current-carrying circuit when a current fault occurs in the power grid; the energy transfer circuit is connected to the coupling energy storage circuit and is used to transfer the energy of the coupling energy storage circuit; the oscillating opening circuit is respectively connected to the main current-carrying circuit, the coupling energy storage circuit, and the energy transfer circuit; the oscillating opening circuit is used to obtain energy through the coupling energy storage circuit and the energy transfer circuit and is used to turn off the fault current of the main current-carrying circuit.

Description

Technical Field

[0001] The present invention belongs to the technical field of power electronics, and particularly relates to a mechanical DC circuit breaker with self-adaptive oscillating capacitor voltage and a control method thereof. Background Art

[0002] Due to the more complex and diverse main wiring structure and operation mode of the flexible DC power grid, the DC system has multiple fault modes, fast fault development, and a wide influence range. Therefore, there is an urgent need for a fault isolation technology for the flexible DC power grid to ensure the safe and reliable operation of the flexible DC power grid. The DC circuit breaker is an ideal choice for realizing DC fault isolation in the DC power transmission and distribution system. Currently, the mechanical DC circuit breaker has problems of mechanical switch re-breakdown when breaking small currents and difficulty in realizing the reclosing function. Moreover, the capacitor discharge energy is designed according to the rated short-circuit current. In most cases, the system breaking current is less than the rated short-circuit current, and the excess energy will flow back into the system, resulting in overcurrent and overvoltage problems.

[0003] Therefore, there is an urgent need for a solution that can solve the inherent problems of mechanical circuit breakers, such as re-breakdown, difficulty in reclosing, and energy backflow. Summary of the Invention

[0004] In view of the above problems, the present invention provides a mechanical DC circuit breaker with self-adaptive oscillating capacitor voltage, including: a main current-carrying circuit, a coupling energy storage circuit, an energy transfer circuit, and an oscillating breaking circuit;

[0005] The main current-carrying circuit is used to connect the circuit breaker to the power grid, so that the normal working current of the power grid flows through the main current-carrying circuit; the main current-carrying circuit includes the primary coil of a coupling reactor.

[0006] The coupling energy storage circuit includes the secondary coil of the coupling reactor, and is coupled to the main current-carrying circuit through the secondary coil of the coupling reactor; the coupling energy storage circuit is used to obtain energy from the main current-carrying circuit and store it when a current fault occurs in the power grid.

[0007] The energy transfer circuit is connected to the coupling energy storage circuit, and the energy transfer circuit is used to transfer the energy of the coupling energy storage circuit.

[0008] The oscillating breaking circuit is respectively connected to the main current-carrying circuit, the coupling energy storage circuit, and the energy transfer circuit;

[0009] The oscillating breaking circuit is used to obtain energy through the coupling energy storage circuit and the energy transfer circuit, and is used to turn off the fault current of the main current-carrying circuit.

[0010] Further,

[0011] The main current-carrying circuit includes an input end and an output end for connecting the circuit breaker to the power grid;

[0012] The input end and the output end of the main current-carrying circuit include a mechanical switch module and the primary coil of a coupling reactor connected in series;

[0013] The mechanical switch module includes a number of first mechanical switches.

[0014] Furthermore,

[0015] The coupling energy storage circuit includes the secondary coil of the coupling reactor and a solid-state switch module connected in parallel.

[0016] Furthermore,

[0017] The coupling circuit further includes a protection branch connected in parallel with the solid-state switch module, and the protection branch includes a protection MOV.

[0018] Furthermore,

[0019] The energy transfer circuit includes a first trigger switch module and a second mechanical switch connected in series.

[0020] Furthermore,

[0021] The oscillating breaking circuit includes a capacitor, a dissipative MOV, and a second trigger switch module;

[0022] The capacitor is connected in parallel with the dissipative MOV;

[0023] The capacitor is connected to the main current-carrying circuit through the second trigger switch module;

[0024] The first end of the capacitor is connected to the first end of the energy transfer circuit, the second end of the capacitor is connected to one end of the coupling energy storage circuit, and the second end of the energy transfer circuit is connected to the other end of the coupling energy storage circuit.

