Multi-objective pitch control, system and equipment for a floating wind turbine

Abstract

A multi-objective pitch control, system and device for a floating wind turbine provided by the present invention include: Step 1, respectively filtering the obtained wind turbine speed signal and the basic pitch angular velocity signal corresponding to the floating wind turbine to obtain the filtered wind turbine speed signal and the filtered basic pitch angular velocity; Step 2, calculating the error variables of the wind turbine speed error and the basic pitch angle error according to the obtained filtered wind turbine speed signal and the filtered basic pitch angular velocity; Step 3, processing the obtained error variables to respectively obtain three gains of the PID controller and the integral separation logic quantity; Step 4, calculating the pitch angle control quantity according to the obtained error variables, three gains of the PID controller and the integral separation logic quantity; Step 5, realizing the pitch control of the blade according to the obtained pitch angle control quantity; The present invention can comprehensively improve the stability of the wind turbine speed and the basic pitch of the floating wind turbine above the rated wind speed.

Description

Technical Field

[0001] The invention belongs to the technical field of wind power generation, and particularly relates to a multi-objective pitch control, system and device for a floating wind turbine generator unit. Background Art

[0002] With the rapid development of the wind power industry, onshore wind energy resources have been gradually exhausted, and offshore wind power has become the focus of new wind power installations. The near-shore wind power installations mainly use fixed offshore wind turbine generator units. From the economic perspective, floating offshore wind turbine generator units are the first choice for deep-water offshore wind power installations. Different from fixed offshore wind turbine generator units and onshore wind turbine generator units, floating wind turbine generator units introduce additional degrees of freedom in the floating foundation, greatly increasing the uncertainty and instability of the system.

[0003] Above the rated wind speed, the objectives of the wind turbine generator unit control system are maximum power and maximum wind turbine speed limitation. At this time, the generator electromagnetic torque often remains at the rated torque or is the ratio of the rated power to the current speed. The pitch control system changes the aerodynamic force of the wind turbine by adjusting the pitch angle, so that the generator speed and power are maintained at the rated values. The classical pitch controller detects the wind turbine speed, compares the wind turbine speed with the rated speed, calculates the pitch angle control quantity through a PID controller, and sends the pitch angle control quantity to the pitch actuator. Since the sensitivity of the speed or power with respect to the pitch angle is significantly different at different wind speeds, that is, the wind turbine speed or power control system is non-linear, the classical PID cannot meet the dynamic performance requirements in a wide range of wind speeds. In order to achieve non-linear control, some existing pitch control technologies perform non-linear scheduling on the gain parameters of the classical PID according to the real-time pitch angle signal or wind speed signal. However, the scheduling rule is based on the steady-state operating point and small disturbance assumption. Due to the problems of large inertia and rapid wind speed change, the wind turbine generator unit often deviates from the steady-state operating point, and its operating conditions do not meet the small disturbance assumption. In addition, for a floating wind turbine generator unit affected by the coupled action of wind, wave and current, its operating conditions do not meet the steady-state operating point and small disturbance assumption even more. More importantly, the pitch control of the floating wind turbine generator unit will induce a negative thrust gradient, which will introduce negative aerodynamic damping in the pitching mode of the floating foundation. If the power constancy is blindly pursued, the pitching amplitude will be significantly increased. Therefore, it is of great significance to develop a non-linear pitch control method for a floating wind turbine generator unit that takes into account the pitching motion of the foundation and the wind turbine speed. Summary of the Invention

[0004] The purpose of the invention is to provide a multi-objective pitch control, system and device for a floating wind turbine generator unit, which solves the defect of poor stability of the wind turbine speed and the foundation pitching of the floating wind turbine generator unit above the rated wind speed.

