CN113300330A - Modular multilevel converter, control method thereof, storage medium, and electronic device - Google Patents
Modular multilevel converter, control method thereof, storage medium, and electronic device Download PDFInfo
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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
- H02H7/1216—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 AC-AC converters
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/32—Means for protecting converters other than automatic disconnection
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M5/00—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases
- H02M5/40—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc
- H02M5/42—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters
- H02M5/44—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters using discharge tubes or semiconductor devices to convert the intermediate dc into ac
- H02M5/453—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters using discharge tubes or semiconductor devices to convert the intermediate dc into ac using devices of a triode or transistor type requiring continuous application of a control signal
- H02M5/458—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters using discharge tubes or semiconductor devices to convert the intermediate dc into ac using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
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Abstract
The invention discloses a modular multilevel converter, a control method thereof, a storage medium and an electronic device, wherein the modular multilevel converter comprises: the multi-phase alternating-current voltage input end is positioned on a power frequency side, a plurality of groups of level conversion control units and the multi-phase alternating-current voltage output end is positioned on a low-frequency side, a plurality of level conversion sub-modules are arranged on each bridge arm branch, the output end of each level conversion sub-module is connected with a first overvoltage protection device in parallel, the input end and the output end of each bridge arm branch are connected through at least one second overvoltage protection device, and the output end of each level conversion sub-module is also connected with a voltage regulation controllable device in parallel. The invention can finally ensure that the whole modular multilevel converter is still in a safe state when overvoltage faults occur on the modular multilevel converter based on the voltage regulation controllable devices under the condition that the first overvoltage protection device and the second overvoltage protection device execute the overvoltage protection improperly.
Description
Technical Field
The invention relates to the technical field of low-frequency power transmission, in particular to a modular multilevel converter, a control method thereof, a storage medium and electronic equipment.
Background
With the rapid development of power electronic technology, Modular Multilevel Converters (MMC for short) are increasingly widely used in flexible ac low-frequency power transmission. The MMC is a novel voltage conversion circuit, and a topological structure is formed in a mode that a plurality of sub-modules are cascaded.
In the prior art, after a short-circuit fault occurs in a flexible alternating-current low-frequency power transmission system, generally, only one overvoltage protection switch is singly connected in parallel at the output end of a submodule of each bridge arm of an MMC, so that an overvoltage phenomenon generated after the short-circuit fault occurs in the flexible alternating-current low-frequency power transmission system is avoided.
At present, after a flexible alternating current low-frequency power transmission system breaks down, the power transmission frequency of the flexible alternating current low-frequency power transmission system is reduced, so that the action speed of the overvoltage protection switch is reduced, and the action time of locking the MMC is far faster than that of the overvoltage protection switch. At this time, the fault point of the MMC still continues to be injected with current, and thus each node inside the flexible alternating-current low-frequency power transmission system still has a higher overvoltage phenomenon, and finally the flexible alternating-current low-frequency power transmission system collapses.
Disclosure of Invention
Therefore, the technical problem to be solved by the present invention is to overcome the defect that when an overvoltage protection switch is used for overvoltage protection in the prior art, each node inside a flexible alternating current low-frequency power transmission system still has a higher overvoltage phenomenon, which finally causes breakdown of the flexible alternating current low-frequency power transmission system, so as to provide a modular multilevel converter, a control method, a device and an electronic device thereof.
According to a first aspect, embodiments of the present invention provide a modular multilevel converter, comprising: the heterogeneous alternating voltage input that is located the power frequency side, multiunit level conversion the control unit and be located the heterogeneous alternating voltage output of low frequency side, wherein, every group level conversion the control unit and include: the bridge arm protection device comprises a plurality of bridge arm branches, each bridge arm branch is connected with an alternating current voltage input end through a follow current device, the output end of each group of level conversion control units is connected with an alternating current voltage output end, a plurality of level conversion sub-modules are arranged on each bridge arm branch, the output end of each level conversion sub-module is connected with a first overvoltage protection device in parallel, the input end and the output end of each bridge arm branch are connected through at least one second overvoltage protection device, and the output end of each level conversion sub-module is further connected with a voltage regulation controllable device in parallel.
