Mechanical direct-current circuit breaker with adaptive reclosing capability and control method, device and equipment of mechanical direct-current circuit breaker

Abstract

The invention relates to a mechanical direct-current circuit breaker with self-adaptive reclosing capability and a control method, device and equipment thereof. The mechanical direct-current circuit breaker comprises a main on branch, a main off branch, an energy absorption branch, a pre-charging branch and a fault identification branch, wherein the pre-charging branch and the fault identification branch are connected with the main off branch; and the pre-charging branch circuit is connected in parallel with the fault identification branch circuit. According to the mechanical direct-current circuit breaker, the capacitor is pre-charged through the pre-charging branch, so that the mechanical direct-current circuit breaker does not need to be additionally provided with a pre-charging device, the manufacturing cost is saved, and the topological complexity of the mechanical direct-current circuit breaker is reduced; the mechanical direct-current circuit breaker is matched with the control method thereof, so that the mechanical direct-current circuit breaker has a self-adaptive reclosing function, and after a fault line of a direct-current line is isolated, the fault property can be identified through the voltage amplitude of the capacitor and the initial voltage of the capacitor, so that the mechanical direct-current circuit breaker is prevented from reclosing in a permanent fault; and secondary fault impact is caused to the power transmission system.

Description

Technical Field

[0001] The present application relates to the technical field of circuit breakers, and in particular to a mechanical DC circuit breaker with adaptive reclosing capability and a control method, device and equipment thereof. Background Art

[0002] Existing mechanical DC circuit breakers use self-excited oscillation to form an artificial current zero point, thereby extinguishing the arc of the switch in the mechanical DC circuit breaker. Active oscillation type mechanical DC circuit breakers use pre-charged capacitors in series with inductors and mechanical switches to form an oscillation circuit. When the capacitor discharge current is equal to the current flowing through the mechanical switch in amplitude and opposite in direction, an artificial current zero point is formed. This type of mechanical DC circuit breaker has a long action delay. With the advancement of technology, additional pre-charging devices are added to the technical solution of DC circuit breakers, which increases the cost and complexity of mechanical DC circuit breakers and limits the application of DC circuit breakers on the passive grid side.

[0003] Considering that DC line faults are divided into transient faults and permanent faults, it is necessary to distinguish the nature of the fault after isolating the fault. If a transient fault occurs, the DC circuit breaker can be directly closed after sufficient deionization. However, when a permanent fault occurs, direct reclosing will cause a secondary fault shock, seriously endangering the safety and stability of the DC power grid. At present, there is no mechanical DC circuit breaker with adaptive reclosing capability. Summary of the invention

[0004] The present application provides a mechanical DC circuit breaker with adaptive reclosing capability and a control method, device and equipment thereof, which are used to solve the technical problem that when a permanent fault occurs in a DC line, direct reclosing of the existing mechanical circuit breaker will cause secondary fault impact, seriously endangering the safety and stability of the DC power grid.

[0005] In order to achieve the above objectives, this application provides the following technical solutions:

[0006] On the one hand, a mechanical DC circuit breaker with adaptive reclosing capability is provided, comprising a main on branch and a main off branch and an energy absorption branch connected in parallel with the main on branch, wherein the main off branch comprises a capacitor, and the mechanical DC circuit breaker further comprises a pre-charging branch and a fault identification branch connected to the main off branch, wherein the pre-charging branch is connected in parallel with the fault identification branch;

[0007] The pre-charging branch is used to pre-charge the capacitor, the pre-charging branch comprises a second switch and a pre-charging resistor connected in series with the second switch, the second switch is also connected to the capacitor, and the pre-charging resistor is also connected to the ground terminal;

[0008] The fault identification branch includes a third switch and a current limiting resistor connected in series with the third switch. The third switch is also connected to the capacitor, and the current limiting resistor is also connected to the ground terminal.

[0009] Preferably, the input end of the main pass branch is connected to the first switch, the output end of the main pass branch is connected to the fourth switch, the first switch is also connected to the current switch, and a recovery resistor is connected in parallel at both ends of the first switch; and / or, the main pass branch includes a fast mechanical switch, the main disconnect branch also includes an inductor and a bidirectional switch tube connected to the capacitor, the bidirectional switch tube includes a first switch tube and a second switch tube, and the energy absorption branch includes a lightning arrester.

[0010] On the other hand, a control method of a mechanical DC circuit breaker with adaptive reclosing capability is provided, which is applied to the mechanical DC circuit breaker with adaptive reclosing capability described above, and is characterized in that the control method comprises the following steps:

[0011] Acquiring a control instruction for controlling the operation of a mechanical DC circuit breaker and an input current input to the mechanical DC circuit breaker, wherein the mechanical DC circuit breaker is connected to a DC line of a power transmission system;

[0012] Controlling the mechanical DC circuit breaker to operate in a pre-charging mode, a fault isolation mode or an adaptive reclosing mode according to the control instruction;

[0013] Wherein, if the control instruction is a normal operation instruction, the mechanical DC circuit breaker is controlled to operate in the pre-charging mode, so as to pre-charge the capacitor of the main breaker branch in the mechanical DC circuit breaker through the input current;

[0014] If the control instruction is an interrupt instruction, controlling the mechanical DC circuit breaker to operate in the fault isolation mode to isolate the fault line of the DC line;

[0015] If the control instruction is a reclosing command, the third switch and the fourth switch are controlled to close to obtain the initial voltage of the capacitor and the capacitor voltage amplitude within the time window, and whether to control the mechanical DC circuit breaker to operate in the adaptive reclosing mode is determined by the capacitor voltage amplitude and the initial voltage of the capacitor.

[0016] Preferably, controlling the mechanical DC circuit breaker to operate in the fault isolation mode to isolate the fault line of the DC line comprises:

[0017] Obtaining a transient interruption voltage of a lightning arrester in the mechanical DC circuit breaker;

[0018] According to the interrupt instruction, the fast mechanical switch is controlled to be disconnected and the first switch tube is controlled to be turned on, so that the capacitor is discharged, and the discharge current of the capacitor is obtained in real time;

[0019] If the discharge current is equal to the input current, the input current is controlled to be switched from the main on branch to the main off branch, so that the input current reversely charges the capacitor through the first switch tube to obtain a charging voltage of the capacitor;

[0020] If the charging voltage is equal to the transient interruption voltage, the capacitor is charged, and the input current is controlled to be switched from the main breaking branch to the energy absorption branch, then the first switch tube is controlled to be turned off, and the input current is absorbed by the lightning arrester to decay to 0, and then the current switch, the first switch and the fourth switch are all controlled to be disconnected to isolate the fault line of the DC line.

