CN116760268A - Harmonic control method and system suitable for grid-connected converter - Google Patents
Harmonic control method and system suitable for grid-connected converter Download PDFInfo
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Classifications
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/12—Arrangements for reducing harmonics from ac input or output
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/01—Arrangements for reducing harmonics or ripples
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
-
- 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
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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
- H02M7/493—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 the static converters being arranged for operation in parallel
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Abstract
The invention belongs to the field of harmonic control of converters, and discloses a harmonic control method and a harmonic control system suitable for a grid-connected converter, wherein the method comprises the following steps: calculating a common connection point voltage by using the sampled output voltage and the sampled output current; extracting the total harmonic of the common connection point voltage and the output current; according to the detected total harmonic wave of the voltage and the current, adopting droop+multi-proportion resonance control to establish a unified droop relation between the voltage of the common connection point and the total harmonic wave of the output current, and obtaining a harmonic compensation reference voltage; and superposing the harmonic compensation reference voltage and the fundamental reference voltage to obtain the output reference voltage of the converter, and superposing and outputting the output reference voltage to the PWM modulation unit. The invention solves the complex treatment of harmonic voltage and current of the grid-structured converter in the grid-connected or off-grid mode, and does not need to extract the harmonic wave of specific order, thus greatly simplifying the operand compared with the prior method.
Description
Technical Field
The invention belongs to the field of harmonic control of converters, and particularly relates to a harmonic control method and system suitable for a grid-built converter.
Background
With the high-speed development of renewable energy sources, the duty ratio of a power electronic converter in a power system is continuously improved, and the novel power system gradually shows the characteristics of high-proportion renewable energy sources and high-proportion power electronic equipment. In order to ensure stable and safe operation of the power grid, grid-structured converter control based on droop control or virtual synchronous machines gradually becomes a mainstream development trend. The grid-structured converter adopts a power synchronization strategy similar to that of a synchronous generator, does not depend on external grid phase information, and can effectively coordinate the operation of a plurality of parallel converters. Aiming at the energy storage converter, the network construction control technology is adopted, so that the requirement of the development of the energy storage high-capacity technology can be met while the stability of the system is met.
The grid-structured converter can construct the AC side output voltage by itself under the condition of not depending on an external AC system, thereby effectively reducing the frequency and voltage fluctuation of the system. Therefore, the grid-structured converter can be operated in a grid-connected mode or off-grid mode, and can be connected in parallel in a plurality of machines during off-grid mode, namely, an island-operated micro-grid is formed.
The power quality problems such as voltage and current distortion can be caused by the connection of nonlinear loads such as power electronic equipment and the like, and the problems can be treated by adjacent grid-connected converters. The current harmonic injected by the nonlinear load can cause voltage harmonic generated by a common connection point during grid-connected operation, the current harmonic counteracted by the current harmonic is required to be generated by the grid-connected converter, and the current is required to be reasonably distributed among a plurality of grid-connected converters connected to the same common connection point. When the load is in off-grid operation, current harmonics of the load are required to be provided by a plurality of grid-structured converters in the micro-grid, harmonic circulation can be generated due to unreasonable current harmonic distribution, and voltage distortion of a public connection point can be caused by the current harmonics generated by the load and the converters, so that the electric energy quality is reduced.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a harmonic control method and a harmonic control system suitable for a grid-connected converter.
The invention aims at realizing the following technical scheme:
a harmonic control method suitable for a grid-tied converter, comprising:
calculating a common connection point voltage by using the sampled output voltage and the sampled output current;
extracting the total harmonic of the common connection point voltage and the output current;
according to the detected total harmonic wave of the voltage and the current, adopting droop+multi-proportion resonance control to establish a unified droop relation between the voltage of the common connection point and the total harmonic wave of the output current, and obtaining a harmonic compensation reference voltage;
and superposing the harmonic compensation reference voltage and the fundamental reference voltage to obtain the output reference voltage of the converter, and superposing and outputting the output reference voltage to the PWM modulation unit.
As a further improvement of the present invention, the calculating the common connection point voltage using the sampled output voltage and the output current includes:
based on kirchhoff's law, the common junction voltage calculation expression is:
wherein ,Vpcc For the common junction voltage, V out 、I out R is the output voltage and the output current of the converter line 、L line The resistance and inductance of the line.
