CN113013898A - Grid-connected inverter subsynchronous oscillation suppression method based on far-end power grid phase locking - Google Patents

Grid-connected inverter subsynchronous oscillation suppression method based on far-end power grid phase locking Download PDF

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CN113013898A
CN113013898A CN202110283400.8A CN202110283400A CN113013898A CN 113013898 A CN113013898 A CN 113013898A CN 202110283400 A CN202110283400 A CN 202110283400A CN 113013898 A CN113013898 A CN 113013898A
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voltage
grid
power grid
link
phase
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CN113013898B (en
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吕佃顺
武鑫
王立鹏
马强
赵世雄
张彦欢
汪浩
王朝
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Jiangsu Guoke Intelligent Electric Co ltd
Huaneng Tongliao Wind 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
    • H02J3/24—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
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H02J3/381—Dispersed generators
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J2300/00—Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation
    • H02J2300/20—The dispersed energy generation being of renewable origin
    • H02J2300/22—The renewable source being solar energy
    • H02J2300/24—The renewable source being solar energy of photovoltaic origin
    • 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
    • Y02E10/50—Photovoltaic [PV] energy
    • Y02E10/56—Power conversion systems, e.g. maximum power point trackers
    • 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
    • Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
    • Y02E40/40—Arrangements for reducing harmonics

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  • Power Engineering (AREA)
  • Inverter Devices (AREA)

Abstract

A subsynchronous oscillation suppression method of a grid-connected inverter based on remote power grid phase locking realizes the function of suppressing the subsynchronous oscillation of the power grid of the grid-connected inverter by sequentially executing a subsynchronous oscillation detection link, a coordinate transformation link, an optimized phase locking link and a reference current calculation link. The subsynchronous oscillation detection link inputs local power grid voltage, judges whether the power grid has subsynchronous oscillation phenomenon or not and outputs virtual internal impedance X of the power grid2(ii) a The coordinate transformation link converts the input local power grid voltage, the inverter current and the filter loop current into DQ axis voltage or current on a two-phase synchronous rotating coordinate system; wherein, the phase-locking optimization link is based on the input virtual internal impedance X of the power grid2Local power grid Q-axis voltage UgqD-axis current I of power gridgdPerforming far-end power grid voltage phase locking with the phase locking target of Ugq＝X2Igd(ii) a Wherein the reference current calculating unitCalculating and outputting active reference current IdRefAnd a reactive reference current IqRef。

Description

Grid-connected inverter subsynchronous oscillation suppression method based on far-end power grid phase locking
Technical Field
The invention relates to a method for suppressing subsynchronous oscillation of a grid-connected inverter.
Background
With the increase of new energy grid-connected capacity such as wind power generation and the like, a new energy power system which takes a multi-source multi-conversion complex alternating current and direct current system as a composition framework is gradually formed by the wide adoption of a high-power electronic technology. In application scenarios of wind power generation, solar power generation, energy storage and the like included in a new energy power system, a Voltage Source Converter (VSC) is generally adopted to be connected to a power grid, and a continuous oscillation phenomenon of the power grid at a specific frequency induced by a Sub-Synchronous Control Interaction (SSCI) may exist when the VSC is connected to the power grid on a large scale, and the oscillation phenomenon is called power grid subsynchronous oscillation. The voltage source inverter connected to the grid is also called grid-connected inverter.
