Economical mechanical high-voltage direct-current circuit breaker and control method and system thereof

Abstract

The invention belongs to the field of high-voltage direct-current circuit breakers, and particularly discloses an economical mechanical high-voltage direct-current circuit breaker and a control method and system thereof. According to the application, the capacitor energy on the commutation branch is multiplexed to realize reclosing, and additional large capacitor secondary energy supply is not needed, so that the complexity and economic investment of an external energy supply system are greatly reduced; the switching-on and switching-off method adaptive to the under-damping-over-damping range current solves the problem that small current switching-on and switching-off of a mechanical direct-current circuit breaker depends on a semiconductor device, and the economic cost of the direct-current circuit breaker is further reduced. And through a current-limiting resistor on the main branch, current limitation during reclosure breaking is realized, the energy absorption pressure of the lightning arrester is reduced, and the economic cost of the direct-current circuit breaker is further reduced.

Description

Technical Field

[0001] The present application relates to the field of high-voltage direct current (HVDC) circuit breakers, and more specifically, to an economical mechanical HVDC circuit breaker and a control method and system thereof. Background Art

[0002] Flexible grid interconnection is a key technological approach to supporting the integration of renewable energy into the grid. However, existing flexible direct current (HVDC) transmission systems lack DC circuit breakers, resulting in complex fault isolation procedures and difficulties in network operation. Mechanical high-voltage DC circuit breakers, due to their simple structure, low conduction losses, and manageable costs, have become a key research area for DC circuit breakers supporting HVDC networking.

[0003] Pre-energy storage mechanical DC circuit breakers generate AC current through resonance between an energy storage capacitor and an inductor. This current is injected into the vacuum interrupter, forcing the arc current to cross zero, thereby extinguishing the arc. DC current then commutates to the commutation branch, charging the energy storage capacitor and triggering the metal oxide varistor (MOV) to conduct, dissipating transient energy and ultimately interrupting the DC current. The entire DC circuit breaker process consists of four key stages: pre-energy storage in the energy storage capacitor; arc extinguishment in the vacuum interrupter; charging the energy storage capacitor; and energy dissipation in the MOV.

[0004] During the capacitor pre-energy storage stage, the energy storage capacitor needs to be charged so that the capacitor electric field energy meets the energy requirements of DC disconnection. Patent CN111371441A discloses a controllable shutdown mechanical DC circuit breaker, which proposes the use of large capacitor devices to quickly charge the energy storage capacitor. This solution has been applied to mechanical high-voltage DC circuit breaker equipment and reliably supports its operation in DC engineering grid connection. However, the transfer and distribution of electric field energy between capacitors is affected by many factors such as capacitance value and coulomb efficiency, resulting in low efficiency of charging the energy storage capacitor by large capacitors. In order to meet the rapid energy storage requirements of reclosing, multiple sets of large capacitor devices are often equipped, resulting in large capacitor devices and high costs.

[0005] During the energy storage capacitor charging phase, the DC system's transient steady-state energy charges the energy storage capacitor until the capacitor voltage exceeds the MOV's operating voltage. However, the low current caused by high-impedance grounding can lead to slow capacitor charging, making it impossible to interrupt the current within 300 ms. Therefore, existing DC circuit breakers, such as CN114243646A, which discloses a DC circuit breaker based on an auxiliary oscillator commutation device and its control method, use semiconductor devices to forcibly interrupt low currents, significantly reducing their economic performance and compactness.

[0006] In summary, the current technical bottleneck of mechanical high-voltage DC circuit breakers is mainly reflected in the "breaking capacity-economy-reliability" triangle contradiction. It is urgently necessary to achieve the following breakthroughs through topological innovation: optimize the energy absorption path and reduce the capacitor cost; master the zero-semiconductor device low-current shutdown technology while still being able to cope with low-current scenarios. Summary of the Invention

[0007] In view of the defects of the existing technology, the purpose of this application is to provide an economical mechanical high-voltage DC circuit breaker and its control method and system, aiming to solve the "breaking capacity-economy-reliability" triangle contradiction, especially the economy problem.

