Energy recovery method and system of direct current circuit breaker

Abstract

The invention discloses an energy recovery method and system for a direct current circuit breaker, and relates to the technical field of electrical equipment, and the method comprises the steps: constructing a direct current circuit breaker which comprises a main branch and a voltage injection unit; when a direct-current fault occurs, direct-current fault isolation is implemented through the direct-current circuit breaker, and after direct-current fault isolation is implemented through the direct-current circuit breaker, a voltage injection unit of the direct-current circuit breaker is used for performing energy recovery on the coupling inductor; the direct current fault isolation comprises forward direct current fault isolation and reverse direct current fault isolation. According to the invention, the energy stored in the coupling inductor winding can be recovered and used for charging the energy storage capacitor, and meanwhile, the energy stored in the winding can be quickly dissipated.

Description

Technical Field

[0001] This invention relates to the field of power equipment technology, specifically to an energy recovery method and system for a DC circuit breaker. Background Technology

[0002] In response to the national "dual-carbon" goal, new energy sources have been vigorously developed. The best solution to integrate these new energy sources into the power grid is to develop DC transmission and distribution networks, which offer advantages over AC grids, such as higher efficiency, greater flexibility, and longer transmission distances. However, due to the low impedance of DC transmission and distribution networks, the fault current rises rapidly when a short-circuit fault occurs. If not cleared in time, this can lead to converter station shutdown, large-scale power outages, and even significant economic losses. The low impedance of DC systems and the lack of a natural zero-crossing point make arc-free interruption of DC short-circuit faults a major challenge, thus highlighting the significant research value and practical potential of DC circuit breakers. Currently, domestic and international research on DC circuit breakers typically only enables unidirectional fault interruption, and the energy in the circuit cannot be recovered and reused after fault interruption. Summary of the Invention

[0003] In view of the above-mentioned problems, the present invention is proposed.

[0004] Therefore, the technical problem solved by this invention is: how to recover and utilize energy after fault isolation.

[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution: an energy recovery method for a DC circuit breaker, comprising the following steps,

[0006] A DC circuit breaker is constructed, comprising a main branch and a voltage injection unit. When a DC fault occurs, DC fault isolation is implemented through the DC circuit breaker. After DC fault isolation is implemented through the DC circuit breaker, energy is recovered from the coupled inductor using the voltage injection unit of the DC circuit breaker. The DC fault isolation includes forward DC fault isolation and reverse DC fault isolation.

[0007] As a preferred embodiment of the energy recovery method of a DC circuit breaker according to the present invention, the main branch includes a mechanical switch, a line parasitic inductance, a current sensor, and a primary winding of a coupling inductor.

[0008] The voltage injection unit includes a first energy storage capacitor, a second energy storage capacitor, a first fully controlled power device, a second fully controlled power device, a third fully controlled power device, a fourth fully controlled power device, a fifth fully controlled power device, a sixth fully controlled power device, and a secondary winding of a coupled inductor.

[0009] As a preferred embodiment of the energy recovery method for a DC circuit breaker according to the present invention, the voltage injection unit has a working mode, including determining the charging sequence and method based on the voltage difference between the first energy storage capacitor and the second energy storage capacitor.

[0010] The charging sequence includes charging the second energy storage capacitor first if the voltage of the first energy storage capacitor is higher than that of the second energy storage capacitor.

[0011] In a preferred embodiment of the energy recovery method for a DC circuit breaker described in this invention, when the positive DC fault isolation occurs, a turn-on signal is applied to the first fully controlled power device, and a turn-off signal is applied to the second, fourth, and sixth fully controlled power devices. The energy in the secondary winding of the coupled inductor charges the second energy storage capacitor through the body diodes of the first, third, and fifth fully controlled power devices.

[0012] When the second energy storage capacitor is charged to the preset voltage, a turn-off signal is applied to the first fully controlled power device, and the energy in the secondary winding of the coupling inductor charges the first energy storage capacitor through the body diodes of the third, fourth, and fifth fully controlled power devices.

[0013] When the first energy storage capacitor is charged to the preset voltage, a conduction signal is applied to the sixth fully controlled power device, and the remaining energy in the coupling inductor is dissipated through the body diode of the third fully controlled power device, the body diode of the fourth fully controlled power device, and the sixth fully controlled power device.

