CN111211675A - Submodule redundancy configuration method and system of modular multilevel converter - Google Patents
Submodule redundancy configuration method and system of modular multilevel converter 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
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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
- H02M1/325—Means for protecting converters other than automatic disconnection with means for allowing continuous operation despite a fault, i.e. fault tolerant converters
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Abstract
The invention discloses a submodule redundancy configuration method and a submodule redundancy configuration system of a modular multilevel converter, wherein the method comprises the following steps: determining the number of fault sub-modules in the modular multilevel converter; calculating to obtain the capacitance reference voltage of the sub-modules of the modular multilevel converter based on the number of the fault sub-modules; acquiring a target output voltage of an upper bridge arm and a target output voltage of a lower bridge arm of the modular multilevel converter; and determining the number of the submodules input by the upper bridge arm by using the capacitance reference voltage and the target output voltage of the upper bridge arm, and determining the number of the submodules input by the lower bridge arm by using the capacitance reference voltage and the target output voltage of the lower bridge arm. The invention keeps the maximum voltage output capability by increasing the capacitor voltage, thereby leading the system to operate stably and enhancing the fault ride-through capability; the loss of the converter valve is reduced, the redundant module is fully utilized, the harmonic content of the output voltage is reduced, and the operation performance of the modular multilevel converter is optimized.
Description
Technical Field
The invention relates to the field of flexible direct current transmission, in particular to a submodule redundancy configuration method and a submodule redundancy configuration system of a modular multilevel converter.
Background
The Modular Multilevel Converter (MMC) has the advantages of high modularization degree, low switching frequency, low harmonic content, flexible and independent control of active and reactive power and the like, is widely applied to the field of medium and high voltage direct current transmission, and is an important technical scheme for constructing a future power grid and transmitting clean energy.
A single bridge arm of the high-voltage large-capacity MMC comprises hundreds of power sub-modules, the output voltage of the bridge arm is formed by superposing the output voltage of each sub-module, in order to ensure that the MMC operates continuously when the sub-modules have faults and improve the operation reliability, redundant sub-modules are configured in engineering, once a sub-module has a fault, a bypass switch acts to cut off the sub-module, and then the redundant module is put into place for operating the fault module. In the existing high-voltage large-capacity MMC engineering, 6% -15% of unequal redundancy sub-modules are configured and used for enabling the MMC to normally operate after sub-module bypass faults occur, and the sub-module redundancy configuration method of the engineering at the current stage adopts the following steps: in the fault-free period, the redundant module only participates in the voltage-sharing switching of the capacitor, and the maximum output level number of the system is not increased; when sub-module faults occur, the redundant module can replace the fault module to participate in maximum level construction, and therefore the redundant module is not fully utilized.
Disclosure of Invention
In view of this, embodiments of the present invention provide a sub-module redundancy configuration method and system for a modular multilevel converter, so as to solve the problems in the prior art that capacitive devices are damaged by overvoltage and redundant modules are not fully utilized due to the fact that the total input power of the system is greater than the output power of the system.
In order to achieve the purpose, the invention provides the following technical scheme:
in a first aspect, an embodiment of the present invention provides a sub-module redundancy configuration method for a modular multilevel converter, including the following steps: determining the number of fault sub-modules in the modular multilevel converter; calculating to obtain the capacitance reference voltage of the sub-modules of the modular multilevel converter based on the number of the fault sub-modules; acquiring a target output voltage of an upper bridge arm and a target output voltage of a lower bridge arm of the modular multilevel converter; and determining the number of the sub-modules input by the upper bridge arm by using the capacitance reference voltage and the target output voltage of the upper bridge arm, and determining the number of the sub-modules input by the lower bridge arm by using the capacitance reference voltage and the target output voltage of the lower bridge arm.
In an embodiment, the obtaining of the target output voltage of the upper leg and the target output voltage of the lower leg of the modular multilevel converter includes the following steps: acquiring direct-current terminal voltage and alternating-current terminal voltage of the modular multilevel converter; and calculating to obtain the target output voltage of the upper bridge arm and the target output voltage of the lower bridge arm by using the direct-current terminal voltage and the alternating-current terminal voltage.
