A voltage-regulated oscillating DC circuit breaker and its control method

Abstract

The present invention provides a voltage-regulated oscillating DC circuit breaker and its control method. The circuit breaker includes: a flow branch, an energy-consuming branch, and a disconnecting branch. The flow branch is connected in series with the power line; the disconnecting branch is connected in parallel with the flow branch; the energy-consuming branch has one end connected to one end of the flow branch and one end of the disconnecting branch, respectively, and the other end connected to the disconnecting branch. When the power line is not faulty, the flow branch conducts the DC load current. When a fault occurs in the power line, by controlling the disconnecting branch to oscillate and generate an oscillating current, and continuously increasing the amplitude of the oscillating current until an oscillating current with the same amplitude and opposite direction as the fault current is generated, the circuit breaker can continuously interrupt the maximum current several times in a short period of time, greatly improving the flexibility and availability of the circuit breaker. It meets the dual technical and economic requirements of DC circuit breakers for large-scale DC power grid construction.

Description

Technical Field

[0001] The present invention relates to the technical field of power electronics, and in particular to a voltage-regulated oscillating DC circuit breaker and a control method thereof. Background Art

[0002] High-voltage DC (HVDC) circuit breakers are a core component of multi-terminal DC (DC) grid construction. Their technical and economic feasibility directly impacts the flexibility and widespread application of DC grids. Currently, there are two main approaches to HVDC circuit breakers: a hybrid DC circuit breaker, in which a mechanical switch conducts current during normal operation. In the event of a fault, auxiliary commutation branches are used to divert the current to a parallel-connected power electronic device branch, which then interrupts the current. This type of breaker offers low conduction losses and fast interruption speeds, but requires a large number of fully controlled devices connected in series and parallel, resulting in high costs. The other type is a mechanical DC circuit breaker, which uses reverse current injection from a pre-charged capacitor to extinguish the arc on the mechanical switch, ultimately completing the DC interruption. This requires large capacitors and high voltages, and faces design challenges in terms of cost-effectiveness and reliability of the high-voltage trigger switch. However, existing solutions, which employ either hybrid or mechanical DC circuit breakers, struggle to simultaneously meet the dual technical and economic requirements of DC circuit breakers for large-scale DC grid construction. This limits the large-scale application of HVDC circuit breakers in multi-terminal DC (DC) grids. Summary of the Invention

[0003] Therefore, the technical problem to be solved by the present invention is to overcome the defect of the DC circuit breaker in the prior art that it is difficult to meet the dual requirements of technical and economic efficiency, thereby providing a voltage-regulated oscillating DC circuit breaker and a control method thereof.

[0004] In order to achieve the above object, the present invention provides the following technical solutions:

[0005] In a first aspect, an embodiment of the present invention provides a voltage-regulated oscillating DC circuit breaker, comprising: a flow branch, an energy consumption branch, and a disconnecting branch, wherein the flow branch is connected in series to the power line; the disconnecting branch is connected in parallel with the flow branch; the energy consumption branch has one end connected to one end of the flow branch and one end of the disconnecting branch, respectively, and the other end connected to the disconnecting branch; when the power line is not faulty, the flow branch conducts the DC load current; when a fault occurs in the power line, the operating state of the disconnecting branch is controlled, and the disconnecting branch generates an oscillating current with an amplitude equal to and an opposite direction to the fault current, so that the flow branch is reliably shut down, and the energy consumption branch ultimately consumes the fault current energy.

[0006] Preferably, the disconnecting branch includes: a controlled voltage conversion circuit and an oscillation circuit, wherein one end of the controlled voltage conversion circuit is connected to one end of the current-passing branch, the other end of the controlled voltage conversion circuit is connected to one end of the oscillation circuit, and the other end of the oscillation circuit is connected to the other end of the current-passing branch; the controlled voltage conversion circuit is used to boost the AC voltage and rectify the output DC voltage; the oscillation circuit is used to receive the DC voltage output by the controlled voltage conversion unit and generate an oscillating current.

[0007] Preferably, the controlled voltage conversion circuit includes: a rectifier isolation circuit and a square wave voltage conversion circuit, wherein the rectifier isolation circuit and the square wave voltage conversion circuit are connected in series.