In one embodiment, the voltage regulation controllable device includes: a bidirectional thyristor.
In one embodiment, each level conversion sub-module has a fully-controlled H-bridge structure.
In one embodiment, the fully-controlled H-bridge comprises: the bridge comprises two groups of power electronic device bridge arms and a direct current capacitor, wherein the two groups of power electronic device bridge arms are connected in parallel, each power electronic device bridge arm comprises two power electronic devices connected in series, and the direct current capacitor is connected with the two groups of power electronic device bridge arms in parallel.
In one embodiment, the freewheeling device is a dc inductor, the first overvoltage protection device is a switching protection device, and the second overvoltage protection device is a surge arrester.
According to a second aspect, an embodiment of the present invention provides a modular multilevel converter control method, for a modular multilevel converter described in the first aspect or any implementation manner of the first aspect, including:
acquiring the current input voltage of the input end of each bridge arm branch of a plurality of groups of level conversion control units and the current output voltage of the output ends of a plurality of level conversion sub-modules on each bridge arm branch;
judging whether the current input voltage is greater than a first preset safe voltage or not;
if the current input voltage is greater than the first preset safety voltage, controlling a second overvoltage protection device to execute overvoltage protection action;
judging whether the current output voltage is greater than a second preset safety voltage or not;
and if the current output voltage is greater than the second preset safety voltage, controlling the voltage-regulating controllable devices connected in parallel with the output end of each level conversion submodule to execute overvoltage protection action.
In one embodiment, before the step of obtaining the current input voltage at the input end of each bridge arm branch of the multiple groups of level conversion control units and the current output voltages at the output ends of the multiple level conversion sub-modules on each bridge arm branch, the method further includes:
and if the multiple groups of level conversion control units detect that the multiple level conversion sub-modules on each bridge arm branch circuit have overvoltage faults, the first overvoltage protection device is controlled to execute overvoltage protection actions.
In one embodiment, the modular multilevel converter control method further includes:
and if the current input voltage is less than or equal to the first preset safe voltage, controlling each bridge arm branch to be in a normal working state.
In one embodiment, the modular multilevel converter control method further includes:
and if the current output voltage is less than or equal to the second preset safe voltage, controlling the voltage-regulating controllable devices connected in parallel with the output end of each level conversion submodule to be in a normal working state.
In an embodiment of the modular multilevel converter control method, the first preset safe voltage is less than or equal to a sum of preset voltages of a plurality of level conversion sub-modules arranged on each bridge arm branch.
According to a third aspect, an embodiment of the present invention provides a computer-readable storage medium, which stores computer instructions for causing a computer to execute the modular multilevel conversion control method according to the second aspect or any implementation manner of the second aspect.
According to a fourth aspect, an embodiment of the present invention provides an electronic device, including: the modular multilevel converter, the memory and the processor of any embodiment of the first aspect, wherein the modular multilevel converter, the memory and the processor are communicatively connected to each other, the memory stores computer instructions, and the processor executes the computer instructions to execute the modular multilevel converter control method of any embodiment of the second aspect.
The technical scheme of the invention has the following advantages:
the invention provides a modular multilevel converter, a control method thereof, a storage medium and an electronic device, wherein the modular multilevel converter comprises: the heterogeneous alternating voltage input that is located the power frequency side, multiunit level conversion the control unit and be located the heterogeneous alternating voltage output of low frequency side, wherein, every group level conversion the control unit and include: the output end of each level conversion submodule is connected with a first overvoltage protection device in parallel, the input end and the output end of each bridge arm branch are connected with at least one second overvoltage protection device, and the output end of each level conversion submodule is also connected with a voltage regulation controllable device in parallel. The invention can finally ensure that the whole modular multilevel converter is still in a safe state when the overvoltage fault occurs, namely all level conversion sub-modules in the whole modular multilevel converter can be quickly cut off.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.
FIG. 1 is a schematic diagram of a modular multilevel converter according to an embodiment of the invention;
FIG. 2 is a schematic structural diagram of a level conversion sub-module according to an embodiment of the present invention;
FIG. 3 is a flow chart of a modular multilevel conversion control method according to an embodiment of the present invention;
fig. 4 is a schematic diagram of a hardware structure of an electronic device according to an embodiment of the present invention.
