CN116667350A - Grid-connected harmonic current suppression method and device for grid-connected inverter based on phase compensation - Google Patents
Grid-connected harmonic current suppression method and device for grid-connected inverter based on phase compensation Download PDFInfo
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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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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
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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
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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
- H02M1/0003—Details of control, feedback or regulation circuits
- H02M1/0025—Arrangements for modifying reference values, feedback values or error values in the control loop of a converter
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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
- 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
- H02M7/53875—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 with analogue control of three-phase output
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- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
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- Y02E40/40—Arrangements for reducing harmonics
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Abstract
The invention relates to the technical field of power conversion and electric energy quality management, and provides a grid-connected harmonic current suppression method and device based on a phase compensation grid-structured inverter, wherein the method comprises the following steps: harmonic detection is carried out on the grid-connected point voltage and the grid-connected current by adopting a reduced-order generalized integrator with phase compensation, and harmonic components of the grid-connected point voltage and the grid-connected current are obtained; determining harmonic compensation voltage according to the grid-connected point voltage and the harmonic component of the grid-connected current; and obtaining a control reference voltage command according to the harmonic compensation voltage and the fundamental wave reference voltage so as to control the inverter through the control reference voltage command. The invention can effectively and timely inhibit harmonic current and improve the stability of the grid-connected system of the grid-formed inverter.
Description
Technical Field
The invention relates to the technical field of power conversion and electric energy quality management, in particular to a grid-connected harmonic current suppression method based on a phase compensation grid-structured inverter and a grid-connected harmonic current suppression device based on the phase compensation grid-structured inverter.
Background
Under the driving of the national double-carbon target of 'carbon peak, carbon neutralization', the grid-structured inverter is increasingly widely applied in a distributed power generation system. The grid-formed inverter increases inertia and damping on the basis of traditional droop control, and can provide voltage and frequency support for the system. In addition, the grid-type inverter has better stability than the grid-type inverter because the grid-type inverter can be operated by being separated from the phase-locked loop.
However, research on grid-connected inverters is mainly focused on inertia, damping, other dynamic performances and the like, and the electric energy quality problem of grid-connected systems of the grid-connected inverters is less concerned. In a distributed power generation system, grid-connected current is easily influenced by a harmonic source to generate distortion, so that a complex harmonic interaction problem between a control system and a distributed power generation network is caused. The grid-built inverter should therefore be more concerned with the quality of the power it injects into the grid.
Because the grid-built inverter does not have internal closed loop current control, under the distorted power grid background, the traditional harmonic suppression scheme is difficult to improve the power quality of the grid-built inverter during grid connection. Most of the current schemes are limited in the methods of remolding the output impedance of a grid-built inverter, such as series-parallel connection negative sequence virtual impedance to establish a harmonic current loop, but are limited in the application occasions of strong dependence on key parameters, large voltage drop amplitude, poor stability, high implementation difficulty and single inverter, so that flexible compensation under the scene of multiple inverters is difficult to realize, harmonic current is difficult to effectively inhibit, and the harmonic suppression response time is long and the system stability is poor.
Disclosure of Invention
The invention aims to solve the technical problems, and provides a grid-connected harmonic current suppression method and a grid-connected harmonic current suppression device based on a phase compensation grid-formed inverter, which can effectively and timely suppress harmonic current and improve the stability of a grid-formed inverter grid-connected system.
The technical scheme adopted by the invention is as follows:
a grid-connected harmonic current suppression method based on phase compensation grid-formed inverter comprises the following steps: harmonic detection is carried out on the grid-connected point voltage and the grid-connected current by adopting a reduced-order generalized integrator with phase compensation, and harmonic components of the grid-connected point voltage and the grid-connected current are obtained; determining harmonic compensation voltage according to the grid-connected point voltage and the harmonic component of the grid-connected current; and obtaining a control reference voltage command according to the harmonic compensation voltage and the fundamental wave reference voltage so as to control the inverter through the control reference voltage command.
Obtaining harmonic components of the grid-connected point voltage and the grid-connected current according to the following steps:
wherein ,for the harmonic component of the grid-connected current, +.>For the harmonic component of the grid-tie voltage, +.>For the grid-connected current, +.>For the grid-connected point voltage, +.>In order to be a harmonic extraction unit,sis a laplace operator.
The harmonic extraction unit is obtained according to the following equation:
wherein ,hin order to require the number of extracted harmonics,jin units of imaginary numbers,for the fundamental angular frequency of the wave,K r in order to integrate the gain,for increased damping term->To the phase angle that needs compensation +.>Can be determined from the nyquist curve before compensation.
