CN111769562A - Virtual impedance-based power quality frequency division control method and system - Google Patents

Virtual impedance-based power quality frequency division control method and system Download PDF

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Publication number
CN111769562A
CN111769562A CN201910261144.5A CN201910261144A CN111769562A CN 111769562 A CN111769562 A CN 111769562A CN 201910261144 A CN201910261144 A CN 201910261144A CN 111769562 A CN111769562 A CN 111769562A
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signal
current
voltage
harmonic
virtual
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宋振浩
盛万兴
吴鸣
郑楠
吕志鹏
孙丽敬
徐斌
王刘芳
李伟
骆晨
丁津津
陈洪波
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State Grid Corp of China SGCC
China Electric Power Research Institute Co Ltd CEPRI
Electric Power Research Institute of State Grid Anhui Electric Power Co Ltd
State Grid Anhui Electric Power Co Ltd
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State Grid Corp of China SGCC
China Electric Power Research Institute Co Ltd CEPRI
Electric Power Research Institute of State Grid Anhui Electric Power Co Ltd
State Grid Anhui Electric Power Co Ltd
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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
    • 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
    • H02J3/40—Synchronising a generator for connection to a network or to another generator
    • H02J3/42—Synchronising a generator for connection to a network or to another generator with automatic parallel connection when synchronisation is achieved
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
    • Y02E40/40—Arrangements for reducing harmonics

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Abstract

The invention relates to a virtual impedance-based power quality frequency division control method and system, which comprises the steps of extracting harmonic voltage and harmonic current except power frequency based on an obtained output voltage signal and an output current signal of a virtual synchronous machine; based on a harmonic frequency band, introducing a virtual resistor matched with a filter inductor at the inverter side and a virtual resistor at the capacitor side, and calculating a current signal and a voltage signal according to the harmonic voltage and the harmonic current; and comparing by using an integral controller to obtain a voltage modulation signal based on the current command signal, the current signal, the voltage signal and the output side current signal.

