Nonlinear sliding mode tracking control method for maximum power point of wind driven generator

Abstract

The invention discloses a wind driven generator maximum power point nonlinear sliding mode tracking control method, which relates to the field of wind power generation control, and comprises the following steps: constructing a comprehensive model of a wind driven generator according to a wind speed random function, a wind wheel kinetic equation and a generator linear relation; defining a maximum output power point and a corresponding optimal rotating speed, deducing an error calculation formula of the rotating angular speed of the wind wheel in the comprehensive model, and constructing a nonlinear sliding mode surface; and a constant-speed approaching rate containing an error upper bound is defined, a segmented controller expression is deduced in combination with a nonlinear sliding mode surface, and the rotating speed of the maximum power point is accurately tracked through the segmented controller expression. According to the method, the nonlinear coupling characteristic of the wind power generation maximum power point tracking controller is accurately described, and the target rotating speed can be accurately tracked by the maximum power point of the wind power generator in a short time without overshoot.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of wind power generation technology, in particular to a wind turbine maximum power point tracking control method. BACKGROUND

[0002] With the continuous growth of global demand for renewable energy, wind power has become an indispensable part of the modern energy system due to its clean, efficient and sustainable characteristics. The core control objective of wind turbines is to track the maximum power point by adjusting the rotor speed in real time, thereby maximizing wind energy capture efficiency and stable output of power grid. However, the random fluctuations and sudden mutations of natural wind speed result in highly nonlinear characteristics of wind turbine input energy, which makes the speed control process extremely complex due to strong uncertainty.

[0003] The above control defects not only cause a significant decline in wind energy conversion efficiency, but also cause accelerated fatigue damage to the transmission chain components, directly threatening the long-term operation reliability and economy of the wind power maximum power point tracking controller. In the face of the fundamental contradiction between wind speed disturbance and controller performance, the existing technology is difficult to achieve effective balance between response speed, stability and robustness. SUMMARY

[0004] In view of the above existing problems, the present application is proposed.

[0005] Therefore, the present application provides a wind turbine maximum power point nonlinear sliding mode tracking control method to solve the problem that the random fluctuations and nonlinear characteristics of wind speed lead to the complication of the control process and the difficulty in balancing the response speed, stability and robustness of the wind power maximum power point tracking controller.

[0006] To solve the above technical problems, the present application provides the following technical solutions:

[0007] The present application provides a wind turbine maximum power point nonlinear sliding mode tracking control method, which comprises: establishing a comprehensive wind turbine model covering wind speed input, wind turbine torque output and generator voltage generation process according to wind speed random function, wind turbine dynamics equation and generator linear relationship;

[0008] According to the real-time operation state of the comprehensive wind turbine model, the maximum output power point and the corresponding optimal speed are defined;

[0009] Based on the optimal speed and the real-time wind turbine angular velocity in the comprehensive wind turbine model, the wind turbine angular velocity error is calculated, and a nonlinear sliding surface is constructed;

[0010] Combined with the disturbance upper bound in the comprehensive wind turbine model, an equal speed approach rate containing error upper bound is defined;

[0011] The piecewise controller expression is derived by combining the constant rate reaching law with the nonlinear sliding mode surface, and the control strategy is switched based on the piecewise controller in different wind wheel rotational angular velocity error regions, so as to accurately track the maximum power point speed.

[0012] As a preferred scheme of the wind turbine maximum power point nonlinear sliding mode tracking control method, the wind turbine comprehensive model comprises a wind speed model, a wind wheel dynamics model and a generator model.

[0013] The wind speed model is constructed by a wind speed random function of position and time, and is used to simulate the random fluctuation of the actual wind speed.

[0014] The wind wheel model is constructed by the moment of inertia, angular velocity, damping coefficient and wind force, and is used to calculate the instantaneous torque of the wind wheel under wind speed disturbance.

[0015] The generator model is constructed by the constants and angular velocity of the generator, and is used to calculate the voltage of the wind turbine.

[0016] As a preferred scheme of the wind turbine maximum power point nonlinear sliding mode tracking control method, the definition of the maximum output power point and the corresponding optimal speed comprises defining the optimal speed corresponding to the maximum output power point according to the real-time running state of the wind turbine comprehensive model.

[0017] According to the defined optimal speed, the maximum output power is defined in combination with the current of the generator.

[0018] As a preferred scheme of the wind turbine maximum power point nonlinear sliding mode tracking control method, the calculation of the wind wheel rotational angular velocity error comprises deriving the wind wheel rotational angular velocity error expression in combination with the defined maximum output power point optimal speed and the wind wheel rotational angular velocity in the comprehensive model, and calculating the real-time wind wheel rotational angular velocity error.

