CN117039931A - Direct-drive wind power alternating-current grid-connected oscillation suppression method and system - Google Patents
Direct-drive wind power alternating-current grid-connected oscillation suppression method and system Download PDFInfo
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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
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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
- H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
- H02J3/381—Dispersed generators
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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
- 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]
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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
- H02J2300/00—Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation
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- H02J2300/28—The renewable source being wind energy
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Abstract
The invention discloses a method and a system for suppressing alternating current grid-connected oscillation of direct-drive wind power, which are characterized in that three-phase filter capacitance current signals of a direct-drive wind power system to be processed and three-phase currents of grid connection points are collected, the three-phase filter capacitance current signals are subjected to transformation processing to obtain shaft components, the shaft components are subjected to enhancement processing to obtain first output quantities, the first output quantities and modulation signals are overlapped to obtain first control signals, passive control of output characteristics of the direct-drive wind power system is carried out according to the first control signals, then the three-phase currents are subjected to transformation processing to obtain amplitude values of external components of fundamental frequency, whether the sum of the amplitude values of the external components of the fundamental frequency is larger than a preset value is judged, if yes, oscillation exists in the direct-drive wind power system, after passive enhancement control is carried out on the direct-drive wind power system, oscillation suppression is carried out on the grid connection system, full-band passive frequency of the output characteristics of the wind power system can be achieved, broadband oscillation is suppressed in the wide-range change process of power network impedance, and filter resonance peaks are suppressed.
Description
Technical Field
The invention relates to the technical field of new energy power generation, in particular to a method and a system for suppressing direct-drive wind power alternating current grid-connected oscillation.
Background
With the aggravation of environmental pollution and exhaustion of fossil energy, the development of new energy is greatly promoted to be a national consensus and a national strategy, so that renewable energy will gradually take the dominant role on the energy supply side. Wind energy is a representative form of renewable energy, occupies a large proportion in the installed capacity of new energy, has rich offshore and onshore wind energy resources in China, and the length of coastline exceeds 1.8 kilometers, so wind power generation is an important mode for realizing energy transformation and deep propulsion energy revolution in China. The national world is the country with the largest development scale and the fastest development of the global wind power generation, and the large-scale development of wind power generation has become an important direction of national energy strategy development. In a wind power system, a power electronic converter is an important interface device for realizing power grid connection, machine grid decoupling, electric energy conversion and power injection. And as a large number of power electronic equipment is connected into a power grid, the strength of a wind power connection system is weakened, complex interaction is easy to generate between the power electronic converter and the power grid, and broadband oscillation phenomenon is caused.
The prior art generally introduces damping control in the control system of the power electronic converter to suppress oscillations in a specific frequency range, or introduces feedforward decoupling control to reduce coupling with the power grid, but these techniques have large limitations and cannot accommodate wide range changes in the power grid impedance. There are also techniques to connect passive or active damping devices to the grid-tie point, but this increases cost and causes power loss.
Disclosure of Invention
In order to solve the technical problems, the embodiment of the invention provides a method and a system for suppressing direct-drive wind power alternating-current grid-connected oscillation, which can realize full-band passive of the output characteristic of a wind power system, effectively suppress broadband oscillation caused by interaction between a power electronic converter and a weak current network, and suppress the resonance peak of an LCL type filter.
The first aspect of the embodiment of the invention provides a method for suppressing direct-drive wind power alternating-current grid-connected oscillation, which comprises the following steps:
collecting a three-phase filter capacitor current signal and a three-phase current of a grid-connected point of a direct-drive wind power system to be processed;
transforming the three-phase filter capacitor current signal to obtain an axis component, wherein the axis component comprises a first axis component and a second axis component;
the method comprises the steps of performing enhancement processing on a shaft component to obtain a first output quantity, and superposing the first output quantity and a modulation signal to obtain a first control signal, so that the direct-drive wind power system performs passive control on output characteristics of the direct-drive wind power system according to the first control signal;
and carrying out transformation processing on the three-phase current to obtain the amplitude of the fundamental frequency external component, judging whether the sum of the amplitudes of the fundamental frequency external component is larger than a preset value, if so, carrying out passive enhancement control on the direct-drive wind power system, and then carrying out oscillation suppression on the grid-connected system, and if not, judging that the direct-drive wind power system does not have oscillation.
