46results about How to "Requirements for downsampling" patented technology

The invention discloses a multi-terminal flexible DC power grid line direction pilot protection method. The method comprises steps: DC current and voltage at two ends of a DC reactor are measured and a DC current mutation rate di/dt and a voltage mutation rate du/dt are calculated; when the di/dt or the du/dt is larger than a threshold value K1-set and K2-set, a protection algorithm is started instantly; fault voltage at two sides of a DC reactor at a protection terminal is measured, and corresponding transient components UM_line and UM_bus (UN_line and UN_bus) are extracted; r1=UM_line/UM_bus (r2=UN_line/UN_bus) is calculated, and a fault direction is judged: if r1>1+epsilon (r2>1+epsilon), epsilon is a reliable margin, positive direction fault is judged and a direction signal RM is equal to 1 (RN=1), or otherwise, reverse direction fault is judged, and a direction signal RM is equal to 0 (RN=0); when RM&RN=1, internal fault is judged; and when RM&RN=0, external fault is judged. The method of the invention has the advantages that data synchronization is not needed; a sampling rate is lowly required; the fault resistance withstanding ability is strong; influences from line distributed capacitance do not exist; engineering implementation is facilitated; and the hardware investment cost is reduced.

The invention discloses a detection device and a detection method for series arc faults. The detection device comprises a continuous current collection module, which is used for continuously collecting current at a fixed sampling rate through an A/D (Analog to Digital) converter, a signal preprocessing module, which is used for carrying out moving average processing on collected data, an arc fault processing and analyzing module, which is used for computing a rate of change of current, a sum of previous N harmonics and a harmonic time domain waveform effective value, identifying an arc according to the three variables and giving a corresponding command, a sound-light alarm module, a drive module and a tripping control module, which are used for deciding whether sound-light alarm is carried out and a circuit is disconnected according to the command of the arc fault processing and analyzing module, and a communication module, which is communicated with the exterior through an RS485 interface. According to the detection device and the detection method, a time domain and a frequency domain are together utilized to judge whether the arc fault occurs, and through analyzing and testing, the method has the advantages of simplicity in operation, easiness in implementation, low cost and misjudgment rate and high detection probability.

The invention relates to the relay protection field of electric transmission line of electric power system, in particular to a distance protection method based on the distributed parameter model. The invention is aimed to solve the problem that the current distance protection is affected by distributed capacitance current and harmonic. The invention uses the voltage and current in the protection mounting place to compensate the end of the section I of the distance according to the distributed parameter model, and simplifies the line between the end of the section I and the fault point into a R-L model. That weather the fault is at inside or outside can be determined by solving differential equation. The invention has the advantages that: comparing to the distance protection based on the R-L model of the electric transmission line, the invention avoids the affect of distributed capacitance current and harmonic; comparing to the distance protection based on the pi model of the electric transmission line, the invention has higher reliability on fault determine; comparing to the distance protection based on the Bergeron model of the electric transmission line, the invention has the advantages of low requirement on sampling rate, low amount of calculation, low requirement on the hardware for the distance protection apparatus.

The invention discloses a quick measurement method and device of underwater sound transmitting transducer wideband sending response, and belongs to the field of the underwater sound transducer measurement. The method comprises the following steps: placing a to-be-measured underwater sound transmitter transducer in a reverb pool, producing wideband continuous white noise signals by a signal producer, and amplifying and stimulating the underwater sound transmitting transducer to emit a sound signal through a power amplifier, utilizing a standard hydrophone with known sensitivity at a reverb control area of the reverb pool, and measuring the reverb sound field space average sound pressure through the standard hydrophone by adopting a standard hydrophone space scanning motion method, and thencomputing the sending response of the underwater sound transmitting transducer. By adopting the method disclosed by the invention, the wideband measurement of the underwater sound transmitting transducer can be realized, the method has the advantages of being accurate in measurement result, simple in measurement step and high in efficiency; in the same reverb pool, the lower limit frequency measured by adopting method disclosed by the invention is lower than the lower limit frequency of the pulse sound technology.