[0019] As a preferred scheme of the wind turbine maximum power point nonlinear sliding mode tracking control method, the construction of the nonlinear sliding mode surface further comprises constructing the nonlinear sliding mode surface based on the wind wheel rotational angular velocity error, in combination with the linear function and the tuning gain of the nonlinear sliding mode surface.

[0020] As a preferred scheme of the wind turbine maximum power point nonlinear sliding mode tracking control method, the linear function is composed of the wind wheel rotational angular velocity error and a switching threshold value, and when the absolute value of the wind wheel rotational angular velocity error is greater than the switching threshold value, the nonlinear function activates the acceleration convergence term.

[0021] When the absolute value of the wind wheel angular velocity error is less than the switching threshold value, the linear function is switched to the chattering suppression term.

[0022] As a preferred scheme of the wind turbine maximum power point nonlinear sliding mode tracking control method, the constant rate of approach with error upper limit is defined by the disturbance upper limit in the wind turbine comprehensive model and the constant rate of approach with error upper limit tuning gain, combined with the sign function.

[0023] The disturbance upper limit in the wind turbine comprehensive model satisfies the constant rate of approach less than or equal to the disturbance upper limit in the wind turbine comprehensive model.

[0024] As a preferred scheme of the wind turbine maximum power point nonlinear sliding mode tracking control method, the accurate tracking of the maximum power point speed by the piecewise controller expression includes, based on the nonlinear sliding mode surface and the constant rate of approach, deriving the piecewise controller expression, when the absolute value of the wind wheel angular velocity error is greater than the switching threshold, the nonlinear function activates the acceleration convergence term, and the directly output wind wheel torque , is expressed as:

[0025] ;

[0026] Wherein, represents the wind wheel torque, represents the moment of inertia, represents the optimal speed at the maximum power point, represents the mechanical damping coefficient, represents the real-time angular velocity, represents the wind power, and represents the nonlinear sliding mode surface tuning gain, represents the nonlinear index, the value range is (0, 1), represents the real-time angular velocity error, represents the tuning gain of the constant rate of approach with error upper limit, represents the disturbance upper limit in the wind turbine comprehensive model, represents the sign function.

[0027] As a preferred scheme of the wind turbine maximum power point nonlinear sliding mode tracking control method, the accurate tracking of the maximum power point speed by the piecewise controller expression also includes, based on the sliding mode surface and the constant rate of approach, deriving the piecewise controller expression, when the absolute value of the wind wheel angular velocity error is less than the switching threshold, the linear function switches to the chattering suppression term, and the directly output wind wheel torque τ is expressed as:

[0028] .

[0029] The beneficial effects of the application are: by constructing a comprehensive model, the nonlinear coupling characteristics of the wind power maximum power point tracking controller are accurately described, and the control mismatch problem caused by model simplification is solved; the piecewise nonlinear sliding mode surface design is innovatively applied to accelerate dynamic convergence in large error area and linearly smooth transition in small error area, and the high-frequency chattering problem of the wind power maximum power point tracking controller is solved; the constant rate of approach containing the error upper bound is used to cover the wind speed mutation and mechanical uncertainty with the disturbance upper bound, combined with the constant forced convergence characteristics of the sign function, the three technical bottlenecks of response lag, severe overshoot and poor disturbance resistance when the wind speed changes are completely solved; by using the segmented controller output torque, the wind turbine maximum power point is accurately tracked to the target speed in a short time without overshoot. BRIEF DESCRIPTION OF DRAWINGS

[0030] In order to more clearly illustrate the technical solutions of the embodiments of the application, the drawings needed in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the application, and other drawings can be obtained by those skilled in the art without creative labor.

[0031] Figure 1 Flow chart of the wind turbine maximum power point nonlinear sliding mode tracking control method.

[0032] Figure 2 Specific flow chart of the nonlinear sliding mode tracking control of the wind turbine maximum power point nonlinear sliding mode tracking control method.

[0033] Figure 3 Speed tracking data chart of the wind turbine maximum power point nonlinear sliding mode tracking control method.

[0034] Figure 4 Speed tracking comparison data chart of the wind turbine maximum power point nonlinear sliding mode tracking control method. DETAILED DESCRIPTION

[0035] In order to make the above-mentioned purposes, features and advantages of the application more obvious and easy to understand, the specific embodiments of the application will be described in detail below with reference to the drawings of the specification.

[0036] In the following description, many specific details are set forth in order to provide a thorough understanding of the application, but the application can also be implemented in other ways different from those described herein, and those skilled in the art can make similar generalizations without departing from the connotation of the application, therefore the application is not limited to the specific embodiments disclosed below.

