CN114374208B - Method and device for prejudging subsynchronous oscillation of direct-drive fan - Google Patents

Method and device for prejudging subsynchronous oscillation of direct-drive fan Download PDF

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CN114374208B
CN114374208B CN202210041132.3A CN202210041132A CN114374208B CN 114374208 B CN114374208 B CN 114374208B CN 202210041132 A CN202210041132 A CN 202210041132A CN 114374208 B CN114374208 B CN 114374208B
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direct
frequency
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drive fan
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CN114374208A (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 prejudging subsynchronous oscillation of a direct-drive fan. The method comprises the following steps: based on a harmonic modulation technology, modulating alternating current voltage at the rectifier side of the direct-driven fan through a constructed machine side converter switching function model to obtain direct current voltage of the rectifier and low-frequency harmonic frequency generated by the rectifier at the direct current side; based on a harmonic modulation technology, modulating the direct-current voltage of a rectifier through a constructed network side converter switching function model to obtain alternating-current voltage of a direct-drive fan inverter side, and combining low-frequency harmonic frequency to obtain inter-harmonic frequency generated by the inverter on the network side; and selecting a target inter-harmonic from all inter-harmonics corresponding to the inter-harmonic frequency, and predicting the sub-synchronous inter-harmonic frequency for inducing 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. The invention 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 the stable and safe operation of the power system.

Description

Method and device for prejudging subsynchronous oscillation of direct-drive fan
Technical Field
The invention relates to the technical field of stability analysis of power systems, in particular to a method and a device for prejudging subsynchronous oscillation of a direct-drive fan.
Background
In recent years, due to dense grid connection of a large number of wind turbine generators 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 frequency spectrum distribution has obvious random time-varying characteristics, and the electric energy quality problem and broadband oscillation accident of the electric power system are frequently caused. The topological structure can generate various inter-harmonics, wherein a part of the inter-harmonics are in a subsynchronous frequency range to induce subsynchronous oscillation, and when the inter-harmonics frequency of the part of the subsynchronous frequency ranges is close to the frequency of some inherent subsynchronous modes existing in the power system, such as the inherent modes of a fan control system, the inherent modes of a turbo generator shafting and the like, forced subsynchronous oscillation can be excited, so that the stability and the safety of the operation of the power system are seriously threatened.
At present, subsynchronous oscillation is predicted mainly by predicting the inter-harmonic frequency generated by a direct-drive fan. The oscillation phenomenon frequently observed when the actual power system operates shows that subsynchronous inter-harmonic waves generated by the direct-driven fan in a weak current network are amplified to cause the risk of subsynchronous oscillation, but the existing method for predicting the frequency of the subsynchronous inter-harmonic waves of the direct-driven fan focuses on high-frequency inter-harmonic waves (i.e. inter-harmonic waves larger than 150 Hz), is almost blank in research on the frequency prediction of the subsynchronous inter-harmonic waves, and is difficult to accurately predict the subsynchronous oscillation of the direct-driven fan, and 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 subsynchronous oscillation pre-judging method and device for a direct-drive fan, which can accurately pre-judge subsynchronous oscillation by predicting the subsynchronous inter-harmonic frequency according to the converter structure of the direct-drive fan, and ensure that an electric power system runs stably and safely.
In order to solve the above technical problems, in a first aspect, an embodiment of the present invention provides a method for pre-judging subsynchronous oscillation of a direct-drive fan, including:
constructing a machine side converter switch function model and a net side converter switch function model of the direct-drive fan;
based on a harmonic modulation technology, modulating alternating current voltage at the rectifier side of the direct-driven fan through a machine side converter switching function model to obtain direct current voltage of the rectifier and low-frequency harmonic frequency generated by the rectifier at the direct current side;
based on a harmonic modulation technology, modulating the direct-current voltage of the rectifier through the network side converter switching function model to obtain alternating-current voltage of the direct-drive fan inverter side, and combining the low-frequency harmonic frequency to obtain inter-harmonic frequency generated by the inverter on the network side;
and selecting a target inter-harmonic from all inter-harmonics corresponding to the inter-harmonic frequency, and predicting a subsynchronous inter-harmonic frequency for inducing subsynchronous oscillation according to the target inter-harmonic so as to judge subsynchronous oscillation according to the subsynchronous inter-harmonic frequency.
