CN116054531A - Mixed MMC bridge arm internal modulation wave distribution control method and system - Google Patents
Mixed MMC bridge arm internal modulation wave distribution control method and system Download PDFInfo
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- H—ELECTRICITY
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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
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- H02J3/36—Arrangements for transfer of electric power between ac networks via a high-tension dc link
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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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- H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
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Abstract
The invention discloses a method and a system for distributing and controlling modulation waves in a mixed MMC bridge arm, wherein the method comprises the following steps: receiving bridge arm voltage modulation waves of each bridge arm, and performing preliminary distribution on the bridge arm voltage modulation waves to obtain half-bridge sub-module voltage preliminary modulation waves and full-bridge sub-module voltage preliminary modulation waves; performing interval judgment, adjustment and amplitude limiting on the half-bridge sub-module voltage primary modulation wave and the full-bridge sub-module voltage primary modulation wave to obtain a half-bridge sub-module voltage modulation wave and a full-bridge sub-module voltage modulation wave; determining a half-bridge submodule to be put into operation according to the voltage modulation wave of the half-bridge submodule and the current direction of a bridge arm, and determining a full-bridge submodule to be put into operation according to the voltage modulation wave of the full-bridge submodule and the current direction of the bridge arm; and the half-bridge submodule and the full-bridge submodule which are input according to the requirement obtain switching signals of the corresponding submodules, so that the input or the cutting of the half-bridge submodule and the Quan Qiaozi module is controlled. And realizing the energy balance of the capacitance voltage of the half-bridge submodule and the full-bridge submodule.
Description
Technical Field
The invention relates to the technical field of flexible direct-current transmission of power systems, in particular to a method and a system for distributing and controlling modulation waves in a mixed MMC bridge arm.
Background
The statements in this section merely provide background information related to the present disclosure and may not necessarily constitute prior art.
In recent years, flexible direct current transmission technology is rapidly developed, and a hybrid Modular Multilevel Converter (MMC) has good development prospect due to the direct current fault blocking capability and higher economical efficiency. The mixed MMC has overmodulation operation capability, direct-current voltage can be reduced by utilizing the capability of the full-bridge submodule to output negative level, at the moment, the phenomenon that bridge arm modulation waves are negative occurs in the mixed MMC, and bridge arm voltages are all output by the full-bridge submodule, so that a half-bridge submodule (HBSM) and a full-bridge submodule (FBSM) in a bridge arm operate under different working conditions, and the energy of the two submodules is unbalanced.
At present, the research on the capacitor voltage balance control of the hybrid MMC half-bridge submodule and the full-bridge submodule mainly takes capacitor voltage sequencing and harmonic injection as main materials. Xu Feng et al propose a hybrid MMC submodule capacitor voltage balance control strategy in a hybrid DC power transmission system based on LCC and FHMMC. The method comprises the steps of sequencing a half-bridge submodule and a full-bridge submodule together when bridge arm modulation waves are positive, and determining input submodules; when the bridge arm modulation wave is negative, sequencing investment is only carried out on the full-bridge submodules, and all the half-bridge submodules are cut off. The method does not consider the problem of voltage balance of the half-bridge submodule when the bridge arm modulation wave is negative, and is not applicable to the working condition of serious bias of bridge arm current.
Cui Mei in the research of the overmodulation operation of the submodule mixed MMC, a secondary circulation injection method is proposed, and the charging and discharging energy of a capacitor in one period is calculated and analyzed by dividing one fundamental frequency period into different intervals. According to the relation between the sub-module energy accumulation process and the bridge arm current, the charge and discharge processes of the capacitor are changed by adopting double frequency negative sequence circulation injection, and the voltage unbalance of the capacitors of the two sub-modules is reduced. The method can reduce the energy difference of the sub-modules, but increases the circulation at the same time, and the calculation process is complex and not intuitive and clear enough.
Cao Xinwei et al propose a sub-module capacitor voltage balancing strategy based on second harmonic compensation in the "capacitor voltage balancing control method of mixed MMC under DC voltage reduction" (application number: 202011461096.3). The MMC operation state is judged, the control strategy is divided into three working modes, and the second harmonic reference amplitude is calculated only when unbalance of capacitor voltage occurs, so that the control strategy is simplified to a certain extent, and the problem of complex operation in the second harmonic amplitude calculation process is solved.
In summary, the existing mixed MMC submodule capacitor voltage balance control has the problems of low applicability, complex control, low calculation efficiency and unclear physical significance.
