Graded current-limiting type bidirectional direct-current solid-state circuit breaker circuit and circuit breaker

Abstract

The invention discloses a graded current-limiting type bidirectional direct-current solid-state circuit breaker circuit and a circuit breaker, and relates to the technical field of electronic circuits or other related fields, the circuit breaker circuit comprises a through-current branch configured in a main loop of a target direct-current system, and the through-current branch at least comprises a forward conduction switch and a reverse conduction switch; the commutation branch is connected with the through-flow branch in parallel and is used for absorbing fault current in the main loop under the condition that the main loop breaks down and generating energy consumption break-over voltage based on the fault current; and the energy consumption branch circuit is connected in parallel with the through-flow branch circuit and is used for switching the branch circuit state to be conducted, absorbing the fault current and consuming the electric energy of the system under the condition that the energy consumption conduction voltage is detected, and switching the branch circuit state to be switched off under the condition that the fault current is reduced to 0. The technical problem that the current limiting speed and the reliability of a switching device cannot be considered at the same time in the existing circuit breaker in the related technology is solved.

Description

Technical Field

[0001] This invention relates to the field of electronic circuit technology, and more specifically, to a graded current-limiting bidirectional DC solid-state circuit breaker circuit and circuit breaker. Background Technology

[0002] In recent years, with the widespread application of new energy sources such as wind and solar power in DC microgrids, the safe operation of DC microgrids faces greater challenges. Low damping characteristics can lead to large short-circuit currents, rapid fault propagation, and even system-wide power outages. Therefore, it is necessary to adopt DC circuit breakers with better safety and reliability to improve the fault protection capabilities of DC microgrids.

[0003] When a short-circuit fault occurs in a DC microgrid system, the short-circuit current rises rapidly. Traditional mechanical DC circuit breakers, due to their internal structure, have prolonged turning-off time due to spring resistance, and are not strong in handling large currents. They also generate an electric arc during turning off, requiring the use of an arc-extinguishing device. Therefore, the entire device is bulky, time-consuming, and has a short electrical life, making it increasingly unsuitable for applications requiring rapid response. When a short-circuit fault occurs, there are two common methods in existing technology to interrupt the short-circuit current.

[0004] The first method is to use a series metal oxide resistor to block the short-circuit current of the faulty branch. This method can quickly block the fault current, but it will generate a large peak voltage across the switch, thus affecting the reliability of the switch. The second method is to connect a large capacitor in series in the faulty branch and a resistor in series to limit the current, thereby changing the blocking characteristics of the branch. By disconnecting the bypass switch across the current-limiting resistor, the current-limiting resistor is continuously connected to the faulty branch, thereby limiting the short-circuit current to a small level. This method can effectively suppress overvoltage, but it requires a high voltage withstand level for the capacitor and also has problems such as slow mechanical switch action, poor consistency, and prolonged switch breaking time, which are not conducive to the rapid operation of DC circuit breakers.

[0005] There is currently no effective solution to the above problems. Summary of the Invention

[0006] This invention provides a graded current-limiting bidirectional DC solid-state circuit breaker circuit and circuit breaker, which at least solves the technical problem in the related art that existing circuit breakers cannot simultaneously achieve current-limiting speed and switching device reliability.

[0007] According to one aspect of the present invention, a graded current-limiting bidirectional DC solid-state circuit breaker circuit is provided, comprising: a current-carrying branch configured in the main circuit of a target DC system, wherein the current-carrying branch includes at least a forward-conducting switch and a reverse-conducting switch; a commutation branch connected in parallel with the current-carrying branch, used to absorb fault current in the main circuit and generate an energy-dissipating conduction voltage based on the fault current in the event of a fault in the main circuit; and an energy-dissipating branch connected in parallel with the current-carrying branch, used to switch the branch state to conduction when the energy-dissipating conduction voltage is detected, absorb the fault current and consume system power, and switch the branch state to cut off when the fault current is reduced to 0.

[0008] Furthermore, the forward conduction switch in the current-carrying branch includes a first field-effect transistor and a forward current-carrying diode, and the reverse conduction switch includes a second field-effect transistor and a reverse current-carrying diode. The first field-effect transistor and the second field-effect transistor are connected in reverse cascade, with the first field-effect transistor and the reverse current-carrying diode connected in parallel with opposite polarity, and the second field-effect transistor and the forward current-carrying diode connected in parallel with opposite polarity.

