Bidirectional power electronic switch, hybrid direct current circuit breaker and control method

Abstract

The invention discloses a bidirectional power electronic switch, a hybrid DC circuit breaker and a control method. The bidirectional power electronic switch comprises a diode bridge module, a buffer circuit, a voltage limiting circuit and an impedance adjusting circuit. The impedance adjusting circuit is connected in parallel with two ends of the diode bridge module; the buffer circuit is connected in parallel with a breaking electronic switch in the diode bridge module; the voltage limiting circuit is connected in parallel with two ends of the breaking electronic switch; the diode bridge module controls the breaking electronic switch to switch current according to a breaking instruction of the power system; when the breaking electronic switch is locked, the buffer circuit suppresses the voltage and current changes of the breaking electronic switch in the switching process, the voltage limiting circuit limits the overvoltage level of the breaking electronic switch, and the impedance adjusting circuit reduces the oscillation frequency. The impedance adjusting circuit reduces the oscillation frequency, reduces the requirement for the reverse recovery speed of the diode, reduces the stress of the diode bridge type module, and enables a conventional common diode to be not liable to be damaged.

Description

Technical Field

[0001] The present invention relates to the technical field of power electronics, and in particular to a bidirectional power electronic switch, a hybrid DC circuit breaker and a control method. Background Art

[0002] DC circuit breakers are essential equipment for building DC power grids and ensuring their reliability and flexibility. They play an irreplaceable role in the control and protection of DC grid systems. Currently, medium and high voltage DC circuit breakers are available in two types: hybrid and mechanical. Hybrid solutions offer greater development prospects due to their advantages, including fast breaking speed, low conduction losses, ease of reclosing, low requirements for post-arc dielectric recovery, and flexible control.

[0003] Currently, there are two main technical approaches for high-voltage hybrid DC circuit breakers. One is the naturally commutated hybrid DC circuit breaker, which uses the arc voltage of fast mechanical switches in the main branch to achieve commutation. However, its commutation capacity is limited by the arc voltage and is generally applicable to voltage levels below 20kV. The other is the forced-commutation hybrid DC circuit breaker, which achieves current transfer by configuring auxiliary commutation modules in the commutation circuit. Both types of hybrid DC circuit breakers require a large number of fully controlled components connected in series, which have low voltage utilization, large size, and poor economic efficiency.

[0004] The DC circuit breaker in the existing technology uses an auxiliary commutation module and a bidirectional power electronic switch to achieve current transfer in the main branch. However, the bidirectional power electronic switch diode in this structure has high stress and high oscillation frequency, requiring the use of high-cost diodes with fast recovery capabilities, resulting in excessively high commutation costs.

[0005] In summary, the prior art has the problem that ordinary diodes in bidirectional power electronic switches have high stress, high oscillation frequency, and are easily damaged. Summary of the Invention

[0006] In order to solve the problems in the prior art that ordinary diodes in bidirectional power electronic switches have high stress, high oscillation frequency and are easily damaged.

[0007] The purpose of the present invention is to adopt the following technical solutions to achieve:

[0008] A bidirectional power electronic switch includes a diode bridge module, a buffer circuit, a voltage limiting circuit, and an impedance adjustment circuit; the impedance adjustment circuit is connected in parallel to both ends of the diode bridge module; the buffer circuit is connected in parallel to the disconnecting electronic switch in the diode bridge module; and the voltage limiting circuit is connected in parallel to both ends of the disconnecting electronic switch.

[0009] The diode bridge module controls the switching current of the disconnecting electronic switch according to the disconnecting instruction of the power system; when the disconnecting electronic switch is locked, the buffer circuit suppresses the voltage and current changes of the disconnecting electronic switch during the switching process, the voltage limiting circuit limits the overvoltage level of the disconnecting electronic switch, and the impedance adjustment circuit reduces the oscillation frequency.

[0010] Preferably, the diode bridge module includes a first diode, a second diode, a third diode, a fourth diode and a disconnecting electronic switch; the disconnecting electronic switch adopts an IGBT tube;

[0011] The positive electrode of the first diode is connected to the negative electrode of the second diode as one end of the diode bridge module; the negative electrode of the first diode is respectively connected to the collector of the IGBT tube and the negative electrode of the fourth diode; the positive electrode of the second diode is respectively connected to the emitter of the IGBT tube and the positive electrode of the third diode; the negative electrode of the third diode is connected to the positive electrode of the fourth diode as the other end of the diode bridge module.

[0012] Furthermore, the buffer circuit includes a buffer capacitor, a static voltage-sharing resistor, a fifth diode and a damping resistor;

[0013] One end of the buffer capacitor is connected in series with the cathode of the fifth diode, the buffer capacitor is connected in parallel with the static balancing resistor, and the fifth diode is connected in parallel with the damping resistor;

[0014] The other end of the buffer capacitor is connected to the emitter of the IGBT tube; the anode of the fifth diode is connected to the collector of the IGBT tube.

[0015] Furthermore, the impedance adjustment circuit includes a low-value capacitor and a low-value resistor;

[0016] The low-value capacitor and the low-value resistor are connected in series, and then connected in parallel to the two ends of the diode bridge module.

