CN113162095A - Direct-current voltage control method of multi-terminal flexible direct-current system - Google Patents

Direct-current voltage control method of multi-terminal flexible direct-current system Download PDF

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CN113162095A
CN113162095A CN202110046091.2A CN202110046091A CN113162095A CN 113162095 A CN113162095 A CN 113162095A CN 202110046091 A CN202110046091 A CN 202110046091A CN 113162095 A CN113162095 A CN 113162095A
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converter
direct
voltage
controller
direct current
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CN113162095B (en
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窦飞
蔡晖
张成龙
刘柏良
彭竹弈
赵菲菲
许偲轩
黄成辰
葛乐
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Nanjing Institute of Technology
State Grid Jiangsu Electric Power Co Ltd
Economic and Technological Research Institute of State Grid Jiangsu Electric Power Co Ltd
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Nanjing Institute of Technology
State Grid Jiangsu Electric Power Co Ltd
Economic and Technological Research Institute of State Grid Jiangsu 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
    • H02J3/36—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
    • 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
    • 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]

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

Abstract

The invention relates to a direct-current voltage control method of a multi-terminal flexible direct-current system, which specifically comprises the following steps: firstly, modeling analysis is carried out on a multi-end flexible direct current system, and a modeled object comprises: a wind farm, a PQ converter and a multi-terminal flexible direct current system of a main converter; secondly, a controller is designed by applying a norm control method, and the method allows the controlled local direct-current voltage to change correspondingly according to the scheduling requirement, so that the control precision of the direct-current voltage of the system is improved; and finally, simulating the system by adopting the control method through MATLAB/SIMULINKR, and verifying the feasibility and effectiveness of the control strategy. Has the advantages that: the power storage can be effectively managed in the form of a wind turbine by adopting the norm controller for voltage regulation, and the robustness and the control precision of the system are improved.

Description

Direct-current voltage control method of multi-terminal flexible direct-current system
Technical Field
The invention relates to the field of power electronics, in particular to a direct-current voltage control method of a multi-terminal flexible direct-current system.
Background
Since the fifty years High Voltage Direct Current (HVDC) transmission systems have been built and operated, Voltage Source Converters (VSC) have only been applied to high voltage direct current transmission systems in the late 90s, although two multi-terminal VSC-HVDC projects have been operated in china, the control of the direct voltage is still the focus of research. The multi-terminal VSC-HVDC system is controlled by direct voltage through only one converter. The remaining converters are operated in a fast active/Passive (PQ) control mode. The droop control method is the expansion of power frequency droop characteristics adopted by the synchronous generator. The main disadvantage of this control logic is that multi-terminal hvdc (mtdc) power flow control is not accurate enough due to the constant droop coefficient employed.
The delivered power of multiple MTDC systems operating globally is derived from a decentralized offshore wind farm. Modern WTGs are considered to be one of the fastest, most efficient power generators. Recent improvements in wind energy prediction accuracy are greatly reducing prediction errors and maintaining sufficient reserves to overcome wind power uncertainty is making wind energy resources more similar to traditional thermal power resources.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides a direct-current voltage control method of a multi-terminal flexible direct-current system, which adopts H∞The norm controller is used for regulating the voltage, can effectively manage power reserve in the form of a wind turbine, and improves the robustness and control accuracy of the system, and is specifically realized by the following technical scheme:
the direct-current voltage control method of the multi-terminal flexible direct-current system is further designed to comprise the following steps of:
step 1) modeling analysis is carried out on the multi-end flexible direct current system, and the modeled objects comprise: the method comprises the steps that a wind power plant, a PQ converter and a multi-terminal flexible direct current system of a main converter are used for obtaining a multi-terminal flexible direct current system and a nonlinear model of the wind power plant;
step 2) carrying out linearization treatment on the multi-end flexible direct current system and the nonlinear model of the wind power plant to obtain a multi-end flexible direct current system and a linear model of the wind power plant;
step 3) based on H∞Norm control method constructs linear H∞And the controller is used for correspondingly changing the controlled local direct-current voltage according to the scheduling requirement, so that the control precision of the direct-current voltage of the system is improved.
