An active support control method, device, system and storage medium for a wind farm connected to a grid through flexible direct current transmission

Abstract

The application discloses a kind of wind farm through flexible direct current transmission grid-connected active support control method, device, system and storage medium, belong to grid active energy frequency modulation technical field.Method includes obtaining including wind farm, direct current transmission line and frequency modulation control model of receiving end grid;First layer collaborative control is carried out to direct current voltage in direct current transmission line;The active power of each wind turbine is second layer collaborative control, including: selecting the active power of wind turbine, the direct current current instruction value variation of direct current transmission line, direct current voltage variation and construct macro variable, obtain the active power of current wind turbine;The active power of current wind turbine is input to the control optimization model that is well constructed in advance, and the active power of wind turbine is obtained quickly frequency modulation coefficient, to control the active power of each wind turbine.The application realizes that grid-connected system utilizes direct current transmission line capacitor energy storage and wind farm active power collaborative provides active energy support, and optimizes grid frequency stability problem.

Description

Technical Field

[0001] This invention belongs to the field of active energy frequency regulation technology of power grid, specifically relating to an active support control method, device, system and storage medium for wind farms connected to the grid via flexible DC transmission. Background Technology

[0002] The inverse distribution of renewable energy and load centers in my country has made the transmission of electricity from renewable energy bases to load centers via flexible DC transmission a primary operating mode. Because DC transmission decouples the converter bus voltage frequency of the wind farm's converter station from the frequency of the receiving-end grid, wind farms cannot quickly detect frequency disturbances in the receiving-end grid under conditions of no or weak communication. Consequently, they cannot utilize additional fast frequency regulation control to provide active support and frequency response to the receiving-end grid, thereby failing to improve its dynamic frequency regulation characteristics.

[0003] Existing literature has discussed the dynamic characteristics of wind farms connected to the grid via flexible DC systems to provide inertia support. A few studies have mentioned the research on wind power connected to the grid via LCC-FHMMC (modular multilevel converter with hybrid full-bridge and half-bridge sub-modules) DC transmission lines to participate in primary frequency regulation and provide active energy support. However, the coordinated control of wind farms and DC lines is still lacking. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide an active support control method, device, system and storage medium for wind farms connected to the grid via flexible DC transmission. By using the DC voltage droop coefficient and the wind turbine's fast frequency regulation coefficient, the grid-connected system can utilize the capacitor energy storage of the DC transmission line and the active power of the wind farm to provide active energy support, thereby optimizing the grid frequency stability problem.

[0005] This invention provides the following technical solution:

[0006] In the first aspect, an active support control method for wind farms connected to the grid via flexible DC transmission is provided, comprising: acquiring a pre-constructed frequency regulation control model including a wind farm, a DC transmission line and a receiving-end power grid, wherein the wind farm includes several wind turbine units;

[0007] Based on the frequency modulation control model, the first layer of coordinated control is performed on the DC voltage in the DC transmission line, including: determining the inertial response of the DC voltage change of the DC transmission line to the frequency change of the receiving end grid, and constructing a coordinated control law of the DC voltage droop coefficient based on the inertial response to control the DC voltage in the DC transmission line.

[0008] After controlling the DC voltage in the DC transmission line through the collaborative control law of DC voltage droop coefficient, the active power of each wind turbine is controlled in the second layer of collaborative control, including: selecting the change in DC current command value of the DC transmission line, the change in DC voltage and the active power of the wind turbine to construct macro variables and obtain the active power of the current wind turbine.

[0009] The active power of the current wind turbine is input into a pre-built control optimization model to obtain the wind turbine's fast frequency regulation coefficient, so as to control the active power of each wind turbine.

[0010] The control optimization model includes an objective function and constraints. The objective function aims to minimize the change in the pitch angle of the wind turbine and the change in the frequency of the receiving-end power grid. The constraints include the pitch angle constraint of the wind turbine and the active power constraint of the wind turbine.

[0011] As an optional technical solution of the present invention, the DC transmission line includes a receiving-end converter and a sending-end converter connected to each other; the input end of the receiving-end converter is connected to a wind farm and is used to control the input active power of the DC transmission line to dynamically track the active power command value, while maintaining the current of the DC transmission line at a set value; the output end of the sending-end converter is connected to the receiving-end power grid and is used to control the output active power of the DC transmission line to dynamically track the input active power of the DC transmission line, while maintaining the voltage of the DC transmission line at a set value.