Description

Virtual impedance-based power quality frequency division control method and system
Technical Field
The invention relates to the field of power distribution networks, in particular to a virtual impedance-based power quality frequency division control method and system.
Background
With the popularization of new energy technology, the tracking accuracy of control power and the improvement of new energy grid-connected friendliness become concerned problems, and the conventional method at present is to virtualize a new energy power station into a synchronous generator set (similar to a thermal power station or a hydropower station) to perform grid-connected control. The virtual synchronous machine has the following structures: as shown in fig. 2, the virtual synchronous machine system structure is composed of a grid-connected inverter and an LCL filter. Because three energy storage elements exist in the LCL filter network shown in FIG. 2, a high-frequency resonance peak exists in a dynamic model of the LCL filter network, so that the system model is difficult to control and grid-connected current resonance can be caused.
The circuit model of the LCL filter shown in FIG. 3(a) is a typical Y-type circuit, and the equivalent circuit model shown in FIG. 3(b) can be obtained by Y-Delta conversion in circuit theory, where R is1And R2Is the resistance of the filter inductor.
In order to suppress the resonance of a single LCL filtering grid-connected inverter, an active or passive damping resistor may be connected in series to the capacitor branches, and although the virtual resistor may avoid extra power loss, if a passive resistor is directly introduced to the branches, the loss of the system may be increased, and the efficiency of the system may be reduced; the method can inhibit higher harmonic resonance and cause the change of power frequency fundamental current components, thereby influencing the tracking precision of grid-connected power.
Disclosure of Invention
In order to solve the problems, the invention provides a virtual impedance-based power quality frequency division control method and system. By using the superposition principle in the circuit, the impedance network can be distinguished according to frequency, the introduced virtual resistor only needs to remold other frequency components except the working frequency in the network, and the fundamental wave impedance and the higher harmonic wave impedance of the virtual synchronous machine grid-connected inverter are considered separately. For fundamental frequency, virtual resistance is not introduced, so that grid-connected power tracking of the grid-connected power tracking is not influenced. For the harmonic frequency band, virtual resistors are introduced, and the grid-connected inverter can bring effective inhibiting effect to network harmonic resonance.
The purpose of the invention is realized by adopting the following technical scheme:
a virtual impedance based power quality divide-by-frequency control method, the method comprising:
extracting harmonic voltage and harmonic current except power frequency based on the obtained output voltage signal and output current signal of the virtual synchronous machine;
based on a harmonic frequency band, introducing a virtual resistor matched with a filter inductor at the inverter side and a virtual resistor at the capacitor side, and calculating a current signal and a voltage signal according to the harmonic voltage and the harmonic current;
and comparing by using an integral controller to obtain a voltage modulation signal based on the current command signal, the current signal, the voltage signal and the output side current signal.
Preferably, the comparing the current command signal, the current signal, the voltage signal and the output side current signal by using an integral controller to obtain the voltage modulation signal includes:
comparing the current instruction signal, the current signal and the output side current signal to obtain an input signal of a proportional-integral controller;
and comparing the per-unit voltage signal with the output signal of the proportional-integral controller to obtain a voltage modulation signal.
Preferably, the extracting of the harmonic voltage and current other than the power frequency includes:
and extracting harmonic voltage and current except power frequency from the output voltage signal and the output current signal by a second-order generalized integral method.
Preferably, the calculating the current signal and the voltage signal comprises:
determining the impedance of the series-parallel resonance branch circuit according to a pre-established equivalent circuit model;
superposing the impedance of the series-parallel resonance branch circuit to form a series resonance loop, and calculating a filter capacitor and an inverter side filter inductor according to the series resonance loop;
introducing a virtual resistor R matched with a filter inductor at the side of the inverter1Connecting corresponding resistors in series or in parallel in the filter inductor and filter capacitor branch, and using the resistors as capacitor side virtual resistors Rpc；
And determining a current signal and a voltage signal according to the harmonic voltage and current except the power frequency based on the introduced virtual resistor matched with the filter inductor at the inverter side and the virtual resistor at the capacitor side.
Further, the voltage modulation signal is obtained by comparing with an integral controller based on the current command signal, the current signal, the voltage signal and the output side current signal:
defining a second-order generalized integral transfer function according to the current signal and the voltage signal;
determining an equivalent circuit of a proportional-integral controller according to the transfer function;
and obtaining a voltage modulation signal through an equivalent circuit of a proportional-integral controller based on the variation obtained by comparing the current command signal, the current signal, the voltage signal and the output side current signal.
Further, the second order generalized integral transfer function of the voltage modulated signal is determined by:
Figure BDA0002015311180000021
where k is the frequency coefficient, ω0For grid fundamental angular frequency, Gf(s) is a second order generalized integral transfer function, and s' represents a Laplace transform factor.
Further, the impedance of the series-parallel resonant branch is determined by:
Zs1(s)＝sL1+R1+1/(Cs1s)
Zs2(s)＝sL2+R2+1/(Cs2s)
Zp(s)＝(L1s+R1)(L2s+R2)Cs+(L1+L2)s+(R1+R2)