[0037] Second, the "one embodiment" or "an embodiment" referred to herein means a specific feature, structure, characteristic, or combination of features and characteristics to be included in at least one implementation of the present application. The various appearances of "in one embodiment" or "in an embodiment" in the specification do not all refer to the same embodiment, although they can.

[0038] Embodiment 1, Reference Figures 1-2 For one embodiment of the present application, the embodiment provides a wind turbine maximum power point nonlinear sliding mode tracking control method, comprising the following steps:

[0039] S1, according to the wind speed random function, the wind wheel dynamics equation and the generator linear relationship, the comprehensive model of wind turbine is constructed.

[0040] The energy conversion process of wind turbine involves multi-link coupling of wind energy capture, mechanical energy transmission and electrical energy output, and its dynamic characteristics are jointly affected by wind speed disturbance, mechanical inertia lag and electromagnetic conversion characteristics. The traditional control method often leads to the decline of control precision due to the mismatch between the simplified model and the actual maximum power point tracking controller, so it is the premise of realizing the efficient tracking of maximum power point to construct a comprehensive model which can accurately reflect the nonlinear coupling characteristics of the maximum power point tracking controller. This step integrates the wind speed model, the wind wheel dynamics model and the generator model to form a mathematical description covering the whole link, providing a reliable controlled object prototype for subsequent control strategy design.

[0041] Wind speed is the original energy input of wind power generation, and its time-varying characteristics directly determine the operation state of the wind turbine. Natural wind speed is affected by many factors such as geographical location, topography, weather conditions, seasonal changes, day and night alternation, etc., and presents random volatility, non-stationarity and suddenness. At different time scales, wind speed shows different disturbance patterns, such as gust in a short time, turbulence in a few minutes, and gradual wind in a few hours to a few days. These characteristics make it completely unsuitable to use a simple constant wind speed assumption for high-performance maximum power point tracking controller. The wind speed model is constructed by the wind speed random function of location and time, and the wind speed of the wind turbine is calculated.

[0042] Further, the wind speed model is represented as:

[0043] ;

[0044] wherein, represents the wind speed, represents a random function affected by geographical location and time, and the wind speed is a random function of geographical location and time, which provides the original input energy for wind power generation and provides the basis variable for subsequent wind torque calculation, reflecting the random disturbance characteristics of wind speed.

[0045] The wind speed model guarantees the authenticity and diversity of the wind speed input data, can cover various working conditions in simulation and actual operation, enables the subsequent controller to adapt to the drastic change of the wind speed in advance, improves the robustness, and can generate different wind condition scenes for controller performance verification by adjusting the random function parameters in the simulation stage.

[0046] The wind wheel is a key component for converting wind energy into mechanical energy, and its dynamic characteristics directly affect the acceleration, deceleration process and steady speed of the wind turbine. The wind wheel dynamics is not only driven by aerodynamic force, but also affected by mechanical inertia, damping, generator counter torque and other factors. If these dynamic characteristics cannot be accurately described, the controller may lag in responding to sudden changes in wind speed, and even cause overshoot or maximum power point tracking controller oscillation.

[0047] The wind wheel model is constructed by the moment of inertia, angular velocity, damping coefficient and wind force, and calculates the moment of the wind turbine.

[0048] Further, the wind wheel dynamics model is represented as:

[0049] ;

[0050] Wherein, represents the output moment of the wind wheel, represents the moment of inertia, represents the real-time angular velocity, represents the mechanical damping coefficient, represents the wind force; Driven by the wind speed model is the output moment of the controller, used to balance the moment of inertia, damping loss and wind force input, and convert wind speed disturbance into mechanical dynamic equation, providing the controlled object type for controller design.

[0051] The wind wheel dynamics model can accurately reflect the transient response of wind speed change to wind wheel speed in the mathematical model; the controller can consider the inertia delay and damping effect when designing, so as to reasonably set the acceleration / braking strategy; and provide an important basis for disturbance compensation in subsequent segmented sliding mode control.

[0052] The generator converts the mechanical speed output by the wind wheel into electrical energy, and the change of its voltage, current and power directly affects the stability of the power output of the power grid. Since the control target of the present application is maximum power point tracking, the corresponding relationship between the speed and the electric power must be clearly defined in the model.

[0053] The generator model is constructed by the electromagnetic constant and angular velocity of the generator, and calculates the voltage of the wind turbine.

[0054] Further, the generator model is represented as:

[0055] ;

[0056] in, This indicates the generator's output voltage. The electromagnetic constant of the generator, with a value ranging from (0.5 to 1.5), can be obtained from the equipment specifications or through actual measurement. The output voltage... With rotational speed Linear correlation, implicit maximum power point tracking target, and speed adjustment It can maximize the power P.

