Abstract: A controller and method is disclosed for operating a variable speed turbine to track wind speed fluctuations for high efficiency in conversion of wind energy to electrical energy. The controller of the invention controls the rotor speed in accordance with a wind speed supplied by a wind observer in order to approximately follow the varying wind speeds. A yaw angle error sensor senses the degree to which the turbine is misaligned with the wind. The wind observer predicts the average wind speed at a subsequent point in time. The average wind speed is applied to a parameter schedule to determine desired values for rotor speed and torque which are used by a rotor speed stabilizer to command a reference load torque. The load torque of the generator is controlled in accordance with the commanded load torque, and therefore the desired rotor speed is approximated.

Abstract: A wind turbine power converter is disclosed herein that smooths the output power from a variable speed wind turbine, to reduce or eliminate substantial power fluctuations on the output line. The power converter has an AC-to-DC converter connected to a variable speed generator that converts wind energy to electric energy, a DC-to-AC inverter connected to a utility grid, and DC voltage link connected to an electrical energy storage device such as a battery or a fuel cell, or a photovoltaic or solar cell. Also, an apparatus and method is disclosed herein for controlling the instantaneous current flowing through the active switches at the line side inverter to supply reactive power to the utility grid. The inverter can control reactive power output as a power factor angle, or directly as a number of VARs independent of the real power.

Abstract: An apparatus and method for compensating a polyphase electrical power supply for reactive power loads on an AC supply line is disclosed. The static VAR compensator disclosed herein can provide a selectable, constant amount of VARs to compensate for reactive loads on the line, or alternately provide a fixed phase angle. The static VAR compensator may be controlled to compensate for fluctuating reactive loads. The static VAR compensator includes a transistorized inverter, connected between the AC supply and a constant voltage, that has switches to control the instantaneous current on each phase line of the AC power supply. By modulating the inverter switches at a high frequency, the instantaneous currents flowing through each of the phase lines can be modulated for precise control of the real and the reactive power. A voltage waveform is obtained from each phase of the utility grid, and used as a reference waveform.

Abstract: A low impedance, high power bus for conduction of electrical power with reduced transient signal effects is described herein. The high power bus can be applied as a high power supply bus between a constant voltage source and a plurality of switching cells positioning at varying locations along the bus, and as branch bus for the switching cells. The power bus can transmit high power: large currents in the hundreds or thousands of amperes, and large voltage potentials in the hundreds or thousands of volts. Particularly, the power bus has use in a DC-to-AC inverter that converts DC from a constant voltage source into three-phase AC for delivery to an electrical power grid. The high power bus includes two conductive bars positioned so that the current flow therethrough is balanced (equal and opposing), and the magnetic field is substantially confined between the bars. The bus includes a dielectric positioned between the conductive bars.

Abstract: A controller and method is disclosed for operating a variable speed turbine to better track wind speed fluctuations for greater efficiency in conversion of wind energy to electrical energy. The controller of the invention controls the rotor speed in accordance with a wind speed supplied by a wind observer in order to approximately follow the varying wind speeds. The wind observer predicts the average wind speed at a subsequent point in time over the cross-section presented to the wind by the wind turbine. The average wind speed is applied to a parameter schedule to determine desired values for rotor speed and torque which are used by arotor speed stabilizer to command a reference load torque. The load torque of the generator is controlled in accordance with the commanded load torque, and therefore the desired rotor speed is approximated. During operation, the wind speed prediction process is repeated at each subsequent time interval, and the load torque, and therefore rotor speed, is controlled accordingly.

Abstract: A variable speed wind turbine is disclosed comprising a turbine rotor that drives an AC induction generator, a power converter that converts the generator output to fixed-frequency AC power, a generator controller, and an inverter controller. The generator controller uses field orientation to regulate either stator currents or voltages to control the torque reacted by the generator. The inverter controller regulates the output currents to supply multi-phase AC power having leading or lagging currents at an angle specified by a power factor control signal.

Abstract: A windpower system includes a support and a turbine having a shaft rotatively mounted to the support. The turbine has variable pitch blades whose pitch is controlled by the differential motion of a rotary control shaft coaxial with the turbine shaft and the turbine shaft itself so that the blade pitch can be varied by a stationary motor without requiring any slip rings or other such wear-prone couplings. In the event of a power failure, rotary motion of the control shaft is prevented so that the turbine blades are feathered solely due to the force developed by the rotating turbine. Also, if the turbine is used to generate electrical power, an induction generator coupled to the turbine shaft is employed whose shaft speed is indicative of generator output power.

Abstract: A windmill employs a separate wind vane pivotably mounted on the chassis of the windmill. An internal sensor detects the relative angle between the wind vane and the windmill and activates the pitch-control mechanism of the windmill to feather the windmill blades whenever the angle exceeds a predetermined maximum.

Abstract: A windmill installation (10) includes a windmill (12) supported on a tower (18) that includes three legs (20, 22, and 24). The connections of the legs (20, 22, and 24) to their respective bases (36, 37, and 38) are provided by compliance members (30, 32, and 34) that are compliant enough that the natural frequency of axial bending of the windmill installation is less than the frequency with which blades (14) of the windmill (12) pass behind the tower (18). Also, a windmill compliance assembly (28) provides the connection between the windmill (12) and the tower (18) and has enough compliance that the natural frequency of pivotal bending is also below that frequency. As a result, vibration at a resonant frequency of the structure is avoided during normal operation.

Abstract: In order to control the turbine speed of a windmill employed for power generation, the pitch of the turbine blades is based on a dual-deadband control strategy. If the current turbine speed is determined to be outside of a relatively wide deadband, action is taken to correct the speed by changing blade pitch accordingly. If the current speed is not outside of the relatively wide deadband, then the average of the turbine speed over a recent interval is compared with a relatively narrow deadband within the wider deadband. Action is then taken to change the blade pitch if the average speed is outside the narrow deadband. In this way, wide excursions of turbine speed are corrected promptly, but the frequency of control actions is minimized by requiring only the average speed to be kept within tight limits.