[0008] Preferably, the rectification and isolation circuit includes: an isolation circuit and a rectification circuit, wherein the isolation circuit and the rectification circuit are connected in series.

[0009] Preferably, the square wave voltage conversion circuit includes: a bridge square wave conversion circuit or a module cascade square wave conversion circuit, wherein the controllable bridge arm unit of the bridge square wave conversion circuit includes multiple first sub-module units; the module cascade square wave conversion circuit includes multiple cascaded second sub-module units.

[0010] Preferably, the through-current branch comprises at least one mechanical switch.

[0011] In a second aspect, an embodiment of the present invention provides a control method for a voltage-regulated oscillating DC circuit breaker. Based on the voltage-regulated oscillating DC circuit breaker of the first aspect, the control method includes: real-time monitoring of whether the power lines connected to the two ends of the flow branch are faulty; when a fault occurs in the power line connected to at least one end of the flow branch, the breaking branch generates an oscillating current with an amplitude equal to and opposite to the fault current by controlling the operating state of the breaking branch, so that the flow branch is reliably shut down.

[0012] Preferably, the control method of the voltage-regulated oscillating DC circuit breaker further comprises: pre-charging the disconnecting branch before the conducting branch is turned on.

[0013] Preferably, by controlling the operating state of the disconnecting branch, the disconnecting branch generates an oscillating current with an amplitude equal to and a direction opposite to the fault current, so that the flow branch is reliably shut down, including: controlling the mechanical switch of the flow branch to open; when the mechanical switch reaches a designed opening distance sufficient to withstand the transient breaking voltage, controlling the sub-module unit of the disconnecting branch to periodically open and close until an oscillating current with an amplitude equal to and a direction opposite to the short-circuit current is generated on the controlled oscillation unit, the mechanical switch current passes through zero, and the arc extinction and breaking are completed.

[0014] Preferably, the control method of the voltage-regulated oscillating DC circuit breaker further comprises: when the voltage of the oscillating capacitor reaches a preset protection voltage threshold, the energy consumption branch is turned on to consume the energy of the fault current.

[0015] The technical solution of the present invention has the following advantages:

[0016] The voltage-regulated oscillating DC circuit breaker provided by the present invention includes: a flow branch, an energy-consuming branch, and a disconnecting branch, wherein the flow branch is connected in series with the power line; the disconnecting branch is connected in parallel with the flow branch; the energy-consuming branch has one end connected to one end of the flow branch and one end of the disconnecting branch, respectively, and the other end connected to the disconnecting branch; when the power line is not faulty, the flow branch conducts the DC load current; when a fault occurs in the power line, the operating state of the disconnecting branch is controlled so that the disconnecting branch generates an oscillating current with an amplitude equal to and in the opposite direction to the fault current, thereby reliably shutting off the flow branch and ultimately consuming the energy of the fault current by the energy-consuming branch. When a fault occurs in the power line, by controlling the disconnecting branch to oscillate and generate an oscillating current, and continuously increasing the amplitude of the oscillating current until an oscillating current with an amplitude equal to and in the opposite direction to the fault current is generated, the circuit breaker can achieve multiple consecutive maximum current interruptions in a short period of time, greatly improving the flexibility and availability of the circuit breaker. It meets the dual technical and economic requirements of DC circuit breakers for large-scale DC power grid construction.

[0017] The control method for a voltage-regulated oscillating DC circuit breaker provided by the present invention includes: real-time monitoring of whether the power lines connected to the two ends of the flow branch are faulty; when a fault occurs in the power line connected to at least one end of the flow branch, the operating state of the disconnecting branch is controlled so that the disconnecting branch generates an oscillating current with an amplitude equal to and in the opposite direction to the fault current, thereby reliably shutting off the flow branch. When a fault occurs in the power line, the disconnecting branch is controlled to oscillate and generate an oscillating current, and the amplitude of the oscillating current is continuously increased until an oscillating current with an amplitude equal to and in the opposite direction to the fault current is generated. This allows the circuit breaker to continuously interrupt the maximum current several times in a short period of time, greatly improving the flexibility and availability of the circuit breaker. This method meets the dual technical and economic requirements of DC circuit breakers for large-scale DC power grid construction. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0019] Figure 1A principle block diagram of a specific example of an oscillating DC circuit breaker provided in an embodiment of the present invention;

