CN112952765B - MMC topology with direct-current fault clearing capability and control method thereof - Google Patents
MMC topology with direct-current fault clearing capability and control method thereof Download PDFInfo
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- CN112952765B CN112952765B CN202110411558.9A CN202110411558A CN112952765B CN 112952765 B CN112952765 B CN 112952765B CN 202110411558 A CN202110411558 A CN 202110411558A CN 112952765 B CN112952765 B CN 112952765B
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
- H02H7/10—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for converters; for rectifiers
- H02H7/12—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for converters; for rectifiers for static converters or rectifiers
- H02H7/122—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for converters; for rectifiers for static converters or rectifiers for inverters, i.e. dc/ac converters
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Abstract
The invention discloses a novel MMC topology with direct-current fault clearing capacity, which is characterized in that three switch branches and two thyristor branches are added on the basis of the traditional half-bridge type MMC, and all half-bridge submodules of a C-phase upper bridge arm are replaced by full-bridge submodules. The switch branch circuit is formed by connecting an Insulated Gate Bipolar Transistor (IGBT) and a thyristor group in series; the thyristor branch is formed by connecting a plurality of thyristors in series. This novel MMC topology is after taking place direct current short circuit fault, through breaking off two switch branch roads, switches on two thyristor branch roads and realize cleaing away of short circuit fault with the two-way ability of blocking that utilizes C looks full-bridge submodule piece, can clear away direct current short circuit fault fast when reduce cost.
Description
Technical Field
The invention belongs to the technical field of flexible direct current power transmission and distribution, and particularly relates to an MMC topology with direct current fault clearing capacity and a control method thereof.
Background
With the continuous expansion of the scale of distributed new energy and direct current loads, the application of direct current transmission and distribution networks is more and more emphasized. Modular Multilevel Converters (MMC)) are widely used in the field of flexible dc power transmission due to their good expansibility, low loss, excellent harmonic characteristics, and the like. However, the current converter topologies applied in the current engineering are half-bridge type MMCs, and even if the current converter is locked after a short-circuit fault occurs on the direct current side, the fault cannot be cleared, so that the safety operation of the current converter equipment and the system is seriously threatened by the extremely large short-circuit fault current.
The current scheme for handling the half-bridge type MMC dc side fault includes: firstly, an alternating current circuit breaker is adopted, but the fault clearing and recovery time is too long due to the slow response speed; secondly, a direct current breaker is adopted, for example, a hybrid direct current breaker is adopted, wherein a large number of fully-controlled power electronic devices are needed for a power electronic branch circuit absorbing fault energy, so that the manufacturing cost of the direct current breaker is high; the development of a rapid high-capacity direct-current circuit breaker is still difficult due to the current capacity of the insulated gate bipolar transistor IGBT; thirdly, various novel sub-module topological structures are adopted, such as clamping dual sub-modules, full-bridge sub-modules and the like. However, the improved sub-modules all obtain the direct current fault blocking capability by increasing more switch tube quantity, loss and control complexity, and the control is complex and has no better economy.
Disclosure of Invention
In order to solve the problems in the prior art, the invention provides an MMC topology with direct-current fault clearing capacity, which can rapidly clear direct-current short-circuit faults while reducing the cost.
The technical problem to be solved by the invention is realized by the following technical scheme:
in a first aspect, an MMC topology with dc fault clearance capability is provided, including: the bridge comprises an A-phase upper bridge arm, an A-phase lower bridge arm, a B-phase upper bridge arm, a B-phase lower bridge arm, a C-phase upper bridge arm and a C-phase lower bridge arm, wherein the six bridge arms are formed by sequentially connecting bridge arm reactances and sub-module units in series;
a first switch branch is connected between the top end of the sub-module unit of the phase A upper bridge arm and the top end of the sub-module unit of the phase B upper bridge arm, a second switch branch is connected between the top end of the sub-module unit of the phase B upper bridge arm and the top end of the sub-module unit of the phase C upper bridge arm, and a third switch branch is connected between the bridge arm reactance of the phase C upper bridge arm and the alternating current outlet;
the circuit also comprises a first thyristor branch circuit and a second thyristor branch circuit, wherein the anode end of the first thyristor branch circuit is connected with the top end of the bridge arm submodule unit of the phase A upper bridge arm and the common end of the first switch branch circuit, and the cathode end of the first thyristor branch circuit is connected with the third switch branch circuit and the common end of the bridge arm reactance of the phase C upper bridge arm; and the anode end of the second thyristor branch is connected with the top end of the bridge arm submodule unit of the B-phase upper bridge arm and the common end of the second switch branch, and the cathode end of the second thyristor branch is connected with the common ends of the third switch branch and the bridge arm reactance of the C-phase upper bridge arm.
