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CN113922363A - Frequency active support strategy based on wind storage system - Google Patents

Frequency active support strategy based on wind storage system Download PDF

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Publication number
CN113922363A
CN113922363A CN202111129031.3A CN202111129031A CN113922363A CN 113922363 A CN113922363 A CN 113922363A CN 202111129031 A CN202111129031 A CN 202111129031A CN 113922363 A CN113922363 A CN 113922363A
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wind
power
frequency
grid
storage system
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Inventor
杨靖
孟明
法拉蒂尔
孙勇
应有
花斌
张书涵
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Zhejiang Windey Co Ltd
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Zhejiang Windey 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
    • H02J3/002—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
    • H02J3/24—Arrangements for preventing or reducing oscillations of power in networks
    • H02J3/241—The oscillation concerning frequency
    • 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
    • H02J3/28—Arrangements for balancing of the load in a network by storage of energy
    • H02J3/32—Arrangements for balancing of the load in a network by storage of energy using batteries with converting means
    • 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
    • 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
    • H02J3/46—Controlling of the sharing of output between the generators, converters, or transformers
    • H02J3/466—Scheduling the operation of the generators, e.g. connecting or disconnecting generators to meet a given demand
    • 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
    • H02J3/46—Controlling of the sharing of output between the generators, converters, or transformers
    • H02J3/50—Controlling the sharing of the out-of-phase component
    • 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
    • H02J2203/10—Power transmission or distribution systems management focussing at grid-level, e.g. load flow analysis, node profile computation, meshed network optimisation, active network management or spinning reserve management
    • 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
    • Y02E70/00—Other energy conversion or management systems reducing GHG emissions
    • Y02E70/30—Systems combining energy storage with energy generation of non-fossil origin

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

Abstract

本发明公开了一种基于风储系统的频率主动支撑策略，其特征在于，包括如下步骤：S1、风速分区；S2、修正频率死区；S3、机组无功补偿；S4、确定协同控制策略；根据风机运行状态判断风机所处的风速区间，并对风储系统进行功率调整以实现频率支撑，在充分利用机组特性与储能系统性能的同时，避免因风机功率恢复而造成的系统频率二次跌落、桨距角机械部件频繁动作而造成的载荷疲劳及限功率调频对风电场并网运行造成的经济性损失。

Figure 202111129031

The invention discloses a frequency active support strategy based on a wind storage system, which is characterized by comprising the following steps: S1, wind speed division; S2, correcting the frequency dead zone; S3, reactive power compensation of the unit; S4, determining a cooperative control strategy; Determine the wind speed range of the fan according to the fan's operating state, and adjust the power of the wind storage system to achieve frequency support. While making full use of the characteristics of the unit and the performance of the energy storage system, it avoids the secondary frequency of the system caused by the power recovery of the fan. The load fatigue caused by falling, the frequent action of the pitch angle mechanical parts and the economic loss caused by the limited power frequency modulation on the grid-connected operation of the wind farm.

Figure 202111129031

Description

Frequency active supporting strategy based on wind storage system
Technical Field
The invention relates to the field, in particular to a frequency active supporting strategy based on a wind storage system.
Background
The wind turbine generator controls the power of the network through a power electronic element, so that the rotation speed of a rotor of the wind turbine generator is not directly coupled with the frequency of a power grid, and the wind turbine generator does not have the frequency supporting capacity of a synchronous machine. Therefore, in a high-proportion wind power access system, the total inertia of the system is reduced due to the replacement of a traditional synchronous unit by a wind turbine unit, and the frequency stability of the system is threatened.
In the prior art, aiming at the problem of frequency stability caused by a large-scale wind power plant access system, a large number of power control links which are responded by adding virtual inertia at home and abroad are adopted, namely, the frequency change rate of the system is used as input, and power output is superposed on the active power set of the maximum power tracking control of a wind turbine generator according to a set inertia time constant, so that the variable speed unit can simulate the inertia response of a synchronous machine, and the support function of the power grid frequency is realized; or the output power of the wind turbine generator is limited through the reserved pitch angle, and when the system needs frequency modulation, the power is released, so that the frequency modulation of the system is achieved. The response capability of the wind power generation system is directly related to the running state of the fan, the fan cannot reliably and durably provide inertia response capability due to random fluctuation of wind speed, and secondary fluctuation of system frequency can be caused due to active power loss or excess generated in the process of rotating speed recovery when the fan exits from a frequency supporting state; although the availability of the power for supporting frequency fluctuation can be improved by reserving the unit reserve capacity in a power limiting mode, the long-term reservation of the power can affect the economic benefit of a wind power plant, the reserved power is released through the pitch angle, not only can the frequent action of mechanical parts be caused, but also the wind power unit is not beneficial to mechanical friendliness, and the mechanical delay can reduce the time performance of power response.
