A Virtual Inertia Control Method and System for Wind Turbines Below Cut-in Wind Speed ​​Based on Control Synchronization

Abstract

This invention discloses a virtual inertia control method and system for wind turbines below the cut-in wind speed based on control synchronization. The invention designs a control strategy capable of simulating the self-synchronization characteristics of a synchronous condenser and achieving inertia support. Specifically, firstly, wind speed, rotor speed, and grid frequency are measured in real time; secondly, the average wind speed is calculated, and the operating condition of the wind turbine is determined based on hysteresis switching logic; then, when a low wind speed condition is determined, the wind turbine is switched to control synchronization mode, and a proportional synchronization relationship between rotor speed and grid frequency is established through the converter to maintain synchronous speed operation and provide inertia support to the grid; finally, when the wind speed recovers to above the cut-in wind speed, it smoothly switches back to maximum power point tracking or constant speed control mode. This invention enables wind turbines to maintain inertia support capability even below the cut-in wind speed or under windless conditions, effectively improving the frequency stability of the power system.

Description

Technical Field

[0001] This invention belongs to the field of wind power generation control technology, and in particular to a virtual inertia control method and system for wind turbines below the cut-in wind speed based on control synchronization. Background Technology

[0002] With the advancement of the global energy transition, the penetration rate of new energy sources, represented by wind power, in the power system is continuously increasing. Because wind turbines are typically connected to the grid via power electronic converters, their rotational speed is decoupled from the grid frequency, preventing them from directly responding to grid frequency changes like traditional synchronous generators. This significantly reduces the equivalent rotational inertia of the power system, leading to more severe frequency fluctuations caused by load disturbances and highlighting increasingly prominent system frequency stability issues. Therefore, enabling wind turbines to possess inertia support capabilities similar to synchronous generators has become an urgent requirement of current grid guidelines and a research hotspot.

[0003] To achieve this goal, existing technologies typically employ virtual inertia control strategies. This strategy simulates the inertial power characteristics of a synchronous generator by attaching a power command proportional to the grid frequency change rate to the maximum power point tracking curve, utilizing the flexible adjustment characteristics of the wind turbine's active power output. However, this power regulation-based control method has a significant limitation: it relies on the wind turbine being in normal generating mode (i.e., wind speed above the cut-in wind speed). When the wind speed is below the cut-in wind speed, the wind turbine is usually shut down or in low-speed standby mode, unable to provide support by adjusting active power. Statistics show that in low-wind-speed sites or inland areas with complex terrain, wind turbines operate below the cut-in wind speed for a significant portion of the year. This means that for a considerable period, the wind turbine's enormous rotor inertia resources are idle and wasted, unable to provide the necessary frequency support to the grid.

[0004] In contrast, while traditional synchronous condensers lack a prime mover, their electromechanical design enables them to maintain synchronous rotation with the grid frequency, providing inertial support by releasing rotor kinetic energy during frequency changes. Wind turbines also possess large-inertia rotors. If the operating mechanism of synchronous condensers can be adopted, breaking away from the traditional control's reliance on aerodynamic power, and simulating self-synchronization characteristics through control measures below the cut-in wind speed, allowing the turbine rotor to maintain synchronous rotation and respond to frequency changes even in weak or no wind conditions, it would significantly extend the ancillary service time of wind turbines and fully exploit their inertial support potential. This is of great significance for improving the all-time frequency stability of high-proportion renewable energy power systems. Summary of the Invention

[0005] The purpose of this invention is to address the problems existing in the prior art by providing a virtual inertia control method and system for wind turbines below the cut-in wind speed based on control synchronization. This invention introduces a control synchronization mechanism into the converter control, dynamically binding the wind turbine rotor speed to the grid frequency, thereby simulating the operating characteristics of a synchronous condenser under low wind speed or even no wind conditions, and achieving inertia support for the grid.

[0006] The technical solution to achieve the purpose of this invention is as follows: On the one hand, a virtual inertia control method for wind turbines below the cut-in wind speed based on control synchronization is provided, the method comprising the following steps:

[0007] Obtain real-time operating parameters of the wind turbine, including at least wind speed, rotor speed and grid frequency;

[0008] Based on real-time wind speed, statistical characteristic values ​​reflecting wind speed trends are determined, and based on preset switching logic, it is determined whether the wind turbine unit should start and enter or exit the control synchronization mode.

