Pitch Control System Research Articles

A Novel Dynamic Co-Simulation Analysis for Overall Closed Loop Operation Control of a Large Wind Turbine

A novel dynamic co-simulation methodology of overall wind turbine systems is presented. This methodology combines aerodynamics, mechanism dynamics, control system dynamics, and subsystems dynamics. Aerodynamics and turbine properties were modeled in FAST (Fatigue, Aerodynamic, Structures, and Turbulence), and ADAMS (Automatic Dynamic Analysis of Mechanical Systems) performed the mechanism dynamics; control system dynamics and subsystem dynamics such as generator, pitch control system, and yaw control system were modeled and built in MATLAB/SIMULINK. Thus, this comprehensive integration of methodology expands both the flexibility and controllability of wind turbines. The dynamic variations of blades, rotor dynamic response, and tower vibration can be performed under different inputs of wind profile, and the control strategies can be verified in the different closed loop simulation. Besides, the dynamic simulation results are compared with the measuring results of SCADA (Supervisory Control and Data Acquisition) of a 2 MW wind turbine for ensuring the novel dynamic co-simulation methodology.

Experimental analysis of vertical axis wind turbine active pitch control system with Permanent Magnet Synchronous Motor using MATLAB Simulink tools

Efficient vertical axis wind turbine (VAWT) technology is a key topic for the future wind energy market. At the moment, VAWTs are seldom used for electricity production. The development of new technologies for building a new generation of VAWTs, which will be more efficient, user-friendly, and with very low noise pollution levels is the target for many researchers. The goal of this research was to analyse an active pitch control system in an experimental setting through construction of an active pitch control system test bench using a Permanent Magnet Synchronous Motor (PMSM) and to develop new testing programmes for analytical system performance tests. The current commercial turbines do not carry an active pitch system for a VAWT; however, the concept of an active turbine blade pitching opens new opportunities for boosting the efficiency, safety, and user-friendliness of VAWTs. The research consists of the mathematical model and control system operating in a simulation environment in a closed loop with the test bench setup consisting of an active pitch control system. By applying a specially developed VAWT simulation model implemented in MATLAB Simulink, an active pitch system was tested and analysed under various conditions, which were as close as possible to the real-world operating conditions. The results of the testing and analysis show that an active pitch system using the PMSM can be very efficient and fast-operating. An active pitch system is able to work on the needed conditions by using the PMSM. Analysis shows that while using the PMSM for a turbine active pitch system, certain conditions should be taken into account in order to achieve the best results and to reduce costs. Full and effective use of active pitch system components can improve VAWT performance.

Research on Fuzzy PID Pitch-Controlled System Based on SVM

In a wind turbine generator, it is difficult to achieve a good control performance using the conventional PID variable pitch controller because of the multi-variables and nonlinearities of the controller. Based on the principles of variable pitch control of a wind generating set, this study introduces a mathematical model for wind turbine generators and proposes a variable pitch fuzzy PID control method by combining the fuzzy control and PID control methods to effectively overcome the deficiencies of the conventional PID controller. In order to enhance self-learning and predictability of the system, an improved method for the variable pitch control of the fuzzy PID is proposed based on an online support vector machine (SVM). Finally, the simulation comparisons show that the fuzzy PID variable pitch control based on the SVM further improves the control performance of a variable pitch wind turbine generator. In addition, it is robust at random wind speeds and can adjust the pitch angle more smoothly. It ensures a stable output power of wind turbine generator, thus effectively improving the control performance of the variable pitch system of the wind generating set.

Fundamental study on aerodynamic force of floating offshore wind turbine with cyclic pitch mechanism

Wind turbines mounted on floating platforms are subjected to completely different and soft foundation properties, rather than onshore wind turbines. Due to the flexibility of their mooring systems, floating offshore wind turbines are susceptible to large oscillations such as aerodynamic force of the wind and hydrodynamic force of the wave, which may compromise their performance and structural stability. This paper focuses on the evaluation of aerodynamic forces depending on suppressing undesired turbine's motion by a rotor thrust control which is controlled by pitch changes with wind tunnel experiments. In this research, the aerodynamic forces of wind turbine are tested at two kinds of pitch control system: steady pitch control and cyclic pitch control. The rotational speed of rotor is controlled by a variable speed generator, which can be measured by the power coefficient. Moment and force acts on model wind turbine are examined by a six-component balance. From cyclic pitch testing, the direction and magnitude of moment can be arbitrarily controlled by cyclic pitch control. Moreover, the fluctuations of thrust coefficient can be controlled by collective pitch control. The results of this analysis will help resolve the fundamental design of suppressing undesired turbine's motion by cyclic pitch control.

