Direct current breaker based on saturated iron core type superconducting current limiter

Abstract

The invention discloses a direct current breaker based on a saturated iron core type superconducting current limiter, which utilizes the characteristic that the saturated iron core type superconducting current limiter can change own impedance according to the change of current, so that when a system is short-circuited, the impedance of the current limiter is increased, the rise rate of short-circuit current is limited, and equipment is protected. When the short-circuit fault is removed, the impedance of the current limiter is recovered along with the recovery of the current, and the additional impedance is not increased when the current is equalized; the resonance branch is utilized to generate artificial current zero crossing, so that the arc generated by inconsistent opening of the vacuum switch can be extinguished, and the difficulty in opening and closing is reduced; the energy consumption branch is used for absorbing residual energy after the circuit breaker is switched off, safe operation of system equipment is ensured, and the problems that in the prior art, when multiple arc extinguish chambers are connected in parallel and current sharing is carried out, increased inductance still exists during rated operation of a system, and due to the fact that switching-off actions are inconsistent, a contact generates an electric arc, the contact is damaged, and the switching-off difficulty is increased are solved.

Description

Technical Field

[0001] The invention relates to the field of direct current circuit breaker, and in particular to a direct current breaker based on a saturated iron core type superconducting current limiter. Background Art

[0002] Flexible DC grids are widely used in long-distance power transmission and renewable energy grid connection due to their high transmission efficiency, long transmission distance, and flexible control. However, DC side fault removal is a key technical problem in the construction of flexible DC grids. DC short-circuit current has no natural zero-crossing point, which needs to be artificially created; and the DC short-circuit fault current has a high rise rate, so removal needs to be rapid. Existing DC fault removal methods such as converter locking, AC circuit breaker isolation, or DC breaker isolation all have limitations. In particular, for flexible DC transmission systems, the converter has no locking capability, and disconnecting the AC side circuit breaker may cause the system to shut down for a short time. Therefore, large-capacity, fast-breaking, and stable DC breakers are essential.

[0003] A Chinese patent application for a current-sharing structure and circuit breaker for a multi-circuit parallel circuit breaker, publication number: CN117457452A, arranges the arc extinguishing chambers in a regular polygonal manner, adds an iron core between the arc extinguishing chambers, increases the reactance of each branch, and uses the reactance to achieve the beneficial effect of current balancing. However, the inductance added by the patent in solving the current balancing problem of multiple arc extinguishing chambers in parallel still exists during the rated operation of the system, increasing the inductive impedance of the system, and multiple arc extinguishing chambers in parallel will cause arcs to be generated in the contacts due to inconsistent opening actions, thereby damaging the contacts, and thus comprehensively increasing the difficulty of breaking. Summary of the invention

[0004] The present invention provides a DC breaker based on a saturated iron core type superconducting current limiter, which can solve the problem of the prior art that the increased inductance when multiple arc extinguishing chambers are connected in parallel to share the current still exists during the rated operation of the system, increasing the inductive impedance of the system, and the multiple arc extinguishing chambers connected in parallel will cause arcs to be generated at the contacts due to inconsistent opening actions, thereby damaging the contacts, thereby comprehensively increasing the difficulty of breaking.

[0005] In order to solve the above technical problems, an embodiment of the present invention provides a DC breaker based on a saturated iron core type superconducting current limiter, comprising: a main current branch, a resonant branch and an energy dissipation branch; the main current branch comprises a first saturated iron core type superconducting current limiter, a second saturated iron core type superconducting current limiter, a first switch and a second switch; the resonant branch comprises an inductor, a capacitor and a third switch; the energy dissipation branch comprises an energy dissipator;

[0006] The output end of the first saturated iron core type superconducting current limiter is connected to the first end of the first switch, the output end of the second saturated iron core type superconducting current limiter is connected to the first end of the second switch, and the second end of the first switch and the second end of the second switch are commonly connected to the first end of the third switch;

[0007] The output end of the first saturated iron core type superconducting current limiter and the output end of the second saturated iron core type superconducting current limiter are commonly connected to the first end of the inductor, the second end of the inductor is connected to the first end of the capacitor, and the second end of the capacitor is connected to the second end of the third switch;

[0008] A first end of the energy consumer is connected to a first end of the inductor, and a second end of the energy consumer is connected to a first end of the third switch.

[0009] Furthermore, the first saturated iron core type superconducting current limiter and the second saturated iron core type superconducting current limiter are both composed of an iron core, a copper winding, a superconducting winding and a diode bridge circuit.

