CN111082436B - Direct-drive wind power plant oscillation suppression method and system based on phase-locked consistency - Google Patents
Direct-drive wind power plant oscillation suppression method and system based on phase-locked consistency Download PDFInfo
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Abstract
The invention relates to a direct-drive wind power plant oscillation suppression method and system based on phase locking consistency, belongs to the technical field of wind power generation systems, and solves the problem that in the prior art, because energy interaction exists among fans, subsynchronous/supersynchronous frequency oscillation divergence is increased. The method is applied to a wind power plant multi-machine system and comprises the following steps: collecting the current and/or voltage of a direct-drive wind power plant of the wind power plant multi-machine system in real time, and judging whether the direct-drive wind power plant generates subsynchronous/supersynchronous oscillation or not; if the judgment result is that the direct-drive fan phase-locked loop occurs, adjusting the voltage of the input end of the direct-drive fan phase-locked loop in the wind power plant multi-machine system to be the voltage of a grid-connected point; and the direct-drive fan phase-locked loop is connected to the outlet of the direct-drive fan. Correct and effective suppression of sub/super synchronous frequency oscillations of the direct-drive wind farm is achieved.
Description
Technical Field
The invention relates to the technical field of wind power generation systems, in particular to a direct-drive wind power plant oscillation suppression method and system based on phase-locked consistency.
Background
With large-scale grid connection of new energy such as wind power and the like, the structure and the operation characteristics of a power grid are remarkably changed, and particularly subsynchronous/supersynchronous frequency oscillation caused by the wind power is increasingly serious. In 7 months of 2015, sub/super synchronous frequency oscillation occurs when a large-scale direct-drive wind power plant in a Hami region in Xinjiang in China is connected to a weak alternating current system, so that the torsional vibration protection action of a thermal power generating unit is close to halt, and the safe operation of a power grid and the stable control of a wind power plant are seriously damaged. Therefore, how to analyze the subsynchronous/supersynchronous frequency oscillation mechanism of the wind power plant and how to inhibit the subsynchronous/supersynchronous frequency oscillation is an important problem to be solved urgently in practical engineering.
At present, relevant researches are carried out at home and abroad aiming at subsynchronous frequency oscillation of a direct-driven wind power plant, but most of the researched control parameters are not comprehensive and are only suitable for a single-machine fan system or a multi-machine aggregated fan system, and corresponding research argumentations are still lacked for the problems of influence of multiple machines of the wind power plant on the subsynchronous frequency oscillation and the vibration interaction among the multiple machines.
Disclosure of Invention
In view of the above analysis, the present invention aims to provide a direct-drive wind farm oscillation suppression method and system based on phase-locked consistency, so as to solve the problem in the prior art that sub/super synchronous frequency oscillation divergence is increased due to energy interaction between wind turbines.
The purpose of the invention is mainly realized by the following technical scheme:
on one hand, the method discloses a direct-drive wind power plant oscillation suppression method based on phase-locked consistency, which is applied to a wind power plant multi-machine system, and comprises the following steps:
collecting the current and/or voltage of a direct-drive wind power plant of the wind power plant multi-machine system in real time, and judging whether the direct-drive wind power plant generates subsynchronous/supersynchronous oscillation or not;
if the judgment result is that the direct-drive fan phase-locked loop occurs, adjusting the voltage of the input end of the direct-drive fan phase-locked loop in the wind power plant multi-machine system to be the voltage of a grid-connected point;
and the direct-drive fan phase-locked loop is connected to the outlet of the direct-drive fan.
On the basis of the scheme, the following improvements are made:
further, the method further comprises:
and if the judgment result is that the subsynchronous oscillation and the supersynchronous oscillation are finished, detecting whether the subsynchronous oscillation and the supersynchronous oscillation are finished in real time, and if the subsynchronous oscillation and the supersynchronous oscillation are finished, restoring the voltage of the input end of each direct-drive fan phase-locked loop to the voltage of the output end of the direct-drive fan connected with the phase-locked loop.
Further, the real-time collection of the current and/or voltage of the direct-drive wind power plant is as follows:
collecting current and/or voltage at a fan grid-connected point in a direct-drive wind power plant;
or,
and (3) current and/or voltage at the outlet of each direct-drive fan in the direct-drive wind power plant.
Further, the judging whether sub/super synchronous oscillation occurs in the direct-drive wind power plant includes:
and if the frequency of the acquired current and/or voltage at the grid-connected point or at the outlet of any direct-drive fan is within the subsynchronous/supersynchronous oscillation frequency range, determining that subsynchronous/supersynchronous oscillation occurs in the direct-drive wind power plant.
