Offshore wind power uncontrolled rectification sending-out system fast frequency support control method and device

Abstract

This invention discloses a fast frequency support control method and apparatus for an offshore wind power uncontrolled rectifier transmission system, comprising: acquiring the frequency of the receiving-end AC grid; detecting a frequency change in the receiving-end AC grid; obtaining an improved DC bus voltage command value for the receiving-end converter based on the frequency information; regulating the DC bus voltage of the receiving-end converter based on the command value, so that the DC bus voltage of the receiving-end converter tracks a reference value of the DC bus voltage of the receiving-end converter, thereby causing a change in the AC voltage amplitude of the offshore wind farm; constructing a power outer loop of active power-voltage amplitude and reactive power-voltage phase angle similar to a synchronous machine based on the change in the AC voltage amplitude of the offshore wind farm, determining a reference value for the terminal voltage of the offshore wind turbine, regulating the terminal voltage of the offshore wind turbine, so that the terminal voltage of the wind turbine tracks the reference value of the terminal voltage, and controlling the active power output of the offshore wind farm. This invention improves the inertia support capability of the offshore wind power uncontrolled rectifier transmission system for the receiving-end grid.

Description

Technical Field

[0001] This application relates to the field of offshore wind power generation technology research, specifically to a fast frequency support control method and device for an offshore wind power uncontrolled rectifier transmission system. Background Technology

[0002] With the rapid development of offshore wind power, wind energy development in nearshore areas has approached saturation, and offshore wind power is gradually moving towards deeper and more remote areas. To ensure reliable transmission of wind power from these areas, high-voltage direct current (HVDC) transmission systems have become the preferred choice. Among these, HVDC transmission systems based on diode rectifier units (DRUs) have attracted significant attention in the field of offshore wind power development due to their high reliability and low cost.

[0003] However, HVDC decouples the sending-end offshore wind turbines from the receiving-end AC grid, causing the offshore wind turbines to be unable to directly obtain frequency information from the receiving-end AC grid, thus making it impossible for them to provide inertial response as in the case of offshore wind turbines connected to the AC grid.

[0004] To enable offshore wind turbines to participate in frequency support from the receiving-end AC grid, existing methods often employ communication to directly transmit the receiving-end AC grid frequency information to the offshore wind turbine, which then adjusts its output power accordingly for inertial response. However, communication equipment not only increases system costs but also presents issues such as reliability and latency. To address these problems, Chi Yongning et al. adjusted the DC bus voltage of the receiving-end converter based on the receiving-end AC grid frequency, and the sending-end converter adjusted the AC grid frequency of the offshore wind farm based on the DC bus voltage. This mapped the changes in the receiving-end AC grid frequency to changes in the offshore grid frequency, allowing the offshore wind turbine to achieve frequency support simply by acquiring the offshore grid frequency information.

[0005] However, for DRU-HVDC, the sending-end converter DRU relies on natural commutation for rectification. Therefore, it cannot regulate the offshore AC grid like a flexible DC transmission system, transmitting the receiving-end AC grid frequency information coupled with the DC bus voltage. H. Xiao et al. adjusted the receiving-end converter DC bus voltage based on the frequency difference, while the offshore wind turbine directly collected the sending-end DRU DC bus voltage to obtain the receiving-end AC grid frequency information and adjust the active power reference value of the offshore wind turbine. Although this method eliminates the communication equipment between the sending and receiving ends, the DC bus voltage information still needs to be transmitted through multiple levels, including the sending-end communication unit, wind farm group communication unit, station controller, collector switch, and wind turbine main control, resulting in a certain delay. In addition, the offshore wind turbine under uncontrolled rectification transmission requires a grid-based control strategy, resulting in slow power regulation speed, which is difficult to meet the requirements of the receiving-end AC grid for rapid frequency support.

[0006] Therefore, avoiding dependence on communication and external information and improving the power response capability of offshore wind turbines are key to enabling offshore wind farms to support the frequency of the receiving-end AC power grid under uncontrolled rectification power transmission. Summary of the Invention

[0007] In view of this, embodiments of this application provide a fast frequency support control method and apparatus for an offshore wind power uncontrolled rectifier transmission system. This method adjusts the DC bus voltage of the receiving-end converter based on changes in the frequency of the receiving-end AC grid, thereby affecting the voltage amplitude of the sending-end AC grid. By constructing a synchronous-machine-like active power-voltage amplitude control loop, the power regulation of the offshore wind turbine is achieved to respond to changes in the frequency of the receiving-end AC grid. This method requires no additional communication and coordinates the energy of the receiving-end converter DC bus capacitor and the frequency regulation energy of the offshore wind turbine, improving the inertial response and frequency support capability of the offshore wind power uncontrolled rectifier transmission system to the onshore grid.

[0008] According to a first aspect of the embodiments of this application, a fast frequency support control method for an offshore wind power uncontrolled rectifier transmission system is provided, comprising:

[0009] The frequency of the receiving-end AC grid is obtained. When a frequency change in the receiving-end AC grid is detected, an improved DC bus voltage command value for the receiving-end converter is obtained based on the frequency information.

[0010] Based on the command value of the DC bus voltage of the receiving-end converter, the DC bus voltage of the receiving-end converter is regulated so that the DC bus voltage of the receiving-end converter tracks the reference value of the DC bus voltage of the receiving-end converter, thereby causing a change in the amplitude of the AC voltage of the offshore wind field.

[0011] Based on the variation of AC voltage amplitude in offshore wind farms, a power outer loop of active power-voltage amplitude and reactive power-voltage phase angle is constructed for a quasi-synchronous machine to determine the terminal voltage reference value of the offshore wind turbine.

