CN116073423A - Flexible grid connection method and device for flexible direct current system of offshore wind farm - Google Patents

Flexible grid connection method and device for flexible direct current system of offshore wind farm Download PDF

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Publication number
CN116073423A
CN116073423A CN202211712652.9A CN202211712652A CN116073423A CN 116073423 A CN116073423 A CN 116073423A CN 202211712652 A CN202211712652 A CN 202211712652A CN 116073423 A CN116073423 A CN 116073423A
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voltage
grid
reference value
value
flexible
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Inventor
陈怡静
郭小江
王海明
申旭辉
李春华
孙栩
李铮
奚嘉雯
王璐知
张钧阳
彭程
张祎
章卓雨
秦猛
赵瑞斌
付明志
姜兴广
汤浩然
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Huaneng Clean Energy Research Institute
Clean Energy Branch of Huaneng Zhejiang Energy Development Co Ltd
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Huaneng Clean Energy Research Institute
Clean Energy Branch of Huaneng Zhejiang Energy Development Co Ltd
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Priority to CN202211712652.9A priority Critical patent/CN116073423A/en
Publication of CN116073423A publication Critical patent/CN116073423A/en
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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
    • H02J3/36—Arrangements for transfer of electric power between ac networks via a high-tension dc link
    • 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
    • H02J3/12—Circuit arrangements for ac mains or ac distribution networks for adjusting voltage in ac networks by changing a characteristic of the network load
    • H02J3/16—Circuit arrangements for ac mains or ac distribution networks for adjusting voltage in ac networks by changing a characteristic of the network load by adjustment of reactive power
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H02J3/381—Dispersed generators
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • 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
    • H02J3/46—Controlling of the sharing of output between the generators, converters, or transformers
    • H02J3/50—Controlling the sharing of the out-of-phase component
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J2300/00—Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation
    • H02J2300/20—The dispersed energy generation being of renewable origin
    • H02J2300/28—The renewable source being wind energy

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Supply And Distribution Of Alternating Current (AREA)

Abstract

The invention provides a flexible grid-connected method and a device of a flexible direct current system of an offshore wind farm, wherein the method comprises the steps of obtaining rated frequency and rated voltage of grid-side grid-connected points, actual reactive power measurement values and reactive power reference values of grid-side converters, direct current voltage measurement values and direct current voltage rated values of direct current sides of the grid-side converters and alternating current voltage measurement values of alternating current sides of the grid-side converters; calculating a phase reference value based on the rated frequency, the direct-current voltage measured value and the direct-current voltage rated value, and calculating a voltage reference value based on the rated voltage, the reactive power actual measured value and the reactive power reference value; and calculating to obtain a three-phase voltage reference value based on the alternating-current voltage measurement value, the phase reference value and the voltage reference value, and controlling the grid-side converter based on the three-phase voltage reference value, so that flexible grid connection is completed. According to the method disclosed by the invention, the flexible direct current transmission system of the offshore wind farm has stronger voltage supporting capability on an access power grid.

Description

Flexible grid connection method and device for flexible direct current system of offshore wind farm
Technical Field
The disclosure relates to the field of flexible direct current transmission of offshore wind farms, in particular to a flexible grid-connected method and device of a flexible direct current system of an offshore wind farm.
Background
With the rapid development of new energy power generation, wind power generation gradually occupies a larger proportion in a power system. Wind power generation includes onshore wind power generation and offshore wind power generation. For offshore wind power generation, the flexible direct current transmission technology is the main stream mode of large-scale wind power transmission in deep open sea at present. The offshore wind power flexible direct current transmission system has two grid connection points, one is a grid connection point for connecting the onshore converter station with a large power grid (namely, an onshore main network), and the other is a grid connection point for connecting the offshore converter station with a wind power plant. Typically, for an onshore grid, a wind-powered flexible-direct system is not typically required to participate in system voltage, frequency regulation. However, as the offshore wind power grid-connected scale is continuously increased, the wind power has an increasingly larger influence on the connected power grid, and the land large power grid hopes that the wind power plant connected by the flexible and straight system can play a certain role in supporting the voltage of the connected power grid to a certain extent. Therefore, a flexible grid-connection technology of a flexible direct current system of an offshore wind farm with strong supporting capability on grid-connection point voltage of an access power grid is urgently needed.
Disclosure of Invention
The present disclosure aims to solve, at least to some extent, one of the technical problems in the related art.
Therefore, a first object of the present disclosure is to provide a flexible grid-connection method of a flexible direct current system of an offshore wind farm, which is mainly aimed at enabling the flexible direct current power transmission system of the offshore wind farm to have a strong voltage supporting capability to an access power grid.
A second object of the present disclosure is to provide a flexible grid-connected device of a flexible dc system of an offshore wind farm.
A third object of the present disclosure is to provide a flexible grid-connected device of a flexible dc system of an offshore wind farm.
To achieve the above object, an embodiment of a first aspect of the present disclosure provides a flexible grid-connected method of a flexible direct current system of an offshore wind farm, the flexible direct current system of the offshore wind farm includes a grid-side converter and a grid-side grid-connected point, the grid-side converter is connected with a land main network via the grid-side grid-connected point, the method includes:
the method comprises the steps of obtaining rated frequency and rated voltage of grid-side grid-connected points, a reactive power actual measurement value and reactive power reference value of a grid-side converter, a direct-current voltage measurement value and a direct-current voltage rated value of a direct-current side of the grid-side converter and an alternating-current voltage measurement value of an alternating-current side of the grid-side converter;
calculating to obtain a phase reference value based on the rated frequency, the direct-current voltage measured value and the direct-current voltage rated value, and calculating to obtain a voltage reference value based on the rated voltage, the reactive power actual measured value and the reactive power reference value;
and calculating to obtain a three-phase voltage reference value based on the alternating-current voltage measurement value, the phase reference value and the voltage reference value, and controlling the grid-side converter based on the three-phase voltage reference value so as to complete flexible grid connection.
