CN113067488B - Control method and device for improving internal dynamic performance of modular multilevel converter - Google Patents

Control method and device for improving internal dynamic performance of modular multilevel converter Download PDF

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CN113067488B
CN113067488B CN201911290641.4A CN201911290641A CN113067488B CN 113067488 B CN113067488 B CN 113067488B CN 201911290641 A CN201911290641 A CN 201911290641A CN 113067488 B CN113067488 B CN 113067488B
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bridge arm
energy
reference value
voltage
lower bridge
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CN113067488A (en
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苟锐锋
苏匀
焦秀英
李少华
李育宁
姚东晓
马小婷
沈开奎
蒋大海
马松江
涂小刚
李孝维
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Xi'an Duanyi Technology Co ltd
China XD Electric Co Ltd
Xian XD Power Systems Co Ltd
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Xi'an Duanyi Technology Co ltd
China XD Electric Co Ltd
Xian XD Power Systems Co Ltd
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/483—Converters with outputs that each can have more than two voltages levels
    • 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
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/53—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M7/537—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters
    • H02M7/5387—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a bridge configuration
    • H02M7/53871—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a bridge configuration with automatic control of output voltage or current
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/60—Arrangements for transfer of electric power between AC networks or generators via a high voltage DC link [HVCD]

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Abstract

The invention provides a control method and a control device for improving the internal dynamic performance of a modular multilevel converter, wherein the method comprises the following steps: generating a direct current component of the unbalanced current based on the sum of the energy of the upper and lower bridge arms and a direct current voltage reference value; generating an alternating current component of the unbalanced current based on the energy difference between the upper and lower bridge arms; generating a reference value of the internal unbalanced voltage of the modular multilevel converter according to the direct current component and the alternating current component; the modular multilevel converter is controlled based on the sum of the energy of the upper bridge arm and the energy of the lower bridge arm and the energy difference of the upper bridge arm and the lower bridge arm, double frequency circulation in the bridge arms can be avoided without overlapping CCSC, meanwhile, the dynamic performance in the MMC can be greatly improved, and overcurrent and oscillation phenomena in the transient process are reduced.

Description

Control method and device for improving internal dynamic performance of modular multilevel converter
Technical Field
The invention relates to the technical field of power electronics, in particular to a control method and a control device for improving the internal dynamic performance of a modular multilevel converter.
Background
The Modular Multilevel Converter (MMC) is a topological structure which is applied to the field of high-capacity direct current transmission and has the most influence at present, compared with the traditional 2/3 level Converter, the MMC has lower switching loss, smaller harmonic output and larger level number output, the requirement on the consistency of IGBT devices is lower, and devices of a bridge arm do not need to be switched on and off simultaneously, so that the Modular Multilevel Converter is easier to modularize, and the ultrahigh-capacity Converter is convenient to construct.
The MMC has the advantages that only the ground capacitance of a direct-current cable on the direct-current side participates in stability control of direct-current voltage, the direct-current voltage is greatly fluctuated due to the fact that the capacitance is relatively small, large power fluctuation of a direct-current bus can cause large fluctuation of the direct-current voltage, in order to increase the equivalent ground capacitance of the direct-current side and solve the technical problems, a circulating current suppression strategy (CCSC) is adopted in the existing strategy, the method is simple and easy to implement, the CCSC does not control the sum of energy of an upper bridge arm and an lower bridge arm, and the phenomenon of overcurrent and oscillation in the transient process can be caused by the uncontrolled unbalanced current direct-current component.
Disclosure of Invention
The present invention provides a control method and apparatus, an electronic device, and a computer-readable storage medium for improving internal dynamic performance of a modular multilevel converter, which can at least partially solve the problems in the prior art.
In order to achieve the purpose, the invention adopts the following technical scheme:
in a first aspect, a control method for improving internal dynamic performance of a modular multilevel converter is provided, including:
generating a direct current component of the unbalanced current based on the sum of the energy of the upper and lower bridge arms and a direct current voltage reference value;
generating an alternating current component of the unbalanced current based on the energy difference between the upper and lower bridge arms;
generating a reference value of the internal unbalanced voltage of the modular multilevel converter according to the direct current component and the alternating current component;
and generating a trigger signal according to the reference value of the internal unbalanced voltage of the modular multilevel converter and the voltage reference value generated by the power control of the alternating current system, thereby realizing the control of the modular multilevel converter.
