Abstract: 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, ?, of the rotor, and an obtaining a pitch angle, ?, of the wind turbine blades. An adjusted pitch angle, ??, is calculated as a sum of the obtained pitch angle, ?, and the derived blade torsion contribution, and a wind speed, vest, is estimated, based on the obtained rotational speed, ?, and the calculated adjusted pitch angle, ??. 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, vest.

Abstract: 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.

Abstract: 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.

Abstract: A high voltage transformer (50) includes a magnetic core (5); a low voltage winding (10); a high voltage winding (20); at least one inner sleeve (30); and a coil bobbin (24) for carrying the high voltage winding (20). The coil bobbin (24) is configured to be arranged inside the at least one inner sleeve (30) and configured to be attached to the at least one inner sleeve (30) at an outer perimeter of the at least one inner sleeve (30). The coil bobbin (24) includes at least one field-control electrode (22), which is adapted to shape an electric field generated by the high voltage winding (20).

Abstract: Non-linearities of a gradient amplifier (1) for powering a gradient coil (16) are caused by the finite dead time of the amplifier and/or by a forward voltage drop. The gradient amplifier (1) includes a controllable full bridge (8) and an output filter (9). The full bridge (8) is controlled to provide a desired coil current (ic), including receiving a desired duty cycle (aeff) of the gradient amplifier (1), measuring an input current (ifilt) and an output voltage (ucfilt) of the output filter (9), evaluating an modulator duty cycle (amod), and providing the modulator duty cycle (amod) for controlling the full bridge (8). The gradient amplifier (1) powers a gradient coil (16) including at least two half bridges (10), each having at least two power switches (11) connected in series. An output filter (9) connected to a tapped center points of the half bridges (10) between two the power switches (11).

Abstract: 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, ?, of the rotor, and an obtaining a pitch angle, ?, of the wind turbine blades. An adjusted pitch angle, ??, is calculated as a sum of the obtained pitch angle, ?, and the derived blade torsion contribution, and a wind speed, vest, is estimated, based on the obtained rotational speed, ?, and the calculated adjusted pitch angle, ??. 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, vest.

Abstract: A method for iteratively 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 minimum tip speed ratio, ?min, is derived, based on an obtained pitch angle, ?. The minimum tip speed ratio, ?min, defines a limit between a stable and an unstable control region. An initial tip speed ratio, ?init>?min, is selected, and an initial estimated wind speed, vinit, is derived based on the initial tip speed ratio, ?int, and an obtained rotational speed, ?, of the rotor. An estimated wind speed, vest, is iteratively derived, based on the obtained rotational speed, ?, and the obtained pitch angle, ?, and using the derived initial estimated wind speed, vinit, as a starting point. The iterative process converges fast and reliably.

Abstract: 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.

Abstract: The invention relates to a high voltage transformer (50) comprising: a magnetic core (5); a low voltage winding (10); a high voltage winding (20); at least one inner sleeve (30); and a coil bobbin (24) for carrying the high voltage winding (20), wherein the coil bobbin (24) is configured to be arranged inside the at least one inner sleeve (30) and configured to be attached to the at least one inner sleeve (30) at an outer perimeter of the at least one inner sleeve (30); and wherein the coil bobbin (24) comprises at least one field-control electrode (22), which is adapted to shape an electric field generated by the high voltage winding (20).

Abstract: The present invention relates to a method for compensating non-linearities of a gradient amplifier (1) for powering a gradient coil (16), wherein the non-linearities are caused by the finite dead time of the amplifier and/or by a forward voltage drop, the gradient amplifier (1) comprising a controllable full bridge (8) and an output filter (9), whereby the full bridge (8) is controlled to provide a desired coil current (ic), comprising the steps of receiving a desired duty cycle (aeff) of the gradient amplifier (1), measuring an input current (ifilt) and an output voltage (ucfilt) of the output filter (9), evaluating an modulator duty cycle (amod) as a function of the desired duty cycle (aeff) and the measured input current (ifilt) and the measured output voltage (ucfilt), and providing the modulator duty cycle (amod) for controlling the full bridge (8).