According to the embodiment, a three-phase filter capacitor current signal of a direct-drive wind power system to be processed and a three-phase current of a grid-connected point are collected, the three-phase filter capacitor current signal is subjected to transformation processing to obtain an axis component, the axis component comprises a first axis component and a second axis component, enhancement processing is carried out on the axis component to obtain a first output quantity, the first output quantity and a modulation signal are overlapped to obtain a first control signal, so that the direct-drive wind power system carries out passive control of the output characteristic of the direct-drive wind power system according to the first control signal, the three-phase current is subjected to transformation processing to obtain the amplitude of an external fundamental frequency component, whether the sum of the amplitudes of the external fundamental frequency component is larger than a preset value is judged, if yes, oscillation exists in the direct-drive wind power system, and after passive enhancement control is carried out on the direct-drive wind power system, oscillation suppression is carried out on the grid-connected system. The method can realize full-band passive of the output characteristic of the wind power system, thereby inhibiting broadband oscillation and inhibiting the resonance peak of the filter in the wide-range change process of the power grid impedance.
In a possible implementation manner of the first aspect, the three-phase filter capacitor current signal is subjected to a transformation process to obtain an axis component, specifically:
and performing alpha beta transformation processing on the three-phase filter capacitance current signal to obtain an alpha beta axis component of the three-phase filter capacitance current signal, wherein the alpha beta axis component comprises an alpha axis component and a beta axis component.
In a possible implementation manner of the first aspect, after the enhancement processing is performed on the shaft component, a first output quantity is obtained, which is specifically:
the method comprises the steps of inputting an axis component as an input quantity into a first gain link for enhancement treatment to obtain a first output quantity, wherein the transfer function frequency domain expression of the first gain link is as follows:
wherein G is K1 (s) gain step 1 transfer function, K p As a proportionality coefficient of a current controller omega s For sampling angular frequency, L 1 For the side filter inductance of the converter, C f Is a filter capacitor.
In one possible implementation manner of the first aspect, after the passive enhancement control is performed on the direct-driven wind power system, oscillation suppression is performed on the grid-connected system, which specifically includes:
obtaining a current error signal, wherein the current error signal is obtained by subtracting a measurement signal of three-phase current from a reference signal of an axis component;
and processing the current error signal sequentially through a second gain link, a band-pass filter and a forward path compensation link to obtain a second output signal, and superposing the second output signal and the modulation signal to obtain second control information, so that the direct-driven wind power system enhances the full-band passivity of the output characteristic of the direct-driven wind power system according to the second control signal, and then performs oscillation suppression on the grid-connected system.
In a possible implementation manner of the first aspect, the frequency domain expression of the second gain element is:
G K2 (s)＝K R
wherein G is K2 (s) is the transfer function of the second gain element, K R Is the coefficient of the second gain element.
In one possible implementation manner of the first aspect, the frequency expression of the band-pass filter is:
wherein G is BPF (s) is a bandpass filter transfer function, K BPF Is the gain coefficient omega of the band-pass filter 1 For a first switching frequency omega 2 S is a complex variable for the second turning frequency.
In a possible implementation manner of the first aspect, the frequency domain expression of the forward path compensation link is:
wherein G is com (s) is a forward path compensation link transfer function, L 1 For the side filter inductance of the converter, C f For filtering capacitance, G K1 (s) is the transfer function of the first gain element, G d And(s) is a delay link transfer function, and s is a complex variable.
