A pitch angle control method considering fast active power regulation of wind turbine

Abstract

The application discloses a pitch angle control method considering fast active power regulation of a wind driven generator, which can reduce pitch angle fluctuation of all PMSGs during fast active power control, minimize fatigue damage of the wind driven generator, prolong the service life of the wind driven generator and reduce maintenance cost. P ; S2, a wake effect model of the wind farm containing mathematical models of the plurality of PMSGs is constructed to determine a plurality of pitch angles beta from the power coefficient c P ; and S3, a fast active power control model of the wind farm is constructed to satisfy minimum pitch angle beta fluctuation of the PMSGs.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of wind power generation technology, and in particular to a pitch angle control method considering fast active power regulation of a wind turbine. BACKGROUND

[0002] In order to slow down climate change and achieve the Paris climate goal, fossil energy must be replaced by renewable energy such as wind energy, hydro energy and solar energy. At present, wind energy is the second largest energy after hydroelectricity. This growth trend seems to continue in the future until 2050 to become the main source of energy production. In order to promote this positive and sustainable trend, research on wind energy and wind turbines must continue and move forward.

[0003] Under the background of the continuous increase of single machine capacity of wind turbine generator and the continuous maturity of wind power technology, the focus of large wind turbine generator is how to reduce the cost of manufacturing and operation at present; an effective way to reduce the cost of wind turbine generator is to reduce the wear of each key component of wind turbine generator, so as to improve the reliability of wind power equipment and prolong the service life of wind turbine. However, under the influence of aerodynamic effects such as wind turbulence, wind shear, tower shadow effect and yaw deviation, large wind turbine will produce unbalanced load on the impeller, and the larger the diameter of the wind wheel is, the more unbalanced the stress on the whole wind wheel surface will be, and the more obvious the unbalanced load on the impeller will be. The unbalanced load on the impeller will cause great fatigue load to the key components of wind turbine generator such as variable pitch bearing, hub, main shaft, yaw bearing and tower, which will increase the operation cost. In theory, if the pitch angle fluctuation of wind turbine is reduced through blade pitch control during the fast active power regulation control of wind turbine, the fatigue damage of wind turbine can be minimized, thereby prolonging the service life and reducing the maintenance cost. However, the pitch angle is determined by the traditional proportional integral controller (PI) at present, which has certain error and makes the result not accurate enough to be used as a basis. Therefore, it is a key problem to be solved to study the pitch control method considering wind turbine. SUMMARY

[0004] In view of the above problems, the purpose of the present application is to provide a pitch angle control method considering fast active power regulation of a wind turbine, so as to solve the problems proposed in the background.

[0005] In order to achieve the above purpose, the present application adopts the following technical solutions:

[0006] A pitch angle control method considering fast active power regulation of a wind turbine, characterized in that it comprises the following steps:

[0007] S1, a wind farm controller in a wind farm sends a reference power to several permanent magnet synchronous generators, then a mathematical model of the permanent magnet synchronous generator is built to obtain a power coefficient c P of the wind turbine;

[0008] S2, a wake effect model of the wind farm containing a plurality of mathematical models of the permanent magnet synchronous generators is built to determine a plurality of pitch angles β from the power coefficient c P ;

[0009] S3, a fast active power control model of the wind farm is built to minimize the fluctuation of the pitch angle β of the permanent magnet synchronous generator.

[0010] Further, in the step S1, the mathematical model of the permanent magnet synchronous generator is expressed as:

[0011] P mech = 0.5 ρ A v 3 c P (λ, β) (1)

[0012] wherein P mech represents the mechanical input power;

[0013] ρ, A and v respectively represent the air density, the blade rotor swept area and the wind speed;

[0014] c P is the power coefficient of the wind turbine;

[0015] λ is the tip speed ratio; β is the pitch angle;

[0016] Further, the power coefficient c P of the wind turbine is expressed as:

[0017]

[0018] wherein,

[0019]

[0020] Further, in the step S2, by building the wake effect model, a resultant wind speed considering the wake effect is obtained, and the expression of the resultant wind speed is:

[0021]

[0022] wherein V i represents the resultant wind speed of the WTG j ;

[0023] WTG j represents the jth wind turbine;