[0025] Furthermore,

[0026] The first end of the capacitor is connected to one end of the mechanical switch module, the second end of the capacitor is connected to one end of the second trigger switch module, and the other end of the second trigger switch module is connected to the other end of the mechanical switch module;

[0027] The second end of the capacitor is connected to the first end of the solid-state switch module, and the second end of the energy transfer circuit is connected to the second end of the solid-state switch module.

[0028] Furthermore,

[0029] A resistive discharge loop is connected in parallel across the capacitor, and the resistive discharge loop includes a resistor and a discharge switch connected in series.

[0030] The present invention provides a method for using a mechanical DC circuit breaker with self-adaptive oscillating capacitor voltage to turn off the fault current in the power grid where it is located, including:

[0031] When the power grid is operating normally, the mechanical switch module of the main current-carrying circuit is in the closed state;

[0032] After a short-circuit fault occurs in the power grid, the fault current in the primary coil rises, inducing a coupled voltage on the secondary side line and storing energy through the secondary coil;

[0033] After a certain fault detection time, the circuit breaker sends a tripping signal to the mechanical switch module of the main current-carrying circuit and the second mechanical switch of the energy transfer circuit;

[0034] At a certain moment just before the second mechanical switch opens, turn off the solid-state switch module and turn on the first trigger switch, and the current will transfer from the solid-state switch module to the capacitor of the oscillating opening circuit;

[0035] After the contact gap of the mechanical switch module of the main current-carrying circuit can withstand the transient recovery voltage, turn on the second trigger switch module in the oscillating opening circuit, and the capacitor discharges to the first mechanical switch of the main current-carrying circuit through the second trigger switch module;

[0036] When the oscillating current is equal in magnitude and opposite in direction to the fault current, the current of the mechanical switch module of the main current-carrying circuit will pass through zero and extinguish the arc. After that, all the fault current will flow to the branch where the capacitor is located and charge the capacitor;

[0037] When the voltage across the capacitor reaches the operating voltage of the energy-consuming MOV, the current will transfer to the energy-consuming MOV.

[0038] Furthermore, the method further includes a reclosing process:

[0039] After a specified reclosing interval, turn on the solid-state switch module and close the resistive discharge circuit in parallel with the capacitor to discharge the charge stored on the capacitor during the opening process. After several resistive-capacitive discharge time constants, if the circuit breaker current rises above the operating threshold at this time, it indicates that the fault is a permanent fault. Execute the opening of the resistive discharge circuit and close the mechanical switch module of the main current-carrying circuit to transfer the current to the main current-carrying circuit, and then the circuit breaker recloses according to the steps of interrupting the fault current in the power grid where it is located; if the circuit breaker current does not exceed the operating threshold, it indicates that the fault is a temporary fault. At this time, close the mechanical switch module of the main current-carrying circuit and open the resistive discharge circuit to transfer the current to the main current-carrying circuit to complete the reclosing.

[0040] The present invention also provides a method for using a mechanical DC circuit breaker with self-adaptive oscillating capacitor voltage to interrupt a specified current in the power grid where it is located. The specified current is the rated current or less than the rated current, including:

[0041] Perform a certain amount of pre-charging on the capacitor;

[0042] When the power grid is operating normally, the mechanical switch module of the main current-carrying circuit is in the closed state;

[0043] When it is necessary to cut off the specified current, a tripping signal is sent to the mechanical switch module of the main current-carrying circuit and the second mechanical switch of the energy transfer circuit;

[0044] At a certain moment before the second mechanical switch just opens, the solid-state switch module is turned off and the first trigger switch is turned on. The current will transfer from the solid-state switch module to the capacitor of the oscillating breaking circuit;

[0045] After the contact gap of the mechanical switch module of the main current-carrying circuit can withstand the transient recovery voltage, the second trigger switch module in the oscillating breaking circuit is turned on, and the capacitor discharges to the first mechanical switch of the main current-carrying circuit through the second trigger switch module;

[0046] When the oscillating current is equal in magnitude and opposite in direction to the specified current, the current of the mechanical switch module of the main current-carrying circuit will pass through zero and extinguish the arc. After that, all the fault current will flow to the branch where the capacitor is located and charge the capacitor;

[0047] When the voltage across the capacitor reaches the operating voltage of the energy-consuming MOV, the current will transfer to the energy-consuming MOV.

