Rotating speed recovery method and system for offshore wind power frequency support

Abstract

The invention relates to the technical field of participation of offshore wind power in power grid frequency modulation, in particular to a rotating speed recovery method and system supported by offshore wind power frequency, and the method comprises the steps: calculating a frequency modulation capability coefficient of a wind turbine generator in real time, judging that the kinetic energy of a rotor is insufficient and triggering rotating speed recovery when the frequency modulation capability coefficient is less than zero, or maintaining the existing power output; based on the triggering result, extracting real-time wind speed data in a preset period to calculate an average wind speed; and based on frequency modulation capability coefficient and disturbance type identification, adopting a differentiated rotating speed recovery trajectory planning algorithm to perform rotating speed recovery on the wind turbine generators with different frequency modulation capability coefficients. Through the method, the problems of secondary frequency drop and insufficient wind speed fluctuation adaptation caused by excessive release of rotor kinetic energy in wind power frequency modulation are effectively solved, dynamic balance of power support and unit stability is realized based on double criteria of dynamic quantitative evaluation of the frequency modulation capability coefficient and natural wind speed / load disturbance, and the wind power rotating speed recovery capability is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of offshore wind power participating in grid frequency regulation, and in particular to a speed recovery method and system for offshore wind power frequency support. Background Art

[0002] As a key frequency-regulating power source for the new era power grid, wind power is gradually transitioning from a supporting role to a core force supporting power system frequency stability. With the increasing penetration of renewable energy into the grid, wind power penetration has made its frequency regulation capability a key factor in maintaining the system's dynamic balance. When grid frequency fluctuates, wind turbines achieve rapid power support by releasing stored kinetic energy in their rotors. This virtual inertia control technology, based on rotor kinetic energy regulation, has become the mainstream frequency regulation method. However, this technology faces significant challenges in practical application: excessive kinetic energy release can cause a sharp drop in rotor speed. When the speed approaches the turbine's safe operating threshold, the wind turbine is forced to exit frequency regulation. The resulting power vacuum not only offsets the initial frequency support effect but can also trigger a more severe secondary frequency drop. This conflict between power support and turbine stability during this dynamic process has become a technical bottleneck restricting the deep involvement of wind power in frequency regulation.

[0003] To address this challenge, the research focus in academia and industry has shifted from simply focusing on suppressing maximum frequency deviation to building a comprehensive control system that balances short-term frequency regulation efficiency and long-term operational stability. Studies have shown that the critical threshold for rotor kinetic energy release is not only related to the mechanical characteristics of the unit itself, but is also affected by multiple factors such as real-time wind speed, grid inertia level, and the coordination status of adjacent units. During the frequency regulation process, how to accurately control the rate and duration of kinetic energy release to prevent the speed from entering an irreversible downward channel has become the core goal of the optimized control strategy. In summary, there is currently little research that considers the impact of offshore wind speed fluctuations in wind power participation in frequency regulation, and further research is still needed. Summary of the Invention

[0004] The present invention provides a rotation speed recovery method and system for offshore wind power frequency support, thereby effectively solving the problems pointed out in the background technology.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is:

[0006] A speed recovery method for offshore wind power frequency support, comprising:

[0007] Calculate the frequency regulation capability coefficient of the wind turbine in real time. When the frequency regulation capability coefficient is less than zero, determine that the rotor kinetic energy is insufficient and trigger speed recovery; otherwise, maintain the current power output;

[0008] Based on the trigger results, the real-time wind speed data within the preset period is extracted to calculate the average wind speed, distinguishing between natural wind speed disturbance and grid load disturbance scenarios;

[0009] Based on the frequency regulation capability coefficient and disturbance type identification, a differentiated speed recovery trajectory planning algorithm is adopted to perform speed recovery on wind turbines with different frequency regulation capability coefficients.

[0010] Furthermore, the calculation formula of the frequency modulation capability coefficient is:

[0011]

[0012] Among them, E w 、E wn 、E wl are the rotor kinetic energy of the wind turbine at the current speed w, rated speed wn and minimum speed wl respectively.

[0013] Furthermore, the calculation formulas for the rotor kinetic energy at the current speed w, rated speed wn and minimum speed wl are respectively:

[0014]

[0015] Among them, J w is the moment of inertia of the fan, ω w is the current speed.

