CN114738181A - A method and system for tracking and controlling the maximum power point of a large wind turbine - Google Patents

Abstract

The invention relates to the field of wind power generation control, in particular to a method and system for tracking and controlling the maximum power point of a large-scale wind turbine. The method specifically includes the steps of: acquiring the wind speed and the real-time rotation speed of the wind rotor; online calculating the optimal torque and real-time rotation speed. torque difference; set the integral sliding mode controller; output the electromagnetic torque through the integral sliding mode controller to track and control the fan. The invention utilizes the rapidity of the integral sliding mode control method and the characteristics of the smooth change of the optimal torque value, takes into account the two objectives of the maximum power point tracking control, and ensures a lower instantaneous load while improving the wind energy capture efficiency. The control method is simple and easy to implement, and the control parameters are easy to adjust.

Description

A method and system for tracking and controlling the maximum power point of a large wind turbine

technical field

The invention relates to the field of wind power generation control, in particular to a maximum power point tracking control method and system of a large wind power generator.

Background technique

In order to ensure the sustainable development of energy, renewable energy has been concerned by countries all over the world in recent years, and among the renewable energy, wind energy is favored by countries, on the one hand, because of the adverse impact of wind energy on the environment compared with other fossil energy On the other hand, as a renewable resource, the total amount of global wind energy is extremely considerable. If it can be efficiently developed and utilized, it will be very beneficial to all countries in the world.

How to improve the power generation efficiency of wind turbines is an important issue in wind power generation technology. Generally, the control strategies of wind power generation can be divided into two categories according to the actual wind speed. The first category: maximum power point tracking (Maximum Power Point Tracking, MPPT) control strategy. At this time, the wind speed is lower than the rated wind speed, and the main goal of the control is to extract the maximum energy from the wind energy. The control strategy is to design different torque controllers so that the rotor speed changes rapidly with the wind speed, and the wind rotor obtains the optimal rotor speed, thereby obtaining the maximum wind energy capture efficiency. The second category: pitch angle control. At this time, the wind speed is higher than the rated wind speed, mainly by controlling the pitch angle to obtain a relatively stable output power. The present invention belongs to the first type of control strategy.

From the point of view of control strategy, the most commonly used methods are the optimal tip speed ratio method (TSR), the optimal torque method (OTC), the power feedback signal method (PFS), and the hill climbing search method (HCS). The optimal tip speed ratio method is actually a method of tracking the optimal rotational speed. Tracking the optimal rotational speed requires the wind turbine to respond to changes in electromagnetic torque in a timely manner. The optimal torque method is widely used in the engineering field because it is easy to implement and can obtain high wind energy capture efficiency. The reference optimal power value is only related to the wind speed, that is, proportional to the cube of the wind speed. Relying on the self-adjustment of the wind turbine system, the control parameters cannot be adjusted, resulting in insufficient control efficiency and dynamic effect of tracking. The power signal feedback method is designed to suppress power fluctuations. One of the more well-known implementations is sliding mode power control (SMPC), but this method is lacking in reducing transient loads. The hill-climbing search method is suitable for small-capacity wind turbines and has the defects that the step size is difficult to determine or the variable step-length coefficient is difficult to calculate. However, the large-scale wind turbine itself has a large moment of inertia, which makes it impossible to keep the wind turbine in the maximum position all the time. The optimal rotor speed operation state will inevitably lead to power loss, and the extracted energy is not the best. In a word, the key problem that needs to be solved urgently in the field of wind power generation control is how to achieve a good dynamic tracking effect and obtain a higher wind energy capture efficiency, while maintaining a lower instantaneous load of the drive shaft and prolonging the service life of wind turbine components. .

It should be noted that the above description of the technical background is only for the convenience of clearly and completely describing the technical solutions of the present application and facilitating the understanding of those skilled in the art. It should not be assumed that the above-mentioned technical solutions are known to those skilled in the art simply because these solutions are described in the background section of this application.

SUMMARY OF THE INVENTION

The purpose of the present invention is: in view of the deficiencies in the above-mentioned background technology, to provide a large-scale wind turbine maximum power point tracking control method and system based on integral sliding mode and optimal torque, in order to improve the wind energy capture efficiency while, Keep the transmission load low.

In order to achieve the above purpose, the present invention provides a method for tracking and controlling the maximum power point of a large-scale wind turbine, comprising the following steps:

S1, obtain the wind speed and the real-time rotational speed of the wind rotor;

S2, online calculation of the difference between optimal torque and real-time torque;

S3, set the integral sliding mode controller;

S3, through the integral sliding mode controller to output the electromagnetic torque, the fan is tracked and controlled.