In order to solve the problem of power grid subsynchronous oscillation possibly induced by new energy power generation grid connection, patent CN201510351331.4 discloses a subsynchronous oscillation suppression device and method based on phase-locked loop error, which adopts a mode of connecting a three-phase inverter in parallel at a generator end, and adjusts the magnitude of electrical damping through the control of reactive current according to a phase-locked error signal obtained by a signal detection module, so as to suppress the subsynchronous oscillation of a system. The patent CN201910868875.6 "a control method of a direct-drive wind farm inductive weak grid-connected subsynchronous oscillation suppression device", includes a subsynchronous oscillation suppression device and an improved virtual synchronous machine control method thereof, and is used for suppressing subsynchronous oscillation of a direct-drive wind farm under the condition of grid-connected inductive weak grid. Additional cost is required due to the inclusion of the battery energy storage system. Patent CN 111082436 a "direct-drive wind farm oscillation suppression method and system based on phase-locked consistency", according to whether the sub-synchronous oscillation sent by the power grid is switched repeatedly between the local power grid voltage (fan outlet voltage) and the remote power grid voltage (wind farm grid-connected point voltage), it is necessary to increase the collection of the remote power grid voltage, there is difficulty in the actual engineering implementation, and there is a problem of repeated switching when the critical sub-synchronous oscillation is not present: and when detecting that subsynchronous oscillation does not exist, the input of the phase-locked loop is switched to the outlet voltage of the fan, the phase-locked loop starts to oscillate and is switched back to the voltage of the grid-connected point after switching, the oscillation disappears and is switched back to the outlet voltage of the fan after switching, and the operation is repeated.
Disclosure of Invention
The invention provides a grid-connected inverter subsynchronous oscillation suppression method based on remote power grid phase locking, aiming at overcoming the defects of the prior art.
The method is realized in a control unit of the grid-connected inverter.
The signal collected by the invention comprises a local power grid three-phase voltage UgabcThree-phase current I of inverteriabcThree-phase current I of filter circuitfabcThe input signal contains active power given PGivenGiven reactive power QGivenThe output signal contains an active reference current IdRefReactive reference current IqRefD-axis current I of inverteridAnd inverter Q-axis current Iiq。
The invention sequentially executes a subsynchronous oscillation detection link, a coordinate transformation link, an optimized phase locking link and a reference current calculation link, and realizes the function of restraining the subsynchronous oscillation of the grid-connected inverter. The subsynchronous oscillation detection link judges whether the subsynchronous oscillation phenomenon occurs in the power grid or not, and outputs virtual internal impedance X of the power grid2(ii) a Local power grid three-phase voltage U to be acquired in coordinate transformation linkgabcThree-phase current I of inverteriabcThree-phase current I of filter circuitfabcConversion to grid voltage based angle theta1The DQ axis voltage or current on the two-phase synchronous rotation coordinate system; the phase-locking link is optimized to realize a phase-locking strategy based on the voltage orientation of a far-end power grid, and the phase-locking target is Ugq＝X2IgdOutputting the grid frequency f1And grid voltage angle theta1(ii) a The reference current calculation link completes the calculation of the active reference current and the reactive reference current and outputs the active reference current IdRefAnd a reactive reference current IqRef。
The signal flows among the subsynchronous oscillation detection link, the coordinate transformation link, the phase locking optimization link and the reference current calculation link are as follows:
the subsynchronous oscillation detection link acquires the three-phase voltage U of the local power gridgabcInputting the power grid frequency f output by the optimized phase-locked loop1Outputting virtual internal impedance X of power grid2Optimizing the phase locking link;
the coordinate transformation link acquires the three-phase voltage U of the local power gridgabcAnd collecting three-phase current I of inverteriabcCollecting three-phase current I of filter circuitfabcThe grid voltage angle theta output by the optimized phase-locked link is input1And D-axis voltage U of local power grid is outputgdLocal power grid Q-axis voltage UgqD-axis current I of filter loopfdAnd the Q-axis current I of the filter loopfqOutputting the Q-axis voltage U of the local power grid to a reference current calculation linkgqSimultaneously entering an optimized phase-locking link; the coordinate transformation link outputs the D-axis current I of the power gridgdOptimizing the phase locking link; the coordinate transformation link simultaneously outputs the current I of the D axis of the inverteridAnd inverter Q-axis current IiqAnd a current closed-loop control link in the control unit is used for subsequent current closed-loop control.
The phase locking optimization link inputs the virtual internal impedance X of the power grid output by the subsynchronous oscillation detection link2Inputting the D-axis current I of the power grid output by the coordinate transformation linkgdAnd local grid Q-axis voltage UgqOutputting the grid frequency f1In the sub-synchronous oscillation detection link, the voltage angle theta of the power grid is output1A coordinate transformation link is carried out;
in the reference current calculation link, active power is input to give PGivenAnd given Q of reactive powerGivenAnd input coordinate transformation link outputD-axis current I of filter loopfdQ-axis current I of filter loopfqLocal grid D-axis voltage UgdAnd local grid Q-axis voltage Ugq(ii) a Output active reference current IdRefAnd a reactive reference current IqRefAnd a current closed-loop control link in the control unit is used for subsequent current closed-loop control.
