CN106684810A - Closed control method for judging DC circuit breaker fault capable of cascading and device thereof - Google Patents

Abstract

The invention relates to a fault type judgment closing control method and device of a cascaded hybrid DC circuit breaker. When the DC circuit breaker is closed, a permanent fault judgment is performed; when it is judged to be a permanent fault, the operation of closing the DC circuit breaker is stopped to ensure the DC circuit breaker The breaker is in the disconnected state; the judgment conditions for permanent faults are: the current flowing through the DC circuit breaker exceeds the secondary overcurrent protection limit, or an overvoltage fault occurs in more than a certain number of sub-modules in the transfer branch. Therefore, when it is judged that it is a permanent fault, it is necessary to stop the operation of closing the DC circuit breaker to ensure that secondary faults are avoided, and damage to equipment in the line is also avoided, which is conducive to system stability.

Description

Fault type discrimination closure control method and device for cascaded hybrid DC circuit breaker

technical field

The invention relates to a fault type discrimination closing control method and device for a cascaded hybrid direct current circuit breaker.

Background technique

The flexible HVDC transmission technology based on the voltage source converter has independent control of active and reactive power decoupling, can be connected to weak grids, supply power to passive loads, has grid black-start capability, fast dynamic response, excellent harmonic characteristics and occupies With many advantages such as small land area, it has been more and more widely used in large-scale intermittent new energy grid connection, island passive load power supply, AC grid interconnection, and urban intelligent power supply and distribution.

There is a problem of DC short-circuit faults in flexible DC transmission, especially when overhead lines are used as DC lines, the probability of DC faults is relatively high. If effective measures are not taken, the power of the system will be interrupted, and at the same time, the overcurrent damage of the electrical equipment will be caused. In order to meet the reliable operation of the flexible DC transmission system, the system needs to have the DC fault ride-through function.

At present, there are two DC fault ride-through schemes in the industry. One scheme is to configure the half-bridge MMC converter with a DC circuit breaker, and use the DC circuit breaker to break the DC short-circuit current; the other is to configure the fast fault self-clearing MMC converter. Mechanical switch to clear fault current using fault self-clearing MMC inverter. For the future development direction of the flexible DC grid, the DC circuit breaker scheme has greater advantages in the stability of the AC grid, and has attracted extensive attention from the industry. Therefore, in general, DC circuit breakers are installed in the DC transmission line to achieve fault isolation.

As shown in Figure 1, it is the overall topology diagram of the DC circuit breaker, including the main branch, the transfer branch and the energy consumption branch. The main branch is equipped with a mechanical switch and several sub-modules in series, and the transfer branch is provided with several sub-modules in series. module, wherein, whether it is a sub-module on the main branch or a sub-module on the transfer branch, it is generally a full-bridge sub-module, but it does not exclude other sub-modules with the same function. module as an example. The energy-consuming branch is composed of lightning arresters, etc., which are used to absorb the short-circuit current of the DC system.

When a fault is detected, such as a DC short-circuit fault, the DC circuit breakers on both sides of the faulty line need to be disconnected immediately. This part belongs to conventional technology and will not be described in detail here. The process of disconnecting the circuit breaker is as follows:

2-a to 2-d are schematic diagrams of the breaking process of the DC circuit breaker. As shown in Figure 2-a, during normal operation, the transfer branch is in the blocking and blocking state, the ultra-high-speed mechanical switch in the main branch is closed, the sub-modules in the main branch are in the conduction state, and the normal load current flows through the main branch ; As shown in Figure 2-b, when a fault occurs and the DC circuit breaker needs to be disconnected, the sub-modules on the transfer branch are turned on to realize the conduction of the transfer branch, and the sub-modules in the main branch are blocked to realize When the main branch is turned off, the fault current is transferred from the main branch to the transfer branch; as shown in Figure 2-c, after the current transfer is completed, the current in the main branch drops to zero, and the mechanical switch is turned off; as shown in Figure 2-d It is shown that after the mechanical switch is disconnected, the sub-modules in the transfer branch are blocked to realize the shutdown of the transfer branch, and the arrester acts to absorb the short-circuit fault energy and suppress the transient voltage until the short-circuit current drops to zero and the breaking process ends.