With reference to the first aspect, further, the first switch branch, the second switch branch, and the third switch branch are each formed by connecting an insulated gate bipolar transistor and a plurality of bidirectional thyristors in series, where each bidirectional thyristor is formed by connecting two unidirectional thyristors in reverse parallel.
With reference to the first aspect, further, the first thyristor branch and the second thyristor branch are each formed by connecting a plurality of unidirectional thyristors in series.
With reference to the first aspect, further, the sub-module units of the C-phase upper bridge arm are formed by full-bridge sub-modules, and the sub-module units of the remaining bridge arms are formed by half-bridge sub-modules.
In a second aspect, a novel MMC topology control method with dc fault clearing capability is provided, where when a dc line fault occurs, the fault clearing includes:
placing all sub-module units in a bypass state, clamping the voltage of a direct current outlet at zero potential, simultaneously turning off the IGBTs in the first, second and third switch branches and triggering and conducting the thyristors in the first and second thyristor branches, and transferring the fault current of the A, B two-phase upper bridge arm to the C-phase upper bridge arm;
after the transfer of the fault current is finished, switching off the thyristor groups in the first, second and third switch branches, and closing the IGBTs in the first and second switch branches after the thyristor groups are switched off;
and locking all the submodule units, and clearing the direct-current short-circuit fault by utilizing the bidirectional blocking capability of the full-bridge submodule.
In combination with the second aspect, further, during normal operation, the first, second, and third switching branches are all turned on, the first, second, and thyristor branches are all turned off, and the full-bridge sub-module operates in a half-bridge mode.
The invention has the beneficial effects that: compared with the prior art, the novel MMC topology structure with the direct-current fault clearing capacity, provided by the invention, only needs a small amount of fully-controlled switching devices and thyristors with relatively low cost on the basis of the traditional half-bridge type MMC, has better economical efficiency, can realize quick absorption of short-circuit fault energy, is short in fault clearing time, and meets the requirement of a flexible direct-current transmission and distribution network on the rapidity of fault clearing speed.
Drawings
FIG. 1 is a schematic diagram of a current MMC topology with DC fault clearance capability according to the present invention;
fig. 2 is a schematic diagram of a dc short fault clearing process according to the present invention.
Detailed Description
To further describe the technical features and effects of the present invention, the present invention will be further described with reference to the accompanying drawings and detailed description.