Further, the subsynchronous oscillation frequency range is 2.5-50Hz; the supersynchronous oscillation frequency range is 50-97.5Hz.
On the other hand, the direct-drive wind power plant oscillation suppression system based on phase locking consistency is disclosed, and is applied to a wind power plant multi-machine system, and the system comprises:
the data acquisition module is used for acquiring the current and/or voltage of a direct-drive wind power plant of the wind power plant multi-machine system in real time;
the oscillation judging module is used for receiving the data acquired by the data acquisition module and judging whether sub/super synchronous oscillation occurs in the direct-drive wind power plant;
the oscillation suppression module is used for adjusting the voltage of the input end of each direct-drive fan phase-locked loop in the wind power plant multi-machine system to be the voltage of a grid-connected point when the judgment result of the oscillation judgment module is that the direct-drive fan phase-locked loop occurs;
and the direct-drive fan phase-locked loop is connected to the outlet of the direct-drive fan.
Further, the system further comprises:
and the oscillation recovery module is used for controlling the data acquisition module and the oscillation judgment module to detect whether sub/super synchronous oscillation is finished or not in real time when the judgment result of the oscillation judgment module is that the sub/super synchronous oscillation is finished, and if the sub/super synchronous oscillation is finished, the voltage at the input end of each direct-drive fan phase-locked loop is recovered to be the voltage at the output end of the direct-drive fan connected with the phase-locked loop.
Further, the real-time collection of the current and/or voltage of the direct-drive wind power plant is as follows:
collecting current and/or voltage at a fan grid-connected point in a direct-drive wind power plant;
or,
and (3) current and/or voltage at the outlet of each direct-drive fan in the direct-drive wind power plant.
Further, in the oscillation determination module, the determining whether sub/super-synchronous oscillation occurs in the direct-drive wind farm includes:
and if the frequency of the acquired current and/or voltage at the grid-connected point or at the outlet of any direct-drive fan is within the subsynchronous/supersynchronous oscillation frequency range, determining that subsynchronous/supersynchronous oscillation occurs in the direct-drive wind power plant.
Further, the subsynchronous oscillation frequency range is 2.5-50Hz; the supersynchronous oscillation frequency range is 50-97.5Hz.
The invention has the following beneficial effects:
the direct-drive wind power plant oscillation suppression method based on phase locking consistency provided by the invention aims at the problem that when a direct-drive wind power plant is connected to a weak grid to generate subsynchronous/super-synchronous frequency oscillation, a grid-side converter has larger dynamic energy interaction among fans with different damping characteristics in the wind power plant in a traditional phase locking mode, so that subsynchronous/super-synchronous frequency oscillation is increased, the direct-drive wind power plant oscillation suppression method based on phase locking consistency is provided, and the correctness of the method is verified through an example. Compared with the traditional phase locking mode, after the phase locking consistency technology is adopted, the interaction energy between the positive damping characteristic fan and the negative damping characteristic fan is inhibited, and the obvious inhibiting effect is achieved on the subsynchronous/supersynchronous frequency oscillation of the direct-drive wind power plant.
The direct-drive wind power plant oscillation suppression system based on phase locking coincidence and the method are based on the same principle, the relevant parts can be referenced mutually, and the same technical effect can be achieved.
In the invention, the technical schemes can be combined with each other to realize more preferable combination schemes. Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
Drawings
The drawings are only for purposes of illustrating particular embodiments and are not to be construed as limiting the invention, wherein like reference numerals are used to designate like parts throughout.
FIG. 1 is a flow chart of a direct-drive wind power plant oscillation suppression method based on phase-locked consistency;
FIG. 2 is a two-machine-infinite system parametric model;
fig. 3 is a control block diagram of a grid-side converter;
FIG. 4 is a two-machine-infinite system parametric model with phase lock matching;
FIG. 5 is a comparison of wind field dissipated energy before and after a scene lock agreement;
FIG. 6 shows the voltage and current of the fan 1 before and after a scene lock phase is consistent;
FIG. 7 shows the dynamic energy of two fans in a conventional phase-locked scenario;
FIG. 8 shows the interaction dynamic energy of the two fans before and after the scene is consistent;
FIG. 9 is a comparison of wind field dissipated energy before and after a scene two phase lock is consistent;
fig. 10 shows the voltage and current of the fan 1 before and after phase locking is consistent in a scene two;
fig. 11 shows dynamic energy of two fans in a conventional phase-locking manner in scene two;
FIG. 12 shows the interactive dynamic energy of the two fans before and after the two phase locks are consistent in the scene two;
FIG. 13 is a comparison of wind field dissipated energy before and after a scene triple phase lock is consistent;
FIG. 14 shows the fan 1 voltage and current before and after the scene triple phase lock is consistent
FIG. 15 shows dynamic energy of two fans in a three-traditional-scenario phase-locked mode
FIG. 16 shows the interactive dynamic energy of the two fans before and after the three phase locks are consistent in the scene;
FIG. 17 is a schematic structural diagram of a direct-drive wind power plant oscillation suppression system based on phase-locked consistency.