wherein Z iss1And Zs2Being an inductance of a series resonant circuit, ZpIs the equivalent inductance of the parallel resonant circuit, S is the current of the series resonant circuit, Cs1And Cs2Respectively equivalent capacitance, L, of the series resonant branch1And L2The filter inductor is an inverter side filter inductor and a network side filter inductor respectively, and R1 and R2 are resistors of the filter inductor.
Further, the filter capacitance is determined by:
Figure BDA0002015311180000031
wherein k represents a frequency coefficient, and k ═ L1s+R1)/(L2s+R2)≈L1/L2Is the ratio of the inverter-side and network-side filter inductances, R1And R2The resistors are all resistors of a filter inductor, and C is a filter capacitor.
Further, the inverter-side filter inductance is determined by:
Figure BDA0002015311180000032
Figure BDA0002015311180000033
wherein, ω iss1,2And ωpResonant frequencies at the series and parallel resonance points in the series and parallel impedance branches, ξ, respectivelys1,2And ξpAre respectively omegas1,2And ωpDamping of the resonant tank.
Preferably, the acquiring the current command signal includes:
the control of an active loop and a reactive loop of the virtual synchronous machine is used for obtaining a command voltage signal, and the comparison of the command voltage and the actual voltage is used for obtaining a current command signal through a PI (proportional-integral) controller.
A virtual impedance based power quality divide-by-frequency control system, the system comprising:
the extraction module is used for extracting harmonic voltage and harmonic current except power frequency based on the obtained output voltage signal and output current signal of the virtual synchronous machine;
the calculation module is used for introducing a virtual resistor matched with a filter inductor at the inverter side and a virtual resistor at the capacitor side based on a harmonic frequency band, and calculating a current signal and a voltage signal according to the harmonic voltage and the harmonic current;
and the comparison module is used for comparing by using an integral controller to obtain a voltage modulation signal based on the current instruction signal, the current signal, the voltage signal and the output side current signal.
Compared with the prior art, the invention has the beneficial effects that:
the invention provides an electric energy quality frequency division control method based on virtual impedance, which comprises the following steps of firstly, extracting harmonic voltage and harmonic current except power frequency based on an obtained output voltage signal and an output current signal of a virtual synchronous machine; and based on the harmonic frequency band, introducing a virtual resistor matched with the filter inductor at the inverter side and a virtual resistor at the capacitor side, and calculating a current signal and a voltage signal according to the harmonic voltage and the harmonic current. The fundamental wave impedance and the higher harmonic wave impedance of the virtual synchronous machine grid-connected inverter are considered separately. For fundamental frequency, virtual resistance is not introduced, so that grid-connected power tracking of the grid-connected power tracking is not influenced. And for the harmonic frequency band, a virtual resistor is introduced, so that the grid-connected inverter can bring effective inhibition effect to network harmonic resonance.
And secondly, comparing by using an integral controller to obtain a voltage modulation signal based on the current command signal, the current signal, the voltage signal and the output side current signal. . The method can inhibit higher harmonic resonance while ensuring that the tracking precision of grid-connected power is not affected.
Drawings
FIG. 1 is a general flow diagram of a method provided in an embodiment of the present invention;
FIG. 2 is a schematic diagram of a system architecture of a single LCL virtual synchronous machine 1 provided in the background art of the present invention;
fig. 3 is a circuit diagram of an LCL filter network provided in the background of the invention; wherein, fig. 3(a) is a Y-type circuit model diagram of the LCL filter, and fig. 3(b) is an equivalent circuit model diagram of the LCL filter;
FIG. 4 is a schematic diagram of impedance reshaping of a virtual synchronous machine provided in an embodiment of the present invention;
FIG. 5 is a block diagram of voltage-current control incorporating a virtual impedance provided in an embodiment of the present invention;
FIG. 6 is an equivalent schematic diagram of a system for introducing virtual impedance provided in an embodiment of the present invention;
FIG. 7 is a schematic diagram of a virtual synchronous machine grid-connected impedance remodeling control strategy provided in an embodiment of the present invention
Fig. 8 is a Bode diagram of an SOGI based trap provided in an embodiment of the present invention;
figure 9 is a wiring diagram of a microgrid feeder branch provided in embodiments of the present invention;
FIG. 10 is a graph of current waveforms at the PCC before and after plunge impedance reshaping as provided in an embodiment of the invention; wherein, fig. 10(a) is a schematic voltage current diagram of PCC before impedance remodeling control; FIG. 10(b) is a schematic voltage current diagram of PCC after impedance remodeling control; FIG. 10(c) is a voltage current harmonic distribution plot before impedance reshaping; FIG. 10(d) is a graph of the harmonic distribution of PCC voltage current after impedance reshaping.
Detailed Description
The following detailed description of embodiments of the invention refers to the accompanying drawings.
The invention provides a virtual impedance-based power quality frequency division control method, as shown in fig. 1, comprising the following steps:
for the harmonic frequency band, introducing a virtual resistor matched with the filter inductor at the inverter side and a virtual resistor at the capacitor side, and calculating a current signal and a voltage signal according to pre-obtained harmonic voltage and current except power frequency;
comparing a current instruction signal obtained in advance with a voltage signal and an output side current signal to obtain an input signal of a proportional-integral controller;
and comparing the per-unit voltage signal with the output signal of the proportional-integral controller to obtain a voltage modulation signal.
S1 extracting harmonic voltage and harmonic current except power frequency based on the obtained output voltage signal and output current signal of the virtual synchronous machine;
