CN114738181A - Maximum power point tracking control method and system for large wind driven generator - Google Patents
Maximum power point tracking control method and system for large wind driven generator Download PDFInfo
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F03—MACHINES OR ENGINES FOR LIQUIDS; WIND, SPRING, OR WEIGHT MOTORS; PRODUCING MECHANICAL POWER OR A REACTIVE PROPULSIVE THRUST, NOT OTHERWISE PROVIDED FOR
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- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
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Abstract
The invention relates to the field of wind power generation control, in particular to a maximum power point tracking control method and a maximum power point tracking control system for a large wind power generator, wherein the method specifically comprises the following steps: acquiring the wind speed and the real-time rotating speed of a wind wheel; calculating the difference between the optimal torque and the real-time torque on line; setting an integral sliding mode controller; and outputting electromagnetic torque through the integral sliding mode controller to perform tracking control on the fan. The method utilizes the rapidity of the integral sliding mode control method and the characteristic that the change of the optimal torque method value is smooth, takes two targets of maximum power point tracking control into account, improves the wind energy capturing efficiency, ensures lower instantaneous load, is simple and easy to implement, and has easily adjusted control parameters.
Description
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 for a large-scale wind power generator.
Background
In order to ensure the sustainable development of energy, renewable energy has been concerned by countries in the world in recent years, and among the renewable energy, wind energy is favored by countries because wind energy has less adverse effect on the environment compared with other fossil energy; on the other hand, as a renewable resource, the total amount of wind energy worldwide is extremely considerable, and if the wind energy can be efficiently developed and utilized, the wind energy is very beneficial to all countries in the world.
In the wind power generation technology, how to improve the power generation efficiency of the wind power generator is an important issue. Generally, the control strategy for wind power generation can be divided into two categories according to the magnitude of the actual wind speed. The first type: maximum Power Point Tracking (MPPT) control strategy. In this case, the wind speed is lower than the rated wind speed, and the main objective of the control is to extract the energy from the wind energy to the maximum. The control strategy is that different torque controllers are designed to enable the speed of the rotor to change rapidly along with the change of the wind speed, and the wind wheel obtains the optimal rotor speed, so that the maximum wind energy capture efficiency is obtained. The second type: and controlling the variable pitch angle. At the moment, the wind speed is higher than the rated wind speed, and the stable output power is obtained mainly by controlling the pitch angle. The present invention belongs to a first class of control strategies.
From the control strategy, the currently used methods include an optimal Tip Speed Ratio (TSR) method, an optimal torque transfer (OTC) method, a Power Feedback Signal (PFS) method, and a Hill Climbing Search (HCS) method. The optimal tip speed ratio method is actually a method for tracking the optimal rotating speed, and the tracking of the optimal rotating speed requires that the wind driven generator can respond to the change of the electromagnetic torque in time. The optimal torque method is widely applied to the engineering field because the optimal torque method is easy to realize and can obtain higher wind energy capture efficiency, the reference optimal power value is only related to the wind speed, namely is in direct proportion to the third power of the wind speed, but the method depends on the self adjustment of a wind turbine system, and the control parameters cannot be adjusted, so that the method has defects in the aspects of both control efficiency and tracking dynamic effect. The power signal feedback method is intended to suppress power fluctuations, and one of the more well-known implementations is Sliding Mode Power Control (SMPC), but this method is deficient in reducing instantaneous load. The hill climbing search method is suitable for fans with small capacity and has the defects that the step length is difficult to determine or the variable step length coefficient is difficult to calculate, but the large-scale wind driven generator has large rotational inertia, so that the wind turbines cannot be in the optimal rotor rotating speed operation state at any moment, power loss is inevitably caused, and the extracted energy is not optimal. In a word, a key problem to be solved urgently in the field of wind power generation control is how to achieve a good dynamic tracking effect, obtain higher wind energy capturing efficiency, keep a lower instantaneous load of a transmission shaft and prolong the service life of wind turbine components.
It should be noted that the above background description is only for the convenience of clear and complete description of the technical solutions of the present application and for the understanding of those skilled in the art. Such solutions are not considered to be known to the person skilled in the art merely because they have been set forth in the background section of the present application.
Disclosure of Invention
The purpose of the invention is: aiming at the defects in the prior art, the method and the system for tracking and controlling the maximum power point of the large-scale wind driven generator based on the integral sliding mode and the optimal torque are provided, so that the wind energy capturing efficiency is improved, and meanwhile, the lower transmission load is kept.
