Method and device for dynamic regulation and control of DC voltage in offshore wind power flexible DC system

Abstract

The present disclosure proposes a method and device for dynamically regulating and controlling the DC voltage of an offshore wind power flexible DC system, which includes obtaining the rated frequency and rated voltage of the grid-side grid-connected point, the reactive power measured value and reactive power reference value of the grid-side converter, the DC voltage measured value and DC voltage rated value of the DC side of the grid-side converter, the AC voltage measured value, the grid-connected point current and the maximum current of the AC side of the grid-side converter; obtaining the phase reference value and the voltage reference value by using the rated frequency, the DC voltage measured value, the DC voltage rated value rated voltage, the reactive power measured value and the reactive power reference value; obtaining the three-phase voltage reference value based on the AC voltage measured value, the phase reference value, the voltage reference value, the grid-connected point current, the maximum current and the current reference value, thereby controlling the grid-side converter to realize the dynamic regulation of the DC voltage. The method disclosed in the present disclosure enables the offshore wind farm flexible DC transmission system to 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 power transmission in offshore wind farms, and in particular to a method and device for dynamically regulating and controlling direct current voltage in an offshore wind power flexible direct current system. Background Art

[0002] With the rapid development of renewable 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. Usually for the onshore power grid, the wind power flexible direct current system is usually not required to 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 getting bigger and bigger. The onshore large power grid hopes that the wind farm connected by 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, there is an urgent need for a dynamic DC voltage regulation and control technology for an offshore wind power flexible direct current system with strong support capability for the voltage at 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 invention is to propose a method for dynamically regulating and controlling the 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.

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

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

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

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

[0009] A phase reference value is calculated based on the rated frequency, the DC voltage measurement value and the DC voltage rated value, and a voltage reference value is calculated based on the rated voltage, the reactive power measured value and the reactive power reference value;

[0010] Calculate and obtain a current reference value based on the AC voltage measurement value, the phase reference value and the voltage reference value;

[0011] A three-phase voltage reference value is calculated based on the grid-connected point current, the maximum current, the phase reference value and the current reference value, and the grid-side converter is controlled based on the three-phase voltage reference value, thereby achieving dynamic regulation of the DC voltage.

[0012] In one embodiment of the present disclosure, the phase reference value is calculated based on the rated frequency, the DC voltage measurement value and the DC voltage rated value, including: calculating a reference frequency based on the regulated voltage, the DC voltage measurement value and the DC voltage rated value, and obtaining the phase reference value based on the reference frequency, wherein the regulated voltage is obtained based on a first damping coefficient, the reference frequency and the rated frequency.

[0013] In one embodiment of the present disclosure, the voltage reference value is calculated based on the rated voltage, the measured reactive power value and the reactive power reference value, including: the voltage reference value is calculated based on the regulated power, the measured reactive power value and the reactive power reference value, wherein the regulated power is obtained based on the second damping coefficient, the voltage reference value and the rated voltage.

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

[0015] In one embodiment of the present disclosure, the three-phase voltage reference value is calculated based on the grid-connected point current, the maximum current, the phase reference value and the current reference value, including: obtaining a d-axis current component and a q-axis current component based on the grid-connected point current and the phase reference value using Park transformation; obtaining a target d-axis current reference component and a target q-axis current reference component based on the maximum current, the d-axis current reference component and the q-axis current reference component; and obtaining a three-phase voltage reference value based on the d-axis current component, the q-axis current component, the target d-axis current reference component and the target q-axis current reference component using Park inverse transformation.

[0016] In one embodiment of the present disclosure, the three-phase voltage reference value is obtained based on the d-axis current component, the q-axis current component, the target d-axis current reference component and the target q-axis current reference component using the inverse Park transform, including: obtaining a d-axis voltage target value based on the d-axis current component, the target d-axis current reference component and the d-axis voltage component; obtaining a q-axis voltage target value based on the q-axis current component, the target q-axis current reference component and the q-axis voltage component; and obtaining a three-phase voltage reference value based on the d-axis voltage target value and the q-axis voltage target value using the inverse Park transform.