Further, generating a trigger signal according to the reference value of the unbalanced voltage inside the modular multilevel converter and the voltage reference value generated by the power control of the alternating current system, comprising:
acquiring voltage wave reference values of the upper bridge arm and the lower bridge arm according to the direct current component and the alternating current component;
and generating a trigger signal according to the voltage wave reference values of the upper and lower bridge arms to realize the control of the modular multilevel converter.
Further, the generating the dc component of the unbalanced current based on the sum of the energy of the upper and lower bridge arms and the dc voltage reference value includes:
and comparing the sum of the energy of the upper bridge arm and the energy of the lower bridge arm with a direct current voltage reference value, and generating a direct current component of the unbalanced current after proportional-integral regulation.
Further, the generating of the alternating current component of the unbalanced current based on the energy difference between the upper and lower bridge arms includes:
and the difference of the bridge arm energy is subjected to proportional integral adjustment to generate an alternating current component of the unbalanced current.
Further, the generating a reference value of an unbalanced voltage inside the modular multilevel converter according to the dc component and the ac component includes:
and after algebraically summing the direct-current component and the alternating-current component, generating a reference value of the internal unbalanced voltage of the modular multilevel converter through an unbalanced current controller.
Further, a voltage reference value generated by the power control of the alternating current system is obtained by adopting a quasi-proportional resonant controller through an inner ring current controller based on a static coordinate system.
In a second aspect, a control apparatus for improving internal dynamic performance of a modular multilevel converter is provided, including:
the direct current component acquisition module generates a direct current component of the unbalanced current based on the sum of the energy of the upper bridge arm and the energy of the lower bridge arm and a direct current voltage reference value;
the alternating current component acquisition module generates an alternating current component of unbalanced current based on the energy difference of the upper bridge arm and the lower bridge arm;
the reference value acquisition module is used for generating a reference value of the internal unbalanced voltage of the modular multilevel converter according to the direct current component and the alternating current component;
and the trigger signal generating module generates a trigger signal according to the reference value of the unbalanced voltage in the modular multilevel converter and the voltage reference value generated by the power control of the alternating current system, so as to realize the control of the modular multilevel converter.
Further, the trigger signal generating module includes:
the voltage wave reference value acquisition unit is used for acquiring voltage wave reference values of the upper bridge arm and the lower bridge arm according to the direct current component and the alternating current component;
and the trigger signal generating unit generates a trigger signal according to the voltage wave reference values of the upper bridge arm and the lower bridge arm to realize the control of the modular multilevel converter.
Further, the direct current component acquisition module includes:
and the direct current component acquisition unit compares the sum of the energy of the upper bridge arm and the energy of the lower bridge arm with a direct current voltage reference value, and generates a direct current component of the unbalanced current after proportional-integral regulation.
Further, the alternating current component acquisition module includes:
and the difference of the bridge arm energy is subjected to proportional integral adjustment to generate an alternating current component of the unbalanced current.
Further, the reference value obtaining module includes:
and the reference value acquisition unit is used for generating a reference value of the internal unbalanced voltage of the modular multilevel converter through the unbalanced current controller after algebraically summing the direct current component and the alternating current component.
Further, a voltage reference value generated by the power control of the alternating current system is obtained by adopting a quasi-proportional resonant controller through an inner ring current controller based on a static coordinate system.
In a third aspect, an electronic device is provided, which includes a memory, a processor, and a computer program stored in the memory and executable on the processor, and when the processor executes the computer program, the steps of the control method for improving the dynamic performance inside the modular multilevel converter are implemented.
In a fourth aspect, a computer-readable storage medium is provided, on which a computer program is stored, and the computer program, when executed by a processor, implements the steps of the above control method for improving the internal dynamic performance of the modular multilevel converter.
The invention provides a control method and a control device for improving the internal dynamic performance of a modular multilevel converter, electronic equipment and a computer readable storage medium, wherein the method comprises the following steps: generating a direct current component of the unbalanced current based on the sum of the energy of the upper and lower bridge arms and a direct current voltage reference value; generating an alternating current component of the unbalanced current based on the energy difference between the upper and lower bridge arms; generating a reference value of the internal unbalanced voltage of the modular multilevel converter according to the direct current component and the alternating current component; the modular multilevel converter is controlled based on the sum of the energy of the upper bridge arm and the energy of the lower bridge arm and the energy difference of the upper bridge arm and the lower bridge arm, double frequency circulation in the bridge arms can be avoided without overlapping CCSC, meanwhile, the dynamic performance in the MMC can be greatly improved, and overcurrent and oscillation phenomena in the transient process are reduced.