[0014] As a preferred embodiment of the energy recovery method of the DC circuit breaker described in this invention, the working mode of the voltage injection unit after the positive DC fault isolation occurs is as follows: after isolating the positive fault, the first fully controlled power device is turned on, the second fully controlled power device, the fourth fully controlled power device and the sixth fully controlled power device are turned off, and the second energy storage capacitor is charged by the energy in the coupling inductor.

[0015] When the second energy storage capacitor is charged to the preset voltage, the first fully controlled power device is turned off, and the first energy storage capacitor is charged by the energy in the coupling inductor.

[0016] When the first energy storage capacitor is charged to the preset voltage, the sixth fully controlled power device is turned on, and the remaining energy in the coupling inductor is dissipated through the body diode of the third fully controlled power device, the body diode of the fourth fully controlled power device, and the sixth fully controlled power device.

[0017] In a preferred embodiment of the energy recovery method for a DC circuit breaker described in this invention, when the reverse DC fault isolation occurs, a turn-on signal is applied to the fourth fully controlled power device, and a turn-off signal is applied to the first, third, and fifth fully controlled power devices. The energy in the secondary winding of the coupled inductor charges the second energy storage capacitor through the body diodes of the second, fourth, and sixth fully controlled power devices.

[0018] When the second energy storage capacitor is charged to the preset voltage, a turn-off signal is applied to the fourth fully controlled power device, and the energy in the secondary winding of the coupling inductor charges the first energy storage capacitor through the body diodes of the first fully controlled power device, the second fully controlled power device, and the sixth fully controlled power device.

[0019] When the first energy storage capacitor is charged to a preset voltage, a conduction signal is applied to the fifth fully controlled power device, and the remaining energy in the coupling inductor is dissipated through the body diode of the first fully controlled power device, the body diode of the second fully controlled power device, and the fifth fully controlled power device.

[0020] As a preferred embodiment of the energy recovery method of the DC circuit breaker described in this invention, the working mode of the voltage injection unit after the reverse DC fault isolation occurs is as follows: after isolating the reverse fault, the fourth fully controlled power device is turned on, the first fully controlled power device, the third fully controlled power device, and the fifth fully controlled power device are turned off, and the second energy storage capacitor is charged by the energy in the coupling inductor.

[0021] When the second energy storage capacitor is charged to the preset voltage, the fourth fully controlled power device is turned off, and the first energy storage capacitor is charged through the energy in the coupling inductor.

[0022] When the first energy storage capacitor is charged to the preset voltage, the fifth fully controlled power device is turned on, and the remaining energy in the coupling inductor is dissipated through the body diode of the first fully controlled power device, the body diode of the second fully controlled power device, and the fifth fully controlled power device.

[0023] Another objective of this invention is to provide an energy recovery system for a DC circuit breaker that can achieve dynamic energy management by efficiently utilizing coupled inductors and fully controlled power devices, thereby solving the problems of high energy loss and slow fault response in existing systems.

[0024] To solve the above-mentioned technical problems, the present invention provides the following technical solution: an energy recovery system for a DC circuit breaker, comprising a main branch module and a voltage injection unit module.

[0025] The main branch module is responsible for fault detection and isolation in the DC circuit breaker.

[0026] The voltage injection unit module manages energy storage and recovery in the DC circuit breaker by controlling the switching on and off of power devices.

[0027] A computer device includes a memory and a processor, the memory storing a computer program, the processor executing the computer program to implement the steps of the energy recovery method for a DC circuit breaker as described above.

[0028] A computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of an energy recovery method for a DC circuit breaker as described above.

[0029] The beneficial effects of the present invention are: the present invention can recover the energy stored in the coupled inductor winding and use it to charge the energy storage capacitor, while enabling the energy stored in the winding to dissipate rapidly. Attached Figure Description

[0030] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 The above is an overall flowchart of an energy recovery method for a DC circuit breaker provided in the first embodiment of the present invention.

[0032] Figure 2 The diagram shows the topology of an energy recovery method for a DC circuit breaker provided in the first embodiment of the present invention.

