CN114374208A - Subsynchronous oscillation prejudging method and subsynchronous oscillation prejudging device for direct-drive fan - Google Patents

Subsynchronous oscillation prejudging method and subsynchronous oscillation prejudging device for direct-drive fan Download PDF

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CN114374208A
CN114374208A CN202210041132.3A CN202210041132A CN114374208A CN 114374208 A CN114374208 A CN 114374208A CN 202210041132 A CN202210041132 A CN 202210041132A CN 114374208 A CN114374208 A CN 114374208A
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direct
harmonic
frequency
inter
drive fan
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CN114374208B (en
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余浩
李柯江
段瑶
张锋
陈鸿琳
彭穗
陈武晖
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Guangdong Power Grid 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
    • H02J2203/00—Indexing scheme relating to details of circuit arrangements for AC mains or AC distribution networks
    • H02J2203/20—Simulating, e g planning, reliability check, modelling or computer assisted design [CAD]
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J2300/00—Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation
    • H02J2300/20—The dispersed energy generation being of renewable origin
    • H02J2300/28—The renewable source being wind energy
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/70—Wind energy
    • Y02E10/76—Power conversion electric or electronic aspects

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Abstract

The invention discloses a method and a device for pre-judging subsynchronous oscillation of a direct-drive fan. The method comprises the following steps: based on a harmonic modulation technology, modulating alternating current voltage on the rectifier side of the direct-drive fan through a constructed machine side converter switching function model to obtain direct current voltage of the rectifier and low-frequency harmonic frequency generated on the direct current side by the rectifier; based on a harmonic modulation technology, the direct current voltage of the rectifier is modulated through the constructed grid-side converter switching function model to obtain the alternating current voltage of the direct-drive fan inverter side, and inter-harmonic frequency generated by the inverter on the grid side is obtained by combining low-frequency harmonic frequency; and selecting a target inter-harmonic from all inter-harmonics corresponding to the inter-harmonic frequency, and predicting a sub-synchronous inter-harmonic frequency causing sub-synchronous oscillation according to the target inter-harmonic to judge the sub-synchronous oscillation according to the sub-synchronous inter-harmonic frequency. The method can accurately pre-judge the subsynchronous oscillation by predicting the subsynchronous inter-harmonic frequency aiming at the converter structure of the direct-drive fan, and ensure the stable and safe operation of the power system.

Description

Subsynchronous oscillation prejudging method and subsynchronous oscillation prejudging device for direct-drive fan
Technical Field
The invention relates to the technical field of power system stability analysis, in particular to a method and a device for pre-judging subsynchronous oscillation of a direct-drive fan.
Background
In recent years, due to dense grid connection of a large number of wind turbine converter, and intermittence, randomness and fluctuation of wind power output, the inter-harmonic content in a new energy grid-connected system is rapidly increased, the frequency spectrum distribution is complex, the random time-varying characteristic is remarkable, and the power quality problem and the broadband oscillation accident of a power system are frequently caused. The AC-DC-AC converter system of the direct-drive fan is connected with two AC systems with different frequencies, the topological structure can generate various inter-harmonics, wherein a part of the inter-harmonics are in a sub-synchronous frequency range to cause sub-synchronous oscillation, and when the inter-harmonic frequency of the sub-synchronous frequency band is close to the frequency of certain inherent sub-synchronous modes in the power system, such as the inherent mode of a fan control system, the inherent mode of a turbonator shafting and the like, forced sub-synchronous oscillation can be excited, so that the stability and the safety of the power system in operation are seriously threatened.
Currently, subsynchronous oscillation is pre-determined mainly by predicting inter-harmonic frequency generated by a direct drive fan. However, the oscillation phenomenon frequently observed when an actual power system operates indicates that subsynchronous inter-harmonics generated by the direct-drive fan in a weak power grid are amplified to cause subsynchronous oscillation, but the existing direct-drive fan inter-harmonic frequency prediction method focuses on high-frequency inter-harmonics (namely inter-harmonics larger than 150 Hz), the research on the subsynchronous inter-harmonic frequency prediction is almost blank, the subsynchronous oscillation of the direct-drive fan is difficult to accurately predict, and the stable and safe operation of the power system cannot be ensured.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention provides a method and a device for pre-judging subsynchronous oscillation of a direct-drive fan, which can accurately pre-judge subsynchronous oscillation by predicting the subsynchronous inter-harmonic frequency aiming at the converter structure of the direct-drive fan, and ensure that a power system stably and safely operates.
In order to solve the above technical problem, in a first aspect, an embodiment of the present invention provides a method for predicting subsynchronous oscillation of a direct-drive fan, including:
constructing a machine side converter switch function model and a grid side converter switch function model of the direct-drive fan;
based on a harmonic modulation technology, modulating alternating current voltage on the rectifier side of the direct-drive fan through a machine side converter switching function model to obtain direct current voltage of the rectifier and low-frequency harmonic frequency generated on the direct current side by the rectifier;
based on a harmonic modulation technology, modulating the direct-current voltage of the rectifier through the grid-side converter switching function model to obtain the alternating-current voltage of the direct-drive fan inverter side, and combining the low-frequency harmonic frequency to obtain the inter-harmonic frequency generated by the inverter on the grid side;
and selecting a target inter-harmonic from all inter-harmonics corresponding to the inter-harmonic frequency, predicting a sub-synchronous inter-harmonic frequency causing sub-synchronous oscillation according to the target inter-harmonic, and judging the sub-synchronous oscillation according to the sub-synchronous inter-harmonic frequency.