In order to make the aforementioned and other objects, features and advantages of the invention comprehensible, preferred embodiments accompanied with figures are described in detail below.
Drawings
In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings used in the embodiments or the prior art descriptions will be briefly described below, and it is obvious that the drawings in the following descriptions are some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative efforts. In the drawings:
FIG. 1 is a detailed topology and equivalent circuit diagram of an MMC converter;
FIG. 2 is a block diagram of an overall MMC control strategy in an embodiment of the present invention;
fig. 3 is a schematic flowchart of a control method for improving the internal dynamic performance of the modular multilevel converter according to an embodiment of the present invention;
fig. 4 shows a specific step of step S400 in fig. 3;
fig. 5 is a block diagram of a control strategy for improving the internal dynamic performance of the modular multilevel converter according to an embodiment of the present invention;
fig. 6 is a block diagram of a control apparatus for improving internal dynamic performance of a modular multilevel converter according to an embodiment of the present invention;
fig. 7 is a block diagram of an electronic device according to an embodiment of the invention.
Detailed Description
In order to make the technical solutions better understood by those skilled in the art, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only partial embodiments of the present application, but not all embodiments. 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 application.
As will be appreciated by one skilled in the art, embodiments of the present invention may be provided as a method, system, or computer program product. Accordingly, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present invention may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.
It should be noted that the terms "comprises" and "comprising," and any variations thereof, in the description and claims of this application and the above-described drawings, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed, but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.
It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict. The present application will be described in detail below with reference to the embodiments with reference to the attached drawings.
The direct current side of the MMC only has the earth capacitance of a direct current cable to participate in the stability control of direct current voltage, because the capacitance is relatively small, the large power fluctuation of a direct current bus can cause the direct current voltage to fluctuate greatly, in order to increase the equivalent earth capacitance of the direct current side and solve the technical problems, the conventional strategy adopts a circulating current suppression strategy (CCSC), the method is simple and easy to implement, but the CCSC does not control the sum of the energy of an upper bridge arm and a lower bridge arm, and the uncontrolled unbalanced current direct current component can cause overcurrent and oscillation phenomena in the transient process.
The topological structure of the MMC is shown in (a) in fig. 1 and comprises ABC three phases, each phase is divided into an upper Bridge arm and a lower Bridge arm, each Bridge arm is cascaded by a plurality of submodules (Half-Bridge Half Bridge, Full-Bridge Full Bridge, clamping double submodule Clamp double or a mixture thereof, shown in (b) in fig. 1) with the same structure and is connected with a Bridge arm inductor L 0 The MMC can be essentially regarded as a voltage source with variable amplitude and phase angle, the active power and the reactive power of an alternating current system can be exchanged by adjusting the amplitude and the phase angle of an output alternating voltage of the MMC, a single-phase equivalent circuit diagram of the three-phase MMC is shown as (c) in figure 1, and L 0 Is a bridge arm reactance, R 0 For simulating bridge arm loss, U dc Is the dc bus voltage. U shape νj (j ═ a, b, c) is the ac phase voltage output of the inverter at point v, i νj And (j) is a, b, c) is an alternating-current phase current. 6 bridge arm valve section parts (without L) 0 ) The voltage can be expressed as u pj And u nj (j ═ a, b, c; p represents the upper arm and n represents the lower arm); i all right angle pj And i nj Representing the bridge arm currents of the upper bridge arm and the lower bridge arm respectively.
As can be seen from FIG. 1, the MMC topology has three-phase symmetry and direct current I dc Evenly distributed among the three phase units. Meanwhile, the upper bridge arm and the lower bridge arm of each phase are mutually symmetrical, so that the current of each phase on the AC side of the MMC is equally divided between the upper bridge arm and the lower bridge arm. Neglecting bridge arm loss R in normal operation 0 The X point and the X 'point in (c) of fig. 1 are at the same potential, so the mathematical property of MMC according to kirchhoff's voltage law can be represented by the following formula:
Figure BDA0002318998640000051
in the formula:
e j -a virtual voltage generated by the j-phase inside the MMC;
u diffj -an unbalanced voltage of the j-phase inside the MMC;
i diffj -unbalanced current of j-phase inside MMC.
