CN116544969A - Control method and device for restraining subsynchronous oscillation of direct-drive wind power plant under weak current network - Google Patents

Control method and device for restraining subsynchronous oscillation of direct-drive wind power plant under weak current network Download PDF

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CN116544969A
CN116544969A CN202310768090.8A CN202310768090A CN116544969A CN 116544969 A CN116544969 A CN 116544969A CN 202310768090 A CN202310768090 A CN 202310768090A CN 116544969 A CN116544969 A CN 116544969A
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grid
direct
side converter
error
current
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CN116544969B (en
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颜景斌
王玺哲
许森洋
朱强
王怡斐
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Harbin University of Science and Technology
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Harbin 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
    • H02J3/002—Flicker reduction, e.g. compensation of flicker introduced by non-linear load
    • 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
    • H02J2203/00—Indexing scheme relating to details of circuit arrangements for AC mains or AC distribution networks
    • H02J2203/20—Simulating, e g planning, reliability check, modelling or computer assisted design [CAD]
    • 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
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/70—Wind energy
    • Y02E10/76—Power conversion electric or electronic aspects

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Nonlinear Science (AREA)
  • Control Of Eletrric Generators (AREA)

Abstract

A control method and device for restraining subsynchronous oscillation of a direct-drive wind power plant under a weak current network relate to the technical field of direct-drive fans, and the method comprises the following steps: collecting parameters of a grid-connected system of the direct-drive wind power plant; equivalent wind turbines and a side converter in the direct-drive wind farm grid-connected system to be controlled current sources; establishing a grid-side converter model based on parameters of the direct-drive wind farm grid-connected system; applying an improved linear first-order active disturbance rejection controller to the grid-side converter model; the method is improved on the basis of the traditional LADRC, so that the whole system has better dynamic response performance and anti-interference capability, and the generation of subsynchronous oscillation can be effectively restrained.

Description

Control method and device for restraining subsynchronous oscillation of direct-drive wind power plant under weak current network
Technical Field
The invention relates to the technical field of direct-drive fans.
Background
Along with the increasing energy consumption in the world, the distributed power generation grid connection of photovoltaic, wind power and the like is promoted, and the construction of a diversified and clean power grid power supply system becomes a primary task. At present, the power system mainly supplies power in a centralized way, and if accidents occur, the power supply of a large scale is interrupted. At present, wind power generation develops rapidly, however, large-scale wind power is connected into an alternating current power grid through long-distance transmission, so that the connection strength of a receiving end power grid can be reduced, the risk of system instability is increased, in recent years, the problem of subsynchronous oscillation of a plurality of direct-drive wind power plants connected into a weak alternating current power grid occurs in China, and corresponding technical measures are needed to prevent the risk of subsynchronous oscillation.
The active disturbance rejection control (Automatic disturbance rejection control, ADRC) is a control method improved on the basis of PID control, the core idea is PI error feedback, and the mathematical model of a control system is not needed to be considered in the design of the ADRC. On the basis, a linear active disturbance rejection control technology (Linear Active Disturbance Rejection Control, LADRC) is also provided, so that the parameter adjustment of the controller is greatly simplified. When LADRC control is adopted, the selection of parameters is easier, and the stable operation of the controller can be ensured. Compared with the existing many other control modes, the method is easy to realize and has better practical value.
However, research shows that although the LADRC controller can effectively inhibit the direct-driven wind power plant from being connected to a weak alternating-current power grid to generate the synchronous oscillation, the existing LADRC controller is weak in stability, and when the LADRC controller is adopted to inhibit the subsynchronous oscillation of the direct-driven wind power plant, the whole anti-interference capability of the system is poor.
Therefore, how to provide a control method and a device for suppressing subsynchronous oscillation of a direct-drive wind power station under a weak current network with strong anti-interference capability becomes a technical problem to be solved in the field.