[0048] The oscillating capacitor voltage adaptive mechanical DC circuit breaker and its control method of the present invention can solve the inherent problems of mechanical circuit breakers such as re-breakdown, difficult reclosing, and energy backflow, and the cost is close to that of traditional circuit breakers.

[0049] Other features and advantages of the present invention will be described in the subsequent specification, and, in part, will be obvious from the specification, or will be understood by implementing the present invention. The objectives and other advantages of the present invention can be realized and obtained through the structures pointed out in the specification, claims, and drawings. Brief Description of the Drawings

[0050] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0051] Figure 1 Shows a schematic structural diagram of an adaptive circuit breaker according to an embodiment of the present invention;

[0052] Figure 2(a) shows a current schematic diagram of the adaptive circuit breaker in the normal working state of the power grid according to an embodiment of the present invention;

[0053] Figure 2(b) shows a current schematic diagram of the induced current generated in the coupling reactor induction after a circuit break fault according to an embodiment of the present invention;

[0054] Figure 2(c) shows a current schematic diagram of current transfer to the oscillating breaking circuit according to an embodiment of the present invention;

[0055] Figure 2(d) shows a current schematic diagram of the current of the second mechanical switch extinguishing the arc at the current zero-crossing according to an embodiment of the present invention;

[0056] Figure 2(e) shows a current schematic diagram of the capacitor discharging to the first mechanical switch of the main current-carrying circuit through the second trigger switch module according to an embodiment of the present invention;

[0057] Figure 2(f) shows a current schematic diagram of the fault current charging the capacitor according to an embodiment of the present invention;

[0058] Figure 2(g) shows a current schematic diagram of the current that will be transferred to the energy-consuming MOV according to an embodiment of the present invention;

[0059] Figure 3 Shows a potential schematic diagram when a permanent short-circuit fault occurs in the adaptive circuit breaker according to an embodiment of the present invention. Detailed implementation manners

[0060] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Apparently, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0061] Therefore, an embodiment of the present invention provides a mechanical DC circuit breaker with oscillating capacitor voltage adaption and its control method (hereinafter referred to as "adaptive circuit breaker" or "circuit breaker"), including: a main current-carrying circuit, a coupled energy storage circuit, an energy transfer circuit, and an oscillating breaking circuit. The main current-carrying circuit is used to connect the circuit breaker to the power grid, and the normal working current of the power grid flows through the main current-carrying circuit. The main current-carrying circuit includes the primary coil of the coupled reactor. The coupled energy storage circuit includes the secondary coil of the coupled reactor and is coupled to the main current-carrying circuit through the secondary coil of the coupled reactor. The energy transfer circuit is connected to the coupled energy storage circuit. The oscillating breaking circuit is respectively connected to the main current-carrying circuit, the coupled energy storage circuit, and the energy transfer circuit. The coupled energy storage circuit is used to obtain and store energy from the main current-carrying circuit when a current fault occurs in the power grid; the energy transfer circuit is used to transfer the energy of the coupled energy storage circuit; the energy transfer circuit is used to bear the current of the coupled energy storage circuit; the oscillating breaking circuit is used to obtain energy through the coupled energy storage circuit and the energy transfer circuit, and is used to turn off the fault current of the main current-carrying circuit.

[0062] The following gives an exemplary description of the specific implementation structure of the adaptive circuit breaker. AsFigure 1 As shown, the main current-carrying circuit of the adaptive circuit breaker includes an input terminal (IN) and an output terminal (OUT), that is, the input and output terminals of the adaptive circuit breaker. During use, the adaptive circuit breaker is connected to the power grid through these input and output terminals.