In one embodiment, the target output voltage of the upper leg and the target output voltage of the lower leg are calculated by the following formulas:
wherein u ispa(t) represents a target output voltage of the upper arm, una(t) represents a target output voltage of the lower arm, UdcRepresents the voltage of the DC terminal usa(t) represents the ac terminal voltage.
In an embodiment, the calculating to obtain the capacitance reference voltage of the sub-modules of the modular multilevel converter based on the number of the faulty sub-modules includes the following steps: acquiring the number of the conventional sub-modules and the total number of the redundant sub-modules, wherein the number of the conventional sub-modules is the number of the sub-modules which are normally put into use under the condition of no fault, and the total number of the redundant sub-modules is the number of all the redundant sub-modules which are preset; and calculating to obtain the capacitance reference voltage by utilizing the number of the conventional sub-modules, the total number of the redundant sub-modules and the number of the fault sub-modules.
In one embodiment, the sub-module capacitance reference voltage is calculated by the following equation:
wherein u iscDenotes the capacitive reference voltage, U, of the submoduledcRepresenting the voltage of the direct current terminal, N representing the number of the conventional submodules, NrRepresenting the total number of said redundant sub-modules, NrAnd (t) representing the number of the fault sub-modules.
In an embodiment, after determining the number of the sub-modules put into the upper arm by using the capacitive reference voltage and the target output voltage of the upper arm and determining the number of the sub-modules put into the lower arm by using the capacitive reference voltage and the target output voltage of the lower arm, the method further includes: and calculating the number of redundant sub-modules to be used by utilizing the number of the sub-modules put into the upper bridge arm, the number of the sub-modules put into the lower bridge arm and the number of the fault sub-modules.
In an embodiment, the number of the sub-modules inputted by the upper bridge arm and the number of the sub-modules inputted by the lower bridge arm are calculated by the following formulas:
wherein N ispa(t) represents the number of submodules put into the upper bridge arm, Nna(t) represents the number of submodules thrown into the lower bridge arm, round (x) represents an integer function, upa(t) represents a target output voltage of the upper arm, una(t) represents a target output voltage of the lower arm, uc-representing a capacitive reference voltage of said sub-module.
In a second aspect, an embodiment of the present invention provides a sub-module redundancy configuration system for a modular multilevel converter, including: the fault sub-module number determining module is used for determining the number of fault sub-modules in the modular multilevel converter; the calculation module is used for calculating and obtaining the capacitance reference voltage of the sub-modules of the modular multilevel converter based on the number of the fault sub-modules; the acquisition module is used for acquiring a target output voltage of an upper bridge arm and a target output voltage of a lower bridge arm of the modular multilevel converter; and the input sub-module number determining module is used for determining the number of the input sub-modules of the upper bridge arm by using the capacitance reference voltage and the target output voltage of the upper bridge arm and determining the number of the input sub-modules of the lower bridge arm by using the capacitance reference voltage and the target output voltage of the lower bridge arm.
In a third aspect, an embodiment of the present invention provides an electronic device, including: the modular multilevel converter comprises at least one processor and a memory which is connected with the at least one processor in a communication mode, wherein the memory stores instructions which can be executed by the at least one processor, and the instructions are executed by the at least one processor so as to enable the at least one processor to execute the submodule redundancy configuration method of the modular multilevel converter in the first aspect of the embodiment of the invention.
In a fourth aspect, an embodiment of the present invention provides a computer-readable storage medium, where computer instructions are stored, and the computer instructions are configured to cause a computer to execute the sub-module redundancy configuration method for a modular multilevel converter according to the first aspect of the embodiment of the present invention.
The technical scheme of the invention has the following advantages:
according to the submodule redundancy configuration method and system of the modular multilevel converter, the capacitance reference voltage of the submodule of the modular multilevel converter is calculated according to the number of the fault submodules, and then the number of the submodules which are input by the upper bridge arm and the lower bridge arm is respectively determined by using the capacitance reference voltage and the target output voltages of the upper bridge arm and the lower bridge arm, so that the capacitance voltage base value is reduced, and the loss of a converter valve is reduced; when the number of fault modules is greater than that of redundant modules, the system can also keep the maximum voltage output capability in a mode of increasing the capacitor voltage, so that violent oscillation cannot be generated, the system can still stably operate, and the fault ride-through capability is enhanced; and the redundant module is fully utilized, the voltage sharing is participated, the level number of a system can be increased, the harmonic content of output voltage is reduced, and the operation performance of the modular multilevel converter is optimized.