Pitch control for wind turbine systems using optimization, estimation and compensation

Delays caused by hydraulic pressure driven units in wind turbines may degrade and even destabilize pitch control system, leading to the performance degradation or collapse of the whole wind turbine energy conversion system. As a result, there is a strong motivation to improve pitch control technique to overcome the adverse effects from the unknown delays caused by the hydraulic driven units. In this study, a novel pitch control approach is developed by integrating optimization, delay-perturbation estimation, and signal compensation techniques. Specifically, an optimal PI controller is designed by applying direct search optimization to ideal delay-free pitch model. A delay estimator is next designed to estimate the perturbation caused by the delay. The signal compensation technique is then implemented to remove the effect from the delay-perturbation to the turbine output so that the actual output is consistent with the optimal output of the ideal delay-free model. Furthermore, the technique is extended to PID-based pitch control systems. The blade-tower dynamics models of three wind turbines, respectively with rated powers 1.5 MW, 275 kW and 50 kW, are investigated and the effectiveness of the proposed techniques are demonstrated by detailed simulation studies. It is worthy to point out a priori on the delay is not necessary in this design, which much meets the situations in practical wind turbine systems. Finally, a 4.8 MW benchmark wind turbine energy conversion system is investigated via the proposed pitch control technique, which has shown that delay perturbation estimate based compensation can effectively improve the pitch control performance in the real-time wind turbine energy conversion system.

Aerodynamic design and analysis of a 10 kW horizontal-axis wind turbine for Tainan, Taiwan

The purpose of the present study is to develop a small-scale horizontal-axis wind turbine (HAWT) suitable for the local wind conditions of Tainan, Taiwan. The wind energy potential was first determined through the Weibull wind speed distribution and then was adapted to the design of the turbine blade. Two numerical approaches were adopted in the design and analysis of the HAWT turbine blades. The blade element momentum theory (BEMT) was used to lay out the shape of the turbine blades (S822 and S823 airfoils). The geometry of the root region of the turbine blade was then modified to facilitate integration with a pitch control system. A mathematical model for the prediction of aerodynamic performance of the S822 and S823 airfoils, in which the lift and drag coefficients are calculated using BEMT equations, was then developed. Finally, computational fluid dynamics (CFD) was used to examine the aerodynamic characteristics of the resulting turbine blades. The resulting aerodynamic performance curves obtained from CFD simulation are in agreement with those obtained using BEMT. It is also observed that separation flow occurred at the turbine blade root at the tip speed ratios of 5 and 7.

신규 익형 KA2가 적용된 풍력 블레이드의 공력 하중에 대한 동특성 해석

This paper proposes a novel airfoil named KA2 for the blade of the wind turbine systems. Dynamic loads characteristics are analyzed and compared using aerodynamic data of ten airfoils including the proposed airfoil. The blade is divided into the sixteen elements in the longitudinal direction of the blade for applying the Blade Element Method Theory (BEMT) method, and in each element, torque, thrust, and pitching moment are calculated using turbulent time varying wind speed and aerodynamic data of each wing. Additionally, each force and torque is accumulated in the whole region of the blade for the estimation of representative values. The magnitude of such forces is comparatively analyzed for different airfoils. The angle of attack is constant below the rated wind speed due to the fact that the tip speed ratio is kept at the constant value, and it increases in the region of over rated wind speed as the tip speed ratio decreasing with constant rated rpm and increasing wind speed. Such increase in the angle of attack causes the changes of the force acting on the airfoil with different characteristics of lift and drag in the stall region of each different airfoil. Even though the mean wind speed is in the rated speed in a given time, because of the turbulence, it has either the over rated or under rated speed most of the time. Furthermore, the dynamic properties of each force are analyzed in this rated wind speed in order to objectively understand the dynamic properties of the blades which are designed based on the different airfoils. These dynamic properties are also compared by the standard deviation of time varying characteristics. Moreover, the output characteristics of the wind turbine are investigated with different airfoils and wind speeds. Based on these investigations, it was revealed that the proposed airfoil (KA2) is well applicable to the blade with passive pitch control system.