As a further improvement of the invention, the method for extracting the total harmonic of the voltage and the output current of the common connection point comprises a biquad generalized integral-positive and negative sequence calculation module, a fast Fourier transform, a phase-locked loop or multiple synchronous harmonic dq transformation.
As a further improvement of the present invention, the extracting the total harmonic of the common connection point voltage and the output current includes:
the sum of harmonic wave and fundamental wave negative sequence is obtained by subtracting the extracted fundamental wave positive sequence from the input quantity of the biquad generalized integral-positive sequence calculation module, and the expression is as follows:
wherein ,xα 、x β Signals are input to the two SOGI modules respectively,respectively a fundamental positive sequence, a fundamental negative sequence and harmonics,>the sum of the harmonic wave and the fundamental wave negative sequence is the quantity to be controlled.
As a further improvement of the invention, the x α The corresponding SOGI module transfer function is:
wherein ,xα Omega is SOGI input signal and frequency, x' α And qx' α K is the gain factor of the closed loop system, which is two mutually orthogonal output signals. X is x β Corresponding transfer function and x α The same applies.
As a further improvement of the present invention, the establishing a unified droop relation between the common connection point voltage and the output current total harmonic includes:
and (3) uniformly drooping control is adopted on the total harmonic components extracted from the common connection point voltage and the output current, so that the total harmonic components meet the following conditions:
wherein ,respectively, the output current harmonic wave and the common connection point voltage harmonic wave under the alpha beta coordinate system, k droop For sag factor, k droop / base =, C is a constant;
according to the harmonic wave uniform droop relation, the droop error is as follows:
the obtained sagging errorThe main harmonic component is zero through multi-proportion resonance control or multi-quasi-proportion resonance control, and the transfer function of the multi-quasi-proportion resonance control is as follows:
wherein ,kp Is a coefficient of proportionality and is used for the control of the power supply,is the resonance coefficient omega c For the cut-off frequency, ω of the resonant controller m The fundamental wave angular frequency, and h is the harmonic frequency.
As a further improvement of the invention, when the obtained converter output reference voltage is overlapped and output to the PWM modulation unit, the current harmonic wave is distributed among the multiple converters according to the capacity.
A harmonic control system suitable for use in a grid-tied converter, comprising:
the calculating module is used for calculating the voltage of the public connection point by utilizing the sampled output voltage and the sampled output current;
the extraction module is used for extracting the total harmonic wave of the common connection point voltage and the output current;
the building module is used for building a unified droop relation between the common connection point voltage and the total harmonic of the output current by adopting droop and multi-proportion resonance control according to the detected total harmonic of the voltage and the current to obtain a harmonic compensation reference voltage;
and the superposition module is used for superposing the harmonic compensation reference voltage and the fundamental reference voltage to obtain the output reference voltage of the converter, and superposing and outputting the output reference voltage to the PWM modulation unit.
An electronic device comprising a memory, a processor and a computer program stored in the memory and executable on the processor, the processor implementing the steps of the harmonic control method suitable for a grid-tied converter when the computer program is executed.
A computer readable storage medium storing a computer program which, when executed by a processor, implements the steps of the harmonic control method applicable to a grid-connected converter.
Compared with the prior art, the harmonic control method has the following advantages:
the harmonic control method suitable for the grid-connected converter, provided by the invention, aims at the multi-converter units connected to the same common connection point, calculates the voltage of the common connection point based on local measurement information, then only extracts the total harmonic of the voltage of the common connection point and the output current to establish a uniform droop relation, adopts a multi-proportion resonance controller to ensure that the droop relation is established in a steady state, and suppresses the voltage harmonic of the common connection point while realizing the distribution of the output current harmonic according to the capacity of the converter. The invention solves the complex treatment of harmonic voltage and current of the grid-structured converter in the grid-connected or off-grid mode, and does not need to extract the harmonic wave of specific order, thus greatly simplifying the operand compared with the prior method.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic diagram of an overall control structure of a current transformer according to an embodiment of the present invention;
FIG. 2 is a block diagram of a harmonic extraction structure according to an embodiment of the present invention;
FIG. 3 is a block diagram of harmonic droop control according to an embodiment of the present invention;
FIG. 4 is a simulation waveform diagram of a grid-tie mode according to an embodiment of the present invention; (a) is a common junction voltage harmonic; (b) is the output current single harmonic distortion;
FIG. 5 is a simulated waveform diagram in off-grid mode according to an embodiment of the present invention; (a) is a common junction voltage harmonic; (b) is the output current single harmonic distortion.