The direct current voltage control method of the multi-end flexible direct current system is further designed in that in the step 2), nonlinear functions of the multi-end flexible direct current system and the wind driven generator are respectively constructed according to the formula (1) and the formula (2);
Figure BDA0002897385140000021
wherein iL1，iL3The inductive currents in the main converter and the PQ converter respectively; the upper point represents the derivative with respect to time;
Figure BDA0002897385140000022
Figure BDA0002897385140000023
the direct current voltage in the main converter, the PQ converter and the converter connected with the wind power plant are respectively; i.e. is，im，iwfThe current in the main converter, the PQ converter and the converter connected with the wind power plant are respectively; pi s，Pi m，PwfThe power converter comprises a main converter, a PQ converter and output power in a converter connected with a wind power plant;
the nonlinear model is described as a function of a standard linear state variable x, a disturbance input w, and a controlled input u:
Figure BDA0002897385140000024
wherein the control output y is the direct voltage of the wind farm terminal;
obtaining deviation values delta x, delta w, delta u and delta y of x, w, u and y and corresponding balance values according to the formula (3);
Figure BDA0002897385140000025
where A is a constant matrix, B1Is a constant matrix, B2Is a constant matrix, C2Is a constant matrix, D21Is a constant matrix, D22Is a matrix of constants.
The direct-current voltage control method of the multi-end flexible direct-current system is further designed in that in the step 3), a combination formula (3) is combined, and a linear H is constructed according to a formula (4)∞A controller for controlling the operation of the electronic device,
Figure BDA0002897385140000026
wherein A isKIs a constant matrix, BKIs a constant matrix, CKIs a constantMatrix, DKIs a constant matrix, xkIs linearization H∞The state variables of the controller,
Figure BDA0002897385140000027
Is linearization H∞Derivative of the state variable of the controller.
The direct-current voltage control method of the multi-terminal flexible direct-current system is further designed in such a way that an objective function delta z is introduced to enable linearity H to be linear∞Controller disturbance output minimization, setting
Figure BDA0002897385140000028
And delta beta are respectively used as the disturbance of the local direct-current voltage balance value and the nominal pitch angle of the wind power plant terminal; filter state ξ including β in δ zβDerivative of (2)
Figure BDA0002897385140000029
To limit the bandwidth of the controller output pitch control signals to keep its slew rate below 8/s.
The direct-current voltage control method of the multi-terminal flexible direct-current system is further designed by restraining
Figure BDA0002897385140000031
Eliminating delta beta high frequency fast changing component, obtaining transfer function of first order high pass filter according to formula (5) (taking initial condition xi)β(0)＝0)：
Figure BDA0002897385140000032
Wherein Γ (·) represents the laplace transform of the signal, and the filter state variables are derived from equation (6)
Figure BDA0002897385140000033
The time derivative of (a) of (b),
Figure BDA0002897385140000034
wherein the time constant T is 1,
Figure BDA0002897385140000035
is xiβAnd δ β, the disturbance output δ z being selected as a weighted parameterization of the disturbance output of the form:
Figure BDA0002897385140000036
wherein, the positive weight c1、c2And c3And all control parameters used in subsequent simulations, as in table 2;
TABLE 2
Table II：Controller details
Figure BDA0002897385140000037
The invention has the following advantages:
the direct-current voltage control method of the multi-terminal flexible direct-current system adopts H∞The norm controller performs voltage regulation, can effectively manage power reserve in the form of a wind turbine, and improves the robustness and control accuracy of the system.
Drawings
Fig. 1 is a topological structure diagram of a multi-terminal direct current transmission (MTDC) system.
Fig. 2 is a view showing a structure of a WTG model.
FIG. 3 is a graph of power as a function of rotational speed. Wherein (a) is related to the wind speed beta being 0, and (b) is related to the pitch change when the wind speed is 12 m/s.
FIG. 4 is a DC voltage calibration plot on a wind farm terminal.
Fig. 5 is a graph of simulation results of the controlled nonlinear MTDC model. Wherein (a) the amount of standby usage and (b) power redistribution within the MTDC.
Detailed Description
The technical solution of the present invention will be described in detail below with reference to the accompanying drawings.