In one embodiment of the present disclosure, the calculating a phase reference value based on the nominal frequency, the dc voltage measurement, and the dc voltage rating includes: a reference frequency is calculated based on a regulated voltage, the dc voltage measurement and the dc voltage rating, the phase reference value is obtained based on the reference frequency, wherein the regulated voltage is obtained based on a first damping coefficient, the reference frequency and the rating.
In one embodiment of the present disclosure, the calculating a voltage reference value based on the rated voltage, the actual reactive power measurement value, and the reactive power reference value includes: a voltage reference value is calculated based on the regulated power, the measured reactive power value, and the reactive power reference value, wherein the regulated power is obtained based on a second damping coefficient, the voltage reference value, and the rated voltage.
In one embodiment of the present disclosure, the calculating to obtain the three-phase voltage reference value based on the ac voltage measurement value, the phase reference value, and the voltage reference value includes: obtaining a d-axis voltage component and a q-axis voltage component based on the ac voltage measurement and the phase reference value using a park transform; the three-phase voltage reference value is obtained based on the d-axis voltage component, q-axis voltage component, and the voltage reference value using inverse park transformation.
In one embodiment of the present disclosure, the voltage reference value includes a d-axis voltage reference component and a q-axis voltage reference component, the obtaining the three-phase voltage reference value based on the d-axis voltage component, the q-axis voltage component, and the voltage reference value using inverse park transformation includes: obtaining a d-axis voltage target value based on the d-axis voltage component and a d-axis voltage reference component; obtaining a q-axis voltage target value based on the q-axis voltage component and a q-axis voltage reference component; three-phase voltage reference values are obtained based on the d-axis voltage target value and the q-axis voltage target value using inverse park transformation.
To achieve the above object, an embodiment of a second aspect of the present disclosure provides a flexible grid-connected device of a flexible direct current system of an offshore wind farm, the flexible direct current system of the offshore wind farm includes a grid-side converter and a grid-side grid-connected point, the grid-side converter is connected with a land main network via the grid-side grid-connected point, the device includes:
the acquisition module is used for acquiring rated frequency and rated voltage of the grid-side grid-connected point, a reactive power actual measurement value and reactive power reference value of the grid-side converter, a direct-current voltage measurement value and a direct-current voltage rated value of the direct-current side of the grid-side converter and an alternating-current voltage measurement value of the alternating-current side of the grid-side converter;
the calculation module is used for calculating and obtaining a phase reference value based on the rated frequency, the direct-current voltage measured value and the direct-current voltage rated value, and calculating and obtaining a voltage reference value based on the rated voltage, the reactive power actual measured value and the reactive power reference value;
and the control module is used for calculating and obtaining a three-phase voltage reference value based on the alternating voltage measurement value, the phase reference value and the voltage reference value, and controlling the grid-side converter based on the three-phase voltage reference value so as to complete flexible grid connection.
In one embodiment of the disclosure, the computing module is specifically configured to: a reference frequency is calculated based on a regulated voltage, the dc voltage measurement and the dc voltage rating, the phase reference value is obtained based on the reference frequency, wherein the regulated voltage is obtained based on a first damping coefficient, the reference frequency and the rating.
In one embodiment of the disclosure, the computing module is specifically configured to: a voltage reference value is calculated based on the regulated power, the measured reactive power value, and the reactive power reference value, wherein the regulated power is obtained based on a second damping coefficient, the voltage reference value, and the rated voltage.
In one embodiment of the disclosure, the control module is specifically configured to: obtaining a d-axis voltage component and a q-axis voltage component based on the ac voltage measurement and the phase reference value using a park transform; the three-phase voltage reference value is obtained based on the d-axis voltage component, q-axis voltage component, and the voltage reference value using inverse park transformation.
To achieve the above object, an embodiment of a third aspect of the present disclosure provides a flexible grid-connected device of a flexible dc system of an offshore wind farm, including: at least one processor; and a memory communicatively coupled to the at least one processor; the memory stores instructions executable by the at least one processor to enable the at least one processor to perform a flexible grid connection method of the offshore wind farm flexible direct current system according to the first aspect of the present disclosure.
In one or more embodiments of the present disclosure, a flexible direct current system of an offshore wind farm includes a grid-side converter and a grid-side grid-tie point, the grid-side converter is connected to a land-based main network via the grid-side grid-tie point, and the flexible grid-tie method includes: the method comprises the steps of obtaining rated frequency and rated voltage of grid-side grid-connected points, a reactive power actual measurement value and reactive power reference value of a grid-side converter, a direct-current voltage measurement value and a direct-current voltage rated value of a direct-current side of the grid-side converter and an alternating-current voltage measurement value of an alternating-current side of the grid-side converter; calculating a phase reference value based on the rated frequency, the direct-current voltage measured value and the direct-current voltage rated value, and calculating a voltage reference value based on the rated voltage, the reactive power actual measured value and the reactive power reference value; and calculating to obtain a three-phase voltage reference value based on the alternating-current voltage measurement value, the phase reference value and the voltage reference value, and controlling the grid-side converter based on the three-phase voltage reference value, so that flexible grid connection is completed. Under the condition, the rated frequency and rated voltage of the grid-connected point at the grid side, the actual reactive power measured value and reactive power reference value of the grid-side converter, the direct current voltage measured value and the direct current voltage rated value of the direct current side of the grid-side converter and the alternating current voltage measured value of the alternating current side of the grid-side converter are synthesized to obtain a three-phase voltage reference value, the grid-side converter is controlled by the three-phase voltage reference value, and at the moment, the flexible direct current system can still maintain the stability of the direct current voltage under the condition that the connected main land grid has small disturbance, so that the flexible direct current power transmission system of the offshore wind farm has stronger voltage supporting capability for the connected power grid according to the method disclosed by the invention.
