CN113193571A - Non-communication control method and system for offshore wind farm to participate in frequency modulation - Google Patents

Non-communication control method and system for offshore wind farm to participate in frequency modulation Download PDF

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CN113193571A
CN113193571A CN202110478229.6A CN202110478229A CN113193571A CN 113193571 A CN113193571 A CN 113193571A CN 202110478229 A CN202110478229 A CN 202110478229A CN 113193571 A CN113193571 A CN 113193571A
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frequency
direct
voltage
converter station
onshore
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CN113193571B (en
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姚伟
熊永新
艾小猛
文劲宇
林思齐
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Huazhong University of Science and Technology
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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
    • H02J3/24—Arrangements for preventing or reducing oscillations of power in networks
    • 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
    • H02J3/36—Arrangements for transfer of electric power between ac networks via a high-tension dc link
    • 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
    • H02J3/381—Dispersed generators
    • 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
    • H02J2300/00—Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation
    • H02J2300/20—The dispersed energy generation being of renewable origin
    • H02J2300/28—The renewable source being wind energy
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/60—Arrangements for transfer of electric power between AC networks or generators via a high voltage DC link [HVCD]

Abstract

The invention discloses a communication-free control method and system for an offshore wind farm to participate in frequency modulation, belonging to the field of power system control, wherein the method comprises the steps of collecting direct-current voltage and direct-current signals of an offshore converter station, and estimating the terrestrial direct-current voltage by combining the resistance value and reactance value of a direct-current line; respectively calculating the power increase generated by droop response and inertia response of the offshore wind farm based on the estimated value of the onshore direct current voltage; the increased power is distributed to adjust the frequency of the land based ac system. Since the onshore direct-current voltage and the onshore alternating-current system frequency are coupled through droop control, after the onshore direct-current voltage is estimated by the offshore converter station, the onshore direct-current system frequency change situation is estimated indirectly, so that the offshore wind farm does not communicate to respond to the onshore alternating-current system frequency change and provides frequency support, the communication cost is reduced, and the influence of the change of the onshore direct-current voltage on the frequency modulation effect in the dynamic frequency adjustment process of the conventional non-communication control method is reduced.

Description

Non-communication control method and system for offshore wind farm to participate in frequency modulation
Technical Field
The invention belongs to the field of power system control, and particularly relates to a communication-free control method and system for an offshore wind farm to participate in frequency modulation.
Background
In recent years, offshore wind farms connected to the grid based on multi-terminal flexible direct current (VSC-MTDC) transmission systems are gradually receiving wide attention of scholars both at home and abroad, since the flexible dc transmission systems decouple offshore wind farms and onshore wind farms, the offshore wind farms cannot directly respond to the frequency change of the onshore ac system to provide supporting power, and the onshore ac system urgently needs the offshore wind farms to provide auxiliary frequency support along with the continuous increase of the capacity of the offshore wind farms, so that the rapid frequency response can be realized when load disturbance occurs, and the development of the onshore ac system into serious faults is avoided.
In the existing control method, a specific communication line is generally adopted to transmit the frequency of the land alternating current system to the offshore wind farm, so that the construction cost is high, and meanwhile, as the offshore wind farm is far away from the land converter station, the phenomenon of communication delay is inevitable even if a special communication line is adopted; the inertial support of the offshore wind farm on the onshore alternating current system needs to be completed within a few seconds, and the effect of the offshore wind farm participating in the frequency adjustment of the system can be directly influenced by overlong communication delay. Therefore, a control strategy that offshore wind farms do not participate in onshore frequency regulation without communication needs to be provided.
However, in the related control strategy for the offshore wind farm to participate in the onshore frequency regulation without communication in the existing research, after the frequency change of the onshore alternating current system is converted into the change of the direct current voltage, the offshore wind farm participates in the frequency modulation by responding to the change of the offshore direct current voltage to change the power, and the control strategy for the frequency modulation without communication has certain defects: when the offshore wind farm changes power in response to changes of the offshore direct-current voltage, the offshore direct-current voltage changes, and the frequency response process of the offshore wind farm is affected. Therefore, in the dynamic process of frequency adjustment, the frequency change of the onshore alternating current system cannot be accurately reflected by the direct current voltage of the offshore converter station, so that the frequency adjustment effect of the offshore wind farm is influenced.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a communication-free control method and a communication-free control system for offshore wind farms connected with a multi-terminal flexible direct current grid, aiming at enabling offshore wind farms connected with the multi-terminal flexible direct current grid to be free of communication and participate in system frequency modulation control, solving the problem of influence of communication delay on the frequency modulation effect of the offshore wind farms, and reducing the influence of change of offshore direct current voltage on the frequency modulation effect in the dynamic frequency adjustment process of the existing communication-free control method.