In the present embodiment, as shown in FIG. 1, based on H∞The direct-current voltage control method of the controlled multi-terminal flexible direct-current system comprises the following steps:
step 1) firstly, carrying out modeling analysis on a multi-terminal flexible direct current system, wherein the objects to be modeled comprise the multi-terminal flexible direct current system (MTDC), a wind power plant and a main converter.
And 2) carrying out linearization treatment on the established MTDC and wind power plant nonlinear model according to the multi-terminal flexible direct current system established in the step 1.
Step 3) adopting H according to the MTDC and wind power field linearization model in the step 2∞The norm control method is used for designing the controller, the method allows the controlled local direct-current voltage to be correspondingly changed according to the scheduling requirement, the control precision of the direct-current voltage of the system is improved, and finally the feasibility and the effectiveness of the control method are verified in a simulation mode. Each step is described in further detail below:
in step 1, a three-terminal MTDC system is selected, and the system consists of a wind power plant, a PQ converter and a main converter station. Fig. 1 shows a modeling approach of MTDC, with a nominal voltage of the common dc link of ± 200 kV. All devices associated with the wind farm are identified by a superscript wf, all devices associated with the PQ converter are identified by a superscript m, and all devices associated with the main converter are identified by a superscript s. The size of the capacitors on the dc side of each converter should be equal to the equivalent capacitance of a Modular Multilevel Converter (MMC).
The link between the equations of the different subsystems is provided by the active power injected into the MTDC. The current flowing into each converter station is:
Figure BDA0002897385140000051
wherein is，im，iwfThe current in the main converter, the PQ converter and the converter connected with the wind power plant are respectively; pi s，Pi m，PwfAre respectively main exchangeA current converter, a PQ current converter, and an output power in a current converter connected to a wind farm;
Figure BDA0002897385140000052
respectively, a main converter, a PQ converter, and a DC voltage in a converter connected to the wind farm.
And sufficient MMC equivalent capacitance is ensured, and the direct-current voltage on each converter terminal represents 1 transient variable. As shown in fig. 1, the state equation can be written as:
Figure BDA0002897385140000053
wherein iL1，iL3The inductive currents in the main converter and the PQ converter respectively; the upper point represents the derivative with respect to time;
because i isL2＝iL1+iL3，iL2Linearly dependent on the other two DC current states, so that the current i can be eliminatedL2. Thus, a non-linear relationship appears to relate voltage to injected power.
The dc current state is given by:
Figure BDA0002897385140000054
Figure BDA0002897385140000055
wherein: d ═ L1L2+L1L3+L2L3；L1，L2，L3The wind power station comprises a main converter, a PQ converter and an inductor in a converter connected with a wind power station; r1，R2，R3The resistance values of the main converter, the PQ converter and the converter connected with the wind power plant are respectively;
Figure BDA0002897385140000061
which are the derivatives of the inductor currents in the main converter and the PQ converter, respectively.
The offshore wind farm is connected through a high-voltage direct-current power transmission network, and is an offshore alternating-current power grid with a converter station controlled in a grid-connected mode, namely, voltage amplitude and frequency are controlled to serve as ideal voltage sources. Thus, the injected power of the high voltage direct current transmission network is not controlled by the high voltage direct current converter, but is only regulated by the wind power plant. The power delivered by the offshore wind farm to the high voltage dc grid can easily be expressed as the sum of the power generated by the different WTGs, assuming no losses of the offshore ac grid occur. 100 identical 2-megawatt permanent magnet synchronous wind driven generators are adopted, and the numerical value of each wind driven generator is shown in table 1.
The WTG is continuously operated at the maximum of the power curve, depending on the wind speed or pitch angle. Fig. 3 shows the shift variation of the power curve. On the power curve, only pitch adjustments are used to eliminate the load of the turbine, rather than moving left and right on the power curve. As shown in fig. 2, the desired speed setting for the rotor is determined by Maximum Power Point Tracking (MPPT) logic using a two-dimensional look-up table, i.e. taking into account the wind speed v and pitch angle β.