[0024] Vj is the WTG j wind speed without any wake of the WTG

[0025] β ji is the WTG i ratio of the area under the shadow to its total area;

[0026] WTG i denotes the i-th wind turbine generator;

[0027] x ji is the radial distance between the j-th and i-th wind turbine units;

[0028] a j is the axial induction factor of the WTG j ;

[0029] D j is the diameter of the rotor area of the WTG j ;

[0030] k represents a constant for implementing the MPPT control;

[0031] n is the total number of wind turbine generators;

[0032] Further, the construction of the fast active power control model comprises the following steps:

[0033] S3.1, the wind farm controller allocates the required power to the permanent magnet synchronous generator to adjust the output power of the point of common coupling, and the allocation rule is:

[0034]

[0035] wherein, and are the reference power, active power control command and available power of the WTG i , respectively;

[0036] WTG i denotes the i-th wind turbine generator;

[0037] 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:

[0038]

[0039] P air = 0.5 ρA v 3 (7)

[0040] wherein, P airis the available air power;

[0041] S3.3, determining the reference power coefficient of the wind turbine determining the optimal tip speed ratio

[0042] Further, determining the minimum fluctuation of the pitch angle

[0043] S4.1, drawing a characteristic curve based on different pitch angles

[0044] S4.2, determining the reference power coefficient of the wind turbine determining the first straight line;

[0045] S4.3, determining the second straight line through the optimal tip speed ratio

[0046] S4.4, determining the intersection point of the characteristic curve, the first straight line and the second straight line, and the intersection point is the optimal pitch angle ref , which satisfies the minimum fluctuation.

[0047] Compared with the prior art, the beneficial effects of the present application are:

[0048] The present application can reduce the fluctuation of the pitch angle of all permanent magnet synchronous generators during fast active power control, that is, from the power coefficient c P After analyzing a number of pitch angles, a fast active power control model is constructed to determine the optimal tip speed ratio during active power regulation, and finally the optimal pitch angle satisfying the minimum fluctuation is obtained ref , so as to not only ensure stable active power control operation with minimum fluctuation of the pitch angle and the rotor speed, but also minimize the fatigue damage of the wind turbine, prolong its service life and reduce maintenance costs.

[0049] The above description is only a summary of the technical solutions of the present application, in order to more clearly understand the technical means of the present application, and the content of the specification can be implemented. The following will be described in detail with the preferred embodiments of the present application and the accompanying drawings. The specific embodiments of the present application are given in detail by the following examples and the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0050] The drawings described herein are used to provide further understanding of the present application, and form a part of the present application. The schematic embodiments of the present application and their descriptions are used to explain the present application, and do not constitute an improper limitation on the present application.

[0051] Figure 1 is a flowchart of the present application;

[0052] Figure 2Fig. 1 is a graph of mechanical input power characteristic curve for a permanent magnet synchronous generator PMSG;

[0053] Figure 3 Fig. 6 is a schematic diagram of power distribution in a wind farm according to the present application;

[0054] Figure 4 Fig. 7 is a graph of c P Fig. 8 is a graph of λ;

[0055] Figure 5a Fig. 9 is a graph of active power of a wind power plant WPP;

[0056] Figure 5b Fig. 10 is a graph of active power of a permanent magnet synchronous generator PMSG in a conventional solution;

[0057] Figure 5c Fig. 11 is a graph of active power of a permanent magnet synchronous generator PMSG in an embodiment according to the present application;

[0058] Figure 5d Fig. 12 is a graph of pitch angle of a permanent magnet synchronous generator PMSG in a conventional solution;

[0059] Figure 5e Fig. 13 is a graph of pitch angle of a permanent magnet synchronous generator PMSG in an embodiment according to the present application;

[0060] Figure 5f Fig. 14 is a graph of rotor speed of a permanent magnet synchronous generator PMSG in a conventional solution;

[0061] Figure 5g Fig. 15 is a graph of rotor speed of a permanent magnet synchronous generator PMSG in an embodiment according to the present application. DETAILED DESCRIPTION

[0062] The principles and advantages of the present application will be described in greater detail below with reference to the accompanying drawings, in which:

[0063] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description herein is for describing particular embodiments only and is not intended to be limiting of the application.