As can be seen from the formula (1), the phase virtual voltage e is controlled j The AC phase current can be controlled by controlling the unbalanced voltage u diffj The MMC system can be decomposed into two completely decoupled independent parts of alternating current and direct current. As can be seen from (c) and equation (1) in fig. 1, the bridge arm voltage reference value of j phase can be defined as:
Figure BDA0002318998640000061
in the formula:
e j_ref -reference value of a j-phase virtual voltage inside the MMC, e αβ_ref Is e j_ref Reference values in the α β coordinate system.
u diffj_ref -a reference value for the j-phase unbalance voltage inside the MMC.
e j_ref Derived from the inner loop current controller, and u diffj_ref Then from the MMC internal dynamics controller. Based on the above thought, an overall control block diagram of the MMC can be obtained, which is shown in detail in fig. 2. The MMC overall control may include: the MMC comprises three parts, namely outer loop power control, inner loop current control and control for improving the internal dynamic performance of the MMC. The outer ring power control is executed by the outer ring power controller, the inner ring current control is executed by the inner ring current controller, and part of the steps in the control method for improving the internal dynamic performance of the modular multilevel converter provided by the embodiment of the invention are executed by the controller for improving the internal dynamic performance of the MMC.
Specifically, the main input quantities of the outer loop controller are: active power definite value, reactive power definite value, alternating voltage definite value and direct voltage definite value, alternating voltage and user control mode selection, output quantity is: generating a current reference constant value through a controller according to the input condition; inner ring input amount: the current constant value output and the alternating voltage of the outer ring have the following output quantities: and generating an alternating voltage reference constant value according to the current constant value. Improve MMC dynamic property controller: the input is the reference fixed value of the bridge arm voltage, the unbalanced current and the direct current voltage, and the output is the reference fixed value of the unbalanced voltage.
The MMC system is decomposed into two completely decoupled independent parts of alternating current and direct current through equivalence and decomposition of the model. The total voltage reference value of the bridge arm comprises a voltage reference value e generated by power control of an alternating current system αβ_ref And a voltage reference value u generated by the dynamic performance control of the DC side diffj_ref Two parts. The alternating current side part is obtained by adopting a quasi-proportional resonant controller through an inner ring current controller based on a static coordinate system, so that the direct current control of the active power and the reactive power of the power grid side is achieved.
For the internal dynamic performance of the direct current side, the control method for improving the internal dynamic performance of the modular multilevel converter provided by the embodiment of the invention is adopted to realize the following steps:
referring to fig. 3, the control method for improving the internal dynamic performance of the modular multilevel converter may include the following steps:
step S100: generating a direct current component of the unbalanced current based on the sum of the energy of the upper and lower bridge arms and a direct current voltage reference value;
specifically, the sum of the energies of the upper and lower bridge arms and the DC voltage reference value u dc_ref And comparing, and generating a direct current component of the unbalanced current after proportional integral adjustment.
Step S200: generating an alternating current component of the unbalanced current based on the energy difference between the upper and lower bridge arms;
specifically, the difference between the bridge arm energies is adjusted by proportional integral PI to generate an alternating current component of the unbalanced current.
It is worth noting that the difference between the two under ideal equilibrium conditions should be 0.
Step S300: generating a reference value of an internal unbalanced voltage of the modular multilevel converter according to the direct current component and the alternating current component;
specifically, after algebraically summing the direct current component and the alternating current component, a reference value u of the internal unbalanced voltage of the modular multilevel converter is generated through the unbalanced current controller diffj_ref 。
Step S400:according to the reference value u of the internal unbalanced voltage of the modular multilevel converter diffj_ref And a voltage reference e generated by AC system power control αβ_ref And generating a trigger signal to realize the control of the modular multilevel converter.
And the voltage reference value generated by the power control of the alternating current system is obtained by adopting a quasi-proportional resonant controller through an inner ring current controller based on a static coordinate system.
In summary, the control method for improving the internal dynamic performance of the modular multilevel converter provided by the embodiment of the invention is controlled based on the sum of the energy of the upper and lower bridge arms and the difference between the energy of the upper and lower bridge arms, the generation of double frequency circulation in the bridge arms can be avoided without overlapping CCSC, the internal dynamic performance of the MMC can be greatly improved, and the overcurrent and oscillation phenomena in the transient process can be reduced.
In an alternative embodiment, referring to fig. 4, this step S400 may include the following:
step S410: acquiring voltage wave reference values of an upper bridge arm and a lower bridge arm according to the direct current component and the alternating current component;
specifically, handle e αβ_ref And u diffj_ref The two are superposed to respectively obtain the voltage wave reference value u of the upper bridge arm and the lower bridge arm pj_ref And u nj_ref 。
Step S420: and generating a trigger signal according to the voltage wave reference values of the upper and lower bridge arms to realize the control of the modular multilevel converter.
