Pitch Control System Research Articles

Nonlinear analysis of gain scheduled controllers for the NREL 5-MW turbine blade pitch control system

Gain-scheduling is a conventional approach for adjusting the wind turbine controller performance against operating point variations in industrial applications. Although the scheduling idea seems uncomplicated, several configurations available in research papers and technical reports are subject to inaccuracy. This paper discusses the effect of inaccurate controller realization by choosing NREL 5-MW, the ubiquitous wind turbine in the research community, and citing various controller configurations available in the literature. By performing a nonlinear analysis, it is shown that hidden terms emerge from inaccurate realizations, which could deteriorate the controller performance or lead to controller structures with different performance indexes from the original design. To remedy this issue, four implementation modifications are introduced to maintain the intended performance of the gain-scheduled controller. Although the paper is focused on the baseline gain-scheduled PI controller, modifications are generalized to arbitrary pitch control systems. Simulations with the full-order dynamics of the FAST code for the pitch angle-based and wind speed-based gain-scheduled baseline controllers and a more complex gain-scheduled fractional-order PI controller verify the presented analysis.

Active blade pitch control and stabilization of a wind turbine driven PMSG for power output regulation

A common strategy in controlling a permanent magnet synchronous generator (PMSG) driven by a wind turbine is the maximization of output power of the wind turbine itself. A control strategy must be adopted, is to deliver a desired reduced amount of power whenever it is required. In order to realize the direct control of wind turbine output power across a wide range of wind speeds, a linearized parameter varying dynamic model of the nonlinear wind turbine system including wind disturbances is developed and used in this paper. The stability of the wind turbine system is analyzed and a blade pitch controller is designed, based on the linearized, parameter-varying, model-predictive control and is validated. Thus, the wind turbine is regulated in a way that the generator delivers the demanded power output to the load. Moreover, the blade pitch control system also performs the key function of augmenting the stability of the wind turbine, for the right choice of the gains.

Experimental investigation on load mitigation of a 5 MW wind turbine in digital fluid power pitch system test rig based on predictive load mitigation controller

ABSTRACT The pitch control system plays a vital role in generating rated power and mitigates mechanical loads during strong wind gusts. Generally, the hydraulic pitch system deployed in a large-scale wind turbine uses a proportional/servo valve to adjust the pitch angle. However, these valves suffer from low operating efficiency which leads to poor pitching performance. Thus, a high-speed digital hydraulic valve-based Digital Fluid Power Pitch System (DFPPS) test rig was proposed in this paper. Moreover, the conventional controller was not able to produce adequate pitching performance during high wind flux. Therefore, a machine learning-based pitch controller was implemented in the developed test rig. The developed DFPPS test rig comprises simulation loop (Wind Generator System (WGS) model, pitch gear model, Predictive Load Mitigation Controller (PLMC), and pitch load model), and DFPPS-hardware interfaced through an I/O interface. Here, PLMC was developed to improve the load mitigation performance without compromising the generator performance at high wind speeds. The proposed PLMC is a cascade arrangement of Recurrent Elman Neural Network (RENN) tuned Fractional-Order Proportional Integral Derivative (FOPID). Further, for collecting the optimal datasets to train the RENNs in PLMC, a Customized Particle Swarm Optimization (CPSO) algorithm was utilized. Two experiments are performed considering the developed WGS model and benchmark Fatigue Aero-elastic Structure Turbulence (FAST) simulator deployed in the DFPPS test rig. The experimental results of PLMC (experiment) were compared to simulation results PLMC (simulation). Further, the experimental output of the PLMC was compared to established controllers in the literature (Radial Basis Function tuned Fractional-Order Proportional Integral Derivative (RBF-FOPID) and baseline Proportional Integral (PI)). In the experiment using FAST, relative to RBF-FOPID, the PLMC (experiment) decreased the Standard Deviation (STD) of blade and tower moment by 81.5% and 81.4%, respectively. Consequently, compared to baseline PI, the PLMC (experiment) reduced the STD of blade and tower moment by 85.6%, and 84.4%, respectively. The proposed controller effectively mitigated the load and also the generator performance was close to the rated value than its counterparts.