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 flowchart of a specific example of a sub-module redundancy configuration method of a modular multilevel converter according to an embodiment of the present invention;
fig. 2 is a topology structure diagram of a modular multilevel converter according to an embodiment of the present invention;
fig. 3 is a flowchart of a specific example of obtaining a target output voltage according to an embodiment of the present invention;
FIG. 4 is a flowchart of a specific example of calculating a capacitance reference voltage according to an embodiment of the present invention;
fig. 5 is a flowchart of a specific example of calculating the number of redundant sub-modules put into use according to the embodiment of the present invention;
FIG. 6 is a diagram illustrating simulation results of voltage waveforms of capacitors according to an embodiment of the present invention;
FIG. 7 is a diagram of device loss simulation results provided by an embodiment of the present invention;
fig. 8 is a diagram of a simulation result of a sub-module fault ride-through waveform in the conventional redundancy configuration method according to an embodiment of the present invention;
fig. 9 is a simulation result diagram of sub-module fault ride-through waveforms of the sub-module redundancy configuration method of the modular multilevel converter according to the embodiment of the present invention;
fig. 10 is a schematic diagram of a sub-module redundancy configuration system of a modular multilevel converter according to an embodiment of the present invention;
fig. 11 is a composition diagram of a specific example of an electronic device according to an embodiment of the present invention.
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.
Example 1
The embodiment of the invention provides a submodule redundancy configuration method of a modular multilevel converter, which comprises the following steps as shown in figure 1:
step S1: and determining the number of fault sub-modules in the modular multilevel converter.
In the embodiment of the invention, as shown in fig. 2, a single bridge arm of the modular multilevel converter comprises hundreds of power sub-modules, the sub-modules can be divided into a half H-bridge type, a full H-bridge type and a double-clamping type, once a sub-module fails, a bypass switch can act to cut off the failed sub-module, then a redundant module is put into place for the failed module to operate, the system can detect the failed module through a fault detector, if the sub-module fails, the fault detector adds 1 to the statistics of the failed sub-module and feeds back the statistics to the system, so that the number of the failed sub-modules in the modular multilevel converter can be determined, wherein the fault detector can be a chip or an actual detection program, and the invention is not limited by the invention.
Step S2: and calculating to obtain the capacitance reference voltage of the sub-modules of the modular multilevel converter based on the number of the fault sub-modules.
In the embodiment of the invention, the capacitance reference voltage of the sub-modules is calculated by dividing the voltage of the direct current end of the current converter by the total number of the normal operation modules, wherein the total number of the normal operation modules can be the sum of the numbers of the conventional sub-modules and the redundant sub-modules, can also be the total number of the conventional sub-modules, the redundant sub-modules and the fault sub-modules, can also be a base number or weighted processing, and can be correspondingly adjusted according to the actual needs of the system in practical application, the proportion of each sub-module and the like, and the invention is not limited by the.
In practical application, each submodule of the modular multilevel converter is provided with a capacitor, the capacitors are not interfered with each other, the capacitor reference voltage of the submodule of the modular multilevel converter is obtained through calculation based on the number of fault submodules, the converter cannot accurately control the continuous charging and discharging process of the submodules when working, and in addition, problems of operation loss and the like can cause the phenomenon of voltage imbalance among the capacitors of the submodules, so that the converter is abnormal in operation, therefore, the capacitor voltage of the submodules needs to be kept in real time, and the converter can normally operate only if the capacitor voltage of the submodules is balanced and stable.
Step S3: and acquiring the target output voltage of an upper bridge arm and the target output voltage of a lower bridge arm of the modular multilevel converter.
In the embodiment of the invention, the target output voltage of the upper bridge arm and the target output voltage of the lower bridge arm of the modular multilevel converter are determined according to the preset alternating-current end voltage and direct-current end voltage of the system, wherein the target output voltages are obtained through preset parameters, and the target output voltages simultaneously determine the adjustment of subsequent modules and the calculation of the number of the input sub-modules.
