Collector anti-wearing and lubrication system for variable speed wind turbine
A variable speed wind turbine having a doubly fed induction generator (DFIG), includes an exciter machine mechanically coupled to the DFIG and a power converter placed between a rotor of the DFIG and the exciter machine. Thus, the power converter is not directly connected to the grid avoiding the introduction of undesired harmonic distortion and achieving a better power quality fed into the utility grid. Moreover, the variable speed wind turbine includes a power control and a pitch regulation.
1. A wind turbine system comprising:
a first rotor shaft including at least one blade;
an electrical generator;
a pitch control system to control a pitch angle of the at least one blade; and
an exciter machine coupled to a shaft of the generator,
wherein a pitch angle setpoint for the pitch angle is based on the exciter machine power.
2. A variable speed wind turbine system comprising:
a rotor including at least one blade;
a drive train coupled to the rotor, the drive train including at least a doubly fed induction generator (DFIG), said DFIG having at least a stator connectable to a power grid;
at least an exciter machine coupled to the drive train; and
at least a power conversion device isolated from the grid and electrically coupled to a rotor of the doubly fed induction generator and to the exciter machine to transfer electrical power between the rotor and the exciter machine, and
a pitch control system to control a pitch angle of the at least one blade, wherein the pitch angle is controlled to a total pitch angle setpoint which is based on base pitch angle setpoint and a varying pitch angle setpoint,
wherein the base pitch angle setpoint is set based on the power consumed or generated by the exciter machine.
3. The variable speed wind turbine system according to claim 2 , wherein the pitch control system controls the varying pitch angle setpoint to vary continuously.
4. The variable speed wind turbine system according to claim 3 , wherein the varying pitch angle setpoint varies from the base pitch angle setpoint following a periodic waveform according to an amplitude and a frequency.
5. The wind turbine systems according to claim 4 , wherein the periodic waveform is a sinusoidal waveform.
6. A method of controlling a pitch angle of a blade in a wind turbine, the method comprising:
determining a base pitch angle setpoint based on operating parameters of the wind turbine;
determining a varying pitch angle set point that varies with time independent of the operating parameters; and
setting the pitch angle of the blade based on the base pitch angle setpoint and the varying pitch angle set point,
wherein the base pitch angle setpoint is based on an exciter machine power setpoint.
7. The method of controlling a pitch angle setpoint according to claim 6 , wherein the pitch angle is set by adding the varying pitch angle to the base pitch angle.
8. The method of controlling a pitch angle setpoint according to claim 6 , wherein the varying pitch angle set point varies following a sinusoidal or any other periodic waveform over time.