CN107181267A - Wind power plant subsynchronous resonance suppressing method and system - Google Patents

Abstract

The invention discloses a method and system for suppressing subsynchronous resonance of a wind farm. The wind farm at least includes: multiple wind turbines, multiple transformers, and wind farm lines, and is characterized in that it includes: acquiring voltage signals and current signals of the wind farm lines , the resistance and inductance of multiple wind turbines, the resistance and inductance of multiple transformers, the resistance and inductance of the wind farm line, and the sub-synchronous suppression system actually output the current signal to the grid; the voltage signal of the wind farm line and the current signal of the wind farm line filter processing, obtain the sub-synchronous frequency signal, and obtain the closed-loop transfer function of the wind farm according to the sub-synchronous frequency signal, the resistance and inductance of multiple wind turbines, the resistance and inductance of multiple transformers, the line resistance and inductance of the wind farm, and according to the The subsynchronous suppression system actually outputs current signals to the grid, and the attenuation rate at different zero points of the closed-loop transfer function is optimized by optimizing parameters. The invention can effectively improve the stability of the wind farm.

Description

Wind power field subsynchronous resonance suppression method and system

technical field

The invention relates to the technical field of power systems, in particular to a subsynchronous resonance suppression method and system for a wind farm.

Background technique

When wind farms are connected to systems with fixed series compensation capacitors, there may be a risk of inducing subsynchronous resonance (SSR). In recent years, there have been many accidents related to fan subsynchronous oscillation at home and abroad. In 2009, a wind farm in Texas, USA, due to a fault in the power transmission system, part of the line was cut off, which increased the series compensation from 50% to 75%, resulting in subsynchronous oscillations in the wind farm, resulting in damage to a large number of wind turbines .

In related technologies, the method of suppressing the subsynchronous resonance of the wind farm is mainly to change the internal control system of the wind turbine, and increase the damping of the electromagnetic torque of the wind turbine to the subsynchronous oscillation through additional damping control; or withdraw the series compensation capacitor during the subsynchronous resonance of the system, Change the series compensation degree of the system to achieve the purpose of suppressing subsynchronous resonance. However, these methods are complex and economical.

Contents of the invention

The present invention aims at solving one of the technical problems in the related art mentioned above at least to a certain extent.

Therefore, an object of the present invention is to propose a subsynchronous resonance suppression method for a wind farm. The subsynchronous resonance suppression method of the wind farm can achieve the purpose of suppressing the subsynchronous resonance and improve the stability of the wind farm.

Another object of the present invention is to propose a subsynchronous resonance suppression system for a wind farm.

In order to achieve the above object, one aspect of the present invention discloses a method for suppressing subsynchronous resonance of a wind farm, the wind farm at least includes: multiple wind turbines, multiple transformers and wind farm lines, characterized in that it includes: obtaining wind farm lines The voltage signal and current signal, the resistance and inductance of multiple wind turbines, the resistance and inductance of multiple transformers, the resistance and inductance of the wind farm line, and the actual output current signal of the sub-synchronous suppression system to the grid; the voltage signal of the wind farm line and the wind power The current signal of the field line is filtered to obtain the sub-synchronous frequency signal, and according to the sub-synchronous frequency signal, the resistance and inductance of multiple wind turbines, the resistance and inductance of multiple transformers, the resistance and inductance of the wind farm line, the closed-loop transmission of the wind farm is obtained function, and according to the actual output current signal of the subsynchronous suppression system to the power grid, the attenuation rate at different zero points of the closed-loop transfer function is optimized by optimizing the parameters.

According to the sub-synchronous resonance suppression method of the wind farm of the present invention, the purpose of suppressing the sub-synchronous resonance can be achieved, and the stability of the wind farm can be improved.

In addition, the wind farm subsynchronous resonance suppression method according to the above-mentioned embodiments of the present invention may also have the following additional technical features:

Further, the formula of the closed-loop transfer function of the wind farm is:

Among them, s represents the complex frequency, z _h is the g zero points of the closed-loop transfer function Z _eq (s), y _q is the p poles of the closed-loop transfer function Z _eq (s), H _i (s) and H _u (s) are the transfer functions for processing the current signal of the wind farm line and the voltage signal of the wind farm line, respectively, r _r0 is the rotor resistance, K _pr is the proportional coefficient of the inner loop of the rotor side controller, K _lr is the integral coefficient of the inner loop of the rotor side controller, K _Dr is the cross gain of the inner loop of the rotor side controller, ω ₀ is the power frequency angular frequency, ω _r is the rotor angular frequency, L _r is the rotor inductance, L _m is the fan excitation inductance, L _s is the fan stator inductance, L _T1 is the inductance of the transformer T1, L _l1 is the wind farm line inductance, r _s is the stator resistance, r _T1 is the transformer T1 resistance, r _l1 is the wind farm line resistance, L _l2 is the series compensation line inductance, L _T2 is the transformer T2 inductance, r _l2 is the series compensation line resistance, r _T2 is the transformer T2 resistance, C is the series compensation capacitor, n is the number of fans.