The second aspect of the embodiment of the invention provides a direct-drive wind power alternating current grid-connected oscillation suppression system, which comprises:
the acquisition module is used for acquiring three-phase filter capacitance current signals of the direct-drive wind power system to be processed and three-phase currents of grid connection points;
the first processing module is used for carrying out conversion processing on the three-phase filter capacitance current signals to obtain shaft components, wherein the shaft components comprise a first shaft component and a second shaft component;
the second processing module is used for carrying out enhancement processing on the shaft component to obtain a first output quantity, and superposing the first output quantity and the modulation signal to obtain a first control signal so that the direct-drive wind power system carries out passive control on the output characteristic of the direct-drive wind power system according to the first control signal;
the third processing module is used for carrying out conversion processing on the three-phase current to obtain the amplitude of the fundamental frequency external component, judging whether the sum of the amplitudes of the fundamental frequency external component is larger than a preset value, if so, carrying out oscillation on the direct-drive wind power system, and carrying out oscillation suppression on the grid-connected system after carrying out passive enhancement control on the direct-drive wind power system.
In a possible implementation manner of the second aspect, the three-phase filter capacitor current signal is subjected to a transformation process to obtain an axis component, specifically:
and performing alpha beta transformation processing on the three-phase filter capacitance current signal to obtain an alpha beta axis component of the three-phase filter capacitance current signal, wherein the alpha beta axis component comprises an alpha axis component and a beta axis component.
In a possible implementation manner of the second aspect, the first output quantity is obtained after the enhancement processing is performed on the shaft component, specifically:
the method comprises the steps of inputting an axis component as an input quantity into a first gain link for enhancement treatment to obtain a first output quantity, wherein the transfer function frequency domain expression of the first gain link is as follows:
wherein G is K1 (s) gain step 1 transfer function, K p As a proportionality coefficient of a current controller omega s For sampling angular frequency, L 1 For the side filter inductance of the converter, C f Is a filter capacitor.
Drawings
Fig. 1: the flow diagram of one embodiment of the direct-drive wind power alternating-current grid-connected oscillation suppression method is provided by the invention;
fig. 2: the control device schematic diagram of one embodiment of the direct-drive wind power alternating-current grid-connected oscillation suppression method is provided by the invention;
fig. 3: the control logic schematic diagram of the main control unit of one embodiment of the direct-drive wind power alternating-current grid-connected oscillation suppression method is provided by the invention;
fig. 4: the system structure schematic diagram of another embodiment of the direct-drive wind power alternating-current grid-connected oscillation suppression method is provided.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. 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.
Example 1
Referring to fig. 1, a schematic flow chart of an embodiment of a method for suppressing direct-drive wind power ac grid-connected oscillation according to an embodiment of the present invention includes steps S11 to S14, where each step is specifically as follows:
s11, collecting three-phase filter capacitance current signals and three-phase current of a grid connection point of the direct-driven wind power system to be processed.
In this embodiment, the method is used in a scenario where direct-driven wind power is integrated into a power grid through a power electronic converter, as shown in fig. 2, fig. 2 is a schematic diagram of a power circuit and a control system of a grid-connected system where direct-driven wind power is integrated into a weak power grid through a power electronic converter, where MSC is a machine side converter, GSC is a grid side converter, and L is a power circuit and control system of a grid-connected system where GSC is a grid side converter 1 Is a machine side filter inductance C f Is a filter capacitor L 2 Is a net side filter inductance, and the three-phase voltage at the PCC is v pcc The three-phase line current is i g_abc . Three-phase filter capacitor current i is collected through an alternating current sampling module c_abc As passive meansThe input signal of the module is realized. In addition, three-phase line current at a point of common coupling is collected, wherein the point of common coupling is a point at which the direct-drive wind power system is connected with a power grid, namely a point of parallel connection, and the point of parallel connection is a PCC point in FIG. 2.
S12, carrying out transformation processing on the three-phase filter capacitor current signals to obtain shaft components, wherein the shaft components comprise a first shaft component and a second shaft component.
In a preferred embodiment, the three-phase filter capacitor current signal is transformed to obtain an axis component, specifically:
and performing alpha beta transformation processing on the three-phase filter capacitance current signal to obtain an alpha beta axis component of the three-phase filter capacitance current signal, wherein the alpha beta axis component comprises an alpha axis component and a beta axis component.
In this embodiment, after the three-phase filter capacitor current signal is collected, the three-phase filter capacitor current is subjected to αβ conversion to obtain an αβ axis component of the three-phase filter capacitor current, where the αβ axis component includes an α axis component and a β axis component.