[0009] When it is determined that the start-up will enter the control synchronization mode, a rotor speed command dynamically associated with the grid frequency is generated, and closed-loop speed control is performed on the wind turbine to provide inertia support for the wind turbine in operating conditions below the cut-in wind speed or in windless conditions.

[0010] When it is determined that the control synchronization mode is to be exited, the closed-loop speed control is released, and the wind turbine is switched to the normal operation control mode.

[0011] Furthermore, the statistical characteristic value reflecting the wind speed trend is the moving average wind speed, and its calculation formula is as follows:

[0012]

[0013] In the formula, The moving average wind speed, The statistical period for average wind speed. This is the current time.

[0014] Furthermore, the preset switching logic specifically includes the following determination process:

[0015] Set the start threshold for control synchronization mode and exit threshold ,and ;

[0016] When the statistical characteristic value decreases and meets the start-up threshold condition, the control synchronization mode is activated, and the wind turbine performs speed tracking based on control synchronization. Simultaneously, the control mode state variable S is set to 1. The start-up threshold condition is that the statistical characteristic value is less than or equal to the start-up threshold. ;

[0017] When the statistical characteristic value rises and meets the exit threshold condition, the control synchronization mode is exited, the wind turbine is switched back to the normal operation control mode, and the control mode state variable S is set to 0; the exit threshold condition is that the statistical characteristic value is greater than the exit threshold. ;

[0018] When the statistical characteristic value is at the start threshold and exit threshold During this period, the wind turbine maintains its current control mode.

[0019] Furthermore, the rotor speed command is determined based on a proportional synchronization relationship, specifically using the following formula:

[0020]

[0021] In the formula, This is the rotor speed command value. Synchronization coefficient; The rated frequency of the power grid; For the corresponding grid rated frequency The synchronous speed of the fan rotor, This is the starting speed of the wind turbine for power generation. This refers to the power grid frequency.

[0022] Furthermore, in the control synchronization mode, the method further includes: when performing closed-loop speed control, dynamically switching and adjusting the upper limit of the active power output of the closed-loop speed controller according to the control mode state variable S, with the specific formula as follows:

[0023]

[0024] In the formula, This represents the upper limit of active power output. The optimal power factor for wind turbine generators; This refers to the rated power of the wind turbine. This represents the rotor speed.

[0025] Furthermore, the closed-loop speed control uses a proportional-integral controller (PI controller) with output limiting to track the rotor speed command.

[0026] Furthermore, the active power reference command of the PI controller is calculated by the following formula and executed by the converter;

[0027]

[0028] In the formula, Active power reference command, The proportional gain of the PI controller; The integral coefficient of the PI controller; This is a limiting function, indicating that the input quantity... Limited to Within the interval, It is used only as an indicator variable and has no actual meaning.

[0029] Furthermore, the conventional operation control mode includes maximum power point tracking control or constant speed control mode.

[0030] On the other hand, a virtual inertia control system for wind turbines below the cut-in wind speed based on control synchronization is provided, the system comprising:

[0031] The first module is used to acquire the real-time operating parameters of the wind turbine, which include at least wind speed, rotor speed and grid frequency.

[0032] The second module is used to calculate statistical characteristic values ​​that reflect wind speed trends and to determine the start and stop status of the synchronization mode based on preset switching logic.

[0033] The third module is used to generate rotor speed commands associated with the grid frequency in control synchronization mode, and to perform closed-loop speed control through the converter to achieve inertia support, or to perform control synchronization mode release operation.

[0034] On the other hand, a computer device is provided, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the virtual inertia control method for wind turbines below the cut-in wind speed based on control synchronization.

[0035] Compared with the prior art, the significant advantages of this invention are:

[0036] (1) It expands the operating range of wind turbine inertia support, enabling wind turbines to provide inertia support even when the cut-in wind speed is below or even when there is no wind.