[0008] In a first aspect, the present application provides an economical mechanical high-voltage DC circuit breaker, comprising a plurality of DC circuit breaker units connected in series, each DC circuit breaker unit including a parallel energy-consuming branch, a main branch and a commutation branch, the commutation branch including a closing switch capable of interrupting an AC oscillating current, a capacitor, an inductor and a power supply device, the capacitor being connected in parallel with the power supply device and then in series with the closing switch and the inductor.

[0009] Preferably, the main branch includes a mechanical switch, a current limiting switch and a current limiting resistor, and the current limiting switch is connected in parallel with the current limiting resistor and then connected in series with the mechanical switch.

[0010] Preferably, the capacitance value of the commutation branch is , inductance value and the inductance value of the smoothing reactor , Transmission line inductance Together they determine the damping equivalent resistance of the entire circuit during the conduction of the commutation branch. ,like , the actual breaking current of the DC transmission system is overdamped current, on the contrary, the actual breaking current of the DC transmission system is underdamped current, It is the actual equivalent resistance of the breaking current.

[0011] Preferably, in the commutation branch, the capacitance value and inductance value Determines the reverse current injection frequency of the mechanical switch .

[0012] Preferably, in the commutation branch, the capacitor pre-charge voltage , capacitance value and inductance value Determines the reverse current amplitude of the mechanical switch , the reverse current amplitude exceeds the maximum fault current that the DC transmission system can withstand.

[0013] Preferably, the overdamping current is The underdamped / critically damped current is eventually interrupted by the delayed closing switch, and the capacitor voltage range is to When the arrester completes its action, the capacitor voltage oscillates to its maximum value. = , capacitor voltage oscillation minimum voltage = , the underdamped current / critical damped current is the time from the moment the arrester completes its action Attenuates to the point where it can be disconnected by the closing switch, and the corresponding capacitor voltage oscillation range is from to Decay to to , capacitor pre-charge voltage = , is the rated voltage of the lightning arrester on the energy consumption branch, is the grid voltage of the DC transmission system.

[0014] Preferably, the closing switch is delayed during the After the switch is opened, the oscillation current is disconnected through zero point, and the delay time At the same time greater than and , the delay time Less than the fault de-isolation time.

[0015] Preferably, the current-limiting resistor is 0.1 to 2 times the rated resistance of the DC grid, and the rated resistance of the DC grid is the ratio of the rated voltage of the DC grid to the rated short-circuit current.

[0016] In a second aspect, the present application provides a control method for the economical mechanical high-voltage DC circuit breaker according to the first aspect, the control method comprising: S1. When the DC transmission system is operating normally, the mechanical switch is in the closed state, the main branch is in a low-resistance state, and the closing switch remains open; S2. Detecting a fault in the DC transmission system, sending an opening signal to the main branch mechanical switch and a closing signal to the commutation branch closing switch; S3. After detecting that the fault current has transferred from the main branch to the commutation branch, the main branch is placed in a high-impedance state; S4. Detects that the fault current is transferred from the commutation branch to the energy consumption branch after the set delay time After that, an opening signal is sent to the closing switch; S5. Send a closing signal to the mechanical switch after the DC transmission system has been freed for a period of time at the time of the fault occurrence; S6. Check whether the fault still exists. If the fault still exists, repeat steps S2 to S4. If the fault disappears, return the main branch to the low-resistance state and conduct.

[0017] In a third aspect, the present application provides a control system for an economical mechanical high-voltage DC circuit breaker, comprising: at least one memory for storing programs; and at least one processor for entering the programs stored in the memory. When the program stored in the memory is entered, the processor is used to enter the control method as described in the second aspect.

[0018] In general, the above technical solutions conceived by this application have the following beneficial effects compared with the existing technologies: (1) This application proposes an economical mechanical high-voltage DC circuit breaker and a new circuit breaker circuit, which realizes reclosing by reusing the capacitor energy on the commutation branch. The capacitor, inductor and main branch form an oscillation circuit to generate a high-frequency oscillating current. No additional large capacitor secondary energy supply is required, which greatly reduces the complexity and economic investment of the external energy supply system.