s2, introducing a virtual resistor matched with a filter inductor at the inverter side and a virtual resistor at the capacitor side based on a harmonic frequency band, and calculating a current signal and a voltage signal according to the harmonic voltage and the harmonic current;
and S3, comparing the current command signal, the current signal, the voltage signal and the output side current signal by using an integral controller to obtain a voltage modulation signal.
Specifically, the method comprises the following steps:
in step S1, the extracting of the harmonic voltage and current other than the power frequency includes:
and extracting harmonic voltage and current except power frequency from the output voltage signal and the output current signal by a second-order generalized integral method.
In step S2, the acquiring the current command signal includes:
the control of an active loop and a reactive loop of the virtual synchronous machine is used for obtaining a command voltage signal, and the comparison of the command voltage and the actual voltage is used for obtaining a current command signal through a PI (proportional-integral) controller.
Calculating the current signal and the voltage signal includes:
a, determining the impedance of a series-parallel resonance branch circuit according to a pre-established equivalent circuit model; the equivalent circuit model established in advance is shown in fig. 3(a) and 3 (b).
b, superposing the impedance of the series-parallel resonance branch to form a series resonance loop, and calculating a filter capacitor and an inverter side filter inductor according to the series resonance loop;
c, introducing a virtual resistor R matched with the filter inductor at the inverter side1Connecting corresponding resistors in series or in parallel in the filter inductor and filter capacitor branch, and using the resistors as capacitor side virtual resistors Rpc；
And d, determining a current signal and a voltage signal according to the harmonic voltage and current except the power frequency based on the introduced virtual resistor matched with the filter inductor at the inverter side and the virtual resistor at the capacitor side.
The impedance of the series-parallel resonant branch is determined by:
Zs1(s)＝sL1+R1+1/(Cs1s)
Zs2(s)＝sL2+R2+1/(Cs2s)
Zp(s)＝(L1s+R1)(L2s+R2)Cs+(L1+L2)s+(R1+R2)
wherein Z iss1And Zs2Is a series resonanceInductance of the loop, ZpIs the equivalent inductance of the parallel resonant circuit, S is the current of the series resonant circuit, Cs1And Cs2Respectively equivalent capacitance, L, of the series resonant branch1And L2The filter inductor is an inverter side filter inductor and a network side filter inductor respectively, and R1 and R2 are resistors of the filter inductor.
The filter capacitance is determined by:
Figure BDA0002015311180000061
wherein k represents a frequency coefficient, and k ═ L1s+R1)/(L2s+R2)≈L1/L2Is the ratio of the inverter-side and network-side filter inductances, R1And R2The resistors are all resistors of a filter inductor, and C is a filter capacitor.
The inverter-side filter inductance is determined by:
Figure BDA0002015311180000062
Figure BDA0002015311180000063
wherein, ω iss1,2And ωpResonant frequencies at the series and parallel resonance points in the series and parallel impedance branches, ξ, respectivelys1,2And ξpAre respectively omegas1,2And ωpOn the one hand, with the damping factor ignored (ξ)s1＝ξs2＝ξp0), the frequency of the series-parallel resonance is equal to ωs1＝ωs2＝ωp. On the other hand, the series and parallel resonant frequencies ωs1,2And ωpξ damping of resonant circuits1,2And ξpIt is related. Meanwhile, the damping determines the amplitude of resonance, and the larger the damping is, the smaller the amplitude of resonance is, and the stronger the inhibition capability on resonance is. The damping magnitude is directly dependent on the resistance of the loop, and its quantitative relationship is:
the omegas1,2And ωpThe damping of the resonant tank is determined by:
Figure BDA0002015311180000064
Figure BDA0002015311180000071
as shown in fig. 4, in the filter inductance L1The resistor corresponding to the capacitor C branch in series or parallel connection can effectively remold the output impedance of the grid-connected inverter, so that harmonic resonance possibly occurring in the network is suppressed. However, if passive resistors are directly introduced into these branches, the loss of the system is increased, and the efficiency of the system is reduced. Furthermore, at L1The series resistance or the parallel resistance in the C branch can change the fundamental wave current tracking performance of the virtual synchronous machine grid-connected inverter.
The principle of introducing a virtual impedance is shown in fig. 6 by providing a virtual output voltage E at the inverteriAnd actual port voltage UoiBetween them introduce a virtual impedance ZviriMake the relative virtual voltage EiThe system equivalent impedance meets the requirement of inverse capacity ratio of the inverter, namely the virtual impedance Z of each VSG unitviriFeed line impedance ZfiThe ratio of the sum is inversely proportional to the capacity, so as to correct the unmatched feeder line impedance, and make the voltage drop generated on the equivalent impedance identical, namely delta E1＝ΔE2And further satisfy E1＝E2And the reactive power accurate distribution of the parallel virtual synchronous machines is realized.
The control block diagram of the voltage-current proportional loop with the output current value feedback and the introduced virtual impedance is shown in fig. 5.
In step S3, comparing the current command signal, the current signal, the voltage signal, and the output-side current signal with an integral controller to obtain a voltage modulation signal, and comparing the current command signal, the current signal, and the output-side current signal to obtain an input signal of a proportional-integral controller; and comparing the per-unit voltage signal with the output signal of the proportional-integral controller to obtain a voltage modulation signal.
The specific steps of utilizing an integral controller to compare and obtain a voltage modulation signal based on a current command signal, the current signal, a voltage signal and an output side current signal comprise:
defining a second-order generalized integral transfer function according to the current signal and the voltage signal;
determining an equivalent circuit of a proportional-integral controller according to the transfer function;