[0012] Based on the aforementioned terminal voltage reference value, the terminal voltage of the offshore wind turbine is regulated to ensure that the terminal voltage of the offshore wind turbine tracks the aforementioned terminal voltage reference value, thereby controlling the active power output of the offshore wind farm.

[0013] Optionally, based on frequency information, an improved DC bus voltage command value for the receiving-end converter is obtained, including:

[0014] Obtain the frequency of the AC grid at the receiving end. If a frequency change in the AC grid at the receiving end is detected, perform an improved calculation of the DC bus voltage command value for the receiving end converter.

[0015] Based on the frequency of the receiving-end AC power grid, calculate the difference between it and the rated frequency of the receiving-end AC power grid to obtain the frequency difference of the receiving-end AC power grid.

[0016] The voltage droop adjustment of the DC bus of the receiving-end converter is obtained by multiplying the frequency difference of the AC grid at the receiving end by the frequency droop control coefficient.

[0017] Based on the frequency of the AC power grid at the receiving end, the rate of change of the AC power grid frequency at the receiving end is obtained by differential processing.

[0018] The voltage inertia adjustment of the DC bus of the receiving-end converter is obtained by multiplying the frequency change rate of the AC grid at the receiving end by the frequency inertia control coefficient.

[0019] Based on the DC bus voltage droop adjustment and inertia adjustment of the receiving-end converter, these are added to the rated DC bus voltage command value of the receiving-end converter to obtain the improved DC bus voltage command value of the receiving-end converter.

[0020] Optionally, based on the command value of the DC bus voltage of the receiving-end converter, the DC bus voltage of the receiving-end converter is regulated to track the reference value of the DC bus voltage of the receiving-end converter, thereby causing a change in the amplitude of the AC voltage of the offshore wind farm, including:

[0021] Based on the commanded DC bus voltage value of the receiving-end converter, the difference between it and the actual DC bus voltage value is calculated and sent to the receiving-end converter DC bus voltage controller based on proportional-integral (PI) control. The output of this controller is used as the grid-connected current of the receiving-end converter. d Reference values ​​for axis components;

[0022] Set the grid-connected current of the receiving-end converter q Reference values ​​for axis components;

[0023] Calculate the grid-connected current of the receiving-end converter. d , q The reference value of the shaft component and the grid-connected current of the receiving-end converter. d , q The difference between the actual values ​​of the shaft components is fed into the PI-controlled receiving-end converter current controller to obtain the receiving-end converter modulation voltage. d , q Axial components;

[0024] According to the modulation voltage of the receiving-end converter d , q The axis component, after coordinate transformation and pulse width modulation, yields a corresponding switching signal, which is applied to the receiving-end converter to make the DC bus voltage of the receiving-end converter track the reference value of the DC bus voltage of the receiving-end converter, thereby causing a change in the amplitude of the AC voltage of the offshore wind farm.

[0025] Optionally, based on the variation of AC voltage amplitude in the offshore wind farm, a power outer loop of active power-voltage amplitude and reactive power-voltage phase angle for a quasi-synchronous machine is constructed to determine the terminal voltage reference value of the offshore wind turbine, including:

[0026] Based on the variation of AC voltage amplitude in offshore wind farms and referencing the active power-frequency response characteristics of synchronous machines, a synchronous-like active power-voltage amplitude control loop is constructed to obtain the reference value of the terminal voltage amplitude of offshore wind turbines.

[0027] Based on the offshore wind farm, a droop-based reactive power-voltage phase angle control loop is constructed to obtain the terminal voltage phase angle reference value and coordinate transformation angle of the offshore wind turbine, so as to realize the synchronous operation of the wind turbine and the equal distribution of reactive power in the offshore wind farm.

[0028] The terminal voltage reference value of the offshore wind turbine is determined based on the terminal voltage amplitude reference value and the terminal voltage phase angle reference value.

[0029] According to a second aspect of the embodiments of this application, a fast frequency support control device for an offshore wind power uncontrolled rectifier transmission system is provided, comprising:

[0030] The receiving-end converter instruction construction module is used to obtain the frequency of the receiving-end AC grid. When a frequency change in the receiving-end AC grid is detected, an improved receiving-end converter DC bus voltage instruction value is obtained based on the frequency information.

[0031] The receiving-end converter control module is used to regulate the DC bus voltage of the receiving-end converter based on the command value of the DC bus voltage of the receiving-end converter, so that the DC bus voltage of the receiving-end converter tracks the reference value of the DC bus voltage of the receiving-end converter, thereby causing the AC voltage amplitude of the offshore wind farm to change.

[0032] The offshore wind turbine power control module is used to construct a power outer loop of active power-voltage amplitude and reactive power-voltage phase angle based on the change of AC voltage amplitude in the offshore wind farm, and to determine the terminal voltage reference value of the offshore wind turbine.

[0033] The offshore wind turbine voltage control module is used to regulate the offshore wind turbine terminal voltage according to the terminal voltage reference value, so that the offshore wind turbine terminal voltage tracks the terminal voltage reference value and controls the active power output of the offshore wind farm.

[0034] According to a third aspect of the embodiments of this application, an electronic device is provided, comprising:

[0035] One or more processors;

[0036] Memory, used to store one or more programs;

[0037] When the one or more programs are executed by the one or more processors, the one or more processors perform the method as described in the first aspect.

[0038] According to a fourth aspect of the embodiments of this application, a computer-readable storage medium is provided that stores computer instructions thereon, which, when executed by a processor, implement the steps of the method as described in the first aspect.