Disclosure of Invention
In order to solve the problems, the invention provides a method and a system for distributing and controlling modulated waves in a bridge arm of a hybrid MMC, which consists of a preliminary distributing link and an adjusting and limiting link, and respectively sorts the capacitance and voltage of the modulated waves of a half-bridge submodule and a full-bridge submodule which are finally determined, determines the submodules which need to be input, and realizes the energy balance of the capacitance and voltage of the half-bridge submodule and the full-bridge submodule.
In order to achieve the above purpose, the present invention adopts the following technical scheme:
in a first aspect, the present invention provides a method for controlling allocation of modulated waves in a bridge arm of a hybrid MMC, including:
receiving bridge arm voltage modulation waves of each bridge arm, and performing preliminary distribution on the bridge arm voltage modulation waves to obtain half-bridge sub-module voltage preliminary modulation waves and full-bridge sub-module voltage preliminary modulation waves;
performing interval judgment, adjustment and amplitude limiting on the half-bridge sub-module voltage primary modulation wave and the full-bridge sub-module voltage primary modulation wave to obtain a half-bridge sub-module voltage modulation wave and a full-bridge sub-module voltage modulation wave;
determining a half-bridge submodule to be put into operation according to the voltage modulation wave of the half-bridge submodule and the current direction of a bridge arm, and determining a full-bridge submodule to be put into operation according to the voltage modulation wave of the full-bridge submodule and the current direction of the bridge arm;
and the half-bridge submodule and the full-bridge submodule which are input according to the requirement obtain switching signals of the corresponding submodules, so that the input or the cutting of the half-bridge submodule and the Quan Qiaozi module is controlled.
As an alternative embodiment, the preliminary allocation procedure comprises:
taking the difference value of the periodic average values of the capacitor voltage of the Quan Qiaozi module and the capacitor voltage of the half-bridge submodule as a control target, adopting PI control, limiting the output to be within plus or minus 1, and obtaining a preliminary distribution coefficient, so that the bridge arm voltage modulation wave is preliminary distributed according to the preliminary distribution coefficient.
As an alternative embodiment, the preliminary allocation procedure comprises:
taking the difference value of the cycle maximum value of the capacitor voltage of the Quan Qiaozi module and the half-bridge submodule as a control target, adopting PI control, limiting the output to be within plus or minus 1, and obtaining a preliminary distribution coefficient, so that the bridge arm voltage modulation wave is preliminary distributed according to the preliminary distribution coefficient.
As an alternative embodiment, the preliminary allocation procedure comprises:
when the bridge arm voltage modulation wave is positive and the bridge arm current is positive, the half-bridge submodule primary modulation wave increases the primary distribution coefficient on the basis of distribution according to the number proportion of the half-bridge submodules, and the full-bridge submodule primary modulation wave decreases the primary distribution coefficient on the basis of distribution according to the number proportion of the full-bridge submodules;
when the bridge arm voltage modulation wave is positive and the bridge arm current is negative, the half-bridge submodule primary modulation wave reduces the primary distribution coefficient on the basis of distribution according to the number proportion of the half-bridge submodules, and the full-bridge submodule primary modulation wave increases the primary distribution coefficient on the basis of distribution according to the number proportion of the full-bridge submodules;
when the bridge arm voltage modulation wave is negative, only the full-bridge submodule is put into a negative level state, and all the half-bridge submodules are bypassed, so that the half-bridge submodule primary modulation wave is zero, and the full-bridge submodule primary modulation wave is equal to the bridge arm voltage modulation wave.
As an alternative embodiment, the process of adjusting clipping by the interval judgment includes:
when half-bridge submodule voltage modulation wave U H_ref_jr Greater than 0 and less than H C When in use;
judging full-bridge submodule voltage modulation wave U F_ref_jr Whether or not it is smaller than F C The method comprises the steps of carrying out a first treatment on the surface of the If so, the voltage modulation waves of the half-bridge sub-module and the Quan Qiaozi module are within the limit range, and adjustment is not needed;
otherwise, the full-bridge submodule is fully put into operation, and the half-bridge submodule distributes residual voltage modulation waves; namely:
U H_ref_jr ＝U arm_ref_jr -F*U C
U F_ref_jr ＝F*U C
wherein H is the number of half-bridge sub-modules, F is the number of full-bridge sub-modules, U C Rated value of capacitance voltage for the submodule; u (U) arm_ref_jr Is a bridge arm voltage modulation wave.