[0020] Figure 2 A principle block diagram of another specific example of an oscillating DC circuit breaker provided by an embodiment of the present invention;

[0021] Figure 3 A principle block diagram of another specific example of an oscillating DC circuit breaker provided by an embodiment of the present invention;

[0022] Figure 4 A circuit structure diagram of a specific example of a rectifier isolation circuit provided in an embodiment of the present invention;

[0023] Figure 5 A circuit structure diagram of a specific example of a full-bridge-to-bridge square wave conversion circuit provided in an embodiment of the present invention;

[0024] Figure 6 A circuit structure diagram of a specific example of a half-bridge to bridge square wave conversion circuit provided in an embodiment of the present invention;

[0025] Figure 7 A circuit structure diagram of a specific example of a first submodule unit provided in an embodiment of the present invention;

[0026] Figure 8 A circuit structure diagram of a specific example of a second submodule unit provided in an embodiment of the present invention;

[0027] Figure 9 A flowchart of a specific example of a control method for an oscillating DC circuit breaker provided by an embodiment of the present invention;

[0028] Figure 10 A circuit structure diagram of a specific example of an oscillating DC circuit breaker provided in an embodiment of the present invention;

[0029] Figure 11 A specific flow diagram of load current provided by an embodiment of the present invention;

[0030] Figure 12 This is an operating state diagram of an oscillating DC circuit breaker provided by an embodiment of the present invention;

[0031] Figure 13 Another specific flow diagram of load current provided by an embodiment of the present invention;

[0032] Figure 14 A specific flow diagram of the oscillating current provided by an embodiment of the present invention;

[0033] Figure 15 Another specific flow diagram of the oscillating current provided by an embodiment of the present invention;

[0034] Figure 16 Another specific flow diagram of the oscillating current provided by an embodiment of the present invention;

[0035] Figure 17 Another specific flow diagram of the oscillating current provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0036] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0037] In the description of the present invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate and simplify the description of the present invention. They are not intended to indicate or imply that the devices or components referred to must have, be constructed, or operate in a specific orientation, and therefore should not be construed as limitations on the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0038] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "installed," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; internal connections between two components; wireless connections or wired connections. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0039] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0040] The embodiment of the present invention provides a voltage-regulated oscillating DC circuit breaker that can be used in high-voltage DC systems. Figure 1As shown, the oscillating DC circuit breaker includes: a flow branch 1, an energy-consuming branch 2, and a disconnecting branch 3. The flow branch 1 is connected in series with the power line; the disconnecting branch 3 is connected in parallel with the flow branch 1; and the energy-consuming branch 2 has one end connected to one end of the flow branch 1 and one end of the disconnecting branch 3, respectively, and the other end connected to the disconnecting branch 3. When the power line is not faulty, the flow branch 1 conducts the DC load current. When a fault occurs in the power line, the operating state of the disconnecting branch 3 is controlled, and the disconnecting branch 3 generates an oscillating current with an amplitude equal to and a direction opposite to the fault current, thereby reliably shutting off the flow branch 1. Ultimately, the energy-consuming branch 2 dissipates the fault current energy.

[0041] In a specific embodiment, if Figure 1 As shown, when no faults occur on either the converter or line side, the pass-through branch 1 is in the on state, enabling the transmission of DC load current between the converter and line sides and pre-charging the disconnecting branch 3 before the DC circuit breaker is activated. When a fault occurs on the converter or line side, such as a short circuit, the pass-through branch 1 is first disconnected. By controlling the operating state of the disconnecting branch 3, the disconnecting branch 3 oscillates and generates an oscillating current. During this process, the amplitude of the oscillating current continuously increases until the disconnecting branch 3 generates an oscillating current with an amplitude equal to and in the opposite direction to the fault current. This oscillating current, with an amplitude equal to and in the opposite direction to the fault current, is then injected into the pass-through branch 1, causing the mechanical switch of the pass-through branch 1 to extinguish the arc, resulting in reliable disconnection. Furthermore, the fault current is transferred to the disconnecting branch 3, and the fault current will charge the disconnecting branch 3. When the charging voltage rises to the preset protection voltage threshold, the energy-consuming branch 2 is turned on, and the fault current is transferred to the energy-consuming branch 2 and absorbed by it until it crosses zero, and the system resumes normal operation.