Mathematical Model for Adaptable Pitch System based on Adaptive Control PID

Wind power is renewable and spotless energy with progress projections. By reason of the effect of randomness, unpredictability of wind quickness, the wind turbine features of movable pitch control system with nonlinear robust coupling, time-varying strictures, it is problematic to acquire the precise mathematical model; and with the intention of comprehend the continuous power output, operating district of the fast, high-precision control dynamic act, this paper planned the AC servo fan adaptable pitch system based on BP network adaptive control PID. Over the simulation, to confirm this system attained the control result that with high steady-state correctness and was rapid to follow control result. Background/Objectives: Wind power generation is to convert wind energy into electrical energy, renewable energy, and clean energy with advance prospects. Due to the impact of randomness, instability and the aerodynamic effect of wind speed, the wind turbine characteristics of variable pitch control system with nonlinear, strong coupling, time-varying parameters, it is difficult to obtain the accurate mathematical model. Results: Self-tuning PID control scheme based on BP neural network made the output state of BP neural network correspond to proportional kp, integral ki, and differential kd of PID. The PID control factors were optimized correction online with the help of neural network's self-learning ability and the ability to approximate any nonlinear function, then weight coefficients of neural network was adjusted, the PID control coefficient under some ideal control rules was achieved when the system in stable states (see the simulation curves of b).

An Integrated Power Smoothing Control for a Grid-Interactive Wind Farm Considering Wake Effects

This paper presents a power smoothing control scheme for a permanent-magnet-synchronous-generator-based wind farm considering wake effects. The integrated power smoothing method consists of a pitch angle control system, a kinetic wind-energy turbine inertia control system, and a dc-link voltage control system. Low frequency range power fluctuations caused by wind speed variations are smoothed by the pitch angle control system and the kinetic wind-energy turbine inertia control system. Power fluctuations in the high frequency range are smoothed by the dc-link voltage control system. This power smoothing approach is cost-effective because the power smoothing is made possible without additional energy storage devices. In addition, the wake effects of the wind farm are considered for power smoothing with different tower spaces. The proposed method is compared with the conventional maximum-power-point-tracking method. Simulation results confirm the proposed method efficacy in smoothing the power injected by a wind farm.

Effects of seismic and aerodynamic load interaction on structural dynamic response of multi-megawatt utility scale horizontal axis wind turbines

Horizontal axis wind turbines can experience significant time varying aerodynamic loads that has the potential to cause adverse effects on structural, mechanical, and power production. The progress in the wind industry has caused the construction of wind farms in areas prone to high seismic activity. With the advances in computational tools, a more realistic representation of the behavior of wind turbines should be performed. One of the simulation platforms was developed using the 5 MW NREL utility scale reference turbine model. The performed simulations will be used to evaluate the effects of aerodynamic and seismic load coupling on the power generation and structural dynamics behavior of this structure. Different turbine operational scenarios such as (i) normal operational condition with no earthquake, (ii) idling condition with the presence of seismic loads, (iii) normal operational condition with earthquake, and (iv) earthquake-induced emergency shutdown will be simulated with various loading conditions to show the differences in generated power and dynamic response. The results of this paper provide formulations for calculating generated power and design deriving parameters by considering different intensity measures. Moreover, the effects of aerodynamic damping and pitch control system are presented to shows reduction in the resulting design demand loads.

Design, modeling and implementation of a novel pitch angle control system for wind turbine

A novel pitch angle control system is proposed to smooth output power and drive-train torque fluctuations for wind turbine. This system is characterized by an outer open control loop for enhancing the direct pitching motion and an intrinsic hydro-mechanical position control loop offering the benefit of sensor-less pitch control. A pragmatic design procedure is provided and several key design parameters are determined or optimized. Modeling, stability analysis and dynamic characteristics of this pitch control system are also presented. Comparative experimental results have validated the effectiveness and efficiency of this system in power and torque regulations.