Step S4: and determining the number of the submodules input by the upper bridge arm by using the capacitance reference voltage and the target output voltage of the upper bridge arm, and determining the number of the submodules input by the lower bridge arm by using the capacitance reference voltage and the target output voltage of the lower bridge arm.
In the embodiment of the invention, the number of the submodules input into the upper bridge arm is obtained by rounding (x) the ratio of the target output voltage of the upper bridge arm to the reference voltage of the capacitor, and the number of the submodules input into the lower bridge arm is obtained by rounding (x) the ratio of the target output voltage of the lower bridge arm to the reference voltage of the capacitor, wherein the round (x) function returns a numerical value which is the result of rounding operation according to the specified decimal place. It should be noted that, for the calculation of the number of submodules put into the upper and lower bridge arms, other rounding functions may be selected, for example, a rounding function, and by using this function, a fractional integer value, such as 4.323, may be returned, and 4 may be returned, which is not rounded, but a rounding method, even 4.987, may also be returned as 4; and an upward rounding function, etc., and in practical applications, the corresponding function may be selected according to different requirements of system accuracy, which is not limited by the present invention.
Optionally, the number of the sub-modules put into the upper and lower bridge arms may be determined by using the capacitance reference voltage and the target output voltage of the upper bridge arm according to the following formula:
wherein N ispa(t) represents the number of submodules thrown into the upper bridge arm, Nna(t) represents the number of submodules invested by a lower bridge arm, round (x) represents an integer function, upa(t) represents the target output voltage of the upper arm, una(t) represents the target output voltage of the lower arm, ucDenotes the capacitive reference voltage of the submodule.
According to the submodule redundancy configuration method of the modular multilevel converter, provided by the invention, the capacitance reference voltage of the submodule of the modular multilevel converter is calculated according to the number of the fault submodules, and then the number of the submodules which are input by the upper bridge arm and the lower bridge arm is respectively determined by utilizing the capacitance reference voltage and the target output voltages of the upper bridge arm and the lower bridge arm, so that the capacitance voltage base value is reduced, and the loss of a converter valve is reduced; when the number of fault modules is greater than that of redundant modules, the system can also keep the maximum voltage output capability in a mode of increasing the capacitor voltage, so that violent oscillation cannot be generated, the system can still stably operate, and the fault ride-through capability is enhanced; and the redundant module is fully utilized, the voltage sharing is participated, the level number of a system can be increased, the harmonic content of output voltage is reduced, and the operation performance of the modular multilevel converter is optimized.
In a specific embodiment, as shown in fig. 3, the obtaining of the target output voltage of the upper bridge arm and the target output voltage of the lower bridge arm of the modular multilevel converter includes the following steps:
step S31: and acquiring the direct-current terminal voltage and the alternating-current terminal voltage of the modular multilevel converter.
In the embodiment of the present invention, the converters can be divided into two types: a Rectifier (Rectifier) and an Inverter (Inverter). The rectifier converts ac power to dc power and the inverter converts dc power to ac power. It should be noted that, in the embodiment of the present invention, the inverter is merely illustrated as a rectifier, and may be another type of inverter in practical application, and the output terminal voltage may also be adjusted according to the actual needs of the system, and the present invention is not limited thereto.
Step S32: and calculating to obtain the target output voltage of the upper bridge arm and the target output voltage of the lower bridge arm by using the direct-current terminal voltage and the alternating-current terminal voltage.
In the embodiment of the invention, the target output voltage of the upper bridge arm can be obtained by subtracting the AC end voltage from the DC end voltage of one base number time, or subtracting the AC end voltage of one base number time; the target output voltage of the lower bridge arm may be a base multiple of a direct current terminal voltage plus an alternating current terminal voltage, or a base multiple of an alternating current terminal voltage, wherein the subtraction of the alternating current terminal voltage or the addition of the direct current terminal voltage is determined according to a preset current flow direction, and the invention is not limited thereto.
Optionally, the target output voltage of the upper bridge arm and the target output voltage of the lower bridge arm are obtained by calculating the direct-current end voltage and the alternating-current end voltage through the following formulas
Wherein u ispa(t) represents the target output voltage of the upper arm, una(t) represents the target output voltage of the lower arm, UdcDenotes the DC terminal voltage usa(t) represents an alternating-current terminal voltage.