According to one embodiment of the invention, the harmonic compensation voltage is obtained according to the following equation:
wherein ,xand (3) withyAre positive scaling factors.
A grid-connected harmonic current suppression device based on phase compensation grid-formed inverter comprises: the detection module is used for carrying out harmonic detection on the grid-connected point voltage and the grid-connected current based on the reduced-order generalized integrator to obtain harmonic components of the grid-connected point voltage and the grid-connected current; the determining module is used for determining harmonic compensation voltage according to the grid-connected point voltage and the harmonic component of the grid-connected current; and the acquisition module is used for acquiring a control reference voltage command according to the harmonic compensation voltage and the fundamental reference voltage so as to control the inverter through the control reference voltage command.
The detection module obtains harmonic components of the grid-connected point voltage and the grid-connected current according to the following formula:
wherein ,for the harmonic component of the grid-connected current, +.>For the harmonic component of the grid-tie voltage, +.>For the grid-connected current, +.>For the grid-connected point voltage, +.>In order to be a harmonic extraction unit,sis a laplace operator.
The detection module obtains the harmonic extraction unit according to the following formula:
wherein ,hin order to require the number of extracted harmonics,jin units of imaginary numbers,for the fundamental angular frequency of the wave,K r in order to integrate the gain,for increased damping term->To the phase angle that needs compensation +.>Can be determined from the nyquist curve before compensation.
The acquisition module acquires the harmonic compensation voltage according to the following formula:
wherein ,xand (3) withyAre positive scaling factors.
The invention has the beneficial effects that:
according to the invention, harmonic detection is carried out by arranging the reduced-order generalized integrator with phase compensation at the grid-connected point, so that harmonic components of grid-connected current and grid-connected point voltage are obtained, further harmonic compensation voltage is determined, and then a control reference voltage command is obtained according to the harmonic compensation voltage and fundamental reference voltage, so that the control of the inverter is realized, and therefore, the harmonic current can be effectively and timely restrained, and the stability of a grid-connected system of the grid-formed inverter is improved.
Drawings
Fig. 1 is a schematic diagram of a topology structure of a grid-connected harmonic current suppression device of a grid-connected inverter based on phase compensation according to an embodiment of the present invention;
fig. 2 is a flowchart of a method for suppressing grid-connected harmonic current of a grid-connected inverter based on phase compensation according to an embodiment of the present invention;
fig. 3 is a diagram of a harmonic equivalent circuit before phase compensation according to an embodiment of the present invention:
fig. 4 is a diagram of a harmonic equivalent circuit after phase compensation according to an embodiment of the present invention:
FIG. 5 is a closed loop transfer function block diagram of a grid-tied inverter grid-tie system according to one embodiment of the present invention;
FIG. 6 is a simulated waveform of grid-tie current over time for one embodiment of the invention;
FIG. 7 is a simulated waveform of grid-tie voltage over time according to one embodiment of the invention;
fig. 8 is a block diagram of a grid-connected harmonic current suppression device based on a phase compensation grid-structured inverter according to an embodiment of the present invention.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described 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 be within the scope of the invention.
As shown in fig. 1, in a grid-connected circuit of a grid-formed inverter, in order to implement the method and the device for suppressing the grid-connected harmonic current of the grid-formed inverter based on phase compensation according to the embodiment of the invention, a reduced-order generalized integrator with phase compensation is arranged at a grid-connected point and is used for voltage of the grid-connected pointAnd grid-connected current->Wherein the reduced-order generalized integrator with phase compensation comprises a harmonic extraction unit +.>. In the figure, the->For grid-side harmonic voltages, < >>For the impedance of the network>For harmonic components of the grid-connected current, +.>Is a harmonic component of the grid-tie voltage,R f 、L f andC f the filter is respectively an inverter side filter resistor, a filter inductor and a filter capacitor.
As shown in fig. 2, the method for suppressing grid-connected harmonic current of a grid-connected inverter based on phase compensation according to the embodiment of the invention comprises the following steps:
s1, harmonic detection is carried out on grid-connected point voltage and grid-connected current by adopting a reduced-order generalized integrator with phase compensation, and harmonic components of the grid-connected point voltage and the grid-connected current are obtained.
Specifically, the grid-connected point voltage can be obtained according to the following formulaAnd grid-connected current->Is a harmonic component of (a):
wherein ,for harmonic components of the grid-connected current, +.>For harmonic components of the grid-connected voltage, +.>For grid-connected current, +.>For grid-connected point voltage, ">In order to be a harmonic extraction unit,sis a laplace operator.