[0016] Furthermore, the steps of using the frequency modulation capability coefficient include:

[0017] After the frequency support phase is over, the frequency regulation capability coefficient is evaluated, and the wind power output reference power is modified according to different conditions of the frequency regulation capability coefficient;

[0018] Different speed recovery strategies are designed based on the different real-time directions of wind speeds, and the power recovered in the speed recovery phase is adaptively modified according to the frequency regulation capability coefficient and wind speed conditions.

[0019] Furthermore, the frequency regulation capability coefficient is evaluated. After the frequency support phase, if the frequency regulation capability coefficient is less than 0, the rotor kinetic energy is overdrawn and the wind power enters the speed recovery phase. If the frequency regulation capability coefficient is greater than or equal to 0, the wind power maintains power output and continues to participate in frequency regulation. The reference power is as follows:

[0020]

[0021] Where, P MPPT is the active reference value under MPPT control, P recover Wind power output power is restored during the speed recovery phase.

[0022] Furthermore, a differentiated speed recovery strategy is designed for different real-time wind speed directions, and the power recovered during the speed recovery phase is adaptively modified according to the frequency regulation capability coefficient and wind speed, including:

[0023] Calculate the average wind speed within a preset period based on the real-time wind speed data, and determine whether the wind speed is currently increasing or decreasing by comparing the deviation direction between the real-time wind speed and the average wind speed;

[0024] When the real-time wind speed is continuously higher than the average wind speed, the wind turbine output power is maintained at the reference value in the maximum power tracking mode, and the aerodynamic power increment generated by the wind speed increase is used to restore the rotor kinetic energy.

[0025] When the real-time wind speed is continuously lower than the average wind speed, a dynamic load reduction coefficient is generated according to the frequency regulation capability coefficient, and the reference power is proportionally reduced. The reference value of the output power after reduction is the product of the reference power and the dynamic load reduction coefficient.

[0026] When the dynamic load reduction factor approaches zero due to the frequency regulation capability factor being too low, the minimum output power is forced to be maintained at a preset percentage of the rated power.

[0027] Furthermore, the mathematical model of the wind turbine generator set is:

[0028]

[0029] Among them, P m is the wind energy capture power of the wind turbine, ρ is the air density, R is the rotor radius, and v is the wind speed; C p is the wind energy utilization coefficient, β is the pitch angle, λ is the tip speed ratio, which is defined as λ=ωR / v, λ1 is the coefficient for calculating the tip speed ratio and the pitch angle, ω is the angular velocity of the wind turbine, ω r is the wind wheel shaft speed, H w is the inertia coefficient of the transmission system, F is the friction coefficient of the transmission system, s is the transformation coefficient, K opt is the optimal wind capture coefficient, λ opt is the optimal tip speed ratio, is the maximum wind energy utilization coefficient, T m is the mechanical torque of the wind turbine, T e is the electromagnetic torque of the wind turbine.

[0030] Furthermore, the frequency modulation capability coefficient and P recover Perform periodic adjustments, including:

[0031] A1, calculating the frequency modulation capability coefficient and setting an update period of the frequency modulation capability coefficient;

[0032] A2, based on load fluctuations, determines whether it is in the frequency regulation moment. If so, proceed to step A1; if not, operate normally under the MPPT strategy;

[0033] A3, after the frequency support ends, the speed recovery phase is entered, and the frequency modulation capability coefficient is determined. If it is greater than 0, normal operation is performed and no speed recovery is required. If it is less than 0, the process proceeds to step A4;

[0034] A4, continuously monitoring the frequency regulation capability coefficient and adjusting the wind power memory power according to the real-time wind speed;

[0035] A5: After the speed recovery is completed, return to normal frequency regulation.

[0036] A speed recovery system for offshore wind power frequency support, comprising:

[0037] The frequency regulation coefficient calculation module calculates the frequency regulation capability coefficient of the wind turbine in real time. When the frequency regulation capability coefficient is less than zero, it determines that the rotor kinetic energy is insufficient and triggers speed recovery; otherwise, it maintains the current power output;

[0038] The disturbance type identification module extracts real-time wind speed data within a preset period based on the trigger result to calculate the average wind speed and distinguish between natural wind speed disturbances and grid load disturbances.

[0039] The differentiated speed recovery module uses a differentiated speed recovery trajectory planning algorithm based on the frequency regulation capability coefficient and disturbance type identification to perform speed recovery on wind turbines with different frequency regulation capability coefficients.