In a specific embodiment, as shown in fig. 4, calculating the capacitance reference voltage of the sub-modules of the modular multilevel converter based on the number of faulty sub-modules includes the following steps:
step S21: and acquiring the number of the conventional sub-modules and the total number of the redundant sub-modules, wherein the number of the conventional sub-modules is the number of the sub-modules which are normally put into use under the condition of no fault, and the total number of the redundant sub-modules is the number of all the redundant sub-modules which are preset.
In the embodiment of the present invention, the number of conventional sub-modules to be put into use and the total number of redundant sub-modules of the system are preset by the system, so that after a module fault occurs, the fault adjustment is adjusted and replaced in time, where the number of conventional sub-modules is the number of sub-modules normally put into use under the condition of no fault, and the total number of redundant sub-modules is the number of all preset redundant sub-modules, it should be noted that, in practical application, the number of the put conventional sub-modules and the total number of the redundant sub-modules are set according to practical needs, which is not limited by the present invention.
Step S22: and calculating to obtain the capacitance reference voltage by using the number of the conventional sub-modules, the total number of the redundant sub-modules and the number of the fault sub-modules.
In the embodiment of the invention, the capacitance reference voltage of the sub-modules is calculated by dividing the voltage of the direct current end of the current converter by the total number of the normal operation modules, wherein the total number of the normal operation modules can be the sum of the number of the conventional sub-modules and the number of the redundant sub-modules, namely under the condition that no sub-modules have faults; the total number of the conventional sub-modules, the redundant sub-modules and the faulty sub-modules may also be added with a base number or weighted processing according to the difference of the performance and the parameters of each sub-module, and in practical application, corresponding adjustment may be performed according to the actual needs of the system, the specific gravity of each sub-module, and the like, and the invention is not limited thereto. Wherein the number of faulty modules varies with the running time t.
Optionally, the sub-module capacitance reference voltage is calculated by the following formula:
wherein u iscDenotes the capacitive reference voltage of the submodule, UdcRepresenting the voltage at the DC end, N representing the number of conventional submodules, NrIndicating the total number of redundant sub-modules, NrAnd (t) represents the number of faulty submodules. In practical application of the embodiment of the invention, the capacitance reference voltage of the conventional redundancy configuration method is a constant which is fixed and invariable and is UdcThe capacitance reference voltage is more and more unstable along with the increase of the number of fault submodules, the loss of a converter valve is increased, and a system is more and more unstable; however, the sub-circuits of the modular multilevel converter proposed by the embodiment of the present inventionThe reference voltage of the capacitor of the module redundancy configuration method is determined according to the number N of the fault modulesfAnd (t) the stability of the capacitance reference voltage is ensured by dynamic adjustment, so that the loss reduction of the converter valve and the stability and the safety of system operation are ensured.
In the embodiment of the invention, the device (N) can be analyzed and operated without faultsf(t) is 0), when the sub-module redundancy configuration method of the modular multilevel converter provided by the embodiment of the invention is adopted, the basic value of the sub-module capacitor voltage is UdcV (N + Nr), and the base value of the capacitor voltage is U in the conventional redundancy configuration methoddcTherefore, by adopting the submodule redundancy configuration method of the modular multilevel converter provided by the embodiment of the invention, the voltage base value of the submodule capacitor is reduced, and the loss of the converter valve is reduced; in addition, the conventional redundancy configuration method has the maximum output level number of N +1, but the submodule redundancy configuration method of the modular multilevel converter provided by the embodiment of the invention has the output level number of N + Nr +1, the level number is increased, and the harmonic content of the output voltage is reduced. Therefore, when a sub-module bypass fault occurs in the system, the sub-module redundancy configuration method of the modular multilevel converter provided by the embodiment of the invention can be used for configuring the sub-module redundancy of the modular multilevel converter according to the number N of the fault modulesfAnd (t) dynamically adjusting the value of the capacitor reference voltage to correspondingly improve the capacitor voltage, thereby not influencing the output capacity of the maximum voltage and realizing fault ride-through.