FIG. 6 is a flowchart of a method for controlling harmonics of a grid-tied converter according to an embodiment of the present invention;
fig. 7 is a block diagram of a harmonic control system suitable for a grid-tied converter according to an embodiment of the present invention.
Detailed Description
In order to make the purpose and technical scheme of the invention clearer and easier to understand. The present invention will now be described in further detail with reference to the drawings and examples, which are given for the purpose of illustration only and are not intended to limit the invention thereto.
The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings and specific embodiments, and it is apparent that the described embodiments are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to fall within the scope of the invention.
In order to solve the problems, a harmonic control method needs to be established for the grid-structured converter, so that the harmonic control method meets the requirements of both common connection point harmonic voltage suppression and current harmonic distribution in two modes of grid connection and grid disconnection under the condition of not considering communication.
Aiming at the grid-connected mode, an active power filter is mainly adopted at present to treat the harmonic wave of a public connection point, and the purpose of restraining the harmonic wave is achieved by injecting the harmonic wave which is equal to the original harmonic wave in size and opposite in phase to the power grid. The technology is mature and widely applied, and the control mode of the technology can be transplanted into a grid-built converter, but a phase-locked loop is usually required to be used in the harmonic extraction link of the technology, so that the grid-built converter can lose the advantage of independent grid connection of the phase-locked loop by adopting the method, and the small signal stability and active supporting capacity of the grid-built converter are reduced. For off-grid mode, one mainstream method is to increase virtual impedance to remodel harmonic suboutput impedance of each converter, so that harmonic suboutput impedance of each converter is inversely proportional to converter capacity, and therefore current harmonic is distributed among converters according to capacity ratio. However, the harmonic output impedance of the converter is increased to generate a larger harmonic voltage drop, so that voltage harmonics appear at the common connection point. The existing method is usually only aimed at one mode analysis and design of grid connection or off-grid, and a harmonic treatment scheme considering two modes of grid-built current transformer and off-grid is seldom discussed.
The invention aims to uniformly control the total harmonic components under the condition that specific order harmonic waves are not required to be extracted respectively, and reduce the voltage harmonic waves of the common connection point while realizing harmonic wave current sharing.
As shown in fig. 6, a first object of the present invention is to provide a harmonic control method suitable for a grid-connected converter, including:
s1, calculating the voltage of a public connection point by using the sampled output voltage and the sampled output current;
s2, extracting the total harmonic wave of the common connection point voltage and the output current;
s3, according to the detected total harmonic wave of the voltage and the current, adopting droop+multi-proportion resonance control to establish a unified droop relation between the voltage of the common connection point and the total harmonic wave of the output current, and obtaining a harmonic compensation reference voltage;
and S4, superposing the harmonic compensation reference voltage and the fundamental reference voltage to obtain the output reference voltage of the converter, and superposing and outputting the output reference voltage to the PWM modulation unit.
At present, most of harmonic control schemes for the grid-built converter need to control after extracting each subharmonic, so that the calculated amount is large, and the embedded controller of the converter needs to have stronger operation capability. The harmonic control method suitable for the grid-connected converter provided by the invention has the advantages that all subharmonics adopt the same sagging curve, only all components of the harmonic are required to be uniformly controlled, and the harmonic of a specific order is not required to be extracted respectively.
For grid-tie mode, existing harmonic control schemes typically require the use of phase-locked loops, making them unsuitable for grid-tie converter control. The harmonic control method suitable for the grid-connected converters can reduce the harmonic voltage of the common connection point without adopting a phase-locked loop, and can realize the distribution of current harmonic waves among a plurality of converters.
The harmonic control method suitable for the grid-connected converter can be applied to two modes of grid connection and grid disconnection, and can compensate voltage and current harmonic without switching harmonic control under the two modes, so that the method has certain advantages.