[0040] The technical solution of the present invention can achieve the following technical effects:

[0041] It effectively solves the difficult problems of secondary frequency drop caused by excessive release of rotor kinetic energy and insufficient adaptation to wind speed fluctuations in wind power frequency regulation. Based on the dynamic quantitative evaluation of the frequency regulation capability coefficient and the dual criteria of natural wind speed / load disturbance, it achieves a dynamic balance between power support and unit stability, and improves the wind power speed recovery capability. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0043] Figure 1 A flow chart of a speed recovery method for offshore wind power frequency support;

[0044] Figure 2 The figure is a flowchart of the steps for using the frequency capacity coefficient;

[0045] Figure 3 Schematic diagram of the process for adaptively modifying the power recovery during the speed recovery phase. DETAILED DESCRIPTION

[0046] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0047] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this invention pertains. The terms used in this specification are for the purpose of describing specific embodiments only and are not intended to limit the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0048] Example 1

[0049] like Figure 1 As shown, the present invention provides a speed recovery method for offshore wind power frequency support, the method comprising:

[0050] S1: Calculate the frequency regulation capability coefficient of the wind turbine in real time. When the frequency regulation capability coefficient is less than zero, the rotor kinetic energy is determined to be insufficient and speed recovery is triggered. Otherwise, the current power output is maintained.

[0051] Specifically, the main purpose of real-time calculation of the frequency regulation capability coefficient of a wind turbine is to evaluate whether the wind turbine can provide sufficient rotor kinetic energy to maintain stable frequency support during the frequency regulation process. If the frequency regulation capability coefficient is less than zero, it means that the rotor kinetic energy of the wind turbine has been consumed too much and cannot continue to effectively support the grid frequency. It is then judged that the rotor kinetic energy is insufficient, and speed recovery needs to be triggered at this time, that is, entering the speed recovery stage. If the frequency regulation capability coefficient is greater than or equal to zero, it means that the wind turbine has sufficient kinetic energy to continue to maintain the support of the grid frequency. At this time, there is no need to recover the speed, but continue to maintain the existing power output.

[0052] S2: Based on the trigger result, the real-time wind speed data within the preset period is extracted to calculate the average wind speed, distinguishing between natural wind speed disturbance and grid load disturbance scenarios;

[0053] Specifically, based on the trigger results, real-time wind speed data for a preset period must be extracted. This data reflects the wind speed environment within the wind turbine during this period. By calculating this wind speed data, the average wind speed for that period is determined. This average provides a benchmark for subsequent analysis and decision-making. This process helps determine the overall trend of wind speed changes and lays the foundation for further adjustments. Next, based on the calculated average wind speed, the wind turbine needs to further analyze the causes of wind speed changes and classify the disturbances into two categories: natural wind speed disturbances and grid load disturbances.

[0054] Natural wind speed disturbances: These disturbances are fluctuations caused by changes in wind speed in the natural environment, usually increases or decreases in wind speed caused by meteorological changes. For example, wind speeds over a certain period of time may fluctuate due to changes in weather systems, temperature differences, or geographical environment. These disturbances are usually periodic or random, but their fluctuations are usually not directly linked to changes in grid load.

[0055] Grid load disturbance: This type of disturbance arises from changes in the load demand within the grid. An increase or decrease in grid load will cause fluctuations in grid frequency, which in turn affects the power output demand of wind turbines. When the grid load increases sharply, wind turbines may need to increase power output to support the frequency; conversely, a decrease in grid load may cause excessive power output, which in turn affects the frequency regulation capability of the unit. Grid load disturbances are usually closely related to the operating status of the grid and may manifest as regulation requirements that are not directly related to wind speed changes.

[0056] By analyzing these wind speed data and disturbance types, it is possible to accurately determine whether the wind turbine is facing natural wind speed fluctuations or changes in grid load. The key role of this step is to provide a basic basis for subsequent speed recovery and power adjustment. Specifically, after identifying the disturbance type, appropriate adjustment measures can be taken according to different situations. For example, in the case of natural wind speed disturbances, it may be necessary to adjust the power output of the wind turbine to cope with changes in wind speed and ensure that the wind turbine can operate within the appropriate power range. In the case of grid load disturbances, it may be necessary to take more active frequency adjustment measures to adjust the power output of the wind turbine in a timely manner to help the grid maintain a stable frequency.

