CN111711350A - A method for improving operation reliability of MMC converter valve - Google Patents

Abstract

The invention discloses a method for improving the operation reliability of an MMC converter valve, which adopts two groups of adjacent MMC sub-modules, and the thyristors of the sub-modules all use bidirectional thyristors; in the same group, the upper ports of the lower sub-module thyristors are connected to the upper The upper end line of the sub-module is connected, the lower port of the thyristor of the lower sub-module is connected with the lower end line of the lower sub-module; the lower port of the thyristor of the upper sub-module is connected with the lower end line of the lower sub-module, and the upper port of the thyristor of the upper sub-module is connected with the upper end line of the upper sub-module Connecting; the power supply board of each submodule and the power supply board of the adjacent submodules in other groups are connected by adding wiring to realize the mutual supply of electric energy between adjacent submodules in two different groups. The invention can effectively avoid the blocking of the MMC converter valve caused by the refusal of the bypass switch of the factor module or the failure of the uplink communication, thereby effectively improving the operation reliability of the MMC converter valve; the invention is based on the atomic module. Retrofit, less workload, low cost of increased retrofit, which is beneficial to the retrofit of existing projects.

Description

A method for improving operation reliability of MMC converter valve

technical field

The invention belongs to the field of flexible direct current transmission and distribution, in particular to a method for improving the operation reliability of an MMC converter valve.

Background technique

The redundant design of sub-modules of the MMC converter valve is the key to greatly improving its operational reliability. When a sub-module fails, the corresponding bypass switch is smoothly closed to realize the removal of the faulty sub-module, thereby ensuring the normal operation of the remaining sound system. However, in the actual operation process of the existing flexible DC, there are problems such as the refusal of the bypass switch of a single sub-module to operate, or the failure of the uplink communication of a single sub-module, which leads to the blocking of the converter valve and the withdrawal of operation. From the perspective of the entire converter valve, it is equivalent to the failure of a single sub-module, which leads to the blocking of the converter valve, which seriously affects the operation reliability of the flexible HVDC transmission system, and also fails to effectively meet the purpose of the redundant design to a certain extent. .

For the sub-module, when it needs to exit the bypass due to failure, the following two points need to be done at the same time to ensure that the converter valve continues to work normally: first, the bypass switch is successfully closed, and the second is the DC control system. Bypass switch closing signal received. If the bypass switch fails to close (refuses to act), then the sub-module will continue to be connected to the bridge arm in series, and IGBTs, capacitors and other equipment will face dangers such as overvoltage. If the DC control system fails to receive relevant signals effectively, even if the bypass switch is closed, the DC control system will also lock the entire converter valve to ensure the safe operation of the entire system. It can be seen that in order to effectively reduce the shutdown of the entire converter valve caused by the internal failure of a single sub-module, it is necessary to propose an improvement strategy to effectively enhance the advantages of redundant configuration.

SUMMARY OF THE INVENTION

In view of the problems existing in the above-mentioned prior art, the present invention provides a method for improving the operation reliability of an MMC converter valve by adopting the method of sub-module transformation under the premise of reducing the transformation cost as much as possible and not destroying the independent control operation of the sub-module, so as to solve the problem of At present, the bypass failure of the neutron module in the flexible straight project causes the overall operation reliability of the converter valve to decrease.

To this end, the present invention adopts the following technical scheme: a method for improving the operation reliability of an MMC converter valve, which adopts two groups of adjacent MMC sub-modules, and the thyristors of the sub-modules all use bidirectional thyristors; The upper port of the thyristor of the module is connected with the upper end line of the upper sub-module, the lower port of the thyristor of the lower sub-module is connected with the lower end line of the lower sub-module; the lower port of the thyristor of the upper sub-module is connected with the lower end line of the lower sub-module, and the upper port of the thyristor of the upper sub-module Connect to the upper end line of the upper sub-module; add a pair of wires between the power supply board of each sub-module and the power supply boards of adjacent sub-modules in other teams to realize the electrical energy between adjacent sub-modules in two different teams. mutual supply;

After the adjacent MMC sub-modules are teamed up in two groups, the corresponding actions are as follows for various working conditions encountered by the sub-modules:

When the sub-module fails and needs to be out of operation, after the sub-module blocks the IGBT trigger signal, a closing command is applied to the bypass switch. If the bypass switch is successfully closed and the DC control system receives the corresponding feedback information, the sub-module bypass is successful. , when the number of bypass sub-modules does not exceed the redundant number, the converter valve continues to operate normally;

If the bypass switch fails to close or the sub-module uplink communication link fails, at this time, regardless of the power board failure, bypass switch drive circuit failure, bypass switch failure, or bypass switch closing command communication link failure, the The sub-module and another sub-module formed with it all issue a triggering instruction to turn on the triac, and the other sub-module needs to block the IGBT trigger pulse first, and the two sub-modules in the team are reliably bypassed.

After the two sub-modules are bypassed by the triac, the capacitors of the sub-modules are no longer charged. Therefore, with the passage of time, the capacitor voltages of the two sub-modules will gradually decrease until they cannot meet the normal power supply requirements. By using the power boards of adjacent sub-modules in other teams to increase the wiring, so that the sub-modules bypassed by the triacs can obtain power from the adjacent sub-modules that are not out of operation to ensure that the triacs are always triggered and conducted. to ensure that the faulty sub-module continues to maintain the bypass exit state.

