Bidirectional dc circuit breaker, rated breaking method and short circuit breaking method

Abstract

The application relates to a bidirectional direct-current circuit breaker, a rated breaking method and a short-circuit breaking method, and belongs to the technical field of fault protection of a direct-current medium-high voltage power system. The bidirectional direct-current circuit breaker comprises a parallel main switch branch, a voltage-limiting energy-dissipating branch and a coupling commutation shutdown branch. The bidirectional direct-current circuit breaker provided by the application can realize breaking of different currents of the system under different operating conditions, such as a rated condition or a short-circuit condition, by controlling conduction of thyristors in the coupling commutation shutdown branch, only one set of pulse discharge circuit is used, current transfer and reliable shutdown of a large-capacity direct-current system under a high-current change rate short-circuit condition can be realized at the same time, and the bidirectional direct-current circuit breaker has the advantages of small size, strong breaking capacity, convenient control and reclosing function under a short-circuit fault condition.

Description

Technical Field

[0001] This invention relates to the field of fault protection technology for DC medium and high voltage power systems, and in particular to a bidirectional DC circuit breaker, a rated breaking method, and a short-circuit breaking method. Background Technology

[0002] With the rapid development of large-scale grid connection of new energy sources, flexible DC transmission, multi-port DC transmission, and DC power systems for ships, the application scope of DC systems is constantly expanding. However, DC systems do not have a natural zero-crossing point, have low line impedance, and a fast short-circuit current rise rate, which places higher demands on breaking speed.

[0003] Existing air circuit breakers mainly rely on increasing the arc voltage to achieve current interruption. However, in the field of medium and high voltage DC power systems, it is difficult to increase the arc voltage by increasing the number of arc-extinguishing grids. On the other hand, adding arc-extinguishing chambers and adopting multi-port designs can lead to larger circuit breakers and higher costs, as well as problems such as uneven voltage and insulation breakdown.

[0004] Hybrid interruption is an effective technical solution for fault protection of medium and high voltage DC power. However, as the system voltage level increases and the capacity increases, on the one hand, the number of series devices in the semiconductor branch of the hybrid circuit breaker increases, and on the other hand, the rise rate of the short-circuit current is higher, which directly leads to difficulties in fault current transfer, a significant increase in transfer time, and even transfer failure.

[0005] Meanwhile, under high current change rate conditions, even if the current transfer is successful, the current value rises to a very high level. If a fully controlled IGBT device is used, multiple branches need to be connected in parallel, which leads to a significant increase in cost. If a thyristor device with strong surge capability is used, an auxiliary turn-off branch needs to be added, and there are problems such as a long small current breaking time.

[0006] In summary, the lack of suitable circuit breakers is one of the technical bottlenecks currently restricting the development of medium- and high-voltage, large-capacity DC power systems. Summary of the Invention

[0007] In view of this, it is necessary to provide a bidirectional DC circuit breaker, a rated breaking method, and a short-circuit breaking method to achieve the purpose of controlling current breaking under different operating conditions.

[0008] To achieve the above objectives, in a first aspect, the present invention provides a bidirectional DC circuit breaker, comprising:

[0009] The main switch branch, voltage limiting and energy dissipation branch and coupling converter turn-off branch are connected in parallel, and the parallel nodes include the first node and the second node.

[0010] The coupled commutation turn-off branch includes a first IGCT device, a second IGCT device, a coupling coil, a first thyristor, a second thyristor, a third thyristor, a fourth thyristor, a fifth thyristor, and a capacitor;

[0011] The coupling coil includes a first inductor and a second inductor that are coupled to each other, and the winding directions of the first inductor and the second inductor are opposite; one pole of the first inductor and the second inductor are connected to the second node;

[0012] The anode of the first IGCT device, the cathode of the second IGCT device, the cathode of the first thyristor, the anode of the third thyristor, and the first node are connected;

[0013] The cathode of the first IGCT device and one pole of the first inductor are connected to form a third node;

[0014] The anode of the first thyristor and the anode of the second thyristor are connected to form a fourth node, and the cathode of the second thyristor is connected to the third node;

[0015] The cathodes of the third thyristor and the fourth thyristor are connected to form a fifth node;

[0016] The fifth thyristor is connected in reverse parallel across the two ends of the second thyristor;

[0017] The anode of the second IGCT device and one pole of the second inductor are connected to form the sixth node;

[0018] The anode of the fourth thyristor is connected to the sixth node;

[0019] The two terminals of the capacitor are connected to the fourth node and the fifth node, respectively.

[0020] In one possible implementation, the main switch branch includes a fast mechanical switch.

[0021] In one possible implementation, the voltage-limiting energy-dissipating branch includes a varistor.

[0022] In one possible implementation, the capacitor is pre-charged with a voltage;

[0023] The pre-charge voltage positive terminal of the capacitor is connected to the fifth node;

[0024] The pre-charge voltage negative terminal of the capacitor is connected to the fourth node.

[0025] Secondly, the present invention also provides a rated breaking method for a bidirectional DC circuit breaker, applied to the bidirectional DC circuit breaker described in any of the above implementations, comprising:

[0026] Under rated operating conditions, the main switch branch is closed;

[0027] During the rated breaking process, a tripping command is sent to the main switch branch, and an opening command is sent to either the first IGCT device or the second IGCT device according to the current direction.

[0028] Once the main switch branch restores its insulation characteristics, a turn-off command is sent to any of the IGCT devices to cause the voltage across the first and second nodes to rise.

[0029] When the voltage across the first and second nodes rises to the turn-on voltage of the voltage-limiting and energy-consuming branch, the voltage-limiting and energy-consuming branch is turned on, so that the current is transferred to the voltage-limiting and energy-consuming branch to complete the rated interruption.

[0030] In one possible implementation, sending an enable command to either the first IGCT device or the second IGCT device according to the current direction includes:

[0031] When the current flows from the first node to the second node, an activation command is sent to the first IGCT device.

