CN216086148U - Current-limiting type multi-port high-voltage direct-current circuit breaker and connection structure thereof in direct-current power grid - Google Patents
Current-limiting type multi-port high-voltage direct-current circuit breaker and connection structure thereof in direct-current power grid Download PDFInfo
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- CN216086148U CN216086148U CN202120961626.4U CN202120961626U CN216086148U CN 216086148 U CN216086148 U CN 216086148U CN 202120961626 U CN202120961626 U CN 202120961626U CN 216086148 U CN216086148 U CN 216086148U
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Abstract
The utility model discloses a current-limiting type multi-port high-voltage direct-current circuit breaker which comprises a main circuit, a current-limiting branch, a current-breaking branch and a grounding branch, wherein the main circuit, the current-limiting branch and the current-breaking branch are sequentially connected to form a loop, one end of the grounding branch is connected to a connection point of the main circuit and the current-breaking branch, and the other end of the grounding branch is grounded. The utility model can inhibit the rise of fault current and reduce the energy consumption of the lightning arrester, and is beneficial to reducing the cost.
Description
Technical Field
The utility model relates to the field of circuit breakers, in particular to a current-limiting type multi-port high-voltage direct-current circuit breaker and a connection structure thereof in a direct-current power grid.
Background
With the continuous innovation of the types of power electronic devices, high-voltage direct-current transmission is also continuously developed. The high-voltage direct-current power grid has the characteristics of large transmission capacity, high transmission efficiency, nearly zero reactive power, small impedance, suitability for long-distance power transmission and the like. When short-circuit fault occurs in the direct-current high-voltage power supply, the fault current on the direct-current side rapidly rises due to the small impedance. Therefore, a high voltage DC circuit breaker (DCCB) having a large switching capacity, a rapid operation, and a ms-level fault removal is required.
In a direct current power grid, two major technical problems mainly exist in the DCCB shutdown: (1) the direct current has no zero crossing phenomenon, so the arc extinguishing difficulty is higher; (2) the impedance of the dc system is much smaller than that of the ac system, and the short-circuit current increases very fast and has a large amplitude. In a dc network, conventional two-port DCCBs are mainly classified into three categories in dc power transmission: mechanical DCCBs, solid DCCBs, and hybrid DCCBs. The hybrid DCCB has the good static characteristics of a mechanical DCCB and the dynamic characteristics of a solid DCCB, and has the advantages of low energy loss in steady-state operation, high breaking speed in short-circuit fault, strong control capability and the like. In these conventional two-port hybrid DCCBs, there is a problem that the cost is too high because the power electronic devices are excessively input due to one main circuit corresponding to one transfer branch. Meanwhile, when the fault is removed, the situation that the energy consumed by the lightning arrester is too much due to overlarge fault current occurs.
SUMMERY OF THE UTILITY MODEL
The utility model aims to provide a current-limiting type multi-port high-voltage direct-current circuit breaker which inhibits the increase of short-circuit fault current and reduces the energy loss on a lightning arrester and a connection structure of the circuit breaker in a direct-current power grid.
The technical scheme adopted by the utility model for solving the problems is as follows:
a current-limiting type multi-port high-voltage direct-current circuit breaker comprises a main circuit, a current-limiting branch, a current-breaking branch and a grounding branch, wherein the main circuit, the current-limiting branch and the current-breaking branch are sequentially connected to form a loop, one end of the grounding branch is connected to a connection point of the main circuit and the current-breaking branch, and the other end of the grounding branch is grounded. The current-limiting branch is composed of a first branch, a second branch and a third branch which are connected in parallel, the first branch is composed of a first thyristor for conducting and bearing short-circuit fault current, so that the fault current can be transferred normally, and the mechanical switch can be safely disconnected in the no-current and no-arc states, the second branch is composed of a second thyristor, a third thyristor, a fourth thyristor, a fifth thyristor, a first capacitor and a second capacitor, the second thyristor, the third thyristor and the first capacitor are sequentially connected in series, the positive end of the first capacitor is connected with the negative end of the current-breaking branch, the rising of the fault current is inhibited and the reliability of the disconnection of the first thyristor is ensured through the first capacitor, the fourth thyristor, the fifth thyristor and the second capacitor are sequentially connected in series, the second capacitor is grounded, and when the current of a power grid is precharged to the first capacitor during normal operation, the voltage division function of the second capacitor is utilized to prevent the high-voltage direct current from breaking down the first capacitor, the third thyristor and the fourth thyristor are connected in parallel, and the third branch circuit is composed of an inductor for limiting current. When the fourth thyristor is turned on, the energy on the inductor can be transferred to the first capacitor, so that the first capacitor is charged again. The cutoff branch is formed by connecting an insulated gate bipolar transistor which is in unidirectional conduction and is used for cutting off fault short-circuit current and a lightning arrester which is used for absorbing redundant energy in a circuit when the insulated gate bipolar transistor is cut off in parallel.