[0005] In order to achieve the above purpose, the technical solution adopted by the invention is:

[0006] A multi-objective pitch control method for a floating wind turbine provided by the present invention includes the following steps:

[0007] Step 1, respectively filter the obtained wind turbine speed signal and the basic pitch angular velocity signal corresponding to the floating wind turbine to obtain the filtered wind turbine speed signal and the filtered basic pitch angular velocity;

[0008] Step 2, calculate the error variables of the wind turbine speed error and the basic pitch angle error according to the obtained filtered wind turbine speed signal and the filtered basic pitch angular velocity;

[0009] Step 3, process the obtained error variables to respectively obtain three gains of the PID controller and the integral separation logic quantity;

[0010] Step 4, calculate the pitch angle control quantity according to the obtained error variables, three gains of the PID controller and the integral separation logic quantity;

[0011] Step 5, realize the pitch control of the blade according to the obtained pitch angle control quantity.

[0012] Preferably, in Step 1, when filtering the wind turbine speed signal, its cut-off frequency is the first natural frequency of the floating foundation pitch mode; when filtering the basic pitch angular velocity signal, its cut-off frequency is twice the first natural frequency of the floating foundation pitch mode.

[0013] Preferably, in Step 2, according to the obtained filtered wind turbine speed signal and the filtered basic pitch angular velocity, calculate the error variables of the wind turbine speed error and the basic pitch angle error. The specific method is:

[0014] First, calculate the wind turbine speed error and the basic pitch angular velocity error respectively according to the obtained filtered wind turbine speed signal and the filtered basic pitch angular velocity;

[0015] Secondly, use the linear quadratic matrix to calculate the error variables of the wind turbine speed error and the basic pitch angle error.

[0016] Preferably, in Step 3, process the obtained error variables to obtain three gains of the PID controller. The specific method is:

[0017] First, calculate the derivative of the error variable;

[0018] Secondly, perform fuzzy processing on the error variable and the derivative of the error variable to obtain three gain increments of the PID controller;

[0019] Finally, add the three gain increments of the obtained PID controller to the corresponding fixed values respectively to obtain three gains of the PID controller.

[0020] Preferably, in step 3, the obtained error variable is processed to obtain an integral separation logic quantity. The specific method is as follows:

[0021] If |h| > ε, the integral separation logic quantity is 0;

[0022] If |h| < ε, the integral separation logic quantity is 1;

[0023] where ε is a positive constant.

[0024] Preferably, in step 4, according to the obtained error variable, the three gains of the PID controller, and the integral separation logic quantity, the pitch angle control quantity is calculated as follows:

[0025]

[0026] where m is the pitch angle control quantity; k p 、k i and k d are respectively the three gains of the PID controller; h is the error variable; j is the integral separation logic quantity.

[0027] A multi-objective pitch control system for a floating wind turbine, comprising:

[0028] A data processing unit for respectively filtering the obtained wind turbine speed signal and the basic pitch angular velocity signal corresponding to the floating wind turbine to obtain a filtered wind turbine speed signal and a filtered basic pitch angular velocity;

[0029] A pitch angle control quantity calculation unit for calculating an error variable of the wind turbine speed error and the basic pitch angle error according to the obtained filtered wind turbine speed signal and the filtered basic pitch angular velocity;

[0030] The obtained error variable is processed to respectively obtain the three gains of the PID controller and the integral separation logic quantity;

[0031] The pitch angle control quantity is calculated according to the obtained error variable, the three gains of the PID controller, and the integral separation logic quantity;

[0032] A control unit for controlling the pitch of the blade according to the obtained pitch angle control quantity.

[0033] A multi-objective pitch control device for a floating wind turbine, comprising a processor and a computer program capable of running on the processor, wherein when the processor executes the computer program, the steps of the method are implemented.

