Coupling inductor current limiting type hybrid direct current circuit breaker topology and working method

Abstract

The invention relates to a coupled inductor current-limiting type hybrid direct-current circuit breaker topology and a working method. The coupled inductor current-limiting type hybrid direct-current circuit breaker comprises a current-carrying part and a breaking part, the current-carrying part is formed by connecting an ultra-fast mechanical switch UFD and a load change-over switch LCS in series, the breaking part comprises a bridge circuit, a first branch circuit, a second branch circuit, a third branch circuit, a fourth branch circuit, a fifth branch circuit and a sixth branch circuit, the fourth branch circuit is formed by connecting a thyristor, a coupling inductor and a primary side inductor in series to form a current-limiting branch circuit, and the fifth branch circuit is formed by connecting a secondary side inductor and a secondary side inductor. The sixth branch is formed by connecting a secondary side inductor of a coupling inductor with a thyristor in series and then connecting the secondary side inductor with a capacitor in parallel; the current limiting of the fault current is realized through the fourth branch, the fault breaking of the primary side inductor of the coupling inductor of the fourth branch is completed through the coupling effect of the secondary side inductor of the coupling inductor of the sixth branch, the peak value of the fault current is obviously reduced, and the breaking time is obviously shortened; the circuit breaker can quickly respond to faults of three working modes of current limiting breaking, reclosing and small current breaking; and the breaking part of the circuit breaker adopts the thyristors instead of the IGBTs, so that the cost of the circuit breaker is reduced.

Description

Technical Field

[0001] This invention relates to the field of power equipment, and particularly to a hybrid DC circuit breaker with coupled inductor current limiting. Background Technology

[0002] DC transmission technology plays a crucial role in promoting the large-scale, cross-regional, and long-distance transmission of clean energy. Among them, flexible DC transmission, with its significant advantages in renewable energy grid connection and transmission, has become a core supporting technology for building new power systems and a global energy internet. However, when a DC system short-circuites, the fault current rises extremely rapidly, quickly reaching a dangerous peak despite being constrained by system impedance. DC circuit breakers, capable of detecting and rapidly isolating faults within a very short time, thus ensuring the safety and stability of the entire system, are key equipment for achieving rapid fault current interruption in flexible DC grids.

[0003] Hybrid DC circuit breakers combine the low operating losses of mechanical DC circuit breakers with the fast dynamic breaking speed of solid-state DC circuit breakers. Under normal operation, current flows through the main branch of the mechanical switch. Once a fault is detected, the current is quickly transferred to a branch composed of power electronic devices for breaking. However, to achieve high-voltage applications, traditional solutions require a large number of cascaded IGBT components in the transfer branch, resulting in high overall costs for high-voltage DC circuit breakers. Furthermore, traditional solutions also suffer from problems such as large fault current peaks and long breaking times. Summary of the Invention

[0004] The purpose of this invention is to provide a hybrid DC circuit breaker topology and operating method with coupled inductor current limiting. This circuit breaker achieves current limiting and interruption through coupled inductor, reducing the peak fault current and shortening the interruption time. It also uses thyristors instead of IGBTs, thus reducing the cost of the circuit breaker.

[0005] To achieve the above-mentioned objectives of this invention, the following technical solutions are used:

[0006] A hybrid DC circuit breaker topology with coupled inductor current limiting includes a current-carrying section and a breaking section;

[0007] The current-carrying part is connected in series in the DC transmission line and consists of an ultra-fast mechanical switch (UFD) and a load transfer switch (LCS) connected in series. The load transfer switch (LCS) is composed of two sets of integrated gate commutating thyristors (IGBTs) connected in reverse parallel with diodes, and then connected in reverse series.

[0008] The disconnected section also includes a bridge circuit, a first branch, a second branch, a third branch, a fourth branch, a fifth branch, and a sixth branch;

[0009] The bridge circuit is composed of two sets of thyristors T7 and T8 and two sets of diodes D1 and D2 connected in series. Thyristor T8 and diode D1 are connected in series on the left side, and thyristor T7 and diode D2 are connected in series on the right side. The bridge circuit is connected in parallel across the current-carrying section.