[0037] (2) The proposed virtual inertia control strategy does not require measuring the rate of change of the grid frequency, thus avoiding the influence of noise and time delay during the differential calculation process.

[0038] (3) The designed hysteresis switching mechanism ensures a smooth transition between the wind turbine in the conventional power generation mode and the control synchronization mode, taking into account both power generation efficiency and auxiliary service functions.

[0039] The present invention will now be described in further detail with reference to the accompanying drawings. Attached Figure Description

[0040] Figure 1 This is a flowchart illustrating the virtual inertia control method for wind turbines below the cut-off wind speed, as described in one embodiment of the present invention.

[0041] Figure 2 This is a control block diagram of a virtual inertia control method for wind turbines below the cut-in wind speed, as shown in one embodiment.

[0042] Figure 3 The diagram shows the topology of a power system dynamic model experimental platform for verifying the proposed method in one embodiment.

[0043] Figure 4 This is an experimental curve diagram of the control method designed according to the present invention in one embodiment. Figure 4 (a) is a schematic diagram of the verification results of the smoothness of the control strategy switching, where (a1) is a schematic diagram of the wind speed curve, the green solid line is the wind speed curve, the red dashed line is the average wind speed curve, (a2) is a schematic diagram of the enabled state of the control synchronization mode, (a3) ​​is a schematic diagram of the rotor speed curve of the wind turbine, and (a4) is a schematic diagram of the active power curve of the wind turbine. Figure 4 (b) is a schematic diagram comparing the frequency response curves of the system under the method of the present invention and the traditional control strategy (i.e., shutdown state) under extremely low wind speed. Detailed Implementation

[0044] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0045] It should be noted that if the embodiments of the present invention involve directional indicators (such as up, down, left, right, front, back, etc.), the directional indicators are only used to explain the relative positional relationship and movement of the components in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicators will also change accordingly.

[0046] Furthermore, if the embodiments of this invention involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. If the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0047] In one embodiment, to address the limitation of existing wind turbines in providing grid inertia support due to constant low-speed operation or shutdown below the cut-in wind speed (including no-wind conditions), this invention provides a virtual inertia control method for wind turbines below the cut-in wind speed based on control synchronization. The method includes the following steps:

[0048] Obtain real-time operating parameters of the wind turbine, including at least wind speed, rotor speed and grid frequency;

[0049] Based on real-time wind speed, statistical characteristic values ​​reflecting wind speed trends are determined, and based on preset switching logic, it is determined whether the wind turbine unit should start and enter or exit the control synchronization mode.

[0050] When it is determined that the start-up will enter the control synchronization mode, a rotor speed command dynamically associated with the grid frequency is generated, and closed-loop speed control is performed on the wind turbine to provide inertia support for the wind turbine in operating conditions below the cut-in wind speed or in windless conditions.

[0051] When it is determined that the control synchronization mode is to be exited, the closed-loop speed control is released, and the wind turbine is switched to the normal operation control mode.

[0052] Furthermore, in one embodiment, the statistical characteristic value reflecting the wind speed trend is the moving average wind speed, which is calculated using the following formula:

[0053]

[0054] In the formula, The moving average wind speed, The statistical period for average wind speed. This is the current time.

[0055] Furthermore, in one embodiment, the preset switching logic specifically includes the following determination process:

[0056] Set the start threshold for control synchronization mode and exit threshold ,and ;

[0057] When the statistical characteristic value decreases and meets the start-up threshold condition, the control synchronization mode is activated, and the wind turbine performs speed tracking based on control synchronization. Simultaneously, the control mode state variable S is set to 1. The start-up threshold condition is that the statistical characteristic value is less than or equal to the start-up threshold. ;

[0058] When the statistical characteristic value rises and meets the exit threshold condition, the control synchronization mode is exited, the wind turbine is switched back to the normal operation control mode, and the control mode state variable S is set to 0; the exit threshold condition is that the statistical characteristic value is greater than the exit threshold. ;

[0059] When the statistical characteristic value is at the start threshold and exit threshold During this period, the wind turbine maintains its current control mode.