[0010] Further, the diode bridge circuit of the first saturated iron core type superconducting current limiter includes a first diode, a second diode, a third diode, and a fourth diode; the diode bridge circuit of the second saturated iron core type superconducting current limiter includes a fifth diode, a sixth diode, a seventh diode, and an eighth diode;

[0011] The input end of the first saturated iron core type superconducting current limiter is respectively connected to the positive end of the first diode and the negative end of the second diode, the output end of the first saturated iron core type superconducting current limiter is respectively connected to the positive end of the third diode and the negative end of the fourth diode, the negative ends of the first diode and the third diode are respectively connected to the input end of the copper winding, and the positive ends of the second diode and the fourth diode are respectively connected to the output end of the copper winding;

[0012] The input end of the second saturated iron core type superconducting current limiter is respectively connected to the positive end of the fifth diode and the negative end of the sixth diode, the output end of the second saturated iron core type superconducting current limiter is respectively connected to the positive end of the seventh diode and the negative end of the eighth diode, the negative ends of the fifth diode and the seventh diode are respectively connected to the input end of the copper winding, and the positive ends of the sixth diode and the eighth diode are respectively connected to the output end of the copper winding.

[0013] Furthermore, the superconducting windings of the first saturated iron-core type superconducting current limiter and the second saturated iron-core type superconducting current limiter are both powered by the same DC power supply.

[0014] Furthermore, the copper winding parameters and superconducting winding parameters of the first saturated iron core type superconducting current limiter and the second saturated iron core type superconducting current limiter are determined by the rated operating current of the power system, the core parameters, the dispersion of the vacuum switch and the vacuum arc voltage; wherein the copper winding parameters include the number of copper winding turns and the cross-sectional area of ​​the copper winding conductor; the superconducting winding parameters include the number of superconducting winding turns and the cross-sectional area of ​​the superconducting winding conductor; the core parameters include the core saturation magnetic field strength and the core magnetic path length.

[0015] Furthermore, the copper winding parameters are determined by the rated operating current of the power system, the core parameters, the dispersion of the vacuum switch and the vacuum arc voltage, including:

[0016] Calculate the initial value of the number of copper winding turns based on the core saturation magnetic field strength, core magnetic path length and rated operating current of the power system;

[0017] Calculate the initial value of the cross-sectional area of ​​the copper winding conductor according to the rated operating current of the power system and the preset copper conductor current density;

[0018] Determining a first margin factor and a second margin factor of the copper winding according to the dispersion of the vacuum switch and the vacuum arc voltage;

[0019] Calculating a final value of the number of turns of the copper winding according to a first margin coefficient of the copper winding, a second margin coefficient of the copper winding, and an initial value of the number of turns of the copper winding;

[0020] The final value of the cross-sectional area of ​​the copper winding wire is calculated according to the first margin coefficient of the copper winding, the second margin coefficient of the copper winding and the initial value of the cross-sectional area of ​​the copper winding wire.

[0021] Furthermore, the superconducting winding parameters are determined by the rated operating current of the power system, the core parameters, the dispersion of the vacuum switch and the vacuum arc voltage, including:

[0022] Calculate the initial value of the number of turns of the superconducting winding according to the saturated magnetic field strength of the iron core, the length of the iron core magnetic path and the rated operating current of the power system;

[0023] Calculate the initial value of the cross-sectional area of ​​the superconducting winding conductor according to the rated operating current of the power system and the preset current density of the superconducting winding conductor;

[0024] Determining a first margin factor and a second margin factor of the superconducting winding according to the vacuum switch dispersion and vacuum arc voltage;

[0025] Calculating a final value of the number of turns of the superconducting winding according to a first margin coefficient of the superconducting winding, a second margin coefficient of the superconducting winding, and an initial value of the number of turns of the superconducting winding;

[0026] The final value of the cross-sectional area of ​​the superconducting winding wire is calculated according to the first margin coefficient of the superconducting winding, the second margin coefficient of the superconducting winding and the initial value of the cross-sectional area of ​​the superconducting winding wire.

[0027] Furthermore, the switch types of the first switch and the second switch are vacuum switches.

[0028] Furthermore, the energy dissipator is a lightning arrester;

[0029] The arrester is used to absorb the residual energy of the inductance and the saturated iron core type superconducting current limiter in the DC breaker after the DC breaker is broken.