A Co-Simulation Analysis of Hydraulic Pitch Control System in Large Wind Turbine

The use of wind power has been rising up rapidly due to its power potential and the improvement of technology. In order to extend the max capacity of power output, the size of wind turbine should grow simultaneously. Therefore, a cost effectiveness of wind power plant is needed to improve the performance. This paper aims at designing a novel hydraulic pitch actuator to implement pitch control effectively even if an impulsive wind peak appears. By developing a novel hydraulic pump control system, the creative design of hydraulic pump control system comprising a fixed displacement pump driven by a servo motor, two unsymmetrical hydraulic cylinders, and hydraulic circuits, could have an excellent response in operation. Furthermore, a feedback linearization controller was designed to compensate for the nonlinearity of hydraulic system and overcome the impulsive loadings from wind peaks. The turbine model was built through FAST released by NREL and the dynamic performance showed the excellent robustness and response with that proposed controller and mechanical design.

Numerical investigation of optimal yaw misalignment and collective pitch angle for load imbalance reduction of rigid and flexible HAWT blades under sheared inflow

Wind shear can strongly influence the cyclic loading on horizontal axis wind turbine blades. These load fluctuation causes a variation of power output and introduces fatigue load. Thus, individual pitch controllers have been developed that are focused on the load alleviations, however, comes at a price of actuator requirements for control. Moreover, these controllers are unable to apply to already existing wind turbines with active yaw and collective pitch control system. Therefore, the investigations for minimizing load imbalance through the adjustments of yaw misalignment and collective pitch angle are implemented for the rigid and flexible blades under the sheared inflow. By applying the optimization process based on a sequential quadratic programming approach, the optimal yaw and pitch angle can be estimated. Then, the numerical simulations for predicting the performance are performed. The results showed that the fluctuation range of the root flapwise bending moment for the rigid blades can be reduced by 84.5%, whereas the vibratory bending moment for the flexible blades can be reduced by up to approximately 82.4% in the best case. Therefore, the magnitudes of load imbalance can be minimized by the adjustment of the optimal yaw misalignment and collective pitch angle without any power loss.

Robotic Fish: Design and Characterization of an Interactive iDevice-Controlled Robotic Fish for Informal Science Education

In this article, we present the design, development, and characterization of a biomimetic robotic fish remotely controlled by an iDevice application (app) for use in informal science education. By leveraging robots, biomimicry, and iDevices, we seek to establish an engaging and unique experience for free-choice learners visiting aquariums, zoos, museums, and other public venues. The robotic fish incorporates a three-degree-of-freedom tail along with a combined pitch and buoyancy control system, allowing for high maneuverability in an underwater three-dimensional (3-D) space. The iDevice app implements three modes of control that offer a vividly colored, intuitive, and user-friendly theme to enhance the user experience when controlling the biomimetic robotic fish. In particular, the implemented modes vary in the degree of autonomy of the robotic fish, from fully autonomous to remotely controlled. A series of tests are conducted to assess the performance of the robotic fish and the interactive control modes. Finally, a usability study on elementary school students is performed to learn about students' perception of the platform and the various control modes.

New application of predictive direct torque control in permanent magnet synchronous generator-based wind turbine

This paper concerns the application of the predictive direct torque control (PDTC) method to a permanent magnet synchronous generator (PMSG). In classical methods for controlling a PMSG, the sampling frequency of the controller must be precisely determined. However, the use of PDTC in this study enables three optimal duty cycles to be predicted at the moment of sampling, significantly reducing the ripple of the electromagnetic torque and the amplitude of the stator flux below those caused by conventional control methods. Therefore, the new method allows a lower sampling frequency than the traditional method. To operate the machine side converter, the DC bus capacitor voltage must be maintained within an acceptable and stable range. Voltage-oriented vector control is used to control the active power and the reactive power, which are delivered from the DC bus capacitor, as well as to control the voltage. In this study, a complete wind turbine system is considered, including a focus on the aerodynamics and structure of each wind turbine, using Fatigue, Aerodynamics, Structures and Turbulence (FAST). Also, to prevent the rotor speed of the wind turbine from exceeding the rated rotor speed too much, a very simple pitch controller system is considered.