[0019] (2) This application proposes an economical mechanical high-voltage DC circuit breaker and a new circuit breaker circuit. When interrupting the over-damping current, the lightning arrester does not operate, the capacitor plays a voltage stabilizing role, and the current in the commutation branch gradually decreases and can be directly interrupted by the closing switch. There is no need to rely on semiconductor devices to interrupt small currents, further reducing the economic cost of the DC circuit breaker.

[0020] (3) The present application proposes an economical mechanical high-voltage DC circuit breaker, which proposes that the current limiting switch on the main branch is connected in parallel with the current limiting resistor and then in series with the mechanical switch. During the reclosing process, the system current is limited by the current limiting resistor, thereby reducing the energy stored in the smoothing reactor absorbed by the lightning arrester. At the same time, the system current is limited, the conduction time of the energy-consuming branch is also reduced, and the energy absorbed by the lightning arrester is correspondingly reduced, further reducing the economic cost of the DC circuit breaker.

[0021] (4) This application proposes a control method for an economical mechanical high-voltage direct current circuit breaker, which realizes a complete breaking process by controlling the opening and closing of a mechanical switch, a closing switch, and a current limiting switch, including the first breaking and reclosing (determining whether a second breaking is required based on the fault). If the reclosing occurs during a transient fault, the system can operate normally after the circuit breaker is reclosed. If the reclosing occurs during a permanent fault, the circuit breaker must be immediately opened for the second time after reclosing. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a schematic diagram of the topological structure of an economical mechanical high-voltage DC circuit breaker provided in an embodiment of the present application.

[0023] Figure 2This is a schematic diagram of the interruption logic for interrupting underdamped current provided in an embodiment of the present application.

[0024] Figure 3 This is a schematic diagram of the interruption logic for interrupting the over-damping current provided in an embodiment of the present application.

[0025] FIG4( a ) is a schematic diagram of the process of breaking the current t1 - t2 provided in an embodiment of the present application.

[0026] FIG4( b ) is a schematic diagram of the process of breaking the current t2 - t3 provided in an embodiment of the present application.

[0027] FIG4( c ) is a schematic diagram of the process of breaking the current t3 - t4 provided in an embodiment of the present application.

[0028] FIG4( d ) is a schematic diagram of the process of breaking the current t4 - t5 provided in an embodiment of the present application.

[0029] FIG4( e ) is a schematic diagram of the process of breaking the current t8 - t9 provided in an embodiment of the present application.

[0030] Figure 5 This is an equivalent circuit diagram of the disconnection process of the end-to-end DC transmission system provided in an embodiment of the present application. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical solutions and advantages of this application more clear, the following further describes this application in detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit this application.

[0032] The term "and / or" in this application describes an association relationship between associated objects, indicating that three relationships can exist. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, or B exists alone. The symbol " / " in this application indicates that the associated objects are in an "or" relationship, for example, A / B means A or B.

[0033] In this application, the terms "first" and "second" are used to distinguish different objects, rather than to describe a specific order of objects. For example, the terms "first response message" and "second response message" are used to distinguish different response messages, rather than to describe a specific order of response messages.

[0034] The term "electrical connection" in this application can be a direct circuit connection or a signal transmission through a communication protocol.

[0035] In the embodiments of this application, words such as "exemplary" or "for example" are used to indicate examples, illustrations, or descriptions. Any embodiment or design described as "exemplary" or "for example" in the embodiments of this application should not be interpreted as being preferred or advantageous over other embodiments or designs. Rather, the use of words such as "exemplary" or "for example" is intended to present the relevant concepts in a concrete manner.

[0036] In the description of the embodiments of the present application, unless otherwise specified, "multiple" means two or more, for example, multiple processing units means two or more processing units, etc.; multiple elements means two or more elements, etc.