[0057] The linear generator model has sufficient accuracy within its rated operating range and low computational complexity, making it suitable for real-time control. This allows the controller to directly influence the generator's output power through speed regulation, simplifying the model structure, reducing real-time computation, while retaining the main dynamic characteristics and providing a direct physical basis for calculating the maximum power point.

[0058] The integrated model includes a wind speed model, a wind turbine dynamics model, and a generator model.

[0059] Furthermore, the comprehensive model of a wind turbine can be represented as follows:

[0060] ;

[0061] Wind speed model output Driven wind turbine dynamics model Generator model that converts wind energy into mechanical energy. mechanical speed Mapped to electrical power output, the control objective is established as regulation. Maximize power. The integrated model provides the controller with the complete dynamic equations of the controlled object, covering the coupling relationship between wind speed disturbance, mechanical response, and electrical energy output. It provides data support for the calculation of the upper bound of the disturbance, enabling the constant velocity approach rate compensation term to accurately cover the actual disturbance. It also lays the foundation for a piecewise control strategy that achieves rapid convergence of large errors and suppresses chattering with small errors.

[0062] S2. Define the maximum output power point and the corresponding optimal speed, derive the error calculation formula for the wind turbine rotation angular velocity in the integrated model, construct a nonlinear sliding surface, and dynamically adjust the error convergence characteristics.

[0063] When the rotor speed is matched with the wind speed, the wind turbine can maximize the capture and conversion of wind energy. The optimal rotational speed corresponds to the state in which the wind turbine can produce maximum output power. If the rotational speed is too high, the rotor speed may cause some wind energy to be inefficiently utilized because the blade angle and speed may no longer be optimized. If the rotational speed is too low, the rotor speed is insufficient to fully capture the kinetic energy of the wind. Therefore, defining the optimal rotational speed ensures that the maximum power point tracking controller can operate at its maximum efficiency under every wind speed, guaranteeing that the wind turbine always operates in an optimal state, thus improving the overall energy efficiency and stability of the wind power generation maximum power point tracking controller.

[0064] The maximum power point is defined based on the optimized matching of wind speed and rotor speed. By finding the optimal speed, the most efficient operating mode of the wind turbine can be found, ensuring that the wind turbine can always operate at its highest efficiency in dynamic environments.

[0065] Define the optimal speed corresponding to the maximum output power point, and define the maximum output power based on the defined optimal speed and the generator current.

[0066] Furthermore, the maximum output power is defined as follows:

[0067] ;

[0068] in, Indicates the maximum power point The optimal speed at which the engine speed is below the specified speed. This indicates the generator's current. The electromechanical coupling coefficient of the generator unit reflects the conversion efficiency of wind energy → mechanical energy → electrical energy and is a core indicator of the energy capture capability of the maximum power point tracking controller. By dynamically adjusting the optimal speed Obtained indirectly.

[0069] By combining the defined optimal rotational speed and the wind turbine rotational angular velocity in the integrated model, a formula for calculating the wind turbine rotational angular velocity error is derived, and the real-time wind turbine rotational angular velocity error is calculated.

[0070] The purpose of defining the angular velocity error of the wind turbine rotation is to adjust the turbine's rotational speed in real time, ensuring that the wind turbine can accurately track the optimal speed and always maintain operation at the maximum power point. The angular velocity error reflects the difference between the current turbine speed and the target optimal speed. Through this error, the maximum power point tracking controller (MPPT) can promptly sense and adjust the turbine's operating status, providing a real-time feedback mechanism. The turbine's rotational speed needs to be continuously adjusted according to changes in external wind speed. The dynamic calculation of the angular velocity error allows the MPPT to adjust the control signal based on real-time wind speed changes, ensuring the turbine speed closely follows the optimal speed and maximizes power output. Changes in wind speed cause fluctuations in the optimal speed; therefore, the definition of the error allows the MPPT to dynamically adapt to wind speed changes, always operating at the maximum power point. Through this feedback mechanism, the MPPT not only avoids speed overshoot and oscillations but also finely adjusts the turbine speed, maintaining the stability and robustness of the MPPT. By monitoring errors in real time, the maximum power point tracking controller can quickly correct deviations and avoid error accumulation, thereby improving control accuracy and operating efficiency, and ensuring that the wind turbine operates efficiently and stably under different wind speed conditions.

[0071] Furthermore, the formula for calculating the angular velocity error of the wind turbine rotation is expressed as follows:

[0072] ;

[0073] in, Indicates the real-time angular velocity error. This indicates the optimal speed at the maximum power point. By controlling the speed tracking deviation to approach zero, maximum power point tracking can be achieved.

