A hybrid dc circuit breaker, control method and dc circuit breaking system

Abstract

The application discloses a hybrid DC circuit breaker, a control method and a DC circuit breaking system. The hybrid DC circuit breaker comprises a main current branch, a commutation branch and an energy consumption branch. The main current branch comprises a mechanical switch, a first power full-control device and a second power full-control device connected in series. The commutation branch comprises a first capacitor, a second capacitor, a first thyristor and a second thyristor. The energy consumption branch comprises a first voltage-dependent resistor and a second voltage-dependent resistor, which are connected in parallel with the first power full-control device and the second power full-control device respectively. Compared with the prior art, the hybrid DC circuit breaker utilizes the resistance and capacitance characteristics in the loop, and relies on the absorption and release of the energy stored in the capacitor during the turn-off process of the device to accelerate the current transfer, so that the arc extinguishing of the mechanical switch and the rapid removal of the fault current are realized. The arcless breaking can be realized by using only a small number of devices, and the hybrid DC circuit breaker has great advantages in volume and cost.

Description

Technical Field

[0001] This invention relates to the field of circuit breaker technology, specifically to a hybrid DC circuit breaker, control method, and DC circuit breaking system. Background Technology

[0002] With the rapid development of new energy power generation technology, grid connection of new energy power generation has become an urgent problem to be solved in the development of power systems. DC power systems, due to their advantages such as large capacity and low grid connection difficulty, have become a current research hotspot. Short-circuit fault current is a core problem that must be overcome in DC power systems—because DC short-circuit fault current has characteristics such as rapid rise and lack of natural zero crossing, interrupting DC fault current has become one of the difficulties restricting the development of DC power systems.

[0003] DC circuit breakers are typically the primary protective devices for interrupting DC faults. Currently, traditional low-voltage DC circuit breakers commonly suffer from problems such as generating strong arcs during current interruption and the inability to reclose quickly. This not only damages the lifespan of the circuit breaker contacts but may also lead to safety accidents. While rapid arc extinguishing can be achieved by adding complex solid-state switches and energy transfer branches, this also brings drawbacks such as high cost, complex structure, and large conduction losses. Therefore, there is an urgent need for a fast arc extinguishing and breaking technology that is simple in structure, fast in action, and low in cost. Summary of the Invention

[0004] The purpose of this invention is to overcome the above-mentioned technical deficiencies and propose a hybrid DC circuit breaker, control method, and DC circuit breaking system to solve the technical problem of the lack of circuit breakers with simple structure, fast operation, and low cost in the prior art.

[0005] To achieve the above-mentioned technical objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a hybrid DC circuit breaker, comprising: a main current branch, a converter branch, and an energy dissipation branch. The main current branch, along the direction of current flow, includes a mechanical switch, a first fully electrically controlled device, and a second fully electrically controlled device connected in series. The commutation branch includes a first capacitor, a second capacitor, a first thyristor, and a second thyristor. The first capacitor and the second capacitor are connected in parallel with the first fully controlled power device and the second fully controlled power device, respectively. The first thyristor is connected in parallel with the mechanical switch and the first fully controlled power device, and the second thyristor is connected in parallel with the first fully controlled power device and the second fully controlled power device.

[0006] The power-consuming branch includes a first varistor and a second varistor, which are connected in parallel with the first fully controlled power device and the second fully controlled power device, respectively.

[0007] In some embodiments, a controller is further included, which is connected to the mechanical switch, the first fully controlled power device, the second fully controlled power device, the first thyristor, and the second thyristor respectively, for controlling their on or off states respectively.

[0008] In some embodiments, the mechanical switch is a gas-filled high-speed mechanical switch with arc-extinguishing capability.

[0009] In some embodiments, the mechanical switch is an air-operated high-speed mechanical switch or an SF6 circuit breaker.

[0010] In some embodiments, both the first varistor and the second varistor are metal oxide varistors.

[0011] In some embodiments, the first varistor and the second varistor are one or any combination of two of the following: metal oxide surge arrester, line-type metal oxide surge arrester, gapless line-type metal oxide surge arrester, fully insulated composite jacket metal oxide surge arrester, and removable surge arrester.