Disclosure of Invention
In order to solve the technical problems, the invention provides a control method and a device for restraining subsynchronous oscillation of a direct-drive wind power plant under a weak current network, wherein the method improves an active disturbance rejection controller and is applied to a network-side converter, and the method is improved on the basis of a traditional LADRC, so that the whole system has better dynamic response performance and anti-disturbance capability, and can effectively restrain the subsynchronous oscillation.
Based on the same inventive concept, the invention has four independent technical schemes:
1. a control method for inhibiting subsynchronous oscillation of a direct-drive wind power plant under a weak current network comprises the following steps:
collecting parameters of a grid-connected system of the direct-drive wind power plant;
equivalent wind turbines and a side converter in the direct-drive wind farm grid-connected system to be controlled current sources;
establishing a grid-side converter model based on parameters of the direct-drive wind farm grid-connected system;
applying an improved linear first-order active disturbance rejection controller to the grid-side converter model;
the improved linear first-order active disturbance rejection controller is represented as follows:
；
wherein ,z1 、z 2 In order to estimate the value of the disturbance,、/>b is the differential of the disturbance estimation 0 As error factor, beta 1 、β 2 For the adjustable parameter, u is the disturbance compensation quantity, < ->For error feedback rate, k p For the bandwidth of the active disturbance rejection controller, y is the system output,/->For neglecting incomplete errors of slight subtended, +.>，e 1 Is an error signal +.>V is the given signal, which is the differential of the system output.
Further, the direct-drive wind farm grid-connected system comprises the wind turbine, the machine side converter, the grid side converter and a weak alternating current power grid.
Further, the mesh side converter model is represented as follows:
；
wherein ω is the synchronous angular velocity of the system, L is the filter inductance of the AC side, R g Is the equivalent resistance of the alternating current side of the network side converter, u cd 、u cq Respectively the d-axis component and the q-axis component, i of the output voltage of the grid-side converter gd 、i gq D-axis and q-axis components of the ac side current of the grid side converter, u gd 、u gq Respectively the d-axis component and the q-axis component, i of the grid voltage of the grid-connected point of the fan g The current of the grid-connected point of the fan is C is the direct-current side capacitor of the grid-side converter, i dc A current supplied to the controlled current source through a DC-side capacitor of the grid-side converter, U dc The voltage value of the capacitor at the direct current side of the grid-side converter.
Further, the improved linear first-order active disturbance rejection controller is obtained through the following steps:
the linear expansion state observer is improved, and the improved linear expansion state observer is expressed as follows:
；
；
；
wherein ,is the differential of the error signal,/>Is a state variable;
estimating a system error based on the improved linear expansion state observer, compensating by a linear state error feedback controller to obtain a compensated output, and representing as follows:
；
wherein E is the ideal error;
and neglecting a differential term in the ideal error to obtain an incomplete error, and replacing the ideal error in the compensated output by the incomplete error to obtain the improved linear first-order active disturbance rejection controller.
Further, the ideal error is expressed as follows:
。
further, when the improved linear first-order active disturbance rejection controller is applied to the network side converter model, voltage outer loop and current inner loop double closed loop control is adopted, wherein a d-axis current inner loop control equation is expressed as follows:
；
wherein ,for d-axis current reference, ">、/>For observer state variables, +.>、/>Differential quantity, which is the observer state variable, +.>Is error factor->To ignore the estimation error of the observer, +.>A disturbance compensation link of the current inner loop controller;
the voltage outer loop control equation is expressed as follows:
；
wherein ,is the reference value of the capacitor voltage at the DC side, < >>、/>For observer state variables, +.>、Differential quantity, which is the observer state variable, +.>Is error factor->To ignore the estimation error of the observer, +.>And the disturbance compensation link of the voltage outer loop controller is adopted.