In order to achieve the above purpose, the present invention provides a maximum power point tracking control method for a large wind power generator, 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.
Further, what is used in the transmission system of the fan in S1 is a single mass model, and the specific formula is as follows:
wherein
Wherein, ω isrRepresenting the rotational speed of the rotor, TrTo represent the torque of the rotor, TgRepresenting the generator-side torque, i.e. the control input, C, of the wind turbine control system proposed by the methodr，CgRespectively representing the rotor-side damping coefficient and the generator-side rotational inertia, Jr，JgRepresenting the moment of inertia of the rotor side and generator side, respectively, ngIs a dimensionless number representing the gear ratio of the gearbox, CpThe method only relates to the adjustment of the rotating speed, and the numerical value of the pitch angle is always kept constant and is 0, so that the magnitude of the wind energy utilization coefficient is only related to the tip speed ratio;
tip speed ratio λ expression of
Further, a torque tracking error is set in S2
Optimum torque
ωoptIn order to optimize the rotational speed of the rotor,
λoptfor optimal tip speed ratio.
Further, in S3, a sliding mode surface S ═ e + K is definediIntegral multiple of e dtiThe introduction of the integral coefficient can further reduce the tracking error of the optimal torque value;
the specific formula of the integral sliding mode controller is as follows:
wherein alpha is>0，k>0，Ki>0
Then the
Defining a Lyapunov function
The invention also provides a maximum power point tracking control system of the large wind driven generator, which comprises 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 the wind wheel, and the integral sliding mode controller is used for outputting electromagnetic torque after calculation and carrying out tracking control on the fan.
The scheme of the invention has the following beneficial effects:
according to the maximum power point tracking control method and system for the large-scale wind driven generator, provided by the invention, the rapidity of an integral sliding mode control method and the characteristic that the change of an optimal torque method value is smooth are utilized, two targets of maximum power point tracking control are taken into consideration, the wind energy capturing efficiency is improved, meanwhile, a lower instantaneous load is ensured, the control method is simple and feasible, and the control parameters are easy to adjust;
other advantages of the present invention will be described in detail in the detailed description that follows.
Drawings
FIG. 1 is a flow chart of the steps of the present invention;
FIG. 2 is a turbulent wind velocity used by a simulation example of the present invention;
FIG. 3 is a graph of captured power versus control method;
fig. 4 is a torque comparison diagram of a generator according to different control methods.
Detailed Description
In order to make the technical problems, technical solutions and advantages of the present invention more apparent, the following detailed description is given with reference to the accompanying drawings and specific embodiments. It is to be understood that the embodiments described are only a few embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, 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 may be combined with each other as long as they do not conflict with each other.
For simplicity of explanation, the method or rules are depicted and described as a series of acts that are not intended to be exhaustive or to limit the order of the acts. For example, the experimental procedures can be performed in various orders and/or simultaneously, and include other experimental procedures not described again. Moreover, the described steps are not required for the methods and algorithms described herein, but rather, the methods and algorithms may be represented as a series of interrelated states via a state diagram or items.
The invention relates to the field of wind power generation control, and the key problem to be solved urgently in the field of wind power generation control at present is how to realize a good dynamic tracking effect, obtain higher wind energy capturing efficiency, keep lower instantaneous load of a transmission shaft and prolong the service life of a wind turbine component. Based on this, the embodiment of the present invention provides a maximum power point tracking control method for a large wind turbine, as shown in fig. 1, generally including the following four steps:
s1, acquiring the wind speed through a wind speed measuring instrument, and acquiring the real-time rotating speed of a wind wheel through a rotating speed sensor;
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 the control quantity electromagnetic torque through the integral sliding mode controller.
In this embodiment, the single-mass model is used for the transmission system of the fan, and the specific formula is as follows:
wherein
In the above formula, ωrRepresenting the rotational speed of the rotor, TrTo represent the torque of the rotor, TgRepresenting the generator-side torque, i.e. the control input, C, of the wind turbine control system proposed in this embodimentr，CgRespectively representing the rotor-side damping coefficient and the generator-side rotational inertia, Jr，JgRepresenting the moment of inertia of the rotor side and generator side, respectively, ngIs a dimensionless number representing the gear ratio of the gearbox, CpThe wind energy utilization coefficient is represented, the value of the wind energy utilization coefficient is related to the size of the pitch angle and the size of the tip speed ratio, and the value of the pitch angle is kept constant and is 0 all the time due to the fact that only the adjustment of the rotating speed is involved in the embodiment, so that the size of the wind energy utilization coefficient is only related to the tip speed ratio.