Further, the machine side converter switching function model is:
Figure BDA0003468919820000021
the network side converter switching function model is as follows:
Figure BDA0003468919820000022
wherein ,
Figure BDA0003468919820000023
for fundamental and baseband harmonic components, +.>
Figure BDA0003468919820000024
Carrier harmonic and sideband harmonic components; omega 1 ＝2πf 1 ，f 1 The fundamental frequency of the three-phase voltage of the direct-drive fan is set; omega c ＝2πf c ，f c Is the carrier frequency; p takes values of 0, 1 and-1, and corresponds to a phase a, b phase and c phase of the direct-drive fan respectively; a is that 0n 、B 0n 、A mn 、B mn The amplitude coefficients of the periodic components are respectively obtained.
Further, the direct current voltage of the rectifier is:
Figure BDA0003468919820000031
wherein ,urx For the ac voltage on the rectifier side of the direct drive fan,
Figure BDA0003468919820000032
U r0 、θ 0 the amplitude and the initial phase of the alternating voltage at the rectifier side of the direct-drive fan are respectively;
the low-frequency harmonic frequency generated by the rectifier on the direct current side is as follows:
Figure BDA0003468919820000033
further, the ac voltage at the inverter side of the direct-drive fan is:
u gx ＝u dc S gx ；
the inter-harmonic frequency generated by the inverter at the network side is as follows:
f s ＝|3kf 1 ±hf 0 |，k，h＝{1，2，3，…}；
wherein 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 (f) 0 Is the fundamental frequency of the power grid.
Further, the subsynchronous 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 device for pre-judging subsynchronous oscillation of a direct-drive fan, including:
the construction module is used for constructing a machine side converter switch function model and a network side converter switch function model of the direct-drive fan;
the modulation module is used for modulating the alternating voltage of the rectifier side of the direct-driven fan through the machine side converter switching function model based on a harmonic modulation technology to obtain the direct-current voltage of the rectifier and the low-frequency harmonic frequency generated by the rectifier on the direct-current side;
the modulation module is further used for modulating the direct-current voltage of the rectifier through the network side converter switching function model based on a harmonic modulation technology to obtain alternating-current voltage of the direct-drive fan inverter side, and combining the low-frequency harmonic frequency to obtain inter-harmonic frequency generated by the inverter on the network side;
and the pre-judging module is used for selecting target inter-harmonic waves from all inter-harmonic waves corresponding to the inter-harmonic waves, and predicting the sub-synchronous inter-harmonic wave frequency for inducing sub-synchronous oscillation according to the target inter-harmonic waves so as to judge the sub-synchronous oscillation according to the sub-synchronous inter-harmonic wave frequency.
Further, the machine side converter switching function model is:
Figure BDA0003468919820000041
the network side converter switching function model is as follows:
Figure BDA0003468919820000042
wherein ,
Figure BDA0003468919820000043
for fundamental and baseband harmonic components, +.>
Figure BDA0003468919820000044
Carrier harmonic and sideband harmonic components; omega 1 ＝2πf 1 ，f 1 The fundamental frequency of the three-phase voltage of the direct-drive fan is set; omega c ＝2πf c ，f c Is the carrier frequency; p takes values of 0, 1 and-1, and corresponds to a phase a, b phase and c phase of the direct-drive fan respectively; a is that 0n 、B 0n 、A mn 、B mn The amplitude coefficients of the periodic components are respectively obtained.
Further, the direct current voltage of the rectifier is:
Figure BDA0003468919820000045
wherein ,urx For the ac voltage on the rectifier side of the direct drive fan,
Figure BDA0003468919820000046
U r0 、θ 0 the amplitude and the initial phase of the alternating voltage at the rectifier side of the direct-drive fan are respectively;
the low-frequency harmonic frequency generated by the rectifier on the direct current side is as follows:
Figure BDA0003468919820000051
further, the ac voltage at the inverter side of the direct-drive fan is:
u gx ＝u dc S gx ；
the inter-harmonic frequency generated by the inverter at the network side is as follows:
f s ＝|3kf 1 ±hf 0 |，k，h＝{1，2，3，…}；
wherein 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 (f) 0 Is the fundamental frequency of the power grid.