[0064] The present embodiment is based on Figure 1A flow chart of a method for pitch angle control considering fast active power regulation of wind power generator is shown, and a pitch angle control model is analyzed.

[0065] Please refer to the attached drawings Figure 1 A method for pitch angle control considering fast active power regulation of wind power generator, comprising the following steps:

[0066] S1, the system controller sends instructions to the wind farm controller (WPP controller) in the wind farm, and then the wind farm controller in the wind farm sends a reference power to a plurality of permanent magnet synchronous generators, and then a mathematical model of the permanent magnet synchronous generator (PMSG) is constructed to obtain the power coefficient c P of the wind power generator.

[0067] In the step S1, the expression of the mathematical model of the permanent magnet synchronous generator is:

[0068] P mech = 0.5 ρ A v 3 c P (λ, β) (1)

[0069] Wherein, P mech represents the mechanical input power; the wind power generator is to convert wind power into mechanical input power P mech .

[0070] ρ, A and v respectively represent air density, blade rotor swept area and wind speed;

[0071] c P is the power coefficient of the wind power generator; the power coefficient c P depends on the tip speed ratio λ and the pitch angle β.

[0072] λ is the tip speed ratio; β is the pitch angle.

[0073] Further, the power coefficient c P of the wind power generator is expressed as:

[0074]

[0075] Wherein,

[0076]

[0077] The typical configuration of the permanent magnet synchronous generator includes a machine side converter (MSC) for extracting maximum power from the wind and a grid side converter (GSC) for maintaining the DC link voltage and injecting the required reactive power to the grid.

[0078] The mechanical input power P of the wind turbine in maximum power point tracking (MPPT) control mode mech With rotor speed ω r The characteristic curves and maximum power curves are as follows: Figure 2 As shown, the mechanical input power P under different wind speeds mech The relationship between the fan speed and the fan rotation speed is expressed as:

[0079]

[0080] Where, k opt It is a constant used for maximum power point tracking control; ω opt That is the optimal rotor speed.

[0081] Figure 1 In the diagram, Tr.1 and Tr.2 represent different connecting transformers;

[0082] WPP stands for Wind Power Plant. Each wind power plant has several wind turbines (WTG), and each wind turbine corresponds to a permanent magnet synchronous generator (PMSG).

[0083] S2. Construct a wake effect model for a wind farm that includes mathematical models of multiple permanent magnet synchronous generators, in order to obtain data from the power coefficient c. P Several pitch angles β are determined in the middle;

[0084] In step S2, multiple wind turbine units in a wind farm may have multiple wakes of varying degrees. Therefore, when determining the wind speed of a wind turbine, the overlapping area between the corresponding wind turbines should be considered. Based on the law of conservation of momentum, WTG... j The composite wind speed V i It can be represented as:

[0085]

[0086] Among them, V i Indicates WTG j The composite wind speed;

[0087] WTG j Let j be the j-th wind turbine;

[0088] V j It's WTG j Wind speed when there is no wake;

[0089] β ji It's WTG i The ratio of the area under shadow to its total area;

[0090] WTG i Let i be the i-th wind turbine;

[0091] x ji is the radial distance between the jth and ith wind turbine units;

[0092] a j is the axial induction factor of the WTG j ;

[0093] D j is the diameter of the WTG j rotor area;

[0094] k represents a constant for implementing MPPT control;

[0095] n is the total number of wind turbines;

[0096] The wake effect mainly affects the wind speed through the wind turbine, so formula (5) is to consider the influence of the wake effect on the wind speed of the wind turbine. The influence of the wake effect on the model is the influence on the wind speed, and the resultant wind speed is the wind speed after considering the influence of the wake effect;

[0097] S3, a fast active power control model of the wind farm is constructed to minimize the fluctuation of the pitch angle β of the permanent magnet synchronous generator;

[0098] The construction of the fast active power control model includes the following steps:

[0099] S3.1, as shown in the accompanying drawings, the wind farm controller allocates the required power to the permanent magnet synchronous generator to adjust the output power of the point of common coupling (i.e. the grid-side coupling point in the PCC) The output power of the point of common coupling (PCC) is adjusted to 20% of the rated capacity of the wind farm controller, and the allocation rule is: Figure 3 Figure 1