[0060] Furthermore, in one embodiment, the rotor speed command is determined based on a proportional synchronization relationship, specifically using the following formula:

[0061]

[0062] In the formula, This is the rotor speed command value. Synchronization coefficient; The rated frequency of the power grid; For the corresponding grid rated frequency The synchronous speed of the fan rotor, This is the starting speed of the wind turbine for power generation. This refers to the power grid frequency.

[0063] Furthermore, in one embodiment, under the control synchronization mode, the method further includes: when performing closed-loop speed control, dynamically switching and adjusting the upper limit amplitude of the active power output of the closed-loop speed controller according to the control mode state variable S, specifically using the following formula:

[0064]

[0065] In the formula, This represents the upper limit of active power output. The optimal power factor for wind turbine generators; This refers to the rated power of the wind turbine. This represents the rotor speed.

[0066] Furthermore, in one embodiment, the closed-loop speed control uses a proportional-integral controller (PI controller) with output limiting to track the rotor speed command.

[0067] Furthermore, in one embodiment, the active power reference command of the PI controller is calculated by the following formula and executed by the converter;

[0068]

[0069] In the formula, Active power reference command, The proportional gain of the PI controller; The integral coefficient of the PI controller; This is a limiting function, indicating that the input quantity... Limited to Within the interval, It is used only as an indicator variable and has no actual meaning.

[0070] Furthermore, in one embodiment, the conventional operation control mode includes maximum power point tracking control or constant speed control mode.

[0071] In one embodiment, a virtual inertia control system for wind turbines below cut-in wind speed based on control synchronization is provided, the system comprising:

[0072] The first module is used to acquire the real-time operating parameters of the wind turbine, which include at least wind speed, rotor speed and grid frequency.

[0073] The second module is used to calculate statistical characteristic values ​​that reflect wind speed trends and to determine the start and stop status of the synchronization mode based on preset switching logic.

[0074] The third module is used to generate rotor speed commands associated with the grid frequency in control synchronization mode, and to perform closed-loop speed control through the converter to achieve inertia support, or to perform control synchronization mode release operation.

[0075] Specific limitations regarding the virtual inertia control system for wind turbines below the cut-in wind speed based on control synchronization can be found in the limitations of the virtual inertia control method for wind turbines below the cut-in wind speed based on control synchronization mentioned above, and will not be repeated here. Each module in the aforementioned virtual inertia control system for wind turbines below the cut-in wind speed based on control synchronization can be implemented entirely or partially through software, hardware, or a combination thereof. These modules can be embedded in or independent of the processor in a computer device in hardware form, or stored in the memory of a computer device in software form, so that the processor can call and execute the corresponding operations of each module.

[0076] In one embodiment, a computer device is provided, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor, when executing the computer program, implements:

[0077] Obtain real-time operating parameters of the wind turbine, including at least wind speed, rotor speed and grid frequency;

[0078] Based on real-time wind speed, statistical characteristic values ​​reflecting wind speed trends are determined, and based on preset switching logic, it is determined whether the wind turbine unit should start and enter or exit the control synchronization mode.

[0079] When it is determined that the start-up will enter the control synchronization mode, a rotor speed command dynamically associated with the grid frequency is generated, and closed-loop speed control is performed on the wind turbine to provide inertia support for the wind turbine in operating conditions below the cut-in wind speed or in windless conditions.

[0080] When it is determined that the control synchronization mode is to be exited, the closed-loop speed control is released, and the wind turbine is switched to the normal operation control mode.

[0081] Further specific limitations can be found in the limitations of the virtual inertia control method for wind turbines below the cut-in wind speed based on control synchronization mentioned above, and will not be repeated here.

[0082] In one embodiment, a computer-readable storage medium is provided having a computer program stored thereon, the computer program being implemented when executed by a processor:

[0083] Obtain real-time operating parameters of the wind turbine, including at least wind speed, rotor speed and grid frequency;

[0084] Based on real-time wind speed, statistical characteristic values ​​reflecting wind speed trends are determined, and based on preset switching logic, it is determined whether the wind turbine unit should start and enter or exit the control synchronization mode.