Further, the harmonic extraction unit may be obtained according to the following equation：
wherein ,hin order to require the number of extracted harmonics,jin units of imaginary numbers,for the fundamental angular frequency of the wave,K r in order to integrate the gain,for increased damping term->For the phase angle to be compensated, wherein +.>The nyquist curve before compensation can be determined, and can be set to 30 degrees to 60 degrees in general to obtain a good stability margin.
It should be noted that, the reduced-order generalized integrator with phase compensation is used for voltage at grid-connected pointAnd grid-connected current->Harmonic detection is carried out simultaneously with the harmonic extraction unit +.>Voltage +.>And grid-connected current->The phase compensation is carried out, so that the harmonic component of the grid-connected current can be restrained, the harmonic control bandwidth and the system stability are effectively improved, and the harmonic restraining performance of the system is improved.
S2, determining harmonic compensation voltage according to the grid-connected point voltage and the harmonic component of the grid-connected current.
Specifically, the harmonic compensation voltage can be obtained according to the following formula：
wherein ,xand (3) withyAre positive scaling factors. In one embodiment of the invention, the scaling factor may be selectedx1, for eliminating harmonic voltage on the grid sideFor->Is appropriately selected for the influence of the ratio coefficientyMaking it 10-20 times the grid impedance +.>For reducing nonlinear load harmonic currents +.>For->Is a function of (a) and (b).
The setting of the scaling factor in this way is described below in connection with FIGS. 3 and 4xAndythe reason for the range of values of (a).
As shown in FIG. 3The harmonic equivalent circuit before phase compensation can obtain grid-connected harmonic current before compensation according to the superposition theorem：
According to the harmonic equivalent circuit after phase compensation shown in fig. 4, the harmonic voltage of the mesh inverter after phase compensation can be obtained according to the following formula：
Substituting the above into the grid-connected harmonic current before compensationIn the expression of (2), the compensated grid-connected harmonic current can be obtained>：
From the above, the ratio coefficient is selectedxWhen the number of the particles is 1, the particles are,for->Can be completely eliminated, and in addition, the proportion coefficient is properly selectedyMaking it 10-20 times the grid impedance +.>Then->For a pair ofI gh The influence of (c) can also be reduced.
And S3, obtaining a control reference voltage command according to the harmonic compensation voltage and the fundamental wave reference voltage so as to control the inverter through the control reference voltage command.
As shown in fig. 1, in one embodiment of the invention, the harmonic compensation voltageFundamental reference voltage given in conjunction with VSG controller>Obtain control reference voltage command +.>Inverter switching tube generated and controlled by SVPWM technologyQ1~ Q6, realizing control of the inverter.
The principle of the grid-connected harmonic current suppression method of the grid-connected inverter based on phase compensation according to the embodiment of the invention is described below with reference to fig. 1 and 3-4.
As shown in FIG. 1, the grid-connected harmonic current suppression method based on the phase compensation grid-formed inverter of one embodiment of the invention is used for suppressing the voltage of a grid-connected point by arranging a reduced-order generalized integrator with phase compensation at the grid-connected pointAnd grid-connected currentIs detected by the harmonic component and at the same time by the harmonic extraction unit +.>Voltage +.>And grid-connected current->Is phase-compensated for the harmonic components of (a),obtaining harmonic components of grid-connected current>And harmonic component of the grid-connected voltage +.>Further determine the harmonic compensation voltage +.>Then compensating the voltage according to the harmonic>And fundamental reference voltage->Obtain control reference voltage command +.>The inverter is controlled, so that the influence of harmonic current is effectively and timely restrained.
As shown in FIG. 1, the reduced-order generalized integrator with phase compensation is used for the voltage of the grid-connected pointAnd grid-connected current->Harmonic component detection, obtaining the grid-connected point voltage according to the following>And grid-connected current->Is a harmonic component of (a):
(1)
wherein ,for harmonic components of the grid-connected current, +.>For harmonic components of the grid-connected voltage, +.>For grid-connected current, +.>For grid-connected point voltage, ">In order to be a harmonic extraction unit,sis a laplace operator. The transfer function of the harmonic extraction unit is as follows:
(2)
wherein ,hin order to require the number of extracted harmonics,jin units of imaginary numbers,for the fundamental angular frequency of the wave,K r in order to integrate the gain,for increased damping term->For the phase angle to be compensated, wherein +.>The nyquist curve before compensation can be determined, and can be set to 30 degrees to 60 degrees in general to obtain a good stability margin.
By voltage of grid-connected pointAnd grid-connected current->The phase compensation can restrain harmonic components of grid-connected current, effectively improve harmonic control bandwidth and system stability, and improve system harmonicInhibition performance.