[0057] S3: Based on the frequency regulation capability coefficient and disturbance type identification, a differentiated speed recovery trajectory planning algorithm is used to recover the speed of wind turbines with different frequency regulation capability coefficients.

[0058] Through the present invention, the difficult problems of secondary frequency drop caused by excessive release of rotor kinetic energy and insufficient adaptation to wind speed fluctuations in wind power frequency regulation are effectively solved. Based on the dynamic quantitative evaluation of the frequency regulation capability coefficient and the dual criteria of natural wind speed / load disturbance, a dynamic balance between power support and unit stability is achieved, thereby improving the wind power speed recovery capability.

[0059] As a preferred embodiment of the above embodiment, the calculation formula of the frequency modulation capability coefficient is:

[0060]

[0061] Among them, E w 、E wn 、E wl are the rotor kinetic energy of the wind turbine at the current speed w, rated speed wn and minimum speed wl respectively.

[0062] Specifically, the meaning of this formula is to calculate a relative value, namely the frequency regulation capability coefficient K, by comparing the rotor kinetic energy of the wind turbine at the current speed, rated speed and minimum speed. w , this coefficient reflects the relative relationship between the kinetic energy of the wind turbine at the current speed and the kinetic energy at the rated speed and the minimum speed, and thus determines the frequency regulation capability that the wind turbine can provide during the frequency regulation process. When the speed of the wind turbine is close to the rated speed, the rotor kinetic energy of the wind turbine is large, E w Close to E wn , at this time the frequency modulation capability coefficient K w The higher the speed, the stronger the frequency regulation capability. When the speed of the wind turbine is close to the minimum speed, the rotor kinetic energy of the wind turbine is low, and E w Close to E wl , at this time the frequency modulation capability coefficient K w If it is low, it means the frequency regulation capability of the unit is limited; when the frequency regulation capability coefficient K w When it is a negative value, it means that the kinetic energy of the unit is insufficient at the current speed and the speed needs to be restored to replenish the kinetic energy; when K w When it is a positive value, it means that the wind turbine has sufficient kinetic energy to continue to maintain the current power output.

[0063] As a preference of the above embodiment, the calculation formulas for the rotor kinetic energy at the current speed w, the rated speed wn and the minimum speed wl are respectively:

[0064]

[0065] Among them, J w is the moment of inertia of the fan, ω w is the current speed.

[0066] Specifically, the rotor kinetic energy at the current speed: when the speed of the wind turbine is at the current value, the rotor kinetic energy is proportional to the square of the speed. The higher the speed, the greater the rotor kinetic energy. The rotor kinetic energy at the current speed represents the energy stored in the wind turbine at this speed.

[0067] Rotor kinetic energy at rated speed: When the wind turbine reaches the rated speed, the rotor kinetic energy will reach its maximum value. The rated speed is usually the speed of the wind turbine in the optimal working state, at which time the turbine can generate the maximum kinetic energy reserve.

[0068] Rotor kinetic energy at the lowest speed: At the lowest speed, the rotor kinetic energy of the wind turbine is the smallest. The lowest speed is usually the minimum limit at which the wind turbine can operate. At this time, the kinetic energy reserve of the wind turbine is low.

[0069] Through the rotor kinetic energy at these three different speeds, we can clearly understand the energy reserve status of the wind turbine under different operating conditions. When the speed of the wind turbine is close to the rated speed, its kinetic energy is sufficient to effectively support the regulation of the grid frequency; when the speed is close to the minimum speed, the unit's kinetic energy reserve is small, and it may be necessary to restore the speed to replenish kinetic energy to ensure continued participation in the frequency regulation of the grid.

[0070] As a preferred embodiment of the above, Figure 2 As shown in Figure 2, the steps for using the frequency modulation capability coefficient include:

[0071] B10: The frequency support phase ends, the frequency regulation capability coefficient is evaluated, and the wind power output reference power is modified according to the different frequency regulation capability coefficients;

[0072] B20: Differentiated speed recovery strategies are designed for different real-time wind speed directions, and the recovery power in the speed recovery phase is adaptively modified according to the frequency regulation capability coefficient and wind speed conditions.