2. A control device for restraining subsynchronous oscillation of a direct-drive wind power plant under a weak current network comprises:
the parameter acquisition module is used for acquiring parameters of the grid-connected system of the direct-driven wind power plant;
the equivalent power supply module is used for equivalent of a wind turbine and a machine side converter in the direct-driven wind power plant grid-connected system into a controlled current source;
the grid-side circulation model building module is used for building a grid-side converter model based on the direct-drive wind power plant grid-connected system parameters;
the control module is used for applying the improved linear first-order active disturbance rejection controller to the network-side converter model;
in the control module, the improved linear first-order active disturbance rejection controller is represented as follows:
；
wherein ,z1 、z 2 In order to estimate the value of the disturbance,、/>b is the differential of the disturbance estimation 0 As error factor, beta 1 、β 2 For the adjustable parameter, u is the disturbance compensation quantity, < ->For error feedback rate, k p For the bandwidth of the active disturbance rejection controller, y is the system output,/->For neglecting incomplete errors of slight subtended, +.>，e 1 Is an error signal +.>V is the given signal, which is the differential of the system output.
3. A computer readable storage medium storing a computer program which when executed by a processor implements the method described above.
4. An electronic device comprises a processor and a storage device, wherein a plurality of instructions are stored in the storage device, and the processor is used for reading the plurality of instructions in the storage device and executing the method.
The control method and the device for inhibiting the subsynchronous oscillation of the direct-drive wind power station under the weak current network provided by the invention at least comprise the following beneficial effects:
(1) The method is improved on the basis of the traditional LADRC, improves an active disturbance rejection controller and is applied to a network side converter, so that the whole system has better dynamic response performance and anti-disturbance capability, and can effectively inhibit the generation of subsynchronous oscillation;
(2) The wind turbine and the machine side converter parts which do not participate in subsynchronous oscillation are replaced by the controlled current source, so that the method is simpler and more convenient;
(3) Compared with the traditional LADRC, the influence of the disturbance quantity on the system output is reduced, the gain of the improved LADRC disturbance is always smaller than that of the traditional LADRC at the middle-low frequency band, the system bandwidth is increased, and the anti-interference capability is strong; compared with a PI controller, the method can obviously inhibit the direct-driven wind power plant from being connected to a weak alternating current power grid to generate subsynchronous oscillation, and under different working conditions, the improved LADRC can effectively inhibit the subsynchronous oscillation.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following description will briefly introduce the drawings that are needed in the embodiments or the description of the prior art, it is obvious that the drawings in the following description are only some embodiments of the present application, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a flowchart of an embodiment of a control method for suppressing subsynchronous oscillations of a direct-drive wind farm in a weak power grid provided by the invention;
fig. 2 is a diagram of a modified ladc-based network side inverter control;
FIG. 3 is a block diagram of a modified LADRC control;
FIG. 4 is a graph showing the contrast of the amplitude-phase characteristic of the disturbance term of the control method before and after the improvement;
FIG. 5 is a graph of PI control versus modified LADRC active power;
fig. 6 is a phase B spectrum analysis of the output current of the PI-controlled down-grid side converter;
FIG. 7 is a graph of a modified LADRC controlled lower network side inverter output current B-phase spectral analysis;
FIG. 8 is a graph showing the comparison of the DC side voltage of two controllers after a DC side current transition under PI control and modified LADRC;
FIG. 9 is a graph of the net side active power comparison of the two controllers after a DC side current transition under the PI control and modified LADRC;
FIG. 10 is a graph of net side active power at 8m/s wind speed under PI control and modified LADRC;
FIG. 11 is a graph of net side active power at 9m/s wind speed under PI control and modified LADRC;
FIG. 12 is a plot of PI control versus net side active power at 10m/s wind speed for the improved LADRC;
FIG. 13 is a graph comparing PI control to a dynamic curve of direct current at grid strength with SCR of 1.7 under modified LADRC;