Further, the subsynchronous 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 switching function model and a network side converter switching function model of a direct-driven fan, modulating alternating current voltage of a rectifier side of the direct-driven fan through the machine side converter switching function model based on a harmonic modulation technology, obtaining 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 network side converter switching function model based on a harmonic modulation technology, obtaining alternating current voltage of an inverter side of the direct-driven fan, obtaining inter-harmonic frequency generated by the inverter on the network side by combining the low-frequency harmonic frequency, selecting target inter-harmonic from all inter-harmonics corresponding to the inter-harmonic frequency, predicting sub-synchronous inter-harmonic frequency for inducing sub-synchronous oscillation according to the target inter-harmonic frequency, and judging the sub-synchronous oscillation according to the sub-synchronous inter-harmonic frequency to realize pre-judgment sub-synchronous oscillation. Compared with the prior art, the embodiment of the invention is based on a harmonic modulation technology, the alternating current voltage of the rectifier side of the direct-driven fan is modulated through the machine side converter switching function model, and the direct current voltage of the rectifier is modulated through the network side converter switching function model, so that the source, the characteristics and the influence factors of subsynchronous inter-harmonic waves capable of inducing subsynchronous oscillation can be analyzed in the modulation process, the intersymbol frequency which is generated on the network side by the inverter obtained after modulation is ignored, the target intersymbol wave which cannot induce subsynchronous oscillation is selected from all intersymbol waves corresponding to the intersymbol wave, the subsynchronous inter-harmonic wave frequency inducing subsynchronous oscillation is predicted according to the target intersymbol wave, and the subsynchronous oscillation is accurately pre-determined according to the subsynchronous inter-harmonic wave frequency, so that the converter structure of the direct-driven fan can be aimed at, and the stable and safe operation of a power system is ensured.
Drawings
Fig. 1 is a schematic flow chart of a method for pre-judging subsynchronous oscillation of a direct-drive fan in a first embodiment of the present invention;
FIG. 2 is a graph showing the distribution of subsynchronous inter-harmonic predicted frequencies with fan speed according to an example of the first embodiment of the present invention;
fig. 3 is a schematic structural diagram of a device for pre-judging subsynchronous oscillation of a direct-drive fan according to a second embodiment of the present invention.
Detailed Description
The following description of the embodiments of the present invention will be made more apparent and fully hereinafter with reference to the accompanying drawings, in which some, but not all embodiments of the invention are shown. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
It should be noted that, the step numbers herein are only for convenience of explanation of the specific embodiments, and are not used as limiting the order of execution of the steps. The method provided in this embodiment may be performed by a related terminal device, and the following description will take a processor as an execution body 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 network side converter switch function model of a direct-drive fan;
s2, modulating alternating current voltage at the rectifier side of the direct-driven 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 by the rectifier at the direct current side;
s3, modulating the direct-current voltage of the rectifier through a network side converter switching function model based on a harmonic modulation technology to obtain alternating-current voltage of the direct-drive fan inverter side, and combining low-frequency harmonic frequency to obtain inter-harmonic frequency generated by the inverter on the network side;
s4, selecting a target inter-harmonic from all inter-harmonics corresponding to the inter-harmonic frequency, and predicting the sub-synchronous inter-harmonic frequency for inducing 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 network side converter switching function model is as follows:
Figure BDA0003468919820000072
wherein ,
Figure BDA0003468919820000073
for fundamental and baseband harmonic components, +.>
Figure BDA0003468919820000074
Carrier harmonic and sideband harmonic components; omega 1 ＝2πf 1 ，f 1 The fundamental frequency of the three-phase voltage of the direct-drive fan is set; omega c ＝2πf c ，f c Is the carrier frequency; p takes values of 0, 1 and-1, and corresponds to a phase, b phase and c phase of the direct-drive fan respectively; a is that 0n 、B 0n 、A mn 、B mn The amplitude coefficients of the periodic components are respectively obtained.
As an example, the current conversion system of the direct drive fan comprises a machine side current converter (Machine side converter, MSC), a direct current bus (DC-link) and a grid side current converter (Grid side converter, GSC). The alternating current generated by the direct-drive fan is rectified into direct current by the MSC, and then is inverted into alternating current meeting the grid-connected requirement by the GSC. The MSC is responsible for maximum power point tracking (Maximum power point tracking, MPPT) control, including speed outer loop and current inner loop control. The GSC adopts power grid voltage vector directional control, a phase-locked loop (Phase locked loop, PLL) provides a directional angle, an outer loop adopts constant direct current voltage control, the voltage of a direct current bus is kept constant, grid-connected current is input into a control system after park conversion to realize current feedback PI control, and after a power grid voltage feedforward decoupling link, a modulating wave signal is formed through park inverse conversion to modulate.
The machine side converter and the net side converter of the direct-driven fan both adopt symmetrical regular sampling space vector modulation (Space vector modulation, SVM) technology, so that the constructed machine side converter switching function model is the same as the net side converter switching function model.
