Koninklijke Philips Corporation N.v.

Vestas Wind Systems A/s

U.S. Philips Corporation

Thomas Scheel

Christian Hattrup

Peter Luerkens

Christoph Loef

Martin Atzler

Lars Finn Sloth Larsen

Olaf Maertens

Gereon Vogtmeier

Roger Steadman Booker

Bernd Ackermann

Erik Carl Lehnskov Miranda

Peter Lürkens

Christian Baeumer

Thomas Krüger

Antonius Johannes Joseph Wismans

Martin Ossmann

Albert Garcia Tormo

Olaf M&auml;rtens

Ralf Kröger

Wolfgang Efftinge

Thorsten Gercke

Shuang Li

A method for estimating a wind speed at a wind turbine is disclosed, said wind turbine comprising a rotor carrying a set of wind turbine blades, each wind turbine blade having a variable pitch angle. A blade torsion contribution, representing torsion introduced in the wind turbine blades, is derived, based on an obtained rotational speed, &#x3c9;, of the rotor, and an obtaining a pitch angle, &#x3b8;, of the wind turbine blades. An adjusted pitch angle, &#x3b8;', is calculated as a sum of the obtained pitch angle, &#x3b8;, and the derived blade torsion contribution, and a wind speed, v, is estimated, based on the obtained rotational speed, &#x3c9;, and the calculated adjusted pitch angle, &#x3b8;&#x2032;. An accurate and reliable estimate for the wind speed is thereby obtained. The wind turbine may be controlled in accordance with the estimated wind speed, v.

Operating a wind turbine using estimated wind speed while accounting for blade torsion

The invention relates to a method of controlling a wind turbine, the wind turbine comprising wind turbine blades attached to a rotor hub and a control system for pitching the blades relative to the rotor hub. The method comprises determining a wind speed and providing a normal pitch mode of operation to control the output power of the wind turbine, where the pitch mode of operation comprises pitch reference values in dependence of the wind speed. The output power of the turbine is controlled according to the normal pitch mode of operation as a function of the wind speed if the wind speed is lower than a first upper level wind speed threshold, and according to a modified mode of operation if the wind speed exceeds the first upper level threshold wind speed, wherein the modified mode of operation comprises decreasing the output power according to a de-rating function which is a function of time. The invention further relates to a control system for controlling a wind turbine according to the above mentioned control method.

Control method for a wind turbine

A fast-converging and reliable method for estimating a wind speed at, for example, a wind turbine comprising a rotor carrying a set of variable pitch angle wind turbine blades. The estimated wind speed is iteratively derived using a wind turbine rotor rotational speed, a turbine blade pitch angle, and a derived initial estimated wind speed. The initial estimated wind speed is based on the rotational speed and an initial tip speed ratio. The initial tip speed ratio is selected to be a value greater than a minimum tip speed ratio, wherein the minimum tip speed ratio defines a control region stability limit as a function of the pitch angle. Thus, for a given pitch angle, a minimum tip speed ratio is derived as a limit or boundary point between a stable control region and an unstable control region.

Method for estimating a wind speed at a wind turbine

A high voltage transformer () includes a magnetic core (); a low voltage winding (); a high voltage winding (); at least one inner sleeve (); and a coil bobbin () for carrying the high voltage winding (). The coil bobbin () is configured to be arranged inside the at least one inner sleeve () and configured to be attached to the at least one inner sleeve () at an outer perimeter of the at least one inner sleeve (). The coil bobbin () includes at least one field-control electrode (), which is adapted to shape an electric field generated by the high voltage winding ().

High voltage transformer comprising a coil bobbin for carrying a high voltage winding

Non-linearities of a gradient amplifier () for powering a gradient coil () are caused by the finite dead time of the amplifier and/or by a forward voltage drop. The gradient amplifier () includes a controllable full bridge () and an output filter (). The full bridge () is controlled to provide a desired coil current (i), including receiving a desired duty cycle (a) of the gradient amplifier (), measuring an input current (i) and an output voltage (uc) of the output filter (), evaluating an modulator duty cycle (a), and providing the modulator duty cycle (a) for controlling the full bridge (). The gradient amplifier () powers a gradient coil () including at least two half bridges (), each having at least two power switches () connected in series. An output filter () connected to a tapped center points of the half bridges () between two the power switches (). A controller provides a desired duty cycle (a) of the gradient amplifier (), a compensation block () for providing an modulator duty cycle (a). A modulator () controls the power switches () according to the modulator duty cycle (a).

Gradient amplifier with compensation for dead time and forward voltage

A state space feedback controller operates in the digital domain for the regulation of the current supply to MRI gradient coils from a multiple-bridge PWM power amplifier. The P1-controller includes an integration part (for the integration of the difference between the demand current and the measured gradient coil current) and a subsequent P-controlled system which in turn includes a delay compensator/stabilizer and a plant. The delay compensator/stabilizer includes a multi-path feedback loop by means of which its digital output signal is fed back through delay blocks, on the one hand, and through filter units, on the other hand. The filter units model the transfer functions of a gradient coil output filter for the gradient coil voltage and the output current of the amplifier inverter units, respectively. In the plant, a filter unit, which models the gradient coil transfer function, is connected in series to a delay chain for the delay of the measurement value of the gradient coil current.