[0009] Further, the converter branch includes: a converter bridge, wherein the converter bridge includes 4 bridge arm branches and 1 diagonal branch, and the conduction direction of each bridge arm branch is opposite to that of the adjacent bridge arm branch; a segmented current limiting module, configured in the diagonal branch of the converter bridge, wherein the segmented current limiting module is used to switch N segmented modes based on the current value of the fault current, and absorb the fault current based on different segmented modes, where N is a positive integer greater than or equal to 2.

[0010] Furthermore, the segmented current limiting module includes N segmented current limiting groups, wherein the N segmented current limiting groups are connected in series, and each segmented current limiting group is used to switch one segmented mode.

[0011] Furthermore, for the first N-1 segmented current limiting groups, each segmented current limiting group includes: a current limiting resistor and a switching device connected in parallel with the current limiting resistor; for the Nth segmented current limiting group, each segmented current limiting group includes: a series combination of the current limiting resistor and a buffer capacitor, and the switching device connected in parallel with the series combination, wherein the buffer capacitor is used to generate the energy-consuming conduction voltage.

[0012] Furthermore, the switching device may be selected from any of the following types: insulated gate bipolar transistor, thyristor, or metal-oxide-semiconductor field-effect transistor.

[0013] Furthermore, the bridge arm branch in the converter bridge includes at least a diode, wherein the diode is used to control the conduction direction of the bridge arm branch.

[0014] Furthermore, the energy-consuming branch includes at least one energy-consuming element, wherein the energy-consuming element is used to absorb the fault current and consume the system power when the energy-consuming branch is turned on.

[0015] Furthermore, the energy-consuming element may be selected from one of the following: a metal oxide surge arrester, a power diode, a metal oxide thermal release device, a ceramic zirconia varistor, or a transient voltage suppressor.

[0016] According to another aspect of the present invention, a circuit breaker is also provided, comprising the graded current-limiting bidirectional DC solid-state circuit breaker circuit described in any one of the preceding embodiments.

[0017] The proposed graded current-limiting bidirectional DC solid-state circuit breaker circuit includes a converter branch and an energy-dissipating branch connected in parallel with the current-carrying branch in the main circuit. Under normal and stable operation of the target DC system, both the converter branch and the energy-dissipating branch are in the off state. If a fault occurs in the target DC system, after the current-carrying branch is cut off, the converter branch is turned on first, taking over the bidirectional fault current in the target DC system, consuming a portion of the system power, reducing the fault current, and generating a voltage across the two ends that enables the energy-dissipating branch to conduct, thereby forcing the energy-dissipating branch to take over the fault current and dissipate the remaining system power, thus completing the main circuit disconnection. Compared to existing technologies, this invention can quickly transfer the fault current in the main circuit by using the commutation branch when a fault occurs, avoiding damage to the switching devices in the branch due to the sudden increase in overcurrent caused by the untimely disconnection of the current-carrying branch, thus protecting the reliability of the switching devices. After the fault current is transferred, the fault current is used to conduct the energy-dissipating branch to further dissipate the system energy and reduce the fault current. Overall, it can also ensure the current limiting speed, thereby solving the technical problem that existing circuit breakers in related technologies cannot take into account both the current limiting speed and the reliability of the switching devices. Attached Figure Description

[0018] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this application, illustrate exemplary embodiments of the invention and, together with their description, serve to explain the invention and do not constitute an undue limitation thereof. In the drawings:

[0019] Figure 1 This is a schematic diagram of an optional graded current-limiting bidirectional DC solid-state circuit breaker according to an embodiment of the present invention;

[0020] Figure 2 This is a schematic diagram of an optional bidirectional flow branch according to an embodiment of the present invention;

[0021] Figure 3This is a schematic diagram of an optional bidirectional conduction converter branch according to an embodiment of the present invention;

[0022] Figure 4 This is a schematic diagram of the structure of an optional segmented current limiting module according to an embodiment of the present invention;

[0023] Figure 5 This is a topology diagram of an optional segmented current-limiting bidirectional DC solid-state circuit breaker according to an embodiment of the present invention;

[0024] Figure 6 This is a schematic diagram of the current path during the steady-state current-carrying stage of an optional segmented current-limiting bidirectional DC solid-state circuit breaker circuit according to an embodiment of the present invention.

[0025] Figure 7 This is a schematic diagram of the current path during the commutation stage of an optional segmented current-limiting bidirectional DC solid-state circuit breaker circuit according to an embodiment of the present invention.

[0026] Figure 8 This is a schematic diagram of the current path when the transfer is completed in an optional segmented current-limiting bidirectional DC solid-state circuit breaker circuit according to an embodiment of the present invention.

[0027] Figure 9 This is a schematic diagram of the current path during the S1 turn-off stage of an optional segmented current-limiting bidirectional DC solid-state circuit breaker circuit according to an embodiment of the present invention.