Detailed Description
The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate preferred embodiments of the invention and together with the description, serve to explain the principles of the invention and not to limit the scope of the invention.
Example 1
The invention discloses a direct-drive wind power plant oscillation suppression method based on phase-locked consistency, which is applied to a wind power plant multi-machine system, and the flow chart is shown as figure 1, and comprises the following steps:
step S1: collecting the current and/or voltage of a direct-drive wind power plant of the wind power plant multi-machine system in real time, and judging whether sub/super synchronous oscillation occurs in the direct-drive wind power plant;
step S2: if the judgment result is that the direct-drive fan phase-locked loop occurs, adjusting the voltage of the input end of the direct-drive fan phase-locked loop in the wind power plant multi-machine system to be the voltage of a grid-connected point;
and the direct-drive fan phase-locked loop is connected to the outlet of the direct-drive fan.
Compared with the prior art, the direct-drive wind power plant oscillation suppression method based on phase locking consistency provided by the embodiment is provided for solving the problem that when the direct-drive wind power plant is connected to a weak grid to generate subsynchronous/supersynchronous frequency oscillation, a grid-side converter has larger dynamic energy interaction among fans with different damping characteristics in the wind power plant in a traditional phase locking mode, and subsynchronous/supersynchronous frequency oscillation is increased. Compared with the traditional phase locking mode, after the phase locking consistency technology is adopted, the interaction energy between the positive damping characteristic fan and the negative damping characteristic fan is inhibited, and the suppression effect on the secondary/super-synchronous frequency oscillation of the direct-drive wind power plant is obvious.
In the method, the direct-drive fan comprises a wind turbine, a generator, a machine side converter, a grid side converter and a grid side converter control system, wherein the wind turbine, the generator, the machine side converter and the grid side converter are sequentially connected, the specific structure of the direct-drive fan can refer to fig. 2, and the output end of the grid side converter is used as the outlet of the direct-drive fan; and the outlets of the multiple direct-drive fans are respectively connected with a reactor in series, and the other ends of the reactors are connected to form a grid-connected point, so that a direct-drive wind power plant is formed.
On the basis of the method, the method also comprises the following steps:
and step S3: and if the judgment result is that the subsynchronous oscillation and the supersynchronous oscillation are finished, detecting whether the subsynchronous oscillation and the supersynchronous oscillation are finished in real time, and if the subsynchronous oscillation and the supersynchronous oscillation are finished, restoring the voltage of the input end of each direct-drive fan phase-locked loop to the voltage of the output end of the direct-drive fan connected with the phase-locked loop.
Preferably, the real-time collection of the current and/or voltage of the direct-drive wind power plant is as follows: collecting current and/or voltage at a fan grid-connected point in a direct-drive wind power plant, or collecting current and/or voltage at an outlet of each direct-drive fan in the direct-drive wind power plant; at this time, in step S1, if the frequency of the collected current and/or voltage at the grid-connected point or at the outlet of any direct-drive fan is within the sub/super synchronous oscillation frequency range, it is determined that sub/super synchronous oscillation occurs in the direct-drive wind farm.
Preferably, the present implementation also gives a sub/super-synchronous oscillation frequency range, so that the skilled person can perform the above-mentioned determination process according to the frequency range: the subsynchronous oscillation frequency range is 2.5-50Hz; the supersynchronous oscillation frequency range is 50-97.5Hz.
