Distributed system-level closed-loop harmonic suppression method, device and equipment based on wind turbine generator converter and medium

Abstract

The invention provides a distributed system-level closed-loop harmonic suppression method, device and equipment based on a wind turbine generator converter and a medium. The method comprises the following steps: S1, measuring each harmonic component of an electric energy quality assessment point at a land station grid-connected point of offshore wind power, and extracting positive and negative sequence components corresponding to each harmonic by adopting a rotating coordinate; s2, generating a corresponding instruction value for the positive / negative sequence component to be suppressed; and S3, performing distributed calculation on the instruction value to obtain an instruction value of each wind turbine generator converter, and transmitting the instruction value to a controller of each wind turbine generator converter after long-distance transmission. According to the suppression method provided by the invention, the positive / negative sequence harmonic component characteristics at the grid-connected point can be extracted, the corresponding harmonic suppression instruction value is further generated according to the harmonic characteristics, and the harmonic suppression amount instruction value fed into each wind turbine generator set is obtained through distributed calculation; and the wind turbine generator effectively suppresses the harmonic current component at the grid-connected point of the wind field according to the instruction value.

Description

Technical Field

[0001] The present invention belongs to the field of offshore wind power AC / DC technology, and mainly relates to the problem of suppressing excessive harmonic amplitude at the onshore station grid connection point by relying on wind turbine converters, and in particular to a distributed system-level closed-loop harmonic suppression method, device, equipment and medium based on wind turbine converters. Background Art

[0002] The offshore wind power is transmitted through the AC submarine cable system. The weak damping resonance formed by the submarine cable's capacitance effect on the ground will amplify the tiny harmonics of the converter, causing the harmonic amplitude at the onshore station to exceed the standard.

[0003] The existing centralized suppression device is applied to the grid connection point of the onshore station. By issuing the suppression amount command value in the control link of the wind turbine converter, the converter of each wind turbine is controlled to inject small harmonics. The small harmonics are amplified by the amplification effect of the long-distance submarine cable and then the harmonic current at the grid connection point is neutralized. However, the amount to be suppressed is the harmonic current component at the landing point at the end of the long-distance submarine cable, and the harmonic injection amount is the converter of each wind turbine at the starting end of the long-distance submarine cable. How to generate the harmonic injection amount of each wind turbine according to the harmonic component of the target location and finally effectively suppress the harmonic component at the grid connection point is of great significance. Summary of the invention

[0004] The first object of the present invention is to provide a distributed system-level closed-loop harmonic suppression method based on a wind turbine converter.

[0005] To this end, the above-mentioned purpose of the present invention is achieved through the following technical solutions:

[0006] A distributed system-level closed-loop harmonic suppression method based on a wind turbine converter, characterized in that the method comprises the following steps:

[0007] S1. Measure the harmonic components of the power quality assessment point at the onshore station of offshore wind power and extract the positive and negative sequence components corresponding to each harmonic using rotating coordinates;

[0008] S2. Generate corresponding command values ​​for the positive / negative sequence components to be suppressed;

[0009] S3. The command value is obtained through distributed computing for the converter of each wind turbine set and is sent to the controller of the converter of each wind turbine set after long-distance transmission.

[0010] While adopting the above technical solutions, the present invention may also adopt or combine the following technical solutions:

[0011] As a preferred technical solution of the present invention: Step S1 is specifically:

[0012] Use power frequency filter, filter A n On the basis of filtering out the power frequency component, a bandpass filter is further applied with the cut-off frequency set to f n , and finally only retain the target frequency component f n ;

[0013] The phase compensation link is expressed as follows:

[0014]

[0015] In the above formula, T s is the time constant. By setting the time constant reasonably, the harmonic components in the system can be reasonably compensated. s is the Laplace operator.