The terminal voltage need not be described in terms of machine variables. The voltage of the motor is driven by internal current control logic and external MPPT logic, which is implemented on the q-axis (torque axis). As shown in figure 2 of the drawings, in which,
Figure BDA0002897385140000062
it represents torque as a function of q-axis current only. Thus, three state variables
Figure BDA0002897385140000063
As the current dq axis quadrature component, it can be expressed as:
Figure BDA0002897385140000064
wherein the content of the first and second substances,
Figure BDA0002897385140000065
denotes dReference values for the axis and q-axis current components; i isd，IqActual values representing d-axis and q-axis current components;
Figure BDA0002897385140000066
is the motor speed reference value given in the look-up table; omegarIs the actual value of the motor speed;
Figure BDA0002897385140000067
is a constant.
Rotor oscillation equation:
Figure BDA0002897385140000068
coefficient of power CpExpressed as:
Figure BDA0002897385140000071
in the formula: beta is the pitch angle, lambdaiIs a function of lambda (tip speed ratio).
The internal power output equation given between the wind farm state variable and the MTDC system state variable is as follows:
Figure BDA0002897385140000072
the state space of the main converter can be expressed as:
Figure BDA0002897385140000073
wherein the current controller defines two new state variables
Figure BDA0002897385140000074
And
Figure BDA0002897385140000075
satisfy the requirement of：
Figure BDA0002897385140000076
The expression for the d-axis state current is as follows:
Figure BDA0002897385140000077
the form of the internal power output equation to the MTDC system is expressed as:
Figure BDA0002897385140000078
in the step 2: equations of state (2) and (5) show the non-linear functions of MTDC and WTG. Thus, the nonlinear model is described as a function of a standard linear state variable x, a disturbance input w, and a controlled input u:
Figure BDA0002897385140000079
wherein the control output y is the dc voltage at the wind farm terminal.
The state vector x (t) is represented as:
x(t)＝[(xwf)T(xm)T(xMTDC)T]T
wherein: subvector xwf、xmAnd xMTDCRespectively related to the wind farm, the main converter and the MTDC, as shown in the following formula:
Figure BDA0002897385140000081
Figure BDA0002897385140000082
Figure BDA0002897385140000083
writing the input in vector form yields:
Figure BDA0002897385140000084
u＝β
linear Time Invariant (LTI) H taking into account non-linear objects∞And (4) designing a controller. Since this state space controller design requires a linearized model, the present embodiment constructs a linearized model of the MTDC object that surrounds a set of equilibrium values for the MTDC that form equilibrium state xeq. This is chosen as the normal operating point for the MTDC, with a fixed wind speed of 12m/s (here the example is simplified assuming constant wind speed), and a wind farm power output of 75% of the rated output (corresponding to β at a given wind speed)nomPitch blade angle of approximately 4 °), perturbing the input nominal value wnom＝[49.8×106 100×106 0]TFor these values of betanomAnd wnomBy solving the equation f (x)eq,βnom,wnom) The equilibrium point x of the nonlinear MTDC model is obtained as 0eq. The relevant jacobian matrix for f in (12) is calculated by calculating the partial derivatives of f (x, w, u) with respect to the vectors x, w and u, and is calculated at the equilibrium point. In summary, a linear time-invariant model is obtained:
Figure BDA0002897385140000085
wherein δ x, δ w and δ u represent the deviation of the quantities x, w and u from the corresponding equilibrium/nominal values; can be expressed as: δ x ═ x-xeq，δw＝w-wnom，δu＝β-βnom。
In step 3, for H∞The design of the controller introduces an objective function deltaz, namely the disturbance output is minimized. Selecting
Figure BDA0002897385140000086
And delta beta is respectively used as the disturbance of the local direct voltage balance value and the nominal pitch angle of the wind power plant terminal. In addition, δ z includes filter state ξ of ββDerivative of (2)
Figure BDA0002897385140000091
To limit the bandwidth of the controller output pitch control signals to keep its slew rate below 8/s. Variable xiβWhich may be considered the output of a first order high pass filter, whose input is δ β. Suppression of
Figure BDA0002897385140000092
Is an alternative method for eliminating delta beta high-frequency fast-changing components. The transfer function of a first order high pass filter is given by (taking the initial condition xi)β(0)＝0)：
Figure BDA0002897385140000093
Where Γ (·) represents the laplace transform of the signal. Returning to the time domain, the filter state variables
Figure BDA0002897385140000094
The time derivative of (a) is given by:
Figure BDA0002897385140000095
wherein the time constant T is 1. Note from (15)
Figure BDA0002897385140000096
Is xiβAnd δ β, and then selecting the disturbance output δ z as a weighted parameterization of the disturbance output of the form:
Figure BDA0002897385140000097
wherein, the positive weight c1、c2And c3And all control parameters used in subsequent simulations, as shown in table 2.