Experimental Study of Ultra-Large Jacket Offshore Wind Turbine under Different Operational States Based on Joint Aero-Hydro-Structural Elastic Similarities

The jacket substructure is generalized for offshore wind farms in the southeastern offshore regions of China. The dynamic characteristics and coupling mechanisms of jacket offshore wind turbines (OWTs) have been extensively investigated using numerical simulation tools. However, limited dynamic model tests have been designed and performed for such types of OWTs. Therefore, the coupling mechanisms of jacket OWTs that are determined using numerical methods require further validation based on experimental tests. Accordingly, an integrated scaled jacket OWT physical test model is designed in this study. It consists of a scaled rotor nacelle assembly (RNA) and support structure model. For the scaled RNA model, a redesigned blade model is adopted to ensure the similarity of the aerodynamic thrust loads without modifying the scaled test winds. Auxiliary scaled drivetrain and blade pitch control system models are designed to simulate the operational states of a practical OWT. The scaled model of the OWT support structure is fabricated on the basis of the joint hydro-structural elastic similarities. A sensor arrangement involving a three-component load cell and acceleration sensors is used to record the OWT thrust loads and model motions, respectively. Then, dynamic model tests under typical scaled wind fields are implemented. Furthermore, the coupling mechanisms of the OWT model under various test winds are investigated using the wavelet packet method, and the influences of inflow winds, operational states, and mechanical strategies are introduced.

Linear Quadratic Regulation Method for a Roll Yaw Coupled Supersonic Flight Vehicle

In this literature, a linear quadratic regulation (LQR) method with controller reconfiguration and state observer is proposed for analyses and designs of a supersonic roll-yaw coupled flight control system. The flight control system of some specially shaped airframe can be decomposed into a Pitch Control System and a Roll-Yaw Coupled Control System. It can be designed separately, no need for three loops to be designed together. The design process is relatively simple, which is conducive to the design of flight control systems in large airspace. The proposed method for the considered system will give the good tracking characteristic at low frequencies and robustness at middle frequencies; simultaneously. All state variables are measurable and found controllers are all realizable either in analog or digital hardware.

An Advanced Neuro-Fuzzy Tuned PID Controller for Pitch Control of Horizontal Axis Wind Turbines

Modern power systems comprise a variety of generating systems, including conventional thermal power stations and advanced renewable generating sources, one contender being a wind energy conversion system (WECS). Blade pitch control is an important part of the highly non-linear WECS. Many control strategies have been proposed by researchers around the globe. Current research work focuses on developing a control structure for a non-linear pitch control system using an advanced neuro-fuzzy tuned PID (NF-PID) controller. This approach utilizes the simplicity of a PID controller and the power of a soft computing technique like neuro-fuzzy to handle non-linearity. The model in this study is developed on the MATLAB Simulink platform and the obtained simulation results satisfy the requirements of constant output power even if the wind speed input changes abruptly.

A New combined MPPT-Pitch Angle control of a Large Variable Speed Wind Turbine in Different Operating Areas based on Synergetic control

The aim of this paper is to create a novel combination between two controls, maximum power point tracking (MPPT) and Pitch angle control system of a variable-speed wind turbine. The main objective sought is to achieve the maximization of the power produced by the fixed pitch angle turbine through the MPPT control in the zone 02 of operation. Then, limit the power to its nominal value by using the Pitch control with variable pitch angle in zone 03 of operation. Our contribution will be to propose strategies based on two types of controllers. The first is the control by the MPPT control, it is applied in light winds to extract the maximum power. The second is Variable Pitch Control, which is applied in strong winds to keep power constant at its nominal value, as well as protecting the wind turbine from high winds. For this, linear and non-linear control laws (PI, SC) respectively are implemented to achieve the defined objective. The simulation results show the feasibility and effectiveness of the techniques used.