[0032] In one possible implementation, sending an enable command to either the first IGCT device or the second IGCT device according to the current direction includes:

[0033] When the current flows from the second node to the first node, an on-state command is sent to the second IGCT device.

[0034] Thirdly, the present invention also provides a short-circuit breaking method for a bidirectional DC circuit breaker, applied to the bidirectional DC circuit breaker described in any of the above implementations, comprising:

[0035] During the short-circuit breaking process, a tripping command is sent to the main switch branch, and an opening command is sent to either the first IGCT device or the second IGCT device according to the current direction.

[0036] When the main switch branch starts to open, a conduction command is sent to the fifth thyristor to discharge the capacitor, generate an induced electromotive force in the coupling coil, and transfer the current in the main switch branch to any of the IGCT devices; after the capacitor has undergone a pulse discharge cycle, the voltage across the capacitor is reversed, with the fourth node corresponding to a positive voltage and the fifth node corresponding to a negative voltage.

[0037] When the main switch branch restores its insulation characteristics, an on-state command is sent to the branch composed of the second and third thyristors or the branch composed of the first and fourth thyristors based on any of the IGCT devices, and a reverse pulse current is injected into any of the IGCT devices.

[0038] When the current in any of the IGCT devices drops below the rated turn-off value, the IGCT devices are turned off so that the current charges the capacitor.

[0039] When the voltage across the capacitor rises to the turn-on voltage of the voltage limiting and energy dissipation branch, the voltage limiting and energy dissipation branch turns on, and the current is transferred to the voltage limiting and energy dissipation branch, thus completing the short circuit breaking.

[0040] In one possible implementation, sending an enable command to either the first IGCT device or the second IGCT device according to the current direction includes:

[0041] When the current flows from the first node to the second node, an activation command is sent to the first IGCT device.

[0042] When the current flows from the second node to the first node, an on-state command is sent to the second IGCT device.

[0043] In one possible implementation, sending an on-state command to the branch composed of the second and third thyristors or the branch composed of the first and fourth thyristors based on any of the IGCT devices includes:

[0044] When the first IGCT device is turned on, an on command is sent to the branch composed of the second and third thyristors;

[0045] When the second IGCT device is turned on, an on command is sent to the branch composed of the first thyristor and the fourth thyristor.

[0046] The beneficial effects of this invention are as follows: The bidirectional DC circuit breaker, rated breaking method, and short-circuit breaking method provided by this invention form a bidirectional DC circuit breaker by connecting a main switch branch, a coupling commutator turn-off branch, and a voltage limiting and energy dissipation branch in parallel. Under different operating conditions, such as rated operating conditions or short-circuit operating conditions, the breaking of different currents in the system can be achieved by controlling the conduction of the thyristors in the coupling commutator turn-off branch. Only one pulse discharge circuit is used, which can simultaneously realize the current transfer and reliable turn-off of a large-capacity DC system under high current change rate short-circuit conditions. It has the advantages of small size, strong breaking capacity, convenient control, and reclosing function under short-circuit fault conditions. Attached Figure Description

[0047] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0048] Figure 1 A circuit diagram of an embodiment of the bidirectional DC circuit breaker provided by the present invention;

[0049] Figure 2 A schematic diagram of the current waveform during the breaking process of the bidirectional DC circuit breaker provided by the present invention at rated and below rated operating conditions.

[0050] Figure 3 One of the schematic diagrams of current flow direction during the rated breaking process provided by the present invention;

[0051] Figure 4 A second schematic diagram of the current flow direction during the rated breaking process provided by the present invention;

[0052] Figure 5 The third schematic diagram of current flow direction during the rated breaking process provided by the present invention;

[0053] Figure 6 Fourth schematic diagram of current flow direction during the rated breaking process provided by the present invention;

[0054] Figure 7 Fifth schematic diagram of current flow direction during the rated breaking process provided by the present invention;

[0055] Figure 8 Sixth schematic diagram of current flow direction during the rated breaking process provided by the present invention;

[0056] Figure 9 A schematic diagram of the current waveform of the bidirectional DC circuit breaker provided by the present invention during the short-circuit breaking process;

[0057] Figure 10 One of the schematic diagrams of current flow during the short-circuit breaking process provided by the present invention;

[0058] Figure 11 The second schematic diagram of current flow direction during the short-circuit breaking process provided by the present invention;

[0059] Figure 12 The third schematic diagram of current flow direction during the short-circuit breaking process provided by the present invention;

[0060] Figure 13 The fourth schematic diagram of current flow direction during the short-circuit breaking process provided by the present invention;

[0061] Figure 14 The fifth schematic diagram of current flow direction during the short-circuit breaking process provided by the present invention;

[0062] Figure 15 The sixth schematic diagram of current flow direction during the short-circuit breaking process provided by the present invention;

[0063] Figure 16The seventh schematic diagram of current flow during the short-circuit breaking process provided by the present invention;

[0064] Figure 17 The eighth schematic diagram of current flow direction during short-circuit breaking process provided by the present invention;

[0065] Figure 18 The ninth schematic diagram of current flow direction during short-circuit breaking process provided by the present invention;

[0066] Figure 19 The tenth schematic diagram of current flow direction during short-circuit breaking process provided by the present invention;

[0067] Figure 20 This is eleventh of the schematic diagrams showing the current flow direction during the short-circuit breaking process provided by the present invention.

[0068] Figure 21 This is the twelfth schematic diagram of the current flow direction during the short-circuit breaking process provided by the present invention. Detailed Implementation

[0069] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0070] In the description of the embodiments of the present invention, unless otherwise stated, "multiple" means two or more. "And / or" describes the relationship between related objects, indicating that there can be three relationships. For example, A and / or B can represent three situations: A exists alone, A and B exist simultaneously, and B exists alone.

[0071] The terms "first," "second," etc., used in the embodiments of this invention are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a technical feature defined with "first" or "second" may explicitly or implicitly include at least one of that feature.

[0072] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of the invention. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0073] This invention provides a bidirectional DC circuit breaker, a rated breaking method, and a short-circuit breaking method, which are described below.

