CN114531050A - Energy-consumption type modular multilevel converter and control method - Google Patents
Energy-consumption type modular multilevel converter and control method Download PDFInfo
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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
- H02M7/00—Conversion of AC power input into DC power output; Conversion of DC power input into AC power output
- H02M7/02—Conversion of AC power input into DC power output without possibility of reversal
- H02M7/04—Conversion of AC power input into DC power output without possibility of reversal by static converters
- H02M7/12—Conversion of AC power input into DC power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/21—Conversion of AC power input into DC power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
- H02M7/217—Conversion of AC power input into DC power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
- H02M7/219—Conversion of AC power input into DC power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only in a bridge configuration
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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
- H02H7/1225—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 responsive to internal faults, e.g. shoot-through
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H9/00—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection
- H02H9/02—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection responsive to excess current
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for AC mains or AC distribution networks
- H02J3/36—Arrangements for transfer of electric power between AC networks via a high-tension DC link
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/60—Arrangements for transfer of electric power between AC networks or generators via a high voltage DC link [HVCD]
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Abstract
The invention belongs to the technical field of flexible direct current transmission, and relates to an energy-consuming modular multilevel converter and a control method thereof, wherein the energy-consuming modular multilevel converter comprises the following steps: the transverter adopts six arm structures of three-phase, including x looks current conversion arm and the power consumption arm of y looks in the three-phase, x + y is 3, and x, y are the integer that more than or equal to 0, and the current conversion arm includes the current conversion module of a plurality of series connection, includes a plurality of power consumption modules on the power consumption arm, and power consumption module includes an IGBT parallelly connected with energy storage capacitor, and under the normal operating condition, the IGBT shutting, power consumption arm are equivalent to current conversion arm, appear excessive pressure or when the shut down at the submodule piece, and the IGBT switches on, and energy storage capacitor discharges fast. The converter topology is optimized and adjusted on the basis of the traditional modularized multi-level converter, overvoltage suppression and surplus power suppression in normal converters and faults are achieved, and the converter topology has the advantages of being few in number of newly added devices, clear in action, compact in configuration, optimized in occupied area, high in economical efficiency and the like.
Description
Technical Field
The invention relates to an energy-consuming modular multilevel converter and a control method thereof, belonging to the technical field of flexible direct current transmission.
Background
The high-capacity flexible direct-current power transmission technology is a novel power transmission mode following alternating-current power transmission and conventional direct-current power transmission, has the characteristics of no charging power limitation of a direct-current line, realization of decoupling of a new energy electric field and an alternating-current power grid and the like, has a plurality of technical advantages of no need of commutation voltage, no commutation failure, capability of alternating-current fault ride-through, high voltage waveform quality, capability of independently controlling active power and reactive power and the like, can realize access and transmission of multiple energy sources such as large-scale wind power, photovoltaic and pumped storage, and is an important development direction for large-scale new energy access.
For a flexible direct current transmission system with a transmitting end island connected with new energy (such as wind power, photovoltaic and the like), when temporary faults such as grounding of a receiving end alternating current power grid occur, active power absorption capacity of a receiving end converter station is reduced due to the fact that alternating current voltage drops, at the moment, a transmitting end new energy unit still continuously outputs active power within a short time, the system generates large surplus power, and direct current voltage of the system rapidly rises. If corresponding control measures are not taken, the direct current voltage rise can further cause system protection action to lock the converter valve, and meanwhile, the alternating current voltage of a grid-connected point of new energy at a sending end can be subjected to linked fluctuation, large-area network disconnection of the new energy, particularly a wind turbine generator, is caused, and the system availability is greatly reduced. Considering that the restart time of the new energy and direct current output system is long, once the system is forced to stop running due to the failure of ride-through under the fault of a receiving end alternating current power grid, serious economic loss can be caused, and larger impact can be generated on the power grid, so that the safe and stable running of the system is influenced.