[0010] The first branch circuit consists of thyristor T1, mechanical switch S, and charging resistor R. g The series grounding component is located on the left side inside the bridge circuit.

[0011] The second branch is connected by thyristor T2 inside the right side of the bridge circuit, in parallel with the series structure of thyristor T7 and diode D2;

[0012] The third branch circuit is formed by connecting one end of the surge arrester MOA to the thyristor T1 and the other end to the thyristor T2;

[0013] The fourth branch is formed by connecting the thyristor T4 and the primary inductor L1 in series, and then connecting them in parallel with the third branch.

[0014] The fifth branch is formed by connecting thyristor T3 and thyristor T6 in antiparallel, then connecting them in series with capacitor C, and finally connecting them in parallel with the fourth branch.

[0015] The sixth branch circuit consists of a coupling inductor secondary side inductor L2 connected in series with thyristor T5 and then connected in parallel with capacitor C.

[0016] Furthermore, in the bridge circuit, the anode of diode D1 and the cathode of thyristor T8 are connected in series, with diode D1 located at the upper end of the series circuit and thyristor T8 located at the lower end of the series circuit. The anode of diode D2 and the cathode of thyristor T7 are connected in series, with diode D2 located at the upper end of the series circuit and thyristor T7 located at the lower end of the series circuit. The cathodes of diode D1 and D2 are connected in series, and the anodes of thyristor T8 and T7 are connected in series. The anodes of diodes D1 and D2 are respectively connected to the left and right ends of the current-carrying section.

[0017] Furthermore, the first branch circuit consists of the cathode of the thyristor T1, the mechanical switch S, and the charging resistor R. g After being connected in series, it passes through the charging resistor R g The other end is grounded, and the anode of the thyristor T1 is connected to the cathode of the diode D1.

[0018] Furthermore, in the second branch, the anode of the thyristor T2 is connected to the cathode of the diode D2, and the cathode of the thyristor T2 is connected to the anode of the thyristor T7.

[0019] Furthermore, the third branch circuit is formed by connecting one end of the surge arrester MOA to the cathode of the thyristor T1 and the other end to the cathode of the thyristor T2.

[0020] Furthermore, the fourth branch is formed by connecting the cathode of the thyristor T4 to the same-name terminal of the primary inductor L1 of the coupling inductor, and connecting the anode of the thyristor T4 to the cathode of the thyristor T1.

[0021] Furthermore, the fifth branch is connected by the cathode of the thyristor T3 and the capacitor C, and the anode of the thyristor T3 is connected to the cathode of the thyristor T1.

[0022] Furthermore, the sixth branch is connected by the same-name terminal of the secondary inductor L2 of the coupling inductor and the cathode of the thyristor T5, and the opposite-name terminal of the secondary inductor L2 of the coupling inductor is connected to the cathode of the thyristor T2.

[0023] Based on the present invention, a method for operating a coupled inductor current-limiting hybrid DC circuit breaker is provided, wherein the circuit breaker has three operating modes:

[0024] If the circuit breaker is placed on the left side of the high-voltage DC line, that is, the current direction is to the right, the capacitor C is pre-charged first. When the power grid system is running normally, the current-carrying part is normally flowing, that is, the ultra-fast mechanical switch UFD and the load transfer switch LCS are both closed, the mechanical switch S is closed, and the thyristors T2 and T6 are turned on. After the capacitor C is fully charged, the thyristors T2 and T6 are naturally turned off, and the mechanical switch S is disconnected.