[0012] As an optional technical solution of the present invention, determining the inertial response of the DC voltage change of the DC transmission line to the frequency change of the receiving-end power grid includes:

[0013] The inertial response of the DC voltage change of the DC transmission line to the frequency change of the receiving-end power grid is expressed as follows:

[0014] ;

[0015] in, This indicates the change in DC voltage in a DC transmission line. This indicates the frequency variation of the receiving-end power grid. Represents the virtual inertial time constant. This represents the DC voltage during steady-state operation of a DC transmission line. This represents the DC voltage droop factor. This represents the change in active power of a wind farm. The value represents the change in the output active power of a DC transmission line, C represents the capacitance of the DC transmission line, and s represents the complex frequency of the transfer function.

[0016] As an optional technical solution of the present invention, the cooperative control law for constructing the DC voltage droop coefficient includes:

[0017] Based on the theory of coordinated control, the frequency change of the receiving-end power grid is selected. and virtual inertial time constant Construct the first macro variable , represented as:

[0018] ;

[0019] in, Represents the first macro variable Frequency change of the receiving-end power grid as the manifold approaches the target position Weight parameters;

[0020] Due to macro variables satisfy Then the virtual inertial time constant is obtained. The control law is expressed as:

[0021] ;

[0022] Where T represents the cooperative motion coefficient. Indicates the rate of change of frequency of the receiving-end power grid. This represents the rate of change of DC voltage in a DC transmission line.

[0023] Based on the inertial response of the DC voltage change of the DC transmission line to the frequency change of the receiving-end power grid, the cooperative control law for the DC voltage droop coefficient is obtained, expressed as:

[0024] ;

[0025] in, The cooperative control law represents the DC voltage droop coefficient.

[0026] As an optional technical solution of the present invention, the step of selecting the change in DC current command value of the DC transmission line, the change in DC voltage, and the active power of the wind farm to construct macro variables and obtain the current active power of the wind farm includes:

[0027] The second macrovariable is constructed by selecting the changes in DC current command value, DC voltage change, and active power of the wind farm from the DC transmission line. , represented as:

[0028] ;

[0029] in, Represents the second macro variable Change in DC current command value of DC transmission line as it approaches the target position along the manifold Adjustment weight for directional displacement change, Represents the second macro variable DC voltage change of DC transmission line as the manifold approaches the target position Adjustment weight for directional displacement change, This indicates the active power of the wind farm;

[0030] Due to macro variables satisfy Then the active power of the wind farm can be obtained. The control law is expressed as:

[0031] ;

[0032] in, This represents the rate of change of DC voltage in a DC transmission line. The variable represents the rate of change of the DC current command value of the DC transmission line, and T represents the cooperative motion coefficient. This represents the rate of change of active power in a wind farm.

[0033] Based on the active power of the wind farm The control law is used to obtain the current active power of the wind turbine.

[0034] As an optional technical solution of the present invention, the active power input of the current wind turbine is pre-constructed into a control optimization model to obtain the fast frequency regulation coefficient of the wind turbine, including:

[0035] The objective function is expressed as:

[0036] ;

[0037] in, This indicates finding the minimum value. The weighted parameter representing the change in the pitch angle of the wind turbine is This represents the change in the pitch angle of the wind turbine. The weighting parameter represents the frequency change of the receiving-end power grid, where f represents the actual frequency of the receiving-end power grid. ref This represents the frequency reference value of the receiving-end power grid;

[0038] The wind turbine pitch angle constraint and the wind turbine active power constraint are respectively expressed as:

[0039] ;

[0040] in, These represent the pitch angles of the wind turbine. The lower and upper limits, These represent the lower and upper limits of the active power of the wind turbine, respectively.

[0041] Based on the objective function and constraints, the control optimization model outputs the fast frequency regulation coefficient of the wind turbine. This is to control the orderly output of active power by each wind turbine unit.

[0042] Secondly, an active support control device for wind farms connected to the grid via flexible DC transmission is provided, comprising: a model acquisition module for acquiring a pre-constructed frequency regulation control model including the wind farm, DC transmission line and receiving-end power grid, wherein the wind farm includes several wind turbine units;

[0043] The first control module is used to perform first-level collaborative control of the DC voltage in the DC transmission line based on the frequency modulation control model, including: determining the inertial response of the DC voltage change of the DC transmission line to the frequency change of the receiving end grid, and constructing a collaborative control law of the DC voltage droop coefficient based on the inertial response to control the DC voltage in the DC transmission line.