[0039] The technical solutions provided by the embodiments of this application may include the following beneficial effects:

[0040] As can be seen from the above embodiments, the method of the present invention does not require communication, and uses the DC bus voltage to couple the frequency information of the receiving-end AC grid and the voltage amplitude information of the sending-end AC grid, resulting in higher system reliability. The present invention constructs a synchronous machine-like active power-voltage amplitude control loop, simulating the characteristics of a synchronous machine, resulting in a faster inertial response. The present invention enhances frequency support by coordinating the regulation of the DC bus capacitor energy of the receiving-end converter and the frequency regulation energy of the offshore wind turbine, thus integrating the two types of frequency regulation resources. The present invention provides a solution for improving the rapid frequency support capability of similar uncontrolled rectifier transmission systems.

[0041] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and do not limit this application. Attached Figure Description

[0042] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0043] Figure 1 This is a flowchart illustrating a fast frequency support control method for an offshore wind power uncontrolled rectifier transmission system according to an exemplary embodiment.

[0044] Figure 2 This is a structural diagram of an offshore wind power uncontrolled rectifier transmission system according to an exemplary embodiment.

[0045] Figure 3 This is a control structure diagram of a fast frequency support method for an uncontrolled rectifier transmission system for offshore wind power, according to an exemplary embodiment.

[0046] Figure 4 Simulation results of AC grid frequency for the traditional strategy and the proposed strategy when a 300MW load is suddenly added to the receiving-end AC grid.

[0047] Figure 5 Simulation results of AC grid frequency at the sending end using the traditional strategy and the proposed strategy when a 300MW load is suddenly added to the receiving-end AC grid.

[0048] Figure 6Simulation results of AC grid amplitude at the sending-end offshore wind farm when a sudden 300MW load is added to the receiving-end AC grid.

[0049] Figure 7 Simulation results of active power of DRU under traditional and proposed strategies when a 300MW load is suddenly added to the receiving-end AC grid.

[0050] Figure 8 The simulation results of reactive power of DRU under the traditional strategy and the proposed strategy when a 300MW load is suddenly added to the AC grid at the receiving end are shown in the figure.

[0051] Figure 9 Simulation results of HVDC DC current for traditional and proposed strategies when a 300MW load is suddenly added to the receiving-end AC grid.

[0052] Figure 10 Simulation results of DC bus voltage at the receiving end converter for the traditional strategy and the proposed strategy when a 300MW load is suddenly added to the receiving end AC grid.

[0053] Figure 11 Simulation results of active power of the receiving-end converter for the traditional strategy and the proposed strategy when a 300MW load is suddenly added to the receiving-end AC grid.

[0054] Figure 12 Simulation results of active power of offshore wind turbines under traditional and proposed strategies when a 300MW load is suddenly added to the receiving-end AC grid.

[0055] Figure 13 Simulation results of reactive power of offshore wind turbines under traditional and proposed strategies when a 300MW load is suddenly added to the receiving-end AC grid.

[0056] Figure 14 Simulation results of AC grid frequency for the traditional strategy and the proposed strategy when the load on the receiving-end AC grid is suddenly reduced by 300MW.

[0057] Figure 15 Simulation results of AC grid frequency at the sending end for the traditional strategy and the proposed strategy when the load on the receiving end AC grid is suddenly reduced by 300MW.

[0058] Figure 16 Simulation results of AC grid amplitude at the sending-end offshore wind farm when the load on the receiving-end AC grid suddenly decreases by 300MW, using both traditional and proposed strategies.

[0059] Figure 17 The simulation results of active power of DRU under the traditional strategy and the proposed strategy when the load of AC grid at the receiving end suddenly decreases by 300MW are shown in the figure.

[0060] Figure 18The simulation results of reactive power of DRU under the traditional strategy and the proposed strategy when the load of AC grid at the receiving end suddenly decreases by 300MW are shown in the figure.

[0061] Figure 19 The simulation results of HVDC DC current for the traditional strategy and the proposed strategy when the load on the receiving-end AC grid is suddenly reduced by 300MW are shown in the figure.

[0062] Figure 20 Simulation results of DC bus voltage at the receiving end converter for the traditional strategy and the proposed strategy when the load on the receiving end AC grid is suddenly reduced by 300MW.

[0063] Figure 21 Simulation results of active power of the receiving-end converter for the traditional strategy and the proposed strategy when the load of the receiving-end AC grid is suddenly reduced by 300MW.

[0064] Figure 22 Simulation results of active power of offshore wind turbines under traditional and proposed strategies when the load on the receiving-end AC grid suddenly decreases by 300MW;

[0065] Figure 23 Simulation results of reactive power of offshore wind turbines under traditional and proposed strategies when the load on the receiving-end AC grid suddenly decreases by 300MW.

[0066] Figure 24 This is a block diagram illustrating a fast frequency support control device for an offshore wind power uncontrolled rectifier transmission system according to an exemplary embodiment. Detailed Implementation

[0067] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this application as detailed in the appended claims.

[0068] The terminology used in this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The singular forms “a,” “the,” and “the” used in this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any or all possible combinations of one or more of the associated listed items.

[0069] It should be understood that although the terms first, second, third, etc., may be used in this application to describe various information, such information should not be limited to these terms. These terms are only used to distinguish information of the same type from one another. For example, without departing from the scope of this application, first information may also be referred to as second information, and similarly, second information may also be referred to as first information. Depending on the context, the word "if" as used herein may be interpreted as "when," "when," or "in response to determination."

[0070] To describe the present invention in more detail, the following description, in conjunction with the accompanying drawings and specific embodiments, will further illustrate the invention.

