DC voltage coordinated control method and device for offshore wind power flexible DC system

Abstract

The present disclosure proposes a method and device for coordinated control of DC voltage of an offshore wind power flexible DC system. The method comprehensively considers the rated frequency and rated voltage of the grid-side grid-connected point, the measured reactive power value and reactive power reference value of the grid-side converter, the measured DC voltage value and the rated DC voltage of the DC side of the grid-side converter, the measured AC voltage value of the AC side of the grid-side converter, the current and the maximum current of the grid-side grid-connected point to obtain a grid-side three-phase voltage reference value to control the grid-side converter. The method comprehensively considers the rated frequency and rated voltage of the machine-side grid-connected point, the measured reactive power value and reactive power reference value of the machine-side converter, the measured DC voltage value and the rated DC voltage of the DC side of the machine-side converter, the measured AC voltage value of the AC side of the machine-side converter, the current and the large current of the machine-side grid-connected point to obtain a machine-side three-phase voltage reference value to control the machine-side converter. According to the present disclosure, the offshore wind farm flexible DC transmission system can have a strong voltage support capability for accessing the power grid.

Description

Technical Field

[0001] The present disclosure relates to the field of flexible direct current (DC) power transmission in offshore wind farms, and in particular to a method and device for coordinated control of DC voltage in an offshore wind farm flexible DC system. Background Art

[0002] With the rapid development of new energy power generation, wind power generation has gradually occupied a large proportion in the power system. Wind power generation includes onshore wind power generation and offshore wind power generation. Among them, for offshore wind power generation, flexible direct current transmission technology is currently the mainstream way to send large-scale wind power in the deep sea. There are two grid connection points in the offshore wind power flexible direct current transmission system, one is the grid connection point where the onshore converter station is connected to the large power grid (i.e., the onshore main grid), and the other is the grid connection point where the offshore converter station is connected to the wind farm. The flexible direct current system itself has limited regulation capabilities. Considering that the flexible direct current converter can generate voltages of any frequency and amplitude within its voltage allowable range. Usually for onshore power grids, it is usually not required that the wind power flexible direct current system participate in the system voltage and frequency regulation. However, with the continuous increase in the scale of offshore wind power grid connection, the impact of wind power on the access grid is increasing. The onshore large power grid hopes that the wind farm connected to the flexible direct current system can play a certain supporting role in the voltage of the access grid connection point to a certain extent. Therefore, the prior art urgently needs a DC voltage coordinated control technology for an offshore wind power flexible direct current system with strong support capabilities for the voltage of the access grid connection point. Summary of the invention

[0003] The present disclosure aims to solve one of the technical problems in the related art at least to some extent.

[0004] To this end, the first purpose of the present disclosure is to propose a DC voltage coordinated control method for an offshore wind power flexible DC system, the main purpose of which is to enable the offshore wind farm flexible DC transmission system to have a stronger voltage support capability for access to the power grid.

[0005] The second objective of the present disclosure is to provide a DC voltage coordinated control device for an offshore wind power flexible DC system.

[0006] The third objective of the present disclosure is to provide a DC voltage coordinated control device for an offshore wind power flexible DC system.

[0007] To achieve the above-mentioned object, the first aspect of the present disclosure proposes a method for coordinated control of DC voltage of an offshore wind power flexible DC system, wherein the offshore wind farm flexible DC system includes a converter and a grid connection point, wherein the converter includes a grid-side converter and a machine-side converter, wherein the grid connection point includes a grid-side grid connection point and a machine-side grid connection point, wherein the grid-side converter is connected to the onshore main grid via the grid-side grid connection point, and the machine-side converter is connected to the offshore wind farm via the machine-side grid connection point, wherein the method includes:

[0008] Obtain the rated frequency and rated voltage of each grid connection point, the measured reactive power value and reactive power reference value of each converter, the measured DC voltage value and rated DC voltage value of the DC side of each converter, the measured AC voltage value of the AC side of each converter, the grid connection point current of each grid connection point, and the maximum current of each converter;

[0009] A grid-side phase reference value and a generator-side phase reference value are calculated based on the rated frequency, the DC voltage measurement value and the DC voltage rated value, and a grid-side voltage reference value and a generator-side voltage reference value are calculated based on the rated voltage, the reactive power measured value and the reactive power reference value;

[0010] A grid-side current reference value is calculated based on the grid-side AC voltage measurement value, the grid-side phase reference value and the grid-side voltage reference value; a grid-side three-phase voltage reference value is calculated based on the grid-side grid-connected point current, the maximum current of the grid-side converter, the grid-side phase reference value and the grid-side current reference value, and the grid-side converter is controlled based on the grid-side three-phase voltage reference value;

[0011] A machine side current reference value is calculated based on the AC voltage measurement value on the machine side, the machine side phase reference value and the machine side voltage reference value; a machine side three-phase voltage reference value is calculated based on the machine side grid-connected point current, the maximum current of the machine side converter, the machine side phase reference value and the machine side current reference value, and the machine side converter is controlled based on the machine side three-phase voltage reference value.

[0012] In one embodiment of the present disclosure, the grid-side phase reference value and the machine-side phase reference value are calculated based on the rated frequency, the DC voltage measurement value and the DC voltage rated value, including: calculating the grid-side reference frequency based on the grid-side regulated voltage, the DC voltage measurement value of the grid-side converter and the DC voltage rated value of the grid-side converter, and obtaining the grid-side phase reference value based on the grid-side reference frequency, wherein the grid-side regulated voltage is obtained based on the grid-side first damping coefficient, the grid-side reference frequency and the rated frequency of the grid-connected point; calculating the machine-side reference frequency based on the machine-side regulated voltage, the DC voltage measurement value of the machine-side converter and the DC voltage rated value of the machine-side converter, and obtaining the machine-side phase reference value based on the machine-side reference frequency, wherein the machine-side regulated voltage is obtained based on the machine-side first damping coefficient, the machine-side reference frequency and the rated frequency of the machine-side grid-connected point.

[0013] In one embodiment of the present disclosure, the grid-side voltage reference value and the machine-side voltage reference value are calculated based on the rated voltage, the reactive power measured value and the reactive power reference value, including: calculating the grid-side voltage reference value based on the grid-side regulated power, the reactive power measured value of the grid-side converter and the reactive power reference value of the grid-side converter, wherein the grid-side regulated power is obtained based on the grid-side second damping coefficient, the grid-side voltage reference value and the rated voltage of the grid-connected point; calculating the machine-side voltage reference value based on the machine-side regulated power, the reactive power measured value of the machine-side converter and the reactive power reference value of the machine-side converter, wherein the machine-side regulated power is obtained based on the machine-side second damping coefficient, the machine-side voltage reference value and the rated voltage of the machine-side grid-connected point.

[0014] In one embodiment of the present disclosure, the grid-side voltage reference value includes a grid-side d-axis voltage reference component and a grid-side q-axis voltage reference component, and the grid-side current reference value is calculated based on the grid-side AC voltage measurement value, the grid-side phase reference value and the grid-side voltage reference value, including: using Park transformation to obtain the grid-side d-axis voltage component and the grid-side q-axis voltage component based on the AC voltage measurement value of the grid-side converter and the grid-side phase reference value; based on the grid-side d-axis voltage reference component, the grid-side q-axis voltage reference component, the grid-side d-axis voltage component, and the grid-side q-axis voltage component, obtaining the grid-side current reference value, and the grid-side current reference value includes the grid-side d-axis current reference component and the grid-side q-axis current reference component.

[0015] In one embodiment of the present disclosure, the calculation based on the grid-side connection point current, the maximum current of the grid-side converter, the grid-side phase reference value and the grid-side current reference value to obtain the grid-side three-phase voltage reference value includes: using Park transformation to obtain the grid-side d-axis current component and the grid-side q-axis current component based on the grid-side connection point current and the grid-side phase reference value; based on the maximum current of the grid-side converter, the grid-side d-axis current reference component and the grid-side q-axis current reference component to obtain the grid-side target d-axis current reference component and the grid-side target q-axis current reference component; using Park inverse transformation to obtain the grid-side three-phase voltage reference value based on the grid-side d-axis current component, the grid-side q-axis current component, the grid-side target d-axis current reference component and the grid-side target q-axis current reference component.

[0016] In one embodiment of the present disclosure, the use of the inverse Park transform to obtain the grid-side three-phase voltage reference value based on the grid-side d-axis current component, the grid-side q-axis current component, the grid-side target d-axis current reference component and the grid-side target q-axis current reference component includes: obtaining the grid-side d-axis voltage target value based on the grid-side d-axis current component, the target grid-side d-axis current reference component and the grid-side d-axis voltage component; obtaining the grid-side q-axis voltage target value based on the grid-side q-axis current component, the target grid-side q-axis current reference component and the grid-side q-axis voltage component; and obtaining the grid-side three-phase voltage reference value based on the grid-side d-axis voltage target value and the grid-side q-axis voltage target value using the inverse Park transform.

