Abstract: A tachometer for a generator is disclosed. The tachometer may include a plurality of filters configured to receive a plurality of generator phase signals, a plurality of zero-cross detectors, and a logic circuit. The filters may be configured to convert each phase signal into a corresponding filtered signal. The zero-cross detectors may be configured to generate pulse signals responsive to zero-crossings detected in each filtered signal. The logic circuit may be in communication with each zero-cross detector and configured to receive the pulse signals. The logic circuit may logically combine the pulse signals into a combined signal, and generate a tachometer signal based on the combined signal, wherein the tachometer signal corresponds to a rotational speed of the generator.

Abstract: A method for preventing over torque and failure of yaw system components in a wind turbine is disclosed. The method may include providing a yaw system having a yaw drive including a drive motor for facing a nacelle positioned on the yaw system in a preferred wind direction. The method may also include preventing operation of the drive motor beyond a normal operating region on a torque-speed curve of the drive motor to avoid torques that may damage the yaw system components.

Abstract: The present invention provides devices for controlling a desired output of an output device. These devices include a first conductor, a second conductor having a varying, predetermined spacing from the first conductor, and a third conductor positioned on the actuator mechanism and having a plurality of interconnecting positions between the first conductor and the second conductor. A predetermined one of a plurality of output signals may be produced when the third conductor connects the first conductor and the second conductor to control the desired output of the output device.

Abstract: The present invention provides systems, devices and methods for controlling a desired output of an output device. These systems, devices and methods include connecting an electrical resistance element having a selected one of a plurality of resistance values with an electrical circuit portion having a plurality of electrical components, determining an electrical characteristic associated with the connected electrical circuit portion and the variable resistance element, and generating a control signal based on the electrical characteristic to control the desired output of the output device.

Abstract: The present invention provides systems, devices and methods for controlling a desired output of an output device. These systems, devices and methods include connecting an electrical resistance element having a selected one of a plurality of resistance values with an electrical circuit portion having a plurality of electrical components, determining an electrical characteristic associated with the connected electrical circuit portion and the variable resistance element, and generating a control signal based on the electrical characteristic to control the desired output of the output device.

Abstract: A wind powered turbine with low voltage ride-through capability. An inverter is connected to the output of a turbine generator. The generator output is conditioned by the inverter resulting in an output voltage and current at a frequency and phase angle appropriate for transmission to a three-phase utility grid. A frequency and phase angle sensor is connected to the utility grid operative during a fault on the grid. A control system is connected to the sensor and to the inverter. The control system output is a current command signal enabling the inverter to put out a current waveform, which is of the same phase and frequency as detected by the sensor. The control system synthesizes current waveform templates for all three-phases based on a sensed voltage on one phase and transmits currents to all three-phases of the electrical system based on the synthesized current waveforms.

Abstract: A wind powered turbine with low voltage ride-through capability. An inverter is connected to the output of a turbine generator. The generator output is conditioned by the inverter resulting in an output voltage and current at a frequency and phase angle appropriate for transmission to a three-phase utility grid. A frequency and phase angle sensor is connected to the utility grid operative during a fault on the grid. A control system is connected to the sensor and to the inverter. The control system output is a current command signal enabling the inverter to put out a current waveform, which is of the same phase and frequency as detected by the sensor. The control system synthesizes current waveform templates for all three-phases based on a sensed voltage on one phase and transmits currents to all three-phases of the electrical system based on the synthesized current waveforms.

Abstract: Techniques for performing Fast Fourier Transforms (FFT) are described. In some aspects, calculating the Fast Fourier Transform is achieved with an apparatus having a memory (610), a Fast Fourier Transform engine (FFTe) having one or more registers (650) and a delayless pipeline (630), the FFTe configured to receive a multi-point input from the main memory (610), store the received input in at least one of the one or more registers (650), and compute either or both of a Fast Fourier Transform (FFT) and an Inverse Fast Fourier Transform (IFFT) on the input using the delayless pipeline.

Abstract: A wind powered turbine with low voltage ride-through capability. An inverter is connected to the output of a turbine generator. The generator output is conditioned by the inverter resulting in an output voltage and current at a frequency and phase angle appropriate for transmission to a three-phase utility grid. A frequency and phase angle sensor is connected to the utility grid operative during a fault on the grid. A control system is connected to the sensor and to the inverter. The control system output is a current command signal enabling the inverter to put out a current waveform, which is of the same phase and frequency as detected by the sensor. The control system synthesizes current waveform templates for all three-phases based on a sensed voltage on one phase and transmits currents to all three-phases of the electrical system based on the synthesized current waveforms.

