Effect of dissipative aerodynamic torque on satellite rotation.

This paper proposes a robust fault diagnosis scheme based on modified sliding mode observer, which reconstructs wind turbine hydraulic pitch actuator faults as well as simultaneous sensor faults. The wind turbine under consideration is a 4.8 MW benchmark model developed by Aalborg University and kk-electronic a/s. Rotor rotational speed, generator rotational speed, blade pitch angle and generator torque have different order of magnitudes. Since the dedicated sensors experience faults with quite different values, simultaneous fault reconstruction of these sensors is a challenging task. To address this challenge, some modifications are applied to the classic sliding mode observer to realize simultaneous fault estimation. The modifications are mainly suggested to the discontinuous injection switching term as the nonlinear part of observer. The proposed fault diagnosis scheme does not require know the exact value of nonlinear aerodynamic torque and is robust to disturbance/modelling uncertainties. The aerodynamic torque mapping, represented as a two-dimensional look up table in the benchmark model, is estimated by an analytical expression. The pitch actuator low pressure faults are identified using some fault indicators. By filtering the outputs and defining an augmented state vector, the sensor faults are converted to actuator faults. Several fault scenarios, including the pitch actuator low pressure faults and simultaneous sensor faults, are simulated in the wind turbine benchmark in the presence of measurement noises. Simulation results show that the modified observer immediately and faithfully estimates the actuator faults as well as simultaneous sensor faults with different order of magnitudes.

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Attempt to quantify the impact of seasonal air density variation on operating tip-speed ratio of small wind turbines

Journal of Physics Conference Series ◽

10.1088/1742-6596/2090/1/012144 ◽

2021 ◽

Vol 2090 (1) ◽

pp. 012144

Author(s):

Hiroki Suzuki ◽

Yutaka Hasegawa ◽

O.D. Afolabi Oluwasola ◽

Shinsuke Mochizuki

Keyword(s):

Wind Turbine ◽

Wind Velocity ◽

Governing Equation ◽

Rotational Speed ◽

Speed Ratio ◽

Tip Speed Ratio ◽

Air Density ◽

Small Wind Turbines ◽

The Impact ◽

Aerodynamic Torque

Abstract This study presents the impact of seasonal variation in air density on the operating tip-speed ratio of small wind turbines. The air density, which varies depending on the temperature, atmospheric pressure, and relative humidity, has an annual amplitude of about 5% in Tokyo, Japan. This study quantified this impact using the rotational speed equation of motion in a small wind turbine informed by previous work. This governing equation has been simplified by expanding the aerodynamic torque coefficient profile for a wind turbine rotor to the tip-speed ratio. Furthermore, this governing equation is simplified by using nondimensional forms of the air density, inflow wind velocity, and rotational speed with their characteristic values. In this study, the generator’s load is set to be constant based on a previous analysis of a small wind turbine. By considering the equilibrium between the aerodynamic torque and the load torque of the governing equation at the optimum tip-speed ratio, the impact of the variation in the air density on the operating tip-speed ratio was expressed using a simple mathematical form. As shown in this derived form, the operating tip-speed ratio was found to be less sensitive to a variation in air density than that in inflow wind velocity.

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Improved estimation of aerodynamic characteristics of a complex geometry nanosatellite

Engineering Journal Science and Innovation ◽

10.18698/2308-6033-2021-10-2116 ◽

2021 ◽

Author(s):

E.V. Barinova ◽

E.A. Boltov ◽

N.A. Elisov ◽

I.A. Lomaka

Keyword(s):

Finite Element ◽

Monte Carlo ◽

Drag Coefficient ◽

Complex Geometry ◽

Direct Simulation Monte Carlo ◽

Aerodynamic Characteristics ◽

Thermal Velocity ◽

Direct Simulation ◽

Simulation Monte Carlo ◽

Aerodynamic Torque

The paper presents an approach to refine the aerodynamic characteristics (drag coefficient, aerodynamic torque) of a complex-geometry nanosatellite. The approach is based on the direct simulation Monte-Carlo method. The calculations took into account gas−surface interaction according to Cercignani—Lampis—Lord model, chemical composition of atmosphere on the orbit altitude and particle thermal velocity. The nanosatellite complex geometry was described as a finite-element grid with the cell size of 5 mm. The results of the engineering and numerical methods were compared. The differences in drag coefficient and aerodynamic torque between the two methods reached 20%.