The invention is described in detail below with reference to specific embodiments and drawings, and the purpose of the invention is achieved by the following technical schemes:
FIG. 1 is a schematic diagram of an overall control structure of a current transformer according to an embodiment of the present invention; specifically, a direct current power supply, a converter and an LCL filter circuit in the main circuit are sequentially connected, and the LCL filter circuit is connected into an alternating current bus through line impedance. The control circuit consists of two parts: the fundamental wave control part adopts virtual synchronous machine (VSG) control and can control the active power and the reactive power (P) through the setting 0 、Q 0 ) And the measured converter output voltage and output current (V out(αβ) 、I out(αβ) ) Obtaining PWM fundamental reference voltage (V) pwm(αβ) ). The harmonic compensation control part is based on harmonic droop control and is responsible for PCC harmonic voltage compensation and harmonic current sharing, and comprises the following steps: PCC voltage estimation link, harmonic extraction link and unified harmonic voltage-current droop controlAnd (3) a multi-proportion resonance control link. First, according to the output voltage (V out(αβ) ) And output current (I) out(αβ) ) For PCC voltage (V pcc(αβ) ) An estimation is made. Subsequently, from the PCC voltage (V pcc(αβ) ) And output current (I) out(αβ) ) Extraction of PCC Voltage Total harmonicAnd the total harmonic of the output current->Finally, the extracted voltage-current harmonics +.>Adjusting by droop control and multi-proportion resonance control to obtain harmonic compensation reference voltage V c(αβ) V output from fundamental control loop pwm(αβ) And superposing to obtain a PWM modulation voltage signal.
Based on fig. 1, a detailed description is given of a harmonic control method applicable to a grid-connected converter, which includes the following steps:
1) Calculating a common connection point voltage by using the sampled output voltage and the sampled output current;
based on kirchhoff's law, the common junction voltage calculation expression is as follows:
wherein ,Vpcc For the common junction voltage, V out 、I out R is the output voltage and the output current of the converter line 、L line Is the line impedance. Typically, the design entity may provide line impedance information.
2) Extracting the total harmonic of the common connection point voltage and the output current;
at present, the existing method for extracting the harmonic wave generally extracts each subharmonic wave respectively, and the adopted method comprises a plurality of methods such as fast Fourier transform, phase-locked loop, multiple synchronous harmonic wave dq transform and the like. The invention only needs to detect the total harmonic component, adopts a biquad generalized integral-positive and negative sequence calculation module (DSOGI-PNSC), and can obtain the sum of the harmonic wave and the fundamental wave negative sequence by subtracting the input quantity of the module from the extracted fundamental wave positive sequence, thereby accurately extracting the fundamental wave negative sequence and the harmonic wave, as shown in figure 2.
And respectively passing the voltage and the current under the alpha beta coordinate system through two biquad generalized integral orthogonal signal generators (SOGI) with the same parameters to obtain two groups of orthogonal signals.
The transfer functions of the SOGI portions are shown as (2) - (3), here in x α Input is exemplified by x β And the same is true.
wherein ,xα Omega is SOGI input signal and frequency, x' α And qx' α K is the gain factor of the closed loop system, which is two mutually orthogonal output signals.
wherein ,xα 、x β Signals are input to the two SOGI modules respectively,respectively a fundamental positive sequence, a fundamental negative sequence and harmonics,>is the sum of the negative sequences of the harmonic wave and the fundamental wave, which is the quantity to be controlled.
The extracted orthogonal signals are passed through a positive and negative sequence calculation module (PNSC) to obtain total harmonic components, and the expression is as follows:
wherein ,xα 、x β Signals are input to the two SOGI modules respectively,respectively a fundamental positive sequence, a fundamental negative sequence and harmonics,>is the sum of the negative sequences of the harmonic wave and the fundamental wave, which is the quantity to be controlled.
3) According to the detected total harmonic wave of the voltage and the current, adopting droop+multi-proportion resonance control to establish a unified droop relation between the voltage of the common connection point and the total harmonic wave of the output current, and obtaining a harmonic compensation reference voltage;
fig. 3 is a block diagram of harmonic droop control, which consists of two parts, unified harmonic voltage-current droop control and multi-scale resonance control.
In the case where a plurality of converters are connected to the same common connection point, in order to distribute the output current harmonic of each unit according to the rated capacity, the common connection point voltage and the total harmonic component extracted from the output current are subjected to uniform droop control, and here, an αβ coordinate system is taken as an example, so that the total droop control is satisfied:
wherein ,respectively outputting current harmonic wave and common connection point voltage harmonic wave under a coordinate system, k droop Is inversely proportional to the capacity of each converter, i.e., k, for sag factor droop * base In the same system, C is a constant.