As shown in FIG. 1, the harmonic compensation voltage can be determined from the harmonic components of the grid tie point voltage and the grid tie current：
(3)
wherein ,xand (3) withyAre positive scaling factors. In one embodiment of the invention, the scaling factor may be selectedx1, for eliminating harmonic voltage on the grid sideFor->Is appropriately selected for the influence of the ratio coefficientyMaking it 10-20 times the grid impedance +.>For reducing nonlinear load harmonic currents +.>For->Is a function of (a) and (b).
As shown in FIG. 3, the harmonic equivalent circuit before phase compensation can obtain grid-connected harmonic current before compensation according to the formula (4)：
(4)
As shown in fig. 4, the harmonic equivalent circuit after phase compensation can be based on the harmonic voltage of the grid-formed inverter after phase compensation according to equation (5)：
(5)
Substituting the formula (5) into the formula (4) to obtain the compensated grid-connected harmonic current：
(6)
From equation (6), the scaling factor is selectedxWhen 1, the harmonic voltage at the power grid sideFor->The influence of the non-linear load harmonic current with less quality control on the grid-connected current can be completely eliminated, and the proportion coefficient can be properly selectedyMaking it 10-20 times the grid impedance +.>。
Thus, the scaling factor can be selectedxFor 1, select the proportionality coefficientyMaking it 10-20 times of power grid impedanceReferring to FIG. 1, a harmonic compensation voltage is determined according to harmonic components of a grid-tied point voltage and a grid-tied current>Fundamental reference voltage +.>Obtain control reference voltage command +.>Inverter switching tube generated and controlled by SVPWM technologyQ1~Q6, realizing control of the inverter. Thus, not only the influence of the harmonic voltage on the power grid side can be completely eliminated, but also the influence of the nonlinear load harmonic current can be reduced.
The beneficial effects of the grid-connected harmonic current suppression method based on the phase compensation grid-structured inverter in the embodiment of the invention are verified by combining with fig. 5-7.
According to the closed loop transfer function model of the grid-connected system of the grid-built inverter shown in FIG. 5, the harmonic output impedance of the whole closed loop system can be obtained：
(7)
wherein ,Y p (s) and Y o (s) The method comprises the following steps:
(8)
(9)
wherein in the formula (8) and the formula (9)R f 、L f 、C f Respectively an inverter side filter resistor, a filter inductor and a filter capacitor,L 1 is a filter inductance near the grid side. In formula (7)G vsg (s) Divided into positive sequencesG vsg+ (s) And negative sequenceG vsg- (s) Two parts:
(10)
(11)
wherein ,f 1 for the fundamental frequency of the wave,V 1 for the amplitude of the fundamental wave of the voltage,I 1 for the amplitude of the fundamental current wave,for the fundamental angular frequency of the wave,is the fundamental current phase angle. In the formula (10) and the formula (11):
(12)
wherein ,E m for a given voltage amplitude value,T s is the sampling time.
(13)
wherein ,Jin order to be an inertia, the mass of the material,D p is damping.
(14)
wherein P e Is the active power reference value.
Harmonic output impedance obtainable according to equation (7)Drawing a Nyquist curve of the grid-connected system of the grid-built inverter, and judging the stability of the grid-built inverter grid-connected system. Wherein, the open loop transfer function T of the system is:
(15)
wherein ,Z g (s) Is the grid side impedance.
FIG. 6 is a simulated waveform of the grid-tie current over time according to one embodiment of the invention, FIG. 7 is a simulated grid-tie voltage over time according to one embodiment of the inventionTrue waveform diagram. As shown in fig. 6 and 7, in case of unbalanced and distorted grid conditions, grid-connected currents (including a, b, c phase grid-connected currentsi ga 、i gb 、i gc ) And grid-connected point voltage (including a, b, c phase grid-connected point voltageu pcca 、u pccb 、u pccc ) The unbalanced and harmonic components in the grid-connected harmonic current suppression method based on the phase compensation grid-connected inverter provided by the invention can effectively suppress harmonic current under the condition of distorting a power grid, and has the advantages of high response time and high stability of the grid-connected inverter grid-connected system.
According to the grid-connected harmonic current suppression method based on the phase compensation grid-connected inverter, which is provided by the invention, harmonic detection is carried out by arranging the reduced generalized integrator with phase compensation at the grid-connected point, so that harmonic components of grid-connected current and grid-connected point voltage are obtained, further harmonic compensation voltage is determined, and then a control reference voltage instruction is obtained according to the harmonic compensation voltage and fundamental reference voltage, so that the inverter is controlled, and therefore, the harmonic current can be effectively and timely suppressed, and the stability of a grid-connected system of the grid-connected inverter is improved.
