Multi-port hybrid direct-current circuit breaker based on LC resonant circuit and control method of multi-port hybrid direct-current circuit breaker

Abstract

The invention discloses a multi-port hybrid DC circuit breaker based on an LC resonant circuit and a control method thereof, a resonant capacitor of an LC resonant branch is charged to a bus voltage through a circuit from a main breaking switch branch, a resonant inductor of the LC resonant branch, the resonant capacitor and a charging resistor branch to the ground, and an external power supply is not needed to pre-charge the capacitor. The method has the advantages of simple topological structure, simplicity and convenience in operation and low investment cost; meanwhile, the LC resonance branch can be used for reversing the polarity of the capacitor, the capacity of secondary current breaking is achieved, and the protection requirement for rapid reclosing can be met. The technical problems that an existing multi-port hybrid direct-current circuit breaker needs to depend on an external power supply to precharge a capacitor turn-off thyristor, so that the extra cost, the structural complexity and the operation difficulty are increased, and a rapid reclosing protection function is lacked are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of direct current circuit breakers, and in particular to a multi-port hybrid direct current circuit breaker based on an LC resonance circuit and a control method thereof. Background Art

[0002] Medium and high voltage direct current (DC) grids have developed rapidly due to their great advantages in renewable energy grid connection, flexible control and long-distance power transmission. However, after a DC circuit breaker fault occurs, the fault current rises rapidly and there is no natural zero crossing point, which seriously affects the safe and stable operation of the power system and becomes one of the main challenges in the development of DC grids.

[0003] DC circuit breakers can quickly and selectively isolate faulty lines, effectively preventing the spread of faults and causing converter station lockout. Current DC circuit breakers are divided into mechanical DC circuit breakers, solid-state DC circuit breakers, and hybrid DC circuit breakers. Mechanical DC circuit breakers based on mechanical switches have extremely low conduction losses, but face problems such as slow operation speed and long response time caused by slow arc extinguishing process. Solid-state DC circuit breakers based on fully controlled semiconductor devices have extremely fast breaking speeds, and there is no arc problem during the breaking process, but their conduction losses and construction costs are very high. Hybrid DC circuit breakers have become a more ideal solution at present because they combine the advantages of low conduction losses of mechanical DC circuit breakers and high breaking speeds of solid-state DC circuit breakers.

[0004] The multi-port hybrid DC circuit breaker shares the expensive main disconnect branch between adjacent lines connected to the common DC bus. Although it reduces the cost of applying the two-port hybrid DC circuit breaker to the multi-terminal DC power grid to a certain extent, the large number of fully controlled semiconductor devices contained in the shared main disconnect branch still makes the total cost high. Compared with fully controlled devices, semi-controlled semiconductor devices such as thyristors have low conduction losses, strong surge current tolerance and low cost. At present, the thyristor-based DC circuit breakers designed for two-port application scenarios cannot meet the needs of multi-port fault current interruption. Although the thyristor-based multi-port DC circuit breakers can be applied to multi-port DC power grids, most of them rely on the capacitor pre-charged by the external power supply to turn off the thyristor, which increases the additional cost, structural complexity and operation difficulty. In addition, most of the existing thyristor-based multi-port DC circuit breakers consider the first fault current interruption process, cannot handle the problem of capacitor energy well, and lack the fast reclosing protection function. Therefore, how to solve the problem that the existing multi-port hybrid DC circuit breaker needs to rely on an external power supply to pre-charge the capacitor to turn off the thyristor, which increases the additional cost, structural complexity and operation difficulty, and lacks a fast reclosing protection function is a technical problem that needs to be urgently solved by technical personnel in this field. Summary of the invention

[0005] The present invention provides a multi-port hybrid DC circuit breaker based on an LC resonant circuit and a control method thereof, which are used to solve the technical problems that the existing multi-port hybrid DC circuit breaker needs to rely on a capacitor pre-charged by an external power supply to turn off a thyristor, which increases the additional cost, structural complexity and operating difficulty, and lacks a fast reclosing protection function.

