CN108766830A - A kind of manifold type high voltage DC breaker - Google Patents

Abstract

The invention provides a novel mechanical high-voltage DC circuit breaker with a coupling reactor, including: a main circuit unit, a charging commutation unit, an energy consumption unit, a trigger unit, and an energy-absorbing voltage-limiting unit; the energy-absorbing voltage-limiting unit and the main The circuit units are connected in parallel, and the charging converter unit is connected in parallel with the main circuit unit; the trigger unit is used to trigger the charging converter unit when the system fails and trigger the energy consumption unit when reclosing; the charging converter unit is used to When a fault occurs, a high-frequency oscillating current is generated, which is reversely superimposed on the fault current to form a zero-crossing breaking fault current, and after the first breaking, the pre-charged capacitor is charged for fault breaking after reclosing; energy-absorbing and voltage-limiting The unit absorbs the energy stored in the inductive elements of the power system after the breaking is completed, and limits the voltage at both ends of the mechanical switch; the energy consumption unit is used to consume the energy of the commutation capacitor when the DC circuit breaker recloses, so that the closing of the mechanical switch The current rapidly decays to zero.

Description

A coupled high voltage DC circuit breaker

technical field

The invention belongs to the field of high-voltage direct current circuit breakers, and more specifically relates to a novel mechanical high-voltage direct current circuit breaker with coupling reactors.

Background technique

In recent years, with the increasing demand for energy and the rapid development of renewable energy, HVDC transmission has attracted widespread attention at home and abroad. Since DC transmission has the advantages of large transmission energy, long transmission distance, and small loss, it has been widely used in domestic and foreign power grids. Traditional DC transmission projects are mostly two-terminal systems, which can only realize energy transmission between two points. When DC transmission is used to transmit power to multiple load centers or DC interconnection is used between multiple AC systems, it is necessary to build multiple DC transmission lines Lines, which will greatly increase investment costs and operating costs. The multi-terminal DC transmission system has fully developed the economic and technical advantages of HVDC transmission technology, and is a more attractive transmission technology to meet the development needs of my country's electric power industry. In addition to the advantages of two-terminal DC transmission, multi-terminal DC transmission also has the advantages of realizing multi-power supply and multi-drop power receiving; higher reliability and flexibility; phased construction and improved investment efficiency.

Due to the very small impedance of the DC side of the multi-terminal DC transmission network, when a short-circuit fault occurs on the DC side, the fault current will rise rapidly. If the fault is not removed in a short time, the AC circuit breaker on the converter side will operate and the converter valve group will be blocked. , affecting the normal operation of the entire system. The high-voltage DC circuit breaker can quickly cut off the fault current and isolate the fault point in a short time to ensure the normal operation of the system. Therefore, high-voltage DC circuit breakers are one of the key equipment for building reliable multi-terminal flexible DC grids.

At present, the main DC circuit breakers at home and abroad are classified into mechanical DC circuit breakers, hybrid DC circuit breakers and all-solid-state DC circuit breakers. The all-solid-state high-voltage DC circuit breaker is mainly composed of power electronic devices. When it is applied to the high-voltage DC power grid, too many devices in series will lead to complex control units, high cost, and large on-state loss. Therefore, the current research and development of high-voltage DC circuit breakers focuses on Mechanical high-voltage DC circuit breakers and hybrid high-voltage DC circuit breakers are mainly used. As for hybrid high-voltage DC circuit breakers, because their current-through and withstand voltage components are power electronic solid-state switches, the cost is high and the on-state loss is large. The control requirements It is also very strict; while traditional mechanical high-voltage DC circuit breakers, if the high-voltage ball gap is used as the commutation branch control switch, the electric spark when it is turned on will pose a threat to the surrounding oil insulation equipment. If the thyristor is used as the commutation branch To control the switch, the thyristor needs to withstand a higher recovery voltage during the breaking process, and the cost will be higher.