[0017] To achieve the above-mentioned object, the second embodiment of the present disclosure proposes a DC voltage dynamic regulation control device for an offshore wind power flexible DC system, wherein the offshore wind farm flexible DC system comprises a grid-side converter and a grid-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 device comprises:

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

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

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

[0021] In one embodiment of the present disclosure, the calculation module is specifically used to: calculate and obtain a reference frequency based on the regulated voltage, the DC voltage measurement value and the DC voltage rated value, and obtain the phase reference value based on the reference frequency, wherein the regulated voltage is obtained based on a first damping coefficient, the reference frequency and the rated frequency; calculate and obtain a voltage reference value based on the regulated power, the reactive power measured value and the reactive power reference value, wherein the regulated power is obtained based on a second damping coefficient, the voltage reference value and the rated voltage.

[0022] In one embodiment of the present disclosure, the control module is specifically used to: obtain a d-axis voltage component and a q-axis voltage component based on the AC voltage measurement value and the phase reference value using Park's transform; obtain a current reference value based on the d-axis voltage reference component, the q-axis voltage reference component, the d-axis voltage component, and the q-axis voltage component, and the current reference value includes a d-axis current reference component and a q-axis current reference component; obtain a d-axis current component and a q-axis current component based on the grid-connected point current and the phase reference value using Park's transform; obtain a target d-axis current reference component and a target q-axis current reference component based on the maximum current, the d-axis current reference component, and the q-axis current reference component; and obtain a three-phase voltage reference value based on the d-axis current component, the q-axis current component, the target d-axis current reference component, and the target q-axis current reference component using an inverse Park's transform.

[0023] To achieve the above-mentioned purpose, the third aspect embodiment of the present disclosure proposes a dynamic regulation and control device for the DC voltage of 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 dynamic regulation and control method for the DC voltage of 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 grid-side converter and a grid-side grid-connected point, the grid-side converter is connected to the onshore main grid via the grid-side grid-connected point, and a control method includes: obtaining 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 grid-connected point current and the maximum current; calculating a phase reference value based on the rated frequency, the measured DC voltage value and the rated DC voltage, and calculating a voltage reference value based on the rated voltage, the measured reactive power value and the reactive power reference value; calculating a current reference value based on the measured AC voltage value, the phase reference value and the voltage reference value; calculating a three-phase voltage reference value based on the grid-connected point current, the maximum current, the phase reference value and the current reference value, and controlling the grid-side converter based on the three-phase voltage reference value, thereby realizing dynamic regulation of the DC voltage. In this case, the three-phase voltage reference value is obtained by comprehensively considering the rated frequency and rated voltage of the grid-side grid connection point, the measured reactive power value and reactive power reference value of the grid-side converter, the DC voltage measurement value and DC voltage rated value of the DC side of the grid-side converter, the AC voltage measurement value of the AC side of the grid-side converter, the grid connection point current and the maximum current. The three-phase voltage reference value is used to control the grid-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, the method disclosed in the present invention can enable the flexible DC transmission system of the offshore wind farm to have a strong voltage support capability for the connected power 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 diagram of a flow chart of a method for dynamically regulating direct current voltage in an offshore wind power flexible direct current 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 block diagram of a DC voltage dynamic regulation control device for an offshore wind power flexible DC system provided by an embodiment of the present disclosure;

[0033] Figure 7 It is a block diagram of an offshore wind power flexible DC system DC voltage dynamic regulation control device used to implement the offshore wind power flexible DC system DC voltage dynamic regulation control method of the embodiment of the present disclosure. DETAILED DESCRIPTION

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] The present invention provides a method and device for dynamically regulating and controlling the 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.

[0039] 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 a grid-side converter, a grid-side grid connection point, a machine-side converter 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.

[0040] 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.

[0041] In a first embodiment, Figure 2 The flowchart of the method for dynamically regulating the DC voltage 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 dynamic regulation control method of the offshore wind power flexible DC system includes the following steps:

[0042] Step S11, obtaining the rated frequency and rated voltage of the grid-side grid-connected point, the reactive power measured value and reactive power reference value of the grid-side converter, the DC voltage measured value and DC voltage rated value of the DC side of the grid-side converter, the AC voltage measured value of the AC side of the grid-side converter, the grid-connected point current and the maximum current.