[0006] In view of this, a first aspect of the present invention provides a multi-port hybrid DC circuit breaker based on an LC resonant circuit, comprising a plurality of current-carrying branches, a plurality of first diodes, a DC bus, a main disconnect switch branch, an LC resonant branch, a charging resistor branch and an energy consumption branch;

[0007] The number of the first diodes is the same as the number of the current-carrying branches;

[0008] Each current-carrying branch includes an ultra-fast mechanical switch and a load transfer switch connected in sequence;

[0009] The input end of each current-passing branch is connected to the cathode of a first diode, and the output end of each current-passing branch is connected to the DC bus;

[0010] One end of the main disconnect switch branch is connected to the DC bus, and the other end of the main disconnect switch branch is connected to the anodes of all the first diodes;

[0011] One end of the LC resonant branch is connected to the DC bus, and the other end of the LC resonant branch is connected to the anodes of all the first diodes;

[0012] One end of the charging resistance branch is connected to an end of the resonant capacitor of the LC resonant branch away from the resonant inductor, and the other end of the charging resistance branch is grounded;

[0013] One end of the energy dissipation branch is connected to an end of the resonant capacitor of the LC resonant branch away from the resonant inductor, and the other end of the energy dissipation branch is connected to the anodes of all the first diodes.

[0014] Optionally, the LC resonant branch includes a second diode, a second thyristor, a resonant capacitor and a resonant inductor;

[0015] The cathode of the second diode is connected to the DC bus, the anode of the second diode is connected to the cathode of the second thyristor, the anode of the second thyristor is connected to the DC bus, the cathode of the second thyristor is connected to one end of the resonant capacitor, the other end of the resonant capacitor is connected to one end of the resonant inductor, and the other end of the resonant inductor is connected to the anodes of all the first diodes.

[0016] Optionally, the main disconnect switch branch includes a first thyristor;

[0017] An anode of the first thyristor is connected to the DC bus, and a cathode of the first thyristor is connected to anodes of all the first diodes.

[0018] Optionally, the charging resistance branch includes a charging resistor, one end of the charging resistor is connected to an end of the resonant capacitor of the LC resonant branch away from the resonant inductor, and the other end of the charging resistor is grounded.

[0019] Optionally, the energy consumption branch includes a lightning arrester, one end of the lightning arrester is connected to the cathode of the second thyristor, and the other end of the lightning arrester is connected to the anodes of all the first diodes.

[0020] Optionally, the lightning arrester is a MOV type lightning arrester.

[0021] A second aspect of the present invention provides a control method for any one of the multi-port hybrid DC circuit breakers based on the LC resonant circuit provided in the first aspect, comprising the following steps:

[0022] S1, turn on the ultra-fast mechanical switches and load transfer switches on all the current branches, where the input end of each current branch i is connected to the corresponding DC line through a preset port ;

[0023] S2, turn on the main disconnect switch branch. When the voltage across the resonant capacitor on the LC resonant branch reaches the DC bus voltage, the main disconnect switch branch is turned off.

[0024] S3. Measuring DC lines The current;

[0025] S4, if the DC line If the current is greater than the current threshold, jump to step S5, otherwise, return to step S3;

[0026] S5, turn on the main disconnect switch branch and turn off the load transfer switch on the current branch i;

[0027] S6, when the current flowing through the ultra-fast mechanical switch on the flow branch i drops to 0, the ultra-fast mechanical switch on the flow branch i is disconnected to a preset mechanical distance;

[0028] S7, turning on the LC resonant branch, turning off the main disconnect switch branch in turn, and the polarity of the resonant capacitor of the LC resonant branch is reversed and charged in reverse;

[0029] S8, when the voltage across the resonant capacitor of the LC resonant branch reaches a preset voltage, the energy consumption branch works;

[0030] S9, after the LC resonant branch is turned off, the main disconnect switch branch is turned on, so that the polarity of the resonant capacitor of the LC resonant branch is reversed and restored to the initial state;

[0031] S10: Measure the DC line again within the preset time. The current;

[0032] S11, if the DC line If the current of the DC line is not greater than the current threshold, then return to step S1. If the current is greater than the current threshold, the LC resonant branch is turned on, which in turn turns off the main disconnect switch and reverses the polarity of the resonant capacitor of the LC resonant branch;

[0033] S12, when the voltage across the resonant capacitor of the LC resonant branch reaches a preset voltage, the energy consumption branch works again.

[0034] Optionally, in step S8 and step S12, the preset voltage is the action voltage of the lightning arrester.

[0035] Optionally, step S7 specifically includes:

[0036] The second thyristor on the LC resonant branch is turned on, which in turn turns off the main switch branch, and the polarity of the resonant capacitor of the LC resonant branch is reversed and charged in reverse.