[0042] In this embodiment of the present invention, when a power line fault occurs, the oscillating DC circuit breaker can achieve bidirectional, rapid interruption of DC current with low operating losses, eliminates the need for a water cooling system, and possesses a strong overload capacity, capable of interrupting currents up to tens of kA, meeting the application requirements of DC transmission and distribution systems. By controlling the oscillation of the interrupting branch 3 and generating an oscillating current, and continuously increasing the amplitude of the oscillating current until an oscillating current with equal amplitude and opposite direction to the fault current is generated, the circuit breaker can achieve multiple consecutive interruptions of the maximum current in a short period of time, significantly improving the circuit breaker's flexibility and availability.

[0043] The voltage-regulated oscillating DC circuit breaker provided by the present invention includes: a flow branch, an energy-consuming branch, and a disconnecting branch, wherein the flow branch is connected in series with the power line; the disconnecting branch is connected in parallel with the flow branch; the energy-consuming branch has one end connected to one end of the flow branch and one end of the disconnecting branch, respectively, and the other end connected to the disconnecting branch; when the power line is not faulty, the flow branch conducts the DC load current; when a fault occurs in the power line, the operating state of the disconnecting branch is controlled so that the disconnecting branch generates an oscillating current with an amplitude equal to and in the opposite direction to the fault current, thereby reliably shutting off the flow branch and ultimately consuming the energy of the fault current by the energy-consuming branch. When a fault occurs in the power line, by controlling the disconnecting branch to oscillate and generate an oscillating current, and continuously increasing the amplitude of the oscillating current until an oscillating current with an amplitude equal to and in the opposite direction to the fault current is generated, the circuit breaker can achieve multiple consecutive maximum current interruptions in a short period of time, greatly improving the flexibility and availability of the circuit breaker. It meets the dual technical and economic requirements of DC circuit breakers for large-scale DC power grid construction.

[0044] In one embodiment, if Figure 2 As shown, the disconnecting branch 3 includes: a controlled voltage conversion circuit 31 and an oscillation circuit 32, wherein one end of the controlled voltage conversion circuit 31 is connected to one end of the flow branch 1, the other end of the controlled voltage conversion circuit 31 is connected to one end of the oscillation circuit 32, and the other end of the oscillation circuit 32 is connected to the other end of the flow branch 1; the controlled voltage conversion circuit 31 is used to boost the AC voltage and rectify the output DC voltage; the oscillation circuit 32 is used to receive the DC voltage output by the controlled voltage conversion unit and generate an oscillating current.

[0045] In a specific embodiment, if Figure 3 As shown, the controlled voltage conversion circuit 31 includes: a rectifier isolation circuit 311 and a square wave voltage conversion circuit 312, wherein the rectifier isolation circuit 311 and the square wave voltage conversion circuit 312 are connected in series. The rectifier isolation circuit 311 is used to boost the AC voltage and rectify the output DC voltage and to achieve voltage isolation between the high potential on the rectifier side and the ground potential; the square wave voltage conversion circuit 312 is used to convert the DC current output by the rectifier isolation circuit 311 into square wave voltages of different levels and then output them to the oscillation circuit 32. In the embodiment of the present invention, as Figure 4 As shown, the rectifier isolation circuit 311 includes: an isolation circuit 3111 and a rectifier circuit 3112, wherein the isolation circuit 3111 and the rectifier circuit 3112 are connected in series. In other embodiments, as Figure 4 As shown, the rectifying and isolating circuit 311 further includes a boosting circuit 3113 , and the boosting circuit 3113 is located between the isolating circuit 3111 and the rectifying circuit 3112 .