[0073] Specifically, first, after the frequency support phase is over, the frequency regulation capability coefficient is evaluated. At this stage, the evaluation results are used to determine whether the wind turbine can continue to provide effective frequency regulation support for the power grid. The frequency regulation capability coefficient reflects the current kinetic energy reserve of the wind turbine. If the frequency regulation capability coefficient is low, it means that the kinetic energy of the turbine is insufficient and may not be able to continue to provide effective frequency regulation support. Therefore, it is necessary to reduce the power output to avoid excessive energy consumption or unnecessary power fluctuations. If the frequency regulation capability coefficient is high, it means that the wind turbine still has sufficient energy to continue to maintain a high power output, thereby supporting the frequency regulation of the power grid. At this stage, the power output of the wind turbine will be dynamically adjusted according to the evaluation results of the frequency regulation capability coefficient to ensure the stability of the power grid frequency. The next step is to design differentiated speed recovery strategies according to the different real-time wind speed directions in the speed recovery phase. At this stage, wind speed changes have a direct impact on the frequency regulation capability of the wind turbine. Therefore, it is necessary to flexibly adjust the speed recovery strategy according to the real-time wind speed changes and the evaluation results of the frequency regulation capability coefficient. If the wind speed is strong and the unit's frequency regulation capability coefficient is high, speed recovery can be quickly accelerated, allowing the wind turbine to quickly return to normal operation. However, if the wind speed is weak or the wind direction changes, a more conservative recovery strategy may be needed to avoid excessive unit operation. By combining wind speed changes and the frequency regulation capability coefficient, the recovery power can be adaptively adjusted to ensure that the wind turbine does not waste energy during the recovery process and can quickly and effectively support the stability of the grid frequency. Ultimately, through this adaptive recovery strategy, the wind turbine can maintain the optimal operating state according to the actual wind speed conditions and energy status during the frequency regulation and speed recovery phases, ensuring the reliable operation of the grid.

[0074] As a preferred embodiment of the above, the frequency regulation capability coefficient is evaluated. After the frequency support phase ends, if the frequency regulation capability coefficient is less than 0, the rotor kinetic energy is overdrawn and the wind power enters the speed recovery phase. If the frequency regulation capability coefficient is greater than or equal to 0, the wind power maintains power output and continues to participate in frequency regulation. The reference power is as follows:

[0075]

[0076] Where, P MPPT is the active reference value under MPPT control, P recover Wind power output power is restored during the speed recovery phase.

[0077] Specifically, after the frequency support phase ends, the evaluation of the frequency regulation capability coefficient is mainly used to determine whether the wind turbine needs to enter the speed recovery phase or can continue to participate in frequency regulation. The frequency regulation capability coefficient K w As a key indicator, it helps wind turbines make decisions on whether to restore the speed.w If it is less than 0, it means that the rotor kinetic energy of the wind turbine has been overdrawn and can no longer provide sufficient frequency regulation support. In this case, the wind turbine will enter the speed recovery stage. The goal of the speed recovery stage is to restore sufficient rotor kinetic energy by increasing the power output of the wind turbine so as to continue to participate in grid frequency regulation. At this time, the reference power of the wind turbine will be based on the output power P in the speed recovery stage. recover To adjust to ensure that the unit can quickly recover and meet the needs of the power grid; if the frequency regulation capability coefficient K w If it is greater than or equal to 0, it means that the kinetic energy of the wind turbine is still sufficient and can continue to provide frequency regulation support. In this case, the wind turbine will maintain power output and continue to participate in frequency regulation without entering the speed recovery phase. At this time, the reference power of the wind turbine will remain at the reference value P under the maximum power point tracking (MPPT) control. MPPT , meaning the wind turbine maintains its optimal power output based on actual wind speed conditions. In general, the frequency regulation capability coefficient assessment determines whether the wind turbine needs to enter the speed recovery phase or continue to maintain maximum power output. Through this dynamic power adjustment, the wind turbine can flexibly respond to grid demands during frequency regulation, ensuring grid frequency stability.

[0078] As a preferred embodiment of the above, Figure 3 As shown in the figure, a differentiated speed recovery strategy is designed for different real-time wind speed directions. According to the frequency regulation capability coefficient and wind speed, the power recovery in the speed recovery phase is adaptively modified, including:

[0079] C10: Calculates the average wind speed within a preset period based on real-time wind speed data. By comparing the deviation direction between the real-time wind speed and the average wind speed, it determines whether the wind speed is currently increasing or decreasing.

[0080] C20: When the real-time wind speed is continuously higher than the average wind speed, the wind turbine output power is maintained at the baseline value in the maximum power tracking mode, and the aerodynamic power increment generated by the wind speed increase is used to restore the rotor kinetic energy.