As a further improvement of the above technical solution, the main circuit is composed of a plurality of bridge arm branches, each bridge arm branch is composed of a bridge arm a branch and a bridge arm b branch, a positive end of the bridge arm a branch is connected with a negative end of the current limiting branch, a negative end of the bridge arm a branch is connected with a positive end of the bridge arm b branch, a negative end of the bridge arm b branch is connected with a positive end of the current breaking branch, the bridge arm a branch and the bridge arm b branch are both composed of a mechanical switch and a load transfer switch in series, and a connection point of the bridge arm a branch and the bridge arm b branch is connected with a port for connecting with a dc power grid.
As a further improvement of the above technical solution, the grounding branch is used for consuming the energy stored at the fault side, and the grounding branch is composed of a resistor, a sixth thyristor and a grounding device, and the resistor, the sixth thyristor and the grounding device are sequentially connected in series.
The utility model provides a connection structure of current-limiting type multiport high voltage direct current circuit breaker at direct current electric wire netting, includes a plurality of electric power output device and load output device, electric power output device and load output device all are connected with the circuit breaker alone, and the circuit breaker is the same with arbitrary one in the above-mentioned current-limiting type multiport high voltage direct current circuit breaker's the technical scheme, and the port quantity on the circuit breaker is no less than electric power output device and load output device's quantity sum, and each electric connection each other between the circuit breaker.
Compared with the prior art, the utility model has the following advantages and effects:
according to the utility model, a plurality of bridge arm branches share one current-cutoff branch, so that the cost is reduced on the basis of the same capacity of cutting off the short-circuit fault current. Furthermore, the current limiting branch circuit, the current breaking branch circuit and the grounding branch circuit are matched for use, the turn-off time is shortened, the size of fault current is suppressed, and the energy consumed by the lightning arrester is reduced.
Drawings
Fig. 1 is a schematic structural principle diagram of a current-limiting type multi-port high-voltage direct-current circuit breaker according to an embodiment.
Fig. 2 is a schematic diagram of the current path of the circuit breaker shown in fig. 1 in a normal operating phase.
Fig. 3 is a schematic diagram of the current path of the circuit breaker shown in fig. 1 in a fault detection phase.
Fig. 4 is a schematic diagram of the current path of the circuit breaker shown in fig. 1 in a current transfer phase.
Fig. 5 is a schematic diagram of the current path of the circuit breaker shown in fig. 1 in the capacitive-inductive current limiting stage.
Fig. 6 is a schematic diagram of the current path of the circuit breaker shown in fig. 1 in the inductive current limiting phase.
Fig. 7 is a schematic diagram of the current path of the circuit breaker shown in fig. 1 during the recharge and power consumption phases.
Fig. 8 is a graph comparing the performance of the circuit breaker shown in fig. 1 with that of a conventional circuit breaker in reducing the magnitude of a fault current.
Fig. 9 is a graph comparing the performance of the circuit breaker shown in fig. 1 with a conventional circuit breaker in reducing the energy absorption of the arrester.
Fig. 10 is a schematic diagram of a connection structure of a current-limiting type multi-port high-voltage direct-current circuit breaker in a four-terminal high-voltage direct-current power grid according to the second embodiment.