[0012] In some embodiments, the first fully controllable power device and the second fully controllable power device are one or a combination of any two of IGBT components, IGCT components, IEGT components, and GTO components.

[0013] In some embodiments, both the first thyristor and the second thyristor are unidirectional thyristors.

[0014] Secondly, the present invention also provides a control method for a hybrid DC circuit breaker, applied to the hybrid DC circuit breaker, comprising the following steps: S1. Under normal conditions, the mechanical switch, the first fully controlled electric device, and the second fully controlled electric device are in the conducting state, and the current flows through the main current branch. S2. When a fault occurs, the mechanical switch is disconnected and the first fully controlled power device is turned off. Current flows through the first capacitor and the second fully controlled power device, and charges the first capacitor. S3. Control the first thyristor to conduct, and under the voltage of the first capacitor, the current flows through the first thyristor and the second fully controlled power device. S4. After the mechanical switch extinguishes the arc, the second thyristor is controlled to turn on, and the energy in the first capacitor is discharged through the second thyristor and the second fully controlled power device circuit, so as to reduce the current flowing through the second fully controlled power device. S5. When the current flowing through the second fully controlled power device decreases to its turn-off capability range, the second fully controlled power device is turned off. The current flows through the branch where the first thyristor and the second capacitor are located, as well as the branch where the first thyristor, the first capacitor, and the second thyristor are located, and charges the first capacitor and the second capacitor. S6. When the voltage of the second capacitor is higher than the operating voltage of the second varistor, the second varistor operates to allow current to flow through the first thyristor and the second varistor. The second varistor converts electrical energy into heat energy and dissipates it until the current decreases to zero. Then, it controls the first thyristor to turn off, completing the turn-off action of the hybrid DC circuit breaker.

[0015] Thirdly, the present invention also provides a DC circuit breaking system, comprising: a DC power grid, a load, and the aforementioned hybrid DC circuit breaker, wherein the DC power grid is connected to the load through a main circuit branch of the hybrid DC circuit breaker.

[0016] Compared with existing technologies, the hybrid DC circuit breaker provided by this invention utilizes the resistance and capacitance characteristics in the circuit and relies on the absorption and release of energy stored in the capacitor during the device turn-off process to accelerate current transfer, thereby achieving rapid arc extinguishing of the mechanical switch and rapid clearance of fault current. Compared with traditional circuit breaker systems, it can achieve arc-free breaking with only a few components, which has significant advantages in terms of size and cost. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the topology of the hybrid DC circuit breaker provided in an embodiment of the present invention; Figure 2 This is the current path in step S1 of the control method for the hybrid DC circuit breaker provided in this embodiment of the invention; Figure 3 This is the current path in step S2 of the control method for the hybrid DC circuit breaker provided in this embodiment of the invention; Figure 4 This is the current path in step S3 of the control method for the hybrid DC circuit breaker provided in this embodiment of the invention; Figure 5 This is the current path in step S4 of the control method for the hybrid DC circuit breaker provided in this embodiment of the invention; Figure 6 This is the current path in step S5 of the control method for the hybrid DC circuit breaker provided in this embodiment of the invention; Figure 7 This is the current path in step S6 of the control method for the hybrid DC circuit breaker provided in this embodiment of the invention. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0019] To address the technical problem of the lack of circuit breakers with simple structure, fast operation, and low cost in the existing technology, this invention provides a hybrid DC circuit breaker that can achieve arc-free interruption with only a few components.

[0020] Please see Figure 1 , Figure 1 This is a schematic diagram of the topology of a hybrid DC circuit breaker provided in an embodiment of the present invention. The hybrid DC circuit breaker includes a main current branch, a converter branch, and an energy dissipation branch.

[0021] The main current branch, along the direction of current flow, includes a mechanical switch MS, a first fully controlled electric device, and a second fully controlled electric device connected in series.