[0043] Specifically, in step S11, the rated frequency of the grid-side grid connection point obtained can be represented by the symbol ω ref The rated voltage of the grid-connected point can be expressed as V mref The reactive power measured value of the grid-side converter can be represented by the symbol Q, and the reactive power reference value of the grid-side converter can be represented by the symbol Q ref Indicates that the DC voltage measurement value of the DC side of the grid-side converter can be represented by the symbol U dc The DC voltage rating of the grid-side converter can be expressed as U dcref The AC voltage measurement value of the AC side of the grid-side converter can be represented by the symbol V ABC The grid-connected point current is the current of the grid-connected point on the grid side. The grid-connected point current can be represented by the symbol I ABC The maximum current can be represented by the symbol I max Indicated by. The maximum current is the upper limit of the current in the converter current limiting capability requirement.

[0044] Step S12, a phase reference value is calculated based on the rated frequency, the DC voltage measurement value and the DC voltage rated value, and a voltage reference value is calculated based on the rated voltage, the reactive power measured value and the reactive power reference value.

[0045] In step S12, the phase reference value may be represented by the symbol θ, and the voltage reference value may be represented by the symbol V.

[0046] In step S12, a phase reference value is calculated based on the rated frequency, the DC voltage measurement value and the DC voltage rated value, including: calculating a reference frequency based on the regulated voltage, the DC voltage measurement value and the DC voltage rated value, and obtaining a phase reference value based on the reference frequency, wherein the regulated voltage is obtained based on the first damping coefficient, the reference frequency and the rated frequency.

[0047] In step S12, a voltage reference value is calculated based on the rated voltage, the actual measured value of reactive power and the reactive power reference value, including: a voltage reference value is calculated based on the regulated power, the actual measured value of reactive power and the reactive power reference value, wherein the regulated power is obtained based on the second damping coefficient, the voltage reference value and the rated voltage.

[0048] Specifically, 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.

[0049] In some embodiments, Figure 3 As shown, calculate the regulation voltage △U and the DC voltage rated value U dcref The sum of the sum and the DC voltage measurement value U is then calculated. dc The first difference is sent to the PI regulator (i.e., proportional integral controller) and the first inertia coefficient J is used to calculate the p An integral calculation is performed (1 / S represents an integral operation) to obtain a reference frequency ω, and the reference frequency ω is sent to the PI regulator for integral calculation to obtain a phase reference value θ, wherein an initial value is set for the adjustment voltage △U in the initial calculation, and an initial value is set for the adjustment voltage △U in the subsequent calculation based on the first damping coefficient D p , reference frequency ω and rated frequency ω ref Updated in real time. Specifically, calculate the rated frequency ω ref The second difference between the reference frequency ω and the reference frequency ω is sent to the PI regulator and the first damping coefficient D P The product is then multiplied to obtain the regulated voltage △U. Calculate the regulated power △Q and the reactive power reference value Q ref The sum of the sum and then calculate the third difference between the sum and the reactive power measured value Q, and send the third difference to the PI regulator to use the second inertia coefficient J q An integral calculation is performed to obtain a voltage reference value V, wherein the adjustment power △Q is set with an initial value in the initial calculation, and the adjustment power △Q is based on the second damping coefficient D in subsequent calculations. q , voltage reference value V and rated voltage V mref Updated in real time. Specifically, calculate the rated voltage V mref The fourth difference between the voltage reference value V and the voltage reference value V is sent to the PI regulator and the second damping coefficient D q Multiply the product to obtain the regulated power △Q.

[0050] Step S13, calculating and obtaining a current reference value based on the AC voltage measurement value, the phase reference value and the voltage reference value.

[0051] In step S13, a current reference value is calculated based on the AC voltage measurement value, the phase reference value and the voltage reference value, including: using Park transformation to obtain a d-axis voltage component and a q-axis voltage component based on the AC voltage measurement value and the phase reference value; obtaining a current reference value based on the d-axis voltage reference component, the q-axis voltage reference component, the d-axis voltage component, and the q-axis voltage component, the current reference value including a d-axis current reference component and a q-axis current reference component.

[0052] 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.

[0053] In step S13, the voltage reference value includes a d-axis voltage reference component and a q-axis voltage reference component. The d-axis voltage component can be represented by V d The q-axis voltage component can be represented by the symbol V q The d-axis voltage reference component can be represented by the symbol V dref The q-axis voltage reference component can be represented by the symbol V qref The d-axis current reference component can be represented by the symbol I dref The q-axis current reference component can be represented by the symbol I qref express.

[0054] Specifically, Figure 4 Another partial schematic diagram of the DC voltage outer loop control of the grid-side converter provided in an embodiment of the present disclosure.