An MMC topology with dc fault clearing capability provided by the present invention is shown in figure 1,
the topology is improved on the basis of the traditional half-bridge MMC, and three switch branches and two thyristor branches are added. The modular multilevel converter comprises A, B, C three-phase bridge arms, each phase of bridge arm consists of an upper bridge arm and a lower bridge arm, and each bridge arm is formed by sequentially connecting bridge arm reactances and sub-module units in series;
the modular multilevel converter further comprises: first thyristor branch T 1 And a second thyristor branch T 2 First thyristor branch T 1 The anode end of the first switch branch S is connected with the top end of the bridge arm submodule unit of the A-phase upper bridge arm and the first switch branch S 1 Is connected to the common terminal of the first switch branch S, and the cathode terminal is connected to the third switch branch S 3 The common end of the bridge arm reactance of the C-phase upper bridge arm is connected with the common end of the bridge arm reactance of the C-phase upper bridge arm; second thyristor branch T 2 The anode end of the first switch branch circuit is connected with the top end of the bridge arm submodule unit of the B-phase upper bridge arm and the second switch branch circuit S 2 Is connected with the common terminal of the first switch branch S, and the cathode terminal of the first switch branch S is connected with the third switch branch S 3 The common end of the bridge arm reactance of the C-phase upper bridge arm is connected with the common end of the bridge arm reactance of the C-phase upper bridge arm;
the modular multilevel converter further comprises: first switch branch S 1 A second switching branch S 2 And a third switching branch S 3 (ii) a A first switch branch S is connected between the top end of the sub-module unit of the phase A upper bridge arm and the top end of the sub-module unit of the phase B upper bridge arm 1 A second switch branch S is connected between the top end of the sub-module unit of the B-phase upper bridge arm and the top end of the sub-module unit of the C-phase upper bridge arm 2 A third switch branch S is connected between the bridge arm reactance of the C-phase upper bridge arm and the alternating current outlet 3 ；
Each switch branch is formed by connecting an Insulated Gate Bipolar Transistor (IGBT) and a plurality of bidirectional thyristor groups in series, wherein each bidirectional thyristor is formed by reversely connecting two unidirectional thyristors in parallel; the thyristor branch is formed by connecting a plurality of unidirectional thyristors in series; and the bridge arm submodule units on the C phase are formed by full-bridge submodules, and the other bridge arm submodule units are formed by half-bridge submodules.
When the MMC topology normally operates, the first branch, the second branch and the third branch are all conducted, the first thyristor branch and the second thyristor branch are all turned off, the full-bridge submodule works in a half-bridge mode, and the working state of the whole MMC is the same as that of a traditional half-bridge MMC.
When a direct current line fault occurs, the novel MMC topology is carried out according to the following steps:
1) placing all the sub-module units in a bypass state, clamping the voltage of a direct current outlet at zero potential, simultaneously turning off the IGBTs in the first, second and third switch branches and triggering and conducting the thyristors in the first and second thyristor branches, and transferring fault current of A, B two-phase upper bridge arms into a C-phase upper bridge arm;
2) after the transfer of the fault current is finished, switching off the thyristor groups in the first, second and third switch branches, and after the thyristor groups are switched off, closing the IGBTs in the first and second switch branches to ensure the voltage sharing between the IGBTs and the thyristor groups;
3) and locking all the submodule units, and eliminating the direct-current short-circuit fault by utilizing the bidirectional blocking capability of the full-bridge submodule.
The above embodiments do not limit the present invention in any way, and all technical solutions obtained by taking equivalent substitutions or equivalent changes fall within the scope of the present invention.
Claims (4)
1. An MMC topology having dc fault clearance capabilities, comprising: the bridge comprises an A-phase upper bridge arm, an A-phase lower bridge arm, a B-phase upper bridge arm, a B-phase lower bridge arm, a C-phase upper bridge arm and a C-phase lower bridge arm, wherein the six bridge arms are formed by sequentially connecting bridge arm reactances and sub-module units in series;
a first switch branch is connected between the top end of the sub-module unit of the phase A upper bridge arm and the top end of the sub-module unit of the phase B upper bridge arm, a second switch branch is connected between the top end of the sub-module unit of the phase B upper bridge arm and the top end of the sub-module unit of the phase C upper bridge arm, and a third switch branch is connected between the bridge arm reactance of the phase C upper bridge arm and the alternating current outlet;
the first switch branch, the second switch branch and the third switch branch are all formed by connecting an insulated gate bipolar transistor and a plurality of bidirectional thyristor groups in series, wherein each bidirectional thyristor is formed by reversely connecting two unidirectional thyristors in parallel;
the submodule units of the upper bridge arm of the phase C are formed by full-bridge submodules, and the submodule units of the other bridge arms are formed by half-bridge submodules;
the circuit also comprises a first thyristor branch circuit and a second thyristor branch circuit, wherein the anode end of the first thyristor branch circuit is connected with the top end of the bridge arm submodule unit of the phase A upper bridge arm and the common end of the first switch branch circuit, and the cathode end of the first thyristor branch circuit is connected with the third switch branch circuit and the common end of the bridge arm reactance of the phase C upper bridge arm; and the anode end of the second thyristor branch is connected with the top end of the bridge arm submodule unit of the phase B upper bridge arm and the common end of the second switch branch, and the cathode end of the second thyristor branch is connected with the third switch branch and the common end of the bridge arm reactance of the phase C upper bridge arm.