[0033] Figure 3 This is a schematic diagram of energy recovery after forward fault isolation in a DC circuit breaker energy recovery method provided in the first embodiment of the present invention.

[0034] Figure 4 This is a schematic diagram of energy recovery after reverse fault isolation in a DC circuit breaker energy recovery method provided in the first embodiment of the present invention.

[0035] Figure 5 The following is an overall framework diagram of an energy recovery system for a DC circuit breaker provided for the second embodiment of the present invention.

[0036] Figure 6 The key waveform diagram for isolating a positive fault in an energy recovery method for a DC circuit breaker provided in the third embodiment of the present invention.

[0037] Figure 7The key waveform diagram for isolating a reverse fault in an energy recovery system of a DC circuit breaker provided in the third embodiment of the present invention. Detailed Implementation

[0038] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the protection scope of the present invention.

[0039] Example 1

[0040] Reference Figures 1-4 As an embodiment of the present invention, an energy recovery method for a DC circuit breaker is provided, characterized in that:

[0041] S1: Construct a DC circuit breaker, which includes a main branch and a voltage injection unit.

[0042] like Figure 1 As shown, Figure 1This is a flowchart of the control method of the present invention. The current sensor collects the current information in the main branch. When the current i1 in the main branch is equal to zero, it is determined that the mechanical switch is open, the fault is isolated, and the energy in the coupling inductor charges the energy storage capacitor. If a forward DC fault is isolated, a turn-on signal is applied to the first fully controlled power device, and a turn-off signal is applied to the second, fourth, and sixth fully controlled power devices. The energy in the secondary winding of the coupling inductor charges the second energy storage capacitor through the body diodes of the first, third, and fifth fully controlled power devices. When the second energy storage capacitor is charged to a preset voltage, a turn-off signal is applied to the first fully controlled power device, and the energy in the secondary winding of the coupling inductor charges the first energy storage capacitor through the body diodes of the third, fourth, and fifth fully controlled power devices. When the first energy storage capacitor is charged to a preset voltage, a turn-on signal is applied to the sixth fully controlled power device, and the remaining energy in the coupling inductor is dissipated through the body diodes of the third, fourth, and sixth fully controlled power devices. If the reverse DC fault is isolated, a turn-on signal is applied to the fourth fully controlled power device, and a turn-off signal is applied to the first, third, and fifth fully controlled power devices. The energy in the secondary winding of the coupling inductor charges the second energy storage capacitor through the body diodes of the second, fourth, and sixth fully controlled power devices. When the second energy storage capacitor is charged to a preset voltage, a turn-off signal is applied to the fourth fully controlled power device, and the energy in the secondary winding of the coupling inductor charges the first energy storage capacitor through the body diodes of the first, second, and sixth fully controlled power devices. When the first energy storage capacitor is charged to a preset voltage, a turn-on signal is applied to the fifth fully controlled power device, and the remaining energy in the coupling inductor is dissipated through the body diodes of the first, second, and fifth fully controlled power devices. If the energy is completely dissipated, the fully controlled power devices Q1 to Q6 are turned off, thus ending the energy recovery operation after the DC circuit breaker isolates the fault.

[0043] The main branch circuit includes mechanical switches, line parasitic inductance, current sensors, and the primary winding of the coupling inductor.

[0044] The voltage injection unit includes a first energy storage capacitor, a second energy storage capacitor, a first fully controlled power device, a second fully controlled power device, a third fully controlled power device, a fourth fully controlled power device, a fifth fully controlled power device, a sixth fully controlled power device, and a secondary winding of a coupled inductor.

[0045] Furthermore, after the DC circuit breaker isolates the DC fault, when the energy in the coupling inductor is used to charge the energy storage capacitor, the voltage injection unit has multiple operating modes. Since the voltage of the first energy storage capacitor is higher than that of the second energy storage capacitor, the second energy storage capacitor must be charged first and then the first energy storage capacitor must be charged.

[0046] Furthermore, after DC fault isolation, energy in the primary winding of the coupled inductor will also be coupled to the secondary winding. Therefore, after the first and second energy storage capacitors are charged to the preset voltage, some energy still needs to be dissipated.

[0047] S2: When a DC fault occurs, DC fault isolation is implemented through a DC circuit breaker.