[0074] Furthermore, the real-time angular velocity input into the integrated model The optimal speed is defined by inversely deriving from the maximum power point equation. Establish the tracking target; construct the error This quantifies the deviation between the actual state and the target, providing input signals for sliding mode control;

[0075] Based on the wind turbine rotation angular velocity error, a nonlinear sliding surface is constructed by combining the parameter adjustment gain of a linear function and a nonlinear sliding surface.

[0076] The role of nonlinear sliding surfaces in wind turbine control is to optimize the control surface, ensuring that the wind turbine can quickly and accurately adjust to the optimal speed to achieve maximum power output. Traditional sliding control surfaces are based on linear error definitions, but due to the nonlinear characteristics of the maximum power point tracking (MPPT) controller, nonlinear sliding surfaces can more effectively capture the complex relationship between the turbine speed and the control signal. By introducing nonlinear functions, the robustness of the MPPT controller to external disturbances such as wind speed fluctuations and mechanical drag is enhanced, enabling the MPPT controller to adapt quickly to changes, reduce overshoot and oscillations, and improve control accuracy and efficiency. Furthermore, nonlinear sliding surfaces can ensure stable operation of the wind turbine and maintain its optimal operating state even when wind speed changes significantly or the MPPT controller state undergoes abrupt changes. Therefore, nonlinear sliding surfaces not only optimize control performance but also significantly improve the stability and robustness of the MPPT controller, providing a reliable guarantee for the efficient operation of wind turbines in complex environments.

[0077] Furthermore, the nonlinear sliding surface is represented as:

[0078] ;

[0079] in, and This represents the gain of the nonlinear sliding surface. Adjusting the linear portion of the sliding surface mainly affects the response speed and stability of the maximum power point tracking controller to errors, ensuring that the maximum power point tracking controller quickly converges to the sliding surface within a small error range. Adjusting the nonlinear part The nonlinear term affects the response of the maximum power point tracking controller to larger errors, enabling the nonlinear term to effectively compensate for external disturbances and improve the robustness of the maximum power point tracking controller. The range of values ​​should be comprehensively considered based on the stability analysis of the maximum power point tracking controller, the estimation of the upper bound of the disturbance, and the control performance requirements. In practical applications, the selection of these parameters is usually adjusted through simulation and experiment to ensure the optimal performance of the maximum power point tracking controller. This represents a linear function, which consists of the wind turbine rotational angular velocity error and the switching threshold.

[0080] Furthermore, linear functions , is represented as:

[0081] ;

[0082] in, This represents the nonlinearity exponent, with a value range of (0,1). It adjusts the nonlinearity intensity to balance the robustness and stability of the maximum power point tracking controller, such as... =0.3 accelerates convergence with large errors; comparisons are made with different simulation platforms. The tracking performance of the values ​​is evaluated by selecting the optimal values ​​based on response time, overshoot, and chatter intensity. This represents the switching threshold, which determines the boundary between linear and nonlinear regions.

[0083] When the absolute value of the wind turbine rotational angular velocity error is greater than the switching threshold, The maximum power point tracking (MPPT) controller is dominated by a nonlinear function that activates an accelerated convergence term, thereby enhancing its correction capability. When the absolute value of the rotor angular velocity error is less than the switching threshold, the linear term... To suppress sliding mode chattering, the maximum power point tracking (MPPT) controller employs a linear function for smooth control, thus suppressing MPT controller oscillations and ensuring its stability and accuracy. The traditional sliding surface has been improved into a dynamic gain structure, balancing response speed and stability.

[0084] Furthermore, nonlinear sliding surfaces are designed, and functions are... The controller operates in segments based on error magnitude. When the absolute value of the rotor angular velocity error exceeds the switching threshold, the controller behaves as a non-linear function. This helps to handle large errors and correct them quickly, preventing the maximum power point tracking (MPPT) controller from responding too slowly. This non-linear part is typically used for the MPPT controller to adjust rapidly under large wind speed changes or other disturbances. When the absolute value of the rotor angular velocity error is less than the switching threshold, the controller behaves as a linear function. This helps the MPPT controller adjust smoothly when the error is small, avoiding excessive oscillations or overshoot. The MPPT controller needs to smoothly handle small error conditions, hence this part is linear.

[0085] S3. Define the constant velocity approach rate with an upper bound on the error, and derive the piecewise controller expression by combining it with the nonlinear sliding surface. The piecewise controller expression is used to accurately track the speed at the maximum power point.