[0037] It should be understood that expressions such as "include" and "may include" used in this application indicate the existence of the disclosed functions, operations, or constituent elements, and do not limit one or more additional functions, operations, and constituent elements. In this application, terms such as "include" and / or "have" may be interpreted as indicating specific characteristics, numbers, operations, constituent elements, components, or combinations thereof, but may not be interpreted as excluding the existence or possibility of adding one or more other characteristics, numbers, operations, constituent elements, components, or combinations thereof.

[0038] In addition, in this application, the expression "and / or" includes any and all combinations of the associated listed words. For example, the expression "A and / or B" may include A, may include B, or may include both A and B.

[0039] The embodiments of the present application are described below in conjunction with the drawings in the embodiments of the present application.

[0040] like Figure 1 As shown, the present application provides an economical mechanical high-voltage DC circuit breaker, comprising DC circuit breaker units connected in series, the number of which is equal to the ratio of the DC system voltage to the mechanical switch voltage. Each DC circuit breaker unit includes a parallel energy-consuming branch, a main branch, and a commutation branch. The commutation branch includes: a closing switch capable of interrupting current, a capacitor, an inductor, and an energy supply device. The energy supply device is connected in parallel with the capacitor and then in series with the closing switch and inductor. The time required for the closing switch to transition from an open state to a fully closed state is less than or equal to the time required for the mechanical switch contacts to separate from the closed state to the rated opening distance.

[0041] Preferably, the energy consumption branch is composed of a zinc oxide arrester.

[0042] Preferably, the main branch includes: a mechanical switch, a current limiting switch and a current limiting resistor, and the current limiting resistor is connected in parallel with the current limiting switch and then in series with the mechanical switch.

[0043] Preferably, the capacitance value of the commutation branch is , inductance value and the inductance value of the smoothing reactor , Transmission line inductance Together they determine the damping equivalent resistance of the entire circuit during the conduction of the commutation branch. ,like , the actual breaking current of the DC transmission system is overdamped current, on the contrary, the actual breaking current of the DC transmission system is underdamped current, It is the actual equivalent resistance of the breaking current.

[0044] Preferably, in the commutation branch, the capacitance value and inductance value Determines the reverse current injection frequency of the mechanical switch , reverse current injection frequency Do not exceed the breaking speed of the mechanical switch.

[0045] Preferably, in the commutation branch, the capacitor pre-charge voltage , capacitance value and inductance value Determines the reverse current amplitude of the mechanical switch , the reverse current amplitude exceeds the maximum fault current that the DC transmission system can withstand.

[0046] Preferably, the overdamping current is The underdamped / critically damped current is eventually interrupted by the delayed closing switch, and the capacitor voltage range is - When the arrester completes its action, the capacitor voltage oscillates to its maximum value. = , capacitor voltage oscillation minimum voltage = , the underdamped current / critical damped current is the time from the moment the arrester completes its action Attenuates to the point where it can be disconnected by the closing switch, and the corresponding capacitor voltage oscillation range is from - Decay to - , capacitor pre-charge voltage = , is the rated voltage of the lightning arrester on the energy consumption branch, is the grid voltage of the DC transmission system.

[0047] Preferably, the closing switch is delayed during the After the switch is opened, the oscillation current is disconnected through zero point, and the delay time At the same time greater than and , the delay time Less than the fault de-isolation time.

[0048] Preferably, the current-limiting resistor is 0.1 to 2 times the rated resistance of the DC grid, and the rated resistance of the DC grid is the ratio of the rated voltage to the rated current of the DC grid.

[0049] Next, we will introduce the working principle of the economical mechanical high-voltage DC circuit breaker when it is applied to the DC transmission system. When the DC system is operating normally, the mechanical switch and the current limiting switch are closed, the system current flows through the main branch, the closing switch is in the open state, and the energy supply device charges the capacitor to the set value. When a DC system needs to interrupt current, it can be divided into three situations according to the size of the interrupted current: ① interrupting underdamped current; ② interrupting critical damped current; ③ interrupting overdamped current.

