CN106532661B - Opening control method of a high-voltage direct current circuit breaker - Google Patents

Abstract

The present invention relates to a kind of separating brake control methods of high voltage DC breaker, comprising: when detecting fault current, conducting cutout branch disconnects through-flow branch；Judge whether to receive the separating brake order of Control protection system；If receiving separating brake order, cutout branch is disconnected, to complete dc circuit breaker separating brake；If dc circuit breaker does not receive separating brake order, through-flow branch is connected again, cutout branch is disconnected, to forbid dc circuit breaker separating brake.This method is by the way that the sub-switching operation of dc circuit breaker to be carried out in two steps, according to whether receiving the separating brake order of Control protection system, separating brake process or reclosing operation is completed, while guaranteeing separating brake precision, hence it is evident that improve the opening velocity of dc circuit breaker.

Description

Opening control method of a high-voltage direct current circuit breaker

technical field

The invention relates to an opening control method of a high-voltage direct current circuit breaker, which belongs to the technical field of direct current transmission.

Background technique

At present, there are mainly three types of technical solutions for DC circuit breakers, namely traditional mechanical DC circuit breakers based on conventional switches, solid-state DC circuit breakers based on pure power electronic devices, and hybrid DC circuit breakers based on the combination of the two. Among them, the breaking time of the traditional mechanical DC circuit breaker is relatively long, and the loss of the solid-state DC circuit breaker is relatively large. With the development of high-voltage and large-capacity semiconductor devices, the hybrid DC circuit breaker technology that combines the characteristics of conventional mechanical switches and power electronic devices has developed rapidly.

The structure of the existing DC circuit breaker is: a parallel connection of the flow branch, the cut-off branch and the energy consumption branch. The flow-through branch is composed of a group (such as 2-3) of auxiliary converter modules and a group of (such as 2-3) mechanical switches in series; the cut-off branch is composed of a large number of cut-off modules in series; The circuit is a surge arrester for absorbing overcurrent. The so-called auxiliary commutation module and interrupter module are switching tubes or specific switching tube topologies (such as H-bridge, half-bridge, etc.). In addition, some DC circuit breakers also include a parallel buffer branch, which is used to play a buffer role when blocking the current-breaking branch.

However, the current hybrid DC circuit breaker has the following defects: On the one hand, if the mechanical switch is not in place during the opening process of the DC circuit breaker, it may cause overvoltage of the DC circuit breaker during the process of blocking the branch circuit On the other hand, in a multi-terminal DC transmission grid equipped with multiple DC circuit breakers, after a single-point DC fault occurs, the control and protection system can complete the fault location after a few milliseconds, and the DC fault current has some The active protection thresholds of several DC circuit breakers may have been exceeded. If the DC circuit breaker performs active protection opening operation before the fault location of the control protection system, it will increase the probability of DC circuit breaker misoperation, thereby expanding the range of fault points in the DC system; and the DC circuit breaker in the fault location of the control protection system Afterwards, the passive protection opening operation will prolong the removal time of the fault point of the DC system and increase the overcurrent risk of the converter valve.

Therefore, how to reduce the risk of overvoltage breakdown of DC circuit breakers, and improve the opening speed of DC circuit breakers while ensuring the opening accuracy of DC circuit breakers has become an important content in the research of hybrid DC circuit breakers.

Contents of the invention

The purpose of the present invention is to provide a high-voltage direct current circuit breaker opening control method, which is used to solve the technical problem that the opening speed and opening accuracy cannot be balanced during the opening process of the direct current circuit breaker.

In order to solve the above technical problems, the present invention provides a method for controlling the opening of a high-voltage DC circuit breaker. Solution 1: including

(1) When a fault current is detected, the cut-off branch is turned on, and the flow-through branch is cut off;

(2) Judging whether the opening command of the control and protection system has been received;

(3) If the DC circuit breaker receives the opening command, it will disconnect the current breaking branch to complete the opening of the DC circuit breaker; if the DC circuit breaker does not receive the opening Open the branch circuit to prohibit the opening of the DC circuit breaker.

Plan 2: On the basis of Plan 1, before step (2), it also includes the step of judging whether the signal of the opening position of the mechanical switch is received. branch road.

Scheme 3: On the basis of Scheme 2, in the step (1), the flow-through branch is disconnected by disconnecting the first set of mechanical switches in the two parallel mechanical switches; in the step (3), by closing The second group of mechanical switches in the two parallel mechanical switches turns on the current branch again.