[0037] Optionally, step S9 specifically includes:

[0038] After the second thyristor on the LC resonant branch is turned off, the main disconnect switch branch is turned on, so that the polarity of the resonant capacitor of the LC resonant branch is reversed and restored to an initial state.

[0039] It can be seen from the above technical solutions that the embodiments of the present invention have the following advantages:

[0040] The present invention provides a multi-port hybrid DC circuit breaker based on an LC resonant circuit and a control method thereof. The resonant capacitor of the LC resonant branch is charged to the bus voltage via a main breaker branch, a resonant inductor of the LC resonant branch, a resonant capacitor and a charging resistor branch to ground, and no external power supply is required to pre-charge the capacitor. The invention has the advantages of simple topological structure, simple operation and low investment cost. At the same time, the polarity of the capacitor can be reversed by using the LC resonant branch, and the ability of secondary current breaking can be possessed, which can meet the protection requirements for fast reclosing. The technical problems that the existing multi-port hybrid DC circuit breaker needs to rely on the capacitor pre-charged by an external power supply to turn off the thyristor, which increases the additional cost, structural complexity and operation difficulty, and lacks the fast reclosing protection function are solved. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0042] Figure 1 A circuit schematic diagram of a multi-port hybrid DC circuit breaker based on an LC resonant circuit provided in an embodiment of the present invention;

[0043] Figure 2 The present invention is a flowchart of a method for controlling a multi-port hybrid DC circuit breaker based on an LC resonant circuit provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0044] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0045] For easier understanding, see Figure 1 , the present invention provides an embodiment of a multi-port hybrid DC circuit breaker based on an LC resonant circuit, comprising a plurality of current-carrying branches, a plurality of first diodes, a DC bus, a main disconnect switch branch, an LC resonant branch, a charging resistor branch and an energy consumption branch;

[0046] The number of the first diodes is the same as the number of the current-carrying branches;

[0047] Each current-carrying branch includes an ultra-fast mechanical switch and a load transfer switch connected in sequence;

[0048] The input end of each current-passing branch is connected to the cathode of a first diode, and the output end of each current-passing branch is connected to the DC bus;

[0049] One end of the main disconnect switch branch is connected to the DC bus, and the other end of the main disconnect switch branch is connected to the anodes of all the first diodes;

[0050] One end of the LC resonant branch is connected to the DC bus, and the other end of the LC resonant branch is connected to the anodes of all the first diodes;

[0051] One end of the charging resistance branch is connected to the DC bus, and the other end of the charging resistance branch is grounded;

[0052] One end of the energy dissipation branch is connected to an end of the resonant capacitor of the LC resonant branch away from the resonant inductor, and the other end of the energy dissipation branch is connected to the anodes of all the first diodes.

[0053] It should be noted that if Figure 1 As shown, in the embodiment of the present invention, there are n through-current branches, each of which is an ultra-fast mechanical switch. and load transfer switches The output ends of the n current-carrying branches are connected to the same common point A on the DC bus BUS, where: The number of first diodes is the same as the number of current-carrying branches, that is, there are n first diodes in total, recorded as The input end of each flow branch is recorded as . The cathodes are connected to the input ends of the corresponding n current branches. , n first diodes The anodes of the main disconnect switch branch are connected to the same common point B to form a half-bridge circuit. One end of the main disconnect switch branch is connected to the DC bus, and the other end of the main disconnect switch branch is connected to all the first diodes. One end of the LC resonant branch is connected to the DC bus BUS, and the other end of the LC resonant branch is connected to all the first diodes. One end of the energy-consuming branch is connected to the end of the resonant capacitor C of the LC resonant branch away from the resonant inductor L, and the other end of the energy-consuming branch is connected to all the first diodes. In the embodiment of the present invention, it is necessary to ensure that the duration of the resonant current of the LC resonant branch being greater than the line fault current is longer than the reverse recovery time of the main disconnect switch branch to ensure that the main disconnect switch branch is reliably turned off.

