36results about How to "Avoid overmodulation" patented technology

A night-vision system for motor vehicles includes a camera having a radiation-sensitive image-sensor surface, which is configured for recording electromagnetic radiation from the infrared range, in particular. To improve distant-vision characteristics beyond the low-beam range, the system according to the present invention includes a filter element which is positioned in the optical path of the night-vision system in such a way that it causes an attenuation of the recorded radiation to predefined partial regions of the image sensor. This allows an attenuation of the radiation from the low-beam range, which would otherwise be too intense.

The aim is to better suppress background noises during the use of hearing devices. To this end, provision is made to record an electrical or electromagnetic useful signal via a corresponding interface and an interference sound by means of a microphone of the hearing device. The processed useful signal is output from a receiver of the hearing device. A vent is formed when the hearing device is worn in or on the ear, through which vent a sound transmission function from the microphone to the eardrum of the hearing device wearer exists. The interference sound signal of the microphone is filtered as a function of the sound transmission function of the vent such that an interference sound reaching the eardrum through the vent is reduced in its effect on the eardrum by means of a balancing sound, which is generated on the basis of an interference sound signal of the microphone from the receiver. The sound reaching the eardrum through a vent can thus be reduced in its interference effect by means of out-of-phase cancellation.

The invention relates to the technical field of display brightness control of an OLED miniaturized display and specifically relates to an OLED miniaturized display constant-brightness modulation method. According to the invention, a compensation coefficient is determined through actual measurement of a difference between a current brightness value and a calibrated brightness value, driving current compensation or driving voltage compensation is carried out through the compensation coefficient, and thus the purpose of maintaining constant brightens of the OLED miniaturized display is realized. According to the invention, modulation stepping is automatically adjusted according to the difference between current brightness and fixed brightness in a modulation process so that the phenomenon of excessive modulation caused by too frequent modulation or mismatch between the modulations stepping and the brightness difference in a conventional modulation mode is avoided.

An audio input signal is filtered using an adaptive filter to generate a prediction output signal with reduced noise, wherein the filter is implemented using a plurality of coefficients to generate a plurality of prediction errors and to generate an error from the plurality of prediction errors, wherein the absolute values of the coefficients are continuously reduced by a plurality of reduction parameters.

A pre-emphasis filter emphasizes a high-frequency component of an input audio signal. A limiter circuit detects that the output signal from the pre-emphasis filter reaches a predetermined upper limit level. A filter adjusting circuit changes the frequency characteristic of the pre-emphasis filter when a limit operation is generated in the limiter circuit.

The invention discloses a motor synchronous control method, an apparatus thereof and a system thereof. The method comprises the following steps: when determining a present modulation mode is synchronous modulation according to an obtained present modulation ratio and stator frequency, determining present frequency division amount; determining preset switching angle and a stator flux threshold corresponding to the modulation ratio and the present frequency division amount; comparing an obtained feedback linkage threshold with the stator linkage threshold, and outputting a control signal according to a comparison result. According to the motor control method disclosed in an embodiment of the invention, through a switching angle calculated in advance corresponding to a modulation ratio, the stator linkage threshold corresponding to the switching angle is determined, an actual feedback linkage threshold and the stator linkage threshold are compared, according to the comparison result a control signal is outputted, over-modulation and a further step of processing over-modulation area caused by adding the modulation ratio are avoided. Control flow of a system is simplified, working efficiency is raised, and an orbit of the motor stator becomes a regular polygon.

The invention relates to a virtual synchronous control method of a cascade inverter based on unit active power standby, aims at solving the problems that a cascade H-bridge photovoltaic inverter doesnot have the characteristic of a synchronous motor, cannot participate in the frequency modulation of a power grid and can cause the over-modulation of an H-bridge unit due to sudden change of illumination. The method comprises the following steps: controlling direct current side voltage; controlling virtual synchronous, namely superposing frequency modulation power on the output power of a standby H bridge unit, and operating the rest of H bridge units at a maximum power point to obtain command values of grid-connected active power and grid-connected reactive power; controlling the current ona grid side; and controlling third harmonic injection, namely injecting reverse third harmonic into the initial modulation signals of the standby H bridge units, and injecting forward third harmonicinto the initial modulation signals of the rest of the H bridge units to reduce the modulation degree of the H bridge units. The virtual synchronous control method of the cascade inverter based on unit active power standby can realize that a single-phase cascade H-bridge photovoltaic inverter has the characteristics of the synchronous motor, participates in the frequency modulation of the power grid, reduces the modulation degree of the H-bridge unit and prevents over-modulation, and is simple in algorithm and easy in engineering realization.

The invention discloses a split-phase control method of an asymmetric three-phase star-shaped cascade multilevel hybrid energy storage system. The method comprises the steps of: analyzing the stable ranges of the output voltage and the output current of a single-phase battery chain link, and determining the working range of a three-phase star-shaped system; performing open-loop voltage control oneach phase of the battery chain link to allow each battery chain link to output a command voltage so as to achieve charge-discharge balance; calculating the phases of the active current and the reactive current of a capacitor chain link according to a power grid voltage and an open-loop voltage; and performing active current control, reactive current control and power grid voltage feedforward control for each phase of the capacitor chain link to allow each capacitor chain link to output a command current and maintain the capacitor voltage to be stable. The split-phase control method of the asymmetric three-phase star-shaped cascade multilevel hybrid energy storage system performs split phase control in the three-phase common stable working range to improve the four-quadrant operation stability of the system, prevent the chain link unit from overmodulation and suppress the output current harmonics, and therefore, the split-phase control method of the asymmetric three-phase star-shaped cascade multilevel hybrid energy storage system is suitable for the asymmetric fault conditions.