The existing thinking for solving the problems is to configure a flexible and controllable energy consumption device so as to realize the power balance of the system and avoid the occurrence of energy surplus. The energy dissipation device can be divided into an alternating current energy dissipation device and a direct current energy dissipation device according to different access positions. However, for the offshore wind power flexible direct-transmission system, the offshore platform is short in area, difficult to operate and maintain and high in manufacturing cost, and the arrangement of the alternating current energy consumption device on the alternating current side of the offshore transmitting-end converter station is not practical. The direct current energy consumption device is a solution mainly adopted in the field of offshore wind power flexible and direct transmission at present, and a large number of power devices or module capacitors need to be additionally introduced; in addition, the independently arranged energy consumption branches may need to be provided with a wall bushing, a current limiting reactor, a switch, a measuring device and the like, and the whole set of energy consumption solution has poor economy.
Disclosure of Invention
In view of the above problems, an object of the present invention is to provide an energy-consuming modular multilevel converter and a control method thereof, which optimize and adjust the topology of the converter based on the traditional modular multilevel converter, and simultaneously have overvoltage suppression and surplus power suppression in normal converter and fault, and have the advantages of small number of newly added devices, clear function, compact configuration, optimized floor area, high economy, etc.
In order to achieve the purpose, the invention provides the following technical scheme: a modular multilevel converter of the energy consuming type, comprising: the transverter adopts six arm structures of three-phase, including x looks current conversion arm and the power consumption arm of y looks in the three-phase, x + y is 3, and x, y are the integer that more than or equal to 0, and the current conversion arm includes the current conversion module of a plurality of series connection, includes a plurality of power consumption modules on the power consumption arm, and power consumption module includes an IGBT parallelly connected with energy storage capacitor, and under the normal operating condition, the IGBT shutting, power consumption arm are equivalent to current conversion arm, appear excessive pressure or when the shut down at the submodule piece, and the IGBT switches on, and energy storage capacitor discharges fast.
Furthermore, each phase of the current conversion arm and each energy consumption arm respectively comprise an upper bridge arm and a lower bridge arm, each bridge arm comprises a plurality of current conversion modules or energy consumption modules which are connected in series, each bridge arm is provided with a buffer inductor, and the buffer inductors are used for inhibiting the circulation current and the fault current rise rate.
Further, the current conversion arm comprises two serially connected submodules, a bypass switch, a bypass thyristor, an energy storage capacitor and a voltage-sharing resistor, wherein the energy storage capacitor and the voltage-sharing resistor are both connected in parallel with the two serially connected submodules, and the energy storage capacitor is connected in parallel with the voltage-sharing resistor; the bypass switch and the bypass thyristor are both connected in parallel with one of the submodules, and the bypass switch and the bypass thyristor are connected in parallel.
Furthermore, the energy consumption module comprises two serially connected submodules, a bypass switch, a bypass thyristor, an energy storage capacitor, a voltage-sharing resistor, a third submodule and an energy consumption resistor, wherein the energy storage capacitor and the voltage-sharing resistor are both connected with the two serially connected submodules in parallel, and the energy storage capacitor is connected with the voltage-sharing resistor in parallel; the bypass switch and the bypass thyristor are connected in parallel with one of the submodules, the bypass switch and the bypass thyristor are connected in parallel, the third submodule and the energy consumption resistor are connected in parallel with the energy storage capacitor, and the third submodule and the energy consumption resistor are connected in series.
Furthermore, the three sub-modules have the same structure and each sub-module comprises an IGBT and a diode connected with the IGBT in an anti-parallel mode.
Further, the energy consuming module comprises two modes of operation: in the normal mode, the IGBT in the third sub-module is locked, the sub-module connected with the bypass switch and the bypass thyristor in parallel is switched on, and when the other sub-module is locked, the sub-module is in a cut-off state, and the output voltage is zero; the sub-module connected with the bypass switch and the bypass thyristor in parallel is locked, when the other sub-module is switched on, the sub-module is in an input state, and the output voltage is the voltage of the energy storage capacitor; the energy consumption mode is activated when the sub-modules are in overvoltage and shutdown, the IGBT in the third sub-module is conducted, and the energy storage capacitor is rapidly discharged through the energy consumption resistor.
The invention also discloses a control method of the energy-consuming type modular multilevel converter, which adopts any one of the energy-consuming type modular multilevel converters and comprises the following steps: when the converter is in normal operation, the IGBT in the third sub-module of the energy consumption module is locked, and the energy consumption arm is equivalent to a converter arm; when the alternating current side has faults, the system power surplus is caused, and the direct current side voltage is too high, a power surplus inhibition control strategy is entered; if only the energy storage capacitors in the individual current conversion modules or the energy consumption modules are in overvoltage, entering a temporary energy consumption control strategy; when the operation is stopped, the rapid discharge is needed, and an accelerated discharge control strategy is entered.