[0054] The present invention provides a multi-port hybrid DC circuit breaker based on an LC resonant circuit and a control method thereof. The resonant capacitor of the LC resonant branch is charged to the bus voltage via a main breaker branch, a resonant inductor of the LC resonant branch, a resonant capacitor and a charging resistor branch to ground, and no external power supply is required to pre-charge the capacitor. The invention has the advantages of simple topological structure, simple operation and low investment cost. At the same time, the polarity of the capacitor can be reversed by using the LC resonant branch, and the ability of secondary current breaking can be possessed, which can meet the protection requirements for fast reclosing. The technical problems that the existing multi-port hybrid DC circuit breaker needs to rely on the capacitor pre-charged by an external power supply to turn off the thyristor, which increases the additional cost, structural complexity and operation difficulty, and lacks the fast reclosing protection function are solved.

[0055] In one embodiment, the LC resonant branch includes a second diode , the second thyristor , resonant capacitor C and resonant inductor L. The second diode The cathode of the second diode is connected to the DC bus BUS. The anode of the second thyristor The cathode connection of the second thyristor The anode of the second thyristor is connected to the DC bus BUS. The cathode of is connected to one end of the resonant capacitor C, the other end of the resonant capacitor C is connected to one end of the resonant inductor L, and the other end of the resonant inductor L is connected to all the first diodes At the same common point B of the anode.

[0056] In one embodiment, the main disconnect switch branch includes a first thyristor . The first thyristor The anode of the first thyristor is connected to the DC bus BUS. The cathode of all first diodes is connected to At the same common point B of the anode.

[0057] In one embodiment, the charging resistor branch includes a charging resistor R, one end of the charging resistor R is connected to the end of the resonant capacitor C of the LC resonant branch away from the resonant inductor L, and the other end of the charging resistor R is grounded. The charging resistor R should have a large resistance value, and the time constant RC should be controlled within a reasonable range, generally several hundred milliseconds. The time constant RC needs to ensure that the auxiliary second thyristor is charged at a reasonable speed while ensuring that the charging speed is not slow. During normal operation, the resonant capacitor C is connected from the DC bus BUS common point A through the first thyristor of the main disconnect switch branch. The resonant inductor L, resonant capacitor C of the LC resonant branch and the circuit from the charging resistor branch to the ground are charged to the bus voltage V of the DC bus BUS. bus , no external charging power supply is required, further reducing the cost and control complexity. To ensure that the resonant current of the LC resonant branch is greater than the line fault current and lasts longer than the first thyristor The reverse recovery time of the first thyristor Reliable shutdown.

[0058] In one embodiment, the energy consumption branch includes a lightning arrester F, one end of which is connected to the second thyristor The cathode of the arrester F is connected to the cathode of all the first diodes. The anodes of the two LCs are connected to the same common point B. Arrester F is a MOV type arrester. Arrester F is connected in parallel at both ends of the LC resonant branch and has two functions: one is to clamp the circuit breaker voltage to protect the power electronic devices; the other is to dissipate the DC system fault energy.

[0059] Since the thyristor has a strong surge current bearing capacity, and the first thyristor in this embodiment and the second thyristor It does not act as a pass switch, so generally only a single set of thyristors is needed in series, rather than in parallel, which further reduces costs. The first thyristor can be turned off by the on-state voltage drop of the power electronic device to improve turn-off reliability and avoid the first thyristor Overvoltage problem during reverse recovery process.

[0060] like Figure 2 As shown, when the multi-port hybrid DC circuit breaker based on the LC resonant circuit provided in the embodiment of the present invention is applied, its control process is:

[0061] S1, turn on the ultra-fast mechanical switches and load transfer switches on all the current branches, where the input end of each current branch i is connected to the corresponding DC line through a preset port .

[0062] It should be noted that under normal operation, the ultra-fast mechanical switches on each flow branch are controlled in sequence. Closed, load transfer switch At this time, the load current only flows through each flow branch, and the power loss is very low. The input end of each flow branch i is connected through the preset port Connect to the corresponding DC line .

[0063] S2, turns on the main disconnect switch branch. When the voltage across the resonant capacitor on the LC resonant branch reaches the DC bus voltage, the main disconnect switch branch is turned off.

[0064] It should be noted that the first thyristor of the main disconnect switch branch is turned on. Waiting for the resonant capacitor C in the LC resonant branch to pass through the first thyristor The resonant inductor L of the LC resonant branch, the resonant capacitor C and the charging resistor branch to the ground circuit are charged to the DC bus voltage V bus , the first thyristor Natural shutdown, then enter step S3.

[0065] S3. Measuring DC lines of current.

[0066] It should be noted that each DC line is tested Current on , then go to step S4.