After the DC circuit breaker is disconnected, that is, after a certain period of time when the fault occurs, the circuit breaker needs to be reclosed. At present, we use the following control process to perform the reclose operation:

Figures 3-a to 3-c, combined with Figures 2-a, 2-c and 2-d, are schematic diagrams of the closing process of the DC circuit breaker. As shown in Figure 2-d, it is a schematic diagram of the circuit breaker in the off state. The mechanical switch of the main branch is in the off state, and the submodules in the main branch and the transfer branch are in the closed state; when the DC circuit breaker needs When it is closed, as shown in Figure 3-a, the sub-modules in the transfer branch are turned on, that is, the sub-modules are switched from the latched off state to the on-state; when all the sub-modules in the transfer branch are turned on, as shown in Figure 2 As shown in -c; as shown in Figure 3-b, after the line current is stabilized, when the sub-module in the main branch is in the locked-off state, close the mechanical switch; as shown in Figure 3-c, gradually open the main branch Then the sub-modules in the transfer branch are gradually blocked and shut down. During this process, the current flowing through the DC circuit breaker is gradually transferred from the transfer branch to the main branch, and all the sub-modules in the main branch are turned on. , all sub-modules in the transfer branch are blocked, and after the current flowing through the circuit breaker reaches a stable level, the reclosing action of the circuit breaker is completed, and the DC circuit breaker is in a normal working state after completion, which can be shown in Figure 2-a.

Reasonable and effective fault recovery strategies, such as DC short-circuit fault recovery strategies, play a key role in the stability of flexible DC systems. However, when the above-mentioned DC circuit breaker is closed, secondary faults are more likely to occur, which is not conducive to system stability and may easily cause damage to equipment in the line.

Contents of the invention

The purpose of the present invention is to provide a cascaded hybrid DC circuit breaker fault type discrimination closure control method to solve the problem that secondary faults are prone to occur when the DC circuit breaker is closed. The invention also provides a cascaded hybrid DC circuit breaker fault type discrimination closing control device.

In order to achieve the above object, the solution of the present invention includes a cascaded hybrid DC circuit breaker fault type discrimination closing control method, including the following steps:

(1) Perform permanent fault judgment when closing the DC circuit breaker;

(2) When it is judged as a permanent fault, stop the operation of closing the DC circuit breaker to ensure that the DC circuit breaker is in the disconnected state;

The judgment conditions of the permanent fault include: the current flowing through the DC circuit breaker exceeds the set secondary overcurrent protection limit, or at least one sub-module in the transfer branch has an overvoltage fault;

The overcurrent limit value is greater than or equal to the maximum value of the charging current of the overhead line.

For the double-terminal DC system, after the first judgment as a permanent fault, reserve the set fault recovery time, retry the DC circuit breaker reclosing operation for a set number of times, if the fault still exists, it is determined as a permanent fault.

For the double-terminal DC system, after the DC circuit breaker is disconnected due to a permanent fault, the converter turns to the STATCOM operating state to provide reactive power support for the AC system.

When it is judged as a non-permanent fault, continue to complete the operation of closing the DC circuit breaker.

In the process of opening the transfer branch, each sub-module on the transfer branch is gradually opened.

A cascaded hybrid DC circuit breaker fault type discrimination closing control device, including:

The judging module is used to judge the permanent fault when the DC circuit breaker is closed;

The control module is used to stop the operation of closing the DC circuit breaker to ensure that the DC circuit breaker is in the disconnected state when it is judged as a permanent fault;

The judgment conditions of the permanent fault include: the current flowing through the DC circuit breaker exceeds the set secondary overcurrent protection limit, or at least one sub-module in the transfer branch has an overvoltage fault;

The overcurrent limit value is greater than or equal to the maximum value of the charging current of the overhead line.

For the double-terminal DC system, after the first judgment as a permanent fault, reserve the set fault recovery time, retry the DC circuit breaker reclosing operation for a set number of times, if the fault still exists, it is determined as a permanent fault.

For the double-terminal DC system, after the DC circuit breaker is disconnected due to a permanent fault, the converter turns to the STATCOM operating state to provide reactive power support for the AC system.