[0017] To achieve the above-mentioned object, the second aspect of the present disclosure proposes a DC voltage coordinated control device for an offshore wind power flexible DC system, wherein the offshore wind farm flexible DC system includes a converter and a grid connection point, wherein the converter includes a grid-side converter and a machine-side converter, wherein the grid connection point includes a grid-side grid connection point and a machine-side grid connection point, wherein the grid-side converter is connected to the onshore main grid via the grid-side grid connection point, and the machine-side converter is connected to the offshore wind farm via the machine-side grid connection point, wherein the device includes:

[0018] An acquisition module is used to obtain the rated frequency and rated voltage of each grid-connected point, the measured reactive power value and reactive power reference value of each converter, the measured DC voltage value and rated DC voltage value of the DC side of each converter, the measured AC voltage value of the AC side of each converter, the grid-connected point current of each grid-connected point, and the maximum current of each converter;

[0019] a calculation module, configured to calculate a grid-side phase reference value and a generator-side phase reference value based on the rated frequency, the DC voltage measurement value and the DC voltage rated value, and to calculate a grid-side voltage reference value and a generator-side voltage reference value based on the rated voltage, the reactive power measured value and the reactive power reference value;

[0020] A control module, used to calculate a grid-side current reference value based on a grid-side AC voltage measurement value, the grid-side phase reference value and the grid-side voltage reference value; calculate a grid-side three-phase voltage reference value based on a grid-side grid-connected point current, a maximum current of the grid-side converter, the grid-side phase reference value and the grid-side current reference value, and control the grid-side converter based on the grid-side three-phase voltage reference value; calculate a machine-side current reference value based on a machine-side AC voltage measurement value, the machine-side phase reference value and the machine-side voltage reference value; calculate a machine-side three-phase voltage reference value based on a machine-side grid-connected point current, a maximum current of the machine-side converter, the machine-side phase reference value and the machine-side current reference value, and control the machine-side converter based on the machine-side three-phase voltage reference value.

[0021] In one embodiment of the present disclosure, the grid-side voltage reference value includes a grid-side d-axis voltage reference component and a grid-side q-axis voltage reference component, and the control module is specifically used to: use Park transformation to obtain a grid-side d-axis voltage component and a grid-side q-axis voltage component based on the AC voltage measurement value of the grid-side converter and the grid-side phase reference value; obtain a grid-side current reference value based on the grid-side d-axis voltage reference component, the grid-side q-axis voltage reference component, the grid-side d-axis voltage component, and the grid-side q-axis voltage component, and the grid-side current reference value includes a grid-side d-axis current reference component and a grid-side q-axis current reference component.

[0022] In one embodiment of the present disclosure, the control module is specifically used to: use Park transformation to obtain a grid-side d-axis current component and a grid-side q-axis current component based on the grid-side grid-connected point current and the grid-side phase reference value; obtain a grid-side target d-axis current reference component and a grid-side target q-axis current reference component based on the maximum current of the grid-side converter, the grid-side d-axis current reference component, and the grid-side q-axis current reference component; use Park inverse transformation to obtain a grid-side three-phase voltage reference value based on the grid-side d-axis current component, the grid-side q-axis current component, the grid-side target d-axis current reference component, and the grid-side target q-axis current reference component.

[0023] To achieve the above-mentioned purpose, the third aspect embodiment of the present disclosure proposes a DC voltage collaborative control device for an offshore wind power flexible DC system, comprising: at least one processor; and a memory communicatively connected to the at least one processor; wherein the memory stores instructions executable by the at least one processor, and the instructions are executed by the at least one processor so that the at least one processor can execute the DC voltage collaborative control method for an offshore wind power flexible DC system of the first aspect embodiment of the present disclosure.

[0024] In one or more embodiments of the present disclosure, an offshore wind farm flexible DC system includes a converter and a grid connection point, the converter includes a grid-side converter and a machine-side converter, the grid connection point includes a grid-side grid connection point and a machine-side grid connection point, the grid-side converter is connected to the onshore main grid via the grid-side grid connection point, and the machine-side converter is connected to the offshore wind farm via the machine-side grid connection point, and the method includes: obtaining the rated frequency and rated voltage of each grid connection point, the reactive power measured value and reactive power reference value of each converter, the DC voltage measurement value and DC voltage rated value of each converter, the AC voltage measurement value of each converter, the grid connection point current of each grid connection point, and the maximum current of each converter; based on the rated frequency, the DC voltage measurement value and the DC voltage rated value, the grid-side phase reference value and the machine-side phase reference value are calculated; based on the rated frequency, the DC voltage measurement value and the DC voltage rated value, the AC voltage measurement value of each converter is calculated; based on the rated frequency, the DC voltage measurement value and the DC voltage rated value, the grid-side phase reference value and the machine-side phase reference value are ... The grid-side voltage reference value and the machine-side voltage reference value are calculated based on the rated voltage, the measured reactive power value and the reactive power reference value; the grid-side current reference value is calculated based on the AC voltage measurement value on the grid, the grid-side phase reference value and the grid-side voltage reference value; the grid-side three-phase voltage reference value is calculated based on the grid-connected point current, the maximum current of the grid-side converter, the grid-side phase reference value and the grid-side current reference value, and the grid-side converter is controlled based on the grid-side three-phase voltage reference value; the machine-side current reference value is calculated based on the AC voltage measurement value on the machine side, the machine-side phase reference value and the machine-side voltage reference value; the machine-side three-phase voltage reference value is calculated based on the machine-connected point current, the maximum current of the machine-side converter, the machine-side phase reference value and the machine-side current reference value, and the machine-side converter is controlled based on the machine-side three-phase voltage reference value. In this case, the rated frequency and rated voltage of the grid-side grid-connected point, the measured reactive power value and reactive power reference value of the grid-side converter, the measured DC voltage value and the rated DC voltage of the DC side of the grid-side converter, the measured AC voltage value of the AC side of the grid-side converter, the current of the grid-side grid-connected point and the maximum current of the grid-side converter are integrated to obtain the grid-side three-phase voltage reference value, and the grid-side converter is controlled by using the grid-side three-phase voltage reference value. The rated frequency and rated voltage of the generator-side grid-connected point, the measured reactive power value and the reactive power reference value of the generator-side converter are integrated to obtain the grid-side three-phase voltage reference value. The three-phase voltage reference value of the machine side is obtained by the measured DC voltage value and the rated DC voltage value of the DC side of the machine side converter, the measured AC voltage value of the AC side of the machine side converter, the current of the machine side grid connection point and the maximum current of the machine side converter. The three-phase voltage reference value of the machine side is used to control the machine side converter. At this time, when there is a small disturbance in the connected onshore main grid, the flexible DC system can still maintain the stability of the DC voltage. Therefore, according to the method disclosed in the present invention, the flexible DC transmission system of the offshore wind farm can have a strong voltage support capability for the connected grid.

[0025] Additional aspects and advantages of the present disclosure will be given in part in the following description and in part will be obvious from the following description or learned through practice of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the specific implementation of the present disclosure or the technical solutions in the prior art, the following will briefly introduce the drawings required for use in the specific implementation or prior art description. Obviously, the drawings described below are some implementations of the present disclosure. For ordinary technicians in this field, other drawings can also be obtained based on these drawings without creative work. The above and / or additional aspects and advantages of the present disclosure will become obvious and easy to understand from the following description of the embodiments in conjunction with the drawings, in which:

[0027] Figure 1 A schematic diagram of the topological structure of an offshore wind farm flexible DC system provided by an embodiment of the present disclosure;

[0028] Figure 2 A schematic flow chart of a DC voltage coordinated control method for an offshore wind power flexible DC system provided in an embodiment of the present disclosure;

[0029] Figure 3 A schematic diagram of a portion of the DC voltage outer loop control of the grid-side converter provided in an embodiment of the present disclosure;

[0030] Figure 4 Another part of the schematic diagram of the DC voltage outer loop control of the grid-side converter provided in the embodiment of the present disclosure;

[0031] Figure 5 A schematic diagram of the inner loop control part of the grid-side converter provided in an embodiment of the present disclosure;

[0032] Figure 6 A schematic diagram of a portion of the DC voltage outer loop control of the machine-side converter provided in an embodiment of the present disclosure;

[0033] Figure 7 Another part of the schematic diagram of the DC voltage outer loop control of the machine-side converter provided in the embodiment of the present disclosure;

[0034] Figure 8 A schematic diagram of the inner loop control part of the machine-side converter provided in an embodiment of the present disclosure;

[0035] Fig. 9 A block diagram of a DC voltage coordinated control device for an offshore wind power flexible DC system provided by an embodiment of the present disclosure;

[0036] Fig.10 It is a block diagram of an offshore wind power flexible DC system DC voltage collaborative control device used to implement the offshore wind power flexible DC system DC voltage collaborative control method of the embodiment of the present disclosure. DETAILED DESCRIPTION

[0037] Exemplary embodiments will be described in detail herein, examples of which are shown in the accompanying drawings. When the following description refers to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The implementations described in the following exemplary embodiments do not represent all implementations consistent with the embodiments of the present disclosure. Instead, they are merely examples of devices and methods consistent with some aspects of the embodiments of the present disclosure as detailed in the appended claims.

[0038] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present disclosure. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0039] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of the features. In the description of the present disclosure, the meaning of "multiple" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined. It should also be understood that the term "and / or" used in the present disclosure refers to and includes any or all possible combinations of one or more associated listed items.

[0040] Embodiments of the present disclosure are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present disclosure, and should not be construed as limiting the present disclosure.