[0025] Current-limiting tripping mode: When the protection device detects a fault, it turns on thyristors T2 and T7, putting the tripping section into operation. Simultaneously, it turns off the load transfer switch LCS, cutting off the current in the current-carrying section. Current then transfers from the current-carrying section to the tripping section. The protection device sends a tripping command to the ultra-fast mechanical switch UFD. When the ultra-fast mechanical switch UFD reaches its rated opening distance, it sends trigger signals to thyristors T1 and T3. Due to reverse voltage, the current flowing through thyristor T2 gradually decreases, and the current gradually flows from thyristor T2 to thyristor T1. Capacitor C discharges into the circuit. After the discharge process ends, the reverse voltage is restored. As the capacitor C is charged in the positive direction, the voltage across it changes to positive on the left and negative on the right. The thyristor T4 is then subjected to a positive voltage. At this time, a trigger signal is given to the thyristor T4, and the primary inductor L1 of the coupling inductor starts to engage to suppress the fault current. When the capacitor C is fully charged, the thyristor T3 naturally turns off. At this time, the primary inductor L1 of the coupling inductor is fully engaged to suppress the fault current, triggering the conduction of the thyristor T5. The capacitor C discharges through the secondary inductor L2 of the coupling inductor. Under the inductive coupling, an induced electromotive force is generated across the primary inductor L1 of the coupling inductor, which causes the surge arrester to engage and absorb energy, thus successfully clearing the system fault.

[0026] Reclosing mode: If a transient short-circuit fault occurs on the high-voltage DC line, when the primary inductor L1 of the coupling inductor is fully engaged to suppress the fault current, the protection device detects that the fault has been cleared and performs a reclosing operation. It closes the ultra-fast mechanical switch UFD. After the closing operation is completed, the protection device sends trigger signals to the load transfer switch LCS and T5. The capacitor C discharges through the thyristor T5 to the secondary inductor L2 of the coupling inductor. The reverse pulse current generated by the coupling effect on the primary inductor L1 forces the thyristor T4 to turn off at zero current. The current flows back from the disconnected portion to the current-carrying portion, the system returns to normal operating current, and the reclosing operation is completed.

[0027] Low current interruption mode: If the fault current of the high voltage DC line does not need to be limited and is directly interrupted, when the reverse charging voltage of the capacitor C reaches the starting voltage of the surge arrester MOA, the surge arrester will start absorbing energy and the fault will be successfully cleared. At this time, the mechanical switch S will be closed and the thyristors T2 and T6 will be triggered to conduct, so as to realize the residual energy discharge operation of the capacitor C.

[0028] Compared with the prior art, the beneficial effects of the present invention are:

[0029] 1. The coupling inductor of the hybrid DC circuit breaker proposed in this invention has both the function of a current limiting inductor and a fault breaking function on the primary side, realizing component reuse, simplifying the number of components, reducing the peak fault current, and shortening the breaking time.

[0030] 2. The coupled inductor current-limiting hybrid DC circuit breaker proposed in this invention utilizes thyristor T2, thyristor T6, and mechanical switches S and R. g Grounding forms a self-charging circuit, which can be adjusted by R. g The resistance value can adjust the charging current to prevent excessive charging current from damaging the equipment.

[0031] 3. The breaking section of the hybrid DC circuit breaker with coupled inductor current limiting proposed in this invention uses thyristors instead of IGBTs, which reduces the cost of the circuit breaker;

[0032] 4. The hybrid DC circuit breaker with coupled inductor current limiting proposed in this invention can quickly respond to faults in three working modes: current limiting interruption, reclosing, and low current interruption. Only in the low current interruption mode is the residual energy of capacitor C discharged, thus avoiding excessive energy loss. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the topology of a hybrid DC circuit breaker with coupled inductor current limiting according to the present invention;

[0034] Figure 2 This is a schematic diagram of the circuit of a coupled inductor current-limiting hybrid DC circuit breaker under normal operation according to the present invention;

[0035] Figure 3 This is a schematic diagram of a capacitor self-charging circuit for a coupled inductor current-limiting hybrid DC circuit breaker according to the present invention.

[0036] Figure 4 This is a schematic diagram of the current path in each operating sequence of a hybrid DC circuit breaker with coupled inductor current limiting under the current limiting and breaking mode of the present invention.

[0037] Figure 5 This is a schematic diagram of the current path of each operating sequence in the reclosing mode of a hybrid DC circuit breaker with coupled inductor current limiting, according to the present invention.