Fig. 11 is a schematic flow diagram of a fault current when a ground fault occurs at point F in the diagram.
Fig. 12 is a schematic diagram of breaker port current and internal component current voltage waveforms at the time of failure of the breaker port line shown in fig. 10.
Detailed Description
The present invention will be described in further detail below by way of examples with reference to the accompanying drawings, which are illustrative of the present invention and are not to be construed as limiting the present invention.
The first embodiment.
Referring to fig. 1, the current-limiting type multi-port high-voltage direct current circuit breaker of the embodiment includes a main circuit, a current-limiting branch, a current-breaking branch and a grounding branch, wherein the main circuit, the current-limiting branch and the current-breaking branch are sequentially connected to form a loop, one end of the grounding branch is connected to a connection point of the main circuit and the current-breaking branch, and the other end of the grounding branch is grounded. The main circuit is composed of a plurality of bridge arm branches, each bridge arm branch is composed of a bridge arm a branch and a bridge arm b branch, the positive end of each bridge arm a branch is connected with the negative end of the current limiting branch, the negative end of each bridge arm a branch is connected with the positive end of each bridge arm b branch, the negative end of each bridge arm b branch is connected with the positive end of the current breaking branch, each bridge arm a branch and each bridge arm b branch are composed of a mechanical switch UFD and a load transfer switch LCS in series, and the connection point of the bridge arm a branch and the bridge arm b branch is connected with a port used for being connected with a direct current power grid.
Referring to fig. 1, the current-limiting branch is formed by connecting a first branch, a second branch and a third branch in parallel, the first branch is formed by a first thyristor T1 for conducting and carrying a short-circuit fault current, the second branch is formed by a second thyristor T2, a third thyristor T3, a fourth thyristor T4, a fifth thyristor T5, a first capacitor C1 and a second capacitor C2, the second thyristor T2, the third thyristor T3 and the first capacitor C1 are sequentially connected in series, a positive terminal of the first capacitor C1 is connected with a negative terminal of the current-breaking branch, the fourth thyristor T4, the fifth thyristor T5 and the second capacitor C2 are sequentially connected in series, the second capacitor C2 is grounded, the third thyristor T3 is connected in parallel with the fourth thyristor T4, and the third branch is formed by an inductor Lv for limiting current.
Referring to fig. 1, the interruption branch is composed of a unidirectionally conducting insulated gate bipolar transistor T0 for turning off fault short-circuit current and a surge arrester MOV for absorbing excess energy in the circuit when the insulated gate bipolar transistor T0 is turned off.
Referring to fig. 1, the grounding branch is used for consuming energy stored at a fault side, and the grounding branch is composed of a resistor Rg, a sixth thyristor Tg and a grounding device, and the resistor Rg, the sixth thyristor Tg and the grounding device are sequentially connected in series.
In summary, according to the path through which the short-circuit fault current flows, the operating principle of the current-limiting type multi-port high-voltage direct-current circuit breaker can be divided into the following stages, t < t0 for normal operation, t0< t < t1 for fault detection, t1< t < t2 for current transfer, t2< t < t3 for capacitive current limiting, t3< t < t4 for inductive current limiting, t4< t < t5 for recharging and energy consumption. The concrete description is as follows:
(1) stage of normal operation
When t < t0, during normal operation, the mechanical switch UFD and the load transfer switch LCS on the main circuit are both in a closed state, and normal operating current flows through the leg a and the leg b of the leg. At this time, the first thyristor T1 and the fifth thyristor T5 are turned on, and a current flows from the grid through the first thyristor T1, the inductor Lv, the first capacitor C1, the fifth thyristor T5 and the second capacitor C2 to charge the first capacitor C1. When the charging of the first capacitor C1 is finished, the current is zero, so that the fifth thyristor T5 is turned off. The current path during the normal operation phase is shown in fig. 2.
(2) Fault detection phase
When t0< t < t1 and t0 and a short-circuit fault occurs in a line connected with the ith port of the current-limiting type multi-port high-voltage direct current circuit breaker MP-DCCB, the short-circuit current rapidly rises, and the fault current is detected. The current path during the fault detection phase is shown in fig. 3.