For example, a chinese patent document discloses a method and a system for tuning a virtual inertia control parameter of a wind turbine generator, which is disclosed in the following publication No.: CN113131495A discloses adjusting virtual inertia parameters to obtain optimal virtual inertia parameters, and the reliability is low.
Disclosure of Invention
Therefore, the frequency active supporting strategy based on the wind storage system provided by the invention can improve the frequency supporting capability of the wind turbine generator, improve the electric energy quality of the wind turbine generator, prolong the service life of the energy storage system, improve the frequency stability of the system and improve the economic benefit of the wind power plant.
In order to achieve the above purpose, the invention provides the following technical scheme:
a frequency active supporting strategy based on a wind storage system comprises the following steps:
s1, partitioning the wind speed;
s2, correcting a frequency dead zone;
s3, performing reactive compensation on the unit;
and S4, determining a cooperative control strategy.
Preferably, S1 includes:
and judging the wind speed interval where the fan is positioned according to the running state of the fan, and adjusting the power of the wind storage system to realize frequency support.
Preferably, the judging the speed-division partition includes:
partitioning the wind speed interval according to a wind power curve and a wind speed-rotating speed curve, wherein the cut-in wind speed and the cut-out wind speed are respectively vin、voutThe wind speeds corresponding to the constant rotation speed stage and the constant power stage are respectively vml、vmhAdditionally, the lowest wind speed v of the fan entering inertia response is definedx: minimum rotational speed omega after inertia release is finishedxAnd corresponding wind speed, wherein the lowest rotating speed is the corresponding rotating speed after the unit provides t-second inertia frequency modulation energy for the power grid according to 10% Pn under the condition that the inertia response power threshold work P required by the power grid is met. According to the wind speed-rotating speed curve, the lowest wind speed entering inertia response is at variable rotating speedControl phase, i.e. cut-in wind speed vinWind speed v corresponding to the stage of entering constant speedmlIn the meantime.
In the variable rotating speed control stage, the maximum power P output by the wind turbine generator is in a cubic relation with the rotating speed, and when the power grid requires the wind turbine generator to perform inertia response, the corresponding rotating speed of the wind turbine generator is obtained through the following formula
Figure BDA0003279818980000021
In the formula, kw＝0.5ρSw(Rw/λopt)3CpmaxAnd is a constant associated with the wind turbine, and the subscript w represents the wind turbine association.
Lowest rotating speed omega for response of fan entering inertiaxCan be obtained by the following formula
Figure BDA0003279818980000031
Wherein JTIs equivalent rotational inertia (high speed) of a transmission chain and can pass through the rotational inertia J of a generator of a unitg(high speed shaft), impeller moment of inertia Jr(Low speed shaft) and gear box transformation ratio n, and is represented by JT＝Jg+Jr/n2(ii) a (ii) a And t is the time for the unit to provide inertia support for the power grid.
Finding out the lowest rotation speed omega according to the wind speed-rotation speed curvexCorresponding minimum wind speed vx。
Preferably, S2 includes:
and calculating the grid-connected point short circuit ratio and judging faults by using the measurement information of the wind turbine generator, calculating the access short circuit ratio when the system where the wind turbine generator is located does not have faults, and correcting the frequency modulation dead zone of the wind turbine generator according to the access short circuit ratio of the wind turbine generator.
Preferably, the frequency dead zone correction further includes:
doubly-fed wind turbine generator connected to Point of connection (POC)Active power P output by wind turbine generatorwReactive power QwAnd voltage U at POC caused by SCR of line resistance R and reactance X, POCpocDisturbance, the unit grid-connected point voltage can be expressed as:
Figure BDA0003279818980000032
in the formula, U is an infinite grid voltage amplitude, and generally U is 1.0 p.u; superscript denotes the complex conjugate form of the original complex number; j is an imaginary unit Pw、QwAnd R are expressed in the form of per unit value.