and obtaining a voltage modulation signal through an equivalent circuit of a proportional-integral controller based on the variation obtained by comparing the current command signal, the current signal, the voltage signal and the output side current signal.
Wherein the second order generalized integral transfer function of the voltage modulated signal is determined by:
Figure BDA0002015311180000072
where k is the frequency coefficient, ω0For grid fundamental angular frequency, Gf(s) is a second order generalized integral transfer function, and s' represents a Laplace transform factor.
Example (b):
step 1: constructing an impedance remodeling original model of the virtual synchronous machine, as shown in FIG. 4, firstly analyzing the impedance remodeling original model at a filter inductor L1The resistor corresponding to the capacitor C branch in series or parallel connection can effectively remold the output impedance of the grid-connected inverter, so that harmonic resonance possibly occurring in the network is suppressed. However, if passive resistors are directly introduced into these branches, the loss of the system is increased, and the efficiency of the system is reduced. Furthermore, at L1The series resistance or the parallel resistance in the C branch can change the fundamental wave current tracking performance of the virtual synchronous machine grid-connected inverter.
Step 2: aiming at the problems, a virtual impedance-based power quality frequency division control method is provided. The fundamental wave impedance and the higher harmonic wave impedance of the virtual synchronous machine grid-connected inverter are considered separately by the superposition principle. For fundamental frequency, no virtual resistance is introducedTherefore, the grid-connected power tracking is not influenced. For harmonic frequency band, virtual resistor R is introduced1And RpcAnd the grid-connected inverter can bring effective inhibition to network harmonic resonance.
① collecting output side voltage u of virtual synchronous machinecSignal and current signal i1Extracting other voltages u except the power frequency by utilizing second-order generalized integral aiming at the obtained voltage and current signalschAnd current ih；
② leading-in and source-side inductance L1Matched virtual resistance R1R connected in parallel with the capacitor sidepcThe harmonic voltage u obtained in the step ①chAnd current ih，Are each independently of RpcAnd R1Calculating to obtain a current signal ivSum voltage signal u1。
③ Current command Signal irefAnd the current signal i obtained in step ②vAnd output current signal i1Comparing to obtain an input signal of a proportional-integral controller (PR);
④ converting the voltage signal u1Per unit of the voltage modulated signal u compared to the PR output of step ③rThe overall control block diagram is shown in fig. 7.
Second order generalized integral transfer function Gf(s) can be represented as
Figure BDA0002015311180000081
Where k is the frequency coefficient, ω0For grid fundamental angular frequency, GfThe Bode plot of(s) is shown in fig. 8, and it can be seen that: the voltage (or current) component of the fundamental frequency is greatly attenuated, while other frequency components can pass through G almost without lossf(s)。
And step 3: to verify the inventive effect of the proposed strategy, an example analysis is given.
Experimental studies were conducted on a feeder branch of a microgrid laboratory, the wiring of which is shown in fig. 9. The feeder line comprises two VSGs with the rated power of 10kW, the effective value and the rated frequency of the line voltage of the power gridThe rates are 190V and 50Hz respectively, and the grid inductance LgThe filter inductance and capacitance of VSG are respectively L0.5 mH and C20 muF, and the passive damping resistance of filter capacitance branch is Rc＝4Ω。
The instructions of grid-connected active power and reactive power of the VSG1 and the VSG2 are 6kW/0var and 4kW/0var respectively, and the local load is about 4kW of resistance load. When the VSG is not put into impedance remodeling control, the voltage current waveform at the PCC is shown at 10. After VSG is subjected to remodeling control, harmonic resonance is obviously inhibited due to the introduction of enough damping components with resistance properties in the network, wherein Rpc＝20Ω、R1＝100Ω。
The analysis result shows that: before impedance remodeling control is put into operation, due to the existence of network harmonic resonance, the voltage at PCC and the network side current iPCCThe THD of (a) was 3.89% and 13.65%, respectively, and the respective harmonic distributions thereof are as shown in fig. 10, in which harmonic resonance around the frequency of the 26 th harmonic occurred. When impedance remodeling control was put into effect, the THD of the grid voltage and grid side current at PCC was reduced to 1.86% and 4.70%, respectively. The virtual output impedance effectively increases the damping of the harmonic loop, suppressing the occurrence of harmonic resonance.
Based on the same technical concept, the invention also provides a virtual impedance-based power quality frequency division control system, which comprises:
the extraction module is used for extracting harmonic voltage and harmonic current except power frequency based on the obtained output voltage signal and output current signal of the virtual synchronous machine;
the calculation module is used for introducing a virtual resistor matched with a filter inductor at the inverter side and a virtual resistor at the capacitor side based on a harmonic frequency band, and calculating a current signal and a voltage signal according to the harmonic voltage and the harmonic current;
and the comparison module is used for comparing by using an integral controller to obtain a voltage modulation signal based on the current instruction signal, the current signal, the voltage signal and the output side current signal.
As will be appreciated by one skilled in the art, embodiments of the present application may be provided as a method, system, or computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.
The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the application. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solutions of the present invention and not for limiting the same, and although the present invention is described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: modifications and equivalents may be made to the embodiments of the invention without departing from the spirit and scope of the invention, which is to be covered by the claims.