[0074] Figure 1 A circuit diagram of an embodiment of the bidirectional DC circuit breaker provided by the present invention is shown below. Figure 1 As shown, the bidirectional DC circuit breaker includes:

[0075] The main switch branch, voltage limiting and energy dissipation branch and coupling converter turn-off branch are connected in parallel, and the parallel nodes include the first node and the second node.

[0076] The coupled commutation turn-off branch includes a first IGCT device, a second IGCT device, a coupling coil, a first thyristor, a second thyristor, a third thyristor, a fourth thyristor, a fifth thyristor, and a capacitor;

[0077] The coupling coil includes a first inductor and a second inductor that are coupled to each other, and the winding directions of the first inductor and the second inductor are opposite; one pole of the first inductor and the second inductor are connected to the second node;

[0078] The anode of the first IGCT device, the cathode of the second IGCT device, the cathode of the first thyristor, the anode of the third thyristor, and the first node are connected;

[0079] The cathode of the first IGCT device and one pole of the first inductor are connected to form a third node;

[0080] The anode of the first thyristor and the anode of the second thyristor are connected to form a fourth node, and the cathode of the second thyristor is connected to the third node;

[0081] The cathodes of the third thyristor and the fourth thyristor are connected to form a fifth node;

[0082] The fifth thyristor is connected in reverse parallel across the two ends of the second thyristor;

[0083] The anode of the second IGCT device and one pole of the second inductor are connected to form the sixth node;

[0084] The anode of the fourth thyristor is connected to the sixth node;

[0085] The two terminals of the capacitor are connected to the fourth node and the fifth node, respectively.

[0086] like Figure 1 As shown, the bidirectional DC circuit breaker includes a main switch branch, a coupling converter turn-off branch, and a voltage limiting and energy dissipation branch connected in parallel, with the first node Y1 and the second node Y2 being the parallel nodes.

[0087] The main switch branch includes a fast mechanical switch S1, and the voltage limiting and energy dissipation branch includes a varistor MOV.

[0088] The coupled commutation turn-off branch includes a first IGCT device T0, a second IGCT device T1, a coupling coil M, a first thyristor T2, a second thyristor T3, a third thyristor T4, a fourth thyristor T5, a fifth thyristor T6, and a capacitor C0.

[0089] The coupling coil M includes two mutually coupled inductors, a first inductor L1 and a second inductor L2, with the two inductors wound in opposite directions.

[0090] The anode of the first IGCT device T0, the cathode of the second IGCT device T1, the cathode of the first thyristor T2, the anode of the third thyristor T4, and the first node Y1 are connected.

[0091] The cathode of the first IGCT device T0 and one pole of the first inductor L1 are connected to form the third node Y3;

[0092] The anode of the first thyristor T2 is connected to the anode of the second thyristor T3 to form the fourth node Y4, and the cathode of the second thyristor T3 is connected to the third node Y3.

[0093] The cathodes of the third thyristor T4 and the fourth thyristor T5 are connected to form the fifth node Y5;

[0094] The fifth thyristor T6 is connected in reverse parallel across the two ends of the second thyristor T3;

[0095] The anode of the second IGCT device T1 is connected to one pole of the second inductor L2 to obtain the sixth node Y6;

[0096] The anode of the fourth thyristor T5 is connected to the sixth node Y6;

[0097] The two terminals of capacitor C0 are connected to the fourth node Y4 and the fifth node Y5, respectively. The pre-charge voltage of capacitor C0 is applied; the positive terminal of the pre-charge voltage of capacitor C0 is connected to the fifth node Y5, and the negative terminal of the pre-charge voltage of capacitor C0 is connected to the fourth node Y4.

[0098] Figure 1 L in S1 and L S2 The stray inductance of the circuit is the parasitic inductance of the copper busbar.

[0099] A bidirectional DC circuit breaker can be connected to the power system in series through the first node Y1 and the second node Y2.

[0100] Under different operating conditions (rated operating conditions or short-circuit operating conditions), the interruption of different currents in the system can be achieved by controlling the conduction of the thyristors in the coupling commutation shut-off branch.

[0101] For example, under rated operating conditions, the fast mechanical switch S1 of the main switch branch is closed to carry the system current.

[0102] During the rated disconnection process, the fast mechanical switch S1 tripping command and the IGCT (first IGCT device T0 or second IGCT device T1) turn-on command are sent simultaneously.

[0103] After a delay, once the fast mechanical switch S1 recovers its insulation characteristics, a turn-off command is sent to the IGCT (either the first IGCT device T0 or the second IGCT device T1). The IGCT (either the first IGCT device T0 or the second IGCT device T1) turns off, and the voltage across the first node Y1 and the second node Y2 rises rapidly.

[0104] When the voltage rises to the turn-on voltage of the varistor MOV in the voltage limiting and energy dissipation branch, the varistor MOV turns on, and the current is transferred to the varistor MOV, completing the switching.

[0105] For example, during the short-circuit breaking process, when the system detects a short-circuit fault, it simultaneously sends a fast mechanical switch S1 tripping command and an IGCT (first IGCT device T0 or second IGCT device T1) turn-on command.

[0106] When the fast mechanical switch S1 starts to operate, it first sends a turn-on command to the fifth thyristor T6, and the capacitor C0 discharges, generating an induced electromotive force in the coupling coil M. Under the action of this induced electromotive force, the current in the fast mechanical switch S1 of the main switch branch is transferred to the coupling commutation turn-off branch IGCT (the first IGCT device T0 or the second IGCT device T1).

[0107] After one cycle of pulse discharge, the voltage across capacitor C0 reverses, with the fourth node Y4 becoming positive and the fifth node Y5 becoming negative.

[0108] After a delay, once the fast mechanical switch S1 has recovered its insulation characteristics, a turn-on command is sent to the corresponding thyristor (second thyristor T3, third thyristor T4) or (first thyristor T2, fourth thyristor T5). A reverse pulse current is injected into the first IGCT device T0 or the second IGCT device T1 to reduce the current in the IGCT to below its rated turn-off value, and then the first IGCT device T0 or the second IGCT device T1 is turned off.