Taking a machine side converter as an example, a switching function model S thereof rx (x=a, b, c) is:
Figure BDA0003468919820000081
in the formula (1), a first term on the right side of the equal sign is a fundamental wave component and a baseband harmonic wave component in a switching function, and a second term is a carrier wave harmonic wave and a sideband harmonic wave component thereof; omega 1 ＝2πf 1 ，f 1 Is directly driven by windFundamental frequency of machine three-phase voltage; omega c ＝2πf c ，f c Is the carrier frequency; p takes values of 0, 1 and-1, and corresponds to a phase, b phase and c phase of the direct-drive fan respectively; a is that 0n 、B 0n 、A mn and Bmn The specific expression of the amplitude coefficient of each periodic component is as follows:
Figure BDA0003468919820000082
in the formula (3), J n (x) As an n-order Bessel function, J 0 and Jk Respectively 0 th order and K th order functions; m is the modulation index (i.e., modulation depth); k is harmonic frequency; q is an intermediate variable which is defined as,
Figure BDA0003468919820000091
ω 0 for fundamental angular frequency, omega c And the carrier angular frequency is used, and m and n are harmonic index variables.
In a preferred embodiment, the dc voltage of the rectifier is:
Figure BDA0003468919820000092
wherein ,urx Is the alternating voltage at the rectifier side of the direct-drive fan,
Figure BDA0003468919820000093
U r0 、θ 0 the amplitude and the initial phase of the alternating voltage at the rectifier side of the direct-drive fan are respectively;
the low-frequency harmonic frequencies generated by the rectifier on the direct current side are:
Figure BDA0003468919820000094
as an example, the modulation effect of the direct drive fan rectifier side ac voltage on the dc bus voltage was explored using harmonic modulation techniques.
Straight setThree-phase voltage u on rectifier side of fan rx The method comprises the following steps:
Figure BDA0003468919820000095
in formula (6), U r0 、θ 0 The amplitude and the initial phase of the alternating voltage at the rectifier side of the direct-drive fan are respectively.
After the modulation of the switching function of the 6-pulse rectifier, the direct-current voltage u of the rectifier can be obtained dc The method comprises the following steps:
Figure BDA0003468919820000096
by calculating u dc Comprises two modulation products, one is u rx Modulation product u of the first term of the switching function of formula (4) dc-1 Its frequency is equal to the AC side frequency f 1 The modulation product may be distributed around the sub/super synchronous band, the other is u rx Modulation product u of the second term of the switching function of formula (4) dc-2 Its frequency and carrier frequency f c In relation, since the carrier frequency in PWM modulation is of the order of kHz, it is not of the order of magnitude with the output voltage frequency, and is therefore omitted.
To sum up, get u dc-1 The expression of (2) is:
Figure BDA0003468919820000101
as can be seen from formula (7), only ω 1 The frequency tripled term amplitude 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:
u gx ＝u dc S gx (8)；
the inter-harmonic frequencies generated by the inverter at the network side are:
f s ＝|3kf 1 ±hf 0 |，k，h＝{1，2，3，…} (9)；
wherein 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 (f) 0 Is the fundamental frequency of the power grid.
As an example, the modulation effect of the dc bus voltage on the dc-fan inverter side ac voltage was explored using harmonic modulation techniques.
Grid side voltage u gx DC bus voltage through network side converter switch function model S gx Modulation generation, S gx And S is equal to rx The modulation relation expression is as follows:
u gx ＝u dc S gx (8)；
sum S and low-frequency harmonic component expressed by equation (5) gx Substituting (8), also neglecting the modulation effect of the carrier wave harmonic related term in the switching function, obviously, the inter-harmonic frequency of the network side can be directly obtained as follows:
f s ＝|3kf 1 ±hf 0 |,k,h＝1,2,3... (9)；
as can be seen from formula (9), when |3kf 1 ±hf 0 I is not f 0 Is an integer multiple of |3kf on the AC side 1 ±hf 0 Inter-harmonics of i. Equation (9) reveals that the source of the inter-harmonic component of the direct-driven fan is mainly generated by modulating the direct-current characteristic harmonic component of the machine side by the grid-side converter, which shows that the inter-harmonic frequency is closely related to the alternating-current frequency at two sides of the converter system.
Consider the satisfied relation between the rotation speed and the frequency of the direct-driven fan
Figure BDA0003468919820000111
The inter-harmonic frequency f of the net side can be further obtained s The expression is as follows:
Figure BDA0003468919820000112
in the formula (10), k is the frequency of low-frequency harmonic waves generated on the direct current side; h is the fundamental frequency harmonic frequency of the power grid; f (f) 0 Is the fundamental frequency of the power grid; n is n g The rotating speed of the direct-drive fan; p is p g Is the pole pair number of the motor.
The formula (10) reveals the mathematical relationship between the inter-harmonic frequency and the rotating speed of the direct-drive fan, and intuitively shows the time-varying characteristic of the inter-harmonic frequency.