[0063] Between the input and output terminals of the main current-carrying circuit, there are a mechanically switched module and the primary coil of a coupling reactor connected in series. Without loss of generality, the mechanically switched module includes several (greater than or equal to 1) first mechanical switches connected in series and / or in parallel, specifically fast mechanical switches. One end of the mechanically switched module is connected to the input terminal, and the other end is connected to one end of the primary coil L1 of the coupling reactor. The other end of the primary coil L1 of the coupling reactor is connected to the output terminal. The coupling reactor is specifically a double-winding coupling reactor.

[0064] The coupling energy storage circuit includes the secondary coil L2 of the coupling reactor and a solid-state switch module connected in parallel. Further, it also includes a protection branch connected in parallel with the solid-state switch module. The solid-state switch module includes several bidirectional solid-state switches, and the protection branch includes a protection MOV. The protection branch is used to protect the solid-state switch module from overvoltage.

[0065] The energy transfer circuit includes a first trigger switch module Tc1 and a second mechanical switch connected in series.

[0066] The oscillatory opening circuit includes a capacitor, a dissipative MOV, and a second trigger switch module Tc2. The capacitor is connected in parallel with the dissipative MOV. The capacitor is connected to the main current-carrying circuit through the second trigger switch module Tc2. Exemplarily, the first end of the capacitor is connected to one end of the mechanically switched module, the second end of the capacitor is connected to one end of the second trigger switch module Tc2, and the other end of the second trigger switch module Tc2 is connected to the other end of the mechanically switched module. Further, a resistive discharge circuit ( Figure 1 not shown in the figure) is connected in parallel across the capacitor. Exemplarily, a resistor and a discharge switch are connected in series and then connected in parallel across the capacitor.

[0067] The first end of the capacitor is also connected to the first end of the energy transfer circuit, the second end of the capacitor is also connected to one end of the coupling energy storage circuit, and the second end of the energy transfer circuit is connected to the other end of the coupling energy storage circuit. Exemplarily, the first end of the capacitor is connected to the second mechanical switch of the energy transfer circuit, the second end of the capacitor is connected to the first end of the solid-state switch module, and the second end of the energy transfer circuit is connected to the second end of the solid-state switch module.

[0068] Specifically, the first mechanical switch and the second mechanical switch can both adopt vacuum fast mechanical switches, gas fast mechanical switches or series-parallel connections of the above switches; the solid-state switch module, its devices can adopt fully controlled power electronic devices such as insulated gate bipolar transistors (IGBTs), integrated gate commutated thyristors (IGCTs), gate injection enhancement transistors (IEGTs) and gate turn-off thyristors (GTOs), and the bidirectional topological structure of the solid-state switch module can adopt an anti-series structure, a full-bridge structure and a diode bridge structure; MOV (including energy-consuming MOV and protection MOV) is a metal oxide varistor; Tc1 and Tc2 respectively include bidirectional trigger switches, such as semi-controlled power electronic devices such as thyristors, and fully controlled power electronic devices or vacuum triggered switches (TVS, Triggered Vacuum Switch) can also be used. Furthermore, Tc1 and Tc2 also include the required protection circuit; the same-name terminals of the coupling reactors such as Figure 1 As shown, the magnetic conductive material can be air or magnetic core; the capacitor is pre-charged with a certain voltage through the charger, and the voltage direction is not limited to Figure 1 as shown in .

[0069] The above is only an exemplary description of the adaptive circuit breaker structure of the embodiment of the present invention, wherein the connection sequence and type of components of each circuit can be set as needed, or other auxiliary components can be added.

[0070] The adaptive circuit breaker of the embodiment of the present invention can solve the problems of heavy breakdown, difficulty in reclosing and energy backflow inherent in mechanical circuit breakers and has a cost close to that of traditional circuit breakers. The following is an exemplary description of the control method of the adaptive circuit breaker in conjunction with the process of cutting off the short-circuit current.

[0071] Sequence 1: When the power grid is operating normally, the current of the adaptive circuit breaker (the lines and devices with current are represented by bold lines, the same below) is shown in Figure 2(a). The mechanical switch module of the main current-carrying circuit is closed, and the line current flows through the primary coil L1 and the mechanical switch module. The solid-state switch module of the coupling energy storage circuit is turned on, but because the line current is DC, the secondary coil of the coupling reactor basically does not induce voltage, and the solid-state switch module is close to no current passing. Since Tc1 and Tc2 are not turned on, the pre-charged charge of the capacitor will not be discharged.