[0016] The harmonic components are further converted from three-phase components to α / β components through coordinate transformation, and their calculation expressions are as follows:

[0017]

[0018] After coordinate transformation, we get the α / β component I α with I β ;

[0019] The harmonic components are further transformed into positive sequence components through coordinate transformation. The expression of positive sequence coordinate transformation is as follows:

[0020]

[0021] The expression for calculating the positive sequence component is as follows:

[0022]

[0023] In the above formula, n is the harmonic order; ω0 is the fundamental rotation angular frequency;

[0024] The above components are further filtered through a low-pass filter to extract the DC component. as well as

[0025] At the same time, the negative sequence harmonic component is extracted to obtain its negative sequence component. The expression of negative sequence coordinate transformation is as follows:

[0026]

[0027] The expression for calculating the negative sequence component is as follows:

[0028]

[0029] The above components are further filtered through a low-pass filter to extract the DC component. as well as

[0030] As a preferred technical solution of the present invention: Step S2 is specifically:

[0031] Extracted positive / negative sequence components as well as It is further fed into the inhibition amount generation link and two PI control links;

[0032] The harmonic current suppression amount generation module includes the following two links: a positive sequence harmonic suppression amount generation link and a negative sequence harmonic suppression amount generation link;

[0033] For the positive sequence component:

[0034]

[0035] In the above formula, K PP With K IP are the proportional and integral coefficients of the positive sequence component PI respectively; s is the Laplace operator; I + dsn_ref is the reference value of the d-axis component of the positive-sequence harmonic current; I + d1 is the measured value of the d-axis component of the positive-sequence harmonic current; I + qsn_ref is the reference value of the q-axis component of the positive-sequence harmonic current; I + q1 is the measured value of the q-axis component of the positive-sequence harmonic current; R + Pd With R + Pq are the reference values ​​of positive sequence d / q axis suppression respectively;

[0036] For negative sequence components:

[0037]

[0038] In the above formula, K pn With K In are the proportional and integral coefficients of PI respectively; s is the Laplace operator; I - dsn_ref is the reference value of the d-axis component of the harmonic current; I - d1 is the measured value of the d-axis component of the negative harmonic current; I - qsn_ref is the reference value of the q-axis component of the harmonic current; I q1 - is the measured value of the q-axis component of the negative-sequence harmonic current; R -nd With R - nq are the reference values ​​of negative sequence d / q axis suppression respectively.

[0039] As a preferred technical solution of the present invention: Step S3 is specifically:

[0040] Distributed calculation is performed on the reference value of the suppression amount of the positive sequence d / q axis component, and the following is obtained:

[0041]

[0042] In the above formula, y + is the positive sequence component reference value, n1 is the number of wind turbines;

[0043] Distributed calculation is performed on the reference value of the suppression amount of the negative sequence d / q axis component, and the following is obtained:

[0044]

[0045] In the above formula, y - is the negative sequence component reference value, n1 is the number of wind turbines;

[0046] y + With y - The components are fed into the d / q axis reference values ​​of the wind turbine converter.

[0047] The second object of the present invention is to provide a distributed system-level closed-loop harmonic suppression device based on a wind turbine converter.

[0048] To this end, the above-mentioned purpose of the present invention is achieved through the following technical solutions:

[0049] A distributed system-level closed-loop harmonic suppression device based on a wind turbine converter, characterized in that the device comprises:

[0050] A harmonic positive and negative sequence component extraction module, which is used to obtain the harmonic components of each harmonic component at the power quality assessment point at the onshore station grid connection point of the offshore wind power and extract the positive and negative sequence components corresponding to each harmonic using rotating coordinates;

[0051] An instruction value generating module, the instruction value generating module is used to generate a corresponding instruction value for the positive / negative sequence component to be suppressed;

[0052] The command value transmission and feeding module is used to obtain the command value of each wind turbine converter through distributed computing and send it to the controller of each wind turbine converter after long-distance transmission.

[0053] The third object of the present invention is to provide a distributed system-level closed-loop harmonic suppression device based on a wind turbine converter.

[0054] To this end, the above-mentioned purpose of the present invention is achieved through the following technical solutions:

[0055] A distributed system-level closed-loop harmonic suppression device based on a wind turbine converter, characterized in that the device comprises:

[0056] at least one processor;

[0057] at least one memory for storing at least one computer program;

[0058] The processor executes the computer program in the memory to implement the steps of the distributed system-level closed-loop harmonic suppression method based on the wind turbine converter as described above.