[0044] The second control module is used to perform a second-level collaborative control on the active power of each wind turbine after controlling the DC voltage in the DC transmission line through a collaborative control law based on the DC voltage droop coefficient. This includes: selecting the change in the DC current command value of the DC transmission line, the change in DC voltage, and the active power of the wind turbine to construct macro variables and obtain the current active power of the wind turbine.

[0045] The model optimization module is used to input the active power of the current wind turbine into a pre-built control optimization model to obtain the wind turbine's fast frequency regulation coefficient, so as to control the active power of each wind turbine.

[0046] The control optimization model includes an objective function and constraints. The objective function aims to minimize the change in the pitch angle of the wind turbine and the change in the frequency of the receiving-end power grid. The constraints include the pitch angle constraint of the wind turbine and the active power constraint of the wind turbine.

[0047] Thirdly, an active support control system for a wind farm connected to the grid via flexible DC transmission is provided, comprising a processor and a storage medium; the storage medium is used to store instructions; the processor is used to operate according to the instructions to execute the steps of the active support control method for a wind farm connected to the grid via flexible DC transmission as described in the first aspect.

[0048] Fourthly, a computer-readable storage medium is provided having a computer program stored thereon, which, when executed by a processor, implements the steps of the active support control method for wind farms connected to the grid via flexible DC transmission as described in the first aspect.

[0049] Compared with the prior art, the beneficial effects of the present invention are:

[0050] This invention provides an active support control method for wind farms connected to the grid via flexible DC transmission. It controls the stability of DC voltage in the DC transmission line by using a DC voltage droop coefficient, and predicts the fast frequency regulation coefficient of wind turbines through a control optimization model to control the active power of each wind turbine. This enables the grid-connected system to provide active energy support by utilizing the capacitor energy storage of the DC transmission line and the active power of the wind farm in coordinated control under conditions without communication, thereby optimizing the grid frequency stability problem. Attached Figure Description

[0051] Figure 1 This is a flowchart of the active support control method for wind farms connected to the grid via flexible DC transmission in an embodiment of the present invention;

[0052] Figure 2 This is a schematic diagram of the frequency modulation control model in an embodiment of the present invention;

[0053] Figure 3 This is a schematic diagram of the frequency regulation principle of the wind turbine generator in an embodiment of the present invention;

[0054] Figure 4 This is a schematic diagram of a wind farm connected to the grid via LCC-FHMMC in an embodiment of the present invention;

[0055] Figure 5 This is a graph showing the variation of the receiving-end power grid frequency under different control conditions in an embodiment of the present invention;

[0056] Figure 6 This is a graph showing the variation of DC line voltage under different control conditions in an embodiment of the present invention;

[0057] Figure 7 This is a graph showing the variation of DC line power under different control conditions in an embodiment of the present invention;

[0058] Figure 8 This is a graph showing the variation of the active power of the wind turbine under different control conditions in an embodiment of the present invention.

[0059] Figure 9 This is a graph showing the variation of the wind turbine pitch angle under different control conditions in an embodiment of the present invention.

[0060] Figure 10 This is a graph showing the change in the rapid frequency regulation coefficient of the wind turbine in an embodiment of the present invention;

[0061] Figure 11 This is a comparison chart of the active power and active power command value of the wind turbine in an embodiment of the present invention. Detailed Implementation

[0062] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and should not be used to limit the scope of protection of the present invention.

[0063] Example 1

[0064] This embodiment provides an active support control method for wind farms connected to the grid via flexible DC transmission. The key to achieving a communication-free, coordinated inertial response in the wind farm-to-grid flexible DC transmission system lies in the adaptive adjustment of the DC voltage droop coefficient. The first is to enable the energy provided by DC capacitor energy storage to vary with the grid frequency deviation, and the second is to adaptively adjust the rapid frequency regulation coefficient of the wind turbine. This allows the reserve capacity provided by the wind farm to dynamically change with the receiving-end grid frequency and DC capacitor energy storage. Therefore, this embodiment uses a robust cooperative control theory to optimize the two parameters. Figure 1 As shown, the specific steps include the following:

[0065] Step 1: As Figure 2 As shown, a pre-constructed frequency regulation control model including a wind farm, a DC transmission line, and a receiving-end power grid is obtained, wherein the wind farm includes several wind turbine units.