[0017] Furthermore, the capacitance of the low-value capacitor is at least one order of magnitude smaller than the capacitance of the buffer capacitor and two orders of magnitude larger than the parasitic capacitance of other components in the bidirectional power electronic switch;

[0018] The resistance of the low-value resistor is two orders of magnitude greater than the parasitic resistance of the remaining components.

[0019] Preferably, the voltage limiting circuit includes a metal oxide varistor;

[0020] The metal oxide varistor is connected in parallel with the disconnecting electronic switch.

[0021] A hybrid DC circuit breaker comprises a current-carrying component, a current-commutating component, a breaking component and a total current measuring device;

[0022] The commutation component and the breaking component are connected in series and then in parallel with the flow component; the flow component and the total current measuring device are connected in series in the DC line;

[0023] The disconnecting component includes one or more bidirectional power electronic switches and energy-consuming components as described above; the energy-consuming components are connected in parallel to one or more bidirectional power electronic switches connected in series.

[0024] Preferably, the commutation component includes: a charging circuit, a commutation circuit, a bypass circuit and a commutation trigger circuit;

[0025] The charging circuit, the commutation circuit and the bypass circuit are connected in parallel and then in series with the commutation trigger circuit;

[0026] The charging circuit includes: a DC power supply and a power switching switch; the DC power supply and the power switching switch are connected in series;

[0027] The commutation circuit includes: an energy storage commutation capacitor, a commutation oscillation inductor, a voltage detection device, and a static voltage grading resistor; the energy storage commutation capacitor and the commutation oscillation inductor are connected in series and in parallel with the static voltage grading resistor, and the voltage detection device is connected in parallel to the energy storage commutation capacitor;

[0028] The bypass circuit includes a first trigger switch and an energy-consuming resistor; the first trigger switch and the energy-consuming resistor are connected in series;

[0029] The commutation trigger circuit includes: a second trigger switch, a static balancing resistor, a dynamic balancing capacitor and a damping resistor; the dynamic balancing capacitor and the damping resistor are connected in series and then connected in parallel with the second trigger switch and the static balancing resistor respectively.

[0030] Preferably, under the same coordinated current, the residual voltage of the energy-consuming component is lower than the sum of the residual voltages of the voltage-limiting circuit;

[0031] During the high current interruption process, the residual voltage of the energy-consuming component is lower than the maximum voltage withstand capability after multiple bidirectional power electronic switches are connected in series, and the absorbed energy should be lower than the design value of the energy absorption capacity.

[0032] Furthermore, during the high current interruption process, the current sharing ratio between the voltage limiting circuit and the energy consuming component is 1:N;

[0033] Wherein, N is an integer greater than 1.

[0034] A method for controlling a hybrid DC circuit breaker as described in any one of the above, comprising:

[0035] receiving a control instruction of the power system through the hybrid DC circuit breaker; the control instruction includes an opening instruction, a closing instruction, or a pre-opening instruction;

[0036] According to the control instructions, the current-carrying component, the current-commutating component and the breaking component in the hybrid DC circuit breaker are controlled to perform corresponding actions, and the total current measuring device in the hybrid DC circuit breaker is used to perform overcurrent detection.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] The present invention provides a bidirectional power electronic switch. This device incorporates an impedance adjustment circuit connected in parallel at both ends of a diode bridge module, and a snubber circuit and a voltage-limiting circuit connected in parallel to the electronic disconnector within the diode bridge module. The snubber circuit suppresses voltage and current changes during the switching process of the electronic disconnector, while the voltage-limiting circuit limits overvoltage levels within the electronic disconnector. The impedance adjustment circuit reduces the oscillation frequency, altering the impedance characteristics of the diode bridge module's ports after the electronic disconnector within the diode bridge module is locked. The impedance adjustment circuit modulates a high-frequency underdamped circuit based on parasitic parameters into a low-frequency overdamped circuit, reducing the reverse recovery speed requirements for the diodes and the stress within the diode bridge module, thereby making conventional diodes less susceptible to damage.

[0039] The present invention provides a hybrid DC circuit breaker and control method. By configuring only a fast mechanical switch in the main branch and a commutation component with both commutation and pressure-bearing functions in the transfer branch, highly reliable commutation is achieved during the DC circuit breaker's disconnection process. At the same time, part of the terminal voltage is borne, reducing the number of fully controlled components connected in series in the disconnection component. The bidirectional power electronic switch and energy-consuming component in the disconnection component can achieve voltage limiting and energy consumption decoupling, reduce the turn-off voltage overshoot of the fully controlled components, further reduce the number of fully controlled components connected in series in the disconnection component, and achieve the goal of reducing the size of the DC circuit breaker and improving economic efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 Schematic diagram of a bidirectional power electronic switch circuit in Example 1 of the present invention;

[0041] Figure 2 This is a schematic diagram of a topology circuit of a hybrid DC circuit breaker in Example 2 of the present invention;

[0042] Figure 3 This is a schematic diagram of the topological circuit of the commutation component in Example 2 of the present invention;

[0043] Figure 4 This is a circuit diagram of a hybrid DC circuit breaker in Example 2 of the present invention;

[0044] Figure 5Schematic diagram of the design of the coordination between the protection MOV and the energy consumption MOV in Example 2 of the present invention;

[0045] Figure 6 Schematic diagram of the reverse 10kA breaking test waveform in Example 2 of the present invention;

[0046] Figure 7 Schematic diagram of the opening control process in Example 3 of the present invention;

[0047] Figure 8 Schematic diagram of the closing control process in Example 3 of the present invention;

[0048] Figure 9 Schematic diagram of the pre-tripping control flow in Example 3 of the present invention. DETAILED DESCRIPTION

[0049] Hereinafter, only certain exemplary embodiments are briefly described. As will be appreciated by those skilled in the art, the described embodiments may be modified in various ways without departing from the spirit or scope of the present invention. Therefore, the drawings and description are to be considered as illustrative in nature and not restrictive.