[0100]

[0101] wherein, and are the reference power, active power control command and available power of the WTG i , respectively;

[0102] WTG i represents the ith wind turbine;

[0103] S3.2, under normal circumstances, the wind turbine controller adjusts the permanent magnet synchronous generator in the MPPT control mode, however, when the wind farm horizontal 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:

[0104] ​​

[0105] P air =0.5ρAv 3 (8)

[0106] Among them, P air It is the available air power;

[0107] S3.3, Based on the reference power factor of the wind turbine. Determine the optimal tip speed ratio λ;

[0108] Further, determining the minimum pitch angle β fluctuation includes the following steps:

[0109] S4.1 Obtain different pitch angles β from the table of functions, and then plot characteristic curves based on different pitch angles β;

[0110] Table functions refer to Figure 4 c in P -λ curve, according to c P -λ curve, converted into tabular form;

[0111] S4.2, Reference power coefficient of wind turbine Determine the first straight line (i.e., a horizontal line);

[0112] S4.3 Determine the second straight line (i.e., a vertical straight line) by using the optimal tip speed ratio λ;

[0113] S4.4. Based on the characteristic curve and the first and second straight lines, determine the intersection point of the three lines. The position of the intersection point is the optimal pitch angle, denoted as β. ref This satisfies the requirement of minimal fluctuation.

[0114] This invention is illustrated using a four-column permanent magnet synchronous generator (hereinafter referred to as PMSG to represent permanent magnet synchronous generator):

[0115] The results correspond to a wind speed of 10 m / s and a wind direction of 0°. The PMSG in the first column reaches a wind speed of 10 m / s, while the wake wind speeds of the other PMSGs in the second, third, and fourth columns are 8.71, 8.56, and 8.51 m / s, respectively. This means that PMSG1 should consume more power than the other PMSGs.

[0116] like Figure 5a As shown, due to the low wind speed, the active power at the point of common coupling (PCC) in both schemes is only 42.1MW before the fast active power control is activated; at 30 seconds, if the fast active power control is activated, the WPP wind farm controller and PMSG controller will reduce the output power to 20MW within 5 seconds.

[0117] As Figure 5b and 5c shown, the active power of PMSG is the same before the fast active power control is deactivated;

[0118] Before the fast active power control, PMSG1, PMSG2, PMSG3 and PMSG4 generate active power of 2.88 MW, 1.91 MW, 1.81 MW and 1.78 MW, respectively;

[0119] After the fast active power control is activated, the output power of each PMSG is successfully reduced to 1.37 MW, 0.90 MW, 0.86 MW and 0.85 MW, respectively;

[0120] The fast active power control can be achieved by adjusting the pitch angle, which indicates that the fast active power control of the wind turbine can be achieved by adjusting the pitch angle;

[0121] In Figure 5d and Figure 5e , the pitch angles of PMSGs show completely different dynamics. In the conventional scheme, the pitch angles of PMSG1, PMSG2, PMSG3 and PMSG4 reach the peak values of 8.3° at 36.0 s, 8.1° at 43.4 s, 81° at 43.5 s and 8.1° at 34.4 s, respectively, and they slowly converge to β ref The pitch angle of PMSG1 with the largest wind speed fluctuates faster than those of the other PMSGs, which is due to the wake effect. The wind speed of each row is actually decreasing, so the rotor speed of PMSG1 increases and fluctuates more than those of the other PMSGs, and the wind speed is larger [see Figure 5f ]. The other PMSGs in the conventional scheme show similar pitch angle and rotor speed dynamics because the PMSGs have similar reached wind speeds. In the proposed scheme of the present application, although the PMSGs have different reached wind speeds, all the PMSGs have the same pitch angle dynamics because the reference power coefficients of all the PMSGs are the same. Compared with the conventional scheme, the pitch angle of the proposed scheme also has smaller fluctuations and is quickly determined to converge to β ref Compared with the conventional scheme, the rotor speed of the proposed scheme has smaller fluctuations because β ref is determined to maintain the optimal rotor speed, and the pitch angle is also quickly determined to converge to 6.9°, see Figure 5g .