Abstract: The invention relates to a state space feedback controller operating in the digital domain for the regulation of the current supply to MRI gradient coils from a multiple-bridge PWM power amplifier. The Pl-controller comprises 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 comprises a delay compensator/stabilizer and a plant. The delay compensator/stabilizer comprises 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, whereby 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.

Abstract: 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 ?, 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 ??-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 ?.

Abstract: 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.

Abstract: A DC/AC power inverter control unit of a resonant-type power converter circuit (400), 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 (406) connected in series to at least one series resonant tank circuit (403a and 403a? or 403b and 403b?) at the output of two DC/AC power inverter stages (402a+b) supplying a multi-primary winding high-voltage transformer (404). The interphase transformer (406) removes a difference (?I) in resonant output currents and (I1 and I2) of the DC/AC power inverter stages (402a+b). In addition, a control method is disclosed which assures that the interphase transformer (406) is not saturated. Furthermore, the control method ensures zero current operation and provides for minimized input power losses.

Abstract: 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.

Abstract: The invention provides a switched mode power converter adapted for zero-voltage transition operation, wherein the converter comprises a half-bridge, having a first power switch (206) and a second power switch, a generator (201) adapted for generating a switching signal S1 after a first period of time, wherein the first period of time starts at the switching off of the second power switch, a controller (202) for converting the switching signal S1 into a control signal S2, wherein the first power switch (206) is switched on in case of the control signal S2, wherein the controller (202) comprises a detector (205), wherein the detector (205) is adapted to generate a first signal S3 in case the voltage over the first power switch (206) is decreasing, a processor (203), wherein the processor (203) is adapted to generate a trigger signal S4 in case of a switching signal S1 and while the first signal S3 is not present, a storage element (204), wherein the storage element (204) is adapted to generate the control signa

Abstract: A resonant DC/DC converter for supplying an output power comprises a switching device (18) for supplying a switched voltage (UWR) to a resonant circuit (20) 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 (18) is selected by a control device (31) 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.

Abstract: The invention provides an X-ray device for controlling a DC-AC converter, wherein the DC-AC converter is adapted for supplying a resonant circuit and a transformer (105) of a computer tomography gantry (91) with electrical energy, wherein the gantry comprises a rotary part (93) and a stationary part (92), wherein the transformer (105) is adapted for providing a current, feeding a high voltage rectifier circuit (106), providing an output voltage (107), the X-ray device comprises a detector for detecting the output voltage, a predictor (501) for calculating a first output with the use of processing the output voltage (107), wherein the first output represents the change of the output voltage (107) for the possible states of the DC-AC converter (102), a control loop (503) for calculating the required change of the output voltage (107) with the use of processing the output voltage (107) and the target specification, a decision block (502) for calculating a control value with the use of processing the first output

Abstract: This invention relates to a method for controlling a switching device (260) for providing a resonant circuit (350) with a switching voltage (Uwr) for generating a resonant current (Ires) in order to provide a required output power (rP) at an output of a resonant power converter (100). The invention further relates to a control device which is adapted to perform the proposed method for controlling a switching device. Moreover the invention relates to a resonant power converter including a control device for performing the proposed controlling method.

Abstract: The present invention refers to a DC/AC power inverter control unit of a resonant-type power converter circuit (400), in particular a DC/DC converter, for supplying an output power for use in, for example, a high-voltage generator circuitry of an X-ray radio-graphic imaging system, 3D rotational angiography device or X-ray computed tomography device of the fan-or cone-beam type. More particularly, the present invention is directed to a resonant-type power converter circuit out which comprises an interphase transformer (406) connected in series to at least one series resonant tank circuit (403a and 403a? or 403b and 403b?) at the output of two DC/AC power inverter stages (402a+b) supplying a multi-primary winding high-voltage transformer (404), wherein said interphase transformer (406) serves for removing the difference (DI) in the resonant output currents (1 and 2) of the DC/AC power inverter stages (402a+b).