State space feedback controller in the digital domain for an MRI gradient coil power supply

The invention relates to an X-ray imaging device, particularly a Spectral-CT scanner, that comprises an X-ray source for generating X-radiation with an energy spectrum which varies continuously during an observation period. In a preferred embodiment, the radiation is attenuated in an object according to an energy-dependent attenuation coefficient &#x3bc;, the transmitted radiation is measured by sensor units of a detector, and the resulting measurement signal is sampled and A/D converted. This is preferably done by an oversampling A/D converter, for example a &#x3a3;&#x394;-ADC. The tube voltage that drives the X-ray source is sampled with high frequency. In an evaluation system, these sampled measurement values can be associated with corresponding effective energy spectra to determine the energy dependent attenuation coefficient &#x3bc;.

Spectrally resolving X-ray imaging device

A method and a control device control a switching device for providing a resonant circuit with a switching voltage for generating a resonant current in order to provide a required output power at an output of a resonant power converter.

Method for controlling a switching device of a resonant power converter, especially in order to provide a required power, especially for an X-ray generator

A DC/AC power inverter control unit of a resonant-type power converter circuit (), in particular a DC/DC converter, for supplying an output power for use in a high-voltage generator circuitry of an X-ray radiographic imaging system, a 3D rotational angiography device, or X-ray computed tomography device, comprises an interphase transformer () connected in series to at least one series resonant tank circuit (and' orand&#x2032;) at the output of two DC/AC power inverter stages () supplying a multi-primary winding high-voltage transformer (). The interphase transformer () removes a difference (&#x394;I) in resonant output currents and (Iand I) of the DC/AC power inverter stages (). In addition, a control method is disclosed which assures that the interphase transformer () is not saturated. Furthermore, the control method ensures zero current operation and provides for minimized input power losses.

DC/AC power inverter control unit of a resonant power converter circuit, in particular a DC/DC converter for use in a high-voltage generator circuitry of a modern computed tomography device or X-ray radiographic system

Current switching point determination devices use two comparators with fixed threshold values. A power inverter control device for switching point determination is provided which includes a filter circuit and a subsequent single comparator. By this arrangement, the time event is independent of the amplitude and for sufficiently small frequencies also of the frequency.

Power inverter control device for switching point determination

A resonant DC/DC converter for supplying an output power comprises a switching device () for supplying a switched voltage (UWR) to a resonant circuit () having a transformer (T). The switched voltage (UWR) is derived from an intermediate circuit voltage (Uz) having a fixed pulse width and frequency so that the zero crossings of the resonant current (Ires) generated in the resonant current are defined. The switching configuration of an inverter circuit () is selected by a control device () to either increase, decrease or maintain at a substantially constant level the resonant current according to the polarity of the switched voltage, so as to control the output power as required.

Resonant DC/DC converter with zero current switching

A description is given of a power supply unit, an X-ray device having a power supply unit, and a method of controlling a power supply unit. In order also to control non-linear control paths, such as of a power supply unit operated with mixed-mode modulation, it is proposed that the control device be designed as a digital control device which calculates at least one correcting variable. The control device processes at least a first actual value U, which depends on the output voltage. A time difference value is calculated from two sample values of the first actual value Uand is multiplied by a first controller coefficient K. The value of the first controller coefficient can in this case change as a function of the operating point of the power supply unit.

Digital state controller for a high-voltage generator using the mixed-mode modulation method

Two proposals are made for power supply systems comprising at least one resonant inverter and one control unit. According to the first proposal the power supply system comprises two inverters and produces two output voltages, the control circuit processing as an actual value on the one hand the sum of and on the other hand the difference between the two output voltages. According to the second proposal a control circuit does not directly process the controlled variables for a power supply system comprising at least one inverter, but difference units for controlled variables determine the deviations from a preceding sampling instant and these difference values are processed. Also the correcting variable calculated in this way is a difference value which is converted into a correcting variable value by a correcting variable summing unit. The two proposals can be advantageously combined. As an important improvement is proposed the use of a limiting controller which generally becomes active in case of imminent transgression of a maximum value and which limits the actuation. The control circuit is preferably used as a digital control circuit for a state space control.

Power supply system

In order to determine the necessary operating parameters of a power supply system with a converter for supplying a resonant arrangement having a transformer, a system having a measuring device is proposed, which activates the converter so that with components of the power supply system initially unenergized a predetermined output voltage is generated, one or more parameters characteristic of the resonant arrangement being determined from the measurement of the resonant current appearing on the primary side of the transformer. In this, after a preferably brief excitation interval, the resonant frequency, the impedance of the resonant arrangement, the capacitance value of the resonant capacitance and the leakage inductance are determined on the basis of the current path.

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Stolberg, Germany

Thomas Scheel