[0046] Specifically, if Figure 4As shown, isolation circuit 3111 is composed of an isolation transformer. Its primary side input is a 220V / 380V AC voltage. After isolation between the primary and secondary sides, it outputs an AC voltage through the secondary side. Boost circuit 3113 receives the AC voltage output from the isolation transformer on its primary side, and outputs the boosted AC voltage at the target value on the secondary side. If a lower boost ratio is required, isolation circuit 3111 and boost circuit 3113 can be integrated into a single isolated boost circuit, implemented using a single isolated boost transformer. Rectifier circuit 3112, which can be a diode-controlled bridge rectifier, rectifies the AC voltage output from the secondary side of boost circuit 3113 into a target DC voltage and outputs it to square wave voltage conversion circuit 312.

[0047] In the embodiment of the present invention, the voltage level of the controlled voltage conversion circuit 31 is much lower than the rated voltage level of the DC circuit breaker. Depending on the target breaking current, it can be designed to be 2%-5% of the rated voltage of the circuit breaker. The number of power electronic components used can be saved by more than 80% compared with a hybrid DC circuit breaker of the same voltage level, significantly improving the economic efficiency of the DC circuit breaker.

[0048] In addition, according to the requirements of specific breaking performance parameters, the controlled voltage source only needs to use a power electronic unit with a rated voltage level of about 2%-6%, which greatly reduces the cost of the circuit breaker.

[0049] In one embodiment, the oscillation circuit 32 is an LC oscillation circuit including an oscillation capacitor C and an oscillation inductor L.

[0050] In a specific embodiment, the energy consumption branch 2 is connected in parallel to both ends of the oscillation capacitor C. In the embodiment of the present invention, the energy consumption branch 2 may also be connected in parallel to both ends of the disconnection branch 3 .

[0051] In one embodiment, the square wave voltage conversion circuit 312 includes: a bridge square wave conversion circuit or a module cascade square wave conversion circuit, wherein the controllable bridge arm unit of the bridge square wave conversion circuit includes multiple first sub-module units; the module cascade square wave conversion circuit includes multiple cascaded second sub-module units.

[0052] In a specific embodiment, the square wave voltage conversion circuit 312 can be divided into a bridge square wave conversion circuit and a module cascade square wave conversion circuit according to its structure. The bridge square wave conversion circuit can be divided into a full bridge type and a half bridge type according to the number of controllable bridge arm units. Figure 5 As shown in FIG, the full-bridge type-bridge square wave conversion circuit is composed of 4 controllable bridge arm units and 1 set of source capacitors. Figure 6 As shown, the half-bridge type-bridge square wave conversion circuit is composed of two controllable bridge arm units and two sets of source capacitors. The bridge square wave conversion circuit outputs the target voltage by periodically controlling the on and off of the bridge arm units. The controllable bridge arm unit in the bridge square wave conversion circuit can be composed of multiple SM1 type-submodule units (i.e., the first submodule unit) connected in series, as shown in FIG. Figure 7 As shown, the first submodule unit includes an IGBT module based on IGBT (IGCT), an IGBT-Diode-HB module and an IGBT-HB module. The module cascade square wave conversion circuit is composed of a plurality of SM2 type submodule units (i.e., the second submodule units) cascaded, as shown in FIG. Figure 8 As shown, the second submodule unit includes an IGBT-FB module, an IGBT-MB module, and an IGBT-CD module based on IGBT (IGCT).

[0053] In the embodiment of the present invention, the source capacitor or submodule capacitor in the square wave voltage conversion circuit 312 carries voltage for a long time, which can provide control energy for power electronic devices and fast mechanical switch control devices, eliminating the need for independent energy transmission devices, simplifying circuit breaker assembly components, and reducing equipment costs.

[0054] In one embodiment, the through-current branch 1 comprises at least one mechanical switch UMS.

[0055] In a specific embodiment, the flow branch 1 is composed of at least one group of mechanical switches UMS. The mechanical switch UMS needs to withstand the system load current and short-term overcurrent, and also needs to withstand the transient overvoltage generated by the DC circuit breaker. Based on the above-mentioned electrical stress, the fast mechanical switch UMS in the flow branch 1 can adopt a multi-break series connection, a multi-branch parallel connection, and a multi-break series-parallel connection. In the embodiment of the present invention, the flow branch 1 has low loss and does not require water cooling. When the power line is not faulty, the fast mechanical switch is in the on state, and the DC system pre-charges the controlled oscillation unit, thereby realizing self-energy extraction of the controlled oscillation unit, saving external power supply equipment, and improving the reliability of the DC circuit breaker. In addition, since only a small number of power electronic devices are used, the purpose of transmitting DC load current and breaking bidirectional short-circuit current and fast reclosing can be achieved.