[0038] Figure 6 This is a schematic diagram of the current path of each operating sequence in the low current breaking mode of a hybrid DC circuit breaker with coupled inductor current limiting, according to the present invention. Detailed Implementation

[0039] This invention proposes a coupled inductor current-limiting hybrid DC circuit breaker and its operating method. The invention will be further described below with reference to the accompanying drawings.

[0040] like Figure 1 As shown, the present invention provides a hybrid DC circuit breaker topology with coupled inductor current limiting, comprising a current-carrying section and a breaking section;

[0041] The current-carrying part is connected in series in the DC transmission line and consists of an ultra-fast mechanical switch (UFD) and a load transfer switch (LCS) connected in series. The load transfer switch (LCS) is composed of two sets of integrated gate commutating thyristors (IGBTs) connected in reverse parallel with diodes, and then connected in reverse series.

[0042] The disconnected section also includes a bridge circuit, a first branch, a second branch, a third branch, a fourth branch, a fifth branch, and a sixth branch;

[0043] The bridge circuit is composed of two sets of thyristors T7 and T8 and two sets of diodes D1 and D2 connected in series. Thyristor T8 and diode D1 are connected in series on the left side, and thyristor T7 and diode D2 are connected in series on the right side. The bridge circuit is connected in parallel across the current-carrying section.

[0044] The first branch circuit consists of thyristor T1, mechanical switch S, and charging resistor R. g The series grounding component is located on the left side inside the bridge circuit.

[0045] The second branch is connected by thyristor T2 inside the right side of the bridge circuit, in parallel with the series structure of thyristor T7 and diode D2;

[0046] The third branch circuit is formed by connecting one end of the surge arrester MOA to the thyristor T1 and the other end to the thyristor T2;

[0047] The fourth branch is formed by connecting the thyristor T4 and the primary inductor L1 in series, and then connecting them in parallel with the third branch.

[0048] The fifth branch is formed by connecting thyristor T3 and thyristor T6 in antiparallel, then connecting them in series with capacitor C, and finally connecting them in parallel with the fourth branch.

[0049] The sixth branch circuit consists of a coupling inductor secondary side inductor L2 connected in series with thyristor T5 and then connected in parallel with capacitor C.

[0050] In the bridge circuit, the anode of diode D1 and the cathode of thyristor T8 are connected in series, with diode D1 located at the upper end of the series circuit and thyristor T8 located at the lower end. The anode of diode D2 and the cathode of thyristor T7 are connected in series, with diode D2 located at the upper end of the series circuit and thyristor T7 located at the lower end. The cathodes of diode D1 and D2 are connected in series, and the anodes of thyristor T8 and T7 are connected in series. The anodes of diodes D1 and D2 are respectively connected to the left and right ends of the current-carrying section.

[0051] The first branch circuit consists of the cathode of the thyristor T1, the mechanical switch S, and the charging resistor R. g After being connected in series, it passes through the charging resistor R g The other end is grounded, and the anode of the thyristor T1 is connected to the cathode of the diode D1.

[0052] The second branch path is formed by connecting the anode of the thyristor T2 to the cathode of the diode D2, and connecting the cathode of the thyristor T2 to the anode of the thyristor T7.

[0053] The third branch circuit is formed by connecting one end of the surge arrester MOA to the cathode of the thyristor T1 and the other end to the cathode of the thyristor T2.

[0054] The fourth branch is formed by connecting the cathode of the thyristor T4 to the same-name terminal of the primary inductor L1 of the coupling inductor, and connecting the anode of the thyristor T4 to the cathode of the thyristor T1.

[0055] The fifth branch is connected by the cathode of the thyristor T3 and the capacitor C, and the anode of the thyristor T3 is connected to the cathode of the thyristor T1.

[0056] The sixth branch is connected by the same-name terminal of the secondary inductor L2 of the coupling inductor and the cathode of the thyristor T5, and the opposite-name terminal of the secondary inductor L2 of the coupling inductor is connected to the cathode of the thyristor T2.