By adopting the technical scheme, the voltage wave reference value can be accurately obtained, and the control of the modular multilevel converter is further optimized.
Fig. 5 is a block diagram of a control strategy for improving internal dynamic performance of a modular multilevel converter according to an embodiment of the present invention; in the figure, u ∑pj Is the sum of the measured values of the capacitance and the voltage of all the sub-modules of the upper bridge arm of the j phase, u △nj The sum of the measured values of the capacitor voltages of all the sub-modules of the j-phase lower bridge arm is input into an adder to obtain the sum of the energy of the upper and lower bridge arms, the sum and a DC voltage reference value u dc_ref PI control of total energy input into upper and lower bridge arms togetherThe system comprises a PI controller for comparing the sum of the energy of the upper and lower bridge arms with a DC voltage reference value and performing PI control, and a divider for dividing the output of the PI controller by the DC bus voltage U dc ；u ∑pj And u △nj Inputting a subtracter to obtain the energy difference between the upper bridge arm and the lower bridge arm, carrying out PI control on the energy difference PI controller of the upper bridge arm and the lower bridge arm according to the energy difference between the upper bridge arm and the lower bridge arm, and multiplying the output of the controller by the AC voltage Uv on the valve side by a multiplier; the output of the divider and the output of the multiplier are input into an adder to be algebraically summed to obtain a current i diffj_ref The unbalanced current controller is based on the i diffj_ref And i diffj Generating a reference value u of an MMC internal unbalance voltage diffj_ref 。
The control method for improving the internal dynamic performance of the modular multilevel converter provided by the embodiment of the invention can greatly improve the internal dynamic performance of the MMC, particularly the unbalanced current and the direct current at the direct current side, and greatly attenuate the oscillation phenomenon in the transient process. By decoupling and decomposing the alternating current-direct current system, the superior performance of the traditional network side power controller is reserved, namely the traditional network side direct current control can be applied to the whole control block diagram and the internal dynamic performance of the MMC is not influenced; the invention has simple strategy, clear structure, excellent performance and strong usability.
Based on the same inventive concept, the embodiment of the present application further provides a control device for improving internal dynamic performance of a modular multilevel converter, which can be used to implement the method described in the foregoing embodiment, as described in the following embodiment. Because the principle of solving the problems of the control device for improving the internal dynamic performance of the modular multilevel converter is similar to that of the method, the implementation of the control device for improving the internal dynamic performance of the modular multilevel converter can refer to the implementation of the method, and repeated details are omitted. As used hereinafter, the term "unit" or "module" may be a combination of software and/or hardware that implements a predetermined function. Although the means described in the embodiments below are preferably implemented in software, an implementation in hardware, or a combination of software and hardware is also possible and contemplated.
Fig. 6 is a block diagram of a control device for improving internal dynamic performance of a modular multilevel converter according to an embodiment of the present invention. As shown in fig. 6, the control device for improving the internal dynamic performance of the modular multilevel converter specifically includes: the device comprises a direct current component acquisition module 10, an alternating current component acquisition module 20, a reference value acquisition module 30 and a trigger signal generation module 40.
The direct current component obtaining module 10 generates a direct current component of the unbalanced current based on the sum of the energy of the upper and lower bridge arms and the direct current voltage reference value;
the alternating current component acquisition module 20 generates an alternating current component of the unbalanced current based on the energy difference between the upper and lower bridge arms;
the reference value obtaining module 30 generates a reference value of the internal unbalanced voltage of the modular multilevel converter according to the dc component and the ac component;
the trigger signal generating module 40 generates a trigger signal according to the reference value of the unbalanced voltage inside the modular multilevel converter and the voltage reference value generated by the power control of the alternating current system, so as to realize the control of the modular multilevel converter.
In summary, the control device for improving the internal dynamic performance of the modular multilevel converter provided by the embodiment of the invention performs control based on the sum of the energy of the upper and lower bridge arms and the difference between the energy of the upper and lower bridge arms, can avoid the generation of double frequency circulation in the bridge arms without overlapping CCSC, can greatly improve the internal dynamic performance of the MMC, and can reduce the overcurrent and oscillation phenomena in the transient process.
In an alternative embodiment, the trigger signal generating module 40 includes: the device comprises a voltage wave reference value acquisition unit and a trigger signal generation unit.
The voltage wave reference value acquisition unit is used for acquiring voltage wave reference values of the upper bridge arm and the lower bridge arm according to the direct current component and the alternating current component;
and the trigger signal generating unit generates a trigger signal according to the voltage wave reference values of the upper bridge arm and the lower bridge arm to realize the control of the modular multilevel converter.