In a preferred embodiment, the subsynchronous inter-harmonic frequencies of the direct drive fan are:
Figure BDA0003468919820000113
as an example, the disturbance capable of inducing subsynchronous oscillation should be a positive-order inter-harmonic of the subsynchronous frequency band (0-50 Hz) and a positive-order inter-harmonic of the supersynchronous frequency band (50-100 Hz) to which it is coupled, i.e., the positive-order inter-harmonic frequency band capable of inducing subsynchronous frequency band power oscillation is 0-100Hz. An inter-harmonic wave satisfying this condition is selected as a target inter-harmonic wave from all inter-harmonics corresponding to the inter-harmonic frequencies generated by the inverter on the network side, the inter-harmonic wave being 3kf for the frequency 1 +hf 0 The phase sequence of the inter-harmonic wave is constant as positive sequence, and f 1 and f0 Is independent of the size of (a). Because the positive sequence inter-harmonic frequency band capable of inducing sub-synchronous frequency band power oscillation is 0-100Hz, and the power grid fundamental frequency f 0 50Hz, so that 3kf is required 1 <100-50h, at this time, the machine side alternating voltage frequency f 1 Lower. For a frequency of |3kf 1 -hf 0 Inter-harmonic of 3kf only 1 <hf 0 I.e. hf 0 -3kf 1 >0, the time harmonic is positive sequence; if 3kf 1 >hf 0 Otherwise, the sequence is negative, and the machine side alternating voltage frequency f at the moment 1 And is also relatively low.
In summary, only the side ac voltage frequency f 1 At lower levels, it is possible to generate positive inter-sequence harmonics that can induce sub-synchronous band power oscillations. Lower machine side ac voltage frequency corresponds to lower machine side ac voltage frequencyThe fan speed, therefore, can only produce the subsynchronous inter-harmonic that can initiate subsynchronous oscillation when the direct drive fan speed is low.
Because the higher the amplitude of the inter-harmonic, the greater the disturbance to the system, the inter-harmonic must also have sufficient amplitude to be able to induce subsynchronous oscillations. The larger the k and h values in equation (9), the lower the corresponding inter-harmonic magnitudes, the less the disturbance effect on the system.
The equation (9) can be used for deducing an inter-harmonic frequency prediction equation capable of inducing sub-synchronous frequency band power oscillation at any frequency.
For case one: k=1, h=1, and the time harmonic frequency prediction formula is f s ＝|3f 1 ±50|；
(1) Let f s ＝3f 1 +50, positive inter-sequence harmonics in the full frequency band, when f 1 <At 16.7Hz, f s Is in the coupled super synchronous frequency band;
(2) let f s ＝|3f 1 -50, when 3f 1 <50Hz, i.e. f 1 <At 16.7Hz, the positive sequence inter-harmonic wave is obtained by the inter-harmonic wave frequency prediction formula: f (f) s ＝50-3f 1 When 3f 1 >50Hz, i.e. f 1 >At 16.7Hz, the harmonic wave is a negative sequence inter-harmonic wave, and cannot cause subsynchronous oscillation of the system and should be ignored;
so when k=1, h=1, only f 1 <16.7Hz, the inter-harmonic wave is positive, and the subsynchronous oscillation of the system can be possibly caused.
For the inter-harmonic wave of the sub-synchronous frequency band, when the wind speed v increases, the rotation speed n increases and the machine side alternating voltage frequency f 1 Increasing, the inter-harmonic frequency decreases; for the coupled super synchronous frequency band, when the wind speed increases, the rotating speed n increases, and the machine side alternating voltage frequency f 1 The inter-harmonic frequency increases with the increase.
For case two: k= 2,h =1, and the time harmonic frequency prediction formula is f s ＝|6f 1 ±50|；
(3) Let f s ＝6f 1 +50, positive inter-sequence harmonics in the full frequency band, when f 1 <At 8.3Hz, f s Is in the coupled super synchronous frequency band;
(4) let f s ＝|6f 1 -50, when 6f 1 <50Hz, i.e. f 1 <8.3Hz, the positive sequence inter-harmonic wave is obtained by the inter-harmonic wave frequency prediction formula: f (f) s ＝50-6f 1 When 6f 1 >50Hz, i.e. f 1 >8.3Hz, which is a negative sequence inter-harmonic wave, cannot cause subsynchronous oscillation of the system and should be ignored;
so when k= 2,h =1, only f 1 <8.3Hz can meet the requirement that the inter-harmonic wave is positive, and the subsynchronous oscillation of the system can be triggered.
For the inter-harmonic of the subsynchronous frequency band, when the wind speed v increases, the frequency of the inter-harmonic is reduced; for the coupled super-synchronous frequency band, as wind speed increases, the time-harmonic frequency increases.