[0048] Furthermore, when no short-circuit fault occurs, the mechanical switch of the main branch module is closed, and the conduction path only contains the mechanical switch, current sensor and primary winding of the coupled inductor, without any power devices, resulting in low conduction loss and the DC circuit breaker being in standby mode.

[0049] S3: After implementing DC fault isolation through a DC circuit breaker, the voltage injection unit of the DC circuit breaker is used to recover energy from the coupled inductor.

[0050] DC fault isolation includes forward DC fault isolation and reverse DC fault isolation.

[0051] When a forward short-circuit fault occurs, the DC circuit breaker has the following operating modes:

[0052] Mode 1: After a forward short-circuit fault occurs, the current in the main branch rises rapidly due to the low inertia of the DC system.

[0053] Mode 2: When the current sensor detects that the current in the main branch reaches the forward action threshold of the DC circuit breaker, the voltage injection unit can start working. It applies a conduction signal to the first fully controlled power device, the second fully controlled power device, and the sixth fully controlled power device, so that the first energy storage capacitor discharges and injects a voltage with a higher amplitude and opposite polarity than the power supply into the main branch through the coupling inductor, so that the fault current in the main branch is rapidly reduced.

[0054] Mode 3: When the fault current in the main branch drops to the trough of the ripple current to be modulated, a turn-off signal is applied to the first fully controlled power device and an turn-on signal is applied to the fourth fully controlled power device. Then, the second energy storage capacitor discharges separately and injects a voltage with an amplitude lower than the power supply and opposite polarity into the main branch through the coupling inductor, causing the fault current in the main branch to start to rise.

[0055] Mode 4: When the current sensor detects that the current in the main branch rises back to the preset ripple current peak value, a turn-on signal is applied to the first fully controlled power device and a turn-off signal is applied to the fourth fully controlled power device. The first energy storage capacitor discharges separately and injects a voltage with a higher amplitude and opposite polarity than the power supply into the main branch through the coupling inductor, so that the fault current in the main branch begins to decrease rapidly again.

[0056] Mode 5: Repeating modes 3 and 4 can modulate the fault current into a ripple current with a very small amplitude. By disconnecting the mechanical switch of the main branch within the time window of the modulated ripple current, arc-free isolation of the positive fault can be achieved.

[0057] Mode 6: After the fault is isolated, a turn-on signal is applied to the first fully controlled power device, and a turn-off signal is applied to the second, fourth, and sixth fully controlled power devices. The energy in the secondary winding of the coupled inductor charges the second energy storage capacitor through the body diodes of the first, third, and fifth fully controlled power devices.

[0058] Mode 7: When the second energy storage capacitor is charged to the preset voltage, a turn-off signal is applied to the first fully controlled power device, and the energy in the secondary winding of the coupling inductor charges the first energy storage capacitor through the body diodes of the third, fourth, and fifth fully controlled power devices.

[0059] Mode 8: When the first energy storage capacitor is charged to the preset voltage, a conduction signal is applied to the sixth fully controlled power device. The remaining energy in the coupling inductor is dissipated through the body diode of the third fully controlled power device, the body diode of the fourth fully controlled power device, and the sixth fully controlled power device.

[0060] Furthermore, in the event of a reverse short-circuit fault, the DC circuit breaker has the following operating modes:

[0061] Mode 1: When no short-circuit fault occurs, the mechanical switch of the main branch module is closed. The conduction path only contains the mechanical switch, current sensor and primary winding of the coupled inductor, and does not contain any power devices. It has low conduction loss and the DC circuit breaker is in standby state.

[0062] Mode 2: After a reverse short-circuit fault occurs, the current in the main branch rises rapidly due to the low inertia of the DC system.

[0063] Mode 3: When the current sensor detects that the current in the main branch reaches the reverse action threshold of the DC circuit breaker, the voltage injection unit can start working and apply a conduction signal to the third fully controlled power device, the fourth fully controlled power device and the fifth fully controlled power device. Then the first energy storage capacitor discharges and injects a voltage with a higher amplitude and opposite polarity than the power supply into the main branch through the coupling inductor, so that the fault current in the main branch is reduced rapidly.