Alternatively, when half-bridge submodule voltage modulates wave U H_ref_jr Greater than H.times.U C When in use;
judging bridge arm voltage modulation wave U arm_ref_jr Whether or not it is greater than H C The method comprises the steps of carrying out a first treatment on the surface of the If yes, the half-bridge submodules are all put into operation, and the full-bridge submodules distribute residual voltage modulation waves; namely:
U H_ref_jr ＝H*U C
U F_ref_jr ＝U arm_ref_jr -H*U C
otherwise, the half-bridge submodule modulation wave is adjusted to be bridge arm voltage modulation wave, and the full-bridge submodule modulation wave is adjusted to be 0.
Alternatively, when half-bridge submodule voltage modulates wave U H_ref_jr Negative;
judging bridge arm voltage modulation wave U arm_ref_jr Whether or not it is greater than F C The method comprises the steps of carrying out a first treatment on the surface of the If yes, the full-bridge submodules are all put into operation, and the half-bridge submodules distribute residual voltage modulation waves;
otherwise, the half-bridge submodule modulation wave is adjusted to be 0, and the full-bridge submodule modulation wave is bridge arm voltage modulation wave.
In a second aspect, the present invention provides a system for controlling modulated wave distribution in a bridge arm of a hybrid MMC, including:
the primary distribution module is configured to receive the bridge arm voltage modulation wave of each bridge arm and perform primary distribution on the bridge arm voltage modulation wave to obtain a half-bridge sub-module voltage primary modulation wave and a full-bridge sub-module voltage primary modulation wave;
the adjusting and limiting module is configured to perform interval judgment, adjustment and limiting on the half-bridge submodule voltage primary modulation wave and the full-bridge submodule voltage primary modulation wave to obtain a half-bridge submodule voltage modulation wave and a full-bridge submodule voltage modulation wave;
the input determining module is configured to determine a half-bridge submodule to be input according to the voltage modulation wave of the half-bridge submodule and the current direction of the bridge arm, and determine a full-bridge submodule to be input according to the voltage modulation wave of the full-bridge submodule and the current direction of the bridge arm;
and the input control module is configured to obtain switching signals of the corresponding sub-modules according to the half-bridge sub-modules and the full-bridge sub-modules which are input as required, so as to control the input or the cutting of the half-bridge sub-modules and the Quan Qiaozi modules.
In a third aspect, the invention provides an electronic device comprising a memory and a processor and computer instructions stored on the memory and running on the processor, which when executed by the processor, perform the method of the first aspect.
In a fourth aspect, the present invention provides a computer readable storage medium storing computer instructions which, when executed by a processor, perform the method of the first aspect.
Compared with the prior art, the invention has the beneficial effects that:
the invention provides a mixed MMC bridge arm internal modulation wave distribution control method and system, which consists of a preliminary distribution link and an adjustment limiting link, wherein the preliminary distribution link is realized through positive and negative judgment of a PI controller and bridge arm modulation wave and bridge arm current, and the adjustment limiting link is realized through judgment of output capacities of preliminarily distributed half-bridge and full-bridge preliminary modulation waves and corresponding bridge arm submodules; and respectively sequencing the capacitance and voltage of the finally determined modulated waves of the half-bridge submodule and the full-bridge submodule, determining the submodule to be put into, realizing the energy balance of the capacitance and voltage of the half-bridge submodule and the full-bridge submodule, and solving the problem of unbalanced energy of the capacitance of the half-bridge submodule and the full-bridge submodule in the operation process of the hybrid MMC.
The invention provides a method and a system for distributing and controlling modulated waves in a bridge arm of a hybrid MMC, which not only can realize the balance of periodic energy of a half-bridge submodule and a full-bridge submodule, but also can realize the balance of the maximum value of capacitance voltage period of the half-bridge submodule and the full-bridge submodule, simplify the complexity of calculation, and have clear and visual physical significance.
The invention provides a method and a system for distributing and controlling modulated waves in a bridge arm of a hybrid MMC, which take the difference of periodic average values or the difference of periodic maximum values of capacitance voltages of a half-bridge submodule and a full-bridge submodule as control objects, and adjust the distribution proportion of the modulated waves between the half-bridge submodule and the full-bridge submodule through PI control, primary distribution of the modulated waves and adjustment of limiting links, so as to finally generate corresponding switching signals, and effectively reduce the energy difference or stress difference of the two submodules.
Additional aspects of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the invention.