In the method for suppressing the subsynchronous oscillation, a subsynchronous oscillation detection link is executed at first. Local power grid three-phase voltage U acquired in subsynchronous oscillation detection linkgabcInput grid frequency f1At the frequency f of the mains voltage1The band elimination filter which is used as the center filters the fundamental frequency component of the power grid voltage to obtain subsynchronous frequency voltage Ugabcss(ii) a Subsynchronous frequency voltage UgabcssThrough an oscillation angle theta based on a subsynchronous frequencyssObtaining subsynchronous frequency D-axis voltage U by coordinate transformation of 3s2rgdssAnd subsynchronous frequency Q-axis voltage Ugqss(ii) a Subsynchronous frequency Q-axis voltage UgqssEntering a PI regulator for closed-loop control to obtain a subsynchronous frequency fss(ii) a Subsynchronous frequency fssObtaining a subsynchronous frequency oscillation angle theta after integral operationss(ii) a According to the subsynchronous frequency D-axis voltage UgdssAnd the subsynchronous frequency fssCalculating the virtual internal impedance X of the power grid by adopting a formula (1)2。
Figure BDA0002979437050000031
In the formula (1), KMFor controlling the sensitivity coefficient, U, for subsynchronous oscillationgss0For subsynchronous oscillation control of sensitivity threshold, UgdssFor a sub-synchronous frequency D-axis voltage, fssIs the detected subsynchronous frequency; virtual internal impedance X of power grid2A value range of
Figure BDA0002979437050000032
Wherein, URateFor rated voltage of the grid-connected inverter, PRateThe rated capacity of the grid-connected inverter.
When X is present2When the voltage orientation of the remote power grid is 0, the phase locking strategy based on the voltage orientation of the remote power grid in the subsequent phase locking optimization link is degenerated to be a phase locking strategy based on the voltage orientation of the local power grid, and the phase locking strategy based on the voltage orientation of the local power grid is also called a traditional phase locking strategy based on the voltage orientation of the power grid; virtual internal impedance X of power grid2Maximum clipping at
Figure BDA0002979437050000033
And the stability margin of the active power control of the grid-connected inverter is ensured.
Secondly, a coordinate transformation link is executed, and the collected three-phase voltage U of the local power grid is obtained in the coordinate transformation linkgabcBy an angle theta based on the grid voltage1The 3s2r coordinate transformation is carried out to obtain the D-axis voltage U of the local power gridgdAnd local grid Q-axis voltage Ugq(ii) a Collected three-phase current I of inverteriabcBy an angle theta based on the grid voltage1The coordinate of the inverter D shaft current I is obtained by the transformation of the 3s2r coordinateidAnd inverter Q-axis current IiqCollected three-phase current I of filter circuitfabcBy an angle theta based on the grid voltage1The 3s2r coordinate transformation is carried out to obtain the D-axis current I of the filter loopfdAnd the Q-axis current I of the filter loopfq(ii) a Inverter D-axis current IidPlus the D-axis current I of the filter loopfdObtaining D-axis current I of power gridgdQ-axis current I of inverteriqPlus filter loop Q-axis current IfqObtaining Q-axis current I of power gridgq。
Performing an optimized phase-locking link again, wherein the optimized phase-locking link adopts a phase-locking strategy based on the voltage orientation of the remote power grid, and the phase-locking target is Ugq＝X2IgdThe phase-locked loop comprises a constructed virtual internal impedance X of the power grid2The information of (1). In the optimized phase-locked link, the input local power grid Q-axis voltage UgqSubtracting the D-axis current I of the power gridgdAnd the virtual internal impedance X of the power grid2The product of the voltage and the voltage of the Q axis of the far-end power grid is obtainedrq(ii) a Far-end power grid Q-axis voltage UrqEntering a PI regulator for control to obtain the frequency f of the power grid1To the grid frequency f1Obtaining the grid voltage angle theta by calculating integral1. When the virtual internal impedance X of the input power grid2When 0, the phase-locked target degenerates to UgqAt 0, the phase-locking strategy based on the far-end grid voltage orientation degenerates to the traditional phase-locking strategy based on the grid voltage orientation. Compared with the traditional phase-locking strategy based on the grid voltage orientation, the synchronous rotating coordinate system corresponding to the phase-locking strategy based on the far-end grid voltage orientation is advanced by one thetaδAnd (4) an angle.