Error-Based Active Disturbance Rejection Control for Pitch Control of Wind Turbine by Improved Coyote Optimization Algorithm

Wind energy systems are expected to supply the majority of future generation from renewables due to the maturity of technology and the availability of energy resources. In this paper, in order to improve the ability of tracking a desired power reference at high wind speed region, a pitch control strategy based on error-based active disturbance rejection control (ADRC) approach is proposed for variable speed wind turbine system, providing a novel practically appealing control structure. The stability analysis of the proposed pitch controller based on singular perturbation theory is provided. Next, an improved coyote optimization algorithm (COA) fused with L <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\rm {\acute{e}}$</tex-math></inline-formula> vy flight and Sinusoidal map is proposed to address the controller parameters tuning issue. Then, the effectiveness of the proposed solution is verified on a 1.5 MW FAST simulator taking into account both multi-step and IEC turbulence wind conditions. Finally, an analysis in frequency domain of the pitch control system with the proposed control strategy is presented.

Model-based design optimisation of digital hydraulic pitch actuator for a large-scale wind turbine

The valve throttle regulation issue in the proportional flow control valves reduces the performance of the hydraulic pitch system in large-scale wind turbines. To overcome this drawback, the high-response hydraulic 2/2 valves are utilised to develop the novel digital hydraulic pitch actuator. Consequently, an intelligent pitch cascade controller was developed to control the wind energy system and digital hydraulic pitch actuator. However, the performance of the digital hydraulic pitch actuator was poor during the preliminary simulation study. Thus model-based design optimisation was carried out to identify the optimal parameters of the digital hydraulic pitch actuator. Furthermore, two case studies were conducted using the developed wind energy system and a 5-MW wind turbine simulator to validate the proposed pitch control system. In all the case studies, the proposed pitch control system performed superior and generated rated power at above-rated wind speed when compared to the baseline proportional integral and neural controllers.

An Active Disturbance Rejection Control of Large Wind Turbine Pitch Angle Based on Extremum-Seeking Algorithm

This paper proposes the analysis and design of the linear active disturbance rejection controller (LADRC) for the pitch angle model of a large wind turbine generator (WTG). Since the transfer function of the pitch control system exhibits nonminimum-phase characteristics, the parameters of LADRC are difficult to tune using the conventional bandwidth method. On the basis of PI controller parameters to first-order LADRC parameters, an optimization problem is proposed in this paper to find the parameters of an LADRC for the pitch control system under the constraint of robustness measure, and the extremum-seeking (ES) algorithm is used to solve the problem. Simulation results show that LADRC can achieve better tracking and disturbance rejection performance than traditional PI control without loss of robustness against time delay.

Stabilisation of network-controlled aircraft pitch control system with time delay

This paper describes the stability assurance of network-controlled aircraft pitch control system with time delays. A frequency-domain method is used to determine the upper bound of time delay for aircraft pitch control system with gain and phase margin constraint. The effectiveness of proportional-integral (PI) and fractional-order PI controller on aircraft pitch control system stability and performance is investigated in presence of time delay. The parametric space of the PI and fractional-order PI controller are plotted in two-dimensional space to determine the stability region and controller is designed with concern to the time delay. The relation between controller parameters and time delay is estimated and these findings contribute significantly for the design of the controller for aircraft pitch control system. The accuracy of the proposed results is validated using simulation benchmark.

Experimental Verification of Wind Power Generation System Using Diode Bridge Rectifier Circuit with Wind Turbine Simulator

This paper presents Wind Power Generation System using Diode Bridge Rectifier (WPGS-DBR method). Experimental results have been obtained by Wind Turbine Simulator (WTS). The WTS emulates wind turbine behavior using a servo motor as a drive system. Mechanical torque references used to drive the motor are calculated using wind turbine data such as wing blade, wind velocity, and wind turbine rotation speed. DBR method has three-mode control for three ranges of wind speed: low, medium, and high, respectively. In low and medium mode, the control system adjusts the armature current of a generator and DC link voltage with a Vector-Controlled Inverter (VCI) to control wind turbine speed. In high mode, the control system modulates the pitch angle of the wind turbine using a pitch angle control system for controlling wind turbine rotational speed. The DBR simplifies the maintenance of WPGS while improving reliability. In addition, the DBR method costs less compared with the WPGS using a PWM converter.