[0055] In some embodiments, Figure 4 As shown, the AC voltage measurement value V ABC After Park transformation (i.e. abc / dq) is performed on the phase reference value θ, the d-axis voltage component V is obtained. d and the q-axis voltage component V q , the voltage reference value V includes the d-axis voltage reference component V dref and the q-axis voltage reference component V qref , where (V dref ) 2 +(V qref ) 2 =V 2 Calculate the d-axis voltage reference component V dref and the d-axis voltage component V d The difference is sent to the PI regulator to calculate the d-axis current reference component I dref ; Calculate the q-axis voltage reference component V qref and the q-axis voltage component Vq The difference is sent to the PI regulator to calculate the q-axis current reference component I qref .

[0056] Step S14, calculating a three-phase voltage reference value based on the grid-connected point current, the maximum current, the phase reference value and the current reference value, and controlling the grid-side converter based on the three-phase voltage reference value, thereby achieving dynamic regulation of the DC voltage.

[0057] In step S14, a three-phase voltage reference value is calculated based on the grid-connected point current, the maximum current, the phase reference value and the current reference value, including: using Park's transformation to obtain a d-axis current component and a q-axis current component based on the grid-connected point current and the phase reference value; obtaining a target d-axis current reference component and a target q-axis current reference component based on the maximum current, the d-axis current reference component and the q-axis current reference component; and using Park's inverse transformation to obtain a three-phase voltage reference value based on the d-axis current component, the q-axis current component, the target d-axis current reference component and the target q-axis current reference component.

[0058] In step S14, a target d-axis current reference component and a target q-axis current reference component are obtained based on the maximum current, the d-axis current reference component, and the q-axis current reference component, including: comparing the maximum current and the d-axis current reference component to select the maximum value as the target d-axis current reference component; and obtaining the target q-axis current reference component using the maximum current, the target d-axis current reference component, and the q-axis current reference component. The target d-axis current reference component satisfies:

[0059] I ’ dref =max(I max ,I dref )

[0060] The target q-axis current reference component satisfies:

[0061]

[0062] Among them, I ’ dref Represents the target d-axis current reference component. I ’ qref Represents the target q-axis current reference component.

[0063] In step S14, a three-phase voltage reference value is obtained based on the d-axis current component, the q-axis current component, the target d-axis current reference component and the target q-axis current reference component using an inverse Park transform, including: obtaining a d-axis voltage target value based on the d-axis current component, the target d-axis current reference component and the d-axis voltage component; obtaining a q-axis voltage target value based on the q-axis current component, the target q-axis current reference component and the q-axis voltage component; and obtaining a three-phase voltage reference value based on the d-axis voltage target value and the q-axis voltage target value using an inverse Park transform.

[0064] In step S14, the d-axis current component can be represented by the symbol I d The q-axis current component can be represented by the symbol I q The d-axis voltage target value can be represented by V cdref The q-axis voltage target value can be represented by V cqref express.

[0065] Specifically, Figure 5 A schematic diagram of the inner loop control portion of the grid-side converter provided in an embodiment of the present disclosure.

[0066] In some embodiments, Figure 5 As shown, the grid-connected current I ABC After Parker transformation (i.e. abc / dq) is performed on the phase reference value θ, the d-axis current component I is obtained. d and the q-axis current component I q ; Calculate the target d-axis current reference component I ’ dref and the d-axis current component I d The difference is sent to the PI regulator to calculate the first voltage V1, based on the inductance L of the grid-side converter and the q-axis current component I q The second voltage V2 is obtained by converting the d-axis voltage component V d Add the second voltage V2 and subtract the first voltage V1 to obtain the d-axis voltage target value V cdref .

[0067] Calculate the target q-axis current reference component I ’ qref and the q-axis current component I q The difference is sent to the PI regulator to calculate the third voltage V3, based on the inductance L of the grid-side converter and the d-axis current component I d The fourth voltage V4 is obtained by converting the q-axis voltage component V q Subtract the third voltage V3 and then subtract the fourth voltage V4 to obtain the q-axis voltage target value V cqref .