The invention relates to a method for measuring a local pulse wave propagation speed of a carotid blood vessel, which comprises the following steps: a step 1 of designing an ultrafast comb-tooth-shaped focus beam transmitting and receiving sequence and simultaneously acquiring a plurality of points of radio frequency echo signals in the long axis direction of the carotid blood vessel; a step 2 of identifying and tracking an echo signal of front and rear walls of the vessel in each scanning line after carrying out filtering preprocessing on a plurality of focus beam echo signals, which are simultaneously received, in the long axis direction of the carotid blood vessel; a step 3 of respectively carrying out one-dimensional self-correlation phase shifting estimation on adjacent frames of echo signals of the front and rear walls of the vessel in each scanning line to obtain a corresponding phase shifting speed waveform and then obtaining a corresponding phase shifting waveform of the vessel wall along with variation of a cardiac cycle in each scanning line; a step 4 of calculating relative time delay between the phase shifting waveforms of the vessel wall in the adjacent scanning lines and carrying out linear fitting on the time delay so as to obtain a reciprocal of a slope, i.e. the estimated local pulse wave propagation speed. The method provides new basis for early detection of the atherosclerosis.

The invention discloses a backup protection method and device for a high-voltage direct current transmission line. The method comprises the following steps: collecting current information of a relay protection device installed on both sides of the high-voltage direct current transmission line; filtering the sampled current information by a low-pass filter to obtain a filtered current sampling value; and filtering the sampled current information by a low-pass filter. Using the filtered current value, the differential current of the positive and negative DC lines after filtering can be calculated. By comparing the difference current of the positive and negative DC lines after filtering with the minimum action current, the faults inside and outside the DC line can be determined. If the faultis located in the DC line protection area, the fault of the positive line, the negative line or the bipolar line can be determined by comparing the difference between the positive and negative filtered current values. The invention has the beneficial effects of simple criterion, fast operation speed and high reliability, and can respond to the high-resistance grounding fault of the DC line, and can solve the problem that the action speed of the backup protection of the DC line is too slow.

The invention discloses a multi-wheel-disc rotor dynamic balancing test method based on a rotating coordinate system. The method includes calibrating an angular coordinate on a wheel disc, and arranging strain sensors on the cross section of shafts on both sides of the wheel disc of a rotor; respectively recording strain values of the wheel disc in the corresponding direction under different stress in two perpendicular direction, and respectively calibrating direction coefficients of the relationship between the strain and force in the two direction; starting a motor to provide a given balancing speed n, and measuring an average value of the strain in the two perpendicular direction of the cross section in the rotating coordinate system; calculating the magnitude of the unbalanced force on the wheel disc and the phase through the obtained average value of the strain and the direction coefficients in the two perpendicular direction, wherein the phase can be directly read out through the rotating coordinate system; obtaining the weight m weighted on the wheel disc and the phase theta through the obtained unbalanced force, the given balancing speed n and the given weighting radius r. The multi-wheel-disc rotor dynamic balancing test method based on the rotating coordinate system can be used for testing without a key phase sensor and data acquisition synchronization of measuring points, thereby greatly reducing the requirement on sampling rate of a data acquisition system.

The invention discloses a high-voltage DC line pilot protection method based on a fault DC component. The method comprises the steps: carrying out the real-time synchronous sampling of a voltage and a current through voltage-dividing/current-dividing devices at two ends of a high-voltage DC power transmission line, and obtaining a real-time voltage and a real-time current; respectively calculating a voltage break variable and a current break variable; extracting corresponding DC components through a DC filter; calculating the transient power of a fault DC component at a rectification-side protection installation position; discriminating the transient power; calculating fault DC impedance according to the discrimination results, and discriminating the fault DC impedance, thereby determining a fault type. The method is low in requirements for a sampling rate, is simple and clear in setting, is not affected by distributed capacitance and current, and can recognize various types of faults quickly and sensitively.

The invention discloses a flexible DC line fault detection method and device. The method comprises the following steps: obtaining an average capacitor voltage of sub-modules of upper and lower bridgearms of any phase of converter stations on both sides of a flexible DC line; and judging the type of a DC line fault according to the relationship between the average capacitor voltage of the sub-modules of the upper and lower bridge arms and a rated capacitor voltage. By adoption of the technical scheme disclosed by the invention, whether the DC line has a unipolar grounding fault or an interpolefault can be judged through the information of the internal capacitor voltages of the converter stations. In the scheme, the fault loop is analyzed, the principle is relatively simple, the detectionresult is reliable, the implementation process requires less equipment, and meanwhile the requirements for the equipment sampling rate are lower.