[0071] Figure 1 This is a flowchart illustrating a fast frequency support control method for an offshore wind power uncontrolled rectifier transmission system according to an exemplary embodiment, such as... Figure 1 As shown, the method may include the following steps:

[0072] S1: Obtain the frequency of the receiving-end AC grid. When a frequency change in the receiving-end AC grid is detected, obtain an improved DC bus voltage command value for the receiving-end converter based on the frequency information. This step includes the following sub-steps:

[0073] S11: Based on the frequency of the AC power grid at the receiving end, if a frequency change of the AC power grid at the receiving end is detected, calculate the difference between the frequency of the AC power grid at the receiving end and the rated frequency of the AC power grid at the receiving end, and obtain the frequency difference of the AC power grid at the receiving end.

[0074] Specifically, taking a 1000MW offshore wind power uncontrolled rectifier transmission system as an example, its main structure diagram is as follows: Figure 2 As shown, the offshore wind farm consists of three converging wind turbines (capacities of 330MW, 330MW, and 340MW respectively). These turbines are connected to a 1000MW rated capacity DRU-HVDC system with a rated DC voltage of ±320kV via a 690V / 66kV step-up transformer and a 66kV / 258kV / 258kV DRU converter transformer. The system then connects to the onshore power grid via a 330kV / 230kV step-down transformer. The onshore power grid consists of a single synchronous generator with an installed capacity of 2000MW and a constant load of 2000MW.

[0075] Collect the three-phase voltage of the receiving end AC power grid U re The frequency of the receiving-end AC power grid is obtained through a phase-locked loop. f re Connect it to the rated frequency of the receiving-end AC power grid. f Subtracting from 0, we obtain the frequency difference Δ between the receiving end and the AC power grid. f ,for:

[0076] (1)

[0077] S12: Based on the frequency difference of the AC grid at the receiving end, multiply by the frequency droop control coefficient to obtain the DC bus voltage droop adjustment amount of the receiving end converter;

[0078] Specifically, based on the frequency difference Δ of the receiving-end AC power grid f Adjustment amount of DC bus voltage droop at the receiving end of the converter for:

[0079] (2)

[0080] in, k D This is the frequency droop control coefficient for the DC bus voltage of the receiving-end converter.

[0081] S13: Differentiate the AC grid frequency at the receiving end to obtain the AC grid frequency change rate at the receiving end;

[0082] Specifically, the frequency of the receiving-end AC power grid is calculated. f re The differential value is used to obtain the frequency change rate of the AC power grid at the receiving end. df / dt ;

[0083] S14: Based on the frequency change rate of the AC grid at the receiving end, multiply by the frequency inertia control coefficient to obtain the DC bus voltage inertia adjustment amount of the receiving end converter;

[0084] Specifically, based on the frequency variation rate of the receiving-end AC power grid df / dt Inertial adjustment of DC bus voltage at the receiving end of the converter for:

[0085] (3)

[0086] in, k I This represents the frequency inertia control coefficient for the DC bus voltage of the receiving-end converter.

[0087] S15: Based on the DC bus voltage droop adjustment amount and inertia adjustment amount of the receiving-end converter, add them to the rated DC bus voltage command value of the receiving-end converter to obtain the improved DC bus voltage command value of the receiving-end converter under the fast frequency support control method.

[0088] Specifically, based on the DC bus voltage droop adjustment amount of the receiving-end converter. and inertia adjustment amount Compare both with the command value of the rated DC bus voltage of the receiving-end converter. The values ​​are added together to obtain the improved DC bus voltage command value of the receiving-end converter under the fast frequency support control method. ,for:

[0089] (4)

[0090] This step converts the AC grid frequency information at the receiving end into a reference value for the DC bus voltage of the receiving-end converter, providing guidance for the regulation of the receiving-end converter and relevant information for the rapid frequency support of offshore wind turbines.

[0091] S2: Based on the DC bus voltage command value of the receiving-end converter, the DC bus voltage of the receiving-end converter is regulated so that the DC bus voltage of the receiving-end converter tracks the DC bus voltage reference value of the receiving-end converter, thereby causing a change in the AC voltage amplitude of the offshore wind field.

[0092] Specifically, based on the DC bus voltage command value of the receiving-end converter Calculate its value relative to the actual value of the DC bus voltage of the receiving-end converter. The difference is fed into the DC bus voltage controller of the receiving-end converter, which is based on proportional-integral (PI) control, and its output is used as the grid-connected current of the receiving-end converter. d Reference values ​​for axis components ,Right now:

[0093] (4)

[0094] in, k preVdc , k ireVdc These are the proportional and integral coefficients of the DC bus voltage loop of the receiving-end converter.

[0095] In addition, the grid-connected current of the receiving-end converter is generally set. q Reference values ​​for axis components for:

[0096] (5)

[0097] Calculate the grid-connected current of the receiving-end converter. d , q Reference values ​​for axis components , Grid-connected current with receiving-end converter d , q Actual value of axis component , The difference is fed into the PI-controlled receiver-end converter current controller to obtain the receiver-end converter modulation voltage. d , q Axial components , :

[0098] (6)

[0099] (7)

[0100] in, k preI , k ireI These are the proportional and integral coefficients of the current loop of the receiving-end converter.

[0101] According to the modulation voltage of the receiving-end converter d , q The axis component, after coordinate transformation and pulse width modulation (PWM), yields a corresponding switching signal, which is applied to the receiving-end converter to make the DC bus voltage of the receiving-end converter track the reference value of the DC bus voltage of the receiving-end converter.