The voltage amplitude variation can be simplified as follows
Figure BDA0003279818980000033
Assuming that the acquisition period of the acquisition device is t, the voltage amplitude variation under three consecutive acquisition periods can be expressed as
Figure BDA0003279818980000034
In the formula, the superscript t is the acquisition period of the acquisition device; and the superscript k is the k-th acquisition amount of the acquisition device.
The line impedance at tk can be found by solving the above equation to be
Figure BDA0003279818980000035
When the system has a fault, voltage mutation is caused, and the reliability of the calculation result is deteriorated when the line impedance is calculated by the formula (5), so the solution of the formula (4) is carried out on the premise of not mutating and can be expressed as the following formula (wherein the deviation is not limited to 0.03, and the low-voltage and medium-voltage fluctuation limit of the voltage fluctuation frequency within 10 times/hour in the national standard GB/T12326 is adopted here)
Figure BDA0003279818980000041
After the formula (6) is satisfied, the formula (4) is solved to obtain the impedance at the tk moment, and then the system short-circuit ratio can be obtained according to the following formula
Figure BDA0003279818980000042
According to the standard NB/T10315, the primary frequency modulation dead zone of the wind turbine generator is within the range of +/-0.03 Hz- +/-0.1 Hz. Under the condition of strong power grid, the power system mainly depends on the traditional hydroelectric/thermal power generating unit to perform primary frequency modulation, the requirement on the frequency modulation of the wind power generating unit is not high, therefore, a frequency dead zone can be set to be 0.1Hz, but along with the gradual weakening of the power grid, the power system gradually changes the primary frequency modulation from the traditional energy to the new energy (the wind power generating unit), the wind power generating unit replaces the hydroelectric/thermal power generating unit to perform frequency modulation at the moment, the frequency dead zone is correspondingly reduced, therefore, the self-adaptive adjustment can be performed on the frequency dead zone based on a linear interpolation method and the short-circuit ratio of the wind power generating unit access system, and the self-adaptive adjustment can be specifically expressed as
Figure BDA0003279818980000043
In the formula (f)dead maxThe maximum value of the frequency modulation dead zone is 0.1 Hz; f. ofdead minTaking the frequency modulation dead zone as the minimum value, wherein the frequency modulation dead zone is 0.03 Hz; SCR (Selective catalytic reduction)thAnd the short circuit ratio threshold is used for judging the strength of the power grid.
Preferably, the frequency dead zone is a maximum of 0.1 Hz; the maximum value of the frequency modulation dead zone is 0.1 Hz; the minimum value of the frequency modulation dead zone is 0.03 Hz; the short circuit ratio threshold is taken to be 20.
Preferably, S3 includes:
and calculating the optimal power factor of the wind turbine generator set by using the impedance angle of the power grid and the real-time output of the wind turbine generator set, and determining the given reactive power value of the wind storage system according to the optimal power factor.
Preferably, S3 further includes:
note Upoc＝UpocAnd (2) solving the equation to obtain a grid-connected point voltage real part and an imaginary part:
Figure BDA0003279818980000044
in the formula, phi is a power factor angle; the reactive output of the unit can be expressed as
Figure BDA0003279818980000045
ψkFor line impedance angle, the line reactance can be expressed as X ═ Rtan ψk。
When the grid topology is determined, the grid impedance angle is also determined (i.e. tan ψ)kConstant), in order to obtain zero drop of the grid-connected point voltage through the feeder line, the amplitude of the grid-connected point voltage needs to be calculated
Figure BDA0003279818980000052
Calculating the optimal power factor angle, and configuring the optimal power factor of the unit to minimize the change of the grid-connected point voltage when the active power output of the wind turbine unit changes, namely
Figure BDA0003279818980000051
Preferably, S4 includes:
and determining a specific reactive power distribution law based on the residual capacity of the converter of the wind storage system and the state of charge of the battery.