Additional aspects and advantages of the disclosure will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the disclosure.
Drawings
In order to more clearly illustrate the embodiments of the present disclosure or the prior art, the drawings that are required in the detailed description or the prior art will be briefly described, it will be apparent that the drawings in the following description are some embodiments of the present disclosure, and other drawings may be obtained according to the drawings without inventive effort for a person of ordinary skill in the art. The foregoing and/or additional aspects and advantages of the present disclosure will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings, in which:
fig. 1 is a schematic diagram of a topology structure of a flexible dc system of an offshore wind farm provided by an embodiment of the disclosure;
FIG. 2 is a schematic flow chart of a flexible grid-connected method of a flexible direct current system of an offshore wind farm provided by an embodiment of the disclosure;
fig. 3 is a schematic diagram of a portion of dc voltage outer loop control of a grid-side converter according to an embodiment of the present disclosure;
fig. 4 is a schematic diagram of another part of dc voltage outer loop control of the grid-side converter according to an embodiment of the present disclosure;
FIG. 5 is a block diagram of a flexible grid-tie device for a flexible DC system of an offshore wind farm provided by an embodiment of the disclosure;
FIG. 6 is a block diagram of a flexible grid-tie device of an offshore wind farm flexible DC system for implementing a flexible grid-tie method of an offshore wind farm flexible DC system according to an embodiment of the disclosure.
Detailed Description
Reference will now be made in detail to exemplary embodiments, examples of which are illustrated in the accompanying drawings. When the following description refers to the accompanying drawings, the same numbers in different drawings refer to the same or similar elements, unless otherwise indicated. The implementations described in the following exemplary embodiments do not represent all implementations consistent with the embodiments of the present disclosure. Rather, they are merely examples of apparatus and methods consistent with aspects of embodiments of the present disclosure as detailed in the accompanying claims.
In the description of the present specification, a description referring to terms "one embodiment," "some embodiments," "examples," "specific examples," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present disclosure. In this specification, schematic representations of the above terms are not necessarily directed to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, the different embodiments or examples described in this specification and the features of the different embodiments or examples may be combined and combined by those skilled in the art without contradiction.
Furthermore, the terms "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include at least one such feature. In the description of the present disclosure, the meaning of "a plurality" is at least two, such as two, three, etc., unless explicitly specified otherwise. It should also be understood that the term "and/or" as used in this disclosure refers to and encompasses any or all possible combinations of one or more of the associated listed items.
Embodiments of the present disclosure are described in detail below, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to like or similar elements or elements having like or similar functions throughout. The embodiments described below by referring to the drawings are exemplary and intended for the purpose of explaining the present disclosure and are not to be construed as limiting the present disclosure.
The invention provides a flexible grid-connected method and device of a flexible direct current system of an offshore wind farm, and mainly aims to enable the flexible direct current power transmission system of the offshore wind farm to have stronger voltage supporting capability on an access power grid.
As will be readily appreciated, the offshore wind farm flexible dc system of the present disclosure is also referred to as an offshore wind farm flexible dc power transmission system. The flexible direct current system of the offshore wind farm comprises a grid-side converter, grid-side grid-connection points, a machine-side converter and machine-side grid-connection points, wherein the grid-side converter is connected with a land main network through the grid-side grid-connection points, and the machine-side converter is connected with the offshore wind farm through the machine-side grid-connection points.
Fig. 1 is a schematic diagram of a topology structure of a flexible dc system of an offshore wind farm according to an embodiment of the disclosure. As shown in fig. 1, the offshore wind farm flexible direct current system comprises a machine side connection transformer, an offshore converter station, a cable line, a land converter station and a network side connection transformer which are connected in sequence. One end of the machine side connecting transformer is connected with an offshore converter station (namely a machine side converter), the other end of the machine side connecting transformer is connected with an offshore wind farm, and the connection point of the machine side connecting transformer and the offshore wind farm is a machine side grid connection point. One end of the network side connecting transformer is connected with the land current converting station (namely the network side current converter), the other end of the network side connecting transformer is connected with the land main network, and the connection point of the network side connecting transformer and the land main network is a network side grid connection point. The onshore and offshore converter stations employ voltage source converters (Voltage Source Converter, VSCs). The cable line is used for conveying high-voltage direct current. The near-land converter station side of the cable line is provided with an energy consumption device. The energy consumption device is used for consuming surplus power on the direct current side of the flexible direct current transmission system, and is matched with the flexible direct current transmission system to realize alternating current fault ride through, and action time is also strived for the fan when faults cannot be cleared, so that the safety and reliability of the whole flexible direct current transmission system are improved.