[0050] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like to indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0051] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, "plurality" means two or more, unless otherwise specifically defined.

[0052] In the present invention, unless otherwise expressly specified or limited, terms such as "mounted," "connected," "connect," and "fixed" should be understood broadly. For example, they may refer to fixed connection, detachable connection, or integration; mechanical connection, electrical connection, or communication; direct connection or indirect connection through an intermediate medium; and internal communication between two components or interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0053] In the present invention, unless otherwise expressly specified or limited, a first feature being "above" or "below" a second feature may include the first and second features being in direct contact, or may include the first and second features being in contact not directly but through another feature between them. Furthermore, a first feature being "above," "above," and "above" a second feature may include the first feature being directly above or obliquely above the second feature, or may simply mean that the first feature is higher in level than the second feature. A first feature being "below," "below," and "below" a second feature may include the first feature being directly above or obliquely above the second feature, or may simply mean that the first feature is lower in level than the second feature.

[0054] It will be understood that when used in this specification and the appended claims, the terms “comprises” and “comprising” indicate the presence of described features, integers, steps, operations, elements and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or groups thereof.

[0055] It should also be understood that the terms used in the present specification are only for the purpose of describing particular embodiments and are not intended to limit the present invention. As used in the present specification and the appended claims, the singular forms "a", "an", and "the" are intended to include the plural forms unless the context clearly indicates otherwise.

[0056] It should be further understood that the term "and / or" used in the present description and the appended claims refers to and includes any and all possible combinations of one or more of the associated listed items.

[0057] The accompanying drawings illustrate various schematic diagrams of structures according to embodiments disclosed herein. These figures are not drawn to scale; for clarity, some details are exaggerated and some details may be omitted. The shapes of the various regions and layers shown in the figures, as well as their relative sizes and positional relationships, are merely exemplary and may deviate in practice due to manufacturing tolerances or technical limitations. Those skilled in the art may design regions / layers with different shapes, sizes, and relative positions as needed.

[0058] The embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0059] Example 1:

[0060] like Figure 1 As shown, in an embodiment of the present invention, a bidirectional power electronic switch includes a diode bridge module, a buffer circuit, a voltage limiting circuit and an impedance adjustment circuit; the impedance adjustment circuit is connected in parallel at both ends of the diode bridge module; the buffer circuit is connected in parallel to the disconnecting electronic switch in the diode bridge module; and the voltage limiting circuit is connected in parallel at both ends of the disconnecting electronic switch.

[0061] The diode bridge module controls the switching current of the disconnecting electronic switch according to the disconnecting instruction of the power system; when the disconnecting electronic switch is locked, the buffer circuit suppresses the voltage and current changes of the disconnecting electronic switch during the switching process, the voltage limiting circuit limits the overvoltage level of the disconnecting electronic switch, and the impedance adjustment circuit reduces the oscillation frequency.

[0062] The present invention discloses a novel low-stress bidirectional power electronic switch. This device connects an impedance adjustment circuit in parallel at both ends of a diode bridge module, and connects a buffer circuit and a voltage-limiting circuit in parallel to the disconnecting electronic switch in the diode bridge module. The buffer circuit suppresses voltage and current changes in the disconnecting electronic switch during switching, and the voltage-limiting circuit limits the overvoltage level of the disconnecting electronic switch. The impedance adjustment circuit reduces the oscillation frequency, altering the impedance characteristics of the diode bridge module's ports after the disconnecting electronic switch in the diode bridge module is locked. The impedance adjustment circuit adjusts a high-frequency underdamped circuit based on parasitic parameters to a low-frequency overdamped circuit, reducing the requirements for the diode's reverse recovery speed. This allows the first, second, third, and fourth diodes to all be conventional diodes, avoiding the high cost of fast-recovery diodes.

[0063] Specifically, the diode bridge module in the embodiment of the present invention includes a first diode, a second diode, a third diode, a fourth diode and a disconnecting electronic switch; the disconnecting electronic switch adopts an IGBT (Insulated Gate Bipolar Transistor); the positive electrode of the first diode is connected to the negative electrode of the second diode as one end of the diode bridge module; the negative electrode of the first diode is respectively connected to the collector of the IGBT tube and the negative electrode of the fourth diode; the positive electrode of the second diode is respectively connected to the emitter of the IGBT tube and the positive electrode of the third diode; the negative electrode of the third diode is connected to the positive electrode of the fourth diode as the other end of the diode bridge module. Figure 1As shown, the bridge arms of the diode bridge module are respectively a first diode D1, a second diode D2, a third diode D3, and a fourth diode D4, with a fully controlled device IGBT (Insulated Gate Bipolar Transistor) G1 in the middle.