When it is judged as a non-permanent fault, continue to complete the operation of closing the DC circuit breaker.

In the process of opening the transfer branch, each sub-module on the transfer branch is gradually opened.

In the DC circuit breaker closing control method provided by the present invention, when closing the DC circuit breaker, especially in the process of switching on the sub-modules in the transfer branch, it is necessary to judge the type of fault to see whether it is a permanent fault, if it is If there is a permanent fault, then if the DC circuit breaker is closed, it may cause a secondary fault, which is not conducive to the stability of the system and may easily cause damage to the equipment in the line. Therefore, when it is judged that it is a permanent fault, it is necessary to stop closing the DC circuit breaker Operation to ensure that secondary failures are avoided, and damage to equipment in the line will also be avoided, which is conducive to system stability.

Moreover, we found that if the system line fault is a permanent fault, when the reverse electromotive force provided by the sub-module in the blocked state in the transfer branch is not enough to support the system DC voltage, the current flowing through the circuit breaker will appear The phenomenon of exceeding the limit value, that is, the overcurrent phenomenon, or the phenomenon that the capacitor voltage of the sub-module exceeds the set overvoltage limit value, that is, the overvoltage fault phenomenon; therefore, by analyzing the possible situations, the permanent fault is obtained Judgment methods include: the current flowing through the DC circuit breaker exceeds the secondary overcurrent protection limit, or at least one sub-module (the specific number is set according to the demand) in the transfer branch has an overvoltage fault. As long as one of these two judgment methods appears, the fault can be judged as a permanent fault. Therefore, when judging the permanent fault, according to the state of the DC line where the permanent fault occurs, the judgment method of the permanent fault is reversely deduced, so this permanent fault judgment method can accurately judge the permanent fault.

The closing control method of the DC circuit breaker is applicable to various flexible DC systems. After a permanent fault is determined, the operation of closing the DC circuit breaker is stopped to ensure that the circuit breaker is in an open state to complete fault recovery.

Description of drawings

Figure 1 is a topological diagram of a DC circuit breaker;

Figure 2-a is a schematic diagram of a DC circuit breaker in normal operation;

Figure 2-b is a schematic diagram of the current transfer during the breaking process of the DC circuit breaker;

Figure 2-c is a schematic diagram when the transfer is completed during the breaking process of the DC circuit breaker;

Fig. 2-d is a schematic diagram when the current is turned off during the breaking process of the DC circuit breaker;

Figure 3-a is a schematic diagram when the sub-modules in the transfer branch of the DC circuit breaker are gradually opened;

Figure 3-b is a schematic diagram of closing the mechanical switch during the opening process of the DC circuit breaker;

Figure 3-c is a schematic diagram of the current transfer during the opening process of the DC circuit breaker;

Figure 4 is a schematic diagram of a double-ended flexible DC system;

Fig. 5 is a schematic diagram of a four-terminal flexible DC grid system;

Fig. 6 is a schematic diagram of a DC fault ride-through process;

Figure 7 is a schematic diagram of the fault handling and recovery strategy flow diagram of the double-ended flexible DC system;

Fig. 8 is a schematic flow diagram of fault handling and restoration strategy of the flexible DC grid system.

detailed description

Embodiment of fault type discrimination closing control method for cascaded hybrid DC circuit breaker

The basic technical solution of the cascaded hybrid DC circuit breaker fault type discrimination closing control method provided by the present invention includes the following steps:

(1) Perform permanent fault judgment when closing the DC circuit breaker;

(2) When it is judged as a permanent fault, stop closing the operation of the DC circuit breaker;

Judgment methods for permanent faults include: the current flowing through the DC circuit breaker exceeds the set secondary overcurrent protection limit, or at least one sub-module in the transfer branch has an overvoltage fault.

Based on the above basic technical solutions, further detailed description will be made below in conjunction with the accompanying drawings.

The closed control method in this embodiment has wide applicability, such as: double-terminal flexible direct current system, multi-terminal flexible direct current system, flexible direct current grid system and hybrid direct current transmission system. The fault recovery method is specifically described below for the double-ended flexible DC system and the flexible DC grid. DC circuit breaker), Figure 5 is a four-terminal flexible DC grid system, that is, a topology diagram of the flexible DC grid.