2. The MMC topology with DC fault clearance of claim 1, wherein the first thyristor branch and the second thyristor branch are each comprised of a plurality of unidirectional thyristors connected in series.
3. An MMC topology control method with DC fault clearance capability based on the topology of claim 1 or 2, characterized in that: when a direct current line fault occurs, fault clearing comprises the following steps:
all the sub-module units are placed in a bypass state, the voltage of a direct current outlet is clamped at zero potential, IGBTs in the first, second and third switch branches are turned off and thyristors in the first and second thyristor branches are triggered and conducted at the same time, and fault current of A, B two-phase upper bridge arms is transferred to a C-phase upper bridge arm;
after the transfer of the fault current is finished, switching off the thyristor group in the first, second and third switch branches, and closing the IGBTs in the first and second switch branches after the thyristor group is switched off;
and locking all the submodule units, and clearing the direct-current short-circuit fault by utilizing the bidirectional blocking capability of the full-bridge submodule.
4. The MMC topology control method with DC fault clearance capability of claim 3, characterized in that: when the full-bridge submodule works in a half-bridge mode, the first, second and third switch branches are all conducted, the first and second thyristor branches are all turned off, and the full-bridge submodule works in the half-bridge mode.
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| CN106058824A (en) * | 2016-05-26 | 2016-10-26 | 华北电力大学 | MMC topology having DC fault removing capability |
| CN106787876A (en) * | 2016-12-05 | 2017-05-31 | 特变电工新疆新能源股份有限公司 | A kind of modularization multi-level converter and its high pressure valve group fault to ground guard method |
| CN106877293A (en) * | 2015-12-10 | 2017-06-20 | 特变电工新疆新能源股份有限公司 | MMC topological structure applied to flexible direct-current power transmission |
| CN209592999U (en) * | 2018-10-19 | 2019-11-05 | 哈尔滨工业大学（深圳） | The flexible DC transmission device and DC transmission system for having fault ride-through capacity |
| CN110995038A (en) * | 2019-11-21 | 2020-04-10 | 中国电力科学研究院有限公司 | MMC (modular multilevel converter) and DC fault isolation method and system based on MMC |
| CN111049407A (en) * | 2020-01-03 | 2020-04-21 | 东南大学 | Series-parallel modular multilevel converter with current-breaking capability and control method thereof |
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2021
- 2021-04-16 CN CN202110411558.9A patent/CN112952765B/en active Active
Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN106877293A (en) * | 2015-12-10 | 2017-06-20 | 特变电工新疆新能源股份有限公司 | MMC topological structure applied to flexible direct-current power transmission |
| CN106058824A (en) * | 2016-05-26 | 2016-10-26 | 华北电力大学 | MMC topology having DC fault removing capability |
| CN106787876A (en) * | 2016-12-05 | 2017-05-31 | 特变电工新疆新能源股份有限公司 | A kind of modularization multi-level converter and its high pressure valve group fault to ground guard method |
| CN209592999U (en) * | 2018-10-19 | 2019-11-05 | 哈尔滨工业大学（深圳） | The flexible DC transmission device and DC transmission system for having fault ride-through capacity |
| CN110995038A (en) * | 2019-11-21 | 2020-04-10 | 中国电力科学研究院有限公司 | MMC (modular multilevel converter) and DC fault isolation method and system based on MMC |
| CN111049407A (en) * | 2020-01-03 | 2020-04-21 | 东南大学 | Series-parallel modular multilevel converter with current-breaking capability and control method thereof |
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