[0122] The test results show that the scheme ensures stable active power control operation with minimal fluctuations in the pitch angle and rotor speed, taking into account the wake effect.

[0123] The present application is a kind of pitch control scheme based on permanent magnet synchronous generator (PMSG) wind farm (WPP) fast active regulation, which can realize the fast control of the active power of the fan by adjusting the pitch angle, so as to reduce the pitch angle fluctuation of all PMSGs during the fast active power control. In order to minimize the pitch angle fluctuation, the pitch angle is determined by using analytical calculation instead of traditional proportional integral controller (PI), when receiving the active power control signal from the power grid, the wind farm controller sends the reference power to each PMSG, the proposed pitch control scheme obtains the reference power coefficient from the reference power and the available power Then it determines the optimal pitch angle that satisfies the reference power coefficient from the reference power coefficient function analytically, in order to reduce the fluctuation of the rotor speed, the pitch angle is determined to keep the optimal tip speed ratio λ during the active power regulation.

[0124] The above is only the preferred embodiment of the present application, and does not limit the present application in any form; any person skilled in the art can easily implement the present application according to the drawings and the above description; however, any equivalent changes, modifications and evolution of the above disclosed technical content within the scope of the technical scheme of the present application are equivalent embodiments of the present application; at the same time, any equivalent changes, modifications and evolution of the above embodiments according to the essential technology of the present application are still within the protection scope of the technical scheme of the present application.

Claims

1. A method of pitch angle control taking into account fast active power regulation of a wind power generator, characterized in that, The method comprises the following steps: S1. A wind farm controller in a wind farm sends a reference power to several permanent magnet synchronous generators, then builds a mathematical model of the permanent magnet synchronous generator to obtain a power coefficient c of the wind generator P ; S2, constructing a wake effect model of the wind farm comprising a plurality of permanent magnet synchronous generator mathematical models to determine a number of pitch angles β from a power coefficient c P from the power coefficient c S3, a fast active power control model of the wind farm is constructed to minimize the pitch angle β fluctuation of the permanent magnet synchronous generator; In the step S1, the expression of the mathematical model of the permanent magnet synchronous generator is: （1） where P mech represents the mechanical input power; ρ, A and v respectively represent air density, blade rotor swept area and wind speed; c P is the power coefficient of the wind turbine; λ is the tip speed ratio; β is the pitch angle; Power coefficient c of a wind turbine P is represented as: （2） Wherein, （3） In the step S2, the synthetic wind speed considering the wake effect is obtained through the construction of the wake effect model, and the expression of the synthetic wind speed is: （4） wherein V i represents the resultant wind speed of the WTG j ; WTG j denotes the jth wind turbine; V j is the WTG j wind speed without any wake at the WTG β ji is the WTG i the ratio of the area under the shadow to its total area; WTG i denotes the i-th wind turbine; x ji is the radial distance between the jth and ith wind turbine units; a j is the axial induction coefficient of the WTG j ; D j is a WTG j diameter of the rotor area; k represents a constant for realizing MPPT control; n is the total number of wind generators; The determination of the minimum pitch angle β fluctuation comprises the following steps: S4.1, a characteristic curve is drawn based on different pitch angles β; S4.2, reference power coefficient of the wind turbine determining a first straight line; S4.3, a second straight line is determined through the optimal tip speed ratio λ; S4.4、According to the characteristic curve and the first straight line, the second straight line, determine the intersection point, the intersection point position is the best pitch angle, recorded as β ref , meet the minimum fluctuation.

2. A pitch angle control method considering fast active power regulation of wind power generators according to claim 1, characterized in that, The construction of the fast active power control model comprises 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 point of common coupling, and the allocation rule is: （5） wherein, , and are the reference power, active power control command and available power of the WTG i , respectively. WTG i denotes the i-th wind turbine; S3.2 The wind generator controller receives a reference power from the wind farm controller to obtain a reference power coefficient for the wind generator with the expression （6） （7） where P air is the available air power; S3.

3. determining an optimum tip speed ratio λ based on a reference power coefficient of the wind power generator , determining an optimum tip speed ratio λ.

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