FIG. 1 is a schematic circuit topology of a hybrid MMC;
fig. 2 is a flowchart of a method for controlling allocation of modulated waves in a bridge arm of a hybrid MMC according to embodiment 1 of the present invention;
fig. 3 is a PI control block diagram of preliminary allocation of bridge arm voltage modulation waves provided in embodiment 1 of the present invention.
Detailed Description
The invention is further described below with reference to the drawings and examples.
It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the invention. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.
It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular forms also are intended to include the plural forms, and furthermore, it is to be understood that the terms "comprises" and "comprising" and any variations thereof are intended to cover non-exclusive inclusions, such as, for example, processes, methods, systems, products or devices that comprise a series of steps or units, are not necessarily limited to those steps or units that are expressly listed, but may include other steps or units that are not expressly listed or inherent to such processes, methods, products or devices.
Embodiments of the invention and features of the embodiments may be combined with each other without conflict.
Example 1
The embodiment provides a method for distributing and controlling modulation waves in a bridge arm of a hybrid MMC, which comprises the following steps:
receiving bridge arm voltage modulation waves of each bridge arm, and performing preliminary distribution on the bridge arm voltage modulation waves to obtain half-bridge sub-module voltage preliminary modulation waves and full-bridge sub-module voltage preliminary modulation waves;
performing interval judgment, adjustment and amplitude limiting on the half-bridge sub-module voltage primary modulation wave and the full-bridge sub-module voltage primary modulation wave to obtain a half-bridge sub-module voltage modulation wave and a full-bridge sub-module voltage modulation wave;
determining a half-bridge submodule to be put into operation according to the voltage modulation wave of the half-bridge submodule and the current direction of a bridge arm, and determining a full-bridge submodule to be put into operation according to the voltage modulation wave of the full-bridge submodule and the current direction of the bridge arm;
and the half-bridge submodule and the full-bridge submodule which are input according to the requirement obtain switching signals of the corresponding submodules, so that the input or the cutting of the half-bridge submodule and the Quan Qiaozi module is controlled.
In this embodiment, as shown in fig. 1, the hybrid MMC includes three phase units with the same structure, where each phase unit includes an upper bridge arm, a lower bridge arm, a bridge arm equivalent resistor, a bridge arm reactance, and the like, and includes six bridge arms in total, and each bridge arm is formed by connecting H half-bridge submodules and F full-bridge submodules in series.
The following describes in detail a specific implementation flow of a modulation wave allocation control method in a mixed MMC bridge arm with reference to the accompanying drawings, as shown in fig. 2, and specifically includes the following steps:
s1: receiving a bridge arm voltage modulation wave (also a bridge arm voltage reference value) U of a j-phase r bridge arm arm_ref_jr Where j=a, b, c, r=p, n;
wherein, bridge arm voltage modulation wave U arm_ref_jr Obtained by a double-loop controller of the upper-stage mixed MMC.
S2: preliminary distribution is carried out on the bridge arm voltage modulation wave to obtain a bridge arm inner half-bridge submodule voltage preliminary modulation wave U H_ref_jr_PI And bridge arm inner full-bridge submodule voltage primary modulation wave U F_ref_jr_PI ；
In this embodiment, the step S2 specifically includes:
s2.1: taking the difference value of the periodic average value or the difference value of the periodic maximum value of the capacitor voltage of the Quan Qiaozi module and the half-bridge sub-module as a control target, inputting the control target into a PI controller for PI control, and limiting the output to be within plus or minus 1 to obtain a primary distribution coefficient K; as shown in fig. 3;
the primary distribution coefficient K is obtained by subtracting the half-bridge sub-module from the full-bridge sub-module and performing PI control, so that the primary distribution coefficient K is defined as the degree that the energy of the Quan Qiaozi module is higher than that of the half-bridge sub-module.
S2.2: judging whether the bridge arm voltage modulation wave is positive or not; if yes, executing S2.3; if not, executing S2.6;
s2.3: judging whether the bridge arm current is positive or not; if yes, executing S2.4; if not, executing S2.5;
s2.4: preliminary distribution is carried out on bridge arm voltage modulation waves, and a preliminary distribution algorithm is as follows:
at this time, both the bridge arm voltage modulation wave and the bridge arm current are positive, and the input sub-module is charged. Therefore, the modulation wave of the half-bridge submodule is increased by K on the basis of being distributed according to the number proportion of the half-bridge submodules, and the modulation wave of the full-bridge submodule is correspondingly reduced by K on the basis of being distributed according to the proportion.