For double-ended flexible DC systems:

The double-ended flexible DC system will cut off the faulty line after a fault occurs, and since there is only one DC transmission line, the power transmission will be interrupted. In addition, when the main power transmission line in the multi-terminal flexible DC system fails, the power transmission of the system will also be interrupted; Power transmission is interrupted after the line is removed.

Figure 6 shows the fault handling process of the system's DC short circuit. When the system detects the occurrence of a DC short circuit fault, it must immediately switch off the DC circuit breakers on both sides of the faulty line.

As for the breaking process of the DC circuit breaker, it has been introduced in the background art, so it will not be described in detail here. In addition, after a fault occurs, the converter in the double-ended flexible DC system can also be adjusted to the STATCOM operating state while the circuit breaker is switched off, which can provide reactive power support to the AC system and facilitate rapid recovery after the fault occurs.

After confirming that the DC circuit breakers on both sides of the faulty line are disconnected, the system needs to wait for a period of time before performing the system reclosing operation, that is, the DC circuit breaker closing operation. This period of time includes two parts, namely the DC arc extinguishing process and the DC line deionization process. DC line arc extinguishing, that is, the process of DC circuit breaker suppressing DC short-circuit current, the maintenance time of this process is related to parameters such as DC circuit breaker, DC line, DC reactor, bridge arm reactor, etc., and generally controlled within 20ms; DC The process of line deionization is that after the arc is extinguished, it takes a period of time to diffuse the conductive ions and electrons in the original arc and cool it in air to avoid the process of re-establishing the arc after reclosing. The time for deionization of DC overhead lines is generally 150ms to 500ms.

First, close the DC circuit breaker at one end of the fault line. The operation of the closing process is as follows:

Before closing, the off state of the DC circuit breaker is shown in Figure 2-d. The mechanical switch of the main branch is in the off state, and the full-bridge sub-modules in the main branch and the transfer branch are in the locked state, that is, in the off state.

Since the number of full-bridge sub-modules in the transfer branch may be more than one, in the process of closing the DC circuit breaker, the full-bridge sub-modules in the transfer branch should be gradually opened first, and the full-bridge sub-modules from the locked state Switching to the activated state can be activated step by step, or all the full-bridge sub-modules can be divided into several groups and activated group by group.

During the step-by-step opening process of each full-bridge sub-module in the transfer branch, it is necessary to judge the type of permanent fault. When the reverse electromotive force is not enough to support the DC voltage of the system, the current flowing through the circuit breaker will exceed the limit, that is, the overcurrent phenomenon, or the capacitor voltage of the full-bridge sub-module in the transfer branch exceeds the set overvoltage limit Value phenomenon, that is, overvoltage fault phenomenon. In addition, the fault type of non-permanent faults can be called transient faults. If the system line fault is a transient fault and the line insulation has been restored, when the DC circuit breaker is turned on, the overhead line charging will also flow on the transfer branch. current.

Therefore, when judging the type of fault, it is necessary to set a secondary overcurrent protection limit, which is greater than or equal to the maximum charging current of the overhead line. The maximum value of the charging current. The overhead line charging current refers to: due to the existence of stray capacitance in the overhead line, then the overhead line charging current refers to the charging current for charging the stray capacitance, and then, the maximum charging current of the overhead line refers to the stray capacitance. The maximum charging current at which the capacitor is charged. In addition, if the fault has been recovered, that is, the system line fault is a transient fault, and the line insulation has been restored, the DC grid will still charge the stray capacitance of the overhead line when the DC circuit breaker is closed, causing the circuit breaker to flow through the overhead line to charge current.

