CN109687386B - Hybrid direct current breaker buffering branch with reclosing capability - Google Patents

Abstract

The invention discloses a buffer branch of a hybrid DC circuit breaker with reclosing capability, comprising a traditional buffer branch module based on an RCD absorption circuit applied to the main breaking branch, and an auxiliary buffer connected in parallel with the RCD module. The branch, and the auxiliary buffer branch includes a semi-controlled semiconductor device and a buffer capacitor. The specific structure is: the semi-controlled semiconductor device and the buffer capacitor are connected in series; The semi-controlled semiconductor device of the auxiliary buffer branch is turned on after confirming that the hybrid DC circuit breaker is reclosed after the fault is confirmed during the reclosing process of the hybrid DC circuit breaker. The buffer branch circuit of the invention can still reliably break the fault current again after the hybrid DC circuit breaker is reclosed in a fault, thereby effectively improving the reliability of the flexible DC power grid.

Description

Hybrid DC Circuit Breaker Buffer Branch with Reclosing Capability

technical field

The invention belongs to the technical field of DC power transmission, and in particular relates to a buffer branch of a hybrid DC circuit breaker with reclosing capability.

Background technique

With the development of HVDC flexible transmission using overhead transmission lines, a large number of transient faults will occur in flexible DC systems. In order to improve the reliability of the flexible DC grid, the reclosing operation needs to be performed after the fault current is interrupted by the hybrid DC circuit breaker.

During the reclosing process of the hybrid DC circuit breaker, the hybrid DC circuit breaker will first reclose its main breaking branch to detect whether the fault still exists. If the fault has been cleared, the reclosing is successful; if the fault continues, the hybrid DC circuit breaker needs to immediately disconnect the main breaking branch again to break the reclosing current.

Before the current hybrid DC circuit breaker is reclosed, the DC circuit breaker needs to bear all the operating voltage of the DC system. Therefore, before the hybrid DC circuit breaker recloses the main breaking branch, even if the capacitance of the traditional RCD buffer branch of the main breaking branch has undergone the discharge process, in order to block the current, the buffer branch at this time is The sum of the capacitor voltages is at least greater than the operating voltage of the DC system. After the hybrid DC circuit breaker is reclosed on a fault, the main breaking branch needs to be opened again immediately. At this time, since the capacitor voltage of the traditional RCD buffer branch of the main breaking branch still exists, the breaking process of the main breaking branch cannot be effectively buffered, which may cause damage to the main breaking branch or even cannot be broken again.

SUMMARY OF THE INVENTION

The technical problem to be solved by the present invention is to provide a buffer branch of a hybrid DC circuit breaker with reclosing capability, which ensures that the hybrid DC circuit breaker can be reliably reclosed after a fault without significantly increasing the design cost of the device. to disconnect again.

In order to solve the above-mentioned technical problems, the technical scheme adopted in the present invention is:

A hybrid DC circuit breaker buffer branch with reclosing capability, comprising a traditional buffer branch module based on RCD absorption circuit applied to the main breaking branch, the hybrid DC circuit breaker buffer branch with reclosing capability The circuit also includes an auxiliary buffer branch connected in parallel with the traditional RCD buffer branch, and the auxiliary buffer branch includes a semi-controlled semiconductor device and a buffer capacitor, and the specific structure is: the semi-controlled semiconductor device and the buffer capacitor. series connection; during normal operation and fault current breaking process, the semi-controlled semiconductor device of the auxiliary buffer branch is in the blocking state; when the hybrid DC circuit breaker is reclosing, confirm that the hybrid DC circuit breaker is reclosing The semi-controlled semiconductor device of the auxiliary buffer branch is turned on only after the fault.

Further, both ends of the semi-controlled semiconductor device are connected in parallel with a discharge resistor.

Further, both ends of the buffer capacitor are also connected in parallel with a discharge resistor.

Compared with the prior art, the beneficial effects of the present invention are: the present invention designs a brand-new buffer branch without significantly increasing the manufacturing cost of the circuit breaker, so that the hybrid DC circuit breaker has the reclosing capability, which can make Hybrid DC circuit breakers can reliably open again after reclosing on a fault.

Description of drawings

Figure 1 shows the topology of the hybrid DC circuit breaker;

Fig. 2 is the sub-module structure of the current branch or the main breaking branch of the hybrid DC circuit breaker adopting the traditional RCD buffer branch solution;

Fig. 3 is the sub-module structure of the current branch or the main breaking branch of the hybrid DC circuit breaker adopting the traditional RCD buffer branch solution;

Fig. 4 is the hybrid DC circuit breaker sub-module structure (1) after adding the buffer branch of the hybrid DC circuit breaker with reclosing capability in the present invention;

Fig. 5 is the hybrid DC circuit breaker sub-module structure (2) after adding the buffer branch of the hybrid DC circuit breaker with reclosing capability in the present invention;

6 shows four structures of the auxiliary buffer branch in the buffer branch of the hybrid DC circuit breaker with reclosing capability in the present invention;

Fig. 7 is the voltage change of the circuit breaker during the opening and reclosing process of the hybrid DC circuit breaker when the traditional RCD buffer branch is used;

8 shows the voltage change of the hybrid DC circuit breaker in the process of breaking the fault and reclosing after the fault when the buffer branch of the hybrid DC circuit breaker with reclosing capability of the present invention is used.