[0034] Compared with the prior art, the beneficial effects of the present invention are:

[0035] A multi-objective pitch control method for a floating wind turbine provided by the present invention calculates the required pitch angle based on the basic pitch angular velocity and the wind turbine rotational speed, taking into account the coupling effect caused by pitch on the basic pitch angular velocity and the wind turbine rotational speed, avoiding excessive pursuit of wind turbine rotational speed stability in pitch control, which may cause violent basic pitch motion, and also being beneficial to reducing the interference caused by excessive basic pitch angular velocity on the wind turbine rotational speed; the method performs low-pass filtering on the wind turbine rotational speed, and its cut-off frequency is the first natural frequency of the floating foundation pitch mode. On the one hand, it avoids the interference of high-frequency disturbances on the rotational speed control system, and on the other hand, it reduces the excessive negative damping introduced by pitch control in the basic pitch mode, preventing excessive pitch vibration amplitude; the method performs low-pass filtering on the basic pitch angular velocity to reduce the interference of high-frequency wave disturbances on pitch control; the method uses a positive definite quadratic matrix to allocate weights to the wind turbine rotational speed error and the basic pitch angular velocity error, constructs an error single variable that takes both errors into account, the method is simple and highly flexible. Based on the single variable to design the controller, multi-objective control can still be achieved, greatly simplifying the controller design process. It is convenient to be based on a single variable; the method adds the PID fixed gain value and the gain calculated by fuzzy control to calculate the total gain, which can ensure the basic performance of the manually adjusted PID controller, avoid control errors caused by improper fuzzy control fuzzification or defuzzification or inference rule setting, and can also achieve parameter non-linear scheduling by fuzzy control, so that the pitch control has good dynamic performance and steady-state accuracy under a wide range of wind speeds and disturbances; the method performs integral separation of PID control according to the size of the deviation h, taking into account the rapidity and steady-state accuracy of the flat pitch control. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a flowchart of the method of the present invention.

[0037] Figure 2 It is a control block diagram of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0038] The present invention will be further described below in conjunction with the accompanying drawings of the specification.

[0039] As Figure 1 shown in FIG. 2, a multi-objective pitch control method for a floating wind turbine specifically includes the following steps:

[0040] S1: Detect the wind turbine rotational speed signal a and the basic pitch angular velocity signal b;

[0041] S2: Perform low-pass filtering on the wind turbine rotational speed signal a and the basic pitch angular velocity signal b obtained in S1 respectively to obtain the filtered wind turbine rotational speed signal denoted as c, and the filtered basic pitch angular velocity denoted as d.

[0042] Among them, when the foundation is in the backward tilt, the basic pitch angle is positive, and when it is in the forward tilt, it is negative.

[0043] The low-pass filtering cut-off frequency of the wind turbine rotational speed signal a is the first natural frequency of the pitch mode of the floating foundation.

[0044] The low-pass filtering cut-off frequency of the foundation pitch angular velocity signal b is twice the first natural frequency of the pitch mode of the floating foundation.

[0045] Advantages: ① The cut-off frequency of the low-pass filtering of the wind turbine rotational speed is the first natural frequency of the pitch mode of the floating foundation. On the one hand, it avoids the interference of high-frequency disturbances to the rotational speed control system. On the other hand, it reduces the excessive negative damping introduced by the pitch control in the pitch mode of the foundation, preventing the excessive amplitude of the pitch vibration. ② The low-pass filtering of the foundation pitch angular velocity can reduce the interference of high-frequency wave disturbances to the pitch control.

[0046] S3: Calculate the wind turbine rotational speed error e and the foundation pitch angular velocity error f based on the filtered wind turbine rotational speed signal c and the filtered foundation pitch angular velocity d obtained in S2.

[0047] Assume that the rated rotational speed of the wind turbine is g, and the expected value of the foundation pitch angular velocity is 0; then:

[0048] e = c - g

[0049] f = d

[0050] S4: Use a linear quadratic matrix to construct an error variable h that comprehensively considers the wind turbine rotational speed error e and the foundation pitch angle error f calculated in S3:

[0051]

[0052] Among them, e is a 2×2 positive definite quadratic matrix, which is used for weight distribution of the wind turbine rotational speed error e and the foundation pitch angle error. P is a positive definite quadratic matrix, which is used for weight planning of e and f.