Therefore, in the process of gradually opening the full-bridge sub-modules in the transfer branch, if it is not certain that the line fault has been restored, then the current flowing through the circuit breaker in the transfer branch and the full-bridge sub-module in the blocked state in the transfer branch should be detected. Capacitor voltage, make the following judgment: If the current flowing through the DC circuit breaker exceeds the above-mentioned secondary overcurrent protection limit, or at least one full-bridge sub-module in the transfer branch has an overvoltage fault (in the judgment condition, the transfer branch The number of overvoltage faults in the full-bridge sub-modules in the system is set according to actual engineering needs), then it is determined that the system fault is a permanent fault. According to the above description, it can be seen that the logical relationship between the above two judging conditions is "or", as long as one of the conditions is satisfied, it can be judged that there is a fault phenomenon. For a double-ended flexible DC system, a permanent fault can be preliminarily judged according to the above judgment conditions. System failure recovery time (the recovery time can be set according to actual needs), retry the set number of DC circuit breaker reclosing operations (the set number of reclosing operations can also be set according to actual needs, such as 2 times or more Multiple times), if the fault phenomenon still exists, it is determined to be a permanent fault.

If it is judged to be a permanent fault, then it is necessary to perform a fault protection operation, immediately block and shut down all the full-bridge sub-modules of the transfer branch, stop the operation of closing the DC circuit breaker, ensure that the DC circuit breaker is in the disconnected state, and ensure the safety and security of the equipment. system security. Furthermore, after confirming that the DC circuit breaker is disconnected, the isolation switches on both sides of the DC circuit breaker can be opened to carry out maintenance work on the faulty line. After the line maintenance work is completed, reclose the system according to the above operation.

Of course, if the judgment does not meet the above judgment conditions, then the system fault is judged as a transient fault, and the system insulation has been restored.

If the system fault detection fault is transient, and the system insulation has been restored, the closing operation continues. Then, the full-bridge sub-modules in the transfer branch will continue to be opened gradually until all of them are opened, as shown in Figure 2-c.

After the line current on the transfer branch is stable, keep the full-bridge sub-module in the main branch in the locked state and close the mechanical switch, as shown in Figure 3-b.

As shown in Figure 3-c, the full-bridge sub-modules in the main branch are gradually activated until all the full-bridge sub-modules in the main branch are activated.

As shown in Figure 2-a, after the line current on the main branch is stable, the full-bridge sub-modules in the transfer branch are gradually blocked and shut down. During this process, the current in the DC circuit breaker is gradually transferred from the transfer branch to the main branch. on the road. After all the full-bridge sub-modules of the transfer branch are locked and shut down, and the current flowing through the DC circuit breaker reaches stability, the single-side circuit breaker reclosing action of the faulty line is completed.

Then, reclose the DC circuit breaker on the other side of the fault line to complete the fault recovery control of the entire double-ended flexible DC system. During the reclosing process of the DC circuit breaker on the other side, there is no need to consider the possibility of permanent failure, and the full-bridge sub-modules on the transfer branch can be turned on at one time.

For the double-ended flexible DC system, it is necessary to convert the control mode of the converter from the STATCOM operation mode to the power transmission mode.

Fig. 7 shows a schematic diagram of the entire process of system fault handling and recovery of the DC circuit breaker in the double-ended flexible DC system. Of course, this is only a specific implementation manner, and the closing control method of the DC circuit breaker provided by the present invention is not limited thereto.

For the flexible DC grid system, the following takes the four-terminal flexible DC grid system as an example:

When the DC short-circuit fault is detected, it is necessary to judge whether the bridge arm overcurrent fault occurs in the converter. If the bridge arm overcurrent fault does not occur in the converter station, the normal operation control is maintained. After the faulty line is cut off, the system passes through other circuits. Transmit power and maintain normal operation; if bridge arm overcurrent occurs in some converters, the converters should be blocked immediately, and after confirming that the operation of the DC circuit breaker is completed, unlock and resume operation. Regardless of whether the bridge arm overcurrent fault occurs in the converter, as long as a DC short-circuit fault is detected, the DC circuit breakers on both sides of the faulty line are immediately disconnected.

After confirming that the DC circuit breakers on both sides of the faulty line are disconnected, the system needs to wait for the DC arc extinguishing process and the DC line de-ionizing process before reclosing the system.

First, close the DC circuit breaker at one end of the faulty line. The operation of the closing process is as follows:

The same as the double-terminal DC system above, before closing, the off state of the DC circuit breaker is shown in Figure 2-d, the mechanical switch of the main branch is in the off state, and the full-bridge sub-modules in the main branch and the transfer branch are all locked state, that is, in the off state.