[0066] Specifically, the DC transmission line includes a receiving-end converter and a sending-end converter connected in series. The input end of the receiving-end converter is connected to a wind farm and uses constant DC current control to control the input active power of the DC transmission line. Dynamic tracking of active power command value Meanwhile, the current of the DC transmission line is maintained at a set value. The output of the sending-end converter is connected to the receiving-end power grid and uses constant DC voltage control to control the output active power of the DC transmission line. Dynamically track the input active power of DC transmission lines At the same time, the voltage of the DC transmission line is maintained at the set value.

[0067] In this embodiment, the receiving-end converter is a line commutated converter (LCC), and the sending-end converter is a full-half bridge modular multilevel converter (FHMMC).

[0068] Furthermore, when the LCC adopts constant DC current control, it can be known from the control principle of the grid commutator that the LCC can adjust according to the change in DC line voltage. Dynamically adjust DC current control command value This enables the wind farm to receive active power through a flexible DC grid connection system. Dynamic tracking of active power command value Ignore the input active power of the LCC Adjusting the DC voltage The transient response of the regulation and the active power loss of the DC line can be considered as the input active power. DC voltage of FHMMC The adjustment remains unchanged. The coordinated operation of the LCC and FHMMC allows for additional DC voltage control within the FHMMC. The droop control compensation component can enable flexible DC to utilize the DC line capacitor energy storage to provide frequency response for frequency disturbances in the receiving-end grid without affecting the wind farm's output power.

[0069] In this embodiment, the frequency regulation control of the wind farm adopts distributed frequency regulation composed of fast frequency regulation of the wind turbine generators. For example... Figure 3 As shown, its basic principle is as follows: the hydraulic pitch control system in the wind turbine adjusts the pitch angle to capture the active power command P that satisfies the optimal torque of the wind turbine. tor The required wind energy is controlled by adjusting the rotor input wind power through pitch angle control, so that the wind turbine stator outputs active power P. s Tracking active command P tor At the same time, maintain the generator speed ω r Tracking generator speed reference value ω ref When a frequency disturbance occurs, the additional frequency modulation inertia control adds the change in active power command ΔP1 to the active power command P. tor This achieves inertial support based on rotor kinetic energy regulation; droop control is achieved by superimposing the change in active power command ΔP2 onto the active power command P of the power station. AGC A pitch backup adjustment is implemented to achieve drive pitch angle compensation. Figure 3 In the middle, P cmd The active power command representing the optimal torque, k d and k p These represent the additional frequency modulation differential parameter and proportional parameter, respectively, k opt T represents the optimal modal gain. ref P represents the rated torque. ref f represents the rated power. s and f N These represent the power grid frequency and its rated value, respectively, P s This indicates the output power of the wind turbine, and PI indicates the PI controller.

[0070] Step 2: Based on the frequency modulation control model, perform the first-level collaborative control of the DC voltage in the DC transmission line, including: determining the inertial response of the DC voltage change of the DC transmission line to the frequency change of the receiving end grid, and constructing a collaborative control law of the DC voltage droop coefficient based on the inertial response to control the DC voltage in the DC transmission line.

[0071] 2.1 The inertial response of the DC voltage change of the DC transmission line to the frequency change of the receiving-end power grid is expressed as follows:

[0072] ;

[0073] in, This indicates the change in DC voltage in a DC transmission line. This indicates the frequency variation of the receiving-end power grid. Represents the virtual inertial time constant. This represents the DC voltage during steady-state operation of a DC transmission line. This represents the DC voltage droop factor. This represents the change in active power of a wind farm. The value represents the change in the output active power of a DC transmission line, C represents the capacitance of the DC transmission line, and s represents the complex frequency of the transfer function.

[0074] 2.2 To enable the DC capacitor to adaptively provide inertia support for the frequency deviation of the receiving-end power grid and to coordinate with the self-recovery of the DC voltage, based on the cooperative control theory, the frequency change of the receiving-end power grid is selected. and virtual inertial time constant Construct the first macro variable , represented as:

[0075] ;

[0076] in, Represents the first macro variable Frequency change of the receiving-end power grid as the manifold approaches the target position The weight parameters. In larger manifolds The greater the proportion, the more energy the manifold constraint of the first macrovariable will release to provide greater virtual inertia support.

[0077] Due to macro variables satisfy Then the virtual inertial time constant is obtained. The control law is expressed as:

[0078] ;

[0079] Where T represents the cooperative motion coefficient. Indicates the rate of change of frequency of the receiving-end power grid. This represents the rate of change of DC voltage in a DC transmission line. (In the context of the virtual inertial time constant) Under the control law, the DC capacitor energy storage adaptively participates in the inertial response based on the frequency deviation of the receiving-end power grid, and the receiving-end power grid operates from the initial state to the manifold. It then runs stably along the manifold until it reaches a stable state.