S2.5: preliminary distribution is carried out on bridge arm voltage modulation waves, and a preliminary distribution algorithm is as follows:
at this time, the bridge arm voltage modulation wave is positive, the bridge arm current is negative, and the input submodule is discharged. Therefore, the modulation wave of the half-bridge submodule is reduced by K on the basis of being distributed according to the number proportion of the half-bridge submodules, and the modulation wave of the full-bridge submodule is correspondingly increased by K on the basis of being distributed according to the proportion.
S2.6: preliminary distribution is carried out on bridge arm voltage modulation waves, and a preliminary distribution algorithm is as follows:
U H_ref_jr_PI ＝0
U F_ref_jr_PI ＝U arm_ref_jr
at this time, the bridge arm voltage modulation wave is negative, only the full-bridge submodule is put into a negative level state, and all the half-bridge submodules are bypassed; therefore, the modulation wave of the half-bridge submodule is 0, and the modulation wave of the full-bridge submodule is equal to the bridge arm voltage modulation wave.
S3: half-bridge submodule voltage primary modulation wave U H_ref_jr_PI And full-bridge submodule voltage primary modulation wave U F_ref_jr_PI Performing interval judgment, adjustment and amplitude limiting to obtain a final bridge arm inner half-bridge submodule voltage modulation waveU H_ref_jr And full-bridge submodule voltage modulation wave U F_ref_jr ；
In this embodiment, the step S3 specifically includes:
s3.1: judging voltage modulation wave U of half-bridge submodule H_ref_jr Whether greater than 0 and less than H C The method comprises the steps of carrying out a first treatment on the surface of the If yes, executing S3.2; if not, executing S3.5; wherein U is C Rated value of capacitance voltage for the submodule;
s3.2: judging full-bridge submodule voltage modulation wave U F_ref_jr Whether or not it is smaller than F C The method comprises the steps of carrying out a first treatment on the surface of the If yes, executing S3.3; if not, executing S3.4;
s3.3: and carrying out amplitude limiting adjustment on the voltage modulation wave of the half-bridge submodule in the bridge arm and the voltage modulation wave of the full-bridge submodule, wherein an adjustment algorithm is as follows:
U H_ref_jr ＝U H_ref_jr_PI
U F_ref_jr ＝U F_ref_jr_PI
at this time, the voltage modulation waves of the half-bridge sub-module and the Quan Qiaozi module are within the limit range, and no adjustment is needed.
S3.4: and carrying out amplitude limiting adjustment on the voltage modulation wave of the half-bridge submodule in the bridge arm and the voltage modulation wave of the full-bridge submodule, wherein an adjustment algorithm is as follows:
U H_ref_jr ＝U arm_ref_jr -F*U C
U F_ref_jr ＝F*U C
at this time, the modulation wave of the full-bridge submodule is higher than the maximum voltage that can be generated, so that the full-bridge submodule is fully put into operation, and the half-bridge submodule distributes the rest of the modulation wave.
S3.5: judging voltage modulation wave U of half-bridge submodule H_ref_jr Whether it is positive; if yes, executing S3.6; if not, executing S3.9;
s3.6: judging bridge arm voltage modulation wave U arm_ref_jr Whether or not it is greater than H C The method comprises the steps of carrying out a first treatment on the surface of the If yes, executing S3.7; if not, executing S3.8;
s3.7: and carrying out amplitude limiting adjustment on the voltage modulation wave of the half-bridge submodule in the bridge arm and the voltage modulation wave of the full-bridge submodule, wherein an adjustment algorithm is as follows:
U H_ref_jr ＝H*U C
U F_ref_jr ＝U arm_ref_jr -H*U C
at this time, the modulated wave of the half-bridge submodule is higher than the maximum voltage that can be generated, so that the half-bridge submodule is fully put into operation, and the full-bridge submodule distributes the remaining modulated wave.
S3.8: and carrying out amplitude limiting adjustment on the voltage modulation wave of the half-bridge submodule in the bridge arm and the voltage modulation wave of the full-bridge submodule, wherein an adjustment algorithm is as follows:
U H_ref_jr ＝U arm_ref_jr
U F_ref_jr ＝0
at this time, the modulation wave of the half-bridge sub-module is higher than the maximum voltage that can be generated by the half-bridge sub-module, but the full-bridge sub-module outputs a negative level, and the bridge arm voltage modulation wave is not higher than the maximum voltage that can be generated by the half-bridge sub-module. Therefore, the half-bridge submodule modulation wave is adjusted to be bridge arm voltage modulation wave, and the full-bridge submodule modulation wave is adjusted to be 0.