Further, by optimizing the parameters, the optimal attenuation rate under different zero points of the transfer function is specifically:

Optimizing the current signal gain K _i , the current signal phase shift parameter _Tai , the voltage signal gain K _u , the voltage signal phase shift parameter T _au , and when z _h =σ _h +jω _h , σ _h is the real part of the zero point z _h , ω _h is the imaginary part of the zero point z _h , the attenuation rate ξ _{h of the mode ω h :}

The decay rate ξ _h satisfies:

Objective function: max f=min(ξ _h )

Restrictions:

pu: standard unit, n _TOT : the maximum number of fans.

The second aspect of the present invention discloses a subsynchronous resonance suppression system for a wind farm, where the wind farm at least includes: multiple wind turbines, multiple transformers, and wind farm lines, including: an acquisition module for acquiring voltage signals of the wind farm lines and current signal, resistance and inductance of multiple wind turbines, resistance and inductance of multiple transformers, resistance and inductance of wind farm line, and subsynchronous suppression system actually output current signal to the grid; processing module is used to process the voltage signal of the wind farm line Filtering and processing the current signal of the wind farm line to obtain the sub-synchronous frequency signal, and according to the sub-synchronous frequency signal, the resistance and inductance of multiple wind turbines, the resistance and inductance of multiple transformers, the resistance and inductance of the line of the wind farm, the wind farm The closed-loop transfer function, and according to the actual output current signal of the sub-synchronous suppression system to the power grid, the attenuation rate at different zero points of the closed-loop transfer function is optimized by optimizing parameters.

According to the wind farm subsynchronous resonance suppression system of the present invention, the purpose of suppressing subsynchronous resonance can be achieved, and the stability of the wind farm can be improved.

In addition, the wind farm subsynchronous resonance suppression system according to the above-mentioned embodiments of the present invention may also have the following additional technical features:

Further, the formula of the closed-loop transfer function of the wind farm is:

Among them, s represents the complex frequency, z _h is the g zero points of the closed-loop transfer function Z _eq (s), y _q is the p poles of the closed-loop transfer function Z _eq (s), H _i (s) and H _u (s) are the transfer functions for processing the current signal of the wind farm line and the voltage signal of the wind farm line, respectively, r _r0 is the rotor resistance, K _pr is the proportional coefficient of the inner loop of the rotor side controller, K _lr is the integral coefficient of the inner loop of the rotor side controller, K _Dr is the cross gain of the inner loop of the rotor side controller, ω ₀ is the power frequency angular frequency, ω _r is the rotor angular frequency, L _r is the rotor inductance, L _m is the fan excitation inductance, L _s is the fan stator inductance, L _T1 is the inductance of the transformer T1, L _l1 is the wind farm line inductance, r _s is the stator resistance, r _T1 is the transformer T1 resistance, r _l1 is the wind farm line resistance, L _l2 is the series compensation line inductance, L _T2 is the transformer T2 inductance, r _l2 is the series compensation line resistance, r _T2 is the transformer T2 resistance, C is the series compensation capacitor, n is the number of fans.

Further, by optimizing the parameters, the optimal attenuation rate under different zero points of the transfer function is specifically: optimizing the current signal gain K _i , the current signal phase shift parameter _Tai , the voltage signal gain K _u , the voltage signal phase shift parameter T _au , And when z _h ＝σ _h +jω _h , σ _h is the real part of the zero point z _h , ω _h is the imaginary part of the zero point z _h , the attenuation rate ξ _{h of the mode ω h :}

The decay rate ξ _h satisfies:

Objective function: max f=min(ξ _h )

Restrictions:

pu: standard unit, n _TOT : the maximum number of fans.

Further, it also includes: power electronic converter and transformer.

Additional aspects 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.

Description of drawings

The above and/or additional aspects and advantages of the present invention will become apparent and comprehensible from the description of the embodiments in conjunction with the following drawings, wherein:

Fig. 1 is the flow chart of the subsynchronous resonance suppressing method of wind farm according to one embodiment of the present invention;

Fig. 2 is a structural diagram of a wind farm access series compensation system according to an embodiment of the present invention;

Fig. 3 is a strategy diagram of a wind farm subsynchronous resonance suppression method according to an embodiment of the present invention;

Fig. 4 is a structural block diagram of a subsynchronous resonance suppression system for a wind farm according to an embodiment of the present invention.

detailed description

Embodiments of the present invention are described in detail below, examples of which are shown in the drawings, wherein the same or similar reference numerals designate the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by referring to the figures are exemplary only for explaining the present invention and should not be construed as limiting the present invention.

The subsynchronous resonance suppression method and subsynchronous resonance suppression system of a wind farm according to the embodiments of the present invention will be described below with reference to the accompanying drawings.

Fig. 1 is a flowchart of a subsynchronous resonance suppression method for a wind farm according to an embodiment of the present invention.