Further, the single-mass model is used in the transmission system of the fan in S1, and the specific formula is as follows:

in

Among them, ω _r represents the rotational speed of the rotor of the wind turbine, Tr _{represents the torque of the wind rotor, and T g represents} the torque on the generator side, that is, the control input of the wind turbine control system proposed by this method, C _r , C _g represents the damping coefficient of the rotor side and the moment of inertia of the generator side, respectively, J _r , J _g represent the moment of inertia of the rotor side and the generator side, respectively, n _g is a dimensionless value, representing the gear ratio of the gearbox, C _p represents the wind energy utilization coefficient, and its value is related to the size of the pitch angle and the size of the blade tip speed ratio. Since this method only involves the adjustment of the rotational speed, the value of the pitch angle has been kept constant and is always 0. Therefore, The wind energy utilization coefficient is only related to the tip speed ratio;

The tip speed ratio λ is expressed as

最优转矩

ω_opt为最优转子转速，

λ_opt为最优叶尖速比。Further, the torque tracking error is set in S2

optimal torque

ω _opt is the optimal rotor speed,

λ _opt is the optimal tip speed ratio.

Further, the sliding mode surface s=e+K _i ∫e dt is defined in S3, wherein K _i is the integral coefficient, and the introduction of the integral coefficient can further reduce the tracking error to the optimal torque value;

The specific formula of the integral sliding mode controller is as follows:

where α>0, k>0, K _i >0

but

Define the Lyapunov function

The invention also provides a large-scale wind turbine maximum power point tracking control system, including a wind speed detection module, a wind rotor speed detection module and an integral sliding mode controller, the wind speed detection module is used to obtain the wind speed, and the wind rotor The rotational speed detection module is used to obtain the real-time rotational speed of the wind rotor, and the integral sliding mode controller is used to output electromagnetic torque after calculation, and to track and control the wind turbine.

The above-mentioned scheme of the present invention has the following beneficial effects:

The maximum power point tracking control method and system for large wind turbines provided by the present invention utilizes the rapidity of the integral sliding mode control method and the characteristics of the gentle change of the optimal torque value, and takes into account the two objectives of the maximum power point tracking control. While improving the wind energy capture efficiency, it ensures a lower instantaneous load, the control method is simple and easy to implement, and the control parameters are easy to adjust;

Other beneficial effects of the present invention will be described in detail in the following detailed description section.

Description of drawings

Fig. 1 is the step flow chart of the present invention;

Fig. 2 is the turbulent wind speed used in the simulation example of the present invention;

Figure 3 is a power comparison diagram captured by different control methods;

FIG. 4 is a comparison diagram of generator torque with different control methods.

Detailed ways

In order to make the technical problems, technical solutions and advantages to be solved by the present invention more clear, the following will be described in detail with reference to the accompanying drawings and specific embodiments. Obviously, the described embodiments are some, but not all, embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention. In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

For simplicity of illustration, the method or rule is depicted or described as a series of operations, which is neither intended to be exhaustive nor to limit the order of the experimental operations. For example, experimental operations can be performed in various orders and/or simultaneously, and include other experimental operations not again described. Furthermore, not all of the steps described are necessary for the methods and algorithms described herein, which may be represented by a state diagram or item as a series of unrelated states.

The invention relates to the field of wind power generation control. The key problem that needs to be solved urgently in the field of wind power generation control is how to not only achieve a good dynamic tracking effect, obtain a higher wind energy capture efficiency, but also maintain a lower instantaneous load of the drive shaft, Extend the service life of wind turbine components. Based on this, an embodiment of the present invention provides a method for tracking the maximum power point of a large-scale wind turbine, as shown in FIG. 1 , which generally includes the following four steps:

S1, obtain the wind speed through an anemometer, and obtain the real-time speed of the wind rotor through a speed sensor;

S2, online calculation of the difference between optimal torque and real-time torque;

S3, set the integral sliding mode controller;

S3, output the electromagnetic torque of the control quantity through the integral sliding mode controller.

In this embodiment, the single-mass model is used in the transmission system of the fan, and the specific formula is as follows:

in

In the above formula, ω _r represents the rotational speed of the rotor of the wind turbine, Tr _{represents the torque of the wind rotor, and T g represents} the torque on the generator side, that is, the control input of the wind turbine control system proposed in this embodiment. , C _r , C _g represent the damping coefficient on the rotor side and the moment of inertia on the generator side, respectively, J _r , J _g represent the moment of inertia on the rotor side and the generator side, respectively, n _g is a dimensionless value, representing the gearbox The gear ratio, C _p represents the wind energy utilization coefficient, and its value is related to the size of the pitch angle and the size of the tip speed ratio. Since only the adjustment of the rotational speed is involved in this embodiment, the value of the pitch angle has been kept constant, is always 0, so the wind energy utilization coefficient is only related to the tip speed ratio.

The tip speed ratio λ is expressed as

最优转矩

ω_opt为最优转子转速，

In S2, set the torque tracking error

optimal torque

ω _opt is the optimal rotor speed,

In S3, define the sliding mode surface s=e+K _i ∫e dt, where K _i is the integral coefficient, and the introduction of the integral coefficient can further reduce the tracking error to the optimal torque value.

The specific formula of the integral sliding mode controller is as follows:

where α>0, k>0, K _i >0

but

Define the Lyapunov function

According to the Lyapunov method, it can be known that V is negative definite, so the proposed controller is stable and can realize the stable control of wind power generation.

