A controller for a wind turbine generator set

Abstract

The present invention discloses a DSP controller for a wind turbine generator set, including a control strategy algorithm module and a power limiting algorithm module, wherein the control strategy algorithm module includes a filtering algorithm unit and a control algorithm unit. The filtering algorithm unit adopts a multi-stage finite step response digital filter algorithm, and adopts a reasonable order to continuously attenuate the target frequency; the control algorithm unit adopts a quadratic optimal control algorithm, which improves the stability and response speed of the original PID algorithm, and realizes that the impeller speed effectively runs at the set target speed by controlling the target speed of the impeller speed, reduces the impeller speed fluctuation range and reduces the impeller speed over-limit fault, and reduces the complete machine limit load and fatigue load; the power limiting algorithm module optimizes the loss coefficient into a set of transfer functions of the relationship between the power demand of the power grid and the loss coefficient, which is conducive to the precise control of the power limiting algorithm of the wind turbine and improves the response rate of the complete machine to the power grid dispatch.

Description

Technical Field

[0001] The present invention relates to the technical field of wind power generation, and in particular to a controller for a wind power generator set. Background Art

[0002] The control algorithm of a wind turbine is the core algorithm that carries the ultimate load and fatigue load of the whole machine. It is the main means to effectively avoid the resonance of the whole machine and the speed limit, and it is also the key solution to avoid damage to the large components of the whole machine. With the continuous iteration and upgrade of the "higher tower, longer blades, and larger capacity" units, compared with the previous small MW units, the resonance points of the new large MW units are increasing, and the probability of blade breakage is increasing, which directly affects the reliability, stability and safety of the whole machine.

[0003] At present, the controllers used in wind turbines are mainly integrated in the PLC of the main control cabinet of the whole machine manufacturer. A low-pass filter, two (or more) band-stop filters, and the classic PID algorithm are used to control the whole machine. The filters used are all classic IIR (infinite response function) type to achieve attenuation filtering of the high-frequency burr signals of the blades, the first-order resonance frequency of the tower, and the resonance frequency of the blades, so as to avoid the continuous accumulation of related frequency energy during the entire control energy cycle and stimulate the resonance of the whole machine. The classic PID algorithm is used to calculate the variable pitch rate and torque requirements of the whole machine, thereby realizing the function of converting mechanical energy into electrical energy for the whole unit and achieving smooth operation of the whole machine.

[0004] At present, wind turbine controllers are used in units with "higher towers, longer blades, and larger capacity", and they mainly have the following shortcomings: 1. The controller algorithm is mainly integrated into the PLC of the whole machine manufacturer, and the optimization and upgrade of the software algorithm can only be realized by the whole machine manufacturer. Third-party manufacturers cannot optimize and upgrade their algorithms; 2. The filter algorithm used cannot effectively attenuate the signals such as the first-order and second-order resonance frequencies of the tower, the inherent modal frequencies of the blades, and the speed frequency in the impeller speed, resulting in an increase in the ultimate load and fatigue load of the whole machine, which directly affects the reliability of large components such as the main bearings, blades, and gearboxes of the generator set; 3. The stability and balance of the impeller speed control of the PID algorithm used are gradually reduced, and there are problems such as large fluctuations in the control target speed and easy over-limit of the impeller speed when encountering strong gusts, which affects the reliability of the impeller and the compliance rate of the whole machine power curve; 4. In the power limiting algorithm, the algorithm obtains a fixed value for the whole machine loss coefficient, which will affect the power grid's higher demand for wind farm energy control. Summary of the invention

[0005] The present invention provides a controller for a wind turbine generator set, which adds corresponding hardware layout and software algorithm on the basis of the original control logic to solve the technical problems raised in the background technology.

[0006] The technical solution adopted by the present invention to solve the above technical problems is:

[0007] A controller for a wind turbine generator set, the wind turbine generator set comprising a main control PLC system, a current conversion system and a pitch control system, the controller being a DSP controller, comprising a control strategy algorithm module and a power limiting algorithm module; the main control PLC system sends a demand instruction to the controller, the controller converts the demand instruction (power grid demand power) sent by the PLC system into corresponding mechanical power through the power limiting algorithm module, calculates the current set speed and set torque of the impeller, and sends the set speed and set torque of the impeller to the control strategy algorithm module;

[0008] The control strategy algorithm module includes a filtering algorithm unit and a control algorithm unit; after the filtering algorithm unit attenuates the abnormal frequency in the impeller speed, the control algorithm unit calculates the required torque and pitch rate of the impeller, and sends the reference torque instruction and pitch rate instruction to the variable flow system and the pitch system respectively through the main control PLC system.