Preferably, S4 further includes:
the minimum State of Charge (SOC) of the battery generally ranges from 10% to 20%, and when the SOC of the battery is lower than min, the battery is not suitable for continuous discharge in consideration of the service life and safety of the battery; the maximum SOC of the battery generally ranges from 80% to 90%, and when the SOC of the battery is larger than max, the battery is not suitable to be charged continuously. When the wind speed is in the three regions, if the cooperative control 3 is adopted, the variable pitch of the wind turbine generator can be caused to frequently act, and the wind turbine generator is not beneficial to mechanical friendliness, so that only energy storage charging is adopted as a frequency modulation means in the wind speed region.
Dividing the frequency modulation time into four sections of [0, 200ms ], [200ms, 10s ], [10s, 15s ], [15s, + ∞ ]), assuming that the frequency command obtained by the main control calculation is delta P, when the cooperative control algorithm gives active power to different execution mechanisms in different sections, the power is positive when the unit rotor absorbs power and increases speed, the energy storage and charging, and the pitch angle is increased, the power is negative when the unit rotor releases power and decreases speed, the energy storage and discharging, and the pitch angle is decreased, the cooperative control algorithm of the vertical coordinate is only used for representing algorithm partitions, and the algorithms in the same partition are not divided into different sizes.
The embodiment of the invention has the following advantages:
(1) the wind speed interval where the fan is located is judged according to the running state of the fan, the power of a wind storage system is adjusted to realize frequency support, the characteristics of a unit and the performance of the energy storage system are fully utilized, and meanwhile, the load fatigue caused by the secondary falling of the system frequency and the frequent action of a mechanical part of a pitch angle due to the power recovery of the fan and the economic loss caused by the grid-connected running of a wind power plant due to the limited power frequency modulation are avoided; (2) the control strategy can utilize wind turbine generator measurement information to calculate the grid-connected point short-circuit ratio and judge faults, calculate the access short-circuit ratio when the system where the wind turbine generator is located does not have faults, and correct the frequency modulation dead zone of the wind turbine generator according to the set access short-circuit ratio; (3) the optimal power factor angle and the reactive power setting of the wind storage integrated system can be automatically calculated according to the line resistance and the line impedance angle of the wind turbine access system and the output active power of the wind turbine, the reactive power setting of the wind storage converter is reasonably distributed according to the charge states of the wind turbine and the energy storage system, and the service life of the energy storage system is prolonged while the electric energy quality of the wind turbine is improved; (4) the secondary influence of the rotation speed recovery of the unit on the frequency is avoided, the power limit of the unit due to the system frequency modulation requirement is reduced, the system frequency stability is improved, and meanwhile, the economic benefit of the wind power plant is improved.
Drawings
In order to more clearly illustrate the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below. It should be apparent that the drawings in the following description are merely exemplary, and that other embodiments can be derived from the drawings provided by those of ordinary skill in the art without inventive effort.
The structures, ratios, sizes, and the like shown in the specification are only used for matching with the contents disclosed in the specification, so that those skilled in the art can understand and read the invention, and do not limit the limit conditions of the invention, so that the invention has no technical essence, and any structural modification, ratio relationship change or size adjustment should still fall within the scope of the technical contents disclosed in the invention without affecting the efficacy and the achievable purpose of the invention.
Fig. 1 is a flow chart of the frequency active support strategy based on the wind storage system of the present invention.
FIG. 2 is a schematic diagram of a grid-connected equivalent model of the doubly-fed wind turbine generator set.
Fig. 3 is a schematic diagram of the reactive power distribution strategy of the wind storage system of the invention.
FIG. 4 is a block diagram of a wind energy storage coordinated control strategy of the present invention.
FIG. 5 is a logic schematic diagram of active set values of different execution mechanisms of the wind storage cooperative control algorithm.
Detailed Description
While embodiments of the present invention will be described with reference to particular embodiments, those skilled in the art will readily appreciate that the present invention has additional advantages and benefits that may be realized from the teachings herein, and that the embodiments described are only a few, but not all embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
As shown in fig. 1-5, in a preferred embodiment, the present invention discloses a frequency active support strategy based on a wind storage system, comprising the following steps:
s1, partitioning the wind speed, partitioning the output characteristics of the wind storage system based on a wind power curve and a wind speed-rotating speed curve, and providing an operation control strategy of the wind storage integrated system under multiple wind conditions;
because the rotating speed of the wind wheel can not change rapidly along with the wind speed, the wind speed interval can be partitioned according to a wind power curve and a wind speed-rotating speed curve, wherein the cut-in wind speed and the cut-out wind speed are respectively vin、voutThe wind speeds corresponding to the constant rotation speed stage and the constant power stage are respectively vml、vmhAdditionally, the lowest wind speed v of the fan entering inertia response is definedx: minimum rotational speed omega after inertia release is finishedxAnd corresponding wind speed, wherein the lowest rotating speed is the corresponding rotating speed after the unit provides t-second inertia frequency modulation energy for the power grid according to 10% Pn under the condition that the inertia response power threshold work P required by the power grid is met. According to the wind speed-rotating speed curve, the lowest wind speed entering inertia response is in the variable rotating speed control stage, namely the cut-in wind speed vinWind speed v corresponding to the stage of entering constant speedmlIn the meantime.