[0080] Based on the inertial response of the DC voltage change of the DC transmission line to the frequency change of the receiving-end power grid, the cooperative control law for the DC voltage droop coefficient is obtained, expressed as:

[0081] ;

[0082] in, The cooperative control law represents the DC voltage droop coefficient.

[0083] As can be seen from the above formula, the DC voltage droop coefficient The first part of the cooperative control law molecule and This is related to the rate of change of the DC voltage, indicating that the DC capacitor can adapt to changes in the frequency and rate of change of the receiving-end power grid. In the initial stage of frequency disturbance at the receiving end of the power grid, the rate of frequency change and the rate of change of the DC voltage are relatively large. The rapid increase in size allows the DC capacitor to quickly release energy, providing greater inertial support. The second part of the control law numerator is related to the rate of change of DC voltage, indicating that the DC capacitor's energy storage regulation can adapt to changes in the rate of change of DC voltage. As the DC capacitor rapidly releases its stored energy for inertial support, the DC voltage decreases rapidly, and the rate of change of DC capacitor voltage increases. Gradually decreasing helps to provide damping. The over-adjustment component is used to avoid DC voltage overshoot during the inertial response process. At the same time, it can provide an optimized dynamic recovery process during the recovery of DC capacitor voltage after inertia support and a damping component to avoid secondary frequency disturbances caused by active power of capacitor charging.

[0084] Step 3: After controlling the DC voltage in the DC transmission line through the collaborative control law of DC voltage droop coefficient, the active power of each wind turbine is controlled in the second layer of collaborative control, including: selecting the change in DC current command value of the DC transmission line, the change in DC voltage and the active power of the wind turbine to construct macro variables, and obtain the active power of the current wind turbine.

[0085] Wind farms use collaborative control to adaptively adjust the frequency regulation coefficient of wind turbine generators. Providing coordinated inertia support, it can dampen changes in the energy storage of DC capacitors and quickly restore the system's DC voltage. Based on this, considering the DC voltage constraint of the DC capacitor, the changes in the DC current command value of the DC transmission line, the changes in the DC voltage, and the active power of the wind farm are selected to construct a second macrovariable. , represented as:

[0086] ;

[0087] in, Represents the second macro variable Change in DC current command value of DC transmission line as it approaches the target position along the manifold Adjustment weight for directional displacement change, Represents the second macro variable DC voltage change of DC transmission line as the manifold approaches the target position Adjustment weight for directional displacement change, This represents the active power of the wind farm. Choose the smaller value. and This can increase the active power of the wind farm, which is beneficial for the wind turbine to participate in the primary frequency regulation of the system and assist in DC voltage recovery.

[0088] Due to macro variables satisfy Then the active power of the wind farm can be obtained. The control law is expressed as:

[0089] ;

[0090] in, This represents the rate of change of DC voltage in a DC transmission line. The value of the DC current command for the DC transmission line represents the rate of change, and T represents the cooperative motion coefficient. This represents the rate of change of active power in a wind farm.

[0091] Observing the above formula, we can see that the active power of the wind farm Control Laws and , This is relevant in two ways: firstly, it indicates that the active power provided by the wind farm can adapt to changes in the DC capacitor voltage and its rate of change; secondly, the wind farm senses changes in the receiving-end grid frequency through changes in DC voltage. In the initial stage of grid frequency disturbance at the receiving end, the rates of change of DC capacitor voltage and DC current are relatively large. Rapid expansion enables wind farms to quickly release reserved energy from the propellers, providing greater active energy support.

[0092] Based on the active power of the wind farm The control law is used to obtain the current active power of the wind turbine.

[0093] Step 4: Input the active power of the current wind turbine into the pre-built control optimization model to obtain the wind turbine's fast frequency regulation coefficient, so as to control the active power of each wind turbine.

[0094] The control optimization model includes an objective function and constraints. The objective function aims to minimize the change in the pitch angle of the wind turbine and the change in the frequency of the receiving-end power grid. The constraints include the pitch angle constraint of the wind turbine and the active power constraint of the wind turbine.

[0095] The objective function is expressed as:

[0096] ;

[0097] in, This indicates finding the minimum value. The weighted parameter representing the change in the pitch angle of the wind turbine is This represents the change in the pitch angle of the wind turbine. The weighting parameter represents the frequency change of the receiving-end power grid, where f represents the actual frequency of the receiving-end power grid. ref This indicates the frequency reference value of the receiving-end power grid.