[0050] The complete breaking process includes the first breaking and reclosing (whether a second breaking is required is determined based on the fault). If the reclosing occurs during a transient fault, the system can operate normally after the circuit breaker is reclosed. If the reclosing occurs during a permanent fault, the circuit breaker must be reclosed immediately after the second breaking. The complete first breaking voltage and current logic diagrams for the reclosing scenario during a permanent fault are as follows: Figure 2 、 Figure 3 As shown, Figure 2 This is the breaking logic diagram for breaking underdamped current. Figure 3 This is a schematic diagram of the interruption logic for interrupting the over-damping current.

[0051] The first breaking process and the control sequence of the DC circuit breaker are as follows: ① At this moment, a fault occurs and the main branch mechanical switch bears the fault current; ② At time t (the moment when the mechanical switch starts to open), the DC circuit breaker receives the opening command issued by the control circuit, the main branch mechanical switch operates to execute the opening command, and the closing switch executes the closing command, as shown in Figure 4(a); ③ At the moment (the moment when the mechanical switch contacts separate to the rated opening distance), the mechanical switch contacts separate to the rated opening distance, the closing switch is completed, and the capacitor and inductor generate an oscillating current superimposed on the main branch, as shown in Figure 4(b); ④ At time t (the time when the main branch current crosses zero), the main branch current crosses zero, the mechanical switch extinguishes the arc and turns off, and the fault current is transferred to the commutation branch. At this time, the current limiting switch can be controlled to open, and the DC system charges the capacitor, as shown in Figure 4(c).

[0052] Combine Figure 2 Explanation for interrupting underdamped current or critical damped current: (1) At time (the moment when the arrester operates), the capacitor is charged to the arrester operating voltage, the arrester operates, the fault current is transferred from the commutation branch to the energy consumption branch, and the arrester operates to absorb the residual energy of the line, as shown in Figure 4(d); (2) At this moment (the moment when the arrester completes its action), the arrester dissipates the fault current to zero, the arrester action is completed, and the capacitor voltage is the arrester residual voltage. , arrester residual pressure Greater than DC system voltage Due to the existence of capacitors, an oscillation circuit is formed between the DC system, the circuit breaker transfer branch and the fault point, and the capacitor voltage is and time-decayed oscillations; (3) At the moment (the moment when the closing switch is disconnected), the closing switch is controlled to disconnect the transfer branch current, and the capacitor voltage value is between, 、 Corresponding respectively 、 The attenuation value of the capacitor voltage can be used as the capacitor voltage of the reclosing switch. The closing switch disconnects the oscillating AC current of the commutation branch after the lightning arrester action is completed, limiting the voltage value on the capacitor.

[0053] Combine Figure 3 Description When interrupting overdamping current: (i) At this moment, the capacitor voltage is charged to the grid voltage , the arrester does not act, the capacitor stabilizes the voltage, the current in the commutation branch gradually decreases, and can be directly interrupted by the closing switch, without relying on semiconductor devices to interrupt small currents, as shown in Figure 4(c); (ii) At this moment, the closing switch is opened, and the main branch, commutation branch, and energy consumption branch of the DC circuit breaker are all disconnected from the DC system.

[0054] The reclosing process and the control sequence of the DC circuit breaker are as follows: (a) At this moment (when the mechanical switch starts to close), the control circuit sends a closing signal to the mechanical switch. and The interval is 300ms; 300ms is the de-ionization time of the DC transmission system in this embodiment. The DC circuit breaker is opened and closed for 300ms and then opened again according to the situation; (b) At time t (the moment when the mechanical switch is closed), the mechanical switch is closed, and the system current flows through the mechanical switch and the current-limiting resistor. The system current is limited by the current-limiting resistor, thereby reducing the energy stored in the smoothing reactor absorbed by the arrester. At the same time, the system current is limited, the conduction time of the energy-consuming branch is also reduced, and the energy absorbed by the arrester is correspondingly reduced, as shown in Figure 4(e). The system then detects whether the fault still exists. (c) At this moment (the moment when the external system completes fault detection), if the detected fault disappears, the current limiting switch is closed and the reclosing is completed. If the detected fault exists, the control circuit sends an opening signal to the mechanical breaker, and the breaking current required for reclosing is less than the first breaking current; (d) At this moment (the moment when the mechanical switch contacts separate to the rated opening distance again), the mechanical switch contacts separate to the rated opening distance, the current limiting switch closes, the closing switch closes, and the capacitor, inductor, main branch mechanical switch, and current limiting switch form an oscillation circuit to generate a high-frequency oscillating current.