[0041] The present disclosure provides a method and device for coordinated control of DC voltage of an offshore wind power flexible DC system, the main purpose of which is to enable the offshore wind farm flexible DC transmission system to have a stronger voltage support capability for access to the power grid.

[0042] It is easy to understand that the offshore wind farm flexible DC system disclosed in the present invention is also called an offshore wind farm flexible DC transmission system. The offshore wind farm flexible DC system includes multiple converters and multiple grid connection points, the multiple converters include grid-side converters and machine-side converters, the multiple grid connection points include grid-side grid connection points and machine-side grid connection points, the grid-side converter is connected to the onshore main grid via the grid-side grid connection point, and the machine-side converter is connected to the offshore wind farm via the machine-side grid connection point.

[0043] Figure 1 This is a schematic diagram of the topological structure of the flexible DC system for an offshore wind farm provided by an embodiment of the present disclosure. Figure 1 As shown in FIG. 1 , the flexible DC system of an offshore wind farm includes a machine-side connection transformer, an offshore converter station, a cable line, an onshore converter station and a grid-side connection transformer connected in sequence. Among them, one end of the machine-side connection transformer is connected to the offshore converter station (i.e., the machine-side converter), and the other end of the machine-side connection transformer is connected to the offshore wind farm. The connection point between the machine-side connection transformer and the offshore wind farm is the machine-side grid connection point. One end of the grid-side connection transformer is connected to the onshore converter station (i.e., the grid-side converter), and the other end of the grid-side connection transformer is connected to the onshore main grid. The connection point between the grid-side connection transformer and the onshore main grid is the grid-side grid connection point. The onshore converter station and the offshore converter station use a voltage source converter (VSC). The cable line is used to transmit high-voltage direct current. An energy-consuming device is provided on the side of the cable line near the onshore converter station. The energy-consuming device is used to consume the surplus power on the DC side of the flexible direct current transmission system, cooperate to realize the AC fault crossing of the flexible direct current system, and also strive for action time for the wind turbine when the fault cannot be cleared, so as to improve the safety and reliability of the entire flexible direct current system.

[0044] In a first embodiment, Figure 2 The flowchart of the DC voltage coordinated control method of the offshore wind power flexible DC system provided by the embodiment of the present disclosure is as follows: Figure 2 As shown, the DC voltage coordinated control method of the offshore wind power flexible DC system includes the following steps:

[0045] Step S11, obtaining the rated frequency and rated voltage of each grid-connected point, the measured reactive power value and reactive power reference value of each converter, the measured DC voltage value and rated DC voltage value of the DC side of each converter, the measured AC voltage value of the AC side of each converter, the grid-connected point current of each grid-connected point, and the maximum current of each converter.

[0046] In step S11, the rated frequency and rated voltage of each grid-connected point include the rated frequency ω of the grid-side grid-connected point ref网 、Rated frequency of the machine side grid connection pointω ref机 , Rated voltage of the grid-side connection point V mref网 and the rated voltage V of the generator side grid connection point mref机The reactive power measured value and reactive power reference value of each converter include the reactive power measured value Q of the grid-side converter. 网 , the measured reactive power value Q of the machine-side converter 机 , reactive power reference value Q of grid-side converter ref网 and the reactive power reference value Q of the generator-side converter ref机 The DC voltage measurement value and DC voltage rating of each converter DC side include the DC voltage measurement value U dc网 , the DC voltage measurement value U of the DC side of the machine-side converter dc机 , DC voltage rating of grid-side converter U dcref网 and the DC voltage rating of the machine-side converter U dcref机 The AC voltage measurement value of each converter AC side includes the AC voltage measurement value V ABC网 (i.e. the AC voltage measurement value on the grid side) and the AC voltage measurement value V on the AC side of the machine-side converter ABC机 (i.e., the AC voltage measurement value on the generator side). The grid-connected point current of each grid-connected point includes the grid-side grid-connected point current I ABC网 And the current of the machine side grid connection point I ABC机 The maximum current of each converter includes the maximum current I max网 and the maximum current I of the machine-side converter max机 Among them, the maximum current is the upper limit of the current in the converter current limiting capability requirement.

[0047] Figure 3 A schematic diagram of a portion of the DC voltage outer loop control of the grid-side converter provided in an embodiment of the present disclosure; Figure 4 Another part of the schematic diagram of the DC voltage outer loop control of the grid-side converter provided in the embodiment of the present disclosure; Figure 5 A schematic diagram of the inner loop control part of the grid-side converter provided in an embodiment of the present disclosure; Figure 6 A schematic diagram of a portion of the DC voltage outer loop control of the machine-side converter provided in an embodiment of the present disclosure; Figure 7 Another partial schematic diagram of the DC voltage outer loop control of the machine-side converter provided in an embodiment of the present disclosure. Figure 8 This is a schematic diagram of the inner loop control part of the machine-side converter provided in an embodiment of the present disclosure. Figure 3 , Figure 4 and Figure 5 The data involved are the relevant data of the grid-side converter and the grid-side connection point. Figure 6 , Figure 7 and Figure 8 The data involved are the relevant data of the machine-side converter and the machine-side grid connection point.

[0048] Step S12, calculating the grid-side phase reference value and the generator-side phase reference value based on the rated frequency, the DC voltage measurement value and the DC voltage rated value, and calculating the grid-side voltage reference value and the generator-side voltage reference value based on the rated voltage, the reactive power measured value and the reactive power reference value.

[0049] In step S12, the grid-side phase reference value and the machine-side phase reference value are calculated based on the rated frequency, the DC voltage measurement value and the DC voltage rating value, including: the grid-side reference frequency is calculated based on the grid-side regulated voltage, the DC voltage measurement value of the grid-side converter and the DC voltage rating value of the grid-side converter, and the grid-side phase reference value is obtained based on the grid-side reference frequency, wherein the grid-side regulated voltage is obtained based on the first damping coefficient of the grid-side, the grid-side reference frequency and the rated frequency of the grid-side grid-connected point. In step S12, the grid-side voltage reference value and the machine-side voltage reference value are calculated based on the rated voltage, the reactive power measurement value and the reactive power reference value, including: the grid-side voltage reference value is calculated based on the grid-side regulated power, the reactive power measurement value of the grid-side converter and the reactive power reference value of the grid-side converter, wherein the grid-side regulated power is obtained based on the second damping coefficient of the grid-side, the grid-side voltage reference value and the rated voltage of the grid-side grid-connected point.

[0050] In some embodiments, Figure 3 As shown, the grid-side regulation voltage △U is calculated 网 and DC voltage rating U dcref网 The sum of the sum and the DC voltage measurement value U is then calculated. dc网 The first difference is sent to the PI regulator (i.e., proportional integral controller) and the first inertia coefficient J of the grid side is used to calculate the p网 Perform integral calculation (1 / S represents integral operation) to obtain the grid-side reference frequency ω 网 , the grid-side reference frequency ω 网 It is sent to the PI regulator for integral calculation to obtain the grid-side phase reference value θ 网 , where the grid-side regulated voltage △U is calculated for the first time 网 An initial value is set, and the grid-side voltage △U is adjusted in subsequent calculations 网 Based on the first damping coefficient D on the grid side p网 , grid-side reference frequency ω 网 and rated frequency ω ref网 Updated in real time. Specifically, calculate the rated frequency ω ref网 and grid-side reference frequency ω 网 The second difference is sent to the PI regulator and the first damping coefficient D on the grid side P网 Multiply to obtain the grid-side regulated voltage △U 网 . Calculate the grid-side regulation power △Q 网 and reactive power reference value Q ref网Then calculate the sum of the result and the reactive power measured value Q 网 The third difference is sent to the PI regulator and the second inertia coefficient J of the grid side is used q网 Perform integral calculation to obtain the grid-side voltage reference value V 网 , where the grid-side adjustment power △Q is calculated for the first time 网 An initial value is set, and the grid side adjusts the power △Q in subsequent calculations 网 Based on the second damping coefficient D on the grid side q网 , grid side voltage reference value V 网 and rated voltage V mref网 Updated in real time. Specifically, calculate the rated voltage V mref网 and grid voltage reference value V 网 The fourth difference is sent to the PI regulator and the second damping coefficient D on the grid side. q网 Multiply to get the grid-side regulation power △Q 网 .

[0051] In step S12, the grid-side phase reference value and the machine-side phase reference value are calculated based on the rated frequency, the DC voltage measurement value and the DC voltage rating value, including: the machine-side reference frequency is calculated based on the machine-side regulated voltage, the DC voltage measurement value of the machine-side converter and the DC voltage rating value of the machine-side converter, and the machine-side phase reference value is obtained based on the machine-side reference frequency, wherein the machine-side regulated voltage is obtained based on the first damping coefficient of the machine-side, the machine-side reference frequency and the rated frequency of the machine-side grid-connected point. In step S12, the grid-side voltage reference value and the machine-side voltage reference value are calculated based on the rated voltage, the reactive power measured value and the reactive power reference value, including: the machine-side voltage reference value is calculated based on the machine-side regulated power, the reactive power measured value of the machine-side converter and the reactive power reference value of the machine-side converter, wherein the machine-side regulated power is obtained based on the second damping coefficient of the machine-side, the machine-side voltage reference value and the rated voltage of the machine-side grid-connected point.