Further, the machine-side converter switching function model is:
Figure BDA0003468919820000021
the switching function model of the grid-side converter is as follows:
Figure BDA0003468919820000022
wherein ,
Figure BDA0003468919820000023
for the fundamental component and the baseband harmonic component,
Figure BDA0003468919820000024
carrier harmonics and sideband harmonic components; omega1＝2πf1，f1The three-phase voltage fundamental frequency of the direct-drive fan is obtained; omegac＝2πfc，fcIs the carrier frequency; the value of p is 0, 1 and-1, and the p respectively corresponds to the phase a, the phase b and the phase c of the direct drive fan; a. the0n、B0n、Amn、BmnThe amplitude coefficients of the periodic components are respectively.
Further, the dc voltage of the rectifier is:
Figure BDA0003468919820000031
wherein ,urxIs the alternating voltage at the rectifier side of the direct drive fan,
Figure BDA0003468919820000032
Ur0、θ0respectively representing the amplitude and the initial phase of the alternating voltage at the rectifier side of the direct-drive fan;
the low-frequency harmonic frequency generated by the rectifier on the direct current side is as follows:
Figure BDA0003468919820000033
further, the alternating voltage at the inverter side of the direct-drive fan is as follows:
ugx＝udcSgx；
the inter-harmonic frequency generated by the inverter on the grid side is as follows:
fs＝|3kf1±hf0|，k，h＝{1，2，3，…}；
wherein k is the number of low-frequency harmonics generated at the DC side; h is the fundamental frequency harmonic frequency of the power grid; f. of0The fundamental frequency of the power grid.
Further, the sub-synchronous inter-harmonic frequency of the direct-drive fan is as follows:
Figure BDA0003468919820000034
in a second aspect, an embodiment of the present invention provides a direct-drive fan subsynchronous oscillation pre-judging device, including:
the building module is used for building a machine side converter switch function model and a grid side converter switch function model of the direct-drive fan;
the modulation module is used for modulating alternating-current voltage on the rectifier side of the direct-drive fan through the machine side converter switching function model based on a harmonic modulation technology to obtain direct-current voltage of the rectifier and low-frequency harmonic frequency generated on the direct-current side by the rectifier;
the modulation module is further used for modulating the direct-current voltage of the rectifier through the grid-side converter switching function model based on a harmonic modulation technology to obtain alternating-current voltage on the inverter side of the direct-drive fan, and obtaining inter-harmonic frequency generated by the inverter on the grid side by combining the low-frequency harmonic frequency;
and the pre-judging module is used for selecting a target inter-harmonic from all inter-harmonics corresponding to the inter-harmonic frequency, predicting the sub-synchronous inter-harmonic frequency causing the sub-synchronous oscillation according to the target inter-harmonic, and judging the sub-synchronous oscillation according to the sub-synchronous inter-harmonic frequency.
Further, the machine-side converter switching function model is:
Figure BDA0003468919820000041
the switching function model of the grid-side converter is as follows:
Figure BDA0003468919820000042
wherein ,
Figure BDA0003468919820000043
for the fundamental component and the baseband harmonic component,
Figure BDA0003468919820000044
carrier harmonics and sideband harmonic components; omega1＝2πf1，f1The three-phase voltage fundamental frequency of the direct-drive fan is obtained; omegac＝2πfc，fcIs the carrier frequency; the value of p is 0, 1 and-1, and the p respectively corresponds to the phase a, the phase b and the phase c of the direct drive fan; a. the0n、B0n、Amn、BmnThe amplitude coefficients of the periodic components are respectively.
Further, the dc voltage of the rectifier is:
Figure BDA0003468919820000045
wherein ,urxIs the alternating voltage at the rectifier side of the direct drive fan,
Figure BDA0003468919820000046
Ur0、θ0respectively representing the amplitude and the initial phase of the alternating voltage at the rectifier side of the direct-drive fan;
the low-frequency harmonic frequency generated by the rectifier on the direct current side is as follows:
Figure BDA0003468919820000051
further, the alternating voltage at the inverter side of the direct-drive fan is as follows:
ugx＝udcSgx；
the inter-harmonic frequency generated by the inverter on the grid side is as follows:
fs＝|3kf1±hf0|，k，h＝{1，2，3，…}；
wherein k is the number of low-frequency harmonics generated at the DC side; h is the fundamental frequency harmonic frequency of the power grid; f. of0The fundamental frequency of the power grid.