[0068] Based on the phase reference value θ, the d-axis voltage target value V cdrefand q-axis voltage target value V cqref The three-phase voltage reference value is obtained by performing the Park inverse transformation (i.e., dq / abc), and the grid-side converter is controlled based on the three-phase voltage reference value, thereby realizing the dynamic regulation of the DC voltage. cAref 、V cBref and V cCref It is the voltage reference value of each phase of the three-phase voltage reference value. The three-phase voltage reference value 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. Controlling the grid-side converter based on the obtained three-phase voltage reference value can ensure the stability of the DC voltage.

[0069] In the method for dynamically regulating the DC voltage of an offshore wind power flexible DC system in an embodiment of the present disclosure, the offshore wind farm flexible DC system includes a grid-side converter and a grid-side grid connection point, and the grid-side converter is connected to the onshore main grid via the grid-side grid connection point. The control method includes: obtaining the rated frequency and rated voltage of the grid-side grid connection 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 grid-connected point current and the maximum current; calculating and obtaining a phase reference value based on the rated frequency, the measured DC voltage value and the rated DC voltage, and calculating and obtaining a voltage reference value based on the rated voltage, the measured reactive power value and the reactive power reference value; calculating and obtaining a current reference value based on the measured AC voltage value, the phase reference value and the voltage reference value; calculating and obtaining a three-phase voltage reference value based on the grid-connected point current, the maximum current, the phase reference value and the current reference value, and controlling the grid-side converter based on the three-phase voltage reference value, thereby realizing dynamic regulation of the DC voltage. In this case, the rated frequency and rated voltage of the grid-side grid connection point, the measured reactive power value and reactive power reference value of the grid-side converter, the DC voltage measurement value and DC voltage rated value of the DC side of the grid-side converter, the AC voltage measurement value of the AC side of the grid-side converter, the grid-connected point current and the maximum current are integrated to obtain the three-phase voltage reference value, and the grid-side converter is controlled by the three-phase voltage reference value. 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 access grid. Compared with the traditional fixed DC voltage control, the present invention is based on the flexible DC system itself has a certain DC voltage fluctuation capability and converter current limiting capability requirements (i.e., maximum current), and changes the DC voltage outer loop, thereby providing a control method that can cope with the grid voltage under small disturbances of the access grid and has a certain support capability for the grid connection point voltage.

[0070] 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.

[0071] The present disclosure relates to a DC voltage dynamic regulation control device for an offshore wind power flexible DC system. The DC voltage dynamic regulation 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 a power grid. The offshore wind farm flexible DC system includes a grid-side converter and a grid-side connection point, and the grid-side converter is connected to an onshore main grid via the grid-side connection point.

[0072] See also Figure 6 , Figure 6 The block diagram of a DC voltage dynamic regulation control device for an offshore wind power flexible DC system provided by an embodiment of the present disclosure. The DC voltage dynamic regulation 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:

[0073] The acquisition module 11 is used to obtain the rated frequency and rated voltage of the grid-side grid connection point, the reactive power measured value and reactive power reference value of the grid-side converter, the DC voltage measured value and DC voltage rated value of the DC side of the grid-side converter, the AC voltage measured value of the AC side of the grid-side converter, the grid connection point current and the maximum current;

[0074] A calculation module 12, configured to calculate a phase reference value based on a rated frequency, a DC voltage measurement value, and a DC voltage rated value, and to calculate a voltage reference value based on a rated voltage, a reactive power measured value, and a reactive power reference value;

[0075] The control module 13 is used to calculate the current reference value based on the AC voltage measurement value, the phase reference value and the voltage reference value; calculate the three-phase voltage reference value based on the grid-connected point current, the maximum current, the phase reference value and the current reference value, and control the grid-side converter based on the three-phase voltage reference value, thereby realizing dynamic regulation of the DC voltage.

[0076] Optionally, the calculation module 12 is specifically used to: calculate a reference frequency based on the regulated voltage, the DC voltage measurement value and the DC voltage rated value, and obtain a phase reference value based on the reference frequency, wherein the regulated voltage is obtained based on the first damping coefficient, the reference frequency and the rated frequency.

[0077] Optionally, the calculation module 12 is specifically used to calculate a voltage reference value based on the regulated power, the measured reactive power value and the reactive power reference value, wherein the regulated power is obtained based on the second damping coefficient, the voltage reference value and the rated voltage.