In the variable rotating speed control stage, the maximum power P output by the wind turbine generator is in a cubic relation with the rotating speed, and when the power grid requires the wind turbine generator to perform inertia response, the corresponding rotating speed of the wind turbine generator is obtained through the following formula
Figure BDA0003279818980000071
In the formula, kw＝0.5ρSw(Rw/λopt)3CpmaxAnd is a constant associated with the wind turbine, and the subscript w represents the wind turbine association.
Lowest rotating speed omega for response of fan entering inertiaxCan be obtained by the following formula
Figure BDA0003279818980000072
Wherein JTIs equivalent rotational inertia (high speed) of a transmission chain and can pass through the rotational inertia J of a generator of a unitg(high speed shaft), impeller moment of inertia Jr(Low speed shaft) and gear box transformation ratio n, and is represented by JT＝Jg+Jr/n2(ii) a (ii) a And t is the time for the unit to provide inertia support for the power grid.
Finding out the lowest rotation speed omega according to the wind speed-rotation speed curvexCorresponding minimum wind speed vx。
According to the wind speed point v given abovein、vout、vml、vmhAnd vxThe wind speed was divided into four wind speed intervals as shown in the following table.
TABLE 1 wind speed zoning
Figure BDA0003279818980000081
S2, correcting a frequency dead zone, and performing self-adaptive selection on a unit frequency modulation dead zone by using a system short circuit ratio so as to avoid overlarge power grid frequency deviation caused by insufficient conventional power supply frequency modulation capability under a weak grid condition and reduce system cracking;
the network topology shown in FIG. 2 illustrates a doubly-fed wind turbine connected to a Point of connection (POC), and the active power P output by the wind turbinewReactive power QwAnd voltage U at POC caused by SCR of line resistance R and reactance X, POCpocDisturbance, the unit grid-connected point voltage can be expressed as:
Figure BDA0003279818980000082
in the formula, U is an infinite grid voltage amplitude, and generally U is 1.0 p.u; superscript denotes the complex conjugate form of the original complex number; j is an imaginary unit Pw、QwAnd R are expressed in the form of per unit value.
The voltage amplitude variation can be simplified as follows
Figure BDA0003279818980000083
Assuming that the acquisition period of the acquisition device is t, the voltage amplitude variation under three consecutive acquisition periods can be expressed as
Figure BDA0003279818980000084
In the formula, the superscript t is the acquisition period of the acquisition device; and the superscript k is the k-th acquisition amount of the acquisition device.
The line impedance at tk can be found by solving the above equation to be
Figure BDA0003279818980000085
When the system has a fault, voltage mutation is caused, and the reliability of the calculation result is deteriorated when the line impedance is calculated by the formula (5), so the solution of the formula (4) is carried out on the premise of not mutating and can be expressed as the following formula (wherein the deviation is not limited to 0.03, and the low-voltage and medium-voltage fluctuation limit of the voltage fluctuation frequency within 10 times/hour in the national standard GB/T12326 is adopted here)
Figure BDA0003279818980000091
After the formula (6) is satisfied, the formula (4) is solved to obtain the impedance at the tk moment, and then the system short-circuit ratio can be obtained according to the following formula
Figure BDA0003279818980000092
According to the standard NB/T10315, the primary frequency modulation dead zone of the wind turbine generator is within the range of +/-0.03 Hz- +/-0.1 Hz. Under the condition of strong power grid, the power system mainly depends on the traditional hydroelectric/thermal power generating unit to perform primary frequency modulation, the requirement on the frequency modulation of the wind power generating unit is not high, therefore, a frequency dead zone can be set to be 0.1Hz, but along with the gradual weakening of the power grid, the power system gradually changes the primary frequency modulation from the traditional energy to the new energy (the wind power generating unit), the wind power generating unit replaces the hydroelectric/thermal power generating unit to perform frequency modulation at the moment, the frequency dead zone is correspondingly reduced, therefore, the self-adaptive adjustment can be performed on the frequency dead zone based on a linear interpolation method and the short-circuit ratio of the wind power generating unit access system, and the self-adaptive adjustment can be specifically expressed as
Figure BDA0003279818980000093
In the formula (f)dead maxThe maximum value of the frequency modulation dead zone is 0.1 Hz; f. ofdead minTaking the frequency modulation dead zone as the minimum value, wherein the frequency modulation dead zone is 0.03 Hz; SCR (Selective catalytic reduction)thAnd the short circuit ratio is a threshold value used for judging the strength of the power grid, and 20 is taken here.