Reference numerals:
11-a level conversion control unit; 12-a freewheeling device; 13-a first overvoltage protection device;
14-a second overvoltage protection device; 15-voltage regulating controllable devices; 16-a direct current capacitor;
17-power electronics; 111-a plurality of level translation sub-modules.
Detailed Description
The technical solutions of the present invention will be described clearly and completely with reference to the accompanying drawings, and it should be understood that the described embodiments are some, but not all embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are only for convenience of description and simplicity of description, but do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.
In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; can be mechanically or electrically connected; the two elements may be directly connected or indirectly connected through an intermediate medium, or may be communicated with each other inside the two elements, or may be wirelessly connected or wired connected. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.
In addition, the technical features involved in the different embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
The embodiment of the invention discloses a Modular Multilevel Converter (MMC), which is usually applied to an application scene of a flexible low-frequency alternating-current power transmission system or industrial production equipment. Since low-frequency power transmission is generally performed in a high-voltage form in a flexible low-frequency ac power transmission system, an overvoltage short-circuit fault phenomenon inevitably occurs in the flexible low-frequency ac power transmission system. In order to avoid system breakdown or device damage caused by overvoltage of the flexible low-frequency alternating-current power transmission system, namely to ensure that the flexible low-frequency alternating-current power transmission system can be in a safe and stable operation state, the embodiment of the invention discloses a modular multilevel converter.
In one embodiment, as shown in fig. 1, a modular multilevel converter disclosed by an embodiment of the present invention includes: and a multi-phase ac voltage input A, B, C on the power frequency side. A plurality of sets of level shift control units 11 and a multiphase alternating voltage output terminal D, E, F located on the low frequency side, wherein each set of level shift control units 11 includes: each bridge arm branch is connected with an alternating current voltage input end through a follow current device 12, the output end of each level conversion control unit 11 is connected with an alternating current voltage output end, a plurality of level conversion sub-modules 111 are arranged on each bridge arm branch, the output end of each level conversion sub-module 111 is connected with a first overvoltage protection device 13 in parallel, the input end and the output end of each bridge arm branch are connected through a second overvoltage protection device 14, and the output end of each level conversion sub-module 111 is further connected with a voltage regulation controllable device 15 in parallel. In fig. 1, the number of second overvoltage protection components 14 is one, and in a further alternative embodiment, the input and output of each bridge leg branch can also be connected to one another via a plurality of second overvoltage protection components 14 connected in series.
In fig. 1, an embodiment of the invention discloses a modular multilevel converter, for example: the power frequency side is the transmission side using 50Hz as the operating frequency of the grid. In fig. 1, the multi-phase ac voltage input may be a three-phase ac voltage input A, B, C, such as: the three-phase ac input voltages are Vsu, Vsv, and Vsw, respectively, the three-phase ac input voltages are power-frequency-side three-phase voltages, and the currents flowing through the three-phase ac transmission line are iu, iv, and iw, respectively. In fig. 1, a plurality of sets of level conversion control units 11 form a modular structure, each set of level conversion control unit 11 includes three bridge arm branches a, b, and c, and each bridge arm branch a, b, and c is correspondingly connected to a three-phase ac voltage input terminal A, B, C through a freewheeling device 12. For example: the free-wheeling device 12 may be a direct current inductor, but is not limited thereto. In fig. 1, the multi-phase ac voltage output may be a three-phase ac voltage output D, E, F, such as: the three-phase alternating-current voltages are VIa, VIb and VIc respectively, and the three-phase alternating-current output voltage is a low-frequency side three-phase voltage. The frequency range on the low frequency side is here preferably 2Hz-48Hz, although other frequencies belonging to the conventional low frequency range are also feasible. In fig. 1, a plurality of level conversion sub-modules 111 are provided on each arm branch, for example: the number of the plurality of level conversion sub-modules 111 may be N, or the number of the cascaded level conversion sub-modules 111 may be increased or decreased according to the power grid requirement to apply to different voltage classes. In fig. 1, a power-frequency-side three-phase input voltage and a low-frequency-side three-phase output voltage are connected in pairs through 9 bridge arm branches, each bridge arm branch is formed by connecting N level conversion sub-modules 111 and a follow current device 12 in series, and each level conversion sub-module 111 is formed by a full-bridge inverter circuit. The modular multilevel converter provided by the embodiment of the invention can realize output of any amplitude, frequency and phase.