[0021] Preferably, judging whether to control the mechanical DC circuit breaker to operate in the adaptive reclosing mode according to the capacitor voltage amplitude and the initial voltage of the capacitor includes:

[0022] Acquire a proportionality coefficient and a rated voltage of the DC line, and calculate comparison data according to the proportionality coefficient and the initial voltage;

[0023] If the capacitor voltage amplitude is greater than the comparison data, the fault of the DC line is a transient fault, and the mechanical DC circuit breaker is controlled to perform a reclosing operation according to the adaptive reclosing mode;

[0024] If the capacitor voltage amplitude is smaller than the comparison data, the fault of the DC line is a permanent fault, and the mechanical DC circuit breaker is controlled not to perform a reclosing operation.

[0025] Preferably, the content of controlling the mechanical DC circuit breaker to perform a closing operation according to the adaptive reclosing mode includes:

[0026] Control the third switch to be opened, the current switch to be closed, the fast mechanical switch to be closed, and the second switch to be closed, charge the capacitor through the input current, and obtain the charge amount of the capacitor and the line voltage of the DC line in real time,

[0027] If the line voltage is equal to the rated voltage and the charging amount is 100%, obtaining an execution instruction;

[0028] The first switch is controlled to close and the second switch is controlled to open according to the execution instruction to complete the reclosing operation of the mechanical DC circuit breaker.

[0029] Preferably, controlling the mechanical DC circuit breaker to operate in the pre-charging mode to pre-charge the capacitor of the main breaker branch in the mechanical DC circuit breaker through the input current includes: controlling the fast mechanical switch, the current switch, the first switch, the second switch and the fourth switch to be closed and operating, and controlling the third switch to be open, and the first switch tube and the second switch tube to be turned off and not operating, so as to pre-charge the capacitor through the input current.

[0030] In yet another aspect, a control device for a mechanical DC circuit breaker with adaptive reclosing capability is provided, which is applied to the mechanical DC circuit breaker with adaptive reclosing capability described above, and the control device includes an acquisition module and an operation control module;

[0031] The acquisition module is used to acquire a control instruction for controlling the operation of a mechanical DC circuit breaker and an input current input to the mechanical DC circuit breaker, wherein the mechanical DC circuit breaker is connected to a DC line of a power transmission system;

[0032] The operation control module is used to control the mechanical DC circuit breaker to operate in a pre-charging mode, a fault isolation mode or an adaptive reclosing mode according to the control instruction;

[0033] Wherein, if the control instruction is a normal operation instruction, the mechanical DC circuit breaker is controlled to operate in the pre-charging mode, so as to pre-charge the capacitor of the main breaker branch in the mechanical DC circuit breaker through the input current;

[0034] If the control instruction is an interrupt instruction, controlling the mechanical DC circuit breaker to operate in the fault isolation mode to isolate the fault line of the DC line;

[0035] If the control instruction is a reclosing command, the third switch and the fourth switch are controlled to close to obtain the initial voltage of the capacitor and the capacitor voltage amplitude within the time window, and whether to control the mechanical DC circuit breaker to operate in the adaptive reclosing mode is determined by the capacitor voltage amplitude and the initial voltage of the capacitor.

[0036] Preferably, the operation control module is also used to control the fast mechanical switch, the current switch, the first switch, the second switch and the fourth switch to be closed and operated, and to control the third switch to be opened and closed, and the first switch tube and the second switch tube to be turned off and not operated, so as to pre-charge the capacitor through the input current.

[0037] In another aspect, a terminal device is provided, comprising a processor and a memory;

[0038] The memory is used to store program codes and transmit the program codes to the processor;

[0039] The processor is used to execute the control method of the mechanical DC circuit breaker with adaptive reclosing capability according to the instructions in the program code.

[0040] The mechanical DC circuit breaker with adaptive reclosing capability and its control method, device and equipment, the mechanical DC circuit breaker with adaptive reclosing capability, comprises a main on branch and a main off branch and an energy absorption branch connected in parallel with the main on branch, the main off branch comprises a capacitor, the mechanical DC circuit breaker also comprises a pre-charging branch and a fault identification branch connected to the main off branch, the pre-charging branch is connected in parallel with the fault identification branch; the pre-charging branch is used to pre-charge the capacitor, the pre-charging branch comprises a second switch and a pre-charging resistor connected in series with the second switch, the second switch is also connected to the capacitor, and the pre-charging resistor is also connected to the ground terminal; the fault identification branch comprises a third switch and a current limiting resistor connected in series with the third switch, the third switch is also connected to the capacitor, and the current limiting resistor is also connected to the ground terminal.

[0041] It can be seen from the above technical scheme that the present application has the following advantages: the mechanical DC circuit breaker with adaptive reclosing capability pre-charges the capacitor according to the current input to the mechanical DC circuit breaker by the flexible DC transmission system through the pre-charging branch, so that the mechanical DC circuit breaker with adaptive reclosing capability does not need to add an additional pre-charging device, thereby saving the manufacturing cost of the mechanical DC circuit breaker with adaptive reclosing capability, reducing the topological complexity of the mechanical DC circuit breaker with adaptive reclosing capability, and solving the technical problem that when a permanent fault occurs in the DC line, the direct reclosing of the existing mechanical circuit breaker will cause a secondary fault shock, seriously endangering the safety and stability of the DC power grid.

[0042] The control method of the mechanical DC circuit breaker with adaptive reclosing capability controls the operation mode of the mechanical DC circuit breaker through control instructions, so that the mechanical DC circuit breaker can operate according to the control instructions; the mechanical DC circuit breaker has an adaptive reclosing function, and after isolating the fault line of the DC line, the nature of the fault can be identified through the capacitor voltage amplitude and the initial voltage of the capacitor, so as to prevent the mechanical DC circuit breaker from reclosing on a permanent fault and causing a secondary fault impact on the power transmission system, thereby solving the technical problem that when a permanent fault occurs in the DC line, the direct reclosing of the existing mechanical circuit breaker will cause a secondary fault impact, which seriously endangers the safety and stability of the DC power grid.