S3, reactive compensation, namely automatically calculating an optimal power factor angle and a wind storage integrated system reactive setting according to the line resistance and the line impedance angle of a wind turbine access system and the wind turbine output active power, reasonably distributing the wind storage converter reactive setting according to the charge states of the wind turbine and the energy storage system, and prolonging the service life of the energy storage system while improving the electric energy quality of the wind turbine;
note Upoc＝UpocAnd (2) solving the equation to obtain a grid-connected point voltage real part and an imaginary part:
Figure BDA0003279818980000094
in the formula, phi is a power factor angle; the reactive output of the unit can be expressed as
Figure BDA0003279818980000095
ψkFor line impedance angle, the line reactance can be expressed as X ═ Rtan ψk。
When the grid topology is determined, the grid impedance angle is also determined (i.e. tan ψ)kConstant), in order to obtain zero drop of the grid-connected point voltage through the feeder line, the amplitude of the grid-connected point voltage needs to be calculated
Figure BDA0003279818980000096
Calculating the optimal power factor angle, and configuring the optimal power factor of the unit to minimize the change of the grid-connected point voltage when the active power output of the wind turbine unit changes, namely
Figure BDA0003279818980000101
The wind storage integrated equipment reactive power distribution strategy shown in fig. 3 can be specifically expressed as follows:
Figure BDA0003279818980000102
in the formula of UsIs the stator voltage amplitude; xmThe stator and the rotor are mutually resisted; s- ωsilp/ω1Slip is operated; SOCmaxRepresents the battery maximum State of Charge (SOC), which is 0.9; SOC is the state of charge of the battery at the moment, and Qb is the actual output reactive power of the energy storage converter; qs is the actual output reactive power of the machine side of the wind turbine generator; qbref is the given value of the reactive power of the energy storage converter; and Qsref and Qgref are respectively a machine side converter reactive instruction and a network side converter reactive instruction.
S4, determining a wind energy storage coordination control strategy, avoiding secondary influence on frequency caused by unit rotation speed recovery, and reducing the limit power of the unit caused by system frequency modulation requirements;
when the detection value of the system frequency change rate exceeds the corrected dead zone, the running state of the fan needs to be judged according to the table 1, and the wind storage system cooperation strategy implementation and instruction issuing are performed according to the running interval, as shown in fig. 4.
The minimum State of Charge (SOC) of the battery generally ranges from 10% to 20%, and when the SOC of the battery is lower than min, the battery is not suitable for continuous discharge in consideration of the service life and safety of the battery; the maximum SOC of the battery generally ranges from 80% to 90%, and when the SOC of the battery is larger than max, the battery is not suitable to be charged continuously. The cooperative control 1 to the cooperative control 4 can be specifically expressed as a control law in table 2, and when the wind speed is in three regions, if the cooperative control 3 is adopted, the pitch of the wind turbine generator is frequently changed, which is not beneficial to the mechanical friendliness of the wind turbine generator, so that in the wind speed region, only energy storage charging is adopted as a frequency modulation means.