[0072] Sequence 2: After a short circuit occurs, as shown in Figure 2(b), the fault current through the primary coil L1 rises, inducing a coupling voltage on the secondary coil L2. At this time, since the solid-state switch module is turned on, the secondary coil L2 of the coupling reactor forms a loop with the solid-state switch module, stimulating a counterclockwise rising current (as shown by the arrow in the figure), and energy is stored in the secondary coil L2.

[0073] Timing 3: After a certain fault detection time, the adaptive circuit breaker receives a tripping command from the upper control system (such as the control and protection system, abbreviated as CP). (Through the control module, etc.) A tripping signal is sent to the mechanical switch module of the main current-carrying circuit and the second mechanical switch of the energy transfer circuit. At a certain moment just before the second mechanical switch opens, the solid-state switch module is turned off and the first trigger switch Tc1 is turned on, and the current will transfer from the solid-state switch module to the capacitor of the oscillating breaking circuit, as shown in Figure 2(c). Due to LC oscillation, the current will change approximately sinusoidally and pass through zero periodically.

[0074] Timing 4: After a period of time, the second mechanical switch just opens, and its contacts continue to move in the tripping direction. When the contact gap is large enough, the current will extinguish the arc at the zero-crossing point, and the oscillation ends. According to the characteristics of LC oscillation, the voltage on the capacitor will be close to the peak value at this time, as shown in Figure 2(d) (the voltage direction is not limited to that shown in the figure). In addition, the mechanical switch module of the main current-carrying circuit will also just open during this period and continue to move in the tripping direction.

[0075] Timing 5: After the contact gap of the mechanical switch module of the main current-carrying circuit can withstand the transient recovery voltage, the second trigger switch module Tc2 in the oscillating breaking circuit is turned on, and the capacitor discharges through Tc2 to the first mechanical switch of the main current-carrying circuit, and a sinusoidal oscillating current is superimposed on the fault current of the first mechanical switch. As shown in Figure 2(e).

[0076] Timing 6: When the oscillating current is equal in magnitude and opposite in direction to the fault current, the current of the mechanical switch module of the main current-carrying circuit will pass through zero and extinguish the arc. After that, all the fault current will flow to the branch where the capacitor is located and charge the capacitor, as shown in Figure 2(f).

[0077] Timing 7: When the voltage across the capacitor reaches the operating voltage of the energy-consuming MOV, the current will transfer to the energy-consuming MOV, as shown in Figure 2(g). After that, the voltage across the circuit breaker is limited by the energy-consuming MOV, and at the same time the fault current gradually decreases and finally drops to zero. At this time, the current of Tc2 passes through zero and turns off.

[0078] The above Timings 1-7 are the timing logics for interrupting the short-circuit current. According to the principle, it can be known that the ability of the oscillating current to interrupt the short-circuit current in Timing 5 is positively correlated with the energy stored in the capacitor, and the energy comes from the coupled energy storage circuit, and the energy stored in it is also positively correlated with the magnitude of the short-circuit current. Therefore, through appropriate parameter design, too much redundant energy will not be generated for short-circuit currents of any magnitude, which may cause problems such as overcurrent, overvoltage in the DC power grid system, and re-breakdown of the mechanical switch. In addition, this adaptive circuit breaker can also easily achieve the secondary interruption of the short-circuit current during the reclosing process because no capacitor pre-charging is required when interrupting the short-circuit current.

[0079] The adaptive circuit breaker according to the embodiment of the present invention can be used to interrupt the rated current and small current (non-short-circuit current). At this time, since the coupled energy storage circuit cannot store energy. Therefore, it is necessary to pre-charge the capacitor with a relatively low voltage (which can be selected according to simulation). When interrupting the rated current, the control timing of each part of the circuit breaker is exactly the same as that of interrupting the short-circuit current in 3-7.