[0030] Further, the third switch includes: a first thyristor, a second thyristor, a first resistor, a capacitor of the third switch and a second resistor;

[0031] The cathode terminal of the first thyristor is connected to the anode terminal of the second thyristor, and the anode terminal of the first thyristor is connected to the cathode terminal of the second thyristor;

[0032] An anode terminal of the second thyristor is connected to a first terminal of the first resistor, and a cathode terminal of the second thyristor is connected to a second terminal of the first resistor;

[0033] The first end of the first resistor is connected to the first end of the capacitor of the third switch, the second end of the capacitor of the third switch is connected to the first end of the second resistor, and the second end of the second resistor is connected to the second end connected to the first resistor.

[0034] Compared with the prior art, the embodiments of the present invention have the following beneficial effects:

[0035] The present invention provides a DC breaker based on a saturated iron core type superconducting current limiter, which is composed of a main current branch, a resonant branch and an energy consumption branch. The main current branch includes a saturated iron core type superconducting current limiter and two vacuum switches, the resonant branch includes an inductor, a capacitor and a switch, and the energy consumption branch includes a lightning arrester; the first output end of the saturated iron core type superconducting current limiter is connected to the first vacuum switch, the second output end of the saturated iron core type superconducting current limiter is connected to the second vacuum switch, the other end of the first vacuum switch and the other end of the second vacuum switch are commonly connected to one end of the switch, the other end of the switch is connected to one end of the capacitor, the other end of the capacitor is connected to one end of the inductor, the other end of the inductor is respectively connected to the first output end and the second output end of the saturated iron core type superconducting current limiter, the other end of the inductor is also connected to one end of the lightning arrester, and the other end of the lightning arrester is connected to one end of the switch; that is, the saturated iron core type superconducting current limiter can be used to adjust the current according to the current. The characteristic of changing its own impedance makes the impedance of the saturated iron core type superconducting current limiter increase when a short circuit occurs in the power system, limiting the rising rate of the short circuit current, avoiding the equipment from being damaged by the short circuit current generated when the short circuit fault occurs. When the short circuit fault is removed, the impedance of the saturated iron core type superconducting current limiter recovers with the recovery of the current, so that the current is evenly distributed. When a short circuit fault occurs, the resonant branch is used to generate an artificial current zero crossing so that the arc generated when the vacuum switch is inconsistently opened can be extinguished, reducing the difficulty of breaking. And the energy-consuming branch is used to absorb the residual energy after the circuit breaker is opened to ensure the safe operation of the system equipment, solving the problem of the existing technology of parallel current sharing of multiple arc extinguishing chambers. The increased inductance still exists during the rated operation of the system, increasing the inductive impedance of the system, and the multiple arc extinguishing chambers in parallel will cause arcs to be generated on the contacts due to inconsistent opening actions, thereby damaging the contacts, thereby comprehensively increasing the difficulty of breaking. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 : A circuit topology diagram of a DC breaker based on a saturated iron core type superconducting current limiter provided in an embodiment of the present invention;

[0037] Figure 2 : A flow chart of the working principle steps of a DC breaker based on a saturated iron core type superconducting current limiter provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0038] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0039] In the description of the present invention, it should be understood that the terms "first", "second", "third", "fourth", "fifth", "sixth", "seventh" and "eighth" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated.

[0040] Embodiment 1:

[0041] Reference Figure 1 , a circuit topology diagram of a DC breaker based on a saturated iron core type superconducting current limiter provided by an embodiment of the present invention; the DC breaker comprises: a main current branch, a resonant branch and an energy dissipation branch; the main current branch comprises a first saturated iron core type superconducting current limiter (corresponding to number 1 of the circuit topology diagram), a second saturated iron core type superconducting current limiter (corresponding to number 2 of the circuit topology diagram), a first switch (corresponding to number 3 of the circuit topology diagram), and a second switch (corresponding to number 4 of the circuit topology diagram); the resonant branch comprises an inductor (corresponding to number 5 of the circuit topology diagram), a capacitor (corresponding to number 6 of the circuit topology diagram) and a third switch (corresponding to number 7 of the circuit topology diagram); the energy dissipation branch comprises an energy dissipator (corresponding to number 8 of the circuit topology diagram);

[0042] The output end of the first saturated iron core type superconducting current limiter is connected to the first end of the first switch, the output end of the second saturated iron core type superconducting current limiter is connected to the first end of the second switch, and the second end of the first switch and the second end of the second switch are commonly connected to the first end of the third switch;

[0043] The output end of the first saturated iron core type superconducting current limiter and the output end of the second saturated iron core type superconducting current limiter are commonly connected to the first end of the inductor, the second end of the inductor is connected to the first end of the capacitor, and the second end of the capacitor is connected to the second end of the third switch;

[0044] A first end of the energy consumer is connected to a first end of the inductor, and a second end of the energy consumer is connected to a first end of the third switch.