[0085] When it is determined that the start-up will enter the control synchronization mode, a rotor speed command dynamically associated with the grid frequency is generated, and closed-loop speed control is performed on the wind turbine to provide inertia support for the wind turbine in operating conditions below the cut-in wind speed or in windless conditions.

[0086] When it is determined that the control synchronization mode is to be exited, the closed-loop speed control is released, and the wind turbine is switched to the normal operation control mode.

[0087] Further specific limitations can be found in the limitations of the virtual inertia control method for wind turbines below the cut-in wind speed based on control synchronization mentioned above, and will not be repeated here.

[0088] As a specific example, in one embodiment, the invention will be further described in detail with reference to the accompanying drawings.

[0089] Combination Figure 1 and Figure 2 This embodiment provides a virtual inertia control method for wind turbines below the cut-in wind speed based on control synchronization. The method includes the following steps:

[0090] Step 1: Measure the wind speed of the wind turbine in real time. Rotor speed and power grid frequency ;

[0091] Step 2, based on real-time wind speed Calculate the moving average wind speed And based on the hysteresis switching logic, it determines whether to start or exit the control synchronization mode;

[0092] Among them, according to real-time wind speed Calculate the moving average wind speed The specific calculation formula is as follows:

[0093]

[0094] In the formula, The statistical period for average wind speed; The current time;

[0095] Specifically, the determination of whether to start or exit the control synchronization mode based on hysteresis switching logic includes:

[0096] Set the start threshold for control synchronization mode and exit threshold ,in The specific determination process of the hysteresis switching logic is as follows:

[0097] (1) When the calculated average wind speed Descend and meet When the wind turbine is determined to be in low wind speed condition, the control mode state variable S is set to 1, that is, the control synchronization mode is started, and the wind turbine converter performs speed tracking based on control synchronization.

[0098] (2) When the calculated average wind speed Rise and satisfy When the wind speed of the wind turbine is restored, the control mode state variable S is set to 0, that is, the control synchronization mode is exited and the wind turbine switches back to the maximum power tracking control mode or the constant speed control mode.

[0099] (3) When the average wind speed In and During this period, the wind turbine should maintain its current control mode.

[0100] Step 3: When the startup conditions in Step 2 are met, switch to control synchronization mode, i.e., generate a frequency synchronized with the power grid. Dynamically associated rotor speed command value The input is then fed into the wind turbine converter to perform closed-loop speed control, thereby achieving inertia support in conditions below the cut-in wind speed or even in windless conditions.

[0101] If the exit conditions are met in step 2, the control synchronization mode is released, and the wind turbine is switched back to maximum power point tracking control or constant speed control mode; otherwise, the control synchronization mode is maintained.

[0102] Among them, generation and grid frequency Dynamically associated rotor speed command value And input the wind turbine converter to perform closed-loop speed control, specifically including:

[0103] The reference input for closed-loop speed control was changed from a low-wind-speed constant-speed command to a rotor speed command value based on proportional synchronization. ;

[0104] Based on the control mode state variable S, switch the upper limit of the active power output of the closed-loop speed controller. The specific expression is:

[0105]

[0106] In the formula, The optimal power factor for wind turbine generators; This refers to the rated power of the wind turbine generator set;

[0107] The wind turbine converter uses a proportional-integral controller (PI controller) with output limiting to process speed commands. Perform tracking and calculate active power reference commands. And it is executed by the wind turbine converter, and its expression is:

[0108]

[0109] In the formula, The proportional gain of the PI controller; The integral coefficient of the PI controller; This is a limiting function, indicating that the input quantity... Limited to Within the interval, It is used only as an indicator variable and has no actual meaning.

[0110] The rotor speed command value The calculation formula is:

[0111]

[0112] In the formula, Synchronization coefficient; The rated frequency of the power grid; For the corresponding grid rated frequency The synchronous speed of the wind turbine rotor can be set to the starting power generation speed of the wind turbine to achieve a smooth switching. .