S3.9: judging bridge arm voltage modulation wave U arm_ref_jr Whether or not it is greater than F C The method comprises the steps of carrying out a first treatment on the surface of the If yes, executing S3.10; if not, executing S3.11;
s3.10: and carrying out amplitude limiting adjustment on the voltage modulation wave of the half-bridge submodule in the bridge arm and the voltage modulation wave of the full-bridge submodule, wherein an adjustment algorithm is as follows:
U H_ref_jr ＝U arm_ref_jr -F*U C
U F_ref_jr ＝F*U C
at this time, the modulation wave of the half-bridge sub-module is smaller than 0, and exceeds the capacity range of the half-bridge sub-module, and meanwhile, the bridge arm voltage modulation wave is larger than the maximum voltage which can be generated by the full-bridge sub-module, so that the full-bridge sub-module is fully put into operation, and the half-bridge sub-module distributes the rest modulation wave.
S3.11: and carrying out amplitude limiting adjustment on the voltage modulation wave of the half-bridge submodule in the bridge arm and the voltage modulation wave of the full-bridge submodule, wherein an adjustment algorithm is as follows:
U H_ref_jr ＝0
U F_ref_jr ＝U arm_ref_jr
at this time, the modulation wave of the half-bridge submodule is smaller than 0 and exceeds the capacity range of the half-bridge submodule; however, the bridge arm voltage modulation wave is not higher than the maximum voltage which can be generated by the full-bridge submodule, so that the modulation wave of the half-bridge submodule is adjusted to be 0, and the full-bridge submodule modulation wave is the bridge arm voltage modulation wave.
S4: determining a submodule to be put into according to the positive and negative of the voltage modulation wave and the direction of bridge arm current by adopting a capacitor voltage sequencing algorithm;
specifically, the half-bridge submodule to be put into is determined according to the positive and negative of the half-bridge submodule voltage modulation wave and the bridge arm current direction, and the full-bridge submodule to be put into is determined according to the positive and negative of the full-bridge submodule voltage modulation wave and the bridge arm current direction.
S5: and generating switching signals of the corresponding sub-modules according to the voltage modulation wave and the sub-modules to be input, so as to respectively control the input or the cutting of the half-bridge sub-modules and the full-bridge half-bridge sub-modules in the bridge arm.
In the embodiment, from the energy angle of the submodule, the difference of the periodic average values of the capacitor voltages of the half-bridge submodule and the full-bridge submodule is taken as a control object, and the energy difference of the half-bridge submodule and the full-bridge submodule is effectively reduced through PI control, primary distribution of modulation waves and amplitude limiting adjustment; or the difference between the maximum values of the capacitor voltage periods of the half-bridge submodule and the full-bridge submodule is used as a control object to balance the voltage stress of the half-bridge submodule and the Quan Qiaozi module, so that the method has strong applicability.
In the embodiment, the modulation wave is divided into the half-bridge sub-module modulation wave and the full-bridge sub-module modulation wave, a new path is provided for the control method, a better control effect can be realized without adopting a method of carrying out complex calculation such as harmonic injection, the control calculation amount is greatly reduced, and the method has clear and visual physical significance.
Example 2
The embodiment provides a mixed MMC bridge arm internal modulation wave distribution control system, which comprises:
the primary distribution module is configured to receive the bridge arm voltage modulation wave of each bridge arm and perform primary distribution on the bridge arm voltage modulation wave to obtain a half-bridge sub-module voltage primary modulation wave and a full-bridge sub-module voltage primary modulation wave;
the adjusting and limiting module is configured to perform interval judgment, adjustment and limiting on the half-bridge submodule voltage primary modulation wave and the full-bridge submodule voltage primary modulation wave to obtain a half-bridge submodule voltage modulation wave and a full-bridge submodule voltage modulation wave;
the input determining module is configured to determine a half-bridge submodule to be input according to the voltage modulation wave of the half-bridge submodule and the current direction of the bridge arm, and determine a full-bridge submodule to be input according to the voltage modulation wave of the full-bridge submodule and the current direction of the bridge arm;
and the input control module is configured to obtain switching signals of the corresponding sub-modules according to the half-bridge sub-modules and the full-bridge sub-modules which are input as required, so as to control the input or the cutting of the half-bridge sub-modules and the Quan Qiaozi modules.
