284 results about "Voltage oscillation" patented technology

The invention discloses a method for diagnosing an interturn short circuit of a rotor winding. The method comprises the following steps of: giving a judgment that a rotor winding has interturn stability short circuit fault through a rotor alternating current impedance test; then judging whether the rotor winding has the interturn instability or stability short circuit fault or not by combining a voltage oscillation wave test; and blending the results of the alternating current impedance test and the oscillation wave test to analyze and find out the position of a short circuit point so as to process the fault in time and recover the rotor winding to be insulated. The invention has the characteristics of simple and convenient measurement, low cost and good practical effect and can be used for detecting and diagnosing the interturn faults of rotors of steam turbine generators, water wheel generators and electric motor generator in a static state.

The present invention discloses a system and method for soft starting of an isolation direct-current converter applied to a direct current distribution network. After a direct-current converter is started, the H-bridge output square-wave voltage duty ratio of an input side is gradually increased from 0 to 0.5 according to a ramp function, and the time of setting the duty ratio from 0 to 0.5 is a starting time; after the direct-current converter is started, the H-bridge output square-wave voltage duty ratio of an output side is always 0.5, and the direct-current converter is started, in the starting time, output given voltage is gradually increased from 0 to a rated value according to the ramp function, and the changing of the output given voltage is consistent to the changing of the H-bridge output square-wave voltage duty ratio of the input side. Through cooperation control of the two methods, the current impact and direct voltage oscillation are effectively inhibited when starting, the system has a good anti-interference capacity and does not need additional circuits and starting resistors, and the starting logic is simple.

A method, device and computer program product for providing improved control of power or voltage oscillation damping in a power transmission system. The device includes a magnitude obtaining element configured to obtain an instantaneous magnitude of a signal representing a deviating oscillation in at least one element of the power transmission system, a slope investigating element configured to determine the rate of change of the signal, and a first processing block including an integrating element configured to integrate the instantaneous magnitudes with an integrating factor that is based on the determined rate of change. The first processing block is further configured to form a phase compensation angle based on the integrated instantaneous magnitude for use in a damping control signal generating unit in order to provide power or voltage oscillation damping of the system.

The invention discloses a device and a method for controlling a synchronous rectifier. The conversion rate of the switching voltage across the two ends of a secondary switch is detected in order to prevent the secondary switch from being triggered falsely due to switching voltage oscillation. The circuit includes a secondary switch coupled to an energy storage element, and a secondary control circuit. The secondary control circuit receives the switching voltage across the two ends of the secondary switch and a conversion rate threshold adjustment signal, and outputs a secondary switch control signal to control on-off of the secondary switch. When the conversion rate of the switching voltage is lower than a preset conversion rate threshold, the secondary switch control signal makes the secondary switch switched off.

Disclosed herein are methods, systems, and devices for identifying a location of a fault in a hybrid high voltage direct current (HVDC) transmission system having a ground or underground cable section and an overhead line section. Some methods comprise determining whether a characteristic voltage oscillation is present at a cable side terminal of the HVDC transmission system, and in response, determining that the fault is located in the overhead line section. Some methods comprise determining whether a characteristic current oscillation or a terminal current exceeding a peak current threshold is present at an overhead line side terminal, and in response, determining that the fault is located in the overhead line section. The methods can be communication-less, wherein the actions are based on local measurements and/or are performed locally to where the fault is located or detected.

The invention discloses a trench gate charge storage-type IGBT and a manufacturing method thereof, which belong to the technical field of power semiconductor devices. Through reasonably introducing asplit trench gate structure and an air floating P-type region, in a condition of not influencing the threshold voltage of the IGBT and conduction, Miller capacitance is reduced, and bad influences brought by Miller effects are improved; the overall gate capacitance is reduced, the device switching speed is improved, the switching losses of the device are reduced, and the compromise between forwardconduction voltage drop and turn-off losses of the traditional CSTBT structure is improved; current and voltage oscillations and EMI problems in the device dynamic starting process are avoided, and the device reliability is improved; electric field concentration effects at the bottom part of the trench are improved, and the breakdown voltage of the device is improved; carrier enhancement effectsat an emitter end of the device are improved, the carrier concentration distribution in a drift region is improved, and the compromise between forward condition voltage drop and turn-off losses is further improved; and besides, the manufacturing method disclosed in the invention has the advantages of low realization difficulty, high product rate and low cost.