[0057] Based on the present invention, a method for operating a coupled inductor current-limiting hybrid DC circuit breaker is provided, wherein the circuit breaker has three operating modes:

[0058] If the circuit breaker is placed on the left side of the high-voltage DC line, that is, the current direction is to the right, the capacitor C is pre-charged first. When the power grid system is running normally, the current-carrying part is normally flowing, that is, the ultra-fast mechanical switch UFD and the load transfer switch LCS are both closed, the mechanical switch S is closed, and the thyristors T2 and T6 are turned on. After the capacitor C is fully charged, the thyristors T2 and T6 are naturally turned off, and the mechanical switch S is disconnected.

[0059] Current-limiting tripping mode: When the protection device detects a fault, it turns on thyristors T2 and T7, putting the tripping section into operation. Simultaneously, it turns off the load transfer switch LCS, cutting off the current in the current-carrying section. Current then transfers from the current-carrying section to the tripping section. The protection device sends a tripping command to the ultra-fast mechanical switch UFD. When the ultra-fast mechanical switch UFD reaches its rated opening distance, it sends trigger signals to thyristors T1 and T3. Due to reverse voltage, the current flowing through thyristor T2 gradually decreases, and the current gradually flows from thyristor T2 to thyristor T1. Capacitor C discharges into the circuit. After the discharge process ends, the reverse voltage is restored. As the capacitor C is charged in the positive direction, the voltage across it changes to positive on the left and negative on the right. The thyristor T4 is then subjected to a positive voltage. At this time, a trigger signal is given to the thyristor T4, and the primary inductor L1 of the coupling inductor starts to engage to suppress the fault current. When the capacitor C is fully charged, the thyristor T3 naturally turns off. At this time, the primary inductor L1 of the coupling inductor is fully engaged to suppress the fault current, triggering the conduction of the thyristor T5. The capacitor C discharges through the secondary inductor L2 of the coupling inductor. Under the inductive coupling, an induced electromotive force is generated across the primary inductor L1 of the coupling inductor, which causes the surge arrester to engage and absorb energy, thus successfully clearing the system fault.

[0060] Reclosing mode: If a transient short-circuit fault occurs on the high-voltage DC line, when the primary inductor L1 of the coupling inductor is fully engaged to suppress the fault current, the protection device detects that the fault has been cleared and performs a reclosing operation. It closes the ultra-fast mechanical switch UFD. After the closing operation is completed, the protection device sends trigger signals to the load transfer switch LCS and T5. The capacitor C discharges through the thyristor T5 to the secondary inductor L2 of the coupling inductor. The reverse pulse current generated by the coupling effect on the primary inductor L1 forces the thyristor T4 to turn off at zero current. The current flows back from the disconnected portion to the current-carrying portion, the system returns to normal operating current, and the reclosing operation is completed.

[0061] Low current interruption mode: If the fault current of the high voltage DC line does not need to be limited and is directly interrupted, when the reverse charging voltage of the capacitor C reaches the starting voltage of the surge arrester MOA, the surge arrester will start absorbing energy and the fault will be successfully cleared. At this time, the mechanical switch S will be closed and the thyristors T2 and T6 will be triggered to conduct, so as to realize the residual energy discharge operation of the capacitor C.

[0062] refer to Figure 2As shown, in one embodiment, the circuit breaker is placed at the left end of the DC transmission line. During normal operation, the current-carrying part carries current normally, and the current path flows from the left end of the circuit breaker through the current-carrying part to the right end of the circuit breaker. At this time, both the ultra-fast mechanical switch UFD and the load transfer switch LCS are in the closed state.

[0063] refer to Figure 3 As shown, before any operating mode, the present invention precharges the internal capacitor C of the circuit breaker. The circuit breaker also includes diode D1, thyristor T2, capacitor C, thyristor T6, mechanical switch S, and charging resistor R. g A charging circuit is formed with ground. During normal operation of the DC transmission line, thyristors T2 and T6 are turned on to pre-charge capacitor C. After charging is complete, the capacitor voltage polarity is negative on the left and positive on the right. As the charging current decreases to 0, thyristors T2 and T6 naturally turn off, and mechanical switch S is disconnected. In the actual charging process, the charging resistance R is changed... g The size of the capacitor allows for adjustment of the charging current.

