CN116928020A - Pitch angle control method considering rapid active power adjustment of wind driven generator - Google Patents

Abstract

The present invention is a pitch angle control method that takes into account the rapid active power adjustment of wind turbines. It can reduce the pitch angle fluctuations of all PMSGs during the rapid active power control period, and can minimize the fatigue damage of the wind turbine and extend its use. life and reduce maintenance costs; including the following steps: S1. The wind farm controller in the wind farm sends reference power to several permanent magnet synchronous generators, and then builds a mathematical model of the permanent magnet synchronous generator to obtain the wind turbine's Power coefficient c _P ; S2. Construct a wake effect model of the wind farm containing multiple mathematical models of permanent magnet synchronous generators to determine several pitch angles β from the power coefficient c _P ; S3. Construct the fast active power of the wind farm The power control model is designed to satisfy the minimum fluctuation of pitch angle β of the permanent magnet synchronous generator.

Description

A pitch angle control method considering rapid active power adjustment of wind turbines

Technical field

The present invention relates to the technical field of wind power generation, and in particular to a pitch angle control method that considers rapid active power adjustment of a wind turbine.

Background technique

To slow climate change and meet the Paris climate goals, fossil energy must be replaced by renewable energy sources such as wind, hydro and solar. Currently, wind energy is the second largest source of energy after hydropower. This growth trend seems set to continue in the future until it becomes the dominant source of energy production in 2050. To promote this positive and sustainable trend, research into wind energy and wind turbines must continue and move forward.

In the context of the current increase in single-machine capacity of wind turbines and the continuous maturation of wind power technology, the focus of large-scale wind turbines today is how to reduce the cost of manufacturing and operation; among them, an effective way to reduce the cost of wind turbines is to reduce the key factors of wind turbines. The wear and tear of components can be improved to improve the reliability of wind power equipment and extend the service life of wind turbines. However, large wind turbines will produce unbalanced loads on the impeller under the influence of wind turbulence, wind shear, tower shadow effect, yaw deviation and other aerodynamic effects. As the diameter of the wind rotor becomes larger, the stress on the entire wind rotor surface will increase. The stronger the imbalance, the more obvious the unbalanced load on the impeller will be, and the unbalanced load on the impeller will cause large fatigue loads on key components of the wind turbine such as pitch bearings, hubs, main shafts, yaw bearings, and towers. , which will also increase operating costs. Theoretically, if the pitch angle fluctuation of the wind turbine is reduced through blade pitch control during the rapid active power adjustment control operation of the wind turbine, the fatigue damage of the wind turbine can be minimized, thereby extending its service life. And reduce maintenance costs, but currently the pitch angle is determined by a traditional proportional integral controller (PI). This method has certain errors, making the results inaccurate and cannot be used as a basis. Therefore, studying and considering the pitch control method of wind turbines is a key issue that needs to be solved urgently.

Contents of the invention

In view of the above problems, the purpose of the present invention is to provide a pitch angle control method that takes into account the rapid active power adjustment of wind turbines, so as to solve the problems raised in the above background technology.

In order to achieve the above objects, the present invention adopts the following technical solutions:

A pitch angle control method considering the rapid active power adjustment of wind turbines, which is characterized by including the following steps:

S1. The wind farm controller in the wind farm sends reference power to several permanent magnet synchronous generators, and then builds a mathematical model of the permanent magnet synchronous generator to obtain the power coefficient c _P of the wind turbine;

S2. Construct a wake effect model of the wind farm containing multiple mathematical models of permanent magnet synchronous generators to determine several pitch angles β from the power coefficient c _P ;

S3. Construct a fast active power control model of the wind farm to minimize the pitch angle β fluctuation of the permanent magnet synchronous generator.