FIG. 14 is a graph comparing PI control to a dynamic curve of direct current for grid strength with SCR of 2.3 under modified LADRC;
FIG. 15 is a graph comparing PI control to a dynamic curve of direct current at grid strength with SCR of 3.0 under modified LADRC;
FIG. 16 is a plot of net side active power versus voltage drop at 0.1p.u. for PI control and modified LADRC;
FIG. 17 is a plot of net side active power versus voltage drop at 0.3p.u. for PI control and modified LADRC;
FIG. 18 is a plot of net side active power versus voltage drop at 0.5p.u. for PI control and modified LADRC;
FIG. 19 is a graph showing the grid-connected voltage and current waveforms at 8m/s wind speed under PI control;
FIG. 20 is a graph showing the grid-connected voltage and current waveforms at 8m/s wind speed under the modified LADRC;
FIG. 21 is a graph showing the grid-connected voltage and current waveforms at a wind speed of 9m/s under PI control;
FIG. 22 is a graph showing the grid-connected voltage and current waveforms at a wind speed of 9m/s for the modified LADRC;
FIG. 23 is a graph showing the grid-connected voltage and current waveforms at a wind speed of 10m/s under PI control;
FIG. 24 is a graph showing the grid-connected voltage and current waveforms at a wind speed of 10m/s for the modified LADRC;
FIG. 25 is a graph showing the grid-connected voltage and current waveforms when the grid strength is 1.7 under PI control;
FIG. 26 is a graph showing the grid-tied voltage and current waveforms for a grid strength of 1.7 under the modified LADRC;
FIG. 27 is a graph showing the grid-connected voltage and current waveforms when the grid strength is 2.3 under PI control;
FIG. 28 is a graph showing the grid-tied voltage and current waveforms for a grid strength of 2.3 under the modified LADRC;
FIG. 29 is a graph showing the grid-connected voltage and current waveforms for a grid strength of 3.0 under PI control;
FIG. 30 is a graph of grid-tied voltage and current waveforms for a grid strength of 3.0 under the modified LADRC.
Detailed Description
In order to better understand the above technical solutions, the following detailed description will be given with reference to the accompanying drawings and specific embodiments.
Embodiment one:
referring to fig. 1, in some embodiments, a control method for suppressing subsynchronous oscillation of a direct-drive wind farm under a weak current network is provided, including:
s1, collecting parameters of a grid-connected system of a direct-drive wind farm;
s2, equivalent wind turbines and a machine side converter in the direct-drive wind farm grid-connected system are controlled current sources;
s3, establishing a grid-side converter model based on parameters of the grid-connected system of the direct-drive wind farm;
s4, applying the improved linear first-order active disturbance rejection controller to the network-side converter model to inhibit subsynchronous oscillation of the direct-drive wind power plant.
Specifically, the direct-drive wind farm grid-connected system in step S1 includes the wind turbine, the machine side converter, the grid side converter, and a weak ac grid. The parameters of the grid-connected system of the direct-driven wind farm comprise the parameters used for calculation.
In step S2, the mesh-side converter model is represented as follows:
；
wherein ω is the synchronous angular velocity of the system, L is the filter inductance of the AC side, R g Is the equivalent resistance of the alternating current side of the network side converter, u cd 、u cq Respectively the d-axis component and the q-axis component, i of the output voltage of the grid-side converter gd 、i gq D-axis and q-axis components of the ac side current of the grid side converter, u gd 、u gq Respectively the d-axis component and the q-axis component, i of the grid voltage of the grid-connected point of the fan g The current of the grid-connected point of the fan is C is the direct-current side capacitor of the grid-side converter, i dc U is the current flowing through the DC side capacitor of the grid-side converter dc The voltage value of the capacitor at the direct current side of the grid-side converter.
The simplified direct-drive wind farm network side converter control block diagram based on the improved LADRC is shown in figure 2. The grid-side converter is connected with the grid after passing through the filter inductor L, and the resistor R1 and the inductor L1 form the impedance of the grid.
When the switch at the weak alternating current power grid in the figure is disconnected, the analog direct-driven fan system is connected to the weak alternating current power grid, the equivalent inductance L1 of the connected line is equivalent in data analysis, and at the moment, mutation current is generated at the fan grid-connected bus due to the change of line impedance, namely secondary synchronous current, delta i is used gsub And (3) representing. At this time, the voltage at the grid-connected bus will change due to abrupt change of current, which will cause instability of both the current and the voltage on the line, thereby causing distortion.