The adjustment process of step S2 in this embodiment is obtained based on the following analysis:
1. establishing a multi-machine dynamic energy model considering a phase-locked loop and a grid-side converter:
in the process of establishing a multi-machine dynamic energy model, an actual physical model which is taken as the basis of the analysis needs to be considered, and the actual physical model comprises the following steps: a multi-machine-infinite system parameter model and a network side converter control model;
in this embodiment, taking a two-machine-infinite system parameter model as an example, the following analysis is performed: as shown in fig. 2, in the two-machine-infinite system parameter model, the model of the fan 1 is different from that of the fan 2, the line reactance of the grid-connected point is also different, the same grid-connected point PCC is connected, and the infinite power grid is connected through a section of transmission line. The wind turbine Generator system comprises a PMSG (Permanent Magnet Synchronous Generator) and a VSC (voltage source Converter), wherein the PMSG (Permanent Magnet Synchronous Generator) represents a Generator connected with a wind turbine, the VSC represents a machine Side Converter, the GSC (Grid Side Converter) represents a Grid Side Converter, and the PLL (Phase-locked loop) represents a Phase-locked loop;
the two-machine-infinite system parametric model port (referred to as a fan port) voltage equation can be expressed as:
u d1 ＝u dPCC -X 1 i q1 (1)
u q1 ＝u qPCC +X 1 i d1 (2)
u d2 ＝u dPCC -X 2 i q2 (3)
u q2 ＝u qPCC +X 2 i d2 (4)
from equations (1) to (4), equations (5), (6) can be derived:
u q1 ＝u q2 -X 2 i d2 +X 1 i d1 (5)
u d1 ＝u d2 +X 2 i q2 -X 1 i q1 (6)
in the formula: u. of d1 、u q1 、i d1 、i q1 Respectively representing the voltage and the current of a port of the fan 1 on a d axis and a q axis; u. of d2 、u q2 、i d2 、i q2 Respectively representing the voltage and the current of a port of the fan 2 on a d axis and a q axis; u. of dPCC 、u qPCC Respectively representing the voltages of the grid-connected point PCC on the d axis and the q axis; x 1 、X 2 Respectively showing the line reactance of the fan 1 and the fan 2 connected to the PCC of the grid-connected point.
Fig. 3 is a block diagram of the grid-side converter control model. The output voltage of the grid-side converter control model may be expressed as (where the output voltage is the output voltage of the grid-side converter GSC, which is also the port voltage of the two-machine-infinite system parameter model):
in the formula: k p 、K i The proportion and the integral coefficient of the current inner ring of the system are respectively controlled by the grid-side converter;
d-axis and q-axis current reference values of a grid-side converter control system are respectively set; omega is the voltage angular frequency of the PCC of the grid-connected point; l is induction reactance of the incoming line reactor; e g Is the voltage amplitude of the point-on-grid PCC.
Through the above analysis, the multi-machine dynamic energy model can be expressed as:
W＝W 1 +W 2 (9)
in the formula: w represents a multi-machine dynamic energy flow, W 1 And W 2 Grid-side converter outlet representing a fan 1 and a fan 2A dynamic energy flow is processed.
Wherein, the dynamic energy flow at the outlet of the wind turbine grid-side converter can be expressed as:
in the formula: p e Is the active power of the fan port, theta is the power angle of the fan port, W p ＝∫P e d theta represents the dynamic energy flow of the port at the outlet of the converter corresponding to the active power of the fan, W q ＝∫(i d du q -i q du d ) A port dynamic energy flow at the outlet of the converter corresponding to the reactive power of the direct-drive wind turbine generator set; subscripts 1, 2 denote the fan 1 and fan 2 grid-side converter outlets, respectively.
2. Extracting non-periodic variation components in the dynamic energy flow, defining the non-periodic variation components as dissipated energy, analyzing key factors influencing the magnitude of the dissipated energy, solving the condition of the minimum value of the dissipated energy, and providing a direct-drive wind power plant oscillation suppression method based on phase locking consistency according to the condition.
In the above process, the following steps may be specifically included:
(1): non-periodic components in the dynamic energy flow are extracted to dissipate energy.
When the single oscillation mode subsynchronous/supersynchronous frequency oscillation of the direct-driven wind power plant occurs, the three-phase current output by the grid-side converter comprises a fundamental current component, a subsynchronous/supersynchronous frequency current component and a supersynchronous current component, and then the phase voltage u of the A phase is connected with the voltage u of the A phase a Current i a Can be expressed as:
in the formula: subscripts 0, -and + denote fundamental, sub/super sync frequency, and super sync, respectively;u 0 、i 0 the amplitude of the fundamental voltage and current component; u. of _ 、i _ The amplitude values of sub/super synchronous frequency voltage and current components; u. of + 、i + The amplitude of the super-synchronous voltage and current components; omega 0 、ω - And omega + Fundamental, subsynchronous and supersynchronous voltage angular frequencies, respectively;
is an initial phase angle.