Further, in step S1, the expression of the mathematical model of the permanent magnet synchronous generator is:

P _mech ＝0.5ρAv ³ c _P (λ,β) (1)

Among them, P _mech represents the mechanical input power;

ρ, A and v represent air density, blade rotor swept area and wind speed respectively;

c _P is the power coefficient of the wind turbine;

λ is the tip speed ratio; β is the pitch angle;

Further, the power coefficient c _P of the wind turbine is expressed as:

in,

Further, in step S2, through the construction of the wake effect model, the synthetic wind speed after considering the wake effect is obtained. The expression of the synthetic wind speed is:

Among them, V _i represents the synthetic wind speed of WTG _j ;

WTG _j is represented as the jth wind turbine;

V _j is the wind speed at WTG _j without any wake;

β _ji is the ratio of the area under the shadow of WTG _i to its total area;

WTG _i is represented as the i-th wind turbine;

x _ji is the radial distance between the j-th and i-th wind turbine units;

a _j is the axial induction coefficient of WTG _j ;

D _j is the diameter of the rotor area of WTG _j ;

k represents the constant used to implement MPPT control;

n is the total number of wind turbines;

Further, the construction of the fast active power control model includes the following steps:

S3.1. The wind farm controller allocates the required power to the permanent magnet synchronous generator to adjust the output power of the public coupling point. The allocation rule is:

in, and/> They are the reference power, active power control command and available power of WTG _i ;

WTG _i is represented as the i-th wind turbine;

S3.2. The wind turbine controller receives the reference power from the wind farm controller. To obtain the reference power coefficient of the wind turbine/> The expression is:

P _air =0.5ρAv ³ (7)

Among them, P _air is the available air power;

S3.3. According to the reference power coefficient of wind turbine Determine the optimal tip speed ratio λ;

Further, determining the minimum fluctuation of pitch angle β includes the following steps:

S4.1. Draw characteristic curves based on different pitch angles β;

S4.2. Reference power coefficient of wind turbine Determine the first straight line;

S4.3. Determine the second straight line through the optimal tip speed ratio λ;

S4.4. According to the characteristic curve and the first straight line and the second straight line, determine the intersection point of the three, then the intersection position is the optimal pitch angle, recorded as β _ref , which satisfies the minimum fluctuation.

Compared with the prior art, the beneficial effects of the present invention are:

This patent can reduce the pitch angle fluctuations of all permanent magnet synchronous generators during fast active power control. That is, after analytically obtaining several pitch angles β from the power coefficient _cP of the wind turbine, by constructing a fast active power control model, determine During the active power adjustment, the optimal tip speed ratio λ is obtained, and finally the optimal pitch angle β _ref that satisfies the minimum fluctuation is obtained, thereby not only ensuring stable active power control operation with minimal fluctuations in pitch angle and rotor speed , and can minimize fatigue damage of wind turbines, extend their service life and reduce maintenance costs.

The above description is only an overview of the technical solutions of the present invention. In order to have a clearer understanding of the technical means of the present invention and implement them according to the contents of the description, the preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings. Specific embodiments of the present invention are given in detail by the following examples and accompanying drawings.

Description of the drawings

The drawings described here are used to provide a further understanding of the present invention and constitute a part of this application. The illustrative embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention.

Figure 1 is a flow chart of the present invention;

Figure 2 is the mechanical input power characteristic curve of the permanent magnet synchronous generator PMSG;

Figure 3 is a schematic diagram of power distribution in the wind farm of the present invention;

Figure 4 is a c _P -λ curve diagram in the present invention;

Figure 5a is a graph of the active power of the wind farm WPP;

Figure 5b is a graph of the active power of the existing conventional scheme permanent magnet synchronous generator PMSG;

Figure 5c is a graph of the active power of the permanent magnet synchronous generator PMSG in the embodiment of the present invention;

Figure 5d is a graph of the pitch angle of the permanent magnet synchronous generator PMSG in the existing conventional solution;

Figure 5e is a graph of the pitch angle of the permanent magnet synchronous generator PMSG in the embodiment of the present invention;

Figure 5f is a graph of the rotor speed of the permanent magnet synchronous generator PMSG in the existing conventional scheme;

Figure 5g is a graph of the rotor speed of the permanent magnet synchronous generator PMSG in the embodiment of the present invention.

Detailed ways

The principles and features of the present invention are described below with reference to the accompanying drawings. The examples cited are only used to explain the present invention and are not intended to limit the scope of the present invention. The invention is described in more detail by way of example in the following paragraphs with reference to the accompanying drawings. The advantages and features of the invention will become more apparent from the following description and claims. It should be noted that the drawings are in a very simplified form and use imprecise proportions, and are only used to conveniently and clearly assist in explaining the embodiments of the present invention.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the technical field to which the invention belongs. The terminology used herein in the description of the invention is for the purpose of describing specific embodiments only and is not intended to limit the invention.