For case three: k=1, h=2, and the time harmonic frequency prediction formula is f s ＝|3f 1 ±100|；
If the inter-harmonic is to be positive, the inter-harmonic is to be satisfied in the coupled super-synchronous frequency band: f (f) s ＝3f 1 +100; the requirement in the sub-synchronous frequency band is that: f (f) s ＝100-3f 1 Due to f 1 Generally, the frequency of the inter-harmonic wave is between 0 and 100Hz, which cannot be satisfied, so that the inter-harmonic wave cannot induce the power oscillation of the sub-synchronous frequency band and is omitted.
For case four: k= 2,h =2, and the time harmonic frequency prediction formula is f s ＝|6f 1 ±100|；
(5) Let f s ＝6f 1 +100, for the same reasons, is not in the scope of the study and is therefore omitted. Let f s ＝|6f 1 -100, when 6f 1 <100Hz, i.e. f 1 <At 16.7Hz, the positive sequence inter-harmonic wave is obtained by the inter-harmonic wave frequency prediction formula: f (f) s ＝100-6f 1 The method comprises the steps of carrying out a first treatment on the surface of the When 6f 1 >100Hz, i.e. f 1 >At 16.7Hz, the harmonic wave between negative sequences cannot induce subsynchronous oscillation of the system, soNeglecting.
So when k= 2,h =2, f 1 <16.7Hz may induce subsynchronous oscillations in the system.
In summary, the inter-harmonic frequencies that may induce subsynchronous oscillations of the system are:
Figure BDA0003468919820000131
according to the above deduction process, other specific direct-drive fan subsynchronous inter-harmonic frequency prediction formulas can be deduced continuously 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 calculated
Figure BDA0003468919820000141
Substituting the formula (11), and predicting the subsynchronous inter-harmonic frequency in the current state by measuring the change of the rotating speed in real time to obtain the distribution condition of the subsynchronous inter-harmonic frequency along with the rotating speed of the direct-driven fan under different working conditions, as shown in the formula (12).
Figure BDA0003468919820000142
In the formula (12), n g The rotating speed of the direct-drive fan; p is p g The pole pair number of the direct-drive fan is.
For example, the direct-driven fan parameter is substituted into the subsynchronous inter-harmonic frequency prediction formula (11) to obtain the distribution situation of the subsynchronous inter-harmonic frequency prediction along with the fan rotating speed shown in fig. 2, and the broken line segment in fig. 2 is the subsynchronous frequency band positive sequence inter-harmonic capable of inducing the subsynchronous oscillation of the system and the supersynchronous frequency band positive sequence inter-harmonic coupled with the subsynchronous frequency band positive sequence inter-harmonic.
Based on the same inventive concept as the first embodiment, a second embodiment provides a direct-drive fan sub-synchronous oscillation pre-judging device as shown in fig. 3, including: the construction module 21 is used for constructing a machine side converter switch function model and a network side converter switch function model of the direct-driven fan; the modulation module 22 is configured to modulate an ac voltage at a rectifier side of the direct-driven fan through a machine side converter switching function model based on a harmonic modulation technique, so as to obtain a dc voltage of the rectifier and a low-frequency harmonic frequency generated by the rectifier at the dc side; the modulation module 22 is further configured to modulate the dc voltage of the rectifier through a network side converter switching function model based on a harmonic modulation technique, obtain an ac voltage of the inverter side of the direct-driven fan, and combine the low-frequency harmonic frequency to obtain an inter-harmonic frequency generated by the inverter on the network side; the pre-judging module 23 is configured to select a target inter-harmonic from all inter-harmonics corresponding to the inter-harmonic frequencies, and predict a sub-synchronous inter-harmonic frequency that causes sub-synchronous oscillation according to the target inter-harmonic frequency, 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 BDA0003468919820000151
the network side converter switching function model is as follows:
Figure BDA0003468919820000152
wherein ,
Figure BDA0003468919820000153
for fundamental and baseband harmonic components, +.>
Figure BDA0003468919820000154
Carrier harmonic and sideband harmonic components; omega 1 ＝2πf 1 ，f 1 The fundamental frequency of the three-phase voltage of the direct-drive fan is set; omega c ＝2πf c ，f c Is the carrier frequency; p takes values of 0, 1 and-1, and corresponds to a phase, b phase and c phase of the direct-drive fan respectively; a is that 0n 、B 0n 、A mn 、B mn The amplitude coefficients of the periodic components are respectively obtained.