In fig. 1, the output end of each level conversion submodule 111 is connected in parallel to a first overvoltage protection device 13, for example: the first overvoltage protection device 13 may be, but is not limited to, a switching protection device. The function of the switch protection device is that when a plurality of level conversion sub-modules 111 arranged on each bridge arm branch have short-circuit faults, the switch protection device executes bypass switch action to bypass the current level conversion sub-module 111. Therefore, the first overvoltage protection device 13 may function to protect the entire modular multilevel converter from safe operation in advance.
In fig. 1, the input end and the output end of each bridge arm branch of the modular multilevel converter disclosed by the invention are connected through a second overvoltage protection device 14, for example: the second overvoltage protection device 14 may be, but is not limited to, an arrester. In fig. 1, a plurality of lightning arresters may be connected in series between the input and output of each bridge arm branch. In fig. 1, the arresters are Aua, Ava, Awa, Aub, Avb, Awb, Auc, Avc, Awc, respectively. The lightning arrester has the function of controlling the lightning arrester to execute overvoltage protection action when the current input voltage of each bridge arm branch is greater than a first preset safe voltage. The lightning arrester absorbs overvoltage energy exceeding a first preset safe voltage, and devices on each bridge arm branch are protected from being damaged due to overhigh voltage. The first preset safe voltage is less than or equal to the sum of preset voltages of a plurality of level conversion sub-modules 111 arranged on each bridge arm branch. Therefore, the second overvoltage protection device 14 further ensures that the entire modular multilevel converter can be operated safely, and the safety of the entire modular multilevel converter can be further improved by the lightning arrester.
As shown in fig. 1 or fig. 2, in the modular multilevel converter disclosed in the present invention, the output terminal of each level conversion sub-module is further connected in parallel to a voltage regulation controllable device 15, for example: the voltage regulating controllable device 15 may be a triac, but is not limited to this device. In fig. 2, two output ends of the level conversion submodule 111 on each bridge arm branch are connected in parallel with a bidirectional thyristor. When the current output voltage of the level conversion sub-modules 111 on each bridge arm branch is greater than a second preset safe voltage, the bidirectional thyristor is controlled to execute an overvoltage protection action, so that each level conversion sub-module 111 is not damaged due to overhigh voltage. Therefore, the voltage regulation controllable device 15 can realize the final overvoltage protection when the first overvoltage protection device 13 and the second overvoltage protection device 14 cannot completely ensure the safety state of the whole modular multilevel converter due to the structural characteristics of the devices. After the flexible alternating-current low-frequency power transmission system breaks down, the switching action speeds of the first overvoltage protection device 13 and the second overvoltage protection device 14 in the modular multilevel converter are reduced, and when the overvoltage protection action is not executed quickly, the flexible alternating-current low-frequency power transmission system is prevented from breaking down due to the fact that the locking action time of the whole modular multilevel converter is faster than the switching action speeds of the first overvoltage protection device 13 and the second overvoltage protection device 14. Therefore, the voltage regulation controllable device 15 can control the bidirectional thyristor to perform an overvoltage protection action when the current output voltage of the plurality of level conversion submodules 111 on each bridge arm branch is greater than the second preset safe voltage, so as to ensure that each level conversion submodule 111 is not damaged due to overhigh voltage.
In one embodiment, in the modular multilevel converter disclosed in the embodiment of the present invention, in fig. 2, each level conversion sub-module is a fully controlled H-bridge structure. This full accuse type H bridge structure includes: the bridge comprises two groups of power electronic device bridge arms and a direct current capacitor 16, wherein the two groups of power electronic device bridge arms are connected in parallel, each power electronic device bridge arm comprises two power electronic devices connected in series, and the direct current capacitor 16 is connected with the two groups of power electronic device bridge arms in parallel. Wherein, two power electronic devices are 2 IGTB devices respectively.