[0064] Mode 4: When the fault current in the main branch drops to the trough of the ripple current to be modulated, a turn-off signal is applied to the fourth fully controlled power device and an turn-on signal is applied to the first fully controlled power device. Then, the second energy storage capacitor discharges separately and injects a voltage with an amplitude lower than the power supply and opposite polarity into the main branch through the coupling inductor, causing the fault current in the main branch to start to rise.

[0065] Mode 5: When the current sensor detects that the current in the main branch rises back to the preset ripple current peak value, a turn-on signal is applied to the fourth fully controlled power device, a turn-off signal is applied to the first fully controlled power device, the first energy storage capacitor discharges alone, and a voltage with a higher amplitude and opposite polarity than the power supply is injected into the main branch through the coupling inductor, so that the fault current in the main branch begins to decrease rapidly again.

[0066] Mode 6: Repetitive modes 4 and 5 can modulate the fault current into a ripple current with a very small amplitude. By disconnecting the mechanical switch of the main branch within the time window of the modulated ripple current, arc-free isolation reverse fault can be achieved.

[0067] Mode 7: After the fault is isolated, a turn-on signal is applied to the fourth fully controlled power device, and a turn-off signal is applied to the first, third, and fifth fully controlled power devices. The energy in the secondary winding of the coupled inductor charges the second energy storage capacitor through the body diodes of the second, fourth, and sixth fully controlled power devices.

[0068] Mode 8: When the second energy storage capacitor is charged to the preset voltage, a turn-off signal is applied to the fourth fully controlled power device, and the energy in the secondary winding of the coupling inductor charges the first energy storage capacitor through the body diode of the first fully controlled power device, the body diode of the second fully controlled power device, and the body diode of the sixth fully controlled power device.

[0069] Mode 9: When the first energy storage capacitor is charged to the preset voltage, a conduction signal is applied to the fifth fully controlled power device. The remaining energy in the coupling inductor is dissipated through the body diode of the first fully controlled power device, the body diode of the second fully controlled power device, and the fifth fully controlled power device.

[0070] Furthermore, it is necessary to add that a DC circuit breaker is connected to the DC transmission and distribution line. When no fault occurs in the line, its function is only to carry the load current. Because there are no power devices in the main branch, its conduction loss is relatively low. When a forward or reverse fault occurs in the line, when the current sensor detects that the fault current reaches the preset operating current threshold of the DC circuit breaker, the voltage injection unit starts to work and modulates the fault current into a ripple current with a very small amplitude. After modulation, the fault current generates a ripple current with a very small amplitude within a time window. Within this window, the mechanical switch in the main branch is turned off, thus achieving arc-free isolation of the DC short-circuit fault. After fault isolation, the energy in the coupled inductor can be recovered by controlling the voltage injection unit to charge the energy storage capacitor. The topology of this invention is as follows: Figure 2 As shown.

[0071] The components are described below: S1: Mechanical switch, L: Line parasitic inductance, T1: Coupling inductance, IM: Current sensor, C1: First energy storage capacitor, C2: Second energy storage capacitor, Q1: First fully controlled power device, Q2: Second fully controlled power device, Q3: Third fully controlled power device, Q4: Fourth fully controlled power device, Q5: Fifth fully controlled power device, Q6: Sixth fully controlled power device.

[0072] The functions of the above devices are described below:

[0073] Mechanical switch (S1): Turns on to carry load current, and turns off to isolate faulty branches.

[0074] Current sensor (IM): Used to monitor whether a fault has occurred in a DC line.

[0075] Coupling transformer (T1): Injects voltage signals into the main branch.

[0076] Energy storage capacitors (C1, C2): Store energy for discharge in case of failure.

[0077] Fully controllable power devices (Q1~Q6): Controlling their on and off states enables different discharge and charging states of the energy storage capacitor.