In order to achieve the purpose, the invention provides a non-communication control method for an offshore wind farm to participate in frequency modulation, which comprises the following steps:
s1: when the frequency variation of the onshore alternating current system exceeds a frequency variation threshold value, converting the frequency variation into a direct current voltage variation of the onshore converter station through droop control, and transmitting the direct current voltage variation to the offshore converter station through a direct current circuit to change the direct current voltage of the offshore converter station;
s2: collecting direct-current voltage and direct-current signals of the offshore converter station, and estimating the onshore direct-current voltage by combining the resistance value and the reactance value of the direct-current line;
s3: respectively calculating the power increase generated by droop response and inertia response of the offshore wind farm based on the estimated value of the onshore direct-current voltage in S2;
s4: and distributing the increased power generated by the droop response and the inertia response of the offshore wind farm to adjust the frequency of the onshore alternating current system.
Further, in step S1, the frequency-voltage droop control coefficient in the droop control is:
Figure BDA0003048105260000021
in the formula, kdf,iRepresenting the frequency-voltage droop control coefficient, k, of the ith land converter stationdf,i_0Indicating an initial value of the frequency-voltage droop control coefficient, α, for the ith land converter station1And alpha2Is a fixed constant, Udc,iRepresenting the measured value of the direct voltage, U, of the ith land converter stationdc,minRepresenting a minimum limit value, f, of the DC voltage of the converter station on landV,iRepresenting the measured value of the frequency of the alternating current system, df, of the ith land converter stationV,i(t)/dt represents the frequency reduction rate of the ith land converter station, t1Indicating an initial time, at, of a frequency dip of the onshore converter station exceeding a frequency change thresholdsRepresenting the duration of the integration.
Further, the power increase power generated by the droop response and the inertia response of the offshore wind farm is respectively as follows:
ΔPwdr_j＝-kwdr_j×(Udc,est,ref-Udc,est)
Figure BDA0003048105260000031
wherein, Δ Pwdr_jAnd Δ Pwin_jGenerating power increasing power generated by droop response and inertia response of the jth wind power plant respectively; k is a radical ofwdr_jAnd kwin_jRespectively obtaining the actual droop response coefficient and the inertia response coefficient of the jth wind power plant; u shapedc,est,refAnd Udc,estRespectively, a reference value and an estimated value of the land dc voltage.
Further, in step S2, the estimating the land dc voltage includes: and estimating the land DC voltage by using kirchhoff's law.
On the other hand, the invention also provides a non-communication control system for the offshore wind farm to participate in frequency modulation, which comprises:
the transmission module is used for converting the frequency variation into a direct-current voltage variation of the onshore converter station through droop control when the frequency variation of the onshore alternating-current system exceeds a frequency variation threshold value, and transmitting the direct-current voltage variation to the offshore converter station through a direct-current line so as to change the direct-current voltage of the offshore converter station;
the estimation module is used for acquiring direct-current voltage and direct-current signals of the offshore converter station and estimating the onshore direct-current voltage by combining the resistance value and the reactance value of the direct-current line;
the calculation module is used for respectively calculating the power increasing power generated by droop response and inertia response of the offshore wind farm based on the estimated value of the onshore direct current voltage obtained by the estimation module;
and the distribution module is used for distributing the increased power generated by the droop response and the inertia response of the offshore wind farm so as to adjust the frequency of the land alternating current system.
