Variable-speed Operation Of Wind Turbines Research Articles

Utilisation of kinetic energy from wind turbine for grid connections: a review paper

Variable-speed operation of wind turbines (WTs) achieved through electronic converters can decouple wind generator dynamics from power systems. Besides, the wide rotor operation range makes it possible for the WT to tap the potential of kinetic energy (KE) in the rotating mass. This study provides an overview of utilising KE from WTs for grid connections. The availability of KE in WTs is acquired by the rotor speed alternation, both in static and dynamic processes. For the static state, the rotors of WTs operate at a pre-defined power curve which leaves the generation margin for KE release; while for the dynamic process, the KE is passively changed by the imbalance between mechanical and electrical power. Some emerging technologies in frequency regulation and low-voltage ride through capability with the participation of KE stored in WTs are investigated. The applications of KE in terms of wind smoothing are summarised as well. Finally, this literature review also discusses some potential future applications of KE management.

Adaptive neuro-fuzzy maximal power extraction of wind turbine with continuously variable transmission

In recent years the use of renewable energy including wind energy has risen dramatically. Because of the increasing development of wind power production, improvement of the control of wind turbines using classical or intelligent methods is necessary. To optimize the power produced in a wind turbine, the speed of the turbine should vary with the wind speed. Variable-speed operation of wind turbines presents certain advantages over constant-speed operation. In this paper, in order to maintain the maximal output power of wind turbine, a novel intelligent controller based on the adaptive neuro-fuzzy inference system (ANFIS) is designed. To improve the wind energy available in an erratic wind speed regime, a wind generator equipped with continuously variable transmission (CVT) was proposed. In this model the ANFIS regulator adjusts the system speed, i.e. CVT ratio, for operating at the highest efficiency point. The performance of proposed controller is confirmed by simulation results. Some outstanding properties of this new controller are online implementation capability, structural simplicity and its robustness against any changes in wind speed and system parameter variations. Based on the simulation results, the effectiveness of the proposed controllers was verified.

Transient analysis of variable-speed wind turbines at wind speed disturbances and a pitch control malfunction

As wind power generation undergoes rapid growth, new technical challenges emerge: dynamic stability and power quality. The influence of wind speed disturbances and a pitch control malfunction on the quality of the energy injected into the electric grid is studied for variable-speed wind turbines with different power-electronic converter topologies. Additionally, a new control strategy is proposed for the variable-speed operation of wind turbines with permanent magnet synchronous generators. The performance of disturbance attenuation and system robustness is ascertained. Simulation results are presented and conclusions are duly drawn.

Fractional-order control and simulation of wind energy systems with PMSG/full-power converter topology

This paper presents a new integrated model for the simulation of wind energy systems. The proposed model is more realistic and accurate, considering a variable-speed wind turbine, two-mass rotor, permanent magnet synchronous generator (PMSG), different power converter topologies, and filters. Additionally, a new control strategy is proposed for the variable-speed operation of wind turbines with PMSG/full-power converter topology, based on fractional-order controllers. Comprehensive simulation studies are carried out with matrix and multilevel power converter topologies, in order to adequately assert the system performance in what regards the quality of the energy injected into the electric grid. Finally, conclusions are duly drawn.

Disturbance Tracking Control and Blade Load Mitigation for Variable-Speed Wind Turbines

A composite linear state-space controller was developed for a multi-objective problem in the variable-speed operation of wind turbines. Disturbance Tracking Control theory was applied to the design of a torque controller to optimize energy capture under the influence of persistent wind disturbances. A limitation in the theory for common multi-state models is described; this led to the design of a complementary pitch controller. The goal of the independent blade pitch design was to minimize blade root fatigue loads. A SymDyn model of a two-bladed, 600-kW machine was used for the simulation studies. Results indicate a 24% reduction in blade fatigue damage using the proposed controllers, compared to a conventional torque-only design. However, energy capture was not improved as much as expected, partly due to nonlinearity effects degrading the performance of the state-space estimator design. Tower base fatigue damage was shown to decrease significantly using active pitch.

Pitch-controlled variable-speed wind turbine generation

This paper covers the operation of variable-speed wind turbines with pitch control. The system the authors considered is controlled to generate maximum energy while minimizing loads. The maximization of energy was only carried out on a static basis and only drive train loads were considered as a constraint. In low to medium wind speeds, the generator and the power converter control the wind turbine to capture maximum energy from the wind. In the high-wind-speed regions, the wind turbine is controlled to maintain the aerodynamic power produced by the wind turbine. Two methods to adjust the aerodynamic power were investigated: pitch control and generator load control, both of which are employed to regulate the operation of the wind turbine. The authors' analysis and simulation show that the wind turbine can be operated at its optimum energy capture while minimizing the load on the mind turbine for a wide range of wind speeds.