Further, the sub-synchronous inter-harmonic frequency of the direct-drive fan is as follows:
Figure BDA0003468919820000052
the embodiment of the invention has the following beneficial effects:
the method comprises the steps of constructing a machine side converter switch function model and a grid side converter switch function model of a direct-drive fan, modulating alternating-current voltage on a rectifier side of the direct-drive fan through the machine side converter switch function model based on a harmonic modulation technology to obtain direct-current voltage of the rectifier and low-frequency harmonic frequency generated by the rectifier on the direct-current side, modulating direct-current voltage of the rectifier through the grid side converter switch function model based on the harmonic modulation technology to obtain alternating-current voltage on an inverter side of the direct-drive fan, obtaining inter-harmonic frequency generated by the inverter on the grid side by combining the low-frequency harmonic frequency, selecting target inter-harmonic from all inter-harmonic corresponding to the inter-harmonic frequency, predicting sub-synchronous inter-harmonic frequency causing sub-synchronous oscillation according to the target inter-harmonic, judging the sub-synchronous oscillation according to the sub-synchronous inter-harmonic frequency, and realizing pre-judgment of the sub-synchronous oscillation. Compared with the prior art, the embodiment of the invention is based on a harmonic modulation technology, modulates the alternating-current voltage at the side of the direct-drive fan rectifier through the machine side converter switching function model and modulates the direct-current voltage of the rectifier through the grid side converter switching function model, can analyze the source, the characteristic and the influence factors of the subsynchronous inter-harmonic wave which can cause the subsynchronous oscillation in the modulation process, ignores the inter-harmonic wave frequency which can not cause the subsynchronous oscillation aiming at the inter-harmonic wave frequency generated at the grid side of the inverter obtained after modulation, selects the target inter-harmonic wave from all the inter-harmonic waves corresponding to the inter-harmonic wave frequency, predicts the subsynchronous inter-harmonic wave frequency which causes the subsynchronous oscillation according to the target inter-harmonic wave frequency, judges the subsynchronous oscillation according to the subsynchronous inter-harmonic wave frequency, and can accurately pre-judge the subsynchronous oscillation by predicting the subsynchronous inter-harmonic wave frequency aiming at the converter structure of the direct-drive fan, the stable and safe operation of the power system is ensured.
Drawings
Fig. 1 is a schematic flow chart of a direct-drive fan subsynchronous oscillation prejudging method in a first embodiment of the invention;
FIG. 2 is a graph illustrating the distribution of the subsynchronous inter-harmonic predicted frequency with the fan speed in accordance with an example of the first embodiment of the present invention;
fig. 3 is a schematic structural diagram of a direct-drive fan subsynchronous oscillation pre-judging device in a second embodiment of the invention.
Detailed Description
The technical solutions in the present invention will be described clearly and completely with reference to the accompanying drawings, and it is obvious that the described embodiments are only some embodiments of the present invention, not all embodiments. 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.
It should be noted that, the step numbers in the text are only for convenience of explanation of the specific embodiments, and do not serve to limit the execution sequence of the steps. The method provided by the embodiment can be executed by the relevant terminal device, and the following description takes a processor as an execution subject as an example.
As shown in fig. 1, a first embodiment provides a method for pre-judging subsynchronous oscillation of a direct-drive fan, which includes steps S1 to S4:
s1, constructing a machine side converter switch function model and a grid side converter switch function model of the direct-drive fan;
s2, based on a harmonic modulation technology, modulating alternating current voltage on the rectifier side of the direct-drive fan through a machine side converter switching function model to obtain direct current voltage of the rectifier and low-frequency harmonic frequency generated on the direct current side by the rectifier;
s3, based on a harmonic modulation technology, modulating direct-current voltage of a rectifier through a grid-side converter switching function model to obtain alternating-current voltage on the inverter side of the direct-drive fan, and combining low-frequency harmonic frequency to obtain inter-harmonic frequency generated by the inverter on the grid side;
and S4, selecting a target inter-harmonic from all inter-harmonics corresponding to the inter-harmonic frequency, and predicting the sub-synchronous inter-harmonic frequency causing the sub-synchronous oscillation according to the target inter-harmonic so as to judge the sub-synchronous oscillation according to the sub-synchronous inter-harmonic frequency.
In a preferred embodiment, the machine side converter switching function model is:
Figure BDA0003468919820000071
the switching function model of the grid-side converter is as follows:
Figure BDA0003468919820000072
wherein ,
Figure BDA0003468919820000073
for the fundamental component and the baseband harmonic component,
Figure BDA0003468919820000074
carrier harmonics and sideband harmonic components; omega1＝2πf1，f1The three-phase voltage fundamental frequency of the direct-drive fan is adopted; omegac＝2πfc，fcIs the carrier frequency; the value of p is 0, 1 and-1, which respectively correspond to the phase a, the phase b and the phase c of the direct-drive fan; a. the0n、B0n、Amn、BmnThe amplitude coefficients of the periodic components are respectively.
As an example, the direct drive wind turbine converter system includes a Machine Side Converter (MSC), a direct current bus (DC-link), and a Grid Side Converter (GSC). Alternating current generated by the direct-drive fan is rectified into direct current by the MSC, and then is inverted into alternating current meeting grid-connected requirements by the GSC. The MSC is responsible for Maximum Power Point Tracking (MPPT) control, including speed outer loop and current inner loop control. GSC adopts grid voltage vector directional control, a Phase Locked Loop (PLL) provides a directional angle, an outer ring adopts fixed direct current voltage control to maintain the voltage of a direct current bus constant, grid-connected current is input into a control system after park transformation to realize current feedback PI control, and a modulation wave signal is formed through park inverse transformation after a grid voltage feedforward decoupling link and is modulated.