And S13, performing enhancement processing on the shaft component to obtain a first output quantity, and superposing the first output quantity and the modulation signal to obtain a first control signal so that the direct-drive wind power system performs passive control on the output characteristic of the direct-drive wind power system according to the first control signal.
In a preferred embodiment, the first output is obtained after the enhancement of the shaft component, specifically:
the method comprises the steps of inputting an axis component as an input quantity into a first gain link for enhancement treatment to obtain a first output quantity, wherein the transfer function frequency domain expression of the first gain link is as follows:
wherein G is K1 (s) gain step 1 transfer function, K p As a proportionality coefficient of a current controller omega s For sampling angular frequency, L 1 For the side filter inductance of the converter, C f Is a filter capacitor.
In this embodiment, as shown in fig. 3, the α β axis component of the three-phase filter capacitor current is used as an input quantity, and the output quantity after passing through the gain link 1 is superimposed on a modulation signal output by the current controller, so as to realize preliminary passive output characteristics of the direct-drive wind power system, and inhibit the resonance peak of the LCL filter, where the frequency domain expression of the transfer function of the gain link 1 is as follows:
wherein G is K1 (s) gain step 1 transfer function, K p As a proportionality coefficient of a current controller omega s For sampling angular frequency, L 1 For the side filter inductance of the converter, C f Is a filter capacitor.
S14, carrying out conversion treatment on the three-phase current to obtain the amplitude of the fundamental frequency external component, judging whether the sum of the amplitudes of the fundamental frequency external component is larger than a preset value, if so, carrying out passive enhancement control on the direct-drive wind power system, and then carrying out oscillation suppression on the grid-connected system.
In a preferred embodiment, after the passive enhancement control is performed on the direct-driven wind power system, the oscillation suppression is performed on the grid-connected system, specifically:
obtaining a current error signal, wherein the current error signal is obtained by subtracting a measurement signal of three-phase current from a reference signal of an axis component;
and processing the current error signal sequentially through a second gain link, a band-pass filter and a forward path compensation link to obtain a second output signal, and superposing the second output signal and the modulation signal to obtain second control information, so that the direct-driven wind power system enhances the full-band passivity of the output characteristic of the direct-driven wind power system according to the second control signal, and then performs oscillation suppression on the grid-connected system.
In a preferred embodiment, the frequency domain expression of the second gain element is:
G K2 (s)＝K R
wherein G is K2 (s) is the firstTransfer function of two gain links, K R Is the coefficient of the second gain element.
In a preferred embodiment, the frequency expression of the band pass filter is:
wherein G is BPF (s) is a bandpass filter transfer function, K BPF Is the gain coefficient omega of the band-pass filter 1 For a first switching frequency omega 2 S is a complex variable for the second turning frequency.
In a preferred embodiment, the frequency domain expression of the forward path compensation element is:
wherein G is com (s) is a forward path compensation link transfer function, L 1 For the side filter inductance of the converter, C f For filtering capacitance, G K1 (s) is the transfer function of the first gain element, G d And(s) is a delay link transfer function, and s is a complex variable.
In this embodiment, the three-phase line current at the point of common coupling is i g_abc And (3) inputting the oscillation monitoring module to perform real-time FFT operation, obtaining the amplitude of the external component of the fundamental frequency, judging whether oscillation occurs currently or not, and controlling whether to switch into the passive enhancement control according to the amplitude. When the sum of the amplitudes of the components outside the fundamental frequency exceeds a given threshold value, judging that oscillation occurs currently, and then controlling to superimpose an output signal of the passive enhancement control on a modulation signal output by the current controller.
The current error signal delta i of the current controller is input g_αβ One path is led out, and then the current error signal is sequentially input into a gain link 2, a band-pass filter and a forward path compensation link.
The gain link 2 frequency domain expression is:
G K2 (s)＝K R
wherein G is K2 (s) is the transfer function of gain element 2, K R The gain is the 2 coefficients.
The band-pass filter frequency expression is:
wherein G is BPF (s) is a bandpass filter transfer function, K BPF Is the gain coefficient omega of the band-pass filter 1 For a first switching frequency omega 2 S is a complex variable for the second turning frequency.