Contents of the invention

In view of the above defects or improvement needs of the prior art, the present invention provides a coupled high-voltage DC circuit breaker, which satisfies the requirements of the DC system for the high-voltage DC circuit breaker itself to act quickly, break large currents, small currents and withstand high voltages. On the one hand, it solves the problems of high cost and high withstand voltage of the thyristor in the existing high-voltage DC circuit breaker; for the coupling type high-voltage DC circuit breaker, the line current will be transferred to the commutation branch after breaking, resulting in the small current freewheeling problem, and the coupled high-voltage DC circuit breaker in the present invention can solve this problem very well. At the same time, the proposed coupled high-voltage DC circuit breaker has the function of bidirectional reclosing and breaking, which can meet the needs of different DC systems.

The present invention provides a coupled high-voltage DC circuit breaker, including: a main circuit unit, a charging commutation unit, an energy consumption unit, a trigger unit, and an energy-absorbing and voltage-limiting unit; the main circuit unit is used to connect to a DC system in series, so The energy absorbing voltage limiting unit is connected in parallel with the main circuit unit, the charging converter unit is connected in parallel with the main circuit unit; the first output terminal of the triggering unit is connected with the charging converter unit, and the triggering unit The second output terminal of is connected with the energy consumption unit, and the trigger unit is used to trigger the charging converter unit when the system fails, and trigger the energy consumption unit when reclosing; the charging converter unit is used for When a fault occurs, a high-frequency oscillating current is generated, which is reversely superimposed on the fault current to form a zero-crossing breaking fault current, and after the first breaking, the pre-charged capacitor is charged for fault breaking after reclosing; the energy absorption The voltage limiting unit is used to absorb the energy stored in the inductive element of the power system after the breaking is completed, and limit the voltage at both ends of the mechanical switch; the energy consumption unit is also connected to the charging and converting unit, and the energy consumption unit is used for When the DC circuit breaker recloses, the energy of the commutation capacitor is consumed so that the closing current on the mechanical switch rapidly decays to zero.

Furthermore, the main circuit unit is a mechanical switch capable of igniting an arc and extinguishing the arc when the current crosses zero.

Furthermore, the charging and converting unit includes: a pre-charging capacitor C11, a thyristor SCR1, an energy storage capacitor C12, a charging resistor R1, a coupling reactor, a commutating capacitor C2, a mechanical switch CB2, and an arrester MOV2; the pre-charging capacitor One end of C11 is connected to one end of the primary side L1 of the coupling reactor, the other end of the precharge capacitor C11 is connected to one end of the thyristor SCR1; the other end of the thyristor SCR1 is connected to the primary side L1 of the coupling reactor The other end of the energy storage capacitor C12 is connected in series with the charging resistor R1 and then connected in parallel with the pre-charging capacitor C11; one end of the commutation capacitor C2 is connected to one end of the secondary side L2 of the coupling reactor, so The other end of the commutation capacitor C2 is connected to one end of the mechanical switch CB2, the arrester MOV2 is connected in parallel with the mechanical switch CB2, the other end of the secondary side L2 of the coupling reactor is connected to the other end of the mechanical switch CB2 respectively connected to the two ends of the main circuit unit.

Furthermore, the energy consumption unit includes: an energy consumption resistor R2 and a thyristor SCR2 connected in series, the non-series connection end of the energy consumption resistor R2 is grounded, and the non-series connection end of the thyristor SCR2 is connected to the charging converter unit and the thyristor SCR2 respectively. connection to the trigger unit described above.

Furthermore, the energy-absorbing and voltage-limiting unit includes: a zinc oxide arrester, the two ends of which are respectively connected to the two ends of the main circuit unit.