To achieve the resonance of (6) when the system is stableWave voltage-current sag relationship, needed to satisfy sag error in FIG. 3Is zero. The sagging error is calculated by the following method:
the obtained sagging errorThe main harmonic component is ensured to be zero through multi-proportion resonance control or multi-quasi-proportion resonance control, and the transfer function of the multi-quasi-proportion resonance control is as follows:
wherein ,kp Is a coefficient of proportionality and is used for the control of the power supply,is the resonance coefficient omega c Is the cut-off frequency (omega of the resonant controller c Multi-ratio resonance control when=0), ω m For fundamental angular frequency, h is the harmonic order, and 5, 7, 11 and 13 harmonics, which are typically the major components, are considered herein.
4) And superposing the harmonic compensation reference voltage and the fundamental reference voltage to obtain an inverter output reference voltage, and superposing and inputting the inverter output reference voltage to the PWM modulation unit.
The capacity-wise distribution of current harmonics among the multiple transformers is achieved while achieving high common-point voltage quality.
Fig. 4 and 5 are simulation waveform diagrams of the harmonic control method of the grid-structured converter. The capacities of the converters are set to be 5kVA and 2.5kVA respectively, and the load comprises the nonlinear load of the uncontrollable rectifier bridge. Fig. 4 shows a grid-connected mode (short-circuit ratio: 4.2), and fig. 5 shows an off-grid mode. Fig. 4 (a) and 5 (a) show the voltage harmonics of the common connection point, and fig. 4 (b) and 5 (b) show the single harmonic distortion of the output current. According to the simulation waveform, under the condition that all subharmonics are not extracted separately, the harmonic control method suitable for the grid-connected converter is suitable for two modes of grid connection and grid disconnection, the voltage harmonic of a public connection point can be effectively reduced, meanwhile, output current harmonic is distributed according to the capacity of the converter, and the two requirements of the voltage quality of the public connection point and harmonic current sharing are met.
As shown in fig. 7, the present invention provides a harmonic control system suitable for a grid-tied converter, which mainly includes:
the calculating module is used for calculating the voltage of the public connection point by utilizing the sampled output voltage and the sampled output current;
the extraction module is used for extracting the total harmonic wave of the common connection point voltage and the output current;
the building module is used for building a unified droop relation between the common connection point voltage and the total harmonic of the output current by adopting droop and multi-proportion resonance control according to the detected total harmonic of the voltage and the current to obtain a harmonic compensation reference voltage;
and the superposition module is used for superposing the harmonic compensation reference voltage and the fundamental reference voltage to obtain the output reference voltage of the converter, and superposing and outputting the output reference voltage to the PWM modulation unit.
The embodiment of the invention is applied to a multi-converter system connected to the same common connection point, and can realize capacity distribution of current harmonic waves among units and reduce voltage harmonic waves at the common connection point under the condition that specific order harmonic waves are not required to be extracted respectively for two modes of grid-connected or off-grid operation.
A third aspect of the present invention provides an electronic device comprising a memory, a processor and a computer program stored in the memory and executable on the processor, the processor implementing the steps of the method for harmonic control of a networked converter, which takes into account multi-interactive functional latency characteristics, when executing the computer program.
A fourth aspect of the present invention provides a computer readable storage medium storing a computer program which, when executed by a processor, implements the steps of the harmonic control method for a grid-connected converter that accounts for multi-interactive functional delay characteristics.
It will be appreciated by those skilled in the art that 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.
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 flowchart illustrations and/or block diagrams, and combinations of flows and/or blocks in the flowchart illustrations 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.
Finally, it should be noted that: the above embodiments are only for illustrating the technical aspects of the present invention and not for limiting the same, and although the present invention has been described in detail with reference to the above embodiments, it should be understood by those of ordinary skill in the art that: modifications and equivalents may be made to the specific embodiments of the invention without departing from the spirit and scope of the invention, which is intended to be covered by the claims.
Claims (10)
1. A harmonic control method for a grid-tied converter, comprising:
calculating a common connection point voltage by using the sampled output voltage and the sampled output current;
extracting the total harmonic of the common connection point voltage and the output current;
according to the detected total harmonic wave of the voltage and the current, adopting droop+multi-proportion resonance control to establish a unified droop relation between the voltage of the common connection point and the total harmonic wave of the output current, and obtaining a harmonic compensation reference voltage;
and superposing the harmonic compensation reference voltage and the fundamental reference voltage to obtain the output reference voltage of the converter, and superposing and outputting the output reference voltage to the PWM modulation unit.