In an optional embodiment, the dc component obtaining module 10 includes: and the direct current component acquisition unit compares the sum of the energy of the upper bridge arm and the energy of the lower bridge arm with a direct current voltage reference value, and generates a direct current component of the unbalanced current after proportional-integral regulation.
In an alternative embodiment, the alternating current component obtaining module 20 includes: and the difference of the bridge arm energy is subjected to proportional integral adjustment to generate an alternating current component of the unbalanced current.
In an alternative embodiment, the reference value obtaining module 30 includes: and the reference value acquisition unit is used for generating a reference value of the internal unbalanced voltage of the modular multilevel converter through the unbalanced current controller after algebraically summing the direct current component and the alternating current component.
In an optional embodiment, the voltage reference value generated by the power control of the alternating current system is obtained by adopting a quasi-proportional resonant controller under the condition that an inner loop current controller is based on a static coordinate system.
The apparatuses, modules or units illustrated in the above embodiments may be implemented by a computer chip or an entity, or implemented by a product with certain functions. A typical implementation device is an electronic device, which may be, for example, a personal computer, a laptop computer, a cellular telephone, a camera phone, a smart phone, a personal digital assistant, a media player, a navigation device, an email device, a game console, a tablet computer, a wearable device, or a combination of any of these devices.
In a typical example, the electronic device specifically includes a memory, a processor, and a computer program stored on the memory and executable on the processor, and the processor implements the following steps when executing the program:
generating a direct current component of the unbalanced current based on the sum of the energy of the upper and lower bridge arms and a direct current voltage reference value;
generating an alternating current component of the unbalanced current based on the energy difference of the upper and lower bridge arms;
generating a reference value of the internal unbalanced voltage of the modular multilevel converter according to the direct current component and the alternating current component;
and generating a trigger signal according to the reference value of the internal unbalanced voltage of the modular multilevel converter and the voltage reference value generated by the power control of the alternating current system, thereby realizing the control of the modular multilevel converter.
As can be seen from the above description, the electronic device provided in the embodiment of the present invention may be used to improve the internal dynamic performance of the modular multilevel converter, and control is performed based on the sum of the energies of the upper and lower bridge arms and the difference between the energies of the upper and lower bridge arms, so that the generation of a double frequency circulation in the bridge arms may be avoided without overlapping CCSC, and meanwhile, the internal dynamic performance of the MMC may be greatly improved, and the overcurrent and oscillation phenomena in the transient process may be reduced.
Referring now to FIG. 7, shown is a schematic diagram of an electronic device 600 suitable for use in implementing embodiments of the present application.
As shown in fig. 7, the electronic apparatus 600 includes a Central Processing Unit (CPU)601 that can perform various appropriate works and processes according to a program stored in a Read Only Memory (ROM)602 or a program loaded from a storage section 608 into a Random Access Memory (RAM)) 603. In the RAM603, various programs and data necessary for the operation of the system 600 are also stored. The CPU601, ROM602, and RAM603 are connected to each other via a bus 604. An input/output (I/O) interface 605 is also connected to bus 604.
The following components are connected to the I/O interface 605: an input portion 606 including a keyboard, a mouse, and the like; an output portion 607 including a display such as a Cathode Ray Tube (CRT), a Liquid Crystal Display (LCD), and the like, and a speaker; a storage section 608 including a hard disk and the like; and a communication section 609 including a network interface card such as a LAN card, a modem, or the like. The communication section 609 performs communication processing via a network such as the internet. The driver 610 is also connected to the I/O interface 605 as needed. A removable medium 611 such as a magnetic disk, an optical disk, a magneto-optical disk, a semiconductor memory, or the like is mounted on the drive 610 as necessary, so that a computer program read out therefrom is mounted as necessary on the storage section 608.
In particular, according to an embodiment of the present invention, the processes described above with reference to the flowcharts may be implemented as computer software programs. For example, an embodiment of the invention includes a computer-readable storage medium having a computer program stored thereon, which when executed by a processor, performs the steps of:
generating a direct current component of the unbalanced current based on the sum of the energy of the upper and lower bridge arms and a direct current voltage reference value;
generating an alternating current component of the unbalanced current based on the energy difference between the upper and lower bridge arms;
generating a reference value of an internal unbalanced voltage of the modular multilevel converter according to the direct current component and the alternating current component;
and generating a trigger signal according to the reference value of the internal unbalanced voltage of the modular multilevel converter and the voltage reference value generated by the power control of the alternating current system, thereby realizing the control of the modular multilevel converter.