[0052] In some embodiments, Figure 6 As shown, the computer side adjusts the voltage △U 机 and DC voltage rating U dcref机 The sum of the sum and the DC voltage measurement value U is then calculated. dc机 The first difference is sent to the PI regulator (i.e., proportional integral controller) and the first inertia coefficient J of the machine side is used to calculate the first inertia coefficient J of the machine side. p机 Perform integral calculation (1 / S represents integral operation) to obtain the machine-side reference frequency ω 机 , the machine side reference frequency ω 机 It is sent to the PI regulator for integral calculation to obtain the machine side phase reference value θ 机 , where the voltage △U is adjusted when the initial calculation is performed 机An initial value is set, and the voltage △U is adjusted when the timing is calculated later 机 Based on the first damping coefficient D on the machine side p机 , machine side reference frequency ω 机 and rated frequency ω ref机 Updated in real time. Specifically, calculate the rated frequency ω ref机 and the machine side reference frequency ω 机 The second difference is sent to the PI regulator and the first damping coefficient D on the machine side P机 Multiply to obtain the machine-side regulated voltage △U 机 . The computer side adjusts the power △Q 机 and reactive power reference value Q ref机 Then calculate the sum of the result and the reactive power measured value Q 机 The third difference is sent to the PI regulator and the second inertia coefficient J of the machine side is used q机 Perform integral calculation to obtain the machine side voltage reference value V 机 , where the power △Q is adjusted at the initial calculation time side 机 An initial value is set, and the power △Q is adjusted when the timing is calculated later 机 Based on the second damping coefficient D on the machine side q机 , machine side voltage reference value V 机 and rated voltage V mref机 Updated in real time. Specifically, calculate the rated voltage V mref机 And the machine side voltage reference value V 机 The fourth difference is sent to the PI regulator and the second damping coefficient D on the machine side q机 Multiply the product to obtain the regulated power △Q 机 .

[0053] Step S13, obtaining a grid-side current reference value based on the grid-side AC voltage measurement value, the grid-side phase reference value and the grid-side voltage reference value; obtaining a grid-side three-phase voltage reference value based on the grid-side grid-connected point current, the maximum current of the grid-side converter, the grid-side phase reference value and the grid-side current reference value, and controlling the grid-side converter based on the grid-side three-phase voltage reference value.

[0054] In this embodiment, the calculation in step S13 is for the grid-side converter.

[0055] In step S13, the grid-side voltage reference value includes a grid-side d-axis voltage reference component and a grid-side q-axis voltage reference component, and the grid-side current reference value is calculated based on the grid-side AC voltage measurement value, the grid-side phase reference value and the grid-side voltage reference value, including: using Park transformation to obtain the grid-side d-axis voltage component and the grid-side q-axis voltage component based on the AC voltage measurement value of the grid-side converter and the grid-side phase reference value; based on the grid-side d-axis voltage reference component, the grid-side q-axis voltage reference component, the grid-side d-axis voltage component, and the grid-side q-axis voltage component, the grid-side current reference value includes the grid-side d-axis current reference component and the grid-side q-axis current reference component.

[0056] It is easy to understand that the Park transformation (i.e. Park matrix transformation) is to project the current or voltage of the three phases a, b, c onto the direct axis (d axis) and the quadrature axis (q axis) to simplify the operation analysis of the synchronous motor, that is, the abc coordinate system is transformed into the dq coordinate system. The inverse Park transformation (i.e. Park matrix inverse transformation) is to transform the dq coordinate system into the abc coordinate system.

[0057] In some embodiments, Figure 4 The AC voltage measurement value V on the grid side is shown ABC网 and grid-side phase reference value θ 网 After Parker transformation (i.e. abc / dq), the grid-side d-axis voltage component V is obtained. d网 and the grid-side q-axis voltage component V q网 , grid side voltage reference value V 网 Including the grid-side d-axis voltage reference component V dref网 and the grid-side q-axis voltage reference component V qref网 , where (V dref网 ) 2 +(V qref网 ) 2 =V 网 2 . Calculate the grid-side d-axis voltage reference component V dref网 The grid-side d-axis voltage component V d网 The difference is sent to the PI regulator to calculate the grid-side d-axis current reference component I dref网 ; Calculate the grid-side q-axis voltage reference component V qref网 The grid-side q-axis voltage component V q网 The difference is sent to the PI regulator to calculate the grid-side q-axis current reference component I qref网 .

[0058] In step S13, the grid-side three-phase voltage reference value is calculated based on the grid-side grid-connected point current, the maximum current of the grid-side converter, the grid-side phase reference value and the grid-side current reference value, including: using Park transformation to obtain the grid-side d-axis current component and the grid-side q-axis current component based on the grid-side grid-connected point current and the grid-side phase reference value; based on the maximum current of the grid-side converter, the grid-side d-axis current reference component and the grid-side q-axis current reference component, obtaining the grid-side target d-axis current reference component and the grid-side target q-axis current reference component; using Park inverse transformation to obtain the grid-side three-phase voltage reference value based on the grid-side d-axis current component, the grid-side q-axis current component, the grid-side target d-axis current reference component and the grid-side target q-axis current reference component.

[0059] In step S13, a grid-side target d-axis current reference component and a grid-side target q-axis current reference component are obtained based on the maximum current of the grid-side converter, the grid-side d-axis current reference component, and the grid-side q-axis current reference component, including:

[0060] Compare the maximum current I of the grid-side converter max网 and the grid-side d-axis current reference component, select the maximum value as the grid-side target d-axis current reference component; use the maximum current I max网 , the grid-side target d-axis current reference component and the grid-side q-axis current reference component to obtain the grid-side target q-axis current reference component. Among them, the grid-side target d-axis current reference component satisfies:

[0061] I ’ dref网 =max(I max网 ,I dref网 )

[0062] The grid-side target q-axis current reference component satisfies:

[0063]

[0064] Among them, I ’ dref网 Indicates the grid-side target d-axis current reference component. I ’ qref网 Represents the grid-side target q-axis current reference component.

[0065] In step S13, a grid-side three-phase voltage reference value is obtained based on a grid-side d-axis current component, a grid-side q-axis current component, a grid-side target d-axis current reference component and a grid-side target q-axis current reference component using an inverse Park transform, including: obtaining a grid-side d-axis voltage target value based on a grid-side d-axis current component, a target grid-side d-axis current reference component and a grid-side d-axis voltage component; obtaining a grid-side q-axis voltage target value based on a grid-side q-axis current component, a target grid-side q-axis current reference component and a grid-side q-axis voltage component; and obtaining a grid-side three-phase voltage reference value based on a grid-side d-axis voltage target value and a grid-side q-axis voltage target value using an inverse Park transform.

[0066] In some embodiments, Figure 5 As shown, the grid-connected point current I ABC网 and grid-side phase reference value θ 网 After Parker transformation (i.e. abc / dq), the grid-side d-axis current component I is obtained. d网 and the grid-side q-axis current component I q网 ; Calculate the grid-side target d-axis current reference component I ’ dref网 The grid-side d-axis current component I d网 The difference is sent to the PI regulator to calculate the first grid-side voltage V 1网 , based on the inductance value L of the grid-side converter 网 and the grid-side q-axis current component I q网 Obtain the second grid-side voltage V 2网 , and then the grid-side d-axis voltage component V d网 Add the second grid-side voltage V 2网 Then subtract the first grid-side voltage V 1网 Get the grid-side d-axis voltage target value V cdref网 . Calculate the grid-side target q-axis current reference component I ’ qref网 The grid-side q-axis current component I q网 The difference is sent to the PI regulator to calculate the third grid-side voltage V 3网 , based on the inductance value L of the grid-side converter 网 and the grid-side d-axis current component I d网 Obtain the fourth grid-side voltage V 4网 , and then the grid-side q-axis voltage component V q网 Subtract the third voltage V on the grid side 3网 Then subtract the fourth grid-side voltage V 4网 Get the grid-side q-axis voltage target value V cqref网 Based on the grid-side phase reference value θ 网 , the target value of the grid-side d-axis voltage V cdref网 and the grid-side q-axis voltage target value V cqref网 Perform Park inverse transformation (i.e. dq / abc) to obtain the grid-side three-phase voltage reference value, V cAref网 、V cBref网 and V cCref网 It is the voltage reference value of each phase of the three-phase voltage reference value on the grid side. The three-phase voltage reference value on the grid side is the modulation reference wave of the grid-side converter, and participates in the control and regulation of the DC voltage and reactive power of the grid-side converter.

[0067] Step S14, obtain the machine side current reference value based on the machine side AC voltage measurement value, the machine side phase reference value and the machine side voltage reference value; obtain the machine side three-phase voltage reference value based on the machine side grid-connected point current, the maximum current of the machine side converter, the machine side phase reference value and the machine side current reference value, and control the machine side converter based on the machine side three-phase voltage reference value.

[0068] Considering that when only the grid-side converter is controlled, the DC voltage will usually deviate from the DC voltage rating of the grid-side converter according to the different supporting capabilities for the grid connection point voltage. The DC voltage rating of the grid-side converter is designed to take into account the voltage withstand capability of the equipment. In order to avoid the DC voltage measurement value having a large voltage change, it is necessary to collect the DC voltage measurement value in real time and improve the control of the machine-side converter (i.e., the offshore converter station). In this embodiment, the calculation in step S14 is for the machine-side converter.