A machine side converter and a grid side converter of the direct-drive fan both adopt a Space Vector Modulation (SVM) technology, so that a constructed machine side converter switch function model is the same as a constructed grid side converter switch function model.
Taking the machine side converter as an example, the switching function model S thereofrx(x ═ a, b, c) is:
Figure BDA0003468919820000081
in the formula (1), the first term on the right side of the equal sign is a fundamental component and a baseband harmonic component in a switching function, and the second term is a carrier harmonic and a sideband harmonic component thereof; omega1＝2πf1，f1The three-phase voltage fundamental frequency of the direct-drive fan is adopted; omegac＝2πfc，fcIs the carrier frequency; the value of p is 0, 1 and-1, which respectively correspond to the phase a, the phase b and the phase c of the direct-drive fan; a. the0n、B0n、Amn and BmnThe specific expression is as follows:
Figure BDA0003468919820000082
in the formula (3), Jn(x) Is a Bessel function of order n, J0 and J k0 order and K order functions respectively; m is the modulation index (i.e., modulation depth); k is the harmonic frequency; q is an intermediate variable which is a variable,
Figure BDA0003468919820000091
ω0at angular frequency of fundamental frequency, ωcThe carrier angular frequency is m, n are harmonic index variables.
In a preferred embodiment, the dc voltage of the rectifier is:
Figure BDA0003468919820000092
wherein ,urxIs an alternating voltage on the rectifier side of the direct drive fan,
Figure BDA0003468919820000093
Ur0、θ0respectively the amplitude and the initial phase of the alternating voltage at the rectifier side of the direct-drive fan;
the low frequency harmonic frequencies generated by the rectifier on the dc side are:
Figure BDA0003468919820000094
illustratively, a harmonic modulation technology is applied to explore the modulation effect of alternating-current voltage on the rectifier side of the direct-drive fan on the direct-current bus voltage.
Three-phase voltage u on rectifier side of direct-drive fanrxComprises the following steps:
Figure BDA0003468919820000095
in formula (6), Ur0、θ0Respectively, the amplitude and the initial phase of the alternating voltage at the rectifier side of the direct drive fan.
After the switching function of the 6-pulse rectifier is modulated, the direct-current voltage u of the rectifier can be obtaineddcComprises the following steps:
Figure BDA0003468919820000096
calculating to obtain udcThe preparation comprises two modulation products, one is urxModulation product u of the first term of the switching function of equation (4)dc-1Frequency thereof and AC side frequency f1Correlation, the modulation products may be distributed around the sub/super-synchronous band, anotherIs urxModulation product u of the second term of the switching function of equation (4)dc-2Frequency and carrier frequency fcIn the PWM modulation, the carrier frequency is in the order of kHz and is not in the order of magnitude of the output voltage frequency, so it is ignored.
To sum up, u is obtaineddc-1The expression of (a) is:
Figure BDA0003468919820000101
as shown in the formula (7), only ω is1The amplitude of the frequency tripling term of (2) is not 0, so the low-frequency harmonic frequency generated by the rectifier on the direct current side is:
Figure BDA0003468919820000102
in a preferred embodiment, the ac voltage on the inverter side of the direct drive fan is:
ugx＝udcSgx (8)；
the inter-harmonic frequency generated by the inverter on the grid side is as follows:
fs＝|3kf1±hf0|，k，h＝{1，2，3，…} (9)；
wherein k is the number of low-frequency harmonics generated at the DC side; h is the fundamental frequency harmonic frequency of the power grid; f. of0The fundamental frequency of the power grid.
Illustratively, a harmonic modulation technology is applied to explore the modulation effect of alternating-current voltage on the inverter side of the direct-drive fan on the direct-current bus voltage.
Grid side voltage ugxConverter switching function model S from direct current bus voltage through network sidegxModulation generation, SgxAnd SrxSimilarly, the modulation relation expression is:
ugx＝udcSgx (8)；
low frequency harmonic component represented by the formula (5) and SgxSubstituted for (8) and in which the carrier harmonic-related terms of the switching function are also ignoredModulation, it is clear that the inter-harmonic frequencies at the net side can be directly obtained as:
fs＝|3kf1±hf0|,k,h＝1,2,3... (9)；
from the formula (9), when |3kf1±hf0I is not f0At integral multiple of (b), a frequency of |3kf appears on the AC side1±hf0The inter-harmonics of l. The formula (9) reveals that the source of the inter-harmonic component of the direct-drive wind turbine is mainly generated by modulating the characteristic harmonic component of the machine-side direct current by the grid-side converter, and the inter-harmonic frequency is closely related to the alternating-current frequency on two sides of the converter system.
Considering that the rotating speed and the frequency of the direct-drive fan meet the relationship
Figure BDA0003468919820000111
The inter-harmonic frequency f of the network side can be further obtainedsThe expression is as follows:
Figure BDA0003468919820000112
in the formula (10), k is the number of low-frequency harmonics generated on the dc side; h is the fundamental frequency harmonic frequency of the power grid; f. of0The fundamental frequency of the power grid; n isgThe rotating speed of the direct-drive fan is set; p is a radical ofgThe number of pole pairs of the motor is shown.