[0067] S4, if the DC line If the current is greater than the current threshold, jump to step S5, otherwise, return to step S3.

[0068] It should be noted that each DC line Current on With current threshold For comparison, if the DC line current Greater than the current threshold , indicating that a ground short circuit fault occurs at the port Connected DC lines The line protection device commands the DC circuit breaker to start current interruption, and then enters step S5. Not greater than the current threshold , then return to step S3,

[0069] S5, turn on the main disconnect switch branch and turn off the load transfer switch on the current branch i.

[0070] It should be noted that the first thyristor in the main disconnect switch branch is turned on. , shut down the DC line with fault Load transfer switch in the connected flow branch i Since the first thyristor In the on state, the rest of the DC lines The current will be transferred into the first thyristor and the first diode The current transfer branch is formed, and then the process enters step S6.

[0071] S6. When the current flowing through the ultra-fast mechanical switch on the flow branch i drops to 0, the ultra-fast mechanical switch on the flow branch i is disconnected to a preset mechanical distance.

[0072] It should be noted that when the current flows through the ultra-fast mechanical switch After the current drops to 0, the segmented ultra-fast mechanical switch To the preset mechanical distance to meet the voltage resistance requirement, and then enter step S7.

[0073] S7, turning on the LC resonant branch, which in turn turns off the main disconnect switch branch, and the polarity of the resonant capacitor of the LC resonant branch is reversed and charged in reverse.

[0074] It should be noted that the second thyristor in the LC resonant branch is turned on. , so that the resonant capacitor C and the resonant inductor L generate a resonant current, the resonant current will gradually increase. When the resonant current is greater than the current flowing through the first thyristor When the fault current is large, it flows through the first thyristor The current of the first diode D j ( ) will turn on naturally, the first thyristor Reverse bearing BD j -UFD j -LCS j -A, the on-state voltage of the power electronic device is reliably shut down, and then the process goes to step S8.

[0075] S8. When the voltage across the resonant capacitor of the LC resonant branch reaches a preset voltage, the energy consumption branch operates.

[0076] It should be noted that after about half a resonance cycle, the polarity of the resonant capacitor C is reversed and reversely charged. When the voltage of the resonant capacitor C reaches the operating voltage of the lightning arrester F, the lightning arrester F starts to dissipate system energy and enters step S9.

[0077] S9, after the LC resonant branch is turned off, the main disconnect switch branch is turned on, so that the polarity of the resonant capacitor of the LC resonant branch is reversed and restored to the initial state.

[0078] It should be noted that after a period of time, the current flowing through the second thyristor The current of the second thyristor is less than its holding current. Natural shutdown. Turn on the first thyristor of the main disconnect switch branch At this time, the resonant capacitor C and the resonant inductor L will generate a resonant current in the opposite direction to the initial direction, and the resonant capacitor C completes the polarity reversal and returns to the initial state. At this time, the circuit breaker can interrupt the fault current again and enter step S10.

[0079] S10: Measure the DC line again within the preset time. of current.

[0080] It should be noted that within the preset time, the DC line is measured again by the line protection device. Current . Go to step S11.

[0081] S11, if the DC line If the current of the DC line is not greater than the current threshold, then return to step S1. If the current is greater than the current threshold, the LC resonant branch is turned on, which in turn turns off the main disconnect switch and reverses the polarity of the resonant capacitor of the LC resonant branch.

[0082] It should be noted that each DC line Current on With current threshold For comparison, if the DC line Current Not greater than the current threshold , the fault is judged to be temporary, and the process returns to step S1 to continue normal operation. Current Greater than the current threshold , then the second thyristor is turned on Generate LC resonance, so that the first thyristor When it is subjected to reverse voltage and turned off again, the polarity of the resonant capacitor in the LC resonant branch is reversed.

[0083] S12, when the voltage across the resonant capacitor of the LC resonant branch reaches a preset voltage, the energy consumption branch works again.

[0084] It should be noted that when the resonant capacitor C is reversely charged and reaches the operating voltage of the lightning arrester F, the lightning arrester F starts to dissipate system energy and realize the fast reclosing protection function.