As can be seen from the above description, the computer-readable storage medium provided in the embodiment of the present invention may be used to improve the internal dynamic performance of the modular multilevel converter, and control is performed based on the sum of the energies of the upper and lower bridge arms and the difference between the energies of the upper and lower bridge arms, so that the generation of a double frequency circulating current in the bridge arms may be avoided without superimposing CCSC, and meanwhile, the internal dynamic performance of the MMC may be greatly improved, and the overcurrent and oscillation phenomena in the transient process may be reduced.
In such an embodiment, the computer program may be downloaded and installed from a network through the communication section 609, and/or installed from the removable medium 611.
Computer-readable media, including both permanent and non-permanent, removable and non-removable media, may implement the information storage by any method or technology. The information may be computer readable instructions, data structures, modules of a program, or other data. Examples of computer storage media include, but are not limited to, phase change memory (PRAM), Static Random Access Memory (SRAM), Dynamic Random Access Memory (DRAM), other types of Random Access Memory (RAM), Read Only Memory (ROM), Electrically Erasable Programmable Read Only Memory (EEPROM), flash memory or other memory technology, compact disc read only memory (CD-ROM), Digital Versatile Discs (DVD) or other optical storage, magnetic cassettes, magnetic tape magnetic disk storage or other magnetic storage devices, or any other non-transmission medium that can be used to store information that can be accessed by a computing device. As defined herein, a computer readable medium does not include a transitory computer readable medium such as a modulated data signal and a carrier wave.
For convenience of description, the above devices are described as being divided into various units by function, and are described separately. Of course, the functionality of the various elements may be implemented in the same one or more pieces of software and/or hardware in the practice of the present application.
The present invention is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
It should also be noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises the element.
As will be appreciated by one skilled in the art, embodiments of the present application may be provided as a method, system, or computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.
The application may be described in the general context of computer-executable instructions, such as program modules, being executed by a computer. Generally, program modules include routines, programs, objects, components, data structures, etc. that perform particular tasks or implement particular abstract data types. The application may also be practiced in distributed computing environments where tasks are performed by remote processing devices that are linked through a communications network. In a distributed computing environment, program modules may be located in both local and remote computer storage media including memory storage devices.
The embodiments in the present specification are described in a progressive manner, and the same and similar parts among the embodiments are referred to each other, and each embodiment focuses on the differences from the other embodiments. In particular, as for the system embodiment, since it is substantially similar to the method embodiment, the description is relatively simple, and reference may be made to the partial description of the method embodiment for relevant points.
The above description is only an example of the present application and is not intended to limit the present application. Various modifications and changes may occur to those skilled in the art. Any modification, equivalent replacement, improvement or the like made within the spirit and principle of the present application shall be included in the scope of the claims of the present application.

Claims (6)

1. A control method for improving internal dynamic performance of a modular multilevel converter is characterized by comprising the following steps:
generating a direct current component of the unbalanced current based on the sum of the energy of the upper and lower bridge arms and a direct current voltage reference value;
generating an alternating current component of the unbalanced current based on the energy difference between the upper and lower bridge arms;
generating a reference value of an internal unbalanced voltage of the modular multilevel converter according to the direct current component and the alternating current component;
generating a trigger signal according to a reference value of unbalanced voltage in the modular multilevel converter and a voltage reference value generated by power control of an alternating current system, and realizing control of the modular multilevel converter, wherein the voltage reference value generated by the power control of the alternating current system is obtained by an inner-ring current controller based on a static coordinate system and by adopting a quasi-proportional resonant controller;
the generating of the DC component of the unbalanced current based on the sum of the energy of the upper and lower bridge arms and the DC voltage reference value comprises:
inputting the energy sum of the upper bridge arm and the energy sum of the lower bridge arm into an adder to obtain the energy sum of the upper bridge arm and the lower bridge arm; the sum value and the direct current voltage reference value are input into the total energy PI controllers of the upper bridge arm and the lower bridge arm together, the total energy PI controllers of the upper bridge arm and the lower bridge arm compare the sum of the energy of the upper bridge arm and the energy of the lower bridge arm with the direct current voltage reference value and then carry out PI control, and a divider divides the output of the total energy PI controllers of the upper bridge arm and the lower bridge arm by the direct current bus voltage to obtain a direct current component;
the alternating current component for generating the unbalanced current based on the energy difference of the upper and lower bridge arms comprises:
inputting the sum of the energy of the upper bridge arm and the sum of the energy of the lower bridge arm into a subtracter to obtain the difference between the energy of the upper bridge arm and the energy of the lower bridge arm; the PI controller for the energy difference of the upper bridge arm and the lower bridge arm performs PI control according to the energy difference of the upper bridge arm and the lower bridge arm, and the multiplier multiplies the output of the controller by the valve side alternating voltage to obtain an alternating current component;
the generating of the reference value of the internal unbalanced voltage of the modular multilevel converter according to the direct current component and the alternating current component comprises:
and inputting the direct current component output by the divider and the alternating current component output by the multiplier into an adder for algebraic summation to obtain target current, and generating a reference value of the unbalanced voltage in the modular multilevel converter by the unbalanced current controller according to the target current and the unbalanced current in the modular multilevel converter.