[0028] Figure 10 This is a schematic diagram of the current path during the S2 turn-off stage of an optional segmented current-limiting bidirectional DC solid-state circuit breaker circuit according to an embodiment of the present invention.

[0029] Figure 11 This is a schematic diagram of the current path during the S3 turn-off stage of an optional segmented current-limiting bidirectional DC solid-state circuit breaker circuit according to an embodiment of the present invention.

[0030] Figure 12 This is a schematic diagram of the current path during the energy dissipation stage of an optional segmented current-limiting bidirectional DC solid-state circuit breaker circuit according to an embodiment of the present invention. Detailed Implementation

[0031] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. 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 scope of protection of the present invention.

[0032] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0033] The present invention will now be described in detail with reference to various embodiments.

[0034] Example 1

[0035] According to an embodiment of the present invention, a graded current-limiting bidirectional DC solid-state circuit breaker circuit embodiment is provided. It should be noted that the steps shown in the flowchart in the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions. Furthermore, although a logical order is shown in the flowchart, in some cases, the steps shown or described may be executed in a different order than that shown here.

[0036] Figure 1 This is a schematic diagram of an optional graded current-limiting bidirectional DC solid-state circuit breaker according to an embodiment of the present invention, as shown below. Figure 1 As shown, the circuit breaker circuit includes:

[0037] The current-carrying branch 101 is configured in the main circuit of the target DC system, wherein the current-carrying branch 101 includes at least a forward conduction switch and a reverse conduction switch.

[0038] The converter branch 102, connected in parallel with the current-carrying branch 101, is used to absorb the fault current in the main circuit in the event of a fault in the main circuit, and to generate an energy-consuming conduction voltage based on the fault current.

[0039] The energy-consuming branch 103 is connected in parallel with the current-carrying branch 101. It is used to switch the branch state to conduction when the energy-consuming conduction voltage is detected, absorb the fault current and consume the system power, and switch the branch state to cut off when the fault current drops to 0.

[0040] The graded current-limiting bidirectional DC solid-state circuit breaker circuit proposed in this embodiment includes a converter branch 102 and an energy-dissipating branch 103 connected in parallel with the current-carrying branch 101 in the main circuit. Under normal and stable operation of the target DC system, both the converter branch 102 and the energy-dissipating branch 103 are in the off state. If a fault occurs in the target DC system, after the current-carrying branch 101 is turned off, the converter branch 102 is turned on first, taking over the bidirectional fault current in the target DC system, consuming a portion of the system power, reducing the fault current, and generating a voltage across the two ends that enables the energy-dissipating branch 103 to conduct, thereby forcing the energy-dissipating branch 103 to take over the fault current and dissipate the remaining system power, thus completing the main circuit disconnection.

[0041] Compared to existing technologies, this invention can quickly transfer the fault current in the main circuit by using the commutation branch when a fault occurs, avoiding damage to the switching devices in the branch due to the sudden increase in overcurrent caused by the untimely disconnection of the current-carrying branch, thus protecting the reliability of the switching devices. After the fault current is transferred, the fault current is used to conduct the energy-dissipating branch to further dissipate the system energy and reduce the fault current. Overall, it can also ensure the current limiting speed, thereby solving the technical problem that existing circuit breakers in related technologies cannot take into account both the current limiting speed and the reliability of the switching devices.

[0042] To achieve bidirectional current flow in the main circuit of the target DC system and ensure that the forward and reverse currents do not interfere with or collide with each other, the forward and reverse conduction switches need to be designed in a coordinated manner. Optionally, the forward conduction switch in the current-carrying branch includes a first field-effect transistor and a forward conduction diode, and the reverse conduction switch includes a second field-effect transistor and a reverse conduction diode. The first and second field-effect transistors are connected in an anti-cascaded configuration, with the first field-effect transistor and the reverse conduction diode connected in parallel with opposite polarity, and the second field-effect transistor and the forward conduction diode connected in parallel with opposite polarity.

[0043] Specifically, Figure 2 This is a schematic diagram of an optional bidirectional flow branch according to an embodiment of the present invention, as shown below. Figure 2 As shown, the current-carrying branch includes a first field-effect transistor Q1, a second field-effect transistor Q2, a forward current-carrying diode D1, and a reverse current-carrying diode D2. The first field-effect transistor Q1 and the second field-effect transistor Q2 are cascaded in reverse. The first field-effect transistor Q1 and the reverse current-carrying diode D2 are connected in parallel with opposite polarities. The second field-effect transistor Q2 and the forward current-carrying diode D1 are connected in parallel with opposite polarities. In terms of conduction effect, the first field-effect transistor Q1 and the forward current-carrying diode D1 form a forward current-carrying branch, which conducts forward current from left to right. The second field-effect transistor Q2 and the reverse current-carrying diode D2 form a reverse current-carrying branch, which conducts reverse current from right to left. Overall, the current-carrying branch achieves a bidirectional conduction effect.