[0059] Another object of the present invention is to provide a computer storage medium.

[0060] To this end, the above-mentioned purpose of the present invention is achieved through the following technical solutions:

[0061] A computer storage medium, characterized in that a computer program is stored on the computer storage medium, and the computer program is executed by a computer to implement the steps of the distributed system-level closed-loop harmonic suppression method based on a wind turbine converter as described above.

[0062] The present invention provides a system-level distributed closed-loop harmonic suppression method, device, equipment and medium for each wind turbine converter to effectively suppress harmonic currents at a long-distance submarine cable land station grid connection point. The method can measure the harmonic components of the power quality assessment point at the land station grid connection point of offshore wind power and extract the positive and negative sequence components corresponding to each harmonic using rotating coordinates; it can generate corresponding command values ​​for the positive / negative sequence components to be suppressed; the command values ​​of each wind turbine converter are obtained by distributed calculation and are sent to the controllers of each wind turbine converter after long-distance transmission. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] Figure 1 This is an action logic block diagram of the distributed system-level closed-loop harmonic suppression method provided by the present invention.

[0064] Figure 2 This is the harmonic suppression logic block diagram of the nth channel.

[0065] Figure 3 This is the waveform of the harmonic current in the system when there are no suppression measures.

[0066] Figure 4 This is the spectrum analysis result of the harmonic current in the system when there are no suppression measures.

[0067] Figure 5 is the output result of controller a.

[0068] Figure 6 This is the current waveform after the suppression measures are taken.

[0069] Figure 7 The spectrum analysis results of the current after the suppression measures were implemented. DETAILED DESCRIPTION

[0070] The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments.

[0071] The system-level distributed closed-loop harmonic suppression method proposed in this paper mainly includes three parts: 1) extraction of target harmonic components; 2) calculation of the suppression amount of target harmonic components; 3) distributed calculation, transmission and feeding of the suppression amount into wind turbines.

[0072] 1) Extraction of target harmonic components at the system grid connection point

[0073] From the grid-connected current, it is necessary to extract each harmonic current separately, taking the nth harmonic component as an example. Use an industrial frequency filter, that is, filter A n On the basis of filtering out the power frequency component, a bandpass filter is further applied with the cut-off frequency set to f n , and finally only retain the target frequency component f n .

[0074] The phase compensation link is expressed as follows:

[0075]

[0076] In the above formula, T s is the time constant. By setting the time constant reasonably, the harmonic components in the system can be compensated reasonably.

[0077] The harmonic components are further converted from three-phase components to α / β components through coordinate transformation, and their calculation expressions are as follows:

[0078]

[0079] After coordinate transformation, we get the α / β component I α with I β .

[0080] The harmonic components are further transformed into positive sequence components through coordinate transformation. The expression of positive sequence coordinate transformation is as follows:

[0081]

[0082] The expression for calculating the positive sequence component is as follows:

[0083]

[0084] The above components are further filtered through a low-pass filter to extract the DC component. as well as

[0085] At the same time, the negative sequence harmonic component is extracted to obtain its negative sequence component. The expression of negative sequence coordinate transformation is as follows:

[0086]

[0087] The expression for calculating the negative sequence component is as follows:

[0088]

[0089] The above components are further filtered through a low-pass filter to extract the DC component. as well as

[0090] 2) Distributed suppression quantity generation link

[0091] Extracted positive / negative sequence components as well as It is further fed into the inhibition amount generation link and two PI control links.

[0092] The harmonic current suppression amount generation module includes the following two links: a positive sequence harmonic suppression amount generation link and a negative sequence harmonic suppression amount generation link.