In a first embodiment, fig. 2 is a schematic flow chart of a flexible grid-connected method of a flexible direct current system of an offshore wind farm according to an embodiment of the disclosure. As shown in fig. 2, the flexible grid-connection method of the flexible direct current system of the offshore wind farm comprises the following steps:
and S11, obtaining the rated frequency and rated voltage of the grid-side grid-connected point, the reactive power actual measurement value and reactive power reference value of the grid-side converter, the direct-current voltage measurement value and the direct-current voltage rated value of the direct-current side of the grid-side converter and the alternating-current voltage measurement value of the alternating-current side of the grid-side converter.
Specifically, in step S11, the obtained nominal frequency of the network-side point of attachment may be represented by symbol ω ref The rated voltage of the acquired grid-side grid-connected point can be represented by a symbol V mref The obtained actual reactive power measurement value of the network-side converter can be represented by a symbol Q, and the obtained reactive power reference value of the network-side converter can be represented by a symbol Q ref The obtained DC voltage measurement value of the DC side of the network side converter can be represented by a symbol U dc The obtained direct voltage rating of the network-side converter can be represented by the symbol U dcref The ac voltage measurement value of the ac side of the network-side converter obtained can be represented by the symbol V ABC And (3) representing.
Step S12, calculating and obtaining a phase reference value based on the rated frequency, the direct current voltage measured value and the direct current voltage rated value, and calculating and obtaining a voltage reference value based on the rated voltage, the reactive power actual measured value and the reactive power reference value.
In step S12, the phase reference value may be represented by the symbol θ, and the voltage reference value may be represented by the symbol V.
In step S12, a phase reference value is obtained based on the nominal frequency, the dc voltage measurement value, and the dc voltage nominal value calculation, including: the reference frequency is calculated based on the regulated voltage, the DC voltage measurement and the DC voltage rating, and the phase reference value is obtained based on the reference frequency, wherein the regulated voltage is obtained based on the first damping coefficient, the reference frequency and the nominal frequency.
In step S12, a voltage reference value is calculated based on the rated voltage, the actual reactive power value, and the reactive power reference value, including: the voltage reference value is calculated based on the regulated power, the reactive power actual measurement value and the reactive power reference value, wherein the regulated power is obtained based on the second damping coefficient, the voltage reference value and the rated voltage.
Specifically, fig. 3 is a schematic diagram of a portion of dc voltage outer loop control of the grid-side converter according to an embodiment of the present disclosure.
In some embodiments, as shown in FIG. 3, the regulated voltage DeltaU and the DC voltage rating U are calculated dcref And then calculate the sum and the DC voltage measurement U dc The first difference value is sent to a PI regulator (i.e. a proportional-integral controller) to utilize a first inertia coefficient J p Performing integral calculation (1/S means integral calculation) to obtain a reference frequency ω, and sending the reference frequency ω to a PI regulator to perform integral calculation to obtain a phase reference value θ, wherein the adjustment voltage Δu is set to an initial value at the time of initial calculation, and the adjustment voltage Δu is based on a first damping coefficient D at the time of subsequent calculation p Reference frequency omega and nominal frequency omega ref And updating in real time. Specifically, the rated frequency ω is calculated ref And a second difference value of the reference frequency omega, the second difference value is sent to the PI regulator and is matched with the first damping coefficient D P The product is performed to obtain the regulated voltage DeltaU. Calculating the regulated power DeltaQ and reactive power referenceQ of (2) ref And then calculates a third difference value between the sum and the actual reactive power Q, and sends the third difference value to the PI regulator to use the second inertia coefficient J q Performing integral calculation to obtain a voltage reference value V, wherein the regulated power DeltaQ is set to an initial value in the initial calculation and the regulated power DeltaQ is based on a second damping coefficient D in the subsequent calculation q Voltage reference value V and rated voltage V mref And updating in real time. Specifically, the rated voltage V is calculated mref And a fourth difference value of the voltage reference value V, and the fourth difference value is sent to the PI regulator and is matched with the second damping coefficient D q The product is performed to obtain the regulated power Δq.
And step S13, calculating to obtain a three-phase voltage reference value based on the alternating-current voltage measurement value, the phase reference value and the voltage reference value, and controlling the grid-side converter based on the three-phase voltage reference value, so that flexible grid connection is completed.
In step S13, a three-phase voltage reference value is calculated based on the ac voltage measurement value, the phase reference value, and the voltage reference value, including: obtaining a d-axis voltage component and a q-axis voltage component based on the ac voltage measurement value and the phase reference value using park transformation; three-phase voltage reference values are obtained based on the d-axis voltage component, the q-axis voltage component, and the voltage reference values using inverse park transformation. It is easy to understand that park transformation is to project the currents or voltages of the three phases a, b, c onto the direct axis (d-axis) and the quadrature axis (q-axis) in order to simplify the analysis of the operation of the synchronous motor, i.e. the abc coordinate system is transformed into the dq coordinate system. The inverse park matrix transform (i.e., the inverse park matrix transform) is a transform of the dq coordinate system to the abc coordinate system.
In step S13, the voltage reference values include a d-axis voltage reference component and a q-axis voltage reference component, and obtaining three-phase voltage reference values based on the d-axis voltage component, the q-axis voltage component, and the voltage reference values using inverse park transformation includes: obtaining a d-axis voltage target value based on the d-axis voltage component and the d-axis voltage reference component; obtaining a q-axis voltage target value based on the q-axis voltage component and the q-axis voltage reference component; three-phase voltage reference values are obtained based on the d-axis voltage target value and the q-axis voltage target value using inverse park transformation.