Design of linear H of MTDC by using the model in (13)∞And a controller. Can be expressed as follows:
Figure BDA0002897385140000098
initial condition xK(0) The controller order is 0, which is the same as the order of the controlled linearized MTDC model, i.e. 16 in the simulation case. Since the controller is designed based on a linearized model, the actual control signal u of the MTDC shown in fig. 4 is:
u＝βnom+δu (17)
according to the controller designed by the method, a simulation test shown in FIG. 1 is constructed to verify the superiority of the controller.
Wind farm at fixed wind speed of 12m/s, at betanomA fixed wind speed of approximately 4 deg. drives, initially 100MW of power is delivered by the main converter, the remaining 50MW being used for the power of the PQ converter and the losses of the various resistances.
In fig. 5a, a PQ converter (P) is showni s) A frequency of 20MW each regulates the interference at t 10s and t 30 s. A power ramp order of 1250MW/s was used in the simulation. As shown in the third diagram of fig. 5a, the main converter is not affected by a frequency regulation load exceeding a minimum deviation. This is due to the release of approximately 3.6MJ by the DC capacitance, and H∞The fine tuning response of the controller when the pitch angle of the blade is adjusted improves the robustness of the system.
At 50s and 70s, the main converter needs to restore the wind farm reserve since the PQ converter has a new power output, which means that
Figure BDA0002897385140000101
A change occurs. The 50MW power shortage can be recovered as soon as possible by the grid side frequency converter. I.e. workThe rate drops by 20MW, but the dynamic speed of the power output of the main converter is higher because the PI structures of the d-axis of the main controller are cascaded. Finally 20MW of power is injected to the main grid side at 90 s. In this case, the disturbance is limited to the ac side of the main converter due to the effective decoupling between the controllers. This shows the effectiveness of the controller on the main inverter in both frequency and voltage regulation.
Figure 5b shows the effect of a standard power redistribution operation on the designed controller. At 10 seconds, the PQ converter and the main converter exchange 450MW power at a rate of ± 20MW/s, bringing the PQ converter to its transmission capacity limit. In actual operation, the power supply circuit of the main converter, as shown in the bottom diagram of fig. 5b
Figure BDA0002897385140000102
It is shown that a new balance point needs to be found. However, at the beginning and at the end of the ramping process, some disturbances occur, affecting the dc voltage and the pitch angle. Therefore, if the PQ converters on the MTDC are to exchange power, the power ramp need not be severely limited. Finally at the end of the simulation, a new balance point is found, but the injected power of the wind farm is slightly larger (smaller β) due to the higher losses on the MTDC.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims (5)

1. A direct-current voltage control method of a multi-terminal flexible direct-current system is characterized by comprising the following steps:
step 1) modeling analysis is carried out on the multi-end flexible direct current system, and the modeled objects comprise: the method comprises the steps that a wind power plant, a PQ converter and a multi-terminal flexible direct current system of a main converter are used for obtaining a multi-terminal flexible direct current system and a nonlinear model of the wind power plant;
step 2) carrying out linearization treatment on the multi-end flexible direct current system and the nonlinear model of the wind power plant to obtain a multi-end flexible direct current system and a linear model of the wind power plant;
step 3) based on H∞Norm control method constructs linear H∞And the controller is used for correspondingly changing the controlled local direct-current voltage according to the scheduling requirement, so that the control precision of the direct-current voltage of the system is improved.