[0045] In this embodiment, the first saturated iron core type superconducting current limiter and the second saturated iron core type superconducting current limiter are both composed of an iron core, a copper winding, a superconducting winding and a diode bridge circuit.

[0046] In this embodiment, the diode bridge circuit can ensure that the current is input into the copper winding according to the current direction designed by the diode bridge circuit.

[0047] In this embodiment, the diode bridge circuit of the first saturated iron core type superconducting current limiter includes a first diode, a second diode, a third diode, and a fourth diode; the diode bridge circuit of the second saturated iron core type superconducting current limiter includes a fifth diode, a sixth diode, a seventh diode, and an eighth diode;

[0048] The input end of the first saturated iron core type superconducting current limiter is respectively connected to the positive end of the first diode and the negative end of the second diode, the output end of the first saturated iron core type superconducting current limiter is respectively connected to the positive end of the third diode and the negative end of the fourth diode, the negative ends of the first diode and the third diode are respectively connected to the input end of the copper winding, and the positive ends of the second diode and the fourth diode are respectively connected to the output end of the copper winding;

[0049] The input end of the second saturated iron core type superconducting current limiter is respectively connected to the positive end of the fifth diode and the negative end of the sixth diode, the output end of the second saturated iron core type superconducting current limiter is respectively connected to the positive end of the seventh diode and the negative end of the eighth diode, the negative ends of the fifth diode and the seventh diode are respectively connected to the input end of the copper winding, and the positive ends of the sixth diode and the eighth diode are respectively connected to the output end of the copper winding.

[0050] In this embodiment, the superconducting windings of the first saturated iron core type superconducting current limiter and the second saturated iron core type superconducting current limiter are both powered by the same DC power supply.

[0051] In this embodiment, the copper winding parameters and superconducting winding parameters of the first saturated iron core type superconducting current limiter and the second saturated iron core type superconducting current limiter are determined by the rated operating current of the power system, the core parameters, the dispersion of the vacuum switch and the vacuum arc voltage; wherein the copper winding parameters include the number of copper winding turns and the cross-sectional area of ​​the copper winding wire; the superconducting winding parameters include the number of superconducting winding turns and the cross-sectional area of ​​the superconducting winding wire; the core parameters include the core saturation magnetic field strength and the core magnetic path length.

[0052] In this embodiment, the copper winding parameters are determined by the rated operating current of the power system, the core parameters, the dispersion of the vacuum switch and the vacuum arc voltage, including:

[0053] Calculate the initial value of the number of copper winding turns based on the core saturation magnetic field strength, core magnetic path length and rated operating current of the power system;

[0054] In this embodiment, the calculation formula for the initial value of the number of turns of the copper winding is: Among them, N cu，initial is the initial value of the number of turns of the copper winding; H c is the saturation magnetic field intensity of the iron core; l c I is the length of the core magnetic path; n is the rated operating current of the power system;

[0055] Calculate the initial value of the cross-sectional area of ​​the copper winding conductor according to the rated operating current of the power system and the preset copper conductor current density;

[0056] In this embodiment, the calculation formula for the initial value of the cross-sectional area of ​​the copper winding conductor is: Among them, A cu，initial is the initial value of the cross-sectional area of ​​the copper winding conductor; I n is the rated operating current of the power system; J cu is the current density of the copper wire;

[0057] Determining a first margin factor and a second margin factor of the copper winding according to the dispersion of the vacuum switch and the vacuum arc voltage;

[0058] In this embodiment, a preset margin coefficient corresponding to the dispersion degree of the vacuum switch dispersion is used as the first margin coefficient of the copper winding, and a preset margin coefficient corresponding to the vacuum arc voltage is used as the second margin coefficient of the copper winding;

[0059] Calculating a final value of the number of turns of the copper winding according to a first margin coefficient of the copper winding, a second margin coefficient of the copper winding, and an initial value of the number of turns of the copper winding;

[0060] In this embodiment, the calculation formula for the final value of the number of turns of the copper winding is:

[0061] N cu，final=N cu，initinal +k1×N cu，initinal +k2×N cu，initinal ;

[0062] Among them, N cu，final is the final value of the number of turns of the copper winding; N cu，initial is the initial value of the number of turns of the copper winding; k1 is the first margin coefficient of the copper winding; k2 is the first margin coefficient of the copper winding;