[0102] Based on the HVDC DC line topology, the DC bus voltage of the sending-end DRU can be obtained. and the DC bus voltage of the receiving-end converter The relation is:

[0103] (8)

[0104] in, I dc HVDC direct current, R dc , I dc For the equivalent resistance and inductance of an HVDC line;

[0105] Due to the regulation of the DC bus voltage of the receiving-end converter, the actual value of the DC bus voltage of the receiving-end converter is equal to its reference value, thereby affecting the DC bus voltage of the sending-end DRU. And so it changes.

[0106] Based on the topology and commutation characteristics of the sending-end DRU, and considering the inductance dynamic characteristics of the converter transformer, the AC voltage amplitude of the sending-end offshore wind farm can be obtained. and the DC bus voltage of the sending end DRU The relation is:

[0107] (9)

[0108] in, The AC voltage frequency for the sending-end offshore wind farm. T DR , L DR The turns ratio and inductance of the DRU converter transformer;

[0109] Sending end DRU DC bus voltage Changes cause variations in the AC voltage amplitude of the offshore wind field at the sending end. change.

[0110] Through this step, the actual value of the DC bus voltage of the receiving-end converter contains the frequency information of the receiving-end AC grid. After passing through physical links such as the HVDC DC line and DRU commutation, it causes a change in the amplitude of the AC voltage of the sending-end offshore wind farm, and the frequency information of the receiving-end AC grid can be mapped without the need for communication lines.

[0111] S3: Based on the variation of AC voltage amplitude in offshore wind farms, construct a power outer loop of active power-voltage amplitude and reactive power-voltage phase angle for a quasi-synchronous machine to determine the terminal voltage reference value of the offshore wind turbine.

[0112] S31: Based on the change in AC voltage amplitude of the offshore wind farm, and referencing the active power-frequency response characteristics of the synchronous machine, construct a synchronous-like active power-voltage amplitude control loop to obtain the reference value of the terminal voltage amplitude of the offshore wind turbine.

[0113] Specifically, in order for offshore wind turbines to autonomously respond to changes in the AC voltage amplitude of the offshore wind farm and adjust their power output, the offshore wind turbines need to exhibit synchronous-like characteristics. Referring to the active power-frequency response characteristics of a synchronous machine, the active power-voltage amplitude response characteristics of a synchronous-like machine can be obtained:

[0114] (10)

[0115] in, , These are the reference and rated values ​​for the terminal voltage amplitude of offshore wind turbines. , This provides reference and actual values ​​for the active power output of offshore wind turbines. J , D The moment of inertia and damping coefficient of the offshore wind turbine;

[0116] Based on the active power-voltage amplitude response characteristics of a synchronous-like machine, an active power-voltage amplitude control loop for the synchronous-like machine is constructed to obtain the terminal voltage amplitude reference value of the offshore wind turbine. :

[0117] (11)

[0118] This step simulates the external characteristics of offshore wind turbines as a quasi-synchronous machine with active power-voltage amplitude correlation, providing a control basis for achieving inertia support for offshore wind turbines.

[0119] S32: Based on the offshore wind farm, construct a droop-based reactive power-voltage phase angle control loop to obtain the terminal voltage phase angle reference value and coordinate transformation angle of the offshore wind turbine, so as to realize the synchronous operation of the offshore wind turbine and the equal distribution of reactive power in the offshore wind farm.

[0120] Specifically, for offshore wind farms that transmit power via uncontrolled rectification, the reactive power output of the offshore wind turbines is proportional to the frequency of the AC voltage at the sending end of the offshore wind farm. Therefore, droop control is used to achieve equal distribution of reactive power among the offshore wind turbines, thereby enabling synchronous operation of all turbines within the offshore wind farm. By constructing a droop-based reactive power-voltage phase angle control loop, a reference value for the terminal voltage frequency of the offshore wind turbines is obtained. :

[0121] (12)

[0122] in, This refers to the rated frequency of the terminal voltage for offshore wind turbines. , This provides reference and actual values ​​for the reactive power output of offshore wind turbines. k G , k T The proportional coefficient and time coefficient for the droop control of offshore wind turbines;

[0123] The terminal voltage frequency reference value of offshore wind turbines By integrating, we can obtain the reference value of the terminal voltage phase angle and the coordinate transformation angle of the offshore wind turbine:

[0124] (13)

[0125] in, ω base This is the reference value for angular frequency.

[0126] This step ensures that the offshore wind turbines share the reactive power required by the offshore wind farm and obtain coordinate change angle information, providing a control basis for the offshore wind turbines to achieve self-synchronous operation.

[0127] S33: Determine the reference value of the terminal voltage of the offshore wind turbine based on the reference value of the terminal voltage amplitude and the reference value of the terminal voltage phase angle;

[0128] Specifically, by orienting the coordinate system of the offshore wind turbine control system to the reference value of the offshore wind turbine terminal voltage phase angle obtained from the reactive power-voltage phase angle control loop, the terminal voltage of the offshore wind turbine can be obtained. d , q Axis component reference value , :

[0129] (14)

[0130] (15)

[0131] This step utilizes known information to obtain the offshore wind turbine terminal voltage. d , q The shaft component reference value provides accurate information for the voltage control of offshore wind turbine terminals.