Further, the frequency-voltage droop control coefficient in the droop control is as follows:
Figure BDA0003048105260000041
in the formula, kdf,iRepresenting the frequency-voltage droop control coefficient, k, of the ith land converter stationdf,i_0Indicating an initial value of the frequency-voltage droop control coefficient, α, for the ith land converter station1And alpha2Is a fixed constant, Udc,iRepresenting the measured value of the direct voltage, U, of the ith land converter stationdc,minRepresenting a minimum limit value, f, of the DC voltage of the converter station on landV,iRepresenting the measured value of the frequency of the alternating current system, df, of the ith land converter stationV,i(t)/dt represents the frequency reduction rate of the ith land converter station, t1Indicating an initial time, at, of a frequency dip of the onshore converter station exceeding a frequency change thresholdsRepresenting the duration of the integration.
Further, the power increase power generated by the droop response and the inertia response of the offshore wind farm is respectively as follows:
ΔPwdr_j＝-kwdr_j×(Udc,est,ref-Udc,est)
Figure BDA0003048105260000042
wherein, Δ Pwdr_jAnd Δ Pwin_jGenerating power increasing power generated by droop response and inertia response of the jth wind power plant respectively; k is a radical ofwdr_jAnd kwin_jRespectively obtaining the actual droop response coefficient and the inertia response coefficient of the jth wind power plant; u shapedc,est,refAnd Udc,estRespectively, a reference value and an estimated value of the land dc voltage.
Further, the estimating the land dc voltage includes: and estimating the land DC voltage by using kirchhoff's law.
Through the technical scheme, compared with the prior art, the invention has the following beneficial effects:
according to the method, the terrestrial direct-current voltage is estimated by collecting direct-current voltage and direct-current signals of the offshore converter station and combining the resistance value and the reactance value of a direct-current line; respectively calculating the power increase generated by droop response and inertia response of the offshore wind farm based on the estimated value of the onshore direct current voltage; the increased power is distributed to adjust the frequency of the land based ac system. Since the onshore direct-current voltage and the onshore alternating-current system frequency are coupled through droop control, after the onshore direct-current voltage is estimated by the offshore converter station, the onshore alternating-current system frequency change situation is estimated indirectly, so that on one hand, the offshore wind farm does not respond to the onshore alternating-current system frequency change in a communication way and provides frequency support, the communication cost is reduced, and meanwhile, the influence of communication delay on the frequency support of the offshore wind farm is reduced; on the other hand, the influence of the change of the marine direct current voltage on the frequency modulation effect in the dynamic frequency adjustment process of the existing communication-free control method is reduced.
Drawings
FIG. 1 is a flow chart of a communication-free control method for participating in frequency modulation of an offshore wind farm provided by an embodiment;
FIG. 2 is a control block diagram of a communication-free frequency modulation control method of an offshore wind farm through a VSC-MTDC grid-connected system according to an embodiment;
fig. 3(a) is a graph of frequency variation with time of a converter station according to the present invention, an existing control method without communication and with communication under a 200MW load sudden-increase disturbance condition provided by an embodiment;
fig. 3(b) is a graph of the frequency of the converter station with time variation corresponding to the existing control method without communication and with communication according to the present invention under the condition of 300MW load sudden increase disturbance provided by the embodiment;
fig. 3(c) is a graph of the frequency of the converter station with time according to the present invention, the existing control method without communication and with communication under the condition of the 400MW load sudden-increase disturbance provided by the embodiment.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
Referring to fig. 1, the present invention provides a non-communication control method for an offshore wind farm to participate in frequency modulation, comprising:
s1: when the frequency variation of the onshore alternating current system exceeds a frequency variation threshold value, converting the frequency variation into a direct current voltage variation of the onshore converter station through droop control, and transmitting the direct current voltage variation to the offshore converter station through a direct current circuit to change the direct current voltage of the offshore converter station;
preferably, in order to prevent the dc voltage variation from exceeding a limit value, a voltage anti-saturation control procedure is added. Specifically, the onshore converter station changes the frequency-voltage droop control coefficient by collecting local frequency changes and performing short-time integration on the frequency change rate. The specific calculation process is as follows:
Figure BDA0003048105260000061
in the formula, kdf,iRepresenting the frequency-voltage droop control coefficient, k, of the ith land converter stationdf,i_0Indicating an initial value of the frequency-voltage droop control coefficient, α, for the ith land converter station1And alpha2Is a fixed constant, Udc,iRepresenting the measured value of the direct voltage, U, of the ith land converter stationdc,minRepresenting a minimum limit value, f, of the DC voltage of the converter station on landV,iRepresenting the measured value of the frequency of the alternating current system, df, of the ith land converter stationV,i(t)/dt represents the frequency reduction rate of the ith land converter station, t1Indicating an initial time, at, of a frequency dip of the onshore converter station exceeding a frequency change thresholdsRepresenting the duration of the short integration.