Further, the power surplus suppression control strategy is as follows: determining the input number of energy consumption modules according to the surplus power, and performing energy consumption by the energy consumption modules with high voltage of the conducting capacitor in turn; when the IGBT in the third sub-module of the energy consumption module is conducted, the current passing through the energy consumption resistor is equal to the sum of the bridge arm current and the energy storage capacitor discharge current of the energy consumption module, and the energy storage capacitor voltage of the energy consumption module is reduced; when the IGBT in the third sub-module is turned off, the current passing through the energy consumption resistor is zero, the total current of the bridge arm is equal to the sum of the charging currents of the energy storage capacitors of the energy consumption modules on the bridge arm, the voltage of the energy storage capacitors of the energy consumption modules is increased, the total energy consumption power of the energy consumption arms is in direct proportion to the input number of the energy consumption modules, and the total energy consumption power of the energy consumption arms reaches the maximum when all the energy consumption modules are input.
Further, the temporary energy consumption control strategy is as follows: when the voltage of the energy consumption module exceeds the preset upper limit Usm(up)When the energy consumption module is in the energy consumption mode, the energy consumption sub-module is reduced to the preset lower limit Usm(low)And if so, the energy consumption module exits the energy consumption mode and enters a normal mode.
Further, the accelerated discharge control strategy comprises the steps of: entering a shutdown strategy, locking the converter, and tripping off the converter transformer incoming line breaker; unlocking a y-phase converter arm of the converter, and controlling the output voltage not to exceed the direct-current voltage; and controlling n energy consumption modules of the x-phase energy consumption arm to enter an energy consumption mode, and accelerating discharge until the control board card cannot be electrified.
Due to the adoption of the technical scheme, the invention has the following advantages:
1. the invention optimizes and adjusts the converter topology on the basis of the traditional modularized multi-level converter, simultaneously has overvoltage suppression and surplus power suppression in normal converter and fault, and has the advantages of less newly added equipment, clear action, compact configuration, optimized floor area, higher economy and the like.
2. The control method has the characteristics of simple and easy steps, clearness and the like, and can effectively solve the problems of difficult power surplus inhibition caused by the fault of the alternating current system, long power failure time in the outage process and the like.
3. In the switching process of an energy consumption device configured independently in the conventional method, the sub-module capacitor has a continuous charging and discharging process, and the sub-module capacitor is large (mF level) in order to limit the voltage fluctuation of the sub-module; the energy consumption power of each distributed energy consumption resistor is MW level, and the distributed energy consumption resistors and the power devices are integrated in the sub-modules, so that the heat dissipation design requirement is high, and a special internal and external cooling system needs to be configured; the invention can share the existing auxiliary system of the original converter, and the cost efficiency is obviously improved.
Drawings
Fig. 1 is a schematic structural diagram of a power consumption type modular multilevel converter according to an embodiment of the invention;
fig. 2 is a schematic structural diagram of a commutation module according to an embodiment of the present invention;
FIG. 3 is a schematic diagram of an energy consuming module according to an embodiment of the present invention;
fig. 4 is an electrical equivalent diagram of the energy consumption arm in the energy consumption state according to an embodiment of the present invention, and fig. 4(a) is a schematic diagram of an operation mode of the energy consumption module of the energy consumption arm; fig. 4(b) is an electrical equivalent circuit diagram of the dissipative arm dissipative module, wherein the sub-mode connected to the positive pole corresponds to the dissipative mode; the sub-mode connected to the negative electrode corresponds to the normal mode.
Detailed Description
The present invention is described in detail with reference to specific embodiments for better understanding of the technical solutions of the present invention. It should be understood, however, that the detailed description is provided for a better understanding of the invention only and that they should not be taken as limiting the invention. In describing the present invention, it is to be understood that the terminology used is for the purpose of description only and is not intended to be indicative or implied of relative importance.