In a preferred embodiment, the dc voltage of the rectifier is:
Figure BDA0003468919820000155
wherein ,urx Is the alternating voltage at the rectifier side of the direct-drive fan,
Figure BDA0003468919820000156
U r0 、θ 0 the amplitude and the initial phase of the alternating voltage at the rectifier side of the direct-drive fan are respectively;
the low-frequency harmonic frequencies generated by the rectifier on the direct current side are:
Figure BDA0003468919820000157
in a preferred embodiment, the ac voltage on the inverter side of the direct drive fan is:
u gx ＝u dc S gx (17)；
the inter-harmonic frequencies generated by the inverter at the network side are:
f s ＝|3kf 1 ±hf 0 |，k，h＝{1，2，3，…} (18)；
wherein 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 (f) 0 Is the fundamental frequency of the power grid.
In a preferred embodiment, the subsynchronous inter-harmonic frequencies of the direct drive fan are:
Figure BDA0003468919820000161
/>
in summary, the embodiment of the invention has the following beneficial effects:
the method comprises the steps of constructing a machine side converter switching function model and a network side converter switching function model of a direct-driven fan, modulating alternating current voltage of a rectifier side of the direct-driven fan through the machine side converter switching function model based on a harmonic modulation technology, obtaining 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 network side converter switching function model based on a harmonic modulation technology, obtaining alternating current voltage of an inverter side of the direct-driven fan, obtaining inter-harmonic frequency generated by the inverter on the network side by combining the low-frequency harmonic frequency, selecting target inter-harmonic from all inter-harmonics corresponding to the inter-harmonic frequency, predicting sub-synchronous inter-harmonic frequency for inducing sub-synchronous oscillation according to the target inter-harmonic frequency, and judging the sub-synchronous oscillation according to the sub-synchronous inter-harmonic frequency to realize pre-judgment sub-synchronous oscillation. According to the embodiment of the invention, based on a harmonic modulation technology, the AC voltage at the rectifier side of the direct-driven fan is modulated through the machine side converter switching function model, and the DC voltage of the rectifier is modulated through the network side converter switching function model, so that the source, the characteristics and the influence factors of subsynchronous inter-harmonic waves capable of inducing subsynchronous oscillation can be analyzed in the modulation process, the inter-harmonic waves which are generated by the inverter on the network side and are incapable of inducing subsynchronous oscillation are ignored aiming at the inter-harmonic waves generated by the inverter obtained after modulation, the target inter-harmonic waves are selected from all inter-harmonic waves corresponding to the inter-harmonic waves, the subsynchronous inter-harmonic waves inducing subsynchronous oscillation are predicted according to the target inter-harmonic waves, and the subsynchronous oscillation is judged according to the subsynchronous inter-harmonic waves, so that the subsynchronous oscillation can be accurately predicted by predicting the subsynchronous inter-harmonic waves according to the converter structure of the direct-driven fan, and the stable and safe operation of a power system is ensured.
While the foregoing is directed to the preferred embodiments of the present invention, it will be appreciated by those skilled in the art that changes and modifications may be made without departing from the principles of the invention, such changes and modifications are also intended to be within the scope of the invention.
Those skilled in the art will appreciate that implementing all or part of the above-described embodiments may be accomplished by way of computer programs, which may be stored on a computer readable storage medium, which when executed may comprise the steps of the above-described embodiments. The storage medium may be a magnetic disk, an optical disk, a Read-Only Memory (ROM), a random access Memory (Random Access Memory, RAM), or the like.

Claims (8)

1. The method for prejudging the subsynchronous oscillation of the direct-drive fan is characterized by comprising the following steps of:
constructing a machine side converter switch function model and a net side converter switch function model of the direct-drive fan;
based on a harmonic modulation technology, modulating alternating current voltage at the rectifier side of the direct-driven fan through a machine side converter switching function model to obtain direct current voltage of the rectifier and low-frequency harmonic frequency generated by the rectifier at the direct current side;
based on a harmonic modulation technology, modulating the direct-current voltage of the rectifier through the network side converter switching function model to obtain alternating-current voltage of the direct-drive fan inverter side, and combining the low-frequency harmonic frequency to obtain inter-harmonic frequency generated by the inverter on the network side;
selecting a target inter-harmonic from all inter-harmonics corresponding to the inter-harmonic frequency, and predicting a subsynchronous inter-harmonic frequency for inducing subsynchronous oscillation according to the target inter-harmonic so as to judge subsynchronous oscillation according to the subsynchronous inter-harmonic frequency;
the machine side converter switching function model is as follows:
Figure FDA0004204061150000011
the network side converter switching function model is as follows:
Figure FDA0004204061150000012
wherein ,
Figure FDA0004204061150000013
for the fundamental component and the baseband harmonic component,
Figure FDA0004204061150000014
carrier harmonic and sideband harmonic components; omega 1 ＝2πf 1 ，f 1 The fundamental frequency of the three-phase voltage of the direct-drive fan is set; omega c ＝2πf c ，f c Is the carrier frequency; p takes values of 0, 1 and-1, and corresponds to a phase a, b phase and c phase of the direct-drive fan respectively; a is that 0n 、B 0n 、A mn 、B mn Amplitude coefficients of the periodic components are respectively; m and n are harmonic index variables.