[0080] The process of reclosing using the adaptive circuit breaker is as follows:

[0081] After the reclosing interval set by the upper-layer control and protection, the solid-state switch module is turned on, and the resistive discharge circuit in parallel with the capacitor is closed ( Figure 1 not shown in the figure), and the charge stored in the capacitor during the opening process is discharged. After several resistive-capacitive discharge time constants, the capacitor charge is basically discharged, and the voltage across the capacitor is very low. If the circuit breaker current rises above the action threshold at this time, it indicates a permanent fault. The reason is that the principle of this circuit breaker is to isolate the DC fault with a capacitor. If it is a permanent short-circuit fault, the fault side of the circuit breaker (a short-circuit fault generally refers to a ground fault, and the fault side is at the ground potential) always remains at a low potential, as Figure 3 shown. When the capacitor discharges and the voltage drops to a certain extent, a voltage will be generated on the stray inductance of the circuit breaker (including the coupling reactor L1), causing the current to rise rapidly. At this time, immediately execute the opening of the resistive discharge circuit and close the mechanical switch module of the main current-carrying circuit. The current will quickly be completely transferred to the main current-carrying circuit, and then the circuit breaker executes the opening timing in 2-7 and completes the re-opening; if the circuit breaker current does not exceed the action threshold, it indicates that the fault is a temporary fault. At this time, close the mechanical switch module of the main current-carrying circuit and open the resistive discharge circuit, and the current will quickly be completely transferred to the main current-carrying circuit to complete the reclosing.

[0082] Although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A mechanical DC circuit breaker with self-adaptive oscillating capacitor voltage, characterized in that Comprising: A main current-carrying circuit, a coupling energy storage circuit, an energy transfer circuit, and an oscillating breaking circuit; The main current-carrying circuit is used to connect the circuit breaker to the power grid, enabling the normal working current of the power grid to flow through the main current-carrying circuit; the main current-carrying circuit includes the primary coil of a coupling reactor and a mechanical switch module; The coupling energy storage circuit includes the secondary coil of the coupling reactor and a solid-state switch module connected in parallel, and is coupled to the main current-carrying circuit through the secondary coil of the coupling reactor; The coupling energy storage circuit is used to obtain energy from the main current-carrying circuit and store it when a current fault occurs in the power grid; The energy transfer circuit is connected to the coupling energy storage circuit, and the energy transfer circuit is used to transfer the energy of the coupling energy storage circuit; The energy transfer circuit includes a first trigger switch module and a second mechanical switch connected in series; The oscillating breaking circuit is respectively connected to the main current-carrying circuit, the coupling energy storage circuit, and the energy transfer circuit; The oscillating breaking circuit is used to obtain energy through the coupling energy storage circuit and the energy transfer circuit, and is used to turn off the fault current of the main current-carrying circuit; The oscillating breaking circuit includes a capacitor, a dissipative MOV, and a second trigger switch module; The capacitor is connected in parallel with the dissipative MOV; The capacitor is connected to the main current-carrying circuit through the second trigger switch module; The first end of the capacitor is connected to the first end of the energy transfer circuit, the second end of the capacitor is connected to one end of the coupling energy storage circuit, the second end of the energy transfer circuit is connected to the other end of the coupling energy storage circuit; The first end of the capacitor is connected to one end of the mechanical switch module, the second end of the capacitor is connected to one end of the second trigger switch module, and the other end of the second trigger switch module is connected to the other end of the mechanical switch module; The second end of the capacitor is connected to the first end of the solid-state switch module, and the second end of the energy transfer circuit is connected to the second end of the solid-state switch module.

2. The mechanical DC circuit breaker with oscillating capacitor voltage self-adaptation according to claim 1, wherein The main current-carrying circuit includes an input end and an output end for connecting the circuit breaker to the power grid; Between the input end and the output end of the main current-carrying circuit, there are a mechanical switch module and the primary coil of a coupling reactor connected in series; The mechanical switch module includes a plurality of first mechanical switches.

3. The mechanical DC circuit breaker with oscillating capacitor voltage self-adaptation according to claim 1, wherein The coupling energy storage circuit further includes a protection branch connected in parallel with the solid-state switch module, and the protection branch includes a protection MOV.