[0063] Calculating a final value of the cross-sectional area of ​​the copper winding conductor according to a first margin coefficient of the copper winding, a second margin coefficient of the copper winding, and an initial value of the cross-sectional area of ​​the copper winding conductor;

[0064] In this embodiment, the calculation formula for the final value of the cross-sectional area of ​​the copper winding conductor is:

[0065] A cu,final =A cu,initinal +k1×A cu,initinal +k2×A cu,initinal ;

[0066] Among them, A cu,final is the final value of the cross-sectional area of ​​the copper winding conductor; A cu,initial is the initial value of the cross-sectional area of ​​the copper winding wire; k1 is the first margin coefficient of the copper winding; k2 is the first margin coefficient of the copper winding.

[0067] In this embodiment, the superconducting winding parameters are determined by the rated operating current of the power system, the core parameters, the dispersion of the vacuum switch and the vacuum arc voltage, including:

[0068] Calculate the initial value of the number of turns of the superconducting winding according to the saturated magnetic field strength of the iron core, the length of the iron core magnetic path and the rated operating current of the power system;

[0069] In this embodiment, the calculation formula for the initial value of the number of turns of the superconducting winding is: Among them, N sc,initial is the initial value of the number of turns of the superconducting winding; N cu,initial is the initial value of the number of turns of the copper winding; H c is the saturation magnetic field intensity of the iron core; l c I is the length of the core magnetic path; n is the rated operating current of the power system;

[0070] Calculate the initial value of the cross-sectional area of ​​the superconducting winding conductor according to the rated operating current of the power system and the preset current density of the superconducting winding conductor;

[0071] In this embodiment, the calculation formula for the initial value of the cross-sectional area of ​​the superconducting winding wire is: Among them, A sc,initial is the initial value of the cross-sectional area of ​​the superconducting winding wire; In is the rated operating current of the power system; J c is the current density of the superconducting winding wire;

[0072] Determining a first margin factor and a second margin factor of the superconducting winding according to the vacuum switch dispersion and vacuum arc voltage;

[0073] In this embodiment, the first margin coefficient of the superconducting winding is the same as the first margin coefficient of the copper winding, and the second margin coefficient of the superconducting winding is the same as the second margin coefficient of the copper winding;

[0074] Calculating a final value of the number of turns of the superconducting winding according to a first margin coefficient of the superconducting winding, a second margin coefficient of the superconducting winding, and an initial value of the number of turns of the superconducting winding;

[0075] In this embodiment, the calculation formula for the final value of the number of turns of the superconducting winding is:

[0076] N sc,final =N sc,initinal +k1×N sc,initinal +k2×N sc,initinal ;

[0077] Among them, N sc，final is the final value of the number of turns of the superconducting winding; N sc，initial is the initial value of the number of turns of the superconducting winding; k1 is the first margin coefficient of the superconducting winding; k2 is the first margin coefficient of the superconducting winding;

[0078] Calculating a final value of the cross-sectional area of ​​the superconducting winding wire according to a first margin coefficient of the superconducting winding, a second margin coefficient of the superconducting winding, and an initial value of the cross-sectional area of ​​the superconducting winding wire;

[0079] In this embodiment, the calculation formula for the final value of the cross-sectional area of ​​the superconducting winding wire is:

[0080] A sc，final =A sc，initinal +k1×A sc，initinal +k2×A sc，initinal ;

[0081] Among them, A sc，final is the final value of the cross-sectional area of ​​the superconducting winding wire; A sc，final is the initial value of the cross-sectional area of ​​the superconducting winding wire; k1 is the first margin coefficient of the superconducting winding; k2 is the first margin coefficient of the superconducting winding.

[0082] In this embodiment, the switch types of the first switch and the second switch are vacuum switches.

[0083] In this embodiment, the energy dissipator is a lightning arrester;

[0084] The arrester is used to absorb the residual energy of the inductance and the saturated iron core type superconducting current limiter in the DC breaker after the DC breaker is broken.

[0085] In this embodiment, the third switch includes: a first thyristor, a second thyristor, a first resistor, a capacitor of the third switch, and a second resistor;

[0086] The cathode terminal of the first thyristor is connected to the anode terminal of the second thyristor, and the anode terminal of the first thyristor is connected to the cathode terminal of the second thyristor;

[0087] An anode terminal of the second thyristor is connected to a first terminal of the first resistor, and a cathode terminal of the second thyristor is connected to a second terminal of the first resistor;

[0088] The first end of the first resistor is connected to the first end of the capacitor of the third switch, the second end of the capacitor of the third switch is connected to the first end of the second resistor, and the second end of the second resistor is connected to the second end of the first resistor.