[0009] Furthermore, the filtering algorithm unit belongs to a FIR (finite step response) filter, and adopts a multi-stage digital filter algorithm, and the formula is as follows:

[0010] ;

[0011] In the formula, Represents the system output value, Represents the system input value, represents the filter coefficient; , .

[0012] Furthermore, the control algorithm unit adopts a quadratic optimal control algorithm, which uses the integral of a quadratic function as a performance indicator, and the integral of the quadratic function is composed of a state variable and a control variable of the system;

[0013] Assume the control state equation of the system is:

[0014] ;

[0015] ;

[0016] In the formula, is an n-dimensional vector, is an r-dimensional vector, is the m-dimensional output vector, They are n*n, n*r, n*m, and m*r matrices respectively, and the quadratic performance index function is:

[0017] ;

[0018] Where F is a symmetric non-negative definite constant matrix, Q is a symmetric non-negative time-varying matrix, and R is a positive definite symmetric time-varying matrix. The optimal state feedback equation is solved as follows:

[0019] ;

[0020] and, ;

[0021] Where P(t) is an n*n dimensional symmetric non-negative matrix, and the above formula is the Riccati matrix differential equation;

[0022] Substituting the optimal state feedback equation into the state equation, the linear vector differential equation is obtained as follows:

[0023] ;

[0024] On the basis of the limiting conditions of the conventional algorithm, a performance index function J is added. By solving the minimum value of the performance index function J, the stability and response speed of the control algorithm can be improved.

[0025] Furthermore, the power limiting algorithm module multiplies the grid demand power by the whole machine loss coefficient , the corresponding mechanical power is obtained, and the mechanical power is calculated by the power limiting algorithm to obtain the set speed and set torque of the current impeller, which are then passed to the control strategy algorithm module for execution; among them, the loss coefficient The calculation formula is as follows:

[0026] ;

[0027] represents the power demand of the power grid, Indicates the power demand of the power grid The loss coefficient is obtained by fitting multiple sets of test data, and the loss coefficient equation is obtained as follows:

[0028] ;

[0029] In the formula, and is the coefficient of the fitting equation; the loss coefficient of each power segment can be calculated through this equation.

[0030] Compared with the prior art, the present invention has the following advantages or technical effects:

[0031] 1. It adopts a multi-stage digital filter algorithm, which belongs to the FIR type (finite step response) filter. This type of filter solution has a linear phase and can use a variety of solutions to achieve low-pass and band-stop filter functions. It can use a reasonable order to continuously attenuate the target frequency, reduce the resonance characteristics of the whole machine, and effectively reduce the limit load and fatigue load of the whole machine.

[0032] 2. A quadratic optimal control algorithm is adopted, and a performance index function J is added based on the limiting conditions of the conventional algorithm. By solving the minimum value of the performance index function J, the stability and response speed of the control algorithm are improved, the target speed of the impeller is better controlled, the fluctuation range of the impeller speed is reduced, and the impeller speed over-limit fault is reduced, so that the impeller control speed can be stably operated at the set target speed and the ultimate load of the whole machine can be effectively reduced.

[0033] 3. The loss coefficient in the adopted power limiting algorithm is optimized as a set of transfer functions of the relationship between the power demand of the power grid and the loss coefficient, which is beneficial to the power control of the wind turbine, improves the response rate of the whole machine to the power grid dispatch, and better meets the dispatch requirements of the power grid.