[0078] Optionally, the control module 13 is specifically used to: obtain a d-axis voltage component and a q-axis voltage component based on the AC voltage measurement value and the phase reference value using Park transformation; obtain a current reference value based on the d-axis voltage reference component, the q-axis voltage reference component, the d-axis voltage component, and the q-axis voltage component, wherein the current reference value includes a d-axis current reference component and a q-axis current reference component.

[0079] Optionally, the control module 13 is specifically used to: use Park's transformation to obtain a d-axis current component and a q-axis current component based on the grid-connected point current and the phase reference value; use Park's inverse transformation to obtain a target d-axis current reference component and a target q-axis current reference component based on the maximum current, the d-axis current reference component, and the q-axis current reference component; use Park's inverse transformation to obtain a three-phase voltage reference value based on the d-axis current component, the q-axis current component, the target d-axis current reference component, and the target q-axis current reference component.

[0080] Optionally, the control module 13 is specifically used to: obtain a d-axis voltage target value based on the d-axis current component, the target d-axis current reference component and the d-axis voltage component; obtain a q-axis voltage target value based on the q-axis current component, the target q-axis current reference component and the q-axis voltage component; and obtain a three-phase voltage reference value based on the d-axis voltage target value and the q-axis voltage target value using an inverse Park transform.

[0081] It should be noted that the above explanation of the embodiment of the DC voltage dynamic regulation control method of the offshore wind power flexible DC system is also applicable to the DC voltage dynamic regulation control device of the offshore wind power flexible DC system of this embodiment, which will not be repeated here.

[0082] In the DC voltage dynamic regulation 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 the grid-side grid-connected point, the reactive power measured value and reactive power reference value of the grid-side converter, the DC voltage measurement value and DC voltage rated value of the DC side of the grid-side converter, the AC voltage measurement value of the AC side of the grid-side converter, the grid-connected point current and the maximum current; the calculation module is used to calculate the phase reference value based on the rated frequency, the DC voltage measurement value and the DC voltage rated value, and calculate the 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 current reference value based on the AC voltage measurement value, the phase reference value and the voltage reference value; the three-phase voltage reference value is calculated based on the grid-connected point current, the maximum current, the phase reference value and the current reference value, and the grid-side converter is controlled based on the three-phase voltage reference value, thereby realizing dynamic regulation of DC voltage. In this case, the rated frequency and rated voltage of the grid-side grid connection point, the measured reactive power value and reactive power reference value of the grid-side converter, the DC voltage measurement value and DC voltage rated value of the DC side of the grid-side converter, the AC voltage measurement value of the AC side of the grid-side converter, the grid-connected point current and the maximum current are integrated to obtain the three-phase voltage reference value, and the grid-side converter is controlled by the three-phase voltage reference value. 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 access grid. Compared with the traditional fixed DC voltage control, the present invention changes the DC voltage outer loop based on the fact that the flexible DC system itself has a certain DC voltage fluctuation capability and the converter current limiting capability requirement (i.e., the maximum current), thereby providing a control device that can cope with the grid voltage under small disturbances of the access grid and has a certain support capability for the grid connection point voltage.

[0083] According to an embodiment of the present disclosure, the present disclosure also provides a direct current voltage dynamic regulation control device for an offshore wind power flexible direct current system, a readable storage medium and a computer program product.

[0084] Figure 7It is a block diagram of an offshore wind power flexible DC system DC voltage dynamic regulation control device used to implement the offshore wind power flexible DC system DC voltage dynamic regulation control method of the embodiment of the present disclosure. The offshore wind power flexible DC system DC voltage dynamic regulation 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 dynamic regulation 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.

[0085] like Figure 7 As shown, the DC voltage dynamic regulation control device 20 of the offshore wind power flexible DC system 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 dynamic regulation control device 20 of the offshore wind power flexible DC system 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.

[0086] Multiple components in the DC voltage dynamic regulation 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 dynamic regulation control device 20 of the offshore wind power flexible DC system to exchange information / data with other DC voltage dynamic regulation control devices of the offshore wind power flexible DC system through a computer network such as the Internet and / or various telecommunication networks.

[0087] 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 performing a method for dynamically regulating the DC voltage of an offshore wind power flexible DC system. For example, in some embodiments, the method for dynamically regulating the DC voltage of an 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 dynamic regulation 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 method for dynamically regulating the DC voltage of an offshore wind power flexible DC system described above may be performed. Alternatively, in other embodiments, the computing unit 21 may be configured to execute the method for dynamically regulating the DC voltage of an offshore wind power flexible DC system in any other appropriate manner (for example, by means of firmware).

