Dynamic response analysis of wind turbines under blade pitch system fault, grid loss, and shutdown events

Abstract

This study focuses on the dynamic responses of land-based and floating wind turbines under blade pitch system fault and emergency shutdown conditions. The NREL 5 MW turbine is studied. A hydraulic pitch system is considered, and the faults under study are events with a seized blade or a blade running out of control. Emergency shutdown is defined as a fast pitch-to-feather maneuver of the blades. Load cases with power production and grid fault with ensuing shutdown are also analysed for comparison. The fault scenarios and the blades' fast pitching activity are simulated using HAWC2 through external Dynamic Link Libraries. On the basis of the time-domain simulations, the response characteristics of the land-based and the floating turbines in the four design load cases are compared. The load effects from the fault conditions are compared with the operational cases. Strong system dynamics and resonant responses, such as the tower elastic mode and the yaw resonant response, are elicited during shutdown. If the pitch system has a fault and one blade is hindered from normal pitching, the uneven load distribution of the blades leads to large structural and motion responses. For both turbines, the response maxima vary cyclically with the instantaneous azimuth when the blades start pitching to feather. For the floating wind turbine, the interaction of waves and wind also affects the results. The effect of the pitch rate during shutdown is analysed. The responses of the land-based turbine in grid loss and shutdown conditions are proportional to the pitch rate, whereas decreased sensitivity is found in the cases with pitch system faults. For the floating turbine, the effect of the pitch rate is small, and reduced pitch and yaw motion extremes are observed as the pitch rate increases. NOMENCLATUREIn the following, some of the abbreviations are defined. The others are defined as they appear in the text. AOA angle of attack (deg) DLL dynamic link library FWT floating wind turbine LWT land-based wind turbine LC load case NREL National Renewable Energy Laboratory NTM normal turbulence model NWP normal wind profile model Pr pitch rate ( /s)

New approach for optimizing energy by adjusting the trade-off coefficient in wind turbines

“…By applying the diagonalized form of the Hamiltonian matrix, it is proven that the solution of Equation 22 is evaluated as P = ψ 21 ψ 11 − 1 (see [12]), where the columns of…”

“…Among the recent new works in this area, it is preferred to emphasize not only on an optimization-based approach to reduce extreme structural loads during rapid and emergency shutdown [9], but also on predicting the maximum generation capacity to obtain power control [10] and extreme seeking to perform maximum point tracking [11] as well dynamic responses of land-based and floating wind turbines under pitch system faults [12].…”

Fault condition effects on the dynamic response of V-shaped offshore wind turbine

“…Normally, the design of a floating wind turbine is dominated by the harshest loads. However, the transient load cases are also important compared to the basic load cases addressing the operational and parked states of offshore wind turbines [5]. Several conditions may result in transient loads such as abnormal wind, shutdown of the turbine, loss of grid connection, faults in the control, and/or protection system.…”

Blade pitch control malfunction simulation in a wind energy conversion system with MPC five-level converter

“…The behavior of the blade pitching system in blade pitch controlled wind turbines influences the overall dynamics [24,25]. So, research should be conducted to anticipate the possible repercussions during different abnormal operating conditions, such as a blade pitch control malfunction.…”