[0022] The commutation branch includes a first capacitor C1, a second capacitor C2, a first thyristor T1, and a second thyristor T2. The first capacitor C1 and the second capacitor C2 are connected in parallel with the first fully controlled electric device and the second fully controlled electric device, respectively. The first thyristor T1 is connected in parallel with the mechanical switch MS and the first fully controlled electric device. The second thyristor T2 is connected in parallel with the first fully controlled electric device and the second fully controlled electric device.

[0023] The power-consuming branch includes a first varistor and a second varistor, which are connected in parallel with the first fully controlled power device and the second fully controlled power device, respectively.

[0024] In some embodiments, the hybrid DC circuit breaker further includes a controller, which is connected to the mechanical switch MS, the first fully controlled power device, the second fully controlled power device, the first thyristor T1 and the second thyristor T2 respectively, for controlling their on or off states respectively.

[0025] In some embodiments, the mechanical switch MS is a gas-filled high-speed mechanical switch with arc-extinguishing capability.

[0026] Based on the above embodiments, the mechanical switch MS can be an air-operated high-speed mechanical switch or an SF6 circuit breaker. Alternatively, a vacuum high-speed mechanical switch based on electromagnetic repulsion can be used.

[0027] A vacuum high-speed mechanical switch is a switching device that uses mechanical contacts to rapidly open and close circuits in a vacuum medium. It effectively suppresses the electric arc generated when the contacts break by utilizing the high insulation strength and arc-extinguishing capability of the vacuum, and achieves millisecond-level high-speed action with the help of springs or electromagnetic drive mechanisms. It combines the low on-resistance of mechanical switches with the reliability of vacuum arc extinguishing, making it suitable for high-voltage, high-current, and high-repetition-frequency pulse power systems, particle accelerators, radar modulators, and other applications, significantly improving system response speed and lifespan.

[0028] High-speed air-operated mechanical switches use atmospheric pressure air as the insulating medium and rely on springs or electromagnetic drive mechanisms to achieve rapid contact opening and closing, with actuation times reaching milliseconds or even sub-milliseconds. Compared to vacuum switches, they have a simpler structure and lower cost, but air has weaker insulation strength and arc-extinguishing ability, making it prone to arcing during breaking. Therefore, they typically require appropriate contact shapes, magnetic blowout, or enclosed arc-extinguishing chambers to accelerate arc extinguishing. These switches are suitable for low-voltage, medium-current applications or situations where size and cost are critical, such as pre-triggered circuits in high-power pulse systems, laboratory discharge testing, and high-speed protection circuits in industrial automation.

[0029] SF6 circuit breakers use sulfur hexafluoride gas as both insulation and arc-extinguishing medium. Utilizing its excellent electronegativity and high thermal conductivity, it can rapidly adsorb free electrons from the electric arc and efficiently dissipate heat, thus achieving extremely strong arc-extinguishing capabilities. The arc generated after the contacts break is confined within the SF6 gas flow, typically extinguishing within hundreds of microseconds to milliseconds, with extremely fast dielectric recovery. Compared to vacuum or air switches, SF6 circuit breakers have higher single-break withstand voltage levels, more compact structures, and larger breaking capacities, making them suitable for ultra-high voltage and extra-high voltage transmission networks at 110kV and above, as well as for circuit breakers at the outlets of large power plants.

[0030] In this embodiment, both the first and second varistors are metal oxide varistors, namely MOV1 and MOV2, respectively. Metal oxide varistors use zinc oxide ceramic as a substrate and exhibit nonlinear volt-ampere characteristics: they present a high resistance state under normal operating voltage with minimal leakage current; once subjected to overvoltage, their resistance drops sharply, conducting and discharging the surge current within nanoseconds, thereby clamping the voltage to a safe level. They have large current-carrying capacity and fast response speed, but experience slight aging after each operation and possess a certain amount of capacitance and leakage current. MOVs are commonly used in power supply surge protection modules, surge protectors, and input overvoltage protection for electronic equipment. When used in conjunction with gas discharge tubes or TVS diodes, they can construct multi-level surge protection circuits with complementary strengths and weaknesses.