[0056] In one embodiment, the energy dissipation branch 2 includes an MOV lightning arrester. In other embodiments, the energy dissipation branch 2 may also be a structure composed of a nonlinear resistor or a lightning arrester connected in series or parallel, which is not specifically limited here.

[0057] The embodiment of the present invention provides a control method for a voltage-regulated oscillating DC circuit breaker. Based on the above-mentioned oscillating DC circuit breaker, as shown in FIG. Figure 9 As shown, the control method includes the following steps:

[0058] Step S1: Real-time monitoring of whether the power lines connected to the two ends of the flow branch are faulty.

[0059] Step S2: When a fault occurs in the power line connected to at least one end of the flow branch, the disconnecting branch generates an oscillating current with the same amplitude and opposite direction as the fault current by controlling the operating state of the disconnecting branch, so that the flow branch is reliably shut down.

[0060] In a specific embodiment, if Figure 10 As shown, a rectification isolation circuit based on an isolation boost integration and a diode full-bridge rectifier circuit and a module cascade square wave voltage conversion circuit based on an IGBT-MB module are used as examples for description.

[0061] Before the current branch is turned on, the disconnect branch is precharged. Specifically, before the oscillating DC circuit breaker is put into operation, switches K0, K1, and K2 are closed, and the secondary side of the transformer is rectified to charge the MB module capacitor C SM1 and C SM2 Charging, current flows as follows Figure 11 As shown. When the MB module capacitor C SM1 and C SM2 After charging to the target voltage, open switches K0, K1, and K2. The circuit breaker is in the off state before the main branch fast mechanical switch UMS is turned on. Figure 12 As shown, after UMS is turned on, the load current flows through the main branch, as shown in Figure 13 As shown, the circuit breaker is put into operation.

[0062] When a fault occurs on the converter side or the line side, such as a short circuit fault, the flow branch is disconnected first. During this process, the amplitude of the oscillating current continues to increase until the disconnected branch generates an oscillating current with an amplitude equal to and opposite to the fault current. The oscillating current with an amplitude equal to and opposite to the fault current is injected into the flow branch, causing the mechanical switch of the flow unit to extinguish the arc and disconnect reliably.

[0063] In one embodiment, by controlling the operating state of the disconnecting branch, the disconnecting branch generates an oscillating current with an amplitude equal to and a direction opposite to the fault current, so that the current-carrying branch is reliably shut off, including the following steps:

[0064] Step S21: Control the mechanical switch of the flow branch to open.

[0065] Step S22: When the mechanical switch reaches the designed opening distance sufficient to withstand the transient breaking voltage, the sub-module unit in the breaking branch is controlled to be periodically opened and closed until an oscillating current with the same amplitude and opposite direction as the short-circuit current is generated on the controlled oscillation unit, and the mechanical switch current passes through zero, completing the arc extinction and breaking.

[0066] In a specific embodiment, when a fault occurs on the line side of the DC circuit breaker, the DC circuit breaker receives a trip command or overcurrent protection is activated, and the main branch fast mechanical switch UMS is opened. When the mechanical switch UMS is opened to a sufficient distance, the MB submodule in the square wave voltage conversion circuit is triggered, and the control submodule IGBT is periodically turned on and off. Among them, the MB module capacitor C SM1 and C SM2, discharges to the loop composed of fast mechanical switch UMS, oscillation capacitor C and inductor L to generate oscillating current. Figure 14 As shown, at this time, T2, T4, and T6 are turned on, and T1, T3, and T5 remain turned off. The MB submodule outputs a 1-fold forward voltage (+UCsm) to the loop in a clockwise direction, generating an oscillating current with a 1-fold amplitude in the same direction as the voltage in the excitation loop.