[0055] and They correspond one to one, so I will not go into details.

[0056] Based on the above, the present application provides a control method for an economical mechanical high-voltage DC circuit breaker, the control method comprising: S1. When the DC transmission system is operating normally, the mechanical switch is in the closed state, the main branch is in the low-resistance state, and the closing switch remains open.

[0057] In an illustrated embodiment, when the DC power transmission system operates normally, the mechanical switch and the current limiting switch are in a closed state, and the closing switch remains open.

[0058] S2. When a fault is detected in the DC transmission system, an opening signal is sent to the main branch mechanical switch and a closing signal is sent to the commutation branch closing switch.

[0059] S3. After detecting that the fault current has been transferred from the main branch to the commutation branch, the main branch is placed in a high-impedance state. In an illustrated embodiment, after detecting that the fault current has transferred from the main branch to the commutation branch, a disconnect signal is sent to the current limiting switch.

[0060] S4. After detecting that the fault current is transferred from the commutation branch to the energy consumption branch after the set delay time, an opening signal is sent to the closing switch.

[0061] S5. After the DC transmission system has been freed for a period of time after the fault occurs, a closing signal is sent to the mechanical switch.

[0062] S6. Check whether the fault still exists. If the fault still exists, repeat steps S2 to S4. If the fault disappears, return the main branch to the low-resistance state and conduct.

[0063] In an illustrated embodiment, it is detected whether the fault still exists. If the fault still exists, steps S2-S4 are repeated; if the fault disappears, a signal is closed to the current limiting switch.

[0064] To achieve the above under the condition of breaking the different characteristic currents from underdamping to overdamping The process requires the capacitance parameters , capacitor pre-charge voltage , inductance parameters Carry out refined design, involving the maximum amplitude of the oscillating current of the transfer branch , oscillation frequency Selection of grid voltage , smoothing reactor , lightning arrester rated voltage , lightning arrester residual pressure This embodiment takes a 500kV DC system as an example to illustrate parameter design.

[0065] Step 1: According to the grid voltage Select the rated voltage of the arrester , residual pressure .

[0066] Specifically, let , , Generally not less than 1.1, It is the arrester pressure ratio, generally between 1.5 and 2.0.

[0067] Step 2: According to the maximum breaking current , reverse current injection frequency get 、 and relationship between them.

[0068] Combine 、 ,Sure 、 、 The relationship between the damping characteristics and the current Simplified to the corresponding resistance ,when , it is an over-damped current, otherwise it is an under-damped current. is the damping equivalent resistance, and the equivalent circuit diagram of the end-to-end DC transmission system breaking process is as follows: Figure 5 As shown, Damping characteristics breaking current The value range is - , The minimum breaking current value of the damping characteristic is The maximum breaking current value for the damping characteristic.

[0069] Step 3: Select capacitor pre-charge voltage = , delay time , thereby determining 、 .

[0070] The overdamping current is interrupted and the overdamping current is Attenuates to 0; interrupts underdamping current, underdamping current / critical damping current from the moment the arrester completes action through Attenuated to the point where it can be disconnected by the closing switch and the arrester completes its action, the capacitor voltage oscillates to its maximum value voltage. = , capacitor voltage oscillation minimum voltage = , after the delay time back, 、 Decay to 、 , select the capacitor pre-charge voltage = and delay time , the delay time Refers to the time interval from the closing moment of the closing switch to the opening moment of the closing switch, the delay time Must be greater than and .

[0071] The above description is merely a specific embodiment of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in this application should be included in the scope of protection of this application. Therefore, the scope of protection of this application should be based on the scope of protection of the claims.