[0069] In step S14, the machine-side voltage reference value includes a machine-side d-axis voltage reference component and a machine-side q-axis voltage reference component, and the machine-side current reference value is calculated based on the AC voltage measurement value, the machine-side phase reference value and the machine-side voltage reference value of the machine side, including: using Park transformation to obtain the machine-side d-axis voltage component and the machine-side q-axis voltage component based on the AC voltage measurement value and the machine-side phase reference value of the machine-side converter; based on the machine-side d-axis voltage reference component, the machine-side q-axis voltage reference component, the machine-side d-axis voltage component, and the machine-side q-axis voltage component, the machine-side current reference value includes the machine-side d-axis current reference component and the machine-side q-axis current reference component.

[0070] In some embodiments, Figure 7 The AC voltage measurement value V on the machine side is shown ABC机 and the machine side phase reference value θ 机 After Parker transformation (i.e. abc / dq), the d-axis voltage component V on the generator side is obtained. d机 and the machine-side q-axis voltage component V q机 , machine side voltage reference value V 机 Including the machine side d-axis voltage reference component V dref机 and the machine-side q-axis voltage reference component V qref机 , where (V dref机 ) 2 +(V qref机 ) 2 =V 机 2 Computer side d-axis voltage reference component V dref机 and the d-axis voltage component V d机 The difference is sent to the PI regulator to calculate the machine-side d-axis current reference component I dref机 ; Computer side q-axis voltage reference component V qref机and the q-axis voltage component V q机 The difference is sent to the PI regulator to calculate the machine-side q-axis current reference component I qref机 .

[0071] In step S14, the machine side three-phase voltage reference value is calculated based on the machine side grid-connected point current, the maximum current of the machine side converter, the machine side phase reference value and the machine side current reference value, including: using Park transformation to obtain the machine side d-axis current component and the machine side q-axis current component based on the machine side grid-connected point current and the machine side phase reference value; based on the maximum current of the machine side converter, the machine side d-axis current reference component and the machine side q-axis current reference component, obtaining the machine side target d-axis current reference component and the machine side target q-axis current reference component; using Park inverse transformation to obtain the machine side three-phase voltage reference value based on the machine side d-axis current component, the machine side q-axis current component, the machine side target d-axis current reference component and the machine side target q-axis current reference component.

[0072] In step S14, a machine-side target d-axis current reference component and a machine-side target q-axis current reference component are obtained based on the maximum current of the machine-side converter, the machine-side d-axis current reference component, and the machine-side q-axis current reference component, including:

[0073] Compare the maximum current I of the machine-side converter max机 and the machine-side d-axis current reference component, select the maximum value as the machine-side target d-axis current reference component; use the maximum current I max机 , the machine side target d-axis current reference component and the machine side q-axis current reference component to obtain the machine side target q-axis current reference component. Among them, the machine side target d-axis current reference component satisfies:

[0074] I ’ dref机 =max(I max机 ,I dref机 )

[0075] The target q-axis current reference component on the generator side satisfies:

[0076]

[0077] Among them, I ’ dref机 Indicates the reference component of the target d-axis current on the machine side. I ’ qref机 Represents the target q-axis current reference component on the machine side.

[0078] In step S14, the machine side three-phase voltage reference value is obtained based on the machine side d-axis current component, the machine side q-axis current component, the machine side target d-axis current reference component and the machine side target q-axis current reference component using the inverse Park transform, including: obtaining the machine side d-axis voltage target value based on the machine side d-axis current component, the target machine side d-axis current reference component and the machine side d-axis voltage component; obtaining the machine side q-axis voltage target value based on the machine side q-axis current component, the target machine side q-axis current reference component and the machine side q-axis voltage component; and obtaining the machine side three-phase voltage reference value based on the machine side d-axis voltage target value and the machine side q-axis voltage target value using the inverse Park transform.

[0079] In some embodiments, Figure 8 As shown, the current I ABC机 and the machine side phase reference value θ 机 After Parker transformation (i.e. abc / dq), the machine-side d-axis current component I is obtained. d机 and the machine-side q-axis current component I q机 ; Computer side target d-axis current reference component I ’ dref机 The d-axis current component I d机 The difference is sent to the PI regulator to calculate the first voltage V on the machine side. 1机 , based on the inductance value L of the machine-side converter 机 and the machine-side q-axis current component I q机 Get the second voltage V on the machine side 2机 , and then the machine side d-axis voltage component V d机 Add the second voltage V 2机 Then subtract the first voltage V on the generator side 1机 Get the target value V of the d-axis voltage on the machine side cdref机 . Computer side target q-axis current reference component I ’ qref机 The q-axis current component I q机 The difference is sent to the PI regulator to calculate the third voltage V on the machine side. 3机 , based on the inductance value L of the machine-side converter 机 and the machine-side d-axis current component I d机 Obtain the fourth voltage V on the machine side 4机 , and then the machine side q-axis voltage component V q机 Subtract the third voltage V on the machine side 3机 Then subtract the fourth voltage V 4机 Get the machine side q-axis voltage target value V cqref机 Based on the machine side phase reference value θ 机 , the target value of the d-axis voltage on the machine side is V cdref机 and the machine side q-axis voltage target value V cqref机Perform Park inverse transformation (i.e. dq / abc) to obtain the three-phase voltage reference value on the generator side, V cAref机 、V cBref机 and V cCref机 It is the voltage reference value of each phase of the three-phase voltage reference value on the machine side. The three-phase voltage reference value on the machine side is the modulation reference wave of the machine side converter, and participates in the control and regulation of the DC voltage and reactive power of the machine side converter.

[0080] In this embodiment, the grid-side three-phase voltage reference value is used to control the grid-side converter, and the machine-side three-phase voltage reference value is used to control the machine-side converter, thereby realizing dynamic regulation of the DC voltage. Controlling the converter based on the obtained grid-side three-phase voltage reference value and the machine-side three-phase voltage reference value can ensure the stability of the DC voltage.

[0081] In the DC voltage coordinated control method of the offshore wind power flexible DC system of the embodiment of the present disclosure, the offshore wind farm flexible DC system includes a converter and a grid connection point, the converter includes a grid-side converter and a machine-side converter, the grid connection point includes a grid-side grid connection point and a machine-side grid connection point, the grid-side converter is connected to the onshore main grid via the grid-side grid connection point, and the machine-side converter is connected to the offshore wind farm via the machine-side grid connection point. The method includes: obtaining the rated frequency and rated voltage of each grid connection point, the reactive power measured value and reactive power reference value of each converter, the DC voltage measurement value and DC voltage rated value of each converter DC side, the AC voltage measurement value of each converter AC side, the grid connection point current of each grid connection point, and the maximum current of each converter; based on the rated frequency, the DC voltage measurement value and the DC voltage rated value, the grid-side phase reference value and the machine-side phase reference value are calculated. Phase reference value, the grid-side voltage reference value and the machine-side voltage reference value are calculated based on the rated voltage, the actual measured value of reactive power and the reactive power reference value; the grid-side current reference value is calculated based on the AC voltage measurement value on the grid side, the grid-side phase reference value and the grid-side voltage reference value; the grid-side three-phase voltage reference value is calculated based on the grid-connected point current, the maximum current of the grid-side converter, the grid-side phase reference value and the grid-side current reference value, and the grid-side converter is controlled based on the grid-side three-phase voltage reference value; the machine-side current reference value is calculated based on the AC voltage measurement value on the machine side, the machine-side phase reference value and the machine-side voltage reference value; the machine-side three-phase voltage reference value is calculated based on the machine-side grid-connected point current, the maximum current of the machine-side converter, the machine-side phase reference value and the machine-side current reference value, and the machine-side converter is controlled based on the machine-side three-phase voltage reference value. In this case, the rated frequency and rated voltage of the grid-side grid-connected point, the measured reactive power value and reactive power reference value of the grid-side converter, the measured DC voltage value and the rated DC voltage of the DC side of the grid-side converter, the measured AC voltage value of the AC side of the grid-side converter, the current of the grid-side grid-connected point and the maximum current of the grid-side converter are integrated to obtain the grid-side three-phase voltage reference value, and the grid-side converter is controlled by using the grid-side three-phase voltage reference value. The rated frequency and rated voltage of the generator-side grid-connected point, the measured reactive power value and the reactive power reference value of the generator-side converter are integrated to obtain the grid-side three-phase voltage reference value. The machine-side three-phase voltage reference value is obtained by using the measured DC voltage value and the rated DC voltage value of the DC side of the machine-side converter, the measured AC voltage value of the AC side of the machine-side converter, the current at the machine-side grid connection point, and the maximum current of the machine-side converter. The machine-side converter is controlled by using the three-phase voltage reference value on the machine side. At this time, the flexible DC system can still maintain the stability of the DC voltage when there is a small disturbance in the connected onshore main grid. Therefore, according to the method disclosed in the present invention, the flexible DC transmission system of the offshore wind farm can have a strong voltage support capability for the access grid. Compared with the traditional fixed DC voltage control, the present invention is based on the flexible DC system itself having a certain DC voltage fluctuation capability and the converter current limiting capability requirement (i.e., the maximum current). It combines the flexible DC system and the offshore wind farm to provide a control method that can cope with the grid connection point voltage with a certain support capability for the grid voltage under small disturbances of the access grid.