[0089] In this embodiment, when selecting the diodes in the first saturated iron core type superconducting current limiter (corresponding to number 1 in the circuit topology diagram) and the second saturated iron core type superconducting current limiter (corresponding to number 2 in the circuit topology diagram), the voltage withstand capability of the diodes should be greater than the rated operating voltage of the system; when selecting the two vacuum switches (corresponding to numbers 3 and 4 in the circuit topology diagram), the rated flow capacity and current breaking capacity of the vacuum switches should meet the system requirements; when selecting the inductance, capacitance and switch of the resonant branch (corresponding to numbers 5, 6 and 7 in the topology diagram respectively), the expected short-circuit current size and rated voltage of the system should be fully considered to ensure that the resonant current generated by the resonance is greater than the expected short-circuit current amplitude of the system and can withstand the voltage of the system; when selecting the lightning arrester of the energy consumption branch, the rated voltage and operating overvoltage of the system should be considered.

[0090] For example, in a DC system with a rated working voltage of 10kV, a rated operating current of 10kA, and an expected short-circuit current of 40kA, the diode should be selected with a maximum reverse working voltage greater than 10kV and a continuous current carrying capacity greater than 10kA. The vacuum switch should be selected with a rated current carrying capacity greater than 5kA and a rated breaking current greater than 20kA. The resonant capacitor and resonant inductor should be selected to be able to generate a resonant current with an amplitude greater than 40kA. Ten capacitors with a capacitance of 0.3mF can be selected in parallel to form a resonant capacitor with a capacitance of 3mF, and the resonant The resonant capacitor is pre-charged with a voltage of 6kV, the resonant inductor is selected with an inductance of 0.03mH, a withstand voltage greater than 10kV, and a peak current greater than 40kA. When a thyristor is selected, its current peak is greater than 40kA, and the short-time withstand voltage should be greater than the residual voltage under the nominal discharge of the lightning arrester. The lightning arrester can be selected with a rated voltage of 10kV and a 1mA reference voltage of 11.5kV, and the residual voltage after the lightning arrester is discharged should be within the tolerance range of other components; in addition, for the above selection that is greater than a certain value, sufficient margin should be left when selecting specific parameters.

[0091] Embodiment 2:

[0092] Reference Figure 2 , is a flowchart of the working principle steps of a DC breaker based on a saturated iron core type superconducting current limiter provided by an embodiment of the present invention; the working principle of the DC breaker includes at least the following steps:

[0093] Step S1: When a short-circuit fault occurs in the power system, the power system generates a short-circuit current, and the short-circuit current is respectively input into a first saturated iron-core type superconducting current limiter and a second saturated iron-core type superconducting current limiter of a main current-carrying branch;

[0094] Step S2: the first saturated iron core type superconducting current limiter and the second saturated iron core type superconducting current limiter enter a non-saturated state, and the first vacuum switch and the second vacuum switch perform a tripping operation according to a preset time sequence;

[0095] In this embodiment, when a short-circuit fault occurs in the power system, a short-circuit current is generated, and the current passing through the copper windings in the first saturated iron-core type superconducting current limiter and the second saturated iron-core type superconducting current limiter increases rapidly, and the magnetic field generated by the copper windings continues to strengthen, causing the iron core to exit the saturated region and enter the unsaturated region to prepare a very large magnetic permeability, and then the superconducting current limiter automatically shows a large impedance to the outside, limiting the short-circuit current rising rate.

[0096] Step S3: After the first vacuum switch and the second vacuum switch are opened according to a preset time sequence, the third switch of the resonant branch is closed, the resonant branch generates a reverse current, and the reverse current is input into the main current branch, an artificial current zero crossing is generated, the arc generated by the first vacuum switch and the second vacuum switch is extinguished, and the short-circuit current is interrupted;

[0097] In this embodiment, since the opening operation is decentralized, that is, when two vacuum switches are opened, there will be a time difference in the generation of arcs in the vacuum switches due to the inconsistency of the opening time. The arc voltage generated by the vacuum switch that operates first will drive the current to transfer to the vacuum switch that operates later, destroying its current sharing characteristics. The relationship of the transferred current is as follows:

[0098]

[0099] In formula (1), i1 is the first branch current, the first branch resistance is R3, i2 and R2 are the second branch current and resistance, Uarc is the arc voltage, i is the system current, and formula (1) can be simplified to obtain:

[0100]

[0101] It can be seen from formula (2) that the current transfer rate is negatively correlated with the impedance in the transfer route, that is, the impedance generated by the saturated iron core type superconducting current limiter connected in series with the vacuum switch will greatly slow down the current transfer rate, thereby improving the current sharing characteristics of the double arc extinguishing chamber parallel structure.