[0078] Figure 3 This is a schematic diagram of energy recovery after positive fault isolation according to the present invention. Figure 3 (a) shows that after positive DC fault isolation, a turn-on signal is applied to the first fully controlled power device, and a turn-off signal is applied to the second, fourth, and sixth fully controlled power devices. The energy in the secondary winding of the coupled inductor charges the second energy storage capacitor through the body diodes of the first, third, and fifth fully controlled power devices. Figure 3(b) shows that when the second energy storage capacitor is charged to a preset voltage, a turn-off signal is applied to the first fully controlled power device, and the energy in the secondary winding of the coupling inductor charges the first energy storage capacitor through the body diodes of the third, fourth, and fifth fully controlled power devices. Figure 3 (c) shows that when the first energy storage capacitor is charged to a preset voltage, a conduction signal is applied to the sixth fully controlled power device, and the remaining energy in the coupling inductor is dissipated through the body diode of the third fully controlled power device, the body diode of the fourth fully controlled power device, and the sixth fully controlled power device.

[0079] Figure 4 This is a schematic diagram of energy recovery after reverse fault isolation according to the present invention. Figure 4 (a) shows that after reverse DC fault isolation, a turn-on signal is applied to the fourth fully controlled power device, and a turn-off signal is applied to the first, third, and fifth fully controlled power devices. The energy in the secondary winding of the coupled inductor charges the second energy storage capacitor through the body diodes of the second, fourth, and sixth fully controlled power devices. Figure 4 (b) shows that when the second energy storage capacitor is charged to a preset voltage, a turn-off signal is applied to the fourth fully controlled power device, and the energy in the secondary winding of the coupling inductor charges the first energy storage capacitor through the body diode of the first fully controlled power device, the body diode of the second fully controlled power device, and the body diode of the sixth fully controlled power device. Figure 4 (c) shows that when the first energy storage capacitor is charged to a preset voltage, a conduction signal is applied to the fifth fully controlled power device, and the remaining energy in the coupling inductor is dissipated through the body diode of the first fully controlled power device, the body diode of the second fully controlled power device, and the fifth fully controlled power device.

[0080] Example 2

[0081] Reference Figure 5 As an embodiment of the present invention, a system for energy recovery method of DC circuit breaker is provided. The system for energy recovery method of DC circuit breaker includes a main branch module and a voltage injection unit module.

[0082] The main branch module is responsible for fault detection and isolation in the DC circuit breaker.

[0083] In a DC circuit breaker, the voltage injection unit module manages energy storage and recovery by controlling the switching on and off of power devices.

[0084] If the aforementioned functions are implemented as software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this invention, essentially, or the part that contributes to the prior art, or a portion of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0085] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as a sequenced list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by, or in conjunction with, an instruction execution system, apparatus, or device (such as a computer-based system, a processor-included system, or other system that can fetch and execute instructions from, an instruction execution system, apparatus, or device). For the purposes of this specification, "computer-readable medium" can be any means that can contain, store, communicate, propagate, or transmit programs for use by, or in conjunction with, an instruction execution system, apparatus, or device.

[0086] More specific examples of computer-readable media (a non-exhaustive list) include: electrical connections (electronic devices) having one or more wires, portable computer disk drives (magnetic devices), random access memory (RAM), read-only memory (ROM), erasable and editable read-only memory (EPROM or flash memory), fiber optic devices, and portable optical disc read-only memory (CDROM). Furthermore, computer-readable media can even be paper or other suitable media on which the program can be printed, because the program can be obtained electronically, for example, by optically scanning the paper or other medium, followed by editing, interpreting, or otherwise processing as necessary, and then stored in computer memory.

[0087] It should be understood that various parts of the present invention can be implemented in hardware, software, firmware, or a combination thereof. In the above embodiments, multiple steps or methods can be implemented in software or firmware stored in memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, it can be implemented using any one or a combination of the following techniques known in the art: discrete logic circuits having logic gates for implementing logical functions on data signals, application-specific integrated circuits (ASICs) having suitable combinational logic gates, programmable gate arrays (PGAs), field-programmable gate arrays (FPGAs), etc.

[0088] Example 3

[0089] Reference Figures 6-7 In this embodiment, in order to verify the beneficial effects of the present invention, scientific demonstration is carried out through economic benefit calculation and simulation experiments.