Before describing this method, as shown in FIG. 2 , the wind farm at least includes: multiple wind turbines, multiple transformers and wind farm lines. The wind farm subsynchronous resonance suppression method is implemented in the wind farm system.

As shown in Figure 1, the subsynchronous resonance suppression method for wind farms according to an embodiment of the present invention includes:

S110: Obtain the voltage signal and current signal of the wind farm line, the resistance and inductance of multiple wind turbines, the resistance and inductance of multiple transformers, the resistance and inductance of the wind farm line, and the actual output current signal of the subsynchronous suppression system to the grid.

As shown in Fig. 2, the voltage signal u _abc of the wind farm line and the current signal i _abc of the wind farm line are obtained, and the subsynchronous suppression system actually outputs the current signal i _out to the grid.

S120: Filter the voltage signal of the wind farm line and the current signal of the wind farm line to obtain the sub-synchronous frequency signal, and according to the sub-synchronous frequency signal, the resistance and inductance of multiple wind turbines, the resistance and inductance of multiple transformers, and the wind farm line The resistance and inductance are used to obtain the closed-loop transfer function of the wind farm, and according to the actual output current signal of the subsynchronous suppression system to the grid, the attenuation rate of the closed-loop transfer function at different zero points is optimal by optimizing the parameters.

Specifically, the voltage signal u _abc of the wind farm line and the current signal i _abc of the wind farm line are filtered to obtain a sub-synchronous frequency signal.

According to the subsynchronous frequency signal, the resistance and inductance of multiple wind turbines, the resistance and inductance of multiple transformers, and the line resistance and inductance of the wind farm, the closed-loop transfer function of the wind farm is obtained. The formula of the closed-loop transfer function of the wind farm is:

Among them, s represents the complex frequency, z _h is the g zero points of the closed-loop transfer function Z _eq (s), y _q is the p poles of the closed-loop transfer function Z _eq (s), H _i (s) and H _u (s) are the transfer functions for processing the current signal of the wind farm line and the voltage signal of the wind farm line, respectively, r _r0 is the rotor resistance, K _pr is the proportional coefficient of the inner loop of the rotor side controller, K _lr is the integral coefficient of the inner loop of the rotor side controller, K _Dr is the cross gain of the inner loop of the rotor side controller, ω ₀ is the power frequency angular frequency, ω _r is the rotor angular frequency, L _r is the rotor inductance, L _m is the fan excitation inductance, L _s is the fan stator inductance, L _T1 is the inductance of the transformer T1, L _l1 is the wind farm line inductance, r _s is the stator resistance, r _T1 is the transformer T1 resistance, r _l1 is the wind farm line resistance, L _l2 is the series compensation line inductance, L _T2 is the transformer T2 inductance, r _l2 is the series compensation line resistance, r _T2 is the transformer T2 resistance, C is the series compensation capacitor, n is the number of fans.

H _i (s) and _Hu (s) are transfer functions for processing the current signal i _abc of the wind farm line and the voltage signal u _abc of the wind farm line respectively:

i _out (s)＝i _abc (s)H _i (s)+u _abc (s)H _u (s)

H _i (s) = H _F (s) K _i H _com,i (s) H _d (s)

H _u (s)＝H _F (s)K _u H _com,u (s)H _d (s)

H _F (s) = H _P (s) H _S (s) H _SH (s)

The transfer function H _P (s) of the band-pass filter makes the subsynchronous signal with ω _P as the central angular frequency pass through, where ζ is the damping coefficient:

The transfer function H _S (s) of the band-stop filter with the corner frequency ω _S filters out the power frequency component:

ω _SH ＝2ω _S -ω _P , the transfer function H _SH (s) of the band-stop filter whose angular frequency is ω _SH , filters out the frequency signal complementary to the subsynchronous component:

Current signal proportional phase-shifting transfer function H _com,i (s), where K _i represents the current signal gain, and _Tai represents the current signal phase-shifting parameter:

The voltage signal proportional phase-shift transfer function H _com,u (s), where K _u represents the voltage signal gain, and T _au represents the voltage signal phase-shift parameter:

The delay signal transfer function H _d (s), where the gain parameter k _d and the phase offset parameter T _d of the delay signal transfer function can be obtained by the open-loop test:

The second step is the selection of wind farm closed-loop transfer function parameters. First, the g zeros of the closed-loop transfer function Z _eq (s) are z _h . The p poles of Z _eq (s) are y _q .

remember:

Let z _h ＝σ _h +jω _h , σ _h is the real part of zero point z _h , ω _h is the imaginary part of zero point z _h

Decay rate ξ _{h for mode ω h :}

Through optimization algorithms such as genetic algorithm or quasi-annealing, calculate the optimal current signal gain K _i , current signal phase shift parameter _Tai , voltage signal gain K _u , voltage signal phase shift parameter T _au , that is, the proportional phase shift link, the gain link , so that the attenuation rate ξ _h satisfies: (1) ξ _h >0; (2) In all working conditions, ω _r ∈ [0.7pu,1.3pu], n=1...n _TOT , the minimum attenuation rate min (ξ _h ) is maximized. pu: standard unit, n _TOT : the maximum number of fans.