[0044] After achieving bidirectional current conduction in the main circuit, if a short-circuit fault occurs in the main circuit, the resulting fault current will also be a bidirectional fault current. As a mechanism for temporarily transferring and taking over the fault current, the converter branch should have bidirectional conduction capability. Therefore, the converter branch also needs to be structurally modified to achieve bidirectional current conduction. Optionally, the converter branch includes: a converter bridge, wherein the converter bridge contains 4 bridge arm branches and 1 diagonal branch, and the conduction direction of each bridge arm branch is opposite to that of the adjacent bridge arm branch; a segmented current limiting module, configured in the diagonal branch of the converter bridge, wherein the segmented current limiting module is used to switch N segmented modes based on the current value of the fault current, and absorb the fault current based on different segmented modes, where N is a positive integer greater than or equal to 2.

[0045] Optionally, the bridge arm branch of the commutation bridge includes at least a diode, wherein the diode is used to control the conduction direction of the bridge arm branch. In addition to diodes, embodiments of the invention may use other devices capable of unidirectional conduction under specific conditions as alternatives, including but not limited to: bipolar transistors, field-effect transistors (especially N-channel MOSFETs), and switching diodes (e.g., Schottky diodes). Schottky diodes have faster switching characteristics and lower forward voltage drop than standard PN junction diodes, and can replace conventional diodes to achieve the effect of controlling the conduction direction of the bridge arm branch in the bridge.

[0046] Specifically, Figure 3 This is a schematic diagram of an optional bidirectional commutator branch according to an embodiment of the present invention, as shown below. Figure 3 As shown, the commutation branch includes commutation diodes D3, D4, D5, and D6, which belong to different bridge arm branches. A segmented current limiting module is connected to the diagonal branch. During fault commutation, the forward fault current flows into the commutation branch through D3, passes through the segmented current limiting module, and then flows out of the commutation branch through D6. The reverse fault current flows into the commutation branch through D4, passes through the segmented current limiting module, and then flows out of the commutation branch through D5, thus realizing bidirectional conduction of the commutation branch.

[0047] To achieve segmented mode switching and absorb fault current based on different segmented modes, the segmented current limiting module optionally includes: N segmented current limiting groups, wherein the N segmented current limiting groups are connected in series, and each segmented current limiting group is used to switch a segmented mode. Specifically, it can be set to one segmented mode for each segmented current limiting group connected, or one segmented current limiting group disconnected.

[0048] Alternatively, for the first N-1 segmented current limiting groups, each segmented current limiting group includes: a current limiting resistor and a switching device connected in parallel with the current limiting resistor; for the Nth segmented current limiting group, the segmented current limiting group includes: a series combination of a current limiting resistor and a buffer capacitor, and a switching device connected in parallel with the series combination, wherein the buffer capacitor is used to generate an energy-consuming conduction voltage.

[0049] Specifically, Figure 4 This is a schematic diagram of an optional segmented current limiting module according to an embodiment of the present invention, such as... Figure 4 As shown, this segmented current limiting module includes three segmented current limiting groups, specifically comprising: switching devices S1, S2, and S3; current-limiting resistors R1, R2, and R3; and a buffer capacitor C. The connection method is as follows: S1 is connected in parallel with R1 as the first segmented current limiting group; S2 is connected in parallel with R2 as the second segmented current limiting group; and R3 is connected in series with C and then in parallel with S3 as the third segmented current limiting group. During the segmented current limiting process, all switching devices S1, S2, and S3 can be turned on in the first stage, allowing the current-limiting resistors R1, R2, R3, and the buffer capacitor C to be connected in series in the converter branch to handle larger fault currents. After the fault current decreases somewhat, S1 and S2 are gradually turned off, that is, R1 and R2 are gradually disconnected, reducing the impedance value in the converter branch to handle smaller fault currents. During the segmented current limiting process, the buffer capacitor C is always connected in series in the converter branch, using the fault current to charge it and obtain a sufficiently large capacitor voltage as the energy-dissipating conduction voltage.

[0050] Alternatively, the switching devices in the commutation branch can be any of the following types: insulated gate bipolar transistor, thyristor, or metal-oxide-semiconductor field-effect transistor.