[0102] Step S4: after the short-circuit current is interrupted, the energy dissipator of the energy dissipation branch absorbs the remaining energy of the inductor and the saturated iron core type superconducting current limiter in the DC breaker;

[0103] Step S5: when the short-circuit fault of the power system is removed, the first saturated iron-core type superconducting current limiter and the second saturated iron-core type superconducting current limiter of the main current branch enter a saturated state, and the first vacuum switch and the second vacuum switch are reclosed;

[0104] In this embodiment, after the short-circuit fault of the power system is removed, the power of the power system returns to normal, the current passing through the copper windings in the first saturated iron-core type superconducting current limiter and the second saturated iron-core type superconducting current limiter returns to normal, the magnetic field generated by the copper windings continues to decrease, and the iron core of the saturated iron-core type superconducting current limiter enters an oversaturated state under the action of the superconducting winding. At this time, the saturated iron-core type superconducting current limiter will automatically enter a low impedance state in a relatively short time.

[0105] Step S6: After the first vacuum switch and the second vacuum switch are reclosed, the third switch of the resonant branch is opened.

[0106] In this embodiment, the working principle of the DC breaker also includes:

[0107] When the power system operates normally, the first saturated iron core type superconducting current limiter and the second saturated iron core type superconducting current limiter of the main current branch are in a saturated state, the first vacuum switch and the second vacuum switch are in a closed state, and the third switch of the resonant branch is in an open state.

[0108] It should be noted that the above-mentioned terminal device may include, but is not limited to, a processor and a memory. Those skilled in the art will understand that the above-mentioned terminal device is merely an example and does not constitute a limitation on the terminal device. It may include more or fewer components, or a combination of certain components, or different components.

[0109] The specific embodiments described above further illustrate the purpose, technical solutions and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. It is particularly pointed out that for those skilled in the art, any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the scope of protection of the present invention.

Claims

1. A DC breaker based on a saturated iron core type superconducting current limiter, characterized in that: include: A main current branch, a resonant branch and an energy consumption branch; the main current branch includes a first saturated iron core type superconducting current limiter, a second saturated iron core type superconducting current limiter, a first switch and a second switch; the resonant branch includes an inductor, a capacitor and a third switch; the energy consumption branch includes an energy dissipator; The output end of the first saturated iron core type superconducting current limiter is connected to the first end of the first switch, the output end of the second saturated iron core type superconducting current limiter is connected to the first end of the second switch, and the second end of the first switch and the second end of the second switch are commonly connected to the first end of the third switch; The output end of the first saturated iron core type superconducting current limiter and the output end of the second saturated iron core type superconducting current limiter are commonly connected to the first end of the inductor, the second end of the inductor is connected to the first end of the capacitor, and the second end of the capacitor is connected to the second end of the third switch; A first end of the energy consumer is connected to a first end of the inductor, and a second end of the energy consumer is connected to a first end of the third switch.

2. A DC breaker based on a saturated iron core type superconducting current limiter according to claim 1, characterized in that: The first saturated iron core type superconducting current limiter and the second saturated iron core type superconducting current limiter are both composed of an iron core, a copper winding, a superconducting winding and a diode bridge circuit.

3. A DC breaker based on a saturated iron core type superconducting current limiter according to claim 2, characterized in that: The diode bridge circuit of the first saturated iron core type superconducting current limiter includes a first diode, a second diode, a third diode, and a fourth diode; the diode bridge circuit of the second saturated iron core type superconducting current limiter includes a fifth diode, a sixth diode, a seventh diode, and an eighth diode; The input end of the first saturated iron core type superconducting current limiter is respectively connected to the positive end of the first diode and the negative end of the second diode, the output end of the first saturated iron core type superconducting current limiter is respectively connected to the positive end of the third diode and the negative end of the fourth diode, the negative ends of the first diode and the third diode are respectively connected to the input end of the copper winding, and the positive ends of the second diode and the fourth diode are respectively connected to the output end of the copper winding; The input end of the second saturated iron core type superconducting current limiter is respectively connected to the positive end of the fifth diode and the negative end of the sixth diode, the output end of the second saturated iron core type superconducting current limiter is respectively connected to the positive end of the seventh diode and the negative end of the eighth diode, the negative ends of the fifth diode and the seventh diode are respectively connected to the input end of the copper winding, and the positive ends of the sixth diode and the eighth diode are respectively connected to the output end of the copper winding.