The relation between the phase angle theta input by the phase-locked loop and the phase angle theta' output by the phase-locked loop to the current inner loop control module is as follows:
θ′＝θ+Δθ PLL (13)
in the formula,
a and ^ B disturbance components generated for phase-locked loop not to fully track power grid phase information>
Respectively disturbance angle delta theta of phase-locked loop PLL Amplitude and initial phase of (d); omega σ ＝ω 0 -ω - Wherein, ω is 0 Representing the voltage fundamental angular frequency output by the grid-side converter; omega s Representing the subsynchronous voltage angular frequency output by the grid-side converter;
disturbance angle delta theta of phase-locked loop PLL The value of (A) is small, and can be simplified to cos (delta theta) in practical calculation PLL )≈1、sin(Δθ PLL )≈Δθ PLL 。
The transformation matrix for transforming the power grid abc coordinate system into the grid-side converter dq coordinate system is as follows:
the fan port voltage current when considering that the phase locked loop cannot track completely can be expressed as:
substituting the current-voltage formula into the dynamic energy formula obtained in the step 1, and extracting the non-periodic component of the dynamic energy formula as the fan dissipated energy W hq1 Comprises the following steps:
in the formula,
ω σ ＝ω 0 -ω - ＝ω + -ω 0 ；Δα u- ＝α u2- -α u1- the phase angle difference of the phase-locked angular frequency/super-synchronous frequency components of the fan 2 and the fan 1 is obtained; delta alpha u+ ＝α u2+ -α u1+ The phase-locked angle super-synchronous frequency component phase angle difference of the fan 2 and the fan 1 is obtained;
Δβ＝β 2 -β 1 Is the disturbance angle delta theta of the phase-locked loop of the fan 2 and the fan 1 PLL Phase angle β of (a).
Port dynamic energy W corresponding to active power of direct-drive wind turbine generator in formula p1 Due to W p1 Active power P in e1 Determined by the wind speed, so W hp1 Phase-locked loop angle and disturbance angle delta theta of phase-locked loop PLL Is independent of the phase angle. Its corresponding dissipationThe energy may be represented as W hp1 。
Similarly, the dissipation energy W corresponding to the reactive power at the outlet of the grid-side converter of the fan 2 can be obtained hq2 Dissipated energy W corresponding to active power hp2 . Wherein, W hq2 Comprises the following steps:
in the formula,
the total dissipated energy of the two-machine-infinity system is then:
W h ＝(W hq1 +W hq2 )+(W hp1 +W hp2 ) (19)
in the formula, W hp1 、W hp2 Independent of the phase angle of the phase-locked loop and the phase angle beta of the disturbance angle of the phase-locked loop.
(2): key factors influencing the size of the dissipated energy are analyzed, the condition of the minimum value of the dissipated energy is solved, and a direct-drive wind power plant oscillation suppression method based on phase locking consistency is provided according to the condition.
The dissipation energy generated during the subsynchronous/supersynchronous frequency oscillation of the system represents the variation trend of the dynamic energy, and the smaller the dissipation energy is, the more beneficial the oscillation suppression is. Because the two fans are connected into the grid-connected point and the line reactance is different (namely X) 1 ≠X 2 ) The voltage phase angles at the outlets of the grid-side converters of the fan 1 and the fan 2 generate a phase difference (namely delta alpha) u- ＝α u2- -α u1- ≠0Δα u+ ＝α u2+ -α u1+ Not equal to 0); and because the two fans use two phase-locked loops, the performances of the two phase-locked loops are not completely consistent, and the phase angle difference of the dynamic angles of the two phase-locked loops is not equal to zero (namely delta beta = beta) 2 -β 1 ≠0)。Δα u- 、Δα u+ And the sum delta beta is not equal to zero, and the total dissipated energy is greatly influenced by the sum delta beta, so that the stable region of the system during subsynchronous/supersynchronous frequency oscillation is influenced.
W h Is Δ α u- 、Δα u+ And Δ β, which can be expressed as a function W h (Δα u- ，Δα u+ Δ β), respectively, for Δ α u- 、Δα u+ And Δ β derivation can give:
in the formula,
order to
Calculating a function W h The only stagnation points of (c) are: (Delta alpha) u- ,Δα u+ Delta beta) = (0, 0), and a Hessian array [ H ] of the extremum of the ternary function is established]：
｜H｜＝∫2B 3 A 1 A 2 (2+A 1 A 2 )u 1- u 2- u 1+ u 2+ (u 1+ u 2+ -u 1- u 2- )dt (30)
In the subsynchronous/supersynchronous frequency oscillation of the direct-drive wind power plant, the supersynchronous voltage is always greater than the subsynchronous/supersynchronous frequency voltage, so u 1+ u 2+ -u 1- u 2- > 0, such that | H | in the formula > 0. And because
Total dissipated energy W of system h (Δα u- ，Δα u+ Δ β) at a point (Δ α) u- ，Δα u+ And delta beta) = (0, 0) to obtain a minimum value, and the suppression effect of direct-drive wind power plant/super-synchronous frequency oscillation is optimal. Therefore, a direct-drive wind power plant subsynchronous/supersynchronous frequency oscillation suppression method based on phase-locked consistency is provided.