[0109] Subsequently, the fault current charges capacitor C0, and the voltage across capacitor C0 rises.

[0110] When the voltage rises to the turn-on voltage of the varistor MOV in the voltage limiting and energy dissipation branch, the varistor MOV turns on, and the current is transferred to the varistor MOV, thus completing the short circuit interruption.

[0111] This invention uses only one pulse discharge circuit, and simultaneously realizes current transfer and reliable shutdown of a large-capacity DC system under short-circuit conditions with high current change rate. It has the advantages of small size, strong breaking capacity, convenient control and reclosing function under short-circuit fault conditions.

[0112] In summary, the bidirectional DC circuit breaker provided in this embodiment of the invention includes a main switch branch, a coupling commutator turn-off branch, and a voltage limiting and energy dissipation branch connected in parallel. Under different operating conditions, such as rated operating conditions or short-circuit operating conditions, the system can achieve the interruption of different currents by controlling the conduction of the thyristors in the coupling commutator turn-off branch. Using only one pulse discharge circuit, it can simultaneously realize the current transfer and reliable turn-off of a large-capacity DC system under high current change rate short-circuit conditions. It has the advantages of small size, strong breaking capacity, convenient control, and reclosing function under short-circuit fault conditions.

[0113] The present invention also provides a rated breaking method for a bidirectional DC circuit breaker, applicable to the bidirectional DC circuit breaker described in any of the above implementations, comprising:

[0114] Under rated operating conditions, the main switch branch is closed;

[0115] During the rated breaking process, a tripping command is sent to the main switch branch, and an opening command is sent to either the first IGCT device or the second IGCT device according to the current direction.

[0116] Once the main switch branch restores its insulation characteristics, a turn-off command is sent to any of the IGCT devices to cause the voltage across the first and second nodes to rise.

[0117] When the voltage across the first and second nodes rises to the turn-on voltage of the voltage-limiting and energy-consuming branch, the voltage-limiting and energy-consuming branch is turned on, so that the current is transferred to the voltage-limiting and energy-consuming branch to complete the rated interruption.

[0118] Under rated operating conditions, the fast mechanical switch S1 of the main switch branch is closed to carry the system current.

[0119] During the rated disconnection process, the fast mechanical switch S1 tripping command and the IGCT (first IGCT device T0 or second IGCT device T1) turn-on command are sent simultaneously.

[0120] After a delay, once the fast mechanical switch S1 recovers its insulation characteristics, a turn-off command is sent to the IGCT (either the first IGCT device T0 or the second IGCT device T1). The IGCT (either the first IGCT device T0 or the second IGCT device T1) turns off, and the voltage across the first node Y1 and the second node Y2 rises rapidly.

[0121] When the voltage rises to the turn-on voltage of the varistor MOV in the voltage limiting and energy dissipation branch, the varistor MOV turns on, and the current is transferred to the varistor MOV, completing the switching.

[0122] The rated breaking method of the bidirectional DC circuit breaker provided in this embodiment of the invention uses IGCT devices to directly turn off at rated and below rated current levels, thus solving the problem of low-current breaking.

[0123] In some embodiments of the present invention, sending an enable command to either the first IGCT device or the second IGCT device according to the current direction includes:

[0124] When the current flows from the first node to the second node, an activation command is sent to the first IGCT device.

[0125] If the system current flows from the first node Y1 to the second node Y2, when the fast mechanical switch S1 is sent to open, the first IGCT device T0 is also sent to open. Under the action of the arc voltage of the fast mechanical switch S1, the current is transferred from the fast mechanical switch S1 to the first IGCT device T0.

[0126] After a delay, once the fast mechanical switch S1 has recovered its insulation characteristics, a turn-off command is sent to the first IGCT device T0, and the first IGCT device T0 turns off.

[0127] In some embodiments of the present invention, sending an enable command to either the first IGCT device or the second IGCT device according to the current direction includes:

[0128] When the current flows from the second node to the first node, an on-state command is sent to the second IGCT device.

[0129] If the system current flows from the second node Y2 to the first node Y1, when the fast mechanical switch S1 is sent to open, the second IGCT device T1 is also sent to open. Under the action of the arc voltage of the fast mechanical switch S1, the current is transferred from the fast mechanical switch S1 to the second IGCT device T1.

[0130] After a delay, once the fast mechanical switch S1 has recovered its insulation properties, a turn-off command is sent to the second IGCT device T1, and the second IGCT device T1 turns off.

[0131] The present invention also provides a short-circuit breaking method for a bidirectional DC circuit breaker, applicable to the bidirectional DC circuit breaker described in any of the above implementations, comprising:

[0132] During the short-circuit breaking process, a tripping command is sent to the main switch branch, and an opening command is sent to either the first IGCT device or the second IGCT device according to the current direction.

[0133] When the main switch branch starts to open, a conduction command is sent to the fifth thyristor to discharge the capacitor, generate an induced electromotive force in the coupling coil M, and transfer the current in the main switch branch to any of the IGCT devices; after the capacitor has undergone a period of pulse discharge, the voltage across the capacitor is reversed, with the fourth node corresponding to a positive voltage and the fifth node corresponding to a negative voltage.

[0134] When the main switch branch restores its insulation characteristics, an on-state command is sent to the branch composed of the second and third thyristors or the branch composed of the first and fourth thyristors based on any of the IGCT devices, and a reverse pulse current is injected into any of the IGCT devices.

[0135] When the current in any of the IGCT devices drops below the rated turn-off value, the IGCT devices are turned off so that the current charges the capacitor.

[0136] When the voltage across the capacitor rises to the turn-on voltage of the voltage limiting and energy dissipation branch, the voltage limiting and energy dissipation branch turns on, and the current is transferred to the voltage limiting and energy dissipation branch, thus completing the short circuit breaking.