[0132] S4: Adjust the terminal voltage of the offshore wind turbine according to the terminal voltage reference value so that the terminal voltage of the offshore wind turbine tracks the terminal voltage reference value, thereby controlling the active power output of the offshore wind farm;

[0133] Specifically, based on the terminal voltage of the offshore wind turbine d , q Axis component reference value , Calculate the voltage at the offshore wind turbine terminals respectively. d , q Actual value of shaft component , The difference is fed into the PI-controlled offshore wind turbine voltage controller, and its output is used as the offshore wind turbine grid-connected current. d , q Reference values ​​for axis components , ,Right now:

[0134] (16)

[0135] (17)

[0136] in, k pgU , k igU For the proportional and integral coefficients of the voltage loop of offshore wind turbines;

[0137] According to the grid connection current of the offshore wind turbine d , q Reference values ​​for axis components , Grid-connected current of offshore wind turbines d , q Actual value of axis component , The difference is fed into a PI-based offshore wind turbine current controller to obtain the offshore wind turbine modulation voltage. d , q Axial components , :

[0138] (18)

[0139] (19)

[0140] in, k pgI , k igI For the proportional and integral coefficients of the current loop of offshore wind turbines;

[0141] According to the offshore wind turbine modulation voltage d , q The axis component, after coordinate transformation and pulse width modulation (PWM), generates a corresponding switching signal, which is then applied to the grid-side converter of the offshore wind turbine.

[0142] In addition, the turbine-side converter of the offshore wind turbine adopts the existing conventional DC bus voltage-current dual closed-loop control structure, which will not be elaborated here.

[0143] Through this step, the offshore wind turbine terminal voltage tracks the terminal voltage reference value obtained from the power loop, thereby controlling the power output of the offshore wind farm and achieving rapid frequency support for the receiving-end AC grid.

[0144] Based on the example described, the control structure diagram of the fast frequency support method for the offshore wind power uncontrolled rectifier transmission system is as follows: Figure 3 As shown.

[0145] Figure 4 Simulation results of AC grid frequency for the traditional strategy and the proposed strategy when a 300MW load is suddenly added to the receiving-end AC grid. Figure 5 Simulation results of AC grid frequency at the sending end using the traditional strategy and the proposed strategy when a 300MW load is suddenly added to the receiving-end AC grid. Figure 6 Simulation results of AC grid amplitude at the sending-end offshore wind farm when a sudden 300MW load is added to the receiving-end AC grid. Figure 7 Simulation results of active power of DRU under traditional and proposed strategies when a 300MW load is suddenly added to the receiving-end AC grid. Figure 8 The simulation results of reactive power of DRU under the traditional strategy and the proposed strategy when a 300MW load is suddenly added to the AC grid at the receiving end are shown in the figure. Figure 9 Simulation results of HVDC DC current for traditional and proposed strategies when a 300MW load is suddenly added to the receiving-end AC grid. Figure 10 Simulation results of DC bus voltage at the receiving end converter for the traditional strategy and the proposed strategy when a 300MW load is suddenly added to the receiving end AC grid. Figure 11 Simulation results of active power of the receiving-end converter for the traditional strategy and the proposed strategy when a 300MW load is suddenly added to the receiving-end AC grid. Figure 12Simulation results of active power of offshore wind turbines under traditional and proposed strategies when a 300MW load is suddenly added to the receiving-end AC grid. Figure 13 Simulation results of reactive power of offshore wind turbines under traditional and proposed strategies when a 300MW load is suddenly added to the receiving-end AC grid. Figure 4-13 It is known that when using the traditional control strategy, the offshore wind turbine does not respond to the frequency changes of the sending-end AC grid, and the power transmitted to the sending-end AC grid through the DRU-HVDC remains almost unchanged. At this time, the frequency of the sending-end AC grid drops to a minimum of 49.8Hz. However, when using the proposed control strategy, the receiving-end converter adjusts its DC bus voltage according to the frequency information of the receiving-end AC grid, and the AC voltage amplitude of the sending-end offshore wind farm changes naturally accordingly. The offshore wind turbine adjusts its power output through the constructed active power-voltage amplitude control loop, and can deliver more active power to the receiving-end AC grid within 500ms, raising the minimum frequency of the receiving-end AC grid to 49.86Hz.

[0146] Figure 14 Simulation results of AC grid frequency for the traditional strategy and the proposed strategy when the load on the receiving-end AC grid is suddenly reduced by 300MW. Figure 15 Simulation results of AC grid frequency at the sending end for the traditional strategy and the proposed strategy when the load on the receiving end AC grid is suddenly reduced by 300MW. Figure 16 Simulation results of AC grid amplitude at the sending-end offshore wind farm when the load on the receiving-end AC grid suddenly decreases by 300MW, using both traditional and proposed strategies. Figure 17 The simulation results of active power of DRU under the traditional strategy and the proposed strategy when the load of AC grid at the receiving end suddenly decreases by 300MW are shown in the figure. Figure 18 The simulation results of reactive power of DRU under the traditional strategy and the proposed strategy when the load of AC grid at the receiving end suddenly decreases by 300MW are shown in the figure. Figure 19 The simulation results of HVDC DC current for the traditional strategy and the proposed strategy when the load on the receiving-end AC grid is suddenly reduced by 300MW are shown in the figure. Figure 20 Simulation results of DC bus voltage at the receiving end converter for the traditional strategy and the proposed strategy when the load on the receiving end AC grid is suddenly reduced by 300MW. Figure 21 Simulation results of active power of the receiving-end converter for the traditional strategy and the proposed strategy when the load of the receiving-end AC grid is suddenly reduced by 300MW. Figure 22 Simulation results of active power of offshore wind turbines under traditional and proposed strategies when the load on the receiving-end AC grid suddenly decreases by 300MW. Figure 23 Simulation results of reactive power of offshore wind turbines under traditional and proposed strategies when the load on the receiving-end AC grid suddenly decreases by 300MW. Figure 14-23It can be seen that when the load on the receiving-end AC grid suddenly decreases, the frequency of the receiving-end AC grid rises to 50.22Hz under the traditional strategy. However, when the proposed control strategy is adopted, the offshore wind turbine responds to the frequency change of the receiving-end AC grid by reducing its output power, thereby reducing the rate of rise of the receiving-end AC grid frequency, and the maximum value of the receiving-end AC grid frequency is reduced to 50.18Hz. It can be seen that the proposed control strategy has excellent rapid frequency support capability under different frequency change conditions.