Wherein, when the system works normally, the mechanical switch CB is closed, and the system current flows to the load through the mechanical switch CB, and its on-state loss is small; Therefore, when the fault current is broken, the mechanical switch CB contacts are opened and arced. After the contact opening distance of the mechanical switch CB reaches the rated opening distance and can withstand the recovery voltage after breaking, The triggering unit triggers the thyristor SCR1, turns on the charging commutation unit, the pre-charging capacitor C11 oscillates with the primary side inductance L1 of the coupling reactor, and makes the secondary side of the coupling reactor The side inductance L2 and the commutation capacitor C2 generate a reverse oscillating current, and the amplitude of the oscillating current exceeds the maximum fault current amplitude of the system, so that the mechanical switch CB generates a zero-crossing arc extinguishment and breaks the fault current; After the mechanical switch CB crosses zero and extinguishes the arc, the line current is transferred to the commutation branch composed of the coupling reactor secondary inductance L2 and the commutation capacitor C2 in series, so that the voltage of the commutation capacitor C2 gradually rises, and Applied to both ends of the mechanical switch CB, when the voltage amplitude rises to the operating voltage of the energy-absorbing and voltage-limiting unit, the energy-absorbing and voltage-limiting unit acts as a lightning protection to absorb the inductive energy in the circuit, and the mechanical switch Voltage limiting protection, at the same time the line current starts to drop.

If the line fault is a ground fault and the magnitude of the fault current is large, the line current will oscillate through the secondary inductance L2 of the coupling reactor and the commutation capacitor C2 after breaking, and the attenuation speed is slow; if the line fault is a high-resistance ground fault , the magnitude of the fault current is small, the commutation branch is in an over-damped state after breaking, and there will be a long tail in the process of line current drop, which will be difficult to meet the system requirements. Therefore, when the breaking is completed and the line current drops to near zero, the trigger unit triggers the thyristor SCR1 again, causing the commutation branch to generate an oscillating current, so that the mechanical switch CB2 disconnects the commutation branch when it crosses zero. circuit current, and the arrester MOV2 functions to limit the voltage across the mechanical switch CB2.

After the first disconnection, the voltage at both ends of the pre-charging capacitor C11 will have more attenuation, and the energy storage capacitor C12 will charge the pre-charging capacitor through the charging resistor R1 so that it can meet the second breaks.

Since the voltage of the commutation capacitor C2 is consistent with the system voltage after the first break, the commutation capacitor C2 and the secondary side L2 of the coupling reactor oscillate to generate an oscillating current with a higher frequency and amplitude during reclosing. affect the second breaking fault current; therefore, when performing reclosing operation, the thyristor SCR2 is first turned on, so that the high-frequency oscillating current generated on the mechanical switch is released through the energy-consuming resistor R2, so that the The mechanical switching current quickly decays to zero.

The present invention has the following advantages:

(1) The thyristor trigger unit is adopted, which has no arc trigger, does not pose a threat to the surrounding oil insulation equipment, and ensures the safe operation of the system; at the same time, the thyristor is placed on the low-voltage side, which significantly reduces the voltage level of the trigger unit and the difficulty of driving control; pre-charging Capacitor C11 is located on the low-voltage side, the pre-charge voltage level is low, and there is no insulation requirement for the ground, so the insulation withstand voltage requirements for live parts are relatively low, and the problem of high-potential and multi-potential charging is solved; the commutation capacitor C2 on the high-voltage side is in Under normal operating conditions, there is no charge, and there is no need for long-term current flow and withstand voltage, so the cost and volume of the capacitor are greatly reduced, its breaking reliability is improved, and the cost of the DC circuit breaker is reduced.

(2) The commutation branch of the medium and high voltage direct current circuit breaker of the present invention is connected in series with the mechanical switch of the commutation branch, and lightning arresters are connected in parallel at both ends. Compared with the traditional coupled mechanical DC circuit breaker, this topology can trigger the thyristor again after the breaking is completed to make the mechanical switch of the commutation branch generate a zero-crossing point, thereby breaking the current of the commutation branch and making the line current quickly decay to zero. At the same time, the voltage at both ends of the mechanical switch of the commutation branch is limited by connecting lightning arresters in parallel to further reduce its cost.