[0051] It should be noted that an Insulated Gate Bipolar Transistor (IGBT) is a power switching device that combines the advantages of bipolar transistors and field-effect transistors. IGBTs have high voltage, high current, and high-speed switching characteristics, making them suitable for high-power and high-frequency circuits. A thyristor, also known as a silicon controlled rectifier (SCR), is a commonly used electronic switching device. Thyristors have the characteristic that once turned on, they can only be turned off by reducing the current to their turn-off current, making them suitable for high-power and high-voltage circuits. A Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET) is a commonly used field-effect transistor. MOSFETs have high input impedance, low switching losses, and high-speed switching characteristics.

[0052] In another optional embodiment, the energy-dissipating branch includes at least one energy-dissipating element, which absorbs fault current and dissipates system power when the energy-dissipating branch is conducting. In this embodiment, an MOV (Metal Oxide Varistor, also called a metal oxide surge arrester) can be used as the energy-dissipating element to protect equipment from overvoltage damage in the circuit. The response time is on the nanosecond level, consuming or transferring the energy of the overvoltage itself, thus limiting the voltage to a level that the equipment can withstand.

[0053] It should be noted that a metal oxide surge arrester is a voltage-dependent resistive device. When a short circuit fault occurs in a DC system, the voltage will suddenly rise to an abnormally high level. The metal oxide surge arrester can respond quickly and absorb and dissipate the overvoltage energy by converting the overvoltage electrical energy into heat energy, thereby maintaining the voltage below a safe level.

[0054] In addition, the types of metal oxide surge arresters that can be selected in the embodiments of the present invention include, but are not limited to: line-type metal oxide surge arresters, gapless line-type metal oxide surge arresters, and fully insulated composite-jacket metal oxide surge arresters. Among them, line-type metal oxide surge arresters are similar to ordinary MOVs, but are generally designed to be more suitable for DC systems; gapless line-type metal oxide surge arresters have higher electrical characteristics and response speed, and are particularly suitable for applications that require faster and more accurate response; fully insulated composite-jacket metal oxide surge arresters combine the advantages of insulating materials and metal oxide surge arresters, and are generally used in applications that require higher safety and environmental adaptability. Their insulating jacket makes them more suitable for operation in harsh environments, while also having efficient energy dissipation capabilities, and can safely manage and eliminate overvoltages in the circuit.

[0055] Furthermore, the power-consuming element can also be any of the following: a power diode, a metal oxide thermal evaporator (MOF), a ceramic zirconia varistor, or a transient voltage suppressor (TVS).

[0056] It should also be noted that power diodes are high-power, high-voltage-tolerance diodes with unidirectional conductivity, high withstand capability, and fast response capability. They can be used to absorb overvoltages and protect circuits, making them suitable for applications requiring high power handling. In circuit breaker circuits, diodes can be connected to the load circuit. When the system voltage exceeds the diode's reverse breakdown voltage, the diode will conduct, short-circuiting the overvoltage to ground and providing protection.

[0057] Metal oxide thermal release elements (MOFs) are similar to metal oxide varistors (MOVs). MOFs are devices that absorb energy by rapidly transitioning to a low-resistance state under overvoltage. They are typically made of metal oxide materials and are used to prevent overvoltage damage to sensitive components in circuits. Ceramic zirconia varistors are devices that can quickly respond to voltage changes and absorb overvoltages. They have high power handling capabilities and fast response characteristics, effectively protecting equipment in circuits.

[0058] A transient voltage suppressor (TVS) is a highly efficient voltage suppressor used to absorb transient overvoltages. It features faster response and higher power handling capacity, effectively protecting sensitive components in a circuit. In a circuit breaker circuit, the TVS is connected in the power-consuming branch. When the system voltage exceeds the TVS's operating range, it quickly conducts, short-circuiting the overvoltage to ground to protect the equipment from damage.

[0059] Optionally, GDTs (Gas Discharge Tubes), avalanche diodes, or solid-state relays can also be used as energy-dissipating components. GDTs offer similar response speed and high energy handling capability to MOVs. Avalanche diodes have high impedance at low voltages, but their impedance decreases sharply after the voltage exceeds the rated value, making them suitable for circuit protection scenarios requiring fast response. Solid-state relays can also provide circuit protection functions, but are typically used in low-power or specific-frequency applications. The embodiments of this invention can select suitable components as energy-dissipating components according to the specific implementation scenario; the specific selection criteria and process will not be elaborated upon here.