PVi,ref＝PVi,0+kdu·[Udci,ref-Udc,i+kdf,i·(fVi,ref-fVi)]
In the formula, PVi,refInjected power reference, P, representing the i-th onshore converter station voltage-power droop controlVi,0Initial injection power value, k, representing droop control of ith land converter stationduThe droop coefficients representing the voltage-power droop control are the same for different land converter stations, and U isdci,refVoltage reference value, f, representing the voltage-power droop control of the ith land converter stationVi,refRepresenting the frequency reference of the ith land converter station.
S2: collecting direct-current voltage and direct-current signals of the offshore converter station, and estimating the onshore direct-current voltage by combining the resistance value and the reactance value of the direct-current line;
specifically, as shown in fig. 2, taking an offshore wind farm with four ports connected to the grid through a flexible direct current as an example, the power generated by the offshore wind farm 1 passes through a VSC of the offshore converter station4Direct current line 4-2 and direct current line 4-1, and land converter station VSC2And VSC1Injecting into a land AC system, wherein the frequency support is provided by the offshore wind farm 1 after the frequency change of the land AC system exceeds a threshold value, and the land converter station VSC2And VSC1The function of the frequency support is to reasonably distribute the power of frequency support increasing. VSC (Voltage Source converter) of offshore converter station4Estimating the terrestrial DC voltage using a non-communicating DC voltage estimator, and thus, seaVSC of upper converter station4Local DC voltage and current signals need to be measured, and the resistance and reactance parameters of the DC line 4-2 and the DC line 4-1 are known, and the land DC voltage estimated value Udc,estAnd its reference value Udc,est,refThe calculation method is as follows:
Figure BDA0003048105260000071
Figure BDA0003048105260000072
Figure BDA0003048105260000073
in the formula of Udc4、Idc41And Idc42Representing a VSC of an offshore converter station4And a measure of the dc voltage of dc line 4-2 and the current of dc line 4-1; rdc41、Rdc42Respectively showing the resistance values, L, of the DC lines 4-2 and 4-1dc41、Ldc42Respectively showing the reactance value, the resistance value and the reactance value of the direct current line 4-2 and the direct current line 4-1, relating to the specific direct current engineering, and determining related parameters after the direct current engineering is put into operation; beta is a1And beta2Respectively representing land converter stations VSC1And VSC1The participation ratio in the estimation of the on-ground DC voltage. Reference value U for on-land DC voltage estimationdc,est,refIs obtained by averaging the estimated values of the offshore wind farm before frequency support, where t2The method represents any time before the offshore wind farm participates in frequency support, the integration duration in the above formula is 0.01s, and the method can be adjusted according to requirements in practical application.
S3: respectively calculating the power increase generated by droop response and inertia response of the offshore wind farm based on the estimated value of the onshore direct-current voltage in S2;
specifically, the power increase power generated by the droop response and the inertia response of the offshore wind farm is respectively as follows:
ΔPwdr_j＝-kwdr_j×(Udc,est,ref-Udc,est)
Figure BDA0003048105260000074
wherein, Δ Pwdr_jAnd Δ Pwin_jGenerating power increasing power generated by droop response and inertia response of the jth wind power plant respectively; k is a radical ofwdr_jAnd kwin_jRespectively obtaining the actual droop response coefficient and the inertia response coefficient of the jth wind power plant; u shapedc,est,refAnd Udc,estRespectively, a reference value and an estimated value of the land dc voltage.
S4: and distributing the increased power generated by the droop response and the inertia response of the offshore wind farm to adjust the frequency of the onshore alternating current system.
Specifically, the onshore converter station adopts a self-adaptive control strategy to reasonably distribute the frequency modulation power increase of the wind power plant, so that more frequency modulation power is injected into the alternating current system from the converter station closer to the disturbance node.