The formula (10) reveals the mathematical relationship between the inter-harmonic frequency and the rotating speed of the direct-drive fan, and intuitively reflects the time-varying characteristic of the inter-harmonic frequency.
In a preferred embodiment, the sub-synchronous inter-harmonic frequency of the direct drive fan is:
Figure BDA0003468919820000113
as an example, the disturbance capable of inducing subsynchronous oscillation should be the positive sequence interharmonic of the subsynchronous band (0-50Hz) and the coupled positive sequence interharmonic of the supersynchronous band (50-100Hz), i.e. the frequency band of the positive sequence interharmonic capable of inducing subsynchronous band power oscillation is 0-100Hz. The inter-harmonic corresponding to the condition is selected from all inter-harmonics corresponding to the inter-harmonic frequency generated by the inverter on the network side as a target inter-harmonic, and the frequency is 3kf1+hf0The phase sequence of the inter-harmonics of (1) is constantly positive, and1 and f0Is irrelevant to the size of the device. The positive sequence inter-harmonic frequency band capable of inducing the subsynchronous frequency band power oscillation is 0-100Hz, and the fundamental frequency f of the power grid0Is 50Hz, so 3kf is required to be satisfied1<100-50h, at which the machine side AC voltage frequency f1Lower. For a frequency of |3kf1-hf0Inter-harmonic of | only when 3kf1<hf0I.e. hf0-3kf1>At 0, the inter-harmonics are in positive order; if 3kf1>hf0If not, the reverse is negative sequence, and the frequency f of the machine side alternating voltage is1And is also relatively low.
In summary, only the AC voltage frequency f of the machine side1Lower, positive sequence inter-harmonics can be generated which can cause subsynchronous band power oscillations. The lower frequency of the machine side alternating voltage corresponds to a lower fan speed, so that subsynchronous inter-harmonics which can cause subsynchronous oscillation can be generated only when the direct drive fan speed is lower.
The higher the amplitude of the inter-harmonics, the greater the disturbance effect on the system, so the inter-harmonics that can cause subsynchronous oscillations also need to have sufficient amplitude. The larger the k and h values in equation (9), the lower the corresponding inter-harmonic amplitude, and the smaller the disturbance influence on the system.
The inter-harmonic frequency prediction formula capable of inducing sub-synchronous frequency band power oscillation in any number of times can be derived by using the formula (9), and the specific direct-drive fan sub-synchronous inter-harmonic frequency prediction formula is derived by taking four inter-harmonics with the highest amplitude as an example.
For case one: k is 1, h is 1, and the time harmonic frequency prediction formula is fs＝|3f1±50|；
Let us assume fs＝3f1+50, when all the harmonics are positive sequence inter-harmonics in the full band, when f1<At 16.7Hz, fsIn a coupled super-synchronous frequency band;
suppose fs＝|3f1-50|, when 3f1<50Hz, i.e. f1<At 16.7Hz, the frequency is positive sequence inter-harmonic, and the inter-harmonic frequency prediction formula is as follows: f. ofs＝50-3f1When 3f is1>50Hz, i.e. f1>At 16.7Hz, the frequency is negative sequence inter-harmonic, which can not cause the subsynchronous oscillation of the system and can be ignored;
so when k is 1 and h is 1, only f1<16.7Hz, the inter-harmonics are in positive order and can cause subsynchronous oscillation of the system.
For the inter-harmonic wave of the sub-synchronous frequency band, when the wind speed v increases, the rotating speed n increases, and the frequency f of the machine side alternating voltage increases1Increasing the inter-harmonic frequency; for the coupled super-synchronous frequency band, when the wind speed increases, the rotating speed n increases, and the machine side alternating voltage frequency f1Increasing the inter-harmonic frequency.
For case two: k is 2, h is 1, and the time harmonic frequency prediction formula is fs＝|6f1±50|；
Let f be assumeds＝6f1+50, when all the harmonics are positive sequence inter-harmonics in the full band, when f1<At 8.3Hz, fsIn a coupled super-synchronous frequency band;
hypothesis fs＝|6f1-50|, when 6f1<50Hz, i.e. f1<At 8.3Hz, the frequency is positive sequence inter-harmonic, and the inter-harmonic frequency prediction formula is as follows: f. ofs＝50-6f1When 6f1>50Hz, i.e. f1>At 8.3Hz, the signal is negative sequence inter-harmonic, cannot cause the subsynchronous oscillation of the system and is ignored;
so when k is 2 and h is 1, only f1<8.3Hz can satisfy that the inter-harmonics are positive order and may cause subsynchronous oscillation of the system.
For the inter-harmonic waves of the sub-synchronous frequency band, when the wind speed v increases, the frequency of the inter-harmonic waves is reduced; for the coupled super-synchronous band, as wind speed increases, the inter-harmonic frequency increases.
For case three: k is 1, h is 2, and the time harmonic frequency prediction formula is fs＝|3f1±100|；
If the inter-harmonic is required to be in positive sequence, the following requirements are met in the coupled super-synchronous frequency band: f. ofs＝3f1+ 100; the requirements in the subsynchronous frequency band are as follows: f. ofs＝100-3f1Due to f1Generally, the frequency of the inter-harmonic wave is from several Hz to tens of Hz, and the frequency of the inter-harmonic wave cannot be in the frequency band of 0-100Hz, so the inter-harmonic wave cannot cause the power oscillation of the subsynchronous frequency band and is omitted.