The input voltage of the phase-locked loop is parallel voltage, so that a subsynchronous angle delta theta is introduced at the output angle of the phase-locked loop sub . In the control strategy of the grid-side converter, in order to facilitate the coordination of the current inner loop and the outer loop, the bandwidth of the voltage outer loop is generally set to be one tenth of that of the current inner loop, but the voltage outer loop is poweredThe bandwidth of the current inner loop is only one tenth of that of the phase-locked loop and the switching equipment, so for subsynchronous oscillation, the response speed of the current inner loop is faster than that of the voltage outer loop due to lower time constant, the generated subsynchronous angle is changed by the control of the network-side converter, the corresponding change of the current inner loop is further caused to generate a new current value, the new superimposed voltage generated by the proportional-integral controller is the subsynchronous voltage, and delta u is used csub-dq And (3) representing. The newly generated subsynchronous current is generated due to positive feedback effect of the previously generated subsynchronous current, so that the vibration of the system is increased, and the subsynchronous oscillation of the system is caused to be unstable.
The control of the grid-side converter can be represented by the following formula:
；(1)
after the wind power system is connected with the weak alternating current power grid, delta u is respectively used csub Representing the subsynchronous voltage Deltau output by the network-side converter gsub Representing the voltage variation quantity delta i at the grid-connected point of the fan gsub Representing the subsynchronous current at the point of the grid connection, equation (1) may be expressed as:
；(2)
the PI controller used for the grid-side converter is expressed as:
；(3)
according to the above, after the subsynchronous current generated by subsynchronous oscillation passes through the PI controller in the network-side converter, the synchronous component generated by the subsynchronous current is continuously superimposed on the basis of the output voltage of the PI controller, and according to time variability, the grid-connected voltage continuously superimposes a new subsynchronous component, thereby finally causing subsynchronous oscillation to occur.
In step S4, the improved linear first-order active-disturbance-rejection controller is obtained by the following steps:
s41, improving a Linear Expansion State Observer (LESO), wherein the improved linear expansion state observer is expressed as follows:
；
wherein ,z1 、z 2 In order to estimate the value of the disturbance,、/>b is the differential of the disturbance estimation 0 As error factor, beta 1 、β 2 Is an adjustable parameter->Is an error signal +.>Is the differential of the error signal,/>U is a system input;
s42, estimating a system error based on the improved linear expansion state observer, and compensating by a linear state error feedback controller (LSEF) to obtain a compensated output, wherein the method is represented as follows:
；
wherein ,kp The bandwidth of the active disturbance rejection controller is provided, E is an ideal error, and v is a given signal;
s43, neglecting a differential term in the ideal error to obtain an incomplete error, and replacing the ideal error in the compensated output by the incomplete error to obtain the improved linear first-order active disturbance rejection controller.
In step S42, the ideal error is expressed as follows:
。
in step S43, the improved linear first-order active-disturbance-rejection controller is represented as follows:
；
wherein ,kp For the bandwidth of the active disturbance rejection controller beta 1 、β 2 For adjustable parameters, z 1 、z 2 B is the disturbance estimation value 0 Is an error factor, y is a system output, e 1 As an error signal, the signal is a signal,、/>for the differential of the disturbance estimation, +.>Is a derivative of the system output.
The following describes the solving process of the improved linear first-order active-disturbance-rejection controller in steps S41-S43:
the conventional LESO is rewritten as follows:
；(4)
the improved LESO is obtained as follows:
；(5)
the observer matrix is:
；(6)
defining the error term outside the ideal closed loop as:
；(7)
the ideal closed loop system eliminates the error term as follows:
；(8)
the output of the LSEF controller with LESO estimation error compensation is:
；(9)
e is an ideal error, not directly available, expressed in known quantities as follows:
；(10)
the product is obtained by Laplace inverse transformation and carried into a formula (7):
；(11)
error e 1 It is known that ignoring differential terms that cannot be directly obtained, an incomplete error result is obtained:
(12)
the output of the improved LSEF controller is:
；(13)
the improved LADRC controller mathematical model is as follows:
；(14)
a modified ladc control block diagram is shown in fig. 3.