Fig. 4 shows a two-machine-infinity system for a direct-drive wind farm with consistent phase lock. Adopting a grid-connected point phase-locked consistency technology, namely: phase-locked loops are installed at a grid-connected point (point PCC) of the wind power plant, and phase angles of the phase-locked loops are taken as reference phase angles by the control systems of the converters on the grid sides of the two fans.
Based on the phase-locked coherent technique, the fan port current voltage can be expressed as:
based on the phase-locked coincidence technology, the extracted dissipation energy is as follows:
fans in the wind field adopt phase-locked loop phase angles of the same grid-connected point (point PCC), and dissipation energy corresponding to active power of the two fans is not influenced; the total dissipated energy of the two-machine-infinity system is then:
W′ h ＝(W′ hq1 +W′ hq2 )+(W hp1 +W hp2 ) (37)
by contrast, after the wind field adopts the phase-locked coincidence technology, the interactive energy dynamically generated by different fan phase angle differences and phase-locked angles in the dissipated energy of the fans is inhibited, and the total dissipated energy of the wind field is reduced, so that subsynchronous/supersynchronous frequency oscillation of the wind field is inhibited.
Example 2
This embodiment is a time domain simulation verification process: in this embodiment, according to the above method, dynamic energy and dissipation energy are obtained to verify the correctness of the theory. In practical application, dissipation energy does not need to be required, only the oscillation is needed to be judged, and if the oscillation occurs, an oscillation suppression measure is adopted, namely, the phase-locked loop control strategy is adjusted to be consistent with phase locking.
A two-machine-infinite system parametric model as shown in fig. 2. Without loss of generality, the output of the fan 1 is set to be greater than that of the fan 2 in the simulation, and the reactance of the two fans connected to the grid-connected point lines is unequal. The parameters are shown in table 1:
table 1 direct-drive fan access weak current grid system main parameters
The time domain simulation verification process sets simulation verification of three oscillation scenes: oscillation divergence, constant amplitude oscillation, and oscillation divergence.
When the two-machine-infinite system uses the traditional phase locking mode, subsynchronous/supersynchronous frequency oscillation divergence (constant amplitude oscillation or oscillation divergence) occurs in a certain operation state, and the operation state of the system is measured; and under the same primary/super-synchronous frequency oscillation, switching the phase locking mode at 3 seconds to make the phase locking of the grid-connected point consistent, and measuring the running state of the system at the moment.
In fig. 5 to 16, wind1 and Wind2 denote a fan 1 and a fan 2; PLLdiff denotes a conventional phase-locked manner, and PLLsame denotes using a phase-locked coincidence technique.
Scene one: as can be seen from fig. 5, before the phase-lock is consistent, the dissipated energy curve is a concave curve, the dissipated energy is continuously increased, and the oscillation is gradually increased; after the phase locking is consistent, the dissipation energy curve is a convex curve, the dissipation energy is increased and reduced gradually, and the oscillation is converged gradually. After the phase locking is consistent, the wind field dissipation energy is smaller than that of the traditional phase locking mode, and subsynchronous/supersynchronous frequency oscillation is restrained. As can be seen from fig. 6, before the phase-lock is consistent, the fan 1 oscillates and diverges; after the phase locking is consistent, the fan 1 gradually converges; the phase-locked phase has obvious inhibition effect on subsynchronous/super-synchronous frequency oscillation.
As can be seen from fig. 7, in this operating state, when the direct-drive wind farm is connected to the weak grid and has sub/super synchronous frequency oscillation, the fan 1 emits dynamic energy, and the fan 2 absorbs the dynamic energy, and a large energy interaction exists between the two fans; the fan 1 is represented as a positive damping unit, the fan 2 is represented as a negative damping unit, and the oscillation condition of the fan in the wind field is very complex. As can be seen from fig. 8, before the phase-lock is consistent, the dynamic energy interaction between the fans is continuously increased; after the phase locking is consistent, the interaction energy between the fans is very small, and the boosting effect of the fan energy flow in the field is inhibited.