Corresponding to the method for suppressing the grid-connected harmonic current of the grid-connected inverter based on the phase compensation in the embodiment, the invention also provides a device for suppressing the grid-connected harmonic current of the grid-connected inverter based on the phase compensation.
As shown in fig. 8, a phase compensation grid-structured inverter grid-connected harmonic current suppression device according to an embodiment of the present invention includes: the device comprises a detection module 10, a determination module 20 and an acquisition module 30. The detection module 10 is used for carrying out harmonic detection on the grid-connected point voltage and the grid-connected current based on the reduced-order generalized integrator to obtain harmonic components of the grid-connected point voltage and the grid-connected current; the determining module 20 is configured to determine a harmonic compensation voltage according to the grid-connected point voltage and the harmonic component of the grid-connected current; the acquisition module 30 is configured to obtain a control reference voltage command according to the harmonic compensation voltage and the fundamental reference voltage, so as to control the inverter by the control reference voltage command.
In one embodiment of the present invention, the detection module 10 obtains the grid-connected point voltage according to the following equationAnd grid-connected current->Is a harmonic component of (a):
wherein ,for harmonic components of the grid-connected current, +.>For harmonic components of the grid-connected voltage, +.>For grid-connected current, +.>For grid-connected point voltage, ">In order to be a harmonic extraction unit,sis a laplace operator.
Further, the detection module 10 may obtain the harmonic extraction unit according to the following formula：
wherein ,hin order to require the number of extracted harmonics,jin units of imaginary numbers,for the fundamental angular frequency of the wave,K r in order to integrate the gain,for increased damping term->For the phase angle to be compensated, wherein +.>The nyquist curve before compensation can be determined, and can be set to 30 degrees to 60 degrees in general to obtain a good stability margin.
It should be noted that, the reduced-order generalized integrator with phase compensation is used for voltage at grid-connected pointAnd grid-connected current->While harmonic detection is performed, by means of a harmonic extraction unit->Voltage +.>And grid-connected current->The harmonic component of the grid-connected current can be restrained by phase compensation, the harmonic control bandwidth and the system stability are effectively improved, and the system harmonic restraining performance is improved.
In one embodiment of the present invention, the determination module 20 may obtain the harmonic compensation voltage according to the following equation：
wherein ,xand (3) withyAre positive scaling factors. In one embodiment of the invention, the scaling factor may be selectedx1, for eliminating harmonic voltage on the grid sideFor->Is appropriately selected for the influence of the ratio coefficientyMaking it 10-20 times the grid impedance +.>For reducing nonlinear load harmonic currents +.>For->Is a function of (a) and (b).
The setting of the scaling factor in this way is described below in connection with FIGS. 3 and 4xAndythe reason for the range of values of (a).
The harmonic equivalent circuit before phase compensation as shown in FIG. 3 can obtain the grid-connected harmonic current before compensation according to the superposition theorem：
According to the phase-compensated harmonic equivalent circuit shown in fig. 4, the harmonic voltage of the phase-compensated grid-formed inverter：
Substituting the above into the grid-connected harmonic current before compensationIn the expression of (2), the compensated grid-connected harmonic current can be obtained>：
From the above, the ratio coefficient is selectedxWhen 1, v is equal toCan be completely eliminated, and in addition, the proportion coefficient is properly selectedyMaking it 10-20 times the grid impedance +.>Then->For a pair ofI gh The influence of (c) can also be reduced.
As shown in FIG. 1, in one embodiment of the invention, the acquisition module 30 compensates the voltage according to harmonicsFundamental reference voltage given in conjunction with VSG controller>Obtain control reference voltage command +.>Inverter switching tube generated and controlled by SVPWM technologyQ1~Q6, realizing control of the inverter.
The principle of the grid-connected harmonic current suppression device based on the phase compensation grid-structured inverter according to the embodiment of the invention is described below with reference to fig. 1 and 3-4.
As shown in fig. 1, a detection module 10 of a grid-connected harmonic current suppression device of a grid-connected inverter based on phase compensation according to an embodiment of the present invention is configured to reduce the voltage of a grid-connected point by providing a generalized integrator with phase compensation at the grid-connected pointAnd grid-connected current->Is detected by the harmonic component and at the same time by the harmonic extraction unit +.>Voltage +.>And grid-connected current->Phase compensation is carried out on harmonic components of the grid-connected current to obtain harmonic components +.>And the harmonic component v of the grid-tie voltage, whereby the determination module 20 is able to determine the harmonic compensation voltage +.>The acquisition module 30 then compensates the voltage according to the harmonics + ->And fundamental reference voltage->Obtain control reference voltage command +.>The inverter is controlled, so that the influence of harmonic current is effectively and timely restrained.