[0113] In step 3, when the exit conditions are met, the control synchronization mode is deactivated, and the wind turbine is switched back to maximum power point tracking control or constant speed control mode; if the conditions are not met, the control synchronization mode continues to operate, specifically including:

[0114] First, based on the hysteresis switching logic in step 2, the average wind speed is continuously calculated. and with exit threshold Compare;

[0115] Secondly, if the calculated average wind speed The exit threshold has not been exceeded. ,Right now If the exit condition is not met, the wind turbine will continue to operate in the control synchronization mode and keep the state variable S=1.

[0116] Finally, if the calculated average wind speed Exceeding the exit threshold ,Right now If the exit conditions are met, the following release operation will be performed:

[0117] (1) Reset the control mode state variable S from 1 to 0;

[0118] (2) Change the reference input of the closed-loop speed controller from the rotor speed command value. command to switch back to constant speed in normal operating mode and the upper limit of active power output amplitude. From rated power Restore to the optimal power curve value ;

[0119] (3) The wind turbine smoothly switches back to the maximum power tracking control mode or the constant speed control mode, and returns to step 2 to continue the cycle.

[0120] based on Figure 3 The power system dynamic model experimental platform shown is used to experimentally verify the method designed in this invention. The dynamic model experimental platform mainly consists of three parts: a 5.5 kW wind turbine simulator, a 6.0 kW synchronous generator simulator, and a 9 kVA regenerative load. The relevant experimental parameters are shown in Tables 1 and 2.

[0121] Table 1 Main parameters of the power system dynamic model test platform

[0122]

[0123] Table 2 shows the main parameters of the simulated wind turbine.

[0124]

[0125] First, the smoothness of the switching between the proposed strategy and the original operation control strategy of the wind turbine was verified. The experiment used a stepped decreasing / increasing wind speed sequence to trigger the hysteresis switching logic. To shorten the experimental time, the statistical period for the average wind speed was set to 10 seconds; in actual engineering, a minute-level period is recommended.

[0126] Figure 4 Figure (a) presents the corresponding experimental results. At t=17.5s, the wind speed began to decrease stepwise from 7m / s in increments of 0.5m / s. During the maximum power point tracking zone, the rotor speed and active power output of the wind turbine decreased as the wind speed decreased. Once the wind speed entered the grid-connected startup zone, the wind turbine switched to constant speed control, maintaining the rotor speed at the initial power generation speed. Furthermore, when the average wind speed at time t1 satisfies... At this time, the control mode state variable S is set to 1, and the wind turbine enters synchronous operation. From Figure 4 As shown in (a), the rotor speed and active power fluctuate little at the moment of switching, and the startup process is smooth, verifying the effectiveness of the switching mechanism designed in this invention. The exit process is similar; at time t2, the wind speed rises above the exit threshold. Afterwards, S is set to 0, and the wind turbine resumes constant speed or maximum power point tracking operation.

[0127] The above results show that the switching mechanism designed in this invention can achieve a smooth switching between the conventional operation mode and the control synchronous operation mode of the wind turbine, laying the foundation for providing inertial support for wind turbines operating below the cut-in wind speed.

[0128] Finally, the proposed method is compared with the traditional control strategy for wind turbines under extremely low wind speeds (i.e., shutdown state) to highlight its engineering application value. In the traditional strategy, when the wind speed is consistently lower than the cut-in wind speed, the wind turbine enters a shutdown state, its rotor inertia is completely idle, and it cannot respond to grid disturbances.

[0129] In contrast, the method proposed in this invention enables wind turbines to remain connected to the grid even under windless conditions and actively releases rotor kinetic energy to provide inertial support during disturbances. Figure 4 The comparative experiment in (b) shows that the system frequency response characteristics are significantly improved after adopting the method proposed in this invention (the lowest frequency point is increased by 0.11 Hz). This strategy enables wind turbines to have inertia support capabilities under all wind conditions, providing a new solution for the frequency stability of high-proportion renewable energy power systems during low wind speeds or no wind, and also fully leveraging the potential grid ancillary service value of wind turbines.

[0130] In summary, this invention enables wind turbines to maintain inertia support even below the cut-in wind speed or under no-wind conditions, effectively improving the frequency stability of the power system.

[0131] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention without departing from its spirit and scope should be included within the protection scope of the present invention.