Control of the rated production power of DFIG-wind turbine using adaptive PSO and PI conventional controllers

Production of rated power and protection of generator and power converter from an overload are necessary. Therefore, measuring the accurate value of the pitch angle of the doubly fed induction generator (DFIG) wind turbine is essential. An assessment study between the adaptive particle swarm optimisation (PSO) technique and conventional proportional integral (PI) controller of the pitch control system in limiting the electrical output power at the rated value of DFIG is introduced in this study. Pitch control with PSO is designed by solving the nonlinear equation of pitch angle at each wind speed higher than rated wind speed. The PI controller gains of the pitch system are evaluated to keep the power limited at rated value. Accuracy in measuring pitch angle is essential because a small difference in pitch angle value results in an overload on the generator. The performance of each parameter of DFIG with a detailed analysis is studied. The simulation shows that the pitch control system with PSO technique gives better results in regulating the DFIG output power compared to PI controller method under wind speed variation.

Robust Controller Design for AUV Subsystem Using µ Synthesis

The paper considers the problem of synthesizing the pitch control system of an autonomous underwater vehicle (AUV), considering the uncertainty of its parameters and underwater disturbances. The µ-synthesis using D-K iteration is applied to solve the problem. For the subsequent implementation of the controller in practice, a method for reducing its order based on the Hankel norm approximation is applied. The proposed approach is tested on the mathematical model of the MAYA AUV with the parameters deviating from the nominal values. The simulation result shows that the proposed robust control scheme effectively compensates for the parametric uncertainty and underwater disturbances.

Application of Nonlinear Correction Method for Attitude Control and Landing Oscillations Prevention

The purpose of this work is to demonstrate the application of the nonlinear correction method to prevent attitude oscillations of flying vehicles. This paper investigates the complications of manual control tasks in aeronautics caused by employing the integral component in the control loop. If the actuators of aircraft controlling surfaces reach their rate limits, the aircraft oscillations can appear for both manually and automatically piloted cases. In this paper, the oscillations alleviation problem is solved using the nonlinear correction method. A general methodology for pilot-induced oscillations prevention is described briefly by the example of an aircraft pitch control system. The obtained pilot model parameters are used for altitude control system examination. The nonlinear systems analysis is carried out by calculating the generalized sensitivity function for the control and disturbance input signal. In the second part, the application of the nonlinear correction method to prevent aircraft and satellite oscillations caused by integrator windup. A comparative analysis of the nonlinear correction and the customary anti-windup feedback is carried out. The results obtained demonstrate that a sequential nonlinear corrective device can be efficiently used to suppress pilot-induced and integrator windup oscillations.

Design and Implementation of an Intelligent Blade Pitch Control System and Stability Analysis for a Small Darrieus Vertical-Axis Wind Turbine

A few studies have been conducted recently in order to improve the aerodynamic performance of Darrieus vertical-axis wind turbines with straight blades (H-type VAWTs). The blade pitch angle control is proposed to enhance the performance of H-type VAWTs. This paper aims to investigate the performance of an H-type VAWT in terms of its power output and self-starting capability using an intelligent blade pitch control strategy based on a multi-layer perceptron artificial neural network (MLP-ANN) method. The performance of the proposed blade pitch controller is investigated by adding a conventional controller (PID) to the MLP-ANN controller (i.e., a hybrid controller). The dynamics of an H-type VAWT is mathematically modeled in a nonlinear state space for the stability analysis in the sense of Lyapunov. The effectiveness of the proposed pitch control system is validated by building an H-type VAWT prototype model that is extensively tested outdoors under different conditions for both fixed and variable pitch angle configurations. Results demonstrated that the blade-pitching technique enhanced the power output of an H-type VAWT by approximately 22%. The hybrid controller that used a high percentage of the MLP-ANN controller achieved a better control performance by reducing the overshoot of the control response at high rotor speeds.

Data Fusion Based on an Iterative Learning Algorithm for Fault Detection in Wind Turbine Pitch Control Systems.