(3) The topology of the coupled high-voltage DC circuit breaker, through the parallel connection of energy-consuming resistors at both ends of the primary side of the coupling reactor, can quickly reduce the current on the mechanical switch to zero when reclosing, avoiding the reclosing current on the second Disconnection has a negative impact.

(4) An energy storage capacitor is connected in parallel at both ends of the pre-charging capacitor, and a charging resistor is connected in series to control the charging time. When this topology is applied to the occasion with high voltage level, the pre-charge capacitor will lose more energy after the first disconnection, and when the second disconnection is performed within the required time, if the transformer is used to charge the pre-charge capacitor, The power of the transformer is required to be extremely large, which puts forward higher requirements for the safety of the equipment. And by connecting the energy storage capacitor in parallel at both ends of the pre-charging capacitor, it can ensure safe and fast charging to the required value, and complete the second disconnection.

Description of drawings

Fig. 1 is a functional block diagram of a coupled high-voltage DC circuit breaker provided by the present invention;

Fig. 2 is a specific structural block diagram of a coupled high voltage DC circuit breaker provided by the present invention;

Fig. 3 is the waveform diagram when the coupled high-voltage direct current circuit breaker provided by the present invention recloses and breaks the fault current;

Fig. 4 is the waveform diagram when the coupled high-voltage DC circuit breaker provided by the present invention breaks a small current;

Fig. 5 is a voltage waveform diagram of the pre-charged capacitor during the reclosing and breaking process of the coupled high-voltage DC circuit breaker provided by the present invention.

Among them, 1 is the main circuit unit, 2 is the charging converter unit, 3 is the energy consumption unit, 4 is the trigger unit, 5 is the energy absorption and voltage limiting unit; CB is the mechanical switch, C11 is the pre-charging capacitor, and C12 is the energy storage capacitor , R1 is the charging resistor, SCR1 and SCR2 are triggerable thyristors, L1 is the primary side of the coupling reactor, L2 is the secondary side of the coupling reactor, C2 is the capacitance of the commutation circuit, CB2 is the mechanical switch of the commutation branch, MOV1 and MOV2 are lightning arrester. In Figure 3 and Figure 4, the x-axis is the time t in s; the y-axis is the current amplitude in kA; the dotted line represents the mechanical switch CB fracture current, and the solid line represents the line current. In FIG. 5 , the x-axis is the time t, and the unit is s; the y-axis is the voltage amplitude, and the unit is kV; the solid line represents the voltage of the pre-charging capacitor C11, and the dotted line represents the voltage of the energy storage capacitor C12.

Detailed ways

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not constitute a conflict with each other.

The purpose of the present invention is to provide a coupled high-voltage DC circuit breaker. On the basis of satisfying the requirements of the DC system for the high-voltage DC circuit breaker itself to act quickly, break large currents and withstand high voltages, the thyristors, pre-charged and The capacitor is placed on the low-voltage side, which reduces equipment cost and improves the reliability of breaking. At the same time, the invention also has the function of bidirectional reclosing breaking, and limits the amplitude of the line current after the breaking is completed, so as to meet the requirements of different systems.