[0043] The control device of the mechanical DC circuit breaker with adaptive reclosing capability can identify the nature of the fault after isolating the fault line through an acquisition module and an operation control module to avoid reclosing on a permanent fault and causing a secondary fault impact on the power transmission system. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0045] Figure 1 A topological diagram of a mechanical DC circuit breaker with adaptive reclosing capability according to an embodiment of the present application;

[0046] Figure 2 A flowchart of the steps of a control method for a mechanical DC circuit breaker with adaptive reclosing capability according to an embodiment of the present application;

[0047] Figure 3 A topological diagram of the pre-charging mode in the control method of the mechanical DC circuit breaker with adaptive reclosing capability described in an embodiment of the present application;

[0048] Figure 4 A capacitor discharge topology diagram of a mechanical DC circuit breaker with adaptive reclosing capability in a fault isolation mode according to an embodiment of the present application;

[0049] Figure 5 A capacitor charging topology diagram of a mechanical DC circuit breaker with adaptive reclosing capability in a fault isolation mode according to an embodiment of the present application;

[0050] Figure 6 It is an energy consumption topology diagram of the fault isolation mode in the control method of the mechanical DC circuit breaker with adaptive reclosing capability described in the embodiment of the present application;

[0051] Figure 7 An equivalent circuit diagram of the adaptive reclosing mode in the control method of the mechanical DC circuit breaker with adaptive reclosing capability described in the embodiment of the present application;

[0052] Figure 8 A topological diagram of a reclosing operation performed in an adaptive reclosing mode in a control method for a mechanical DC circuit breaker with an adaptive reclosing capability according to an embodiment of the present application;

[0053] Fig. 9 A topological diagram of a four-terminal DC power grid in which the control method of a mechanical DC circuit breaker with adaptive reclosing capability described in an embodiment of the present application is applied;

[0054] Fig.10A current waveform diagram of a fault isolation process of a four-terminal DC power grid when the control method of a mechanical DC circuit breaker with adaptive reclosing capability described in an embodiment of the present application is applied;

[0055] Fig.11 A waveform diagram of a lightning arrester voltage during a fault isolation process of a four-terminal DC power grid when the control method of a mechanical DC circuit breaker with adaptive reclosing capability described in an embodiment of the present application is applied;

[0056] Fig.12 A line graph of a permanent fault capacitor voltage of a four-terminal DC power grid when the control method of a mechanical DC circuit breaker with adaptive reclosing capability described in an embodiment of the present application is applied;

[0057] Fig.13 A line graph of instantaneous fault capacitor voltage of a four-terminal DC power grid when the control method of a mechanical DC circuit breaker with adaptive reclosing capability described in an embodiment of the present application is applied;

[0058] Fig.14 A schematic diagram of a framework of a control device for a mechanical DC circuit breaker with adaptive reclosing capability according to an embodiment of the present application;

[0059] Fig.15 A schematic diagram of a terminal device according to an embodiment of the present application;

[0060] Fig.16 This is a topological diagram of the existing DC circuit breaker. DETAILED DESCRIPTION

[0061] In order to make the purpose, features, and advantages of the invention of this application more obvious and easy to understand, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the drawings in the embodiments of this application. Obviously, the embodiments described below are only part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0062] In the description of the embodiments of the present application, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the embodiments of the present application, the meaning of "multiple" is two or more, unless otherwise clearly and specifically defined.

[0063] In the embodiments of the present application, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral one; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the embodiments of the present application can be understood according to the specific circumstances.

[0064] The flexible DC transmission system based on modular multilevel converter has great application prospects due to its flexible active and reactive power control. However, when a fault occurs in the flexible DC transmission system, the submodule capacitors of the modular multilevel converter discharge to the fault line, and the fault current increases rapidly, seriously endangering the safety and stability of the flexible DC transmission system. The DC circuit breaker can quickly and selectively isolate the fault line of the DC line to ensure the normal operation of the non-fault line.

[0065] DC circuit breakers are usually divided into mechanical DC circuit breakers, solid-state DC circuit breakers and hybrid DC circuit breakers. Solid-state DC circuit breakers use fully controlled semiconductor devices to commutate fault currents, and have fast isolation speeds; however, the presence of a large number of semiconductor devices will increase the conduction loss and cost of solid-state DC circuit breakers. Hybrid DC circuit breakers and mechanical DC circuit breakers are current research hotspots, such as 200kV hybrid DC circuit breakers and 160kV mechanical DC circuit breakers. Fig.16 As shown, the topological structures of typical mechanical DC circuit breakers and hybrid DC circuit breakers both include a main branch, a transfer branch and an energy consumption branch. The main branch of the mechanical DC circuit breaker includes a fast mechanical switch CB, the transfer branch of the mechanical DC circuit breaker includes a capacitor C1, an inductor L1, a coupling inductor L2 and a capacitor C2, and the energy consumption branch of the mechanical DC circuit breaker includes a lightning arrester MOV.

[0066] The working principle of the mechanical DC circuit breaker is: under normal conditions, the fast mechanical switch CB conducts the load current, and the conduction loss can be ignored. After a fault occurs in the DC line, the fast mechanical switch CB performs the opening operation, and then turns on the thyristor SCR to discharge the capacitor C1 with the initial voltage through the inductor L1, and the coupled inductor L2 generates an induced current, and the flow path of the induced current is coupled inductor L2-capacitor C2-fast mechanical switch CB; when the induced current flowing through the fast mechanical switch CB is equal to the fault current in magnitude and opposite in direction, the fast mechanical switch CB extinguishes the arc, and the fault current flows through the transfer branch connected in series with the coupled inductor L2 and the capacitor C2; when the capacitor C2 is charged to exceed the residual voltage of the arrester MOV, the fault current is transferred to the energy consumption branch of the arrester MOV, so that the fault current gradually drops to 0, completing the current interruption.

[0067] The working principle of the hybrid DC circuit breaker is: the main branch consists of a fast switch and a small number of full-bridge sub-modules. Under normal conditions, the main branch conducts the load current with less loss; after a fault occurs in the DC line, all full-bridge sub-modules of the transfer branch are turned on, and the full-bridge sub-modules of the main branch are turned off. The fault current is transferred to the transfer branch, and the fast switch begins to perform the opening operation; once the fast switch completes the opening operation, all full-bridge sub-modules of the transfer branch are turned off, and the fault current is transferred to the energy-consuming branch composed of lightning arresters. The fault current gradually drops to 0, and the current is interrupted.

[0068] Compared with hybrid DC circuit breakers, mechanical DC circuit breakers can isolate faults with lower manufacturing costs and lower conduction losses.

[0069] The embodiments of the present application provide a mechanical DC circuit breaker with adaptive reclosing capability and a control method, device and equipment thereof, which solve the technical problem that when a permanent fault occurs in a DC line, direct reclosing of the existing mechanical circuit breaker will cause a secondary fault shock, seriously endangering the safety and stability of the DC power grid.

[0070] Embodiment 1:

[0071] Figure 1 This is a topological diagram of a mechanical DC circuit breaker with adaptive reclosing capability described in an embodiment of the present application.

[0072] like Figure 1 As shown, an embodiment of the present application provides a mechanical DC circuit breaker with adaptive reclosing capability, including a main on branch 10 and a main off branch 20 and an energy absorption branch 30 connected in parallel with the main on branch 10, the main off branch 20 includes a capacitor C, and the mechanical DC circuit breaker also includes a pre-charging branch 40 and a fault identification branch 50 connected to the main off branch 20, and the pre-charging branch 40 is connected in parallel with the fault identification branch 50.