And finally, executing a reference current calculation link, wherein the reference current calculation link adopts a formula (2) to obtain an active reference current IdRefAnd a reactive reference current IqRef。
Figure BDA0002979437050000041
In the formula (2), PGivenFor input active power given, QGivenSetting the input reactive power; u shapegdFor input local grid D-axis voltage, UgqThe input local power grid Q-axis voltage is obtained; i isfdFor input of filter loop D-axis current, IfqIs the input filter loop Q-axis current.
The subsynchronous oscillation detection link, the coordinate transformation link, the phase locking optimization link and the reference current calculation link are sequentially executed, and the obtained active reference current IdRefReactive reference current IqRefD-axis current I of inverteridInverter Q-axis current IiqObtaining alpha axis control voltage U after current closed loop controlcαAnd beta axis control voltage Ucβ(ii) a Alpha axis control voltage UcαAnd beta axis control voltage UcβAfter the PWM link, a pulse width modulation signal is output, and the function of restraining the sub-synchronous oscillation of the power grid by the grid-connected inverter is realized by controlling the on-off of power electronic devices in the main circuit.
The key point of the vector control technology is the selection of a synchronous rotating coordinate system. The invention has the advantages that the voltage and current information based on the far-end power grid is fixed on the premise that the collected voltage and current information is consistent with the traditional phase-locking strategy based on the voltage orientation of the power gridAnd a phase locking strategy is based on the acquired grid-connected inverter local power grid voltage, whether the power grid has a subsynchronous oscillation phenomenon is detected through a subsynchronous oscillation detection link, the virtual internal impedance of the power grid is output, and the information of the remote power grid voltage is constructed according to the virtual internal impedance of the power grid in an optimization phase locking link. Compared with the traditional phase-locking strategy based on the voltage orientation of the power grid, the synchronous rotating coordinate system corresponding to the phase-locking strategy based on the voltage orientation of the remote power grid needs to be advanced by thetaδAngle thetaδThe introduction of the angle can effectively realize the function of restraining the sub-synchronous oscillation of the power grid by the grid-connected inverter. Meanwhile, double-end amplitude limiting is carried out on the virtual internal impedance of the power grid in the sub-synchronous oscillation detection link, the minimum amplitude limiting 0 realizes smooth switching with the traditional phase-locking strategy based on power grid voltage orientation, and the problem of repeated switching during critical sub-synchronous oscillation is effectively avoided; maximum clipping
Figure BDA0002979437050000051
The stability margin of active control of the grid-connected inverter is ensured.
Drawings
FIG. 1 is a schematic diagram of a grid-connected inverter connected to a power grid;
FIG. 2 is a schematic diagram of a main circuit and control unit of the grid-connected inverter;
FIG. 3 is a signal transmission block diagram of each link of the subsynchronous oscillation suppression method;
FIG. 4 is a voltage current vector diagram based on a remote grid voltage orientation synchronous rotation coordinate system;
fig. 5 is a block diagram of an optimized phase-locked loop control.
Detailed Description
The invention is further described below with reference to the accompanying drawings and the detailed description.
As shown in fig. 1, the grid-connected inverter is connected to the outside through an ac side and a dc side, where the ac side is connected to a local grid 101, and a connection Point is also called a PCC Point (Point of Common Coupling), as shown at 120 in fig. 1; the direct current side is connected with an external direct current power supply, if the direct current side is applied to the field of wind power generation, the direct current side is connected with a machine side converter direct current bus, when the direct current side is applied to solar power generation, the direct current side is connected with a photovoltaic cell panel, and when the direct current side is applied to the field of energy storage, the direct current side is connected with an energy storage battery.