This embodiment analyzes the pitch angle control model according to the flow chart of a pitch angle control method that considers rapid active power adjustment of a wind turbine shown in Figure 1 .

Please refer to Figure 1, a pitch angle control method considering rapid active power adjustment of wind turbines, including the following steps:

S1. The system controller sends instructions to the wind farm controller in the wind farm (that is, the WPP controller). Then the wind farm controller in the wind farm sends reference power to several permanent magnet synchronous generators, and then constructs a permanent magnet synchronous generator. Mathematical model of the magnetic synchronous generator (PMSG) to obtain the power coefficient c _P of the wind turbine;

In step S1, the expression of the mathematical model of the permanent magnet synchronous generator is:

P _mech ＝0.5ρAv ³ c _P (λ,β) (1)

Among them, P _mech represents the mechanical input power; the wind turbine converts wind power into mechanical input power P _mech ;

ρ, A and v represent air density, blade rotor swept area and wind speed respectively;

c _P is the power coefficient of the wind turbine; the power coefficient c _P depends on the tip speed ratio λ and the pitch angle β;

λ is the tip speed ratio; β is the pitch angle;

Further, the power coefficient c _P of the wind turbine is expressed as:

in,

Typical configurations of permanent magnet synchronous generators include a machine-side converter (MSC) and a grid-side converter (GSC). The machine-side converter (MSC) is used to extract maximum power from the wind, and the grid-side converter ( GSC) is used to maintain the DC link voltage and inject the required reactive power into the grid;

The characteristic curve of the mechanical input power P _mech and the rotor speed ω _r and the maximum power curve of the wind turbine in the maximum power tracking (MPPT) control mode are shown in Figure 2, which is the relationship between the mechanical input power P _mech and the wind turbine speed under different wind speeds. ,Expressed as:

Among them, k _opt is the constant used for maximum power tracking control; ω _opt is the optimal rotor speed.

In Figure 1, Tr.1 and Tr.2 respectively represent different connection transformers;

WPP represents a wind farm. Each wind farm has several wind turbines WTG, and each wind turbine corresponds to a permanent magnet synchronous generator PMSG;

S2. Construct a wake effect model of the wind farm containing multiple mathematical models of permanent magnet synchronous generators to determine several pitch angles β from the power coefficient c _P ;

In step S2, multiple wind turbine units in the wind farm may have multiple wakes with different degrees. Therefore, when determining the wind speed of the wind turbine, the overlapping area between the corresponding wind turbines should be considered. Then based on the law of conservation of momentum, the synthetic wind speed V _i of WTG _j can be expressed as:

Among them, V _i represents the synthetic wind speed of WTG _j ;

WTG _j is represented as the jth wind turbine;

V _j is the wind speed at WTG _j without any wake;

β _ji is the ratio of the area under the shadow of WTG _i to its total area;

WTG _i is represented as the i-th wind turbine;

x _ji is the radial distance between the j-th and i-th wind turbine units;

a _j is the axial induction coefficient of WTG _j ;

D _j is the diameter of the rotor area of WTG _j ;

k represents the constant used to implement MPPT control;

n is the total number of wind turbines;

The wake effect mainly affects the wind speed passing through the fan, so formula (5) considers the impact of the wake effect on the wind speed of the fan. The impact of the wake effect on the model is the impact on the wind speed. The synthetic wind speed is the result after considering the impact of the wake. wind speed;

S3. Construct a fast active power control model of the wind farm to minimize the pitch angle β fluctuation of the permanent magnet synchronous generator;

Wherein, the construction of the fast active power control model includes the following steps:

S3.1. As shown in Figure 3, the wind farm controller allocates the required power to the permanent magnet synchronous generator to adjust the output power of the common coupling point (that is, the grid-side coupling point in Figure 1). The common coupling point ( The output power of PCC) is adjusted to 20% of the rated capacity of the wind farm controller, and the distribution rule is:

in, and/> They are the reference power, active power control command and available power of WTG _i ;

WTG _i is represented as the i-th wind turbine;