Scheme 4: On the basis of Scheme 3, before step (2), it also includes the step of judging whether the opening position signal of the first group of mechanical switches is received, if not received, by closing the second group The mechanical switch re-conducts the flow branch.

The beneficial effects of the present invention are: before the DC circuit breaker receives the opening command from the control and protection system, the "pre-shutdown" process is carried out first, that is, the cut-off branch is turned on, and the fault current is transferred to the cut-off branch ; At the same time, it is judged whether the opening command of the control and protection system has been received, if received, continue to complete the opening operation, and if not received, close the DC circuit breaker again. This method divides the opening operation of the DC circuit breaker into two steps. According to whether the opening command of the control and protection system is received, the opening process is completed when the opening is required, and the reclosing operation is performed when the opening is not required. As in the prior art, the whole action process is performed before or after the fault location, so that the opening speed of the DC circuit breaker can be significantly improved while ensuring the opening accuracy.

Further, it is determined whether to continue the opening operation by judging the opening arrival signal of the mechanical switch, so as to ensure that the DC circuit breaker will not cause overvoltage breakdown during the process of disconnecting the current breaking branch.

Furthermore, the mechanical switch is designed as two sets of parallel mechanical switches to ensure safety; at the same time, on the basis of the same mechanical switch performance, the second set of mechanical switches can also be designed as a switch with a fast closing speed to further ensure safety .

Description of drawings

Fig. 1 is the structural diagram of the high-voltage DC circuit breaker of embodiment 1;

Fig. 2 is the structural diagram of the high-voltage DC circuit breaker of embodiment 2;

Fig. 3 is the structural diagram of the high-voltage DC circuit breaker of embodiment 3;

Fig. 4 is a structural diagram of the high-voltage direct current circuit breaker of the fourth embodiment.

Detailed ways

The technical solution of the present invention will be described in detail below in conjunction with the accompanying drawings.

Embodiment 1 of the opening control method of the high-voltage DC circuit breaker:

As shown in Fig. 1, the high-voltage direct current circuit breaker includes a current flow branch, a current interruption branch and an energy consumption branch connected in parallel. Among them, the flow-through branch is composed of a group of mechanical switches K and a group of auxiliary commutation modules SMC connected in series, the cut-off branch is composed of a group of cut-off modules SMB connected in series, and the energy-dissipating branch is composed of a lightning arrester Z to consume the fault current. The specific structures of the auxiliary commutation module SMC and the current breaking module SMB can adopt the common H-bridge structure, half-bridge structure or other modules that can be used for current flow or current interruption.

Under normal operating conditions, all mechanical switches in the flow branch of the high-voltage branch circuit breaker are closed, all auxiliary converter modules are unlocked, and direct current flows through all mechanical switches and auxiliary converter modules in the flow branch. When the active protection of the DC circuit breaker detects a fault current and needs to cut off the DC fault connected in series with it, the opening control process of the DC circuit breaker is as follows:

(1) Control and unlock all the current-breaking modules SMB in the current-breaking branch of the DC circuit breaker, block all the auxiliary commutation modules SMC in the current-flowing branch of the DC circuit breaker, and transfer the fault current from the current-through branch to the current-breaking branch road.

(2) When the DC fault current is transferred to the cut-off branch, all the mechanical switches K in the flow-through branch of the DC circuit breaker are turned off.

(3) Judging whether the opening command of the control and protection system has been received.

(4) If the DC circuit breaker receives the opening command, it will block all the current-breaking modules SMB in the current-breaking branch of the DC circuit breaker, and transfer the fault current to the energy-consuming branch in parallel with the current-breaking branch to complete the DC circuit breaker. Opening of the circuit breaker; if the DC circuit breaker does not receive the opening command, control and close all the mechanical switches K in the flow branch of the DC circuit breaker, unlock all the auxiliary commutation modules SMC in the flow branch of the DC circuit breaker, Finally, all the current-breaking modules SMB in the current-breaking branches of the DC circuit breaker are blocked.

Among them, the time for the DC circuit breaker to wait for the opening command of the protection system is determined by the physical characteristics of the mechanical switch K. During this time, if it is determined that the DC circuit breaker needs to be opened, the opening process will continue. If it is determined that the DC circuit breaker If the switch does not need to be opened, perform reclosing operation.

In addition, before step (3), that is, after the mechanical switch is turned off, the DC circuit breaker needs to judge whether it has received the opening position signal of the mechanical switch. If it does not receive the opening position signal of the mechanical switch, close the DC circuit breaker again All the mechanical switches K in the flow branch of the DC circuit breaker unlock all the auxiliary commutation modules SMC in the flow branch Flow module SMB, disconnect the cut-off branch.