[0088] 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.

[0089] 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.

[0090] 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.

[0091] 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).

[0092] 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.

[0093] 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.

[0094] 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.

[0095] 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 dynamically regulating and controlling DC voltage of an offshore wind power flexible DC system, characterized in that: The offshore wind farm flexible direct current system comprises a grid-side converter and a grid-side grid connection point, the grid-side converter is connected to the onshore main grid via the grid-side grid connection point, and the method comprises: Obtain the rated frequency and rated voltage of the grid-side connection point, the measured reactive power value and reactive power reference value of the grid-side converter, the measured DC voltage value and rated DC voltage value of the DC side of the grid-side converter, the measured AC voltage value of the AC side of the grid-side converter, the grid-connection point current and the maximum current; A phase reference value is calculated based on the rated frequency, the DC voltage measurement value and the DC voltage rated value, and a voltage reference value is calculated based on the rated voltage, the reactive power measured value and the reactive power reference value; Calculate and obtain a current reference value based on the AC voltage measurement value, the phase reference value and the voltage reference value; A three-phase voltage reference value is calculated based on the grid-connected point current, the maximum current, the phase reference value and the current reference value, and the grid-side converter is controlled based on the three-phase voltage reference value, thereby realizing dynamic regulation of the DC voltage; A phase reference value is calculated based on the rated frequency, the DC voltage measurement value and the DC voltage rated value, including: a reference frequency is calculated based on the regulated voltage, the DC voltage measurement value and the DC voltage rated value, and the phase reference value is obtained based on the reference frequency, wherein the regulated voltage is obtained based on a first damping coefficient, the reference frequency and the rated frequency.

2. The method for dynamically regulating and controlling DC voltage of an offshore wind power flexible DC system according to claim 1 is characterized in that: The step of calculating and obtaining a voltage reference value based on the rated voltage, the reactive power measured value, and the reactive power reference value comprises: A voltage reference value is calculated based on the regulated power, the reactive power measured value and the reactive power reference value, wherein the regulated power is obtained based on the second damping coefficient, the voltage reference value and the rated voltage.

3. The method for dynamically regulating and controlling DC voltage of an offshore wind power flexible DC system according to claim 2 is characterized in that: The voltage reference value includes a d-axis voltage reference component and a q-axis voltage reference component, and the current reference value is obtained by calculation based on the AC voltage measurement value, the phase reference value and the voltage reference value, including: Using Park transformation, a d-axis voltage component and a q-axis voltage component are obtained based on the AC voltage measurement value and the phase reference value; a current reference value is obtained based on the d-axis voltage reference component, the q-axis voltage reference component, the d-axis voltage component, and the q-axis voltage component, and the current reference value includes a d-axis current reference component and a q-axis current reference component.

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

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

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

7. The DC voltage dynamic regulation control device for an offshore wind power flexible DC system according to claim 6 is characterized in that: The voltage reference value is calculated based on the rated voltage, the reactive power measured value and the reactive power reference value, comprising: A voltage reference value is calculated based on the regulated power, the reactive power measured value and the reactive power reference value, wherein the regulated power is obtained based on the second damping coefficient, the voltage reference value and the rated voltage.

8. The DC voltage dynamic regulation control device for an offshore wind power flexible DC system according to claim 7 is characterized in that: The control module is specifically used to: obtain a d-axis voltage component and a q-axis voltage component based on the AC voltage measurement value and the phase reference value using Park transformation; obtain a current reference value based on the d-axis voltage reference component, the q-axis voltage reference component, the d-axis voltage component, and the q-axis voltage component, wherein the current reference value includes a d-axis current reference component and a q-axis current reference component; Obtaining a d-axis current component and a q-axis current component based on the grid-connected point current and the phase reference value using a Park transformation; obtaining a target d-axis current reference component and a target q-axis current reference component based on the maximum current, the d-axis current reference component, and the q-axis current reference component; A three-phase voltage reference value is obtained based on the d-axis current component, the q-axis current component, the target d-axis current reference component, and the target q-axis current reference component using an inverse Park transform.

9. A DC voltage dynamic regulation and 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 dynamic regulation and control of DC voltage of an offshore wind power flexible DC system according to any one of claims 1-5.

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