In order to solve the problem that a large number of power devices or module capacitors are additionally introduced in the prior art; the independently arranged energy-consuming branches require the whole set of energy-consuming solutions to have poor economy. The invention provides an energy-consumption type modular multilevel converter and a control method thereof, wherein a three-phase six-bridge arm structure is adopted, and the converter is composed of x converter arms and y energy-consumption arms (x + y is 3, x is more than or equal to 0, and y is more than or equal to 0). In normal operation, the IGBT in the energy consumption module is locked, and the energy consumption arm is equivalent to a current conversion arm; and surplus power suppression and direct-current voltage overvoltage suppression can be realized through the input of the energy consumption module during fault. Compared with the conventional method of independently configuring the direct current energy consumption device, the method saves a large number of power devices and capacitors, has good economy and high technical maturity, and can be widely applied to the technical field of flexible direct current power transmission, particularly offshore wind power flexible direct output. The invention will be explained in detail by means of embodiments with reference to the accompanying drawings.
Example one
The embodiment discloses a power consumption type modular multilevel converter, as shown in fig. 1, including: the transverter adopts six arm structures of three-phase, including x looks current conversion arm and the power consumption arm of y looks in the three-phase, x + y is 3, and x, y are the integer that more than or equal to 0, current conversion arm includes the current conversion module (SM) of a plurality of series connections, including a plurality of power consumption modules (CSM) on the power consumption arm, power consumption module includes one and the parallelly connected IGBT of energy storage capacitor, under the normal operating condition, the IGBT shutting, power consumption arm is equivalent to current conversion arm, when the submodule piece appears excessive pressure or the shut down, the IGBT switches on, energy storage capacitor discharges fast.
Each phase of current conversion arm and each energy consumption arm respectively comprises an upper bridge arm and a lower bridge arm, each bridge arm comprises a plurality of current conversion modules or energy consumption modules which are connected in series, each bridge arm is provided with a buffer inductor, and the buffer inductors are used for inhibiting circulation currents and the rise rate of fault current.
As shown in fig. 2, the commutation arm includes two serially connected submodules, a bypass switch, a bypass thyristor, an energy storage capacitor and a voltage-sharing resistor, wherein the energy storage capacitor and the voltage-sharing resistor are both connected in parallel with the two serially connected submodules, and the energy storage capacitor and the voltage-sharing resistor are connected in parallel; the bypass switch and the bypass thyristor are both connected in parallel with one of the submodules, and the bypass switch and the bypass thyristor are connected in parallel. The three sub-modules have the same structure and each sub-module comprises an IGBT and a diode connected with the IGBT in an anti-parallel mode.
As shown in fig. 3, the energy consumption module includes two serially connected submodules, a bypass switch, a bypass thyristor, an energy storage capacitor, a voltage-sharing resistor, a third submodule, and an energy consumption resistor, wherein the energy storage capacitor and the voltage-sharing resistor are both connected in parallel with the two serially connected submodules, and the energy storage capacitor and the voltage-sharing resistor are connected in parallel; the bypass switch and the bypass thyristor are connected in parallel with one of the submodules, the bypass switch and the bypass thyristor are connected in parallel, the third submodule and the energy consumption resistor are connected in parallel with the energy storage capacitor, and the third submodule and the energy consumption resistor are connected in series.
As shown in fig. 4, the energy consuming module includes two modes of operation: a normal mode and an energy consumption mode,
in a normal mode, the IGBT in the third sub-module is locked, the sub-module connected with the bypass switch and the bypass thyristor in parallel is switched on, and when the other sub-module is locked, the sub-module is in a cut-off state, and the output voltage is zero; the sub-module connected with the bypass switch and the bypass thyristor in parallel is locked, when the other sub-module is switched on, the sub-module is in an input state, and the output voltage is the voltage of the energy storage capacitor;
the energy consumption mode is activated when the sub-modules are in overvoltage and need to be accelerated to discharge when the sub-modules are stopped, the IGBT in the third sub-module is conducted, and the energy storage capacitor is rapidly discharged through the energy consumption resistor.
Example two
Based on the same inventive concept, the embodiment discloses a control method of an energy-consuming modular multilevel converter, which adopts any one of the energy-consuming modular multilevel converters, and comprises the following steps: when the converter is in normal operation, the IGBT in the third sub-module of the energy consumption module is locked, the energy consumption arm is equivalent to a current conversion arm, and the converter is operated in a normal mode; when the alternating current side has faults, the system power surplus is caused, and the direct current side voltage is too high, a power surplus inhibition control strategy is entered; if only the energy storage capacitors in the individual current conversion modules or the energy consumption modules are in overvoltage, entering a temporary energy consumption control strategy; when the operation is stopped, the rapid discharge is needed, and an accelerated discharge control strategy is entered.