The forward path compensation link frequency domain expression is:
wherein G is com (s) is a forward path compensation link transfer function, L 1 For the side filter inductance of the converter, C f For filtering capacitance, G K1 (s) gain step 1 transfer function, G d And(s) is a delay link transfer function, and s is a complex variable.
And the current error signal is sequentially input into the gain link 2, the band-pass filter and the output signal after the forward path compensation link, is superimposed on the modulation signal output by the current controller according to the output of the oscillation monitoring module, so that the full-band passivity of the output characteristic of the direct-drive wind power system is enhanced, and the oscillation suppression is carried out on the grid-connected system.
It should be noted that the method is implemented only in the controller of the grid-side converter of the direct-drive wind power system, and the cost and the power loss of the extra controller and the oscillation suppression equipment are not required.
The method comprises the steps of collecting three-phase filter capacitance current signals of a direct-drive wind power system to be processed and three-phase currents of grid connection points, carrying out conversion processing on the three-phase filter capacitance current signals to obtain shaft components, carrying out enhancement processing on the shaft components to obtain first output quantity, superposing the first output quantity and modulation signals to obtain first control signals, enabling the direct-drive wind power system to carry out passive control on output characteristics of the direct-drive wind power system according to the first control signals, carrying out conversion processing on the three-phase currents to obtain amplitude values of fundamental frequency external components, judging whether the sum of the amplitude values of the fundamental frequency external components is larger than a preset value, if so, carrying out passive enhancement control on the direct-drive wind power system, and then carrying out oscillation suppression on the grid connection system.
Example two
Correspondingly, referring to fig. 4, fig. 4 is a direct-drive wind power ac grid-connected oscillation suppression system provided by the invention, as shown in the figure, the direct-drive wind power ac grid-connected oscillation suppression system includes:
the acquisition module 401 is used for acquiring a three-phase filter capacitor current signal of a direct-drive wind power system to be processed and a three-phase current of a grid-connected point;
a first processing module 402, configured to perform a transformation process on the three-phase filter capacitive current signal to obtain an axis component, where the axis component includes a first axis component and a second axis component;
the second processing module 403 is configured to perform enhancement processing on the shaft component to obtain a first output quantity, and superimpose the first output quantity and the modulation signal to obtain a first control signal, so that the direct-drive wind power system performs passive control on output characteristics of the direct-drive wind power system according to the first control signal;
and the third processing module 404 is configured to perform conversion processing on the three-phase current to obtain an amplitude of an external component of the fundamental frequency, determine whether a sum of the amplitudes of the external components of the fundamental frequency is greater than a preset value, if so, oscillate the direct-drive wind power system, and perform passive enhancement control on the direct-drive wind power system, and then perform oscillation suppression on the grid-connected system.
In a preferred embodiment, the three-phase filter capacitor current signal is transformed to obtain an axis component, specifically:
and performing alpha beta transformation processing on the three-phase filter capacitance current signal to obtain an alpha beta axis component of the three-phase filter capacitance current signal, wherein the alpha beta axis component comprises an alpha axis component and a beta axis component.
In a preferred embodiment, the first output is obtained after the enhancement of the shaft component, specifically:
the method comprises the steps of inputting an axis component as an input quantity into a first gain link for enhancement treatment to obtain a first output quantity, wherein the transfer function frequency domain expression of the first gain link is as follows:
wherein G is K1 (s) gain step 1 transfer function, K p As a proportionality coefficient of a current controller omega s For sampling angular frequency, L 1 For the side filter inductance of the converter, C f Is a filter capacitor.
In a preferred embodiment, after the passive enhancement control is performed on the direct-driven wind power system, the oscillation suppression is performed on the grid-connected system, specifically:
obtaining a current error signal, wherein the current error signal is obtained by subtracting a measurement signal of three-phase current from a reference signal of an axis component;
and processing the current error signal sequentially through a second gain link, a band-pass filter and a forward path compensation link to obtain a second output signal, and superposing the second output signal and the modulation signal to obtain second control information, so that the direct-driven wind power system enhances the full-band passivity of the output characteristic of the direct-driven wind power system according to the second control signal, and then performs oscillation suppression on the grid-connected system.