This method takes advantage of the rapidity of the integral sliding mode control method and the smooth change of the optimal torque value, and takes into account the two objectives of MPPT control. It improves the wind energy capture efficiency while ensuring a lower instantaneous load, and the control method is simple. It is easy to operate, and the control parameters are easy to adjust.

At the same time, this embodiment also provides a corresponding system, including a wind speed detection module, a wind wheel rotational speed detection module, and an integral sliding mode controller, wherein the wind speed detection module is used to obtain the wind speed, and the wind wheel rotational speed detection module is used to obtain the wind speed. The real-time speed of the wheel is calculated, and the integral sliding mode controller is used to calculate and output the electromagnetic torque to track and control the fan.

The following provides a detailed description of a specific implementation example. The professional simulation software FAST (Fatigue, Aerodynamics, Strustures and Turbulence) in the field of wind power generation used in this example, and the wind turbine object is the Test18 prototype provided by NREL (National Renewable Energy Laboratory). , the prototype is a 5MW terrestrial horizontal three-blade wind turbine, its specific parameters are shown in Table 1, the software version used is Fast v8.16, and the co-simulation is carried out in the Matlab_simulink environment.

Table 1: Specific parameters of 5MW horizontal axis wind turbine

In order to simulate the actual wind speed under realistic conditions, TurbSim software developed by NREL was used in the simulation, and a 120s turbulent wind speed sequence was generated based on the Kaimal power spectrum. As shown in Figure 2, the average wind speed of the turbulent wind speed is 7m/s , the turbulence intensity is 10%.

In the MPPT process, there are two control objectives, one is to maximize the wind energy capture efficiency, and the other is to make the instantaneous load of the generator as small as possible. Combining with Fig. 2, it can be seen that the optimal torque method only relies on the characteristics of the wind turbine itself for adjustment, and the overall captured energy is the smallest among the three. Compared with the optimal torque method, this method captures the wind energy and obtains a better performance. big improvement. Compared with the sliding mode power control, this method is slightly weaker in the overall tracking effect of power, but it takes advantage of the integral sliding mode control in the initial stage and has a faster response speed. 100s) utilizes the inertial effect of large wind turbines and has a higher wind energy capture effect.

It can be seen from Figure 3 that the optimal torque method sacrifices the tracking of the optimal rotor speed to obtain the smallest generator torque fluctuation, while this method has a significantly higher generator torque fluctuation compared with the sliding mode power control method. Smaller, which is very beneficial to prolong the service life of wind turbine components.

In a word, this method fully considers the characteristics of different control methods, utilizes the characteristics of large inertia of the wind turbine and the rapidity of the integral sliding mode control method, and maintains a low instantaneous load while improving the wind energy capture capability of the wind turbine.

The above are the preferred embodiments of the present invention. It should be pointed out that for those skilled in the art, without departing from the principles of the present invention, several improvements and modifications can be made. It should be regarded as the protection scope of the present invention.

Claims (5)

1. A maximum power point tracking control method for a large wind driven generator is characterized by comprising the following steps:

s1, acquiring the wind speed and the real-time rotating speed of the wind wheel;

s2, calculating the difference between the optimal torque and the real-time torque on line;

s3, setting an integral sliding mode controller;

and S3, outputting electromagnetic torque through the integral sliding mode controller, and performing tracking control on the fan.

2. The maximum power point tracking control method for the large wind driven generator according to claim 1, wherein a single-mass model is used for a transmission system of the fan in the step S1, and a specific formula is as follows:

wherein

Wherein, ω is_rRepresenting the rotational speed of the rotor, T_rTo represent the torque of the rotor, T_gRepresenting the torque on the generator side, C_r，C_gRespectively representing the rotor side damping coefficient and the generator side rotational inertia, J_r，J_gRepresenting the moment of inertia of the rotor and generator sides, respectively, n_gIs a dimensionless number representing the gear ratio of the gearbox, C_pRepresenting the wind energy utilization coefficient, wherein the magnitude of the wind energy utilization coefficient is only related to the tip speed ratio;

tip speed ratio λ expression of

3. The maximum power point tracking control method for the large wind driven generator according to claim 2, wherein a torque tracking error is set in S2

Optimum torque

ω_optIn order to optimize the rotational speed of the rotor,

λ_optfor optimal tip speed ratio.

4. The maximum power point tracking control method for the large wind driven generator according to claim 3, wherein S3 defines a sliding mode surface S ═ e + K_iIntegral whole number edt, wherein K_iIs an integral coefficient;

the specific formula of the integral sliding mode controller is as follows:

wherein alpha is>0，k>0，K_i>0

Then

Defining a Lyapunov function

5. The maximum power point tracking control system of the large wind driven generator is characterized by comprising a wind speed detection module, a wind wheel rotating speed detection module and an integral sliding mode controller, wherein the wind speed detection module is used for acquiring the wind speed, the wind wheel rotating speed detection module is used for acquiring the real-time rotating speed of a wind wheel, and the integral sliding mode controller is used for outputting electromagnetic torque after calculation and tracking and controlling a fan.

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