[0073] In an embodiment of the present application, the pre-charging branch 40 is used to pre-charge the capacitor C. The pre-charging branch 40 includes a second switch S2 and a pre-charging resistor R2 connected in series with the second switch S2. The second switch S2 is also connected to the capacitor C, and the pre-charging resistor R2 is also connected to the ground terminal.

[0074] It should be noted that the mechanical DC circuit breaker with adaptive reclosing capability is connected to the flexible DC power transmission system, and the capacitor C is precharged according to the current input to the mechanical DC circuit breaker from the flexible DC power transmission system through the precharging branch 40, so that the mechanical DC circuit breaker with adaptive reclosing capability does not need to add an additional precharging device, thereby saving the manufacturing cost of the mechanical DC circuit breaker with adaptive reclosing capability and reducing the topological complexity of the mechanical DC circuit breaker with adaptive reclosing capability.

[0075] In the embodiment of the present application, the fault identification branch 50 includes a third switch S3 and a current limiting resistor R3 connected in series with the third switch S3. The third switch S3 is also connected to the capacitor C, and the current limiting resistor R3 is also connected to the ground terminal.

[0076] In the embodiment of the present application, the mechanical DC circuit breaker with adaptive reclosing capability cooperates with the fault identification branch 50, the main on branch 10 and the main off branch 20 so that the mechanical DC circuit breaker with adaptive reclosing capability has an adaptive reclosing function, which can avoid the fault current shock when reclosing on a permanent fault, and solves the problem that direct reclosing of the mechanical circuit breaker will cause secondary fault shock, seriously endangering the safety and stability of the DC power grid.

[0077] like Figure 1 As shown, in one embodiment of the present application, the input end of the main pass branch 10 is connected to the first switch S1, the output end of the main pass branch 10 is connected to the fourth switch S4, the first switch S1 is also connected to the current switch S0, and a recovery resistor R1 is connected in parallel at both ends of the first switch S1; and / or, the main pass branch 10 includes a fast mechanical switch MS, the main disconnect branch 20 also includes an inductor L connected to the capacitor C and a bidirectional switch tube, the bidirectional switch tube includes a first switch tube T1 and a second switch tube T2, and the energy absorption branch 30 includes a lightning arrester MOV.

[0078] It should be noted that both the first switch tube T1 and the second switch tube T2 can be selected as thyristors. In this embodiment, the bidirectional switch tube is also connected to the pre-charging branch 30 and the fault identification branch 40 .

[0079] Embodiment 2:

[0080] Figure 2 This is a flowchart of the steps of a control method for a mechanical DC circuit breaker with adaptive reclosing capability described in an embodiment of the present application.

[0081] like Figure 2 As shown, an embodiment of the present application provides a control method for a mechanical DC circuit breaker with adaptive reclosing capability, which is applied to the above-mentioned mechanical DC circuit breaker with adaptive reclosing capability. The control method includes the following steps:

[0082] S1. Obtaining a control instruction for controlling the operation of a mechanical DC circuit breaker and an input current input to the mechanical DC circuit breaker; the mechanical DC circuit breaker is connected to a DC line of a power transmission system.

[0083] It should be noted that the content of the mechanical DC circuit breaker with adaptive reclosing capability in this embodiment has been described in the embodiment, and will not be repeated in this embodiment. In step S1, the first is to obtain a control instruction for controlling the operation of the mechanical DC circuit breaker, and the second is the input current of the mechanical DC circuit breaker input by the power transmission system, which provides data for the subsequent control of the operation of the mechanical DC circuit breaker.

[0084] S2. Control the mechanical DC circuit breaker to operate in pre-charging mode, fault isolation mode or adaptive reclosing mode according to the control instruction;

[0085] Wherein, if the control instruction is a normal operation instruction, the mechanical DC circuit breaker is controlled to operate in a pre-charging mode, so as to pre-charge the capacitor of the main breaker branch in the mechanical DC circuit breaker through the input current;

[0086] If the control instruction is an interruption instruction, the mechanical DC circuit breaker is controlled to operate in a fault isolation mode to isolate the fault line of the DC line;

[0087] If the control instruction is a reclosing command, the third switch and the fourth switch are controlled to close to obtain the initial voltage of the capacitor and the capacitor voltage amplitude within the time window, and whether to control the mechanical DC circuit breaker to operate in the adaptive reclosing mode is determined by the capacitor voltage amplitude and the initial voltage of the capacitor.

[0088] It should be noted that in step S2, the mechanical DC circuit breaker is controlled to operate in which mode according to the control instruction obtained in step S1, so that the mechanical DC circuit breaker can operate according to the control instruction. The time window can be set according to demand. In this embodiment, the mechanical DC circuit breaker has an adaptive reclosing function. After isolating the fault line of the DC line, the nature of the fault can be identified by the capacitor voltage amplitude and the initial voltage of the capacitor, so as to prevent the mechanical DC circuit breaker from reclosing on a permanent fault and causing a secondary fault impact on the power transmission system. The time window can be selected as 10ms.

[0089] The present application provides a control method for a mechanical DC circuit breaker with adaptive reclosing capability, comprising the following steps: obtaining a control instruction for controlling the operation of the mechanical DC circuit breaker and an input current input to the mechanical DC circuit breaker, wherein the mechanical DC circuit breaker is connected to a DC line of a power transmission system; controlling the mechanical DC circuit breaker to operate in a pre-charging mode, a fault isolation mode or an adaptive reclosing mode according to the control instruction; wherein, if the control instruction is a normal operation instruction, the mechanical DC circuit breaker is controlled to operate in the pre-charging mode, and the capacitor of the main breaking branch in the mechanical DC circuit breaker can be pre-charged by the input current; if the control instruction is an interruption instruction, the mechanical DC circuit breaker is controlled to operate in the fault isolation mode to isolate the fault line of the DC line; if the control instruction is a reclosing command, the third switch and the fourth switch are controlled to be closed to obtain the initial voltage of the capacitor and the capacitor voltage amplitude within the time window, and whether to control the mechanical DC circuit breaker to operate in the adaptive reclosing mode is determined by the capacitor voltage amplitude and the initial voltage of the capacitor. The control method of the mechanical DC circuit breaker with adaptive reclosing capability controls the operation mode of the mechanical DC circuit breaker through control instructions, so that the mechanical DC circuit breaker can operate according to the control instructions; the mechanical DC circuit breaker has an adaptive reclosing function, and after isolating the fault line of the DC line, the nature of the fault can be identified through the capacitor voltage amplitude and the initial voltage of the capacitor, so as to prevent the mechanical DC circuit breaker from reclosing on a permanent fault and causing a secondary fault impact on the power transmission system, thereby solving the technical problem that when a permanent fault occurs in the DC line, the direct reclosing of the existing mechanical circuit breaker will cause a secondary fault impact, which seriously endangers the safety and stability of the DC power grid.