The power surplus inhibition control strategy is as follows: determining the input number of energy consumption modules according to the surplus power, and performing energy consumption by the energy consumption modules with high voltage of the conducting capacitor in turn; when the IGBT in the third sub-module of the energy consumption module is conducted, the current passing through the energy consumption resistor is equal to the sum of the bridge arm current and the energy storage capacitor discharge current of the energy consumption module, and the energy storage capacitor voltage of the energy consumption module is reduced; when the IGBT in the third sub-module is turned off, the current passing through the energy consumption resistor is zero, the total current of the bridge arm is equal to the sum of the charging currents of the energy storage capacitors of the energy consumption modules on the bridge arm, the voltage of the energy storage capacitors of the energy consumption modules is increased, the total energy consumption power of the energy consumption arms is in direct proportion to the input number of the energy consumption modules, and the total energy consumption power of the energy consumption arms reaches the maximum when all the energy consumption modules are input.
In the power surplus inhibition control strategy, when the direct current voltage rises to a preset value Udc(set)And then, the following conditions are met, and a power surplus suppression control strategy is input.
Udc≥Udc(set) (1)
In the process of power surplus inhibition, the total number of energy consumption type submodules input by an upper bridge arm and a lower bridge arm of an energy consumption arm is N, the number of the submodules in an energy consumption mode is N, and direct-current voltage is UdcCurrent of the energy dissipation arm is IRThe total energy consumption power of each energy consumption arm is P, and the maximum energy consumption power is PmaxThen, there are:
Ptotal＝xP (6)
Ptotal(max)＝xPmax (7)
the temporary energy consumption control strategy is as follows: when the voltage of the energy consumption module exceeds the preset upper limit Usm(up)When the energy consumption module is in the energy consumption mode, the energy consumption sub-module is reduced to the preset lower limit Usm(low)And if so, the energy consumption module exits the energy consumption mode and enters a normal mode.
The accelerated discharge control strategy comprises the steps of: entering a shutdown strategy, locking the converter, and tripping off the converter transformer incoming line breaker; unlocking a y-phase converter arm of the converter, and controlling the output voltage not to exceed the direct-current voltage; and controlling n energy consumption modules of the x-phase energy consumption arm to enter an energy consumption mode, and accelerating discharge until the control board card cannot be electrified.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solutions of the present invention and not for limiting the same, and although the present invention is described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: modifications and equivalents may be made to the embodiments of the invention without departing from the spirit and scope of the invention, which is to be covered by the claims. The above description is only for the specific embodiments of the present application, but the scope of the present application is not limited thereto, and any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present application, and shall be covered by the scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.
Claims (10)
1. A modular multilevel converter of the energy consuming type, comprising: the converter adopts six arm structures of three-phase, including x looks current conversion arm and the power consumption arm of y looks in the three-phase, x + y is 3, and x, y are the integer more than or equal to 0, the current conversion arm includes the current conversion module of a plurality of series connections, including a plurality of power consumption modules on the power consumption arm, power consumption module includes an IGBT parallelly connected with energy storage capacitor, under the normal operating condition, IGBT shutting, power consumption arm are equivalent to current conversion arm, and when the submodule piece appeared excessive pressure or shut down, IGBT switched on, energy storage capacitor discharged fast.
2. The energy consuming modular multilevel converter according to claim 1, wherein each of the converter arms and the energy consuming arms comprises an upper bridge arm and a lower bridge arm, each bridge arm comprises a plurality of converter modules or energy consuming modules connected in series, and each bridge arm is provided with a buffer inductor for suppressing circulating currents and the rate of rise of fault current.
3. The energy consuming modular multilevel converter according to claim 2, wherein the converter arm comprises two serially connected submodules, a bypass switch, a bypass thyristor, an energy storage capacitor and a voltage-sharing resistor, wherein the energy storage capacitor and the voltage-sharing resistor are both connected in parallel with the two serially connected submodules, and the energy storage capacitor is connected in parallel with the voltage-sharing resistor; the bypass switch and the bypass thyristor are both connected in parallel with one of the submodules, and the bypass switch and the bypass thyristor are connected in parallel.