[0060] In this embodiment of the invention, two switching devices cascaded in reverse in the main circuit are set to achieve bidirectional current conduction. Combined with the converter branch composed of power electronic devices, the fault current is taken over when the current-carrying branch is cut off. The converter branch is set with a multi-level segmented current limiting mode. Different current limiting modes can be selected and switched according to the magnitude of the fault current to achieve the best current limiting effect and initially reduce the fault current.

[0061] In this embodiment of the invention, an energy-consuming branch is also provided. The switching on and off of the energy-consuming element is controlled according to the voltage at both ends indicated in the converter branch. In this embodiment of the invention, an MOV surge arrester is used as an energy-consuming element to take over the fault current after the initial reduction by the converter branch, dissipate the remaining system power, and achieve the technical effect of completely reducing the fault current to 0 and clearing the main circuit fault.

[0062] The present invention will now be described in conjunction with another specific embodiment.

[0063] Figure 5 This is a topology diagram of an optional segmented current-limiting bidirectional DC solid-state circuit breaker according to an embodiment of the present invention, such as... Figure 5As shown, the circuit breaker circuit includes switching devices Q1, Q2, S1, S2, S3, diodes D1, D2, D3, D4, resistors R1, R2, R3, capacitor C, and surge arrester MOV.

[0064] It should be noted that the switching devices Q1 and Q2 constitute the main circuit (i.e., the current-carrying branch of the target DC system in the above embodiment 1), and the connection method is anti-cascaded to achieve bidirectional current conduction. In the embodiment of the present invention, silicon carbide (SiC) MOSFETs can be selected as the switching devices in the main circuit.

[0065] In addition, the commutation branch is composed of switching devices S1, S2, S3, diodes D1, D2, D3, D4, resistors R1, R2, R3, and capacitor C. It adopts a modular segmented current limiting strategy to limit the rate of rise of fault current and can switch between different segmented current limiting modes to deal with fault currents of different magnitudes. Capacitor C is used as a buffer capacitor to absorb the fault current flowing through the commutation branch and limit the fault current to a safe level in the shortest possible time.

[0066] In this embodiment of the invention, diodes D1, D2, D3, and D4 are used to construct a diode bridge, which, like the main circuit, supports bidirectional current conduction. The segmented current limiting module, composed of switching devices S1, S2, and S3, resistors R1, R2, and R3, and capacitor C, is connected in series on the diagonal branch of the diode bridge. Under the action of the diode bridge, both the forward fault current and the reverse fault current flow through the segmented current limiting module in a unified direction, especially the buffer capacitor.

[0067] In addition, the function of the surge arrester MOV is to absorb short-circuit current and dissipate system energy caused by short-circuit faults.

[0068] The following is a guide from left to right (i.e., from...) Figure 5 Taking the positive current (from the first end to the second end of the circuit being connected) as an example, the working process and current conduction status of the above-mentioned segmented current-limiting bidirectional DC solid-state circuit breaker circuit are explained.

[0069] Figure 6 This is a schematic diagram of the current path during the steady-state current-carrying stage of an optional segmented current-limiting bidirectional DC solid-state circuit breaker circuit according to an embodiment of the present invention, as shown below. Figure 6 As shown, the SiC MOSFET carries the steady-state operating current. The forward current flows through the SiC MOSFET in Q1 and the freewheeling diode connected in parallel in Q2, forming a current path from the first terminal to the second terminal. If a short-circuit fault occurs in the main circuit, the fault current in the main circuit will rise rapidly.

[0070] Figure 7 This is a schematic diagram of the current path during the commutation stage of an optional segmented current-limiting bidirectional DC solid-state circuit breaker circuit according to an embodiment of the present invention, as shown below. Figure 7 As shown, when a short-circuit fault is detected in the main circuit, S1, S2, and S3 of the converter branch are immediately turned on, and then Q1 and Q2 are quickly turned off. Under the action of the turn-off voltage, the fault current is transferred from the main current-carrying branch to the converter branch.

[0071] Figure 8 This is a schematic diagram of the current path after the transfer is completed in an optional segmented current-limiting bidirectional DC solid-state circuit breaker circuit according to an embodiment of the present invention, as shown below. Figure 8 As shown, the fault current in the main current-carrying branch is completely transferred to the converter branch. After the positive current enters the first terminal, it flows through diode D1 and the segmented current-limiting module, and then flows out of the second terminal through diode D4.

[0072] Figure 9 This is a schematic diagram of the current path during the S1 turn-off stage of an optional segmented current-limiting bidirectional DC solid-state circuit breaker circuit according to an embodiment of the present invention, as shown below. Figure 9 As shown, when all switching devices S1, S2, and S3 are turned on, the fault current flows through the switching devices. At this time, S1 can be turned off, and the fault current that originally flowed through S1 is transferred to resistor R1. This is the first-level current limiting, which limits the rate of increase of the fault current.

