Individual pitch control for 2‐bladed wind turbines via multiblade multilag transformation

Abstract

Two-bladed wind turbines have regained the attention of the community thanks to the advantages in manufacturing cost provided by the lower number of blades and the ease of implementation of effective passive systems for load reduction (ie, teetering pin). Considering both teetering and nonteetering architectures, the dynamics of 2-bladed turbines is different from that of 3-bladed machines especially in terms of how multiples of the rotor frequencies in blade signals are translated on the fixed system. Such characteristics have hampered the adoption of active control laws for load mitigation based on individual pitch control, extensively studied for 3-bladed turbines. A basic element for control development allowing to capture the essence of the relationship between signals on the blades and the fixed system on 2-bladed turbines-represented by the Coleman transformation for 3-bladed turbines-has not been identified yet. The present paper tries to fill the gap, presenting an extended transformation-called multiblade multilag-applicable to turbines with an arbitrary number of blades, providing a systematic way to link rotor signals to fixed system signals, thus allowing the application of control algorithms for individual pitch control developed for 3-bladed turbines to the 2-bladed case. The paper addresses the problem first at a theoretical level, and subsequently providing applicative results from simulations on virtual models of teetering and nonteetering 2-bladed turbines. The proposed transformation algorithm and control laws allow to effectively reduce some relevant loads and motions respectively in the nonteetering and teetering scenarios, through a cyclic pitch input

Equalizing Aerodynamic Blade Loads Through Individual Pitch Control Via Multiblade Multilag Transformation

“…Furthermore, the effects on the stability of the present control are under investigation using an identification-based stability analysis tool [18]. The application of the MBML transformation to active load mitigation for twobladed rotors will be presented in a forthcoming publication [19].…”

A Research Framework for the Multidisciplinary Design and Optimization of Wind Turbines

“…Concerning outer layers, the frequency band of pitch actuators can be employed to target the lower per-revolution frequencies showing up in the spectra of load signals from the blades, tower, and shaft. Works by Bossanyi [33] propose an approach based on Coleman's transformation, developed to target higher harmonics in the works of Cacciola [40][41][42], whereas Bottasso et al [32] describe a modelbased approach for deterministic loads and a model-free approach for residual noise components, typically due to high-frequency turbulence. Synthesizing the gains of this control layer, whatever the selected approach, can be done according to heuristics or optimal numerical procedures [43].…”

Investigation of power quality and structural loads for two‐bladed wind turbines with rigid and teetered rotors using a wind turbine emulator

“…Two‐bladed WTs have been recently regained community attention as these WTs could be an interesting alternative to reduce the cost of energy for offshore WECSs [5]. The cost of two‐bladed WTs may be less than three‐bladed WTs due to the number of blades [5, 6]. In the industry, some companies such as 2‐B energy [7], WES [8], Carter wind energy [9] are working to develop state‐of‐the‐art two‐bladed WTs.…”

“…In the industry, some companies such as 2‐B energy [7], WES [8], Carter wind energy [9] are working to develop state‐of‐the‐art two‐bladed WTs. In academia, different research works have been recently done to develop two‐bladed WTs [5, 10–14]. Most of these works have studied the structural loads of two‐bladed WECSs, and few works have concentrated on the power quality of these WECSs.…”