As shown in fig. 1, the detection module 10 uses a reduced-order generalized integrator with phase compensation to detect the voltage of the grid-connected pointAnd grid-connected current->Is obtained according to the following formulaDot voltage->And grid-connected current->Is a harmonic component of (a):
(1)
wherein ,for harmonic components of the grid-connected current, +.>For harmonic components of the grid-connected voltage, +.>For grid-connected current, +.>For grid-connected point voltage, ">In order to be a harmonic extraction unit,sis a laplace operator. The transfer function of the harmonic extraction unit is as follows:
(2)
wherein ,hin order to require the number of extracted harmonics,jin units of imaginary numbers,for the fundamental angular frequency of the wave,K r in order to integrate the gain,for increased damping term->For the phase angle to be compensated, wherein +.>The nyquist curve before compensation can be determined, and can be set to 30 degrees to 60 degrees in general to obtain a good stability margin.
By voltage of grid-connected pointAnd grid-connected current->The phase compensation can restrain harmonic components of grid-connected current, effectively improve harmonic control bandwidth and system stability, and improve system harmonic suppression performance.
As shown in FIG. 1, the determination module 20 may determine the harmonic compensation voltage based on the harmonic components of the grid tie point voltage and the grid tie current：
(3)
wherein ,xand (3) withyAre positive scaling factors. In one embodiment of the invention, the scaling factor may be selectedx1, for eliminating harmonic voltage on the grid sideFor->Is appropriately selected for the influence of the ratio coefficientyMaking it 10-20 times the grid impedance +.>For reducing nonlinear load harmonic currents +.>For->Is a function of (a) and (b).
As shown in FIG. 3, the harmonic equivalent circuit before phase compensation can obtain grid-connected harmonic current before compensation according to the formula (4)：
(4)
As shown in fig. 4, the harmonic equivalent circuit after phase compensation can be based on the harmonic voltage of the grid-formed inverter after phase compensation according to equation (5)：
(5)
Substituting the formula (5) into the formula (4) to obtain the compensated grid-connected harmonic current：
(6)
From equation (6), the scaling factor is selectedxWhen 1, the harmonic voltage at the power grid sideFor->The influence of the non-linear load harmonic current with less quality control on the grid-connected current can be completely eliminated, and the proportion coefficient can be properly selectedyMaking it 10-20 times the grid impedance +.>。
Thus, the scaling factor can be selectedxFor 1, select the proportionality coefficientyMaking it 10-20 times of power grid impedanceReferring to FIG. 1, a harmonic compensation voltage is determined according to harmonic components of a grid-tied point voltage and a grid-tied current>Fundamental reference voltage +.>Obtain control reference voltage command +.>Inverter switching tube generated and controlled by SVPWM technologyQ1~Q6, realizing control of the inverter. Thus, not only the influence of the harmonic voltage on the power grid side can be completely eliminated, but also the influence of the nonlinear load harmonic current can be reduced.
The beneficial effects of the grid-connected harmonic current suppression device based on the phase compensation grid-structured inverter in the embodiment of the invention are verified by combining with fig. 5-7.
According to the closed loop transfer function model of the grid-connected system of the grid-built inverter shown in FIG. 5, the harmonic output impedance of the whole closed loop system can be obtained：
(7)
wherein ,Y p (s) and Y o (s) The method comprises the following steps:
(8)
(9)
wherein in the formula (8) and the formula (9)R f 、L f 、C f Respectively an inverter side filter resistor, a filter inductor and a filter capacitor,L 1 is a filter inductance near the grid side. In formula (7)G vsg (s) Divided into positive sequencesG vsg+ (s) And negative sequenceG vsg- (s) Two parts:
(10)
(11)
wherein ,f 1 for the fundamental frequency of the wave,V 1 for the amplitude of the fundamental wave of the voltage,I 1 for the amplitude of the fundamental current wave,for the fundamental angular frequency of the wave,is the fundamental current phase angle. In the formula (10) and the formula (11):
(12)
wherein ,E m for a given voltage amplitude value,T s is the sampling time.
(13)
wherein ,Jin order to be an inertia, the mass of the material,D p is damping.
(14)
wherein P e Is the active power reference value.
Harmonic output impedance obtainable according to equation (7)Drawing a Nyquist curve of the grid-connected system of the grid-built inverter, and judging the stability of the grid-built inverter grid-connected system. Wherein, the open loop transfer function T of the system is:
(15)
wherein ,Z g (s) Is the grid side impedance.