[0064] Specifically, the snubber circuit in the embodiment of the present invention is an RCD snubber circuit, including a snubber capacitor C2, a static voltage balancing resistor R5, a fifth diode D5 and a damping resistor R6;

[0065] The snubber capacitor C2 is connected in series with the fifth diode D5, which is in parallel with the static balancing resistor R5. The fifth diode D5 is connected in parallel with the damping resistor R6. The other end of the snubber capacitor is connected to the emitter of the IGBT G1; the anode of the fifth diode is connected to the collector of the IGBT G1.

[0066] Specifically, the impedance adjustment circuit in this embodiment of the present invention includes a low-value capacitor C3 and a low-value resistor R7; the low-value capacitor C3 and the low-value resistor R7 are connected in series and then connected in parallel to the two ends of the diode bridge module. The impedance adjustment circuit reduces the stress on the bridge arm diodes in the bidirectional power electronic switch, and the bridge arm diodes are all ordinary diodes instead of fast recovery diodes.

[0067] It should be further explained that the impedance adjustment circuit parameters in the embodiment of the present invention should satisfy a certain coordination relationship with the overall impedance parameters of the remaining components of the bidirectional power electronic switch, including:

[0068] The capacitance of the low-value capacitor C3 in the impedance adjustment circuit should be at least one order of magnitude smaller than that of the buffer capacitor C2 and two orders of magnitude larger than the parasitic capacitance of the remaining components of the bidirectional power electronic switch;

[0069] The resistance of the low-value resistor R7 in the impedance adjustment circuit should be two orders of magnitude greater than the parasitic resistance of other components of the bidirectional power electronic switch.

[0070] For example, in the embodiment of the present invention, under the condition that the capacitance of the buffer capacitor C2 is 10 to 100 μF, the capacitance of the low-value capacitor C3 in the impedance adjustment circuit is in the range of 1 to 10 μF, and the resistance of the low-value resistor R7 in the impedance adjustment circuit is in the range of 1 to 50 Ω.

[0071] Specifically, the voltage limiting circuit in the embodiment of the present invention includes a metal oxide varistor MOV1 ; the metal oxide varistor MOV1 is connected in parallel with the disconnecting electronic switch of the diode bridge module.

[0072] Specifically, the connection relationship of the bidirectional power electronic switch in the embodiment of the present invention is as follows: Figure 1As shown, it includes a first diode D1, a second diode D2, a third diode D3, a fourth diode D4, a fifth diode D5, an IGBT tube G1, a buffer capacitor C2, a static grading resistor R5, a damping resistor R6 and a metal oxide varistor MOV1.

[0073] The anode of the first diode D1 is connected to the cathode of the second diode D2, and the cathode of the first diode D1 is respectively connected to the collector of the IGBT tube G1, the anode of the fifth diode D5, and the cathode of the fourth diode D4; the cathode of the fifth diode D5 is connected to one end of the buffer capacitor C2; the damping resistor R6 is connected in parallel to the fifth diode D5; and the static balancing resistor R5 is connected in parallel to the second capacitor C2.

[0074] The anode of the second diode D2 is respectively connected to the emitter of the IGBT tube G1, the other end of the buffer capacitor C2, and the anode of the third diode D3; the cathode of the third diode D3 is connected to the anode of the fourth diode D4.

[0075] Two ends of the metal oxide varistor MOV1 are respectively connected to the collector and emitter of the IGBT tube G1.

[0076] The energy dissipation component MOV is connected in parallel at both ends of one or more bidirectional power electronic switches connected in series.

[0077] Example 2:

[0078] The present invention based on the same inventive concept also provides a compact hybrid DC circuit breaker, such as Figure 2 As shown, it includes a current-passing component, a commutation component, a breaking component and a total current measuring device;

[0079] The commutation component and the breaking component are connected in series and then in parallel with the flow component; the flow component and the total current measuring device are connected in series in the DC line;

[0080] The disconnecting component includes one or more bidirectional power electronic switches and energy-consuming components as in Example 1; the energy-consuming components are connected in parallel to one or more bidirectional power electronic switches connected in series.

[0081] The current-carrying component consists of a single-break electromagnetic repulsion-type fast mechanical switch, used to carry operating current, short-time withstand current, peak withstand current, and transfer fault current. The commutation component and the disconnecting component are connected in series, used to transfer and shut off current under various transient and steady-state conditions. The first trigger switch K1 and the second trigger switch K2 of the commutation component are composed of anti-parallel thyristors, and the power switching switch K0 is a high-speed mechanical switch. In the embodiment of the present invention, the fully controlled device in the bidirectional power electronic switch is preferably an IGBT, such as but not limited to a 4.5kV-rated IGBT. The energy-dissipating MOV component is composed of multiple lightning arrester units connected in parallel, used to suppress the transient tripping voltage of the circuit breaker and absorb energy stored in the inductive element.

[0082] Specifically, the total current measuring device CT1 in the embodiment of the present invention may be a photoelectric current transformer or a current Hall effect sensor.