[0090] Figure 3 This is a topological diagram of the pre-charging mode in the control method of the mechanical DC circuit breaker with adaptive reclosing capability described in an embodiment of the present application.

[0091] like Figure 3 As shown, in one embodiment of the present application, controlling the mechanical DC circuit breaker to operate in a pre-charging mode to pre-charge the capacitor of the main breaker branch in the mechanical DC circuit breaker through the input current includes: controlling the fast mechanical switch MS, the current switch S0, the first switch S1, the second switch S2 and the fourth switch S4 to be closed and operated, and controlling the third switch S3 to be opened, and the first switch tube T1 and the second switch tube T2 to be turned off and not operated, so as to pre-charge the capacitor C through the input current.

[0092] It should be noted that when the mechanical DC circuit breaker is in a normal state, the fast mechanical switch MS, the current switch S0, the first switch S1, the second switch S2 and the fourth switch S4 are all in a closed state, the third switch S3 is in an open state, and the first switch tube T1 and the second switch tube T2 are not turned on. The input current of the power transmission system pre-charges the capacitor C, and its pre-charging current path is as follows Figure 3 The arrows shown point to: S0-S1-MS-LC-S2-R2. After the pre-charging is completed, the second switch S2 is disconnected, the polarity of the left end of the capacitor C is negative, and the polarity of the right end of the capacitor C is positive. In this embodiment, the control method of the mechanical DC circuit breaker with adaptive reclosing capability can realize the pre-charging of the capacitor through the cooperation of the main on branch, the main off branch and the pre-charging branch.

[0093] Figure 4 This is a capacitor discharge topology diagram of the fault isolation mode in the control method of the mechanical DC circuit breaker with adaptive reclosing capability described in the embodiment of the present application, Figure 5 This is a capacitor charging topology diagram of a fault isolation mode in a control method for a mechanical DC circuit breaker with adaptive reclosing capability according to an embodiment of the present application. Figure 6 This is an energy consumption topology diagram of the fault isolation mode in the control method of the mechanical DC circuit breaker with adaptive reclosing capability described in an embodiment of the present application.

[0094] like Figures 4 to 6 As shown, in one embodiment of the present application, controlling the mechanical DC circuit breaker to operate in a fault isolation mode to isolate a fault line of the DC line includes:

[0095] Obtaining the transient interruption voltage of the arrester in the mechanical DC circuit breaker;

[0096] According to the interrupt instruction, the fast mechanical switch is controlled to be disconnected and the first switch tube is controlled to be turned on, so that the capacitor is discharged, and the discharge current of the capacitor is obtained in real time;

[0097] If the discharge current is equal to the input current, the input current is controlled to switch from the main on branch to the main off branch, and the input current reversely charges the capacitor through the first switch tube to obtain the charging voltage of the capacitor;

[0098] If the charging voltage is equal to the transient interruption voltage, the capacitor is charged, and the input current is controlled to be switched from the main breaking branch to the energy absorption branch. The first switch tube is controlled to be turned off, and the input current is absorbed by the lightning arrester to decay to 0. After that, the current switch, the first switch and the fourth switch are all controlled to be disconnected to isolate the fault line of the DC line.

[0099] It should be noted that when a DC line fault occurs, once the mechanical DC circuit breaker receives an interruption command, the fast mechanical switch MS is turned on, the first switch tube T1 is turned on, and the capacitor C starts to discharge. The discharge path is as follows: Figure 4 The arrow shown points to: CL-MS-T1. Since the input current (also called fault current) flowing through the fast mechanical switch MS is in opposite directions to the discharge current of the capacitor C, once the input current flowing through the fast mechanical switch MS is equal to the discharge current of the capacitor C, the arc of the fast mechanical switch MS is extinguished. After that, the insulation strength between the contacts of the fast mechanical switch MS is restored, and no input current (also called fault current) flows through the fast mechanical switch MS. Therefore, the input current (also called fault current) is completely switched from the main on branch to the main off branch. The input current (also called fault current) charges the capacitor C in reverse, and its charging path is as follows: Figure 5 The arrow points to the direction shown. When the voltage of capacitor C is charged to the transient interruption voltage of the arrester MOV, the charging of capacitor C is completed. After that, the input current (also called fault current) is completely switched to the energy absorption branch, and no input current (also called fault current) flows through the main disconnection branch, and the first switch tube T1 is naturally turned off. Figure 6 As shown. At this time, the polarity of the left end of capacitor C is positive and the polarity of the right end is negative. Then, under the action of the arrester MOV, the input current (also called fault current) decays to 0. Finally, the current switch S0, the first switch S1 and the fourth switch S4 are disconnected to isolate the fault line of the DC line on the power transmission system.

[0100] Figure 7 is an equivalent circuit diagram of the adaptive reclosing mode in the control method of the mechanical DC circuit breaker with adaptive reclosing capability described in the embodiment of the present application, Figure 7 In the figure, a is the equivalent circuit of a permanent fault, and b is the equivalent circuit of a transient fault.

[0101] like Figure 7 As shown, in one embodiment of the present application, judging whether to control the mechanical DC circuit breaker to operate in the adaptive reclosing mode according to the capacitor voltage amplitude and the initial voltage of the capacitor includes:

[0102] Obtain the proportionality factor and the rated voltage of the DC line, and calculate comparative data according to the proportionality factor and the initial voltage;

[0103] If the capacitor voltage amplitude is greater than the comparison data, the fault of the DC line is a transient fault, and the mechanical DC circuit breaker is controlled to perform a reclosing operation according to the adaptive reclosing mode;

[0104] If the capacitor voltage amplitude is smaller than the comparison data, the fault of the DC line is a permanent fault, and the mechanical DC circuit breaker is controlled not to perform a reclosing operation.