In a preferred embodiment, the frequency domain expression of the second gain element is:
G K2 (s)＝K R
wherein G is K2 (s) is the transfer function of the second gain element, and KR is the coefficient of the second gain element.
In a preferred embodiment, the frequency expression of the band pass filter is:
wherein G is BPF (s) is a bandpass filter transfer function, K BPF Is the gain coefficient omega of the band-pass filter 1 For a first switching frequency omega 2 S is a complex variable for the second turning frequency.
In a preferred embodiment, the frequency domain expression of the forward path compensation element is:
wherein G is com (s) is a forward path compensation link transfer function, L 1 For the side filter inductance of the converter, C f For filtering capacitance, G K1 (s) is the transfer function of the first gain element, G d And(s) is a delay link transfer function, and s is a complex variable.
The more detailed working principle and the step flow of this embodiment can be, but not limited to, those described in the related embodiment one.
In summary, the embodiment of the invention has the following beneficial effects:
the method comprises the steps of collecting three-phase filter capacitance current signals of a direct-drive wind power system to be processed and three-phase currents of grid connection points, carrying out conversion processing on the three-phase filter capacitance current signals to obtain shaft components, carrying out enhancement processing on the shaft components to obtain first output quantity, superposing the first output quantity and modulation signals to obtain first control signals, enabling the direct-drive wind power system to carry out passive control on output characteristics of the direct-drive wind power system according to the first control signals, carrying out conversion processing on the three-phase currents to obtain amplitude values of fundamental frequency external components, judging whether the sum of the amplitude values of the fundamental frequency external components is larger than a preset value, if so, carrying out oscillation on the direct-drive wind power system, and carrying out passive enhancement control on the direct-drive wind power system, and then carrying out oscillation suppression on the grid connection system. The method can realize full-band passive of the output characteristic of the wind power system, thereby inhibiting broadband oscillation and inhibiting the resonance peak of the filter in the wide-range change process of the power grid impedance.
The foregoing embodiments have been provided for the purpose of illustrating the general principles of the present invention, and are not to be construed as limiting the scope of the invention. It should be noted that any modifications, equivalent substitutions, improvements, etc. made by those skilled in the art without departing from the spirit and principles of the present invention are intended to be included in the scope of the present invention.
Claims (10)
1. The direct-drive wind power alternating-current grid-connected oscillation suppression method is characterized by comprising the following steps of:
collecting a three-phase filter capacitor current signal and a three-phase current of a grid-connected point of a direct-drive wind power system to be processed;
performing transformation processing on the three-phase filter capacitor current signal to obtain an axis component, wherein the axis component comprises a first axis component and a second axis component;
performing enhancement processing on the shaft component to obtain a first output quantity, and superposing the first output quantity and a modulation signal to obtain a first control signal, so that the direct-drive wind power system performs passive control on the output characteristic of the direct-drive wind power system according to the first control signal;
and carrying out conversion treatment on the three-phase current to obtain the amplitude of the fundamental frequency external component, judging whether the sum of the amplitudes of the fundamental frequency external component is larger than a preset value, if so, carrying out oscillation on the direct-drive wind power system, and carrying out passive enhancement control on the direct-drive wind power system, and then carrying out oscillation suppression on a grid-connected system.
2. The method for suppressing direct-drive wind power alternating-current grid-connected oscillation as claimed in claim 1, wherein the transforming process is performed on the three-phase filter capacitor current signal to obtain an axis component, specifically:
and performing alpha beta transformation processing on the three-phase filter capacitor current signal to obtain an alpha beta axis component of the three-phase filter capacitor current signal, wherein the alpha beta axis component comprises an alpha axis component and a beta axis component.