[0093] For the positive sequence component:

[0094]

[0095] In the above formula, K PP With K IP are the proportional and integral coefficients of the positive sequence component PI respectively; s is the Laplace operator; I + dsn_ref is the reference value of the d-axis component of the positive-sequence harmonic current; I + d1 is the measured value of the d-axis component of the positive-sequence harmonic current; I + qsn_ref is the reference value of the q-axis component of the positive-sequence harmonic current; I + q1 is the measured value of the q-axis component of the positive-sequence harmonic current; R + Pd With R + Pqare the reference values ​​of suppression of positive sequence d / q axis components respectively;

[0096] For negative sequence components:

[0097]

[0098] In the above formula, K pn With K In are the proportional and integral coefficients of PI respectively; s is the Laplace operator; I - dsn_ref is the reference value of the d-axis component of the harmonic current; I - d1 is the measured value of the d-axis component of the negative harmonic current; I - qsn_ref is the reference value of the q-axis component of the harmonic current; I q1 - is the measured value of the q-axis component of the negative-sequence harmonic current; R - nd With R - nq are the reference values ​​of suppression of negative sequence d / q axis components respectively;

[0099] In the above formula, n1 is the number of wind turbines.

[0100] 3) Distributed calculation and transmission of suppression quantity and feeding into wind turbines

[0101] Distributed calculation is performed on the reference value of the suppression amount of the positive sequence d / q axis component, and the following is obtained:

[0102]

[0103] In the above formula, y + is the positive sequence component reference value, n1 is the number of wind turbines;

[0104] Distributed calculation is performed on the reference value of the suppression amount of the negative sequence d / q axis component, and the following is obtained:

[0105]

[0106] In the above formula, y - is the negative sequence component reference value, n1 is the number of wind turbines;

[0107] y + With y - The components are fed into the d / q axis reference values ​​of the wind turbine converter.

[0108] The above suppression amount is transmitted through optical fiber and fed into the converter of the wind turbine generator set, and then the converter feeds harmonics into the system according to the superimposed harmonic instructions.

[0109] Inhibitory effect:

[0110] Figure 1 In the offshore wind power grid-connected system shown in , when the suppression measures in the system are not put into use, the waveform of the grid-connected point current is as follows Figure 3 As shown, the current is obviously distorted. Fourier analysis is performed on it. The results of Fourier analysis are as follows Figure 4 As shown, it can be seen that it contains 13th harmonic components close to 76A, and the power quality does not meet the requirements.

[0111] In 20s, Figure 2 The harmonic suppression method in the system is started, and the reference value is automatically generated according to the harmonic current of the grid connection point and sent to the wind turbine converter. Figure 5 As shown in Figure 1, when the suppression measures are put into use, the suppressor will dynamically adjust its output according to the suppression target. Finally, when the suppression is complete, the suppressor output will no longer change. The current waveform is as follows: Figure 6 As shown in Figure 1, there is no distortion in the current. The Fourier analysis is performed on it, and the results are as follows: Figure 7 As shown, it can be seen that the current harmonic component in the system is only 0.2 A. It will no longer affect the power quality of the wind farm.

[0112] The above-mentioned specific implementation cases are used to illustrate the present invention and are only preferred embodiments of the present invention, rather than limiting the present invention. Any modifications, equivalent substitutions, improvements, etc. made to the present invention within the spirit of the present invention and the protection scope of the claims shall fall within the protection scope of the present invention.

Claims

1. A distributed system-level closed-loop harmonic suppression method based on a wind turbine converter, characterized in that: The method comprises the following steps: S1. Measure the harmonic components of the power quality assessment point at the onshore station of offshore wind power and extract the positive and negative sequence components corresponding to each harmonic using rotating coordinates; S2. Generate corresponding command values ​​for the positive / negative sequence components to be suppressed; S3. The command value is obtained through distributed computing for the converter of each wind turbine set and is sent to the controller of the converter of each wind turbine set after long-distance transmission.