[0105] It should be noted that the initial voltage refers to the initial voltage of the capacitor C when the mechanical DC circuit breaker performs the reclosing operation. The proportional coefficient can be set as required. The adaptive reclosing mode first obtains parameters for identifying the fault type in the DC line through the fault identification branch operation of the mechanical DC circuit breaker, and then determines whether to perform the reclosing operation based on the identified fault type, so as to avoid reclosing on a permanent fault and causing a secondary fault impact on the power transmission system. In this embodiment, the proportional coefficient k0 can be selected as 0.2, and the comparison data refers to the product of the proportional coefficient and the absolute value of the initial voltage. After isolating the fault for several hundred milliseconds, the DC line restores insulation through the mechanical DC circuit breaker, and the mechanical DC circuit breaker can perform the reclosing operation. When the mechanical DC circuit breaker receives the reclosing command, it controls the third switch S3 and the fourth switch S4 to close. When the fault of the DC line is a permanent fault, its equivalent circuit is as follows. Figure 7 As shown in a, capacitor C forms a discharge loop through the fault point f, and the voltage of capacitor C can drop to about 0; when the fault of the DC line is a transient fault, its equivalent circuit is as follows Figure 7 As shown in b, capacitor C forms a discharge loop through the line to ground capacitor C1, capacitor C discharges to capacitor C1, and the final voltage U Cf As shown in formula 1; formula 1 is:

[0106]

[0107] Among them, Figure 7 In the equivalent circuit diagram, R S3 and R S4 are the equivalent resistances of the third switch S3 and the fourth switch S4 respectively; L S3 and L S4 are the equivalent inductances of the third switch S3 and the fourth switch S4, respectively. Generally speaking, R S3 , R S4 , L S3 and L S4 The value of is very small, close to 0. f is the fault resistance. C L , L L , R L are the equivalent capacitance, equivalent inductance and equivalent resistance of the DC line respectively. r is the discharge current during reclosing, C is the capacitance of the capacitor, and U0 is the initial voltage of capacitor C during reclosing operation of the mechanical DC circuit breaker. Considering that there is a large difference between the voltage of capacitor C when transient faults and permanent faults occur, the voltage amplitude of capacitor C during reclosing is marked as U cr Therefore, the fault type of the DC line during reclosing is determined by Formula 2, which is:

[0108]

[0109] Since the capacitor voltage of a transient fault may also drop to around 0 after a long time, it is necessary to detect the change of the capacitor voltage within a time window T to avoid misjudgment caused by too long measurement time. Considering the speed and accuracy of detection, the time window T can be set to 10ms.

[0110] Figure 8 A topological diagram of a reclosing operation performed in an adaptive reclosing mode in a control method for a mechanical DC circuit breaker with adaptive reclosing capability described in an embodiment of the present application.

[0111] like Figure 8 As shown, in one embodiment of the present application, the content of controlling the mechanical DC circuit breaker to perform a closing operation in an adaptive reclosing mode includes:

[0112] Control the third switch to open, the current switch to close, the fast mechanical switch to close, and the second switch to close, charge the capacitor through the input current, and obtain the charge amount of the capacitor and the line voltage of the DC line in real time.

[0113] If the line voltage is equal to the rated voltage and the charge capacity is 100%, an execution instruction is obtained;

[0114] The first switch is controlled to close and the second switch is controlled to open according to the execution instruction to complete the reclosing operation of the mechanical DC circuit breaker.

[0115] It should be noted that the third switch S3 is first opened, and then the current switch S0 and the fast mechanical switch MS are closed, and the input current flows through Figure 8 The arrow points to the loop to slowly charge the capacitor. When the capacitor C is fully charged (it can be understood that the capacitor C is fully charged) and the DC line voltage is restored to the rated voltage of the input DC transmission system, the first switch S1 is then closed and the second switch S2 is opened to complete the reclosing operation of the mechanical DC circuit breaker.

[0116] Fig. 9 A topological diagram of a four-terminal DC power grid in which the control method of a mechanical DC circuit breaker with adaptive reclosing capability described in an embodiment of the present application is applied. Fig.10 The control method of the mechanical DC circuit breaker with adaptive reclosing capability described in the embodiment of the present application is applied to the current waveform in the fault isolation process of a four-terminal DC power grid. Fig.11 The control method of the mechanical DC circuit breaker with adaptive reclosing capability described in the embodiment of the present application is applied to the arrester voltage waveform in the fault isolation process of a four-terminal DC power grid. Fig.12 A line graph of a permanent fault capacitor voltage of a four-terminal DC power grid in which the control method of a mechanical DC circuit breaker with adaptive reclosing capability described in an embodiment of the present application is applied. Fig.13A control method for a mechanical DC circuit breaker with adaptive reclosing capability described in an embodiment of the present application is applied to a transient fault capacitor voltage line graph of a four-terminal DC power grid.

[0117] In the embodiments of the present application, Fig. 9 As shown, a four-terminal DC grid model is established in the grid simulation software to verify the control method of the mechanical DC circuit breaker with adaptive reclosing capability to achieve the fault isolation capability and adaptive reclosing capability of the mechanical DC circuit breaker. Fig.10 and Fig.11 As shown in the figure, during the fault isolation process, at t1=0ms, a single-pole ground short circuit fault is set at the head end of the line where bus 1 is located, marked as f. The mechanical DC circuit breaker receives an interruption command or an isolation command at t2=2ms and opens the fast mechanical switch MS. At t3=5ms, the contact spacing of the fast mechanical switch MS has reached the rated distance. Therefore, the first switch tube T1 is triggered to turn on, and the capacitor C is discharged rapidly. At t4=5.06ms, the capacitor discharge current i C The magnitude is equal to the input current (also called fault current) and the direction is opposite, so the current i flowing through the fast mechanical switch MS is MS Drops to 0. After t=t4, the input current (also called fault current) completely switches to the main breaking branch. Capacitor C is charged in reverse, and the input current (also called fault current) gradually increases, with a maximum value of 9.51kA. At t5=5.4ms, the capacitor voltage of capacitor C reaches the transient interruption voltage of the arrester MOV, and the charging of capacitor C ends. Then, the input current (also called fault current) switches to the energy absorption branch at t6=5.63ms. Since the transient interruption voltage of the arrester MOV is greater than the rated voltage, the input current (also called fault current) gradually decreases. Finally, at t6=12.86ms, the input current (also called fault current) decays to approximately 0, allowing the mechanical DC circuit breaker to complete the breaking of the fault current. From Fig.10 and Fig.11 It can be seen that there is a significant difference between the capacitor voltage amplitudes of transient faults and permanent faults. The proportional constant k0 is set to 0.2. Within the time window T, during the permanent fault time, the capacitor voltage amplitude is less than 0.2|U0|; during the transient fault time, the capacitor voltage amplitude is greater than 0.2|U0|. In the process of reclosing during a permanent fault, if Fig.12 As shown in FIG. 1 , after the fault isolation is completed, the mechanical DC circuit breaker starts to reclose at tp=1.215s. Therefore, the third switch S3 and the fourth switch S4 are closed. The capacitor C discharges quickly, and the discharge path is: fault point f-fourth switch S4-inductor L-capacitor C-third switch S3-current limiting resistor R3-ground terminal, and the voltage of capacitor C eventually drops to 0. During the reclosing process for transient faults, Fig.13As shown, the mechanical DC circuit breaker still starts to reclose at tp=1.215s, and the third switch S3 and the fourth switch S4 are closed. The discharge path of capacitor C is the same as the permanent fault discharge path, except that: under the equivalent grounding capacitance of the DC line, the capacitor voltage drops slowly, and at 1.5s, the capacitor voltage has not dropped to 0.