Fig. 6 is a simulated waveform diagram of a grid-connected current versus time according to an embodiment of the present invention, and fig. 7 is a simulated waveform diagram of a grid-connected voltage versus time according to an embodiment of the present invention. As shown in fig. 6 and 7, in case of unbalanced and distorted grid conditions, grid-connected currents (including a, b, c phase grid-connected currentsi ga 、i gb 、i gc ) And grid-connected point voltage (including a, b, c phase grid-connected point voltageu pcca 、u pccb 、u pccc ) The unbalanced and harmonic components in the grid-connected harmonic current suppression device based on the phase compensation grid-connected inverter provided by the invention can effectively suppress harmonic current under the condition of a distorted power grid, and has the advantages of high response time and high stability of the grid-connected inverter grid-connected system.
According to the grid-connected harmonic current suppression device based on the phase compensation grid-connected inverter, which is provided by the invention, harmonic detection is carried out by arranging the reduced generalized integrator with phase compensation at the grid-connected point, so that harmonic components of grid-connected current and grid-connected point voltage are obtained, further harmonic compensation voltage is determined, then a control reference voltage command is obtained according to the harmonic compensation voltage and fundamental reference voltage, and the inverter is controlled, so that the harmonic current can be effectively and timely suppressed, and the stability of a grid-connected system of the grid-connected inverter is improved.
In the description of the present invention, the terms "first," "second," and the like are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include one or more such feature. The meaning of "a plurality of" is two or more, unless specifically defined otherwise.
In the present invention, unless explicitly specified and limited otherwise, the terms "mounted," "connected," "secured," and the like are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally formed; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium, and can be communicated with the inside of two elements or the interaction relationship of the two elements. The specific meaning of the above terms in the present invention can be understood by those of ordinary skill in the art according to the specific circumstances.
In the present invention, unless expressly stated or limited otherwise, a first feature "up" or "down" a second feature may be the first and second features in direct contact, or the first and second features in indirect contact via an intervening medium. Moreover, a first feature being "above," "over" and "on" a second feature may be a first feature being directly above or obliquely above the second feature, or simply indicating that the first feature is level higher than the second feature. The first feature being "under", "below" and "beneath" the second feature may be the first feature being directly under or obliquely below the second feature, or simply indicating that the first feature is less level than the second feature.
In the description of the present specification, a description referring to terms "one embodiment," "some embodiments," "examples," "specific examples," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms are not necessarily for the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, the different embodiments or examples described in this specification and the features of the different embodiments or examples may be combined and combined by those skilled in the art without contradiction.
Any process or method descriptions in flow charts or otherwise described herein may be understood as representing modules, segments, or portions of code which include one or more executable instructions for implementing specific logical functions or steps of the process, and further implementations are included within the scope of the preferred embodiment of the present invention in which functions may be executed out of order from that shown or discussed, including substantially concurrently or in reverse order, depending on the functionality involved, as would be understood by those reasonably skilled in the art of the present invention.
Logic and/or steps represented in the flowcharts or otherwise described herein, e.g., a ordered listing of executable instructions for implementing logical functions, can be embodied in any computer-readable medium for use by or in connection with an instruction execution system, apparatus, or device, such as a computer-based system, processor-containing system, or other system that can fetch the instructions from the instruction execution system, apparatus, or device and execute the instructions. For the purposes of this description, a "computer-readable medium" can be any means that can contain, store, communicate, propagate, or transport the program for use by or in connection with the instruction execution system, apparatus, or device. More specific examples (a non-exhaustive list) of the computer-readable medium would include the following: an electrical connection (electronic device) having one or more wires, a portable computer diskette (magnetic device), a Random Access Memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber device, and a portable compact disc read-only memory (CDROM). In addition, the computer readable medium may even be paper or other suitable medium on which the program is printed, as the program may be electronically captured, via, for instance, optical scanning of the paper or other medium, then compiled, interpreted or otherwise processed in a suitable manner, if necessary, and then stored in a computer memory.
It is to be understood that portions of the present invention may be implemented in hardware, software, firmware, or a combination thereof. In the above-described embodiments, the various steps or methods may be implemented in software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, may be implemented using any one or combination of the following techniques, as is well known in the art: discrete logic circuits having logic gates for implementing logic functions on data signals, application specific integrated circuits having suitable combinational logic gates, programmable Gate Arrays (PGAs), field Programmable Gate Arrays (FPGAs), and the like.
Those of ordinary skill in the art will appreciate that all or a portion of the steps carried out in the method of the above-described embodiments may be implemented by a program to instruct related hardware, where the program may be stored in a computer readable storage medium, and where the program, when executed, includes one or a combination of the steps of the method embodiments.