[0090] Figure 6 This is a key waveform diagram for isolating a forward fault in this invention. Before time t0, the DC circuit breaker operates in standby mode. At time t0, a forward short-circuit fault occurs in the DC system, and the fault current rises rapidly. At time t1, the current sensor detects that the current in the main branch reaches the operating threshold current of the DC circuit breaker. Simultaneously, the fully controlled power devices Q1, Q2, and Q6 are turned on, and the energy storage capacitor C1 discharges alone, injecting a voltage with a higher amplitude and opposite polarity to the power supply into the main branch through the coupling inductor, causing the fault current to drop rapidly. At time t2, the fault current drops to the trough of the desired modulated ripple current. At this time, the fully controlled power device Q1 is turned off, and the fully controlled power device Q4 is turned on. The energy storage capacitor C2 discharges alone, injecting a voltage with a lower amplitude and opposite polarity to the power supply into the main branch through the coupling inductor, causing the fault current to start to rise again. When the fault current rises to the peak of the desired modulated ripple current, the fully controlled power device Q1 is turned on, and the fully controlled power device Q4 is turned off, causing the fault current to start to drop again. This process is repeated to obtain the following waveform diagram. Figure 6 As shown in (a), the ripple current from t2 to t4, during which turning off mechanical switch S1 during this ripple current window period can achieve arc-free isolation of positive faults. Figure 6 (b) is the charging and discharging of energy storage capacitors C1 and C2. From t1 to t4, the first and second energy storage capacitors discharge. From t4 to t5, the energy in the coupling inductor is used to charge the second energy storage capacitor. From t5 to t6, the energy in the coupling inductor is used to charge the first energy storage capacitor.

[0091] Figure 7This is a key waveform diagram for isolating reverse faults in this invention. Before time t0, the DC circuit breaker operates in standby mode. At time t0, a reverse short-circuit fault occurs in the DC system, and the fault current rises rapidly. At time t1, the current sensor detects that the current in the main branch reaches the operating threshold current of the DC circuit breaker. Simultaneously, the fully controlled power devices Q3, Q4, and Q5 are turned on, and the energy storage capacitor C1 discharges alone, injecting a voltage with a higher amplitude and opposite polarity to the power supply into the main branch through the coupling inductor, causing the fault current to drop rapidly. At time t2, the fault current drops to the trough of the desired modulated ripple current. At this time, the fully controlled power device Q4 is turned off, and the fully controlled power device Q1 is turned on. The energy storage capacitor C2 discharges alone, injecting a voltage with a lower amplitude and opposite polarity to the power supply into the main branch through the coupling inductor, causing the fault current to start to rise again. When the fault current rises to the peak of the desired modulated ripple current, the fully controlled power device Q4 is turned on, and the fully controlled power device Q1 is turned off, causing the fault current to start to drop again. This process is repeated to obtain the following waveform diagram. Figure 7 As shown in (a), the ripple current from t2 to t4, during which turning off the mechanical switch S1 during this ripple current window period can achieve arc-free isolation of reverse faults. Figure 7 (b) is the charging and discharging of energy storage capacitors C1 and C2. From t1 to t4, the first and second energy storage capacitors discharge. From t4 to t5, the energy in the coupling inductor is used to charge the second energy storage capacitor. From t5 to t6, the energy in the coupling inductor is used to charge the first energy storage capacitor.

[0092] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for energy recovery from a DC circuit breaker, characterized in that, include: Construct a DC circuit breaker, which includes a main branch and a voltage injection unit; When a DC fault occurs, DC fault isolation is implemented through a DC circuit breaker. After DC fault isolation is implemented by DC circuit breaker, energy is recovered from the coupled inductor by the voltage injection unit of DC circuit breaker. The DC fault isolation includes forward DC fault isolation and reverse DC fault isolation.

2. The energy recovery method for a DC circuit breaker as described in claim 1, characterized in that: The main branch circuit includes a mechanical switch, a line parasitic inductance, a current sensor, and a primary winding of a coupling inductor; The voltage injection unit includes a first energy storage capacitor, a second energy storage capacitor, a first fully controlled power device, a second fully controlled power device, a third fully controlled power device, a fourth fully controlled power device, a fifth fully controlled power device, a sixth fully controlled power device, and a secondary winding of a coupled inductor.

3. The energy recovery method for a DC circuit breaker as described in claim 2, characterized in that: The voltage injection unit has a working mode, including determining the charging sequence and method based on the voltage difference between the first energy storage capacitor and the second energy storage capacitor; The charging sequence includes charging the second energy storage capacitor first if the voltage of the first energy storage capacitor is higher than that of the second energy storage capacitor.