Parametric study on off-design aerodynamic performance of a horizontal axis wind turbine blade and proposed pitch control

In this paper, a 200kW horizontal axis wind turbine (HAWT) blade is designed using an efficient iterative algorithm based on the blade element momentum theory (BEM) on aerodynamic of wind turbines. The effects of off-design variations of wind speed are investigated on the blade performance parameters according to constant rotational speed of the rotor. The performance parameters considered are power coefficient, axial and angular induction factors, lift and drag coefficients on the blade, angle of attack and angle of relative wind. At higher or lower wind speeds than the designed rated speed, the power coefficient is reduced due to considerable changes in the angle of attacks. Therefore, proper pitch control angles were calculated to extract maximum possible power at various off-design speeds. The results showed a considerable improvement in power coefficient for the pitch controlled blade as compared with the baseline design in whole operating range. The present approach can be equally employed for determining pitch angles to design pitch control system of medium and large-scale wind turbines.

Experimental Assessment with Wind Turbine Emulator of Variable-Speed Wind Power Generation System using Boost Chopper Circuit of Permanent Magnet Synchronous Generator

This paper presents experimental results and its assessment of a variable-speed wind power generation system (VSWPGS) using permanent magnet synchronous generator (PMSG) and boost chopper circuit (BCC). Experimental results are obtained by a test bench with a wind turbine emulator (WTE). WTE reproduces the behaviors of a windmill by using servo motor drives. The mechanical torque references to drive the servo motor are calculated from the windmill wing profile, wind velocity, and windmill rotational speed. VSWPGS using PMSG and BCC has three speed control modes for the level of wind velocity to control the rotational speed of the wind turbine. The control mode for low wind velocity regulates an armature current of generator with BCC. The control mode for middle wind velocity regulates a DC link voltage with a vector-controlled inverter. The control mode for high wind velocity regulates a pitch angle of the wind turbine with a pitch angle control system. The hybrid of three control modes extends the variable-speed range. BCC simplifies the maintenance of VSWPGS while improving reliability. In addition, VSWPGS using PMSG and BCC saves cost compared with VSWPGS using a PWM converter.

Research on Compound Pitch Control Technology of Direct-drive Permanent Magnet Wind Turbine

The conventional PID pitch controller was usually used in direct-drive permanent magnet wind turbine in order to maintain the output power unchanged above the rated wind speed. However, due to the complex structure of wind turbine as well as high nonlinearity of wind speed, the effect of PID control method is often less than ideal. A new pitch control method combined with fuzzy adaptive PID and fuzzy feed forward controller is proposed in this paper. The fuzzy adaptive PID controller is able to ensure the unit having a better control result than PID controller at various wind speeds. The fuzzy feed forward controller has improved the responsiveness of pitch control system. With the simulation of a 1.5MW wind turbine, the responsiveness and stability of wind turbine can be effectively proved by the new pitch control method above the rated wind speed, the system’s overshoot is also reduced, which satisfies the demand of power control.

Fault Prediction of Pitch Actuator for Wind Turbines

Hydraulic pitch-controlled system is one of the components of wind turbines which are frequently prone to faults. Early fault prediction of the pitch control system can improve the operation reliability effectively and reduce the unnecessary loss. Wind turbines suffer much environmental interference; moreover, data-based fault prediction is vulnerable to occur false alarms by the impact of these factors. And it is difficult to implement the fault isolation. So this paper presents a fault prediction method for the pitch-controlled system, which is based on the mathematical model of wind turbines physical properties. The residual root mean square (RMS) is used as residual evaluation function. In the end of the paper, by the simulation using the hydraulic pitch actuator fault as the example, the effectiveness of the proposed fault prediction scheme is verified.

Model Based Automatic Regulation Process for Guidance and Control of Quadrotor UAV

In this literature, model based automatic regulation process is proposed for guidance control of a Quadrotor UAV. The performance of the system will be first tuned to match the performance of the reference model. It gives more convenient way for cope with different load for different mission. The automatic regulation process is used to adjust parameters of the basic control system that is well designed. The basic control system includes: (a) height control system using velocity stabilizing in the inner loop; (b) roll, pitch and yaw attitude control systems using angular rate stabilizing in inner loops. Base upon the basic control system, X_B and Y_B body axes velocities control laws and locus tracking laws can be added also. This application is different from conventional velocity, and position control techniques of conventional fix-fin UAV's. The proposed method is verified by vast digital simulations.