In the above embodiments, the flow branch includes a plurality of auxiliary commutation modules and a plurality of mechanical switches. As other implementation manners, the above flow branch may only include one auxiliary commutation module SMC and a mechanical switch K, The current breaking branch may also contain only one current breaking module SMB.

Embodiment 2 of the opening control method of the high-voltage DC circuit breaker:

As shown in FIG. 2 , the high-voltage direct current circuit breaker includes a current flow branch, a current interruption branch and an energy consumption branch connected in parallel. Among them, the flow-through branch is composed of the first group of mechanical switches K1 and the first group of mechanical switches K2 connected in parallel and connected in series with a group of auxiliary commutation modules SMC, the cut-off branch is composed of a group of cut-off modules SMB in series, and the energy-consuming branch is composed of The arrester Z is composed to consume the fault current. The specific structures of the auxiliary commutation module SMC and the current breaking module SMB can adopt the common H-bridge structure, half-bridge structure or other modules that can be used for current flow or current interruption.

Under normal operating conditions, the first group of mechanical switches K1 in the flow branch of the high-voltage branch circuit breaker are closed, all auxiliary converter modules are unlocked, and the DC current flows through the first group of mechanical switches K1 in the flow branch and all auxiliary switches. Converter module. Of course, as an alternative, the second group of mechanical switches K2 may also be selected to be closed. When the active protection of the DC circuit breaker detects a DC fault and needs to cut off the DC fault current connected in series with it, the opening control process of the DC circuit breaker is as follows:

(1) Control and unlock all the current-breaking modules SMB in the current-breaking branch of the DC circuit breaker, block all the auxiliary commutation modules SMC in the current-flowing branch of the DC circuit breaker, and transfer the fault current from the current-through branch to the current-breaking branch road.

(2) After the DC fault current is transferred to the cut-off branch, turn off the first group of mechanical switches K1 in the flow-through branch of the DC circuit breaker.

(3) According to whether the DC circuit breaker receives the opening position signal of the first group of mechanical switches K1 within the set time deltT1, it can be divided into two situations:

Case 1 If the DC circuit breaker does not receive the opening position signal of the first group of mechanical switches K1 within the set time deltT1, control the closing of the second group of mechanical switches K2 in the flow branch of the DC circuit breaker, and unlock the DC circuit breaker. All the auxiliary commutation modules SMC in the flow branch simultaneously send an alarm signal of not allowing opening to the control and protection system.

Case 2: If the DC circuit breaker receives the opening position signal of the first group of mechanical switches K1 within the set time deltT1, it is determined whether the DC circuit breaker has received the opening command of the control and protection system within the set time deltT2, and it is also divided. for two cases:

a. If the DC circuit breaker does not receive the opening command from the control and protection system within the set time deltT2, control and close the second group of mechanical switches K2 in the flow branch of the DC circuit breaker, and unlock the flow branch of the DC circuit breaker All the auxiliary commutation modules SMC, and finally block all the current-breaking modules SMB in the current-breaking branch of the DC circuit breaker.

b. If the DC circuit breaker receives the opening command from the control and protection system within the specified time deltT2, all the current-breaking modules SMB in the current-breaking branch of the DC circuit breaker will be blocked, and the fault current will be transferred to parallel connection with the current-breaking branch. The energy-consuming branch, so as to complete the removal of DC current.

The set time deltT1 for the DC circuit breaker to wait for the opening position signal of the first group of mechanical switches K1 and the set time deltT2 for waiting for the opening command of the protection system are both determined by the physical characteristics of the mechanical switch K.

In this embodiment, the mechanical switches are designed as two sets of parallel mechanical switches to ensure safety; at the same time, on the basis of the same mechanical switch performance, the second set of mechanical switches can also be designed as switches with fast closing speed, further ensure safety.

It should be noted that in Embodiments 3 and 4, the other two types of mechanical switches are connected in parallel, which will be described in detail below.

Embodiment 3 of the opening control method of the high-voltage direct current circuit breaker:

As shown in Figure 3, different from the DC circuit breaker in Embodiment 2, the flow branch of the high-voltage DC circuit breaker in this embodiment is composed of two branches connected in parallel, wherein the first branch is composed of the first group of mechanical The switch K1 and the first group of auxiliary commutation modules SMC1 are connected in series, and the second branch is formed by the second group of mechanical switches K2 and the second group of auxiliary commutation modules SMC2 connected in series.