For case four: k is 2, h is 2, and the time harmonic frequency prediction formula is fs＝|6f1±100|；
Suppose fs＝6f1+100, for the same reason as above, is not within the scope of investigation and is therefore omitted. Suppose fs＝|6f1-100|, when 6f1<100Hz, i.e. f1<At 16.7Hz, the frequency is positive sequence inter-harmonic, and the inter-harmonic frequency prediction formula is as follows: f. ofs＝100-6f1(ii) a When 6f1>100Hz, i.e. f1>16.7Hz is negative sequence inter-harmonic, which can not induce the subsynchronous oscillation of the system, so it is neglected.
So when k is 2 and h is 2, f1<16.7Hz may induce a subsynchronous oscillation of the system.
In summary, the inter-harmonic frequencies that may induce the subsynchronous oscillation of the system are:
Figure BDA0003468919820000131
according to the derivation process, other specific direct-drive fan subsynchronous inter-harmonic frequency prediction formulas can be continuously derived to obtain
Figure BDA0003468919820000132
Considering the relation between the rotating speed and the frequency of the direct-drive fan, the relation between the rotating speed and the frequency of the direct-drive fan is considered
Figure BDA0003468919820000141
Substituting into formula (11), and measuring rotation speed change in real timeAnd predicting the sub-synchronous inter-harmonic frequency in the current state to obtain the distribution condition of the sub-synchronous inter-harmonic frequency along with the rotating speed of the direct-drive fan under different working conditions, as shown in the formula (12).
Figure BDA0003468919820000142
In the formula (12), ngThe rotating speed of the direct-drive fan is set; p is a radical ofgThe number of pole pairs of the direct-drive fan is.
For example, the direct-drive fan parameters are substituted into the subsynchronous interharmonic frequency prediction formula (11) to obtain the distribution situation of the subsynchronous interharmonic prediction frequency along with the fan rotating speed as shown in fig. 2, and the dotted line segment in fig. 2 is the subsynchronous frequency band positive sequence interharmonic wave capable of triggering the subsynchronous oscillation of the system and the super-synchronous frequency band positive sequence interharmonic wave coupled with the subsynchronous frequency band positive sequence interharmonic wave.
Based on the same inventive concept as the first embodiment, a second embodiment provides a direct-drive fan subsynchronous oscillation pre-judging device as shown in fig. 3, including: the building module 21 is used for building a machine side converter switch function model and a grid side converter switch function model of the direct-drive fan; the modulation module 22 is used for modulating alternating-current voltage on the rectifier side of the direct-drive fan through a machine side converter switching function model based on a harmonic modulation technology to obtain direct-current voltage of the rectifier and low-frequency harmonic frequency generated on the direct-current side by the rectifier; the modulation module 22 is further configured to modulate the direct-current voltage of the rectifier through a grid-side converter switching function model based on a harmonic modulation technology to obtain an alternating-current voltage at the inverter side of the direct-drive fan, and obtain inter-harmonic frequency generated by the inverter at the grid side by combining with low-frequency harmonic frequency; and the prejudging module 23 is configured to select a target inter-harmonic from all inter-harmonics corresponding to the inter-harmonic frequency, predict a sub-synchronous inter-harmonic frequency causing sub-synchronous oscillation according to the target inter-harmonic, and judge the sub-synchronous oscillation according to the sub-synchronous inter-harmonic frequency.
In a preferred embodiment, the machine side converter switching function model is:
Figure BDA0003468919820000151
the switching function model of the grid-side converter is as follows:
Figure BDA0003468919820000152
wherein ,
Figure BDA0003468919820000153
for the fundamental component and the baseband harmonic component,
Figure BDA0003468919820000154
carrier harmonics and sideband harmonic components; omega1＝2πf1，f1The three-phase voltage fundamental frequency of the direct-drive fan is adopted; omegac＝2πfc，fcIs the carrier frequency; the value of p is 0, 1 and-1, which respectively correspond to the phase a, the phase b and the phase c of the direct-drive fan; a. the0n、B0n、Amn、BmnThe amplitude coefficients of the periodic components are respectively.
In a preferred embodiment, the dc voltage of the rectifier is:
Figure BDA0003468919820000155
wherein ,urxIs an alternating voltage on the rectifier side of the direct drive fan,
Figure BDA0003468919820000156
Ur0、θ0respectively the amplitude and the initial phase of the alternating voltage at the rectifier side of the direct-drive fan;
the low frequency harmonic frequencies generated by the rectifier on the dc side are:
Figure BDA0003468919820000157
in a preferred embodiment, the ac voltage on the inverter side of the direct drive fan is:
ugx＝udcSgx (17)；
the inter-harmonic frequency generated by the inverter on the grid side is as follows:
fs＝|3kf1±hf0|，k，h＝{1，2，3，…} (18)；
wherein k is the number of low-frequency harmonics generated at the DC side; h is the fundamental frequency harmonic frequency of the power grid; f. of0The fundamental frequency of the power grid.