Tip speed ratio λ expression of
In S2, a torque tracking error is set
Optimum torque
ωoptIn order to optimize the rotational speed of the rotor,
in S3, a slip form surface S ═ e + K is definediIntegral multiple of e dtiThe introduction of the integration coefficient, which is an integration coefficient, can further reduce the tracking error to the optimal torque value.
The specific formula of the integral sliding mode controller is as follows:
wherein alpha is>0，k>0，Ki>0
Then
Defining a Lyapunov function
According to the lyapunov method, it can be known that V is negative, and thus the proposed controller is stable, enabling stable control of wind power generation.
The method utilizes the rapidity of the integral sliding mode control method and the characteristic that the change of the optimal torque method value is smooth, takes two targets of MPPT control into account, improves the wind energy capture efficiency, ensures lower instantaneous load, is simple and easy to implement, and has easily adjusted control parameters.
Meanwhile, the embodiment also provides a corresponding system, which comprises 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 the wind wheel, and the integral sliding mode controller is used for calculating and then outputting the electromagnetic torque to track and control the fan.
Specific example embodiments are provided below to explain in detail, in the present embodiment, special simulation software FAST (Fatigue, aerodynes, Strustures and Turbulence) in the wind power generation field is used, and a wind turbine object is Test18 prototype provided by NREL (national renewable energy laboratory), the prototype is a 5MW land-level three-blade wind turbine generator, specific parameters of which are shown in table 1, and the software version used is FAST v8.16, and joint simulation is performed in Matlab _ simulink environment.
Table 1: specific parameters of 5MW horizontal-axis wind turbine
In order to simulate the actual wind speed under real conditions, the TurbSim software developed by NREL was used in the simulation, and 120s turbulent wind speed sequence was generated based on Kaimal power spectrum, as shown in FIG. 2, with average wind speed of 7m/s and turbulence intensity of 10%.
In the MPPT process, there are two control objectives, one is to maximize wind energy capture efficiency and the other is to make the instantaneous load of the generator as small as possible. As can be seen from the combination of FIG. 2, the optimal torque method is adjusted only by the characteristics of the wind turbine, the overall captured energy is the minimum of the three, and the method for capturing wind energy is greatly improved compared with the optimal torque method. Compared with sliding mode power control, the method is slightly weaker in overall tracking effect in power, but the advantages of integral sliding mode control are exerted in the initial stage, the method has higher response speed, the inertia effect of a large wind turbine is utilized in the stage (about 100 s) of wind speed reduction in a low wind speed area, and the wind energy capturing effect is higher.
As can be seen from FIG. 3, the optimal torque method sacrifices the tracking of the optimal rotor speed to obtain the minimum generator torque fluctuation, and compared with the sliding mode power control method, the method has the advantage that the torque fluctuation of the generator is obviously smaller, which is beneficial to prolonging the service life of the wind turbine component.
In a word, the method fully considers the characteristics of different control methods, utilizes the characteristic of large inertia of the fan and the rapidity of the integral sliding mode control method, improves the wind energy capturing capability of the wind turbine and keeps lower instantaneous load.
While the foregoing is directed to the preferred embodiment of the present invention, it will be appreciated by those skilled in the art that various changes and modifications may be made therein without departing from the principles of the invention as set forth in the appended claims.
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 isrRepresenting the rotational speed of the rotor, TrTo represent the torque of the rotor, TgRepresenting the torque on the generator side, Cr，CgRespectively representing the rotor side damping coefficient and the generator side rotational inertia, Jr，JgRepresenting the moment of inertia of the rotor and generator sides, respectively, ngIs a dimensionless number representing the gear ratio of the gearbox, CpRepresenting 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
ωoptIn order to optimize the rotational speed of the rotor,
λoptfor 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 + KiIntegral whole number edt, wherein KiIs an integral coefficient;
the specific formula of the integral sliding mode controller is as follows:
wherein alpha is>0，k>0，Ki>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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