Further, the type of the MMC sub-module is a half-bridge sub-module, a full-bridge sub-module or a clamp-type dual sub-module.

Compared with the prior art, the present invention has the following beneficial effects:

(1) The present invention can effectively avoid the blocking of the MMC converter valve caused by the refusal of the bypass switch of the factor module or the failure of the uplink communication, thereby effectively improving the operation reliability of the MMC converter valve.

(2) The method adopted in the present invention is applicable to the existing topologies such as the half-bridge sub-module, the full-bridge sub-module, and the clamped double sub-module.

(3) The present invention carries out a simple transformation on the basis of the atomic module, with less workload and low increased transformation cost, which is beneficial to the transformation of existing projects.

Description of drawings

Fig. 1 is the sub-module structural transformation schematic diagram of the present invention;

FIG. 2 is a schematic diagram of the wiring modification of the sub-module of the present invention.

Detailed ways

In order to describe the present invention more specifically, the technical solutions and related principles of the present invention are described in detail below with reference to the accompanying drawings and specific embodiments.

As shown in FIG. 1, the present invention adopts the adjacent MMC sub-module (this embodiment takes the half-bridge sub-module as an example, in fact, the topological forms such as the full-bridge sub-module and the clamped double sub-module are equally applicable) The sub-modules are in the form of two or two teams, and the sub-modules are modified in three places:

First, the unidirectional thyristors of the sub-modules are all changed to bidirectional thyristors, and the bidirectional thyristors have bidirectional current conduction capability;

Second, in the same team, the upper port of the thyristor of the lower submodule is changed to be connected to the upper end line of the upper submodule, and the lower port of the thyristor of the lower submodule is still connected to the lower end line of the lower submodule; the lower port of the thyristor of the upper submodule is changed to The lower end line of the lower sub-module is connected, and the upper port of the thyristor of the upper sub-module is still connected to the upper end line of the upper sub-module, as shown in Figure 2.

Third, the power supply board of each submodule and the power supply board of the adjacent submodules in other teams are connected to each other to realize the mutual supply of electric energy between the adjacent submodules of the two different teams, which is used to be bypassed. The sub-modules have continuous power supply.

After the sub-modules are transformed in two groups, the corresponding actions are as follows for various working conditions encountered by the sub-modules:

When the sub-module fails and needs to be out of operation, after the sub-module blocks the IGBT trigger signal, a closing command is applied to the bypass switch. If the bypass switch is successfully closed and the DC control system receives the corresponding feedback information such as closing, the sub-module If the bypass is successful and the number of bypass sub-modules does not exceed the redundant number, the converter valve can continue to operate normally.

If the bypass switch fails to close or the sub-module uplink communication link fails, at this time, regardless of the power board failure, bypass switch drive circuit failure, bypass switch failure, or bypass switch closing command communication link failure, the Both the sub-module and the other sub-module teamed with it issue a triggering instruction to turn on the triac (the other sub-module needs to block the IGBT trigger pulse first), and the two sub-modules in the team are reliably bypassed.

After the two sub-modules are bypassed by the triac, the capacitors of the sub-modules are no longer charged. Therefore, with the passage of time, the capacitor voltages of the two sub-modules will gradually decrease until they cannot meet the normal power supply requirements. By using the power boards of adjacent sub-modules in other teams to increase the wiring, so that the sub-modules bypassed by the triacs can obtain power from the adjacent sub-modules that are not out of operation to ensure that the triacs are always triggered and conducted. to ensure that the faulty sub-module continues to maintain the bypass exit state.

Those skilled in the art can easily understand that the above are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention, etc., All should be included within the protection scope of the present invention.

Claims (2)

1. A method for improving the operation reliability of an MMC converter valve is characterized in that adjacent MMC sub-modules are grouped pairwise, and thyristors of the sub-modules all adopt bidirectional thyristors; in the same team, the upper port of the lower submodule thyristor is connected with the upper end line of the upper submodule, and the lower port of the lower submodule thyristor is connected with the lower end line of the lower submodule; the lower port of the upper submodule thyristor is connected with the lower end line of the lower submodule, and the upper port of the upper submodule thyristor is connected with the upper end line of the upper submodule; a butt joint line is added between the power supply board card of each sub-module and the power supply board cards of adjacent sub-modules in other teams, so that mutual power supply between the adjacent sub-modules in two different teams is realized;

after two liang of teams of adjacent MMC submodule pieces, to the various operating modes that the submodule piece met, the corresponding action is as follows:

when the submodule fails and needs to quit operation, the submodule blocks an IGBT trigger signal and then applies a closing command to the bypass switch, if the bypass switch is closed smoothly and the direct current control system receives corresponding feedback information, the submodule bypasses successfully, and the converter valve continues to operate normally under the condition that the number of the bypass submodules does not exceed the redundancy number;

if the bypass switch fails to be switched on or the uplink communication link of the submodule fails, no matter the power board card fails, the bypass switch driving circuit fails, the bypass switch fails and the bypass switch switching-on command communication link fails, the submodule and the other submodule of the team of the submodule send a conduction command of triggering the bidirectional thyristor, the other submodule needs to lock an IGBT triggering pulse first, and the two submodules of the team are reliably bypassed.

2. The method for improving the operational reliability of the MMC converter valve according to claim 1, wherein the MMC sub-module is a half-bridge sub-module, a full-bridge sub-module or a clamp type dual sub-module.

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