Fig. 1 is a functional block diagram of a coupled high-voltage DC circuit breaker provided by the present invention, and Fig. 2 is a specific structural block diagram of a coupled high-voltage DC circuit breaker provided by the present invention. The coupled high-voltage DC circuit breaker provided by the present invention includes: a main circuit unit 1, a charging and converting unit 2, an energy consumption unit 3, a trigger unit 4, and an energy absorption and voltage limiting unit 5; wherein, the main circuit unit 1 is connected in series to the DC system Among them, the charging converter unit 2 and the energy absorbing voltage limiting unit 5 are connected in parallel with the main circuit unit 1, and the trigger unit 4 is respectively connected in parallel with the charging converter unit 2 and the energy consumption unit 3; where the main circuit unit 1 is a mechanical switch CB, and the mechanical The switch CB is a breaker capable of igniting an arc and extinguishing the arc when the current crosses zero. The charging and converting unit 2 includes a pre-charging capacitor C11, an energy storage capacitor C12, a charging resistor R1, a thyristor SCR1, a coupling reactor, a commutating capacitor C2, a mechanical switch CB2 of a commutating branch, and an arrester MOV2, wherein the pre-charging capacitor C11, the thyristor SCR1 is connected in series with the primary inductance L1 of the coupling reactor, the energy storage capacitor C12 is connected in series with the charging resistor R1, and the two are connected in parallel at both ends of the pre-charging capacitor C11, which is used to charge the pre-charging capacitor C11 after the first disconnection; the commutation capacitor C2 is connected in series with the secondary side L2 of the coupling reactor and the mechanical switch CB2 of the commutation branch, and the lightning arrester MOV2 is connected in parallel at both ends of the mechanical switch CB2 of the commutation branch to limit the voltage at both ends. The energy consumption unit 3 includes a thyristor SCR2 and an energy consumption resistor R2, which are connected in series with the primary side inductance L1 of the coupling reactor, and are used to consume the energy of the commutation capacitor when the DC circuit breaker recloses, so that the closing current on the mechanical switch is fast Decays to zero. The output terminal of the trigger unit 4 is connected to the control terminals of the charging converter unit 2 and the energy consumption unit 3. When the power system fails, the trigger unit 4 is used to generate a trigger signal to trigger the charging converter unit 2 to conduct and generate an oscillating current Superimposed with the fault current to generate a zero-crossing point; when reclosing, the trigger unit 4 triggers the energy consumption unit 3 so that the energy consumption unit 3 absorbs energy and accelerates the decay speed of the mechanical switch current. The energy-absorbing voltage-limiting unit 5 is a zinc oxide arrester, which is used to limit the voltage across the mechanical switch CB of the main circuit unit.

In the example of the present invention, the main function of the main circuit unit 1 is to break the fault current by the mechanical switch CB at the zero crossing point of the current; Frequency oscillating current, the oscillating current is generated in the commutation branch through the coupling reactor, superimposed on the mechanical switch CB, and the mechanical switch CB is broken by artificially creating a zero-crossing point; The thyristor SCR1 is triggered to generate oscillating current in the commutation branch, and the mechanical switch CB2 of the commutation branch is disconnected, thereby breaking the current of the commutation branch and making the line current drop to zero rapidly; ③After the first disconnection, the storage The energy capacitor C12 charges the precharge capacitor C11 through the charging resistor R1 to make its voltage meet the second breaking requirement; the function of the energy consumption unit 3 is to consume the energy in the commutation capacitor C2 during the reclosing operation to make the closing The gate current quickly decays to zero to avoid the impact on the second breaking process; the main function of the energy-absorbing voltage-limiting unit 5 is to absorb the energy stored in the inductive element in the DC system after the fault current is cut off to realize the mechanical switch CB The main function of the trigger unit 4 is to trigger the charging converter unit to conduct after the system fails, and trigger the energy consumption unit to absorb energy when reclosing.

In order to further illustrate the coupled high-voltage DC circuit breaker provided by the embodiment of the present invention, its working process is described in detail as follows:

When the system is working normally, the mechanical switch CB is in the closing state, the system current flows to the load through the mechanical switch CB, and the on-state loss is small.

When a fault occurs in the system, since the used breaking unit is a mature AC breaking unit, it only has the ability to break the current at zero crossing, so when breaking the fault current, the contacts of the mechanical switch CB will separate and arc.