TABLE 2 cooperative control law
Figure BDA0003279818980000103
Figure BDA0003279818980000111
Dividing the frequency modulation time into four sections of [0, 200ms ], [200ms, 10s ], [10s, 15s ], [15s, + ∞), assuming that the frequency command obtained by the main control calculation is Δ P, the cooperative control algorithm gives active power to different execution mechanisms in different sections, as shown in fig. 5, the power is positive when the unit rotor absorbs power and increases speed, energy storage and charging, and the pitch angle increases, the power is negative when the unit rotor releases power and decreases speed, energy storage and discharging, and the pitch angle decreases, the cooperative control algorithm of the ordinate is only for representing algorithm partitions, and the algorithms in the same partition have no size partition. The frequency stability of the system is improved, and meanwhile, the economic benefit of the wind power plant is improved.
Although the invention has been described in detail above with reference to a general description and specific examples, it will be apparent to one skilled in the art that modifications or improvements may be made thereto based on the invention. Accordingly, such modifications and improvements are intended to be within the scope of the invention as claimed.

Claims (10)

1. A frequency active supporting strategy based on a wind storage system is characterized by comprising the following steps:
s1, partitioning the wind speed;
s2, correcting a frequency dead zone;
s3, performing reactive compensation on the unit;
and S4, determining a cooperative control strategy.
2. The wind storage system based frequency active support strategy of claim 1, wherein the S1 comprises:
and judging the wind speed interval where the fan is positioned according to the running state of the fan, and adjusting the power of the wind storage system to realize frequency support.
3. The frequency active support strategy based on the wind storage system according to claim 1 or 2, wherein the judging of the speed division areas comprises:
partitioning the wind speed interval according to a wind power curve and a wind speed-rotating speed curve, wherein the cut-in wind speed and the cut-out wind speed are respectively vin、voutThe wind speeds corresponding to the constant rotation speed stage and the constant power stage are respectively vml、vmhDefining the minimum wind speed v of the fan entering inertia responsexIs the lowest rotating speed omega after inertia release is finishedxAnd corresponding wind speed, wherein the lowest rotating speed is the corresponding rotating speed after the unit provides t-second inertia frequency modulation energy for the power grid according to 10% Pn under the condition that the inertia response power threshold work P required by the power grid is met.
In the variable rotating speed control stage, the maximum power P output by the wind turbine generator is in a cubic relation with the rotating speed, and when the power grid requires the wind turbine generator to perform inertia response, the corresponding rotating speed of the wind turbine generator is obtained through the following formula
Figure FDA0003279818970000011
In the formula, kw＝0.5ρSw(Rw/λopt)3CpmaxAnd is a constant associated with the wind turbine, and the subscript w represents the wind turbine association.
Lowest rotating speed omega for response of fan entering inertiaxCan be obtained by the following formula
Figure FDA0003279818970000012
Wherein JTIs equivalent rotational inertia (high speed) of a transmission chain and can pass through the rotational inertia J of a generator of a unitg(high speed shaft), impeller moment of inertia Jr(Low speed shaft) and gear box transformation ratio n, and is represented by JT＝Jg+Jr/n2(ii) a And t is the time for the unit to provide inertia support for the power grid.
4. The wind storage system based frequency active support strategy of claim 1 or 2, wherein the S2 comprises:
and calculating the grid-connected point short circuit ratio and judging faults by using the measurement information of the wind turbine generator, calculating the access short circuit ratio when the system where the wind turbine generator is located does not have faults, and correcting the frequency modulation dead zone of the wind turbine generator according to the access short circuit ratio of the wind turbine generator.
5. The active frequency support strategy based on a wind storage system according to claim 4, wherein the frequency dead zone correction further comprises:
doubly-fed wind turbine generator connected to Point of connection (POC), active power P output by wind turbine generatorwReactive power QwAnd voltage U at POC caused by SCR of line resistance R and reactance X, POCpocDisturbance, the unit grid-connected point voltage can be expressed as:
Figure FDA0003279818970000021
in the formula, U is an infinite grid voltage amplitude, and generally U is 1.0 p.u.; the superscript denoting the original plural numberA complex form of conjugation; j is an imaginary unit; pw、QwR, X are each expressed in per unit values.
The voltage amplitude variation can be simplified as follows
Figure FDA0003279818970000022
Assuming that the acquisition period of the acquisition device is t, the voltage amplitude variation under three consecutive acquisition periods can be expressed as
Figure FDA0003279818970000023
Figure FDA0003279818970000024
In the formula, the superscript t is the acquisition period of the acquisition device; and the superscript k is the k-th acquisition amount of the acquisition device.