On the other hand, the invention also provides a non-communication control system for the offshore wind farm to participate in frequency modulation, which comprises:
the transmission module is used for converting the frequency variation into a direct-current voltage variation of the onshore converter station through droop control when the frequency variation of the onshore alternating-current system exceeds a frequency variation threshold value, and transmitting the direct-current voltage variation to the offshore converter station through a direct-current line so as to change the direct-current voltage of the offshore converter station;
the estimation module is used for acquiring direct-current voltage and direct-current signals of the offshore converter station and estimating the onshore direct-current voltage by combining the resistance value and the reactance value of the direct-current line;
the calculation module is used for respectively calculating the power increasing power generated by droop response and inertia response of the offshore wind farm based on the estimated value of the onshore direct current voltage obtained by the estimation module;
and the distribution module is used for distributing the increased power generated by the droop response and the inertia response of the offshore wind farm so as to adjust the frequency of the land alternating current system.
The division of each module in the non-communication control system for the offshore wind farm to participate in frequency modulation is only used for illustration, and in other embodiments, the non-communication control system for the offshore wind farm to participate in frequency modulation can be divided into different modules as required to complete all or part of functions of the non-communication control system for the offshore wind farm to participate in frequency modulation.
In order to verify the practicability of the present invention, the present embodiment performs simulation experiments under different load disturbances, and the simulation results are as shown in fig. 3(a) to fig. 3(c), where fig. 3(a) is a converter station VSC adopting the present invention and the existing communication-free and communication-equipped control method under the 200MW load sudden increase disturbance condition provided by the embodiment1Frequency f of measurementVSC1A graph of time; FIG. 3(b) is a schematic diagram of a VSC of a converter station using the present invention and the existing control method without communication and with communication under the condition of sudden load increase disturbance of 300MW provided by the embodiment1Frequency f of measurementVSC1A graph of time; FIG. 3(c) is a schematic diagram of a VSC of a converter station using the present invention and the existing communication-free and communication-equipped control method under the condition of 400MW load sudden-increase disturbance provided by the embodiment1Frequency f of measurementVSC1Graph over time. As can be seen from fig. 3(a) to 3(c), the non-communication control method for the offshore wind farm to participate in frequency modulation, which is provided by the invention and is based on VSC-MTDC grid connection, can realize the frequency adjustment of the non-communication participation system of the offshore wind farm, and reduce the influence of communication delay on the frequency modulation effect of the offshore wind farm.
As will be appreciated by one skilled in the art, embodiments of the present invention may be provided as a method, system, or computer program product. Accordingly, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present invention may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.
The present invention is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the 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.
The 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 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 (8)

1. A non-communication control method for an offshore wind farm to participate in frequency modulation is characterized by comprising the following steps:
s1: when the frequency variation of the onshore alternating current system exceeds a frequency variation threshold value, converting the frequency variation into a direct current voltage variation of the onshore converter station through droop control, and transmitting the direct current voltage variation to the offshore converter station through a direct current circuit to change the direct current voltage of the offshore converter station;
s2: collecting direct-current voltage and direct-current signals of the offshore converter station, and estimating the onshore direct-current voltage by combining the resistance value and the reactance value of the direct-current line;
s3: respectively calculating the power increase generated by droop response and inertia response of the offshore wind farm based on the estimated value of the onshore direct-current voltage in S2;
s4: and distributing the increased power generated by the droop response and the inertia response of the offshore wind farm to adjust the frequency of the onshore alternating current system.
2. The method of claim 1, wherein in step S1, the frequency-voltage droop control coefficient in the droop control is:
Figure FDA0003048105250000011
in the formula, kdf,iRepresenting the frequency-voltage droop control coefficient, k, of the ith land converter stationdf,i_0Indicating an initial value of the frequency-voltage droop control coefficient, α, for the ith land converter station1And alpha2Is a fixed constant, Udc,iRepresenting the measured value of the direct voltage, U, of the ith land converter stationdc,minRepresenting a minimum limit value, f, of the DC voltage of the converter station on landV,iRepresenting the measured value of the frequency of the alternating current system, df, of the ith land converter stationV,i(t)/dt represents the frequency reduction rate of the ith land converter station, t1Indicating frequency sag over land converter stationsInitial moment of the frequency change threshold, Δ tsRepresenting the duration of the integration.