[0083] Specifically, in the embodiment of the present invention, the current-passing component includes a fast mechanical switch FTS (Fast Transfer Switch, referred to as fast mechanical switch) and a current measuring device CT2; the fast mechanical switch FTS and the current measuring device CT2 are connected in series.

[0084] It should be further explained that the fast mechanical switch FTS can be a permanent magnet vacuum switch, an electromagnetic repulsion vacuum switch or a semi-permanent magnet vacuum switch; the current measuring device CT2 can be a photoelectric current transformer or a current Hall.

[0085] like Figure 3 As shown, an embodiment of the present invention provides a commutation component with both dynamic commutation and static pressure bearing functions that does not rely on current direction detection, including a charging circuit, a commutation circuit, a bypass circuit, and a commutation trigger circuit;

[0086] The charging circuit, commutation circuit and bypass circuit are connected in parallel and then in series with the commutation trigger circuit;

[0087] The charging circuit includes: a DC power supply U0 and a power supply switching switch K0; the DC power supply U0 and the power supply switching switch K0 are connected in series.

[0088] The commutation circuit includes: an energy storage commutation capacitor C0, a commutation oscillation inductor L0, a voltage detection device V0, and a static equalizing resistor R1; the energy storage commutation capacitor C0 and the commutation oscillation inductor L0 are connected in series, and then connected in parallel with the static equalizing resistor R1, and the voltage detection device V0 is connected in parallel to the energy storage commutation capacitor C0.

[0089] The bypass circuit includes a first trigger switch K1 and an energy-consuming resistor R0 ; the first trigger switch K1 and the energy-consuming resistor R0 are connected in series.

[0090] The commutation trigger circuit includes: a second trigger switch K2, a static balancing resistor R2, a dynamic balancing capacitor C1, and a damping resistor R3; the dynamic balancing capacitor C1 and the damping resistor R3 are connected in series and then in parallel with the second trigger switch K2 and the static balancing resistor R2 respectively.

[0091] Specifically, the power switching switch K0, the first trigger switch K1, and the second trigger switch K2 in the embodiment of the present invention can be a high-speed mechanical switch, an anti-parallel thyristor (such as Figure 4 Components with switching characteristics include the anti-parallel thyristor T1 and thyristor T2, the anti-parallel thyristor T3 and thyristor T4), the controllable gap, etc.

[0092] like Figure 4 As shown, the fault current interrupting component includes multiple bidirectional power electronic switches and one energy consuming component.

[0093] The multiple bidirectional power electronic switches are connected in series and then in parallel with the energy dissipation component MOV; the energy dissipation component MOV includes a multiple metal oxide varistors in a series-parallel structure.

[0094] It should be further explained that in the embodiment of the present invention, the transient steady-state voltages of the commutation component and the disconnecting component are divided according to a certain distribution relationship, including:

[0095] When the DC circuit breaker is in the open state, the commutation component and the breaking component divide the voltage according to the preset static voltage distribution relationship, which depends on the resistance values ​​of the static grading resistor R1, the static grading resistor R2 and the static grading resistor R5.

[0096] When the DC circuit breaker is in the open state, the commutation components and the breaking components divide the voltage according to the preset transient voltage distribution relationship. The transient voltage distribution relationship depends on the capacitance of the commutation capacitor C0, the buffer capacitors C1 and C2.

[0097] During the opening process of the DC circuit breaker, the breaking component withstands 100% of the DC circuit breaker breaking overvoltage.

[0098] It should be further explained that the energy-consuming component MOV in the breaking assembly and the bidirectional power electronic switch voltage-limiting circuit MOV1 in the embodiment of the present invention need to satisfy a certain coordination relationship during the energy absorption process of the circuit breaker, including:

[0099] If the disconnecting component consists of N bidirectional power electronic switches connected in series, then under the same coordinated current, the residual voltage of the energy-consuming component MOV should be lower than the sum of the residual voltages of the N voltage-limiting circuits MOV1.

[0100] During the high current interruption process, the residual voltage of the voltage limiting circuit MOV1 should be lower than the safe operating voltage of the fully controlled device, and the absorbed energy should be lower than the design value of its energy absorption capacity.

[0101] During high current interruption, the residual voltage of the energy-consuming component MOV should be lower than the maximum voltage withstand capability after N bidirectional power electronic switches are connected in series, and the absorbed energy should be lower than the design value of its energy absorption capacity.

[0102] It should be further explained that the flow-through assembly, the commutation assembly, and the disconnection assembly in the embodiment of the present invention need to satisfy certain coordination relationships during the oscillation commutation process, including:

[0103] The fast mechanical switch FTS, energy storage commutation capacitor C0, commutation oscillation inductor L0, bridge arm diodes D1 to D4, and full control device G1 constitute a commutation oscillation circuit;

[0104] The energy storage commutation capacitor C0 discharges the commutation oscillation circuit to form an oscillating current that gradually decays;

[0105] The first peak value of the oscillating current should not be greater than the maximum tolerance of the fully controlled device G1;

[0106] The second peak value of the oscillating current should not be less than the maximum commutation current value.

[0107] Specifically, in the embodiment of the present invention, during the high current interruption process, the current sharing ratio between the voltage limiting circuit and the energy consuming component is 1:N; wherein N is an integer greater than 1.