The invention discloses a modular multilevel converter, which has the specific working principle that: when a short-circuit overcurrent phenomenon occurs at a fault point of the modular multilevel converter, the current continues to flow through the follow current device 12, and then flows through the plurality of level conversion sub-modules 111 on each bridge arm branch. At this time, each group of level conversion control units 11 first determines whether the current input voltage of each bridge arm branch is greater than a first preset safe voltage, and then charges the dc capacitor 16 connected in parallel to each level conversion sub-module 111 based on the current if the current input voltage of each bridge arm branch is less than or equal to the first preset safe voltage, so that when the current output voltage of each level conversion sub-module 111 is greater than the second preset safe voltage, after the preset time, the first overvoltage protection device 13 quickly performs a switching action, so as to bypass the conversion submodule 111, and further trigger the voltage regulation controllable device 15 connected in parallel with each level conversion submodule 111 to perform an overvoltage protection action, so that the whole modular multilevel converter is in a safe state, i.e. all level conversion sub-modules 111 of the entire modular multilevel converter are brought into an off-state. In the above explanation, if the current input voltage of each leg branch is greater than the first preset safe voltage, all the level conversion sub-modules 111 of the entire modular multilevel converter are directly and rapidly switched off.
According to the modular multilevel converter disclosed by the embodiment of the invention, the input end and the output end of each bridge arm branch are connected through the second overvoltage protection device, and the output end of each level conversion submodule is also connected in parallel with the voltage regulation controllable device to work in a mutual matching manner, so that the whole modular multilevel converter can be ensured to be still in a safe state when overvoltage faults occur to the whole modular multilevel converter, and all level conversion submodules in the whole modular multilevel converter can be quickly cut off.
Based on the same concept, the embodiment of the present invention further discloses a modular multilevel converter control method, which is used for the modular multilevel converter in the above embodiment, as shown in fig. 3, and includes the following steps:
step S31: the current input voltage of the input end of each bridge arm branch of the multiple groups of level conversion control units and the current output voltage of the output ends of the multiple level conversion sub-modules on each bridge arm branch are obtained. Here, the present input voltage of each bridge arm branch input end of the multiple groups of level conversion control units is obtained simultaneously.
For example: in fig. 1, for the arm branch a, the current input voltage at the input end of the arm branch a is 166v, and the current input voltage at the input end of the arm branch b is 205 v. For example: and obtaining the current output voltage of the output ends of the plurality of level conversion sub-modules as 208 v. The current input voltage and the current output voltage may be collected by a voltage collection module.
Step S32: and judging whether the current input voltage is greater than a first preset safety voltage or not.
The first preset safe voltage is less than or equal to the sum of preset voltages of a plurality of level conversion sub-modules arranged on each bridge arm branch. The first preset safe voltage is the maximum reference safe voltage which ensures that the current input voltage of the input end of each bridge arm branch can be within the safe range voltage. For example: the first preset safe voltage is 200v, and the current input voltage 166v of the input end of the middle bridge arm branch a is compared with the first preset safe voltage of 200v, so that the obtained judgment result is that the current input voltage is smaller than the first preset safe voltage. For example: the current input voltage 166v of the input end of the bridge arm branch a is compared with the first preset safe voltage of 200v, so that the judgment result is that the current input voltage is smaller than the first preset safe voltage. For example: the current input voltage 208v of the input end of the bridge arm branch b is compared with the first preset safe voltage of 200v, so that the judgment result is that the current input voltage is greater than the first preset safe voltage.
Step S33: and if the current input voltage is greater than the first preset safety voltage, controlling the second overvoltage protection device to execute overvoltage protection action.
For example: in the above example, the current input voltage 208v of the input end of the bridge arm branch b is compared with the first preset safety voltage of 200v, so that the judgment result is that the current input voltage is greater than the first preset safety voltage, and at this time, the first overvoltage protection device (lightning arrester) is controlled to perform an overvoltage protection action, so that all level conversion sub-modules in the modular multilevel converter in the above embodiment are cut off, the modular multilevel converter can be ensured to be in a safe state, and the flexible low-frequency alternating-current power transmission system in which the modular multilevel converter is located can be ensured to be operated safely.