[0082] The following are embodiments of the device disclosed herein, which can be used to execute the method embodiments disclosed herein. For details not disclosed in the device embodiments disclosed herein, please refer to the method embodiments disclosed herein.

[0083] The present disclosure relates to a DC voltage coordinated control device for an offshore wind power flexible DC system. The DC voltage coordinated control device for an offshore wind power flexible DC system can be used to enable an offshore wind farm flexible DC transmission system to have a strong voltage support capability for accessing the power grid. The offshore wind farm flexible DC system includes multiple converters and multiple grid connection points, the multiple converters include grid-side converters and machine-side converters, the multiple grid connection points include grid-side grid connection points and machine-side grid connection points, the grid-side converter is connected to the onshore main grid via the grid-side grid connection point, and the machine-side converter is connected to the offshore wind farm via the machine-side grid connection point.

[0084] See also Fig. 9 , Fig. 9 A block diagram of a DC voltage coordinated control device for an offshore wind power flexible DC system provided by an embodiment of the present disclosure. The DC voltage coordinated control device 10 for an offshore wind power flexible DC system includes an acquisition module 11, a calculation module 12, and a control module 13, wherein:

[0085] The acquisition module 11 is used to obtain the rated frequency and rated voltage of each grid connection point, the reactive power measured value and reactive power reference value of each converter, the DC voltage measured value and DC voltage rated value of each converter DC side, the AC voltage measured value of each converter AC side, the grid connection point current of each grid connection point, and the maximum current of each converter;

[0086] A calculation module 12, configured to calculate a grid-side phase reference value and a generator-side phase reference value based on the rated frequency, the DC voltage measurement value and the DC voltage rated value, and to calculate a grid-side voltage reference value and a generator-side voltage reference value based on the rated voltage, the reactive power measured value and the reactive power reference value;

[0087] The control module 13 is used to calculate the grid-side current reference value based on the grid-side AC voltage measurement value, the grid-side phase reference value and the grid-side voltage reference value; calculate the grid-side three-phase voltage reference value based on the grid-side grid-connected point current, the maximum current of the grid-side converter, the grid-side phase reference value and the grid-side current reference value, and control the grid-side converter based on the grid-side three-phase voltage reference value; calculate the machine-side current reference value based on the machine-side AC voltage measurement value, the machine-side phase reference value and the machine-side voltage reference value; calculate the machine-side three-phase voltage reference value based on the machine-side grid-connected point current, the maximum current of the machine-side converter, the machine-side phase reference value and the machine-side current reference value, and control the machine-side converter based on the machine-side three-phase voltage reference value.

[0088] Optionally, the calculation module 12 is specifically used to: calculate the grid-side phase reference value and the machine-side phase reference value based on the rated frequency, the DC voltage measurement value and the DC voltage rated value, including: calculating the grid-side reference frequency based on the grid-side regulated voltage, the DC voltage measurement value of the grid-side converter and the DC voltage rated value of the grid-side converter, and obtaining the grid-side phase reference value based on the grid-side reference frequency, wherein the grid-side regulated voltage is obtained based on the first grid-side damping coefficient, the grid-side reference frequency and the rated frequency of the grid-side grid-connected point; calculating the machine-side reference frequency based on the machine-side regulated voltage, the DC voltage measurement value of the machine-side converter and the DC voltage rated value of the machine-side converter, and obtaining the machine-side phase reference value based on the machine-side reference frequency, wherein the machine-side regulated voltage is obtained based on the first machine-side damping coefficient, the machine-side reference frequency and the rated frequency of the machine-side grid-connected point.

[0089] Optionally, the calculation module 12 is specifically used to: calculate the grid-side voltage reference value based on the grid-side regulation power, the actual measured value of the reactive power of the grid-side converter and the reactive power reference value of the grid-side converter, wherein the grid-side regulation power is obtained based on the second damping coefficient of the grid-side, the grid-side voltage reference value and the rated voltage of the grid-connected point; calculate the machine-side voltage reference value based on the machine-side regulation power, the actual measured value of the reactive power of the machine-side converter and the reactive power reference value of the machine-side converter, wherein the machine-side regulation power is obtained based on the second damping coefficient of the machine-side, the machine-side voltage reference value and the rated voltage of the machine-side grid-connected point.

[0090] Optionally, the control module 13 is specifically used to: use Park transformation to obtain a grid-side d-axis voltage component and a grid-side q-axis voltage component based on the AC voltage measurement value of the grid-side converter and the grid-side phase reference value; obtain a grid-side current reference value based on the grid-side d-axis voltage reference component, the grid-side q-axis voltage reference component, the grid-side d-axis voltage component, and the grid-side q-axis voltage component, and the grid-side current reference value includes a grid-side d-axis current reference component and a grid-side q-axis current reference component.

[0091] Optionally, the control module 13 is specifically used to: use Park transformation to obtain the grid-side d-axis current component and the grid-side q-axis current component based on the grid-side grid-connected point current and the grid-side phase reference value; obtain the grid-side target d-axis current reference component and the grid-side target q-axis current reference component based on the maximum current of the grid-side converter, the grid-side d-axis current reference component, and the grid-side q-axis current reference component; use Park inverse transformation to obtain the grid-side three-phase voltage reference value based on the grid-side d-axis current component, the grid-side q-axis current component, the grid-side target d-axis current reference component, and the grid-side target q-axis current reference component.

[0092] Optionally, the control module 13 is specifically used to: obtain a grid-side d-axis voltage target value based on the grid-side d-axis current component, the target grid-side d-axis current reference component and the grid-side d-axis voltage component; obtain a grid-side q-axis voltage target value based on the grid-side q-axis current component, the target grid-side q-axis current reference component and the grid-side q-axis voltage component; and obtain a grid-side three-phase voltage reference value based on the grid-side d-axis voltage target value and the grid-side q-axis voltage target value using an inverse Park transformation.

[0093] Optionally, the control module 13 is specifically used to: use Park transformation to obtain a machine side d-axis voltage component and a machine side q-axis voltage component based on the AC voltage measurement value of the machine side converter and the machine side phase reference value; obtain a machine side current reference value based on the machine side d-axis voltage reference component, the machine side q-axis voltage reference component, the machine side d-axis voltage component, and the machine side q-axis voltage component, and the machine side current reference value includes a machine side d-axis current reference component and a machine side q-axis current reference component.

[0094] Optionally, the control module 13 is specifically used to: use Park transformation to obtain the machine side d-axis current component and the machine side q-axis current component based on the machine side grid-connected point current and the machine side phase reference value; obtain the machine side target d-axis current reference component and the machine side target q-axis current reference component based on the maximum current of the machine side converter, the machine side d-axis current reference component, and the machine side q-axis current reference component; use Park inverse transformation to obtain the machine side three-phase voltage reference value based on the machine side d-axis current component, the machine side q-axis current component, the machine side target d-axis current reference component, and the machine side target q-axis current reference component.

[0095] Optionally, the control module 13 is specifically used to: obtain a machine side d-axis voltage target value based on the machine side d-axis current component, the target machine side d-axis current reference component and the machine side d-axis voltage component; obtain a machine side q-axis voltage target value based on the machine side q-axis current component, the target machine side q-axis current reference component and the machine side q-axis voltage component; and obtain a machine side three-phase voltage reference value based on the machine side d-axis voltage target value and the machine side q-axis voltage target value using an inverse Park transformation.

[0096] It should be noted that the above explanation of the embodiment of the DC voltage coordinated control method of the offshore wind power flexible DC system is also applicable to the DC voltage coordinated control device of the offshore wind power flexible DC system of this embodiment, which will not be repeated here.