A microscope includes at least one illuminating light source and an illumination beam path for guiding the illuminating light to a specimen. A detection beam path guides detected light from the specimen to a detector. An activatable element is positioned in the detection beam path for regulating and/or limiting the light power level in the detection beam path.

The invention discloses a DC-side voltage variable control method applied to a static var generator (SVG). A reactive compensation current required to be sent out by the SVG is determined according toa load reactive power current detected in real time, and minimum DC-side voltage conforming to a phase voltage modulation rule is further obtained. A current ring employs direct current control undera dq-coordinate system, a modulation voltage of the SVG under a three-phase static coordination system is obtained by coordinate conversion, a switch sequence is generated, a power device is driven,and control of the SVG is completed. The DC-side voltage is flexibly regulated according to the detected load reactive power current, the SVG is expected to run under relatively high modulation degreeall the way when different load reactive powers are compensated, the DC-side voltage utilization ratio is improved, so that high-efficient control of the SVG is achieved.

The invention discloses an optimization control method of a multi-section zero sequence voltage approximation HANPC multi-level converter. The method comprises the following steps of: modulating an HANPC multi-level converter according to a corresponding relationship between different switch states and output levels in the HANPC multi-level converter; determining a corresponding relation between decoupling control and duty ratio adjustment of capacitor voltages of a suspension capacitor and a direct-current side midpoint capacitor of the HANPC multi-level converter; establishing constraint conditions between the zero-sequence voltage and the voltage controller output of the suspension capacitor, the voltage controller output of the direct-current side midpoint capacitor and the linear adjustment range of the zero-sequence voltage; and calculating a zero-sequence voltage value by adopting a sectional type zero-sequence voltage approximation method based on the constraint condition. According to the invention, the zero-sequence voltage value can be solved more accurately, the effects of improving the working efficiency of the converter and reducing the volume of the upper bus and the lower bus are achieved, the constraint of the linear modulation range is considered, overmodulation can be effectively avoided, and the situation of level jump is reduced.

The invention relates to a static var compensator and a control method based on model prediction. The method comprises the steps of obtaining the electrical parameters of a DC side and an AC side of any one power submodule in the static var compensator based on the improved topology of the static var compensator, and predicting switching coefficients of two bridge arm switches of an H bridge in the power sub-module according to the electrical parameters, and controlling the bridge arm switches of the H bridge according to the switching coefficients. Based on this, based on a circuit structure different from a traditional static var compensator, linear control is carried out through a control method based on model prediction, and the problem of overmodulation caused by linear superposition of an AC side and a DC side in the static var compensator is avoided.

The invention discloses an inverter based on input end series voltage switching and a short-circuit loss suppression method thereof, the method comprises the following steps: taking output DC voltageof a preceding stage DC-DC converter as input DC voltage of a post stage inverter; performing double closed-loop control through a post stage inverter outer voltage loop feed-back inverter output voltage and an inductive current signal, obtaining a pulse control signal of a bridge arm switch device of the post stage inverter, thereby realizing inverter output short circuit current limitation; moreover, converting the inductive current signal into a DC voltage signal through rectifying and filtering, comparing the DC voltage signal with a comparison reference signal, controlling an output series module of the preceding stage DC-DC converter according to the comparison result, and adjusting the DC voltage. The inverter comprises the preceding stage converter and the post stage inverter, a short-circuit state keeping judgement module and an output series voltage switching module. with the inverter and the method provided by the invention, reduction of voltage stress of the inverter can berealized more quickly at the moment when short circuit happens, and loss of the switch device caused when the inverter is in short circuit state can be suppressed better during a dynamic process.

The invention discloses a reactive power exchange method and system for a photovoltaic grid-connected CHB of a faulty module. The method comprises the steps that: a plurality of faulty CHB units are detected, bypass switches of the faulty CHB units are switched on, and the faulty CHB units are short circuited through the bypass switches; after the plurality of faulty CHB units are short-circuited, the magnitude and phase of zero-sequence voltage needing to be injected into the photovoltaic grid-connected CHB are calculated according to active power and reactive power exchanged between the photovoltaic grid-connected CHB and a power grid; the relation between the phase cluster voltage effective value of the photovoltaic grid-connected CHB and the active power and reactive power of the photovoltaic grid-connected CHB is calculated; the photovoltaic grid-connected CHB injects the zero-sequence voltage into the power grid, and a control system adopts PWM clamping control to track the magnitude and phase of the zero-sequence voltage. The method can be used for expanding the reactive power exchange capacity of the CHB units and the power grid in the fault state, balancing the current of the power grid after a converter has a fault module, preventing the overmodulation of the CHB units, and facilitating the equalization of the active power and reactive power of each phase of the photovoltaic grid-connected CHB.

The invention relates to a method for providing a detection signal for objects (70) to be detected, wherein by means of a first optical non-linear 3-wave process (30, 30a), from a light beam of a light source (10) having an output frequency (f<laser>), at least one first and one second light beam are generated, which have different frequencies (f<obj>, f<ref>) and wherein the first light beam having a reference frequency (f<ref>) is detected and wherein the second light beam having an object frequency (f<obj>) is emitted and, after reflection on an object (70), is received, and wherein the light beam having the output frequency (f<laser>) and the second light beam having the object frequency (f<obj>) are superimposed, and wherein by means of a second optical non-linear 3-wave process (30,30b), from the two superimposed light beams having the output frequency (f<laser>) and having the object frequency (f<obj>), a reference beam having a reference frequency (f<ref>) is generated, and wherein a detection signal is generated such that, based on the time difference between the detection of the first light beam having the reference frequency (f<ref>) and a detection of a change in the reference beam having reference frequency (f<ref>) on the basis of said superimposition, the distance (d) of the object (70) can be determined.