Scene two: as can be seen from fig. 9, before the phase locking is consistent, the dissipation energy curve of the wind farm is a straight line, dissipation energy is continuously emitted, and the sub/super synchronous frequency oscillation occurs in the system; after the phase locking is consistent, the dissipation energy is a concave curve, the dissipation energy is smaller than that of the traditional phase locking, and the system stability is higher. As can be seen from fig. 10, before the phase-locking is consistent, the wind farm generates constant amplitude oscillation, and after the phase-locking is consistent, the wind farm/super-synchronous oscillation converges, and the system operation gradually stabilizes.
As can be seen from fig. 11 and 12, after the phase locking is consistent, the dynamic energy of the two fans is positive, and there is no interaction energy between the two fans.
Scene three: as can be seen from fig. 13, before and after the phase locking is consistent, the dissipated energy curve of the wind field is a convex curve, and the system tends to be stable; as can be seen from fig. 14, in this scenario, the wind field has subsynchronous/supersynchronous frequency oscillation and the oscillation converges; after the phase locking is consistent, the wind field oscillation is converged, the oscillation intensity is weakened, and the convergence speed is obviously accelerated. And after the phase locking is consistent, the dissipation energy is smaller than that of the traditional phase locking, and the system stability is better. As shown in fig. 15, in the conventional phase-locked mode, both fans emit dynamic energy, and no dynamic energy interaction exists in the field; as shown in fig. 16, after the phase locking is consistent, there is no energy interaction between the fans, and the dynamic energy emitted is reduced, and the oscillation intensity is obviously weakened.
Therefore, compared with the traditional phase locking technology, the phase locking consistency technology is adopted, the dissipated energy curve generated after the subsynchronous/supersynchronous frequency oscillation of the system is changed from a convex curve to a concave curve, the magnitude of the curve is obviously reduced, and the stability margin of the system is increased; the interaction energy between the positive damping characteristic fan and the negative damping characteristic fan is inhibited, the dynamic energy emitted by the wind field is obviously reduced, and the oscillation strength is weakened; the wind power plant changes oscillation divergence into oscillation convergence, and has obvious suppression effect on subsynchronous/supersynchronous frequency oscillation of a direct-drive wind power plant.
Example 3
In embodiment 3 of the present invention, a direct-drive wind farm oscillation suppression system based on phase-locked consistency is disclosed, a schematic structural diagram is shown in fig. 17, and the system is applied to a wind farm multi-machine system, and the system includes the following modules:
the data acquisition module is used for acquiring the current and/or voltage of a direct-drive wind power plant of the wind power plant multi-machine system in real time; the oscillation judging module is used for receiving the data acquired by the data acquisition module and judging whether sub/super synchronous oscillation occurs in the direct-drive wind power plant; the oscillation suppression module is used for adjusting the voltage of the input end of each direct-drive fan phase-locked loop in the wind power plant multi-machine system to be the voltage of a grid-connected point when the judgment result of the oscillation judgment module is that the direct-drive fan phase-locked loop occurs; and the direct-drive fan phase-locked loop is connected to the outlet of the direct-drive fan.
Preferably, the system further comprises: and the oscillation recovery module is used for controlling the data acquisition module and the oscillation judgment module to detect whether the subsynchronous/supersynchronous oscillation is finished or not in real time when the judgment result of the oscillation judgment module is that the subsynchronous/supersynchronous oscillation is finished, and if the subsynchronous/supersynchronous oscillation is finished, the voltage at the input end of each direct-drive fan phase-locked loop is recovered to be the voltage at the output end of the direct-drive fan connected with the phase-locked loop.
The method embodiment and the system embodiment are based on the same principle, and related parts can be referenced mutually, and the same technical effect can be achieved.
Those skilled in the art will appreciate that all or part of the flow of the method implementing the above embodiments may be implemented by a computer program, which is stored in a computer readable storage medium, to instruct related hardware. The computer readable storage medium is a magnetic disk, an optical disk, a read-only memory or a random access memory, etc.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention.