[0031] In other embodiments, the first varistor and the second varistor may also be one or a combination of any two of the following: metal oxide surge arrester, line-type metal oxide surge arrester, gapless line-type metal oxide surge arrester, fully insulated composite jacket metal oxide surge arrester, and removable surge arrester.

[0032] In some embodiments, the first fully controllable power device and the second fully controllable power device are one or a combination of any two of IGBT components, IGCT components, IEGT components, and GTO components.

[0033] IGBT modules are composite power devices that integrate high voltage and high current handling capabilities with high input impedance and low on-state voltage drop. They control turn-on and turn-off via gate voltage, combining the advantages of MOSFETs (fast switching speed and low drive power) and power transistors (low saturation voltage drop). IGBT modules are widely used in motor drives, frequency converters, switching power supplies, and electric vehicle traction control, and are indispensable core switching devices in modern power electronic systems.

[0034] An IGCT (Inductively Coupled Thyristor) module is a fully controllable device that integrates the gate drive circuit and the gate commutation thyristor. Utilizing high-power, low-inductance hard-gate drive technology, it achieves turn-off capability similar to an IGBT module, while its conduction losses are comparable to those of a GTO (Gateway Tolerant Rotation) module. IGCT modules eliminate the need for a bulky snubber circuit, improving system power density and reliability. They are primarily used in high-voltage, high-capacity applications such as HVDC transmission, medium-voltage frequency converters, and high-power traction systems.

[0035] The IEGT module is a high-power voltage-controlled device developed by Toshiba using the electron injection enhancement effect. It can be understood as a performance-optimized IGBT module. Through enhanced injection structure, it significantly reduces the on-state voltage, achieving low saturation voltage drop, a wide safe operating area, and low gate drive power (two orders of magnitude lower than GTO modules), while maintaining a high operating frequency. IEGT modules are mainly used in high-power drivers, flexible DC transmission, and other applications requiring high reliability. Its press-fit package (PPI) supports double-sided heat dissipation and multi-device series connection.

[0036] GTO (Gate Tolerant Transistor) components are fully controllable thyristors that are turned off by a negative gate pulse signal, overcoming the limitation of ordinary thyristors that can only be controlled to conduct. They can withstand high voltage and high current and have strong surge withstand capability, and are mainly used in electric locomotive traction, power grid reactive power compensation, and high-power variable frequency speed control. However, their drive circuit is complex, requires a large reverse current for turn-off, and has a slow switching speed.

[0037] In this embodiment, both the first fully controllable power device and the second fully controllable power device use IGBT components, namely IGBT1 and IGBT2, respectively.

[0038] In some embodiments, both the first thyristor T1 and the second thyristor T2 are unidirectional thyristors. A unidirectional thyristor is a three-terminal semiconductor switching device with a four-layer PNPN structure. Its conduction is controlled by the gate trigger current, while its turn-off depends on the anode current dropping below the holding current (e.g., during circuit commutation or the application of reverse voltage). Therefore, it combines rectification and controllable switching functions. It can only conduct in one direction and has advantages such as high blocking voltage, strong current carrying capacity, and good surge tolerance. However, once turned on, it loses its gate control capability until the current crosses zero. It is widely used in phase-controlled rectification, AC voltage regulation, high-power DC power supplies, and soft-start circuits, and is a classic power device in high-voltage, high-current applications.

[0039] Please see Figures 2 to 7 , Figures 2 to 7 The current paths in each step of the control method for the hybrid DC circuit breaker provided in the embodiments of the present invention are shown. The control method for the hybrid DC circuit breaker described above includes the following steps: See step S1 Figure 2 Under normal conditions, i.e. before time t0, the system is in normal operating condition. Mechanical switch MS, the first fully controlled electric device, and the second fully controlled electric device are in the conducting state, and current flows through the main current branch.

[0040] See step S2 Figure 3 The fault current is in the time interval t0 to t1. At time t0, the fault current begins to rise. At time t1, when the controller detects the fault current, it sends a command to open the mechanical switch MS and turn off the first fully controlled power device, i.e., IGBT1. Current flows through the first capacitor C1 and the second fully controlled power device, i.e., IGBT2, and charges the first capacitor C1.