Claims (11)

1. A power quality frequency division control method based on virtual impedance is characterized by comprising the following steps:
extracting harmonic voltage and harmonic current except power frequency based on the obtained output voltage signal and output current signal of the virtual synchronous machine;
based on a harmonic frequency band, introducing a virtual resistor matched with a filter inductor at the inverter side and a virtual resistor at the capacitor side, and calculating a current signal and a voltage signal according to the harmonic voltage and the harmonic current;
and comparing by using an integral controller to obtain a voltage modulation signal based on the current command signal, the current signal, the voltage signal and the output side current signal.
2. The method of claim 1, wherein comparing with an integral controller based on the current command signal, the current signal, the voltage signal, and the output side current signal to obtain a voltage modulated signal comprises:
comparing the current instruction signal, the current signal and the output side current signal to obtain an input signal of a proportional-integral controller;
and comparing the per-unit voltage signal with the output signal of the proportional-integral controller to obtain a voltage modulation signal.
3. The method of claim 1, wherein extracting harmonic voltages and currents other than power frequency comprises:
and extracting harmonic voltage and current except power frequency from the output voltage signal and the output current signal by a second-order generalized integral method.
4. The method of claim 1, wherein the calculating the current signal and the voltage signal comprises:
determining the impedance of the series-parallel resonance branch circuit according to a pre-established equivalent circuit model;
superposing the impedance of the series-parallel resonance branch circuit to form a series resonance loop, and calculating a filter capacitor and an inverter side filter inductor according to the series resonance loop;
introducing a virtual resistor R matched with a filter inductor at the side of the inverter1Connecting corresponding resistors in series or in parallel in the filter inductor and filter capacitor branch, and using the resistors as capacitor side virtual resistors Rpc；
And determining a current signal and a voltage signal according to the harmonic voltage and current except the power frequency based on the introduced virtual resistor matched with the filter inductor at the inverter side and the virtual resistor at the capacitor side.
5. The method of claim 4, wherein the comparing with an integral controller based on the current command signal, the current signal, the voltage signal, and the output side current signal to obtain the voltage modulation signal:
defining a second-order generalized integral transfer function according to the current signal and the voltage signal;
determining an equivalent circuit of a proportional-integral controller according to the transfer function;
and obtaining a voltage modulation signal through an equivalent circuit of a proportional-integral controller based on the variation obtained by comparing the current command signal, the current signal, the voltage signal and the output side current signal.
6. The method of claim 5, wherein the second order generalized integral transfer function of the voltage modulated signal is determined by:
Figure FDA0002015311170000021
where k is the frequency coefficient, ω0For grid fundamental angular frequency, Gf(s) is a second order generalized integral transfer function, and s' represents a Laplace transform factor.
7. The method of claim 4, wherein the impedance of the series-parallel resonant branch is determined by:
Zs1(s)＝sL1+R1+1/(Cs1s)
Zs2(s)＝sL2+R2+1/(Cs2s)
Zp(s)＝(L1s+R1)(L2s+R2)Cs+(L1+L2)s+(R1+R2)
wherein Z iss1And Zs2Being an inductance of a series resonant circuit, ZpIs the equivalent inductance of the parallel resonant circuit, S is the current of the series resonant circuit, Cs1And Cs2Respectively equivalent capacitance, L, of the series resonant branch1And L2The filter inductor is an inverter side filter inductor and a network side filter inductor respectively, and R1 and R2 are resistors of the filter inductor.
8. The method of claim 7, wherein the filter capacitance is determined by:
Figure FDA0002015311170000022
wherein k represents a frequency coefficient, and k ═ L1s+R1)/(L2s+R2)≈L1/L2Is the ratio of the inverter-side and network-side filter inductances, R1And R2The resistors are all resistors of a filter inductor, and C is a filter capacitor.
9. The method of claim 8, wherein the inverter-side filter inductance is determined by:
Figure FDA0002015311170000023
Figure FDA0002015311170000024
wherein, ω iss1,2And ωpResonant frequencies at the series and parallel resonance points in the series and parallel impedance branches, ξ, respectivelys1,2And ξpAre respectively omegas1,2And ωpDamping of the resonant tank.
10. The method of claim 1, wherein obtaining the current command signal comprises:
the control of an active loop and a reactive loop of the virtual synchronous machine is used for obtaining a command voltage signal, and the comparison of the command voltage and the actual voltage is used for obtaining a current command signal through a PI (proportional-integral) controller.
11. A virtual impedance based power quality divide-by-frequency control system, the system comprising:
the extraction module is used for extracting harmonic voltage and harmonic current except power frequency based on the obtained output voltage signal and output current signal of the virtual synchronous machine;
the calculation module is used for introducing a virtual resistor matched with a filter inductor at the inverter side and a virtual resistor at the capacitor side based on a harmonic frequency band, and calculating a current signal and a voltage signal according to the harmonic voltage and the harmonic current;
and the comparison module is used for comparing by using an integral controller to obtain a voltage modulation signal based on the current instruction signal, the current signal, the voltage signal and the output side current signal.
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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN113484607A (en) * 2021-06-18 2021-10-08 国网安徽省电力有限公司电力科学研究院 Detection method for low-frequency non-stationary signals