Under normal operation, the first group of mechanical switches K1 in the flow branch of the high-voltage branch circuit breaker is closed, the first group of auxiliary commutation module SMC1 is unlocked, and the DC current flows through the first group of mechanical switches K1 in the flow branch and the first group of auxiliary converter modules SMC1. Of course, as an alternative, the second group of mechanical switches K2 may also be selected to be closed, and the second group of auxiliary converter modules SMC2 to be unlocked. When the active protection of the DC circuit breaker detects a DC fault and needs to cut off the DC fault current connected in series with it, the opening control process of the DC circuit breaker is as follows:

(1) Control and unlock all the current-breaking modules SMB in the current-breaking branch of the DC circuit breaker, block the first group of auxiliary commutation modules SMC1 in the current-flowing branch of the DC circuit breaker, and transfer the fault current from the current-through branch to the breaker stream branch.

(2) After the DC fault current is transferred to the cut-off branch, turn off the first group of mechanical switches K1 in the flow-through branch of the DC circuit breaker.

(3) According to whether the DC circuit breaker receives the opening position signal of the first group of mechanical switches K1 within the set time deltT1, it can be divided into two situations:

Case 1 If the DC circuit breaker does not receive the opening position signal of the first group of mechanical switches K1 within the set time deltT1, it controls to unlock the second group of auxiliary commutation modules SMC2 in the flow branch of the DC circuit breaker, and closes the DC circuit breaker The second group of mechanical switches K2 in the flow branch of the device, and at the same time send an alarm signal that does not allow opening to the control and protection system.

Case 2: If the DC circuit breaker receives the opening position signal of the first group of mechanical switches K1 within the set time deltT1, it is determined whether the DC circuit breaker has received the opening command of the control and protection system within the set time deltT2, or Divided into two situations:

a. If the DC circuit breaker does not receive the opening command from the control and protection system within the set time deltT2, close the second set of mechanical switches K2 in the flow branch of the DC circuit breaker, and unlock the flow branch of the DC circuit breaker The second group of auxiliary commutation modules SMC2, and finally block all the current-breaking modules SMB in the current-breaking branches of the DC circuit breaker.

b. If the DC circuit breaker receives the opening command from the control and protection system within the specified time deltT2, all the current-breaking modules SMB in the current-breaking branch of the DC circuit breaker will be blocked, and the fault current will be transferred to parallel connection with the current-breaking branch. The energy-consuming branch, so as to complete the removal of DC current.

The set time deltT1 for the DC circuit breaker to wait for the opening position signal of the first group of mechanical switches K1 and the set time deltT2 for waiting for the opening command of the protection system are both determined by the physical characteristics of the mechanical switch K.

Embodiment 4 of the opening control method of the high-voltage DC circuit breaker:

As shown in Figure 4, the parallel connection of mechanical switches different from that of Embodiments 2 and 3 is adopted, which is equivalent to connecting two sets of auxiliary converter modules in parallel with the series points of two sets of mechanical switches on the basis of Embodiment 3. In this way, it is possible to flexibly select the auxiliary converter module group and the mechanical switch group corresponding to the path, and the specific control method is similar to that of Embodiment 2 or 3, and will not be repeated here.

Claims (3)

1. a kind of separating brake control method of high voltage DC breaker, which comprises the following steps:

(1) when detecting fault current, conducting cutout branch disconnects through-flow branch；

(2) judge whether to receive the separating brake order of Control protection system；

(3) if dc circuit breaker receives separating brake order, cutout branch is disconnected, to complete dc circuit breaker separating brake；If direct current Breaker does not receive separating brake order, then through-flow branch is connected again, cutout branch is disconnected, to forbid dc circuit breaker separating brake；

Before step (2), further include the steps that judge whether to receive mechanical switch open position signal weighs if not receiving Through-flow branch is newly connected, disconnects cutout branch.

2. the separating brake control method of high voltage DC breaker according to claim 1, which is characterized in that the step (1) In, first group of mechanical switch in mechanical switch by disconnecting two-way parallel connection disconnects through-flow branch；In the step (3), lead to Through-flow branch is connected in the second group of mechanical switch crossed in the mechanical switch of closure two-way parallel connection again.

3. the separating brake control method of high voltage DC breaker according to claim 2, which is characterized in that step (2) it Before, further include the steps that judging whether to receive first group of mechanical switch open position signal passes through closure if not receiving Through-flow branch is connected in second group of mechanical switch again.