[0098] The wind turbine pitch angle constraint and the wind turbine active power constraint are respectively expressed as:

[0099] ;

[0100] in, These represent the pitch angles of the wind turbine. The lower and upper limits, These represent the lower and upper limits of the active power of the wind turbine, respectively.

[0101] Based on the objective function and constraints, the control optimization model outputs the fast frequency regulation coefficient of the wind turbine. This is to control the orderly output of active power from each wind turbine. Specifically, the control optimization model solves for the output active power over a future period, and the result of each round of solution serves as the input for the next round of control optimization model solution, thereby enabling the orderly release of active power from each wind turbine in the wind farm to support DC voltage recovery and frequency disturbances in the receiving-end power grid.

[0102] Example 2

[0103] This embodiment is based on embodiment 1, and applies, as follows: Figure 4 A simulation experiment was conducted on the scenario of the wind farm shown being connected to the grid via LCC-FHMMC.

[0104] This embodiment is built in MATLAB / Simulink as follows: Figure 4 The model shown includes a wind farm connected to the DC grid via LCC-FHMMC. In the model, the wind farm is represented by an equivalent wind turbine using the wind turbine equivalent modeling method based on wind speed, with an input wind speed of 12 m / s. The active load of the receiving-end grid is set to increase by 0.4 pu at t=5.0s. This is compared to the receiving-end grid system with no additional control response when the wind farm is connected to the LCC-FHMMC, and only the FHMMC uses additional control. The dynamic response characteristics of droop control (one-layer collaborative control), wind farm, and FHMMC under the control method (two-layer collaborative control) described in Example 1 are shown in the simulation. In the FHMMC collaborative control, T1 = 0.1s, T2 = 0.02s, , , .

[0105] like Figures 5-7 As shown, the receiving-end grid frequency, DC line voltage, and DC line transmission power curves under three control strategies are compared. Without additional control, the DC line transmission power remains constant, and the receiving-end grid frequency drops to its lowest point of 49.829Hz, indicating that it cannot sense changes in the receiving-end grid frequency and does not provide active energy support. When using FHMMC control (one-layer collaborative control) and the control method of Example 1 (two-layer collaborative control), the DC voltage releases energy to provide inertial support, causing the lowest point of the receiving-end grid frequency to rise to 49.858Hz. This demonstrates that with additional droop control in FHMMC, the wind farm can sense the drop in the receiving-end grid frequency through DC voltage changes, thereby effectively improving the inertial support capability of the wind power connected to the LCC-FHMMC grid system. Under the control method of Example 1, the receiving-end grid frequency exhibits a better frequency recovery dynamic process.

[0106] like Figure 8 and Figure 9 As shown, the pitch angle and active power curves of wind turbines (DFIG) are compared under no additional control and dual-layer coordinated control. Without additional control, the turbine pitch angle remains unchanged, preventing the release of active reserve capacity, and the active power also remains unchanged, indicating that it cannot provide active energy support for primary frequency regulation of the receiving-end grid. With dual-layer coordinated control, as... Figure 10 As shown, when the fan passes the rapid frequency regulation coefficient When the frequency of the receiving-end power grid changes, the additional frequency regulation control and pitch angle control of the wind turbine reduce the pitch angle of the wind turbine, release the active power reserve capacity, increase the active power of the wind turbine, and participate in the primary frequency regulation of the power system.

[0107] like Figure 11 As shown, by adjusting the fast frequency modulation coefficient The adjustment makes the active power of the wind turbine roughly the same as the active power command value of the second-level collaborative control law.

[0108] Example 3

[0109] This embodiment provides an active support control device for wind farms connected to the grid via flexible DC transmission, including:

[0110] The model acquisition module is used to acquire a pre-built frequency regulation control model that includes a wind farm, a DC transmission line and a receiving-end power grid, wherein the wind farm includes several wind turbine units;

[0111] The first control module is used to perform first-level collaborative control of the DC voltage in the DC transmission line based on the frequency modulation control model, including: determining the inertial response of the DC voltage change of the DC transmission line to the frequency change of the receiving end grid, and constructing a collaborative control law of the DC voltage droop coefficient based on the inertial response to control the DC voltage in the DC transmission line.

[0112] The second control module is used to perform a second-level collaborative control on the active power of each wind turbine after controlling the DC voltage in the DC transmission line through a collaborative control law based on the DC voltage droop coefficient. This includes: selecting the change in the DC current command value of the DC transmission line, the change in DC voltage, and the active power of the wind turbine to construct macro variables and obtain the current active power of the wind turbine.