In a preferred embodiment, the sub-synchronous inter-harmonic frequency of the direct drive fan is:
Figure BDA0003468919820000161
in summary, the embodiment of the present invention has the following advantages:
the method comprises the steps of constructing a machine side converter switch function model and a grid side converter switch function model of a direct-drive fan, modulating alternating-current voltage on a rectifier side of the direct-drive fan through the machine side converter switch function model based on a harmonic modulation technology to obtain direct-current voltage of the rectifier and low-frequency harmonic frequency generated by the rectifier on the direct-current side, modulating direct-current voltage of the rectifier through the grid side converter switch function model based on the harmonic modulation technology to obtain alternating-current voltage on an inverter side of the direct-drive fan, obtaining inter-harmonic frequency generated by the inverter on the grid side by combining the low-frequency harmonic frequency, selecting target inter-harmonic from all inter-harmonic corresponding to the inter-harmonic frequency, predicting sub-synchronous inter-harmonic frequency causing sub-synchronous oscillation according to the target inter-harmonic, judging the sub-synchronous oscillation according to the sub-synchronous inter-harmonic frequency, and realizing pre-judgment of the sub-synchronous oscillation. The embodiment of the invention is based on a harmonic modulation technology, modulates alternating current voltage at the rectifier side of a direct-drive fan through a machine side converter switch function model and modulates direct current voltage of the rectifier through a grid side converter switch function model, can analyze subsynchronous inter-harmonic sources, characteristics and influence factors which can cause subsynchronous oscillation in the modulation process, ignores inter-harmonic frequency which can not cause subsynchronous oscillation aiming at inter-harmonic frequency generated at the grid side of an inverter obtained after modulation, selects target inter-harmonic from all inter-harmonic corresponding to the inter-harmonic frequency, predicts the subsynchronous inter-harmonic frequency which causes the subsynchronous oscillation according to the target inter-harmonic frequency, judges the subsynchronous oscillation according to the subsynchronous inter-harmonic frequency, thereby accurately pre-judging the subsynchronous oscillation by predicting the subsynchronous inter-harmonic frequency aiming at a converter structure of the direct-drive fan, the stable and safe operation of the power system is ensured.
While the foregoing is directed to the preferred embodiment of the present invention, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention.
It will be understood by those skilled in the art that all or part of the processes of the above embodiments may be implemented by hardware related to instructions of a computer program, and the computer program may be stored in a computer readable storage medium, and when executed, may include the processes of the above embodiments. The storage medium may be a magnetic disk, an optical disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), or the like.

Claims (10)

1. A subsynchronous oscillation prejudging method of a direct-drive fan is characterized by comprising the following steps:
constructing a machine side converter switch function model and a grid side converter switch function model of the direct-drive fan;
based on a harmonic modulation technology, modulating alternating current voltage on the rectifier side of the direct-drive fan through a machine side converter switching function model to obtain direct current voltage of the rectifier and low-frequency harmonic frequency generated on the direct current side by the rectifier;
based on a harmonic modulation technology, modulating the direct-current voltage of the rectifier through the grid-side converter switching function model to obtain the alternating-current voltage of the direct-drive fan inverter side, and combining the low-frequency harmonic frequency to obtain the inter-harmonic frequency generated by the inverter on the grid side;
and selecting a target inter-harmonic from all inter-harmonics corresponding to the inter-harmonic frequency, predicting a sub-synchronous inter-harmonic frequency causing sub-synchronous oscillation according to the target inter-harmonic, and judging the sub-synchronous oscillation according to the sub-synchronous inter-harmonic frequency.
2. The direct drive fan subsynchronous oscillation prejudging method of claim 1, wherein the machine side converter switching function model is as follows:
Figure FDA0003468919810000011
the switching function model of the grid-side converter is as follows:
Figure FDA0003468919810000012
wherein ,
Figure FDA0003468919810000013
for the fundamental component and the baseband harmonic component,
Figure FDA0003468919810000014
carrier harmonics and sideband harmonic components; omega1＝2πf1，f1The three-phase voltage fundamental frequency of the direct-drive fan is obtained; omegac＝2πfc，fcIs the carrier frequency; the value of p is 0, 1 and-1, and the p respectively corresponds to the phase a, the phase b and the phase c of the direct drive fan; a. the0n、B0n、Amn、BmnThe amplitude coefficients of the periodic components are respectively.
3. The direct-drive fan subsynchronous oscillation prejudging method of claim 2, wherein the direct-current voltage of the rectifier is as follows:
Figure FDA0003468919810000021
wherein ,urxIs the alternating voltage at the rectifier side of the direct drive fan,
Figure FDA0003468919810000022
Ur0、θ0respectively representing the amplitude and the initial phase of the alternating voltage at the rectifier side of the direct-drive fan;
the low-frequency harmonic frequency generated by the rectifier on the direct current side is as follows:
Figure FDA0003468919810000023
4. the method for pre-judging subsynchronous oscillation of the direct-drive fan as recited in claim 3, wherein the alternating voltage at the inverter side of the direct-drive fan is as follows:
ugx＝udcSgx；
the inter-harmonic frequency generated by the inverter on the grid side is as follows:
fs＝|3kf1±hf0|，k，h＝{1，2，3，…}；
wherein k is the number of low-frequency harmonics generated at the DC side; h is the fundamental frequency harmonic frequency of the power grid; f. of0The fundamental frequency of the power grid.