[0053] Advantages: ① Use a positive definite quadratic matrix to perform weight distribution on the wind turbine rotational speed error e and the foundation pitch angular velocity error, and the flexibility of weight distribution is strong; ② The constructed error variable h already includes the wind turbine rotational speed error and the foundation pitch angular velocity error. Subsequent control based on the error variable h can take into account both the wind turbine rotational speed and the foundation pitch angular velocity performance indicators, facilitating the subsequent design of a controller based on a single variable h, and still achieving multi-objective control, greatly simplifying the controller design process.

[0054] S5: Use the error variable h obtained in S4 and its derivative as the input of the fuzzy controller, fuzzify it, calculate the fuzzy control quantity using the Mandani inference rule, and defuzzify the fuzzy control quantity through proportional conversion to resolve it into three gain increments of the PID controller, which are Δk p, Δk i , Δk d . The Mandani inference rule has been widely applied and will not be elaborated here.

[0055] S6: Add the PID controller gain increment obtained in S5 to its fixed value to obtain the total PID controller gain k p , k i , k d :

[0056] k p = k p0 + Δk p

[0057] k i = k i0 + Δk i

[0058] k d = k d0 + Δk d

[0059] where k p0 , k i0 , k d0 are positive constants, representing the fixed parts of the proportional, integral, and derivative gains.

[0060] Advantages: The fixed gain value can be set by the online manual parameter adjustment method, ensuring the most basic performance of the pitch controller under certain working conditions. The gain calculated by fuzzy control is adaptively adjusted according to the error variable h and its derivative , with good nonlinear performance. Adding the fixed gain value to the gain calculated by fuzzy control to calculate the total gain can ensure the basic control performance, avoid control errors caused by improper fuzzyfication, defuzzyfication, or inference rule setting of fuzzy control, and can also achieve non-linear parameter scheduling by fuzzy control, enabling the pitch control to have good dynamic performance and steady-state accuracy under a wide range of wind speeds and disturbances.

[0061] S7: Calculate the integral separation logic quantity j, specifically as follows:

[0062] ① If |h| > ε, then j = 0;

[0063] ② If |h| < ε, then j = 1;

[0064] where ε is a positive constant.

[0065] Advantages of integral separation: When the fan starts or the wind speed changes greatly, the integral link is likely to accumulate the control quantity, which is likely to cause a large overshoot or even oscillation of the system. Integral separation is performed according to the magnitude of the deviation h to balance the rapidity and steady-state accuracy of the pitch control. Specifically, ① when the error is large, the integral separation takes effect, the integral action is cancelled, the pitch control response speed is fast, and at the same time, excessive overshoot is avoided; ② when the error is small and the steady-state error is an important index, the integral action is introduced to ensure the tracking accuracy.

[0066] S8: Based on the error variable h obtained from S4 and the total PID controller gains k obtained from S6 p 、k i 、k d and the integral separation logic quantity of S7, calculate the pitch angle control quantity m:

[0067]

[0068] S9: After the pitch angle actuator receives the pitch angle control quantity m calculated in S8, the pitch motor drives the blade to pitch to the specified angle.

[0069] The present invention also provides a multi-objective pitch control system for a floating wind turbine, including:

[0070] A data processing unit for respectively performing filtering processing on the obtained wind turbine speed signal and the basic pitch angular velocity signal corresponding to the floating wind turbine to obtain a filtered wind turbine speed signal and a filtered basic pitch angular velocity;

[0071] A pitch angle control quantity calculation unit for calculating error variables of the wind turbine speed error and the basic pitch angle error according to the obtained filtered wind turbine speed signal and the filtered basic pitch angular velocity;

[0072] Process the obtained error variables to respectively obtain three gains of the PID controller and the integral separation logic quantity;

[0073] Calculate the pitch angle control quantity according to the obtained error variables, three gains of the PID controller and the integral separation logic quantity;

[0074] A control unit for controlling the pitching of the blade according to the obtained pitch angle control quantity.

[0075] The present invention also provides a multi-objective pitch control device for a floating wind turbine. The multi-objective pitch control device for a floating wind turbine may be a computing device such as a desktop computer, a notebook, a palm computer, and a cloud server. The multi-objective pitch control device for a floating wind turbine may include, but is not limited to, a processor and a memory.....