[0137] During the short-circuit breaking process, when the system detects a short-circuit fault, it simultaneously sends a fast mechanical switch S1 tripping command and an IGCT (first IGCT device T0 or second IGCT device T1) turn-on command.

[0138] When the fast mechanical switch S1 starts to operate, it first sends a turn-on command to the fifth thyristor T6, and the capacitor C0 discharges, generating an induced electromotive force in the coupling coil M. Under the action of this induced electromotive force, the current in the fast mechanical switch S1 of the main switch branch is transferred to the coupling commutation turn-off branch IGCT (the first IGCT device T0 or the second IGCT device T1).

[0139] After one cycle of pulse discharge, the voltage across capacitor C0 reverses, with the fourth node Y4 becoming positive and the fifth node Y5 becoming negative.

[0140] After a delay, once the fast mechanical switch S1 has recovered its insulation characteristics, a turn-on command is sent to the corresponding thyristor (second thyristor T3, third thyristor T4) or (first thyristor T2, fourth thyristor T5). A reverse pulse current is injected into the first IGCT device T0 or the second IGCT device T1 to reduce the current in the IGCT to below its rated turn-off value, and then the first IGCT device T0 or the second IGCT device T1 is turned off.

[0141] Subsequently, the fault current charges capacitor C0, and the voltage across capacitor C0 rises.

[0142] When the voltage rises to the turn-on voltage of the varistor MOV in the voltage limiting and energy dissipation branch, the varistor MOV turns on, and the current is transferred to the varistor MOV, thus completing the short circuit interruption.

[0143] The short-circuit breaking method of the bidirectional DC circuit breaker provided in this invention, under short-circuit conditions, firstly utilizes half a cycle of the pulse capacitor discharge circuit to reliably transfer the short-circuit fault current from the fast mechanical switch to the semiconductor device. Simultaneously, during the other half cycle of the pulse capacitor discharge, a reverse pulse current is injected into the conducting IGCT, reducing the fault current below the IGCT device's turn-off value, thus achieving reliable turn-off of large-capacity short-circuit faults. Furthermore, this topology also utilizes the system fault current to charge the pulse capacitor, providing a reclosing function under short-circuit fault conditions.

[0144] In some embodiments of the present invention, sending an activation command to either the first IGCT device or the second IGCT device according to the current direction includes:

[0145] When the current flows from the first node to the second node, an activation command is sent to the first IGCT device.

[0146] When the current flows from the second node to the first node, an on-state command is sent to the second IGCT device.

[0147] In some embodiments of the present invention, sending an activation command to a branch composed of a second thyristor and a third thyristor or a branch composed of a first thyristor and a fourth thyristor based on any of the IGCT devices includes:

[0148] When the first IGCT device is turned on, an on command is sent to the branch composed of the second and third thyristors;

[0149] When the second IGCT device is turned on, an on command is sent to the branch composed of the first thyristor and the fourth thyristor.

[0150] (1) If the system current flows from the first node Y1 to the second node Y2, when the fast mechanical switch S1 is sent to open, the first IGCT device T0 is sent to open at the same time.

[0151] When the fast mechanical switch S1 starts to operate, it sends a turn-on command to the fifth thyristor T6. The capacitor C0, the first inductor L1, and the fifth thyristor T6 form a pulse discharge circuit. An induced electromotive force with "negative on the left and positive on the right" is generated across the first inductor L1. Under the action of this induced electromotive force, the current in the fast mechanical switch S1 is rapidly transferred to the first IGCT device T0.

[0152] After one cycle of pulse discharge, the voltage across capacitor C0 reverses, the fourth node Y4 becomes positive, the fifth node Y5 becomes negative, and the fifth thyristor T6 is turned off under the reverse voltage.

[0153] After a delay, once the fast mechanical switch S1 recovers its insulation characteristics, the second thyristor T3 and the third thyristor T4 are turned on. The circuit of capacitor C0-second thyristor T3-first IGCT device T0-third thyristor T4 is turned on, capacitor C0 discharges, and a reverse pulse current is injected into the first IGCT device T0. Under the action of this pulse current, the current in the first IGCT device T0 drops rapidly. When the current drops below the turn-off value of the first IGCT device T0, a turn-off command for the first IGCT device T0 is sent, and the fault current is transferred to the branch of third thyristor T4-capacitor C0-second thyristor T3-first inductor L1. The system begins to reverse charge capacitor C0.

[0154] When the voltage across capacitor C0 rises to the turn-on voltage of the varistor MOV in the voltage limiting and energy dissipation branch, the varistor MOV turns on, and the current is transferred to the varistor MOV, thus completing the short-circuit interruption.

[0155] Meanwhile, after the system is charged, capacitor C0 returns to its initial voltage, and the circuit breaker has the function of reclosing.

[0156] (2) If the system current flows from the second node Y2 to the first node Y1, when the fast mechanical switch S1 is sent to open, the second IGCT device T1 is also sent to open.

[0157] When the fast mechanical switch S1 starts to operate, it sends a turn-on command to the fifth thyristor T6. The capacitor C0, the first inductor L1, and the fifth thyristor T6 form a pulse discharge circuit, and an induced electromotive force with "negative on the left and positive on the right" is generated at both ends of the first inductor L1.

[0158] Since the first inductor L1 and the second inductor L2 are coupled to each other, the second inductor L2 couples out an induced electromotive force with "positive on the left and negative on the right". Under the action of this induced electromotive force, the current in the fast mechanical switch S1 is rapidly transferred to the second IGCT device T1.

[0159] After one cycle of pulse discharge, the voltage across capacitor C0 reverses, the fourth node Y4 becomes positive, the fifth node Y5 becomes negative, and the fifth thyristor T6 is turned off under the reverse voltage.