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Experiences with the GPS in Unstabilized CubeSat

International Journal of Aerospace Engineering ◽

10.1155/2020/8894984 ◽

2020 ◽

Vol 2020 ◽

pp. 1-12

Author(s):

Pavel Kovar

Keyword(s):

Experimental Data ◽

Signal Acquisition ◽

Gps Receiver ◽

Small Satellite ◽

Power Budget ◽

Successful Operation ◽

Polar Orbit ◽

Position Information ◽

Space Experiments ◽

Satellite Rotation

The paper summarizes the experiences with the operation of the piNAV GPS receiver in a 1U unstabilized CubeSat operated on LEO orbit. piNAV L1 is a GPS receiver developed by an author for small satellite missions. The receiver is equipped with the 15 GPS L1 C/A channels and acquisition accelerator that shortens the cold start of the receiver on LEO to 65 s. The typical power consumption is 120 mW. Lucky-7 is a private 1U technological CubeSat with power budget 1 W that operates on the quasisynchronous polar orbit at altitude 520 km. One of its scientific missions is to test the operation of GPS. The space experiments proved the successful operation of the GPS receiver. The position information was available for approximately 80% of the time, where the position outage was caused by a satellite rotation and relatively long navigation signal reacquisition. The experimental data proved that the position availability can be improved by a higher-performance signal acquisition engine.

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On Empirical Model of Aerodynamic Torque Acting on Savonius Rotor

2020 15th International Conference on Stability and Oscillations of Nonlinear Control Systems (Pyatnitskiy's Conference) (STAB) ◽

10.1109/stab49150.2020.9140701 ◽

2020 ◽

Author(s):

Anna Masterova ◽

Yury Selyutskiy ◽

Alexander Zubkov ◽

Rinaldo Garziera

Keyword(s):

Empirical Model ◽

Savonius Rotor ◽

Aerodynamic Torque

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Vibration Reduction Strategy for Offshore Wind Turbines

Applied Sciences ◽

10.3390/app10176091 ◽

2020 ◽

Vol 10 (17) ◽

pp. 6091

Author(s):

Haoming Liu ◽

Suxiang Yang ◽

Wei Tian ◽

Min Zhao ◽

Xiaoling Yuan ◽

...

Keyword(s):

Wind Turbine ◽

Output Power ◽

Wind Turbines ◽

Reference Signal ◽

Offshore Wind ◽

Wave Load ◽

Offshore Wind Turbines ◽

Pitch Control ◽

Simulation Results ◽

Aerodynamic Torque

The operational environment of offshore wind turbines is much more complex than that of onshore wind turbines. Facing the persistent wind and wave forces, offshore wind turbines are prone to vibration problems, which are not conducive to their long-term operation. Under this background, first, how the wave affects the vibration characteristics of offshore wind turbines is analyzed. Based on the existing wave and wave load models, we analytically show that there exist fluctuating components related to the hydrodynamic frequency in the aerodynamic load and aerodynamic torque of offshore wind turbines. Simulation results based on a GH Bladed platform further validates the analysis. Second, in order to reduce the joint impacts of the wave, wind shear and tower shadow on the wind turbine, a variable pitch control method is proposed. The integrated tower top vibration acceleration signal is superimposed on the collective pitch reference signal, then the triple frequency (3P) fluctuating component of the wind turbine output power and the azimuth angle of each blade are converted into the pitch angle adjustment signal of each blade, which is superimposed on the collective pitch signal for individual pitch control. The simulation results show that the proposed pitch control strategy can effectively smooth the fluctuation of blade root flap-wise load caused by wind and wave, and significantly reduce the fluctuation of aerodynamic torque and output power of offshore wind turbines.

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Nonlinear Maximum Power Point Tracking Control Method for Wind Turbines Considering Dynamics

Applied Sciences ◽

10.3390/app10030811 ◽

2020 ◽

Vol 10 (3) ◽

pp. 811 ◽

Cited By ~ 4

Author(s):

Liangwen Qi ◽

Liming Zheng ◽

Xingzhi Bai ◽

Qin Chen ◽

Jiyao Chen ◽

...

Keyword(s):

Wind Turbine ◽

Pitch Angle ◽

Maximum Power Point ◽

Feed Forward ◽

Point Tracking ◽

Power Point Tracking ◽

Power Capture ◽

Power Point ◽

Aerodynamic Torque ◽

Blade Pitch Angle

A combined strategy of torque error feed-forward control and blade-pitch angle servo control is proposed to improve the dynamic power capture for wind turbine maximum power point tracking (MPPT). Aerodynamic torque is estimated using the unscented Kalman filter (UKF). Wind speed and tip speed ratio (TSR) are estimated using the Newton–Raphson method. The error between the estimated aerodynamic torque and the steady optimal torque is used as the feed-forward signal to control the generator torque. The gain parameters in the feed-forward path are nonlinearly regulated by the estimated generator speed. The estimated TSR is used as the reference signal for the optimal blade-pitch angle regulation at non-optimal TSR working points, which can improve the wind power capture for a wider non-optimal TSR range. The Fatigue, Aerodynamics, Structures, and Turbulence (FAST) code is used to simulate the aerodynamics and mechanical aspects of wind turbines while MATLAB/SIMULINK is used to simulate the doubly-fed induction generator (DFIG) system. The example of a 5 MW wind turbine model reveals that the new method is able to improve the dynamic response of wind turbine MPPT and wind power capture.

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