After the contact of the mechanical switch CB reaches the rated opening distance, the trigger unit sends out a signal to trigger the primary side thyristor SCR1 to be turned on, and the precharge capacitor C11 and the primary side L1 of the coupling reactor generate a high-frequency oscillating current, thereby coupling the secondary side of the reactor L2 and commutation capacitor C2 will also generate a high-frequency oscillating current, and the amplitude exceeds the system fault current amplitude. This current is superimposed with the fault current, so that the mechanical switch CB generates a zero crossing point, which is the mechanical switch CB to extinguish the arc and break the fault current. After the mechanical switch CB is extinguished, the line current is transferred to the commutation branch formed by the secondary side L2 of the coupling reactor and the commutation capacitor C2, and the recovery voltage of the commutation capacitor C2 gradually rises, and when the recovery voltage amplitude reaches the energy absorption limit voltage When the operating voltage of the unit arrester is exceeded, the energy-absorbing voltage-limiting unit arrester MOV1 operates to absorb the energy of the inductive elements in the system, thereby limiting the voltage protection of the mechanical switch CB.

After the arrester MOV1 in the energy absorbing voltage limiting unit 5 operates, the line current starts to drop. Due to the low impedance in the line, the current decays very slowly when it reaches near zero. At this time, the thyristor SCR1 is triggered again to make the commutation branch generate a small oscillating current, so that the mechanical switch CB2 of the commutation branch generates a zero-crossing point, breaking the current of the commutation branch, and the line current quickly decays to zero, completing the first stage One-time fault disconnection. The commutation branch arrester MOV2 is used to limit the voltage across the mechanical switch CB2 of the commutation branch.

After the first disconnection, the energy of the pre-charging capacitor C11 will be greatly consumed, and the energy storage capacitor C12 will charge the pre-charging capacitor C11 through the charging resistor R1, so that its energy can meet the requirement of the second disconnection.

After that, the reclosing operation is performed. Before the first breaking is completed, the DC system will charge the commutation capacitor C2 through the commutation capacitor C2 and the secondary inductance L2 of the coupling reactor. When reclosing, the energy of the commutation capacitor C2 will be released through the secondary side L2 of the coupling reactor and the mechanical switch CB to generate a current with high frequency oscillation and slow decay. Therefore, the energy dissipation resistor R2 is connected in parallel at both ends of the primary side inductance L2 of the coupling reactor, and the thyristor SCR2 is turned on during reclosing, and the energy on the commutation capacitor is consumed through the energy dissipation resistor R2, so that the reclosing current quickly decays to zero.

After the reclosing, the breaking process of the second fault current is as mentioned above, so I won't repeat it here.

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with the accompanying drawings. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention.

The invention relates to a coupled high-voltage direct current circuit breaker, which has the functions of bidirectional breaking rated small current and interpolar short-circuit large current and reclosing. After breaking, the line current can quickly decay to zero to meet the needs of different systems. In order to further illustrate the coupled high-voltage DC circuit breaker provided by the embodiment of the present invention, it is now described in detail in conjunction with the drawings and specific examples as follows:

Figure 3 is the current waveform when the coupled high-voltage DC circuit breaker recloses and breaks a large current of 25kA.

Fig. 4 is the current waveform diagram when the high-voltage DC circuit breaker provided by the present invention breaks a small current of 100A, wherein the x-axis is the time t, and the unit is s; the y-axis is the current amplitude, and the unit is kA; the solid line represents the line current, and the dotted line represents mechanical switching current. Fig. 5 is the oscillogram of the pre-charged capacitor during the breaking process of the DC circuit breaker provided by the present invention, wherein the x-axis is the time t, and the unit is s; the y-axis is the voltage amplitude, and the unit is kV; the solid line represents the value of the pre-charged capacitor C11 voltage, the dotted line represents the voltage of the energy storage capacitor C12.

For Figure 3, when reclosing breaks the 25kA fault current, the thyristor SCR1 acts at t1 to break the fault current, and the current of the mechanical switch CB quickly reaches zero; after that, the current is transferred to the commutation branch to charge the commutation capacitor C2. The voltage of the current capacitor C2 is applied to both ends of the mechanical switch CB. When the voltage of the mechanical switch CB reaches the operating voltage of the energy-absorbing voltage-limiting unit MOV, the arrester MOV operates to absorb the energy of the inductive elements in the system, and the line current slowly drops to zero, and Continue to oscillate; turn on the thyristor SCR1 again at t2, the commutation branch generates an oscillating current, the commutation branch mechanical switch CB2 breaks the commutation branch current, and the line current rapidly decays to zero; at t3, the circuit breaker In the reclosing operation, the thyristor SCR2 is turned on at this time, the energy of the commutation capacitor C2 is rapidly consumed through the energy dissipation resistor R2, and the closing current of the mechanical switch rapidly decays to zero. Then perform the second breaking of the recloser according to the aforementioned breaking principle.