[0073] Figure 10 This is a schematic diagram of the current path during the S2 turn-off stage of an optional segmented current-limiting bidirectional DC solid-state circuit breaker circuit according to an embodiment of the present invention, as shown below. Figure 10 As shown, when S2 is turned off, the fault current that originally flowed through S2 is transferred to resistor R2. That is, R1 and R2 are both connected in series in the commutation branch. At this time, it is a second-level current limiting, which further limits the rate of increase of the fault current.

[0074] Figure 11 This is a schematic diagram of the current path during the S3 turn-off stage of an optional segmented current-limiting bidirectional DC solid-state circuit breaker circuit according to an embodiment of the present invention, as shown below. Figure 11 As shown, when S3 is turned off, the fault current that originally flowed through S3 is transferred to resistor R3 and capacitor C. That is, R1, R2, R3 and C are all connected in series in the commutation branch. At this time, it is a three-stage current limiting. The main task of this stage is to charge capacitor C, and the voltage across it continues to rise.

[0075] Figure 12 This is a schematic diagram of the current path in the energy dissipation stage of an optional segmented current-limiting bidirectional DC solid-state circuit breaker circuit according to an embodiment of the present invention, as shown below. Figure 12 As shown, after the voltage across capacitor C reaches the discharge voltage of the surge arrester MOV, MOV changes from a high impedance state to a low impedance state, the energy dissipation branch is turned on, and the fault current of the commutation branch is transferred to the energy dissipation branch, where MOV dissipates the final energy. When the fault current is about to be 0, the fault circuit is disconnected.

[0076] In this embodiment of the invention, the main circuit uses two anti-cascaded SiC MOSFETs to achieve bidirectional current conduction. The commutation branch employs diode bridges, IGBT chips, and current-limiting resistors to achieve commutation and current-limiting functions, and a segmented resistor current-limiting module is used to limit the rate of rise of the fault current. The fault current is absorbed by a buffer capacitor. The proposed DC solid-state circuit breaker can limit the fault current to a safe level in a very short time. It utilizes power electronic devices for rapid commutation while simultaneously using resistors to limit the rise of the short-circuit current. It features fast current limiting speed, good operational consistency, and rapid switching, making it suitable for DC microgrid applications.

[0077] The invention will now be described in conjunction with another alternative embodiment.

[0078] Example 2

[0079] This embodiment provides a circuit breaker comprising a graded current-limiting bidirectional DC solid-state circuit breaker circuit according to any one of the above embodiments, including at least:

[0080] The current-carrying branch 101 is configured in the main circuit of the target DC system, wherein the current-carrying branch 101 includes at least a forward conduction switch and a reverse conduction switch.

[0081] The converter branch 102, connected in parallel with the current-carrying branch 101, is used to absorb the fault current in the main circuit in the event of a fault in the main circuit, and to generate an energy-consuming conduction voltage based on the fault current.

[0082] The energy-consuming branch 103 is connected in parallel with the current-carrying branch 101. It is used to switch the branch state to conduction when the energy-consuming conduction voltage is detected, absorb the fault current and consume the system power, and switch the branch state to cut off when the fault current drops to 0.

[0083] The circuit breaker proposed in this embodiment includes a converter branch 102 and an energy dissipation branch 103 connected in parallel with the current-carrying branch 101 in the main circuit. Under normal and stable operation of the target DC system, both the converter branch 102 and the energy dissipation branch 103 are in the off state. If a fault occurs in the target DC system, after the current-carrying branch 101 is turned off, the converter branch 102 is turned on first, taking over the bidirectional fault current in the target DC system, consuming a portion of the system power, reducing the fault current, and generating a voltage across the two ends that enables the energy dissipation branch 103 to conduct, thereby forcing the energy dissipation branch 103 to take over the fault current and dissipate the remaining system power, thus completing the main circuit disconnection.

[0084] Compared to existing technologies, this invention can quickly transfer the fault current in the main circuit by using the commutation branch when a fault occurs, avoiding damage to the switching devices in the branch due to the sudden increase in overcurrent caused by the untimely disconnection of the current-carrying branch, thus protecting the reliability of the switching devices. After the fault current is transferred, the fault current is used to conduct the energy-dissipating branch to further dissipate the system energy and reduce the fault current. Overall, it can also ensure the current limiting speed, thereby solving the technical problem that existing circuit breakers in related technologies cannot take into account both the current limiting speed and the reliability of the switching devices.