Claims

1. An economical mechanical high-voltage DC circuit breaker, comprising a plurality of DC circuit breaker units connected in series, each DC circuit breaker unit comprising an energy consumption branch, a main branch, and a commutation branch connected in parallel, characterized in that: The commutation branch includes a closing switch capable of interrupting AC oscillating current, a capacitor, an inductor and an energy supply device. The capacitor is connected in parallel with the energy supply device and then in series with the closing switch and the inductor.

2. The high-voltage DC circuit breaker according to claim 1, characterized in that: The main branch includes a mechanical switch, a current limiting switch and a current limiting resistor. The current limiting switch is connected in parallel with the current limiting resistor and then connected in series with the mechanical switch.

3. The high-voltage DC circuit breaker according to claim 1, wherein: The capacitance value of the commutation branch , inductance value and the inductance value of the smoothing reactor , Transmission line inductance Together they determine the damping equivalent resistance of the entire circuit during the conduction of the commutation branch. ,like , the actual breaking current of the DC transmission system is overdamped current, on the contrary, the actual breaking current of the DC transmission system is underdamped current, It is the actual equivalent resistance of the breaking current.

4. The high-voltage DC circuit breaker according to claim 1, wherein: In the commutation branch, the capacitance value and inductance value Determines the reverse current injection frequency of the mechanical switch in the main branch .

5. The high-voltage DC circuit breaker according to claim 1, wherein: In the commutation branch, the capacitor pre-charge voltage , capacitance value and inductance value Determines the reverse current amplitude of the mechanical switch in the main branch , the reverse current amplitude exceeds the maximum fault current that the DC transmission system can withstand.

6. The high-voltage DC circuit breaker according to claim 1, wherein: Overdamping current flows from the time the closing switch is closed The underdamped / critically damped current is eventually interrupted by the delayed closing switch, and the capacitor voltage range is to When the arrester completes its action, the capacitor voltage oscillates to its maximum value. = , capacitor voltage oscillation minimum voltage = , the underdamped current / critical damped current is the time from the moment the arrester completes its action Attenuates to the point where it can be disconnected by the closing switch, and the corresponding capacitor voltage oscillation range is from to Decay to to , capacitor pre-charge voltage = , is the rated voltage of the lightning arrester on the energy consumption branch, is the grid voltage of the DC transmission system.

7. The high-voltage DC circuit breaker according to claim 1, wherein: The closing switch is delayed during the After the switch is opened, the oscillation current is disconnected through zero point, and the delay time At the same time greater than and , the delay time Less than the fault de-isolation time.

8. The high-voltage DC circuit breaker according to claim 2, wherein: The current limiting resistor is 0.1 to 2 times the rated resistance of the DC grid, and the rated resistance of the DC grid is the ratio of the rated voltage of the DC grid to the rated short-circuit current.

9. A control method for an economical mechanical high-voltage DC circuit breaker according to any one of claims 1 to 8, characterized in that: The control method includes: S1. When the DC transmission system is operating normally, the main branch mechanical switch is in the closed state, the main branch is in the low-resistance state, and the closing switch remains open; S2. Detecting a fault in the DC transmission system, sending an opening signal to the main branch mechanical switch and a closing signal to the commutation branch closing switch; S3. After detecting that the fault current has transferred from the main branch to the commutation branch, the main branch is placed in a high-impedance state; S4. Detects that the fault current is transferred from the commutation branch to the energy consumption branch after the set delay time After that, an opening signal is sent to the closing switch; S5. After the DC transmission system has been freed for a period of time after the fault occurs, a closing signal is sent to the main branch mechanical switch; S6. Check whether the fault still exists. If the fault still exists, repeat steps S2 to S4. If the fault disappears, return the main branch to the low-resistance state and conduct.

10. A control system for an economical mechanical high-voltage DC circuit breaker, characterized in that: include: at least one memory for storing a program; At least one processor is configured to enter the program stored in the memory, and when the program stored in the memory is entered, the processor is configured to enter the control method according to claim 9.

Images