Figure 4 is a waveform diagram of breaking a small current of 100A. At t1, the thyristor SCR1 operates, and the oscillating current of the primary side passes through the coupling reactor to make the commutation branch also generate oscillating current, which is superimposed on the mechanical switch CB to produce zero-crossing arc extinguishing, and the circuit The current will pass through the smoothing reactor L0, the commutation capacitor C2 and the secondary inductance L2 of the coupling reactor to the load. Since the equivalent impedance of the load is relatively large, the commutation branch is in the over-damped state of the second-order circuit, and the line current follows an exponential law Decays slowly to zero, with a long tail. At t2, the thyristor SCR1 is triggered again, the commutation branch generates an oscillating current, and the mechanical switch CB2 of the commutation branch generates a zero-crossing point, breaking the current of the commutation branch, and the line current drops rapidly and quickly decays to zero.

FIG. 5 shows the voltage waveforms of the pre-charging capacitor C11 and the energy storage capacitor C12 during the breaking process. It can be seen from the figure that after the first disconnection, the voltage of the pre-charged capacitor C11 drops rapidly from the pre-charged 150kV to about 65kV, which will hardly meet the demand for the second disconnection. Therefore, the energy storage capacitor C12 charges the pre-charging capacitor C11 through the charging resistor R2, and finally the voltage between the two equals to 100 kV, which can meet the second breaking requirement.

It is easy for those skilled in the art to understand that the above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention, All should be included within the protection scope of the present invention.

Claims (9)