[0097] In the DC voltage coordinated control device of the offshore wind power flexible DC system of the embodiment of the present disclosure, the acquisition module is used to obtain the rated frequency and rated voltage of each grid-connected point, the reactive power measured value and reactive power reference value of each converter, the DC voltage measurement value and DC voltage rated value of each converter, the AC voltage measurement value of the AC side of each converter, the grid-connected point current of each grid-connected point, and the maximum current of each converter; the calculation module is used to calculate the grid-side phase reference value and the machine-side phase reference value based on the rated frequency, the DC voltage measurement value and the DC voltage rated value, and calculate the grid-side voltage reference value and the machine-side voltage reference value based on the rated voltage, the reactive power measured value and the reactive power reference value. ; The control module is used to calculate the grid-side current reference value based on the grid-side AC voltage measurement value, the grid-side phase reference value and the grid-side voltage reference value; calculate the grid-side three-phase voltage reference value based on the grid-side grid-connected point current, the maximum current of the grid-side converter, the grid-side phase reference value and the grid-side current reference value, and control the grid-side converter based on the grid-side three-phase voltage reference value; calculate the machine-side current reference value based on the machine-side AC voltage measurement value, the machine-side phase reference value and the machine-side voltage reference value; calculate the machine-side three-phase voltage reference value based on the machine-side grid-connected point current, the maximum current of the machine-side converter, the machine-side phase reference value and the machine-side current reference value, and control the machine-side converter based on the machine-side three-phase voltage reference value. In this case, the rated frequency and rated voltage of the grid-side grid-connected point, the measured reactive power value and reactive power reference value of the grid-side converter, the measured DC voltage value and the rated DC voltage of the DC side of the grid-side converter, the measured AC voltage value of the AC side of the grid-side converter, the current of the grid-side grid-connected point and the maximum current of the grid-side converter are integrated to obtain the grid-side three-phase voltage reference value, and the grid-side converter is controlled by using the grid-side three-phase voltage reference value. The rated frequency and rated voltage of the generator-side grid-connected point, the measured reactive power value and the reactive power reference value of the generator-side converter are integrated to obtain the grid-side three-phase voltage reference value. The three-phase voltage reference value of the machine side is obtained by using the measured DC voltage value and the rated DC voltage value of the DC side of the machine side converter, the measured AC voltage value of the AC side of the machine side converter, the current at the machine side grid connection point and the maximum current of the machine side converter. The three-phase voltage reference value of the machine side is used to control the machine side converter. At this time, the flexible DC system can still maintain the stability of the DC voltage when there is a small disturbance in the connected onshore main grid. Therefore, according to the method disclosed in the present invention, the flexible DC transmission system of the offshore wind farm can have a strong voltage support capability for the access grid. Compared with the traditional fixed DC voltage control, the present invention is based on the flexible DC system itself having a certain DC voltage fluctuation capability and the converter current limiting capability requirement (i.e., the maximum current). It combines the flexible DC system and the offshore wind farm to provide a control device that can cope with the grid connection point voltage under small disturbances of the access grid and has a certain support capability for the grid voltage.

[0098] According to an embodiment of the present disclosure, the present disclosure also provides a DC voltage coordinated control device for an offshore wind power flexible DC system, a readable storage medium and a computer program product.

[0099] Fig.10 It is a block diagram of an offshore wind power flexible DC system DC voltage collaborative control device used to implement the offshore wind power flexible DC system DC voltage collaborative control method of the embodiment of the present disclosure. The offshore wind power flexible DC system DC voltage collaborative control device is intended to represent various forms of digital computers, such as laptop computers, desktop computers, workbenches, personal digital assistants, servers, blade servers, mainframe computers, and other suitable computers. The offshore wind power flexible DC system DC voltage collaborative control device can also represent various forms of mobile devices, such as personal digital processing, cellular phones, smart phones, wearable electronic devices and other similar computing devices. The components shown in the present disclosure, the connections and relationships of the components, and the functions of the components are merely examples and are not intended to limit the implementation of the present disclosure described and / or required in the present disclosure.

[0100] like Fig.10 As shown, the DC voltage coordinated control device 20 of the flexible DC system of offshore wind power includes a computing unit 21, which can perform various appropriate 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 to a random access memory (RAM) 23. In RAM 23, various programs and data required for the operation of the DC voltage coordinated control device 20 of the flexible DC system of offshore wind power can also be stored. The computing unit 21, ROM 22 and RAM 23 are connected to each other through a bus 24. An input / output (I / O) interface 25 is also connected to the bus 24.

[0101] Multiple components in the DC voltage coordinated control device 20 of the offshore wind power flexible DC system are connected to the 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, etc.; a storage unit 28, such as a disk, an optical disk, etc., which is communicatively connected to the computing unit 21; and a communication unit 29, such as a network card, a modem, a wireless communication transceiver, etc. The communication unit 29 allows the DC voltage coordinated control device 20 of the offshore wind power flexible DC system to exchange information / data with other DC voltage coordinated control devices of the offshore wind power flexible DC system through a computer network such as the Internet and / or various telecommunication networks.

[0102] The computing unit 21 may be a variety of general and / or special processing components with processing and computing capabilities. Some examples of the computing unit 21 include, but are not limited to, a central processing unit (CPU), a graphics processing unit (GPU), various dedicated artificial intelligence (AI) computing chips, various computing units running machine learning model algorithms, digital signal processors (DSPs), and any appropriate processors, controllers, microcontrollers, etc. The computing unit 21 performs the various methods and processes described above, such as executing the DC voltage coordinated control method of the offshore wind power flexible DC system. For example, in some embodiments, the DC voltage coordinated control method of the offshore wind power flexible DC system may be implemented as a computer software program, which is tangibly contained in a machine-readable medium, such as a storage unit 28. In some embodiments, part or all of the computer program may be loaded and / or installed on the offshore wind power flexible DC system DC voltage coordinated control device 20 via ROM 22 and / or 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 DC voltage coordinated control method of the offshore wind power flexible DC system described above may be executed. Alternatively, in other embodiments, the computing unit 21 may be configured to execute the DC voltage coordinated control method of the offshore wind power flexible DC system in any other appropriate manner (for example, by means of firmware).

[0103] Various embodiments of the systems and techniques described above in the present disclosure may be implemented in digital electronic circuit systems, integrated circuit systems, field programmable gate arrays (FPGAs), application specific integrated circuits (ASICs), application specific standard products (ASSPs), systems on chips (SOCs), load programmable logic devices (CPLDs), computer hardware, firmware, software, and / or combinations thereof. These various embodiments may include: being implemented in one or more computer programs that can 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 can receive data and instructions from a storage system, at least one input device, and at least one output device, and transmit data and instructions to the storage system, the at least one input device, and the at least one output device.

[0104] The program code for implementing the method of the present disclosure may be written in any combination of one or more programming languages. These program codes may be provided to a processor or controller of a general-purpose computer, a special-purpose computer, or other programmable data processing device, so that the program code, when executed by the processor or controller, enables the functions / operations specified in the flow chart and / or block diagram to be implemented. The program code may be executed entirely on the machine, partially on the machine, partially on the machine and partially on a remote machine as a stand-alone software package, or entirely on a remote machine or server.

[0105] In the present disclosure, a machine-readable medium may be a tangible medium that may contain or store a program for use by or in conjunction with an instruction execution system, device, or equipment. A machine-readable medium may be a machine-readable signal medium or a machine-readable storage medium. A machine-readable medium may include, but is not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, device, or electronic device, or any suitable combination of the foregoing. A more specific example of a machine-readable storage medium may include an electrical connection based on one or more lines, a portable computer disk, 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 disk read-only memory (CD-ROM), an optical storage electronic device, a magnetic storage electronic device, or any suitable combination of the foregoing.

[0106] To provide interaction with a user, the systems and techniques described herein 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 the user; and a keyboard and pointing device (e.g., a mouse or trackball) through which the user can provide input to the computer. Other types of devices can also be used to provide interaction with the user; for example, the feedback provided to the user can be any form of sensory feedback (e.g., visual feedback, auditory feedback, or tactile feedback); and input from the user can be received in any form (including acoustic input, voice input, or tactile input).

[0107] The systems and techniques described herein can be implemented in a computing system that includes backend components (e.g., as a data server), or a computing system that includes middleware components (e.g., an application server), or a computing system that includes frontend components (e.g., a user computer with a graphical user interface or a web browser through which a user can interact with implementations of the systems and techniques described herein), or a computing system that includes any combination of such backend components, middleware components, or frontend 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: a local area network (LAN), a wide area network (WAN), the Internet, and a blockchain network.

[0108] A computer system may include a client and a server. The client and the server are generally remote from each other and usually interact through a communication network. The relationship between the client and the server is generated by computer programs running on the corresponding computers and having a client-server relationship with each other. The server may be a cloud server, also known as a cloud computing server or cloud host, which is a host product in the cloud computing service system to solve the defects of difficult management and weak business scalability in traditional physical hosts and VPS services ("Virtual Private Server", or "VPS" for short). The server may also be a server of a distributed system, or a server combined with a blockchain.

[0109] It should be understood that the various forms of processes shown above can be used to reorder, add or delete steps. For example, the steps recorded in this disclosure can be executed in parallel, sequentially or in different orders, as long as the desired results of the technical solutions disclosed in this disclosure can be achieved, and this disclosure is not limited here.

[0110] The above specific implementations do not constitute a limitation on the protection scope of the present disclosure. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modification, equivalent substitution and improvement made within the spirit and principle of the present disclosure shall be included in the protection scope of the present disclosure.