[0081] C30: When the real-time wind speed is continuously lower than the average wind speed, a dynamic load reduction factor is generated according to the frequency regulation capability coefficient, and the reference power is proportionally reduced. The reference value of the output power after reduction is the product of the reference power and the dynamic load reduction factor.

[0082] C40: When the dynamic load reduction factor approaches zero due to the frequency regulation capability factor being too low, the minimum output power is forced to be maintained at a preset percentage of the rated power.

[0083] Specifically, first, the wind turbine calculates the average wind speed within a preset period using real-time wind speed data. The calculation formula is:

[0084] Where T is the fixed cycle duration, and v(t) is the real-time wind speed. This calculation helps understand the overall trend of wind speed and determine the current wind speed state of the wind turbine. By comparing the deviation between the real-time wind speed and the average wind speed, the wind turbine can determine whether the wind speed is currently increasing or decreasing. If the real-time wind speed is higher than the average wind speed, it indicates that the wind speed is increasing; if the real-time wind speed is lower than the average wind speed, it indicates that the wind speed is decreasing. When the wind turbine is in the stage of increasing wind speed, it means that the wind turbine can restore the speed by using the additional energy brought by the increase in wind speed. In this stage, the wind turbine will continue to maintain the output power in the maximum power tracking (MPPT) mode, and use the aerodynamic power increment generated by the increase in wind speed to restore the rotor kinetic energy. In this way, the wind turbine can use the additional energy brought by the increase in wind speed to quickly restore the speed, ensuring that the turbine can continue to effectively participate in the grid frequency regulation. However, when the wind turbine enters the stage of decreasing wind speed, the real-time wind speed is lower than the average wind speed. At this time, the power output of the turbine needs to be adaptively adjusted. Specifically, the wind turbine will calculate a dynamic load reduction coefficient based on the current frequency regulation capability coefficient and apply it to the adjustment of the reference power. Through the dynamic load reduction coefficient, the output power of the wind turbine will be reduced proportionally to avoid excessive consumption of rotor kinetic energy and effectively reduce the pressure on the grid. The change of the dynamic load reduction coefficient is adjusted in real time according to the frequency regulation capability coefficient to ensure that the output power of the turbine can adapt to the current operating state. At this time, the output power P recover The calculation formula is: recover =(1+K w )P MPPT In extreme cases, when the frequency regulation capability coefficient is too low, the dynamic load reduction coefficient may be close to zero. At this time, the output power of the wind turbine will be forced to maintain at a minimum level to avoid complete shutdown or inability to provide sufficient frequency regulation support for the power grid. At this time, the output power of the wind turbine will be maintained at a preset percentage of the rated power to ensure that even in the case of a low frequency regulation capability coefficient, the wind turbine can still provide the minimum support to ensure the stability of the power grid frequency.

[0085] As a preferred embodiment of the above, the mathematical model of the wind turbine is:

[0086]

[0087] Among them, P m is the wind energy capture power of the wind turbine, ρ is the air density, R is the rotor radius, and v is the wind speed; C p is the wind energy utilization coefficient, β is the pitch angle, λ is the tip speed ratio, which is defined as λ=ωR / v, λ1 is the coefficient for calculating the tip speed ratio and the pitch angle, ω is the angular velocity of the wind turbine, ω r is the wind wheel shaft speed, Hw is the inertia coefficient of the transmission system, F is the friction coefficient of the transmission system, s is the transformation coefficient, K opt is the optimal wind capture coefficient, λ opt is the optimal tip speed ratio, is the maximum wind energy utilization coefficient, T m is the mechanical torque of the wind turbine, T e is the electromagnetic torque of the wind turbine.

[0088] Specifically, the mathematical model of a wind turbine essentially describes how the turbine captures the kinetic energy of wind through its rotors and converts it into mechanical torque, which is then output as electrical energy by the generator. First, it emphasizes the critical influence of wind speed on the power that can be captured—with every increase in wind speed, the theoretically usable wind energy increases significantly. The actual energy capture efficiency is characterized by the power coefficient, which is closely related to the ratio of the blade rotation speed to the wind speed (tip speed ratio) and the blade pitch angle. By adjusting the pitch angle, the turbine can always maintain a position close to the optimal wind energy utilization point at different wind speeds. Furthermore, the model also considers the inertia and internal friction of rotating components, as well as the dynamic balance between mechanical torque and electromagnetic torque. The interaction between the aerodynamic torque driving the rotor and the electromagnetic torque applied by the generator determines the acceleration or deceleration process of the rotor. During steady-state operation, the two are essentially balanced. However, when wind speed fluctuates or grid frequency regulation is required, the turbine dynamically adjusts the generator torque and pitch angle to ensure maximum wind energy capture while quickly responding to grid frequency changes. Through this integrated control, wind turbines can maintain efficient and stable power output under changing wind conditions and grid conditions.