2. The control method for improving the internal dynamic performance of the modular multilevel converter according to claim 1, wherein the generating the trigger signal according to the reference value of the internal unbalanced voltage of the modular multilevel converter and the voltage reference value generated by the power control of the alternating current system comprises:
acquiring voltage wave reference values of an upper bridge arm and a lower bridge arm according to the direct current component and the alternating current component;
and generating a trigger signal according to the voltage wave reference values of the upper bridge arm and the lower bridge arm to realize the control of the modular multilevel converter.
3. A control device for improving dynamic performance in a Modular Multilevel Converter (MMC), comprising:
the direct current component acquisition module generates a direct current component of the unbalanced current based on the sum of the energy of the upper bridge arm and the energy of the lower bridge arm and a direct current voltage reference value;
the alternating current component acquisition module generates an alternating current component of the unbalanced current based on the energy difference of the upper bridge arm and the lower bridge arm;
the reference value acquisition module is used for generating a reference value of the internal unbalanced voltage of the modular multilevel converter according to the direct current component and the alternating current component;
the trigger signal generation module generates a trigger signal according to a reference value of unbalanced voltage in the modular multilevel converter and a voltage reference value generated by power control of an alternating current system to realize control of the modular multilevel converter, wherein the voltage reference value generated by the power control of the alternating current system is obtained by an inner ring current controller based on a static coordinate system and by adopting a quasi-proportional resonant controller;
the direct current component acquisition module is specifically configured to:
inputting the energy sum of the upper bridge arm and the energy sum of the lower bridge arm into an adder to obtain the energy sum of the upper bridge arm and the lower bridge arm; the sum value and the direct current voltage reference value are input into the total energy PI controllers of the upper bridge arm and the lower bridge arm together, the total energy PI controllers of the upper bridge arm and the lower bridge arm compare the sum of the energy of the upper bridge arm and the energy of the lower bridge arm with the direct current voltage reference value and then carry out PI control, and a divider divides the output of the total energy PI controllers of the upper bridge arm and the lower bridge arm by the direct current bus voltage to obtain a direct current component;
the alternating current component acquisition module is specifically configured to:
inputting the sum of the energy of the upper bridge arm and the sum of the energy of the lower bridge arm into a subtracter to obtain the difference between the energy of the upper bridge arm and the energy of the lower bridge arm; the PI controller for the energy difference of the upper bridge arm and the lower bridge arm performs PI control according to the energy difference of the upper bridge arm and the lower bridge arm, and the multiplier multiplies the output of the controller by the valve side alternating voltage to obtain an alternating current component;
the reference value acquisition module is specifically configured to:
and inputting the direct current component output by the divider and the alternating current component output by the multiplier into an adder for algebraic summation to obtain a target current, and generating a reference value of the unbalanced voltage in the modular multilevel converter by the unbalanced current controller according to the target current and the unbalanced current in the modular multilevel converter.
4. The control device for improving the internal dynamic performance of the modular multilevel converter according to claim 3, wherein the trigger signal generating module comprises:
the voltage wave reference value acquisition unit is used for acquiring voltage wave reference values of the upper bridge arm and the lower bridge arm according to the direct current component and the alternating current component;
and the trigger signal generating unit generates a trigger signal according to the voltage wave reference values of the upper bridge arm and the lower bridge arm to realize the control of the modular multilevel converter.
5. An electronic device comprising a memory, a processor and a computer program stored on the memory and executable on the processor, wherein the processor implements the steps of the control method for improving the internal dynamic performance of the modular multilevel converter according to any one of claims 1 to 2 when executing the program.
6. A computer readable storage medium, on which a computer program is stored, wherein the computer program, when being executed by a processor, implements the steps of the control method for improving the internal dynamic performance of a modular multilevel converter according to any one of claims 1 to 2.
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