3. The method for controlling the offshore wind farm to participate in frequency modulation without communication according to claim 1 or 2, wherein the power increase generated by the droop response and the inertia response of the offshore wind farm is respectively as follows:
ΔPwdr_j＝-kwdr_j×(Udc,est,ref-Udc,est)
Figure FDA0003048105250000021
wherein, Δ Pwdr_jAnd Δ Pwin_jGenerating power increasing power generated by droop response and inertia response of the jth wind power plant respectively; k is a radical ofwdr_jAnd kwin_jRespectively obtaining the actual droop response coefficient and the inertia response coefficient of the jth wind power plant; u shapedc,est,refAnd Udc,estRespectively, a reference value and an estimated value of the land dc voltage.
4. The method of claim 3, wherein the estimating the onshore DC voltage in step S2 comprises: and estimating the land DC voltage by using kirchhoff's law.
5. A non-communication control system for an offshore wind farm to participate in frequency modulation is characterized by comprising:
the transmission module is used for converting the frequency variation into a direct-current voltage variation of the onshore converter station through droop control when the frequency variation of the onshore alternating-current system exceeds a frequency variation threshold value, and transmitting the direct-current voltage variation to the offshore converter station through a direct-current line so as to change the direct-current voltage of the offshore converter station;
the estimation module is used for acquiring direct-current voltage and direct-current signals of the offshore converter station and estimating the onshore direct-current voltage by combining the resistance value and the reactance value of the direct-current line;
the calculation module is used for respectively calculating the power increasing power generated by droop response and inertia response of the offshore wind farm based on the estimated value of the onshore direct current voltage obtained by the estimation module;
and the distribution module is used for distributing the increased power generated by the droop response and the inertia response of the offshore wind farm so as to adjust the frequency of the land alternating current system.
6. The system of claim 5, wherein the droop control medium frequency-voltage droop control coefficient is:
Figure FDA0003048105250000022
in the formula, kdf,iRepresenting the frequency-voltage droop control coefficient, k, of the ith land converter stationdf,i_0Indicating an initial value of the frequency-voltage droop control coefficient, α, for the ith land converter station1And alpha2Is a fixed constant, Udc,iRepresenting the measured value of the direct voltage, U, of the ith land converter stationdc,minRepresenting a minimum limit value, f, of the DC voltage of the converter station on landV,iRepresenting the measured value of the frequency of the alternating current system, df, of the ith land converter stationV,i(t)/dt represents the frequency reduction rate of the ith land converter station, t1Indicating an initial time, at, of a frequency dip of the onshore converter station exceeding a frequency change thresholdsRepresenting the duration of the integration.
7. The system of claim 5 or 6, wherein the droop response and the inertia response of the offshore wind farm generate power gains of:
ΔPwdr_j＝-kwdr_j×(Udc,est,ref-Udc,est)
Figure FDA0003048105250000031
wherein, Δ Pwdr_jAnd Δ Pwin_jGenerating power increasing power generated by droop response and inertia response of the jth wind power plant respectively; k is a radical ofwdr_jAnd kwin_jRespectively obtaining the actual droop response coefficient and the inertia response coefficient of the jth wind power plant; u shapedc,est,refAnd Udc,estRespectively, a reference value and an estimated value of the land dc voltage.
8. The system of claim 7, wherein the estimating the onshore dc voltage comprises: and estimating the land DC voltage by using kirchhoff's law.
CN202110478229.6A 2021-04-30 2021-04-30 Non-communication control method and system for offshore wind farm to participate in frequency modulation Active CN113193571B (en)

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CN111711203A (en) * 2020-01-15 2020-09-25 华中科技大学 Two-stage coordination control method and system for offshore wind farm participating in frequency modulation
CN111817326A (en) * 2020-06-18 2020-10-23 浙江大学 Distributed energy storage SOC control and integration method under alternating current micro-grid island mode
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CN110492524A (en) * 2019-07-24 2019-11-22 全球能源互联网研究院有限公司 Active-control method for frequency and system without the communication soft direct join net of marine wind electric field
CN111711203A (en) * 2020-01-15 2020-09-25 华中科技大学 Two-stage coordination control method and system for offshore wind farm participating in frequency modulation
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