S3.2. Under normal circumstances, the wind turbine controller regulates the permanent magnet synchronous generator in MPPT control mode. However, when the wind farm level control is activated, the wind turbine controller receives the reference power from the wind farm controller. To obtain the reference power coefficient of the wind turbine/> The expression is:

P _air =0.5ρAv ³ (8)

Among them, P _air is the available air power;

S3.3. According to the reference power coefficient of wind turbine Determine the optimal tip speed ratio λ;

Further, determining the minimum fluctuation of pitch angle β includes the following steps:

S4.1. Obtain different pitch angles β from the table function table, and then draw characteristic curves based on different pitch angles β;

Table function refers to the c _P -λ curve in Figure 4, which is converted into a table form based on the c _P -λ curve;

S4.2. Reference power coefficient of wind turbine Determine the first straight line (i.e. a horizontal line);

S4.3. Determine the second straight line (i.e. a vertical line) through the optimal tip speed ratio λ;

S4.4. According to the characteristic curve and the first straight line and the second straight line, determine the intersection point of the three, then the intersection position is the optimal pitch angle, recorded as β _ref , which satisfies the minimum fluctuation.

The present invention takes a 4-row permanent magnet synchronous generator (only PMSG represents the permanent magnet synchronous generator below) as an example:

Corresponding to the results of wind speed 10m/s and wind direction 0°, the arrival wind speed of the PMSG in the first column is 10m/s, and the wake wind speeds of other PMSGs in the second, third and fourth columns are 8.71, 8.56 and 8.56 respectively. 8.51m/s, which means PMSG1 should consume more power than other PMSGs.

As shown in Figure 5a, due to the small wind speed, before fast active power control is activated, the active power at the common coupling point (PCC) in the two schemes is only 42.1MW; at 30 seconds, if fast active power control is activated, WPP The wind farm controller and PMSG controller will reduce the output power to 20MW within 5 seconds;

As shown in Figures 5b and 5c, the active power of the PMSG is the same before fast active power control is deactivated;

Before fast active power control, PMSG1, PMSG2, PMSG3 and PMSG4 generate active power of 2.88MW, 1.91MW, 1.81MW and 1.78MW respectively;

After activation of fast active power control, the output power of each PMSG was successfully reduced to 1.37MW, 0.90MW, 0.86MW and 0.85MW respectively;

It means fast active power control, and the active power of the wind turbine can be quickly controlled by adjusting the pitch angle;

In Figure 5d and Figure 5e, the pitch angle of the PMSG shows completely different dynamics. In the traditional scheme, the pitch angles of PMSG1, PMSG2, PMSG3 and PMSG4 reach peak values of 8.3° at 36.0 seconds, 8.1° at 43.4 seconds, 81° at 43.5 seconds and 8.1° at 34.4 seconds respectively, and they Slowly converges to β _ref . The pitch angle of PMSG1 with the highest wind speed fluctuates faster than other PMSGs. This is due to the wake effect. The wind speed in each column actually decreases. Then the rotor speed of PMSG1 increases and fluctuates more than other PMSGs, and the wind speed is larger [ see Figure 5f]. Other PMSGs in the traditional scheme show similar pitch angle and rotor speed dynamics because the PMSGs have similar arriving wind speeds, in the proposed scheme all PMSGs have the same propeller although the PMSGs have different arriving wind speeds pitch angle dynamics, this is because in the solution proposed by the present invention, the reference power coefficients of all PMSG are all the same. Compared with the traditional scheme, the pitch angle of the scheme proposed by the present invention also has smaller fluctuations and is determined through analysis. It quickly converges to β _ref . Compared with the traditional scheme, the scheme proposed by the present invention has The rotor speed fluctuates less because β _ref is determined to maintain the optimal rotor speed, and the pitch angle also quickly converges to 6.9°, see Figure 5g.

Test results show that: taking the wake effect into account, this scheme ensures stable active power control operation with minimal fluctuations in pitch angle and rotor speed.