A system for monitoring a brain wave response of a fetus in utero, comprises removably connecting an auditory transducer, including at least one biosensor electrode, producing pulsed auditory sounds to a mother's abdomen to detect brain wave activity in a fetus. The transducer is pulsed with one of rectangular waves and tone pips of a selected frequency to emit pulsed audible sounds at predetermined times. The at least one biosensor electrode, including connected amplifier, detects brain stem auditory responses (BAER) of the fetus. For each pulsed audible sound a series of voltage oscillations corresponding to BAER of the fetus are time-locked to the corresponding audible sound. BAER analog output is converted to BAER digital data. A computer-based QEEG (Quantitative EEG) system improves a signal to noise ratio of the BAER digital data using an adaptive optimum filtering algorithm and analyzes the BAER digital data relative to a reference database.

This DC converter belongs to the energy converter and consists of the DC power supply (Vin), two inverter bridge arms, the resonance inductance, the isolation transformer and the rectifier / filter circuit. Its character lays on that; there is an auxiliary winding (n3) in the isolation transformer beside the primary and the secondary windings (n1, n2). One end of n3 is connected to n1 and to two clamp diodes from the joint point to form a clamping circuit. Another end of n3 is connected to the resonance inductance. This converter realizes the zero voltage switching on the rectifier. This can eliminate the voltage oscillation induced by the reverse restoration of the output rectifier. It decrease the voltage stress across the output rectifier and reduces rapidly and effectively the currents through the clamping diodes. All these raise the conversion efficiency and improve the work condition of clamping diodes during light load.

The invention relates to the field of direct current-direct current convertors, in particular to a method and a unit for modulating number of drive pulses of an LLC resonant converter. A voltage loop controller of an LLC realizes regulation on output voltage by regulating drive pulse frequency; when drive pulse frequency converted by an output value of the voltage loop controller is higher than maximum operating frequency of the LLC resonant converter, the method for modulating the number of the drive pulses is adopted, i.e., regulation on the output voltage is performed by regulating number of turn-on drive pulses and turn-off drive pulses. The method effectively realizes wide-voltage-range output of the LLC resonant converter, effectively reduces voltage ripples during idle load or light load, avoids voltage oscillation caused by simply turning on and turning off the drive pulses in the existing technical scheme, has a better current stabilizing effect when the LLC outputs relatively low voltage and outputs in constant current, and effectively reduces voltage overshoot during idle-load starting.

The present invention provides a doubly-fed wind farm sub-synchronous oscillation SVG suppressing method and a device. The method comprises the following steps: acquiring voltage signal(s), current signal(s) and wind farm parameters of the output end(s) of a doubly-fed wind farm, wherein the wind farm parameters comprises a wind speed and a power-transmission line series compensation degree; determining active power signal(s), voltage oscillation amplitude(s) and current oscillation amplitude(s) according to the voltage signal(s) and the current signal(s); determining the working mode of a SVGcontroller; determining module parameter(s) of the SVG controller according to the determined working mode, the voltage oscillation amplitude(s), the current oscillation amplitude(s), oscillation frequencies, the wind farm parameters and a pre-established SVG parameter table, wherein the SVG parameter table is a pre-established corresponding table of the SVG function module parameter(s) and system operation information under different working modes; and performing sub-synchronous oscillation SVG suppressing on the wind farm by using the SVG controller with the determined parameter(s). According to the method, sub-synchronous frequency band signal(s) are filtered from sampling signal(s), and the doubly-fed wind farm is subjected to sub-synchronous oscillation SVG suppressing by using the voltage(s) and the active power(s).

The invention discloses a method for extracting stray parameters of a laminated bus bar based on frequency characteristics of a SiC MOSFET. The method comprises the following steps of firstly settingup a SiC MOSFET double-pulse test platform, and externally connecting the section under test of the laminated bus bar to the test platform; connecting multiple sets of additional capacitors in parallel at both ends of the SiC MOSFET, using the frequency information of oscillation in the off-voltage waveform of the SiC MOSFET before and after the additional capacitors are connected in parallel to obtain the resonance angular frequencies of multiple sets of equivalent circuit models, and further calculating the stray inductance and parasitic capacitance of the laminated bus bar to achieve the extraction of stray parameters of the laminated bus bar. The invention utilizes the high switching speed characteristics of the SiC MOSFET to excite obvious off-voltage oscillations. Compared with the traditional indirect measurement method, the measurement deviation caused by human factors is reduced. In addition, the invention can measure the stray inductance and parasitic capacitance in any section of the laminated bus bar, and the measurement is more flexible and comprehensive.