In the process of closing the DC circuit breaker, first of all, the full-bridge sub-modules in the transfer branch should be gradually opened, that is, the full-bridge sub-modules should be converted from the blocked state to the open state.

During the step-by-step opening process of the full-bridge sub-modules in the transfer branch, it is necessary to judge the type of permanent fault. When the electromotive force is not enough to support the DC voltage of the system, the current flowing through the circuit breaker will exceed the limit, that is, the overcurrent phenomenon, or the capacitor voltage of the full-bridge sub-module in the transfer branch exceeds the set overvoltage limit The phenomenon, that is, the overvoltage fault phenomenon. In addition, the fault type of non-permanent faults can be called transient faults. If the system line fault is a transient fault and the line insulation has been restored, when the DC circuit breaker is turned on, the overhead line charging will also flow on the transfer branch. current.

Therefore, when judging the type of fault, it is necessary to set a secondary overcurrent protection limit, which is greater than or equal to the maximum charging current of the overhead line. The maximum value of the charging current.

Therefore, in the process of gradually opening the full-bridge sub-module in the transfer branch, detect the current flowing through the circuit breaker in the transfer branch and the capacitor voltage of the full-bridge sub-module in the locked state in the transfer branch, and make the following judgment: if the current The current through the DC circuit breaker exceeds the above-mentioned secondary overcurrent protection limit, or at least one full-bridge sub-module in the transfer branch has an overvoltage fault (in the judgment condition, the full-bridge sub-module in the transfer branch has an over-voltage fault The number is set according to the actual engineering needs), then, it is determined that the system failure is a permanent failure.

The logical relationship between the above two judgment conditions is "or", as long as one of the conditions is met, it can be judged as a permanent fault. If it is judged to be a permanent fault, then it is necessary to perform a fault protection operation, immediately block and shut down all the full-bridge sub-modules of the transfer branch, stop the operation of closing the DC circuit breaker, ensure that the DC circuit breaker is in the disconnected state, and ensure the safety and security of the equipment. system security. Furthermore, after confirming that the DC circuit breaker is disconnected, the isolation switches on both sides of the DC circuit breaker can be opened to carry out maintenance work on the faulty line. After the line maintenance work is completed, reclose the system according to the above operation.

Of course, if the above judgment conditions are not met, then the system fault is judged as a transient fault, and the system insulation has been restored.

If the system fault detection fault is transient, and the system insulation has been restored, the closing operation continues. Then, the full-bridge sub-modules in the transfer branch will continue to be opened gradually until all of them are opened, as shown in Figure 2-c.

After the line current on the transfer branch is stable, keep the full-bridge sub-module in the main branch in the locked state and close the mechanical switch, as shown in Figure 3-b.

As shown in Figure 3-c, the full-bridge sub-modules in the main branch are gradually activated until all the full-bridge sub-modules in the main branch are activated.

As shown in Figure 2-a, after the line current on the main branch is stable, the full-bridge sub-modules in the transfer branch are gradually blocked and shut down. During this process, the current in the DC circuit breaker is gradually transferred from the transfer branch to the main branch. on the road. After all the full-bridge sub-modules of the transfer branch are locked and shut down, and the current flowing through the DC circuit breaker reaches stability, the single-side circuit breaker reclosing action of the faulty line is completed.

Then, the same reclosing operation is performed on the DC circuit breaker on the other side of the fault line to complete the fault recovery control of the entire double-ended flexible DC system. During the reclosing process of the DC circuit breaker on the other side, there is no need to consider the possibility of permanent failure, and the full-bridge sub-modules on the transfer branch can be turned on at one time.

Fig. 8 shows a schematic diagram of the entire process of system fault handling and recovery of a DC circuit breaker in a four-terminal flexible DC grid system. Of course, this is only a specific implementation manner, and the closing control method of the DC circuit breaker provided by the present invention is not limited thereto.

Embodiment of cascaded hybrid DC circuit breaker fault type discrimination closing control device

In this embodiment, the device includes two modules, namely a judging module and a control module, wherein the judging module is used to judge a permanent fault when the DC circuit breaker is closed.