[0041] See step S3. Figure 4 The time period is from t1 to t2. At time t2, the controller turns on the first thyristor T1, and under the voltage of the first capacitor C1, the current flows through the first thyristor T1 and the second fully controlled power device, i.e., IGBT2.

[0042] See step S4 Figure 5 The time period is between t2 and t3. At time t3, after the mechanical switch MS extinguishes the arc, the controller controls the second thyristor T2 to conduct, and the energy in the first capacitor C1 is discharged through the second thyristor T2 and the second fully controlled power device, i.e., IGBT2. Figure 5 The loop formed by the solid arrowhead.

[0043] See step S5. Figure 6The current flows through the second fully controlled power device, IGBT2, gradually decreasing from time t3 to t4. When the current flowing through the second fully controlled power device, i.e. IGBT2, decreases to within its turn-off capability range, the controller turns off the second fully controlled power device, i.e. IGBT2. The current flows through the branch containing the first thyristor T1 and the second capacitor C2, as well as the branch containing the first thyristor T1, the first capacitor C1, and the second thyristor T2, and charges the first capacitor C1 and the second capacitor C2.

[0044] See step S6. Figure 7 The fault occurs during the time interval t4 to t5. At time t5, when the voltage of the second capacitor C2 is higher than the operating voltage of the second varistor MOV2, MOV2 activates, allowing current to flow through the first thyristor T1 and the second varistor MOV2. MOV2 dissipates the electrical energy as heat until the current decreases to zero, at which point it controls the first thyristor T1 to turn off, completing the switching action of the hybrid DC circuit breaker. In other words, the fault current is completely cleared at time t5.

[0045] The present invention also provides a DC circuit breaking system, including a DC power grid, a load, and the aforementioned hybrid DC circuit breaker, wherein the DC power grid is connected to the load through the main circuit branch of the hybrid DC circuit breaker.

[0046] To better understand this invention, the following is combined with... Figures 2 to 7 The technical solution of the present invention will be described in detail below: During normal operation, no fault current occurs, mechanical switches MS, IGBT1, and IGBT2 are all in the on state, all load current flows through the main current branch, neither capacitor is charged, the thyristor is in the off state, no current flows through the commutation branch, and the conduction loss is extremely low.

[0047] When a short-circuit fault occurs in the power grid, upon detecting the fault current signal, the controller first issues a disconnection command, controlling the mechanical switch MS to begin disconnection and simultaneously turning off IGBT1. At this time, the main current branch is disconnected at IGBT1, and the fault current transfers to the first capacitor C1 branch, starting to charge C1. As C1 charges, the voltage across C1 gradually increases, and the voltage across IGBT1 also gradually increases accordingly. When the voltage across C1 rises to a level higher than the anode turn-on voltage of thyristor T1, the first thyristor T1 is triggered to conduct, and the entire fault current transfers to the T1 branch. At this point, the mechanical switch MS is clamped at a low voltage level by C1, achieving arc-free disconnection, waiting for the moving contact of the mechanical switch MS to completely separate and establish sufficient insulation strength.

[0048] After the mechanical switch MS completes the arc extinguishing, the controller triggers the second thyristor T2 to conduct. The charged first capacitor C1 discharges through the circuit formed by T1 and T2, and the capacitor voltage gradually decreases. The current flowing through IGBT2 also gradually decreases as the capacitor discharges. When the current flowing through IGBT2 decreases to its rated turn-off capacity, the controller issues a turn-off command to turn off IGBT2. The fault current is then further transferred to the branch of the second capacitor C2 to charge the second capacitor C2.

[0049] As C2 charges, the voltage across it continues to rise. When the voltage rises to the action threshold of the second varistor MOV2, MOV2 enters the breakdown conduction state, and all the fault current is transferred to the MOV2 branch. MOV2 begins to dissipate the fault energy, converting electrical energy into heat energy and releasing it. The fault current continues to decay until the current drops to zero, eventually triggering the first thyristor T1 to turn off, completing the entire disconnection process and achieving complete fault isolation.