In step S13In which the d-axis voltage component may be represented by the symbol V d And (3) representing. The q-axis voltage component may be denoted by the symbol V q And (3) representing. The d-axis voltage reference component may be denoted by the symbol V dref And (3) representing. The q-axis voltage reference component may be denoted by the symbol V qref And (3) representing. The d-axis voltage target value may be denoted by the symbol V cd And (3) representing. The q-axis voltage target value may be denoted by the symbol V cq And (3) representing.
Specifically, fig. 4 is another schematic diagram of a dc voltage outer loop control of a grid-side converter according to an embodiment of the present disclosure.
In some embodiments, as shown in FIG. 4, for an AC voltage measurement V ABC After Park transformation (i.e. Park matrix change) is performed on the phase reference value theta, a d-axis voltage component V is obtained d And q-axis voltage component V q The voltage reference value V includes a d-axis voltage reference component V dref And q-axis voltage reference component V qref Wherein (V) dref ) 2 +(V qref ) 2 ＝V 2 . Calculating d-axis voltage reference component V dref With d-axis voltage component V d And send the difference value into a PI regulator to calculate a d-axis voltage target value V cd The method comprises the steps of carrying out a first treatment on the surface of the Calculating the q-axis voltage reference component V qref With q-axis voltage component V q And send the difference value into a PI regulator to calculate a q-axis voltage target value V cq 。
In step S13, the d-axis voltage target value V cd And q-axis voltage target value V cq And performing park inverse transformation (i.e. park matrix inverse transformation) to obtain a three-phase voltage reference value, and controlling the grid-side converter based on the three-phase voltage reference value, so as to complete flexible grid connection. The three-phase voltage reference value is a modulation reference wave of the grid-side converter and participates in the control and regulation of the voltage and reactive power of the grid-side converter. The control of the grid-side converter based on the obtained three-phase voltage reference value ensures the stability of the direct voltage.
In the flexible grid-connected method of the flexible direct current system of the offshore wind farm in the embodiment of the disclosure, the flexible direct current system of the offshore wind farm comprises a grid-side converter and a grid-side grid-connected point, the grid-side converter is connected with a land main network through the grid-side grid-connected point, and the flexible grid-connected method comprises the following steps: the method comprises the steps of obtaining rated frequency and rated voltage of grid-side grid-connected points, a reactive power actual measurement value and reactive power reference value of a grid-side converter, a direct-current voltage measurement value and a direct-current voltage rated value of a direct-current side of the grid-side converter and an alternating-current voltage measurement value of an alternating-current side of the grid-side converter; calculating a phase reference value based on the rated frequency, the direct-current voltage measured value and the direct-current voltage rated value, and calculating a voltage reference value based on the rated voltage, the reactive power actual measured value and the reactive power reference value; and calculating to obtain a three-phase voltage reference value based on the alternating-current voltage measurement value, the phase reference value and the voltage reference value, and controlling the grid-side converter based on the three-phase voltage reference value, so that flexible grid connection is completed. Under the condition, the rated frequency and rated voltage of the grid-connected point at the grid side, the actual reactive power measured value and reactive power reference value of the grid-side converter, the direct current voltage measured value and the direct current voltage rated value of the direct current side of the grid-side converter and the alternating current voltage measured value of the alternating current side of the grid-side converter are synthesized to obtain a three-phase voltage reference value, the grid-side converter is controlled by the three-phase voltage reference value, and at the moment, the flexible direct current system can still maintain the stability of the direct current voltage under the condition that the connected main land grid has small disturbance, so that the flexible direct current power transmission system of the offshore wind farm has stronger voltage supporting capability for the connected power grid according to the method disclosed by the invention. Compared with the traditional constant direct current voltage control, the control method has the advantages that the flexible direct current system has certain direct current voltage fluctuation capacity, and the direct current voltage outer ring is changed, so that the control method capable of coping with the grid-connected point voltage with certain supporting capacity under the condition of small disturbance of the connected power grid is provided.
The following are device embodiments of the present disclosure that may be used to perform method embodiments of the present disclosure. For details not disclosed in the embodiments of the apparatus of the present disclosure, please refer to the embodiments of the method of the present disclosure.
The disclosure relates to a flexible grid-connected device of a flexible direct current system of an offshore wind farm. The flexible grid-connected device of the flexible direct current system of the offshore wind farm can enable the flexible direct current power transmission system of the offshore wind farm to have stronger voltage supporting capability on an access power grid. The flexible direct current system of the offshore wind farm comprises a grid-side converter and grid-side grid-connection points, and the grid-side converter is connected with the land main network through the grid-side grid-connection points.
Referring to fig. 5, fig. 5 is a block diagram of a flexible grid-connected device of a flexible dc system of an offshore wind farm according to an embodiment of the disclosure. The flexible grid-connected device 10 of the flexible direct current system of the offshore wind farm comprises an acquisition module 11, a calculation module 12 and a control module 13, wherein:
the acquisition module 11 is used for acquiring rated frequency and rated voltage of the grid-side grid-connected point, a reactive power actual measurement value and reactive power reference value of the grid-side converter, a direct-current voltage measurement value and a direct-current voltage rating value of the direct-current side of the grid-side converter and an alternating-current voltage measurement value of the alternating-current side of the grid-side converter;
a calculation module 12 for calculating a phase reference value based on the rated frequency, the dc voltage measurement value, and the dc voltage rating value, and calculating a voltage reference value based on the rated voltage, the reactive power actual measurement value, and the reactive power reference value;
the control module 13 is configured to calculate and obtain a three-phase voltage reference value based on the ac voltage measurement value, the phase reference value and the voltage reference value, and control the grid-side inverter based on the three-phase voltage reference value, thereby completing flexible grid connection.