[0034] 4. Using a hardware technology layout solution, with the controller as a separate component, third-party manufacturers can test, compare, and verify their own algorithms on the wind turbine to increase the scope of use of the control algorithm. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the technical solutions implemented in the present invention, the accompanying drawings required for describing the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0036] Figure 1 A logic diagram of the controller and other systems of the whole machine provided in this embodiment;

[0037] Figure 2 It is the logic diagram of the torque control algorithm of the DSP controller;

[0038] Figure 3 It is the logic relationship diagram of the pitch rate control algorithm of the DSP controller;

[0039] Figure 4 This is the flow chart of the power limiting algorithm. DETAILED DESCRIPTION

[0040] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0041] like Figure 1 As shown, this embodiment provides a controller for a wind turbine generator set, the wind turbine generator set includes a main control PLC system, a current conversion system and a pitch control system, and the DSP controller includes a control strategy algorithm module and a power limiting algorithm module; wherein the current conversion system and the pitch control system are the actuators of the wind turbine. The main control PLC system sends a demand instruction to the DSP controller, and the controller converts the demand instruction (grid demand power) sent by the PLC system into the corresponding mechanical power through the power limiting algorithm module, calculates the current set speed and set torque of the impeller, and sends the set speed and set torque of the impeller to the control strategy algorithm module. The control strategy algorithm module includes a filtering algorithm unit and a control algorithm unit. After the filtering algorithm unit attenuates the abnormal frequency in the impeller speed, the required torque and pitch control rate are calculated by the control algorithm unit, and the reference torque instruction and pitch control rate instruction are sent to the current conversion system and the pitch control system respectively through the main control PLC system. Under the whole system process, the efficient and stable operation of the wind turbine generator set is realized.

[0042] The filter used in existing wind turbines is an IIR (infinite step response) filter, and the filter algorithm is as follows:

[0043] ,

[0044] The low-pass filter and band-stop filter used in fans belong to this category. The disadvantage is that the parameter design of such filters is difficult, and there are too many filter groups that cannot be used, which can easily lead to problems such as speed oscillation and incomplete attenuation of abnormal frequency signals, making it difficult to ensure the stable operation of the entire machine.

[0045] The controller provided in this embodiment adopts a multi-stage digital filter in its filtering algorithm unit, which belongs to a FIR (finite step response) filter. The algorithm of the multi-stage digital filter is as follows:

[0046] ;

[0047] In the formula, Represents the system output value, Represents the system input value, represents the filter coefficient; , .

[0048] This type of filter solution has a linear phase and can adopt a variety of solutions to realize low-pass and band-stop filter functions. It can use a reasonable order to continuously attenuate the target frequency, thereby achieving stable operation of the target speed, reducing the resonance characteristics of the whole machine, and effectively reducing the ultimate load and fatigue load of the whole machine.

[0049] The control algorithm used by existing wind turbines is a conventional PID algorithm, which consists of three control links: proportional link, integral link and differential link; the specific transfer function is as follows:

[0050] ;

[0051] Where T is the sampling period, , , are proportional constant, integral constant and differential constant respectively. The intermediate variables are calculated without any control constraints.

[0052] The controller provided in this embodiment adopts the optimal LQR control algorithm in its control algorithm unit, and uses the integral of a quadratic function as a performance indicator, where the integral of the function is composed of the state variables and control variables of the system;

[0053] Assume the control state equation of the system is:

[0054] ;

[0055] ;

[0056] In the formula, is an n-dimensional vector, is an r-dimensional vector, is the m-dimensional output vector, They are n*n, n*r, n*m, and m*r matrices respectively, and the quadratic performance index function is:

[0057] ;

[0058] Where F is a symmetric non-negative definite constant matrix, Q is a symmetric non-negative time-varying matrix, and R is a positive definite symmetric time-varying matrix. The optimal state feedback equation is solved as follows:

[0059] ;

[0060] and, ;

[0061] Where P(t) is an n*n dimensional symmetric non-negative matrix, and the above formula is the Riccati matrix differential equation;

[0062] Substituting the optimal state feedback equation into the state equation, the linear vector differential equation is obtained as follows:

[0063] ;

[0064] On the basis of the limiting conditions of the conventional algorithm, a performance index function J is added. By solving the minimum value of the performance index function J, the stability and response speed of the control algorithm can be improved.

[0065] Compared with the classic PID control algorithm, the optimal LQR control algorithm forms a performance index function with input u(t) and intermediate state variable x(t) as variables. The state equation has high stability and can better control the target speed of the impeller, reduce the fluctuation range of the impeller speed and reduce the impeller speed over-limit fault.