[0050] The specific embodiments of the present invention described above do not constitute a limitation on the scope of protection of the present invention. Any other corresponding changes and modifications made in accordance with the technical concept of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A hybrid DC circuit breaker, characterized in that, include: The main current branch, along the direction of current flow, includes a mechanical switch, a first fully electrically controlled device, and a second fully electrically controlled device connected in series. The commutation branch includes a first capacitor, a second capacitor, a first thyristor, and a second thyristor. The first capacitor and the second capacitor are connected in parallel with the first fully controlled power device and the second fully controlled power device, respectively. The first thyristor is connected in parallel with the mechanical switch and the first fully controlled power device, and the second thyristor is connected in parallel with the first fully controlled power device and the second fully controlled power device. The energy-consuming branch includes a first varistor and a second varistor, which are connected in parallel with the first fully controlled power device and the second fully controlled power device, respectively.

2. The hybrid DC circuit breaker according to claim 1, characterized in that, It also includes a controller, which is connected to the mechanical switch, the first fully controlled power device, the second fully controlled power device, the first thyristor and the second thyristor respectively, and is used to control their on or off states respectively.

3. The hybrid DC circuit breaker according to claim 1, characterized in that, The mechanical switch is a gas-filled high-speed mechanical switch with arc-extinguishing capability.

4. The hybrid DC circuit breaker according to claim 3, characterized in that, The mechanical switch is an air-operated high-speed mechanical switch or an SF6 circuit breaker.

5. The hybrid DC circuit breaker according to claim 1, characterized in that, Both the first varistor and the second varistor are metal oxide varistors.

6. The hybrid DC circuit breaker according to claim 1, characterized in that, The first varistor and the second varistor are one or any combination of two of the following: metal oxide surge arrester, line-type metal oxide surge arrester, gapless line-type metal oxide surge arrester, fully insulated composite jacket metal oxide surge arrester, and detachable surge arrester.

7. The hybrid DC circuit breaker according to claim 1, characterized in that, The first fully controllable power device and the second fully controllable power device are one or any combination of two of the following: IGBT module, IGCT module, IEGT module, and GTO module.

8. The hybrid DC circuit breaker according to claim 1, characterized in that, Both the first thyristor and the second thyristor are unidirectional thyristors.

9. A control method for a hybrid DC circuit breaker, characterized in that, The hybrid DC circuit breaker described in any one of claims 1-8 comprises the following steps: S1. Under normal conditions, the mechanical switch, the first fully controlled electric device, and the second fully controlled electric device are in the conducting state, and the current flows through the main current branch. S2. When a fault occurs, the mechanical switch is disconnected and the first fully controlled power device is turned off. Current flows through the first capacitor and the second fully controlled power device, and charges the first capacitor. S3. Control the first thyristor to conduct, and under the voltage of the first capacitor, the current flows through the first thyristor and the second fully controlled power device. S4. After the mechanical switch extinguishes the arc, the second thyristor is controlled to turn on, and the energy in the first capacitor is discharged through the second thyristor and the second fully controlled power device circuit, so as to reduce the current flowing through the second fully controlled power device. S5. When the current flowing through the second fully controlled power device decreases to its turn-off capability range, the second fully controlled power device is turned off. The current flows through the branch where the first thyristor and the second capacitor are located, as well as the branch where the first thyristor, the first capacitor, and the second thyristor are located, and charges the first capacitor and the second capacitor. S6. When the voltage of the second capacitor is higher than the operating voltage of the second varistor, the second varistor operates to allow current to flow through the first thyristor and the second varistor. The second varistor converts electrical energy into heat energy and dissipates it until the current decreases to zero. Then, it controls the first thyristor to turn off, completing the turn-off action of the hybrid DC circuit breaker.

10. A DC circuit breaking system, characterized in that, include: The DC grid, the load, and the hybrid DC circuit breaker as described in any one of claims 1-8, wherein the DC grid is connected to the load via a main circuit branch of the hybrid DC circuit breaker.

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