[0147] In summary, this invention proposes a rapid frequency support control method for offshore wind power uncontrolled rectifier transmission systems. The innovation of this method lies in adjusting the DC bus voltage of the receiving-end converter based on changes in the frequency of the receiving-end AC grid, thereby influencing the voltage amplitude of the sending-end AC grid. By constructing a synchronous-machine-like active power-voltage amplitude control loop, the power regulation of the offshore wind turbine is achieved to respond to changes in the receiving-end AC grid frequency. This method requires no additional communication and coordinates the energy of the receiving-end converter DC bus capacitor and the frequency regulation energy of the offshore wind turbine, improving the inertial response and frequency support capability of the offshore wind power uncontrolled rectifier transmission system to the onshore grid. This invention provides a framework for improving the rapid frequency support capability of similar uncontrolled rectifier transmission systems.

[0148] Corresponding to the aforementioned embodiments of the fast frequency support control method for offshore wind power uncontrolled rectifier transmission systems, this application also provides embodiments of a fast frequency support control device for offshore wind power uncontrolled rectifier transmission systems.

[0149] Figure 24 This is a block diagram illustrating a fast frequency support control device for an uncontrolled rectifier power transmission system for offshore wind power, according to an exemplary embodiment. (Refer to...) Figure 24 The device includes:

[0150] The receiving-end converter instruction construction module 1 is used to obtain the frequency of the receiving-end AC grid and, when a frequency change of the receiving-end AC grid is detected, to obtain an improved receiving-end converter DC bus voltage instruction value based on the frequency information.

[0151] The receiving-end converter control module 2 is used to regulate the DC bus voltage of the receiving-end converter based on the command value of the DC bus voltage of the receiving-end converter, so that the DC bus voltage of the receiving-end converter tracks the reference value of the DC bus voltage of the receiving-end converter, thereby causing the AC voltage amplitude of the offshore wind farm to change.

[0152] The offshore wind turbine power control module 3 is used to construct a power outer loop of active power-voltage amplitude and reactive power-voltage phase angle based on the change of AC voltage amplitude in the offshore wind farm, and to determine the terminal voltage reference value of the offshore wind turbine.

[0153] The offshore wind turbine voltage control module 4 is used to regulate the offshore wind turbine terminal voltage according to the terminal voltage reference value, so that the offshore wind turbine terminal voltage tracks the terminal voltage reference value and controls the active power output of the offshore wind farm.

[0154] Regarding the apparatus in the above embodiments, the specific manner in which each module performs its operation has been described in detail in the embodiments related to the method, and will not be elaborated upon here.

[0155] For the device embodiments, since they basically correspond to the method embodiments, the relevant parts can be referred to in the description of the method embodiments. The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this application according to actual needs. Those skilled in the art can understand and implement this without creative effort.

[0156] Accordingly, this application also provides an electronic device, comprising: one or more processors; a memory for storing one or more programs; and when the one or more programs are executed by the one or more processors, causing the one or more processors to implement the fast frequency support control method for the offshore wind power uncontrolled rectifier transmission system as described above.

[0157] Accordingly, this application also provides a computer-readable storage medium storing computer instructions that, when executed by a processor, implement the fast frequency support control method for an uncontrolled rectifier power transmission system for offshore wind power as described above.

[0158] Other embodiments of this application will readily occur to those skilled in the art upon consideration of the specification and practice of the disclosure herein. This application is intended to cover any variations, uses, or adaptations of this application that follow the general principles of this application and include common knowledge or customary techniques in the art not disclosed herein. The specification and embodiments are to be considered exemplary only, and the true scope and spirit of this application are indicated by the claims.

[0159] It should be understood that this application is not limited to the precise structure described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of this application is limited only by the appended claims.

Claims

1. A method for fast frequency support control of offshore wind power uncontrolled rectifier transmission system, characterized in that, include: The frequency of the receiving-end AC grid is obtained. When a frequency change in the receiving-end AC grid is detected, an improved DC bus voltage command value for the receiving-end converter is obtained based on the frequency information. The step of obtaining the improved DC bus voltage command value of the receiving-end converter based on frequency information includes: calculating the difference between the frequency of the receiving-end AC grid and the rated frequency of the receiving-end AC grid to obtain the frequency difference of the receiving-end AC grid; multiplying the frequency difference of the receiving-end AC grid by a frequency droop control coefficient to obtain the DC bus voltage droop adjustment amount of the receiving-end converter; differentiating the frequency of the receiving-end AC grid to obtain the frequency change rate of the receiving-end AC grid; multiplying the frequency change rate of the receiving-end AC grid by a frequency inertia control coefficient to obtain the DC bus voltage inertia adjustment amount of the receiving-end converter; and adding the DC bus voltage droop adjustment amount and the inertia adjustment amount to the rated DC bus voltage command value of the receiving-end converter to obtain the improved DC bus voltage command value of the receiving-end converter. Based on the command value of the DC bus voltage of the receiving-end converter, the DC bus voltage of the receiving-end converter is regulated so that the DC bus voltage of the receiving-end converter tracks the reference value of the DC bus voltage of the receiving-end converter, thereby causing a change in the amplitude of the AC voltage of the offshore wind field. Based on the variation of AC voltage amplitude in offshore wind farms, a power outer loop of active power-voltage amplitude and reactive power-voltage phase angle is constructed for a quasi-synchronous machine to determine the terminal voltage reference value of the offshore wind turbine. Specifically, this includes: constructing a quasi-synchronous machine active power-voltage amplitude control loop based on the variation of AC voltage amplitude in the offshore wind farm and referencing the active power-frequency response characteristics of the synchronous machine to obtain the terminal voltage amplitude reference value of the offshore wind turbine; constructing a droop-based reactive power-voltage phase angle control loop based on the offshore wind farm to obtain the terminal voltage phase angle reference value and coordinate transformation angle of the offshore wind turbine, thereby achieving synchronous operation of the offshore wind turbines and equal distribution of reactive power within the offshore wind farm; and determining the terminal voltage reference value of the offshore wind turbine based on the terminal voltage amplitude reference value and the terminal voltage phase angle reference value. Based on the aforementioned terminal voltage reference value, the terminal voltage of the offshore wind turbine is regulated to ensure that the terminal voltage of the offshore wind turbine tracks the aforementioned terminal voltage reference value, thereby controlling the active power output of the offshore wind farm.