[0067] In the next control cycle, T2, T4, and T6 are turned off, and T1, T3, and T5 are turned on. The MB submodule outputs a negative voltage (-2UCsm) twice the value to the circuit in a counterclockwise direction, and an oscillating current with an amplitude twice the value of the voltage is generated in the excitation circuit. At this time, the oscillating current generated by the excitation in the circuit has reversed, and the amplitude is further increased under the excitation of the power supply. Figure 15 shown.

[0068] During the periodic output voltage of the square wave voltage conversion circuit, when the direction of the oscillating current generated by the excitation is opposite to the fault current and the amplitude is equal to the fault current, the fault current crosses the zero point and the arc of the mechanical switch is extinguished. The fault current is transferred from the flow branch to the disconnect branch. At this time, all IGBTs of the MB submodule remain turned off, and the current flows through the anti-parallel diode T6 and the capacitor C SM1 , T4 anti-parallel diode, capacitor C SM2 , and the T4 anti-parallel diode flows, the current charges the oscillating capacitor C of the disconnect branch, and the voltage of the oscillating capacitor C increases to the MOV action voltage, such as Figure 16 shown.

[0069] Furthermore, when the voltage of the oscillating capacitor C of the disconnecting branch reaches the MOV action voltage, the fault current is commutated to the energy-consuming branch, the MOV absorbs the fault current energy, and completes the fault current breaking, as shown in FIG. Figure 17 shown.

[0070] It should be noted that the above method and the accompanying drawings are only described by taking the case where a short circuit fault occurs in the power line on the line side and the current flows from the converter side to the line side as an example. If the current flows from the line side to the converter side, the working principle of the DC circuit breaker is the same as above.

[0071] The control method for a voltage-regulated oscillating DC circuit breaker provided by the present invention includes: real-time monitoring of whether the power lines connected to the two ends of the flow branch are faulty; when a fault occurs in the power line connected to at least one end of the flow branch, the operating state of the disconnecting branch is controlled so that the disconnecting branch generates an oscillating current with an amplitude equal to and in the opposite direction to the fault current, thereby reliably shutting off the flow branch. When a fault occurs in the power line, the disconnecting branch is controlled to oscillate and generate an oscillating current, and the amplitude of the oscillating current is continuously increased until an oscillating current with an amplitude equal to and in the opposite direction to the fault current is generated. This allows the circuit breaker to continuously interrupt the maximum current several times in a short period of time, greatly improving the flexibility and availability of the circuit breaker. This method meets the dual technical and economic requirements of DC circuit breakers for large-scale DC power grid construction.

[0072] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will appreciate that other variations or modifications can be made based on the above description. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. A voltage-regulated oscillating DC circuit breaker, characterized in that: include: Flow branches, energy consumption branches and disconnection branches, among which, A flow branch, which is connected in series with the power line; a disconnecting branch connected in parallel with the through-flow branch; an energy-consuming branch, one end of which is respectively connected to one end of the through-flow branch and one end of the disconnecting branch, and the other end of which is connected to the disconnecting branch; When the power line is not faulty, the flow branch conducts the DC load current; when a fault occurs in the power line, the operation state of the disconnecting branch is controlled so that the disconnecting branch generates an oscillating current with an amplitude equal to and a direction opposite to the fault current, so that the flow branch is reliably shut off, and the energy of the fault current is ultimately consumed by the energy-consuming branch; The disconnecting branch includes: a controlled voltage conversion circuit and an oscillation circuit, wherein: One end of the controlled voltage conversion circuit is connected to one end of the current-passing branch, the other end of the controlled voltage conversion circuit is connected to one end of the oscillation circuit, and the other end of the oscillation circuit is connected to the other end of the current-passing branch; The controlled voltage conversion circuit is used to boost the AC voltage and rectify it to output a DC voltage; The oscillation circuit is used to receive the DC voltage output by the controlled voltage conversion unit and generate an oscillating current; The controlled voltage conversion circuit includes: a rectifier isolation circuit and a square wave voltage conversion circuit, wherein the rectifier isolation circuit and the square wave voltage conversion circuit are connected in series; The square wave voltage conversion circuit comprises: a module cascade square wave conversion circuit, wherein the module cascade square wave conversion circuit comprises a plurality of cascaded second submodule units; The second submodule unit includes an IGBT-MB module; After the DC circuit breaker fails, in the first control cycle, IGBT modules T2, IGBT modules T4, and IGBT modules T6 are turned on, IGBT modules T1, IGBT modules T3, and IGBT modules T5 remain off, and the MB module capacitor C SM1 and C SM2 , discharges to the loop formed by the fast mechanical switch UMS, the oscillation capacitor C and the inductor L to generate an oscillating current. The MB submodule outputs a 1x forward voltage (+UCsm) to the loop in a clockwise direction, exciting the loop to generate an oscillating current with an amplitude of 1x the voltage in the same direction. In the next control cycle, IGBT modules T2, T4, and T6 are turned off, IGBT modules T1, T3, and T5 are turned on, and the MB module capacitor C SM1 and C SM2 , discharges into the loop composed of the fast mechanical switch UMS, the oscillation capacitor C and the inductor L to generate an oscillating current. The MB submodule outputs a negative voltage (-2UCsm) twice the value to the loop in a counterclockwise direction, and generates an oscillating current with an amplitude twice that of the voltage in the same direction in the excitation loop.