[0108] It should be further explained that the relationship between the nonlinear circuit parameters inside and outside the breaking component in the embodiment of the present invention is as follows. During the large current breaking process, the current shunting ratio between the voltage limiting circuit and the energy consuming component MOV is preferably 1:9. Under this ratio, the voltage limiting circuit only uses a single zinc oxide resistor, avoiding the current unevenness problem of multiple low-voltage resistors in parallel, thereby improving reliability and reducing costs. Figure 5 shown.

[0109] The voltage distribution relationship between the commutation component and the disconnecting component in the embodiment of the present invention is as follows: for a DC circuit breaker with a rated voltage of 30kV, the commutation component has a rated voltage of 6kV, and the disconnecting component has a rated voltage of 24kV. During the opening process, the disconnecting component withstands a total disconnecting overvoltage of 48kV (generally 1.6 times the rated voltage).

[0110] A medium-voltage compact DC circuit breaker produced according to an embodiment of the present invention has a rated DC voltage of 30 kV, a maximum breaking current of 10 kA, a cut-off time of 3 ms, 13 bidirectional power electronic switches in series (including one-level series redundancy), and a bidirectional power electronic switch using an IGBT with a rated voltage of 4.5 kV and a rated current of 1.2 kA. Its breaking waveform is as follows: Figure 6 shown.

[0111] The hybrid DC circuit breaker in the embodiments of the present invention can solve the problems of high cost and large size caused by the large number of fully controlled devices connected in series and low voltage utilization in hybrid DC circuit breakers. By configuring a commutation component with both commutation and pressure-bearing functions and a nonlinear coordination circuit inside and outside the breaking component, a compact topological structure of the hybrid DC circuit breaker is achieved. The solution is self-cooling and does not require a water cooling system. At the same time, compared with conventional hybrid DC circuit breaker solutions of the same voltage level, the number of fully controlled devices connected in series at the same voltage level used in this solution can be reduced by more than 30%, providing a high-tech and economical solution for the large-scale promotion and application of medium and high voltage hybrid DC circuit breakers.

[0112] Example 3

[0113] The present invention based on the same inventive concept further provides a control method for a hybrid DC circuit breaker, which performs opening, closing, and pre-opening actions based on a hybrid DC circuit breaker in Example 2, including:

[0114] receiving a control instruction of the power system through the hybrid DC circuit breaker; the control instruction includes an opening instruction, a closing instruction, or a pre-opening instruction;

[0115] According to the control instructions, the current-carrying component, the current-commutating component and the breaking component in the hybrid DC circuit breaker are controlled to perform corresponding actions, and the total current measuring device in the hybrid DC circuit breaker is used to perform overcurrent detection.

[0116] Specifically, such as Figure 7 As shown, the hybrid DC circuit breaker in the embodiment of the present invention performs a tripping operation specifically including:

[0117] The DC circuit breaker is in the closed state, the fast mechanical switch in the current-passing component is in the closed state, the charging switch in the commutation component is in the closed state, other switches are in the open state, and the disconnecting electronic switch is in the locked state;

[0118] After receiving the trip command, the DC circuit breaker simultaneously issues the mechanical switch trip command and the commutation component charging switch trip command; the fast mechanical switch receives the mechanical switch trip command and trips; the charging switch in the commutation component trips and isolates the charging circuit; the charging circuit is in a pre-charging state, that is, the capacitor is fully charged in advance when the circuit breaker is closed, and the commutation capability is available at any time.

[0119] When the fast mechanical switch and the charging switch reach the disconnection point, they issue a triggering instruction for the bidirectional power electronic switch and a triggering instruction for the commutation thyristor circuit;

[0120] When the system current is commutated from the pass-through component to the bidirectional power electronic switch (i.e., the delay T1 or the charging circuit overvoltage protection setting U1 or the main branch current ≤ I1), the commutation component bypass circuit triggers the conduction instruction to release the residual energy of the commutation capacitor;

[0121] Among them, the delay T1 refers to a fixed delay, which depends on the operating characteristics and timing coordination between the various switches inside the circuit breaker. In the 30kV circuit breaker example, the value is preferably 500us; the charging circuit overvoltage protection constant U1 refers to more than 1.1 times the charging voltage; I1 depends on the maximum ability of the mechanical switch to open the DC current. In the embodiment of the present invention, it is 5A.

[0122] The first trigger switch (i.e., bypass thyristor) in the bypass circuit of the commutation component receives the closing command and closes. After the fast mechanical switch reaches the dynamic insulation tolerance opening distance, the bidirectional power electronic switch is locked (i.e., the power electronic switch is opened), the current begins to transfer to the energy-consuming component, and the system fault current begins to decrease. The system enters the hold-open state and reports the successful opening.

[0123] When the energy-consuming components finish consuming energy, the impedance adjustment circuit of the bidirectional power electronic switch and the system circuit form an over-damped oscillation, which accelerates the system oscillation process after the DC circuit breaker is opened and reduces the internal stress of the circuit breaker and the system.