Claims

1. A virtual inertia control method for wind turbines below cut-in wind speed based on control synchronization, characterized in that, The method includes the following steps: Obtain real-time operating parameters of the wind turbine, including at least wind speed, rotor speed and grid frequency; Based on real-time wind speed, statistical characteristic values ​​reflecting wind speed trends are determined, and based on preset switching logic, it is determined whether the wind turbine unit should start and enter or exit the control synchronization mode. When it is determined that the start-up will enter the control synchronization mode, a rotor speed command dynamically associated with the grid frequency is generated, and closed-loop speed control is performed on the wind turbine to provide inertia support for the wind turbine in operating conditions below the cut-in wind speed or in windless conditions. When it is determined that the control synchronization mode is to be exited, the control synchronization mode is to be released, that is, the closed-loop speed control is released, and the wind turbine is switched to the normal operation control mode. The statistical characteristic value reflecting the wind speed trend is the moving average wind speed, and its calculation formula is as follows: ； In the formula, The moving average wind speed, The statistical period for average wind speed. The current time; The preset switching logic, specifically the determination process includes: Set the start threshold for control synchronization mode and exit threshold ,and ; When the statistical characteristic value decreases and meets the start-up threshold condition, the control synchronization mode is activated, and the wind turbine performs speed tracking based on control synchronization. Simultaneously, the control mode state variable S is set to 1. The start-up threshold condition is that the statistical characteristic value is less than or equal to the start-up threshold. ; When the statistical characteristic value rises and meets the exit threshold condition, the control synchronization mode is exited, the wind turbine is switched back to the normal operation control mode, and the control mode state variable S is set to 0; the exit threshold condition is that the statistical characteristic value is greater than the exit threshold. ; When the statistical characteristic value is at the start threshold and exit threshold During this period, the wind turbine maintains its current control mode. The rotor speed command is determined based on a proportional synchronization relationship, and the specific formula is as follows: ； In the formula, This is the rotor speed command value. Synchronization coefficient; The rated frequency of the power grid; For the corresponding grid rated frequency The synchronous speed of the fan rotor, This is the starting speed of the wind turbine for power generation. This refers to the power grid frequency.

2. The virtual inertia control method for wind turbines below the cut-in wind speed based on control synchronization according to claim 1, characterized in that, In the control synchronization mode, the method further includes: when performing closed-loop speed control, dynamically switching and adjusting the upper limit of the active power output of the closed-loop speed controller according to the control mode state variable S, with the specific formula as follows: ； In the formula, This represents the upper limit of active power output. The optimal power factor for wind turbine generators; This refers to the rated power of the wind turbine. This represents the rotor speed.

3. The virtual inertia control method for wind turbines below the cut-in wind speed based on control synchronization according to claim 2, characterized in that, The closed-loop speed control uses a proportional-integral controller (PI controller) with output limiting to track the rotor speed command.

4. The virtual inertia control method for wind turbines below the cut-in wind speed based on control synchronization according to claim 3, characterized in that, The active power reference command of the PI controller is calculated by the following formula and executed by the converter; ； In the formula, Active power reference command, The proportional gain of the PI controller; The integral coefficient of the PI controller; This is a limiting function, indicating that the input quantity... Limited to Within the interval, It is used only as an indicator variable and has no actual meaning.

5. The virtual inertia control method for wind turbines below the cut-in wind speed based on control synchronization according to claim 1, characterized in that, The conventional operation control modes include maximum power point tracking control or constant speed control mode.

6. A virtual inertia control system for wind turbines below the cut-in wind speed based on control synchronization, according to any one of claims 1 to 5, characterized in that, The system includes: The first module is used to acquire the real-time operating parameters of the wind turbine, which include at least wind speed, rotor speed and grid frequency. The second module is used to calculate statistical characteristic values ​​that reflect wind speed trends and to determine the start and stop status of the synchronization mode based on preset switching logic. The third module is used to generate rotor speed commands associated with the grid frequency in control synchronization mode, and to perform closed-loop speed control through the converter to achieve inertia support, or to perform control synchronization mode release operation.

7. A computer device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the method according to any one of claims 1 to 5.

8. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, it implements the method of any one of claims 1 to 5.

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