Objective function: max f=min(ξ _h )

Restrictions:

That is to say, as shown in Figure 3, the present invention filters the voltage signal and current signal of the wind farm line to obtain the sub-synchronous frequency signal, and according to the sub-synchronous frequency signal, it passes through the proportional phase-shifting link, and the phase-shifting step after the gain link Add the current reference signal i _ref . The power electronic converter outputs current according to the current reference signal i _ref sent by the controller and obtains the actual output current signal i _out of the sub-synchronous suppression system to the grid through the transformer.

Fig. 4 is a structural diagram of a subsynchronous resonance suppression system for a wind farm according to an embodiment of the present invention.

As shown in FIG. 4 , according to a wind farm subsynchronous resonance suppression system 400 according to an embodiment of the present invention, the wind farm at least includes: multiple wind turbines, multiple transformers and wind farm lines, including: an acquisition module 410 and a processing module 420 .

Among them, the acquisition module 410 is used to acquire the voltage signal and current signal of the wind farm line, the resistance and inductance of multiple wind turbines, the resistance and inductance of multiple transformers, the resistance and inductance of the wind farm line, and the actual output current signal of the subsynchronous suppression system to the grid. The processing module 420 is used to filter the voltage signal of the wind farm line and the current signal of the wind farm line to obtain the sub-synchronous frequency signal, and according to the sub-synchronous frequency signal, the resistance and inductance of multiple wind turbines, the resistance and inductance of multiple transformers, The closed-loop transfer function of the wind farm is obtained from the line resistance and inductance of the wind farm, and the current signal is actually output to the grid according to the subsynchronous suppression system. By optimizing the parameters, the attenuation rate of the closed-loop transfer function at different zero points is optimal.

According to the wind farm subsynchronous resonance suppression system of the present invention, the purpose of suppressing subsynchronous resonance can be achieved, and the stability of the wind farm can be improved.

Furthermore, the formula of the closed-loop transfer function of the wind farm is:

Among them, s represents the complex frequency, z _h is the g zero points of the closed-loop transfer function Z _eq (s), y _q is the p poles of the closed-loop transfer function Z _eq (s), H _i (s) and H _u (s) are the transfer functions for processing the current signal of the wind farm line and the voltage signal of the wind farm line, respectively, r _r0 is the rotor resistance, K _pr is the proportional coefficient of the inner loop of the rotor side controller, K _lr is the integral coefficient of the inner loop of the rotor side controller, K _Dr is the cross gain of the inner loop of the rotor side controller, ω ₀ is the power frequency angular frequency, ω _r is the rotor angular frequency, L _r is the rotor inductance, L _m is the fan excitation inductance, L _s is the fan stator inductance, L _T1 is the inductance of the transformer T1, L _l1 is the wind farm line inductance, r _s is the stator resistance, r _T1 is the transformer T1 resistance, r _l1 is the wind farm line resistance, L _l2 is the series compensation line inductance, L _T2 is the transformer T2 inductance, r _l2 is the series compensation line resistance, r _T2 is the transformer T2 resistance, C is the series compensation capacitor, n is the number of fans.

Further, by optimizing the parameters, the optimal attenuation rate under different zero points of the transfer function is specifically: optimizing the current signal gain K _i , the current signal phase shift parameter _Tai , the voltage signal gain K _u , the voltage signal phase shift parameter T _au , And when z _h ＝σ _h +jω _h , σ _h is the real part of the zero point z _h , ω _h is the imaginary part of the zero point z _h , the attenuation rate ξ _{h of the mode ω h :}

The decay rate ξ _h satisfies:

Objective function: max f=min(ξ _h )

Restrictions:

pu: standard unit, n _TOT : the maximum number of fans.

It should be noted that the specific implementation of the wind farm subsynchronous resonance suppression system in the embodiment of the present invention is similar to that of the wind farm subsynchronous resonance suppression method in the embodiment of the present invention. For details, please refer to the subsynchronous resonance suppression method in the wind farm. Description, in order to reduce redundancy, details are not repeated here.

In some examples, as shown in FIG. 3 , it further includes: a power electronic converter and a transformer.

Specifically, as shown in Figure 3, the voltage signal u _abc and current signal i _abc of the wind farm line are subjected to signal filtering processing to obtain a sub-synchronous frequency signal, and according to the sub-synchronous frequency signal, pass through a proportional phase shifting link and a gain link After the addition, the current reference signal i _ref is obtained. The current reference signal i _ref outputs the current through the power electronic converter and obtains the sub-synchronous suppression system through the transformer to actually output the current signal i _out to the grid, and flows into the grid.