3. The method for suppressing direct-drive wind power alternating-current grid-connected oscillation according to claim 1, wherein the first output quantity is obtained after the enhancement treatment is performed on the axis component, specifically:
the axis component is used as an input quantity to be input into a first gain link for enhancement treatment, and then a first output quantity is obtained, wherein the transfer function frequency domain expression of the first gain link is as follows:
wherein G is K1 (s) gain step 1 transfer function, K p As a proportionality coefficient of a current controller omega s For sampling angular frequency, L 1 For the side filter inductance of the converter, C f Is a filter capacitor.
4. The method for suppressing the ac grid-connected oscillation of the direct-drive wind power system according to claim 1, wherein the method for suppressing the oscillation of the grid-connected system after the passive enhancement control of the direct-drive wind power system is performed is specifically as follows:
obtaining a current error signal, wherein the current error signal is obtained by subtracting a measurement signal of the three-phase current from a reference signal of an axis component;
and processing the current error signal sequentially through a second gain link, a band-pass filter and a forward path compensation link to obtain a second output signal, and superposing the second output signal and a modulation signal to obtain second control information, so that the direct-driven wind power system can carry out oscillation suppression on the grid-connected system after the full-band passivity of the output characteristic of the direct-driven wind power system is enhanced according to the second control signal.
5. The method for suppressing direct-drive wind power alternating-current grid-connected oscillation as set forth in claim 4, wherein the frequency domain expression of the second gain link is:
G K2 (s)＝K R
wherein G is K2 (s) is the transfer function of the second gain element, and KR is the coefficient of the second gain element.
6. The method for suppressing direct-drive wind power alternating-current grid-connected oscillation as set forth in claim 4, wherein the frequency expression of the band-pass filter is:
wherein G is BPF (s) is a bandpass filter transfer function, K BPF Is the gain coefficient omega of the band-pass filter 1 For a first switching frequency omega 2 S is a complex variable for the second turning frequency.
7. The method for suppressing direct-drive wind power alternating-current grid-connected oscillation as set forth in claim 4, wherein the frequency domain expression of the forward path compensation link is:
wherein G is com (s) is a forward path compensation link transfer function, L 1 For the side filter inductance of the converter, C f For filtering capacitance, G K1 (s) is the transfer function of the first gain element, G d And(s) is a delay link transfer function, and s is a complex variable.
8. The direct-drive wind power alternating-current grid-connected oscillation suppression system is characterized by comprising:
the acquisition module is used for acquiring three-phase filter capacitance current signals of the direct-drive wind power system to be processed and three-phase currents of grid connection points;
the first processing module is used for carrying out conversion processing on the three-phase filter capacitance current signals to obtain shaft components, and the shaft components comprise a first shaft component and a second shaft component;
the second processing module is used for carrying out enhancement processing on the shaft component to obtain a first output quantity, and superposing the first output quantity and the modulation signal to obtain a first control signal so that the direct-drive wind power system carries out passive control on the output characteristic of the direct-drive wind power system according to the first control signal;
and the third processing module is used for carrying out conversion processing on the three-phase current to obtain the amplitude of the fundamental frequency external component, judging whether the sum of the amplitudes of the fundamental frequency external component is larger than a preset value, if so, oscillating the direct-drive wind power system, and carrying out passive enhancement control on the direct-drive wind power system and then carrying out oscillation suppression on the grid-connected system.
9. The direct-drive wind power alternating current grid-connected oscillation suppression system according to claim 8, wherein the transformation processing is performed on the three-phase filter capacitor current signal to obtain an axis component, specifically:
and performing alpha beta transformation processing on the three-phase filter capacitor current signal to obtain an alpha beta axis component of the three-phase filter capacitor current signal, wherein the alpha beta axis component comprises an alpha axis component and a beta axis component.
10. The direct-drive wind power alternating current grid-connected oscillation suppression system according to claim 8, wherein after the enhancement treatment is performed on the axis component, a first output quantity is obtained, and specifically:
the axis component is used as an input quantity to be input into a first gain link for enhancement treatment, and then a first output quantity is obtained, wherein the transfer function frequency domain expression of the first gain link is as follows:
wherein the method comprises the steps of，G K1 (s) gain step 1 transfer function, K p As a proportionality coefficient of a current controller omega s For sampling angular frequency, L 1 For the side filter inductance of the converter, C f Is a filter capacitor.
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