[0113] The model optimization module is used to input the active power of the current wind turbine into a pre-built control optimization model to obtain the wind turbine's fast frequency regulation coefficient, so as to control the active power of each wind turbine.

[0114] The control optimization model includes an objective function and constraints. The objective function aims to minimize the change in the pitch angle of the wind turbine and the change in the frequency of the receiving-end power grid. The constraints include the pitch angle constraint of the wind turbine and the active power constraint of the wind turbine.

[0115] Example 4

[0116] This embodiment provides an active support control system for a wind farm connected to the grid via flexible DC transmission, including a processor and a storage medium; the storage medium is used to store instructions.

[0117] The processor is used to operate according to the instructions to execute the steps of the active support control method for wind farm connected to the grid via flexible DC transmission as described in Embodiment 1.

[0118] Example 5

[0119] This embodiment provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the steps of the active support control method for wind farms connected to the grid via flexible DC transmission as described in Embodiment 1.

[0120] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0121] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0122] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0123] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0124] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. An active support control method for wind farms connected to the grid via flexible DC transmission, characterized in that, include: Obtain a pre-built frequency regulation control model that includes a wind farm, a DC transmission line, and a receiving-end power grid, wherein the wind farm includes several wind turbine units; Based on the frequency modulation control model, the first layer of coordinated control is performed on the DC voltage in the DC transmission line, including: determining the inertial response of the DC voltage change of the DC transmission line to the frequency change of the receiving end grid, and constructing a coordinated control law of the DC voltage droop coefficient based on the inertial response to control the DC voltage in the DC transmission line. After controlling the DC voltage in the DC transmission line using a collaborative control law based on the DC voltage droop coefficient, a second layer of collaborative control is implemented for the active power of each wind turbine. This includes constructing a second macro-variable by selecting the changes in the DC current command value of the DC transmission line, the changes in the DC voltage, and the active power of the wind turbine. , represented as: ； in, Represents the second macro variable Change in DC current command value of DC transmission line as it approaches the target position along the manifold Adjustment weight for directional displacement change, Represents the second macro variable DC voltage change of DC transmission line as the manifold approaches the target position Adjustment weight for directional displacement change, This indicates the active power of the wind turbine generator; Due to macro variables satisfy Then the active power of the wind turbine can be obtained. The control law is expressed as: ； in, This represents the rate of change of DC voltage in a DC transmission line. The value of the DC current command for the DC transmission line represents the rate of change, and T represents the cooperative motion coefficient. This represents the rate of change of active power in a wind farm. Based on the active power of the wind turbine The control law is used to obtain the current active power of the wind turbine. The active power of the current wind turbine is input into a pre-built control optimization model to obtain the wind turbine's fast frequency regulation coefficient, so as to control the active power of each wind turbine. The control optimization model includes an objective function and constraints. The objective function aims to minimize the change in the pitch angle of the wind turbine and the change in the frequency of the receiving-end power grid. The constraints include the pitch angle constraint of the wind turbine and the active power constraint of the wind turbine.

2. The active support control method for wind farms connected to the grid via flexible DC transmission according to claim 1, characterized in that: The DC transmission line includes a receiving-end converter and a sending-end converter connected in series. The input terminal of the receiving-end converter is connected to the wind farm and is used to control the input active power of the DC transmission line to dynamically track the active power command value, while keeping the current of the DC transmission line at a set value. The output of the sending-end converter is connected to the receiving-end power grid and is used to control the output active power of the DC transmission line to dynamically track the input active power of the DC transmission line, while maintaining the voltage of the DC transmission line at a set value.

3. The active support control method for wind farms connected to the grid via flexible DC transmission according to claim 1, characterized in that: Determining the inertial response of the DC voltage change of the DC transmission line to the frequency change of the receiving-end power grid includes: The inertial response of the DC voltage change of the DC transmission line to the frequency change of the receiving-end power grid is expressed as follows: ； in, This indicates the change in DC voltage in a DC transmission line. This indicates the frequency variation of the receiving-end power grid. Represents the virtual inertial time constant. This represents the DC voltage during steady-state operation of a DC transmission line. This represents the DC voltage droop factor. This represents the change in active power of a wind farm. The value represents the change in the output active power of a DC transmission line, C represents the capacitance of the DC transmission line, and s represents the complex frequency of the transfer function.