[0064] refer to Figure 4 As shown, the circuit breaker of this invention operates in current-limiting breaking mode, and the red path represents the current loop under the corresponding timing sequence:

[0065] in Figure 4 (a) Diode D1, thyristor T2 and T7 form a transfer branch. When the protection device detects a fault, it turns on thyristor T2 and T7, and the fault current is transferred from the current-carrying part to the transfer branch. The disconnecting part is put into operation. The protection device sends a turn-off signal to the load transfer switch LCS and a trip command to the ultra-fast mechanical switch UFD. When the ultra-fast mechanical switch UFD reaches the rated opening distance, the trip is completed.

[0066] Figure 4 (b) Trigger signals are given to thyristors T1 and T3. Because thyristor T2 is subjected to reverse voltage, the current flowing through it gradually decreases. The current gradually flows from thyristor T2 to thyristor T1, and thyristor T2 is naturally turned off. Capacitor C discharges to the circuit. After the discharge process ends, the reverse charging begins.

[0067] Figure 4 (c) The thyristor T4 and the primary side inductor L1 of the coupling inductor form a current limiting branch. When the capacitor C starts to charge in the reverse direction, the voltage across its terminals becomes positive on the left and negative on the right. The thyristor T4 is subjected to a positive voltage, and the thyristor T4 is turned on. The current limiting branch starts to be engaged to limit and suppress the fault current.

[0068] Figure 4 (d) When capacitor C completes reverse charging, thyristor T3 turns off naturally. At this time, the current limiting branch is fully engaged to limit and suppress fault current.

[0069] Figure 4 (e) The thyristor T5, capacitor C and the secondary inductor L2 of the coupling inductor form the discharge circuit of capacitor C, triggering the thyristor T5 to conduct, and capacitor C discharges through the secondary inductor L2 of the coupling inductor.

[0070] Figure 4 (f) During the discharge process of capacitor C through the secondary inductor L2 of the coupling inductor, under the action of inductive coupling, an induced electromotive force is generated across the primary inductor L1 of the coupling inductor, causing the surge arrester to absorb energy and the system fault is successfully cleared.

[0071] refer to Figure 5 As shown, the circuit breaker of this invention operates in reclosing mode, and the red path represents the current loop under the corresponding timing sequence:

[0072] in Figure 5 (a)- Figure 5 (d) The operating timing circuit and circuit breaker operate in current-limiting and breaking mode. Figure 4 (a)- Figure 4 (d) Same, if the fault is a transient short circuit in the high voltage DC line, when the primary side inductor L1 of the coupling inductor is fully engaged to suppress the fault current, the protection device detects that the fault has been cleared and a reclosing operation is required.

[0073] Figure 5 (e) After closing the ultra-fast mechanical switch UFD and completing the closing operation, the protection device sends a trigger signal to the load transfer switch LCS and thyristor T5. The capacitor C discharges to the secondary inductor L2 of the coupling inductor through the thyristor T5. The reverse pulse current generated on the primary inductor L1 of the coupling inductor through the coupling effect forces the thyristor T4 to turn off when the current crosses zero.

[0074] Figure 5 (f) The current flows back from the disconnected part to the current-carrying part, the system returns to the normal operating current, and the reclosing operation is completed.

[0075] refer to Figure 6 As shown, the circuit breaker of this invention operates in low-current breaking mode, and the red path represents the current loop under the corresponding timing sequence:

[0076] If the fault current in a high-voltage DC line does not require current limiting and is directly interrupted, its operating sequence circuit loop... Figure 6 (a)- Figure 6 (b) The operating timing circuit and circuit breaker operate in current-limiting and breaking mode. Figure 4 (a)-4(b) are the same;

[0077] Figure 6 (c) After capacitor C has finished discharging, it is charged in the reverse direction;

[0078] Figure 6 (d) When the capacitor C is charged in the reverse direction, the voltage reaches the starting voltage of the surge arrester MOA. The surge arrester then absorbs energy, and the fault is successfully cleared.