[0085] The sequence numbers of the above embodiments of the present invention are for descriptive purposes only and do not represent the superiority or inferiority of the embodiments.

[0086] In the above embodiments of the present invention, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0087] In the several embodiments provided in this application, it should be understood that the disclosed technical content can be implemented in other ways. The device embodiments described above are merely illustrative; for example, the division of units can be a logical functional division, and in actual implementation, there may be other division methods. For instance, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the displayed or discussed mutual coupling, direct coupling, or communication connection may be through some interfaces; the indirect coupling or communication connection between units or modules may be electrical or other forms.

[0088] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0089] Furthermore, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0090] If the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. 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 the present invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, read-only memory (ROM), random access memory (RAM), portable hard drives, magnetic disks, or optical disks.

[0091] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A hierarchical current limiting bidirectional DC solid-state circuit breaker circuit, characterized in that: include: A flow branch is arranged in a main circuit of a target DC system, wherein the flow branch at least comprises a forward conducting switch and a reverse conducting switch; a commutation branch connected in parallel with the current-carrying branch, and configured to absorb the fault current in the main circuit when a fault occurs in the main circuit, and generate an energy-consuming conduction voltage based on the fault current; The energy-consuming branch is connected in parallel with the current-carrying branch, and is used to switch the branch state to on when the energy-consuming conduction voltage is detected, absorb the fault current and consume system energy, and switch the branch state to off when the fault current is reduced to 0.

2. The hierarchical current limiting bidirectional DC solid-state circuit breaker circuit according to claim 1, characterized in that: The forward conducting switch in the current branch includes: a first field effect transistor and a forward current diode, and the reverse conducting switch includes: a second field effect transistor and a reverse current diode, wherein the first field effect transistor and the second field effect transistor are connected in an anti-cascade connection, the first field effect transistor is connected in parallel with the reverse current diode in reverse polarity, and the second field effect transistor is connected in parallel with the forward current diode in reverse polarity.

3. The hierarchical current limiting bidirectional DC solid-state circuit breaker circuit according to claim 1, characterized in that: The commutation branch comprises: A commutation bridge, wherein the commutation bridge comprises four bridge arm branches and one diagonal branch, and each of the bridge arm branches has a conduction direction opposite to that of an adjacent bridge arm branch; A segmented current limiting module is configured in the diagonal branch of the commutation bridge, wherein the segmented current limiting module is used to switch N segment modes based on the current value of the fault current, and absorb the fault current based on different segment modes, and N is a positive integer greater than or equal to 2.

4. The hierarchical current limiting bidirectional DC solid-state circuit breaker circuit according to claim 3, characterized in that: The segmented current limiting module includes: N segmented current limiting groups, wherein the N segmented current limiting groups are connected in series, and each segmented current limiting group is used to switch one of the segmented modes.

5. The hierarchical current limiting bidirectional DC solid-state circuit breaker circuit according to claim 4, characterized in that: For the first N-1 segmented current limiting groups, the segmented current limiting groups include: a current limiting resistor, and a switching device connected in parallel with the current limiting resistor; for the Nth segmented current limiting group, the segmented current limiting group includes: a series combination of the current limiting resistor and the buffer capacitor, and the switching device connected in parallel with the series combination, wherein the buffer capacitor is used to generate the energy-consuming conduction voltage.

6. The hierarchical current limiting bidirectional DC solid-state circuit breaker circuit according to claim 5, characterized in that: The switch device is selected from any one of the following types: an insulated gate bipolar transistor, a thyristor or a metal oxide semiconductor field effect transistor.

7. The hierarchical current limiting bidirectional DC solid-state circuit breaker circuit according to claim 3, characterized in that: The bridge arm branch in the commutation bridge includes at least a diode, wherein the diode is used to control the conduction direction of the bridge arm branch.

8. The hierarchical current limiting bidirectional DC solid-state circuit breaker circuit according to claim 1, characterized in that: The energy consumption branch at least includes: an energy consumption element, wherein the energy consumption element is used to absorb the fault current and consume the system electric energy when the energy consumption branch is turned on.

9. The hierarchical current limiting bidirectional DC solid-state circuit breaker circuit according to claim 8, characterized in that: The energy dissipation element is selected from one of the following: a metal oxide arrester, a power diode, a metal oxide thermal releaser, a ceramic zirconia varistor or a transient voltage suppressor.

10. A circuit breaker, characterized in that: It comprises a hierarchical current limiting bidirectional DC solid-state circuit breaker circuit as described in any one of claims 1 to 9.

Images