Abstract: An FFT engine implementing a cycle count method of applying twiddle multiplications in multi-stages. When implementing a multistage FFT, the intermediate values need to be multiplied by various twiddle factors. The FFT engine utilizes a minimal number of multipliers to perform the twiddle multiplications in an efficient pipeline. Optimizing a number of complex multipliers based on an FFT radix and a number of values in each row of memory allows the FFT function to be performed using a reasonable amount of area and in a minimal number of cycles. Strategic ordering and grouping of the values allows the FFT operation to be performed in a fewer number of cycles.

Abstract: An FFT processor for an OFDM receiver includes multiple interrelated operational blocks. The FFT processor is configured to perform data demodulation, channel estimation, and fine timing acquisition on received OFDM symbols. The FFT processor incorporates a pipelined FFT engine using a memory architecture shared with channel estimation and demodulation blocks. The combination of the shared memory structure and the pipelined FFT operation enable the channel estimation and demodulation processing to be completed during the time used to capture the next received symbol.

Abstract: Apparatus and methods of determining a modulo count of a synchronization number in a sleep capable system. The synchronization number is stored in a comparison register, and a comparison number equal to the largest power of two multiple of the modulus within a predetermined range is subtracted from the synchronization number. If the difference is zero, the difference is stored in the comparison register, replacing the previous number stored in the register. If the difference is less than zero, the number stored in the register remains unchanged. The comparison number is right shifted, resulting in division by two. The process is repeated for a number of loops equal to the power of two, or until the difference is less than the modulus.

Abstract: Channel estimation in a spectrally shaped wireless communication system in which an initial frequency response estimate is obtained for a first set of P uniformly spaced subbands (1) based on pilot symbols received on a second set of subbands used for pilot transmission and (2) using extrapolation and/or interpolation. A channel impulse response estimate is obtained by performing an IFFT on a frequency response estimate. The number of taps in the channel impulse response can be truncated to a predetermined number of taps determined based on an operating mode of the second set of P uniformly spaced subbands. The energy of each tap value remaining after truncation can be compared to a predetermined threshold and modified based on the results of the comparison. The predetermined threshold can be determined based on an operating mode. A final frequency response estimate for each mode within each OFDM symbol is derived.

Abstract: In an OFDM system, multiple (M) interlaces are defined for M non-overlapping sets of frequency subbands, and M slots with fixed indices are also defined. Data streams and pilot are mapped to slots, which are in turn mapped to interlaces based on a slot-to-interlace mapping scheme that can achieve frequency diversity and good performance for all slots. At a transmitter, a slot-to-interlace converter maps the slots to the interlaces. The slot-to-interlace converter includes multiple multiplexers and a control unit. The multiplexers map the M slots to the M interlaces based on the slot-to-interlace mapping scheme. The control unit generates at least one control signal for the multiplexers. The multiplexers may be arranged and controlled in various manners depending on the slot-to-interlace mapping scheme. At a receiver, a complementary interlace-to-slot converter maps the interlaces to the slots.

Abstract: A variable speed system for use in systems, such as, for example, wind turbines, is described. The system comprises a wound rotor induction generator, a torque controller and a proportional, integral derivative (PID) pitch controller. The torque controller controls generator torque using field oriented control, and the PID controller performs pitch regulation based on generator rotor speed.

Abstract: The present invention provides systems, devices and methods for controlling a desired output of an output device. These systems, devices and methods include connecting an electrical resistance element having a selected one of a plurality of resistance values with an electrical circuit portion having a plurality of electrical components, determining an electrical characteristic associated with the connected electrical circuit portion and the variable resistance element, and generating a control signal based on the electrical characteristic to control the desired output of the output device.

Abstract: A wind powered turbine with low voltage ride-through capability. An inverter is connected to the output of a turbine generator. The generator output is conditioned by the inverter resulting in an output voltage and current at a frequency and phase angle appropriate for transmission to a three-phase utility grid. A frequency and phase angle sensor is connected to the utility grid operative during a fault on the grid. A control system is connected to the sensor and to the inverter. The control system output is a current command signal enabling the inverter to put out a current waveform, which is of the same phase and frequency as detected by the sensor. The control system synthesizes current waveform templates for all three-phases based on a sensed voltage on one phase and transmits currents to all three-phases of the electrical system based on the synthesized current waveforms.

Abstract: A variable speed wind turbine employing a rotor connected to a multiplicity of synchronous generators with wound field or permanent magnet rotors. A passive rectifier and an inverter are used for power transfer back to the grid. A Turbine Control Unit (TCU) commands a required generator torque based on rotor speed and power output of the turbine inverters. Torque is controlled by regulating the DC current by control of the inverter. A main-shaft-damping filter is provided by measurement of the DC bus voltage. In high winds the turbine remains at a constant average output power through a constant torque command and a varying pitch command to a rotor pitch servo system. A set point is fixed at the inverter output such that output VAR load is minimized running the turbine at very nearly unity power factor. Dynamic VAR and power factor control is provided by a separate VAR apparatus.