1. A coupled high-voltage DC circuit breaker, characterized in that it comprises: a main circuit unit (1), a charging commutation unit (2), an energy consumption unit (3), a trigger unit (4) and an energy absorption and voltage limiting unit (5); The main circuit unit (1) is connected in series to the DC system, the energy absorbing voltage limiting unit (5) is connected in parallel with the main circuit unit (1), and the charging converter unit (2) is connected to the The main circuit unit (1) is connected in parallel; The first output terminal of the trigger unit (4) is connected to the charging and converting unit (2), the second output terminal of the trigger unit (4) is connected to the energy consumption unit (3), and the trigger unit ( 4) used to trigger the charging converter unit (2) when the system fails, and trigger the energy consumption unit (3) when reclosing; The charging commutation unit (2) is used to generate a high-frequency oscillating current when a fault occurs, superimposed on the fault current in reverse to form a zero-crossing breaking fault current, and charges the pre-charging capacitor for Fault disconnection after reclosing; The energy-absorbing voltage-limiting unit (5) is used to absorb the energy stored in the inductive element of the power system after the breaking is completed, and limit the voltage at both ends of the mechanical switch; The energy consumption unit (3) is also connected to the charging converter unit (2), and the energy consumption unit (3) is used to consume the energy of the commutation capacitor when the DC circuit breaker is reclosed so that the The closing current rapidly decays to zero. 2. The coupled high voltage DC circuit breaker according to claim 1, characterized in that the main circuit unit (1) is a mechanical switch capable of igniting an arc and extinguishing the arc when the current crosses zero. 3. The coupled high-voltage DC circuit breaker according to claim 1 or 2, characterized in that, the charging commutation unit (2) includes: a pre-charging capacitor C11, a thyristor SCR1, an energy storage capacitor C12, a charging resistor R1, Coupling reactor, commutation capacitor C2, mechanical switch CB2 and arrester MOV2; One end of the pre-charging capacitor C11 is connected to one end of the primary side L1 of the coupling reactor, the other end of the pre-charging capacitor C11 is connected to one end of the thyristor SCR1; the other end of the thyristor SCR1 is connected to the coupling reactor The other end of the primary side L1 of the reactor is connected, and the energy storage capacitor C12 is connected in series with the charging resistor R1 and then connected in parallel with the pre-charging capacitor C11; One end of the commutation capacitor C2 is connected to one end of the secondary side L2 of the coupling reactor, the other end of the commutation capacitor C2 is connected to one end of the mechanical switch CB2, and the arrester MOV2 is connected to the mechanical switch CB2 In parallel connection, the other end of the secondary side L2 of the coupling reactor and the other end of the mechanical switch CB2 are respectively connected to the two ends of the main circuit unit (1). 4. The coupled high-voltage DC circuit breaker according to any one of claims 1-3, characterized in that, the energy consumption unit (3) comprises: energy consumption resistor R2 and thyristor SCR2 connected in series, energy consumption resistor R2 The non-serial connection end of the thyristor SCR2 is connected to the charging converter unit (2) and the trigger unit (4) respectively. 5. The coupled high-voltage DC circuit breaker according to any one of claims 1-4, characterized in that, the energy-absorbing voltage-limiting unit (5) comprises: a zinc oxide arrester, the two ends of which are respectively connected to the main both ends of the loop unit (1). 6. The coupled high-voltage DC circuit breaker according to any one of claims 1-5, wherein when the system is operating normally, the mechanical switch CB is closed, and the system current flows to the load through the mechanical switch CB, and its on-state Less loss; When a short-circuit fault occurs in the system, the contacts of the mechanical switch CB are opened and arced. After the contact opening distance of the mechanical switch CB reaches the rated opening distance and can withstand the recovery voltage after breaking, the trigger unit triggers the The thyristor SCR1 turns on the charging commutation unit, the pre-charging capacitor C11 oscillates with the coupling reactor primary inductance L1, and the coupling reactor secondary inductance L2 and the commutation reactor The flow capacitor C2 generates a reverse oscillating current, and the amplitude of the oscillating current exceeds the maximum fault current amplitude of the system, so that the mechanical switch CB generates a zero-crossing arc extinguishment and breaks the fault current; After the mechanical switch CB crosses zero and extinguishes the arc, the line current is transferred to the commutation branch composed of the coupling reactor secondary inductance L2 and the commutation capacitor C2 in series, so that the voltage of the commutation capacitor C2 gradually rise, and applied to both ends of the mechanical switch CB, when the voltage amplitude rises to the operating voltage of the energy-absorbing voltage-limiting unit, the energy-absorbing voltage-limiting unit acts as lightning protection, absorbing the inductive energy in the line, and The above-mentioned mechanical switch voltage limiting protection, at the same time the line current starts to drop. 7. The coupled high-voltage DC circuit breaker according to any one of claims 1-6, wherein when the line fault is a ground fault, the line current passes through the coupling reactor secondary inductance L2, commutates Capacitor C2 oscillates and decays slowly; When the line fault is a high-resistance ground fault, the commutation branch is in an over-damped state after breaking, and there will be a long tail during the line current drop. When the line current drops to near zero, the trigger unit will again The thyristor SCR1 is triggered to make the commutation branch generate oscillating current, so that the mechanical switch CB2 cuts off the commutation branch current when it crosses zero. 8. The coupled high-voltage DC circuit breaker according to any one of claims 1-7, characterized in that, after the first breaking is completed, the voltage at both ends of the pre-charging capacitor C11 will decay, and the energy storage The capacitor C12 charges the pre-charging capacitor through the charging resistor R1 so that it can be turned off for the second time. 9. The coupled high-voltage DC circuit breaker according to any one of claims 1-8, characterized in that, during the reclosing operation, the thyristor SCR2 is turned on, so that the high-frequency oscillation generated on the mechanical switch The current is discharged through the energy consumption resistor R2, so that the mechanical switch current quickly decays to zero.