[0160] After a delay, once the fast mechanical switch S1 recovers its insulation characteristics, the first thyristor T2 and the fourth thyristor T5 are turned on. The circuit of capacitor C0-first thyristor T2-second IGCT device T1-fourth thyristor T5 is turned on, capacitor C0 discharges, and a reverse pulse current is injected into the second IGCT device T1. Under the action of this pulse current, the current in the second IGCT device T1 drops rapidly. When the current drops below the turn-off value of the second IGCT device T1, a turn-off command for the second IGCT device T1 is sent, and the fault current is transferred to the branch of second inductor L2-fourth thyristor T5-capacitor C0-first thyristor T2. The system begins to reverse charge capacitor C0.

[0161] When the voltage across capacitor C0 rises to the turn-on voltage of the varistor MOV in the voltage limiting and energy dissipation branch, the varistor MOV turns on, and the current is transferred to the varistor MOV, thus completing the short-circuit interruption.

[0162] Meanwhile, after the system is charged, capacitor C0 returns to its initial voltage, and the circuit breaker has the function of reclosing.

[0163] For example, Figure 2 The schematic diagram of the current waveform during the breaking process of the bidirectional DC circuit breaker provided by the present invention at rated and below rated operating conditions is shown below. Figure 2 As shown, a control method for a high-capacity bidirectional DC circuit breaker and its interruption method, under rated and below rated current conditions, includes the following steps.

[0164] t 0~ t In stage 1, the system operates under rated current-carrying conditions, with the main branch fast mechanical switch S1 closed, and the rated current-carrying capacity is maintained. i 0.

[0165] (1) If the system current flows from the first node Y1 to the second node Y2.

[0166] t At time 1, the circuit breaker receives the tripping command and simultaneously sends the tripping command of the fast mechanical switch S1 and the turn-on command of the first IGCT device T0.

[0167] t At time 2, the fast mechanical switch S1 begins to open and generates an electric arc. Under the influence of the arc voltage, the current is transferred from the fast mechanical switch S1 to the first IGCT device T0, and... t At time 3, the transfer is complete, as follows: Figure 3 As shown, Figure 3 This is one of the schematic diagrams of current flow during the rated breaking process provided by the present invention.

[0168] t 3~ tDuring period 4, the first IGCT device T0 carries the system current, such as Figure 4 As shown, Figure 4 This is the second schematic diagram of the current flow direction during the rated breaking process provided by the present invention.

[0169] t At time 4, the fast mechanical switch S1 restores its insulation characteristics and sends a turn-off command to the first IGCT device T0. The first IGCT device T0 turns off, and the voltage across the first node Y1 and the second node Y2 rises rapidly, and the current begins to transfer to the varistor MOV.

[0170] t At time 5, the current is completely transferred to the varistor MOV and begins to decrease until it reaches zero, as shown below. Figure 5 As shown, Figure 5 This is the third schematic diagram of the current flow direction during the rated breaking process provided by the present invention.

[0171] (2) If the system current flows from the second node Y2 to the first node Y1:

[0172] t At time 1, the circuit breaker receives the tripping command and simultaneously sends the tripping command of the fast mechanical switch S1 and the turn-on command of the second IGCT device T1.

[0173] t At time 2, the fast mechanical switch S1 begins to open and generates an electric arc. Under the influence of the arc voltage, the current is transferred from the fast mechanical switch S1 to the second IGCT device T1, and... t At time 3, the transfer is complete, as follows: Figure 6 As shown, Figure 6 The fourth schematic diagram of the current flow direction during the rated breaking process provided by the present invention.

[0174] t 3~ t During period 4, the second IGCT device T1 carries the system current, such as Figure 7 As shown, Figure 7 The fifth schematic diagram of the current flow direction during the rated breaking process provided by the present invention.

[0175] t At time 4, the fast mechanical switch S1 restores its insulation characteristics and sends a turn-off command to the second IGCT device T1. The second IGCT device T1 turns off, and the voltage across the first node Y1 and the second node Y2 rises rapidly, and the current begins to transfer to the varistor MOV.

[0176] t At time 5, the current is completely transferred to the varistor MOV and begins to decrease until it reaches zero, as shown below. Figure 8 As shown, Figure 8This is the sixth schematic diagram of the current flow direction during the rated breaking process provided by the present invention.

[0177] Figure 9 A schematic diagram of the current waveform of the bidirectional DC circuit breaker during short-circuit breaking process provided by the present invention is shown below. Figure 9 As shown, the short-circuit breaking process includes the following steps.

[0178] (1) If the system current flows from the first node Y1 to the second node Y2.

[0179] t 0~ t In stage 1, the system operates under rated current-carrying conditions, with the main branch fast mechanical switch S1 closed, and the rated current-carrying capacity is maintained. i 0.

[0180] t If a short circuit fault occurs at moment 1, the system current rises rapidly.

[0181] t At time 2, the system detects a short circuit fault and simultaneously sends a fast mechanical switch S1 tripping command and a first IGCT device T0 turn-on command.

[0182] t At time 3, the fast mechanical switch S1 begins actual opening. First, a turn-on command is sent to the fifth thyristor T6, causing capacitor C0 to discharge. A pulse discharge circuit is formed between capacitor C0, the first inductor L1, and the fifth thyristor T6. An induced electromotive force (EMF) with a "negative on the left and positive on the right" configuration is generated across the first inductor L1. Under the influence of this EMF, the current in the fast mechanical switch S1 rapidly transfers to the first IGCT device T0, and... t The transfer is complete at time 4.

[0183] After one cycle of pulse discharge, the voltage across capacitor C0 reverses, with the fourth node Y4 becoming positive and the fifth node Y5 becoming negative. The fifth thyristor T6 is then turned off under the reverse voltage. Figure 10 As shown, Figure 10 This is one of the schematic diagrams of current flow during the short-circuit breaking process provided by the present invention.

[0184] t 4~ t During period 5, the first IGCT device T0 carries the system fault current, such as... Figure 11 As shown, Figure 11 This is the second schematic diagram of the current flow direction during the short-circuit breaking process provided by the present invention.