The control module is used to stop the operation of closing the DC circuit breaker to ensure that the DC circuit breaker is in an open state when it is judged as a permanent fault.

These two modules are software modules, which are loaded into the control system to realize corresponding functions. Therefore, these two modules are essentially two steps of the DC circuit breaker closing control method, so the device is still essentially a DC circuit breaker closing control method. As for the control method, since the method has been described in detail in the foregoing method embodiments, details will not be repeated here.

Specific embodiments have been given above, but the present invention is not limited to the described embodiments. The basic idea of the present invention is to judge the type of fault during the opening process of the sub-module on the transfer branch, and if it is a permanent fault, stop closing the DC circuit breaker to ensure that the DC circuit breaker is in an open state. For other parts, such as when a fault occurs, the DC circuit breaker is disconnected, and other processes belong to the prior art, and are not the invention of the present invention. Therefore, without departing from the above-mentioned basic ideas of the present invention, the Changes, modifications, substitutions and variants of the embodiments still fall within the protection scope of the present invention.

Claims (10)

1. a kind of cascade connection type mixed DC circuit breaker failure type identification closure control method, it is characterised in that including following step Suddenly：

(1) when dc circuit breaker is closed, permanent fault judgement is carried out；

(2) when permanent fault is judged as, closure dc circuit breaker operation is stopped, it is ensured that dc circuit breaker is in disconnection shape State；

The Rule of judgment of the permanent fault has：The electric current for flowing through dc circuit breaker exceedes the secondary overcurrent protection limit of setting There is at least one submodule over-voltage fault occur in value, or transfer branch road；

It is described to cross maximum of the restriction value more than or equal to overhead transmission line charging current.

2. cascade connection type mixed DC circuit breaker failure type identification closure control method according to claim 1, its feature It is, for both-end straight-flow system, after permanent fault is judged as first, to reserve the failure recovery time of setting, tastes again Examination dc circuit breaker reclosing operation set point number, if failure is still present, it is determined that for permanent fault.

3. cascade connection type mixed DC circuit breaker failure type identification closure control method according to claim 1, its feature It is that, for both-end straight-flow system, after because of permanent fault disconnecting dc circuit breaker, inverter switchs to STATCOM fortune Row state, for AC system reactive power support is provided.

4. the cascade connection type mixed DC circuit breaker failure type identification according to claim 1-3 any one closes controlling party Method, it is characterised in that when non-permanent failure is judged as, continues to complete closure dc circuit breaker operation.

5. cascade connection type mixed DC circuit breaker failure type identification closure control method according to claim 1, its feature It is during transfer branch road is opened, progressively to open each submodule on transfer branch road.

6. a kind of cascade connection type mixed DC circuit breaker failure type identification closes control device, it is characterised in that include：

Judge module, for when dc circuit breaker is closed, carrying out permanent fault judgement；

Control module, for when permanent fault is judged as, stopping closure dc circuit breaker operation, it is ensured that at dc circuit breaker In off-state；

The Rule of judgment of the permanent fault has：The electric current for flowing through dc circuit breaker exceedes the secondary overcurrent protection limit of setting There is at least one submodule over-voltage fault occur in value, or transfer branch road；

It is described to cross maximum of the restriction value more than or equal to overhead transmission line charging current.

7. cascade connection type mixed DC circuit breaker failure type identification according to claim 6 closes control device, its feature It is, for both-end straight-flow system, after permanent fault is judged as first, to reserve the failure recovery time of setting, tastes again Examination dc circuit breaker reclosing operation set point number, if failure is still present, it is determined that for permanent fault.

8. cascade connection type mixed DC circuit breaker failure type identification according to claim 6 closes control device, its feature It is that, for both-end straight-flow system, after because of permanent fault disconnecting dc circuit breaker, inverter switchs to STATCOM fortune Row state, for AC system reactive power support is provided.

9. the cascade connection type mixed DC circuit breaker failure type identification closure control according to claim 6-8 any one is filled Put, it is characterised in that when non-permanent failure is judged as, continue to complete closure dc circuit breaker operation.

10. cascade connection type mixed DC circuit breaker failure type identification according to claim 6 closes control device, its feature It is during transfer branch road is opened, progressively to open each submodule on transfer branch road.