[0086] The constant velocity approach rate with error upper bound is obtained by adjusting the gain of the disturbance upper bound and the constant velocity approach rate with error upper bound in the wind turbine integrated model, combined with the definition of the sign function, to force the maximum power point tracking controller state convergence and cover sudden changes in wind speed.

[0087] The definition of the constant-velocity approaching law ensures that the maximum power point tracking controller (MPPT) approaches the sliding surface at a constant rate during sliding mode control, and ensures a stable transition to the target state. Its main function is to ensure that the MPPT approaches the sliding surface smoothly and stably, avoiding oscillations or instability caused by excessively large or small errors. By utilizing the constant-velocity approaching law with an upper bound on the error, the MPPT can maintain robustness in the face of external disturbances or uncertainties, and ensure stable operation within a certain error range.

[0088] The constant velocity approach rate is closely related to the nonlinear sliding surface. In nonlinear sliding surface design, the maximum power point tracking controller (MPPT) state consists of linear and nonlinear components. Adjusting the error and control gain ensures that the MPPT controller can adjust quickly and effectively. The constant velocity approach rate controls the rate at which the MPPT controller approaches the sliding surface, keeping its speed constant as it approaches the surface, thus avoiding overshoot or oscillation.

[0089] The goal of sliding mode control is to enable the maximum power point tracking controller to reach the target state as quickly as possible and maintain it in that state. The constant velocity approach rate ensures a stable approach rate, which accelerates convergence when the maximum power point tracking controller is dealing with large errors and smoothly transitions when the error is small, thereby enhancing the stability and responsiveness of the maximum power point tracking controller.

[0090] Furthermore, the isotropic reaching rate with an upper bound on the error is expressed as:

[0091] ;

[0092] in, Denotes the upper bound of the disturbance in the integrated model of the wind turbine and satisfies ≤ ,cover Mutations and model uncertainties, The parameter tuning gain, representing the constant velocity convergence rate with an upper bound on the error, is mainly obtained through simulation experiments under abrupt wind speed changes. It is optimized with the goals of disturbance suppression and overshoot-free convergence, by gradually increasing or decreasing the gain. The values ​​of the maximum power point tracking controller are analyzed, and indicators such as the stability, speed, and overshoot of the controller's response are observed to select a suitable value. value. and Cooperative forced sliding surface convergence, The sign function is used to force the maximum power point tracking controller state to converge along the nonlinear sliding surface.

[0093] Based on the nonlinear sliding surface and the constant velocity approaching rate, the expression for the piecewise controller is derived.

[0094] The core purpose of a nonlinear sliding surface tracking controller is to precisely adjust the rotational speed of the wind turbine, ensuring that the controller is always in maximum power point tracking (MPPT) mode. This means that the rotor speed can quickly adapt to changes in wind speed and disturbances, maximizing wind energy conversion efficiency. The controller combines linear and nonlinear components. The linear component ensures smooth adjustment under small errors, while the nonlinear component handles rapid correction under large errors, ensuring that the MPT controller avoids entering an inefficient operating range.

[0095] The controller design enhances the robustness and stability of the maximum power point tracking (MPPT) controller, particularly in the face of external disturbances and uncertainties in the MPPT controller, enabling stable operation and timely response to wind speed changes. Sliding mode control adjusts the MPPT controller state to ensure the wind turbine remains within the ideal speed range, avoiding oscillations and overshoot.

[0096] Gain parameter adjustment ensures that the maximum power point tracking controller can dynamically adjust the sliding surface. The definition of the constant velocity approach rate ensures that the maximum power point tracking controller stably and constantly approaches the sliding surface, thereby avoiding unstable transitions and ensuring that the wind turbine always operates at the optimal operating point.

[0097] Furthermore, when the absolute value of the wind turbine rotational angular velocity error exceeds the switching threshold... When the linear function activates the accelerated convergence term, the wind turbine torque is directly output. , is represented as:

[0098] ;