[0066] Figure 2 The logical relationship diagram of the torque control algorithm of the DSP controller provided in this embodiment, after the impeller speed attenuates the abnormal frequency through the multi-stage digital filter, the reference torque of the impeller is calculated by the optimal LQR control algorithm, and the reference torque command is sent to the converter system, achieving the goal of converting the mechanical energy of the fan into electrical energy. By replacing the classic PID control algorithm with the optimal LQR control algorithm, the fluctuation range of the target speed of the impeller speed is better controlled, the limit load of the whole machine is effectively reduced, and the stability of the whole machine is effectively improved.

[0067] Figure 3 The logical relationship diagram of the pitch control algorithm of the DSP controller provided in this embodiment, after the impeller speed attenuates the abnormal frequency through the multi-stage digital filter, the required pitch rate of the blade is calculated through the optimal LQR control algorithm and the gain scheduling function, and the pitch rate command is sent to the pitch system to achieve the control demand target of more stable impeller speed. By replacing the classic PID control algorithm with the optimal LQR control algorithm, the optimization of the whole machine control logic algorithm can be achieved, and the whole machine control target can be more stable and the response speed can be faster.

[0068] Therefore, this embodiment adopts a multi-stage digital filter algorithm and an LQR algorithm, which can better attenuate the abnormal resonance frequency in the impeller speed, better control the fluctuation range of the speed, and achieve the effective operation of the machine's limit load and fatigue load within a controllable range, and reduce resonance failures and impeller speed over-limit failures, thereby protecting the safety and reliability of large components.

[0069] The power limiting algorithm used by the controller in the existing wind turbine generator set is mainly to multiply the power demanded by the grid by the fixed loss coefficient K of the whole machine to obtain the corresponding mechanical power. The mechanical power is calculated by the power limiting algorithm to obtain the set speed and torque of the current impeller and passed to the control strategy algorithm module for execution. The calculation formula of the whole machine loss coefficient K is as follows:

[0070] ,

[0071] It can be seen from the above formula that the loss coefficient k of the unit is calculated based on the maximum mechanical power corresponding to the rated power value of the unit. It is a fixed value coefficient, but the k values ​​corresponding to different power points are slightly different, which affects the power grid's power regulation of the entire machine.

[0072] like Figure 4 As shown, the power limiting algorithm module provided in this embodiment is to multiply the grid demand power by the whole machine loss gain coefficient , the corresponding mechanical power is obtained, and the mechanical power is calculated by the power limit algorithm to obtain the current impeller set speed and set torque, which are passed to the control strategy algorithm module for execution; among them, the loss gain coefficient The calculation formula is as follows:

[0073] ,

[0074] represents the power demand of the power grid, Indicates the power demand of the power grid The loss coefficient is obtained by fitting multiple sets of test data, and the loss coefficient equation is obtained as follows:

[0075] ;

[0076] In the formula, and is the coefficient of the fitting equation; the loss coefficient of each power segment can be calculated through this equation.

[0077] From the above formula, we can know that the loss gain function of the unit is It is calculated based on the fitting of each power point of the unit and the corresponding loss value. Compared with the single K value in the original plan, the calculated mechanical power point value will better meet the needs of the power grid.

[0078] In addition, the controller provided in this embodiment can be used as a separate component, and a third-party manufacturer can test, compare, and verify its own algorithm on the wind turbine to improve the scope of use of the control algorithm.