The invention relates to an implementation method of a 3D (three-dimensional) metal printing system, in particular to a 3D metal printing method, which belongs to the technical field of 3D metal printing. In combination with a current or voltage oscillation (or resonance) circuit, the 3D metal printing method adopts a printing method like a ball pen discharging ink and a rolling bearing rolling on a surface to leave an ink print to implement the fast melting of metal powder and fine printing; because a printing head of the 3D metal printing method is a high-temperature part, which still can keep constant high temperature on a printed object like an iron, the problem that metal does not completely melt does not exist, and because of the distance of heat transfer, the printing head also naturally cannot melt the printed object surface, thus truly realizing 3D printing like painting and iron soldering on the printed object surface. Consequently, the method does not have the problem that melted liquid metal is cooled into a drop-like solid once the melted liquid metal gets out of the printing head, as well as the problem of powdery pits which is caused by the incomplete sintering of part of the printed object in the process of laser sintering formation.

The invention discloses a grid-connected converter series virtual impedance method for virtual inertia control. The method comprises the steps that a direct current micro-grid system is established; signal measurement and processing are carried out; small signal analysis is carried out on a reference current equation; small signal analysis is carried out on a grid-connected converter mathematicalmodel and a current inner loop control model; small signal analysis is carried out a power equation; output impedance Zo(s) is calculated; a spike function is extracted and multiplied with a low-passfilter to form a compensation amount; series virtual impedance is applied to a current reference value; PI control and feedforward decoupling control are carried out; alpha beta transform and SVPWM modulation are carried out. According to the invention, the method has the advantages of simple structure and high efficiency; when the direct current micro-grid system is unstable, the control goals ofincreasing system damping, suppressing direct current voltage oscillation, and ensuring voltage quality during steady-state operation are realized.

A system for the production of localized audible sound, including a source of voltage oscillations in the ultrasonic frequency range, at a reference frequency. The voltage source is connected to a first ultrasonic transducer, emitting a first beam of ultrasonic waves (the reference beam) in a relatively narrow beam, in a desired direction. The same voltage source is connected to a phase shifter, feeding a second ultrasonic transducer from which an ultrasonic wave is emitted, of the same frequency and intensity as the reference beam, but phase shifted relative to it.

The invention relates to a stable control method for inhibiting voltage oscillation of a flexible DC power transmission system. The method is characterized by comprising that an axis-d control channeland/or an axis-q control channel are/is provided with an AC voltage stabilizer in the outer ring of a flexible DC converter station control system in the flexible DC power transmission system; a gaincoefficient and an output amplitude limit value of the AC voltage stabilizer are determined; an output current compensation value of the AC voltage stabilizer after that the gain coefficient and output amplitude limit value are determined is obtained, and added to an original reference current in the outer ring of the flexible DC converter station control system to obtain a reference current in the outer ring of the flexible DC converter station control system; and the reference current is output to the inner ring of the flexible DC converter station control system, and voltage oscillation ofthe flexible DC power transmission system is inhibited. The method can be widely applied to the field of flexible DC power transmission.

The invention provides a double-fed wind power plant sub-synchronous oscillation SVC suppression method and device. The method comprises the following steps: acquiring a voltage signal, a current signal and wind power plant parameters of the double-fed wind power plant output end, wherein the wind power plant parameters comprise wind speed and power transmission line series compensation; ;determining an active power signal, a voltage oscillation amplitude and a current oscillation amplitude according to the voltage signal and the current signal; determining a work mode of a SVC controller; determining module parameters of the SVC controller according to the determined work mode, the voltage oscillation amplitude, the current oscillation amplitude, the oscillation frequency, the wind powerfield parameter and a pre-established SVC parameter table, wherein the SVC parameter table is the pre-established SVC function module parameter and system operation information corresponding table under different work modes; and performing sub-synchronous oscillation SVC suppression on the wind power field by using the SVC controller with determined parameter. The sub-synchronous band signal is filtered from a sampling signal, and the sub-synchronous oscillation SVC suppression is performed on the double-fed wind power plant by using the voltage and the active power.

The invention discloses a reverse blocking type IGBT and a manufacturing method therefor, and belongs to the technical field of a semiconductor power device. By introducing trench emitter and trench collector structures, the reverse breakdown voltage of a device is improved without influencing the threshold voltage and switch-on of an IGBT device; the overall gate capacitance is lowered, the switching speed of the device is improved, the switching loss and driving power consumption of the device are lowered, and the compromising relation between forward switch-on voltage drop and switch-off loss of the conventional CSTBT structure is improved; the problems of current, voltage oscillation and EMI in the device starting dynamic process can be avoided, and device reliability is improved; theelectric field concentration effect at the bottom of the trench is improved, the forward breakdown voltage of the device is improved, and reliability of the device is further improved; and the currentcarrier enhancement effect at the emitter end of the device is further improved, the current carrier concentration distribution in a drift region can be improved, and compromising between forward switch-on voltage drop and switch-off loss can be further improved. The manufacturing method disclosed in the invention is compatible with the existing manufacturing process of a CSTBT device.