4. The energy recovery method for a DC circuit breaker as described in claim 3, characterized in that: When the positive DC fault isolation occurs, a turn-on signal is applied to the first fully controlled power device, and a turn-off signal is applied to the second, fourth, and sixth fully controlled power devices. The energy in the secondary winding of the coupled inductor charges the second energy storage capacitor through the body diodes of the first, third, and fifth fully controlled power devices. When the second energy storage capacitor is charged to the preset voltage, a turn-off signal is applied to the first fully controlled power device, and the energy in the secondary winding of the coupling inductor charges the first energy storage capacitor through the body diodes of the third, fourth, and fifth fully controlled power devices. When the first energy storage capacitor is charged to the preset voltage, a conduction signal is applied to the sixth fully controlled power device, and the remaining energy in the coupling inductor is dissipated through the body diode of the third fully controlled power device, the body diode of the fourth fully controlled power device, and the sixth fully controlled power device.

5. The energy recovery method for a DC circuit breaker as described in claim 4, characterized in that: The operating mode of the voltage injection unit after the positive DC fault isolation is as follows: after isolating a positive fault, the first fully controlled power device is turned on, and the second, fourth, and sixth fully controlled power devices are turned off, and the energy in the coupling inductor is used to charge the second energy storage capacitor. When the second energy storage capacitor is charged to the preset voltage, the first fully controlled power device is turned off, and the first energy storage capacitor is charged by the energy in the coupling inductor. When the first energy storage capacitor is charged to the preset voltage, the sixth fully controlled power device is turned on, and the remaining energy in the coupling inductor is dissipated through the body diode of the third fully controlled power device, the body diode of the fourth fully controlled power device, and the sixth fully controlled power device.

6. The energy recovery method for a DC circuit breaker as described in claim 5, characterized in that: When the reverse DC fault isolation occurs, a turn-on signal is applied to the fourth fully controlled power device, and a turn-off signal is applied to the first, third, and fifth fully controlled power devices. The energy in the secondary winding of the coupled inductor charges the second energy storage capacitor through the body diodes of the second, fourth, and sixth fully controlled power devices. When the second energy storage capacitor is charged to the preset voltage, a turn-off signal is applied to the fourth fully controlled power device, and the energy in the secondary winding of the coupling inductor charges the first energy storage capacitor through the body diode of the first fully controlled power device, the body diode of the second fully controlled power device, and the body diode of the sixth fully controlled power device. When the first energy storage capacitor is charged to a preset voltage, a conduction signal is applied to the fifth fully controlled power device, and the remaining energy in the coupling inductor is dissipated through the body diode of the first fully controlled power device, the body diode of the second fully controlled power device, and the fifth fully controlled power device.

7. The energy recovery method for a DC circuit breaker as described in claim 6, characterized in that: The operating mode of the voltage injection unit after the reverse DC fault isolation occurs is as follows: after isolating the reverse fault, the fourth fully controlled power device is turned on, and the first, third, and fifth fully controlled power devices are turned off, and the second energy storage capacitor is charged by the energy in the coupling inductor. When the second energy storage capacitor is charged to the preset voltage, the fourth fully controlled power device is turned off, and the first energy storage capacitor is charged by the energy in the coupling inductor. When the first energy storage capacitor is charged to the preset voltage, the fifth fully controlled power device is turned on, and the remaining energy in the coupling inductor is dissipated through the body diode of the first fully controlled power device, the body diode of the second fully controlled power device, and the fifth fully controlled power device.

8. A system employing an energy recovery method for a DC circuit breaker as described in any one of claims 1 to 7, characterized in that: Includes the main branch module and the voltage injection unit module; The main branch module is responsible for fault detection and isolation in the DC circuit breaker; The voltage injection unit module manages energy storage and recovery in the DC circuit breaker by controlling the switching on and off of power devices.

9. A computer device comprising a memory and a processor, wherein the memory stores a computer program, characterized in that, When the processor executes the computer program, it implements the steps of the energy recovery method for a DC circuit breaker according to any one of claims 1 to 7.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the steps of the energy recovery method for a DC circuit breaker as described in any one of claims 1 to 7.

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