(3) Current transfer phase
T1< T < T2, T1, when the current is detected to reach the action current, the first thyristor T1 and the insulated gate bipolar transistor T0 are turned on to turn on the device. And simultaneously turning off the main circuit load transfer switches LCS and ia and the load transfer switches LCS and jb (j is 1 … n, j is not equal to i), wherein the current on the main circuit load transfer switches LCS and ia and the load transfer switches LCS and jb (j is 1 … n, j is not equal to i) rapidly drops, and the current is transferred to the first thyristor T1 on the current limiting branch and the insulated gate bipolar transistor T0 on the current breaking branch. When the current on the main circuit that is turned off is zero, the mechanical switches UFD, ia and UFD, jb on the main circuit are turned off (j is 1 … n, j is not equal to i). The fault current at this time flows through the first thyristor T1 and the insulated gate bipolar transistor T0. The current path during the current transfer phase is shown in fig. 4.
(4) Current limiting stage of capacitor and inductor
When T2< T < T3, T2 and the mechanical switch UFD, ia on the main circuit is completely turned off, the second thyristor T2 and the third thyristor T3 are turned on by pulse signals, and the first capacitor C1 on the branch starts to discharge current for limiting. Since the second thyristor T2 and the third thyristor T3 are in the on state, the first thyristor T1 is turned off instantaneously by the reverse voltage of the first capacitor C1, and the current iT1 is zero. When the discharge of the first capacitor C1 is finished, the voltage uC1 of the first capacitor C1 is zero; the first capacitor C1 is then reverse charged to continue limiting current. In this stage, the first capacitor C1 and the inductor Lv are connected in parallel and are in a current-limiting operation state. The current path during the capacitive-inductive current limiting phase is shown in fig. 5.
(5) Inductive current limiting stage
When T3< T < T4 and T3, the reverse voltage charging of the first capacitor C1 is completed, the current iC1 is zero, the third thyristor T3 is turned off immediately, and the fault current flows only in the branch of the inductor Lv. The current path during the inductive current limiting phase is shown in fig. 6.
(6) Recharge and energy consumption phases
When T4< T < T5, T4 turns off the igbt T0 in the breaker branch and turns on the sixth thyristor Tg and the fourth thyristor T4, and the current on the fault side flows through and is consumed by the ground resistor Rg and the sixth thyristor Tg in the ground branch. The current on the non-fault side inductor Lv is transferred to the first capacitor C1 through the fifth thyristor T5, and the first capacitor C1 is charged again. The arrester MOV dissipates excess energy in the inductor Lv. The current path during the recharge and power consumption phases is shown in fig. 7.
Example two.
Referring to fig. 10, this embodiment is a connection structure of a current-limiting type multi-port high-voltage direct-current circuit breaker in a four-terminal high-voltage direct-current power grid according to an embodiment, and the connection structure includes two power output devices and two load output devices, where the power output devices and the load output devices are both connected with circuit breakers separately, the structure of the circuit breaker is the same as that of the current-limiting type multi-port high-voltage direct-current circuit breaker according to the embodiment, the number of ports on the circuit breaker is not less than the sum of the number of the power output devices and the number of the load output devices, and the circuit breakers are electrically connected with each other.