Optionally, the computing module 12 is specifically configured to: the reference frequency is calculated based on the regulated voltage, the DC voltage measurement and the DC voltage rating, and the phase reference value is obtained based on the reference frequency, wherein the regulated voltage is obtained based on the first damping coefficient, the reference frequency and the nominal frequency.
Optionally, the computing module 12 is specifically configured to: the voltage reference value is calculated based on the regulated power, the reactive power actual measurement value and the reactive power reference value, wherein the regulated power is obtained based on the second damping coefficient, the voltage reference value and the rated voltage.
Optionally, the control module 13 is specifically configured to: obtaining a d-axis voltage component and a q-axis voltage component based on the ac voltage measurement value and the phase reference value using park transformation; three-phase voltage reference values are obtained based on the d-axis voltage component, the q-axis voltage component, and the voltage reference values using inverse park transformation.
Optionally, the voltage reference value includes a d-axis voltage reference component and a q-axis voltage reference component. The control module 13 is specifically configured to: obtaining a d-axis voltage target value based on the d-axis voltage component and the d-axis voltage reference component; obtaining a q-axis voltage target value based on the q-axis voltage component and the q-axis voltage reference component; three-phase voltage reference values are obtained based on the d-axis voltage target value and the q-axis voltage target value using inverse park transformation.
It should be noted that the explanation of the foregoing embodiment of the flexible grid-connection method of the flexible direct current system of the offshore wind farm is also applicable to the flexible grid-connection device of the flexible direct current system of the offshore wind farm in this embodiment, and is not described herein.
In the flexible grid-connected device of the flexible direct current system of the offshore wind farm, an acquisition module acquires rated frequency and rated voltage of grid-side grid-connected points, a reactive power actual measurement value and reactive power reference value of a grid-side converter, a direct current voltage measurement value and a direct current voltage rated value of a direct current side of the grid-side converter and an alternating current voltage measurement value of an alternating current side of the grid-side converter; the calculation module calculates and obtains a phase reference value based on the rated frequency, the direct-current voltage measured value and the direct-current voltage rated value, and calculates and obtains a voltage reference value based on the rated voltage, the reactive power actual measured value and the reactive power reference value; the control module calculates and obtains a three-phase voltage reference value based on the alternating-current voltage measurement value, the phase reference value and the voltage reference value, and controls the grid-side converter based on the three-phase voltage reference value, so that flexible grid connection is completed. Under the condition, the rated frequency and rated voltage of the grid-connected point at the grid side, the actual reactive power measured value and reactive power reference value of the grid-side converter, the direct current voltage measured value and the direct current voltage rated value of the direct current side of the grid-side converter and the alternating current voltage measured value of the alternating current side of the grid-side converter are synthesized to obtain a three-phase voltage reference value, the grid-side converter is controlled by the three-phase voltage reference value, and at the moment, the flexible direct current system can still maintain the stability of the direct current voltage under the condition that the connected main land grid has small disturbance, so that the device according to the disclosure can enable the flexible direct current power transmission system of the offshore wind farm to have stronger voltage supporting capability for the connected power grid. Compared with the traditional constant direct current voltage control, the control device has certain direct current voltage fluctuation capacity based on the flexible direct current system, and changes the direct current voltage outer ring, so that the control device which can deal with the grid-connected point voltage of the power grid under the small disturbance of the accessed power grid and has certain supporting capacity is provided.
According to embodiments of the present disclosure, the present disclosure also provides a flexible grid-tie device, a readable storage medium and a computer program product of a flexible direct current system of an offshore wind farm.
FIG. 6 is a block diagram of a flexible grid-tie device of an offshore wind farm flexible DC system for implementing a flexible grid-tie method of an offshore wind farm flexible DC system according to an embodiment of the disclosure. The flexible grid-tie device of the offshore wind farm flexible DC system is intended to represent various forms of digital computers, such as laptops, desktops, workstations, personal digital assistants, servers, blade servers, mainframes, and other suitable computers. The flexible grid-tie devices of the offshore wind farm flexible dc system may also represent various forms of mobile devices, such as personal digital processing, cellular phones, smart phones, wearable electronics, and other similar computing devices. The components, connections and relationships of components, and functions of components shown in this disclosure are exemplary only, and are not meant to limit implementations of the disclosure described and/or claimed in this disclosure.
As shown in fig. 6, the flexible grid-tie device 20 of the offshore wind farm flexible direct current system comprises a computing unit 21, which may perform various suitable actions and processes according to a computer program stored in a Read Only Memory (ROM) 22 or a computer program loaded from a storage unit 28 into a Random Access Memory (RAM) 23. In RAM 23, various programs and data required for the operation of the flexible grid-tie device 20 of the offshore wind farm flexible dc system may also be stored. The computing unit 21, the ROM 22 and the RAM 23 are connected to each other via a bus 24. An input/output (I/O) interface 25 is also connected to bus 24.
The various components in the flexible grid-tie device 20 of the offshore wind farm flexible DC system are connected to an I/O interface 25, including: an input unit 26 such as a keyboard, a mouse, etc.; an output unit 27 such as various types of displays, speakers, and the like; a storage unit 28, such as a magnetic disk, an optical disk, or the like, the storage unit 28 being communicatively connected to the computing unit 21; and a communication unit 29 such as a network card, modem, wireless communication transceiver, etc. The communication unit 29 allows the flexible grid-tie device 20 of the offshore wind farm flexible direct current system to exchange information/data with flexible grid-tie devices of other offshore wind farm flexible direct current systems via a computer network such as the internet and/or various telecommunication networks.