[0076] The processor may be a Central Processing Unit (CPU), or may also be other general-purpose processors, Digital Signal Processors (DSPs), Application Specific Integrated Circuits (ASICs), Field-Programmable Gate Arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. ……

Claims

1. A multi-objective pitch control method for a floating wind turbine, characterized in that, It includes the following steps: Step 1: Filter the obtained wind turbine rotational speed signal and the foundation pitch angular velocity signal corresponding to the floating wind turbine respectively to obtain the filtered wind turbine rotational speed signal and the filtered foundation pitch angular velocity; Step 2: Calculate the error variables of the wind turbine rotational speed error and the foundation pitch angle error according to the obtained filtered wind turbine rotational speed signal and the filtered foundation pitch angular velocity; Step 3: Process the obtained error variables to obtain the three gains of the PID controller and the integral separation logic quantity respectively; Step 4: Calculate the pitch angle control quantity according to the obtained error variables, the three gains of the PID controller and the integral separation logic quantity; Step 5: Control the pitch change of the blade according to the obtained pitch angle control quantity; In Step 3, the method of processing the obtained error variables to obtain the three gains of the PID controller is as follows: First, calculate the derivative of the error variable; Secondly, perform fuzzy processing on the error variable and the derivative of the error variable to obtain the three gain increments of the PID controller; Finally, add the three gain increments of the obtained PID controller to the corresponding fixed values respectively to obtain the three gains of the PID controller; In Step 3, the method of processing the obtained error variables to obtain the integral separation logic quantity is as follows: If , the integral separation logic quantity is 0; If , the integral separation logic quantity is 1; Among them, is a positive constant; In Step 4, the method of calculating the pitch angle control quantity according to the obtained error variables, the three gains of the PID controller and the integral separation logic quantity is as follows: wherein, is the pitch angle control amount; , and are respectively the three gains of the PID controller; is the error variable; is the integral separation logic quantity.

2. The multi-objective pitch control method for a floating wind turbine unit according to claim 1, wherein In Step 1, when filtering the wind turbine rotational speed signal, its cut-off frequency is the first natural frequency of the floating foundation pitch mode; when filtering the foundation pitch angular velocity signal, its cut-off frequency is twice the first natural frequency of the floating foundation pitch mode.

3. A multi-objective pitch control method for a floating wind turbine according to claim 1, characterized in that In Step 2, the method of calculating the error variables of the wind turbine rotational speed error and the foundation pitch angle error according to the obtained filtered wind turbine rotational speed signal and the filtered foundation pitch angular velocity is as follows: First, calculate the wind turbine rotational speed error and the foundation pitch angular velocity error respectively according to the obtained filtered wind turbine rotational speed signal and the filtered foundation pitch angular velocity; Secondly, calculate the error variables of the wind turbine rotational speed error and the foundation pitch angle error by using the linear quadratic matrix.

4. A multi-objective pitch control system for a floating wind turbine unit, characterized in that, The method according to any one of claims 1-3 includes: A data processing unit for filtering the obtained wind turbine rotational speed signal and the foundation pitch angular velocity signal corresponding to the floating wind turbine respectively to obtain the filtered wind turbine rotational speed signal and the filtered foundation pitch angular velocity; A pitch angle control quantity calculation unit for calculating the error variables of the wind turbine rotational speed error and the foundation pitch angle error according to the obtained filtered wind turbine rotational speed signal and the filtered foundation pitch angular velocity; Process the obtained error variables to obtain the three gains of the PID controller and the integral separation logic quantity respectively; Calculate the pitch angle control quantity according to the obtained error variables, the three gains of the PID controller and the integral separation logic quantity; A control unit for controlling the pitch change of the blade according to the obtained pitch angle control quantity.

5. A floating wind turbine multi-objective pitch control device, characterized in that, Comprising a processor and a computer program capable of running on the processor, characterized in that when the processor executes the computer program, the steps of the method according to any one of claims 1-3 are implemented.

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