[0099] in, Indicates the wind turbine torque. Indicates the moment of inertia. This indicates the optimal speed at the point of maximum power. Indicates the mechanical damping coefficient. Represents real-time angular velocity. Indicates wind force. and This represents the gain of the nonlinear sliding surface. Adjusting the linear portion of the sliding surface mainly affects the response speed and stability of the maximum power point tracking controller to errors, ensuring that the maximum power point tracking controller quickly converges to the sliding surface within a small error range. Adjusting the nonlinear part The nonlinear term affects the response of the maximum power point tracking controller to larger errors, enabling the nonlinear term to effectively compensate for external disturbances and improve the robustness of the maximum power point tracking controller. The range of values ​​should be comprehensively considered based on the stability analysis of the maximum power point tracking controller, the estimation of the upper bound of the disturbance, and the control performance requirements. In practical applications, the selection of these parameters is usually adjusted through simulation and experiment to ensure the optimal performance of the maximum power point tracking controller. This represents a nonlinear exponent, with values ​​ranging from (0, 1). Different exponents are compared in the simulation platform. The tracking performance of the values ​​is evaluated by selecting the optimal values ​​based on response time, overshoot, and chatter intensity. Indicates the real-time angular velocity error. The parameter tuning gain, representing the constant velocity convergence rate with an upper bound on the error, is mainly obtained through simulation experiments under abrupt wind speed changes. It is optimized with the goals of disturbance suppression and overshoot-free convergence, by gradually increasing or decreasing the gain. The values ​​of the maximum power point tracking controller are analyzed, and indicators such as the stability, speed, and overshoot of the controller's response are observed to select a suitable value. value, This represents the upper bound of the disturbance in the integrated model of the wind turbine generator. Represents a symbolic function.

[0100] Furthermore, the wind turbine output torque It is a controllable variable. The controller adjusts... To offset Disturbances (such as sudden changes in wind speed) should be mitigated to ensure that the rotational speed remains stable at the maximum power point.

[0101] Furthermore, feedforward compensation term To cancel out known dynamics, nonlinear acceleration terms use The exponential convergence accelerates, and the robust term... Suppress disturbances.

[0102] Furthermore, when the absolute value of the wind turbine angular velocity error is less than the switching threshold... At this time, the linear function switches to the blower torque suppression term and directly outputs the wind turbine torque. , is represented as:

[0103] ;

[0104] accrued items Replaces nonlinear exponents, smooths output control, and increases sign function gain. Direct output avoids high-frequency jitter.

[0105] In summary, this invention solves the control mismatch problem caused by the simplification of traditional models by: constructing a comprehensive model to accurately characterize the nonlinear coupling characteristics of the maximum power point tracking controller for wind power generation; innovatively applying piecewise nonlinear sliding surface design to accelerate dynamic convergence in the large error region and achieve linear smooth transition in the small error region, overcoming the high-frequency chattering problem of traditional sliding mode control; using a constant velocity approach rate with an upper bound on the error to cover wind speed mutations and mechanical uncertainties with the upper bound of the disturbance, combined with the constant velocity forced convergence characteristics of the sign function, completely solving the three major technical bottlenecks of traditional PID control in response to wind speed mutations: lag, severe overshoot, and poor disturbance rejection; and achieving accurate tracking of the target speed by the maximum power point of the wind turbine without overshoot in a short time by outputting torque through a piecewise controller.

[0106] Example 2, refer to Figures 3-4 As an embodiment of the present invention, a nonlinear sliding mode tracking control method for the maximum power point of a wind turbine is provided. To verify the beneficial effects of the present invention, scientific demonstration is carried out through economic benefit calculations and simulation experiments.

[0107] Test environment: The theoretical model was built and run on a simulation platform. With 1000 r / min as the tracking target, the control method proposed in this invention and the traditional PID method were tested, and the comparative test results were obtained. The simulation test of the theoretical model was implemented by turning on the automated test equipment and running MATLAB software. The simulation data was obtained based on the experimental results.

[0108] Test parameters: , , , , , , , , , , .

[0109] Reference Figure 3 This is a schematic diagram of speed tracking in the nonlinear sliding mode tracking control method for the maximum power point of a wind turbine; for example... Figure 3 As shown, the curve is a speed tracking graph of the control method proposed in this invention. It can be seen from the graph that the method has fast tracking performance. When the running time reaches 1 second, the speed reaches a balanced state of 1000 r / min.

[0110] Reference Figure 4 This is a comparison method (traditional PID method) for the nonlinear sliding mode tracking control method at the maximum power point of a wind turbine, illustrated in the speed tracking diagram; for example... Figure 4As shown, the traditional PID method exhibits significant fluctuations in tracking performance and poor speed, with a settling time of approximately 6 seconds and a maximum overshoot of 80%.

[0111] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A nonlinear sliding mode tracking control method for the maximum power point of a wind turbine generator, characterized in that: include, Based on the wind speed random function, the wind turbine dynamics equation and the generator linear relationship, a comprehensive wind turbine generator model covering wind speed input, wind turbine torque output and generator voltage generation process is established. Based on the real-time operating status of the wind turbine integrated model, the maximum output power point and the corresponding optimal speed are defined; Based on the optimal rotational speed and the real-time wind turbine rotational angular velocity in the integrated model of the wind turbine generator, the wind turbine rotational angular velocity error is calculated, and a nonlinear sliding surface is constructed. Based on the upper bound of the disturbance in the integrated model of wind turbine generators, a constant velocity approach rate with an upper bound of error is defined; The expression for the piecewise controller is derived by combining the constant velocity approach rate and the nonlinear sliding surface. Based on the piecewise controller, the control strategy is switched in different wind turbine rotational angular velocity error regions, and the speed at the maximum power point is accurately tracked based on the control strategy.