The computing unit 21 may be a variety of general and/or special purpose processing components having processing and computing capabilities. Some examples of computing unit 21 include, but are not limited to, a Central Processing Unit (CPU), a Graphics Processing Unit (GPU), various specialized Artificial Intelligence (AI) computing chips, various computing units running machine learning model algorithms, a Digital Signal Processor (DSP), and any suitable processor, controller, microcontroller, etc. The computing unit 21 performs the various methods and processes described above, for example, performing a flexible grid-tie method of the offshore wind farm flexible direct current system. For example, in some embodiments, the flexible grid-tie method of the offshore wind farm flexible DC system may be implemented as a computer software program tangibly embodied on a machine-readable medium, such as storage unit 28. In some embodiments, part or all of the computer program may be loaded and/or installed onto the flexible grid-tie device 20 of the offshore wind farm flexible direct current system via the ROM 22 and/or the communication unit 29. When the computer program is loaded into RAM 23 and executed by the computing unit 21, one or more steps of the flexible grid-tie method of the offshore wind farm flexible direct current system described above may be performed. Alternatively, in other embodiments, the computing unit 21 may be configured to perform the flexible grid-tie method of the offshore wind farm flexible direct current system in any other suitable way (e.g. by means of firmware).
Various implementations of the systems and techniques described above in this disclosure may be implemented in digital electronic circuitry, integrated circuit systems, field Programmable Gate Arrays (FPGAs), application Specific Integrated Circuits (ASICs), application Specific Standard Products (ASSPs), systems On Chip (SOCs), load programmable logic devices (CPLDs), computer hardware, firmware, software, and/or combinations thereof. These various embodiments may include: implemented in one or more computer programs, the one or more computer programs may be executed and/or interpreted on a programmable system including at least one programmable processor, which may be a special purpose or general-purpose programmable processor, that may receive data and instructions from, and transmit data and instructions to, a storage system, at least one input device, and at least one output device.
Program code for carrying out methods of the present disclosure may be written in any combination of one or more programming languages. These program code may be provided to a processor or controller of a general purpose computer, special purpose computer, or other programmable data processing apparatus such that the program code, when executed by the processor or controller, causes the functions/operations specified in the flowchart and/or block diagram to be implemented. The program code may execute entirely on the machine, partly on the machine, as a stand-alone software package, partly on the machine and partly on a remote machine or entirely on the remote machine or server.
In this disclosure, a machine-readable medium may be a tangible medium that can contain, or store a program for use by or in connection with an instruction execution system, apparatus, or device. The machine-readable medium may be a machine-readable signal medium or a machine-readable storage medium. The machine-readable medium may include, but is not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or electronic device, or any suitable combination of the preceding. More specific examples of a machine-readable storage medium would include an electrical connection based on one or more wires, a portable computer diskette, a hard disk, a Random Access Memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage electronic device, a magnetic storage electronic device, or any suitable combination of the foregoing.
To provide for interaction with a user, the systems and techniques described here can be implemented on a computer having: a display device (e.g., a CRT (cathode ray tube) or LCD (liquid crystal display) monitor) for displaying information to a user; and a keyboard and pointing device (e.g., a mouse or trackball) by which a user can provide input to the computer. Other kinds of devices may also be used to provide for interaction with a user; for example, feedback provided to the user may be any form of sensory feedback (e.g., visual feedback, auditory feedback, or tactile feedback); and input from the user may be received in any form, including acoustic input, speech input, or tactile input.
The systems and techniques described here can be implemented in a computing system that includes a background component (e.g., as a data server), or that includes a middleware component (e.g., an application server), or that includes a front-end component (e.g., a user computer having a graphical user interface or a web browser through which a user can interact with an implementation of the systems and techniques described here), or any combination of such background, middleware, or front-end components. The components of the system can be interconnected by any form or medium of digital data communication (e.g., a communication network). Examples of communication networks include: local Area Networks (LANs), wide Area Networks (WANs), the internet, and blockchain networks.
The computer system may include a client and a server. The client and server are typically remote from each other and typically interact through a communication network. The relationship of client and server arises by virtue of computer programs running on the respective computers and having a client-server relationship to each other. The server can be a cloud server, also called a cloud computing server or a cloud host, and is a host product in a cloud computing service system, so that the defects of high management difficulty and weak service expansibility in the traditional physical hosts and VPS service ("Virtual Private Server" or simply "VPS") are overcome. The server may also be a server of a distributed system or a server that incorporates a blockchain.
It should be appreciated that various forms of the flows shown above may be used to reorder, add, or delete steps. For example, the steps described in the present disclosure may be performed in parallel, sequentially, or in a different order, so long as the desired result of the technical solution of the present disclosure can be achieved, and the present disclosure is not limited herein.
The above detailed description should not be taken as limiting the scope of the present disclosure. It will be apparent to those skilled in the art that various modifications, combinations, sub-combinations and alternatives are possible, depending on design requirements and other factors. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present disclosure are intended to be included within the scope of the present disclosure.