It should be noted that the above modules correspond to the steps described in embodiment 1, and the above modules are the same as examples and application scenarios implemented by the corresponding steps, but are not limited to those disclosed in embodiment 1. It should be noted that the modules described above may be implemented as part of a system in a computer system, such as a set of computer-executable instructions.
In further embodiments, there is also provided:
an electronic device comprising a memory and a processor and computer instructions stored on the memory and running on the processor, which when executed by the processor, perform the method described in embodiment 1. For brevity, the description is omitted here.
It should be understood that in this embodiment, the processor may be a central processing unit CPU, and the processor may also be other general purpose processors, digital signal processors DSP, application specific integrated circuits ASIC, off-the-shelf programmable gate array FPGA or other programmable logic device, discrete gate or transistor logic devices, discrete hardware components, or the like. A general purpose processor may be a microprocessor or the processor may be any conventional processor or the like.
The memory may include read only memory and random access memory and provide instructions and data to the processor, and a portion of the memory may also include non-volatile random access memory. For example, the memory may also store information of the device type.
A computer readable storage medium storing computer instructions which, when executed by a processor, perform the method described in embodiment 1.
The method in embodiment 1 may be directly embodied as a hardware processor executing or executed with a combination of hardware and software modules in the processor. The software modules may be located in a random access memory, flash memory, read only memory, programmable read only memory, or electrically erasable programmable memory, registers, etc. as well known in the art. The storage medium is located in a memory, and the processor reads the information in the memory and, in combination with its hardware, performs the steps of the above method. To avoid repetition, a detailed description is not provided herein.
Those of ordinary skill in the art will appreciate that the elements of the various examples described in connection with the present embodiments, i.e., the algorithm steps, can be implemented as electronic hardware or combinations of computer software and electronic hardware. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the solution. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present application.
While the foregoing description of the embodiments of the present invention has been presented in conjunction with the drawings, it should be understood that it is not intended to limit the scope of the invention, but rather, it is intended to cover all modifications or variations within the scope of the invention as defined by the claims of the present invention.
Claims (10)
1. The method for controlling the distribution of the modulation waves in the bridge arm of the mixed MMC is characterized by comprising the following steps:
receiving bridge arm voltage modulation waves of each bridge arm, and performing preliminary distribution on the bridge arm voltage modulation waves to obtain half-bridge sub-module voltage preliminary modulation waves and full-bridge sub-module voltage preliminary modulation waves;
performing interval judgment, adjustment and amplitude limiting on the half-bridge sub-module voltage primary modulation wave and the full-bridge sub-module voltage primary modulation wave to obtain a half-bridge sub-module voltage modulation wave and a full-bridge sub-module voltage modulation wave;
determining a half-bridge submodule to be put into operation according to the voltage modulation wave of the half-bridge submodule and the current direction of a bridge arm, and determining a full-bridge submodule to be put into operation according to the voltage modulation wave of the full-bridge submodule and the current direction of the bridge arm;
and the half-bridge submodule and the full-bridge submodule which are input according to the requirement obtain switching signals of the corresponding submodules, so that the input or the cutting of the half-bridge submodule and the Quan Qiaozi module is controlled.
2. The method for controlling modulated wave allocation in a bridge arm of a hybrid MMC according to claim 1, wherein the preliminary allocation process includes:
taking the difference value of the periodic average values of the capacitor voltage of the Quan Qiaozi module and the capacitor voltage of the half-bridge submodule as a control target, adopting PI control, limiting the output to be within plus or minus 1, and obtaining a preliminary distribution coefficient, so that the bridge arm voltage modulation wave is preliminary distributed according to the preliminary distribution coefficient.
3. The method for controlling modulated wave allocation in a bridge arm of a hybrid MMC according to claim 1, wherein the preliminary allocation process includes:
taking the difference value of the cycle maximum value of the capacitor voltage of the Quan Qiaozi module and the half-bridge submodule as a control target, adopting PI control, limiting the output to be within plus or minus 1, and obtaining a preliminary distribution coefficient, so that the bridge arm voltage modulation wave is preliminary distributed according to the preliminary distribution coefficient.