5. The direct drive fan subsynchronous oscillation prejudging method of claim 4, wherein the subsynchronous inter-harmonic frequency of the direct drive fan is as follows:
Figure FDA0003468919810000031
6. the utility model provides a device is prejudged in subsynchronous oscillation of direct-driven fan which characterized in that includes:
the building module is used for building a machine side converter switch function model and a grid side converter switch function model of the direct-drive fan;
the modulation module is used for modulating alternating-current voltage on the rectifier side of the direct-drive fan through the machine side converter switching function model based on a harmonic modulation technology to obtain direct-current voltage of the rectifier and low-frequency harmonic frequency generated on the direct-current side by the rectifier;
the modulation module is further used for modulating the direct-current voltage of the rectifier through the grid-side converter switching function model based on a harmonic modulation technology to obtain alternating-current voltage on the inverter side of the direct-drive fan, and obtaining inter-harmonic frequency generated by the inverter on the grid side by combining the low-frequency harmonic frequency;
and the pre-judging module is used for selecting a target inter-harmonic from all inter-harmonics corresponding to the inter-harmonic frequency, predicting the sub-synchronous inter-harmonic frequency causing the sub-synchronous oscillation according to the target inter-harmonic, and judging the sub-synchronous oscillation according to the sub-synchronous inter-harmonic frequency.
7. The direct drive fan subsynchronous oscillation prejudging device of claim 6, wherein the machine side converter switching function model is as follows:
Figure FDA0003468919810000032
the switching function model of the grid-side converter is as follows:
Figure FDA0003468919810000033
wherein ,
Figure FDA0003468919810000041
for the fundamental component and the baseband harmonic component,
Figure FDA0003468919810000042
carrier harmonics and sideband harmonic components; omega1＝2πf1，f1The three-phase voltage fundamental frequency of the direct-drive fan is obtained; omegac＝2πfc，fcIs the carrier frequency; the value of p is 0, 1 and-1, and the p respectively corresponds to the phase a, the phase b and the phase c of the direct drive fan; a. the0n、B0n、Amn、BmnThe amplitude coefficients of the periodic components are respectively.
8. The direct-drive fan subsynchronous oscillation prejudging device of claim 7, wherein the direct-current voltage of the rectifier is as follows:
Figure FDA0003468919810000043
wherein ,urxIs the alternating voltage at the rectifier side of the direct drive fan,
Figure FDA0003468919810000044
Ur0、θ0respectively representing the amplitude and the initial phase of the alternating voltage at the rectifier side of the direct-drive fan;
the low-frequency harmonic frequency generated by the rectifier on the direct current side is as follows:
Figure FDA0003468919810000045
9. the direct drive fan subsynchronous oscillation prejudging device of claim 8, wherein the alternating voltage at the inverter side of the direct drive fan is as follows:
ugx＝udcSgx；
the inter-harmonic frequency generated by the inverter on the grid side is as follows:
fs＝|3kf1±hf0|，k，h＝{1，2，3，…}；
wherein k is the number of low-frequency harmonics generated at the DC side; h is the fundamental frequency harmonic frequency of the power grid; f. of0The fundamental frequency of the power grid.
10. The direct drive fan subsynchronous oscillation prejudging device of claim 9, wherein the subsynchronous inter-harmonic frequency of the direct drive fan is as follows:
Figure FDA0003468919810000051
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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN106953348A (en) * 2017-04-27 2017-07-14 华南理工大学 A kind of Power network fault calculation method containing back-to-back DC power transmission
CN109103903A (en) * 2018-09-13 2018-12-28 华北电力大学 A kind of judgment method causing sub-synchronous oscillation for straight drive blower
CN110676874A (en) * 2019-10-09 2020-01-10 西安热工研究院有限公司 Direct-drive fan subsynchronous oscillation electrical quantity analysis method considering frequency coupling effect
CN113346513A (en) * 2021-03-09 2021-09-03 江苏大学 Method for identifying forced subsynchronous oscillation of direct-drive fan

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN106953348A (en) * 2017-04-27 2017-07-14 华南理工大学 A kind of Power network fault calculation method containing back-to-back DC power transmission
CN109103903A (en) * 2018-09-13 2018-12-28 华北电力大学 A kind of judgment method causing sub-synchronous oscillation for straight drive blower
CN110676874A (en) * 2019-10-09 2020-01-10 西安热工研究院有限公司 Direct-drive fan subsynchronous oscillation electrical quantity analysis method considering frequency coupling effect
CN113346513A (en) * 2021-03-09 2021-09-03 江苏大学 Method for identifying forced subsynchronous oscillation of direct-drive fan

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
吴佳佳等: "三电平 VSC-HVDC 系统谐波间谐波产生机理分析", 《电力系统及其自动化学报》, vol. 29, no. 5, pages 78 - 82 *
徐衍会等: "直驱风机网侧换流器引发次/超同步振荡机理研究", 《电网技术》, vol. 42, no. 5, pages 1556 - 1564 *

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