[0185] tAt time 5, the fast mechanical switch S1 restores its insulation characteristics, turning on the second thyristor T3 and the third thyristor T4. The circuit of capacitor C0-second thyristor T3-first IGCT device T0-third thyristor T4 is completed, capacitor C0 discharges, and a reverse pulse current is injected into the first IGCT device T0. Under the action of this pulse current, the current in the first IGCT device T0 drops rapidly, as... Figure 12 As shown, Figure 12 This is the third schematic diagram of the current flow direction during the short-circuit breaking process provided by the present invention.

[0186] t At time 6, the current drops below the turn-off value, and the first IGCT device T0 turn-off command is sent.

[0187] t 6~ t During period 7, the fault current is transferred to the branch of the third thyristor T4 - capacitor C0 - second thyristor T3 - first inductor L1, and the system begins to reverse charge capacitor C0, such as... Figure 13 As shown, Figure 13 The fourth schematic diagram of current flow during the short-circuit breaking process provided by the present invention.

[0188] t At time 7, when the voltage across capacitor C0 rises to the turn-on voltage of the varistor MOV in the voltage-limiting and energy-dissipating branch, the varistor MOV turns on, and the fault current begins to transfer to the varistor MOV. Figure 14 As shown, Figure 14 This is the fifth schematic diagram illustrating the current flow during the short-circuit breaking process provided by the present invention. Simultaneously, after system charging, capacitor C0 returns to its initial voltage, and the circuit breaker acquires the fault reclosing function.

[0189] t At time 8, the fault current is completely transferred to the varistor MOV and begins to decrease until it reaches zero, as shown below. Figure 15 As shown, Figure 15 This is the sixth schematic diagram of the current flow direction during the short-circuit breaking process provided by the present invention.

[0190] (2) If the system current flows from the second node Y2 to the first node Y1.

[0191] t 0~ t In stage 1, the system operates under rated current-carrying conditions, with the main branch fast mechanical switch S1 closed, and the rated current-carrying capacity is maintained. i 0.

[0192] t If a short circuit fault occurs at moment 1, the system current rises rapidly.

[0193] tAt time 2, the system detects a short circuit fault and simultaneously sends a fast mechanical switch S1 trip command and a second IGCT device T1 turn-on command.

[0194] t At time 3, the fast mechanical switch S1 begins to open, sending a turn-on command to the fifth thyristor T6. A pulse discharge circuit is formed by capacitor C0, first inductor L1, and fifth thyristor T6, generating an induced electromotive force with "negative on the left and positive on the right" across the first inductor L1.

[0195] Since the first inductor L1 and the second inductor L2 are coupled to each other, the second inductor L2 couples out an induced electromotive force with "positive on the left and negative on the right". Under the action of this induced electromotive force, the current in the fast mechanical switch S1 is rapidly transferred to the second IGCT device T1.

[0196] After one cycle of pulse discharge, the voltage across capacitor C0 reverses, with node Y4 becoming positive and node Y5 becoming negative. The fifth thyristor T6 is then turned off under the reverse voltage. Figure 16 As shown, Figure 16 This is the seventh schematic diagram of the current flow direction during the short-circuit breaking process provided by the present invention.

[0197] t 4~ t During period 5, the second IGCT device T1 carries the system fault current, such as Figure 17 As shown, Figure 17 This is the eighth schematic diagram of the current flow direction during the short-circuit breaking process provided by the present invention.

[0198] t At time 5, the fast mechanical switch S1 restores its insulation characteristics, turning on the first thyristor T2 and the fourth thyristor T5. The circuit of capacitor C0-first thyristor T2-second IGCT device T1-fourth thyristor T5 is completed, capacitor C0 discharges, and a reverse pulse current is injected into the second IGCT device T1. Under the action of this pulse current, the current in the second IGCT device T1 drops rapidly, as... Figure 18 As shown, Figure 18 This is the ninth schematic diagram of the current flow direction during the short-circuit breaking process provided by the present invention.

[0199] t At time 6, the current drops below the turn-off value, and the second IGCT device T1 is sent off.

[0200] t 6~ t During period 7, the fault current is transferred to the branch of the second inductor L2-the fourth thyristor T5-capacitor C0-the first thyristor T2, and the system begins to reverse charge capacitor C0, such as... Figure 19 As shown, Figure 19This is the tenth schematic diagram of the current flow direction during the short-circuit breaking process provided by the present invention.

[0201] t At time 7, when the voltage across capacitor C0 rises to the turn-on voltage of the varistor MOV in the voltage-limiting and energy-dissipating branch, the varistor MOV turns on, and the fault current begins to transfer to the varistor MOV. Figure 20 As shown, Figure 20 This is eleventh of the schematic diagrams showing the current flow direction during the short-circuit breaking process provided by the present invention.

[0202] Meanwhile, after the system is charged, capacitor C0 is restored to its initial voltage, and the circuit breaker has the function of fault reclosing.

[0203] t At time 8, the fault current is completely transferred to the varistor MOV and begins to decrease until it reaches zero, as shown below. Figure 21 As shown, Figure 21 This is the twelfth schematic diagram of the current flow direction during the short-circuit breaking process provided by the present invention.

[0204] This invention provides a control method for a high-capacity bidirectional DC circuit breaker. By controlling the conduction of the thyristors in the coupled switching branch under different operating conditions, the system can achieve the breaking of different currents. This invention uses only one pulse discharge circuit, and simultaneously realizes current transfer and reliable shutdown of a high-capacity DC system under high current change rate short-circuit conditions. It has the advantages of small size, strong breaking capacity, convenient control, and reclosing function under short-circuit fault conditions.