2. The nonlinear sliding mode tracking control method for the maximum power point of a wind turbine generator as described in claim 1, characterized in that: The integrated model of the wind turbine includes a wind speed model, a wind turbine dynamics model, and a generator model.

3. The nonlinear sliding mode tracking control method for the maximum power point of a wind turbine generator as described in claim 2, characterized in that: The wind speed model is constructed from a location-time random function of wind speed to simulate the random fluctuations of actual wind speed. The wind turbine dynamics model is constructed from rotational inertia, angular velocity, damping coefficient, and wind force, and is used to calculate the instantaneous torque of the wind turbine under wind speed disturbance. The generator model is constructed from the generator's constants and angular velocities and is used to calculate the voltage of the wind turbine.

4. The nonlinear sliding mode tracking control method for the maximum power point of a wind turbine generator as described in claim 3, characterized in that: The definition of the maximum output power point and the corresponding optimal speed includes defining the optimal speed corresponding to the maximum output power point based on the real-time operating status of the wind turbine integrated model. The maximum output power is defined based on the defined optimal speed and the generator current.

5. The nonlinear sliding mode tracking control method for the maximum power point of a wind turbine generator as described in claim 4, characterized in that: The calculation of wind turbine rotational angular velocity error refers to deriving the expression for wind turbine rotational angular velocity error by combining the optimal speed at the defined maximum output power point and the wind turbine rotational angular velocity in the comprehensive model, and then calculating the real-time wind turbine rotational angular velocity error.

6. The nonlinear sliding mode tracking control method for the maximum power point of a wind turbine generator as described in claim 5, characterized in that: The construction of the nonlinear sliding surface also includes constructing a nonlinear sliding surface based on the wind turbine rotation angular velocity error, combined with the parameter adjustment gain of the linear function and the nonlinear sliding surface.

7. The nonlinear sliding mode tracking control method for the maximum power point of a wind turbine generator as described in claim 6, characterized in that: The linear function is composed of the wind turbine rotational angular velocity error and the switching threshold. When the absolute value of the wind turbine rotational angular velocity error is greater than the switching threshold, the nonlinear function activates the accelerated convergence term. When the absolute value of the wind turbine angular velocity error is less than the switching threshold, the linear function switches to the flutter suppression term.

8. The nonlinear sliding mode tracking control method for the maximum power point of a wind turbine generator as described in claim 7, characterized in that: The constant velocity approach rate with an upper bound on error is defined by the disturbance upper bound and the constant velocity approach rate with an upper bound on error in the wind turbine integrated model, combined with the sign function definition. The upper bound of the disturbance in the integrated model of the wind turbine generator satisfies that the constant velocity approach rate is less than or equal to the upper bound of the disturbance in the integrated model of the wind turbine generator.

9. The nonlinear sliding mode tracking control method for the maximum power point of a wind turbine generator as described in claim 8, characterized in that: The precise tracking of the maximum power point rotational speed via a piecewise controller expression includes deriving the piecewise controller expression based on a nonlinear sliding surface and a constant velocity approach rate. When the absolute value of the rotor rotational angular velocity error exceeds a switching threshold... At that time, the nonlinear function activates the accelerated convergence term, directly outputting the wind turbine torque. , is represented as: ； in, This indicates the output torque of the wind turbine. Indicates the moment of inertia. This indicates the optimal speed at the point of maximum power. Indicates the mechanical damping coefficient. Represents real-time angular velocity. Indicates wind force. and This represents the gain of the nonlinear sliding surface. This represents a nonlinear exponent, with a value range of (0,1). Indicates the real-time angular velocity error. The parameter-tuned gain represents the constant-rate approach rate with an upper bound on the error. This represents the upper bound of the disturbance in the integrated model of the wind turbine generator. Represents a symbolic function.

10. The nonlinear sliding mode tracking control method for the maximum power point of a wind turbine generator as described in claim 9, characterized in that: The precise tracking of the maximum power point speed via the segmented controller expression also includes deriving the segmented controller expression based on the sliding surface and the constant velocity approach rate. When the absolute value of the rotor angular velocity error is less than the switching threshold... At this time, the linear function switches to the blower torque suppression term and directly outputs the wind turbine torque. , is represented as: 。

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