In addition, each functional unit in the embodiments of the present invention may be integrated in one processing module, or each unit may exist alone physically, or two or more units may be integrated in one module. The integrated modules may be implemented in hardware or in software functional modules. The integrated modules may also be stored in a computer readable storage medium if implemented in the form of software functional modules and sold or used as a stand-alone product.
While embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and not to be construed as limiting the invention, and that variations, modifications, alternatives and variations may be made to the above embodiments by one of ordinary skill in the art within the scope of the invention.
Claims (2)
1. The grid-connected harmonic current suppression method for the grid-formed inverter based on phase compensation is characterized by comprising the following steps of:
harmonic detection is carried out on the grid-connected point voltage and the grid-connected current by adopting a reduced-order generalized integrator with phase compensation, and harmonic components of the grid-connected point voltage and the grid-connected current are obtained;
determining harmonic compensation voltage according to the grid-connected point voltage and the harmonic component of the grid-connected current;
obtaining a control reference voltage command based on the harmonic compensation voltage and the fundamental reference voltage to control the inverter by the control reference voltage command,
obtaining harmonic components of the grid-connected point voltage and the grid-connected current according to the following steps:
,
wherein ,for the harmonic component of the grid-connected current, +.>For the harmonic component of the grid-tie voltage, +.>For the grid-connected current, +.>For the grid-connected point voltage, +.>In order to be a harmonic extraction unit,sin order for the laplace operator to be useful,
the harmonic extraction unit is obtained according to the following equation:
,
wherein ,hin order to require the number of extracted harmonics,jin units of imaginary numbers,for the fundamental angular frequency of the wave,K r for integral gain +.>For increased damping term->To the phase angle that needs compensation +.>Determined from the nyquist curve before compensation,
the harmonic compensation voltage is obtained according to the following steps:
,
wherein ,xand (3) withyAre positive scaling factors.
2. The utility model provides a grid-connected harmonic current suppression device based on phase compensation grid-formed inverter which characterized in that includes:
the detection module is used for carrying out harmonic detection on the grid-connected point voltage and the grid-connected current based on the reduced-order generalized integrator to obtain harmonic components of the grid-connected point voltage and the grid-connected current;
the determining module is used for determining harmonic compensation voltage according to the grid-connected point voltage and the harmonic component of the grid-connected current;
an acquisition module for acquiring a control reference voltage command according to the harmonic compensation voltage and the fundamental reference voltage to control the inverter by the control reference voltage command,
the detection module obtains harmonic components of the grid-connected point voltage and the grid-connected current according to the following formula:
,
wherein ,for the harmonic component of the grid-connected current, +.>For the harmonic component of the grid-tie voltage, +.>For the grid-connected current, +.>For the grid-connected point voltage, +.>In order to be a harmonic extraction unit,sin order for the laplace operator to be useful,
the detection module obtains the harmonic extraction unit according to the following formula:
.
wherein ,hin order to require the number of extracted harmonics,jin units of imaginary numbers,for the fundamental angular frequency of the wave,K r for integral gain +.>For increased damping term->To the phase angle that needs compensation +.>According toThe nyquist curve before compensation is determined,
the acquisition module acquires the harmonic compensation voltage according to the following formula:
,
wherein ,xand (3) withyAre positive scaling factors.
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| CN110544956A (en) * | 2018-05-29 | 2019-12-06 | 特变电工新疆新能源股份有限公司 | Control method for inhibiting voltage distortion of grid-connected point |
| CN111446716A (en) * | 2020-03-31 | 2020-07-24 | 东南大学 | Harmonic voltage and harmonic current suppression method for VSG grid-connected system |
| CN114597939A (en) * | 2022-03-07 | 2022-06-07 | 阳光电源股份有限公司 | Method and system for suppressing grid-connected current harmonic waves of inverter |
| CN116436005A (en) * | 2023-03-09 | 2023-07-14 | 国网江苏省电力有限公司常州供电分公司 | Grid-connected harmonic current suppression method and device for grid-formed inverter |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN110544956A (en) * | 2018-05-29 | 2019-12-06 | 特变电工新疆新能源股份有限公司 | Control method for inhibiting voltage distortion of grid-connected point |
| CN111446716A (en) * | 2020-03-31 | 2020-07-24 | 东南大学 | Harmonic voltage and harmonic current suppression method for VSG grid-connected system |
| CN114597939A (en) * | 2022-03-07 | 2022-06-07 | 阳光电源股份有限公司 | Method and system for suppressing grid-connected current harmonic waves of inverter |
| CN116436005A (en) * | 2023-03-09 | 2023-07-14 | 国网江苏省电力有限公司常州供电分公司 | Grid-connected harmonic current suppression method and device for grid-formed inverter |
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