In fig. 1, the inverter three-phase current output by the power module PM is defined as I iabc130 in fig. 1; the three-phase current of the filter circuit is defined as IfabcSuch as 131 in fig. 1; the three-phase current connected into the local power grid is defined as IgabcSuch as 132 in fig. 1; the three-phase voltage output by the PM of the power component is defined as U cabc102 in fig. 1; the three-phase voltage of the local power grid is defined as UgabcSuch as 101 in fig. 1; the three-phase voltage of the far-end power grid is defined as U rabc100 in fig. 1; power grid virtual internal impedance X constructed by local power grid 101 and remote power grid 100 through subsynchronous oscillation detection link2And (4) connecting.
The grid-connected inverter electrical principle shown in fig. 1 is shown in fig. 2. The grid-connected inverter includes a main circuit 200 and a control unit 210. The main loop 200 comprises a filter capacitor C1Filter inductance L1Power electronic device S1、S2、S3、S4、S5、S6Constituting the power module PM in fig. 1; filter inductance L1Connected to a local power grid 201, such as 202 in fig. 2; the positive bus P and the negative bus N of the power component PM are connected to a direct current bus capacitor C2Such as 205 in fig. 2. The suppression method is realized in the control unit 210, and the control unit 210 collects the three-phase voltage U of the local power grid gabc202, 220 in FIG. 2, the inverter three-phase current I is collectediabc203, 222 in FIG. 2, collecting the three-phase current I of the filter circuit fabc204, 221 in fig. 2, collect the dc bus voltage UdcAs at 223 in fig. 2. The control unit 210 outputs a PWM modulation signal SPWMTo the main loop for controlling S in the main loop power module1、S2、S3、S4、S5、S6And switching on and off six power electronic devices.
The inventive method is implemented in the control unit 210 shown in fig. 2.
The method of the invention sequentially executes a subsynchronous oscillation detection link 320, a coordinate transformation link 310, an optimization phase locking link 330 and a reference current calculation link 300 shown in fig. 3, thereby realizing the function of restraining the subsynchronous oscillation of the grid-connected inverter. The signal flow among the four links is shown in fig. 3.
In the subsynchronous oscillation detection link 320 shown in fig. 3, the three-phase voltage U of the local power grid is collectedgabc321 in FIG. 3, the grid frequency f output by the optimized phase-locked loop 330 is input1Output grid virtual internal impedance X, as 322 in FIG. 32To the optimization phase-locking element 330, e.g., 323, 332 in fig. 3;
in the coordinate transformation link 310 shown in fig. 3, the local grid three-phase voltage U is collectedgabc313 in FIG. 3, the three-phase current I of the inverter is collectediabcCollecting three-phase current I of filter circuit, 311 in FIG. 3fabcThe grid voltage angle θ output by the optimized phase-locked loop is input, as shown in 312 of FIG. 31323 in fig. 3; outputting local grid D-axis voltage UgdLocal power grid Q-axis voltage UgqD-axis current I of filter loopfdQ-axis current I of filter loopfqTo the reference current calculation stage 300, such as 305, 306, 303, 304 in fig. 3; output local power grid Q-axis voltage UgqAnd simultaneously input to the optimized phase-lock loop 330, as shown at 331 in fig. 3; outputting the D-axis current I of the power gridgdTo the optimization phase lock loop 330, 318 in fig. 3. The coordinate transformation link 310 shown in fig. 3 simultaneously outputs the inverter D-axis current IidAnd inverter Q-axis current IiqA current closed-loop control segment 340 into the control unit for subsequent current closed-loop control, such as 314, 315 in fig. 3;
in the optimized phase-locked loop 330 shown in fig. 3, the virtual internal impedance X of the power grid output by the sub-synchronous oscillation detection loop 320 is input2As shown in fig. 3 at 332, the grid D-axis current I output by the coordinate transformation element 310 is inputgdThe local grid Q-axis voltage U output by the coordinate transformation link is input, as 318 in FIG. 3gqOutput grid voltage angle θ, as shown in FIG. 3, 3311To the coordinate transformation element 310, e.g. 333, 323 in fig. 3, the grid frequency f is output1To the subsynchronous oscillation detection stage, such as 334 and 322 in fig. 3;