Step S34: and judging whether the current output voltage is greater than a second preset safety voltage.
The second preset safe voltage is the maximum reference safe voltage which ensures that the current output voltage of the plurality of level conversion sub-modules arranged on each bridge arm branch can be within the safe range voltage. For example: the second preset safety voltage is 220v, and the current output voltage of the medium three-phase alternating voltage output end D, E, F is compared with the second preset safety voltage, so that a judgment result is obtained. For example: the present output voltage of the three-phase alternating voltage output terminal D is 200v, the present output voltage of the three-phase alternating voltage output terminal E is 228v, and the present output voltage of the three-phase alternating voltage output terminal E is 232 v. As can be seen, 200v <220v,228v >220v,232v >220 v. Therefore, it can be known from the comparison that the current output voltage of the three-phase ac voltage output terminal D is smaller than the second preset safe voltage, the current output voltage of the three-phase ac voltage output terminal E is greater than the second preset safe voltage, and the current output voltage of the three-phase ac voltage output terminal F is greater than the second preset safe voltage.
Step S35: and if the current output voltage is greater than the second preset safe voltage, controlling the voltage-regulating controllable devices connected in parallel with the output end of each level conversion submodule to execute overvoltage protection action.
As can be seen from the foregoing illustration of the example, since 228v >220v,232v >220v, the current output voltage of the three-phase ac voltage output terminal E is greater than the second preset safe voltage, and the current output voltage of the three-phase ac voltage output terminal F is greater than the second preset safe voltage, an overvoltage phenomenon occurs in the current output voltages of the three-phase ac voltage output terminal E and the three-phase ac voltage output terminal F, and at this time, the voltage regulation controllable devices connected in parallel to each level conversion submodule are controlled, that is, in fig. 2, the bidirectional thyristor is controlled to perform an overvoltage protection action.
In an implementation manner, the modular multilevel conversion control method disclosed in the embodiment of the present invention, before step S31, further includes:
step S30: and if the multiple groups of level conversion control units detect that the multiple level conversion sub-modules on each bridge arm branch circuit have overvoltage faults, the first overvoltage protection device is controlled to execute overvoltage protection actions.
For example: when a flexible alternating-current low-frequency power transmission system where the modular multilevel converter is located has a fault, the first overvoltage protection device (the switch protection device) is controlled to execute an overvoltage protection action, namely, the level conversion sub-module with the fault is quickly bypassed, and simultaneously, all the level conversion sub-modules are quickly disconnected. At the moment, the modular multilevel converter is enabled to quickly execute a locking action, namely, the modular multilevel converter is enabled to be in an off state, and the driving signals of all level conversion sub-modules are locked out, namely, the power output is stopped. Therefore, the flexible alternating current low-frequency power transmission system where the modular multilevel converter is located can be quickly ensured to be in a safe state by controlling the first overvoltage protection device to execute the overvoltage protection action.
Therefore, when the current output voltage of the three-phase alternating voltage output end is greater than the second preset safety voltage, the current output voltage of the three-phase alternating voltage output end can be prevented from still presenting an overvoltage phenomenon on the basis of controlling the second overvoltage protection device to execute a protection action. Therefore, the modular multilevel converter control method disclosed in the embodiment of the invention can finally ensure that the whole modular multilevel converter is still in a safe state when overvoltage faults occur, namely all level conversion sub-modules in the whole modular multilevel converter can be quickly cut off.
In an implementation manner, a modular multilevel conversion control method in an embodiment of the present invention is further included in fig. 3:
step S36: and if the current input voltage is less than or equal to the first preset safe voltage, controlling each bridge arm branch to be in a normal working state. Here, when the current input voltage of the input end of each bridge arm branch of the multiple groups of level conversion control units is less than or equal to the first preset safe voltage, each bridge arm branch is controlled to be in a normal working state. When the current input voltage of the input end of any bridge arm branch is larger than the first preset safe voltage, the whole modular multilevel converter is in an unsafe state.