4. A DC breaker based on a saturated iron core type superconducting current limiter according to claim 3, characterized in that: The superconducting windings of the first saturated iron core type superconducting current limiter and the second saturated iron core type superconducting current limiter are both powered by the same DC power supply.

5. A DC breaker based on a saturated iron core type superconducting current limiter according to claim 4, characterized in that: The copper winding parameters and superconducting winding parameters of the first saturated iron core type superconducting current limiter and the second saturated iron core type superconducting current limiter are determined by the rated operating current of the power system, the iron core parameters, the dispersion of the vacuum switch and the vacuum arc voltage; wherein the copper winding parameters include the number of copper winding turns and the cross-sectional area of ​​the copper winding wire; the superconducting winding parameters include the number of superconducting winding turns and the cross-sectional area of ​​the superconducting winding wire; the iron core parameters include the iron core saturation magnetic field strength and the iron core magnetic path length.

6. A DC breaker based on a saturated iron core type superconducting current limiter according to claim 5, characterized in that: The copper winding parameters are determined by the rated operating current of the power system, the core parameters, the dispersion of the vacuum switch and the vacuum arc voltage, and include: Calculate the initial value of the number of copper winding turns based on the core saturation magnetic field strength, core magnetic path length and rated operating current of the power system; Calculate the initial value of the cross-sectional area of ​​the copper winding conductor according to the rated operating current of the power system and the preset copper conductor current density; Determining a first margin factor and a second margin factor of the copper winding according to the dispersion of the vacuum switch and the vacuum arc voltage; Calculating a final value of the number of turns of the copper winding according to a first margin coefficient of the copper winding, a second margin coefficient of the copper winding, and an initial value of the number of turns of the copper winding; The final value of the cross-sectional area of ​​the copper winding wire is calculated according to the first margin coefficient of the copper winding, the second margin coefficient of the copper winding and the initial value of the cross-sectional area of ​​the copper winding wire.

7. A DC breaker based on a saturated iron core type superconducting current limiter according to claim 6, characterized in that: The superconducting winding parameters are determined by the rated operating current of the power system, the core parameters, the dispersion of the vacuum switch and the vacuum arc voltage, and include: Calculate the initial value of the number of turns of the superconducting winding according to the saturated magnetic field strength of the iron core, the length of the iron core magnetic path and the rated operating current of the power system; Calculate the initial value of the cross-sectional area of ​​the superconducting winding conductor according to the rated operating current of the power system and the preset current density of the superconducting winding conductor; Determining a first margin factor and a second margin factor of the superconducting winding according to the vacuum switch dispersion and vacuum arc voltage; Calculating a final value of the number of turns of the superconducting winding according to a first margin coefficient of the superconducting winding, a second margin coefficient of the superconducting winding, and an initial value of the number of turns of the superconducting winding; The final value of the cross-sectional area of ​​the superconducting winding wire is calculated according to the first margin coefficient of the superconducting winding, the second margin coefficient of the superconducting winding and the initial value of the cross-sectional area of ​​the superconducting winding wire.

8. A DC breaker based on a saturated iron core type superconducting current limiter according to claim 7, characterized in that: The switch types of the first switch and the second switch are vacuum switches.

9. A DC breaker based on a saturated iron core type superconducting current limiter according to claim 8, characterized in that: The energy dissipator is a lightning arrester; The arrester is used to absorb the residual energy of the inductance and the saturated iron core type superconducting current limiter in the DC breaker after the DC breaker is broken.

10. A DC breaker based on a saturated iron core type superconducting current limiter according to claim 9, characterized in that: The third switch comprises: a first thyristor, a second thyristor, a first resistor, a capacitor of the third switch and a second resistor; The cathode terminal of the first thyristor is connected to the anode terminal of the second thyristor, and the anode terminal of the first thyristor is connected to the cathode terminal of the second thyristor; An anode terminal of the second thyristor is connected to a first terminal of the first resistor, and a cathode terminal of the second thyristor is connected to a second terminal of the first resistor; The first end of the first resistor is connected to the first end of the capacitor of the third switch, the second end of the capacitor of the third switch is connected to the first end of the second resistor, and the second end of the second resistor is connected to the second end connected to the first resistor.

Images