2. The method of claim 1, wherein, Based on the command value of the DC bus voltage of the receiving-end converter, the DC bus voltage of the receiving-end converter is regulated to track the reference value of the DC bus voltage of the receiving-end converter, thereby causing changes in the amplitude of the AC voltage of the offshore wind farm, including: Based on the commanded DC bus voltage value of the receiving-end converter, the difference between it and the actual DC bus voltage value is calculated and sent to the receiving-end converter DC bus voltage controller based on proportional-integral (PI) control. The output of this controller is used as the grid-connected current of the receiving-end converter. d Reference values ​​for axis components; Setting grid-connected current of receiving end converter q reference value of shaft component Calculate the grid-connected current of the receiving-end converter. d , q The reference value of the shaft component and the grid-connected current of the receiving-end converter. d , q The difference between the actual values ​​of the shaft components is fed into the PI-controlled receiving-end converter current controller to obtain the receiving-end converter modulation voltage. d , q Axial components; According to the modulation voltage of the receiving-end converter d , q The axis component, after coordinate transformation and pulse width modulation, yields a corresponding switching signal, which is applied to the receiving-end converter to make the DC bus voltage of the receiving-end converter track the reference value of the DC bus voltage of the receiving-end converter, thereby causing a change in the amplitude of the AC voltage of the offshore wind farm.

3. A device for fast frequency support control of offshore wind farm uncontrolled rectifier based transmission system, characterized in that, include: The receiving-end converter instruction construction module is used to obtain the frequency of the receiving-end AC grid. When a frequency change in the receiving-end AC grid is detected, an improved receiving-end converter DC bus voltage instruction value is obtained based on the frequency information. The step of obtaining the improved DC bus voltage command value of the receiving-end converter based on frequency information includes: calculating the difference between the frequency of the receiving-end AC grid and the rated frequency of the receiving-end AC grid to obtain the frequency difference of the receiving-end AC grid; multiplying the frequency difference of the receiving-end AC grid by a frequency droop control coefficient to obtain the DC bus voltage droop adjustment amount of the receiving-end converter; differentiating the frequency of the receiving-end AC grid to obtain the frequency change rate of the receiving-end AC grid; multiplying the frequency change rate of the receiving-end AC grid by a frequency inertia control coefficient to obtain the DC bus voltage inertia adjustment amount of the receiving-end converter; and adding the DC bus voltage droop adjustment amount and the inertia adjustment amount to the rated DC bus voltage command value of the receiving-end converter to obtain the improved DC bus voltage command value of the receiving-end converter. The receiving-end converter control module is used to regulate the DC bus voltage of the receiving-end converter based on the command value of the DC bus voltage of the receiving-end converter, so that the DC bus voltage of the receiving-end converter tracks the reference value of the DC bus voltage of the receiving-end converter, thereby causing the AC voltage amplitude of the offshore wind farm to change. The offshore wind turbine power control module is used to construct a power outer loop of active power-voltage amplitude and reactive power-voltage phase angle based on the changes in AC voltage amplitude in the offshore wind farm, and to determine the terminal voltage reference value of the offshore wind turbine. Specifically, it includes: constructing a synchronous-machine-like active power-voltage amplitude control loop based on the changes in AC voltage amplitude in the offshore wind farm and referencing the active power-frequency response characteristics of the synchronous machine to obtain the terminal voltage amplitude reference value of the offshore wind turbine; constructing a droop-based reactive power-voltage phase angle control loop based on the offshore wind farm to obtain the terminal voltage phase angle reference value and coordinate transformation angle of the offshore wind turbine, so as to achieve synchronous operation of the offshore wind turbines and equal distribution of reactive power within the offshore wind farm; and determining the terminal voltage reference value of the offshore wind turbine based on the terminal voltage amplitude reference value and the terminal voltage phase angle reference value. The offshore wind turbine voltage control module is used to regulate the offshore wind turbine terminal voltage according to the terminal voltage reference value, so that the offshore wind turbine terminal voltage tracks the terminal voltage reference value and controls the active power output of the offshore wind farm.

4. An electronic device, comprising: include: One or more processors; Memory, used to store one or more programs; When the one or more programs are executed by the one or more processors, the one or more processors implement the method as described in any one of claims 1-2.

5. A computer readable storage medium having stored thereon computer instructions, wherein, When executed by the processor, this instruction implements the steps of the method as described in any one of claims 1-2.

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