Pitch-controlled variable-speed wind turbine generation

Abstract

-Wind energy is a viable option to complement other types of pollution-free generation. In the early development of wind energy, the majority of wind turbines were operated at constant speed. Recently, the number of variable-speed wind turbines installed in wind farms has increased and more wind turbine manufacturers are making variable-speed wind turbines. This paper covers the operation of variablespeed wind turbines with pitch control. The system we 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 medium wind speeds, the generator and power converter control the wind turbine to capture maximum energy from the wind. In the high wind speed region, 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 control the operation of the wind turbine.Our analysis and simulation shows that the wind turbine can be operated at its optimum energy capture while minimizing the load on the wind turbine for a wide range of wind speeds. INDEX TERMSWind turbine generator, renewable energy, pitchcontrolled, variable speed.

General Model for Representing Variable-Speed Wind Turbines in Power System Dynamics Simulations

“…• a slight overspeeding of the rotor above its nominal value can be allowed and poses no problems for the wind turbine construction [19]; • the system is never in steady state due to the varying wind speed, so that the advantage of an integral controller, which can achieve zero steady state error, is not applicable.…”

“…At medium wind speeds, the rotor speed varies proportional to the wind speed, and thus, with the cubic root of the power, according to (3). When the rotor speed reaches its maximum value, generator torque is kept at its maximum [19].…”

Stability Analysis of DFIG based Wind Energy System

“…Therefore, as the wind speed doubles, output power will increment by eight times. The figure 2 shows different power curves of a wind turbine [13][14][15][16][17][18]. At various wind speeds, if the operating point is along the maximum power locus, which will be carried out by controlling the load on the wind turbine, then the wind energy system will be highly efficient.…”

Fundamental performance similarities between individual pitch control strategies for wind turbines

“…As a consequence, a growing body of research has emerged in recent years, seeking to establish the best way of designing individual pitch control (IPC) systems. Typically, and for reasons of simplicity of implementation favoured by the industry, IPCs are designed separately from a collective pitch control (CPC) system, whose role is to regulate the rotor speed in above-rated wind conditions by collectively adjusting the pitch angle of each blade by the same amount (Muljadi & Butterfield, 2001;Pao & Johnson, 2009). The IPC provides an additional pitch angle demand signal, typically in response to measurements of the flap-wise blade root bending moments, in order to attenuate the effects of unsteady spatio-temporal rotor loads.…”