[0085] The present invention uses cheap semi-controlled power electronic devices, thyristors, to design the main disconnect switch of a multi-port DC circuit breaker, which greatly reduces the investment cost compared to solutions based on fully controlled devices. In addition, no external power supply is required to pre-charge the capacitor during the current interruption process and the reclosing process, further reducing the investment cost, design complexity, and operation difficulty. The LC resonant branch is used to reverse the polarity of the capacitor, so that the DC circuit breaker has the ability to interrupt the current again, meeting the protection requirements of fast reclosing. The first thyristor By shutting down through the on-state voltage drop of the power electronic device, not only the reliability of thyristor shutdown can be improved, but also the overvoltage problem during the reverse recovery process of the thyristor can be avoided.

[0086] For easier understanding, see Figure 2 The present invention provides an embodiment of a control method for a multi-port hybrid DC circuit breaker based on an LC resonant circuit. The control method is applied to any of the embodiments of the multi-port hybrid DC circuit breaker based on an LC resonant circuit provided in the present invention. The control method comprises the following steps:

[0087] S1, turn on the ultra-fast mechanical switches and load transfer switches on all the current branches, where the input end of each current branch i is connected to the corresponding DC line through a preset port ;

[0088] S2, turn on the main disconnect switch branch. When the voltage across the resonant capacitor on the LC resonant branch reaches the DC bus voltage, the main disconnect switch branch is turned off.

[0089] S3. Measuring DC lines The current;

[0090] S4, if the DC line If the current is greater than the current threshold, jump to step S5, otherwise, return to step S3;

[0091] S5, turn on the main disconnect switch branch and turn off the load transfer switch on the current branch i;

[0092] S6, when the current flowing through the ultra-fast mechanical switch on the flow branch i drops to 0, the ultra-fast mechanical switch on the flow branch i is disconnected to a preset mechanical distance;

[0093] S7, turning on the LC resonant branch, turning off the main disconnect switch branch in turn, and the polarity of the resonant capacitor of the LC resonant branch is reversed and charged in reverse;

[0094] S8, when the voltage across the resonant capacitor of the LC resonant branch reaches a preset voltage, the energy consumption branch works;

[0095] S9, after the LC resonant branch is turned off, the main disconnect switch branch is turned on, so that the polarity of the resonant capacitor of the LC resonant branch is reversed and restored to the initial state;

[0096] S10: Measure the DC line again within the preset time. The current;

[0097] S11, if the DC line If the current of the DC line is not greater than the current threshold, then return to step S1. If the current is greater than the current threshold, the LC resonant branch is turned on, which in turn turns off the main disconnect switch and reverses the polarity of the resonant capacitor of the LC resonant branch;

[0098] S12, when the voltage across the resonant capacitor of the LC resonant branch reaches a preset voltage, the energy consumption branch works again.

[0099] In one embodiment, in step S8 and step S12, the preset voltage is the action voltage of the lightning arrester.

[0100] In one embodiment, step S7 specifically includes:

[0101] The second thyristor on the LC resonant branch is turned on, which in turn turns off the main switch branch, and the polarity of the resonant capacitor of the LC resonant branch is reversed and charged in reverse.

[0102] In one embodiment, step S9 specifically includes:

[0103] After the second thyristor on the LC resonant branch is turned off, the main switch branch is turned on, so that the polarity of the resonant capacitor of the LC resonant branch is reversed and restored to the initial state. The control method of the multi-port hybrid DC circuit breaker based on the LC resonant circuit provided in the present invention has been described in the embodiment of the multi-port hybrid DC circuit breaker based on the LC resonant circuit provided in the present invention, and will not be repeated here.

[0104] As described above, the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features thereof may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A multi-port hybrid DC circuit breaker based on an LC resonant circuit, characterized in that: It includes a plurality of current-passing branches, a plurality of first diodes, a DC bus, a main disconnect switch branch, an LC resonance branch, a charging resistor branch and an energy consumption branch; The number of the first diodes is the same as the number of the current-carrying branches; Each current-carrying branch includes an ultra-fast mechanical switch and a load transfer switch connected in sequence; The input end of each current-passing branch is connected to the cathode of a first diode, and the output end of each current-passing branch is connected to the DC bus; One end of the main disconnect switch branch is connected to the DC bus, and the other end of the main disconnect switch branch is connected to the anodes of all the first diodes; One end of the LC resonant branch is connected to the DC bus, and the other end of the LC resonant branch is connected to the anodes of all the first diodes; One end of the charging resistance branch is connected to an end of the resonant capacitor of the LC resonant branch away from the resonant inductor, and the other end of the charging resistance branch is grounded; One end of the energy dissipation branch is connected to an end of the resonant capacitor of the LC resonant branch away from the resonant inductor, and the other end of the energy dissipation branch is connected to the anodes of all the first diodes.