[0118] Embodiment three:

[0119] Fig.14 A schematic diagram of the framework of a control device for a mechanical DC circuit breaker with adaptive reclosing capability described in an embodiment of the present application.

[0120] like Fig.14 As shown, an embodiment of the present application provides a control device for a mechanical DC circuit breaker with adaptive reclosing capability, which is applied to the above-mentioned mechanical DC circuit breaker with adaptive reclosing capability. The control device includes an acquisition module 100 and an operation control module 200;

[0121] An acquisition module 100 is used to acquire a control instruction for controlling the operation of a mechanical DC circuit breaker and an input current input to the mechanical DC circuit breaker, wherein the mechanical DC circuit breaker is connected to a DC line of a power transmission system;

[0122] An operation control module 200, used to control the mechanical DC circuit breaker to operate in a pre-charging mode, a fault isolation mode or an adaptive reclosing mode according to a control instruction;

[0123] Wherein, if the control instruction is a normal operation instruction, the mechanical DC circuit breaker is controlled to operate in a pre-charging mode, so as to pre-charge the capacitor of the main breaker branch in the mechanical DC circuit breaker through the input current;

[0124] If the control instruction is an interruption instruction, the mechanical DC circuit breaker is controlled to operate in a fault isolation mode to isolate the fault line of the DC line;

[0125] If the control instruction is a reclosing command, the third switch and the fourth switch are controlled to close to obtain the initial voltage of the capacitor and the capacitor voltage amplitude within the time window, and whether to control the mechanical DC circuit breaker to operate in the adaptive reclosing mode is determined by the capacitor voltage amplitude and the initial voltage of the capacitor.

[0126] It should be noted that the content of the module in the control device of the mechanical DC circuit breaker with adaptive reclosing capability corresponds to the step content of the control method of the mechanical DC circuit breaker with adaptive reclosing capability. The step content of the control method of the mechanical DC circuit breaker with adaptive reclosing capability has been described in the second embodiment, and the content of the module in the control device of the mechanical DC circuit breaker with adaptive reclosing capability will not be repeated in this embodiment. The control device of the mechanical DC circuit breaker with adaptive reclosing capability can identify the nature of the fault after isolating the fault line through the acquisition module and the operation control module, so as to avoid reclosing on a permanent fault and causing a secondary fault impact on the power transmission system.

[0127] In one embodiment of the present application, the operation control module 200 is also used to control the fast mechanical switch, the current switch, the first switch, the second switch and the fourth switch to be closed and operated, and to control the third switch to be opened and closed, and the first switch tube and the second switch tube to be turned off and not operate, so as to pre-charge the capacitor through the input current.

[0128] Embodiment 4:

[0129] Fig.15 A schematic diagram of a terminal device described in an embodiment of the present application.

[0130] like Fig.15 As shown, an embodiment of the present application provides a terminal device, including a processor and a memory;

[0131] A memory, used for storing program codes and transmitting the program codes to a processor;

[0132] The processor is used to execute the control method of the mechanical DC circuit breaker with adaptive reclosing capability according to the instructions in the program code.

[0133] It should be noted that the processor is used to execute the steps in the above-mentioned control method embodiment of a mechanical DC circuit breaker with adaptive reclosing capability according to the instructions in the program code. Alternatively, the processor implements the functions of each module / unit in the above-mentioned system / device embodiments when executing the computer program.

[0134] Exemplarily, the computer program may be divided into one or more modules / units, one or more modules / units are stored in a memory and executed by a processor to complete the present application. One or more modules / units may be a series of computer program instruction segments capable of completing a specific function, and the instruction segments are used to describe the execution process of the computer program in a terminal device.

[0135] The terminal device may be a computing device such as a desktop computer, a notebook, a PDA, or a cloud server. The terminal device may include, but is not limited to, a processor and a memory. Those skilled in the art will appreciate that this does not constitute a limitation on the terminal device, and may include more or fewer components than shown in the figure, or a combination of certain components, or different components. For example, the terminal device may also include input and output devices, network access devices, buses, etc.

[0136] The processor may be a central processing unit (CPU), other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (dSIC), field-programmable gate arrays (FPGAs) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor may be a microprocessor or any conventional processor, etc.

[0137] The memory may be an internal storage unit of the terminal device, such as a hard disk or memory of the terminal device. The memory may also be an external storage device of the terminal device, such as a plug-in hard disk, a smart memory card (SMC), a secure digital (SD) card, a flash card, etc. equipped on the terminal device. Furthermore, the memory may include both an internal storage unit of the terminal device and an external storage device. The memory is used to store computer programs and other programs and data required by the terminal device. The memory may also be used to temporarily store data that has been output or is to be output.

[0138] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working processes of the systems, devices and units described above can refer to the corresponding processes in the aforementioned method embodiments and will not be repeated here.

[0139] In the several embodiments provided in the present application, it should be understood that the disclosed systems, devices and methods can be implemented in other ways. For example, the device embodiments described above are only schematic. For example, the division of the units is only a logical function division. There may be other division methods in actual implementation, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be an indirect coupling or communication connection through some interfaces, devices or units, which can be electrical, mechanical or other forms.

[0140] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0141] In addition, each functional unit in each embodiment of the present application may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit. The above-mentioned integrated unit may be implemented in the form of hardware or in the form of software functional units.

[0142] If the integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present application is essentially or the part that contributes to the prior art or all or part of the technical solution can be embodied in the form of a software product. The computer software product is stored in a storage medium, including several instructions for a computer device (which can be a personal computer, server, or network device, etc.) to perform all or part of the steps of the method described in each embodiment of the present application. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM), random access memory (RAM), disk or optical disk, etc., various media that can store program codes.

[0143] As described above, the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A mechanical DC circuit breaker with adaptive reclosing capability, comprising a main on branch and a main off branch and an energy absorbing branch connected in parallel with the main on branch, wherein the main off branch comprises a capacitor, characterized in that: The mechanical DC circuit breaker further comprises a pre-charging branch and a fault identification branch connected to the main breaking branch, wherein the pre-charging branch is connected in parallel with the fault identification branch; The pre-charging branch is used to pre-charge the capacitor, the pre-charging branch comprises a second switch and a pre-charging resistor connected in series with the second switch, the second switch is also connected to the capacitor, and the pre-charging resistor is also connected to the ground terminal; The fault identification branch includes a third switch and a current limiting resistor connected in series with the third switch. The third switch is also connected to the capacitor, and the current limiting resistor is also connected to the ground terminal.