Claims (6)
1. A direct-drive wind power plant oscillation suppression method based on phase locking consistency is applied to a wind power plant multi-machine system, and is characterized by comprising the following steps:
taking the output end of a grid-side converter in the direct-drive fan as the outlet of the direct-drive fan, and connecting a direct-drive fan phase-locked loop to the outlet of the direct-drive fan;
collecting the current and/or voltage of a direct-drive wind power plant of the wind power plant multi-machine system in real time, and judging whether sub/super synchronous oscillation occurs in the direct-drive wind power plant; the real-time acquisition of the current and/or voltage of the direct-drive wind power plant is as follows: the current and/or voltage at a fan grid-connected point in the direct-drive wind power plant; or the current and/or the voltage at the outlet of each direct-drive fan in the direct-drive wind power plant;
if the judgment result is that the direct-drive fan phase-locked loop is in the grid-connected point, adjusting the voltage of the input end of the direct-drive fan phase-locked loop in the wind power plant multi-machine system to be the voltage of the grid-connected point, and enabling the phase-locked loop control strategy to be consistent in phase locking;
the method further comprises the following steps:
and if the judgment result is that the secondary/super-synchronous oscillation is finished, detecting whether the secondary/super-synchronous oscillation is finished or not in real time, and if the secondary/super-synchronous oscillation is finished, restoring the voltage of the input end of each direct-drive fan phase-locked loop to the voltage of the output end of the direct-drive fan connected with the phase-locked loop.
2. The direct-drive wind power plant oscillation suppression method based on phase locking consistency according to claim 1, wherein the step of judging whether the direct-drive wind power plant has subsynchronous/supersynchronous oscillation comprises the following steps:
and if the frequency of the acquired current and/or voltage at the grid-connected point or at the outlet of any direct-drive fan is within the subsynchronous/supersynchronous oscillation frequency range, determining that subsynchronous/supersynchronous oscillation occurs in the direct-drive wind power plant.
3. The direct-drive wind power plant oscillation suppression method based on phase locking coincidence as recited in claim 2, wherein the subsynchronous oscillation frequency range is 2.5-50Hz; the supersynchronous oscillation frequency range is 50-97.5Hz.
4. A direct-drive wind power plant oscillation suppression system based on phase locking consistency is applied to a wind power plant multi-machine system, and is characterized in that the system comprises:
taking the output end of a grid-side converter in the direct-drive fan as the outlet of the direct-drive fan, and connecting a direct-drive fan phase-locked loop to the outlet of the direct-drive fan;
the data acquisition module is used for acquiring the current and/or voltage of a direct-drive wind power plant of the wind power plant multi-machine system in real time; the real-time acquisition of the current and/or voltage of the direct-drive wind power plant is as follows: the current and/or voltage at a fan grid-connected point in the direct-driven wind power plant; or the current and/or the voltage at the outlet of each direct-drive fan in the direct-drive wind power plant;
the oscillation judging module is used for receiving the data acquired by the data acquisition module and judging whether sub/super synchronous oscillation occurs in the direct-drive wind power plant;
the oscillation suppression module is used for adjusting the voltage of the input end of each direct-drive fan phase-locked loop in the wind power plant multi-machine system to be the voltage of a grid-connected point when the judgment result of the oscillation judgment module is that the direct-drive fan phase-locked loops occur, so that the phase-locked loops are consistent in control strategy;
the system further comprises:
and the oscillation recovery module is used for controlling the data acquisition module and the oscillation judgment module to detect whether sub/super synchronous oscillation is finished or not in real time when the judgment result of the oscillation judgment module is that the sub/super synchronous oscillation is finished, and if the sub/super synchronous oscillation is finished, the voltage at the input end of each direct-drive fan phase-locked loop is recovered to be the voltage at the output end of the direct-drive fan connected with the phase-locked loop.
5. The phase-locked consistency-based direct-drive wind power plant oscillation suppression system according to claim 4, wherein in the oscillation judgment module, the judgment of whether the direct-drive wind power plant has sub/super synchronous oscillation comprises:
and if the frequency of the acquired current and/or voltage at the grid-connected point or at the outlet of any direct-drive fan is within the subsynchronous/supersynchronous oscillation frequency range, determining that subsynchronous/supersynchronous oscillation occurs in the direct-drive wind power plant.
6. The phase-locked coherence based direct-drive wind farm oscillation suppression system according to claim 5, wherein the subsynchronous oscillation frequency range is 2.5-50Hz; the supersynchronous oscillation frequency range is 50-97.5Hz.
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| CN114759594B (en) * | 2021-11-16 | 2024-08-06 | 华北电力大学 | Direct-drive wind farm stability assessment method and system considering interaction between machines |
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| CN105515020A (en) * | 2016-01-19 | 2016-04-20 | 思源清能电气电子有限公司 | Sub-synchronous oscillation suppression control method and system based on SVG |
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