The line impedance at t (k) can be obtained by solving the above equation
Figure FDA0003279818970000025
When the system has a fault, voltage mutation is caused, and the reliability of the calculation result is deteriorated when the line impedance is calculated by the formula (5), so the solution of the formula (4) is carried out on the premise of not mutating and can be expressed as the following formula (wherein the deviation is not limited to 0.03, and the low-voltage and medium-voltage fluctuation limit of the voltage fluctuation frequency within 10 times/hour in the national standard GB/T12326 is adopted here)
Figure FDA0003279818970000026
Figure FDA0003279818970000027
After the formula (6) is satisfied, the formula (4) is solved to obtain the impedance at the time t (k), and then the system short-circuit ratio can be obtained according to the following formula
Figure FDA0003279818970000028
Based on a linear interpolation method, the short circuit ratio of the wind turbine generator access system is adaptively adjusted to the frequency dead zone, which can be specifically expressed as
Figure FDA0003279818970000029
In the formula (f)dead maxIs the maximum value of the frequency modulation dead zone, fdead minFor minimum frequency-modulated dead-zone, SCRthAnd the short circuit ratio threshold is used for judging the strength of the power grid.
6. The active frequency support strategy based on the wind storage system is characterized in that the frequency dead zone is a maximum value of 0.1 Hz; the maximum value of the frequency modulation dead zone is 0.1 Hz; the minimum value of the frequency modulation dead zone is 0.03 Hz; the short circuit ratio threshold is taken to be 20.
7. The wind storage system based frequency active support strategy of claim 1, wherein the S3 comprises:
and calculating the optimal power factor of the wind turbine generator set by using the impedance angle of the power grid and the real-time output of the wind turbine generator set, and determining the given reactive power value of the wind storage system according to the optimal power factor.
8. The active frequency support strategy based on a wind storage system according to claim 7, wherein the S3 further comprises:
note Upoc＝UpocAngle theta is a + jb, wherein a is the real part of the voltage of the grid-connected point, and b is the virtual part of the voltage of the grid-connected pointAnd the part can solve the equation to obtain a real part and an imaginary part of the grid-connected point voltage:
Figure FDA0003279818970000031
Figure FDA0003279818970000032
in the formula (I), the compound is shown in the specification,
Figure FDA0003279818970000033
is a power factor angle; the reactive output of the unit can be expressed as
Figure FDA0003279818970000037
ψkFor line impedance angle, the line reactance can be expressed as X ═ Rtan ψk。
When the grid topology is determined, the grid impedance angle is also determined (i.e. tan ψ)kConstant), in order to obtain zero drop of the grid-connected point voltage through the feeder line, the amplitude of the grid-connected point voltage needs to be calculated
Figure FDA0003279818970000038
Calculating the optimal power factor angle, and configuring the optimal power factor of the unit to minimize the change of the grid-connected point voltage when the active power output of the wind turbine unit changes, namely
Figure FDA0003279818970000034
Figure FDA0003279818970000035
Figure FDA0003279818970000036
9. The wind storage system based frequency active support strategy of claim 1, wherein the S4 comprises:
and determining a specific reactive power distribution law based on the residual capacity of the converter of the wind storage system and the state of charge of the battery.
10. The active frequency support strategy based on a wind storage system according to claim 9, wherein the S4 further comprises:
the minimum State of Charge (SOC) of the battery generally ranges from 10% to 20%, and when the SOC is lower than the minimum SOC of the battery, the battery is not suitable for continuous discharge in consideration of the service life and safety of the battery; the maximum charge state of the battery generally ranges from 80% to 90%, and when the charge state of the battery is larger than the maximum charge state of the battery, the battery is not suitable to be charged continuously.
Dividing the frequency modulation time into four sections of [0, 200ms ], [200ms, 10s ], [10s, 15s ], [15s, + ∞), assuming that the frequency command obtained by the main control calculation is Δ P, the active power given to different execution mechanisms in different sections by the cooperative control algorithm can be expressed as: the power of the rotor of the unit is positive when the rotor absorbs power and is accelerated, the energy is stored and charged, the pitch angle is increased, the power of the rotor of the unit is negative when the rotor releases power and is decelerated, the energy is stored and discharged, and the pitch angle is decreased, the cooperative control algorithm is only used for representing algorithm subareas, and the algorithms in the same subarea are not divided into different sizes.
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