in the reference current calculation stage 300 shown in FIG. 3Input active power given PGivenAnd given Q of reactive powerGivenThe D-axis current I of the filter loop output by the coordinate transformation element 310 is input as 301 and 302 in FIG. 3fdAnd the Q-axis current I of the filter loopfqThe local grid D-axis voltage U output by the coordinate transformation link 310 is input, as 303 and 304 in FIG. 3gdAnd local grid Q-axis voltage U gq305, 306 in fig. 3; output active reference current IdRefAnd a reactive reference current IqRefA current closed-loop control segment 340 into the control unit for subsequent current closed-loop control, such as 307, 308 in fig. 3;
the inhibition method comprises the following steps:
step 1: the grid-connected inverter control unit 210 in fig. 2 initializes and reads the control parameters required by the subsynchronous oscillation suppression method of the present invention, including the subsynchronous oscillation control sensitivity coefficient KMSubsynchronous oscillation control sensitivity threshold Ugss0Rated voltage U of grid-connected inverterRateRated capacity P of grid-connected inverterRate；
Step 2: in the subsynchronous oscillation detection link 320 shown in fig. 3, the three-phase voltage U of the local power grid is collectedgabcInput grid frequency f1At the grid frequency f1The band elimination filter which is used as the center filters the fundamental wave component of the power grid voltage to obtain subsynchronous frequency voltage Ugabcss(ii) a Subsynchronous frequency voltage UgabcssThrough an oscillation angle theta based on a subsynchronous frequencyssObtaining subsynchronous frequency D-axis voltage U by coordinate transformation of 3s2rgdssAnd subsynchronous frequency Q-axis voltage Ugqss(ii) a Subsynchronous frequency Q-axis voltage UgqssEntering a PI regulator for closed-loop control to obtain a subsynchronous frequency fss(ii) a Subsynchronous frequency fssObtaining a subsynchronous frequency oscillation angle theta after integral operationss(ii) a According to the subsynchronous frequency D-axis voltage UgdssAnd the subsynchronous frequency fssCalculating virtual internal impedance X of power grid by adopting formula (1)2。
And step 3: in the coordinate transformation link 310 in fig. 3, the collected local grid three-phase voltage UgabcThrough the process based onGrid voltage angle theta1The 3s2r coordinate transformation is carried out to obtain the D-axis voltage U of the local power gridgdAnd local grid Q-axis voltage Ugq(ii) a Collected three-phase current I of inverteriabcBy an angle theta based on the grid voltage1The coordinate of the inverter D shaft current I is obtained by the transformation of the 3s2r coordinateidAnd inverter Q-axis current IiqCollected three-phase current I of filter circuitfabcBy an angle theta based on the grid voltage1The 3s2r coordinate transformation is carried out to obtain the D-axis current I of the filter loopfdAnd the Q-axis current I of the filter loopfq(ii) a Inverter D-axis current IidPlus the D-axis current I of the filter loopfdObtaining D-axis current I of power gridgdQ-axis current I of inverteriqPlus filter loop Q-axis current IfqObtaining Q-axis current I of power gridgq；
And 4, step 4: in the optimized phase-locking link 330 shown in fig. 3, a phase-locking strategy based on far-end grid voltage orientation is adopted, and the phase-locking target is Ugq＝X2Igd. Phase locking strategy based on far-end grid voltage orientation is shown in fig. 5, wherein an input local grid Q-axis voltage U is shown in fig. 5gqSubtracting the D-axis current I of the power gridgdAnd the virtual internal impedance X of the power grid2The product of the voltage and the voltage of the Q axis of the far-end power grid is obtainedrq500, 501, 502, 503 in fig. 5; far-end power grid Q-axis voltage UrqThe frequency f of the power grid is obtained by the control of a PI regulator 5041505 in FIG. 5, grid frequency f1The grid voltage angle theta is obtained after the integral of the grid voltage enters an integrator 5061As in 507 in fig. 5.