[0205] The advantages of this invention are as follows: Through innovative topology design, it solves the problem of low-current interruption by directly turning off IGCT devices at rated and below current levels. Under short-circuit conditions, it first utilizes half a cycle of the pulse capacitor discharge circuit to reliably transfer the short-circuit fault current from the fast mechanical switch to the semiconductor device. Simultaneously, during the other half cycle of the pulse capacitor discharge, a reverse pulse current is injected into the conducting IGCT, reducing the fault current below the IGCT device's turn-off value, thus achieving reliable turn-off for large-capacity short-circuit faults. Furthermore, this topology utilizes the system fault current to charge the pulse capacitor, providing reclosing functionality under short-circuit faults. The entire topology uses only one pulse discharge circuit, featuring large current capacity, strong turn-off capability, small size, and convenient control, providing a reliable protection scheme for fault protection of medium- and high-voltage, large-capacity DC power systems.

[0206] Those skilled in the art will understand that all or part of the processes of the methods described in the above embodiments can be implemented by a computer program instructing related hardware (such as a processor, controller, etc.), and the computer program can be stored in a computer-readable storage medium. The computer-readable storage medium may be a disk, optical disk, read-only memory, or random access memory, etc.

[0207] The bidirectional DC circuit breaker, rated breaking method, and short-circuit breaking method provided by the present invention have been described in detail above. Specific examples have been used to illustrate the principle and implementation of the present invention. The description of the above embodiments is only for the purpose of helping to understand the method and core idea of ​​the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation and application scope based on the idea of ​​the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A bidirectional DC circuit breaker, characterized in that, include: The main switch branch, voltage limiting and energy dissipation branch and coupling converter turn-off branch are connected in parallel, and the parallel nodes include the first node and the second node. The coupled commutation turn-off branch includes a first IGCT device, a second IGCT device, a coupling coil, a first thyristor, a second thyristor, a third thyristor, a fourth thyristor, a fifth thyristor, and a capacitor; The coupling coil includes a first inductor and a second inductor that are coupled to each other, and the winding directions of the first inductor and the second inductor are opposite. The anode of the first IGCT device, the cathode of the second IGCT device, the cathode of the first thyristor, the anode of the third thyristor, and the first node are connected; The cathode of the first IGCT device and the cathode of the second thyristor are connected to form a third node; the two poles of the first inductor are respectively connected to the third node and the second node; The anodes of the first thyristor and the second thyristor are connected to form a fourth node; The cathodes of the third thyristor and the fourth thyristor are connected to form a fifth node; The fifth thyristor is connected in reverse parallel across the two ends of the second thyristor; The anode of the second IGCT device and the anode of the fourth thyristor are connected to form a sixth node; the two poles of the second inductor are respectively connected to the sixth node and the second node; The two terminals of the capacitor are respectively connected to the fourth node and the fifth node; The voltage-limiting and energy-dissipating branch includes a varistor.

2. The bidirectional DC circuit breaker according to claim 1, characterized in that, The main switch branch includes a fast mechanical switch.

3. The bidirectional DC circuit breaker according to claim 1, characterized in that, The capacitor is precharged with voltage; The pre-charge voltage positive terminal of the capacitor is connected to the fifth node; The pre-charge voltage negative terminal of the capacitor is connected to the fourth node.

4. A rated breaking method for a bidirectional DC circuit breaker, characterized in that, The bidirectional DC circuit breaker according to any one of claims 1 to 3 comprises: Under rated operating conditions, the main switch branch is closed; During the rated breaking process, a tripping command is sent to the main switch branch, and an opening command is sent to either the first IGCT device or the second IGCT device according to the current direction. Once the main switch branch restores its insulation characteristics, a turn-off command is sent to any of the IGCT devices to cause the voltage across the first and second nodes to rise. When the voltage across the first and second nodes rises to the turn-on voltage of the voltage-limiting and energy-consuming branch, the voltage-limiting and energy-consuming branch is turned on, so that the current is transferred to the voltage-limiting and energy-consuming branch to complete the rated interruption.

5. The rated breaking method according to claim 4, characterized in that, Sending an activation command to either the first IGCT device or the second IGCT device according to the current direction includes: When the current flows from the first node to the second node, an activation command is sent to the first IGCT device.

6. The rated breaking method according to claim 4, characterized in that, Sending an activation command to either the first IGCT device or the second IGCT device according to the current direction includes: When the current flows from the second node to the first node, an on-state command is sent to the second IGCT device.

7. A short-circuit breaking method for a bidirectional DC circuit breaker, characterized in that, The bidirectional DC circuit breaker according to any one of claims 1 to 3 comprises: During the short-circuit breaking process, a tripping command is sent to the main switch branch, and an opening command is sent to either the first IGCT device or the second IGCT device according to the current direction. When the main switch branch starts to open, a conduction command is sent to the fifth thyristor to discharge the capacitor, generate an induced electromotive force in the coupling coil, and transfer the current in the main switch branch to any of the IGCT devices; after the capacitor has undergone a pulse discharge cycle, the voltage across the capacitor is reversed, with the fourth node corresponding to a positive voltage and the fifth node corresponding to a negative voltage. When the main switch branch restores its insulation characteristics, an on-state command is sent to the branch composed of the second and third thyristors or the branch composed of the first and fourth thyristors based on any of the IGCT devices, and a reverse pulse current is injected into any of the IGCT devices. When the current in any of the IGCT devices drops below the rated turn-off value, the IGCT devices are turned off so that the current charges the capacitor. When the voltage across the capacitor rises to the turn-on voltage of the voltage limiting and energy dissipation branch, the voltage limiting and energy dissipation branch turns on, and the current is transferred to the voltage limiting and energy dissipation branch, thus completing the short circuit breaking.

8. The short-circuit breaking method according to claim 7, characterized in that, Sending an activation command to either the first or second IGCT device based on the current direction includes: When the current flows from the first node to the second node, an activation command is sent to the first IGCT device. When the current flows from the second node to the first node, an on-state command is sent to the second IGCT device.

9. The short-circuit breaking method according to claim 7, characterized in that, The step of sending an activation command to the branch composed of the second and third thyristors or the branch composed of the first and fourth thyristors based on any of the IGCT devices includes: When the first IGCT device is turned on, an on command is sent to the branch composed of the second and third thyristors; When the second IGCT device is turned on, an on command is sent to the branch composed of the first thyristor and the fourth thyristor.

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