Detailed ways

The present invention will be described in further detail below with reference to the accompanying drawings and specific embodiments.

FIG. 1 is a topology structure of a hybrid DC circuit breaker, in which the sub-module structures of the current-passing branch and the main breaking branch are shown in FIGS. 2 and 3 . The sub-module structures shown in Figures 2 and 3 can be applied to the main breaking branch or the flow branch, depending on actual engineering needs, where the RCD module represents a traditional buffer branch module based on an RCD absorption circuit. The invention discloses a buffer branch of a hybrid DC circuit breaker with reclosing capability, which can be applied to the sub-module of the main breaking branch of the hybrid DC circuit breaker shown in FIG. 1 .

Figures 4 and 5 show the sub-module structure using the snubber branch of the hybrid DC circuit breaker with reclosing capability, where TRC represents the proposed auxiliary buffer branch, and the auxiliary buffer branch TRC is the same as the traditional buffer branch RCD The modules are directly connected in parallel.

Figure 6 shows four structures of the buffer branch of the hybrid DC circuit breaker with reclosing capability. During the normal operation and fault current breaking process, the semi-controlled semiconductor devices (with sufficient withstand voltage) of the TRC auxiliary buffer branch are all blocked; only during the reclosing process of the hybrid DC circuit breaker, confirm that the hybrid The semi-controlled semiconductor device of the TRC snubber branch is turned on only after the DC circuit breaker is reclosed after the fault.

The principle of the TRC auxiliary buffer branch of the four structures is the same. After the hybrid DC circuit breaker confirms that the reclosing is in fault, the main breaking branch will be disconnected again. However, during the reclosing process of the main breaking branch, the RCD module of the conventional buffer branch has already been charged and the discharge has not been completed. Therefore, in the process of re-opening the main breaking branch, a new buffer branch needs to be added, and the buffer branch must only be put into operation during the reclosing process. In order to achieve the design goal, the present invention designs four kinds of buffer branches of the hybrid DC circuit breaker with reclosing capability in combination with semi-controlled semiconductor devices. The four structures of the auxiliary buffer branch TRC are shown in FIG. 6 . After it is determined by the protection system that the hybrid DC circuit breaker has been reclosed in a fault, a high-level conduction signal is immediately applied to the semi-controlled semiconductor device of the TRC, and then the main breaking branch is disconnected. The capacitive element in the TRC is connected in parallel with the main breaking branch, which will buffer the breaking process of the main breaking branch and ensure the stable and reliable breaking of the main breaking branch.

Figure 7 shows the voltage change of the hybrid DC circuit breaker during the breaking and reclosing process of the hybrid DC circuit breaker when the traditional RCD snubber branch design scheme is adopted. The traditional RCD snubber design scheme cannot provide an effective snubber effect again because the snubber capacitor of the RCD snubber branch has been charged during the reclosing process of the hybrid DC circuit breaker after a fault. Therefore, the voltage of the DC circuit breaker will directly rise to the voltage of the buffer capacitor of the main breaking branch during the re-opening process. Figure 8 shows the voltage change of the hybrid DC circuit breaker in the process of breaking the fault and reclosing after the fault when the proposed TRC buffer branch design scheme is adopted. After adopting the proposed scheme, the reclosing of the DC circuit breaker still has an obvious buffering effect during the re-opening process of the main breaking branch after the fault, and the voltage of the DC circuit breaker rises slowly. It can prevent the main breaking branch from being damaged or even unable to break again during the re-opening process, effectively improving the reliability of the DC circuit breaker, and ensuring that the DC circuit breaker can be reliably opened again after reclosing in a fault.

Claims (3)

1. A buffer branch of a hybrid DC circuit breaker with reclosing capability, the hybrid DC circuit breaker comprises a current-passing branch, a main breaking branch and an energy consumption branch connected in parallel with each other, and the hybrid DC circuit breaker has a reclosing branch. The hybrid DC circuit breaker buffer branch with high capability includes an RCD buffer branch module based on the RCD absorption circuit applied to the main breaking branch, characterized in that the hybrid DC circuit breaker buffer branch with reclosing capability also has It includes an auxiliary buffer branch connected in parallel with the RCD buffer branch module, and the auxiliary buffer branch includes a semi-controlled semiconductor device and a buffer capacitor, and the specific structure is: the semi-controlled semiconductor device and the buffer capacitor are connected in series; During the normal operation and fault current breaking process, the semi-controlled semiconductor device of the auxiliary buffer branch is in the blocking state; during the reclosing process of the hybrid DC circuit breaker, it is confirmed that the hybrid DC circuit breaker is reclosed in the fault. Then, the semi-controlled semiconductor device of the auxiliary buffer branch is turned on. 2 . The hybrid DC circuit breaker buffer branch with reclosing capability according to claim 1 , wherein a discharge resistor is connected in parallel at both ends of the semi-controlled semiconductor device. 3 . 3 . The buffer branch of the hybrid DC circuit breaker with reclosing capability according to claim 1 or 2 , wherein a discharge resistor is connected in parallel at both ends of the buffer capacitor. 4 .

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