[0079] Figure 6 (e) Close the mechanical switch S and trigger the thyristors T2 and T6 to conduct, thereby discharging the residual energy of the capacitor C.

[0080] For those skilled in the art, any details not described in detail in the specification should not be construed as limiting the scope of protection of this invention. Based on the technical essence of this invention, any person skilled in the art can make appropriate modifications, improvements, or adjustments, and such modifications should also be considered to be included within the scope of this invention and fall within the protection scope of the claims of this invention.

Claims

1. A hybrid DC circuit breaker topology with coupled inductor current limiting, characterized in that, Includes the current-carrying part and the breaking part; The current-carrying part is connected in series in the DC transmission line and consists of an ultra-fast mechanical switch (UFD) and a load transfer switch (LCS) connected in series. The load transfer switch (LCS) is composed of two sets of integrated gate commutating thyristors (IGBTs) connected in reverse parallel with diodes, and then connected in reverse series. The disconnected section also includes a bridge circuit, a first branch, a second branch, a third branch, a fourth branch, a fifth branch, and a sixth branch; The bridge circuit is composed of two sets of thyristors T7 and T8 and two sets of diodes D1 and D2 connected in series. Thyristor T8 and diode D1 are connected in series on the left side, and thyristor T7 and diode D2 are connected in series on the right side. The bridge circuit is connected in parallel across the current-carrying section. The first branch circuit consists of thyristor T1, mechanical switch S, and charging resistor R. g The series grounding component is located on the left side inside the bridge circuit. The second branch is connected by thyristor T2 inside the right side of the bridge circuit, in parallel with the series structure of thyristor T7 and diode D2; The third branch circuit is formed by connecting one end of the surge arrester MOA to the thyristor T1 and the other end to the thyristor T2; The fourth branch is formed by connecting the thyristor T4 and the primary inductor L1 in series, and then connecting them in parallel with the third branch. The fifth branch is formed by connecting thyristor T3 and thyristor T6 in antiparallel, then connecting them in series with capacitor C, and finally connecting them in parallel with the fourth branch. The sixth branch circuit consists of a coupling inductor secondary side inductor L2 connected in series with thyristor T5 and then connected in parallel with capacitor C.

2. The coupled inductor current-limiting hybrid DC circuit breaker topology as described in claim 1, characterized in that, In the bridge circuit, the anode of diode D1 and the cathode of thyristor T8 are connected in series, with diode D1 located at the upper end of the series circuit and thyristor T8 located at the lower end. The anode of diode D2 and the cathode of thyristor T7 are connected in series, with diode D2 located at the upper end of the series circuit and thyristor T7 located at the lower end. The cathodes of diode D1 and D2 are connected in series, and the anodes of thyristor T8 and T7 are connected in series. The anodes of diodes D1 and D2 are respectively connected to the left and right ends of the current-carrying section.

3. The coupled inductor current-limiting hybrid DC circuit breaker topology as described in claim 1, characterized in that, The first branch circuit consists of the cathode of the thyristor T1, the mechanical switch S, and the charging resistor R. g After being connected in series, it passes through the charging resistor R g The other end is grounded, and the anode of the thyristor T1 is connected to the cathode of the diode D1.

4. The coupled inductor current-limiting hybrid DC circuit breaker topology as described in claim 1, characterized in that, The second branch path is formed by connecting the anode of the thyristor T2 to the cathode of the diode D2, and connecting the cathode of the thyristor T2 to the anode of the thyristor T7.

5. The coupled inductor current-limiting hybrid DC circuit breaker topology as described in claim 1, characterized in that, The third branch circuit is formed by connecting one end of the surge arrester MOA to the cathode of the thyristor T1 and the other end to the cathode of the thyristor T2.