2. The mechanical DC circuit breaker with adaptive reclosing capability according to claim 1, characterized in that: The input end of the main pass branch is connected to the first switch, the output end of the main pass branch is connected to the fourth switch, the first switch is also connected to the current switch, and recovery resistors are connected in parallel at both ends of the first switch; and / or, the main pass branch includes a fast mechanical switch, the main disconnect branch also includes an inductor and a bidirectional switch tube connected to the capacitor, the bidirectional switch tube includes a first switch tube and a second switch tube, and the energy absorption branch includes a lightning arrester.

3. A control method for a mechanical DC circuit breaker with adaptive reclosing capability, applied to the mechanical DC circuit breaker with adaptive reclosing capability as claimed in claim 1 or 2, characterized in that: The control method comprises the following steps: Acquiring a control instruction for controlling the operation of a mechanical DC circuit breaker and an input current input to the mechanical DC circuit breaker, wherein the mechanical DC circuit breaker is connected to a DC line of a power transmission system; Controlling the mechanical DC circuit breaker to operate in a pre-charging mode, a fault isolation mode or an adaptive reclosing mode according to the control instruction; Wherein, if the control instruction is a normal operation instruction, the mechanical DC circuit breaker is controlled to operate in the pre-charging mode, so as to pre-charge the capacitor of the main breaker branch in the mechanical DC circuit breaker through the input current; If the control instruction is an interrupt instruction, controlling the mechanical DC circuit breaker to operate in the fault isolation mode to isolate the fault line of the DC line; If the control instruction is a reclosing command, the third switch and the fourth switch are controlled to close to obtain the initial voltage of the capacitor and the capacitor voltage amplitude within the time window, and whether to control the mechanical DC circuit breaker to operate in the adaptive reclosing mode is determined by the capacitor voltage amplitude and the initial voltage of the capacitor.

4. The control method of a mechanical DC circuit breaker with adaptive reclosing capability according to claim 3, characterized in that: Controlling the mechanical DC circuit breaker to operate in the fault isolation mode to isolate the fault line of the DC line includes: Obtaining a transient interruption voltage of a lightning arrester in the mechanical DC circuit breaker; According to the interrupt instruction, the fast mechanical switch is controlled to be disconnected and the first switch tube is controlled to be turned on, so that the capacitor is discharged, and the discharge current of the capacitor is obtained in real time; If the discharge current is equal to the input current, the input current is controlled to be switched from the main on branch to the main off branch, so that the input current reversely charges the capacitor through the first switch tube to obtain a charging voltage of the capacitor; If the charging voltage is equal to the transient interruption voltage, the capacitor is charged, and the input current is controlled to be switched from the main breaking branch to the energy absorption branch, then the first switch tube is controlled to be turned off, and the input current is absorbed by the lightning arrester to decay to 0, and then the current switch, the first switch and the fourth switch are all controlled to be disconnected to isolate the fault line of the DC line.

5. The control method of a mechanical DC circuit breaker with adaptive reclosing capability according to claim 3, characterized in that: Judging whether to control the mechanical DC circuit breaker to operate in the adaptive reclosing mode according to the capacitor voltage amplitude and the initial voltage of the capacitor includes: Acquire a proportionality coefficient and a rated voltage of the DC line, and calculate comparison data according to the proportionality coefficient and the initial voltage; If the capacitor voltage amplitude is greater than the comparison data, the fault of the DC line is a transient fault, and the mechanical DC circuit breaker is controlled to perform a reclosing operation according to the adaptive reclosing mode; If the capacitor voltage amplitude is smaller than the comparison data, the fault of the DC line is a permanent fault, and the mechanical DC circuit breaker is controlled not to perform a reclosing operation.

6. The control method of a mechanical DC circuit breaker with adaptive reclosing capability according to claim 5, characterized in that: The contents of controlling the mechanical DC circuit breaker to perform a closing operation according to the adaptive reclosing mode include: Control the third switch to be opened, the current switch to be closed, the fast mechanical switch to be closed, and the second switch to be closed, charge the capacitor through the input current, and obtain the charge amount of the capacitor and the line voltage of the DC line in real time, If the line voltage is equal to the rated voltage and the charging amount is 100%, obtaining an execution instruction; The first switch is controlled to close and the second switch is controlled to open according to the execution instruction to complete the reclosing operation of the mechanical DC circuit breaker.

7. The control method of a mechanical DC circuit breaker with adaptive reclosing capability according to claim 3, characterized in that: Controlling the mechanical DC circuit breaker to operate in the pre-charging mode, and pre-charging the capacitor of the main breaker branch in the mechanical DC circuit breaker through the input current includes: controlling the fast mechanical switch, the current switch, the first switch, the second switch and the fourth switch to be closed and working, and controlling the third switch to be open, and the first switch tube and the second switch tube to be turned off and not working, so as to pre-charge the capacitor through the input current.

8. A control device for a mechanical DC circuit breaker with adaptive reclosing capability, applied to the mechanical DC circuit breaker with adaptive reclosing capability as claimed in claim 1 or 2, characterized in that: The control device comprises an acquisition module and an operation control module; The acquisition module is used to acquire a control instruction for controlling the operation of a mechanical DC circuit breaker and an input current input to the mechanical DC circuit breaker, wherein the mechanical DC circuit breaker is connected to a DC line of a power transmission system; The operation control module is used to control the mechanical DC circuit breaker to operate in a pre-charging mode, a fault isolation mode or an adaptive reclosing mode according to the control instruction; Wherein, if the control instruction is a normal operation instruction, the mechanical DC circuit breaker is controlled to operate in the pre-charging mode, so as to pre-charge the capacitor of the main breaker branch in the mechanical DC circuit breaker through the input current; If the control instruction is an interrupt instruction, controlling the mechanical DC circuit breaker to operate in the fault isolation mode to isolate the fault line of the DC line; If the control instruction is a reclosing command, the third switch and the fourth switch are controlled to close to obtain the initial voltage of the capacitor and the capacitor voltage amplitude within the time window, and whether to control the mechanical DC circuit breaker to operate in the adaptive reclosing mode is determined by the capacitor voltage amplitude and the initial voltage of the capacitor.

9. The control device for a mechanical DC circuit breaker with adaptive reclosing capability according to claim 8, characterized in that: The operation control module is also used to control the fast mechanical switch, the current switch, the first switch, the second switch and the fourth switch to be closed and operated, and to control the third switch to be opened and closed, and the first switch tube and the second switch tube to be turned off and not operated, so as to pre-charge the capacitor through the input current.

10. A terminal device, characterized in that: including a processor and a memory; The memory is used to store program codes and transmit the program codes to the processor; The processor is used to execute the control method of the mechanical DC circuit breaker with adaptive reclosing capability according to any one of claims 3 to 7 according to the instructions in the program code.

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