[0089] As a preferred embodiment of the above, the frequency modulation capability coefficient and P recover Perform periodic adjustments, including:

[0090] A1, calculates the frequency modulation capability coefficient and sets the update cycle of the frequency modulation capability coefficient;

[0091] A2, based on load fluctuations, determines whether it is in the frequency regulation moment. If so, proceed to step A1; if not, operate normally under the MPPT strategy;

[0092] A3: After the frequency support ends, the speed recovery phase begins. The frequency modulation capability coefficient is determined. If it is greater than 0, the system is operating normally and does not need to recover the speed. If it is less than 0, the system proceeds to step A4.

[0093] A4, continuously monitors the frequency regulation capability coefficient and adjusts the wind power memory power according to the real-time wind speed;

[0094] A5: After the speed recovery is completed, return to normal frequency regulation.

[0095] Example 2

[0096] Based on the same inventive concept as the rotational speed recovery method for offshore wind power frequency support in the aforementioned embodiment, the present invention further provides a rotational speed recovery system for offshore wind power frequency support, the system comprising:

[0097] The frequency regulation coefficient calculation module calculates the frequency regulation capability coefficient of the wind turbine in real time. When the frequency regulation capability coefficient is less than zero, it determines that the rotor kinetic energy is insufficient and triggers speed recovery; otherwise, it maintains the current power output;

[0098] The disturbance type identification module extracts real-time wind speed data within a preset period based on the trigger result to calculate the average wind speed and distinguish between natural wind speed disturbances and grid load disturbances.

[0099] The differentiated speed recovery module uses a differentiated speed recovery trajectory planning algorithm based on the frequency regulation capability coefficient and disturbance type identification to recover the speed of wind turbines with different frequency regulation capability coefficients.

[0100] The above-mentioned system in the present invention can effectively implement the speed recovery method of offshore wind power frequency support, and the technical effects that can be achieved are as described in the above-mentioned embodiments and will not be repeated here.

[0101] Although the present application has been described with reference to specific features and embodiments thereof, it is apparent that various modifications and combinations thereof may be made without departing from the spirit and scope of the present application. Accordingly, this specification and the drawings are merely illustrative of the present application as defined herein, and are intended to cover any and all modifications, variations, combinations or equivalents within the scope of the present application.

[0102] Obviously, those skilled in the art can make various changes and modifications to the present application without departing from the scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the present application and its equivalents, the present application is intended to include these modifications and variations.

Claims

1. A method for speed recovery of offshore wind power frequency support, characterized in that: include: Calculate the frequency regulation capability coefficient of the wind turbine in real time. When the frequency regulation capability coefficient is less than zero, determine that the rotor kinetic energy is insufficient and trigger speed recovery; otherwise, maintain the current power output; Based on the trigger results, the real-time wind speed data within the preset period is extracted to calculate the average wind speed, distinguishing between natural wind speed disturbance and grid load disturbance scenarios; Based on the frequency regulation capability coefficient and disturbance type identification, a differentiated speed recovery trajectory planning algorithm is adopted to perform speed recovery on wind turbines with different frequency regulation capability coefficients.

2. The speed recovery method of offshore wind power frequency support according to claim 1, characterized in that: The calculation formula of the frequency modulation capability coefficient is: Among them, E w 、E wn 、E wl are the rotor kinetic energy of the wind turbine at the current speed w, rated speed wn and minimum speed wl respectively.

3. The speed recovery method of offshore wind power frequency support according to claim 2, characterized in that: The calculation formulas for the rotor kinetic energy at the current speed w, rated speed wn and minimum speed wl are respectively: Where Jw is the moment of inertia of the fan, and ωw is the current speed.