[0079] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A controller for a wind turbine generator set, characterized in that: The wind turbine generator set includes a main control PLC system, a current conversion system and a pitch control system. The controller is a DSP controller, including a control strategy algorithm module and a power limiting algorithm module. The main control PLC system sends a demand instruction to the controller, and the controller converts the demand instruction sent by the main control PLC system into corresponding mechanical power through the power limiting algorithm module, calculates the current set speed and set torque of the impeller, and sends the set speed and set torque of the impeller to the control strategy algorithm module. The control strategy algorithm module includes a filtering algorithm unit and a control algorithm unit; after the filtering algorithm unit attenuates the abnormal frequency in the impeller speed, the control algorithm unit calculates the required torque and pitch rate of the impeller, and sends the reference torque instruction and pitch rate instruction to the variable flow system and the pitch system respectively through the main control PLC system; The specific steps of converting the demand instruction sent by the main control PLC system into the corresponding mechanical power through the power limiting algorithm module and calculating the set speed and set torque of the current impeller are: The power limiting algorithm module multiplies the grid demand power by the whole machine loss coefficient K i (P i ), the corresponding mechanical power is obtained, and the mechanical power is calculated by the power limiting algorithm to obtain the set speed and set torque of the current impeller, which are then passed to the control strategy algorithm module for execution; among them, the loss coefficient K i (P i ) is calculated as follows: P i Indicates the power demand of the power grid, K i (P i ) represents the grid demand power P i The loss coefficient is obtained by fitting multiple sets of test data, and the loss coefficient equation is obtained as follows: k i (P i )=a*P i +b; In the formula, a and b are the coefficients of the fitting equation; the loss coefficient of each power range can be calculated through this equation; The specific steps of calculating the required torque and pitch rate of the impeller through the control algorithm unit are as follows: The control algorithm unit adopts a quadratic optimal control algorithm, which uses the integral of a quadratic function as a performance indicator, and the integral of the quadratic function is composed of a state variable and a control variable of the system; Assume the control state equation of the system is: y(t)=C(t)*x(t)+D(t)*u(t); Where x(t) is an n-dimensional vector, u(t) is an r-dimensional vector, y(t) is an m-dimensional output vector, A(t), B(t), C(t), and D(t) are n*n, n*r, n*m, and m*r matrices respectively, and the quadratic performance index function is: Where F is a symmetric non-negative definite constant matrix, Q is a symmetric non-negative time-varying matrix, and R is a positive definite symmetric time-varying matrix. The optimal state feedback equation is solved as follows: u * (t)=R -1 (t)*B T (t)*P(t)*x(t); and, Where P(t) is an n*n dimensional symmetric non-negative matrix, and the above formula is the Riccati matrix differential equation; Substituting the optimal state feedback equation into the state equation, the linear vector differential equation is as follows:

2. A controller for a wind turbine generator set according to claim 1, characterized in that: The filtering algorithm unit adopts a multi-stage digital filter algorithm, and the formula is as follows: f(x1)=f(x 11 )*h 11 +f(x 12 )*h 12 +f(x 13 )*h 13 +f(x 14 )*h 14 +f(x 15 )*h 15 +f(x 16 )*h 16 +f(x 17 )*h 17 +f(x 18 )*h 18 ; f(x2)=f(x 21 )*h 21 +f(x 22 )*h 22 +f(x 23 )*h 23 +f(x 24 )*h 24 +f(x 25 )*h 25 +f(x 26 )*h 26 +f(x 27 )*h 27 +f(x 28 )*h 28 ; f(x3)=f(x 31 )*h 31 +f(x 32 )*h 32 +f(x 33 )*h 33 +f(x 34 )*h 34 +f(x 35 )*h 35 +f(x 36 )*h 36 +f(x 37 )*h 37 +f(x 38 )*h 38 ; f(x4)=f(x 41 )*h 41 +f(x 42 )*h 42 +f(x 43 )*h 43 +f(x 44 )*h 44 +f(x 45 )*h 45 +f(x 46 )*h 46 +f(x 47 )*h 47 +f(x 48 )*h 48 ; f(x5)=f(x 51 )*h 51 +f(x 52 )*h 52 +f(x 53 )*h 53 +f(x 54 )*h 54 +f(x 55 )*h 55 +f(x 56 )*h 56 +f(x 57 )*h 57 +f(x 58 )*h 58 ; f(x6)=f(x 61 )*h 61 +f(x 62 )*h 62 +f(x 63 )*h 63 +f(x 64 )*h 64 +f(x 65 )*h 65 +f(x 66 )*h 66 +f(x 67 )*h 67 +f(x 68 )*h 68 ; f(x7)=f(x 71 )*h 71 +f(x 72 )*h 72 +f(x 73 )*h 73 +f(x 74 )*h 74 +f(x 75 )*h 75 +f(x 76 )*h 76 +f(x 77 )*h 77 +f(x 78 )*h 78 ; In the formula, f(x n ) represents the system output value, f(x nm ) represents the system input value, h nm Represents the filter coefficients; n=1, 2, 3, 4, 5, 6, 7, m=1, 2, 3, 4, 5, 6, 7, 8.

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