4. The method for controlling modulated wave allocation in a bridge arm of a hybrid MMC according to claim 2 or 3, wherein the preliminary allocation process includes:
when the bridge arm voltage modulation wave is positive and the bridge arm current is positive, the half-bridge submodule primary modulation wave increases the primary distribution coefficient on the basis of distribution according to the number proportion of the half-bridge submodules, and the full-bridge submodule primary modulation wave decreases the primary distribution coefficient on the basis of distribution according to the number proportion of the full-bridge submodules;
when the bridge arm voltage modulation wave is positive and the bridge arm current is negative, the half-bridge submodule primary modulation wave reduces the primary distribution coefficient on the basis of distribution according to the number proportion of the half-bridge submodules, and the full-bridge submodule primary modulation wave increases the primary distribution coefficient on the basis of distribution according to the number proportion of the full-bridge submodules;
when the bridge arm voltage modulation wave is negative, only the full-bridge submodule is put into a negative level state, and all the half-bridge submodules are bypassed, so that the half-bridge submodule primary modulation wave is zero, and the full-bridge submodule primary modulation wave is equal to the bridge arm voltage modulation wave.
5. The method for controlling allocation of modulated waves in a bridge arm of a hybrid MMC according to claim 1, wherein the process of determining and adjusting clipping in the interval includes:
when half-bridge submodule voltage modulation wave U H_ref_jr Greater than 0 and less than H C When in use;
judging full-bridge submodule voltage modulation wave U F_ref_jr Whether or not it is smaller than F C The method comprises the steps of carrying out a first treatment on the surface of the If so, the voltage modulation waves of the half-bridge sub-module and the Quan Qiaozi module are within the limit range, and adjustment is not needed;
otherwise, the full-bridge submodule is fully put into operation, and the half-bridge submodule distributes residual voltage modulation waves; namely:
U H_ref_jr ＝U arm_ref_jr -F*U C
U F_ref_jr ＝F*U C
wherein H is the number of half-bridge sub-modules, F is the number of full-bridge sub-modules, U C Rated value of capacitance voltage for the submodule; u (U) arm_ref_jr Is a bridge arm voltage modulation wave.
6. The method for controlling modulated wave distribution in a hybrid MMC bridge arm of claim 5,characterized in that when the half-bridge submodule voltage modulates the wave U H_ref_jr Greater than H.times.U C When in use;
judging bridge arm voltage modulation wave U arm_ref_jr Whether or not it is greater than H C The method comprises the steps of carrying out a first treatment on the surface of the If yes, the half-bridge submodules are all put into operation, and the full-bridge submodules distribute residual voltage modulation waves; namely:
U H_ref_jr ＝H*U C
U F_ref_jr ＝U arm_ref_jr -H*U C
otherwise, the half-bridge submodule modulation wave is adjusted to be bridge arm voltage modulation wave, and the full-bridge submodule modulation wave is adjusted to be 0.
7. The method for distributing and controlling modulated waves in a bridge arm of a hybrid MMC according to claim 6, wherein when the voltage of the half-bridge submodule modulates the modulated waves U H_ref_jr Negative;
judging bridge arm voltage modulation wave U arm_ref_jr Whether or not it is greater than F C The method comprises the steps of carrying out a first treatment on the surface of the If yes, the full-bridge submodules are all put into operation, and the half-bridge submodules distribute residual voltage modulation waves;
otherwise, the half-bridge submodule modulation wave is adjusted to be 0, and the full-bridge submodule modulation wave is bridge arm voltage modulation wave.
8. A mixed MMC bridge arm internal modulation wave distribution control system is characterized by comprising:
the primary distribution module is configured to receive the bridge arm voltage modulation wave of each bridge arm and perform primary distribution on the bridge arm voltage modulation wave to obtain a half-bridge sub-module voltage primary modulation wave and a full-bridge sub-module voltage primary modulation wave;
the adjusting and limiting module is configured to perform interval judgment, adjustment and limiting on the half-bridge submodule voltage primary modulation wave and the full-bridge submodule voltage primary modulation wave to obtain a half-bridge submodule voltage modulation wave and a full-bridge submodule voltage modulation wave;
the input determining module is configured to determine a half-bridge submodule to be input according to the voltage modulation wave of the half-bridge submodule and the current direction of the bridge arm, and determine a full-bridge submodule to be input according to the voltage modulation wave of the full-bridge submodule and the current direction of the bridge arm;
and the input control module is configured to obtain switching signals of the corresponding sub-modules according to the half-bridge sub-modules and the full-bridge sub-modules which are input as required, so as to control the input or the cutting of the half-bridge sub-modules and the Quan Qiaozi modules.
9. An electronic device comprising a memory and a processor and computer instructions stored on the memory and running on the processor, which when executed by the processor, perform the method of any one of claims 1-7.
10. A computer readable storage medium storing computer instructions which, when executed by a processor, perform the method of any of claims 1-7.
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