2. The method for controlling the direct current voltage of the multi-terminal flexible direct current system according to claim 1, wherein in the step 2), non-linear functions of the multi-terminal flexible direct current system and the wind driven generator are respectively constructed according to the formula (1) and the formula (2);
Figure FDA0002897385130000011
wherein iL1，iL3The inductive currents in the main converter and the PQ converter respectively; the upper point represents the derivative with respect to time;
Figure FDA0002897385130000012
the direct current voltage in the main converter, the PQ converter and the converter connected with the wind power plant are respectively; i.e. is，im，iwfThe current in the main converter, the PQ converter and the converter connected with the wind power plant are respectively; pi s，Pi m，PwfThe power converter comprises a main converter, a PQ converter and output power in a converter connected with a wind power plant;
the nonlinear model is described as a function of a standard linear state variable x, a disturbance input w, and a controlled input u:
Figure FDA0002897385130000013
wherein the control output y is the direct voltage of the wind farm terminal;
obtaining deviation values delta x, delta w, delta u and delta y of x, w, u and y and corresponding balance values according to the formula (3);
Figure FDA0002897385130000014
where A is a constant matrix, B1Is a constant matrix, B2Is a constant matrix, C2Is a constant matrix, D21Is a constant matrix, D22Is a matrix of constants.
3. The method for controlling the DC voltage of the multi-terminal flexible DC system according to claim 2, wherein in the step 3), in accordance with formula (3), a linear H is constructed according to formula (4)∞A controller for controlling the operation of the electronic device,
Figure FDA0002897385130000021
wherein A isKIs a constant matrix, BKIs a constant matrix, CKIs a constant matrix, DKIs a constant matrix, xkIs linearization H∞The state variables of the controller,
Figure FDA00028973851300000210
Is linearization H∞Derivative of the state variable of the controller.
4. The method for controlling the DC voltage of the multi-terminal flexible DC system according to claim 3, wherein an objective function δ z is introduced to make the linearity H∞Controller disturbance output minimization, setting
Figure FDA0002897385130000022
And delta beta are respectively used as the disturbance of the local direct-current voltage balance value and the nominal pitch angle of the wind power plant terminal; filter state ξ including β in δ zβDerivative of (2)
Figure FDA0002897385130000023
To limit the bandwidth of the controller output pitch control signals to keep its slew rate below 8/s.
5. The method of claim 4, wherein the DC voltage control of the multi-terminal flexible DC system is performed by suppressing
Figure FDA0002897385130000024
Eliminating delta beta high frequency fast changing component, obtaining transfer function of first order high pass filter according to formula (5) (taking initial condition xi)β(0)＝0)：
Figure FDA0002897385130000025
Wherein Γ (·) represents the laplace transform of the signal, and the filter state variables are derived from equation (6)
Figure FDA0002897385130000026
The time derivative of (a) of (b),
Figure FDA0002897385130000027
wherein the time constant T is 1,
Figure FDA0002897385130000028
is xiβAnd δ β, the disturbance output δ z being selected as a weighted parameterization of the disturbance output of the form:
Figure FDA0002897385130000029
wherein, the positive weight c1、c2And c3And is followed byAll control parameters used in the post-simulation, as in table 2;
TABLE 2
Table II：Controller details
Figure FDA0002897385130000031
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* Cited by examiner, † Cited by third party
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CN106410835A (en) * 2016-10-12 2017-02-15 北京科东电力控制系统有限责任公司 Power grid simulation realization method of multi-terminal flexible direct-current transmission system
CN107302224A (en) * 2017-07-17 2017-10-27 南京南瑞集团公司 A kind of multi-terminal direct current transmission system current conversion station control method based on interior point method
CN111711217A (en) * 2020-05-21 2020-09-25 东北电力大学 Direct-current voltage control method of multi-terminal flexible direct-current system facing alternating-current power fluctuation

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN106410835A (en) * 2016-10-12 2017-02-15 北京科东电力控制系统有限责任公司 Power grid simulation realization method of multi-terminal flexible direct-current transmission system
CN107302224A (en) * 2017-07-17 2017-10-27 南京南瑞集团公司 A kind of multi-terminal direct current transmission system current conversion station control method based on interior point method
CN111711217A (en) * 2020-05-21 2020-09-25 东北电力大学 Direct-current voltage control method of multi-terminal flexible direct-current system facing alternating-current power fluctuation

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