[0124] Specifically, such as Figure 8 As shown, the closing action of the hybrid DC circuit breaker in the embodiment of the present invention specifically includes:

[0125] The DC circuit breaker is in the open state, all switches are in the open state, and all devices are in the locked state;

[0126] After receiving the closing command, the DC circuit breaker sends the closing command to the commutation component bypass circuit, commutation trigger circuit and bidirectional power electronic switch;

[0127] The total current measuring device performs overcurrent detection (i.e., the circuit breaker control protection fault determines overcurrent). If the overcurrent protection set value is reached, a bidirectional power electronic switch opening command is issued, and the switch enters the hold state. If the overcurrent protection set value is not reached, a fast mechanical switch closing command is issued, and the fast mechanical switch closes.

[0128] After waiting for a certain time T2 (generally the closing time of the fast mechanical switch), the control and protection determines whether the fast mechanical switch has reached the closed position. If the fast mechanical switch has reached the closed position, it will issue a bidirectional power electronic switch opening command and a commutation component charging switch closing command, and enter the hold closed state; otherwise, it will issue a fast mechanical switch opening command, and after waiting for a certain time T3 (generally the mechanical switch opening time), it will issue a bidirectional power electronic switch opening command, enter the hold open state and report the closing failure.

[0129] Specifically, such as Figure 9 As shown, the pre-tripping action of the hybrid DC circuit breaker in the embodiment of the present invention specifically includes:

[0130] The DC circuit breaker is in the closed state, the fast mechanical switch of the current-carrying component is in the closed state, the charging switch of the commutation component is in the closed state, other switches are in the open state, and the disconnecting electronic switch is in the locked state.

[0131] After receiving the pre-tripping command, the DC circuit breaker simultaneously issues the tripping command to the fast mechanical switch of the current-carrying component and the charging switch of the commutation component; the charging switch of the commutation component is opened to isolate the charging circuit; the fast mechanical switch receives the mechanical switch tripping command and trips.

[0132] When the fast mechanical switch and charging switch reach the initial disconnection point, a trigger-on command for the bidirectional power electronic switch and a command to turn on the commutation trigger circuit are issued. The commutation thyristors in the commutation assembly and the IGBTs in the bidirectional power electronic switch receive the closing command and close. After the system current commutates from the pass assembly to the bidirectional power electronic switch (delay T1, charging circuit overvoltage protection setting U1, or main branch current ≤ I1), a trigger-on command is issued for the commutation assembly bypass circuit (bypass thyristors) to release residual energy in the commutation capacitors. The total current measuring device performs overcurrent detection (current reaches the overcurrent setting) or receives a trip command. If the current exceeds the pre-tripping action current setting or receives a trip command from the upper-level control and protection system, the bidirectional power electronic switch (i.e., the IGBT) is locked, current is transferred to the energy-consuming components, and the system fault current begins to decrease. A successful trip is reported, and the system enters the maintained trip state. Otherwise, a closing command for the fast mechanical switch is issued, exiting the pre-tripping mode, locking the IGBT and closing the charging switch, and entering the maintained closed state.

[0133] It should be further explained that the pre-tripping circuit breaker uses the line current and the superior control and protection instructions as the judgment basis, completes the fast mechanical switch tripping action in advance, and achieves fast disconnection in hundreds of microseconds after the fault is confirmed.

[0134] It should be further explained that the basis for judging the switching of the system current from the current-carrying components to the breaking components during the opening action of the hybrid DC circuit breaker includes:

[0135] Monitor the commutation capacitor voltage V0. If the capacitor voltage reaches the overvoltage protection set value during the tripping process, the commutation component bypass circuit triggers the conduction instruction.

[0136] By setting a fixed delay, the bypass circuit of the commutation component is triggered to conduct.

[0137] Monitor the fast mechanical switch current CT2. When the fast mechanical switch current reaches the set value for determining successful commutation during the opening process, the commutation component bypass circuit triggers the conduction instruction.

[0138] The present invention can solve the problems of high cost and large size caused by the large number of fully controlled devices connected in series and low voltage utilization in hybrid DC circuit breakers. By configuring a commutation component with both commutation and pressure-bearing functions and a nonlinear coordination circuit inside and outside the breaking component, a compact topological structure of the hybrid DC circuit breaker is achieved. The solution is self-cooling and does not require a water cooling system, reducing the number of cooling devices by 50%. At the same time, compared with conventional hybrid DC circuit breaker solutions of the same voltage level, the number of fully controlled devices connected in series at the same voltage level used in this solution can be reduced by more than 30%, and the bidirectional power electronic switch bridge arm diodes can all use conventional diodes instead of fast recovery diodes, providing a high-tech and economical solution for the large-scale promotion and application of medium and high voltage hybrid DC circuit breakers.

[0139] In addition, it should be understood that although this specification describes the embodiments, not every embodiment contains only one independent technical solution. This description is for clarity only. Those skilled in the art should consider the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art. The above content is only for the purpose of illustrating the technical concept of the present invention and cannot be used to limit the scope of protection of the present invention. Any changes made based on the technical solution in accordance with the technical concept proposed by the present invention fall within the scope of protection of the claims of the present invention.