In step S4, voltage outer loop and current inner loop dual closed loop control is adopted, wherein the d-axis current inner loop control equation is expressed as follows:
；(15)
wherein ,for d-axis current reference, ">、/>Observer state variables, +.>As an error factor, the error factor is,to ignore the estimation error of the observer, +.>For disturbance compensation of the current inner loop controller, < >>Incomplete error for neglecting slight entries;
the voltage outer loop control equation is expressed as follows:
；(16)
wherein ,is the reference value of the capacitor voltage at the DC side, < >>、/>For observer state variables, +.>Is error factor->To ignore the estimation error of the observer, +.>And the disturbance compensation link of the voltage outer loop controller is adopted.
The relationship between the system output term and the disturbance term of the traditional LADRC is:
；(17)
the relation between the system output term and the disturbance term of the improved LADRC is as follows:
；(18)
the beneficial effects of this embodiment are further illustrated by comparative experiments as follows:
and (3) building a direct-drive fan in Matlab/Simulink simulation software, accessing the Matlab/Simulink simulation software into a weak alternating-current power grid system, reproducing subsynchronous oscillation, comparing the oscillation conditions of the distributed direct-drive wind power system under PI control and improved linear active disturbance rejection control, and carrying out experimental verification. The weak ac power network system is constructed by adjusting the equivalent reactance of the transmission line. The disturbance term amplitude-phase characteristic curve pair of the conventional ladc control method and the improved control method provided in this embodiment is shown in fig. 4.
In a specific application scenario, the wind speed v=8m/s is set, when the system is in a stable state, when t=0.4s, the access weak ac power grid SCR is set to 2.5, and the active power comparison chart is shown in fig. 5
The spectral analysis of the grid-side inverter output current B phase is shown in fig. 6-7. As can be seen from fig. 6, the output current of the grid-side converter contains sub-synchronous components, wherein the sub-synchronous components of 35Hz, 68Hz are relatively high. As can be seen from fig. 7, the output current sub-synchronous component of the grid-side converter has been effectively eliminated, and only the current of 50Hz at the power frequency exists.
The two controller comparisons after the dc side voltage transition under normal operating conditions are shown in fig. 8-9. Both the PI controller and the LADRC controller can track rapidly when the reference value of the capacitor voltage at the direct current side is changed; for the power output by the fan, the PI controller and the LADRC controller recover the original output power after a transient process only when the direct current voltage of the fan changes in a step mode.
When the set wind speeds are 8m/s, 9m/s and 10m/s respectively and scr=1.9, the comparison LADRC inhibits subsynchronous oscillation effects as shown in fig. 10-12, and SSO inhibition effect comparison diagrams at different wind speeds are shown. Subsynchronous oscillation occurs at all three wind speeds, the damping of the fan system is increased along with the increase of the wind speed, the subsynchronous oscillation phenomenon is obviously weakened, and compared with the active power curve of the fan system under the control of the LADRC, the subsynchronous oscillation phenomenon is obviously weakened under the control of the LADRC, the inhibition effect is more obvious under the condition of low wind speed, and the control parameters of the LADRC are not changed, so that the fact that the LADRC does not influence the stable operation of the fan under the condition of different wind speeds and can effectively inhibit the subsynchronous oscillation can be proved.
When the initial wind speed is set to 8m/s and t=0.4 s, the direct-driven fan system is connected to an alternating-current power grid, and is respectively connected to weak alternating-current lines with SCR of 3.0, 2.3 and 1.7, the control parameters of the fixed LADRC are unchanged, the response curve of the LADRC to the intensity of the alternating-current power grid is shown as fig. 13-15, and PI control data are added as a comparison.
The initial wind speed is set to 8m/s, and the t=0.4s direct-drive wind farm is connected to a weak alternating-current power grid. At t=0.5 s, the grid-side voltage drops were set to 10%, 30% and 50% of the rated grid-connected voltage, respectively, for 0.2s, the grid-side active power pairs such as shown in fig. 16-18, and PI-controlled data were added as controls.