In addition, the terms "first" and "second" are used for descriptive purposes only, and cannot be interpreted as indicating or implying relative importance or implicitly specifying the quantity of indicated technical features. Thus, the features defined as "first" and "second" may explicitly or implicitly include at least one of these features. In the description of the present invention, "plurality" means at least two, such as two, three, etc., unless otherwise specifically defined.

In the present invention, unless otherwise clearly specified and limited, terms such as "installation", "connection", "connection" and "fixation" should be understood in a broad sense, for example, it can be a fixed connection or a detachable connection , or integrated; it may be mechanically connected or electrically connected; it may be directly connected or indirectly connected through an intermediary, and it may be the internal communication of two components or the interaction relationship between two components, unless otherwise specified limit. Those of ordinary skill in the art can understand the specific meanings of the above terms in the present invention according to specific situations.

In the description of this specification, descriptions referring to the terms "one embodiment", "some embodiments", "example", "specific examples", or "some examples" mean that specific features described in connection with the embodiment or example , structure, material or characteristic is included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms are not necessarily directed to the same embodiment or example. Furthermore, the described specific features, structures, materials or characteristics may be combined in any suitable manner in any one or more embodiments or examples. In addition, those skilled in the art can combine and combine different embodiments or examples and features of different embodiments or examples described in this specification without conflicting with each other.

Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention, those skilled in the art can make the above-mentioned The embodiments are subject to changes, modifications, substitutions and variations.

Claims (7)