In a specific embodiment, as shown in fig. 5, after determining the number of the sub-modules put into the upper arm by using the capacitance reference voltage and the target output voltage of the upper arm, and determining the number of the sub-modules put into the lower arm by using the capacitance reference voltage and the target output voltage of the lower arm, the method further includes the following steps:
step S6: and calculating the number of redundant sub-modules to be used by utilizing the number of the sub-modules put into the upper bridge arm, the number of the sub-modules put into the lower bridge arm and the number of the fault sub-modules.
In practical application, parameter setting is carried out according to simulation model parameters in table 1, simulation calculation is carried out, and a voltage waveform diagram of a capacitor obtained through simulation is shown in fig. 6, wherein when a conventional redundancy configuration method is adopted, the average value of the capacitor voltage of the sub-modules is about 1.6 kV; when the submodule redundancy configuration method of the modular multilevel converter is adopted, the mean value of the submodule capacitor voltage is about 1.45kV, and the submodule capacitor voltage is obviously reduced.
In the embodiment of the invention, the model parameters are adopted for simulation calculation, and a device loss histogram obtained by simulation is shown in fig. 7, wherein (a) and (b) respectively represent the average loss 2094W of the Submodule (SM) under a rectification working condition and the average loss 3068W under an inversion working condition when a conventional redundancy configuration method is adopted; (c) when the sub-module redundancy configuration method of the modular multilevel converter provided by the embodiment of the invention is adopted, the sub-module (SM) has an average loss of 2016W under a rectification working condition and an average loss of 2887W under an inversion working condition; therefore, the loss of the sub-modules is reduced after the sub-module redundancy configuration method of the modular multilevel converter is adopted, and the reduction amplitude is larger under the inversion working condition.
In the embodiment of the invention, the model parameters are adopted for simulation calculation, when a conventional redundancy configuration method is adopted, the obtained sub-module fault ride-through waveform diagram is shown in fig. 8, when the sub-module redundancy configuration method of the modular multilevel converter is provided by the embodiment of the invention, the obtained sub-module fault ride-through waveform diagram is shown in fig. 9, when a system suffers from sub-module bypass faults, the faults are lighter in a T1 interval, the number of bypass fault modules is less, and at the moment, the conventional redundancy configuration method and the sub-module redundancy configuration method of the modular multilevel converter provided by the embodiment of the invention can realize fault ride-through; when serious sub-module bypass faults occur, a large number of sub-modules are bypassed in a T2 interval, and then a system is seriously oscillated by adopting a conventional redundancy configuration method, so that the system is broken down along with overvoltage and overcurrent; when the submodule redundancy configuration method of the modular multilevel converter is adopted, the system keeps the maximum voltage output capacity in a mode of improving the voltage of the submodule capacitor, and can continue to operate.
According to the submodule redundancy configuration method of the modular multilevel converter, provided by the invention, the capacitance reference voltage of the submodule of the modular multilevel converter is calculated according to the number of the fault submodules, and then the number of the submodules which are input by the upper bridge arm and the lower bridge arm is respectively determined by utilizing the capacitance reference voltage and the target output voltages of the upper bridge arm and the lower bridge arm, so that the capacitance voltage base value is reduced, and the loss of a converter valve is reduced; when the number of fault modules is greater than that of redundant modules, the system can also keep the maximum voltage output capability in a mode of increasing the capacitor voltage, so that violent oscillation cannot be generated, the system can still stably operate, and the fault ride-through capability is enhanced; and the redundant module is fully utilized, the voltage sharing is participated, the level number of a system can be increased, the harmonic content of output voltage is reduced, and the operation performance of the modular multilevel converter is optimized.
Example 2
An embodiment of the present invention provides a sub-module redundancy configuration system of a modular multilevel converter, as shown in fig. 10, including:
the fault submodule number determining module 1 is used for determining the number of fault submodules in the modular multilevel converter; this module executes the method described in step S1 in embodiment 1, and is not described herein again.
The calculating module 2 is used for calculating and obtaining the capacitance reference voltage of the sub-modules of the modular multilevel converter based on the number of the fault sub-modules; this module executes the method described in step S2 in embodiment 1, and is not described herein again.
The acquisition module 3 is used for acquiring a target output voltage of an upper bridge arm and a target output voltage of a lower bridge arm of the modular multilevel converter; this module executes the method described in step S3 in embodiment 1, and is not described herein again.