4. The active support control method for wind farms connected to the grid via flexible DC transmission according to claim 3, characterized in that: The cooperative control law for constructing the DC voltage droop coefficient includes: Based on the theory of coordinated control, the frequency change of the receiving-end power grid is selected. and virtual inertial time constant Construct the first macro variable , represented as: ； in, Represents the first macro variable Frequency change of the receiving-end power grid as the manifold approaches the target position Weight parameters; Due to macro variables satisfy Then the virtual inertial time constant is obtained. The control law is expressed as: ； Where T represents the cooperative motion coefficient. Indicates the rate of change of frequency of the receiving-end power grid. This represents the rate of change of DC voltage in a DC transmission line. Based on the inertial response of the DC voltage change of the DC transmission line to the frequency change of the receiving-end power grid, the cooperative control law for the DC voltage droop coefficient is obtained, expressed as: ； in, The cooperative control law represents the DC voltage droop coefficient.

5. The active support control method for wind farms connected to the grid via flexible DC transmission according to claim 1, characterized in that: The active power of the current wind turbine is input into a pre-built control optimization model to obtain the fast frequency regulation coefficient of the wind turbine, including: The objective function is expressed as: ； in, This indicates finding the minimum value. The weighted parameter representing the change in the pitch angle of the wind turbine is This represents the change in the pitch angle of the wind turbine. The weighting parameter represents the frequency change of the receiving-end power grid, where f represents the actual frequency of the receiving-end power grid. ref This represents the frequency reference value of the receiving-end power grid; The wind turbine pitch angle constraint and the wind turbine active power constraint are respectively expressed as: ； in, These represent the pitch angles of the wind turbine. The lower and upper limits, These represent the lower and upper limits of the active power of the wind turbine, respectively. Based on the objective function and constraints, the control optimization model outputs the fast frequency regulation coefficient of the wind turbine. This is to control the orderly output of active power by each wind turbine unit.

6. An active support control device for wind farms connected to the grid via flexible DC transmission, characterized in that, include: The model acquisition module is used to acquire a pre-built frequency regulation control model that includes a wind farm, a DC transmission line and a receiving-end power grid, wherein the wind farm includes several wind turbine units; The first control module is used to perform first-level collaborative control of the DC voltage in the DC transmission line based on the frequency modulation control model, including: determining the inertial response of the DC voltage change of the DC transmission line to the frequency change of the receiving end grid, and constructing a collaborative control law of the DC voltage droop coefficient based on the inertial response to control the DC voltage in the DC transmission line. The second control module is used to perform a second-level coordinated control of the active power of each wind turbine after controlling the DC voltage in the DC transmission line through a coordinated control law based on the DC voltage droop coefficient. This includes: selecting the change in the DC current command value of the DC transmission line, the change in DC voltage, and the active power of the wind turbine to construct a second macro variable. , represented as: ； in, Represents the second macro variable Change in DC current command value of DC transmission line as it approaches the target position along the manifold Adjustment weight for directional displacement change, Represents the second macro variable DC voltage change of DC transmission line as the manifold approaches the target position Adjustment weight for directional displacement change, This indicates the active power of the wind turbine generator; Due to macro variables satisfy Then the active power of the wind turbine can be obtained. The control law is expressed as: ； in, This represents the rate of change of DC voltage in a DC transmission line. The value of the DC current command for the DC transmission line represents the rate of change, and T represents the cooperative motion coefficient. This represents the rate of change of active power in a wind farm. Based on the active power of the wind turbine The control law is used to obtain the current active power of the wind turbine. The model optimization module is used to input the active power of the current wind turbine into a pre-built control optimization model to obtain the wind turbine's fast frequency regulation coefficient, so as to control the active power of each wind turbine. The control optimization model includes an objective function and constraints. The objective function aims to minimize the change in the pitch angle of the wind turbine and the change in the frequency of the receiving-end power grid. The constraints include the pitch angle constraint of the wind turbine and the active power constraint of the wind turbine.

7. An active support control system for a wind farm connected to the grid via flexible DC transmission, characterized in that, Includes a processor and a storage medium; the storage medium is used to store instructions; The processor is configured to operate according to the instructions to execute the steps of the active support control method for wind farms connected to the grid via flexible DC transmission as described in any one of claims 1 to 5.

8. A computer-readable storage medium having a computer program stored thereon, characterized in that, When executed by the processor, the program implements the steps of the active support control method for wind farms connected to the grid via flexible DC transmission as described in any one of claims 1 to 5.

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