2. The direct-drive fan sub-synchronous oscillation pre-judging method as claimed in claim 1, wherein the direct-current voltage of the rectifier is:
Figure FDA0004204061150000021
wherein ,urx For the ac voltage on the rectifier side of the direct drive fan,
Figure FDA0004204061150000022
U r0 、θ 0 the amplitude and the initial phase of the alternating voltage at the rectifier side of the direct-drive fan are respectively;
the low-frequency harmonic frequency generated by the rectifier on the direct current side is as follows:
Figure FDA0004204061150000023
3. the direct-drive fan subsynchronous oscillation pre-judging method of claim 2, wherein the alternating-current voltage of the direct-drive fan inverter side is:
u gx ＝u dc S gx ；
the inter-harmonic frequency generated by the inverter at the network side is as follows:
f s ＝|3kf 1 ±hf 0 |，k，h＝{1，2，3，…}；
wherein 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 (f) 0 Is the fundamental frequency of the power grid.
4. The method for pre-judging subsynchronous oscillation of a direct-drive fan according to claim 3, wherein the subsynchronous inter-harmonic frequency of the direct-drive fan is as follows:
Figure FDA0004204061150000024
5. the utility model provides a device is prejudged to synchronous vibration of direct-drive fan time which characterized in that includes:
the construction module is used for constructing a machine side converter switch function model and a network side converter switch function model of the direct-drive fan;
the modulation module is used for modulating the alternating voltage of the rectifier side of the direct-driven fan through the machine side converter switching function model based on a harmonic modulation technology to obtain the direct-current voltage of the rectifier and the low-frequency harmonic frequency generated by the rectifier on the direct-current side;
the modulation module is further used for modulating the direct-current voltage of the rectifier through the network side converter switching function model based on a harmonic modulation technology to obtain alternating-current voltage of the direct-drive fan inverter side, and combining the low-frequency harmonic frequency to obtain inter-harmonic frequency generated by the inverter on the network side;
the pre-judging module is used for selecting target inter-harmonic waves from all inter-harmonic waves corresponding to the inter-harmonic waves, and predicting subsynchronous inter-harmonic wave frequencies for inducing subsynchronous oscillation according to the target inter-harmonic waves so as to judge subsynchronous oscillation according to the subsynchronous inter-harmonic wave frequencies;
the machine side converter switching function model is as follows:
Figure FDA0004204061150000031
the network side converter switching function model is as follows:
Figure FDA0004204061150000032
wherein ,
Figure FDA0004204061150000033
for fundamental and baseband harmonic components, +.>
Figure FDA0004204061150000034
Carrier harmonic and sideband harmonic components; omega 1 ＝2πf 1 ，f 1 The fundamental frequency of the three-phase voltage of the direct-drive fan is set; omega c ＝2πf c ，f c Is the carrier frequency; p takes values of 0, 1 and-1, and corresponds to a phase a, b phase and c phase of the direct-drive fan respectively; a is that 0n 、B 0n 、A mn 、B mn Amplitude coefficients of the periodic components are respectively; m and n are harmonic index variables.
6. The direct-drive fan subsynchronous oscillation pre-judging device of claim 5, wherein the direct-current voltage of the rectifier is:
Figure FDA0004204061150000041
wherein ,urx For the ac voltage on the rectifier side of the direct drive fan,
Figure FDA0004204061150000042
U r0 、θ 0 respectively the intersection of the rectifier sides of the direct-drive fanAmplitude and initial phase of the streaming voltage;
the low-frequency harmonic frequency generated by the rectifier on the direct current side is as follows:
Figure FDA0004204061150000043
7. the direct-drive fan subsynchronous oscillation pre-judging device according to claim 6, wherein the alternating-current voltage of the direct-drive fan inverter side is:
u gx ＝u dc S gx ；
the inter-harmonic frequency generated by the inverter at the network side is as follows:
f s ＝|3kf 1 ±hf 0 |，k，h＝{1，2，3，…}；
wherein 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 (f) 0 Is the fundamental frequency of the power grid.
8. The direct-drive fan subsynchronous oscillation pre-judging device of claim 7, wherein the subsynchronous inter-harmonic frequency of the direct-drive fan is:
Figure FDA0004204061150000044
/>
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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
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

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* Cited by examiner, † Cited by third party
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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

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