1. A wind farm subsynchronous resonance suppression method, the wind farm at least includes: a plurality of wind turbines, a plurality of transformers and a wind farm circuit, characterized in that, comprising: Obtain the voltage signal and current signal of the wind farm line, the resistance and inductance of multiple wind turbines, the resistance and inductance of multiple transformers, the resistance and inductance of the wind farm line, and the actual output current signal of the subsynchronous suppression system to the grid; Filtering the voltage signal of the wind farm line and the current signal of the wind farm line to obtain a sub-synchronous frequency signal, and according to the sub-synchronous frequency signal, the resistance and inductance of multiple wind turbines, the resistance and inductance of multiple transformers, and the wind power Field line resistance and inductance to obtain the closed-loop transfer function of the wind farm, and according to the sub-synchronous suppression system to actually output current signals to the grid, the attenuation rate at different zero points of the closed-loop transfer function is optimized by optimizing parameters. 2. The wind farm subsynchronous resonance suppression method according to claim 1, wherein the formula of the wind farm closed-loop transfer function is: <mfenced open = "" close = ""> <mtable> <mtr> <mtd> <mrow> <msub> <mi>Z</mi> <mrow> <mi>e</mi> <mi>q</mi> </mrow> </msub> <mrow> <mo>(</mo> <mi>s</mi> <mo>)</mo> </mrow> <mo>=</mo> <mfrac> <mrow> <mfrac> <mrow> <mo>(</mo> <msub> <mi>sL</mi> <mi>r</mi> </msub> <mo>+</mo> <msub> <mi>r</mi> <mi>r</mi> </msub> <mo>)</mo> <msub> <mi>sL</mi> <mi>m</mi> </msub> </mrow> <mrow> <mi>n</mi> <mrow> <mo>(</mo> <msub> <mi>sL</mi> <mi>r</mi> </msub> <mo>+</mo> <msub> <mi>sL</mi> <mi>m</mi> </msub> <mo>+</mo> <msub> <mi>r</mi> <mi>r</mi> </msub> <mo>)</mo> </mrow> </mrow> </mfrac> <mo>+</mo> <mi>s</mi> <mrow> <mo>(</mo> <msub> <mi>L</mi> <mi>s</mi> </msub> <mo>/</mo> <mi>n</mi> <mo>+</mo> <msub> <mi>L</mi> <mrow> <mi>T</mi> <mn>1</mn> </mrow> </msub> <mo>/</mo> <mi>n</mi> <mo>+</mo> <msub> <mi>L</mi> <mn>11</mn> </msub> <mo>)</mo> </mrow> <mo>+</mo> <msub> <mi>r</mi> <mi>s</mi> </msub> <mo>/</mo> <mi>n</mi> <mo>+</mo> <msub> <mi>r</mi> <mrow> <mi>T</mi> <mn>1</mn> </mrow> </msub> <mo>/</mo> <mi>n</mi> <mo>+</mo> <msub> <mi>r</mi> <mn>11</mn> </msub> </mrow> <mrow> <mn>1</mn> <mo>+</mo> <msub> <mi>H</mi> <mi>i</mi> </msub> <mrow> <mo>(</mo> <mi>s</mi> <mo>)</mo> </mrow> <mo>+</mo> <msub> <mi>H</mi> <mi>u</mi> </msub> <mrow> <mo>(</mo> <mi>s</mi> <mo>)</mo> </mrow> <mrow> <mo>(</mo> <mfrac> <mrow> <mo>(</mo> <msub> <mi>sL</mi> <mi>r</mi> </msub> <mo>+</mo> <msub> <mi>r</mi> <mi>r</mi> </msub> <mo>)</mo> <msub> <mi>sL</mi> <mi>m</mi> </msub> </mrow> <mrow> <mi>n</mi> <mrow> <mo>(</mo> <msub> <mi>sL</mi> <mi>r</mi> </msub> <mo>+</mo> <msub> <mi>sL</mi> <mi>m</mi> </msub> <mo>+</mo> <msub> <mi>r</mi> <mi>r</mi> </msub> <mo>)</mo> </mrow> </mrow> </mfrac> <mo>+</mo> <mi>s</mi> <mo>(</mo> <mrow> <msub> <mi>L</mi> <mi>s</mi> </msub> <mo>/</mo> <mi>n</mi> <mo>+</mo> <msub> <mi>L</mi> <mrow> <mi>T</mi> <mn>1</mn> </mrow> </msub> <mo>/</mo> <mi>n</mi> <mo>+</mo> <msub> <mi>L</mi> <mn>11</mn> </msub> </mrow> <mo>)</mo> <mo>+</mo> <msub> <mi>r</mi> <mi>s</mi> </msub> <mo>/</mo> <mi>n</mi> <mo>+</mo> <msub> <mi>r</mi> <mrow> <mi>T</mi> <mn>1</mn> </mrow> </msub> <mo>/</mo> <mi>n</mi> <mo>+</mo> <msub> <mi>r</mi> <mn>11</mn> </msub> <mo>)</mo> </mrow> </mrow> </mfrac> </mrow> </mtd> </mtr> <mtr> <mtd> <mrow> <mo>+</mo> <mi>s</mi> <mrow> <mo>(</mo> <msub> <mi>L</mi> <mn>12</mn> </msub> <mo>+</mo> <msub> <mi>L</mi> <mrow> <mi>T</mi> <mn>2</mn> </mrow> </msub> <mo>)</mo> </mrow> <mo>+</mo> <msub> <mi>r</mi> <mn>12</mn> </msub> <mo>+</mo> <msub> <mi>r</mi> <mrow> <mi>T</mi> <mn>2</mn> </mrow> </msub> <mo>+</mo> <mfrac> <mn>1</mn> <mrow> <mi>s</mi> <mi>C</mi> </mrow> </mfrac> </mrow> </mtd> </mtr> <mtr> <mtd> <mrow> <mo>=</mo> <mfrac> <mrow> <munderover> <mo>&amp;Pi;</mo> <mrow> <mi>h</mi> <mo>=</mo> <mn>1</mn> </mrow> <mi>g</mi> </munderover> <mrow> <mo>(</mo> <mi>s</mi> <mo>-</mo> <msub> <mi>z</mi> <mi>h</mi> </msub> <mo>)</mo> </mrow> </mrow> <mrow> <munderover> <mo>&amp;Pi;</mo> <mrow> <mi>q</mi> <mo>=</mo> <mn>1</mn> </mrow> <mi>p</mi> </munderover> <mrow> <mo>(</mo> <mi>s</mi> <mo>-</mo> <msub> <mi>y</mi> <mi>q</mi> </msub> <mo>)</mo> </mrow> </mrow> </mfrac> </mrow> </mtd> </mtr> </mtable> </mfenced> Among them, s represents the complex frequency, z _h is the g zero points of the closed-loop transfer