4. The energy consuming modular multilevel converter according to claim 2, wherein the energy consuming module comprises two serially connected submodules, a bypass switch, a bypass thyristor, an energy storage capacitor, a voltage-sharing resistor, a third submodule and an energy consuming resistor, wherein the energy storage capacitor and the voltage-sharing resistor are both connected in parallel with the two serially connected submodules, and the energy storage capacitor is connected in parallel with the voltage-sharing resistor; the bypass switch and the bypass thyristor are connected in parallel with one of the submodules, the bypass switch and the bypass thyristor are connected in parallel, the third submodule and the energy consumption resistor are connected in parallel with the energy storage capacitor, and the third submodule and the energy consumption resistor are connected in series.
5. The energy consuming modular multilevel converter according to claim 3 or 4, wherein the three sub-modules have the same structure and each comprises an IGBT and a diode connected in anti-parallel with the IGBT.
6. The energy consuming modular multilevel converter according to claim 4, wherein the energy consuming module comprises two operation modes: in the normal mode, the IGBT in the third sub-module is locked, the sub-module connected with the bypass switch and the bypass thyristor in parallel is switched on, and when the other sub-module is locked, the sub-module is in a cut-off state, and the output voltage is zero; the sub-module connected with the bypass switch and the bypass thyristor in parallel is locked, when the other sub-module is switched on, the sub-module is in an input state, and the output voltage is the voltage of the energy storage capacitor; the energy consumption mode is activated when the sub-modules are in overvoltage and shutdown, the IGBT in the third sub-module is conducted, and the energy storage capacitor is rapidly discharged through the energy consumption resistor.
7. A method for controlling a modular multilevel converter according to any of claims 1-6, comprising:
when the energy consumption module normally operates, the IGBT in the third sub-module of the energy consumption module is locked, the energy consumption arm is equivalent to a current conversion arm, and the energy consumption mode operates in a normal mode;
when the alternating current side has faults, the system power surplus is caused, and the direct current side voltage is too high, a power surplus inhibition control strategy is entered;
if only the energy storage capacitors in the individual current conversion modules or the energy consumption modules are in overvoltage, entering a temporary energy consumption control strategy;
when the operation is stopped, the rapid discharge is needed, and an accelerated discharge control strategy is entered.
8. The method of claim 7, wherein the power surplus suppression control strategy is: determining the input number of energy consumption modules according to the surplus power, and conducting energy consumption modules with corresponding number in turn to consume energy; when the IGBT in the third sub-module of the energy consumption module is conducted, the current passing through the energy consumption resistor is equal to the sum of the bridge arm current and the energy storage capacitor discharge current of the energy consumption module, and the energy storage capacitor voltage of the energy consumption module is reduced; when the IGBT in the third sub-module is turned off, the current passing through the energy consumption resistor is zero, the total current of the bridge arm is equal to the sum of the charging currents of the energy storage capacitors of the energy consumption modules on the bridge arm, the voltage of the energy storage capacitors of the energy consumption modules is increased, the total energy consumption power of the energy consumption arms is in direct proportion to the input number of the energy consumption modules, and the total energy consumption power of the energy consumption arms reaches the maximum when all the energy consumption modules are input.
9. The method of controlling a power consuming modular multilevel converter according to claim 7, wherein the temporary power consuming control strategy is: when the voltage of the energy consumption module exceeds a preset upper limit Usm(up)And when the energy consumption module is in the energy consumption mode, the energy consumption module is reduced to a preset lower limit Usm(low)And if so, the energy consumption module exits the energy consumption mode and enters a normal mode.
10. The method of controlling a power consuming modular multilevel converter according to claim 7, wherein the boost discharge control strategy comprises the steps of: entering a shutdown strategy, locking the converter, and tripping off the converter transformer incoming line breaker; unlocking a y-phase converter arm of the converter, and controlling the output voltage of the converter not to exceed the direct-current voltage; and controlling n energy consumption modules in the x-phase energy consumption arm to enter an energy consumption mode, and accelerating discharge until the control board card cannot be electrified.
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