For example: as illustrated in the above example, the current input voltage at the input end of the bridge arm branch a is 166v, the first preset safe voltage is 200v, and 166v <200 v.
In an embodiment, the modular multilevel conversion control method in the embodiment of the present invention further includes:
step S37: and if the current output voltage is less than or equal to the second preset safe voltage, controlling the voltage-regulating controllable device connected in parallel with the output end of each level conversion submodule to be in a normal working state. Here, when the current output voltage of each ac voltage output terminal of the multiple sets of level conversion control units is less than or equal to the second preset safe voltage, the voltage-regulating controllable devices connected in parallel with the output terminals of each level conversion submodule are controlled to be in a normal working state. And once the current output voltage of any one alternating-current voltage output end is greater than the second preset safety voltage, the whole modular multilevel converter is in an unsafe state.
For example: as explained in the above example, the present output voltage of the three-phase alternating voltage output terminal E is 200v, 200v <220v, and thus the present output voltage of the three-phase alternating voltage output terminal E is within the safe voltage range. At this time, if the current output voltages of the other ac voltage output terminals are also less than or equal to the second preset safety voltage, it means that the entire modular multilevel converter is in a safe state.
Based on the same concept, the embodiment of the present invention further provides an electronic device, as shown in fig. 4, which may include a processor 41, a memory 42 and a modular multilevel converter 43, wherein the processor 41, the memory 42 and the modular multilevel converter 43 may be connected by a bus or in other manners, and the connection by the bus is taken as an example in fig. 4.
The processor 41 may be a Central Processing Unit (CPU). The Processor 41 may also be other general purpose processors, Digital Signal Processors (DSPs), Application Specific Integrated Circuits (ASICs), Field Programmable Gate Arrays (FPGAs) or other Programmable logic devices, discrete Gate or transistor logic devices, discrete hardware components, or combinations thereof.
The memory 42, which is a non-transitory computer readable storage medium, may be used to store non-transitory software programs, non-transitory computer executable programs, and modules, such as program instructions/modules corresponding to the modular multilevel conversion control method in the embodiments of the present invention. The processor 41 executes various functional applications and data processing of the processor by running non-transitory software programs, instructions and modules stored in the memory 42, that is, implements the modular multilevel conversion control method in the above method embodiment.
The memory 42 may include a storage program area and a storage data area, wherein the storage program area may store an operating system, an application program required for at least one function; the storage data area may store data created by the processor 41, and the like. Further, the memory 42 may include high speed random access memory, and may also include non-transitory memory, such as at least one magnetic disk storage device, flash memory device, or other non-transitory solid state storage device. In some embodiments, memory 42 may optionally include memory located remotely from processor 41, which may be connected to processor 41 via a network. Examples of such networks include, but are not limited to, the power grid, the internet, intranets, local area networks, mobile communication networks, and combinations thereof.
The one or more modules are stored in the memory 42 and, when executed by the processor 41, perform a modular multilevel conversion control method as in the embodiment of fig. 3.
The details of the electronic device may be understood by referring to the corresponding descriptions and effects in the embodiments shown in fig. 1 to fig. 3, and are not described herein again.
It will be understood by those skilled in the art that all or part of the processes of the methods of the embodiments described above can be implemented by a computer program, which can be stored in a computer-readable storage medium, and when executed, can include the processes of the embodiments of the methods described above. The storage medium may be a magnetic Disk, an optical Disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), a Flash Memory (Flash Memory), a Hard Disk (Hard Disk Drive, abbreviated as HDD), a Solid State Drive (SSD), or the like; the storage medium may also comprise a combination of memories of the kind described above.
It should be understood that the above examples are only for clarity of illustration and are not intended to limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. And obvious variations or modifications therefrom are within the scope of the invention.
Claims (12)
1. A modular multilevel converter comprising: the heterogeneous alternating voltage input that is located the power frequency side, multiunit level conversion the control unit and be located the heterogeneous alternating voltage output of low frequency side, wherein, every group level conversion the control unit and include: the bridge arm protection device comprises a plurality of bridge arm branches, each bridge arm branch is connected with an alternating current voltage input end through a follow current device, the output end of each group of level conversion control units is connected with an alternating current voltage output end, a plurality of level conversion sub-modules are arranged on each bridge arm branch, the output end of each level conversion sub-module is connected with a first overvoltage protection device in parallel, the bridge arm protection device is characterized in that the input end and the output end of each bridge arm branch are connected through at least one second overvoltage protection device, and the output end of each level conversion sub-module is further connected with a voltage regulation controllable device in parallel.