Referring to fig. 11 and 12, when a 2 nd port line of the current-limiting type multi-port high-voltage direct current circuit breaker MP-DCCB1 has a fault, in the MP-DCCB1 connected to the modular multilevel converter MMC1, current flows into the circuit breaker from ports 1, 3 and 4 of the MP-DCCB1, respectively, and the port 2 flows to a fault point directly. The working principle of the current-limiting type multi-port high-voltage direct current circuit breaker MP-DCCB1 is as follows:
when t0 is 2s, a short-circuit fault occurs, and the short-circuit fault current i2 rises rapidly;
when it is detected that the fault current reaches the operating current at t1 ═ 2.001s, the load transfer switches LCS,2a, LCS,1b, LCS,3b, LCS,4b are turned off, and the current flowing decreases; simultaneously turning on the insulated gate bipolar transistor T0 and the first thyristor T1 to generate a commutation phenomenon;
when T2 is 2.003s, the mechanical switches UFD,2a, UFD,1b, UFD,3b, and UFD,4b are completely turned on, and turn on signals to the second thyristor T2 and the third thyristor T3, and since the first thyristor T1 is instantaneously turned off by the reverse voltage of the first capacitor C1, the fault current at this time flows through the second thyristor T2, the third thyristor T3, the first capacitor C1, the inductor Lv, and the insulated gate bipolar transistor T0;
when T3 is 2.0046, the reverse voltage charging of the first capacitor C1 is finished, the current iC1 is zero, the third thyristor T3 is turned off immediately, and the fault current flows only in the inductor Lv branch;
when T4 is 2.005s, the igbt T0 is turned off, the fourth thyristor T4 and the sixth thyristor Tg are turned on simultaneously, the energy stored in the non-fault side inductor Lv charges the first capacitor C1, and the fault current stored energy on the fault side is consumed by the ground branch.
The above description of the present invention is intended to be illustrative. Various modifications, additions and substitutions for the specific embodiments described may be made by those skilled in the art without departing from the scope of the utility model as defined in the accompanying claims.
Claims (4)
1. A current-limiting type multiport high-voltage direct-current circuit breaker is characterized in that: the current limiting branch circuit is formed by connecting a first branch circuit, a second branch circuit and a third branch circuit in parallel, the first branch circuit is formed by a first thyristor for conducting and bearing short-circuit fault current, the second branch circuit is formed by a second thyristor, a third thyristor, a fourth thyristor, a fifth thyristor, a first capacitor and a second capacitor, the second thyristor, the third thyristor and the first capacitor are connected in series in sequence, the positive end of the first capacitor is connected with the negative end of the cutoff branch circuit, the fourth thyristor, the fifth thyristor and the second capacitor are connected in series in sequence, the second capacitor is grounded, the third thyristor is connected in parallel with the fourth thyristor, the third branch circuit is composed of an inductor for limiting current, and the current-breaking branch circuit is composed of a unidirectional conducting insulated gate bipolar transistor for cutting off fault short-circuit current and a lightning arrester for absorbing redundant energy in the circuit when the insulated gate bipolar transistor is cut off.
2. A current limiting multi-port hvdc breaker according to claim 1 wherein: the main circuit is composed of a plurality of bridge arm branches, each bridge arm branch is composed of a bridge arm a branch and a bridge arm b branch, the positive end of each bridge arm a branch is connected with the negative end of the current limiting branch, the negative end of each bridge arm a branch is connected with the positive end of each bridge arm b branch, the negative end of each bridge arm b branch is connected with the positive end of the current breaking branch, each bridge arm a branch and each bridge arm b branch are composed of a mechanical switch and a load transfer switch in series, and the connection point of the bridge arm a branch and the bridge arm b branch is connected with a port used for being connected with a direct current power grid.
3. A current limiting multi-port hvdc breaker according to claim 1 wherein: the grounding branch circuit is used for consuming energy stored at the fault side and consists of a resistor, a sixth thyristor and a grounding device, and the resistor, the sixth thyristor and the grounding device are sequentially connected in series.
4. A connection structure of a current-limiting type multi-port high-voltage direct-current circuit breaker in a direct-current power grid comprises a plurality of power output devices and a load output device, and is characterized in that: the power output device and the load output device are both independently connected with circuit breakers, the circuit breakers are the same as any one of the claims 1 to 3, the number of ports on the circuit breakers is not less than the sum of the number of the power output device and the load output device, and the circuit breakers are electrically connected with each other.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202120961626.4U CN216086148U (en) | 2021-05-07 | 2021-05-07 | Current-limiting type multi-port high-voltage direct-current circuit breaker and connection structure thereof in direct-current power grid |
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| Application Number | Priority Date | Filing Date | Title |
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| CN202120961626.4U CN216086148U (en) | 2021-05-07 | 2021-05-07 | Current-limiting type multi-port high-voltage direct-current circuit breaker and connection structure thereof in direct-current power grid |
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