The invention provides a fault distance measurement method based on direct-current circuit breaker structure multiplexing, and the method comprises the steps: employing the existing charging capacitor and inductor of a typical direct-current circuit breaker transfer branch, and forming a modified direct-current circuit breaker through adding a grounding point, a relay and an inductance element under the condition that a system loses power after fault isolation, and forming an RLC damped oscillation circuit by the modified direct-current circuit breaker and a line fault point and adopting the Prony algorithmto extract and process the discharge current to obtain the characteristic parameters of the distance measurement loop, and establishing the fault distance measurement algorithm to solve the fault distance. The method provided by the invention can accurately and reliably position fault points of a single-pole grounding fault and a double-pole short-circuit fault of the direct-current line, and is simple and clear in principle, low in sampling frequency requirement and low in construction and transformation cost.

The invention discloses an automatic control method for improving the efficiency of a radio frequency power amplifier. The real-time adjustment of a static operating point of the radio frequency poweramplifier is achieved through the automatic control of a gate-source voltage Vgs of the radio frequency power amplifier, and mixing and low-pass filtering are performed on an input signal and an output signal of the radio frequency power amplifier after performing coupling on the same to obtain a DC signal; an analog-to-digital converter in a single-chip microcontroller collects the voltage information of the DC signal in real time and compares the voltage information with a known ideal value, and the compared difference is provided for the analog-to-digital converter in the single-chip microcontroller for outputting a matched voltage, an output end of the analog-to-digital converter is connected with an inductor L1 and is connected to the grid of the radio frequency power amplifier so asto adjust the gate-source voltage Vgs of the radio frequency power amplifier in real time. By adoption of the automatic control method, the effective balance between additional efficiency and error vector magnitude is achieved. In other words, the additional efficiency is maximized while the output error vector magnitude is guaranteed, and the circuit configuration is extremely streamlined, so that the automatic control method is suitable for wide range application.

The invention relates to a bus protection method based on line mode current S transformation argument detection, and belongs to the technical field of power system relay protection. When a fault happens to a line or a bus, three-phase current data of each line of the bus in a short-time window is extracted after the fault, and a line mode current containing a fault phase is calculated through the three-phase current data. The method carries out the S transformation of the line mode current, and obtains an amplitude matrix of the line mode current. The method determines the arrival moment of a traveling wave through an abrupt change point of the highest-frequency component in the S transformation amplitude matrix, and solves an argument difference between the line mode current and the remaining line mode currents. The phase relation of high-frequency components of all line mode currents at the starting moment of the fault forms the criterion. The method achieves the discrimination of a line fault and a bus fault according to the criterion. Large amount of simulation analysis indicates that the method can reliably discriminate an outgoing line fault and the bus fault, is simple in theory, is reliable and effective.

The invention relates to an ultrahigh-voltage DC line protection method based on specific frequency band current, which comprises the steps of firstly extracting real-time current values measured by current dividers at a rectification-side protection installation part and a rectification-side smoothing reactor valve side; calculating fault current of the protection installation part and the smoothing reactor valve side, namely, the difference between the real-time current and steady-state current of an ultrahigh-voltage DC system in normal operation; extracting a specific frequency band current component of the fault current by a filter; performing comparative judgment on a specific frequency band current effective value at the rectification-side protection installation part, a specific frequency band current effective value at the rectification-side smoothing reactor valve side and a protection threshold to obtain whether the DC line has a fault or not; and then obtaining the type ofthe fault. According to the invention, fault judgment is performed by only using the single-end specific frequency band current, data synchronization is not required to be performed, requirements forthe sampling rate is low, and various DC line faults can be recognized quickly and accurately.

The invention discloses a method and a system for positioning a single-pole grounding fault section of a direct-current power distribution network, and the method comprises the steps: cooperatively inputting a resonant branch to inject a current detection signal through an MMC additional control strategy, then setting an action sequence of a load switch/circuit breaker based on a delay level difference principle, and completing the positioning and isolation of a fault section based on single-end information. The section positioning method avoids the installation of additional devices, and has the characteristics of high sensitivity and no need of double-end communication.

The invention relates to a single-ended protection method for a high-voltage transmission line based on a specific frequency band energy ratio, and the method comprises the steps: calculating the energy of specific frequency bands of an AC side and a DC side through collecting the current and voltage parameters in the specific frequency bands of the current side and the DC side; when the protection element is started, current and voltage parameters, energy of a corresponding specific frequency band and the ratio of the energy of the direct current side to the energy of the alternating current side continue to be refreshed, a blocking signal is sent to protection of the alternating current side when fault judgment is carried out on the direct current side, the fault type of the direct current side is judged, and protection of a corresponding pole trips quickly to remove the fault; when the fault judgment is located on the alternating current side, a blocking signal is sent to the direct current side protection, the fault type of the alternating current side is judged, and the corresponding protection rapidly trips to remove the fault.