The present invention is a pitch control scheme based on the rapid active power adjustment of a permanent magnet synchronous generator (PMSG) wind farm (WPP). The active power of the wind turbine can be quickly controlled by adjusting the pitch angle to reduce the amount of active power during the rapid active power control period. The pitch angle of all PMSGs fluctuates. To minimize pitch angle fluctuations, the pitch angle is determined by using analytical calculations rather than traditional proportional-integral controllers (PI). The wind farm controller sends an active power control signal to each PMSG when it receives an active power control signal from the grid. Reference power, the proposed pitch control scheme obtains the reference power coefficient from the reference power and available power Then it analytically determines the optimal pitch angle that satisfies the reference power coefficient from the reference power coefficient function. In order to reduce the fluctuation of the rotor speed, the pitch angle is determined to maintain the optimal tip speed ratio λ during active power regulation.

The above are only preferred embodiments of the present invention, and do not limit the present invention in any form; any person of ordinary skill in the industry can smoothly implement the present invention as shown in the accompanying drawings and the above description. ; However, any modifications, modifications and equivalent changes made by those skilled in the art by utilizing the technical content disclosed above without departing from the scope of the technical solution of the present invention are all equivalent implementations of the present invention. For example; at the same time, any equivalent changes, modifications and evolutions made to the above embodiments based on the essential technology of the present invention still fall within the protection scope of the technical solution of the present invention.

Claims (6)

1. A pitch angle control method considering the rapid active power adjustment of wind turbines, which is characterized by including the following steps: S1. The wind farm controller in the wind farm sends reference power to several permanent magnet synchronous generators, and then builds a mathematical model of the permanent magnet synchronous generator to obtain the power coefficient c _P of the wind turbine; S2. Construct a wake effect model of the wind farm containing multiple mathematical models of permanent magnet synchronous generators to determine several pitch angles β from the power coefficient c _P ; S3. Construct a fast active power control model of the wind farm to minimize the pitch angle β fluctuation of the permanent magnet synchronous generator. 2. A pitch angle control method considering rapid active power adjustment of wind turbines according to claim 1, characterized in that in step S1, the expression of the mathematical model of the permanent magnet synchronous generator is: P _mech ＝0.5ρAv ³ c _P (λ,β) (1) Among them, P _mech represents the mechanical input power; ρ, A and v represent air density, blade rotor swept area and wind speed respectively; c _P is the power coefficient of the wind turbine; λ is the tip speed ratio; β is the pitch angle. 3. A pitch angle control method considering the rapid active power adjustment of wind turbines according to claim 1, characterized in that the power coefficient c _P of the wind turbine is expressed as: in, 4. A pitch angle control method considering the rapid active power adjustment of wind turbines according to claim 1, characterized in that, in step S2, through the construction of a wake effect model, the method is obtained considering the wake effect. The resulting synthetic wind speed, the expression of the synthetic wind speed is: Among them, V _i represents the synthetic wind speed of WTG _j ; WTG _j is represented as the jth wind turbine; V _j is the wind speed at WTG _j without any wake; β _ji is the ratio of the area under the shadow of WTG _i to its total area; WTG _i is represented as the i-th wind turbine; x _ji is the radial distance between the j-th and i-th wind turbine units; a _j is the axial induction coefficient of WTG _j ; D _j is the diameter of the rotor area of WTG _j ; k represents the constant used to implement MPPT control; n is the total number of wind turbines. 5. A pitch angle control method considering rapid active power adjustment of wind turbines according to claim 1, characterized in that the construction of the rapid active power control model includes the following steps: S3.1. The wind farm controller allocates the required power to the permanent magnet synchronous generator to adjust the output power of the public coupling point. The allocation rule is: in, and/> They are the reference power, active power control command and available power of WTG _i ; WTG _i is represented as the i-th wind turbine; S3.2. The wind turbine controller receives the reference power from the wind farm controller. To obtain the reference power coefficient of the wind turbine/> The expression is: P _air =0.5ρAv ³ (7) Among them, P _air is the available air power; S3.3. According to the reference power coefficient of wind turbine Determine the optimal tip speed ratio λ. 6. A pitch angle control method considering rapid active power adjustment of wind turbines according to claim 1, characterized in that determining the minimum fluctuation of pitch angle β includes the following steps: S4.1. Draw characteristic curves based on different pitch angles β; S4.2. Reference power coefficient of wind turbine Determine the first straight line; S4.3. Determine the second straight line through the optimal tip speed ratio λ; S4.4. According to the characteristic curve and the first straight line and the second straight line, determine the intersection point of the three, then the intersection position is the optimal pitch angle, recorded as β _ref , which satisfies the minimum fluctuation.