2. The modular multilevel converter according to claim 1, wherein the voltage regulation controllable device comprises: a bidirectional thyristor.
3. The modular multilevel converter according to claim 1, wherein each level conversion sub-module is a fully controlled H-bridge structure.
4. The modular multilevel converter of claim 3, wherein the fully-controlled H-bridge comprises: the bridge comprises two groups of power electronic device bridge arms and a direct current capacitor, wherein the two groups of power electronic device bridge arms are connected in parallel, each power electronic device bridge arm comprises two power electronic devices connected in series, and the direct current capacitor is connected with the two groups of power electronic device bridge arms in parallel.
5. The modular multilevel converter according to any of claims 1 to 4, wherein the freewheeling device is a direct current inductor, the first overvoltage protection device is a switching protection device, and the second overvoltage protection device is a surge arrester.
6. A modular multilevel converter control method for a modular multilevel converter according to any of claims 1 to 5, comprising:
acquiring the current input voltage of the input end of each bridge arm branch of a plurality of groups of level conversion control units and the current output voltage of the output ends of a plurality of level conversion sub-modules on each bridge arm branch;
judging whether the current input voltage is greater than a first preset safe voltage or not;
if the current input voltage is greater than the first preset safety voltage, controlling a second overvoltage protection device to execute overvoltage protection action;
judging whether the current output voltage is greater than a second preset safety voltage or not;
and if the current output voltage is greater than the second preset safety voltage, controlling the voltage-regulating controllable devices connected in parallel with the output end of each level conversion submodule to execute overvoltage protection action.
7. The modular multilevel conversion control method according to claim 6, further comprising, before the step of obtaining the current input voltage at the input terminal of each bridge arm branch of the plurality of sets of level conversion control units and the current output voltages at the output terminals of the plurality of level conversion sub-modules on each bridge arm branch:
and if the multiple groups of level conversion control units detect that the multiple level conversion sub-modules on each bridge arm branch circuit have overvoltage faults, the first overvoltage protection device is controlled to execute overvoltage protection actions.
8. The modular multilevel converter control method of claim 6, further comprising:
and if the current input voltage is less than or equal to the first preset safe voltage, controlling each bridge arm branch to be in a normal working state.
9. The modular multilevel converter control method of claim 6, further comprising:
and if the current output voltage is less than or equal to the second preset safe voltage, controlling the voltage-regulating controllable devices connected in parallel with the output end of each level conversion submodule to be in a normal working state.
10. The modular multilevel converter control method according to any one of claims 6 to 9, wherein the first preset safety voltage is less than or equal to a sum of preset voltages of a plurality of level conversion sub-modules arranged on each bridge arm branch.
11. A computer-readable storage medium storing computer instructions for causing a computer to perform the modular multilevel conversion control method of any one of claims 6 to 10.
12. An electronic device, comprising: modular multilevel converter according to any of claims 1 to 5, a memory and a processor, communicatively connected to each other, the memory having stored therein computer instructions, the processor performing the modular multilevel converter control method according to any of claims 6 to 10 by executing the computer instructions.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN114297874A (en) * | 2022-01-04 | 2022-04-08 | 国网浙江省电力有限公司电力科学研究院 | Method and system for determining capacitance value of frequency conversion valve submodule capacitor for flexible low-frequency power transmission |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN114297874A (en) * | 2022-01-04 | 2022-04-08 | 国网浙江省电力有限公司电力科学研究院 | Method and system for determining capacitance value of frequency conversion valve submodule capacitor for flexible low-frequency power transmission |
| CN114297874B (en) * | 2022-01-04 | 2023-03-10 | 国网浙江省电力有限公司电力科学研究院 | Method and system for determining capacitance value of frequency conversion valve submodule capacitor for flexible low-frequency power transmission |
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