The input sub-module number determining module 4 is used for determining the number of the sub-modules input by the upper bridge arm by using the capacitance reference voltage and the target output voltage of the upper bridge arm, and determining the number of the sub-modules input by the lower bridge arm by using the capacitance reference voltage and the target output voltage of the lower bridge arm; this module executes the method described in step S4 in embodiment 1, and is not described herein again.
According to the submodule redundancy configuration system of the modular multilevel converter, provided by the invention, the capacitance reference voltage of the submodule of the modular multilevel converter is calculated according to the number of the fault submodules, and then the number of the submodules which are input by the upper bridge arm and the lower bridge arm is respectively determined by utilizing the capacitance reference voltage and the target output voltages of the upper bridge arm and the lower bridge arm, so that the capacitance voltage base value is reduced, and the loss of a converter valve is reduced; when the number of fault modules is greater than that of redundant modules, the system can also keep the maximum voltage output capability in a mode of increasing the capacitor voltage, so that violent oscillation cannot be generated, the system can still stably operate, and the fault ride-through capability is enhanced; and the redundant module is fully utilized, the voltage sharing is participated, the level number of a system can be increased, the harmonic content of output voltage is reduced, and the operation performance of the modular multilevel converter is optimized.
Example 3
An embodiment of the present invention provides an electronic device, as shown in fig. 11, including: at least one processor 401, such as a CPU (Central Processing Unit), at least one communication interface 403, memory 404, and at least one communication bus 402. Wherein a communication bus 402 is used to enable connective communication between these components. The communication interface 403 may include a Display (Display) and a Keyboard (Keyboard), and the optional communication interface 403 may also include a standard wired interface and a standard wireless interface. The Memory 404 may be a RAM (random Access Memory) or a non-volatile Memory (non-volatile Memory), such as at least one disk Memory. The memory 404 may optionally be at least one memory device located remotely from the processor 401. The processor 401 may execute the sub-module redundancy configuration method of the modular multilevel converter of embodiment 1. A set of program codes is stored in the memory 404, and the processor 401 calls the program codes stored in the memory 404 for executing the sub-module redundancy configuration method of the modular multilevel converter of embodiment 1.
The communication bus 402 may be a Peripheral Component Interconnect (PCI) bus or an Extended Industry Standard Architecture (EISA) bus. The communication bus 402 may be divided into an address bus, a data bus, a control bus, and the like. For ease of illustration, only one line is shown in FIG. 11, but this does not represent only one bus or one type of bus.
The memory 404 may include a volatile memory (RAM), such as a random-access memory (RAM); the memory may also include a non-volatile memory (english: non-volatile memory), such as a flash memory (english: flash memory), a hard disk (english: hard disk drive, abbreviation: HDD), or a solid-state drive (english: SSD); the memory 404 may also comprise a combination of memories of the kind described above.
The processor 401 may be a Central Processing Unit (CPU), a Network Processor (NP), or a combination of a CPU and an NP.
The processor 401 may further include a hardware chip. The hardware chip may be an application-specific integrated circuit (ASIC), a Programmable Logic Device (PLD), or a combination thereof. The aforementioned PLD may be a Complex Programmable Logic Device (CPLD), a field-programmable gate array (FPGA), a General Array Logic (GAL), or any combination thereof.
Optionally, the memory 404 is also used to store program instructions. The processor 401 may call a program instruction to implement the method for configuring redundancy of sub-modules of the modular multilevel converter in embodiment 1.
The embodiment of the present invention further provides a computer-readable storage medium, where a computer-executable instruction is stored on the computer-readable storage medium, and the computer-executable instruction can execute the sub-module redundancy configuration method of the modular multilevel converter according to embodiment 1. 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 of the invention may be made without departing from the spirit or scope of the invention.
Claims (10)
1. A submodule redundancy configuration method of a modular multilevel converter is characterized by comprising the following steps:
determining the number of fault sub-modules in the modular multilevel converter;
calculating to obtain the capacitance reference voltage of the sub-modules of the modular multilevel converter based on the number of the fault sub-modules;
acquiring a target output voltage of an upper bridge arm and a target output voltage of a lower bridge arm of the modular multilevel converter;
and determining the number of the sub-modules input by the upper bridge arm by using the capacitance reference voltage and the target output voltage of the upper bridge arm, and determining the number of the sub-modules input by the lower bridge arm by using the capacitance reference voltage and the target output voltage of the lower bridge arm.