Building the proposed topology structure on an RT Box experiment platform, inputting a control program into a DSP, and displaying the experimental results in the figures 19-30; 19-24 are PI control and improved LADRC entity comparison diagrams at different wind speeds; fig. 25-30 are comparison graphs of PI control and modified ladc for different grid strengths, and the observed object is a grid-connected voltage-current waveform.
As can be seen from the test results of fig. 10-30, in the case that the strength, the wind speed and the voltage drop of each power grid fall, the control method for suppressing the subsynchronous oscillation of the direct-drive wind power plant provided by the embodiment can enable the whole system to have better dynamic response performance and anti-interference capability, and can effectively suppress the subsynchronous oscillation.
Embodiment two:
in some embodiments, a control device for suppressing subsynchronous oscillation of a direct-drive wind farm under a weak power grid is provided, including:
the parameter acquisition module is used for acquiring parameters of the grid-connected system of the direct-driven wind power plant;
the equivalent power supply module is used for equivalent of a wind turbine and a machine side converter in the direct-driven wind power plant grid-connected system into a controlled current source;
the grid-side circulation model building module is used for building a grid-side converter model based on the direct-drive wind power plant grid-connected system parameters;
and the control module is used for applying the improved linear first-order active disturbance rejection controller to the network-side converter model.
Embodiment III:
in some embodiments, a computer readable storage medium is provided, which stores a computer program which, when executed by a processor, implements the above method.
Embodiment four:
in some embodiments, an electronic device is provided that includes a processor and a storage device having a plurality of instructions stored therein, the processor configured to read the plurality of instructions in the storage device and perform the method described above.
The control method and the device for restraining the subsynchronous oscillation of the direct-drive wind power plant under the weak current network are improved on the basis of the traditional LADRC, the active disturbance rejection controller is improved and applied to the network-side converter, so that the whole system has better dynamic response performance and anti-disturbance capability, and the subsynchronous oscillation can be restrained effectively; the wind turbine and the machine side converter parts which do not participate in subsynchronous oscillation are replaced by the controlled current source, so that the method is simpler and more convenient; compared with the traditional LADRC, the influence of the disturbance quantity on the system output is reduced, the gain of the improved LADRC disturbance is always smaller than that of the traditional LADRC at the middle-low frequency band, the system bandwidth is increased, and the anti-interference capability is strong; compared with a PI controller, the method can obviously inhibit the direct-driven wind power plant from being connected to a weak alternating current power grid to generate subsynchronous oscillation, and under different working conditions, the improved LADRC can effectively inhibit the subsynchronous oscillation.
While preferred embodiments of the present invention have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. It is therefore intended that the following claims be interpreted as including the preferred embodiments and all such alterations and modifications as fall within the scope of the invention. It will be apparent to those skilled in the art that various modifications and variations can be made to the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention also include such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.

Claims (9)

1. A control method for inhibiting subsynchronous oscillation of a direct-drive wind power plant under a weak current network is characterized by comprising the following steps:
collecting parameters of a grid-connected system of the direct-drive wind power plant;
equivalent wind turbines and a side converter in the direct-drive wind farm grid-connected system to be controlled current sources;
establishing a grid-side converter model based on parameters of the direct-drive wind farm grid-connected system;
applying an improved linear first-order active disturbance rejection controller to the grid-side converter model;
the improved linear first-order active disturbance rejection controller is represented as follows:
；
；
；
；
wherein ,z1 、z 2 In order to estimate the value of the disturbance,、/>b is the differential of the disturbance estimation 0 As error factor, beta 1 、β 2 For the adjustable parameter, u is the disturbance compensation quantity, < ->For error feedback rate, k p For the bandwidth of the active disturbance rejection controller, y is the system output,/->For neglecting incomplete errors of slight subtended, +.>，e 1 Is an error signal +.>V is the given signal, which is the differential of the system output.