2. The multi-port hybrid DC circuit breaker based on LC resonant circuit according to claim 1, characterized in that: The LC resonant branch includes a second diode, a second thyristor, a resonant capacitor and a resonant inductor; The cathode of the second diode is connected to the DC bus, the anode of the second diode is connected to the cathode of the second thyristor, the anode of the second thyristor is connected to the DC bus, the cathode of the second thyristor is connected to one end of the resonant capacitor, the other end of the resonant capacitor is connected to one end of the resonant inductor, and the other end of the resonant inductor is connected to the anodes of all the first diodes.

3. The multi-port hybrid DC circuit breaker based on LC resonant circuit according to claim 1, characterized in that: The main disconnect switch branch includes a first thyristor; An anode of the first thyristor is connected to the DC bus, and a cathode of the first thyristor is connected to anodes of all the first diodes.

4. The multi-port hybrid DC circuit breaker based on LC resonant circuit according to claim 1, characterized in that: The charging resistor branch comprises a charging resistor, one end of which is connected to an end of the resonant capacitor of the LC resonant branch away from the resonant inductor, and the other end of which is grounded.

5. The multi-port hybrid DC circuit breaker based on LC resonant circuit according to any one of claims 2 to 4, characterized in that: The energy consumption branch comprises a lightning arrester, one end of the lightning arrester is connected to the cathode of the second thyristor, and the other end of the lightning arrester is connected to the anodes of all the first diodes.

6. The multi-port hybrid DC circuit breaker based on LC resonant circuit according to claim 5, characterized in that: The arrester is a MOV type arrester.

7. A control method for a multi-port hybrid DC circuit breaker based on an LC resonant circuit according to any one of claims 1 to 6, characterized in that: The following steps are involved: S1, turn on the ultra-fast mechanical switches and load transfer switches on all the current branches, where the input end of each current branch i is connected to the corresponding DC line through a preset port ; S2, turn on the main disconnect switch branch. When the voltage across the resonant capacitor on the LC resonant branch reaches the DC bus voltage, the main disconnect switch branch is turned off. S3. Measuring DC lines The current; S4, if the DC line If the current is greater than the current threshold, jump to step S5, otherwise, return to step S3; S5, turn on the main disconnect switch branch and turn off the load transfer switch on the current branch i; S6, when the current flowing through the ultra-fast mechanical switch on the flow branch i drops to 0, the ultra-fast mechanical switch on the flow branch i is disconnected to a preset mechanical distance; S7, turning on the LC resonant branch, turning off the main disconnect switch branch in turn, and the polarity of the resonant capacitor of the LC resonant branch is reversed and charged in reverse; S8, when the voltage across the resonant capacitor of the LC resonant branch reaches a preset voltage, the energy consumption branch works; S9, after the LC resonant branch is turned off, the main disconnect switch branch is turned on, so that the polarity of the resonant capacitor of the LC resonant branch is reversed and restored to the initial state; S10: Measure the DC line again within the preset time. The current; S11, if the DC line If the current of the DC line is not greater than the current threshold, then return to step S1. If the current is greater than the current threshold, the LC resonant branch is turned on, which in turn turns off the main disconnect switch and reverses the polarity of the resonant capacitor of the LC resonant branch; S12, when the voltage across the resonant capacitor of the LC resonant branch reaches a preset voltage, the energy consumption branch works again.

8. The control method of a multi-port hybrid DC circuit breaker based on an LC resonant circuit according to claim 7, characterized in that: In step S8 and step S12, the preset voltage is the operating voltage of the lightning arrester.

9. The control method of a multi-port hybrid DC circuit breaker based on an LC resonant circuit according to claim 7, characterized in that: Step S7 specifically includes: The second thyristor on the LC resonant branch is turned on, which in turn turns off the main switch branch, and the polarity of the resonant capacitor of the LC resonant branch is reversed and charged in reverse.

10. The control method of a multi-port hybrid DC circuit breaker based on an LC resonant circuit according to claim 7, characterized in that: Step S9 specifically includes: After the second thyristor on the LC resonant branch is turned off, the main disconnect switch branch is turned on, so that the polarity of the resonant capacitor of the LC resonant branch is reversed and restored to an initial state.

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