2. The voltage-regulated oscillating DC circuit breaker according to claim 1, characterized in that: The rectifier isolation circuit includes an isolation circuit and a rectifier circuit, wherein the isolation circuit and the rectifier circuit are connected in series.

3. The voltage-regulated oscillating DC circuit breaker according to claim 1, characterized in that: The square wave voltage conversion circuit includes: a bridge square wave conversion circuit, wherein the controllable bridge arm unit of the bridge square wave conversion circuit includes a plurality of first submodule units.

4. The voltage-regulated oscillating DC circuit breaker according to claim 3, characterized in that: The flow branch includes at least one mechanical switch.

5. A control method for a voltage-regulated oscillating DC circuit breaker, characterized in that: Based on the voltage-regulated oscillating DC circuit breaker according to any one of claims 1 to 4, the control method comprises: real-time monitoring of whether the power lines connected to both ends of the current-carrying branch are faulty; When a fault occurs in the power line connected to at least one end of the flow branch, the operation state of the disconnecting branch is controlled so that the disconnecting branch generates an oscillating current with an amplitude equal to and opposite to the fault current, so that the flow branch is reliably shut down; The method of controlling the operating state of the disconnecting branch so that the disconnecting branch generates an oscillating current having an amplitude equal to and a direction opposite to the fault current, so that the flow branch is reliably shut down, includes: Controlling the opening of the mechanical switch of the through-current branch; When the mechanical switch reaches a designed opening distance sufficient to withstand the transient breaking voltage, the submodule unit in the breaking branch is controlled to be periodically opened and closed until an oscillating current with an amplitude equal to and opposite to the short-circuit current is generated on the controlled oscillation unit, and the mechanical switch current passes through zero, completing the arc extinction and breaking. In the first control cycle, IGBT modules T2, T4, and T6 are turned on, while IGBT modules T1, T3, and T5 are kept off. The MB module capacitor C SM1 and C SM2 , discharges to the loop formed by the fast mechanical switch UMS, the oscillation capacitor C and the inductor L to generate an oscillating current. The MB submodule outputs a 1x forward voltage (+UCsm) to the loop in a clockwise direction, exciting the loop to generate an oscillating current with an amplitude of 1x the voltage in the same direction. In the next control cycle, IGBT modules T2, T4, and T6 are turned off, IGBT modules T1, T3, and T5 are turned on, and the MB module capacitor C SM1 and C SM2 , discharges into the loop composed of the fast mechanical switch UMS, the oscillation capacitor C and the inductor L to generate an oscillating current. The MB submodule outputs a negative voltage (-2UCsm) twice the value to the loop in a counterclockwise direction, and generates an oscillating current with an amplitude twice that of the voltage in the same direction in the excitation loop.

6. The control method of a voltage-regulated oscillating DC circuit breaker according to claim 5, characterized in that: Also includes: Before the flow branch is turned on, the disconnect branch is pre-charged.

7. The control method of a voltage-regulated oscillating DC circuit breaker according to claim 5, characterized in that: Also includes: When the voltage of the oscillating capacitor reaches the preset protection voltage threshold, the energy consumption branch is turned on to consume the energy of the fault current.

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