function Z _eq (s), y _q is the p poles of the closed-loop transfer function Z _eq (s), H _i (s) and H _u (s) are the transfer functions for processing the current signal of the wind farm line and the voltage signal of the wind farm line, respectively, r _r0 is the rotor resistance, K _pr is the proportional coefficient of the inner loop of the rotor side controller, K _lr is the integral coefficient of the inner loop of the rotor side controller, K _Dr is the cross gain of the inner loop of the rotor side controller, ω ₀ is the power frequency angular frequency, ω _r is the rotor angular frequency, L _r is the rotor inductance, L _m is the fan excitation inductance, L _s is the fan stator inductance, L _T1 is the inductance of the transformer T1, L _l1 is the wind farm line inductance, r _s is the stator resistance, r _T1 is the transformer T1 resistance, r _l1 is the wind farm line resistance, L _l2 is the series compensation line inductance, L _T2 is the transformer T2 inductance, r _l2 is the series compensation line resistance, r _T2 is the transformer T2 resistance, C is the series compensation capacitor, n is the number of fans. 3. The wind farm subsynchronous resonance suppression method according to claim 2, characterized in that, by optimizing the parameters, the optimal attenuation rate under different zero points of the transfer function is specifically: Optimizing the current signal gain K _i , the current signal phase shift parameter _Tai , the voltage signal gain K _u , the voltage signal phase shift parameter T _au , and when z _h =σ _h +jω _h , σ _h is the real part of the zero point z _h , ω _h is the imaginary part of the zero point z _h , the attenuation rate ξ _{h of the mode ω h :} <mrow> <msub> <mi>&amp;xi;</mi> <mi>h</mi> </msub> <mo>=</mo> <mfrac> <mrow> <mo>-</mo> <msub> <mi>&amp;sigma;</mi> <mi>h</mi> </msub> </mrow> <msqrt> <mrow> <msup> <msub> <mi>&amp;sigma;</mi> <mi>h</mi> </msub> <mn>2</mn> </msup> <mo>+</mo> <msup> <msub> <mi>&amp;omega;</mi> <mi>h</mi> </msub> <mn>2</mn> </msup> </mrow> </msqrt> </mfrac> <mo>,</mo> </mrow> The decay rate ξ _h satisfies: Objective function: max f=min(ξ _h ) Restrictions: pu: standard unit, n _TOT : the maximum number of fans. 4. A subsynchronous resonance suppression system for a wind farm, characterized in that the wind farm at least includes: multiple wind turbines, multiple transformers and wind farm lines, including: The acquisition module is used to acquire the voltage signal and current signal of the wind farm line, the resistance and inductance of multiple wind turbines, the resistance and inductance of multiple transformers, the resistance and inductance of the wind farm line, and the actual output current signal of the sub-synchronous suppression system to the grid; A processing module, configured to filter the voltage signal of the wind farm line and the current signal of the wind farm line to obtain a sub-synchronous frequency signal, and perform The closed-loop transfer function of the wind farm is obtained from the resistance and inductance, the line resistance and inductance of the wind farm, and the current signal is actually output to the power grid according to the sub-synchronous suppression system, and the attenuation rate at different zero points of the closed-loop transfer function is optimized by optimizing parameters. 5. The wind farm subsynchronous resonance suppression system according to claim 4, wherein the formula of the wind farm closed-loop transfer function is: <mfenced open = "" close = ""> <mtable> <mtr> <mtd> <mrow> <msub> <mi>Z</mi> <mrow> <mi>e</mi> <mi>q</mi> </mrow> </msub> <mrow> <mo>(</mo> <mi>s</mi> <mo>)</mo> </mrow> <mo>=</mo> <mfrac> <mrow> <mfrac> <mrow> <mo>(</mo> <msub> <mi>sL</mi> <mi>r</mi> </msub> <mo>+</mo> <msub> <mi>r</mi> <mi>r</mi> </msub> <mo>)</mo> <msub> <mi>sL</mi> <mi>m</mi> </msub> </mrow> <mrow> <mi>n</mi> <mrow> <mo>(</mo> <msub> <mi>sL</mi> <mi>r</mi> </msub> <mo>+</mo> <msub> <mi>sL</mi> <mi>m</mi> </msub> <mo>+</mo> <msub> <mi>r</mi> <mi>r</mi> </msub> <mo>)</mo> </mrow> </mrow> </mfrac> <mo>+</mo> <mi>s</mi> <mrow> <mo>(</mo> <msub> <mi>L</mi> <mi>s</mi> </msub> <mo>/</mo> <mi>n</mi> <mo>+</mo> <msub> <mi>L</mi> <mrow> <mi>T</mi> <mn>1</mn> </mrow> </msub> <mo>/</mo> <mi>n</mi> <mo>+</mo> <msub> <mi>L</mi> <mn>11</mn> </msub> <mo>)</mo> </mrow> <mo>+</mo> <msub> <mi>r</mi> <mi>s</mi> </msub> <mo>/</mo> <mi>n</mi> <mo>+</mo> <msub> <mi>r</mi> <mrow> <mi>T</mi> <mn>1</mn> </mrow> </msub> <mo>/</mo> <mi>n</mi> <mo>+</mo> <msub> <mi>r</mi> <mn>11</mn> </msub> </mrow> <mrow> <mn>1</mn> <mo>+</mo> <msub> <mi>H</mi> <mi>i</mi> </msub> <mrow> <mo>(</mo> <mi>s</mi> <mo>)</mo> </mrow> <mo>+</mo> <msub> <mi>H</mi> <mi>u</mi> </msub> <mrow> <mo>(</mo> <mi>s</mi> <mo>)</mo> </mrow> <mrow> <mo>(</mo> <mfrac> <mrow> <mo>(</mo> <msub> <mi>sL</mi> <mi>r</mi> </msub> <mo>+</mo> <msub> <mi>r</mi> <mi>r</mi> </msub> <mo>)</mo> <msub> <mi>sL</mi> <mi>m</mi> </msub> </mrow> <mrow> <mi>n</mi> <mrow> <mo>(</mo> <msub> <mi>sL</mi> <mi>r</mi> </msub> <mo>+</mo> <msub> <mi>sL</mi> <mi>m</mi> </msub> <mo>+</mo> <msub> <mi>r</mi> <mi>r</mi> </msub> <mo>)</mo> </mrow> </mrow> </mfrac> <mo>+</mo> <mi>s</mi> <mo>(</mo> <mrow> <msub> <mi>L</mi> <mi>s</mi> </msub> <mo>/</mo> <mi>n</mi> <mo>+</mo> <msub> <mi>L</mi> <mrow> <mi>T</mi> <mn>1</mn> </mrow> </msub> <mo>/</mo> <mi>n</mi> <mo>+</mo> <msub> <mi>L</mi> <mn>11</mn> </msub> </mrow> <mo>)</mo> <mo>+</mo> <msub> <mi>r</mi> <mi>s</mi> </msub> <mo>/</mo> <mi>n</mi> <mo>+</mo> <msub> <mi>r</mi> <mrow> <mi>T</mi> <mn>1</mn> </mrow> </msub> <mo>/</mo> <mi>n</mi> <mo>+</mo> <msub> <mi>r</mi> <mn>11</mn> </msub> <mo>)</mo> </mrow> </mrow> </mfrac> </mrow> </mtd> </mtr> <mtr> <mtd> <mrow> <mo>+</mo> <mi>s</mi> <mrow> <mo>(</mo> <msub> <mi>L</mi> <mn>12</mn> </msub> <mo>+</mo> <msub> <mi>L</mi> <mrow> <mi>T</mi> <mn>2</mn> </mrow> </msub> <mo>)</mo> </mrow> <mo>+</mo> <msub> <mi>r</mi> <mn>12</mn> </msub> <mo>+</mo> <msub> <mi>r</mi> <mrow> <mi>T</mi> <mn>2</mn> </mrow> </msub> <mo>+</mo> <mfrac> <mn>1</mn> <mrow> <mi>s</mi> <mi>C</mi> </mrow> </mfrac> </mrow> </mtd> </mtr> <mtr> <mtd> <mrow> <mo>=</mo> <mfrac> <mrow> <munderover> <mo>&amp;Pi;</mo> <mrow> <mi>h</mi> <mo>=</mo> <mn>1</mn> </mrow> <mi>g</mi> </munderover> <mrow> <mo>(</mo> <mi>s</mi> <mo>-</mo> <msub> <mi>z</mi> <mi>h</mi> </msub> <mo>)</mo> </mrow> </mrow> <mrow> <munderover> <mo>&amp;Pi;</mo> <mrow> <mi>q</mi> <mo>=</mo> <mn>1</mn> </mrow> <mi>p</mi> </munderover> <mrow> <mo>(</mo> <mi>s</mi> <mo>-</mo> <msub> <mi>y</mi> <mi>q</mi> </msub> <mo>)</mo> </mrow> </mrow> </mfrac> </mrow> </mtd> </mtr> </mtable> </mfenced> Among them, s represents the complex frequency, z _h is the g zero points of the closed-loop transfer function Z _eq (s), y _q is the p poles of the closed-loop transfer function Z _eq (s), H _i (s) and H _u (s) are the transfer functions for processing the current signal of the wind farm line and the voltage signal of the wind farm line, respectively, r _r0 is the rotor resistance, K _pr is the proportional coefficient of the inner loop of the rotor side controller, K _lr is the integral coefficient of the inner loop of the rotor side controller, K _Dr is the cross gain of the inner loop of the rotor side controller, ω ₀ is the power frequency angular frequency, ω _r is the rotor angular frequency, L _r is the rotor inductance, L _m is the fan excitation inductance, L _s is the fan stator inductance, L _T1 is the inductance of the transformer T1, L _l1 is the wind farm line inductance, r _s is the stator resistance, r _T1 is the transformer T1 resistance, r _l1 is the wind farm line resistance, L _l2 is the series compensation line inductance, L _T2 is the transformer T2 inductance, r _l2 is the series compensation line resistance, r _T2 is the transformer T2 resistance, C is the series compensation capacitor, n is the number of fans. 6. The wind farm subsynchronous resonance suppression system according to claim 5, characterized in that, by optimizing the parameters, the optimal attenuation rate under different zero points of the transfer function is specifically: Optimizing the current signal gain K _i , the current signal phase shift parameter _Tai , the voltage signal gain K _u , the voltage signal phase shift parameter T _au , and when z _h =σ _h +jω _h , σ _h is the real part of the zero point z _h , ω _h is the imaginary part of the zero point z _h , the attenuation rate ξ _{h of the mode ω h :} <mrow> <msub> <mi>&amp;xi;</mi> <mi>h</mi> </msub> <mo>=</mo> <mfrac> <mrow> <mo>-</mo> <msub> <mi>&amp;sigma;</mi> <mi>h</mi> </msub> </mrow> <msqrt> <mrow> <msup> <msub> <mi>&amp;sigma;</mi> <mi>h</mi> </msub> <mn>2</mn> </msup> <mo>+</mo> <msup> <msub> <mi>&amp;omega;</mi> <mi>h</mi> </msub> <mn>2</mn> </msup> </mrow> </msqrt> </mfrac> <mo>,</mo> </mrow> 2 The decay rate ξ _h satisfies: Objective function: max f=min(ξ _h ) Restrictions: pu: standard unit, n _TOT : the maximum number of fans. 7. The subsynchronous resonance suppression system for wind farm according to claim 4, further comprising: a power electronic converter and a transformer.