2. The method of claim 1, wherein the direct drive wind farm grid-tie system comprises the wind turbine, the machine side converter, the grid side converter, and a weak ac grid.
3. A method according to claim 1, characterized in that the mesh side converter model is represented as follows:
；
wherein ω is the synchronous angular velocity of the system, L is the filter inductance of the AC side, R g Is the equivalent resistance of the alternating current side of the network side converter, u cd 、u cq Respectively the d-axis component and the q-axis component, i of the output voltage of the grid-side converter gd 、i gq D-axis and q-axis components of the ac side current of the grid side converter, u gd 、u gq Respectively the d-axis component and the q-axis component, i of the grid voltage of the grid-connected point of the fan g The current of the grid-connected point of the fan is C is the direct-current side capacitor of the grid-side converter, i dc A current supplied to the controlled current source through a DC-side capacitor of the grid-side converter, U dc The voltage value of the capacitor at the direct current side of the grid-side converter.
4. The method of claim 1, wherein the improved linear first order active disturbance rejection controller is obtained by:
the linear expansion state observer is improved, and the improved linear expansion state observer is expressed as follows:
；
；
；
wherein ,is the differential of the error signal,/>Is a state variable;
estimating a system error based on the improved linear expansion state observer, compensating by a linear state error feedback controller to obtain a compensated output, and representing as follows:
；
wherein E is the ideal error;
and neglecting a differential term in the ideal error to obtain an incomplete error, and replacing the ideal error in the compensated output by the incomplete error to obtain the improved linear first-order active disturbance rejection controller.
5. The method of claim 4, wherein the ideal error is represented as follows:
。
6. the method of claim 1, wherein a voltage outer loop and current inner loop double closed loop control is employed when applying the improved linear first order active disturbance rejection controller to the grid-side converter model, wherein a d-axis current inner loop control equation is expressed as follows:
；
wherein ,for d-axis current reference, ">、/>For observer state variables, +.>、/>Differential quantity, which is the observer state variable, +.>Is error factor->To ignore the estimation error of the observer, +.>A disturbance compensation link of the current inner loop controller;
the voltage outer loop control equation is expressed as follows:
；
wherein ,is the reference value of the capacitor voltage at the DC side, < >>、/>For observer state variables, +.>、/>Differential quantity, which is the observer state variable, +.>Is error factor->To ignore the estimation error of the observer, +.>And the disturbance compensation link of the voltage outer loop controller is adopted.
7. The control device for inhibiting subsynchronous oscillation of the direct-drive wind power plant under the weak current network is characterized by comprising the following components:
the parameter acquisition module is used for acquiring parameters of the grid-connected system of the direct-driven wind power plant;
the equivalent power supply module is used for equivalent of a wind turbine and a machine side converter in the direct-driven wind power plant grid-connected system into a controlled current source;
the grid-side circulation model building module is used for building a grid-side converter model based on the direct-drive wind power plant grid-connected system parameters;
the control module is used for applying the improved linear first-order active disturbance rejection controller to the network-side converter model;
in the control module, the improved linear first-order active disturbance rejection controller is represented as follows:
；
；
；
；
wherein ,z1 、z 2 In order to estimate the value of the disturbance,、/>b is the differential of the disturbance estimation 0 As error factor, beta 1 、β 2 For the adjustable parameter, u is the disturbance compensation quantity, < ->For error feedback rate, k p For the bandwidth of the active disturbance rejection controller, y is the system output,/->For neglecting incomplete errors of slight subtended, +.>，e 1 Is an error signal +.>V is the given signal, which is the differential of the system output.
8. A computer readable storage medium storing a computer program, which when executed by a processor performs the method according to any one of claims 1-6.
9. An electronic device comprising a processor and a memory means, wherein a plurality of instructions are stored in the memory means, the processor being arranged to read the plurality of instructions in the memory means and to perform the method of any of claims 1-6.
CN202310768090.8A 2023-06-28 2023-06-28 Control method and device for restraining subsynchronous oscillation of direct-drive wind power plant under weak current network Active CN116544969B (en)

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