When a phase-locking strategy based on remote power grid voltage orientation is adopted, a voltage and current vector diagram on a two-phase synchronous rotating coordinate system is shown in fig. 4. In FIG. 4, 400, 401 and 402 are local grid voltage vectors and D-axis voltages UgdAnd Q-axis voltage UgqIn FIG. 4, 420, 421 and 422 are inverter current vectors and D-axis currents IidAnd Q-axis current IiqIn FIG. 4, 430, 431 and 432 are filter loop current vectors and D-axis currents IfdAnd Q-axis current IfqIn FIG. 4, 440, 441, 442 are grid current vectors and D-axis currents IgdAnd Q-axis current Igq41 in FIG. 40 is the far-end power grid voltage vector and D-axis voltage Urd. Under the steady state condition, the D-axis voltage U of the remote power gridrdEqual to the far-end grid voltage vector UrRemote end grid Q-axis voltage U rq0. Local grid voltage vector U when adopting phase-locking strategy based on far-end grid voltage orientationgLeading remote grid voltage vector UrOne thetaδAngle, 450 in fig. 4. That is, the synchronous rotating coordinate system corresponding to the phase-locking strategy based on the far-end grid voltage orientation should be one θ before the traditional phase-locking strategy based on the grid voltage orientationδAnd (4) an angle.
And 5: in the reference current calculation section 300 of fig. 3, the active reference current I is calculated by using the formula (2)dRefAnd a reactive reference current IqRef。
Step 6: inverter D-axis current I output by coordinate transformation link 310 in step 3idAnd inverter Q-axis current IiqStep 5, the active reference current I output by the reference current calculating unit 300dRefAnd a reactive reference current IqRefEntering a current closed-loop control link 340 in the control unit 210, and obtaining an alpha axis control voltage U after passing through the current closed-loop control link 340cαAnd beta axis control voltage U cβ342, 343 in fig. 3; alpha axis control voltage UcαAnd beta axis control voltage UcβAfter passing through a PWM (pulse-Width modulation) link 350, a pulse width modulation signal S is outputPWM351 in fig. 3; pulse width modulation signal SPWMBy controlling S of the power component PM of the main circuit 200 in FIG. 21、S2、S3、S4、S5、S6And the power electronic device is switched on and off, so that the function of restraining the sub-synchronous oscillation of the power grid by the grid-connected inverter is realized.

Claims (4)

1. A grid-connected inverter subsynchronous oscillation suppression method based on remote power grid phase locking is characterized by comprising the following steps: the method sequentially executes a subsynchronous oscillation detection link, a coordinate transformation link, an optimized phase locking link and a reference current calculation link, and realizes the function of restraining the subsynchronous oscillation of the grid-connected inverter; the subsynchronous vibrationThe oscillation detection link judges whether the power grid has subsynchronous oscillation phenomenon or not and outputs virtual internal impedance X of the power grid2(ii) a Local power grid three-phase voltage U to be acquired in coordinate transformation linkgabcThree-phase current I of inverteriabcThree-phase current I of filter circuitfabcConversion to grid voltage based angle theta1The DQ axis voltage or current on the two-phase synchronous rotation coordinate system; the phase-locking link is optimized to realize a phase-locking strategy based on the voltage orientation of a far-end power grid, and the phase-locking target is Ugq＝X2IgdOutputting the grid frequency f1And grid voltage angle theta1(ii) a Calculating and outputting active reference current I in reference current calculation linkdRefAnd a reactive reference current IqRef；
After the four links are sequentially executed, the obtained active reference current IdRefReactive reference current IqRefD-axis current I of inverteridInverter Q-axis current IiqObtaining alpha axis control voltage U through current closed loop controlcαAnd beta axis control voltage Ucβ(ii) a Alpha axis control voltage UcαAnd beta axis control voltage UcβAnd after PWM modulation, a pulse width modulation signal is output for controlling the on-off of power electronic devices in the main circuit, so that the function of restraining sub-synchronous oscillation of a power grid by the grid-connected inverter is realized.