4. The mechanical DC circuit breaker with oscillating capacitor voltage self-adaptation according to claim 3, wherein A resistive discharge circuit is connected in parallel across the capacitor, and the resistive discharge circuit includes a resistor and a discharge switch connected in series.

5. A method for using a mechanical DC circuit breaker with self - adaptive oscillating capacitor voltage, characterized in that, Using the circuit breaker according to claim 1 to turn off the fault current of the power grid where it is located, includes: When the power grid is operating normally, the mechanical switch module of the main current-carrying circuit is in the closed state; After a short-circuit fault occurs in the power grid, the fault current of the primary coil rises, inducing a coupling voltage on the secondary side and storing energy through the secondary coil; After a certain fault detection time, the circuit breaker sends a tripping signal to the mechanical switch module of the main current-carrying circuit and the second mechanical switch of the energy transfer circuit; At a certain moment before the second mechanical switch just opens, turn off the solid-state switch module and turn on the first trigger switch. The current will transfer from the solid-state switch module to the capacitor of the oscillating breaking circuit; After the contact gap of the mechanical switch module in the main current-carrying circuit can withstand the transient recovery voltage, turn on the second trigger switch module in the oscillating breaking circuit. The capacitor discharges to the first mechanical switch of the main current-carrying circuit through the second trigger switch module; When the oscillating current is equal in magnitude and opposite in direction to the fault current, the current of the mechanical switch module in the main current-carrying circuit will pass through zero and extinguish the arc. After that, all the fault current will flow to the branch where the capacitor is located and charge the capacitor; When the voltage across the capacitor reaches the operating voltage of the energy-consuming MOV, the current will transfer to the energy-consuming MOV.

6. The method for using a mechanical DC circuit breaker with oscillation capacitor voltage self - adaptation according to claim 5, characterized in that, It also includes the reclosing process: After a specified reclosing interval, turn on the solid-state switch module and close the resistive discharge circuit in parallel with the capacitor to discharge the charge stored in the capacitor during the opening process. After several resistive-capacitive discharge time constants, if the breaker current rises above the operating threshold at this time, it indicates that the fault is a permanent fault. Execute opening the resistive discharge circuit and closing the mechanical switch module of the main current-carrying circuit to transfer the current to the main current-carrying circuit, and then the breaker recloses according to the steps of interrupting the fault current in the power grid where the turn-off is located; if the breaker current does not exceed the operating threshold, it indicates that the fault is a temporary fault. At this time, close the mechanical switch module of the main current-carrying circuit and open the resistive discharge circuit to transfer the current to the main current-carrying circuit to complete the reclosing.

7. A method for using a mechanical DC circuit breaker with oscillation capacitance voltage self - adaptation, characterized in that, Using the breaker as claimed in claim 1 to interrupt the specified current in the power grid where the turn-off is located, the specified current being the rated current or less than the rated current includes: Performing a certain amount of pre-charging on the capacitor; When the power grid is operating normally, the mechanical switch module in the main current-carrying circuit is in the closed state; When it is necessary to interrupt the specified current, send a tripping signal to the mechanical switch module in the main current-carrying circuit and the second mechanical switch of the energy transfer circuit; At a certain moment before the second mechanical switch just opens, turn off the solid-state switch module and turn on the first trigger switch. The current will transfer from the solid-state switch module to the capacitor of the oscillating breaking circuit; After the contact gap of the mechanical switch module in the main current-carrying circuit can withstand the transient recovery voltage, turn on the second trigger switch module in the oscillating breaking circuit. The capacitor discharges to the first mechanical switch of the main current-carrying circuit through the second trigger switch module; When the oscillating current is equal in magnitude and opposite in direction to the specified current, the current of the mechanical switch module in the main current-carrying circuit will pass through zero and extinguish the arc. After that, all the fault current will flow to the branch where the capacitor is located and charge the capacitor; When the voltage across the capacitor reaches the operating voltage of the energy-consuming MOV, the current will transfer to the energy-consuming MOV.

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