In this article, we propose a recent iterative learning algorithm for sensor data fusion to detect pitch actuator failures in wind turbines. The development of this proposed approach is based on iterative learning control and Lyapunov’s theories. Numerical experiments were carried out to support our main contribution. These experiments consist of using a well-known wind turbine hydraulic pitch actuator model with some common faults, such as high oil content in the air, hydraulic leaks, and pump wear.

Intelligent Pitch Controller Identification and Design

This paper exhibits a comparative assessmentbased on time response specification performance between modern and classical controller for a pitch control system of an aircraft system. The dynamic modeling of pitch control system is considered on the design of an autopilot that controls the pitch angle It starts with a derivation of a suitable mathematical model to describe the dynamics of an aircraft. For getting close to actual conditionsthe white noise disturbance is applied to the system.In this paper it is assumed that the modelpitch control systemis not available. So using the identification system and Box-Jenkins model estimator we identify the pitch control system System’s identification is a procedure for accurately characterizing the dynamic response behavior of a complete aircraft, of a subsystem, or of an individual component from measureddata.To study the effectiveness of the controllers, the LQR Controller and PID Controller and fuzzy controller is developed for controlling the pitch angle of an aircraft system. Simulation results for the response of pitch controller are presented instep’s response. Finally, the performances of pitch control systems are investigated and analyzed based on common criteria of step’s response in order to identify which control strategy delivers better performance with respect to the desired pitch angle. It is found from simulation, that the fuzzy controller gives the best performance compared to PID and LQR controller.

Fault Detection for Pitch System of Wind Turbine-Driven Doubly Fed Based on IHHO-LightGBM

To address the issue of a large calculation and difficult optimization for the traditional fault detection of a wind turbine-based pitch control system, a fault detection model, based on LightGBM by the improved Harris Hawks optimization algorithm (light gradient boosting machine by the improved Harris Hawks optimization, IHHO-LightGBM) for the wind turbine-based pitch control system, is proposed in this article. Firstly, a trigonometric function model is introduced by IHHO to update the prey escape energy, to balance the global exploration ability and local development ability of the algorithm. In this model, the fault detection false alarm rate is used as the fitness function, and the two parameters are used as the optimization objects of the improved Harris Hawks optimization algorithm, to optimize the parameters, so as to achieve the global optimal parameters to improve the performance of the fault detection model. Three different fault data of the pitch control system in actual operations of domestic wind farms are used as the experimental data, the Pearson correlation analysis method is introduced, and the wind turbine power output is taken as the main state parameter, to analyze the correlation degree of all the characteristic variables of the data and screen the important characteristic variables out, so as to achieve the effective dimensionality reduction process of the data, by using the feature selection method. Three established fault detection models are selected and compared with the proposed method, to verify its feasibility. The experimental data indicate that compared with other algorithms, the fault detecting ability of the proposed model is improved in all aspects, and the false alarm rate and false negative rate are lower.

Remote Monitoring and Diagnostics of Pitch-Bearing Defects in an MW-Scale Wind Turbine Using Pitch Symmetrical-Component Analysis

Recently, multiple wind turbine failure databases have reviewed that the pitch system is one of the subassemblies with the highest failure rates and largest contributors to the overall downtime. Therefore, there has been an increasing interest to provide remote health monitoring for wind turbine pitch system. While most of the research articles are discussing pitch actuation system (hydraulic or electric actuator) faults only, there is very limited research on pitch-bearing-defect detection. This article provides a remote and hardware-free solution to monitor multiaxis pitch-bearing health condition called pitch symmetrical-component analysis. It leverages readily available low-resolution (100 Hz) electrical measurements, mechanical measurements, and control signals from the existing pitch control platform, and innovatively applies symmetrical-component analysis in multiphase ac system to multiaxis pitch control system and introduces multiaxis pitch-bearing degradation trending curves. This hardware-free solution can be directly applied to the existing wind turbines and successfully give the wind farm operator an early warning before multiaxis pitch bearing fails. It has been proved to be accurate, low cost, and has minimum impacts on turbine normal operation, and has been validated by field data from several North America MW-scale wind farms. This approach turns out to be the first hardware-free (no additional hardware needed) method to remotely monitor and diagnose multiaxis wind turbine pitch-bearing condition.