Abstract: A gas turbine engine bleed air system in which air flow from a high pressure and a low pressure compressor stage of a gas turbine engine are mixed together by controlling the pressure at the outlet of a proportional valve. The pressure is controlled by modulating the flow area of the proportional valve through which the high pressure air flows in order to achieve a scheduled pressure value. The scheduled pressure value is determined as a function of a temperature error at a location downstream of the proportional valve in the bleed air system.

Abstract: An automatic control system includes a multiplier for multiplying the error signal fed to an integrator in accordance with the state of the integrator. The multiplier multiplies the error signal by a unity gain factor over the normal range of integral control; whereas, the multiplier multiplies the error signal by a factor greater than one, typically ten, when the integrator output is saturated at either the minimum or maximum values. The high multiplication value of the error signal ensures a sufficiently quick recovery from an integrator saturation condition.

Abstract: A variable speed wind turbine is controlled in a way which avoids the turbine lingering at a critical speed which would otherwise tend to cause excessive vibration. The disclosed method and apparatus increases speed at a selected rate with respect to generator output power except in the vicinity of the critical speed. The selected rate is changed in the vicinity of the critical speed to a different rate which is selected slower in the selected embodiment, to avoid commanding the critical speed. After the output power increases or decreases beyond the critical point, a deliberate discontinuity in the speed command signal is induced. A rapid speed change through the critical speed is accompanied by a corresponding power output change.

Abstract: A variable speed wind turbine includes a frequency converter which converts variable frequency AC from a turbine driven AC generator to fixed frequency AC for delivery to a power grid. The frequency converter is typically an electronic cycloconverter or rectifier-inverter and is also used to control the power flow from the AC generator to the grid which thereby controls the air gap torque between the generator stator and rotor. The turbine speed is maneuvered to increase efficiency by precisely controlling the air gap torque according to a schedule defining sensed generator speed versus sensed generated power.

Abstract: Damping of the primary bending mode of a tower (12) mounting a wind turbine having a control (36) for providing a pitch blade angle reference signal (40) to modulate the pitch of the turbine blades (1) through a pitch change mechanism (38) for constant power is provided by generating the pitch blade angle reference signal as the integral (104) of the summation (266) of a torque/power controlling blade pitch angle reference rate signal (98) with an estimated acceleration signal (255) generated by filtering (250, 252, 254) the blade pitch angle reference signal (40) with the following transfer function ##EQU1##

Abstract: An accelerometer (1) disposed on the support tower (12) of a wind turbine electric generating system in the vicinity of the rotor (10, 16) thereof provides a signal (1) indicative of acceleration of the tower in the direction of the rotor rotational axis. The signal (2) is passed through a band-pass filter (4) for summation (9) with a torque/power controlled (100) blade pitch angle reference rate signal (98), the integral (104) of which provides a blade pitch angle reference signal (40) to control the pitch angle of the rotor blades (10) through a pitch change mechanism (38), thereby to provide additional, positive aerodynamic damping to the tower while modulating blade angle for constant torque/power in response to wind turbulence.

Abstract: A blade pitch angle control for a wind turbine-generator establishing an optimum power or torque reference signal which, when operating conditions so warrant, is not limited by the nominal torque or power ratings of various turbine generator components. The reference signal is indicative of a maximum blade angle setting for safe operation of the wind turbine. An integral or lag compensation circuit for enhanced transient and steady-state operation may be employed.

Abstract: A multi-mode electronic wind turbine control system establishes a reference blade angle for a two-bladed, horizontal axis, variable pitch wind turbine rotor, the blade angle being regulated by a hydraulic pitch change mechanism. The rotor, via appropriate shafts and a gearbox, is coupled to a synchronous generator to produce electrical energy which is fed to a power utility grid. The control system provides closed loop pitch control for rotor acceleration rate during start-up, for rotor deceleration rate during shutdown, for speed control when the synchronous generator is off-line, and for power control when the synchronous generator is on-line. A single control integrator is used for all closed loop operating modes, with a rate limiter circuit in front of the control integrator to prevent integrator overtravel. The integrator has maximum and minimum blade angle stops, the minimum stop being variable as a function of rotor speed and wind speed.

Abstract: Wind energy is used to drive a wind turbine, which is in turn connected to an electrical generator to produce electrical power. The pitch angle of the wind turbine blades is controlled in a closed loop manner to maintain either a constant generator speed for isolated power generating stations or when the generator is synchronized to the load, or constant generator output power or shaft torque when the generator is connected to an electrical grid. Open loop acceleration and deceleration schedules are provided to minimize blade stress and shaft torque variations during start up and shutdown transients, limiting blade angle excursions as a function of wind velocity and speed. The schedules may be implemented either electronically or by a suitably programmed digital computer. The gains in the speed, torque and power loop controls are scheduled as a function of average wind velocity to optimize stability and response.