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN104362645A (en) * 2014-10-27 2015-02-18 西安交通大学 Active harmonic wave resistance control method of reactive compensation capacitor based on injection type
CN104795821A (en) * 2015-04-29 2015-07-22 中国电力科学研究院 Suppression method of harmonic wave frequency division in inverter
CN106787894A (en) * 2016-12-22 2017-05-31 中南大学 A kind of off-network inverter control method based on frequency dividing virtual impedance
CN108023352A (en) * 2017-11-27 2018-05-11 国网宁夏电力有限公司经济技术研究院 Suppress the power grid high-frequency impedance remodeling device and method of distributed power generation resonance

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN104362645A (en) * 2014-10-27 2015-02-18 西安交通大学 Active harmonic wave resistance control method of reactive compensation capacitor based on injection type
CN104795821A (en) * 2015-04-29 2015-07-22 中国电力科学研究院 Suppression method of harmonic wave frequency division in inverter
CN106787894A (en) * 2016-12-22 2017-05-31 中南大学 A kind of off-network inverter control method based on frequency dividing virtual impedance
CN108023352A (en) * 2017-11-27 2018-05-11 国网宁夏电力有限公司经济技术研究院 Suppress the power grid high-frequency impedance remodeling device and method of distributed power generation resonance

Non-Patent Citations (3)

* Cited by examiner, † Cited by third party
Title
吕志鹏 等: "不同容量微源逆变器并联功率鲁棒控制", 《中国电机工程学报》 *
曾正 等: "光伏并网逆变器的阻抗重塑与谐波谐振抑制", 《中国电机工程学报》 *
雪晓菲 等: "基于 SOGI 虚拟阻抗的电流下垂控制研究", 《北京信息科技大学学报》 *

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN113484607A (en) * 2021-06-18 2021-10-08 国网安徽省电力有限公司电力科学研究院 Detection method for low-frequency non-stationary signals

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