2. The method for suppressing harmonics at a distributed system level closed loop based on a wind turbine converter according to claim 1, characterized in that: Step S1 is specifically as follows: Use power frequency filter, filter A n On the basis of filtering out the power frequency component, a bandpass filter is further applied with the frequency set to f n , and finally only retain the target frequency component f n ; The phase compensation link is expressed as follows: In the above formula, T s is the time constant. By setting the time constant reasonably, the harmonic components in the system can be reasonably compensated. s is the Laplace operator. The harmonic components are further converted from three-phase components to α / β components through coordinate transformation, and their calculation expressions are as follows: After coordinate transformation, we get the α / β component I α with I β ; The harmonic components are further transformed into positive sequence components through coordinate transformation. The expression of positive sequence coordinate transformation is as follows: The expression for calculating the positive sequence component is as follows: In the above formula, n is the harmonic order; ω0 is the fundamental rotation angular frequency; The above components are further filtered through a low-pass filter to extract the DC component. as well as At the same time, the negative sequence harmonic component is extracted to obtain its negative sequence component. The expression of negative sequence coordinate transformation is as follows: The expression for calculating the negative sequence component is as follows: The above components are further filtered through a low-pass filter to extract the DC component. as well as 3. The method for suppressing harmonics at a distributed system level closed loop based on a wind turbine converter according to claim 1, characterized in that: Step S2 is specifically as follows: Extracted positive / negative sequence components as well as It is further fed into the inhibition amount generation link and two PI control links; The harmonic current suppression amount generation module includes the following two links: a positive sequence harmonic suppression amount generation link and a negative sequence harmonic suppression amount generation link; For the positive sequence component: In the above formula, K PP With K IP are the proportional and integral coefficients of the positive sequence component PI respectively; s is the Laplace operator; I + dsn_ref is the reference value of the d-axis component of the positive-sequence harmonic current; I + d1 is the measured value of the d-axis component of the positive-sequence harmonic current; I + qsn_ref is the reference value of the q-axis component of the positive-sequence harmonic current; I + q1 is the measured value of the q-axis component of the positive-sequence harmonic current; R + Pd With R + Pq are the reference values ​​of suppression of positive sequence d / q axis components respectively; For negative sequence components: In the above formula, K pn With K In are the proportional and integral coefficients of PI respectively; s is the Laplace operator; I - dsn_ref is the reference value of the d-axis component of the harmonic current; I - d1 is the measured value of the d-axis component of the negative harmonic current; I - qsn_ref is the reference value of the q-axis component of the harmonic current; I q1 - is the measured value of the q-axis component of the negative-sequence harmonic current; R - nd With R - nq are the reference values ​​of suppression of negative sequence d / q axis components respectively.

4. The method for suppressing harmonics at a closed-loop distributed system level based on a wind turbine converter according to claim 1, characterized in that: Step S3 is specifically as follows: Distributed calculation is performed on the reference value of the suppression amount of the positive sequence d / q axis component, and the following is obtained: In the above formula, y + is the positive sequence component reference value, n1 is the number of wind turbines; Distributed calculation is performed on the reference value of the suppression amount of the negative sequence d / q axis component, and the following is obtained: In the above formula, y - is the negative sequence component reference value, n1 is the number of wind turbines; y + With y - The components are fed into the d / q axis reference values ​​of the wind turbine converter.

5. A distributed system-level closed-loop harmonic suppression device based on a wind turbine converter, characterized in that: The device comprises: A harmonic positive and negative sequence component extraction module, which is used to obtain the harmonic components of each harmonic component at the power quality assessment point at the onshore station grid connection point of the offshore wind power and extract the positive and negative sequence components corresponding to each harmonic using rotating coordinates; An instruction value generating module, the instruction value generating module is used to generate a corresponding instruction value for the positive / negative sequence component to be suppressed; The command value transmission and feeding module is used to obtain the command value of each wind turbine converter through distributed computing and send it to the controller of each wind turbine converter after long-distance transmission.

6. A distributed system-level closed-loop harmonic suppression device based on a wind turbine converter, characterized in that: The device comprises: at least one processor; at least one memory for storing at least one computer program; The processor executes the computer program on the memory to implement the steps of the distributed system-level closed-loop harmonic suppression method based on the wind turbine converter as described in any one of claims 1-4.

7. A computer storage medium, characterized in that: The computer storage medium stores a computer program, and the computer program is executed by a computer to implement the steps of the distributed system-level closed-loop harmonic suppression method based on a wind turbine converter as claimed in any one of claims 1 to 4.

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