2. A harmonic control method for a grid-tied converter according to claim 1, wherein deriving the common-point voltage using the sampled output voltage and the output current comprises:
based on kirchhoff's law, the common junction voltage calculation expression is:
wherein ,Vpcc For the common junction voltage, V out 、I out R is the output voltage and the output current of the converter line 、L line The resistance and inductance of the line.
3. The method for controlling harmonic waves suitable for use in a grid-connected converter according to claim 1, wherein the method for extracting the total harmonic waves of the voltage and the output current of the common connection point comprises a biquad generalized integral-positive-negative sequence calculation module, a fast fourier transform, a phase-locked loop, or a multiple synchronous harmonic dq transform.
4. The harmonic control method for a grid-tied converter according to claim 1, wherein the extracting the total harmonic of the common-point voltage and the output current comprises:
the sum of harmonic wave and fundamental wave negative sequence is obtained by subtracting the extracted fundamental wave positive sequence from the input quantity of the biquad generalized integral-positive sequence calculation module, and the expression is as follows:
wherein ,xα 、x β Signals are input to the two SOGI modules respectively,respectively a fundamental positive sequence, a fundamental negative sequence and harmonics,>the sum of the harmonic wave and the fundamental wave negative sequence is the quantity to be controlled.
5. According to claimThe harmonic control method for a grid-connected converter as set forth in claim 4, wherein said x is α The corresponding SOGI module transfer function is:
wherein ,xα Omega is SOGI input signal and frequency, x' α And qx' α K is the gain coefficient of the closed loop system; x is x β Corresponding transfer function and x α The same applies.
6. A harmonic control method for a grid-tied converter according to claim 1, wherein establishing a unified droop relationship of the common-point voltage and the total harmonic of the output current comprises:
and (3) uniformly drooping control is adopted on the total harmonic components extracted from the common connection point voltage and the output current, so that the total harmonic components meet the following conditions:
wherein ,respectively, the output current harmonic wave and the common connection point voltage harmonic wave under the alpha beta coordinate system, k droop For sag factor, k droop *S base =c, C is a constant;
according to the harmonic wave uniform droop relation, the droop error is as follows:
the obtained sagging errorThe main harmonic component is zero through multi-proportion resonance control or multi-quasi-proportion resonance control, and the transfer function of the multi-quasi-proportion resonance control is as follows:
wherein ,kp Is a coefficient of proportionality and is used for the control of the power supply,is the resonance coefficient omega c For the cut-off frequency, ω of the resonant controller m The fundamental wave angular frequency, and h is the harmonic frequency.
7. The harmonic control method for a grid-connected converter according to claim 1, wherein the obtained converter output reference voltage is superimposed and output to the PWM modulation unit, and the current harmonics are distributed among the converters according to capacity.
8. A harmonic control system for a grid-tied converter, comprising:
the calculating module is used for calculating the voltage of the public connection point by utilizing the sampled output voltage and the sampled output current;
the extraction module is used for extracting the total harmonic wave of the common connection point voltage and the output current;
the building module is used for building a unified droop relation between the common connection point voltage and the total harmonic of the output current by adopting droop and multi-proportion resonance control according to the detected total harmonic of the voltage and the current to obtain a harmonic compensation reference voltage;
and the superposition module is used for superposing the harmonic compensation reference voltage and the fundamental reference voltage to obtain the output reference voltage of the converter, and superposing and outputting the output reference voltage to the PWM modulation unit.
9. An electronic device comprising a memory, a processor and a computer program stored in the memory and executable on the processor, the processor implementing the steps of the harmonic control method for a networked converter according to any one of claims 1-7 when the computer program is executed.
10. A computer-readable storage medium, characterized in that the computer-readable storage medium stores a computer program which, when executed by a processor, implements the steps of the harmonic control method applicable to a grid-connected converter as claimed in any one of claims 1-7.
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| CN117526428B (en) * | 2024-01-05 | 2024-04-09 | 清华大学 | Inverter networking control method based on Landolt-Stuttgart vibrator |
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