2. The grid-connected inverter subsynchronous oscillation suppression method according to claim 1, characterized in that: in the subsynchronous oscillation detection link, the three-phase voltage U of the local power grid is acquiredgabcInputting the power grid frequency f output by the optimized phase-locked loop1Outputting virtual internal impedance X of power grid2Optimizing the phase locking link; the coordinate transformation link is used for acquiring the three-phase voltage U of the local power gridgabcAnd collecting three-phase current I of inverteriabcCollecting three-phase current I of filter circuitfabcThe grid voltage angle theta output by the optimized phase-locked link is input1And D-axis voltage U of local power grid is outputgdLocal power grid Q-axis voltage UgqD-axis current I of filter loopfdAnd the Q-axis current I of the filter loopfqRadix GinsengThe voltage U of the Q axis of the local power grid output in the step of calculating the currentgqSimultaneously entering an optimized phase-locking link; coordinate transformation link outputs power grid D-axis current IgdOptimizing the phase locking link; coordinate transformation link for simultaneously outputting D-axis current I of inverteridAnd inverter Q-axis current IiqA current closed-loop control link in the control unit is used for subsequent current closed-loop control; the phase locking optimization link inputs the virtual internal impedance X of the power grid output by the subsynchronous oscillation detection link2And the D-axis current I of the power grid output by the coordinate transformation linkgdAnd local grid Q-axis voltage UgqOutputting the grid frequency f1In the sub-synchronous oscillation detection link, the voltage angle theta of the power grid is output1A coordinate transformation link is carried out; in the reference current calculation link, active power is input to give PGivenAnd given Q of reactive powerGivenInputting the D-axis current I of the filter loop output by the coordinate transformation linkfdQ-axis current I of filter loopfqLocal grid D-axis voltage UgdAnd local grid Q-axis voltage UgqOutput active reference current IdRefAnd a reactive reference current IqRefAnd a current closed-loop control link in the control unit is used for subsequent current closed-loop control.
3. The grid-connected inverter subsynchronous oscillation suppression method according to claim 1, characterized in that: in the subsynchronous oscillation detection link, the three-phase voltage U of the local power grid is acquiredgabcInput grid frequency f1At the grid frequency f1After the band elimination filter for the center filters the fundamental wave component of the grid voltage, the subsynchronous frequency voltage U is obtainedgabcss(ii) a Subsynchronous frequency voltage UgabcssThrough an oscillation angle theta based on a subsynchronous frequencyssObtaining subsynchronous frequency D-axis voltage U by coordinate transformation of 3s2rgdssAnd subsynchronous frequency Q-axis voltage Ugqss(ii) a Subsynchronous frequency Q-axis voltage UgqssEntering a PI regulator for closed-loop control to obtain a subsynchronous frequency fss(ii) a Subsynchronous frequency fssObtaining a subsynchronous frequency oscillation angle theta after integral operationss(ii) a According to the orderSynchronous frequency D-axis voltage UgdssAnd the subsynchronous frequency fssCalculating the virtual internal impedance X of the power grid by adopting a formula (1)2；
Figure FDA0002979437040000021
In the formula (1), KMFor controlling the sensitivity coefficient, U, for subsynchronous oscillationgss0For subsynchronous oscillation control of sensitivity threshold, UgdssFor a sub-synchronous frequency D-axis voltage, fssFor the detected subsynchronous frequency, the virtual internal impedance X of the grid2Has a value range of
Figure FDA0002979437040000022
Wherein, URateFor rated voltage of the grid-connected inverter, PRateThe rated capacity of the grid-connected inverter.
4. The grid-connected inverter subsynchronous oscillation suppression method according to claim 1, wherein the optimization phase-locking link adopts a phase-locking strategy based on remote grid voltage orientation, and the phase-locking target is Ugq＝X2IgdThe phase-locking strategy comprises a power grid virtual internal impedance X constructed by a subsynchronous oscillation detection link2The information of (a);
in the optimized phase-locked link, the input local power grid Q-axis voltage UgqSubtracting the D-axis current I of the power gridgdAnd the virtual internal impedance X of the power grid2The product of the voltage and the voltage of the Q axis of the far-end power grid is obtainedrq(ii) a Far-end power grid Q-axis voltage UrqEntering a PI regulator for control to obtain the frequency f of the power grid1To the grid frequency f1Obtaining the grid voltage angle theta by calculating integral1。
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