4. The speed recovery method for offshore wind power frequency support according to claim 1, characterized in that: The steps of using the frequency modulation capability coefficient include: After the frequency support phase is over, the frequency regulation capability coefficient is evaluated, and the wind power output reference power is modified according to different conditions of the frequency regulation capability coefficient; Different speed recovery strategies are designed based on the different real-time directions of wind speeds, and the power recovered in the speed recovery phase is adaptively modified according to the frequency regulation capability coefficient and wind speed conditions.

5. The speed recovery method for offshore wind power frequency support according to claim 4, characterized in that: The frequency regulation capability coefficient is evaluated. After the frequency support phase, if the frequency regulation capability coefficient is less than 0, the rotor kinetic energy is overdrawn and the wind power enters the speed recovery phase. If the frequency regulation capability coefficient is greater than or equal to 0, the wind power maintains power output and continues to participate in frequency regulation. The reference power is as follows: Where PMPPT is the active power reference value under MPPT control, and Precover is the wind power recovery output power in the speed recovery stage.

6. The speed recovery method for offshore wind power frequency support according to claim 4, characterized in that: Different speed recovery strategies are designed based on the different real-time wind speed directions. The power recovery in the speed recovery phase is adaptively modified according to the frequency regulation capability coefficient and wind speed, including: Calculate the average wind speed within a preset period based on the real-time wind speed data, and determine whether the wind speed is currently increasing or decreasing by comparing the deviation direction between the real-time wind speed and the average wind speed; When the real-time wind speed is continuously higher than the average wind speed, the wind turbine output power is maintained at the reference value in the maximum power tracking mode, and the aerodynamic power increment generated by the wind speed increase is used to restore the rotor kinetic energy. When the real-time wind speed is continuously lower than the average wind speed, a dynamic load reduction coefficient is generated according to the frequency regulation capability coefficient, and the reference power is proportionally reduced. The reference value of the output power after reduction is the product of the reference power and the dynamic load reduction coefficient. When the dynamic load reduction factor approaches zero due to the frequency regulation capability factor being too low, the minimum output power is forced to be maintained at a preset percentage of the rated power.

7. The speed recovery method for offshore wind power frequency support according to claim 1, characterized in that: The mathematical model of the wind turbine is: Among them, P m is the wind energy capture power of the wind turbine, ρ is the air density, R is the rotor radius, and v is the wind speed; C p is the wind energy utilization coefficient, β is the pitch angle, λ is the tip speed ratio, which is defined as λ=ωR / v, λ1 is the coefficient for calculating the tip speed ratio and the pitch angle, ω is the angular velocity of the wind turbine, ω r is the wind wheel shaft speed, H w is the inertia coefficient of the transmission system, F is the friction coefficient of the transmission system, s is the transformation coefficient, K opt is the optimal wind capture coefficient, λ opt is the optimal tip speed ratio, is the maximum wind energy utilization coefficient, T m is the mechanical torque of the wind turbine, T e is the electromagnetic torque of the wind turbine.

8. The speed recovery method for offshore wind power frequency support according to claim 1, characterized in that: The frequency modulation capability coefficient and P recover Perform periodic adjustments, including: A1, calculating the frequency modulation capability coefficient and setting an update period of the frequency modulation capability coefficient; A2, based on load fluctuations, determines whether it is in the frequency regulation moment. If so, proceed to step A1; if not, operate normally under the MPPT strategy; A3, after the frequency support ends, the speed recovery phase is entered, and the frequency modulation capability coefficient is determined. If it is greater than 0, normal operation is performed and no speed recovery is required. If it is less than 0, the process proceeds to step A4; A4, continuously monitoring the frequency regulation capability coefficient and adjusting the wind power memory power according to the real-time wind speed; A5: After the speed recovery is completed, return to normal frequency regulation.

9. A speed recovery system for offshore wind power frequency support, characterized in that: include: The frequency regulation coefficient calculation module calculates the frequency regulation capability coefficient of the wind turbine in real time. When the frequency regulation capability coefficient is less than zero, it determines that the rotor kinetic energy is insufficient and triggers speed recovery; otherwise, it maintains the current power output; The disturbance type identification module extracts real-time wind speed data within a preset period based on the trigger result to calculate the average wind speed and distinguish between natural wind speed disturbances and grid load disturbances. The differentiated speed recovery module uses a differentiated speed recovery trajectory planning algorithm based on the frequency regulation capability coefficient and disturbance type identification to perform speed recovery on wind turbines with different frequency regulation capability coefficients.

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