Claims

1. A method for coordinated control of DC voltage in an offshore wind power flexible DC system, characterized in that: The offshore wind farm flexible DC system includes a converter and a grid connection point, the converter includes a grid-side converter and a machine-side converter, the grid connection point includes a grid-side grid connection point and a machine-side grid connection point, the grid-side converter is connected to the onshore main grid via the grid-side grid connection point, and the machine-side converter is connected to the offshore wind farm via the machine-side grid connection point, and the method includes: Obtain the rated frequency and rated voltage of each grid connection point, the measured reactive power value and reactive power reference value of each converter, the measured DC voltage value and rated DC voltage value of the DC side of each converter, the measured AC voltage value of the AC side of each converter, the grid connection point current of each grid connection point, and the maximum current of each converter; A grid-side phase reference value and a generator-side phase reference value are calculated based on the rated frequency, the DC voltage measurement value and the DC voltage rated value, and a grid-side voltage reference value and a generator-side voltage reference value are calculated based on the rated voltage, the reactive power measured value and the reactive power reference value; A grid-side current reference value is calculated based on the grid-side AC voltage measurement value, the grid-side phase reference value and the grid-side voltage reference value; a grid-side three-phase voltage reference value is calculated based on the grid-side grid-connected point current, the maximum current of the grid-side converter, the grid-side phase reference value and the grid-side current reference value, and the grid-side converter is controlled based on the grid-side three-phase voltage reference value; The machine-side current reference value is calculated based on the machine-side AC voltage measurement value, the machine-side phase reference value and the machine-side voltage reference value; the machine-side three-phase voltage reference value is calculated based on the machine-side grid-connected point current, the maximum current of the machine-side converter, the machine-side phase reference value and the machine-side current reference value, and the machine-side converter is controlled based on the machine-side three-phase voltage reference value; The method for determining the grid-side phase reference value includes: calculating a grid-side reference frequency based on a grid-side regulated voltage, a DC voltage measurement value of a grid-side converter, and a DC voltage rated value of the grid-side converter, and obtaining a grid-side phase reference value based on the grid-side reference frequency, wherein the grid-side regulated voltage is obtained based on a grid-side first damping coefficient, the grid-side reference frequency, and a rated frequency of a grid-side grid connection point; The method for determining the machine-side phase reference value includes: calculating a machine-side reference frequency based on a machine-side regulation voltage, a DC voltage measurement value of a machine-side converter and a DC voltage rated value of the machine-side converter, and obtaining a machine-side phase reference value based on the machine-side reference frequency, wherein the machine-side regulation voltage is obtained based on a first machine-side damping coefficient, the machine-side reference frequency and a rated frequency of a machine-side grid-connected point.

2. The DC voltage coordinated control method of the offshore wind power flexible DC system according to claim 1 is characterized in that: The calculating and obtaining the grid-side voltage reference value and the generator-side voltage reference value based on the rated voltage, the reactive power measured value and the reactive power reference value includes: A grid-side voltage reference value is calculated based on the grid-side regulated power, the measured reactive power value of the grid-side converter and the reactive power reference value of the grid-side converter, wherein the grid-side regulated power is obtained based on the second grid-side damping coefficient, the grid-side voltage reference value and the rated voltage of the grid-side grid connection point; The machine side voltage reference value is calculated based on the machine side regulation power, the actual measured value of the reactive power of the machine side converter and the reactive power reference value of the machine side converter, wherein the machine side regulation power is obtained based on the second damping coefficient of the machine side, the machine side voltage reference value and the rated voltage of the machine side grid connection point.

3. The DC voltage coordinated control method of the offshore wind power flexible DC system according to claim 2 is characterized in that: The grid-side voltage reference value includes a grid-side d-axis voltage reference component and a grid-side q-axis voltage reference component, and the grid-side current reference value is obtained by calculating based on the grid-side AC voltage measurement value, the grid-side phase reference value and the grid-side voltage reference value, including: A grid-side d-axis voltage component and a grid-side q-axis voltage component are obtained based on the AC voltage measurement value of the grid-side converter and the grid-side phase reference value using Park transformation; a grid-side current reference value is obtained based on the grid-side d-axis voltage reference component, the grid-side q-axis voltage reference component, the grid-side d-axis voltage component, and the grid-side q-axis voltage component, and the grid-side current reference value includes a grid-side d-axis current reference component and a grid-side q-axis current reference component.

4. The DC voltage coordinated control method of the offshore wind power flexible DC system according to claim 3 is characterized in that: The calculating and obtaining the grid-side three-phase voltage reference value based on the grid-side grid connection point current, the maximum current of the grid-side converter, the grid-side phase reference value and the grid-side current reference value includes: Obtaining a grid-side d-axis current component and a grid-side q-axis current component based on the grid-side grid-connected point current and the grid-side phase reference value by using Park transformation; Obtaining a grid-side target d-axis current reference component and a grid-side target q-axis current reference component based on the maximum current of the grid-side converter, the grid-side d-axis current reference component, and the grid-side q-axis current reference component; A grid-side three-phase voltage reference value is obtained based on the grid-side d-axis current component, the grid-side q-axis current component, the grid-side target d-axis current reference component and the grid-side target q-axis current reference component using an inverse Park transformation.

5. The DC voltage coordinated control method of the offshore wind power flexible DC system according to claim 4 is characterized in that: The method of obtaining a grid-side three-phase voltage reference value based on the grid-side d-axis current component, the grid-side q-axis current component, the grid-side target d-axis current reference component, and the grid-side target q-axis current reference component by using an inverse Park transformation includes: Obtaining a grid-side d-axis voltage target value based on a grid-side d-axis current component, a target grid-side d-axis current reference component, and a grid-side d-axis voltage component; Obtaining a grid-side q-axis voltage target value based on a grid-side q-axis current component, a target grid-side q-axis current reference component, and a grid-side q-axis voltage component; A grid-side three-phase voltage reference value is obtained based on the grid-side d-axis voltage target value and the grid-side q-axis voltage target value using an inverse Park transformation.

6. A DC voltage coordinated control device for an offshore wind power flexible DC system, characterized in that: The offshore wind farm flexible DC system includes a converter and a grid connection point, wherein the converter includes a grid-side converter and a machine-side converter, wherein the grid connection point includes a grid-side grid connection point and a machine-side grid connection point, wherein the grid-side converter is connected to the onshore main grid via the grid-side grid connection point, and the machine-side converter is connected to the offshore wind farm via the machine-side grid connection point, wherein the device includes: An acquisition module is used to obtain the rated frequency and rated voltage of each grid-connected point, the measured reactive power value and reactive power reference value of each converter, the measured DC voltage value and rated DC voltage value of the DC side of each converter, the measured AC voltage value of the AC side of each converter, the grid-connected point current of each grid-connected point, and the maximum current of each converter; a calculation module, configured to calculate a grid-side phase reference value and a generator-side phase reference value based on the rated frequency, the DC voltage measurement value and the DC voltage rated value, and to calculate a grid-side voltage reference value and a generator-side voltage reference value based on the rated voltage, the reactive power measured value and the reactive power reference value; A control module, configured to calculate a grid-side current reference value based on a grid-side AC voltage measurement value, the grid-side phase reference value, and the grid-side voltage reference value; calculate a grid-side three-phase voltage reference value based on a grid-side grid-connected point current, a maximum current of the grid-side converter, the grid-side phase reference value, and the grid-side current reference value, and control the grid-side converter based on the grid-side three-phase voltage reference value; calculate a machine-side current reference value based on a machine-side AC voltage measurement value, the machine-side phase reference value, and the machine-side voltage reference value; calculate a machine-side three-phase voltage reference value based on a machine-side grid-connected point current, a maximum current of the machine-side converter, the machine-side phase reference value, and the machine-side current reference value, and control the machine-side converter based on the machine-side three-phase voltage reference value; The method for determining the grid-side phase reference value includes: calculating a grid-side reference frequency based on a grid-side regulated voltage, a DC voltage measurement value of a grid-side converter, and a DC voltage rated value of the grid-side converter, and obtaining a grid-side phase reference value based on the grid-side reference frequency, wherein the grid-side regulated voltage is obtained based on a grid-side first damping coefficient, the grid-side reference frequency, and a rated frequency of a grid-side grid connection point; The method for determining the machine-side phase reference value includes: calculating a machine-side reference frequency based on a machine-side regulation voltage, a DC voltage measurement value of a machine-side converter and a DC voltage rated value of the machine-side converter, and obtaining a machine-side phase reference value based on the machine-side reference frequency, wherein the machine-side regulation voltage is obtained based on a first machine-side damping coefficient, the machine-side reference frequency and a rated frequency of a machine-side grid-connected point.

7. The DC voltage coordinated control device for an offshore wind power flexible DC system according to claim 6 is characterized in that: The grid-side voltage reference value includes a grid-side d-axis voltage reference component and a grid-side q-axis voltage reference component. The control module is specifically used for: A grid-side d-axis voltage component and a grid-side q-axis voltage component are obtained based on the AC voltage measurement value of the grid-side converter and the grid-side phase reference value using Park transformation; a grid-side current reference value is obtained based on the grid-side d-axis voltage reference component, the grid-side q-axis voltage reference component, the grid-side d-axis voltage component, and the grid-side q-axis voltage component, and the grid-side current reference value includes a grid-side d-axis current reference component and a grid-side q-axis current reference component.

8. The DC voltage coordinated control device for an offshore wind power flexible DC system according to claim 7 is characterized in that: The control module is specifically used for: Obtaining a grid-side d-axis current component and a grid-side q-axis current component based on the grid-side grid-connected point current and the grid-side phase reference value by using Park transformation; Obtaining a grid-side target d-axis current reference component and a grid-side target q-axis current reference component based on the maximum current of the grid-side converter, the grid-side d-axis current reference component, and the grid-side q-axis current reference component; A grid-side three-phase voltage reference value is obtained based on the grid-side d-axis current component, the grid-side q-axis current component, the grid-side target d-axis current reference component and the grid-side target q-axis current reference component using an inverse Park transformation.

9. A DC voltage coordinated control device for an offshore wind power flexible DC system, characterized in that: include: at least one processor; as well as a memory communicatively connected to the at least one processor; wherein, The memory stores instructions executable by the at least one processor, and the instructions are executed by the at least one processor so that the at least one processor can execute the method for coordinated control of DC voltage of an offshore wind power flexible DC system according to any one of claims 1-5.

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