Claims (10)

1. The flexible grid-connected method of the flexible direct current system of the offshore wind farm is characterized in that the flexible direct current system of the offshore wind farm comprises a grid-side converter and grid-side grid-connected points, and the grid-side converter is connected with a land main network through the grid-side grid-connected points, and the method comprises the following steps:
the method comprises the steps of obtaining rated frequency and rated voltage of grid-side grid-connected points, a reactive power actual measurement value and reactive power reference value of a grid-side converter, a direct-current voltage measurement value and a direct-current voltage rated value of a direct-current side of the grid-side converter and an alternating-current voltage measurement value of an alternating-current side of the grid-side converter;
calculating to obtain a phase reference value based on the rated frequency, the direct-current voltage measured value and the direct-current voltage rated value, and calculating to obtain a voltage reference value based on the rated voltage, the reactive power actual measured value and the reactive power reference value;
and calculating to obtain a three-phase voltage reference value based on the alternating-current voltage measurement value, the phase reference value and the voltage reference value, and controlling the grid-side converter based on the three-phase voltage reference value so as to complete flexible grid connection.
2. The method of flexible grid connection of a flexible dc system for an offshore wind farm according to claim 1, wherein the calculating a phase reference value based on the nominal frequency, the dc voltage measurement and the dc voltage rating comprises:
a reference frequency is calculated based on a regulated voltage, the dc voltage measurement and the dc voltage rating, the phase reference value is obtained based on the reference frequency, wherein the regulated voltage is obtained based on a first damping coefficient, the reference frequency and the rating.
3. The method for flexible grid connection of a flexible direct current system of an offshore wind farm according to claim 2, wherein the calculating the voltage reference value based on the rated voltage, the actual reactive power value and the reactive power reference value comprises:
a voltage reference value is calculated based on the regulated power, the measured reactive power value, and the reactive power reference value, wherein the regulated power is obtained based on a second damping coefficient, the voltage reference value, and the rated voltage.
4. A method of flexible grid connection of a flexible dc system for an offshore wind farm according to claim 3, wherein the calculating based on the ac voltage measurement, the phase reference and the voltage reference to obtain a three-phase voltage reference comprises:
obtaining a d-axis voltage component and a q-axis voltage component based on the ac voltage measurement and the phase reference value using a park transform; the three-phase voltage reference value is obtained based on the d-axis voltage component, q-axis voltage component, and the voltage reference value using inverse park transformation.
5. The method of flexible grid-tie of a flexible direct current system of an offshore wind farm according to claim 4, wherein the voltage reference values comprise a d-axis voltage reference component and a q-axis voltage reference component, the obtaining the three-phase voltage reference values based on the d-axis voltage component, the q-axis voltage component, and the voltage reference values using inverse park transformation comprising:
obtaining a d-axis voltage target value based on the d-axis voltage component and a d-axis voltage reference component;
obtaining a q-axis voltage target value based on the q-axis voltage component and a q-axis voltage reference component;
three-phase voltage reference values are obtained based on the d-axis voltage target value and the q-axis voltage target value using inverse park transformation.
6. A flexible grid-connected device of a flexible direct current system of an offshore wind farm, the flexible direct current system of the offshore wind farm comprising a grid-side converter and a grid-side grid-connected point, the grid-side converter being connected to a land-based main network via the grid-side grid-connected point, the device comprising:
the acquisition module is used for acquiring rated frequency and rated voltage of the grid-side grid-connected point, a reactive power actual measurement value and reactive power reference value of the grid-side converter, a direct-current voltage measurement value and a direct-current voltage rated value of the direct-current side of the grid-side converter and an alternating-current voltage measurement value of the alternating-current side of the grid-side converter;
the calculation module is used for calculating and obtaining a phase reference value based on the rated frequency, the direct-current voltage measured value and the direct-current voltage rated value, and calculating and obtaining a voltage reference value based on the rated voltage, the reactive power actual measured value and the reactive power reference value;
and the control module is used for calculating and obtaining a three-phase voltage reference value based on the alternating voltage measurement value, the phase reference value and the voltage reference value, and controlling the grid-side converter based on the three-phase voltage reference value so as to complete flexible grid connection.
7. The flexible grid-tie device of a flexible direct current system of an offshore wind farm according to claim 6, wherein the computing module is specifically configured to:
a reference frequency is calculated based on a regulated voltage, the dc voltage measurement and the dc voltage rating, the phase reference value is obtained based on the reference frequency, wherein the regulated voltage is obtained based on a first damping coefficient, the reference frequency and the rating.
8. The flexible grid-tie device of a flexible direct current system of an offshore wind farm according to claim 7, wherein the computing module is specifically configured to:
a voltage reference value is calculated based on the regulated power, the measured reactive power value, and the reactive power reference value, wherein the regulated power is obtained based on a second damping coefficient, the voltage reference value, and the rated voltage.
9. The flexible grid-tie device of a flexible direct current system of an offshore wind farm according to claim 8, wherein the control module is specifically configured to:
obtaining a d-axis voltage component and a q-axis voltage component based on the ac voltage measurement and the phase reference value using a park transform; the three-phase voltage reference value is obtained based on the d-axis voltage component, q-axis voltage component, and the voltage reference value using inverse park transformation.
10. A flexible grid-connected device of a flexible direct current system of an offshore wind farm, comprising:
at least one processor; and
a memory communicatively coupled to the at least one processor; wherein,,
the memory stores instructions executable by the at least one processor to enable the at least one processor to perform the flexible grid-tie method of the offshore wind farm flexible direct current system of any of claims 1-5.
CN202211712652.9A 2022-12-29 2022-12-29 Flexible grid connection method and device for flexible direct current system of offshore wind farm Pending CN116073423A (en)

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