Claims

1. A bidirectional power electronic switch, characterized in that: It includes a diode bridge module, a buffer circuit, a voltage limiting circuit and an impedance adjustment circuit; the impedance adjustment circuit is connected in parallel to both ends of the diode bridge module; the buffer circuit is connected in parallel to the disconnecting electronic switch in the diode bridge module; the voltage limiting circuit is connected in parallel to both ends of the disconnecting electronic switch; The diode bridge module controls the switching current of the disconnecting electronic switch according to the disconnecting instruction of the power system; when the disconnecting electronic switch is locked, the buffer circuit suppresses the voltage and current changes of the disconnecting electronic switch during the switching process, the voltage limiting circuit limits the overvoltage level of the disconnecting electronic switch, and the impedance adjustment circuit reduces the oscillation frequency.

2. A bidirectional power electronic switch according to claim 1, characterized in that: The diode bridge module includes a first diode, a second diode, a third diode, a fourth diode and a disconnecting electronic switch; the disconnecting electronic switch adopts an IGBT tube; The positive electrode of the first diode is connected to the negative electrode of the second diode as one end of the diode bridge module; the negative electrode of the first diode is respectively connected to the collector of the IGBT tube and the negative electrode of the fourth diode; the positive electrode of the second diode is respectively connected to the emitter of the IGBT tube and the positive electrode of the third diode; the negative electrode of the third diode is connected to the positive electrode of the fourth diode as the other end of the diode bridge module.

3. A bidirectional power electronic switch according to claim 2, characterized in that: The buffer circuit includes a buffer capacitor, a static voltage-sharing resistor, a fifth diode and a damping resistor; One end of the buffer capacitor is connected in series with the cathode of the fifth diode, the buffer capacitor is connected in parallel with the static balancing resistor, and the fifth diode is connected in parallel with the damping resistor; The other end of the buffer capacitor is connected to the emitter of the IGBT tube; the anode of the fifth diode is connected to the collector of the IGBT tube.

4. A bidirectional power electronic switch according to claim 3, characterized in that: The impedance adjustment circuit includes a low-value capacitor and a low-value resistor; The low-value capacitor and the low-value resistor are connected in series, and then connected in parallel to the two ends of the diode bridge module.

5. A bidirectional power electronic switch according to claim 4, characterized in that: The capacitance of the low-value capacitor is at least one order of magnitude smaller than the capacitance of the buffer capacitor and two orders of magnitude larger than the parasitic capacitance of other components in the bidirectional power electronic switch; The resistance of the low-value resistor is two orders of magnitude greater than the parasitic resistance of the remaining components.

6. The bidirectional power electronic switch according to claim 1, characterized in that: The voltage limiting circuit includes a metal oxide varistor; The metal oxide varistor is connected in parallel with the disconnecting electronic switch.

7. A hybrid DC circuit breaker, characterized in that: It includes a current-passing component, a current-commutating component, a breaking component and a total current measuring device; The commutation component and the breaking component are connected in series and then in parallel with the flow component; the flow component and the total current measuring device are connected in series in the DC line; The disconnecting component comprises one or more bidirectional power electronic switches and energy-consuming components according to any one of claims 1 to 7; and the energy-consuming components are connected in parallel to one or more bidirectional power electronic switches connected in series.

8. The hybrid DC circuit breaker according to claim 7, characterized in that: The commutation component includes: a charging circuit, a commutation circuit, a bypass circuit and a commutation trigger circuit; The charging circuit, the commutation circuit and the bypass circuit are connected in parallel and then in series with the commutation trigger circuit; The charging circuit includes: a DC power supply and a power switching switch; the DC power supply and the power switching switch are connected in series; The commutation circuit includes: an energy storage commutation capacitor, a commutation oscillation inductor, a voltage detection device, and a static voltage grading resistor; the energy storage commutation capacitor and the commutation oscillation inductor are connected in series and in parallel with the static voltage grading resistor, and the voltage detection device is connected in parallel to the energy storage commutation capacitor; The bypass circuit includes a first trigger switch and an energy-consuming resistor; the first trigger switch and the energy-consuming resistor are connected in series; The commutation trigger circuit includes: a second trigger switch, a static balancing resistor, a dynamic balancing capacitor and a damping resistor; the dynamic balancing capacitor and the damping resistor are connected in series and then connected in parallel with the second trigger switch and the static balancing resistor respectively.

9. The hybrid DC circuit breaker according to claim 7, characterized in that: Under the same coordinated current, the residual voltage of the energy-consuming component is lower than the sum of the residual voltages of the voltage-limiting circuit; During the high current interruption process, the residual voltage of the energy-consuming component is lower than the maximum voltage withstand capability after multiple bidirectional power electronic switches are connected in series, and the absorbed energy should be lower than the design value of the energy absorption capacity.

10. The hybrid DC circuit breaker according to claim 9, characterized in that: During high current interruption, the current splitting ratio between the voltage limiting circuit and the energy consuming component is 1:N; Wherein, N is an integer greater than 1.

11. A method for controlling a hybrid DC circuit breaker according to any one of claims 7 to 10, characterized in that: include: receiving a control instruction of the power system through the hybrid DC circuit breaker; the control instruction includes an opening instruction, a closing instruction, or a pre-opening instruction; According to the control instructions, the current-carrying component, the current-commutating component and the breaking component in the hybrid DC circuit breaker are controlled to perform corresponding actions, and the total current measuring device in the hybrid DC circuit breaker is used to perform overcurrent detection.

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