6. The coupled inductor current-limiting hybrid DC circuit breaker topology as described in claim 1, characterized in that, The fourth branch is formed by connecting the cathode of the thyristor T4 to the same-name terminal of the primary inductor L1 of the coupling inductor, and connecting the anode of the thyristor T4 to the cathode of the thyristor T1.

7. The coupled inductor current-limiting hybrid DC circuit breaker topology as described in claim 1, characterized in that, The fifth branch is connected by the cathode of the thyristor T3 and the capacitor C, and the anode of the thyristor T3 is connected to the cathode of the thyristor T1.

8. The coupled inductor current-limiting hybrid DC circuit breaker topology as described in claim 1, characterized in that, The sixth branch is connected by the same-name terminal of the secondary inductor L2 of the coupling inductor and the cathode of the thyristor T5, and the opposite-name terminal of the secondary inductor L2 of the coupling inductor is connected to the cathode of the thyristor T2.

9. The operating method of a coupled inductor current-limiting hybrid DC circuit breaker topology as described in claim 1, characterized in that, The circuit breaker has three operating modes: If the circuit breaker is placed on the left side of the high-voltage DC line, that is, the current direction is to the right, the capacitor C is pre-charged first. When the power grid system is running normally, the current-carrying part is normally flowing, that is, the ultra-fast mechanical switch UFD and the load transfer switch LCS are both closed, the mechanical switch S is closed, and the thyristors T2 and T6 are turned on. After the capacitor C is fully charged, the thyristors T2 and T6 are naturally turned off, and the mechanical switch S is disconnected. Current-limiting tripping mode: When the protection device detects a fault, it turns on thyristors T2 and T7, putting the tripping section into operation. Simultaneously, it turns off the load transfer switch LCS, cutting off the current in the current-carrying section. Current then transfers from the current-carrying section to the tripping section. The protection device sends a tripping command to the ultra-fast mechanical switch UFD. When the ultra-fast mechanical switch UFD reaches its rated opening distance, it sends trigger signals to thyristors T1 and T3. Due to reverse voltage, the current flowing through thyristor T2 gradually decreases, and the current gradually flows from thyristor T2 to thyristor T1. Capacitor C discharges into the circuit. After the discharge process ends, the reverse voltage is restored. As the capacitor C is charged in the positive direction, the voltage across it changes to positive on the left and negative on the right. The thyristor T4 is then subjected to a positive voltage. At this time, a trigger signal is given to the thyristor T4, and the primary inductor L1 of the coupling inductor starts to engage to suppress the fault current. When the capacitor C is fully charged, the thyristor T3 naturally turns off. At this time, the primary inductor L1 of the coupling inductor is fully engaged to suppress the fault current, triggering the conduction of the thyristor T5. The capacitor C discharges through the secondary inductor L2 of the coupling inductor. Under the inductive coupling, an induced electromotive force is generated across the primary inductor L1 of the coupling inductor, which causes the surge arrester to engage and absorb energy, thus successfully clearing the system fault. Reclosing mode: If a transient short-circuit fault occurs on the high-voltage DC line, when the primary inductor L1 of the coupling inductor is fully engaged to suppress the fault current, the protection device detects that the fault has been cleared and performs a reclosing operation. It closes the ultra-fast mechanical switch UFD. After the closing operation is completed, the protection device sends trigger signals to the load transfer switch LCS and T5. The capacitor C discharges through the thyristor T5 to the secondary inductor L2 of the coupling inductor. The reverse pulse current generated by the coupling effect on the primary inductor L1 forces the thyristor T4 to turn off at zero current. The current flows back from the disconnected portion to the current-carrying portion, the system returns to normal operating current, and the reclosing operation is completed. Low current interruption mode: If the fault current of the high voltage DC line does not need to be limited and is directly interrupted, when the reverse charging voltage of the capacitor C reaches the starting voltage of the surge arrester MOA, the surge arrester will start absorbing energy and the fault will be successfully cleared. At this time, the mechanical switch S will be closed and the thyristors T2 and T6 will be triggered to conduct, so as to realize the residual energy discharge operation of the capacitor C.

Images