2. The method for configuring redundancy of sub-modules of a modular multilevel converter according to claim 1, wherein the obtaining the target output voltages of the upper and lower legs of the modular multilevel converter comprises:
acquiring direct-current terminal voltage and alternating-current terminal voltage of the modular multilevel converter;
and calculating to obtain the target output voltage of the upper bridge arm and the target output voltage of the lower bridge arm by using the direct-current terminal voltage and the alternating-current terminal voltage.
3. The modular multilevel converter sub-module redundancy configuration method according to claim 2, wherein the target output voltage of the upper bridge arm and the target output voltage of the lower bridge arm are calculated by the following formulas:
wherein u ispa(t) represents a target output voltage of the upper arm, una(t) represents a target output voltage of the lower arm, UdcRepresents the voltage of the DC terminal usa(t) represents the ac terminal voltage.
4. The method according to claim 2, wherein the calculating of the capacitance reference voltage of the sub-modules of the modular multilevel converter based on the number of the faulty sub-modules comprises:
acquiring the number of the conventional sub-modules and the total number of the redundant sub-modules, wherein the number of the conventional sub-modules is the number of the sub-modules which are normally put into use under the condition of no fault, and the total number of the redundant sub-modules is the number of all the redundant sub-modules which are preset;
and calculating to obtain the capacitance reference voltage by utilizing the number of the conventional sub-modules, the total number of the redundant sub-modules and the number of the fault sub-modules.
5. The method for configuring redundancy of sub-modules of a modular multilevel converter according to claim 4, wherein the sub-module capacitance reference voltage is calculated by the following formula:
wherein u iscDenotes the capacitive reference voltage, U, of the submoduledcRepresenting the voltage of the direct current terminal, N representing the number of the conventional submodules, NrRepresenting the total number of said redundant sub-modules, NrAnd (t) representing the number of the fault sub-modules.
6. The method of claim 4, wherein after determining the number of the sub-modules put into the upper bridge arm by using the capacitive reference voltage and the target output voltage of the upper bridge arm and determining the number of the sub-modules put into the lower bridge arm by using the capacitive reference voltage and the target output voltage of the lower bridge arm, the method further comprises:
and calculating the number of redundant sub-modules to be used by utilizing the number of the sub-modules put into the upper bridge arm, the number of the sub-modules put into the lower bridge arm and the number of the fault sub-modules.
7. The method for configuring redundancy of sub-modules of a modular multilevel converter according to claim 1, wherein the number of sub-modules put into the upper bridge arm and the number of sub-modules put into the lower bridge arm are calculated by the following formulas:
wherein N ispa(t) represents the number of submodules put into the upper bridge arm, Nna(t) represents the number of submodules thrown into the lower bridge arm, round (x) represents an integer function, upa(t) represents a target output voltage of the upper arm, una(t) represents a target output voltage of the lower arm, uc-representing a capacitive reference voltage of said sub-module.
8. A sub-module redundancy configuration system of a modular multilevel converter is characterized by comprising the following components:
the fault sub-module number determining module is used for determining the number of fault sub-modules in the modular multilevel converter;
the calculation module is used for calculating and obtaining the capacitance reference voltage of the sub-modules of the modular multilevel converter based on the number of the fault sub-modules;
the acquisition module is used for acquiring a target output voltage of an upper bridge arm and a target output voltage of a lower bridge arm of the modular multilevel converter;
and the input sub-module number determining module is used for determining the number of the input sub-modules of the upper bridge arm by using the capacitance reference voltage and the target output voltage of the upper bridge arm and determining the number of the input sub-modules of the lower bridge arm by using the capacitance reference voltage and the target output voltage of the lower bridge arm.
9. A computer-readable storage medium, characterized in that the computer-readable storage medium stores computer instructions which, when executed by a processor, implement the sub-module redundancy configuration method of a modular multilevel converter according to any of claims 1-7.
10. An electronic device, comprising:
a memory and a processor, wherein the memory and the processor are connected with each other in a communication manner, the memory stores computer instructions, and the processor executes the computer instructions to execute the sub-module redundancy configuration method of the modular multilevel converter according to any one of claims 1 to 7.
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